Crystal of isomannide-bis (trimellitate anhydride) and producing method thereof

Abstract

The objective of this invention is to provide a high-purity crystal of isomannitol-bis(triphenylamine anhydride) suitable as a resin raw material. The means by which this invention solves the objective is a crystal of isomannitol-bis(triphenylamine anhydride), particularly a crystal of isomannitol-bis(triphenylamine anhydride) exhibiting a specific range of melting endothermic peaks as measured by differential scanning calorimetry, or exhibiting specific peaks in the powder X-ray diffraction peak pattern measured by Cu-Kα lines.

Description

Technical Field

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

[0002] Carboxylic anhydrides are compounds widely used in the fields of organic chemistry and polymer chemistry, and are a useful group of compounds in various fields such as raw materials for medical and agricultural chemicals, resin raw materials, and electronic information materials. Among them, they are frequently used as monomers for polymer materials, for example, as raw materials for polyimides or polyamides, polyester modifiers, epoxy resin curing agents, etc. In recent years, among these polymer materials, bio-based resins using raw materials derived from biomass resources have attracted attention as environmentally friendly materials. For example, dianhydrohexitol having hydroxyl groups that are easily modified, which is derived from an alicyclic structure, is expected to have high transparency and excellent heat resistance, and is being applied. There are few reported examples of modifying the acid anhydride structure of dianhydrohexitol. If the modification is limited to trimellitic acid that can be easily modified with an acid anhydride structure, there is only Patent Document 1. [Prior Art Documents] [Patent Documents]

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

[0004] Although Patent Document 1 describes isomannide-bis(trimellitic anhydride) (hereinafter sometimes also referred to as Compound A ) represented by Formula (A), it only presents its production method and NMR data of the obtained substance. When the present inventors conducted a reproduction experiment of this production method, the purity of the obtained substance was low and it was impossible to obtain crystals of a single substance. In view of the above circumstances, the present inventors have made a study, and the problem is to provide crystals of Compound A with high purity and suitable as a resin raw material. Means for Solving the Problems

[0005] The inventors of the present invention have conducted in-depth studies to solve the above problems, and as a result, have found crystals of compound A, particularly crystals having a melting endothermic peak within a specific range measured by differential scanning calorimetry, or crystals having specific peaks in a powder X-ray diffraction peak pattern measured by Cu-Kα rays, and a method for producing the same, thereby completing the present invention.

[0006] The present invention is as follows. 1. A crystal of isomannide-bis(trimellitic anhydride). 2. The crystal according to 1., wherein the melting endothermic peak measured by differential scanning calorimetry is in the range of 108 to 116 °C. 3. The crystal according to 1., wherein in the powder X-ray diffraction peak pattern measured by Cu-Kα rays, diffraction peaks are present at diffraction angles 2θ of 5.9 ± 0.2°, 7.4 ± 0.2°, 14.5 ± 0.2°, 15.9 ± 0.2° and 24.4 ± 0.2°. 4. The crystal according to 1., wherein the melting endothermic peak measured by differential scanning calorimetry is in the range of 198 to 206 °C. 5. The crystal according to 1., wherein in the powder X-ray diffraction peak pattern measured by Cu-Kα rays, diffraction peaks are present at diffraction angles 2θ of 17.4 ± 0.2°, 19.4 ± 0.2°, 21.9 ± 0.2° and 24.4 ± 0.2°. 6. The crystal according to any one of 1. to 5., wherein in the measurement by gel permeation chromatography, the purity of isomannide-bis(trimellitic anhydride) is 90.0% or more. 7. A method for producing a crystal according to 1., which comprises reacting isomannide with a trimellitic anhydride halide in the presence of a base and an aliphatic nitrile solvent. 8. A method for producing a crystal according to 1., which comprises purifying a solid of isomannide-bis(trimellitic anhydride) with a solvent containing an aromatic hydrocarbon solvent. 9. A method for producing a crystal according to 1., which comprises: a step (step 1) of reacting isomannide with a trimellitic anhydride halide in the presence of a base and an aliphatic nitrile solvent to obtain crude crystals, and a step (step 2) of purifying the obtained crude crystals with a solvent. Advantages of the Invention

[0007] Compound A obtained by a conventional known method is a viscous liquid. In contrast, according to the present invention, it can be processed in a form with good handleability. Furthermore, according to the manufacturing method of the present invention, compound A can be stably obtained in high purity and in crystalline form. Moreover, compared to previously known methods, crystallization can be achieved with a small amount of solvent; therefore, in addition to improving industrial production efficiency, it is also expected to reduce waste, thus benefiting the industrial production of compound A and being extremely useful. In other words, the crystallization method and manufacturing method of this invention are very useful for the industrial use of compound A. Simple Explanation of the Diagram

[0008] Figure 1 is a graph showing the differential scanning calorimetry data of the crystals obtained in Example 1. Figure 2 is a graph showing the powder X-ray diffraction data of the crystal obtained in Example 1, measured by Cu-Kα lines. Figure 3 is a graph showing the differential scanning calorimetry data of the crystals obtained in Example 2. Figure 4 is a graph showing the powder X-ray diffraction data of the crystal obtained in Example 2, measured by Cu-Kα lines. Implementation

[0009] <Synthetic Method of Compound A> The method for synthesizing the crystalline compound A of the present invention is not particularly limited, and for example, a method of reacting isomannitol with trimellitic anhydride halide in the presence of a base and a reaction solvent can be used. (In the formula, X represents a halogen atom)

[0010] Examples of trimellitic anhydride halides include trimellitic anhydride chloride, trimellitic anhydride bromide, trimellitic anhydride iodide, and trimellitic anhydride fluoride. Among these trimellitic anhydride halides, trimellitic anhydride chloride is preferred from the viewpoint of being inexpensive and readily available. The amount of trimellitic anhydride halide used is not particularly limited as long as it is greater than the theoretical value (2.0) relative to the addition of isomannitol. It is usually used in the range of 2 to 10 times the amount of moles, preferably in the range of 2 to 6 times the amount of moles, and even more preferably in the range of 2 to 4 times the amount of moles.

[0011] Isomannitol reacts with trimellitic anhydride halides to produce hydrogen halides; therefore, a base is used to capture these hydrogen halides. The base is not particularly limited and can include: 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. However, from the perspectives of post-reaction separation, cost, and toxicity, pyridine is preferred. The amount of alkali used is not particularly limited as long as it is greater than the theoretical value (2.0) relative to the added molar ratio of isomannitol. It is usually used in the range of 2 to 20 molars, preferably in the range of 2 to 10 molars, and even more preferably in the range of 2 to 5 molars.

[0012] Regarding the reaction solvent, there are no particular restrictions as long as it does not distill off the reaction vessel at the reaction temperature and is inactive to the reaction. Examples 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; and solvents such as tetrahydrofuran and dimethyl ethyl ketone. Aliphatic ether solvents such as alkanes and methyl tributyl ether; aliphatic nitrile solvents such as acetonitrile and propionitrile. These reaction solvents can be used individually or in combination, or two or more can be used together to adjust the polarity. Aliphatic nitrile solvents are preferred. The amount of reaction solvent used is preferably 1 to 50 times the weight of isomannitol, more preferably 2 to 20 times the weight, and even more preferably 4 to 15 times the weight.

[0013] Regarding reaction conditions, the preferred reaction temperature is in the range of -20 to 50°C, and more preferably in the range of -10 to 25°C. If the reaction temperature is too high, the yield will decrease due to hydrolysis of the generated ester compounds, while if the reaction temperature is too low, the reaction rate will be slow and unsatisfactory. Furthermore, regarding reaction pressure, it is usually carried out at atmospheric pressure, but depending on the boiling point of the organic solvent used, it can be carried out under pressure or reduced pressure to maintain the reaction temperature within the aforementioned range. The reaction endpoint can be confirmed by analysis using liquid chromatography or gas chromatography, including gel permeation chromatography. Preferably, the endpoint is defined as the point at which "unreacted isomannitol disappears and the increase in compound A, the target analyte, cannot be identified." The reaction time varies depending on reaction conditions such as temperature, and typically ranges from 1 to 30 hours.

[0014] (Method 1 for manufacturing crystals according to the present invention) The crystals of this invention can be produced by reacting isomannitol with trimellitic anhydride halides in the presence of an alkali and an aliphatic nitrile solvent. The trimellitic acid halides that can be used, the aliphatic nitrile solvents used as bases and reaction solvents, the amounts of these used, and the reaction conditions are the same as those for the synthesis of compound A. After the reaction is complete, crystals of the desired compound A precipitate from the reaction mixture. Alternatively, crystals of compound A precipitate by cooling the reaction mixture.

[0015] (Method 2 for manufacturing crystals according to the present invention) The crystals of this invention can be produced by purifying the solid of compound A with a solvent containing aromatic hydrocarbons. Furthermore, "purification" in this manufacturing method 2 refers to dissolving the solid of compound A in a solvent and performing a crystallization operation, or re-slurrying the solid of compound A in a solvent.

[0016] The solid of compound A can be obtained by solvent removal, dropwise addition to a lean solvent, column purification, or by performing the crystallization method 1 described above, in the reaction mixture of compound A obtained by the above-described synthesis method. The solid can be amorphous or crystalline. Purifying the solid of compound A using this method 2 can further improve its purity, and sometimes yields crystals with a different chemical structure than the crystals before purification. Examples of aromatic hydrocarbon solvents used include toluene and xylene. The amount of aromatic hydrocarbon solvent used is preferably 0.5 to 20 times the weight of the solid compound A, more preferably 1 to 10 times the weight, and even more preferably 2 to 6 times the weight. The solvents used can be any solvent other than aromatic hydrocarbon solvents. 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; and solvents such as tetrahydrofuran and dimethyl ethyl ketone. The solvent comprises aliphatic ethers such as alkanes and methyl-tert-butyl ethers; aliphatic nitrile solvents such as acetonitrile and propionitrile; and water. The aliphatic nitrile solvent is preferred. The amount of this solvent used is preferably 0.1 to 4 times by weight, more preferably 0.1 to 3 times by weight, even more preferably 0.1 to 2 times by weight, and particularly preferably 0.1 to 1.5 times by weight, relative to the amount of aromatic hydrocarbon solvent used. In this manufacturing method 2, acid anhydrides such as acetic anhydride can be used. The purpose is to allow the acid anhydride portion of compound A to undergo dehydration and condensation to revert to acid anhydride if it is partially or completely hydrolyzed by moisture in the air during processing.

[0017] When dissolving the solid of compound A in a solvent and performing crystallization, the following steps can be taken: add the solid of compound A to the solvent used for purification and heat it to form a solution, then cool it. When re-slurrying the solid of compound A with a solvent, the following steps can be taken: add the solid of compound A to the solvent used for purification and heat it to form a slurry, then cool it. The order of adding and heating is not fixed. If purification is performed using a re-slurrying process, seed crystals are not required, and high-purity crystals of compound A can be obtained, which is therefore preferable. The heating temperature range is 40 to 100°C, preferably 60 to 85°C. The optimal cooling rate is 1 to 40°C per hour, even better is 2 to 30°C per hour, and even better is 5 to 20°C per hour. The temperature range after cooling is 0 to 40°C, preferably 20 to 30°C.

[0018] (Method 3 for manufacturing crystals according to the present invention) The crystallization system of the present invention can be produced by a method comprising the following steps: a step of reacting isomannitol with trimellitic anhydride halide in the presence of an alkali and an aliphatic nitrile solvent to obtain crude crystals (step 1), and a step of purifying the obtained crude crystals with a solvent (step 2).

[0019] In step 1, the available trimellitic acid halides, bases, aliphatic nitrile solvents used as reaction solvents, their amounts, and 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 from the reaction mixture. Alternatively, crude crystals of compound A precipitate by cooling the reaction mixture.

[0020] Step 2 is the step of purifying the crude crystals obtained in Step 1 with a solvent. Furthermore, "purification" in Step 2 refers to dissolving the crude crystals in a solvent and performing crystallization, or re-slurrying the crude crystals with a solvent. The solvents used in step 2 can be, for example: 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; tetrahydrofuran, diethyl ethyl ketone ... Alkane, methyl-tert-butyl ether and other aliphatic ether solvents; acetonitrile, propionitrile and other aliphatic nitrile solvents; and water. These solvents can be used individually or in combination, or two or more can be used together to adjust polarity. Aliphatic nitrile solvents and aromatic hydrocarbon solvents are preferred. The amount of solvent used in step 2 is preferably 0.5 to 20 times the weight of the crude crystals of compound A obtained in step 1, more preferably 1 to 10 times the weight, and even more preferably 2 to 6 times the weight. In step 2, acid anhydrides such as acetic anhydride can be used. The purpose is to allow the anhydride portion of compound A to undergo dehydration and condensation to revert to an acid anhydride if it is partially or completely hydrolyzed due to moisture in the air during the treatment.

[0021] When dissolving the crude crystals of compound A in a solvent and performing crystallization, the following steps can be taken: add the crude crystals of compound A to the solvent used for purification and heat to form a solution, then cool. When re-slurrying the crude crystals of compound A with a solvent, the following steps can be taken: add the crude crystals of compound A to the solvent used for purification and heat to form a slurry, then cool. The order of adding and heating is not fixed. In step 2, if purification is carried out by re-slurrying, seed crystals are not required, and high-purity crystals of compound A can be obtained, which is therefore preferable. The heating temperature range is 40 to 100°C, preferably 60 to 85°C. The optimal cooling rate is 1 to 40°C per hour, even better is 2 to 30°C per hour, and even better is 5 to 20°C per hour. The temperature after cooling is in the range of 0 to 40°C, preferably in the range of 20 to 30°C.

[0022] The crystals obtained by the above method can be isolated by conventional methods, such as centrifugation and filtration. Furthermore, it is preferable to further wash the crystals with a solvent. The solvents used at this time can be, for example, 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, and dimethyl ethyl ketone. Alkane, methyl tributyl ether, acetonitrile, propionitrile, more preferably toluene, γ-butyrolactone, acetone, methyl ethyl ketone, tetrahydrofuran, acetonitrile, especially acetonitrile. 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 the weight, and particularly preferably in the range of 1 to 4 times the weight.

[0023] The resulting crystals can be dried to remove the solvent used, or dehydrated and condensed at the anhydride site of compound A during the operation to form an anhydride. The drying operation is preferably 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 under normal or reduced pressure; however, in industrial applications, drying under reduced pressure of around 10 kPa is preferred as it allows for more efficient removal of the solvent. When the crystals of compound A obtained in this way are used as polyimide monomers for polymerization, their high purity is expected to enhance reactivity and provide excellent processability.

[0024] <Crystallization of the Invention> This invention relates to isomannitol-bis(triphenylamine anhydride) crystals. The crystals of this invention contain at least two types of crystals, crystal A and crystal B. The crystal A of the present invention is a crystal having a melting endothermic peak measured by differential scanning calorimetry in the range of 108 to 116°C, preferably in the range of 109 to 115°C, more preferably in the range of 110 to 114°C, and even more preferably in the range of 111 to 114°C. Furthermore, the crystal A of the present invention is a crystal with diffraction peaks at diffraction angles 2θ of 5.9±0.2°, 7.4±0.2°, 14.5±0.2°, 15.9±0.2° and 24.4±0.2° in the powder X-ray diffraction peak pattern measured by Cu-Kα lines. The crystal B of the present invention is a crystal having a melting endothermic peak measured by differential scanning calorimetry in the range of 198 to 206°C, preferably in the range of 199 to 205°C, more preferably in the range of 200 to 204°C, and even more preferably in the range of 201 to 204°C. Furthermore, the crystal B of the present invention is a crystal with diffraction peaks at diffraction angles 2θ of 17.4±0.2°, 19.4±0.2°, 21.9±0.2° and 24.4±0.2° in the powder X-ray diffraction peak pattern measured by Cu-Kα lines. The crystallization of the present invention is determined by gel permeation chromatography, wherein the purity of compound A is 90.0% or more. Specifically, relative to the total amount of all components detected by gel permeation chromatography, compound A is contained in an area of ​​90.0% or more, preferably 95.0% or more, more preferably 97.0% or more, and even more preferably 98.0% or more. (Example)

[0025] The present invention will be specifically described below by way of examples, but the present invention is not limited to these examples. The analysis method is as follows. <Analytical Methods> 1. Gel permeation chromatography (GPC) Device: HLC-8320GPC (manufactured by TOSOH Corporation). Detector: Differential refractometer (RI). (Measurement conditions) Mobile phase: Tetrahydrofuran (containing stabilizer). Flow rate: 1.0 mL / min. Injection volume: 100μL. Column temperature: 40℃. Columns: 1 TSKgel guardcolumn HXL-L, 2 TSKgel G2000HXL, 1 TSKgel G3000HXL, 1 TSKgel G4000HXL. 2. Differential Scanning Calorimetry (DSC) The crystals were precisely weighed into an aluminum pot, and the following differential scanning calorimetry device was used, with alumina as a control group, and the determination was carried out according to the following determination conditions. Device: DSC7020 (manufactured by Hitachi High Technology Scientific Co., Ltd.) (Measurement conditions) Heating rate: 10℃ / minute. Measurement temperature range: 30 to 300℃. Measurement environment: Open, nitrogen gas 50 mL / min. Sample amount: 3mg ± 1mg. 3. Powder X-ray diffraction (XRD) 0.1 g of crystals was filled into the sample filling section of a glass test plate, and the determination was performed using the powder X-ray diffraction apparatus described below, under the following conditions. Device: MiniFlex600 (manufactured by Rigaku Co., Ltd.) (Measurement conditions) X-ray source: Cu-Kα. Scan axis: 2θ / θ. Mode: Continuous. Measurement range: 2θ = 5° to 90°. Step size: 0.02°. Speed ​​measurement time: 2θ = 10° / minute. Diverging slit: 1 / 4. Light-receiving slit: 13.00mm. Output: 40kV-15mA.

[0026] <Example 1> (The crystallization of this invention: an embodiment of step 1 of manufacturing method 1 and manufacturing method 3) In a four-necked flask equipped with a thermometer, stirrer, and cooling tube, 59.4 g (0.28 mol) of trimellitic anhydride chloride and 80.0 g of acetonitrile were added. While stirring to dissolve, the reaction vessel was purged with nitrogen and cooled to below 5°C. Then, while maintaining the temperature below 5°C, a prepared solution consisting of 20.0 g (0.14 mol) of isomannitol, 100.0 g of acetonitrile, and 32.5 g (0.41 mol) of pyridine was added dropwise at a fixed rate over 2 hours. After the addition was complete, the mixture was stirred below 5°C for 1 hour. The temperature was then raised to 25°C and stirred overnight. The resulting white solid was filtered to obtain 54.0 g. GPC analysis of the white solid showed that compound A had an area percentage (purity 99.6%) relative to the total amount of all components detected by GPC. Differential scanning calorimetry (DSC) analysis was performed on the obtained white solid, and a melting endothermic peak was observed. This result indicates that the obtained white solid is crystalline. The data from this DSC analysis are presented in Figure 1. The melting endothermic peaks measured by this DSC analysis are at 112.5℃ and 199.7℃. Furthermore, the obtained white solid was subjected to powder X-ray diffraction using the Cu-Kα line. The results, as shown by the peak pattern, indicate that the white solid was crystalline. A graph presenting the powder X-ray diffraction data obtained using the Cu-Kα line is shown in Figure 2. The diffraction angle 2θ (°) of the diffraction peaks and the relative intensity based on the strongest peak are shown in Table 1.

[0027] [Table 1]

[0028] <Example 2> (The crystallization of this invention: an embodiment of step 2 of manufacturing method 2 and manufacturing method 3) 50.0 g of the white solid obtained in Example 1 was subjected to a re-slurrying operation at 80°C using 125.0 g of acetonitrile, 100.0 g of toluene, and 2.5 g of acetic anhydride. After cooling to 25°C, the solid was filtered, heated to 80°C under reduced pressure, and dried to obtain 38.0 g of white solid. The white solid obtained by GPC determination showed that compound A had an area percentage (purity 99.7%) relative to the total amount of all components detected by GPC. Differential scanning calorimetry (DSC) analysis was performed on the obtained white solid, and a melting endothermic peak was observed. This result indicates that the obtained white solid is crystalline. The data from this DSC analysis are presented in Figure 3. The melting endothermic peak measured by this DSC analysis is 201.9℃. Furthermore, the obtained white solid was subjected to powder X-ray diffraction using the Cu-Kα line. The results, as shown by the peak pattern, indicate that the white solid was crystalline. A graph presenting the powder X-ray diffraction data obtained using the Cu-Kα line is shown in Figure 4. The diffraction angle 2θ (°) of the diffraction peaks and the relative intensity based on the strongest peak are shown in Table 2.

[0029] [Table 2]

[0030] <Comparative Example 1> In a four-necked flask equipped with a thermometer, stirrer, and cooling tube, 10.0 g (0.07 mol) of isomannitol, 7.6 g of triethylamine, and 226.5 g of dehydrated dimethylacetamide were added. While stirring to dissolve the substances, the reaction vessel was purged with nitrogen gas and cooled to 20°C. Subsequently, while maintaining the temperature of the reaction vessel at 20°C, 32.1 g (0.15 mol) of trimellitic anhydride chloride was added. After the addition was complete, the mixture was stirred at 20°C for 28 hours. The precipitate was removed by filtration, yielding a homogeneous yellow solution. When the resulting yellow solution was slowly added dropwise to 34 times its volume of petroleum ether, no solid precipitated out; the yellow, viscous oil adhered to the bottom of the container, and no crystals or solids could be obtained. The obtained yellow viscous oil contained 32.6% isomannitol-bis(tribenzoic anhydride) in area (32.6% purity) relative to the total amount of all components detected by gel permeation chromatography.

Claims

1. A crystal of isomannitol-bis(trimethylbenzene tricarboxylic anhydride) having the following characteristics (1) and / or (2), or having the following characteristics (3) and / or (4): (1) the melting endothermic peaks measured by differential scanning calorimetry are in the range of 108 to 116 °C; (2) in the powder X-ray diffraction peak pattern measured by Cu-Kα lines, there are diffraction peaks at diffraction angles 2θ of 5.9±0.2°, 7.4±0.2°, 14.5±0.2°, 15.9±0.2° and 24.4±0.2°; (3) the melting endothermic peaks measured by differential scanning calorimetry are in the range of 198 to 206 °C; (4) In the powder X-ray diffraction peak pattern measured by Cu-Kα line, diffraction peaks are present at diffraction angles 2θ of 17.4±0.2°, 19.4±0.2°, 21.9±0.2° and 24.4±0.2°.

2. Crystallization as described in claim 1, wherein, In the gel permeation chromatography determination, the purity of isomannitol-bis(triphenylamine) was above 90.0%.

3. A method for producing crystals as described in claim 1, comprising reacting isomannitol with trimellitic anhydride halides in the presence of an alkali and an aliphatic nitrile solvent.

4. A method for producing crystals as described in claim 1, comprising purifying isomannitol-bis(trimethylammonium trioxide) solid with a solvent containing an aromatic hydrocarbon solvent.

5. A method for producing crystals as described in claim 1, comprising: a step of reacting isomannitol with trimellitic anhydride halide in the presence of an alkali and an aliphatic nitrile solvent to obtain crude crystals (step 1), and a step of purifying the obtained crude crystals with a solvent (step 2).

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