PURPOSE: To obtain a highly irregular copolymer useful as a paper surface sizing agent by a process in which a styrenic monomer and (meth)acrylic acid is copolymerized by a specified method and the reaction product is subjected to specified treatment.
CONSTITUTION: First, (A) a monomer of a formula (R is H, 1-4 alkyl; R is H, halogen or the like), (B) (meth)acrylic acid, and required (C) a hydrophobic monomer other than the component A are dissolved in an unsubstituted hydrocarbon alcohol/water mixture to obtain a homogeneous solution. Next, when the solution is heat-refluxed in the presence of 1-3 wt.%, based on the monomer, of a water-soluble free radical generating catalyst in the absence of oxygen, a portion of the catalyst which is necessary to start the polymerization is added into the reaction system before the polymerization, and the rest of the catalyst is added gradually over the whole process of heating to advance the reaction. Next, while the alcohol/water mixture being separated, the acid part of the produced polymer is neutralized, and a polymer solution 25% or less in solid content is obtained.
DEIBITSUDO ERU DAUPUREIZU
ROBAATO JIEI PUROBAABU
