CA2073956A1

CA2073956A1 - Process and apparatus for the production of wound tubes

Info

Publication number: CA2073956A1
Application number: CA002073956A
Authority: CA
Inventors: Ulrich Knipp; Paul Vente; Heinrich Pesch; Udo Post
Original assignee: Individual
Current assignee: Bayer AG
Priority date: 1991-07-19
Filing date: 1992-07-15
Publication date: 1993-01-20
Also published as: DE4123920A1; EP0523509A2; DE59203808D1; EP0523509B1; EP0523509A3; DE4123920C2; DK0523509T3; JPH05200857A; ATE128408T1

Abstract

PROCESS AND APPARATUS FOR THE PRODUCTION OF WOUND TUBES
ABSTRACT OF THE DISCLOSURE
Wound tubes of plastic can be produced economically by feeding a polyurethane reaction mixture onto a moving substrate and allowing it to cure to form a strip. Immediately afterwards, the strip is wound at a winding angle onto a cylinder and the gap formed between adjacent windings is also filled with a polyurethane reaction mixture. The tube formed as a continuous run is continuously drawn off from the cylinder.

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Description

2 ~ 6 PROCESS AND APPARATUS FOR THE PRODUCTIQN OF WOUND TUBES
BACKGROUND OF THE INVENTION
The present invention relates to a process and an apparatus for the production of wound tubes of plastic. A strip of plastic is wound at a winding angle onto a cylinder and the adjacent windings are bonded together by filling the gap between them. A process similar to the present invention is described in British Patent 1,514,321. According to this prior art, prefabricated strips of plastic in a deformable condition are wound onto a cylinder and the windings are welded together.
In addition, ~he cylinder has a rubber coating and is heated before winding~ and the tube can be drawn off after cooling.
This is a slow, discontinuous process of low profitability.
On the other hand, a process and an apparatus are known from U.S. Patent 4,082,597, wherein a continuous conveyor belt is first wound onto a cylinder. A curing resin is then applied to the winding. After the resin has cured to give the tube, the conveyor belt end is removed and returned. Continuous operation of this process is, however, costly, since the cylinder must be relatively long, and the production rate is limited because of the return of the conveyor belt.
It is also known to feed an extruded strand or band onto a ~;nd;ng drum (see, e.g., U.S. Patents 3,658,625, 3,917,500, 3,926,223 and 4,033,808, and German Patent 3,827,486). This technique is also not completely satisfactory.
The problem is to improve the technique for producing wound plastic tubes by simplifying the procedure and the apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS 0- Figure 1 shows a first apparatus with drivable cylinder in side view, Figure 2 shows the apparatus according to Figure 1 in plan view, Figure 3 shows a section along line A-B of Figure 2, Mo3752 Le A 28 474-US/CA

-- 2 -- ~ C~ 3 ~ !~
Figure 4 shows a section along line C-D of Figure 2, Figures 5 to 7 show sections through various embodiments of the tube, Figure 8 shows another embodiment with stationary cylinder in side view, Figure 9 shows the apparatus according to Figure 8 in plan view, Figure 10 a third embodiment with a stationary cylinder in side view, and Figure 11 the apparatus according to Figure 10 in front view.
D CRIPTION OF THE INVENTION
The above problem is solved by the present invention. A poly-urethane reaction mixture is cast on a linearly moving supporting Film tape and upon curing forms a strip. The adjacent windings are bonded by filling the gap with a polyurethane reaction mixture and the tuhe so formed is continuously stripped from the cylinder.
The special advantage of the new process lies in the fact that it can be carried out continuously, that the strip can be produced immediately before winding, and that the strip, on being wound onto the cylinder, is surprisingly already so far cured that pressure can be exerted against the last winding and the tube being formed can be continuously pushed away from the cylinder. This could not have been foreseen, since there is powerful friction between the windings and the cylinder.
It is obvious that before or after applying the reaction mix-ture to the supporting film, inorganic or organic reinforcing materials in the form of strips, films, cloths, or reinforcements of cut fib~rs or powders can be fed and embedded in the reaction mixture. Reinforcing materials or fillers in powder form can also be incorporated in one of the reaction components or in the reaction mixture before its application. Alternatively, such reinforcing materials can be spread beforehand onto the supporting film.
Finally, such reinforcing materials can be strewn onto and allowed to sink into the reaction mixture after it has been applied to the supporting film. Materials suitable as fillers include chalk, slate flour, quartz flour, spar, aluminium hydroxide, wood flour, Mo3752 Le A 28 474 US/CA

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comminuted plas-tics, and recycled materials (such as crushed glass or powdered plastics). Additional strips of plastic film or metal foil can also be laid under, embedded or laid on and co-processed during the casting of the strip. If strips of film are embedded, the strips used are suitably perforated, so that the reaction mixture is able to pass through. The winding angle, i.e. the angle between the support-ing film feed and the axis of the cylinder, is less than 90. The supporting film preferabl~y consists of a readily separable plastic, such as polyethylene, polypropylene or polytetrafluoroethylene, or of paper coated with a release agent, for example silicone. A metal sheet can also be used as the supporting film, in which case a soap solution can for example be used as the release agent. Due to the rigidity of the metal sheet it can be used as a continuous belt or can be re-used as a finite strip. Instead of a supporting film strip it is also possible to use a continuous conveyor belt which must be of such a length that the strip produced from the reaction mixture is already sufficiently solid on leaving the conveyor belt.
The filling of the gap between the windings is preferably carried out with the same polyurethane reaction mixture by means of a second casting device, that is preferably at the highest point of the cylinder or of the winding.
The stripping from the cylinder of the tube being produced is carried out preferably by guides positioned in the take-off direct-ion in accordance with the winding angle and which press against the last-applied winding. These guides are, for example, pressure pads or rollers.
It was surprising that the plastic strip just produced by . : casting and the material curing in the gaps already possess suffi-cient strength so that they are not damaged by the pressure required to strip the tube. If necessary, removal aids can also be used that act on the part of the tube that has already left the cylinder.
According to a further embodiment of the process, the support-ing film tape has, at least on the side facing away from the take-off direction, an edge projecting beyond the width of the strip.
This has the advantage that upon winding an overlap is formed, Mo3752 Le A 28 474-US/CA

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so that the cylinder shell itself is completely covered by the sup-porting film tape and the casting material required for closing the gaps cannot soil the cylinder shell.
According to a further development of the process, the support-ing film tape is folded up at the edges like a trough and the poly-urethane reaction mixture is cast into the trough so formed. Before the strip is wound, the edge facing away from the take-off direction is laid flat and the edge pointing in the take-off direction is folded under the strip formed. In this way, a plastic strip with precisely formed edges and constant width is obtained. If the edges of the supporting film are folded upwards by more than 90, a cham-fering of the strip which forms can be produced.
Alternatively it is possible to cut off the edge facing in the take-off direction, which is advantageous inasmuch as there is present one film thickness less, compared with the under-folding.
Preferably the supporting film tape is removed after the tube has left the cylinder. This is important in particular when the supporting film tape would interfere with the use of the tube. The tape must be removed and led away by means of the cylinder, prefer-ably through a hollow axis.
Such profiles can also be formed during the filling of the gapswith the aid of contour-providing means, for example a co-rotating double V-belt drive.
According to a further development of the new process, when the gaps are filled, profiles provided with undercuts are inserted.
Such profiles can be used as spacers or anchoring means, for example, for a tube jacket. They consist for example of plastic, : metal or stiff fiber products or of the gap composition itself.
It is also possible to wind several strips over each other and to fill the gaps with a polyurethane reaction mixture. As a result, higher strengths of the tube are obtained. Such strips can be wound in layers in opposite directions, and still other layers can be applied between the layers of strips, for example an inter-mediate layer of a polyurethane reaction mixture or a polyurethane - 35 rigid foam layer for thermal insulation. In both cases appropriate Mo3752 Le A 28 47~-US/CA

~17~5 reaction mixtures, which cure on the cylinder, are preferably used.
Obviously, in such intermediate layers, reinforcing inlays also can be worked in, for example windings of rovings or fiber fabrics or the like. When applying several layers of strips, it is usually neces-sary that from the second layer onwards the supporting film tapes bepeeled off.
Polyurethane casting materials suitable for the present invent-ion are known are are described, e.g., in the "Kunststoff Handbuch", Volume VII, Polyurethane, Carl-Hanser-Verlag (1966), on page 241, in Table 31, right-hand column. Optionally, the system can be acceler-ated by addition of 0.5 to 2 g of amine catalysts, e.g., N,N-di-methylcyclohexylamine.
One apparatus for the production of wound tubes from a strip of plastic by bonding the windings of this strip requires a cylinder provided with a rotary drive with a take-off device for the tube.
The novelty of the apparatus can be seen in the fact that 1) an unwinding station for a supporting film tape is arranged before this cylinder, 2) a casting device for a polyurethane reaction mixture is arranged over the transport path of the supporting film tape, and 3) another casting device is provided over the cylinder for filling the gap between the windings. By this means, the plastic strip only needs to be produced immediately before the winding process, as a result of which storage and other operations are omitted. This mode of production permits the use of strips which, if fully cured, could no longer be wound. This is possible with the new apparatus since, by taking into account the winding rate, the time that the strip requires for transportation from the feed point of the reaction mixture to the winding-up point can be adjusted, by choosing the distance of the feed point from the winding-up point, so that the strip is still sufficiently deformable during the winding.
An alternative embodiment of the apparatus is characteri~ed by a stationary cylinder with an opening in its shell. A friction roller, which acts on the windings of the strip, is arranged in the opening. In addition, an unwinding station for a supporting film tape is arranged before the cylinder and a casting device for Mo3752 Le A 28 474-US/CA

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a polyurethane reaction mixture is located over the transport path of the supporting film tape. Finally, another casting device is located above the cylinder for filling the gap between the windings.
Preferably with both embodiments, guides for the tape to be wound are associated with the cylinder as take-off devices, which are adjusted to the winding angle. These guides consist of pressure pads, rails or rollers which press the strip or the windings and thereby the tube being formed away from the cylinder. In the second embodiment, with stationary cylinder, these guides are largely unloaded when the friction rollers are so adjusted that they transport the windings both radially and axially, that is at the winding angle. Further take-off aids can be provided on the tube already produced.
Naturally, for peeling off the supporting film tape, a peeling device may be provided. It can be arranged at the end of the cylinder. Alternatively, the supporting film tape to be peeled off is led away backwards through the cylinder.
Both the unwinding station for the supporting film and the casting device must lie on the transport path determined by the winding angle.
If the supporting film tapes are turned up at the sides like a trough, appropriate folding devices must be provided.
If the edge facing away from the take-off direction has to be laid flat and the edge pointing in the take-off direction folded under the strip formed, guides for this must be provided. If the edge protruding in the take-off direction has to be cut off, a cutting device must be provided.
If, during filling of the gap, profiles provided with undercuts are to be inserted, a feeding device for these profiles must be provided.
If several strips are to be wound to one tube, an unwinding station for a supporting film tape as well as a casting device must be provided for each strip. Whether for the lowest tape layer another casting device for filling the gap between the wind;ngs ;s prov;ded or one cast;ng dev;ce Mo37~2 Le A 28 474-US/CA

~ ~.~ 5 which casts over the whole area of the gaps and windings depends on the desired tube structure. -If further intermediate layers, for example a polyurethane foam insulating layer, are to be applied, an appropriate device for applying a foamable reaction mixture is provided over the cylinder. If an intermediate layer is requ;red~ a feed device must be provided before the ~eed device or feed position for the next layer of a stripj at such a distance that the reaction mixture can cure beforehand to a load-bearing form.
Reference will now be made to the drawings.
In Figures 1 and 2, the apparatus has a cylinder 2, mounted on one side and rotatable by means of a rotary drive 1.
The cylinder's shell 3 has the internal diameter of the tube 4 to be produced. An unwinding stat;on 6 for a supporting f;lm tape 7, which is led over a guide roller 8, is arranged at an angle ~ of 80 to the axis 5 of the cylinder 2. Over the supporting film tape 7, a second unwinding station 9 for a reinforcing fabric 10 and a guide roller 11 are provided. A
folding device 12 serves to fold up the edges 13, 14 of the supporting film tape 7 and to guide the upfolded edges 13, 14 laterally ;n the region of a casting clevice 15, arranged over it, for a polyurethane reaction mixture 17 which forms a strip 16. The folding device 12 is of such a form that, shortly before the cylinder 2, the edge 13 facing the take-off side of the tube 4 is again laid flat and the edge 14 is folded by 180 under the strip 16 and accordingly no longer stands up. There are arranged above the periphery of the cylinder shell 3, corresponding to the winding angle ~, on a frame which is not shown, guides in the form of pressure pads 18 and rollers 19, which lie against the first winding 20. Over the highest point o~ the cylinder 2, there is arranged a further casting device 21, which fills the gap 22 between the windings 20 with a polyurethane reaction mixture 23. In addition, take-off ~ids, which are not shown, are associated with the tube 4 which has already been produced. The peeling device for the supporting ~o3752 Le A 28 474-US/CA
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film tape 7, which must be provided statically at the free end of the cylinder 2 by means of a bracket reaching through the axis 5, is not shown for the sake of improved clarity.
In Figure 3, in the folding device 12, there can be seen the supporting film tape 7 with its upfolded edges 13 and 14 which form a trough 24 in which the solidifying strip 16 lies. The edge 14 is folded further inwards, so that the strip 16 receives a chamfer.
In Figure 4, the strip 16 is already cured, the left-hand edge 13 of the supporting film 7 standing up above the strip 16, while the right-hand edge 14 is partly peeled from the underside of the strip 16 and folded by 180 underneath it.
In Figure 5, windings 31 are shown, the strip 32 being chamfered on one side. A profile 34 with undercuts 35 is laid over the gap formed, and also cast into the gap material 36.
In Figure 6, a profile 41 is likewise cast into the gap material 42. But here the profile 41 has a semicircular cross-section.
In Figure 7, two layers of strips 51, 52 are arranged over each other.
In Figures 8 and 9, a cylinder 62 is mounted on a stand 61.
The shell 63 of the cylinder 62 has an opening 64 in the wall there-of. A friction roller 65 lies in the interior of the cylinder and presses against the interior of the windings 66 of the strip 67 through the opening 64 and causes these to rotate around the cylinder 62. Counter-pressure rollers 68 press from outside at this same point against the windings 66. The unwinding station for the supporting film tape, the folding device and the casting device correspond to those of the apparatus according to Figures 1 and 2 ; ~ and are omitted here. The gap 69 between the windings 66 is filled with the same casting material as that from which the strip 67 is produced.
In Figures 10 and 11 a cylinder 72 is fastened as the stator to a stand 71. The shell 73 of the cylinder 72 has an opening 74 through which a continuous steel ribbon 75 serving as a release sheet leaves the interior of the cylinder and an opening 76 through which the steel ribbon reenters the interior and then returns to Mo3752 Le A 28 474-US/CA
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opening 74. This steel ribbon 75 surrounds the shell 73 for more than one winding 77. A casting device 79 for a polyurethane react-ion mixture is arranged above the steel ribbon 75. A continuous conveyor belt 80 is arranged upstream of the cylinder 72, above which S another polyurethane casting device 81 is arranged. The polyurethane strip 82 is formed on the moving conveyor belt 80 and is fed on to the steel ribbon 75, being driven by means of a roller 83. The gap 84 between the windings 85 is filled with the same composition as that employed for the formation oF the strip 82. A double V-belt 78 determines the contour of the filli.ng for the gap 84.
The invention is further illustrated but is not intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified.

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' EXAMPLES
Process ExamPle 1 The apparatus according to Figures 1 and 2 was used~ The cylinder 2, 1000 mm in diameter, rotates at 1 rpm. At the same time, the strip 16 is fed to it at a winding angle of 86. To produce this strip, the supporting film 7, which has a polyethyléne coating, is unwound from the unwinding station 6 and transported via a guide roller 8 in the direction of the cylinder 2. It is led into the folding device 12, which folds up the edges 13 and 14 of the supporting film 7, so that a trough 24 is formed. In this trough 24 a reinforcing strip 10 of glass fiber weave is fed from an unwind;ng station 9 via a guide roller 11, and a polyurethane reaction mixture is poured onto it by means of a casting device 15. Suitable reaction mixtures are described below. The reaction mixture forms the strip 16. The folding device lays the edge 13 flat again and folds the edge 14 by 180 under the strip 16. On winding onto the cyl;nder 2, the last winding 20 lies on the flattened edge 13 of the previous winding 20. The winding-on process is 20 assisted by guides in the form of pressure pads 18 and rollers 19, which simultaneously provide for the forward movement in the direction of the axis of the cylinder 2 of the continuous tube 4 being produced. The gap 22 formed between the wind;ngs 20 when winding on is filled with a polyurethane reaction mixture 23 by means of a second casting device 21. After leaving the ylinder 2, the supporting film 7 is removed. The tube 4 is transported in the axial direction by means of additional take-off aids and the continuous run then cut up into desired tube lengths~
Process Example 2 The apparatus according to Figures 8 and 9 was used.
The plastic strip 67 is produced and guided as in Process Example 1. The windings 66 lying round the shell 63 of the cylinder 62 are driven by the friction roller 65, so that the tube being produced rotates about the stationary cylinder 62, Mo3752 Le A 28 474-US/CA

, ' ; ' the friction between the shell 63 and the windings 66 being reduced by lubricants. The gap 69 between the windings 66 is also filled according to Process Example 1.
Composition Example 1 Polvol 1: a polyol mixture having an OH number of about 355 and a viscosity at 25 of about 1200 mPa.s, consisting of a~ 60 parts of a so-called polymer polyol prepared by polymerizing 20 parts of a 40:60 mixture of styrene and acrylonitrile in a polyether of OH value 36, that has been obtained by addition of a mixture of 83%
propylene oxide and 17% ethylene oxide to trimethylolpropane, b) 10 parts of diethylene glycol, c) 10 parts of dipropylene glycol, d) 20 parts of a polyether of OH value 790 that has been obta;ned by addition of 3.75 moles of propylene oxide to ethylenediamine, e) 3 parts of a paste consisting of 50% zeolite (potassium/sodium aluminosilicate) and 50% castor oil, and f) 0.15 parts of dibutyltin dil,aurate.
1s~5~n3~ 1: a polyisocyanate with an NCO content oF about 31.5% and a viscosity at 25C of 200 mPa.s, prepared by phosgenation of an aniline-formaldehyde condensate.
The reaction mixture of 100 parts of Polyol 1 and 97 parts of Isocyanate 1 yields a hard and heat-stable polyurethane product with a resistance to heat of about 110C.
Composition Example 2 Isocvanate 2: a polyisocyanate/polyether prepolymer with an NCO
content of about 20% and a viscosity at 25~C of about 1500 mPa.s, prepared by reacting 36 parts of the polymer polyol used to produce Polyol 1 w;th 64 parts of Isocyanate 1.
The reaction mixture of 100 parts of Polyol 1, 0.10 parts of dibutylt;n dilaurate and 150 parts of Isocyanate 2 yields a Mo3752 Le A 28 474-US/CA

medium-hard, viscoplastic polyurethane product with high impact resistance.
Composition Example 3 Polyol 2: a polyol mixture of OH value 56 and a viscosiky at 25C of 840 mPa.s, consisting of a) 91 parts of a polyether of OH value 36 that has been obtained by addition of a mixture of 83% propylene oxide and 17% ethylene oxide to trimethylolpropane, b) 0.9 parts of a polyether of OH value 150 that was obtained by addition of a mixture of 87% propylene oxide and 13% ethylene oxide to propylene glycol, and c) 0.9 parts of a solution of alkali acetate in diethylene glycol.
Isocvanate 3: a polyisocyanate mixture with an NCO content of 28 % and a viscosity at 25C of 300 mPa.s, consisting of a) 100 parts of a semiprepolymer, having an NCO content of 24.5%, that was prepared by reaction of i) 100 parts of a mixture of 1) 80 parts of 4,4'-diisocyanato diphenylmethane, 2) 10 parts of tri- and higher-functional polyisocyanates of the diphenylmethane series with ii) 12.5 parts of a polypropylene glycol of OH value 485, and b) 100 parts of a polyisocyanate that was prepared by phosgenation of an aniline-formaldehyde condensate and which has an NCO content of 31.5% and a viscosity at 25C of 60 mPa.s.
The isocyanate index was adjusted by varying the amount of the polyisocyanate mixture. 100 parts of the mixture per 100 parts of Polyol 2 corresponded to an isocyanate index of about 670; and 200 parts of Isocyanate 3 per 100 parts of Polyol 2 to an isocyanate index of about 1330.

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13-- ~ , 3 The reaction mixture of 100 parts of Polyol 2, 0 to 2 parts of a solution of alkali acetate in diethylene glycol and from 100 to 200 parts of Isocyanate 3 yielded a polyisocyanurate product which could be varied from soft to hard via alteration of the isocyanate index. The product is high-temperature stable (>200C).
Although the invention has been descr;bed in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

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Claims

1. In a process for the production of wound tubes of plastic, comprising winding a strip of plastic onto a cylinder at a winding angle .alpha. and bonding adjacent windings together by filling the gap between them, the improvement wherein i) a polyurethane reaction mixture is cast on a linearly moving supporting film tape, which reaction mixture upon curing forms the strip, ii) said gap is filled with a polyurethane reaction mixture, which upon curing bonds adjacent windings together, and iii) the tube so formed is continuously stripped from the cylinder.

2. The process of Claim 1, wherein the tube being produced is stripped from the cylinder by guides positioned in the take-off direction at an angle corresponding to the winding angle and which guides press against the last applied winding.

3. The process of Claim 1, wherein the supporting film tape has, at least on the side facing away from the take-off direction, an edge projecting beyond the width of the strip.

4. The process of Claim 1, wherein the supporting film tape is folded up at the sides like a trough and the polyurethane reaction mixture is cast in the trough so formed, and before the strip is wound on the cylinder, the edge facing away from the take-off direction is laid flat and the edge pointing in the take-off direction is folded under the strip formed.

5. The process of Claim 1, wherein the supporting film tape is peeled off after the tube has left the cylinder.

6. The process of Claim 1, wherein during the filling of the gap, profiles provided with undercuts are inserted therein.

7. The process of Claim 1, wherein several strips are wound on over each other and the gaps are filled with a polyurethane reaction mixture.

8. The process of Claim 1, wherein a conveyor belt is used instead of the supporting film tape and a steel ribbon is arranged on the cylinder beneath the gap of the strip which advances to-gether with the strip and serves as a release sheet.
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9. The process of Claim 1, wherein the gap filling is provided with undercuts directly during the filling process with the aid of contour-providing means.

10. An apparatus for the production of wound tubes from a strip of plastic by bonding the windings comprising a cylinder provided with a rotary drive and with a take-off device for the tube, an unwinding station for a supporting film tape arranged before said cylinger, a casting device for a polyurethane reaction mixture arranged between said cylinder and said unwinding station such that reaction mixture can be deposited over the transport path of the supporting film tape, and a second casting device arranged over the cylinder for filling gaps formed between adjacent windings.

11. An apparatus for the production of wound tubes from a strip of plastic by bonding the windings, comprising a stationary cylinder with a take-off device for the tube, said cylinder having an opening in its shell, a friction roller arranged in said open-ing, an unwinding station for a supporting film tape arranged before said cylinder, a casting device for a polyurethane reaction mixture arranged between said cylinder and said unwinding station such that reaction mixture can be deposited over the transport path of the supporting film tape, and a second casting device arranged over the cylinder for filling gaps formed between adjacent windings.

12. An apparatus for the production of wound tubes from a strip of plastic by bonding the windings of the strip, comprising a cylinder with a take-off device, characterized by a stationary cylinder having two openings in its shell for the exit and re-entry of a steel ribbon which is continuously rotated and surrounds the cylinder for at least one winding and by a continuous conveyor belt arranged upstream of the cylinder, above which a casting device for a polyurethane reaction mixture is arranged, and by an additional casting device above the steel ribbon for filling the gap between the windings of the strip.

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