Patent ID: 7087706

Claim:
A resin comprising: polyethylene terephthalate or a copolyester of polyethylene terephthalate and a dicarboxylic acid or its ester equivalent or a copolyester of polyethylene terephthalate and a diol, and substituted cyclic anhydride, said substituted cyclic anhydride being not more than 100 microequivalents per gram of said polyester or copolyester, said resin having a CEG content greater than about 25 microequivalents per gram, said substituted cyclic anhydride is selected form the class consisting of: a) substituted succinic anhydrides where R 1 , R 2 , R 3 , and R 4 can be hydrogen, alkyl, alkenyl or aryl groups, and at least one group is not hydrogen; b) substituted maleic anhydride where R 1 and R 2 can be hydrogen, alkyl, alkenyl or aryl groups, and at least one group is not hydrogen; c) substituted glutaric anhydride where R 1 , R 2 , R 3 , R 4 , R 5 and R 6 can be hydrogen, alkyl, alkenyl or aryl groups, and at least one group is not hydrogen; d) diglycolic anhydride and substituted diglycolic anhydride where R 1 , R 2 , R 3 and R 4 can be hydrogen, alkyl, alkenyl or aryl groups; e) Substituted phthalic anhydride where R 1 , R 2 , R 3 , and R 4 can be hydrogen, alkyl, alkenyl or aryl groups, and at least one group is not hydrogen; f) diphenic anhydride and substituted diphenic anhydride where R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 can be hydrogen, alkyl, alkenyl or aryl groups.