Transparent plastic article
View Patent ↗A plastic article is described having a thickness of 0.5 mm to 5 mm, comprising a polycarbonate thermoplastic composition including polycarbonates containing phthalimidine carbonate units, said composition providing a heat deflection temperature of at least 145° C., a light transmittance of at least 85%, and CIE 1976 L*, a*, b* values of L* greater than 92, a* between −1.5 and 1.5, and b* between −2.0 and 3.0, when tested in the form of a 3.2 mm thick test sample molded at 580° F. (304° C.) with a 1.7 minute residence time, using CIE illuminant C and 2 degree observer.
1. A plastic article having a thickness of 0.5 mm to 5 mm, derived from a thermoplastic composition comprising a polycarbonate, said thermoplastic composition comprising:
1 mole % to 50 mole % of carbonate units represented by the formula (I)
wherein R 2 is hydrogen, a C 1-25 hydrocarbyl group, or halogen, and R 3 hydrogen or a C 1-25 hydrocarbyl group;
50 mole % to 99 mole % of carbonate units represented by the formula (II)
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 moieties, with the proviso that the carbonate units of formula (II) are not within the scope of formula (I), the mole percentages of formulas (I) and (II) based on the total number of carbonate units in the thermoplastic composition; and
from 0.1 to 10 ppm by weight of an acid additive;
wherein the thermoplastic composition has:
a heat deflection temperature of at least 145° C. when tested in the form of a 3.2 mm thick test sample according to ASTM D648-06 under a load of 0.45 MPa;
a light transmittance of at least 85% when tested in the form of a 3.2 mm thick test sample according to ASTM D1003-00 using procedure A and CIE illuminant C and 2 degree observer on a CE7000A using an integrating sphere with 8°/diffuse geometry, specular component included, UV included, large lens, and large area view, with the percent transmittance value reported as Y (luminous transmittance) taken from the CIE 1931 tristimulus values XYZ; and
CIE1976 L*, a*, b* values determined according to ASTM E308-08 of L* greater than 92, a* between −1.5 and 1.5, and b* between −2.0 and 3.0, when tested in the form of a 3.2 mm thick test sample molded at 580° F. (304° C.) with a 1.7 minute residence time, using CIE illuminant C and 2 degree observer.
2. The article of claim 1 , wherein R 3 is a C 6-10 aromatic group.
3. The article of claim 1 , wherein R 2 is hydrogen.
4. The article of claim 1 , wherein the units of formula (II) are derived from bisphenol A.
5. The article of claim 1 , wherein the units of formula (I) are derived from 2-phenyl-3,3′-bis(4-hydroxy phenyl)phthalimidine, and the units of formula (II) are derived from bisphenol A.
6. The article of claim 1 , wherein the thermoplastic composition comprises from 3 to 5 ppm by weight of the acid additive.
7. The article of claim 1 , wherein the acid additive is phosphorous acid, hypophosphorous acid, phosphoric acid, or combinations comprising at least one of the foregoing.
8. The article of claim 1 , wherein the thermoplastic composition is free of epoxy additive.
9. The article claim 1 , wherein the weight average molecular weight of the polycarbonate in the thermoplastic composition, as determined by gel permeation chromatography, using a crosslinked styrene-divinylbenzene column and calibrated to polycarbonate references, changes by less than 1500 Daltons from before extrusion to after extrusion at 600° F. (316° C.).
10. The article of claim 1 , wherein the thermoplastic composition further comprises from 0.00005 wt. % to 0.01 wt. % of a colorant, based on the weight of the thermoplastic composition.
11. The article of claim 1 , having a thickness of 2 mm to 4 mm.
12. The article of claim 1 , wherein the b* value of the thermoplastic composition differs by less than 0.7 when the molding residence time of the test sample is changed from 1.7 minutes to 6.8 minutes.
13. The article of claim 12 , wherein the b* value of the thermoplastic composition differs by less than 0.5 when the molding cycle time of the test sample is changed from 1.7 minutes to 6.8 minutes.
14. The article of claim 1 , wherein the thermoplastic composition comprises a blend of a first polycarbonate comprising units of formula (I) and a second polycarbonate comprising units of formula (II).
15. The article of claim 14 , wherein the second polycarbonate comprises 100 mole % of units of formula (II), based on the total number of carbonate units in the second polycarbonate.
16. The article of claim 14 , wherein the thermoplastic composition comprises from 5 wt. % to 95 wt. % of the first polycarbonate and from 95 wt. % to 5 wt. % of the second polycarbonate, based on the total weight of weight of polycarbonate in the thermoplastic composition.
17. The article of claim 14 , wherein the first polycarbonate comprises units of formula (I) and units of formula (II).
18. The article of claim 17 , wherein the first polycarbonate comprises from 10 mole % to 70 mole % of units of formula (I), and from 30 mole % to 90 mole % of units of formula (II), based on the total number of carbonate units in the first polycarbonate.
19. The article of claim 1 , that is an illumination device lens.
20. The article of claim 19 that is a motor vehicle headlight lens or cover.