Color-stable polycarbonate composition and articles molded therefrom

Abstract

A thermoplastic polycarbonate molding composition free from organo phosphorus compounds and having an improved resistance to discoloration caused by exposure to High Intensity Discharge (HID) light and heat is disclosed. Accordingly, the molding composition contains (co)polycarbonate resin, a dimeric benzotriazole and an ester of a 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid. In a preferred embodiment, a sheet made of (co)polycarbonate resin is rendered improved resistance to discoloration by having applied to at least one of its surfaces an adherent protective film prepared from the polycarbonate composition of the invention.

What is claimed is:  
     
       1. A thermoplastic molding composition free from organic phosphorous compounds, comprising polycarbonate  ( co ) polycarbonate  resin the structure of which entail units derived from one or more bis( hydroxyphenyl )- cycloalkane  and 
       (i) about 1.0 to 30 percent of a bis-benzotriazole conforming structurally to                    
       wherein R 1  and R 2  independent of each other are a hydrogen or a halogen atom, a C 1 -C 12  alkoxy, C 7 -C 18  arylalkoxy or a C 1 -C 10  alkyl, cycloalkyl, arylalkyl or an aryl radical and (Bridge) is either                    
       where p is 0 to 3, q is 1 to 10, Y denotes any of —CH 2 —CH 2 —,                    
       R 3  and R 4  independent of each other are a hydrogen atom, a C 1 -C 10  alkyl, cycloalkyl, arylalkyl or an aryl radical, and 
       (ii) about 0.1 to 5.0 percent of a stabilizer conforming to                    
       wherein R is a linear or branched C 1-24 -alkyl radical, said percent, both occurrences, being in relation to the weight of said composition. 
     
     
       2. The thermoplastic molding composition of claim  1  wherein said (i) is present in an amount of about 1.0 to 15 percent, and said (ii) is present in an amount of about 0.1 to 3.0 percent, said percent, both occurrences, being in relation to the weight of said composition. 
     
     
       3. The composition of claim  1  wherein said benzotriazole conforms to                    
     
     
       4. The composition of claim  3  wherein said stabilizer conforms to                    
     
     
       5. A thermally stable laminate comprising 
       (a) a (co)polycarbonate sheet having a thickness of about 0.8 to 13.0 millimeter, and  
       (b) a protective film having a thickness of about 0.05 to 1.2 millimeter adherent to at least one surface of said sheet, containing the composition of claim  1 .  
     
     
       6. The laminate of claim  5  prepared by co-extrusion. 
     
     
       7. A thermally stable laminate comprising 
       (a) a (co)polycarbonate sheet having a thickness of about 0.8 to 13.0 millimeter, and  
       (b) a protective film having a thickness of about 0.05 to 1.2 millimeter adherent to at least one surface of said sheet, containing the composition of claim  3 .  
     
     
       8. The laminate of claim  7  wherein the stabilizer conforms to                    
     
     
       9. The laminate of claim  7  made by co-extrusion. 
     
     
       10. The laminate of claim  8  made by co-extrusion. 
     
     
       11. The thermoplastic molding composition of claim  1  wherein said units are derived from at least one member selected from the group consisting of  1 , 1 - bis -(   4   - hydroxyphenyl )- cyclohexane and  2 , 2 , 4   - trimethylcyclohexyl  1 , 1   - diphenol.