Methods for converting linear polyesters to macrocyclic oligoester compositions and macrocyclic oligoesters

Abstract

Macrocyclic oligoesters and compositions comprising macrocyclic oligoesters are prepared from intermediate molecular weight polyesters. In one embodiment, a diol is contacted with a dicarboxylic acid or a dicarboxylate in the presence of a catalyst to produce a composition comprising a hydroxyalkyl-terminated polyester oligomer. The hydroxyalkyl-terminated polyester oligomer is heated to produce a composition comprising an intermediate molecular weight polyester which preferably has a molecular weight between about 20,000 Daltons and about 70,000 Daltons. The intermediate molecular weight polyester is heated and a solvent is added prior to or during the heating process to produce a composition comprising a macrocyclic oligoester. An optional step is to separate the macrocyclic oligoester from the composition comprising the macrocyclic oligoester.

1 - 44 . (canceled) 
     
     
         45 . A method for preparing a macrocyclic oligoester, the method comprising:
 (a) depolymerizing a polyester to produce a composition comprising macrocyclic oligoester and linear polyester; and   (b) separating the linear polyester from the composition and converting the linear polyester to macrocyclic oligoester.   
     
     
         46 . The method of  claim 45 , wherein the method is conducted continuously or semi-continuously. 
     
     
         47 . The method of  claim 45 , wherein the polyester comprises poly(butylene terephthalate) and the macrocyclic oligoester comprises macrocyclic poly(butylene terephthalate). 
     
     
         48 . The method of  claim 45 , wherein the polyester comprises at least one member selected from the group consisting of poly(butylene terephthalate), poly(ethylene terephthalate), and a poly(butylene terephthalate)/poly(ethylene terephthalate) copolymer. 
     
     
         49 . The method of  claim 45 , wherein the separating step comprises filtering the composition at reduced temperature. 
     
     
         50 . The method of  claim 45 , wherein the polyester in step (a) comprises an intermediate molecular weight polyester. 
     
     
         51 . The method of  claim 50 , wherein the molecular weight of the intermediate molecular weight polyester is between about 20,000 Daltons and about 70,000 Daltons. 
     
     
         52 . The method of  claim 45 , wherein step (a) comprises heating at temperature between about 150° C. and about 200° C. 
     
     
         53 . The method of  claim 45 , wherein the linear polyester comprises residual end groups.