Modeling of industrial nylon‐6,6 polycondensation process in a twin‐screw extruder reactor. I. phenomenological model and parameter adjusting

Abstract

This article describes a mathematical model for the finishing stage of nylon-6,6 polycondensation in a twin-screw extruder reactor. In the model, the extruder is conceptually divided into two regions. The first one is the partially filled degassing zone, which is operated under low pressure and where the evaporation of water from the polymer takes place. The rate of evaporation is considered to depend on an overall mass transfer coefficient and is limited by the water-polymer physical equilibrium. In the second region, which is fully filled, the polymer flow is assumed to be plug-flow and, in this region, the reversible polycondensation reaction occurs, as well as degradation reactions. A comparison with experimental data obtained in an industrial plant shows fairly good agreement with model predictions after optimal fitting of the rate coefficients.

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

“…When nylon 6,6 is heated beyond 265 °C, the concentration of these cyclopentanone end groups (denoted by S in reactions R9 and R10) tends to increase over time, accompanied by an increase in [ A ] and a corresponding decrease in [ C ] . Reactions R9 and R10 were included in nylon 6,6 modeling studies by Steppan et al., Giudici et al., and Schaffer et al., to account for end‐group concentration changes in their data and models …”

Dynamic Modeling of the Reactive Twin-Screw Corotating Extrusion Process: Experimental Validation by Using Inlet Glass Fibers Injection Response and Application to Polymers Degassing

“…In Equation (9), we have assumed that the degassing process occurs at the melt-gaseous phase interface 3,40 , ! c i W ,eq being the melt equilibrium water concentration corresponding to the vent pressure !…”

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

“…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.…”

“…Mass transfer of volatile species during nylon 6 and nylon 6,6 polymerization has been considered in previous modeling studies . A literature review by Schaffer et al 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 lab‐scale reactor system with no nitrogen bubbling or stirring to a high value of 324 h ‐1 obtained in a two‐phase twin‐screw extruder reactor.…”