| 摘要 |
Polyvinyl acetals are prepared by starting from a vinyl ester which has been purified to contain less than ,05 per cent of aldehyde and has been polymerized before it has had time to regenerate aldehyde above that amount. In examples, products obtained by starting from vinyl acetate containing 1 per cent, ,5 per cent, ,2 per cent, ,025 per cent and ,02 per cent and prepared by polymerizing the ester, dissolving in acetic acid and formaldehyde and heating with acetic acid and sulphuric acid are compared. Specifications 337,806, [Class 2 (iii)], 351,082, 387,353, 409,507, 410,770, 430,136, and 436,072 are referred to. |
