Hot-melt pressure-sensitive adhesive composition

Abstract

To provide a hot-melt pressure-sensitive adhesive composition having improved holding power even in a high temperature environment of 40°C or higher without impairing excellent advantages of the hot-melt pressure-sensitive adhesive composition such as environmental performance, convenience and labor saving.SOLUTION: A hot-melt pressure-sensitive adhesive composition contains: (1) an acrylic block copolymer (X) represented by the formula -[A1]-[B]-[A2] (where A1 and A2 represent polymer blocks having a glass transition temperature (Tg) higher than 30°C, and B represents a polymer block having a Tg lower than 20°C; and (2) one or more tackifiers (Y) selected from the group consisting of acid-modified rosin, very light-colored rosin, hydrogenated rosin, aliphatic-modified styrene resin, alkylphenol-modified xylene resin, acrylic oligomer having a Tg of higher than 30°C, and acrylic styrene oligomer having a Tg of higher than 30°C; wherein the mass ratio of the acrylic block copolymer (X) to the tackifier (Y) is 35-90:10-65.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hot melt pressure-sensitive adhesive composition, and more particularly to a hot melt pressure-sensitive adhesive composition having excellent heat resistance retention.

[0002] In recent years, due to safety and environmental protection concerns, hot melt adhesives that do not use organic solvents have become widely used in fields such as bookbinding, food packaging, sanitary materials, textiles, building materials, and automobiles. For example, compared to solvent-based adhesives, solvent-free hot melt adhesives offer advantages such as reduced volatile organic compounds (VOCs) and convenience and labor savings due to the elimination of the need for solvent heating and drying processes and post-crosslinking, leading to growing interest in environmentally friendly hot melt adhesives.

[0003] Various applications have been proposed for hot melt adhesives that offer advantages such as environmental friendliness, productivity, convenience, and labor savings. For example, there is an alkali-dispersible hot melt adhesive containing a (meth)acrylic block copolymer, a rosin-based tackifier resin, and a sebacic acid ester for removing adhesive residue from PET bottles even in low-temperature environments (Patent Document 1), a vibration-damping hot melt adhesive composition containing a (meth)acrylic block copolymer and a tackifier for use in vibrating parts within equipment (Patent Document 2), an adhesive composition containing an acrylic copolymer and a tackifier for forming an adhesive layer of a display label to be adhered to an olefin resin (Patent Document 3), an adhesive composition containing a triblock copolymer and a tackifier for use in the adhesive layer of a label for shrink packaging (Patent Document 4), and an adhesive composition for a low-density polyethylene film tape that exhibits reduced deterioration over time in adhesive strength to SUS plates and polyethylene resins. Patent Document 5 proposes a hot-melt adhesive for attaching road marking materials, which contains a block copolymer and a combination of a tackifier with a softening point of 130°C or higher and a tackifier with a softening point of less than 130°C, for use in an adhesive layer, and which is composed of an acrylic polymer, a light-colored rosin-based tackifier, and a styrene-based tackifier. Patent Document 6 proposes a hot-melt adhesive for attaching road marking materials, etc., to a road surface such as asphalt, which contains a block copolymer and a tackifier with a softening point of 130°C or higher and a tackifier with a softening point of less than 130°C. Patent Document 7 proposes a hot-melt adhesive for attaching road marking materials, which contains a block copolymer and a tackifier (polymerized rosin ester) formed by hot-melt molding on a low-density polyethylene film or polyethylene terephthalate cloth substrate layer, and which is used in an adhesive tape that has adhesion to polyolefin-based materials with low polarity and silicone-based materials with releasability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-28124 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-209527 [Patent Document 3] Japanese Patent Application Publication No. 2019-65242 [Patent Document 4] Japanese Patent Publication No. 2022-12938 [Patent Document 5] Japanese Patent Application Publication No. 2023-13841 [Patent Document 6] Japanese Patent Application Publication No. 2023-59831 [Patent Document 7] Japanese Patent Application Publication No. 2023-64959 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, in building materials and automobile interior parts that are exposed to high temperature environments of 40°C or higher, such as in summer, the adhesive layer formed from the hot melt adhesive composition becomes hot, reducing the holding power and making the adherend prone to peeling or slippage. The composition has the problem that its holding power decreases in a high temperature environment.

[0006] An object of the present invention is to provide a hot melt pressure-sensitive adhesive composition that has improved holding power even in a high temperature environment of 40°C or higher, without compromising the excellent advantages of hot melt pressure-sensitive adhesive compositions, such as environmental friendliness, convenience, and labor saving. [Means for solving the problem]

[0007] In view of the above circumstances, the present inventors have conducted extensive research and found that by combining an acrylic block copolymer (X) and a tackifier (Y) in a specific mass ratio, a hot-melt pressure-sensitive adhesive composition having excellent holding power even in a high-temperature environment (hereinafter also referred to as heat-resistant holding power) can be obtained, thereby completing the present invention.

[0008] That is, the present invention provides: (1) the following formula: -[A1]-[B]-[A2]- wherein each of A1 and A2 represents a polymer block having a glass transition temperature (Tg) greater than 30°C; A1 and A2 represent the same polymer block or different polymer blocks, and an acrylic block copolymer (X) represented by the formula (X), wherein B represents a polymer block having a Tg lower than 20°C; and (2) one or more tackifiers (Y) selected from the group consisting of acid-modified rosin, very light-colored rosin, hydrogenated rosin, aliphatic-modified styrene resin, alkylphenol-modified xylene resin, acrylic oligomer having a Tg of higher than 30°C, and acrylic styrene oligomer having a Tg of higher than 30°C; Including, the mass ratio of the acrylic block copolymer (X) to the tackifier (Y) is 35-90:10-65; The present invention relates to a hot melt pressure sensitive adhesive composition.

[0009] The tackifier (Y) preferably contains one or more tackifiers (Y1) having an acid value of 160 mgKOH / g or more and 350 mgKOH / g or less and a softening point of 110°C or more.

[0010] The tackifier (Y1) preferably has an acid value of 300 mgKOH / g or more and 350 mgKOH / g or less.

[0011] The hot melt pressure-sensitive adhesive composition preferably further contains a tackifier (Y2) (excluding the tackifier (Y)).

[0012] The hot melt pressure-sensitive adhesive composition preferably further contains an antioxidant.

[0013] The hot melt pressure-sensitive adhesive composition preferably does not contain a plasticizer.

[0014] The hot melt pressure-sensitive adhesive composition preferably contains more than 0 mass % and 10 mass % or less of one or more plasticizers selected from the group consisting of phthalate esters, hydrogenated phthalate esters, alkyl esters of aliphatic dibasic acids, liquid acrylic oligomers having a Tg of less than 0°C, and xylene resins, based on the total mass of the composition. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a hot melt pressure-sensitive adhesive composition that has improved holding power even in a high temperature environment of 40°C or higher, without compromising excellent advantages such as environmental friendliness, convenience, and labor saving. DETAILED DESCRIPTION OF THE INVENTION

[0016] The hot melt pressure-sensitive adhesive composition of the present invention comprises: (1) the following formula: -[A1]-[B]-[A2]- (wherein A1 and A2 each represent a polymer block having a glass transition temperature (Tg) higher than 30°C, A1 and A2 represent the same polymer block or represent different polymer blocks, and B represents a polymer block having a Tg lower than 20°C), and (2) containing one or more tackifiers (Y) selected from the group consisting of acid-modified rosin, very light-colored rosin, hydrogenated rosin, aliphatic-modified styrene resin, alkylphenol-modified xylene resin, acrylic oligomer having a Tg higher than 30°C, and acrylic styrene oligomer having a Tg higher than 30°C; The mass ratio of the acrylic block copolymer (X) to the tackifier (Y) is 35-90:65-10. Each component will be described below.

[0017] <Acrylic block copolymer (X)> The acrylic block copolymer (X) contained in the hot melt pressure-sensitive adhesive composition of the present invention is represented by the following formula: -[A1]-[B]-[A2]- wherein A1 and A2 each represent a polymer block having a glass transition temperature (Tg) greater than 30°C, A1 and A2 may represent the same polymer block or different polymer blocks, and B represents a polymer block having a Tg less than 20°C. Any one of the polymer block represented by A1 (hereinafter also referred to as polymer block [A1]), the polymer block represented by A2 (hereinafter also referred to as polymer block [A2]), and the polymer block represented by B (hereinafter also referred to as polymer block [B]) may be an acrylic polymer block, but it is preferable that all of them are acrylic polymer blocks.

[0018] The acrylic block copolymer (X) is clearly divided into polymer blocks [A1] and [A2] having a Tg higher than 30°C and a polymer block [B] having a Tg lower than 20°C. Therefore, the hot melt pressure-sensitive adhesive composition of the present invention has adhesiveness to adherends without heating due to the polymer block [B], and has high cohesive strength due to the polymer blocks [A1] and [A2].

[0019] The polymer block [A1] and the polymer block [A2] may be the same polymer block or different polymer blocks, but are preferably the same polymer block.

[0020] The Tg of the polymer blocks [A1] and [A2] is not particularly limited as long as it is higher than 30°C, but is, for example, a temperature higher than 30°C, 40°C or higher, 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, 110°C or higher, or 120°C or higher, preferably 80°C or higher, and more preferably 100°C or higher. The upper limit of the Tg of the polymer blocks [A1] and [A2] is not particularly limited. For example, The temperature is 250°C or less, 220°C or less, 200°C or less, 190°C or less, 180°C or less, 170°C or less, 160°C or less, 150°C or less, 140°C or less, 130°C or less, or 120°C or less, preferably 160°C or less, and more preferably 120°C or less. If the Tg of the polymer blocks [A1] and [A2] is 30°C or lower, the melting point of the hot-melt pressure-sensitive adhesive composition will be low, and the heat resistance retention may be reduced. If it exceeds 250°C, the melting point will be too high, making handling difficult and making it difficult to use as a hot-melt pressure-sensitive adhesive composition.

[0021] The polymer blocks [A1] and [A2] may be polymer blocks of (meth)acrylic acid and (meth)acrylate alone, or may be copolymer blocks of a combination of two or more types. In this specification, (meth)acrylic acid means acrylic acid or methacrylic acid, (meth)acrylate means acrylate or methacrylate, and (meth)acrylic monomer means (meth)acrylic acid or (meth)acrylate.

[0022] Usable (meth)acrylic acid and (meth)acrylate include, for example, acrylic acid, methacrylic acid, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, acrylonitrile, acrylamide, isobornyl (meth)acrylate, and glycidyl methacrylate. Of the structural units of the polymer block, structural units derived from methyl methacrylate preferably account for 80% or more, and more preferably 100%.

[0023] The upper limit of the Tg of the polymer block [B] is not particularly limited as long as it is lower than 20°C. Examples include less than 20°C, 10°C or lower, 0°C or lower, -10°C or lower, -20°C or lower, -30°C or lower, and -40°C or lower, with -20°C or lower being preferred and -40°C or lower being more preferred. The lower limit of the Tg of the polymer block [B] is not particularly limited, but examples thereof include -150°C or higher, -100°C or higher, -90°C or higher, -80°C or higher, -70°C or higher, and -60°C or higher, with -100°C or higher being preferred and -60°C or higher being more preferred.

[0024] Examples of the polymer block [B] include a polymer block derived from a (meth)acrylate, such as a polymer block derived from a (meth)acrylate having an alkyl group with 2 to 12 carbon atoms, a polymer block derived from the random copolymerization of two or more types of (meth)acrylates having alkyl groups with 2 to 12 carbon atoms, and a polymer block derived from the random copolymerization of a (meth)acrylate and one or more types of (meth)acrylates having an alkyl group with 2 to 12 carbon atoms. Examples of (meth)acrylates having an alkyl group having 2 or more and 12 or less carbon atoms include n-butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, dodecyl acrylate, ethyl acrylate, nonyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, n-propyl acrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, dodecyl methacrylate, ethyl methacrylate, nonyl methacrylate, octyl methacrylate, and n-propyl methacrylate, of which n-butyl acrylate, nonyl acrylate, octyl acrylate, and 2-ethylhexyl acrylate, and combinations thereof, are preferred, and n-butyl acrylate, 2-ethylhexyl acrylate, and combinations thereof are more preferred.

[0025] In the acrylic block copolymer, the total content of the polymer blocks [A1] and [A2] is, for example, 10% by mass or more and 55% by mass or less, or 10% by mass or more and 40% by mass or less, and the content of the polymer block [B] is, for example, 45% by mass or more and 90% by mass or less. That is, the content is 60% by mass or more and 90% by mass or less. However, the range of the content can be appropriately adjusted as long as the effect of the present invention is not impaired. For example, the total content range of the polymer blocks [A1] and [A2] is 10 mass%, 11 mass%, 12 mass%, 13 mass%, 14 mass%, 15 mass%, 16 mass%, 17 mass%, 18 mass%, 19 mass%, 20 mass%, 21 mass%, 22 mass%, 23 mass%, 24 mass%, 25 mass%, 26 mass%, 27 mass%, 28 mass%, 29 mass%, 30 mass%, 31 mass%, 32 mass%, 33 mass%, 34 mass%, 35 mass%, 36 mass%, 37 mass%, 38 mass%, 39 mass%, 40 mass%, 41 mass%, 42 mass%, 43 mass%, 44 mass%, 45 mass%, 46 mass%, 47 mass%, 48 mass%, 49 mass%, 50 mass%, 51 mass%, 52 mass%, 53 mass%, 54 mass%, 55 mass%, 56 mass%, 57 mass%, 58 mass%, 59 mass%, 60 mass%, 61 mass%, 62 mass%, 63 mass%, 64 mass%, 65 mass%, 66 mass%, 67 mass%, 68 mass%, 69 mass%, 70 mass%, 71 mass%, 72 mass%, 73 mass%, 74 mass%, 75 mass%, 76 mass%, 77 mass%, 78 mass%, 79 mass%, 80 mass%, 81 mass%, 82 mass%, 83 mass%, 84 mass%, 85 mass%, 86 mass%, 87 mass%, 88 mass%, 89 mass%, 90 mass%, 91 mass%, 92 mass%, 93 mass%, 94 mass%, 95 mass%, 96 mass%, 97 mass%, 98 mass%, 99 mass%, 100 mass%, 101 mass%, 102 The upper and lower limits of the content of polymer block [B] can be arbitrarily selected from the following: 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, and 55% by mass. The upper and lower limits of the range of the content of polymer block [B] are calculated by subtracting the lower and upper limits of the contents of polymer blocks [A1] and [A2] from 100% by mass. If the content of polymer blocks [A1] and [A2] is less than 10% by mass (if the content of polymer block [B] is higher than 90% by mass), the softening point of the hot melt pressure-sensitive adhesive composition may decrease, resulting in a decrease in heat resistance retention. Also, if the content of polymer blocks [A1] and [A2] is more than 55% by mass (if the content of polymer block [B] is less than 45% by mass), the softening point of the hot melt pressure-sensitive adhesive composition may increase, requiring high temperatures during use, which may result in a decrease in workability.

[0026] The acrylic block copolymer (X) used in the present invention may be a commercially available product, and examples thereof include KURARITY LA2114 (MMA-BA / triblock copolymer, mass ratio of MMA: 10% by mass), KURARITY LA2140 (MMA-BA / triblock copolymer, mass ratio of MMA: 20% by mass), KURARITY LA2250 (MMA-BA / triblock copolymer, mass ratio of MMA: 30% by mass), KURARITY LA2330 (MMA-BA / triblock copolymer, mass ratio of MMA: 20% by mass), KURARITY LA3320 (MMA-BA / triblock copolymer, mass ratio of MMA: 15% by mass), KURARITY LA3710 (MMA-BA / triblock copolymer, mass ratio of MMA: 12% by mass), KURARITY LA2270 (MMA-BA / triblock copolymer, mass ratio of MMA: 40% by mass), and KURARITY LA3810 (MMA-BA / triblock copolymer, mass ratio of MMA: 40% by mass). % by mass), KURARITY LA4285 (MMA-BA / triblock copolymer, MMA mass ratio: 50% by mass), KURARITY LA1892 (MMA-BA / triblock copolymer, MMA mass ratio: 52% by mass), KURARITY LK9243 (MMA-(BA-2EHA) / triblock copolymer, MMA mass ratio: 17% by mass), KURARITY KL-LK9333 (MMA(BA-2EHA) / triblock copolymer, MMA mass ratio: 20% by mass), KURARITY KL-LH8156 (MMA-(MA-BA) / triblock copolymer, MMA mass ratio: 30% by mass), KURARITY KL-LK9211 (MMA-2EHA / triblock copolymer, MMA mass ratio: 12% by mass), and the like, all manufactured by Kuraray Co., Ltd., and these can be used alone or in combination. Furthermore, from the viewpoint of adhesiveness, Kurariti LA3320, Kurariti LA2114, Kurariti LA2140, Kurariti LA3710, Kurariti LK9243, Kurariti KL-LH8156, Kurariti KL-LK9211, and combinations thereof are preferred. In the above, MA represents a polymethyl methacrylate block, MMA represents a polymethyl methacrylate block, BA represents a polyn-butyl acrylate block, and 2EHA represents a poly2-ethylhexyl acrylate block.

[0027] The content of the acrylic block copolymer (X) relative to 100% by mass of the hot melt pressure-sensitive adhesive composition of the present invention is, for example, 35% by mass to 90% by mass, 45% by mass to 90% by mass, 55% by mass to 90% by mass, or 65% by mass to 90% by mass. However, the range of the content can be appropriately adjusted as long as it is within a range that does not impair the effects of the present invention. The range is, for example, 35% by mass to 90% by mass, relative to 100% by mass of the hot melt pressure-sensitive adhesive composition. %, 36% by mass, 37% by mass, 38% by mass, 39% by mass, 40% by mass, 41% by mass, 42% by mass, 43% by mass, 44% by mass, 45% by mass, 46% by mass, 47% by mass, 48% by mass, 49% by mass, 50% by mass %, 51% by mass, 52% by mass, 53% by mass, 54% by mass, 55% by mass, 56% by mass, 57% by mass, 58% by mass, 59% by mass, 60% by mass, 61% by mass, 62% by mass, 63% by mass, 64% by mass, 65% by mass The upper and lower limits can be adjusted by any combination from among 66 mass%, 67 mass%, 68 mass%, 69 mass%, 70 mass%, 71 mass%, 72 mass%, 73 mass%, 74 mass%, 75 mass%, 76 mass%, 77 mass%, 78 mass%, 79 mass%, 80 mass%, 81 mass%, 82 mass%, 83 mass%, 84 mass%, 85 mass%, 86 mass%, 87 mass%, 88 mass%, 89 mass%, and 90 mass%. The hot melt pressure-sensitive adhesive composition of the present invention can have excellent coatability and holding power by containing the acrylic block copolymer (X) in the above range.

[0028] <Tackifier (Y)> The tackifier (Y) contained in the hot melt pressure-sensitive adhesive composition of the present invention is one or more tackifiers selected from the group consisting of acid-modified rosin, very light-colored rosin, hydrogenated rosin, aliphatic-modified styrene resin, alkylphenol-modified xylene resin, acrylic oligomer having a Tg of higher than 30°C, and acrylic styrene oligomer having a Tg of higher than 30°C.

[0029] Examples of the acid-modified rosin include unmodified rosins such as tall oil rosin, gum rosin, wood rosin, and purified rosin modified with carboxylic acids such as maleic acid, maleic anhydride, and acrylic acid, or anhydrides of these carboxylic acids.

[0030] Examples of the very light-colored rosin include very light-colored rosin, very light-colored rosin ester, and acid-modified very light-colored rosin.

[0031] Examples of the hydrogenated rosin include rosins obtained by hydrogenating the unmodified rosin or acid-modified rosin.

[0032] The aliphatic modified styrene resin may be, for example, a copolymer of a styrene monomer and an aliphatic monomer.

[0033] Examples of alkylphenol-modified xylene resins include xylene resins modified with alkylphenol resins.

[0034] Examples of the acrylic oligomer having a Tg of higher than 30°C include low-molecular-weight acrylic oligomers having a weight-average molecular weight of 1,000 or more and 30,000 or less, such as polymers of (meth)acrylic monomers such as ethyl acrylate, methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, and (meth)acrylic acid.

[0035] Examples of the acrylic styrene oligomer having a Tg of higher than 30°C include low-molecular-weight acrylic oligomers having a weight-average molecular weight of 1,000 or more and 30,000 or less, and examples thereof include polymers of (meth)acrylic monomers such as ethyl acrylate, methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, or acrylic acid with styrene-based monomers such as styrene or α-methylstyrene.

[0036] As the tackifier (Y), known tackifiers used in hot melt type pressure sensitive adhesive compositions can be used. For example, commercially available products include Marquid #31, #32, and #33 ( Examples of the solvent include, but are not limited to, Pine Crystal KE-604, Pine Crystal KR-612, Pine Crystal KR-614, Pine Crystal KR-616, Pine Crystal KR-120, and Pine Crystal KR-85 (manufactured by Arakawa Chemical Industries, Ltd.), Forarin 5020F (manufactured by Eastman Chemical Company), FTR (registered trademark) 6100, FTR 6110, and FTR 6125 (manufactured by Mitsui Chemicals, Inc.), Nikanol (registered trademark) HP-100, FTR-120, FTR-210, FTR-70, and FHP-150 (manufactured by Fudow Co., Ltd.), and Alphon (registered trademark) UH-2170, UC-3000, UC-3080, and UF-5080 (manufactured by Toagosei Co., Ltd.). Preferred examples of the tackifier (Y) include, but are not limited to, Marquid #33, Pine Crystal KE-604, Pine Crystal KR-612, Pine Crystal KR-120, Pine Crystal KR-85, Forarin 5020F, FTR (registered trademark) 6100, Nikanol (registered trademark) HP-100, Arfon (registered trademark) UC-3000, and Arfon (registered trademark) UF-5080.

[0037] The tackifier (Y) used in the present invention can be appropriately selected depending on the required performance. For example, in order to improve the adhesive strength to polar adherends such as vinyl chloride resins and the cohesive strength of the adhesive layer, thereby increasing heat resistance retention, the tackifier (Y) used in the present invention preferably contains a tackifier (Y1) having an acid value of 160 mg KOH / g or more and 350 mg KOH / g or less and a softening point of 110°C or more. The tackifier (Y1) more preferably has an acid value of 300 mg KOH / g or more and 350 mg KOH / g or less. The tackifier (Y1) can be used alone or in combination of two or more types.

[0038] The softening point of the tackifier (Y1) may be 110° C. or higher, and preferably 120° C. or higher. The upper limit of the softening point of the tackifier (Y1) is not particularly limited as long as it is within a practical range, and is, for example, 250° C. or lower, 200° C. or lower, 180° C. or lower, or 160° C. or lower.

[0039] In this specification, the softening point is measured in accordance with JIS K6863 (1994), and the acid value is measured by the neutralization titration method in accordance with JIS-K0070 (1992).

[0040] When a tackifier (Y1) is used, it is not particularly limited, but is preferably 1% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass or more relative to the total mass of the tackifier (Y).

[0041] The content of the tackifier (Y) in the hot melt pressure-sensitive adhesive composition of the present invention is, for example, 10% by mass to 65% by mass, 10% by mass to 55% by mass, 10% by mass to 45% by mass, 10% by mass to 35% by mass, or 10% by mass to 30% by mass, based on the total mass of the hot melt pressure-sensitive adhesive composition. However, the range of the content can be adjusted appropriately as long as it does not impair the effects of the present invention. The range is 10% by mass, 11% by mass, 12% by mass, 13% by mass, 14% by mass, 15% by mass, 16% by mass, 17% by mass, 18% by mass, 19% by mass, 20% by mass, 21% by mass based on 100% by mass of the hot melt adhesive composition. Amount%, 22% by mass, 23% by mass, 24% by mass, 25% by mass, 26% by mass, 27% by mass, 28% by mass, 29% by mass, 30% by mass, 31% by mass, 32% by mass, 33% by mass, 34% by mass, 35% by mass, 36% by mass, 37% by mass, 38 mass%, 39 mass%, 40 mass%, 41 mass%, 42 mass%, 43 mass%, 44 mass%, 45 mass%, 46 mass%, 47 mass%, 48 mass%, 49 mass%, 50 mass%, 51 mass%, 52 mass%, 53 mass%, 54 The lower limit and upper limit can be adjusted in any combination from among % by mass, 55% by mass, 56% by mass, 57% by mass, 58% by mass, 59% by mass, 60% by mass, 61% by mass, 62% by mass, 63% by mass, 64% by mass, and 65% by mass. By containing the tackifier (Y) in the above range, the hot melt pressure-sensitive adhesive composition of the present invention can have good wettability and adhesiveness to the adherend.

[0042] The content of the tackifier (Y) is determined by the ratio of the acrylic block copolymer (X) to the tackifier (Y). The mass ratio of the acrylic block copolymer (X):tackifier (Y) is 35-90:65-10, for example, 65-90:35-10, for example, 75-90:25-10. By setting the ratio of the acrylic block copolymer (X) and the tackifier (Y) within the above ranges, the hot melt pressure-sensitive adhesive composition of the present invention can further improve the heat resistance holding power without impairing the excellent advantages of hot melt pressure-sensitive adhesive compositions, such as environmental friendliness, convenience, and labor saving.

[0043] The total content of the acrylic block copolymer (X) and tackifier (Y) contained in the hot melt pressure-sensitive adhesive composition of the present invention is not particularly limited as long as the effects of the present invention are not impaired, and is, for example, 30% by mass or more, 50% by mass or more, 65% by mass or more, or 69% by mass or more. The upper limit is not particularly limited, and is, for example, 100% by mass or less, 99% by mass or less, 95% by mass or less, or 90% by mass or less. By setting the total content of the acrylic block copolymer (X) and tackifier (Y) within the above range, the hot melt pressure-sensitive adhesive composition of the present invention can further improve heat resistance retention without impairing the excellent advantages of hot melt pressure-sensitive adhesive compositions, such as environmental friendliness, convenience, and labor savings.

[0044] The hot-melt pressure-sensitive adhesive composition of the present invention may also contain a tackifier (Y2) other than the tackifier (Y), provided that the effects of the present invention are not impaired. Known tackifiers (Y2) can be used. Examples include rosin esters, disproportionated rosin esters, polymerized rosins, aliphatic hydrocarbon resins, aliphatic-aromatic copolymer resins, aromatic petroleum resins, hydrogenated petroleum resins, terpene resins, hydrogenated terpene resins, modified terpene resins, hydrogenated modified terpene resins, terpene phenolic resins, hydrogenated terpene phenolic resins, styrene-based resins, xylene-based resins (excluding alkylphenol-modified xylene resins), coumarone resins, and indene resins. These may be used alone or in combination of two or more. Hydrogenated petroleum resins and terpene phenolic resins are preferred. When other tackifiers (Y2) are contained, the content thereof is 30% by mass or less, 20% by mass or less, 10% by mass or less, 6% by mass or less, or 3% by mass or less, based on the total mass of the hot-melt pressure-sensitive adhesive composition.

[0045] <Plasticizer> The hot-melt pressure-sensitive adhesive composition of the present invention may contain a plasticizer within a range that does not impair the effects of the present invention. By containing a plasticizer, the viscosity of the hot-melt pressure-sensitive adhesive composition can be reduced, making it easier to handle. The content of the plasticizer is not particularly limited, but is, for example, 70% by mass or less, 50% by mass or less, 35% by mass or less, or 30% by mass or less, relative to 100% by mass of the hot-melt pressure-sensitive adhesive composition. If the content of the plasticizer exceeds 70% by mass, bleeding from the pressure-sensitive adhesive layer may occur, and the holding power may decrease over time, and the adherend may be contaminated or deteriorated.

[0046] Examples of plasticizers include paraffin oil, phthalate esters, hydrogenated phthalate esters, alkyl esters of aliphatic dibasic acids, liquid acrylic oligomers with a Tg of less than 0°C, xylene resins, ester compounds, and glycerol esters of fatty acids.

[0047] Examples of paraffin oils include naphthenic process oils, white mineral oils, mineral oils, paraffin wax, and liquid paraffin. Commercially available products include, but are not limited to, Diana Process Oil PW-90, PW-100, and PW-32 (manufactured by Idemitsu Kosan Co., Ltd.). Examples of phthalate esters include dibutyl phthalate, diisononyl phthalate (DINP), diheptyl phthalate, di(2-ethylhexyl) phthalate, and diisodecyl phthalate. butyl benzyl phthalate (DIDP), and butyl benzyl phthalate. Examples of hydrogenated phthalate esters include, but are not limited to, 1,2-cyclohexanedicarboxylic acid diisononyl ester. Alkyl esters of aliphatic dibasic acids include, but are not limited to, diisononyl adipate, bis(2-ethylhexyl) adipate, di-n-octyl adipate, and bis(2-ethylhexyl) azelate. Examples of liquid acrylic oligomers having a Tg of less than 0°C include copolymers of (meth)acrylic monomers such as ethyl acrylate, methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, or acrylic acid, or copolymers of these with styrene-based monomers such as styrene or α-methylstyrene. Commercially available products include, but are not limited to, Alphon (registered trademark) UP-1000, UP-1021, UP-1061, and UP-1110 (manufactured by Toagosei Co., Ltd.). Examples of xylene resins include, but are not limited to, commercially available Nikanol (registered trademark) Y-50, Y-100, Y-300, Y-1000, LLL, LL, L, GH, and G (manufactured by Fudow Co., Ltd.). Examples of ester compounds include, but are not limited to, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB). Glycerol esters of fatty acids include, but are not limited to, vegetable oils such as olive oil, sunflower oil, linseed oil, soybean oil, and their derivatives.

[0048] As the plasticizer, one type may be used alone, or two or more types may be used in combination. Preferred examples include, but are not limited to, Diana Process Oil PW-90, diisononyl phthalate (DINP), di(2-ethylhexyl) phthalate, 1,2-cyclohexanedicarboxylic acid diisononyl ester, diisononyl adipate, Alphon (registered trademark) UP-1000, UP-1021, UP-1061, UP-1110, TXIB, and olive oil.

[0049] The hot-melt pressure-sensitive adhesive composition of the present invention may contain additives used in pressure-sensitive adhesives, etc., as long as the effects of the present invention are not impaired. Examples of such additives include, but are not limited to, antioxidants, UV absorbers, light stabilizers, fillers, pigments, dyes, antistatic agents, flame retardants, antifoaming agents, antifoaming agents, antibacterial agents, deodorizers, emulsifiers, and surfactants. When the hot-melt pressure-sensitive adhesive composition of the present invention contains the various additives, the content of the various additives in 100% by mass of the hot-melt pressure-sensitive adhesive composition is preferably 5% by mass or less.

[0050] <Antioxidants> As the antioxidant, known antioxidants used in hot melt pressure-sensitive adhesive compositions can be used, such as hindered phenols, polyphenols, bisphenols, phosphates, thioethers, hydrosultites, benzimidazoles, and aromatic secondary amines.

[0051] Examples of commercially available antioxidants include, but are not limited to, Irganox (registered trademark) 1010, 1035, 1076, 1098, 1330, 245, 259, 3114, 565, and Irgafos (registered trademark) 168 (manufactured by BASF), and Adekastab (registered trademark) AO-20, AO-30, AO-40, AO-50, AO-60, AO-80, AO-330, PEP-8, PEP-36, HP-10, 2112, and AO-412S (manufactured by ADEKA Corporation). The antioxidants may be used alone or in combination of two or more kinds. Addition of an antioxidant can effectively inhibit discoloration and deterioration of the hot melt pressure-sensitive adhesive composition due to oxidation.

[0052] <UV absorber> The ultraviolet absorber is not particularly limited, and a wide variety of known ultraviolet absorbers can be used, including benzotriazole-based ultraviolet absorbers such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-t-butylphenyl)benzotriazole, and 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole; benzophenone-based ultraviolet absorbers such as 2-hydroxy-4-methoxybenzophenone; salicylic acid ester-based ultraviolet absorbers; cyanoacrylate-based ultraviolet absorbers; and hindered amine-based light stabilizers. These ultraviolet absorbers can be used alone or in combination of two or more.

[0053] In the present invention, heat-resistant holding power means the ability to maintain high holding power even in a high-temperature environment, and high temperatures refer to, for example, 100°C or higher, 90°C or higher, 80°C or higher, 70°C or higher, 60°C or higher, 50°C or higher, and 40°C or higher. Furthermore, "maintaining holding power" specifically refers to a process in which the hot-melt pressure-sensitive adhesive composition of the present invention is applied to a general-purpose substrate for pressure-sensitive adhesive tape or the like to prepare a pressure-sensitive adhesive tape, and the pressure-sensitive adhesive tape is then attached to a general-purpose stainless steel plate so that the adhesive area is, for example, 25 mm × 25 mm to prepare a test specimen with the pressure-sensitive adhesive tape attached thereto; one end of the stainless steel plate is fastened with a fastener at the above-mentioned temperature so that the test specimen hangs down vertically; and after leaving it for, for example, 10 minutes or more, a load is applied to the lower end of the pressure-sensitive adhesive tape attached to the test specimen with, for example, a weight of 500 g, 1 kg, or 2 kg; and the time until the pressure-sensitive adhesive tape slips off the stainless steel plate due to this load is, for example, 1 hour or more, 2 hours or more, 5 hours or more, 6 hours or more, 24 hours or more, 48 hours or more, 96 hours or more, 168 hours or more, or 200 hours or more. The time it takes for the adhesive tape to slip off the stainless steel plate can vary within the above-mentioned range of time depending on the temperature range referred to as the high temperature, the time it is left at a high temperature within the above-mentioned temperature range, and the weight of the weight applied. A hot melt pressure sensitive adhesive composition that maintains its heat resistance at 80° C. under a 1 kg weight for 1 hour or more, preferably 24 hours or more, is preferred.

[0054] Since the acrylic block copolymer (X) is thermoplastic, soluble in a solvent, and dispersible in water, the hot-melt pressure-sensitive adhesive composition of the present invention can be used not only as a hot-melt pressure-sensitive adhesive composition but also as a solvent-based pressure-sensitive adhesive composition or an aqueous emulsion-based pressure-sensitive adhesive composition. For example, the hot-melt pressure-sensitive adhesive composition of the present invention can be coated by being melted under heat, dissolved in an organic solvent, or uniformly dispersed in an aqueous solvent.

[0055] When used as a solvent-based pressure-sensitive adhesive composition, the acrylic block copolymer (X), the tackifier (Y), and optionally a plasticizer and other additives may be dissolved in an organic solvent, or each component may be dissolved in a solvent and then mixed together. The solvent may be any known solvent that can be used in a solvent-based pressure-sensitive adhesive composition, and examples thereof include aromatic hydrocarbons such as benzene, toluene, xylene, and mesitylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane; halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform; alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol; ketone-based solvents such as acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, and acetophenone; cellosolves such as methyl cellosolve and ethyl cellosolve; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and butyl formate; Examples of suitable solvents include glycol ether solvents such as ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-iso-butyl ether, triethylene glycol mono-n-butyl ether, and tetraethylene glycol mono-n-butyl ether. Preferred examples include the aromatic hydrocarbons, ester solvents, alcohol solvents, and ketone solvents, and more preferred examples include organic solvents such as ethyl acetate, butyl acetate, methyl ethyl ketone, toluene, and xylene. The solvent-based pressure-sensitive adhesive composition is not particularly limited, but the solid content of the entire solvent-based pressure-sensitive adhesive composition is, for example, 30% by mass to 90% by mass, or 40% by mass to 80% by mass. In this specification, the solid content refers to the components remaining after excluding water or organic solvents from the composition.

[0056] When used as an aqueous emulsion-type pressure-sensitive adhesive composition, the acrylic block copolymer (X), tackifier (Y), and optionally a plasticizer and other additives can be dispersed in water to which an emulsifier has been added as needed. The emulsifier can be any known emulsifier that can be used in an aqueous emulsion-type pressure-sensitive adhesive composition, and examples thereof include anionic surface-active compounds such as alkyl sulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, alkylbenzene sulfonates, alkyl ether disulfonates, fatty acid salts, naphthalenesulfonic acid-formalin condensates, and sulfosuccinates; and nonionic surface-active compounds such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, sorbitan higher fatty acid esters, polyoxyethylene sorbitan higher fatty acid esters, polyoxyethylene higher fatty acid esters, and glycerin higher fatty acid esters. When an emulsifier is used, its content is from 0.01% by mass to 5% by mass relative to the acrylic block copolymer (X). Within this range, the acrylic block copolymer (X), the tackifier (Y), and water are less likely to separate from each other during storage, making it possible to provide an aqueous emulsion-type PSA composition with good adhesiveness. The solid content of the aqueous emulsion-type pressure-sensitive adhesive composition is, for example, 30% by mass or more and 90% by mass or less, and 40% by mass or more and 80% by mass or less, based on the total amount of the pressure-sensitive adhesive composition.

[0057] <Method for producing hot melt pressure sensitive adhesive composition> The hot-melt pressure-sensitive adhesive composition can be produced by a known method, and the production method is not particularly limited, for example, a method in which the acrylic block copolymer (X), the tackifier (Y), and, if necessary, the various additives are charged into a stirring kneader equipped with a heating device and kneaded while heating.

[0058] The heating temperature during kneading is not particularly limited as long as it is equal to or higher than the softening points of the acrylic block copolymer (X) and tackifier (Y) used, and is preferably 100° C. or higher and 200° C. or lower, more preferably 120° C. or higher and 180° C. or lower. The kneading time is not particularly limited as long as the mixture becomes homogeneous, and is, for example, 5 minutes or higher and 300 minutes or lower, 30 minutes or higher and 180 minutes or lower, or 60 minutes or higher and 120 minutes or lower.

[0059] The solvent-based or aqueous emulsion-based pressure-sensitive adhesive composition can be produced by a known method, and the production method is not particularly limited. A solvent-based pressure-sensitive adhesive composition can be produced, for example, by heating the kneaded product obtained above, if necessary, to a temperature not higher than the boiling point of the organic solvent, and gradually adding the organic solvent to dissolve the kneaded product, or by adding the kneaded product to an organic solvent that has been heated, if necessary, to a temperature not higher than the boiling point, and stirring the mixture. In the case of an aqueous emulsion type pressure-sensitive adhesive composition, for example, a solution of an emulsifier dissolved in water is poured into a tank equipped with a pressurizable agitator, and heated to a temperature above the melting point of the kneaded product obtained above. The kneaded material can also be added and emulsified by stirring to produce an aqueous emulsion.

[0060] <Adhesive body and its manufacturing method> An adhesive body can be formed by a method including a coating step of applying the hot melt pressure-sensitive adhesive composition of the present invention to one surface of a first substrate to form a pressure-sensitive adhesive layer, and a bonding step of bonding the first substrate and a second substrate via the pressure-sensitive adhesive layer.

[0061] The substrates used as the first substrate and the second substrate are not particularly limited, and examples thereof include wood-based materials such as paper and wood; porous substrates made from natural materials such as cellulose-based materials and cotton-based materials, and fabric materials such as nonwoven fabrics; plastic materials such as polyvinyl chloride resin, polyolefin (polypropylene, polyethylene, ethylene-propylene copolymer, etc.), polyurethane, polyester, epoxy, nylon, polycarbonate, acrylic, ABS, polycarbonate (PC) ABS, etc.; rubber materials such as natural rubber and synthetic rubber; metal materials such as aluminum, iron, stainless steel, etc.; and inorganic materials such as ceramics. The shape of each substrate is not particularly limited and may be, for example, a sheet, foil, plate, molded product, etc. Furthermore, each substrate may be made of only one type of material, or may be made of two or more types of material.

[0062] In the coating step, known methods can be used to coat the substrate, such as spiral spray coating, slot coater coating, curtain spray coating, roll coater coating, omega coating, dot coating, and bead coating. The application temperature to a substrate when applying the hot-melt pressure-sensitive adhesive composition can be appropriately selected depending on the viscosity of the hot-melt pressure-sensitive adhesive composition, and the composition can be applied in a molten state by heating at a temperature of 140°C or higher and 200°C or lower. The application step may also be a step of forming a pressure-sensitive adhesive layer by applying the composition to a release film or release paper, and then transferring the pressure-sensitive adhesive layer to a first substrate. When applying the composition as a solvent-based or aqueous emulsion-based pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition can be applied by, for example, applying the composition at room temperature using a slot coater, a roll coater, or the like, and then heating and drying the organic solvent or water in a drying oven. The precoated substrate (first substrate containing a pressure-sensitive adhesive layer) obtained after the coating step may be directly subjected to the next bonding step, or may be stored before being subjected to the next bonding step. During storage, a release film or release paper may be adhered to the exposed pressure-sensitive adhesive layer. When the surface of the first substrate not having the pressure-sensitive adhesive layer is a surface treated with a release film, release paper, or release coating such as silicone, the precoated substrate may be rolled into a cylindrical shape and stored.

[0063] In addition, in the coating step, the hot melt pressure-sensitive adhesive composition of the present invention is coated on a release film or release paper to form a pressure-sensitive adhesive layer, and then a release film or release paper is attached to the side of the pressure-sensitive adhesive layer that does not have the release paper. This allows the preparation and use of a so-called substrateless double-sided tape in which the pressure-sensitive adhesive layer made of the hot melt pressure-sensitive adhesive composition of the present invention is sandwiched between release films or release papers. In this case, the coating step may be a step of peeling off one of the release films or release papers and attaching the tape to a first substrate. In this case, the precoated substrate has the other release film or release paper attached to the pressure-sensitive adhesive layer, and in the bonding step described below, the other release film or release paper is peeled off and the tape is then bonded to a second substrate.

[0064] The adhesive step is a step of pressure-bonding the precoated substrate and the second substrate. Since the adhesive layer formed from the hot-melt adhesive composition of the present invention has adhesiveness even when not heated, the adhesive step does not require a heating step, and the adhesive can be bonded by pressure-bonding under pressure. If necessary, the pressure-sensitive adhesive layer may be heated and activated to melt it again. The means for heat activation include, for example, methods using heat, ultrasonic waves, high frequency waves, microwaves, etc., but there is no particular limitation. When reactivation is carried out, it may be carried out immediately before the precoated substrate and the second substrate are pressed together, simultaneously with the application of pressure, or after the pressing. When heat activation is performed, the temperature should be such that the adhesive layer melts, for example, the surface temperature of the adhesive layer is 100°C or higher and 200°C or lower, preferably 100°C or higher and 180°C or lower.

[0065] The pressure-bonding method is not particularly limited, and may be a known method such as a known press pressure-bonding method, vacuum forming method, etc. Furthermore, since the hot-melt pressure-sensitive adhesive composition of the present invention can be applied and bonded without heating, pressure-bonding can be achieved by a simple method such as using fingers, a trowel, or a roller without using any equipment.

[0066] The hot melt pressure-sensitive adhesive composition of the present invention can be used in a variety of applications, including pressure-sensitive adhesive tape applications such as pressure-sensitive adhesive sheets, pressure-sensitive adhesive labels, protective films, masking tapes, and process tapes; applications for fixing automobile interior materials and electronic components; applications for processing clothing and other fibers; applications for joining nonwoven fabrics and other fabric materials; and applications for joining plastic parts together.

[0067] The pressure-sensitive adhesive tape such as the pressure-sensitive adhesive sheet can be produced by a known method, and as described above, a hot-melt pressure-sensitive adhesive composition is applied to one side of a substrate, with heating as necessary, to form a pressure-sensitive adhesive layer, which is then wound up in the form of a tape log and cut to a desired width, thereby forming the tape into a tape shape. The above-mentioned solvent-based or aqueous emulsion-based pressure-sensitive adhesive composition may be used instead of the hot-melt pressure-sensitive adhesive composition of the present invention. When a solvent-based or aqueous emulsion-based pressure-sensitive adhesive composition is used, a method may be employed in which the solvent-based or aqueous emulsion-based pressure-sensitive adhesive composition is applied to one side of a substrate as described above, and the organic solvent or water is then thoroughly removed in a drying oven to form a hot-melt pressure-sensitive adhesive layer. An adhesive tape such as an adhesive sheet produced using the hot melt adhesive composition of the present invention can be easily adhered to the above-mentioned substrate by the above-mentioned method. [Example]

[0068] The present invention will be described in more detail below with reference to examples. However, these examples are merely one embodiment of the present invention, and the present invention is not limited to these examples.

[0069] The abbreviations for each component in Tables 1 to 8 below are as follows: (1) Acrylic block copolymer (X) LA3320: Acrylic block copolymer having polymethyl methacrylate, polybutyl acrylate, and polymethyl acrylate structures (Kuraray Co., Ltd., Clarity LA3320) LA2114: Acrylic block copolymer having polymethyl methacrylate, polybutyl acrylate, and polymethyl acrylate structures (Kuraray Co., Ltd., Clarity LA2114) LA2140: Acrylic block copolymer having polymethyl methacrylate, polybutyl acrylate, and polymethyl acrylate structures (Kuraray Co., Ltd., Clarity LA2140) LA3710: Acrylic block copolymer having polymethyl methacrylate, polybutyl acrylate, and polymethyl acrylate structures (Kuraray Co., Ltd., Clarity LA3710) LK9243: A random copolymer of polymethyl methacrylate, butyl acrylate / 2-ethylhexyl acrylate, and an acrylic block copolymer with a polymethyl acrylate structure (Kuraray Co., Ltd., Clarity LK9243) LK-LH8156: Polymethyl methacrylate, random copolymer of methyl acrylate / 2-ethylhexyl acrylate, and acrylic acid with polymethyl acrylate structure. Kuril block copolymer (Kuraray Co., Ltd., Clarity LK-LH8156) LK-LH9211: Acrylic block copolymer with polymethyl methacrylate, poly(2-ethylhexyl acrylate), and polymethyl acrylate structures (Kuraray Co., Ltd., Clarity LK-LH9211) (2) Thermoplastic elastomer 3433N: Thermoplastic elastomer with a block structure of polystyrene and polyisoprene (Zeon Corporation, Quintac (registered trademark) 3433N) (3) Tackifier (Y) (a) Tackifier (Y1) KE-604: Ultra-light-colored rosin derivative (Arakawa Chemical Industries, Ltd., Pine Crystal (registered trademark) KE-604, acid value: 230 mg KOH / g or more and 245 mg KOH / g or less, softening point: 124°C or more and 134°C or less) KR-120: Ultra-light-colored rosin derivative (Arakawa Chemical Industries, Ltd., Pine Crystal (registered trademark) KR-120, acid value: 305 mg KOH / g or more and 345 mg KOH / g or less, softening point: 110°C or more and 130°C or less) #33: Maleic acid resin (manufactured by Arakawa Chemical Industries, Ltd., Marquid #33, acid value: 305 mg KOH / g, softening point: 140°C to 160°C) (b) Tackifier (Y) other than tackifier (Y1) KR-612: Ultra-light-colored rosin derivative (Arakawa Chemical Industries, Ltd., Pine Crystal (registered trademark) KR-612, acid value: 160 mg KOH / g or more and 175 mg KOH / g or less, softening point: 80°C or more and 90°C or less) KR-85: Ultra-light-colored rosin derivative (Arakawa Chemical Industries, Ltd., Pine Crystal (registered trademark) KR-85, acid value: 165 mg KOH / g or more and 175 mg KOH / g or less, softening point: 80°C or more and 87°C or less) #32: Maleic acid resin (manufactured by Arakawa Chemical Industries, Ltd., Marquid #32, acid value: 120 mg KOH / g or more and 140 mg KOH / g or less, softening point: 130°C or more and 140°C or less) FTR6100: Aliphatic modified styrene resin (aromatic hydrocarbon resin) (Mitsui Chemicals, Inc., FTR (registered trademark) 6100, acid value: less than 160 mg KOH / g, softening point: 95°C) HP-100: Alkylphenol-modified xylene resin (Nikanol (registered trademark) HP-100, manufactured by Fudow Co., Ltd., oxidation temperature less than 160 mg KOH / mg, softening point 105°C to 125°C) UC-3000: Acrylic oligomer (manufactured by Toagosei Co., Ltd., Alphon (registered trademark) UC-3000, acid value: less than 74 mg KOH / g, Tg 65°C) UF-5080: Acrylic styrene oligomer (manufactured by Toagosei Co., Ltd., Alphon (registered trademark) UF-5080, acid value: less than 170 mg KOH / g, Tg 75°C) 5020F: Hydrogenated rosin (Eastman Chemical Co., Foralin 5020F, oxidation: less than 160 mg KOH / g, softening point: 5°C) (5) Tackifier (Y2) P-100: Hydrogenated petroleum resin (manufactured by Arakawa Chemical Industries, Ltd., Alcon (registered trademark) P-100, acid value: less than 160 mg KOH / g, softening point: 100°C) P-115: Hydrogenated petroleum resin (manufactured by Arakawa Chemical Industries, Ltd., Alcon (registered trademark) P-115, acid value: less than 160 mg KOH / g, softening point: 115°C) P-140: Hydrogenated petroleum resin (manufactured by Arakawa Chemical Industries, Ltd., Alcon (registered trademark) P-115, acid value: less than 160 mg KOH / g, softening point: 140°C) SX-100: Styrene resin (Yasuhara Chemical Co., Ltd., YS Resin (registered trademark) SX-100, acid value: less than 160 mg KOH / g, softening point: 95°C to 105°C) T-160: Terpene phenol resin (Yasuhara Chemical Co., Ltd., YS Polyster T-160, acid value: less than 160 mg KOH / g, softening point: 160°C) (6) Plasticizers PW-90: Paraffin oil (Idemitsu Kosan Co., Ltd., Diana Process Oil PW- 90) DINP: Diisononyl phthalate (manufactured by C.G. Ester Co., Ltd.) UP-1000: Acrylic oligomer (manufactured by Toagosei Co., Ltd., Arfon (registered trademark) UP-1000, Tg -77°C) UP-1021: Acrylic oligomer (manufactured by Toagosei Co., Ltd., Alphon (registered trademark) UP-1021, Tg -71°C) UP-1061: Acrylic oligomer (manufactured by Toagosei Co., Ltd., Alphon (registered trademark) UP-1061, Tg -60°C) UP-1110: Acrylic oligomer (manufactured by Toagosei Co., Ltd., Alphon (registered trademark) UP-1061, Tg -64°C) CS-16: 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (manufactured by JNC Corporation, CS-16) Olive oil: Olive oil (extra virgin olive oil, manufactured by J-Oil Mills Co., Ltd.) DEHT: Di(2-ethylhexyl) terephthalate (Sigma-Aldrich) DINCH: 1,2-cyclohexanedicarboxylic acid diisononyl ester (Tokyo Chemical Industry Co., Ltd.) DINA: Diisononyl adipate (manufactured by J-Plus Co., Ltd.) Y-300: Xylene resin (Nikanol (registered trademark) Y-300, manufactured by Fudow Co., Ltd.) (7) Antioxidant 1010: Hindered phenolic antioxidant (manufactured by BASF Japan, Irganox (registered trademark) 1010) PEP-36: Phosphite antioxidant (ADEKA CORPORATION, ADK STAB (registered trademark) PEP-36) 168: Phosphorus-based processing stabilizer (BASF Japan, Irgafos (registered trademark) 168)

[0070] Example 1 69% by mass of LA2140, 30% by mass of KE-604, and 1% by mass of 1010 (total of 1000 g) were placed in a stirring kneader equipped with a heating device (manufactured by Moriyama Manufacturing Co., Ltd., SV1-1), and the temperature of the heating device was set to 160°C. The mixture was kneaded for 2 hours while heating to obtain a uniform liquid composition. This was then cooled to room temperature to obtain a hot-melt pressure-sensitive adhesive composition (HM1).

[0071] (Examples 2 to 105) Hot melt pressure-sensitive adhesive compositions (HM2 to HM105) were obtained in the same manner as in Example 1, except that the compositions were changed to those listed in Tables 1 to 7 below, and that the set temperature of the heating device was changed to 180°C for those that could not be sufficiently kneaded at a set temperature of 160°C. The content of each component in the compositions in Tables 1 to 7 below is expressed in "% by mass."

[0072] (Comparative Examples 1 to 4) Hot melt pressure-sensitive adhesive compositions (HM106 to HM109) were obtained in the same manner as in Example 1, except that the composition was changed to each composition listed in Table 8 below, and the setting temperature of the heating device was changed to 180°C for those that could not be sufficiently kneaded at a setting temperature of 160°C. The content of each component in the composition in Table 8 below is expressed in "mass %."

[0073] <Evaluation of compatibility> When the appearance of the produced hot melt pressure sensitive adhesive compositions (HM1 to HM109) was visually transparent or uniformly milky, the compatibility was evaluated as ◯, and when it was non-uniform, the compatibility was evaluated as ×. The evaluation results are shown in Tables 1 to 8 below. HM106 of Comparative Example 1 is a mixture of an acrylic block copolymer (X) and a tackifier component. Since the two compounds were not uniformly mixed, the following heat resistance holding power evaluation test and adhesive strength evaluation test were not carried out.

[0074] <Heat resistance retention evaluation test> The heat resistance retention evaluation test was carried out with reference to JIS Z 0237:2022 and JIS Z1541:2009. A hot melt adhesive composition (HM1 to HM105, HM107 to HM109) was applied to a release paper placed on a hot plate at 180°C using a baker applicator (YBA-1, manufactured by Yoshimitsu Seiki Co., Ltd.) to a thickness of 120 μm to form an adhesive layer. The formed adhesive layer was transferred to a 100 μm thick polyethylene terephthalate (PET) film to prepare an adhesive tape sheet. At room temperature (23±2°C), adhesive tape cut to a width of 25 mm and a length of 50 mm was attached to a degreased stainless steel plate (SUS-BA plate, thickness 1 mm) so that the adhesive area was 25 mm x 25 mm, and a 2 kg roller was used to press the tape back and forth twice to create a test specimen. One end of the SUS-BA plate was fastened with a fastener so that the test specimen hung vertically in an incubator at 80°C, and after curing for 30 minutes, a load was applied to the lower end of the adhesive tape with a 1 kg weight, and the time until the adhesive tape slipped off the SUS-BA plate due to this load was measured. The adhesive tape that did not slip off even after 24 hours or more was evaluated as ⊚, the adhesive tape that slipped off in 1 hour or more but less than 24 hours was evaluated as ◯, and the adhesive tape that slipped off in less than 1 hour was evaluated as ×. The number of test specimens was N=3, and the average evaluation results are shown in Tables 1 to 8 below.

[0075] <Adhesion evaluation test> Adhesive tape sheets were prepared in the same manner as in the heat-resistance holding power evaluation test. The adhesive tape was cut to a width of 25 mm and a length of 75 mm. Leaving a non-adhesive area of ​​at least 10 mm at the end of the tape, the tape was attached to a degreased SUS-BA plate (1 mm thick) and pressed with a 2 kg roller twice to create a test specimen. After curing the test specimen at room temperature for 30 minutes, it was gripped with the gripping tool of a digital force gauge (IMADA Co., Ltd., DSN-500N) and peeled in a 180-degree direction. The maximum peel force (N) was measured and recorded as the adhesive strength (N / 25 mm). N = 3 test specimens were used, and the average test results are shown in Tables 1 to 8.

[0076] [Table 1] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6] [Table 7] [Table 8]

[0077] Tables 1 to 8 show that HM1 to HM105, which contain the acrylic block copolymer (X) and the tackifier (Y), exhibited excellent compatibility, whereas HM106, which contained only a tackifier other than the tackifier (Y), did not exhibit uniform compatibility. This indicates that the compositions of the present invention are hot-melt pressure-sensitive adhesive compositions that can be applied by heating.

[0078] Tables 1 to 7 show that HM1 to HM105 of the present invention are hot melt pressure-sensitive adhesive compositions capable of forming pressure-sensitive adhesive layers having a heat resistance holding power of 1 hour or more and a wide range of adhesive strength from 3 N / 25 mm to 30 N / 25 mm. On the other hand, Table 8 shows that comparative examples HM107 to HM109 are hot melt pressure-sensitive adhesive compositions that have a wide range of adhesive strength from 4 N / 25 mm to 50 N / 25 mm, but do not have sufficient heat resistance retention. [Industrial Applicability]

[0079] The hot melt pressure-sensitive adhesive composition of the present invention has improved heat resistance retention without impairing the excellent advantages of hot melt pressure-sensitive adhesive compositions, such as environmental friendliness, convenience, and labor saving. Therefore, it can be used, for example, for tape applications such as pressure-sensitive adhesive sheets, pressure-sensitive adhesive labels, protective films, and masking tapes; for fixing automobile interior materials, electronic components, etc.; for processing clothing and other textiles; for joining nonwoven fabrics and other fabric materials; and for joining plastic material parts together.

Claims

1. (1) The following formula: -[A1]-[B]-[A2]- wherein each of A1 and A2 represents a polymer block having a glass transition temperature (Tg) greater than 30°C; A1 and A2 represent the same polymer block or different polymer blocks, and B represents a polymer block having a Tg lower than 20°C); and (2) one or more tackifiers (Y) selected from the group consisting of acid-modified rosin, very light-colored rosin, hydrogenated rosin, aliphatic-modified styrene resin, alkylphenol-modified xylene resin, acrylic oligomer having a Tg higher than 30°C, and acrylic styrene oligomer having a Tg higher than 30°C; Including, the mass ratio of the acrylic block copolymer (X) to the tackifier (Y) is 35 to 90:10 to 65; A hot melt pressure sensitive adhesive composition.

2. The hot melt pressure-sensitive adhesive composition according to claim 1, wherein the tackifier (Y) further comprises one or more tackifiers (Y1) having an acid value of 160 mg KOH / g or more and 350 mg KOH / g or less and a softening point of 110°C or more.

3. The hot melt pressure-sensitive adhesive composition according to claim 2, wherein the tackifier (Y1) has an acid value of 300 mgKOH / g or more and 350 mgKOH / g or less.

4. The hot melt pressure-sensitive adhesive composition according to claim 1 , further comprising a tackifier (Y2) (excluding the tackifier (Y)).

5. The hot melt pressure-sensitive adhesive composition according to claim 1 , further comprising an antioxidant.

6. The hot melt pressure-sensitive adhesive composition according to claim 1 , which does not contain a plasticizer.

7. 6. The hot melt pressure-sensitive adhesive composition according to claim 1, further comprising one or more plasticizers selected from the group consisting of phthalate esters, hydrogenated phthalate esters, alkyl esters of aliphatic dibasic acids, liquid acrylic oligomers having a Tg of less than 0°C, and xylene resins in an amount of more than 0 mass% and 10 mass% or less, based on the total mass of the composition.

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