Terephthalic acid compound and use of the same

Abstract

To provide a new terephthalic acid compound and use of the same, specifically, a new terephthalic acid compound, a crosslinking agent for an epoxy resin containing the terephthalic acid compound, a resin composition containing the crosslinking agent for the epoxy resin, and a cured product thereof.SOLUTION: A terephthalic acid compound is represented by the chemical formulae (I-1) to (I-3).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a novel terephthalic acid compound, a curing agent for epoxy resin containing the terephthalic acid compound, a resin composition containing the curing agent for epoxy resin, and a cured product thereof.

Background Art

[0002] Epoxy resin compositions can easily obtain cured products having excellent electrical properties, mechanical properties, and thermal properties by combining various epoxy resins (referring to epoxy compounds before curing) and curing agents, and thus are adopted in many fields. Further, usually, an epoxy resin composition uses an epoxy resin having an epoxy group in the molecule, a curing agent, and a curing accelerator for the purpose of accelerating curing as necessary.

[0003] As conventionally known curing agents for epoxy resins, acidic compounds such as dibasic acids, acid anhydrides, and phenol compounds, and basic compounds such as amines, ureas, and imidazoles are properly used according to the required properties of the cured product.

[0004] For example, Patent Document 1 proposes a one-component epoxy resin composition containing a dibasic acid as a curing agent, and discloses isophthalic acid, phthalic acid, etc. as the dibasic acid. However, epoxy resin compositions containing these dibasic acids have a still room for improvement in terms of storage stability because of their fast curing.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a novel terephthalic acid compound and its use. Specifically, an object is to provide a novel terephthalic acid compound, a curing agent for an epoxy resin containing the terephthalic acid compound, a resin composition containing the curing agent for an epoxy resin, and a cured product thereof.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that a terephthalic acid compound having 2 to 3 iodine atoms in the molecule is a novel compound, and an epoxy resin composition containing the compound has good storage stability and good curability (relatively long gel time), and thus completed the present invention. That is, the first invention is a terephthalic acid compound represented by chemical formulas (I-1) to (I-3).

[0008]

Chemical formula

[0009] The second invention is a curing agent for an epoxy resin containing the terephthalic acid compound of the first invention. The third invention is an epoxy resin composition containing the curing agent for an epoxy resin of the second invention and an epoxy resin. The fourth invention is an epoxy resin composition of the third invention containing a curing accelerator. The fifth invention is a cured product obtained by curing the resin composition of any one of the third to fourth inventions.

Effects of the Invention

[0010] Since the terephthalic acid compound of the present invention has two carboxyl groups in the molecule, it is expected to be used as a curing agent for epoxy resins. And, the terephthalic acid compound of the present invention has 2 to 3 iodine atoms in the molecule. When used as a curing agent for an epoxy resin composition, it exhibits good storage stability and curability compared to the case of using a conventional curing agent, and is expected to provide a cured product having excellent heat resistance and electrical properties.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail. <Terephthalic Acid Compound> The present invention relates to terephthalic acid compounds represented by chemical formulas (I-1) to (I-3) (hereinafter sometimes referred to as "the terephthalic acid compounds of the present invention").

[0012]

Chemical Formula

[0013] Examples of the method for synthesizing the terephthalic acid compound of the present invention include the methods of synthesis methods (1) and (2).

[0014] <Synthesis Method (1)> The terephthalic acid compound of the present invention can be synthesized by iodinating the amino group of a terephthalic acid compound having an amino group and hydrogenating the amino group of an iodoterephthalic acid compound having an amino group (Sandmeyer reaction). Specifically, it can be synthesized by diazotizing the amino group of a terephthalic acid compound having an amino group with a nitrous acid compound and reacting the resulting product with an iodinating agent, and by diazotizing the amino group of an iodoterephthalic acid compound having an amino group with a nitrous acid compound and reacting the resulting product with hypophosphorous acid.

[0015] Examples of the terephthalic acid compound having an amino group include compounds represented by chemical formulas (II-1-1) to (II-3-3).

[0016]

Chemical Formula

[0017] These compounds can be used by purchasing commercially available reagents, and can also be synthesized by introducing iodine atoms into terephthalic acid compounds having amino groups, oxidizing the methyl groups of p-xylene compounds having amino groups and iodine atoms, or introducing amino groups into terephthalic acid compounds having iodine atoms.

[0018] Examples of the nitrous acid compounds include sodium nitrite, potassium nitrite, methyl nitrite, ethyl nitrite, n-propyl nitrite, isopropyl nitrite, isobutyl nitrite, n-butyl nitrite, tert-butyl nitrite, n-pentyl nitrite, isoamyl nitrite, and the like. These nitrous acid compounds can be used by purchasing commercially available reagents.

[0019] The amount of the nitrous acid compound used is in the range of 1 to 100 times the molar amount of the terephthalic acid compound having an amino group, and preferably in the range of 1 to 2 times the molar amount.

[0020] Examples of the iodinating agent include potassium iodide, sodium iodide, copper(I) iodide, and the like. These iodinating agents can be used by purchasing commercially available reagents.

[0021] The amount of the iodinating agent used is preferably in the range of 1 to 100 times the molar amount of the terephthalic acid compound having an amino group, and more preferably in the range of 1 to 10 times the molar amount.

[0022] In carrying out this reaction, if necessary, a reaction solvent (i) may be appropriately used.

[0023] The reaction solvent (i) is not particularly limited as long as it does not inhibit the reaction. For example, acetonitrile, pyridine, water, alcohols such as methanol, ethanol, and isopropyl alcohol, aliphatic hydrocarbons such as hexane and heptane, esters such as ethyl acetate and butyl acetate, aromatic hydrocarbons such as benzene, toluene, and xylene, halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, chlorotrifluoromethane, dichloroethane, chlorobenzene, and dichlorobenzene, ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, dimethoxyethane, and diethylene glycol dimethyl ether, amides such as formamide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and hexamethylphosphoramide, sulfoxides such as dimethyl sulfoxide, etc. can be mentioned. This reaction solvent (i) is used alone or in combination of two or more.

[0024] In this reaction, the reaction temperature is preferably set in the range of -30 to 150°C. Also, the reaction time is appropriately set according to the set reaction temperature, but it is preferably set in the range of 1 to 48 hours.

[0025] After completion of this reaction, the terephthalic acid compound of the present invention, which is the target product, can be taken out from the obtained reaction solution by means such as concentration of the reaction solution by distilling off the reaction solvent or solvent extraction method. Furthermore, if necessary, it can be purified by means such as washing with water or the like, activated carbon treatment, silica gel chromatography, recrystallization, etc.

[0026] <Synthesis method (2)> The terephthalic acid compound of the present invention can be synthesized by oxidizing the methyl group of a p-xylene compound having an iodine atom. Specifically, it can be synthesized by oxidizing the methyl group of a p-xylene compound having an iodine atom with potassium permanganate.

[0027] Examples of the p-xylene compound having an iodine atom include p-xylene compounds having an iodine atom represented by Chemical Formula (III-1) to Chemical Formula (III-3).

[0028]

Chem.

[0029] These compounds can be purchased and used as commercially available reagents, or can be synthesized by introducing an iodine atom into a p-xylene compound.

[0030] The amount of potassium permanganate used is in the range of 1 to 100 times the molar amount, preferably in the range of 2 to 10 times the molar amount, relative to the amount of the p-xylene compound having an iodine atom.

[0031] In carrying out this reaction, if necessary, a reaction solvent (i) may be appropriately used.

[0032] The reaction solvent (i) is not particularly limited as long as it does not inhibit the reaction, and examples thereof include acetonitrile; pyridine; water; alcohols such as methanol, ethanol, and isopropyl alcohol; aliphatic hydrocarbons such as hexane and heptane; esters such as ethyl acetate and butyl acetate; aromatic hydrocarbons such as benzene, toluene, and xylene; halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, chlorotrifluoromethane, dichloroethane, chlorobenzene, and dichlorobenzene; ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, dimethoxyethane, and diethylene glycol dimethyl ether; amides such as formamide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and hexamethylphosphoramide; sulfoxides such as dimethyl sulfoxide, etc. This reaction solvent (i) is used alone or in combination of two or more.

[0033] In this reaction, the reaction temperature is preferably set in the range of -10 to 150°C. Also, the reaction time is appropriately set according to the set reaction temperature, but it is preferably set in the range of 1 to 200 hours.

[0034] After the completion of this reaction, the terephthalic acid compound of the present invention, which is the target product, can be taken out from the obtained reaction solution by means such as concentration of the reaction solution by distilling off the reaction solvent or solvent extraction method. Furthermore, if necessary, it can be purified by using means such as washing with water or the like, activated carbon treatment, silica gel chromatography, recrystallization, etc.

[0035] When the terephthalic acid compound of the present invention is used as a curing agent for an epoxy resin, the epoxy resin having an epoxy group in the molecule and the terephthalic acid compound can be blended in the range of an equivalent ratio of epoxy group / carboxyl group of 1 to 15. Also, if necessary, a conventionally known curing accelerator can be used in combination in the range of 0.1 to 10 parts by weight based on 100 parts by weight of the epoxy resin.

[0036] The epoxy resin used in the present invention is not particularly limited as long as it has an epoxy group in the molecule. Typical epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, novolac type epoxy resins such as phenol novolac type epoxy resins and cresol novolac type epoxy resins, alicyclic epoxy resins, cyclic alicyclic epoxy resins such as 3′,4′-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, nitrogen-containing cyclic epoxy resins such as triglycidyl isocyanurate and hydantoin type epoxy resins, hydrogenated bisphenol A type epoxy resins, aliphatic epoxy resins, glycidyl ether type epoxy resins, bisphenol S type epoxy resins, biphenyl type epoxy resins, dicyclo ring type epoxy resins, naphthalene type epoxy resins, halogenated epoxy resins, and epoxy-modified organopolysiloxane compounds obtained by hydrosilylation addition reaction of an organic compound having a carbon-carbon double bond and a glycidyl group with a silicon compound having an SiH group (for example, epoxy-modified organopolysiloxane compounds disclosed in JP-A-2004-99751 and JP-A-2006-282988), but are not limited thereto. These epoxy resins may be used alone or in combination of two or more.

[0037] In addition, examples of conventionally known curing accelerators include amine compounds such as 1,8-diazabicyclo[5.4.0]-7-undecene, diethylenetriamine, triethylenetetramine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, tris(dimethylaminomethyl)phenol, imidazole compounds such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole, organic phosphine compounds such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, phenylphosphine, phosphonium compounds such as tetrabutylphosphonium bromide, tetrabutylphosphonium diethyl phosphorodithioate, tetraphenylborate salts such as tetraphenylphosphonium·tetraphenylborate, 2-methyl-4-methylimidazole·tetraphenylborate, N-methylmorpholine·tetraphenylborate, and aliphatic acid metal salts such as lead acetate, tin octylate, cobalt hexanoate, and the like.

[0038] In the epoxy resin composition of the present invention, various additives such as diluents, flexibility imparting agents, silane coupling agents, defoaming agents, leveling agents, fillers, pigments, dyes, etc. can be added as necessary.

[0039] The terephthalic acid compound of the present invention is useful as a curing agent for epoxy resin compositions for printed wiring boards, paints for electronic parts, encapsulants, adhesives, resist inks, etc., as well as for woodworking paints, coating agents for protecting the surfaces of optical fibers, plastics, and cans, epoxy resin compositions for ball grid array semiconductor encapsulation, epoxy resin compositions for optical semiconductor element encapsulation, epoxy resin compositions for semiconductor encapsulation used as underfill, and epoxy resin compositions for forming a resist underlayer film for lithography.

Examples

[0040] Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited thereto. The main raw materials used in the examples are as follows.

[0041] · 2-Aminoterephthalic acid (manufactured by Fujifilm Wako Pure Chemical Corporation) · Iodine monochloride (manufactured by Fujifilm Wako Pure Chemical Corporation) · Sodium nitrite (manufactured by Fujifilm Wako Pure Chemical Corporation) · Sodium iodide (manufactured by Fujifilm Wako Pure Chemical Corporation) · 50% Aqueous hypophosphorous acid solution (manufactured by Sigma-Aldrich)

[0042] The main raw materials and the like used in the preparation of the resin composition are as follows. (A) Epoxy resin · Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name: "jER828", epoxy equivalent 189) (B) Curing agent · 2,5-Diiodoisophthalic acid (synthesized according to the method described in Synthetic Communications (2013), 43(13), 1831-1836.) · 2,3,5,6-Tetraiodoterephthalic acid (synthesized according to the method described in U.S. Patent No. 10342232.) (C) Curing accelerator · 2-Ethyl-4-methylimidazole (manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name "Curezol 2E4MZ", hereinafter referred to as "2E4MZ".)

[0043] [Synthesis Example 1] (Synthesis of <2-Amino-3,5-diiodoterephthalic acid (Chemical formula (II-3-3))> Into a 200 mL flask, 7.25 g (40 mmol) of 2-aminoterephthalic acid and 16 mL of acetic acid were charged, and a mixture of 25.9 g (160 mmol) of iodine monochloride, 3.0 g (30.2 mmol) of 36% concentrated hydrochloric acid, and 52 g of ion-exchanged water was added dropwise while stirring at room temperature. Subsequently, the mixture was stirred at 50 °C for 85 hours. After filtering the reaction solution, tetrahydrofuran and toluene were added to the obtained solid for recrystallization. This was filtered and dried to obtain 14.3 g of a yellow solid (yield: 82%).

[0044] For the obtained yellow solid 1 The 1H-NMR spectral data was as follows. · 1 1H-NMR(CDCl 3 ) δ: 8.11(s, 1H). From this spectral data, the obtained yellow solid was identified as the title compound (2-amino-3,5-diiodoterephthalic acid) represented by chemical formula (II-3-3).

[0045] Example 1 <Synthesis of 2,6-diiodoterephthalic acid (chemical formula (I-1))> Into a 100 mL flask, 6.50 g (15 mmol) of 2-amino-3,5-diiodoterephthalic acid, 6.42 g of ion-exchanged water, 7.52 g of acetonitrile, and 3.1 g (30 mmol) of 95% sulfuric acid were charged. After purging with nitrogen, while stirring at -10 °C, 4.31 g (25 mmol) of a 40% aqueous sodium nitrite solution was added dropwise. After stirring at -10 °C for 1 hour, 19.8 g (150 mmol) of a 50% aqueous hypophosphorous acid solution was added dropwise at -10 °C, and stirring was continued for another 12 hours. After filtering the reaction solution, butyl acetate was added to the obtained solid for recrystallization. This was filtered and dried to obtain 2.20 g of a yellow solid (yield: 35%).

[0046] · 1 1H-NMR(CDCl 3 ) δ: 8.28(s, 2H). From this spectral data, the obtained yellow solid was identified as the title compound (2,6-diiodoterephthalic acid) represented by chemical formula (I-1).

[0047] Example 2 <Synthesis of 2,3,5-triiodoterephthalic acid (chemical formula (I-3))> Into a flask with a capacity of 1000 mL, 4.33 g (10 mmol) of 2-amino-3,5-diiodoterephthalic acid, 10.00 g of ion-exchanged water, 10.00 g of acetonitrile, and 2.06 g (20 mmol) of 95% sulfuric acid were charged. After nitrogen substitution, while stirring at -10°C, 5.18 g (30 mmol) of a 40% aqueous sodium nitrite solution was added dropwise. After stirring at -10°C for 1 hour, 11.31 g (40 mmol) of a 53% aqueous sodium iodide solution was added dropwise at -10°C, and stirring was continued for another 12 hours. After quenching with a 35% aqueous sodium bisulfite solution, the solid was recovered by filtration. 25 g of ion-exchanged water was added to the filtrate for reslurrying, followed by filtration and drying to obtain 4.24 g of a brown solid (yield: 78%).

[0048] The obtained brown solid's 1 1H-NMR spectral data was as follows. · 1 1H-NMR(CDCl 3 ) δ: 7.88(s, 1H). From this spectral data, the obtained brown solid was identified as the title compound (2,3,5-triiodoterephthalic acid) represented by chemical formula (I-3).

[0049] 〔Example 3〕 Epoxy resin (jER828) and a curing agent (the terephthalic acid compound of Example 1) were blended at a ratio such that the equivalent ratio of epoxy group / carboxyl group was 2:1, and further 2.0 parts by weight of a curing accelerator (2E4MZ) was mixed per 100 parts by weight of the epoxy resin to prepare an epoxy resin composition. Regarding this epoxy resin composition, the gel time at 180°C was measured by the hot plate method (JIS C-2105) to evaluate the curing performance. For those with a gel time of 25 minutes or more, it was designated as "N.D." The results obtained were as shown in Table 1.

[0050] 〔Example 4, Comparative Examples 1 - 2〕 As a curing agent, instead of the terephthalic acid compound of Example 1, the terephthalic acid compound of Example 2 (Example 4), 2,5-diiodoterephthalic acid (Comparative Example 1), and 2,3,5,6-tetraiodoterephthalic acid (Comparative Example 2) were used. In the same manner as in Example 3, each epoxy resin composition was prepared, and the gel time was measured to evaluate the curing performance. For those with a gel time of 25 minutes or more, "N.D." was used. The obtained evaluation results are shown in Table 1.

[0051]

Table 1

[0052] From Table 1, when the terephthalic acid compound of the present invention was used as the curing agent (Examples 3 and 4), it was confirmed that the gel time was longer compared to the case where a conventional curing agent was used (Comparative Example 1), indicating excellent storage stability. Therefore, the terephthalic acid compound of the present invention is considered to be more suitable as a curing agent for epoxy resins than conventional curing agents.

Industrial Applicability

[0053] Since the terephthalic acid compound of the present invention has iodine atoms in its molecule, when used as a curing agent for epoxy resin compositions, it is expected to exhibit better storage stability compared to the case of using conventional curing agents, and to provide a cured product having excellent heat resistance and electrical properties. Therefore, the terephthalic acid compound of the present invention is considered to be suitable as a curing agent for epoxy resins.

Claims

1. Terephthalic acid compounds represented by chemical formulas (I-1) to (I-3). 【Chemistry 1】

2. A curing agent for epoxy resins, comprising the terephthalic acid compound according to claim 1.

3. An epoxy resin composition comprising the epoxy resin curing agent according to claim 2 and an epoxy resin.

4. 4. The epoxy resin composition according to claim 3, which further comprises a curing accelerator.

5. A cured product obtained by curing the resin composition according to any one of claims 3 to 4.

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