GB477885A - Improvements in vinyl resins - Google Patents

Abstract

Relates to production of substantially colourless polyvinyl acetal resins from interpolymers of one or more vinyl esters of low molecular weight (e.g. vinyl acetate, propionate, or butyrate) with up to 15 per cent of a vinyl ester of high molecular weight (e.g. vinyl oleate or stearate) or with up to 40 per cent of an acrylic ester or a vinyl halide. Esters of low and high molecular weight are defined as those in which the acid radical contains up to 4, or from 6 to 22, carbon atoms respectively. The polymers are hydrolyzed and simultaneously or subsequently condensed with one or more saturated aliphatic aldehydes in the presence of a catalyst, an organic solvent (which may or may not include alcohol), and water (or water and alcohol) in amount such that homogeneous reaction conditions are maintained when 80 or more per cent of the hydroxyl groups formed are acetalized, but large enough to give a colourless product By employing mild hydrolysis conditions, the product may include a substantial proportion of vinyl ester groups of high molecular weight or of acrylic ester or vinyl halide groups and have an improved water resistance. In examples: (1) an interpolymer of vinyl acetate and stearate is treated with paraformaldehyde in solution in ethyl acetate, ethyl alcohol, water, and sulphuric acid to give a product containing stearyl, acetyl, methylal and hydroxy groups; (2) an interpolymer of vinyl acetate and oleate is treated with paraldehyde, propionaldehyde, or butyraldehyde as in example 1, to give a product containing oleyl, acetyl, acetal and hydroxy groups; (3) an interpolymer of vinyl acetate and methyl acrylate is treated with formalin in solution in acetic and sulphuric acids to give a product containing methyl ester, acetyl, methylal, and hydroxyl groups Specifications 396,186, 436,072, 454,691, and 466,598 are referred to. The Provinional Specification refers to the use of aldehydes in general and of ketones.