A pretreatment method for MXDA raw materials

Abstract

The invention discloses a pretreatment method for an MXDA raw material, which comprises the following steps: ammonia washing and water washing; in the ammonia washing, a toluene solution of an IPN to be treated is subjected to countercurrent washing by using an ammonia-containing aqueous solution to obtain a toluene solution of the IPN after ammonia washing; in the preparation method of the ammonia-containing aqueous solution, an ammonia source is mixed with a solvent to obtain an ammonia-containing aqueous solution; in the preparation method of the toluene solution of the IPN to be treated, toluene and the IPN to be treated are mixed and stirred until the IPN to be treated is completely dissolved in toluene to obtain a toluene solution of the IPN to be treated; in the water washing, water is used to conduct countercurrent washing on the toluene solution of the IPN after ammonia washing to obtain the pretreated MXDA raw material; the invention can solve the problems of complicated operation and low removal efficiency in the current pretreatment method of the MXDA raw material, and has low energy consumption and low cost.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemical industry, and in particular to a pretreatment method of MXDA raw material. Background Art

[0002] MXDA is the abbreviation of meta-phenylenediamine, also known as 1,3-phenylenediamine, meta-dimethylaminobenzene, 1,3-dimethylaminobenzene, etc. Its molecular formula is C 8 H 12 N 2 , density is 1.032g / cm 3 The melting point is 14℃ (lit.), the boiling point is 247.0±0.0℃, and it is a colorless to yellow liquid at room temperature.

[0003] MXDA is an important chemical raw material, mainly used as epoxy resin curing agent, with excellent curing performance, good heat resistance, water resistance and chemical corrosion resistance, and can produce transparent and extremely smooth surface cured resin. The new MXD6 resin made with MXDA as a modified monomer has good oxygen permeability resistance and carbon dioxide loss resistance. MXDA can also be used to synthesize the monomer of polyurethane - meta-xylene dicyanate XDI. Compared with the commonly used diphenylmethane diisocyanate, XDI products are not easy to yellow, have a short drying time, and can obtain a paint film with high hardness and good stability. In addition, MXDA is widely used in rubber products, pesticides, fiber finishing agents, rust inhibitors, chelating agents, lubricants, paper and electronic products industries.

[0004] Isophthalonitrile (hereinafter referred to as IPN) is the main raw material of MXDA, which is produced by hydrogenation reaction of IPN. Industrial IPN contains about 2-4% of formic acid, amide, and miscellaneous nitrile impurities, including but not limited to: benzoic acid, isophthalic acid, 2-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, m-cyanobenzoic acid, 3,5-dicyanobenzoic acid, isophthalamide, m-cyanobenzamide, etc. Among them, formic acid impurities will cause the nickel-based hydrogenation catalyst used in the synthesis of MXDA to be poisoned and deactivated, while amide impurities will affect the product purity of MXDA and increase the difficulty of purification.

[0005] Chinese patent CN109456200B discloses a method for preparing m-xylene diamine, which converts m-xylene into isophthalonitrile by ammoxidation, and the obtained isophthalonitrile is extracted by N-alkylpyrazole, and the isophthalonitrile solution obtained by extraction is then removed by resin to remove carboxylic acid, and then enters a hydrogenation reactor for hydrogenation reaction to obtain a m-xylene diamine reaction liquid, and finally distills and separates to obtain high-purity m-xylene diamine. However, the method has the following problems: first, the isophthalonitrile solution is decarboxylated by resin, and since the content of formic acid impurities in the industrial product isophthalonitrile is relatively high, the resin is very easy to adsorb formic acid impurities and then saturated, thereby losing adsorption capacity, so the resin adsorption service life is short, generally only a few days, the cost is high, and it is difficult to apply it on a large scale industrially; second, the resin can only remove carboxylic acid in the isophthalonitrile solution, and cannot effectively remove amide impurities, so the isophthalonitrile solution after the resin removes carboxylic acid still contains a relatively high content of impurities.

[0006] Chinese patent CN112079746A discloses a purification process and catalytic hydrogenation process of isophthalonitrile, wherein the purification process includes two steps: the first purification and the use of toluene and wastewater. The catalytic hydrogenation process uses the isophthalonitrile wet material produced in the isophthalonitrile purification process step as a raw material, and catalytic hydrogenation is used to prepare meta-xylylenediamine. The first purification is to mix the isophthalonitrile crude product with toluene, wash it with distilled water four times under heating conditions, then cool it down and crystallize it, and filter out toluene to obtain the isophthalonitrile wet material; the use of toluene and wastewater is to use the mixed solution of the wastewater produced by the first washing and the second washing in the first purification to recover toluene from the meta-xylylenediamine and wash it once under heating conditions, then add the mixed solution of the wastewater produced by the third washing and the fourth washing, recover the isophthalonitrile-toluene solution, the isophthalonitrile crude product, wash it under heating conditions and separate the water layer; then wash it with distilled water twice under heating conditions; then cool it down and crystallize it, and filter out toluene to obtain the isophthalonitrile wet material. However, this method has the following problems: first, the isophthalonitrile solution dissolved in toluene needs to be washed with water six times, which is cumbersome and time-consuming; second, due to the large number of washing times, a certain amount of toluene will be lost each time, so the toluene loss is large; third, the total water consumption for washing is 10 times the mass of IPN, which not only wastes a lot of water, but also generates a large amount of wastewater and has high treatment costs; fourth, it requires two cooling recrystallizations, which consumes a lot of heat energy for heating and refrigeration energy for cooling; fifth, the solubility of isophthalonitrile in toluene changes with temperature. At 10°C, the solubility of isophthalonitrile in toluene is below 3%. Therefore, a low-concentration isophthalonitrile solution below 3% needs to be prepared for purification by water washing, which will result in a large amount of solvent circulation during the synthesis of meta-xylylenediamine, and the energy consumption is very high. Sixth, the water washing process can only remove meta-cyanobenzamide, but the removal efficiency of harmful impurities such as formic acid is low. Therefore, after the water washing process, the content of formic acid impurities in isophthalonitrile is still high, making it difficult to ensure the operating life of the nickel-based hydrogenation catalyst used in the synthesis of meta-xylylenediamine.

[0007] Chinese patent CN110963942A discloses a method for refining phthalonitrile, which comprises the following steps: mixing isophthalonitrile to be refined with liquid ammonia and fully dissolving them at a certain temperature and pressure; then filtering and separating insoluble substances while maintaining the temperature and pressure; volatilizing the filtrate with ammonia or separating part of the refined product by crystallization, and then volatilizing the crystallization mother liquor with ammonia, vacuum drying, and obtaining high-quality isophthalonitrile. However, this method has the following problems: first, the solubility of isophthalonitrile in liquid ammonia is very low, and the concentration of the prepared solution is very low, requiring a large amount of liquid ammonia; second, the boiling point of liquid ammonia is -33°C, so it needs to be under a higher pressure to maintain the liquid state. The highest dissolution temperature in this method is 150°C. At this temperature, a pressure of more than 4MPa is required to maintain the liquid state. Considering that the solubility of isophthalonitrile in liquid ammonia is extremely low, the technical difficulty is very high; third, a low-temperature kettle is used to crystallize and separate the liquid ammonia solution of isophthalonitrile, which consumes a lot of energy; fourth, formic acid impurities will not react with liquid amino groups at room temperature and in the absence of a catalyst, so the removal ability of formic acid impurities is weak.

[0008] In summary, the existing IPN solution impurity removal process has the problems of complex process and high cost, and can only remove some impurities, which has obvious limitations. Therefore, it is necessary to invent an IPN pretreatment method with simple process, low operating cost and high efficiency in removing impurities, which can remove formic acid and amide impurities in IPN, thereby avoiding the poisoning and deactivation problem of nickel-based hydrogenation catalyst and improving the purity of MXDA product. Summary of the invention

[0009] In view of the shortcomings of the prior art, the present invention provides a pretreatment method for MXDA raw materials, which can solve the problems of complicated operation and low removal efficiency in the current pretreatment method for MXDA raw materials, and has low energy consumption and low cost.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0011] A method for pretreating MXDA raw materials, comprising the following steps: ammonia washing, water washing;

[0012] The ammonia washing comprises using an aqueous ammonia solution to perform convection washing on the toluene solution of the IPN to be treated to obtain a toluene solution of the IPN after ammonia washing;

[0013] The method for preparing the aqueous ammonia solution comprises mixing an ammonia source with a solvent to obtain the aqueous ammonia solution;

[0014] In the preparation of the aqueous ammonia solution, the ammonia source is one of liquid ammonia, gaseous ammonia and aqueous ammonia;

[0015] When the ammonia source is aqueous ammonia, the mass concentration of aqueous ammonia is 5-25%;

[0016] The solvent is one of distilled water or desalted water;

[0017] The mass ratio of ammonia source to solvent is 7.5-75:75-585;

[0018] The method for preparing the toluene solution of the IPN to be treated is to mix toluene and the IPN to be treated and then stir until the IPN to be treated is completely dissolved in the toluene to obtain the toluene solution of the IPN to be treated;

[0019] The mass concentration of the toluene solution of the IPN to be treated is 10-15%;

[0020] The mass ratio of the ammonia source in the aqueous ammonia solution to the IPN to be treated in the toluene solution of the IPN to be treated is 7.5-75:150;

[0021] In the preparation of the toluene solution of the IPN to be treated, the temperature during stirring is 70-90° C.;

[0022] The ammonia washing convection washing comprises introducing an ammonia-containing aqueous solution and a toluene solution of the IPN to be treated from the upper side and the lower side of the convection tube, respectively, convection washing at 70-90° C. for 40-80 minutes, standing at 70-90° C. for 40-60 minutes, and removing the water layer;

[0023] In the countercurrent washing of the ammonia washing, the flow rate of the ammonia-containing aqueous solution is 45-55 mL / min;

[0024] The flow rate of the toluene solution of the IPN to be treated is 20-25 mL / min;

[0025] The water washing comprises using water to perform convection washing on the toluene solution of the IPN after the ammonia washing to obtain the pretreated MXDA raw material;

[0026] In the water washing, the water is one of distilled water or desalted water;

[0027] The mass ratio of water to the IPN in the toluene solution of IPN after ammonia washing is 150-600:150;

[0028] The water-washing convection washing comprises introducing water and ammonia-washed IPN toluene solution from the upper and lower sides of the convection tube, respectively, convection washing at 70-90° C. for 30-60 min, standing at 70-90° C. for 30-60 min, and removing the water layer;

[0029] In the countercurrent washing of the water washing, the flow rate of water is 45-55 mL / min;

[0030] The flow rate of the toluene solution of the IPN to be treated is 20-25 mL / min;

[0031] The number of times of the ammonia washing is 1 time;

[0032] The number of times of washing with water is greater than or equal to 1 time.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The pretreatment method of the MXDA raw material of the present invention can simultaneously remove formic acid and amide impurities in IPN with high removal efficiency. The purity of the pretreated MXDA raw material, i.e., IPN, is high, thereby significantly improving the service life of the hydrogenation catalyst. When the unpretreated IPN raw material is used to produce MXDA, the hydrogenation catalyst will be deactivated within 48 hours of use. After the IPN raw material is pretreated by the method of the present invention, the activity of the hydrogenation catalyst is not significantly attenuated after 500 hours of use.

[0035] (2) The pretreatment method of MXDA raw material of the present invention has simple process and convenient operation;

[0036] (3) The pretreatment method of MXDA raw materials of the present invention is low-cost and suitable for large-scale industrial production and application, which helps to improve the product competitiveness of MXDA prepared by IPN;

[0037] (4) The pretreatment method of the MXDA raw material of the present invention is to pretreat the industrial-grade IPN with a liquid chromatography purity of 97.86%. The liquid chromatography purity of the pretreated MXDA raw material, i.e., IPN, can reach 99.20-99.77%. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the liquid chromatogram of industrial-grade IPN without pretreatment;

[0039] Figure 2 It is the liquid chromatogram of the MXDA raw material after pretreatment in Example 2. DETAILED DESCRIPTION

[0040] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described.

[0041] The liquid chromatography purity of the industrial grade IPN used in the examples is 97.86%.

[0042] Example 1

[0043] A pretreatment method for MXDA raw materials, specifically:

[0044] Add 850g of toluene to a 2L stirred tank, then add 150g of industrial-grade IPN, heat to 80°C and stir to fully dissolve the IPN in the toluene to prepare an IPN solution with a mass concentration of 15%. Then use a metering pump to extract the IPN solution from the bottom of the tank and pass it into the convection tube from the bottom at a flow rate of 25mL / min;

[0045] 150 g of distilled water is added to a container with a specification of 500 mL, and a metering pump is used to extract distilled water at a flow rate of 50 mL / min, and the water flow rate is controlled to 0.5 m / s. The outlet pipe of the metering pump is connected to a jet mixer, and the three-way connection of the mixer is connected to a liquid ammonia pipe, and the liquid ammonia pipe is connected to a container containing 7.5 g of liquid ammonia. A vacuum is formed in the ejector by water jetting to extract liquid ammonia, and the distilled water and liquid ammonia in the ejector are mixed to obtain ammonia water, and then the ammonia water is introduced into the convection tube from the upper side of the convection tube, flows out from the bottom of the convection tube, and returns to the container containing the distilled water for circulation;

[0046] The IPN solution enters the tube from the lower side of the convection tube, and the ammonia water enters the tube from the upper side and flows out from the bottom. The ammonia water and the IPN solution are washed by convection. The formic acid and amide impurities in the IPN solution react with the ammonia water or dissolve in the ammonia water, thereby taking out the impurities and completing the purification of IPN. During the convection washing process, the temperature of the convection tube is controlled to 80°C to prevent the precipitation and crystallization of IPN due to the temperature drop;

[0047] After 40 minutes of convection washing, the circulating washing of ammonia water was stopped, the IPN solution in the convection tube was allowed to stand at 80°C for 40 minutes, the water layer containing impurities at the bottom of the convection tube was drained, and the waste water containing impurities in the container of distilled water was poured out;

[0048] Then, 150 g of distilled water was added to the container containing distilled water, and the metering pump was turned on to extract distilled water at a flow rate of 50 mL / min, and the water flow rate was controlled to 0.5 m / s. According to the above method, the IPN solution in the convection tube was convection-washed for 30 min, and then the circulating washing of distilled water was stopped. The solution in the convection tube was allowed to stand at 80° C. for 30 min, and the impurity-containing water layer at the bottom of the tube was discharged to obtain the pretreated MXDA raw material;

[0049] The specification of the convection tube is 3L, and the size is Φ80×600mm.

[0050] The liquid chromatography purity of the pretreated MXDA raw material after sampling and testing was 99.21%.

[0051] Example 2

[0052] A pretreatment method for MXDA raw materials, specifically:

[0053] Add 850g of toluene to a 2L stirred kettle, then add 150g of industrial-grade IPN, heat to 80°C and stir to allow IPN to fully dissolve in toluene to prepare an IPN solution with a mass concentration of 15%. Then use a metering pump to extract the IPN solution from the bottom of the kettle and pass it into the convection tube from the lower side at a flow rate of 25mL / min;

[0054] 150 g of distilled water was added to a container with a specification of 500 mL, and a metering pump was used to extract distilled water at a flow rate of 50 mL / min, and the water flow rate was controlled to 0.5 m / s. The outlet pipe of the metering pump was connected to a jet mixer, and the three-way connection of the mixer was connected to a gas ammonia pipe, and the gas ammonia pipe was connected to a container containing 7.5 g of gas ammonia. A vacuum was formed in the ejector by water jetting to extract gas ammonia. The distilled water and gas ammonia in the ejector were mixed to form ammonia water, and then the ammonia water was passed into the tube from the upper side of the convection tube, and then flowed out from the bottom of the convection tube and returned to the container containing distilled water for circulation;

[0055] The IPN solution enters the tube from the lower side of the convection tube, and the ammonia water enters the tube from the upper side and flows out from the bottom. The ammonia water and the IPN solution are washed by convection. The formic acid and amide impurities in the IPN solution react with the ammonia water or dissolve in the ammonia water, thereby taking out the impurities and completing the purification of IPN. During the convection washing process, the temperature of the convection tube is controlled to 80°C to prevent the precipitation and crystallization of IPN due to the temperature drop;

[0056] After 40 minutes of convection washing, the circulating washing of ammonia water was stopped, the IPN solution in the convection tube was allowed to stand at 80°C for 40 minutes, the water layer containing impurities at the bottom of the convection tube was drained, and the waste water containing impurities in the container of distilled water was poured out;

[0057] Then, 150 g of distilled water was added to the container containing distilled water, and the metering pump was turned on. At a flow rate of 50 mL / min, the water flow rate was controlled to 0.5 m / s, and the IPN solution in the convection tube was convection-washed for 30 min according to the above method. Then, the circulating washing of distilled water was stopped, and the solution in the convection tube was allowed to stand at 80° C. for 30 min, and the impurity-containing water layer at the bottom of the tube was discharged to obtain the pretreated MXDA raw material;

[0058] The specification of the convection tube is 3L, and the size is Φ80×600mm.

[0059] The liquid chromatography purity of the pretreated MXDA raw material after sampling and testing was 99.20%.

[0060] Example 3

[0061] A pretreatment method for MXDA raw materials, specifically:

[0062] 850 g of toluene was added to a 2 L stirring kettle, and then 150 g of industrial grade IPN was added, and the mixture was heated to 80 ° C and stirred to allow the IPN to fully dissolve in the toluene to prepare an IPN solution with a mass concentration of 15%. Then, a metering pump was used to extract the IPN solution from the bottom of the kettle and introduced into the convection tube from the lower side at a flow rate of 25 mL / min.

[0063] 75 g of desalted water is added into a container with a specification of 500 mL, and a metering pump is used to extract the desalted water at a flow rate of 50 mL / min, and the water flow rate is controlled to 0.5 m / s. The outlet pipe of the metering pump is connected to a jet mixer, and the three-way connection of the mixer is connected to an ammonia pipe, and the ammonia pipe is connected to 75 g of ammonia water with a mass concentration of 10%. A vacuum is formed in the ejector by water jetting to extract the ammonia water, and the desalted water in the ejector is mixed with the ammonia water to form dilute ammonia water, and then the dilute ammonia water is passed into the convection tube from the upper side of the convection tube, flows out from the bottom of the convection tube, and returns to the container containing the desalted water for circulation;

[0064] The IPN solution enters the tube from the lower side of the convection tube, and the dilute ammonia water enters the tube from the upper side and flows out from the bottom. The dilute ammonia water and the IPN solution are washed by convection. The formic acid and amide impurities in the IPN solution react with the ammonia water or dissolve in the dilute ammonia water, thereby taking out the impurities and completing the purification of IPN. During the convection washing process, the temperature of the convection tube is controlled to 80°C to prevent the precipitation and crystallization of IPN due to the temperature drop;

[0065] After 40 minutes of convection washing, the circulating washing of ammonia water was stopped, the IPN solution in the convection tube was allowed to stand at 80°C for 40 minutes, the water layer containing impurities at the bottom of the convection tube was drained, and the waste water containing impurities in the container containing desalted water was poured out;

[0066] Then, 150 g of desalted water was added to the container containing desalted water, and the metering pump was turned on to extract the desalted water at a flow rate of 50 mL / min, and the water flow rate was controlled to 0.5 m / s. According to the above method, the desalted water was convectively washed with the IPN solution in the convection tube for 30 min, and then the circulation washing of the desalted water was stopped. The solution in the convection tube was allowed to stand at 80° C. for 30 min, and the impurity-containing water layer at the bottom of the tube was discharged to obtain the pretreated MXDA raw material;

[0067] The specification of the convection tube is 3L, and the size is Φ80×600mm.

[0068] The liquid chromatography purity of the pretreated MXDA raw material after sampling and testing was 99.23%.

[0069] Example 4

[0070] 1350g of toluene was added to a 2L stirring kettle, and then 150g of industrial-grade IPN was added, and the mixture was heated to 80°C and stirred to allow the IPN to fully dissolve in the toluene to prepare an IPN solution with a mass concentration of 10%; then a metering pump was used to extract the IPN solution from the bottom of the kettle and introduced into the convection tube from the lower side at a flow rate of 20mL / min;

[0071] 585 g of desalted water is added to a container with a specification of 1000 mL, and a metering pump is used to extract the desalted water at a flow rate of 50 mL / min, and the water flow rate is controlled to 1.0 m / s. The outlet pipe of the metering pump is connected to a jet mixer, and the three-way connection of the mixer is connected to a liquid ammonia pipe, and the liquid ammonia pipe is connected to a container containing 15 g of liquid ammonia. A vacuum is formed in the ejector by water jetting to extract liquid ammonia. The water in the ejector is mixed with the liquid ammonia to obtain ammonia water, and then the ammonia water is passed into the convection tube from the upper side of the convection tube, and then flows out from the bottom of the convection tube and returns to the container containing the desalted water for circulation;

[0072] The IPN solution enters the tube from the lower side of the convection tube, and the ammonia water enters the tube from the upper side and flows out from the bottom. The ammonia water and the IPN solution are washed by convection. The formic acid and amide impurities in the IPN solution react with the ammonia water or dissolve in the ammonia water, thereby taking out the impurities and completing the purification of IPN. During the convection washing process, the temperature of the convection tube is controlled to 80°C to prevent the precipitation and crystallization of IPN due to the temperature drop;

[0073] After 80 minutes of convection washing, the circulating washing of ammonia water was stopped, the IPN solution in the convection tube was allowed to stand at 80°C for 60 minutes, the water layer containing impurities at the bottom of the tube was drained, and the waste water containing impurities in the container containing desalted water was poured out;

[0074] Then, 600 g of desalted water was added to the container containing desalted water, and the metering pump was turned on. The water flow rate was controlled to 1.0 m / s at a flow rate of 50 mL / min, and the water was washed with the IPN solution in the convection tube for 60 min according to the above method. Then, the circulating washing of the desalted water was stopped, and the solution in the convection tube was allowed to stand at 80° C. for 60 min, and the impurity-containing water layer at the bottom of the tube was discharged to obtain the pretreated MXDA raw material;

[0075] The specification of the convection tube is 3L, and the size is Φ80×600mm.

[0076] The liquid chromatography purity of the pretreated MXDA raw material after sampling and testing was 99.52%.

[0077] Example 5

[0078] A pretreatment method for MXDA raw materials, specifically:

[0079] 1350g of toluene was added to a 2L stirring kettle, and then 150g of industrial-grade IPN was added, and the mixture was heated to 80°C and stirred to allow the IPN to fully dissolve in the toluene to prepare an IPN solution with a mass concentration of 10%; then a metering pump was used to extract the IPN solution from the bottom of the kettle and introduced into the convection tube from the lower side at a flow rate of 20mL / min;

[0080] 525 g of distilled water was added to a container with a specification of 1000 mL, and a metering pump was used to extract distilled water at a flow rate of 50 mL / min, and the water flow rate was controlled to 1.0 m / s. The outlet pipe of the metering pump was connected to a jet mixer, and the three-way connection of the mixer was connected to an ammonia pipe, and the ammonia pipe was connected to 75 g of ammonia water with a mass concentration of 20%. A vacuum was formed in the ejector by water jetting to extract ammonia water, and the water in the ejector was mixed with ammonia water to form dilute ammonia water, and then the dilute ammonia water was introduced into the tube from the upper side of the convection tube, and then flowed out from the bottom of the convection tube and returned to the container for circulation;

[0081] The IPN solution enters the tube from the lower side of the convection tube, and the dilute ammonia water enters the tube from the upper side and flows out from the bottom. The dilute ammonia water and the IPN solution are washed by convection. The formic acid and amide impurities in the IPN solution react with the ammonia water or dissolve in the dilute ammonia water, thereby taking out the impurities and completing the purification of IPN. During the convection washing process, the temperature of the convection tube is controlled to 80°C to prevent the precipitation and crystallization of IPN due to the temperature drop;

[0082] After 80 minutes of convection washing, the circulating washing of ammonia water was stopped, the IPN solution in the convection tube was allowed to stand at 80°C for 60 minutes, the water layer containing impurities at the bottom of the convection tube was drained, and the waste water containing impurities in the container of distilled water was poured out;

[0083] Add 600 g of distilled water to the container containing distilled water again, start the metering pump, control the water flow rate to 1.0 m / s at a flow rate of 50 mL / min, perform convection washing with the IPN solution in the convection tube for 60 min according to the above method, then stop the circulating washing with distilled water, let the solution in the convection tube stand at 80° C. for 30 min, drain the impurity-containing water layer at the bottom of the tube, and obtain the pretreated MXDA raw material;

[0084] The specification of the convection tube is 3L, and the size is Φ80×600mm.

[0085] The liquid chromatography purity of the pretreated MXDA raw material after sampling and testing was 99.55%.

[0086] Example 6

[0087] 1350g of toluene was added to a 2L stirring kettle, and then 150g of industrial-grade IPN was added, and the mixture was heated to 80°C and stirred to allow the IPN to fully dissolve in the toluene to prepare an IPN solution with a mass concentration of 10%; then a metering pump was used to extract the IPN solution from the bottom of the kettle and introduced into the convection tube from the lower side at a flow rate of 20mL / min;

[0088] Add 525g of distilled water into a container with a specification of 1000mL, use a metering pump to control the water flow rate to 1.0m / s at a flow rate of 50mL / min, connect the outlet pipe of the metering pump to a jet mixer, connect the three-way joint of the mixer to an ammonia pipe, and the ammonia pipe is connected to 75g of ammonia water with a mass concentration of 20%. A vacuum is formed in the ejector by water jetting to extract ammonia water. The water in the ejector is mixed with ammonia water to form dilute ammonia water, and then the dilute ammonia water is introduced into the tube from the upper side of the convection tube, and then flows out from the bottom of the convection tube and returns to the container for circulation.

[0089] The IPN solution enters the tube from the lower side of the convection tube, and the dilute ammonia water enters the tube from the upper side and flows out from the bottom. The dilute ammonia water and the IPN solution are washed by convection. The formic acid and amide impurities in the IPN solution react with the ammonia water or dissolve in the dilute ammonia water, thereby taking out the impurities and completing the purification of IPN. During the convection washing process, the temperature of the convection tube is controlled to 80°C to prevent the precipitation and crystallization of IPN due to the temperature drop;

[0090] After 80 minutes of convection washing, the circulating washing of ammonia water was stopped, the IPN solution in the convection tube was allowed to stand at 80°C for 60 minutes, the water layer containing impurities at the bottom of the convection tube was drained, and the waste water containing impurities in the container of distilled water was poured out;

[0091] Add 600 g of distilled water to the container containing distilled water again, start the metering pump, control the water flow rate to 1.0 m / s at a flow rate of 50 mL / min, and perform convection washing with the IPN solution in the convection tube for 60 min according to the above method, then stop the circulating washing of distilled water, let the solution in the convection tube stand at 80° C. for 60 min, and drain the water layer containing impurities at the bottom of the tube;

[0092] Add 600 g of distilled water to the container containing distilled water again, start the metering pump, control the water flow rate to 1.0 m / s at a flow rate of 50 mL / min, and perform convection washing with the IPN solution in the convection tube for 30 min according to the above method, then stop the circulating washing with distilled water, let the solution in the convection tube stand at 80° C. for 30 min, and drain the impurity-containing water layer at the bottom of the tube to obtain the pretreated MXDA raw material;

[0093] The specification of the convection tube is 3L, and the size is Φ80×600mm.

[0094] The liquid chromatography purity of the pretreated MXDA raw material after sampling and testing was 99.77%.

[0095] Unless otherwise specified, all percentages used in the present invention are by mass.

[0096] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for pretreating MXDA raw materials, characterized in that: It consists of the following steps: ammonia washing, water washing; The ammonia washing comprises using an aqueous ammonia solution to perform convection washing on the toluene solution of the IPN to be treated to obtain a toluene solution of the IPN after ammonia washing; In the ammonia washing, the mass ratio of the ammonia source in the ammonia-containing aqueous solution to the IPN to be treated in the toluene solution of the IPN to be treated is 7.5-75:150; The ammonia washing convection washing comprises introducing an ammonia-containing aqueous solution and a toluene solution of the IPN to be treated from the upper side and the lower side of the convection tube, respectively, convection washing at 70-90° C. for 40-80 minutes, standing at 70-90° C. for 40-60 minutes, and removing the water layer; In the countercurrent washing of the ammonia washing, the flow rate of the ammonia-containing aqueous solution is 45-55 mL / min; The flow rate of the toluene solution of the IPN to be treated is 20-25 mL / min; The method for preparing the aqueous ammonia solution comprises mixing an ammonia source with a solvent to obtain the aqueous ammonia solution; In the preparation of the aqueous ammonia solution, the ammonia source is one of liquid ammonia, gaseous ammonia and aqueous ammonia; When the ammonia source is aqueous ammonia, the mass concentration of aqueous ammonia is 5-25%; The solvent is one of distilled water or desalted water; The mass ratio of ammonia source to solvent is 7.5-75:75-585; The method for preparing the toluene solution of the IPN to be treated is to mix toluene and the IPN to be treated and then stir until the IPN to be treated is completely dissolved in the toluene to obtain the toluene solution of the IPN to be treated; The water washing comprises using water to perform convection washing on the toluene solution of the IPN after the ammonia washing to obtain the pretreated MXDA raw material; In the water washing, the water is one of distilled water or desalted water; The mass ratio of water to the IPN in the toluene solution of IPN after ammonia washing is 150-600:150; The water-washing convection washing comprises introducing water and ammonia-washed IPN toluene solution from the upper and lower sides of the convection tube, respectively, convection washing at 70-90° C. for 30-60 min, standing at 70-90° C. for 30-60 min, and removing the water layer; In the countercurrent washing of the water washing, the flow rate of water is 45-55 mL / min; The flow rate of the toluene solution of the IPN to be treated is 20-25 mL / min; The number of times of the ammonia washing is 1 time; The number of times of water washing is 1 time.

2. The pretreatment method of MXDA raw material according to claim 1, characterized in that: The mass concentration of the toluene solution of the IPN to be treated is 10-15%; In the preparation of the toluene solution of the IPN to be treated, the temperature during stirring is 70-90°C.

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