JPH02300174A - New diamide compound, method for synthesizing same compound and method for curing epoxy resin with same compound - Google Patents

Abstract

NEW MATERIAL:A diamide compound expressed by formula I (n is 10 or 18). EXAMPLE:N,N'-Bis(2-methylimidazolyl-1)-ethyl-dodecanedioxyl-diamide. USE:Useful as a curing agent for epoxy resin or curing accelerator. The diamide compound expressed by formula I has middle-temperature curable property or both characteristics of fast curing properties and shelf life and has no limitation on blending and no restriction on uses. PREPARATION:1-(beta-Aminoethyl)-2-methylimidazole expressed by formula II is thermally reacted with dodecanedioic acid or eicosanedioic acid to provide the compound expressed by formula I. Furthermore, the starting compound expressed by formula II is obtained by heating diethylene triamine and acetic acid, distilling water produced by the condensation reaction out of system, subjecting the resultant product to heat dehydrogenation in the presence of a nickel catalyst, further hydrolyzing the resultant product with potassium hydroxide and water and removing an acetyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel diamide compound, a method for synthesizing the compound, and a method for curing an epoxy resin using the compound.

The compounds of the present invention are useful as curing agents or curing accelerators for epoxy resins.

BACKGROUND OF THE INVENTION Conventionally, various imidazole compounds have been used as curing agents or curing accelerators for epoxy resins.

However, when an imidazole compound is used as a curing agent, it is necessary to select either medium-temperature curing property or storage stability properties such as one-component property, and it has been extremely difficult to achieve both properties at the same time.

2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-phenylimidazole, etc. are often used because they have medium-temperature curability and can produce cured products with high heat distortion temperatures. There is. However, when these compounds are used, the pot life of the formulation is very short, about one day at room temperature, and in the case of 2-methylimidazole, which has the best curability, it has a pot life of only a few hours.

For this reason, attempts have been made to develop a curing agent that takes advantage of the medium-temperature curing properties of imidazole compounds, prolongs the pot life, and enables one-component curing.

For example, adducts of 2-methylimidazole with epoxy resins such as bisphenol A diglycidyl ether (
A method of forming a fine powder of an adduct compound and then coating its surface with a polyisocyanate compound to form a kind of microencapsulated curing agent (Japanese Patent Laid-Open No. 58-1362
3, No. 61-192722) and a method using a salt of the above-mentioned adduct and a polyhydric phenol compound as a curing agent (Japanese Unexamined Patent Publication No. 59-53526). The epoxy resin formulation using the imidazole epoxy resin adduct hardener has a long pot life of 6 months or more at room temperature, so it can be made into a one-component product, and it can be used in the medium temperature range (80
"c)" can be thermally cured in 30 to 60 minutes, and in a high temperature range (150°C) in 0.5 to 2 minutes, and the heat distortion temperature of the cured resin is as high as 150°C.

Organic acid anhydride compounds, dicyandiamide, cyanamide,
When imidazole compounds are used as curing accelerators for curing agents such as guanamines, biguanides, aromatic polyamines, alicyclic amines, hydrazine derivatives, and organic acid hydrazides, these curing agents, imidazole compounds, and epoxy resins are As long as no liquid compatibilizer is formed at room temperature, the storage stability of the formulation is similar to that obtained when the imidazole compound described above is used as a curing agent.

Problems to be Solved by the Invention However, the above imidazole-epoxy resin adduct curing agent has serious defects in that it has poor compatibility with epoxy resins even when heated and forms a thixotropic structure during curing. there were. for example,
When used as a curing agent for epoxy resin paints, the surface of the paint film becomes matte and matte, and when used as a casting material, the surface of the cured product becomes matte and voids form inside the cured resin. The problem was that it was easy. In particular, when the filler is highly loaded, such serious defects are likely to occur, and even when the amount of filler is relatively small, the mechanical strength of the cured resin decreases, the water absorption rate increases, etc. This curing agent also had limitations in terms of formulation design.

The main object of the present invention is to provide a curing agent that has both properties of medium-temperature curing or fast curing and storage stability (pot life or one-component stability), and has no formulation restrictions or usage restrictions. It's about doing.

Means for Solving the Problems In view of the above circumstances, the inventors of the present invention have carried out extensive testing and research, and have found that a diamide compound obtained from 1-aminoethyl-2-methylimidazole and a specific dicarboxylic acid is
It was discovered that it is excellent as a curing agent or curing accelerator for epoxy resins, and the present invention was completed.

1-Amino-2-methylimidazole, which is the starting material for the compound of the present invention, can be easily synthesized by the method described below.

That is, by heating diethylenetriamine and acetic acid and distilling off the water produced by the condensation reaction, 1
-Acetylaminoethyl-2-methylimidacyline is obtained, and then heated and dehydrogenated in the presence of a nickel catalyst to obtain 1-acetylaminoethyl-2-methylimidazole. Furthermore 1. By hydrolyzing this imidazole with caustic alkali and water to remove the acetyl group, ■-aminoethyl-2-methylimidazole is obtained. (Refer to JP-A-62-198668) The 1-aminoethyl-2-methylimidazole (hereinafter referred to as A
The diamide compound of the present invention can be obtained by heating a predetermined amount of dicarboxylic acid (represented by MZ) and a predetermined amount of dicarboxylic acid. This can be expressed as a chemical reaction formula as follows.

[However, n in the formula is 10 or 18] When synthesizing the compound of the present invention, AMZ and dicarboxylic acid are charged at a molar ratio of 2:1, and the contents of the reaction vessel are heated to a temperature of 120.
The mixture is heated at ~140° C. for about 1 hour until distillation of the produced water stops, and the solidified reaction product is cooled, followed by recrystallization using a conventional method to obtain the purified compound of the present invention.

The properties of the compound of the present invention are as follows.

N,N"-bis(2-methylimidazolyl-1)-ethyl-dodecanedioyl-diamide Structural formula Colorless crystals, basic. Level, ρ, 131-135°C, easily soluble in methanol, ethanol and hot acetonitrile. Slightly soluble in cold acetonitrile and toluene.Insoluble in water, acetone, carbon tetrachloride and n-hexane.

TLC (silica, methanol): Rf O, 26-0
．． 43 (B, T, B, color development) 1350 (15),
1277(10), 1225(20), 11
55(22).

1137 (27), 975 (30), 782 (23)
, 762(22).

NMR (CD20D, TMS): δ6.96.
s, 211 and 6.80. s, 2H (4,5 position proton); 4.03. t (J=6Hz), 4H (a-methylene); 3.47. t (J=6Hz), 4H (β-methylene); 2.34. s, 6H (methyl); 2.14. t(
, r=7,5Hz), 4H (α-methylene to carbonyl group); 1.55. s, i (β-methylene for carbonyl group); 1.29. s, 12H (hexamethylene) M A S S: ta/e 444 (M”
), 363 (M”-imidazole), 362, 2
92.278.250.236.222.208.19
4.180.167, 152.125 N, N'-bis(2-methylimidazolyl-1)-ethyl-eicosandioyl-diamide structural formula Colorless crystals. basic. Steel, p, 125-135°C (acetonitrile). Easily soluble in methanol, ethanol, DMF and hot acetonitrile. Slightly soluble in water and acetone.

TLC (silica, methanol): Rf O, 40-0
．． 50 (B, T, B, color development) 1535 (24)
, 1500 (30) , 1420 (26) ,
1355 (32).

1280 (30), 1158 (42), 1140 (47
), 980(49).

785 (47), 765 (46), 715 (55)
, 670(44)NMR(CDffOD) :δ
6.97. a+, 2H and 6.81. a+, 2H(4,
5th proton); 4.03. t(J=6flz), 4H
(cx-methylene); 3.48. t(J=6Hz), 4
H (β-methylene); 2.35. t, 6H (methyl); 2.14. q, 4H (α- to carbonyl group
methylene); 1.54 (β-methylene for carbonyl group); 1.27. s, 28H (tetradecamethylene)
MASS: Peng/e 556 (M”)
, 474 (M'-imidazo-8), 390.180
, 167.108.83 (imidazole+H) Next, the application of the compound of the present invention as an epoxy resin curing agent will be described.

Typical epoxy resins used in the present invention include polyglycidyl ether compounds obtained from polyhydric phenols such as bisphenol A1 bisphenol F1 bisphenol AD and novolac resins, and polycarboxylic acid compounds such as phthalic acid and adipic acid. These include polyglycidyl ester compounds obtained from acids, polyglycidyl ether compounds obtained from polyhydric alcohols such as polyethylene glycol, polypropylene glycol, or glycerin, alicyclic epoxy resins, triglycidyl isocyanurate, and epoxidized polyolefins. They may be used, or two or more kinds may be used in combination. Furthermore, if necessary, a low-viscosity monoepoxy compound or the like may be blended as a reactive diluent, and a halogenated epoxy resin may be appropriately used to achieve flame retardance.

When the compound of the present invention is used as a curing agent, the blending ratio with respect to the epoxy resin is 3 to 20 phr (the number of parts by weight of the curing agent per 100 parts by weight of the epoxy resin), and if the blending ratio exceeds 20 phr, the moisture resistance of the cured resin will deteriorate. If the curing rate is lower than 3 phr, the curing rate will be poor, and the curing rate should preferably be between 5 and 15 phr. In addition, when the toughness of the cured resin and the adhesion to oil-wet surfaces are particularly required, the amount added may be increased.

In applications where the composition of the compound of the present invention and an epoxy resin exhibits rapid curing properties at high temperatures, such as liquid epoxy resin injection molding, the surface of the compound of the present invention may be coated or a conventional method may be used. It may also be microencapsulated.

When the compound of the present invention is used as a curing accelerator for other curing agents, examples of other curing agents include organic polybasic acid anhydrides, polyhydric phenol compounds, dicyandiamide, cyanamide, guanamines, biguanides, aromatic polyamines, and fatty acids. Examples include cyclic amines, hydrazine derivatives, and organic acid hydrazides.

Typical examples are hexahydrophthalic anhydride, methylhexahydrophthalic anhydride (the methyl group can be substituted at any position), succinic anhydride, polyadipic anhydride, and organic polybasic acid anhydrides such as trimellitic anhydride. , polyhydric phenol compounds such as novolak resin, Talezol novolak resin, benzoguanamine, orthotoluyl biguanide, monoepoxide adducts and cyanoethylated products of orthotoluyl biguanide, dicyandiamide, monoepoxide adducts of dicyandiamide, metaphenylene diamine, metaphenylene diamine Monoepoxide adducts and cyanoethyl compounds, diaminodiphenylmethane, monoepoxide adducts of diaminodiphenylmethane, isophthalic acid dihydrazide, 2,4-dihydrazine-6-methylamino-S-triazine, 2,4-dihydrazine-6-methylamino -S-triazine monoepoxide adducts and the like.

When the compound of the present invention is used as a curing accelerator, the appropriate blending ratio with respect to the epoxy resin is 0.05 to 5 ph.
r, and if the amount added is large, a formulation with excellent fast curing properties will be obtained, and if the amount added is small, a formulation with excellent storage stability will be obtained.

In carrying out the method of curing the epoxy resin of the present invention, dyes or coloring pigments for coloring,
Extender pigments, fibrous reinforcing materials, whiskers, light scattering agents (@granulated pigments) for light scattering, etc. can be blended to strengthen the cured product. In addition, when curing the resin composition of the present invention, additives for improving workability such as a mold release agent, internal mold release agent, lubricant, antifoaming agent, leveling agent, and penetrant may be added to the resin composition according to the present invention. It can be used as long as it does not have a negative effect on the

Effects of the Invention Table 1 shows the results of comparing the curability and pot life of the compound of the present invention for epoxy resin (manufactured by Asahi Kasei Kogyo ■, trade name: AER-331) with conventional imidazole curing agents that can be cured at medium temperatures. It was as shown.

Table 1 *Pot life was measured by the time the formulation was stored at room temperature until its viscosity exceeded twice its initial value.

As is clear from the test results, the diamide compound according to the present invention is a useful substance that can achieve both medium-temperature curability or fast curability and storage stability when used as an epoxy resin formulation.

In addition, when the compound of the present invention is used as an epoxy resin curing agent, the strength of adhesion to oil-wet surfaces is thought to be due to its alkylene structure, and the toughness of the cured resin is thought to be due to its amide structure. Both characteristics can be improved.

Example Hereinafter, the present invention will be specifically explained with reference to Examples.

In addition, the evaluation in each Example was performed by cutting the cured product obtained by painting or casting into a predetermined size to prepare a test piece, and under the following test standards and conditions.

Bending strength JIS K-720325°C Bending modulus JIS K-720325°C Heat distortion temperature JIS K-72072°C/min Volume resistivity
JIS K-6911 Volume resistivity after boiling at 25°C JIS K-69111 25°C after boiling for 1 hour Dielectric constant JIS K-691125'C, 6
0Hz dielectric loss tangent JIS K-691125°
C160Hz boiling water absorption rate JIS K-7209
Dielectric breakdown voltage after boiling for 1 hour JIS K-6911
Test thickness: 1.5g, 20°C Example 1 1-(β-aminoethyl)-2-methylimidazole 0
．． 158 mol (19.7 g) and 0.075 mol (17.3 g) of dodecanoic acid (manufactured by Okamura Oil Co., Ltd., trade name 5L-12)
was charged into a Claisen flask and heated at a maximum temperature of 250'C for 2 hours while distilling the produced water out of the system. The system was then subjected to vacuum for a short time to completely remove the produced water. The reaction product solidified by cooling was washed with acetone and then recrystallized three times with acetonitrile to obtain the target product N.

N”-bis(2-methylimidazolyl-1)-ethyl-
Dodecanedioyl-diamide 0.054 mol (23°8
g, yield of 71 mol% based on dicarboxylic acid) was obtained.

Example 2 1-(β-aminoethyl)-2-methylimidazole 0
．． 126 mol (15.8 g) and 0.06 mol (20.5 g) of eicosanniic acid (manufactured by Okamura Oil Co., Ltd., trade name 5L-20)
) was reacted under the same conditions as in Example 1, and the reaction product solidified by cooling was recrystallized twice using a mixed solvent of DMF and acetone to obtain the target product N,N'-bis(2-methylimidazolyl- 1) 0.049 mol (27.4 g, yield of 82 mol % based on dicarboxylic acid) of -ethyl-eicosandioyl-diamide was obtained.

Examples 3 and 4 Bisphenol A diglycidyl ether type epoxy resin (manufactured by Asahi Kasei Corporation, trade name: AIR-331) 100
N and N obtained in Example 1 as a curing accelerator were added to a mixture of 90 parts by weight of 4-methylhexahydrophthalic anhydride (manufactured by Shin Nippon Rika ■, trade name: Rikazid Mll-700). ”-bis(2-methylimidazolyl-1
)-ethyl-dodecanedioyldiamide (0.5 parts by weight) was added and mixed with stirring to obtain the formulation of Example 3. Further, using N,N'-bis(2-methylimidazolyl-1)-ethyl-eicosandioyl di-amide as a curing accelerator, the same treatment as above was performed to obtain a formulation of Example 4.

Each of the obtained formulations was heated to a thickness of 3 mm x 100 + nn
After pouring it into a 150-kaku mold and heat curing it at a temperature of 100°C for 2 hours and then at a temperature of 150°C for 4 hours,
Test pieces were cut into predetermined dimensions and their performance was evaluated, with the results shown in Table 2.

Table 2 Characteristics of cured epoxy resin Examples 5 and 6 Bisphenol A diglycidyl ether type epoxy resin (manufactured by Yuka Shell Epoxy ■, product name: Epicote 82B
), N,N'-bis(2-methylimidazolyl-1)-ethyl-dodecanedioyl-diamide and N,N'-bis(2-methylimidazolyl-1)-ethyl as curing agents. 10 parts by weight of each of -eicosandioyl-diamide were blended to obtain the formulations of Example 5 and Example 6.

The dispersion of these diamide compounds into epoxy resin is as follows:
This was carried out using a three-roll machine so that the particle size was 5 μm or less. The curing agent in each formulation was in a finely powdered and dispersed state at room temperature, but when the curing temperature (75° C. or higher) was reached, it rapidly dissolved in the epoxy resin and hardened.

Table 3 shows the performance of the cured products obtained by thermally curing each formulation at a temperature of 80° C. for 30 minutes.

Table 3 Properties of cured epoxy resin ** Measurement of shear adhesive strength was in accordance with JIS K-6850.

The oil-lubricated surface was adjusted by paper blasting the steel surface and then applying lubricating oil PBK-180 manufactured by Nippon Oil Co., Ltd.

Claims (3)

[Claims] (1) General formula ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ [However, n in the formula is 10 or 18] A diamide compound represented by (2) A claim characterized in that 1-(β-aminoethyl)-2-methylimidazole represented by the structural formula ▲There are mathematical formulas, chemical formulas, tables, etc.▼ and dodecanedioic acid or eicosanedioic acid are heated and reacted. A method for synthesizing a diamide compound according to (1). (3) Curing of an epoxy resin characterized by using a diamide compound represented by the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ [However, n in the formula is 10 or 18] as a curing agent or curing accelerator. Method.