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SynopsisA method to determine the concentration of t-aminocaproic acid (ACA) in poly-t-caprolactam by high-pressure liquid chromatography is established. The polymerizations for initial water concentrations of 0.42,0.82, and 1.18 mol/kg and temperatures of 230,240,250,260,270, and 280°C were performed and concentration-versus-time curves were obtained for ACA, c-caprolactam (CL), and endgroups (EG). Each curve for ACA and EG has a maximum which increases monotonically in its value and shifts from right to left in position with increasing either the temperature or the initial water concentration. The reaction rates of CL, EG, and ACA were also evaluated numerically from the concentration data. The observed kinetic data were compared with those obtained by the numerical solution of the rate equations with Reimschuessel's kinetic constants. Good agreement is found in C L and EG concentrations but discrepancies in ACA concentration and rates are considerable, particularly in the early stage of the polymerization.

Polarized far-infrared spectra of aliphatic polyesters [–(CH2)z–CO–O–O]n with z = 1, 2, and 5 (z = 4, nonpolarized) and α-polyamide (nylon 6 and its N-deuteroderivative) have been measured in the region up to 80 cm−1. All these polymers have essentially planar zigzag conformations. The normal vibrations of these polymers were calculated for the far-infrared regions by using the Urey–Bradley force field with some modifications. For the series of polyesters, several far-infrared bands were found to appear systematically at nearly the same positions with similar intensities. The similarities between these series of bands of the polyesters and those of polyamides were interpreted from the point of view of the normal modes of vibrations.

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SynopsisThe concrete simulation models dealiig with the kinetic behavior of the hydrolytic polymerization of e-caprolactam (CL) in various polymerization reactors used in the industry were described, and the method for their numerical solutions was presented. The characteristic data of the polymerization such as the concentrations of CL, end group, water, c-aminocaproic acid, cyclic dimer, and the hot-water-soluble component, conversion, number average, and weight average molecular weights, and solution and melt viscosities can be calculated at every stage of the polymerization reaction, at every part of the reactors, and/or at the outlet of the reactors. The calculated values based upon the models were found to be quite compatible with the observed values for the reactors. The applicability of the technique was well confirmed for the quality control, process control, modification of existing plants, and development of new chemical process plants.