Polyester Carbonates Consisting of Different Diols in a Defined Ratio

A polyestercarbonate, comprising the structural formula (1)

• in which
• A independently per repeating unit represents at least either structural unit (A) or structural unit (B), where
• (A) represents chemical formula (2)
• and
• (B) represents chemical formula (3)
• *—X—* (3),
• where x represents a branched alkylene group having 4 to 20 carbon atoms, which may optionally be interrupted by at least one heteroatom, or a cycloalkylene group comprising at least one branch, wherein the cycloalkylene group has 4 to 20 carbon atoms, which may optionally be interrupted by at least one heteroatom,
• y each independently represents chemical formula (IIIa) or (IIIb)
• in which B each independently represents a CH2 group or a heteroatom selected from the group consisting of O and S,
• R1 each independently represents a single bond or an alkylene group having 1 to 10 carbon atoms,
• n is a number between 0 and 3, and
• 0<x<1,
• where the * in each case indicate the position at which the chemical formulae are incorporated into the polyestercarbonate,
• wherein the polyestercarbonate comprises
• 98 mol % to 75 mol % of structural unit (A) and
• 2 mol % to 25 mol % of structural unit (B),
• based in each case on the sum of the structural units (A) and (B), and
• wherein the polyestercarbonate has a relative solution viscosity, measured in dichloromethane at a concentration of 5 g/l at 25° C. with an Ubbelohde viscometer, of 1.20 to 1.70.