Hydrolytic Caprolactam Polymerization - Progress in Dynamic Simulation

Abstract

The modeling of hydrolytic caprolactam polymerization is reviewed and a state-of-the-art mathematical model is proposed. The model includes the basic reactions of reversible ringopening, polyaddition, and polycondensation as well as the reversible formation/hydrolysis and polyaddition of cyclic oligomers. For the first time, a method is proposed to implement stabilization with acids of any functionality so that their impact on the molecular weight distribution can be analyzed. A comparison of the model predictions with experimental data taken from the literature reveals excellent agreement. As shown in this work, the proposed model for the synthesis of polyamide 6 can be used to dynamically compute the complete molecular weight distribution. Therefore, it gives access to desired product designs for this industrially important polymer. The method presented for modeling multichain hydrolysis may also be of interest for other polycondensation systems that result in star-shaped polymers.

Modeling Equilibrium Behavior of Nylon 6, Nylon 6,6 and Nylon 6/6,6 Copolymer

“…Table shows six reversible reactions for copolymerization of caprolactam with HMD and ADA . This reaction scheme applies for hydrolytic polymerization of caprolactam to produce nylon 6, so the first five reactions in Table (i.e., the main reactions) have been used in a large number of nylon 6 modeling studies . The sixth reaction (transamidation), which does not influence DP nor the concentrations of amine and carboxyl end groups, is included in the mechanism because reaction R6 helps to randomize the polymer chains .…”

“…However, aside from the work of Steppan et al. and Schaffer et al., modelers of nylon polymerization systems have tended ignore activity coefficients when developing kinetic and reaction equilibrium models . One reason that detailed modeling of activity coefficients has been avoided in the open literature is to keep models as simple as possible, so that a large number of thermodynamic parameters is not required.…”

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

“…Table 1 has been widely used for modeling nylon 6 production (often without transamidation reaction R6) 11–14,32–45. The model used by Arai et al for their parameter estimation study neglects reaction R6 and accounts for the catalytic influence of carboxyl end‐groups ( C ) in reactions R1–R5 using composite rate constant expressions proposed by Hermans et al8,9 In Equation , is the “uncatalyzed” rate constant for the i th reaction ( i = 1, 2,… 5), which is important when the concentration of carboxyl ends is low, and is the “catalyzed” rate constant that accounts for the catalytic influence of carboxyl end groups when their concentration is high.…”

“…Over the years, a large number of mathematical modeling studies have relied on the data in Table 6. In particular, the composite rate constant expressions of Hermans et al, combined with Arai's parameter values, have been widely used in nylon 6 models 33–44. These rate expressions and parameter values are easy to use and they provide reasonable predictions for monomer conversion and end‐group concentrations over much of the range of nylon 6 conditions considered by Arai et al and other research groups.…”

Mathematical Modeling of Nylon 6/6,6 Copolymerization: Beneficial Influence of Comonomers on Degree of Polymerization in Batch Reactor

“…Over the years, many PA6 mathematical models have been developed using Arai's kinetic parameters to simulate homopolymerization in a variety of reactors (i.e., batch and plug‐flow reactors, continuous stirred tank reactors and reactor systems involving multiple reactors in series or single reactors with multiple reaction zones; e.g., refs …”