JPH0651783B2 - Curing agent for epoxy resin - Google Patents

Description

The present invention relates to a curing agent for epoxy resin.
More specifically, the present invention relates to a one-component type epoxy resin curing agent that has excellent storage stability at room temperature, is cured in a short time under heat curing conditions, and provides excellent curing performance.

[Conventional technology]

The curing agent for the epoxy resin includes a curing agent that exhibits a curing action at room temperature and a curing agent that exhibits a curing action under heating. Examples of the former include alkylpolyamines and polymercaptans, but the epoxy resin composition containing such a curing agent cannot be stored for a long period of time.
On the other hand, examples of the latter include various types such as aromatic amines and carboxylic acid anhydrides. Guanidines and hydrazides are known as latent curing agents that are stable at room temperature and exhibit a curing action when heated as an epoxy resin composition. One-component epoxy resin compositions containing these curing agents, especially latent curing agents, can be stored for a relatively long period of time, but have the drawback of requiring a high curing temperature and a very long curing time during heat curing. is there.

[Problems to be solved by the invention]

As described above, the one-component epoxy resin composition using the conventionally proposed latent curing agent has a problem in storage stability and curability balance, and a curing for one-component epoxy resin that satisfies both performances. There has been a great demand for the emergence of agents.

The present inventors have made extensive studies in view of this point, and the epoxy resin composition containing a specific imidazole or imidazoline derivative can be stably stored for a long period of time, and the curing conditions are low temperature and short time as compared with the conventional one. The present invention was found to be cured by the above method.

[Means for solving problems]

The present invention comprises reacting an imidazole compound or an imidazoline compound with a monoepoxy compound, and further reacting the reaction product with a monoisocyanate compound to obtain the 1-position and 3-position structures represented by the following general formula (1) and / or It is a curing agent for epoxy resin characterized by being represented by (2).

_{[R 1} and _{R 2} are _C 1 _{-C 1 2} alkyl group, an optionally substituted phenyl _group, C 1 _{-C 1 2} alkoxy methyl group, which may have a substituent Fuenokishimechiru group,
C ₁ -C _{1 2} acyloxymethyl group, which may have a substituent benzoyloxy methyl group, _{R 3} is _C 1 -C
_{1 2} alkyl group, will be described in more detail epoxy resin curing agent according to the present invention below that shows] a a phenyl group which may have a substituent.

The imidazole or imidazoline derivative of the present invention can be easily obtained by, for example, adding a monoisocyanate compound to a reaction product of an imidazole compound or an imidazoline compound and a monoepoxy compound.

Examples of the imidazole compound used as a raw material include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 2-dodecylimidazole, 2-phenylimidazole, 2-ethyl-4-azole. Methyl imidazole, 2-benzyl imidazole, 2,4,5-trimethyl imidazole and the like can be mentioned.

Examples of the imidazoline compound used as a raw material include imidazoline, 2-methylimidazoline, 2-ethylimidazoline, 2-isopropylimidazoline, 2-undencylimidazoline, 2-dodecylimidazoline, 2-phenylimidazoline, 2-ethyl- 4-methylimidazoline, 2-benzylimidazoline, 2,4,5-trimethylimidazoline and the like can be mentioned. The preferable imidazole compound or imidazoline compound is one selected from 2-methylimidazole or 2-ethyl-4-methylimidazole or a mixture thereof. The monoepoxy compound used as the raw material is 1,2-epoxybutane, 1,2-epoxyhexane, 1,2-epoxyoctane, styrene oxide, butyl glycidyl ether, hexyl glycidyl ether, phenyl glycidyl ether, glycidyl acetate. , Glycidyl butyrate, glycidyl hexoate, glycidyl benzoate and the like. Preferred is phenyl glycidyl ether.

As the monoisocyanate compound used as the raw material, phenyl isocyanate, p-methylphenyl isocyanate, o-methylphenyl isocyanate, p-
Examples thereof include methoxyphenyl isocyanate, 2,4-dimethylphenyl isocyanate, o-chlorophenyl isocyanate, p-chlorophenyl isocyanate, methyl isocyanate, ethyl isocyanate, propyl isocyanate, butyl isocyanate and hexyl isocyanate. Preferred is phenyl isocyanate.

When the imidazole or imidazoline derivative of the present invention is prepared by adding a monoisocyanate compound to a reaction product of an imidazole compound or an imidazoline compound and a monoepoxy compound, for example, it can be obtained by controlling the molar ratio of each compound. That is, the structural formula
(1) is obtained when the molar ratio of the imidazole compound or imidazoline compound to the monoepoxy compound and the monoisocyanate compound is 1/1/1. In the case of structural formula (2), the molar ratio is 1/2/1. Also, the molar ratio is 1/1/1
In the case of 1/2/1, the mixture of the structural formula (1) and the structural formula (2) is obtained, but there is no problem in curability and storage stability, and accordingly, the desired balance between storage stability and curability is achieved. The curing agent removed can be obtained by controlling this molar ratio.

The curing agent of the present invention can be used in liquid form or solid form with respect to an epoxy resin having two or more epoxy groups per molecule on average. For example, polyhydric phenol such as bisphenol A, bisphenol F, catechol and resorcin, or polyglycidyl ether obtained by reacting polyhydric alcohol such as glycerin or polyethylene glycol with epichlorohydrin, or p-oxybenzoic acid, β- Glycidyl ether ester obtained by reacting hydroxycarboxylic acid such as oxynaphthoic acid with epichlorohydrin, or polyglycidyl ester obtained by reacting polycarboxylic acid such as phthalic acid or terephthalic acid with epichlorohydrin, or 4,4 ′ -Glycidylamine obtained by reacting diaminodiphenylmethane, m-aminophenol, etc. with epichlorohydrin, and further epoxidized novolak resin, epoxidized cresol novolak resin, ether Like alkoxy of polyolefin, but not limited thereto. A preferred epoxy resin is diglycidyl ether of bisphenol A.

The amount of the curing agent of the present invention added to the epoxy resin is determined from the viewpoint of curability, cured physical properties, storage stability, and is not particularly limited, but preferably 100 parts by weight of the epoxy resin. The curing agent of the present invention is 0.1 to 50 parts by weight. That is, if the amount is less than 0.1 parts by weight, it takes a very long time to obtain sufficient curing performance, which is not practical.
On the other hand, if it exceeds 50 parts by weight, the heat generated during the curing process becomes large and it becomes difficult to control the curing, and the handling becomes complicated. Particularly preferred is 1 to 40 parts by weight of the curing agent of the present invention with respect to 100 parts by weight of the epoxy resin.

The curing agent of the present invention may be used in combination with another type curing agent, if desired. For example, carcidine compounds such as dicyandiamide, methylguanidine, and phenylguanidine, carboxylic acid anhydride compounds such as phthalic anhydride, trimellitic anhydride, and hexahydrophthalic anhydride, and aromatic compounds such as diaminodiphenylmethane and diaminodiphenylsulfone. Examples thereof include group amine compounds, hydrazide compounds such as adibic acid dihydrazide, isophthalic acid dihydrazide, and terephthalic acid dihydrazide, and phenol resins, melamine resins, and urea resins.

When the curing agent of the present invention is used to cure an epoxy resin, the formulation can optionally include extenders, reinforcing agents, fillers, pigments and the like. For example, coal tar, glass fiber, asbestos fiber, boron fiber, carbon fiber, cellulose, polyethylene powder, polypropylene powder,
Quartz powder, mineral silicate, mica, asbestos powder, slate powder, kaolin, aluminum oxide trihydrate, aluminum hydroxide, Chiyoke powder, gypsum, calcium carbonate, antimony trioxide, penton, silica, aerosol, lithophone, Examples thereof include barite, titanium dioxide, carbon black, graphite, iron oxide, gold, aluminum and iron powder. All of these are effectively used depending on the application.

When the curing agent of the present invention is used to cure the epoxy resin, the formulation may optionally include organic solvent reactive diluents, non-reactive diluents, modified epoxy resins and the like. Examples of the organic solvent include toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, ethanol, butanol and the like. Examples of the reactive diluent include butyl glycidyl ether, N, N'-diglycidyl-o-toluidine, phenyl glycidyl ether, styrene oxide, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,6-hexanediol di Glycidyl ether, etc. are mentioned. Examples of non-reactive diluents include dioctyl phthalate, dibutyl phthalate, dioctyl adipate, petroleum-based solvents and the like. Examples of the modified epoxy resin include urethane modified epoxy resin, rubber modified epoxy resin, and alkyd modified epoxy resin.

〔The invention's effect〕

The thus obtained curing agent for epoxy resin of the present invention has excellent storage stability at room temperature, has significantly improved curability as compared with conventional latent curing agents, and has good performance. It gives a cured product.

The epoxy resin composition using the curing agent of the present invention has excellent cured physical properties and can be used in a wide variety of fields. For example, in the field of adhesives, in the automotive field, headlights, gasoline tanks, hemming flanges such as bonnets, body and roof sheet steel joining, or in the electrical field speaker magnets, motor coil impregnation and Adhesive, tape head,
Examples include adhesives for buttery, adhesives for fluorescent lamp safety devices, and adhesives for die bonding in the electronic field.
Regarding paints, for powder paints, or as a special field, solder resist inks, conductive paints and the like can be mentioned. It can also be used as an electrically insulating material and a laminated structure.

The present invention will be described below with reference to examples, but the scope of the present invention is not limited by these examples. "Parts" in the examples indicate parts by weight.

Example 1 82 parts of 2-methylimidazole and 150 parts of phenylglycidyl ether were dissolved in 232 parts of methyl isobutyl ketone,
Allow to react for 6 hours under reflux. After that, the temperature is returned to room temperature and the solvent is removed. After removing the solvent, 116 parts of the solid product and 59.5 parts of phenylisocyanate are dissolved in 702 parts of carbon tetrachloride and reacted at 40 ° C. for 4 hours with stirring. After the reaction, the solvent is removed to obtain the adduct I
Got From infrared and'H-NMR, the structure in the present invention is
It was confirmed that it corresponds to (1). Softening point 160 ° C Additive I
21.4 parts of AER331 (Asahi Kasei Co., Ltd., bisphenol A
100 parts of epoxy resin having an epoxy equivalent of 189) was added, and the composition was obtained by passing through a triple roll twice. Using this composition, curability and storage stability were measured. The results are shown in Table-2.

Examples 2 to 4 Table 1 shows the results of synthesizing the adducts II to IV according to the synthesis method of Example 1. The results of curability and storage stability with the epoxy resin are shown in Table-2.

Comparative Example 1 Table 1 shows the curability and storage stability when 5 parts of 2-methylimidazole was synthesized into 100 parts of AER331.

From the above results, it can be seen that the imidazole or imidazoline derivative of the present invention exhibits good storage stability and its curability is not different from that of the imidazole or imidazoline compound.

Claims (1)

[Claims] 1. A structure in which the 1-position and 3-position obtained by reacting an imidazole compound or an imidazoline compound with a monoepoxy compound and further reacting the reaction product with a monoisocyanate compound is represented by the following general formula (1) and / or Or a curing agent for an epoxy resin, which is represented by (2).