SOLID-STATE POLYAMIDATION PROCESSES

Low reaction rates and distinct transition phenomena from the solid to the melt state restrain solid state polymerisation (SSP) reactions of nylon salts for industrial application. To alleviate these problems, catalysts containing nylon salts are employed. In this study, hexamethylenediammonium adipate (HMA) particles were used containing a strictly controlled amount of catalyst, either phosphoric acid, sulphuric acid or boric acid. The results show considerable acceleration of the reaction rate, especially in the presence of boric acid, while the solid state character of the process is maintained throughout the total course of the reaction. Comparative polymerisation runs were monitored both by end-group and quantitative water determinations of the reacting material to exclude any accumulation of the water of polycondensation within the reacting particles. The results obtained support further the mechanism proposed for the transition solid-melt in SSP runs of nylon salts in the absence of catalysts. In the latter case extended water accumulation is the rule.