Process for the preparation of reinforced rubber vulcanisates and the use thereof

In a process for the preparation of reinforced vulcanizates by vulcanization of compositions comprising natural rubber or synthetic diene rubber with novolak resins in the presence of sulfur as a vulcanizing agent in conjunction with a known acelerator and of from 2 to 120% by weight, based on the novolak resin, of a hardener for the novolak resin being an aminoplast forming compound containing hydroxyl groups other than a reactive melamine resin obtained by reacting one mole of melamine with 0.5 to 6 moles of an aldehyde or a mixture of such other aminoplast with said reactive melamine resin obtained by reacting 1 mol of melamine with 0.5 to 6 mols of an aldehyde, the novolak resin being present in the final composition in an amount of from 1 to 30% by weight based on the rubber, and the phenolic component of said novolak resin being selected from the group consisting of phenol, bisphenols, alkylphenols having one alkyl group with 2 to 12 carbon atoms, a combination of alkylphenols with phenol, and a combination of at least one of said phenols with a further phenol selected from the group consisting of resorcinol, phenylphenol and poly-alkylphenols, said further phenols being employed in such a quantity that the molar ratio of the total quantity of the further phenols to the total quantity of the other phenols is not more than 1:2.