EP2409829A2 - Pressure pad for a hydraulic press - Google Patents

Abstract

The press pad (7) comprises a primary impermeable layer (9) for fluids, which has an elastomeric material and linked fibers, and a secondary impermeable layer (10), which is connected with the primary impermeable layer. The primary impermeable layer is provided with multiple channels (15). The secondary impermeable layer is made of polymer, particularly silicon elastomer. A supporting tissue (12) is provided, which is made of fluoroelastomer or a fluorosilicon elastomer. The primary impermeable layer is made of carbon or metal wires, particularly brass, copper, stainless steel, or aluminum.

Description

introduction

The invention relates to a press pad for a hydraulic press having a first fluid impermeable layer comprising an elastomeric material and fibers associated therewith and having a second layer joined to the first layer which is also impermeable to fluids.

State of the art

Such a press pad is from the EP 0 235 582 A2 known. The prior art press pad is intended to serve in particular in the production of multilayer and flexible printed circuit boards for printed electronic circuits in so-called high-pressure presses. Press pads for the production of materials for electronic printed circuit boards are manufactured using high pressures (up to about 1000 N / cm ² or 100 bar) and at the same time high temperatures (up to about 220 ° C) by means of a lamination process. The sandwiched press pads contain a reinforcing layer of fibers, for example in the form of a central fiberglass fabric, in order to reduce the deformation both in the pressing operation as well as in the removal of the finished pressed material and the assembly with a new compact and thus to increase the service life of the press pad. In addition, in the case of press pads for printed circuit board production, non-stick layers, for example in the form of a film of polytetrafluoroethylene (PTFE), are frequently arranged on the surface. Further, it is important to prevent abrasion of fibers or particles from the press pad during operation of such high pressure press pads, as such wear would contaminate the printed circuit board material and thus result in quality degradation or even technical abuse thereof.

In addition, press cushions are also very frequently used in the production of wood-based materials with a coated surface. Such laminates are used primarily in the field of furniture production and as flooring materials. Thus, for example, on wood fiber boards ("chipboard" or MDF boards) decorative layers in the form of abrasion-resistant plastic films with a variety of decors (wood imitation, tile replica, stone replica, etc.) are applied. The connection between the decorative layer and the carrier material of the fiberboard is typically carried out using melamine resin, which under the action of pressure and temperature (up to 50 bar or 500 N / cm ² pressing pressure and up to 220 ° C pressing temperature) is cured in a laminating press.

Both in the application of press pads in the field of printed circuit board production, as well as the application of decorative layers on fiber materials, the press pads has the task of compensating for thickness or height tolerances in the hydraulic press area. Such thickness or height differences come about by deviations in the area of the material to be pressed (fiberboard or decorative film or printed circuit board starting materials), but especially in the press itself. Thus, the press lines typically dimensions of their heated press plates of a few meters, so that in addition to manufacturing tolerances also problems with a distortion of the plates by different temperature distribution in the press operation occur. Even with the so-called press plates, which come into contact with the pressed material on both sides, dimensional tolerances can occur. Thus, a first important characteristic of press pads is the compensation of such dimensional tolerances in the area of the system "hot plate press plate pressed product press plate hot plate". In order to exercise such a thickness compensation permanently, without damaging the press pad, the press pad must have sufficient elastic, that is, spring properties, have that convict it automatically after a pressure relief back to its original shape. Typically, elastomeric materials are used in the known press pads to obtain the desired spring properties. Silicone elastomers or fluoroelastomers or fluorosilicone elastomers in particular are frequently used in press pads because of their good temperature resistance and their resistance to various chemical substances.

Due to the good thermal conductivity to be demanded of press pads, which enables the necessary rapid heat flow from the hot plate, via the press pad and the press plate into the pressed material, press pads regularly comprise constituents of good heat-conductive materials, in particular of metals. Often copper and / or brass and / or stainless steel and / or other metal alloys are used for this purpose.

In principle, a distinction is made in the known press pads between those which are textile fabrics and those which have a closed material layer. A press pad with a closed material layer is for example from the DE 23 19 593 A or the EP 1 300 235 A known. In order to ensure lasting integrity even under high pressing pressures, as well as during the handling of the press pads, a supporting fabric is used in the silicone elastomer used embedded for example of bronze threads. In order to increase the thermal conductivity is in the press pad according to the EP 1 300 235 A a superficial projection of the metallic support fabric provided over the elastomeric material. To further increase the thermal conductivity, particles with higher thermal conductivity (metal powder, quartz powder) can also be introduced into the elastomer material.

As already indicated, it is also in many press pads to textile fabrics, which may be designed in particular as a woven, knitted or non-woven. In this way, due to the geometry of the press pad or the threads processed therein, a good shape change capability and therefore a good thickness compensation are ensured. This is especially true when the threads have a high inherent elasticity in a direction transverse to its longitudinal axis, in particular made of elastomeric material or have a tensile core (made of metal or a synthetic fiber), which is coated with an elastomeric material. Such press pads are for example from the EP 0 735 949 A , of the EP 1 136 248 A and the EP 1 779 999 A known in the form of woven press pads. Press pads based on crocheted fabrics are especially in the EP 1 033 237 A , of the EP 1 040 910 A and the EP 1 040 909 A disclosed. To give the press pad a particularly good point elasticity, it is from the EP 1 386 723 A known to use alternately coated with elastomer threads, whose elasticity is transverse to the longitudinal axis of the thread alternately higher or lower. Furthermore, press pads or press pad press plate combinations are known in which a contiguous cavity of the press pad or the combination is filled with a flowable material at the operating temperature of the press ( EP 2 189 276 ).

Disadvantage of the mat-like press pad according to the DE 23 19 593 A is their comparatively high rigidity and lack of selective elasticity. By contrast, press pads, which are designed as a textile fabric, comparatively expensive to manufacture. This is especially true when covered threads are used, possibly in different ways, including in the first step, the material of the soul must be provided in the course of an extrusion process with the elastomeric material of the shell. The textile technology processing (weaving or knitting), which takes place in a second step, once again requires a great deal of effort, since the processed elastomeric threads or metal threads, in contrast to conventional textiles, are much more difficult and can be processed at a lower speed.

task

The invention has for its object to propose a press pad, which is characterized by a good punctual elasticity, at the same time as easy to manufacture.

solution

Based on a press pad of the type mentioned, the underlying object is achieved in that the first layer is provided on its side facing the second layer with a plurality of channels in which there is a flowable material at least at the operating temperature of the press and the at least sealed fluid-tight by the second layer.

On the arrangement and dimension of the channels, the elasticity properties of the pad can be set very individually and easily over its surface. Also, on the elastic properties of the elastomeric material on the one hand and the flowable material at operating temperature of the material in the channels on the other hand, the cushioning properties can be varied according to the invention within very wide limits. In addition, it is easily possible to realize different effective elasticities in different zones of the press pad.

According to a preferred embodiment, in addition to the first and the second layer, a third layer is provided, which is connected on the side facing away from the second layer of the first layer with this and is also impermeable to fluids. In this case, either the first layer is also provided on its side facing the third layer with a further plurality of channels, or the third layer is provided on its side facing the first layer with a further plurality of channels. In the latter case, as well as the first layer, the third layer comprises an elastomeric material and associated fibers. In any case, the further plurality of channels is fluid-tightly sealed by the connection between the first layer and the third layer.

Two levels of channels are thus created in the aforementioned manner, which further increases the possibilities for shaping the elasticity distribution and elasticity characteristics.

Typically, the press pad according to the invention, based on existing press systems, rectangular and in at least one edge region, preferably circumferentially in all edge regions, free of channels. The width, depending on the respective Heizplattenformates, the at least one edge region is preferably between 1 cm and 20 cm. In the abovementioned edge regions, it is possible in a simple manner to produce a full-surface, continuous fluid-tight connection between the first layer and the second layer or the first layer and the third layer, since a comparatively large-area contact can be realized. The edge regions are therefore particularly suitable for closing the channels in their frontal direction in order to achieve the fluid tightness in this direction.

It is particularly favorable if the first layer and the second layer and / or the first layer and the third layer are adhesively bonded or welded to one another, wherein in particular the technique of laser welding or ultrasonic welding can also be advantageously used.

According to a preferred development of the invention, the plurality of channels comprises a first group of channels which run parallel to one another, wherein preferably there is a second group of channels, which in turn run parallel to each other and perpendicular to the channels of the first group. It is possible that the channels of both groups communicate with each other or not. In the former case, a system of intersecting and interconnected channels thus arises. These then preferably extend within a plane or form a single "channel layer". In the event that the two groups do not communicate with each other, they are preferably spaced apart as seen in the thickness direction of the press pad, resulting in two separate "channel layers". With intersecting groups of channels, a particularly homogeneous distribution of the channels over the surface of the press pad is achieved, so that local deviations in the elasticity of the press pad can be small.

With regard to the production of the press pad according to the invention, the channels can be introduced into the relevant layer by molding technology, in particular by casting or doctoring into a suitable mold or by forming, in particular by embossing, stamping or cutting, or by removal, in particular by laser processing or milling ,

In order to obtain a particularly well-predictable elastic behavior of the pad over its entire surface, a certain number of channels or all channels should be completely filled with the material flowable at the operating temperature of the press. Under a "flowable material at the operating temperature of the press" is any fluid, that is both a compressible fluid (gas) but also any incompressible fluid (liquid) are understood. The material can also be in solid state at temperatures below the operating temperature. Suitable fluids for the press pad according to the invention are in particular air or other (inert) gases or oils (mineral or synthetic oils or mixtures thereof) or (inert) liquids or metals with a low melting point. These are, in particular, lead or tin or alloys which contain at least one of the abovementioned elements and which may be in a solid state of aggregation at room temperature.

While the plurality of channels may also be partially arranged both in the first and the second layer, as well as in the first and third layers, it is particularly advantageous for the second layer and / or the third layer for a film to be easier to produce having a thickness of between 10 μm and 1000 μm and comprising or consisting of a polymer, preferably for example polytetrafluoroethylene (PTFE) or fluororubber or silicone or fluorosilicone elastomers.

In order to ensure the long-term integrity of the press pad, even under the high constantly changing pressure load, the first layer and / or the second layer and / or the third layer may comprise a support fabric, which in the elastomeric material, preferably a silicone elastomer or a fluoroelastomer or a fluorosilicone elastomer or a blended elastomer containing at least two of the aforementioned elastomers is embedded. A measure increasing the stability of the press pad can be that the fibers contained in at least the first layer high-temperature synthetic fibers, in particular those of aramid, Kevlar, polyester, melamine resin, carbon, glass, or metal wires, in particular those of brass, copper, stainless steel , The fibers may be in the form of monofilament or multifilament yarns, preferably the fibers being present as individual staple fibers with a length of between 1 mm and 50 mm and / or in the form of a textile fabric, in particular a woven, knitted, knitted, laid or nonwoven fabric ,

Since elastomeric materials inherently have a moderate thermal conductivity, the elastomeric material of the first layer and / or the third layer and / or the material flowable at the operating temperature of the press may contain particles having a high thermal conductivity, in particular metal powder or quartz powder. This makes it possible to accelerate heat transfer to the material to be pressed, in particular in press systems which are operated with short cycle times, which in turn allows the heating plate temperature to be selected to be lower.

Typically, the area fraction of the channels, based on the total area of the press pad, is between 5% and 50%, preferably between 10% and 20%. If channels are arranged in multiple "channel layers", the channels must be considered in all layers. If the channels are arranged congruently one above the other in several layers, only the channels of a single layer, in the calculation of the aforementioned area ratio, are to be used.

While the distribution of the channels in the area of the heating plates or press plates is usually homogeneous in "unproblematic" press systems, in the case of pressure-problematic press systems with different pressure distribution, an inhomogeneous distribution of the channels can be provided. The inhomogeneity may be of the shape that in certain areas of the press pad, the distance of adjacent channels to each other is greater or smaller than in other areas of the press pad and / or in certain areas of the press pad, the dimensions of the channels, in particular their width and / or Depth is greater or less than in other areas of the press pad.

Finally, it is provided according to the invention that the width of the channels between 5 mm and 20 mm and / or the depth of the channels, measured in a direction perpendicular to a surface of the press pad, between 1 mm and 5 mm and / or the clear distance adjacent, parallel channels from each other between 1 mm and 50 mm.

embodiments

The invention will be explained in more detail with reference to several embodiments of a press pad, which are illustrated in the drawing.

Fig. 1:

einen Vertikalschnitt durch eine Heizpresse,

Fig. 2:

einen Vertikalschnitt durch eine erste Ausführungsform eines Presspolsters in explosionsartiger Darstellung,

Fig. 3:

einen Vertikalschnitt durch eine zweite Ausführungsform eines Presspolsters,

Fig. 4:

einen Vertikalschnitt durch eine dritte Ausführungsform eines Presspolsters,

Fig. 5:

eine perspektivische Ansicht auf die erste Schicht des Presspolsters gemäß Figur 3 und

Fig. 6:

eine Draufsicht auf einen Eckbereich der ersten Schicht des Presspolsters gemäß Figur 3.

It shows:

Fig. 1:

a vertical section through a hot press,

Fig. 2:

a vertical section through a first embodiment of a press pad in an exploded view,

3:

a vertical section through a second embodiment of a press pad,

4:

a vertical section through a third embodiment of a press pad,

Fig. 5:

a perspective view of the first layer of the press pad according to FIG. 3 and

Fig. 6:

a plan view of a corner region of the first layer of the press pad according to FIG. 3 ,

An in FIG. 1 schematically illustrated press 1 is constructed mirror-symmetrically to a horizontal center plane 2 and has two provided with a plurality of heating channels 3 heating plates 4, and two metallic press plates 5, facing with their facing each other, in particular engraved, surfaces in the middle arranged pressed material. The product to be pressed is, for example, an MDF board to be coated, which is covered on both sides with a decorative film which is to be connected to the MDF board by means of a melamine resin under pressure and temperature.

To compensate for thickness tolerances in the pressed material 6 and other height differences both in the press plates 5, as well as in the heating plates 4 (for example, by default), is located between a press plate 5 and the associated heating plate 4, a press pad 7. The press pad protrudes with edge regions 8 on all sides on the rectangular heating plate 4 and the same dimension having press plate 5 addition, which serves for fastening purposes.

The structure of the press pad 7 is in the vertical section according to FIG. 2 closer
illustrated. The press pad 7 is shown in a kind of exploded view, in which a central first layer 9 and an upper second layer 10 and a lower third layer 11 are spaced apart for clarity. In reality, however, these aforementioned three layers 9, 10, 11 are firmly and in particular fluid-tightly interconnected as will also be explained in more detail below.

The press pad 7 and also the first layer 9 are constructed symmetrically to the center plane 2. In the middle plane 2 is located in the interior of the first layer 9, embedded in the elastomeric material, in particular silicone elastomer, a support fabric 12 in cloth weave, of which a wavy extending warp thread and the cut weft threads are visible. Above an upper side 13 of the first layer 9 and below a lower side 14 of the first layer 9 are the second layer 10 and the third layer 11.

Essential for the press pad 7 according to the invention is the presence of a first plurality of channels 15 in the upper side 13 of the first layer 9 and, in the case of present embodiment - also a second plurality of channels 16 in the bottom 14 of the first layer 9. Both the channels 15 and the channels 16 each extend within their "group", but also with respect to the channels 15, 16 of both groups parallel to each other and are arranged equidistant from each other. The channels 15 in the top 13 of the first layer 9 are offset by the amount of half the distance of each adjacent channels 15, 16 offset from each other, so that there is a typical "gap" arrangement.

To obtain fluid-tight sealed channels 15, 16, the top 13 of the first layer 9 is glued or welded to the second layer 10. A possible adhesive layer of a known adhesive is not shown in the figures for the sake of simplicity. The second layer 10 is a foil of, for example, silicone elastomer. The same applies with respect to the underside of the press pad 7, for the connection of the third layer 11 with the bottom 14 of the first layer 9. As will be described in more detail below with reference to a further embodiment of the invention, edge regions of the press pad 7 are circumferentially free from Channels 15, 16, so that the latter are also closed fluid-tight frontally. In the present case of the press pad 7, the channels 15, 16 are filled with air. But also the filling with any other gas is conceivable, as well as a filling with any liquids or with a metal or a metal alloy, which is or at the operating temperature of the press (from about 80 to 220 ° C) in the liquid state.

In contrast to the three-layer construction according to FIG. 2 owns the press pad 17 according to FIG. 2 only a two-layer construction. Here is a fluid-tight connection between a first layer 19 and a second layer 20 before. Starting from a top 21 of the first layer 19 are channels 22 in the first layer 19. The channels 22 are parallel and equidistant in a measured in a direction parallel to the top 21 of the press pad 17 distance 23 to each other.

A depth 24 of the channels 22 is (measured from the top 21 of the first layer 19) about 1 mm. A width 25 measured perpendicular to the depth 24 is 2 mm. A thickness 26a of the first layer 19 is 2 mm, whereas a thickness 26b of the second layer 20 is about 1 mm.

From the view according to FIG. 5 can be seen that the press pad 17 according to FIG. 3 not only has a first group of mutually parallel channels 22, but also a second group of perpendicular thereto, running parallel and equidistant within the second group channels 28. In this way, a kind of check pattern is formed on the top 21 of the first layer 19 ,

FIG. 6 illustrates that peripheral edge portions 30 of the press pad 17 are free of channels. The edge regions 29, 30 have a width 31, 32 of about 1 cm. The edge regions 29, 30 preferably protrude laterally beyond the heating plates 4 and press plates 5 of the press 1 and thus, unlike a central part of the press pad 17 provided with the channels 22, 28, are not in the area of transmission of compressive forces during the pressing operation. Due to the edge region 29, 30, the channels 22, 28 terminate in front of the edges 33, 34 of the press pad 17 and thus provide a fludend closure of the channels 22, 28 on the face side.

An alternative embodiment of a press pad 27 is shown in a vertical section in FIG FIG. 4 shown. The press pad 27 consists of a first layer 39 and a fluid-tightly bonded thereto second layer 40, both of which consist of an elastomeric material, in particular a silicone elastomer and both have the same thickness 35 of about 1 mm.

The equidistant and mutually parallel channels 36 of the press pad 27 have a circular cross-section and are each formed in half in the first layer 39 and the second layer 40. In each layer 39, 40 are thus semi-circular in cross-section channel halves, which complement each other when joining the identically constructed first and second layers 39, 40 to the complete channel 36 with circular cross-section. In the production of the press pad 27, therefore, it is important for the spacing 38 of adjacent channels 36 to be exactly the same and for the fluid-tight connection of the first and second layers 39, 40 to take place in such a way that the channels 36 form with a circular cross section. The diameter 37 of the channels 36 is 1.5 mm, which corresponds to a (length) proportion of about 43% with a total thickness 41 of the press pad of 3.5 mm.

The elastomeric materials of all the aforementioned press pads 7, 17, 27 may be provided with particles of heat-conductive material, in particular metal powder, for the purpose of increasing the thermal conductivity. The same applies to the material with which the channels 15, 16, 22, 28 are filled, provided that this is a liquid, such as oil.

LIST OF REFERENCE NUMBERS

1

Press

2

midplane

3

heating duct

4

heating plate

5

press plate

6

pressed material

7

press pad

8th

border area

9

First shift

10

Second shift

11

Third shift

12

supporting tissue

13

top

14

bottom

15

channel

16

channel

17

press pad

18a

thickness

18b

thickness

19

layer

20

layer

21

top

22

channel

23

distance

24

depth

25

width

26a

thickness

26b

thickness

27

press pad

28

channel

29

border area

30

border area

31

width

32

width

33

edge

34

edge

35

thickness

36

channel

37

diameter

38

distance

39

First shift

40

Second shift

41

thickness

Claims (16)

Press pad (7, 17, 27) for a hydraulic press (1) having a first fluid impermeable layer (9, 19, 39) comprising an elastomeric material and fibers associated therewith, and one with the first layer (9, 19 , 39) connected to the second layer (10, 20, 40), which is also impermeable to fluids, characterized in that the first layer (9, 19, 39) on its the second layer (10, 20, 40) facing side with a plurality of channels (15, 22, 28, 36) is provided, in which there is a flowable material at least at the operating temperature of the press (1) and which are fluid-tightly sealed at least by the second layer (10, 20, 40). Press pad according to claim 1, characterized by a third layer (11) which is connected to the second layer (10) facing away from the first layer (9) with this and is also impermeable to fluids, wherein either the first layer (9) is also provided on its third layer (11) facing side with a further plurality of channels (16) and / or the third layer is provided on its side facing the first layer with a further plurality of channels, in the latter case, the third Layer has an elastomeric material and associated fibers and the further plurality of channels (16) through the connection between the first layer (9) and the third layer (11) is fluid-tightly sealed. Press pad according to claim 1 or 2, characterized in that the press pad (7, 17, 27) is rectangular and that at least one edge region (29, 30), preferably circumferentially all edge regions (29, 30), of the press pad (7, 17, 27) are free of channels (15, 16, 22, 28, 36), wherein the width (31, 32) of the at least one edge region (29, 30) is preferably between 1 cm and 20 cm. Press pad according to one of claims 1 to 3, characterized in that the first layer (9, 19, 39) and the second layer (10, 20, 40) and / or the first layer (9) and the third layer (11) glued or welded together. Press pad according to one of claims 1 to 4, characterized in that the plurality of channels (22, 28) comprises a first group of channels (22) which run parallel to one another, preferably a second group of channels (28). is present, which in turn run parallel to each other and perpendicular to the channels (22) of the first group, more preferably, the channels (22, 28) of both groups communicate with each other or not. Press pad according to one of claims 1 to 5, characterized in that channels (15, 16, 22, 28, 36) by molding technology, in particular by casting or doctoring into a corresponding shape, or by forming, in particular by embossing, punching or cutting, or erosive , In particular by laser machining or milling, are introduced into the relevant layer. Press pad according to one of claims 1 to 6, characterized in that a certain number or all channels (15, 16, 22, 28, 36) are completely filled with the at operating temperature of the press (1) flowable material. Press pad according to one of claims 1 to 7, characterized in that in the channels (15, 16, 22, 28, 36) located material is a gas, in particular air or other inert gases, or a liquid, in particular an oil or other inert Liquids, or a metal which is solid at room temperature, but liquid at the operating temperature of the press (1), in particular lead, tin or an alloy containing the aforementioned elements. Press pad according to one of claims 1 to 8, characterized in that the second layer (10, 20, 40) and / or the third layer (11) is a film having a thickness between 10 .mu.m and 1000 .mu.m and having a polymer, preferably a silicone elastomer. Press pad according to one of claims 1 to 9, characterized in that the first layer (9, 19, 39) and / or the second layer and / or the third layer (11) has a supporting fabric (12), which in the elastomeric material , preferably a silicone elastomer or a fluoroelastomer or a fluorosilicone elastomer or a blended elastomer, containing at least two of the aforementioned elastomers embedded. Press pad according to one of claims 1 to 10, characterized in that the fibers contained in the first layer (9, 19, 39) high-temperature resistant synthetic fibers, in particular those of aramid, melamine resin, Nomex, Kevlar, carbon, Glass, or metal wires, in particular those of brass, copper, stainless steel, aluminum, are. Press pad according to one of Claims 1 to 11, characterized in that the fibers contained in the first layer (9, 19, 39) are in the form of monofilament or multifilament yarns, preferably the fibers being individual staple fibers having a length of between 1 mm and 50 mm mm and / or in the form of a textile fabric, in particular a woven, knitted, knitted, laid or nonwoven fabric. Press pad according to one of claims 1 to 12, characterized in that in the elastomeric material of the first layer (9, 19, 39) and / or the third layer (11) and / or in the at operating temperature of the press (1) flowable material Particles with a high thermal conductivity, in particular metal powder or quartz powder, are embedded. Press pad according to one of claims 1 to 13, characterized in that the area proportion of the channels (15, 16, 22, 28, 36), relative to the entire surface of the press pad (7, 17, 27), between 5% and 50% , preferably between 10% and 30%. Press pad according to one of claims 1 to 14, characterized in that the distribution of the channels over the surface of the press pad is inhomogeneous, in particular that in certain areas of the press pad, the distance between adjacent channels to each other larger or smaller and / or the dimensions of the channels, in particular their Width or depth, larger or smaller than in other areas of the press pad. Press pad according to one of claims 1 to 15, characterized in that the width (25, 37) of the channels (15, 16, 22, 28, 36) between 5 mm and 20 mm and / or the depth (24) of the channels ( 15, 16, 22, 28, 36), measured in a direction perpendicular to a surface of the press pad, between 1 mm and 5 mm and / or the spacing (38) of adjacent parallel channels (36) from 1 mm to 50 mm ,

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