Thermosetting acrylic copolymer usable as a powder paint and method for producing the same

A method for producing a thermosetting acrylic polymer for the use as powder paint, which comprises copolymerizing, by way of a suspension copolymerization in an aqueous medium at a pH of 7 or less,

• (1) 3 to 30% by weight of at least one comonomer of the formula (I'):
• ##STR19## wherein R.sub.1 represents a hydrogen atom or methyl group and R.sub.2 represents an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 6 to 8 carbon atoms,
• (2) 1 to 50% by weight of at least one comonomer selected from the compounds of the formulae (II') and (III'):
• ##STR20## wherein R.sub.1a represents a hydrogen atom or methyl group, R.sub.3 represents an alkylene group having 2 to 6 carbon atoms, R.sub.4 represents an aliphatic group containing or not containing a carboxyl group and having 2 to 12 carbon atoms or an aromatic group containing or not containing a carboxyl group and having 6 to 12 carbon atoms, R.sub.5 represents an aliphatic group containing or not containing a hydroxyl group and having 1 to 18 carbon atoms or an aromatic group containing or not containing a hydroxyl group and having 6 to 18 carbon atoms, and n represents an integer of 1 or 2, and
• (3) 20 to 96% by weight of at least one comonomer of the formula (IV'):
• ##STR21## wherein R.sub.1b represents a hydrogen atom or methyl group, and X represents an ester, nitrile, amide, R.sub.6 COO-- wherein R.sub.6 represents an alkyl group having 1 to 18 carbon atoms, glycidylester, glycidylether or aromatic group having 6 to 18 carbon atoms or a halogen atom, in the presence of a hydrophobic radical polymerization initiator and chain transfer agent, catalyst, to form a copolymer having a weight average molecular weight of 4,000 to 30,000 and being in solid state at a normal temperature.

A thermosetting acrylic powder paint which comprises an acrylic copolymer comprising:

• (1) 3 to 30% by weight of at least one repeating unit of the formula (I):
• ##STR22## wherein R.sub.1 represents a hydrogen atom or methyl group and R.sub.2 represents an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 6 to 8 carbon atoms,
• (2) 1 to 50% by weight of at least one repeating unit selected from the groups of the formulae (II) and (III):
• ##STR23## wherein R.sub.1a represents a hydrogen atom or methyl group, R.sub.3 represents an alkylene group having 2 to 6 carbon atoms, R.sub.4 represents an aliphatic group containing or not containing a carboxyl group and having 2 to 12 carbon atoms or an aromatic group containing or not containing a carboxyl group and having 6 to 12 carbon atoms, R.sub.5 represents an aliphatic group containing or not containing a hydroxyl group and having 1 to 18 carbon atoms or an aromatic group containing or not containing a hydroxyl group and having 6 to 18 carbon atoms, and n represents an integer of 1 or 2, and
• (3) 20 to 96% by weight of at least one repeating unit of the formula (IV):
• ##STR24## wherein R.sub.1b represents a hydrogen atom or methyl group, and X represents an ester, nitrile, amide, R.sub.6 COO-- in which R.sub.6 represents an alkyl group having 1 to 18 carbon atoms, glycidylester, glycidylether or aromatic group having 6 to 18 carbon atoms or a halogen atom, said polymer having a weight average molecular weight of 4,000 to 30,000 and being in solid state at normal temperature.