Titanium-based catalyst showing excellent activity and selectivity in polycondensation reactions

Abstract

Method for producing polyesters using titanium atrane catalysts is disclosed. Also disclosed are methods for making the titanium atrane catalysts of the present invention. The titanium atrane catalysts are useful as esterification and/or polycondensation catalysts, have similar activity, color and byproduct formation as conventional catalyst systems, but with reduced toxicity and regulatory concerns.

1 . A method for producing a polyester comprising:
 esterifying a polyacid and a polyol to produce a monomer; and   polymerizing the monomer by way of polycondensation in the presence of an atrane containing catalyst to form an acyclic polyester.   
     
     
         2 . The method according to  claim 1  wherein the atrane-containing catalyst is a titanium atrane catalyst. 
     
     
         3 . The method according to  claim 2  wherein the polyacid is terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, naphthalinedicarboxylic acid, trimesinic acid, trimellitic acid or its anhydride. 
     
     
         4 . The method according to  claim 3  wherein the polyol is ethylene glycol, diethylene glycol, cyclohexanedimethanol, 1,3-propanediol, 1,4-butanediol, isosorbide, resorcinol, hydroquinone, trimethylolpropane, or pentaerythritol. 
     
     
         5 . The method according to  claim 4  wherein the polyester is polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, or polyethylene naphthalate. 
     
     
         6 . The method according to  claim 5  wherein the catalyst is present in the polycondensation step in a concentration of from 5 to 250 ppm. 
     
     
         7 . The method according to  claim 1  wherein the esterification step is conducted at a temperature of above 200° C. 
     
     
         8 . The method according to  claim 1  wherein the polycondensation step, comprising a melt phase and a solid state phase, is conducted at a temperature of from 260° C. to 290° C. for the melt phase and a temperature of from 190° C. to 230° C. for the solid state phase. 
     
     
         9 . The method according to  claim 1  wherein the esterification step is conducted at a pressure of from 1 to 10 bar. 
     
     
         10 . The method according to  claim 1  wherein the polycondensation step, comprising a melt phase and a solid state phase, is conducted at a pressure of from 3.0 to 0.1 mbar. 
     
     
         11 . A catalyst comprising a titanium atrane for use in acyclic ester polycondensation. 
     
     
         12 . The catalyst according to  claim 11  wherein the catalyst has a structure: 
       
         
           
           
               
               
           
         
       
       wherein R is H, C 1 -C26-alkyl-, aryl-, or hetaryl; R 1  is H, or methyl-, or ethyl- or ethenyl-aryl, or hetaryl; R 2  is H, or methyl-, or ethyl, or ethenyl-aryl, or hetaryl and R 3  is H, or methyl- or ethyl-, or ethenyl-aryl, hetaryl. 
     
     
         13 . A method for making a titanium atrane catalyst comprising:
 (a) contacting a solution comprising a titanium (IV) alkoxide compound and a first solvent with an organic acid;   (b) contacting the solution formed in step (a) with a substituted or unsubstituted trialkanolamine to form an impure catalyst; and   (c) purifying the impure catalyst to form the titanium atrane catalyst.   
     
     
         14 . The method according to  claim 13  wherein the titanium (IV) alkoxide compound is titanium n-butylate, titanium isopropylate, titanium n-propylate, titanium t-buylate, or titanium ethylate. 
     
     
         15 . The method according to  claim 14  wherein the first solvent is a primary alcohol, a secondary alcohol, or a tertiary alcohol. 
     
     
         16 . The method according to  claim 15  wherein the organic acid is a carboxylic acid. 
     
     
         17 . The method according to  claim 16  wherein the organic acid is acetic acid or propionic acid. 
     
     
         18 . The method according to  claim 17  wherein the trialkanolamine is triethanolamine, triisopropanolamine, or a substituted triethanolamine. 
     
     
         19 . The method according to  claim 13  wherein step (c) further comprises:
 c1) evaporating the first solvent from the impure catalyst to remove undesired byproducts; 
 c2) contacting the product from step c1 with a second solvent to form a suspended solid; and 
 c3) boiling the suspended solid to form a purified titanium atrane catalyst. 
 
     
     
         20 . The method according to  claim 19  wherein the second solvent in step c2 is selected from the group consisting of toluene, alkylsubstituted aromatics and long chain alkanes.