Use of sulfonic acid as stabilizer in polycarbonate

Abstract

A composition includes a polycarbonate resin formed via an interfacial polymerization process and from 0.05 ppm to 50 ppm of a sulfonic acid. A molded article formed from the composition may exhibit a yellowness index that is less than that of a reference molded article formed from substantially similar polycarbonate composition comprising the polycarbonate resin but in the absence of the sulfonic acid. Methods for forming the molded article in accordance with the above are also described.

That which is claimed is: 
     
         1 . A method of preparing an injection molded article, comprising: injection molding a composition comprising a polycarbonate resin formed via an interfacial polymerization process and having 0.05 ppm to 50 ppm by weight of a sulfonic acid, based on a total weight of the composition. 
     
     
         2 . The method of  claim 1 , wherein a 3.2 mm molded plaque formed from the composition exhibits when tested in accordance with ASTM D1925(1988), exhibits a yellowness index that is less than 4. 
     
     
         3 . The method of  claim 1 , wherein a 3.2 mm molded plaque formed from the composition exhibits when tested in accordance with ASTM D1925(1988), exhibits a yellowness index that is less than 2. 
     
     
         4 . The method of  claim 1 , wherein a 3.2 mm molded plaque formed from the composition exhibits when tested in accordance with ASTM D1925(1988), exhibits a yellowness index that is between 1.5 and 2. 
     
     
         5 . The method of  claim 1 , wherein all of the polycarbonate in the composition was formed via an interfacial polymerization process. 
     
     
         6 . The method of  claim 1 , wherein the polycarbonate resin is substantially free of polycarbonate resin formed via a melt polycarbonate process. 
     
     
         7 . The method of  claim 1 , wherein the polycarbonate resin is free of polycarbonate resin formed via a melt polycarbonate process. 
     
     
         8 . The method of  claim 1 , wherein the polycarbonate resin comprises a polycarbonate homopolymer. 
     
     
         9 . The method of  claim 1 , wherein the sulfonic acid comprises an organosulfonic stabilizer of the formula 
       
         
           
           
               
               
           
         
         wherein each R 7  is independently a C 1-30  alkyl, C 6-30  aryl, C 7-30  alkylarylene, C 7-30  arylalkylene, or a polymer unit derived from a C 2-32  ethylenically unsaturated aromatic sulfonic acid or its ester, and R 8  is hydrogen. 
       
     
     
         10 . The method of  claim 1 , wherein the polycarbonate resin has a hydroxyl phenolic endgroup concentration of 150 ppm or fewer by weight, based on a total weight of the composition. 
     
     
         11 . The method of  claim 10 , wherein the sulfonic acid comprises an alkylbenzene sulfonic acid, a polystyrene sulfonic acid, or a p-toluene sulfonic acid anhydride. 
     
     
         12 . The method of  claim 1 , wherein the sulfonic acid comprises an alkylbenzene sulfonic acid, a polystyrene sulfonic acid, or a p-toluene sulfonic acid anhydride. 
     
     
         13 . The method of  claim 1 , wherein the polycarbonate resin has a purity greater than 99.60% or of at least 99.70% as measured by high performance liquid chromatography. 
     
     
         14 . The method of  claim 1 , wherein the sulfonic acid comprises a p-toluene sulfonic acid. 
     
     
         15 . The method of  claim 1 , wherein the sulfonic acid is present in an amount from 0.5 ppm to 5 ppm by weight, based on a total weigh of the composition. 
     
     
         16 . The method of  claim 1 , wherein the composition comprises a colorant. 
     
     
         17 . The method of  claim 1 , wherein at least a portion of the injection molding is performed at or 370° C. 
     
     
         18 . The method of  claim 1 , wherein the injection molded article at 3.2 mm thickness exhibits a yellowness index when tested in accordance with ASTM D1925(1988) that is less than that of a reference molded plaque injection molded from a substantially similar reference composition consisting essentially of the polycarbonate resin and in the absence of the sulfonic acid. 
     
     
         19 . An injection molded article prepared by the method according to  claim 1 . 
     
     
         20 . The injection molded article of  claim 19 , wherein the article is selected from the group consisting of a lens, a vehicle light, a waveguide element, a reflector, a collimator, a housing for a light source, a lamp bezel, a lamp holder, a lamp cover, a display screen, glazing, a safety goggle, a visor, a medical device, a face shield, an optical fiber, a fuse, a component of a domestic appliance, a machine housing, a fire shield, a food tray, a packaging film, an animal cage, a tray, an optical film, a light bulb, or a film laminate.