Method for preparing a finely divided, free flowing organosiloxane elastomer base exhibiting reduced compression set

摘要

Reduction of the compression set of a cured elastomer prepd. from curable organosiloxane elastomer base in the form of a free flowing powder comprises:(1) maintaining in the fluidised state a finely divided form of a previously prepd. non-creping organosiloxane elastomer base comprising a curable polyorganosiloxane gum and reinforcing silica filler having silanol gps. on its surface, where a portion of the silanol gps. sufficient to reduce creping have been converted to organosiloxy gps.;(2) blending the base with an organosilicon cpd. of formulae: (R1)3SiX or [(R1)3]2NR2 under conditions sufficient to react the cpd. with at least a portion of the residual silanol gps. in the base, where the molar ratio of the organosilicon cpd. to the combined concn. of silanol and silicon-bonded hydrolysable gps. present in the base is at least 0.5:1; and (3) isolating the resulting organosiloxane compsn. as a free flowing powder.