JPH0543857A - Radiation-curable self-adhesive and self-adhesive tape prepared therefrom - Google Patents

Abstract

PURPOSE:To provide a radiation-curable self-adhesive which can be applied using no or little solvent and is excellent in adhesive power and holding power, and to provide a self-adhesive tape from the adhesive. CONSTITUTION:A radiation-curable self-adhesive based on a block copolymer which has, on average, 0.5-4 radiation-reactive unsatd. bonds in the molecule and consists of a polymer block contg. at least 50wt.% units derived from an acrylic monomer of the general formula: CH2=C(R<1>)COOR<2> (wherein R<1> is H or methyl; and R<2> is H or 1-6C alkyl) and having a glass transition temperature of 50 deg.C or higher and a polymer block contg. at least 50wt.% units derived from an acrylic monomer of the general formula: CH2=C(R<3>)COOR<4> (wherein R<3> is H or methyl; and R<4> is 1-4C alkyl) and having a glass transition temperature of -20 deg.C or lower, and a self-adhesive tape which comprises a substrate and a layer or layers of the self adhesive formed on one side or both sides of the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation-curable pressure-sensitive adhesive having excellent adhesion and holding power, and a pressure-sensitive adhesive tape using the same.

[0002]

2. Description of the Related Art In consideration of environmental hygiene and safety, it is required to reduce the amount of solvent used as much as possible, and a solventless coating type that can be used without solvent or with a small amount of solvent. Various curable pressure-sensitive adhesives have been proposed (for example, JP-A-59-215372). Such a radiation-curable pressure-sensitive adhesive has the advantage of being superior in water resistance and heat resistance as compared with an emulsion-type pressure-sensitive adhesive and a hot-melt type pressure-sensitive adhesive. However, among the conventional radiation-curable pressure-sensitive adhesives, those having a solvent-free coating type in which the base polymer has a low molecular weight have a problem that the cohesive force is lowered and the holding power is poor. In addition, the solventless coating type diluted with a reactive monomer has a problem of poor adhesive strength, and in any case, it is difficult to achieve both adhesive strength and holding power. It was

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a radiation-curable pressure-sensitive adhesive or pressure-sensitive adhesive tape which is a solventless coating type and is excellent in adhesive strength and holding power.

[0004]

The present invention comprises, as a component, a block copolymer having an average of 0.5 to 4 radiation-reactive unsaturated bonds in the molecule, and the block copolymer has the general formula:
CH ₂ ═C (R ¹ ) COOR ² (provided that R ¹ is hydrogen or a methyl group, R ² is hydrogen or an alkyl group having 1 to 6 carbon atoms), and the acrylic monomer component is 50 A polymer block containing at least 50% by weight and having a glass transition temperature of 50 ° C. or higher, and a general formula: CH ₂ ═C (R ³ ) COOR ⁴ (however,
R ³ is hydrogen or a methyl group, and R ⁴ is an alkyl group having 1 to 14 carbon atoms. 5) the acrylic monomer component represented by
A radiation-curable pressure-sensitive adhesive comprising a polymer block containing 0% by weight or more and having a glass transition temperature of -20 ° C or less, and a cured layer comprising the radiation-curable pressure-sensitive adhesive on one side or both sides of a support. The present invention provides an adhesive tape characterized by having

[0005]

By using the above block copolymer, it is possible to obtain a solventless coating type pressure-sensitive adhesive which can be coated without using a solvent or a small amount of solvent, and is cured by irradiation with radiation, Moreover, the degree of curing can be made suitable for developing the adhesive property. As a result, a pressure-sensitive adhesive layer having excellent adhesive strength and holding power is formed.

[0006]

[Exemplary constituent elements of the invention] The radiation-curable pressure-sensitive adhesive of the present invention comprises a polymer block (A) and a polymer block (B), and has an average of 0.5 radiation-reactive unsaturated bonds in the molecule.
A block copolymer having 4 to 4 is a component. The block copolymer which can be preferably used from the viewpoints of solvent-free coating property and adhesive property is an A / B type having a weight average molecular weight of 50,000 to 300,000,
To A / B / A type.

The polymer block (A) has the general formula:
CH ₂ ═C (R ¹ ) COOR ² (provided that R ¹ is hydrogen or a methyl group, R ² is hydrogen or an alkyl group having 1 to 6 carbon atoms), and the acrylic monomer component is 50 It contains at least 50% by weight and has a glass transition temperature of 50 ° C. or higher. Such a polymer block may use two or more kinds of acrylic monomer components. The content ratio of the polymer block (A) in the block copolymer is preferably 5 to 40% by weight from the viewpoint of adhesive properties and the like.

Specific examples of the acrylic monomer component include acrylic acid, methacrylic acid, their methyl esters, ethyl esters, propyl esters, butyl esters, isobutyl esters, isoamyl esters, hexyl esters and the like.

Other monomer components that the polymer block (A) may contain for the purpose of controlling the adhesive properties are, for example, acrylamide, methacrylamide, acrylonitrile, vinyl acetate, vinyl propionate, styrene, N.
-Vinylpyrrolidone, N-methylolacrylamide,
Examples thereof include glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate.

The polymer block (B) forming the other block of the block copolymer has the general formula: CH ₂ ═C
(R ³ ) COOR ⁴ (wherein R ³ is hydrogen or a methyl group,
R ⁴ is an alkyl group having 1 to 14 carbon atoms. ) Containing 50% by weight or more of an acrylic monomer component represented by the formula (1) and having a glass transition temperature of -20 ° C or lower. Such a polymer block may use two or more kinds of acrylic monomer components. The content ratio of the polymer block (B) in the block copolymer is preferably 60 to 95% by weight from the viewpoint of adhesive properties and the like.

Specific examples of the acrylic monomer component include a methyl ester of acrylic acid or methacrylic acid,
Ethyl ester, propyl ester, butyl ester,
Examples thereof include isobutyl ester, isoamyl ester, hexyl ester, 2-ethylhexyl ester, octyl ester, isononyl ester and isodecyl ester.

Other monomer components that the polymer block (B) may contain for the purpose of controlling the adhesive properties are, for example, acrylic acid, methacrylic acid, acrylamide, methacrylamide, acrylonitrile, vinyl acetate, vinyl propionate, styrene. , N-vinylpyrrolidone, N-methylolacrylamide, glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate and the like. ..

The block copolymer may be prepared by a suitable method such as an iniferter method, a polymer azo initiator method, a polymer peroxide method or an anionic polymerization method.
The polymer block (A) and the polymer block (B) which form the block copolymer may contain a common monomer (monomer) component, but as a whole, they have a different composition. To be done.

The block copolymer used in the present invention is a radiation-reactive unsaturated bond, that is, one of vinyl group, acryloyl group, methacryloyl group, vinylbenzyl group and the like which can be cured (crosslinked) by irradiation with radiation. It has 0.5 to 4 unsaturated bonds of two or more kinds on average. When the average number of the radiation-reactive unsaturated bonds is less than 0.5, the pressure-sensitive adhesive has poor holding power, and when it exceeds 4, the pressure-sensitive adhesive has poor adhesion.

The introduction of the radiation-reactive unsaturated bond into the block copolymer can be appropriately carried out. By the way, as an example, a compound having a radiation-reactive unsaturated bond and a functional group capable of reacting with a functional group such as a carboxyl group, a hydroxyl group or an amino group at the terminal or side chain of the block copolymer, for example, glycidyl acrylate , Glycidyl methacrylate, 2-methacryloyloxyethylisocyanate, etc. are reacted with a block copolymer, and a compound having two or more radical-reactive unsaturated bonds containing a radiation-reactive unsaturated bond is used in combination for block copolymerization. Examples thereof include a method of preparing the combined product by a radical polymerization method.

The radiation-curable pressure-sensitive adhesive of the present invention contains a monomer having one or more radical-reactive unsaturated bonds (radiation-reactive unsaturated bonds) for the purpose of controlling the adhesive properties and coating properties. Can be added. The amount of addition is appropriately determined, but in general, the block copolymer 100
It is 100 parts by weight or less, especially 50 parts by weight or less, per part by weight.

Examples of such added monomers include alkyl esters of acrylic acid or methacrylic acid having an alkyl group such as ethyl group, butyl group and 2-ethylhexyl group, 3-phenoxy 2-hydroxypropyl acrylate, dicyclopentenyloxyethylene. Acrylate, vinyl acetate, ethylene glycol diacrylate,
Examples thereof include ethylene glycol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, dipentaerythritol hexaacrylate, and dipentaerythritol hexamethacrylate.

In the radiation-curable pressure-sensitive adhesive of the present invention, additives usually used for pressure-sensitive adhesives, for example, tackifiers, fillers such as glass fibers and metal powders, pigments, colorants, plasticizers and the like are usually added. It can be added.

The radiation-curable pressure-sensitive adhesive of the present invention can be cured by irradiation with active energy rays, such as α-rays, β-rays, γ-rays, neutron rays and electron rays, such as ionizing radiation and ultraviolet rays. Is. In the case of ionizing radiation, the irradiation dose is usually about 0.5 to 20 Mrad, especially 1 to 10 M.
rad is preferred. In the case of ultraviolet light, it is usually 400 to 30
It is about 00 mj / cm ² .

The wavelength of the ultraviolet rays is preferably in the range of 180 to 460 nm, and a mercury lamp is preferable as the source of the ultraviolet rays. When curing by ultraviolet irradiation, it is desirable to use a photoreaction initiator (photosensitizer) together. Examples of the photoinitiator include benzoin, benzoin methyl ether,
Examples thereof include benzoin ethyl ether, dibenzyl and benzyl dimethyl ketal. The amount of the photoreaction initiator added is 0.1 to 1 per 100 parts by weight of the block copolymer.
0 parts by weight is common.

The pressure-sensitive adhesive tape of the present invention has a cured layer comprising the above radiation-curable pressure-sensitive adhesive on one side or both sides of the support. The pressure-sensitive adhesive layer may be fixed to the support or may be peelable from the support. The peelable type can be formed, for example, by a method using a support treated with a release agent. As the support, for example, a suitable material such as a plastic film, paper, non-woven fabric, or metal foil may be used. The thickness of the pressure-sensitive adhesive layer provided on the support is generally 1 to 500 μm, but is not limited to this and may be an appropriate thickness.

[0022]

The pressure-sensitive adhesive of the present invention can be applied with no solvent or with a small amount of solvent used. Further, it can be cured by irradiation with radiation, and by curing, a pressure-sensitive adhesive layer having excellent adhesive strength and holding power is formed.

[0023]

【Example】

Reference Example 1 In a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, an ultraviolet irradiation device, and a stirrer, 65 parts of 2-ethylhexyl acrylate (parts by weight;
Parts, acrylamide 5 parts, xylylene bis (N, N-diethyldithiocarbamate) 0.2 parts, ethyl acetate 40
Parts, and after polymerization treatment for 10 hours under UV irradiation in a nitrogen stream, 20 parts of methyl methacrylate, 2 parts of methacrylic acid
-Hydroxyethyl (0.1 part) and ethyl acetate (10 parts) were added, and the polymerization treatment was further performed for 10 hours under irradiation of ultraviolet rays.

Next, 0.13 parts of 2-methacryloyloxyethyl isocyanate and 0.1 part of dibutyltin dilaurate were added to the above reaction solution and reacted to give a weight average molecular weight of 280,000 and a number average molecular weight of 160,000 (gel permeation). A block copolymer of polystyrene conversion by chromatography (the same applies hereinafter) was obtained. The number of radiation-reactive unsaturated bonds in this block copolymer was 1.5 per molecule as a result of gel permeation chromatography and NMR analysis (the same applies hereinafter).

Reference Example 2 68 parts of butyl acrylate, 2 parts of acrylic acid, a polymer azo initiator (4,4'-azobis-4-cyanopentane) were placed in a reaction vessel equipped with a cooling pipe, a nitrogen introducing pipe, a thermometer and a stirrer. A reaction product of acid chloride and hexamethylene diol, 3 parts of a number average molecular weight of 8000) is reacted in 40 parts of toluene for 2 hours, and then 15 parts of butyl methacrylate, 12 parts of styrene and 3 parts of methacrylic acid are added for 5 hours. After the reaction, 0.2 part of glycidyl methacrylate was reacted with triethylamine as a catalyst to obtain a block copolymer having a weight average molecular weight of 180,000 and a number average molecular weight of 80,000. The number of radiation-reactive unsaturated bonds in this block copolymer was 1.2 per molecule.

Reference Example 3 A block copolymer was obtained in the same manner as in Reference Example 1 except that the radiation-reactive unsaturated bond was not introduced by the addition of 2-methacryloyloxyethyl isocyanate and dibutyltin dilaurate. Saturated bond: 0
Individual).

Reference Example 4 A block copolymer having a weight average molecular weight of 190,000 and a number average molecular weight of 90,000 was obtained according to Reference Example 2 except that the amount of glycidyl methacrylate used was 1 part. The radiation-reactive unsaturated bond in this block copolymer is 6.5 per molecule.
It was an individual.

Reference Example 5 68 parts of butyl acrylate and 1 part of butyl methacrylate were placed in a reaction vessel equipped with a cooling pipe, a nitrogen introducing pipe, a thermometer and a stirrer.
5 parts, 12 parts of styrene, 3 parts of methacrylic acid, 2 parts of acrylic acid, and 0.3 parts of 2,2'-azobisisobutyronitrile were reacted in 40 parts of toluene for 8 hours, and then 0.2 parts of glycidyl methacrylate. Was reacted with triethylamine as a catalyst to obtain a copolymer having a weight average molecular weight of 220,000 and a number average molecular weight of 90,000 (having the same monomer composition as in Reference Example 2, but not a block copolymer). The number of radiation-reactive unsaturated bonds in this copolymer was 1.3 per molecule.

Example 1 A radiation-curable pressure-sensitive adhesive comprising the reaction solution containing the block copolymer obtained in Reference Example 1 was coated on a 38 μm-thick polyester film, dried at 80 ° C. for 3 minutes, and then irradiated with an electron beam. 2M
Curing treatment was performed by rad irradiation to obtain an adhesive tape having a cured layer having a thickness of about 50 μm.

Example 2 The block copolymer-containing reaction liquid obtained in Reference Example 1 was mixed with 3-
An adhesive tape was obtained in the same manner as in Example 1 except that the radiation-curable adhesive obtained by adding 10 parts of phenoxy 2-hydroxypropyl acrylate was used.

Example 3 To the reaction solution containing the block copolymer obtained in Reference Example 1, 20 parts of rosin resin (trade name: Foral 85, manufactured by Rika Hercules Co., Ltd.) and 5 parts of neopentyl glycol dimethacrylate were added. An adhesive tape was obtained in the same manner as in Example 1 except that the radiation-curable pressure-sensitive adhesive prepared as above was used and the electron beam irradiation dose was set to 3 Mrad.

Example 4 A radiation-curable pressure-sensitive adhesive prepared by adding 20 parts of rosin resin and 5 parts of neopentyl glycol dimethacrylate to the reaction solution containing the block copolymer obtained in Reference Example 2 was used. In the same manner as in Example 3, an adhesive tape was obtained.

Comparative Example 1 An adhesive tape was obtained in the same manner as in Example 1 except that the radiation curable pressure sensitive adhesive comprising the reaction solution containing the block copolymer obtained in Reference Example 3 was used.

Comparative Example 2 An adhesive tape was obtained in the same manner as in Example 1 except that the radiation curable pressure sensitive adhesive comprising the reaction solution containing the block copolymer obtained in Reference Example 4 was used.

Comparative Example 3 An adhesive tape was obtained in the same manner as in Example 1 except that the radiation-curable pressure-sensitive adhesive comprising the copolymer-containing reaction solution obtained in Reference Example 5 was used.

Evaluation Test The adhesive tapes obtained in Examples and Comparative Examples were subjected to the following tests. Adhesive strength A 20 mm x 100 mm adhesive tape was pressed against a stainless steel surface sanded with sandpaper (# 280) by a method of reciprocating a 2 kg roller once, and after leaving for 15 minutes, the force required for peeling was measured (180 degree peeling). , Peeling speed 3
00 mm / min, 23 ° C, 65% RH).

Holding power 10mm width adhesive tape 10mm against phenol resin plate
Adhere with an adhesive area of × 20 mm, and after 20 minutes at room temperature,
After leaving it in an atmosphere of 0 ° C. for 20 minutes, a phenol resin plate was hung down, a uniform load of 400 g was applied to the free end of the adhesive tape, and the dropping time of the adhesive tape at 80 ° C. was measured.

The results are shown in Table 1.

[Table 1]

From Table 1, it can be seen that the pressure-sensitive adhesive tape using the radiation-curable pressure-sensitive adhesive of the present invention is excellent in adhesive strength and holding power, and they are well balanced.

Claims (2)

[Claims] 1. A block copolymer having an average of 0.5 to 4 radiation-reactive unsaturated bonds in a molecule as a component, and the block copolymer has the general formula: CH ₂ ═C (R ¹ ) COOR.
² (provided that R ¹ is hydrogen or a methyl group, R ² is hydrogen or an alkyl group having 1 to 6 carbon atoms) and has a glass transition temperature of 50% by weight or more. A polymer block of 50 ° C. or higher, and a general formula: CH ₂ ═C
(R ³ ) COOR ⁴ (wherein R ³ is hydrogen or a methyl group,
R ⁴ is an alkyl group having 1 to 14 carbon atoms. ) A radiation-curable pressure-sensitive adhesive, comprising a polymer block containing an acrylic monomer component represented by 50% by weight or more and having a glass transition temperature of -20 ° C or less. 2. A pressure-sensitive adhesive tape comprising a support, and one or both surfaces of the support having a cured layer made of the radiation-curable pressure-sensitive adhesive according to claim 1.