JPS61268723A - Curing agent for epoxy resin - Google Patents

Abstract

PURPOSE:To provide the titled curing agent of good storage stability at ambient temperatures, giving excellent curing performance by curing in a short time in curing conditions under heating, useful for adhesives, coatings, etc., consisting either of imidazole- or imidazoline derivative each having specific structure. CONSTITUTION:The objective curing agent consisting either of imidazole- or imidazoline derivative with their 1- and 3-sites structures represented respectively by (A) formulae I and II, or by (B) formulae III and IV [R1 and R2 are each 1-12C alkyl, (substituted)phenyl, 1-12C alkoxymethyl, (substituted) phenoxymethyl, 1-12C acyloxymethyl, or (substituted)benzoyloxymethyl; R3 is 1-12C alkyl or (substituted)phenyl].

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a curing agent for epoxy resin.

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

[Conventional technology]

There are two types of curing agents for 4-kiss resins: those that exhibit a curing effect at room temperature, and those that exhibit a curing effect under heating. Examples of the former include alkyl polyamines and polymercaptans, but epoxy resin compositions containing such curing agents cannot be stored for long periods of time.

On the other hand, there are various examples of the latter, such as aromatic amines and carunic acid anhydride. In addition, guanidines and hydrazides are known as latent curing agents for epoxy resin compositions that are stable at room temperature and exhibit a curing action when heated. One-component epoxy resin compositions containing these curing agents, especially latent curing agents, can be stored for a relatively long period of time, but they have the disadvantage of requiring high curing temperatures and extremely long curing times when heat curing. be. [Problems to be Solved by the Invention] As described above, 1. The one-component epoxy resin compositions using latent curing agents that have been proposed so far have problems with storage stability and curability. There has been a great demand for a one-component curing agent for epoxy resins that satisfies both properties.

In view of this, the present inventors conducted extensive research and found that epoxy resin compositions containing specific imidazole or imidazoline derivatives can be stored stably for long periods of time, and may require lower curing conditions than conventional ones. The present invention was achieved by discovering that it cures in a short time.

[Means to solve the problem]

The present invention is an epoxy resin curing agent characterized in that the structures at the first and third positions of an imidazole or imidazoline derivative are represented by the following general formula (1) or (2).

[R1 and R are a self-C12 alkyl group, a phenyl group that may have a substituent, a C1-CI2 alkoxymethyl group, a phenoxymethyl group that may have a substituent, c
+-ct acyloxymethyl group, optionally substituted benzoyloxymethyl group, R3 is C1 to Ct
t represents an alkyl group and a phenyl group which may have a substituent] The curing agent for epoxy resin according to the present invention will be described in more detail below.

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

Imidazole compounds used as raw materials include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 2-)"7'cylimidazole, 2-phenylimidazole, 2-ethyl Examples include -4-methylimidazole, 2-pene climidazole, 2,4.5-)limethylimidazole, and the like.

Imidazoline compounds used as raw materials include imidazoline, 2-methylimidazoline, 2-ethylimidazoline, 2-isozolobyl imidazoline, 2-undecylimidazoline, 2-dodecylimidazoline, 2-phenylimidazoli/, 2-ethyl -4-methylimidazoline, 2-benzylimidazoline, 2,4.5-trimethylimidazoline and the like. Preferred imidazole compounds or imidazoline compounds are one selected from 2-methylimidazole and 2-ethyl-4-methylimidazole, or a mixture thereof. Epoxy compounds used as raw materials include 1,2-epoxybutane, 1,2-epoxyhexane, 1,2-epoxyoctane, styrene oxide, butyl glycidyl ether, hexyl glycidyl ether, phenyl glycidyl ether, glycidiacetate, Examples include glycidyl butyrate, glycidyl hexoate, glycidiacetate, and the like. Preferred is phenyl glycidyl ether.

In addition, the isocyanate compounds used as raw materials include:
Phenyl isocyanate, p-methylphenylisocyanate, O-methylphenylinocyanate, p-methoxyphenylisocyanate), 2,4-dimethylphenylisocyanate, 6-porophenylisocyanate, p-chlorophenylisocyanate, methylisocyanate, ethyl isocyanate , propyl isocyanate, butyl isocyanate, hexyl isocyanate, and the like. Preferred is phenyl isocyanate.

When the imidazole or imidazoline derivative of the present invention is prepared, for example, by adding an isocyanate or a compound to a reaction product of an imidazole compound or an imidazoline compound and an epoxy compound, by controlling the molar ratio of each compound, K can be obtained. . That is, in structural formula (1), the molar ratio of the imidazole compound or imidazoline compound to the epoxy compound and the isocyanate compound is 1/1.
/ Obtained at 1. In the case of structural formula (2), the molar ratio is 1/2/l. Also, the molar ratio is 1/1
/1 to 1/2/1, it becomes a mixture of Structural Formula (1) and Structural Formula (2), but there is no problem with both curability and storage stability, and therefore the desired storage stability and curability are achieved. A well-balanced curing agent can be obtained by controlling this molar ratio.

The curing agent of the present invention can be used in either liquid or solid form for epoxy resins having two or more epoxy groups per molecule on average. For example, bisphenol A1
Bisphenol F1 Polyglycidyl ether obtained by reacting polyhydric phenols such as catechol and resorcin, or polyhydric 7A/cols such as glycerin and polyethylene glycol with epichlorohydrin, or p-oxybenzoic acid and β-oxynaphthoic acid. Glycidyl ether ester obtained by reacting hydroxycarzenic acid with epichlorohydrin, or polyglycidyl ester obtained by reacting polycarboxylic acid such as phthalic acid or terephthalic acid with epichlorohydrin, or 4,4'-diaminodiphenylmethane or m
- Glycidylamine obtained by reacting aminophenol etc. with epichlorohydrin, furthermore, I-oxidized Nozelac resin, epoxidized cresol Norac resin,
Examples include, but are not limited to, epoxidized polyolefins. 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 viewpoints of curability, cured physical properties, and storage stability, and is not limited by IrfK, but is preferably based on 100 parts by weight of the epoxy resin. The curing agent of the present invention is from 0.1 to
It is 50 parts by weight. That is, if the amount is less than 0.1 part by weight, it will take a long time to obtain sufficient curing performance, which is impractical. Moreover, if the amount exceeds 50 parts by weight, the heat generated during the curing process becomes large, making it difficult to control the curing and making handling complicated. Particularly preferably, the curing agent of the present invention is used in an amount of 1 to 40 parts by weight per 100 parts by weight of the epoxy resin.

The curing agent of the present invention may be used in combination with other polar curing agents, if desired. For example, carenic compounds such as dicyandiamide, methylguanidine, and phenylguanidine, or carzenic anhydride compounds such as phthalic anhydride, trimellitic anhydride, and hexahydrophthalic anhydride, or aromatic amines such as diaminodiphenylmethane and diaminodiphenylsulfone. Examples include compounds, hydrazide compounds such as adipic acid dihydrazide, isophthalic acid dihydrazide, and terephthalic acid dihydrazide, phenol resins, melamine resins, and area resins.

When curing epoxy resins using the curing agent of the present invention, extenders, reinforcing agents, fillers, pigments, and the like can be added to the formulation as desired.

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, chalk powder, gypsum,
Calcium carbonate, antimony trioxide, bentone, silica, aerosol, lidhon, )9 light, titanium dioxide,
Examples include casen black, graphite, iron oxide, gold, aluminum powder, and iron powder. Any of these can be used effectively depending on the purpose.

When curing epoxy resins using the curing agent of the present invention, the formulation optionally includes an organic solvent-reactive diluent,
Non-reactive diluents, modified epoxy resins, etc. can be added.

Examples of the organic solvent include toluene, xylene, -methyl ethyl ketone, methyl imbutyl ketone, ethyl acetate, butyl acetate, ethanol, butanol, and the like. Examples of the reactive diluent include butyl glycidyl ether, N,N'-diglycidyl-o-toluidine, phenylcricidyl ether, styrene oxide,
Examples include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and 1,6-hexanediol diglycidyl ether. Non-reactive diluents include, for example, dioctyl 7-talate,
Examples include dibutyl 7-thalerate, dioctyl adipate, petroleum solvents, and the like. Examples of modified epoxy resins include urethane modified epoxy resins, rubber modified epoxy resins,
Examples include alkyd-modified epoxy resins.

〔Effect of the invention〕

The thus obtained curing agent for epoxy resins of the present invention has excellent storage stability at room temperature, has greatly improved curing properties compared to conventional latent curing agents, and has good performance. It gives a cured product.

Is it possible to use the curing agent of the present invention? The xylene resin composition provides excellent cured physical properties and can be used in a wide range of fields. For example, in the automotive field, adhesives are used to bond headlights, gasoline tanks, hemming flanges of Zennets, etc., and to join steel plates for l-day and roof sections, and in the electrical field, speaker magnets are bonded.
Examples include impregnation and adhesion of motor coils, adhesion of tape heads and notch terry, adhesion of fluorescent lamp safety devices, and adhesives for guiding in the electronic field. In the paint field, examples include solder resist ink, conductive paint, etc. for powder paints and in special fields. Further, electrical insulating materials, laminated structures, etc. can also be used.

The present invention will be explained 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 phenyl glycidyl ether are dissolved in 232 parts of methyl isobutyl ketone and reacted under reflux for 6 hours. Thereafter, the temperature is returned to room temperature and the solvent is removed. Six parts of the solid material after solvent removal, 5 parts of phenyl isocyanate, and 5 parts of phenyl isocyanate are dissolved in 702 parts of carbon tetrachloride, and reacted at 40° C. for 4 hours with stirring. After the reaction,
Adduct I was obtained by removing the solvent. It was confirmed by infrared and 'H-NMR that the structure corresponds to (1) in the present invention. 21.4 parts of adduct I with a softening point of 160°C and an AER of 33
1 (Asahi Kasei Kogyo (&), bisphenol A type epoxy m
Ill, engineering 4 xy equivalent 189) 100 parts,
A shredded product was obtained by passing through the 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 adducts ① to ② according to the synthesis method of Example 1. Table 2 shows the results of curability and storage stability with the epoxy resin.

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

The above results show that the imidazole or imidazoline derivative of the present invention exhibits good storage stability, and its curability is no different from that of imidazole or imidazoline compounds.

Table-1 Table-2 ◆Storage stability indicates the number of days until the composition gels at 25°C.

Tsubohata hardenability indicates the time until 0.5 g of the composition is placed on an iron plate at 120° C. and no strings are drawn.

Claims (1)

[Scope of Claims] An epoxy resin curing agent characterized in that the structure of the first and third positions of imidazole or imidazoline derivatives is represented by the following general formula (1) or (2) ▲ Numerical formula, chemical formula, table There are ▼ and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼... (1) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼... (2) [R_1 and R_2 is an alkyl group of C_1 to C_1_2, a phenyl group which may have a substituent, C_1 to C_2
_1_2 alkoxymethyl group, optionally substituted phenoxymethyl group, C_1 to C_1_2 acyloxymethyl group, optionally substituted benzoyloxymethyl group, R_3 is C_1 to C_1_2 alkyl group, Indicates a phenyl group that may have a substituent]