A comprehensive model for nylon melt equilibria and kinetics

Abstract

ABSTRACT:A model for handling the effect of water on nylon equilibria and kinetics has been developed and tested. Observed variations in the equilibria and kinetics are attributed to microscopic phenomena, not an empirical expression. The equilibrium variation is modeled based on two states of water in the nylon melt, and the kinetic variation is modeled as due to a changing dielectric constant. All reactions are assumed to be acid catalyzed. Results are good at water to polymer ratios ranging from 0.01 to 30 and from temperatures from 200 to 280ЊC. The model framework also allowed the calculation of interchange rates and ring oligomer concentrations. The model is compared with published data and other proposed models.

An Advanced Kinetic Model of Hydrolytic Polymerization of e-Caprolactam Including the Amide Interchange Reactions

“…Ray [13] also agreed to the assumption that the amide interchange reaction is mainly the interaction between the P n+2 n = 1, 2, 3 ...…”

Polycondensation

“…Mallon and Ray [191] have suggested that its initial rate is determined by the presence of impurities. Mallon and Ray [191] have suggested that its initial rate is determined by the presence of impurities.…”

“…It should also be possible to predict the concentrations of higher cyclic oligomers, but the only usable data concern the equilibrium concentrations, and experimental confirmation has not yet been possible [191].…”

Improved Kinetic Rate Constants for Nylon 6, Nylon 6,6, and Nylon 6/6,6 Copolymer

“…Simulation results from our nylon 6/6,6 copolymer modeling studies (and nearly all nylon 6 modeling studies in the literature) rely on values of rate constants and equilibrium constants determined by Arai et al, who estimated their parameters using nylon 6 batch reactor data from a large number of experiments at relatively low water concentrations (0.8–2.1 wt%) 11. Due to the limited range of operating conditions, several research groups5,6,14–16 have expressed concerns about using Arai's parameter values over the much wider range of conditions that are typically encountered during nylon 6,6 homopolymerization and nylon 6/6,6 copolymerization. For example, it is well known that Arai's parameters do not account for the complex influence of water on nylon 6 and nylon 6,6 reaction equilibria that has been observed in the literature, especially for polycondensation reaction R2 17–27.…”