Abstract: A process for preparing a liquid silicone rubber base composition of the type which comprises (A) an organopolysiloxane of the following average compositional formula (1)R.sub.a SiO.sub.(4-a)/2 (1)wherein each R independently represents an unsubstituted or substituted monovalent hydrocarbon group and a is a value of from 1.95 to 2.05, and (B) a finely divided silica filler is described. The process comprises the steps of mixing a first portion of the ingredient (A) and the ingredient (B) at a temperature not higher than 80.degree. C., further mixing a second portion of the ingredient (A) with the mixture obtained in the first step at a temperature not higher than 80.degree. C. and subjecting the resultant mixture to thermal treatment at a temperature of 130.degree. to 200.degree. C. By this, the base composition has good fluidity and is able to yield a cured product having good tear strength under stress.

Abstract: A novel self-adhesive silicone rubber composition is disclosed which gives a cured silicone rubber capable of being firmly bonded to the surface of various kinds of substrate materials even without the pre-treatment of the substrate surface with a primer so that the composition is useful as a coating material in the preparation of a silicone rubber-coated cloth advantageous in respect of the firm adhesion of the cured silicone rubber layer to the substrate cloth. The composition is characterized by the formulation of a unique component which is an organosilane compound having an isocyanato-containing group and a hydrolyzable group in a molecule such as 3-isocyanatopropyl trimethoxy silane.