Modeling of Falling Film Reactor for Manufacture of Nylon 6

摘要

Commercially, nylon 6 is produced by the hydrolytic polymerization of #epsilon# caprolactam. It consists of polymerizing caprolactam in the presence of water at temperatures ranging from 230 to 270 deg C. The reactions are cararied out till an equilibrium polymer is formed with a degree of polymerization (DP) depending upon the initial concentration of caprolactam, water and cyclic oligomers. These have to be removed before the polymer can be further processed into finished products. As DP of the equilibrium polymer is generally above 100, the viscosity is of the order of a few thousand poise. The mass transfer coefficients of the volatile components are extremely small. Thus in order to reduce the mass transfer resistance, special thin film reactors are used in the industry. Such reactors may be classified as wiped film reactors, partially filled screw extruders, etc. Denson and Amon [1]. A comprehensive model for the finishing stages of PET synthesis has been developed by Ravindranath & Masahelkar [2]. Sittig [3] descreibed the various patented processes for the removal of monomer and oligomers from nylon 6 melt. Continuous vertical operation can be carraied out in a vertical falling film reactor with intermediate mixing and sketch of such a reactor is given in Figure 1. Vacuum of the order of 2 mm Hg is usually applied to remove the volatile species. At the same time, the reactor temperature is maintained above 260 deg C by a heating jacket.