GB686624A - Improvements in or relating to the process for the preparation of unsaturated ester monomers - Google Patents

Abstract

High molecular weight esters of acrylic or methacrylic acids having from 5 to 30 carbon atoms in the ester group derived from the alcohol are made by reacting at below 130 DEG C. a low molecular weight ester of the said acids having less than 5 carbon atoms in the ester group derived from the alcohol and an alcohol having from 5 to 30 carbon atoms in the molecule in the presence of an acidic esterification catalyst and a polymerization inhibitor while passing a stream of an oxygen-containing gas through the reaction mixture, the products of the reaction being subjected successively to a stripping step and a washing step to recover the final product. Phenolic inhibitors, e.g. quinone, hydroquinone or tert.-butyl catechol, are preferred. Generally an excess of the lower ester, e.g. methyl acrylate and methacrylate, is used reaction preferably being effected under reflux at about 90-120 DEG C., whilst a stream of air and nitrogen containing 1 part of air to 5 to 20 parts of nitrogen is passed through during the reaction and stripping operations. In the stripping stages lower molecular weight alcohol is removed together with excess lower ester. When the bottoms temperature during atmospheric stripping reaches 110-120 DEG C. vacuum stripping is effected until the temperature is again within these limits. The product is washed with water to remove catalyst, alkali to remove inhibitor and finally with water. In experiments mixed alcohols obtained by hydrogenating coconut oil, C8 oxo alcohols, or mixed hydrogenated coconut oil and C8 oxo alcohols are treated with methyl acrylate and methacrylate in the presence of p-toluene sulphonic acid and the three specified inhibitors whilst various mixtures of air and nitrogen or nitrogen alone are passed through and the products isolated as above. In one case no inhibitor is used. Specification 573,175 is referred to.