Curable organopolysiloxane composition

摘要

A curable organopolysiloxane composition comprising a vinyl-containing organopolysiloxane, organohydrogenpolysiloxane and platinum catalyst is proposed which is cured into a gel-like material suitable as a potting and encapsulating agent for protecting, for example, electronic components from mechanical shocks and adverse influence of the ambient atmosphere. Different from conventional similar compositions, the gelled material from the inventive composition little suffers from the problem of bleeding of oily materials contained therein on the surface. This unique advantage is obtained by using, in place of the conventional vinyl-containing organopolysiloxanes in which the vinyl groups are bonded to the silicon atoms at random position in the molecular chain, a combination of two vinyl-containing organopolysiloxanes having a specified viscosity in a limited proportion, of which one has two and only two vinyl groups in a molecular each bonded to one of the silicon atoms at the molecular chain ends and the other has one and only one vinyl group in a molecule bonded to one of the silicon atoms at the molecular chain ends alone. The composition may further contain a low-viscosity dimethylpolysiloxane so that the silicone gel can be imparted with softness and adhesiveness without increasing the amount of bleeding of the oily constituents.