| 摘要 |
Polyvinyl alcohol is made, preferably continuously, by boiling with agitation an anhydrous mixture of a polyvinyl ester and a hydrolytic alcohol containing from 1 to 4 carbon atoms, in the presence of an alkali metal alcoholate maintained at a concentration of not less than 0.1 per cent by weight of the mixture, removing the evolved vapours from the mixture and obtaining the polyvinyl alcohol as a finely divided suspension, e.g. in an excess of the alcohol. Specified catalysts are sodium methylate, potassium ethylate, lithium butyrate, sodium propylate, sodium butylate and sodium decylate. The alcohol may be methanol ethanol, propanol or butanol. Polyvinyl esters mentioned are polyvinyl formate, polyvinyl acetate, polyvinyl propionates and polyvinyl butyrates. |
