JP2020122082A - Composite body - Google Patents

Abstract

To provide a composite body as an adhesive agent capable of exhibiting sufficient adhesion strength by releasing stress after adhering dissimilar materials each other.SOLUTION: A composite body 1 comprises a laminate structure in which a first thin layer 2 comprising an epoxy resin is sandwiched by a second thin layer 3a and a third thin layer 3b comprising a phenol resin and a nitrile rubber so as to take the surfaces of the second layer and the third layer as adhesion surfaces. In the composite body, a surface direction maximum elongation of the first layer after being hardened is smaller than surface direction maximum elongations of the second layer and the third layer. As a result of this, an adhesive agent having stress relieve and high adhesion strength can be obtained and used for bonding dissimilar materials such as metals and plastics.SELECTED DRAWING: Figure 1

Description

The present invention relates to a composite, and more particularly to a composite that can be used as an adhesive between different materials.

In recent years, there has been a demand for weight reduction of automobile parts, and application studies of metal materials such as aluminum alloys and magnesium alloys and lightweight materials such as plastics and carbon fiber reinforced plastics are being promoted. In order to realize weight reduction, it is essential to combine conventional metal materials and light weight materials. An adhesive is mainly used as a joining method when forming a composite.

For example, a (meth)acrylic-based adhesive component or an epoxy-based adhesive component and an imine-based adhesive component as an adhesive for indirect wearing of different materials capable of exhibiting sufficient adhesive force even between different materials such as metal-plastic and glass-plastic. An adhesive containing a modified polyvinyl acetal having a structure is disclosed (Patent Document 1).

As a method for joining polyethylene and dissimilar materials, a thermoplastic polymer having styrene and rubber segments is fixed to the surface of polyethylene, and then a dissimilar material other than polyethylene is bonded using an adhesive containing rubber as an essential component. The joining method described above is known (Patent Document 2).

An adhesive tape having an ABC3 layer product structure is disclosed as a double-sided adhesive tape for adhering two different substrates to each other (Patent Document 3). The A layer is a heat-activatable adhesive having a characteristic activation temperature T _A of at least +30° C., the B layer is composed of a crosslinked polyurethane carrier material, the C layer is a polyacrylate and/or It is a pressure sensitive adhesive based on polymethacrylate and showing a static glass transition temperature of +15°C or less.

JP, 2017-128652, A JP-A-8-41215 JP, 2003-138230, A

In the technique described in Patent Document 1, the adhesive layer after curing is hard, and the difference in linear expansion coefficient between different materials cannot be reduced. Therefore, stress may be applied to the adhesive layer, and sufficient adhesive strength may not be exhibited.

The joining method described in Patent Document 2 is a technique for adhering polyethylene to another material, and does not consider the difference in linear expansion coefficient between different materials. Therefore, there is a possibility that sufficient adhesive strength cannot be exhibited.

Patent Document 3 discloses an adhesive tape having a three-layer structure, but no consideration is given to an epoxy adhesive that can increase the adhesive strength, and sufficient adhesive strength to structural materials such as automobile parts cannot be exhibited. There is a risk.

The present invention has been made to address such a problem, and an object thereof is to provide a composite as an adhesive that can relieve stress after bonding different kinds of materials and exhibit sufficient adhesive strength. To do.

In the composite of the present invention, the first thin layer (hereinafter, also referred to as the first layer) is the second thin layer (hereinafter, also referred to as the second layer) and the third thin layer (hereinafter, the third layer). (Also referred to as “)”, and is a composite body composed of a laminated structure in which the respective surfaces of the second layer and the third layer serve as adhesive surfaces. This composite is characterized in that the maximum elongation in the plane direction of the first layer after curing is smaller than the maximum elongation in the plane direction of the second layer and the third layer. Here, the maximum elongation in the plane direction means the strain rate at the time of breaking the measurement sample measured according to JIS K7161. In addition, the samples of the first layer, the second layer, and the third layer were individually cured under the curing conditions when cured as a composite to obtain measurement samples.

In the composite of the present invention, the maximum elongation in the plane direction of the first layer is 3 to 10%, and the maximum elongation in the plane direction of the second layer and the third layer is 20 to 70%.
Further, the first layer is a thin layer made of an epoxy resin, and the second layer and the third layer are thin layers made of a phenol resin and a nitrile rubber.
Further, the laminated structure is a film- or sheet-shaped adhesive agent for adhering different materials.

The composite of the present invention is a composite composed of a three-layer laminated structure, and since the maximum elongation in the plane direction of the adhesive layer at the center is smaller than the maximum elongation in the plane direction of the adhesive layer on the surface, The difference in linear expansion coefficient can be relaxed. Therefore, the stress on the adhesive layer can be suppressed to a low level, and sufficient adhesive strength can be exhibited.

It is an expanded sectional view which shows an example of the composite_body|complex of this invention. It is a figure which shows an adhesion test piece.

An example of the complex of the present invention will be described with reference to FIG. FIG. 1 shows an enlarged cross-sectional view of the composite when used as an adhesive.
The composite 1 is a three-layer laminated structure in which the first layer 2 is sandwiched between the second layer 3a and the third layer 3b. The maximum elongation in the plane direction of the first layer 2 is 3 to 10%, and the maximum elongation in the plane direction of the second layer and the third layer is 20 to 70%. That is, the maximum elongation in the plane direction of the first layer 2 is smaller than the maximum elongation in the plane direction of the second layer 3a and the third layer 3b. By laminating the adhesive layers having different maximum elongations in the surface direction, in the adhesion between the adherend 4 and the adherend 5, the stress after the adhesive curing is relaxed and a high adhesive strength is obtained. In particular, even if the adherends 4 and 5 are different materials (for example, the adherend 4 is a metal and the adherend 5 is a plastic), the second layer 3a and the third layer 3b can provide a role of stress relaxation according to each material, and the first layer 2 can provide adhesive strength. Therefore, the composite 1 has higher adhesive strength than the single adhesive layer.

The second layer 3a and the third layer 3b can be changed according to the materials of the adherend 4 and the adherend 5, or the same material, as long as the maximum elongation in the plane direction is within the above range. Can also It is preferable to use the same material in order to make the composite 1 easy.

The layer thicknesses of the first layer 2, the second layer 3a, and the third layer 3b can be set in an optimum range depending on the materials, shapes, and bonding modes of the adherends 4 and 5. The layer thickness of the entire composite body is preferably 0.05 mm to 0.3 mm.

When the composite 1 is used as an adhesive for adhering the adherend 4 and the adherend 5, it is preferable to bond the both in an uncured state and heat-cure them. Therefore, as a method of manufacturing the first layer 2, the second layer 3a, and the third layer 3b, a method of manufacturing each uncured layer and laminating each in an uncured state, and a method of forming a second layer on the surface of an adherend Examples include a method of applying the layers 3a and 3b and laminating them with the first layer 2, a combination thereof, and the like.

The first layer 2 can be used if the maximum elongation in the plane direction after curing is 3 to 10%, preferably 3 to 6%. If the maximum elongation in the surface direction is less than 3%, the central adhesive layer becomes too hard, and if it exceeds 10%, the adhesive strength decreases. The first layer 2 is preferably an epoxy resin for adhesives. As the epoxy resin for adhesives, any compound having an epoxy group that can be cured with amines or acid anhydrides can be used. As the epoxy resin for adhesives, either one-liquid type or two-liquid type can be used. Also, an epoxy resin sheet as an adhesive sheet can be used. Examples of commercially available products of the epoxy resin sheet include Somar EF type, trade name, manufactured by Somar Corporation.

The second layer 3a and the third layer 3b can be used if the maximum elongation in the plane direction after curing is 20 to 70%, preferably 50 to 70%, more preferably 50 to 60%. If the maximum elongation in the surface direction is less than 20%, it will be difficult to relax the stress of the adhesive layer, and if it exceeds 70%, the adhesive strength will decrease.
For the second layer and the third layer, a thermosetting adhesive made of phenol resin and nitrile rubber can be preferably used. Nitrile rubber has a highly polar group in the molecule and therefore has a strong adhesive force as a structural adhesive and the like, and phenol resin has excellent heat resistance. Phenolic resins include reactive phenolic resins that can be used as adhesives. Examples of the reactive phenol resin include a resol type phenol resin which is itself cured by a thermal reaction, or a novolac type phenol resin containing a crosslinkable functional group and a curing agent. Further, by blending the phenolic resin, a reaction with an epoxy group occurs at the bonding interface of the first layer 2 and the interfacial adhesive force with the second layer 3a and the third layer 3b is enhanced.

Examples of commercially available thermosetting adhesives composed of a phenol resin and nitrile rubber include a heat-activatable film (trade name: TESA HAF) manufactured by TESA Corporation. Since both surfaces of the thermoactive film have a light tackiness, they can be temporarily bonded to other materials, and are softened at a low temperature of, for example, 80° C. to 100° C. to have thermoreversible tackiness. Express. Further, at a high temperature of over 120° C., for example, within a range of 120° C. to 220° C. for about 10 to 30 minutes, crosslinking is performed by an irreversible chemical reaction to exert a strong bonding force. This cross-linking reaction is irreversible, and when cross-linked at a sufficient curing temperature, curing time and high pressure, heat resistance of 150° C. or higher and high adhesive strength of 12 N/mm ² or higher can be obtained.

Since the composite of the present invention is excellent in adhesion between different materials, it is possible to bond a cold rolled steel plate (hereinafter referred to as SPCC) to a carbon fiber reinforced plastic (hereinafter referred to as CFRP), aluminum, titanium. It can be used for joining lightweight metals such as magnesium and magnesium, and resins to resins such as SPCC.

Example 1
As the adherend 4, an SPCC having an adhesive surface arithmetic average roughness (Ra) of 0.93 to 1.25 is used, and as the adherend 5, an adhesive surface arithmetic average roughness (Ra) of 0.68 to 0. Each CFRP of 0.76 was prepared.
The composite 1 is a three-layer laminated structure in which an epoxy resin-based adhesive sheet, Somar EF brand name Somar EF type, is sandwiched between a phenol resin and a nitrile rubber, Tesa Co., Ltd. brand name HAF8402 sheet. The adhesive sheet was made of a material.
The composite 1 was sandwiched and adhered to the joint surface between the adherend 4 and the adherend 5. A shear tensile test was performed to evaluate the bond strength. The adhesion test piece is shown in FIG. FIG. 2A is a plan view and FIG. 2B is a side view. The composite was cured by applying a pressure of 0.25 kgf and a temperature of 150° C. perpendicularly to the joint surface 6 using a hot press. The bonding area on the bonding surface 6 was 50 mm ² . The method for measuring the adhesive strength was in accordance with ISO19095-3. The test was performed by a stroke control using a universal testing machine. The stroke speed during the test is 10 mm/min. The results are shown in Table 1.

Further, with respect to the relationship between the curing temperature and the maximum elongation in the plane direction, an experiment was performed by changing the curing temperature and preparing an epoxy resin adhesive sheet and a composite sheet of phenol resin and nitrile rubber independently. .. In this experiment, the maximum elongation in the plane direction (%) was measured at a test speed of 10 mm/min based on JISK7161. Five test sheets were produced under each condition, and the maximum elongation in the plane direction (%) is an average value thereof. The results are shown in Table 2.
In addition, from Table 2, under the same conditions as in Example 1 (curing temperature 150° C.), the maximum elongation in the plane direction of the epoxy resin adhesive sheet alone is 6%, which is also the composite of the phenol resin and the nitrile rubber. The maximum elongation in the plane direction of the sheet alone was 60%.

Comparative Example 1
The same conditions as in Example 1 except that the adhesive layer was sandwiched between the adherends of the adherends 4 and 5 in the same manner as in Example 1 except that the epoxy resin-based adhesive sheet used in Example 1 was used alone. And the adhesive strength was measured. The results are shown in Table 1.

Comparative example 2
Example in which the adhesive layer was sandwiched between the adherends of the adherends 4 and 5 in the same manner as in Example 1 except that the composite sheet of the phenolic resin and the nitrile rubber used in Example 1 was used alone. Adhesion was performed under the same conditions as in Example 1 and the adhesive strength was measured. The results are shown in Table 1.

By making the adhesive into a composite, higher adhesive strength was obtained than when used alone. In Table 1, the adhesive layer was evaluated as x when the adhesive strength was 0 to 10 MPa, Δ when the adhesive strength was 11 to 20 MPa, and ◯ when the adhesive strength was 21 MPa or more.

When the composite of the present invention has a laminated structure, an adhesive having stress relaxation and high adhesive strength can be obtained and can be used for adhesion of different materials such as metals and plastics.

DESCRIPTION OF SYMBOLS 1 Composite body 2 1st layer 3a 2nd layer 3b 3rd layer 4 Adherent 5 Adherent 6 Bonding surface

Claims (4)

A composite comprising a laminated structure in which a first thin layer is sandwiched between second and third thin layers, and the respective surfaces of the second and third thin layers serve as adhesive surfaces,
A composite, wherein the maximum elongation in the planar direction of the first thin layer after curing the composite is smaller than the maximum elongation in the planar direction of the second and third thin layers. The maximum elongation in the plane direction of the thin layer of the first layer is 3 to 10%, and the maximum elongation in the plane direction of the second and third thin layers is 20 to 70%. 1. The complex according to 1. The first thin layer is a thin layer made of an epoxy resin, and the second and third thin layers are a thin layer made of a phenol resin and a nitrile rubber. The described complex. The composite structure according to claim 1, wherein the laminated structure is a film- or sheet-like adhesive agent for adhering different kinds of materials to each other.

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