A method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor

Abstract

The invention provides a method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane by using a dynamic tubular reactor, and belongs to the field of organic material synthesis. The invention uses o-toluidine and formaldehyde as raw materials, and catalytically synthesizes 3,3'-dimethyl-4,4'-diaminodiphenylmethane in a dynamic tubular reactor under the action of a catalyst. The invention is simple to operate, has accurate control of reaction conditions, short reaction time, good reaction selectivity, and high product purity.

Description

Technical Field

[0001] The invention relates to the technical field of synthesis of organic monomers and discloses a method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane by utilizing a dynamic tubular reactor. Background Art

[0002] 3,3'-Dimethyl-4,4'-diaminodiphenylmethane is an important chemical raw material. It is a white or off-white frond or needle-shaped body (mainly depending on the solvent used in the refining process). It is mainly used as an adhesive and curing agent for epoxy resins and polyurethane resins. It is characterized by heat resistance, chemical resistance, and excellent electrical properties. 3,3'-Dimethyl-4,4'-diaminodiphenylmethane is combined with maleic anhydride and then prepolymerized with diamine to obtain polyimide resin. Furthermore, 3,3'-Dimethyl-4,4'-diaminodiphenylmethane is condensed with pyromellitic anhydride to obtain polyimide resin. Products processed with the above materials have excellent heat resistance, insulation properties and stability to solvents, so they are mostly used in high-temperature varnishes, capacitor films, printed circuit boards, and aviation parts. In addition, 3,3'-dimethyl-4,4'-diaminodiphenylmethane is also commonly used as an epoxy resin crosslinker, circuit insulation coating, glass fiber lubricant, and epoxy resin curing agent. It can be seen that 3,3'-dimethyl-4,4'-diaminodiphenylmethane has a wide range of uses. Although the amount used is not large, it still needs to be imported into China at present, and the price is relatively high. Its structural formula is:

[0003]

[0004] The method reported by Scanlan et al. is to react o-toluidine, hydrochloric acid and formaldehyde solution, and under alkaline conditions, steam distills out the unreacted raw material o-toluidine, and the obtained reactant is recrystallized twice to obtain 3,3'-dimethyl-4,4'-diaminodiphenylmethane with a yield of 63% (J.Am.Chem.Soc., 1935, May: 887-892). This method has high reaction temperature, many by-products, complicated post-processing, low yield, multiple recrystallizations, high cost, and little prospect for industrialization.

[0005] Barluenga et al. reported a method in which o-toluidine reacts with paraformaldehyde in the presence of sodium methoxide to obtain N-methoxymethyl o-toluidine, which is then refluxed with o-toluidine hydrochloride to obtain 3,3'-dimethyl-4,4'-diaminodiphenylmethane (J. Chem. Soc. Perkin Trans I, 1988: 1631-1636). The raw materials of this preparation method are expensive, sodium methoxide is inconvenient to store and transport, and the intermediate product N-methoxymethyl o-toluidine needs to be separated and then reacted with another molecule of o-toluidine hydrochloride, which is cumbersome and costly.

[0006] The preparation method of MDT reported by Zhang Shuqin et al. (Chemistry and Adhesion, 1989, 2, 217-219) is to mix o-toluidine, water and hydrochloric acid, stir and heat to a predetermined temperature, add formaldehyde dropwise, condense and transfer until the reaction is complete, cool, neutralize with sodium hydroxide aqueous solution to make the solution alkaline, and the precipitate is MDT.

[0007] Chinese patent CN1948267A reports that o-toluidine reacts with hydrochloric acid to form a salt, which is then condensed with formaldehyde in the presence of a catalyst 4,4'-dimethylaminopyridine, and then neutralized with an alkaline solution to obtain MDT.

[0008] Chinese patent CN102249931 uses o-toluidine and formaldehyde as raw materials, undergoes a condensation reaction in the absence of a catalyst, and then undergoes post-treatment to obtain MDT.

[0009] Chinese patent CN101007767A reports a catalytic synthesis process of MDA, which uses aniline and formaldehyde as raw materials and is prepared by an intermittent one-step condensation reaction under the action of a solid acid catalyst.

[0010] Chinese patent CN103130654B provides a method for preparing MDT using a solid acid catalyst instead of an inorganic acid, using o-toluidine and formaldehyde as raw materials, using a solid acid as a catalyst, after the reaction, filtering, cooling the filtrate to room temperature for recrystallization, filtering, and drying to obtain MDT.

[0011] Chinese patent CN105294448A provides a method for continuously preparing 4,4'-diaminodiphenylmethane derivatives with solid acid catalysis, wherein a condensation reaction is carried out with solid acid catalysis in a one-stage or two-stage fixed bed reactor to obtain 4,4'-diaminodiphenylmethane derivatives.

[0012] Most of the methods used in the above reports are intermittent reactions carried out in traditional reactors, which have long reaction times and complex operating steps, and are not conducive to large-scale production. When solid materials are involved in the microreactor or solids are produced, it will cause pipeline blockage and incomplete reaction. Summary of the invention

[0013] The following is a summary of some aspects of the present invention, but is not intended to limit the present invention. When there is a discrepancy between the disclosure of this specification and the referenced document, the disclosure of this specification shall prevail.

[0014] The object of the present invention is to provide a method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane by using a dynamic tubular reactor. The dynamic tubular reactor can be used to control the reaction pressure and temperature well.

[0015] The technical solution adopted by the present invention is:

[0016] A method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor comprises the following steps:

[0017] o-Toluidine, formaldehyde and catalyst are pumped into the dynamic tubular reactor at a certain flow rate. The reaction liquid is fully mixed in the reactor, heated under a certain pressure, and flows out of the reactor after staying for a certain time. The reaction liquid is cooled, and sodium hydroxide aqueous solution is added dropwise to adjust the pH. After filtering, ethanol is added for recrystallization to obtain 3,3'-dimethyl-4,4'-diaminodiphenylmethane. The reaction formula is as follows:

[0018]

[0019] Furthermore, the method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor is characterized in that the formaldehyde is an aqueous solution with a concentration of 35-40%, preferably 37%.

[0020] Furthermore, the method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor is characterized in that the catalyst is selected from one or more of concentrated hydrochloric acid, concentrated sulfuric acid, p-toluenesulfonic acid, solid acid, and methanesulfonic acid, preferably concentrated hydrochloric acid.

[0021] Furthermore, the method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor is characterized in that the concentration of the hydrochloric acid is 20%-40%, preferably 30%.

[0022] Furthermore, the method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor is characterized in that the molar ratio of o-toluidine to formaldehyde is 2:1 to 2, preferably 2:1.

[0023] Furthermore, the method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor is characterized in that the molar ratio of formaldehyde to concentrated hydrochloric acid is 1:0.5-1.5, preferably 1:0.8.

[0024] Furthermore, the method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor is characterized in that the reaction temperature of the dynamic tubular reactor is 60-80°C, preferably 70°C.

[0025] Furthermore, the method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor is characterized in that the reaction residence time of the dynamic tubular reactor is 5 to 10 minutes, preferably 7 minutes.

[0026] Furthermore, the method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor is characterized in that the reaction solution is cooled to 15-20°C, preferably 18°C.

[0027] Furthermore, the method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor is characterized in that the pH is 7.5 to 8.5, preferably pH 8.

[0028] Beneficial technical effects of the present invention

[0029] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0030] First, a continuous preparation process is realized, the reaction speed is fast, and the reaction time is shortened; second, the rapid heat transfer capability makes it easy to achieve constant temperature reaction, improve the reaction yield, and the reaction temperature is mild, which reduces safety hazards; finally, it avoids problems such as pipeline blockage and incomplete reaction caused by the generation of solid particles in the product, which is more conducive to industrial production. DETAILED DESCRIPTION

[0031] Unless otherwise indicated or there is an obvious conflict in the context, all technical and scientific terms used herein have the same meaning as those generally understood by those of ordinary skill in the art to which the invention belongs. If there is a conflict, the definitions provided in the application shall prevail. When a trade name appears in this article, it is intended to refer to the corresponding commodity or its active ingredient. All patents, published patent applications and publications cited herein are incorporated herein by reference.

[0032] Embodiment 1:

[0033] (1) o-toluidine, formaldehyde (37%), and concentrated hydrochloric acid (30%) are pumped into a dynamic tubular reactor at a certain flow rate, and the flow rate ratio of the three reaction liquids in the step is adjusted to control the molar ratio of o-toluidine: formaldehyde: concentrated hydrochloric acid to be 2:1:0.8;

[0034] (2) Set the reaction temperature to 70 °C and the residence time to 7 min;

[0035] (3) The outlet is connected to the reaction liquid, the temperature is lowered to 18° C., and a sodium hydroxide aqueous solution is added dropwise until the pH value is about 8. After filtering the solid, ethanol is added for recrystallization to obtain 3,3'-dimethyl-4,4'-diaminodiphenylmethane with a yield of 93% and a purity of 99.5%.

[0036] Embodiment 2:

[0037] (1) o-toluidine, formaldehyde (35%), and concentrated hydrochloric acid (20%) are pumped into a dynamic tubular reactor at a certain flow rate, and the flow rate ratio of the three reaction liquids in the step is adjusted to control the molar ratio of o-toluidine: formaldehyde: concentrated hydrochloric acid to be 2:1:0.5;

[0038] (2) Set the reaction temperature to 60 °C and the residence time to 5 min;

[0039] (3) The outlet is connected to the reaction liquid, the temperature is lowered to 15° C., and a sodium hydroxide aqueous solution is added dropwise until the pH value is about 7.5. After filtering the solid, ethanol is added for recrystallization to obtain 3,3'-dimethyl-4,4'-diaminodiphenylmethane with a yield of 90% and a purity of 99.3%.

[0040] Embodiment 3:

[0041] (1) pumping o-toluidine, formaldehyde (40%), and concentrated hydrochloric acid (40%) into a dynamic tubular reactor at a certain flow rate, respectively, and adjusting the flow ratio of the three reaction liquids in the step to control the molar ratio of o-toluidine: formaldehyde: concentrated hydrochloric acid to be 2:1:1.5;

[0042] (2) Set the reaction temperature to 80 °C and the residence time to 10 min;

[0043] (3) The outlet is connected to the reaction liquid, the temperature is lowered to 20° C., and a sodium hydroxide aqueous solution is added dropwise until the pH value is about 8.5. After filtering the solid, ethanol is added for recrystallization to obtain 3,3'-dimethyl-4,4'-diaminodiphenylmethane with a yield of 89% and a purity of 99.2%.

[0044] Embodiment 4:

[0045] (1) o-toluidine, formaldehyde (30%), and concentrated hydrochloric acid (15%) are pumped into a dynamic tubular reactor at a certain flow rate, and the flow rate ratio of the three reaction liquids in the step is adjusted to control the molar ratio of o-toluidine: formaldehyde: concentrated hydrochloric acid to be 2:1:0.3;

[0046] (2) Set the reaction temperature to 65 °C and the residence time to 6 min;

[0047] (3) The outlet is connected to the reaction liquid, cooled to 17° C., and sodium hydroxide aqueous solution is added dropwise until the pH value is about 7.8. After filtering the solid, ethanol is added for recrystallization to obtain 3,3'-dimethyl-4,4'-diaminodiphenylmethane with a yield of 80% and a purity of 98.1%.

[0048] Embodiment 5:

[0049] (1) pumping o-toluidine, formaldehyde (45%), and concentrated hydrochloric acid (45%) into a dynamic tubular reactor at a certain flow rate, respectively, and adjusting the flow ratio of the three reaction liquids in the step to control the molar ratio of o-toluidine: formaldehyde: concentrated hydrochloric acid to be 2:1:2;

[0050] (2) Set the reaction temperature to 68 °C and the residence time to 8 min;

[0051] (3) The outlet is connected to the reaction liquid, cooled to 19° C., and sodium hydroxide aqueous solution is added dropwise until the pH value is about 8.2. After filtering the solid, ethanol is added for recrystallization to obtain 3,3'-dimethyl-4,4'-diaminodiphenylmethane with a yield of 81% and a purity of 98.5%.

[0052] Embodiment 6:

[0053] (1) o-toluidine, formaldehyde (35%), and concentrated hydrochloric acid (20%) are pumped into a dynamic tubular reactor at a certain flow rate, and the flow rate ratio of the three reaction liquids in the step is adjusted to control the molar ratio of o-toluidine: formaldehyde: concentrated hydrochloric acid to be 2:1:0.7;

[0054] (2) Set the reaction temperature to 50 °C and the residence time to 3 min;

[0055] (3) The outlet is connected to the reaction liquid, cooled to 12° C., and sodium hydroxide aqueous solution is added dropwise until the pH value is about 7.2. After filtering the solid, ethanol is added for recrystallization to obtain 3,3'-dimethyl-4,4'-diaminodiphenylmethane with a yield of 78% and a purity of 98.2%.

[0056] Embodiment 7:

[0057] (1) pumping o-toluidine, formaldehyde (37%), and concentrated hydrochloric acid (32%) into a dynamic tubular reactor at a certain flow rate, respectively, and adjusting the flow ratio of the three reaction liquids in the step to control the molar ratio of o-toluidine: formaldehyde: concentrated hydrochloric acid to be 2:1:1;

[0058] (2) Set the reaction temperature to 90 °C and the residence time to 15 min;

[0059] (3) The outlet is connected to the reaction liquid, cooled to 25° C., and sodium hydroxide aqueous solution is added dropwise until the pH value is about 9. After filtering the solid, ethanol is added for recrystallization to obtain 3,3'-dimethyl-4,4'-diaminodiphenylmethane with a yield of 85% and a purity of 97.2%.

[0060] The above is a description of a specific embodiment of the present invention. It should be understood that the present invention is not limited to the above embodiment, and the above embodiment and description are only for illustrating the principle of the present invention.

[0061] Those skilled in the art may make various non-substantial changes and improvements to the present invention without departing from the concept of the present invention, all of which fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor, characterized in that: o-Toluidine, formaldehyde and catalyst are pumped into the dynamic tubular reactor at a certain flow rate. The reaction liquid is fully mixed in the reactor, heated under a certain pressure, and flows out of the reactor after staying for a certain time. The reaction liquid is cooled, and sodium hydroxide aqueous solution is added dropwise to adjust the pH. After filtering, ethanol is added for recrystallization to obtain 3,3'-dimethyl-4,4'-diaminodiphenylmethane. The reaction formula is as follows:

2. A method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor according to claim 1, characterized in that: The formaldehyde is an aqueous solution with a concentration of 35-40%, preferably 37%.

3. A method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor according to claim 1, characterized in that: The catalyst is selected from one or more of concentrated hydrochloric acid, concentrated sulfuric acid, p-toluenesulfonic acid, solid acid, and methanesulfonic acid, preferably concentrated hydrochloric acid.

4. A method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor according to claim 1, characterized in that: The hydrochloric acid has a concentration of 20%-40%, preferably 30%.

5. A method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor according to claim 1, characterized in that: The molar ratio of o-toluidine to formaldehyde is 2:1-2, preferably 2:

1.

6. A method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor according to claim 1, characterized in that: The molar ratio of formaldehyde to concentrated hydrochloric acid is 1:0.5-1.5, preferably 1:0.

8.

7. A method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor according to claim 1, characterized in that: The reaction temperature of the dynamic tubular reactor is 60-80°C, preferably 70°C.

8. A method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor according to claim 1, characterized in that: The reaction residence time of the dynamic tubular reactor is 5 to 10 minutes, preferably 7 minutes.

9. A method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane using a dynamic tubular reactor according to claim 1, characterized in that: The reaction solution is cooled to 15-20°C, preferably 18°C.

10. The method for preparing 3,3'-dimethyl-4,4'-diaminodiphenylmethane by using a dynamic tubular reactor according to claim 1, characterized in that: The pH is 7.5 to 8.5, preferably pH 8.

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