Polyvinyl Formal: Polyvinyl Acetate Acetalised with Formalin, Shawinigan 1933

Polyvinyl acetate dissolved in glacial acetic acid, with formalin and a little sulfuric acid, kept stirred 24 hours at 70 °C, loses its acetate groups and takes up formaldehyde: polyvinyl formal, a hard, tough, pale resin. Shawinigan's patent (1933) gives the recipe; it is the resin of 'Formvar' magnet-wire enamel. The picture: our diagram of the reaction.