Method for preparing 1,5-pentamethylene diisocyanate

Abstract

The invention relates to a method for preparing 1,5-pentamethylene diisocyanate (PDI). The method comprises the following steps: taking o-dichlorobenzene as a solvent and trimethylchlorosilane as a catalyst, carrying out luminescence reaction on 1,5-pentanediamine and phosgene at 15-30 DEG C under normal pressure to generate diaminoformyl chloride; after the reaction is finished, heating the reaction materials to 110-120 DEG C, and evaporating out a small amount of solvent and all the catalyst for recycling; continuously introducing a certain amount of phosgene into the diaminoformyl chloride,heating to 150-170 DEG C, and carrying out thermal photo-chemical reaction until the material becomes clear and transparent; and after the photo-chemical reaction is finished, carrying out reduced pressure distillation to remove the solvent, and continuously carrying out reduced pressure distillation to obtain the 1,5-pentamethylene diisocyanate product. Trimethylchlorosilane is used as a catalyst, so that the generation of hydrochloride can be avoided, and the generation of polymerization byproducts caused by the secondary reaction of amine with acyl chloride and isocyanate generated in thelow-temperature photo-chemical reaction can also be avoided; the PDI product yield and the product quality in the photo-chemical reaction process are greatly improved.

Description

technical field [0001] The invention belongs to the field of chemical industry, and in particular relates to a method for preparing 1,5-pentane diisocyanate. Background technique [0002] 1,5-pentanediisocyanate (PDI) is an aliphatic isocyanate with yellowing resistance, and is used in the manufacture of yellowing-resistant polyurethane coatings, inks and artificial leather in the form of biuret and trimer. Since the structure and chemical properties are similar to HDI, and the carbon content is higher, there is a possibility of replacing HDI for downstream products. Moreover, PDA, the raw material of PDI products, can be prepared by biological methods, which avoids the disadvantages of complicated HDI raw material HDA process and high technical difficulty. At present, there is no industrial production device for 1,5-pentanediisocyanate in the world. The construction of 1,5-pentane diisocyanate and the development of its industrialization will also attract widespread attent...

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Problems solved by technology

Moreover, PDA, the raw material of PDI products, can be prepared by biological methods, which avoids the disadvantages of complicated HDI raw material HDA process and high technical difficulty. At present, there is no industrial production device for 1,5-pentanediisocyanate in the world. The construction of 1,5-pentane diisocyanate and its industrial development will also attract widespread attention

[0003] The laboratory has completed the research on the traditional batch-type phosgene process: the process is simple and mature, with low equipment requirements, good operability, and micro-positive pressure reaction; however, due to the violent luminescence reaction, partial amine (PDA) 1,5-Pentanediamine hydrochloride (PDA·2HCI) was produced to varying degrees, and even a small amount of amine was coated with hydrochloride, which greatly reduced the conversion rate of luminescence reaction and the yield of dicarbamoyl chloride; Under the conditions of thermal and photochemical reactions, it is difficult for 1,5-pentanediamine hydrochloride to produce PDI products. 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 photochemical reaction PDI. Yield increases the difficulty of the product distillation process and the environmental protection pressure of the process equipment

At present, the PDI yield of the traditional batch-type phosgenation reaction in the laboratory is only 85%.

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