Polyester polymerization process

Abstract

The present invention relates to a process for producing PET based on titanium catalyst having acceptable properties for resin used in the production of bottles for beverages. More particularly the invention relates to a process in which the incoming pre-polymer temperature is higher than the final outlet temperature in the final melt phase polycondensation reactor.

The invention claimed is:  
     
       1. A method for the production of solid polyester polymer resin comprising:
 a) esterifying the diacids and diols to form an oligomer mixture with a DP of less than 20; and 
 b) polycondensing the oligomer mixture in the presence of a polycondensation catalyst composition comprising titanium species at a temperature of greater than 284° C. to an IV of about 0.4 dl/g; and 
 c) completing the polycondensation by increasing the IV by at least 0.2 dl/g and cooling the polymer melt temperature to less than 282° C.; and 
 d) solidifying and cutting the molten polyester polymer composition into solid polyester polymer particles; and optionally 
 e) solid state polymerizing the solid polyester polymer particles to increase the IV by more than 0.05 dl/g. 
 
     
     
       2. The method of  claim 1 , wherein step a) esterifies the diester of the said diacids. 
     
     
       3. The method of  claim 1 , wherein the mole ratio of said diol to said diacid is less than about 1.15. 
     
     
       4. The method of  claims 1  or  2 , wherein the said diacids comprise at least 80 weight % of terephthalic acid or 2,6-naphthalene dicarboxylic acid. 
     
     
       5. The method of  claim 4 , wherein said diols comprise at least 80 weight % of ethylene glycol.