DE3307090A1 - Process for producing a laminated material of carbon - Google Patents

Abstract

A process for producing a porous laminated material consisting of carbon, in which layers of carbon felt or carbon fabric and films of a thermoplastic are alternately stacked one on top of the other and the stack is heated to approximately 1200 K under pressure to carbonise the plastics inserts. The self-supporting laminated material can be relatively simply deformed to form elements, for example sheets for thermal insulation or porous flow-through electrodes.

Description

Method for producing a layer

material made of carbon The invention relates to a method for production a laminate, the layers of which are connected by a carbonized binder and contains at least one layer made of a textile carbon form. Under The term “textile carbon form” will be made more textile by carbonization in the following Fabrics made from rayon, polyacrylonitrile and other fibers understood flexible and porous carbon bodies.

To produce one consisting essentially of carbon Laminate, it is known, layers or webs of carbon felt, fleece or -to coat the coated webs with a carbonizable binder stack on top of each other and the stack for carbonization of the binder, if necessary under pressure to be heated (DE-PS 12 87 499). Thermosetting synthetic resins are used as binders have been proposed whose coke residue is particularly large in the heat treatment such as phenol-formaldehyde resins, epoxy resins and furan resins, and the solid laminated body with a comparatively high flexural strength. Achieved similar results one with coal tar pitch, which initially softens when the stack of layers is heated (DE-PS 15 71 390). The binder gets onto the surfaces of each carbon layer sprayed, brushed or applied by dipping. A part the binder diffuses during this treatment and the heating of the layer stack in the core of each layer and it is obvious that the properties of the finished laminate depends on the amount of that formed within the layers secondary coke are also determined. Determining variables for the amount of coke are i.a.

the viscosity of the binder, the porosity of the carbon layer and the method used to apply the binder. Since the parameters are only up to are constant to a certain extent, the spread of the product properties is proportional great. In order to improve the product it has therefore been proposed that the carbon layer completely with a binder, optionally with a solvent is diluted, to impregnate and then to remove a larger part of the binder, so that only small ones are more reproducible and uniform over the entire cross-section distributed amounts remain in the carbon layer (DE-PS 27'00 866). The excess binder is extracted for this purpose by rolling, pressing, spinning, etc. and is obtained a fiber layer, the individual fibers of which with a binder layer of substantially are coated with a uniform thickness. The layers are then made in a known manner stacked one on top of the other and a heat treatment for carbonization of the binder under pressure subject. The carbon composite is of uniform texture and has a comparatively low flexural rigidity. The laminates are alone or in connection with other temperature-resistant materials, such as graphite foil, excellent insulation for high temperatures. Other uses are porous flow electrodes and supports for catalysts.

A disadvantage of the extraction process is the great technical effort. Special rolling mills are required Centrifuges and the like. And especially when using dilute binders, effective means of collecting the released solvents. Finally, procedures have become known in which textile fabrics, such as fabrics and unidirectional fiber ribbons with a film made of a thermoplastic plastic, preferably a plastic with a high softening point, covered and exposed to temperature and pressure are connected to one another (EP-A 0 040 967).

A layered fiber-reinforced thermoplastic is obtained, its thermal and chemical resistance is very limited. The invention now lies the object of an improved method for producing an exclusively to create a carbon laminate that has at least one layer contains from a textile carbon form. The laminate should have a large porosity have high uniformity and limited flexural rigidity.

The object is achieved in that the forming the laminate Layers are stacked with a thermoplastic film between each two layers Plastic arranged and the stack under pressure to carbonize the plastic is subjected to a heat treatment. According to a preferred embodiment of the method thermoplastic plastic films are used, the coking residue of which is 10 up to 20%.

The advantage of the method according to the invention is that in the porous layers of the laminate only slightly when the arrangement is heated Quantities of the thermoplastic material that can be precisely determined by the process conditions flow, whose coking residue is also small compared to the known binders is. The embrittlement of the laminate due to the coke education is correspondingly low without impairing the connection strength. Of the Laminate is self-supporting due to its flexural strength, on the other hand it is but so flexible that it can be adapted to curved contours by bending.

The layers used to manufacture the laminate exist preferably made of carbon felt with a bulk density of 0.07 to 0.10 g / cm, what corresponds approximately to a porosity of 95%. Other suitable layers are carbon cloth or fleece and graphite foil, which because of their low permeability especially as outer layer of the laminate is advantageous. The use is particularly favorable of thermoplastic plastic films that are wholly or partly made of polyethylene exist. The ratio of the layer thicknesses of the porous carbon layers and of the foils should expediently be 10: 1 to 10: 2, the first limit value applies generally for thermoplastic plastic films with a large coking residue, the second limit value for foils with a small amount of coking residue. The alternating Stacked porous carbon layers and foils are under one Pressure of approx.

0.05 to 0.2 N / mm2 for coking the thermoplastic synthetic resin heated to about 700 to 1000 0C in an inert or reducing atmosphere. The heating rate is below 250 to 300 0C approx.

30 to 100 K / h, above these temperatures about 120 to 200 K / h.

The invention is illustrated below with the aid of examples: Example 1 Two layers of carbon felt, each 10 mm thick, with a bulk density of 0.09 g / cm³, and a 2.1 mm thick polyethylene film, corresponding to an area weight of 180 g / m², were alternately stacked one on top of the other and the stack under one Pressure of 0.1 N / mm2 with a gradient of 50 K / h to 260 ° C and 150 K / h in Argon heated to 1000 ° C. The by heating the foil in helium to 1000 ° C with Coking residue determined using a gradient of 10 K / min was 14.5%.

The laminate was of uniform consistency, the bulk density 0.13 g / cm3 and the flexural strength 0.4 N / mm2.

Example 2 A stack of four carbon felt layers was produced from in Example 1 described nature and three arranged between two layers Films based on polyethylene-vinyl acetate and styrene-butadiene copolymers, weight per unit area 190 g / m2, thickness 2.1 mm, coking residue 11.5%, formed and the stack below heated to a pressure of approx. 0.08 N / mm as in Example 1 to 1000 ° C. With the same Density of 0.13 g / cm3, the flexural strength was 0.6 N / mm2.

Example 3 A stack with the sequence graphite felt, foil, graphite fabric, Foil, graphite foil formed. The properties of the components were: graphite felt - Density 0.07 g / cm³, thickness 9 mm, graphite fabric - weight per unit area 350 g / cm2, graphite foil - gross density 1.0 g / cm3, thickness 0.35 mm, polyamide film - weight per unit area 180 g / m2, thickness 1.6 mm, coking residue 11.0%. The layer stack was taken in nitrogen a pressure of 0.12 N / mm² with a gradient of 30 K / h to 250 0C and with a Gradients from 200 K / h to 950 K heated. The laminate used as a heat shield had an apparent density of about 0.15 g / cm³ and a flexural strength of about 1.0 N / mm².

Claims (5)

Claims: j1. Method of manufacturing a laminate, the layers of which are connected by a carbonized binder and at least contains a layer made of a textile carbon form, thereby g e n n e c e i c h -n e t that the layers are stacked, one between each two layers Foil made of a thermoplastic material arranged and the stack under pressure is subjected to a heat treatment to carbonize the plastic. 2. The method according to claim 1, characterized in that g e k e n n -z e i c h n e t that a thermoplastic film is used, the coking residue 10 to 20 % amounts to. 3. The method according to claim 1 and 2, characterized in that g e -k e n n z e i c Note that a polyethylene film is used 4. The method of claim 1 up to 3, in that layers and thermoplastic foils can be used in a thickness ratio of 10: 1 to 10: 2. 5. The method according to claim 1 to 4, dadruch g e -k e n n z e i c Not that the textile form of carbon is carbon felt with a bulk density of 0.07 to 0.10 g / cm3 is used.