Semiconductive silicone elastomer compositions and method for making

A method for preparing a semiconductive silicone elastomer composition comprising the steps of:

• (a) kneading all or a part of an organopolysiloxane containing at least two aliphatic unsaturated hydrocarbon groups each attached to a silicon atom in a molecule with conductive carbon at a temperature of 100.degree. to 200.degree. C.,
• (b) cooling the kneaded mixture to room temperature,
• (c) adding a conductive filler other than conductive carbon having a volume resistivity of 10.sup.1 to 10.sup.8 .OMEGA.-cm to the mixture, and
• (d) mixing the resulting mixture again at a temperature of 0.degree. to 60.degree. C.,
• wherein the amount of conductive carbon is from 1-10 wt. % and the amount of conductive filler other than carbon is from 99-90 wt. %, each based on the total weight of conductive carbon and conductive filler other than carbon.

A semiconductive silicone elastomer composition comprising:

• (a) an organopolysiloxane containing at least two aliphatic unsaturated hydrocarbon groups each attached to a silicon atom in a molecule, having a viscosity of about 20-200,000 cs at 25.degree. C.,
• (b) an organohydrogenpolysiloxane containing at least two hydrogen atoms each attached to a silicon atom in a molecule, having a degree of polymerization of 3 to 300, and
• (c) a conductive agent consisting essentially of 1 to 10% by weight of conductive carbon and 99 to 90% by weight of a conductive filler other than conductive carbon having a volume resistivity of 10.sup.1 to 10.sup.8 .OMEGA.-cm, said conductive agent being blended in an amount of 20 to 60% by weight of the entire composition,
• said composition yielding a semiconductive silicone elastomer having a volume resistivity of 10.sup.5 to 10.sup.10 .OMEGA.-cm with a dispersity of from 1 to 10.