DE102019220384A1 - Monoaxially stretched polyolefin film - Google Patents

Abstract

The invention relates to a monoaxially stretched polyolefin film which can be produced by blown film extrusion and subsequent monoaxial stretching. The tube obtained by blown film extrusion is laid flat and thermally bonded to itself during the monoaxial stretching.

Description

The invention relates to a monoaxially stretched polyolefin film which can be produced by blown film extrusion and subsequent monoaxial stretching. The tube obtained by blown film extrusion is laid flat and thermally bonded to itself during the monoaxial stretching.

Blown films are manufactured with the help of blown film extruders in which a polymer melt is pressed into a film die. When exiting the film die, a tubular, vertical film bubble is created, which is controlled and cooled by air exchange inside (inside air) and air flow from outside (outside air). The film bubble is then - still provided with residual heat - folded into a tube via a flattening unit (flattening) and guided through the flattening unit via nip rollers. Depending on the blown film system, the flattened tube can then be further processed inline, e.g. slit and stretched, or immediately pulled to a winder via a film take-off unit and a film guide track and rolled up into rolls.

In the case of blown film extrusion, minimal differences in thickness arise over the circumference of the bubble, which would add up when the blown film is wound up. In order to prevent these so-called "piston rings" and to produce a smooth film wrap, the entire lay-flat unit including the film take-off unit is rotated back and forth (reversed) by up to 360 °, thus distributing the thick and thin areas evenly over the circumference. Since the film web can be rotated by up to 360 ° due to the reversing after leaving the film take-off unit, it is brought back into a position with turning bars (horizontal or vertical) where it can be transported further in the fixed part of the system. Alternatively, systems are also known in which the film blow head is rotatably mounted.

Due to the manufacturing process, the maximum total layer thickness of blown films is often limited to approx. 200 µm. By increasing the film thickness - partly due to the production process "from bottom to top" - the increased weight of the polymer melt or blown film means that the not yet solidified part of the film bubble can no longer be blown out in a stable / controlled manner and pulled off upwards . In the event of a malfunction, the melt hits the blown film head and causes the system to come to a standstill.

In contrast to blown film extrusion, no film bubble is processed in flat or cast film extrusion, but a polymer melt is pumped through a wide nozzle. The melt passes through this nozzle onto a rotating and cooled roller body and is then wound up. Tolerance deviations can be recognized by thickness measurement and compensated for with tension and compression screws. This is a top-down production process. The above-mentioned problem of the blown film process does not apply to flat or cast film extrusion. Through flat or cast film extrusion, total layer thicknesses of the cast films can also be achieved well above 200 µm.

The stretched polyolefin cast films found on the market use mixtures of several different polymers, including polyethylene, polypropylene, their copolymers or elastomers. This fact is also supported by various prior art.

WO 2010/019943 A1 describes a stretched film consisting of ethylene-propylene copolymer and a propylene-butene elastomer.

WO 2012/016075 A1 describes a stretched film consisting of a "random" propylene copolymer and a low-density ethylene homopolymer.

WO 2012/016075A1 describes an adhesive tape which comprises a stretched film consisting of various propylene compositions, in particular propylene homopolymer, propylene copolymer and an elastomer in the form of an ethylene-propylene copolymer.

EP 3 290 205 A1 discloses that it is known from practice that polypropylene with a melt flow index higher than 4.0 g / 10min cannot be reliably processed on conventional blown film systems, since stable blown film extrusion is no longer guaranteed with increasing melt flow index. In addition, polypropylene with a high melt flow index of 5.0 to 15 g / 10min ( ISO 1133 at 230 ° C. and 2.16 kg) as being processable primarily as cast film in the prior art. These statements can be confirmed from practice. In addition, the statements apply not only to polypropylene, but also to all thermoplastic polymers, especially polyolefins.

Monoaxially stretched polyolefin films are characterized by particularly advantageous mechanical properties, since the polymers align themselves in the machine direction during stretching (MDO, machine direction orientation). This changes the morphology of the film material significantly. Both the amorphous and crystalline structures are oriented in the machine direction and the alignment of the molecular structure leads to a higher density, and in the case of partially crystalline polymers also to a higher degree of crystallization. These changes in morphology have a significant influence on the properties of the film. As the degree of stretching increases, the mechanical properties in the stretching direction are significantly increased, in particular rigidity, tensile strength, puncture resistance and tear strengths. But the optical properties and the barrier effect of the film can also be improved.

WO 95/20633 relates to a tear-resistant adhesive tape based on monoaxially oriented polyethylene, in particular a polymeric carrier with a pressure-sensitive adhesive coating with high tensile strength, high tear strength and low elongation at break, the carrier containing a low-pressure polyethylene monoaxially oriented in the longitudinal direction.

WO 2005/113370 relates to a pouch with a flat end, comprising a body and a bottom, in particular a flat bottom, the body of the pouch comprising at least one film stretched in one direction.

WO 2007/076918 relates to a blown film made from a composition comprising a) a propylene heterophase copolymer (A) with a matrix propylene polymer and an ethylene propylene rubber, the film being oriented monoaxially in the machine direction with an elongation in the ratio of 1: 1.1 to 1:10.

WO 2009/092641 relates to a polyolefin film, in particular for an adhesive tape, which is stretched monoaxially in the longitudinal direction, the film containing a mixture of an olefinic and a polar non-olefinic polymer.

WO 2016/178965 discloses machine direction oriented coextruded multilayer film structures for use as label stock and die cut adhesive labels. The label materials include extruded, machine direction oriented multilayer films and an adhesive layer.

WO 2016/193186 relates to a film containing a blend of a special multimodal linear low density polyethylene and a tubular or autoclave low density polyethylene that has been uniaxially stretched in the machine direction with a stretch ratio of less than 1: 4.

DE 10 2016 210374 relates to a sealable polyolefin film, preferably polyethylene film, with a uniaxial stretching, which is a blown film, the stretching ratio of the uniaxial stretching being no higher than 1: 3 and no lower than 1: 1.9 and the film thickness being no more than 30 μm .

In the MDO process, films produced in the blown film or cast film process are continuously stretched in the machine direction. For this purpose, the tubular or flat film is brought to a suitable stretching temperature, which is usually in the range from 60 to 150 ° C., via several heating rollers, depending on the material. The heated film is stretched in the machine direction by the speed difference between one or two temperature-controlled roller pairs. This stretching process reduces the film thickness and deliberately changes the morphology of the film. To adjust the shrinkage behavior or to ensure dimensional stability, the stretched film is relaxed on subsequent annealing rollers under the influence of tension and temperature. The stretching process is completed after the film has been cooled down to almost ambient temperature by cooling rollers. MDO stretching units can be used inline in a blown or cast film line, whereby high efficiency is achieved with low investment and operating costs.

shows schematically and greatly simplified a conventional blown film line with an integrated MDO stretching unit. First, with the help of an extruder ( 1 ) a polymer melt is produced from a granulate, which a film die head ( 2 ) is supplied. With the help of blown indoor air ( 3a ) and blown outside air ( 3b ) a tubular blown film ( 4a ), whose properties are also generated by a calibration head ( 5 ) can be controlled. The tubular blown film ( 4a ) is carried out via a lay-flat unit 6th ) laid flat and the tubular film laid flat ( 4b ) over two nip rollers ( 7th ) to a turning bar system ( 8th ) guided. The entire lay-flat unit ( 6th ) together with the film take-off mechanism rotated up to 360 ° forwards and backwards (reversed). A The reversing mechanism rotates the flattening unit ( 6th ), the nip rollers ( 7th ) and part of the turning bar system ( 8th ), where the turning bar system ( 8th ) compensates for the initial rotation. In this way, the flattened tubular film ( 4b ) brought back into a position in which it can be transported further in the fixed part of the system. The running behavior of the film is stabilized by reversing; Long paths that are not guided over rollers would otherwise lead to unstable running behavior, which could potentially lead to wrinkles and optical defects, for example so-called “stress whitening” in the case of polypropylene. From the turning bar system ( 8th ) the flattened tubular film ( 4b ) then by knife ( 9 ) slotted on one or both sides in order to avoid undesired air intake within the film tube. The foil slit in this way ( 4c ) is then put into an MDO stretching unit ( 10 ) by first passing over several heating rollers ( 11a ) as well as adjacent contact rollers ( 11b ) is heated up. The film then runs through two roller systems operated at different speeds; the first roller system comprises a driven slower roller ( 12a ) as well as a slower feed roller ( 12b ), whereby usually at least one of the slower rollers ( 12a, b ) is heated. The second roller system comprises a driven, faster roller ( 13a ) as well as a faster feed roller ( 13b ), whereby usually at least one of the faster rollers ( 13a, b ) is heated. The speed of rotation of the faster rollers ( 13a, b ) is greater than the speed of rotation of the slower rollers ( 12a, b ), whereby the slit film ( 4c ) is stretched in the machine direction. Then the monoaxially stretched film ( 4d ) on subsequent annealing rollers ( 14th ) and chill rolls ( 15th ) relaxed under the influence of tension and temperature and finally a relaxed film ( 4e ), which can then be further processed, in particular pulled apart and rolled up. On the rollers (12, 13, 14th , 15th ) lie according to each additional contact rollers, which are indicated by small circles and for the annealing rollers ( 14th ) as well as chill rolls ( 15th ) are not provided with reference symbols for reasons of clarity.

WO 2011/057918 relates to a device for longitudinally stretching a film web with at least one heating device in which the film web can be heated, at least one cooling device in which the film web can be cooled again, and at least one stretching unit in which the film web can be stretched in its longitudinal direction, the stretching unit being a first transport roller with a first rotational speed during the stretching process and a second transport roller downstream of the first transport roller in the direction along the transport path of the film web with a second rotational speed, the second rotational speed being greater than the first rotational speed.

WO 2015/007356 relates to a device for the production of tubular films which are stretched in series in a blow molding process, comprising an extruder, a blown film system, a smoothing unit, an oscillating take-off unit and a stretching system for monoaxially stretching the film in a machine direction. The stretching system is arranged above the extruder between the flattening unit and the oscillating take-off unit.

Particularly advantageous mechanical properties are achieved when the stretching ratio is in the range from approx. 1: 3 to 1: 8. As a result of the monoaxial stretching by such a stretching ratio, the layer thickness of the stretched polyolefin film decreases by the corresponding factor, that is, a film with an original total layer thickness of, for example, 200 μm before the monoaxial stretching then has a total layer thickness of, for example, only at a stretching ratio of 1: 5 about 40 µm.

A total layer thickness that is as uniform as possible, which influences the quality of the flatness, is fundamentally desirable, in particular if the monoaxially stretched polyolefin film is then subjected to further processing steps. If, for example, the monoaxially stretched polyolefin film is to be coated after the monoaxial stretching, an uneven overall layer thickness, i.e. poor flatness, would lead to coating difficulties. Modern coating systems can compensate for such irregularities to a certain extent, in particular by exerting local tensile forces in areas of greater layer thickness. However, monoaxially stretched polyolefin films usually have such a high tensile strength that poor flatness can hardly be compensated for with these methods; the monoaxially stretched polyolefin films withstand the local tensile forces and do not give way.

The monoaxial stretching also leads to a non-uniform reduction in the total layer thickness along the width of the film, ie in the transverse direction, due to the manufacturing process. When the film is stretched in the machine direction, not only is the film thickness reduced, but there is also a reduction in the film width due to constriction. This so-called “neck-in effect” leads to a film thickness profile in the transverse direction with pronounced thick spots in the edge areas. In the case of monoaxial stretching, for example, the total layer thickness is greatest in the middle of the film web and least at the edges of the film web reduced. If a polyolefin film with a planar, uniform total layer thickness along the width of the film were used as the starting material before the stretching, ie with an almost rectangular cross-section, a polyolefin film with a biconcave cross-section would be obtained after the monoaxial stretching.

This is in illustrated schematically. shows a polymer film produced, for example, by blown film extrusion, with an idealized rectangular cross section along the width of the film before the monoaxial stretching; Figure 10 shows the biconcave cross-section after monoaxial stretching in the machine direction. For better illustration, the dimensions are shown greatly exaggerated.

However, in order to ensure problem-free further processing of the stretched film in the subsequent production steps, this neck-in area must be removed by trimming the edge on both sides prior to winding. Since the edge strips to be removed can each have a considerable width, the net output of the system is thus reduced.

There are various known ways of reducing or compensating for the neck-in effect. A stretching gap that is as short as possible reduces the neck-in effect. However, the minimum gap width depends on the material, structure and application of the film to be stretched. Another important parameter is the positioning of additional pressure rollers on the temperature-controlled rollers, especially on the rollers of the stretching nip. With the help of these pressure rollers, not only is the heat transfer between the temperature control roller and film improved, but they also fix the film on the rollers and thus ensure defined stretching.

In addition, the use of modern processes for the targeted control of the film thickness in inline MDO applications opens up potential for material savings. These processes influence the profile of the as yet unstretched primary film via the profile control system of the extrusion plant in such a way that a defined film profile is realized after the stretching process. With the help of this strategy, up to 50% of the edge trim can be saved, which in turn significantly improves the efficiency of the stretching process (cf. Th. Leopold, Gestreckte Limits, Kunststoffe, Carl Hanser Verlag, 10/2014, pages 182-5 ).

In order to counteract the neck-in effect, modern manufacturing plants can be operated in such a way that the total layer thickness is unevenly uneven along the width of the film, i.e. polyolefin films with an initially biconvex cross-section can be obtained and then stretched monoaxially. With correct adjustment, the monoaxial stretching in the middle of the film web then leads to the fact that the greater total layer thickness there before the stretching due to the biconvex cross-section is compensated for by the greater reduction in the total layer thickness during the stretching, so that a monoaxially stretched polyolefin film with a largely constant total layer thickness along the width of the film. The initially biconvex configuration of the cross section is thus compensated for in the monoaxial stretching as a result of the relative tapering of the total layer thickness of the polyolefin film in the center of the film.

This is in illustrated schematically. shows a polymer film produced, for example, by blown film extrusion, with an idealized biconvex cross section along the width of the film before the monoaxial stretching; shows the cross-section with improved flatness after the monoaxial stretching in the machine direction. The total layer thickness is only significantly greater at the outer edges, which is why the edges are usually cut off. For better illustration, the dimensions are also shown greatly exaggerated.

WO 2014/177235 relates to a method for regulating the thickness profile of inline-oriented films that are produced by a blow molding process, laid flat in an oscillating take-off unit and repositioned and then oriented monoaxially in the machine direction in an orientation unit, the thickness profile of the film being regulated in such a way that a The result is a film that has a certain thickening in its edge area in relation to the average film thickness over its entire width with the exception of the edge areas.

EP 0 432 423 relates to a method for the axial, preferably biaxial, stretching of tubular films which, after their production, are laid flat on a blown film extruder system and which are again inflated to form a tubular film bubble or expanded into a film tube. In the inflated or expanded state, these then pass through an oven, from which they are drawn off with renewed flattening at a speed that is increased compared to the inlet speed by an amount that corresponds to the desired stretching ratio. To make sure that the stretched tubular film is over their circumference have an essentially equal distribution of thickness, the film thickness of the stretched tubular film emerging from the oven is measured over its circumference before or after it is flattened. The distribution over the circumferential profile of the tubular film produced on the blown film extruder line is adjusted in accordance with the measured thicknesses of the circumferential profile so that deviations from the mean film thickness arising in the oven during stretching due to uneven heating and possibly other disruptive influences are largely compensated for.

EP 2 277 681 relates to a method for producing a film which contains an extruded film tube. The tube is laid flat to form the film. The film is repositioned by an oscillating take-off unit. The film is oriented monoaxially in the machine direction by an orientation unit in order to produce the film with a transverse thickness profile which deviates from an average film thickness over the entire film width. The extruded film tube is adjusted to a specific nominal thickness profile along the circumference of the extruded film tube.

There is a need for monoaxially stretched polyolefin films with a total layer thickness of 10 to 100 μm, preferably 10 to 85 μm (after stretching) and a stretching ratio in the range from 1: 3 to 1: 8, preferably 1: 4 to 1: 7. Since the total layer thickness in the blown film extrusion (before stretching) is limited due to the manufacturing process, total layer thicknesses in the desired range cannot easily be obtained by blown film extrusion and subsequent monoaxial stretching in the desired stretching ratio.

It has been proposed to glue the tubular, vertical film bubble formed when it emerges from the film blow head to itself while it is being laid flat, so that the total layer thickness is doubled. This procedure is also known as "hose bonding". For this purpose, the squeegee rollers after the lay-flat unit and / or the film during and / or in front of the lay-flat unit (radiant heater) are heated to a temperature that is sufficient to thermally bond the two insides of the tubular bladder together while they are pressed onto one another by the squeegee rollers, or the unchanged residual heat of the film tube is used for bonding in the nip rollers without additional heating, especially with low system heights.

WO 2019/036565 relates to multilayer blocked shrink films which contain at least one layer which contains a blocking polymer. Materials and methods for forming multilayer, blocked shrink films by means of a blown film extrusion process are described, with the tube being glued in the lay-flat unit.

EP 0 519 251 and U.S. 5,804,020 relate to laminated films, the cut ends of which are fused together. The composite is produced on nip rolls and comprises strongly connected sections at the ends and weakly connected sections in the middle.

EP 1 147 877 relates to a method for producing a stretch plastic film comprising the extrusion of a suitable plastic material from an annular nozzle as a tubular film and the shaping of the extruded film into a bubble with air trapped therein by simultaneously collapsing and connecting the tubular film bubble at a predetermined distance from the annular nozzle. The temperature of the tubular film as it collapses is sufficiently high to cause opposing sides of the collapsed film to bond together to form a single layer stretch plastic film which can then be stretched to reduce its thickness. The film contains neither antiblocking agents nor lubricants.

WO 2010/075946 relates to an at least contact-transparent single or multilayer film that absorbs and / or reflects UV radiation and short-wave visible light. The multilayer film can be produced by blown film co-extrusion and tube gluing.

The gluing of the tubular film bubble to itself in the lay-flat unit or via heated nip rollers of the lay-flat, i.e. before the monoaxial stretching, has the disadvantage, however, that air inclusions can occur, which considerably impair the appearance and the mechanical properties of the monoaxially stretched polyolefin film. Air inclusions occur in particular when the polyolefin used has a certain rigidity and / or greater film thicknesses, so that the tubular film laid flat is curved at its edges. If, in addition, a biconvex cross-section is produced over the film die in order to obtain the most uniform possible overall layer thickness and correspondingly good flatness after the monoaxial stretching, the flattened tubular film bubble is particularly susceptible to air inclusions.

In the WO 2019/036565 The non-mentioned susceptibility to air inclusions of the tube-bonded film mentioned is based on the fact that the film thicknesses of the extruded film are described below 100 μm and, moreover, only polymers of low rigidity are used. The susceptibility found when a certain rigidity and / or greater film thicknesses are present, so that the tubular film laid flat is curved at its edges, among other things, is in for the products WO 2019/036565 extremely low.

This is in illustrated schematically. shows the cross section of a tubular film produced by blown film extrusion with an idealized biconvex cross section on the two opposite sides of the tube (top and bottom); shows the cross section of the flattened tubular film after passing through the flattening unit but before passing through the nip rollers; shows the cross-section after gluing the flattened tubular film to itself before the monoaxial stretching with the formation of air pockets; shows the cross-section after monoaxial stretching with damage that can be attributed to the air inclusions. For better illustration, the dimensions are also shown greatly exaggerated.

The prior art monoaxially stretched polyolefin films are not satisfactory in all respects and it is an object of the invention to provide monoaxially stretched polyolefin films which have advantages over the prior art. The polyolefin films should be monoaxially stretched inline during their production, have excellent mechanical properties and, for this purpose, have a sufficient total layer thickness with a sufficient stretching ratio. In addition, the monoaxially stretched polyolefin films should be characterized by an overall layer thickness that is as uniform as possible (flatness), in particular coatable, for example siliconizable. In addition, the monoaxially stretched polyolefin films should be thermally stable, preferably not shrink by more than 1.0% of their original surface area after 1 minute when heated in an oil bath at 120 ° C.

This problem is solved by the subject matter of the claims.

It has surprisingly been found that a flat tubular film bubble can be glued to itself without air inclusions if the gluing does not take place during the flat laying after exiting the film die, but only after cooling and subsequent renewed heating during the monoaxial stretching.

1. (a) es werden trotz Blasfolienextrusion größere Gesamtschichtdicken zugänglich, welche ansonsten nur durch Flach- bzw. Gießfolienextrusion erhältlich sind (Castfolien);
2. (b) damit können erfindungsgemäß alle Vorteile, welche die Blasfolienextrusion im Vergleich zur Flach- bzw. Gießfolienextrusion hat, für die erfindungsgemäßen Polyolefinfolien genutzt werden, wie z.B. (i) große Flexibilität hinsichtlich der Anzahl und Beschaffenheit der einzelnen Schichten im Mehrschichtverbund, (ii) verbesserte Planlage, (iii) bessere Wirtschaftlichkeit, (iv) bessere Automatisierungsmöglichkeiten, wie softwaregesteuerte und automatisierte Reduzierung des Randaufbaus, (v) große Flexibilität hinsichtlich Polymeren mit niedriger Schmelzviskosität, welche von Flach- bzw. Gießfolienextrusion nur schwer genutzt werden können;
3. (c) es werden Polyolefinblasfolien mit vorteilhaften mechanischen Eigenschaften zugänglich gemacht, insbesondere im Hinblick auf (i) Zugfestigkeit in Maschinenrichtung und besonders (ii) Zugfestigkeit in Maschinenrichtung im geringen Dehnungsbereich;
4. (d) es werden gereckte Polyolefinblasfolien mit ähnlich vorteilhaften mechanischen Eigenschaften wie gereckte Polyolefincastfolien zugänglich gemacht, insbesondere im Hinblick auf (i) Zugfestigkeit in Maschinenrichtung und besonders (ii) Zugfestigkeit in Maschinenrichtung im geringen Dehnungsbereich; und
5. (e) es werden Polyolefinfolien mit vorteilhaften homogenen Eigenschaften zugänglich gemacht, insbesondere im Hinblick auf das Selbstverschließen von kleinen Löchern bedingt durch das Recken einer Stippe oder eines Gel-Teilchens. Die Schlauchverklebung heilt sich sozusagen selbst durch das Verkleben. Die Wahrscheinlichkeit, dass 2 Löcher überhaupt genau gegenüberliegen ist nahezu nicht vorhanden.

Compared to conventional monoaxially stretched polyolefin films, the monoaxially stretched polyolefin films according to the invention have, inter alia, the following advantages:

1. (a) despite blown film extrusion, greater overall layer thicknesses are accessible which are otherwise only obtainable by flat or cast film extrusion (cast films);
2. (b) According to the invention, all advantages that blown film extrusion has compared to flat or cast film extrusion can be used for the polyolefin films according to the invention, such as (i) great flexibility with regard to the number and nature of the individual layers in the multilayer composite, (ii) improved flatness, (iii) better economy, (iv) better automation options, such as software-controlled and automated reduction of the edge build-up, (v) great flexibility with regard to polymers with low melt viscosity, which can only be used with difficulty by flat or cast film extrusion;
3. (c) Blown polyolefin films with advantageous mechanical properties are made available, in particular with regard to (i) tensile strength in the machine direction and especially (ii) tensile strength in the machine direction in the low elongation range;
4. (d) stretched polyolefin blown films with similar advantageous mechanical properties as stretched polyolefin cast films are made available, in particular with regard to (i) tensile strength in the machine direction and especially (ii) tensile strength in the machine direction in the low elongation range; and
5. (e) Polyolefin films with advantageous homogeneous properties are made available, in particular with regard to the self-closing of small holes caused by the stretching of a speck or a gel particle. The hose gluing heals itself, so to speak, through the gluing. The probability that 2 holes are exactly opposite at all is almost non-existent.

In addition, according to the invention, pure polyolefin films can be produced, ie polyolefin films which are essentially composed of only a single type of polymer, possibly in different layers. This has advantages not only in terms of good recyclability, but also in terms of the raw materials used. So some polymer manufacturers take rejects, which for example, if the edge areas of the film according to the invention are missed, only recovered if the rejects are sorted.

In addition, the trimmed edges of the single-variety polyolefin films according to the invention form far fewer specks in a single-variety polyolefin film with recycled material if the trimmed edge is returned to the extrusion process directly or indirectly as recycled material for the single-variety polyolefin films.

• - eine erste Schicht basierend auf Polyolefin mit einer VICAT-Erweichungstemperatur T₁,
• - eine zweite Schicht basierend auf Polyolefin mit einer VICAT-Erweichungstemperatur T₂, und
• - eine Kernschicht umfassend ein thermoplastisches Polymer mit einer VICAT-Erweichungstemperatur T₃,

wobei die Kernschicht zwischen der ersten Schicht und der zweiten Schicht angeordnet ist und ein Antiblockmittel enthält; und wobei T₃ um mindestens 5°C, bevorzugt mindestens 10°C, unterhalb von T₁ und T₂ liegt.A first aspect of the invention relates to a monoaxially stretched polyolefin film comprising

• - a first layer based on polyolefin with a VICAT softening temperature T ₁ ,
• - A second layer based on polyolefin with a VICAT softening temperature T ₂ , and
• - a core layer comprising a thermoplastic polymer with a VICAT softening temperature T ₃ ,

wherein the core layer is disposed between the first layer and the second layer and contains an antiblocking agent; and where T ₃ is at least 5 ° C., preferably at least 10 ° C., below T ₁ and T ₂ .

The polyolefin of the first layer and the polyolefin of the second layer are particularly preferably selected from polypropylene homopolymers and polypropylene copolymers. If the core layer also comprises a polyolefin in addition to the thermoplastic polymer, this polyolefin is preferably also selected from polypropylene homopolymers and polypropylene copolymers.

In addition to the thermoplastic polymer, the core layer preferably comprises a polyolefin which is identical to the polyolefin on which the first layer is based and which is identical to the polyolefin on which the second layer is based; wherein the thermoplastic polymer increases the bond strength within the thermally bonded core layer along the mutually bonded layers while the stretching temperature remains the same.

In addition to the thermoplastic polymer, the core layer preferably comprises a polyolefin which is identical to the polyolefin on which the first layer is based and which is identical to the polyolefin on which the second layer is based; wherein the thermoplastic polymer has a lower melting temperature, ie the polyolefin of the core layer and thus the melting temperature of the entire core layer is reduced.

Preferably, the VICAT softening temperature T _{1 of} the polyolefin on which the first layer is based essentially corresponds to the VICAT softening temperature T _{2 of} the polyolefin on which the second layer is based. The relative difference between T ₁ and T _{2 is} preferably at most 10 ° C., more preferably at most 7.5 ° C., even more preferably at most 5 ° C., particularly preferably at most 2.5 ° C., most preferably at most 1 ° C.

The VICAT softening temperature T _{3 of} the thermoplastic polymer comprising the core layer is lower than the VICAT softening temperature T _{1 of} the polyolefin on which the first layer is based and lower than the VICAT softening temperature T _{2 of} the polyolefin on which the second Layer based. The relative difference between T ₃ and T ₁ or T ₂ is preferably at least 5 ° C., more preferably at least 7.5 ° C., even more preferably at least 10 ° C., particularly preferably at least 12.5 ° C., most preferably at least 15 ° C.

According to the invention, the polyolefin film is not thermally bonded to itself with the aid of the squeegee rollers of the lay-flat unit, but only then in the stretching unit.

schematically illustrates various configurations of the film according to the invention. shows a three-layer structure with an outer first layer and an outer second layer as well as an intermediate core layer directly adjoining it. shows a five-layer structure with two additional layers. shows a nine-layer structure with four additional layers. The embodiments according to , and all have a symmetrical structure of the multilayer film, ie in the cross section shown there is a mirror plane in the middle of the core layer, which is indicated in each case by a line.

shows a section of a variant of the blown film line according to the invention with a turning bar system ( 8th ) as well as integrated MDO stretching unit ( 10 ). The slotted film runs through ( 4c ) on their transport route after leaving the turning bar system ( 8th ) (ie after reversing) and before reaching the MDO stretching unit ( 10 ) a series of rolls arranged one after the other in the machine direction ( 16 ), whereby the wraps around the slit film ( 4c ) on the rollers ( 16 ) each be at least 45 ° and at most 160 ° and with rollers arranged one after the other in the machine direction ( 16 ) have a distance of no more than 5 m from each other.

The polyolefin film according to the invention is stretched monoaxially, typically in the machine direction of the system on which the polyolefin film according to the invention is produced. According to the invention, the polyolefin film is preferably produced on a blown film line, which preferably has an integrated MDO stretching unit. The polyolefin film according to the invention is preferably stretched by a stretching ratio in the range from 1: 3 to 1: 8, preferably from 1: 4 to 1: 7, preferably in the machine direction.

The polyolefin film according to the invention preferably has a symmetrical structure, a mirror plane lying in the cross-sectional area of the polyolefin film preferably within the core layer. Accordingly, starting from the center of the core layer in the direction of the first layer, the layer sequence preferably corresponds to that starting from the center of the core layer in the direction of the second layer. Individual layers that are projected onto one another through the mirror plane have essentially the same layer thickness and essentially the same chemical composition. The symmetry results from the preferred manufacturing process according to the invention, a tubular film with an initially centrosymmetrical structure of the film bubble being glued to itself over the inner layer. However, the polyolefin film according to the invention does not necessarily have to be completely symmetrical; For example, it is possible that one or more additional layers are subsequently laminated in a separate step on one of the two outer sides.

• - auf einer der beiden Außenseiten mit Release-Eigenschaften ausgerüstet, vorzugsweise durch Silikonisierung;
• - auf beiden Außenseiten mit Release-Eigenschaften ausgerüstet, vorzugsweise durch Silikonisierung;
• - auf einer der beiden Außenseiten mit selbstklebenden Eigenschaften ausgerüstet, vorzugsweise durch Aufbringen eines Haftklebstoffs;
• - auf beiden Außenseiten mit selbstklebenden Eigenschaften ausgerüstet, vorzugsweise durch Aufbringen eines Haftklebstoffs;
• - auf einer der beiden Außenseiten mit Release-Eigenschaften ausgerüstet, vorzugsweise durch Silikonisierung, und auf der anderen der beiden Außenseiten mit selbstklebenden Eigenschaften ausgerüstet, vorzugsweise durch Aufbringen eines Haftklebstoffs;
• - auf beiden Außenseiten mit Release-Eigenschaften ausgerüstet, vorzugsweise durch Silikonisierung; und darüber auf einer der beiden Außenseiten mit selbstklebenden Eigenschaften ausgerüstet, vorzugsweise durch Aufbringen eines Haftklebstoffs.

In a preferred embodiment, the polyolefin film according to the invention is made in separate steps

• - Equipped with release properties on one of the two outer sides, preferably by siliconization;
• - Equipped with release properties on both outer sides, preferably by siliconization;
• - Equipped with self-adhesive properties on one of the two outer sides, preferably by applying a pressure-sensitive adhesive;
• - Equipped with self-adhesive properties on both outer sides, preferably by applying a pressure-sensitive adhesive;
• - equipped on one of the two outer sides with release properties, preferably by siliconization, and equipped on the other of the two outer sides with self-adhesive properties, preferably by applying a pressure-sensitive adhesive;
• - Equipped with release properties on both outer sides, preferably by siliconization; and on top of it equipped with self-adhesive properties on one of the two outer sides, preferably by applying a pressure-sensitive adhesive.

The polyolefin film according to the invention can have a comparatively simple structure, for example consist only of the first layer, the second layer and the third layer. According to the invention, however, it is also possible for the polyolefin film to contain one or more additional layers, these additional layers between the core layer and the first layer or between the core layer and the second layer and / or seen from the core layer to the outside beyond the first Layer or beyond the second layer can be arranged. The one or more additional layers are preferably each based, if appropriate, independently of one another on polyolefin.

In a preferred embodiment, the core layer is in direct contact with the first layer and / or the second layer. In a preferred embodiment, there are no additional layers apart from the core layer between the first layer and the second layer. In the case of such a three-layer structure, the first layer and the second layer then form the two outer layers of the polyolefin film according to the invention. In the case of a five-layer or multi-layer structure, the first layer and the second layer then preferably form inner layers of the polyolefin film according to the invention, which are each arranged between the core layer and additional layers, two of these additional layers in turn preferably forming the outer layers of the polyolefin film according to the invention.

In a preferred embodiment, the first layer and / or the second layer forms the outer layers of the polyolefin film.

While the core layer of the polyolefin film according to the invention contains an antiblocking agent, the first layer and / or the second layer preferably contains no antiblocking agent. However, it is possible that the first layer and / or the second layer also contain antiblocking agents. If the polyolefin film according to the invention contains additional layers in addition to the first layer, the second layer and the core layer, these additional layers also preferably contain no antiblocking agent, ie the core layer is preferably the only layer of the polyolefin film according to the invention which contains an antiblocking agent. However, it is possible for the additional layers to contain antiblocking agents. A person skilled in the art recognizes that in the border area of two directly adjoining layers, migration effects can lead to antiblocking agents possibly migrating to a small extent from one layer into the directly adjoining layer. However, such migration effects should not be taken into account in the above definition.

The core layer of the polyolefin film according to the invention preferably consists of two layers which are thermally bonded to one another. This bonding can be detected with suitable analytical methods, e.g. electron microscopy.

The polyolefin film according to the invention preferably has a total layer thickness of at least 5 μm, at least 10 μm, or at least 15 μm, or at least 20 μm, or at least 25 μm, or at least 30 μm. The polyolefin film according to the invention preferably has a total layer thickness of at most 200 μm, or at most 150 μm, or at most 120 μm, or at most 100 μm, or at most 80 μm. The polyolefin film according to the invention preferably has a total layer thickness in the range from 5 to 100 μm, preferably from 10 to 80 μm.

In preferred embodiments, the polyolefin film according to the invention has a total layer thickness in the range of 50 ± 40 µm, or 60 ± 40 µm, or 70 ± 40 µm, or 80 ± 40 µm, or 90 ± 40 µm, or 50 ± 30 µm, or 60 ± 30 µm, or 70 ± 30 µm, or 80 ± 30 µm, or 90 ± 30 µm, or 50 ± 20 µm, or 60 ± 20 µm, or 70 ± 20 µm, or 80 ± 20 µm, or 90 ± 20 µm , or 50 ± 10 µm, or 60 ± 10 µm, or 70 ± 10 µm, or 80 ± 10 µm, or 90 ± 10 µm.

Suitable methods for determining the total layer thickness are known to a person skilled in the art, e.g. microscopic analysis on a microtome section.

Blown film lines are mostly designed for a maximum total thickness of the non-stretched films of 200 µm. With stretching factors of 1: 4 to 1: 7, films with a total layer thickness in the range of e.g. 70-80 µm cannot be produced in this way, since stretching in the machine direction reduces the film thickness by approximately the same factor. However, foils in the thickness range 70-80 µm are required. However, if the tubular film laid flat is stretched as a tube according to the invention and glued to itself on the inside, the possible final thickness is doubled after the monoaxial stretching, so that the invention makes monoaxially stretched polyolefin films of greater overall thickness accessible, which are not produced by conventional methods of blown film extrusion can.

The layer thickness of the core layer of the polyolefin film according to the invention is preferably comparatively small. The layer thickness of the first layer and / or the layer thickness of the second layer is preferably greater than the layer thickness of the core layer. The layer thickness of the first layer and / or the layer thickness of the second layer is preferably at least twice as great as the layer thickness of the core layer. The layer thickness of the core layer is preferably at most 30%, preferably at most 20%, more preferably at most 10% of the total layer thickness of the polyolefin film.

In a preferred embodiment of the polyolefin film according to the invention, the core layer contains a polyolefin in addition to the thermoplastic polymer. This polyolefin is preferably at least chemically related to the polyolefins on which the first layer and the second layer are based.

The first layer, the second layer and optionally also the core layer of the polyolefin film according to the invention are each based, independently of one another, on polyolefins. If additional layers are present, these in each case preferred, independently of one another, are likewise based on polyolefins.

For the purpose of description, the term “based” in connection with the composition of a layer means that the constituent on which the respective layer is based is the main constituent of this layer, ie makes up a greater proportion by weight than any other constituent of this layer. This does not necessarily mean that the main constituent makes up more than 50% by weight of the respective layer. Preferably, the content of the constituent on which the layer is based is each independent at least 70% by weight of one another, more preferably at least 80% by weight, even more preferably at least 90% by weight, in each case based on the total weight of the layer.

The polyolefin of the first layer, the polyolefin of the second layer and optionally also the polyolefin of the core layer are preferably each independently of one another homopolymers or copolymers which have been produced by polymerizing at least one common olefin monomer. In a preferred embodiment, the polyolefin film according to the invention comprises, in addition to the first layer, the second layer and the core layer, at least two, or at least four, or at least six, or at least eight, or at least ten, or at least twelve, or at least fourteen additional layers, based independently of one another on polyolefins, these polyolefins also being, independently of one another, homopolymers or copolymers which have been produced by polymerizing this at least one common olefin monomer from which the polyolefin of the first layer, the polyolefin of the second layer and possibly also the polyolefin of the core layer were produced .

Preference is given to the polyolefin of the first layer, the polyolefin of the second layer and, if applicable, also the polyolefin of the core layer, each independently of one another homopolymers or copolymers which have been produced by polymerizing consistently common olefin monomers, in the case of copolymers the common comonomers preferably in the same relative Quantity ratio are present. In a preferred embodiment, the polyolefin film according to the invention comprises, in addition to the first layer, the second layer and the core layer, at least two, or at least four, or at least six, or at least eight, or at least ten, or at least twelve, or at least fourteen additional layers, based independently of one another on polyolefins, these polyolefins also being, independently of one another, homopolymers or copolymers which have been produced by polymerizing these common olefin monomers from which the polyolefin of the first layer, the polyolefin of the second layer and possibly also the polyolefin of the core layer have been produced; and where, in the case of copolymers, these common comonomers are also preferably each present in this same relative quantitative ratio.

In the case of homopolymers, the common olefin monomer is preferably selected from the group consisting of ethylene, propylene, n-butylene and isobutylene. In the case of copolymers (e.g. terpolymers), all of the common olefin monomers are preferably selected from the group consisting of ethylene, propylene, n-butylene and isobutylene.

The polyolefin of the first layer, the polyolefin of the second layer and possibly also the polyolefin of the core layer are preferably each independently of one another homopolymers or copolymers which have essentially the same chemical composition and essentially the same weight-average molecular weight. In a preferred embodiment, the polyolefin film according to the invention comprises, in addition to the first layer, the second layer and the core layer, at least two, or at least four, or at least six, or at least eight, or at least ten, or at least twelve, or at least fourteen additional layers, based independently of one another on polyolefins, these polyolefins also having essentially the same chemical composition and essentially the same weight-average molecular weight as the polyolefin of the first layer, the polyolefin of the second layer and possibly also the polyolefin of the core layer.

The polyolefin of the first layer, the polyolefin of the second layer and / or the polyolefin of the core layer preferably contain or consist of a propylene homopolymer and / or a propylene copolymer, independently of one another. The polyolefin of the first layer, the polyolefin of the second layer and / or the polyolefin of the core layer preferably contain, independently of one another, a propylene copolymer, the content of which is in each case at least 70% by weight, more preferably at least 80% by weight, even more preferably at least 90% by weight .-%, each based on the total weight of the respective layer.

Propylene homopolymers and / or propylene copolymers with a melt flow index of less than 4.0 g / 10 min (ISO 1133 at 230 ° C. and 2.16 kg), preferably less than 3.0 g / 10 min (ISO 1133 at 230 ° C.) are particularly preferred and 2.16 kg), particularly preferably less than 2.0 g / 10min (ISO 1133 at 230 ° C. and 2.16 kg).

Ethylene homopolymers and / or an ethylene copolymer with a melt flow index of less than 4.0 g / 10 min (ISO 1133 at 190 ° C. and 2.16 kg), preferably less than 3.0 g / 10 min (ISO 1133 at 190 °), are particularly preferred C and 2.16 kg), particularly preferably less than 2.0 g / 10min (ISO 1133 at 190 ° C and 2.16 kg).

The polyolefin content of the core layer is preferably at least 30% by weight, more preferably at least 35% by weight, even more preferably at least 40% by weight, particularly preferably at least 45% by weight, most preferably at least 50% by weight, based on the total weight of the core layer.

The polyolefin content of the core layer is preferably at most 90% by weight, more preferably at most 85% by weight, even more preferably at most 80% by weight, particularly preferably at most 75% by weight, most preferably at most 70% by weight, based on the total weight of the core layer.

Preferably, the VICAT softening temperature T _{4 of} the polyolefin, which preferably comprises the core layer, essentially _{corresponds to the VICAT softening temperature T 1 of} the polyolefin on which the first layer is based, as well as essentially the VICAT softening temperature T _{2 of} the polyolefin on which the second layer based. The relative difference between T ₄ and T ₁ or T _{2 is} preferably at most 10 ° C., more preferably at most 7.5 ° C., even more preferably at most 5 ° C., particularly preferably at most 2.5 ° C., most preferably at most 1 ° C. .

The core layer of the polyolefin film according to the invention comprises a thermoplastic polymer whose VICAT softening temperature (VICAT temperature) T _{3 is} lower than the VICAT softening temperature T _{1 of} the polyolefin on which the first layer is based and is lower than the VICAT softening temperature T ₂ of the polyolefin on which the second layer is based.

The VICAT softening temperatures of commercial polymers are usually specified by the manufacturer and preferably determined according to the invention in accordance with A50-50 ° C./10 N in accordance with DIN EN ISO 306.

The thermoplastic polymer of the core layer preferably has a VICAT softening temperature T ₃ of at most 140 ° C, more preferably at most 130 ° C, even more preferably at most 120 ° C, particularly preferably at most 110 ° C, most preferably at most 100 ° C.

• - Polyethylenen, bevorzugt Ethylen-Homopolymer (Polyethylen, PE), Polyethylen niedriger Dichte (LDPE), lineares Polyethylen niedriger Dichte (LLDPE), Polyethylen sehr niedriger Dichte (VLDPE), auf Basis von Metallocen-Katalysatoren polymerisiertes Polyethylen (mPE), Polyethylen hoher Dichte (HDPE);
• - Propylen-Olefin-Copolymeren, bevorzugt statistische heterophasige Polypropylen (Block)-Copolymere oder statistische Propylen-Ethylen-Copolymere, besonders bevorzugt mit einem Ethylenanteil von 2 Gew.-% bis 4 Gew.-%;
• - thermoplastischen Elastomeren (TPE), bevorzugt Polyolefin basierte Elastomere, besonders bevorzugt Propylen basierte Elastomere mit einem Propylenanteil von mindestens 80 Gew.-%;
• - Butylen-Homopolymeren (Polybutylen, PB);
• - Isobutylen-Homopolymeren (Polyisobutylen, PI);
• - 1-Buten Copolymeren, bevorzugt statistische 1-Buten Copolymere, bevorzugter statistische Ethylen-1-Buten-Copolymere oder statistische Propylen-1-Buten-Copolymere;
• - Olefin basierten Plastomeren, bevorzugt Ethylen basierte Octen Plastomere;
• - Acrylsäure basierten Copolymeren, bevorzugt Ethylen-Methacrylsäure-Copolymere oder Ethylen-Acrylsäure-Copolymere; und
• - Vinylacetat Copolymeren, bevorzugt Ethylen-Vinylacetat-Copolymere (EVA).

In preferred embodiments of the polyolefin film according to the invention, the thermoplastic polymer of the core layer is selected from the group consisting of

• - Polyethylene, preferably ethylene homopolymer (polyethylene, PE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), polyethylene (mPE) polymerized on the basis of metallocene catalysts, high-density polyethylene Density (HDPE);
• Propylene-olefin copolymers, preferably random heterophase polypropylene (block) copolymers or random propylene-ethylene copolymers, particularly preferably with an ethylene content of 2% by weight to 4% by weight;
• - Thermoplastic elastomers (TPE), preferably polyolefin-based elastomers, particularly preferably propylene-based elastomers with a propylene content of at least 80% by weight;
• - butylene homopolymers (polybutylene, PB);
• - Isobutylene homopolymers (polyisobutylene, PI);
• 1-butene copolymers, preferably random 1-butene copolymers, more preferably random ethylene-1-butene copolymers or random propylene-1-butene copolymers;
• - Olefin-based plastomers, preferably ethylene-based octene plastomers;
• - Acrylic acid-based copolymers, preferably ethylene-methacrylic acid copolymers or ethylene-acrylic acid copolymers; and
• - Vinyl acetate copolymers, preferably ethylene-vinyl acetate copolymers (EVA).

The content of the thermoplastic polymer of the core layer is preferably at least 10% by weight, more preferably at least 15% by weight, even more preferably at least 20% by weight, particularly preferably at least 25% by weight, most preferably at least 30% by weight based on the total weight of the core layer.

The content of the thermoplastic polymer of the core layer is preferably at most 70% by weight, more preferably at most 65% by weight, even more preferably at most 60% by weight, particularly preferably at most 55% by weight, most preferably at most 50% by weight based on the total weight of the core layer.

The polyolefin of the first layer and the polyolefin of the second layer preferably have a VICAT softening temperature T ₁ and T ₂ of at least 100 ° C, more preferably at least 110 ° C, even more preferably at least 120 ° C, particularly preferably at least 130 ° C, on most preferably at least 140 ° C.

• - Propylen-Olefin-Copolymeren, bevorzugt statistische heterophasige Polypropylen (Block)-Copolymere oder statistische Propylen-Ethylen-Copolymere, besonders bevorzugt mit einem Ethylenanteil von 2 Gew.-% bis 4 Gew.-%;
• - thermoplastischen Elastomeren (TPE), bevorzugt Polyolefin basierte Elastomere, besonders bevorzugt Propylen basierte Elastomere mit einem Propylenanteil von mindestens 80 Gew.-%; und
• - 1-Buten Copolymeren, bevorzugt statistische 1-Buten Copolymere, bevorzugter statistische Ethylen-1-Buten-Copolymere oder statistische Propylen-1-Buten-Copolymere.

In a particularly preferred embodiment of the polyolefin film according to the invention, the polyolefin of the first layer and the polyolefin of the second layer and optionally the polyolefin of the core layer are selected independently of one another from the group consisting of polypropylene homopolymers and polypropylene copolymers; and the thermoplastic polymer of the core layer is selected from the group consisting of

• Propylene-olefin copolymers, preferably random heterophase polypropylene (block) copolymers or random propylene-ethylene copolymers, particularly preferably with an ethylene content of 2% by weight to 4% by weight;
• - Thermoplastic elastomers (TPE), preferably polyolefin-based elastomers, particularly preferably propylene-based elastomers with a propylene content of at least 80% by weight; and
• 1-butene copolymers, preferably random 1-butene copolymers, more preferably random ethylene-1-butene copolymers or random propylene-1-butene copolymers.

• - Polyethylenen, bevorzugt Ethylen-Homopolymer (Polyethylen, PE), Polyethylen niedriger Dichte (LDPE), lineares Polyethylen niedriger Dichte (LLDPE), Polyethylen sehr niedriger Dichte (VLDPE), auf Basis von Metallocen-Katalysatoren polymerisiertes Polyethylen (mPE), Polyethylen hoher Dichte (HDPE);
• - Olefin basierten Plastomeren, bevorzugt Ethylen basierte Octen Plastomere; und
• - Vinylacetat Copolymeren, bevorzugt Ethylen-Vinylacetat-Copolymere (EVA).

In a particularly preferred embodiment of the polyolefin film according to the invention, the polyolefin of the first layer and the polyolefin of the second layer and optionally the polyolefin of the core layer are selected independently of one another from the group consisting of polypropylene homopolymers and polypropylene copolymers; and the thermoplastic polymer of the core layer is selected from the group consisting of

• - Polyethylene, preferably ethylene homopolymer (polyethylene, PE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), polyethylene (mPE) polymerized on the basis of metallocene catalysts, high-density polyethylene Density (HDPE);
• - Olefin-based plastomers, preferably ethylene-based octene plastomers; and
• - Vinyl acetate copolymers, preferably ethylene-vinyl acetate copolymers (EVA).

In another preferred embodiment, the core layer consists essentially entirely of the thermoplastic polymer described above, that is to say does not additionally comprise any (possibly further) polyolefin in the mixture. To improve the bond between the core layer and the layers adjoining it (e.g. the first layer and the second layer), it may be preferable to equip the polyolefin film with additional intermediate layers, which are arranged between the core layer and the first layer or the second layer are. These additional intermediate layers then preferably comprise mixtures of the thermoplastic polymer, of which the core layer essentially consists, with the polyolefin on which the first layer or the second layer is based. Suitable weight ratios of thermoplastic polymer to polyolefin in the additional intermediate layers can be determined by simple routine tests and are preferably in the range from 90:10 to 10:90, more preferably from 70:30 to 30:70.

The core layer of the polyolefin film according to the invention contains an antiblocking agent. The core layer can contain a single antiblocking agent or mixtures of different antiblocking agents. It is also possible for the core layer to contain different types of antiblocking agent, e.g. types of different mean particle sizes that are mixed with one another.

Antiblocking agents are known to a person skilled in the art. Antiblocking agents usually reduce the adhesion of the product during extrusion and increase the lubricity. According to the invention, the antiblocking agent in the core layer enables the film tube laid flat after the blown film extrusion to be guided via nip rollers to a turning bar system without prematurely sticking to one another. The antiblocking agent helps air to escape from the film tube.

The antiblocking agent in the core layer is, among other things, a structural difference between the polyolefin films according to the invention and conventional polyolefin films, which are glued to one another when they are laid flat after exiting the film die, but not, as in accordance with the invention, only after cooling and subsequent reheating for the monoaxial Stretching.

The antiblocking agent is preferably selected from inorganic antiblocking agents and polymeric antiblocking agents.

Polymeric antiblocking agents are known to a person skilled in the art and, according to the invention, include in particular crosslinked silicone polymers, polymethyl (meth) acrylates or also other thermoplastic polymer particles with a significantly higher melting point than the main polymer of the inventive film.

Inorganic antiblocking agents are also known to a person skilled in the art. In a preferred embodiment, the inorganic antiblocking agent is selected from the group consisting of titanium dioxide, calcium sulfate, silicon oxides, amorphous silica, amorphous silica, aluminum oxides, silicates, aluminosilicates, calcium carbonates and mixtures thereof. In another preferred embodiment, the inorganic antiblocking agent is selected from the group consisting of silicon oxides and silicates; preferably silicon dioxide, quartz, cristobalite, talc, kaolin, mica, feldspar, and precipitated aluminum silicate; especially talc. In a preferred embodiment, the inorganic antiblocking agent is selected from the group consisting of carbonates; preferably calcium carbonate, chalk, limestone, preferably calcite and / or argonite, and magnesium carbonate, preferably magnesite; especially calcium carbonate.

The antiblocking agent preferably has an average particle size d50 in the range from 1 to 10 μm, preferably from 1 to 5 μm.

The antiblocking agent preferably has an average particle size d95 in the range from 2 to 20 μm, preferably from 3 to 15 μm.

The content of the antiblocking agent is preferably in the range from 1.0 to 20.0% by weight, preferably from 1.0 to 10.0% by weight, very particularly preferably from 1.0 to 5.0% by weight is based in each case on the total weight of the core layer.

In preferred embodiments, the content of the antiblocking agent is in the range of 2.5 ± 2.0% by weight, 3.0 ± 2.0% by weight, 3.5 ± 2.0% by weight, 4.0 ± 2.0% by weight, 4.5 ± 2.0% by weight, 5.0 ± 2.0% by weight, 5.5 ± 2.0% by weight, 6.0 ± 2 , 0% by weight, 6.5 ± 2.0% by weight, 2.0 ± 1.5% by weight, 2.5 ± 1.5% by weight, 3.0 ± 1.5 % By weight, 3.5 ± 1.5% by weight, 4.0 ± 1.5% by weight, 4.5 ± 1.5% by weight, 5.0 ± 1.5% by weight -%, 5.5 ± 1.5% by weight, 6.0 ± 1.5% by weight, 6.5 ± 1.5% by weight, 2.0 ± 1.0% by weight , 2.5 ± 1.0% by weight, 3.0 ± 1.0% by weight, 3.5 ± 1.0% by weight, 4.0 ± 1.0% by weight, 4 , 5 ± 1.0% by weight, 5.0 ± 1.0% by weight, 5.5 ± 1.0% by weight, 6.0 ± 1.0% by weight, 6.5 ± 1.0% by weight, 2.0 ± 0.5% by weight, 2.5 ± 0.5% by weight, 3.0 ± 0.5% by weight, 3.5 ± 0 , 5% by weight, 4.0 ± 0.5% by weight, 4.5 ± 0.5% by weight, 5.0 ± 0.5% by weight, 5.5 ± 0.5 % By weight, 6.0 ± 0.5% by weight, or 6.5 ± 0.5% by weight, in each case based on the total weight of the core layer.

According to the invention, in addition to the core layer, further layers of the polyolefin film according to the invention can also contain antiblocking agents. In a preferred embodiment, the two outer layers of the polyolefin film according to the invention each also contain antiblocking agents, the preferred nature and preferred amount of which are analogous to those described above for the core layer, but are fundamentally independent of the antiblocking agent contained in the core layer.

In a particularly preferred embodiment, the polyolefin film according to the invention has three layers, so that the first layer and the second layer form the two outer layers of the polyolefin film. The core layer, the first layer and the second layer are preferably based on the same polyolefin, preferably on polypropylene. The core layer and the two outer layers (in this case the first layer and the second layer) preferably contain antiblocking agents.

In another particularly preferred embodiment, the polyolefin film according to the invention has five layers, so that in addition to the core layer, the first layer and the second layer, there are two further layers which preferably form the two outer layers of the polyolefin film. The core layer, the first layer, the second layer and the two further layers are preferably based on the same polyolefin, preferably on polypropylene. The core layer and the two outer layers preferably contain antiblocking agents.

In a further particularly preferred embodiment, the polyolefin film according to the invention has seven layers, so that there are four further layers in addition to the core layer, the first layer and the second layer, two of the total of four further layers preferably forming the two outer layers of the polyolefin film. The core layer, the first layer and the second layer are preferably based and the four other layers on the same polyolefin, preferably on polypropylene. The core layer and the two outer layers preferably contain antiblocking agents.

In another particularly preferred embodiment, the polyolefin film according to the invention has nine layers, so that there are six further layers in addition to the core layer, the first layer and the second layer, two of the total of six further layers preferably forming the two outer layers of the polyolefin film. The core layer, the first layer, the second layer and the six further layers are preferably based on the same polyolefin, preferably on polypropylene. The core layer and the two outer layers preferably contain antiblocking agents.

In another particularly preferred embodiment, the polyolefin film according to the invention has eleven layers, so that there are eight further layers in addition to the core layer, the first layer and the second layer, two of the eight further layers preferably forming the two outer layers of the polyolefin film. The core layer, the first layer, the second layer and the eight further layers are preferably based on the same polyolefin, preferably on polypropylene. The core layer and the two outer layers preferably contain antiblocking agents.

In another particularly preferred embodiment, the polyolefin film according to the invention has thirteen layers, so that there are ten further layers in addition to the core layer, the first layer and the second layer, two of the ten further layers preferably forming the two outer layers of the polyolefin film. The core layer, the first layer, the second layer and the ten further layers are preferably based on the same polyolefin, preferably on polypropylene. The core layer and the two outer layers preferably contain antiblocking agents.

In another particularly preferred embodiment, the polyolefin film according to the invention has fifteen layers, so that there are twelve further layers in addition to the core layer, the first layer and the second layer, two of the total of twelve further layers preferably forming the two outer layers of the polyolefin film. The core layer, the first layer, the second layer and the twelve further layers are preferably based on the same polyolefin, preferably on polypropylene. The core layer and the two outer layers preferably contain antiblocking agents.

In another particularly preferred embodiment, the polyolefin film according to the invention has seventeen layers, so that there are fourteen further layers in addition to the core layer, the first layer and the second layer, two of the total of fourteen further layers preferably forming the two outer layers of the polyolefin film. The core layer, the first layer, the second layer and the fourteen further layers are preferably based on the same polyolefin, preferably on polypropylene. The core layer and the two outer layers preferably contain antiblocking agents.

In a preferred embodiment, the polyolefin film according to the invention contains further layers, such as, for example, barrier layers based on the barrier polymers known to those skilled in the art. These barrier layers preferably serve as gas barrier layers, particularly preferably as oxygen barrier layers and / or water vapor barrier layers. The barrier layers can preferably be based on at least one ethylene-vinyl alcohol copolymer, at least one polyvinyl alcohol, at least one metal, preferably aluminum, or at least one metal oxide, preferably SiOx or aluminum oxide, wherein the metal can be in the form of a film or can be vapor-deposited like a metal oxide. The barrier layers can be based on an ethylene-vinyl alcohol copolymer (EVOH), which was obtained by essentially complete hydrolysis of a corresponding, ethylene-containing polyvinyl acetate (EVA). These fully saponified ethylene-containing polyvinyl acetates typically have a degree of saponification ≥ 98% and an ethylene content of 0.01-80 mol%, preferably 1-50 mol%. The barrier layers can also be based on a polyvinyl alcohol which was obtained by essentially complete hydrolysis of a polyvinyl acetate (PVA) and, as fully saponified polyvinyl acetate, typically has a degree of saponification 98%. The barrier layers are particularly preferably based on polyamide or EVOH. Because of the preferably symmetrical structure of the polyolefin film according to the invention, in this case it preferably has an even number of barrier layers, particularly preferably two barrier layers.

In a preferred embodiment, the polyolefin film according to the invention contains further layers, such as, for example, adhesion-promoting layers based on the modified polymers known to the person skilled in the art. The adhesion-promoting layers are preferably based on at least one modified thermoplastic polymer, preferably on at least one modified olefin homo- or copolymer. The same olefin homopolymers or copolymers can be used as olefin homopolymers or copolymers that have already been used above only that these are modified. The adhesion-promoting layers are particularly preferably based, independently of one another, on at least one modified ethylene homo- or copolymer and / or at least one modified propylene homo- or copolymer which is treated with at least one organic acid or at least one preferably cyclic organic acid anhydride, preferably with maleic anhydride ( MAH), is modified. Ethylene-vinyl acetate, ethylene-vinyl alcohol (EVOH) and ethylene (meth) acrylate copolymers, in their modified or unmodified form, are also suitable as adhesion promoters. Maleic anhydride (MAH) modified polyolefins, in particular polypropylene, ethylene vinyl acetate or ethylene acrylate, which are each grafted with MAH, are particularly preferred. Because of the preferably symmetrical structure of the polyolefin film according to the invention, in this case it preferably has an even number of adhesion-promoting layers, particularly preferably two or four adhesion-promoting layers. Preferably, two adhesion-promoting layers each flank a barrier layer on both sides.

All layers of the polyolefin film according to the invention can optionally contain, independently of one another, conventional additives, such as antioxidants, antifog agents, antistatic agents, antimicrobial agents, light stabilizers, UV absorbers, UV filters, dyes, color pigments, stabilizers, preferably heat stabilizers, process stabilizers and UV and / or light stabilizers, processing aids, flame retardants, nucleating agents, crystallization agents, preferably crystal nucleating agents, lubricants, optical brighteners, plasticizers, silanes, spacers, fillers, peel additives, sealing additives, waxes, wetting agents, surface-active compounds, preferably surfactants , Dispersants or mixtures thereof.

The polyolefin films according to the invention are distinguished by particularly advantageous properties.

The polyolefin film according to the invention preferably has a composite adhesion of at least 30 cN / cm, more preferably at least 35 cN / cm, even more preferably at least 40 cN / cm, particularly preferably at least 45 cN / cm, most preferably at least 50 cN / cm, and in particular at least 55 cN /cm. The core layer of the polyolefin film according to the invention preferably consists of two layers which are glued to one another, and the bond strength is determined along the contact surface of these two layers. The composite adhesion is preferably measured mechanically using a tensile testing machine with a peel angle of 90 ° at a speed of 300 mm / min at 23 ° C. and 50% RH, particularly preferably as described in the experimental part (machine test). In another preferred embodiment, the composite adhesion is measured according to DIN EN ISO 11339 .

The polyolefin film according to the invention preferably has a tensile force in the machine direction at 10% elongation [F10%] of at least 100 N, more preferably at least 110 N, even more preferably at least 120 N, particularly preferably at least 130 N, measured in each case based on a film thickness of 80 μm DIN EN ISO 527-3 .

The polyolefin film according to the invention preferably has a dimensional change after hot storage for 1 min in an oil bath of at most 2.0%, more preferably at most 1.5%, particularly preferably at most 1.0%, most preferably at most 0.5%; the dimensional change being measured at a temperature of 100 ° C, preferably 110 ° C, more preferably 120 ° C, even more preferably 130 ° C, particularly preferably 140 ° C.

Another aspect of the invention relates to the use of the above-described polyolefin film according to the invention as a release film, carrier film for adhesive tapes, tear strips, carrier tape, packaging tape, or as a label.

1. (a) Erzeugen einer mehrschichtigen Schlauchfolie durch Blasfolienextrusion, wobei die Schlauchfolie eine nicht-innenliegende Schicht basierend auf Polyolefin und eine innenliegende Schicht umfassend ein thermoplastisches Polymer, ggf. im Gemisch mit einem Polyolefin, umfasst und wobei die innenliegende Schicht ein Antiblockmittel enthält;
2. (b) Flachlegen der Schlauchfolie, wobei die innenliegende Schicht der einen Seite der flachgelegten Schlauchfolie mit der innenliegenden Schicht der gegenüberliegenden Seite der flachgelegten Schlauchfolie in Kontakt kommt, jedoch noch nicht thermisch mit ihr verklebt wird;
3. (c) ggf. Reversieren der flachgelegten Schlauchfolie;
4. (d) ggf. Kühlen der flachgelegten Schlauchfolie;
5. (e) ggf. Erzeugen von Öffnungen am Rand oder in einem Randbereich der flachgelegten Schlauchfolie, ohne die Schlauchfolie vollständig entlang ihres Randes aufzuschlitzen;
6. (f) ggf. Vorheizen und monoaxiale Anreckung der flachgelegten Schlauchfolie;
7. (g) monoaxiale Reckung der flachgelegten Schlauchfolie;
8. (h) ggf. Entspannen der monoaxial gereckten Schlauchfolie unter Spannungs- und Temperatureinfluss;
9. (i) ggf. Kühlen der monoaxial gereckten Schlauchfolie;
10. (j) ggf. Besäumen des Rands oder des Randbereichs der monoaxial gereckten Schlauchfolie, welcher ggf. die in Schritt (e) eingebrachten Öffnungen aufweist; und
11. (k) ggf. Aufwickeln der monoaxial gereckten Polyolefinfolie.

Another aspect of the invention relates to a method for producing the above-described polyolefin film according to the invention, the method according to the invention comprising the following steps:

1. (a) producing a multilayer tubular film by blown film extrusion, the tubular film comprising a non-internal layer based on polyolefin and an internal layer comprising a thermoplastic polymer, optionally mixed with a polyolefin, and the internal layer containing an antiblocking agent;
2. (b) laying the tubular film flat, wherein the inner layer of one side of the tubular film laid flat comes into contact with the inner layer of the opposite side of the tubular film laid flat but is not yet thermally bonded to it;
3. (c) if necessary, reversing the laid-flat tubular film;
4. (d) if necessary, cooling the laid-flat tubular film;
5. (e) if necessary, creating openings at the edge or in an edge region of the tubular film laid flat without completely slitting the tubular film along its edge;
6. (f) if necessary, preheating and monoaxial stretching of the tubular film laid flat;
7. (g) monoaxially stretching the laid-flat tubular film;
8. (h) if necessary, relaxation of the monoaxially stretched tubular film under the influence of tension and temperature;
9. (i) optionally cooling the monoaxially stretched tubular film;
10. (j) if necessary, trimming of the edge or the edge region of the monoaxially stretched tubular film, which optionally has the openings introduced in step (e); and
11. (k) if necessary, winding up the monoaxially stretched polyolefin film.

Steps (c), (d), (e), (f), (h), (i), (j) and (k) of the method according to the invention are merely optional, i.e. do not necessarily have to be implemented. The method according to the invention thus comprises at least steps (a), (b) and (g).

The steps are preferably run through one after the other in alphabetical order, it being possible in individual cases for several steps to be carried out at least partially simultaneously.

The method according to the invention ultimately provides a polyolefin blown film which is glued in the stretching unit and which is constructed in such a way that it is not glued to itself on the inside before the stretching unit. This is preferably ensured, among other things, by cooled nip rollers. Due to the non-blocking formulation, the air can flow outwards over the width of the film web during monoaxial stretching, distribute itself and be present in a stable manner in front of the stretching unit as an air cushion without affecting the film quality during production. If the amount of air becomes too much over time, i.e. if there is a risk of air being drawn through the stretching gap, any air can be released or introduced directly in front of the stretching unit from the flattened bladder using a slit knife, perforation knife, punch knife or needle perforation There is a connection between the layers.

In step (a) of the method according to the invention, a multilayer tubular film is produced by blown film extrusion, the tubular film comprising a non-internal layer based on polyolefin and an internal layer comprising a thermoplastic polymer, optionally mixed with a polyolefin, and the internal layer contains an antiblocking agent. In the polyolefin film according to the invention, which is produced by the method according to the invention, the first layer and the second layer each emerge from the non-inner layer and the core layer emerges from the inner layer, namely in the form of two thermally bonded layers. If the polyolefin film according to the invention comprises additional layers, these are preferably already layers of the tubular film produced in step (a). If the polyolefin film produced has three layers, the non-internal layer is at the same time also the external layer of the tubular film. If the polyolefin film produced has five or more layers, the non-internal layer can at the same time also be the external layer of the tubular film or it can form an intermediate layer.

As already mentioned in connection with to explained, the monoaxial stretching of an absolutely flat film in the machine direction leads to a non-optimal end profile. According to the invention, the blown film system used according to the invention therefore preferably calculates and controls this effect with a deliberately misshapen thickness profile in the cross section of the film bubble. As a result, an improved final profile and a more economical production of the polyolefin film according to the invention are ultimately achieved.

In step (b) of the method according to the invention, the tubular film is laid flat; preferably using a flattening unit with downstream nip rollers. According to the invention, the inner layer of one side of the tubular film laid flat comes into contact with the inner layer of the opposite side of the tubular film laid flat, but is not yet thermally bonded to it. This is an essential difference to the "hose gluing" according to the state of the art, whereby a thermal gluing already takes place in the lay-flat unit, e.g. on the nip rollers.

The flattening in step (b) is preferably carried out using a flattening unit with downstream nip rollers, the nip rollers being cooled; preferably to a temperature of at most 80 ° C; more preferably at most 60 ° C; particularly preferably at most 50.degree. This cooling of the squeegee rollers when laying flat is a difference to the known hose bonding, in which the squeegee rollers are used be heated in the lay-flat unit in order to cause the inside of the laid-flat hose to stick to itself.

In the optional step (c) of the method according to the invention, the flattened tubular film is reversed, preferably using a downstream turning bar system.

In the optional step (d) of the method according to the invention, the tubular film laid flat is cooled.

In the optional step (e) of the method according to the invention, openings are created at the edge or in an edge region of the tubular film laid flat, preferably without completely slitting the tubular film along its edge, whereby air trapped in the tubular film can escape if necessary. In step (e), openings are preferably produced with the aid of punches, slitting knives, perforation knives or by needle perforation. The edge or edge region of the tubular film laid flat preferably makes up no more than 15% of the width of the tubular film laid flat, preferably not more than 10%. Since this edge or edge area may be trimmed in the optional step (j), it is preferred to produce the openings as close as possible to the outer edge of the tubular film laid flat in order to keep the rejects as low as possible by trimming.

According to the invention, the flattened film is preferably stretched as a tube in order to avoid elongation and to achieve the desired final thickness after the monoaxial stretching. However, in a tube that is completely closed all around, any air in the flattened film tube in front of the stretching device could not be discharged. In addition, when laying flat, during the control state or also regulated, air at the edges can flow into the film tube through the not fully applied rollers of the flattening unit and then later concentrate in front of the stretching unit. This can lead to wrinkles or, later in step (g), even to tearing off the layers of the thermal bond in the heated stretching nip. By punching holes or slots in the edge area in step (e) according to the invention, which is then later removed via an edge trimming, the air can flow out or in. However, since the slit is not completely slit, the tubular shape is retained and elongation is avoided (see below).

In the optional step (f) of the method according to the invention, the tubular film laid flat is preheated and stretched; preferably using one or more pairs of rollers, each consisting of a heating roller and a contact roller lying against it; wherein the heating rollers arranged one after the other in the machine direction are heated to different temperatures for preheating, the temperatures increasing in the machine direction from heating roller to heating roller; and wherein the heating rollers arranged one after the other in the machine direction or the respective contact rollers lying thereon are driven for tensioning at different speeds of rotation, the speeds of rotation increasing in the machine direction from roller pair to roller pair.

Step (f) is preferably carried out using one or more pairs of rollers, each comprising a heating roller and a contact roller, the contact roller being applied to the heating roller at a pressure of no more than 2 bar, more preferably no more than 1 bar, in the pair of rollers through which the film first passes. is particularly preferably 0 to 0.5 bar, or wherein the contact roller rests against the heating roller without pressure or is particularly preferably completely pivoted away. The pair of rollers through which the film passes first according to is the slower pair of rollers ( 12a, b ).

The intentionally misshapen thickness profile of the blown film in its cross-section created in step (a) ensures that the middle, intentionally thicker, regulated area pushes open after it has been laid flat and, if necessary, reversed in the first pair of rollers of the stretching unit (contact roller and driven, possibly heated roller). This can cause unwanted wrinkles to be drawn in. According to the invention, this can be counteracted by the application pressure falling at least below 1 bar, in particular in the range from 0 bar (0 open) to 0.5 bar.

In step (f), the monoaxial stretching is preferably carried out by a stretching ratio in the range from 1.00: 1.01 to 1.00: 1.50, preferably from 1.00: 1.05 to 1.00: 1.30.

In step (g) of the method according to the invention, the tubular film laid flat is stretched monoaxially; preferably using a slower-running pair of rollers comprising an operated slower roller and a slower contact roller, with at least one of the slower rollers being heated and operated, and a faster-running pair of rollers consisting of an operated, faster roller and a faster contact roller, with at least one of the faster rollers being heated and operated, with simultaneous thermal bonding of the inner layers to one another to form a core layer. For the purpose of description, the terms “faster” or “slower” refer to the rotational speeds of the rollers relative to one another, ie the rotational speed of the faster rollers is greater than the rotational speed of the slower rollers.

According to the invention, thermal bonding is preferably carried out without the use of further aids, such as laminating adhesives, but merely by heating the material on the surfaces of the inner layers so that these soften or melt on the surface and can be glued to one another. After cooling, the result is a firm bond of two layers glued together, which is characterized by good resistance to delamination.

In step (g), the monoaxial stretching is preferably carried out by a stretching ratio in the range from 1: 3 to 1: 8, preferably from 1: 4 to 1: 7.

In step (g), the monoaxial stretching is preferably carried out using a slower-running roller pair consisting of an operated slower roller and slower feed roller and a faster-running roller pair composed of an operated faster roller and faster feed roller, with at least one of the slower or faster rollers being heated to a temperature, which is not less than 5 ° C. below the VICAT softening temperature T _{3 of} the thermoplastic polymer which comprises the inner layer of the multilayer tubular film produced in step (a). The temperature is preferably not less than 4 ° C., preferably not less than 3 ° C., even more preferably not less than 2 ° C., most preferably not less than 1 ° C. below the VICAT softening temperature T _{3 of} the thermoplastic polymer, in particular corresponding to Temperature preferably the VICAT softening temperature T _{3 of} the thermoplastic polymer. The VICAT softening temperature is preferably determined in each case according to DIN EN ISO 306 , preferably according to the parameter combination A50-50 ° C / 10 N according to DIN EN ISO 306 .

The temperature, which is not less than 5 ° C. below the VICAT softening temperature of the thermoplastic polymer which comprises the inner layer of the multilayer tubular film produced in step (a), can be present in the temperature control rollers, forging rollers or annealing rollers. The temperature is preferably present in at least one of all three types of roll, particularly preferably in the forging rolls and annealing rolls, particularly preferably in the forging rolls.

The temperature is preferably at least 2.5 ° C., preferably at least 5 ° C., even more preferably at least 7.5 ° C., most preferably at least 10 ° C. below the VICAT softening temperature T _{1 of} the polyolefin on which the first layer is based, as well the VICAT softening temperature T _{2 of} the polyolefin on which the second layer is based. If the core layer comprises a polyolefin in addition to the thermoplastic polymer, the temperature is preferably at least 2.5 ° C., preferably at least 5 ° C., even more preferably at least 7.5 ° C., most preferably at least 10 ° C. below the VICAT softening temperature T ₄ this polyolefin which comprises the core layer.

The film laid flat is preferably stretched as a tube. This can be ensured, inter alia, in that the openings, if necessary in step (e) of the method according to the invention, are produced on the edge or in an edge area of the tubular film laid flat without completely slitting the tubular film along its edge. The tubular design is retained, the openings only form perforations at the edge.

Any subsequent stretching that may take place in step (f) and the monoaxial stretching in step (g) are improved in that the film laid flat is still present as a tube. The stretching unit comprises several pairs of rollers, including feed rollers and driven main rollers. Since the feed rollers themselves are not driven, they brake a little, e.g. from above, whereas the driven rollers pull on the opposite side, e.g. from below.

If only two films that are not (no longer) connected to one another were loosely on top of one another, i.e. the hose would enter the stretching unit with a completely slit, one of the two layers of film in front of the stretching unit would slowly but steadily elongate and lead, among other things, to inlet creases. According to the invention, this is avoided if the hose is not completely slit, but rather the upper and lower parts are still connected to one another at the edge and thereby the lower part of the hose laid flat pulls the upper part of the hose laid flat with it.

If, instead, the contact roller were not applied at all in the case of a completely slotted hose, the lower layer would lengthen because it would take the shorter path because of the looping. This effect would be particularly visible in the case of stiff and thick polyolefin films, whereas thin polyolefin films show this effect less or hardly at all.

In the optional step (h) of the method according to the invention, the monoaxially stretched tubular film is relaxed under the influence of tension and temperature; preferably using one or more annealing rollers.

In the optional step (i) of the method according to the invention, the monoaxially stretched tubular film is cooled; preferably using one or more chill rolls.

In the optional step (j) of the method according to the invention, the edge or the edge region of the monoaxially stretched tubular film, which optionally has the openings introduced in step (e), is trimmed.

In the optional step (k) of the process according to the invention, the monoaxially stretched polyolefin film is wound up into rolls; preferably iridescent.

When the rollers rotate, a one-sided elongation of the tubular film laid flat can lead to creases after a roller with a strong wrap. These folds can extend into the stretching mechanism. This can be avoided by reducing the wrap. It is best not to wrap a roller more than 75%. The tubular film laid flat should be laid flat around the rollers, but not too flat either. In a preferred embodiment of the method according to the invention, the tubular film laid flat is between the turning bar system ( 8th ) and the MDO stretching unit ( 10 ), ie after step (d) and before step (g) or, if present, before step (f), it is guided exclusively over rollers on which the wraps are in each case at most 160 °, preferably at most 140 °. The wraps are preferably each at least 45 °, preferably at least 60 °. The distance between two rollers arranged one after the other is preferably at most 5 m, more preferably at most 3 m.

Another aspect of the invention relates to a polyolefin film which can be obtained by the method according to the invention described above.

• Satz 1: Eine monoaxial gereckte Polyolefinfolie umfassend eine erste Schicht basierend auf Polyolefin mit einer VICAT-Erweichungstemperatur T1; eine zweite Schicht basierend auf Polyolefin mit einer VICAT-Erweichungstemperatur T2; und eine Kernschicht umfassend ein thermoplastisches Polymer mit einer VICAT-Erweichungstemperatur T3; wobei die Kernschicht zwischen der ersten Schicht und der zweiten Schicht angeordnet ist und ein Antiblockmittel enthält; und wobei T3 um mindestens 5°C, bevorzugt mindestens 10°C, unterhalb von T1 und T2 liegt.
• Satz 2: Die Polyolefinfolie nach Satz 1, welche einen symmetrischen Aufbau hat.
• Satz 3: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei die Kernschicht in direktem Kontakt mit der ersten Schicht und/oder der zweiten Schicht steht.
• Satz 4: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei die Kernschicht aus zwei Lagen besteht, welche thermisch miteinander verklebt sind.
• Satz 5: Die Polyolefinfolie nach einem der vorstehenden Sätze, welche eine Gesamtschichtdicke im Bereich von 5 bis 100 µm, bevorzugt von 10 bis 80 µm aufweist.
• Satz 6: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei die erste Schicht und/oder die zweite Schicht die Außenschichten der Polyolefinfolie bildet.
• Satz 7: Die Polyolefinfolie nach einem der vorstehenden Sätze, welche neben der ersten Schicht, der zweiten Schicht und der Kernschicht eine oder mehrere zusätzliche Schichten umfasst.
• Satz 8: Die Polyolefinfolie nach Satz 7, wobei die eine oder mehreren zusätzlichen Schichten ggf. unabhängig voneinander jeweils auf Polyolefin basieren.
• Satz 9: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei die Schichtdicke der ersten Schicht und/oder die Schichtdicke der zweiten Schicht jeweils größer ist als die Schichtdicke der Kernschicht.
• Satz 10: Die Polyolefinfolie nach Satz 9, wobei die Schichtdicke der ersten Schicht und/oder die Schichtdicke der zweiten Schicht jeweils mindestens doppelt so groß ist wie die Schichtdicke der Kernschicht.
• Satz 11: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei die Schichtdicke der Kernschicht höchstens 30%, bevorzugt höchstens 20%, bevorzugter höchstens 10% der Gesamtschichtdicke der Polyolefinfolie beträgt.
• Satz 12: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei die Kernschicht neben dem thermoplastischen Polymer ein Polyolefin enthält.
• Satz 13: Die Polyolefinfolie nach Satz 12, wobei das Polyolefin der ersten Schicht, das Polyolefin der zweiten Schicht und ggf. auch das Polyolefin der Kernschicht jeweils unabhängig voneinander Homopolymere oder Copolymere sind, welche durch Polymerisation mindestens eines gemeinsamen Olefinmonomers hergestellt wurden.
• Satz 14: Die Polyolefinfolie nach Satz 13, welche neben der ersten Schicht, der zweiten Schicht und der Kernschicht mindestens zwei, oder mindestens vier, oder mindestens sechs, oder mindestens acht, oder mindestens zehn, oder mindestens zwölf, oder mindestens vierzehn zusätzliche Schichten unabhängig voneinander basierend auf Polyolefinen umfasst, wobei auch diese Polyolefine unabhängig voneinander Homopolymere oder Copolymere sind, welche durch Polymerisation dieses mindestens einen gemeinsamen Olefinmonomers hergestellt wurden.
• Satz 15: Die Polyolefinfolie nach Satz 13 oder 14, wobei das Polyolefin der ersten Schicht, das Polyolefin der zweiten Schicht und ggf. auch das Polyolefin der Kernschicht jeweils unabhängig voneinander Homopolymere oder Copolymere sind, welche durch Polymerisation durchweg gemeinsamer Olefinmonomere hergestellt wurden, wobei im Falle von Copolymeren die gemeinsamen Comonomere bevorzugt jeweils im selben relativen Mengenverhältnis vorliegen.
• Satz 16: Die Polyolefinfolie nach einem der Sätze 13 bis 15, welche neben der ersten Schicht, der zweiten Schicht und der Kernschicht mindestens zwei, oder mindestens vier, oder mindestens sechs, oder mindestens acht, oder mindestens zehn, oder mindestens zwölf, oder mindestens vierzehn zusätzliche Schichten unabhängig voneinander basierend auf Polyolefinen umfasst, wobei auch diese Polyolefine unabhängig voneinander Homopolymere oder Copolymere sind, welche durch Polymerisation dieser durchweg gemeinsamen Olefinmonomere hergestellt wurden.
• Satz 17: Die Polyolefinfolie nach einem der Sätze 13 bis 16, wobei das gemeinsame Olefinmonomer ausgewählt ist bzw. die durchweg gemeinsamen Olefinmonomere jeweils allesamt ausgewählt sind aus der Gruppe bestehend aus Ethylen, Propylen, n-Butylen und Isobutylen.
• Satz 18: Die Polyolefinfolie nach einem der Sätze 12 bis 17, wobei das Polyolefin der ersten Schicht, das Polyolefin der zweiten Schicht und ggf. auch das Polyolefin der Kernschicht jeweils unabhängig voneinander Homopolymere oder Copolymere sind, welche im Wesentlichen dieselbe chemische Zusammensetzung und im Wesentlichen dasselbe gewichtsmittlere Molekulargewicht aufweisen.
• Satz 19: Die Polyolefinfolie nach Satz 18, welche neben der ersten Schicht, der zweiten Schicht und der Kernschicht mindestens zwei, oder mindestens vier, oder mindestens sechs, oder mindestens acht, oder mindestens zehn, oder mindestens zwölf, oder mindestens vierzehn zusätzliche Schichten unabhängig voneinander basierend auf Polyolefinen umfasst, wobei auch diese Polyolefine diese im Wesentlichen selbe chemische Zusammensetzung und dieses im Wesentlichen selbe gewichtsmittlere Molekulargewicht aufweisen.
• Satz 20: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das Polyolefin der ersten Schicht, das Polyolefin der zweiten Schicht und/oder das Polyolefin der Kernschicht unabhängig voneinander ein Propylenhomopolymer und/oder ein Propylencopolymer enthält oder daraus besteht.
• Satz 21: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das Polyolefin der ersten Schicht, das Polyolefin der zweiten Schicht und/oder das Polyolefin der Kernschicht unabhängig voneinander ein Propylencopolymer enthält und wobei dessen Gehalt wenigstens 70 Gew.-% beträgt, bezogen auf das Gesamtgewicht der Schicht.
• Satz 22: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das Polyolefin der ersten Schicht, das Polyolefin der zweiten Schicht und/oder das Polyolefin der Kernschicht ein Propylenhomopolymere und/oder ein Propylencopolymere ist und einen Schmelzflussindex von weniger als 4,0 g/10min ( ISO 1133 bei 230 °C und 2,16 kg), bevorzugt weniger als 3,0 g/10min (ISO 1133 bei 230 °C und 2,16 kg), besonders bevorzugt von weniger als 2,0 g/10min ( ISO 1133 bei 230 °C und 2,16 kg) besitzt.
• Satz 23: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das Polyolefin der ersten Schicht, das Polyolefin der zweiten Schicht und/oder das Polyolefin der Kernschicht ein Ethylenhomopolymere und/oder ein Ethylencopolymere ist und einen Schmelzflussindex von weniger als 4,0 g/10min ( ISO 1133 bei 190 °C und 2,16 kg), bevorzugt weniger als 3,0 g/10min (ISO 1133 bei 190 °C und 2,16 kg), besonders bevorzugt von weniger als 2,0 g/10min ( ISO 1133 bei 190 °C und 2,16 kg) besitzt.
• Satz 24: Die Polyolefinfolie nach einem der Sätze 12 bis 23, wobei der Gehalt des Polyolefins der Kernschicht mindestens 30 Gew.-%, bevorzugter mindestens 50 Gew.-% beträgt, bezogen auf das Gesamtgewicht der Kernschicht.
• Satz 25: Die Polyolefinfolie nach einem der Sätze 12 bis 24, wobei der Gehalt des Polyolefins der Kernschicht höchstens 90 Gew.-%, bevorzugter höchstens 70 Gew.-% beträgt, bezogen auf das Gesamtgewicht der Kernschicht.
• Satz 26: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das thermoplastische Polymer der Kernschicht eine VICAT Erweichungstemperatur T3 von höchstens 140°C, bevorzugter höchstens 120°C, noch bevorzugter höchstens 100°C aufweist.
• Satz 27: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das thermoplastische Polymer der Kernschicht ausgewählt ist aus der Gruppe bestehend aus (i) Polyethylenen, bevorzugt Ethylen-Homopolymer (Polyethylen, PE), Polyethylen niedriger Dichte (LDPE), lineares Polyethylen niedriger Dichte (LLDPE), Polyethylen sehr niedriger Dichte (VLDPE), auf Basis von Metallocen-Katalysatoren polymerisiertes Polyethylen (mPE), Polyethylen hoher Dichte (HDPE); (ii) Propylen-Olefin-Copolymeren, bevorzugt statistische heterophasige Polypropylen (Block)-Copolymere oder statistische Propylen-Ethylen-Copolymere, besonders bevorzugt mit einem Ethylenanteil von 2 Gew.- % bis 4 Gew.-%; (iii) thermoplastischen Elastomeren (TPE), bevorzugt Polyolefin basierte Elastomere, besonders bevorzugt Propylen basierte Elastomere mit einem Propylenanteil von mindestens 80 Gew.-%; (iv) Butylen-Homopolymeren (Polybutylen, PB); (v) Isobutylen-Homopolymeren (Polyisobutylen, PI); (vi) 1-Buten Copolymeren, bevorzugt statistische 1-Buten Copolymere, bevorzugter statistische Ethylen-1-Buten-Copolymere oder statistische Propylen-1-Buten-Copolymere; (vii) Olefin basierten Plastomeren, bevorzugt Ethylen basierte Octen Plastomere; (viii) Acrylsäure basierten Copolymeren, bevorzugt Ethylen-Methacrylsäure-Copolymere oder Ethylen-Acrylsäure-Copolymere; und (ix) Vinylacetat Copolymeren, bevorzugt Ethylen-Vinylacetat-Copolymere (EVA).
• Satz 28: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei der Gehalt des thermoplastischen Polymers der Kernschicht mindestens 10 Gew.-%, bevorzugter mindestens 20 Gew.-% beträgt, bezogen auf das Gesamtgewicht der Kernschicht.
• Satz 29: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei der Gehalt des thermoplastischen Polymers der Kernschicht höchstens 70 Gew.-%, bevorzugter höchstens 50 Gew.-% beträgt, bezogen auf das Gesamtgewicht der Kernschicht.
• Satz 30: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das Polyolefin der ersten Schicht sowie das Polyolefin der zweiten Schicht eine VICAT Erweichungstemperatur T1 bzw. T2 von jeweils mindestens 100°C, bevorzugter mindestens 120°C, noch bevorzugter mindestens 140°C aufweisen.
• Satz 31: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das Polyolefin der ersten Schicht und das Polyolefin der zweiten Schicht und ggf. das Polyolefin der Kernschicht unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus Polypropylenhomopolymeren und Polypropylencopolymeren, und wobei das thermoplastische Polymer der Kernschicht ausgewählt ist aus der Gruppe bestehend aus (i) Propylen-Olefin-Copolymeren, bevorzugt statistische heterophasige Polypropylen (Block)-Copolymere oder statistische Propylen-Ethylen-Copolymere, besonders bevorzugt mit einem Ethylenanteil von 2 Gew.-% bis 4 Gew.-%; (ii) thermoplastischen Elastomeren (TPE), bevorzugt Polyolefin basierte Elastomere, besonders bevorzugt Propylen basierte Elastomere mit einem Propylenanteil von mindestens 80 Gew.-%; und (iii) 1-Buten Copolymeren, bevorzugt statistische 1-Buten Copolymere, bevorzugter statistische Ethylen-1-Buten-Copolymere oder statistische Propylen-1-Buten-Copolymere.
• Satz 32: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das Polyolefin der ersten Schicht und das Polyolefin der zweiten Schicht und ggf. das Polyolefin der Kernschicht unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus Polypropylenhomopolymeren und Polypropylencopolymeren, und wobei das thermoplastische Polymer der Kernschicht ausgewählt ist aus der Gruppe bestehend aus (i) Polyethylenen, bevorzugt Ethylen-Homopolymer (Polyethylen, PE), Polyethylen niedriger Dichte (LDPE), lineares Polyethylen niedriger Dichte (LLDPE), Polyethylen sehr niedriger Dichte (VLDPE), auf Basis von Metallocen-Katalysatoren polymerisiertes Polyethylen (mPE), Polyethylen hoher Dichte (HDPE); (ii) Olefin basierten Plastomeren, bevorzugt Ethylen basierte Octen Plastomere; und (iii) Vinylacetat Copolymeren, bevorzugt Ethylen-Vinylacetat-Copolymere (EVA).
• Satz 33: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das Antiblockmittel ausgewählt ist aus anorganischen Antiblockmitteln und polymeren Antiblockmitteln.
• Satz 34: Die Polyolefinfolie nach Satz 33, wobei das Antiblockmittel ein polymeres Antiblockmittel ist ausgewählt aus der Gruppe bestehend aus quervernetzten Silikonpolymeren und Polymethylmethacrylaten.
• Satz 35: Die Polyolefinfolie nach Satz 33, wobei das Antiblockmittel ein anorganisches Antiblockmittel ist ausgewählt aus der Gruppe bestehend aus Titandioxid, Calciumsulfat, Siliziumoxiden, amorphem Silica, amorpher Kieselsäure, Aluminiumoxiden, Silikaten, Alumosilikaten, Calciumcarbonaten und deren Mischungen.
• Satz 36: Die Polyolefinfolie nach Satz 35, wobei das Antiblockmittel ein anorganisches Antiblockmittel ist ausgewählt aus der Gruppe bestehend aus Siliziumoxiden und Silikaten; bevorzugt Siliziumdioxid, Quarz, Cristobalit, Talkum, Kaolin, Glimmer, Feldspat, und gefälltes Aluminiumsilikat; insbesondere Talkum.
• Satz 37: Die Polyolefinfolie nach Satz 35, wobei das Antiblockmittel ein anorganisches Antiblockmittel ist ausgewählt aus der Gruppe bestehend aus Carbonaten; bevorzugt Calciumcarbonat, Kreide, Kalkstein bevorzugt Calcit und/oder Argonit, und Magnesiumcarbonat bevorzugt Magnesit; insbesondere Calciumcarbonat.
• Satz 38: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das Antiblockmittel eine mittlere Partikelgröße d50 im Bereich von 1 bis 10 µm, bevorzugt von 1 bis 5 µm hat.
• Satz 39: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei das Antiblockmittel eine mittlere Partikelgröße d95 im Bereich von 2 bis 20 µm, bevorzugt von 3 bis 15 µm hat.
• Satz 40: Die Polyolefinfolie nach einem der vorstehenden Sätze, wobei der Gehalt des Antiblockmittels im Bereich von 1,0 bis 20,0 Gew.-%, bevorzugt von 1,0 bis 10,0 Gew.-%, ganz besonders bevorzugt von 1,0 bis 5,0 Gew.-% liegt, jeweils bezogen auf das Gesamtgewicht der Kernschicht.
• Satz 41: Die Polyolefinfolie nach einem der vorstehenden Sätze, welche um ein Reckverhältnis im Bereich von 1:3 bis 1:8, bevorzugt von 1:4 bis 1:7 gereckt wurde.
• Satz 42: Die Polyolefinfolie nach einem der vorstehenden Sätze, welche durch Blasfolienextrusion hergestellt wurde.
• Satz 43: Die Polyolefinfolie nach einem der vorstehenden Sätze, welche eine Verbundhaftung von mindestens 30 cN/cm hat, bevorzugt von mindestens 40 cN/cm.
• Satz 44: Die Polyolefinfolie nach einem der vorstehenden Sätze, welche eine Zugkraft in Maschinenrichtung bei 10 % Dehnung [F10%] von mindestens 100 N, bevorzugt von mindestens 120 N, bezogen auf eine Foliendicke von 80 µm gemessen nach DIN EN ISO 527-3 hat.
• Satz 45: Die Polyolefinfolie nach einem der vorstehenden Sätze, welche eine Maßänderung nach Warmlagerung 1 min im Ölbad bei 120°C Temperatur, bevorzugt bei 130°C, besonders bevorzugt bei 140°C, von höchstens 2,0%, bevorzugt von höchstens 1,0% hat.
• Satz 46: Ein Verfahren zur Herstellung einer Polyolefinfolie nach einem der Sätze 1 bis 45 umfassend die Schritte (a) Erzeugen einer mehrschichtigen Schlauchfolie durch Blasfolienextrusion, wobei die Schlauchfolie eine nicht-innenliegende Schicht basierend auf Polyolefin und eine innenliegende Schicht umfassend ein thermoplastisches Polymer, ggf. im Gemisch mit einem Polyolefin, umfasst und wobei die innenliegende Schicht ein Antiblockmittel enthält; (b) Flachlegen der Schlauchfolie, wobei die innenliegende Schicht der einen Seite der flachgelegten Schlauchfolie mit der innenliegenden Schicht der gegenüberliegenden Seite der flachgelegten Schlauchfolie in Kontakt kommt, jedoch noch nicht thermisch mit ihr verklebt wird; (c) ggf. Reversieren der flachgelegten Schlauchfolie; (d) ggf. Kühlen der flachgelegten Schlauchfolie; (e) ggf. Erzeugen von Öffnungen am Rand oder in einem Randbereich der flachgelegten Schlauchfolie, ohne die Schlauchfolie vollständig entlang ihres Randes aufzuschlitzen, wodurch in der Schlauchfolie eingeschlossene Luft ggf. entweichen kann; (f) ggf. Vorheizen und monoaxiale Anreckung der flachgelegten Schlauchfolie; (g) monoaxiale Reckung der flachgelegten Schlauchfolie unter gleichzeitiger thermischer Verklebung der innenliegenden Schichten miteinander unter Bildung einer Kernschicht; (h) ggf. Entspannen der monoaxial gereckten Schlauchfolie unter Spannungs- und Temperatureinfluss; (i) ggf. Kühlen der monoaxial gereckten Schlauchfolie; (j) ggf. Besäumen des Rands oder des Randbereichs der monoaxial gereckten Schlauchfolie, welcher ggf. die in Schritt (e) eingebrachten Öffnungen aufweist; und (k) ggf. Aufwickeln der monoaxial gereckten Polyolefinfolie; bevorzugt changierend.
• Satz 47. Das Verfahren nach Satz 46, wobei das Flachlegen Schritt (b) unter Einsatz einer Flachlegeeinheit (6) und nachgeschalteten Quetschwalzen (7) erfolgt, wobei die Quetschwalzen (7) gekühlt sind; bevorzugt auf eine Temperatur von höchstens 80°C; bevorzugter höchstens 60°C; besonders bevorzugt höchstens 50°C.
• Satz 48. Das Verfahren nach Satz 46 oder 47, wobei in Schritt (e) das Erzeugen von Öffnungen mit Hilfe von Stanzen, Schlitzmessern, Perforationsmessern oder durch Nadelperforation erfolgt.
• Satz 49. Das Verfahren nach einem der Sätze 46 bis 48, wobei Schritt (f) unter Einsatz einer oder mehrerer Walzenpaare aus jeweils einer Heizwalze (11a) und einer daran anliegenden Anlegewalze (11b) erfolgt, wobei im zuerst von der Folie durchlaufenen Walzenpaar die Anlegewalze (11b) mit einem Druck an der Heizwalze (11a) anliegt, welcher höchstens 2 bar, bevorzugter höchstens 1 bar, besonders bevorzugt 0 bis 0,5 bar beträgt, oder wobei die Anlegewalze (11b) drucklos an der Heizwalze (11a) anliegt.
• Satz 50. Das Verfahren nach einem der Sätze 46 bis 49, wobei Schritt (f) unter Einsatz einer oder mehrerer Walzenpaare aus jeweils einer Heizwalze (11a) und einer daran anliegenden Anlegewalze (11b) erfolgt, wobei im zuerst von der Folie durchlaufenen Walzenpaar die Anlegewalze (11b) vollkommen abgeschwenkt ist.
• Satz 51. Das Verfahren nach einem der Sätze 46 bis 50, wobei in Schritt (f) die monoaxiale Anreckung um ein Anreckverhältnis im Bereich von 1,00:1,01 bis 1,00:1,50, bevorzugt von 1,00:1,05 bis 1,00: 1,30 erfolgt.
• Satz 52. Das Verfahren nach einem der Sätze 46 bis 51, wobei in Schritt (g) die monoaxiale Reckung um ein Reckverhältnis im Bereich von 1:3 bis 1:8, bevorzugt von 1:4 bis 1:7 erfolgt.
• Satz 53. Das Verfahren nach einem der Sätze 46 bis 52, wobei die flachgelegte Schlauchfolie nach Schritt (b) bzw. sofern vorhanden nach Schritt (c), und vor Schritt (g) bzw. sofern vorhanden vor Schritt (f) ausschließlich über Walzen (16) geführt wird, auf welchen die Umschlingungen jeweils höchstens 160° betragen.
• Satz 54. Das Verfahren nach einem der Sätze 46 bis 53, wobei die flachgelegte Schlauchfolie nach Schritt (b) bzw. sofern vorhanden nach Schritt (c), und vor Schritt (g) bzw. sofern vorhanden vor Schritt (f) ausschließlich über Walzen (16) geführt wird, auf welchen die Umschlingungen jeweils mindestens 45° betragen.
• Satz 55. Das Verfahren nach einem der Sätze 46 bis 54, wobei die flachgelegte Schlauchfolie nach Schritt (b) bzw. sofern vorhanden nach Schritt (c), und vor Schritt (g) bzw. sofern vorhanden vor Schritt (f) ausschließlich über Walzen (16) geführt wird, wobei der Abstand von zwei nacheinander angeordneten Walzen (16) jeweils höchstens 5 m, bevorzugt höchstens 3 m beträgt.
• Satz 56. Das Verfahren nach einem der Sätze 46 bis 55, wobei in Schritt (g) die monoaxiale Reckung unter Einsatz eines Walzenpaars aus betriebener (12a) und Anlegewalze (12b) erfolgt, wobei wenigstens eine der Walzen (12a,b) auf eine Temperatur beheizt ist, welche nicht weniger als 5°C unterhalb der VICAT-Erweichungstemperatur T3 des thermoplastischen Polymers liegt, welches die innenliegende Schicht der in Schritt (a) erzeugten mehrschichtigen Schlauchfolie umfasst.
• Satz 57. Das Verfahren nach Satz 56, wobei die Temperatur nicht weniger als 4°C, bevorzugt nicht weniger als 3°C, noch bevorzugter nicht weniger als 2°C, am bevorzugten nicht weniger als 1°C unterhalb der VICAT-Erweichungstemperatur T3 des thermoplastischen Polymers liegt, insbesondere der VICAT-Erweichungstemperatur des thermoplastischen Polymers entspricht.
• Satz 58. Eine Polyolefinfolie erhältlich nach dem Verfahren nach einem der Sätze 46 bis 57.
• Satz 59: Verwendung der Polyolefinfolie nach einem der Sätze 1 bis 45 oder 58 als Trennfolie, Trägerfolie für Klebebänder, Aufreißstreifen, Trageband, Verpackungsband, oder als Label.

Particularly preferred embodiments of the invention are summarized below as sentences 1 to 59:

• Set 1: A monoaxially stretched polyolefin film comprising a first layer based on polyolefin with a VICAT softening temperature T1; a second layer based on polyolefin with a VICAT softening temperature T2; and a core layer comprising a thermoplastic polymer having a VICAT softening temperature T3; wherein the core layer is disposed between the first layer and the second layer and contains an antiblocking agent; and where T3 is at least 5 ° C., preferably at least 10 ° C., below T1 and T2.
• Sentence 2: The polyolefin film according to sentence 1, which has a symmetrical structure.
• Sentence 3: The polyolefin film according to one of the preceding sentences, wherein the core layer is in direct contact with the first layer and / or the second layer.
• Sentence 4: The polyolefin film according to one of the preceding sentences, wherein the core layer consists of two layers which are thermally bonded to one another.
• Sentence 5: The polyolefin film according to one of the preceding sentences, which has a total layer thickness in the range from 5 to 100 μm, preferably from 10 to 80 μm.
• Sentence 6: The polyolefin film according to one of the preceding sentences, wherein the first layer and / or the second layer forms the outer layers of the polyolefin film.
• Sentence 7: The polyolefin film according to one of the preceding sentences, which comprises one or more additional layers in addition to the first layer, the second layer and the core layer.
• Sentence 8: The polyolefin film according to sentence 7, the one or more additional layers, if necessary, each being based on polyolefin independently of one another.
• Sentence 9: The polyolefin film according to one of the preceding sentences, wherein the layer thickness of the first layer and / or the layer thickness of the second layer is in each case greater than the layer thickness of the core layer.
• Clause 10: The polyolefin film according to Clause 9, the layer thickness of the first layer and / or the layer thickness of the second layer being at least twice as great as the layer thickness of the core layer.
• Sentence 11: The polyolefin film according to one of the preceding sentences, the layer thickness of the core layer being at most 30%, preferably at most 20%, more preferably at most 10% of the total layer thickness of the polyolefin film.
• Sentence 12: The polyolefin film according to one of the preceding sentences, wherein the core layer contains a polyolefin in addition to the thermoplastic polymer.
• Sentence 13: The polyolefin film according to sentence 12, wherein the polyolefin of the first layer, the polyolefin of the second layer and optionally also the polyolefin of the core layer are each, independently of one another, homopolymers or copolymers which have been produced by polymerizing at least one common olefin monomer.
• Clause 14: The polyolefin film according to Clause 13, which, in addition to the first layer, the second layer and the core layer, has at least two, or at least four, or at least six, or at least eight, or at least ten, or at least twelve, or at least fourteen additional layers independently based on one another on polyolefins, these polyolefins also being, independently of one another, homopolymers or copolymers which have been prepared by polymerizing this at least one common olefin monomer.
• Sentence 15: The polyolefin film according to sentence 13 or 14, the polyolefin of the first layer, the polyolefin of the second layer and possibly also the polyolefin of the core layer are each independently of one another homopolymers or copolymers, which were produced by polymerization of common olefin monomers, with im In the case of copolymers, the common comonomers are preferably each present in the same relative quantitative ratio.
• Sentence 16: The polyolefin film according to one of sentences 13 to 15, which, in addition to the first layer, the second layer and the core layer, has at least two, or at least four, or at least six, or at least eight, or at least ten, or at least twelve, or at least comprises fourteen additional layers, independently of one another, based on polyolefins, these polyolefins also being, independently of one another, homopolymers or copolymers which have been produced by polymerizing these olefin monomers which are all common.
• Set 17: The polyolefin film according to any one of Sentences 13 to 16, wherein the common olefin monomer is selected or all common olefin monomers are each selected from the group consisting of ethylene, propylene, n-butylene and isobutylene.
• Sentence 18: The polyolefin film according to one of sentences 12 to 17, wherein the polyolefin of the first layer, the polyolefin of the second layer and possibly also the polyolefin of the core layer are each independently of one another homopolymers or copolymers which have essentially the same chemical composition and essentially have the same weight average molecular weight.
• Clause 19: The polyolefin film according to Clause 18, which, in addition to the first layer, the second layer and the core layer, has at least two, or at least four, or at least six, or at least eight, or at least ten, or at least twelve, or at least fourteen additional layers independently based on one another on polyolefins, these polyolefins also having essentially the same chemical composition and essentially the same weight-average molecular weight.
• Sentence 20: The polyolefin film according to one of the preceding sentences, wherein the polyolefin of the first layer, the polyolefin of the second layer and / or the polyolefin of the core layer independently of one another contains or consists of a propylene homopolymer and / or a propylene copolymer.
• Sentence 21: The polyolefin film according to one of the preceding sentences, wherein the polyolefin of the first layer, the polyolefin of the second layer and / or the polyolefin of the core layer independently of one another contains a propylene copolymer and the content of which is at least 70% by weight, based on the Total weight of the layer.
• Sentence 22: The polyolefin film according to one of the preceding sentences, wherein the polyolefin of the first layer, the polyolefin of the second layer and / or the polyolefin of the core layer is a propylene homopolymer and / or a propylene copolymer and a melt flow index of less than 4.0 g / 10 min ( ISO 1133 at 230 ° C and 2.16 kg), preferably less than 3.0 g / 10min (ISO 1133 at 230 ° C and 2.16 kg), particularly preferably less than 2.0 g / 10min ( ISO 1133 at 230 ° C and 2.16 kg).
• Sentence 23: The polyolefin film according to one of the preceding sentences, wherein the polyolefin of the first layer, the polyolefin of the second layer and / or the polyolefin of the core layer is an ethylene homopolymer and / or an ethylene copolymer and a melt flow index of less than 4.0 g / 10 min ( ISO 1133 at 190 ° C and 2.16 kg), preferably less than 3.0 g / 10min (ISO 1133 at 190 ° C and 2.16 kg), particularly preferably less than 2.0 g / 10min ( ISO 1133 at 190 ° C and 2.16 kg).
• Sentence 24: The polyolefin film according to one of sentences 12 to 23, the polyolefin content of the core layer being at least 30% by weight, more preferably at least 50% by weight, based on the total weight of the core layer.
• Sentence 25: The polyolefin film according to one of sentences 12 to 24, the polyolefin content of the core layer being at most 90% by weight, more preferably at most 70% by weight, based on the total weight of the core layer.
• Sentence 26: The polyolefin film according to one of the preceding sentences, wherein the thermoplastic polymer of the core layer has a VICAT softening temperature T3 of at most 140 ° C, more preferably at most 120 ° C, even more preferably at most 100 ° C.
• Sentence 27: The polyolefin film according to one of the preceding sentences, wherein the thermoplastic polymer of the core layer is selected from the group consisting of (i) polyethylenes, preferably ethylene homopolymer (polyethylene, PE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low density polyethylene (VLDPE), polyethylene (mPE) polymerized on the basis of metallocene catalysts, high density polyethylene (HDPE); (ii) propylene-olefin copolymers, preferably random heterophase polypropylene (block) copolymers or random propylene-ethylene copolymers, particularly preferably with an ethylene content of 2% by weight to 4% by weight; (iii) thermoplastic elastomers (TPE), preferably polyolefin-based elastomers, particularly preferably propylene-based elastomers with a propylene content of at least 80% by weight; (iv) butylene homopolymers (polybutylene, PB); (v) isobutylene homopolymers (polyisobutylene, PI); (vi) 1-butene copolymers, preferably random 1-butene copolymers, more preferably random ethylene-1-butene copolymers or random propylene-1-butene copolymers; (vii) olefin-based plastomers, preferably ethylene-based octene plastomers; (viii) acrylic acid-based copolymers, preferably ethylene-methacrylic acid copolymers or ethylene-acrylic acid copolymers; and (ix) vinyl acetate copolymers, preferably ethylene-vinyl acetate copolymers (EVA).
• Sentence 28: The polyolefin film according to one of the preceding sentences, wherein the content of the thermoplastic polymer of the core layer is at least 10% by weight, more preferably at least 20% by weight, based on the total weight of the core layer.
• Sentence 29: The polyolefin film according to one of the preceding sentences, the content of the thermoplastic polymer of the core layer being at most 70% by weight, more preferably at most 50% by weight, based on the total weight of the core layer.
• Sentence 30: The polyolefin film according to one of the preceding sentences, the polyolefin of the first layer and the polyolefin of the second layer each having a VICAT softening temperature T1 and T2 of at least 100 ° C, more preferably at least 120 ° C, even more preferably at least 140 ° C .
• Sentence 31: The polyolefin film according to one of the preceding sentences, wherein the polyolefin of the first layer and the polyolefin of the second layer and optionally the polyolefin of the core layer are independently selected from the group consisting of polypropylene homopolymers and polypropylene copolymers, and the thermoplastic polymer of the core layer is selected from the group consisting of (i) propylene-olefin copolymers, preferably random heterophase polypropylene (block) copolymers or random propylene-ethylene copolymers, particularly preferably with an ethylene content of 2% by weight to 4% by weight ; (ii) thermoplastic elastomers (TPE), preferably polyolefin-based elastomers, particularly preferably propylene-based elastomers with a propylene content of at least 80% by weight; and (iii) 1-butene copolymers, preferably 1-butene random copolymers, more preferably ethylene-1-butene random copolymers or propylene-1-butene random copolymers.
• Sentence 32: The polyolefin film according to one of the preceding sentences, wherein the polyolefin of the first layer and the polyolefin of the second layer and optionally the polyolefin of the core layer are independently selected from the group consisting of polypropylene homopolymers and polypropylene copolymers, and the thermoplastic polymer of the core layer is selected from the group consisting of (i) polyethylene, preferably ethylene homopolymer (polyethylene, PE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), based on metallocene Catalysts polymerized polyethylene (mPE), high polyethylene Density (HDPE); (ii) olefin-based plastomers, preferably ethylene-based octene plastomers; and (iii) vinyl acetate copolymers, preferably ethylene-vinyl acetate copolymers (EVA).
• Sentence 33: The polyolefin film according to one of the preceding sentences, wherein the antiblocking agent is selected from inorganic antiblocking agents and polymeric antiblocking agents.
• Clause 34: The polyolefin film according to Clause 33, wherein the antiblocking agent is a polymeric antiblocking agent selected from the group consisting of cross-linked silicone polymers and polymethyl methacrylates.
• Clause 35: The polyolefin film according to Clause 33, the antiblocking agent being an inorganic antiblocking agent selected from the group consisting of titanium dioxide, calcium sulfate, silicon oxides, amorphous silica, amorphous silica, aluminum oxides, silicates, aluminosilicates, calcium carbonates and mixtures thereof.
• Clause 36: The polyolefin film according to Clause 35, wherein the antiblocking agent is an inorganic antiblocking agent selected from the group consisting of silicon oxides and silicates; preferably silicon dioxide, quartz, cristobalite, talc, kaolin, mica, feldspar, and precipitated aluminum silicate; especially talc.
• Clause 37: The polyolefin film according to Clause 35, wherein the antiblocking agent is an inorganic antiblocking agent selected from the group consisting of carbonates; preferably calcium carbonate, chalk, limestone, preferably calcite and / or argonite, and magnesium carbonate, preferably magnesite; especially calcium carbonate.
• Sentence 38: The polyolefin film according to one of the preceding sentences, the antiblocking agent having an average particle size d50 in the range from 1 to 10 μm, preferably from 1 to 5 μm.
• Sentence 39: The polyolefin film according to one of the preceding sentences, the antiblocking agent having an average particle size d95 in the range from 2 to 20 μm, preferably from 3 to 15 μm.
• Sentence 40: The polyolefin film according to one of the preceding sentences, the content of the antiblocking agent in the range from 1.0 to 20.0% by weight, preferably from 1.0 to 10.0% by weight, very particularly preferably from 1 , 0 to 5.0% by weight, based in each case on the total weight of the core layer.
• Sentence 41: The polyolefin film according to one of the preceding sentences, which has been drawn by a draw ratio in the range from 1: 3 to 1: 8, preferably from 1: 4 to 1: 7.
• Clause 42: The polyolefin film according to any of the preceding sentences, which was produced by blown film extrusion.
• Sentence 43: The polyolefin film according to one of the preceding sentences, which has a bond strength of at least 30 cN / cm, preferably of at least 40 cN / cm.
• Sentence 44: The polyolefin film according to one of the preceding sentences, which has a tensile force in the machine direction at 10% elongation [F10%] of at least 100 N, preferably of at least 120 N, based on a film thickness of 80 μm measured DIN EN ISO 527-3 Has.
• Sentence 45: The polyolefin film according to one of the preceding sentences, which shows a dimensional change after warm storage for 1 min in an oil bath at 120 ° C temperature, preferably at 130 ° C, particularly preferably at 140 ° C, of at most 2.0%, preferably of at most 1 , Has 0%.
• Sentence 46: A method for the production of a polyolefin film according to one of sentences 1 to 45 comprising the steps (a) producing a multilayer tubular film by blown film extrusion, the tubular film having a non-internal layer based on polyolefin and an internal layer comprising a thermoplastic polymer, if necessary in a mixture with a polyolefin, and wherein the inner layer contains an antiblocking agent; (b) laying the tubular film flat, wherein the inner layer of one side of the tubular film laid flat comes into contact with the inner layer of the opposite side of the tubular film laid flat but is not yet thermally bonded to it; (c) if necessary, reversing the laid-flat tubular film; (d) if necessary, cooling the laid-flat tubular film; (e) if necessary, creating openings at the edge or in an edge area of the tubular film laid flat, without completely slitting the tubular film along its edge, as a result of which air trapped in the tubular film can possibly escape; (f) if necessary, preheating and monoaxial stretching of the tubular film laid flat; (g) monoaxial stretching of the tubular film laid flat with simultaneous thermal bonding of the inner layers to one another to form a core layer; (h) if necessary, relaxation of the monoaxially stretched tubular film under the influence of tension and temperature; (i) optionally cooling the monoaxially stretched tubular film; (j) if necessary, trimming of the edge or the edge region of the monoaxially stretched tubular film, which optionally has the openings introduced in step (e); and (k) optionally winding up the monoaxially stretched polyolefin film; preferably iridescent.
• Theorem 47. The method of Clause 46, wherein flattening step (b) using a flattening unit ( 6th ) and downstream nip rollers ( 7th ) takes place, whereby the nip rollers ( 7th ) are cooled; preferably to a temperature of at most 80 ° C; more preferably at most 60 ° C; particularly preferably at most 50.degree.
• Clause 48. The method of Clause 46 or 47, wherein in step (e) openings are created using punches, slitting knives, perforating knives, or needle perforation.
• Sentence 49. The method of any of sentences 46 to 48, wherein step (f) using one or more pairs of rollers each comprising a heating roller ( 11a ) and a contact roller ( 11b ), whereby in the pair of rollers through which the film first passes the feed roller ( 11b ) with one pressure on the heating roller ( 11a ) is applied, which is at most 2 bar, more preferably at most 1 bar, particularly preferably 0 to 0.5 bar, or where the contact roller ( 11b ) pressureless on the heating roller ( 11a ) is present.
• Sentence 50. The method of any one of Sentences 46 to 49, wherein step (f) using one or more pairs of rollers each comprising a heating roller ( 11a ) and a contact roller ( 11b ), whereby in the pair of rollers through which the film first passes the feed roller ( 11b ) is completely swiveled away.
• Sentence 51. The method according to one of sentences 46 to 50, wherein in step (f) the monoaxial stretching by a stretching ratio in the range from 1.00: 1.01 to 1.00: 1.50, preferably 1.00: 1.05 to 1.00: 1.30 takes place.
• Sentence 52. The method according to one of sentences 46 to 51, wherein in step (g) the monoaxial stretching takes place by a stretching ratio in the range from 1: 3 to 1: 8, preferably from 1: 4 to 1: 7.
• Sentence 53. The method according to any one of Sentences 46 to 52, wherein the laid-flat tubular film after step (b) or, if present, after step (c), and before step (g) or, if present, before step (f) exclusively via rollers ( 16 ) is performed, on which the wraps are each at most 160 °.
• Sentence 54. The method according to any one of sentences 46 to 53, wherein the laid-flat tubular film after step (b) or, if present, after step (c), and before step (g) or, if present, before step (f) exclusively via rollers ( 16 ) is performed, on which the wrap is at least 45 °.
• Sentence 55. The method according to one of sentences 46 to 54, wherein the laid-flat tubular film after step (b) or, if present, after step (c), and before step (g) or, if present, before step (f) exclusively via rollers ( 16 ), whereby the distance between two consecutive rollers ( 16 ) each is a maximum of 5 m, preferably a maximum of 3 m.
• Theorem 56. The method according to any of the sentences 46 to 55, wherein in step (g) the monoaxial stretching using a pair of rollers from operated ( 12a ) and feed roller ( 12b ) takes place, with at least one of the rollers ( 12a, b ) is heated to a temperature which is not less than 5 ° C. below the VICAT softening temperature T3 of the thermoplastic polymer which comprises the inner layer of the multilayer tubular film produced in step (a).
• Clause 57. The method of Clause 56, wherein the temperature is no less than 4 ° C, preferably no less than 3 ° C, more preferably no less than 2 ° C, most preferably no less than 1 ° C below the VICAT softening temperature T3 of the thermoplastic polymer, in particular corresponds to the VICAT softening temperature of the thermoplastic polymer.
• Clause 58. A polyolefin film obtainable by the process of any one of Clauses 46-57.
• Sentence 59: Use of the polyolefin film according to one of sentences 1 to 45 or 58 as a release film, carrier film for adhesive tapes, tear strips, carrier tape, packaging tape, or as a label.

List of reference symbols

8th

Turning bar system

1

Extruder

2

Foil die head

3a

blown indoor air

3b

blown outside air

4a

tubular blown film

4b

tubular film laid flat

4c

slotted foil

4d

monoaxially stretched film

4e

relaxed slide

5

Calibration head

6th

Lay-flat unit

7th

Squeegee

9

knife

10

MDO stretching system

11a

Heating roller

11b

contact rollers resting on heating rollers

12a

slower roller

12b

slower feed roller

13a

faster roller

13b

faster lay roller

14th

Annealing roller

15th

Chill roll

16

roller

The invention is illustrated by the following examples:

The settings of the MDO stretching unit used in the production of the films are summarized in the table below, whereby the names of the rollers are based on Respectively. Rolls of the same reference number according to are named in the order in which the film web runs through them from top to bottom: roller temperature speed Train factor Pressure roller 11a 55 ° C 10.7 m / min 120 N From 11a 65 ° C 12.9 m / min -1810 N 1,100 At 11a 130 ° C 13.0 m / min -1420 N 1,100 At 11a 145 ° C 14.5 m / min 1703 N. 1,100 At 12a 145 ° C 15.7 m / min -1233 N 1,100 At 13a 145 ° C 67.9 m / min 2514 N. 4,300 At 14th 150 ° C 62.4 m / min 68 N. 0.920 At 14th 150 ° C 60.9 m / min 94 N. 0.975 At 15th 60 ° C 59.6 m / min -201 N 0.980 At 15th 30 ° C 60.3 m / min 194 N. 1.010 At

PP I

Polypropylen; heterophasiges (Block) Copolymer der Firma Borealis (Ethylen-Anteil 7- 9 %); Schmelzpunkt 165°C; VICAT Temperatur 150°C (A50-50°C/ 10 N nach DIN EN ISO 306);

LD I

LDPE (Low Density Polyethylene) der Firma Dow; VICAT Temperatur 98°C (A50-50°C/ 10 N nach DIN EN ISO 306 );

EVA I

EVA Copolymer (Ethylen Vinyl Acetat Copolymer) der Firma Total; Schmelzpunkt 89°C; VICAT Temperatur 69°C (A50-50°C/ 10 N nach DIN EN ISO 306 );

PP II

Polypropylen; random Copolymer der Firma Basell (Ethylen-Anteil 2 - 5 %); Schmelzpunkt 144°C; VICAT Temperatur 134°C (A50-50°C/ 10 N nach DIN EN ISO 306 ); und

AB I

Talkum Masterbatch der Firma Omya (Talkum-Anteil 60%) mit einer Korngrößenverteilung von D50 [µ] < 10 und D95[µ] <20.

The films had the following layer structure: example V1 V2 V3 B1 B2 B3 Total thickness 80 µm 80 µm 80 µm 70 µm 70 µm 80 µm 1 PP I 97% 97% 97% 97% 97% 97% ABI 3% 3% 3% 3% 3% 3% thickness 22nd 8.5 8.5 8.5 8.5 8.5 2 PP I 100% 100% 100% 100% 100% 100% thickness 11 3.65 3.65 3.65 3.65 3.65 3 PP I 100% 100% 100% 100% 100% 100% thickness 12th 4.8 4.8 4.8 4.8 4.8 4-8 PP I - 100% 100% 100% 100% 100% thickness - 3.65 3.65 3.65 3.65 3.65 9 PP I - 95% 100% 62% - 65% PP II - - - - - 30% EVA I - - - - 48% - LDI - - - 33% 47% - ABI - 5% - 5% 5% 5% thickness - 4.8 4.8 4.8 4.8 4.8 10 PP I - 95% 100% 62% - 65% PP II - - - - - 30% EVA I - - - - 48% - LDI - - - 33% 47% - ABI - 5% - 5% 5% 5% thickness - 4.8 4.8 4.8 4.8 4.8 11-15 PP I - 100% 100% 100% 100% 100% thickness - 3.65 3.65 3.65 3.65 3.65 16 PP I - 100% 100% 100% 100% 100% thickness - 4.8 4.8 4.8 4.8 4.8 17th PPI 100% 100% 100% 100% 100% 100% thickness 11 3.65 3.65 3.65 3.65 3.65 18th PP I 97% 97% 97% 97% 97% 97% ABI 3% 3% 3% 3% 3% 3% thickness 22nd 8.5 8.5 8.5 8.5 8.5

PP I

Polypropylene; heterophasic (block) copolymer from Borealis (ethylene content 7-9%); Melting point 165 ° C; VICAT temperature 150 ° C (A50-50 ° C / 10 N according to DIN EN ISO 306);

LD I

LDPE (Low Density Polyethylene) from Dow; VICAT temperature 98 ° C (A50-50 ° C / 10 N according to DIN EN ISO 306 );

EVA I

EVA copolymer (ethylene vinyl acetate copolymer) from Total; Melting point 89 ° C; VICAT temperature 69 ° C (A50-50 ° C / 10 N according to DIN EN ISO 306 );

PP II

Polypropylene; random copolymer from Basell (ethylene content 2-5%); Melting point 144 ° C; VICAT temperature 134 ° C (A50-50 ° C / 10 N according to DIN EN ISO 306 ); and

AB I

Talc masterbatch from Omya (talc content 60%) with a particle size distribution of D50 [µ] <10 and D95 [µ] <20.

• W1 = 50 µm Cast-MoPP - Folie der Firma Nowofol
• W2 = 70 µm Cast-MoPP - Folie der Firma Nowofol
• W3 = 80 µm Cast-MoPP - Folie der Firma Nowofol

In addition, the following commercially available films were examined:

• W1 = 50 μm Cast-MoPP film from Nowofol
• W2 = 70 μm Cast-MoPP film from Nowofol
• W3 = 80 μm Cast-MoPP film from Nowofol

The film thickness was determined in each case by mechanical scanning in accordance with DIN 53370.

The mechanical data - measured by DIN EN ISO 527-3 - are summarized in the following table: E.g. Production technology Stretched? [Yes No] Film thickness Main polymer class Force in MD at x% elongation F1% F2.5% F5% F10% F25% V1 Blown film No 80 µm PP 18.1 28.4 33.6 36 37.4 W1 Cast film Yes 50 µm PP 19.1 38.4 69.4 127.4 - W2 Cast film Yes 70 µm PP 13.5 25.4 39.5 65.6 124.5 W3 Cast film Yes 80 µm PP 37.4 74.2 128.1 211.3 341.1 B1 Blown film Yes 70 µm PP 20.0 36.9 60.6 103.2 185.8 B2 Blown film Yes 70 µm PP 19.3 35.4 58.1 98.7 177.9 B3 Blown film Yes 80 µm PP 23.3 45.1 77.9 131.1 220.3

The bond strength of the thermal hose bond was determined by two independent methods.

For manual testing, an adhesive tape (adhesive tape A 7475 from Tesa) was stuck to a sample on both sides. The tape stuck out over the edge of the sample. Both ends of the adhesive tape were grabbed and then pulled apart with a jerk at a right angle to the adhesive surface. The test was repeated 10 times by pressing the adhesive tape back on and pulling it apart again abruptly at a right angle to the adhesive surface. In order to pass the test, the layers that were glued together were not allowed to separate from one another. A film was also considered to be "separable" if, due to the test, only separated at the edge for a few mm.

For a machine test (based on the FINAT test method), the two layers of film were carefully pulled apart along the bond area until two initial tabs each approx. 4 cm long were obtained. These tabs were needed later to clamp the test strip in a universal tensile testing machine. The film prepared in this way was cut to 25 mm wide strips with a plan cutter. The strips were then taped off on both sides with red CMC adhesive tape in order to prevent the test strips from stretching when they were pulled apart in the tensile testing machine. The prepared test strips were clamped in the jaws of a tensile testing machine. The composite was at 300 mm / min. pulled apart. The test angle was 90 °; this corresponded to a direct deduction. The test temperature was 23 ° C ± 2 ° C with an RH of 50% ± 5% according to FINAT 10.

The results are summarized in the following table: E.g. Stretching temperatures of the rolls according to 11a / 11a / 12a / 13a / 14/14 VICAT temperature main polymer inner layer DSC peak Delamination manual test Bond adhesion machine test [° C] [° C] [° C; 2nd run] [Yes No] [cN / cm] V2 110/140/143/143/135/130 150 165 Yes 27.3 V3 Production stopped due to air inclusions B1 130/145/145/145/150/150 150 165 No 62.9 B2 130/145/145/145/150/150 150 165 No 45.0 B3 130/145/145/145/150/150 150 165 No 98.0

As the experimental data in the table above show, the films according to the invention according to Examples B1 to B3 produced according to the inventive method show no delamination and a significantly higher bond strength compared to the comparative films according to Examples V2 and V3.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 2010/019943 A1 [0007]
• WO 2012/016075 A1 [0008, 0009]
• EP 3290205 A1 [0010]
• WO 9520633 [0012]
• WO 2005/113370 [0013]
• WO 2007/076918 [0014]
• WO 2009/092641 [0015]
• WO 2016/178965 [0016]
• WO 2016/193186 [0017]
• DE 102016210374 [0018]
• WO 2011/057918 [0021]
• WO 2015/007356 [0022]
• WO 2014/177235 [0032]
• EP 0432423 [0033]
• EP 2277681 [0034]
• WO 2019/036565 [0037, 0042]
• EP 0519251 [0038]
• US 5804020 [0038]
• EP 1147877 [0039]
• WO 2010/075946 [0040]

Non-patent literature cited

• ISO 1133 [0010, 0154]
• Th. Leopold, Gestreckte Limits, Kunststoffe, Carl Hanser Verlag, 10/2014, pages 182-5 [0029]
• DIN EN ISO 11339 [0118]
• DIN EN ISO 527-3 [0119, 0154, 0160]
• DIN EN ISO 306 [0141, 0157]

Claims (22)

A monoaxially stretched polyolefin film comprising - a first layer based on polyolefin with a VICAT softening temperature T ₁ , - a second layer based on polyolefin with a VICAT softening temperature T ₂ , and - a core layer comprising a thermoplastic polymer with a VICAT softening temperature T ₃ wherein the core layer is disposed between the first layer and the second layer and contains an antiblock agent; and where T ₃ is at least 5 ° C., preferably at least 10 ° C., below T ₁ and T ₂ . The polyolefin film after Claim 1 , which has a symmetrical structure. The polyolefin film according to any one of the preceding claims, wherein the core layer is in direct contact with the first layer and / or the second layer. The polyolefin film according to one of the preceding claims, wherein the core layer consists of two layers which are thermally bonded to one another. The polyolefin film according to one of the preceding claims, which has a total layer thickness in the range from 5 to 100 µm, preferably from 10 to 80 µm. The polyolefin film according to one of the preceding claims, wherein the layer thickness of the first layer and / or the layer thickness of the second layer is in each case greater than the layer thickness of the core layer. The polyolefin film according to one of the preceding claims, wherein the layer thickness of the core layer is at most 30%, preferably at most 20%, more preferably at most 10% of the total layer thickness of the polyolefin film. The polyolefin film according to one of the preceding claims, wherein the core layer contains a polyolefin in addition to the thermoplastic polymer. The polyolefin film according to one of the preceding claims, wherein the polyolefin of the first layer, the polyolefin of the second layer and / or the polyolefin of the core layer independently of one another contains or consists of a propylene homopolymer and / or a propylene copolymer. The polyolefin film according to one of the preceding claims, wherein the polyolefin of the first layer, the polyolefin of the second layer and / or the polyolefin of the core layer, independently of one another, contain a propylene copolymer and the content thereof is at least 70% by weight, based on the total weight of the layer . The polyolefin film according to one of the preceding claims, wherein the polyolefin of the first layer, the polyolefin of the second layer and / or the polyolefin of the core layer is a propylene homopolymer and / or a propylene copolymer and a melt flow index of less than 4.0 g / 10 min (ISO 1133 at 230 ° C and 2.16 kg), preferably less than 3.0 g / 10min (ISO 1133 at 230 ° C and 2.16 kg), particularly preferably less than 2.0 g / 10min (ISO 1133 at 230 ° C and 2.16 kg). The polyolefin film according to one of the preceding claims, wherein the polyolefin of the first layer, the polyolefin of the second layer and / or the polyolefin of the core layer is an ethylene homopolymer and / or an ethylene copolymer and a melt flow index of less than 4.0 g / 10 min (ISO 1133 at 190 ° C and 2.16 kg), preferably less than 3.0 g / 10min (ISO 1133 at 190 ° C and 2.16 kg), particularly preferably less than 2.0 g / 10min (ISO 1133 at 190 ° C and 2.16 kg). The polyolefin film according to one of the preceding claims, wherein the thermoplastic polymer of the core layer has a VICAT softening temperature T ₃ of at most 140 ° C, more preferably at most 120 ° C, even more preferably at most 100 ° C. The polyolefin film according to one of the preceding claims, wherein the thermoplastic polymer of the core layer is selected from the group consisting of - Polyethylene, preferably ethylene homopolymer (polyethylene, PE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), polyethylene (mPE) polymerized on the basis of metallocene catalysts, high density polyethylene (HDPE); Propylene-olefin copolymers, preferably random heterophase polypropylene (block) copolymers or random propylene-ethylene copolymers, particularly preferably with an ethylene content of 2% by weight to 4% by weight; - Thermoplastic elastomers (TPE), preferably polyolefin-based elastomers, particularly preferably propylene-based elastomers with a propylene content of at least 80% by weight; - butylene homopolymers (polybutylene, PB); - Isobutylene homopolymers (polyisobutylene, PI); 1-butene copolymers, preferably random 1-butene copolymers, more preferably random ethylene-1-butene copolymers or random propylene-1-butene copolymers; - Olefin-based plastomers, preferably ethylene-based octene plastomers; - Acrylic acid-based copolymers, preferably ethylene-methacrylic acid copolymers or ethylene-acrylic acid copolymers; and - vinyl acetate copolymers, preferably ethylene-vinyl acetate copolymers (EVA). The polyolefin film according to one of the preceding claims, wherein the content of the thermoplastic polymer of the core layer is at least 10% by weight, more preferably at least 20% by weight, based on the total weight of the core layer. The polyolefin film according to one of the preceding claims, wherein the content of the thermoplastic polymer of the core layer is at most 70% by weight, more preferably at most 50% by weight, based on the total weight of the core layer. The polyolefin film according to one of the preceding claims, wherein the polyolefin of the first layer and the polyolefin of the second layer have a VICAT softening temperature T ₁ and T ₂ of at least 100 ° C, more preferably at least 120 ° C, even more preferably at least 140 ° C. The polyolefin film according to one of the preceding claims, wherein the content of the antiblocking agent is in the range from 1.0 to 20.0% by weight, preferably from 1.0 to 10.0% by weight, very particularly preferably from 1.0 to 5.0% by weight, based in each case on the total weight of the core layer. The polyolefin film according to one of the preceding claims, which has been stretched by a stretching ratio in the range from 1: 3 to 1: 8, preferably from 1: 4 to 1: 7. The polyolefin film according to any one of the preceding claims made by blown film extrusion. The polyolefin film according to one of the preceding claims, which has a bond strength of at least 30 cN / cm, preferably of at least 40 cN / cm. The polyolefin film according to one of the preceding claims, which has a tensile force in the machine direction at 10% elongation [F10%] of at least 100 N, preferably of at least 120 N, based on a film thickness of 80 µm measured according to DIN EN ISO 527-3.

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