Active energy ray curable adhesive composition and its uses

Abstract

To provide an active energy ray curable adhesive composition that offers excellent hot-melt coating properties, superior adhesive properties such as adhesion strength and holding power to the substrate of an adhesive sheet using a PVC substrate, and excellent gasoline resistance. [Solution] An active energy ray curable adhesive composition containing a (meth)acrylic resin (A) and a tackifier (B). The (meth)acrylic resin (A) contains constituent units derived from alkyl (meth)acrylate (a1) having an alkyl group having 4 or more carbon atoms, constituent units derived from alkoxyalkyl (meth)acrylate (a2), constituent units derived from monomer (a3) ​​having an active energy ray active site, and constituent units derived from polar group-containing ethylenically unsaturated monomer (a4), and has a weight-average molecular weight of 200,000 or less. The tackifier (B) contains a rosin-based resin (B1) with an acid value of 100 mgKOH / g or more.

Description

Technical Field

[0001] The present invention relates to an active energy ray curable adhesive composition and its uses, and more particularly, to an active energy ray curable adhesive composition suitable for hot melt coating, an adhesive obtained by crosslinking the adhesive composition, a laminate having an adhesive layer composed of the adhesive, and an adhesive sheet.

Background Art

[0002] As adhesives used for adhesive layers such as adhesive tapes and adhesive sheets, rubber-based adhesives and acrylic-based adhesives are known. As acrylic-based adhesives, (co)polymers having specific alkyl (meth)acrylate as an essential constituent unit have been developed.

[0003] In recent years, due to the increasing concern for the environment, adhesive compositions that do not use organic solvents have attracted attention. For example, hot melt type adhesive compositions that apply a resin melted by heat onto a base sheet without using an organic solvent have been proposed. Patent Document 1 and the like describe crosslinking a hot melt coated acrylic-based adhesive composition by irradiation with active energy rays. However, the acrylic-based adhesive composition described in Patent Document 1 had a high melt viscosity, so it was necessary to raise the temperature during coating.

[0004] In order to solve this problem, Patent Document 2 proposes an adhesive composition containing an acrylic copolymer having a constituent unit derived from a macromonomer. According to this adhesive composition, an adhesive excellent in low temperature coating property, excellent in holding power even with a low ultraviolet irradiation amount, and improved in adhesive residue when re-peeled can be obtained.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] On the other hand, marking films are used instead of paint for purposes such as displaying, decorating, and advertising vehicles, containers, and signs. Marking films consist of a base sheet that is colored or surface-printed, with an adhesive applied to one side. Polyvinyl chloride (PVC) sheets are generally used as the base sheet for these marking films due to their weather resistance, colorability, and cost-effectiveness, and there is a need for adhesive compositions with excellent adhesive properties such as adhesion strength and holding power to the adherend.

[0007] Furthermore, in marking films used on vehicles such as automobiles and motorcycles that run on gasoline, the PVC substrate has the property of both permeating and absorbing gasoline, so the adhesive composition used in the marking film is required to have excellent gasoline resistance.

[0008] The present invention aims to provide an active energy ray curable adhesive composition that exhibits excellent hot-melt coating properties, superior adhesive properties such as adhesion strength and holding power to the adherend of an adhesive sheet using a PVC substrate, and also excellent gasoline resistance. The present invention also aims to provide an adhesive obtained by crosslinking the adhesive composition, an adhesive sheet having an adhesive layer made of the adhesive, and a laminate in which the adhesive layer and other members are laminated together. [Means for solving the problem]

[0009] However, in view of these circumstances, the inventors conducted extensive research and, as a result, discovered that the above objective can be achieved by combining a (meth)acrylic resin containing constituent units derived from specific monomers with a tackifier having specific physical properties, thus completing the present invention.

[0010] That is, the present invention includes the following embodiments. One aspect of the present invention is an active energy ray curable adhesive composition (hereinafter also simply referred to as "adhesive composition") containing a (meth)acrylic resin (A) and a tackifier (B), wherein the (meth)acrylic resin (A) contains constituent units derived from alkyl (meth)acrylate (a1) having an alkyl group having 4 or more carbon atoms, constituent units derived from alkoxyalkyl (meth)acrylate (a2), constituent units derived from monomer (a3) ​​having an active energy ray active site, and constituent units derived from polar group-containing ethylenically unsaturated monomer (a4), the weight-average molecular weight of the (meth)acrylic resin (A) is 200,000 or less, and the tackifier (B) is a rosin resin (B1) with an acid value of 100 mgKOH / g or more.

[0011] Aspect (2) of the present invention is the adhesive composition of aspect (1), wherein the glass transition temperature of the (meth)acrylic resin (A) is -30°C or lower.

[0012] Aspect (3) of the present invention is the adhesive composition of aspect (1) or (2), wherein the alkoxyalkyl (meth)acrylate (a2) is methoxyethyl (meth)acrylate.

[0013] Aspect (4) of the present invention is an adhesive composition of any of aspects (1) to (3), wherein the (meth)acrylic resin (A) further contains constituent units derived from alkyl (meth)acrylate (a5) having an alkyl group having 3 or fewer carbon atoms.

[0014] Aspect (5) of the present invention is an adhesive composition of any of aspects (1) to (4) wherein the content of the rosin-based resin (B1) is 1 to 50 parts by weight per 100 parts by weight of the (meth)acrylic resin (A).

[0015] Aspect (6) of the present invention is an adhesive composition of any of aspects (1) to (5) that further contains a plasticizer (C).

[0016] Aspect (7) of the present invention is an adhesive composition according to any one of aspects (1) to (6), wherein the content of the thermal crosslinking agent is less than 0.1% by weight of the whole composition.

[0017] Aspect (8) of the present invention is an active energy ray-curable adhesive obtained by crosslinking an adhesive composition according to any one of aspects (1) to (7).

[0018] Aspect (9) of the present invention is an adhesive sheet having an adhesive layer composed of the active energy ray-curable adhesive of aspect (8).

[0019] Aspect (10) of the present invention is an adhesive sheet having a polyvinyl chloride base sheet and an adhesive layer composed of the active energy ray-curable adhesive of aspect (8).

[0020] Aspect (11) of the present invention is a laminate in which an adhesive layer composed of the active energy ray-curable adhesive of aspect (8) and another member are laminated.

[0021] In addition, the (meth)acrylic resin in this specification represents an acrylic resin or a methacrylic resin. Further, (meth)acrylic means acrylic or methacrylic, (meth)acryloyl means acryloyl or methacryloyl, and (meth)acrylate means acrylate or methacrylate, respectively. Also, the "adhesive sheet" in this specification conceptually includes an adhesive sheet, an adhesive film, and an adhesive tape.

Advantages of the Invention

[0022] The adhesive obtained by using the adhesive composition of the present invention has high thermal stability of the resin, good hot melt coating properties, and excellent adhesive properties such as adhesive force and holding force to adherends, particularly low-polarity adherends such as polyolefins. Further, the adhesive sheet obtained by coating and crosslinking the adhesive composition of the present invention on a PVC substrate is excellent in adhesive force and holding force to adherends. Furthermore, since the adhesive obtained by using the adhesive composition of the present invention is excellent in gasoline resistance, it can be suitably used for a marking film for a vehicle using gasoline as fuel.

Embodiments for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described in detail, but these are examples of preferred embodiments, and the present invention is not limited to these embodiments. Hereinafter, the present invention will be described in detail. In this specification, “(iso)alkyl” represents branched alkyl or linear alkyl. In addition, when expressed as “X to Y” (X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of “X or more and Y or less” and also the meaning of “preferably larger than X” or “preferably smaller than Y”. In addition, when expressed as “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), it also includes the meaning of “preferably larger than X” or “preferably less than Y”. Furthermore, “y and / or z” (y and z are arbitrary configurations) means at least one of y and z, and means three cases: only y, only z, and both y and z. In the plurality of numerical ranges described stepwise in this specification, each upper limit value and each lower limit value can be the upper limit value or the lower limit value of an arbitrarily combined numerical range. For example, when there is a description of “5 to 20% by mass, 10 to 15% by mass” for the content of a certain component, numerical ranges of “5 to 15% by mass”, “10 to 20% by mass”, “5 to 10% by mass”, and “15 to 20% by mass” can be constituted. Furthermore, within the numerical ranges described herein, the upper or lower limits of those ranges may be replaced with values ​​shown in the examples or values ​​uniquely derived from the examples.

[0024] (1) Adhesive composition The adhesive composition of the present invention contains a (meth)acrylic resin (A) and a tackifier (B) as essential components. First, these essential components will be described in order.

[0025] <(Meth)acrylic resin (A)> The (meth)acrylic resin (A) used in the present invention is a polymer obtained by polymerizing copolymer component (a). Copolymer component (a) contains at least an alkyl (meth)acrylate (a1) having an alkyl group having 4 or more carbon atoms, an alkoxyalkyl (meth)acrylate (a2), a monomer (a3) ​​having an active energy ray active site, and a polar group-containing ethylenically unsaturated monomer (a4), and optionally contains an alkyl (meth)acrylate (a5) having an alkyl group having 3 or fewer carbon atoms, and other polymerizable monomers (a6). In other words, the acrylic resin (A) obtained by copolymerizing copolymer components (a) containing these monomers contains at least structural units derived from alkyl (meth)acrylate (a1) having an alkyl group having 4 or more carbon atoms, structural units derived from alkoxyalkyl (meth)acrylate (a2), structural units derived from monomer (a3) ​​having an active energy ray active site, and structural units derived from polar group-containing ethylenically unsaturated monomer (a4), and optionally further contains structural units derived from alkyl (meth)acrylate (a5) having an alkyl group having 3 or fewer carbon atoms, and structural units derived from other polymerizable monomers (a6). In the acrylic resin (A) obtained by copolymerizing copolymer component (a), the content of constituent units derived from each monomer relative to the total constituent units shall be the same as the amount (content) of each monomer added to copolymer component (a).

[0026] [Alkyl (meth)acrylate (a1) having an alkyl group with 4 or more carbon atoms] Examples of alkyl(meth)acrylates (a1) having an alkyl group with four or more carbon atoms (hereinafter sometimes simply referred to as "alkyl(meth)acrylate (a1)") include n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl(meth)acrylate, (iso)octyl acrylate, (iso)decyl acrylate, (iso)nonyl acrylate, lauryl(meth)acrylate, and isostearyl acrylate. One of these selected alkyl(meth)acrylates (a1) can be used alone or in combination of two or more. The number of carbon atoms in the alkyl(meth)acrylate (a1) is preferably 20 or less, more preferably 15 or less, and particularly preferably 10 or less. Among these, n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred from the viewpoint of having a low glass transition temperature.

[0027] It is preferable that the alkyl (meth)acrylate (a1) does not contain polar groups such as hydroxyl groups, carboxyl groups, or amino groups. Alkyl (meth)acrylate (a1) is excluded from monomers having active energy ray active sites (a3) ​​and polar group-containing ethylenically unsaturated monomers (a4) described later.

[0028] The glass transition temperature when forming a homopolymer using alkyl (meth)acrylate (a1) is usually measured by differential scanning calorimeter (DSC), and can be measured according to methods compliant with JIS K7121-1987 or JIS K 6240.

[0029] The content of alkyl (meth)acrylate (a1) is preferably 1 to 99% by weight, more preferably 30 to 97% by weight, and particularly preferably 50 to 95% by weight, relative to copolymer component (a). If the content is too low, the balance between tackiness and holding power tends to decrease, and if the content is too high, the balance between tackiness and holding power also tends to decrease.

[0030] [Alkoxyalkyl (meth)acrylate (a2)] The number of carbon atoms in the alkoxyalkyl (meth)acrylate (a2) is preferably 1 to 20, more preferably 1 to 16, particularly preferably 1 to 12, and even more preferably 1 to 10. Examples of alkoxyalkyl (meth)acrylate (a2) include methoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate. One of these can be used alone or in combination of two or more as the alkoxyalkyl (meth)acrylate (a2). Among these, methoxyethyl (meth)acrylate is preferred due to its low glass transition temperature, high polarity, and versatility, and methoxyethyl acrylate is more preferred.

[0031] It is preferable that the alkoxyalkyl (meth)acrylate (a2) does not contain polar groups such as hydroxyl groups, carboxyl groups, or amino groups. The alkoxyalkyl (meth)acrylate (a2) is excluded from the monomers having active energy ray active sites (a3) ​​and polar group-containing ethylenically unsaturated monomers (a4) described later.

[0032] The content of alkoxyalkyl (meth)acrylate (a2) is preferably 1 to 99% by weight, more preferably 5 to 70% by weight, and particularly preferably 10 to 50% by weight, relative to copolymer component (a). If the content is too low, gasoline resistance cannot be ensured, and if the content is too high, gelation during polymerization and tackiness may decrease.

[0033] [Monomers with active energy ray active sites (a3)] An active energy ray site is a site that, upon irradiation with an active energy ray, can form a cross-linked structure with another site within the same (meth)acrylic resin (A) molecule or with another (meth)acrylic resin (A) molecule. A monomer (a3) ​​having an active energy ray site (hereinafter sometimes simply referred to as "monomer (a3)") is a monomer that has such an active site in its molecule. When performing active energy ray irradiation, various types of light rays can be used, including far ultraviolet, ultraviolet, near ultraviolet, and infrared rays, as well as electromagnetic waves such as X-rays and gamma rays, and electron beams, proton beams, and neutron beams. However, due to factors such as curing speed, availability of irradiation equipment, and cost, curing by ultraviolet irradiation is advantageous. While not limited to a specific monomer (a3), for example, a (meth)acrylate having such an active site can be used.

[0034] Examples of active sites for active energy rays include benzophenone structures, benzyl structures, o-benzoylbenzoic acid ester structures, thioxanthone structures, 3-ketocoumarin structures, 2-ethylanthraquinone structures, and camphaquinone structures. Each of these structures can be excited by irradiation with active energy rays, and in their excited state, they can abstract hydrogen radicals from (meth)acrylic resin (A) molecules. In this way, radicals are generated on the (meth)acrylic resin (A) molecules. Various reactions are triggered in the system, such as the formation of crosslinked structures by the bonding of the generated radicals to each other, the generation of peroxide radicals by reaction with oxygen molecules, the formation of crosslinked structures via the generated peroxide radicals, and the abstraction of other hydrogen radicals by the generated radicals, and the (meth)acrylic resin (A) is ultimately crosslinked.

[0035] Among the structures described above, the benzophenone structure is preferred when considering transparency, reactivity, etc. Examples of (meth)acrylates having such a benzophenone structure include, but are not limited to, 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, 4-acryloyloxyethoxy-4'-bromobenzophenone, 4-methacryloyloxybenzophenone, 4-methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-bromobenzophenone, and mixtures thereof.

[0036] As monomer (a3), one of these can be used alone or in combination of two or more. Monomer (a3) ​​is excluded from alkyl (meth)acrylate (a1), alkoxyalkyl (meth)acrylate (a2), and polar group-containing ethylenically unsaturated monomer (a4) described later.

[0037] The monomer (a3) ​​content is preferably 0.1 to 10% by weight, preferably 0.15 to 5% by weight, and more preferably 0.2 to 3% by weight, relative to copolymer component (a). If the content is too low, the curability upon irradiation with active energy rays tends to be low, and if the content is too high, the curability improves, but the gel fraction increases too much, which tends to reduce the adhesive strength.

[0038] [Polar group-containing ethylenically unsaturated monomer (a4)] Polar group-containing ethylenically unsaturated monomers (a4) are ethylenically unsaturated monomers that contain polar groups excluding the active energy ray site. Examples of polar group-containing ethylenically unsaturated monomers (a4) include hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, and cyano group-containing monomers. Among these, carboxyl group-containing monomers are preferred because they exhibit excellent adhesive strength as the (meth)acrylic resin (A) obtained by copolymerization.

[0039] Examples of the hydroxyl group-containing monomers mentioned above include primary hydroxyl group-containing monomers, secondary hydroxyl group-containing monomers, and tertiary hydroxyl group-containing monomers. Examples of primary hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylate monomers such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate; and others such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, N-methylol (meth)acrylamide, and hydroxyethylacrylamide. Examples of secondary hydroxyl group-containing monomers include 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate. Examples of monomers containing tertiary hydroxyl groups include 2,2-dimethyl-2-hydroxyethyl (meth)acrylate. Among these, hydroxyalkyl ester monomers of (meth)acrylate are preferred, and 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are more preferred, with 4-hydroxybutyl acrylate being particularly preferred, due to their low levels of impurities such as di(meth)acrylate and ease of production.

[0040] Examples of the above-mentioned carboxyl group-containing monomers include (meth)acrylic acid, β-carboxyethyl (meth)acrylate, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, N-glycolic acid, and cinnamic acid. Among these, (meth)acrylic acid is preferred because it readily incorporates carboxyl groups and is easy to manufacture.

[0041] Examples of the above-mentioned amino group-containing monomers include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and their quaternary derivatives.

[0042] Examples of the above-mentioned amide group-containing monomers include (meth)acrylamide, N-(n-butoxyalkyl)(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, vinylpyrrolidone, and acryloylmorpholin.

[0043] Examples of the above-mentioned cyano group-containing monomers include acrylonitrile and methacrylonitrile.

[0044] As the polar group-containing ethylenically unsaturated monomer (a4), one selected from these can be used alone or in combination of two or more.

[0045] The content of the polar group-containing ethylenically unsaturated monomer (a4) is preferably less than 15% by weight, more preferably 0.1% to less than 13.5% by weight, particularly preferably 0.5 to 12% by weight, even more preferably 1 to 11% by weight, and especially preferably 2 to 10% by weight, relative to the copolymer component (a), in order to achieve both thermal stability and adhesive properties of the resin. If the content is too high, the thermal stability of the (meth)acrylic resin (A) obtained by copolymerization tends to decrease. Conversely, if the content is too low, the adhesive strength of the adhesive obtained by crosslinking tends to decrease.

[0046] [Alkyl (meth)acrylate (a5) having an alkyl group with 3 or fewer carbon atoms] The (meth)acrylic resin (A) may contain constituent units derived from alkyl (meth)acrylate (a5) having an alkyl group having 3 or fewer carbon atoms. Examples of alkyl (meth)acrylate (a5) having an alkyl group having 3 or fewer carbon atoms (hereinafter sometimes simply referred to as "alkyl (meth)acrylate (a5)") include methyl (meth)acrylate and ethyl (meth)acrylate. One of these selected alkyl (meth)acrylates (a5) can be used alone or in combination of two or more. Among these, methyl acrylate is preferred because it is highly polar and can contribute to improved gasoline resistance.

[0047] The content of alkyl (meth)acrylate (a5) is preferably 1 to 40% by weight, more preferably 5 to 30% by weight, and particularly preferably 10 to 20% by weight, relative to copolymer component (a). Having the alkyl (meth)acrylate (a5) content within the above range has the advantage of improving gasoline resistance.

[0048] [Other polymerizable monomers (a6)] Other polymerizable monomers (a6) can be any polymerizable monomer other than those listed in (a1) to (a5) above. Examples include alicyclic structure-containing monomers, aromatic monomers, vinyl monomers, etc. One of these can be used alone or in combination of two or more.

[0049] Examples of monomers containing the above-mentioned alicyclic structure include (meth)acrylates having an alicyclic structure, such as cyclohexyl (meth)acrylate, isobornyl acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and 2-adamantyl (meth)acrylate.

[0050] Examples of the above aromatic monomers include (meth)acrylates having one aromatic ring, such as phenyl(meth)acrylate, benzyl(meth)acrylate, phenoxyethyl(meth)acrylate, phenoxypropyl(meth)acrylate, phenoxydiethylene glycol(meth)acrylate, phenoxydipropylene glycol(meth)acrylate, phenoxypolyethylene glycol(meth)acrylate, phenoxypolyethylene glycol(meth)acrylate, and phenoxypolypropylene glycol-(meth)acrylate; and (meth)acrylates having two aromatic rings, such as phenoxybenzyl(meth)acrylate and ethoxylated o-phenylphenol(meth)acrylate.

[0051] Examples of the vinyl monomers mentioned above include vinyl propionate, vinyl stearate, vinyl acetate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyltoluene, vinylpyridine, vinylpyrrolidone, methyl vinyl ketone, and dimethylallyl vinyl ketone.

[0052] Other polymerizable monomers (a6) can be included in a range that does not impair the effects of the present invention, and their content is preferably 20% by weight or less, more preferably 15% by weight or less, and the lower limit is 0% by weight, relative to copolymer component (a).

[0053] <Meth)acrylic resin (A) manufacturing method> The method for producing the (meth)acrylic resin (A) is not particularly limited, but known polymerization methods using the copolymer component (a) can be employed, such as solution radical polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. For example, one method involves mixing or dropwise adding appropriately selected copolymer component (a) and a polymerization initiator to an organic solvent and polymerizing under predetermined polymerization conditions. Among the above polymerization methods, solution radical polymerization and bulk polymerization are preferred, and solution radical polymerization is more preferred in that it can stably produce the (meth)acrylic resin (A).

[0054] Examples of organic solvents used in the polymerization method described above include aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane; esters such as ethyl acetate and butyl acetate; aliphatic alcohols such as n-propyl alcohol and isopropyl alcohol; and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. These organic solvents can be used individually or in combination of two or more.

[0055] Among these organic solvents, from the viewpoint of ease of polymerization reaction, chain transfer effect, ease of drying during application of the adhesive composition, and safety, the use of esters such as ethyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; and aliphatic alcohols such as n-propyl alcohol and isopropyl alcohol alone, or in combination with esters or ketones and aliphatic alcohols such as n-propyl alcohol and isopropyl alcohol is preferred. In particular, from the viewpoint of chain transfer effect, the use of methyl ethyl ketone and / or isopropyl alcohol alone or in combination is more preferred. The amount of organic solvent used is typically 10 to 900 parts by weight per 100 parts by weight of copolymer component (a).

[0056] Conventional chain transfer agents can be used in such solution radical polymerization. Examples of chain transfer agents include thiols such as 1-butanethiol, 1-decanethiol, 2-ethylhexyl mercaptoacetate, ethyl mercaptoacetate, 2-mercaptoethanol, 3-mercapto-1,2-propanediol, mercaptoacetic acid, 3-mercaptopropionic acid, ethyl mercaptoacetate, mercaptosuccinic acid, and thiophenol; and α-methylstyrenes such as 2,4-diphenyl-4-methylpentene. These chain transfer agents can be used individually or in combination of two or more.

[0057] Furthermore, conventional radical polymerization initiators can be used in such solution radical polymerization. Examples of radical polymerization initiators include azo-based initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 4,4'-azobis(4-cyanovaleric acid), and 2,2'-azobis(methylpropionic acid); organic peroxides such as benzoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, and cumene hydroperoxide; and these can be appropriately selected and used depending on the monomer used. These polymerization initiators can be used individually or in combination of two or more. The amount of polymerization initiator used is typically 0.005 to 1 part by weight per 100 parts by weight of copolymer component (a).

[0058] By the above method, a (meth)acrylic resin (A) is obtained that contains a structural unit derived from an alkyl (meth)acrylate (a1) having an alkyl group having 4 or more carbon atoms, a structural unit derived from an alkoxyalkyl (meth)acrylate (a2), a structural unit derived from a monomer (a3) ​​having an active energy ray active site, and a structural unit derived from a polar group-containing ethylenically unsaturated monomer (a4), and may optionally contain a structural unit derived from an alkyl (meth)acrylate (a5) having an alkyl group having 3 or fewer carbon atoms, and a structural unit derived from other polymerizable monomers (a6).

[0059] <(Meth)acrylic resin (A) physical properties> The glass transition temperature (Tg) of the (meth)acrylic resin (A) is preferably -30°C or lower, more preferably -70 to -30°C, particularly preferably -60 to -31°C, even more preferably -50 to -32°C, and especially preferably -47 to -33°C. If the glass transition temperature is too low, the gasoline resistance tends to decrease, and if it is too high, the tack before curing tends to decrease, making it difficult to adhere to the substrate.

[0060] The glass transition temperature mentioned above is calculated using Fox's formula, which is shown below.

[0061]

number

[0062] Specifically, these are values ​​calculated by applying Fox's formula to the glass transition temperature and weight fraction of homopolymers prepared from each monomer constituting the (meth)acrylic resin (A). The glass transition temperatures of homopolymers prepared from each monomer constituting (meth)acrylic resin (A) are typically measured using a differential scanning calorimeter (DSC) according to JIS K7121-1987 or JIS K6240, as well as the values ​​listed in the catalog.

[0063] In the present invention, the weight-average molecular weight (Mw) of the (meth)acrylic resin (A) is 600,000 or less, preferably 10,000 to 500,000, more preferably 30,000 to 400,000, particularly preferably 50,000 to 300,000, and even more preferably 100,000 to 200,000. If the weight-average molecular weight is too small, the cohesive force tends to decrease and the holding power decreases, and if it is too large, the melt viscosity tends to become too high, making it unsuitable for hot-melt coating.

[0064] Furthermore, the degree of dispersion of the (meth)acrylic resin (A) [weight-average molecular weight (Mw) / number-average molecular weight (Mn)] is preferably 10 or less, and more preferably 7 or less. If the degree of dispersion is too high, the cohesive force tends to decrease. The lower limit of the degree of dispersion is usually 1.

[0065] The weight-average molecular weight of (meth)acrylic resin (A) is the weight-average molecular weight converted to the standard polystyrene molecular weight, and was measured using a high-performance liquid chromatograph (Waters Japan, "Waters 2695 (main unit)" and "Waters 2414 (detector)") with a column: Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10⁶). 7 Separation range: 100~2×10 7 The measurement can be performed using a system in which three units of a styrene-divinylbenzene copolymer (with 10,000 theoretical plates per unit, 10 μm particle size) are connected in series. The number-average molecular weight can also be measured using the same method. Furthermore, the degree of dispersion can be determined from the measured values ​​of the weight-average molecular weight and the number-average molecular weight.

[0066] The viscosity of the (meth)acrylic resin (A) diluted with an organic solvent is preferably 100 to 30,000 mPa·s / 25°C, and more preferably 400 to 10,000 mPa·s / 25°C, as measured by a Type B viscometer. If the viscosity is too low, components with a high specific gravity tend to settle, resulting in an uneven concentration of components in the (meth)acrylic resin (A).

[0067] (Meth)acrylic resin (A) is the main component of the adhesive composition of the present invention, and its content is preferably 50% by weight or more, more preferably 60-98% by weight, particularly preferably 70-95% by weight, and even more preferably 75-93% by weight relative to the adhesive composition. Outside of this range, the effects of the present invention tend to be difficult to obtain.

[0068] <Tackifier (B)> The adhesive composition of the present invention contains a tackifier (B). The tackifier (B) contains at least a rosin-based resin (B1) with an acid value of 100 mgKOH / g or more, and may contain other tackifiers (B) to an extent that does not affect the effects of the present invention. For example, rosin-based resins (B'1) with an acid value of less than 100 mgKOH / g, terpene-based resins such as terpene resins, terpene phenol resins, aromatically modified terpene resins, and hydrogenated terpene phenol resins; petroleum resin-based resins such as aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, and hydrogenated petroleum resins; and other examples include phenol resins, xylene resins, and coumarone-indene resins. One of these can be used alone or in combination of two or more as the other tackifier (B).

[0069] Examples of rosin-based resins (B1) with an acid value of 100 mg KOH / g or higher include modified rosin-based resins such as hydrogenated rosin, disproportionated rosin, and polymerized rosin, or rosin esters obtained by esterifying unmodified rosin with alcohols. Among these, rosin esters are preferred from the viewpoint of forming a hot melt composition because they have high thermal stability at high temperatures when mixed with solvent-free (meth)acrylic resins (A).

[0070] The acid value of the rosin-based resin (B1) is preferably 100 mg KOH / g or higher, and more preferably 120 mg KOH / g or higher. The upper limit of the acid value is usually 300 mg KOH / g. An acid value of 100 mg KOH / g or higher is preferable because it has good compatibility with the (meth)acrylic resin (A) of the present invention, and a transparent and uniform coating film can be obtained. The acid value (mgKOH / g) of rosin resin (B1) is the amount of KOH required to neutralize 1 g of rosin resin (B1), and can be measured according to the test method of JIS K0070 (1992). For example, 1 g of rosin resin (B1) can be dissolved in 100 g of xylene heated to 100°C, and then titrated with a 0.1 mol / L potassium hydroxide ethanol solution using phenolphthalein as an indicator at the same temperature. The amount of potassium hydroxide required for this titration can then be converted to mg to calculate the acid value (mgKOH / g).

[0071] The softening point of the rosin-based resin (B1) is preferably 20 to 180°C, more preferably 50 to 170°C, and particularly preferably 70 to 160°C. If the softening point is too high or too low, the tackiness tends to decrease. The softening point of rosin-based resin (B1) can generally be determined by the R&B (ring and ball) method in accordance with the methods described in JIS K-5902 and JIS K-5903. The softening point can be measured, for example, by an automated softening point measuring device (manufactured by Elex Scientific Co., Ltd.) that automates the heating and softening point measurement. Furthermore, if there is a range in the softening point, the average of the sum of the upper and lower limits is used as the softening point.

[0072] The content of rosin resin (B1) is preferably 1 to 50 parts by weight, more preferably 2 to 35 parts by weight, and even more preferably 3 to 20 parts by weight, per 100 parts by weight (solids) of (meth)acrylic resin (A). Particularly preferably it is 5 to 15 parts by weight. If the content is too high or too low, the effects of the present invention tend to be difficult to obtain.

[0073] The content of rosin-based resin (B1) in the tackifier (B) is preferably 50 to 100% by weight, and more preferably 80 to 100% by weight.

[0074] The total content of the tackifier (B) containing the rosin-based resin (B1) is preferably 1 to 100 parts by weight, more preferably 2 to 70 parts by weight, even more preferably 3 to 40 parts by weight, and particularly preferably 4 to 30 parts by weight, per 100 parts by weight (solids) of the (meth)acrylic resin (A). If the content is too high, the effects of the present invention tend to be difficult to obtain.

[0075] The softening point of the tackifier (B) as a whole is preferably 20 to 180°C, more preferably 50 to 170°C, and particularly preferably 70 to 160°C. If the temperature is too high or too low, the tackiness tends to decrease. The softening point of the tackifier (B) as a whole can be measured in accordance with the methods described in JIS K-5902 and JIS K-5903, similar to the measurement of the softening point of the rosin resin (B1).

[0076] <Plasticizer (C)> The adhesive composition of the present invention may further contain a plasticizer (C). The plasticizer (C) is not particularly limited as long as it has good miscibility and compatibility with the (meth)acrylic resin (A) described above, and conventionally known plasticizers can be appropriately selected and used. Non-limiting examples of such plasticizers include phthalate compounds, terephthalate compounds, trimellitic acid compounds, cyclohexanedicarboxylic acid ester compounds, phosphoric acid compounds, adipic acid compounds, citrate compounds, polyether compounds, and polyester compounds.

[0077] Examples of the phthalate compounds include dialkyl phthalates such as bis(2-ethylhexyl) phthalate, dioctyl phthalate, diisononyl phthalate, and diisodecyl phthalate; alkylbenzyl phthalates such as butylbenzyl phthalate; alkylaryl phthalates; dibenzyl phthalates; and diaryl phthalates. Examples of the aforementioned terephthalic acid compounds include bis(2-ethylhexyl) terephthalate. Examples of the trimellitic acid compounds include trialkyl trimellitic acid such as tris(2-ethylhexyl) trimellitic acid. Examples of the cyclohexanedicarboxylic acid ester compounds include cyclohexane-1,2-dicarboxylic acid diisononyl. Examples of the phosphate compounds include triaryl phosphates such as tricresyl phosphate, trialkyl phosphates, and alkylaryl phosphates. Examples of the aforementioned adipic acid compounds include adipic acid esters such as bis(2-ethylhexyl) adipate. Examples of the aforementioned citrate-based compounds include citrate esters such as tributyl acetylcitrate. Examples of the polyether compounds include polyalkylene glycols such as polyethylene glycol and polypropylene glycol. Examples of the aforementioned polyester compounds include polyesters of dibasic acids such as adipic acid, sebatic acid, or phthalic acid, and glycols such as 1,2-propanediol or butanediol.

[0078] The plasticizer (C) is preferably at least one selected from the group consisting of phthalate compounds, terephthalate compounds, trimellitic acid compounds, cyclohexanedicarboxylic acid ester compounds, phosphoric acid compounds, adipic acid compounds, citrate compounds, polyether compounds, and polyester compounds. More preferably, at least one selected from the group consisting of bis(2-ethylhexyl) phthalate, bis(2-ethylhexyl) terephthalate, tris(2-ethylhexyl) trimellitic acid, bis(2-ethylhexyl) adipate, tributyl acetylcitrate, polyethylene glycol, and polypropylene glycol is even more preferred due to its high affinity with the (meth)acrylic resin (A).

[0079] When the adhesive composition of the present invention contains a plasticizer (C), its content is preferably 50 parts by weight or less, more preferably 35 parts by weight or less, particularly preferably 20 parts by weight or less, and even more preferably 15 parts by weight or less, per 100 parts by weight (solids) of (meth)acrylic resin (A). If the content is too high, the effects of the present invention tend to be difficult to obtain.

[0080] In the present invention, the molecular weight of the plasticizer (C) is preferably 250 to 2000, more preferably 300 to 1000, and particularly preferably 350 to 500 if it is a monomer. If it is a polymer such as polyalkylene glycol, the number average molecular weight is preferably 250 to 2000, more preferably 300 to 1000, and particularly preferably 350 to 500. When the molecular weight is within the above range, it not only provides good compatibility with the (meth)acrylic resin (A) and appropriate wettability to polyolefins, but also tends to reduce the melt viscosity, thus improving hot-melt coating properties. Furthermore, the number-average molecular weight of the polymer plasticizer (C) can be measured using the same method as the weight-average molecular weight of the (meth)acrylic resin (A), and the molecular weight of the monomeric plasticizer (C) can be estimated by identifying the structure of the plasticizer (C) using nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, etc. The above molecular weights and weight-average molecular weights can also be based on catalog values.

[0081] <Optional ingredients> In addition to the above components, the adhesive composition of the present invention may also contain various additives as optional components, such as conductive agents like carbon or metal, inorganic fillers like metal particles or glass particles, fillers, antioxidants, polymerization inhibitors, ultraviolet absorbers, weathering agents, ionic compounds, peroxides, silane coupling agents, crosslinking promoters such as urethane catalysts, crosslinking retarders such as acetylacetone, antistatic agents such as surfactants or polyethers, monofunctional monomers, polyfunctional monomers, and urethane acrylates. These can be used individually or in combination of two or more.

[0082] In addition to the optional components mentioned above, the adhesive composition of the present invention may also contain impurities, etc., contained in the raw materials for the production of the constituent components of the adhesive composition, to the extent that they do not impair the effects of the present invention.

[0083] When using the above optional components, their content is preferably 5 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 1 part by weight or less, per 100 parts by weight of (meth)acrylic resin (A). If the content is too high, it tends to impair the effects of the present invention.

[0084] <Method for producing an adhesive composition> The adhesive composition of the present invention can be obtained by mixing at least the above-mentioned acrylic resin (A) and tackifier (B), and optionally a plasticizer (C) and other optional components. The method of mixing these components is not particularly limited, and various methods can be employed, such as mixing each component all at once, or mixing any component first and then mixing the remaining components all at once or sequentially.

[0085] The total content of (meth)acrylic resin (A) and tackifier (B) in the adhesive composition is preferably 90% by weight or more, more preferably 95% by weight or more, and particularly preferably 98% by weight or more.

[0086] The adhesive composition of the present invention is useful as an adhesive component, and is particularly useful as an adhesive component for hot melts. When used for hot melts, the adhesive composition may be prepared by blending the above components to obtain an adhesive composition solution and then distilling off the solvent; or by mixing each component with a (meth)acrylic resin (A) from which the solvent has been distilled off; or, for example, by mixing a (meth)acrylic resin (A) and a tackifier (B), then distilling off the solvent, and blending the remaining components.

[0087] The step of removing the solvent from a solution of (meth)acrylic resin (A) or an adhesive composition obtained by compounding it can be carried out by known methods. Methods for removing the solvent include heating and reducing the pressure, but from the viewpoint of efficiently removing the solvent, heating under reduced pressure is preferred.

[0088] When heating to remove the solvent, a temperature of 60 to 150°C is preferred. In particular, it is preferable to maintain the reaction solution after polymerization of (meth)acrylic resin (A) at 60 to 80°C to distill off the solvent, and then distill off the remaining solvent at 80 to 150°C, as this minimizes the amount of residual solvent. Furthermore, to suppress the gelation of (meth)acrylic resin (A), it is preferable not to perform the solvent distillation at a temperature above 150°C.

[0089] When removing the solvent by reducing the pressure, a pressure of 20 to 101.3 kPa is preferred. In particular, it is preferable to maintain the pressure in the range of 50 to 101.3 kPa to distill off the solvent in the reaction solution, and then distill off the remaining solvent at 0 to 50 kPa, as this minimizes the amount of remaining solvent. Thus, the active energy ray-curable adhesive composition of the present invention can be manufactured.

[0090] The adhesive composition of the present invention preferably contains substantially no solvent, more preferably has a solvent content of 2% by weight or less, particularly preferably 0.00001 to 2% by weight, even more preferably 0.0001 to 1% by weight, and most preferably 0.001 to 0.1% by weight. If the solvent content is too high, bubbles tend to form, and the physical properties after curing with active energy rays tend to deteriorate.

[0091] Furthermore, the adhesive composition of the present invention preferably contains substantially no thermal crosslinking agent, more preferably the thermal crosslinking agent content is less than 0.1% by weight of the total adhesive composition, particularly preferably 0.00001 to 0.05% by weight, and even more preferably 0.0001 to 0.01% by weight. By substantially omitting the thermal crosslinking agent, its usefulness as an adhesive component for hot melt applications becomes even more pronounced. Examples of thermal crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, and aziridine-based crosslinking agents.

[0092] The melt viscosity of the adhesive composition of the present invention at 130°C is preferably 1 to 1500 Pa·s, more preferably 2 to 500 Pa·s, and particularly preferably 5 to 100 Pa·s. If the melt viscosity of the adhesive composition is too high, the coatability during hot melt coating tends to decrease. On the other hand, if the melt viscosity of the adhesive composition is too low, this means that the molecular weight of the (meth)acrylic resin (A) is small, which reduces the crosslinking efficiency by active energy rays.

[0093] The melt viscosity of the adhesive composition is measured using a solvent-free adhesive composition with a rotational rheometer under the following conditions. • Measuring instrument: MCR301 (manufactured by Anton Paar) • Parallel plate diameter: 25mm • Measurement distance: 0.5mm • Measured shear rate: 0.001~0.1 (1 / S) ·Measurement temperature: 130℃

[0094] <Adhesives, adhesive sheets, and laminates> The adhesive composition of the present invention can be made into an adhesive by crosslinking a (meth)acrylic resin (A). Furthermore, by laminating an adhesive layer containing this adhesive onto a base sheet such as a plastic film, an adhesive sheet having a laminated structure of base sheet / adhesive layer can be obtained. Moreover, by laminating this adhesive layer onto an adherend, a laminate having a laminated structure of adherend / adhesive layer can be obtained. Hereinafter, the base sheet and adherend will be collectively referred to as "components". That is, the concept of a laminate encompasses the concept of an adhesive sheet.

[0095] The above-mentioned adhesive sheets include not only adhesive sheets in which an adhesive layer is laminated on a base sheet, but also base-less double-sided adhesive sheets in which release films are laminated on both sides of the adhesive layer. Double-sided adhesive sheets are preferred in terms of ease of handling. When using adhesive sheets or double-sided adhesive sheets, the release film is peeled off from the adhesive layer before use.

[0096] The adhesive layer described above may be the adhesive composition of the present invention itself, or it may be formed by curing (crosslinking) the adhesive composition of the present invention. While there are curing methods such as curing with active energy rays or curing by crosslinking with a thermal crosslinking agent, the adhesive composition of the present invention substantially does not contain a thermal crosslinking agent, so crosslinking is performed by active energy rays.

[0097] Adhesive sheets can be manufactured, for example, as follows: First, an adhesive layer of a predetermined thickness is formed on one or both sides of a base sheet by methods such as applying the melted adhesive composition to one or both sides of a base sheet and then cooling it, or by melting the adhesive composition by heating it and extruding it onto the base sheet using a T-die or the like, or by drying the solvent after coating if a solvent is included. Then, if necessary, an adhesive sheet can be produced by laminating a release film onto the surface of the adhesive layer. An adhesive sheet can be produced having an adhesive layer formed on a base sheet, followed by active energy ray irradiation and, if applicable, aging treatment, which hardens (crosslinks) the adhesive composition. Alternatively, an adhesive sheet can be created by forming an adhesive layer on a release film, irradiating it with active energy rays, and then bonding it to a base sheet. Furthermore, a substrate-less double-sided adhesive sheet can be produced by forming an adhesive layer on a release film and then laminating another release film to the adhesive layer on the opposite side. The resulting adhesive sheet or double-sided adhesive sheet is used after peeling off the release film from the adhesive layer.

[0098] Examples of base sheets include polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate / isophthalate copolymers; polyolefin resins such as polyethylene, polypropylene (PP), and polymethylpentene; polyfluoroethylene resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyfluoroethylene; polyamides such as nylon 6 and nylon 6,6; vinyl polymers such as polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and vinylon; cellulose resins such as cellulose triacetate and cellophane; acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; synthetic resin sheets such as polystyrene, polycarbonate, polyarylate, and polyimide; metal foils of aluminum, copper, and iron; paper such as fine paper and glassine paper; and textiles and nonwoven fabrics made of glass fibers, natural fibers, and synthetic fibers. These base sheets can be used as single layers or as multi-layered structures made by laminating two or more types. Among these, synthetic resin sheets are preferred from the viewpoint of weight reduction and other factors.

[0099] As the release film, for example, various synthetic resin sheets as exemplified in the above-mentioned base sheet, paper, cloth, nonwoven fabric, etc., that have undergone a release treatment can be used. It is preferable to use a silicone-based release film as the release film.

[0100] As for the coating method of the above adhesive composition, general coating methods can be employed, such as roll coating, die coating, gravure coating, comma coating, and screen printing.

[0101] Regarding the gel fraction of the adhesive layer of the above-mentioned adhesive sheet, it is preferably 20-95%, more preferably 30-80%, and particularly preferably 40-70%, from the viewpoint of balancing physical properties such as adhesive strength, holding power, and gasoline resistance. If the gel fraction is too low, the holding power tends to decrease due to a decrease in cohesive force. Conversely, if the gel fraction is too high, the adhesive strength tends to decrease due to an increase in cohesive force.

[0102] Furthermore, adjusting the gel fraction to the above range can be achieved, for example, by adjusting the amount of active energy radiation or the type and amount of monomers (a3) ​​that have active energy radiation sites.

[0103] The gel fraction mentioned above serves as an indicator of the degree of crosslinking (degree of hardening) and can be calculated, for example, by the following method: The adhesive layer crosslinked by active energy ray irradiation is wrapped in a 200-mesh stainless steel wire mesh and immersed in a solvent such as toluene at 23°C for 24 hours. The weight of the adhesive layer is measured before and after solvent immersion, and the difference between the two weights is taken as the weight of the insoluble adhesive component remaining in the wire mesh. The gel fraction is the weight percentage of the insoluble adhesive component remaining in the wire mesh relative to the weight of the adhesive layer before solvent immersion.

[0104] The thickness of the adhesive layer of the above adhesive sheet is preferably 5 to 2000 μm, more preferably 7 to 100 μm, and particularly preferably 10 to 60 μm. If the thickness of the adhesive layer is too thin, the adhesiveness tends to decrease, and if it is too thick, the adhesive tends to ooze out when used as an adhesive label.

[0105] The thickness of the adhesive layer mentioned above was determined by subtracting the measured thickness of the components other than the adhesive layer from the measured thickness of the entire adhesive sheet containing the adhesive layer, using a Mitutoyo ID-C112B.

[0106] According to the adhesive composition of the present invention, an adhesive can be obtained that not only exhibits excellent adhesive properties such as adhesive strength and holding power to low-polarity substrates such as polyolefins, but also has excellent hot-melt coating properties and gasoline resistance. Therefore, the adhesive composition of the present invention is useful for various applications in hot melt coating, such as caution labels, frozen food labels, building materials, automotive parts, electronic components, heat dissipation sheets, FPC manufacturing, semiconductor manufacturing processes, component sealing, aerospace parts, and sporting goods. In particular, it is preferably used for automotive parts and marking films (adhesive sheets, adhesive tapes) used in gasoline-powered vehicles. [Examples]

[0107] 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 unless it exceeds the gist of the invention. In the examples, "parts" and "%" refer to weight basis. Furthermore, the weight-average molecular weight, degree of dispersion, and glass transition temperature (Tg) of the (meth)acrylic resin (A) in the following examples were measured according to the method described above. Viscosity was measured according to the rotational viscometer method of JIS K 5400 (1990), 4.5.3. The molecular weight and number-average molecular weight of the plasticizer (C) were adopted from catalog values. First, prior to the examples, the following components were prepared.

[0108] <(Meth)acrylic resin (A)> The following were used as raw material monomers for the (meth)acrylic resin. • Alkyl (meth)acrylate (a1) having an alkyl group with 4 or more carbon atoms BA: n-butyl acrylate (Tg=-55℃, manufactured by Mitsubishi Chemical Corporation) • Alkoxyalkyl (meth)acrylate (a2) MEA: Methoxyethyl acrylate (Tg = -50℃, manufactured by Osaka Organic Chemical Industry Co., Ltd.) • A monomer having an active energy ray-active site (a3) MBP: 4-Methacryloyloxybenzophenone (Tg=118℃, manufactured by Shinryo Co., Ltd.) • Polar group-containing ethylenically unsaturated monomer (a4) Aac: Acrylic acid (Tg=106℃, manufactured by Nippon Shokubai Co., Ltd.) • Alkyl (meth)acrylate having an alkyl group with 3 or fewer carbon atoms (a5) EA: Ethyl acrylate (Tg=-22℃, manufactured by Mitsubishi Chemical Corporation) MA: Methyl acrylate (Tg=8℃, manufactured by Mitsubishi Chemical Corporation)

[0109] <(Meth)acrylic resin (A-1) solution manufacturing> In a four-necked round-bottom flask equipped with a reflux condenser, stirrer, nitrogen gas inlet, and thermometer, 100 parts of methyl ethyl ketone (MEK) were charged and heated under reflux in the flask. A monomer mixture solution of 52 parts BA, 40 parts MEA, 0.50 parts MBP, and 7.5 parts Aac was then prepared. A mixture solution of 2.86 parts methyl ethyl ketone (MEK) and 0.093 parts azobis(2,4-dimethylvaleronitrile) (ADVN) as a polymerization initiator was added to the monomer mixture solution and added dropwise over 2 hours. One hour after the end of monomer addition, 0.057 parts of polymerization initiator (ADVN) and 2.86 parts of MEK were added and the mixture was reacted for 1 hour. Then, another 0.057 parts of polymerization initiator (ADVN) and 2.86 parts of MEK were added and the mixture was reacted for another 1 hour. Further additions of 0.057 parts of polymerization initiator (ADVN) and 2.86 parts of MEK were added, and the mixture was reacted for 2 hours to obtain a (meth)acrylic resin (A-1) solution [solid content concentration 59.5%, viscosity 2449 mPa·s, weight-average molecular weight (Mw) 162,000, dispersion degree 2.75 (Mw / Mn), calculated Tg = -45.2℃].

[0110] <(Meth)acrylic resin (A-2, A'-1) solution manufacturing> (Meth)acrylic resins (A-2, A'-1) were obtained by polymerizing the (meth)acrylic resin (A-1) solution by changing the proportions of various copolymer components (a) as shown in Table 1. The copolymerization ratio (content) of structural units derived from each monomer in the obtained (meth)acrylic resin (A) was as shown in the amount of monomer used.

[0111] [Table 1]

[0112] <Tackifier (B)> The following materials were prepared as tackifiers (B). (B-1) Rosin ester (manufactured by Arakawa Chemical Industries, Ltd., Pine Crystal KR612, acid value 170 mg KOH / g, softening point: 85℃) (B'-1) Rosin ester (manufactured by Arakawa Chemical Industries, Ltd., Pine Crystal KE100, acid value 5 mg KOH / g, softening point: 100℃)

[0113] <Plasticizer (C)> The following was prepared as plasticizer (C): (C-1) Tributyl acetyl citrate (manufactured by Tokyo Chemical Industry Co., Ltd.) Molecular weight 402 (C-2)PEG-400 (Polyethylene glycol manufactured by Sanyo Chemical Industries, Ltd., number average molecular weight 400) (C-3) Sannix PP-400 (Polypropylene glycol manufactured by Sanyo Chemical Industries, Ltd., number average molecular weight 400)

[0114] <Preparation of base material> A PVC film (80 μm thick) was prepared by performing corona treatment on one side. A TEC-4AX manufactured by Kasuga Electric Co., Ltd. was used for the corona treatment, with the output fixed at 40 W and the electrode movement speed fixed at 4.4 m / min. The gap between the ground plate and the electrode was then adjusted so that the dyne number was between 44 and 48.

[0115] <Example 1: Preparation of adhesive sheet S1> 100 parts of (meth)acrylic resin (A-1) and 10 parts of tackifier (B-1) were prepared and diluted and mixed with ethyl acetate to a solid content of 42%. Then, a layer of the adhesive composition was formed by coating a 38 μm thick release film (Mitsui Chemicals Tohcello Co., Ltd., "SPPET0138BU") with an applicator to a dry thickness of 25 μm. Next, the mixture was irradiated with a UV device using a high-pressure mercury lamp at a predetermined dose (140 mW / cm²). 2 , 100 mJ / cm 2 After irradiating with ultraviolet light, the above-mentioned PVC film, which had been pre-treated with corona, was laminated to obtain an adhesive sheet S1 (a laminate of corona-treated PVC film / adhesive layer / release film).

[0116] <Examples 2-7, Comparative Examples 1-6> Adhesive sheet S1 was prepared in the same manner as in Example 1, except that the (meth)acrylic resin solution (A), tackifying resin (B), and plasticizer (C) were blended according to Table 2. Table 3 shows the results of the physical property evaluation of the adhesive sheet S1 in the above examples and comparative examples.

[0117] [Table 2]

[0118] <Gasoline resistance> A Paltec melamine-coated board (cold-rolled steel sheet: SPCC-SD, shape: 0.4 x 70 x 150 mm, corner radius: φ (diameter) 5-1, paint color: white) was prepared, and the melamine-coated surface was wiped with ethanol. Next, an adhesive sheet S1 was punched out in a 38 x 38 mm square shape, the release film was peeled off, and the adhesive layer side was attached to the melamine-coated surface of the board. The evaluation sample thus prepared was placed in a metal pan, and a toluene / isooctane (=50 / 50 vol%) mixed solution was poured in until the melamine-coated board was submerged. After standing for 20 minutes, the evaluation sample was removed, its appearance was observed, and it was evaluated according to the following criteria. The results are summarized in Table 3. (Evaluation Criteria) ○: No lifting or peeling. △: There is floating and peeling at the end ×: There is floating and peeling

[0119] <SUS Adhesive Strength> A test piece with a width of 25 mm and a length of 170 mm was prepared from the adhesive sheet S1. After peeling off the release film, it was pressure-bonded to a SUS plate (compliant with JIS G 4305, SUS304, 0.5×70×150 mm) manufactured by Engineering Test Service Co., Ltd. with a 2 kg rubber roller reciprocated twice under an atmosphere of 23°C and 50% RH, and then left standing at 23°C for 30 minutes. Thereafter, in accordance with JIS Z 0237, the 180° peel strength (N / 25 mm) was measured at a peel rate of 300 mm / min and evaluated as follows. The results were summarized in Table 3. (Evaluation Criteria) ○: Adhesive strength is 15 N / 25 mm or more, and peeling occurs at the interface with the adherend side ×: There are sticking marks

[0120] <PP Adhesive Strength> Measurements similar to those for SUS adhesive strength were performed, except that a PP plate (2.0×70×150 mm) manufactured by Nippon Test Panel Industry Co., Ltd. was used instead of the SUS plate. Evaluation was carried out as follows, and the results were summarized in Table 3. (Evaluation Criteria) ○: Adhesive strength is 10 N / 25 mm or more, and peeling occurs at the interface with the adherend side △: Adhesive strength is 10 N / 25 mm or more, and there are sticking marks ×: Adhesive strength is less than 10 N / 25 mm

[0121] <PE Adhesive Strength> Measurements similar to those for SUS adhesive strength were performed, except that a PE plate (2.0×70×150 mm) manufactured by Nippon Test Panel Industry Co., Ltd. was used instead of the SUS plate. Evaluation was carried out as follows, and the results were summarized in Table 3. (Evaluation Criteria) ○: Adhesive strength is 7 N / 25 mm or more, and peeling occurs at the interface with the adherend side △: Adhesive strength is 7 N / 25 mm or more, and there are sticking marks ×: Adhesive strength is less than 7 N / 25 mm

[0122] <Retention Force> A test specimen measuring 25 mm x 70 mm was prepared from adhesive sheet S1. After removing the release film, it was pressed onto a stainless steel plate (SUS304) polished with sandpaper using a 2 kg roller (attachment area 25 mm x 25 mm). The adhesive layer portion of adhesive sheet S1 not attached to the stainless steel plate was protected with PET film, and cellophane tape was applied to the PVC film on the opposite side of the adhesive layer to create an evaluation sample. The holding force was measured using a creep tester (BE-501, a holding force tester with a constant temperature and humidity chamber, manufactured by Tester Sangyo Co., Ltd.) under a load of 1 kg for 24 hours in a 40°C atmosphere. The evaluation criteria for holding force are as follows. The results are summarized in Table 3. (Evaluation Criteria) ○: Held for 1440 minutes or more, and without any shifting. ×: Held for less than 1440 minutes, or held for 1440 minutes or more but there is a discrepancy.

[0123] <Preparation of adhesive sheet S2> Each adhesive composition from Examples 1-7 and Comparative Examples 1-6 was mixed with ethyl acetate and diluted until the solid content concentration reached 42%. The mixture was then applied to a 38 μm thick light-release film (Mitsui Chemicals Tohcello Co., Ltd., "SPPET01 38BU") using an applicator to form a layer of the adhesive composition with a dry thickness of 25 μm. A UV irradiation device using a high-pressure mercury lamp was used to obtain a predetermined dose (140 mW / cm²). 2 , 100 mJ / cm 2 An adhesive layer was formed by irradiating it with ultraviolet light. An adhesive sheet S2 was fabricated by laminating the surface of the adhesive layer onto a 38 μm thick heavy release film (manufactured by Mitsui Chemicals Tohcello, "SPPET03 38BU") (a laminate of heavy release film / adhesive layer / light release film).

[0124] <Gel fraction> The adhesive sheet S2 prepared above was cut to 38 x 38 mm, the light release film was peeled off, and the adhesive layer side was bonded to a 50 mm x 100 mm SUS mesh sheet (200 mesh), and the heavy release film was peeled off. The SUS mesh sheet was folded over from the center along its longitudinal direction to enclose the adhesive layer of the sample, and immersed in a sealed container containing 250 g of toluene for 24 hours. The weight of the adhesive before toluene immersion and the amount of insoluble adhesive component remaining in the mesh after immersion were weighed, and the percentage of the value obtained by dividing the weight of the insoluble adhesive component by the weight of the adhesive before immersion was defined as the gel fraction (%). The results are summarized in Table 3.

[0125] [Table 3]

[0126] Examples 1 to 7, using the adhesive composition of the present invention, showed excellent gasoline resistance and superior adhesive strength and holding power to adherends such as SUS plates, PP plates, and PE plates.

[0127] On the other hand, in Comparative Examples 1 to 6, the (meth)acrylic resin (A) or tackifier (B) deviated from the provisions of the present invention, or the tackifier (B) was not included, and as a result, the gasoline resistance was at least inferior and the adhesive strength to the adherend was sometimes inferior. [Industrial applicability]

[0128] The adhesive obtained using the adhesive composition of the present invention has good hot-melt coating properties, so the volatilization of organic solvents after use is less likely, reducing harmful effects on humans and animals. Furthermore, the adhesive of the present invention has excellent adhesion and holding power to polyolefins, which are difficult to adhere to, so it can be applied to various uses such as automotive parts, building materials, electronic components, and office automation equipment. Moreover, the adhesive of the present invention has excellent gasoline resistance, so it can be suitably used in marking films for gasoline-fueled vehicles.

Claims

1. An active energy ray curable adhesive composition containing a (meth)acrylic resin (A) and a tackifier (B), The (meth)acrylic resin (A) is It contains a structural unit derived from an alkyl (meth)acrylate (a1) having an alkyl group with 4 or more carbon atoms, a structural unit derived from an alkoxyalkyl (meth)acrylate (a2), a structural unit derived from a monomer (a3) ​​having an active energy ray active site, and a structural unit derived from a polar group-containing ethylenically unsaturated monomer (a4), The weight-average molecular weight of the (meth)acrylic resin (A) is 200,000 or less. An active energy ray-curable adhesive composition wherein the tackifier (B) comprises a rosin-based resin (B1) having an acid value of 100 mg KOH / g or more.

2. The active energy ray curable adhesive composition according to claim 1, wherein the glass transition temperature of the (meth)acrylic resin (A) is -30°C or lower.

3. The active energy ray curable adhesive composition according to claim 1 or 2, wherein the alkoxyalkyl (meth)acrylate (a2) is methoxyethyl (meth)acrylate.

4. The active energy ray curable adhesive composition according to claim 1 or 2, wherein the (meth)acrylic resin (A) further contains constituent units derived from alkyl (meth)acrylate (a5) having an alkyl group having 3 or fewer carbon atoms.

5. The active energy ray curable adhesive composition according to claim 1 or 2, wherein the content of the rosin-based resin (B1) is 1 to 50 parts by weight per 100 parts by weight of the (meth)acrylic resin (A).

6. The active energy ray curable adhesive composition according to claim 1 or 2, further containing a plasticizer (C).

7. The active energy ray curable adhesive composition according to claim 1 or 2, wherein the content of the thermal crosslinking agent is less than 0.1% by weight of the total composition.

8. An active energy ray-curable adhesive comprising the active energy ray-curable adhesive composition according to claim 1 or 2, which is crosslinked.

9. An adhesive sheet having an adhesive layer made of the active energy ray curable adhesive described in claim 8.

10. An adhesive sheet comprising a polyvinyl chloride base sheet and an adhesive layer made of the active energy ray curable adhesive described in claim 8.

11. A laminate comprising an adhesive layer made of the active energy ray curable adhesive described in claim 8 and other components laminated together.

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