JP2022155542A - Adhesive and adhesive tape - Google Patents

Abstract

To provide an adhesive that barely shows a decrease in gel fraction even after subjected to a wet heat process simulating long-term storage.SOLUTION: An adhesive contains an acrylic resin (A), an epoxy crosslinker (B), and an epoxy compound (C), the acrylic resin (A) including a carboxy group-containing monomer (a1) unit.SELECTED DRAWING: None

Description

The present invention relates to an adhesive, and more specifically, an adhesive that suppresses a decrease in gel fraction after wet heat treatment assuming long-term storage, and suppresses dripping and bleeding of the adhesive layer when used as an adhesive tape. It relates to agents and adhesive tapes.

Conventionally, when using an acrylic resin for the adhesive layer of an adhesive tape, it is easy to stably obtain an adhesive tape with excellent adhesive strength. rice field. For example, in Patent Document 1, a (meth)acrylic pressure-sensitive adhesive has a pressure-sensitive adhesive layer containing a tackifier with a softening point of 150°C or higher and a polyfunctional epoxy cross-linking agent, and there is no foaming even when exposed to a high temperature of 300°C. , a heat-resistant adhesive tape having sufficient adhesive strength is disclosed.

JP 2017-106013 A

However, the initial gel fraction of the adhesive layer of the adhesive tape disclosed in Patent Document 1 is 50 to 70% by mass, and although it has sufficient adhesive strength even when exposed to high temperatures, after long-term storage Suppression of the decrease in the gel fraction after wet heat treatment assuming , and suppression of dripping and bleeding of the adhesive layer due to it have not been sufficiently studied.

Under such circumstances, an object of the present invention is to provide a pressure-sensitive adhesive in which the decrease in gel fraction is suppressed even after wet heat treatment, which is assumed to be after long-term storage.

However, as a result of intensive research in view of such circumstances, the present inventors have found that a pressure-sensitive adhesive containing an acrylic resin having a carboxyl group-containing monomer unit, an epoxy-based cross-linking agent, and an epoxy-based compound does not gel even after wet heat treatment. The inventors have found that the decrease in the fraction can be suppressed, and completed the present invention.

That is, the present invention has the following aspects.
[1]
A pressure-sensitive adhesive comprising an acrylic resin (A), an epoxy cross-linking agent (B), and an epoxy compound (C), wherein the acrylic resin (A) contains carboxy group-containing monomer (a1) units.
[2]
The pressure-sensitive adhesive according to [1], wherein the epoxy compound (C) is an epoxy compound having a gel fraction of 5% by mass or less under the following measurement conditions.
<Measurement conditions>
A mixture obtained by adding 0.024 parts by mass of the epoxy compound (C) to 100 parts by mass of the acrylic resin (A) and mixing was applied to the film-like material so that the thickness after drying was 110 μm. After drying at °C for 5 minutes, the coated surface was adhered to the substrate, and the gel fraction of the mixture after standing at 40°C for 7 days.
[3]
The pressure-sensitive adhesive according to [1] or [2], wherein the carboxy group-containing monomer (a1) unit in the acrylic resin (A) is 0.1 to 20% by mass.
[4]
The adhesive according to any one of [1] to [3], wherein the carboxy group-containing monomer (a1) is a (meth)acrylic acid monomer.
[5]
An adhesive tape having the adhesive according to any one of [1] to [4] on at least one side of a substrate.
[6]
The pressure-sensitive adhesive tape of [5], wherein the substrate contains flat yarn cloth.

The present invention is a pressure-sensitive adhesive containing an acrylic resin having a carboxyl group-containing monomer unit, an epoxy-based cross-linking agent, and an epoxy compound, and is a pressure-sensitive adhesive that suppresses a decrease in gel fraction after wet heat treatment. be. A pressure-sensitive adhesive tape having the pressure-sensitive adhesive of the present invention on at least one surface of a base material also suppresses a decrease in the gel fraction after wet heat treatment, thereby suppressing dripping and bleeding of the pressure-sensitive adhesive layer.

In the present invention, especially when the base material is a base material containing a flat yarn cloth, the hand-cutting property can be further improved.

The present invention will be described in more detail below based on embodiments of the present invention, but the present invention is not limited to these embodiments.
In the present invention, "(meth)acryl" means acryl or methacryl, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate.
An acrylic resin is a resin obtained by polymerizing a copolymerization monomer containing at least one (meth)acrylate monomer.

A pressure-sensitive adhesive according to one embodiment of the present invention (hereinafter referred to as "this pressure-sensitive adhesive") contains an acrylic resin (A), an epoxy-based cross-linking agent (B), and an epoxy compound (C). Components contained in the pressure-sensitive adhesive will be described in order below.

<Acrylic resin (A)>
Acrylic resin (A) contains a carboxy group-containing monomer (a1) unit.

In addition to the carboxy group-containing monomer (a1) unit, the acrylic resin (A) preferably has a hydroxyl group-containing monomer (a2) unit from the viewpoint of improving adhesive strength. It has units (a3) to (a5). Each monomer unit will be described below.

[Monomer (a1) unit]
Examples of copolymerizable monomers for forming the carboxy group-containing monomer (a1) unit include (meth)acrylic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydro Phthalic acid, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxypropyl maleate, 2-( meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxypropylsuccinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, monomethyl itaconate and the like. Among them, (meth)acrylic acid is preferred. That is, the acrylic resin (A) preferably contains (meth)acrylic acid monomer units.

The content of the carboxy group-containing monomer (a1) units is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and still more preferably 1, based on the total acrylic resin (A). ~5% by mass. If the content is too small or too large, the adhesiveness tends to decrease.

In addition, the content ratio of (meth)acrylic acid monomer units in the carboxy group-containing monomer (a1) units is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass. % or more, particularly preferably 80 mass % or more. The upper limit is usually 100% by mass. If the (meth)acrylic acid monomer unit is too small, the adhesiveness tends to decrease.

[Monomer (a2) unit]
The acrylic resin (A) preferably has hydroxyl group-containing monomer (a2) units in addition to the monomer (a1) units.
Comonomers for forming the hydroxyl group-containing monomer (a2) units include, for example, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6- (meth)acrylic acid hydroxyalkyl esters such as hydroxyhexyl (meth)acrylate and 8-hydroxyoctyl (meth)acrylate, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate, diethylene glycol (meth)acrylate, polyethylene glycol Oxyalkylene-modified monomers such as (meth)acrylates, hydroxy group-containing (meth)acrylamides such as N-methylol (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-methylolpropane (meth)acrylamide, 2-acryloy Primary hydroxyl group-containing monomers such as loxyethyl-2-hydroxyethyl phthalate and allyl alcohol; 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate , 2-hydroxy-3-phenoxypropyl (meth)acrylate; and tertiary hydroxyl group-containing monomers such as 2,2-dimethyl-2-hydroxyethyl (meth)acrylate.

Among these, primary hydroxyl group-containing monomers are preferable in terms of excellent adhesive strength of the adhesive, more preferably (meth)acrylic acid hydroxyalkyl ester, still more preferably (meth) acrylic having an alkyl group having 2 to 8 carbon atoms Acid hydroxyalkyl esters, particularly preferably (meth)acrylic acid hydroxyalkyl esters having an alkyl group of 2 to 4 carbon atoms, specifically 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate. preferable.

The content of the hydroxyl group-containing monomer (a2) units is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, and still more preferably 0% of the total acrylic resin (A). 0.05 to 2% by mass. Too little or too much monomer (a2) units tend to reduce adhesiveness.

[Monomer (a3) unit]
The acrylic resin (A) desirably has a (meth)acrylate monomer (a3) unit having an alkyl group of 4 to 24 carbon atoms in addition to the above monomer (a1) units and (a2) units. As a copolymerization monomer for forming the (meth)acrylate monomer (a3) unit having an alkyl group having 4 to 24 carbon atoms, a (meth)acrylate monomer having an alkyl group having 4 to 7 carbon atoms (a3-1 ), and a (meth)acrylate monomer (a3-2) having an alkyl group having 8 to 24 carbon atoms.

Examples of the (meth)acrylate monomer (a3-1) having an alkyl group having 4 to 7 carbon atoms include n-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n- Hexyl (meth)acrylate and the like can be mentioned. Among them, n-butyl (meth)acrylate is preferred because it is easily available and economical.

Examples of the (meth)acrylate monomer (a3-2) having an alkyl group having 8 to 24 carbon atoms include 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl ( meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, isotridecyl (meth)acrylate, myristyl (meth)acrylate, isomyristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate ) acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate and the like. Among them, (meth)acrylates having an alkyl group of 8 to 12 carbon atoms are preferred because of their low polarity and low glass transition temperature, and 2-ethylhexyl (meth)acrylate is particularly preferred.

The content of the monomer (a3) unit is preferably 55 to 97% by mass, more preferably 70 to 95% by mass, and still more preferably 80 to 93% by mass of the total acrylic resin (A). . If the content is too small, the adhesiveness tends to decrease, and if it is too large, the adhesiveness tends to decrease and the gel fraction tends to decrease.

Further, the content ratio of the monomer (a3-1) unit to the monomer (a3-2) unit is (a3-1)/(a3-2) = 1/99 to 99/1 in mass ratio. is preferred, more preferably 20/80 to 80/20, still more preferably 30/70 to 70/30, particularly preferably 40/60 to 60/40, particularly preferably 45/55 to 55/45. If the content of the monomer (a3-1) unit is too small, the gel fraction tends to decrease, and if it is too large, the adhesiveness tends to decrease.

[Monomer (a4) unit]
Acrylic resin (A), in addition to the above monomers (a1) to (a3) units, further includes a (meth)acrylate monomer (a4-1) unit having an alkyl group having 1 to 3 carbon atoms, and a cyclic structure-containing monomer. (a4-2) units or vinyl ester monomers having 3 to 10 carbon atoms (a4-3) units, more preferably vinyl ester monomers having 3 to 10 carbon atoms (a4-3) units That is. The general term for the above (a4-1) to (a4-3) is the monomer (a4).

Examples of the copolymerizable monomer for forming the (meth)acrylate monomer (a4-1) unit having an alkyl group having 1 to 3 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, ) acrylates and the like. Among them, methyl (meth)acrylate and ethyl (meth)acrylate are preferred.

The copolymerization monomer for forming the cyclic structure-containing monomer (a4-2) unit is usually an acrylic monomer having a substituent containing a cyclic structure, for example, N- (meth) acryloylmorpholine, N- Vinylpyrrolidone, N-vinylcaprolactam, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, etc. Heterocyclic ring-containing (meth)acrylates having heterocyclic rings such as morpholine rings, piperidine rings, pyrrolidine rings, piperazine rings, etc. , phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenyldiethylene glycol (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, benzyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) ) acrylate, dicyclopentanyl (meth) acrylate, nonylphenol polyethylene glycol (meth) acrylate, nonylphenoxy polyethylene glycol (meth) acrylate, isobornyl (meth) acrylate, biphenyloxyethyl (meth) acrylate, others, styrene, α-methyl Styrene and the like can be mentioned. Among them, a heterocycle-containing (meth)acrylate having a morpholine ring is preferred because of its well-balanced properties, and N-(meth)acryloylmorpholine is particularly preferred from the viewpoints of availability and safety.

Examples of copolymerizable monomers for forming the vinyl ester monomer (a4-3) unit having 3 to 10 carbon atoms include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, iso vinyl butyrate, vinyl pivalate, and the like. Among them, vinyl acetate is preferable because of its easy availability.

The content of the monomer (a4) units is preferably 11% by mass or less, more preferably 10% by mass or less, and still more preferably 8% by mass or less based on the total acrylic resin (A). If the content of component (a4) is too high, the adhesiveness to the adherend tends to decrease. In addition, the lower limit of the content of the component (a4) is usually 0% by mass, preferably 1% by mass or more.

[Monomer (a5) unit]
Acrylic resin (A), in addition to the monomers (a1) to (a4) units, may optionally have other copolymerization monomer (a5) units, and other copolymerization monomers (a5 ) Examples of copolymerizable monomers for forming units include functional group-containing monomers such as acetoacetyl group-containing monomers, isocyanate group-containing monomers, glycidyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, and other copolymers. A polymerizable monomer can be mentioned.

Examples of the acetoacetyl group-containing monomer include 2-(acetoacetoxy)ethyl (meth)acrylate and allylacetoacetate.

Examples of the isocyanate group-containing monomer include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts thereof.

Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate and allylglycidyl (meth)acrylate.

Examples of the amino group-containing monomer include monomers having an ethylenically unsaturated double bond and an amino group (unsubstituted or substituted amino group), such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate. , N-alkylaminoalkyl (meth)aminoalkyl (meth)acrylates such as aminopropyl (meth)acrylate and aminoisopropyl (meth)acrylate and N-alkylaminoalkyl (meth)acrylates such as N-(t-butyl)aminoethyl (meth)acrylate ) monosubstituted amino group-containing (meth)acrylic acid esters such as acrylic acid ester; Disubstituted amino group-containing (meth)acrylic acid esters such as N,N-dialkylaminoalkyl (meth)acrylic acid esters such as N-dimethylaminopropyl; dialkylaminos such as N,N-dimethylaminopropyl (meth)acrylamide Alkyl (meth)acrylamides, quaternized salts of these amino group-containing monomers; amino group-containing styrenes such as p-aminostyrene; dialkylamino groups such as 3-(dimethylamino)styrene and dimethylaminomethylstyrene; styrenes; dialkylaminoalkyl vinyl ethers such as N,N-dimethylaminoethyl vinyl ether and N,N-diethylaminoethyl vinyl ether; allylamine, 4-diisopropylamino-1-butene, trans-2-butene-1,4-diamine , 2-vinyl-4,6-diamino-1,3,5-triazine and the like.

Examples of the amide group-containing monomer include monomers having an ethylenically unsaturated double bond and an amide group (a group having an amide bond), such as (meth)acrylamide; N-methyl(meth)acrylamide, N-ethyl (Meth)acrylamide, N-propyl (meth)acrylamide, N-isopropyl (meth)acrylamide, Nn-butyl (meth)acrylamide, N-isobutyl (meth)acrylamide, Ns-butyl (meth)acrylamide, N -t-butyl (meth)acrylamide, N-hexyl (meth)acrylamide, diacetone (meth)acrylamide, N,N'-methylenebis (meth)acrylamide, N-(1,1-dimethyl-3-oxobutyl) (meth) ) N-alkyl (meth)acrylamides such as acrylamide; N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dipropyl (meth)acrylamide, N,N-diisopropyl (meth) Acrylamide, N,N-di(n-butyl)(meth)acrylamide, N,N-diisobutyl(meth)acrylamide, N,N-di(s-butyl)(meth)acrylamide, N,N-di(t- butyl) (meth)acrylamide, N,N-dipentyl (meth)acrylamide, N,N-dihexyl (meth)acrylamide, N,N-diheptyl (meth)acrylamide, N,N-dioctyl (meth)acrylamide, N,N - N,N-dialkyl(meth)acrylamides such as diallyl(meth)acrylamide, N,N-ethylmethylacrylamide; dialkylaminoalkyl(meth)acrylamides such as N,N-dimethylaminopropyl(meth)acrylamide; N-vinyl Substituted amide group-containing monomers such as acetamide, N-vinylformamide, (meth)acrylamidoethylethylene urea, (meth)acrylamido-t-butylsulfonic acid; N-methoxymethyl (meth)acrylamide, N-(n-butoxymethyl) Alkoxy group-containing (meth)acrylamides such as (meth)acrylamide; quaternary salts of these amide group-containing monomers;

Other copolymerizable monomers include, for example, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxydiethyleneglycol (meth)acrylate, ethoxydiethyleneglycol (meth)acrylate, methoxypolyethyleneglycol (meth)acrylate. , polypropylene glycol-mono(meth)acrylate containing alkoxy or oxyalkylene groups; Acid dialkyl esters, acryl chloride, methyl vinyl ketone, allyltrimethylammonium chloride, dimethyl allyl vinyl ketone and the like.

Other copolymerizable monomers (a5) may be contained in an amount that does not impair the effects of the present invention, for example, 10% by mass or less, in order to adjust the physical properties according to the application. In addition, the lower limit of the content of the component (a5) is usually 0% by mass.

In one embodiment of the present invention, the acrylic resin (A) is obtained by polymerizing the monomer (a1), preferably the monomer (a2), and optionally the monomers (a3) to (a5). be done. That is, by such polymerization, an acrylic resin (A) having the above monomer (a1) units, preferably further monomer (a2) units, and optionally further monomer (a3) to (a5) units is obtained.
Incidentally, each of the monomers (a1) to (a5) as a copolymerizable monomer can be used alone or in combination of two or more. Each of these monomers (a1) to (a5) units is an acrylic resin ( A) may contain each alone or in combination of two or more.

In the above polymerization, solution polymerization is preferred because the acrylic resin (A) can be safely and stably produced with an arbitrary monomer composition.

Such solution polymerization is carried out according to a conventional method, for example, by mixing or dropping a copolymerization monomer such as the monomers (a1) to (a5) and a polymerization initiator into an organic solvent, and heating the mixture in a reflux state or at 50 to 98°C. for 0.1 to 20 hours. The acrylic resin (A) polymerized in an organic solvent is an organic solvent-based acrylic resin.

Examples of such polymerization initiators include azo polymerization initiators such as azobisisobutyronitrile and azobisdimethylvaleronitrile, which are ordinary radical polymerization initiators, benzoyl peroxide, lauroyl peroxide, and di-t-butyl peroxide. Specific examples thereof include peroxide polymerization initiators such as cumene hydroperoxide and the like. These may be used alone or in combination of two or more. Among them, an azo polymerization initiator is preferably used.
The amount of the polymerization initiator to be used is usually 0.001 to 5 parts by weight per 100 parts by weight of the copolymerizable monomer.

The acrylic resin (A) thus obtained preferably has a weight average molecular weight of 100,000 to 5,000,000, more preferably 300,000 to 1,500,000, still more preferably 400,000 to 900,000. If the weight average molecular weight is too small, the durability tends to decrease, and if it is too large, the adhesive strength tends to decrease.

Further, the degree of dispersion (weight average molecular weight/number average molecular weight) of the acrylic resin (A) is preferably 20 or less, more preferably 15 or less, still more preferably 10 or less, and particularly preferably 7 or less. If the degree of dispersion is too high, the durability of the pressure-sensitive adhesive layer is lowered, and foaming and the like tend to occur easily. In addition, the lower limit of the degree of dispersion is usually 1.1 in view of manufacturing limitations.

The weight-average molecular weight of the acrylic resin (A) is the weight-average molecular weight in terms of standard polystyrene molecular weight, and is measured by high-performance liquid chromatograph (Japan Waters Co., Ltd., "Waters 2695 (body)" and "Waters 2414 (detector)". ), column: Shodex GPC KF-806L (exclusion limit molecular weight: 2×10 ⁷ , separation range: 100 to 2×10 ⁷ , number of theoretical plates: 10000 plates/line, filler material: styrene-divinylbenzene copolymer, The particle size of the filler: 10 μm) is measured by using three in series, and the number average molecular weight can be measured by the same method.

The glass transition temperature (Tg) of the acrylic resin (A) is preferably -80 to -10°C, more preferably -70 to -10°C, and still more preferably -65 to -20°C. If the glass transition temperature is too high, the tack tends to be insufficient, and if it is too low, the heat resistance tends to decrease.

The glass transition temperature (Tg) is a value calculated by applying the glass transition temperature and mass fraction when each monomer constituting the acrylic resin (A) is a homopolymer to the following Fox formula. .

Ｔｇ： アクリル系樹脂（Ａ）のガラス転移温度（Ｋ）
Ｔｇａ： モノマーＡのホモポリマーのガラス転移温度（Ｋ）
Ｗａ： モノマーＡの質量分率
Ｔｇｂ： モノマーＢのホモポリマーのガラス転移温度（Ｋ）
Ｗｂ： モノマーＢの質量分率
Ｔｇｎ： モノマーＮのホモポリマーのガラス転移温度（Ｋ）
Ｗｎ： モノマーＮの質量分率
（Ｗａ＋Ｗｂ＋・・・＋Ｗｎ＝１）

Tg: Glass transition temperature (K) of acrylic resin (A)
Tga: Glass transition temperature of homopolymer of monomer A (K)
Wa: mass fraction of monomer A Tgb: glass transition temperature (K) of homopolymer of monomer B
Wb: mass fraction of monomer B Tgn: glass transition temperature (K) of homopolymer of monomer N
Wn: Mass fraction of monomer N (Wa+Wb+...+Wn=1)

Here, the glass transition temperature when the monomer constituting the acrylic resin (A) is a homopolymer is usually measured by a differential scanning calorimeter (DSC) by a method conforming to JIS K7121-1987 or JIS K 6240. The values given in the catalog and the catalog values are used.

The acrylic resin (A) is usually adjusted in viscosity with a solvent or the like, and applied as an acrylic resin (A) solution for coating. The viscosity of the acrylic resin (A) solution is preferably 500 to 20,000 mPa·s, more preferably 1,000 to 18,000 mPa·s, still more preferably 2,000 to 15,000 mPa·s from the viewpoint of ease of handling. If the viscosity is too high, the fluidity tends to be low and handling tends to be difficult. Incidentally, the concentration of the solution during coating is usually 10 to 70% by mass.

The solvent is not particularly limited as long as it dissolves the acrylic resin (A). Examples include ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, and ethyl acetoacetate; Ketone solvents such as methyl isobutyl ketone, aromatic solvents such as toluene and xylene, and alcohol solvents such as methanol, ethanol and propyl alcohol can be used. Among these, ethyl acetate, methyl ethyl ketone, and particularly ethyl acetate are preferably used in terms of solubility, drying property, price, and the like. These above solvents may be used alone, or two or more of them may be used in combination.

The viscosity of the acrylic resin (A) solution can be measured according to JIS K5400 (1990) 4.5.3 Rotational viscometer method.

The acrylic resin (A) is the main component of the present pressure-sensitive adhesive (or pressure-sensitive adhesive composition), and the content of the acrylic resin (A) is preferably 50% by mass or more of the entire pressure-sensitive adhesive. More preferably 60% by mass or more, still more preferably 70% by mass or more, particularly preferably 80% by mass or more, particularly preferably 90% by mass or more. The upper limit is usually 99.99% by mass.

<Epoxy-based cross-linking agent (B)>
This pressure-sensitive adhesive contains an epoxy-based cross-linking agent (B) in addition to the acrylic resin (A).

The above-mentioned epoxy-based cross-linking agent (B) refers to those that sufficiently react with carboxy groups under mild conditions without the addition of a catalyst. For example, aliphatic epoxy cross-linking agents such as diglycidylamine; 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine alicyclic epoxy cross-linking agents such as; aromatic epoxy cross-linking agents such as diglycidylaniline; 1,3,5-tris-(2,3-epoxybutyl)-isocyanurate; (3,4-epoxybutyl)-isocyanurate, 1,3,5-tris-(4,5-epoxypentyl)-isocyanurate, and other heterocyclic epoxy cross-linking agents. Epoxy-based cross-linking agents are preferred. These can be used alone or in combination of two or more.

The content of the epoxy-based cross-linking agent (B) is preferably 0.001 to 5 parts by mass, more preferably 0.005 to 1 part by mass, with respect to 100 parts by mass of the acrylic resin (A). More preferably, it is 0.01 to 0.1 parts by mass. If the content is too small, the gel fraction tends to decrease, and if it is too large, the adhesiveness to various adherends tends to decrease.

The above-mentioned epoxy-based cross-linking agent (B) can be used after being diluted with a solvent or the like, but the above content and content ratio indicate the actual content and content ratio of the cross-linking agent excluding the solvent and the like.

<Epoxy compound (C)>
This pressure-sensitive adhesive contains an epoxy compound (C) in addition to the above components (A) and (B).

As the epoxy compound (C), for example, it does not have a structure such as a tertiary amine skeleton that activates the epoxy group, and a high temperature is required to react with the carboxy group in the acrylic resin without adding a catalyst. refers to compounds that require

The epoxy compound (C) is preferably an epoxy compound having a gel fraction of 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, according to the following measurement conditions. In addition, a lower limit is 0 mass % normally.
<Measurement conditions>
A mixture obtained by adding 0.024 parts by mass of the epoxy compound (C) to 100 parts by mass of the acrylic resin (A) and mixing was applied to the film-like material so that the thickness after drying was 110 μm. After drying at °C for 5 minutes, the coated surface was adhered to the substrate, and the gel fraction of the mixture after standing at 40°C for 7 days.

A more preferable epoxy compound (C) is an epoxy compound having a gel fraction of 5% by mass or less under the following measurement conditions.
<Measurement conditions>
A mixture obtained by adding 1 part by mass of the epoxy compound (C) to 100 parts by mass of the acrylic resin (A) and mixing was applied to the film-like material so that the thickness after drying was 110 μm, and the mixture was heated at 80 ° C. After drying for 5 minutes, the coated surface was adhered to the substrate, and the gel fraction of the mixture after standing at 40°C for 7 days.

The gel fraction is a measure of the degree of cross-linking (degree of curing), and is calculated, for example, by the following method. That is, for a test piece obtained by applying a mixture of an acrylic resin (A) and an epoxy compound (C) to a film-like material, drying, and aging, a 200-mesh SUS wire mesh having a size that can wrap the test piece is prepared and the mass is measured. (1). The film-like material is peeled off from the test piece, wrapped in the SUS wire mesh described above, and the tape mass is measured together with the wire mesh (2). After being immersed in toluene kept at 23° C. for 48 hours, it is dried sufficiently and the weight of the test piece is measured together with the wire mesh (3). After immersion, the specimen is removed from the wire mesh, the remaining mixture is removed, and the substrate mass is measured (4). Subtraction is performed as shown in the following formula, and the mass percentage of the mixture after immersion to that before immersion is defined as the gel fraction.
[Formula] Gel fraction (%) = (mass of test piece after immersion including SUS wire mesh mass (3) - substrate mass (4) - SUS wire mesh mass (1)) / (SUS wire mesh mass Weight of test piece before immersion including (2) - Base material weight (4) - SUS wire mesh weight (1)) × 100

That is, the epoxy compound (C) is a compound that does not form a crosslinked structure even after being mixed with the acrylic resin (A) and undergoing a normal pressure-sensitive adhesive forming step, and has a gel fraction of more than 5% by mass. preferably not. In other words, the epoxy-based cross-linking agent (B) that forms a cross-linked structure with the acrylic resin (A) is excluded from the epoxy compound (C).

Examples of such epoxy compounds (C) include alcohol type epoxy compounds, glycol type epoxy compounds, bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, naphthalene type epoxy compounds, phenol novolac type epoxy compounds, cresol novolac type epoxy compounds, compounds, phenol aralkyl type epoxy compounds, biphenyl type epoxy compounds, triphenylmethane type epoxy compounds, dicyclopentadiene type epoxy compounds, glycidyl ester type epoxy compounds, polyfunctional phenol type epoxy compounds, aliphatic epoxy compounds, rubber-modified epoxy compounds, etc. and various epoxy compounds. These can be used alone or in combination of two or more. Among them, bisphenol A type epoxy compounds and phenol novolac type epoxy compounds are preferably used in terms of gel fraction.

Examples of bisphenol A type epoxy compounds include commercially available products such as EPON825, jER826, jER827, jER828, jER834, and jER1001 (manufactured by Mitsubishi Chemical Corporation), Epiclon 850 (manufactured by DIC Corporation), Epotote YD-128 (Nippon Steel Sumikin Chemical Co., Ltd.), DER-331, DER-332 (manufactured by Dow Chemical Japan), Bakelite EPR154, Bakelite EPR162, Bakelite EPR172, Bakelite EPR173, Bakelite EPR174 (manufactured by Bakelite AG) and the like. .

Examples of the phenol novolac type epoxy compounds include commercially available jER152 and jER154 (manufactured by Mitsubishi Chemical Corporation), Epiclon N-730A, Epiclon N-740, Epiclon N-770 and Epiclon N-775 (manufactured by DIC Corporation). made), etc.

Examples of rubber-modified epoxy compounds include commercially available ADEKA RESIN EPR series (EPR-1415-1, EPR-2000, EPR-2007, EPR-1630) (manufactured by ADEKA), EPON Resin 58005 and EPON Resin 58006. (manufactured by Momentive), Hypox series (Hypox RA 840, Hypox RA 1340, Hypox RF 1341) (manufactured by CVC Thermoset Specialties).

Examples of glycol-type epoxy compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, polypropylene glycol diglycidyl ether, butanediol diglycidyl ether, and hexanediol diglycidyl ether, which are commercially available. In terms of products, the Decanal EX-800 series (EX-810, EX-850, EX-821, EX-830) (manufactured by Nagase ChemteX Corporation), the Decanal EX-200 series (EX-211, EX-212, EX -214) (manufactured by Nagase ChemteX Corporation), Decanal EX-900 series (EX-920, EX-931), Epolite series (40E, 100E, 200E, 400E, 70P, 200P, 400P, 1500NP, 1600, 80 MF, 100 MF) (manufactured by Kyoeisha Chemical Co., Ltd.).

The epoxy equivalent of the epoxy compound (C) is preferably 110 g/eq or more, more preferably 150 g/eq or more. Epoxy equivalent is measured according to JIS K7236.

The epoxy compound (C) may be used alone, or two or more thereof may be used in any combination and ratio.

The content of the epoxy compound (C) is preferably 0.005 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and still more preferably 100 parts by mass of the acrylic resin (A). is 0.05 to 1 part by mass. If the content is too small, the gel fraction after wet heat treatment tends to decrease, and if it is too large, the adhesiveness to various adherends tends to decrease.

The total amount of the content of the epoxy-based cross-linking agent (B) and the content of the epoxy compound (C) is preferably 0.006 to 15 parts by mass with respect to 100 parts by mass of the acrylic resin (A). , more preferably 0.01 to 5 parts by mass, more preferably 0.03 to 1 part by mass. If the content is too small, the holding power tends to decrease, and if it is too large, the adhesiveness to various adherends tends to decrease.

Although it is not clear why the pressure-sensitive adhesive containing the epoxy compound (C) can suppress the decrease in the gel fraction after wet heat treatment, the cross-linking point between the acrylic resin (A) and the epoxy cross-linking agent (B) is Either the epoxy compound (C) inhibits decomposition by the wet heat treatment, or the acrylic resin (A) and the epoxy compound (C) form a strong bond under the conditions of the wet heat treatment, or both. It is possible that something is happening.

The present adhesive (or adhesive composition) contains, as other components, a resin component other than (A) to (C), a tackifier, a polymerization inhibitor, an antioxidant, as long as the effects of the present invention are not impaired. agents, corrosion inhibitors, cross-linking accelerators, radical generators, peroxides, UV absorbers, plasticizers, pigments, stabilizers, fillers, various additives such as radical scavengers, metal and resin particles, etc. can do. These can be used alone or in combination of two or more. In addition to the above, the adhesive may contain a small amount of impurities contained in raw materials for manufacturing the constituent components of the present pressure-sensitive adhesive.

The content of the other components is preferably 5 parts by mass or less, more preferably 1 part by mass or less, and still more preferably 0.5 parts by mass or less with respect to 100 parts by mass of the acrylic resin (A). . The lower limit is usually 0 parts by mass. If the content is too large, the compatibility with the acrylic resin (A) tends to decrease, resulting in a decrease in durability. However, with respect to additives (pigments, fillers, metals, resin particles, etc.) that do not exhibit their effects in the above content, an appropriate amount is added within a range that does not impede the effects of the present invention while exhibiting the effects of the additives. sometimes.

As the tackifier, a resin that exhibits compatibility with the acrylic resin (A) is used. be done. These tackifiers may be used alone or in combination of two or more. Among these, rosin-based resins, terpene-based resins, and petroleum-based resins are preferred, and rosin-based resins are preferred in terms of efficiently improving adhesive strength.

As the rosin-based resin, for example, a raw rosin is hydrogenated (hydrogenated), disproportionated, dimerized, or acid-added, and then esterified with glycerin or pentaerythritol. The softening point of the rosin ester resin is preferably 70 to 130°C, more preferably 75 to 90°C.

In addition to the acrylic resin (A), the epoxy-based cross-linking agent (B) and the epoxy compound (C), as described above, the adhesive (or adhesive composition) may contain other components as necessary. contains. The pressure-sensitive adhesive or pressure-sensitive adhesive composition in which the acrylic resin (A) is an organic solvent-based acrylic resin is an organic solvent-based pressure-sensitive adhesive or an organic solvent-based pressure-sensitive adhesive composition.
A PSA composition is obtained by mixing each of the above components, and the PSA is obtained by cross-linking this PSA composition. And this adhesive can be applied to various substrates and used as an adhesive for adhesive tapes. In particular, since it has a high gel fraction even after wet heat treatment assuming long-term storage, it can be suitably used as an adhesive for adhesive tapes for airtight and waterproof applications.

<Adhesive tape>
A pressure-sensitive adhesive tape according to one embodiment of the present invention (hereinafter referred to as "the present pressure-sensitive adhesive tape") contains, as a pressure-sensitive adhesive layer, a pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition. Specifically, the pressure-sensitive adhesive composition is dissolved in a solvent such as ethyl acetate to prepare a pressure-sensitive adhesive composition solution for coating so that the solid content concentration is 10 to 70% by mass. By coating the solution on at least one side of the base material and drying it, an adhesive tape having an adhesive on at least one side of the base material can be obtained.

As a method for manufacturing such an adhesive tape, a known general method for manufacturing an adhesive tape may be used. For example, an adhesive is applied to one surface of a base material, dried, and released on the surface of the formed adhesive layer. It can be manufactured by a method of stacking a liner, or a method of coating and drying an adhesive on one side of a release liner and stacking a substrate on the surface of the formed adhesive layer. Among them, the method of applying an adhesive to one surface of the release liner, drying it, and stacking the base material on the surface of the adhesive layer thus formed is preferable from the point of view of handling and the like.

In addition, the above-mentioned substrate is preferably one that is hand-cuttable, and the surface of the hand-cuttable substrate is subjected to, for example, physical treatments such as corona discharge treatment and plasma treatment, chemical treatments such as undercoating treatment, and the like. A known and commonly used surface treatment may be applied as appropriate.

The base material is not particularly limited as long as it is a conventionally known base material. A laminated film in which a plastic film is laminated on a yarn cloth, or the like can be mentioned. These substrates can be used alone or in combination of two or more. Among them, those containing a flat yarn cloth are preferable from the viewpoint of high tensile strength in the longitudinal direction and excellent hand tearability.

Flat yarn cloth is a woven fabric made by weaving flat yarns that are strong by cutting a polyethylene or polypropylene film called flat yarn into strips and stretching them. A flat yarn that intersects laterally is fixed by heat-sealing the intersecting portion so as not to be misaligned. As the material of the flat yarn, olefin resins such as polyethylene and polypropylene are preferable, polyethylene is more preferable, and high-density polyethylene is particularly preferable.

It is preferable to use a base material in which a plastic film is laminated to a flat yarn cloth, since stable adhesive strength and releasability can be obtained. In the case of double-sided adhesive tape, having a plastic film prevents the adhesive on one side from passing through the base material and mixing with the adhesive on the other side, or prevents the adhesive layer on one side from being added. This is thought to be because agents such as cross-linking agents, flame retardants, and plasticizers can be prevented from migrating to the pressure-sensitive adhesive layer on the other side. In addition, by laminating the plastic film on the flat yarn cloth, the breaking point is smoothly propagated, and the hand tearability is improved, and the straightness of the broken surface is improved. As the plastic film, a polyethylene film is preferable, and a low-density polyethylene film is more preferable.

Further, it is preferable that the base material in which the plastic film is laminated to the flat yarn cloth is lightweight, and the plastic film is preferably a thin film. The thickness of the plastic film is preferably 10-80 μm. The plastic film may be laminated on only one side of the flat yarn cloth or may be laminated on both sides. As for the method of laminating the film to the flat yarn cloth, extrusion lamination is preferable because it can reduce the weight without using an adhesive.

The thickness of the substrate including the flat yarn cloth is preferably 10-200 μm, more preferably 50-100 μm, still more preferably 60-90 μm. If the thickness is too thin, although the hand-cutting property is improved, there is a tendency for defects such as wrinkles to be mixed in during the production of the adhesive tape. is required, and there is a tendency for the hand-cutting property to decrease.

Examples of the release liner include plastic films made of plastics such as polyolefin resins such as polyethylene, polyester resins such as polyethylene terephthalate, vinyl acetate resins, polyimide resins, fluorine resins, and cellophane; kraft paper, Japanese paper, and the like. rubber sheets made of natural rubber, butyl rubber, etc.; foam sheets made by foaming polyurethane, polychloroprene rubber, etc.; metal foils such as aluminum foil, copper foil, etc.; In addition, they may be subjected to surface treatment such as corona treatment on one side or both sides thereof.
Examples of the release liner include glassine paper, kraft paper, clay-coated paper laminated with a film of polyethylene or the like, paper coated with a resin such as polyvinyl alcohol or acrylic acid ester copolymer, polyester or polypropylene. A release agent such as fluorine-based resin or silicone-based resin may also be applied to a synthetic resin film or the like.
These can be used alone or in combination of two or more.

Among these, a release liner made of paper is preferable because it can be easily torn by hand, and the basis weight of the base paper is preferably 40 to 120 g/m ² , more preferably 50 to 80 g/m ² . is particularly preferred. Further, the thickness of the release liner is preferably 40-180 μm, more preferably 60-140 μm, and still more preferably 80-120 μm. If the thickness is too thin, it tends to be wrinkled during winding, making production difficult.

As a coating device used for coating one surface of the base material or the release liner with the pressure-sensitive adhesive, a commonly used coating device may be used, such as a roll knife coater, a die coater, and a roll coater. , bar coater, gravure roll coater, reverse roll coater, dipping, blade coater and the like.

The thickness of the pressure-sensitive adhesive layer after drying is preferably 5 to 200 μm, more preferably 10 to 150 μm, still more preferably 15 to 130 μm.
If the thickness is too thick, it tends to be difficult to apply the adhesive, and if it is too thin, there is a tendency that sufficient adhesive strength cannot be obtained.

Moreover, this adhesive tape may be a single-sided adhesive tape or a double-sided adhesive tape. Moreover, the pressure-sensitive adhesive layers of the double-sided pressure-sensitive adhesive tape may be the same pressure-sensitive adhesive layer, or may be pressure-sensitive adhesive layers having different compositions.

When laminating a release liner on the adhesive layer of a double-sided adhesive tape, each release liner should be selected so that the peel strength of the release liner laminated on both sides is different in order to improve workability. is preferred. For example, if the release liner on the first side of the double-sided pressure-sensitive adhesive tape has a lower peel strength than the release liner on the next side, workability is improved.

The above drying conditions are such that the solvent and residual monomers in the adhesive are dried and removed during drying, and the functional group of the acrylic resin (A) reacts with the epoxy crosslinking agent (B) to form a crosslinked structure. Any condition is acceptable as long as it is possible. Preferred drying conditions are, for example, 60 to 120° C. for 1 to 5 minutes. After drying, aging is performed with the pressure-sensitive adhesive layer sandwiched between sheet-like substrates, and the cross-linking reaction can be further advanced.

The pressure-sensitive adhesive tape may be in the form of a roll, sheet, or may be processed into various shapes.
When the pressure-sensitive adhesive tape is a double-sided pressure-sensitive adhesive tape and is in a sheet state, release liners are preferably provided on both surfaces of the two pressure-sensitive adhesive layers. A release liner is preferably provided on only one surface of the two pressure-sensitive adhesive layers.

Thus, the present pressure-sensitive adhesive tape is obtained, and the present pressure-sensitive adhesive tape has a high gel fraction even after wet heat treatment assuming long-term storage. Furthermore, when a base film that can be cut by hand is used as the base film, the tape can be easily cut by hand at any position without using a tape cutter or the like in the width direction of the tape. It becomes especially useful as an adhesive tape.

The gel fraction of the adhesive in the present adhesive tape is preferably 30% by mass or more, more preferably 35% by mass or more, and still more preferably 40% by mass or more in terms of suppressing dripping and bleeding of the adhesive layer. is. On the other hand, it is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. If the gel fraction is too low, the adhesive layer tends to sag or ooze out, and if it is too high, the adhesiveness tends to decrease.
In addition, in adjusting the gel fraction of the adhesive to the above range, it is achieved by adjusting the type and amount of the epoxy-based cross-linking agent (B).

The gel fraction of the pressure-sensitive adhesive after the present pressure-sensitive adhesive tape is placed in a constant temperature and humidity chamber adjusted to 60° C. and 90% RH for 4 weeks and subjected to wet heat treatment is also preferably 30% by mass or more, more preferably 35%. It is at least 40% by mass, more preferably at least 40% by mass. On the other hand, it is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less.

The gel fraction is a measure of the degree of crosslinking (degree of curing), and can be measured, for example, by the method described in Examples below.

As for the adhesive strength of the adhesive in the adhesive tape, it is preferable that the 180° peel strength according to JIS Z0237 is 1 to 100 N/25 mm with respect to the adherend that is usually used.

As for the adhesive strength of the adhesive in the adhesive tape, when a SUS304 steel test plate is used as the adherend, the 180° peel strength is preferably 25 N/25 mm or more, more preferably 30 N/25 mm or more. More preferably, it is 35 N/25 mm or more. Incidentally, the normal upper limit is about 100 N/25 mm.

Since the adhesive strength varies depending on the composition (material), surface condition (surface roughness) of the adherend, treatment (cleaning) conditions, etc., the peel strength is not limited to the range described above.

The measurement of such adhesive strength is a value measured according to JIS Z0237.

When the test piece is a double-sided adhesive tape, the non-tested adhesive surface can be covered with a polyethylene terephthalate film (Lumirror S10 manufactured by Toray Industries, Inc.) having a nominal thickness of 25 μm specified in JIS C2318.

In addition, the present adhesive tape preferably has a high tensile strength, and when attached to an adherend or the like, it is required to have the strength necessary to pull it without being distorted or to remove it for position correction. The tensile strength of the adhesive tape is preferably 20 N/25 mm or more, more preferably 30 N/25 mm or more, particularly 50 N/25 mm or more. The upper limit of tensile strength is usually 250N/25mm. A double-sided pressure-sensitive adhesive tape with high tensile strength can be achieved by using a film having a tensile strength equal to or greater than the tensile strength of the target pressure-sensitive adhesive tape.

This adhesive tape includes, for example, packaging tapes such as kraft tape, OPP tape, cloth adhesive tape, cellophane adhesive tape for light packaging, foam tape for automobiles, damping sheet, housing curing tape, soundproof seal, and double-sided tape for fixing carpets. Tape, vinyl tape for electrical insulation, anti-corrosion outdoor tape, indoor display tape, anti-slip tape, airtight and waterproof adhesive tape, adhesive base material for medical first-aid plasters, surgical tape, adhesive bandage, tape for electrical and electronic equipment, It can be used in a wide range of applications such as double-sided optical tape, semiconductor dicing tape, heat conductive tape, heat resistant tape, and conductive tape.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples, "parts" and "%" mean mass standards.

First, various acrylic resins (A) were prepared as follows.
The weight average molecular weight, dispersity, glass transition temperature and viscosity of the acrylic resin (A) were measured according to the methods described above.

<Acrylic resin (A)>
Prior to the production of acrylic resin (A), the following were prepared as copolymerizable monomers (a) used for production.
(a1) component Acrylic acid (AAc)
(a2) component 2-hydroxyethyl methacrylate (HEMA)
(a3-1) component n-butyl acrylate (BA)
(a3-2) component 2-ethylhexyl acrylate (2EHA)
(a4) component vinyl acetate

[Production of acrylic resin (A-1)]
In a reactor equipped with a thermometer, stirrer and reflux condenser, 2.9 parts of acrylic acid (a1), 0.1 part of 2-hydroxyethyl methacrylate (a2), n-butyl acrylate ( a3-1) 46 parts, 2-ethylhexyl acrylate (a3-2) 46 parts, vinyl acetate (a4) 5 parts, further ethyl acetate 40 parts as a solvent, and azobisisobutyronitrile 0.1 part as a polymerization initiator was charged, the temperature was raised while stirring, and the mixture was polymerized at the reflux temperature of ethyl acetate (mixture) for 9 hours, then the reaction mixture was diluted with toluene to obtain a 45% solids acrylic resin (A-1) solution. got
The obtained acrylic resin (A-1) had a weight average molecular weight of 600,000, a dispersity of 4.8, a viscosity of 7500 mPa·s/25°C, and a glass transition temperature of -57°C.

[Production of acrylic resin (A-2)]
In a reactor equipped with a thermometer, a stirrer and a reflux condenser, 1.8 parts of acrylic acid (a1), 93.2 parts of 2-ethylhexyl acrylate (a3-2), vinyl acetate (a4 ), 40 parts of ethyl acetate as a solvent, and 0.05 part of azobisisobutyronitrile as a polymerization initiator were charged, heated with stirring, and polymerized at the reflux temperature of the ethyl acetate (mixture) for 9 hours. After that, 3.5 parts of Super Ester A-75 (manufactured by Arakawa Chemical Co., Ltd., rosin ester resin, softening point 80 ° C.) as a tackifier was charged, and the reaction mixture was diluted with toluene to obtain an acrylic resin having a solid content of 53%. A system resin (A-2) solution was obtained.
The obtained acrylic resin (A-2) had a weight average molecular weight of 500,000, a dispersity of 4.5, a viscosity of 10000 mPa·s/25°C, and a glass transition temperature of -65°C.

<Epoxy-based cross-linking agent (B)>
・Mitsubishi Gas Chemical Co., Ltd., Tetrad C (1,3-bis (N, N'-diglycidylaminomethyl) cyclohexane)

<Epoxy compound (C)>
· (C1) component: manufactured by Mitsubishi Chemical Corporation, jER828, epoxy equivalent: 189 g / eq (bisphenol A type epoxy compound)
· (C2) component: manufactured by Mitsubishi Chemical Corporation, jER154, epoxy equivalent: 178 g / eq (phenol novolac type epoxy compound)
・ (C3) component: EX-810 manufactured by Nagase ChemteX Corporation, epoxy equivalent: 113 g / eq (ethylene glycol diglycidyl ether)

<Example 1>
[Preparation of adhesive tape]
Per 100 parts of the solid content of the acrylic resin (A-1) prepared in Production Example 1, 0.013 parts of the epoxy cross-linking agent (B) (manufactured by Mitsubishi Gas Chemical Co., Ltd., "Tetrad C"), an epoxy compound As (C), 0.5 parts of (C1) ("jER828" manufactured by Mitsubishi Chemical Co., Ltd.) and an appropriate amount of ethyl acetate are added and mixed until uniform, and a paper release liner (manufactured by Shinomura Chemical Co., " SS-70-SBX”) using an applicator so that the thickness after coating was 110 μm, and dried at 80° C. for 5 minutes to produce a paper release liner with an adhesive layer.
Then, the pressure-sensitive adhesive surface of the paper release liner with the pressure-sensitive adhesive layer is a base material including a flat yarn cloth as a base material having hand tearability, and a normal type base material in which polyethylene films are laminated on both sides of a polyethylene flat yarn cloth. (manufactured by Diatex Co., Ltd.: mass 112 g/m ² , thickness 130 μm), and then subjected to heat aging treatment in a 40° C. dryer for 7 days to obtain an adhesive tape of Example 1.

<Examples 2 to 5>
Adhesive tapes of Examples 2 to 5 were obtained in the same manner as in Example 1 except that the acrylic resin (A) and epoxy compound (C) in the adhesive were changed as shown in Table 1.

<Comparative Example 1>
A pressure-sensitive adhesive tape of Comparative Example 1 was obtained in the same manner as in Example 1 above, except that the epoxy compound (C) was not contained in the pressure-sensitive adhesive.

<Comparative Examples 2 to 4>
In Example 1 above, the adhesive layer did not contain the epoxy-based cross-linking agent (B), and as the epoxy compound (C), components (C1), (C2) and (C3) were used, respectively, as shown in Table 1. Adhesive tapes of Comparative Examples 2 to 4 were obtained in the same manner except for changing to .

<Comparative Example 5>
The adhesive tape of Comparative Example 5 was prepared in the same manner as in Example 1 above, except that the acrylic resin (A-2) was used as the acrylic resin (A) and the epoxy compound (C) was not contained in the adhesive. Obtained.

<Comparative Examples 6 and 7>
In the above Comparative Example 4, the adhesive layer did not contain the epoxy-based cross-linking agent (B), and as the epoxy compound (C), the components (C1) and (C2) were used, respectively, and changed as shown in Table 1. was performed in the same manner to obtain pressure-sensitive adhesive tapes of Comparative Examples 6 and 7.

The following evaluation was performed using the obtained said adhesive tape. The evaluation results are shown in Table 1 below.

<Gel fraction>
A 200-mesh SUS wire mesh having a size capable of wrapping the adhesive tape is prepared and its mass is measured (1). The paper release liner is peeled off from the adhesive tape, wrapped with the SUS wire mesh described above, and the weight of the tape is measured together with the wire mesh (2). After being immersed in toluene maintained at 23° C. for 48 hours, the tape is thoroughly dried and the weight of the tape is measured together with the wire mesh (3). The tape after immersion is taken out from the wire mesh, and after removing the remaining adhesive layer, the substrate mass is measured (4). Subtraction was performed as shown in the following formula, and the mass percentage of the adhesive component after immersion to that before immersion was defined as the gel fraction.
[Formula] Gel fraction (%) = (Tape mass after immersion including SUS wire mesh mass (3) - Base material mass (4) - SUS wire mesh mass (1)) / (Immersion including SUS wire mesh mass Previous tape mass (2) - Base material mass (4) - SUS wire mesh mass (1)) × 100

<Gel fraction after wet heat treatment>
After the pressure-sensitive adhesive tape was placed in a constant temperature and humidity chamber adjusted to 60° C. and 90% RH for 4 weeks for wet heat treatment, the gel fraction was measured in the same manner as described above.

From the results in Table 1 above, it can be seen that in Examples 1 to 5 containing an acrylic resin (A) containing a carboxy group-containing monomer unit, an epoxy cross-linking agent (B), and an epoxy compound (C), the gel fraction after wet heat treatment was is not much different from the initial gel fraction, and it can be seen that the decrease in gel fraction was suppressed. A pressure-sensitive adhesive tape whose gel fraction does not decrease can suppress dripping and seepage of the pressure-sensitive adhesive layer even after wet heat treatment.

On the other hand, in Comparative Examples 1 and 5, which do not contain the epoxy compound (C), the initial gel fraction is normal, but the gel fraction after the wet heat treatment is greatly reduced. Adhesive tapes with a greatly reduced gel fraction are thought to cause the adhesive layer to drip or seep out after wet heat treatment.

Comparative Examples 2 to 4, 6, and 7, which do not contain the epoxy-based cross-linking agent (B), have an extremely low initial gel fraction of less than 2%, and no cross-linking between the epoxy compound (C) and the acrylic resin (A). It can be seen that the reaction has hardly progressed. In addition, the initial gel fractions of the adhesives of Comparative Examples 2 and 6 containing 1 part of the epoxy compound C1 were 1.2% and 0.8%, respectively, and the content was reduced to 0.024 parts. The initial gel fractions of the pressure-sensitive adhesives of Comparative Examples 3 and 7 containing 1 part of epoxy compound C2 were 0.9% and 0.7%, respectively. Even if the content is reduced to 0.024 parts, it is clear that the gel fraction is 5% or less, and the initial gel content of the pressure-sensitive adhesive of Comparative Example 4 containing 1 part of epoxy compound C3 The ratio is 1.1%, and it is clear that even if the content is reduced to 0.024 parts, the gel fraction will be 5% or less. Therefore, in Comparative Examples 2 to 4, 6, and 7, dripping and bleeding of the pressure-sensitive adhesive layer are thought to occur from the beginning.

An epoxy compound (C) having no cross-linking reactivity with the acrylic resin (A) was added to the pressure-sensitive adhesive containing the epoxy-based cross-linking agent (B) whose gel fraction was lowered by wet heat treatment as in Comparative Examples 1 and 5. By containing, it is an unexpected effect that it is possible to suppress the decrease in gel fraction due to wet heat treatment, which suppresses the decrease in gel fraction even after long-term storage, and the adhesive layer does not drip or seep out. It is possible to provide a high-performance adhesive that does not generate.

In Examples 1 to 5, since flat yarn cloth was used as the base material, they were excellent in hand tearability.

Since this adhesive can suppress the decrease in the gel fraction after wet heat treatment assuming long-term storage, it is excellent as an adhesive used for the adhesive layer of the adhesive tape, and is highly expected.

Claims (6)

A pressure-sensitive adhesive comprising an acrylic resin (A), an epoxy cross-linking agent (B), and an epoxy compound (C), wherein the acrylic resin (A) contains carboxy group-containing monomer (a1) units. 2. The pressure-sensitive adhesive according to claim 1, wherein the epoxy compound (C) has a gel fraction of 5% by mass or less under the following measurement conditions.
<Measurement conditions>
A mixture obtained by adding 0.024 parts by mass of the epoxy compound (C) to 100 parts by mass of the acrylic resin (A) and mixing was applied to the film-like material so that the thickness after drying was 110 μm. After drying at °C for 5 minutes, the coated surface was adhered to the substrate, and the gel fraction of the mixture after standing at 40°C for 7 days. 3. The pressure-sensitive adhesive according to claim 1, wherein the carboxy group-containing monomer (a1) unit in the acrylic resin (A) is 0.1 to 20% by mass. The adhesive according to any one of claims 1 to 3, wherein the carboxy group-containing monomer (a1) is a (meth)acrylic acid monomer. An adhesive tape having the adhesive according to any one of claims 1 to 4 on at least one side of a substrate. 6. The adhesive tape of Claim 5, wherein the substrate comprises a flat yarn cloth.