JP7276092B2 - Adhesive composition and adhesive product - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive composition and an adhesive product, and more particularly to an adhesive composition containing a (meth)acrylic copolymer and uses thereof.

Acrylic pressure-sensitive adhesives are used in a wide range of applications because they have advantages such as excellent weather resistance and transparency and a high degree of design freedom. In addition, various materials such as plastics, papers, metals, wood, glass, fiber fabrics, etc. are applied to objects to be adhered with acrylic pressure-sensitive adhesives (see, for example, Patent Documents 1 and 2). .

Patent Literature 1 discloses that a thermal adhesive tape in which an adhesive material such as an acrylic resin is partially arranged is inserted between fiber fabrics, and the fabrics are bonded by heating and fusing. It is Further, Patent Document 2 discloses a polymer block composed of a structural unit derived from a methacrylate ester (A1), a structural unit derived from an acrylic ester (B), and a structural unit derived from a methacrylate ester (A2). A pressure-sensitive adhesive using a gradient copolymer having a copolymer block consisting of and the copolymer block having a distribution gradient of monomer units is disclosed.

JP-A-2002-338908 WO2014/185350

In the case of the method of joining fabrics with the thermal adhesive tape described in Patent Document 1, the adhesive strength is not sufficient, and if tensile stress is applied to the adhesive portion or repeated use, the adhesive portion may come off. .

In addition, in order to obtain a pressure-sensitive adhesive with high adhesive strength, it is possible to increase the toughness by increasing the ratio of the hard segment in the polymer chain in a copolymer having a hard segment and a soft segment as in Patent Document 2. Conceivable. However, increasing the ratio of hard segments in the polymer chain tends to lower the wettability of the adhesive. As a result, the interface between the pressure-sensitive adhesive and the adherend is likely to break, and the adhesion strength may not be sufficiently high.

The present invention has been made in view of the above problems, and a main object thereof is to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having high wettability and excellent adhesive strength.

The present inventors have made intensive studies to solve the above problems, and found that the above problems can be solved by providing a pressure-sensitive adhesive composition containing a gradient copolymer having a specific structure. The present invention has been completed based on these findings. According to the present invention, the following means are provided.

[1] It contains an ABA-type gradient copolymer having a segment A and a segment B, and the segment A is a structural unit derived from a monomer X whose homopolymer has a glass transition point of 50° C. or higher. , and a structural unit derived from a monomer Y whose homopolymer glass transition point is 10° C. or lower, and the segment B is a monomer Z whose homopolymer glass transition point is 10° C. or lower and has a glass transition point of 10° C. or lower, and in the segment A, the content of the structural unit derived from the monomer X is in the direction from the segment A to the segment B The pressure-sensitive adhesive composition, wherein the content of structural units derived from the monomer Y continuously decreases and continuously increases in the direction from the segment A to the segment B.

[2] The segment A includes, as a structural unit derived from the monomer X, a structural unit derived from at least one selected from the group consisting of a styrene compound, an imide group-containing vinyl compound, and an amide group-containing vinyl compound. The pressure-sensitive adhesive composition of [1].
[3] The content of the structural unit derived from the monomer X with respect to all the constituent monomer units of the segment A is from 50 to 100% by mass toward the other end of the segment A. The pressure-sensitive adhesive composition of [1] or [2], which is continuously reduced to ~30% by mass.
[4] Any one of [1] to [3], wherein the gradient copolymer has a ratio of the segment A to the total amount of the segment A and the segment B of 5% by mass or more and 40% by mass or less. 1 adhesive composition.
[5] The segment B, as a structural unit derived from the monomer Z, is selected from the group consisting of an alkyl (meth)acrylate compound, an alkoxyalkyl (meth)acrylate compound, and a hydroxyalkyl (meth)acrylate compound. The pressure-sensitive adhesive composition according to any one of [1] to [4], which has a structural unit derived from at least one of

[6] The segment A includes, as a structural unit derived from the monomer Y, a structural unit derived from at least one selected from the group consisting of an alkyl (meth)acrylate compound and an alkoxyalkyl (meth)acrylate compound. The pressure-sensitive adhesive composition according to any one of [1] to [5].
[7] The pressure-sensitive adhesive composition according to any one of [1] to [6], wherein the gradient copolymer has a number average molecular weight of 10,000 or more and 500,000 or less.
[8] A pressure-sensitive adhesive product comprising a support and a pressure-sensitive adhesive layer formed on the support using the pressure-sensitive adhesive composition of any one of [1] to [7] above.

According to the pressure-sensitive adhesive composition of the present invention, a pressure-sensitive adhesive with high wettability can be obtained. Moreover, a pressure-sensitive adhesive layer with high adhesive strength can be formed.

The present disclosure will be described in detail below. In this specification, "(meth)acryl" means acryl and/or methacryl, and "(meth)acrylate" means acrylate and/or methacrylate. A "(meth)acryloyl group" means an acryloyl group and/or a methacryloyl group.

<<Adhesive composition>>
The pressure-sensitive adhesive composition of the present invention contains a gradient copolymer (hereinafter also referred to as "gradient copolymer (P)") having segment A, which is a hard segment, and segment B, which is a soft segment. The gradient copolymer (P) blended in the present pressure-sensitive adhesive composition and components blended as necessary will be described in detail below.

<Gradient copolymer (P)>
The gradient copolymer (P) is an ABA type copolymer in which two segments A and one segment B form a segment A-segment B-segment A structure. Among segments A and B, segment A has a gradient composition in which the monomer composition changes continuously along the molecular chain. The gradient copolymer (P) is a copolymer capable of forming pseudo-crosslinks by forming a microphase-separated structure or the like. When the adhesive layer is formed, if the copolymer forms a pseudo-crosslinked structure, the cohesive force tends to be improved, which is preferable in that the adhesive strength can be increased.

(Segment A)
Although the monomer constituting segment A is not particularly limited, it is preferably a vinyl compound. Examples of vinyl compounds used in the production of segment A include styrene compounds, imide group-containing vinyl compounds (maleimide compounds such as maleimide and N-substituted maleimide compounds, citraconimide compounds, (meth)acrylimide compounds, etc.), amide groups containing vinyl compound, alkyl (meth)acrylate compound, alkoxyalkyl (meth)acrylate compound, aliphatic cyclic ester compound of (meth)acrylic acid, aromatic cyclic ester compound of (meth)acrylic acid, olefin compound, Diene compounds, nitrogen-containing vinyl compounds, cyclic group-containing vinyl compounds, cyclic vinyl compounds, vinyl compounds having a crosslinkable functional group, and the like can be mentioned. Segment A includes a structural unit (hereinafter also referred to as “structural unit U1”) derived from a monomer X that makes the homopolymer have a glass transition point of 50 ° C. or higher when a homopolymer is formed, and a homopolymer and a structural unit (hereinafter also referred to as “structural unit U2”) derived from a monomer Y such that the homopolymer has a glass transition point of 10° C. or less when formed.

・Regarding the monomer X Specific examples of the monomer X include acrylic acid, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, methoxymethyl methacrylate, 2-hydroxyethyl methacrylate, and methacrylic acid. Acid 2-hydroxypropyl, sec-butyl methacrylate, tert-butyl methacrylate, 2-bromoethyl methacrylate, 2-cyanoethyl methacrylate, cyanomethyl methacrylate, 2,3-dihydroxypropyl methacrylate, phenyl methacrylate, methacrylic acid 2 , 2,2-trifluoroethyl, 2-phenylethyl methacrylate, 2-cyclohexyl acrylate, isobornyl acrylate, isobornyl methacrylate and other (meth)acrylic compounds;
Styrene, α-methylstyrene, p-methylstyrene, p-hydroxystyrene, p-fluorostyrene, p-bromostyrene, p-chlorostyrene, m-chlorostyrene, o-chlorostyrene, p-methoxystyrene, p-phenyl Styrenic compounds such as styrene; Vinyl compounds containing imide groups such as N-ethylmaleimide, N-phenylmaleimide, N-adamantylmaleimide;
Amide group-containing vinyl compounds such as acrylic acid amide, N-methylacrylamide, N,N-dimethylacrylamide, N-(1-methylethyl)acrylamide, acryloylmorpholine, N-hydroxyethylacrylamide; acrylonitrile, allylamine, 4-vinylpyridine , 2-vinylpyridine, N-vinyl-2-pyrrolidone and other nitrogen-containing vinyl compounds;
cyclic group-containing vinyl compounds such as vinylcyclohexane, 1-methylethenylcyclohexane, 1-vinylnaphthalene, 2-vinylnaphthalene, and 2-(1-methylethenyl)naphthalene; cyclic vinyl compounds such as 2,3-dihydrofuran; mentioned. As the monomer X, one type may be used alone, or two or more types may be used.

Monomer X can impart good heat resistance and durability to the gradient copolymer (P). It is preferably at least one selected from the group consisting of: Further, the monomer X is preferably a monomer having a glass transition point of 60° C. or higher when converted into a homopolymer, and more preferably a monomer having a glass transition point of 70° C. or higher. In addition, in this specification, the glass transition point of the polymer is a value measured by differential scanning calorimetry (DSC). The details of the measurement method can follow the operations described in the examples below. The glass transition point of the polymer can be arbitrarily selected by changing the type and composition of the constituent monomers.

When segment A has a structural unit derived from a styrenic compound, the content of structural units derived from a styrenic compound relative to all constituent monomer units of segment A is preferably 1 mol% or more, more preferably is 2 mol % or more, more preferably 5 mol % or more. Further, the upper limit of the content of the structural unit derived from the styrene compound with respect to all the constituent monomer units of the segment A is preferably 50 mol% or less with respect to all the constituent monomer units of the segment A, It is more preferably 40 mol % or less, still more preferably 20 mol % or less.

When segment A has a structural unit derived from an imide group-containing vinyl compound, the ratio of structural units derived from the imide group-containing vinyl compound to all constituent monomer units of segment A is preferably 1 mol% or more, and more It is preferably 2 mol % or more, more preferably 5 mol % or more. Including a structural unit derived from an imide group-containing vinyl compound is preferable in that a gradient copolymer (P) having excellent heat resistance and adhesiveness can be obtained. Further, when the ratio of the structural units derived from the imide group-containing vinyl compound is 50 mol% or less with respect to the total monomer units constituting each block of the segment A, the adhesiveness of the gradient copolymer (P) is improved. It is preferable because it can be sufficiently secured. The proportion of the structural units derived from the imide group-containing vinyl compound is more preferably 40 mol % or less, still more preferably 30 mol % or less, relative to all constituent monomer units of each block of segment A.

When segment A has a structural unit derived from an amide group-containing vinyl compound, the content of the structural unit derived from the amide group-containing vinyl compound is preferably at least 1 mol% with respect to all constituent monomer units of segment A. more preferably 2 mol % or more, and still more preferably 5 mol % or more. The upper limit of the content of the structural unit derived from the amide group-containing vinyl compound is not particularly limited, but is preferably 50 mol% or less, more preferably 30 mol%, based on the total constituent monomer units of segment A. or less, more preferably 10 mol % or less.

The styrenic compound may have the property of improving the polymerizability of the imide group-containing vinyl compound. Therefore, when an imide group-containing vinyl compound (preferably a maleimide compound) is used as a constituent monomer unit of segment A, it is preferable to improve the polymerizability of the imide group-containing vinyl compound by using a styrenic compound in combination. . From this point of view, segment A preferably has a structural unit derived from a styrene compound and a structural unit derived from an imide group-containing vinyl compound, and a structural unit derived from a styrene compound and a maleimide compound. Structural units are particularly preferred.

When the gradient copolymer (P) contains a segment A having a structural unit derived from a styrene compound and a structural unit derived from an imide group-containing compound, in the segment A, a structural unit derived from an imide group-containing vinyl compound The content of the structural unit derived from the styrenic compound per 1 mol is preferably 0.01 to 100 mol, more preferably 0.1 to 10 mol, still more preferably 0.2 to 5 mol. and particularly preferably 0.5 to 1.5 mol.

- Regarding the monomer Y Specific examples of the monomer Y include olefinic compounds such as 1-butene, 2-methyl-1-propene, 1-hexene, 1-octene, and 1-decene;
Ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, 2-methoxyethyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, ( 2-(2-Methoxyethoxy)ethyl meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2,2,3,3,3-acrylate (Meth)acrylic compounds such as pentafluoropropyl, dodecyl acrylate, and 2-hydroxyethyl acrylate; 1,3-butadiene, 2-methyl-1,3-butadiene, 4-phenyl-1-butene, etc. is mentioned. As the monomer Y, one type may be used alone, or two or more types may be used.

Among these, the monomer Y is preferably a (meth)acrylic compound from the viewpoint of obtaining a gradient copolymer (P) having excellent adhesive performance, and a (meth)acrylic acid alkyl compound and a (meth) More preferably, it is at least one monomer selected from the group consisting of alkoxyalkyl acrylate compounds (hereinafter also referred to as "monomer C1"). The glass transition point of the homopolymer composed of the monomer Y is preferably 0° C. or lower, more preferably -10° C. or lower, and even more preferably -20° C. or lower.

The content of structural units derived from monomer C1 in segment A is preferably 1 mol% or more, more preferably 5 mol% or more, relative to all constituent monomer units of segment A. , more preferably 10 mol % or more. In addition, the content of structural units derived from monomer C1 is preferably 80 mol% or less, more preferably 70 mol% or less, relative to all constituent monomer units of segment A. It is more preferably 60 mol % or less.

In this specification, segment A is a polymer block in which the content of structural unit U1 derived from monomer X is 5% by mass or more per number average molecular weight Mn of 10,000. Segment B is a polymer block in which the content of structural unit U1 derived from monomer X is 0% by mass or more and less than 5% by mass based on the number average molecular weight Mn of 10,000.

In segment A, the content of structural unit U1 continuously decreases in the direction from segment A to segment B, and the content of structural unit U2 derived from monomer Y decreases from segment A to segment B. It has a gradient composition that continuously increases in the direction. Specifically, the content of the structural unit U1 with respect to all the constituent monomer units of the segment A is from one end of the segment A to the other end, from the viewpoint of obtaining a polymer having sufficiently high toughness and excellent adhesive strength. On the other hand, it is preferable to continuously decrease from 50 to 100% by mass to 5 to 30% by mass, more preferably to continuously decrease from 60 to 100% by mass to 5 to 25% by mass. More preferably, it decreases continuously from 80-100% by mass to 5-20% by mass.

In this case, the content of the structural unit U2 with respect to all constituent monomer units of the segment A continuously increases from 0 to 50% by mass to 70 to 95% by mass from one end of the segment A to the other end. Preferably, it is more preferably continuously increased from 0 to 40% by mass to 75 to 95% by mass, and continuously increased from 0 to 20% by mass to 80 to 95% by mass. is more preferred. The structures of the two segments A of the gradient copolymer (P) may be the same or different.

In the segment A, the ratio (U1/U2) of the structural unit U1 and the structural unit U2 is preferably 5/95 to 40/60 by mass. When U1/U2 is within the above range, it is preferable in that the toughness of the pressure-sensitive adhesive layer can be further increased and a copolymer having higher adhesive strength can be obtained. From this point of view, U1/U2 is more preferably 10/90 to 35/65, even more preferably 15/85 to 30/70.

Segment A is a structural unit derived from a monomer different from monomer X and monomer Y (hereinafter also referred to as "structural unit (U3)"), as long as it does not impair the effect of the gradient copolymer (P). ). The content of structural unit U3 in segment A is preferably 10 mol% or less, more preferably 5 mol% or less, and 1 mol% or less with respect to the total monomer units of segment A. is more preferred.

The number average molecular weight of segment A is preferably in the range of 1,000 to 300,000. When the number average molecular weight is 1,000 or more, the cohesive force of the gradient copolymer (P) can be sufficiently secured, and when it is 300,000 or less, the peel strength to the adherend is sufficiently increased. It is preferable in that it can The number average molecular weight of segment A is preferably 3,000 or more, more preferably 4,000 or more, and even more preferably 10,000 or more. Also, the number average molecular weight of segment A is preferably 250,000 or less, more preferably 200,000 or less, and even more preferably 100,000 or less. The molecular weight of segment A is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

The "number average molecular weight of segment A" means the total number average molecular weight of two segments A in one molecule of the gradient copolymer (P). That is, the number average molecular weight of segment A in the ABA-type gradient copolymer (P) is the sum of the number average molecular weights of two segments A.

The segment A preferably has the property of phase-separating from the segment B. Having such properties is preferable in that the gradient copolymer (P) easily forms a microphase-separated structure. A person skilled in the art can easily design the segment A that phase separates from the segment B based on the common general knowledge as of the filing of the present application. For example, the difference ΔSP (absolute value) when comparing the SP value of segment A calculated by a known method for calculating the SP value (e.g., Fedors method) with the SP value of segment B is 0.01 or more. do. The difference ΔSP may be, for example, 0.05 or more, or, for example, 0.1 or more, or, for example, 0.2 or more, or, for example, 0.5 or more. According to the Fedors method, the SP value is F. It can be calculated by the calculation method described in Fedors, "Polymer Engineering and Science" 14(2), 147 (1974). Also, the SP value can be used to easily estimate the phase separation by observing the structure of the intended gradient copolymer (P) with an electron microscope, atomic force microscope, small-angle X-ray scattering, or the like.

(Segment B)
Segment B is a segment having a structural unit derived from a monomer having a homopolymer glass transition point of 10° C. or lower (hereinafter also referred to as “monomer Z”), and has a glass transition point of 10° C. or lower. is. When the segment B has a glass transition point (hereinafter also referred to as “glass transition point TgB”) of 10° C. or lower, the gradient copolymer (P) exhibits good adhesiveness. The glass transition point TgB is preferably 0° C. or lower, more preferably −10° C. or lower, from the viewpoint of further increasing adhesive performance.

As a specific example of the monomer Z, the explanation of the compound exemplified as a specific example of the monomer Y is applied. Among these, the monomer Z is preferably a (meth)acrylic compound in that a copolymer having a sufficiently low glass transition point and good adhesiveness can be obtained. At least one monomer selected from the group consisting of an acid alkyl compound, an alkoxyalkyl (meth)acrylate compound and a hydroxyalkyl (meth)acrylate compound (hereinafter also referred to as "compound C2") is particularly preferred. preferable. As the monomer Z, one type may be used alone, or two or more types may be used. Moreover, as the monomer Z, the same compound as the monomer Y may be used, or a different compound may be used.

In segment B, the content of structural units derived from monomer C2 is preferably 20 to 100 mol%, and 50 to 100 mol%, relative to all constituent monomer units of segment B. is more preferred, more preferably 80 to 100 mol %, and particularly preferably 90 to 100 mol %. When the content of the structural unit derived from the monomer C2 is within the above range, it tends to be possible to obtain a gradient copolymer (P) having better adhesive properties.

As the monomer C2, an alkyl acrylate compound having an alkyl group having 4 to 12 carbon atoms and an alkoxy At least one selected from the group consisting of alkoxyalkyl acrylate compounds having an alkyl group is preferred. In consideration of adhesive performance, the monomer C2 is selected from the group consisting of an alkyl acrylate compound having an alkyl group having 4 to 8 carbon atoms and an alkoxyalkyl acrylate compound having an alkoxyalkyl group having 2 to 4 carbon atoms. At least one selected is more preferred.

Segment B is mainly composed of a structural unit derived from a (meth)acrylic compound whose homopolymer has a glass transition point of 10° C. or lower, from the viewpoint of obtaining a copolymer capable of forming an adhesive layer exhibiting high adhesiveness. It is particularly preferable that the segment is Specifically, the structural unit derived from the (meth)acrylic compound contained in segment B is preferably 50 mol% or more, and preferably 70 mol% or more, relative to the total constituent monomer units of segment B. It is more preferably 80 mol % or more, and particularly preferably 90 mol % or more. In the segment B, the content of the structural unit derived from the (meth)acrylic compound can be 100 mol % or less with respect to all constituent monomer units of the segment B.

The segment B may have a structural unit derived from a monomer different from the monomer Z as long as the effect of the gradient copolymer (P) is not impaired. In segment B, the content of structural units derived from a monomer different from monomer Z is preferably 10 mol% or less, and 5 mol% or less, relative to the total monomer units of segment B. is more preferably 0 mol % or more and 1 mol % or less.

In the production of segment B, a vinyl compound having a crosslinkable functional group is used in at least one of monomer Z and other monomers so that segment B has a structure having a crosslinkable structural unit. can be done. Segment B having a crosslinkable structural unit is preferable in that the heat resistance and durability of the pressure-sensitive adhesive layer obtained using the pressure-sensitive adhesive composition can be improved. The vinyl compound having a crosslinkable functional group is not particularly limited, but examples include unsaturated carboxylic acids, unsaturated acid anhydrides, hydroxyl group-containing vinyl compounds, epoxy group-containing vinyl compounds, reactive silicon group-containing vinyl compounds, and the like. mentioned.

Specific examples of the vinyl compound having a crosslinkable functional group include unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, cinnamic acid, and unsaturated dicarboxylic acids. Alkyl esters (monoalkyl esters of maleic acid, fumaric acid, itaconic acid, citraconic acid, etc.), etc.; unsaturated acid anhydrides such as maleic anhydride, itaconic anhydride, citraconic anhydride, etc.;
2-Hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and (meth)acrylate as hydroxy group-containing vinyl compounds Hydroxyalkyl (meth)acrylate compounds such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth)acrylate, unsaturated alcohols such as allyl alcohol, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate , polyalkylene glycol mono (meth) acrylate compounds such as polyethylene glycol-polypropylene glycol mono (meth) acrylate, and hydroxyl group-containing styrene compounds such as o-hydroxystyrene, m-hydroxystyrene, and p-hydroxystyrene;
Examples of epoxy group-containing vinyl compounds include epoxy group-containing (meth)acrylic acid ester compounds such as glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate. ;
Examples of reactive silicon group-containing vinyl compounds include vinylsilane compounds such as vinyltrimethoxysilane, vinyltritoxysilane, vinylmethyldimethoxysilane and vinyldimethylmethoxysilane, trimethoxysilylpropyl (meth)acrylate, and triethoxy (meth)acrylate. Silyl group-containing (meth)acrylic acid ester compounds such as silylpropyl, methyldimethoxysilylpropyl (meth)acrylate and dimethylmethoxysilylpropyl (meth)acrylate, silyl group-containing vinyl ether compounds such as trimethoxysilylpropyl vinyl ether, and tri A silyl group-containing vinyl ester compound such as vinyl methoxysilylundecanoate and the like can be mentioned, respectively. Also, as a vinyl monomer having a crosslinkable functional group, an oxazoline group-containing vinyl compound, an isocyanate group-containing vinyl compound, or the like may be used. In producing the segment B, one or two or more vinyl compounds having a crosslinkable functional group can be used.

When the segment B has a crosslinkable structural unit, the content of the crosslinkable structural unit is preferably 0.01 mol% or more, more preferably 0.1 mol%, based on the total monomer units constituting the segment B. mol % or more, more preferably 0.5 mol % or more. By setting the content of the crosslinkable structural unit in the segment B to 0.01 mol% or more, a favorable crosslinked structure is formed, making it easier to obtain a gradient copolymer (P) exhibiting higher heat resistance and durability. . In addition, although the upper limit of the content of the crosslinkable structural unit is not particularly limited, from the viewpoint of sufficiently ensuring the flexibility of the pressure-sensitive adhesive layer to be obtained, with respect to all the constituent monomer units of the segment B, It is preferably 30 mol % or less, more preferably 20 mol % or less, still more preferably 15 mol % or less, even more preferably 10 mol % or less, and particularly preferably 7 mol % or less.

Among the above, the crosslinkable structural unit of segment B is preferably a structural unit derived from a (meth)acrylic compound. Among these, at least one selected from the group consisting of (meth)acrylic acid, (meth)acrylic acid hydroxyalkyl compounds, epoxy group-containing (meth)acrylic acid ester compounds, and silyl group-containing (meth)acrylic acid ester compounds is more preferably a structural unit derived from a monomer of Moreover, since the adhesive strength of segment B tends to increase, the crosslinkable structural unit is particularly preferably a structural unit derived from a hydroxyalkyl (meth)acrylate compound. As the hydroxyalkyl (meth)acrylate compound, a compound having a hydroxyalkyl group having 2 to 8 carbon atoms is preferable, and a compound having a hydroxyalkyl group having 2 to 4 carbon atoms is particularly preferable, from the viewpoint of adhesion performance.

(Structure of gradient copolymer (P))
The gradient copolymer (P) has a structure in which the segment A has a gradient composition in order to ensure wettability while increasing the proportion of the segment A in one polymer molecule from the viewpoint of sufficiently increasing the adhesive strength. good.

As for the ratio of segment A and segment B in one molecule of the gradient copolymer (P), the ratio of segment A to the total amount of segment A and segment B is preferably 5% by mass or more. When the ratio of segment A is 5% by mass or more, a polymer having segment A that constitutes a hard segment and can serve as a cross-linking point and segment B that serves as a soft segment makes it possible to obtain a pressure-sensitive adhesive exhibiting excellent peel strength. Cheap. Moreover, the upper limit of the ratio of segment A to the total amount of segment A and segment B is preferably 40% by mass or less. When the ratio of segment A is 40% by mass or less, the polymer in the pressure-sensitive adhesive layer exhibits sufficient fluidity during bonding to an adherend by heat, thereby ensuring high adhesive strength, which is preferable.

From this point of view, the proportion of segment A is more preferably 7% by mass or more, still more preferably 10% by mass or more, and 12% by mass or more with respect to the total amount of segment A and segment B. It is particularly preferred to have In addition, the proportion of segment A is more preferably 30% by mass or less, more preferably 25% by mass or less, and 20% by mass or less with respect to the total amount of segment A and segment B. is particularly preferred.

The number average molecular weight (Mn) of the gradient copolymer (P) is preferably 10,000 or more, more preferably 20,000 or more, still more preferably 40,000 or more, and 60 from the viewpoint of exhibiting good adhesiveness. ,000 or more is particularly preferred. In addition, Mn of the gradient copolymer (P) is preferably 500,000 or less, more preferably 400,000 or less, from the viewpoint of ease of production and the viewpoint of sufficiently ensuring good fluidity and coatability. It is preferably 350,000 or less, more preferably 250,000 or less. The range of Mn of the gradient copolymer (P) is preferably 10,000 or more and 500,000 or less, more preferably 20,000 or more and 500,000 or less, and still more preferably 40,000 or more and 400,000. It is below. The molecular weight of the gradient copolymer (P) is a polystyrene equivalent value measured by GPC.

For the gradient copolymer (P), the molecular weight distribution represented by the ratio of the weight average molecular weight (Mw) to Mn (Mw/Mn) is determined by the formation of a pseudo-crosslinked structure to improve adhesive physical properties (adhesiveness, cohesiveness, etc.). From the viewpoint of sufficiently ensuring, it is preferably 5.0 or less, more preferably 4.0 or less, still more preferably 3.5 or less, and particularly preferably 2.5 or less. Although the lower limit of Mw/Mn of the gradient copolymer (P) is not particularly limited, it is preferably 1.05 or more from the viewpoint of ease of production.

Although the reason why the pressure-sensitive adhesive composition of the present invention can form a pressure-sensitive adhesive layer exhibiting high adhesive strength is not clear, the following reasons are conceivable. When an adhesive layer is formed from an ABA-type block copolymer having a hard segment (segment A) and a soft segment (segment B), in the adhesive layer, microphase separation between the hard segment and the soft segment results in pseudo It is believed that a crosslinked structure is formed. Here, it is considered possible to improve the toughness by increasing the ratio of the hard segment in the ABA-type block copolymer. Rather, it is thought that the resulting pressure-sensitive adhesive layer is likely to cause interfacial failure because the wettability with respect to the adherend is lowered. On the other hand, in the case of the gradient copolymer (P), it is possible to have sufficient fluidity even when the ratio of the hard segment is increased, and as a result, the adhesive strength can be increased. guessed.

<Method for producing gradient copolymer (P)>
The gradient copolymer (P) is not particularly limited in production method as long as an ABA-type gradient copolymer having two segments A and one segment B can be obtained, and can be produced by a known production method. Obtainable. For example, the gradient copolymer (P) can be prepared by [1] a method of continuously adding a monomer mixture while changing the composition during the reaction for polymerization, [2] a method of utilizing the difference in reactivity of the monomers, and the like. Obtainable.

As the method for producing the gradient copolymer (P), a living radical polymerization method is preferable in that the controllability of polymerization is high and the monomer composition of the segment A can be precisely controlled. Living radical polymerization may employ any process such as a batch process, a semi-batch process, a dry continuous polymerization process, a continuous stirred tank process (CSTR), and the like. Moreover, the polymerization system can be applied to various modes such as bulk polymerization without solvent, solvent-based solution polymerization, water-based emulsion polymerization, mini-emulsion polymerization, and suspension polymerization.

The type of living radical polymerization method is not particularly limited, and reversible addition-fragmentation chain transfer polymerization method (RAFT method), nitroxy radical method (NMP method), atom transfer radical polymerization method (ATRP method), organic tellurium compound. (TERP method), a polymerization method using an organic antimony compound (SBRP method), a polymerization method using an organic bismuth compound (BIRP method), and an iodine transfer polymerization method. Among these, the RAFT method, the NMP method and the ATRP method are preferable from the viewpoint of controllability of polymerization and simplicity of implementation.

In the RAFT method, controlled polymerization proceeds via a reversible chain transfer reaction in the presence of a polymerization control agent (RAFT agent) and a general free radical polymerization initiator. As the RAFT agent, various known RAFT agents such as dithioester compounds, xanthate compounds, trithiocarbonate compounds and dithiocarbamate compounds can be used. The use of a bifunctional compound as the RAFT agent is preferable in that the gradient copolymer (P) can be obtained efficiently. The amount of the RAFT agent used is appropriately adjusted depending on the type of monomer and RAFT agent used.

As the polymerization initiator used for polymerization by the RAFT method, known radical polymerization initiators such as azo compounds, organic peroxides and persulfates can be used. Among these, azo compounds are preferred because they are easy to handle safely and less likely to cause side reactions during polymerization. Specific examples of azo compounds include 2,2′-azobis(isobutyronitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′-azobis(4-methoxy-2, 4-dimethylvaleronitrile), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile) and the like. Only one type of radical polymerization initiator may be used, or two or more types may be used in combination. The ratio of the radical polymerization initiator to be used is not particularly limited, but from the viewpoint of stably carrying out the polymerization reaction and obtaining a polymer with a narrower molecular weight distribution, the amount of the radical polymerization initiator to be used is 0.00 per 1 mol of the RAFT agent. It is preferably 01 mol or more and 0.5 mol or less. The reaction temperature during polymerization is preferably 40° C. or higher and 100° C. or lower, more preferably 45° C. or higher and 90° C. or lower.

In the NMP method, a specific alkoxyamine compound or the like having nitroxide is used as a living radical polymerization initiator, and polymerization proceeds via nitroxide radicals derived from the living radical polymerization initiator. In the production of the gradient copolymer (P), the type of nitroxide radical is not particularly limited, and commercially available nitroxide polymerization initiators can be used. From the viewpoint of easily obtaining the gradient copolymer (P) efficiently, it is preferable to use a bifunctional polymerization precursor having two active sites in the molecule. The amount of the nitroxide compound used is appropriately adjusted depending on the type of the monomer and nitroxide compound used. Further, when the gradient copolymer (P) is produced by the NMP method, polymerization may be carried out by adding a nitroxide radical to 1 mol of the nitroxide compound. The reaction temperature in the NMP method is preferably 50°C or higher and 140°C or lower, more preferably 60°C or higher and 130°C or lower.

In the ATRP method, a polymerization reaction is generally carried out using an organic halide as an initiator and a transition metal complex as a catalyst. The organic halide used as the initiator may be monofunctional or bifunctional or higher. It is preferable to use a bifunctional compound from the viewpoint that the gradient copolymer (P) can be obtained efficiently. Preferred types of halogen are bromides and chlorides. The reaction temperature in the ATRP method is preferably 20°C or higher and 200°C or lower, more preferably 50°C or higher and 150°C or lower. A reaction temperature of 20° C. or higher is preferable in that the polymerization reaction can proceed smoothly.

In the polymerization reaction, a known polymerization solvent can be used in living radical polymerization. Specifically, aromatic compounds such as benzene, toluene, xylene and anisole; ester compounds such as methyl acetate, ethyl acetate, propyl acetate and butyl acetate; ketone compounds such as acetone and methyl ethyl ketone; alcohol, water, and the like. Alternatively, bulk polymerization or the like may be performed without using a polymerization solvent. Moreover, the polymerization of the gradient copolymer (P) may be carried out in the presence of a known chain transfer agent, if necessary.

As an example of the production method, as a method utilizing the difference in reactivity of monomers, first, monomer X and monomer Y having different reactivities, a bifunctional RAFT agent, and a polymerization initiator are put into a reactor. and polymerize. At this time, as the monomer X, a compound having higher reactivity than the monomer Y is used. As a result, one end of the polymer chain (both terminal sides of the RAFT agent) is rich in the structural unit U1 derived from the monomer X, and as the polymerization progresses, the content of the structural unit U1 decreases, and the monomer It is possible to obtain a polymer chain with an increasing content of structural units U2 derived from body Y, ie a segment A in which the structural units U1 are arranged in a tilted manner from one end of the polymer chain to the other. Further, during the reaction in the polymerization step for obtaining segment A, or subsequently after the completion of the polymerization step, by supplying a monomer for constituting segment B (that is, monomer Z), segment A Polymerization of the monomer Z is carried out in succession to the polymerization for obtaining As a result, a gradient copolymer (P) having an ABA type structure of segment A-segment B-segment A can be obtained.

<Other ingredients>
The gradient copolymer (P) can be used alone as a pressure-sensitive adhesive material, but if necessary, components such as polymers other than the gradient copolymer (P) and additives (hereinafter also referred to as "other components") ) may be blended into the adhesive composition and used. Other components that may be blended in the pressure-sensitive adhesive composition are described below.

(crosslinking agent)
When the gradient copolymer (P) has a crosslinkable functional group in at least one of segment A and segment B, a crosslinker capable of reacting with the crosslinkable functional group may be added to the pressure-sensitive adhesive composition. Moreover, it may be designed to obtain a pressure-sensitive adhesive according to the application by further performing heat treatment or the like as necessary.

Examples of crosslinking agents (curing agents) include glycidyl compounds having two or more glycidyl groups, isocyanate compounds having two or more isocyanate groups, aziridine compounds having two or more aziridinyl groups, oxazoline compounds having an oxazoline group, metal chelate compounds, butylated melamine compounds, and the like. Among these, isocyanate compounds are preferable because they have excellent adhesive properties under high temperature conditions.

Specific examples of cross-linking agents include glycidyl compounds such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and tetraglycidylxylenediamine. , 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, polyfunctional glycidyl compounds such as trimethylolpropane polyglycidyl ether;
Examples of isocyanate compounds include diphenylmethane diisocyanate (MDI), tolylene diisocyanate, naphthalene diisocyanate (NDI), p-phenylene diisocyanate (PPDI), xylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), and the like. Aromatic isocyanate compounds; Aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI) and lysine diisocyanate (LDI); isophorone diisocyanate (IPDI), cyclohexyl diisocyanate (CHDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI) ) and other alicyclic isocyanate compounds; urethane modified products, dimers, trimers, carbodiimide modified products, urea modified products, isocyanurate modified products, oxazolidone modified products, modified isocyanate compounds such as isocyanate group-terminated prepolymers, etc. ;
As aziridine compounds, 1,6-bis(1-aziridinylcarbonylamino)hexane, 1,1′-(methylene-di-p-phenylene)bis-3,3-aziridylurea, ethylenebis-(2-aziridyl lysinylpropionate), 2,4,6-triaziridinyl-1,3,5-triazine, trimethylolpropane-tris-(2-aziridinylpropionate), and the like.

When the pressure-sensitive adhesive composition contains a cross-linking agent, its content is not particularly limited. 0.03 to 5% by weight, more preferably 0.05 to 2% by weight.

(Tackifier)
The adhesive composition may further contain a tackifier. Examples of tackifiers include rosin derivatives such as rosin ester, gum rosin, tall oil rosin, hydrogenated rosin ester, maleated rosin, and disproportionated rosin ester; terpene phenol resin, α-pinene, β-pinene, limonene, etc. (hydrogenated) petroleum resin; coumarone-indene resin; hydrogenated aromatic copolymer; styrene resin; phenol resin; xylene resin; . Only one tackifier may be used, or two or more tackifiers may be used in combination.

As the tackifier, a (meth)acrylic acid ester oligomer can be preferably used from the viewpoint of transparency and the like. The glass transition point of the (meth)acrylate oligomer used as a tackifier is usually 10 to 300°C, preferably 15 to 250°C, more preferably 20 to 200°C, and still more preferably 30 to 150°C. is. When the glass transition point of the (meth)acrylic ester oligomer is within the above range, the effect of improving adhesion by adding the (meth)acrylic ester oligomer can be enhanced. More specifically, a (meth)acrylic acid ester oligomer having a glass transition point of 30 to 150° C. and a polystyrene-equivalent number average molecular weight measured by GPC of 500 to 10,000 can be preferably used.

The content of the tackifier in the pressure-sensitive adhesive composition is preferably 0 to 40% by mass, more preferably 0 to 20% by mass, and still more preferably the total amount of the gradient copolymer (P). is 0 to 10% by mass.

Other additives to be incorporated into the pressure-sensitive adhesive composition include, for example, plasticizers, antioxidants, ultraviolet absorbers, antioxidants, flame retardants, antifungal agents, silane coupling agents, fillers, colorants, and the like. is mentioned. The content of the additive can be appropriately set according to various compounds within a range that does not impair the effects of the present invention.

The pressure-sensitive adhesive composition may be a liquid composition in which the gradient copolymer (P) and optionally other components are dissolved or dispersed in a solvent. The solvent used for preparing the pressure-sensitive adhesive composition includes an organic solvent capable of dissolving the gradient copolymer (P) and an aqueous medium capable of dispersing the gradient copolymer (P). Specific examples of the organic solvent include aprotic polar solvents, phenol solvents, alcohol solvents, ester solvents, ketone solvents, ether solvents, hydrocarbon solvents and the like. The organic solvent may be one of these, or a mixed solvent of two or more.

When the pressure-sensitive adhesive composition is liquid, the solid content concentration in the pressure-sensitive adhesive composition (that is, the ratio of the mass of components other than the solvent in the pressure-sensitive adhesive composition to the total mass of the pressure-sensitive adhesive composition) is not particularly limited. is preferably 1 to 70% by mass. A solid content concentration of 1% by mass or more is preferable in that a pressure-sensitive adhesive layer having a sufficient thickness can be formed. Moreover, when the solid content concentration is 70% by mass or less, good coatability can be ensured, and a pressure-sensitive adhesive layer having a uniform thickness can be easily formed, which is preferable. The solid content concentration in the pressure-sensitive adhesive composition is more preferably 5 to 50% by mass, still more preferably 10 to 45% by mass.

By coating the present pressure-sensitive adhesive composition on a support such as a separator to form a pressure-sensitive adhesive layer, pressure-sensitive adhesive products such as pressure-sensitive adhesive sheets and pressure-sensitive adhesive tapes can be obtained. This adhesive product can be used as an adhesive for adhering to adherends.

As the support, resin films (separators) made of various resin materials, substrates, and the like are used. Resin materials for forming the separator include polyester resins such as polyethylene terephthalate, polyethersulfone resins, acetate resins, polycarbonate resins, and polyolefin resins. Examples of the base material include, but are not particularly limited to, fiber fabrics, resin films, elastomer sheets, papers, and metal films.

The pressure-sensitive adhesive layer is formed by, for example, applying a liquid pressure-sensitive adhesive composition to a support by a known coating method, and preferably removing the solvent in the pressure-sensitive adhesive composition by drying treatment such as heating. The heating temperature and heating time for forming the pressure-sensitive adhesive layer may be set as long as the solvent can be removed, and can be appropriately set according to the solvent, solid content concentration, and the like of the pressure-sensitive adhesive composition.

The adhesive product may be a so-called substrate-less embodiment in which an adhesive layer is sandwiched between two types of separators having different peel strengths, or may use one of the objects to be laminated as a substrate. . Also, the shape of the adhesive product is not particularly limited, and is appropriately set according to the usage conditions. For example, the pressure-sensitive adhesive sheet may be in the shape of a sheet, a roll, or cut into strips, or may have any shape depending on the joint. The thickness of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive product may be appropriately set according to the object to be bonded, the area and shape of the bonding portion, and the like. The thickness of the adhesive layer is usually 1-200 μm. Moreover, in order to obtain a desired thickness of the adhesive layer of the adhesive product, the adhesive layer of the adhesive product may be formed by laminating a plurality of adhesive layers.

In order to adhere the pressure-sensitive adhesive layer formed using the present pressure-sensitive adhesive composition to the adherend, first, the laminate obtained by laminating the pressure-sensitive adhesive layer to the adherend is heated (preferably thermocompression). It can be carried out. When the pressure-sensitive adhesive layer is bonded to the adherend by thermocompression, the pressure during bonding may be appropriately set so as to obtain the desired bonding strength. Moreover, the heating temperature is preferably lower than the heat resistance temperature of the adherend to be used. The pressure-sensitive adhesive layer formed using the present pressure-sensitive adhesive composition, when the adherend is a fiber fabric, is flexible at the joint and has a high adhesive strength even if the resin is impregnated into the mesh of the fiber fabric during thermocompression bonding. It is preferable in that it can be adhered with strength.

The pressure-sensitive adhesive composition and pressure-sensitive adhesive products of the present invention can be applied to various uses. Specifically, for example, it can be applied to clothing (including fashion goods), electronic equipment, automotive interior and exterior products, optical equipment, handicrafts, toys, household goods, household goods, furniture, etc. can. In particular, the pressure-sensitive adhesive composition of the present invention can maintain the flexibility and texture of the fabric after bonding even when fibers are used as the adherend, and can form a pressure-sensitive adhesive layer with high adhesiveness. is. Therefore, the pressure-sensitive adhesive composition of the present invention can be suitably used as a pressure-sensitive adhesive for fiber fabrics (e.g., woven fabrics, knitted fabrics, non-woven fabrics, laces, leather (natural leather, synthetic leather, artificial leather, etc.), fur, etc.), Among others, it can be suitably used for textile fabrics for clothing.

Fiber fabrics to be joined are not particularly limited, and fiber fabrics used for clothing and handicrafts, such as synthetic fibers such as polyester, polyamide and acrylic fibers; regenerated fibers such as rayon and cupra; semi-synthetic fibers such as acetate; Natural fibers such as cotton, hemp, and wool can be used as appropriate. Also, the surfaces of the fiber fabrics to be joined may be subjected to a water-repellent treatment or the like. There are no particular restrictions on the clothing produced using the present pressure-sensitive adhesive composition. It can be used as an adhesive when manufacturing a wide range of clothing such as clothes, tops, bottoms, outdoor goods, work clothes, uniforms, formal clothes, swimwear, sportswear, socks, hats, shoes, etc., and for handicrafts. .

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. In the following, "parts" and "%" mean parts by mass and % by mass unless otherwise specified. The analysis methods and production methods of the polymers used in Examples and Comparative Examples are as follows.

<Molecular weight measurement>
Using a gel permeation chromatograph (model name “HLC-8320”, manufactured by Tosoh Corporation), the number average molecular weight (Mn) and weight average molecular weight (Mw) in terms of polystyrene were obtained under the following conditions. Also, the molecular weight distribution (Mw/Mn) was calculated from the obtained values.
○ Measurement conditions Column: TSKgel Super Multipore HZ-M × 4 columns manufactured by Tosoh Corporation Column temperature: 40 ° C.
Eluent: Tetrahydrofuran Detector: RI
Flow rate: 600 μL/min

<Polymer composition>
The polymer composition was calculated from the charged monomer amount and the monomer consumption calculated by gas chromatography (GC).
GC: Agilent Technologies (7820A GC System)
Detector: FID
Column: 100% dimethylsiloxane (CP-Sil 5CB) length 30 m, inner diameter 0.32 mm
Calculation method: internal standard method

<Measurement of glass transition point (Tg)>
The glass transition point (Tg) of the polymer was determined from the intersection of the baseline of the heat flux curve obtained using a differential scanning calorimeter and the tangent line at the point of inflection. The heat flux curve was obtained by cooling about 10 mg of the sample to -50°C, holding it for 5 minutes, heating it to 300°C at 10°C/min, cooling it to -50°C, holding it for 5 minutes, and heating it to 10°C. /min to 350°C.
Measuring instrument: DSC6220 manufactured by SII Nano Technology Co., Ltd.
Measurement atmosphere: nitrogen atmosphere The glass transition point of each segment was obtained by producing a homopolymer of the segment to be measured and performing differential scanning calorimetry (DSC) measurement according to the above measurement method.
The glass transition point of the homopolymer of each monomer is as follows.
・Styrene: 80°C
・N-phenylmaleimide: 316°C
・2-Methoxyethyl acrylate: -35°C
・n-Butyl acrylate: -49°C
・2-Hydroxyethyl acrylate: -15°C

1. Synthesis of Polymer [Synthesis Example 1]
A 1 L flask equipped with a stirrer and a thermometer was charged with 0.22 g of dibenzyltrithiocarbonate (hereinafter also referred to as "DBTTC") as a RAFT agent and 2,2'-azobis(2-methylbutyronitrile) as a polymerization initiator. ) (hereinafter also referred to as “ABN-E”) 0.044 g, 2-methoxyethyl acrylate as a monomer (hereinafter also referred to as “MEA”) 85.2 g, n-butyl acrylate (hereinafter referred to as “BA” ) 18.6 g, 2-hydroxyethyl acrylate (hereinafter also referred to as “HEA”) 5.5 g, styrene (hereinafter also referred to as “St”) 16.9 g, and N-phenylmaleimide (hereinafter referred to as “PhMI ”) and 81.3 g of ethyl acetate as a solvent were charged, sufficiently degassed by nitrogen bubbling, and polymerization was initiated in a constant temperature bath at 70°C. A feed tank was charged with 113.7 g of MEA, 24.8 g of BA, 7.3 g of HEA, and 108 g of ethyl acetate, and continuously fed into the flask for a period of 1 to 2 hours after the initiation of polymerization, and reacted for 8 hours. let me After that, the polymerization was terminated by cooling to obtain a polymer solution containing copolymer (P-1).

After the start of polymerization, samples were taken 6 times at predetermined time intervals, and the elapsed time from the start of polymerization was calculated from the molecular weight determined by GPC measurement (converted to polystyrene) and the amount of monomer consumption determined by GC measurement each time. The monomer composition of the polymer chains produced by the polymerization in each period (period 1 to period 6) determined accordingly was calculated. Table 1 shows the results. The "increase Mn" in Table 1 is the molecular weight increased by polymerization in each period, and was calculated from the difference between the number average molecular weight Mn in the previous period and the number average molecular weight Mn in the current period. "No." in Table 1 is a numerical value corresponding to each number of the first period to the sixth period. According to the calculation results of the monomer composition in each period, the content of the structural unit U1 derived from the monomer X is 5% by mass or more per number average molecular weight Mn 10000 Segment A, Segment B less than 5% by mass .

The calculation results of the monomer composition show that in the first period (0 to 0.5 hours from the start of polymerization), the increase Mn was 13000, and the ratio of structural units derived from the monomer X (hereinafter also referred to as “U1 ratio”) was In the second period (0.5 to 1.0 hours from the start of polymerization), the increase Mn was 20200, the U1 ratio was 61% by mass, and the third period (1.0 to 3 .0 hour), the increase Mn was 22000 and the U1 ratio was 30% by mass, and in the fourth period (3.0 to 4.5 hours after the start of polymerization), the increase Mn was 31000 and the U1 ratio was 15% by mass. Yes, in the fifth period (4.5 to 6.0 hours from the start of polymerization), the increase Mn is 40500, the U1 ratio is 3% by mass, and the sixth period (6.0 to 8.0 hours from the start of polymerization) , the increase Mn was 30000 and the U1 ratio was 0.5% by mass. From this calculation result, it was found that the obtained copolymer (P-1) was an ABA-type gradient copolymer. The copolymer (P-1) had a molecular weight of Mn of 156,700, an Mw/Mn of 1.87, and a U1 ratio of 17% by mass.

[Synthesis Example 2]
DBTTC (0.5 g) as a RAFT agent, ABN-E (0.07 g) as a polymerization initiator, MEA (168 g), BA (37 g) and HEA as monomers are placed in a 1 L flask equipped with a stirrer and a thermometer. (11 g), St (20 g), PhMI (34 g), and 170 g of ethyl acetate as a solvent were charged, sufficiently degassed by nitrogen bubbling, and polymerization was initiated in a constant temperature bath at 70°C. After reacting for 8 hours, the polymerization was terminated by cooling to obtain a polymer solution containing copolymer (P-2).

After the initiation of the polymerization, the monomer composition of the polymer chain produced by the polymerization was calculated for each period according to the elapsed time from the initiation of the polymerization in the same manner as in Synthesis Example 1. The calculation result of the monomer composition was that the increase Mn was 13200 and the U1 ratio was 61% by mass in the first period (0 to 0.5 hours after the start of polymerization), and the second period (0.5 to 1.5 hours after the start of polymerization). 0 hour), the increase Mn is 22000 and the U1 ratio is 36% by mass, and in the third period (1.0 to 3.0 hours from the start of polymerization), the increase Mn is 21000 and the U1 ratio is 25% by mass. , In the fourth period (3.0 to 4.5 hours from the start of polymerization), the increase Mn is 26000 and the U1 ratio is 18% by mass, and in the fifth period (4.5 to 6.0 hours from the start of polymerization) , the increase Mn was 45300 and the U1 ratio was 12% by mass, and in the sixth period (6.0 to 8.0 hours after the start of polymerization), the increase Mn was 22000 and the U1 ratio was 0.4% by mass. From this calculation result, it was found that the obtained copolymer (P-2) was an ABA-type gradient copolymer. The copolymer (P-2) had a molecular weight of Mn of 149,500, an Mw/Mn of 1.85, and a U1 ratio of 16% by mass.

[Synthesis Example 3]
DBTTC (1.9 g) as a RAFT agent, ABN-E (0.25 g) as a polymerization initiator, styrene (75 g) as a monomer, and PhMI (125 g) were added to a 1 L flask equipped with a stirrer and a thermometer, and a solvent. Acetonitrile (457 g) was charged as a solution, degassed sufficiently by nitrogen bubbling, and polymerization was initiated in a constant temperature bath at 70°C. After 3 hours, the reaction was terminated by cooling to room temperature. The resulting polymer A had an Mn of 20,800 and a Tg of 210°C. Next, in a 1 L flask equipped with a stirrer and a thermometer, the obtained polymer A solution (125 g), MEA (210 g), BA (46 g), and HEA (14 g) as monomers, and acetonitrile as a solvent ( 48 g) was charged, sufficiently degassed by nitrogen bubbling, and polymerization was initiated in a constant temperature bath at 70°C. After 6 hours, the mixture was cooled to room temperature, and acetonitrile was added to adjust the solid content concentration to 30%, thereby obtaining a polymer solution containing copolymer (Q-1).

After the initiation of polymerization, the monomer composition of the polymer chain produced by polymerization in each period was calculated in the same manner as in Synthesis Example 1. The calculation result of the monomer composition was that the increase Mn was 12000 and the U1 ratio was 100% by mass in the first period (0 to 0.5 hours from the start of polymerization), and the second period (0.5 to 1.5 hours after the start of polymerization). 0 hours), the increase Mn is 10100 and the U1 ratio is 100% by mass, and in the third period (1.0 to 3.0 hours from the start of polymerization), the increase Mn is 25000 and the U1 ratio is 1.2% by mass. In the fourth period (3.0 to 4.5 hours after the start of polymerization), the increase Mn was 26700 and the U1 ratio was 0.5 mass%, and in the fifth period (4.5 to 6.5 hours after the start of polymerization). 0 hour), the increase Mn is 35000 and the U1 ratio is 0.1% by mass, and in the sixth period (6.0 to 8.0 hours from the start of polymerization) the increase Mn is 39000 and the U1 ratio is 0.1. % by mass. From this calculation result, it was found that the obtained copolymer (Q-1) was an ABA-type triblock copolymer. The copolymer (Q-1) had a molecular weight of Mn of 145,800, an Mw/Mn of 1.81, and a U1 ratio of 15% by mass.

[Synthesis Example 4]
DBTTC (1.2 g) as a RAFT agent, ABN-E (0.16 g) as a polymerization initiator, styrene (75 g) as a monomer, and PhMI (125 g) as a solvent were placed in a 1 L flask equipped with a stirrer and a thermometer. Acetonitrile (457 g) was charged as a solution, degassed sufficiently by nitrogen bubbling, and polymerization was initiated in a constant temperature bath at 70°C. After 3 hours, the reaction was terminated by cooling to room temperature. The resulting polymer A had an Mn of 32,300 and a Tg of 212°C. Next, in a 1 L flask equipped with a stirrer and a thermometer, the obtained polymer A solution (161 g), MEA (175 g), BA (38 g), and HEA (11 g) as monomers, and acetonitrile as a solvent ( 53 g) was charged, sufficiently degassed by nitrogen bubbling, and polymerization was initiated in a constant temperature bath at 70°C. After 6 hours, the mixture was cooled to room temperature, and acetonitrile was added to adjust the solid content concentration to 30%, thereby obtaining a polymer solution containing copolymer (Q-2).

After the initiation of polymerization, the monomer composition of the polymer chain produced by polymerization in each period was calculated in the same manner as in Synthesis Example 1. The calculation result of the monomer composition is that the increase Mn is 16000 and the U1 ratio is 100% by mass in the first period (0 to 0.5 hours from the start of polymerization), and the second period (0.5 to 1.5 hours from the start of polymerization). 0 hour), the increase Mn is 14000 and the U1 ratio is 100% by mass, and in the third period (1.0 to 3.0 hours from the start of polymerization), the increase Mn is 35000 and the U1 ratio is 1.3% by mass. In the fourth period (3.0 to 4.5 hours after the start of polymerization), the increase Mn was 26200 and the U1 ratio was 0.6% by mass, and in the fifth period (4.5 to 6.5 hours after the start of polymerization). 0 hour), the increase Mn is 32500 and the U1 ratio is 0.2% by mass, and in the sixth period (6.0 to 8.0 hours from the start of polymerization), the increase Mn is 22500 and the U1 ratio is 0.1. % by mass. From this calculation result, it was found that the obtained block copolymer (Q-2) was an ABA-type triblock copolymer. The copolymer (Q-2) had a molecular weight of Mn of 146,200, an Mw/Mn of 1.75, and a U1 ratio of 22% by mass.

2. Preparation and Evaluation of Adhesive Composition [Example 1]
Ethyl acetate was added to the polymer solution obtained in Synthesis Example 1 to prepare an adhesive composition having a solid concentration of 30% by mass. This adhesive composition was applied onto a polyethylene terephthalate separator having a thickness of 50 μm so that the thickness of the adhesive layer after drying would be 100 μm. Ethyl acetate was removed by drying the adhesive composition at 100° C. for 6 minutes with an air dryer. After drying, a separator made of polyethylene terephthalate having a thickness of 38 μm and having a different peeling force from the above separator was laminated to obtain an adhesive film sample with a double-sided separator. Using the obtained adhesive film sample, the adhesive strength was evaluated by the method shown below. Table 1 shows the evaluation results.
<Evaluation of adhesive strength>
An adhesive film sample cut to a width of 10 mm was used to bond two sheets of polyester cloth together to obtain a laminate in which the polyester cloth/adhesive film/polyester cloth were laminated in this order. The obtained laminate was crimped by heat press treatment (conditions: 130° C., 3 kg/cm ² , 10 seconds). Using the laminated body after crimping as a test piece, the T-type peel strength [N /10 mm] was measured to evaluate the adhesive strength.

[Example 2 and Comparative Examples 1 and 2]
The polymer used was changed as shown in Table 1, and a pressure-sensitive adhesive composition having a solid content concentration of 30% by mass was obtained. Moreover, the adhesive strength was evaluated in the same manner as in Example 1 using the obtained pressure-sensitive adhesive composition. Table 1 shows the results. Table 1 shows the measurement results of the peel strength and the monomer composition in the polymer chain calculated for each synthesis example.

As shown in Table 1, in Examples 1 and 2 using the adhesive composition containing the gradient copolymer (P), the T-type peel strength is as high as 9.5 N / 10 mm and 5.2 N / 10 mm, respectively. and the fiber fabrics were difficult to separate from each other. Moreover, in Examples 1 and 2, the failure during the peel strength measurement was caused by the cohesive failure of the adhesive layer. From this, it can be said that the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Examples 1 and 2 have high toughness and the wettability of the pressure-sensitive adhesive composition is high. In particular, the U1 ratio of the entire polymer (Total U1) is approximately the same value, but the U1 ratio at both ends of the polymer is higher (U1 ratio: 85% by mass). In Example 1 using the copolymer (P-1) , the peel strength was higher and the adhesive properties were better.
On the other hand, in Comparative Examples 1 and 2 using the ABA-type triblock copolymer, the peel strength values were lower than those in Examples 1 and 2. In Comparative Examples 1 and 2, the wettability of the pressure-sensitive adhesive composition was low, and breakage during peel strength measurement was caused by interfacial breakage between the adhesive layer and the fiber fabric.
From the above, according to the pressure-sensitive adhesive composition containing the gradient copolymer (P), it is possible to make a pressure-sensitive adhesive with high wettability and to form a pressure-sensitive adhesive layer with high adhesive strength. Do you get it.

Claims (8)

Containing an ABA-type gradient copolymer having a segment A and a segment B,
The segment A is a structural unit derived from a monomer X whose homopolymer glass transition point is 50 ° C. or higher, and a structure derived from a monomer Y whose homopolymer glass transition point is 10 ° C. or lower. having units and
The segment B has a structural unit derived from a monomer Z whose homopolymer glass transition point is 10° C. or lower, and has a glass transition point of 10° C. or lower,
In the segment A, the content of the structural unit derived from the monomer X continuously decreases in the direction from the segment A toward the segment B, and the content of the structural unit derived from the monomer Y The adhesive composition, the amount of which continuously increases in the direction from said segment A toward said segment B. The segment A has, as a structural unit derived from the monomer X, a structural unit derived from at least one selected from the group consisting of styrene-based compounds, imide group-containing vinyl compounds, and amide group-containing vinyl compounds. Item 1. The pressure-sensitive adhesive composition according to item 1. The content of the structural unit derived from the monomer X with respect to all the constituent monomer units of the segment A is from 50 to 100% by mass to 5 to 30% by mass from one end to the other end of the segment A. % continuously decreasing. The gradient copolymer according to any one of claims 1 to 3, wherein the ratio of the segment A to the total amount of the segment A and the segment B is 5% by mass or more and 40% by mass or less. Adhesive composition. In the segment B, as a structural unit derived from the monomer Z, at least The pressure-sensitive adhesive composition according to any one of claims 1 to 4, which has structural units derived from one species. The segment A has, as a structural unit derived from the monomer Y, a structural unit derived from at least one selected from the group consisting of an alkyl (meth)acrylate compound and an alkoxyalkyl (meth)acrylate compound. The adhesive composition according to any one of claims 1-5. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the gradient copolymer has a number average molecular weight of 10,000 or more and 500,000 or less. A pressure-sensitive adhesive product comprising a support and a pressure-sensitive adhesive layer formed on the support using the pressure-sensitive adhesive composition according to any one of claims 1 to 7.