Adhesives and adhesive sheets

Abstract

To provide an adhesive and an adhesive sheet using the same, which exhibits excellent low-temperature adhesion, cohesive force (holding power), and curved surface properties. [Solution] An adhesive comprising a styrene-based block copolymer (A), a tackifying resin (B) having a softening point of 100 to 160°C, and a liquid component (C) that is liquid at 30°C, wherein the tackifying resin (B) comprises two or more selected from the group consisting of rosin-based tackifying resins, terpene-based tackifying resins, and petroleum-based tackifying resins, and the liquid component (C) comprises one or more selected from the group consisting of tackifying resins, liquid rubber, and plasticizers.

Description

Technical Field

[0001] Embodiments of the present invention relate to an adhesive comprising a styrenic block copolymer (A), a tackifier resin (B) having a softening point of 100 to 160°C, and a liquid component (C) that is liquid at 30°C. The present invention also relates to an adhesive sheet provided with an adhesive layer formed from such an adhesive.

Background Art

[0002] An adhesive sheet having an adhesive layer formed from an adhesive is easy to handle, and thus is used in a wide range of fields such as labels, tapes, and adhesive applications. For example, a synthetic rubber-based adhesive in which a tackifier resin such as a petroleum resin is blended with a thermoplastic block copolymer such as a styrenic block copolymer as a base polymer has become widely popular because of its excellent adhesiveness, durability, etc.

[0003] On the other hand, it is known that synthetic rubber-based adhesives exhibit their adhesiveness by blending more tackifier resin than acrylic adhesives from the viewpoint of adhesiveness, and the adhesiveness at low temperatures is significantly deteriorated.

[0004] In Patent Document 1, a hot-melt adhesive containing at least one copolymer of styrene-butadiene block copolymer and styrene-isoprene block copolymer, a tackifier resin that is solid at 25°C, a tackifier resin that is liquid at 25°C, and oil is used as an adhesive for positioning absorbent articles. After storing the absorbent article in a wide temperature range (0 to 40°C), even when the absorbent article is used at that temperature (especially low or high temperature), the absorbent article does not shift from the position where it is adhered to the clothing, and even when used for a long time, there is no glue residue on the clothing when peeling from the clothing, and no destruction of the base material occurs during peeling.

[0005] Furthermore, Patent Document 2 discloses a hot-melt adhesive composition characterized by containing 100 parts by weight of a thermoplastic block copolymer containing at least one selected from the group consisting of styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, and styrene-butadiene / butylene-styrene block copolymer; 0.05 to 10 parts by weight of liquid rubber having carboxyl groups and / or carboxylic acid anhydride groups in the molecule; 30 to 150 parts by weight of naphthenic process oil or 20 to 120 parts by weight of paraffinic process oil; and a tackifying resin, which exhibits excellent creep resistance and thermal stability, as well as excellent adhesive strength even to a wet hydrophilic porous substrate. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2019 / 131972 [Patent Document 2] Japanese Patent Publication No. 2015-028119 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, although the adhesive described in Patent Document 1 has good re-peelability, it contains a small amount of tackifying resin compared to the styrene-based block copolymer, resulting in insufficient adhesion and cohesive force, and in particular, there was a problem with peeling at low temperatures (low-temperature adhesion).

[0008] Furthermore, the adhesive described in Patent Document 2 uses a petroleum-based tackifying resin, and while high adhesion to low-polarity substrates is expected, its adhesion to polar substrates is not mentioned. Our inventors' investigations revealed that its adhesion to polar substrates is insufficient.

[0009] The object of the present invention is to provide an adhesive that is excellent in low-temperature adhesion, cohesive force (holding force), and curved surface properties. [Means for solving the problem]

[0010] The inventors of this invention have diligently studied and completed the present invention in order to solve the above problems. Specifically, embodiments of the present invention relate to the following. However, the present invention is not limited to the embodiments described below and includes various embodiments.

[0011] The present invention relates to an adhesive comprising a styrene-based block copolymer (A), a tackifying resin (B) having a softening point of 100 to 160°C, and a liquid component (C) that is liquid at 30°C, wherein the tackifying resin (B) comprises two or more selected from the group consisting of rosin-based tackifying resins, terpene-based tackifying resins, and petroleum-based tackifying resins, and the liquid component (C) comprises one or more selected from the group consisting of tackifying resins (C1), liquid rubber (C2), and plasticizers (C3).

[0012] Furthermore, the present invention relates to the adhesive, characterized in that the styrene-based block copolymer (A) comprises at least one of styrene-butadiene-styrene block copolymer and styrene-isoprene-styrene block copolymer.

[0013] Furthermore, the present invention relates to an adhesive characterized in that the styrene-based block copolymer (A) comprises a styrene-based block copolymer in which the diblock ratio in the total mass of the styrene-based block copolymer is 40% by mass or more and less than 80% by mass and the styrene content is 14 to 40% by mass.

[0014] Furthermore, the present invention relates to an adhesive characterized in that the content of the tackifying resin (B) is 25 to 250 parts by mass per 100 parts by mass of the styrene-based block copolymer (A).

[0015] Furthermore, the present invention relates to the adhesive, characterized in that it has an adhesive strength of 5N or more to stainless steel in a -10℃ environment.

[0016] The present invention also relates to an adhesive sheet, characterized in that it has an adhesive layer made of the above-mentioned adhesive on at least one surface of a resin film.

Effects of the Invention

[0017] According to the present invention, it is possible to provide an adhesive excellent in low-temperature adhesiveness, cohesive force (holding power), and flexibility. Further, it is possible to provide an adhesive sheet using the above-mentioned adhesive.

Modes for Carrying Out the Invention

[0018] Terms are defined before the description of the present invention. As used herein, the "adhesive sheet" means having a base material and an adhesive layer made of the adhesive of the present invention.

[0019] As used herein, a numerical range specified using "~" means including the numerical values described before and after "~" as the range of the lower limit value and the upper limit value.

[0020] In this specification, the styrenic block copolymer (A) may be abbreviated as the block copolymer (A). Further, the tackifier resin (B) having a softening point of 100 to 160°C may be abbreviated as the tackifier resin (B), and the liquid component (C) that is liquid at 30°C may be abbreviated as the liquid component (C).

[0021] Hereinafter, embodiments of the present invention will be described in detail. However, the following description is an example (representative example) of the embodiments of the present invention, and the present invention is not limited to these contents as long as it does not exceed the gist thereof. <>

[0022] <> ≪Adhesive≫ An adhesive according to an embodiment of the present invention is an adhesive containing a styrenic block copolymer (A), a tackifier resin (B) having a softening point of 100 to 160°C, and a liquid component (C) that is liquid at 30°C.

[0023] <Block copolymer (A)> The styrenic block copolymer (A) is a copolymer of styrene and a conjugated diene compound and usually has thermoplasticity. The adhesive of the present invention can exhibit sufficient adhesive properties by containing the block copolymer (A).

[0024] In the present invention, the "block copolymer of styrene and a conjugated diene compound" refers to a block polymer having at least one hard segment (hereinafter also referred to as "segment H") composed of a polymer containing 50% by mass or more of polystyrene and at least one soft segment (hereinafter also referred to as "segment S") composed of a polymer containing 50% by mass or more of a conjugated diene compound. Representative structures of the block copolymer include a triblock copolymer (H-S-H structure) having segment H at both ends of segment S, a diblock copolymer (H-S structure) composed of one segment H and one segment S, and the like. Generally, the glass transition temperature of segment H is higher than that of segment S, and segment H is called a hard segment and segment S is called a soft segment.

[0025] Specific examples of the conjugated diene compound include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, etc., and they can be used alone or in combination of two or more. 1,3-butadiene and isoprene are preferred in terms of excellent solubility in organic solvents when used in solvent-based adhesives and high adhesive strength (low-temperature adhesion) even at low temperatures.

[0026] In the block copolymer (A), segment H (hard segment) preferably has a styrene content of 70% by mass or more, more preferably 90% by mass or more, and may be substantially 100% by mass, in 100% by mass of monomers constituting segment H. In the block copolymer, segment S (soft segment) preferably has a conjugated diene compound content of 70% by mass or more, more preferably 90% by mass or more, and may be substantially 100% by mass, in 100% by mass of monomers constituting segment S. With such a block copolymer (A), a more high-performance adhesive sheet can be realized.

[0027] The block copolymer (A) may be in the form of a diblock, a triblock, a radial, or a mixture thereof. In the triblock and radial forms, it is preferable that segments H are located at the ends of the polymer chains. Segments H located at the ends of the polymer chains readily aggregate to form rigid domains, thereby creating a pseudo-crosslinked structure that improves the cohesive force (holding force) of the adhesive. On the other hand, the diblock form has improved wettability due to the high mobility of segments S.

[0028] In the present invention, the block copolymer (A) preferably has a diblock ratio of 40% by mass or more and less than 80% by mass of the total mass of the block copolymer (A), and more preferably 40% by mass or more and less than 70% by mass. By keeping it within the above range, the cohesive force (holding force) can be maintained. Furthermore, a styrene-based block copolymer having at least one styrene block as a hard segment is preferred, and the styrene content (St content) is preferably 14 to 40% by mass. The "styrene content" of a styrene-based block copolymer refers to the mass ratio of the styrene component to the total mass of the block copolymer. A styrene content of 15 to 35% by mass is more preferable. By keeping the content within this range, it becomes easier to achieve both low-temperature adhesion (adhesion at low temperatures) and cohesive force (holding power). The above styrene content can be confirmed from the manufacturer's catalog value.

[0029] Examples of styrene-based block copolymers include styrene-isoprene-styrene block copolymer (also known as "SIS"), styrene-butadiene-styrene block copolymer (also known as "SBS"), hydrogenated styrene-isoprene-styrene block copolymer (also known as "SEPS"), and hydrogenated styrene-butadiene-styrene block copolymer (also known as "SEBS"). Among these, it is preferable to include at least one of SIS and SBS from the viewpoint of increasing adhesive strength. It is more preferable to include SIS, and even more preferable to include both SIS and SBS simultaneously.

[0030] By using two or more types of styrene-based block copolymers (A) in combination, compatibility with tackifying resins (B) can be improved, and high adhesive performance can be achieved. In particular, combining SBS and SIS can achieve a high level of balance between low-temperature adhesion and holding power.

[0031] <Tackifying resin (B)> The tackifying resin (B) has a softening point of 100 to 160°C and contains two or more selected from the group consisting of rosin-based tackifying resins, terpene-based tackifying resins, and petroleum-based tackifying resins. The inclusion of tackifying resin (B) makes it possible to exhibit excellent adhesive properties at room temperature, and by using two or more selected from the group consisting of rosin-based tackifying resins, terpene-based tackifying resins, and petroleum-based tackifying resins in combination, the adhesion of the adhesive to the substrate is improved, and low-temperature adhesiveness and curved surface flexibility can be enhanced. Of the rosin-based tackifying resins, terpene-based tackifying resins, and petroleum-based tackifying resins, it is preferable to include a rosin-based tackifying resin, and in particular, it is preferable to include both a rosin-based tackifying resin and a terpene-based tackifying resin simultaneously. It is preferable that the tackifying resin (B) contains 15% by mass or more of rosin-based tackifying resin, and more preferably 50% by mass or more. Furthermore, it is preferable that it contains 95% by mass or less, and more preferably 80% by mass or less. When the tackifying resin (B) contains a rosin-based tackifying resin, the total content of the terpene-based tackifying resin and / or petroleum-based tackifying resin used in combination is preferably 0.05 times or more, more preferably 1.2 times or more, relative to the amount of the rosin-based tackifying resin. Furthermore, it is preferably 6.5 times or less, and less than 5.8 times. If the total content is 0.05 times or more relative to the amount of the rosin-based tackifying resin, low-temperature adhesion can be improved, and if it is 6.5 times or less, tack can be ensured.

[0032] Examples of rosin-based tackifying resins include rosin esters obtained by esterifying unmodified rosin such as gum rosin, tall oil rosin, and wood rosin with alcohol, modified rosins such as disproportionated rosin, polymerized rosin, and hydrogenated rosin obtained by modifying unmodified rosin, modified rosin esters such as disproportionated rosin esters, polymerized rosin esters, and hydrogenated rosin esters obtained by further esterifying these modified rosins with alcohol, and rosinphenols obtained by adding phenol to unmodified rosin. Examples include Pine Crystal KE-359, Super Ester A-75, Super Ester A-100, Pencel D-125 (all manufactured by Arakawa Chemical Co., Ltd.), SYLVALITE RE80HP, SYLVALITE 85GB, SYLVALITE RE105L (all manufactured by Kraton Chemical Corporation), and Foralin 85E and Foralin 110 (both manufactured by Eastman Chemical Corporation).

[0033] Examples of terpene-based tackifying resins include polyterpene resins, terpene phenol resins, and hydrogenated terpene resins. Examples include YS Resin PX1000, YS Resin PX1250, YS Polystar T115, YS Polystar T130, Clearon P105 (all manufactured by Yasuhara Chemical Co., Ltd.), SYLVARES TR105, and SYLVARES TP2040 (both manufactured by Kraton Co., Ltd.).

[0034] Examples of petroleum-based tackifying resins include C9-type petroleum resins and C5 / C9-type petroleum resins, such as Alcon P-90, Alcon P-100, Alcon P-125, Alcon M-115, Alcon M-135 (all manufactured by Arakawa Chemical Co., Ltd.), and iMarb S-100, iMarb S-110, iMarb P-100 (all manufactured by Idemitsu Kosan Co., Ltd.).

[0035] The softening point of the tackifying resin (B) is more preferably 125 to 140°C, from the viewpoint of improving cohesive force (holding force) and low-temperature adhesiveness.

[0036] The content of the tackifying resin (B), which has a softening point of 100 to 160°C, is preferably 25 parts by mass or more, more preferably 80 parts by mass or more, per 100 parts by mass of block copolymer (A). It is also preferably 250 parts by mass or less, and more preferably 200 parts by mass or less. When the amount of tackifying resin (B) is 25 parts by mass or more, low-temperature adhesion can be improved, and when it is 250 parts by mass or less, tack can be ensured and adhesion to the adherend can be improved.

[0037] <Liquid component (C)> The liquid component (C) is a component that is liquid at 30°C and contains one or more selected from the group consisting of tackifying resin (C1), liquid rubber (C2), and plasticizer (C3). The inclusion of the liquid component (C) makes it possible to exhibit excellent adhesive properties at low temperatures. To further improve adhesive properties at low temperatures, it is preferable that the liquid component (C) contains two or more selected from the group consisting of tackifying resin (C1), liquid rubber (C2), and plasticizer (C3). In particular, by using tackifying resin (C1) and plasticizer (C3) in combination, it is possible to achieve both adhesion to curved surfaces without impairing the adhesive properties at low temperatures. The liquid component (C) content is preferably 50 to 100 parts by mass per 100 parts by mass of block copolymer (A). This amount of 50 to 100 parts by mass is preferable because it provides good adhesion at low temperatures without impairing cohesive force.

[0038] (Adhesion-enhancing resin (C1)) Examples of tackifying resins (C1) include SYLVALITE RE12, SYLVALITE RE25, SYLVALITE 2038, and SYLVALITE RE5S (all manufactured by Kraton Chemical Corporation), as well as Foralin 5020F (manufactured by Eastman Chemical Corporation), KE-364C (manufactured by Arakawa Chemical Corporation), YS Resin LP, YS Resin CP, and Daimaron (all manufactured by Yasuhara Chemical Corporation).

[0039] The softening point of the tackifying resin (C1) is preferably 40°C or lower. It is also acceptable for the resin to have no softening point. A softening point of 40°C or lower, or the absence of a softening point, ensures sufficient tackiness to the adhesive and sufficient adhesion at low temperatures. The softening point is defined as the value measured according to the softening point test method (ring-ball method) specified in JIS K 5902.

[0040] The content of the tackifying resin (C1) in the adhesive of the present invention is preferably 30 to 150 parts by mass, more preferably 35 parts by mass or more and less than 120 parts by mass, and even more preferably 40 parts by mass or more and less than 100 parts by mass, per 100 parts by mass of block copolymer (A). By blending 30 parts by mass or more of liquid tackifying resin, tack can be imparted to the adhesive, and by blending 120 parts by mass or less, cohesive force (holding force) can be ensured.

[0041] In the adhesive of the present invention, the total content of the tackifying resin (B), which has a softening point of 100 to 160°C, and the tackifying resin (C1), which is liquid at 30°C, is preferably 170 parts by mass or more, more preferably 180 parts by mass or more, per 100 parts by mass of block copolymer (A). Furthermore, it is preferably 320 parts by mass or less, and more preferably 300 parts by mass or less. When the total content of the tackifying resin (B) and the liquid tackifying resin (C1) is 170 parts by mass or more, low-temperature adhesion can be improved, and when it is 320 parts by mass or less, cohesive force (holding force) can be ensured.

[0042] In the adhesive of the present invention, if V1 is the content of tackifying resin (B) having a softening point of 100 to 160°C, and V2 is the content of tackifying resin (C1) that is liquid at 30°C, then V1 / V2 is preferably 0.5 or more, more preferably 1.0 or more. Furthermore, it is preferably 10.0 or less, and more preferably 5.0 or less. When V1 / V2 is 1.0 or more, tack can be imparted to the adhesive, and when it is 5.0 or less, cohesive force (holding force) can be ensured.

[0043] (Liquid rubber (C2)) Examples of liquid rubber (C2) include liquid rubber in which the main chain consists of an α-olefin homopolymer, ethylene-α-olefin copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, hydrogenated ethylene-propylene-diene copolymer, ethylene-butylene copolymer, polyisoprene, polyisobutene, polybutadiene, styrene-butadiene block copolymer, acrylonitrile-butadiene copolymer, or hydrogenated acrylonitrile-butadiene copolymer, and the main chain has polar groups at its ends or side chains. Liquid rubber (C2) may be used alone or in combination of two or more types. If a liquid rubber containing a carboxyl group or a carboxylic acid anhydride group in its molecule is used, its compatibility with the styrene-based block copolymer (A) will be poor, making it impossible to obtain sufficient cohesive force. Therefore, it is preferable to use a liquid rubber that does not contain a carboxyl group or a carboxylic acid anhydride group in its molecule.

[0044] In particular, the main chain of the liquid rubber (C2) is preferably made of polyisoprene, polybutadiene, or styrene-butadiene block copolymer, and more preferably of polyisoprene. Since such liquid rubber has excellent compatibility with the styrene-based block copolymer (A) described above, it can impart high cohesive force without reducing adhesion at low temperatures.

[0045] The number-average molecular weight (Mn) of the liquid rubber (C2) is preferably 1,000 to 150,000, and more preferably 2,000 or more and less than 50,000. If the number-average molecular weight (Mn) of the liquid rubber is too low, the cohesive force of the adhesive may decrease, potentially resulting in insufficient cohesive force and adhesion to curved surfaces. Conversely, if the number-average molecular weight (Mn) of the liquid rubber is too high, the compatibility with styrene-based block copolymers may be poor. In this invention, the number-average molecular weight (Mn) of liquid rubber (C2) refers to the measurement value obtained by converting it to standard polystyrene using a gel permeation chromatography analyzer.

[0046] Furthermore, commercially available liquid rubber (C2) can be used. Examples include LIR-30, LIR-50, and LIR-390 (all manufactured by Kuraray Co., Ltd.).

[0047] The liquid rubber (C2) content in the adhesive of the present invention is preferably 1 to 100 parts by mass, and more preferably 10 to 50 parts by mass, per 100 parts by weight of block copolymer (A). If the liquid rubber content is 1 part by mass or more, adhesion and tack at low temperatures can be improved, and if it is 100 parts by mass or less, cohesive force (holding force) can be ensured.

[0048] (Plasticizer (C3)) Examples of plasticizers (C3) include monoesters, diesters, and triesters of monobasic or polybasic acids having 1 to 18 carbon atoms and monofunctional alcohols having 1 to 18 carbon atoms; esters of unsaturated fatty acids or branched acids having 14 to 18 carbon atoms and dihydric or tetrahydric alcohols; esters of monobasic or polybasic acids having 1 to 18 carbon atoms and polyalkylene glycols; diesters, triesters, and tetraesters of hydroxy acids and monobasic acids or alcohols; fatty acid esters, phosphate esters, paraffinic oils, naphthenic oils, and aromatic oils in which the unsaturated portion has been epoxidized with peroxides, etc. Among these, esters of hydroxy acids and monobasic acids or alcohols, paraffinic oils, and naphthenic oils are preferred, with paraffinic oils being particularly preferred.

[0049] Examples of esters of monobasic or polybasic acids having 1 to 18 carbon atoms with monofunctional alcohols having 1 to 18 carbon atoms include 2-ethylhexyl oleate, isostearyl palmitate, isopropyl myristate, isostearyl laurate, dibutyl sebacate, diisodecyl adipate, tri(2-ethylhexyl) trimellitate, dimethyl phthalate, dibutyl phthalate, and di(2-ethylhexyl) phthalate.

[0050] The following are examples of C14-C18 unsaturated fatty acids and C2-C4 alcohols that constitute esters of C14-C18 unsaturated fatty acids or branched acids with C2-C4 functional alcohols. Examples of C14-C18 unsaturated fatty acids or branched acids include myristoleic acid, oleic acid, linoleic acid, linolenic acid, isopalmitic acid, and isostearic acid. Examples of C2-C4 functional alcohols include ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, and sorbitan.

[0051] Examples of esters of monobasic or polybasic acids having 1 to 18 carbon atoms with polyalkylene glycols include polyethylene glycol dihexylate, polyethylene glycol di-2-ethylhexylate, polyethylene glycol dilaurylate, polyethylene glycol dioleate, and methyl dipolyethylene glycol adipate.

[0052] Examples of esters of hydroxy acids with monobasic acids or alcohols include octyldodecyl lactate, diisostearyl malate, methyl 2-hydroxymyristate, 2-ethylhexyl 12-hydroxystearate, ethyl ricinoleate, methyl acetylricinoleate, butyl acetylricinoleate, triethyl citrate, tributyl acetylcitrate, and tri(2-ethylhexyl) acetylcitrate.

[0053] Examples of fatty acid esters in which the unsaturated portion is epoxidized with peroxides include epoxidized oils and fats such as epoxidized soybean oil, epoxidized linseed oil, and epoxidized cottonseed oil, as well as ester compounds of epoxidized unsaturated fatty acids having 8 to 18 carbon atoms and linear or branched alcohols having 1 to 6 carbon atoms.

[0054] Phosphate esters include, for example, ester compounds of phosphoric acid with linear or branched alcohols having 2 to 18 carbon atoms, specifically tributyl phosphate, 2-ethylhexyl diphenyl phosphate, oleyl acid phosphate, and ethylene glycol acid. Phosphates are examples.

[0055] Commercially available products were used for the paraffinic oils, naphthenic oils, and aromatic oils. It is possible. For example, Diana Fresia S32 and Diana Processo manufactured by Idemitsu Kosan Co., Ltd. Oil PW-90, DN Oil KP-68, Process Oil NS100, BP Chemicals Co. Enerper M1930 made by [company name], Kaydol made by Crompton, Esso made by [company name] Examples include Primol352.

[0056] The content of the plasticizer (C3) in the adhesive of the present invention is preferably 5 to 30 parts by mass, and more preferably 10 to 20 parts by mass, per 100 parts by mass of block copolymer (A). When the content of the plasticizer (C3) is 5 parts by mass or more, the adhesion between adhesive surfaces is enhanced by improving tack, and when it is 30 parts by mass or less, cohesive force (holding force) can be ensured.

[0057] <Other ingredients> An adhesive according to one embodiment of the present invention may further contain, in addition to the above components, a general curing agent, a tackifying resin other than the tackifying resin (B) having a softening point of 100 to 160°C and the tackifying resin (C1) that is liquid at 30°C, additives, etc., as long as it does not significantly degrade the adhesive properties. Examples of usable curing agents include isocyanate curing agents, epoxy curing agents, melamine curing agents, carbodiimide curing agents, oxazoline curing agents, and aziridine curing agents. Examples of usable additives include antioxidants, UV absorbers, light stabilizers, leveling agents, antistatic agents, release modifiers, fillers, colorants, anti-aging agents, and surfactants. Examples of antioxidants include phenolic antioxidants, sulfuric antioxidants, and phosphorusic antioxidants.

[0058] The adhesive of the present invention is preferably a one-component adhesive that does not contain a curing agent. Because it does not contain a curing agent, the block copolymers (A) do not crosslink by covalent bonding, which improves the adhesion between adhesive surfaces.

[0059] <Adhesive performance> The adhesive of the present invention possesses adhesive strength not only to polar and low-polarity substrates at room temperature, but also to polar and low-polarity substrates at low temperatures. However, in terms of low-temperature adhesion, it is preferable that the adhesive strength to stainless steel (hereinafter referred to as SUS) at a -10°C environment is 5N or higher. If the adhesive strength to SUS at a -10°C environment is 5N or higher, it will not peel off even in low-temperature environments, making it suitable for applications requiring strong adhesion. A more preferable adhesive strength is 10N or higher.

[0060] Adhesive Sheet Another embodiment of the present invention relates to an adhesive sheet. The adhesive sheet has an adhesive layer formed from the adhesive of the above embodiment on at least one surface of a resin film. That is, the adhesive sheet has a resin film and an adhesive layer composed of the adhesive of the above embodiment. In one embodiment, a release sheet may be provided on the other surface of the adhesive layer that is not in contact with the resin film to prevent the adhesion of foreign matter. Typically, the adhesive layer is protected by the release sheet until immediately before use.

[0061] The substrate may be a laminate made of a resin film or the like. The surface of the substrate that comes into contact with the adhesive layer may be subjected to a simple bonding treatment to improve adhesion. For example, a dry treatment such as corona discharge treatment or a wet treatment such as anchor coating can be applied.

[0062] In one embodiment, the plastic material constituting the base material is, for example, polyethylene Examples include ester resins such as terephthalate (PET) and polyethylene naphthalate (PEN); olefin resins such as polyethylene (PE), polypropylene (PP), and cycloolefin polymer (COP); vinyl resins such as polyvinyl chloride (PVC); amide resins such as nylon 66; and urethane resins (including foams).

[0063] Suitable methods for molding the above-mentioned resin into a base material (sheet) include extrusion molding, in which the sheet extruded using a T-die in an extruder is cooled and solidified with a cast roll, and molding using an inflation molding machine.

[0064] The thickness of the substrate can generally be 10 to 300 μm. When using a polyurethane sheet (including foam) as the substrate, the thickness of the substrate (sheet) can generally be 20 to 50,000 μm.

[0065] The release sheet may be a release sheet having a known configuration. For example, a release sheet can be used that has been treated with a known release agent, such as a silicone-based release agent, on the surface of a sheet-like material such as plastic or paper.

[0066] One method for manufacturing an adhesive sheet is to apply the adhesive according to the above embodiment to the surface or both sides of a substrate to form a coating layer, and then, if necessary, dry and cure the coating layer to form an adhesive layer. The adhesive may be dissolved in an organic solvent and applied, or it may be applied by thermal melting without a solvent. The heating and drying temperature may generally be 60 to 200°C. The thickness of the adhesive layer may generally be 1 to 200 μm.

[0067] Methods of coating by dissolving in an organic solvent include applicators, gravure coaters, die coaters, lip coaters, comma coaters, knife coaters, reverse coaters, and spin coaters, while methods of coating by thermal melting include applicators, gravure coaters, roll coaters, die coaters, and slit coaters.

[0068] Another method, separate from the above, involves applying the adhesive of the above embodiment to the surface of a release sheet to form a coating layer, then drying and curing the coating layer as needed to form an adhesive layer, and finally bonding the substrate to the exposed surface of the adhesive layer. In this method, if a release sheet is bonded to the adhesive layer instead of the substrate, a cast adhesive sheet having a release sheet / adhesive layer / release sheet configuration is obtained. [Examples]

[0069] The embodiments of the present invention will be described below with reference to examples. Needless to say, the examples are not limited to those described below. The "%" mentioned below refers to "mass percent". Furthermore, the amounts of raw materials (excluding solvents) listed in the examples and tables below are calculated on a non-volatile content basis.

[0070] The materials listed in Tables 1-7 are as follows: <Block copolymer (A)> Quintac(R) 3620: SIS, St content 14%, Diblock ratio 12%, manufactured by Nippon Zeon Corporation. Quintac(R) 3433N:SIS, St content 16%, Diblock ratio 56%, manufactured by Nippon Zeon Corporation. Clayton D1119: SIS, St content 22%, Ziploc ratio 66%, manufactured by Clayton. Clayton D1101: SBS, St content 33%, Ziploc ratio 16%, manufactured by Clayton. Clayton D1118: SBS, St content 30%, Ziploc ratio 78%, manufactured by Clayton. Clayton D1155: SBS, St content 40%, Zibloc ratio 0%, manufactured by Clayton. Kraton D1162: SIS, St content 43%, Ziploc ratio 0%, manufactured by Kraton. Kraton G1726: SEBS, St content 30%, Ziploc ratio 70%, manufactured by Kraton.

[0071] <Tackifying resin (B)> [Tackifying resin (B) with a softening point of 100-160°C] Super Ester A-100: Rosin ester, softening point 100°C, manufactured by Arakawa Chemical Co., Ltd. Super Ester A-125: Rosin ester, softening point 125°C, manufactured by Arakawa Chemical Co., Ltd. Pencel D-135: Polymerized rosin ester, softening point 135°C, manufactured by Arakawa Chemical Co., Ltd. Pencel D-160: Polymerized rosin ester, softening point 160°C, manufactured by Arakawa Chemical Co., Ltd. YS Resin PX1000: Polyterpene resin, softening point 100°C, manufactured by Yasuhara Chemical Co., Ltd. iMarb P-100: Petroleum-based resin, softening point 100℃, manufactured by Idemitsu Kosan Co., Ltd.

[0072] <Liquid component (C)> Tackifying resin (C1) Foralin 5020F: Hydrogenated rosin ester, no softening point, manufactured by Eastman Chemical Company. Liquid rubber (C2) LIR-390: Polyisoprene, manufactured by Kuraray Co., Ltd. LIR-410: Polyisoprene, containing carboxyl groups, manufactured by Kuraray Co., Ltd. Plasticizer (C3) N-90: Diana Process Oil N-90, naphthenic oil, manufactured by Idemitsu Kosan Co., Ltd.

[0073] <Other ingredients> Super Ester A-75: Softening point 75°C, manufactured by Arakawa Chemical Co., Ltd. Pencel KK: Softening point 165℃, manufactured by Arakawa Chemical Co., Ltd.

[0074] [Examples of adhesive and adhesive sheet manufacturing] (Example 1) To a 140 ml mayonnaise bottle, 100 parts Quintac(R) 3433N, 5 parts Super Ester A-100, 5 parts YS Resin PX1000, 30 parts Foralin 5020F, and 10 parts N-90 were added. To toluene was then added to dissolve the mixture until the non-volatile content reached 40%, obtaining an adhesive solution. The prepared adhesive solution was applied to a 50 μm thick polyethylene terephthalate (PET) sheet using an applicator to a dry thickness of 20 μm. The adhesive layer was then dried in a hot air oven at 100°C for 2 minutes. After drying, the layer was laminated to a 38 μm thick release sheet (made of PET) to obtain an adhesive sheet.

[0075] (Examples 2-87, Comparative Examples 1-6) The materials and proportions (parts by mass) of Example 1 were changed as shown in Tables 1 to 7, and otherwise the procedure was the same as in Example 1 to obtain the adhesives and adhesive sheets of Examples 2 to 87 and Comparative Examples 1 to 6, respectively.

[0076] The adhesive strength at room temperature and low temperature was measured for adhesive sheets manufactured using the adhesives obtained in Examples 1 to 87 and Comparative Examples 1 to 6, using the method described below.

[0077] (Measurement of adhesive strength at room temperature) The obtained adhesive sheet was cut to a size of 25 mm in width and 150 mm in length. Next, under conditions of 23°C and 50% relative humidity (50% RH), the release sheet was peeled off the adhesive sheet, and the exposed adhesive layer was attached to a stainless steel (SUS) plate and a polypropylene (PP) plate, respectively, and measured samples were prepared by passing them back and forth once using a 2 kg roll. After storing these measured samples under conditions of 23°C and 50% RH for 24 hours, the peel strength was measured using a tensile testing machine (Orientec Co., Ltd. "Tensilon") under conditions of a peel speed of 300 mm / min and a peel angle of 180°.

[0078] (Measurement of low-temperature adhesion) The obtained adhesive sheet was cut to a size of 25 mm in width and 150 mm in length. Next, under conditions of 23°C and 50% RH, the release sheet was peeled off the adhesive sheet, and the exposed adhesive layer was attached to a stainless steel (SUS) plate and a polypropylene (PP) plate, respectively, and measured samples were prepared by passing them back and forth once with a 2 kg roll. After storing these measured samples at -10°C for 24 hours, the peel strength was measured using a tensile testing machine (Orientec Co., Ltd. "Tensilon") under conditions of a peel speed of 300 mm / min and a peel angle of 180°.

[0079] [Evaluation of adhesive sheets] For adhesive sheets manufactured using the adhesives obtained in Examples 1-87 and Comparative Examples 1-6, measurement samples were prepared according to the following method, and various evaluations were performed. The results are shown in Tables 1-7.

[0080] (1) 40℃ holding power The obtained adhesive sheet was cut to a size of 25 mm in width and 150 mm in length. The release sheet was peeled off the cut adhesive sheet, and the exposed adhesive layer was attached to a 25 mm wide and 25 mm long portion of the lower end of a 30 mm wide and 150 mm long stainless steel plate. A measurement sample was prepared by rolling it back and forth once with a 2 kg roll. After storing this measurement sample in a 40°C environment for 20 minutes, a 1 kg weight was applied to the lower end of the adhesive sheet, and the holding force was measured by leaving it for 70,000 seconds. For evaluation, the length by which the upper end of the adhesive surface of the adhesive sheet shifted downward from its original position was measured. Evaluation Criteria ◎: No misalignment, or misalignment of less than 0.5 mm (Excellent) ○: The displacement is between 0.5 mm and less than 3.0 mm (good) △: The misalignment is 3.0 mm or more (usable) ×: Adhesive sheet falls off SUS plate (unusable)

[0081] (2) Curved surface The obtained adhesive sheet was cut to a size of 15 mm in width and 25 mm in length. The release sheet was peeled off the cut adhesive sheet, and the exposed adhesive layer was attached to a 10 mm diameter polypropylene (PP) rod parallel to the circumferential direction of the adhesive sheet in the longitudinal direction to prepare a measurement sample. This measurement sample was stored in a 23°C environment for 20 minutes, and then kept in a 40°C environment for 24 hours. The evaluation was performed by measuring the length at which the edge of the adhesive surface peeled off. Evaluation Criteria ◎: No peeling, or peeled length is less than 0.1 mm (Excellent) ○: Peeled length is 0.1 mm or more but less than 0.5 mm (good) △: Peeled length is 0.5mm or more but less than 1.0mm (usable) ×: Peeled length is 1.0 mm or longer (not usable)

[0082] (3) Ball tuck The obtained adhesive sheet was prepared to a size of 25 mm wide and 250 mm long. The release sheet was peeled off the adhesive sheet and fixed with the adhesive side facing up to an inclined plate at a 30-degree angle. A PET film for the run-up was attached to the top, and a steel ball (1 / 32 to 32 / 32 inch) was rolled onto the sample, which had a 10 cm run-up and a 10 cm adhesive surface. The diameter number of the ball that stopped near the center of the adhesive surface was recorded. The measurements were performed in an atmosphere of 23°C and 50% relative humidity. Evaluation criteria under conditions of 23°C and 50% relative humidity. ◎: Ball diameter number 15 or higher (Excellent) ○: Ball diameter number 10-14 (good) △: Ball diameter numbers 3-9 (usable) ×: Ball diameter number is 2 or less (not usable)

[0083] (4) Low-temperature adhesion The obtained adhesive sheet was cut to a size of 25 mm in width and 150 mm in length. Next, under conditions of 23°C and 50% RH, the release sheet was peeled off the adhesive sheet, and the exposed adhesive layer was attached to a stainless steel (SUS) plate. A measurement sample was prepared by passing it back and forth once using a 2 kg roll. This measurement sample was stored at -10°C for 24 hours, and then its appearance was observed. Evaluation was based on checking for the presence or absence of lifting or peeling. ○: No lifting or peeling. (Good condition) △: There is lifting or peeling of 5mm or less at the edges. (Usable) ×: Lifting / peeling exceeding 5mm. .....(Unusable)

[0084] [Table 1]

[0085] [Table 2]

[0086] [Table 3]

[0087] [Table 4]

[0088] [Table 5]

[0089] [Table 6]

[0090] [Table 7]

[0091] As shown in Tables 1-6, the adhesive of the present invention (examples) was found to fully satisfy the adhesive properties by containing a specific styrene-based block copolymer (A), a tackifying resin (B) with a softening point of 100-160°C, and a liquid component (C) that is liquid at 30°C.

[0092] On the other hand, as shown in Table 7, it was difficult to obtain the desired adhesive properties with the adhesives of the comparative examples. Comparative Example 1 used only one type of tackifying resin (B). Comparative Example 2 did not use tackifying resin (B), and used only block copolymer (A) and liquid component (C). Comparative Example 4, like Comparative Example 1, used only one type of tackifying resin (B). Comparative Examples 3 and 5 used tackifying resins with a softening point other than 100-160°C. Comparative Example 6 did not use liquid component (C). From the above, it can be concluded that the adhesive of the present invention can exhibit desired adhesive properties by including a styrene-based block copolymer (A), a tackifying resin (B), and liquid rubber (C) or plasticizer (D).

Claims

1. An adhesive comprising a styrene-based block copolymer (A), a tackifying resin (B) having a softening point of 100 to 160°C, and a liquid component (C) that is liquid at 30°C, The tackifying resin (B) comprises two or more types selected from the group consisting of rosin-based tackifying resins, terpene-based tackifying resins, and petroleum-based tackifying resins. The liquid component (C) is characterized by containing one or more selected from the group consisting of tackifying resin (C1), liquid rubber (C2), and plasticizer (C3).

2. The adhesive according to claim 1, characterized in that the styrene-based block copolymer (A) comprises at least one of styrene-butadiene-styrene block copolymer and styrene-isoprene-styrene block copolymer.

3. The adhesive according to claim 1, characterized in that the styrene-based block copolymer (A) comprises a styrene-based block copolymer in which the diblock ratio in the total mass of the styrene-based block copolymer is 40% by mass or more and less than 80% by mass and the styrene content is 14% to 40% by mass.

4. The adhesive according to claim 1, characterized in that the content of the tackifying resin (B) is 25 to 250 parts by mass per 100 parts by mass of the styrene-based block copolymer (A).

5. The adhesive according to claim 1, characterized in that it has an adhesive strength of 5N or more to stainless steel in a -10°C environment.

6. An adhesive sheet characterized by having an adhesive layer made of the adhesive described in any one of claims 1 to 5 on at least one surface of a resin film.

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