Branched, high-molecular weight thermoplastic polycarbonates

In a process for the preparation of a high molecular weight branched polycarbonate substantially free of cross linking comprising reacting a carbonic acid derivative with aromatic dihydroxy compounds, from about 0.05 to about 2 mol % of a branching agent and about 0.1 to about 8 mol % of a monohydric phenol (the mol percentages being based on the mols of the aromatic dihydroxy compound), the improvement wherein the branching agent is a 3,3-bis-(4-hydroxyaryl)-oxindole.

A thermoplastic high molecular weight polycarbonate having a relative viscosity of about 1.230 to 1.450 measured in a solution of 0.5 g in 100 ml of methylene chloride at 25.degree. C. and an average light scattering molecular weight, M.sub.LS, of about 10,000 to 100,000 said polycarbonate being branched by about 0.05 to 2 mol % of a 3,3-bis-(4-hydroxyaryl)-oxindole.

The process for the preparation of a thermoplastic, branched-chain, high molecular weight, soluble polycarbonate comprising condensing a difunctional aromatic halogen-free or halogen-containing dihydroxy compound or a mixture thereof in the presence of from about 0.05 to 2 mol % of a branching agent and from about 0.1 to 8.0 mol % of a monofunctional aromatic hydroxy compound, in each case relative to the mols (100 mol %) of the difunctional aromatic dihydroxy compound, with phosgene, a bis-chlorocarbonic acid ester or another compound which forms carbonate groups, in solution or by means of a phase boundary reaction, at a temperature of from about 20.degree. to 80.degree. C., or with a carbonic acid diaryl ester in the melt at a temperature of from about 150.degree. to 300.degree. C., the said branching agent being a 3,3-bis-(4-hydroxyaryl)-oxindole of the formula (I):

• ##STR9## wherein R.sub.1 is a radical of the formula ##STR10## wherein R.sub.4 and R.sub.5 can be identical or different and denote methyl or hydrogen, and
• R.sub.2 and R.sub.3 are hydrogen.

A high molecular weight branched polycarbonate substantially free of crosslinking which comprises a polycarbonate polymer containing residues of aromatic dihydroxy compounds, about 0.05 to 2 mol % of a 3,3-bis-(4-hydroxyaryl)-oxindole of the formula ##STR11## wherein R.sub.1 is a radical of the formula ##STR12## wherein R.sub.4 and R.sub.5 can be identical or different and denote methyl or hydrogen, and

• R.sub.2 and R.sub.3 are hydrogen, and about 0.1 to about 8 mol percent of a monohydric phenol, the mol percentages being based on the mols of the aromatic dihydroxy compounds, said branched polycarbonate having an average molecular weight by light scattering, M.sub.LS of about 10,000 to 100,000.