DE2939377C2 - Composite molded part made from a film or sheet made from a fluoropolymer and from a glass or mineral fiber fabric, as well as glass or mineral fiber fabric intended for this purpose - Google Patents

Description

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Lining with polytetrafhiethylene (im following PTFE) from z. B. Apparatus, containers and pipelines have long been state of the art. Of the The purpose of such linings is the use of corrosion resistance, non-wettability or also the low coefficient of friction of PTFE. The attachment of the PTFE lining to the workpieces to be lined creates difficulties because PTFE cannot be wetted by adhesives and, when mechanically fastened, tends to flow due to its low permanent pressure resistance, especially at elevated temperatures attaching side of the PTFE liner, e.g. B. by Etching with alkaline earths or by electrical discharges that cause microscopic burnouts, PTFE can be made bondable, however, the surfaces pretreated in this way tend to have only a molecular thickness as a result treated surface gradually lose their wettability.

For the fastening of linings, other fluoropolymers are also bad or even bad are not wettable by adhesives, but have a real thermoplastic behavior, a melting of a glass fiber fabric into the surface of the Fluoropolymers are already known as a base for an adhesive. According to US-PS 39 34 064 are Foils or plates made of polychlorotrifluoroethylene, perfluoroethylene-propylene, perfluoroalkyl vinyl ether or polyethylene-tetrafluoroethylene by melting or Melting connected to a fabric knitted from glass fibers. To improve the fusion bond can the knitted fiberglass z. T. from monofilaments of thermoplastically processed perfluorinated Polymers are made.

By DE-OS 25 47 547 a process is published that the melting down of glass fabrics into the outer surface of fluoroplastics pipelines. In the end a process was protected by US-PS 37 79 854 to melt glass fabric into the surface of polyvinylidene fluoride or polyvinylidene copolymers and thus create substrates that can be bonded.

In each case, however, it is a question of the connection of fluoropolymers which can be processed in the molten state with glass fiber fabrics or Knitted, which by heat and possibly additional pressure in the surface of the real thermoplastic

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" ⁰ elastic fluoropolymer moldings are embedded.

The films and sheets made of fluorothermoplastics, the can be used as lining elements by the prior art described above however, with regard to their heat resistance, permeation and the manufacturing price PTFE films and - Place plates underneath.

A compound of glass fibers, mineral fibers or whose fabrics with PTFE is because of the lack of thermoplastic properties of this plastic not possible. PTFE does not become liquid even after it has reached its melting point (gel point) at 327 ° C and it does not wet glass, even in the gel state. However, it is known from plastics process engineering that thermoplastic fluoropolymers, such as perfluoroethylene propylene (hereinafter FEP) and periluoroalkoxy (Perfluoroalkyl perfluorovinyl ether) (in the following * -jden PFA), Wet PTFE well in its thermoplastic liquid state and, on the other hand, are able to do so in this State of melting glass fibers at the same time.

Recently, monofilament fabrics (from FET) on the market, fabrics made from PFA are being developed or tested by manufacturers.

It is the object of the invention. Composite molded parts in To create the form of films and plates that have a wettable side by adhesives, which is a safe possibility of connection with the substrate and their wettability by adhesives is not dependent on time, while the opposite side consisting of the fluoropolymer the molded part has high corrosion and temperature resistance as well as low wettability and has a low coefficient of friction.

According to the invention, this object is achieved by using polytetrafluoroethylene as a fluoropolymer for the composite molding. The wettability is achieved in that a fabric made of thermoplastic fluoroplastic wires (monofilament fabric), for example made of FEP or PFA is thermally welded to the PTFE part by pressing with simultaneous exposure to heat, wherein this fabric made of fluorothermoplastics in turn is glass fibers, mineral fibers or their fabrics / Knitted fabric tightly binds. With the help of a fabric mat attached in this way, the composite molding can be made on the usual Paths are fastened to the subsurface by connecting materials.

An advantageous embodiment of the lias or mineral fiber fabric, one component of which is the monofilaments, for carrying out the use consists in that di-ΐ monofilaments and the glass or mineral fibers are arranged next to one another in the form of strips in the warp and / or weft direction Arrangement, a mixed fabric is produced that contains, for example, half or a third of fluorothermoplastic threads. By means of a suitable heating treatment using a press or a calender, this mixed fabric of glass fabric threads and thermoplastic threads is melted onto PTFE sheets or foils with the aid of the latter A cheap and not too thick connecting layer is achieved, which also keeps the consumption of connecting materials low.

For reasons of liability and also for cost reasons, it is advisable to use the To keep fluorothermoplastic thread fraction so small that it ensures good adhesion when the

Tissue to the PTFE is just enough. It is thereby achieved at the same time that the proportion of the Connection material wettable glass thread for attachment on the surface is as large as possible.

This makes it possible with PTFE lining foils or -Plates to glue these only in strips or in a checkerboard shape to the subsurface in order to avoid the different To compensate for thermal expansion of the PTFE parts to the substrate, for example made of metal. This zone-like or checkerboard-like gluing to avoid tension in the connection However, between the lining and the substrate is already from DE-GM 72 20 884 and 76 08 976 known, but it should be achieved in these protective rights in a different way. With the present Solution compared to this prior art is no special procedure when connecting the PTFE parts with the substrate required, as in certain zones only well-adhering glass fabric and in other zones exclusively melted fabric made of fluorothermoplastic threads, which in turn for Adhesive is not wettable, is present.

The invention described above solves the connection problems between PTFE and the substrate, for example in the case of containers to be lined, which has long been a known process engineering problem represent. In addition, a new mineral fiber / perfluoropolymer blend fabric was designed for zoning Connection with the subsurface described that the differences in thermal expansion compensated between the lining and the subsurface and the smallest possible proportion of the costly Fluoropolymer monofilaments in blended fabrics made possible

Claims (1)

Patent claims: 1. Use of polytetrafluoroethylene as Fluoropolymer for one with a subsurface bondable composite molded part made of a film or plate consisting of a> fluoropolymer, the by means of monofilaments made from a fusible fluoropolymer under heat and pressure with a Glass or mineral fiber fabric is connected. Z Glass or mineral fiber fabric, one of which is m Component which are monofilaments for carrying out the use according to claim 1, characterized in that characterized in that the monofilaments and the glass or mineral fibers in Ken and / or Weft direction in each case in strips next to one another ι -> are arranged