JPH0680938A - Thermally foamable and curable adhesive and adhesive sheet - Google Patents

Abstract

(57) [Abstract] [Purpose] As a thermosetting adhesive that cures at low temperature in a short time when used for adhesion and exhibits good high-temperature adhesiveness, it has an excellent balance between shear adhesive strength and peel adhesive strength, (EN) Provided is one which can secure a sufficient adhesive area even when a body has a warp or a sink mark. [Structure] A polymer having a radical reactive unsaturated bond in the molecule and having a glass transition temperature of −50 to 50 ° C., a monomer having a radical reactive unsaturated bond in the molecule, a radical reaction initiator and a foaming agent. A thermo-foaming curable adhesive is constituted by the composition containing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermo-foam-curable adhesive which foams and hardens when heated, and a sheet-like or tape-like adhesive using the same.
The present invention relates to adhesive sheets such as a puddle.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for simplifying bonding work or improving safety and health, and instead of liquid adhesives,
Adhesive sheets such as sheets and tapes have been widely used, but in order to exhibit good adhesive strength, for example, high temperature adhesive sheets such as epoxy adhesive sheets are used. Since heating for a long time is required, productivity is low and deterioration of the adherend at high temperature is also a problem.

On the other hand, an adhesive sheet which can be adhered in a relatively short time.
Hot melt type adhesive sheets are also commercially available as sheets, but these are not so useful because they have poor adhesive strength at high temperatures.

Further, as disclosed in Japanese Patent Publication No. 13425/1982, adhesive sheets prepared by impregnating a porous sheet-like base material with a radical reaction initiator and further laminating an unsaturated compound layer thereon. However, the balance property between the shear adhesive force and the peel adhesive force was poor, and when the adherend had a warp or sink, it was difficult to secure a sufficient adhesive area.

Further, JP-A-53-118439, JP-A-3-502214, and JP-A-3-6677.
Various adhesive sheets using thermosetting adhesives have been proposed in Japanese Patent Laid-Open No. 9-66782 and Japanese Patent Laid-Open No. 3-66782, all of which are disclosed in Japanese Patent Publication No. 57-13425. There was a problem similar to the adhesive sheets of the above.

[0006]

As described above, the conventionally known adhesive sheets have a problem that they require heating at a high temperature for a long time when they are used for bonding, or they have a problem of poor adhesive strength at a high temperature. However, there is a problem in that it is difficult to secure a sufficient bonding area when the adherend has a warp or sink mark and the balance property between the shear adhesive strength and the peel adhesive strength is poor.

In view of the above-mentioned conventional problems, the present invention provides a thermosetting adhesive which is cured at a low temperature in a short time when used for adhesion and exhibits a good high temperature adhesive force, and a balance between shear adhesive force and peel adhesive force. It is an object of the present invention to provide a product having excellent characteristics and capable of ensuring a sufficient adhesion area even when the adherend has a warp or a sink mark.

[0008]

DISCLOSURE OF THE INVENTION As a result of intensive studies to achieve the above object, the present inventors have found that an unsaturated monomer radical-reactive with a specific polymer, a radical reaction initiator and a foaming agent. It functions as a thermosetting adhesive that cures in a short time at low temperature and exhibits good high-temperature adhesiveness, and this adhesive provides a balance property between shear adhesive strength and peel adhesive strength. The present invention has been completed, knowing that it is excellent and that a sufficient bonding area can be secured even when the adherend has a warp or a sink mark.

That is, the present invention has a glass transition temperature of -50 to 50 ° C. having a radical-reactive unsaturated bond in the molecule.
Polymer, a monomer having a radical-reactive unsaturated bond in the molecule, a thermal foaming-curable adhesive characterized by containing a radical reaction initiator and a foaming agent as essential components,
The present invention relates to an adhesive sheet having a layer of the heat-foam-curable adhesive on one side or both sides of the support.

[0010]

The polymer of the present invention has a glass transition temperature of a radical-reactive unsaturated bond in the molecule of-.
A polymer at 50 to 50 ° C., for example, an acrylic polymer,
Examples thereof include polyester-based polymers, vinyl acetate-based polymers, hydrogenated rubber-based polymers and the like. Here, when the glass transition temperature of the polymer is lower than -50 ° C, the shear adhesive strength is poor and the polymer is 50 ° C.
If it is higher, the impact resistance is inferior, which is not preferable.

The above-mentioned radical-reactive unsaturated bond is, for example, a vinyl group, an acryloyl group, a methacryloyl group or a vinylbenzyl group which reacts with a monomer and a radical reaction disclosing agent which will be described later in combination with this polymer. Yes,
From the balance characteristics of shear adhesive strength and peel adhesive strength, 8 or less per molecule is preferable.

Such a radical-reactive unsaturated bond is
An unsaturated compound having a reactive functional group such as glycidyl acrylate, glycidyl methacrylate, and 2-methacryloyloxyethyl isocyanate is reacted with the functional groups at the terminal and / or side chain of the polymer. It can be introduced. In addition, a method of copolymerizing a small amount of monomers having two or more radical-reactive unsaturated bonds in the molecule in radical polymerization, or a small amount of monomers having a radical-reactive unsaturated bond in ionic polymerization such as epoxy. It can also be introduced by a method such as copolymerization.

The monomer having a radical-reactive unsaturated bond in the molecule in the present invention is one having at least one unsaturated bond in the molecule, such as epoxy (meth) acrylate and polyester ( (Meth) acryl
And urethane (meth) acrylates and general polyfunctional acrylic monomers are preferably used. In addition, (meth) acrylate having an alkyl group having 1 to 14 carbon atoms, divinyl adipate, vinyl 2-ethylhexanoate,
It is also possible to use vinyl monomers such as divinylbenzene and triallyl cyanurate.

As the above-mentioned general polyfunctional acrylic monomer, pentaerythritol tri (meth) acrylate is used.
To, pentaerythritol tetra (meth) acrylate
G, trimethylolpropane tri (meth) acrylate
, EO (ethylene oxide) modified trimethylolpropane tri (meth) acrylate, PO (propylene oxide) modified trimethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di ( (Meth) acryl
And tetraethylene glycol di (meth) acrylate.

In the present invention, among the monomers having a radical-reactive unsaturated bond in such a molecule, one type thereof may be used alone or two or more types may be used in combination. From the viewpoint of workability and adhesive strength, the amount used is that of the above-mentioned polymer 1
It is usually 1 to 100 parts by weight, preferably 5 to 50 parts by weight, relative to 00 parts by weight.

As the radical reaction initiator in the present invention, an organic peroxide such as lauroyl peroxide, benzoyl peroxide, 1.1-bis (t-butylperoxy) 3.3.5-trimethylcyclohexane, or 2. There are azo-based initiators such as 2′-azobisisobutyronitrile and 2.2′-azobis (2-methylbutyronitrile), and among these, one kind may be used alone or two or more kinds may be mixed. To use. The amount used is usually 0.2 to 5 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymer.
It is preferable to use about 3 parts by weight.

Examples of the foaming agent in the present invention include heat-expandable hollow elastic microspheres, inorganic foaming agent, nitroso type foaming agent, azo type foaming agent, sulfonylhydrazide type foaming agent and the like. The amount used is required to balance the adhesive area, impact resistance, and shear adhesive strength, so the expansion ratio during foam curing is 1.
It is preferable to be 2 to 5 times, preferably 1.5 to 3 times. Generally, it may be used in an amount of about 0.2 to 10 parts by weight based on 100 parts by weight of the polymer.

The thermal foaming-curable adhesive of the present invention contains the above-mentioned polymer, monomer, radical reaction initiator and foaming agent as essential components, and when foamed and cured by heating,
Sufficient adhesion area can be obtained even for adherends with warpage and sink marks, and the adhesive properties exhibit excellent balance between shear adhesive strength and peel adhesive strength, and also have excellent impact resistance.

If necessary, the heat-foaming-curable adhesive of the present invention may contain a crosslinking agent such as an epoxy compound or an isocyanate compound, a filler such as glass fiber or metal powder, a pigment, a coloring agent, a plasticizer or the like. Various additives to be added to the adhesive may be included.

The adhesive sheet of the present invention comprises a support, and one or both surfaces of which a layer comprising the above-mentioned heat-foaming-curable adhesive is generally provided to a thickness of about 20 to 200 μm.
The above layer may be fixed to the support or may be peeled from the support. As the support, for example, a plastic film, paper, non-woven fabric, metal foil or the like having a thickness of usually about 10 to 200 μm is used, and one or both of which may be subjected to a peeling treatment or an adhesive treatment. .

[0021]

As described above, according to the present invention, since the above-mentioned specific polymer, monomer, radical reaction initiator and foaming agent are contained, an adherend having a warp or a sink mark can be obtained. A thermo-foam-curing adhesive and its adhesive sheets that have a sufficient adhesive area, and exhibit excellent balance between shear adhesive strength and peel adhesive strength, as well as excellent adhesive strength against impact. Can be provided.

[0022]

EXAMPLES Next, examples of the present invention will be described to more specifically describe. In the following, "parts" means "parts by weight". The weight average molecular weight of the polymer is a value based on polystyrene conversion by gel permeation chromatography.

Example 1 A reaction vessel equipped with a cooling tube, a nitrogen introducing tube, a thermometer, and a stirrer was used as a solvent containing 20 parts of ethyl acetate and 80 parts of toluene, and 82 parts of butyl acrylate and 10 parts of methyl acrylate.
Parts, acrylamide 8 parts, 2-hydroxyethyl acrylate 0.1 parts, 2-mercaptoethanol 0.05 parts,
0.2 parts of 2.2'-azobis2-cyanopropanol was added, and the mixture was polymerized in a nitrogen stream.

Next, 0.1 part of dibutyltin dilaurate and 0.25 part of 2-methacryloyloxyethyl isocyanate are added to this polymerization treatment solution and reacted to give radicals in the molecule. A solution containing an acrylic polymer having a reactive unsaturated bond and having a weight average molecular weight of 370,000 and a glass transition temperature of −40 ° C. was obtained.

Polyester acrylate [trade name Aronix M-8030 manufactured by Toagosei Co., Ltd.] per 100 parts of the solid content (acrylic polymer) of this solution was used.
Part, polyester acrylate [trade name Alonix M-6100 manufactured by Toagosei Co., Ltd.] 10 parts, lauroyl peroxide 1.5 parts, foaming agent [Matsumoto Microsphere F, trade name of Matsumoto Yushi-Seiyaku Co., Ltd.] -301D] 1.5 parts was added to prepare a solution of the heat-foaming-curable adhesive. This solution was applied onto a separator so that the thickness after drying was 50 μm, and dried at 80 ° C. for 2 minutes to prepare an adhesive tape.

Example 2 The adhesive tape prepared in Example 1 was attached to both sides of a polyester film having a thickness of 25 μm to obtain an adhesive tape.

Example 3 The adhesive tape prepared in Example 1 was attached to both sides of a rayon nonwoven fabric having a basis weight of 14 g / m ² to obtain an adhesive tape.

Comparative Example 1 An adhesive tape was prepared in the same manner as in Example 1 except that 1.5 parts of a foaming agent [Matsumoto Yushi-Seiyaku Co., Ltd. trade name Matsumoto Microsphere-F-301D] was not added. -I made a burp.

Example 4 100 parts of a polyester polymer [Vylon 300 manufactured by Toyobo Co., Ltd.] was dissolved in 100 parts of toluene, and 0.1 part of dibutyl tin laurate and 2-methacryloyloxyethyl isocyanate were dissolved in the solution. By adding 2 parts of net and reacting them, a solution containing a polymer having a radical-reactive unsaturated bond in the molecule and having a glass transition temperature of 6 ° C. was obtained.

The solid content (polymer) 100 was added to this solution.
Per part, EO-modified trimethylolpropane triacrylate 5 parts, tetraethylene glycol diacrylate 25 parts, benzoyl peroxide 2 parts, foaming agent [Matsumoto Yushi-Seiyaku Co., Ltd. trade name Matsumoto Microsphere] F-50]
5 parts was added to prepare a solution of the heat-foaming-curable adhesive. Using this solution, an adhesive tape was obtained in the same manner as in Example 1 below.

Example 5 Using 20 parts of ethyl acetate and 80 parts of toluene as a solvent, 50 parts of 2-ethylhexyl acrylate, 20 parts of ethyl acrylate, 25 parts of methyl methacrylate, 4 parts of acrylic acid,
1 part of 2-hydroxypropyl acrylate and 0.2 part of vinyl methacrylate were polymerized in a nitrogen stream according to Example 1 using 0.2 part of 2.2′-azobisisobutyronitrile. .

A solution containing an acrylic polymer having a weight-average molecular weight of 480,000 having a radical-reactive unsaturated bond in the molecule thus obtained and a glass transition temperature of -27 ° C. was used, and the following Example 1 was used. An adhesive tape was prepared in the same manner as in.

With respect to the adhesive tapes of Examples 1 to 5 and Comparative Example 1 described above, the shear adhesive strength, peel adhesive strength and impact resistance were examined and the performance thereof was evaluated. The results are shown in Table 1 below.

<Shearing adhesive strength> 10 mm × 10 mm adhesive tape
Adhesive tape between 0.5 mm × 20 mm × 100 mm aluminum plates, and cured and adhered under the conditions of 140 ° C × 0.5 Kg / cm ² × 1 minute, and allowed to stand for 2 hours. It was measured under the conditions of 10 mm / min, 23 ° C. and 65% RH.

<Peeling Adhesiveness> 10 mm × 50 mm adhesive tape
A 0.5 mm x 20 mm x 100 mm aluminum plate,
It is stuck between 1 mm × 20 mm × 100 mm stainless SUS304, cured and adhered under the condition of 120 ° C. × 0.5 Kg / cm ² × 2 minutes, and left for 2 hours, and the force required for peeling is pulled at a speed of 10 mm / min. , 23 ° C., 65% RH.

<Impact resistance> An adhesive tape of 10 mm × 10 mm and a Bakelite plate of 2 mm × 60 mm × 60 mm and 0.5
It is attached to a stainless steel SUS304 of mm × 50 mm × 50 mm, cured and adhered under the condition of 140 ° C. × 0.5 Kg / cm ² × 1 minute, left at 23 ° C. and 65% RH for 2 hours, and then 0 ° C.
It was left to stand for 2 hours, dropped from a height of 80 cm onto the concrete, and the number of times required until destruction was measured.

[0037]

[Table 1]

As is clear from the results shown in Table 1 above, the adhesive tapes of Examples 1 to 5 of the present invention have excellent balance characteristics of shear adhesive strength and peel adhesive strength, and also have excellent impact resistance. It can be seen that it exhibits excellent adhesive strength. In addition, Example 1
If the amount of foaming agent used in the adhesive is excessive, for example 20 parts, the shear adhesive strength will be 34 Kg.
As described above, the foaming agent is used in an appropriate amount so that the expansion ratio is 1.2 to 5 times, since it causes such inconveniences as a decrease in pressure / cm ² and a decrease in impact resistance to 5 times. It is desirable to use it.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Miji Hasegawa 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Koichi Nakamura 1-1-1, Shimohozumi, Ibaraki-shi, Osaka No. 2 Nitto Denko Corporation

Claims (3)

[Claims] 1. A polymer having a radical-reactive unsaturated bond in the molecule and having a glass transition temperature of −50 to 50 ° C., a monomer having a radical-reactive unsaturated bond in the molecule, a radical reaction initiator and foaming. A thermo-foam-curable adhesive, which contains an agent as an essential component. 2. The thermal foaming-curable adhesive according to claim 1, wherein the foaming ratio during foaming and curing is 1.2 to 5 times. 3. An adhesive sheet comprising a support and a layer comprising the heat-foam-curable adhesive according to claim 1 or 2 on one side or both sides of the support.