Method for synthesizing m-xylylene diisocyanate by low-temperature salifying method

Abstract

The invention relates to a method for synthesizing m-xylylene diisocyanate (M-XDI) by a low-temperature salifying method, which comprises the following steps: dissolving m-xylylenediamine (M-XDA) in an organic solvent o-dichlorobenzene (ODCB) according to a certain proportion, slowly introducing hydrogen chloride gas under the test conditions of the temperature of -10 to -5 DEG C and the pressureof 0.1-0.2 MPa, and carrying out acid-base neutralization reaction to generate m-xylylenediamine hydrochloride (M-XDA. 2HCI); enabling the M-XDA. 2HCI to be subjected to luminescence and thermophotochemical reactions to synthesize M-XDI; and distilling the photochemical liquid containing the M-XDI product to remove the solvent, and rectifying to obtain the high-purity M-XDI product. The salt forming reaction temperature is low, isocyanate and acyl chloride generated in the photochemical reaction can be prevented from reacting with amine again to generate polymerization byproducts, and the saltforming conversion rate can reach 100%.

Description

technical field [0001] The invention belongs to the field of chemical industry, and in particular relates to a method for synthesizing m-xylylene diisocyanate by a low-temperature salt-forming method. Background technique [0002] M-xylylene diisocyanate (M-XDI) is a colorless or light yellow liquid. It is a raw material for polyurethane. Its products have properties such as light stability and yellowing resistance. It is mainly used in the field of high-grade polyurethane ophthalmic lenses. It is also known as XDI -The product forms of TMP and XDI trimer curing agent are used in the fields of paint coating, ink and artificial leather. It is usually made by reacting m-xylylenediamine (M-XDA) with HCl to generate hydrochloride, and then phosgenating it. The most common synthesis method of M-XDI is mainly the batch-tank phosgenation method. [0003] The traditional intermittent kettle-type salt formation and phosgenation method: the process is simple and mature, and can effe...

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Problems solved by technology

[0003] The traditional intermittent kettle-type salt formation and phosgenation method: the process is simple and mature, and can effectively avoid the occurrence of polymerization side reactions, low requirements on equipment, good operability, and slight positive pressure reaction; but due to the salt formation reaction The temperature is high (reaction temperature ≥ 30°C), and the reaction is violent, resulting in a small amount of amine (M-XDA) being coated with hydrochloride (M-XDA·2HCl) to varying degrees, reducing the conversion rate of the salt-forming reaction, and the batch big difference

During the photochemical reaction, once the coated amine is released, it is easy to react with isocyanate and acid chloride to form a polymerization by-product, which directly affects the yield of salt formation and photochemical reaction, and increases the difficulty of the product distillation process and the loss of tar substances. Generation

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