JPS6241548B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to adhesive compositions, and more particularly to epoxy resin adhesive compositions with improved heat resistance, water resistance, and storage stability. Epoxy resin adhesives are widely used as structural adhesives in various industries such as automobiles, railways, aircraft, and construction because of their high adhesive strength and low cost. However, each of these adhesives has problems with water resistance, heat resistance, pot life, storage stability, etc., and adhesive strength decreases significantly when exposed to high temperature and high humidity conditions for a long time. There was a drawback to it. In order to improve the water resistance of epoxy resin adhesives, there are epoxy/phenolic adhesives modified with phenolic resin, but this adhesive is an adhesive composition consisting of resol type phenolic resin and epoxy resin and has high heat resistance. Moreover, adhesive compositions made of novolac type phenolic resin and epoxy resin have the disadvantage that a large amount of an amine compound must be added to improve heat resistance, resulting in a short shelf life. The presence of an amine compound is important in the curing reaction of the composition consisting of the novolak type phenolic resin and epoxy resin, and in systems without the amine compound, the curing speed is slow and only the phenolic resin flows out due to the curing pressure, resulting in poor performance. Adhesive strength cannot be obtained. As described above, although favorable water resistance can be obtained in epoxy/phenolic adhesive compositions, one that also has good adhesive strength, heat resistance, and storage stability has not yet been obtained. An object of the present invention is to meet such demands by providing an adhesive composition having good adhesive strength, water resistance, heat resistance, and storage stability. The present inventors have conducted research to further improve the adhesive strength, heat resistance, and storage stability of epoxy/phenolic adhesive compositions with good water resistance. The present invention has been completed based on the discovery that a composition containing a type phenolic resin, (iii) a novolak type phenolic resin, and (iv) an amine compound has excellent adhesive strength, heat resistance, water resistance, and storage stability. I came to the point. In this composition, it is not clear how the resol-type phenolic resin and the novolac-type phenolic resin, as well as each phenolic resin and epoxy resin, react during curing and what structure they take, but in the presence of an amine compound, It is thought that the resol type phenolic resin and the novolac type phenolic resin assume a three-dimensional structure during the curing reaction and are dispersed in the cured epoxy resin as microgels. It is believed that because of the formation of this microgel, the composition exhibits tough properties after curing and has excellent adhesive strength and heat resistance. The epoxy resin used in the present invention is not particularly limited in type and usually has two epoxy groups in one molecule.
It is sufficient that the composition has at least 100% acetate, and that it cures and becomes insoluble and infusible only when exposed to heat or other stimuli in the composition. For example, bisphenol type epoxy resin, glycerin glycidyl ether type epoxy resin, phenol or cresol novolak type epoxy resin, brominated bisphenol type epoxy resin, dimer acid glycidyl ester type epoxy resin, urethane modified epoxy resin, polybutadiene with glycidyl terminals at both ends. Examples include ether type epoxy resin, glycidyl ester ether type epoxy resin of oxybenzoic acid, and glycidyl ether type epoxy resin of diaminodiphenylmethane. These epoxy resins can be used alone or in combination of two or more. The resol type phenolic resin used in the present invention is a phenolic resin having 1 to 2 methylol groups per phenyl group, and includes phenol, m-cresol, o-cresol, p-cresol, various xylenol, and various dihydroxy It refers to a product obtained by reacting an excess of formaldehyde with benzene or the like using an alkali catalyst, and 2,6 dimethylolphenol is preferred because of its high reactivity. The novolak type phenolic resin is a dihydroxydiphenylmethane derivative, and is a reaction product obtained by adding an excess of the above-mentioned phenols to formaldehyde and using an acid as a catalyst. Phenol resins used industrially for grindstones, shell molds, brakes, adhesives, etc. are useful, and various modified phenol resins can also be used. In the present invention, when the amine compound is used as it is, it is preferable to select a tertiary amine, and in particular, hexamethylenetetramine generates ammonia and formaldehyde upon hydrolysis and is therefore effective in curing the phenolic resin. Primary amines and secondary amines are undesirable because they accelerate the curing reaction of epoxy resins at room temperature, but latent amines capped with phenols, isocyanates, acid anhydrides, etc. or intramolecular condensed anhydrides and amines are Metal salts of the reaction products of
No.) etc. are used in the present invention because they do not shorten the shelf life. Examples of the amine compounds used in the present invention include hexamethylenetetramine, triethylenediamine, 1,8-diazabixilo(5,4,0)undecene-7, trimethylamine, triethylamine, etc. as tertiary amines, and latent amines such as is a reaction product of primary and secondary amines such as ethylenediamine, aniline, hexamethylenediamine, m-phenylenediamine, p-phenylenediamine, dimethylamine, and diethylamine, and phenol, tolylene diisocyanate, and phthalic anhydride. be. The amount of the resol type phenol resin used in the adhesive composition of the present invention is 3 to 50 parts by weight per 100 parts by weight of the epoxy resin. If the amount is less than 3 parts by weight, no effect will be produced. In addition, 1 to 20 parts by weight of novolak type phenolic resin is blended with 100 parts by weight of epoxy resin.
If the amount is more than 20 parts by weight, the shelf life of the adhesive composition will be shortened, and if it is less than 1 part by weight, no effect will be produced. The amount of the amine compound used in the adhesive composition of the present invention is 1 to 20 parts by weight per 100 parts by weight of the total amount of resol type phenolic resin and novolak type phenolic resin, and if it exceeds 20 parts by weight,
If a latent amine is used, the storage stability of the composition is reduced, and if a latent amine is used, the price of the composition increases.
If the amount added is less than 1 part by weight, there will be no effect on the reaction of the phenolic resin. Dicyandiamide, melamine, and benzoguanamine are used as the epoxy resin curing agent in the adhesive composition of the present invention, and it is preferable to use them in combination with an accelerator such as an imidazole derivative or a urea compound because the curing temperature can be lowered. Imidazole derivatives include 2-phenylimidazole, 2-methylimidazole, 2-ethyl, 4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenyl, 4-methylimidazole, 1-benzyl, There are 2-methylimidazole, 2-ethylimidazole, and 2-isobutylimidazole, but in terms of storage stability, the above-mentioned imidazole with a cyanoethyl group substituted in the 1st position, or imidazoles with a cyanoethyl group substituted in the 1st position are recommended. Preferred are trimellistate salts and s-triazine salts of imidazoles. Examples of urea compounds include 3-(p-chlorophenyl)-1,1-dimethylurea, 3-(3,
4-dichlorophenyl)-1,1-dimethylurea is used. In addition to the above-mentioned epoxy resin, resol type phenolic resin, novolac type phenolic resin, amine compound, curing agent, and accelerator, the adhesive composition of the present invention uses carboxyl group-containing butadiene acrylonitrile copolymer, nylon polyamide resin, etc. This is useful because it promotes improvement of adhesive strength, especially peel strength. Also, talc,
The use of silica, calcium carbonate, aluminum powder, iron powder, short gypsum fibers, short glass fibers, etc.
You can expect the effects of preventing sagging and increasing weight. The adhesive composition of the present invention is mainly for adhering metal substrates, and the adherend metals include:
Examples include aluminum, iron, steel, magnesium, molybdenum, and tungsten. In addition,
The compositions are also useful as adhesives for paper, wood, glass, plastics, etc. It is desirable to subject these adherends to degreasing with a solvent, acid etching, or the like, or to apply a primer as a preadhesion treatment, since this improves adhesive strength and durability. When producing the present invention as a structural adhesive, the composition may be mixed with methyl ethyl ketone, acetone,
It can be dissolved in an organic solvent such as toluene and used as a varnish, or it can be used in a crusher, without using an organic solvent.
Using a mixer such as a triple roll or kneader,
Although it can be used as a paste, it can also be used as a tape-like adhesive with a support such as woven fabric or non-woven fabric. Since variations in adhesive strength largely depend on the thickness of the adhesive between adherends, it is preferable to use the adhesive in the form of a tape. Hereinafter, the present invention will be specifically explained with reference to Examples. The adhesive strength is measured according to the U.S. Federal Standard MMM.
- It was carried out in accordance with A-132. Example 1 As an epoxy resin, 100 parts by weight of Epicoat 828 (manufactured by Mitsubishi Yuka Co., Ltd., epoxy equivalent: 184-194) and Epicoat 1007 (manufactured by Mitsubishi Yuka Co., Ltd., epoxy equivalent: 1750-1750) were used as epoxy resins.
2100) 50 parts by weight as a resol type phenolic resin, Sumilite Resin PR-51501AB (manufactured by Sumitomo Durez, melting point 85-95℃) 20 parts by weight, as a novolac type phenolic resin Sumilite Resin PR-
5 parts by weight of 12686 (manufactured by Sumitomo Durez, melting point 70-83°C) and 0.5 parts by weight of hexamethylenetetramine as an amine compound are dissolved in 75 parts by weight of methyl ethyl ketone to produce a varnish with a solid content of 70%. Next, 7 parts by weight of dicyandiamide and 2 parts by weight of 2-phenyl and 4-hydroxyethylimidazole are ground and mixed in a mortar. The aforementioned varnish and powdered dicyandiamide, 2-phenyl, 4-methyl, and 5-hydroxymethylimidazole are stirred and mixed using a mixer. Spread the mixture on a glass cloth and let it dry.
400 (g/m ² ) of adhesive tape is obtained. The adhesive strength is shown in Table 1. Comparative Examples 1-a, 1-b, 1-c Sumilite Resin PR from the formulation of Example 1
Comparative Examples 1-a, 1-b, 1- were prepared using adhesives obtained by removing one component each of 51501AB, Sumilite Resin PR-12686, and hexamethylenetetramine.
Let it be c. The adhesive strength is shown in Table 1.

[Table] From Table 1, compared to Example 1 of the present invention, the formulation lacking resol type phenol resin (Comparative Example 1-
A) has poor storage stability, a formulation lacking novolac type phenolic resin (Comparative Example 1-b) has poor heat resistance, and a formulation lacking hexamethylenetetramine (Comparative Example 1-c) has poor heat resistance and water resistance. I know it's bad. Example 2 Sumi Epoxy ELM128 as epoxy resin
(manufactured by Sumitomo Chemical Co., Ltd., epoxy equivalent 184-194) 100
Parts by weight, 50 parts by weight of Sumi Epoxy ESA011 (manufactured by Sumitomo Chemical Co., Ltd., epoxy equivalent: 450-500), 10 parts by weight of CTBN x 13 (manufactured by Gutudoritsu Chemical Co., Ltd.) as a carboxyl group-terminated liquid butadiene acrylonitrile copolymer, resol type phenolic resin 10 parts by weight of Sumilight Resin PR-51501AB (manufactured by Sumitomo Durez Co., Ltd.), and Sumilight Resin PR-12987 (manufactured by Sumitomo Durez Co., Ltd.) as novolac type phenolic resin containing hexamethylenetetramine (contains 8% hexamethylenetetramine as amine).
10 parts by weight (0.8 parts by weight of amine), dicyandiamide
12 parts by weight and 3 parts by weight of 2,4-diamino-6(2-methylimidazoyl-1)ethyl-s-triazine are stirred and mixed using a kneader to obtain a paste-like mixture. This paste is applied onto a glass nonwoven fabric to obtain a tape-like adhesive having a weight of 400 (g/m ² ). The adhesive strength is shown in Table 2.

Table 2 shows that the formulation of Example 2 is excellent in various properties such as heat resistance, storage stability, and water resistance. In particular, since the above formulation contains a liquid butadiene-acrylonitrile copolymer containing terminal carboxyl groups, the adhesive strength is significantly improved compared to the formulation of Example 1. Example 3 Sumi Epoxy ELA128 as epoxy resin
(Manufactured by Sumitomo Chemical Industries, Ltd., Epoxy 184-194) 100 parts by weight, Sumitomo Epoxy ESA017 (Manufactured by Sumitomo Chemical Industries, Ltd.,
Epoxy equivalent (1750-2100) 50 parts by weight, 20 parts by weight of PR-175 (manufactured by Sumitomo Durez, melting point 65°C) as a resol type phenolic resin, 5 parts by weight of PR-12686 (manufactured by Sumitomo Durez) as a novolac type phenolic resin, amine compound 1 part by weight of hexamethylenetetramine, 225 parts by weight of Diamide T250P ₁ (manufactured by Daicel Chemical Industries) as a nylon polyamide resin, 10 parts by weight of dicyandiamide, Kyuazol
Mix and stir 2 parts by weight of 2MZ-AZINE (manufactured by Shikoku Kasei) using a mixer to obtain a paste-like mixture. Glass cloth is impregnated with this paste to produce a tape-shaped adhesive. The adhesive strength is shown in Table 3. The measurement method for climbing drum peels is based on American standards.
In accordance with MIL-A-25463A.

【table】

Table 3 shows that the formulation of Example 3 has excellent heat resistance, storage stability, and water resistance. Furthermore, the above formulation has excellent releasability due to the presence of the nylon-based polyamide resin. T-
The values of peel and climbing drum peel are only 2 to 3 kg/in and 2 to 3 kg/cm/cm, respectively, in the formulation in which the nylon polyamide resin is omitted from the above formulation. As explained above, an epoxy resin adhesive composition characterized by reacting a resol type phenolic resin and a novolak type phenolic resin in the presence of an amine compound improves heat resistance, water resistance, and storage stability. Therefore, it is useful as a structural adhesive for automobiles, railways, aircraft, architecture, etc.

Claims (1)

[Scope of Claims] 1 (i) 100 parts by weight of epoxy resin, (ii) 3 to 50 parts by weight of resol type phenolic resin, (iii) 1 to 20 parts by weight of novolac type phenolic resin, and (iv) amine compound. is the total amount of the resol type phenolic resin and the novolac type phenolic resin.
An adhesive composition having improved heat resistance, water resistance, etc. after curing, characterized in that it contains 1 to 20 parts by weight per 100 parts by weight.