POLYSILOXANE-POLYALKYLENE GLYCOL BLOCK COPOLYMER AND METHOD FOR PRODUCING SAME

A polysiloxane-polyalkylene glycol block copolymer obtained by reacting a polysiloxane (A) having a functional group selected from a carboxylic anhydride group, a hydroxyl group, an epoxy group, an amino group, and a thiol group with a polyalkylene glycol (B) having a functional group selected from a carboxylic anhydride group, a hydroxyl group, an amino group, an epoxy group, and a thiol group to obtain a polysiloxane-polyalkylene glycol block copolymer intermediate, and further reacting a part of the carboxyl groups of the polysiloxane-polyalkylene glycol block copolymer intermediate with a compound reactive with a carboxyl group, wherein a content of a structure derived from the polysiloxane (A) is 30% by mass or more and 70% by mass or less with respect to 100% by mass of the entire polysiloxane-polyalkylene glycol block copolymer, and wherein the polysiloxane-polyalkylene glycol block copolymer has a carboxyl group content of 0.1 mmol/g to 0.75 mmol/g and a weight average molecular weight of 5,000 to 500,000. Provided is a polysiloxane-polyalkylene glycol block copolymer which is well dispersed in an epoxy resin in the case of being blended with the epoxy resin, and can achieve a decreased stress of the cured epoxy resin.