Polyphenylene ether resin composition

A process for producing a compound-rubber-based graft copolyemr which comprises:

• (a) emulsion-polymerizing an organo-siloxane with a cross-linking agent fro polyorganosiloxane rubber and a graft-linking agent for polyorganosiloxane rubber to obtain a polyorganosiloxane rubber component;
• (b) polymerizing an alky (methacrylate with a cross-linking agent for polyalky (meth)acrylate rubber and a graft-linking agent for polyalkyl (methacrylate rubber in a state where they are impregnated into said polyorganosiloxane rubber component, said second polymerization providing a compound rubber having an average particle diameter of 0.08 to 0.6 .mu.m and a structure wherein 7.2 to 92.8% by weight of the polyorganosiloxane rubber component and 92.8 to 7.2% by weight of the polyalkyl (meth)-acrylate rubber component are tangled with each other so as not to separate, the total amount of the polyorganosiloxane rubber component and the polyalkyl (meth)acrylate rubber component being 100% by weight of the compound rubber;
• and
• (c) graft-polymerizing one or more vinyl monomer onto the compound rubber.