Chap._600002 - Poly(vinyl alcohol cannot be prepared from...

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OH O CH 2 =CH CH 3 -C-H Poly(vinyl alcohol) cannot be prepared from its monomer by the usual techniques, due to the monomer difficulties. Vinyl alcohol has not been isolated in the free state; the keto tautomer, acetaldehyde, is much more satble form and is always obtained: The preferred method of preparing PVOH is the solution polymerization of vinyl acetate in methanol. The resulting PVAc solution can be used directly without the need for isolating the polymer before hydrolysis. This method is the most suitable for continuous processes. The most common commercial types of PVOH are the partially hydrolysed grades in which 87-89% of the acetate groups have been replaced and the completely hydrolysed grades in which 99-100% of acetate groups have been replaced. The degree of alcoholysis has an effect on the properties of the polymer. * Synthesis of Poly(vinyl acetal)s Poly(vinyl formal) is generally prepared directly from PVAc
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