Color stable thermoplastic composition

1. A plastic article formed from a thermoplastic composition comprising a polycarbonate having repeating structural carbonate units according to the formula

in which at least 60 percent of the total number of R 1 groups contain aromatic moieties and the balance thereof are aliphatic, alicyclic, or aromatic; the polycarbonate having been prepared through an interfacial polymerization process from BPA monomer having an organic purity higher than 99.70% by weight and having a hydroxyl content lower than 150 ppm by weight;

wt. % to 0.30 wt. %, based on the total weight of the thermoplastic composition, of an epoxy additive having at least two epoxy groups per molecule; and

wt. % to 0.30 wt. %, based on the total weight of the thermoplastic composition, of a phenolic diphosphite derived from pentaerythritol;

wherein the thermoplastic composition has a sulfur content lower than 2 ppm, and

wherein the thermoplastic composition exhibits a dE (2000 hrs.) value of less than 2.0 after 2000 hours of heat aging at 130° C., measured according ISO 11664-4:2008(E)/CIE S 014-4/E:2007 using CIE illuminant D65 and a 2.5 mm thick molded plaque of the thermoplastic composition.

2. The plastic article of claim 1 , wherein the thermoplastic composition exhibits a dE76 value of less than 1.50 after 2000 hours of heat aging at 130° C., measured according ISO 11664-4:2008(E)/CIE S 014-4/E:2007 using CIE illuminant D65 and a 2.5 mm thick molded plaque of the thermoplastic composition.

3. The plastic article of claim 1 , wherein the thermoplastic composition exhibits a b*<0.56 and a L*>95.85 as specified by ISO 11664-4:2008(E)/CIE S 014-4/E:2007 using CIE illuminant D65 and a 2.5 mm thick molded plaque of the thermoplastic composition.

4. The plastic article of claim 1 , wherein the thermoplastic composition exhibits a b* of <0.52 and a L*>98.85 as specified by ISO 11664-4:2008(E)/CIE S 014-4/E:2007, measured according ISO 11664-4:2008(E)/CIE S 014-4/E:2007 using CIE illuminant D65 and a 2.5 mm thick molded plaque of the thermoplastic composition.

5. The plastic article of claim 1 , wherein the epoxy additive is an aliphatic epoxide having at least two epoxy groups per molecule and a molecular weight less than 600 g/mol.

6. The plastic article of claim 5 , wherein the epoxy additive is a carboxylate epoxy resin.

7. The plastic article of claim 6 , wherein the epoxy additive is a carboxylate epoxy resin comprising a carboxylate diepoxide according to the formula:

8. The plastic article of claim 1 , wherein the phenolic diphosphite is according to the formula:

wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 each independently represents hydrogen or a C 1-20 organic radical.

9. The plastic article of claim 8 , wherein R 1 , R 3 , R 6 , and R 8 are each cumyl.

10. The plastic article of claim 8 , wherein at least 40% of the R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 groups are cumyl.

11. The plastic article of claim 1 , wherein at least 90% of the R 1 groups are derived from a bisphenol.

12. The plastic article of claim 10 , wherein all of the R 1 groups are derived from a bisphenol.

13. The plastic article of claim 10 , wherein the bisphenol is bisphenol A.

14. The plastic article of claim 1 , wherein the thermoplastic composition comprises from 0.01 wt. % to 0.25 wt. % of the epoxy additive.

15. The plastic article of claim 1 , wherein the thermoplastic composition comprises from 0.02 wt. % to 0.30 wt. % of the phenolic diphosphite.

16. The plastic article of claim 1 , wherein the light-transmitting article is an illuminant lens, illuminant cover, a light guide, or an optical sheet.

17. The plastic article of claim 16 , that is an illuminant lens or cover.

18. The plastic article of claim 17 , wherein the illuminant is a light emitting diode.

19. The plastic article of claim 1 , that is configured to have a viewing surface and a thickness of at least 0.5 cm as measured perpendicular to the viewing surface.

20. The plastic article of claim 1 , that is a light guide or light transmitting device having a light transmission path of at least 3 mm.

21. The plastic article of claim 20 , wherein the light transmission path is at least 10 mm.

22. The plastic article of claim 1 , that is a sheet configured to have a viewable edge surface.