Isothermal polymerization of e-caprolactam

The use of various thermal methods to investigate e-caprolactam polymerization allowed us to determine the expression for the kinetic function f(P) for this monomer 29 32 

This function corresponds to the first order kinetic equation (first term on the right-hand side of the equation) and also reflects the effect of self-acceleration (second term on the right-hand side of the equation) the quantitative measure of this effect is the constant co. Thus the reaction rate is determined by two independent constants co and K. The fit of this equation to experimental data is illustrated in Fig. 2.4. The effect of self-acceleration in anionic polymerization of e-caprolactam was also discussed in other publications, 33 35 The kinetic equation of isothermal polymerization based on Eq. (2.13) can be written as 

This integral function is shown in Fig. 2.5 a. This type of kinetic curve can be treated as a description of a reaction with an apparent induction period ti. The method of estimating this apparent induction period is also shown in Fig. 2.5. The influence of the constant co on the form of the integral kinetic curve is illustrated in Fig. 2.5 b, where a dimensionless parameter (Kot) is used as the argument. At co=0 an apparent induction period is absent (in this case we are dealing with a standard first-order reaction), but with increasing co an apparent induction period appears and becomes longer. At the same time the slope of the main (central) part of the dependence of Kot on co also increases. 

Experiments have confirmed that the pre-exponential factor Ko and the constant co, which characterizes the self-acceleration effect, both depend on the concentration of the catalytic complex, i.e., on the concentrations of the catalyst [C] and the activator [A]. On the basis of purely chemical 

The adequacy of these relationships can be seen from Fig. 2.6, where a coordinate system linearizing these equations was chosen. On the basis of Eqs (2.13), (2.17) and (2.18), it is possible to formulate the final equation of the kinetic model for anionic polymerization of e-caprolactam  

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Analysis of the non-isothermal polymerization of E-caprolactam is based on the equations for isothermal polymerization discussed above. At the same time, it is also important to estimate the effect of non-isothermal phenomena on polymerization, because in any real situation, it is impossible to avoid exothermal effects. First of all, let us estimate what temperature increase can be expected and how it influences the kinetics of reaction. It is reasonable to assume that the reaction proceeds under adiabatic conditions as is true for many large articles produced by chemical processing. The total energy produced in transforming e-caprolactam into polyamide-6 is well known. According to the experimental data of many authors, it is close to 125 -130 J/cm3. If the reaction takes place under adiabatic conditions, the result is an increase in temperature of up to 50 - 52°C this is the maximum possible temperature increase Tmax- In order to estimate the kinetic effect of this increase... 

For continuous isothermal polymerization of e-caprolactam the system iV-benzoyl-6-caprolactam-sodium bis-(2-methoxyethoxy)alumjnium hydride (NBAS) has been suggested for temperatures above the melting point. Solution polymerization in hetero neous medium in chlorobenzene or toluene with NBAS as catalyst has been investigated. The effect of stirring, reaction temperature, solvent dielectric constant, and catalyst concentration on rate and the form of the polymer particles was evaluated. ... 

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