DK164779B - LAMINATED, CRIMMABLE PACKAGING MATERIAL - Google Patents

Description

DK 164779 B

The present invention relates to a laminated packaging material which is shrinkable and heat sealable, which packaging material is of the kind specified in the preamble of claim 1.

5 So far, heat-shrinkable plastic foil has been extensively used for packaging various foods.

Heat-shrinkable, laminated packaging materials are commonly used for heat-shrink wrapped bags. A laminated packaging material consisting of a heat shrinkable base foil and a sealing foil on a surface of the base foil is made into bags by a mold-sealing method! or by an adhesive-sealing method. A laminated packaging material consisting of a heat shrinkable base foil and a sealing foil laminated on both sides of the base foil 15 is made into bags by, for example, packing-sealing methods. The bags made are used for hams, sausages, cheeses or other goods and after pumping, the bags are heat sealed. Thereafter, the bag is subjected to heat shrinkage treatment in hot air or hot water to obtain a sealed package.

It is necessary that the packaging materials have certain characteristic properties, puncture resistance, cold resistance, oxygen barrier, depending on the goods to be wrapped. For food wrapping, a biaxially stretched nylon foil is usually used as the heat shrinkable base foil.

In the case of nylon foil, however, the oxygen barrier is reduced and the foil tends to be misaligned depending on the moisture absorption. Therefore, the nylon foils are usually used in the form of a laminate in which a heat-sealing and non-shrinkable sealing foil or a moisture-impervious sealing foil is laminated to both surfaces of the nylon foil.

Conventional heat-shrinking and heat-sealing laminated packaging materials are described in U.S. Patent No. 35,015,779. However, these packaging materials consist of a multilayer film in which a sealing film having no significant heat shrinking properties is laminated on one or both sides of a heat shrinkable base film or a multilayer 2.

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foil which is produced by laminating a sealing foil to a base foil and stretching the resulting laminate.

Other packaging materials of this type are described in EP-A-0065278, GB-A-2055688, DE-A-1769510 and US-A-4501779. For all of these laminated films, it is considered advantageous to stretch the film after lamination.

However, these multilayer foils do not have sufficient heat shrinkage, since the sealing foil of the multilayer foil does not have a good heat shrinkage. When multilayered 10 sheets are used for shrink wrapping, poor density is achieved and empty spaces appear inside the wrapper, resulting in a poor appearance due to the smaller density. These empty spaces can also result in an increase in the amount of bacteria because dew drops occur in these voids.

When a heat shrinkage treatment experiment is carried out at higher temperatures to avoid the above-mentioned drawbacks, no satisfactory appearance of the finished product is obtained. Furthermore, some of the packaged goods have deteriorated due to the shrinkage at this higher temperature. One of the objects of the invention is to create a heat shrinkable and heat sealing laminated packaging material which has excellent heat shrinkability.

This primary object is met in accordance with the invention in that the heat shrinkable sealing foil is stretched to provide heat shrinkability prior to the lamination on the surfaces of one of the heat shrinkable base foil stretched prior to the lamination.

More specifically, the heat-shrinkable and heat-sealed laminated packaging material of the present invention is a laminate consisting of a base film which is provided with a heat-shrinkability at biaxial stretch in the direction of the lamination, such as biaxially stretched polyamide foil or biaxially stretched plug. foil, and, a sealing foil equipped with a heat shrinkability at stretching in the direction of the lamination, such as biaxially stretched polyethylene foil or biaxially stretched polypropylene foil. The sealing foil is laminated to one or both surfaces of the base foil.

The laminated packaging material of the present invention is superior in heat shrinkage and is 3

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capable of being heat sealed. When the packaging material is used in heat shrink packaging, it will give a satisfactory appearance of the final product.

5 DETAILED DESCRIPTION

When heat shrinkable film is used as the base film of the present invention, any heat shrinkable film which is biaxially stretched in a stretching ratio of at least 1.5, preferably 1.5 to 7.0, can be used in both longitudinal and transverse directions. which has a hot water shrinkage of 15 to 50% at 95 ° C, preferably 20 to 50% in both longitudinal and transverse directions.

Examples of polymer raw materials for the biaxially stretched film are, for example: polyamide resin such as, for example, 6-nylon, 6,6-nylon, 6,10-nylon, 6,6,6-copolymerized nylon, 6,12-nylon, 11 nylon and 12-nylon? polyester resins such as polyethylene, terephthalate and polybutyrene terephthalate, vinyl chloride polymers, acrylonitrile polymers; styrene polymers, olefin polymers such as polypropylene; polyvinyl alcohol; hydrolyzed ethylene vinyl acetate copolymer (EVOH), mixtures of two or more of the foregoing polymers; and polymer blends containing one or more of the foregoing polymers as the major component.

These polymers are formed as foils and the resulting foils 25 are biaxially stretched to obtain biaxially stretched foils having a stretching ratio and a heat shrinkage which are within the above limits. These foils are not limited to the range of the base foil.

A preferred heat shrinkable base foil has a heat shrinkage greater than said heat shrinkable sealing foil. The heat-shrinkable base film may be covered with a vinylidene chloride resin, an imprint layer and the like. The sealing foil used in the present invention is a heat shrinkable sealing foil having a lower melting point than the heat shrinkable base foil. For example, heat-shrinkable films such as linear low-density ethylene polymer (L-LDPE) films, low-density ethylene polymer (LDPE) films, propylene polymer films, ionomer resin films, and blends of mixtures of two or more of the previous films having 4

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a heat shrinkability at biaxial stretching in a stretching ratio of at least 1.5, preferably 1.5 to 7.0, both longitudinally and transversely, and having a hot water shrinkage at 95 ° C of 10-50%, preferably 15-50%, in both longitudinal and transverse directions. Among these shrinking foils, heat shrinkable L-LDPE films are preferred because they have excellent puncture resistance and heat sealing strength. For practical use, it is convenient to select a shrinkable film having the same degree of heat shrinkage as the heat shrinkable base film used.

Usually, the thickness of heat shrinkable base film is from 5 to 50 µm. A base foil having a thickness of 10-35 µm is preferred. Usually, the heat shrinkable sealing film has a thickness of 10-50 µm. A sealing foil having a thickness of 10-40 µm is preferred. IN

The composition of base foil and sealing foil is approximately selected from the considerations of the required properties such as oxygen barrier, puncture resistance and heat seal length, depending on the particular use of the packaging material. The preferred laminated packaging material is one in which the heat shrinkable film is a biaxially stretched film consisting of a polyamide and the heat shrinkable sealing film is a biaxially stretched film consisting of a linear low density ethylene polymer laminated on both surfaces of the heat shrinkable foil.

The heat-shrinkable laminated film of the present invention is obtained by co-lamination of the above heat-shrinkable base film and heat-shrinkable sealing film by a conventional lamination method, for example, pressing lamination or dry lamination. In pressing lamination, a foil-forming thermoplastic resin is melted through a narrow crack of a press T and applied to a base foil, while a sealing foil is simultaneously applied to the extruded thermoplastic resin layer with subsequent solidification upon cooling. Dry lamination 35 consists of applying an adhesive organic solvent, for example, polyurethane adhesive, to a base foil, followed by removal of the solvent by drying and laminating a sealing foil to the thus treated foil by heating under pressure.

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5

The circumstances of the above lamination are suitably selected depending on the combination of the base foil and the sealing foil to be co-laminated.

The laminated film thus produced according to the invention is capable of heat sealing on the side having a sealing layer and having sufficient heat shrinkage without damaging the heat shrinkability of the heat shrinkable base film resulting from the lamination of the base sheet.

Furthermore, the laminated packaging material 10 of the invention can be used in many different ways, because it has not only a good heat shrinkage but also a good heat sealing ability. For example, a laminated foil having a sealing foil on one side can be used as a shrinkable, heat-sealed adhesive tape if cut into strips. Further, this laminated foil and the laminated foil having a sealing foil on both sides can be used as packaging material for packing bags. Otherwise, the laminated foil of the first type of latfes can be made into bags by rib sealing method, the adhesive sealing method, etc. and the last laminated foil of the last type can be made into bags by the packing sealing method, etc. The bag obtained is filled with a product and heat sealed after filling. Subsequently, the bag containing the product is subjected to a heat shrinkage by, for example, immersion in warm water to create a tight covering package.

In particular, a laminated foil in which the base foil is a heat shrinkable nylon foil and the heat shrinkable sealing foil of L-LDPE is laminated on both surfaces of the base foil is a remarkable and excellent heat shrinkable packaging material because it has excellent properties such as the oxygen barrier, hardly affected by the humidity of the air. Furthermore, since the L-LDPE sealing foil exhibits a high heat sealing feature, a thin sealing foil can be used, and it is possible to narrow the width of the overlapping portion at the package, giving a good appearance of the fused die region.

The laminated packaging material of the present invention is suitable for wrapping meat and other foods.

6

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The packaging material of the present invention, which is a laminate made by laminating a base film which is heat shrinkable by stretching and a sealing film which is heat shrinkable by stretching, has the following advantages over, for example, a packaging material produced in the manufacture of a laminate consisting of a base layer and a sealing layer by co-extrusion and stretching of the resulting laminate. According to the present invention, a base film having a printing layer and a sealing film may be laminated to each other so that the printing is located on the inside of the laminate, which makes the printing fine and clearly visible and protects the printing from removal caused by wear and effects of oil, water and the like. . These advantages cannot be obtained with the above packaging materials made by stretching the co-extruded or laminated film. With this packaging material, printing is only possible on the surface of the final product after stretching.

Furthermore, one-layer foil used according to the present invention is suitable for mass production, compared to a multi-layer foil because a simple production device is suitable for producing one-layer foil and the quality can be checked immediately. According to the present invention, a laminated film having desired properties such as shrinkage, oxygen barrier, heat sealing ability and puncture resistance 25 can be quickly obtained by combining approximately stretched one-layer foil which is quickly prepared as aforementioned from a: base foil and a sealing foil. This is also an advantage compared to the aforementioned packaging material which achieves the heat shrinkage capacity by stretching the pre-made multilayer film.

The present invention is more specifically described and explained in the following Examples. It is to be understood that the present invention is not limited to the Examples, and various changes and modifications may be made to the invention without departing from the spirit and scope thereof.

The principle properties to be measured according to the invention are measured by the following methods:

DK 164779B

7 1. Hot water shrinkage

A sample of the size foil! of approx.

20 cm x 20 cm is cut from the packaging material to be tested under conditions of 20 ° C and 65% RH for 24 hours. Then, the length of the film is measured in both length (machine) and transverse direction (each measurement value is denoted by A). The specimen is completely immersed in hot water under the aforementioned conditions and then taken up, wiped off for adherent moisture on the surface with a filter paper and allowed to stand at 20 ° C and 65% for 24 hours. The length of the film in both length and transverse direction is accurately measured (each measurement value is denoted by B).

Hot water shrinkage is calculated as follows: Hot water shrinkage (%) = ((A-B) / A) x 100

Submerged conditions: 15 (i) A laminate with a sealing foil on a surface of a base foil. Specimen is immersed in boiling water (98-100 ° C) for 10 seconds.

(ii) A laminate with sealing foil on both sides of a base foil. The sample is immersed in boiling water (98-100 ° C) for 5 minutes.

(iii) A laminate with an LDPE sealing foil on a surface of a base foil. The sample is immersed in warm water (95 ° C) for 10 seconds.

25 2. Heat seal

Packaging material to be tested is set aside at 20 ° C and 65% RH for 24 hours. Two specimens with a size of 25 mm x 300 mm are cut by the packaging material. A 3Q specimen is placed on a second specimen with the sealing foil surface of the first pointing towards that of the last. The specimen system is subjected to heat sealing by using a tape sealer set to a predetermined temperature (pneumatic cylinder diameter: 50 mm, sealing tape size: 10 mm x 300 mm) under the following conditions: pressure 1 kg / cm2 (pneumatic cylinder pressure range) with the sealing time 1 second . Next, the sample system is allowed to stand at 20 ° C and 65% RH for 24 hours, followed by a cut of a strip from the sample having a width of 8

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15 mm in the direction perpendicular to the sealing direction. The tape is held by the clip of a Tensilon test apparatus and extended at a speed of 300mm / mimit. The strength (Tenacity value) is read on the Tensilon diagram.

5 The strip of the test system sealed by the rib seal method is extended such that the elongation bill forms an angle of 90 ° with the foil direction of the sealed portion.

The tape from the test system sealed by the package sealing method is extended such that the various sample copies of the foils are respectively clamped and pulled in opposite directions.

3. Puncture resistance

The puncture resistance is represented by the needle pressure strength measured as follows:

The packaging material to be tested is placed on a circular frame with an internal diameter of 60 mm. A needle, where the tip is a hemisphere with a radius of 0.5 mm, touches the center of the foil with the needle located perpendicular to the foil surface. Thereafter, the needle is moved downward at a rate of 50 + 5 mm / minute and the maximum resistance is measured as the foil breaks.

The measured resistance value (kg) is referred to as the needle pressure resistance.

25 4. Oxygen barrier

The oxygen barrier is represented by an oxygen gas permeability which is measured with an oxygen gas permeability measuring device (Mocon TR-TRAN Model 100, Moders Controls Inc. in USA) according to ASTM D-1434.

Measurement conditions: Dry: Oxygen permeability is measured under dry conditions with respect to the specimen, which is deposited in a dryer with complete dryness for 24 hours.

Wet: Oxygen permeability is measured under wet conditions with respect to the specimen immersed in water for 24 hours. i t 9

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Example 1

A simultaneous, biaxially stretched, heat-shrinkable nylon 6 film having a thickness of 15 µm (available under the commercial name "BONYL-S", manufactured by Kohjin Co., Ltd.) (hereinafter referred to as "Film A") and a simultaneous, biaxially stretched, 5 heat-shrinkable L-LDPE foil having a specific weight of 0.92 and a thickness of 30 µm, which has been corona treated on one surface and has a wetting stress of 40 dynes / cm with respect to the corona treated surface, (available under the commercial name "KOHJIN BO-LS", manufactured by Kohjin Co., Ltd.), (hereinafter referred to as "Film D") was dry laminated at 70 ° C by using an adhesive to dry laminate, which consisted of 90% by weight polyester resin (available under the commercial name "AD-503" manufactured by Toyo-Morton Co., Ltd.) and 10% by weight of isocyanate component (available under the commercial name "CAT-10" , manufactured by Toyo-Morton Co., Ltd.) so that the corona-treated surface of the L-LDPE film faces nylonfolien. After aging at Λ 35-40 C for 2 days, the physical grades of the laminate obtained were assessed. The results are shown in Table 1.

20

Comparative Example 1

The same heat-shrinkable nylon-6 film (Film A) used in Example 1 and a non-extensible L-LDPE film having a specific weight of 0.92, a thickness of 30 µm which has been corona treated on one surface and having a wetting stress of 40 dynes / cm with respect to the corona treated surface (hereinafter referred to as "Film G") was dry laminated at about 70 ° C using the same adhesive used in Example 1. After aging under the the same conditions as in Example 1, the physical properties of the laminate obtained were assessed. The results are shown in Table 1.

As the results suggest, the laminated film of Example 1 of the invention was comparable in hot water shrinkage with the heat shrinkable nylon 6 layer, considerably higher in heat sealing strength than the L-LDPE one layer film and had a shrink-almost appearance after shrinkage.

DK 164779 B

and wrinkles.

Conversely, in Comparative Example 1, the laminated film was significantly lower in hot water shrinkage than the heat shrinkable nylon 6 film, was also lower in heat shrinkage than the L-LDPE one-layer film, underwent significant wrinkling during the 5 aging or hot water shrinkage, and was additionally unsatisfactory to many. small wrinkles in the sealed area.

Example 2 10

A solution of vinylidene chloride resin (available under the commercial name "Saran F-216", The Dow Chemical Company) (hereinafter referred to as PVDC) in a mixed solvent consisting of tetrahydrofuran and methyl ethyl ketone (50:50 by weight) was added to a surface. of the same heat-shrinkable nylon-6 film (Film A) used in Example 1 at a coverage thickness of 2 pn on the dried basis (the covered film will then be designated "Film B"). To; the vinylidene chloride resin-covered side of this film was laminated to the same heat-shrinkable L-LDPE (Film D) used in Example 1 in the pressing lamination using a low-density polyethylene (LDPE) to obtain the film composition set forth below. The physical properties of the laminated film obtained were assessed. The results are shown in Table 1.

25

Foil composition $ 15 µm thick BO heat shrinkable nylon-6 film / 2 µm thick PVDC layer / 20 µm thick LDPE layer / 30 µm thick BO-L-LDPE film.

"BO" in the above states that the film is a biaxial stretched type (hereinafter referred to as "BO").

Comparative Example 2

For the PVDC covered surface of the PVDC covered 35 heat shrinkable nylon 6 film made according to Example 2, the same non-stretched L-LDPE film (Film G) used in Comparative Example 1 was laminated by co-extrusion. addition using LDPE so that the film composition shown below was obtained. The physical properties of the laminated film thus produced were assessed. The results are shown in Table 1.

11

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5 Film composition: 15 µm thick BO heat shrinkable nylon-6/2 µm thick PVCD layer / 20 µm thick LDPE layer / 30 µm thick L-LDPE film.

The laminated film in Comparative Example 2 revealed a reduction of about 30% in hot water shrinkage compared to the nylon base film. In contrast, the laminated foil of Example 2 of the invention showed no reduction and hot water shrinkage compared to the nylon base foil, underwent only slight curling during the aging period or hot water shrinkage, and additionally exhibited good appearance with only a small number of wrinkles in the area around the heat seal.

Example 3

20 A simultaneous, biaxially stretched, heat shrinkable L-LDPE

foil having a specific weight of 0.92, a thickness of 15 pxa, corona-treated on one surface and having a wetting stress of 40 dynes / cm with respect to the corona-treated surface (hereinafter referred to as "Film E") was dry-laminated on both sides of the same heat-shrinkable nylon-6 film (Film A) used in Example 1, so that the corona-treated surface of the L-LDPE film faced the nylon-6 film. After aging under the same conditions as in Example 1, the physical properties of the laminated film produced were evaluated. The results are shown in Table 1.

The laminated foil was made into a tube system by packing sealing with a 2 mm overlap and one end of the tube was round sealed with a 2 mm sealing tape resulting in a 300 mm long bag and with a round base of 165 mm lying surface width. The bag was filled with an indefinite beef roast and with a length of 25 cm. After the bag was emptied of air, the open end was flattened with a 2 mm width seal. Subsequently, the bag containing contents was subjected to a heat shrinkage treatment 12

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by rinsing with warm water at 95 ° C for 5 minutes and further by a hot bath of 90 ° C for 10 minutes.

In the resulting packaging, the laminated foil covered so tightly that no void was formed between the contents of an indeterminate form and the bag, thus resulting in no air pockets being formed. Furthermore, the bag had an amazingly beautiful look. The tightness was maintained 10 days after packing and no air pockets were observed.

Example 4

The same procedure as in Example 3 was repeated with the difference that a simultaneous biaxially stretched heat shrinkable polypropylene film having a thickness of 15 µm, having a corona treated surface and having a wetting stress of 40 dynes / cm with respect to the corona treated surface (available under the commercial name "KOHJIN KORAP", Kohjin éo., Ltd.) (hereinafter referred to as "Film F") was used as a sealing foil instead of the heat-shrinkable L-LDPE foil to provide a 2Q laminated packaging material. The physical properties of the packaging material were assessed. The results are shown in Table 1.

Comparative Example 3 25 *

The same procedure as in Example 3 was repeated with the exception that a 15 µm thick non-stretched L-LDPE film, corona treated on a surface with a wetting stress of 40 dynes / cm with respect to the corona treated surface (available under the commercial name " KOHJIN L ACE ", 30 KohjinCo., Ltd.) (hereinafter referred to as" Film H ") was used as a sealing foil instead of the heat-permeable l-foil foil to provide a laminated packaging material. The physical properties of the packaging material were assessed. The results are shown in Table 1.

The results indicate that the laminated packaging material of Example 4 had slightly lower heat shrinkage and puncture resistance than the material of Example 3, but greater heat shrinkage capacity than the material of Comparative Example 3, using a non-shrinkable mold.

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seglingsfolie.

Example 5

A copolymerized polyamide consisting of 6-nylon / 6,6-nylon = 85/15 (by weight) (available under the commercial name "Novamid", Mitsubishi Chemical Industries Ltd.) was pressed at 250-260 ° C to obtain a unstretched tubular film with a diameter of 66 mm and a thickness of 145 µm.

The unstretched tubular film was subjected to a 10 o simultaneous biaxial stretch treatment at 75-80 ° C by the pipe stretching method. The stretched tubular film is cut and heat-treated at 150 ° C for 10 seconds by means of a tensioning frame to obtain a heat-shrinkable film with a thickness of 15.5 µm (hereinafter referred to as "Film K"). The heat shrinkage of the foil is shown in Table 2.

For both surfaces of the heat shrinkable film obtained above, the heat shrinkable L-LDPE film (Film E) used in Example 3 and in the same way as in Example 3 is laminated. The physical properties of the obtained laminated film were assessed. The results are shown in Table 1.

Comparative Example 4 The same procedure as in Example 5 was repeated with the difference that an unstretched L-LDPE film (Film H) was used as a sealing film instead of the heat shrinkable L-LDPE film (Film E) to obtain a laminated packaging material. The physical properties of the packaging material were assessed 50. The results are shown in Table 1.

Comparative Example 5

A commercially available, heat shrinkable polyvinylidene chloride packaging film with heat sealing ability on both surfaces was obtained and the physical properties assessed. The results are shown in Table 1.

The results obtained in Examples 3, 4 and 5 Comparative Examples 3, 4 and 5 suggest that the heat shrinkable, laminated packaging material with heat shrinkability on both

DK 164779B

14 surfaces of the invention were superior in heat shrinkability, puncture resistance and as oxygen barrier compared to the conventional heat shrinkable polyvinylidene chloride packaging film with heat shrinkability on both surfaces, although the heat shrinkage of the former was somewhat inferior.

Example 6 A biaxially stretched heat-shrinkable polypropylene film of 20 microns thickness (available under the commercial name "KOHJIN KORAP", Kohjin Co., Ltd.) was corona treated on both surfaces to obtain a film having a wetting stress of 39 µm. dyn / cm on both sides (hereinafter referred to as "Film c") 15 L '*

A large dotted pattern was printed on a surface of the above shrinkable film using a blue ink for polypropylene film. The printing was carried out without any difficulties.

2Q On both surfaces of the film, the heat-shrinkable L-LDPE film (Film E) was laminated using the same dry laminating adhesive used in Example 1 so that the corona-treated surface of the L-LDPE film faced the polypropylene film. The prepared laminated film was left for 2 days at 40 ° C. Thereafter, the physical properties of the laminated film were assessed. The results are shown in Table 1.

Bags were made from the aforementioned laminated foil by means of an automatic bag making machine.

Ie. that the laminated foil was made into a packet sealing tube with a 2 mm overlap and an end of the tube was round-sealed with a 2 mm sealing width to obtain a 300 mm length bag and a 165 mm round bottom. fleet. There were no problems with the preparation of the 25 bags.

As described above, the laminated packaging material of Example 6 not only had excellent heat shrinkability and puncture resistance, but also excellent print susceptibility and processability in bag production. The reason for the synergistic effect must be 15

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projecting heat shrinkage and processability is attributed to the polypropylene foil layer as a core layer, while the excellent heat shrinkage and puncture resistance must be attributed to the sealing foil layer.

5

Example 7

The same procedure as in Example 1 was repeated except that a heat shrinkable polyester film of 12 µm thickness (made by Dia Foil Kabushiki Kaisha) (hereinafter referred to as "Film I") was used as the heat shrinkable film, and a Biaxially stretched LDPE film of 30 µm thickness (hereinafter referred to as "Film J") was used as a sealing film to obtain a laminated packaging material.

The physical properties of the packaging material are shown in Table 1.

15

The packaging material was cut into strips 6 mm wide. When the tapes were used as sealing tape in bag productions with the same packaging material, the fabrication proceeded very smoothly due to the excellent toughness of the polyester film.

The bags made were suitable for use in the outer wrapping of hams, sausages, etc.

The packaging material of Example 7 had particularly excellent properties in terms of its heat shrinkage, its heat sealing strength and its puncture resistance.

Comparative Example 6

A low density polyethylene with a m.p. at 111.5 ° C and a specific weight of 0.920 at 25 ° C (available under the name 30 "UBE HF 019", Ube Industries Ltd.) were melted at 200-250 ° C in a press. In another press, a polyethylene terephthalate having an internal viscosity of 0.7 was melted at 287 ° C. in

The two molten resins were extruded through a double, circular die with slit diameter of 75 mm, so that the polyethylene terephthalate layer became inner layer and the inner layer thickness / outer layer thickness was 1: 2. The extruded tubular two-layer film was indirectly cooled by sliding contact between the inner surface of the film and the outer surface of a cylindrical mandrel having an outer diameter of 66 mm in which 16

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cooling water at a temperature of 30 ° C was circulated which was located immediately below the piston, while a cold air blow-in took place on the outer surface of the high-speed film in the region of the mandrel to cool the film's exterior. This resulted in an unstretched, laminated tubular film of 66 mm diameter and a thickness of 234 µm, with the degree of crystallization of the polyethylene terephthalate layer being 18%.

The non-stretched tubular film was subjected to a concurrent biaxial stretching treatment by the pipe method as follows: The tubular film was preheated in hot air to 70 ° C. Thereafter, the tubular film was stretched in a stretching zone in which the temperature at the starting point of the stretching was 107 ° C, the temperature of the starting area of 1/3 of the entire length of the stretching zone was 105-108 ° C, and the temperature of the rest of the area of the stretching zone decreased. continuously from 104 to 75 ° C.

The stretched tubular film was cooled to room temperature resulting in a biaxial stretched tubular laminated film of 200 mm diameter and a thickness of 41 µm. Then the stretched film was heat treated at 80 ° C for 10 seconds. The physical properties of the laminated film obtained are shown in Table 1.

The results suggest that the laminated foil in it! Comparative Example 6 has a heat shrinkability significantly lower than the laminated film of Example 6 in which the stretched, heat shrinkable film and the stretched sealing film were laminated to each other. Furthermore, the phenomenon was observed that the laminated foil was remarkably curled towards the side with the polyethylene terephthalate layer. The reason for this must be found in the fact that when the polyethylene seal layer was stretched simultaneously with the polyethylene terephthalate layer, after stretching the polyethylene seal layer had virtually no shrinkage, thereby reducing the shrinkage capacity of the polyethylene terephthalate layer.

35 17

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FOOTNOTES

1) The properties of the film are indicated by letter symbols. The meaning of the symbols is shown in Table 2. The symbol "A // D" means that the film A and film D are laminated to each other.

^ This also applies to the other symbols.

2) The term "dry" means dry lamination. The term "extrusion" means the lamination / where an extruded LDPE layer having a thickness of 20 µm is used. The term "fco-extrusion" means that a laminated film is produced by co-extrusion of two or more starting resins followed by a stretch of the resulting film.

3) "A", "B" and "C" mean the following conditions when measuring hot water shrinkage: 15 A: 100 ° C for 5 minutes B: 100 ° C for 10 seconds C: 95 ° C for 10 seconds 20 25 30 ii 35 21

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25!

In addition to the constituents or elements used in the examples, other constituents and elements can be used in the examples as predicted in the specification to achieve essentially the same results.

in

Claims (7)

1. Shrinkable Laminated Packaging Material! and heat sealable, comprising a heat-shrinkable base film and a heat-shrinkable sealing film laminated to at least one of the surfaces of the heat-shrinkable base film, characterized in that the heat-shrinkable sealing film is stretched to provide the heat-shrinkable prior to the lamination. heat shrinkable bare foil surfaces which, for the purpose of shrinkability, are stretched prior to lamination. Packaging material according to claim 1, characterized in that the heat-shrinkable sealing foil is a biaxially stretched olefin polymeric film having a lower melting point than the heat-shrinkable base foil and a heat shrinkage of 10-50% in both the longitudinal and transverse layers. Packaging material according to claim 1, characterized in that the heat shrinkable base foil is either a biaxially stretched polyamide foil having a heat shrinkage 20 of 15-50% in both the longitudinal and transverse direction or a biaxially stretched polypropylene foil having a heat shrinkage of 15-50%. 50% in both longitudinal and transverse directions. Packaging material according to claim 1, characterized in that the heat-shrinkable sealing foil is laminated to a surface of the heat-shrinkable base foil. Packaging material according to claim 1, characterized in that the heat-shrinkable sealing foil is laminated on both surfaces of the heat-shrinkable base foil. Packaging material according to claim 1, characterized in that the heat-shrinkable sealing foil is a biaxially stretched foil containing a linear low-density polyethylene polymer. Packaging material according to claim 1, characterized in that the heat-shrinkable base film is a biaxially stretched film containing a polyamide and the heat-shrinkable sealing film is a biaxially stretched film containing a linear, low-density ethylene polymer both laminated surface of the heat shrinkable base foil.