| abstract |
A method for producing a millable silicone rubber sponge is a method for producing a millable silicone rubber sponge with an open cell ratio of not lower than 20%, comprising:n performing a heat treatment on a silicone rubber composition at 200° C. or higher, the silicone rubber composition containing: (A) an organopolysiloxane having at least two alkenyl groups in one molecule and a polymerization degree of not lower than 3,000; (B) a reinforcing silica; (C) thermally expandable microcapsules exhibiting an expansion starting temperature of 90 to 150° C., and contracting from a maximum expansion volume by 20% or more when heated at 200° C. for 5 min; (D) a curing agent; and (E) an open cell-forming agent which is a solid high temperature decomposition-type organic foaming agent having a decomposition starting temperature of not lower than. 180° C., and starting to decompose after the component (A) is cured. |