JP7275650B2 - Adhesive composition for difficult-to-adhere adherends, adhesive for difficult-to-adhere adherends, and adhesive tape for difficult-to-adhere adherends - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition for difficult-to-adhere adherends, more specifically, highly polar adherends, low-polar adherends, rubber-based difficult-to-adhere adherends, especially ethylene propylene diene rubber ( The present invention relates to a pressure-sensitive adhesive composition for difficult-to-bond adherends having high adhesion to EPDM), and a pressure-sensitive adhesive for difficult-to-bond adherends and a pressure-sensitive adhesive tape for difficult-to-bond adherends using the same.

Conventionally, adhesives and adhesive tapes using acrylic resins have been used, for example, for packaging tapes such as kraft tape, OPP (Oriented Poly Propylene) tape, cloth adhesive tape, cellophane adhesive tape for light packaging, temporary fixing tape, automobile foam tape, damping sheet, flame-retardant adhesive tape, removable double-sided tape, housing curing tape, soundproof seal, double-sided tape for fixing carpet, temporary fixing tape, vinyl tape for electrical insulation, outdoor anti-corrosion tape, indoor display Tapes, anti-slip tapes, various masking tapes, various surface protection tapes, airtight and waterproof adhesive tapes, adhesive base materials for medical first-aid bandages, surgical tapes, adhesive bandages, tapes for electrical and electronic equipment, double-sided optical tapes, It is used in a wide range of applications such as surface protection films, dicing tapes for semiconductors, heat conductive tapes, heat resistant tapes, and conductive tapes.

As the acrylic resin used for the pressure-sensitive adhesives and pressure-sensitive adhesive tapes, acrylic resins obtained by copolymerizing alkyl (meth)acrylate as a main component are generally used. Also known are acrylic resins using a carboxy group-containing monomer as a copolymerization component in order to improve adhesiveness to adherends.

Furthermore, in order to improve adhesion to adherends, it has been proposed to use an acrylic acid adduct having a specific structure as a carboxy group-containing monomer (see, for example, Patent Documents 1 to 3).

JP-A-2-196879 JP 2008-127431 A Japanese Unexamined Patent Application Publication No. 2014-40500

However, in the technique disclosed in Patent Document 1, by containing a specific acrylic acid adduct as a copolymer component in a relatively large amount, the adhesive strength to adherends with high polarity and adherends with low polarity is improved. However, polypropylene is specifically evaluated as an adherend with low polarity, and it is evaluated for difficult-to-adhere adherends such as ethylene propylene diene rubber (EPDM), which is difficult to improve adhesive strength. not

In the technique disclosed in Patent Document 2, an acrylic resin having an acid value of 1 to 50 mgKOH/g, a hydroxyl value of 10 to 60 mgKOH/g, and a number average molecular weight of 50,000 to 500,000, which is obtained by copolymerizing an acrylic acid adduct, and a poly In a pressure-sensitive adhesive composition containing an isocyanate compound, it is described that a pressure-sensitive adhesive composition having excellent tackiness/adhesive strength retention over time, moist heat resistance, heat resistance, and rework adhesiveness can be obtained. The content of the acrylic acid adduct is relatively small, at 1% by weight, based on the copolymerization component. Moreover, the adherend in Patent Document 2 adheres to a glass substrate or the like, and is different from a difficult-to-adhere adherend.

In the technology disclosed in Patent Document 3, an acrylic resin (A ), a solvent (B) and a cross-linking agent (C), wherein the (meth)acrylic monomer having a carboxy group contains (meth)acrylic acid and 2 to 6 carbonyl groups When containing a (meth) acrylic monomer having a range of, it is described that a pressure-sensitive adhesive with little decrease in adhesive strength and holding power even in a high-temperature environment can be obtained, but difficult-to-adhere adherends Adhesive strength and holding power to the adhesive were not taken into consideration, and were still unsatisfactory.

In general, adhesive tapes using acrylic resins show excellent adhesion to adherends with high polarity, but they are difficult to adhere to rubber-based adherends, especially ethylene propylene diene rubber (EPDM). It does not exhibit sufficient adhesion to adherents with low polarity.
From this, polymer roof sheet materials (for example, sheets made of difficult-to-bond members such as ethylene propylene diene rubber (EPDM), butyl rubber (IIR), chloroprene rubber (CR), thermoplastic polyolefin rubber, modified asphalt, and polychlorinated When using adhesive tape for the purpose of airtightness and waterproofing of seams such as vinyl, sheets made of chlorinated polyethylene, etc., adhesive tape using butyl rubber and asphalt with high adhesion to these difficult-to-adhere adherends is used. However, adhesive tapes using butyl rubber and adhesive tapes using asphalt have poor durability and heat resistance. There are problems such as slippage. Moreover, tapes using conventional acrylic pressure-sensitive adhesive compositions have hardly been used because of their poor adhesiveness to difficult-to-adhere adherends such as polymer roof sheet materials. However, from the market, it has the same adhesiveness as adhesive tapes using butyl rubber and adhesive tapes using asphalt to difficult-to-adhere adherends such as polymer roof sheet materials, and has improved holding power. A tape using such an acrylic pressure-sensitive adhesive composition is desired.
Further, the pressure-sensitive adhesive tape is required to strongly adhere to low-polarity difficult-to-adhere adherends such as EPDM, and to have a high holding power so that the sheet fixed with the tape does not shift.

Therefore, in the present invention, under such a background, it is applied to difficult-to-adhere adherends such as ethylene propylene diene rubber (EPDM), butyl rubber (IIR), chloroprene rubber (CR), thermoplastic polyolefin rubber and modified asphalt. It is an object of the present invention to provide a PSA composition for difficult-to-adhere adherends that firmly adheres to a substrate and has high holding power, and is particularly useful for ethylene propylene diene rubber (EPDM). be.

However, as a result of extensive research in view of such circumstances, the present inventors have found that in a pressure-sensitive adhesive composition using an acrylic resin, a specific terminal carboxy group-containing monomer and ( We have found that when meth)acrylic acid is contained, a pressure-sensitive adhesive composition that strongly adheres to rubber-based adherends with poor adhesion, especially to difficult-to-adhere adherends such as EPDM, has been found. completed the invention.

That is, the present invention provides an acrylic resin ( A first aspect of the present invention is a pressure-sensitive adhesive composition for difficult-to-bond adherends containing A).

[Formula] CH ₂ =CR ¹ --CO--O--(R ² --COO--) _n H (1)
(Here, R ¹ is hydrogen or a methyl group, R ² is a saturated aliphatic, unsaturated aliphatic, aromatic, saturated alicyclic, or divalent unsaturated alicyclic hydrocarbon, n is 1 or more positive number.)

Further, the present invention provides, as a second aspect, a pressure-sensitive adhesive for difficult-to-bond adherends obtained by cross-linking the pressure-sensitive adhesive composition for difficult-to-bond adherends according to the first aspect. A third gist of the present invention is a pressure-sensitive adhesive tape for difficult-to-bond adherends, in which a pressure-sensitive adhesive for adherends is formed on a base material.

It is generally known that the adhesive strength is improved by using the terminal carboxyl group-containing monomer (a1) represented by the general formula (1) as a copolymer component in the pressure-sensitive adhesive composition. However, by including such a terminal carboxyl group-containing monomer (a1), it is feared that the holding power and the like will usually decrease due to the extension of the distance of the cross-linking points, etc. Coexistence was considered difficult. However, in the present invention, when a difficult-to-adhere adherend such as a rubber-based adherend, especially ethylene propylene diene rubber (EPDM), is used as the adherend, acrylic It has been found that the use of a base resin unexpectedly results in a pressure-sensitive adhesive composition having excellent adhesiveness without lowering the holding power.

The present invention provides an acrylic resin (A) obtained by copolymerizing a copolymer component (a) containing a terminal carboxy group-containing monomer (a1) and (meth)acrylic acid (a2) represented by the following general formula (1): Since it is a pressure-sensitive adhesive composition for difficult-to-adhere adherends containing, it has good adhesion to rubber-based difficult-to-adhere adherends, especially to difficult-to-adhere adherends such as EPDM. It also has excellent holding power. Therefore, it is useful as various pressure-sensitive adhesives and pressure-sensitive adhesive tapes used for difficult-to-adhere adherends, and can be particularly suitably used as pressure-sensitive adhesive tapes for fixing EPDM sheets and the like used in buildings and the like.
[Formula] CH ₂ =CR ¹ --CO--O--(R ² --COO--) _n H (1)
(Here, R ¹ is hydrogen or a methyl group, R ² is a saturated aliphatic, unsaturated aliphatic, aromatic, saturated alicyclic, or divalent unsaturated alicyclic hydrocarbon, n is 1 or more positive number.)

Among the present invention, in particular, the acrylic resin (A) is an acrylic resin obtained by copolymerizing a copolymer component (a) including the following (a1) to (a4). Adhesiveness and holding power to the body can be improved.
(a1) 1 to 20% by weight of a terminal carboxy group-containing monomer represented by the general formula (1)
(a2) (meth)acrylic acid 0.1 to 5% by weight
(a3) (meth)acrylate having an alkyl group having 4 to 24 carbon atoms (excluding t-butyl (meth)acrylate) 55 to 97% by weight
(a4) at least one selected from the group consisting of (meth)acrylates having an alkyl group having 1 to 3 carbon atoms, t-butyl (meth)acrylate, cyclic structure-containing monomers and vinyl ester monomers having 3 to 10 carbon atoms; 11% by weight or less

Further, among the present invention, in particular, the (meth)acrylate (a3) having an alkyl group having 4 to 24 carbon atoms is a (meth)acrylate (a3-1) having an alkyl group having 4 to 7 carbon atoms, and a (meth)acrylate (a3-2) having an alkyl group of 8 to 24 carbon atoms, the adhesiveness to adherends can be further improved.

Further, among the present invention, in particular, the (meth)acrylate (a3-2) having an alkyl group having 8 to 24 carbon atoms of the (meth)acrylate (a3-1) having an alkyl group having 4 to 7 carbon atoms When the content ratio is (a3-1)/(a3-2)=1/99 to 85/15 in terms of weight ratio, the adhesiveness to the adherend can be further improved.

In the present invention, in particular, the content of the (meth)acrylic acid (a2) with respect to 100 parts by weight of the terminal carboxy group-containing monomer (a1) represented by the general formula (1) is 10 to 400 parts by weight. If there is, the adhesiveness to the adherend can be made more excellent.

Further, in the present invention, when the copolymer component (a) further contains a hydroxyl group-containing monomer (a5), the adhesiveness to the adherend can be further improved.

Further, the pressure-sensitive adhesive for difficult-to-bond adherends obtained by cross-linking the pressure-sensitive adhesive composition for difficult-to-bond adherends can have more excellent adhesiveness to adherends.

The present invention will be described in detail below.
In the present invention, "(meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate. . Further, "acrylic resin" is a resin obtained by polymerizing a polymerizable component containing at least one (meth)acrylate monomer.

The pressure-sensitive adhesive composition for hard-to-adhere adherends of the present invention contains an acrylic resin (A) obtained by copolymerizing a copolymer component (a) containing a specific monomer component.

<Acrylic resin (A)>
The acrylic resin (A) used in the present invention is a copolymer component (a) containing a terminal carboxy group-containing monomer (a1) and (meth)acrylic acid (a2) represented by the following general formula (1). It is what you do.

[Component (a1)]
The (a1) component used in the present invention is a terminal carboxy group-containing monomer represented by the following general formula (1).

[Formula] CH ₂ =CR ¹ --CO--O--(R ² --COO--) _n H (1)
(Here, R ¹ is hydrogen or a methyl group, R ² is a saturated aliphatic, unsaturated aliphatic, aromatic, saturated alicyclic, or divalent unsaturated alicyclic hydrocarbon, n is 1 or more positive number.)

The hydrocarbon represented by R ² is preferably an alkylene group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms such as a methylene group, phenyl, or phenylene, and n is preferably 1 to 10, more preferably 1 to 5.

The content of the component (a1) is preferably 1 to 20% by weight, particularly 1.5 to 15% by weight, and further 2 to 8.5% by weight based on the total copolymer component (a). %. If the content is too low, the adhesiveness to difficult-to-bond adherends tends to decrease, and if it is too high, the adhesiveness to difficult-to-bond adherends tends to decrease.

[(a2) component]
The content of (meth)acrylic acid (a2) is preferably 0.1 to 5% by weight, particularly 0.5 to 4.5% by weight, based on the total copolymer component (a). is preferably 1 to 4% by weight. If the content is too low, the adhesiveness to difficult-to-bond adherends tends to decrease, and if it is too high, the adhesiveness to difficult-to-bond adherends tends to decrease.

The content ratio of the component (a1) and the component (a2) is usually 10 to 400 parts by weight, particularly 20 to 200 parts by weight, of the component (a2) per 100 parts by weight of the component (a1). parts, more preferably 25 to 100 parts by weight, particularly preferably 30 to 75 parts by weight. If the amount of component (a2) is too small, the holding power tends to decrease, and if it is too large, the adhesion to difficult-to-adhere adherends tends to decrease.

In the present invention, from the viewpoint of adhesion, the main component of the copolymer component (a) is a (meth)acrylate having an alkyl group having 4 to 24 carbon atoms (excluding t-butyl (meth)acrylate) (a3 ) is preferably contained. In addition, from the viewpoint of adhesiveness, a (meth)acrylate having an alkyl group having 1 to 3 carbon atoms, t-butyl (meth)acrylate, a cyclic structure-containing monomer and a vinyl having 3 to 10 carbon atoms are further used as a copolymer component (a). It preferably contains at least one (a4) selected from the group consisting of ester monomers. .

[(a3) component]
The (meth)acrylate having an alkyl group having 4 to 24 carbon atoms (excluding t-butyl (meth)acrylate) (a3) includes a (meth)acrylate having an alkyl group having 4 to 7 carbon atoms (a3 -1) and (meth)acrylate (a3-2) having an alkyl group having 8 to 24 carbon atoms.

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

Examples of the (meth)acrylate (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, ) 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, isostearyl (meth)acrylate, behenyl (meth)acrylate and the like. Of these, (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 component (a3) is preferably 55 to 97% by weight, particularly 70 to 95% by weight, and further 80 to 93% by weight, based on the total copolymer component (a). is preferred. If the content is too small, the adhesiveness to difficult-to-adhere adherends tends to decrease, and if the content is too large, the adhesiveness tends to decrease and the holding power tends to decrease.

Further, the content ratio of the component (a3-1) to the component (a3-2) is (a3-1)/(a3-2)=1/99 to 85/15, particularly 2/ It is preferably 98 to 75/25, more preferably 3/97 to 70/30, especially 5/95 to 60/40. If the content of component (a3-1) is too small, the holding power tends to decrease, and if it is too large, the adhesion to hard-to-bond adherends tends to decrease.

[(a4) component]
The component (a4) is selected from the group consisting of (meth)acrylates having alkyl groups of 1 to 3 carbon atoms, t-butyl (meth)acrylate, cyclic structure-containing monomers and vinyl ester monomers of 3 to 10 carbon atoms. is at least one Among them, (meth)acrylates having an alkyl group having 1 to 3 carbon atoms are preferred.

Examples of (meth)acrylates having an alkyl group having 1 to 3 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate. Among them, methyl (meth)acrylate and ethyl (meth)acrylate are preferred.

The cyclic structure-containing monomer is usually an acrylic monomer having a substituent containing a cyclic structure, such as N-(meth)acryloylmorpholine, N-vinylpyrrolidone, N-vinylcaprolactam, vinylpyrrolidone, N-( meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, morpholine ring, piperidine ring, pyrrolidine ring, heterocyclic ring-containing (meth)acrylate having a heterocycle such as piperazine ring, phenyl (meth)acrylate, phenoxyethyl (meth) ) acrylate, phenyldiethylene glycol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (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 - Methylstyrene and the like. Among them, a heterocycle-containing (meth)acrylate having a morpholine ring is preferred because of its well-balanced physical properties, and N-(meth)acryloylmorpholine is particularly preferred from the viewpoints of availability and safety.

Examples of vinyl ester monomers having 3 to 10 carbon atoms include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, and vinyl pivalate. Among them, vinyl acetate is preferable because of its easy availability.

The content of (a4) is preferably 11% by weight or less, particularly 10% by weight or less, further 8% by weight or less, and particularly 5% by weight, based on the total copolymer component (a). % or less. If the content of component (a4) is too high, the adhesiveness to adherends tends to decrease. The lower limit of the content of component (a4) in copolymer component (a) is usually 1% by weight.

[Component (a5)]
It is desirable that the copolymerization component (a) used in the present invention further contains a hydroxyl group-containing monomer (a5) as a copolymerization component.

Examples of the hydroxyl group-containing monomer (a5) include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8- (meth)acrylate hydroxyalkyl esters such as hydroxyoctyl (meth)acrylate, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate, oxyalkylene-modified diethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, etc. Monomers, primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl-2-hydroxyethyl phthalic acid; 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-chloro 2-hydroxypropyl (meth) ) secondary hydroxyl group-containing monomers such as acrylate; and tertiary hydroxyl group-containing monomers such as 2,2-dimethyl-2-hydroxyethyl (meth)acrylate.

Among these, primary hydroxyl group-containing monomers are preferred from the viewpoint of excellent reactivity with the cross-linking agent, and 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are particularly preferred.

The hydroxyl group-containing monomer (a5) is useful because it serves as a cross-linking point when a cross-linking agent is added, and is particularly effective when an isocyanate-based cross-linking agent is used as the cross-linking agent. In such a case, it is usually 0.01 to 5% by weight, particularly preferably 0.05 to 3% by weight, more preferably 0.05 to 2% by weight, based on the total copolymer component (a). If the amount of component (a5) is too small, the holding power tends to decrease, and if it is too large, the adhesion to difficult-to-adhere adherends tends to decrease.

<Other polymerizable monomer (a6)>
In the present invention, if necessary, other polymerizable monomers (a6) may be used. Examples of other polymerizable monomers (a6) include acetoacetyl group-containing monomers, isocyanate group-containing monomers, and glycidyl group-containing monomers. , amino group-containing monomers, amide group-containing monomers, and other copolymerizable monomers.

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-methylol (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, hydroxyl group-containing (meth)acrylamides such as N-methylolpropane (meth)acrylamide; alkoxy group-containing (meth)acrylamides such as N-methoxymethyl (meth)acrylamide and N-(n-butoxymethyl) (meth)acrylamide; Examples include quaternary salts of amide group-containing monomers.

Examples of the other copolymerizable monomers include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, ethoxydiethyleneglycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate. Monomers containing an alkoxy group or an oxyalkylene group such as acrylate, polypropylene glycol-mono (meth) acrylate; Dialkyl fumarate, allyl alcohol, acryl chloride, methyl vinyl ketone, allyl trimethyl ammonium chloride, dimethyl allyl vinyl ketone and the like.

The above other polymerizable monomer (a6) is contained in the copolymer component (a) to the extent that the effect of the present invention is not impaired in order to adjust the physical properties according to the application.

Thus, by polymerizing the above components (a1) to (a2), preferably further components (a3) and (a4), and optionally further components (a5) and (a6) as a copolymer component (a), acrylic A system resin (A) is obtained. Each of these components (a1) to (a6) may be used 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 the copolymerization component (a) of (a1) to (a6) and a polymerization initiator into an organic solvent, and adding the for 0.1 to 20 hours.

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.

The weight average molecular weight of the acrylic resin (A) thus obtained is generally 100,000 to 5,000,000, preferably 300,000 to 1,500,000, and particularly preferably 500,000 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, particularly preferably 15 or less, further preferably 10 or less, and particularly preferably 7 or less. preferable. If the degree of dispersion is too high, the durability performance 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.

Further, the glass transition temperature (Tg) of the acrylic resin (A) is usually -80 to 10°C, particularly -70 to -10°C, and preferably -65 to -20°C. If it 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 weight fraction when each monomer constituting the acrylic resin (A) is a homopolymer to the following Fox formula. .

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 are used.

The acrylic resin (A) is usually adjusted in viscosity with a solvent or the like, and then applied as an acrylic resin (A) solution. The viscosity of the acrylic resin (A) solution is preferably 500 to 20,000 mPa·s, particularly preferably 1,000 to 18,000 mPa·s, further 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.

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 and methyl ethyl ketone are preferably used in terms of solubility, drying property, price, and the like. These above solvents may be used alone or in combination of two or more.

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

<Crosslinking agent (B)>
The pressure-sensitive adhesive composition for difficult-to-adhere adherends of the present invention preferably contains a cross-linking agent (B) in addition to the acrylic resin (A) from the viewpoint of adhesiveness and holding power.

The cross-linking agent (B) reacts with the functional groups in the acrylic resin (A) to form a cross-linked structure. Examples include cross-linking agents, aldehyde-based cross-linking agents, amine-based cross-linking agents, and metal chelate-based cross-linking agents. Among these, it is preferable to use an epoxy-based cross-linking agent in terms of achieving a good balance between adhesiveness and holding power to various adherends. Further, it is preferable to use an isocyanate-based cross-linking agent in order to obtain an effect of excellent temporal stability as an adhesive tape and excellent adhesiveness even in a high-temperature environment.

Examples of the epoxy-based cross-linking agent include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, ethylene glycol di glycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, diglycidylamine and the like.

The isocyanate-based cross-linking agent contains two or more isocyanate groups, and examples thereof include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; Alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate, biuret forms and isocyanurate forms thereof, and low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. and an adduct which is a reactant of.

Examples of the aziridine-based cross-linking agents include diphenylmethane-4,4′-bis(1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethane tri-β-aziridinyl lpropionate, toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1-(2-methylaziridine), tris-1-(2-methylaziridine)phosphine , trimethylolpropane tri-β-(2-methylaziridine) propionate, and the like.

Examples of the melamine cross-linking agent include melamine, amino group-containing methylol melamine obtained by condensing melamine and formaldehyde, imino group-containing methylol melamine, methylol melamine derivatives such as hexamethylol melamine, methyl alcohol and butyl Partially or completely alkylated methylolmelamine, imino group-containing partially or completely alkylated methylolmelamine, which is partially or completely etherified by reacting a lower alcohol such as alcohol, and the like.

Examples of the aldehyde cross-linking agent include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, glyoxal, glutaraldehyde, dialdehyde starch, hexamethylenetetramine, 1,4-dioxane-2,3-diol, 1,3-bis (Hydroxymethyl)-2-imidazolidine, dimethylol urea, N-methylolacrylamide, urea-formalin resin, aldehyde-based compounds that release aldehydes in aqueous solutions such as melamine-formalin resin, or benzaldehyde, 2-methylbenzaldehyde, 4-methyl Aromatic aldehyde compounds such as benzaldehyde, p-hydroxybenzaldehyde and m-hydroxybenzaldehyde can be mentioned.

Examples of the amine-based cross-linking agent include 4,4'-methylene-bis(2-chloroaniline) (hereinafter abbreviated as "MOCA"), modified MOCA, and diethyltoluenediamine.

Examples of the metal chelate-based cross-linking agent include chelate compounds whose metal atoms are aluminum, zirconium, titanium, zinc, iron, tin, etc. Aluminum chelate compounds are preferred from the viewpoint of performance. Examples of aluminum chelate compounds include diisopropoxyaluminum monooleyl acetoacetate, monoisopropoxyaluminum bisoleyl acetoacetate, monoisopropoxyaluminum monooleate monoethylacetoacetate, diisopropoxyaluminum monolaurylacetoacetate, diisopropoxy aluminum monostearylacetoacetate, diisopropoxyaluminum monoisostearylacetoacetate and the like.

The cross-linking agent (B) may be used alone or in combination of two or more.

The content of the crosslinking agent (B) is usually 0.01 to 5 parts by weight, particularly 0.01 to 4 parts by weight, and further 0.02 to 3 parts by weight with respect to 100 parts by weight of the acrylic resin (A). Parts by weight are preferred. 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.

Among the cross-linking agents (B), the above epoxy-based cross-linking agents are preferably used in that both adhesion to adherends and holding power can be achieved in a well-balanced manner. In the case of using the epoxy-based cross-linking agent, the content of the cross-linking agent (B) is usually 0.005 to 1 part by weight, particularly 0.01 to 1 part by weight, with respect to 100 parts by weight of the acrylic resin (A). 0.5 parts by weight, more preferably 0.02 to 0.1 parts by weight. If the content is too small, the holding power tends to decrease, and if it is too large, the adhesiveness to the adherend tends to decrease.

Among the above-mentioned cross-linking agents (B), it is preferable to use the above-mentioned isocyanate-based cross-linking agents from the viewpoint of strong bonding and excellent durability. When the isocyanate-based crosslinking agent is used, the content of the crosslinking agent (B) is usually 0.1 to 5 parts by weight, particularly 0.1 to 5 parts by weight, relative to 100 parts by weight of the acrylic resin (A). 3 parts by weight, more preferably 0.3 to 2 parts by weight. If the content is too small, the holding power tends to decrease, and if it is too large, the adhesiveness to low-polar adherends tends to decrease.

<Tackifier (C)>
The tackifier (C) is used to further exhibit the good physical properties of the acrylic resin (A), and is preferably contained in the adhesive composition for difficult-to-adhere adherends of the present invention. . Examples of the tackifier (C) include resins that are compatible with the acrylic resin (A), such as rosin-based resins, terpene-based resins, xylene-based resins, phenol-based resins, coumarone-based resins, and petroleum-based resins. be done. These tackifiers (C) can be used alone or in combination of two or more. Among these, rosin-based resins, terpene-based resins, and petroleum-based resins are preferred.

Examples of the rosin-based resin include rosin ester resins obtained by hydrogenating (hydrogenating), disproportionating, dimerizing, and acid-adding raw material rosin and esterifying it with glycerin or pentaerythritol, and phenol. Added rosin phenolic resins are included. Although any rosin-based resin can be used to further exhibit the good physical properties of the acrylic resin (A), among them, the raw material rosin is disproportionated and esterified with glycerin or pentaerythritol to have a softening point of 70 ° C. or higher. Disproportionated rosin esters in the range of 130°C, polymerized rosin esters with a softening point in the range of 110°C to 170°C by dimerizing raw rosin and esterifying it with pentaerythritol, and adding phenol to raw rosin. Rosin phenol having a softening point in the range of 120 to 160° C. is preferred.

The terpene-based resin is a general term for compounds represented by the molecular formula (C ₅ H ₈ ) _n based on the isoprene rule. β-pinene, limonene, etc.) as a raw material, and a resin obtained by homopolymerization or copolymerization with a Friedel-Crafts catalyst. Specifically, monoterpene homo- or copolymerized resins include, for example, α-pinene resin, β-pinene resin, dipentene resin, terpene phenol resin, aromatic modified terpene resin, and hydrogenated terpene resin obtained by hydrogenating these. etc. Among these, the terpene phenol resin is preferable because it has good compatibility with the acrylic resin (A), and any terpene phenol resin further exhibits the good physical properties of the acrylic resin (A). Those having a softening point of 90° C. to 170° C. and a hydroxyl value of 20 to 250 mgKOH/g are preferable, and those having a softening point of 100° C. to 150° C. and a hydroxyl value of 50 to 150 mgKOH/g are more preferable.

The above petroleum-based resins are obtained, for example, by polymerization of C4-C5 and C9-C11 fraction monomers generated by thermal decomposition of naphtha and the like, and further by hydrogenation. family (C5) petroleum resins, aromatic (C9) petroleum resins, hydrogenated petroleum resins, and the like. Any petroleum-based resin can further exhibit the good physical properties of the acrylic resin (A). It is preferable to use a copolymerized resin with a group-based monomer.

The content of the tackifier (C) is usually 1 to 50 parts by weight, particularly 5 to 30 parts by weight, and further 5 to 20 parts by weight with respect to 100 parts by weight of the acrylic resin (A). It is preferably blended in an appropriate amount depending on the required physical properties.

Furthermore, the pressure-sensitive adhesive composition for difficult-to-adhere adherends of the present invention may contain, as other components, a resin component other than the acrylic resin (A), an acrylic monomer, a polymerization inhibitor, as long as the effects of the present invention are not impaired. additives such as agents, antioxidants, corrosion inhibitors, cross-linking accelerators, radical generators, peroxides, UV absorbers, plasticizers, pigments, stabilizers, fillers, radical scavengers, flame retardants, etc. Metal, resin particles, and the like can be blended. In addition to the above, it may contain a small amount of impurities contained in the manufacturing raw materials of the constituent components of the pressure-sensitive adhesive composition for adherends with poor adhesion.

The content of the above other components is preferably 5 parts by weight or less, particularly preferably 1 part by weight or less, and further preferably 0.5 parts by weight or less with respect to 100 parts by weight of the acrylic resin (A). . If the content is too large, the compatibility with the acrylic resin (A) tends to decrease, resulting in a decrease in durability. However, in the above content of pigments, fillers, flame retardants, metals, resin particles, etc., for additives etc. that do not exhibit their effects, an appropriate amount within a range that does not hinder the effects of the present invention while exhibiting the effects of the additives may be added.

As described above, in addition to the acrylic resin (A), the pressure-sensitive adhesive composition for a difficult-to-adhere adherend of the present invention preferably contains a cross-linking agent (B) and a tackifier (C), and if necessary and other ingredients.
By mixing the above components, the pressure-sensitive adhesive composition for difficult-to-bond adherends of the present invention can be obtained. In addition, the pressure-sensitive adhesive for hard-to-bond adherends of the present invention can be obtained by cross-linking the pressure-sensitive adhesive composition for hard-to-bond adherends. And this pressure-sensitive adhesive for hard-to-bond adherends can be suitably used as the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape for hard-to-bond adherends of the present invention.

<Adhesive tape for difficult-to-adhere adherends>
The pressure-sensitive adhesive tape for difficult-to-bond adherends of the present invention contains, as a pressure-sensitive adhesive layer, the pressure-sensitive adhesive for difficult-to-bond adherends obtained by cross-linking the adhesive composition for difficult-to-bond adherends. be. Specifically, the pressure-sensitive adhesive composition for difficult-to-adhere adherends is dissolved in a solvent such as ethyl acetate, and the solid content concentration is 10 to 70% by weight. A pressure-sensitive adhesive tape for difficult-to-adhere adherends can be obtained by preparing a solution of the pressure-sensitive adhesive composition for adhesion, applying this solution to a substrate, and drying the solution.

As a method for producing such an adhesive tape, a known general method for producing an adhesive tape may be used. For example, an adhesive is applied to one surface of a base material and dried, and the adhesive layer is 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. Among these, those containing flat yarn cloth are preferable because of their high tensile strength in the longitudinal direction.

The above-mentioned 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 vertically and horizontally is fixed by heat-sealing to prevent misalignment.

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. Fluorine-based resin or silicone-based resin, etc., which is a releasing agent, is coated on a synthetic resin film such as the above.

Among these, a paper release liner is preferable because it is easily torn by hand, and a paper release liner having a base paper basis weight of 40 to 120 g/m ² , preferably 50 to 80 g/m ² is particularly preferred. preferable. Furthermore, the thickness of the release liner is preferably 40 to 180 μm, particularly preferably 60 to 140 μm, further preferably 80 to 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 side 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.

Also, the thickness of the adhesive layer after drying is preferably 5 to 200 μm, particularly preferably 10 to 150 μm, further 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.

The pressure-sensitive adhesive tape for a difficult-to-bond adherend of the present invention may be a single-sided pressure-sensitive adhesive tape or a double-sided pressure-sensitive 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, in order to improve workability, each release liner laminated on both sides should be selected so that the peel strength of each release liner is different. is preferred. For example, if the release liner on the first side of the double-sided pressure-sensitive adhesive tape has a release liner that is easier to release 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 when the cross-linking agent (B) is used, the functional group of the acrylic resin (A) and the cross-linking agent (B) Any conditions are acceptable as long as they can react with each other to form a crosslinked structure. 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 for difficult-to-adhere adherends of the present invention may be in the form of a roll, a sheet, or may be processed into various shapes.
When the pressure-sensitive adhesive tape for difficult-to-adhere adherends 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, and the pressure-sensitive adhesive tape is in a roll state. In the case of (2), it is preferable that only one surface of the two pressure-sensitive adhesive layers is provided with a release liner.

Thus, the pressure-sensitive adhesive tape for difficult-to-adhere adherends of the present invention is obtained. There is no decrease in the strength and it has a good holding power. Furthermore, when a hand-cuttable base material is used as the base material, it can be easily cut by hand at any position without using a tape cutter or the like in the width direction of the tape, and the adhesive It becomes especially useful as a tape.

As for the adhesive strength of the adhesive layer in the adhesive tape for difficult-to-adhere adherends, the 180° peel strength to the adherend used is usually 1 to 100 N/25 mm.

Among them, test plates of ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), natural rubber (NR), styrene-butadiene rubber (SBR), and butyl rubber (IIR), which are difficult-to-adhere adherends, were used as adherends. When used, the 180° peel strength is preferably 10 N/25 mm or more, particularly preferably 15 N/25 mm or more, further preferably 17 N/25 mm or more. The upper limit is usually about 100N/25mm.
Further, when a test plate of SUS304 steel, which has relatively high polarity, is used as the adherend, the 180° peel strength is preferably 25 N/25 mm or more, particularly preferably 30 N/25 mm or more, further preferably 35 N/ 25 mm or more. The upper limit is usually about 100N/25mm.

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. Specifically, it can be measured by the method described in Examples below.

In addition, when the test piece is a double-sided adhesive tape, the adhesive surface that is not tested is covered with a polyethylene terephthalate film (manufactured by Toray Industries, Inc., Lumirror S10) having a nominal thickness of 25 μm specified in JIS C 2318. The adhesive strength of the target adhesive surface can be measured.

In addition, as the holding power of the adhesive layer in the adhesive tape for adherends difficult to adhere of the present invention, when measured by the method described in Examples below, the test piece does not fall off the test plate after 24 hours. Preferably, even if the test piece drops within 24 hours, the retention time is preferably 80 minutes or longer, more preferably 150 minutes or longer.

Furthermore, the gel fraction of the pressure-sensitive adhesive layer in the above pressure-sensitive adhesive tape for adherends difficult to adhere to is preferably 10 to 70% by weight, particularly preferably 20 to 60% by weight, from the viewpoint of adhesiveness and holding power. Yes, more preferably 25 to 50% by weight. If the gel fraction is too low, the holding power to the adherend tends to decrease, and if it is too high, the adhesiveness to the adherend tends to decrease.

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, the adhesive layer was collected by picking from the adhesive tape for difficult-to-adhere adherends, wrapped in a 200-mesh SUS wire mesh, immersed in toluene maintained at 23 ° C. for 48 hours, and wrapped in the wire mesh. The weight percentage of the remaining undissolved pressure-sensitive adhesive component is defined as the gel fraction.

In addition, in adjusting the gel fraction of the pressure-sensitive adhesive to the above range, it is achieved by adjusting the type and amount of the cross-linking agent (B).

The pressure-sensitive adhesive tape for hard-to-bond adherends of the present invention preferably has a high tensile strength. Required strength is required. The tensile strength of the pressure-sensitive adhesive tape for difficult-to-bond adherends is usually 20 N/25 mm or more, preferably 30 N/25 mm or more, and particularly preferably 50 N/25 mm or more. The upper limit of tensile strength is usually 250N/25mm. A double-faced pressure-sensitive adhesive tape with high tensile strength can be achieved by using a base material having a tensile strength equal to or greater than the tensile strength of the target pressure-sensitive adhesive tape.

The adhesive tape for difficult-to-adhere adherends of the present invention includes, for example, packaging tapes such as kraft tape, OPP tape, and cloth adhesive tape, cellophane adhesive tapes for light packaging, foamed tapes for automobiles, damping sheets, and flame-retardant adhesive tapes. , residential curing tape, soundproof seal, double-sided tape for fixing carpets, vinyl tape for electrical insulation, outdoor anti-corrosion tape, indoor display tape, anti-slip tape, airtight and waterproof adhesive tape, adhesive base for medical first-aid bandages, etc. , surgical tape, adhesive bandage, tape for electrical and electronic equipment, double-sided tape for optical use, dicing tape for semiconductors, heat conductive tape, heat resistant tape, conductive tape, etc.

The pressure-sensitive adhesive tape can be used, for example, for housing structures, members thereof, gaps between members, and the like. The adherend is not particularly limited, but when used as an adhesive tape, for example, ethylene propylene diene rubber (EPDM), butyl rubber (IIR), chloroprene rubber (CR), natural rubber (NR ), styrene-butadiene rubber (SBR), polyvinyl chloride, chlorinated polyethylene, thermoplastic polyolefin rubber, and modified asphalt.

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 weight 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 the acrylic resin (A), the following were prepared as the copolymerization component (a) used for the production.
Component (a1) Terminal carboxy group-containing monomer represented by the following general formula (1) CH ₂ =CR ¹ --CO--O--(R ² --COO--) _n H (1)
In the above general formula (1), R ¹ is hydrogen, R ² is an ethylene chain, n is 1 to 5
(a2) component Acrylic acid (AAc)
(a3-1) component n-butyl acrylate (BA)
(a3-2) component 2-ethylhexyl acrylate (2EHA)
(a-4) component Methyl acrylate (MA)
(a-5) component 2-hydroxyethyl methacrylate (HEMA)

For the component (a1), "Cipomer H" manufactured by Solvay Nikka Co., Ltd. was used.
Saipomer H is a mixture containing 75% of compound (a1) of general formula (1) where R ¹ is hydrogen, R ² is ethylene chain, n = 1 to 5, and acrylic acid (a2) is 25% ( Hereinafter, Cypomer H will be referred to as "β-CEA", and the compound of general formula (1) contained in Cypomer H may be collectively referred to as "CAO").

[Production of acrylic resin (A-1)]
In a reactor equipped with a thermometer, stirrer and reflux condenser, Cypomer H5 parts [CAO (a1) 3.75 parts, acrylic acid (a2) 1.25 parts], n-butyl acrylate (a3-1) 26.7 parts, 2-ethylhexyl acrylate (a3-2) 65.2 parts, methyl acrylate (a4) 3 parts, 2-hydroxyethyl methacrylate (a5) 0.1 parts, ethyl acetate 55 parts, and as a polymerization initiator 0.15 parts of azobisisobutyronitrile was charged, the temperature was raised while stirring, and the mixture was polymerized at the reflux temperature of ethyl acetate for 7 hours. -1) A solution was obtained.
The obtained acrylic resin (A-1) had a weight average molecular weight of 550,000, a dispersity of 4.3, and a glass transition temperature of -61°C.

[Production of acrylic resins (A-2) to (A-4) and (A'-1)]
In the production of acrylic resin (A-1), the same procedure was followed except that the composition of the copolymer component was changed as shown in Table 1 below, and acrylic resins (A-2) to (A-4) and (A A solution of '-1) was obtained.

<Crosslinking agent (B)>
The following were prepared as a crosslinking agent (B).
・ B-1: Epoxy-based cross-linking agent: Tetrad C (1,3-bis (N, N-diglycidylaminomethyl) cyclohexane) manufactured by Mitsubishi Gas Chemical Company, Inc.

<Tackifier (C)>
The following tackifiers were prepared.
・ C-1: Disproportionated rosin ester: Super Ester A-100 (disproportionated rosin glycerin ester, softening point 95 to 105 ° C.) manufactured by Arakawa Chemical Industries, Ltd.
・ C-2: Petroleum-based resin: FTR6100 manufactured by Mitsui Chemicals Co., Ltd. (copolymer resin of styrene-based monomer and aliphatic monomer, softening point 95 ° C.)

<Example 1>
For the acrylic resin (A-1) solution prepared and prepared as described above, 0.04 of the cross-linking agent (B-1) [epoxy cross-linking agent (Tetrad C)] is added to 100 parts of the solid content. 15 parts of tackifier (C-1) [disproportionated rosin ester (super ester A-100)]. Thereafter, the solution was prepared with ethyl acetate so as to have a solid content concentration of 40%, and the mixture was stirred until uniform to obtain a solution of the pressure-sensitive adhesive composition for hard-to-adhere adherends.

<Examples 2 to 5 and Comparative Example 1>
In the above Example 1, the same procedure was performed except that the composition of the adhesive composition for difficult-to-bond adherends was changed as shown in Table 2 below. A solution of the agent composition was obtained.

From the obtained adhesive compositions for difficult-to-bond adherends of Examples 1 to 5 and Comparative Example 1, pressure-sensitive adhesive tapes for difficult-to-bond adherends were produced as follows, and the following evaluations were performed. Evaluation results are shown in Table 2 below.

[Preparation of adhesive tape for difficult-to-adhere adherends]
The solution of the pressure-sensitive adhesive composition for difficult-to-adhere adherends prepared as described above was dried on the release surface of a paper release liner [SS-70-SBX (manufactured by Shinomura Chemical Industry Co., Ltd.)] to a thickness of 110 μm. After that, it was dried at 80° C. for 5 minutes, and flat yarn (manufactured by Diatex Co., thickness 130 μm) was attached. After that, heat aging treatment was performed for 7 days in a drier at 40° C. to prepare a pressure-sensitive adhesive tape for a difficult-to-adhere adherend.

<Gel fraction>
The paper release liner was peeled off from the resulting adhesive tape for adherends with poor adhesion, the adhesive was picked from the adhesive layer surface, wrapped in a SUS 200 mesh wire mesh, and then placed in toluene maintained at 23°C for 48 hours. After immersion, the weight percentage of the undissolved adhesive component remaining in the wire mesh was defined as the gel fraction.
Gel fraction (%)
= weight of undissolved adhesive component (g) / weight of adhesive component before immersion (g) × 100

<180° peel strength>
A test piece was prepared by cutting the adhesive tape into a width of 25 mm and a length of 150 mm. In addition, ethylene propylene diene rubber (EPDM) (manufactured by Engineering Test Service Co., Ltd., standard test plate EPDM-70), chloroprene rubber (CR) (manufactured by Nippon Test Panel Co., Ltd., standard test plate), natural rubber (NR) ( Japan Test Panel Co., standard test plate), styrene-butadiene rubber (SBR) (Japan Test Panel Co., standard test plate), and butyl rubber (IIR) (Japan Test Panel Co., standard test plate) were tested with methanol. After washing the surface, it was left standing overnight in an atmosphere of 23° C. and 50% RH. The paper release liner was peeled off from the test piece, and the pressure-sensitive adhesive layer of the test piece was pressed onto the test plate by reciprocating a roller weighing 2 kg twice at a pressing speed of 10 mm/s. After crimping, leave it for 30 minutes in an atmosphere of 23 ° C. and 50% RH, fold the play part of the test piece 180 °, peel it off 30 mm, and then put the test plate on the chuck at the bottom of the peel strength tester in the same atmosphere. , each end of the test piece was fixed to an upper chuck, the adhesive tape was peeled off from the adherend at a peeling angle of 180° and a speed of 300 mm/min, and the peel strength was measured and evaluated as follows.
〔Evaluation criteria〕
A: Peel strength of 17 N/25 mm or more B: Peel strength of 15 N/25 mm or more and less than 17 N/25 mm C: Peel strength of less than 15 N/25 mm

<Holding power>
A test piece was prepared by cutting the adhesive tape into a width of 25 mm and a length of 75 mm. An EPDM test plate was used as an adherend. A roller with a weight of 2 kg is pressed against this test plate so that the contact area between the adhesive layer of the test piece with the paper release liner peeled and the test plate is 25 mm in width × 25 mm in length. It was crimped by reciprocating twice at 10 mm/s. Also, the part where the adhesive of the test piece was exposed was folded back. After the pressure bonding, it was allowed to stand in an environment of 23° C. and 50% RH for 30 minutes, and then moved to an environment of 40° C. and allowed to stand for 20 minutes. A weight of 1000 g was attached to the test plate so that the test piece hung vertically, and then the time for the test piece to drop was measured in an environment of 40° C., and the holding time was evaluated as follows.
〔Evaluation criteria〕
A: 150 minutes or more B: 80 minutes or more and less than 150 minutes C: less than 80 minutes

<Comparative Example 2>
In Example 1, the same evaluation was performed by changing the adhesive tape to a commercial asphalt-based adhesive tape that is often used for fixing hard-to-bond rubber-based adherends.

<Comparative Example 3>
In Example 1, the same evaluation was carried out by changing the adhesive tape to a commercially available butyl rubber adhesive tape which is often used for fixing hard-to-adhere rubber-based adherends.

From the results in Table 2 above, all the example products of the present invention have high peel strength even to difficult-to-bond adherends such as EPDM, CR, NR, SBR, and IIR. It was firmly attached. In addition, the holding power for EPDM was high and the creep property was excellent under constant stress.

On the other hand, Comparative Example 1 exhibited low peel strength and poor adhesion to difficult-to-bond adherends such as EPDM, CR, NR, SBR and IIR.
In addition, the products of Comparative Examples 2 and 3 had high peel strength to difficult-to-adhere adherends such as EPDM, but low holding power and poor creep property under constant stress.

That is, in the case of highly polar adherends such as SUS, the selectivity of the acrylic resin is unnecessary, but in the case of difficult-to-adhere adherends such as EPDM, CR, NR, SBR, and IIR, the terminal carboxy group It can be seen that the acrylic resin (A) obtained by copolymerizing the copolymer component (a) containing the contained monomer (a1) and (meth)acrylic acid (a2) has excellent adhesiveness. . In addition, the example products of the present invention had significantly higher holding power than the adhesive tape using butyl rubber or the adhesive tape using asphalt, and both excellent adhesion and high holding power were achieved.

The pressure-sensitive adhesive composition for difficult-to-bond adherends of the present invention has excellent adhesion to rubber-based difficult-to-bond adherends, particularly to difficult-to-bond adherends such as ethylene propylene diene rubber (EPDM). Therefore, packaging tapes such as kraft tape, OPP tape, cloth adhesive tape, cellophane adhesive tape for light packaging, foam tape for automobiles, damping sheet, flame-retardant adhesive tape, curing tape for housing, soundproof seal, double-sided carpet fixing 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, dicing tape for semiconductors, heat-conductive tape, heat-resistant tape, and conductive tape.

Claims (8)

A pressure-sensitive adhesive composition for a difficult- to-bond adherend containing an acrylic resin (A) and a cross-linking agent (B) ,
The acrylic resin (A) is obtained by copolymerizing a copolymer component (a) containing the following (a1) to (a4), and the following (a3) has an alkyl group having 4 to 7 carbon atoms (meta) A pressure-sensitive adhesive composition for difficult-to-bond adherends, comprising an acrylate (a3-1) and a (meth)acrylate (a3-2) having an alkyl group having 8 to 24 carbon atoms.
(a1) 1 to 20% by weight of a terminal carboxy group-containing monomer represented by the following general formula (1)
[Formula] CH ₂ =CR ¹ --CO--O--(R ² --COO--) _n H (1)
(Here, R ¹ is hydrogen or a methyl group, R ² is a saturated aliphatic, unsaturated aliphatic, aromatic, saturated alicyclic, or divalent unsaturated alicyclic hydrocarbon, n is 1 or more positive number.)
(a2) (meth)acrylic acid 0.1 to 5% by weight
(a3) (meth)acrylate having an alkyl group having 4 to 24 carbon atoms (excluding t-butyl (meth)acrylate) 55 to 97% by weight
(a4) at least one selected from the group consisting of (meth)acrylates having an alkyl group having 1 to 3 carbon atoms, t-butyl (meth)acrylate, cyclic structure-containing monomers and vinyl ester monomers having 3 to 10 carbon atoms; 1-11% by weight The content ratio of the (meth)acrylate (a3-1) having an alkyl group having 4 to 7 carbon atoms to the (meth)acrylate (a3-2) having an alkyl group having 8 to 24 carbon atoms is, in terms of weight ratio, ( 2. The pressure-sensitive adhesive composition for a difficult-to-bond adherend according to claim 1 , wherein a3-1)/(a3-2)=1/99 to 85/15. The content of the (meth)acrylic acid (a2) with respect to 100 parts by weight of the terminal carboxy group-containing monomer (a1) represented by the general formula (1) is 10 to 400 parts by weight or 2. The pressure-sensitive adhesive composition for difficult-to-adhere adherends according to 2 above. 4. The pressure-sensitive adhesive composition for hard-to-bond adherends according to any one of claims 1 to 3 , further comprising a hydroxyl group-containing monomer (a5) as the copolymer component (a). The pressure-sensitive adhesive composition for difficult-to-bond adherends according to any one of claims 1 to 4 , further comprising a tackifier (C). A pressure-sensitive adhesive for difficult-to-bond adherends, characterized in that the pressure-sensitive adhesive composition for difficult-to-bond adherends according to any one of claims 1 to 5 is crosslinked. 7. A pressure-sensitive adhesive tape for a difficult-to-bond adherend, wherein the pressure-sensitive adhesive for a difficult-to-bond adherend according to claim 6 is formed on a substrate. The adhesive composition for a difficult-to-bond adherend according to any one of claims 1 to 5, wherein the difficult-to-bond adherend is ethylene propylene diene rubber.