JPH07109261A - 1-bensylimidazole compound and epoxy resin curing agent - Google Patents

Abstract

PURPOSE:To provide the novel compound capable of developing epoxy resin curing at relatively low temperatures in a short time even with small amounts thereof, also capable of improving the transparency and flexural strength of epoxy resins, thus useful as an curing agent for epoxy resins. CONSTITUTION:The compound of formula I (R is benzyl, 3'-methylphenyl or 4'-methylphenyl), e.g. 1,2-dibenzylimidazole. The compound of the formula I can be obtained by the following processes: benzyl cyanide or a substituted benzonitrile is reacted with ethylenediamine in the presence of simple substance sulfur to produce a 2-substituted imidazoline compound, which is, in turn, dehydrogenated using a nickel catalyst into a 2-substituted imidazole compound, and the 1-site of this compound is then benzylated.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel 1-benzylimidazole compound, and the compound of the present invention is useful as a curing agent or curing accelerator for epoxy resins.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 2-53777 discloses a method of reacting benzyl alcohol or tribenzyl borate in the presence of a mineral acid as a method for benzylating the 1-position of a 1-position unsubstituted imidazole compound. However, a 1-benzylimidazole compound having a benzyl group or a substituted phenyl group at the 2-position has not been synthesized yet.

[0003]

The object of the present invention is to provide a novel compound having a benzyl group or a substituted phenyl group at the 2-position.
-Providing a benzylimidazole compound, and a curing agent and a curing accelerator for an epoxy resin using the novel compound.

[0004]

Means for Solving the Problems As a result of intensive studies in view of such circumstances, the present inventors have found that benzyl cyanide or substituted benzonitrile and 1,2-aliphatic diamine are reacted with each other and then dehydrated. By synthesizing a 2-substituted imidazole compound and further benzylating the 1-position of the imidazole ring of the compound to give a novel 1
It was found that a -benzylimidazole compound was obtained, and the present invention was completed.

[0005]

[Chemical 1]

(In the formula, R represents a benzyl group, a 3'-methylphenyl group or a 4'-methylphenyl group.)

The 2-substituted imidazole compound which is the starting material of the compound of the present invention is obtained by reacting benzyl cyanide or substituted benzonitrile with a 1,2-aliphatic diamine in the presence of elemental sulfur to obtain a 2-substituted imidazoline compound. Then, it is obtained by dehydrogenating the imidazoline ring using a nickel catalyst to convert it to an imidazole ring. This reaction formula is as shown in Chemical formula 2.

[0008]

[Chemical 2]

Then, in the presence of phthalic anhydride, the 2-substituted imidazole compound is reacted with benzyl alcohol or tribenzylborate by heating, the resulting reaction mixture is neutralized with an aqueous alkali solution or an alkaline methanol solution, and then the solvent is removed. Distill off and wash the residue with water,
By distilling this under reduced pressure, the desired 1-benzyl-
A 2-substituted imidazole compound is obtained. This reaction formula is as shown in Chemical formula 3.

[0010]

[Chemical 3]

In the production of the compound of the present invention, the treatment method for benzylating a 1-position-unsubstituted imidazole compound with benzyl alcohol may be carried out by heating under normal pressure or under reduced pressure at which benzyl alcohol is not distilled. May be heated. The 1-benzylimidazole compound of the present invention and its physical properties are as follows.

1,2-dibenzylimidazole

[0013]

[Chemical 4]

Basic pale yellow crystals. m. p. : 60-64
C, bp ₁ : 160-165 C Soluble in methanol and acetone. Insoluble in water. TLC (silica, chloroform / methanol = 10 /
1): Rf0.66 IR (KBr): ν 3110 (62), 3058 (62), 3029 (55), 1719 (66), 1
603 (70), 1522 (83) 1493 (16), 1449 (31), 1433 (53), 1420 (52), 1358 (58), 1306
(81) 1283 (43), 1250 (71), 1181 (79), 1156 (65), 1109 (48), 1070
(71) 1028 (65), 970 (86), 936 (90), 835 (81), 795 (86), 739
(5) 723 (18), 695 (31) cm ^-1 (% transmittance in parentheses) NMR (CDCl ₃ ): δ6.78-7.27 (12H, s, 4,5-position of imidazole ring, phenyl Group) 4.85 (2H, s, methylene of 1-position benzyl group), 4.03 (2H, s, 2-position BenMass: m / e 248 (M ⁺ ), 157,91,66

1-benzyl-2- (4'-methylphenyl) imidazole

[0016]

[Chemical 5]

Basic pale yellow liquid. bp ₁ : 170-18
0 ° C Soluble in methanol and acetone. TLC (silica, chloroform / methanol = 10 /
1): Rf0.63 IR (KBr): ν 3648 (87), 3370 (69), 3108 (66), 3063 (63), 3
031 (58), 2923 (67) 1773 (84), 1713 (37), 1649 (69), 1610 (72), 1509 (43), 1499
(43) 1470 (27), 1453 (27), 1426 (30), 1397 (59), 1360 (56), 1279
(43) 1186 (72), 1127 (60), 1111 (65), 1080 (74), 1032 (67), 1017
(67) 918 (77), 826 (22), 727 (10), 637 (72), 608 (73) cm ^-1 NMR (CDCl ₃ ): δ6.90 to 7.50 (11H, m, phenyl group, benzyl Phenyl group, 4,5-position of the imidazole ring), 5.13 (2
H, s, methylene of 1-benzyl group), 2.30 (3H, s, 4'-methyl) Mass: m / e 248 (M ⁺ ), 157,142, 91,77,65

1-benzyl-2- (3'-methylphenyl) imidazole

[0019]

[Chemical 6]

Basic pale yellow liquid. bp ₁ : 169-18
0 ° C Soluble in methanol and acetone. TLC (silica, chloroform / methanol = 10 /
1): Rf 0.65 IR (KBr): ν 3063 (44), 3033 (40), 2921 (49), 1952 (78), 1
771 (71), 1717 (25) 1607 (39), 1587 (46), 1524 (49), 1497 (17), 1452 (13), 1420
(26) 1398 (39), 1360 (36), 1273 (16), 1204 (61), 1173 (60), 1126
(34) 1100 (42), 1078 (48), 1030 (50), 1001 (64), 914 (48), 889
(61) 849 (47), 793 (18), 720 (8), 698 (13), 673 (54), 635 (6
3) cm ^-1 NMR (CDCl ₃ ): δ6.92 to 7.33 (11H, m, phenyl group, phenyl group of benzyl, 4,5-position of imidazole ring), 5.17 (2
H, s, methylene of 1-position benzyl group), 2.33 (3H, s, 4'-methyl) Mass: m / e 248 (M ⁺ ), 157,142, 91,77,65

[0021]

【Example】

(Example 1) 41 g (0.683 mol) of ethylenediamine and 0.02 g of elemental sulfur were heated and stirred at a temperature of 100 to 110 ° C., and 40 g (0.341 mol) of benzyl cyanide was added dropwise thereto over 30 minutes, and then 3 more. The mixture was heated and stirred for 5 hours, 50 ml of methanol and 0.83 g of sodium hydroxide were added to the reaction mixture, and the mixture was refluxed for 2 hours for desulfurization. Then, filtration, concentration, extraction with chloroform-water and drying with magnesium sulfate,
Concentration was performed to obtain 45.2 g of 2-benzylimidazoline (yield 82.6%).

36.7 g of the above-mentioned 2-benzylimidazoline
Stabilized nickel (1.1 g) was added to (0.229 mol), and 225
The mixture was heated and stirred in the temperature range of ~ 230 ° C for 2 hours. After completion of the reaction, methanol was added to collect insoluble nickel by filtration, and the mother liquor was concentrated and recrystallized from toluene to give 2-benzylimidazole (23.5 g, yield 64.8).
%) Was obtained.

Then, 10 g (0.063 mol) of 2-benzylimidazole described above and 10.75 g of benzyl alcohol
(0.099 mol) and phthalic anhydride 0.94 g (0.006 mol)
Were heated and stirred at a temperature of 220 to 230 ° C. for 8 hours. After completion of the reaction, the product was distilled under reduced pressure and subjected to a predetermined post-treatment to give 13.7 g of 1,2-dibenzylimidazole.
(Yield 87.3%) was obtained.

(Example 2) 19.2 g of ethylenediamine
(0.32 mol) and 0.08 g of elemental sulfur at 100-110 ° C
25g of p-tolunitrile was stirred by heating at the temperature of
(0.213 mol) was added dropwise over 30 minutes, and then 5 more
Continue heating and stirring for 50 hours, and add 50 mL of methanol to the reaction mixture.
ml and 0.37 g of sodium hydroxide were added, and the mixture was refluxed for 2 hours for desulfurization. Then, filtration and concentration were carried out, and the crude crystals were distilled under reduced pressure to obtain 30.8 g of 2- (4′-methyl) phenylimidazoline (yield 90.1%).

To 20 g (0.125 mol) of 2- (4'-methyl) phenylimidazoline thus obtained, 0.6 g of stabilized nickel was added, and the mixture was heated and stirred at a temperature range of 260 to 270 ° C. for 3 hours. After completion of the reaction, methanol was added to collect insoluble nickel by filtration, and the mother liquor was concentrated to give 2- (4′-methyl) phenylimidazole 1
9.7 g (100% crude yield) was obtained.

Then, 18.2 g (0.115 mol) of 2- (4'-methyl) phenylimidazole, 24.9 g (0.23 mol) of benzyl alcohol and 1.
7 g (0.012 mol) of the three were heated and stirred at a temperature of 220 to 230 ° C. for 7 hours. After completion of the reaction, the product was distilled under reduced pressure and subjected to a predetermined post-treatment to give oily 1-benzyl-2-
9.6 g of (4'-methyl) phenylimidazole was obtained (yield 33.6%).

(Example 3) 25.1 g of ethylenediamine
(0.418 mol) and 0.08 g of elemental sulfur at 100-110 ° C
The mixture was heated and stirred at a temperature of m-tolunitrile 24.5
After g (0.209 mol) was added dropwise over 30 minutes, heating and stirring were continued for a further 8.5 hours, 50 ml of methanol and 0.75 g of sodium hydroxide were added to the reaction mixture, and the mixture was refluxed for 2 hours for desulfurization. Then, filtration and concentration were carried out, and the crude crystals were concentrated under reduced pressure to obtain 2- (3′-methyl) phenylimidazoline 25.5 g (yield 76.0%).

0.6 g of stabilized nickel was added to 20 g (0.125 mol) of 2- (3'-methyl) phenylimidazoline.
Was added and the mixture was heated and stirred in the temperature range of 260 to 270 ° C. for 3 hours. After completion of the reaction, methanol was added to collect insoluble nickel by filtration, and then the mother liquor was concentrated and recrystallized from toluene. As a result, 2- (3′-methyl) phenylimidazole (15.6 g, yield 78.8) was obtained. %) Was obtained.

Then, 11.0 g (0.07 mol) of 2- (3'-methyl) phenylimidazole, 15.0 g (0.139 mol) of benzyl alcohol and 1.
0 g (0.007 mol) of the three was heated and stirred at a temperature of 220 to 230 ° C. for 12 hours. After the reaction is completed, vacuum distillation is performed,
After the prescribed post-treatment, oily 1-benzyl-2
-(3'-Methyl) phenylimidazole 11.7 g
(Yield 67.8%) was obtained.

(Example 4) Epoxy resin [trade name: AE
R-331, bisphenol A glycidyl ether, manufactured by Asahi Chemical Industry Co., Ltd.] 100 parts by weight, methyl tetrahydrophthalic anhydride [trade name: Epicron B-570, Dainippon Ink and Chemicals, Inc.] 87.4 parts by weight and examples. The epoxy resin composition was prepared by stirring and mixing 1.0 parts by weight of the 1-benzylimidazole compound obtained in Example 1, Example 2 and Example 3 at a mixing ratio, and further kneading the mixture with a three-roll mill. did. When the gelling time and the pot life at a temperature of 180 ° C. were measured using the epoxy resin composition thus obtained, the results are shown in Table 1. The pot life was the number of days required for the viscosity at a temperature of 25 ° C to exceed 10 times the initial viscosity.

[0031]

[Table 1]

Example 5 The epoxy resin composition obtained in Example 4 was poured into a mold having a size of 3 mm × 100 mm × 150 mm and heat-cured at a temperature of 120 ° C. for 3 hours, and then, to a predetermined size. The physical performance of the resin after cutting and curing was measured. The measurement conditions and measured values are as shown in Table 2.

[0033]

[Table 2]

[0034]

EFFECT OF THE INVENTION The compound of the present invention can be used as a curing agent for epoxy resins in a small amount to develop curing at low temperature in a short period of time, and can improve transparency and bending strength of the resin. is there.

Claims (2)

[Claims] 1. A 1-benzylimidazole compound represented by the general formula of Chemical formula 1. [Chemical 1] (However, in the formula, R represents a benzyl group, a 3′-methylphenyl group or a 4′-methylphenyl group) 2. An epoxy resin curing agent containing a 1-benzylimidazole compound represented by the general formula of Chemical Formula 1 as an active ingredient.