Electrically conductive rubber material used for electrophotographic copying apparatus

In an electrically conductive rubber material for use as a charging member for an electrophotocopying apparatus, which rubber comprises:

• 100 parts by weight of total rubber comprising:
• synthetic rubber consisting essentially of:
• a diene rubber comprising butadiene rubber, and
• EPDM rubber containing no double bonds in the principal chain thereof,
• a cross linking agent,
• a conductivity enhancing additive, and
• at least one oily component;
• the improvement, whereby at least reducing bleeding of said oily component out of said rubber material, and blooming of a cross linking agent comprising sulfur, out of said rubber, which improvement comprises:
• said cross linking agent consisting essentially of a metal salt,
• said oily component consisting essentially of not more than 3 parts by weight, as measured by solvent extraction in acetone, per 100 parts by weight of total rubber,
• said carbon black consisting essentially of a conductivity enhancing amount of 5 to 100 parts by weight per 100 parts by weight of total rubber,
• said total rubber comprising 10 to 30 parts by weight of butadiene rubber per 100 parts by weight of said total rubber;
• and
• said EPDM rubber comprising at least 15 parts by weight per 100 parts by weight of total rubber.