Verfahren zur Herstellung von kautschukelastischen Produkten

Rubbers are reinforced by heating a major amount of a curable rubber with a minor amount of a fine pigment of an inorganic compound containing both silicon and oxygen at a temperature above the normal milling temperature but below its decomposition point for a time sufficient to increase the absorption of the rubber on the surface of the pigment whilst maintaining constant the inherent viscosity of the rubber. The viscosity constancy is maintained by heating under non-oxidizing conditions or in the presence of a primary polyamine having the amino groups attached to C atoms of an aromatic nucleus, or compounds, e.g. polyisocyanates giving rise to such amines. The rubber can be natural or synthetic, e.g. diene polymers or copolymers and terpolymers of dienes with e.g. styrene or isobutylene amongst the many listed; polysulphide rubbers, silicone rubbers and the polyester urethanes and the mixtures. The pigments include various forms of silicas, silicon monoxide and silicates, and they may be augmented by other coloured pigments. The pigments can also be coated by e.g. silicones, amines or alcohols. Specifications 804,992, 804,993, 804,994 and 807,911 are referred to.