Curable organopolysiloxane compositions comprising microencapsulated hardening accelerators

Claim 1

A composition of matter comprising (A) 100 parts by weight of an α,ω-di(hydroxy)diorganopolysiloxane polymer having a viscosity of from 700 to 1,000,000 mPa.s at 25° C., which comprises diorganosiloxy recurring units of the formula R 2 SiO, in which the symbols R, which may be identical or different, represent hydrocarbon radicals having from 1 to 8 carbon atoms, or substituted such hydrocarbon radicals bearing at least one halogen atom or cyano substituent, (B) 2 to 20 parts by weight of a cross-linking agent of the general formula: R.sub.p Si(OCOR').sub.4- p' in which the symbol R is as defined above, the symbol R' represents a hydrocarbon radical devoid of aliphatic unsaturation and having from 1 to 15 carbon atoms and the symbol p represents zero or one, (C) 0.01 to 7 parts by weight, per 100 parts by weight of (A)+(B)+(C), of hardening accelerator therefor, said accelerator containing and/or generating water by chemical reaction when said accelerator is placed in contact with the polyacyloxysilane (B), and said accelerator being protectively microencapsulated within impermeable outer skin membranes adopted to be disrupted by thermal, irradiation or mechanical treatment to permit the release of said accelerator (C) therefrom and consequent curing of said composition.