Transparent moulding composition of a polycarbonate and a resin

Abstract

A transparent moulding composition comprising a bisphenol polycarbonate having a low refractive index due to a content of alkyl substitution and a rubber and/or a resin.

We claim: 
     
       1. A transparent moulding compound which comprises a. 10 to 95% by weight of a transparent aromatic polycarbonate.Iadd., .Iaddend.the linear chains of which consist .[.to.]. .Iadd.of .Iaddend.at least 50% of recurrent structural units of .Iadd.the .Iaddend.formula .[.(1).]. ##STR3## in which R 1  to R 8 , which may be the same or different, represent hydrogen or alkyl .Iadd.with the proviso that at least one of the R 1  to R 8  substitutents is an alkyl group .Iaddend.and X represents a single bond, a C 1  to C 12  alkylene or alkylidene group or ##STR4## .[.if at least one of the R 1  to R 8  substituents is an alkyl group or represents a C 6  to C 12  alkylene or alkylidene group if R 1  to R 8  is hydrogen.]. and   b. 5 to 90% by weight of a transparent rubber and/or a transparent resin which contains rubber, the difference in refractive indices between (a) and (b) being not more than 0.010.   
     
     
       2. A moulding compound as claimed in claim 1 in which, in the general formula (1) of claim 1, R 1  to R 8  represents hydrogen or a C 1  to C 5  alkyl group. 
     
     
       3. A moulding compound as claimed in claim 1, in which in the general formula (1), R 1 , R 2 , R 7  and R 8  represent C 1  -C 3  alkyl, R 3 , R 4 , R 5  and R 6  represent H, and X represents C 1  -C 12  alkylene or alkylidene. 
     
     
       4. A moulding compound as claimed in claim 1, in which the structural units of the formula (1) are based on 2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane or 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane. 
     
     
       5. A moulding compound as claimed in claim 1, in which the polycarbonate (a) contains up to 50% of structural units based on bis-(4-hydroxyphenyl)-methane; 2,2-bis-(4-hydroxyphenyl)-propane; 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane or α,α'-bis-(4-hydroxyphenyl)-p.diisopropylbenzene. 
     
     
       6. A moulding compound as claimed in claim 1, in which the polycarbonate (a) is branched by the incorporation of small quantities of polyhydroxyl compound. 
     
     
       7. A moulding compound as claimed in claim 6 in which the polycarbonate contains from 0.05 to 2.0 mols percent of polyhydroxyl compound. 
     
     
       8. A moulding compound as claimed in claim 1, in which the polycarbonate (a) has a molecular weight of from 10,000 to 200,00. 
     
     
       9. A moulding compound as claimed in claim 8, in which the polycarbonate (a) has a molecular weight of from 20,000 to 60,000. 
     
     
       10. A moulding compound as claimed in claim 1, in which the rubber (b) has a refractive index of n D   20  >1.50. 
     
     
       11. A moulding compound as claimed in claim 1, in which the rubber is polybutadiene, polyisoprene, a copolymer of butadiene or isoprene with styrene and/or acrylonitrile or a transpolypentenamer. 
     
     
       12. A moulding compound as claimed in claim 1, in which the component (b) is a transparent graft polymer into which rubber has been mixed, a transparent mixture of a graft polymer, a thermoplastic resin and rubber or a transparent mixture of a thermoplastic resin and rubber, said thermoplastic resin being a homopolymer or copolymer of styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, methylacrylate, methylmethacrylate, ethylacrylate or ethylmethacrylate. 
     
     
       13. A moulding compound as claimed in claim 1, in which the component (b) is a transparent graft polymer or transparent mixture of a graft polymer and a thermoplastic resin, said thermoplastic resin being a homopolymer or copolymer of styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, methylacrylate, methylmethacrylate, ethylacrylate or ethylmethacrylate. 
     
     
       14. A moulding compound as claimed in claim 1, in which the total rubber content is between 5 and 40% by weight. 
     
     
       15. A moulding compound as claimed in claim 12 in which the graft polymer is obtained by grafting one or several of the monomers styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, methylacrylate, methylacrylate, ethylacrylate and ethylmethacrylate onto a diene rubber.