Trimellitus anhydride ester and method for producing the same

Abstract

To provide a method for producing trimellitic anhydride ester with high purity and low chlorine content in high yield using simple operations. [Solution] The above method for producing trimellitic anhydride includes step A, reacting trimellitic anhydride halide with a specific branched alkanediol to obtain crude trimellitic anhydride, and step B, purifying the crude trimellitic anhydride. The step B, adding a purification solvent containing at least one of a hydrocarbon solvent with an SP value of 7.8 or more and an ester solvent with an SP value of 7.8 or more and 9.1, and water to the crude trimellitic anhydride and separating the solution at 30°C or more and 70°C or less, and step C, adding acetic anhydride to the solution containing the crude trimellitic anhydride after separation and purification and heating, and distilling off the purification solvent from the heated solution.

Description

[Technical Field]

[0001] The present invention relates to trimellitic anhydride ester and a method for producing the same. [Background technology]

[0002] Acid dianhydrides are industrially useful chemicals, serving as raw materials for polyimide, a heat-resistant resin, and as curing agents for epoxy and polyurethane resins. Various manufacturing methods are being investigated. In recent years, polyimide, epoxy, and urethane resins have also been used in materials for electronic information equipment (referred to as "electronic materials" in this specification). However, when some acid anhydrides were used as curing agents for electronic materials, their adhesion was sometimes insufficient. Furthermore, warping sometimes occurred in electronic materials using some acid anhydrides. Therefore, trimellitic anhydride esters, which offer high flexibility, are attracting attention as acid dianhydrides. Additionally, with the miniaturization of electronic information equipment in recent years, stricter quality standards are being applied to electronic materials. For example, there is a growing demand for improved electrical reliability, as well as stronger demands for improved product purity and reduced foreign matter.

[0003] Conventionally, a method for producing trimellitic anhydride ester has been reported, which involves reacting trimellitic anhydride halide with alcohols to prepare the ester. It has also been proposed to wash the trimellitic anhydride ester prepared by these methods with solvents such as dimethylformamide or nitriles (Patent Documents 1 and 2). Furthermore, it has been proposed to increase the purity of the trimellitic anhydride ester by crystallization (Patent Document 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-6330 [Patent Document 2] Japanese Patent Publication No. 2017-203005 [Patent Document 3] Japanese Patent Publication No. 2013-10897 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, when trimellitic anhydride ester is in liquid form, it is difficult to purify it using the methods described in Patent Documents 1 to 3 above. Furthermore, when trimellitic anhydride is in gel form, even if production can be carried out using the above methods, the yield is significantly reduced. Moreover, strict standards are set for the reduction of impurities and purity in applications such as electronic materials, but it is difficult to meet these standards using only the methods described in the above Patent Documents. In particular, there were concerns that it would be difficult to meet the standards in terms of high purity and chlorine reduction.

[0006] This invention has been made in view of these circumstances. The problem that this invention aims to solve is to provide a method for producing trimellitic anhydride ester that is highly pure and low in chlorine content in high yield with simple operations. [Means for solving the problem]

[0007] The inventors of the present invention conducted diligent studies to solve the above problems. As a result, they found that the above problems can be solved by first obtaining crude trimellitic anhydride, then separating and purifying the crude trimellitic anhydride using a specific purification solvent and water at a temperature of 30°C to 70°C, and further cyclizing the crude trimellitic anhydride and distilling off the purification solvent, thereby completing the present invention.

[0008] The method for producing trimellitic anhydride ester according to the present invention is as follows. A method for producing trimellitic anhydride, comprising: step A, reacting trimellitic anhydride halide with a branched alkanediol represented by the following general formula (1) to obtain a crude trimellitic anhydride containing a trimellitic anhydride represented by the following general formula (2); and step B, purifying the crude trimellitic anhydride, wherein the step of purifying the crude trimellitic anhydride comprises adding a purification solvent containing at least one of a hydrocarbon solvent with an SP value of 7.8 or more and an ester solvent with an SP value of 7.8 or more and 9.1, and water, and performing liquid-liquid purification at 30°C or more and 70°C or less; and step C, adding acetic anhydride to a solution containing the crude trimellitic anhydride after liquid-liquid purification and the purification solvent, and heating, and distilling off the purification solvent from the heated solution. [ka] (In general formula (1), R 1 (This represents an alkylene group having a branched structure with 3 to 17 carbon atoms.)

[0009] [ka] (In general formula (2), R 1 (This represents an alkylene group having a branched structure with 3 to 17 carbon atoms.)

[0010] The trimellitic anhydride ester of the present invention is as follows: A trimellitic anhydride ester represented by the following general formula (2), with a chlorine content of 20 ppm or less. [ka] (In general formula (2), R 1 (This represents an alkylene group having a branched structure with 3 to 17 carbon atoms.) [Effects of the Invention]

[0011] According to the manufacturing method of the present invention, trimellitic anhydride ester, which is highly pure and has a low chlorine content, can be obtained in high yield through simple operations.

Mode for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in detail.

[0013] The present invention is a method for producing a trimellitic anhydride ester represented by the following general formula (2) by reacting trimellitic anhydride halide with a branched alkanediol represented by the following general formula (1).

[0014]

Chemical formula

[0015] In the method for producing a trimellitic anhydride ester of the present invention, step A of reacting trimellitic anhydride halide and a branched alkanediol to obtain a crude trimellitic anhydride ester, and a step of purifying the crude trimellitic anhydride ester are performed. Hereinafter, each step will be described.

[0016] 〔Reaction of trimellitic anhydride halide and branched alkanediol (step A for obtaining a crude trimellitic anhydride ester)〕 In this step (hereinafter, also referred to as "reaction step A"), trimellitic anhydride halide and a branched alkanediol having a specific structure are reacted. The trimellitic anhydride halide used in this step may be produced by a known method or may be purchased. The "trimellitic anhydride halide" in this specification means a halogenated derivative of trimellitic anhydride.

[0017] Examples of the anhydrous trimellitic acid halide include anhydrous trimellitic acid chloride, anhydrous trimellitic acid bromide, anhydrous trimellitic acid iodide, and anhydrous trimellitic acid fluoride. Among these anhydrous trimellitic acid halides, anhydrous trimellitic acid chloride is preferred because it is inexpensive and easily available.

[0018] On the other hand, the branched alkanediol is a compound represented by the following general formula (1). [Chemical formula] In general formula (1), R 1 represents an alkylene group having a branched structure with 3 to 17 carbon atoms. That R 1 has a branched structure means that R 1 has a main chain connecting two hydroxy groups and a side chain bonded thereto.

[0019] R 1 The number of carbon atoms in the main chain may be 2 or more and 16 or less, but from the viewpoints of availability and reactivity (presence or absence of steric hindrance) between the branched alkanediol and the anhydrous trimellitic acid halide, 2 or more and 10 or less is preferable, and 2 or more and 5 or less is more preferable. On the other hand, the number of side chains bonded to the main chain may be 1 or may be 2 or more. The number of side chains is preferably 1 or more and 10 or less, and more preferably 1 or more and 5 or less. When there are two or more side chains, these may be bonded to the same carbon or different carbons. Further, when there are two or more side chains, these may have the same structure or different structures. The side chain is a linear or branched alkyl group. The number of carbon atoms in each side chain is preferably 1 or more and 12 or less, and more preferably 1 or more and 8 or less from the viewpoint of being difficult to inhibit the reaction between the branched alkanediol and the anhydrous trimellitic acid halide.

[0020] Examples of the above-mentioned branched alkanediols include 1,2-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propylpropane-1,3-diol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2,2-diisobutyl-1,3-propanediol, 2,2-diisoamyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-pentanediol, 3-methyl-1,3-butanediol, and 2,3-dimethylbutane-2 Examples include 3-diol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 2,4-dimethylpentane-2,4-diol, 2,4-diethylpentane-1,5-diol, 2,2,4-trimethylpentane-1,3-diol, 1,2-hexanediol, 2,5-hexanediol, 2-ethylhexane-1,3-diol, 2,5-dimethylhexane-2,5-diol, 2-ethylhexane-1,3-diol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 1,2-dodecanediol, 5,6-undecanediol, and 1,2-tetradecanediol. Among these, 3-methyl-1,5-pentanediol, 1,2-butanediol, 2,4-diethylpentane-1,5-diol, and 2-butyl-2-ethyl-1,3-propanediol are particularly preferred in terms of availability and reactivity with trimellitic anhydride halides.

[0021] In reaction step A, the ratio of branched alkanediol to trimellitic anhydride halide used is sufficient if it is approximately 1 mole equivalent of trimellitic anhydride halide per mole of hydroxyl groups of branched alkanediol. However, to complete the reaction, it is also possible to use an excess of trimellitic anhydride halide relative to the hydroxyl groups of branched alkanediol. In this case, the amount of trimellitic anhydride halide used is preferably between 1.0 mole equivalent and 1.5 mole equivalents, and more preferably between 1.0 mole equivalent and 1.2 mole equivalents, per 1.0 mole of hydroxyl groups of branched alkanediol. If the amount of trimellitic anhydride halide is insufficient relative to the amount of hydroxyl groups, a reaction may occur between the hydroxyl groups and the acid anhydride portion, potentially generating by-products. In contrast, by using the above ratio, the generation of by-products can be suppressed, and the reaction can be carried out efficiently.

[0022] Furthermore, in the reaction between trimellitic anhydride halide and branched alkanediol, hydrogen chloride is produced as a by-product during the reaction. Therefore, a base may be used to neutralize the hydrogen chloride during these reactions. Examples of bases that can be used as neutralizing agents include inorganic bases such as sodium hydroxide and sodium carbonate; basic ion exchange resins; organic tertiary amines such as triethylamine and tributylamine; and aromatic amines such as pyridine. Among these, amines are preferred, and pyridine is particularly suitable. The amount of neutralizing agent used is preferably equal to or greater than the amount of hydrogen chloride produced. Specifically, the lower limit is usually 1.0 molar equivalent and the upper limit is usually 2.0 molar equivalent relative to the amount of hydrogen chloride produced.

[0023] The reaction between trimellitic anhydride halide and branched alkanediols is usually carried out using a solvent. Examples of solvents include ether-based solvents such as diethyl ether, diisopropyl ether, di-n-butyl ether, tetrahydrofuran, dioxane, and t-butyl methyl ether; hydrocarbon solvents such as toluene, heptane, and cyclohexane; amide-based solvents such as N-methylpyrrolidone and dimethylformamide; ester-based solvents such as ethyl acetate and γ-butyrolactone; and ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. However, the solvent is not particularly limited as long as there are no problems with the solubility of trimellitic anhydride halide, branched alkanediol, and neutralizing agent (e.g., amine). Among these, solvents that are miscible with water or have a boiling point of 140°C or lower are more preferable from the viewpoint of facilitating solvent removal in the purification process described later. Furthermore, different solvents may be used for dissolving the branched alkanediol, the trimellitic anhydride halide, and the neutralizing agent (e.g., pyridine). In other words, a mixture of these solvents may be used. Tetrahydrofuran, diisopropyl ether, methyl ethyl ketone, and methyl isobutyl ketone are preferred as such solvents. Furthermore, these solvents can be combined and mixed as needed. In this case, the composition ratio of the solvents used is arbitrary.

[0024] The amount of solvent used should be such that the concentration of both trimellitic anhydride halide and the concentration of branched alkanediol are 1% by mass or more, and preferably 5% by mass or more. The upper limit is such that the concentration of both trimellitic anhydride halide and the concentration of branched alkanediol are 50% by mass or less, and more preferably 30% by mass or less.

[0025] When carrying out the above reaction, the order in which the raw materials are added is arbitrary and not particularly limited. For example, when using an amine as a neutralizing agent, trimellitic anhydride halide or a solution thereof may be added to a mixture of branched alkanediol and amine, or a mixture of these with a solvent. Alternatively, a mixture of branched alkanediol and amine, or a mixture of these with a solvent may be added to trimellitic anhydride halide or a solution thereof. Furthermore, branched alkanediol and amine may be added individually to trimellitic anhydride halide or a solution thereof, or a solution of branched alkanediol and a solution of amine may be added separately. Of these methods, if heat is generated, it may cause a decrease in purity due to side reactions. Therefore, the method of adding a mixed solution of branched alkanediol and amine dropwise to a solution of trimellitic anhydride halide is preferred.

[0026] The temperature when mixing the raw materials, and more specifically the reaction temperature, is usually preferably between -10°C and 25°C, and more preferably between 15°C and 20°C. When the reaction temperature exceeds 25°C, the amount of by-products tends to increase. The reaction time is not particularly limited; in some cases, the reaction finishes immediately after the addition of the raw materials. The reaction time is usually preferably within 3 hours, and more preferably around 1 hour.

[0027] [Purification process of the generated crude trimellitic anhydride ester] After the completion of reaction step A described above, a purification step (purification process) is performed on the obtained crude trimellitic anhydride ester. The reaction solution obtained in reaction step A with trimellitic anhydride halide and branched alkanediol contains not only the desired trimellitic anhydride ester, but also ring-opened trimellitic anhydride esters, unreacted products, chlorine compounds, etc. In this specification, these are collectively referred to as "crude trimellitic anhydride ester". Therefore, in order to obtain the desired trimellitic anhydride ester, the crude trimellitic anhydride ester is purified.

[0028] The purification process involves two steps: Step B (hereinafter also referred to as "separation process B"), in which a specific purification solvent and water are added to crude trimellitic anhydride and liquid-liquid purification is performed at 30°C to 70°C; and Step C (hereinafter also referred to as "ring-closing and solvent removal process C"), in which acetic anhydride is added to the solution containing the crude trimellitic anhydride and the above-mentioned purification solvent and heated, and the above-mentioned purification solvent is distilled off from the heated solution. However, other steps may be performed in addition to these steps in the purification process.

[0029] For example, if a neutralizing agent is used in reaction step A, it is preferable to remove the neutralizing agent before liquid-liquid purification step B. The method of removing the neutralizing agent is appropriately selected depending on the type of neutralizing agent. For example, if amines are used, their hydrochloride salts are formed and should be removed by filtration or the like. If no neutralizing agent is used, it is preferable to remove as much dissolved hydrogen chloride gas as possible from the system by bubbling with nitrogen gas or heating and stirring before proceeding with liquid-liquid purification step B.

[0030] Furthermore, the solvent used in reaction step A may be removed before liquid-liquid purification step B, if necessary. The method of solvent removal is not particularly limited and can be, for example, by distillation under reduced pressure.

[0031] (Separation purification process B) In the liquid-liquid purification step, the crude trimellitic anhydride ester obtained in reaction step A described above is mixed with a purification solvent and water, and then liquid-liquid purification is performed. The trimellitic anhydride ester in the crude trimellitic anhydride ester dissolves in the purification solvent. On the other hand, water-soluble impurities (e.g., chlorine compounds) dissolve in water. Therefore, by performing this liquid-liquid purification, the purity of the obtained trimellitic anhydride ester can be increased.

[0032] The purification solvent used in this process is a solvent containing at least one of the following: a hydrocarbon solvent with an SP value of 7.8 to 9.1 and an ester solvent with an SP value of 7.8 to 9.1. Examples of such solvents include ester solvents such as ethyl acetate (SP value: 9.1), propyl acetate (SP value: 8.8), isopropyl acetate (SP value: 8.4), butyl acetate (SP value: 8.5), and isobutyl acetate (SP value: 8.3); and hydrocarbon solvents such as cyclohexane (SP value: 8.2), methylcyclohexane (SP value: 7.8), toluene (SP value: 8.9), and xylene (SP value: 8.8). Among these, butyl acetate, propyl acetate, and methylcyclohexane are preferred because they are less likely to dissolve impurities and chlorine-containing compounds such as hydrogen chloride, and furthermore, the purification solvent can be easily removed in the ring-closing and solvent distillation step C described later.

[0033] The amounts of the purifying solvent and water used in liquid-liquid purification are appropriately selected according to the amount of crude trimellitic anhydride. The amount of purifying solvent is not particularly limited, as long as it is sufficient to sufficiently dissolve the trimellitic anhydride in the crude trimellitic anhydride. For example, 1900 parts by mass or more and 150 parts by mass or less, and 550 parts by mass or more and 250 parts by mass or less, per 100 parts by mass of crude trimellitic anhydride, is preferred. When the amount of purifying solvent is within this range, it becomes easier to further dissolve the trimellitic anhydride. Also, the distillation of the purifying solvent in the ring-closing and distillation step C described later is less likely to be excessively long. On the other hand, the amount of water is not particularly limited, as long as it is sufficient to sufficiently dissolve the water-soluble components in the crude trimellitic anhydride. For example, 10 parts by mass or more and 100 parts by mass or less, and 30 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the total amount of purifying solvent and crude trimellitic anhydride, is preferred. When the amount of water is within this range, the purity of the obtained trimellitic anhydride tends to be further increased.

[0034] There are no particular limitations on the method of mixing the crude trimellitic anhydride with the purification solvent and water. For example, the purification solvent and water may be mixed directly with the solution containing the crude trimellitic anhydride obtained in reaction step A described above. Alternatively, the solvent used in the reaction may be removed from the solution obtained in reaction step A as described above, and the purification solvent and water may be mixed with the remaining components. In this case, the purification solvent and water may be mixed at once, but it is more preferable from the viewpoint of yield, etc., to first mix the purification solvent to dissolve the trimellitic anhydride in the purification solvent, and then add water.

[0035] Crude trimellitic anhydride is mixed with the purification solvent and water, and then thoroughly mixed by shaking or other means. After mixing, the mixture is allowed to stand to separate it into a purification solvent layer (organic layer) and an aqueous layer, and the aqueous layer is removed. Water is added again to the purification solvent layer, and the shaking, standing, and aqueous layer removal process is repeated in the same manner. This liquid-liquid separation treatment is preferably performed multiple times, i.e., two or more times, and more preferably three to five times.

[0036] During the above-described liquid-liquid separation process, the temperature of the mixture of crude trimellitic anhydride, purification solvent, and water is adjusted to be between 30°C and 70°C. By adjusting the temperature of the mixture to this range, the trimellitic anhydride becomes more easily soluble in the purification solvent, and the water-soluble components in the crude trimellitic anhydride migrate more easily into the aqueous layer. In other words, the purity of the resulting trimellitic anhydride is increased, and the chlorine content can be reduced.

[0037] The method for adjusting the temperature of the above mixture is not particularly limited. For example, the temperature of the purification solvent or water may be adjusted before mixing with the crude trimellitic anhydride. Alternatively, after mixing the crude trimellitic anhydride, the purification solvent, and water, these may be heated as appropriate to adjust the temperature to fall within the above temperature range. The temperature of the above mixture is preferably 30°C to 60°C, and more preferably 40°C to 50°C. When the temperature of the mixture is within this range, the above effects are more easily obtained.

[0038] (Ring closure and solvent removal process C) In the ring-closing and solvent-removal step, acetic anhydride is mixed with the solution containing the crude trimellitic anhydride and the purification solvent after the liquid-liquid purification step B, and the mixture is heated. The purification solvent is then removed from the heated solution by distillation. As mentioned above, the crude trimellitic anhydride contains some of the ring-opened trimellitic anhydride. Therefore, by mixing the crude trimellitic anhydride with acetic anhydride and heating the mixture, the ring-opened portion of the trimellitic anhydride is closed. Consequently, the purity of the resulting trimellitic anhydride is further increased.

[0039] When performing the ring closure described above, it is preferable to mix 160 to 230 parts by mass of acetic anhydride with 100 parts by mass of crude trimellitic anhydride. If the amount of acetic anhydride is less than 160 parts by mass per 100 parts by mass of crude trimellitic anhydride, a decrease in purity may occur. On the other hand, if the amount of acetic anhydride exceeds 230 parts by mass, a decrease in purity may also occur. The amount of acetic anhydride is preferably 180 to 220 parts by mass, and more preferably 190 to 210 parts by mass, per 100 parts by mass of crude trimellitic anhydride.

[0040] The temperature for the ring-closing reaction is preferably between 80°C and 110°C, and more preferably between 90°C and 100°C. Below 80°C, the redissolution of trimellitic anhydride ester in the purification solvent may be insufficient, and above 110°C, impurities may be generated, leading to a decrease in purity. The heating time is usually preferably between 30 minutes and 160 minutes, and more preferably between 60 minutes and 120 minutes.

[0041] After the ring-closing reaction described above, the aforementioned purification solvent is removed from the solution by distillation. It is preferable to simultaneously remove acetic anhydride. The method for removing the purification solvent is not particularly limited and can be carried out according to conventional methods. For example, it can be done by vacuum distillation. This allows for the acquisition of the desired trimellitic anhydride ester with high purity and low chlorine content in high yield.

[0042] (Regarding trimellitic anhydride esters) The viscosity of the trimellitic anhydride ester obtained by the above method is not particularly limited, but from the viewpoint of efficient production by the above method (especially solvent removal), it is preferable that the viscosity at 40°C be 1000 Pa·s or less, more preferably 600 Pa·s or less, even more preferably 400 Pa·s or less, and particularly preferable to be 300 Pa·s or less. Furthermore, it is preferable that the viscosity at 40°C be 1 Pa·s or more, more preferably 10 Pa·s or more, even more preferably 100 Pa·s or more, and particularly preferable to be 200 Pa·s or more. The viscosity of the trimellitic anhydride ester can be measured using general-purpose devices such as B-type viscometers and E-type viscometers. For example, when using an E-type viscometer, the viscosity can be measured by using a device such as a TV-25 viscometer (manufactured by Toki Sangyo Co., Ltd.) and setting an appropriate cone plate, rotation speed, temperature, and sample amount according to the properties of the liquid.

[0043] Furthermore, the chlorine content of the trimellitic anhydride ester obtained above is preferably 20 ppm or less, and more preferably less than 10 ppm. When the chlorine content of the trimellitic anhydride ester is 20 ppm or less, it becomes easier to use the trimellitic anhydride ester in electronic materials. The chlorine content in the trimellitic anhydride ester can be determined by potentiometric titration. [Examples]

[0044] The present invention will be described in more detail below with reference to examples, but the present invention will not exceed its gist. However, this is not limited to the following embodiments.

[0045] [Example 1] (Reaction step A) 50.0 g (0.24 mol) of trimellitic anhydride chloride was dissolved in 200.0 g of tetrahydrofuran (THF), charged into a reactor under nitrogen, and cooled to 15°C in a water bath. To this, a solution of 18.1 g (0.11 mol) of 2-butyl-2-ethyl-1,3-propanediol and 18.8 g (0.24 mol) of pyridine dissolved in 18.1 g of THF was added dropwise over 30 minutes. During this time, pyridine hydrochloride precipitated, and the internal temperature of the reaction mixture rose to 25°C. The reaction was continued at this temperature for another hour. After the reaction was complete, pyridine hydrochloride was filtered off, and the resulting filtrate was distilled off under reduced pressure at 300 mmHg and 60°C. The remaining amount of THF at this time was 7.5 g.

[0046] (Separation purification process B) To the solution after distillation under reduced pressure, 230.0 g of ethyl acetate (boiling point 77°C, SP value: 9.1) was mixed as a purification solvent so that the concentration of crude trimellitic anhydride was 20% by mass. Then, 76.7 g of water was added and the mixture was shaken at 40°C. After standing for 10 minutes, the lower aqueous layer was removed. Furthermore, the separation procedure consisting of adding water, shaking, standing, and removing the aqueous layer was repeated three times. This yielded an ethyl acetate solution containing trimellitic anhydride.

[0047] (Ring closure and solvent removal process C) To the above ethyl acetate solution containing trimellitic anhydride, 121.2 g of acetic anhydride was added and heated and stirred at 85°C. After stirring for 2 hours, the mixture was distilled under reduced pressure at 40 mmHg until no more purifying solvent flowed out, yielding 46.4 g of a gum-like substance.

[0048] [Example 2] (Reaction step A) 50.0 g (0.24 mol) of trimellitic anhydride chloride was dissolved in 200.0 g of tetrahydrofuran (THF), charged into a reactor under nitrogen, and cooled to 15°C in a water bath. To this, a solution of 18.1 g (0.11 mol) of 2-butyl-2-ethyl-1,3-propanediol and 18.8 g (0.24 mol) of pyridine dissolved in 18.1 g of THF was added dropwise over 30 minutes. During this time, pyridine hydrochloride precipitated, and the internal temperature of the reaction mixture rose to 25°C. The reaction was continued at this temperature for another hour. After the reaction was complete, pyridine hydrochloride was filtered off, and the resulting filtrate was distilled off under reduced pressure at 300 mmHg and 60°C. The remaining amount of THF at this time was 7.5 g.

[0049] (Separation purification process B) To the solution after distillation under reduced pressure, 230.0 g of butyl acetate (boiling point 126°C, SP value: 8.5) was mixed as a purification solvent so that the concentration of crude trimellitic anhydride was 20% by mass. Then, 76.7 g of water was added and the mixture was shaken at 60°C. After standing for 10 minutes, the lower aqueous layer was removed. Furthermore, the separation procedure consisting of adding water, shaking, standing, and removing the aqueous layer was repeated three times. This yielded a butyl acetate solution containing trimellitic anhydride.

[0050] (Ring closure and solvent removal process C) To the above butyl acetate solution containing trimellitic anhydride, 121.2 g of acetic anhydride was added and heated and stirred at 85°C. After stirring for 2 hours, the mixture was distilled under reduced pressure at 40 mmHg until no more purifying solvent flowed out, yielding 52.6 g of a gum-like substance.

[0051] [Example 3] The preparation of trimellitic anhydride was carried out in the same manner as in Example 2, except that the temperature of butyl acetate and water in liquid-liquid purification step B was set to 40°C, and the separation operation was performed only three times. This yielded 51.5 g of a gum-like substance.

[0052] [Example 4] The trimellitic anhydride ester was prepared in the same manner as in Example 2, except that methylcyclohexane (boiling point 101°C, SP value: 7.8) was used as the purification solvent in liquid-liquid purification step B. This yielded 47.5 g of a gum-like substance.

[0053] [Example 5] The trimellitic anhydride ester was prepared in the same manner as in Example 1, except that toluene (boiling point 111°C, SP value: 8.9) was used as the purification solvent in liquid-liquid purification step B. This yielded 46.4 g of a gum-like substance.

[0054] [Comparative Example 1] The trimellitic anhydride ester was prepared in the same manner as in Example 1, except that the temperature of the purification solvent and water in liquid-liquid purification step B was set to 20°C. This yielded 39.2 g of a gum-like substance.

[0055] [Comparative Example 2] The trimellitic anhydride ester was prepared in the same manner as in Example 1, except that the temperature of the purification solvent and water in liquid-liquid purification step B was set to 80°C. This yielded 41.9 g of a gum-like substance.

[0056] [Comparative Example 3] The reaction process A and the separatory purification process B were carried out in the same manner as in Example 1, except that hexane (boiling point 69°C, SP value: 7.3) was used as the purification solvent in the separatory purification process B. However, the trimellitic anhydride ester did not dissolve in hexane in the separatory purification process B and could not be purified.

[0057] [Comparative Example 4] Reaction step A and liquid-liquid purification step B were carried out in the same manner as in Example 1, except that methyl ethyl ketone (boiling point 56.1°C, SP value: 9.3) was used as the purification solvent in liquid-liquid purification step B, and the temperature of the purification solvent and water was set to 80°C. However, a mixed layer of the aqueous layer and organic layer was generated in liquid-liquid purification step B, making liquid-liquid purification difficult.

[0058] [evaluation] The trimellitic anhydride esters obtained in the examples and comparative examples were analyzed as follows. The results are shown in Table 1.

[0059] (1) Yield The yield was calculated based on the following formula. Yield = Actual yield / Theoretical yield × 100 The final amount of trimellitic anhydride ester obtained was defined as the yield. The amount of moles of raw material used was also defined as the theoretical yield, calculated by multiplying the amount of trimellitic anhydride ester by its molecular weight. The evaluation criteria were as follows:

[0060] <Evaluation Criteria> ◎: Yield is 90% or higher. ○: Yield is between 70% and 90% ×: Yield is 70% or less.

[0061] (2) Analysis of purity by high-performance liquid chromatography The purity of the obtained trimellitic anhydride ester was determined as follows: 0.35 g of aniline and 0.90 g of NMP (N-methylpyrrolidone) were weighed out, and 0.10 g of trimellitic anhydride ester prepared in the examples and comparative examples were added to each, and the mixture was stirred for 1 hour to convert them into anilide derivatives. 0.4 g of the resulting anilide derivative solution was diluted with 3 mL of eluent to prepare the measurement solution. High-performance liquid chromatography analysis was then performed under the following conditions, and the purity was determined based on the following formula. Purity (%) = (Area derived from trimellitic anhydride (target product) / (Area derived from target product + Area of ​​the one-ring open form of trimellitic anhydride + Area of ​​the two-ring open form of trimellitic anhydride) × 100 The evaluation criteria are shown below.

[0062] (Measurement conditions) Equipment: Shimadzu High-Speed ​​Liquid Chromatograph Detector: UV absorption photometer (measurement wavelength 254 nm) Column: YMC-PackODS-A Column temperature: 40℃ Flow rate: 1.0mL / min Measurement time: 20 min Eluent: Acetonitrile / 0.1% phosphoric acid aqueous solution = 60 / 40 (v / v) Sample adjustment:

[0063] <Evaluation Criteria> ◎: Purity is 99% or higher ○: Purity is between 97% and 99%. ×: Purity is less than 97%

[0064] (3) Analysis of chlorine content by potentiometric titration The chlorine content of the trimellitic anhydride esters obtained in the examples and comparative examples was analyzed using the following analytical apparatus. The evaluation criteria are shown below.

[0065] <Analyzer> Equipment: Hiranuma Automatic Titrator COM-1700 Eluent: THF / 30% nitric acid = 60 / 10 (mL) Titrant: 0.002M silver nitrate aqueous solution (2mM silver nitrate aqueous solution)

[0066] <Evaluation Criteria> ◎: Chlorine content is less than 10 ppm ○: Chlorine content is between 10 ppm and 20 ppm. ×: Chlorine content exceeds 20 ppm

[0067] [result] [Table 1]

[0068] As shown in Table 1, when a purification solvent containing at least one of a hydrocarbon solvent with an SP value of 7.8 to 9.1 and an ester solvent with an SP value of 7.8 to 9.1 was used in separation and purification step B, and liquid-liquid purification was performed at a temperature of 30°C to 70°C, the yield was 83% or higher (Examples 1-5). Furthermore, the purity of the obtained trimellitic anhydride ester was 97% or higher, and the chlorine content was kept below 10 ppm.

[0069] In contrast, when the temperature in the liquid-liquid purification process was below 30°C, the yield decreased and the chlorine content increased (Comparative Example 1). Also, when the temperature in the liquid-liquid purification process exceeded 70°C, the purity decreased and the chlorine content increased (Comparative Example 2).

[0070] Furthermore, when the SP value of the purification solvent was less than 7.8 or greater than 9.1, trimellitic anhydride ester could not be separated (Comparative Examples 3 and 4). [Industrial applicability]

[0071] The trimellitic anhydride ester obtained in this invention is a heat-resistant resin such as polyimide and In addition to being a raw material for riamic acid, it is also advantageous as a curing agent for epoxy resins and polyurethane resins. It can be used. In particular, since the present invention yields a high-purity product, it can be used in electronic component materials and optical applications where high-purity quality is required in recent years.

Claims

1. Step A involves reacting trimellitic anhydride halide with a branched alkanediol represented by the following general formula (1) to obtain a crude trimellitic anhydride containing a trimellitic anhydride represented by the following general formula (2). 【Chemistry 1】 (In general formula (1), R １ (This represents an alkylene group having a branched structure with 3 to 17 carbon atoms.) 【Chemistry 2】 (In general formula (2), R １ (This represents an alkylene group having a branched structure with 3 to 17 carbon atoms.) The process of purifying the crude trimellitic anhydride ester, Includes, The step of purifying the crude trimellitic anhydride ester is as follows: Step B involves adding a purification solvent containing at least one of a hydrocarbon solvent with an SP value of 7.8 or more and an ester solvent with an SP value of 7.8 or more and 9.1, as well as water, to the crude trimellitic anhydride ester and performing liquid-liquid purification at 30°C or more and 70°C or less. Step C involves adding acetic anhydride to the solution containing the crude trimellitic anhydride and the purification solvent after liquid-liquid purification and heating it, and then distilling off the purification solvent from the heated solution. A method for producing trimellitic anhydride ester, including the method described above.

2. It is expressed by the following general formula (2), 【Transformation 3】 (In general formula (2), R １ (This represents an alkylene group having a branched structure with 3 to 17 carbon atoms.) The chlorine content is 20 ppm or less. Trimellitus anhydride.

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