GB427810A - Improvements in or relating to the production of esters of methacrylic acid - Google Patents

Abstract

In the manufacture of esters of methacrylic acid according to the parent Specification, the reaction product from acetone cyanhydrin and sulphuric acid is heated with a quantity of water, preferably not exceeding four molecular proportions based on the cyanhydrin, either before or during the heating with a monohydric alcohol. The reaction is preferably carried out by mixing acetone cyanhydrin with sulphuric acid or oleum in the presence of an antipolymerization catalyst at about 80--100 DEG C., heating the mixture to 100--140 DEG C. for some time, e.g. about an hour, adding water, preferably about two molecular proportions, refluxing, e.g. for about three hours, then adding the alcohol and refluxing for a further 2--3 hours. Alternatively, the water and alcohol may be added simultaneously and the mixture refluxed, e.g. for 15 hours. In examples: (1) crude acetone cyanhydrin (prepared by reacting acetone with hydrocyanic acid in the presence of caustic soda) is purified by distillation, heated with sulphuric acid containing flowers of sulphur, and the product is refluxed with water and methyl alcohol with the addition of tannic acid; (2) crude acetone cyanhydrin is heated with oleum containing flowers of sulphur and the product is treated as in (1); (3) crude acetone cyanhydrin is heated with sulphuric acid containing copper bronze powder and the product is refluxed with water and then with methyl alcohol; (4) the methyl alcohol in (3) is replaced by isopropyl alcohol; (5) as in (2) but using slightly stronger oleum and a lower temperature in the first stage; (6) rectified acetone cyanhydrin is heated with sulphuric acid containing sulphur, and the product is refluxed with water and butyl alcohol; (7) crude acetone cyanhydrin is heated with sulphuric acid containing flowers of sulphur, and the product is refluxed with water and n-butyl alcohol with the addition of tannic acid; (8) crude acetone cyanhydrin is heated with sulphuric acid containing copper bronze and the product is refluxed with water and then with isobutyl alcohol; (9) crude acetone cyanhydrin is heated with sulphuric acid containing a little sulphuric anhydride and also containing copper bronze powder, and the product is refluxed with water and then with glycol monoethyl ether containing tannic acid.