JP2000290257A - New imidazoline compound and epoxy resin curing agent comprising imidazoline compound as active ingredient - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new imidazoline 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 imidazoline compound is obtained by reacting an isocyanate group-containing compound with an imidazoline compound of formula I (R1 is an alkyl, an aryl or an aralkyl; R2 and R3 are each H, an alkyl, an aryl or an aralkyl), for example, a compound of formula II obtained by reacting n-propyl isocyanate with 2-phenylimidazoline. An epoxy resin curing agent is obtained by making the alicyclic 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.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel compound obtained by reacting a compound having an isocyanate group with an imidazoline compound, and an epoxy resin curing agent containing a compound obtained by the reaction as an active ingredient. The epoxy resin composition using the above compound as a curing agent is particularly useful in the field of powder coatings.

[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, as a curing agent for epoxy resin,
Many types of compounds are known, specifically, aliphatic amine compounds such as diethylenetriamine and triethylenetetramine, alicyclic amine compounds such as menthanediamine and isophoronediamine, and aromatic amines such as metaxylenediamine and diaminodiphenylmethane. Compounds, various polyamide compounds, phthalic anhydride, tetrahydrophthalic anhydride,
Examples thereof include acid anhydride compounds such as trimellitic anhydride, polyphenol compounds, polymercaptan compounds, imidazole compounds and dicyandiamide compounds.

An imidazole / epoxy adduct compound obtained by previously reacting an imidazole compound with an epoxy resin has been put to practical use (for example, Japanese Patent Application Laid-Open No. Sho 64-70523).
No. JP-A-4-72849). Further, it has been already proposed to use a certain kind of imidazoline compound as a curing agent for an epoxy resin, and a resin composition containing an imidazoline compound and a salt of the imidazoline compound and a carboxylic acid as a curing agent for an epoxy resin is used for powder coating. (Eg, JP-A-49-133423, JP-A-50-133)
48036, JP-A-52-41643, JP-A-59-59
213774, JP-A-07-216295, JP-A-07-206762, and JP-A-07-216296. Attempts have also been made to directly add an isocyanate group using the NH group of the imidazole ring (for example, JP-A-59-227925, JP-A-53-3793).
No. 7663).

[0004]

As the curing agent for the epoxy resin, various curing agents are properly used depending on the application.
In the field of powder coatings, dicyandiamide, adipic dihydrazide, imidazole compounds, imidazoline compounds and salts thereof have been put to practical use. There are various types of powder coatings, such as epoxy powder coatings, epoxy / polyester (so-called hybrid) powder coatings, and urethane powder coatings. Hardening agents are used according to each system. ing. In epoxy-based powder coatings, dicyandiamide, adipic dihydrazide, imidazoline compounds, and the like are often used as main curing agents, and imidazole compounds are often used as curing accelerators.

[0005] Recent needs for epoxy powder coatings include a need for low-temperature rapid curing in which curing is completed at about 120 to 130 ° C / about 20 minutes and a demand for improvement in storage stability.
In light of these needs, current curing agents each have disadvantages. In a system in which dicyandiamide and adipic dihydrazide are used as a main curing agent and an imidazole compound is used as a curing accelerator, the curing temperature is high, and the demand for low-temperature fast curing cannot be tolerated. Further, in a system in which an imidazoline compound is used as a main curing agent and an imidazole compound is used in combination as a curing accelerator, the requirement of low-temperature rapid curing is satisfied, but storage stability is poor. Further, in the powder coating, a solid epoxy resin, a curing agent, other fillers, pigments, etc. are melt-mixed and pulverized at a temperature of 80 to 120 ° C. in the production process, and therefore, it is desired that the curing reaction does not start during the melt-mixing. It is rare. The present invention provides a novel imidazoline compound which is useful as an epoxy resin curing agent which is excellent in curability in view of such circumstances and has excellent storage stability, particularly an epoxy resin curing agent suitable for powder coating applications. It is.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and as a result, have obtained a compound obtained by reacting an imidazoline compound with a compound having an isocyanate group to obtain an epoxy resin. It has been found that a powder coating excellent in curability and storage stability and excellent in physical properties of a coating film can be obtained by using it as a curing agent, and the present invention has been completed. That is, the compound of the present invention is represented by the following general formula. This compound is stable at room temperature, but decomposes reversibly when heated. Therefore, at room temperature, NH
Since the group is protected and NH is regenerated again upon heating to start reaction with the epoxy resin, the storage stability at room temperature can be drastically improved.

[0007]

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[0008]

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 imidazoline compound used in the present invention is 2-methylimidazoline, 2-ethylimidazoline,
-2-alkylimidazoline compounds such as hexylimidazoline, 2-undecylimidazoline, 2-heptylimidazoline, 2-methyl-4-methylimidazoline, 2-undecyl-4-methylimidazoline, 2-phenylimidazoline, 2-phenyl-4 2-arylimidazoline compounds such as -methylimidazoline; 2-aralkylimidazoline compounds such as 2-benzylimidazoline and 2-benzyl-4-methylimidazoline;

The epoxy resin used in the present invention may be any resin that 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, may be mentioned, and one or more kinds selected from the group consisting of these are used.

The imidazoline compound is added to the epoxy resin in an amount of 0.002 to 50 parts by weight, preferably 0.01 to 30 parts by weight, based on 100 parts by weight of the epoxy resin.

Further, if necessary, fillers such as quartz glass powder, crystalline silica, glass fiber, talc, alumina, calcium silicate, calcium carbonate, barium sulfate, magnesia, etc. may be added to the compound comprising the epoxy resin and the imidazoline compound. Carbon black, titanium oxide,
A pigment such as red iron oxide may be mixed. Further, although the imidazoline compound according to the present invention can be used alone as a curing agent, other epoxy resins such as various amine compounds, dicyandiamide, adipic dihydrazide, imidazole compounds, and acid anhydride compounds which are used in the above-mentioned practical use are used. May be used in combination with the curing agent.

[0013]

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

Example 1 3.00 g (20.521 mmol) of 2-phenylimidazoline was added to 30 ml of toluene.
l) was added thereto, and while stirring at room temperature, 2.1 ml (22.573 mmol) of n-propyl isocyanate was added dropwise while paying attention to heat generation. After stirring at 70 ° C. for 1 hour and 30 minutes, the mixture was concentrated under reduced pressure. 15 ml of hexane was added to the obtained pale yellow syrup-like concentrated residue, and the resulting white powdery product was separated by filtration to obtain 4.55 g of the compound represented by the formula (6) (yield: 9).
6%).

[0015]

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White powder, melting point 87-90 ° C. ¹ H-NMR (chloroform-d) δ 0.69 (t, 3 H, J = 9 H
z), 1.07 ~ 1.38 (m, 2H), 2.93 ~ 3.15 (m, 2H), 3.94 ~ 4.05
(m, 4H), 4.40 (br.S.1H), 7.36-7.65 (m, 5H)

Example 2 2.00 g (13.681 mmol) of 2-phenylimidazoline was added to 20 ml of toluene.
l) was added, and 1.6 ml (15.049 mmol) of phenyl isocyanate was added dropwise while stirring at room temperature while paying attention to heat generation. After stirring at 70 ° C. for 3 hours, the resulting white powder was collected by filtration and dried under reduced pressure to obtain 3.46 g (yield: 95%) of the compound represented by the formula (7).

[0018]

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White powder, melting point: 144 to 147 ° C. ¹ H-NMR (chloroform-d) δ 4.00 to 4.16 (m, 4H),
6.32 (br.S, 1H), 6.89-7.19 (m, 10H)

Example 3 In 30 ml of toluene, 3.00 g (20.521 mmol) of 2-phenylimidazoline was added.
l) was added, and 2.9 ml (22.573 mmol) of cyclohexyl isocyanate was added dropwise while stirring at room temperature while paying attention to heat generation. After stirring at 60 ° C. for 1 hour 30 minutes,
The resulting white powder is collected by filtration and dried under reduced pressure.
4.83 g (yield 87%) of the compound represented by was obtained.

[0021]

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White powder, melting point 131-139 ° C. ¹ H-NMR (chloroform-d) δ 0.66-1.99 (m, 10
H), 3.44 to 3.47 (m, 1H), 3.94 to 4.05 (m, 4H), 4.32 (br.
S), 7.36-7.64 (m, 5H)

Example 4 In 20 ml of acetonitrile,
2.00 g of 2-phenylimidazoline (13.681 m
mol), and 1,6-hexamethylene diisocyanate (1.0 ml, 6.156 mmol) was stirred at room temperature.
l) was added dropwise, paying attention to the exotherm. After stirring at 70 ° C. for 2 hours and 30 minutes, the mixture was concentrated under reduced pressure. 20 ml of diethyl ether was added to the concentration residue in the form of a colorless syrup, and the resulting white powder was collected by filtration and dried under reduced pressure to obtain 2.70 g (yield: 95%) of the compound represented by the formula (9).

[0024]

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White powder, melting point: 172 to 175 ° C. ¹ H-NMR (chloroform-d) δ 1.04 to 1.28 (m, 4H),
3.04 (m, 2H), 3.99 (br.t, 4H), 4.42 (br.S, 1H), 7.39 to 7.
64 (m, 5H)

Example 5 In 15 ml of acetonitrile,
1.50 g of 2-phenylimidazoline (10.261 m
mol) and 1.1 ml of isophoronediamine diisocyanate (IPDI) (5.13) while stirring at room temperature.
0 mmol) was added dropwise, paying attention to the exotherm. After stirring at 60 ° C. for 3 hours, the mixture was concentrated under reduced pressure. 15 ml of diethyl ether was added to the concentrated residue, and the resulting white powdery product was separated by filtration, dried under reduced pressure, and 2.48 g of the compound represented by the formula (10).
(94% yield).

[0027]

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White powder ¹ H-NMR (chloroform-d) δ 0.26 to 1.99 (m, 14
H), 2.70 to 2.79 (m, 2H), 3.95 to 4.08 (m, 8H), 4.4 (br.S, 2
H), 7.40-7.63 (m, 10H)

Example 6 The novel imidazoline compounds synthesized in Examples 1 to 5 were tested for their ability as epoxy resin curing agents. An optimal amount of a novel imidazoline compound is added to 100 parts by weight of a bisphenol A type epoxy resin (trade name “Epicoat # 1001” manufactured by Shell),
The mixture was melt-mixed with a hot roll, crushed and classified to obtain a powder coating. The gel time of the obtained powder coating was measured on a hot plate. At the same time, a storage stability test was performed. It was stored in a thermostat at 40 ° C. for 2 weeks, after which the gel time was measured again. Storage stability was judged based on the degree of shortening of the gel time. The results are shown in Table 1.

Comparative Example 1 The same test as in Example 6 was conducted using adipic dihydrazide. The results are as shown in Table 1, which shows that although the storage stability is relatively good, the curing speed is low.

Comparative Example 2 The same test as in Example 10 was performed using dicyandiamide. However, in this case, 0.5 parts by weight of 2-methylimidazole was added as a curing accelerator. The results are as shown in Table 1, which shows that the storage stability is relatively good as in Comparative Example 1, but the curing speed is low.

Comparative Example 3 The same test as in Example 10 was performed using commercially available 2-phenylimidazoline. The results are as shown in Table 1. The curing speed is high, but it can be seen that the gel time after leaving at 40 ° C. is greatly reduced and the storage stability is poor.

[0033]

[Table 1]

[0034]

Industrial Applicability The novel imidazoline compound of the present invention is useful as a curing agent for an epoxy resin. When this kind of imidazoline compound is used as a curing agent for an epoxy resin, the curability and storage stability of the resin are improved. Thus, an epoxy resin composition particularly suitable for an epoxy powder coating can be obtained.

Claims (4)

[Claims] 1. A compound having an isocyanate group and a compound
A novel imidazoline compound obtained by reacting the imidazoline compound represented by the formula: Embedded image (In the formula, R ₁ represents an alkyl group, an aryl group, or an aralkyl group, and R ₂ and R ₃ represent a hydrogen atom, or an alkyl group, an aryl group, or an aralkyl group.) 2. A compound having an isocyanate group and a compound
A novel imidazoline compound obtained by reacting a 2-phenylimidazoline compound represented by the formula: Embedded image (Wherein, R ₁ and R ₂ represent a hydrogen atom or an alkyl group,
Represents an aryl group or an aralkyl group. ) 3. A compound having an isocyanate group and a compound
An epoxy resin curing agent containing an imidazoline compound obtained by reacting the imidazoline compound represented by the formula (1) as an active ingredient. Embedded image (In the formula, R ₁ represents an alkyl group, an aryl group, or an aralkyl group, and R ₂ and R ₃ represent a hydrogen atom, or an alkyl group, an aryl group, or an aralkyl group.) 4. A compound having an isocyanate group and
An epoxy resin curing agent containing, as an active ingredient, an imidazoline compound obtained by reacting a 2-phenylimidazoline compound represented by the formula: Embedded image (Wherein, R ₁ and R ₂ represent a hydrogen atom or an alkyl group,
Represents an aryl group or an aralkyl group. )