Process for the preparation of flame-resistant polycarbonate moulding compositions containing tetrafluoroethylene polymers

Claim 1

A process for the preparation of a flame-resistant polycarbonate moulding composition, consisting of (a) thermoplastic, halogen-free, sulphur-free and phosphorus-free polycarbonate, based on at least 1 diphenol of the formula ##STR5## wherein A is a single bond, C 1 -C 5 alkylene, C 2 -C 5 alkylidene or C 5 -C 6 cycloalkylidene, x is 0, 1 or 2 and n is 1 or 0, (b) an alkali metal salt of an organic or inorganic acid, (c) tetrafluoroethylene polymer with mean particle sizes from 0.05 μm to 20 μm, and (d) halogen-free graft polymer comprising: (1) 5 to 90 parts by weight of a mixture of (i) 50 to 95% by weight of styrene, α-methyl-styrene, nuclear-substituted styrene, methyl methacrylate, or mixtures thereof, and (ii) 50 to 5% by weight of (meth)acrylonitrile, methyl methacrylate, maleic anhydride, N-substituted maleimide, or mixtures thereof, onto (2) 95 to 10 parts by weight of a rubber having a glass temperature T G ≦10° C., where the component (a) is present in amounts of 86 to 99.85% by weight, component (b) is present in amounts of 0.02 to 1% by weight, component (c) is present in amounts of 0.05 to 5% by weight, and component (d) is present in amounts of 0.08 to 8% by weight, and where the total of components (a)+(b)+(c)+(d) is, in each case, 100% by weight, in which the components (a) to (d) are, after having been mixed, melt-compounded or melt-extruded at temperatures of 260° C. to 320° C., component (c) being used in the form of a coagulated mixture of emulsions of the tetrafluoroethylene polymer (c) with emulsions of the graft polymer (d), the ratio of mixing of component (c) to component (d) being between 5:95 and 40:60 in each case.