Electrically conductive rubber composition, transfer roller, production method for the transfer roller, and image forming apparatus

A transfer roller production method comprising the steps of:

• extruding an electrically conductive rubber composition into a tubular body, the electrically conductive rubber composition comprising:
• a rubber component consisting of ethylene propylene diene rubber, epichlorohydrin rubber, butadiene rubber, and at least one polar rubber selected from the group consisting of acrylonitrile butadiene rubber, chloroprene rubber and acryl rubber;
• a crosslinking component for crosslinking the rubber component;
• a foaming agent thermally decomposable to generate gas, the foaming agent being present in the rubber composition in a proportion of not less than 4 parts by mass and not greater than 6 parts by mass based on 100 parts by mass of the overall rubber component;
• and a foaming assisting agent which accelerates decomposition of the foaming agent, the foaming assisting agent being present in the rubber composition in a proportion of not less than 1.5 parts by mass and not greater than 2.7 parts by mass based on 100 parts by mass of the overall rubber component;
• and
• foaming and crosslinking the electrically conductive rubber composition extruded into the tubular body in a vulcanization can by applying pressure and heat to the tubular body with pressurized steam through an in-can vulcanization process.