GB883344A - Improvements in and relating to the production of hard rubber compositions - Google Patents

Abstract

A granular mixture for compression moulding or extrusion and vulcanization to rigid rubber articles such as battery boxes is made by mixing an aqueous dispersion of a vulcanizable rubbery polymer with a composition of dry, finely-divided, solid compounding ingredients, the amount of dispersion being insufficient to prevent formation of a granular product and being such that the rubber content of the resulting mixture is 5-25%, and drying the mixture by hot gas to a moisture content of less than 2%, the mixture being taken out of contact with the hot gas before a temperature of 250 DEG F. is reached, so as to avoid scorching. The rubber dispersion may be a latex, of 15-70% solids content, of natural rubber, reclaim rubber, a polymer of butadiene, isoprene, dimethylbutadiene, chloroprene, or cyanoprene, a copolymer of such a diolefine with a mono-olefine such as styrene, acrylonitrile, or an acrylic or methacrylic ester, or butyl rubber. The compounding ingredients are exemplified by sulphur, preferably in the proportion of 10-40 parts per 100 parts of rubber, powdered anthracite, or semi-anthracite coal, china clay, talc and diatomaceous earth: accelerators and activators of vulcanization, e.g. a butyraldehyde-aniline condensation product, lime, or zinc oxide, and rubber-compatible, petroleum-base, oily plasticizers are preferably incorporated after the drying of the latex-compounding ingredients mixture. An example is concerned with blending ground semi-anthracite coal, sulphur, SBR latex, a petroleum-base oil, an aldehyde-amine accelerator and a primary fatty amine.