JPH02145316A - Method and device for manufacturing sheet for thermoforming from thermoplastic substance - Google Patents

Abstract

PURPOSE: To remove a wave existing on a sheet web by holding the web at a substantially lateral extending temperature, guiding it without lateral movement until the wave is eliminated to become completely flat, and then cooling it by a cooling roller. CONSTITUTION: A sheet web 2 is guided at a sheet web winding angle if 150 deg. at a maximum along outer peripheries of discs 8, 8', and laterally extended at a ratio having a lateral shrinkage of 8% at a maximum of the wound sheet. Then, after the web 2 is output from a lateral extending unit, a wave existing on the web is removed at a passage thereafter by first holding it at substantially lateral extending temperature, guiding it without laterally moving until the wave is eliminated to become completely flat, and then cooling it by cooling rollers 12, 13. Then, the wound sheet is guided by a tension to have a longitudinal shrinkage of 10% at a maximum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention provides a sheet web in which the starting material is a thermoplastic material which is substantially unstretched in an elastic temperature range and which is suitable for thermoforming. producing a thermoformable sheet from a thermoplastic material, in which the required shrinkage value is imparted to this sheet web by stretching with a rotatable disk placed at an angle to the running of the sheet; The invention further relates to a device for carrying out the method.

[Conventional technology]

When thermoforming sheets of thermoplastic material to produce aged-shaped articles such as cups, lids, dishes, lidded cases, compartmental inserts, etc., the clamping frame of the thermoforming machine is , the sheet heated to thermoforming temperature is essentially under tension like a drum skin. Therefore, it is called sheet drumming (the ripening of sheets made of thermoplastics is carried out in particular by the deformation method of stretch molding using vacuum means, and the temperature of the sheet, i.e. the thermoforming temperature, is determined by the elasticity of the sheet. temperature range).

Thermoplastics are preferably polyethylene, polypropylene, polyester and polyvinyl chloride (PVC).
), this polyvinyl chloride is particularly preferred.
Therefore, for the sake of simplicity, only PvC will be described below.

PV obtained by conventional extrusion or calendering
The C-sheet necessarily undergoes a rather large longitudinal extension within the temperature range of the thermoelastic state (elastic temperature range), especially when passing through the drawing and temperature control devices of the calendering unit and the extrusion unit. And because of this longitudinal stretching, the sheet width shrinks or decreases (width loss) to a more or less large extent; the said longitudinal stretching of the sheet is -i, less than 10% (i.e. less than 1:1.1). stretch ratio), which is disadvantageous for thermoforming of sheets. This is because when the sheet is heated to the thermoforming temperature it will undergo a corresponding amount of shrinkage (negative change in dimension in one direction), this shrinkage favoring the desired tensile behavior of the sheet. do. In contrast, a forced loss in width of the sheet results in a corresponding increase in sheet width (width increase) upon heating the sheet to the thermoforming temperature. This is very disadvantageous.

This is because, as a result, the heated sheet is no longer completely stretched within the clamping frame of the thermoforming machine, but takes on a somewhat wavy shape.

This formation of waves is, of course, less of a problem when the sheet is greatly deformed in thermoforming, i.e. deformed in such a way that the surface area is greatly increased, since in this case the waves form in the cold mold. If contact is not made quickly, the wave will be immediately pulled and removed. On the contrary,
If the deformation is relatively small, as is the case, for example, in the production of flat lids or compartmental inserts, i.e. when the increase in the area of the sheet subjected to thermal deformation is approximately the same as the deformation due to the waves, the waves are no longer present. The same thing happens if the waves contact the cold mold too early and are not completely removed. The articles produced then have waves and folds, especially at the edges. These waves and folds impair the appearance or function of the item.

For PVC sheet, which is very suitable for aged form,
The longitudinal contraction is at most 10%, preferably 2-7% (as a result of longitudinal stretching in the elastic temperature range with a ratio of at most 1:1.2 or 1:1.02-1°07)
and the lateral shrinkage is at most 8%, preferably from 0.5 to
5% (maximum 1:1.0B or 1:1.005~1.0
(occurs as a result of lateral stretching in the elastic temperature range with a ratio of 5). As is clear from the above explanation,
Such sheets can be produced by conventional calendering or extrusion of PvC, unless said width contraction is generally prevented by complex equipment and/or if the sheet is not subjected to lateral stretching (width stretching). You can't get it.

The lateral stretching of PvC sheets is generally carried out by so-called lateral stretching frames or by rotatable discs arranged at an angle to the running direction of the sheet. Said laterally extending frame consists of two rails extending apart, on which the sheet is held and guided at the edges by positive elements, for example clips. Lateral extension is based on U.S. Patent No. 3
．． No. 004,284, No. 3,807, 004
and British Patent No. 1.368,914. According to U.S. Pat. No. 3,807,004 and British Patent No. 1,368,914, a sheet web made of a thermoplastic material is used to maintain the sheet web within the elastic temperature range of the plastic material. It is heated to a temperature and stretched laterally. The sheet web heated in this way passes through a lateral stretching device for lateral stretching. The lateral extension device comprises at least a pair of rotatable discs arranged at an angle to the direction of sheet travel, the edges of the sheet web being held by a frictional connection to the outer circumferential surface of the discs. . After exiting the transverse stretching device, the transversely stretched sheet web is cooled by cooling rollers and wound up. This lateral stretching method, which is advantageous in itself, and the corresponding lateral stretching device are not suitable for lateral stretching to produce thermoformed sheets for several reasons.

As pointed out in U.S. Pat. No. 3,807,004, a sheet web passing through a lateral stretching device is
It has the shape of a slightly sagging saddle-like surface. Therefore, in this range a relatively large number of long waves are formed, which waves extend from the disk edge to the sheet web. Disadvantages caused by the device recommended in the specification publication, since it is not possible to prevent saddle-like surfaces of the sheet web and thus waves between laterally extending disks such as supporting rollers or supporting metal sheets. Apart from t, the sheet web passes through the transverse stretching device under relatively high longitudinal tension. Although the formation of waves in the sheet web can be largely removed by large longitudinal tensions, in addition to the transverse shrinkage caused by transverse stretching, sheets are formed with longitudinal shrinkage that is too large for ripening.

SUMMARY OF THE INVENTION The present invention eliminates the use of large longitudinal tensions and supporting devices in the transverse stretching region during lateral stretching of thermoplastic sheets using lateral stretching discs. It is surprising that, if said waves are removable and a series of special measures are maintained, relatively small longitudinal and transverse extension values, and thus drumming, desired for thermoforming can be obtained. Based on discovery. Furthermore, with the method according to the invention and the apparatus according to the invention it is easy and simple to produce thermoformed sheets of thermoplastic plastics, either in conjunction with a conventional calender or extrusion or separately from a twenty calender or extrusion. It is economically possible.

A sheet web consisting of a thermoplastic material that is substantially unstretched in the elastic temperature range is heated to a temperature within the elastic temperature range of the plastic material, and the sheet web thus heated is For stretching, it passes through a lateral stretching device consisting of at least one pair of rotatable discs, which discs are arranged at an angle to the running direction of the sheet, and the edges of the sheet web are brought into contact with the outer periphery of the discs by means of a frictional connection. In a method for producing thermoformable sheets from thermoplastics, the sheet web held in a plane and after exiting a transverse stretching device, the laterally stretched sheet web is cooled on cooling rollers and wound up. a) While passing through the lateral stretching device, the sheet web is guided along the outer circumferential surface of the disc with a sheet web winding angle of at most 150a, such that the wound sheet has a lateral contraction of at most 8%. (b) first in order to remove any waves present in the sheet web in subsequent passages after the laterally stretched sheet web exits the lateral stretching device; , is held at approximately the lateral extension temperature, and at this temperature is guided without lateral movement until the waves become completely flat, followed by cooling with cooling rollers, and (c) winding. Maximum lO%
With a longitudinal tension such that the sheet web has an amount of longitudinal contraction of , the sheet web is guided to and through the transverse stretching device and through subsequent passages until it is wound up.

The starting material in the process according to the invention is a thermoplastic sheet, preferably a PVC sheet, of a type that stretches only slightly in the elastic temperature range (as is known, the elastic temperature range of PVC is from 85 to 140 °C , preferably 90-1
30°C).

The method according to the invention is particularly advantageous if the starting material is a sheet of the type obtained by conventional calendering or extrusion of thermoplastics. During molding, the width contraction mentioned at the outset and a slight stretching in the longitudinal direction take place, which likewise results in the width increase and the longitudinal contraction mentioned at the beginning. Therefore, this sheet is a sheet that does not substantially stretch in the elastic temperature range.

According to the invention, when the sheet web passes through the lateral stretching device, the maximum winding angle of the sheet edge around the outer circumferential surface of the disk is 150', preferably 90-150@;
In particular, it is held between 100 and 130@. At wrap angles of 150° and above, the long wave formation mentioned at the beginning begins in the sheet web, and at angles of 90' and below, the frictional connection of the sheet web edge to the disc is unable to withstand lateral extension forces at all. By the means according to the invention of special winding of the edges of the sheet web, the formation of waves in the sheet web is reduced, even without supporting devices and or strong longitudinal tensions, and a small number of short waves are formed close to the disc. It exists only in the edge range of the sheet web. Elimination of this wave is achieved according to the invention by maintaining the transversely stretched sheet web with said waves after exiting the transverse stretching device at a temperature of approximately: This is achieved by maintaining the temperature at which the sheet web is stretched laterally and at which it is subsequently guided along a short or long section of the path (until the onset of appropriate cooling).

During the guidance of the sheet web, it is guided in such a way that no directional forces act on the sheet web in the transverse direction (in the longitudinal direction, the sheet web is pulled under a relatively small longitudinal tension). The free movement of the sheet web in the transverse direction causes the waves to disappear, resulting in a completely flat sheet web without waves. The sheet web continues until it is wave-free on said passage section (this part of the passage is, as it were, a homogenization zone for the corrugated sheet web, in which the three-dimensional expansion that occurred during the transverse stretching is doubled). (reverted back to dimensional expansion), it was found that a somewhat larger portion of the width increase caused by lateral extension is again lost. This contraction of the sheet web in the transverse direction, which occurs due to the above-mentioned (inward) free movement, acts in such a way that the sheet web loses its waves and flattens out as desired. The rolled-up sheet has a width that increases even when the entire increase in width is offset by shrinkage in the homogenization region.
It was found that it still had lateral shrinkage. in general,
The lateral extension increases approximately by the amount lost due to stretching of the sheet web in the homogenization region.

A transversely movable guide of the sheet web held at approximately the transverse extension temperature in order to eliminate waves and flatten it.
This is preferably achieved by guiding the sheet web over a substantially unsupported area or over at least three freely rotating rollers. The rollers are arranged side by side and have a diameter significantly smaller than the diameter of the expansion disc. Areas or sections that are substantially unsupported are
As already mentioned, the length is such that the waves in the sheet web are removed until the start of cooling, i.e. until the sheet web runs over the cooling rollers (this section is generally about 100-300 m mm) 0. For example, in order to prevent the sheet web from wobbling in this section, the sheet web passes through rollers that serve as support aids. - This roller, which is adjustable horizontally and vertically within the shell, is preferably arranged approximately in the center of the homogenization area. In a second preferred variant, the homogenization area comprises at least 3, preferably 5 to 9 rollers. The diameter of the 20 rollers is considerably smaller than the diameter of the extensor disk, they are preferably arranged side by side with a spacing of 50 mm and are free to rotate.

In other words, it is not driven. When the sheet web with the above-mentioned waves coming from the stretching disc is guided over this roller, the sheet web is placed on the roller (roller winding) and runs freely in the space between the rollers (short free path). ) and continuously alternately. As a result, the waves are removed and the desired flattening occurs. As already mentioned,
The sheet web in the homogenization zone is maintained at approximately the temperature at which lateral stretching occurs. This temperature can be maintained, for example, by radiation, by the use of fuel gas or by suitable heating of the rollers over which the sheet web passes.

After the transversely stretched sheet web has passed through the homogenization zone, which is free of waves and has a flat shape, the sheet web is cooled to approximately room temperature by passing through one or more cooling rollers and is then wound up. It will be done. The original sheet web, which is not substantially stretched, is rolled up (finished)
The sheet has a longitudinal shrinkage of about 10% or less, preferably 2 to 7
% longitudinal tension, is guided to a transverse stretching device and guided along a subsequent path through the transverse stretching device until it is wound up.

The heating of the sheet web to the transverse stretching temperature in the elastic temperature range and the transverse stretching of the sheet web are carried out in known manner. For example, the PvC sheet web is heated at 85-140°C, preferably at 90-13°C.
Heating to 0° C. is carried out by irradiation, by the use of fuel gas and/or by guiding the sheet web along a pair of heated intake rollers. A lateral extension for a lateral contraction of less than about 8%, especially 0.5-5%, is achieved by positioning the disc at an appropriate angle. The relatively small lateral extension desired in the method according to the invention is achieved - in boat fishing, by one or two pairs of lateral extension discs. This disk is rotatably mounted and preferably not driven.

That is, the disks are preferably moved together only by the attachment of the sheet web edges. Furthermore, the disc is preferably heated to a temperature at which the sheet web is stretched laterally. Heating of the disc can be effected, for example, by heating gas or liquid or by electrically operated devices. In order to achieve a particularly firm frictional connection between the sheet web edge and the disc, pressing down on the sheet web disc when the sheet web edge runs over the disc, as mentioned in the prior art, is a method according to the invention. is not necessary in the case of , because the stretch ratio is relatively small.
This is because the generated tensile force is small. Said heating of the sheet web and disc is generally sufficient to adhere the sheet web edge to the disc.

The device according to the invention for carrying out the method according to the invention essentially comprises at least one intake roller which, when necessary, serves to adjust the temperature of the sheet web to the stretching temperature; a pair of rotatable extension discs, the extension discs being arranged at an angle to the direction of travel of the sheet, the edges of the sheet web riding on the outer circumferential surface of the discs and wrapped around the discs in a frictional connection. a first pair of discs in the direction of travel of the sheet web; A roller for feeding the sheet web to the disc (the diameter of which is much smaller than the diameter of the stretching disc) and a roller for removing the stretched sheet web from the last disc of the pair (the diameter of this roller is (approximately the diameter of the feed roller), at least one cooling roller (for cooling the stretched, wave-free, flat sheet web to approximately room temperature), and a winding device. A device of this type is known from the publications mentioned at the outset. In order to carry out the method according to the invention, this known device uses rollers for feeding the sheet web to the first disk of the pair and for removing the stretched sheet web from the last disk of the pair. rollers are arranged such that the winding angle of the sheet web edge on the disk is at most 150°;
Between the take-off roller and the first cooling roller, an area is provided for free movement of the sheet web laterally (to homogenize and remove waves in the stretched sheet web leaving the disk), and two pairs of disks are provided. In the case where the above-mentioned discs are provided, the pairs of discs are arranged side by side so that the above-mentioned winding angle is given to each disc pair.

The rollers or rolls for feeding the sheet web into the first two discs and the rollers or rolls for removing the finished stretched sheet web from the discs are
placed in contact with or somewhat close to the disk (this spacing is approximately 1 to 511 I
11 is suitable), and the web edge is at most 150 @, preferably 90~ on the outer peripheral surface of the disc.
It is positioned to produce a wrap angle of 150°, in particular 100-130'. The supply roll and take-off roll are also conveniently adjustable horizontally and vertically. The diameter of the lateral extension disc is preferably 100
~300 tm.

Downstream of the rollers for removing the finished stretched sheet web from the disc (up to the first cooling roller in the sheet web running direction), according to the invention, the sheet web can be moved laterally in order to remove said waves. A section or area is provided. As already mentioned, this area is formed according to the invention in such a way that the sheet web is substantially unsupported. According to another preferred variant, this region is formed by the above-mentioned minimum number of three rollers, preferably from 5 to 9 rollers. Where two or more pairs of discs are provided for laterally extending the sheet web, the individual pairs of discs are substantially closely spaced from each other and each pair of discs The sheet web is guided along the individual pairs of discs so that the winding angle is achieved. Therefore, in the case of two pairs of discs, the sheet web is guided in alternating windings around both closely spaced pairs of discs, maintaining the above-mentioned winding angle on each pair of discs. . In this case, the supply roll is arranged before the first pair of discs, and the take-off roll is arranged after the second pair of discs.

(Example〕 The invention will be explained in more detail with reference to the figures.

In the example of FIG. 1, polyvinyl chloride (PVC)
A sheet web 2 is unwound from the spool 1 and heated by two preheating rollers 4.6 to a transverse stretching temperature of 120°C. The sheet web is pressed against this preheated roll by contact rollers 3, 5 with rubber coatings. The heated sheet web reaches a pair of laterally extending discs 8/8' via a feed roller 7 and exits said laterally extending discs via a take-off roller 9. The sheet web stretched in the transverse direction passes through the homogenization zone S by means of deflecting and pointing rollers IO, while maintaining a sufficient transverse stretching temperature. In this homogenization region, the waves present in the sheet web are eliminated. The transversely stretched, wave-free sheet web is pressed against a cooling roller 12 by a contact roller 11 provided with a rubber coating, while being pressed against a cooling roller 12.
It is cooled by two cooling rollers 12, 13 and wound onto a roll 14.

In the embodiment of FIG. 2, the homogenization area S' is
4.1 to 24.7.

Sheet web 16 and devices 15.17-23.25-28
are similar to that in FIG.
' in the same way as in FIG. In the embodiment of FIG. 2, a sheet laterally stretched at 120 DEG C. is guided through region S' in order to eliminate waves. This area has seven rollers 24.1~ that rotate freely and are not heated.
It consists of 24.7. In this case, the sheet web is kept approximately at the transverse stretching temperature to remove any waves present in it (the diameter of the seven rollers arranged directly next to each other is about 30 mm).

In the embodiment of FIG. 1, the sheet web passes almost freely through the homogenization zone, whereas in the embodiment of FIG. It receives a continuous alternation of short support on the top and free guidance between the rollers.

In the case of the embodiment of FIG. 3, it is manufactured with a 40-roller calender having four rollers 29 to 32, inf, = P V
The C seat tow nib 33 is connected to the rollers 34.1 to 34.4.
is removed from the last calender roller 32 by a removal device consisting of the following three cooling rollers 35.1.
~35.3 results in a transverse extension temperature of 110°C.

The sheet web heated in this way is transferred to the guide roller 3
6 and supply roller 37 to the lateral stretching device. This lateral extension device consists of two pairs of lateral extension discs 38.
It consists of ゜38' and 39.39'. The sheet web stretched in the transverse direction and having corrugations is removed by a take-off roller 4
0 into the homogenization region S#. The sheet web at the transverse extension temperature passes almost freely through the homogenization zone,
It is supported and guided only by rollers 41.

The sheet web without waves is cooled by cooling rollers 42.1 to 42.3.
The film is cooled to approximately room temperature by a winder and wound up on a winder (not shown) (roller 42 is not used in the embodiment according to the invention, but is used in the comparative tests described below).

Next, the characteristics of the process when implementing the present invention will be explained according to FIGS. 1 to 3.

When implementing the invention according to FIG. 1, the PvC sheet web used has a width of 1.000 m and a thickness of 0.
．． It is 15mm. The sheet web passes through a pair of transverse extension discs at a winding angle of 120° and at a transverse extension temperature of 120"C, 1:
It is stretched laterally with a ratio of 1.1. The length of the homogenization region S is 300 rttm. A perfectly flat sheet web without waves (which has a temperature of 119 °C on leaving the homogenization zone and therefore passes through the homogenization zone at approximately the transverse extension temperature) has a width of 1 .020 mm
It is.

As a result of the treatment according to the invention, the shrinkage values of the sheet web used, measured in a circulating air heating chamber at a sheet temperature of 100°C and a shrinkage time of 15 minutes, are: As is known, it means an increase in the width of the sheet.

Sheets produced according to the present invention are processed using conventional thermoforming machines (
A deep drawing machine) up to a temperature of 180°C was tested.

During heating, when the temperature of 92° C. was reached, it was taut so that there were no waves, and it remained taut without waves during subsequent heating.

When implementing the invention according to FIG. 2, the PV used
The C sheet web likewise has a width of 1+000 arms,
It has a thickness of 0.15 mm. In this case too, the sheet web is passed through a pair of transverse extension discs at a winding angle of about 120° and at 120°C and 1:1.
It is laterally stretched with a ratio of 1 and then passes through a homogenization zone S'. A perfectly flat sheet with no waves (this sheet passed through the homogenization zone at approximately the transverse extension temperature) has a width of 1
, 040mat. The sheets obtained according to the invention have the following summarized shrinkage values (measured according to the above data):

Sheets according to the invention were tested in a conventional thermoforming machine at a temperature of 180°C. Upon heating, it became taut with no waves when a temperature of 90°C was reached, and remained taut without waves during subsequent heating.

When carrying out the invention according to FIG. 3, the calendered PvC sheet web has a width of 2.000 mm and a thickness of 0.4 m. The sheet web passes through a first pair of laterally extending discs at a wrap angle of approximately 90°;
It then passes through a second pair of transverse extension disks at a wrap angle of about 1306 and is laterally extended at said transverse extension temperature of 110° C. and in a ratio of 1:1.15. Region S where the sheet web substantially maintains the lateral extension temperature
"The length is 300 m. A completely flat sheet web without waves has a width of 2.030 m.

This is obtained when the sheet web does not pass through the devices 36 to 41 according to the invention of FIG. The shrinkage values of the sheets obtained according to the invention in comparison with the sheets are shown below (again, the shrinkage values are measured according to the above data).

FIG. 3 schematically shows an embodiment according to the invention formed by an area that is not supported or by a plurality of rolls arranged side by side; FIG. FIG.

2... Sheet web, 4.6... Take-in roller, 7... Supply roller, 8.8'... Extension disk, 9... Take-out roller, 12.13
... cooling rollers, 14 ... winding device 4° Sheets produced according to the invention were tested up to 180° C. in a conventional thermoforming machine. During heating, when the temperature reached 87°C, the wave disappeared and became taut, and the taut state without waves was maintained during subsequent heating.

[Brief explanation of the drawing]

Figures 1 and 2 show that the homogenized region is a real agent.
Patent Attorney Hikaru Esaki Good Agent Patent Attorney Hikaru Esaki

Claims (1)

[Claims] 1. A sheet web consisting of a thermoplastic material that is substantially unstretched in its elastic temperature range is heated to a temperature within the elastic temperature range of the plastic material; For lateral stretching, the sheet web passed through a lateral stretching device consisting of at least one pair of rotatable discs, the discs being arranged at an angle to the direction of travel of the sheet and extending the sheet web. For thermoforming from thermoplastics, the edges are held to the outer peripheral surface of the disc by frictional connections, and after exiting the transverse stretching device, the transversely stretched sheet web is cooled on cooling rollers and wound up. A method of manufacturing a sheet, comprising: (a) a sheet web being guided along the outer circumferential surface of a disk at a sheet web winding angle of up to 150° while passing through a lateral stretching device, the wound sheet having a winding angle of up to 8 %
(b) laterally stretching the web at a ratio such that the sheet web has a lateral contraction of To remove the waves, it is first held at approximately the lateral extension temperature and guided at this temperature without any lateral movement until completely flat without waves, and then cooled on cooling rollers. (c) the sheet web is passed to and through a transverse stretching device until it is wound, with a longitudinal tension such that the wound sheet has a maximum longitudinal shrinkage of 10%; , and a subsequent passageway for producing a thermoformable sheet from a thermoplastic material. 2. (a) The sheet web is guided at a winding angle of 90 to 150°, and the rolled sheet is 0.5 to 5%
(b) the laterally stretched sheet web passes through a substantially unsupported region to allow free lateral movement; (c) the sheet web is guided until it is wound up under such longitudinal tension that the wound sheet has a longitudinal shrinkage of 2 to 7%. A method of producing thermoformable sheets from thermoplastics. 3. (a) The sheet web is guided at a winding angle of 90 to 150°, and the rolled sheet is 0.5 to 5%
(b) the laterally stretched sheet web is laterally stretched in such a ratio that it has a lateral contraction amount of (c) in the longitudinal direction such that the wound sheet has a longitudinal shrinkage of between 2 and 7%; 2. A method for producing thermoformable sheets from thermoplastics according to claim 1, characterized in that the sheet web is guided under tension until it is wound up. 4. Producing a thermoformable sheet from the thermoplastic material according to any one of claims 1 to 3, characterized in that the sheet web is guided at a winding angle of 100 to 130°. Method. 5. Apparatus for carrying out the method according to claim 1, comprising substantially at least one intake roller (4, 6).
and at least one pair of rotatable extension discs (8, 8
'), the extensible disc is arranged at an angle to the direction of travel of the sheet, the edge of the sheet web rides on the outer circumferential surface of the disc and is guided in a frictional connection around the disc; a heating device for maintaining the sheet web temperature in the stretching region and for heating the discs approximately to the stretching temperature of the sheet web (2), and a pair of discs in the running direction of the sheet web ( a roller (7) for feeding the sheet web (2) to the disk (8, 8') and a roller (9) for removing the stretched sheet web from the last disk of the pair (8, 8'); At least one cooling roller (12
, 13) and a winding device (14), a roller (7) for feeding the sheet web (2) to a first pair of discs (8, 8'), and a winding device (14). A roller (9) for removing the stretched sheet web from the last disc (8, 8') which has formed a
') is arranged so that the winding angle of the sheet web edge is a maximum of 150°, and the take-out roller (9)
and the first cooling roller (12), an area (s) is provided for free movement of the sheet web laterally, and if two or more pairs of disks are provided, each pair of disks has the above-mentioned winding angle. A device characterized in that a pair of disks are arranged side by side so that a