Process for preparing polyisocyanate by solid phosgene

Abstract

The invention relates to a method for preparation of 1, 2-dialkoxy-3-fluorobenzene by an intermediate of 2-fluorin-6-halogenated phenol. The said method consists of selecting 2-fluorophenol as its stock, and obtaining the intermediate of 2-fluorin-6-halogenated phenol; afterwards, performing multiple steps such as etherifing the said intermediate and etherifing again by introducing the hydroxyl group, alternatively, hydroxylating and etherifing the said intermediate; finally, obtaining the said 1, 2-dialkoxy-3-fluorobenzene. The method is of low cost, high yield rate, so it is suitable for the industrial production.

Description

technical field [0001] The invention relates to a method for preparing polyisocyanate by using solid phosgene and polyamine or its salt. Background technique [0002] Isocyanates are commonly used in the preparation of polyurethane resins, coatings and adhesives. As we all know, polyurethane has a wide range of applications in optical materials, automotive and construction materials, sealing materials, and daily necessities due to its good mechanical properties. In addition, polyisocyanates and polyurethane resins prepared from amino acids, such as lysine, can be used in biomedicine due to their good biocompatibility. [0003] Current methods for preparing isocyanates generally utilize the reaction of phosgene with amines. In patents US5,136,086, US4,419,295, JP2002-003462, JP06-234722, CN1125718A, CN1197793A, CN1516688A and EP424836, phosgene is used to phosgenate amines to prepare isocyanates. However, there are many problems in this method due to the use of phosgene. F...

AI Technical Summary

Problems solved by technology

These methods are to control the condensation reaction process of amine and solid phosgene by adding materials at low temperature, and then heating for elimination reaction. The reaction needs to be cooled first and then heated, and the process is more cumbersome.

Moreover, in the patent CN1394851, the phosgenation reaction is carried out under pressurized conditions, and the requirements for the reaction equipment are relatively high. At the same time, the HCl formed in the reaction cannot be discharged, so that the HCl content in the final product increases.

In addition, the 1,5-diaminonaphthalene solution is added to the solid phosgene solution at a faster rate, which may cause local overheating, increase side reactions, and may form a large amount of tarry products

The increase in the number of by-products in the final product makes the post-treatment purification process of the reaction more complicated and greatly reduces the purity of the product

All of these will cause the obtained isocyanate to fail to meet the use requirements in terms of color and mechanical properties when preparing polyurethane.

[0007] The above methods for preparing isocyanates using solid phosgene are limited to primary amines and diamines, and the phosgenation reactions of polyamines above triamines and salts of amines and acids are not discussed.