High-molecular weight linear polyesters and a process for preparing them

Abstract

High molecular weight linear polyesters advantageous for use as hot melt adhesives and powder coating agents, are prepared by a process for preparing a high-molecular weight, linear copolyester by condensing 40-85 molar percent of terephthalic acid optionally in the form of a dialkyl ester, half of which component can optionally be replaced by another dicarboxylic acid also optionally in the dialkyl ester form, and 60-15 molar percent of adipic acid, with an alkanediol of 2-6 carbon atoms in its carbon chain, at an elevated temperature in the presence of a conventional catalyst, in a first condenstation stage which is an interesterification or esterification stage and a second condenstation stage which is a polycondensation stage, whereby a copolyester melt is produce. The process comprises, before or during the first condensation stage, adding 0.005-01 molar percent, based on the total acid component, of a C.sub.6 - aryl or C.sub.7 - alkaryl ester of phosphorous acid or of phosphoric acid to the reaction mixture; and, after termination of the second condensation stage, adding 0.01-0.2 molar percent, based on the total acid component, of hypophosphorous acid to the finished copolyester melt.

Dependencies are inferred from the claim text.