Adhesive composition

Abstract

To provide an adhesive composition which suppresses temporal degradation of adhesive force to a soft vinyl chloride resin, without impairing excellent advantages such as environmental performance, convenience and labor saving.SOLUTION: An adhesive composition contains (1) an acrylic block copolymer (X) represented by the following expression: -[A1]-[B]-[A2]-, and (2) one or more tackifiers (Y) selected from the group consisting of acid-modified rosin, ultralight-colored rosin, hydrogenated rosin, an aliphatic-modified styrene resin, an acrylic oligomer having a Tg higher than 30°C, and an acrylic styrene oligomer having a Tg higher than 30°C, wherein a mass ratio of the acrylic block copolymer (X) to the tackifiers (Y) is 35 to 90:65 to 10, and the tackifier (Y) contains a tackifier (Y1) having an acid value of 161 mgKOH / g or more to 350 mgKOH / g or less and a softening point of 120°C or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition, and more particularly to a pressure-sensitive adhesive composition that exhibits excellent adhesion over time to soft vinyl chloride resins.

[0002] Flexible polyvinyl chloride resins are flexible and have good moldability, such as in embossing and foaming processes. Therefore, they are used in a variety of fields where improved texture and design are required, such as building materials such as wallpaper, carpets, and decorative sheets, as well as synthetic leather and automotive interior parts. However, because soft vinyl chloride resins contain plasticizers, when an adherend and soft vinyl chloride resin are adhered via an adhesive layer, the plasticizer migrates from the soft vinyl chloride resin to the adhesive layer, causing a problem in that the adhesive performance of the adhesive significantly deteriorates over time.

[0003] Examples of pressure-sensitive adhesives that are less susceptible to the migration of plasticizers contained in soft vinyl chloride resins include a pressure-sensitive adhesive composition containing a crosslinker and a copolymer obtained by copolymerizing a monomer mixture containing n-butyl acrylate, methyl methacrylate, an ethylenically unsaturated carboxylic acid, and a hydroxyl group-containing unsaturated monomer (Patent Document 1); a pressure-sensitive adhesive composition containing a rubber component, a petroleum resin mixture, and a softener (Patent Document 2); an acrylic pressure-sensitive adhesive containing a rubber component, a vinyl monomer having no carboxyl group, an acrylic copolymer, and a polyfunctional isocyanate compound (Patent Document 3); an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer resin obtained by copolymerizing an acrylic acid alkyl ester, a nitrogen-containing vinyl monomer, and a caprolactone-modified (meth)acrylate, and a polyisocyanate compound (Patent Document 4); a pressure-sensitive adhesive composition containing a (meth)acrylate and an acrylic copolymer (Patent Document 5); and a water-dispersible pressure-sensitive adhesive composition mainly composed of an acrylic copolymer emulsion containing a (meth)acrylate and a copolymerizable monomer (Patent Document 6).

[0004] In recent years, due to safety and environmental concerns, it has become desirable to avoid the use of organic solvents in bonding building materials and automotive interior materials. For example, compared to solvent-based adhesives, solvent-free hot-melt adhesives offer advantages such as reduced volatile organic compounds (VOCs) and improved productivity due to the omission of the drying process, and interest in them as environmentally friendly adhesives is growing.

[0005] Examples of hot melt pressure sensitive adhesive compositions include an alkali dispersible hot melt pressure sensitive adhesive containing a (meth)acrylic block copolymer, a rosin tackifier resin, and a sebacic acid ester, which is used to remove adhesive residue from PET bottles even in low temperature environments (Patent Document 7); a vibration damping hot melt pressure sensitive adhesive composition containing a (meth)acrylic block copolymer and a tackifier, which is used for vibrating parts in equipment (Patent Document 8); a pressure sensitive adhesive composition containing an acrylic copolymer and a tackifier, which is used to form an adhesive layer for a display label to be adhered to an olefin resin (Patent Document 9); a pressure sensitive adhesive composition containing a triblock copolymer and a tackifier, which is used for the adhesive layer of a label for shrink packaging (Patent Document 10); and a hot-melt adhesive for attaching road marking materials, which comprises a block copolymer and a combination of a tackifier having a softening point of 130°C or higher and a tackifier having a softening point of less than 130°C, for laminating and adhering road marking materials and the like to road surfaces such as asphalt surfaces (Patent Document 12). A first block copolymer formed by hot-melt molding on a low-density polyethylene film or polyethylene terephthalate cloth substrate layer, which is used in an adhesive tape having adhesive strength to low-polarity polyolefin materials and silicone materials with releasability. A pressure-sensitive adhesive layer containing a block copolymer containing a first block copolymer and a second block copolymer and a tackifier (polymerized rosin ester) has been proposed (Patent Document 13). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-2024 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-240828 [Patent Document 3] Japanese Patent Application Publication No. 8-209099 [Patent Document 4] Japanese Patent Application Publication No. 5-163480 [Patent Document 5] Japanese Patent Application Publication No. 5-105857 [Patent Document 6] Japanese Patent Application Publication No. 5-105856 [Patent Document 7] Japanese Patent Application Laid-Open No. 2015-028124 [Patent Document 8] Japanese Patent Application Laid-Open No. 2015-209527 [Patent Document 9] Japanese Patent Application Publication No. 2019-65242 [Patent Document 10] Japanese Patent Publication No. 2022-12938 [Patent Document 11] Japanese Patent Application Publication No. 2023-13841 [Patent Document 12] Japanese Patent Application Publication No. 2023-59831 [Patent Document 13] Japanese Patent Application Laid-Open No. 202364959 Summary of the Invention [Problem to be solved by the invention]

[0007] The hot melt pressure sensitive adhesive compositions described in Patent Documents 7 to 13 were not intended to be used to bond flexible polyvinyl chloride resin as an adherend, and had the problem of insufficient tackiness and adhesion to flexible polyvinyl chloride resin over time. Furthermore, in building materials and automobile interior parts that are exposed to environments approaching 40°C, such as in the summer, migration of plasticizer from the soft polyvinyl chloride resin to the adhesive layer is accelerated, making the adhesive strength of the adhesive layer more likely to decrease. The pressure-sensitive adhesive compositions described in Patent Documents 1 to 6 have the problem that their adhesiveness to soft polyvinyl chloride resin decreases over time in high-temperature environments of 40°C.

[0008] An object of the present invention is to provide a pressure-sensitive adhesive composition that inhibits deterioration of adhesive strength over time to soft vinyl chloride resins without impairing excellent advantages such as environmental friendliness, convenience, and labor savings. [Means for solving the problem]

[0009] 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 pressure-sensitive adhesive composition can be obtained that suppresses deterioration over time in adhesive strength to soft vinyl chloride resins, and have thus completed the present invention.

[0010] That is, the present invention provides a pressure-sensitive adhesive composition, (1) the following formula: -[A1]-[B]-[A2]- (In the formula, each of A1 and A2 represents 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, 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 to 90:65 to 10; The tackifier (Y) relates to a pressure-sensitive adhesive composition containing a tackifier (Y1) having an acid value of 161 mgKOH / g or more and 350 mgKOH / g or less and a softening point of 120°C or more.

[0011] The acid value of the tackifier (Y1) is preferably 300 mgKOH / g or more and 350 mgKOH / g or less.

[0012] The tackifier (Y) contained in the adhesive composition preferably has an acid value of less than 161 mgKOH / g and a softening point of 120°C or higher, or preferably contains a tackifier (Y2) having an acid value of 161 mgKOH / g or higher and 350 mgKOH / g or lower and a softening point of less than 120°C.

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

[0014] The pressure-sensitive adhesive composition preferably contains 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% by mass and 10% by mass or less, based on 100% by mass of the composition.

[0015] The pressure-sensitive adhesive composition preferably further contains an antioxidant.

[0016] The pressure-sensitive adhesive composition can be used as a hot-melt type, solvent type or aqueous emulsion type pressure-sensitive adhesive composition. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition that inhibits deterioration over time in adhesive strength to soft vinyl chloride resins, without compromising excellent advantages such as environmental friendliness, convenience, and labor savings. DETAILED DESCRIPTION OF THE INVENTION

[0018] The 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, 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 to 90:65 to 10; The tackifier (Y) contains a tackifier (Y1) having an acid value of 161 mgKOH / g or more and 350 mgKOH / g or less and a softening point of 120°C or more. Each component will be described below.

[0019] <Acrylic block copolymer (X)> The acrylic block copolymer (X) contained in the 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.

[0020] The polymer block represented by A1 (hereinafter also referred to as polymer block [A1]) and the polymer block represented by A2 (hereinafter also referred to as polymer block [A2]) may be the same polymer block or different polymer blocks, but are preferably the same polymer block.

[0021] 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 pressure-sensitive adhesive composition of the present invention has adhesiveness to soft vinyl chloride resins without heating due to the polymer block [B], and has high cohesive strength due to the polymer blocks [A1] and [A2].

[0022] 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, but is, for example, 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 pressure-sensitive adhesive composition will be low, and the heat resistance after adhesion may be reduced. If the Tg exceeds 250°C, the melting point will be too high, making handling difficult, and it will be difficult to use the composition as a hot-melt pressure-sensitive adhesive composition in particular.

[0023] 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, and (meth)acrylate means acrylate or methacrylate.

[0024] 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%.

[0025] 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, and -30°C or lower, with -20°C or lower being preferred and -40°C or lower being particularly 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.

[0026] Examples of the polymer block [B] include polymer blocks derived from (meth)acrylates, for example, polymer blocks derived from (meth)acrylates having an alkyl group having 2 or more and 12 or less 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, 2-ethylhexyl acrylate, and combinations thereof are preferred, and n-butyl acrylate, 2-ethylhexyl acrylate, and combinations thereof are more preferred.

[0027] In the acrylic block copolymer, the total content of the polymer blocks [A1] and [A2] is, for example, from 10% by mass to 55% by mass, or from 10% by mass to 40% by mass, and the content of the polymer block [B] is, for example, from 45% by mass to 90% by mass, or from 60% by mass to 90% by mass. However, the range of the content can be appropriately adjusted as long as it does not impair the effects of the present invention. For example, the total content range of the polymer blocks [A1] and [A2] 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, 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% 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, 66% by mass, 67% by mass, 68% by mass, 69% by mass, 70% by mass, 71% by mass, 72% by mass, 73% by mass, 74% by mass, 75% by mass, 7 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 more than 90% by mass), the softening point of the adhesive composition will decrease, which may result in a decrease in holding power in high-temperature environments. 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 adhesive composition will increase, which may result in a decrease in workability due to the need to heat the adhesive to a high temperature during use.

[0028] The acrylic block copolymer (X) used in the present invention may be a commercially available product, such as KURARITY LA2140E (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 LA3170 (M MA-BA / triblock copolymer, MMA mass ratio: 12% by mass), KuraRity LA2270 (MMA-BA / triblock copolymer, MMA mass ratio: 40% 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 or more, manufactured by Kuraray Co., Ltd., and the like can be used alone or in combination. Furthermore, from the viewpoint of adhesiveness, KURARITY LA3320, KURARITY LA3170, KURARITY LK9243, and combinations thereof are preferred. In the above, MMA represents a polymethyl methacrylate block, BA represents a polyn-butyl acrylate block, and 2EHA represents a poly2-ethylhexyl acrylate block.

[0029] The content of the acrylic block copolymer (X) relative to 100% by mass of the pressure-sensitive adhesive composition of the present invention is, for example, 35% by mass to 90% by mass, or 35% by mass to 70% by mass. However, the content range can be appropriately adjusted as long as it is within a range that does not impair the effects of the present invention. The ranges are, relative to 100% by mass of the pressure-sensitive adhesive composition, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, 100%, 110%, 112%, 113%, 114%, 115%, 116%, 117%, 118%, 119%, 120%, 121%, 122%, 123%, 124%, 125%, 126%, 127%, 128%, 129%, 130%, 131%, 132%, 133%, 134%, 135%, Amount%, 64% by mass, 65% by mass, 66% by mass, 67% by mass, 68% by mass, 69% by mass, 70% by mass, 71% by mass, 72% by mass, 73% by mass, 74% by mass, 75% by mass, 76% by mass, 77% by mass, 78% by mass, 79% by mass %, 80% by mass, 81% by mass, 82% by mass, 83% by mass, 84% by mass, 85% by mass, 86% by mass, 87% by mass, 88% by mass, 89% by mass, and 90% by mass, and the lower and upper limits can be adjusted in any combination. If the content of the acrylic block copolymer (X) is less than 30% by mass, the cohesive strength of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention may decrease, whereas if the proportion of the acrylic block copolymer (X) exceeds 90% by mass, the coatability of the pressure-sensitive adhesive composition of the present invention may deteriorate.

[0030] <Tackifier (Y)> The tackifier (Y) contained in the 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, acrylic oligomer having a Tg higher than 30°C, and acrylic styrene oligomer having a Tg higher than 30°C, and includes tackifier (Y1) having an acid value of 161 mgKOH / g or more and 350 mgKOH / g or less and a softening point of 120°C or more. The tackifier (Y1) more preferably has an acid value of 300 mgKOH / g or more and 350 mgKOH / g or less. The tackifier (Y1) can be used alone or in combination of two or more kinds.

[0031] The content of the tackifier (Y) in the pressure-sensitive adhesive composition of the present invention is 10% by mass or more and 65% by mass or less, and preferably 25% by mass or more and 55% by mass or less, based on the total mass of the pressure-sensitive adhesive composition. However, the content range can be adjusted appropriately as long as it does not impair the effects of the present invention. The ranges are 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, 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% 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, 66% by mass, 67% by mass, 68 Amount%, 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% 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, and the lower and upper limits can be adjusted in any combination. By containing the tackifier (Y) in the above range, the pressure-sensitive adhesive composition of the present invention can It can have good wettability and adhesion to soft vinyl chloride resin.

[0032] The content of the tackifier (Y) is such that the mass ratio of the acrylic block copolymer (X) to the tackifier (Y) (acrylic block copolymer (X): tackifier (Y)) is 35-90:65-10, preferably 45-75:55-25. If the proportion of tackifier (Y) exceeds 65, the adhesive strength and holding power of the adhesive composition may decrease, and if the proportion of tackifier (Y) is less than 10, the wettability with respect to the soft vinyl chloride resin may decrease, resulting in a decrease in adhesive strength. The total content of the acrylic block copolymer (X) and tackifier (Y) contained in the pressure-sensitive adhesive composition of the present invention is not particularly limited as long as it does not impair the effects of the present invention, but 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, but is, for example, 100% by mass or less, or 95% by mass or less. If it is less than 30% by mass, sufficient adhesion to soft vinyl chloride resin may not be exhibited.

[0033] If the acid value of the tackifier (Y1) contained in the tackifier (Y) used in the present invention is less than 161 mgKOH / g, the wettability of the pressure-sensitive adhesive composition to a soft vinyl chloride resin may decrease, and the adhesive strength to the soft vinyl chloride resin may decrease. If the acid value is more than 350 mgKOH / g, the pressure-sensitive adhesive composition may thicken over time and the insulation resistance may deteriorate.

[0034] The softening point of the tackifier (Y1) is 120° C. or higher. If the tackifier (Y) consists solely of a tackifier having a softening point of less than 120° C., the cohesive strength of the adhesive layer formed from the pressure-sensitive adhesive composition may decrease, resulting in a decrease in holding power. 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 less, 200° C. or less, 180° C. or less, or 160° C. or less. If the softening point exceeds 250° C., the tackifier (Y1) may be incompatible with the acrylic block copolymer (X), and the production and application of the PSA composition may need to be carried out at high temperatures.

[0035] Examples of acid-modified rosins include those obtained by modifying unmodified rosins such as tall oil rosin, gum rosin, wood rosin, and purified rosin with carboxylic acids such as maleic acid, maleic anhydride, and acrylic acid, or anhydrides of these carboxylic acids.

[0036] Examples of the very light-colored rosin include very light-colored rosin, very light-colored rosin ester, and acid-modified very light-colored rosin.

[0037] Examples of hydrogenated rosins include rosins obtained by hydrogenating the unmodified rosin or acid-modified rosin.

[0038] Examples of the aliphatic modified styrene resin include copolymers of styrene monomers and aliphatic monomers.

[0039] Examples of acrylic oligomers having a Tg of higher than 30° C. include carboxyl group-containing acrylic oligomers having a low molecular weight of several hundred to several tens of thousands. Examples of acrylic styrene oligomers having a Tg of higher than 30°C 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.

[0040] As the tackifier (Y1) used in the present invention, commercially available tackifiers can be used, for example, For example, acidic rosins include Marquid #31 and #33 (manufactured by Arakawa Chemical Industries, Ltd.), ultra-light-colored rosins include Pine Crystal KE-604 and KR-120 (manufactured by Arakawa Chemical Industries, Ltd.), and acrylic oligomers with a Tg of higher than 30°C include Arfon UC-3080 and UF-3080 (manufactured by Toagosei Co., Ltd.).

[0041] 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).

[0042] The pressure-sensitive adhesive composition of the present invention may contain a tackifier (Y2) other than the tackifier (Y1) as long as the effects of the present invention are not impaired. Examples of the tackifier (Y2) include tackifiers having an acid value of less than 161 mgKOH / g and a softening point of 120°C or higher, or tackifiers having an acid value of 161 mgKOH / g or higher and 350 mgKOH / g or lower and a softening point of less than 120°C. The tackifier (Y2) can be used alone or in combination of two or more kinds.

[0043] As the tackifier (Y2), any known tackifier can be used as long as it does not impair the effects of the present invention. For example, any of phenolic resins, modified phenolic resins, terpene resins, terpene phenolic resins, xylene phenolic resins, xylene resins, α-methylstyrene resins, cyclopentadiene-phenolic resins, aliphatic and aromatic petroleum resins, phenol-modified petroleum resins, rosin esters, polymerized rosins, hydrogenated rosin esters and polymerized rosins, low-molecular-weight polystyrene resins, terpene resins, hydrogenated aliphatic and aromatic petroleum resins, and the like can be used. By using the tackifier (Y1) and the tackifier (Y2) in combination, it is possible to improve the compatibility between the acrylic block copolymer (X) and the tackifier (Y) and to adjust the wettability and adhesion to adherends other than soft vinyl chloride resins.

[0044] When the tackifier (Y1) and the tackifier (Y2) are used in combination, the content of the tackifier (Y1) is 30% by mass or more, preferably 40% by mass or more, and more preferably 50% by mass or more, based on the total mass of the tackifier (Y) (total mass of the tackifier (Y1) and the tackifier (Y2)). If the content of tackifier (Y1) is less than 30 mass% relative to the total mass of tackifier (Y), the wettability of the pressure-sensitive adhesive composition of the present invention to soft vinyl chloride resins may decrease, or the adhesive strength retention over time may decrease.

[0045] The tackifier (Y2) may be any commercially available tackifier as long as it has an acid value and softening point within the above ranges. Examples of the tackifier (Y2) include acid-modified rosin, very light-colored rosin, hydrogenated rosin, rosin ester, disproportionated rosin ester, hydrogenated rosin ester, polymerized rosin, aliphatic hydrocarbon resin, aliphatic-aromatic copolymer resin, aromatic petroleum resin, hydrogenated petroleum resin, terpene resin, hydrogenated terpene resin, modified terpene resin, hydrogenated modified terpene resin, terpene phenol resin, hydrogenated terpene phenol resin, styrene resin, coumarone resin, indene resin, and the like. Among these, from the viewpoint of compatibility with the acrylic block copolymer (X), very light-colored rosin or terpene phenol resin is preferable.

[0046] Examples of commercially available tackifiers (Y2) include, but are not limited to, Alcon (registered trademark) P-140, Pine Crystal (registered trademark) KE-604, KR-85, and Marquid (registered trademark) #32, all manufactured by Arakawa Chemical Co., Ltd., and YS Polystar (registered trademark) T-160, all manufactured by Yasuhara Chemical Co., Ltd.

[0047] The pressure-sensitive adhesive composition of the present invention may contain a tackifier other than the tackifier (Y1) and the tackifier (Y2), provided that the effects of the present invention are not impaired. Known tackifiers can be used. When other tackifiers are contained, the content thereof is, for example, 10% by mass or less, for example, 6% by mass or less, based on the total mass of the tackifiers.

[0048] <Plasticizer> The 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 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 pressure-sensitive adhesive composition. If the content of the plasticizer exceeds 70% by mass, migration of the plasticizer occurs between the pressure-sensitive adhesive layer and the adherend, such as a soft vinyl chloride resin, which may result in a decrease in holding power over time and contamination or deterioration of the adherend.

[0049] Examples of the plasticizer include phthalate esters, hydrogenated phthalate esters, alkyl esters of aliphatic dibasic acids, liquid acrylic oligomers with a Tg of less than 0° C., and xylene resins.

[0050] Examples of phthalate esters include dibutyl phthalate, diisononyl phthalate (DINP), diheptyl phthalate, di(2-ethylhexyl) phthalate, diisodecyl phthalate (DIDP), and butyl benzyl phthalate. Examples of hydrogenated phthalic acid esters include 1,2-cyclohexanedicarboxylic acid diisononyl ester. Examples of alkyl esters of aliphatic dibasic acids include 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, and acrylic acid, as well as copolymers of these with styrene or α-methylstyrene and other styrene-based monomers. Examples of xylene resins include commercially available Nikanol (registered trademark) Y-50, Y-100, Y-300, Y-1000, LLL, LL, L, GH, and G (manufactured by Fudow Co., Ltd.). The plasticizer may be used alone or in combination of two or more. A preferred example is Nikanol (registered trademark) Y-300, an environmentally friendly xylene resin with low heat loss and volatile component content.

[0051] The 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 pressure-sensitive adhesive composition of the present invention contains the various additives, the content of the various additives in 100% by mass of the pressure-sensitive adhesive composition is preferably 5% by mass or less.

[0052] <Antioxidants> As the antioxidant, known antioxidants used in pressure-sensitive adhesive compositions can be used, such as hindered phenols, polyphenols, bisphenols, phosphates, thiophenes, etc. Examples include oethers, hydrosaltites, benzimidazoles, and aromatic secondary amines.

[0053] Examples of commercially available antioxidants include, but are not limited to, Irganox (registered trademark) 1010, 1035, 1076, 1098, 1330, 245, 259, 3114, 565, and 168 manufactured by BASF Corporation, and ADK STAB (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 prevent discoloration and deterioration of the pressure-sensitive adhesive composition due to oxidation.

[0054] <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.

[0055] Since the acrylic block copolymer (X) is thermoplastic, soluble in a solvent, and dispersible in water, the pressure-sensitive adhesive composition of the present invention can also be used as a hot-melt pressure-sensitive adhesive composition, a solvent-based pressure-sensitive adhesive composition, or an aqueous emulsion pressure-sensitive adhesive composition. For example, the pressure-sensitive adhesive composition of the present invention can be coated by being heated and melted, dissolved in an organic solvent, or uniformly dispersed in an aqueous solvent.

[0056] 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 organic solvents such as ester-based solvents such as ethyl acetate and butyl acetate; alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, butanol, hexanol, and octanol; and ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and 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.

[0057] 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. As the emulsifier, any known emulsifier that can be used in an aqueous emulsion-type pressure-sensitive adhesive composition can be used, for example, anionic surfactants such as alkyl sulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, alkylbenzene sulfonates, alkyl ether disulfonates, fatty acid salts, naphthalene sulfonate-formalin condensates, and sulfosuccinates. or 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.

[0058] <Method of manufacturing pressure-sensitive adhesive composition> The PSA 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.

[0059] 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.

[0060] 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 material 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 material, or by adding the kneaded material 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 can be placed in a tank equipped with a pressurizable stirrer, heated to a temperature equal to or higher than the melting point of the kneaded product obtained above, and the molten kneaded product can be added and emulsified by stirring to produce an aqueous emulsion.

[0061] <Adhesive body and its manufacturing method> An adhesive body can be formed by a method including a coating step of applying the 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.

[0062] 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.

[0063] 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. When applying the adhesive composition as a hot-melt type, the application temperature to the substrate can be selected appropriately depending on the viscosity of the adhesive composition, and the adhesive 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 an adhesive layer by applying the adhesive composition to a release film or release paper, and then transferring the adhesive layer to the first substrate. When applying the adhesive composition as a solvent-based or aqueous emulsion-based adhesive composition, the adhesive composition can be applied by, for example, applying the adhesive 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.

[0064] In addition, in the coating step, the 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 pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition of the present invention to be sandwiched between release films or release papers, thereby producing and using a so-called substrate-less double-sided tape. In this case, the coating step may be a step of peeling off one of the release films or release papers and attaching the precoated substrate to a first substrate. In this case, the other release film or release paper is attached to the pressure-sensitive adhesive layer of the precoated substrate, and in the bonding step described below, the other release film or release paper is peeled off and the precoated substrate is then bonded to a second substrate.

[0065] The adhesive step is a step of pressure-bonding the precoated substrate and the second substrate. Since the adhesive layer formed from the 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 re-melted by heat activation. The heat activation method may be, for example, a method using heat, ultrasonic waves, high frequency waves, or microwaves, but is not particularly limited. When reactivation is performed, it may be performed immediately before the precoated substrate and the second substrate are pressure-bonded, or may be performed simultaneously with the pressure application, or may be performed after the pressure-bonding. 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.

[0066] The pressure-bonding method is not particularly limited, and may be a known method such as a known press-bonding method, vacuum forming method, etc. Furthermore, since the 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.

[0067] The pressure-sensitive adhesive composition of the present invention can be applied to a soft vinyl chloride resin substrate and used for applications such as pressure-sensitive adhesive tapes, building materials such as wallpaper, and pressure-sensitive adhesive tapes, pressure-sensitive adhesive films, and pressure-sensitive adhesive sheets such as covering materials for automobile interiors. The adhesive tape, adhesive film, and adhesive sheet can be produced by a known method, and as described above, an adhesive composition is applied to one side of a substrate, with heating as necessary, to form an 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. When the pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive layer of a pressure-sensitive adhesive tape or pressure-sensitive adhesive film, a method may be employed in which a 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 pressure-sensitive adhesive layer.

[0068] The pressure-sensitive adhesive tape, pressure-sensitive adhesive film and pressure-sensitive adhesive sheet produced using the pressure-sensitive adhesive composition of the present invention can be easily adhered to the above-mentioned substrate by the above-mentioned method. [Example]

[0069] 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.

[0070] The abbreviations for each component in Tables 1 and 2 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) LA3710: Acrylic block copolymer having polymethyl methacrylate, polybutyl acrylate, and polymethyl acrylate structures (Kuraray Co., Ltd., Clarity LA3710) LK9243: Acrylic block copolymer with polymethyl methacrylate, butyl acrylate / 2-ethylhexyl acrylate, and polymethyl acrylate structure (Kuraray Co., Ltd., Clarity LK9243) (2) Thermoplastic elastomer Thermoplastic elastomer with a block structure of polystyrene and polyisoprene (Zeon Corporation, Quintac® 3433N) (3) 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) #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) (4) Tackifier (Y2) P-140: Hydrogenated petroleum resin (manufactured by Arakawa Chemical Industries, Ltd., Alcon (registered trademark) P-115, acid value: less than 161 mg KOH / g, softening point: 140°C) KR-612: Ultra-light-colored rosin derivative (Arakawa Chemical Industries, Ltd., Pine Crystal (registered trademark) KR-612, acid value: 161 mg KOH / g or more and 175 mg KOH / g or less, softening point: 80°C or more and 90°C or less) T-160: Terpene phenol resin (Yasuhara Chemical Co., Ltd., YS Polyster T-160, acid value: less than 161 mg KOH / g, softening point: 160°C) (5) Tackifier (other than Y1 and Y2) P-100: Hydrogenated petroleum resin (manufactured by Arakawa Chemical Industries, Ltd., Alcon (registered trademark) P-100, acid value: less than 161 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 161 mg KOH / g, softening point: 115°C) FTR-6100: Aliphatic modified styrene resin (aromatic hydrocarbon resin) (Mitsui Chemicals, Inc., FTR-6100, acid value: less than 161 mg KOH / g, softening point: 95°C) SX-100: Styrene resin (Yasuhara Chemical Co., Ltd., YS Resin (registered trademark) SX-100, acid value: 161 mg KOH / g, softening point: 95°C to 105°C) 5020F: Hydrogenated rosin methyl ester (Eastman Chemical Company, Foralin 5020F, acid value: less than 161 mg KOH / g, softening point: 5°C) UH2170: Acrylic polymer (Toagosei Co., Ltd., Alphon UH2170, acid value: less than 161 mg KOH / g, glass transition temperature: 60°C) (6) Plasticizers PW-90: Paraffin oil (Idemitsu Kosan Co., Ltd., Diana Process Oil PW-90) DINP: Diisononyl phthalate (manufactured by C.G. Ester Corporation) UP1061: Acrylic polymer (Toagosei Co., Ltd., Alphon UP1061, glass transition temperature -60°C) Y300: Xylene resin (Nikanol Y300, manufactured by Fudow Co., Ltd.) (7) Antioxidants 1010: Hindered phenolic antioxidant (BASF Japan, Irganox 1010) (8) Emulsifier E-118B: Polyoxyethylene alkyl sulfate sodium ester (Kao Corporation) Latemul E-118B)

[0071] Example 1 Into a stirring kneader equipped with a heating device (manufactured by Moriyama Manufacturing Co., Ltd., SV1-1), 10 parts by mass of LA3710, 60 parts by mass of LK9243, 25 parts by mass of KE-604, 4 parts by mass of DINP, and 1 part by mass of 1010 (total of 1010 g) were placed, 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 pressure-sensitive adhesive composition (HM1).

[0072] (Examples 2 to 7) Pressure-sensitive adhesive compositions (HM2 to HM7) were obtained in the same manner as in Example 1, except that the compositions were changed to those shown in Table 1 below and the temperature of the heating device was set to 180°C. The content of each component in the composition in Table 1 below is expressed in "parts by mass."

[0073] Example 8 23.3 parts by mass of LA3710, 23.3 parts by mass of LK9243, 23.3 parts by mass of #33, 3.0 parts by mass of P-140, 26.0 parts by mass of 5020F, and 1 part by mass of 1010 (total of 100 g) were placed into a stainless steel tank equipped with a stirrer containing 200 parts by mass (200 g) of ethyl acetate, and dissolved with stirring at room temperature to prepare a pressure-sensitive adhesive composition coating solution (Sol8) with a solids concentration of 33% by mass. The obtained coating solution of the adhesive composition was applied using a roll knife coater to the release surface of a release liner consisting of a 38 μm thick polyethylene terephthalate film with a silicone-based release agent layer formed on one side thereof, and the resulting coating film was dried at 120°C for 1 minute to form an adhesive layer with a thickness of 50 μm. The adhesive layer side of the laminate of the release liner and adhesive layer obtained as described above was bonded to one side of a polyethylene terephthalate film (thickness 25 μm) serving as a substrate, to obtain an adhesive sheet having the substrate, adhesive layer, and release liner laminated in this order.

[0074] Example 9 23.3 parts by mass of LA3710, 23.3 parts by mass of LK9243, 23.3 parts by mass of #33, 3.0 parts by mass of P-140, 26.0 parts by mass of 5020F, and 1 part by mass of 1010 (total of 999.9 g) were placed into a stirring kneader equipped with a heating device (manufactured by Moriyama Seisakusho Co., Ltd., SV1-1), and the temperature of the heating device was set to 180°C. The mixture was kneaded for 2 hours while heating, to obtain a uniform liquid composition (HM7). A solution of 2 parts by mass of E-118B dissolved in 100 parts by mass of water was placed in a pressure vessel equipped with a stirrer, and the solution was heated to 150°C under a pressure of 0.6 MPa and stirred. To the solution, the above-mentioned HM7 in a molten state at 150°C was added dropwise, and after emulsification, the solution was cooled to room temperature (23°C) to prepare an aqueous emulsion-type coating solution (AQ9) of a pressure-sensitive adhesive composition with a solids concentration of 33% by mass. The obtained adhesive composition coating solution was applied to a polyethylene terephthalate film having a thickness of 38 μm. The adhesive was applied using a roll knife coater to the release surface of a release liner having a silicone-based release agent layer formed on one side of the film, and the resulting coating was dried at 120°C for 5 minutes to form a 50 μm thick adhesive layer. The adhesive layer side of the laminate of the release liner and adhesive layer obtained as described above was bonded to one side of a polyethylene terephthalate film (thickness 25 μm) serving as a substrate, to obtain an adhesive sheet having the substrate, adhesive layer, and release liner laminated in this order.

[0075] (Comparative Examples 1 to 6) Pressure-sensitive adhesive compositions (HM8 to HM13) were obtained in the same manner as in Example 1, except that the compositions were changed to those shown in Table 1 below and the temperature of the heating device was set to 180°C in Comparative Example 3 only.

[0076] (Comparative Examples 7 and 8) For Comparative Example 7, a commercially available double-sided adhesive tape having an acrylic adhesive layer on a nonwoven fabric substrate (MonotaRO Co., Ltd., MonotaRO Double-Sided Tape Super Strong for Polyethylene and Polypropylene (Order Code: 19016165), thickness 160 μm) was used, and for Comparative Example 8, a commercially available double-sided adhesive tape having an acrylic adhesive layer on a nonwoven fabric substrate (Teraoka Seisakusho Co., Ltd., PVC Double-Sided Tape No. 773, thickness 200 μm) was used.

[0077] <Evaluation of compatibility> When the appearance of the produced pressure-sensitive adhesive compositions (HM1 to HM13) was visually transparent or uniformly milky, the compatibility was evaluated as ◯, and when it was heterogeneous, the compatibility was evaluated as ×. The evaluation results are shown in Tables 1 and 2 below. In addition, for HM8 of Comparative Example 1 and HM9 of Comparative Example 2, the acrylic block copolymer (X) and the tackifier component were not uniformly compatible with each other, so the following holding power evaluation test, adhesive strength evaluation test, and adhesive strength retention evaluation test were not performed.

[0078] <Holding force evaluation test> The heat resistance retention evaluation test was carried out with reference to JIS Z 0237:2022 and JIS Z1541:2009. The adhesive compositions (HM1 to HM13) were applied to a thickness of 120 μm onto release paper placed on a hot plate heated to 180°C using a baker applicator (YBA-1, manufactured by Yoshimitsu Seiki Co., Ltd.) to form an adhesive layer. The formed adhesive layer was transferred to a 100 μm thick polyethylene terephthalate (PET) film to produce an adhesive tape sheet. For Examples 8 and 9, the adhesive tape prepared as described above was used as is, while for Comparative Examples 7 and 8, the release paper on one side was peeled off and the tape was attached to a 100 μm thick polyethylene terephthalate (PET) film to produce 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 and 2 below.

[0079] <Adhesion evaluation test> An adhesive tape sheet was prepared in the same manner as in the holding power evaluation test. The adhesive tape was cut to a width of 25 mm and a length of 75 mm, and the tape was then attached to a degreased SUS 404 sheet, leaving a non-adhesive area of ​​10 mm or more at the end of the tape. The specimen was then laminated to a 1mm thick BA plate and pressed with a 2kg roller twice to create a test specimen. After curing the 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 pulled away in a 180-degree direction, and the maximum peel force (N) was measured and used as the adhesive strength (N / 25mm). Three specimens were tested, and the average test results are shown in the SUS adhesive strength column in Tables 1 and 2.

[0080] <Adhesion retention rate evaluation test for soft vinyl chloride resin sheets> A pressure-sensitive adhesive composition (HM1 to HM13) was applied to a release paper placed on a hot plate at 180°C using a baker applicator to a thickness of 50 μm to form a pressure-sensitive adhesive layer. The formed pressure-sensitive adhesive layer was transferred to a 25 μm thick PET film to produce a pressure-sensitive adhesive tape. For Examples 8 and 9, the pressure-sensitive adhesive tape produced above was used as is, while for Comparative Examples 7 and 8, the release paper on one side was peeled off and the tape was attached to a 25 μm thick polyethylene terephthalate (PET) film to produce a pressure-sensitive adhesive tape sheet. The adhesive tape was cut to a width of 25 mm and a length of 75 mm, and attached to a 25 mm wide, 75 mm long, 0.5 mm thick soft vinyl chloride resin sheet, leaving at least 10 mm of non-adhesive space at the end of the tape. The tape was then pressed with a 2 kg roller, rolling it back and forth twice, and cured in a 40°C incubator for 1 day and 28 days to prepare test specimens. The test specimens were then removed from the incubator and allowed to cool at room temperature for 30 minutes. A T-peel test was then performed at a pulling rate of 300 mm / min using a universal testing machine (Shimadzu Corporation, Autograph AGS-J). The adhesive strength at the start of the peeling 25 mm was ignored, and the average resistance (peel force) (N) from 25 mm to 50 mm thereafter was taken as the adhesive strength (N / 25 mm). The adhesive strength retention rate for the soft vinyl chloride resin sheet was calculated as (adhesive strength after 28 days at 40°C) / (adhesive strength after 1 day at 40°C). Adhesive strength retention rates of 50% or more were evaluated as ⊚, 25% or more as ◯, and less than 25% as ×. The number of test specimens was N=3, and the average evaluation results are shown in Tables 1 and 2.

[0081] [Table 1] [Table 2]

[0082] As can be seen from Table 1, HM1 to HM7 containing the acrylic block copolymer (X) and the tackifier (Y1) showed excellent compatibility, whereas HM8 and HM9 containing tackifiers (other than Y1 and Y2) were not uniformly compatible, indicating that the compositions of the present invention are pressure-sensitive adhesive compositions that can be applied by heating.

[0083] As can be seen from Table 1, HM1, HM6, and HM7 of the present invention and the commercially available product HM14 had holding power of more than 1 hour, whereas the comparative examples HM2 to HM13 and the commercially available product HM15 did not have sufficient holding power, indicating that an adhesive layer with sufficient cohesive strength can be obtained from the adhesive composition of the present invention.

[0084] From Table 1, HM1 to HM7 of the present invention had an adhesive strength of 15 N / 25 mm or more to the SUS-BA plate, whereas HM12, which did not contain the tackifier (Y), had an adhesive strength of 15 N / 25 mm or more to the SUS-BA plate. When used as an S-BA plate, it showed insufficient adhesion of 4N / 25mm or less.

[0085] As shown in Table 1, HM1 to HM7 of the present invention were shown to have an adhesive strength retention rate of 25% or more when tested against soft vinyl chloride resin at 40°C for 28 days, demonstrating that they are adhesive compositions that inhibit the decrease in adhesive strength over time when used against soft vinyl chloride resin. On the other hand, HM8 to HM13, which do not contain tackifier (Y1), and commercially available HM14 and HM15, showed an adhesion retention rate of less than 25% in the adhesion strength retention rate test, indicating that the adhesion rate to soft polyvinyl chloride significantly decreased over time. [Industrial Applicability]

[0086] The pressure-sensitive adhesive composition of the present invention can suppress deterioration over time in adhesive strength to soft vinyl chloride resins, and can therefore be used as a pressure-sensitive adhesive composition for a vinyl chloride resin adherend, or as a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer in a pressure-sensitive adhesive tape, pressure-sensitive adhesive film, pressure-sensitive adhesive sheet, etc., which have a vinyl chloride resin substrate. Examples of the pressure-sensitive adhesive composition include tape applications such as pressure-sensitive adhesive sheets, pressure-sensitive adhesive labels, protective films, and masking tapes; applications for fixing automobile interior materials, electronic components, etc.; applications for processing clothing and other textiles; applications for joining nonwoven fabrics and other fabric materials; and applications for joining plastic material parts together.

Claims

1. A pressure-sensitive adhesive composition, (1) The following formula: -[A1]-[B]-[A2]- (In the formula, A1 and A2 each represent 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; B represents a polymer block having a Tg below 20°C. An acrylic block copolymer (X) represented by the formula: (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, 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 90:65 to 10; The tackifier (Y) contains a tackifier (Y1) having an acid value of 161 mgKOH / g or more and 350 mgKOH / g or less and a softening point of 120°C or more. Pressure-sensitive adhesive composition.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the tackifier (Y1) has an acid value of 300 mg KOH / g or more and 350 mg KOH / g or less.

3. The pressure-sensitive adhesive composition according to claim 1 or 2, which does not contain a plasticizer.

4. 3. The pressure-sensitive adhesive composition according to claim 1 or 2, further comprising 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 100 mass % of the composition.

5. The pressure-sensitive adhesive composition according to claim 1 or 2, further comprising an antioxidant.

6. The pressure-sensitive adhesive composition according to claim 1 or 2, which is a hot-melt type, a solvent type, or an aqueous emulsion type.

7. the tackifier (Y) further contains a tackifier (Y2), The tackifier (Y2) is The acid value is less than 161 mg KOH / g and the softening point is 120°C or higher, or The acid value is 161 mgKOH / g or more and 350 mgKOH / g or less, and the softening point is less than 120°C. The pressure-sensitive adhesive composition according to claim 1 or 2.

8. The pressure-sensitive adhesive composition according to claim 7, which does not contain a plasticizer.

9. 8. The pressure-sensitive adhesive composition according to claim 7, further comprising 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 100 mass % of the composition.

10. The pressure-sensitive adhesive composition according to claim 7 , further comprising an antioxidant.

11. The pressure-sensitive adhesive composition according to claim 7, which is a hot-melt type, a solvent type, or an aqueous emulsion type.

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