A kind of preparation method of diacetone acrylamide

Abstract

The present invention discloses a method for preparing diacetone acrylamide, and relates to the technical field of preparation of fine chemical products. The method solves the technical problem of high by-product content in the preparation of diacetone acrylamide in the prior art. The present invention uses diacetoneamine and methyl 2,3-dibromopropionate as main raw materials, generates a diacetone acrylamide bromide intermediate by reaction, and then undergoes a debromination reaction to generate diacetone acrylamide. Finally, the diacetone acrylamide finished product is obtained through recrystallization and drying. Compared with the prior art, the present invention overcomes some shortcomings of traditional methods, has fewer side reactions, avoids the generation of easily polymerizable impurities such as acrylamide, mesityl oxide, and N-tert-butyl acrylamide, and has the advantages of good product quality, high yield, and a wide range of applications.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of fine chemical products, and in particular to a method for preparing diacetone acrylamide. Background Art

[0002] Diacetone acrylamide is a new type of vinyl functional monomer with two reactive groups in its structure, namely N-substituted amide and ketone. It can easily copolymerize with other vinyl monomers and introduce ketone carbonyl groups into the polymer. The active exothermic chemical properties of the ketone carbonyl groups can then be used to cause the polymer to undergo cross-linking and grafting reactions. Therefore, it is widely used in many fields such as coatings, adhesives, photosensitive resin additives, epoxy resin curing agents, etc.

[0003] The research reports on the preparation of diacetone acrylamide in the prior art mainly include:

[0004] A method for synthesizing diacetone acrylamide (MedChemComm (2011), 2(6), 466-470) involves adding triethylamine, diacetoneamine, and dichloromethane to a reaction flask, then adding acryloyl chloride dropwise. The mixture is stirred at room temperature for 72 hours, and then subjected to extraction, neutralization, water washing, drying, filtration, distillation, evaporation, and recrystallization to obtain the finished diacetone acrylamide in a yield of 72%. This method has a long reaction time, and acryloyl chloride easily self-polymerizes, producing a large amount of polymer. Furthermore, acryloyl chloride easily undergoes a Michael addition reaction with diacetoneamine under alkaline conditions, producing a large amount of impurities.

[0005] Application No. 201210561875X discloses a method for preparing diacetone acrylamide, comprising the following steps: sequentially adding concentrated sulfuric acid, acrylonitrile, and mesityl oxide to acetone to obtain a mixed solution; adding the mixed solution to aqueous ammonia to obtain a mixture; adding toluene to the mixture for extraction, separating the oil phase after separation, and distilling the oil phase to remove impurities such as toluene, acetone, acrylonitrile, and mesityl oxide; then performing vacuum distillation, collecting the distillate to obtain a crude diacetone acrylamide; dissolving the diacetone acrylamide in toluene for recrystallization, and drying the solid product after solid-liquid separation to obtain diacetone acrylamide.

[0006] Application No. 2022116793879 discloses diacetone acrylamide, a preparation method, and applications thereof. The method comprises reacting acetone or diacetone alcohol with acrylonitrile to prepare an oxazine sulfate mixed solution; then adding water to the mixed solution to obtain an oxazine sulfate mixed ion solution; adding an adsorbent to the oxazine sulfate mixed ion solution to remove organic matter in the ion solution; and finally, alkali washing and crystallization to obtain diacetone acrylamide.

[0007] Currently, the industrial production of diacetone acrylamide primarily uses acrylonitrile and acetone as raw materials. It is obtained through condensation, hydrolysis, neutralization, water extraction, distillation, evaporation, and crystallization. This process utilizes inexpensive and readily available raw materials, but is associated with numerous side reactions. Acetone readily condenses and dehydrates to form byproducts such as diacetone alcohol and mesityl oxide, while acrylonitrile readily hydrolyzes to form acrylamide, which also produces derivatives such as N-tert-butyl acrylamide. These byproducts often undergo further side reactions, generating vinyl-based polymer impurities. This makes the separation of diacetone acrylamide difficult and significantly impacts the quality of the finished product. Literature reports indicate that the yield of this process is relatively low, typically between 55% and 65%. The diacetone acrylamide obtained using this process often contains a high level of impurities. This can easily lead to demulsification of the pre-emulsion or finished emulsion during emulsion polymerization, resulting in significant slag production and poor mechanical stability. This, in turn, limits the application prospects of diacetone acrylamide in high-end chemical applications.

[0008] This shows that the prior art needs to be further improved. Summary of the Invention

[0009] In order to solve the technical problem of the large number of by-products generated during the industrial preparation of diacetone acrylamide in the above-mentioned prior art, the present invention provides a method for preparing diacetone acrylamide, which can reduce the generation of by-products by providing a new process route.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A method for preparing diacetone acrylamide comprises the following steps in sequence:

[0012] Step 1: Selecting raw materials diacetoneamine and methyl 2,3-dibromopropionate, and reacting them under the action of a catalyst to generate an intermediate, wherein the intermediate is diacetone acrylamide bromide;

[0013] Step 2: purifying the diacetone acrylamide bromide;

[0014] Step 3: Debromination of the purified diacetone acrylamide bromide:

[0015] Zinc powder, glacial acetic acid, and DMF are added to the reactor, and then a mixed solution of purified diacetone acrylamide bromide and toluene is added dropwise. After the addition is complete, a certain temperature is set to react to obtain a crude diacetone acrylamide reaction solution;

[0016] Step 4: purify the crude diacetone acrylamide reaction solution to obtain diacetone acrylamide.

[0017] The beneficial technical effects directly brought about by the above technical solution are:

[0018] In terms of raw material selection, the present invention selects diacetoneamine and methyl 2,3-dibromopropionate as main raw materials, sets conditions to allow the two to react, and generates diacetone acrylamide bromide as an intermediate. The intermediate is then purified and debrominated to obtain diacetone acrylamide.

[0019] Since the above preparation method is a completely new process route, which is completely different from the raw materials acrylonitrile and acetone in the prior art, the raw materials of the present invention avoid the production of easily polymerizable impurities such as isopropylidene oxide, acrylamide, and N-tert-butylacrylamide during the reaction. In other words, the process route of the present invention can reduce the formation of by-products such as polymerizable impurities.

[0020] In the above-mentioned method for preparing diacetone acrylamide, in step 1, the solvent is toluene, benzene or xylene; the amount of solvent added is 3 to 6 times the mass of diacetone acrylamide.

[0021] In the above-mentioned method for preparing diacetone acrylamide, the catalyst is sodium methoxide or sodium ethoxide, and the amount of the catalyst is 2-4% of the mass of diacetoneamine; the molar ratio of diacetoneamine to methyl 2,3-dibromopropionate is 1:0.9-1.1; the reaction temperature in step 1 is 70-85°C, and the reaction time is 2-4 hours.

[0022] The above-mentioned method for preparing diacetone acrylamide, step 2 specifically includes: pouring diacetone acrylamide bromide into an appropriate amount of water to quench the reaction, stirring thoroughly and then standing, washing the obtained organic phase with water until neutral after separation, then distilling the organic phase and removing the solvent to obtain a crude diacetone acrylamide bromide; and recrystallizing the crude diacetone acrylamide bromide using toluene to obtain purified diacetone acrylamide bromide.

[0023] The above-mentioned method for preparing diacetone acrylamide, step 4 specifically comprises:

[0024] The crude diacetone acrylamide reaction solution was filtered, and the filtrate was collected. The filtrate was added to water, stirred, and allowed to stand to obtain an upper organic phase. The aqueous layer was extracted with toluene, combined with the organic phase, and washed with water until neutral to obtain a neutral organic phase.

[0025] Add an appropriate amount of polymerization inhibitor to the neutral organic phase and remove toluene by distillation;

[0026] The residue is collected, crystallized and dried to obtain diacetone acrylamide.

[0027] In the above-mentioned method for preparing diacetone acrylamide, in the quenching reaction, the mass of water is 30% to 60% of the mass of diacetoneamine; and the mass ratio of the crude diacetone acrylamide bromide to toluene is 1:1.5 to 2.5.

[0028] The above-mentioned method for preparing diacetone acrylamide, in step 3, the mass ratio of diacetone acrylamide bromide to zinc powder is 1:0.3-0.8; the mass ratio of glacial acetic acid to zinc powder is 0.2-0.5:1; the mass ratio of diacetone acrylamide bromide to DMF is 1:1-2; the mass ratio of diacetone acrylamide bromide to toluene is 1:3-5; the reaction temperature is 40-55°C, and the holding time is 1-2 hours.

[0029] In the above-mentioned method for preparing diacetone acrylamide, the polymerization inhibitor is one or more of p-methylphenol, 2,6-di-tert-butyl-p-cresol, and hydroquinone.

[0030] In the above-mentioned method for preparing diacetone acrylamide, the distillation temperature is 80-110° C. and the pressure is 5-30 KPa; the above-mentioned methyl 2,3-dibromopropionate can also be replaced by ethyl 2,3-dibromopropionate.

[0031] The above-mentioned method for preparing diacetone acrylamide has the following drying conditions: pressure 5-10 KPa and temperature 30-45°C.

[0032] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0033] The invention adopts diacetoneamine and methyl 2,3-dibromopropionate as main raw materials, generates a diacetone acrylamide bromide intermediate through reaction, then performs a debromination reaction to generate diacetone acrylamide, and finally obtains the diacetone acrylamide finished product through recrystallization and drying.

[0034] Compared with the prior art, the present invention overcomes some shortcomings of traditional methods, has fewer side reactions, avoids the generation of easily polymerizable impurities such as acrylamide, mesityl oxide, and N-tert-butylacrylamide, has the advantages of good product quality, high yield, and wide application fields, and is suitable for industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below with reference to the accompanying drawings:

[0036] Figure 1 The preparation route of diacetone acrylamide of the present invention is as follows;

[0037] Figure 2 This is a GC analysis chart of diacetone acrylamide in Example 1 of the present invention;

[0038] Figure 3This is a GC-MS analysis chart of diacetone acrylamide in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application.

[0040] The technical solution of the present application is further described in detail below with reference to the accompanying drawings.

[0041] The raw materials described in the present invention can all be purchased through commercial channels.

[0042] like Figure 1 As shown, the present invention provides a method for preparing diacetone acrylamide, which can reduce the generation of by-products by improving the raw materials and the method route.

[0043] A method for preparing diacetone acrylamide comprises the following steps:

[0044] (1) First, diacetoneamine, a reaction solvent, a catalyst, and methyl 2,3-dibromopropionate are mixed and reacted within a certain temperature range to generate an intermediate diacetone acrylamide bromide; the reaction equation is shown in formula (1).

[0045]

[0046] The reaction solvent is toluene, benzene or xylene, preferably toluene, and the amount of the reaction solvent is 3 to 6 times the weight of diacetoneamine;

[0047] The catalyst is one of sodium methoxide or sodium ethoxide, and its amount is 2% to 4% by weight of diacetoneamine;

[0048] The molar ratio of the raw materials diacetoneamine and methyl 2,3-dibromopropionate is 1:0.9-1.1; the reaction temperature is 70-85° C., and the reaction time is 2-4 hours.

[0049] (2) Purifying the intermediate diacetone acrylamide bromide in the above step (1)

[0050] The reaction solution obtained in step (1) is poured into an appropriate amount of water to quench the reaction, stirred thoroughly, and allowed to stand. After separation, the resulting organic phase is washed with water until neutral, and then the organic phase is distilled to remove the solvent to obtain a crude diacetone acrylamide bromide intermediate. The resulting crude intermediate is recrystallized from toluene to obtain a pure diacetone acrylamide bromide intermediate.

[0051] In the quenching reaction, the mass of water is 30% to 60% of the weight of the diacetoneamine feed in this batch; when the crude intermediate is recrystallized with toluene, the weight ratio of the crude intermediate to toluene is 1:1.5 to 2.5;

[0052] (3) Debromination reaction

[0053] At room temperature, zinc powder, glacial acetic acid, and DMF are added to a reaction flask, and then a mixed solution of the pure diacetone acrylamide bromide intermediate obtained in step (2) and toluene is added dropwise. After the addition is complete, the temperature is raised to a certain temperature, and then the temperature is kept to react until the reaction is completed to obtain a diacetone acrylamide crude product reaction solution.

[0054] The weight ratio of diacetone acrylamide bromide to zinc powder is 1:0.3-0.8; the mass ratio of glacial acetic acid to zinc powder is 0.2-0.5:1; the mass ratio of diacetone acrylamide bromide to DMF is 1:1-2; the mass ratio of diacetone acrylamide bromide to toluene is 1:3-5; the reaction insulation temperature is 40-55°C, and the insulation time is 1-2 hours;

[0055] The reaction equation of the debromination reaction is shown in formula (2).

[0056]

[0057] (4) Purification of diacetone acrylamide

[0058] The crude diacetone acrylamide reaction solution obtained in step (3) is filtered to remove insoluble matter. The resulting filtrate is added to water, stirred, and allowed to stand for stratification to obtain an upper organic phase. The resulting aqueous layer is extracted with toluene, and then all organic phases are combined and washed with water until neutral. An appropriate amount of polymerization inhibitor is added to the neutral organic phase, and then toluene is distilled off. After the toluene is completely distilled off, the residue in the reaction flask is the crude diacetone acrylamide, which is recrystallized from toluene and then dried to obtain the finished diacetone acrylamide.

[0059] The weight ratio of water to filtrate and extracted toluene is 0.5-1:1:0.5-0.7; the polymerization inhibitor is one of p-methylphenol, 2,6-di-tert-butyl-p-cresol, and hydroquinone, or a combination thereof, and the amount thereof is 0.01%-0.03% of the weight of the pure diacetone acrylamide bromide intermediate in this batch of reactions; the weight ratio of toluene to crude diacetone acrylamide in the recrystallization process is 1.5-3:1; the distillation temperature is 80-110° C. and the pressure is 5-30 KPa; and the drying conditions for the diacetone acrylamide are a pressure of 5-10 KPa and a temperature of 30-45° C.

[0060] The present invention will be further described below with reference to specific embodiments.

[0061] Example 1:

[0062] Step 1: Add 345 g of solvent benzene, 115 g (1 mol) of diacetoneamine, 221.5 g (0.9 mol) of methyl 2,3-dibromopropionate, and 2.3 g of sodium methoxide to a 1 L reaction flask, stir thoroughly, and heat to 70°C to 75°C. Keep the reaction within this temperature range for 4 hours, then stop and cool the reaction solution to room temperature.

[0063] Step 2: Pour the reaction solution cooled to room temperature into 34.5 g of water, stir thoroughly, and allow to stand for stratification. Then, separate the upper organic phase. Wash the resulting organic phase with water until neutral, separate the organic phase, and evaporate the benzene from the resulting organic phase on a rotary evaporator (5 kPa-15 kPa, 40°C-50°C) to obtain 295.0 g of a residue, which was dissolved in 590 g of toluene and recrystallized to obtain 236.9 g of a diacetone acrylamide bromide intermediate.

[0064] Step 3: At room temperature, add 14.2 g of glacial acetic acid, 236.9 g of DMF, and 71.1 g of zinc powder to a 2 L reaction flask. Stir thoroughly to disperse the mixture. Then, dropwise add a mixed solution of 236.9 g of diacetone acrylamide bromide dissolved in 710.7 g of toluene. After the addition is complete, slowly raise the temperature to 40-45 ° C and keep the reaction for 1 hour before stopping the reaction. Then, cool the mixture to room temperature. After cooling, filter and remove insoluble matter to obtain 1110.5 g of filtrate.

[0065] Step 4: Add the obtained filtrate to 556.0 g of water, stir thoroughly, let stand, and separate the upper organic phase. Then add 556.0 g of toluene to the aqueous phase for extraction, combine all organic phases, wash with water until neutral, add 0.025 g of 2,6-di-tert-butyl-p-cresol to the obtained organic phase, and then evaporate the toluene on a rotary evaporator (5 KPa ~ 15 KPa, 80 ° C ~ 90 ° C) to obtain 116.8 g of residue, which is recrystallized with 175 g of toluene and then dried (5 KPa ~ 10 KPa, 30 ° C ~ 45 ° C) to constant weight to obtain 108.4 g of white diacetone acrylamide, GC = 99.75% (area normalization method, see attached Figure 2 and Table 1), mass spectrometry analysis: MS (EI) m / z: 169.0 [M + ](See attached Figure 3 ).

[0066] Calculated on the basis of methyl 2,3-dibromopropionate, the yield of diacetone acrylamide is 71.3%.

[0067] Example 2:

[0068] Step 1: Add 460 g of toluene solvent, 115 g (1 mol) of diacetoneamine, 246 g (1 mol) of methyl 2,3-dibromopropionate, and 3.5 g of sodium methoxide to a 1 L reaction flask, stir thoroughly, and heat to 75°C to 80°C. Keep the reaction within this temperature range for 3 hours, then stop and cool the reaction solution to room temperature.

[0069] Step 2: Pour the reaction solution cooled to room temperature into 46 g of water, stir thoroughly, and allow to stand for stratification. Then, separate the upper organic phase. Wash the resulting organic phase with water until neutral, separate the organic phase, and evaporate the toluene from the resulting organic phase on a rotary evaporator (5 kPa-15 kPa, 40°C-60°C) to obtain 329.0 g of a residue, which was dissolved in 822 g of toluene and recrystallized to obtain 264.2 g of a diacetone acrylamide bromide intermediate.

[0070] Step 3: At room temperature, add 46.2g of glacial acetic acid, 396.2g of DMF, and 132g of zinc powder to a 2L reaction flask, stir and disperse thoroughly, then dropwise add a mixed solution of 264.2g of diacetone acrylamide bromide dissolved in 1056.8g of toluene. After the addition is complete, slowly raise the temperature to (45-50)°C and keep the reaction for 2h before stopping the reaction, then cool to room temperature. After cooling, filter and remove insoluble matter to obtain 1630.7g of filtrate.

[0071] Step 4: Add the resulting filtrate to 1223 g of water, stir thoroughly, allow to stand, and separate the upper organic phase. 978 g of toluene is then added to the aqueous phase for extraction. All organic phases are combined and washed with water until neutral. 0.053 g of hydroquinone is added to the resulting organic phase, and the toluene is then evaporated on a rotary evaporator (15 kPa to 20 kPa, 90° C. to 100° C.) to obtain 131.7 g of a residue, which is recrystallized from 263 g of toluene and then dried (5 kPa to 10 kPa, 30° C. to 45° C.) to constant weight to obtain 125.3 g of white diacetone acrylamide, GC=99.82% (area normalization method).

[0072] Calculated based on methyl 2,3-dibromopropionate, the yield of diacetone acrylamide is 74.1%.

[0073] Example 3:

[0074] Step 1: Add 483 g of xylene, 80.5 g (0.7 mol) of diacetoneamine, 189.5 g (0.77 mol) of methyl 2,3-dibromopropionate, and 3.2 g of sodium ethoxide to a 1 L reaction flask, stir thoroughly, and heat to 80°C to 85°C. Keep the reaction within this temperature range for 2 hours, then stop and cool the reaction solution to room temperature.

[0075] Step 2: Pour the reaction solution cooled to room temperature into 48.3 g of water, stir thoroughly, and allow to stand for stratification. Then, separate the upper organic phase. Wash the resulting organic phase with water until neutral, separate the organic phase, and evaporate xylene from the resulting organic phase on a rotary evaporator (5 kPa-15 kPa, 60°C-80°C) to obtain 232.0 g of a residue, which is dissolved in 580 g of toluene and recrystallized to obtain 183.3 g of a diacetone acrylamide bromide intermediate.

[0076] Step 3: At room temperature, add 73.3g of glacial acetic acid, 366.6g of DMF, and 146.6g of zinc powder to a 2L reaction flask, stir and disperse thoroughly, then dropwise add a mixed solution of 183.3g of diacetone acrylamide bromide dissolved in 916.5g of toluene. After the addition is complete, slowly raise the temperature to (50-55)°C and keep the reaction for 2h before stopping the reaction, then cool to room temperature. After cooling, filter and remove insoluble matter to obtain 1448g of filtrate.

[0077] Step 4: Add the resulting filtrate to 1448 g of water, stir thoroughly, allow to stand, and separate the upper organic phase. 1013 g of toluene is then added to the aqueous phase for extraction. All organic phases are combined and washed with water until neutral. 0.055 g of p-methylphenol is added to the resulting organic phase, and then toluene is evaporated on a rotary evaporator (20 kPa to 30 kPa, 100° C. to 110° C.) to obtain 95.2 g of a residue, which is recrystallized from 285.6 g of toluene and then dried (5 kPa to 10 kPa, 30° C. to 45° C.) to constant weight to obtain 84.5 g of white diacetone acrylamide, GC=99.81% (area normalization method).

[0078] Calculated on diacetoneamine, the yield of diacetone acrylamide is 71.4%.

[0079] Table 1

[0080]

[0081] Comparative Example 1:

[0082] Step 1: Add 460 g of toluene solvent, 115 g (1 mol) of diacetoneamine, 157 g (1 mol) of methyl 2,3-dichloropropionate, and 3.5 g of sodium methoxide to a 1 L reaction flask, stir thoroughly, and heat to 75°C to 80°C. Keep the reaction within this temperature range for 3 hours, then stop and cool the reaction solution to room temperature.

[0083] Step 2: Pour the reaction solution cooled to room temperature into 46 g of water, stir thoroughly, and allow to stand for stratification. Then, separate the upper organic phase. Wash the resulting organic phase with water until neutral, separate the organic phase, and evaporate the toluene from the resulting organic phase on a rotary evaporator (5 kPa to 15 kPa, 40° C. to 60° C.) to obtain 239 g of the residue, which was dissolved in 597 g of toluene and recrystallized to obtain 168 g of diacetone acrylamide chloride intermediate.

[0084] Step 3: At room temperature, add 29.3g of glacial acetic acid, 252g of DMF, and 83.7g of zinc powder to a 2L reaction flask. Stir thoroughly to disperse the mixture. Then, dropwise add a mixed solution of 168g of diacetone acrylamide chloride dissolved in 672g of toluene. After the addition is complete, slowly raise the temperature to (45-50)°C and keep the reaction for 2h before stopping the reaction. Then, cool the mixture to room temperature. After cooling, filter and remove insoluble matter to obtain 1120.3g of filtrate.

[0085] Step 4: The filtrate was added to 840 g of water, stirred thoroughly, and allowed to stand to separate the upper organic phase. 672 g of toluene was then added to the aqueous phase for extraction. All organic phases were combined and washed with water until neutral. 0.034 g of hydroquinone was added to the resulting organic phase, and the toluene was then evaporated on a rotary evaporator (15 kPa to 20 kPa, 90° C. to 100° C.) to obtain 108 g of a residue, which was recrystallized from 216 g of toluene and then dried (5 kPa to 10 kPa, 30° C. to 45° C.) to constant weight to obtain 88.5 g of white diacetone acrylamide with a GC content of 99.70% (area normalization method, see Table 2).

[0086] Calculated based on methyl 2,3-dichloropropionate, the yield of diacetone acrylamide is 52.4%.

[0087] Table 2

[0088]

[0089] Under the guidance of Examples 1 to 3, those skilled in the art can also use ethyl 2,3-dibromopropionate to replace methyl 2,3-dibromopropionate.

[0090] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present application and are not intended to limit the present application. As long as they are within the spirit of the present application, appropriate changes and modifications to the above embodiments are within the scope of protection claimed in the present application.

Claims

1. An industrial preparation method of diacetone acrylamide, characterized in that: The following steps are included in sequence: Step 1: Selecting raw materials diacetoneamine and methyl 2,3-dibromopropionate, and reacting them under the action of a catalyst to generate an intermediate, wherein the intermediate is diacetone acrylamide bromide; Step 2: purifying the diacetone acrylamide bromide; Step 3: Debromination of the purified diacetone acrylamide bromide: Zinc powder, glacial acetic acid, and DMF are added to the reactor, and then a mixed solution of purified diacetone acrylamide bromide and toluene is added dropwise. After the addition is complete, a certain temperature is set to react to obtain a crude diacetone acrylamide reaction solution; Step 4: purifying the crude diacetone acrylamide reaction solution to obtain; In step 1, the solvent is toluene, benzene or xylene; the amount of solvent added is 3 to 6 times the mass of diacetoneamine; The catalyst is sodium methoxide or sodium ethoxide, and the amount of the catalyst is 2-4% of the mass of diacetoneamine; the molar ratio of diacetoneamine to methyl 2,3-dibromopropionate is 1:0.9-1.1; the reaction temperature in step 1 is 70-85°C, and the reaction time is 2-4 hours; In step 3, the mass ratio of diacetone acrylamide bromide to zinc powder is 1:0.3-0.8; the mass ratio of glacial acetic acid to zinc powder is 0.2-0.5:1; the mass ratio of diacetone acrylamide bromide to DMF is 1:1-2; the mass ratio of diacetone acrylamide bromide to toluene is 1:3-5; the reaction temperature is 40-55°C, and the holding time is 1-2 hours; Step 4 specifically comprises: filtering the crude diacetone acrylamide reaction solution, collecting the filtrate, adding the obtained filtrate to water, stirring, and standing to obtain an upper organic phase; extracting the aqueous layer with toluene, combining the aqueous layer with the organic phase, and washing with water until neutral to obtain a neutral organic phase; Add an appropriate amount of polymerization inhibitor to the neutral organic phase and remove toluene by distillation; The residue is collected, crystallized and dried to obtain diacetone acrylamide.

2. The industrial preparation method of diacetone acrylamide according to claim 1, characterized in that: The second step specifically comprises: pouring diacetone acrylamide bromide into an appropriate amount of water to quench the reaction, stirring thoroughly and then standing, washing the obtained organic phase with water until it is neutral after separation, and then distilling the organic phase to remove the solvent to obtain a crude diacetone acrylamide bromide; and recrystallizing the crude diacetone acrylamide bromide using toluene to obtain purified diacetone acrylamide bromide.

3. The industrial preparation method of diacetone acrylamide according to claim 2, characterized in that: In the quenching reaction, the mass of water is 30% to 60% of the mass of diacetoneamine; and the mass ratio of the crude diacetone acrylamide bromide to toluene is 1:1.5 to 2.

5.

4. The industrial preparation method of diacetone acrylamide according to claim 2, characterized in that: The polymerization inhibitor is one or more of p-methylphenol, 2,6-di-tert-butyl-p-cresol and hydroquinone.

5. The industrial preparation method of diacetone acrylamide according to claim 2, characterized in that: The distillation temperature is 80-110° C. and the pressure is 5-30 KPa. The methyl 2,3-dibromopropionate can also be replaced by ethyl 2,3-dibromopropionate.

6. The industrial preparation method of diacetone acrylamide according to claim 3, characterized in that: The drying conditions are: pressure 5-10KPa, temperature 30-45℃.

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