A core containing a polymerization unit of a monoethylene unsaturated carboxylic acid core monomer and a nonionic ethylenically unsaturated core monomer, a nonionic ethylenically unsaturated core monomer, a monoethylene unsaturated carboxylic acid core monomer, And an inner shell containing a polymerization unit of an aliphatic inner shell monomer, a nonionic ethylenically unsaturated outer shell monomer, an aliphatic outer shell monomer, a monoethylene unsaturated non-carboxylic acid outer shell monomer, and an ethylenically unsaturated interface. An SPF enhancer containing a multi-stage polymer particle having an outer shell containing a polymerization unit of an activator outer shell monomer is provided, in which the core contains cavities upon drying and the multi-stage polymer particles are 50 to 1,000 nm upon drying. Has an average particle size of. [Selection diagram] Noneモノエチレン性不飽和カルボン酸コアモノマー、および非イオン性エチレン性不飽和コアモノマーの重合単位を含むコアと、非イオン性エチレン性不飽和内殻モノマー、モノエチレン性不飽和カルボン酸内殻モノマー、および脂肪族内殻モノマーの重合単位を含む内殻と、非イオン性エチレン性不飽和外殻モノマー、脂肪族外殻モノマー、モノエチレン性不飽和非カルボン酸外殻モノマー、およびエチレン性不飽和界面活性剤外殻モノマーの重合単位を含む外殻と、を有する多段ポリマー粒子を含むＳＰＦ増強剤が提供され、このコアは、乾燥時に空洞を含み、多段ポリマー粒子は、乾燥時に５０～１，０００ｎｍの平均粒径を有する。 【選択図】なし
