阅读说明：本技术 合成3,3’-二甲基-4,4’-二氨基二苯甲烷方法 (Method for synthesizing 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane ) 是由 徐晓秋 李子剑 刘长乐 宋伟 王长锦 陈昞志 李亚峰 于 2021-10-22 设计创作，主要内容包括：本发明提供一种合成3,3’-二甲基-4,4’-二氨基二苯基甲烷即MDT的方法,包括以邻甲苯胺和甲醛水溶液为原料,以苯磺酸为催化剂,在醇类溶剂条件下加热升温搅拌反应,反应结束后降温得到所述MDT,所述醇类溶剂为三碳至六碳的醇中的一种或多种。本发明提供的MDT合成方法环保且高收率,所得MDT产品的收率在93.8～97.1％之间,同时所得MDT的色谱纯度在98.3％以上。(The invention provides a method for synthesizing 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane (MDT), which comprises the steps of taking o-toluidine and formaldehyde aqueous solution as raw materials, taking benzenesulfonic acid as a catalyst, heating, stirring and reacting under the condition of an alcohol solvent, and cooling after the reaction is finished to obtain the MDT, wherein the alcohol solvent is one or more of alcohols with three carbon to six carbon. The method for synthesizing the MDT is environment-friendly and high in yield, the yield of the obtained MDT product is 93.8-97.1%, and the chromatographic purity of the obtained MDT is more than 98.3%.)

1. The method for synthesizing the 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane is characterized in that the 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane is MDT, and is characterized in that o-toluidine and formaldehyde aqueous solution are used as raw materials, benzenesulfonic acid is used as a catalyst, the raw materials are heated and stirred to react under the condition of an alcohol solvent, the temperature is reduced after the reaction is finished, and the MDT is obtained, wherein the alcohol solvent is one or more of alcohols with three carbon to six carbon.

2. The method according to claim 1, wherein the heating, temperature-raising and stirring reaction comprises a first stage and a second stage, the reaction temperature of the first stage is 45-60 ℃, preferably 50-55 ℃, and the reaction time of the first stage is more than 1 hour, preferably 2-6 hours, more preferably 3-5 hours; the reaction temperature in the second stage is 70-90 ℃, preferably 75-80 ℃, and the reaction time in the second stage is more than 1 hour, preferably 2-6 hours, and more preferably 3-4 hours.

3. The method according to claim 1, wherein the alcoholic solvent is one of n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, 2-methyl-2-butanol, and 2-methyl-2-pentanol.

4. The method according to claim 1, wherein the amount of the alcohol solvent is 2 to 4 times the sum of the mass of the o-toluidine and the mass of the aqueous formaldehyde solution.

5. The method according to claim 1, wherein the mass ratio of o-toluidine to formaldehyde is 1.9 to 2.3: 1, preferably 2 to 2.1: 1.

6. the method according to claim 1, wherein the catalyst benzenesulfonic acid is added in an amount of 5 to 30 wt%, preferably 10 to 20 wt%, based on the mass of o-toluidine.

7. The method according to claim 1, wherein the temperature is reduced to 0-20 ℃, preferably 5-15 ℃ after the reaction is completed, and then the solid obtained by solid-liquid separation is dried to obtain the MDT product, preferably the solid-liquid separation is filtration under washing with an alcohol solvent.

8. The method as claimed in claim 7, wherein the alcohol solvent is recovered by rectifying the liquid obtained by solid-liquid separation, and the alcohol solvent is used for the next reaction after dehydration.

9. The method as claimed in claim 8, wherein the liquid after rectification to recover the alcohol solvent is subjected to reduced pressure distillation to recover the catalyst benzenesulfonic acid.

10. The method according to any one of claims 1 to 9, wherein the raw materials o-toluidine and formalin are added into a certain amount of alcohol solvent, the catalyst benzenesulfonic acid is added, and the MDT product is obtained after heating, stirring, reacting, cooling and crystallizing.

Technical Field

The invention belongs to the technical field of fine chemical engineering, and particularly relates to a method for synthesizing 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane.

Background

The isocyanate obtained by processing MDT as a raw material can be used as a curing agent and has good adhesiveness when cured at room temperature. MDT can also be used as raw material of polyimide and impregnating varnish, and can also be used as epoxy resin cross-linking agent, insulating coating of circuit and fire retardant of polyamide fibre.

The traditional process route for synthesizing MDT and similar derivatives thereof takes hydrochloric acid as a catalyst, and aniline derivatives and formaldehyde are condensed to obtain the MDT and similar derivatives. For example, Chinese patent CN1948267A reports that o-toluidine forms a salt with hydrochloric acid, then the salt and formaldehyde undergo a condensation reaction, and finally the salt is neutralized by an alkali solution, and the MDT is obtained by removing the salt, washing and recrystallizing. CN106986777B discloses a method for preparing 4, 4-diaminodiphenylmethane derivatives by using a microreactor, in which aniline derivative hydrochloride and formaldehyde solution are respectively conveyed into the microreactor through a advection pump to contact, mix and react. The yield of MDT prepared by the method is 80-84%, but the problem of a large amount of high-salt high-COD wastewater generated in the reaction process needs to be solved by the traditional process route. In order to overcome the defect, the applicant of the present invention previously developed a synthesis route using a solid acid as a catalyst, wherein CN103130654B uses o-toluidine and formaldehyde as raw materials, and uses a solid acid as a catalyst, and after reaction, the raw materials are filtered, and the filtrate is cooled to room temperature for recrystallization, filtration and drying to obtain MDT. In CN105294448A, solid acid is used to catalyze two-stage condensation reaction in a fixed bed reactor to obtain 4, 4' -diaminodiphenylmethane derivatives.

The above method has a drawback that the conventional hydrochloric acid process faces a problem of wastewater treatment. The solid acid process, because of the activity of the catalyst, requires high temperature reaction, which results in inferior reaction selectivity to the hydrochloric acid process, for example, the method for continuously preparing 4, 4' -diaminodiphenylmethane derivatives by using CN105294448A solid acid catalyst, the reaction is carried out in a two-stage fixed bed reactor; wherein the stage I is a reaction stage, the stage II is a rearrangement stage, the temperature of the reaction stage is 140-. The yield of MDT in the specific embodiment of CN103130654B is 49-87.5%, but the yield of MDT is 68-82% in most cases.

Therefore, there is a need in the art for a process for preparing 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane in a safe and environmentally friendly manner but in high yield.

Disclosure of Invention

Therefore, the invention provides a method which can solve the problem of environmental protection and can obtain the 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane with high yield.

The method comprises the steps of taking o-toluidine and formaldehyde water solution as raw materials, taking benzenesulfonic acid as a catalyst, heating, stirring and reacting under the condition of an alcohol solvent, and cooling after the reaction is finished to obtain the MDT, wherein the alcohol solvent is one or more of alcohols with three carbon to six carbon.

In a specific embodiment, the heating, temperature-raising and stirring reaction comprises a first stage and a second stage, the reaction temperature of the first stage is 45-60 ℃, preferably 50-55 ℃, and the reaction time of the first stage is more than 1 hour, preferably 2-6 hours, and more preferably 3-5 hours; the reaction temperature in the second stage is 70-90 ℃, preferably 75-80 ℃, and the reaction time in the second stage is more than 1 hour, preferably 2-6 hours, and more preferably 3-4 hours.

In the invention, the reaction temperature of the first stage is 45-60 ℃, preferably 50-55 ℃, and the temperature is favorable for the condensation reaction; the reaction temperature of the second stage in the invention is 70-90 ℃, preferably 75-80 ℃, and the temperature is favorable for the transformation reaction.

In one embodiment, the alcoholic solvent is one of n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, 2-methyl-2-butanol, and 2-methyl-2-pentanol.

In the invention, the boiling point of the alcohols is between 82 and 122 ℃, and the boiling point of the alcohols is obviously different from the boiling point of 190 ℃ of benzene sulfonic acid, so that the distillation separation of the solvent and the catalyst is convenient. And the solubility of MDT in the alcohol is low, so that trimer impurities generated by the re-reaction of MDT and o-toluidine can be effectively reduced. Furthermore, these alcohols generally have a boiling point comparable to or higher than the temperature of the second stage of the reaction for the formation of MDT, i.e., the metathesis reaction, and therefore the solvent is advantageous for the formation of MDT smoothly. The stirring time for the low-temperature crystallization is preferably 10 minutes or longer, more preferably 30 minutes or longer.

In one embodiment, the amount of the alcohol solvent is 2 to 4 times of the sum of the mass of the o-toluidine and the mass of the aqueous formaldehyde solution.

In one embodiment, the mass ratio of o-toluidine to formaldehyde is 1.9 to 2.3: 1, preferably 2 to 2.1: 1.

in the invention, when the using amount of formaldehyde is too much, side reaction is easy to occur to generate other impurities; when the amount of o-toluidine is too large, more o-toluidine needs to be recovered, which increases energy consumption.

In one embodiment, the benzene sulfonic acid catalyst is added in an amount of 5 to 30 wt%, preferably 10 to 20 wt% of the mass of o-toluidine.

In a specific embodiment, after the reaction is completed, the temperature is reduced to 0-20 ℃, preferably 5-15 ℃, and then the solid obtained by solid-liquid separation is dried to obtain the MDT product, preferably, the solid-liquid separation is filtration under the washing of an alcohol solvent.

In the invention, after the reaction is finished, the temperature is reduced to 0-20 ℃, preferably 5-15 ℃, and the temperature is favorable for MDT crystallization.

In a specific embodiment, the alcohol solvent is recovered by rectifying the liquid obtained by solid-liquid separation, and the alcohol solvent is used for the next reaction after dehydration.

In a specific embodiment, the liquid obtained after the alcohol solvent is recovered by rectification is subjected to reduced pressure distillation to recover the catalyst benzenesulfonic acid.

In a specific embodiment, raw materials of o-toluidine and formaldehyde aqueous solution are added into a certain amount of alcohol solvent, catalyst benzenesulfonic acid is added, and the MDT product is obtained after heating, stirring, reaction and cooling crystallization.

Compared with the prior art, the invention at least has the following advantages:

1) the alcohol is selected as the solvent, so that the reaction selectivity can be improved, the generated MDT is difficult to dissolve in the alcohol solvent and is separated out, and trimer impurities generated by the re-reaction of the MDT and the o-toluidine are effectively reduced.

2) The benzene sulfonic acid is used as a catalyst, and has higher reaction activity compared with solid acid, so that the reaction temperature is relatively low, and the problem of more byproducts caused by high temperature of the solid acid process is solved.

3) The benzene sulfonic acid is selected as a catalyst and can be recycled by distillation, so that the problem of waste water and waste salt in the hydrochloric acid process is solved.

4) The process has good environmental protection.

In general, the invention provides an environment-friendly method for synthesizing 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane with high yield, the yield of the obtained MDT product is 93.8-97.1%, and the chromatographic purity of the obtained MDT is more than 98.3%.

Detailed Description

Example 1

107g of o-toluidine, 41.7g of 36 wt% formaldehyde aqueous solution, 446g of isopropanol and 10.7g of benzenesulfonic acid are added into a four-mouth bottle, stirred, heated to 50-55 ℃, stirred for 4 hours, heated to 75-80 ℃ and continuously stirred for 4 hours. Cooling to 10-15 deg.C, stirring for 1h, vacuum filtering, rinsing with 30g isopropanol, and drying to obtain MDT106g with molar yield of 93.8% and GC content of 99.1%. The filtrate was distilled to recover 490.0g of isopropyl alcohol (water content: 7.3%), and finally 9.6g of benzenesulfonic acid (water content: 0.2%) and 19.8g of high boiling compounds in the residue were recovered under reduced pressure. The isopropanol is dehydrated by a molecular sieve and then recycled.

Example 2

107g of o-toluidine, 41.7g of 36 wt% formaldehyde aqueous solution, 446g of isopropanol and 17.2g of benzenesulfonic acid are added into a four-mouth bottle, stirred, heated to 50-55 ℃, stirred for 3 hours, heated to 75-80 ℃ and continuously stirred for 4 hours. Cooling to 10-15 deg.C, stirring for 1h, vacuum filtering, rinsing with 30g isopropanol, and drying to obtain MDT109.7g, with molar yield of 97.1% and GC content of 98.3%. 485g of isopropanol (water content: 7.3%) is recovered by rectifying the filtrate, and finally 16.5g of benzenesulfonic acid (water content: 0.1%) and 25.2g of high boiling point compounds are recovered from the residue under reduced pressure. The isopropanol is dehydrated by a molecular sieve and then recycled.

Example 3

107g of o-toluidine, 41.7g of 36 wt% formaldehyde aqueous solution and 446g of isopropanol (recovered) are added into a four-mouth bottle, 9.6g of benzenesulfonic acid is recovered, 1g of new benzenesulfonic acid is added, stirring is started, the temperature is increased to 50-55 ℃, stirring is carried out for 4 hours, and then the temperature is increased to 75-80 ℃ and stirring is carried out for 4 hours. Cooling to 10-15 deg.C, stirring for 1h, vacuum filtering, rinsing with 30g isopropanol, and drying to obtain MDT107.2g, with molar yield of 94.8% and GC content of 98.9%. The filtrate was distilled to recover 483.7g of isopropyl alcohol (water content: 7.2%), and finally 10.0g of benzenesulfonic acid (water content: 0.1%) and 21.2g of high boiling compounds in the residue were recovered under reduced pressure. The isopropanol is dehydrated by a molecular sieve and then recycled.

Example 4

107g of o-toluidine, 41.7g of 36 wt% formaldehyde aqueous solution and 446g of n-butanol are added into a four-mouth bottle, 9.6g of recovered benzenesulfonic acid is added, 1g of new benzenesulfonic acid is added, stirring is started, the temperature is increased to 50-55 ℃, stirring is carried out for 4 hours, and then the temperature is increased to 75-80 ℃ and stirring is continued for 4 hours. Cooling to 10-15 deg.C, stirring for 1h, vacuum filtering, rinsing with 30g n-butanol, and drying to obtain MDT108.3g, with 95% molar yield and 98.5% GC content. 481g of n-butanol (water content is 7.2%) is recovered by rectifying the filtrate, and finally 9.4g of benzenesulfonic acid (water content is 0.1%) and 21.2g of high boiling point compound in the kettle residue are recovered under reduced pressure. The isopropanol is dehydrated by a molecular sieve and then recycled.

The above-mentioned embodiments are only preferred embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical scope of the present invention by equivalent substitutions or modifications according to the technical solutions and inventive concepts of the present invention within the technical scope of the present invention.