JPH05271640A - Epoxy resin adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition as a structural adhesive excellent in the adhesion to a steel sheet with an oiled surface and good in the balance between shearing strength and peeling strength. CONSTITUTION:This composition comprises 100 pts.wt. modified epoxy resin obtained by reacting an epoxy prepolymer containing an epoxy compound modified with a liquid carboxyl-terminated diene rubber of a number-average molecular weight of 1000-7000 (the amount of the liquid diene rubber component being within 40wt.% based on the epoxy prepolymer) with a urethane prepolymer obtained by reacting a polyether polyol of a number-average molecular weight of 500-3000 with a polyisocyanate compound, 0.5-100 pts.wt. saturated polyester resin and 2-30 pts.wt. latent curing agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin adhesive composition, and more particularly to a resin adhesive composition having a good balance between shear strength and peel strength in terms of adhesiveness to oily steel sheet as a structural adhesive.

[0002]

2. Description of the Related Art Structural adhesives are used in a wide range of industrial fields such as aviation, space, vehicles, ships, construction, civil engineering, electricity and electronics.

In recent years, thin steel plates, laminated steel plates and the like have come to be used in order to reduce the weight of steel materials, which are structural members conventionally used in these fields, and metallic materials such as aluminum.

Along with this, the conventional welded joints have problems such as reduction of joint strength and deformation of welded portions, and expectations for welded joints and adhesive joints are increasing.

Industrially, if the step of removing the press oil, the rust preventive oil, etc. can be omitted, there is a high economic merit, and there are some parts that are difficult to remove even in the step of removing. Oil surface adhesiveness is an essential condition for adhesion of such a part.

Epoxy resin adhesives, acrylic adhesives, polyurethane adhesives and the like are known as adhesives having the above-mentioned properties. (For example, JP-A-60-235877, JP-A-54-26000, and JP-A-6-235877.
0-206882, 49-97052, 50-
35232, 54-86562, etc.)

[0007]

However, acrylic adhesives have problems of deterioration in strength under heat and workability, and polyurethane adhesives have poor oil surface adhesion and poor water resistance. There was a problem. On the other hand, regarding an epoxy resin adhesive, an improvement example thereof is disclosed in Japanese Patent Laid-Open No.
An adhesive composition composed of a urethane-modified epoxy resin proposed in Japanese Patent Laid-Open No. 4-26000 is known, but it cannot be said to have sufficient oil surface adhesiveness although it has excellent adhesive strength. In view of the present situation, the present applicant has found that a composition of a modified epoxy resin (A) obtained by reacting a rubber-modified epoxy resin and a urethane prepolymer with a latent curing agent (B) has excellent oil surface adhesion. It was found that the material exhibits excellent properties, and it was previously proposed (Japanese Patent Laid-Open No. 63-205379,
JP-A-2-45587). These have certainly excellent oil surface adhesiveness as compared with the above-mentioned adhesive composition, but depending on the use condition of the steel sheet adhesive structure, the structure and form of the applied steel sheet adhesive structure, the adhesive force, It was found that the balance between shear strength and peel strength was not always sufficient.

[0008]

Accordingly, the present invention provides an epoxy resin adhesive composition as a structural adhesive, which has good adhesiveness to oily steel sheets and excellent mechanical strength. The main purpose is that.

And, according to the present invention, the object is:
(A) Modified epoxy resin obtained by reacting the following (a) and (b) (a) Number average molecular weight 1,0 having terminal carboxyl group
An epoxy prepolymer containing a modified epoxy compound modified with a diene liquid rubber of 0 to 7,000 (however, the amount of the diene liquid rubber component in the epoxy prepolymer is 40
(B) Within 100% by weight of a urethane prepolymer obtained by reacting a polyether polyol having a number average molecular weight of 500 to 3,000 with a polyisocyanate compound, and (B) a saturated polyester resin of 0.5 to 100. And an epoxy resin adhesive composition containing 2 to 30 parts by weight of a latent curing agent (C).

The present invention will be described in detail below. The component A blended in the adhesive composition of the present invention has a number average molecular weight of 1,000 to 7,000 having a carboxyl group at the terminal (a).
0, an epoxy prepolymer containing a modified epoxy compound modified with a diene liquid rubber of 0 (however, the amount of the diene liquid rubber component in the epoxy prepolymer is within 40% by weight), and (b) a number average molecular weight of 500 to It is a modified epoxy resin obtained by reacting a urethane prepolymer obtained by reacting 3,000 polyether polyols with a polyisocyanate compound.

The component A may be derived from the above modified epoxy resin, or may be a mixture of the above modified epoxy resin and an unmodified epoxy compound. As the epoxy compound used to obtain the epoxy prepolymer of the component (a), an epoxy compound having an average of two or more epoxy groups in one molecule, which is used as a component of an ordinary epoxy resin adhesive, is used. .. Examples of such epoxy compounds include bisphenol A type epoxy resins, bisphenol F type epoxy resins, novolac type epoxy resins, polyfunctional phenol type epoxy resins, and various halogenated epoxy resins. Further, a diglycidyl ether compound obtained by the reaction of resorcinol and epihalohydrin, a glycidyl ester type epoxy resin, a polyglycol type epoxy resin, a cycloaliphatic epoxy resin, a hydantoin type epoxy resin, a glycidyl amine type epoxy resin and the like can also be used. .. The epoxy compounds can be used alone or in combination of two or more.

Examples of the diene liquid rubber having a terminal carboxyl group used for modifying the epoxy compound include:
Carboxyl group-terminated acrylonitrile butadiene rubber, polybutadiene rubber, polyisoprene rubber, polychloroprene rubber, etc., having a number average molecular weight of 1,000
Liquid rubber of about 7,000 can be mentioned. In particular, acrylonitrile butadiene rubber and polybutadiene rubber are preferable. Typical products include Hicar CTBN 1300 × 8 Hicar CTBN 1300 × 13 Hycar CTBN 2000 × 162 (all are manufactured by BF Goodrich Co., Ltd.) NISSO PB C-1000 NISSO PBC-2000 (all manufactured by Nippon Soda Co., Ltd.) POly bd R-45MA (manufactured by Idemitsu Petrochemical Co., Ltd.) and the like can be mentioned.

These number average molecular weights can be measured by the VPO method or the like. The amount of the diene liquid rubber contained in the epoxy prepolymer as the component (a) is 40% by weight or less, and if it exceeds this amount, it becomes rubbery and the shear strength decreases. Note that (a)
The diene liquid rubber contained in the component epoxy prepolymer is preferably 3 to 35% by weight. The reaction between the epoxy compound and the carboxyl group-terminated diene liquid rubber is usually carried out at 80 to 200 ° C, preferably 100 to 170 ° C.

Polyols and polyester polyols can be used as the polyol for preparing the urethane prepolymer as the component (b), and the polyether polyol is particularly desirable. The polyether polyol is
The compounds generally used in the synthesis of polyurethane may be used, and specific examples thereof include the compounds listed below, but are not limited thereto. That is, ethylene oxide, propylene oxide, cyclic oxides such as butylene oxide and oxycyclobutane, ring-opening polymers and copolymers of cyclic compounds such as tetrahydrofuran, alkylene oxide as a basic catalyst and glycol, polyhydric alcohols such as glycerol or What is called polyoxyalkylene glycol obtained by polymerizing in the presence of a primary monoamine is used.

Among the polyether polyols used in the present invention, polyoxytetramethylene glycol, polyoxypropylene glycol and the like are preferred. The number average molecular weight of the polyether polyol used in the present invention is preferably from 500 to 3,000, particularly preferably from 500 to 2,000, and when the molecular weight is less than 500, the adhesive strength is not improved, and when it exceeds 3,000, oil surface adhesion is achieved. Sex decreases.

The polyisocyanate compound for preparing the urethane prepolymer of the component (b) is a compound having a plurality of isocyanate groups in one molecule, such as hexamethylene diisocyanate and 2,4-diisocyanate-1. In addition to aliphatic or alicyclic diisocyanate compounds such as -methylcyclohexane, 2,6-diisocyanate-1-methylcyclohexane, diisocyanate cyclobutane, tetramethylene diisocyanate, xylylene diisocyanate and dicyclohexylmethane diisocyanate, 2,4-tolylene diisocyanate Isocyanate, tolylene-2,6-diisocyanate, diphenylmethane-4,4'-diisocyanate, 3-methyldiphenylmethane-4 ', 4-diisocyanate,
Phenylene diisocyanate, chlorophenylene-2,
6-diisocyanate, naphthalene-1,5-diisocyanate, diphenyl-4 ', 4'-diisocyanate, 1,3,5-triisopropylbenzidine-2,4-
Triisocyanate compounds such as diisocyanate and diphenyl ether diisocyanate may be used alone or as a mixture.

The polyisocyanates preferably used in the present invention include 2,4-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate,
Examples include xylylene diisocyanate and 2,6-tolylene diisocyanate. The method of reacting the polyether polyol and polyisocyanate in order to obtain a urethane prepolymer having an isocyanate group at the molecular end is a general synthetic method used when synthesizing a urethane prepolymer is applied, It is obtained by a method of sequentially adding a polyol to a polyisocyanate having an excess molar ratio with respect to the polyol.

In the preparation of the urethane prepolymer having an isocyanate group at the molecular end in the present invention, the isocyanate group in the polyisocyanate compound is reacted in excess of the hydroxyl group in the polyether polyol. Otherwise, the oil surface adhesive strength will decrease. (A)
The reaction between the epoxy prepolymer as the component and the urethane prepolymer as the component (b) may be carried out at 100 to 150 ° C. for 2 to 3 hours, and the reaction is performed until the isocyanate group disappears.

The urethane prepolymer of (b) contained in the component (A) is the epoxy prepolymer 100 of (a).
It is preferable to react 2 to 40 parts by weight, preferably 2 to 30 parts by weight with respect to parts by weight. If it exceeds 40 parts by weight, the oil surface adhesiveness will decrease, and if it is less than 2 parts by weight, the adhesive strength will not improve.

The saturated polyester resin as the component (B) can be produced by a generally known method, and includes succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and 1,9-nonane. Dicarboxylic acid,
1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,2-dodecanedicarboxylic acid, 1,2-
Octadecane dicarboxylic acid, eicosane dicarboxylic acid,
Cyclohexanedicarboxylic acid, hexahydrophthalic acid,
Tetrahydrophthalic acid, terephthalic acid, isophthalic acid,
Dicarboxylic acid components such as phthalic acid and naphthalene dicarboxylic acid, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol,
Propylene glycol, trimethylene glycol, 1,
4-butanediol, 1,5-pentanediol, 1,
6-hexanediol, 1,9-nonanediol, 1,
10-decanediol, neopentyl glycol, spiroglycol, 1,4-cyclohexanedimethanol,
Glycol components such as 2,2,4-trimethylpentane-1,3-diol and oxycarboxylic acid components such as malic acid, tartaric acid, ε-oxycaproic acid, 1,2-hydroxystearic acid and β-hydroxyethoxybenzoic acid And so on. Further, a compound having 3 or more ester-forming functional groups in one molecule, such as trimellitic acid, trimesic acid, pyromellitic acid, trimethylolpropane, glycerin and pentaerythritol in an amount within the range not impairing the gist of the present invention. Of course, it does not matter if you use. The molecular weight of the saturated polyester of the present invention is
Usually, 1,000 to 30,000, preferably 2,0
It is from 00 to 20,000.

The glass transition temperature of the saturated polyester used in the present invention is preferably -15 ° C or lower, and particularly -20.
-50 degreeC is preferable. If it exceeds −15 ° C., the adhesive strength will be low and the balance between shear strength and peel strength will be poor. The addition amount of the saturated polyester of the present invention is 0.5 to 10
0 parts by weight. If it is less than 0.5 part by weight, the peel strength is not improved, and if it exceeds 100 parts by weight, the shear strength is too low. It is preferably 5 to 70 parts by weight.

UE3400 (manufactured by Unitika) Glass transition temperature -20 ° C Byron GN-915P (Toyobo) Glass transition temperature -20 ° C Byron GN-935P (Toyobo) Glass transition temperature -25 ° C PES 095P ( Toa Gosei) Glass transition temperature -40 ° C PES 110P (Toa Gosei) Glass transition temperature -32 ° C.

Next, as the latent curing agent used as the component (C), one generally used as a curing agent for epoxy resin is used. For example, dicyandiamide, guanidine derivative, triazine derivative, imidazole derivative, 4,4'-diaminodiphenyl sulfone, acid hydrazide compound, N, N'-dialkylurea derivative, N,
Examples thereof include N'-dialkylthiourea derivatives and amine adduct compounds, and at least one of them is used. The compounding amount of the latent curing agent is 100 parts of the modified epoxy resin of component A.
2 to 30 parts by weight, preferably 5 to 30 parts by weight may be selected with respect to parts by weight. If it is less than 2 parts by weight, the adhesive strength will not be exhibited due to insufficient curing, and if it exceeds 30 parts by weight, it will become glassy and brittle.

The epoxy resin adhesive composition of the present invention can be prepared by blending the above-mentioned components (A), (B) and (C) in a predetermined ratio. If necessary, known additives may be added. For example, fillers (calcium carbonate, clay, silica, carbon black, metal powder), pigments, flameproofing agents, leveling agents, thixotropy imparting agents, etc. may be added. Mixing with the component A (modified epoxy resin), the component B (saturated polyester resin), the component (C) (latent curing agent), addition of various additives, and the like are performed using various mixing devices. Examples of the mixing device used for such purpose include rolls, kneaders, extruders, and the like.

[0025]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The modified epoxy resin as the component (A) was prepared as follows. Example 1 (a) 100 parts of a commercially available epoxy compound [(Product of Yuka Shell Epoxy Co.) Epicoat 828 (23 parts), Epicoat 1001 (23 parts), Epicoat 872 (flexible epoxy, 54 parts)] and Hiker (B) F. Goodrich) 55 parts [CTBN1300 × 13 (number average molecular weight 3500)] was charged into a reaction vessel, and in a nitrogen stream, 150
The reaction was performed at 3 ° C. for 3 hours to obtain an epoxy prepolymer.
The diene liquid rubber component in the epoxy prepolymer is 3
It is 5.4% by weight. (B) In a reaction vessel, 23 parts of 2,4-tolylene diisocyanate (TDI) was charged, and after nitrogen substitution, 100 parts of polytetramethylene ether glycol [PTG1500.
(Hodogaya Chemical Co., Ltd., number average molecular weight 1500)],
PTG: TDI (molar ratio) = 1: 2 was added dropwise at 110 ° C. and then reacted for 3 hours to obtain a urethane prepolymer.

A Synthesis of modified epoxy resin (a) The reaction between the epoxy prepolymer and the (b) urethane prepolymer was carried out by heating 100 parts (a) and 3.3 parts (b) under nitrogen gas until they became liquid. After mixing, 120 ℃,
The reaction was carried out until the infrared absorption peak of the isocyanate group disappeared for 3 hours to obtain a modified epoxy resin.

Examples 2 and 3 Modified epoxy resins were obtained under exactly the same reaction conditions as in Example 1 except that the type and blending amount of each raw material in Example 1 were changed. The formulations are shown in Table 1.

[0028]

[Table 1]

Adhesive Compositions The component (A) -modified epoxy resins prepared in Examples 1 to 3 and the components (B) and (C) are blended at the compounding ratios shown in Table 2, and Brabender (resin temperature 94 to 95 ° C., Rotation speed 25-30 rp
m, kneading for 30 to 240 minutes) and then defoaming to obtain an epoxy resin adhesive composition. Table 2 shows these physical properties. The method for testing physical properties is as follows. Shear strength: Measured according to JIS K6850.
The test piece has a lap length of 12.5 mm and a bonding thickness of 0.15 mm between a steel plate having a thickness of 1.6 mm according to JIS G3141.
An adhesive agent was applied to the composition and cured at 170 ° C. for 30 minutes to prepare a film. The test was performed using a Tensilon tensile tester manufactured by Toyo Baldwin Co., Ltd. at a tensile speed of 5 mm / min. Peel strength: A T-type peel test was performed according to JIS K6854. A test piece was prepared by applying an adhesive with a bonding thickness of 0.15 mm between steel plates having a thickness of 0.8 mm according to JIS G3141 and curing at 170 ° C. for 30 minutes. The test was performed using a Tensilon tensile tester manufactured by Toyo Baldwin Co., Ltd. at a tensile speed of 200 mm / min. Note that the above steel plates are rust preventive oil (Metal Guard # 83
(1. manufactured by Mobil Petrochemical Co., Ltd.) and then suspended in the atmosphere for 24 hours.

As is clear from the results of the above Examples and Comparative Examples, according to the epoxy resin adhesive composition of the present invention, a good balance between excellent adhesive strength and excellent shear strength / peel strength is achieved even for oil-faced steel sheets. Indicates. Incidentally, it goes without saying that the epoxy resin adhesive composition of the present invention is also effective for degreased steel sheets.

[0031]

[Table 2]

Claims (2)

[Claims] 1. (A) Modified epoxy resin obtained by reacting (a) and (b) below (a) Number average molecular weight 1,0 having terminal carboxyl group
An epoxy prepolymer containing a modified epoxy compound modified with a diene liquid rubber of 0 to 7,000 (however, the amount of the diene liquid rubber component in the epoxy prepolymer is 40
(B) Within 100% by weight of a urethane prepolymer obtained by reacting a polyether polyol having a number average molecular weight of 500 to 3,000 with a polyisocyanate compound, and (B) a saturated polyester resin of 0.5 to 100. An epoxy resin adhesive composition comprising 2 parts by weight and (C) 2 to 30 parts by weight of a latent curing agent. 2. The epoxy resin adhesive composition according to claim 1, wherein the saturated polyester resin (B) has a glass transition temperature of −15 ° C. or lower.