Impact modified polycarbonate compositions

1. A composition consisting of

A) from 60 to 86 parts by weight, based on the sum of components A+B+C, of an aromatic polycarbonate and/or an aromatic polyester carbonate,

B) from 4 to 12 parts by weight, based on the sum of components A+B+C, of a graft polymer comprising

B.1 from 10 to 50 wt. %, based on the graft polymer B, of a shell of at least one vinyl monomer, and

B.2 from 90 to 50 wt. %, based on the graft polymer B, of a graft base of a silicone-acrylate composite rubber, wherein the silicone-acrylate composite rubber comprises an interpenetrating network of silicone rubber and acrylate rubber,

C) from 10 to 30 parts by weight, based on the sum of components A+B+C, of at least one rubber-free vinyl (co)polymer of

C.1 from 50 to 99 parts by weight, based on component C, of a vinyl aromatic compound and/or a vinyl aromatic compound substituted on the ring and/or a (meth)acrylic acid (C1-C8)-alkyl ester, and

C.2 from 1 to 50 parts by weight, based on component C, of a vinyl cyanide and/or a (meth)acrylic acid (C1-C8)-alkyl ester and/or an unsaturated carboxylic acid and/or an anhydride of an unsaturated carboxylic acid and an imide of an unsaturated carboxylic acid, and

D) from 0 to 20 parts by weight, based on the sum of components A+B+C, of at least one polymer additive selected from the group consisting of flameproofing agents, flameproofing synergists, antidripping agents, lubricants and mould release agents, nucleating agents, stabilisers, antistatics, colourings and pigments wherein components B and C are present in a ratio of the parts by weight of B:C in a range from 1:1.3 to 1:3.5, and wherein the composition is free of inorganic filler.

2. A composition according to claim 1 , consisting of

A) from 70 to 80 parts by weight, based on the sum of components A+B+C, of an aromatic polycarbonate and/or an aromatic polyester carbonate,

B) from 6 to 10 parts by weight, based on the sum of components A+B+C, of said graft polymer,

C) from 14 to 20 parts by weight, based on the sum of components A+B+C, of at least one rubber-free vinyl (co)polymer, and

D) from 0.2 to 5 parts by weight, based on the sum of components A+B+C, of at least one polymer additive,

wherein components B and C are present in a ratio of the parts by weight of B:C in a range from 1:1.6 to 1:2.7.

3. A composition according to claim 1 comprising as the graft base B.2, a composite rubber comprising from 10 to 70 wt. % silicone rubber and from 90 to 30 wt. % butyl acrylate rubber, based in each case on the weight of graft base B.2.

4. A composition according to claim 3 comprising as the graft base B.2, a composite rubber comprising from 20 to 60 wt. % silicone rubber and from 80 to 40 wt. % butyl acrylate rubber, based in each case on the weight of graft base B.2.

5. A composition according to claim 1 comprising as component A, an aromatic polycarbonate and/or aromatic polyester carbonate having a weight-average molecular weight M w , of from 22,000 to 32,000 g/mol.

6. A composition according to claim 1 comprising as component A, an aromatic polycarbonate and/or aromatic polyester carbonate having a weight-average molecular weight of from 24,000 to 28,000 g/mol.

7. A composition according to claim 1 comprising as the graft base B.2, a silicone-acrylate composite rubber having at least one graft-active site, wherein the silicone rubber and the acrylate rubber interpenetrate in the composite rubber so that said silicone rubber and said acrylate rubber cannot substantially be separated from each another.

8. A composition according to claim 1 comprising as the graft shell B.1, a methyl methacrylate and/or a mixture of styrene and acrylonitrile.

9. A composition according to claim 1 comprising as component C, a copolymer of C.1 styrene and C.2 acrylonitrile.

10. A composition according to claim 1 comprising as component C, polymethyl methacrylate and/or a vinyl copolymer comprising at least 70 parts by weight based on component C, of methyl methacrylate and up to 30 parts by weight based on component C, of at least one comonomer selected from the group consisting of styrene, n-butyl acrylate, tert-butyl acrylate and ethyl acrylate.

11. A moulding comprising a composition according to claim 1 .

12. A polycarbonate composition according to claim 1 , which does not display a splintering fracture in a multiaxial dart-penetration test at −10°, has a melt viscosity at 260° C. and a shear rate of 1000 s −1 of not more than 250 Pas and exhibits a Vicat B120 heat distortion resistance temperature of at least 125° C.

13. A method for making a composition of claim 1 comprising mixing A, B, C and optionally D and melt extruding the resultant.