Hot melt type adhesive composition

Abstract

To provide a hot melt type adhesive composition which is excellent in adhesive force to various adherends, and can suppress an adhesive residue on an adherend when the hot melt type adhesive composition is peeled off.SOLUTION: A hot melt type adhesive composition contains a styrene-based block copolymer (A), an acrylic block copolymer (B), a tackifier resin (C), and a softening agent (D), and satisfies conditions (1) to (6).SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a hot-melt type adhesive composition. [Background technology]

[0002] Hot-melt adhesives are obtained by applying them in a heated and molten state, followed by cooling. Because they do not use solvents in the manufacturing process, they are highly safe and environmentally friendly. Therefore, hot-melt adhesives are widely used in fields such as paper processing, woodworking, and electronics.

[0003] Examples of hot-melt adhesives include those using styrene-based elastomers. While hot-melt adhesives using styrene-based elastomers exhibit good adhesion to polymethyl methacrylate (PMMA) sheets and stainless steel (SUS) sheets, they have the problem of leaving adhesive residue at relatively high temperatures due to their high tackiness. In contrast, hot-melt adhesives using acrylic block copolymers have low tackiness, which reduces the problem of adhesive residue. However, they have a problem in that their adhesive strength to non-polar resins such as polyethylene (PE) is weak, which limits the types of substrates to which they can be adhered.

[0004] To address these problems, extensive research is being conducted on hot-melt adhesives. For example, Patent Document 1 proposes a hot-melt adhesive combining a styrene-based block copolymer and an acrylic-based block copolymer. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2015 / 076332 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the hot-melt adhesive described in Patent Document 1, there was a problem that the styrene block copolymer and the acrylic block copolymer were not uniformly compatible and sufficient adhesive strength could not be obtained.

[0007] The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a hot-melt adhesive composition that is excellent in adhesive strength to various adherends and can suppress adhesive residue on the adherend when the hot-melt adhesive composition is peeled off.

Means for Solving the Problems

[0008] As a result of investigations by the present inventors, it was found that among styrene block copolymers, a styrene block copolymer having high fluidity has high affinity with an acrylic block copolymer and is easily compatible with each other. Further investigations revealed that by satisfying specific melt viscosity conditions for the styrene block copolymer with high fluidity and the acrylic block copolymer, and further blending materials that satisfy various conditions, it is possible to adjust to appropriate tack-promoting properties and have excellent adhesiveness to a wide variety of adherends. Furthermore, it was found that the obtained hot-melt adhesive composition can also suppress adhesive residue, and the present invention was completed.

[0009] The present invention has the following gists [1] to [4]. [1] A hot-melt adhesive composition comprising a styrene block copolymer (A), an acrylic block copolymer (B), an adhesion-imparting resin (C), and a softening agent (D), and satisfying the following conditions (1) to (6). <Condition (1)> The melt viscosity (P A ) of the styrene block copolymer (A) at 190 ° C. and the melt viscosity (P B ) of the acrylic block copolymer (B) at 190 ° C. satisfy the relationship of P A <P B . <Condition (2)> The mass ratio [(A) / (B)] of the content of the styrenic block copolymer (A) to the acrylic block copolymer (B) is 10 / 90 to 95 / 5. <Condition (3)> The styrenic block copolymer (A) is a hydrogenated product of a block copolymer (P1) having one or more polymer blocks (a11) containing structural units derived from styrenic compounds and one or more polymer blocks (a12) containing structural units derived from conjugated diene compounds. The melt viscosity (P A ) measured at a temperature of 190 °C and a shear rate of 121.6 (1 / sec) in accordance with ISO 11443:1995 is 100 Pa·s or more and less than 600 Pa·s. <Condition (4)> The acrylic block copolymer (B) has one or more polymer blocks (b11) containing structural units derived from acrylic esters and one or more polymer blocks (b12) containing structural units derived from methacrylic esters, has a number average molecular weight (Mn) of 50,000 to 300,000, and the content of the polymer block (b12) in the acrylic block copolymer (B) is 5 to 30% by mass. <Condition (5)> The tackifier resin (C) is a tackifier resin having a softening point of 80 to 160 °C, and is two or more selected from the group consisting of rosin resins, terpene resins, phenolic resins, terpene phenolic resins, hydrogenated petroleum resins, styrenic resins, xylene resins, hydrogenated aromatic copolymers, and coumarone-indene resins. <Condition (6)> The softener (D) is one or more selected from the group consisting of liquid acrylic polymers, acrylic oligomers, paraffinic process oils, naphthenic process oils, and aromatic process oils. [2] The melt viscosity (P B ) of the acrylic block copolymer (B) at 190 °C is more than 100 Pa·s and 1,200 Pa·s or less, and the hot-melt type adhesive composition according to [1] above. [3] The content of the styrenic block copolymer (A) contained in the hot-melt adhesive composition is 3 to 70% by mass, and the hot-melt adhesive composition according to [1] or [2] above. [4] The content of the acrylic block copolymer (B) contained in the hot-melt adhesive composition is 0.5 to 50% by mass, and the hot-melt adhesive composition according to any one of [1] to [3] above.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a hot-melt adhesive composition that is excellent in adhesion to various adherends and can suppress adhesive residue on the adherend when the hot-melt adhesive composition is peeled off.

Embodiments for Carrying Out the Invention

[0011] [Hot-Melt Adhesive Composition] The hot-melt adhesive composition of the present invention contains a styrenic block copolymer (A), an acrylic block copolymer (B), a tackifying resin (C), and a softening agent (D), and is characterized by satisfying the following conditions (1) to (6).

[0012] <Condition (1)> In the present invention, the melt viscosity (P A ) at 190°C of the styrenic block copolymer (A) and the melt viscosity (P B ) at 190°C of the acrylic block copolymer (B) satisfy the relationship of P A <P B . When the melt viscosity (P A ) and the melt viscosity (P B ) satisfy the above relationship, the compatibility between the styrenic block copolymer (A) and the acrylic block copolymer (B) is improved. As a result, the adhesiveness of the hot-melt adhesive composition of the present invention is improved. In addition, since the adhesiveness enhancing property can be adjusted within an appropriate range, adhesive residue on the adherend can be suppressed. From these viewpoints, P B is P AIt is preferable that it is 5 Pa·s or more greater than [the specified value], more preferably 50 Pa·s or more greater, and even more preferably 100 Pa·s or more greater. In this specification, "Melting viscosity at 190°C (P A ) and "Melting viscosity at 190°C (P B ")" refers to the melt viscosity measured in accordance with ISO 11443:1995 at a temperature of 190°C and a shear rate of 121.6 (1 / sec).

[0013] <Condition (2)> The present invention is characterized in that the mass ratio of the content of styrene-based block copolymer (A) to acrylic-based block copolymer (B) [(A) / (B)] is 10 / 90 to 95 / 5. When the mass ratio is within the range described above, the styrene-based block copolymer (A) and the acrylic-based block copolymer (B) become more uniformly compatible, thereby improving the tackiness of the hot-melt adhesive composition. From this viewpoint, the mass ratio [(A) / (B)] is preferably 10 / 90 to 95 / 5, more preferably 20 / 80 to 90 / 10, more preferably 30 / 70 to 85 / 15, and even more preferably 40 / 60 to 80 / 20.

[0014] <Condition (3)> The present invention relates to a hydrogenated block copolymer (P1) in which the styrene-based block copolymer (A) has one or more polymer blocks (a11) containing structural units derived from styrene compounds and one or more polymer blocks (a12) containing structural units derived from conjugated diene compounds, and the melt viscosity (P1) was measured in accordance with ISO 11443:1995 at a temperature of 190°C and a shear rate of 121.6 (1 / sec). A ) is characterized by being 100 Pa·s or more and less than 600 Pa·s.

[0015] <Condition (4)> The present invention is characterized in that the acrylic block copolymer (B) has one or more polymer blocks (b11) containing structural units derived from acrylic acid esters and one or more polymer blocks (b12) containing structural units derived from methacrylic acid esters, has a number average molecular weight (Mn) of 50,000 to 300,000, and the content of the polymer blocks (b12) in the acrylic block copolymer (B) is 5 to 30% by mass.

[0016] <Condition (5)> The present invention is characterized in that, as the tackifying resin (C), two or more types selected from the group consisting of rosin resins, terpene resins, phenolic resins, terpenephenolic resins, hydrogenated petroleum resins, styrene resins, xylene resins, hydrogenated aromatic copolymers, and coumarone-indene resins are used, and the tackifying resin (C) has a softening point of 80 to 160°C.

[0017] <Condition (6)> The present invention is characterized by using one or more selected from the group consisting of liquid acrylic polymers, acrylic oligomers, paraffinic process oils, naphthenic process oils, and aromatic process oils as the softening agent (D). By using the above as the softening agent in the present invention, the fluidity of the hot melt adhesive composition is improved, and each component becomes more uniformly compatible, resulting in improved tackiness of the hot melt adhesive composition.

[0018] <Styrene-based block copolymer (A)> The hot-melt adhesive composition of the present invention contains a styrene-based block copolymer (A). In the present invention, the use of a styrene-based block copolymer (A) can improve adhesion to a variety of substrates. The styrene-based block copolymer (A) used in the present invention is a hydrogenated block copolymer (P1) having one or more polymer blocks (a11) containing structural units derived from styrene compounds and one or more polymer blocks (a12) containing structural units derived from conjugated diene compounds. One type of styrene-based block copolymer (A) may be used alone, or two or more types may be used in combination.

[0019] [Polymer block (a11)] The polymer block (a11) contained in the block copolymer (P1) contains structural units derived from styrene compounds. Examples of the styrene compounds include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 2,4,6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, vinylanthracene, N,N-diethyl-4-aminoethylstyrene, vinylpyridine, 4-methoxystyrene, monochlorostyrene, dichlorostyrene, and divinylbenzene. These styrene compounds may be used individually or in combination of two or more. Among these, styrene, α-methylstyrene, and 4-methylstyrene are preferred, with styrene being more preferred.

[0020] The polymer block (a11) may contain structural units derived from monomers other than styrene compounds, such as conjugated dienes that constitute the polymer block (a12) described later. However, the content of structural units derived from styrene compounds in the polymer block (a11) is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably substantially 100% by mass.

[0021] [Polymer block (a12)] The polymer block (a12) contained in the block copolymer (P1) contains structural units derived from a conjugated diene compound. Examples of the conjugated diene include butadiene, isoprene, 2,3-dimethylbutadiene, 2-phenylbutadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3-octadiene, 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7-octatriene, myrcene, farnesene, and chloroprene. These conjugated dienes may be used individually or in combination of two or more. Among these, butadiene, isoprene, and farnesene are preferred conjugated dienes.

[0022] The polymer block (a12) may contain structural units derived from monomers other than conjugated dienes, such as styrene compounds that constitute the polymer block (a11) described above. However, the content of structural units derived from conjugated diene compounds in the polymer block (a12) is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably substantially 100% by mass.

[0023] (Degree of vinylization of polymer block (a12)) The degree of vinylization of the structural units derived from the conjugated diene compound contained in the polymer block (a12) is not particularly limited, but is preferably 1 to 95 mol%, more preferably 2 to 90 mol%, even more preferably 3 to 85 mol%, and even more preferably 4 to 80 mol%. The degree of vinylization can be adjusted when producing a styrene-based block copolymer by anionic polymerization as described later, by controlling the type of solvent used, the type and amount of Lewis base used as needed, the polymerization temperature, etc.

[0024] In the present invention, "degree of vinylization" means the total mole percent of structural units derived from conjugated diene compounds that are bonded by 1,2-bonds, 3,4-bonds (except for farnesene), and 3,13-bonds (except for farnesene) out of a total of 100 mole percent of structural units derived from conjugated diene compounds contained in a specific polymer block (for example, polymer block (a12)). In this invention, the degree of vinylization determined from the bonding configuration of structural units derived from conjugated diene compounds contained in the polymer before hydrogenation is defined as the degree of vinylization of the polymer after hydrogenation. The degree of vinylization is, in the polymer before hydrogenation, 1 The peaks are calculated using 1H-NMR from the area ratio of peaks derived from structural units of conjugated diene compounds linked by 1,2-bonds, 3,4-bonds (except farnesene), and 3,13-bonds (except farnesene), and from peaks derived from structural units of conjugated diene compounds linked by 1,4-bonds (except farnesene) and 1,13-bonds (except farnesene).

[0025] [Bonding configuration of polymer block (a11) and polymer block (a12)] The bonding configuration of polymer blocks (a11) and polymer blocks (a12) contained in the block copolymer (P1) is not particularly limited and may be linear, branched, radial, or a combination of two or more of these. Among these, a configuration in which each block is linked in a linear manner is preferred, and when polymer block (a11) is represented as a11 and polymer block (a12) as a12, (a11-a12) l a11-(a12-a11) m a12-(a11-a12) n A combination form represented by a12-a11-a12-a11-a12 is preferred. Note that l, n, and m each independently represent an integer of 1 or more.

[0026] As for the bonding configuration, from the viewpoint of adhesion, processability, and handling of the resulting hot-melt adhesive composition, it is preferable that the blocks are arranged in the order of polymer block (a11), polymer block (a12), polymer block (a11) (with two polymer blocks (a11) bonded to both ends of polymer block (a12)), and the styrene-based block copolymer (A) is preferably a hydrogenated triblock copolymer represented as a11-a12-a11. Furthermore, from the viewpoint of fluidity, the styrene-based block copolymer (A) may be a mixture of a hydrogenated triblock copolymer represented as a11-a12-a11 and a hydrogenated diblock copolymer represented as a11-a12. When used as a mixture, the mass ratio [mass ratio of hydrogenated triblock copolymer to hydrogenated diblock copolymer] is preferably 99 / 1 to 1 / 99, more preferably 85 / 15 to 15 / 85, even more preferably 80 / 20 to 20 / 80, and even more preferably 75 / 25 to 25 / 75.

[0027] Furthermore, if the block copolymer (P1) has two or more polymer blocks (a11), each polymer block (a11) may be composed of the same structural units or different structural units. Similarly, if the block copolymer (P1) has two or more polymer blocks (a12), each polymer block (a12) may be composed of the same structural units or different structural units. For example, in the two polymer blocks (a11) of the triblock copolymer represented as a11-a12-a11, the styrene-based compounds used in each polymer block may be of the same type or different types.

[0028] In this specification, when identical polymer blocks are linked in a linear manner via an n-valent coupling agent, the entire linked polymer block is treated as a single polymer block. Accordingly, a polymer block that should strictly be written as a11-X-a11 (where X represents a coupling agent residue) is written as a11 as a whole. In this specification, since polymer blocks of this type containing coupling agent residues are treated as described above, for example, a block copolymer containing coupling agent residues that should strictly be written as a11-a12-X-a12-a11 is written as a11-a12-a11 and treated as an example of a triblock copolymer.

[0029] [Content of each polymer block] The content of polymer blocks (a11) in the block copolymer (P1) is preferably 8 to 45% by mass. When the content of polymer blocks (a11) is within the above range, the flexibility of the hot-melt adhesive composition is improved and the adhesion to the adherend is improved. From this viewpoint, the content of polymer blocks (a11) is more preferably 11 to 40% by mass, even more preferably 14 to 37% by mass, and still more preferably 17 to 35% by mass. If the adhesive composition of the present invention contains two or more styrene-based block copolymers (A), it is preferable that the polymer blocks (a11) of at least one block copolymer (P1) are within the above range, and more preferably that the polymer blocks (a11) of all block copolymers (P1) are within the above range.

[0030] The content of polymer blocks (a12) in the block copolymer (P1) is preferably 55 to 92% by mass, more preferably 60 to 89% by mass, even more preferably 63 to 86% by mass, and still more preferably 65 to 83% by mass. If the hot-melt adhesive composition of the present invention contains two or more styrene-based block copolymers (A), it is preferable that the polymer blocks (a12) of at least one block copolymer (P1) are within the above range, and more preferably that the polymer blocks (a12) of all block copolymers (P1) are within the above range.

[0031] The total content of polymer blocks (a11) and polymer blocks (a12) in the block copolymer (P1) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably substantially 100% by mass. If the adhesive composition of the present invention contains two or more styrene-based block copolymers (A), it is preferable that the total content of polymer blocks (a11) and polymer blocks (a12) in the entire mixture of block copolymers (P1) is within the above range.

[0032] [Hydrogenation rate of styrene-based block copolymer (A)] In the present invention, the styrene-based block copolymer (A) is a hydrogenated product of the block copolymer (P1). From the viewpoint of heat resistance and weather resistance, the hydrogenation rate of the carbon-carbon double bond in the polymer block (a12) is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 75 to 100 mol%, even more preferably 80 to 100 mol%, particularly preferably 85 to 100 mol%, and most particularly preferably 90 to 100 mol%. When the hot-melt adhesive composition of the present invention contains two or more styrene-based block copolymers (A), it is preferable that the hydrogenation rate of the entire mixture of these styrene-based block copolymers (A) is within the above range, and it is more preferable that the hydrogenation rate of all styrene-based block copolymers (A) is within the above range. When the content of conjugated diene compound units in the polymer block (a12) is above the lower limit, the compatibility between the styrene-based block copolymer (A) and the acrylic-based block copolymer (B) improves, and excellent adhesive strength is achieved. The hydrogenation rate is determined by the ratio of the block copolymer (P1) and the styrene-based block copolymer (A) after hydrogenation. 1 This can be calculated by measuring H-NMR.

[0033] [Melting viscosity of styrene-based block copolymer (A) at 190°C] The melt viscosity of the styrene-based block copolymer (A) at 190°C is 100 Pa·s or more and less than 600 Pa·s, preferably 200 Pa·s or more and less than 580 Pa·s, and is lower than the melt viscosity of the acrylic-based block copolymer (B) at 190°C, as described later. This further improves the compatibility between the styrene-based block copolymer (A) and the acrylic-based block copolymer (B).

[0034] From the viewpoint of compatibility, the melt viscosity of the styrene-based block copolymer (A) at 190°C is more preferably 210 to 570 Pa·s, even more preferably 220 to 560 Pa·s, and even more preferably 230 to 560 Pa·s. If the hot-melt adhesive composition of the present invention contains two or more styrene-based block copolymers (A), it is sufficient that at least one of the styrene-based block copolymers (A) is within the above range, but it is preferable that the melt viscosity of the entire mixture of these styrene-based block copolymers (A) (for example, the sum of the products of the weight fraction of each copolymer and its melt viscosity) is within the above range, and it is more preferable that the melt viscosity of the mixture of these styrene-based block copolymers (A) is within the above range, and that the melt viscosity of all of the styrene-based block copolymers (A) is within the above range.

[0035] [Melting viscosity of styrene-based block copolymer (A) at 230°C] The melt viscosity of the styrene-based block copolymer (A) at 230°C is preferably 25 Pa·s or more and less than 155 Pa·s. Including a styrene-based block copolymer (A) with a melt viscosity within the above range in the hot-melt adhesive composition further improves the processability of the hot-melt adhesive composition. In this specification, "melt viscosity at 230°C" refers to the melt viscosity measured at a temperature of 230°C and a shear rate of 121.6 (1 / sec) in accordance with ISO 11443:1995.

[0036] From the viewpoint of improving the processability and adhesion of the hot-melt adhesive composition, the melt viscosity of the styrene-based block copolymer (A) at 230°C is more preferably 30 to 152 Pa·s, even more preferably 35 to 149 Pa·s, even more preferably 40 to 146 Pa·s, and even more preferably 45 to 143 Pa·s. If the hot-melt adhesive composition of the present invention contains two or more styrene-based block copolymers (A), it is sufficient that at least one of the styrene-based block copolymers (A) is within the above range, but it is preferable that the melt viscosity of the entire mixture of these styrene-based block copolymers (A) (for example, the sum of the products of the weight fraction of each copolymer and its melt viscosity) is within the above range, and it is more preferable that the melt viscosity of the entire mixture of these styrene-based block copolymers (A) is within the above range, and that the melt viscosity of all of the styrene-based block copolymers (A) is within the above range.

[0037] [Number average molecular weight of styrene-based block copolymer (A)] The number-average molecular weight (Mn) of the styrene-based block copolymer (A) is preferably 10,000 to 500,000, more preferably 20,000 to 400,000, even more preferably 30,000 to 300,000, even more preferably 40,000 to 100,000, even more preferably 45,000 to 75,000, and particularly preferably 50,000 to 70,000. When the number-average molecular weight of the styrene-based block copolymer (A) is above the lower limit, the tackiness of the hot-melt adhesive composition to various adherends is improved. On the other hand, when the number-average molecular weight is below the upper limit, the tackiness of the hot-melt adhesive composition can be maintained while suppressing adhesive residue.

[0038] The molecular weight distribution (Mw / Mn), which is the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the styrene-based block copolymer (A), is preferably 1.00 to 6.00, more preferably 1.00 to 4.00, even more preferably 1.00 to 3.00, even more preferably 1.00 to 2.00, and particularly preferably 1.00 to 1.30. When Mw / Mn is within the above range, the viscosity variation of the styrene-based block copolymer (A) is small, making it easy to handle and suppressing the bleed-out of the hot-melt adhesive composition to the adherend. Furthermore, if the hot-melt adhesive composition of the present invention contains two or more styrene-based block copolymers (A), it is preferable that the Mw / Mn of at least one styrene-based block copolymer (A) is within the above range, and it is more preferable that the Mw / Mn of all styrene-based block copolymers (A) is within the above range.

[0039] In this specification, the number-average molecular weight (Mn) and weight-average molecular weight (Mw) for the styrene-based block copolymer (A) are values ​​obtained by gel permeation chromatography on a standard polystyrene basis, and the molecular weight distribution (Mw / Mn) is a value calculated from the above Mw and Mn values.

[0040] [Other polymer blocks] The block copolymer (P1) may contain polymer blocks composed of other monomers, in addition to polymer blocks (a11) and polymer block (a12), as long as they do not hinder the effects of the present invention. Examples of other monomers include unsaturated hydrocarbon compounds such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, and 1-eicosene; and functional group-containing unsaturated compounds such as acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile, methacrylonitrile, maleic acid, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2-methacryloylethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, vinyl acetate, and methyl vinyl ether. These may be used individually or in combination of two or more types. If the block copolymer (P1) contains other polymer blocks, the content of these blocks is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0041] [Melt flow rate of styrene-based block copolymer (A)] The melt flow rate (MFR) of the styrene-based block copolymer (A) is preferably 30 to 260 g / 10 min, more preferably 35 to 250 g / 10 min, even more preferably 40 to 240 g / 10 min, and still more preferably 45 to 230 g / 10 min. When the MFR of the styrene-based block copolymer (A) is within the above range, the compatibility between the styrene-based block copolymer (A) and the acrylic-based block copolymer (B) is improved, and the coating properties of the hot-melt adhesive composition are improved. In this specification, the melt flow rate of styrene-based block copolymer (A) refers to the value measured in accordance with JIS K7210-1:2014 at a temperature of 230°C and a load of 2.16 kg.

[0042] [Content of styrene-based block copolymer (A)] The content of styrene-based block copolymer (A) in the hot-melt adhesive composition of the present invention is preferably 3 to 70% by mass, more preferably 5 to 60% by mass, and even more preferably 10 to 55% by mass. If the content of styrene-based block copolymer (A) is above the lower limit, the tackiness can be sufficiently improved, and if it is below the upper limit, the compatibility with acrylic-based block copolymer (B) is improved.

[0043] [Method for producing styrene-based block copolymer (A)] The styrene-based block copolymer (A) can be suitably produced, for example, by a polymerization step of obtaining a block copolymer (P1) by anionic polymerization, and a step of hydrogenating the carbon-carbon double bonds in the polymer block (a12) within the block copolymer (P1).

[0044] (Polymerization process) The block copolymer (P1) can be produced by solution polymerization or by methods described in Japanese Patent Publication No. 2012-502135 and Japanese Patent Publication No. 2012-502136. Among these, solution polymerization is preferred, and known methods such as ionic polymerization methods such as anionic polymerization and cationic polymerization, and radical polymerization can be applied. Among these, anionic polymerization is preferred. As an anionic polymerization method, a method is preferred in which monomers such as styrene compounds and conjugated dienes are sequentially added in a solvent such as a hydrocarbon, and optionally in the presence of a Lewis base such as an ether compound or a tertiary amine, using an anionic polymerization initiator such as an organoalkali metal, to obtain the block copolymer (P1). The polymerization reaction can be stopped by adding an alcohol such as methanol or isopropanol as a polymerization stopper. The resulting polymerization reaction solution can be poured into a poor solvent such as methanol to precipitate the block copolymer (P1), or the polymerization reaction solution can be washed with water, separated, and then dried to isolate the block copolymer (P1).

[0045] The block copolymer (P1) may also be produced by polymerizing polymer blocks (a11), polymer blocks (a12), etc., in that order, and coupling the ends of the polymer blocks (a12) using a coupling agent such as a halogenated silane compound or an alkoxysilyl group-containing compound.

[0046] The block copolymer (P1) may be modified before the hydrogenation step described later. Examples of functional groups that can be introduced include amino groups, alkoxysilyl groups, hydroxyl groups, epoxy groups, carboxyl groups, carbonyl groups, mercapto groups, isocyanate groups, and acid anhydride groups. Methods for modifying the block copolymer (P1) include, for example, adding a coupling agent such as tin tetrachloride, which can react with the polymerization active ends, a polymerization end modifier such as 4,4'-bis(diethylamino)benzophenone, or other modifiers described in Japanese Patent Application Publication No. 2011-132298, before adding a polymerization inhibitor. Another method involves grafting maleic anhydride or the like onto the copolymer after isolation.

[0047] (Hydrogenation process) A styrene-based block copolymer (A) can be obtained by subjecting the block copolymer (P1) obtained by the above method or a modified block copolymer (P1) to a hydrogenation step. Known methods can be used for hydrogenation. For example, a hydrogenation catalyst such as a Ziegler catalyst, a metallocene catalyst, or palladium carbon can be added to a solution in which the block copolymer (P1) is dissolved in a solvent that does not affect the hydrogenation reaction, and the hydrogenation reaction is carried out at an appropriate hydrogen pressure and reaction temperature.

[0048] <Acrylic block copolymer (B)> The hot-melt adhesive composition of the present invention contains an acrylic block copolymer (B). In the present invention, by using an acrylic block copolymer (B), it is possible to suppress adhesive residue on the adherend when the hot-melt adhesive composition is peeled off. As described above, the acrylic block copolymer (B) used in the present invention has one or more polymer blocks (b11) containing structural units derived from acrylic acid esters and one or more polymer blocks (b12) containing structural units derived from methacrylic acid esters, has a number average molecular weight (Mn) of 50,000 to 300,000, and the content of the polymer block (b12) in the acrylic block copolymer (B) is 5 to 30% by mass. The hot-melt adhesive composition of the present invention may contain one acrylic block copolymer (B) alone, or it may contain two or more types.

[0049] [Polymer block (b11)] The polymer block (b11) contains structural units derived from acrylic acid esters. The acrylic acid ester has the general formula CH2=CH-COOR 1 (X) (In formula (X), R 1 Acrylic acid esters (hereinafter also called acrylic acid esters (b11-1)), represented by the formula CH2=CH-COOR (where represents an organic group with 4 to 6 carbon atoms), have the general formula CH2=CH-COOR 2 (Y)(In equation (Y), R 2 Acrylic acid esters are broadly classified into those represented by (where represents an organic group with 7 to 12 carbon atoms) (hereinafter also called acrylic acid esters (b11-2)) and other acrylic acid esters.

[0050] In the above formula (X), the R 1Examples of organic groups having 4 to 6 carbon atoms include alkyl groups having 4 to 6 carbon atoms such as butyl groups, amyl groups (pentyl groups), hexyl groups, and cyclohexyl groups; aromatic ring groups having 6 carbon atoms such as phenyl groups; and organic groups containing elements other than carbon, such as oxygen, with a total of 4 to 6 carbon atoms, such as ethoxyethyl groups, tetrahydrofurfuryl groups, and diethylaminoethyl groups.

[0051] Examples of the acrylic acid ester (b11-1) include acrylic acid esters without functional groups such as n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, and phenyl acrylate; and acrylic acid esters having functional groups such as ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, and diethylaminoethyl acrylate.

[0052] In the above formula (Y), the R 2 Examples of organic groups having 7 to 12 carbon atoms include alkyl groups having 7 to 12 carbon atoms such as ethylhexyl, octyl, decyl, isobornyl, and lauryl groups; aromatic ring groups having 7 to 12 carbon atoms such as benzyl groups; and organic groups containing elements other than carbon, such as oxygen, with a total of 7 to 12 carbon atoms, such as phenoxyethyl groups.

[0053] Examples of the acrylic acid ester (b11-2) include acrylic acid esters without functional groups such as 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, decyl acrylate, isobornyl acrylate, lauryl acrylate, and benzyl acrylate; and acrylic acid esters having functional groups such as phenoxyethyl acrylate.

[0054] Examples of acrylic acid esters other than acrylic acid ester (b11-1) and acrylic acid ester (b11-2) include acrylic acid esters without functional groups such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, and octadecyl acrylate; and acrylic acid esters having functional groups such as methoxyethyl acrylate, 2-hydroxyethyl acrylate, 2-aminoethyl acrylate, and glycidyl acrylate.

[0055] Among acrylic acid esters (b11-1), acrylic acid esters without functional groups are preferred from the viewpoint of the flexibility of the resulting hot-melt adhesive composition, and n-butyl acrylate is more preferred.

[0056] The proportion of structural units derived from acrylic acid ester (b11-1) contained in the polymer block (b11) [(b11-1) / (b11) × 100] is preferably 10 to 100% by mass, more preferably 30 to 100% by mass, even more preferably 50 to 100% by mass, and may be substantially 100% by mass. When it is within the above range, the moldability of the hot melt adhesive composition of the present invention is good. The content of the polymer block (b11), a structural unit derived from acrylic acid ester (b11-1), is: 1 This can be determined by 1H-NMR, specifically by the method described in the examples.

[0057] Among acrylic acid esters (b11-2), acrylic acid esters without functional groups are preferred from the viewpoint of exhibiting high cohesive force when used in a hot-melt adhesive composition, as the polarity difference between polymer block (b11) and polymer block (b12) becomes larger, resulting in clearer phase separation between polymer block (b11) and polymer block (b12). Ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, and benzyl acrylate are more preferred. Furthermore, ethylhexyl acrylate is more preferred because the resulting hot-melt adhesive composition exhibits stable durability over a wide temperature range.

[0058] The acrylic acid ester may be used alone or in combination of two or more types. Furthermore, the content of structural units derived from the acrylic acid ester in the polymer block (b11) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be substantially 100% by mass.

[0059] Among these, the acrylic acid ester is preferably at least one selected from acrylic acid ester (b11-1) and acrylic acid ester (b11-2), with acrylic acid ester (b11-1) being more preferred, from the viewpoint of improving compatibility between the acrylic block copolymer (B) and the styrene block copolymer (A) and exhibiting stable adhesion and processability.

[0060] Furthermore, from the above viewpoint, the acrylic acid ester that forms the structural unit derived from the acrylic acid ester contained in the polymer block (b11) may include at least one selected from acrylic acid ester (b11-1) and at least one selected from acrylic acid ester (b11-2). In this case, the mass ratio [(b11-1) / (b11-2)] of the structural unit derived from acrylic acid ester (b11-1) to the structural unit derived from acrylic acid ester (b11-2) is preferably 90 / 10 to 10 / 90, more preferably 80 / 20 to 20 / 80, more preferably 70 / 30 to 30 / 70, and even more preferably 60 / 40 to 40 / 60.

[0061] By having the aforementioned mass ratio [(b11-1) / (b11-2)] within the aforementioned range, the compatibility between the acrylic block copolymer (B) and the styrene block copolymer (A) is further improved, and more stable adhesion and processability can be achieved. The mass ratio of structural units derived from acrylic acid ester (b11-1) to structural units derived from acrylic acid ester (b11-2) is 1 This can be determined by 1H-NMR measurement.

[0062] Examples of combinations of acrylic acid esters (b11-1) and acrylic acid esters (b11-2) used in the polymer block (b11) include a combination of n-butyl acrylate and 2-ethylhexyl acrylate. In this case, the acrylic acid ester (b11-1) and acrylic acid ester (b11-2) used should have a difference in solubility parameters of 0.3 to 2.5 (MPa). 1 / 2 It is preferable that it be so. The aforementioned solubility parameters can be calculated using the methods described in "POLYMER HANDBOOK Fourth Edition," VII, pp. 675-714 (Wiley Interscience, 1999) and "Polymer Engineering and Science," 1974, Vol. 14, pp. 147-154. Furthermore, if the acrylic block copolymer (B) contains two or more polymer blocks (b11), the combination and proportion of acrylic acid esters constituting those polymer blocks (b11) may be the same or different.

[0063] If the polymer block (b11) is a copolymer containing both structural units derived from acrylic acid ester (b11-1) and structural units derived from acrylic acid ester (b11-2), it may consist of a random copolymer of acrylic acid ester (b11-1) and acrylic acid ester (b11-2), a block copolymer, or a gradient copolymer, but it is generally preferable that it consists of a random copolymer. If the acrylic block copolymer (B) contains two or more polymer blocks (b11), the structures of these polymer blocks (b11) may be the same or different. Furthermore, the proportion of the total structural units derived from acrylic acid ester (b11-1) and acrylic acid ester (b11-2) contained in the polymer block (b11) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be substantially 100% by mass.

[0064] The glass transition temperature of the polymer block (b11) is preferably -100 to 30°C, more preferably -80 to 10°C, even more preferably -70 to 0°C, and even more preferably -60 to -10°C. When the glass transition temperature of the polymer block (b11) is within the above range, the hot-melt adhesive composition of the present invention, which includes the acrylic block copolymer (B), can have excellent adhesion at room temperature.

[0065] [Potassium block (b12)] Polymer block (b12) contains structural units derived from methacrylic acid esters. Examples of the methacrylic acid esters include methacrylic acid esters without functional groups such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, isobornyl methacrylate, phenyl methacrylate, and benzyl methacrylate; and methacrylic acid esters having functional groups such as methoxyethyl methacrylate, ethoxyethyl methacrylate, diethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, 2-aminoethyl methacrylate, glycidyl methacrylate, and tetrahydrofurfuryl methacrylate.

[0066] Among these, methacrylate esters without functional groups are preferred from the viewpoint of improving the heat resistance and durability of the resulting hot-melt adhesive composition, with methyl methacrylate, ethyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, phenyl methacrylate, and benzyl methacrylate being more preferred. Furthermore, methyl methacrylate is even more preferred from the viewpoint of improving the mechanical properties of the hot-melt adhesive composition by making the phase separation between polymer block (b11) and polymer block (b12) clearer. The polymer block (b12) may be composed of one of these methacrylic acid esters or of two or more. Furthermore, it is preferable for the acrylic block copolymer (B) to have two or more polymer blocks (b12) from the viewpoint of improving adhesive durability. In that case, these polymer blocks (b12) may be the same or different.

[0067] The glass transition temperature of the polymer block (b12) is preferably 80 to 140°C, more preferably 90 to 130°C, and even more preferably 100 to 120°C. When the glass transition temperature is within this range, at the normal operating temperature of the hot-melt adhesive composition, the polymer block (b12) acts as a physical pseudo-crosslinking point for the acrylic block copolymer (B), thereby improving the adhesion, durability, and heat resistance of the resulting hot-melt adhesive composition.

[0068] The polymer block (b11) may contain structural units derived from methacrylic acid esters, to the extent that it does not impair the effects of the present invention, and the polymer block (b12) may contain structural units derived from acrylic acid esters, to the extent that it does not impair the effects of the present invention. Furthermore, polymer blocks (b11) and (b12) may optionally contain structural units derived from monomers other than (meth)acrylic acid esters. Examples of such other monomers include vinyl monomers having carboxyl groups such as (meth)acrylic acid, crotonic acid, maleic acid, and fumaric acid; styrene monomers such as styrene, α-methylstyrene, p-methylstyrene, and m-methylstyrene; conjugated diene monomers such as butadiene and isoprene; olefin monomers such as ethylene, propylene, isobutene, and octene; lactone monomers such as ε-caprolactone and valerolactone; and (meth)acrylamide, (meth)acrylonitrile, maleic anhydride, vinyl acetate, vinyl chloride, and vinylidene chloride. When these other monomers are used, the amount used is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, relative to the total mass of monomers used in each polymer block.

[0069] The acrylic block copolymer (B) used in the present invention may, in addition to the polymer block (b11) and polymer block (b12), optionally contain other polymer blocks. Examples of these other polymer blocks include polymer blocks or copolymer blocks containing structural units derived from monomers such as styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, acrylonitrile, methacrylonitrile, ethylene, propylene, isobutene, butadiene, isoprene, octene, vinyl acetate, maleic anhydride, vinyl chloride, and vinylidene chloride; and polymer blocks made of polyethylene terephthalate, polylactic acid, polyurethane, and polydimethylsiloxane. Furthermore, the polymer blocks also include hydrogenated polymer blocks containing structural units derived from conjugated diene compounds such as butadiene and isoprene.

[0070] The acrylic block copolymer (B) is expressed by the following general formula when polymer block (b11) is denoted as b11, polymer block (b11) with a different structure from polymer block (b11) (excluding polymer block (b12)) is denoted as b'11, and polymer block (b12) is denoted as b12: (b12-b11) n (b12-b11) n -b12 b11-(b12-b11) n (b12-b11) n - '11 (b12-b11) n -Z (b11-b12) n -Z (In the formula, n is an integer from 1 to 30, Z is a coupling site (a coupling site after the coupling agent reacts with the polymer ends to form a chemical bond, and - indicates a bond in each polymer block.) It is preferable that the formula is represented as follows: (If multiple b11 and b12 are included in the formula, they may be polymer blocks of the same structure or polymer blocks of different structures.) Here, "different structures" means structures in which at least one of the following is different: the monomer units constituting the polymer block, molecular weight, molecular weight distribution, stereoregularity, and, if there are multiple monomer units, the ratio of each monomer unit and the copolymerization morphology (random, gradient, block).

[0071] The value of n is preferably 1 to 15, more preferably 1 to 8, and even more preferably 1 to 4. Among the above structures, (b12-b11) are preferred from the viewpoint of improving the durability of the hot melt adhesive composition. n (b12-b11) n -b12, b11-(b12-b11) n (b12-b11) nA linear block copolymer represented by -b'11 is preferred, a diblock copolymer represented by b12-b11, a triblock copolymer represented by formula:b12-b11-b'11 having blocks in the order of polymer block (b12), polymer block (b11), and polymer block (b'11), and a triblock copolymer represented by formula:b12-b11-b12 having blocks in the order of polymer block (b12), polymer block (b11), and polymer block (b12) are more preferred, and a triblock copolymer represented by formula:b12-b11-b12 is even more preferred.

[0072] Furthermore, the acrylic block copolymer (B) in the present invention may be a mixture of a diblock copolymer and a triblock copolymer. In this case, a mixture of a triblock copolymer represented by b12-b11-b'11 and a diblock copolymer represented by b12-b11 is more preferred, a mixture of a triblock copolymer represented by b12-b11-b12 and a diblock copolymer represented by b12-b11 is more preferred, and a mixture of a triblock copolymer represented by b12-b11-b12 and a diblock copolymer represented by b12-b11 is even more preferred.

[0073] [Melting viscosity of acrylic block copolymer (B) at 190°C] The melt viscosity of the acrylic block copolymer (B) at 190°C is preferably greater than 100 Pa·s and less than or equal to 1,200 Pa·s, which is lower than the melt viscosity of the styrene block copolymer (A) at 190°C. This further improves the compatibility between the styrene block copolymer (A) and the acrylic block copolymer (B).

[0074] From the viewpoint of compatibility, the melt viscosity of the acrylic block copolymer (B) at 190°C is more preferably 160 to 1,150 Pa·s, even more preferably 200 to 1,050 Pa·s, and even more preferably 240 to 950 Pa·s. If the hot-melt adhesive composition of the present invention contains two or more acrylic block copolymers (B), it is sufficient that the melt viscosity of at least one acrylic block copolymer (B) is within the above range, but it is preferable that the melt viscosity of the mixture of these acrylic block copolymers (B) (for example, the sum of the products of the weight fraction of each copolymer and its melt viscosity) is within the above range, and it is more preferable that the melt viscosity of the mixture of these acrylic block copolymers (B) is within the above range, and that the melt viscosity of all acrylic block copolymers (B) is within the above range.

[0075] [Melting viscosity of acrylic block copolymer (B) at 230°C] The melt viscosity of the acrylic block copolymer (B) at 230°C is preferably 20 to 550 Pa·s. By including the acrylic block copolymer (B) with a melt viscosity within the above range in the hot-melt adhesive composition of the present invention, a hot-melt adhesive composition is obtained that has better adhesion to substrates made of highly polar resins such as PMMA boards and has better processability. From the viewpoint of improving the processability of the hot-melt adhesive composition and improving compatibility with the styrene-based block copolymer (A), the melt viscosity of the acrylic-based block copolymer (B) is more preferably 25 to 450 Pa·s, even more preferably 30 to 350 Pa·s, and even more preferably 35 to 250 Pa·s. When the hot-melt adhesive composition of the present invention contains two or more acrylic-based block copolymers (B), it is preferable that the melt viscosity of the mixture of these copolymers (for example, the sum of the products of the weight fraction and melt viscosity of each copolymer) is within the above range. In this specification, the melt viscosity of acrylic block copolymer (B) at 230°C refers to the melt viscosity measured at a temperature of 230°C and a shear rate of 121.6 (1 / sec) in accordance with ISO 11443:1995.

[0076] [Number average molecular weight of acrylic block copolymer (B)] The number-average molecular weight (Mn) of the acrylic block copolymer (B) is 50,000 to 300,000. By using an acrylic block copolymer (B) with a number-average molecular weight within the above range, the resulting hot-melt adhesive composition exhibits excellent tackiness and processability. In particular, from the viewpoint of improving the tackiness of the hot-melt adhesive composition obtained in the present invention, the Mn is preferably 51,000 to 270,000, more preferably 52,000 to 250,000, even more preferably 53,000 to 230,000, and even more preferably 53,000 to 200,000. If the hot-melt adhesive composition of the present invention contains two or more types of acrylic block copolymers (B), it is preferable that the number-average molecular weight of at least one type of acrylic block copolymer (B) is within the above range, and it is more preferable that the number-average molecular weight of all types of acrylic block copolymers (B) is within the above range.

[0077] The molecular weight distribution (Mw / Mn) of the acrylic block copolymer (B) is preferably 1.00 to 1.40. From the viewpoint of improving the durability when used as a hot-melt adhesive composition, the Mw / Mn is more preferably 1.00 to 1.35, even more preferably 1.00 to 1.30, even more preferably 1.00 to 1.25, and particularly preferably 1.00 to 1.20. If the hot-melt adhesive composition of the present invention contains two or more acrylic block copolymers (B), it is preferable that the Mw / Mn of at least one acrylic block copolymer (B) is within the above range, and it is more preferable that the Mw / Mn of all acrylic block copolymers (B) is within the above range. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) for the acrylic block copolymer (B) were determined by gel permeation chromatography on a standard polystyrene basis, and the molecular weight distribution (Mw / Mn) was calculated from the aforementioned Mw and Mn values.

[0078] [Content of each polymer block] The content of the polymer block (b11) in the acrylic block copolymer (B) is preferably 70 to 95% by mass. When the content of the polymer block (b11) in the acrylic block copolymer (B) is within the above range, flexibility is imparted to the hot-melt adhesive composition, and it exhibits better adhesion to substrates made of highly polar resins such as PMMA boards. From the viewpoint of imparting flexibility to the hot-melt adhesive composition, the content of the polymer block (b11) in the acrylic block copolymer (B) is more preferably 72 to 93% by mass, and even more preferably 74 to 91% by mass. When the hot-melt adhesive composition of the present invention contains two or more types of acrylic block copolymers (B), it is preferable that the polymer block (b11) of at least one type of acrylic block copolymer (B) is within the above range, and it is more preferable that the polymer block (b11) of all types of acrylic block copolymers (B) is within the above range.

[0079] The content of the polymer block (b12) in the acrylic block copolymer (B) is 5 to 30% by mass. When the polymer block (b12) content is within the above range, the processability of the hot-melt adhesive composition of the present invention is better, and it exhibits better adhesion to PMMA boards. From the viewpoint of processability, the polymer block (b12) content is more preferably 7 to 28% by mass, and even more preferably 9 to 26% by mass. When the hot-melt adhesive composition of the present invention contains two or more acrylic block copolymers (B), it is preferable that the polymer block (b12) of at least one acrylic block copolymer (B) is within the above range, and it is more preferable that the polymer block (b12) of all acrylic block copolymers (B) is within the above range. The content of polymer block (b11) and polymer block (b12) is: 1 This can be determined by 1H-NMR, specifically by the method described in the examples.

[0080] [Content of acrylic block copolymer (B)] The content of the acrylic block copolymer (B) in the hot-melt adhesive composition of the present invention is preferably 0.5 to 50% by mass, more preferably 1.0 to 45% by mass, and even more preferably 1.5 to 40% by mass. When the content of the acrylic block copolymer (B) is above the lower limit, it is possible to suppress adhesive residue while maintaining excellent tackiness.

[0081] [Method for producing acrylic block copolymer (B)] The method for producing the acrylic block copolymer (B) is not particularly limited as long as the desired polymer can be obtained, and methods similar to known methods can be employed. Generally, as a method for obtaining a block copolymer with a narrow molecular weight distribution, a method of living polymerization of monomers that form structural units can be employed. Examples of such living polymerization methods include a method of living polymerization using an organo-rare earth metal complex as a polymerization initiator (see Japanese Patent Publication No. 06-93060), a method of living anionic polymerization using an organo-alkali metal compound as a polymerization initiator in the presence of a mineral salt such as an alkali metal or alkaline earth metal salt (see Japanese Patent Publication No. 05-507737), a method of living anionic polymerization using an organo-alkali metal compound as a polymerization initiator in the presence of an organo-aluminum compound (see Japanese Patent Publication No. 11-335432), and atomic transfer radical polymerization (ATRP) (see Macromolecular Chemistry and Physics, 2000, Vol. 201, pp. 1108-1114).

[0082] Of the above-mentioned manufacturing methods, the method of living anionic polymerization using an organoalkali metal compound as a polymerization initiator in the presence of an organoaluminum compound is preferred because it results in a highly transparent block copolymer, has fewer residual monomers and suppresses odor, and suppresses the generation of bubbles when molding the hot-melt adhesive composition. It is also preferred because the molecular structure of the structural units derived from methacrylic acid ester becomes highly syndiotactic, which has the effect of improving the heat resistance of the resulting hot-melt adhesive composition. In the above-mentioned method of living anionic polymerization using an organoalkali metal compound as a polymerization initiator in the presence of an organoaluminum compound, polymerization is usually preferably carried out in an organic solvent such as a hydrocarbon. Furthermore, it is preferable to add ether compounds, nitrogen-containing organic compounds, etc. to the reaction system as needed.

[0083] <Tackifying resin (C)> The hot-melt adhesive composition of the present invention contains a tackifying resin (C). In the present invention, the tackiness of the hot-melt adhesive composition can be improved by using the tackifying resin (C). The tackifying resin (C) used in the present invention has a softening point of 80 to 160°C and is selected from the group consisting of rosin resins, terpene resins, phenolic resins, terpene-phenolic resins, hydrogenated petroleum resins, styrene resins, xylene resins, hydrogenated aromatic copolymers, and coumarone-indene resins, and has a softening point of 80 to 160°C. Among these, for example, rosin compounds such as natural rosin, modified rosin, glycerol ester of natural rosin, glycerol ester of modified rosin, pentaerythritol ester of natural rosin, pentaerythritol ester of modified rosin, hydrogenated rosin, pentaerythritol ester of hydrogenated rosin; copolymers of natural terpenes, three-dimensional polymers of natural terpenes, aromatically modified terpene resins, hydrogenated derivatives of aromatically modified terpene resins, terpene phenol resins, hydrogenated derivatives of terpene phenol resins, and terpene resins (monoterpenes, diterpenes, triterpenes). It is preferable to use two or more hydrocarbon resins selected from the group consisting of terpene compounds such as polypertenes, hydrogenated terpene resins, aliphatic petroleum hydrocarbon resins (C5 resins), hydrogenated derivatives of aliphatic petroleum hydrocarbon resins, aromatic petroleum hydrocarbon resins (C9 resins) such as styrene oligomers, hydrogenated derivatives of aromatic petroleum hydrocarbon resins, dicyclopentadiene resins, hydrogenated derivatives of dicyclopentadiene resins, C5 / C9 copolymer resins, hydrogenated C5 / C9 copolymer resins, cyclic aliphatic petroleum hydrocarbon resins, hydrogenated cyclic aliphatic petroleum hydrocarbon resins, etc.

[0084] In the present invention, among these, from the viewpoint of improving compatibility with styrene-based block copolymer (A), hydrocarbon resins are preferred, and from the viewpoint of compatibility with acrylic-based block copolymer (B), aromatic petroleum hydrocarbon resins (C9 resins), particularly styrene oligomers, are preferred, and it is even more preferable to use two or more of these in combination.

[0085] The content of the tackifying resin (C) in the hot-melt adhesive composition of the present invention is preferably 5 to 40% by mass, more preferably 10 to 38% by mass, and even more preferably 15 to 35% by mass. If the content of the tackifying resin (C) in the hot-melt adhesive composition is above the lower limit, sufficient adhesive strength can be obtained. On the other hand, if the content of the tackifying resin (C) in the hot-melt adhesive composition is below the upper limit, adhesive residue can be suppressed.

[0086] <Softener (D)> The hot-melt adhesive composition of the present invention further contains a softening agent (D). In the present invention, the use of the softening agent (D) improves the fluidity of the hot-melt adhesive composition, making it easier for each component to become uniformly compatible, and as a result, the tackiness of the hot-melt adhesive composition is improved. In the present invention, one or more materials selected from the group consisting of liquid acrylic polymers, acrylic oligomers, paraffinic process oils, naphthenic process oils, and aromatic process oils are used as softeners. The softener (D) is a component other than the aforementioned styrene-based block copolymer (A), acrylic-based block copolymer (B), and tackifying resin (C). Among these, the softening agent (D) is preferably an acrylic polymer such as a liquid acrylic polymer or acrylic oligomer, or a paraffinic process oil.

[0087] The content of the softener (D) in the hot-melt adhesive composition of the present invention is preferably 1 to 30% by mass, more preferably 3 to 25% by mass, and even more preferably 5 to 20% by mass. When the content of the softener (D) in the hot-melt adhesive composition is above the lower limit, each component of the hot-melt adhesive composition is uniformly mixed. On the other hand, when the content of the softener (D) in the hot-melt adhesive composition is below the upper limit, a good balance is achieved between the effect of the softener (D) and the cost.

[0088] <Optional ingredients> The hot-melt adhesive composition of the present invention may contain optional components other than those mentioned above, as necessary, within a range that does not impair the effects of the present invention. Examples of optional components used in the present invention include antioxidants, inorganic fillers, other thermoplastic polymers (excluding styrene-based block copolymer (A) and acrylic-based block copolymer (B)), lubricants, light stabilizers, processing aids, colorants such as pigments and dyes, flame retardants, antistatic agents, matting agents, silicone oils, antiblocking agents, ultraviolet absorbers, mold release agents, foaming agents, antibacterial agents, antifungal agents, and fragrances. These optional components may be used individually or in combination of two or more.

[0089] Examples of the aforementioned antioxidants include hindered phenol-based, phosphorus-based, lactone-based, and hydroxyl-based antioxidants. Among these, hindered phenol-based antioxidants are preferred. The aforementioned antioxidants may be used individually or in combination of two or more.

[0090] The inorganic filler may be included in the hot-melt adhesive composition of the present invention for the purpose of improving physical properties such as heat resistance and weather resistance, adjusting hardness, and improving economic efficiency as a bulking agent. Examples of inorganic fillers include calcium carbonate, talc, magnesium hydroxide, aluminum hydroxide, mica, clay, natural silicic acid, synthetic silicic acid, titanium dioxide, carbon black, barium sulfate, glass balloons, and glass fibers. The inorganic filler may be used alone or in combination of two or more types.

[0091] If the hot-melt adhesive composition of the present invention contains the above-mentioned optional component, its content is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass, and even more preferably 1 to 3% by mass.

[0092] <Melting viscosity (Type B viscosity) of hot-melt adhesive compositions> The melt viscosity of the hot-melt adhesive composition at 160°C is preferably 5,000 to 50,000 mPa·s, more preferably 7,000 to 45,000 mPa·s, and even more preferably 8,000 to 40,000 mPa·s. If the melt viscosity of the hot-melt adhesive composition at 160°C is above the lower limit, it exhibits excellent tackiness. On the other hand, if it is below the upper limit, the residue of the hot-melt adhesive composition can be suppressed. In this specification, the melt viscosity of the hot-melt adhesive composition is a value measured using a B-type viscometer, and can be specifically measured by the method described in the examples.

[0093] <Method for producing a hot-melt adhesive composition> The method for producing the hot-melt adhesive composition of the present invention is not particularly limited. For example, it can be produced by mixing each component using a known mixing or kneading device such as a kneader-ruder, extruder, mixing roll, or Banbury mixer, usually at a temperature in the range of 100 to 250°C. Alternatively, it may be produced by dissolving each component in an organic solvent, mixing them, and then distilling off the organic solvent. The obtained hot-melt adhesive composition can be used after heating and melting, or it can be dissolved in a solvent and used as a solution-type adhesive. Examples of solvents include toluene, ethyl acetate, ethylbenzene, methylene chloride, chloroform, tetrahydrofuran, methyl ethyl ketone, dimethyl sulfoxide, and toluene-ethanol mixed solvents. Among these, toluene, ethylbenzene, ethyl acetate, and methyl ethyl ketone are preferred.

[0094] When using the hot-melt adhesive composition of the present invention by heating and melting, a low melt viscosity is preferable from the viewpoint of processability and handling. On the other hand, a high melt viscosity is preferable from the viewpoint of achieving both adhesive properties and high retention force (creep resistance) of the hot-melt adhesive composition. The hot-melt adhesive composition of the present invention is suitably used in adhesive products in the form of an adhesive layer made of the hot-melt adhesive composition, or a laminate (for example, a laminated film or laminated sheet) containing the adhesive layer.

[0095] As for methods for forming the adhesive layer, when using the hot-melt adhesive composition of the present invention by heating and melting it, examples of methods for forming it into a sheet-like or film-like shape include hot-melt coating, T-die method, inflation method, calendering method, lamination method, etc. When the melt viscosity of the hot-melt adhesive composition of the present invention is high, a hot-melt coating method in which the heated molten material is applied to the support from a T-die without contact is preferred from the viewpoint of controlling the thickness of the adhesive layer, homogeneity, and the heat resistance required for the support, in order to heat and melt it at a higher temperature. Furthermore, when the hot-melt adhesive composition of the present invention is used dissolved in a solvent, for example, a heat-resistant material such as polyethylene terephthalate or a flat plate or roll such as a steel belt can be used as a support, and a solution of the hot-melt adhesive composition of the present invention dissolved in a solvent can be applied to these using a bar coater, roll coater, die coater, comma coater, etc., and the solvent can be removed by drying (solution casting method) to form an adhesive layer.

[0096] The method for removing the solvent by drying is not particularly limited, and conventionally known methods can be used, but it is preferable to perform the drying in multiple stages. When drying in multiple stages, it is more preferable to perform the first stage of drying at a relatively low temperature to suppress foaming due to the rapid evaporation of the solvent, and to perform the second and subsequent stages of drying at a high temperature in order to sufficiently remove the solvent.

[0097] The concentration of the hot-melt adhesive composition in the solution is appropriately determined considering the solubility of the composition in the solvent, the viscosity of the resulting solution, etc., but is preferably 5% by mass or more, and more preferably 70% by mass or less.

[0098] <Applications of hot-melt adhesive compositions> The hot-melt adhesive composition of the present invention can be used for a variety of applications. Furthermore, the adhesive layer made from the hot-melt adhesive composition can be used as an adhesive sheet on its own, and laminates containing the hot-melt adhesive composition can also be applied to a variety of applications. Examples include adhesives, adhesive tapes, films, or sheets for surface protection, masking, bundling, packaging, office use, labeling, decoration / display, bonding, dicing tape, sealing, corrosion / waterproofing, medical / hygiene use, glass shatter prevention, electrical insulation, electronic equipment holding and fixing, semiconductor manufacturing, optical display films, adhesive optical films, electromagnetic wave shielding, or as sealing materials for electrical / electronic components. Specific examples are given below.

[0099] Surface protection adhesives, tapes, or films can be used on various materials such as metals, plastics, rubber, and wood. Specifically, they can be used for surface protection of painted surfaces, during plastic deformation and deep drawing of metals, and for automotive and optical components. Examples of automotive components include painted body panels, wheels, mirrors, windows, lights, and light covers. Examples of optical components include various image display devices such as liquid crystal displays, organic EL displays, plasma displays, and field emission displays; polarizing films, polarizing plates, phase difference plates, light guide plates, diffusers, and optical disc components such as DVDs; and precision fine-coated faceplates for electronic and optical applications.

[0100] Applications for masking adhesives, tapes, and films include masking during the manufacturing of printed circuit boards and flexible printed circuit boards; masking during plating and soldering processes in electronic equipment; and masking during the manufacturing of automobiles and other vehicles, painting and printing of vehicles and buildings, and masking during civil engineering work.

[0101] Applications for bundling include wire harnesses, electric wires, cables, fibers, pipes, coils, windings, steel materials, ducts, plastic bags, food products, vegetables, flowers, and more. Packaging applications include packaging heavy goods, export packaging, sealing cardboard boxes, and can seals.

[0102] For office use, examples include general office work, sealing envelopes, repairing books, drafting, and taking notes. Labels can be used for price, product information, shipping tags, point-of-purchase (POP) displays, stickers, stripes, nameplates, decoration, and advertising.

[0103] Examples of labels include paper, processed paper (paper treated with aluminum vapor deposition, aluminum lamination, varnish, resin processing, etc.), synthetic paper, etc.; labels using cellophane, plastic materials, cloth, wood, and metal films as substrates. Examples of substrates include fine paper, art paper, cast paper, thermal paper, foil paper; polyethylene terephthalate film, polyvinyl chloride film, OPP film, polylactic acid film, synthetic paper, synthetic thermal paper, overlaminate film, etc. In particular, the hot-melt adhesive composition of the present invention has excellent weather resistance and shows little discoloration over time, making it suitable for use in thermal labels using thermal paper or synthetic thermal paper as substrates.

[0104] Examples of surfaces to which the label may be applied include plastic products such as plastic bottles and foamed plastic cases; paper and cardboard products such as cardboard boxes; glass products such as glass bottles; metal products; and other inorganic material products such as ceramics.

[0105] A label made of a laminate containing an adhesive layer made of the hot-melt adhesive composition of the present invention exhibits minimal adhesion enhancement when stored at temperatures slightly above room temperature (e.g., 40°C) and can be peeled off without leaving any adhesive residue after use. Moreover, it can be adhered to a substrate even at low temperatures (-40 to +10°C) and will not peel off even when stored at low temperatures (-40 to +10°C).

[0106] Examples of decorative and display applications include hazard warning stickers, line tapes, wiring markings, phosphorescent tapes, and reflective sheets. Examples of applications for adhesive optical films include polarizing films, polarizing plates, phase difference films, viewing angle expanding films, brightness enhancing films, anti-reflective films, anti-glare films, color filters, light guide plates, diffusion films, prism sheets, electromagnetic wave shielding films, near-infrared absorbing films, functional composite optical films, ITO laminating films, impact-resistant films, brightness enhancing films, and visibility enhancing films, in which an adhesive layer is formed on at least part or all of one or both sides of an optical film. Such adhesive optical films include films in which an adhesive layer made of the hot-melt adhesive composition of the present invention is formed on a protective film used to protect the surface of the optical film. Adhesive optical films are suitably used in various image display devices such as liquid crystal displays, PDPs, organic EL displays, electronic paper, game consoles, and mobile terminals.

[0107] Electrical insulation applications include protective coating or insulation for coils, and interlayer insulation for motors, transformers, etc. Applications for holding and securing electronic equipment include carrier tapes, packaging, cathode ray tube (CRT) mounting, splicing, and rib reinforcement.

[0108] For semiconductor manufacturing applications, examples include protecting silicon wafers. Applications for bonding include various adhesive fields, automobiles, trains, electrical equipment, printing plate fixing, construction, nameplate fixing, general household use, and bonding to rough, uneven, and curved surfaces.

[0109] Sealing applications include thermal insulation, vibration damping, waterproofing, moisture protection, soundproofing, and dustproofing. Corrosion prevention and waterproofing applications include corrosion protection for gas and water pipes, corrosion protection for large-diameter pipes, and corrosion protection for civil engineering structures.

[0110] For medical and health applications, it includes transdermal absorption drug applications such as analgesic and anti-inflammatory agents (plasters, patches), drugs for treating ischemic heart diseases, female hormone replacement agents, bronchodilators, cancer pain relievers, smoking cessation aids, cold patches, antipruritic patches, keratolytic agents, etc.; various tape applications such as first aid bandages (with bactericides), surgical dressings · surgical tapes, band-aids, hemostatic bandages, tapes for human excrement handling appliances (artificial anus fixation tapes), suturing tapes, antibacterial tapes, fixed taping, self-adhesive bandages, oral mucosal patches, sports tapes, depilation tapes, etc.; beauty applications such as face packs, eye area moisturizing sheets, keratin peeling packs, etc.; cooling sheets, heat packs, dustproof, waterproof, pest trapping, etc. For use as a sealing material for electronic and electrical components, it includes liquid crystal monitors, solar cells, etc.

Examples

[0111] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples. The physical properties of the examples and comparative examples were measured or evaluated by the following methods.

[0112] [Measurement methods and evaluation methods] <Melt viscosity> The melt viscosities of the styrene block copolymer (A), styrene block copolymer (A’), acrylic block copolymer (B) and acrylic block copolymer (B’) were measured using a capillary graph in accordance with ISO11443:1995. The measurement was carried out 3 times, and the average value was taken as the melt viscosity. · Equipment: Toyo Seiki Seisakusho Co., Ltd., product name “CAPIROGRAPH 1C” · Temperature: 190 °C or 230 °C · Shear rate: 121.6 (1 / sec) · Inner diameter of capillary die: 1.0 mm in diameter · Length of capillary die: 10.0 mm · Piston diameter: 9.510 mm in diameter · Furnace body diameter: 9.55 mm

[0113] <B-type viscosity measurement> The melt viscosity of the hot-melt adhesive composition was measured using a B-type viscometer. • Equipment: BLOOKFIELD (DV2T (RV type)) • Rotation speed: 6-50 rpm ·Measurement temperature: 160℃ • Spindle: SC4-29

[0114] <Number average molecular weight (Mn), molecular weight distribution (Mw / Mn)> The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were determined using polystyrene-based molecular weight calculations via gel permeation chromatography (hereinafter referred to as "GPC"). From these values, the molecular weight distribution (Mw / Mn) was calculated. Details are as follows. • Equipment: GPC system "HLC-8020" manufactured by Tosoh Corporation • Separation column: "TSKgel GMHXL", "G4000HXL", and "G5000HXL" manufactured by Tosoh Corporation are connected in series. • Eluent: Tetrahydrofuran • Eluent flow rate: 1.0 ml / min Column temperature: 40°C • Detection method: Differential refractive index (RI)

[0115] <Mass ratio of each polymer block in styrene-based block copolymer (A), styrene-based block copolymer (A'), acrylic-based block copolymer (B), and acrylic-based block copolymer (B')> The compositional ratio of each polymer block and the composition ratio of each polymer block in styrene-based block copolymer (A) (block copolymer (P1)), styrene-based block copolymer (A') (block copolymer (P2)), acrylic-based block copolymer (B), and acrylic-based block copolymer (B') were measured under the following conditions. 1 H-NMR ( 1 (H-nuclear magnetic resonance) measurements were performed, and the peaks were assigned to characteristic groups of each monomer unit and determined from the integrated values ​​of the peaks. [Measurement conditions] ·Equipment: Nuclear magnetic resonance apparatus “JNM-LA400” manufactured by JEOL Ltd. • Deuterated solvent: Deuterated chloroform

[0116] For styrene-based block copolymers, the block copolymers before hydrogenation (block copolymer (P1), block copolymer (P2), etc.) were dissolved in deuterated chloroform, and the content of each polymer block was calculated using the apparatus described above, from the ratio of the integrated value of the peaks derived from styrene to the integrated value of the peaks derived from the conjugated diene.

[0117] For acrylic block copolymer (B) and acrylic block copolymer (B'), the content of each polymer block was calculated as follows: 1 In the 1H-NMR spectrum, the signals around 3.6 ppm and 4.0 ppm are attributed to hydrogen atoms bonded to carbon atoms adjacent to oxygen atoms in the ester group of the structural unit derived from methyl methacrylate (-O-CH3) and hydrogen atoms bonded to carbon atoms adjacent to oxygen atoms in the ester group of the structural unit derived from n-butyl acrylate (-O-CH2-CH2-CH2-CH3), respectively. The molar ratio of each monomer unit was determined from the ratio of the cumulative values ​​of these signals, and this was converted to a mass ratio based on the molecular weight of the monomer unit. The content of each polymer block was then calculated.

[0118] <Amount of 1,2-bonds and 3,4-bonds (degree of vinylization)> The amount of 1,2-bonds and 3,4-bonds (degree of vinylization) of styrene-based block copolymer (A) and styrene-based block copolymer (A') was determined under the following measurement conditions: 1 H-NMR ( 1 (H-nuclear magnetic resonance) measurements were performed, and the peaks were attributed to characteristic groups of each monomer unit and determined from the integral values ​​of the peaks. ·Equipment: Nuclear magnetic resonance apparatus “JNM-LA400” manufactured by JEOL Ltd. • Deuterated solvent: Deuterated chloroform

[0119] [Raw materials used in the examples] <Production of styrene-based block copolymer (A) and styrene-based block copolymer (A')> (A-1) and (A-2), which correspond to styrene-based block copolymer (A), and (A'-1), which corresponds to styrene-based block copolymer (A'), were manufactured as follows. In cyclohexane solvent, and optionally in the presence of a Lewis base such as tetrahydrofuran, monomers corresponding to each block (styrene, isoprene, butadiene) were sequentially added using sec-butyllithium (cyclohexane solution), an organoalkali metal, as a polymerization initiator to obtain a polymerization reaction solution containing a block copolymer (P1) or (P2) consisting of multiple polymer blocks by anionic polymerization. After stopping the polymerization reaction, palladium carbon, a hydrogenation catalyst, was added to the reaction solution containing the block copolymer (P1) or (P2) to carry out a hydrogenation reaction. After stopping the hydrogenation reaction, the mixture was allowed to cool and the pressure was released, the palladium carbon was removed by filtration, the filtrate was concentrated, and further vacuum-dried to obtain styrene-based block copolymers (A-1), (A-2), and (A'-1). Detailed manufacturing conditions can be determined by referring to the synthesis examples described in, for example, Japanese Patent No. 5936791. Table 1 summarizes the properties of the styrene-based block copolymers (A-1), (A-2), and (A'-1) obtained by the above manufacturing method.

[0120] • Styrene-based block copolymer (A-1) Styrene-based block copolymer (A-1) is a hydrogenated triblock copolymer consisting of a styrene polymer block, a butadiene polymer block, and a styrene polymer block.

[0121] • Styrene-based block copolymer (A-2) Styrene-based block copolymer (A-2) is a hydrogenated triblock copolymer consisting of a styrene polymer block, an isoprene polymer block, and a styrene polymer block.

[0122] • Styrene-based block copolymer (A'-1) Styrene-based block copolymer (A'-1) is a mixture of a hydrogenated triblock copolymer consisting of a styrene polymer block / isoprene polymer block / styrene polymer block and a hydrogenated diblock copolymer consisting of a styrene polymer block / isoprene polymer block. In the case of styrene-based block copolymer (A'-1), the content of styrene polymer blocks in the entire mixture is taken as the content of polymer blocks (a11), and the Mn, Mw / Mn, melt viscosity, and degree of vinylization of the entire mixture are taken as the respective values ​​for styrene-based block copolymer (A'-1).

[0123] [Table 1]

[0124] <Acrylic block copolymer (B), acrylic block copolymer (B')> Acrylic block copolymers (B) (B-1) to (B-3) and acrylic block copolymer (B') (B'-1) were produced by living anionic polymerization as follows. In toluene solvent, in the presence of the ether compound 1,2-dimethoxyethane and the organoaluminum compound isobutylbis(2,6-di-tert-butyl-4-methylphenoxy)aluminum, the organoalkali metal compound sec-butyllithium was used as a polymerization initiator, and a predetermined amount of methyl methacrylate was first charged according to the charging ratio of each polymer block listed in Table 2. The reaction solution was initially colored yellow, but became colorless after stirring at room temperature for 60 minutes. Subsequently, the internal temperature of the polymerization solution was cooled to -30°C, and a predetermined amount of n-butyl acrylate was continuously charged, ensuring that the temperature did not exceed -20°C, and the mixture was stirred at -30°C for 5 minutes after charging. Furthermore, a predetermined amount of methyl methacrylate was charged, and the mixture was stirred at room temperature overnight to obtain a polymerization reaction solution containing an acrylic block copolymer (B) or an acrylic block copolymer (B') consisting of multiple polymer blocks. After stopping the polymerization reaction, the aluminum and lithium components were removed, and the polymerization reaction solution was introduced into a defoliating twin-screw extruder to remove volatile components, thereby obtaining acrylic block copolymer (B) and acrylic block copolymer (B'). Table 2 summarizes the properties of acrylic block copolymers (B-1) to (B-3) and (B'-1).

[0125] • Acrylic block copolymer (B-1) As shown in Table 2 below, the acrylic block copolymer (B-1) is a triblock copolymer of methyl methacrylate polymer block (PMMA), n-butyl acrylate polymer block (PnBA), and methyl methacrylate polymer block (PMMA).

[0126] • Acrylic block copolymer (B-2) Acrylic block copolymer (B-2) is a triblock copolymer of methyl methacrylate polymer block (PMMA), n-butyl acrylate polymer block (PnBA), and methyl methacrylate polymer block (PMMA).

[0127] • Acrylic block copolymer (B-3) Acrylic block copolymer (B-3) is a triblock copolymer of methyl methacrylate polymer block (PMMA), n-butyl acrylate polymer block (PnBA), and methyl methacrylate polymer block (PMMA).

[0128] • Acrylic block copolymer (B'-1) Acrylic block copolymer (B'-1) is a triblock copolymer of methyl methacrylate polymer block (PMMA), n-butyl acrylate polymer block (PnBA), and methyl methacrylate polymer block (PMMA).

[0129] [Table 2]

[0130] <Adhesive-granting resin> Table 3 lists the tackifying resin (C) used in the examples and comparative examples.

[0131] [Table 3]

[0132] <Softener> Table 4 lists the softening agents (D) used in the examples and comparative examples.

[0133] [Table 4]

[0134] <Examples 1-10, Comparative Examples 1-6> [Method for producing a hot-melt adhesive composition] A hot-melt adhesive composition was produced by melt-kneading a styrene-based block copolymer, an acrylic-based block copolymer, a tackifying resin, and a softening agent in the proportions shown in Table 5, using the following kneader, at the following melting temperature and kneading conditions. Kneading machine: BENCH KNEADER PBV-0.3K (Irie Shokai Co., Ltd.) Melting temperature: 180℃ Rotation speed: 40 rpm

[0135] Next, the obtained hot-melt adhesive composition was hot-melt coated onto the unreleased surface of a polyethylene terephthalate (PET) film (Ester Film A3100, manufactured by Toyobo Co., Ltd., 50 μm thick) using the following roll coater at the following melting temperature to obtain an adhesive roll film consisting of a PET film layer and an adhesive layer. Coating machine: Hot Melt Trabocoater KMD-HML10 (Kubo Design Co., Ltd.) Melting temperature: 160℃ The obtained adhesive roll film was cut into strips measuring 25 mm in width and 150 mm in length to form adhesive tapes, and their adhesive properties were evaluated using the following method.

[0136] <Method for testing adhesive strength> Adhesive tape was bonded to substrates (acrylic plate [PMMA], stainless steel plate [SUS304], polyethylene plate [HDPE plate], rigid polyvinyl chloride plate [rigid PVC plate]) at 23°C using a laminating machine (ChemInstruments; 2kg rubber roller, 10mm / sec) and then adjusted for 24 hours at 23°C and 50%RH, and for 168 hours at 60°C and 50%RH. Subsequently, in accordance with JIS Z0237:2009, the force applied when peeling off the bonded film was measured under the following measurement environment and tensile conditions (tensile speed, peel angle) using the following tensile testing machine, and the average value of 5 measurements was obtained. Tensile testing machine: Tabletop tensile testing machine (AGS-X: manufactured by Shimadzu Corporation) Tensile speed: 300 mm / min Peeling angle: 180° Measurement environment: 23℃ × 50RH

[0137] The results are shown in Table 5. Note that the rate of change in adhesive strength in Table 5 means "adhesive strength after storage at 60°C for 168 hours" / "adhesive strength after storage at 23°C, 50%RH for 24 hours".

[0138] <Glue residue> After removing the adhesive tape, the residue left on the substrate was visually inspected, and the degree of contamination on the substrate was evaluated according to the following criteria. E (Excellent): No traces of adhesive tape are visible on the surface to which it was applied. G (Good): There are faint traces of adhesive tape on the surface to which it is applied, but this does not pose a practical problem. P (Poor): The adhesive tape residue is clearly visible on the surface to which it is applied.

[0139] [Table 5]

[0140] As is clear from the results of the examples and comparative examples, the hot-melt adhesive composition of the present invention exhibits excellent adhesion to various substrates and can suppress adhesive residue on the substrate when the hot-melt adhesive composition is peeled off.

Claims

1. A hot melt pressure-sensitive adhesive composition comprising a styrene-based block copolymer (A), an acrylic block copolymer (B), a tackifier resin (C), and a softener (D), and satisfying the following conditions (1) to (6): <Condition (1)> The melt viscosity (PA) of the styrene block copolymer (A) at 190°C and the melt viscosity (PB) of the acrylic block copolymer (B) at 190°C satisfy the relationship PA < PB. <Condition (2)> The mass ratio of the content of the styrene-based block copolymer (A) to the acrylic-based block copolymer (B) [(A) / (B)] is 10 / 90 to 95 / 5. <Condition (3)> The styrene-based block copolymer (A) is a hydrogenated product of a block copolymer (P1) having one or more polymer blocks (a11) containing structural units derived from a styrene-based compound and one or more polymer blocks (a12) containing structural units derived from a conjugated diene compound, and has a melt viscosity (PA) measured in accordance with ISO 11443:1995 at a temperature of 190°C and a shear rate of 121.6 (1 / sec) of 100 Pa s or more but less than 600 Pa s. <Condition (4)> The acrylic block copolymer (B) has one or more polymer blocks (b11) containing structural units derived from an acrylic acid ester and one or more polymer blocks (b12) containing structural units derived from a methacrylic acid ester, and has a number average molecular weight (Mn) of 50,000 to 300,000, and the content of the polymer block (b12) in the acrylic block copolymer (B) is 5 to 30 mass%. <Condition (5)> The tackifier resin (C) is a tackifier resin having a softening point of 80 to 160°C, and is two or more types selected from the group consisting of rosin-based resins, terpene-based resins, phenol-based resins, terpene-phenol-based resins, hydrogenated petroleum-based resins, styrene-based resins, xylene-based resins, hydrogenated aromatic copolymers, and coumarone-indene-based resins. <Condition (6)> The softener (D) is at least one selected from the group consisting of liquid acrylic polymers, acrylic oligomers, paraffinic process oils, naphthenic process oils, and aromatic process oils.

2. 2. The hot melt pressure-sensitive adhesive composition according to claim 1, wherein the acrylic block copolymer (B) has a melt viscosity (PB) at 190°C of more than 100 Pa·s and not more than 1,200 Pa·s.

3. 3. The hot melt pressure-sensitive adhesive composition according to claim 1, wherein the content of the styrene block copolymer (A) in the hot melt pressure-sensitive adhesive composition is 3 to 70 mass %.

4. 3. The hot melt pressure-sensitive adhesive composition according to claim 1, wherein the content of the acrylic block copolymer (B) in the hot melt pressure-sensitive adhesive composition is 0.5 to 50 mass %.