Method for preparing isocyanate monomer

Abstract

The invention discloses a method for preparing an isocyanate monomer. The method comprises the following steps: adding a first batch of solvents in a reaction kettle and circulating; compressing HCl, conveying HCl in a salt-forming reaction kettle through the outer tube of a mixer, carrying out gas-liquid separation and then circulating HCl in a system through a Venturi mixer; mixing diamine with the residual solvents in the inner tube of the mixer, then mixing the mixture with HCl in the outer tube, and then conveying the mixture in the salt-forming reaction kettle and reacting to obtain a diamine hydrochloride solution; reacting the diamine hydrochloride solution with phosgene under a pressurization condition to obtain an isocyanate photochemical solution. The mixer comprises the inner tube and the outer tube, wherein a spiral plate is installed in the thick-diameter part of the inner tube, a hole is formed in the tube wall of the thin-diameter part of the inner tube, and the bottom of the inner tube is a detachable bottom plate; the outer tube sleeves outside the inner tube, and the bottom of the outer tube is a mixer outlet. The method disclosed by the invention reinforces the mixing effect of the gas-liquid reaction, the obtained hydrochloride particles are uniform, the use efficiency of HCl is high, the energy consumption is low, and the purity of the photochemical solution after a phosgenation reaction is high.

Description

technical field [0001] The present invention relates to a kind of method for preparing isocyanate monomer, more specifically, relate to a kind of method for preparing diisocyanate based on salt-forming phosgenation reaction. Background technique [0002] In the prior art, the phosgene method of preparing isocyanates by reacting organic primary amines and phosgene in an inert solvent is well known. The phosgene method can be divided into a direct method and a salt-forming method. The direct method is to prepare the corresponding isocyanate by directly reacting primary amine and phosgene; the salt-forming method first reacts the corresponding amine with an acid gas such as hydrogen chloride, carbon dioxide, etc. to prepare an amine salt, and then react the amine salt with phosgene. Due to the fast reaction rate of aliphatic amines and phosgene, it is easy to cause amine coating and produce urea by-products in the subsequent thermophotochemical process. The generation of amin...

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Problems solved by technology

[0007] The purpose of the present invention is to provide a method for preparing isocyanate monomers, which can overcome the incomplete salt-forming reaction in the existing salt-forming process, the hydrochloride salt particles are large, and a large amount of amines that do not participate in the salt-forming process are wrapped, and the internal materials are difficult to participate in the process. One-step photochemical reaction, resulting in the generation of urea impurities during the photochemical process, resulting in many side reactions; it can handle higher concentrations of hydrochloride, make it undergo phosgenation reaction to obtain qualified isocyanate, and solve the problem of low utilization of HCl , the problem of high energy consumption

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