Powdery copolymer comprising methyl methacrylate and monomer having a basic nitrogen atom

A powdery copolymer having a powder particle size from 0.1 to 200 microns, said copolymer comprising 50 to 99.8 percent by weight of methyl methacrylate, 0.2 to 10 percent by weight of at least one monomer having a basic nitrogen atom, 0 to 49.8 percent by weight of at least one other monomer selected from the group consisting of alkyl acrylates having 1 to 4 carbon atoms in the alkyl group, alkyl methacrylates having 2 to 4 carbon atoms in the alkyl group, acrylonitrile, styrene, vinyl toluene, .alpha.-methyl styrene, and vinyl esters, and 0 to 10 percent by weight of at least one member selected from the group consisting of vinyl pyrrolidone and the hydroxyalkyl esters, amides, methylolamides, and methylol ether amides of acrylic acid and methacrylic acid, said copolymer being prepared by emulsion copolymerization such that at least 50 percent by weight of the monomer or monomers having a basic nitrogen atom is first added to the monomer or monomers not having a basic nitrogen atom after the polymerization of at least half of said monomer or monomers not having a basic nitrogen atom, the resulting copolymer then being recovered from the resultant latex in powder form.