Simple prepn. of polymerisable UV absorber with little intrinsic colour

摘要

Prepn. of a UV absorber of formula R'-CH2-R'' (I), which is capable of free radical polymerisation, comprises condensing a 2-(2'-hydroxyphenyl)-benzotriazole of formula R'-H (II) with N-methylol(meth)acrylamide in homogeneous phase in H2SO4 in 1 stage. The novel features are that (a) condensation is carried out at 0-10 deg C and (b) pptn. of the condensate dissolved in H2SO4 is effected by addn. of excess water at over 80 deg C, where R' = a 2-hydroxy-3-benzotriazol-2-ylphenyl gp. of formula (III): R1 = H, 1-12C alkyl or 6-10C aryl; R2 = halogen or as R1; R'' = -NH-CO-CR3=CH2; R3 = H or Me. Also claimed is (I) prepd. in this way, a 2% soln. of which in methyl methacrylate (MMA) has a colour no. of less than 50, pref. less than 30.