CH699390B1 - Composite sheet and process for their preparation. - Google Patents

Abstract

A chemical-resistant, rigid composite panel comprises a rigid core layer (2) arranged between two cover layers (4, 4a) and a border (10) connecting the two cover layers. Each cover layer has an outer layer (6, 6a) made of a fluoroplastic and an adhesion layer (8, 8a) arranged on the inside thereof, which interacts with the adjacent core layer in a form-fitting manner. The border is formed of the same fluoroplastic as the cover layers and welded with these to a circulating medium-tight termination.

Description

Technical area

The invention relates to a composite panel according to the preamble of claim 1 and a method for their preparation according to claim 8.

State of the art

Plate-shaped elements made of fiber-reinforced plastics, such as glass fiber reinforced plastics, are already known in large numbers and variety. For the choice of plastic material, the most diverse criteria are applied, which include not only the mechanical and thermal requirements of the component, but also cost considerations. Very often used are, for example, epoxy resins, polyester resins and melamine resins. However, a disadvantage of such resins lies in their low chemical resistance.

Although there are many plastics with excellent chemical resistance, but due to their mechanical properties as well as cost reasons, these can only be used to a limited extent for the production of fiber-reinforced plastic components.

For the storage and transport of aggressive media, it is known to line containers and pipes with an inner layer of a chemical-resistant plastic, in particular of a fluoroplastic. For example, DE-OS 1 936 118 describes such a container which has a mechanically or chemically roughened fluoroplastic body with a jacket of glass fiber reinforced epoxy or polyester resin arranged around it. DE-PS 10 203 123 C1 describes a composite pipe with an inner layer of a polytetrafluoroethylene (PTFE) and a cover layer of fiber-reinforced plastic, which are non-positively and positively connected to each other via an intermediate layer.

Chemical-resistant lining laminates are known for use in corrosive environments, comprising a layer of a fluoroplastic with a one-sided embedded adhesion promoter in the form of a knitted fabric. The primer is intended to attach the laminate to the structure to be lined. However, the fluoroplastics used for such liner laminates are quite pliable, especially in the heated state, so that during processing - e.g. when welding together individual sections - must be mechanically supported. Also, their bending stiffness is comparatively low even at room temperature, so they can not be used directly as structural elements.

Presentation of the invention

The object of the invention is to provide a rigid chemical resistant composite panel and to provide a method for their preparation.

The object is achieved by the characterizing features of claim 1 and by the manufacturing method according to claim 8.

The composite panel according to the invention comprises a rigid core layer arranged between two cover layers and a border which connects the two cover layers. By virtue of the fact that each cover layer comprises an outer layer of a fluoroplastic and an adhesion layer arranged on the inside thereof, which interacts with the adjoining core layer in a form-fitting manner, the chemical-resistant cover layers are provided with the mechanical stability of the intermediate core layer. By virtue of the fact that the border is formed from the same fluoroplastic as the cover layers and welded to a peripheral medium-tight seal, the entire composite panel becomes a chemical-resistant unit.

The novel composite panels can be used in particular as a cover or as sidewalls for wet chemical systems (so-called "wet benches"), as linings for wind turbine housing (so-called "nacelles") and in the semiconductor industry as a wafer holder plates.

According to a second aspect of the invention, a method for producing a composite panel is given, wherein: inserting a first cover layer with an upwardly facing adhesive layer into the lower mold half of a pressing tool, laying a core layer thereon, wherein the core layer has been preheated to a temperature above the softening point of the core layer material; on it a second cover layer hangs down with adhesive layer, closing the tool with its upper mold half compressing the tool with a predetermined pressing pressure for a predetermined holding time, thereby forming a composite blank plate; the tool cools during the holding time and then removes the composite slab blank therefrom; the entire circumference of the composite slab blank fitted with matching sections of the fluoroplastic and by welding the sections with the cover layers and each other forms the circulating medium-tight closure.

Preferred embodiments of the invention are defined in the dependent claims.

The welded to the two cover layers welded to a peripheral end border can be shaped in itself in various ways. For example, it may be formed from rectangular strips of fluoroplastic whose width substantially corresponds to the distance between the two cover layers. To form the circumferential termination, it must then be welded along the edges of the composite panel. Advantageously, however, the border is formed from a U-profile whose inner leg distance substantially corresponds to the distance between the outer sides of the two outer layers. Thus, the skirt portions may be slid over the edges of the cover layers and at the leg tips of the U-profile, i. at a certain distance from the edges of the composite panel to be welded. This simplifies the manufacturing process and reduces the susceptibility of the composite panel to edge damage.

In principle, come as a material for the outer layers of various fluoroplastics in question. Advantageously, the fluoroplastic is a perfluoroethylene-propylene copolymer.

The adhesion layer located on the inside of the cover layers is intended to interact positively with the adjacent core layer in order to bring about an anchoring of the cover layer to the core layer. For this purpose, the adhesion layer is advantageously a partially embedded and partially projecting fabric or fabric in the outer layer of the cover layer, the partially protruding parts of which interact with corresponding depressions of the core layer.

In principle, the core layer may consist of different materials. Preferably, it is formed from a fiber-reinforced plastic, which is characterized among other things by an advantageous ratio of the mechanical properties in relation to the weight. In principle, as the matrix for the fiber-reinforced plastic, various polymers such as epoxy resins or polyester resins in question, and as reinforcing fibers, glass fibers, carbon fibers or synthetic fibers may be used. In a preferred embodiment, the core layer is a glass mat reinforced thermoplastic (also referred to as "GMT"), for example, glass mat reinforced polypropylene. In a further embodiment, the core layer is a carbon fiber mat reinforced thermoplastic, in particular carbon fiber reinforced polypropylene or polyetheretherketone (PEEK).

When pressing under elevated temperature penetrate the projections of the adhesive layer in the softened core material and form matching wells.

Accordingly, according to a preferred manufacturing method, a core layer of glass mat reinforced polypropylene is used, wherein the blank is preheated to 180 to 220 ° C and the pressing is 2 to 60 minutes long.

It is understood that the individual layers can be dimensioned according to the intended use. For example, depending on the bending load, a more or less thick core layer can be provided. If appropriate, a multi-layer core layer can also be used.

In principle, however, it is also conceivable to use a thermoset matrix instead of a thermoplastic matrix for the core layer. However, in such a case, a modified manufacturing method must be used, in which the positive connection between the adhesion layer and the core layer is not produced by thermal impressions. For this purpose, for example, an adhesion layer having protrusions forming a regular pattern may be provided; the core layer is then to be provided with a corresponding pattern of depressions.

Brief description of the drawings

Embodiments of the invention are described below with reference to the drawings, in which: <Tb> FIG. 1 <sep> a section of a composite panel, in vertical sectional view; <Tb> FIG. 2 <sep> an edge region of a composite panel being produced, prior to the compression of the cover layers on the core layer, in a vertical sectional view; <Tb> FIG. 3 <sep> the edge region of the composite panel of Figure 2 after completion, in vertical sectional view; and <Tb> FIG. 4 shows a corner region of the finished composite panel of FIG. 3, in plan view.

Ways to carry out the invention

The composite panel shown in the figures comprises a rigid core layer 2, which is arranged between two cover layers 4 and 4a. Each of these cover layers 4 and 4a has an outer layer 6 or 6a of a fluoroplastic and an adhesion layer 8 or 8a arranged on one side thereof. In this case, each of the cover layers is oriented such that its adhesive layer faces the core layer arranged between the cover layers.

The core layer 2 is formed for example of a fiber-reinforced plastic, in particular made of glass mat reinforced polypropylene. The outer layer of each cover layer is formed for example from a perfluoroethylene propylene copolymer (also referred to as FEP), in which the adhesion layer is embedded, for example in the form of a knitted fabric or fabric of glass fibers, carbon fibers or synthetic fibers. As shown particularly in FIGS. 2 and 3 there, however, only schematically - shown, the adhesion layer comprises a plurality of small projections, which protrude from the fluoroplastic bed of the cover layer. These projections engage in corresponding recesses of the adjacent core layer and thereby form a positive connection between the cover layer and the core layer. As a result, in particular slippage of the layers in the plane of the composite plate is avoided.

In addition, the composite plate has a border 10, which is formed from the same fluoroplastic as the cover layers. The border 10 is welded to the two cover layers 4 and 4a by appropriate welds to a circumferential medium-tight termination. As can be seen in particular from FIGS. 3 and 4, the border 10 can be made of U-shaped profile parts 12, 12a, etc., which are pushed over the edges of the composite plate. In the example shown, the profile parts 12 and 12a at 45 ° bevelled end edges 14 and 14a. To form the medium-tight closure corresponding welds 16 and 16a between the profile parts 12 and 12a and the upper cover layer 2, a weld 18 between the two beveled end edges 14 and 14a and a corner seam 20 between the straight end edges 22 and 22a of the two profile parts appropriate. It is understood that corresponding welds are also to be attached to the other, not visible in FIG. 4 connection zones of the composite panel. As a result, the welds should form a circumferential medium-tight completion of the composite panel.

To produce the composite panel, first two blanks of a laminate comprising a fluoroplastic layer having an adhesion layer embedded on one side therein are provided. For example, for this purpose, a glass mesh-laminated FEP lining laminate can be cut. Thereafter, the first blank of the laminate is placed with the adhesive layer facing up in the lower mold half of a tool. Subsequently, a corresponding blank of the core layer material, for example a glass mat reinforced thermoplastic is placed, which was first preheated to a temperature above the softening point of the thermoplastic matrix. Finally, the second blank of the laminate is placed on the core layer with the adhesive layer facing down and the tool is closed with its upper half of the mold.

As a result, the tool is compressed in a hot press to form a composite slab blank. The pressing pressure is maintained for a predetermined holding time. During this time, the tool is cooled so that the thermoplastic matrix can solidify. Thereafter, the blank is removed from the pressing tool. Finally, as already explained above, the entire circumference of the blank is fitted with suitable sections of the fluoroplastic and formed by welding the sections with the cover layers as well as with each other around the surrounding medium-tight closure.

The above-described method assumes that the softening temperature of the core layer material must be lower than the maximum allowable processing temperature of the fluoroplastic laminate used for the cover layers. In any case, an excessive heating of the outer layers during the pressing process is to be avoided.

Examples

The production of composite panels with a 9.6 mm thick core layer and various dimensions (see below) is described below:

For the core layer in each case two corresponding blanks of a glass mat reinforced polypropylene material (GMT B 110 F 30, available from Quadrant Plastic Composites AG, Lenzburg, Switzerland) were provided with a thickness of 4.8 mm. These blanks were preheated in an infrared continuous furnace to 220 ° C within about 4 minutes.

For the outer layers were appropriate blanks of a glass-knitted laminated FEP lining laminate (FEP GGS 60 or FEP GGS 90 with a layer thickness of about 1.55 or 2.3 mm, available from Quadrant EPP AG, Lenzburg, Switzerland). These blanks were not preheated.

In general, the pressing tool was preheated to about 80 ° C. Then the first FEP blank was placed with the adhesive layer facing up into the tool, then the two pre-heated GMT blanks were placed one at a time, and finally the second FEP blank with the adhesive layer laid down on top of the GMT blank. Subsequently, the pressing pressure was built up. As a result, the crimping tool with the blanks contained therein was allowed to cool, keeping the pressing pressure. Typically, a temperature of 30 ° C is reached after about 60 minutes. At this time, the pressing pressure is released and removed the resulting composite slab blank.

Dimensions of the composite panels produced (length × width) and pressing pressures used: 30 × 30 cm <2>, 400-ton press, pressing pressure = 444 kp / cm <2> <tb> (a) <sep> (43541.5 kPa) 100 x 100 cm <2>, 1500 ton press, pressing pressure = 150 kp / cm <2> <tb> (b) <sep> (14709.9 kPa) 90 × 90 cm <2>, platen press, pressing pressure = 2 kp / cm <2> <> <tb> (c) <sep> (196.1 kPa)

To form the border, U-shaped profile parts of FEP with a thickness of e.g. 1.5 mm, a leg length of e.g. 10 mm and an inner leg distance of e.g. 8 mm (corresponding to the total thickness of the composite panel) over the edges of the composite panel blank. The cutting of the profile parts and their welding with the outer layers is carried out as explained above.

Claims (9)

A composite panel comprising a rigid core layer (2) arranged between two cover layers (4, 4a) and a border (10) connecting the two cover layers, characterized in that each cover layer has an outer layer (6, 6a) of a fluoroplastic and an inner side arranged thereon adhesion layer (8, 8a) which cooperates positively with the adjacent core layer, and that the border of the same fluoroplastic as the cover layers is formed and welded thereto to a circulating medium-tight termination. 2. Composite panel according to claim 1, wherein the border (10) from a U-profile (12) is formed. A composite panel according to claim 1 or 2, wherein the fluoroplastic is a perfluoroethylene-propylene copolymer. 4. Composite panel according to one of claims 1 to 3, wherein the adhesion layer (8, 8a) of the respective cover layer (4, 4a) in its outer layer (6, 6a) partially embedded and partially projecting fabric or fabric, the partial projecting parts cooperate with corresponding recesses of the core layer. 5. Composite panel according to one of claims 1 to 4, wherein the core layer is formed of a fiber-reinforced plastic. 6. Composite panel according to claim 5, wherein the core layer of a glass mat reinforced thermoplastic, in particular of glass mat reinforced polypropylene, is formed. 7. Composite panel according to claim 5, wherein the core layer of a carbon fiber mat reinforced thermoplastic, in particular carbon fiber mat reinforced polypropylene or polyetheretherketone is formed. 8. A method for producing a composite panel according to claim 1, wherein: - a first cover layer with upwardly facing adhesive layer in the lower mold half of a pressing tool inserts, - Laying on a core layer, wherein the core layer was preheated to a temperature above the softening point of the core layer material; - it hangs up a second cover layer with downwardly facing adhesive layer, - The pressing tool closes with its upper mold half, - Pressing the pressing tool with a predetermined pressing pressure for a predetermined holding time, whereby a composite plate blank is formed, - The pressing tool still cools during the holding time and then removes the composite slab blank therefrom; - The entire circumference of the composite slab blank fitted with matching sections of the fluoroplastic as a border and forms by welding the sections with the cover layers and each other the circumferential medium-tight closure. 9. The method of claim 8, wherein the thermoplastic core layer material is glass mat reinforced polypropylene, the blank is preheated to 180 to 220 ° C and the holding time is 2 to 60 minutes.