Simulation Model of Polyamide-6,6 Polymerization in a Continuous Two-Phase Flow Coiled Tubular Reactor

Abstract

A mathematical model was developed to simulate an industrial-scale continuous process of polyamide-6,6 polymerization composed by two reactors in series: a coiled tubular reactor operating partially under onephase flow and partially under two-phase flow conditions, followed by a continuous stirred tank reactor. The mass, heat, and momentum balances for the single and two-phase flows were considered in the tubular reactor model. Water and hexamethylenediamine evaporation rates were evaluated according to the thermodynamic vapor-liquid equilibrium equations. Frictional, gravitational, and accelerational terms, as well as fittings for tube expansions, were considered in the pressure drop calculations. The model developed is an improved version of a previous one (Giudici et al., Chem. Eng. Sci. 1999, 54, 3243-3252) and was tested and validated with industrial data under a wider range of conditions, including the effect of catalyst.

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

“…Reversible reaction (1.2) in Table is the main reaction that occurs during nylon 6,6 production. Undesirable thermal degradation reactions involving adipic acid end groups occur in the high temperature conditions (i.e., > 265 °C) encountered during the final stages of nylon 6,6 production . These reactions are unimportant at lower temperatures and are neglected in the proposed model, which focuses on nylon 6/6,6 copolymerization at lower temperatures near 250 °C.…”

“…Appropriate values of k w A s for use in mathematical models depend on the type and size of reactor and agitator, the agitation speed, reactor geometry and physical properties of the liquid phase. Henry's law, Raoult's Law and Flory‐Huggins‐based correlations have been used to calculate [ W ] eq and similar equilibrium concentrations for caprolactam and HMD …”

“…Undesirable thermal degradation reactions involving adipic acid end groups occur in the high temperature conditions (i.e., > 265 °C) encountered during the final stages of nylon 6,6 production. [50][51][52][53][54][55][56] These reactions are unimportant at lower temperatures and are neglected in the proposed model, which focuses on nylon 6/6,6 copolymerization at lower temperatures near 250 °C. Another focus of nylon 6,6 model development is establishment of the relationship between the equilibrium constant for reaction (1.2) and the water content in the reaction mixture.…”

“…Mass transfer of volatile species during nylon 6 and nylon 6,6 polymerization has been considered in previous modeling studies. [37,38,40,46,48,[53][54][55][56][59][60][61][62][63][64][65][66][67][68][69][70][71] A literature review by Schaffer et al [71] found that typical values of the lumped mass-transfer coefficient k w A s , where A s is the surface area, range from a low value of 8 h -1 for a labscale reactor system with no nitrogen bubbling or stirring to a high value of 324 h -1 obtained in a two-phase twinscrew extruder reactor. Appropriate values of k w A s for use in mathematical models depend on the type and size of reactor and agitator, the agitation speed, reactor geometry and physical properties of the liquid phase.…”

A Kinetic Model for Non‐Oxidative Thermal Degradation of Nylon 66

“…Although the model by Steppan et al7 is in agreement with the data they used, it does not account for the formation of cyclopentanone (CPK) and for branches that result from amine end‐group condensation [reactions (a.7) and (a.8) in Table 2]. Pimentel and Giudici11 used Steppan's kinetic scheme and rate constants to develop a mathematical model for nylon 66 production in a two‐phase continuous tubular reactor, followed by a continuous stirred tank, and validated their model using industrial data.…”