WO2001060578A1

WO2001060578A1 - Method and apparatus for production of composite sheets

Info

Publication number: WO2001060578A1
Application number: PCT/DK2001/000109
Authority: WO
Inventors: Claus Burchardt
Original assignee: THERMOCOMP AS
Current assignee: THERMOCOMP AS
Priority date: 2000-02-17
Filing date: 2001-02-16
Publication date: 2001-08-23
Anticipated expiration: 2002-08-17
Also published as: DK200000252A; DK173918B1; AU2001233616A1

Abstract

Method and apparatus for production of composite sheets, where a weave comprising at least two materials is passed over at least one rotating hot roller heated up to a temperature above melting point for that of said at least two materials, which has the lowest melting point, and below melting point for that of said at least two materials, which has the highest melting point, and where said temperature is below the decomposition temperature for any of said at least two materials, where said weave is passed through a heating process, pressing in hot conditions and cooling process to form a composite sheet, and where said weave during said pressing process is subjected to pressure of said at least one rotating hot roller, which is heated up to the above mentioned temperature.

Description

METHOD AND APPARATUS FOR PRODUCTION OF COMPOSITE SHEETS.

The present invention relates to a method for production of composite sheets as described in the introductory part of claim 1. The invention is also relates to an apparatus for production of the composite sheets.

It is a well-known technology to produce composite sheets from matrices comprising threads of different materials. A widely used method is production of those sheets in moulds with heat and pressure applied to the matrix with or without an adhesive component. In cases where an adhesive component is not used, the threads consist of a polymer which is melted by heating, after which the finished sheet is produced after cooling and setting. For reinforcement of the material it is a usual practice to mix polymer threads and glass fibres, where the polymer threads are melted during composite formation with the polymer enclosing the non-melted glass fibres, which then function as reinforcing material.

To produce composite sheets with smooth and even surface and more or less homogenous thickness, it is necessary to use long and well-arranged fibres, which means that the threads have certain prefeπed directions, for example, lying at certain angles with respect to the direction of production. Such matrices are called weave. This term not only covers matrices that are woven but also matrices where long, arranged threads are assembled by stitching. The term "weave" is used for composites with long fibres in contrast to "non-woven" materials, which are mixtures of short fibres and are used, for example, in insulation mats.

To produce composite sheets as long, continuos webs, a so-called belt press can be used, which is known, for example, from international patent application W097/26397. A matrix of threads is passed through a heating process and a pressing process, where the pressing process takes place between pressure rollers with belts around them arranged in such a way, that the composite sheet in the form of a continuos web is pro- duced between the belts on each side of the sheet. However, belt presses are very ex-

C0NFIRMATI0N COPY pensive machines, why other apparatuses have been developed for production of composite sheets in the form of a continuos web without using belts around the rollers. Such an apparatus costs only a small fraction of the price for a corresponding belt press.

Such an apparatus is described in Norwegian patent application NO 984275, with original international patent application WO98/31857. In this apparatus, composite sheets are produced as continuos webs from a weave of polymer threads and reinforcing threads, preferably glass fibres. The weave is passed through a first heating zone, where it is heated up by thermal radiation to a first temperature. Then the weave is passed over a number of warm rods, which heat the weave up to a temperature above melting point. After this heating stage, the weave is cooled down and pressed to form composite sheets. During the pressing process, the melted polymer settles around glass fibres forming the composite with a more or less smooth surface.

This method has a lot of disadvantages. To achieve a complete melting of the weave, it is exposed to a strong thermal radiation on a preheating stage. The disadvantage of the preheating stage is that a temperature is reached on the external side of the weave, which is close to the decomposition temperature for the polymer, for example, 230°C for polypropylene, abbreviated PP, while the temperature in the centre of the weave is much lower, for example, 140°C, and often below melting point, which for PP is 165°C. Consequently, a decomposition of external polymer fibres takes place in the weave, which is extremely inappropriate, but accepted in order to obtain necessary heating to the final temperature, where the polymer is melted to form the composite.

Another disadvantage of the process, when the weave is first heated up to the melting temperature and then pressed at a lower temperature, is lack of homogenisation in the material. Homogenisation is a function, by which the polymer melts completely and then settles around the reinforcement material. Hitherto known systems necessarily run with a relatively high speed in order to minimise the time span between the heating and the subsequent pressing with cold rollers. But at high speed it is impossible to heat ^

the weave up to the right working temperature, which is somewhat higher than the melting temperature and preferably close to the decomposition point. This is one of the reasons why a thermal radiation preheating stage is used in prior art systems. It has however not been possible to solve the problem completely, as high process rate re- suits in poor heating and unsatisfactory homogenisation of the material, while a slow process rate results in better heating, but, on the other hand, it takes longer time for the weave to reach the pressing rollers, whereby the pressing takes place at a too low temperature, which also results in unsatisfactory homogenisation.

The purpose of the invention is to provide a method and an apparatus for production of composite sheets from a weave, where the above-described disadvantages are avoided, and where heating of the weave preferably takes place without thermal radiation preheating.

This purpose is achieved by a method of the type mentioned in the introduction and characterised as described in the characterising part of claim 1.

By including one or several hot rollers heated up to the hot rolling temperature in the pressing process, it is ensured, that the pressing takes place while the polymer is melted. This is an important aspect, as it minimises the void volume in the final composite sheet. The void volume is that volume of the composite which consists of air. The bigger the void volume, the less strength has the composite.

Furthermore, it is ensured that individual reinforcing threads in the composite sheet are enclosed to a most possible extent and preferably completely by the first melted and then hardened polymer. By optimal enclosing of the reinforcing material, the highest strength of the material is achieved.

In another embodiment, the invention is characterised in that the weave comprises polymer threads, preferably PP, PET or PTFE plus threads of a reinforcing material, preferably glass fibres, but carbon fibres or fibres of other materials could be used as well.

In a further embodiment, the invention is characterised in that the share of glass threads in the weave is between 55% and 75%, preferably between 60% and 70%, and most preferably 60%. Using a weave where the share of reinforcing material, like glass, is high, a much higher strength of the material is achieved. On the other hand, it is difficult to obtain a smooth surface of the material with a high share of reinforcing material. Therefore, selection of reinforcing material is a compromise between these two considerations. It has surprisingly turned out that if the share of glass fibres in a weave also containing polymer fibres is close to 60%, the strength of the weave is very high, while it is still possible to produce composite sheets with a very smooth surface.

A further embodiment of the invention is characterised in that the hot rolling tempera- ture is between 0° and 20° below the decomposition temperature for that of the at least two materials that has the lowest decomposition temperature, preferably between 0° and 10° below the decomposition temperature and most preferably between 0° and 6° below the decomposition temperature. The decomposition temperature for PP is 220°. At heating above that temperature, a decomposition process of the fibres begins. Therefore, it is important that the polymer is not heated up to a temperature higher than the decomposition temperature. On the other hand, it is important that the polymer is as viscous as possible, so that it finally can settle around the reinforcing fibres to a sufficient extent.

In a further embodiment, the invention is characterised in that hot rolling pressure is between 20 N/mm and 50 N/mrn, preferably between 20 N/mm and 40 N/mm, and most preferably 30 N/mm. The pressure is given in force units per mm roll length. Pressure in the pressing process must be adjusted very accurately with the production rate and the temperature in the composite material. At low temperatures, the polymer is viscous, and it requires more pressure to distribute the liquid polymer, while the composite at high temperatures may not be exposed to high pressure, as it will damage the structure of the smooth composite sheet. The pressure of 30 N/mm in a method according to the invention has proven to be very appropriate.

In a further embodiment, the invention is characterised in that the process rate is be- tween 0.5 m/min and 2 m/min, preferably between 1.4 and 1.6 m/min. It is appropriate to have a high production rate, as in this case the product can be manufactured in a shortest possible time. Especially in a pressing process, which includes both hot rollers and cold rollers, it is important, that the composite sheet is transported from the hot process to the cold pressing process before the material is cooled off so much, that a sufficient homogenisation and shaping of the material can not take place during the final pressing process with cold rollers. However, the production must not be so fast, that a sufficient homogenisation, that is flowing of the polymer and enclosure of the glass fibres, does not occur. "Cold" in this context means a temperature significantly lower than the melting temperature of the polymer. Heating up the weave with rollers and maintaining this temperature during the pressing process with hot rollers makes it possible to run the process at a rate low enough to ensure satisfactory homogenisation of the melted material. In a pressing process, where the pressure roller has the hot roller temperature, the composite sheet will still have a temperature, at which the polymer material is melted, when it leaves that part of the pressing process that in- eludes the hot roller, which has proven to be a great advantage.

In a further embodiment, the invention is characterised in that that supply of heat to the weave that takes place by heat transfer from the at least one hot roller to the weave, when the weave comes into contact with the hot roller, constitutes between 80% and 100%, preferably 100% of the total heat supply during the heating process.

The use of the method according to the invention, where the weave is heated up by the heat from the rollers at the hot rolling temperature and where the weave is pressed by a roller at the hot rolling temperature, has surprisingly shown, that the composite pro- duced in accordance with the invention has a much higher stiffness than the corresponding composite sheets produced until now, which is a sign of a good moulding. High stiffness of the material is an advantage, when the composite sheet is included as a component in larger, complex structures, where it is desirable that the composite sheet contributes to the structural stability.

The stiffness is expressed with a so-called Young's modulus, which is a ratio between a compressive or tensile stress on the material in the composite sheet's longitudinal direction and the corresponding relative linear expansion. At a certain tensile stress on the composite sheet, the Young's modulus is the bigger, the less the sheet is extended as a result of tension.

There have been taken measurements of the Young's modulus for composite sheets produced by the method according to the invention and with a starting material with orthotropic fibre structure as reinforcing material, where the fibre distribution in the weave was 50% in the longitudinal direction and 50% in the transverse direction. The value for Young's modulus was measured to 14 GPa.

There have also been taken measurements of composite sheets, which result from the same starting weave, but which have been produced by Netrotex as described in Norwegian patent application NO 984275. The Young's modulus for the material was 7-8 GPa.

The reason why composite sheets produced according to the invention have twice as high a strength as composite sheets produced previously is not clarified in detail, but the above mentioned arguments for influence of temperature, heating method, pressure and process rate indicate that the enhanced stiffness is a result of a combination of these factors, where pressing with a roller that has a hot rolling temperature is the key point of the process.

In a further embodiment, the invention is characterised in that the heating process in- eludes heating with thermal radiation. This is a possibility, which can be used in connection with the invention. It has however turned out that the stage can be omitted. In a further embodiment, the invention is characterised in that the heating by thermal radiation provides a temperature of the weave between 1 10° and 170°C, preferably between 120°C and 160°C, and most preferably 140°C. Provided that preheating is used, this temperature has proven to be advantageous. However, it is important that during the thermal radiation treatment, the surface of the weave is not supplied with so much heat that it decomposes. In general, it is not necessary to preheat the weave, but it is not impossible in certain cases that an advantage can be obtained by heating in addition to the hot pressing rollers.

In a further embodiment, the invention is characterised in that during the pressing process the weave is subjected to a rolling pressure only where the thickness of the composite sheet is larger than a certain adjustable minimum thickness. The minimum thickness is adjusted to an appropriate value with regard for the weave's thickness and the number of the weaves melted and pressed together.

In a further embodiment, the invention is characterised in that during the cooling down process, the weave is subjected to a cold rolling pressure of at least one rotating cold roller. After the first step of the pressing process, where the composite sheet is formed with the weave as a starting material, one or more subsequent pressing stages can be used with advantage, where the coπesponding rollers have a much lower temperature than the hot rolling temperature. During the process, the not yet hardened composite sheet can be shaped in accordance with predetermined profiles. The sheet can, for example, be given a wavy or serrated shape depending on the required final product. The cold rollers must therefore be appropriately designed for such special purposes.

In a further embodiment, the invention is characterised in that the weave is subjected to surface structuring during the pressing process in hot conditions and/or by pressing during the cooling down process. Such structuring of the weave can, for example, be carried out by cold rollers if they have a surface design which after pressing is trans- ferred to the composite sheet surface. As for the weave, it can be furnished with holes of different shapes to supplement specific structuring of the weave.

An apparatus for production of composite sheets comprising one or more mediums for feeding in of at least one matrix of threads, preferably a weave with polymer threads and glass threads, at least one device for heating of the matrix, at least one heated rotating roller, over which the matrix is passed, and where the rotating roller is heated up to a hot rolling temperature which is above melting point for that of the at least two materials in the matrix with the lowest melting point and below melting point for that of the at least two materials with the highest melting point, and where the hot rolling temperature is below the decomposition temperature for any of the at least two materials, at least one arrangement for pressing the matrix together, and at least one device for cooling the matrix down is according to the invention characterised in that the matrix pressing arrangement includes at least one rotating hot roller, which is heated up to the hot rolling temperature.

In a further embodiment, the apparatus is characterised in that said at least one arrangement for pressing said at least one matrix comprises at least one set of two hot rollers with parallel rotation axes and rotating in opposite directions with equal surface speed, wherein said two hot rollers are heated up to said hot rolling temperature, wherein said hot rollers are arranged with a mutual spacing, preferably adjustable, and with a pressure, preferably adjustable, between said two hot rollers directed towards their rotation axes in such a way that said at least one matrix passing through said hot rollers is simultaneously subjected to both heating and pressing.

In a further embodiment, the apparatus is characterised in that said arrangement for pressing said at least one matrix comprises at least one set of two cold rollers with parallel rotation axes and rotating in opposite directions with equal surface speed, wherein said cold rollers have a surface temperature, which is below melting tempera- ture of the materials in the weave, wherein said cold rollers are placed behind said hot rollers and arranged with a mutual spacing, preferably adjustable, and a pressure, pref- erably adjustable, between said two cold rollers directed towards their rotation axes in such a way that said at least one matrix passing through said cold rollers is subjected to additional pressing.

In a further embodiment, the apparatus is characterised in that said at least one device for heating up said at least one matrix comprises at least one rotating preheating roller, which is heated up to said hot rolling temperature and which is placed before said at least one arrangement for pressing said at least one matrix.

In a further embodiment, the apparatus is characterised in that the diameter of said hot rollers is between 300 mm and 500 mm, preferably between 350 mm and 450 mm, most preferably 400 mm. It is advantageous, that the hot rollers have a relatively large diameter, as it gives the possibility for the weave to get in contact with the rollers surface over a larger area, which results in a thorough penetration of heat into the mate- rial. With small diameters, for example 40 mm, the heat penetration into the material is so insufficient that there occurs a significant temperature difference between the surface of the formed composite sheet and the centre plane of the composite sheet. Due to the fact that during melting and pressing, the polymer must completely enclose the reinforcing threads, it is advantageous to use bigger rollers for contact heating of the weave.

In a further embodiment, the apparatus is characterised in that said hot rollers and or said cold rollers are provided as a solid of revolution with a surface profile deviating from cylindrical shape such that the resulting composite sheet is given a shape deviat- ing from a planar shape.

In a further embodiment, the apparatus is characterised in that said at least one arrangement for pressing said at least one matrix has an adjustable minimum opening for the passage of said matrix though this arrangement, wherein said minimum opening defines a limit for the pressing of said at least one composite sheet. In a further embodiment, the apparatus is characterised in that said at least one heating device contain at least one station with thermal radiation. Testing of the invention has shown, that heating of the weave with thermal radiation is not necessary. However, the invention is not restricted to not using this form of heating, and in special cases it may be an advantage to apply this heating stage.

Composite sheets produced in accordance with the invention can with advantage be used in complex structures, where the sheets are included as a replacement for aluminium sheets. Composite sheets have better weight to stiffness ratio than aluminium sheets, and much higher impact strength. These parameters are often key components for the selection of the material. Thus, the composite sheets produced according to the invention can replace aluminium surfaces in food production industry, for example in refrigeration trucks. Composite sheets are already used in refrigeration trucks, but those composite sheets are made of thermosetting plastic material based on hardening resin and, possibly, embedded glass as reinforcing material. Composite sheets produced under the invention contain a thermoplastic material plus a reinforcing material, like glass. They can be produced much faster, cheaper and can even be reshaped and thus tailored to fit very specific tasks.

Other areas of application are refrigeration containers, dry cargo containers, body parts for agricultural machines, components for aeroplanes, boats or automobiles, reinforced cabinets for electronic industry, components for weapons industry, components for construction industry, for example coverings for facades and partition walls, as well as components for furniture industry.

Examples

In the table below, different parameters are given which were used in the production method according to the invention, where composite sheets were made from a weave comprising 60% glass fibres and 40% polypropylene fibres (PP).

For some of the weaves, preheating has been applied, which, however, proved to be unnecessary for the particular weave. As it is shown by example 3 in the table, it has even been possible to increase the process rate, when the preheating was not used. In such case, it was not necessary to apply higher pressure, however, the temperature was close to the weave's decomposition temperature, which is about 220° C.

Besides the parameters given in the above table, an experiment has been made with varying pressure between 20 N/mm and 600 N/mm for the hot rollers and for cold rollers. However, 20 N/mm proved to be a very appropriate value.

The invention will be further explained with reference to the drawings, where FIG.1 is a sketch of an apparatus for the production method according to the invention,

FIG.2 is another embodiment of an apparatus according to the invention, FIG.3 illustrates various embodiments of roller profiles, and FIG.4 is a third embodiment of an apparatus according to the invention.

FIG.1 is a sketch of an apparatus for a production method according to the invention. Weave 1, which is a long fibre composite, for example a woven or stitched matrix of polypropylene fibres and glass fibres, is transported from roll 2 to a hot roller 3, which is heated up to a hot rolling temperature T_l5 where the hot rolling temperature T, is a temperature above the melting point for that of the at least two materials which has the lowest melting point and below melting point for that of the at least two materials which has the highest melting point, and where the hot rolling temperature is below the decomposition temperature for any one of the materials. During contact 4 with hot roller 3, the weave is heated up to the temperature above melting point for one or more composite materials, after which the weave under pressure Pj from the roller, normally against another hot roller 3', is shaped to a composite sheet 5, which is partially melted. Optionally, another set of rollers 6 and 6', which are cold rollers, is used for further pressing with pressure P₂ and shaping of the composite sheet 5, 7. The cold rollers 6, 6' have a temperature T₂, which is considerably lower than the hot rolling temperature T,, for example room temperature. Cooling of the composite sheet 5, 7 can take place during the second pressing as well as during additional active cooling afterwards; or cooling can be done by passive cooling, that is by emission of heat to surroundings.

On FIG. 1 , two sheets of the weave 1 and 1 ' are shown, which are pressed together to form one composite sheet. It is possible to use only one sheet. By using two sheets with a certain thickness, which are melted together, instead of one sheet with double thickness, a better penetration of heat into the weaves before pressing is achieved. Alternatively, a larger number of the weaves can be pressed together, possibly with several pressing stages in a more complex design of the apparatus.

FIG. 2 is another design version of an apparatus according to the invention, where one hot roller 3 and one preheating roller 8 are used for heating up the weave 1 to a hot rolling temperature. The preheating roller 8 has a temperature T₀, which can be equal to or different from the hot roller temperature. The contact surface 4 with the hot rollers will then be larger, which ensures heat penetration into the weave before pressing with pressure Pj. This is a big advantage especially for thicker weaves 1. Between the preheating roller 8 and the hot roller 3, the weave is likewise subjected to pressure P₀ , which is variable.

If it appears to be necessary, it is possible to use several subsequent hot rollers. The different hot rollers can have equal or different temperature. Furthermore, between individual set of rollers, the weave is subjected to pressure of different strengths. An apparatus according to the invention can thus be designed in different ways depending on the required process stages.

Rollers rotation speed, wO, w0', wl, wl ', w2 and w2' is mutually adjusted to the di- ameters of rollers 3, 3', 6, 6' in such a way that the weave is not subjected to an inappropriate stretching, but is yet transported through the apparatus in stretched conditions.

FIG. 1 also illustrates other devices 9 for heating of the weave 1. The devices 9 consist of heating units with thermal radiation. In most of the cases there will be no need for the heating units 9, as heating by hot rollers is sufficient. However, in certain cases it can appear to be useful to heat the weave first in this heating unit.

FIG. 3 illustrates different profiles for the rollers in the direction perpendicular to the rotation axes 10, 10' o the rollers 6, 6'. The rollers 6, 6' are placed opposite to each other with a certain minimum spacing 11, which can be adjusted depending on the weave's thickness. Further, the rollers 6, 6' can be provided with a surface structure which is transferred to the weave during pressing.

(FIG.4) Weave 1 can during composite sheet formation also be coated with a surface layer 12, 12', for example, a smooth synthetic sheet, a metal sheet or other material, which is sketched in FIG. 4. The surface sheet 12 will normally be fed in between the hot rollers 3, 3' and cold rollers 6, 6'. In order for the surface sheet 12, 12' along with the melted composite sheet 5 to form the final composite sheet 7, the surface sheet 12, 12' is fed in while the composite sheet 5 has not yet hardened. It is also possible to heat the cold rollers 6,6' up to a temperature such that the surface sheet 12, 12' is heated prior to coming into contact with the composite sheet 5. As an alternative, the thermal radiation heating 13 of the surface sheet 12, 12' can be applied.

Claims

1. Method of production of composite sheets, wherein a weave comprising at least two materials is passed over at least one rotating hot roller heated up to a hot rolling tem- perature, wherein said hot rolling temperature is a temperature which is above melting point for that of said at least two materials that has the lowest melting point and below melting point for that of said at least two materials that has the highest melting point, wherein said hot rolling temperature is below the decomposition temperature for any of said at least two materials, wherein said weave undergoes a heating process, a pressing process in hot conditions and a cooling process to form a composite sheet, characterised in that the weave in said pressing process is subjected to a hot rolling pressure from at least one rotating hot roller which is heated up to said hot rolling temperature.

2. Method according to claim 1, characterised in that said weave comprises polymer threads, preferably PP, PET or PTFE, as well as threads of a reinforcing material, preferably glass fibre.

3. Method according to claim 1 or 2, characterised in that the share of said glass fibres in said weave is between 55% and 75%, preferably between 60% and 70%, and most preferably 60%.

4. Method according to any one of the previous claims, characterised in that said hot rolling temperature is between 0° and 20° below the decomposition tempera- ture of the material with the lowest decomposition temperature, preferably between 0° and 10° below said decomposition temperature, and most preferably between 0° and 6° below said decomposition temperature.

5. Method according to any one of the previous claims, characterised in that said hot rolling pressure is between 10 N/mm and 50 N/mm, preferably between 20

N/mm and 40 N/mm, and most preferably 30 N/mm.

6. Method according to any one of the previous claims, characterised in that the process rate is between 0.5 m/min and 2 m/min, preferably between 1.4 and 1.6 m/min.

7. Method according to any of the previous claims, characterised in that that supply of heat to said weave which takes place by heat transfer from said at least one hot roller to said weave when said weave is in contact with said hot roller constitutes between 80% and 100%, preferably 100%. of the total heat transfer during said heating process.

8. Method according to any one of the previous claims, characterised in that said heating process includes heating by thermal radiation.

9. Method according to claim 8, characterised in that said heating by theπnal radiation provides a temperature of between 110°C and 170°C, preferably between 120°C and 160°C, and most preferably 140°C.

10. Method according to any one of the previous claims, characterised in that during said pressing process said weave is subjected to a rolling pressure only where the thickness of said composite sheet is larger than a certain adjustable minimum thickness.

11. Method according to any one of the previous claims, characterised in that said weave is subjected to a cold rolling pressure of at least one rotating cold roller during said cooling process.

12. Method according to any one of the previous claims, characterised in that said weave is subjected to surface structuring in hot conditions during said pressing process and/or during pressing in said cooling process.

13. Apparatus for production of composite sheets comprising:

- one or several means for feeding in of at least one matrix of threads comprising at least two materials, preferably a weave with polymer threads and glass fibres,

- at least one device for heating up said at least one matrix, - at least one heated rotating roller, over which said at least one matrix is passed, wherein said rotating roller is heated up to a hot rolling temperature, wherein said hot rolling temperature is a temperature which is above melting point for that of said at least two materials which has the lowest melting point and below melting point for that of said at least two materials which has the highest melting point, and wherein said hot rolling temperature is below the decomposition temperature for any of said at least two materials,

- at least one arrangement for pressing said at least one matrix,

- at least one device for cooling said at least one matrix, c h a r a c t e r i s e d in that said arrangement for pressing said at least one matrix comprises at least one rotating hot roller heated up to said hot rolling temperature.

14. Apparatus according to claim 12, c h a r a c t e r i s e d in that said at least one arrangement for pressing said at least one matrix comprises at least one set of two hot rollers with parallel rotation axes and rotating in opposite directions with equal surface speed, wherein said two hot rollers are heated up to said hot rolling temperature, wherein said hot rollers are aπanged with a mutual spacing, preferably adjustable, and with a pressure, preferably adjustable, between said two hot rollers directed towards their rotation axes such that said at least one matrix passing through said hot rollers is simultaneously subjected to both heating and pressing.

15. Apparatus according to claims 13 and 14, c h a r a c t e r i s e d in that said arrangement for pressing said at least one matrix comprises at least one set of two cold rollers with parallel rotation axes and rotating in opposite directions with equal surface speed, wherein said cold rollers have a surface temperature which is below melting temperature of the materials in the weave, wherein said cold rollers are placed behind said hot rollers and arranged with a mutual spacing, preferably adjustable, and a pres- sure, preferably adjustable, between said two cold rollers directed towards their rotation axes in such a way that said at least one matrix passing through said cold rollers is subjected to additional pressing.

16. Apparatus according to claims 13- 15, characterised in that said at least one device for heating up said at least one matrix comprises at least one rotating preheating roller, which is heated up to said hot rolling temperature and which is placed before said at least one arrangement for pressing said at least one matrix.

17. Apparatus according to claims 13-16, characterised in that the diameter of said hot rollers is between 300 mm and 500 mm, preferably between 350 mm and 450 mm, most preferably 400 mm.

18. Apparatus according to claims 13-17, characterised in that said hot rollers and/or said cold rollers are provided as solids of revolution with a surface profile deviating from a cylindrical shape such that the resulting composite sheet is given a shape deviating from a planar shape.

19. Apparatus according to claims 13-18, characterised in that said at least one arrangement for pressing said at least one matrix has an adjustable minimum opening for the passage of said matrix though this arrangement, wherein said minimum opening defines a limit for the pressing of said at least one composite sheet.

20. Apparatus according to claims 13-19, characterised in that said at least one heating device contains at least one station with thermal radiation.