| 摘要 |
<p>Film- and fibre-forming light-coloured polyesters with low yellowing are produced by 2-step process; (1) alcoholysis of a mixture containing a dialkyl ester of an aromatic dicarboxylic acid and a dihydric alcohol and (2) polycondensation of bi-ester formed from dihydric alcohol and the aromatic dicarboxylic acid, where both steps take place in the presence of a catalyst system which consists of a mixture of (a) a metal salt containing the anion of a weak acid, including oxide, and (b) a cpd. X3-O-ZX1X2(=O) (where X1 is -R or -OR, X2 is R and X3 is H or R, and R is a monovalent opt. substd. hydrocarbyl, and Z is a Group VB element with atomic No. above 7). Pref. R has 1 - 8C, and Z is P, suitable P cpds. being dialkyl alkyl phosphonates.</p> |
