Maleimide compound and method for producing the same

Abstract

To provide a novel bismaleimide compound capable of comprehensively achieving high degrees of dielectric properties, mechanical strength and dimensional stability.SOLUTION: The invention provides a maleimide compound represented by the general formula (1) in the figure. (In the formula, R1 to R8 are each independently selected from the group consisting of hydrogen, fluorine, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aromatic group, provided that at least one of R1 to R8 is a substituted or unsubstituted aromatic group.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a maleimide compound and a method for producing the same. [Background technology]

[0002] Bismaleimides are widely used as laminating materials, sealing materials, electrical insulating materials, conductive pastes, adhesives, pressure-sensitive adhesives, structural materials, and more. In particular, in recent years, laminates have been used as circuit boards for mounting electronic components, and the properties required of laminates have become more extensive and sophisticated. For example, as clock frequencies increase with the speed of devices, signal propagation delay and transmission loss become problems, leading to the need for laminates with low dielectric constants and low dielectric dissipation factors. At the same time, the increased speed of devices has led to increased heat generation from chips, necessitating the need for heat-resistant materials. Bismaleimides are used in interlayer insulating films in multilayer wiring structures, and for these reasons, there is a demand for bismaleimides that can maintain heat resistance and strength while also having a low dielectric constant.

[0003] Meanwhile, in order to ensure the insulation reliability and dimensional stability that are essential for high-density packaging that has accompanied the recent development of electronic materials, resins for electronic materials are required to maintain their dielectric properties even under high humidity conditions, and also to avoid dimensional changes such as expansion and contraction.However, bismaleimides generally have issues in applying them to electronic materials, such as the imide group easily absorbing moisture, which changes their dielectric properties and has a large thermal expansion coefficient.

[0004] In order to meet these demands, various maleimides and their raw materials, bismaleic acids, have been proposed (for example, JP-A-6-016627, etc.), but these are not necessarily satisfactory in terms of meeting the demand for increasingly higher performance in the field of electronic materials in recent years. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-016627 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, an object of the present invention is to provide a novel bismaleimide compound which can comprehensively achieve high levels of dielectric properties, mechanical strength, and dimensional stability.

[0007] Another object of the present invention is to provide a method for producing the above bismaleimide compound. [Means for solving the problem]

[0008] The present inventors have discovered that bismaleimides obtained by using diamine compounds having a specific chemical structure as diamine compounds, which are raw materials for bismaleimide compounds, reacting them with maleic acid to form maleamic acids, and then maleimiding these, can comprehensively achieve high levels of dielectric properties, mechanical strength, and dimensional stability. The present invention is based on this discovery. Specifically, the gist of the present invention is as follows.

[0009] [1] The following general formula (1): [ka] (In the formula, R1 to R8 are each independently selected from the group consisting of hydrogen, fluorine, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aromatic group, and at least one of R1 to R8 is a substituted or unsubstituted aromatic group.) A maleimide compound represented by the formula: [2] The maleimide compound according to [1], wherein in the formula (1), R1 to R4 are hydrogen, and R5 to R8 each independently represent an aromatic group having 6 to 10 carbon atoms, a phenoxy group, a benzyl group, a benzyloxy group, or hydrogen, and at least one of R5 to R8 is an aromatic group having 6 to 10 carbon atoms, a phenoxy group, a benzyl group, or a benzyloxy group, and the remaining R5 to R8 are hydrogen. [3] The maleimide compound according to [2], wherein the aromatic group having 6 to 10 carbon atoms is a phenyl group or a methylphenyl group. [4] A method for producing the maleimide compound according to any one of [1] to [3], comprising the steps of: The following formula (2): [ka] (In the formula, R1 to R8 have the same definitions as above.) with maleic anhydride to obtain bismaleamic acid; Next, a step of imidizing the bismaleamic acid by dehydration and ring closure; A method for producing a maleimide compound, comprising: [5] The method according to [4], further comprising a step of purifying the solution containing the crude maleimide compound obtained in the imidization step by crystallization, reprecipitation, or washing with water. [6] The method according to [4] or [5], wherein the imidization is carried out in the presence of a dehydrating agent or an acid catalyst. [Effects of the Invention]

[0010] According to the present invention, by using the diamine compound represented by the above formula (2) as the starting diamine compound to produce a maleimide compound, it is possible to obtain a maleimide compound that can comprehensively achieve high levels of dielectric properties, mechanical strength, and dimensional stability. [Brief explanation of the drawings]

[0011] [Figure 1] 1 shows a 1H-NMR chart of the maleimide compound obtained in Example 1. [Figure 2] 1 shows an FT-IR chart of the maleimide compound obtained in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Maleimide compounds> The maleimide compound of the present invention is represented by the following general formula (1): [ka] (In the formula, R1 to R8 are each independently selected from the group consisting of hydrogen, fluorine, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aromatic group, and at least one of R1 to R8 is a substituted or unsubstituted aromatic group.) It is expressed as:

[0013] In formula (1), R1 to R8 are each independently selected from the group consisting of hydrogen, fluorine, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aromatic group, and at least one of R1 to R8 is an aromatic group. Preferably, one or two of R1 to R8 are aromatic groups. Preferably, one or two of R5 to R8 are substituted or unsubstituted aromatic groups, and more preferably, at least R5 or R7 is an aromatic group. By having an aromatic group at the above-mentioned position, the steric hindrance of the maleimide compound can be reduced, and as a result, a maleimide compound with excellent crystallinity can be obtained.

[0014] In a particularly preferred embodiment, one or two of R5 to R8 are substituted or unsubstituted aromatic groups, and R1 to R8 other than the aromatic groups are selected from the group consisting of hydrogen, fluorine, and substituted or unsubstituted alkyl groups. Specific examples include the following compounds (embodiments in which R7 is an aromatic group, and R1 to R6 other than R7 and R8 are hydrogen): [ka]

[0015] In the present invention, the alkyl group includes a linear one, a branched one, and a cyclic one, and further includes an alkoxy group, an alkylamino group, etc., which are bonded to the main skeleton via an oxygen atom or a nitrogen atom. Similarly, the aromatic group includes a substituent which is bonded to the main skeleton via an oxygen atom, a nitrogen atom, or a carbon atom. Furthermore, the aromatic group includes a heteroaromatic group such as a pyrrole group.

[0016] The alkyl group and aromatic group are preferably unsubstituted from the viewpoint of ease of synthesis of the maleimide compound of the present invention and application in the field of electronic component materials, but may have a substituent, for example, an alkyl group, a halogen group such as a fluoro group or a chloro group, an amino group, a nitro group, a hydroxyl group, a cyano group, a carboxyl group, a sulfonic acid group, etc. The alkyl group and aromatic group may have one or more of these substituents, or two or more of these substituents.

[0017] The alkyl group preferably has 1 to 10 carbon atoms, and more preferably 1 to 3. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, an n-pentyl group, a sec-pentyl group, an n-hexyl group, a cyclohexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a chloromethyl group, a dichloromethyl group, a trichloromethyl group, a bromomethyl group, a dibromomethyl group, a tribromomethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a chloroethyl group, a dichloromethyl group, a fluoroethyl group, a di ... fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a chloroethyl group, a dichloromethyl group, a bromomethyl group, a dibromomethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a chloroethyl group, a bromomethyl group, a dibromomethyl group, a fluoroethyl group, a difluoroethyl group, a bromoethyl group, a bromoethyl group, a difluoroethyl group, a bromoethyl group, a bromoethyl group, a difluoroethyl group, a bromoethyl group, a bromoethyl group, a bromoethyl group, a bromoethyl group, a bromoethyl group, a bromoethyl group, a bromoethyl group, a bromoethyl group, a bromoethyl group, a bromoethyl Examples include a chloroethyl group, a trichloroethyl group, a bromoethyl group, a dibromoethyl group, a tribromoethyl group, a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, a sec-pentyloxy group, an n-hexyloxy group, a cyclohexyloxy group, an n-heptyloxy group, an n-octyloxy group, an n-nonyloxy group, an n-decyloxy group, a trifluoromethoxy group, a methylamino group, a dimethylamino group, a trimethylamino group, an ethylamino group, a propylamino group, etc. Among the above alkyl groups, a methyl group, an ethyl group, a methoxy group, an ethoxy group, and a trifluoromethyl group are preferred from the standpoint of steric hindrance and heat resistance.

[0018] The aromatic group preferably has 5 to 20 carbon atoms, more preferably 6 to 10. Examples of the aromatic group having 5 to 20 carbon atoms include a phenyl group, a tolyl group, a methylphenyl group, a dimethylphenyl group, an ethylphenyl group, a diethylphenyl group, a propylphenyl group, a butylphenyl group, a fluorophenyl group, a pentafluorophenyl group, a chlorophenyl group, a bromophenyl group, a methoxyphenyl group, a dimethoxyphenyl group, an ethoxyphenyl group, a diethoxyphenyl group, a benzyl group, a methoxybenzyl group, a dimethoxybenzyl group, an ethoxybenzyl group, a diethoxybenzyl group, an aminophenyl group, an aminobenzyl group, a nitrophenyl group, a nitrobenzyl group, a cyanophenyl group, a cyanobenzyl group, a phenethyl group, a phenylpropyl group, a phenoxy group, a benzyloxy group, a phenylamino group, a diphenylamino group, a biphenyl group, a naphthyl group, Examples of heteroaromatic groups include a phenyl group, a phenylnaphthyl group, a diphenylnaphthyl group, an anthryl group, an anthrylphenyl group, a phenylanthryl group, a naphthacenyl group, a phenanthryl group, a phenanthrylphenyl group, a phenylphenanthryl group, a pyrenyl group, a phenylpyrenyl group, a fluorenyl group, a phenylfluorenyl group, a naphthylethyl group, a naphthylpropyl group, an anthracenylethyl group, a phenanthrylethyl group, a pyrrole group, an imidazole group, a thiazole group, an oxazole group, a furan group, a thiophene group, a triazole group, a pyrazole group, an isoxazole group, an isothiazole group, a pyridine group, a pyrimidine group, a benzofuran group, a benzothiophene group, a quinoline group, an isoquinoline group, an indolyl group, a benzothiazolyl group, and a carbazolyl group. Among the above-mentioned aromatic groups, a phenyl group, a phenoxy group, a benzyl group, and a benzyloxy group are preferred in terms of availability of starting materials and synthesis costs.

[0019] <Method of producing maleimide compound> The maleimide compound is The following formula (2): [ka] (In the formula, R1 to R8 have the same definitions as above.) The maleimide compound of the present invention can be obtained by reacting a diamine compound represented by the formula (I) with maleic anhydride to obtain a bismaleamic acid, and then subjecting the bismaleamic acid to dehydration ring closure for imidization. The method for producing the maleimide compound of the present invention will be described in detail below.

[0020] In the method for producing maleimide of the present invention, the diamine compound (compound of formula (2)) used as a raw material can be obtained by reacting a compound represented by the following general formula (3) with a compound represented by the following general formula (4), followed by reducing the nitro group. [ka] [ka]

[0021] In the above formula, R1' to R8' are each independently selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aromatic group, and at least one of R1' to R8' is an aromatic group. Preferably, at least one of R5' to R8' is a substituted or unsubstituted aromatic group, and more preferably, at least R5' or R7' is an aromatic group. In a particularly preferred embodiment, one of R5' to R8' is a substituted or unsubstituted aromatic group, and R1' to R8' other than the aromatic group are hydrogen. In the above formula, X represents a hydroxyl group or a halogen group selected from a fluoro group, a chloro group, a bromo group, and an iodo group. From the viewpoint of reactivity with the compound represented by general formula (4), X is preferably a halogen group, and particularly preferably a chloro group or a bromo group.

[0022] In the above general formula (3), when X is a hydroxyl group, the reaction of the compounds represented by the above general formulas (3) and (4) is preferably carried out in the presence of a dehydration condensation agent such as N,N'-dicyclohexylcarbodiimide (DCC) or an organic acid catalyst such as p-toluenesulfonic acid. Furthermore, when X in the above general formula (3) is a halogen group, the reaction of the compounds represented by the above general formulas (3) and (4) is preferably carried out in the presence of an acid acceptor such as triethylamine.

[0023] More specifically, the diamine compound represented by the above formula (1-I) can be obtained by reacting compounds represented by the following formulas (5) and (6). [ka] [ka]

[0024] The compound represented by the general formula (4) can be obtained by nitrating a commercially available or synthesized compound represented by the following general formula (7). The nitration of the compound represented by the general formula (7) can be carried out by a conventionally known nitration method using a mixed acid of concentrated sulfuric acid and concentrated nitric acid, nitric acid, fuming nitric acid, an alkali metal salt of an acid in concentrated sulfuric acid, acetyl nitrate, a nitronium salt, a nitrogen oxide, or the like.

[0025] [ka]

[0026] R5" to R8" are each independently selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aromatic group. Preferably, at least one of R5" to R8", more preferably one or two, is an aromatic group.

[0027] In the method for producing maleimide of the present invention, the diamine compound described above is prepared, and then the diamine compound is reacted with maleic anhydride to obtain bismaleamic acid. The reaction is preferably carried out in an organic solvent. There are no limitations on the solvent used, but hydrocarbon solvents such as toluene, xylene (o-xylene, m-xylene, p-xylene), ethylbenzene, and mesitylene, amide solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP), and mixed solvents of hydrocarbon solvents and amide solvents are preferred.

[0028] The concentration of the reaction raw materials (i.e., diamine compound and maleic anhydride) is usually 2 to 50 mass %, preferably 5 to 30 mass %, and the reaction temperature is usually 60°C or lower, preferably 50°C or lower. The reaction pressure is not particularly limited, and the reaction can usually be carried out at normal pressure. The reaction time is usually 0.5 to 24 hours.

[0029] The bismaleamic acid obtained as described above is then imidized by dehydration and ring closure. The imidization reaction may be carried out after isolating the bismaleamic acid obtained by reacting a diamine compound with maleic anhydride, or may be carried out directly without isolating the bismaleamic acid.

[0030] The imidization can be performed by utilizing known reactions, such as a method of adding a dehydrating agent such as acetic anhydride and a catalyst, or a method of heating in an aromatic hydrocarbon solvent in the presence of an acid catalyst to perform dehydration and cyclization to form an imidized product, but is not limited to these methods.

[0031] Examples of solvents for the imidization reaction to which a dehydrating agent is added include fatty acid esters such as butyl formate, isobutyl formate, t-butyl formate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, and ethyl propionate, ethylene glycol monoalkyl ethers such as methyl cellosolve and ethyl cellosolve, and ethers such as tetrahydrofuran, dioxane, dipropyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, and diethylene glycol diethyl ether, but are not limited to these as long as the resulting bismaleamic acid is soluble in the solvent. These reaction solvents can be used alone or in combination of two or more.

[0032] The carboxylic acid anhydride used as the dehydrating agent is primarily, but not limited to, acetic anhydride. The catalyst used in the dehydration ring-closing reaction includes carbonates, bicarbonates, sulfates, nitrates, phosphates, acetates, formates, and salts of higher fatty acids of alkali metals (preferably sodium, potassium, and lithium), as well as salts and halides of transition metals such as nickel, cobalt, and manganese, with potassium acetate being preferred. The total amount of the dehydrating agent and catalyst added is preferably 0.1 to 4.0 moles per mole of bismaleamic acid group. Furthermore, if necessary, a tertiary amine or pyridine derivative can be appropriately added to promote the dehydration ring-closing reaction. Examples include triethylamine, tripropylamine, tributylamine, triphenylamine, pyridine, methylpyridine, and 2,6-dimethylpyridine. The amount of the reaction accelerator added is approximately 0.1 to 2.0 moles per mole of amic acid group. The reaction temperature in the dehydration ring-closing reaction is 0 to 60°C, preferably 10 to 40°C, and the reaction time is usually 0.5 to 100 hours.

[0033] Examples of solvents for the imidization reaction, which is heated in the presence of an acid catalyst, include aromatic hydrocarbon solvents such as benzene, toluene, xylene, and ethylbenzene, and, if necessary, aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide may be added. The amount of the aprotic polar solvent used in the reaction solvent is 0.05 to 20% by weight, preferably 1 to 30% by weight, and the maleimide compound is preferably obtained by cyclization dehydration at a temperature in the range of 100 to 200°C while azeotropically removing the generated water.

[0034] It is preferable to extract the solution containing the maleimide compound obtained as described above with water or an alcohol solvent such as methanol, and crystallize it to obtain a high-purity maleimide compound, or to purify the maleimide compound by a known method such as reprecipitation to increase its purity. For example, ion-exchanged water can be added to the reaction product obtained by the dehydration ring-closure reaction as described above, and the maleimide compound can be crystallized from the reaction product. Alternatively, a high-purity maleimide compound can be purified by adding acetone to the crystallized maleimide compound to dissolve it, and then adding toluene to the solution.

[0035] <Uses of maleimide compounds> The maleimide compound of the present invention can be used in combination with known resins such as epoxy resins, compounds having a polymerizable unsaturated group, cyanate ester compounds, and benzoxazine resins to form curable resins.

[0036] As the epoxy resin, generally known ones can be used. Examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, xylene novolac type epoxy resin, triglycidyl isocyanurate, alicyclic epoxy resin, dicyclopentadiene novolac type epoxy resin, biphenyl novolac type epoxy resin, etc. These epoxy resins can be used alone or in combination of two or more.

[0037] Compounds having a polymerizable unsaturated group can be generally known. Examples include (meth)acrylates of monohydric or polyhydric alcohols such as ethylene, propylene, styrene, methyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate, as well as epoxy (meth)acrylate, benzocyclobutene resin, triallyl isocyanurate (TAIC), and triallyl cyanurate (TAC). These compounds having an unsaturated group can be used alone or in combination.

[0038] Examples of cyanate ester compounds include bisphenol A dicyanate ester, bisphenol F dicyanate ester, bisphenol M dicyanate ester, bisphenol P dicyanate ester, bisphenol E dicyanate ester, phenol novolac cyanate ester, cresol novolac cyanate ester, dicyclopentadiene novolac cyanate ester, tetramethylbisphenol F dicyanate ester, and biphenol dicyanate ester. These cyanate ester compounds can be used alone or in combination. Known curing catalysts can be used to cure the cyanate ester compounds. Examples include metal salts such as zinc octylate, zinc naphthenate, cobalt naphthenate, copper naphthenate, and iron acetylacetonate, as well as compounds with active hydroxyl groups such as phenols, alcohols, and amines.

[0039] When a curable resin composition containing the maleimide compound of the present invention and the above-described resin is prepared, it may contain a photopolymerization initiator, a thermal polymerization initiator, a photosensitizer, a curing agent, etc. Furthermore, it may contain a polymerization inhibitor to adjust the degree of curing of the cured product.

[0040] When preparing the curable resin composition, known additives such as a coupling agent, a thermoplastic resin, an inorganic filler, a coloring pigment, an antifoaming agent, a surface conditioner, a flame retardant, an ultraviolet absorber, an antioxidant, and a flow conditioner may be added as needed.

[0041] The curable resin composition containing the maleimide compound of the present invention and the above-described resin can be used, for example, as a prepreg by dissolving it in a solvent, impregnating glass cloth, aramid nonwoven fabric, liquid crystal polyester nonwoven fabric, or the like with the composition, and then drying and removing the solvent; or as a curable film by applying the composition to a substrate such as a polycarbonate film, a polyethylene terephthalate film, an ethylene tetrafluoroethylene copolymer film, a polyimide film, copper foil, aluminum foil, a glass plate, or a SUS plate.

[0042] Furthermore, the curable resin composition is useful for various applications such as insulating materials for printed wiring boards, resist resins, semiconductor packaging materials, semiconductor sealing resins, adhesives for printed wiring boards, build-up laminate materials, resins for fiber-reinforced plastics, sealing resins for liquid crystal display panels, resins for liquid crystal color filters, paints, various coating agents, and adhesives. [Example]

[0043] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0044] [Example 1] <Synthesis of diamine compounds> 500 g of toluene and 51.06 g (0.30 mol) of commercially available o-phenylphenol (manufactured by Wako Pure Chemical Industries, Ltd.) were added to a 1 L four-neck flask equipped with a thermometer and a stirrer, and 30 g (0.33 mol) of 70 wt% nitric acid (d = 1.42) was added dropwise over 2 hours while cooling and maintaining the reaction temperature at -5 to 0°C. The mixture was further stirred at the same temperature for 3 hours to complete the reaction. The product slurry was collected by filtration and washed with aqueous sodium bicarbonate solution and then with water. Next, it was dried under reduced pressure to obtain pale yellow to yellow 2-hydroxy-5-aminobiphenyl represented by the following formula (6). [ka]

[0045] The purity was 97.01% by HPLC analysis (area %), and the melting point was 128°C (endothermic peak) by DSC measurement. 1 H-NMR (CDCl3) σ 5.84 ppm (1H of OH of phenol), σ 6.99 ppm (1H of o-position of phenol), σ 7.15-7.50 ppm (5H of o-phenyl), σ 8.12-8.20 ppm (2H of m-position of phenol), confirming that a nitro group had been introduced at the p-position of phenol.

[0046] Into a 1 L four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser, 43.04 g (0.20 mol) of 2-hydroxy-5-nitrobiphenyl synthesized as described above, 45.53 g (0.24 mol) of commercially available 4-nitrobenzoyl chloride represented by the following formula (5), and 500 g of N,N'-dimethylformamide were added, and the mixture was stirred while maintaining the temperature at approximately 15°C. [ka]

[0047] Next, 30.36 g (0.30 mol) of triethylamine was slowly added. After the addition was completed, the reaction was continued for 3 hours while heating at 50°C. After the reaction was completed, the mixture was cooled to 25°C, and ion-exchanged water was added to obtain a precipitate. After the temperature reached 25°C, the precipitate was collected by filtration, washed several times with methanol and ion-exchanged water, and dried under reduced pressure to obtain a compound represented by the following formula (8). [ka]

[0048] 22 g (0.06 mol) of the compound represented by the above chemical formula (8), 150 ml of dimethylacetamide, and 5% Pd-carbon (as a dry product) were placed in a 500 cc autoclave equipped with a thermometer and a stirrer, and the atmosphere was replaced with nitrogen and then with hydrogen. Hydrogen pressure 9kg / cm 2 The mixture was reduced at a temperature of 80°C (gauge pressure), and hydrogen absorption ceased after approximately two hours. After further aging at 80°C for one hour, it was cooled to room temperature. After nitrogen replacement, the product solution was taken out and filtered to remove the catalyst. The filtrate was poured into 50% methanol to precipitate crystals, which were collected and dried under vacuum at 50°C to obtain a diamine compound represented by the following chemical formula (2-I). The purity was 99.04% by HPLC analysis (area %), and the melting point was 154°C (endothermic peak) by DSC measurement. 1 H-NMR, 13 The structure was confirmed by C-NMR, FT-IR, and elemental analysis. [ka]

[0049] <Synthesis of Maleamic Acid> A glass vessel equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube was filled with nitrogen gas, and 30.05 g (1.00 mol) of the diamine compound represented by formula (2-I) obtained above, 183 ml of toluene, and 7.5 ml of dimethylacetamide were added and stirred. Next, 23.22 g (2.40 mol) of maleic anhydride was added dropwise to the solution over 30 minutes while maintaining the temperature at 20°C, and the precipitated yellow-brown crystals were collected to obtain bismaleamic acid.

[0050] <Synthesis of maleimide compounds> To the glass vessel containing the precipitated bismaleamic acid, 5.34 g (0.33 mol) of iron(III) chloride was added, and the mixture was heated to 113°C and stirred for 4.5 minutes to complete the dehydration ring-closing reaction, yielding a maleimide compound. 2 mL of water was distilled off during this process. Subsequently, 146 mL of ion-exchanged water was added to the solution that had undergone the dehydration ring-closure reaction to precipitate and separate crystals. The resulting crystals weighed 46.35 g. 40 mL of acetone was added to 20 g of the collected crystals to dissolve the crystals, yielding an acetone solution of the maleimide compound. 30 mL of toluene was added dropwise to the solution while stirring, yielding a crystallized, purified maleimide compound.

[0051] Regarding the maleimide compound obtained as described above, 1 Identification was carried out by H-NMR and FT-IR. 1 The results of H-NMR (400.13 MHz, measuring device: AV400 manufactured by Bruker Biospin, deuterated solvent: DMSO-d6) and FT-IR (KBr method, measuring device: FTIR-410 spectrometer) are shown in Figures 1 and 2.

[0052] [Comparative Example 1] A maleimide compound was obtained in the same manner as in Example 1, except that 4-aminophenyl-4-aminobenzoate represented by the following formula was used instead of the diamine compound represented by chemical formula (2-I) in Example 1. [ka]

Claims

1. The following general formula (1): 【Chemistry 1】 (In the formula, R １ ~R ４ is hydrogen, and R ５ ~R ８ each independently represents a phenyl group, a methylphenyl group, a phenoxy group, a benzyl group, a benzyloxy group, or hydrogen, and R ５ ~R ８ At least one of is a phenyl group or a methylphenyl group. A method for producing a maleimide compound represented by the following formula: The following formula (2): 【Transformation 3】 (In the formula, R 1 to R 8 are defined as above.) with maleic anhydride to obtain bismaleamic acid; Next, a step of imidizing the bismaleamic acid by dehydration and ring closure; A method for producing a maleimide compound, comprising:

2. The method according to claim 1, further comprising a step of purifying the solution containing the crude maleimide compound obtained in the imidization step by crystallization, reprecipitation, or water washing.

3. 3. The method according to claim 1, wherein the imidization is carried out in the presence of a dehydrating agent or an acid catalyst.

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