JPH07331214A - Adhesive composition - Google Patents

Abstract

PURPOSE:To obtain an adhesive composition sufficiently high in the initial adhesive force to an adherend under room temperature, capable of being thermally treated to extremely lower the adhesive force, and optimal as an adhesive for repeelable adhesive tapes. CONSTITUTION:The adhesive composition is produced by dispersing the particles of an epoxy resin having two or more epoxy groups in the molecule, a melting point of 40-180 deg.C and an epoxy equivalent of 120-800 in an acrylic adhesive having at least one kind of functional groups selected from hydroxyl groups, carboxyl groups and amino groups.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive composition which can be re-peeled by heating.

[0002]

2. Description of the Related Art Conventionally, there is a demand for an adhesive tape which can be used as a masking tape when painting an automobile, can be easily removed by heating after painting, and can be peeled off by heating for the purpose of simplifying the work. It had been. Further, there is a demand for an adhesive tape that is used for temporary fixing in an electronic component assembling process and that can be easily peeled off by heating after the work. As an adhesive tape for achieving the object, an adhesive tape having a base sheet provided with an adhesive layer containing a heat-expandable resin is disclosed in JP-A-56-61468.
It is reported in Japanese Patent Laid-Open No. 60-252681.

[0003]

However, the heat-expandable resin used in the above-mentioned pressure-sensitive adhesive tape contains a flammable gas, and there is a risk of ignition depending on the working environment. It is not desirable from a viewpoint.

The present invention solves the above-mentioned conventional problems and provides a pressure-sensitive adhesive composition which has a high room-temperature adhesive strength and which can be easily peeled off after heating while maintaining a safety and hygienic environment. It is intended.

[0005]

That is, the present invention is a pressure-sensitive adhesive composition in which particulate epoxy resin is dispersed in an acrylic pressure-sensitive adhesive, which can be used as a pressure-sensitive adhesive in a pressure-sensitive adhesive tape or can be used as it is as an adhesive. To use as.

The epoxy resin used in the present invention is No. 1
It has two or more epoxy groups in the molecule and has a melting point of 4
0 to 180 ° C., and an epoxy equivalent of 120 to
800.

Examples of such epoxy resins include:
"YX4000" TBA type epoxy resin including "Epicoat 5051" (made by Yuka Shell Epoxy Co., Ltd.)
(Okaka Shell Epoxy Co., Ltd.) and other biphenyl type epoxy resins, "E1032H60" (Okaka Shell Epoxy Co., Ltd.) and other trishydroxyphenylmethane type epoxy resins, "ESX-220" (Sumitomo Chemical Co., Ltd.) ) And other alkyl-substituted trifunctional epoxy resins, such as "VG3101" (manufactured by Mitsui Petrochemical Co., Ltd.) and trifunctional epoxy resins, "E1031S" (manufactured by Yuka Shell Epoxy Co., Ltd.). Examples thereof include tetraphenylol ethane type epoxy resin and dicyclopentadiene phenol type epoxy resin such as "DEC400" (manufactured by Sanyo Kokusaku Pulp Co., Ltd.).

In the present invention, these epoxy resins are granular materials crushed by a ball mill or the like. The size of the granules is measured by a light scattering method, and the average particle size is 0.1 to 50.
μm is preferred. The smaller the average particle size, the better the reaction efficiency, but if it is less than 0.1 μm, secondary agglomeration is likely to occur and it becomes difficult to handle. When it exceeds 50 μm, when it is used for an adhesive tape, it exceeds the thickness of an ordinary adhesive tape, which is not desirable in terms of product appearance.

The acrylic pressure-sensitive adhesive used in the present invention must have at least one functional group selected from the group consisting of hydroxyl group, carboxyl group and amino group.

The main component of the above acrylic adhesive is 2-
Ethylhexyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate,
A copolymer of an alkyl (meth) acrylate monomer such as isooctyl (meth) acrylate or isononyl (meth) acrylate and a vinyl monomer having a hydroxyl group, a carboxyl group or an amino group, further comprising vinyl acetate, vinylpyrrolidone, vinylcaprolactam. It may be copolymerized with a copolymerizable vinyl monomer such as.

As the vinyl monomer having a hydroxyl group,
For example, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate and the like can be mentioned. Further, examples of the vinyl monomer having a carboxyl group include (meth) acrylic acid, maleic acid, fumaric acid, and itaconic acid. Examples of the vinyl monomer having an amino group include amino (meth) acrylate.

The blending amount of the vinyl monomer is preferably 1 to 100 parts by weight with respect to 100 parts by weight of the alkyl (meth) acrylate monomer. Especially, the compounding amount is 30
When the amount is more than the amount by weight, self-crosslinking is likely to occur when the (meth) acrylic copolymer is polymerized, and therefore it is preferable to use a monomer containing two or more kinds of glycidyl groups. Moreover, you may use together 1 or more types also about an alkyl (meth) acrylate monomer and a vinyl monomer.

A crosslinking agent may be added to increase the cohesive strength of the acrylic pressure-sensitive adhesive. As a cross-linking agent, 1,6
-Hexadiol diacrylate, N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide), N, N'-diphenylmethane-4,4'-bis (1-aziridinecarboxamide), trimethylol Bifunctional or higher functional aziridine compounds such as propane-tri-β-aziridinylpropionate are desirable. The addition amount of the cross-linking agent is adjusted so that the gel fraction after polymerization is 25 to 85%. The gel fraction referred to herein is the insoluble content which cannot pass through a 200-mesh wire net when the polymer is dissolved in tetrahydroxyfuran to give a 0.2% solution, and is represented by weight%.

To polymerize the above-mentioned monomer, a usual solution polymerization method or photopolymerization method is used. In the case of solution polymerization, benzoyl peroxide, azoisobutyronitrile or the like is used as a polymerization initiator. In the case of photopolymerization,
4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone as a photopolymerization initiator, α-
Acetophenone type such as hydroxy-α, α′-dimethyl-acetophenone, benzoin ether type such as benzoylethyl ether, benzoinpropyl ether,
Benzyl dimethyl ether ketal is used. In the case of the photopolymerization method, a composition such as a monomer is used as a photopolymerizable composition, which is applied to a substrate sheet or a transfer sheet and irradiated with ultraviolet rays to simultaneously polymerize the monomers and form the adhesive layer. It is convenient to do.

A tackifying resin is added to increase the adhesive strength of the adhesive. Examples of the tackifying resin include rosin-based resins such as hydrogenated rosin ester and pentaerythritol ester of polymerized rosin, alicyclic saturated hydrocarbon resin, terpene resin, terpene phenol resin, aromatic modified terpene resin, carbon number 5 or 9 Examples include petroleum-based resins and coumarone indene resins. The addition amount of the tackifier is preferably 10 to 70 parts by weight with respect to 100 parts by weight of the above copolymer.

The pressure-sensitive adhesive composition of the present invention can be obtained by stirring a granular epoxy resin having an epoxy group in the above acrylic pressure-sensitive adhesive with a disperser or the like to uniformly disperse the resin. The one in which the particles are dispersed in a uniform state
The peelability can be efficiently expressed during the reaction. The blending amount of the granular epoxy resin is preferably 1 to 80 parts by weight with respect to 100 parts by weight of the acrylic pressure-sensitive adhesive. If it is less than 1 part by weight, removability due to heating is not sufficient. If it exceeds 80 parts by weight, it becomes difficult to obtain the initial adhesive strength.

If necessary, an organic or inorganic viscosity modifier may be added to the pressure-sensitive adhesive composition, especially when the pressure-sensitive adhesive composition is produced by a photopolymerization method.
When the viscosity is increased, the thickness can be kept constant during coating, and the thickness of the pressure-sensitive adhesive layer can be easily adjusted. As the viscosity modifier, acrylic rubber is used for organic type, and Aerosil is used for inorganic type.

[0018]

In the pressure-sensitive adhesive composition of the present invention, at room temperature, the epoxy resin is in a solid state and does not react with the hydroxyl group, carboxyl group or amino group of the acrylic pressure-sensitive adhesive.
The adhesive property of the acrylic pressure-sensitive adhesive is the main component, and high adhesive force is exhibited. However, once heated above the melting point of the epoxy resin, the epoxy resin melts,
Two epoxy groups in the molecule of the epoxy resin react with the hydroxyl group, carboxyl group or amino group of the acrylic pressure-sensitive adhesive to further increase the degree of crosslinking in the pressure-sensitive adhesive. Furthermore,
When the degree of cross-linking is increased, the tackifying resin in the pressure-sensitive adhesive bleeds onto the pressure-sensitive adhesive surface, which has the effect of lowering the adhesive force to the adherend.

[0019]

EXAMPLES Next, the pressure-sensitive adhesive composition of the present invention will be described with reference to Examples. Example 1 100 parts by weight of an acrylic copolymer obtained by polymerizing 82% by weight of 2-ethylhexyl acrylate, 8% by weight of vinylpyrrolidone, and 10% by weight of carboxyethyl acrylate were added as a tackifier with a hydrogenated coal-based aroma. Group resin ("S-Crystal A-120" manufactured by Nippon Steel Chemical Co., Ltd.
S "), 18 parts by weight, 0.06 parts by weight of 1,6-hexanediol diacrylate as a cross-linking agent, and acrylic rubber (" PS-25 "manufactured by Toa Paint Co., Ltd. as a viscosity modifier.
0 ") was added in an amount of 2.5 parts by weight to prepare an acrylic pressure-sensitive adhesive, and a biphenyl type epoxy resin (" YX4000 "manufactured by Yuka Shell Epoxy Co., Ltd.) granular material (average particle size: 5μ)
m) 10 parts by weight was stirred with a disper and uniformly dispersed to prepare an adhesive composition.

This adhesive composition was roll-coated on a polyester film and dried at a low temperature to produce an adhesive tape having an adhesive layer of 50 μm. 2 this adhesive tape
Cut it to a size of 0 x 100 mm, attach the adhesive surface to a stainless steel plate, leave it at room temperature for 30 minutes, and then remove it at a temperature of 23 ° C and a humidity of 65% by a 180 degree peeling force according to JIS.
-When measured according to Z1528, 1460 gf /
It was 20 mm. In addition, after the hot air at 120 ° C. was blown for 10 minutes on the back surface of the adhesive tape adhered by the same method as described above and cooled to room temperature, the adhesive force after heating was measured by the same measurement method as above. 360gf /
It had dropped to 20 mm.

(Example 2) An alkyl-substituted trifunctional epoxy resin ("ESX-220" manufactured by Sumitomo Chemical Co., Ltd.) was used as the epoxy resin in Example 1, and other examples were used.
It was manufactured and evaluated under the same conditions as. As a result, the adhesive force before heating was 1450 gf / 20 mm, and the adhesive force after heating was lowered to 390 gf / 20 mm.

(Comparative Example) The acrylic pressure-sensitive adhesive composition was exactly the same as in Example 1, except that the epoxy resin particles were not mixed,
Otherwise, a pressure-sensitive adhesive composition was prepared and evaluated under the same conditions as in Example 1. As a result, the adhesive strength before heating was 1470.
gf / 20mm, adhesive strength after heating is 1620gf / 2
It was slightly higher than 0 mm.

[0023]

As described above and as can be seen from the evaluation of the examples, the pressure-sensitive adhesive composition of the present invention has a sufficiently high initial pressure-sensitive adhesive force to an adherend at room temperature, and when it is subjected to heat treatment, The adhesive strength can be reduced.
Therefore, the pressure-sensitive adhesive composition of the present invention can be suitably used as a pressure-sensitive adhesive for a removable pressure-sensitive adhesive tape.

Claims (1)

[Claims] 1. A molecule having two or more epoxy groups, a melting point of 40 to 180 ° C., and an epoxy equivalent of 12.
An adhesive characterized in that an epoxy resin particle having a size of 0 to 800 is dispersed in an acrylic adhesive having at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group and an amino group. Agent composition.