PROBLEM TO BE SOLVED: To provide a surface treatment agent which is a cosmetic material, is hydrophobic during dry and achieves cosmetic maintaining and wash-off property when become hydrophilic by contacting with water.SOLUTION: There is provided a surface treatment powder where a surface of the powder is coated by a first block copolymer represented by the formula (1). (1), where R1 and R2 are each independently an alkyl group, a polyoxyalkylene group, an acyl group, a phenyl group and an aralkyl group, X is a C1 to 18 alkyl chain which may form ether by substituting not-neighboring carbon with oxygen, Y is a single bond or a bivalent connecting group, Z1 is H or a methyl group and n and m are polymerization degrees.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2016,JPO&INPIT【課題】化粧料であって、乾燥時には疎水性であるが、水に接触すると親水性となることで、化粧もちと洗い流し性とを両立した表面処理粉体の提供。【解決手段】式(1)で表される第1のブロック共重合体ブロック共重合体で粉体表面が被覆されている表面処理粉体。(R1、R2は各々独立にアルキル基、ポリオキシアルキレン基、アシル基、フェニル基、アラルキル基;Xは隣接しない炭素が酸素に置換されてエーテルを形成してもよいC1~18のアルキル鎖;Yは単結合又は2価の連結基;Z1はH、又はメチル基;n及びmは重合度)【選択図】図1
