Preparation method of isocyanates

Abstract

The invention discloses a preparation method of isocyanates. A high-concentration isocyanate actinic solution is prepared based on a salification phosgenation reaction, and a polyester hyperdispersant is added in a diamine salification procedure; and anchoring groups of the hyperdispersant are converted into tertiary amine salts which are adsorbed to the surface of diamine hydrochloride particles in the salification procedure, and steric hindrance is formed through the solvation chain, so that hydrochloride particles are separated, thereby avoiding the phenomena of aggregation, agglomeration and the like, obviously enhancing the salification concentration and effects, and further greatly enhancing the yield of the isocyanate product.

Description

technical field [0001] The invention relates to a method for preparing high-concentration isocyanate, in particular to adding a polyester hyperdispersant in the reaction process of diamine and hydrogen chloride, which can effectively increase the salt-forming concentration and efficiency of diamine, thereby preparing isocyanate. Background technique [0002] Aliphatic and cycloaliphatic diisocyanate (ADI) has become the research focus of major polyurethane companies and scientific research institutions around the world. Its products are widely used in coatings, car paints, Adhesives and medical materials and other fields. [0003] The preparation of isocyanates by liquid phase phosgenation can be divided into cold and hot phosgenation and salt-forming phosgenation. One disadvantage is that it is impossible to reduce the generation of urea by-products; the salt formation method first reacts the corresponding amine with acid gas such as hydrogen chloride, carbon dioxide, etc....

AI Technical Summary

Problems solved by technology

[0003] The preparation of isocyanates by liquid phase phosgenation can be divided into cold and hot phosgenation and salt-forming phosgenation. One disadvantage is that it is impossible to reduce the generation of urea by-products; the salt formation method first reacts the corresponding amine with acid gas such as hydrogen chloride, carbon dioxide, etc. to obtain amine hydrochloride or carbonate, and then reacts the amine salt with phosgene, Can effectively inhibit urea by-products in the photochemical process

[0004] Chinese published patent CN200680022170 reports that the salt formation process is carried out at 0.01Mpa above atmospheric pressure and at a temperature of 120°C. Although high-temperature pressurization can reduce the viscosity of hydrochloride and improve the conversion rate and space-time efficiency of salt formation, there are two defects. On the one hand, it is only suitable for diamines with high stability at high temperatures, and will seriously affect the color number of the salt-forming and photochemical solutions; on the other hand, the rate of salt-forming at high temperatures is extremely fast, so the heat transfer and Diamine wrapping problem

[0005] The British published patent GB1086782A mentions that the condition of salt-forming phosgenation is that diamine and hydrogen chloride form a salt at 0-60°C, the reaction concentration of hydrochloride is below 5.5wt%, and the conversion rate is very high, although low temperature and low concentration can reduce by-products generation, but the space-time yield is not high, and a large amount of solvent needs to be removed by distillation, which reduces its economy

[0006] Chinese published patent CN1045578A discloses the use of aliphatic esters as solvents, and the salt-forming temperature is controlled at 0-30°C. This can significantly reduce the generation of monochloroisocyanates in the photochemical process, but the aliphatic esters selected in this method The price of the solvent is higher than that of traditional benzene-based solvents, and the stability of the photochemical process at high temperature is poor

[0007] At present, the main factor limiting the industrialization of salt-forming liquid-phase phosgenation is the low salt-forming concentration of the raw material diamine, which leads to the inability to improve the space-time benefit and economic benefit, especially for short-chain aliphatic or alicyclic diamines in the formation process. The concentration in the salting process should not be too high. Due to the small molecular weight, the viscosity of the obtained hydrochloride slurry increases rapidly, which brings about unfavorable conditions such as stirring, dispersing, and heat transfer difficulties.

For example, in the salt-forming process, if the concentration of diamine in the inert solvent is set to 6-10%, then the organic solvent in which the raw material amine is dissolved is mixed with hydrogen chloride gas, as the reaction proceeds, the hydrochloride The viscosity of the slurry rises rapidly. In the later stage of the reaction, the hydrochloride will form agglomerates on the bottom and wall of the kettle, and it is difficult to disperse it by stirring, resulting in a decrease in production efficiency.

[0008] Therefore, it is necessary to develop a new method for the preparation of isocyanate by salt-forming liquid phase phosgenation to solve the disadvantages of hydrochloride agglomeration, difficulty in dispersing, and low production efficiency.

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