A preparation method of N,N'-dicyanoethyl-diaminodiphenylmethane

Abstract

The invention discloses a method for preparing N,N'-dicyanoethyl-diaminodiphenylmethane, wherein acrylonitrile and a composite acid catalyst are added to a reactor for reaction, and after an intermediate is generated, a cyanoethylamine compound with stable properties is prepared by Michael addition reaction with diaminodiphenylmethane. The production method of N,N'-dicyanoethyl-diaminodiphenylmethane provided by the invention has the advantages of stable operation control, high yield, high product quality, etc., and fills the production technology gap of domestic N,N'-dicyanoethyl-diaminodiphenylmethane; and the N,N'-dicyanoethyl-diaminodiphenylmethane obtained by the invention also has good reactivity with epoxy resin, isocyanate, etc., and compared with the existing diaminodiphenylmethane, it has less toxicity, a shorter trial period, and stronger toughness.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis, and specifically relates to a method for preparing N,N'-dicyanoethyl-diaminodiphenylmethane. Background Art

[0002] Epoxy resin is a type of linear thermoplastic resin. Due to its excellent physical properties, electrical insulation properties and adhesion, it is widely used in many fields such as coatings, composite materials and adhesives. However, since epoxy resin itself cannot be cured and does not have any performance, it only has excellent practical value when compounded with a curing agent to produce a cured product with a three-dimensional network structure. Therefore, the curing agent is an indispensable and important component in the use of epoxy resin.

[0003] There are many types of epoxy resin curing agents, the most common ones are fatty amines, alicyclic amines, aromatic amines, polyamides, tertiary amines, modified amines, etc., and the different curing agent structures will directly affect the process and physical and chemical properties of the products, so it is necessary to select the corresponding types of epoxy resin curing agents according to different application scenarios. For aromatic amine curing agents, due to their rigid benzene ring structure, the cured products with epoxy resins have stronger impact resistance, compression resistance and tensile resistance to a certain extent, so they are widely used in potting or casting materials. Aromatic amine curing agents usually have the characteristics of long service life and better heat resistance, chemical resistance, aging resistance, electrical properties and mechanical properties of the cured products, but there are also some defects: first, most aromatic amine curing agents are solid and can only be cured with epoxy resin in a high-temperature molten state. In addition, the alkalinity of aromatic amines is weaker than that of aliphatic amines. In addition, the steric hindrance of the aromatic ring makes the reactivity with epoxy resin much slower, so it must be heated for curing, which will shorten the trial period of the compound and may have an adverse effect on the process performance of the product; second, aromatic amines are more toxic and will release amine vapor under high-temperature curing conditions, which is harmful to human health, so chemical modification is essential to reduce their toxicity; third, the epoxy resin product cured by aromatic amines is not tough enough, so if necessary, a flexible chain can be connected to the amino end to improve the toughness and strength of the product.

[0004] Aromatic amine curing agent modification technology includes addition modification with epoxy resin, addition modification with ethylene oxide or propylene oxide, Michael addition modification, Mannich reaction modification, ketimization modification, etc. Among them, for Michael addition modification technology, such as using acrylonitrile to Michael addition modification of aromatic amines, etc. This type of modification method has the following advantages: First, the β-cyanoethylated aromatic amines after addition can be used as important intermediates for fine chemicals such as pesticides, dyes, medicines, pigments and resin curing agents; second, the aminopropyl aromatic amines obtained by hydrogenating β-cyanoethylated aromatic amines have the advantages of lowering the curing temperature of epoxy resins, extending the application period, reducing toxicity and enhancing toughness.

[0005] Patent CN 107235844 A discloses a method for synthesizing a room temperature curing high temperature resistant epoxy resin curing agent, which uses diaminodiphenylmethane and acrylonitrile as raw materials, mixes the two in a certain mass ratio to obtain a mixed solution, then adds the mixed solution into a reactor and stirs and heats it; when the mixed solution reaches a certain temperature, the pressure in the reactor is equivalent to the critical vapor pressure of acrylonitrile, and when the pressure drops to normal pressure, it indicates that the reaction is over, and the reaction temperature is 130-160°C, and the reaction pressure does not exceed 1.5MPa. This method simplifies the preparation process to a certain extent, but the reaction temperature is too high, and considering the risk of acrylonitrile being easily ignited and exploded under high heat, it is not suitable for industrial production. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing N,N'-dicyanoethyl-diaminodiphenylmethane in view of the shortage and existing problems of existing domestic production technology, which has the advantages of stable operation control, high yield and high product quality. In order to achieve the above invention purpose, the present invention adopts the following technical scheme to achieve the above invention purpose:

[0007] A method for preparing N,N'-dicyanoethyl-diaminodiphenylmethane is obtained by reacting diaminodiphenylmethane and acrylonitrile in the presence of a composite acid catalyst. As a preferred solution, the method comprises the following steps:

[0008] (1) adding acrylonitrile, hydroquinone and a composite acid catalyst in a certain proportion into a reaction kettle at room temperature, so that acrylonitrile and the catalyst are pre-reacted to obtain a reaction mixture containing an intermediate;

[0009] (2) heating to the reaction temperature, continuously dripping a diaminodiphenylmethane organic solution of a corresponding proportion into the reaction mixture of step (1), keeping the reaction temperature constant, and continuing the addition reaction for a period of time to obtain a crude N,N'-dicyanoethyl-diaminodiphenylmethane product.

[0010] The reaction of the present invention is as follows: Formula I.

[0011]

[0012] The inventors have found that in the addition reaction of diaminodiphenylmethane and acrylonitrile, acrylonitrile is first pre-reacted with a composite acid catalyst to generate a reaction mixture containing an intermediate. After the pre-reaction is carried out to a certain extent, diaminodiphenylmethane is added for addition reaction. This can effectively reduce the reaction temperature and achieve a high yield of N,N'-dicyanoethyl-diaminodiphenylmethane. The process has a high safety factor and is easy to industrialize.

[0013] Preferably, the method further comprises step (3), wherein the crude product is subjected to atmospheric distillation to remove low-boiling acrylonitrile and organic solvent, and then the crude product is transferred into a beaker containing warm water, and the mixture is stirred continuously and naturally cooled to room temperature, and then filtered, washed with water, and dried to obtain N,N'-dicyanoethyl-diaminodiphenylmethane.

[0014] Preferably, the diaminodiphenylmethane is one or both of 4,4'-diaminodiphenylmethane and 2,4'-diaminodiphenylmethane.

[0015] Preferably, in step (1), the molar ratio of acrylonitrile to the composite acid catalyst is 1:0.005-0.1, preferably 1:0.025-0.05.

[0016] Preferably, in step (1), the molar ratio of acrylonitrile to hydroquinone is 1:0.005-0.02 preferably 1:0.075-0.01.

[0017] Preferably, in step (1), the composite acid catalyst is selected from at least one of ZnCl2 / HAc, CuCl / HAc, Zn(AcO)2 / HAc, Al(AcO)3 / HAc, Cu(AcO)2 / HAc, ZnCl2 / benzoic acid, ZnCl2 / HCl, FeCl3 / HCl, AlCl3 / ZnCl2, AlCl3 / CuCl2, AlCl3 / CuSO4, AlCl3 / FeCl3, and AlCl3 / Cu(AcO)2·3H2O, preferably Zn(AcO)2 / HAc.

[0018] In step (1), the molar ratio of the two components in the composite acid catalyst is 1:0.25-1.5, preferably 1:0.75-1.25.

[0019] Preferably, in step (1), the pre-reaction has a reaction temperature of 30 to 50° C. and a reaction time of 30 to 60 min.

[0020] Preferably, in step (2), the molar ratio of diaminodiphenylmethane to acrylonitrile is 1:1.5-2.5, preferably 1:2.0-2.2.

[0021] Preferably, in step (2), the organic solvent is selected from at least one of methanol, ethanol, isopropanol, tetrahydrofuran, cyclohexane and ethyl acetate, preferably tetrahydrofuran; and the mass ratio of diaminodiphenylmethane to the organic solvent is 1:0.5-5, preferably 1:1-3.

[0022] Preferably, in step (2), the addition reaction has a reaction temperature of 50 to 120° C., preferably 80 to 100° C., and a reaction time of 6 to 18 hours, preferably 10 to 12 hours.

[0023] Preferably, in step (3), the atmospheric distillation temperature is 80 to 120° C., preferably 90 to 110° C.; the treatment time is 0.5 to 5 h, preferably 1 to 3 h.

[0024] The beneficial effects of the present invention are:

[0025] (1) The amino group on the aromatic amine has weak alkalinity, and its cyanoethylation reaction is difficult to carry out. In addition, due to the electronic conjugation effect of the bicyclic aromatic amine, the cyanoethylation technology is very difficult to implement. The present invention provides an improved method for preparing N, N'-dicyanoethyl-diaminodiphenylmethane. The method uses a composite acid catalyst, has a high product yield, and a large safety factor, filling the domestic N, N'-dicyanoethyl-diaminodiphenylmethane production technology gap.

[0026] (2) First, acrylonitrile and a composite acid catalyst are pre-reacted to generate an intermediate, which fully improves the reaction activity of acrylonitrile, and then diaminodiphenylmethane is added to the reaction mixture to promote the smooth progress of the addition reaction; especially when there is an excess of acrylonitrile, adding diaminodiphenylmethane by continuous dropwise feeding can accelerate the reaction process.

[0027] (3) The composite acid catalyst used in the present invention is a composite of Lewis acid / organic acid, Lewis acid / Lewis acid, etc. The polarity of the catalyst itself is very small and can be well dissolved in acrylonitrile; and the metal cation has a strong coordination ability with the nitrogen atom on acrylonitrile, and the catalytic efficiency will be higher under the action of the acid. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited to the listed embodiments.

[0029] Gas chromatograph: Agilent 7890 and DB-5 (30m×0.25mmID×0.25μm) were used, the injector temperature was 280℃, and the detector temperature was 300℃. The heating program was as follows: the initial column temperature was 50℃, maintained for 2min; the temperature was increased to 80℃ at 5℃ / min, maintained for 0min; the temperature was increased to 300℃ at 15℃ / min, maintained for 15min. The content of each component was determined by normalization method.

[0030] Example 1

[0031] (1) Add 2.0 mol acrylonitrile, 0.15 mol hydroquinone, 0.04 mol Zn(AcO)2 and 0.04 mol HAc into a 2 L reactor and stir continuously for 60 min at 30 °C under nitrogen atmosphere until the catalyst is completely dissolved.

[0032] (2) The reaction temperature was raised to 80° C. within half an hour, and then a THF solution containing 1.0 mol of diaminodiphenylmethane (the mass ratio of diaminodiphenylmethane to THF was 1:1) was continuously added dropwise to the reaction mixture. The addition time did not exceed 1 hour. After the addition was completed, the reaction was carried out at a temperature of 80-85° C. for 12 hours until the diaminodiphenylmethane was completely reacted. Three drops of the reaction solution were diluted to 1 ml with ethanol for chromatographic analysis. The results showed that 20 ppm of acrylonitrile remained and the conversion rate of diaminodiphenylmethane was 98.9%.

[0033] (3) The material was transferred to a 1L flask, heated to 110°C in an oil bath, and treated for 1 hour to remove low-boiling acrylonitrile and tetrahydrofuran. The material was then transferred to a beaker containing 500 ml of 70°C water, stirred continuously, and cooled naturally to room temperature. The material was then filtered, washed with water until neutral, and dried to obtain off-white flaky crystals, namely N,N'-dicyanoethyl-diaminodiphenylmethane.

[0034] The composition of the chromatographic analysis product is as follows: the content of one molecule of adduct is 2.4wt%, the content of two molecules of adduct is 96.3wt%, the content of three molecules of adduct is 1.0wt%, and the content of four molecules of adduct is 0.3wt%.

[0035] Example 2

[0036] (1) Add 2.0 mol acrylonitrile, 0.15 mol hydroquinone, 0.04 mol Cu(AcO)2 and 0.04 mol HAc into a 2 L reactor and stir continuously for 60 min at 30 °C under nitrogen atmosphere until the catalyst is completely dissolved.

[0037] (2) The reaction temperature was raised to 80° C. within half an hour, and then 1.0 mol of a THF solution of diaminodiphenylmethane (the mass ratio of diaminodiphenylmethane to THF was 1:1) was continuously added dropwise to the reaction mixture for no more than 1 hour. After the addition was completed, the mixture was reacted at a temperature of 80-85° C. for 12 hours until the diaminodiphenylmethane was completely reacted. Three drops of the reaction solution were diluted to 1 ml with ethanol for chromatographic analysis. The results showed that 45 ppm of acrylonitrile remained and the conversion rate of diaminodiphenylmethane was 97.2%.

[0038] (3) The material was transferred to a 1L flask, heated to 110°C in an oil bath, and treated for 1 hour to remove low-boiling acrylonitrile and tetrahydrofuran. The material was then transferred to a beaker containing 500 ml of 70°C water, stirred continuously, and cooled naturally to room temperature. The material was then filtered, washed with water until neutral, and dried to obtain off-white flaky crystals, namely N,N'-dicyanoethyl-diaminodiphenylmethane.

[0039] The composition of the chromatographic analysis product is as follows: the content of one molecule of adduct is 3.8wt%, the content of two molecules of adduct is 95.2wt%, the content of three molecules of adduct is 0.8wt%, and the content of four molecules of adduct is 0.2wt%.

[0040] Example 3

[0041] (1) Add 2.0 mol acrylonitrile, 0.15 mol hydroquinone, 0.04 mol Al(AcO)3 and 0.04 mol HAc into a 2 L reactor and stir continuously for 60 min at 30 °C under nitrogen atmosphere until the catalyst is completely dissolved.

[0042] (2) The reaction temperature was raised to 80° C. within half an hour, and then 1.0 mol of a THF solution of diaminodiphenylmethane (the mass ratio of diaminodiphenylmethane to THF was 1:1) was continuously added dropwise to the reaction mixture for no more than 1 hour. After the addition was completed, the mixture was reacted at a temperature of 80-85° C. for 12 hours until the diaminodiphenylmethane was completely reacted. Three drops of the reaction solution were diluted to 1 ml with ethanol for chromatographic analysis. The results showed that 32 ppm of acrylonitrile remained and the conversion rate of diaminodiphenylmethane was 98.0%.

[0043] (3) The material was transferred to a 1L flask, heated to 110°C in an oil bath, and treated for 1 hour to remove low-boiling acrylonitrile and tetrahydrofuran. The material was then transferred to a beaker containing 500 ml of 70°C water, stirred continuously, and cooled naturally to room temperature. The material was then filtered, washed with water until neutral, and dried to obtain off-white flaky crystals, namely N,N'-dicyanoethyl-diaminodiphenylmethane.

[0044] The composition of the chromatographic analysis product is as follows: the content of one molecule of adduct is 3.0wt%, the content of two molecules of adduct is 95.8wt%, the content of three molecules of adduct is 0.9wt%, and the content of four molecules of adduct is 0.3wt%.

[0045] Example 4

[0046] (1) Add 2.2 mol of acrylonitrile, 0.16 mol of hydroquinone, 0.04 mol of Zn(AcO)2 and 0.04 mol of HAc into a 2 L reactor and stir continuously for 30 min at 50 °C under nitrogen atmosphere until the catalyst is completely dissolved.

[0047] (2) The reaction temperature was raised to 100° C. within half an hour, and then 1.0 mol of a THF solution of diaminodiphenylmethane (the mass ratio of diaminodiphenylmethane to THF was 1:3) was continuously added dropwise to the reaction mixture. The addition time did not exceed 1 hour. After the addition was completed, the reaction was carried out at a temperature of 100-105° C. for 12 hours until the diaminodiphenylmethane was completely reacted. Three drops of the reaction solution were diluted to 1 ml with ethanol for chromatographic analysis. The results showed that the residual acrylonitrile was 50 ppm and the conversion rate of diaminodiphenylmethane was 99.4%.

[0048] (3) The material was transferred to a 1L flask, heated to 90°C in an oil bath, and treated for 3 hours to remove low-boiling acrylonitrile and tetrahydrofuran. The material was then transferred to a beaker containing 500 ml of 70°C water, stirred continuously, and cooled naturally to room temperature. The material was then filtered, washed with water until neutral, and dried to obtain off-white flaky crystals, namely N,N'-dicyanoethyl-diaminodiphenylmethane.

[0049] The composition of the chromatographic analysis product is as follows: the content of monomolecular adduct is 1.5wt%, the content of dimolecular adduct is 97.0wt%, the content of trimolecular adduct is 1.2wt%, and the content of tetramolecular adduct is 0.3wt%.

[0050] Example 5

[0051] (1) Add 2.0 mol acrylonitrile, 0.15 mol hydroquinone, 0.05 mol Zn(AcO)2 and 0.05 mol HAc into a 2 L reactor and stir continuously for 45 min at 40 °C under nitrogen atmosphere until the catalyst is completely dissolved.

[0052] (2) The reaction temperature was raised to 90° C. within half an hour, and then 1.0 mol of a THF solution of diaminodiphenylmethane (the mass ratio of diaminodiphenylmethane to THF was 1:2) was continuously added dropwise to the reaction mixture for no more than 1 hour. After the addition was completed, the mixture was reacted at a temperature of 90-95° C. for 12 hours until the diaminodiphenylmethane was completely reacted. Three drops of the reaction solution were diluted to 1 ml with ethanol for chromatographic analysis. The results showed that 15 ppm of acrylonitrile remained and the conversion rate of diaminodiphenylmethane was 99.2%.

[0053] (3) The material was transferred to a 1L flask, heated to 100°C in an oil bath, and treated for 2 hours to remove low-boiling acrylonitrile and tetrahydrofuran. The material was then transferred to a beaker containing 500 ml of 70°C water, stirred continuously, and cooled naturally to room temperature. The material was then filtered, washed with water until neutral, and dried to obtain off-white scaly crystals, namely N,N'-dicyanoethyl-diaminodiphenylmethane.

[0054] The composition of the product by chromatographic analysis is as follows: the content of monomolecular adduct is 1.3wt%, the content of dimolecular adduct is 97.1wt%, the content of trimolecular adduct is 1.2wt%, and the content of tetramolecular adduct is 0.4wt%.

[0055] Comparative Example 1

[0056] No catalyst was added, and a mixed feed method was adopted, and the operation was performed with reference to Example 1 of patent CN 107235844 A.

[0057] Add 2.0 mol acrylonitrile, 0.15 mol hydroquinone, and 1 mol tetrahydrofuran solution of diaminodiphenylmethane to a 2L reactor; seal the reactor, heat it to 140°C, raise the maximum pressure of the reactor to 0.5 MPa, and then keep it warm. As the reaction proceeds, the pressure gradually decreases. After 16 hours, the pressure drops to 0.1 MPa, and the temperature is lowered to room temperature. Take 3 drops of the reaction solution and dilute it to 1 ml with ethanol for chromatographic analysis. The results show that the residual acrylonitrile is 200 ppm and the conversion rate of diaminodiphenylmethane is 95.6%.

[0058] The composition of the product by chromatographic analysis is as follows: the content of monomolecular adduct is 10.6wt%, the content of dimolecular adduct is 87.2wt%, the content of trimolecular adduct is 1.8wt%, and the content of tetramolecular adduct is 0.4wt%.

[0059] Comparative Example 2

[0060] No catalyst was added, and a mixed feed method was adopted, and the operation was performed with reference to Example 1 of patent CN 107235844 A.

[0061] Add 2.0 mol acrylonitrile, 0.15 mol hydroquinone, and 1 mol tetrahydrofuran solution of diaminodiphenylmethane to a 2L reactor; seal the reactor, heat it to 160°C, and raise the maximum pressure of the reactor to 0.6 MPa, then keep it warm. As the reaction proceeds, the pressure gradually decreases. After 16 hours, the pressure drops to 0.1 MPa, and the temperature is lowered to room temperature. Take 3 drops of the reaction solution and dilute it to 1 ml with ethanol for chromatographic analysis. The results show that the residual acrylonitrile is 300 ppm and the conversion rate of diaminodiphenylmethane is 94.2%.

[0062] The composition of the product by chromatographic analysis is as follows: the content of monomolecular adduct is 11.2wt%, the content of dimolecular adduct is 86.4wt%, the content of trimolecular adduct is 1.6wt%, and the content of tetramolecular adduct is 0.8wt%.

[0063] The above examples are merely examples for illustrating the present invention, and are not intended to limit the embodiments of the present invention. For researchers in the field, changes or modifications can be made based on the above description, and it is impossible to list all the embodiments here. Any changes or modifications based on the technical solution of the present invention are within the scope of the present invention.

Claims

1. A method for preparing N,N'-dicyanoethyl-diaminodiphenylmethane, characterized in that: In the presence of a composite acid catalyst, diaminodiphenylmethane and acrylonitrile are reacted to obtain the product, comprising the following steps: (1) adding acrylonitrile, hydroquinone and a composite acid catalyst in a certain proportion into a reaction kettle, so that acrylonitrile and the catalyst are pre-reacted to obtain a reaction mixture containing an intermediate; (2) continuously dripping a diaminodiphenylmethane organic solution of a corresponding proportion into the reaction mixture of step (1) to carry out an addition reaction for a period of time to obtain a crude product of N,N'-dicyanoethyl-diaminodiphenylmethane; In step (1), the pre-reaction has a reaction temperature of 30 to 50° C. and a reaction time of 30 to 60 min; In step (1), the composite acid catalyst is selected from at least one of ZnCl2 / HAc, CuCl / HAc, Zn(AcO)2 / HAc, Al(AcO)3 / HAc, Cu(AcO)2 / HAc, ZnCl2 / benzoic acid, ZnCl2 / HCl, FeCl3 / HCl, AlCl3 / ZnCl2, AlCl3 / CuCl2, AlCl3 / CuSO4, AlCl3 / FeCl3, and AlCl3 / Cu(AcO)2·3H2O.

2. The method according to claim 1, characterized in that The diaminodiphenylmethane is one or both of 4,4'-diaminodiphenylmethane and 2,4'-diaminodiphenylmethane.

3. The method according to claim 1, characterized in that: In step (1), the molar ratio of acrylonitrile to the composite acid catalyst is 1:0.005-0.

1.

4. The method according to claim 3, characterized in that: In step (1), the molar ratio of acrylonitrile to the composite acid catalyst is 1:0.025-0.

05.

5. The method according to any one of claims 1 to 4, characterized in that: In step (1), the molar ratio of acrylonitrile to hydroquinone is 1:0.005-0.

02.

6. The method according to claim 5, characterized in that: In step (1), the molar ratio of acrylonitrile to hydroquinone is 1:0.075-0.

01.

7. The method according to claim 1, wherein in step (1), the composite acid catalyst is selected from Zn(AcO)2 / HAc.

8. The method according to claim 1, characterized in that: In step (1), the molar ratio of the two components in the composite acid catalyst is 1:0.25-1.

5.

9. The method according to claim 8, characterized in that: In step (1), the molar ratio of the two components in the composite acid catalyst is 1:0.75-1.

25.

10. The method according to any one of claims 1 to 4, characterized in that: In step (2), the molar ratio of diaminodiphenylmethane to acrylonitrile is 1:1.5-2.

5.

11. The method according to claim 10, characterized in that: In step (2), the molar ratio of diaminodiphenylmethane to acrylonitrile is 1:2.0-2.

2.

12. The method according to any one of claims 1 to 4, characterized in that: In step (2), the solvent in the diaminodiphenylmethane organic solution is selected from at least one of methanol, ethanol, isopropanol, tetrahydrofuran, cyclohexane, and ethyl acetate; and the mass ratio of diaminodiphenylmethane to the organic solvent is 1:0.5-5.

13. The method according to claim 12, characterized in that: In step (2), the solvent in the diaminodiphenylmethane organic solution is selected from tetrahydrofuran; the mass ratio of diaminodiphenylmethane to the organic solvent is 1:1-3.

14. The method according to any one of claims 1 to 4, characterized in that: In step (2), the addition reaction has a reaction temperature of 50 to 120° C. and a reaction time of 6 to 18 hours.

15. The method according to claim 14, characterized in that: In step (2), the addition reaction has a reaction temperature of 80 to 100° C. and a reaction time of 10 to 12 h.

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