JP7300599B2 - Adhesive composition and adhesive sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition having good pressure-sensitive adhesive physical properties and particularly suitable as a curing pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition.

After protecting the adherend, the adhesive tape for curing is removable without leaving adhesive on the adherend, and adheres well regardless of the material of the adherend or the shape of the adherend surface. There are various required performances such as the appropriate adhesive strength that can be achieved, and the holding power for temporary fixing and fixing, but it is required to improve these performances in a well-balanced manner.

Methods for improving the removability and holding force include a method of increasing the crosslink density and a method of increasing the glass transition point (Tg) of the polymer as in Patent Document 1. However, these methods have a problem that the stress relaxation property is lowered due to hardening of the pressure-sensitive adhesive layer. Therefore, one of the general techniques for imparting flexibility is to add a plasticizer to the pressure-sensitive adhesive composition. However, the use of phthalate-based plasticizers, which are typical plasticizers, has been viewed as a problem from the standpoint of the environment and toxicity. Until now, it has been difficult to obtain a pressure-sensitive adhesive composition that satisfies the required performance as a curing pressure-sensitive adhesive while using a non-phthalate ester plasticizer with a low environmental load. In addition, there are cases in which sufficient adhesiveness cannot be obtained for adherends such as polyolefins.

JP 2016-188272 A

The present invention provides a pressure-sensitive adhesive composition having good adhesive physical properties such as removability, curved surface adhesion, holding power, and polyolefin adhesion, and is particularly suitable as a curing adhesive, and an adhesive having a layer comprising the composition. The task is to provide a sheet.

As a result of intensive studies to solve the above problems, the present inventors have found that an acrylic pressure-sensitive adhesive composition containing a tackifying resin and a plasticizer together and a pressure-sensitive adhesive sheet using the same can solve the above problems. I found that it can be done, and completed the present invention.

That is, the gist of the present invention relates to the following [1] to [7].
[1] A pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A), a tackifying resin (B), a plasticizer (C), and a cross-linking agent (D),
The plasticizer (C) has a freezing point of −35° C. or higher, is compatible with isopropyl alcohol, and is incompatible with methanol,
The pressure-sensitive adhesive composition, wherein the amount of the plasticizer (C) is 0.1 parts by mass or more and less than 8 parts by mass with respect to 100 parts by mass of the (meth)acrylic polymer (A).

[2] The (meth)acrylic polymer (A) is
(a1) 50% by mass or more of a (meth)acrylic acid alkyl ester monomer having an alkyl group having 4 to 6 carbon atoms;
(a2) The pressure-sensitive adhesive composition of [1] above, which is a copolymer of a monomer component containing 1 to 8% by mass of a monomer having a carboxy group.
[3] The pressure-sensitive adhesive composition of [1] or [2] above, wherein the (meth)acrylic polymer (A) has a weight average molecular weight of 300,000 or more and 1,200,000 or less.
[4] The pressure-sensitive adhesive composition according to any one of [1] to [3] above, wherein the tackifying resin (B) is a rosin-based tackifying resin.

[5] The pressure-sensitive adhesive composition according to any one of [1] to [4] above, wherein the plasticizer (C) is a fatty acid alkyl ester plasticizer.
[6] The pressure-sensitive adhesive composition according to any one of [1] to [5] above, which is for curing.
[7] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of any one of [1] to [6] above. Adhesive sheet especially for curing.

According to the present invention, it has removability in a low-temperature environment and retention of adhesive strength, and exhibits sufficient adhesive physical properties even for adherends such as polyolefins, which are generally difficult to obtain adhesiveness, and is used for curing and the like. and an adhesive tape and an adhesive sheet using the adhesive composition.

The present invention will be specifically described below.
In the present invention, "(meth)acryl" is used as a generic term for acryl and methacryl. For example, "(meth)acrylic acid" means acrylic acid or methacrylic acid. Further, in the present invention, A to B representing a numerical range means from A to B, unless otherwise specified.

<Adhesive composition>
The pressure-sensitive adhesive composition of the present invention contains a (meth)acrylic polymer (A), a tackifying resin (B), a plasticizer (C), and a cross-linking agent (D).

(Meth)acrylic polymer (A)
The pressure-sensitive adhesive composition of the present invention contains a (meth)acrylic polymer (A).
As the (meth)acrylic polymer (A) according to the present invention, a polymer or copolymer using (meth)acrylic acid alkyl ester as at least a part of the monomer component can be used without particular limitation.

- Monomer component of (meth)acrylic polymer (A) As the (meth)acrylic acid alkyl ester used as the monomer component forming the (meth)acrylic polymer (A), the alkyl group preferably has 1 to 1 carbon atoms. (Meth)acrylic acid alkyl esters of 18 (CH ₂ ═CR ¹ —COOR ² ; R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 18 carbon atoms), more preferably is a (meth)acrylic acid alkyl ester having an alkyl group of 4 to 10 carbon atoms, more preferably a (meth)acrylic acid alkyl ester monomer (a1) having an alkyl group of 4 to 6 carbon atoms.

Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, Acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl ( meth)acrylate, decyl (meth)acrylate, undeca (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate.

Among these, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, which is a (meth)acrylic acid alkyl ester (a1) in which the alkyl group has 4 to 6 carbon atoms, Pentyl (meth)acrylate and hexyl (meth)acrylate are particularly preferred.

These (meth)acrylic acid alkyl esters may be used singly or in combination of two or more.
In 100% by mass of the monomer component forming the (meth)acrylic polymer (A), the total amount of the (meth)acrylic acid alkyl ester used is usually 50% by mass or more, preferably 60 to 99% by mass, more preferably 75% by mass. It is in the range of ~98% by mass.

The (meth)acrylic polymer (A) according to the present invention preferably contains a monomer (a2) having a carboxy group as a monomer component.

A monomer (a2) having a carboxy group is a monomer having a carboxyl group in the molecule. Specific examples of the monomer (a2) having a carboxy group include acrylic acid, methacrylic acid, β-carboxyethyl(meth)acrylate, 5-carboxypentyl(meth)acrylate, succinic acid mono(meth)acryloyloxyethyl ester, ω -Carboxypolycaprolactone mono(meth)acrylate, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid and the like. In this specification, the monomer having a carboxyl group also includes a monomer containing an acid anhydride group formed by dehydration condensation of two carboxyl groups. things are mentioned.

As the monomer (a2) having a carboxy group, it is preferable to use at least one monomer selected from acrylic acid, methacrylic acid, and β-carboxyethyl (meth)acrylate, and at least one selected from acrylic acid and methacrylic acid. More preferably, one type of monomer is used. These monomers are preferred because they are readily available industrially.
These carboxy group-containing monomers (a2) may be used singly or in combination of two or more.

The amount of the monomer (a2) having a carboxy group used is preferably 0.01 to 15% by mass, more preferably 0.1 to 10% by mass, still more preferably 1 to 8% by mass, based on 100% by mass of the monomer component. be. When the amount of the monomer having a carboxy group is not more than the upper limit, the pressure-sensitive adhesive layer to be formed has appropriate mechanical strength. Moreover, the crosslink density formed by the (meth)acrylic polymer (A) and the crosslinker (D) does not become too high, and a pressure-sensitive adhesive composition having excellent stress relaxation properties can be obtained. In addition, when the amount of the monomer having a carboxyl group is at least the above lower limit, a crosslinked structure is effectively formed, and it has an appropriate strength at room temperature and adequate adhesion to a highly polar adherend. A pressure-sensitive adhesive layer having properties is obtained.

The monomer component forming the (meth)acrylic polymer (A) according to the present invention is other (meth)acrylic monomers other than the (meth)acrylic acid alkyl ester monomer and the carboxy group-containing monomer (a2) described above. It may contain a monomer component.

Other (meth)acrylic monomer components include, for example, polar group-containing monomers other than carboxy group-containing monomers, such as hydroxyl group-containing monomers, acid group-containing monomers other than carboxy group-containing monomers, and amino group-containing monomers. , amide group-containing monomers, nitrogen heterocycle-containing monomers, and cyano group-containing monomers. As the polar group-containing monomer, it is preferable to use a monomer having a polar group (crosslinkable functional group) capable of reacting with the crosslinkable functional group of the crosslinking agent (D) described below.

Examples of hydroxyl-containing monomers include hydroxyl-containing (meth)acrylates, specifically 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. , 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate and other hydroxyalkyl (meth)acrylates. The number of carbon atoms in the hydroxyalkyl group in the hydroxyalkyl (meth)acrylate is generally 2-8, preferably 2-6.

The hydroxyl group contained in the hydroxyl group-containing monomer may function as a crosslinkable functional group with the crosslinking agent (D). When the monomer component contains a hydroxyl group-containing monomer, a crosslinked structure is effectively formed, and a pressure-sensitive adhesive layer having appropriate strength at room temperature can be obtained, which is preferable. The amount of the hydroxyl group-containing monomer used is preferably 0 to 15% by mass, more preferably 0.05 to 10% by mass, still more preferably 0.1 to 7% by mass, based on 100% by mass of the monomer component. When the amount of the hydroxyl group-containing monomer used is not more than the upper limit, the crosslink density formed by the (meth)acrylic polymer (A) and the crosslinker (D) does not become too high, and the pressure-sensitive adhesive has excellent stress relaxation properties. layers are obtained.

Examples of the acid group of the acid group-containing monomer other than the carboxy group-containing monomer include a phosphoric acid group and a sulfuric acid group. Phosphate group-containing monomers include (meth)acrylic monomers having phosphoric acid groups in side chains, and sulfate group-containing monomers include (meth)acrylic monomers having sulfate groups in side chains.

Examples of amino group-containing monomers include amino group-containing (meth)acrylates such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate. Examples of amide group-containing monomers include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, and N-hexyl(meth)acrylamide. Nitrogen-based heterocyclic ring-containing monomers include, for example, vinylpyrrolidone, acryloylmorpholine, and vinylcaprolactam. Examples of cyano group-containing monomers include cyano(meth)acrylate and (meth)acrylonitrile.
Such polar group-containing monomers may be used singly or in combination of two or more.

In addition, the monomer component forming the (meth)acrylic polymer (A) according to the present invention is a range that does not impair the physical properties of the (meth)acrylic polymer (A), for example, alkoxyalkyl (meth)acrylate, alkoxypoly Other (meth)acrylic acid esters can be included, such as alkylene glycol mono(meth)acrylates, alicyclic group- or aromatic ring-containing (meth)acrylates.

Alkoxyalkyl (meth)acrylates include, for example, methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl ( meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate.

Examples of alkoxypolyalkylene glycol mono(meth)acrylates include methoxydiethylene glycol mono(meth)acrylate, methoxydipropylene glycol mono(meth)acrylate, ethoxytriethylene glycol mono(meth)acrylate, ethoxydiethylene glycol mono(meth)acrylate, Methoxytriethylene glycol mono(meth)acrylate is mentioned.

Alicyclic group- or aromatic ring-containing (meth)acrylates include, for example, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and phenyl (meth)acrylate.

Furthermore, the (meth)acrylic polymer (A) according to the present invention contains, in the monomer components, for example, styrene, methylstyrene, dimethylstyrene, trimethylstyrene, propylstyrene, butylstyrene, to the extent that its physical properties are not impaired. alkylstyrenes such as xylstyrene, heptylstyrene and octylstyrene; styrenic monomers such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, iodinated styrene, nitrostyrene, acetylstyrene and methoxystyrene; A copolymerizable monomer other than (meth)acrylic may also be included. The amount of such non-(meth)acrylic copolymerizable monomer used is preferably 30% by mass or less, more preferably 20% by mass or less, based on 100% by mass of the monomer component.

The (meth)acrylic polymer (A) according to the present invention is preferably a copolymer of monomer components containing a (meth)acrylic acid alkyl ester monomer and a monomer having a polar group, more preferably ( A copolymer of a monomer component containing a meth)acrylic acid alkyl ester monomer and a monomer (a2) having a carboxy group, more preferably a (meth)acrylic acid alkyl ester having an alkyl group having 4 to 6 carbon atoms. It is a copolymer of monomer components containing a monomer (a1) and a monomer (a2) having a carboxy group.

The monomer components forming the (meth)acrylic polymer (A) include a (meth)acrylic acid alkyl ester monomer (a1) having an alkyl group with 4 to 6 carbon atoms and a monomer (a2) having a carboxy group. In this case, the monomer component is preferably 50 mass% or more, more preferably 70 to 99 mass%, still more preferably 75 to 98 mass% (meth)acrylic acid alkyl ester monomer (a1) having an alkyl group with 4 to 6 carbon atoms. %, preferably 1 to 8% by mass, more preferably 1.5 to 7% by mass, still more preferably 2 to 6% by mass, of the monomer (a2) having a carboxy group.

Further, the (meth)acrylic polymer (A) according to the present invention is particularly preferably, from the viewpoint of improving adhesiveness, a (meth)acrylic acid alkyl ester monomer (a1) having an alkyl group having 4 to 6 carbon atoms, A copolymer of monomer components containing a monomer (a2) having a carboxy group and a hydroxyl group-containing monomer is desirable.

- Production conditions for (meth)acrylic polymer (A) The (meth)acrylic polymer (A) according to the present invention may be obtained by polymerizing or copolymerizing the monomer components described above, and the production conditions is not particularly limited, but can be produced, for example, by a solution polymerization method. Specifically, a polymerization solvent, a monomer component, and, if necessary, a chain transfer agent are charged in a reaction vessel, a polymerization initiator is added under an inert gas atmosphere such as nitrogen gas, and the reaction initiation temperature is usually set to 40 to 40. The temperature is set to 100° C., preferably 50 to 80° C., and the reaction system is generally maintained at a temperature of 50 to 90° C., preferably 70 to 90° C., and reacted for 4 to 20 hours. Moreover, a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent may be added as appropriate during the polymerization reaction.

Examples of the polymerization solvent include aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane and n-octane; cyclopentane, cyclohexane and cycloheptane. , alicyclic hydrocarbons such as cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, diphenyl ether; Halogenated hydrocarbons such as 1,2-dichloroethane and chlorobenzene; Esters such as ethyl acetate, propyl acetate, butyl acetate and methyl propionate; Ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone and cyclohexanone; N , N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; sulfoxides such as dimethylsulfoxide and sulfolane. These polymerization solvents may be used singly or in combination of two or more.

Examples of chain transfer agents include n-decyl mercaptan and α-methylstyrene dimer. By using a chain transfer agent, the molecular weight of the produced copolymer (A) can be controlled. These chain transfer agents may be used singly or in combination of two or more.

The chain transfer agent is usually 0.1 parts by mass or less, preferably in an amount within the range of 0.01 to 0.09 parts by mass, relative to 100 parts by mass of the monomer component forming the (meth)acrylic polymer (A). can be used in

Examples of polymerization initiators include azo initiators and peroxide initiators. Specific examples include azo compounds such as 2,2'-azobisisobutyronitrile, and peroxides such as benzoyl peroxide and lauroyl peroxide. Among these, azo compounds are preferred. Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropyl propionitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′-azobis(2-methylbutyronitrile), 1,1′-azobis(cyclohexane-1-carbonitrile) , 2-(carbamoyl azo) isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2′-azobis(2-amidinopropane) dihydrochloride, 2,2′-azobis ( N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutylamide) dihydrate, 4,4 '-azobis(4-cyanopentanoic acid), 2,2'-azobis(2-cyanopropanol), dimethyl-2,2'-azobis(2-methylpropionate). These polymerization initiators may be used individually by 1 type, and may use 2 or more types.

The polymerization initiator is usually in the range of 0.01 to 5 parts by mass, preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the monomer component forming the (meth)acrylic polymer (A) according to the present invention. used in amounts within

- Characteristics of (meth)acrylic polymer (A) The (meth)acrylic polymer (A) according to the present invention is obtained by copolymerizing the monomer components described above, but may be a random copolymer or a block copolymer. May be combined. Among these, random copolymers are preferred. The (meth)acrylic polymer (A) according to the present invention preferably comprises (a1) 70% by mass or more of a (meth)acrylic acid alkyl ester monomer having an alkyl group having 4 to 6 carbon atoms, and (a2) a carboxy group It is a copolymer of a monomer component containing 1 to 8% by mass of a monomer having

The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) measured by gel permeation chromatography (GPC) is not particularly limited, but is usually 200,000 to 150 in terms of polystyrene. 10,000, preferably 300,000 to 1,200,000, more preferably 350,000 to 1,200,000, still more preferably 400,000 to 1,000,000. The molecular weight distribution (Mw/Mn) of the (meth)acrylic polymer (A) measured by GPC method is usually 10 or less, preferably 1-8, more preferably 1-5.

In the pressure-sensitive adhesive composition of the present invention, the content of the (meth)acrylic polymer (A) is not particularly limited. % by mass or more, preferably 60 to 98 mass %, more preferably 70 to 95 mass %. When the content of the (meth)acrylic polymer (A) is within the above range, the performance as an adhesive is well balanced and the adhesive properties are excellent.

Tackifying resin (B)
The pressure-sensitive adhesive composition of the present invention contains a tackifying resin (B). In the present invention, the pressure-sensitive adhesive composition contains the tackifying resin (B), so that it exhibits good adhesive strength and constant-load peelability even when adhered to polyolefin-based low-polarity materials such as polyethylene and polypropylene. An adhesive layer can be formed.

Examples of the tackifying resin (B) include rosin-based tackifying resins such as rosin ester-based resins, terpene-based tackifying resins such as terpene-phenol-based resins, styrene-based tackifying resins, and alicyclic saturated hydrocarbon resins. rosin ester-based resin is preferred.

A rosin ester-based resin is a resin obtained by esterifying a rosin-based resin with alcohol. Examples of rosin-based resins include rosin resins, disproportionated rosin resins, and hydrogenated rosin resins containing resin acids such as abietic acid as main components, and dimers of resin acids such as abietic acid (polymerized rosin resins). is mentioned. Examples of alcohols include polyhydric alcohols such as ethylene glycol, glycerin, and pentaerythritol.

A resin obtained by esterifying a rosin resin is a rosin ester resin, a resin obtained by esterifying a disproportionated rosin resin is a disproportionated rosin ester resin, and a resin obtained by esterifying a hydrogenated rosin resin is a hydrogenated rosin ester resin. A polymerized rosin ester resin is obtained by esterifying a polymerized rosin resin.
A terpene phenolic resin is a resin obtained by polymerizing a terpene in the presence of phenol.

The softening temperature of the tackifying resin (B) is preferably 70-170°C, more preferably 100-170°C. The softening temperature is measured by the JIS K2207 ring and ball method.
Examples of disproportionated rosin ester resins include Superester A75 (75°C), Superester A100 (100°C), Superester A115 (115°C), and Superester A125 (125°C). Hydrogenated rosin ester resins include, for example, Pine Crystal KE-359 (100° C.) and Ester Gum H (70° C.). Examples of polymerized rosin ester resins include Pencel D-135 (135° C.), Pencel D-125 (125° C.), and Pencel D-160 (160° C.). The above products are manufactured by Arakawa Chemical Industries, Ltd. The temperature in parentheses is the softening temperature.

Examples of terpene-based tackifying resins include YS polyester G150 (150°C), YS polyester T100 (100°C), YS polyester G125 (125°C), YS polyester T115 (115°C), YS polyester T145 (145°C), YS Polyster T130 (130° C.) can be mentioned. The above products are manufactured by Yasuhara Chemical Co., Ltd. The temperature in parentheses is the softening temperature.

Examples of styrene-based tackifying resins include FMR-0150 (145°C), FTR-6100 (100°C), FTR-6110 (110°C), FTR-6125 (125°C), FTR-7100 (100°C), FTR-8120 (120°C), FTR-0100 (100°C), FTR-2120 (120°C), FTR-2140 (145°C). The above products are manufactured by Mitsui Chemicals, Inc. The temperature in parentheses is the softening temperature. SX-100 (100° C., manufactured by Yasuhara Chemical Co., Ltd.) is also included.

Examples of alicyclic saturated hydrocarbon resins include Alcon P-90 (90° C.), Alcon P-100 (100° C.), Alcon P-115 (115° C.), Alcon P-125 (125° C.), Alcon M -90 (90°C), Alcon M-100 (100°C), Alcon M-115 (115°C), Alcon P-135 (135°C). The above products are manufactured by Arakawa Chemical Industries, Ltd. The temperature in parentheses is the softening temperature.
The tackifying resin (B) may be used alone or in combination of two or more.

In the pressure-sensitive adhesive composition of the present invention, the amount of the tackifying resin (B) is not particularly limited, but for example 1 to 50 parts per 100 parts by mass of the (meth)acrylic polymer (A). Part by mass, preferably 1 to 40 parts by mass, more preferably 5 to 30 parts by mass. The pressure-sensitive adhesive composition of the present invention contains the tackifying resin (B), so that the pressure-sensitive adhesive layer obtained has appropriate tackiness, and excellent adhesion even to polyolefin-based low-polarity materials. indicates

Plasticizer (C)
The pressure-sensitive adhesive composition of the present invention contains a plasticizer (C). By containing the plasticizer (C), the pressure-sensitive adhesive composition of the present invention has flexibility, and a pressure-sensitive adhesive tape or the like having a layer made of the pressure-sensitive adhesive composition can be attached to an adherend. In this case, the conformability to the shape of the adherend is improved, and good adhesion can be achieved regardless of the material of the adherend or the shape of the application surface.

The plasticizer (C) used in the present invention has a freezing point of −35° C. or higher, is compatible with isopropyl alcohol, and is incompatible with methanol. In the present invention, a solvent such as isopropyl alcohol or methanol and the plasticizer (C) are compatible with each other. It means that they are compatible (dissolved or dispersed, not separated) when placed and visually confirmed. When the plasticizer (C) is such, it is easily dispersed uniformly in the pressure-sensitive adhesive composition, and the plasticizer (C) bleeds out in the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition. It is preferable because it is difficult to The freezing point of the plasticizer (C) is preferably -30°C or higher, more preferably in the range of -30 to 30°C. Further, the plasticizer (C) may be either liquid or solid at room temperature.

In the pressure-sensitive adhesive composition of the present invention, the plasticizer (C) satisfies such conditions, so that the pressure-sensitive adhesive sheet or the like using it exhibits excellent adhesive strength even at low temperatures and is also excellent in removability. It becomes a thing.

Examples of such a plasticizer (C) include known plasticizers such as fatty acid alkyl ester plasticizers, adipic acid plasticizers, polybutene plasticizers, butadiene plasticizers, isoprene plasticizers, and phthalic acid plasticizers. Among them, one that satisfies the above conditions can be used. Specifically, for example, Unistar MB-816 (manufactured by NOF Corporation), Unistar MB-1381 (manufactured by NOF Corporation), Unistar HR-20B (manufactured by NOF Corporation), Vinicizer 124 (manufactured by Kao Corporation) ) , Excepar BS (manufactured by Kao Corporation), Excepar EH-S (manufactured by Kao Corporation), and the like.

Among these, it is preferable to use plasticizers other than phthalic acid-based plasticizers, and it is more preferable to use fatty acid alkyl ester-based plasticizers, from the viewpoint of environmental load.

In the pressure-sensitive adhesive composition of the present invention, the amount of the plasticizer (C) is usually 0.1 parts by mass or more and less than 8 parts by mass, preferably 100 parts by mass of the (meth)acrylic polymer (A). It ranges from 0.5 to 7.5 parts by mass, more preferably from 1 to 7 parts by mass.

Crosslinking agent (D)
The pressure-sensitive adhesive composition of the present invention contains a cross-linking agent (D).
The cross-linking agent (D) is not particularly limited, but epoxy-based cross-linking agents, isocyanate-based cross-linking agents, chelate-based cross-linking agents, and the like can be used. The cross-linking agents may be used singly or in combination of two or more.

Examples of epoxy-based cross-linking agents include (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglydyl-m-xylylenediamine, N,N,N', N'-tetraglydylaminophenylmethane, triglycidyl isocyanate, m-N,N-diglycidylaminophenylglycidyl ether, N,N-diglycidyltoluidine, N,N-diglycidylaniline, pentaerythritol polyglycidyl ether, 1 , 6-hexanediol diglycidyl ether and the like.

Isocyanate-based cross-linking agents include isocyanate monomers such as tolylene diisocyanate, chlorophenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, and Isocyanate compounds obtained by adding trimethylolpropane to these isocyanate monomers, burette-type isocyanate compounds, and urethane prepolymers obtained by adding polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, and polyisoprene polyols to isocyanate monomers. type isocyanate.

Examples of chelate cross-linking agents include compounds in which polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium are coordinated with alkoxides, acetylacetone, ethyl acetoacetate, and the like. metal chelate compounds such as Specific examples include aluminum isopropylate, aluminum secondary butyrate, aluminum ethylacetoacetate/diisopropylate, aluminum trisethylacetoacetate, and aluminum trisacetylacetonate.

As the cross-linking agent (D), an isocyanate-based cross-linking agent is preferable because of its excellent cross-linking properties.
The pressure-sensitive adhesive composition of the present invention can form a three-dimensional crosslinked structure by reacting the cross-linking agent, and can exhibit high adhesive strength and cohesive strength.

In the pressure-sensitive adhesive composition of the present invention, the amount of the cross-linking agent (D) is not particularly limited, but is preferably 0.05 per 100 parts by mass of the (meth)acrylic polymer (A). to 15 parts by mass, more preferably 0.1 to 10 parts by mass.

Other Components The pressure-sensitive adhesive composition of the present invention may contain other components as long as the purpose thereof is not impaired. Other components include, for example, polymers other than the (meth)acrylic polymer (A) and the tackifying resin (B), various additives, and the like. Examples of additives include antistatic agents, silane coupling agents, antioxidants, UV absorbers, fine particles, dyes, and the like. When the pressure-sensitive adhesive composition of the present invention contains components other than (A) to (D), the content of components other than (A) to (D) in 100% by mass of the solid content of the pressure-sensitive adhesive composition The amount (solid content) can be, for example, 0.03 to 30% by mass, preferably 0.05 to 25% by mass, more preferably 0.08 to 20% by mass.

The pressure-sensitive adhesive composition of the present invention may contain an organic solvent in addition to the components described above within a range that does not impair the effects of the present invention.
Examples of the organic solvent include the polymerization solvents described in the description of the conditions for producing the (meth)acrylic polymer (A). The organic solvent may be one added during preparation of the pressure-sensitive adhesive composition, or may be added to the pressure-sensitive adhesive composition by using a polymer solution containing the (meth)acrylic polymer (A) and a polymerization solvent as raw materials. may be included.
In the pressure-sensitive adhesive composition of the present invention, the content of the organic solvent can be appropriately adjusted depending on the desired viscosity and the like, and is not particularly limited. %.

<Method for producing pressure-sensitive adhesive composition>
The pressure-sensitive adhesive composition of the present invention can be obtained by mixing the components (A) to (D) described above by a known method using a stirring device or the like. That is, the pressure-sensitive adhesive composition of the present invention can be obtained by mixing and stirring the respective components constituting the composition all at once or sequentially. The stirring time is not particularly limited, but from the standpoint of workability and productivity, it may be about 10 to 120 minutes at room temperature.

<Adhesive layer>
The pressure-sensitive adhesive layer according to the present invention is formed from the above-described pressure-sensitive adhesive composition of the present invention. The pressure-sensitive adhesive layer is obtained, for example, by promoting the cross-linking reaction in the pressure-sensitive adhesive composition described above, specifically by cross-linking the (meth)acrylic polymer (A) with the cross-linking agent (D).

The conditions for forming the pressure-sensitive adhesive layer are, for example, as follows. The pressure-sensitive adhesive composition of the present invention is applied onto a substrate or release-treated surface of a release sheet, and is usually heated at 50 to 150°C, preferably 60 to 100°C for 1 to 10 minutes, depending on the type of solvent. It is preferably dried for 2-7 minutes to remove the solvent and form a coating. The thickness of the dried coating film is not particularly limited, but is usually 5 to 125 μm, preferably 10 to 100 μm.

As a method for applying the pressure-sensitive adhesive composition, known methods such as spin coating, knife coating, roll coating, bar coating, blade coating, die coating, and gravure coating may be used to obtain a predetermined thickness. A method of coating and drying can be used.

The pressure-sensitive adhesive layer is formed, for example, by coating the pressure-sensitive adhesive composition of the present invention on the release-treated surface of a substrate or a release sheet, forming a coating film under the above conditions, and attaching a release sheet on the formed coating film. After that, usually 3 days or more, preferably 7 to 10 days, usually 5 to 60 ° C., preferably 15 to 40 ° C., usually 5 to 70% RH, preferably 5 to 50% RH By curing in an environment Obtainable. Crosslinking under the aging conditions as described above enables efficient formation of a crosslinked body (network polymer).

The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention preferably has a gel fraction of 10 to 95% by mass, more preferably 20 to 80% by mass, from the viewpoints of adhesive strength, cohesive strength, and removability. , more preferably 30 to 70% by mass.

<Adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention described above. The pressure-sensitive adhesive sheet of the present invention may be a pressure-sensitive adhesive sheet consisting only of a pressure-sensitive adhesive layer produced from the pressure-sensitive adhesive composition, or a pressure-sensitive adhesive sheet that is a laminate having a substrate layer and a pressure-sensitive adhesive layer. good too. Moreover, a tape-shaped adhesive sheet (adhesive tape) may be used.

The thickness of the pressure-sensitive adhesive layer may be appropriately set according to the use of the pressure-sensitive adhesive sheet, and is not particularly limited, but is usually 5-125 μm, preferably 10-100 μm.

When the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet consisting only of a pressure-sensitive adhesive layer produced from the pressure-sensitive adhesive composition, for example, the pressure-sensitive adhesive composition is applied onto a release-treated substrate and dried. and, if necessary, a release-treated base material is placed on the coating surface to form a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet consisting of only the pressure-sensitive adhesive layer is stored, moved, etc., together with the release-treated base material during storage, movement, etc., but when used, the release-treated base material is peeled off, and the pressure-sensitive adhesive layer is removed. It is used as an adhesive sheet consisting of only layers.

When the pressure-sensitive adhesive sheet of the present invention is a laminate having a base material layer and a pressure-sensitive adhesive layer, for example, the pressure-sensitive adhesive composition is applied onto the base material, dried, and if necessary, Furthermore, a method of placing a release-treated substrate on the coated surface; the adhesive composition is applied onto the release-treated substrate and dried, and the substrate is placed on the formed adhesive layer. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed on a substrate can be obtained by the method described above. At the time of use, the pressure-sensitive adhesive layer is used as a pressure-sensitive adhesive sheet consisting of the base layer and the pressure-sensitive adhesive layer after the release-treated base material is peeled off.
As another example, a pressure-sensitive adhesive sheet may be obtained by providing pressure-sensitive adhesive layers on both sides of a base material layer and disposing a release-treated base material on both sides thereof.

The substrate constituting the substrate layer is preferably in the form of a film or a sheet. Examples of the base material include, but are not particularly limited to, plastic, glass, woven fabric, nonwoven fabric, paper, and metal foil. As plastics, polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polyurethane (PU), acrylonitrile-butadiene-styrene copolymer (ABS), polyamide (nylon) and the like. These plastics may be sheet-like or film-like, and may be foams (foam substrates).

Since the pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed from the above-described pressure-sensitive adhesive composition, it has good adhesive physical properties such as removability, curved surface adhesion, holding power, and polyolefin adhesion.
The use of the pressure-sensitive adhesive sheet of the present invention is not particularly limited. It can be particularly preferably used as.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. In the following descriptions of Examples and the like, "parts" means "parts by mass" unless otherwise specified.
In the following, various physical properties were measured or evaluated as follows.

Solubility test Put 5 g of isopropyl alcohol or methanol in a 30 mL glass bottle (As One Co., Ltd., No. 4K), add 0.5 g of plasticizer (C) used in Examples, etc., shake temperature 25 ° C., amplitude 10 mm, a shaking speed of 120 r/min, and a shaking time of 10 minutes. The evaluation criteria were as follows. Table 1 shows the results of the solubility test.
◯: Uniformly compatible.
x: separated.

Weight average molecular weight (Mw)
The weight average molecular weight (Mw) of the copolymer was measured by gel permeation chromatography (GPC method) under the following conditions.
・ Measuring device: HLC-8320GPC (manufactured by Tosoh)
・ GPC column configuration: the following quadruple columns (all manufactured by Tosoh)
(1) TSKgel HxL-H (guard column)
(2) TSKgel GMHxL
(3) TSKgel GMHxL
(4) TSKgel G2500HxL
・Flow rate: 1.0 mL/min
・Column temperature: 40°C
・Sample concentration: 1.5% (w/v) (diluted with tetrahydrofuran)
・Mobile phase solvent: Tetrahydrofuran ・Converted to standard polystyrene

About 0.1 g of the adhesive layer was collected in a sample bottle from the adhesive sheets obtained in Gel Fraction Examples and Comparative Examples, and 30 mL of ethyl acetate was added and immersed for 24 hours. It was filtered through a mesh stainless wire mesh, and the residue on the wire mesh was dried at 100° C. for 2 hours to measure the dry weight. The gel fraction of the pressure-sensitive adhesive layer was determined by the following formula.
・Gel fraction (%) = (dry weight/adhesive layer collection weight) x 100

Adhesive strength/peelability Under conditions of 23°C and 50% RH, the PET separator of the test piece (25 mm width) of the adhesive sheet obtained in Examples etc. was peeled off, and the exposed adhesive layer surface was placed on a SUS plate (polished stainless steel plate). , and pressed back and forth three times using a roller of 2 kg. After holding this for 20 minutes or 1 week after attachment under the measurement environment (23 ° C., 50% RH condition, or 5 ° C., dry condition), the adhesive sheet was peeled from the SUS plate at a peel angle of 180 ° under the same measurement environment. , at a tensile speed of 300 mm/min, and the adhesive strength of the adhesive layer of the adhesive sheet and the peeling form were evaluated based on the following criteria.
〇: Interface failure (af)
△: Contamination (adhesive residue) ×: Cohesive failure (cf), adhesive transfer, or substrate failure

Using a test piece (25 mm × 60 mm) of the adhesive sheet obtained in the removability example, etc., the PET separator was peeled off, and the exposed adhesive layer surface was applied to the adherend (BA-SUS plate (mirror-finished stainless steel plate) or soft vinyl chloride cushion floor) under conditions of 23° C. and 50% RH, and pressed back and forth three times using a 2 kg roller. After standing at 23° C. for 30 days, the pressure-sensitive adhesive sheet was peeled off at a peeling angle of 180° and a tensile speed of 3 m/min under the temperature conditions at which it was left standing. It was visually confirmed and evaluated. The evaluation criteria were as follows.
◯: Stain or adhesive residue on the adherend after peeling is less than 10% of the area of the adhesive sheet attached.
Δ: Contamination or adhesive residue on the adherend after peeling is observed in 10% or more and less than 50% of the area of the adhesive sheet attached.
x: Stain or adhesive residue on the adherend after peeling is observed in 50% or more of the area of the adhesive sheet attached.

Curved surface adhesiveness Under conditions of 23 ° C. and 50% RH, using a test piece (25 mm × 60 mm) of the adhesive sheet obtained in Examples etc., peel off the PET separator, and cover the exposed adhesive layer surface with a curing sheet (kraft paper (both sides of which are laminated with polyethylene sheets and embossed), and crimped three times using a roller of 2 kg. The test piece was fixed in a cylinder with a diameter of 3 cm with the curing sheet inside so that the long side of the test piece was curved, and allowed to stand in an environment of 40° C. for 7 days. After that, the adhesion state of the test piece was visually confirmed and evaluated. The evaluation criteria were as follows.
◯: Peeling is observed in less than 1% of the area of the adhered test piece.
Δ: Peeling is observed in 1% or more and less than 5% of the area of the adhered test piece.
x: Peeling is observed in 5% or more of the area of the adhered test piece.

Production of (meth)acrylic polymer (A) [Synthesis Example 1]
97.8 parts of n-butyl acrylate (BA), 2.0 parts of acrylic acid (AA), and 2-hydroxyethyl acrylate (2HEA) were added to a flask equipped with a stirrer, nitrogen gas inlet, thermometer and reflux condenser. ) was introduced, and 150 parts of ethyl acetate was introduced as a solvent.

Then, 0.05 part of 2,2′-azobisisobutyronitrile (AIBN) was added as a polymerization initiator while stirring in a nitrogen gas atmosphere, and reaction was carried out at 70° C. for 7 hours. After completion of the reaction, the reaction solution was diluted with ethyl acetate to prepare a polymer solution containing the acrylic polymer A1 and having a solid concentration of 20% by mass. The weight average molecular weight (Mw) of acrylic polymer A1 was 420,000.

[Synthesis Example 2]
In the same manner as in Synthesis Example 1 except that the polymerizable monomers used in the polymerization reaction were changed as shown in Table 2 and 0.05 parts of AIBN was added, the solid content containing acrylic polymer A2 was 20 mass. % polymer solution was prepared. In Table 2, 2EHA is 2-ethylhexyl acrylate. Mw of acrylic polymer A2 was 420,000.

[Synthesis Example 3]
In the same manner as in Synthesis Example 1 except that the polymerizable monomers used in the polymerization reaction were changed as shown in Table 2 and 0.04 parts of AIBN was blended, the solid content containing acrylic polymer A3 was 20 mass. % polymer solution was prepared. Mw of acrylic polymer A3 was 550,000.

[Synthesis Example 4]
In the same manner as in Synthesis Example 1 except that the polymerizable monomers used in the polymerization reaction were changed as shown in Table 2 and 0.025 parts of AIBN was added, the solid content containing acrylic polymer A4 was 20 mass. % polymer solution was prepared. Mw of acrylic polymer A4 was 900,000.

[Synthesis Example 5]
A polymer solution with a solid content of 20% by mass containing acrylic polymer A5 was prepared in the same manner as in Synthesis Example 1 except that the polymerizable monomers used in the polymerization reaction were changed as shown in Table 2. Mw of acrylic polymer A5 was 420,000.

[Synthesis Example 6]
A polymer solution with a solid content of 20% by mass containing acrylic polymer A6 was prepared in the same manner as in Synthesis Example 1 except that the polymerizable monomers used in the polymerization reaction were changed as shown in Table 2. Mw of acrylic polymer A6 was 420,000.

[Synthesis Example 7]
A polymer solution with a solid content of 20% by mass containing acrylic polymer A7 was prepared in the same manner as in Synthesis Example 1 except that the polymerizable monomers used in the polymerization reaction were changed as shown in Table 2. Mw of acrylic polymer A7 was 450,000.

[Example 1] (Production of adhesive composition and adhesive sheet)
Polymer solution of acrylic polymer A1 obtained in Synthesis Example 1 (solid content concentration 20% by mass), a polymerized rosin ester resin (Pencel D-135, manufactured by Arakawa Chemical Industries, Ltd.) as a tackifying resin, and Excepal as a plasticizer ( Registered trademark) BS (manufactured by Kao Corporation, freezing point: 25 ° C.), a polyisocyanate-based cross-linking agent (Coronate L, manufactured by Tosoh Corporation), and other components with respect to 100 parts by mass of the solid content of the acrylic polymer A1. They were mixed at a blending ratio such that the solid content was the parts by mass shown in Table 3, respectively, to obtain a pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition obtained was applied onto a polyethylene substrate sheet so that the film thickness after drying was 30 μm, and dried at 90° C. for 3 minutes to form a pressure-sensitive adhesive layer. This was laminated with a polyethylene terephthalate (PET) separator and aged at 40° C. for 3 days to obtain an adhesive sheet.
Using the obtained pressure-sensitive adhesive sheet, the peel form and removability were evaluated by the methods described above. The results are also shown in Table 3.

[Examples 2 to 13, Comparative Examples 1 to 10]
The pressure-sensitive adhesive composition and the pressure-sensitive adhesive composition were prepared in the same manner as in Example 1, except that the type of acrylic polymer and the types and blending amounts of the tackifying resin, plasticizer, and cross-linking agent were as shown in Tables 3 and 4. A pressure-sensitive adhesive sheet was produced, and the release form and removability were evaluated. The results are also shown in Tables 3 and 4.

In Tables 3 and 4, "SEA-100" is a polymerized rosin ester resin tackifying resin manufactured by Arakawa Chemical Industries, Ltd., and "Exepar EH-S" is manufactured by Kao Corporation and has a solidification point of 15°C. agent, "MB-816" manufactured by NOF Corporation, a freezing point: 0 ° C. plasticizer, "MB-1381" manufactured by NOF Corporation, a freezing point: -30 ° C. plasticizer, " HR-32" is manufactured by NOF Corporation and is a plasticizer with a freezing point of -50°C. "DOP" is manufactured by J-Plus Co., Ltd. and is a plasticizer with a freezing point of -40°C. is a plasticizer with a freezing point of −5° C. manufactured by Kao Corporation, and “Trimex T-10” is a plasticizer with a freezing point of −48° C. manufactured by Kao Corporation.

The pressure-sensitive adhesive composition of the present invention is suitable for use in forming a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive sheet of the present invention is suitable as a pressure-sensitive adhesive sheet used for protecting various structures, particularly as a curing pressure-sensitive adhesive sheet. be.

Claims (6)

A pressure-sensitive adhesive composition comprising a (meth)acrylic polymer (A), a tackifying resin (B), a plasticizer (C), and a cross-linking agent (D),
The plasticizer (C) has a freezing point of −35° C. or higher, is compatible with isopropyl alcohol, and is incompatible with methanol, and includes 2 - ethylhexyl palmitate, butyl stearate, 2-stearate containing either ethylhexyl or a dialkyl phthalate having an alkyl group of 10 to 12 carbon atoms,
The pressure-sensitive adhesive composition, wherein the amount of the plasticizer (C) is 0.1 parts by mass or more and less than 8 parts by mass with respect to 100 parts by mass of the (meth)acrylic polymer (A). The (meth)acrylic polymer (A) is
(a1) 50% by mass or more of a (meth)acrylic acid alkyl ester monomer having an alkyl group having 4 to 6 carbon atoms;
2. The pressure-sensitive adhesive composition according to claim 1, which is a copolymer of a monomer component containing (a2) 1 to 8% by mass of a monomer having a carboxy group. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the (meth)acrylic polymer (A) has a weight average molecular weight of 300,000 or more and 1,200,000 or less. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the tackifying resin (B) is a rosin-based tackifying resin. The pressure-sensitive adhesive composition according to any one of claims 1 to 4 , which is for curing. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 5 .