Crystals of isosorbide-bis(trimellitate anhydride) and method for producing the same

Abstract

The present invention addresses the problem of providing a highly pure isosorbide-bis(trimellitate anhydride) crystal that is suitable as a resin starting material. As a solution to this problem, the present invention provides an isosorbide-bis(trimellitate anhydride) crystal, specifically, an isosorbide-bis(trimellitate anhydride) crystal that has an endothermic peak in a specific range in differential scanning calorimetry, or a specific peak in a powder X-ray diffraction peak pattern by Cu-Kα rays.

Description

[Technical Field]

[0001] The present invention relates to a crystal of isosorbide-bis(trimellitate anhydride) and a method for producing the same. [Background Art]

[0002] Carboxylic acid anhydrides are compounds widely used in the fields of organic chemistry and polymer chemistry, and are a group of compounds useful in a wide range of fields such as medical and agrochemical raw materials, resin raw materials, and electronic information materials. Among these, for material applications, they are frequently used as monomers for polymer materials, for example, raw materials for polyimides and polyamides, polyester modifiers, epoxy resin curing agents, and the like. In recent years, bio-based resins using raw materials derived from biomass resources for these polymer materials have attracted attention as environmentally friendly materials. For example, dianhydrohexitol having a hydroxyl group that can be easily modified is increasingly applied because high transparency and excellent heat resistance derived from its alicyclic structure are expected therefrom. There are few reports on modifying dianhydrohexitol with an acid anhydride structure, and only Patent Document 1 discloses modification with trimellitic acid, which allows easy introduction of an acid anhydride structure. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Chinese Patent Application Publication No. 101648958 Specification [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] Although Patent Document 1 describes isosorbide-bis(trimellitate anhydride) represented by formula (A) (hereinafter sometimes referred to as compound A), it only discloses the production method thereof and NMR data of the obtained substance. When the present inventor conducted a reproduction experiment of the production method, the purity of the obtained substance was low, and a single substance could not be obtained as a crystal. [ka] This invention was made against the background described above, and aims to provide crystals of compound A that are of high purity and suitable as a resin raw material. [Means for solving the problem]

[0005] As a result of diligent research to solve the above-mentioned problems, the present inventors have discovered crystals of compound A, particularly crystals having a specific range of melting endothermic peaks as determined by differential scanning calorimetry, and crystals having specific peaks in the powder X-ray diffraction peak pattern using Cu-Kα rays, as well as a method for producing the same, and have completed the present invention.

[0006] The present invention is as follows: 1. Crystals of isosorbido-bis(trimellitate anhydride). 2. The crystal described in 1., wherein the melting endothermic peak determined by differential scanning calorimetry is in the range of 214-220°C. 3. The crystal according to 1, wherein the powder X-ray diffraction peak pattern using Cu-Kα rays has diffraction peaks at diffraction angles 2θ of 17.8±0.2°, 23.4±0.2°, 24.8±0.2°, 27.0±0.2°, and 30.4±0.2°. 4. The crystal described in 1., wherein the melting endothermic peak determined by differential scanning calorimetry is in the range of 225-231°C. 5. The crystal according to 1, wherein the powder X-ray diffraction peak pattern using Cu-Kα rays has diffraction peaks at diffraction angles 2θ of 15.1±0.2°, 17.9±0.2°, 19.8±0.2°, and 29.1±0.2°. 6. A crystal described in any one of items 1 to 5, in which the purity of isosorbide-bis(trimellitate anhydride) is 90.0% or higher as measured by gel permeation chromatography. 7. A method for producing the crystal described in 1, wherein isosorbide and trimellitic anhydride halide are reacted in the presence of a base and an aliphatic nitrile solvent. 8. A method for producing crystals according to 1, wherein a solid isosorbide-bis(trimellitate anhydride) is purified with a solvent containing an aromatic hydrocarbon solvent. 9. A method for producing crystals as described in 1, comprising the steps of: reacting isosorbide with trimellitic anhydride halide in the presence of a base and an aliphatic nitrile solvent to obtain crude crystals (step 1); and purifying the obtained crude crystals with a solvent (step 2). [Effects of the Invention]

[0007] The crystal of the present invention makes it possible to handle compound A in a form that is of higher purity and easier to handle than conventional methods. Furthermore, the manufacturing method of the present invention makes it possible to obtain compound A in high purity and stably as crystals. In addition, since it is possible to obtain crystals with a small amount of solvent compared to conventionally known methods, it is advantageous and very useful for the industrial production of compound A, as it improves industrial production efficiency and reduces waste. In other words, the crystals and methods for producing them according to the present invention are extremely useful in the industrial use of compound A. [Brief explanation of the drawing]

[0008] [Figure 1] This chart shows the differential scanning calorimetry data of the crystal obtained in Example 1. [Figure 2] This chart shows the powder X-ray diffraction data obtained using Cu-Kα rays for the crystal obtained in Example 1. [Figure 3] This chart shows the differential scanning calorimetry data of the crystal obtained in Example 2. [Figure 4] This chart shows the powder X-ray diffraction data obtained using Cu-Kα rays for the crystals obtained in Example 2. [Modes for carrying out the invention]

[0009] <Method for synthesizing compound A> There are no particular restrictions on the method for synthesizing Compound A relating to the crystal of the present invention, and examples thereof include a method of reacting isosorbide with trimellitic anhydride halide in the presence of a base and a reaction solvent.

Chemical Formula

[0010] Examples of the trimellitic anhydride halide include trimellitic anhydride chloride, trimellitic anhydride bromide, trimellitic anhydride iodide, and trimellitic anhydride fluoride. Among these trimellitic anhydride halides, trimellitic anhydride chloride is preferably used because it is inexpensive and readily available. The amount of the trimellitic anhydride halide to be used is not particularly limited as long as the charged molar ratio relative to isosorbide is equal to or greater than the theoretical value (2.0). It is usually used in an amount ranging from 2 to 10 times by mole, preferably from 2 to 6 times by mole, more preferably from 2 to 4 times by mole.

[0011] The reaction between isosorbide and trimellitic anhydride halide generates hydrogen halide, so a base is used to trap the hydrogen halide. The base is not particularly limited, and organic tertiary amines such as pyridine, triethylamine, and N,N-dimethylaniline, epoxides such as propylene oxide, and inorganic bases such as potassium carbonate and sodium hydroxide can be used. Among these, pyridine is preferably used from the viewpoints of separation operation after reaction, cost, harmfulness and the like. The amount of the base to be used is not particularly limited as long as the charged molar ratio relative to isosorbide is equal to or greater than the theoretical value (2.0). It is usually used in an amount ranging from 2 to 20 times by mole, preferably from 2 to 10 times by mole, more preferably from 2 to 5 times by mole.

[0012] The reaction solvent is not particularly limited as long as it does not distill out of the reaction vessel at the reaction temperature and is inert to the reaction. Examples thereof include aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbon solvents such as pentane, hexane, heptane and cyclohexane; aliphatic ester solvents such as ethyl acetate and n-butyl acetate; lactone solvents such as γ-butyrolactone; aliphatic ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; aliphatic ether solvents such as tetrahydrofuran, dioxane and methyl t-butyl ether; and aliphatic nitrile solvents such as acetonitrile and propionitrile. These reaction solvents may be used alone, respectively, or two or more kinds may be used in combination as appropriate in order to adjust polarity. Among them, aliphatic nitrile solvents are preferred. The amount of the reaction solvent used is preferably in the range of 1 to 50 times by weight, more preferably in the range of 2 to 20 times by weight, and still more preferably in the range of 4 to 15 times by weight relative to isosorbide.

[0013] As reaction conditions, the reaction temperature is preferably in the range of -20 to 50°C, more preferably in the range of -10 to 25°C. If the reaction temperature is high, the yield decreases due to hydrolysis or the like of the produced ester compound, and if the reaction temperature is low, the reaction rate becomes slow, which is not preferable. In addition, the reaction is usually carried out under normal pressure; however, depending on the boiling point of the organic solvent used, the reaction may be carried out under increased or reduced pressure so that the reaction temperature falls within the above range. The end point of the reaction can be confirmed by liquid chromatography including gel permeation chromatography or gas chromatography analysis. It is preferable to take the point at which unreacted isosorbide disappears and no further increase in the target compound A is observed as the end point of the reaction. Although the reaction time varies depending on reaction conditions such as the reaction temperature, the reaction is usually completed in about 1 to 30 hours.

[0014] (Method 1 for producing the crystal of the present invention) The crystal of the present invention can be produced by reacting isosorbide and trimellitic anhydride halide in the presence of a base and an aliphatic nitrile solvent. The trimellitic acid halide, base, and aliphatic nitrile solvent used as reaction solvent, their amounts, and reaction conditions are the same as those for the synthesis of compound A described above. After the reaction is complete, crystals of the target compound A precipitate in the reaction product mixture. Alternatively, crystals of compound A precipitate upon cooling of the reaction product mixture.

[0015] (Method for producing the crystal of the present invention 2) The crystals of the present invention can be produced by purifying a solid of compound A with a solvent containing an aromatic hydrocarbon solvent. In this manufacturing method 2, "purification" means dissolving the solid compound A in a solvent and performing a crystallization operation, or performing a reslurry operation on the solid compound A in a solvent.

[0016] The solid of compound A can be obtained by removing the solvent from the reaction product mixture of compound A obtained by the synthesis method described above, by adding it dropwise to a poor solvent, by column purification, or by carrying out the crystal production method 1 described above. Such a solid may be amorphous or crystalline. By purifying the solid of compound A using this production method 2, it is possible to increase its purity, and in some cases, crystals with a different chemical structure from the crystals before purification may be obtained. Examples of aromatic hydrocarbon solvents that can be used include toluene and xylene. The amount of aromatic hydrocarbon solvent used is preferably in the range of 0.5 to 20 times the weight of the solid compound A, more preferably in the range of 1 to 10 times, and even more preferably in the range of 2 to 6 times. Other solvents besides aromatic hydrocarbon solvents may be used in combination. Examples of such solvents include aliphatic hydrocarbon solvents such as pentane, hexane, heptane, and cyclohexane; aliphatic ester solvents such as ethyl acetate and n-butyl acetate; lactone solvents such as γ-butyrolactone; aliphatic ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aliphatic ether solvents such as tetrahydrofuran, dioxane, and methyl-t-butyl ether; aliphatic nitrile solvents such as acetonitrile and propionitrile; and water. Among these, aliphatic nitrile solvents are preferred. The amount of such solvent used is preferably 0.1 to 4 times the weight of the aromatic hydrocarbon solvent used, more preferably 0.1 to 3 times, even more preferably 0.1 to 2 times, and particularly preferably 0.1 to 1.5 times. In this manufacturing method 2, if the acid anhydride portion of compound A undergoes hydrolysis in part or all due to moisture in the air during handling, an acid anhydride such as acetic anhydride may be used for the purpose of dehydrating and condensing it back into an acid anhydride.

[0017] When performing a crystallization operation by dissolving the solid compound A in a solvent, the solid compound A is added to the solvent used for purification, heated to a solution state, and then cooled. When performing a slurry procedure on the solid compound A in a solvent, the solid compound A is added to the solvent used for purification, heated to form a slurry, and then cooled. The order of these addition and heating steps does not matter. Purification by slurry operation is preferable because it eliminates the need for seed crystals and allows for the acquisition of high-purity crystals of compound A. The heating temperature range is 40 to 100°C, with a range of 60 to 85°C being more preferable. The cooling rate is preferably in the range of 1 to 40°C per hour, more preferably in the range of 2 to 30°C per hour, and even more preferably in the range of 5 to 20°C per hour. The temperature range after cooling is 0 to 40°C, and more preferably 20 to 30°C.

[0018] (Method for producing the crystal of the present invention 3) The crystals of the present invention can be produced by a method comprising the steps of: reacting isosorbide and trimellitic anhydride halide in the presence of a base and an aliphatic nitrile solvent to obtain crude crystals (step 1); and purifying the obtained crude crystals with a solvent (step 2).

[0019] In step 1, the trimellitic acid halide, base, aliphatic nitrile solvent used as the reaction solvent, the amounts of these used, and the reaction conditions are the same as those for the synthesis of compound A described above. After the reaction is complete, crude crystals of compound A precipitate in the reaction product mixture. Alternatively, crude crystals of compound A precipitate by cooling the reaction product mixture.

[0020] Step 2 is the process of purifying the crude crystals obtained in Step 1 with a solvent. In Step 2, "purification" means dissolving the crude crystals in a solvent and performing a crystallization operation, or performing a reslurry operation on the crude crystals with a solvent. Examples of solvents used in step 2 include aromatic hydrocarbon solvents such as toluene and xylene, aliphatic hydrocarbon solvents such as pentane, hexane, heptane, and cyclohexane, aliphatic ester solvents such as ethyl acetate and n-butyl acetate, lactone solvents such as γ-butyrolactone, aliphatic ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, aliphatic ether solvents such as tetrahydrofuran, dioxane, and methyl-t-butyl ether, aliphatic nitrile solvents such as acetonitrile and propionitrile, and water. These solvents may be used individually, or two or more may be used in combination as appropriate to adjust the polarity. Among these, aliphatic nitrile solvents and aromatic hydrocarbon solvents are preferred. The amount of solvent used in step 2 is preferably in the range of 0.5 to 20 times the weight of the crude crystal of compound A obtained in step 1, more preferably in the range of 1 to 10 times, and even more preferably in the range of 2 to 6 times. In step 2, if the acid anhydride portion of compound A undergoes hydrolysis in part or all due to moisture in the air during handling, an acid anhydride such as acetic anhydride may be used for the purpose of dehydrating and condensing it back into an acid anhydride.

[0021] When performing crystallization by dissolving crude crystals of compound A in a solvent, the crude crystals of compound A are added to the solvent used for purification, heated to a solution state, and then cooled. When performing a slurry procedure on crude crystals of compound A in a solvent, the crude crystals of compound A are added to the solvent used for purification, heated to form a slurry, and then cooled. The order of these addition and heating steps does not matter. In step 2, purification by reslurry operation is preferable because it eliminates the need for seed crystals and allows for the acquisition of high-purity crystals of compound A. The heating temperature range is 40 to 100°C, more preferably 60 to 85°C. The cooling rate is preferably in the range of 1 to 40°C per hour, more preferably in the range of 2 to 30°C per hour, and even more preferably in the range of 5 to 20°C per hour. The temperature after cooling is in the range of 0 to 40°C, and more preferably in the range of 20 to 30°C.

[0022] The crystals obtained by the method described above can be isolated using conventional methods, for example, by centrifugal filtration. Furthermore, it is preferable to wash the crystals with a solvent. Examples of solvents that can be used at this time include aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, aliphatic ester solvents, aliphatic ketone solvents, aliphatic ether solvents, aliphatic nitrile solvents, and water. Specifically, toluene, xylene, pentane, hexane, heptane, cyclohexane, ethyl acetate, n-butyl acetate, γ-butyrolactone, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, methyl-t-butyl ether, acetonitrile, and propionitrile are preferred, with toluene, γ-butyrolactone, acetone, methyl ethyl ketone, tetrahydrofuran, and acetonitrile being more preferred, and acetonitrile being particularly preferred. The amount of solvent used is in the range of 0.5 to 10 times the weight of the obtained crystals, preferably in the range of 0.5 to 6 times, and particularly preferably in the range of 1 to 4 times.

[0023] The obtained crystals can be dried to remove the solvent used, and if the acid anhydride portion of compound A hydrolyzed during the operation, it can be dehydrated and condensed to produce the acid anhydride. The drying operation can preferably be carried out at a temperature in the range of 30 to 100°C, more preferably in the range of 40 to 80°C. Drying can be carried out at atmospheric pressure or reduced pressure, but in industrial operations, it is preferable to carry it out under reduced pressure of about 10 kPa because it is more efficient in removing the solvent used. The crystals of compound A obtained in this way are expected to have improved reactivity due to their high purity when used in polymerization as a polyimide monomer, as well as excellent handling properties.

[0024] <Crystal of the present invention> This invention relates to isosorbide-bis(trimellitate anhydride) crystals. The crystal of the present invention includes at least two types of crystals: crystal A and crystal B. Crystal A of the present invention is a crystal having a melting endothermic peak determined by differential scanning calorimetry in the range of 214 to 220°C, preferably in the range of 215 to 219°C, more preferably in the range of 216 to 219°C, and even more preferably in the range of 217 to 219°C. Furthermore, crystal A of the present invention is a crystal having diffraction peaks at diffraction angles 2θ of 17.8±0.2°, 23.4±0.2°, 24.8±0.2°, 27.0±0.2°, and 30.4±0.2° in its powder X-ray diffraction peak pattern using Cu-Kα rays. Crystal B of the present invention is a crystal in which the melting endothermic peak determined by differential scanning calorimetry is in the range of 225 to 231°C, preferably in the range of 226 to 230°C, more preferably in the range of 227 to 230°C, and even more preferably in the range of 228 to 230°C. Furthermore, crystal B of the present invention is a crystal having diffraction peaks at diffraction angles 2θ of 15.1±0.2°, 17.9±0.2°, 19.8±0.2°, and 29.1±0.2° in its powder X-ray diffraction peak pattern using Cu-Kα rays. The crystals of the present invention contain compound A with a purity of 90.0% or higher in gel permeation chromatography measurements, more specifically, compound A in an area of ​​90.0% or higher, preferably 95.0% or higher, more preferably 97.0% or higher, and even more preferably 98.0% or higher, relative to the total amount of all components detected by gel permeation chromatography measurements. [Examples]

[0025] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The analysis method is as follows: <Analysis method> 1. Gel Permeation Chromatography (GPC) Equipment: HLC-8320GPC (manufactured by Tosoh Corporation) Detector: Differential refractometer (RI) (Measurement conditions) Mobile phase: Tetrahydrofuran (containing stabilizer) Flow rate: 1.0mL / min Injection volume: 100 μL Column temperature: 40℃ Columns: 1 x TSKgel guardcolumn HXL-L, 2 x TSKgel G2000HXL, 1 x TSKgel G3000HXL, 1 x TSKgel G4000HXL 2. Differential Scanning Calorimetry (DSC) The crystals were precisely weighed into an aluminum pan and measured using the differential scanning calorimetry apparatus described below, with aluminum oxide as a control, under the measurement conditions described below. Equipment: DSC7020 (manufactured by Hitachi High-Tech Science Co., Ltd.) (Measurement conditions) Heating rate: 10℃ / min Measurement temperature range: 30~300℃ Measurement atmosphere: Open, 50 mL / min nitrogen Sample volume: 3 mg ± 1 mg 3. Powder X-ray diffraction (XRD) 0.1 g of crystals was placed in the sample packing area of ​​a glass test plate, and measured using the following powder X-ray diffractometer under the following conditions. Device: MiniFlex600 (manufactured by Rigaku Corporation) (Measurement conditions) X-ray source:Cu-Kα Scan axis: 2θ / θ Mode: Continuous Measurement range: 2θ = 5° to 90° Step: 0.02° Speed ​​measurement time: 2θ = 10° / min Divergence slit: 1 / 4 Light-receiving slit: 13.00 mm Output: 40kV-15mA

[0026] <Example 1> (Crystals of the present invention: Examples of step 1 of manufacturing method 1 and manufacturing method 3) In a four-necked flask equipped with a thermometer, stirrer, and condenser, 59.1 g (0.28 mol) of trimellitic chloride anhydride and 80.0 g of acetonitrile were charged. The reaction vessel was purged with nitrogen while stirring to dissolve the compounds, and cooled to below 5°C. Subsequently, a preparation containing 20.0 g (0.14 mol) of isosorbide, 100.0 g of acetonitrile, and 32.5 g (0.41 mol) of pyridine was added dropwise at a constant rate over 2 hours while maintaining the temperature in the reaction vessel below 5°C. After the addition was complete, the mixture was stirred at below 5°C for 1 hour. Then, the temperature was raised to 25°C and stirred overnight. The resulting white solid was filtered to obtain 48.2 g. GPC analysis of the obtained white solid showed that compound A accounted for 96.3 area% (purity 96.3%) of the total amount of all components detected by GPC. Differential scanning calorimetry (DSC) analysis of the obtained white solid revealed endothermic melting peaks. This result clearly indicates that the obtained white solid is crystalline. Figure 1 shows a chart illustrating the DSC data. The endothermic melting peaks observed in this DSC analysis were at 217.6°C and 225.1°C. Furthermore, powder X-ray diffraction measurements using Cu-Kα rays were performed on the obtained white solid, and the peak pattern clearly indicated that the obtained white solid was crystalline. A chart showing the powder X-ray diffraction data using Cu-Kα rays is shown in Figure 2. The diffraction angle 2θ(°) of the observed diffraction peaks and the relative intensity relative to the peak with the strongest intensity are shown in Table 1.

[0027] [Table 1]

[0028] <Example 2> (Crystals of the present invention: Examples of step 2 of manufacturing methods 2 and 3) 46.0 g of the white solid obtained in Example 1 was subjected to a reslurrying procedure at 80°C with 114.8 g of acetonitrile, 92.3 g of toluene, and 2.2 g of acetic anhydride. After cooling to 25°C, the solid was filtered, and the temperature was raised to 80°C under reduced pressure to dry it, yielding 36.7 g of white solid. GPC analysis of the obtained white solid revealed that compound A accounted for 99.0 area percent (purity 99.0%) of the total amount of all components detected by GPC. Differential scanning calorimetry (DSC) analysis of the obtained white solid revealed an endothermic melting peak. This result clearly indicates that the obtained white solid is crystalline. Figure 3 shows a chart illustrating the DSC data. The endothermic melting peak obtained from this DSC analysis was at 228.0°C. Furthermore, powder X-ray diffraction measurements using Cu-Kα rays were performed on the obtained white solid, and the peak pattern clearly indicated that the obtained white solid was crystalline. A chart showing the powder X-ray diffraction data using Cu-Kα rays is shown in Figure 4. The diffraction angle 2θ(°) of the observed diffraction peaks and the relative intensity relative to the peak with the strongest intensity are shown in Table 2.

[0029] [Table 2]

[0030] <Comparative Example 1> In a four-necked flask equipped with a thermometer, stirrer, and condenser, 10.0 g (0.07 mol) of isosorbide, 6.0 g of pyridine, and 168.0 g of anhydrous tetrahydrofuran were charged. The reaction vessel was cooled to 10°C while stirring to dissolve the substances, and the reaction vessel was purged with nitrogen. Subsequently, 33.2 g (0.16 mol) of trimellitic anhydride chloride was added while maintaining the temperature in the reaction vessel at 10°C. After the addition was complete, the mixture was stirred at 10°C for 24 hours, and the resulting precipitate was filtered off to obtain a homogeneous yellow solution. The resulting yellow solution was slowly added dropwise to 34 volumes of petroleum ether, the resulting solid was filtered, and dried under reduced pressure at 80°C to obtain 10.7 g of a white solid. GPC analysis of the obtained white solid revealed that compound A accounted for 49.8 area% (purity 49.8%) of the total amount of all components detected by GPC. Differential scanning calorimetry of the obtained white solid revealed no melting endothermic peaks. This result clearly indicates that the obtained white solid is not crystalline.

Claims

1. A crystal of isosorbidobis(trimellitate anhydride) having diffraction peaks at diffraction angles 2θ of 17.8±0.2°, 23.4±0.2°, 24.8±0.2°, 27.0±0.2° and 30.4±0.2° in the powder X-ray diffraction peak pattern using Cu-Kα rays.

2. The crystal according to claim 1, wherein the melting endothermic peak determined by differential scanning calorimetry is in the range of 214 to 220°C.

3. A crystal of isosorbido-bis(trimellitate anhydride) exhibiting diffraction peaks at diffraction angles 2θ of 15.1±0.2°, 17.9±0.2°, 19.8±0.2°, and 29.1±0.2° in its powder X-ray diffraction peak pattern using Cu-Kα rays.

4. The crystal according to claim 3, wherein the melting endothermic peak determined by differential scanning calorimetry is in the range of 225 to 231°C.

5. The crystal according to any one of claims 1 to 4, wherein the purity of isosorbido-bis(trimellitate anhydride) is 90.0% or higher in gel permeation chromatography measurements.

6. A method for producing crystals according to claim 1 or 2, comprising reacting isosorbide with trimellitic anhydride halide in the presence of a base and an aliphatic nitrile solvent.

7. A method for producing crystals according to claim 3 or 4, comprising purifying a solid isosorbido-bis(trimellitate anhydride) with a solvent containing an aromatic hydrocarbon solvent.

8. A method for producing crystals according to claim 3 or 4, comprising the steps of: reacting isosorbide with trimellitic anhydride halide in the presence of a base and an aliphatic nitrile solvent to obtain crude crystals (step 1); and purifying the obtained crude crystals with a solvent (step 2).

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