JP2014177525A - Bisimidazole compound, epoxy resin curing agent comprising bisimidazole compound, and one-pack curable epoxy resin composition comprising epoxy resin curing agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compound excellent as a latent curing agent which can provide a one-pack curable epoxy resin with excellent storage stability and curability.SOLUTION: A bisimidazole compound is represented by general formula (I), where R, Rand Rindependently represent a hydrogen atom, an alkyl group or an aryl group, and A represents an alkylene group or an arylene group.

Description

  The present invention relates to a bisimidazole compound, and in particular, has a low volatility and, when used in combination with a polyepoxy compound, can provide an epoxy resin excellent in storage stability and curability, About.

  Epoxy resins have excellent adhesion to various substrates, and cured products obtained by curing epoxy resins with curing agents have relatively good heat resistance, chemical resistance, electrical properties, mechanical properties, etc. Therefore, it is used in a wide range of applications such as paints, adhesives, and various molding materials.

  Conventionally, epoxy resin compositions have been mainly two-component systems in which a curing agent or a curing accelerator is added immediately before use. However, the two-component system has the advantage that it can be cured at room temperature or low temperature, but it must be weighed and mixed immediately before use, and the usable time is short. It has a drawback that the use conditions are limited, such as difficulty.

  In order to solve such a problem, a one-part curable epoxy resin composition has been proposed. In order to obtain such a one-part curable resin composition, heating is performed without causing a curing reaction at room temperature. Therefore, it is necessary that a curing agent that initiates the curing reaction, that is, a latent curing agent is blended. As the latent curing agent, for example, dicyandiamide, dibasic acid dihydrazide, boron trifluoride amine complex salt, guanamines, melamine, imidazoles and the like have been proposed.

  However, for example, a one-part curable epoxy resin composition using dicyandiamide, melamine, and guanamine as a latent curing agent is excellent in storage stability, but is cured at a high temperature of 150 ° C. or higher for a long time. There is the problem of requiring heating. Furthermore, it is widely practiced to shorten the curing time by using these latent curing agents and curing accelerators in combination, but there arises a problem that storage stability is significantly impaired.

  On the other hand, when dibasic acid dihydrazide or imidazole is used as a latent curing agent, it cures at a relatively low temperature but has poor storage stability. In addition, the one-part curable epoxy resin composition using boron trifluoride amine complex salt has the advantages of excellent storage stability and a short curing time, but is inferior in water resistance and corrosive to metals. Have the disadvantages.

  Moreover, although using an imidazole-acrylic-acid reaction product (patent document 1) is proposed, it is not described regarding the bisimidazole compound.

JP-A-6-179657

Accordingly, a first object of the present invention is to provide a compound excellent as a latent curing agent for a one-pack type curable epoxy resin composition, which is excellent in storage stability and curability.
The second object of the present invention is to provide a latent curing agent capable of providing a one-part curable epoxy resin composition excellent in storage stability and curability.
The third object of the present invention is to provide a novel one-component curable epoxy resin composition that is excellent in storage stability and curability.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a specific bisimidazole compound is a compound that can achieve the above object, and have reached the present invention.

  That is, the present invention provides a bisimidazole compound represented by the following general formula (I), a curing agent for an epoxy resin containing the bisimidazole compound, and an epoxy resin and the bisimidazole. A one-component curable epoxy resin composition comprising a latent curing agent for an epoxy resin containing a compound.

但し、式中のＲ_１、Ｒ_２及びＲ_３は、互いに独立して、水素原子、アルキル基又はアリール基であり、Ａはアルキレン基又はアリーレン基である。

However, R ₁ , R ₂ and R ₃ in the formula are each independently a hydrogen atom, an alkyl group or an aryl group, and A is an alkylene group or an arylene group.

  The compound of the present invention can be produced using readily available raw materials, has low volatility, and has a balance between appropriate curing characteristics and storage stability, and thus becomes a practical curing agent. Using the compound of the present invention, particularly when it is a one-pack type curable epoxy resin composition that does not contain a curable resin component that is solid at room temperature, it is excellent in workability, and adhesion or impregnation adhesion in narrow spaces It becomes a one-pack type curable epoxy resin composition suitable for the above.

The bisimidazole compound of the present invention is a compound represented by the general formula (I).
R ₁ , R ₂ and R ₃ in the formula each independently represent a hydrogen atom, an alkyl group or an aryl group. Examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, amyl group, isoamyl group, tert-amyl group, hexyl group, isohexyl group, octyl group, A 2-ethylhexyl group, a tertiary octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group and the like can be mentioned. Examples of the aryl group include a phenyl group and a naphthyl group.

R ₁ is preferably an alkyl group having 1 to 11 carbon atoms or a phenyl group, and R ₂ is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. R ₃ is preferably a hydrogen atom or a methyl group.

A is an alkylene group or an arylene group. Examples of the alkylene group include methylene, ethylene, propylene, isopropylene, butylene, isobutylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, decamethylene, undeca Examples thereof include a methylene group and a dodecamethylene group. Examples of the arylene group include a phenylene group and a naphthylene group.
A is preferably an alkylene group having 1 to 10 carbon atoms.

  Examples of the bisimidazole compound of the present invention include compounds represented by the following formulas (I-1) to (I-8).

上記反応に使用される触媒としては、例えば、ジブチルスズラウレート、ジ(2-エチルヘキサン酸)スズ等のスズ化合物、テトラアルキルチタネート等のチタン化合物、トリフェニルホスフィン、トリブチルホスフィン、トリシクロヘキシルホスフィン等のホスフィン類、トリエチルアミン、トリブチルアミン、ジアザビシクロウンデセン、ジアザビシクロノネン、1,4-ジアザビシクロ[2.2.2]オクタン等の3級アミン、ピリジン、N,N-ジメチルアミノピリジン等のピリジン類、1-メチルイミダゾール等のイミダゾール類等が挙げられる。 The bisimidazole compound of the present invention can be produced by a reaction represented by the following formula.

Examples of the catalyst used in the above reaction include tin compounds such as dibutyltin laurate and di (2-ethylhexanoic acid) tin, titanium compounds such as tetraalkyl titanate, triphenylphosphine, tributylphosphine, and tricyclohexylphosphine. Phosphines, triethylamine, tributylamine, diazabicycloundecene, diazabicyclononene, tertiary amines such as 1,4-diazabicyclo [2.2.2] octane, pyridines such as pyridine and N, N-dimethylaminopyridine, Examples include imidazoles such as 1-methylimidazole.

  Examples of the solvent include ketones such as methyl ethyl ketone, methyl amyl ketone, diethyl ketone, acetone, methyl isopropyl ketone, propylene glycol monomethyl ether acetate, cyclohexanone; tetrahydrofuran, 1,2-dimethoxyethane, 1,2-diethoxy. Ethers such as ethane and propylene glycol monomethyl ether; esters such as ethyl acetate and n-butyl acetate; alcohols such as iso- or n-butanol, iso- or n-propanol and amyl alcohol; benzene, toluene and xylene Aromatic hydrocarbons such as carbon tetrachloride, chloroform, trichloroethylene, and methylene chloride; halogenated aromatic hydrocarbons such as chlorobenzene, and the like.

  The reaction temperature is preferably from room temperature to 200 ° C, particularly preferably from 50 to 150 ° C. The reaction time is preferably 0.5 hours to 72 hours, particularly preferably 1 hour to 8 hours.

The curing agent for epoxy resin of the present invention contains the bisimidazole compound of the present invention.
In particular, when a latent curing agent for a one-pack type curable epoxy resin composition is used, the bisimidazole compound of the present invention is preferably liquid at room temperature from the viewpoint of being easily blended uniformly into the epoxy resin. .

  In addition, a general-purpose curing agent for epoxy resin can be used in combination with the curing agent for curable epoxy resin of the present invention, if necessary. Examples of general-purpose curing agents for epoxy resins include imidazoles such as 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, and 1- (2-methylimidazol-1-ylmethyl) naphthalen-2-ol; Polyalkylpolyamines such as diethylenetriamine, triethylenetriamine and tetraethylenepentamine; alicyclic polyamines such as 1,2-diaminocyclohexane, 1,4-diamino-3,6-diethylcyclohexane and isophoronediamine; Aromatic polyamines such as range amine, diaminodiphenylmethane, diaminodiphenylsulfone and the like can be mentioned.

  Also, these polyamines are reacted with various epoxy resins such as glycidyl ethers such as phenyl glycidyl ether, butyl glycidyl ether, bisphenol A-diglycidyl ether, bisphenol F-diglycidyl ether, or glycidyl esters of carboxylic acid. Polyepoxy addition-modified products produced by the above; amidation-modified products produced by reacting these organic polyamines with carboxylic acids such as phthalic acid, isophthalic acid, and dimer acid; these polyamines and formaldehyde And aldehydes such as phenol, cresol, xylenol, tert-butylphenol, resorcin and the like, which are produced by reacting with a phenol having at least one aldehyde-reactive site in the nucleus. Mannich modifications thereof, can also be used in combination. Furthermore, latent curing agents such as dicyandiamide, acid anhydrides, and imidazoles can be used in combination.

  The one-component curable epoxy resin composition of the present invention is obtained by blending the latent curing agent for epoxy resin (B) containing the polyepoxy compound (A) and the bisimidazole compound of the present invention.

  Examples of the epoxy resin as the component (A) include polyglycidyl ether compounds of mononuclear polyhydric phenol compounds such as hydroquinone, resorcin, pyrocatechol, and phloroglucinol; dihydroxynaphthalene, biphenol, methylene bisphenol (bisphenol F) , Methylenebis (orthocresol), ethylidenebisphenol, isopropylidenebisphenol (bisphenol A), isopropylidenebis (orthocresol), tetrabromobisphenol A, 1,3-bis (4-hydroxycumylbenzene), 1,4-bis (4-hydroxycumylbenzene), 1,1,3-tris (4-hydroxyphenyl) butane, 1,1,2,2-tetra (4-hydroxyphenyl) ethane, thiobisphenol, sulfo Polyglycidyl ether compounds of polynuclear polyhydric phenol compounds such as rubisphenol, oxybisphenol, phenol novolak, orthocresol novolak, ethylphenol novolak, butylphenol novolak, octylphenol novolak, resorcin novolak, terpene phenol; ethylene glycol, propylene glycol, butylene glycol , Hexanediol, polyglycol, thiodiglycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, polyglycidyl ethers of polyhydric alcohols such as bisphenol A-ethylene oxide adduct; maleic acid, fumaric acid, itaconic acid, succinic acid , Glutaric acid, suberic acid, adipic acid, azelaic acid, sebacic acid, dimer acid, Limeric acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid, pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid, endomethylenetetrahydrophthalic acid, etc. Glycidyl esters of acid and homopolymers or copolymers of glycidyl methacrylate; glycidyl such as N, N-diglycidylaniline, bis (4- (N-methyl-N-glycidylamino) phenyl) methane, diglycidyl orthotoluidine An epoxy compound having an amino group; vinylcyclohexene diepoxide, dicyclopentanediene diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-6 Epoxidized products of cyclic olefin compounds such as methylcyclohexanecarboxylate and bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate; epoxidized conjugated diene polymers such as epoxidized polybutadiene and epoxidized styrene-butadiene copolymer, Examples include heterocyclic compounds such as triglycidyl isocyanurate.

  In addition, these epoxy resins may be those internally crosslinked by a prepolymer having an isocyanate group at the end, but by a polyvalent active hydrogen compound such as a polyhydric phenol, a polyamine, a carbonyl group-containing compound, or a polyphosphate ester. It may be one having a high molecular weight.

  Moreover, the epoxy equivalent of a polyepoxy compound needs to be 70-3000, and it is preferable that it is 90-2000. If the epoxy equivalent is less than 70, the physical properties of the cured product may be lowered, and if it is greater than 3000, sufficient curability may not be obtained.

  In addition, the one-component curable epoxy resin composition of the present invention includes a curing catalyst; reactive or non-reactive dilution such as a curing catalyst; monoglycidyl ethers, dioctyl phthalate, dibutyl phthalate, benzyl alcohol, coal tar, and the like. Agent (plasticizer): glass fiber, carbon fiber, cellulose, silica sand, cement, kaolin, clay, aluminum hydroxide, bentonite, talc, silica, fine powder silica, titanium dioxide, carbon black, graphite, iron oxide, bituminous substance Fillers or pigments such as γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -N′-β- (aminoethyl) -Γ-aminopropyltriethoxysilane, γ-anilinopropyltriethoxysilane, γ- Glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, vinyltriethoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltriethoxysilane, γ Silane coupling agents such as methacryloxypropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane; candelilla wax, carnauba wax, wood wax, ibotarou, beeswax, lanolin, spermaceti, Lubricants such as montan wax, petroleum wax, fatty acid wax, fatty acid ester, fatty acid ether, aromatic ester, aromatic ether; thickener; thixotropic agent; antioxidant; light stabilizer; ultraviolet absorber; Antifoaming agent; rust preventive agent; colloid Silica, may contain additives customary for such colloidal alumina, further, xylene resin may be used in combination an adhesive resin such as petroleum resin.

  The one-component curable epoxy resin composition of the present invention includes, for example, paints or adhesives for concrete, cement mortar, various metals, leather, glass, rubber, plastic, wood, cloth, paper, etc .; adhesive tape for packaging, adhesive Labels, frozen food labels, removable labels, POS labels, adhesive wallpaper, adhesives for adhesive flooring; art paper, lightweight coated paper, cast coated paper, coated paperboard, carbonless copier, impregnated paper and other processed paper; natural Fiber treatment agents such as fibers, synthetic fibers, glass fibers, carbon fibers, metal fibers, etc., fraying preventives, processing agents, etc .; building materials such as sealing materials, cement admixtures, waterproofing materials; sealing for electronic and electrical equipment It can be used for a wide range of applications such as stoppers.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these.

[Synthesis of Compound A]
To a 500 ml separable flask, 116.1 g of 2-methylimidazole (hereinafter abbreviated as “2MZ”) was added, and 116.1 g of propylene glycol monomethyl ether was further added to dissolve 2MZ. Further, 167.8 g of 1,6-hexamethylene diacrylate was added and aged at 120 ° C. for 2 hours. After confirming the completion of the reaction by gas chromatography, the temperature was raised to 150 ° C. and the pressure was reduced to remove propylene glycol monomethyl ether in the system to obtain the target compound, a yellow liquid compound A.

[Synthesis of Compound B]
To a 500 ml separable flask, 106.6 g of 2-ethyl-4-methylimidazole (hereinafter abbreviated as “2E4MZ”) was added, and 106.6 g of propylene glycol monomethyl ether was further added to dissolve 2E4MZ. Further, 143.4 g of 1,10-decamethylene diacrylate was added and aged at 120 ° C. for 2 hours. After confirming the completion of the reaction by gas chromatography, the temperature was raised to 150 ° C. and the pressure was reduced to remove propylene glycol monomethyl ether in the system to obtain the target compound, a brown liquid compound B.

[Synthesis of Comparative Compound C]
11M of 2MZ was added to a 500 ml separable flask, and 116.0 g of propylene glycol monomethyl ether was further added to dissolve 2MZ. 268.0 g of 2-ethylhexyl acrylate was added and aged at 120 ° C. for 2 hours. After confirming the completion of the reaction by gas chromatography, the temperature was raised to 150 ° C. and the pressure was reduced to remove propylene glycol monomethyl ether in the system to obtain a yellow liquid comparative compound C as the target compound. .

  78.8 g of 2MZ was added to a 300 ml separable flask, and 78.8 g of propylene glycol monomethyl ether was further added to dissolve 2MZ. Further, 142.4 g of 1,10-decamethylene diacrylate was added and aged at 120 ° C. for 2 hours. After confirming that the reaction was completed by gas chromatography, the temperature was raised to 150 ° C. and the pressure was reduced. The propylene glycol monomethyl ether was removed, and a crystalline light yellow solid compound D was obtained.

[Evaluation]
The volatility of the obtained compounds A to D was evaluated by Tg-DTA (differential thermal-thermogravimetric measurement). The results are shown in Table 1.

  From Table 1, it was confirmed that the compounds A, B and D, which are bisimidazoles, have significantly higher thermogravimetric reduction temperatures and lower volatility than the comparative compound C, which is monoimidazole.

[Examples 4 and 5 and Comparative Example 2]
The compounds A to C obtained in the above examples were set as latent curing agents A to C, respectively, and Adeka Resin EP-4901E (Adeka Bisphenol F type epoxy resin, epoxy equivalent 170) and [Table 2] One-part curable epoxy resin compositions A to C were prepared by blending in the indicated amounts.

The curability (GT), initial viscosity, and storage stability of the obtained one-component curable epoxy resin composition were evaluated by the following methods. The results are shown in Table 2.
[G. T]
The one-component curable epoxy resin composition of the sample was placed on a hot plate at 150 ° C., and the time until curing was measured.
(Initial viscosity)
The one-component curable epoxy resin composition of the sample was measured with an E-type viscometer at 25 ° C.
[Storage stability]
The viscosity of the one-component curable epoxy resin composition of the sample after storage at 25 ° C. for 1 day and 2 days was measured by the same method as the initial viscosity, and the viscosity increase rate relative to the initial viscosity was determined and evaluated.

※EP-4901E：ビスフェノールF型エポキシ樹脂（エポキシ当量：170）

* EP-4901E: Bisphenol F type epoxy resin (epoxy equivalent: 170)

  The one-component curable epoxy resin composition (A) is superior to the composition (C) in spite of having the same curability as the one-component curable epoxy resin composition (C). It shows storage stability. On the other hand, the one-component curable epoxy resin composition (B) cures slower than the one-component curable epoxy resin compositions (A) and (C), but the storage stability is one-component curable epoxy resin composition. It was confirmed that significantly better results were obtained than the product (A) and the comparative one-component curable epoxy resin composition (C).

  The bisimidazole compound of the present invention can be used as a compound for a latent curing agent that can provide a one-part curable epoxy resin that has excellent storage stability and excellent curability. In addition, the one-component curable epoxy resin composition of the present invention can be used for a wide range of applications such as paints, adhesives, various molding materials, and the like, and thus is extremely useful industrially.

Claims (8)

A bisimidazole compound represented by the following general formula (I):

However, R ₁ , R ₂ and R ₃ in the formula are each independently a hydrogen atom, an alkyl group or an aryl group, and A is an alkylene group or an arylene group. The bisimidazole compound according to claim 1, wherein R ₁ in the general formula (I) is an alkyl group having 1 to 11 carbon atoms or a phenyl group. The bisimidazole compound according to claim 1 or 2, wherein R ₂ in the general formula (I) is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. The imidazole compound according to any one of claims 1 to 3, wherein R ₃ in the general formula (I) is a hydrogen atom or a methyl group.   The bisimidazole compound described in any one of Claims 1-4 whose A in the said general formula (I) is a C1-C10 alkylene group.   The bisimidazole compound according to any one of claims 1 to 5, which is liquid at normal temperature.   A curing agent for epoxy resins, comprising the bisimidazole compound according to any one of claims 1 to 6.   A one-pack type curable epoxy resin composition comprising a latent curing agent for an epoxy resin containing a polyepoxy compound and the bisimidazole compound according to claim 6.