Microencapsulated rubber additive

Composition according to one of the preceding claims, characterized in that the vulcanization accelerator is selected from the group consisting of xanthates, dithiocarbamates, tetramethylthiuram disulphide and other thiurams, thiazoles, sulphenamides, guanidines, thiourea derivatives and amine derivatives.

Composition according to one of the preceding claims, characterized in that the coating material (b) is insoluble in rubber or in rubber mixtures up to temperatures of 120 to 140° C., in particular up to roughly 130° C.

Composition according to one of the preceding claims, characterized in that the coating material (b) is soluble or melts at temperatures above 120 to 140° C., in particular above 130° C., in rubber or in rubber mixtures.

Composition according to one of the preceding claims, characterized in that the coating material (b) is selected from the group consisting of waxes, paraffins, polyethylene, ethylene-vinyl acetate copolymers, polyvinyl alcohols and mixtures of same.

Composition according to one of the preceding claims, characterized in that the microcapsules display a size of 1 to 75 μm, more preferably 3 to 30 μm and most preferably 5 to 8 μm.

Composition according to one of the preceding claims, characterized in that the additive in the capsule is liquid and/or solid.

Composition according to one of the preceding claims, characterized in that it contains

• a) 99 to 40 wt.-%, more preferably 80 to 50 wt.-% and most preferably 70 to 60 wt.-% additive and
• b) 1 to 60 wt -%, more preferably 20 to 50 wt.-% and most preferably 30 to 40 wt.-% coating material.

Process for the preparation of a rubber additive composition according to one of the preceding claims, characterized in that a mixture which contains at least one additive and coating material in liquid, dissolved, suspended or emulsified form solidifies to form microcapsules according to one of the preceding claims.