Treatment of poly(vinyl alcohol) with aldehydes or ketones results in the
formation of poly(vinyl acetal)s and poly(vinyl ketal)s, of which only the
former products are of commercial significance. At the present time,
poly(vinyl formal) and poly(vinyl butyral) are the most important members of
this group; poly(vinyl acetal) itself now finds little application.
The preparation of a poly(vinyl acetal) from poly(vinyl alcohol) may be
represented as follows:
Thus, in practice, a poly(vinyl acetal) contains acetal groups, hydroxyl groups
(which become isolated and cannot undergo reaction with the aldehyde) and
acetate groups (which are due to incomplete hydrolysis of the parent
poly(vinyl acetate)). Differing proportions of these groups lead to various
grades of materials.
