Biodegradable polymers, the production thereof and the use thereof for producing biodegradable moldings

A foamed article comprising a biodegradable polyester Q2 having a molecular weight (Mn) of from 6000 to 60,000 g/mol, a viscosity number of from 30 to 350 g/ml (measured in 50:50 w/w o-dichlorobenzene/phenol at a concentration of 0.5% by weight of polyester Q2 at 25° C.), and a melting point of from 50 to 170° C., Q2 being obtained by reaction of a mixture consisting essentially of

• (d1) from 95 to 99.9% by weight of a polyester P1 having a molecular weight (Mn) of from 5000 to 50,000 g/mol, a viscosity number of from 30 to 350 g/ml (measured in 50:50 w/w o-dichlorobenzene/phenol at a concentration of 0.5% by weight of polyester P1 at 25° C.) and a melting point of from 50 to 170° C., P1 being obtained by reaction of a mixture consisting essentially of
• (a1) 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,
• the sum of the individual mole percentages being 100 mol %,
• (a2) a dihydroxy compound selected from the group consisting of C2-C6-alkanediols and C5-C10-cycloalkanediols, and
• (a3) from 0.01 to 5 mol %, based on (a1), of a compound D having at least three groups capable of ester formation selected from the group consisting of hydroxyl and carboxyl,
• the molar ratio of (a1) to (a2) being from 0.4:1 to 1.5:1, or a polyester PWD or a mixture of P1 and PWD, the polyester PWD having a molecular weight (Mn) of from 5000 to 50,000 g/mol, a viscosity number of from 30 to 350 g/ml (measured in 50:50 w/w o-dichlorobenzene/phenol at a concentration of 0.5% by weight of polyester PWD at 25° C.) and a melting point of from 50 to 170° C., and PWD being obtained by reaction of a mixture consisting essentially of components (a1) and (a2),
• the molar ratio of (a1) to (a2) being from 0.4:1 to 1.5:1, with
• (d2) from 0.1 to 5% by weight of a diisocyanate C1, and
• (d3) from 0 to 5 mol %, based on (a1), of compound D.