On the condensation equilibrium in polymerization of caprolactam

Abstract

synopsisThe investigation of the condensation equilibrium of the hydrolytic polymerization is described for systems obtained by polymerizing caprolactam in the presence of water (or aminocaproic acid) and any of the following additives: mono-di-, and tricarboxylic acids, mono-and diamines, and the salts derived from a monoamine and either a monoor dicarboxylic acid. Relationships in terms of the equilibrium constant Kz, the equilibrium conversion (&), and the initial composition were derived for the calculation of the molecular weights of the corresponding equilibrium polymers. Very good agreement between calculated and experimental data was observed. The results show that the thermodynamical quantities derived for the pure caprolactam-water system are also valid for polymerizations that involve the participat,ion of organic acids, amines, and their salts in the initiation and equilibration.Caprolactam. High-purity-grade commercial (Allied) caprolactam was distilled prior to use under nitrogen a t 1 mm Hg. rived by Majury.' * An equivalent relationship for the system caprolactam-water-acetic acid was de-POI~YMERIZATlON OF CAPROLACTAM 2345 e-Aminocaproic Acid. A commercial product (Eastern Chemical Co.) was purified by carbon treatment of a hot aqueous solution and repeated recrystallizations from water-ethanol. Sebacic Acid and Trimesic Acid. Commercial products (EastmanOrganic Chemicals) were purified by carbon treatment of the hot aqueous solutions and repeated recrystallizations from water.

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

“…This assumption does not match the prior experimental findings of Hermans, Reimschussel, and Arai et al. who showed that reactions R1–R3 follow mixed‐order kinetics . For example, these three research groups expressed the rate of the forward polycondensation reaction as where is an “uncatalyzed” (second‐order) rate constant and is a third‐order rate constant that accounts for the catalytic effect of carboxyl ends.…”

“…The idealized equilibrium constants in Equations – depend on temperature according to where Δ H i and Δ S i are the enthalpy and entropy changes, respectively, of the i th reaction. Table 3 provides values of Δ H i and Δ S i that have been fitted from equilibrium and/or dynamic data by various research groups . The values of Arai et al.…”

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

“…Recently, our research group developed a batch reactor nylon 6/6,6 copolymerization model, using the proposed reaction mechanism in Table 1 , to investigate the influence of different recipes on polymerization rates and copolymer properties 5,6. This copolymerization model builds on nylon 6 and nylon 6,6 homopolymerization models developed by other research groups 7–13. A key innovation of the copolymerization model is a series of probability factors introduced to keep the model equations relatively simple while tracking copolymer end groups of different types.…”

“…[5,6] This copoly merization model builds on nylon 6 and nylon 6,6 homopoly merization models developed by other research groups. [7][8][9][10][11][12][13] A key innovation of the copolymerization model is a series of probability factors introduced to keep the model equations rela tively simple while tracking copolymer end groups of different types. For example, factor f 1 is the fraction of amine ends on copolymer chains associated with a terminal caprolactam unit (rather than a terminal HMD unit).…”

“…Reaction scheme for nylon 6/6,6 copolymerization. [5][6][7][8]10,11,13] R1 R2 R3 R4 R5 R6 www.advancedsciencenews.com www.mre-journal.de Table 1 shows six reversible reactions for copolymerization of caprolactam with an aqueous solution of HMD and ADA. Reaction R1 is the initiation reaction, that is, ring opening of caprolactam by water to form aminocaproic acid (LM).…”