Method for preparing short-carbon-chain nylon through polycondensation

Abstract

The invention belongs to the field of preparation of nylon, and particularly relates to a method for preparing short-carbon-chain nylon through polycondensation. The method for preparing the short-carbon-chain nylon through polycondensation comprises the following steps of (1) carrying out salt forming reaction on short-carbon-chain diamine and binary acid in a solvent at the temperature of 80-140DEG C under the conditions of heat preservation and pressure maintaining, and then removing the solvent to obtain dry nylon salt, 2) mixing nylon salt, an antioxidant, a catalyst, a surfactant and the pellets, and carrying out solid-phase pre-polymerization and solid-phase post-polymerization in a dynamic mixing state, in the solid-phase post-polymerization process, gradually reducing the systempressure to vacuum and keeping for at least 1 hour in a vacuum state. The temperature of the solid-phase post-polymerization is not lower than the termination temperature of the solid-phase pre-polymerization. The synthesis method solves the problem that the product is easy to cake and adhere to the wall in the industrial production process of nylon, the product is discharged in the form of powder, the melting point, intrinsic viscosity and initial thermal decomposition temperature indexes of the product are good, and the overall quality of the product is excellent.

Description

technical field [0001] The invention belongs to the field of nylon preparation, and in particular relates to a method for preparing short carbon chain nylon by polycondensation. Background technique [0002] There are many types of short carbon chain nylon and its copolymers prepared by polycondensation. Aliphatic short carbon chain nylon includes PA46, PA410, PA412, PA56, PA510, PA512, PA66, PA610, PA612, semi-aromatic short carbon chain Nylon copolymers include PA4T / 46, PA5T / 56, PA6T / 66, PA6T / 6I, PA6T / 6I / 66, etc. This kind of nylon not only has good heat resistance, mechanical properties, solvent resistance and chemical resistance, good insulation and low moisture absorption rate, but also has good toughness and low melting point, so it has good processing performance and high cost performance. The comprehensive performance is excellent, which makes it widely used in the automotive and electrical and electronic industries. The market demand continues to increase, and the ...

AI Technical Summary

Problems solved by technology

CN 104558593 A introduces a method for preparing nylon 6T / 6I using the "one-step" melt polymerization method, but when the product has a high viscosity, it is difficult to discharge the material, which wastes time and reduces production efficiency; at the same time, the inner wall of the polymerization tank will A large amount of product remains, affecting the appearance and performance of the next batch of products

[0004] CN 104327265 A and CN 101768266 A introduce the use of "one-step" solid-phase polymerization in a polymerization kettle to prepare semi-aromatic nylon, but during the polymerization process, there will be lumpy products due to the melting of part of the raw materials, which will block the discharge pipe, resulting in failure to discharge normally. materials, so it cannot be applied to industrial production

CN 105339415 A introduces the preparation of semi-aromatic nylon by "one-step" solid-state polymerization using a closed small cup (the small cup cover has a small opening for balancing the environmental pressure), but when the temperature is raised under normal pressure, the nylon salt will be decomposed into two Amines and dibasic acids, diamines will be discharged in the form of steam, resulting in an imbalance in the molar ratio between the two, and the molecular weight of the product cannot be increased

CN 104817693 A introduces the use of a drum reactor for salt formation and polymerization to prepare PA11T, but nylon 11T salt is easily soluble in water, that is, the essence of this reaction is solution polymerization, and the product is easy to stick to the wall and cannot be discharged

CN 110467724 A has introduced and utilized drum reactor to prepare semiaromatic nylon, and it has the following problems: the minimum melting point of nylon 66 prepolymer is only 145 ℃ (Pierfrancesco Cerruti, et al.Chemiluminescence from oxidation of polyamide 66.I.The oxidation of pure polyamide.), which makes the solid-phase polymerization temperature must be lower than 145°C, otherwise the solid-phase polymerization cannot be carried out smoothly. In Examples 1-3, the initial reaction temperature is directly set to 180°C, nylon 66 pre- The polymer will melt and stick to the wall, and the powder product cannot be obtained

[0005] In short, the existing industrial synthesis methods of nylon have prominent problems of product sticking to the wall or difficult discharge, which will seriously affect the production efficiency and the synthesis quality of subsequent batches of products.

Images