Clear polycarbonate polyester blend

Abstract

An optically clear thermoplastic resin composition is disclosed which comprises structural units derived from substituted or unsubstituted polycarbonate and substituted or unsubstituted polyester, wherein said polyester comprises structural units derived from terephthalic acid and a mixture of 1,4-cyclohexane dimethanol and ethylene glycol, wherein said ethylene glycol is greater than about 60 mole percent based on total moles of 1,4-cyclohexane dimethanol and ethylene glycol. In addition the composition disclosed possess good environmental stress cracking resistance, flow and thermal properties.

1 . An optically clear thermoplastic resin composition comprising: structural units derived from substituted or unsubstituted polycarbonate and substituted or unsubstituted polyester, wherein said polyester comprises structural units derived from terephthalic acid and a mixture of 1,4-cyclohexane dimethanol and ethylene glycol, wherein said ethylene glycol is greater than about 60 mole percent based on total moles of 1,4-cyclohexane dimethanol and ethylene glycol.  
     
     
         2 . The composition of  claim 1 , wherein said polycarbonate comprises repeating units of the formula:  
       
         
           
           
               
               
           
         
       
       wherein R 1  is a divalent aromatic radical derived from a dihydroxyaromatic compound of the formula HO-D-OH, wherein D has the structure of formula:  
       
         
           
           
               
               
           
         
         wherein A 1  represents an aromatic group; E comprises a sulfur-containing linkage, sulfide, sulfoxide, sulfone; a phosphorus-containing linkage, phosphinyl, phosphonyl; an ether linkage; a carbonyl group; a tertiary nitrogen group; a silicon-containing linkage; silane; siloxy; a cycloaliphatic group; cyclopentylidene, cyclohexylidene, 3,3,5-trimethylcyclohexylidene, methylcyclohexylidene, 2-[2.2.1]-bicycloheptylidene, neopentylidene, cyclopentadecylidene, cyclododecylidene, adamantylidene; an alkylene or alkylidene group, which group may optionally be part of one or more fused rings attached to one or more aromatic groups bearing one hydroxy substituent; an unsaturated alkylidene group; or two or more alkylene or alkylidene groups connected by a moiety different from alkylene or alkylidene and selected from the group consisting of an aromatic linkage, a tertiary nitrogen linkage; an ether linkage; a carbonyl linkage; a silicon-containing linkage, silane, siloxy; a sulfur-containing linkage, sulfide, sulfoxide, sulfone; a phosphorus-containing linkage, phosphinyl, and phosphonyl;  
         R 1  independently at each occurrence comprises a mono-valent hydrocarbon group, alkenyl, allyl, alkyl, aryl, aralkyl, alkaryl, or cycloalkyl;  
         Y 1  independently at each occurrence is selected from the group consisting of an inorganic atom, a halogen; an inorganic group, a nitro group; an organic group, a monovalent hydrocarbon group, alkenyl, allyl, alkyl, aryl, aralkyl, alkaryl, cycloalkyl, and an alkoxy group;  
         the letter “m” represents any integer from and including zero through the number of replaceable hydrogens on A 1  available for substitution;  
         the letter “p” represents an integer from and including zero through the number of replaceable hydrogens on E available for substitution;  
         the letter “t” represents an integer equal to at least one;  
         the letter “s” represents an integer equal to either zero or one; and  
         “u” represents any integer including zero.  
       
     
     
         3 . The composition of  claim 2 , wherein the dihydroxyaromatic compound from which D is derived is bisphenol A.  
     
     
         4 . The composition of  claim 1 , wherein said optically clear thermoplastic resin composition comprises structural units derived from polyester and polycarbonate in a range of about 10-90 percent by weight of polyester and 90-10 percent by weight of polycarbonate.  
     
     
         5 . The composition of  claim 1 , wherein said optically clear thermoplastic resin composition comprises structural units derived from polyester and polycarbonate in a range of about 25-75 percent by weight of polyester and 75-25 percent by weight of polycarbonate.  
     
     
         6 . The composition of  claim 1 , wherein said optically clear thermoplastic resin composition comprises about 25 percent by weight of polyester and 75 percent by weight of polycarbonate.  
     
     
         7 . The composition of  claim 1 , wherein said optically clear resin composition has a yellowness index of about less than 17.  
     
     
         8 . The composition of  claim 1 , wherein said optically clear resin composition transmits about greater than 70 percent light in the region of about 250 nm to about 300 nm.  
     
     
         9 . The composition of  claim 1 , wherein said optically clear resin composition has a haze value about less than 30.  
     
     
         10 . An article comprising the composition of  claim 1 .  
     
     
         11 . A reactive extrusion process to prepare an optically clear thermoplastic resin composition comprising: structural units derived from substituted or unsubstituted polycarbonate and substituted or unsubstituted polyester, wherein said polyester comprises structural units derived from terephthalic acid and a mixture of 1,4-cyclohexane dimethanol and ethylene glycol, wherein said ethylene glycol is greater than about 60 mole percent based on total moles of 1,4-cyclohexane dimethanol and ethylene glycol and wherein said process comprises the steps of 
 a. melting said polycarbonate and polyester to form a molten mixture; 
 b. extruding said molten mixture in an extruder to form an extrudate; and  
 c. molding said extrudate.  
   
     
     
         12 . The method according to  claim 11 , further comprising the step of pelletizing the extrudate.  
     
     
         13 . The method according to  claim 11 , wherein said melting is carried out at in temperature range between about 240° C. and about 300° C.  
     
     
         14 . The method according to  claim 11 , wherein said extruding is carried out at a temperature range between about 250° C. and about 280° C.  
     
     
         15 . The method according to  claim 11 , wherein said extrusion is carried out in an extruder.  
     
     
         16 . The method according to  claim 11 , wherein said extruder has at least one vacuum vent.  
     
     
         17 . The method according to  claim 11 , wherein said extrusion is carried out at a torque in the range of between about 55 percent and about 65 percent.  
     
     
         18 . The method according to  claim 11 , wherein said extrusion is carried out at a specific energy consumption in the range of between about 0.288 and about 0.365 kWh/kg.