Preparation method of dinitrodiphenol compound

Abstract

The invention relates to synthesis of a polyimide raw material, in particular to a preparation method of a dinitrodiphenol compound. The method specifically comprises the following steps: reacting a compound 1 with a nitration reagent at a low temperature of-15 to 15 DEG C in the presence of a reaction solvent, washing and distilling after the reaction to obtain a dinitrodiphenol compound crude product shown as a compound 2, and recrystallizing the crude product through a crystallization solvent to obtain the high-purity dinitrodiphenol compound shown as the compound 2. The method has the advantages that the process route is simple, the yield is high, industrial implementation is easy, a post-treatment method is established for obtaining a crude product, and the purity of the treated product can reach 99% or above.

Description

Technical Field

[0001] This invention relates to the synthesis of polyimide raw materials, specifically a method for preparing dinitrodiphenol compounds. Background Technology

[0002] Polyimide (PI) is a polymer material containing imide functional groups in its main chain. Polyimide possesses many excellent properties, such as heat stability, good mechanical properties, outstanding corrosion resistance, high light transmittance and resistance to light radiation, as well as a low coefficient of linear expansion and dielectric properties. These characteristics make polyimide widely used in many fields. Polyimides are typically produced by the polymerization of diamine and dianhydride monomers, followed by cyclization and dehydration to form polymers with five-membered heterocyclic imide rings. Diaminodiphenols are important monomers for polyimide preparation, such as the diamine monomer 6-FAP. Dinitrodiphenols can be reduced to prepare diaminodiphenol compounds.

[0003] Dinitrodiphenol compounds (structure shown in Compound 2) are mainly obtained from diphenol compounds (structure shown in Compound 1) through nitration. Due to the presence of reactive hydroxyl groups, two nitro groups easily form at the ortho position of the hydroxyl group. The product purity is generally between 80-90%, and direct reduction to diaminodiphenol compounds is not possible, as this would increase the difficulty of subsequent processing. To obtain high-purity dinitrodiphenol compounds, post-processing is necessary to ensure that the product purity meets the requirements for preparing diaminodiphenol compounds. Diaminodiphenol compounds are a major type of diamine monomer in polyimides, and this structure is currently one of the research directions. Chinese patent CN119899117 A describes the preparation of diaminodiphenol compounds, but this patent only describes the nitro reduction process and does not describe the preparation of the dinitro compound. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing dinitrodiphenol compounds.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a dinitrodiphenol compound, wherein compound 1 is reacted with a nitrating agent at a low temperature of -15-15℃ (preferably -10-5℃) in the presence of a reaction solvent, and after the reaction, the product is washed with water and distilled to obtain a crude dinitrodiphenol compound as shown in compound 2. The crude product is recrystallized with a crystallization solvent to obtain a high-purity dinitrodiphenol compound as shown in compound 2.

[0006] The structures of compound 1 and compound 2 are as follows:

[0007] Compound 1 Compound 2 A is , , , or

[0008] R1 and R2 can be the same or different, and can be independently H, halogen, or C. 1-6 alkyl, C 1-6 The alkyl halogroup, or, R1 and R2 form a C12 with the adjacent carbon atom. 3-10 The cycloalkyl group formed may be substituted with at least one of the following groups: halogen, C 1-6 alkyl or C 1-6 alkyl halogenates; R3 represents H, halogen, or C. 1-6 alkyl, C 1-6 The alkyl halogroups, n = 1, 2, 3, 4, 5 or 6, m = 1-8, where m is an integer. When m is greater than 1, each R3 may be the same or different.

[0009] Preferably, in the structures shown by compounds 1 and 2, A is , , , or

[0010] R1 and R2 can be the same or different, and can be independently H, halogen, or C. 1-4 alkyl, C 1-4 The alkyl halogroup, or, R1 and R2 form a C12 with the adjacent carbon atom. 4-8 The cycloalkyl group formed may be substituted with at least one of the following groups: halogen, C 1-4 alkyl or C 1-4 alkyl halogenates; R3 represents H, halogen, or C. 1-4 alkyl, C 1-4 The alkyl halogroups, n = 1, 2, 3, 4, 5 or 6, m = 1-6, where m is an integer. When m is greater than 1, each R3 may be the same or different.

[0011] Further preferably, in the structures shown by compounds 1 and 2,

[0012] The nitrating agent is 50-98% nitric acid or a mixed acid; wherein the mixed acid is a mixture of fuming nitric acid and concentrated sulfuric acid, and the proportion of fuming nitric acid in the mixed acid is 50-80%; preferably, the nitric acid concentration is 50-70%, and the proportion of fuming nitric acid in the mixed acid is 50-60%. The reaction solvent is one or more of dichloromethane, dichloroethane, chloroform, nitrobenzene, toluene, and concentrated sulfuric acid; preferably one or more of dichloromethane, dichloroethane, and toluene.

[0013] The crude product is added to the crystallization solvent, and the temperature is raised to the solvent reflux temperature under stirring until the crude product is completely dissolved. Then, the temperature is lowered to 8-10℃, and the mixture is stirred thoroughly for 2-4 hours to precipitate the solid. After precipitation, the temperature is further lowered to -5-5℃, and the mixture is stirred for another 2-4 hours to fully crystallize. The product is then filtered, dried, and discharged. After discharge, the product can be recrystallized again according to the above method until a high-yield, high-purity dinitrophenol compound as shown in compound 2 is obtained.

[0014] The crystallization solvent is toluene, ethyl acetate, acetone, or an aqueous solution of acetone; preferably, an aqueous solution of acetone has a concentration range of 55-65%.

[0015] Advantages of this invention: This invention discloses a method for preparing dinitrodiphenol compounds. At low temperature, dinitration can be achieved using 50-70% nitric acid, resulting in complete conversion of the raw materials and a product selectivity of approximately 90%. A post-processing method is established for obtaining the crude product. After one treatment, the product purity can reach over 98%, and after a second treatment, the purity can reach over 99%. Compared with existing routes, this invention has the advantages of a simple process route, high yield, and ease of industrial implementation. Detailed Implementation

[0016] The present invention will be further illustrated by the following embodiments. However, the present invention is by no means limited thereto.

[0017] Example 1 Reaction equation

[0018] Add 81g of 4,4'-(1,3-dimethylbutyl)diphenol and 500mL of dichloromethane to a flask, cool to -5℃, and add 66.88g of 65% nitric acid dropwise over 3 hours. After the addition is complete, maintain the temperature at -5℃ and stir for 4 hours. Take a sample for analysis; 0.5% of the raw material remains. After the reaction is complete, add 160mL of water to the reaction solution each time, wash three times with water, remove the upper layer of water, and remove the dichloromethane by vacuum distillation to obtain 108g of crude nitro compound with a purity of 90.3%. The water obtained from the separation can be reused after distillation, and the dichloromethane obtained from vacuum distillation can also be reused.

[0019] Post-processing: The crude product was added to 291.6 g of acetone and 157 g of water, heated to reflux until completely dissolved, stirred under reflux for 1 h, then cooled to 8 °C, stirred thoroughly for 2 h, and a yellow solid precipitated. After precipitation, the temperature was further lowered to 0 °C, and stirring was continued for 2 h to allow for complete crystallization. The product was filtered, dried, and discharged to obtain a yellow solid. Sample analysis showed that the product purity was approximately 98.1%. After drying, 88.9 g was obtained, with a yield of 82.3%.

[0020] 88.9g of the primary refined product was added to 240g of acetone and 130g of water, heated to reflux until completely dissolved, stirred under reflux for 1 hour, then cooled to 8℃ and stirred thoroughly for 2 hours, after which a yellow solid precipitated. After precipitation, the temperature was further lowered to 0℃ and stirred for another 2 hours to allow for complete crystallization. The product was filtered, dried, and discharged to obtain a yellow solid. Sample analysis showed that the product purity was approximately 99.2%. After drying, 77.7g was obtained, with a total yield of 71.9%.

[0021] Example 2 Reaction equation

[0022] Add 68.4 g of 4,4'-(1,3-dimethylbutyl)diphenol and 400 mL of dichloroethane to a flask, cool to 3 °C, and add 72.45 g of 60% nitric acid dropwise over a period of 4 hours. After the addition is complete, maintain the temperature at 3 °C with stirring for 4 hours. Take a sample for analysis; the remaining raw material is 0.32%. After the reaction is complete, add 160 mL of water to the reaction solution each time, wash three times with water, remove the upper layer of water, and remove the dichloroethane by vacuum distillation to obtain 95 g of crude nitro compound with a purity of 88.5%. The water obtained from the separation can be reused after distillation, and the dichloroethane obtained from vacuum distillation can also be reused.

[0023] Post-processing: The crude product was added to 380g of ethyl acetate, heated to reflux until completely dissolved, stirred under reflux for 1h, then cooled to 0℃, kept warm and stirred for 2h to allow full crystallization, filtered, dried and discharged to obtain a yellow solid. Sample analysis showed that the product purity was about 98.2%, and after drying, 74.6g was obtained, with a yield of 78.2%.

[0024] 74.6g of the primary purified product was added to 225g of ethyl acetate, heated to reflux until completely dissolved, stirred under reflux for 2 hours, then cooled to 0℃ and stirred thoroughly for 2 hours. A yellow solid precipitated out, filtered, dried and discharged to obtain a yellow solid. Sample analysis showed that the product purity was about 99.3%. After drying, 64.9g was obtained, with a total yield of 68%.

[0025] Example 3 Reaction equation

[0026] Add 80.4 g of 4,4'-dihydroxydiphenylcyclohexane and 500 mL of dichloromethane to a flask, cool to 5 °C, and add 62.1 g of 70% nitric acid dropwise over 5 hours. After the addition is complete, maintain the temperature at 5 °C and stir for 3 hours. Sampling and analysis revealed that 0.29% of the raw material remained. After the reaction was complete, add 160 mL of water to the reaction solution each time, wash three times, remove the upper layer of water, and remove the dichloromethane by vacuum distillation to obtain 107 g of crude nitro compound with a purity of 89.6%. The water obtained from the separation can be reused after distillation, and the dichloromethane obtained from vacuum distillation can also be reused.

[0027] Post-processing: The crude product was added to 291.6 g of acetone and 194.4 g of water, heated to reflux until completely dissolved, stirred under reflux for 1 h, then cooled to 5 °C, and stirred thoroughly for 3 h. A yellow solid precipitated out. After precipitation, the temperature was further lowered to 0 °C, and stirring was continued for 2 h to allow for complete crystallization. The product was filtered, dried, and discharged to obtain a yellow solid. Sample analysis showed that the product purity was approximately 98.2%. After drying, 87.4 g was obtained, with a yield of 81.4%.

[0028] 87.4g of the primary purified product was added to 236g of acetone and 157.3g of water, heated to reflux until completely dissolved, stirred under reflux for 1 hour, then cooled to 5℃ and stirred thoroughly for 2 hours, after which a yellow solid precipitated. After precipitation, the temperature was further lowered to 0℃ and stirred for another 2 hours to allow for complete crystallization. The product was filtered, dried, and discharged to obtain a yellow solid. Sample analysis showed that the product purity was approximately 99.1%. After drying, 75.9g was obtained, with a total yield of 70.7%.

[0029] Example 4 Reaction equation

[0030] Add 67.2 g of hexafluorobisphenol A and 400 mL of dichloroethane to a flask, cool to 8 °C, and add 55 g of 55% nitric acid dropwise over 4 hours. After the addition is complete, maintain the temperature at 8 °C with stirring for 6 hours. Sampling and analysis revealed 0.44% of the raw material remaining. After the reaction is complete, add 160 mL of water to the reaction solution each time, wash three times, remove the upper water layer, and remove the dichloroethane by vacuum distillation to obtain 85.2 g of crude nitro compound with a purity of 87.8%. The water obtained from the separation can be reused after distillation, and the dichloroethane obtained from vacuum distillation can also be reused.

[0031] Post-processing: The crude product was added to 425g of toluene, heated to reflux until completely dissolved, stirred under reflux for 1h, then cooled to 0℃, kept warm and stirred for 2h to allow full crystallization, filtered, dried and discharged to obtain a yellow solid. Sample analysis showed that the product purity was about 98.1%, and after drying, 68.1g was obtained, with a yield of 79.9%.

[0032] 68.1g of the primary purified product was added to 340g of toluene, heated to reflux until completely dissolved, stirred under reflux for 2 hours, then cooled to -5℃ and stirred thoroughly for 2 hours. A yellow solid precipitated out, filtered, dried and discharged to obtain a yellow solid. Sample analysis showed that the product purity was 99.3%. After drying, 54.7g was obtained, with a total yield of 64.2%.

Claims

1. A method for preparing a dinitrodiphenol compound, characterized in that, At a low temperature of -15 to -15°C, in the presence of a reaction solvent, compound 1 reacts with a nitrating agent. After the reaction, the product is washed with water and distilled to obtain crude dinitrodiphenol compound 2. The crude product is recrystallized with a crystallization solvent to obtain high-purity dinitrodiphenol compound 2.

2. The method for preparing dinitrodiphenol compounds according to claim 1, characterized in that, The structures of compound 1 and compound 2 are as follows: Compound 1 Compound 2 A is , , , or R1 and R2 can be the same or different, and can be independently H, halogen, or C. 1-6 alkyl, C 1-6 The alkyl halogroup, or, R1 and R2 form a C12 with the adjacent carbon atom. 3-10 The cycloalkyl group formed may be substituted with at least one of the following groups: halogen, C 1-6 alkyl or C 1-6 alkyl halogenates; R3 represents H, halogen, or C. 1-6 alkyl, C 1-6 The alkyl halogroups, n = 1, 2, 3, 4, 5 or 6, m = 1-8, where m is an integer. When m is greater than 1, each R3 may be the same or different.

3. The method for preparing dinitrodiphenol compounds according to claim 2, characterized in that, In the structures shown by compounds 1 and 2, A is , , , or R1 and R2 can be the same or different, and can be independently H, halogen, or C. 1-4 alkyl, C 1-4 The alkyl halogroup, or, R1 and R2 form a C12 with the adjacent carbon atom. 4-8 The cycloalkyl group formed may be substituted with at least one of the following groups: halogen, C 1-4 alkyl or C 1-4 alkyl halogenates; R3 represents H, halogen, or C. 1-4 alkyl, C 1-4 The alkyl halogroups, n = 1, 2, 3, 4, 5 or 6, m = 1-6, where m is an integer. When m is greater than 1, each R3 may be the same or different.

4. The method for preparing dinitrodiphenol compounds according to claim 1, characterized in that, The nitrating agent is 50-98% nitric acid or a mixed acid; wherein the mixed acid is a mixture of fuming nitric acid and concentrated sulfuric acid, and the proportion of fuming nitric acid in the mixed acid is 50-80%.

5. The method for preparing dinitrodiphenol compounds according to claim 1, characterized in that, The reaction solvent is one or more of dichloromethane, dichloroethane, chloroform, nitrobenzene, toluene, and concentrated sulfuric acid.

6. The method for preparing dinitrodiphenol compounds according to claim 1, characterized in that, The crude product is added to the crystallization solvent, and the temperature is raised to the solvent reflux temperature under stirring until the crude product is completely dissolved. Then the temperature is lowered to 8-10℃, and the mixture is stirred thoroughly for 2-4 hours to precipitate the solid. After precipitation, the temperature is further lowered to -5-5℃, and the mixture is stirred for another 2-4 hours to allow for complete crystallization. The product is then filtered, dried, and discharged to obtain a high-yield, high-purity dinitrophenol compound as shown in compound 2.

7. The method for preparing dinitrodiphenol compounds according to claim 6, characterized in that, The crystallization solvent is toluene, ethyl acetate, acetone, or an aqueous solution of acetone.

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