JP2000290260A - New imidazole compound and epoxy resin curing agent comprising imidazole compound as active ingredient - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new imidazole compound capable of developing excellent curability and storage stability, useful as an epoxy resin curing agent by reacting an imidazoline compound with an isocyanate group-containing compound. SOLUTION: This imidazole compound is obtained by reacting an isocyanate group-containing compound (e.g. n-propyl isocyanate) with 1-(2-aminoethyl)-2- methulimidazole of formula I, for example, a compound of formula II. The epoxy resin curing agent is obtained by making the curing agent include the imidazoline compound as an active ingredient. The amount of the imidazoline compound as a curing agent added is preferably 0.002-50 pts.wt. based on 100 pts.wt. of an epoxy resin. Consequently the objective high-purity imidazole compound having a high molecular weight and a slight volatile content during curing is provided and an excellent epoxy resin curing agent can be expected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel compound obtained by reacting a compound having an isocyanate group with 1- (2-aminoethyl) -2-methylimidazole, and a compound obtained by this reaction as an active ingredient. The compound of the present invention is excellent in curability to epoxy resin, and has a low generation of volatile components in the curing process, to obtain an epoxy resin composition excellent in safety And particularly useful in the field of laminates.

[0002]

2. Description of the Related Art Epoxy resins are used as excellent thermosetting resins in various fields such as civil engineering, electricity, automobiles, and paints. Also, various types of compounds are known as curing agents for epoxy resins, specifically, aliphatic amine compounds such as diethylenetriamine and triethylenetetramine, alicyclic amine compounds such as menthanediamine and isophoronediamine, and meta-xylene. Diamines, aromatic amine compounds such as diaminodiphenylmethane, various polyamide compounds, phthalic anhydride, tetrahydrophthalic anhydride, acid anhydride compounds such as trimellitic anhydride, polyphenol compounds, polymercaptan compounds, imidazole compounds and dicyandiamide compounds. Can be

An imidazole / epoxy adduct compound obtained by reacting an imidazole compound and an epoxy resin in advance has been put to practical use (for example, Japanese Patent Application Laid-Open No. Sho 64-7052).
No. 3, JP-A-4-72849). Attempts have also been made to directly add an isocyanate group using the NH group of the imidazole ring. However, conventionally known compounds are thermally unstable and dissociate again into an imidazole compound and an isocyanate compound at a high temperature, and the dissociated isocyanate compound volatilizes at the curing temperature to cause a foaming phenomenon in the epoxy resin. Are not preferable (for example, JP-A-59-227925 and JP-A-53-37663).

[0004]

As the curing agent for the epoxy resin, various curing agents are properly used depending on the application.
In the field of laminates, dicyandiamide, imidazole compounds, imidazole / epoxy adducts and the like have been put to practical use, but each has its own advantages and disadvantages. In addition, dicyandiamide is used as a main curing agent, and a method in which various imidazole compounds are used in combination as a curing accelerator has been adopted.However, in such a system, although the curing speed is high,
The pot life is short and it is not suitable for long-term preservation. Further, problems in the working environment such as low-molecular-weight imidazole compounds evaporating and scattering during curing and contaminating the curing furnace have not been solved.

[0005] On the other hand, imidazole / epoxy adducts cure faster than dicyandiamide / imidazole curing systems. Furthermore, since imidazole / epoxy adduct is a prepolymer obtained by preliminarily addition-reacting imidazole and epoxy resin, the molecular weight is increased and the volatile matter during thermosetting is reduced. However, imidazole / epoxy adducts have drawbacks in that it is difficult to control the reaction at the time of synthesis, that the quality at the time of production and the curing characteristics at the time of use tend to vary, and that the storage stability is poor. That is, since the imidazole compound alone acts as a curing agent for the epoxy resin, if it is reacted with heat, the polymerization reaction of the epoxy resin proceeds catalytically to produce a high molecular weight polymer. As shown in the case of the imidazole / epoxy adduct compound, it is very difficult to stop the reaction at the stage where the epoxy group and the imidazole are added, and the composition of the imidazole / epoxy adduct compound that is currently in practical use has a high molecular weight. A mixture containing a polymer or a partially unreacted imidazole compound and an adduct of the desired imidazole and an epoxy resin. Therefore, various variations may occur in the actual production and use process of the imidazole / epoxy adduct, which may cause variations in the quality of the final product, and unreacted imidazole compounds may evaporate during the thermosetting process. Problems in the working environment, such as scattering and contaminating the curing furnace, have not been solved. An object of the present invention is to provide an imidazole compound having excellent curability to an epoxy resin and storage stability when blended with the epoxy resin, and having a high purity useful as an epoxy resin curing agent having a small volatile content during curing.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have obtained a compound obtained by reacting a specific imidazole compound with a compound having an isocyanate group. The inventors have found that the use of the epoxy resin as a curing agent has excellent curability and storage stability, and that the content of volatile components during the curing reaction is small, thus completing the present invention. That is, the present invention provides a novel imidazole compound by reacting 1- (2-aminoethyl) -2-methylimidazole with a compound having an isocyanate group. When used as a hardener, the desired effect is exhibited.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The compounds having an isocyanate group used in the present invention include compounds having one isocyanate group in one molecule such as propyl isocyanate, phenyl isocyanate, cyclohexyl isocyanate and tolylene diisocyanate. , Diphenylmethane diisocyanate, hexamethylene diisocyanate,
Isophorone diisocyanate, dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, xylene diisocyanate, naphthalene diisocyanate, trimethylhexamethylene diisocyanate, p-phenylene diisocyanate, cyclohexylene diisocyanate, halogenated Compounds having two isocyanate groups in one molecule such as xylene diisocyanate and norbornane diisocyanate, and compounds having three or more isocyanate groups in one molecule such as triphenylmethane triisocyanate are exemplified. Further, a compound having an isocyanate group and another functional group in one molecule may be used. The novel imidazole compounds obtained by reacting these compounds having an isocyanate group with a 1- (2-aminoethyl) -2-methylimidazole compound may be used alone or as a mixture of two or more.

The epoxy resin used in the present invention may be any resin which is generally used as an epoxy resin. As the epoxy resin, for example, glycidyl ether type epoxy resin and glycidyl ester type epoxy resin such as bisphenol type epoxy resin, phenol novolak type epoxy resin, fresole novolak type epoxy resin, glycidyl amine type epoxy resin, alicyclic epoxy resin, complex An epoxy resin having two or more epoxy groups in one molecule, such as a cyclic epoxy resin and a halogenated epoxy resin, is used, and one or two or more selected from the group consisting of these are used in combination. . The amount of the imidazole compound added to the epoxy resin is 0.002 to 50 parts by weight, preferably 0.1 to 50 parts by weight, based on 100 parts by weight of the epoxy resin.
It is blended in the range of 01 to 35 parts by weight.

[0009] Further, if necessary, for example, a quartz glass powder,
Crystalline silica, glass fiber, talc, alumina, calcium silicate, calcium carbonate, barium sulfate, magnesia, etc. may be added. Further, although the imidazole compound according to the present invention can be used alone as a curing agent, it can be used in combination with other epoxy resin curing agents, such as the various amine compounds, dicyandiamide, and acid anhydride compounds used for the above-mentioned practical use. No problem.

[0010]

The present invention will be specifically described below with reference to examples and comparative examples.

[Example 1] 1- (2-aminoethyl)-
2.00 g of 2-methylimidazole (15.978 mm
ol) was dissolved in 20 ml of acetonitrile, and 1.5 ml of n-propyl isocyanate (1
5.978 mmol) was added dropwise, paying attention to the exotherm. After stirring at room temperature for 2 hours, the mixture was concentrated under reduced pressure, and the obtained yellow solid was recrystallized from acetonitrile to obtain 3.21 g of the compound represented by Formula 3 (yield: 95%).

[0012]

Embedded image

White powder, melting point 110 ° C. ¹ H-NMR (chloroform-d) δ 0.90 (t, 3H, J = 7)
Hz), 1.49 (sext, 2H, J = 7 Hz), 2.26 (s, 3H), 3.03〜
3.24 (m, 2H), 3.38 to 3.56 (m, 2H), 3.96 (br.t, 2H, J =
5 Hz), 5.70 and 5.77 (br.s overlap, total 2H), 6.74 and 6.76 (s
Overlap, total 2H)

Example 2 1- (2-aminoethyl)-
1.50 g of 2-methylimidazole (11.984 mm
ol) was dissolved in 12 ml of acetonitrile, and 1.7 ml of cyclohexyl isocyanate (1 ml) was stirred at room temperature.
1.984 mmol) was added dropwise, paying attention to the exotherm. 70
After stirring at 時間 80 ° C. for 1 hour and 30 minutes, the resulting white precipitate was separated by filtration and dried under reduced pressure to obtain 2.75 g of the compound represented by Chemical Formula 4 (yield: 92%).

[0015]

Embedded image

White powder, melting point 171-173 ° C. ¹ H-NMR (methanol-d ₄ ) δ 1.18-1.89 (m, 10
H), 2.33 (s, 3H), 3.27 to 3.54 (overlap of t and m, 3H in total),
4.00 (t, 2H, J = 6 Hz), 6.80 (d, 1H, J = 6 Hz), 6.80
(d, 1H, J = 1.5 Hz), 6.96 (d, 1H, J = 1.5 Hz)

Example 3 1- (2-aminoethyl)-
3.00 g (23.967 mm) of 2-methylimidazole
ol) was dissolved in 60 ml of acetonitrile and stirred at room temperature with 1.6 hexamethylene diisocyanate 1.7.
ml (10.785 mmol) was added dropwise, paying attention to the exotherm. After stirring at 60 to 65 ° C. for 1 hour and 45 minutes, the generated white precipitate was separated by filtration and dried under reduced pressure to obtain 4.38 g of the compound represented by Chemical Formula 5 (yield 97%).

[0018]

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White powder, melting point: 142-146 ° C. ¹ H-NMR (methanol-d ₄ ) δ 1.36 (br.s, 8H), 2.
34 (s, 6H), 3.08 (br.t, 4H, J = 5 Hz), 3.39 (t, 4H, J
= 6Hz), 4.01 (t, 4H, J = 6 Hz), 6.80 (d, 2H, J = 1.
4 Hz)

Example 4 1- (2-aminoethyl)-
2.00 g of 2-methylimidazole (15.978 mm
ol) was dissolved in 20 ml of acetonitrile, and 1.7 ml (7.190 mmol) of 1.3-bis (1-isocyanato-1-methyl) benzene was added dropwise while stirring at room temperature while paying attention to heat generation. After stirring at 70 ° C. for 2 hours, the mixture was concentrated under reduced pressure. The light-yellow concentrated dried product is treated with diethyl ether 20
Then, 3.11 g of the compound represented by Chemical Formula 6 was obtained.
(88% yield).

[0021]

Embedded image

White powder, melting point: 183 to 186 ° C. ¹ H-NMR (chloroform-d) δ 1.63 (s, 12H), 2.2
1 (s, 6H), 3.40 (m, 4H), 3.89 (t, 4H, J = 5 Hz), 5.28
(br.s, 2H), 5.63 (s, 2H), 6.69 (s, 2H), 6.72 (s, 2H),
7.27 (s, 3H), 7.43 (s, 1H)

Example 5 1- (2-aminoethyl)-
2.00 g of 2-methylimidazole (15.978 mm
ol) was dissolved in 20 ml of acetonitrile, and 1.7 m of isophorone diamine diisocyanate was stirred at room temperature.
l (7.989 mmol) was added dropwise, paying attention to the exotherm.
After stirring for 3 hours under reflux, the mixture was allowed to cool to room temperature and the upper layer separated into two layers was discarded. The lower layer was dissolved by adding 20 ml of chloroform, and concentrated to dryness under reduced pressure. After adding 40 ml of diethyl ether to the form-shaped concentrated residue and stirring at room temperature, the precipitate was separated by filtration and dried under reduced pressure to obtain 3.29 g of the compound represented by the formula (7) (yield 87%). Was.

[0024]

Embedded image

Milky white powder, melting point: softened from 65 ° C. ¹ H-NMR (chloroform-d) δ 0.55 to 1.81 (3
s and m overlap, total 15H), 2.28 (s, 6H), 2.43 (m, 1H), 2.8
8 (m, 2H), 3.47 (br.s, 4H), 3.97 (br.s, 4H), 5.4 ~ 6.1
(3m overlap, 4H total), 6.76 (s) and 6.80 (s), 4H total

Example 6 1- (2-aminoethyl)-
2.00 g of 2-methylimidazole (15.978 mm
ol) was dissolved in 20 ml of acetonitrile and stirred at room temperature while stirring 1,3,5-tris (6-isocyanato-n-
Hexyl) -isocyanuric acid 2.42 g (4.793 m
mol) was added dropwise, paying attention to the exotherm. After stirring under reflux for 4 hours, the mixture was concentrated under reduced pressure to dryness. After 30 ml of diethyl ether was added to the form-shaped concentrated residue and the mixture was stirred at room temperature, the precipitate was separated by filtration and dried under reduced pressure to obtain 4.00 g of the compound represented by the formula (8) (yield: 95%). Was.

[0027]

Embedded image

Milky white powder, melting point: 55 ° C. softened ¹ H-NMR (methanol-d ₄ ) δ1.38 to 1.62 (br.s, 8
H), 2.34 (s, 3H), 3.08 (br.t, 2H, J = 6 Hz), 3.39 (t,
2H, J = 6 Hz), 3.77 to 4.07 (m, 4H), 6.80 (d, 1H, J =
1.5 Hz), 6.96 (d, 1H, J = 1.4Hz)

Example 7 1- (2-aminoethyl)-
2.00 g of 2-methylimidazole (15.978 mm
ol) in 20 ml of acetonitrile and 2.42 g (7.190 mmol) of 1,3-bis (6-isocyanato-n-hexyl) -uretdione while stirring at room temperature.
Was added dropwise while paying attention to heat generation. After stirring under reflux for 4 hours,
The mixture was allowed to cool to room temperature, and the upper layer separated into two layers was discarded. The lower layer was dissolved by adding 20 ml of chloroform, and concentrated to dryness under reduced pressure. 40 ml of diethyl ether is added to the concentrated form residue.
After stirring at room temperature, the precipitate was separated by filtration and dried under reduced pressure to give 4.00 g of the compound represented by Chemical Formula 9 (yield 95).
%)Obtained.

[0030]

Embedded image

Milky white candy solid ¹ H-NMR (methanol-d ₄ ) δ 1.25 (br.s, 8H), 2.34 (s, 3H), 3.08 (m, 2H), 3.3 to
3.6 (overlap of t and m, 4H), 4.00 (t, 2H, J = 6 Hz), 6.80
(d, 1H, J = 1.4 Hz), 6.96 (d, 1H, J = 1.4 Hz)

Example 8 1- (2-aminoethyl)-
3.00 g (23.967 mm) of 2-methylimidazole
ol) was dissolved in 30 ml of acetonitrile and stirred at room temperature while stirring with 1,5-naphthalenediisocyanate 2.27.
g (10.785 mmol) was added dropwise, paying attention to the heat generation. After stirring for 6 hours under reflux, the white precipitate was separated by filtration and dried under reduced pressure to give 3.56 g of the compound represented by Chemical Formula 10.
(71% yield).

[0033]

Embedded image

White powder, decomposition point 210 ° C. ¹ H-NMR (DMSO-d ₆ ) δ 2.30 (s, 6H), 3.40 (b
rt, J = 5.7Hz), 4.00 (t, 4H, J = 5.7Hz), 6.57 ~ 8.59
(arom.m, total 10H)

Example 9 1- (2-aminoethyl)-
2.00 g of 2-methylimidazole (15.978 mm
ol) in 20 ml of acetonitrile and 1.25 g of 2,4-toluene diisocyanate while stirring at room temperature.
(7.190 mmol) was added dropwise, paying attention to heat generation. 6
After stirring at 0 ° C. for 3 hours, the resulting white precipitate was separated by filtration and dried under reduced pressure to give the compound represented by Chemical formula 2.6.
g (86% yield).

[0036]

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Milky white powder, melting point 190-195 ° C. ¹ H-NMR (methanol-d ₄ ) δ 2.14 (s, 3 H), 2.36
(s, 6H), 3.48 (t, 4H, J = 6 Hz), 4.06 (t, 4H, J = 6 H
z), 6.82 (d, 2H, J = 1.5 Hz), 6.92 (d, 2H, J = 1.4 H
z), 7.06 (d, 2H, J = 1.4 Hz), 7.42 (br.s, 1H)

Example 10 The novel imidazole compounds synthesized in Examples 1 to 9 were tested for their ability as epoxy resin curing agents. 100 g of bisphenol A type epoxy resin (trade name “Epicoat # 828” manufactured by Shell)
0.098 mol of new imidazole compound to
(However, 0.049 mol when one molecule has two imidazole rings, and 0.033 mol when one molecule has three imidazole rings), and the mixture was uniformly dispersed with three rolls. The gel time of the obtained epoxy resin composition was measured on a hot plate. Further, a storage stability test of the obtained epoxy resin composition was performed. It was stored in a constant temperature bath at 40 ° C., and the number of days until no fluidity was exhibited was measured. The results are shown in Table 1.

Comparative Example 1 A test similar to that of Example 10 was performed using 2-methylimidazole as a representative of the conventional imidazole compound. Table 1 shows the results. It can be seen that the imidazole compound has a lower curing speed and lower storage stability than the present invention.

Comparative Example 2 The same test as in Example 10 was performed using a commercially available imidazole / epoxy adduct (trade name “P-1” manufactured by Shell Chemicals). Table 1 shows the results. It can be seen that the so-called imidazole / epoxy adduct has almost the same curing rate as the compound of the present invention, but is clearly inferior in storage stability.

[0041]

[Table 1]

[0042]

The novel imidazole compound of the present invention is useful as a curing agent for epoxy resins. When this kind of imidazole compound is used as an epoxy resin curing agent, the curing characteristics and storage stability of the epoxy resin are improved, and since these compounds have high purity and large molecular weight, the generation of volatile components during curing is small. Therefore, the quality of the cured product is improved, and the working environment can be dramatically improved.

Claims (2)

[Claims] 1. A compound having an isocyanate group and a compound
A novel imidazole compound obtained by reacting 1- (2-aminoethyl) -2-methylimidazole represented by the formula: Embedded image 2. A compound having an isocyanate group and a compound
An epoxy resin curing agent containing an imidazole compound obtained by reacting 1- (2-aminoethyl) -2-methylimidazole represented by the formula (1) as an active ingredient. Embedded image