Method and equipment for nylon 66 short-flow continuous polymerization

Abstract

The invention relates to a method and equipment for nylon 66 short-flow continuous polymerization. The method comprises the steps of carrying out heating, evaporation, concentration and polycondensation of 30-70% of a nylon 66 salt solution in a normal pressure pre-polypolycondensation tower by adopting a reaction distillation method to obtain a prepolymer with a polymerization degree of 5-50 (preferably 20-40) and equimolar terminal carboxy group and terminal amine group, and allowing the prepolyer to directly produce a polymer with a polymerization degree meeting technical indicators without flash distillation. A falling film devolatilization method is adopted in the polycondensation kettle to accelerate distillation out of condensation water, reduce reaction temperature, shorten reaction time and reduce gel; and the falling liquid film is used to seal and cover the kettle wall to avoid scarring of the kettle wall. Compared with the traditional nylon 66 continuous polymerization device, the method and the equipment provided by the invention has the advantages of short process, large single line scale, less investment, low operating cost, good product quality, long continuous operation cycle, and environmental friendliness.

Description

technical field [0001] The invention relates to the field of polymer production, in particular to a short-flow continuous polymerization method and equipment for nylon 66. Background technique [0002] Nylon 66 is produced by polycondensation of adipic acid and hexamethylenediamine. In order to obtain a high degree of polymerization, the equimolar ratio of adipic acid and hexamethylenediamine must be strictly guaranteed. Otherwise, after the depletion of less components, the functional groups of more components occupy both ends of the polymer molecular chain, and the molecular chain cannot continue to grow. Therefore, the polymerization of nylon 66 uses equimolar adipic acid and hexamethylenediamine to prepare neutral nylon 66 salt as raw material. The melting temperature of nylon 66 salt is 192.5°C, the activation temperature of polycondensation reaction is about 210°C, and the boiling point of hexamethylenediamine is only 196°C. If solid nylon 66 salt is directly melted a...

AI Technical Summary

Problems solved by technology

[0005] After the flash evaporation of the above-mentioned four processes, the viscosity of the feed liquid in the normal pressure or reduced pressure polymerization link is relatively high, and the condensation water is not easy to evaporate, which restricts the growth of molecular chains. Higher reaction temperature and longer reaction time are required to achieve the process requirements. Polymerization index, resulting in more gels, affecting the quality of the polymer, the entrained mist splashed to the reactor wall when the condensation water evaporates from the liquid phase, and the fluctuation of the reactor liquid level are likely to cause scarring on the reactor wall, which must be regularly It is more troublesome to stop production to clear scars or configure online standby to switch in turn

[0006] The high-pressure precondensation and flash evaporation steps of the above four processes discharge more hexamethylenediamine, and Liaohua (Rhone-Planck) and Shenma (Asahi Kasei) devices discharge 2.5-3kg of hexamethylenediamine per 1 ton of polymer produced; Monsanto and DuPont plants discharge about 2kg of hexamethylenediamine per ton of polymer produced, increasing material consumption and affecting the environment

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