EP2347894A2 - Pressure pad - Google Patents

Abstract

The pad (16) has a carrier i.e. single-layer fabric (1), formed from heat guides and pad threads (4). The pad threads consist of a coating (14) of flexible plastic, where thickness of the coating amounts to greater than 60 percent of thickness of core threads (11). The heat guides run transverse to the pad threads, and are made of metal e.g. copper, copper alloy, brass, aluminum and silver, and carbon. An elastomeric layer (20) is placed in the carrier, and has form-fit, detention- and/or chemical connection with the coating of the pad threads.

Description

The invention relates to a press pad for presses for the production of laminated sheets, with a carrier of intersecting threads, wherein the unidirectional threads are formed as upholstery threads, each consisting of a core thread and a coating coating this consists of a rubber-elastic plastic whose Thickness is at least 50%, in particular more than 60% of the thickness of the core thread, and wherein the transverse to the padding threads are formed as Wärmeleitfäden using metal.

The production of laminated panels, for example decorative coated chipboard, takes place in laminating presses, which can be designed as low or high-pressure floor presses or short-cycle presses. In this case, press pads are inserted into the press between the heated press plates and the press plate, which have the task on the one hand to transfer the pressure over the entire surface and evenly on the pressed material and on the other hand transfer the outgoing heat from the press plates quickly and without great losses to the pressed material. The press pads must be able to withstand high pressures and the temperatures present in such presses. To avoid heat loss, the press pads should have a high thermal conductivity in the thickness direction.

In the prior art, press pads are known in which a carrier consisting of a metal fabric is coated with a silicone elastomer in such a way that the silicone elastomer forms a matrix for the metal fabric (cf. DE 23 19 563 B ; DE 100 34 374 A1 ). Instead of a metal fabric comes as a carrier and a random fiber fleece in question (see. DE 26 27 442 A1 ). Furthermore, the proposal has been made to provide a fabric of aromatic polyamide threads and metal threads at least on one side only superficially with a coating in the form of a continuous layer, which consists of an elastomeric material, in particular silicone elastomer (see. DE 200 11 432 U1 ). In the EP 0 488 071 A2 there is disclosed a press pad made of a multi-ply fabric impregnated with a heat-resistant resin to stabilize the fabric structure and improve surface smoothness. Another variant of this type of press pads is in the DE 23 38 749 A disclosed. In this press pad is a glass fiber fabric as a carrier. The warp and weft threads are coated with a plastic, for example silicone rubber. Alternatively, or in combination with it, the entire fabric may be coated with a plastic, wherein also here silicone rubber is proposed.

The aforementioned press pads have just because of the coating with silicone or resin unsatisfactory thermal conductivity in the thickness direction, ie perpendicular to the plane of the press pad. In the EP 1 300 235 B1 Therefore, the proposal has been made to equip the carrier with Wärmeleitfäden, in particular metal filaments and to provide this carrier with a cushion layer whose thickness is less than that of the carrier, wherein the cushion layer is embedded in the carrier so that the heat conducting threads project on both outer sides of the press pad over the cushion layer. With this press pad, despite the presence of a continuous cushion layer, a good heat transfer with good cushioning properties is achieved.

In the EP 1 136 248 A1 Also, a press pad is proposed in which the fabric is coated with a fluorine and / or a silicone fluoroelastomer. Alternatively, it is proposed to effect the cushioning properties of the base fabric by using warp and / or weft yarns in which a core yarn is encased in an elastomer. In this type of press pads so dispensed with a coating. Variants of such press pads can be the EP 0 713 762 A2 . EP 0 735 949 B1 . DE 297 04 258 U1 . EP 0 920 983 A1 and EP 1 779 999 A1 remove. In this case, the upholstery threads usually form the weft threads, while the warp threads metal threads are used to assist the heat transfer.

The type of press pads that relate their cushioning properties solely by the padding threads of an elastomer or with an elastomer sheath of a core thread, although good cushioning properties and when using between the flat sides of the press pad reciprocating Wärmeleitfäden also good heat transfer properties. However, their dimensional stability is not optimal, even if the carrier fabric is woven so tightly that the Wärmeleitfäden dig into the rubber-elastic material of the upholstery threads (see. EP 0 920 983 A1 ). It also comes with the pressures in the press Such press pads to dimensional changes in the plane in the form of cuts in the longitudinal and transverse directions, which do not reset or only inadequate after pressure relief. This limits the life of such press pads and occurs especially with frequent format changes of the material to be pressed.

The invention is therefore based on the object, press pad of the type mentioned, ie those whose cushioning properties is caused solely by the upholstery threads, to improve the dimensional stability and in particular to reduce the tendency to shorten or eliminate.

This object is achieved in that in the entire support in addition a layer of rubber-elastic material, preferably a silicone elastomer, a fluoroelastomer and / or fluorosilicone elastomer is incorporated, which has a form-fitting, adhesive and / or chemical compound with the coating of the upholstery threads , The basic idea of the invention is therefore to store an additional rubber-elastic element in the form of a layer in the support of the press pad despite its actually sufficient cushioning property, in such a way that a connection between the coating of the upholstery threads and the layer of rubber-elastic material is produced. The preparation of the layer can be done by doctoring the liquid to pasty coating material in the previously prepared carrier from one or both sides. It has been found that the additional layer due to its rubber-elastic property for effective recovery of the deformed during the pressing process press pad in Plane direction, ie the dimensional stability is improved significantly and with long-term effect. The service life of the press pad increases significantly as a result, and the press pad can be used more universally, especially with frequent format changes in production.

In an embodiment of the invention, it is provided that the threads form gaps between them, which are filled by the layer. This gap filling makes the restoring effect of this layer particularly effective.

Normally, the threads, ie both the upholstery and the heat conducting threads, should protrude from the layer on at least one side, preferably on both sides. As a result, the heat conduction get a good contact both to the heated press plate and the press plate, so that a good heat transfer is ensured. When working without a press plate and a special texture is to be achieved on the pressed material, the layer can also be used to provide on at least one side, preferably the side facing the pressed material in the application of the press pad, for the formation of a smooth surface, by applying the layer so that the threads on this side do not protrude beyond the outside of the layer. The heat conduction takes place just below the surface, so that the thin layer has little insulating effect. This reduction of the heat conduction can be taken into account by incorporating heat-conducting particles into the layer and / or the coating of the upholstery threads, as will be discussed below which promote the heat transfer through the layer up to the Wärmeleitfäden.

The rubber-elastic layer may be symmetrical to a median plane of the carrier, wherein the median plane extends perpendicular to the thickness of the press pad and in the thickness center. Such a symmetrical arrangement is achieved in particular when the material for the production of the layer is doctored from both sides. However, it can also be provided that the layer lies more than 50% of its thickness on one side of the mid-plane of the carrier, that is to say with regard to the thickness of the layer asymmetrically with respect to the mid-plane. The latter arrangement is achieved in particular when the material for the production of the layer is only scanned on one side.

In the dimensioning of the thickness of the layer, a compromise between the restoring property of this layer in the plane direction, the material consumption and the influence on the cushioning properties of the press pad is to be concluded. It has been found that good recovery properties are achieved with a layer thickness equal to or greater than 60% of the thickness of the support. With this thickness, the cushioning behavior of the press pad is only slightly influenced.

As for the hardness of the coating of the upholstery threads, a value of 50 to 90, preferably 60 to 75 Shore A hardness, has proven to be useful. The rubber-elastic layer should also have a hardness that lies within this range. In this case, the hardness of the layer may be greater than that of the coating of the upholstery threads, in particular good recovery properties to realize. The difference should be at least 10 Shore A hardness.

In a manner known per se, the threads of the carrier should form a preferably single-layered fabric, wherein in particular a plain weave is offered because of the favorable course of the heat-conducting threads. This does not exclude that other weaves and also multi-layered fabrics can be considered, for example in the form of spacer fabrics.

In order to obtain a good dimensional stability even without the layer, the heat conducting fibers should enclose the upholstery threads in cranks, if possible so that the heat conducting fibers dig into the upholstery threads to prevent slippage of the heat conducting fibers with respect to the upholstery threads. The upholstery threads then run essentially straight.

For a uniform heat distribution, it is favorable if the distribution of the cranks of the Wärmeleitfäden is as even as possible. In this case, the number of offsets of the thermal conductors should be on each side of the fabric between 10 to 40, preferably 15 to 30 per cm ² . The high density of the cranks ensures good and even heat transfer over the surface. In the same direction, the condition is that thermal conductors form on the outer sides of the press pad 10 to 40, preferably 15 to 30 contact points per cm ² .

In a further embodiment of the invention, it is provided that heat conducting filaments, preferably all thermal conduction filaments, between the outsides of the press pad switch back and forth. In this way, the Wärmeleitfäden form continuous Wärmeleitpfade for the heat transfer.

According to a further feature of the invention, it is provided that the thread density of the cushioning threads is so large that the heat conducting threads only pass through compression of the rubber-elastic material of the cushioning threads between them, in particular the distance between the cushioning threads is less than the average diameter of the heat conducting threads. Preferably, the distance should be at least 10% less than the diameter of the Wärmeleitfäden. This very dense arrangement of the upholstery threads has a positive influence on the heat transfer, because the Wärmeleitfäden be forced due to the small distance between the upholstery threads to pass very steeply between these threads. This results in short heat paths between the two surfaces of the press pad with the result that the heating of the pressed material is much faster. Therefore, in spite of the existence of the additional layer, short cycle times can be achieved, and also the power consumption is low.

Due to the high density of the upholstery threads, the heat conducting fibers dig into the upholstery threads with elastic compression of the rubber-elastic material, with the result that slippage of the threads against each other is avoided. As a result, the processing of the carrier, so the internal wear, kept comparatively low. In addition, the dimensional stability in the direction of the Wärmeleitfäden is much better.

According to a further feature of the invention, it is provided that the heat conducting threads do not protrude beyond the plane formed by the outermost points of the upholstery threads, better still have a distance to this plane. This design has the advantage that the heat conducting threads are protected against abrasion when handling the press pad. Only when subjected to compressive stress in the press, the thermal conductors get in contact with the adjacent surfaces of the heated pressure plate and the press plate and then ensure good heat conduction.

For the rubber-elastic material, in particular silicone elastomers are suitable both in the coating of the upholstery threads and in the additional layer, since they are able to withstand the temperatures in the presses without loss of elasticity. However, fluoroelastomers or fluorosilicone elastomers are also suitable.

For the Wärmeleitfäden such metal materials should be used, which have a high thermal conductivity. In particular, copper or copper alloys and combinations of copper and plastic threads, eg aramid threads, are suitable for this purpose. Instead of copper, however, it is also possible to use brass, aluminum, silver and / or alloys of these materials as well as carbon and combinations of metal and carbon. As a result of the choice of material for the heat conduction fibers, as well as their number, thickness and arrangement, the heat conductivity of the press pad in the thickness direction can be optimally adapted to the respective requirements.

There is also here - as known in the art - the ability to distribute both in the coating and in the layer - or only in one of the two - filling materials whose specific gravity is less than that of the rubber-elastic material. As a result, the weight of the press pad can be kept low. For example, glass hollow spheres, powders, short cut fibers and / or microspheres are suitable for this purpose.

If a particularly good heat transfer is desired, should be distributed in the coating of the cushioning threads and / or the layer Wärmeleitteilchen whose specific thermal conductivity is higher than that of the coating or layer, the Wärmeleitteilchen particular as powder and / or fibers of metal and / or carbon and / or as Carbonanotubes (CNT), in particular multiwall Carbonanotubes (MWCNT) may be formed. As far as metal is used, can be made of the above-mentioned materials for the Wärmeleitfäden.

For the dimensioning of the upholstery threads, an outer diameter of 0.8 to 2.5 mm and for the Wärmeleitfäden a diameter of 0.15 to 0.8 mm has proved to be useful.

The Wärmeleitfäden may consist entirely of the metal used in each case. But they can also be formed so that a core thread is provided of a plastic, such as aramid, which is wrapped by at least one wire or ribbon, or are stranded around the wires or ribbons, which consist of a material whose specific thermal conductivity is greater is as the soul thread, for example, one of the aforementioned metals. Such thermal conductors are for example also made DE 297 21 494 U1 known.

According to the invention it is further provided that the core threads of the upholstery threads are each formed of a core thread and these surrounding wires or ribbons, which consist of a material whose specific thermal conductivity is greater than that of the core thread. For the core thread temperature-resistant plastic threads, for example of aramid in question, while for the surrounding wires or tapes metals are useful, as they are also proposed for the Wärmeleitfäden. The core threads and / or the Wärmeleitfäden may be formed by their structure as threads, braids, knitting threads, multifilaments or strands.

The rubber-elastic material of coating and / or layer should additionally have at least one heat stabilizer. Examples of such heat stabilizers are the EP 0 189 899 A2 refer to. In particular, antioxidants come into question.

Finally, according to the invention, it can be provided that the layer has passage channels which are open towards the outer sides of the press pad, so that the press pad is permeable to air in the thickness direction at these points. Incidentally, the layer may also be provided with dyes to achieve a desired mark.

Figur 1

einen Querschnitt durch einen Teil des Trägers des erfindungsgemäßen Presspolsters längs eines Polsterfadens und ohne elastomere Schicht;

Figuren 2 bis 5

Querschnitte durch erfingungsgemäße Presspolster mit dem Träger gemäß Figur 1 in einer Ebene senkrecht zur Ebene des Querschnitts gemäß Figur 1;

Figur 6

eine perspektivische Ansicht eines Wärmeleitfadens des Presspolsters gemäß den Figuren 1 bis 5 und

Figur 7

eine perspektivische Ansicht eines Polsterfadens des Presspolsters gemäß den Figuren 2 und 5.

In the drawing, the invention with reference to an embodiment is illustrated in more detail. Show it:

FIG. 1

a cross section through a portion of the carrier of the press pad according to the invention along a cushioning thread and without elastomeric layer;

FIGS. 2 to 5

Cross sections through erfingungsgemäße press pad with the carrier according to FIG. 1 in a plane perpendicular to the plane of the cross section according to FIG. 1 ;

FIG. 6

a perspective view of a Wärmeleitfadens the press pad according to the FIGS. 1 to 5 and

FIG. 7

a perspective view of a cushioning thread of the press pad according to the FIGS. 2 and 5 ,

The FIGS. 1 to 5 show as a carrier a single-layer fabric 1 in plain weave. The fabric 1 has heat-conducting threads-exemplarily designated 3-forming warp threads and upholstery threads-designated by way of example by 4-forming weft threads. The upholstery threads 4 run substantially stretched, ie they are not pressed out substantially by the integration with the thermal conduction 3 from the tissue plane. As can be seen in particular from the FIGS. 2 to 5 can be seen, put the heat conducting 3 around the upholstery threads 4 around and form at the top and bottom of the cushioning threads 4 pronounced kinks - exemplified with 5, 6 - which flatten during operation under pressure and the between the upholstery threads 4 by intermediate portions - for example denoted by 7 - are connected. In this way, a meandering course of the thermal conductors 3 results.

In FIG. 6 a heat conduction 3 is shown in detail. It comprises a twisted core thread 9 of aramid around which the six metal wires - designated by way of example by 10 - are struck in a stranding manner, such that the core thread 9 is completely enveloped by the metal wires 10. This results in a very closed and relatively smooth surface of the Wärmeleitfadens 3, which ensures good contact with the press plates and the press plate. The heat conduction thread 3 has a diameter of about 0.4 to 0.5 mm.

The in FIG. 7 shown enlarged padding thread 4 has a core thread 11 of about 0.6 mm in diameter, which consists of a core thread 12 of aramid and six metal wires - exemplified by 13 - which are stranded around the core thread 12. The metal wire 13 is made of copper. The core thread 11 is surrounded by an extruded elastomer sheath 14 made of a silicone elastomer. The diameter of the cushioning thread 4 is about 1.5 mm.

As in FIG. 1 to recognize, the heat conducting 3 dig into the elastic material of the elastomer sheathing 14 of the cushioning threads 4 a. This not only has the advantage that the thermal conductors 3 can not shift in the direction of the longitudinal axes of the cushioning threads 4, but force the thermal conductors 3 to form steeply extending and thus short intermediate sections 7. Dabei In the area of their cranks 5, 6, the heat conducting filaments 3 dig so strongly into the material of the elastomer coating 14 of the upholstery threads 4 that they do not protrude beyond the level 15 formed by the outer points of the upholstery threads 4 in the non-compressed state, but even distance therefrom have this level 15. Only under compression they get in contact with the heated press plates or the press plate.

The FIGS. 2 to 5 show various embodiments of press pads 16, 17, 18, 19, which have the same carrier 1, which is why for the parts of which for the FIGS. 1 as well as 6 and 7 reference numerals used for these figures. The press pads 16, 17, 18, 19 differ only in that in the carriers 1 different elastomeric layers 20, 21, 22, 23 are embedded.

In the press pad 16 according to FIG. 2 the elastomeric layer 20 is scribed on one side from the top into the fabric 1 in such a way that the top ends are also covered with elastomeric material of the layer 20, ie they do not project outwardly beyond the layer 20. In the press pad 17 according to FIG. 2 the fabric 1 has been coated on both sides, so that the resulting elastomeric layer 21 completely encloses the fabric 1, in contrast to FIG. 2 So also forms the bottom and covers the local cranks 6 there. In the press pad 18 according to FIG. 4 is used for the existing there elastomeric layer 22 less elastomeric material and has been sclerosed from the top, in such a way that it is abgerakelt of the cranks 5, the cranks 5 so over the Projecting layer 22. The thickness of the elastomeric layer 22 goes down to only slightly over half the thickness of the fabric 1, so that also the lower offsets 6 are exposed, the layer 22 is thus completely within the space formed by the fabric 1. In the press pad 19 according to FIG. 5 an elastomeric layer 23 has been formed in the fabric 1 by doctoring on both sides, wherein less material than for the press pads 16, 17 according to the FIGS. 2 and 3 has been used. Here are both cranks 5, 6 freigerakelt, ie they are above the layer 23 before. The layer 23 also lies within the fabric 2 in this exemplary embodiment.

The additional elastomeric layer 20, 21, 22, 23 respectively forms buffer between the cushioning threads 4 in the plane direction and, after a pressing operation, provides for a return of the press pad 16, 17, 18, 19 in the plane direction. The layers 20, 21, 22, 23 thus ensure good and long-lasting dimensional stability.

Claims (17)

Press pads (16, 17, 18, 19) for presses for the production of laminated panels, comprising a support (1) of intersecting filaments (3, 4), the unidirectional filaments being formed as upholstery threads (4) each of a core thread (11) and a coating (14) made of a rubber-elastic plastic whose thickness is at least 50%, in particular more than 60% of the thickness of the core thread (11), and wherein the transverse to the padding threads (4 ) extending threads are formed as heat conducting filaments (3) using metal, characterized in that in the carrier (2) in addition a layer (20, 21, 22, 23) of elastomeric material is incorporated, which has a form-locking, adhesive and / or chemical compound with the coating (14) of the cushioning threads (4). Press pad according to claim 1, characterized in that the threads (3, 4) between them form gaps which are filled by the layer (20, 21, 22, 23) and / or form a preferably single-layered fabric, in particular in plain weave. Press pad according to claim 1 or 2, characterized in that the threads (3, 4) protrude from the layer (20, 21, 22, 23) at least on one side, in particular on both sides. Press pad according to one of claims 1 to 3, characterized in that the layer (20, 21, 22, 23) is more than 50% of its thickness on one side of a median plane of the carrier (1). Press pad according to one of claims 1 to 4, characterized in that the thickness of the layer (20, 21, 22, 23) is equal to or greater than 60%, in particular more than 70% of the thickness of the carrier (1) and / or that the Hardness of coating (14) and layer (20, 21, 22, 23) is between 50 to 90 Shore A. Press pad according to one of claims 1 to 5, characterized in that the coating (14) of the cushioning threads (4) has a lower Shore A hardness than the embedded layer (20, 21, 22, 23). Press pad according to one of Claims 1 to 6, characterized in that the heat conducting threads (3) enclose the upholstery threads (4) in offsets (5, 6), in particular the number of offsets (5, 6) of the heat conducting threads (3) on each a fabric side is between 10 to 40 per cm ² , preferably 15 to 30 per cm ² . Press pad according to one of claims 1 to 7, characterized in that heat conducting threads (3) form on the outer sides of the press pad (16, 17, 18, 19) 10 to 40, preferably 15 to 30 contact points per cm ² and / or that Wärmeleitfäden ( 3) between the outer sides of the press pad back and forth. Press pad according to one of claims 1 to 8, characterized in that the thread density of the cushioning threads (4) is so large that the heat conducting threads (3) only below Compressing the coating (14) of the cushioning threads (4) pass between them, in particular the free distance between the cushioning threads (4) is less than the average diameter of the heat conducting threads (3). Press pad according to one of claims 1 to 9, characterized in that the heat conducting threads (3) do not project beyond the plane formed by the outermost points of the padding threads (4). Press pad according to one of claims 1 to 10, characterized in that the rubber-elastic material is a silicone elastomer, a fluoroelastomer and / or Fluorsilikonelastomer and / or the rubber-elastic material is provided with at least one heat stabilizer. Press pad according to one of claims 1 to 11, characterized in that the heat conducting filaments (3) consist of copper or a copper alloy and / or for the heat conducting filaments (3) metals such as copper, brass, aluminum, silver and / or alloys thereof and carbon and / or combinations of metal and carbon are used. Press pad according to one of claims 1 to 12, characterized in that in the coating (14) and / or the layer (20, 21, 22, 23) filling materials are distributed whose specific gravity is less than that of the rubber-elastic material, wherein the Fillers, in particular glass hollow spheres, powder, short cut fibers and / or microspheres exist. Press pad according to one of claims 1 to 13, characterized in that in the coating (14) and / or the layer (20, 21, 22, 23) Wärmeleitteilchen are distributed whose specific thermal conductivity is higher than that of the coating (14) or Layer (20, 21, 22, 23), wherein the Wärmeleitteilchen in particular as a powder and / or fibers of metal and / or carbon and / or as Carbonanotubes (CNT), in particular multiwall Carbonanotubes (MWCNT) are formed. Press pad according to one of claims 1 to 14, characterized in that the padding threads (4) have a diameter of 0.8 to 2.5 mm and the heat conducting threads (3) have a diameter of 0.15 to 0.8 mm. Press pad according to one of claims 1 to 15, characterized in that the heat conducting threads (3) have a core thread (9), which is wrapped by at least one wire (10) or ribbon or stranded or twisted around the wires (10) or ribbon , which consist of a material whose specific thermal conductivity is greater than that of the core thread (9) and / or that the core threads (11) of the cushioning threads (4) each formed from a core thread (12) and surrounding wires (13) or ribbon are made of a material whose specific thermal conductivity is greater than that of the core thread (12). Press pad according to one of claims 1 to 16, characterized in that the layer (20, 21, 22, 23) has passage channels which are open to the outer sides of the press pad (16, 17, 18, 19).

Images