Preparation method of 1, 3-dimethyl-1, 2, 3, 4-cyclobutane tetracarboxylic dianhydride

Abstract

The invention relates to the technical field of preparation of organic photoelectric materials, in particular to a preparation method of 1, 3-dimethyl-1, 2, 3, 4-cyclobutane tetracarboxylic dianhydride. The preparation method comprises the following steps: (1) carrying out addition reaction on dimethyl carbonate, a catalyst and dimethyl citraconate under the irradiation of a mercury lamp source to obtain an intermediate S1; (2) adding the intermediate S1 into an acidic solution, heating and carrying out hydrolysis reaction to obtain an intermediate S2; and (3) adding the intermediate S2 into acetic anhydride, heating and stirring, and carrying out dehydration ring closing reaction to obtain the finished product 1, 3-DMCBDA. According to the method, the defects in the prior art are overcome, the purity of the produced 1, 3-dimethyl-1, 2, 3, 4-cyclobutane tetracarboxylic dianhydride is improved, and the content of isomers and the content of metal impurities are greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic photoelectric material preparation, and particularly relates to a preparation method of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride. BACKGROUND

[0002] In recent years, with the rapid development of the integrated circuit industry, in order to better apply CPI films with excellent comprehensive performance to electronic devices in the industry, researchers have become increasingly enthusiastic about the low CTE research of CPI films. Hasegawa et al. synthesized alkyl-substituted cyclobutane tetracarboxylic dianhydride (CBDA) using alkyl-substituted maleic anhydride as a raw material, and obtained a dimethyl-substituted tetracarboxylic dianhydride DM-CBDA by modifying CBDA through ultraviolet irradiation of citraconic anhydride (CTA). The polymerizability of DM-CBDA with various diamines is much higher than that of traditional aliphatic cyclic tetracarboxylic dianhydride, which leads to a higher molecular weight of PI precursors.

[0003] 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride (1,3-DMCBDA) is an important organic synthesis intermediate, and is particularly concerned as a key monomer for preparing high-performance polyimide (PI). The polyimide material synthesized by 1,3-DMCBDA has excellent electrical properties, optical properties, high heat resistance and good mechanical properties, and shows important application value in the field of electronic materials such as flexible display screens and liquid crystal displays. Compared with CBDA, 1,3-DMCBDA increases two methyl groups on the non-conjugated aliphatic ring structure, which can further increase the molecular chain spacing of polyimide, obtain a transparent film with good performance, meet the demand of photo-alignment film, and be widely used in the field of photoelectric display.

[0004] Japanese Patent Publication No. 4-106127 discloses a preparation method by citraconic anhydride photodimerization reaction, and the obtained mixed product contains more than half of 1,2-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride (1,2-DMCBDA) in addition to the target product 1,3-DMCBDA. The light yellow and low symmetry of 1,2-DMCBDA itself will affect the transparency and molecular weight of polyimide. CN105916866A discloses a method of obtaining 1,3-DMCBDA by refluxing acetic anhydride, but it still contains 0.5% 1,2-DMCBDA. CN109422762A discloses a method of using a ketone containing more than 5 carbon atoms for dissolution and filtration, but a large amount of solvent is used in the preparation process, and the content of 1,2-DMCBDA can only be reduced to 0.5%; therefore, how to prepare high-purity 1,3-DMCBDA is a problem to be solved in the current industrialization process. It is necessary to continuously develop a preparation method capable of reducing the content of isomers and to find a suitable production process for producing 1,3-DMCBDA to solve the above problems. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a preparation method of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride. It can effectively improve the production purity of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride and is convenient for industrial production.

[0006] The present application is realized by the following technical solutions: The present application provides a preparation method of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride, which comprises the following steps: adding dimethyl citraconate and dimethyl carbonate under the irradiation of a mercury lamp source to perform an addition reaction, then adding an acid solvent to perform a hydrolysis reaction, then cooling and filtering, then adding acetic anhydride to perform a dehydration ring closure reaction, and finally obtaining 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride.

[0007] Further, the preparation method comprises the following steps: (1) adding dimethyl citraconate to dimethyl carbonate and performing an addition reaction under the irradiation of a mercury lamp source, then distilling, filtering and drying to obtain an intermediate S1; (2) adding the intermediate S1 obtained in step (1) to an acid solution under stirring, performing a hydrolysis reaction, cooling to 20-25 DEG C after the reaction is completed, then filtering to obtain an intermediate S2; (3) adding acetic anhydride and the intermediate S2 obtained in step (2) to a reaction device to perform a dehydration ring closure reaction, slowly increasing the temperature in a stepwise manner until the reaction is completed, cooling to 20-25 DEG C after the reaction is completed, filtering, then filtering and drying the filter cake after beating with ethyl acetate to obtain the finished product 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride.

[0008] Preferably, the molar ratio of dimethyl carbonate to dimethyl citraconate in step (1) is 9:1-20:1.

[0009] Preferably, a catalyst is added in the addition reaction in step (1), and the catalyst is selected from the group consisting of benzophenone, 2,4-diethylthioxanthone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; the molar ratio of the catalyst to dimethyl citraconate is 1:90-1:350.

[0010] Preferably, the reaction temperature of the addition reaction in step (1) is 20-50 DEG C, and the reaction time is 20-30 h.

[0011] Preferably, the acid solution in step (2) is a hydrochloric acid solution, a phosphoric acid solution or a sulfuric acid solution.

[0012] Preferably, the pH of the acidic solution in step (2) ranges from 1 to 3.

[0013] Preferably, the reaction temperature of the hydrolysis reaction in step (2) ranges from 80 to 100 ℃, and the reaction time ranges from 12 to 16 h.

[0014] Preferably, the stepwise slow temperature increase in step (3) is first increased to 50 to 70 ℃ for 0.5 to 2 h, then increased to 80 to 100 ℃ for 0.5 to 2 h, and finally increased to 110 to 130 ℃ for 14 to 15 h.

[0015] Compared with the prior art, the present application has the following advantages: (1) The present application effectively inhibits the generation of 1,2-DMCBDA by precisely controlling the reaction process, and significantly reduces the proportion of isomers in the finished product; (2) The present application enhances the metal impurity removal capacity by optimizing the reaction system and hydrolysis step, so that the metal impurity content in the obtained finished product is controlled within 500 ppb; (3) The present application simplifies the post-treatment process, and the reaction product does not need to be subjected to a sublimation purification step, so that the target product with high purity can be directly obtained. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Gas chromatography analysis spectrum of the finished product 1,3-DMCBDA prepared in Example 1; Figure 2 Nuclear magnetic structure spectrum of the finished product 1,3-DMCBDA prepared in Example 1; Figure 3 Metal ion content analysis spectrum of the finished product 1,3-DMCBDA prepared in Example 1. DETAILED DESCRIPTION

[0017] The technical solutions of the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0018] The present application provides a preparation method of high-purity 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride. Dimethyl citraconate is subjected to an addition reaction under irradiation of a mercury lamp source, and then subjected to a hydrolysis reaction with an acid solvent under heating. After cooling and filtration, the product is subjected to a dehydration ring closure reaction with acetic anhydride to obtain 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride.

[0019] Further, the preparation method comprises the following steps: (1) adding dimethyl carbonate and dimethyl citraconate to a mercury lamp source, and performing an addition reaction under irradiation of the mercury lamp source arranged in a photocatalytic reaction kettle, a reaction temperature is 20~50℃, a reaction time is 20~30h, the reaction is detected by GC detection tracking, and when the raw material is <10%, the reaction is ended, and then distillation, filtration and drying are performed to obtain an intermediate S1; It is worth noting that the molar ratio of dimethyl carbonate and dimethyl citraconate in step (1) is 9:1~20:1, preferably, the molar ratio of dimethyl carbonate and dimethyl citraconate is 13:1~17:1; further, a catalyst is added in the addition reaction of the step, the catalyst is selected from benzophenone, 2,4-diethylthioxanthone and 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, wherein benzophenone is the most preferred, the molar ratio of the catalyst and dimethyl citraconate is 1:90~1:350; the reaction system is optimized, the mercury lamp source of the photocatalytic reaction kettle is irradiated, the addition reaction is not required to be performed in a specific wavelength environment, and the reaction efficiency is improved; (2) adding the intermediate S1 obtained in step (1) to an acidic solution under stirring, performing a hydrolysis reaction by heating to 80~100℃, the reaction time is 12~16h, after the reaction is ended, the temperature is reduced to 20~25℃, and then direct filtration is performed to obtain an intermediate S2; It is worth noting that the acidic solution in step (2) is a hydrochloric acid solution, a phosphoric acid solution or a sulfuric acid solution, wherein the hydrochloric acid solution is the most preferred, the pH range of the acidic solution is 1~3, the hydrolysis reaction is performed completely, metal ions can be efficiently removed, and the content of isomer 1,2-DMCBDA in the product is reduced; (3) adding acetic anhydride and the intermediate S2 obtained in step (2) to a reaction device to perform a dehydration ring closure reaction, stepwise slow temperature increase is set to 50~70℃ for 30min, then the temperature is increased to 80~100℃ for 30min, and finally the temperature is increased to 110~130℃ for 14h. After the reaction is ended, the temperature is reduced to 20~25℃ for filtration, the filter cake is beaten with ethyl acetate for 10min, then filtration is performed, and the filter cake is placed in a vacuum drying box for stepwise drying to obtain a finished product 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride.

[0020] The application will be specifically described in combination with specific examples. All raw materials and solvents in the synthesis examples are commercially available and are directly used without further treatment, unless otherwise specified.

[0021] The purity, chemical structure and metal impurity content of the finished product material are characterized by the following analysis test means without limitation: The chemical purity of the product was determined by gas chromatography. The sample was dissolved and filtered before being injected into a gas chromatograph equipped with an FID detector. An AVANCE NEO nuclear magnetic resonance spectrometer was used to collect the hydrogen spectrum (1H NMR) and carbon spectrum (13C NMR) of the product to confirm whether the molecular structure of the product was consistent with the target compound. Inductively coupled plasma mass spectrometry was used to accurately determine the content of trace metal ions in the product to obtain the total content and individual content of key metal impurities such as sodium, potassium, calcium, iron, and nickel.

[0022] Synthesis Examples The following examples of compound synthesis, ingredients, devices, or methods are only provided to give a general method in the industry field, and are not used to limit the protection scope of the patent. The data (quantity, temperature, etc.) mentioned in the patent are as accurate as possible, but there may be some errors. Unless otherwise specified, the weighing is separately weighed, the temperature is °C, or it is room temperature, and the pressure is close to atmospheric pressure.

[0023] The following examples provide a method for preparing new compounds, but the preparation of such compounds is not limited to this method. In the technical field, the compounds protected in the patent are easily modified and prepared, so their preparation can use the methods listed below or other methods. The following examples are only examples and are not used to limit the protection scope of the patent. The temperature, catalyst, concentration, reactants, and reaction process can be changed to prepare the compounds under different conditions for different reactants.

[0024] Synthesis Route

[0025] Example 1: Synthesis of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride 1) Add 40.00 kg of dimethyl carbonate, 0.05 kg of catalyst benzophenone, and 5.00 kg of dimethyl citraconate to a photocatalytic reaction kettle, and perform an addition reaction under the irradiation of a mercury lamp source. The reaction temperature is 25°C, and the reaction time is 25 h. Then, distillation, filtration, and drying are performed to obtain 4.98 kg of intermediate S1; 2) Add 2.00 kg of concentrated hydrochloric acid (mass fraction of 37%) and 13.00 kg of ultrapure water to a glass reaction kettle to prepare a hydrochloric acid solution, and then add 4.98 kg of intermediate S1 obtained in step 1) to perform a hydrolysis reaction. The reaction temperature is controlled at 80°C, and the reaction time is 12 h. After the reaction is completed, the material is cooled to 25°C, and then filtered and dried to obtain 1.60 kg of intermediate S2; 3) Add 5.00 kg of acetic anhydride and 1.60 kg of intermediate S2 obtained in step 2) to the reaction kettle, stir and slowly increase the temperature in steps, first increase the temperature to 50°C for 0.5 h, then increase the temperature to 90°C for 0.5 h, and finally increase the temperature to 120°C for 15 h. After the reaction is completed, cool to 25°C for filtration. The filter cake is slurried with ethyl acetate for 10 min, then filtered and vacuum dried to obtain 1.2 kg of finished product 1,3-DMCBDA; The product purity is 99.93% by analysis with a Shimadzu GC-2030 gas chromatograph, Figure 1 The gas chromatogram of the finished product 1,3-DMCBDA prepared is shown in Figure 1. Figure 1 As shown, the product purity is >99.9%. The product purity is >99.9% by optimizing the post-processing process and simplifying the sublimation purification steps, and the target product with high purity can be directly obtained; The product is analyzed by AVANCE NEO nuclear magnetic resonance spectrometer. Figure 2 The nuclear magnetic structure spectrum of the finished product 1,3-DMCBDA prepared is shown in Figure 2. Figure 2 As shown in the spectrum, the product has an opening rate of 0.4% and no isomer is generated. The preparation method of the present application significantly reduces the proportion of isomer 1,2-DMCBDA in the product, and has excellent application performance. The metal impurity content in the product is less than 500 ppb by ICP-MS analysis, Figure 3 The metal ion content analysis spectrum of the finished product 1,3-DMCBDA is shown in Figure 3. Figure 3 As shown, the product prepared has a low metal impurity content. The present application optimizes the reaction system to effectively control and reduce the content of metal impurities in the product.

[0026] Example 2: Synthesis of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride 1) Add 40.00 kg of dimethyl carbonate, 0.10 kg of benzophenone and 5.00 kg of dimethyl citraconate to a photocatalytic reaction kettle, and perform addition reaction under mercury lamp irradiation. The reaction temperature is 30°C, and the reaction time is 22 h. Then distill, filter and dry to obtain 4.95 kg of intermediate S1; 2) Prepare a hydrochloric acid solution by adding 4.00 kg of concentrated hydrochloric acid (mass fraction 37%) and 11.00 kg of ultrapure water to a glass reaction kettle, then add 4.95 kg of intermediate S1 obtained in step 1) and stir. The reaction temperature is controlled at 90°C, and the reaction time is 15 h. After the reaction is completed, cool the material to 25°C, then filter and dry to obtain 1.70 kg of intermediate S2; 3) 6.80 kg of acetic anhydride and 1.70 kg of the intermediate S2 obtained in step 2) were added into a reaction kettle, stirred and slowly increased in temperature in steps, first increased to 60°C for 1 h, then increased to 100°C for 1 h, and finally increased to 110°C for 15 h, after the reaction was completed, the temperature was decreased to 25°C for filtration, the filter cake was slurried with ethyl acetate for 10 min, then filtered and vacuum dried to obtain 1.24 kg of 1,3-DMCBDA product.

[0027] Example 3: Synthesis of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride 1) 40.00 kg of dimethyl carbonate, 0.050 kg of benzophenone and 5.00 kg of dimethyl citraconate were added into a photocatalytic reaction kettle, and an addition reaction was carried out under mercury lamp irradiation, the reaction temperature was 20°C, and the reaction time was 25 h, then distilled, filtered and dried to obtain 4.91 kg of intermediate S1; 2) 6.00 kg of concentrated hydrochloric acid (mass fraction 37%) and 9.00 kg of ultrapure water were added into a glass reaction kettle to prepare a hydrochloric acid solution, then 4.91 kg of the intermediate S1 obtained in step 1) was added for stirring, the reaction temperature was controlled at 85°C, the reaction time was 16 h, after the reaction was completed, the material was cooled to 20°C, then filtered and dried to obtain 1.85 kg of intermediate S2; 3) 9.25 kg of acetic anhydride and 1.85 kg of the intermediate S2 obtained in step 2) were added into a reaction kettle, stirred and slowly increased in temperature in steps, first increased to 70°C for 1 h, then increased to 100°C for 1 h, and finally increased to 130°C for 14 h, after the reaction was completed, the material was cooled to 25°C for filtration, the filter cake was slurried with ethyl acetate for 10 min, then filtered and vacuum dried to obtain 1.27 kg of 1,3-DMCBDA product.

[0028] Example 4: Synthesis of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride 1) 40.00 kg of dimethyl carbonate, 0.05 kg of catalyst 2,4-diethylthioxanthone and 5.00 kg of dimethyl citraconate were added into a photocatalytic reaction kettle, and an addition reaction was carried out under mercury lamp irradiation, the reaction temperature was 20°C, and the reaction time was 29 h, then distilled, filtered and dried to obtain 4.92 kg of intermediate S1; 2) 2.00 kg of concentrated phosphoric acid solution (mass fraction 37%) and 12.00 kg of ultrapure water were added into a glass reaction kettle to prepare a phosphoric acid solution, then 4.92 kg of the intermediate S1 obtained in step 1) was added for stirring, the reaction temperature was controlled at 80°C, the reaction time was 12 h, after the reaction was completed, the material was cooled to 25°C, then filtered and dried to obtain 1.40 kg of intermediate S2; 3) Add 5.00 kg of acetic anhydride and 1.40 kg of the intermediate S2 obtained in step 2) into the reaction kettle, stir and slowly increase the temperature in stages, first increase the temperature to 70°C for 0.5 h, then increase the temperature to 90°C for 0.5 h, and finally increase the temperature to 130°C for 14 h. After the reaction is completed, cool the material to 25°C for filtration. Use ethyl acetate to pulp the filter cake for 10 min, then filter and vacuum dry to obtain 1.10 kg of 1,3-DMCBDA finished product.

[0029] Example 5: Synthesis of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride 1) Add 40.00 kg of dimethyl carbonate, 0.10 kg of catalyst 2,4-diethylthioxanthone, and 5.00 kg of dimethyl citraconate into the photocatalytic reaction kettle, and perform addition reaction under mercury lamp source irradiation. The reaction temperature is 20°C, and the reaction time is 26 h. Then distill, filter, and dry to obtain 4.93 kg of intermediate S1; 2) Add 6.00 kg of concentrated phosphoric acid solution (mass fraction of 37%) and 9.00 kg of ultrapure water to prepare a phosphoric acid solution, and then add 4.93 kg of the intermediate S1 obtained in step 1) into the glass reaction kettle. Stir, and the reaction temperature is 90°C. The reaction time is 12 h. After the reaction is completed, cool the material to 25°C, and then filter and dry to obtain 1.78 kg of intermediate S2; 3) Add 5.00 kg of acetic anhydride and 1.78 kg of the intermediate S2 obtained in step 2) into the reaction kettle, stir and slowly increase the temperature in stages, first increase the temperature to 50°C for 1 h, then increase the temperature to 90°C for 0.5 h, and finally increase the temperature to 120°C for 14 h. After the reaction is completed, cool the material to 25°C for filtration. Use ethyl acetate to pulp the filter cake for 10 min, then filter and vacuum dry to obtain 1.19 kg of 1,3-DMCBDA finished product.

[0030] Example 6: Synthesis of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride 1) Add 40.00 kg of dimethyl carbonate, 0.05 kg of catalyst 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 5.00 kg of dimethyl citraconate into the photocatalytic reaction kettle, and perform addition reaction under mercury lamp source irradiation. The reaction temperature is 20°C, and the reaction time is 29 h. Then distill, filter, and dry to obtain 4.91 kg of intermediate S1; 2) Add 2.00 kg of sulfuric acid (mass fraction 50%) and 13.00 kg of ultrapure water to a glass reaction kettle to prepare a sulfuric acid solution, then add 4.91 kg of intermediate S1 obtained in step 1), stir, control the reaction temperature to be 95°C, and the reaction time to be 15h. After the reaction is completed, the material is cooled to 25°C, and then filtered and dried to obtain 1.45 kg of intermediate S2; 3) Add 5.00 kg of acetic anhydride and 1.45 kg of intermediate S2 obtained in step 2) to a reaction kettle, stir and slowly increase the temperature in stages, first increase the temperature to 60°C for 1h, then increase the temperature to 100°C for 1h, and finally increase the temperature to 130°C for 15h. After the reaction is completed, the material is cooled to 25°C for filtration. The filter cake is slurried with ethyl acetate for 10 min, then filtered and vacuum dried to obtain 1.13 kg of 1,3-DMCBDA finished product.

[0031] Example 7: Synthesis of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride 1) Add 40.00 kg of dimethyl carbonate, 0.10 kg of catalyst 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 5.00 kg of dimethyl citraconate to a photocatalytic reaction kettle. Perform addition reaction under mercury lamp source irradiation, reaction temperature is 20°C, reaction time is 29h, and then distill, filter and dry to obtain 4.95 kg of intermediate S1; 2) Add 6.00 kg of sulfuric acid (mass fraction 50%) and 9.00 kg of ultrapure water to a glass reaction kettle to prepare a sulfuric acid solution, then add 4.95 kg of intermediate S1 obtained in step 1), stir, control the reaction temperature to be 80°C, and the reaction time to be 12h. After the reaction is completed, the material is cooled to 25°C, and then filtered and dried to obtain 1.71 kg of intermediate S2; 3) Add 5.00 kg of acetic anhydride and 1.71 kg of intermediate S2 obtained in step 2) to a reaction kettle, stir and slowly increase the temperature in stages, first increase the temperature to 70°C for 0.5h, then increase the temperature to 90°C for 0.5h, and finally increase the temperature to 120°C for 14h. After the reaction is completed, the material is cooled to 25°C for filtration. The filter cake is slurried with ethyl acetate for 10 min, then filtered and vacuum dried to obtain 1.14 kg of 1,3-DMCBDA finished product.

[0032] Example 8: Synthesis of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride 1) To the photo-catalytic reactor, 40.00 kg of dimethyl carbonate, 0.05 kg of catalyst benzophenone and 4.00 kg of dimethyl citraconate were added, and the addition reaction was carried out under the irradiation of a mercury lamp source, the reaction temperature was 20 ℃, and the reaction time was 25 h, and then distillation, filtration and drying were carried out to obtain 3.97 kg of intermediate S1; 2) To the glass reactor, 2.00 kg of concentrated hydrochloric acid (mass fraction 37%) and 13.00 kg of ultrapure water were added to prepare a hydrochloric acid solution, and then 3.97 kg of intermediate S1 obtained in step 1) was added for hydrolysis reaction, the reaction temperature was controlled at 80 ℃, the reaction time was 12 h, after the reaction was completed, the material was cooled to 25 ℃, and then filtration and drying were carried out to obtain 1.31 kg of intermediate S2; 3) To the reactor, 4.00 kg of acetic anhydride and 1.31 kg of intermediate S2 obtained in step 2) were added, stirring and slowly increasing the temperature in stages, first increasing the temperature to 70 ℃ for 0.5 h, then increasing the temperature to 90 ℃ for 0.5 h, and finally increasing the temperature to 130 ℃ for 15 h, after the reaction was completed, the material was cooled to 25 ℃ for filtration, the filter cake was slurried with ethyl acetate for 10 min, then filtered and vacuum dried to obtain 0.95 kg of 1,3-DMCBDA finished product.

[0033] Example 9: Synthesis of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride 1) To the photo-catalytic reactor, 40.00 kg of dimethyl carbonate, 0.10 kg of catalyst benzophenone and 4.00 kg of dimethyl citraconate were added, and the addition reaction was carried out under the irradiation of a mercury lamp source, the reaction temperature was 22 ℃, and the reaction time was 23 h, and then distillation, filtration and drying were carried out to obtain 3.98 kg of intermediate S1; 2) To the glass reactor, 6.00 kg of concentrated hydrochloric acid (mass fraction 37%) and 9.00 kg of ultrapure water were added to prepare a hydrochloric acid solution, and then 3.98 kg of intermediate S1 obtained in step 1) was added for hydrolysis reaction, the reaction temperature was controlled at 80 ℃, the reaction time was 12 h, after the reaction was completed, the material was cooled to 25 ℃, and then filtration and drying were carried out to obtain 1.38 kg of intermediate S2; 3) To the reactor, 4.05 kg of acetic anhydride and 1.38 kg of intermediate S2 obtained in step 2) were added, stirring and slowly increasing the temperature in stages, first increasing the temperature to 50 ℃ for 0.5 h, then increasing the temperature to 90 ℃ for 0.5 h, and finally increasing the temperature to 120 ℃ for 14 h, after the reaction was completed, the material was cooled to 25 ℃ for filtration, the filter cake was slurried with ethyl acetate for 10 min, then filtered and vacuum dried to obtain 0.97 kg of 1,3-DMCBDA finished product.

[0034] Example 10: Synthesis of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride 1) 40.00 kg of dimethyl carbonate, 0.05 kg of catalyst benzophenone and 8.00 kg of dimethyl citraconate were added to a photocatalytic reaction kettle, and an addition reaction was carried out under the irradiation of a mercury lamp source, the reaction temperature was 20℃, the reaction time was 25h, and then distillation, filtration and drying were carried out to obtain 7.95 kg of intermediate S1; 2) 4.00 kg of concentrated hydrochloric acid (mass fraction 37%) and 15.00 kg of ultrapure water were added to a glass reaction kettle to prepare a hydrochloric acid solution, and then 7.95 kg of intermediate S1 obtained in step 1) was added to carry out a hydrolysis reaction, the reaction temperature was controlled at 80℃, the reaction time was 12h, after the reaction was completed, the material was cooled to 25℃, and then filtration and drying were carried out to obtain 2.50 kg of intermediate S2; 3) 7.00 kg of acetic anhydride and 2.50 kg of intermediate S2 obtained in step 2) were added to a reaction kettle, stirred and slowly increased in temperature in stages, first increased to 50℃ for 0.5h, then increased to 90℃ for 0.5h, and finally increased to 120℃ for 14h, after the reaction was completed, the material was cooled to 25℃ for filtration, the filter cake was slurried with ethyl acetate for 10min, then filtered and vacuum dried to obtain 1.70 kg of 1,3-DMCBDA product.

[0035] The present application uses dimethyl citraconate to prepare 1,3-DMCBDA, avoids the problem of low final yield caused by the deterioration of raw materials due to water absorption, and further optimizes the reaction system to greatly reduce the content of isomer 1,2-DMCBDA in the reaction process, thereby obtaining high-purity target product.

[0036] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for producing 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, characterized by, Dimethyl citraconate and dimethyl carbonate are subjected to addition reaction under irradiation of mercury lamp source, then subjected to hydrolysis by reaction with acid solvent after being heated, then filtered after being cooled, then subjected to dehydration ring closure by reaction with acetic anhydride to obtain 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride.

2. The production method according to claim 1, characterized by, The preparation method comprises the following steps: (1) dimethyl citraconate is added to dimethyl carbonate, and addition reaction is carried out under irradiation of a mercury lamp source, and then distillation, filtration and drying are carried out to obtain an intermediate S1; (2) the intermediate S1 obtained in step (1) is added to an acid solution under stirring, and hydrolysis reaction is carried out by heating, the temperature is cooled to 20-25 DEG C after the reaction is completed, and then direct filtration is carried out to obtain an intermediate S2; (3) acetic anhydride and the intermediate S2 obtained in step (2) are added to a reaction device to carry out dehydration ring closure, the temperature is increased step by step to the reaction end, the temperature is cooled to 20-25 DEG C after the reaction is completed, and then filtration is carried out, the filter cake is beaten with ethyl acetate and then filtered and dried to obtain finished product 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride.

3. The production method according to claim 2, characterized by, In step (1), the molar ratio of dimethyl carbonate to dimethyl citraconate is 9:1-20:

1.

4. The production method according to claim 2, characterized by, In step (1), a catalyst is added in the addition reaction, and the catalyst is selected from benzophenone, 2,4-diethylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; the molar ratio of the catalyst to dimethyl citraconate is 1:90-1:

350.

5. The preparation method according to claim 2, characterized in that, In step (1), the reaction temperature of the addition reaction is 20-50 DEG C, and the reaction time is 20-30 h.

6. The preparation method according to claim 2, characterized in that, In step (2), the acid solution is a hydrochloric acid solution, a phosphoric acid solution or a sulfuric acid solution.

7. The preparation method according to claim 2, characterized in that, In step (2), the pH of the acid solution ranges from 1 to 3.

8. The method of claim 2, wherein, In step (2), the reaction temperature of the hydrolysis reaction is 80-100 DEG C, and the reaction time is 12-16 h.

9. The method of claim 2, wherein, In step (3), the step-by-step slow temperature increase is first heating to 50-70 DEG C for 0.5-2 h, then heating to 80-100 DEG C for 0.5-2 h, and finally heating to 110-130 DEG C for 14-15 h.

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