Aliphatic hydrocarbon group-containing resin composition for cationic electrocoating and cationic electrocoating composition

An aliphatic hydrocarbon group-containing resin composition for cationic electrocoating, which comprises a resin having a skeleton of epoxy resin and has a number average molecular weight of 500 to 20,000, and which contains, per 100 grams of the nonvolatile matter in said resin composition,

• (a) 5 to 400 millimoles of sulfonium group;
• (b) 80 to 355 millimoles of at least one aliphatic hydrocarbon group containing 8 to 24 carbon atoms and optionally containing unsaturated double bond within its chain;
• and
• (c) 10 to 315 millimoles of at least one member selected from among propargyl group and a terminal unsaturated double bond-containing organic group containing 3 to 7 carbon atoms;
• the total content of (a) the sulfonium group, (b) the aliphatic hydrocarbon group containing 8 to 24 carbon atoms and optionally containing unsaturated double bond within its chain and (c) the at least one member selected from among propargyl group and a terminal unsaturated double bond-containing organic group containing 3 to 7 carbon atoms being not more than 500 millimoles per 100 grams of the nonvolatile matter in said resin composition.