Branched polyamide

Abstract

The invention relates to a branched polyamide prepolymer obtained or obtainable by polymerization of a polyamide forming monomer mixture, comprising AA-BB repeat units and branching units derived from diamines (monomer A) dicarboxylic acids (monomer B), and/or a salt of A and B, and a higher functional monomer (monomer C) present in a molar amounts defined by formula I and formula II: MC=(Q/FC)*(MA+MB) (Formula I) and R=((MA*2)+(MC*FCA))/((MB*2)+(MC*FCB)) (Formula II) wherein—MA, MB and MC represent the molar amounts of repeat units derived from the monomers A, B and C, respectively; —FC represent the functionality of monomer C, and is equal to FC-A+FC-B; —FC-A is the number of the amino functional groups comprised by monomer C; —FC-B is the number of carboxyl functional groups or precursor groups thereof comprised by monomer C; —Q is a number in the range of 0.06-1.00; and —R is a number in the range of 0.7-1.3, which polyamide prepolymer has a viscosity number (VN), measured according to ISO 307, in the range of 7-30 mL/g. The invention also relates to a process for preparing a branched polyamide polymer, comprising (1) a melt-mixing step wherein an essentially linear polyamide (pre)polymer and a branched polyamide prepolymer are provided to and mixed and heated in a melt mixing apparatus, thereby forming a mixed melt, and the mixed melt being cooled, thereby forming a solid mixture; and (2) a solid state post condensation step wherein the solid mixture is post-condensed at elevated temperature in the solid state, thereby forming a high molecular weight branched polyamide polymer.