Method for continuously preparing 3, 3'-dichloro-4, 4'-diaminodiphenyl methane

Abstract

The invention relates to a method for continuously preparing 3, 3'-dichloro-4, 4'-diaminodiphenyl methane, which comprises the following steps: respectively continuously and simultaneously dropwise adding a hydrochloric acid solution, o-chloroaniline and a formaldehyde aqueous solution into a primary reaction kettle to carry out salification and condensation reaction; carrying out continuous rearrangement reaction and neutralization reaction by adopting a double-kettle switching mode; and carrying out continuous oil-water separation and continuous washing on the product. The purity and chromaticity stability of the obtained MOCA product are obviously improved. According to the invention, the ubiquitous problems of easy discoloration of MOCA and unreacted o-chloroaniline due to long-time heat storage, unstable chroma of the MOCA product, limited capacity scale and the like in the prior art are effectively solved, moreover, the synthesis process is automatically and continuously controlled, the overall production efficiency is remarkably improved, the acid consumption, the alkali consumption and the salt-containing wastewater discharge amount are remarkably reduced, the environmentalprotection effect is remarkably enhanced, the operation is simple, the economic cost is low, the capacity scale of a single production line is large, and the method is suitable for popularization andapplication.

Description

technical field [0001] The invention relates to the technical field of fine chemicals, in particular to a method for continuously preparing 3,3'-dichloro-4,4'-diaminodiphenylmethane. Background technique [0002] 3,3'-dichloro-4,4'-diaminodiphenylmethane is a commonly used aromatic diamine chain extender, commonly known as MOCA, which can be used as a crosslinking agent and curing agent for polyurethane and epoxy resins , can also be used as a vulcanizing agent for rubber, and can also be used to prepare some products with high electrical resistance. It is widely used in automobiles, machinery manufacturing, mining, sports facilities and other fields. DuPont of the United States took the lead in developing the synthesis process of MOCA. This process uses o-chloroaniline, formaldehyde and hydrochloric acid as raw materials. First, o-chloroaniline and hydrochloric acid are reacted to form o-chloroaniline hydrochloride, and then condensed with formaldehyde to form MOCA hydrochl...

AI Technical Summary

Problems solved by technology

[0003] In the prior art, US3297759A discloses a method for continuous preparation of 4,4'-diaminodiphenylmethane compounds. In the method, formaldehyde aqueous solution and aniline derivatives are mixed through a metering pump in a primary kettle, and the two Add hydrochloric acid to the first-stage kettle to mix, and finally enter the rearrangement kettle for rearrangement; in this process, o-chloroaniline and formaldehyde are fed into the first-stage kettle, which is easy to generate Schiff base impurities, and the product quality is low; hydrochloric acid, hydrochloric acid and formaldehyde The molar ratio is greater than 4:1, resulting in high hydrochloric acid unit consumption

[0004] US3478099A discloses a method for continuous preparation of 4,4'-diaminodiphenylmethane compounds. In this method, hydrochloric acid and aniline are mixed in a first-stage kettle to form a salt, and formaldehyde aqueous solution is added through a second-stage tubular reactor to mix. Finally, the crude product is obtained after rearrangement, neutralization, and water washing; this process uses a tubular reactor for condensation rearrangement, without stirring to promote mass transfer and heat transfer, which will easily lead to excessive local formaldehyde concentration and unstable product quality, and this method does not Mention post-processing serialization process

[0005] CN110818573A provides a preparation method of 3,3'-dichloro-4,4'-diaminodiphenylmethane, using the form of mixed acid composed of solid acid and liquid acid as catalyst and adopting azeotropic distillation to recycle the reaction liquid The liquid acid in the method makes full use of the respective advantages of solid acid and liquid acid, effectively reduces the consumption of liquid acid, reduces the corrosion loss of equipment, and improves the yield of MOCA; but this method still has a certain degree of operational complexity, limited capacity

Images