Preparation method of benzotriazole ultraviolet light absorber

The invention relates to a preparation method of a benzotriazole ultraviolet light absorber, which comprises the steps of taking 3-[3-(2-H-benzotriazole-2-yl)-4-hydroxy-5-tert-butylphenyl]-methyl propionate and C7-9 alkyl alcohol as raw materials, carrying out transesterification under the action of a catalyst to prepare 3-(2H-benzotriazole-2-yl)-5-(1,1-dimethyl ethyl)-4-hydroxy-C7-9 alkyl ester, wherein the catalyst is lithium methoxide and/or zinc isooctanoate. The product prepared by the method is not easy to oxidize, and the appearance and chromaticity of the product can be ensured; and meanwhile, the problem of acid residues in a reaction system can be effectively solved, and the problem of application limitation of the product due to the acid residues is avoided. 本发明涉及一种苯并三氮唑类紫外线吸收剂的制备方法，包括以下步骤：以3-[3-(2-H-苯并三唑-2-基)-4-羟基-5-叔丁基苯基]-丙酸甲酯、C7-9的烷基醇为原料，在催化剂作用下发生酯交换反应，制备得到3-(2氢-苯并三唑-2-基)-5-(1,1-二甲基乙基)-4-羟基-C7-9烷基酯；所述催化剂为甲醇锂和/或异辛酸锌。本发明制得产品不容易被氧化，可以保证产品的外观和色度；同时可以有效改善反应体系中酸的残留问题，避免了产品因酸残留问题造成应用受限问题。