JP2009203351A - Adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive sheet having an adhesive layer which includes excellent water-resistant adhesive force, holding force and adhesion to a base material even when a synthetic resin film is used as the base material. <P>SOLUTION: The adhesive sheet includes a base material and an adhesive layer provided on at least one surface of the base material. The adhesive layer is formed of an aqueous dispersion-type adhesive containing (A) an emulsion composition containing a copolymer having a hydrophilic functional group, obtained by emulsion-polymerizing a monomer mixture comprising (a1) an ethylenically unsaturated acid monomer and (a2) another monomer, (B) a crosslinking agent, and (C) a compound having one reactive group capable of forming a chemical bond with the hydrophilic functional group in the copolymer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive sheet having good water resistance. More specifically, it has a pressure-sensitive adhesive layer that can be applied to a film such as a synthetic resin, which is one of difficult-to-adhere substrates, and the pressure-sensitive adhesive layer has excellent water-resistant adhesive strength and is coated with the pressure-sensitive adhesive sheet. The present invention relates to a pressure-sensitive adhesive sheet that has little decrease in adhesive strength even after being stuck on a body and immersed in water, and has good holding power and adhesion to a substrate.

In recent years, from the viewpoint of environmental problems and the like, the transition from organic solvent-type resins to water-based resins is generally progressing in the material field. Many efforts are being made to replace it with solvent-based adhesives.
Of these, many studies have been made on emulsion-type pressure-sensitive adhesives that use water as a dispersion medium because of their high safety and easy cost advantages. In such an emulsion-type pressure-sensitive adhesive, hydrophilic components such as an emulsifier and a hydrophilic monomer are contained in order to obtain emulsion polymerization stability, storage stability of the resulting emulsion, and mechanical stability.
However, in an emulsion-type pressure-sensitive adhesive, these hydrophilic components remain in the pressure-sensitive adhesive layer formed on the substrate even after drying, and thus it is difficult to obtain sufficient water resistance.
Therefore, a method of adding a cross-linking agent to the emulsion and consuming the hydrophilic component with the cross-linking agent is taken, but if the amount of the cross-linking agent added is too much to improve water resistance, the cross-linking density, Since the elastic modulus of the pressure-sensitive adhesive film is excessively increased, the adhesion to the substrate and the wettability to the adherend are reduced.

In order to improve the water resistance of emulsion-type pressure-sensitive adhesives, many patent applications relating to pressure-sensitive adhesives that have been subjected to emulsion polymerization in the presence of a polymerizable surfactant having a radically polymerizable unsaturated group in the molecule have been reported. Even with these pressure-sensitive adhesives, hydrophilic groups such as carboxylic acid, sulfonic acid, phosphoric acid and the like remain in the pressure-sensitive adhesive layer after drying, so that water resistance is not essentially overcome.
For example, two types of copolymers each having a different functional group in the side chain (a copolymer comprising an epoxy group-containing monomer and an ethylenically unsaturated monomer, an unsaturated carboxylic acid and an ethylenically unsaturated monomer) A one-part cold crosslinking emulsion composition comprising a low molecular weight monofunctional epoxy compound and a low molecular weight monofunctional epoxy compound (for example, see Patent Document 1).
However, since the emulsion composition of Patent Document 1 is a one-pack type that can be crosslinked at room temperature, there is a problem in pot life, and mechanical stability tends to decrease over time.

Further, the resin particles have a core-shell structure and an average particle size of 0.3 μm or less, the Tg of the resin constituting the core is 15 ° C. or more, and the Tg of the resin constituting the shell is −30 ° C. An aqueous emulsion-type pressure-sensitive adhesive in which the following resin particles are emulsified and dispersed in an aqueous medium (for example, see Patent Document 2) is known.
The aqueous emulsion type pressure-sensitive adhesive of Patent Document 2 has a good water-resistant adhesive force, but requires emulsion polymerization in two steps, which is complicated in production and disadvantageous in terms of cost.

Also obtained by emulsion polymerization of a monomer mixture containing a (meth) acrylic acid alkyl ester having a C 1-12 alkyl group as a main component and this component and a polymerizable monomer copolymerizable with this component. A pressure-sensitive adhesive resin composition containing a (meth) acrylic polymer aqueous emulsion having a gel content insoluble in tetrahydrofuran of 20 to 50% by mass is also known (for example, see Patent Document 3).
The pressure-sensitive adhesive resin composition of Patent Document 3 has good water-resistant adhesive strength, but has a limitation that the gel fraction must be limited to 20 to 50 mass%, and the gel fraction is 20 to 50 mass. %, The adhesive is likely to protrude from the end face of the cutting roll and lacks suitability for processing such as punching of the adhesive sheet.
The techniques of Patent Documents 2 and 3 contain a certain amount of hydrophilic components in the pressure-sensitive adhesive film after drying, and cannot essentially solve the lack of water resistance of the emulsion-type pressure-sensitive adhesive.
Japanese Patent Laid-Open No. 10-158528 (Patent No. 3155480) JP 2003-292922 A JP 2007-056135 A

  The present invention has been made under such circumstances, and since it has a hydrophilic group as an essential component, the emulsion-type pressure-sensitive adhesive having poor water resistance is essentially modified to improve water resistance and further maintain It is an object of the present invention to provide a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer that is excellent in strength and adhesion to a substrate.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found an emulsion composition having a hydrophilic functional group, a crosslinking agent, and a reactive group capable of forming a chemical bond with the hydrophilic functional group. The present inventors have found that a pressure-sensitive adhesive sheet prepared using a pressure-sensitive adhesive formed from a water-dispersed pressure-sensitive adhesive containing one compound can achieve the above-described object, and has completed the present invention.

That is, the present invention is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on at least one surface of the following (1) substrate, the pressure-sensitive adhesive layer,
An emulsion containing a copolymer having a hydrophilic functional group, obtained by emulsion polymerization of a mixture of (A) (a1) an ethylenically unsaturated acid monomer and (a2) another monomer. Composition,
(B) a crosslinking agent and
(C) A pressure-sensitive adhesive sheet formed from a water-dispersed pressure-sensitive adhesive containing a compound having one reactive group capable of forming a chemical bond with the hydrophilic functional group in the copolymer,
(2) The pressure-sensitive adhesive sheet according to (1), wherein (a1) in the copolymer is 0.5 to 10.0% by mass, and (a2) is 90.0 to 99.5% by mass,
(3) The pressure-sensitive adhesive sheet according to (1) or (2), wherein the content of (C) is 0.1 to 1 equivalent relative to 1 equivalent of hydrophilic functional group in the copolymer. ,
(4) The content according to any one of (1) to (3), wherein the content of (B) is 0.1 to 1 equivalent relative to 1 equivalent of hydrophilic functional group in the copolymer. Adhesive sheet,
(5) The pressure-sensitive adhesive sheet according to any one of (1) to (4), wherein (a1) is acrylic acid or methacrylic acid,
(6) The hydrophilic functional group in the copolymer is at least one selected from a carboxyl group, a hydroxyl group, a sulfonic acid group, a phosphoric acid group, and an amino group, as described in any one of (1) to (5) above Adhesive sheet,
(7) The pressure-sensitive adhesive sheet according to the above (1) to (6), wherein (C) is at least one selected from epoxy-based, amine-based, carbodiimide-based, oxazoline-based, isocyanate-based and aziridinyl-based compounds; ) The pressure-sensitive adhesive sheet according to any one of the above (1) to (7), wherein the substrate is a synthetic resin film.

  According to the present invention, it has an adhesive layer that can be applied to a film such as a synthetic resin, the adhesive layer is excellent in water-resistant adhesive strength, and the adhesive sheet is attached to an adherend and immersed in water. There is provided a pressure-sensitive adhesive sheet that is less susceptible to lowering of adhesive strength and has good holding power and adhesion to a substrate.

The present invention is described in detail below.
In the present invention, the base material that is the support for the pressure-sensitive adhesive layer is not particularly limited, and is a known synthetic resin film, high-quality paper, coated paper, impregnated paper, or other synthetic paper having a cavity inside, Nonwoven fabrics can be used. Among these, a synthetic resin film is preferable in consideration of applications for which water resistance is expected.
The material of the synthetic resin film is not particularly limited. Polyethylene resin such as polyethylene resin and polypropylene resin, polyester resin such as polybutylene terephthalate resin and polyethylene terephthalate resin, acetate resin, acrylonitrile / butadiene / styrene (ABS) resin, Examples include synthetic resin films such as polystyrene resin, vinyl chloride resin, polyimide resin, and polyamide resin, and those obtained by depositing metal such as aluminum on these films.
The synthetic resin film used as the substrate may be unstretched, or may be stretched in a uniaxial direction or a biaxial direction such as longitudinal or lateral.

Although the thickness of a base material does not have a restriction | limiting in particular, Usually, it is the range of 10-200 micrometers, Preferably it is 25-150 micrometers from the surface of the ease of handling.
The substrate may be colored or colorless and transparent. Further, printing, printing, or the like may be performed on one surface of the base material.
Therefore, a surface for performing printing, printing, etc. of the base material may be provided with a heat-sensitive recording layer, a print image receiving layer capable of performing thermal transfer, inkjet, laser printing, etc., a printability improving layer, and the like.
In addition, the surface for forming the pressure-sensitive adhesive layer of the substrate may be subjected to easy adhesion treatment such as primer treatment or corona treatment for the purpose of improving the adhesion (keying force) with the pressure-sensitive adhesive layer. .

  In order to form the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer comprises a monomer mixture containing an ethylenically unsaturated acid monomer (a1) and another monomer (a2). Emulsion composition (A) containing a copolymer having a hydrophilic functional group obtained by emulsion polymerization, crosslinker (B), and the hydrophilic functional group of the copolymer in the component (A) and chemical A pressure-sensitive adhesive containing the compound (C) having one reactive group capable of forming a bond as an essential component is used.

First, component (A) will be described.
Examples of the ethylenically unsaturated acid monomer of component (a1) include unsaturated monomers having a carboxyl group such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, vinyl sulfonic acid, styrene sulfonic acid, ( Unsaturated monomers having an organic sulfonic acid group such as sulfoethyl (meth) acrylate, sulfopropyl (meth) acrylate, (meth) allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, acid phosphooxyethyl ( Unsaturated acid monomers having a phosphoric acid group such as (meth) acrylate, acid phosphooxypropyl (meth) acrylate, and acid phosphooxypolyethylene glycol (meth) acrylate, and sodium salts and potassium salts of these unsaturated acid monomers Is used. The component (a1) may be used alone or in combination of two or more.
Among these, acrylic acid and / or methacrylic acid are preferably used from the viewpoint of easy balance of the adhesive physical properties and easy availability.

Other unsaturated monomers that are component (a2) include alkyl groups such as butyl acrylate, hexyl (meth) acrylate, 2-ethylhexyl acrylate, lauryl (meth) acrylate, and the like having 1 to 20 carbon atoms. (Meth) acrylic acid alkyl ester, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and other hydroxyl-containing unsaturated monomers such as (meth) acrylic acid hydroxyalkyl esters , Acetoacetoxy group-containing unsaturated monomers such as acetoacetoxymethyl acrylate, acetoacetoxymethyl methacrylate, amide group-containing unsaturated monomers such as acrylamide, methacrylamide, diacetone acrylamide, dimethyl (meth) acrylate Aminoethyl, (meth) acrylic amino group-containing unsaturated monomers such as t-butylaminoethyl, glycidyl group-containing unsaturated monomers such as glycidyl (meth) acrylate and allyl glycidyl ether, γ- (meth) acryloxypropyltrimethoxysilane, Alkoxysilyl group-containing unsaturated monomers such as (meth) acryloxybutyltrimethoxysilane and vinyltrimethoxysilane, methylol group-containing unsaturated monomers such as methylolacrylamide and butoxy N-methylolacrylamide, 2-methoxyethyl (meta ), Acrylate, butoxyethyl (meth) acrylate, alkoxy group-containing unsaturated monomers such as methoxytriethylene glycol (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,6 hexanedio Polyfunctional unsaturated monomers such as urdi (meth) acrylate, 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (meth) acrylate, β- (par Fluorine-containing unsaturated monomers such as fluorooctyl) ethyl (meth) acrylate, nitrogen-containing unsaturated monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, cyclohexylmaleimide, methyl vinyl ether, butyl vinyl ether, hexyl Vinyl ethers such as vinyl ether, vinyl esters such as vinyl acetate and vinyl propionate, olefins such as ethylene, propylene and isobutylene, halogenated olefins such as vinyl chloride and chloroprene, styrenes such as styrene and t-butylstyrene, Dibutadiene such as butadiene and isoprene Nines unsaturated monomers such as enes, (meth) acrylonitrile, chloroacrylonitrile and the like are used. Among them, butyl acrylate, 2-ethylhexyl acrylate, hexyl methacrylate, 2-hydroxyethyl acrylate (2-HEA), and 2-hydroxyethyl methacrylate (2-HEMA) are preferably used from the viewpoint of balance of performance. .
The component (a2) may be used alone or in combination of two or more.
In addition, since the hydroxyl group which originates in the monomer which has a hydroxyl group like 2-HEA and 2-HEMA and exists in the copolymer in (A) component is also a hydrophilic functional group, it mentions in detail later May have reactivity with (B) and (C). Moreover, since these monomers may lower the water resistance of the pressure-sensitive adhesive, the amount of the monomer having a hydroxyl group is preferably 10% by mass or less in the component (a2).

The ratio of components (a1) and (a2) in the copolymer is such that (a1) is 0.5 to 10.0% by mass and (a2) is 90.0 from the viewpoint that strong adhesive strength and water resistance can be imparted. It is preferable that it is -99.5 mass%, More preferably, (a1) is 1.0-5.0 mass%, (a2) is 95.0-99.0 mass% [(a1) + (a2) is 100% by mass].
By setting the content of the component (a1) to 0.5% by mass or more, emulsion polymerization stability, storage stability of the resulting emulsion, mechanical stability, and adhesive strength and cohesive strength of the adhesive after drying are improved. By adjusting the content to 10.0% by mass or less, adhesion to the substrate, wettability to the adherend, and water resistance are improved.

In the pressure-sensitive adhesive sheet of the present invention, the emulsion composition (A), which is one of the components for forming the pressure-sensitive adhesive layer, is obtained by emulsion polymerization of the monomer mixture (a1) and (a2) using an emulsifier. Is obtained.
As such an emulsifier, an anionic or nonionic reactive emulsifier or a non-reactive emulsifier is used.

Examples of the anionic reactive emulsifier include “Adekalia Soap SE-20N”, “Adekalia Soap SE-10N”, “Adekalia Soap PP-70”, “Adekalia Soap PP-710”, “Adekalia Soap SR-”. 10 "," Adekaria Soap SR-20 "(manufactured by Asahi Denka Kogyo Co., Ltd.)," Eleminol JS-2 "," Eleminol RS-30 "(manufactured by Sanyo Chemical Industries Ltd.)," Latemul E-118B " “Latemul S-180A”, “Latemul S-180”, “Latemul PD-104” (manufactured by Kao Corporation), “Aqualon BC-05”, “Aqualon BC-10”, “Aqualon BC-20”, “Aqualon HS-05”, “Aquaron HS-10”, “Aquaron HS-20”, “New Frontier S-510”, “Aquaron KH-05” , "Aqualon KH-10" more than [manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.], "phosphino - Le TX" [manufactured by Toho Chemical Industry Co., Ltd.], and the like.
Nonionic reactive emulsifiers include “Adekalia Soap NE-10”, “Adekalia Soap NE-20”, “Adekalia Soap NE-30”, “Adekalia Soap NE-40”, “Adekalia Soap ER-”. 10 ”,“ Adekaria soap ER-20 ”,“ Adekaria soap ER-30 ”,“ Adekaria soap ER-40 ”(manufactured by Asahi Denka Kogyo Co., Ltd.),“ Aquaron RN-10 ”,“ Aquaron RN- ” 20 "," AQUALON RN-30 "," AQUALON RN-50 "[above, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], and the like, but it is only necessary to have reactivity, and it is not particularly limited thereto. .

  In consideration of emulsion polymerization stability and mechanical stability of the emulsion, a non-reactive emulsifier may be used, or it may be used in combination with the aforementioned reactive emulsifier. Such a non-reactive emulsifier is not particularly limited, and a known emulsifier usually used for emulsion polymerization is used. For example, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene Anionic emulsifiers such as sodium alkylsulfosuccinate, for example, nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene polyoxypropylene block polymer.

  The amount of these emulsifiers used is preferably 0.1 to 8.0 parts by weight, and 0.5 to 5.0 parts by weight, based on 100 parts by weight of the monomer mixture, as active ingredients (components excluding solvents and various additives). Part is more preferable. By setting the amount used to be 0.1 parts by mass or more, emulsion polymerization stability, storage stability of the resulting emulsion, and mechanical stability are ensured, and by setting the amount to 8.0 parts by mass or less, hydrophilicity is increased. This prevents the water resistance from decreasing too much.

The conditions for emulsion polymerization for preparing an emulsion composition containing a copolymer having a hydrophilic functional group as component (A) are not particularly limited, and the conditions applied in ordinary emulsion polymerization are applied as they are. be able to. In general, after replacing the inside of the reactor with an inert gas, the temperature is increased while stirring under reflux, and the polymerization is carried out for about 1 to 8 hours after starting the temperature increase in a temperature range of about 40 to 100 ° C.
When preparing an emulsion composition by an emulsion polymerization method, a polymerization initiator is usually used. As the polymerization initiator, azo compounds such as 2,2′-azobis (2-methylpropionamidine) dihydrochloride, persulfates such as potassium persulfate, and peroxides such as benzoyl peroxide can be used.

The average particle diameter of the emulsion particles made of the copolymer in the emulsion composition which is the component (A) in the pressure-sensitive adhesive sheet of the present invention is about 100 to 500 nm, preferably 100 to 300 nm. If the average particle size is within the above range, emulsion polymerization stability, storage stability of the resulting emulsion, mechanical stability, and physical property balance of the pressure-sensitive adhesive film after drying, that is, adhesion to the substrate, adherend A pressure sensitive adhesive with a good balance of wettability, water resistance, cohesive strength and transparency can be obtained.
When the average particle size is 100 nm or more, stable emulsion particles can be obtained, and an increase in the amount of emulsifier used can be prevented. When the average particle size is 500 nm or less, adhesion to the substrate, transparency of the resulting pressure-sensitive adhesive layer, and water resistance are ensured. The average particle size of the emulsion particles can be controlled by the type and concentration of the emulsifier added during polymerization, the concentration of the polymerization initiator, and the like.
Here, the average particle diameter of the emulsion particles is based on a volume-based median diameter value obtained by measurement with a laser diffraction / scattering particle size distribution measuring apparatus.

Next, component (B) will be described.
The cross-linking agent of component (B) is not particularly limited as long as it is cross-linked by the hydrophilic functional group of the copolymer in the emulsion composition that is component (A), but the adhesion and adhesive force to the substrate, Epoxy-based, aziridine-based, melamine-based, metal complex-based, amine-based, oxazoline-based, carbodiimide-based, hydrazide-based, and isocyanate-based compounds are mainly used because of their excellent cohesive strength and availability. Among these, epoxy-based, oxazoline-based, carbodiimide-based and isocyanate-based compounds are preferably used.

As an epoxy-type compound, what is necessary is just to have two or more epoxy groups or glycidyl groups in a molecule, for example, bisphenol A / epichlorohydrin type epoxy resin, sorbitol polyglycidyl ether (for example, manufactured by Nagase ChemteX Corporation, “Denacol EX-611”, “Denacol EX-612”, “Denacol EX-614”, “Denacol EX-614B”, “Denacol EX-622”, etc.), polyglycerol polyglycidyl ether (for example, manufactured by Nagase ChemteX Corporation) , “Denacol EX-512”, “Denacol EX-521”, etc.), pentaerythritol polyglycidyl ether (for example, “Denacol EX-411” manufactured by Nagase ChemteX Corporation), diglycerol polyglycidyl ether (for example, Nagaseke). "Denacol EX-421" manufactured by Tex Corporation), glycerol polyglycidyl ether (for example, "Denacol EX-313", "Denacol EX-314" manufactured by Nagase ChemteX Corporation), etc.), trimethylolpropane polyglycidyl ether (for example, , "Denacol EX-321" manufactured by Nagase ChemteX Corporation), neopentyl glycol diglycidyl ether (for example, "Denacol EX-211" manufactured by Nagase ChemteX Corporation), 1,6-hexanediol diglycidyl ether ( For example, “Denacol EX-212” manufactured by Nagase ChemteX, Inc.), ethylene glycol diglycidyl ether (eg, “Denacol EX-810”, “Denacol EX-811” manufactured by Nagase ChemteX, Inc.), diethylene glycol diglycidyl, etc. Ether (for example, “Denacol EX-850”, “Denacol EX-851”, etc., manufactured by Nagase ChemteX Corporation), polyethylene glycol diglycidyl ether (for example, “Denacol EX-821”, “Denacol EX, manufactured by Nagase ChemteX Corporation) -830 "," Denacol EX-832 "," Denacol EX-841 "," Denacol EX-861 ", etc.), propylene glycol diglycidyl ether (for example," Denacol EX-911 "manufactured by Nagase ChemteX Corporation), Polypropylene glycol diglycidyl ether (for example, “Denacol EX-941”, “Denacol EX-920”, “Denacol EX-931”, etc., manufactured by Nagase ChemteX Corporation), diglycidylaniline, N, N, N ′, N ′ -Tetraglycidyl-m-xyle Diamine, 1,3-bis (N, N'-diglycidylaminomethyl) cyclohexane and the like.
Among these, the aqueous type is preferable.

  Any oxazoline-based compound may be used as long as it contains at least two oxazoline groups in the molecule, and an addition-polymerizable 2-oxazoline having a substituent having an unsaturated carbon-carbon bond at the 2-position carbon position (for example, 2-isopropenyl-2-oxazoline) and other unsaturated monomers, etc., and commercially available products such as “Epocross WS-500”, “Epocross WS-700” manufactured by Nippon Shokubai Co., Ltd. “Epocross K-2010E”, “Epocross K-2020E”, “Epocross K-2030E” and the like.

  The carbodiimide-based compound may be any compound containing at least two carbodiimide groups in the molecule. For example, “Carbodilite V-02”, “Carbodilite V-02-L2”, and “Carbodilite V-04” manufactured by Nisshinbo Co., Ltd. ”,“ Carbodilite V-06 ”,“ Carbodilite E-01 ”,“ Carbodilite E-02 ”,“ Carbodilite E-04 ”and the like.

  The hydrazide compound may be any compound having at least two hydrazide groups in the molecule. For example, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, malein Examples include acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide and the like.

  The isocyanate compound may be any compound containing at least two isocyanate groups in the molecule. For example, toluylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate. , 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, tetramethylxylene diisocyanate, etc., "Sumijour N" (manufactured by Sumitomo Bayer Urethane Co., Ltd.) Buret polyisocyanate compounds such as "Desmodur IL", "Desmodur HL" (Bayer AG) ), Polyisocyanate compounds having an isocyanurate ring such as “Coronate EH” (manufactured by Nippon Urethane Co., Ltd.), adduct-type polyisocyanate compounds such as “Sumijour L” (manufactured by Sumitomo Bayer Urethane Co., Ltd.), “Coronate HL” Adduct polyisocyanate compounds such as “Aquanate 100”, “Aquanate 110”, “Aquanate 200”, “Aquanate 210” (manufactured by Nippon Polyurethane) And water-dispersed polyisocyanate compounds. Among these, the aqueous type is preferable. Moreover, you may use block isocyanate.

These crosslinking agents are usually preferably used in an amount of 0.1 to 1 equivalent with respect to 1 equivalent of hydrophilic group of the copolymer in the emulsion composition (A), preferably 0.1 to 0.8 equivalent. More preferably, the amount is as follows. By making the addition amount 0.1 equivalent or more, a substantial effect is exhibited, and the substrate adhesion and the cohesive force are ensured. By setting the amount to 1 equivalent or less, bleeding to the interface between the adherend and the base material layer and the pressure-sensitive adhesive layer is prevented, thereby causing contamination of the adherend and a decrease in adhesion to the base material.
In addition, these crosslinking agents are preferably water-based, and may be used alone or in combination of two or more.

Next, component (C) will be described.
The compound (C) having one reactive group capable of forming a chemical bond with a hydrophilic functional group (hereinafter referred to as a monofunctional compound (C) including those in the table) may be used in the emulsion composition (A). It is possible to form a chemical bond with the hydrophilic functional group of this copolymer, and those having a hydrophobic group in the molecule are preferred, but not particularly limited. Specifically, epoxy, amine, carbodiimide, oxazoline, isocyanate, and aziridinyl are mainly used because of their availability. In particular, a monofunctional compound having a hydrophobic group such as an aliphatic group, an aromatic group, an alicyclic group, or a heterocyclic group in the molecule greatly contributes to improving water resistance.

  Specific examples of these monofunctional compounds (C) include allyl glycidyl ether, normal butyl glycidyl ether, 2-ethylhexyl glycidyl ether, isobutyl glycidyl ether, dodecyl glycidyl ether, hexadecyl glycidyl ether, phenyl glycidyl ether, phenyl polyoxy Epoxy such as ethylene glycidyl ether, p-tert-butylphenyl glycidyl ether, lauryl alcohol polyoxyethylene glycidyl ether, 1,2-epoxy-4-vinylcyclohexane, 3,4-epoxycyclohexylmethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, etc. Monofunctional compounds, propylamine, butylamine, hexylamine, decylamine, laurylamine, diethylamine, Carbodiimide monofunctional compounds such as isopropylamine, dimethyllaurylamine, dicyclohexylamine, aniline, benzylamine, dimethylaniline, dimethylaminoethyl (meth) acrylate amine monofunctional compounds, dicyclohexylcarbodiimide, diisopropylcarbodiimide, di-tert-butylcarbodiimide 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl-4-ethyl-2-oxazoline, 2-vinyl-5 -Ethyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-4-ethyl Oxazoline monofunctional compounds such as 2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-4, 5-dimethyl-2-oxazoline, propyl isocyanate, butyl isocyanate, lauryl isocyanate, phenyl isocyanate , Cyclohexyl isocyanate, 2,6-diisopropylphenyl isocyanate, isocyanate monofunctional compounds such as 2-methacryloxyethyl isocyanate, aziridinyl such as 2-aziridinylethyl (meth) acrylate and 3-aziridinylpropyl (meth) acrylate A monofunctional compound can be used.

These monofunctional compounds (C) are preferably used in an amount of 0.1 to 1 equivalent, more preferably 0.1 to 0 with respect to the hydrophilic functional group of the copolymer in the emulsion composition (A). .8 equivalent amount.
By making the addition amount 0.1 equivalent or more, a substantial effect is exhibited. By setting the amount to 1 equivalent or less, bleeding to the interface between the adherend and the base material layer and the pressure-sensitive adhesive layer is prevented, thereby causing contamination of the adherend and a decrease in adhesion to the base material.
These monofunctional compounds (C) may be used alone or in combination of two or more.

  Although the gel fraction of the adhesive layer in the adhesive sheet of this invention is not specifically limited, Preferably it is 30 to 90%. When the gel fraction is less than 30%, the cohesive force and water resistance of the pressure-sensitive adhesive are impaired, and when it exceeds 90%, the adhesion to the substrate and the wettability to the adherend are impaired. The gel fraction of the pressure-sensitive adhesive layer is the ratio of the solvent-insoluble portion of the pressure-sensitive adhesive layer. When the pressure-sensitive adhesive layer dried at 90 ° C. for 1 minute is immersed in tetrahydrofuran at 23 ° C. for 72 hours and dried. It is calculated | required as a ratio (%) of the residual adhesive layer mass after immersion with respect to the adhesive layer mass before immersion.

Further, the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of the present invention, if necessary, a tackifier (for example, modified rosin such as maleated rosin, fumarated rosin, acrylated rosin, disproportionation, dimerization, hydrogenation) Rosin resins such as those obtained by esterifying the rosin with glycerin or pentaerythritol, xylene resin, terpene resin, terpene phenol resin, petroleum resin, coumarone indene resin, styrene resin, ethylene / Vinyl acetate resin, etc.), plasticizers (eg liquid polybutene, mineral oil, lanolin, liquid polyisoprene, liquid polyacrylate, dioctyl phthalate, glycerin, ethanolamine, etc.), antiseptics, rust preventives, freeze-thaw stabilizers, Pigment, colorant, filler (zinc white, titanium white, calcium carbonate, clay, etc.), metal powder Neutralizing agent (aqueous ammonia, sodium hydroxide, potassium hydroxide, etc.), wetting agents, antifoaming agents, thickeners, surfactants, antioxidants, may be added as appropriate ultraviolet absorbers.
The additive is often added to the water-dispersed pressure-sensitive adhesive composition after polymerization, but can also be added before emulsion polymerization or during emulsion polymerization.

The pressure-sensitive adhesive used in the pressure-sensitive adhesive sheet of the present invention has a resin solid content of usually about 30 to 65% by mass, preferably 40 to 60% by mass. The viscosity is about 50 to 12,000 mPa · s (BM type viscometer, 60 rotations, 25 ° C.), preferably 100 to 10,000 mPa · s. Furthermore, it is preferable that pH exists in the range of 6-9 normally.
The resin solid content concentration, viscosity, and pH of the pressure-sensitive adhesive are preferably in the above ranges from the viewpoints of drying property, coating property, coating solution dispersion stability, storage stability, mechanical stability, and handling.
There is no restriction | limiting in particular in the thickness of an adhesive layer, Usually, 10-50 micrometers, Preferably it is about 15-35 micrometers.

  The method for producing the pressure-sensitive adhesive sheet of the present invention is not particularly limited. For example, the pressure-sensitive adhesive layer comprises the emulsion composition (A), the crosslinking agent (B), the monofunctional compound (C) and the like. Mix, and if necessary, add a thickener or diluent such as polyacrylic acid to the release sheet and apply a pressure-sensitive adhesive consisting of a mixture adjusted to an appropriate viscosity. It is also possible to adopt a transfer coating method in which the adhesive is directly applied to the surface of the substrate first, and a direct coating method in which the adhesive is bonded to the release sheet after drying.

The release sheet is not particularly limited. Examples of the base material for the release sheet include paper, synthetic paper, and synthetic resin film.
As the paper, for example, a paper base such as fine paper, glassine paper, coated paper, a paper base such as a laminated paper obtained by laminating a thermoplastic resin such as polyethylene or polypropylene to these paper bases, and high-quality paper, Examples include plastic substrates such as glass paper, coated paper, etc. that have been treated with cellulose, starch, polyvinyl alcohol, acrylic-styrene resin, etc., and examples of plastic synthetic resin films include polyolefin resins such as polyethylene resins and polypropylene resins. , Films made of polyester resins such as polybutylene terephthalate resin and polyethylene terephthalate resin, and films obtained by subjecting these synthetic resin films to an easy adhesion treatment, and the like, preferably having a release treatment applied thereto. .

As the release treatment agent, for example, known treatment agents such as rubber-based elastomers such as polyolefin-based resins, isoprene-based resins, butadiene-based resins, silicone resins, alkyd resins, fluororesins, and long-chain alkyl-containing resins can be used. It is.
The thickness of the release treatment agent layer is preferably 0.05 to 2.0 μm, more preferably 0.1 to 1.5 μm.
There is no restriction | limiting in particular in the thickness of the base material for release sheets, Usually, it is 30-200 micrometers.

  The method for applying the adhesive is not particularly limited, and a conventionally known coating method can be used. For example, a knife coater, a roll coater, a roll knife coater, a gravure coater, a vario gravure coater, an air knife coater, a bar coater, Examples thereof include a method using a coating apparatus such as a die coater or a curtain coater.

  The thickness of the pressure-sensitive adhesive sheet obtained by laminating the base material, the pressure-sensitive adhesive layer and the release sheet is usually 50 to 300 μm, preferably 60 to 250 μm, and may be a flat sheet or wound into a roll. It may be.

The pressure-sensitive adhesive sheet of the present invention is, for example, packaging / bundling, office / household, bonding, coating masking, surface protection, anticorrosion / waterproofing, sealing, electrical insulation, electronic equipment / optical components, medical / Sanitary materials, identification / decoration, labels, advertising stickers, display stickers, marking films, windows and displays, adhesive tapes, sheets, and labels for vehicles, paper, natural and synthetic resins It can be used for various adherends such as glass and metal adherends.
Moreover, the water resistance as described above can be imparted to the existing emulsion-type pressure-sensitive adhesive composed of the components (A) and (B) by adding the (C).

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples.

<Example 1>
In a container equipped with a stirrer, a thermometer, and a dropping funnel, 87.0 parts by mass of 2-ethylhexyl acrylate (2-EHA), 10.0 parts by mass of butyl acrylate (BA), 2-hydroxyethyl methacrylate (2 -HEMA) 1.0 part by mass and 2.0 parts by mass of methacrylic acid (MAA) are charged, and polyoxyethylene alkyl ether sulfate sodium salt (trade name: LATEMUL E-118B) 0.5 is added thereto. Part by weight, 1.5 parts by weight of allyl alkyl sulfosuccinate ester salt (manufactured by Sanyo Chemical Co., Ltd., trade name: Eleminol JS-2) and 56 parts by weight of ion-exchanged water are added, and the mixture is stirred at room temperature, An emulsion containing the mixture was prepared in advance.
Separately, 28 parts by mass of ion-exchanged water was charged into a reactor equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen introduction tube, and a dropping funnel, nitrogen was sealed, and the internal temperature was raised to 80 ° C. While maintaining, 2 parts by mass of a 10% by mass aqueous ammonium persulfate solution was charged to prepare an aqueous polymerization initiator solution.
Next, an emulsion containing a mixture of unsaturated monomers prepared in advance was transferred to a dropping funnel and dropped into the polymerization initiator aqueous solution over 4 hours. At the same time, 4 parts by mass of a 5% by mass ammonium persulfate aqueous solution was added dropwise to carry out emulsion polymerization at an internal temperature of 80 ° C.
After completion of dropping, the mixture was aged at 80 ° C. for 4 hours to obtain a composition having an average particle diameter of 200 nm.
Then, after cooling to room temperature and neutralizing with aqueous ammonia, water was added to obtain an emulsion composition (A) containing a (acrylic) copolymer having a solid content of 50% by mass and pH 8.0.
Next, a polyacrylic acid-based thickener (Rohm and Haas, trade name: ASE-60) was added to the emulsion composition (A), and a viscosity at 25 ° C. was 8,000 mPa · s (B-type viscometer, 60 rpm).
Furthermore, with respect to 100 parts by mass of the (acrylic) copolymer in the emulsion composition (A) containing the (acrylic) copolymer, “Denacol EX-421” ( 1.5 parts by mass of a trifunctional epoxy resin (epoxy equivalent: 159) manufactured by Nagase ChemteX Corporation, and “Denacol EX-141” (manufactured by Nagase ChemteX Corporation, 1 1.5 parts by mass of a functional epoxy resin, epoxy equivalent: 151) was added, and the resulting adhesive was peeled off from a release sheet “SP-8K Ao” (made by Lintec Co., Ltd., glassine paper peeled with a silicone resin). On the surface of the treatment agent, coating was performed using a roll knife coater so that the coating thickness after drying was 20 μm, and drying was performed at 90 ° C. for 2 minutes to form an adhesive layer. Subsequently, it was bonded to a PET film “Lumirror # 50S10” (manufactured by Toray Industries, Inc.), which is a substrate having a thickness of 50 μm, to produce an adhesive sheet.
The pressure-sensitive adhesive sheet obtained as described above was cured for 7 days in an environment of 23 ° C. and 50% RH, and then evaluated for normal-state adhesive strength, water-resistant adhesive strength, and adhesion to a substrate.

<Example 2>
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that 1.7 parts by mass of “Denacol EX-121” (manufactured by Nagase ChemteX Corporation, epoxy equivalent: 187) was used as the epoxy-based monofunctional compound (C). Then, normal adhesive strength, water-resistant adhesive strength, and adhesion to a substrate were evaluated.

<Examples 3 to 7>
Monofunctional compound (C) 0.7 parts by mass (Example 3) butylamine (Tokyo Chemical Industry Co., Ltd.), 0.8 part by mass of N, N-dimethyldodecylamine (Tokyo Chemical Industry Co., Ltd.) (Example) 4) 1.0 part by mass of benzylamine (Tokyo Chemical Industry Co., Ltd.) (Example 5), 2.0 parts by mass of diisopropylamine (Tokyo Chemical Industry Co., Ltd.) (Example 6), dicyclohexylcarbodiimide (Tokyo Chemical Industry) Kogyo Co., Ltd.) A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that 1.9 parts by mass (Example 7) was used, and normal-state adhesive strength, water-resistant adhesive strength, and substrate adhesion were evaluated. It was.

<Examples 8 and 9>
The composition of the copolymer in the component (A) is changed to the monomer mixture shown in Table 1, and the component (B) is an oxazoline-based crosslinking agent WS-700 [manufactured by Nippon Shokubai Co., Ltd., oxazoline value: 4 .5 mmol / g] and V-02 [Nisshinbo Co., Ltd., chemical formula amount per mole of carbodiimide group: 590] which is a carbodiimide-based crosslinking agent, the monofunctional compound (C) was changed to hexyl isocyanate. Except for the above, a pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1, and the normal-state adhesive strength, water-resistant adhesive strength, and substrate adhesion were evaluated. In the table, AA represents acrylic acid, and MMA represents methyl methacrylate.

<Comparative Example 1-Example in which no monofunctional compound (C) is added>
A comparative adhesive sheet was prepared after preparing the composition in the same manner as in Example 1 except that the monofunctional compound (C) was not added, and evaluation of normal adhesive strength, water-resistant adhesive strength, and substrate adhesion was performed. Went.

<Comparative Examples 2-9—Examples in which no crosslinking agent (B) is added>
A comparative pressure-sensitive adhesive sheet was prepared after preparing the composition in the same manner as in Examples 1 to 8 except that the crosslinking (B) agent was not added. Evaluation was performed.
The composition of each component in Examples 1 to 9 and the evaluation results thereof are summarized in Table 1, and those in Comparative Examples 1 to 9 are summarized in Table 2.

The performance evaluation was performed according to the following measurement method or calculation method.
(1) Average particle diameter A volume-based median diameter was measured using a laser diffraction / scattering particle size distribution analyzer (product name: LA-920) manufactured by Horiba, Ltd.
(2) Gel fraction Apply to the release surface of release sheet (SP-8K Ao, manufactured by Lintec) so that the coating thickness after drying is 20 μm, and heat at 100 ° C. for 1 minute to form an adhesive layer did. The pressure-sensitive adhesive layer and another release sheet (SP-PET 3801, manufactured by Lintec Corporation) were bonded together to obtain a pressure-sensitive adhesive sheet.
The pressure-sensitive adhesive sheet was allowed to stand for 1 week in an atmosphere of 23 ° C. and 50% humidity. Then, about 0.2 g of the pressure-sensitive adhesive was taken out from the pressure-sensitive adhesive sheet, wrapped in a stainless mesh (# 300), and placed in 30 ml of tetrahydrofuran at 23 ° C. After immersion for 72 hours, the whole stainless steel mesh was taken out, dried at 120 ° C. for 3 hours, and calculated from the mass ratio before immersion (unit:%).
(3) Normal adhesive strength (α)
An adhesive sheet test piece cut to 25 mm × 300 mm was attached to an adherend (SUS304) to prepare a test sample in an environment of 23 ° C. and 50% RH. The adhesive strength 24 hours after application was measured at a pulling speed of 300 mm / min by 180 ° peeling method (based on JIS Z0237).
(4) Water-resistant adhesive strength (β)
In a 23 ° C., 50% RH environment, an adhesive sheet test piece cut to 25 mm × 300 mm was attached to an adherend (SUS304). The sample was allowed to stand for 1 day in an environment of 23 ° C. and 50% RH and then immersed in purified water for 1 day in an environment of 40 ° C. to obtain a test sample. The adhesive strength of the test sample immediately after removal was measured by a 180 ° peeling method at a pulling rate of 300 mm / min (based on JIS Z0237).
(5) Ratio of adhesive strength to normal state Calculated as water-resistant adhesive strength (β) / normal state adhesive strength (α).
(6) Holding power After the pressure-sensitive adhesive sheet was prepared, the pressure-sensitive adhesive sheet test piece cut to 25 mm × 100 mm was pasted on the adherend (SUS304) so that the application area was 25 mm × 25 mm in an environment of 23 ° C. and 50% RH. This was used as a test sample. Thereafter, a holding force was measured by applying a load (9.8 N) with a 1 kg weight in a 40 ° C. environment. The test time was set to 70000 seconds, and ○ in the table indicates that the test piece did not fall even if it exceeded 70000 seconds (according to JIS Z0237).
The numerical value of the holding force in Table 2 is the time (seconds) until the weight falls.
(7) Adhesiveness to base material After peeling the release sheet from the adhesive sheet, the adhesive layer was rubbed with a finger 5 times to evaluate the adhesiveness to the base material (base material adhesiveness). The case where the pressure-sensitive adhesive layer was not peeled off from the PET film was marked with ◯, and the case where peeling occurred was marked with x.

  From Tables 1 and 2, the pressure-sensitive adhesive sheets of the examples are superior in water-resistant pressure-sensitive adhesive force (ratio to normal pressure-sensitive adhesive force) even when a synthetic resin film is used as a base material, as compared with a comparative pressure-sensitive adhesive sheet, It can be seen that the pressure-sensitive adhesive sheet has good adhesion to the material.

  The pressure-sensitive adhesive sheet of the present invention is used for packaging / bundling, office / household, bonding, coating masking, surface protection, anticorrosion / waterproofing, sealing, electrical insulation, electronic equipment / optical components, medical / hygiene It can be advantageously used as adhesive tapes, adhesive sheets, and adhesive labels for materials, identification / decoration, labels, advertisement stickers, display stickers, marking films, windows and displays, vehicles and the like.

Claims (8)

A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on at least one surface of a substrate, the pressure-sensitive adhesive layer,
An emulsion containing a copolymer having a hydrophilic functional group, obtained by emulsion polymerization of a mixture of (A) (a1) an ethylenically unsaturated acid monomer and (a2) another monomer. Composition,
(B) a crosslinking agent and
(C) A pressure-sensitive adhesive sheet formed from a water-dispersed pressure-sensitive adhesive containing a compound having one reactive group capable of forming a chemical bond with the hydrophilic functional group in the copolymer.   The pressure-sensitive adhesive sheet according to claim 1, wherein (a1) in the copolymer is 0.5 to 10.0% by mass and (a2) is 90.0 to 99.5% by mass.   The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the content of (C) is an amount that is 0.1 to 1 equivalent with respect to 1 equivalent of the hydrophilic functional group in the copolymer.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the content of the (B) is 0.1 to 1 equivalent with respect to 1 equivalent of the hydrophilic functional group in the copolymer.   The pressure-sensitive adhesive sheet according to claim 1, wherein (a1) is acrylic acid or methacrylic acid.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the hydrophilic functional group in the copolymer is at least one selected from a carboxyl group, a hydroxyl group, a sulfonic acid group, a phosphoric acid group, and an amino group.   The pressure-sensitive adhesive sheet according to claim 1, wherein (C) is at least one selected from an epoxy-based, amine-based, carbodiimide-based, oxazoline-based, isocyanate-based, and aziridinyl-based compound.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the substrate is a synthetic resin film.