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Abstract

Biodegradable polyesters having a molecular weight (M.sub.n) of from 5000 to 50,000 g/mol (measured by gel permeation chromatography), a viscosity number of from 30 to 350 g/ml (measured in 50:50 by weight of o-dichlorobenzene/phenol at a concentration of 0.5% by weight of polyester at 25.degree. C.), and a melting point of from 50 to 170.degree. C., and having both hydroxyl and carboxyl end groups, the molar ratio of carboxyl end groups to hydroxyl end groups being greater than one, which is obtained by reacting a mixture consisting essentially of a.sub.1) a mixture consisting essentially of from 45 to 80 mol % of adipic acid or ester-forming derivatives thereof, or mixtures thereof, from 20 to 55 mol % of terephthalic acid or ester-forming derivatives thereof, or mixtures thereof, and from 0 to 5 mol % of a sulfonate compound, where the sum of the individual mole percentages is 100 mol %, and a.sub.2) a dihydroxy compound selected from the group consisting of C.sub.2 -C.sub.6 -alkanediols and C.sub.5 -C.sub.10 -cycloalkanediols, in the presence of from 0.01 to 5 mol %, per mol of component a.sub.1), of a compound D having at least three groups capable of ester formation, the molar ratio of a.sub.1) to a.sub.2) being from 0.4:1 to 1.5:1, polymers and biodegradable thermoplastic molding compositions, processes for their preparation and their use for producing biodegradable moldings, adhesives, foams and blends with starch obtained from the polymers or molding compositions.

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