CS218422B1 - Method of making the pressing material for thermal resistant pressings - Google Patents

Abstract

A method for producing a thermoformed molding composition resistant moldings by exposure to low modulus carbon fiber impregnating phenol-formaldehyde mixtures resin, solvent, zinc stearate and powdered graphite and removal excess impregnation mixture as follows by centrifugation and subsequent drying of the impregnated ones carbon fiber in the air and then drying at 40 to 150 ° C.

Description

The present invention relates to a process for the manufacture of a carbon fiber molding composition and a phenol-formaldehyde resin, which is particularly suitable for the production of moldings resistant to high ablation temperatures, such as rocket motor nozzles.

Methods for producing molding compositions from a mixture of various inorganic materials, or from a mixture containing both organic, inorganic, components for producing high temperature resistant moldings are known. These are processes in which mixing, calendering, mixing and other processes are used to form homogeneous mixtures of particles of different size and shape, containing mainly silica, silicates, graphite, carbides, metal oxides, borides, nitrides, etc. for example kaolin, water glass and other substances. In most cases, the moldings of these molding compositions must be heat treated, usually under a controlled thermal regime, often up to very high temperatures, usually up to the melting point and sintering of the individual components of the mixture. This process is expensive because it is laborious and requires a significant amount of energy. When using organic binders such as silicones, polyimides, epoxy resins and other substances, the moldings of these molding compositions do not achieve sufficient resistance to high ablation temperatures.

This disadvantage is overcome by a method of manufacturing a molding composition for heat-resistant moldings which consists in exposing the low-modulus carbon fiber in an impregnation device such as a malaxer at a temperature of 1 (0 to 60 ° C for 5 hours). 40 to 90 parts by weight of a solvent, for example ethanol, 0.2 to 2.6 parts by weight of zinc stearate, and 1 to 22 parts by weight of powdered graphite and thereafter the carbon fibers are freed of excess impregnation mixture, for example by centrifugation, and then left at 12 to 30 ° C for 5 to 48 hours and finally dried at 40 to 150 ° C.

The molding material produced by the process according to the invention has the required fluidity and can be processed on conventional thermosetting molding presses. Extrusions of this material, stressed by high ablation temperatures, have high resistance.

The invention is further illustrated by examples

Example 1

Weigh 9 kg of low modulus carbon fiber into the malaxer. Separately, 26 kg of a 40% phenol-formaldehyde resin solution with 0.1 kg of zinc stearate and 2 kg of graphite powder are prepared. The mixture is sprinkled with a fiber in the malaxer and mixing is started. After. for about half an hour, the fibers are homogeneously impregnated. Stirring is stopped and the product is freed of excess impregnation mixture in a centrifuge. Thereafter, the impregnated fiber is spread on drying sheets in a maximum layer of 2 cm and dried for 24 to 48 hours, freely in the air. Drying of the product to a volatile content of 2 to 5% and corresponding fluidity is carried out in an explosion-proof oven. Optimum drying is achieved in 20 to Λ min. at SO · ° C.

Example 2

In this example, using the same procedure as in Example 1, a different ratio of components was used, namely 7 kg of low modulus carbon fibers, the impregnation composition consisting of 26 kg of a 40% phenolformaldehyde resin solution, 0.1 kg of zinc stearate. and 0 ', 4 kg of graphite powder.

Claims (1)

Subject Method for producing a molding composition for heat-resistant moldings, characterized in that the low-modulus carbon fiber is subjected to an impregnation device such as a malaxer at a temperature of 10 to 60 ° C for a period of 5 to 60 minutes. 20 to 60 wt. parts by weight of phenol-formaldehyde resin, 40 to 60 wt. 0.2 parts by weight of solvent, for example ethanol OF THE INVENTION parts by weight of zinc stearate and 1 to 22 wt. parts of the graphite powder and then the carbon fibers are freed of excess impregnation mixture, for example by centrifugation, and then left at 12-30 ° C for 5-48 hours and finally dried at 40-150 ° C.