JPH0436311A - Curing agent and curing accelerator for epoxy resin, and epoxy resin composition containing the same - Google Patents

Abstract

PURPOSE:To facilitate the mixing with a high-viscosity epoxy resin and improve the water resistance of the resulting epoxy resin compsn. by using a polymer which is liq. at room temp. and has side chains, each having an imidazole structure bound through a covalent bond. CONSTITUTION:A monomer having a polymerizable group such as a vinyl group and an imidazole structure is (co)polymerized if necessary with a monomer copolymerizable therewith, to give a polymer which is liq. at room temp. and has a number average mol.wt. of 500-100000, a viscosity at 25 deg.C of 300-20000P, and side chains each having an imidazole structure bound through a covalent bond. The polymer is compounded as a curing agent and/or a curing accelerator into an epoxy resin, if necessary, compounded with a flexibilizer, giving an epoxy resin compsn.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides an epoxy resin composition that has excellent heat resistance, flexibility, workability, etc. and does not reduce water resistance, and a method for obtaining this composition. The present invention relates to a curing agent for epoxy resins and a curing accelerator for epoxy resins.

[Prior art] Epoxy resin has mechanical properties, electrical properties, solvent resistance,
Due to its excellent adhesive properties, it can be used for paints, adhesives, cast materials, etc.
It is used in a wide range of fields, including as electrical insulating materials such as semiconductor encapsulation materials.

Epoxy resins are usually cured using amines, organic acid anhydrides, dicyandiamide, etc. as a curing agent, and if necessary, a curing accelerator or co-curing agent. Among these, imidazoles are used as anionic polymerization type curing agents for epoxy resins or as curing accelerators in combination with other curing agents, and are known to exhibit excellent characteristics.

However, when imidazoles are added as a curing agent or curing accelerator to a high viscosity epoxy resin compound containing, for example, liquid rubber, there is a problem in that it is very difficult to mix imidazoles which are in powder form. Moreover, since these imidazoles have a small molecular weight, there is also the problem that the water resistance of the cured product generally decreases.

Therefore, in order to solve these problems, we developed a carboxylic acid by reacting a liquid oligomer such as a butadiene-acrylonitrile copolymer containing carboxyl groups at both ends with imidazole so that the imidazole was 2 moles per 1 mole of the oligomer. A method (Japanese Unexamined Patent Publication No. 154499/1989) has been disclosed in which a compound made into an imidazole salt is used as a curing agent.

[Problems to be Solved by the Invention] However, in this method, the molar ratio of oligomer and imidazole is fixed at 1:2, so there is a problem that the blending ratio of the epoxy resin, the flexibility imparting agent, and the imidazole is limited. be. Further, it is known that imidazole salts of carboxylic acids dissociate as curing progresses, and the physical properties of the cured product are the same as those obtained by separately blending oligomer and imidazole. Therefore, with this method, the problem of decreased water resistance remains unsolved.

[Means for Solving the Problems] As a result of intensive research in view of the above situation, the present inventors found that a polymer compound that is liquid at room temperature and has a covalently bonded imidazole structure on the side U is a high-viscosity epoxy resin. It was discovered that the epoxy resin composition can be easily mixed with a compound and contains it as a curing agent or curing accelerator, and there is no decrease in water resistance, leading to the completion of the present invention.

That is, the present invention provides: a curing agent for epoxy resin characterized by comprising a polymer compound that is liquid at room temperature and has a covalently bonded imidazole structure in its side chain; A curing accelerator for epoxy resin characterized by comprising a compound, an epoxy resin composition characterized by containing as an essential component a polymer compound which is liquid at room temperature and has an imidazole structure covalently bonded to the epoxy resin in its side chain. and a polymer compound which is liquid at room temperature and has an imidazole structure covalently bonded to an epoxy resin curing agent in its side chain as essential components.

The polymer compound that is liquid at room temperature (hereinafter referred to as imidazole copolymer) used in the present invention is a polymer compound that is liquid at room temperature and has an imidazole structure bonded by a covalent bond in its side chain. You can use any of them.

As a method for producing this imidazole copolymer, for example, an imidazole structure-containing monomer having a polymerizable functional group such as a vinyl group (hereinafter referred to as an imidazole monomer) can be copolymerized with the monomer as necessary. Other monomers such as
A method of (co)polymerization with other monomers (referred to as other monomers), ■
Examples include a method in which a polymer compound obtained by a known method is reacted with an imidazole to introduce an imidazole structure into the polymer compound.

For example, when the imidazole monomer and other monomers are radically polymerizable, the method for producing the above item
Polymerization in a solvent as necessary in the presence of a peroxide such as -t-butylcyclohexyl) peroxycarbonate, lauroyl peroxide, or benzoyl peroxide, or an azo compound such as 2,2'-azobisisobutyronitrile. In addition, there are other polymerization methods such as emulsion polymerization, suspension polymerization, and dispersion polymerization.

In addition, as for the production method (2), for example, after copolymerizing chloromethylstyrene and other monomers by a known method, the active hydrogen at the 1st position of the imidazole ring is added to the chloromethyl group contained in the resulting polymer with sodium chloride. There is a method of introducing an imidazole structure into a polymer by reacting a sodium derivative of a substituted imidazole.

Examples of the imidazole monomer used in the production method (2) above include 1-vinylimidazole, 2-methyl-1-vinylimidazole, 2-vinylimidazole, 1-methyl-2-vinylimidazole, 4-vinylimidazole, 5- Vinylimidazoles such as vinylimidazole; Allylimidazoles such as 1-allylimidazole; Vinylbenzimidazoles such as 5-vinylbenzimidazole; 1-(p-vinylbenzyl)imidazole, 1-(m-vinylbenzyl)imidazole and A mixture of these, 2-methyl-1-(p-vinylbenzyl)
Examples include vinylbenzylimidazoles such as imidazole, 2-methyl-1-(m-vinylbenzyl)imidazole, and mixtures thereof.

Other monomers to be copolymerized with the imidazole monomer include, for example, acrylic acid; methyl ester, ethyl ester, propyl ester, n-butyl ester, 1so-butyl ester, 2-ethylhexyl ester, lauryl ester of acrylic acid; , acrylic acid esters such as tetradecyl ester, hexadecyl ester, octadecyl ester, glycidyl ester; methacrylic acid; methyl ester, ethyl ester, propyl ester, n-butyl ester, l5O-butyl ester, 2-ethylhexyl ester of methacrylic acid , lauryl ester, tetradecyl ester, hexadecyl ester,
Methacrylic acid esters such as octadecyl ester and glycidyl ester; Diene compounds such as 1,2-butadiene, 1,3-butadiene, and isoprene; Vinyl ethers such as ethyl vinyl ether and 1so-butyl vinyl ether; Isobutylene, vinyl chloride, vinyl acetate, Acrylonitrile, methacrylonitrile, styrene,
Examples include α-methylstyrene, p-methylstyrene, and other styrene derivatives. One type of these other monomers may be used to make moyo (or two or more types may be used.

In addition, when producing these imidazole copolymers, for the purpose of partially crosslinking, some of the other monomers are replaced with monomers having two or more polymerizable reactive groups such as divinylbenzene and ethylene glycol dimethacrylate. It may be replaced with a quantity.

In the production of the above imidazole copolymer, the ratio of imidazole monomer to other monomers is not particularly limited, but the amount of imidazole monomer is within the range of 0.1 to 40 mol%. It is preferable that there be.

The imidazole copolymer used in the present invention is a polymer compound that is liquid at room temperature (hereinafter referred to as liquid (referred to as rubber) is preferable, and examples thereof include imidazole copolymers containing other monomers such as butyl acrylate, 2-ethylhexyl acrylate, 1,3-butadiene, isobutylene, and the like.

Among these, butyl acrylate copolymers and butadiene copolymers are preferred, and those containing highly polar monomers such as acrylic acid, methacrylic acid, acrylonitrile, and methacrylonitrile as copolymerization components are preferred as epoxy copolymers. It is particularly preferred in terms of its excellent compatibility with resins.

The molecular weight of the imidazole copolymer is not particularly limited, but it has a number average molecular weight of 500 to 10, because it has excellent mechanical strength, water resistance, solubility in epoxy resin, and workability.
The range of 0,000 is preferable, especially 1,000 to 3
A range force 5 of 0,000 is particularly preferred. Regarding viscosity,
Even if it is 300 to 20,000 poise at room temperature (25° C.), it is preferably 500 to 15,000 poise.

The above-mentioned imidazole copolymer in the present invention is used as a curing agent for epoxy resin and/or as a low molecular weight imidazole.
Alternatively, it can be used as a curing accelerator.

Epoxy resins used in the present invention include those having two or more epoxy groups in the molecule, typical examples of which include bis(4-hydroxyphenyl)propane, 4. 4'-dioxydiphenylmethane, 4. 4
' -dioxydiphenylethane, resorcinol, hydroquinone, 2,27-bis(4-hydroxy-2,6-
dibromophenyl)propane, 4. 4'-dioxydiphenyl sulfone, 4. Diglycidyl ethers of diphenols such as 4'-dioxydiphenyl ether; polyglycidyl ethers of condensates of formaldehyde and phenol (phenol novolak resin); condensates of formaldehyde and cresol (cresol novolac resin) Polyglycidyl ethers of condensates of formaldehyde, phenol, and bisphenol A; 1,4-butanediol, neopentyl glycol, dipropylene glycol,
Diethylene glycol, glycerin, trimethylolpropane, pentaerythrol, 2. 2'-bis(2
Di- or polyglycidyl ethers of diols or polyols such as -hydroxycyclohexyl)propane; bis(4-hydroxyphenyl)propane or bis(
di- or polyglycidyl ethers of diols or polyols obtained by the addition reaction of 2-hydroxyphenyl)methane with ethylene oxide or propylene oxide; diglycidylhydantoins such as diglycidyldimethylhydantoin; diaminodiphenylmethane or p- or m-amine phenols; Alternatively, glycidylamines of xylylene diamine; cyclohexene oxide or cyclopentene oxides obtained by epoxidizing a cyclohexene or cyclopentene ring-containing compound with a suitable oxidizing agent such as a peroxide, and the like.

Furthermore, the imidazole copolymer of the present invention can be used in combination with a conventionally used composition comprising an epoxy resin and a flexibility-imparting agent.

Examples of the flexibility-imparting agent include alkylene ether-based flexibility-imparting agents, long-chain fatty acid-based flexibility-imparting agents, aromatic crosslinking density-lowering agents, and liquid rubber.

Among these, butadiene-based liquid rubbers, butadiene-acrylonitrile-based liquid rubbers, etc. are preferred, and in particular groups that react with functional groups or epoxy groups in the curing agent, such as carboxyl groups, hydroxy groups, epoxy groups, mercapto groups, amide groups, Preferred are the above-mentioned liquid rubbers having vinyl groups at both ends of the molecule and/or side chains, and modified epoxy resins obtained by precondensing the liquid rubbers with epoxy resins.

The epoxy resin composition of the present invention may also contain other additives, such as glass fiber, carbon fiber, clay,
Mica, aluminum powder, talc, calcium carbonate, etc. may be added, and if necessary, a diluent, a flame retardant, etc. may be added.

Specific uses of the epoxy resin composition of the present invention include coating the interior and exterior surfaces of food cans and drums, various coatings for civil engineering and construction, factory equipment, automobiles, ships, etc., adhesives for various industrial parts, printed wiring boards, etc. Examples include laminates used, sealing materials for electronic devices, molding materials for tools, and casting materials.

[Example] The present invention will be specifically described below with reference to Examples and Comparative Examples.

Examples 1-3 100 ethanol in a 300 wlL flask with a stirrer
g was charged and the temperature was raised to 65°C. Next, a solution consisting of 125 g of monomers mixed at the molar ratio shown in Table 1, 2.5 g of azobisisobutyronitrile (hereinafter abbreviated as AIBN), and 25 g of ethanol was added dropwise over 1 hour, and after the addition was completed, The reaction was continued for an additional 10 hours. After the reaction, the solvent and unreacted monomers were distilled off under reduced pressure to synthesize a butyl acrylate-based imidazole copolymer having the number average molecular weight and viscosity shown in Table 1.

The imidazole copolymers obtained in Examples 1 to 3 are hereinafter referred to as (A1), (A2), and (A3), respectively.

Examples 4-6 250 g of monomers mixed at the molar ratio shown in Table 15
A solution consisting of AIBNlog and 250 g of dimethylformamide was placed in an autoclave equipped with an IQ stirrer.60
The reaction was carried out at ℃ for 40 hours.

After the reaction, the solvent and unreacted monomers were distilled off under reduced pressure, and
A butadiene-based imidazole copolymer having the number average molecular weight and viscosity shown in Table 1 was synthesized by separating the liquid copolymer in twice the amount of methanol.

The imidazole copolymers obtained in Examples 4 to 6 are hereinafter referred to as (B1), (B2), and (B3), respectively.

Example 7 Bisphenol A diglycidyl ether [Evicron 840 manufactured by Dainippon Ink & Chemicals, epoxy equivalent 184,
100 parts by weight [hereinafter referred to as Epicron 840] and 25 parts by weight of imidazole copolymer (AI) were dissolved in 125 parts by weight of 1,2-dichloroethane to obtain a 1,2-dichloroethane solution of an epoxy resin composition. Next, this solution was applied to a tin plate using a bar coater to a dry film thickness of 40 microns, and then heated and dried at 150°C for 2 hours to prepare a coating film test piece, and the following tests were conducted. The results are shown in Table 2.

(1) Adhesion: According to JIS-8400, a cut is made in the shape of the substrate and a cellophane tape peeling test is performed. No peeling is ◎, peeling is less than 10%: ○, peeling is 1
0 to 40% is △, and peeling is more than 40% ×
And so.

(2) Secondary adhesion: After immersing the test piece in boiling water for 5 hours, the same test as in (1) was conducted to judge.

(3) ITFJ impact property; evaluated by DuPont impact test method using 1/2 inch dart Example 8 Example except that imidazole copolymer (B2) was used instead of imidazole copolymer (A1) A 1,2-dichloroethane solution of the epoxy resin composition was obtained in the same manner as in Example 7, and then a coating film test piece was prepared in the same manner and tested. The results are shown in Table 2.

Example 9 Ebicuron 840.
100 g of a butazine acrylonitrile copolymer containing a terminal carboxyl group (B, F, Hiker CTBN 1300X13 manufactured by Gutdrich, hereinafter referred to as CTBN), and 0.3 g of l-liphenylphosphine were charged and heated at 120°C for 3 hours. A butadiene-acrylonitrile liquid rubber-modified epoxy resin (hereinafter referred to as rubber-modified epoxy resin) which had been reacted and precondensed in advance was synthesized. The rubber content of this rubber-modified epoxy resin was 50% by weight, and the epoxy equivalent was 780.

Next, 840.100 parts by weight of Evicron, 36 parts by weight of a rubber-modified epoxy resin, and 1 part by weight of imidazole copolymer (Bl) 13] as a hardening agent were dissolved in 125 parts by weight of 1°2-dichloroethane to create an epoxy resin. Composition 1,2
- A dichloroethane solution was obtained, and then a coating film test piece was prepared in the same manner and tested. The results are shown in Table 2.

Comparative Example 1 840.100 parts by weight of Epiclon and 365 parts by weight of 2-methylimidazole were added to 10 L of 1,2-dichloro-1
1,2- of the epoxy resin composition by dissolving in 5 parts by weight
A dichloroethane solution was obtained, and then a coating film test piece was prepared in the same manner and tested. The results are shown in Table 2.

Comparative Example 2 CTBN6 g g and 2 in a flask with a 300 mm stirrer
- 3.3 g of methylimidazole were charged and reacted at 100°C for 1 hour and then at 150''C for 30 minutes to synthesize an imidazole salt compound (hereinafter referred to as imidazole salt compound).

Next, 840.100 parts by weight of Epiclon and 25 parts by weight of the imidazole salt compound were added to 125 parts by weight of 1,2-dichloroethane.
A 1,2-dichloroethane solution of the epoxy resin composition was obtained by dissolving the epoxy resin composition in parts by weight, and then coating film test pieces were prepared in the same manner and tested.

The results are shown in Table 2.

Comparative Example 3 840.100 parts by weight of Evicron, 66 parts by weight of the rubber-modified epoxy resin obtained in Example 9, and 4.5 parts by weight of 2-methylimidazole were mixed in 1. 2-dichloroethane 170.5
A 1,2-dichloroethane solution of the epoxy resin composition was obtained by dissolving the epoxy resin composition in parts by weight, and then a coating film test piece was prepared in the same manner and tested. The results are shown in Table 2.

In addition, the epoxy resin compositions shown in the Examples and Comparative Examples in Table 2 were made so that the compounding ratio of the imidazole structural part to the epoxy resin and the rubber content in the flexibility imparting agent to the epoxy resin was constant. . However, in Comparative Example 2, when the blending ratio of the flexibility imparting agent to the epoxy resin was kept constant, there was a problem that the blending ratio of the imidazole structure portion was not uniform.

As is clear from Table 2, Comparative Examples 1.2 and 3 had lower secondary adhesion than Examples 7.8 and 9, indicating that they were inferior in water resistance.

Example 10 Epiclon 840.100 parts by weight Tomethyltetrahydrophthalic anhydride [Epiclon B manufactured by Dainippon Ink & Chemicals ■
-570, hereinafter referred to as Epiclon B-570] and 46 parts by weight of imidazole copolymer (A2) to obtain an epoxy resin composition. This composition was poured into a glass casting plate and cured by heating at 80°C for 5 hours and then at 150°C for 5 hours. The tensile strength of this cured product,
Tensile modulus and elongation were measured according to JIS-6911. Furthermore, the rate of weight increase of the cured product when soaked in boiling water for 6 hours was also measured. The results are shown in Table 3.

Example 11 An epoxy resin composition was obtained in the same manner as in Example 10 except that imidazole copolymer (B3) was used instead of imidazole copolymer (A2), and then a cured product was prepared in the same manner and measured. I did it. The results are shown in Table 3.

Example 12 Epicuron 840.100 parts by weight and Epicuron B-57
0.104 parts by weight, 66 parts by weight of the rubber-modified epoxy resin obtained in Example 9, and 25 parts by weight of imidazole copolymer (A3) were blended to obtain an epoxy resin composition. A cured product was prepared and measured in the same manner as in Example 10 except that this composition was used. The results are shown in Table 3.

Comparative Example 4 840.100 parts by weight of Epiclon, 140 parts by weight of the rubber-modified epoxy resin obtained in Example 9, and Epiclon B-570
, and 3 parts by weight of 2-methylimidazole to obtain an epoxy resin composition. A cured product was prepared and measured in the same manner as in Example 10 except that this composition was used. The results are shown in Table 3.

In addition, the epoxy resin compositions shown in the Examples and Comparative Examples in Table 3 have a constant blending ratio of the epoxy resin, the curing agent, the imidazole structure part in the curing accelerator, and the rubber content in the flexibility imparting agent. I made it so that

As is clear from Table 3, the water absorption rate of Comparative Example 4 is higher than that of Examples 10, 11 and 12, indicating that the water resistance is inferior.

[Effects of the Invention] The curing agent for epoxy resin and the curing accelerator for epoxy resin of the present invention can be easily mixed with an epoxy resin, and the epoxy resin composition of the present invention obtained by mixing them is water resistant. It has the advantage that there is no decrease in sex.

Moreover, the curing agent for epoxy resin and the curing accelerator for epoxy resin of the present invention can be used in combination with a conventionally used composition comprising an epoxy resin and a flexibility imparting agent.

Claims (1)

[Scope of Claims] 1. A curing agent for epoxy resins, comprising a polymer compound that is liquid at room temperature and has a covalently bonded imidazole structure in its side chain. 2. The curing agent according to claim 1, wherein the polymer compound that is liquid at room temperature is a polymer compound that generates rubber elasticity through a crosslinking reaction. 3. The curing agent according to claim 1, wherein the polymer compound which is liquid at room temperature is a butadiene copolymer or a butyl acrylate copolymer. 4. A curing accelerator for epoxy resins comprising a polymer compound that is liquid at room temperature and has a covalently bonded imidazole structure in its side chain. 5. The curing accelerator according to claim 4, wherein the polymer compound that is liquid at room temperature is a polymer compound that generates rubber elasticity through a crosslinking reaction. 6. The curing accelerator according to claim 4, wherein the polymer compound that is liquid at room temperature is a butadiene copolymer or a butyl acrylate copolymer. 7. An epoxy resin composition containing as an essential component an epoxy resin and a polymer compound that is liquid at room temperature and has an imidazole structure in its side chain that is covalently bonded to the epoxy resin. 8. The epoxy resin composition according to claim 7, wherein the polymer compound that is liquid at room temperature is a polymer compound that generates rubber elasticity through a crosslinking reaction. 9. The epoxy resin composition according to claim 7, wherein the polymer compound that is liquid at room temperature is a butadiene copolymer or a butyl acrylate copolymer. 10. The epoxy resin composition according to claim 7, 8 or 9, further comprising a flexibility imparting agent as an essential component. 11. The epoxy resin composition according to claim 10, wherein the flexibility imparting agent is butadiene and/or butadiene-acrylonitrile liquid rubber. 12. An epoxy resin composition containing as essential components an epoxy resin, a curing agent for epoxy resin, and a polymer compound that is liquid at room temperature and has an imidazole structure in its side chain that is covalently bonded. 13. The epoxy resin composition according to claim 12, wherein the polymer compound that is liquid at room temperature is a polymer compound that generates rubber elasticity through a crosslinking reaction. 14. Claim 12, wherein the polymer compound that is liquid at room temperature is a butadiene-based copolymer or a butyl acrylate-based copolymer.
The epoxy resin composition described. 15. The epoxy resin composition according to claim 12, 13 or 14, further comprising a flexibility imparting agent as an essential component. 16. The epoxy resin composition according to claim 15, wherein the flexibility imparting agent is butadiene and/or butadiene-acrylonitrile liquid rubber.