A CURING AGENT FOR POWDER COATING AND THE PREPARATION METHOD OF THE LONG CHAIN DICARBOXYLIC ACID POLYANHYDRIDE USED IN SAID POWDER COATING

摘要

A high quality long chain dicarboxylic acid polyanhydride curing agent product is prepared by an biological process using alkane or fatty acid as starting raw material. The dicarboxylic acid polyanhydride curing agent can be used in curing of the powder coating. A method for manufacturing the long chain dicarboxylic acid polyanhydride curing agent is closed, which including first producing long chain dicarboxylic acid from alkane or fatty acid by applying biological fermentation process, and then obtaining desired dicarboxylic acid by a special purification process. The dicarboxylic acid is undergone dehydration reaction at normal pressure in combined with other reactant, in which the temperature of the resultant mixture is 100-140, the distillation time is 1-6 hours. The final product is obtained by vacuum distillation at the temperature of 110-140 and the vacuum of less than 15 mmHg, or distilling in the scraped film evaporator to remove small molecule substances. The long chain dicarboxylic acid polyanhydride curing agent product prepared by the present invention has a Gardner chromaticity of less than 2, an ash concentration of not more than 80 ppm, and a residual nitrogen concentration of not more than 60 ppm. The melting point of the curing agent product can be adjusted according to the desired practical application. The curing agent has an excellent yellowing resistance and sufficiently satisfies the requirement of curing agent for using in powder coating.