Preparation method of alkyl substitution diphenylmethane diisocyanate

Abstract

The invention discloses a preparation method of alkyl substitution diphenylmethane diisocyanate, which includes the following steps: weighing alkylaniline and urea, placing the alkylaniline and the urea in a reactor, heating the alkylaniline and the urea to the temperature ranging from 100 DEG C to 200 DEG C, stirring the mixture for 10 to 20 minutes, stopping reaction when red liquid is changed to solid, cooling the mixture to the room temperature, washing the mixture for 3 to 6 times through alcohol to obtain dialkyl group diphenyl urea, adding dimethyl carbonate into dialkyl group diphenyl urea, conducting back flowing reaction on the mixture under the temperature ranging from 110 DEG C to 250 DEG C for 6 to 12 hours, adding sodium methoxide into the mixture, conducting filtering after reaction is finished, conducting reduced pressure distillation on filtering liquid, conducting crystallization on normal hexane to obtain alkyl aniline methyl formate, adding lewis acid and methylation agent into the alkyl aniline methyl formate, increasing the temperature to the range from 70 DEG C to 100 DEG C, conducting reaction for 4 to 7 hours, cooling the mixture to the room temperature, conducting filtering on the mixture and washing the mixture through alcohol for 3 to 6 times to obtain alkyl aniline methyl formate and conducting decomposition reaction on the dialkyl group diphenylmethane dicarbamic acid ester. The preparation method of the alkyl substitution diphenylmethane diisocyanate is strong in stability, low in toxicity and controllable in reaction process.

Description

technical field [0001] The invention relates to a preparation method of diphenylmethane diisocyanate, in particular to a preparation method of alkyl-substituted diphenylmethane diisocyanate. Background technique [0002] Isocyanate is one of the raw materials for synthesizing polyurethane resin, which is widely used in civilian and military fields. At present, isocyanate monomers are mainly used in China, toluene diisocyanate (TDI) and diphenylmethylene diisocyanate (MDI), and the preparation method is generally based on the phosgene method. This method is Amino (NH 2 ) into isocyanate groups (NCO). However, there are two major drawbacks in the preparation of TDI and MDI by the phosgene method. One, the activity of phosgene is extremely high, it is difficult to control the stability of its reaction when reacting with other raw materials, and the activity of phosgene can change with the change of its content in the reaction process, when preparing TDI or MDI More by-produ...

AI Technical Summary

Problems solved by technology

Second, phosgene is very toxic to the human body and pollutes the environment very seriously, so it is difficult to transport, store and use

In fact, the phosgene synthesis of TDI and MDI has a long process route, complex technology, expensive raw material costs, and high equipment costs.

However, due to the high activity and strong toxicity of phosgene itself, it cannot be popularized and applied on a large scale and is strictly controlled.