Abstract: Disclosed is a vinyl polymer powder which is superior to dispersibility to curable resin compositions, which immediately gives a gel state for curable resin compositions by short-time heating with predetermined temperature, which is with high ion concentration, and which is useful as a pre-gel agent suitable for fields of electronic materials, to provide a curable resin composition comprising the vinyl polymer powder, and to provide a cured substance of the curable resin composition. The vinyl polymer powder of the present invention has an acetone-soluble component of 30% by mass or more, mass average molecular weight of the acetone-soluble component of 100,000 or more, a content of an alkali metal ion of 10 ppm or less, and a volume average primary particle size (Dv) of 200 nm or more.

Abstract: Disclosed is a vinyl polymer powder which is superior to dispersibility to curable resin compositions, which immediately gives a gel state for curable resin compositions by short-time heating with predetermined temperature, which is with high ion concentration, and which is useful as a pre-gel agent suitable for fields of electronic materials, to provide a curable resin composition comprising the vinyl polymer powder, and to provide a cured substance of the curable resin composition. The vinyl polymer powder of the present invention has an acetone-soluble component of 30% by mass or more, mass average molecular weight of the acetone-soluble component of 100,000 or more, a content of an alkali metal ion of 10 ppm or less, and a volume average primary particle size (Dv) of 200 nm or more.