DE102011000488A1 - Method for producing an extrudate - Google Patents

Abstract

In a method for producing an extrudate (2), in particular flat sheet goods, in particular foils or sheets, with at least one roller (3, 7, 13) around which the flat sheet goods runs, a roller jacket (9) and / or a Roller surface (15, 16) is heated, the roller jacket (9) and / or roller surface (15, 16) should only be heated in a circular arc section (10.1, 10.2, 10.3) running parallel to the roller axis (N, M, O).

Description

TECHNICAL AREA

The invention relates to a method for producing an extrudate, in particular flat sheet goods according to the features of the preamble of claim 1, as well as a corresponding device for carrying out the method according to the features of the preambles of claims 6 and 7.

STATE OF THE ART

In the extrusion of plastic molding compositions and the associated production flat sheet goods, such as films or plates, by rolling in calenders, calenders or similar devices, there is a limitation on the rolling temperatures such that the individual rolling temperatures can not be higher than the bonding temperature of the plastic to be processed , Adhesive temperature means in this case the temperature of the plastic, above which it sticks to the previous roller during the transition of the web from one to the next roller and below which the transition to the following roller is reliably ensured.

Furthermore, the rolls are generally tempered homogeneously in calenders, calenders or similar devices. This means they have the same temperature over the circumference and across the width. For the process of film or board making, this means that the selected roll temperature must be below the above-defined bonding temperature at the time the film leaves the roll, and thus also at the time the sheeting or sheet passes Roller initially touched.

However, attempts at injection molding have shown that especially at wall temperatures above the sticking temperature, in particular in the range of the glass transition temperature up to the melt temperature of the processed plastic, the impression of microstructures is greatly improved. The reason for this is the better flowability of the plastic associated with the higher wall temperature, in particular directly on the tool wall, ie in the microstructures. In the conventional injection molding process, with mold wall temperatures below the bonding temperature, the injected melt freezes as it contacts the cold mold wall, thereby at least degrading, if not completely preventing, the molding of the microstructures.

The problem that arises during injection molding with mold wall temperatures in the range between glass transition temperature and melt temperature that is above the sticking temperature, is that the molding can not be safely removed from the mold at these high wall temperatures. It is therefore necessary to lower the wall temperature of the tool again below the sticking temperature before demoulding the component. This process of mold filling at high temperatures and demolding at low temperatures is referred to as "variothermic" in injection molding.

The idea underlying the present invention is to transfer the variothermic process control of injection molding to the field of film and sheet extrusion. Also in the extrusion, the difficulty in the molding of microstructured rolls, the microstructure is completely transferred to the film or plate. Because even here, the melt freezes on the surface as soon as it touches the cold roller, and thus no longer flows into the microstructures.

The transfer of variothermal process control to the extrusion process means that the roll must have a temperature above the sticking temperature when impinging the film (to improve the molding of the microstructures), while at the time of peeling the film, it should be below the temperature Sticking temperature must have (so that it dissolves safely and without sticking from the roller).

As the closest prior art is the DE 2 039 359 to call. This discloses a roller which is heated by induction via an inductor from the outside and cooled by a cooling medium in the interior. Since the heating over the circumference is performed only in one place, the cooling, however, is active over the entire circumference, it is with the device according to the DE 2039359 possible to achieve an oscillating roller temperature. In this method, the inductor is mounted in the region in front of the retracting gap, that is to say also in front of the location of the impact of the film or plate.

Own experiments of the applicant have shown, however, that with the method or the device according to the DE 2 039 359 the amplitude of the roll surface temperature from the impact of the film or plate in the nip to the detachment from the roll is very low. This has the following reason: The penetration depth of the introduced via the inductor by induction heat into the roller is only a few tenths of a millimeter to a few millimeters deep. However, the outflow of heat into the interior of the roll by means of heat conduction is very large and leads to the fact that even a few angular degrees later a large part of the heat energy introduced by induction has flowed to the interior of the roll and thus to the cooling medium. For the roll surface temperature, this means that it has already dropped back below the melt temperature after the inductor has been rotated a few degrees.

The problem that with the device after DE 2 039 359 The roller surface temperature in the nip can not be raised above the melt temperature can not be corrected by approaching the inductor to the gap, because this is not possible for geometric reasons. On the one hand, the inductor has a certain size in order to perform this stable, on the other hand, the extrusion nozzle for discharging the plastic melt occupies the predominant part in the region of the retracting nip.

The problem that with the device after DE 2 039 359 The roller surface temperature in the nip can not be raised above the melt temperature can not be eliminated by increasing the induction power. If one wanted to increase the induction power such that the surface temperature of the roller in the nip is still at melt temperature, one would have to raise the temperature in the region of the inductor to temperatures at which the roll material is thermally overstressed, which can lead to loss of strength or microstructural changes. Furthermore, an ever greater cooling capacity would have to be installed to dissipate the increased induction power, thereby protecting the roller from overheating and thus ensuring the oscillation of the wall temperature. This would make the whole process increasingly uneconomical.

Furthermore, from the JP 2010/017943 an inductively heated roll for the film extrusion process of plastics known. The aim of this invention, however, is to produce a temperature that differs across the width, which is homogenous over the circumference and does not change over time. For this purpose, the inductor is tangentially wound around the roll in various sections. The aim is that the thickness and the surface properties of the film over the width are carried out more uniformly.

DESCRIPTION OF THE INVENTION

The object of the invention is the o. G. Disadvantages to fix or at least minimize.

In the method according to the invention, the roll shell is to be heated only in a circular arc section running parallel to a roll axis. The roller must therefore have an oscillating wall temperature. In this case, the temperature of the surface oscillates each time the roller between a temperature above the melt temperature (impingement of the film or plate) and a temperature below the sticking temperature (peeling of the film or plate). Thus, the task and solution includes the technological implementation of the oscillating roller temperature. A method and a device are provided with which it is possible to achieve a high frequency and amplitude of the temperature oscillation and to oscillate only the near-surface layers of the roll mantle in an oscillating manner.

In a method for producing flat web goods, in particular films or plates, with at least one roller around which the flat web material runs, the roll surface is heated in circular arc sections. Preferably, a circular arc section includes an angle between 1 ° and 90 °, more preferably an angle between 5 ° and 45 °, and most preferably an angle between 10 ° and 30 °. This results in the advantage that the roll shell and / or the roll surface is heated only in a region in which the elevated temperature is desired. This results in the advantage that the desired ideal oscillating temperature of the roll shell is achieved.

As the heating takes place, should be of minor importance, in the context of the invention are many conceivable possibilities. For example, the roll, seen radially, divided into circular arc segments and these are filled with a heat-carrying medium. Also conceivable is the arrangement of axially parallel running or looped hoses or pipes, which are flowed through by a heat-carrying medium. Here are many possibilities conceivable and should be encompassed by the invention. However, inductive heating is preferred.

In a typical embodiment, the roll shell and / or the roll surface is cooled in other circular arc sections. This results in the advantage that the ideal desired oscillating temperature distribution is achieved independently of the outside temperature or of a material of the roll shell and circular arc sections in which a low temperature is required, in particular the Ablöspunkt, can actually be cooled to this low temperature.

Separately, protection is claimed for a device for carrying out the described method. Conveniently, in a simplest embodiment, the device comprises only one active roller. In the following, the term "active roll" always means a roll which comprises an induction heater which is suitable for at least partially heating a roll jacket of the active roll.

Conveniently, this roll shell of the active roll comprises a ferromagnetic material which is suitable to be heated inductively. This results in the advantage that the roll shell can be heated very quickly. The active roller preferably has a drive. From the idea of the invention is also included that the active roller does not have its own drive, but is driven by other rollers.

The embodiment with only a single active roller is particularly suitable for cast film extrusion.

The device preferably also comprises a passive roller in addition to at least one active roller. In the following, the term "passive roller" always means a roller which does not comprise a heater which is suitable for heating the surface of the passive roller or other rollers at least in regions. Furthermore, the passive roller also does not include any means capable of inducing heat in other components. However, it is certainly encompassed by the idea of the invention that the passive roller can be uniformly tempered over its entire circumference.

In a further embodiment of the invention, the device for carrying out the o. G. Procedure an induction roller. The term "induction roller" in the following means a roller which comprises an induction heater, which at least partially inductively heats a roller surface of another of the induction rollers associated with the induction rollers.

The device expediently comprises, in addition to the induction roller, a passive roller with a roller surface which forms a nip with the induction roller and which can be heated in sections by the induction roller.

In typical embodiments, the induction heating of the induction roller generates an electromagnetic field. Preferably, the electromagnetic field is generated so that it lies in the region of the nip. This results in the advantage that the roller surface of the passive rollers in the nip passes through the electromagnetic field or is in the electromagnetic field and is inductively heated.

Alternatively, the induction roller may also generate an electromagnetic field that is concentric with a center of the roller axis. This results in the advantage that a plurality of passive rollers, combined with the induction roller, and whose arcuate sections, which form a nip with the induction roller, can be heated inductively.

Preferably, the induction heating is arranged along a parallel of a roll axis. This results in the advantage that the roll shell is heated along a circular arc section extending parallel to the roll axis. The roll surface is thus heated over the entire length of the roll in segments but evenly in the segment.

The induction heater preferably has a plurality of conductor loops. Preferably, the conductor loops can be connected in such a way that individual arc sections can be heated with the induction heating. Particularly preferably, each of the conductor loops has its own power connection. This results in the advantage that the induction heating can be heated in a circular arc section. This results in the advantage that only a selective heating of the roll shell in the desired circular arc sections is possible. This results in the advantage that the desired optimum oscillating temperature distribution can be achieved.

Advantageously, the device has an incremental encoder. Preferably, the incremental encoder is suitable for detecting an angular position of the induction heater. This results in the advantage that the induction heating or the individual conductor loops of the induction heating can be activated so that only certain circular arc sections are heated. Particularly preferred are heated only arc sections that form the nip with. This results in the advantage that a temperature distribution according to the optimum desired oscillating roller temperature is achieved.

In typical embodiments, the roll shell and / or the roll surface of the active roll includes ferromagnetic elements suitable to be heated by the induction heating to a temperature.

Conveniently, the roller surface of the passive roller includes ferromagnetic elements suitably heated by the induction roller to a maximum temperature.

Preferably, the device comprises a cooling. Particularly preferably, the cooling is suitable for cooling the roll shell or the roll surface of the active roll and / or the passive roll, in particular outside the nip, to a temperature below the bonding temperature. This results in the advantage that the optimum desired oscillating temperature distribution can be achieved and it is ensured that the temperature of the roll mantle cools down to the detachment point such that detachment of the extrudate is possible.

Preferably, the device comprises a plurality of rollers, preferably three rollers. For example, a first nip is formed by an induction roller and a passive roller. Preferably, the second nip is formed between the passive roller and an active or another passive roller. In typical further embodiments, the first nip is formed between a passive roll and an active roll. The second nip is then formed between the active roll and another passive roll or another active roll. Here are many variations conceivable.

DESCRIPTION OF THE FIGURES

The invention will be briefly described with reference to the accompanying drawings; this shows in

1 a schematic representation of an apparatus for producing flat sheet goods, in particular films, according to the prior art;

2 a development of a roll shell of the device according to 1 and an optimal desired temperature distribution shown above;

3 a schematic representation of an inventive device for producing flat sheet goods with an active roll and a passive roll;

4 a schematic representation of another embodiment of an inventive device for producing sheet-like web products with an induction roller and a passive roller;

5 a schematic representation of another embodiment of an inventive device for producing sheet-like web products with an active roller as a single roller;

6 to 9 schematic representations of possible embodiments of inventive devices with a plurality of rollers in different combinations of passive rollers, active rollers and / or induction rollers;

10 a schematic perspective view of an induction heater with a plurality of conductor loops for an active roll and / or an induction roller.

1 shows a device 1 for producing flat sheet goods from an extrudate 2 According to the state of the art. The device 1 includes a first passive roller 3.1 and a second passive roller 3.2 , By "passive roller" is meant in the following that the roller does not have its own heating device which is suitable for oscillatingly heating a roll shell.

The two passive rollers 3.1 and 3.2 close a nip 4 one. In the nip 4 is by means of a nozzle 5 the extrudate 2 brought in. For rolling or processing the extrudate 2 can the rollers 3.1 and 3.2 be driven and adjusted to each other.

At a transfer point 6 dissolves the flat web 2 from the roller 3.1 from and is then transferred to another, not shown, processing device or other roller combination. A position of the separation point 6 on a circumference of the roller 3.1 depends in particular on the further processing and positioning of the subsequent processing stations.

2 shows a development of a surface of the roller 3.1 with a corresponding optimal desired temperature distribution, for optimum product properties and impressions of the extrudate 2 to achieve. In the X-axis direction, a roll revolution is indicated. The unit of measurement "1" corresponds to a complete roller revolution of 360 °. In the Y direction is the optimum desired temperature of the roll shell of the roll 3.1 applied.

Ideally, the surface of the roller should 3.1 in the nip 4 the highest temperature namely T _max have. The temperature T _max is above the melting temperature T _{s of} the material to be processed. In the detachment point 6 to a temperature T _min below a sticking temperature T _K lie in order to obtain an optimal detaching of the web from the roll goods and optimum impression results. Between the melting temperature T _S and the sticking temperature T _K is the glass transition temperature T _G.

Such an optimal temperature distribution according to the diagram of 2 can by one of the inventive devices 1.1 to 1.7 as in the 3 to 9 represented reached.

The device 1.1 according to 3 includes a passive roller 3 and an active roller 7 , The active roller 7 and the passive roller 3 form the nip 4 out. The passive roller 3 revolves around a central axis N. The active roller 7 rotates about a central axis M and has a roll shell 9 with a roller surface made of ferromagnetic material, the induction heating 8th encloses.

The induction heating 8th is in a perspective schematic representation of 10 shown in more detail. It shows the active roller 7 without the roll shell 9 so that the induction heating 8th easy to recognize. The active roller 7 is viewed radially or in cross section, divided into a plurality of circular arc sections. Preferably, each arc section includes an angle between 1 ° and 90 °, more preferably between 5 ° and 45 ° and even more preferably between 10 ° and 30 °. In 10 are three circular arc sections 10.1 . 10.2 and 10.3 recognizable. In each of the circular arc sections a separate conductor loop is laid. In the circular arc section 10.1 is the conductor loop 11.1 in the circular arc section 10.2 the conductor loop 11.2 and in the circular arc section 10.3 the conductor loop 11.3 arranged. Each of the conductor loops has a separate connection 12 so that an electrical current for generating an electromagnetic field can be applied to each conductor loop independently of other conductor loops, individually or briefly overlapping for a short time. As a result, only the roll shell in the circular arc section, in which the current-loaded conductor loop is located, then heated.

The conductor loops 11.1 to 11.3 are in the axial direction along the active roller 7 arranged. The conductor loops are preferred 11.1 to 11.3 along a parallel to the center axis M of the active roller 7 arranged.

Analogous to the device 1 also includes the device 1.1 the nozzle 5 for introducing the extrudate 2 in the nip 4 , Not shown is a shaft of the roller 7 assigned incremental encoder, so that it is detected in which position the roller is currently. This can be detected by a control, which of the circular arc sections just the nip 4 with training and should be heated.

The operation of the device 1.1 according to 3 is the following:
The extrudate 2 or the flat web goods with the nozzle 5 in the nip 4 the device 1.1 brought in. Always the arc section of the roll mantle 9 the active roller 7 , after indicating the incremental encoder, not shown, the nip 4 with is formed by means of induction heating 8th heated, so that an oscillating roll jacket temperature after 2 results. To the desired cooling of the roll shell 9 up to the separation point 6 To achieve that, the active roller can 7 comprise a cooling, not shown.

4 shows a further embodiment of an inventive device 1.2 , The device 1.2 includes an induction roller 13 with a central axis O and the passive roller 3 , The induction roller 13 and the passive roller 3 form the nip 4 out. The device 1.2 also includes the nozzle 5 by means of the extrudate 2 in the nip 4 is introduced.

The induction roller 13 includes an induction heater 14 , It can be analogous to induction heating 8th the active roller 7 to 10 be constructed, but without a ferromagnetic roll shell.

Alternatively, however, the induction heating 14 the induction roller 13 completely encase. A roller surface 15 the induction roller 13 does not have to consist of an inductively heatable or ferromagnetic material, because it is not necessary to heat them, but this may also be possible. With the induction roller 13 is in the nip 4 an electromagnetic field 17 generated.

In further embodiments, not shown, it is possible that the induction roller 13 generates an electromagnetic field concentric with a circumference of the induction roller 13 is, thereby, a similar effect can be achieved, namely that only a warming of the passive roller 3 in the area of the nip 4 he follows.

The electromagnetic field 17 in the nip 4 or the area of the electromagnetic field in the nip 4 lies, heats a roller surface 16 the passive roller 3 inductive.

Furthermore, the passive roller includes 3 the device 1.2 preferably a cooling, not shown. This allows the roll surface 16 the roller 3 oscillating according to the in 2 heated temperature distribution and cooled.

5 shows a further inventive device 1.3 , It only includes the active roller 7 with induction heating 8th and the roll shell 9 , The device 1.3 from the only active roller 7 is particularly suitable for cast film extrusion. In cast film extrusion, no second roll is needed. The roll jacket 9 the active roller 7 is through the induction heating 8th and preferably in combination with a cooling, not shown, according to the optimum temperature distribution of 2 heated and cooled.

Furthermore, the show 6 to 9 devices 1.4 to 1.7 with different combinations of active rollers, passive rollers and induction rollers.

The device 1.4 according to 6 includes the induction roller 13 , This forms with a passive roller 3.3 a first nip 4 out. The third roller is another passive roller 3.6 with the passive roller 3.3 a second nip 19 out.

The induction roller 13 has the induction heater 14 on. This generates the magnetic field 17 , By means of the nozzle 5 becomes the extrudate 2 in the first nip 4 the device 1.4 brought in. Analogous to the device 1.2 becomes the roller surface of the passive roller 3.3 inductively heated.

The device 1.5 includes an induction roller 13 , This forms with the passive roller 3 the first nip 4 into the extrudate 2 by means of the nozzle 4 is introduced, out. The roll surface of the passive roll 3 is in the electromagnetic field 17 heated. The device 1.5 comprises as third roller an active roller 7 , This forms with the passive roller 3 the second nip 19 out. The active roller 7 heats its own roll jacket. Preferably, the active roll heats 7 their own roll mantle only in the second nip 19 ,

The device 1.6 according to 8th includes a passive roller 3.4 , This forms with the active roller 7 the first nip 4 out. Furthermore, the device comprises 1.6 as third roller another passive roller 3.5 , This forms with the active roller 7 the second nip 19 out. The induction heating is preferred 8th the active roller 7 switched so that only ever arc sections that are in the nip 4 and in the nip 19 be heated.

The device 1.7 according to 9 includes the passive roller 3 , This forms with an active roller 7.1 the first nip 4 out. By means of induction heating 8th the active roller 7.1 becomes the surface of the active roller 7.1 in the nip 4 heated. Furthermore, the device comprises 1.7 as the third roller, a second active roller 7.2 , This forms with the active roller 7.1 the second nip 19 out. Both rollers are then switched so that the two roller shells only when forming the respective nip 4 . 19 are heated. LIST OF REFERENCE NUMBERS 1 contraption 34 67 2 extrudate 35 68 3 passive roller 36 69 4 nip 37 70 5 jet 38 71 6 transfer point 39 72 7 active roller 40 73 8th induction heating 41 74 9 roll shell 42 75 10 Arc segments 43 76 11 conductor loops 44 77 12 connection 45 78 13 induction roller 46 79 14 induction heating 47 15 roll surface 48 16 roll surface 49 17 field 50 18 51 19 second nip 52 20 53 M central axis 21 54 N central axis 22 55 O central axis 23 56 24 57 P arrow 25 58 26 59 27 60 28 61 29 62 30 63 31 64 32 65 33 66

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 2039359 [0008, 0008, 0009, 0010, 0011]
• JP 2010/017943 [0012]

Claims (16)

Method for producing an extrudate ( 2 ), in particular flat sheet goods, in particular films or sheets, with at least one roller ( 3 . 7 . 13 ), around which the flat web material runs, wherein a roll shell ( 9 ) and / or a roll surface ( 15 . 16 ) is heated, characterized in that roll shell ( 9 ) and / or roll surface ( 15 . 16 ) only in a parallel to the roll axis (N, M, O) extending arc section ( 10.1 . 10.2 . 10.3 ) is heated. A method according to claim 1, characterized in that roll shell ( 9 ) and / or roll surface ( 15 . 16 ) in other circular arc sections ( 10.1 . 10.2 . 10.3 ) is cooled. A method according to claim 1 or 2, characterized in that the heating is carried out inductively. A method according to claim 3, characterized in that the heating of the own roll mantle ( 9 ) he follows. Method according to claim 3, characterized in that the heating of the roll surface ( 16 ) of a participating passive roller ( 3 ) he follows. Device for carrying out the method according to at least one of claims 1 to 5, characterized in that the extrudate is at least one active roller ( 7 . 7.1 . 7.2 ) with an induction heater ( 8th ), which the roll shell ( 9 ) of the active roller ( 7 . 7.1 . 7.2 ) at least partially heated, at least partially circumscribes. Device for carrying out the method according to at least one of claims 1 or 6, characterized in that the extrudate ( 2 ) at least one passive roller ( 3 . 3.3 ) revolving around an induction roller ( 13 ) with an induction heater ( 14 ) assigned. Apparatus according to claim 6 or 7, characterized in that a passive roller ( 3 . 3.3 . 3.4 . 3.5 . 3.6 ) with a roll surface ( 16 ) with an induction roller ( 13 ) and / or an active roller ( 7 . 7.1 ) a nip ( 4 . 19 ) trains. Apparatus according to claim 7 or 8, characterized in that the induction roller ( 13 ) the roll surface ( 16 ) of the passive roller ( 3 . 3.3 ) at least partially, preferably in the nip ( 4 ), heated. Device according to one of claims 6 to 9, characterized in that the induction heating ( 8th . 14 ) is arranged along a parallel of a roll axis (M, O). Device according to one of claims 6 to 10, characterized in that the induction heating ( 8th . 14 ) a plurality of conductor loops ( 11.1 . 11.2 . 11.3 ), so that arc sections ( 10.1 . 10.2 . 10.3 ) of the passive roller ( 3 . 3.3 ) and / or the active roller ( 7 . 7.1 . 7.2 ) are individually heated. Device according to claim 11, characterized in that each of the conductor loops ( 11.1 . 11.2 . 11.3 ) own power connection ( 12 ) having. Device according to one of the preceding claims, characterized by an incremental encoder, suitable an angular position of the induction heating ( 8th . 14 ), so that roll shell and / or roll surface is heated only in a circular arc section. Device according to one of the preceding claims, characterized in that the roll shell ( 9 ) of the active roller ( 7 . 7.1 . 7.2 ) and / or the roll surface ( 16 ) of the passive roller ( 3 . 3.3 ) is at least partially ferromagnetic, suitable by the induction heating ( 8th . 14 ) to be heated to a temperature (T _max ). Device according to one of the preceding claims, characterized by cooling, suitable the roll shell of the active roll ( 7 . 7.1 . 7.2 ,) and / or the roller surface of the passive roller ( 3 . 3.3 ), in particular outside the nips, to a temperature below the sticking temperature (T _K ) to cool. Device according to one of the preceding claims, characterized in that the device comprises a third or further roller, which is a passive roller ( 3.5 . 3.6 ), an active roller ( 7 . 7.2 ) or an induction roller ( 13 ).

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