Polysiloxane-polycarbonate block cocondensates

A polysiloxane-polycarbonate block cocondensate derived from

• (A) at least one hydroxyaryl-terminated siloxane of the formula (1) (siloxane component)
• in which
• R1 is H, Cl, Br or C1 to C4-alkyl,
• R2 and R3 are the same or different and each independently from one another selected from aryl, C1 to C10-alkyl and C1 to C10-alkylaryl,
• X is a single bond, —CO—, —O—, C1- to C6-alkylene, C2 to C5-alkylidene, C5 to C12-cycloalkylidene or C6 to C12-arylene which may optionally be fused to further aromatic rings containing heteroatoms,
• n is a number from 10 to 100,
• m is a number from 2 to 5, and
• p is 0 or 1;
• (B) and at least one polycarbonate
• wherein the polysiloxane-polycarbonate block cocondensate contains at least one of the following structures (I) to (IV):
• in which
• the phenyl rings are unsubstituted or independently mono- or disubstituted by C1 to C8-alkyl and/or halogen,
• X is a single bond, C1 to C6-alkylene, C2 to C5-alkylidene or C5 to C6-cycloalkylidene,
• the linkages indicated by—in the structural units (I) to (IV) are each part of a carboxylate group;
• and wherein the amount of the structural units (I) to (IV) totals 60 to 1500 ppm (determined after hydrolysis, based on the polysiloxane-polycarbonate block cocondensate), wherein the polysiloxane-polycarbonate block cocondensate has a relative solution viscosity of 1.26 to 1.40, determined in dichloromethane at a concentration of 5 g/l at 25° C. using a Ubbelohde viscosimeter.