JPH05295340A - Adhesive composition - Google Patents

Abstract

PURPOSE:To provide an adhesive compsn. which provides a high adhesive strength and stable adhesive power and is excellent in resistance to heat and water. CONSTITUTION:An adhesive compsn. comprises an epoxy resin, a curing agent, and a filler comprising a mixture of calcium carbonate and talc. The content of talc in the mixture is 2-10wt.%. The compsn. undergoes cohesive failure when adherends bonded with the compsn. are peeled apart, thus providing stable adhesive power.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an adhesive composition, particularly an epoxy resin adhesive composition, and more particularly to a heat-curable epoxy resin adhesive composition useful as an adhesive for steel plates. ..

[0002]

2. Description of the Related Art Epoxy resin adhesives have excellent adhesiveness to various materials such as metals, plastics, woods and ceramics and have been widely used. With respect to this epoxy resin adhesive, various studies have been made to further improve various performances such as heat resistance and water resistance. Among them, for example, heat resistance by increasing the crosslink density by blending a polyfunctional epoxy resin, a polyfunctional curing agent,
A method of improving water resistance, a method of mixing a hydrophobic epoxy resin and a coupling agent to improve water resistance, and the like have been proposed (JP-A-58-118875 and JP-A-60-94419). Japanese Patent Laid-Open No. 1-247
No. 416, etc.).

[0003]

By the way, in order to judge the characteristics of an adhesive, in addition to the adhesive strength, the state of destruction when an external force is applied after adhering a certain material is also an important evaluation. Has become a means. The fracture state includes cohesive fracture that causes fracture in the adhesive layer, interface fracture that causes fracture at the interface between the adhesive layer and the adherend, adherend fracture that causes fracture in the adherend layer, and cohesive fracture. There are four fracture states of mixed fracture that occur when interface fractures are mixed. From the viewpoint of stable adhesiveness, it is most desirable that the adhesive has high adhesive strength and causes cohesive failure.

However, in the above-mentioned conventional means, the cohesive force of the adhesive is generally high, so that the interface is easily broken. As a result, not only the adhesive strength is often lowered, but also expensive materials are used, which is economically disadvantageous.

The present invention has been made in order to solve the above problems, and its purpose is to obtain an adhesive composition having high adhesive strength and stable adhesive strength, and having excellent heat resistance and water resistance. To provide things.

[0006]

Means for Solving the Problems The present inventor has found and completed the present invention as a result of extensive studies to achieve the above object. That is, the present invention, in an adhesive composition containing an epoxy resin, a curing agent, a filler, while using a mixture of calcium carbonate and talc as the filler,
The proportion of talc in the filler is 2% by weight or more and 10
It should be less than weight%.

As the epoxy resin in the present invention, usual epoxy compounds known in the art can be used. For example, bisphenol A type epoxy resin, bisphenol F
Type epoxy resin, polyglycol type epoxy resin, dimer acid modified epoxy resin, rubber modified epoxy resin, urethane modified epoxy resin, acryl modified epoxy resin and the like, and one kind or a mixture of two or more kinds thereof may be used.

Further, as the curing agent in the present invention, a usual curing agent exhibiting curability by heating can be used.
Examples thereof include dicyandiamide, polycarboxylic acid anhydride, boron trifluoride complex salts, imidazole derivatives, hydrazides, urea derivatives, and the like. One or a mixture of two or more of these may be added in a suitable amount depending on the curing conditions. You can use it in.

In the present invention, calcium carbonate and talc are blended as a filler. The blending amount of the mixture of calcium carbonate and talc is not particularly limited, but is preferably 30 to 60 parts by weight with respect to 100 parts by weight of the epoxy resin. Further, the proportion of talc in the filler needs to be 2% by weight or more and 10% by weight or less. If the proportion of talc is less than 2% by weight, the rate of cohesive failure decreases and interface failure tends to occur. Further, if the proportion of talc is more than 10% by weight, the adhesive strength will be remarkably reduced, which is unsuitable. As other fillers, clay, aluminum hydroxide, titanium oxide, carbon black, graphite, silica, metal powder such as aluminum and iron, glass fiber and the like can be added as required.

[0010]

[Function] Talc has a flat particle shape, a high aspect ratio, is easily oriented in a specific direction, and has little interaction with the epoxy resin, so that the epoxy resin / talc interface is not broken in the adhesive layer. It is thought to occur easily. Therefore, by blending talc, the cohesive force is appropriately weakened, and as a result, the cohesive failure rate is increased,
It shows a stable adhesive force.

[0011]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. In addition, "parts" in the examples means "parts by weight" unless otherwise specified.

(Example 1) Epoxy equivalent 180 to 190
70 parts of liquid bisphenol A type epoxy resin, dimer acid-modified epoxy resin 1 having an epoxy equivalent of 600 to 700
0 part, 20 parts of a rubber-modified epoxy resin having an epoxy equivalent of 450 to 500 was placed in a stainless steel flask, and the mixture was kept at 80 ° C. for 3 days.
Stir and mix for 0 minutes. Next, specific surface area of 10000 cm ² /
34 parts of heavy calcium carbonate, specific surface area 35000 cm
1 part of ² / g talc was added, and the mixture was further stirred and mixed for 30 minutes. Next, after lowering the temperature to 60 ° C., 8 parts of dicyandiamide and 1 part of 2,4-diamino-6 {2′-methylimidazole- (1 ′)}-ethyl-S-triazine were added and mixed with stirring for 20 minutes. Finally, the target adhesive composition was prepared by defoaming under reduced pressure.

(Example 2) Heavy calcium carbonate was added to 47
An adhesive composition was prepared in the same manner as in Example 1 except that 3 parts of talc and 3 parts of talc were used.

(Example 3) 45 wt.
An adhesive composition was prepared in the same manner as in Example 1 except that 5 parts of talc and 5 parts of talc were used.

(Comparative Example 1) 50 wt.
An adhesive composition was prepared in the same manner as in Example 1 except that the parts and talc were changed to 0 parts.

(Comparative Example 2) 40 wt.
An adhesive composition was prepared in the same manner as in Example 1 except that 10 parts of talc and 10 parts of talc were used.

The adhesive properties of each of the adhesive compositions obtained in the above Examples and Comparative Examples were evaluated by the following test methods. The evaluation results are shown in Table 1. <Tensile shear adhesive strength> Cold-rolled steel sheet (JI
S-G3141, SPCC-D) 100 x 25 x 1.6
Using tmm, adhesive thickness 0.15mm, wrap width 1
A 2.5 mm single lap test piece was heated at 180 ° C. for 30 minutes to prepare an adhesion test piece.

Then, in accordance with JIS-K6850, 23
After immersion in warm water at ℃, 80 ℃ and 40 ℃ for 30 days (measurement temperature is 2
The tensile shear bond strength (3 ° C.) was measured. Further, the fractured state was evaluated by visually observing the fractured surface.

<T-Peel Adhesion> As an adherend, cold rolled steel plate (JIS-G3141, SPCC-D) 200 × 2
Using 5 × 0.8 tmm, a test piece having an adhesive thickness of 0.15 mm and an adhesive application portion of 150 mm was heated at 180 ° C. for 30 minutes to produce an adhesion test piece.

Then, in accordance with JIS-K6850, 23
After soaking in warm water at ℃, 80 ℃ and 40 ℃ for 30 days (measurement temperature is 2
The T-peel adhesion strength at 3 ° C) was measured. Further, the fractured state was evaluated by visually observing the fractured surface.

[0021]

[Table 1]

As shown in the table, when the proportion of talc in the filler is 2.9% by weight (Example 1), 6% by weight (Example 2) and 10% by weight (Example 3), respectively. All had excellent adhesive strength, and also showed excellent heat resistance and water resistance. Most of the fracture modes at the time of fracture were cohesive fracture. That is, it shows that the adhesive force is stable.

On the other hand, the proportion of talc in the filler is 0.
In the case of weight% (Comparative Example 1), the initial decrease in adhesive strength was not observed, but the failure mode was such that interface failure was likely to occur. That is, in this case, it indicates that the adhesive force was unstable.

Further, the proportion of talc in the filler is 2
In the case of 0% by weight (Comparative Example 2), the adhesive strength was remarkably lowered. Thus, in this embodiment,
Since the proportion of talc in the filler is 2% by weight or more and 10% by weight or less, high adhesive strength can be obtained. Further, even when exposed to harsh conditions such as heat and water, a high strength retention rate is exhibited, and a stable adhesive force can be retained even against heat and water. Further, most of the breaking modes at the time of breaking are cohesive breaking, and stable adhesive force can be obtained.

[0025]

As described above in detail, according to the adhesive composition of the present invention, it is possible to obtain high adhesive strength and stable adhesive force, and at the same time, it has excellent heat resistance and water resistance. ..

Claims (1)

[Claims] 1. In an adhesive composition containing an epoxy resin, a curing agent, and a filler, a mixture of calcium carbonate and talc is used as the filler, and the proportion of talc in the filler is 2% by weight or more. An adhesive composition comprising 10% by weight or less.