To improve a photoprotection effect with less volatility by polymerizing a compd. obtd. by reacting a compd. having a sterically hindered piperidine group with an acrylic acid compd.

A compd. of formula III obtd. by reacting a compd. of formula I with an acrylic acid compd. of formula II at a molar ratio of 10:1-1:10 for 12-72 hr, is polymerized to provide a polyacrylate of formula IV [wherein (n) is 2-1,000; R1 and R2 are each H, a 1-18C alkyl or chloro; R3 is formula V (where R4 is H, a 1-20C alkyl, oxygen radical O*, OH, NO, CH2-CN, benzyl, allyl, a 1-30C alkyloxy, a 2-10C alkenyl, a 3-6C alkynyl, a 1-10C acyl, a halogen, or phenyl which may be substd. by a 1-4C alkyl; R5 is H or a 1-18C alkyl; and R6 and R7 are each H, a 1-18C alkyl or form a 5-13 membered ring together with a carbon connecting them, or a group of formula VI together with a carbon connecting them)] or a copolymer comprising a structure unit of formula IV in the polymer chain.