Preparation of polyhexamethyleneadipamide prepolymer by a low‐temperature process

Abstract

Abstract The polyhexamethyleneadipamide (PA 6,6) prepolymer is prepared starting from dry hexamethylenediammonium adipate (PA 6,6 salt) by a low‐temperature polyamidation technique, which ensures balanced and free‐of‐thermal‐degradation products. The operating temperature is chosen in the vicinity of the melting point of the polyamide salt, to avoid thermal decomposition, which accompanies the higher temperatures of the conventional polyamidation processes. Two stages of prepolymerization are suggested: First, the reaction is carried out under autogenous conditions (pressurized system) to or beyond the point where diamine ends have reacted; hereafter, the system is vented so as to remove the produced water and to drive the condensation reaction toward a higher degree of polymerization. The process is demonstrated using both shaker tubes and a modified, intensively stirred autoclave. The products have balanced ends and no detectable thermal degradation effects and are used as a starting material for solid‐state finishing toward high molecular weight polyamides. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 301–306, 2004