Studies on polycondensation reactions of nylon salt. I. The equilibrium in the system of polyhexamethylene adipamide and water

Abstract

The solubility of water in molten polyhexamethylene adipamide (nylon 66) has been measured in urder to investigate the equilibrium in the system of nylon 66 and water. The solubility of water n, (mole/mole of fundamental structural unit) increases with the rise of the vapour pressure p (mm. Hg) of water and HENRY'S law holds well within the range of water contents of less than 0.1 yo. The following equation is obtained.log (nw/p) = 3050/T -10.09Under the same vapour pressure of water, the number of amino groups in the polymer increases markedly with the rise of temperature, while that of carboxyl groups decreases. The equilibrium constant K of the condensation reaction between the linear polymers can be expressed in the following equation.The relationship between the number average degree of polymerigation Pn and p can be expressed as follows: log P, = 0.73 + 1375/T -'/2. log p ZUSAMMENFASSUNG: Um das Gleichgewicht des Systems Nylon 66-Wasser zu untersuchen, wurde die Loslichkeit von Wasser in geschmolzenem Polyhexamethylenadipinsaureamid (Nylon 66) gemessen. Die Loslichkeit des Wassers nw (Mol pro Mol des Grundbausteins) nimmt mit steigendem Wasserdampfdruck p (mm Hg) zu und das HENRYsahe Gesetz gilt fur Ansatze mit einem Wassergehalt unter 0,l yo. Hierfiir gilt die Formel log (nw/p) = 3050/T-10,09 Bei konstantem Wasserdampfdruck nimmt mit steigender Temperatur die Zahl der Aminogruppen im Polymeren merklich zu, wahrend sich die Zahl der Carboxylgruppen vermindert. Die Gleichgewichtskonstante K der Kondensationsreaktion zwischen den Kettenmolekiilen kann in folgender Formel ausgedriickt werden: log K = 5800/T -8,32 Der Abhiingigkeit des Zahlenmittels des Polymerisationsgrads Pn von p ist: log P, = 0,73+ 1375/T-1'/,*log p 3, H. YUMOTO, Bull. chem. SOC. Japan 28 (1955) 94 and 101.

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

“…As shown in Table 7 , they used these data to estimate 20 kinetic parameters (including 10 activation energies) and 10 equilibrium parameters (including 5 reaction enthalpies). Parameter values estimated by other research groups (using smaller data sets or unpublished data) are also shown in Table 7 11,14–16,18,24,25,32,35,42,45–547 are similar for different research groups (e.g., the activation energy estimate of 78.7 kJ mol −1 for R1 reported by Arai et al11 is similar to 78.5 kJ mol −1 reported by Reimschussel et al,45 other parameter estimates differ by orders of magnitude between research groups.…”

“…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. To address the problem of complex equilibrium behavior for reactions R1–R5 in Table 1, we recently developed a series of mechanistically motivated semi‐empirical equilibrium expressions for nylon 6, nylon 6,6, and nylon 6/6,6 copolymer 28 .…”

“…Appropriate values of kinetic rate constants are also desired to enable accurate simulation of a wide variety of industrially relevant homopolymerization and copolymerization conditions. As summarized in Table 6 and Table S1.1, Supporting Information8,11,17–27,29–31 several research groups have published a large amount of kinetic and equilibrium data for nylon 6 and nylon 6,6 homopolymerizations. Unfortunately, literature nylon 6/6,6 copolymerization data are non‐existent, except for two dynamic batch reactor experiments reported by Heikens et al involving caprolactam, water, and either ADA or HMD 29.…”

A comprehensive model for nylon melt equilibria and kinetics

“…The experimental To compare the model described above to experimental data, the experimental results of value of enthalpy for water sorption ( 018.3 kcal/ mol) 18 was used to reduce the number of fitted Ogata, 2, 20 Wiloth, 1,21, 22 Giori and Hayes, 6 and Tai et al 9 were collected. These data sets represent parameters.…”

“…To model the change in reaction rate with dielectric constant, a mixing rule for dielectric conEquation (20) gives the density in kg/L. The caprolactam density was calculated as 0.91 of the stants is needed to predict what happens as composition varies.…”