Solvent-free, fine white powders of a copolymer of maleic anhydride and a c1-c4 alkyl vinyl ether substantially free of poly(alkyl vinyl ether) homopolymer

(57) A summary and subject Including the solvent of the copolymer of the maleic anhydride and アルキル vinyl ether which do not include the poly (アルキル vinyl ether) homopolymerization object substantially white fine powder is offered. Solution By adding the depressant which prevents that アルキル vinyl ether homopolymerizes into a maleic anhydride, アルキル vinyl ether, and the reaction mixture of a polymerization initiator, poly (アルキル vinyl ether) is not included substantially -- the white fine powder which does not contain the solvent of the copolymer of a maleic anhydride and C-C アルキル vinyl ether is obtained.