JPH061954A - Radiation-curing tack agent and self-adhesive tape using the same - Google Patents

Abstract

PURPOSE:To provide the subject tack agent excellent in adhesive force, holding ability, adhesion sustainability and heat resistance, useful for self-adhesive tapes, etc., comprising each specific acrylic polymer, nitrogen-contg. monomer and polyfunctional monomer at specified proportion. CONSTITUTION:The objective tack agent comprising (A) 100 pts.wt. of an acrylic polymer <=-20 deg.C in glass transition temperature consisting mainly of acrylic monomer unit of formula I (R<1> is H or methyl; R<2> is 1-14C alkyl) such as methyl (meth)acrylate and also containing 1-15wt.% of an acid group-contg. monomer unit such as acrylic acid, (B) 1-30 pts.wt. of a nitrogen-contg. monomer of formula II [R<6> is H or methyl; X is Y-(CH2)n or CO (Y is COO or CONH); n is 1-10; R<4> and R<5> are each H or 1-5C alkyl] such as N,N-dimethylaminoethyl acrylate, and (C) 1-30 pts.wt. of a polyfunctional monomer having at least two radiation- reactive unsaturated bonds, such as diethylene glycol diacrylate.

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 an excellent balance between adhesive strength and holding power and excellent adhesion durability even on curved surfaces, and an adhesive tape using the same.

[0002]

2. Description of the Related Art Conventionally, from the viewpoint of environmental hygiene and safety,
There has been known a solventless coating type and radiation curing type pressure-sensitive adhesive capable of being coated with a solvent by reducing the molecular weight of a base polymer or by diluting with a reactive monomer or using a small amount of solvent. Radiation-curable pressure-sensitive adhesives have the advantage of superior water resistance and heat resistance as compared with emulsion-type and hot-melt type adhesives.

However, in the case of a solventless coating type in which the base polymer has a low molecular weight, there is a problem that the cohesive force is lowered and the holding power is poor. On the other hand, a solventless coating type diluted with a reactive monomer such as an N-alkyl-carbamoyloxyalkyl (meth) acrylate-based monomer having a low glass transition temperature has a poor adhesive strength and a long-lasting adhesion to a curved surface. In particular, there was a problem inferior to that under heat history (Japanese Patent Laid-Open No. 62-16737).
No. 8). Therefore, in either case, it was difficult to satisfy both the adhesive force and the holding force while satisfying the solventless coating.

[0004]

DISCLOSURE OF THE INVENTION The present invention is 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, and is also excellent in adhesion sustainability on curved surfaces under heat history. Is the development of.

[0005]

The present invention has the general formula: CH
₂ = C (R ¹ ) COOR ² (wherein R ¹ is hydrogen or a methyl group, R ² is an alkyl group having 1 to 14 carbon atoms) as a main component, and 100 parts by weight of an acrylic polymer containing an acidic group-containing monomer unit in an amount of 1 to 15% by weight and having a glass transition temperature of −20 ° C. or lower, and a general formula: CH ₂ ═CR ³ —X—NR ⁴ R ⁵ (however,
R ³ is hydrogen or a methyl group, X is —Y— (CH ₂ ) _n — or —CO— (wherein Y is —COO— or —CONH—,
n is an integer of 1-10. ), R ⁴ and R ⁵ are hydrogen or an alkyl group having 1 to 5 carbon atoms. ) 1 to 30 parts by weight of a nitrogen-containing monomer represented by 1) and 1 to 30 parts by weight of a polyfunctional monomer having two or more radiation-reactive unsaturated bonds in the molecule. And a layer comprising such a radiation-curable pressure-sensitive adhesive on one side or both sides of a support.

[0006]

With the above composition, a solventless coating type pressure-sensitive adhesive that can be coated with a solvent-free or a small amount of solvent is used, while curing by irradiation of radiation to achieve a balance between adhesive strength and holding power. A pressure-sensitive adhesive having excellent adhesive properties can be obtained. Further, by using a nitrogen-containing monomer having a high glass transition temperature and an acrylic polymer containing an acidic group, the cohesive force is improved by hydrogen bonding between the amino group or the amide group and the acidic group due to the contained nitrogen, and the thermal history The durability of adhesion to curved surfaces in is dramatically improved.

[0007]

Examples of constituent elements of the invention The radiation-curable pressure-sensitive adhesive of the present invention has the general formula: CH ₂ ═C (R ¹ ) COOR ² (provided that R ¹
Is hydrogen or a methyl group, and R ² is an alkyl group having 1 to 14 carbon atoms. ) Is a main component, and an acrylic polymer having a glass transition temperature of -20 [deg.] C. or lower and containing 1 to 15% by weight of an acidic group-containing monomer unit is a component. Acrylic polymers that can be preferably used in terms of adhesive properties such as cohesive force and solventless coating properties are
It has a weight average molecular weight of 50,000 to 800,000, especially 100,000 to 400,000.

Specific examples of the acrylic monomer unit include methyl group, ethyl group, propyl group, butyl group, isobutyl group, isoamyl group, hexyl group, 2-ethylhexyl group, isooctyl group, isononyl group and isodecyl group. Examples thereof include esters of acrylic acid and methacrylic acid having an alkyl group. The content of the acrylic monomer unit in the acrylic polymer can be appropriately determined within the range of 50 to 99% by weight.

Specific examples of the acid group-containing monomer unit include acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-hydroxyethylacryloyl phosphate, and 2-hydroxy. Examples include propyl acryloyl phosphate. The content of the acidic group-containing monomer unit is 1 to 15% by weight, and particularly 2 to 12% by weight. If the content is less than 1% by weight, the cohesive force is poor and 1
If it exceeds 5% by weight, the initial adhesive strength becomes poor.

The acrylic polymer may be prepared using one or more kinds of acrylic monomers and acidic group-containing monomers. Examples of other monomer units that the acrylic polymer may contain for the purpose of controlling adhesive properties and the like include vinyl acetate, styrene, glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate and 2-methacrylic acid. Examples thereof include hydroxyethyl, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate.

The radiation-curable adhesive of the present invention has the general formula:
^{_{CH 2 = CR 3 -X-NR}} 4 R 5 ( provided that, R ³ is hydrogen or a methyl group, X is -Y- (CH _{2) n} - or -CO- (although, Y is -COO- or -CONH- , N is an integer of 1 to 10), and R ⁴ and R ⁵ are hydrogen or an alkyl group having 1 to 5 carbon atoms). And In the present invention, it is preferable that both R ⁴ and R ⁵ are alkyl groups.

Specific examples of the nitrogen-containing monomer include, for example, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl metallate, N,
N-dimethylaminopropyl acrylamide, N, N-
Dimethylaminopropyl methacrylamide, N, N-diethylaminoethyl acrylate, N, N-diethylaminoethyl methacrylate and the like, general formula: CH ₂ ═C
^{_{R 3 -COO- (CH 2) n}} -NR 4 R 5 or CH ₂ = CR ³
-CONH- (CH ₂₎ those represented by _n -NR ⁴ R ⁵ and the like.

Further, for example, acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N, N-dimethylacrylamide, N, N
- dimethyl methacrylamide, such as N-t-butyl acrylamide, it may be mentioned those represented by _{^{CH 2 = CR 3 -CONR 4 R}} 5.

The amount of the nitrogen-containing monomer blended is 1 to 30 parts by weight per 100 parts by weight of the acrylic polymer. If the blending amount is less than 1 part by weight, the cohesive force becomes poor, and 30
If it exceeds the weight part, the adhesive strength becomes poor. A preferable blending ratio of the nitrogen-containing monomer is 0.1 to 10 mol with respect to 1 mol of the acidic group-containing monomer unit in the acrylic polymer.

The radiation-curable pressure-sensitive adhesive of the present invention is one or more radiation-reactive compounds which can be crosslinked (cured) by irradiation with radiation such as vinyl group, acryloyl group, methacryloyl group and vinylbenzyl group in the molecule. A polyfunctional monomer having two or more functional unsaturated bonds is a component. When the number of the radiation-reactive unsaturated bonds is less than 2, it is difficult to balance the adhesive properties such as holding power and adhesive force of the obtained pressure-sensitive adhesive. Generally, those containing 10 or less radiation-reactive unsaturated bonds are used, but the number is not limited to this. Two or more kinds of polyfunctional monomers can be used in combination.

Specific examples of polyfunctional monomers that can be preferably used include diethylene glycol diacrylate, diethylene glycol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, neopentyl glycol diacrylate. , Neopentyl glycol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipentaerythritol Hexaacrylate, dipentaerythritol Le hexa methacrylate, divinyl benzene, vinyl acrylate, vinyl methacrylate, divinyl adipate, N, etc. N'- methylenebisacrylamide and the like.

The compounding amount of the polyfunctional monomer is 1 to 30 parts by weight per 100 parts by weight of the acrylic polymer. If the amount is less than 1 part by weight, the cohesive force is poor, and if it exceeds 30 parts by weight, the adhesive force is poor.

The radiation-curable pressure-sensitive adhesive of the present invention can be prepared by mixing the ingredients. that time,
Additives that are commonly used in adhesives, such as tackifiers, fillers such as glass fibers and metal powders, pigments, colorants, plasticizers, etc., can also be added in conventional amounts.

The radiation-curable pressure-sensitive adhesive of the present invention is one that is cured by irradiation with active energy rays such as ionizing radiation such as α-ray, β-ray, γ-ray, neutron ray and electron beam, and ultraviolet rays. The irradiation dose is usually 0.5 for ionizing radiation.
It is about 20 Mrad, and preferably 1-10 Mrad.
In the case of ultraviolet rays, it is usually about 400 to 3000 mj / cm ² .

The wavelength of ultraviolet rays is preferably in the range of 180 to 460 nm, and a mercury lamp or a metal halide lamp is preferable as a source of the ultraviolet rays. When curing by ultraviolet irradiation, it is desirable to use a photoreaction initiator (photosensitizer) together. Examples of the photoreaction initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, dibenzyl, benzyl dimethyl ketal and the like.

The pressure-sensitive adhesive tape of the present invention has a 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 by, for example, a method using a support treated with a release agent. As the support, an appropriate material such as a plastic film, paper, non-woven fabric, or metal foil may be used. From the viewpoint of adhesion persistence to a curved surface or the like under heat history, it is preferable that it is difficult to deform due to heat history. 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 radiation-curable pressure-sensitive adhesive of the present invention is solvent-free or can be applied with a small amount of solvent and is cured by irradiation with radiation, and the cured pressure-sensitive adhesive layer has an excellent balance between adhesive strength and holding power. Excellent adhesion durability to curved surfaces under heat history.

[0023]

【Example】

Reference Example 1 In a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, and a stirring device, 65 parts of 2-ethylhexyl acrylate (parts by weight,
The same shall apply hereinafter), butyl acrylate 30 parts, methacrylic acid 5
Part, 2-mercaptoethanol 0.1 part, 2,2′-azobisisobutyronitrile 0.2 part, and toluene 40 parts, and subjected to polymerization treatment in a nitrogen stream to give a weight average molecular weight of 160,000 (gel permeation). Acrylic polymer of polystyrene conversion by solution chromatography (the same applies hereinafter) was obtained.

Reference Example 2 85 parts of isononyl acrylate, 5 parts of vinyl acetate, 10 parts of acrylic acid, 2,2'-azobisisobutyro were placed in a reaction vessel equipped with a cooling tube, a nitrogen introducing tube, a thermometer and a stirrer. 0.1 part of nitrile, 0.06 part of lauryl mercaptan, 20 parts of ethyl acetate, and 20 parts of toluene were added and polymerized in a nitrogen stream to obtain an acrylic polymer having a weight average molecular weight of 280,000.

Reference Example 3 90 parts of isoamyl acrylate, 7 parts of vinyl acetate, 3 parts of itaconic acid, 2,2'-azobisisobutyro were placed in a reaction vessel equipped with a cooling pipe, a nitrogen introducing pipe, a thermometer and a stirrer. 0.15 parts of nitrile, 0.12 parts of lauryl mercaptan, 20 parts of ethyl acetate and 10 parts of methanol were added, and the mixture was subjected to polymerization treatment in a nitrogen stream to obtain an acrylic polymer having a weight average molecular weight of 120,000.

Reference Example 4 65 parts of 2-ethylhexyl acrylate, 35 parts of butyl acrylate, 0.1 part of 2-mercaptoethanol were placed in a reaction vessel equipped with a cooling tube, a nitrogen introducing tube, a thermometer and a stirrer.
0.2 parts of 2,2′-azobisisobutyronitrile and 40 parts of toluene were added, and the mixture was polymerized in a nitrogen stream to obtain an acrylic polymer having a weight average molecular weight of 160,000.

Example 1 100 parts of the acrylic polymer obtained in Reference Example 1, 2 parts of N, N-dimethylaminoethyl acrylate, 2 parts of N, N-dimethylaminopropyl acrylamide and 3 parts of trimethylolpropane triacrylate were added. The radiation-curable pressure-sensitive adhesive obtained by mixing is coated on a separator, and the mixture is cured at 80 ° C for 3 hours.
After being dried for 3 minutes, it was cured by irradiation with an electron beam of 3 Mrad to obtain an adhesive tape having an adhesive layer with a thickness of about 50 μm.

Example 2 100 parts of the acrylic polymer obtained in Reference Example 2, 10 parts of N, N-dimethylaminoethyl acrylate, 4 parts of N, N-dimethylaminopropyl acrylamide, and 5 parts of tetraethylene glycol dimethacrylate were added. A radiation curable pressure sensitive adhesive and a pressure sensitive adhesive tape were obtained in the same manner as in Example 1 except that the above was used.

Example 3 100 parts of the acrylic polymer obtained in Reference Example 2, 2 parts of N-methylacrylamide, 2 parts of N, N-dimethylaminopropylmethacrylamide, 5 parts of trimethylolpropane trimethacrylate and penta of polymerized rosin. A radiation-curable pressure-sensitive adhesive and pressure-sensitive adhesive tape were obtained in the same manner as in Example 1 except that 20 parts of erythritol ester was used.

Example 4 100 parts of the acrylic polymer obtained in Reference Example 3, 2 parts of N, N-dimethylacrylamide, 5 parts of N, N-diethylaminoethyl acrylate, 10 parts of tetraethylene glycol dimethacrylate, and a phenol-modified terpene. A radiation curable pressure sensitive adhesive and a pressure sensitive adhesive tape were obtained in the same manner as in Example 1 except that 20 parts of the resin was used.

Comparative Example 1 N, N-dimethylaminoethyl acrylate and N, N-
An adhesive tape was obtained in the same manner as in Example 1 except that the radiation-curable adhesive containing no dimethylaminopropylacrylamide was used.

Comparative Example 2 An adhesive tape was obtained in the same manner as in Example 2 except that a radiation-curable pressure sensitive adhesive containing no tetraethylene glycol dimethacrylate was used.

Comparative Example 3 A radiation curable pressure sensitive adhesive and a pressure sensitive adhesive tape were obtained in the same manner as in Example 1 except that the acrylic polymer obtained in Reference Example 4 was used.

Evaluation Test The adhesive tapes obtained in Examples and Comparative Examples were subjected to the following tests. Peel adhesion 25 μm thick on the adhesive surface of 20 mm x 100 mm adhesive tape
After adhering the polyester film of No. 2, the separator was peeled off, and the adhesive surface was attached to a stainless plate (sandpaper # 28).
0 kg sanding surface) was crimped by a method of reciprocating a 2 kg roller once, and after 15 minutes, the force required for peeling was measured (180 degree peeling, pulling speed 300 mm /
Min, 23 ° C, 65% RH).

Holding power: A polyester film having a thickness of 25 μm was adhered to the adhesive surface of an adhesive tape having a width of 10 mm, the separator was peeled off, and a part of the adhesive surface was adhered to a phenol resin plate with an adhesive area of 10 mm × 20 mm. After 20 minutes, it was left at 80 ° C. for 20 minutes, then a phenol resin plate was hung down to apply a uniform load of 400 g to the free end of the adhesive tape, and the time until the adhesive tape dropped at 80 ° C. was measured. .

Heat Cycle Test After the adhesive surface of the adhesive tape was adhered to an aluminum plate having a thickness of 0.5 mm (area: 10 mm × 100 mm), the separator was peeled off, and the adhesive surface was applied to an aluminum cylinder having a diameter of 300 mm and a roller of 5 kg. Crimping by reciprocating one time (20 ° C,
65% RH), 20 ℃ x 1 hour (starting point) → 60
C. × 1 hour → 20 ° C. × 1 hour → 0 ° C. × 1 hour → After being subjected to a test in which the thermal cycle of the starting point is repeated twice, the peeled state of the end of the aluminum plate was observed and judged according to the following criteria. . ⊚: When the edge peeling height is 0.5 mm or less ◯: When the edge peeling height is 0.5 to 1.0 mm Δ: When the edge peeling height is 1.0 to 2.0 mm ×: When the edge peeling height is 2.0 mm or more

The above results are shown in Table 1.

[Table 1]

From Table 1, it can be seen that the adhesive layer comprising the radiation-curable adhesive of the present invention has an excellent balance of peel adhesion and holding power, exhibits excellent adhesion sustainability even on curved surfaces, and has a severe heat history. It can be seen that it withstands heat and has excellent heat resistance.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Moroishi 1-2-1, Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (2)

[Claims] 1. A general formula: CH ₂ ═C (R ¹ ) COOR
² (However, R ¹ is hydrogen or a methyl group, and R ² has 1 carbon atom.
~ 14 alkyl groups. 100 parts by weight of an acrylic polymer whose main component is an acrylic monomer unit represented by the formula (1) and which contains an acidic group-containing monomer unit in an amount of 1 to 15% by weight and has a glass transition temperature of -20 ° C or lower; ₂
^{= CR 3 -X-NR 4 R} 5 ( provided that, R ³ is hydrogen or a methyl group, X is -Y- (CH _{2) n} - or -CO- (However, Y
Is -COO- or -CONH-, and n is an integer of 1-10. ), R ⁴ and R ⁵ are hydrogen or an alkyl group having 1 to 5 carbon atoms. ) 1 to 30 parts by weight of a nitrogen-containing monomer represented by 1) and 1 to 30 parts by weight of a polyfunctional monomer having two or more radiation-reactive unsaturated bonds in the molecule. . 2. A pressure-sensitive adhesive tape, comprising a layer comprising the radiation-curable pressure-sensitive adhesive according to claim 1 on one side or both sides of a support.