GB542595A - Polyvinyl acetal resins - Google Patents

Abstract

542,595. Polyvinyl acetal resins ; methylol sulphonic acid. DU PONT DE NEMOURS &, CO., E. I., and STAMATOFF, G. S. May 16, 1940, No. 8758. [Class 2 (iii)] Resins are prepared by re-acting polyvinyl alcohol, or partially hydroly ed polyvinyl esters with an organic compound having an active carbonyl group, e.g. an aldehyde or ketone, in the presence of methylol sulphonic acid, such sulphonic acid being preformed except when the carbonyl compound employed is formaldehyde, when, if desired the sulphonic acid may be produced in s tu by employing a quantity of formaldehyde in excess of that required to condense with the polyvinyl alcohol and adding sulphur dioxide to the reaction mixture. The process of converting the polyvinyl ester, e.g. polyvinyl acetate, completely or partially into polyvinyl alcohol and effecting the condensation with the carbonyl compound may be effected in one step. In examples, resins are prepared by heating an aqueous solution of methylol sulphonic acid with (a) a mixture of polyvinyl alcohol, a liquid vehicle, and either formaldehyde, n- or iso-butyraldehyde, cyclohexanone, methylcyclohexanone, acetophenone, or benzophenone, or (b) a mixture of polyvinyl acetate, ethyl alcohol and n-butyrald ehyde. In a further example, a mixture of polyvinyl alcohol, water and formalin is heated with a previously prepared solution of sulphur dioxide in ethanol. Polyvinyl formate and propionate and valeraldehyde are also specified as starting materials. The resins are separated from the re-action mixture by known methods, e.g. by precipitation by water. Methylol sulphonic acid is prepared by passing sulphur dioxide into formalin. Specifications 436,072 and 477,446 are referred to.