Process for preparing amine-modified polyester resins with improved melt flow

A solvent-free process for preparing an amine-modified thermoplastic polyester resin of Formula 2:

• comprising:
• mixing at a temperature in the range of 200° C. to 350° C. in a single screw or twin screw extruder with no external vacuum applied a melted polyester of Formula 1:
• wherein:
• each T is independently a divalent C6-10 aromatic group derived from a dicarboxylic acid or a chemical equivalent thereof;
• each D is independently a divalent C2-8 alkylene group derived from a dihydroxy compound or a chemical equivalent thereof;
• and
• m and n vary from 25 to 1000 and n is less than m;
• and a melted amine, having the formula NHR1R2,
• wherein:
• R1 is C6-36 alkyl, R2 is hydrogen, C1-C36 alkyl, C1-C36 alkylene-aryl, C1-C36 alkylene-heteroaryl, C1-C36 alkylene-cycloalkyl, or C1-C36 alkylene-heterocycloalkyl, and NHR1R2 contains at least 10 carbons;
• thereby forming an amine-modified thermoplastic polyester resin characterized by one or both of the following properties:
• (i) the resin comprises 0.01 to 5 weight percent of the amine;
• and
• (ii) the ratio of the melt flow of the amine-modified resin of Formula 2 compared to the unmodified polyester of Formula 1, as measured according to ASTM D1238, is at least 1.05:1.