Adhesive composition and adhesive tape

Abstract

To provide an acrylic adhesive composition that can yield an adhesive tape with excellent self-adhesiveness and terminal peeling resistance.SOLUTION: A form of the present invention comprises an ABA-type triblock copolymer (a) that includes a segment A predominantly composed of methacrylate and a segment B predominantly composed of acrylate, an ABA-type triblock copolymer (b) that includes a segment A predominantly composed of methacrylate and a segment B predominantly composed of acrylate, an AB-type diblock copolymer (c) that includes a segment A predominantly composed of methacrylate and a segment B predominantly composed of acrylate, and a tackifier resin (d) with a softening point of 120°C or higher. When the total amount of triblock copolymer (a) and triblock copolymer (b) is 100 pts.mass, the content of the tackifier resin (d) is 45 pts.mass or more and 105 pts.mass or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an adhesive composition and an adhesive tape.

Background Art

[0002] (Meth)acrylate-based monomers-containing acrylic adhesives are excellent in weather resistance, transparency, heat resistance, solvent resistance, etc., and also have the advantage that the adhesive strength can be easily controlled by changing the composition of the constituent monomers. Therefore, in recent years, extensive research has been conducted (for example, see Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, even if the basic properties required for an adhesive tape of the acrylic adhesive composition according to the prior art are at a practical level, there are cases where sufficient performance is not achieved depending on the usage method.

[0005] In particular, when such an acrylic adhesive composition is applied to a label tape used for applications such as winding around thin objects (for example, cables, tools such as drivers and wrenches), the self-adhesive property is not sufficient, and there are cases where the peel resistance at the end during winding is not sufficient, such as peeling occurring at the end.

[0006] Therefore, the present invention has been made in view of the above problems, and aims to provide an acrylic adhesive composition that can obtain an adhesive tape with excellent self-adhesion and resistance to peeling at the ends. [Means for solving the problem]

[0007] As a result of diligent research, the inventors of this invention have discovered that the above problems can be solved by using a predetermined adhesive composition, and have completed the present invention.

[0008] In other words, one embodiment of the present invention is ABA-type triblock copolymer (a) consisting of segment A mainly composed of methacrylate ester and segment B mainly composed of acrylic acid ester, ABA-type triblock copolymer (b) consisting of segment A mainly composed of methacrylate ester and segment B mainly composed of acrylic acid ester, A diblock copolymer of type AB (c) consisting of segment A mainly composed of methacrylate ester and segment B mainly composed of acrylic acid ester, It contains a tackifying resin (d) with a softening point of 120°C or higher, The aforementioned triblock copolymer (a) does not contain 2-ethylhexyl acrylate as a constituent monomer of segment B. The triblock copolymer (b) has 2-ethylhexyl acrylate as a constituent monomer of segment B. When the total amount of the triblock copolymer (a) and the triblock copolymer (b) is 100 parts by mass, the content of the triblock copolymer (b) is 5 parts by mass or more and 55 parts by mass or less. When the total amount of the triblock copolymer (a) and the triblock copolymer (b) is 100 parts by mass, the content of the diblock copolymer (c) is 60 parts by mass or more and 120 parts by mass or less. The adhesive composition is such that when the total amount of the triblock copolymer (a) and the triblock copolymer (b) is 100 parts by mass, the content of the tackifying resin (d) is 45 parts by mass or more and 105 parts by mass or less.

[0009] It is preferable that the content of plasticizer (e) is 5 parts by mass or less when the total amount of the triblock copolymer (a) and the triblock copolymer (b) is 100 parts by mass.

[0010] Another embodiment of the present invention is, The adhesive tape comprises a base material and an adhesive layer formed of the adhesive composition, provided on at least one surface of the base material. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an acrylic adhesive composition that can be used to obtain an adhesive tape with excellent self-adhesion and resistance to peeling at the ends. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 shows the method for evaluating terminal peel resistance in the embodiment. [Modes for carrying out the invention]

[0013] Preferred embodiments of the present invention will be described in detail below.

[0014] The adhesive composition relating to this disclosure will be described in the following order. 1. Composition of the adhesive composition 1-1 Triblock copolymer (a) 1-2 Triblock copolymer (b) 1-3 Diblock copolymer (c) 1-4 Tackifying resin (d) 1-5 Optional components 2. Forms of adhesive compositions 3. Uses of adhesive compositions

[0015] Hereinafter, the weight average molecular weight shall be the value determined from the polystyrene equivalent molecular weight measured by gel permeation chromatography (GPC). Hereinafter, when a plurality of upper limit values and a plurality of lower limit values are separately described, it shall be assumed that all numerical ranges that can be freely combined and set from these upper limit values and lower limit values are described. Hereinafter, unless otherwise specified, various measurements shall be assumed to have been carried out with the environmental temperature being room temperature (for example, 25°C). Hereinafter, unless otherwise specified, the content, blending amount, etc. of each component shall indicate the amount based on the components excluding volatile components (solid content). Hereinafter, when a certain compound is described, its isomers shall also be assumed to be described simultaneously.

[0016] <<<Composition of the Adhesive Composition>>> The adhesive composition according to the present disclosure contains at least two types of ABA-type triblock copolymers (triblock copolymer (a), triblock copolymer (b)) and an AB-type diblock copolymer (c), and further contains a tackifying resin (d) having a softening point of 120°C or higher. The triblock copolymer (a), the triblock copolymer (b), and the diblock copolymer (c) constitute the base polymer.

[0017] The adhesive composition according to the present disclosure may contain other components (optional components).

[0018] Hereinafter, each component in the adhesive composition according to the present disclosure will be described in order.

[0019] <<Triblock Copolymer (a)>> The triblock copolymer (a) is an ABA-type triblock copolymer composed of a segment A mainly composed of a methacrylate and a segment B mainly composed of an acrylate.

[0020] Furthermore, the triblock copolymer (a) does not contain 2-ethylhexyl acrylate as a constituent monomer of segment B.

[0021] Here, the term "segment" as used in this disclosure refers to the structural units that constitute each block in a triblock copolymer. For example, in the case of an ABA-type triblock copolymer in which structural units (polymer or oligomer) A derived from monomer a, structural units (polymer or oligomer) B derived from monomer b, and structural units (polymer or oligomer) A derived from monomer a are bonded together in sequence, structural units A and B become segments A and B, respectively. The same explanation applies to the ABA-type triblock copolymer (b) and the AB-type diblock copolymer (c) described later.

[0022] <Segment A of triblock copolymer (a)> The segment A of the triblock copolymer (a) is not particularly limited as long as it mainly consists of methacrylic acid ester as its constituent monomer.

[0023] Here, in the case of monomers that constitute a polymer (constituent monomers), a monomer is said to be "the main component of the constituent monomers" to mean that the composition ratio of that monomer to the total amount of constituent monomers is preferably 50% by mass or more, 80% by mass or more, or 90% by mass or more.

[0024] Examples of methacrylate esters that constitute segment A include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, 1-methylcyclohexyl methacrylate, 2-methylcyclohexyl methacrylate, 3-methylcyclohexyl methacrylate, 4-methylcyclohexyl methacrylate, and 2-phenoxyethyl methacrylate. Examples include methyl methacrylate, 2-methoxyethyl methacrylate, 2-(N,N-dimethylamino)ethyl methacrylate, trifluoromethyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, stearyl methacrylate, 2-methoxypentyl methacrylate, 2-(N,N-dimethylamino)pentyl methacrylate, perfluoropentyl methacrylate, and 2-trimethoxysilylpentyl methacrylate.

[0025] As the main constituent monomer of segment A, it is preferable to use esters of methacrylic acid and alcohols with 3 or fewer carbon atoms, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and isopropyl methacrylate. Including such monomers in the constituent monomers can improve the adhesive properties.

[0026] The constituent monomers of segment A may include monomers other than methacrylate esters.

[0027] Other monomers that can be used as constituent monomers for segment A, besides methacrylate esters, include, for example, Methacrylamides such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-isopropylmethacrylamide, N,N-dimethylmethacrylamide, and N,N-diethylmethacrylamide, Acrylamides such as acrylamide, N-methylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide, Vinyl monomers having carboxyl groups such as methacrylic acid, acrylic acid, crotonic acid, maleic acid, maleic anhydride, and fumaric acid. Aromatic vinyl monomers such as styrene, α-methylstyrene, and p-methylstyrene, Conjugated diene monomers such as butadiene and isoprene, Ethylene, propylene and other olefins, Lactones such as ε-caprolactone and valerolactone These are some examples.

[0028] Segment A constitutes, for example, a hard segment of the triblock copolymer (a).

[0029] <Segment B of triblock copolymer (a)> The segment B of the triblock copolymer (a) is not particularly limited as long as it mainly consists of acrylic acid esters as constituent monomers.

[0030] Examples of acrylic acid esters that constitute segment B include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, tridecyl acrylate, stearyl acrylate, cyclohexyl acrylate, isobornyl acrylate, 2-methoxyethyl acrylate, 2-(N,N-dimethylamino)ethyl acrylate, trifluoromethyl acrylate, trimethoxysilylpropyl acrylate, lauryl acrylate, 2-methylbutyl acrylate, 4-methyl-2-pentyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxypropyl acrylate.

[0031] Other monomers that can be used as constituent monomers for segment B, besides acrylic acid esters, include, for example, Alkyl methacrylates, including methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, and methacrylate esters, which are constituent monomers of segment A as described above. Methacrylamides such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-isopropylmethacrylamide, N,N-dimethylmethacrylamide, and N,N-diethylmethacrylamide, Acrylamides such as acrylamide, N-methylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide, Vinyl monomers having carboxyl groups such as methacrylic acid, acrylic acid, crotonic acid, maleic acid, maleic anhydride, and fumaric acid. Aromatic vinyl monomers such as styrene, o-methylstyrene, and p-methylstyrene, Conjugated diene monomers such as butadiene and isoprene, Ethylene, propylene and other olefins, Lactones such as ε-caprolactone and valerolactone These are some examples.

[0032] Segment B, for example, constitutes a soft segment of the triblock copolymer (a).

[0033] <Weight-average molecular weight of triblock copolymer (a)> The weight-average molecular weight of the triblock copolymer (a) is preferably 60,000 or more, 80,000 or more, 100,000 or more, or 150,000 or more, and also preferably 1,000,000 or less, 800,000 or less, or 600,000 or less. By setting the weight-average molecular weight of the triblock copolymer (a) within this range, the adhesive properties of the adhesive composition can be improved.

[0034] <Content of segment A in triblock copolymer (a)> The content of segment A in the triblock copolymer (a) is preferably 5 to 30% by mass, more preferably 5 to 25% by mass, and particularly preferably 10 to 20% by mass, based on the total mass of the triblock copolymer (a).

[0035] <Method for synthesizing / obtaining triblock copolymer (a)> The triblock copolymer (a) relating to this disclosure may be synthesized by polymerizing each constituent monomer, or a commercially available product may be used.

[0036] The polymerization method for the triblock copolymer (a) is not particularly limited, and known methods can be used, such as anionic polymerization or atom transfer radical polymerization (ATRP).

[0037] Examples of anionic polymerization methods include methods in which anionic polymerization is carried out in the presence of mineral salts such as alkali metal or alkaline earth metal salts using an organoalkali metal compound as a polymerization initiator, methods in which anionic polymerization is carried out in the presence of organoaluminum compounds using an organoalkali metal compound as a polymerization initiator, and methods in which anionic polymerization is carried out using an organorare earth metal complex as a polymerization initiator. Examples of ATRPs include methods of polymerization using organic halides or sulfonyl halogenated compounds as initiators in the presence of transition metal compounds and nitrogen-containing compounds.

[0038] Examples of commercially available triblock copolymers (a) include the "Clarity® series" manufactured by Kuraray Co., Ltd.

[0039] <<Triblock copolymer (b)>> Triblock copolymer (b), like triblock copolymer (a), is an ABA-type triblock copolymer consisting of segment A, which is mainly composed of methacrylate ester, and segment B, which is mainly composed of acrylic acid ester.

[0040] However, the triblock copolymer (b) has 2-ethylhexyl acrylate as a constituent monomer of segment B.

[0041] Thus, triblock copolymer (a) does not have 2-ethylhexyl acrylate as a constituent monomer of segment B, while triblock copolymer (b) has 2-ethylhexyl acrylate as a constituent monomer of segment B, thus having different structures from triblock copolymer (a) and triblock copolymer (b).

[0042] <Segment A of triblock copolymer (b)> Since segment A of triblock copolymer (b) is the same as segment A of triblock copolymer (a) described above, a detailed explanation is omitted here.

[0043] Segment A of triblock copolymer (a) and segment A of triblock copolymer (b) may be the same or different. Considering the compatibility between triblock copolymer (a) and triblock copolymer (b), it is preferable that segment A of both be the same.

[0044] Segment A constitutes, for example, a hard segment of the triblock copolymer (b).

[0045] <Segment B of triblock copolymer (b)> As mentioned above, segment B of the triblock copolymer (b) has 2-ethylhexyl acrylate as a constituent monomer.

[0046] Segment B of the triblock copolymer (b) may have constituent monomers other than 2-ethylhexyl acrylate.

[0047] Other constituent monomers besides 2-ethylhexyl acrylate can be those that can be used as constituent monomers for segment B of the triblock copolymer (a).

[0048] As a constituent monomer other than 2-ethylhexyl acrylate, it is preferable to use n-butyl acrylate because it can improve compatibility with triblock copolymer (a). Specifically, the constituent monomers of segment B of triblock copolymer (b) are preferably n-butyl acrylate and 2-ethylhexyl acrylate.

[0049] In segment B of the triblock copolymer (b), the mixing ratio of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) is preferably 95:5 to 0:100, more preferably 75:25 to 5:95, and even more preferably 60:40 to 5:95 (mass ratio) of BA:2EHA. By setting the mixing ratio of BA to 2EHA within this range, the adhesive properties of the adhesive composition can be improved.

[0050] The constituent monomers other than 2-ethylhexyl acrylate in segment B of triblock copolymer (b) and the constituent monomers in segment B of triblock copolymer (a) may be the same or different. Considering the compatibility between triblock copolymer (a) and triblock copolymer (b), it is preferable that the constituent monomers of both be the same.

[0051] Segment B, for example, constitutes a soft segment of the triblock copolymer (b).

[0052] <Weight-average molecular weight of triblock copolymer (b)> The weight-average molecular weight of the triblock copolymer (b) is preferably 30,000 or more, or 50,000 or more, and more preferably 800,000 or less, or 600,000 or less. By setting the weight-average molecular weight of the triblock copolymer (b) within this range, the adhesive properties of the adhesive composition can be improved.

[0053] <Content of segment A of triblock copolymer (b)> The content of segment A in the triblock copolymer (b) is preferably 10 to 40% by mass, and more preferably 15 to 30% by mass, based on the total mass of the triblock copolymer (b).

[0054] <Method for synthesizing / obtaining triblock copolymer (b)> The triblock copolymer (b) relating to this disclosure may be synthesized by polymerizing each constituent monomer, or a commercially available product may be used.

[0055] The polymerization method for triblock copolymer (b) is not particularly limited, and the same method as for triblock copolymer (a) can be applied.

[0056] Examples of commercially available triblock copolymers (b) include the "Clarity® series" manufactured by Kuraray Co., Ltd.

[0057] <<Diblock copolymer (c)>> The diblock copolymer (c) is an AB-type diblock copolymer consisting of segment A, which is mainly composed of methacrylic acid ester, and segment B, which is mainly composed of acrylic acid ester.

[0058] By using such a diblock copolymer, compatibility with triblock copolymer (a) and triblock copolymer (b) can be improved, thereby enhancing the self-adhesion and end-peel resistance of the adhesive composition.

[0059] <Segment A of diblock copolymer (c)> As the constituent monomers of segment A of the diblock copolymer (c), those disclosed as constituent monomers of segment A in the triblock copolymer (a) can be used.

[0060] The constituent monomers of segment A in the diblock copolymer (c) and segment A in the triblock copolymer (a) may be the same or different. By making these constituent monomers the same, the compatibility of each component can be further enhanced.

[0061] Segment A constitutes, for example, a hard segment of a triblock copolymer (c).

[0062] <Segment B of diblock copolymer (c)> As the constituent monomer of segment B of the diblock copolymer (c), those disclosed as constituent monomers of segment B in the triblock copolymer (a) can be used.

[0063] The constituent monomers of segment B in the diblock copolymer (c) and segment B in the triblock copolymer (a) may be the same or different. By making these constituent monomers the same, the compatibility of each component can be further enhanced.

[0064] Segment B, for example, constitutes a soft segment of the triblock copolymer (c).

[0065] <Weight-average molecular weight of diblock copolymer (c)> The weight-average molecular weight of the diblock copolymer (c) is preferably 30,000 or more, 40,000 or more, or 50,000 or more, and also preferably 1,000,000 or less, 800,000 or less, or 600,000 or less. By setting the weight-average molecular weight of the diblock copolymer (c) within this range, the adhesive properties of the adhesive composition can be improved.

[0066] <Content of segment A of diblock copolymer (c)> The content of segment A in the diblock copolymer (c) is preferably 5 to 30% by mass, more preferably 5 to 20% by mass, and particularly preferably 5 to 15% by mass, based on the total mass of the diblock copolymer (c).

[0067] <Method for synthesizing / obtaining diblock copolymer (c)> The diblock copolymer (c) relating to this disclosure may be synthesized by polymerizing each constituent monomer, or a commercially available product may be used.

[0068] The polymerization method for the diblock copolymer (c) is not particularly limited, and the same method as for the triblock copolymer (a) can be applied.

[0069] Examples of commercially available diblock copolymers (c) include the "Clarity® series" manufactured by Kuraray Co., Ltd.

[0070] <<Tackifying resin (d)>> The adhesive composition according to this disclosure preferably contains a tackifying resin (d) having a softening point of 120°C or higher.

[0071] The tackifying resin (d) is not particularly limited, but it is preferably a resin that is compatible with triblock copolymer (a) and triblock copolymer (b) so that it can form a polymer blend with triblock copolymer (a) and triblock copolymer (b). More specifically, the tackifying resin (d) is preferably a rosin-based resin or a terpene-based resin, and more preferably a rosin-based resin.

[0072] Examples of rosin-based resins include rosin esters, hydrogenated rosin esters, disproportionated rosin esters, polymerized rosin esters, gum rosin, tall oil rosin, maleated rosin, and maleic acid-modified rosin.

[0073] Examples of terpene resins include terpene phenol resins, hydrogenated terpene phenol resins, aromatically modified terpene resins, aromatically modified hydrogenated terpene resins, hydrogenated terpene resins, and those mainly composed of α-pinene, β-pinene, limonene, etc.

[0074] The softening point of the tackifying resin (d) is preferably 125°C or higher, and more preferably 200°C or lower, or 180°C or lower. Having the softening point of the tackifying resin (d) within this range improves the adhesive properties of the adhesive composition.

[0075] The tackifying resin (d) (tackifying resin having a softening point of 120°C or higher) is preferably 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more, based on the total amount of tackifying resins (tackifying resins having a softening point of 120°C or higher and tackifying resins having a softening point of less than 120°C) in the adhesive composition.

[0076] <<Optional ingredients>> Optional components include known additives such as softeners, fillers, antioxidants, heat stabilizers, UV absorbers, light stabilizers, antistatic agents, flame retardants, foaming agents, colorants, and dyes.

[0077] Examples of softeners include petroleum-based softeners, vegetable oil-based softeners, liquid rubber, and plasticizers. However, as will be described later, it is preferable that the adhesive composition does not contain plasticizers (plasticizer(e)) or has a low content of plasticizer(e).

[0078] Examples of plasticizers (e) include phthalate derivatives such as diethyl phthalate and dibutyl phthalate; isophthalate derivatives such as dimethyl isophthalate and diisooctyl phthalate; tetrahydrophthalate derivatives such as di-(2-ethylhexyl)tetrahydrophthalate; adipic acid derivatives such as di-n-butyl adipate and di-(2-ethylhexyl) adipate; azelaine derivatives such as diisooctyl azelate; sebaciate derivatives such as di-n-butyl sebacate; maleic acid derivatives such as dimethyl maleate; fumaric acid derivatives such as di-n-butyl fumarate; trimellitic acid derivatives such as triisooctyl trimellitate; citric acid derivatives such as triethyl citrate; and diethyl butyl Examples include itaconic acid derivatives such as conate; oleic acid derivatives such as glyceryl monooleate; ricinol derivatives such as butyl acetyl ricinolate; stearic acid derivatives such as n-butyl stearate; fatty acid derivatives such as diethylene glycol monouralate; sulfonic acid derivatives such as benzenesulfone and butylamide; phosphoric acid derivatives such as trimethyl phosphate; monoester plasticizers such as tetra-2-ethylhexyl pyromelitate; glycol derivatives such as diethylene glycol and dibenzoate; glycerin derivatives such as glycerol monoacetate; paraffin derivatives such as chlorinated paraffin; epoxy derivatives, polyester plasticizers, polyether plasticizers, and the like.

[0079] <<Content of each component in the adhesive composition>> <Content ratio of triblock copolymer (a) and triblock copolymer (b)> The content of triblock copolymer (b) in the adhesive composition is preferably 1 part by mass or more, 5 parts by mass or more, or 10 parts by mass or more, and also preferably 70 parts by mass or less, 55 parts by mass or less, or 50 parts by mass or less, when the total amount of triblock copolymer (a) and triblock copolymer (b) is 100 parts by mass. By setting the amount of triblock copolymer (b) within this range, the adhesive properties of the adhesive composition can be improved.

[0080] <Content of diblock copolymer (c)> The content of diblock copolymer (c) in the adhesive composition is preferably 20 parts by mass or more, 40 parts by mass or more, 60 parts by mass or more, or 65 parts by mass or more, when the total amount of triblock copolymer (a) and triblock copolymer (b) is 100 parts by mass, and also preferably 200 parts by mass or less, 150 parts by mass or less, 120 parts by mass or less, or 100 parts by mass or less. By setting the amount of diblock copolymer (c) within this range, the self-adhesion and end-peel resistance of the adhesive composition can be improved.

[0081] <Content of tackifying resin (d)> The content of the tackifying resin (d) in the adhesive composition is preferably 45 parts by mass or more, 50 parts by mass or more, 60 parts by mass or more, 70 parts by mass or more, or 80 parts by mass or more, when the total of the triblock copolymer (a) and triblock copolymer (b) is 100 parts by mass, and is also preferably 105 parts by mass or less, or 100 parts by mass or less.

[0082] The adhesive composition contains a triblock copolymer (a), a triblock copolymer (b), a diblock copolymer (c), and a tackifying resin (d), and the content of the tackifying resin (d) is within the aforementioned range (high concentration). As a result, the adhesiveness of the adhesive composition is within an appropriate range, and the balance of the overall compatibility of the adhesive composition is appropriate, thereby significantly improving the self-adhesion and resistance to terminal peeling of the adhesive composition.

[0083] Furthermore, from another perspective, in order to significantly improve the self-adhesion and end-peel resistance of the adhesive composition, the content of the tackifying resin (d) [(d) / (c)] relative to the content of the diblock copolymer (c) is preferably 0.60 or more, 0.65 or more, 0.70 or more, or 0.75 or more, and also preferably 1.80 or less, 1.70 or less, 1.60 or less, 1.50 or less, or 1.40 or less.

[0084] <Amount of optional ingredients> The content of any optional component in the adhesive composition may be the residue of each component mentioned above, for example, 25% by mass or less, 10% by mass or less, 5% by mass or less, or 1% by mass or less, based on the total amount of the adhesive composition.

[0085] Here, it is preferable that the content of plasticizer (e) is 5 parts by mass or less when the total amount of triblock copolymer (a) and triblock copolymer (b) is 100 parts by mass. That is, it is preferable that the adhesive composition does not contain plasticizer (e) or has a low content of plasticizer (e). By setting the plasticizer content within this range, the adhesive properties of the adhesive composition can be improved.

[0086] <<<Adhesive composition form>>> The adhesive composition according to this disclosure is preferably a hot-melt type (also called a solvent-free type) adhesive composition obtained by melting and kneading each component.

[0087] The adhesive composition according to this disclosure may also be a solution-type adhesive composition in which each component is dissolved in a predetermined solvent. Examples of solvents used when the adhesive composition according to this disclosure is in solution form include organic solvents such as toluene and ethyl acetate.

[0088] <<<Uses of the adhesive composition>>> The adhesive composition relating to this disclosure can be used to form the adhesive layer of an adhesive tape.

[0089] The following primarily describes a single-sided adhesive tape formed by applying the aforementioned adhesive composition to one side of a substrate, as an example of the use of the adhesive composition according to this disclosure. The same description can be applied when forming a double-sided adhesive tape using the adhesive composition according to this disclosure, except that the adhesive is applied to both sides of the substrate.

[0090] The adhesive tape according to this disclosure comprises a base material and an adhesive layer formed of an adhesive composition provided on at least one surface of the base material.

[0091] Furthermore, other layers (for example, a release layer such as release paper) may be laminated on the surface of the adhesive layer as needed.

[0092] The shape of the substrate is not particularly limited, and film-like or sheet-like substrates can be used. Furthermore, the material of the substrate is not particularly limited, and any material to which an adhesive composition can be applied can be used.

[0093] More specifically, the base material can be paper such as kraft paper, Japanese paper, or crepe paper; nonwoven fabrics made of rayon, cotton, acetate, polyethylene (PE), or polypropylene (PP); resin films such as cellophane, polyvinyl chloride, PE, stretched polypropylene (OPP), polyethylene terephthalate (PET), tetrafluoroethylene, polyimide, polycarbonate (PC), or polystyrene (PS); resin foams such as polyurethane, PE, or butyl rubber; metal foils such as aluminum or copper; or rubber sheets such as natural rubber, SBR, or butyl rubber.

[0094] The method for applying the adhesive composition to the substrate is not particularly limited, but known methods such as a method of applying by thermally melting the adhesive raw material (hot melt method), a method of applying by thinly dispensing with multiple hot rolls (calender method), and a method of applying by dissolving the raw material in an organic solvent (solvent application method) can be used.

[0095] The adhesive tape may be formed in long lengths or wound into a roll.

[0096] The adhesive tape relating to this disclosure can be used for various purposes and is preferably used as a label tape.

[0097] Furthermore, because the adhesive tape according to this disclosure has excellent self-adhesion and resistance to peeling at the ends, it is particularly preferred for use as a label tape that is wrapped around thin objects (such as wires, cables, ropes, and tools such as screwdrivers and wrenches). In this case, the diameter (maximum diameter) of the thin object is, for example, 0.5 to 50 mm. [Examples]

[0098] Next, the present disclosure will be described in more detail by examples and comparative examples, but the present disclosure is not limited in any way by these examples.

[0099] <<Ingredients>> <Triblock copolymer (a)> [Triblock copolymer (a-1)] Clarity LA2330 (manufactured by Kuraray Co., Ltd.) Methyl methacrylate (MMA) / n-butyl acrylate (n-BA) copolymer (triblock compound) Segment A (Hard Segment): MMA Segment B (Soft Segment): n-BA Weight average molecular weight: 98,000 [Triblock copolymer (a-2)] Clarity LA3320 (manufactured by Kuraray Co., Ltd.) Methyl methacrylate (MMA) / n-butyl acrylate (n-BA) copolymer (triblock compound) Segment A (Hard Segment): MMA Segment B (Soft Segment): n-BA Weight average molecular weight: 155,000 [Triblock copolymer (a-3)] Clarity LA3710 (manufactured by Kuraray Co., Ltd.) Methyl methacrylate (MMA) / n-butyl acrylate (n-BA) copolymer (triblock compound) Segment A (Hard Segment): MMA Segment B (Soft Segment): n-BA Weight average molecular weight: 216,000

[0100] <Triblock copolymer (b)> [Triblock copolymer (b-1)] Clarity LK9243 (manufactured by Kuraray Co., Ltd.) Methyl methacrylate / n-butyl acrylate / 2-ethylhexyl acrylate (2EHA) copolymer (triblock compound) Segment A (Hard Segment): MMA Segment B (Soft Segment): n-BA, 2EHA Weight average molecular weight: 74,000

[0101] <Diblock copolymer (c)> [Diblock copolymer (c-1)] Clarity LA2114 (manufactured by Kuraray Co., Ltd.) Methyl methacrylate / n-butyl acrylate copolymer (diblock) Segment A (Hard Segment): MMA Segment B (Soft Segment): n-BA Weight average molecular weight 68,000

[0102] <Tackifying resin (d)> [Tackifying resin (d-1)] Tamanoru 901 (manufactured by Arakawa Chemical Industries, Ltd.) Rosinphenol resin Softening point 130℃ [Tackifying resin (d-2)] Pencel D-125 (manufactured by Arakawa Chemical Industries, Ltd.) Polymerized rosin ester Softening point 125℃ [Tackifying resin (d-3)] Pencel D-153 (manufactured by Arakawa Chemical Industries, Ltd.) Polymerized rosin ester Softening point 153℃ [Tackifying resin (d-4)] YS Polystar T115 (manufactured by Yasuhara Chemical Co., Ltd.) Terpene phenol resin Softening point 115 degrees [Tackifying resin (d-5)] Super Ester A115 (manufactured by Arakawa Chemical Industries, Ltd.) Rosin ester Softening point 115℃ [Tackifying resin (d-6)] KE311 (manufactured by Arakawa Chemical Industries, Ltd.) Rosin ester Softening point 95℃

[0103] <Plasticizer (e)> [Plasticizer (e-1)] Alphon® UP-1010 (manufactured by Toagosei Co., Ltd.) Unfunctionalized acrylic polymers

[0104] <<Manufacturing of adhesive tape>> A mixture containing each raw material in the proportions shown in Table 1 (unit: parts by mass) was melt-kneaded in a twin-screw kneader to obtain an adhesive composition. After mixing, the adhesive composition was coated onto a substrate (PET 38μm) so that the thickness of the adhesive layer was 0.018 mm, resulting in the adhesive tapes of Examples 1-12 and Comparative Examples 1-18.

[0105] <<Rating>> The adhesive tapes of Examples 1-12 and Comparative Examples 1-18 were evaluated for their respective properties using the following method. The evaluation results are shown in Table 1.

[0106] <Self-adhesive (wire mark)> A 2mm diameter wire was wrapped with 20mm wide adhesive tape, and the two ends of the adhesive tape were joined together to secure it. The excess adhesive tape was trimmed so that the length of the overlapping section was 10 mm, and this was used as an evaluation sample. The evaluation samples were kept at a temperature of 40°C for 3 days. After holding the samples for three days, the remaining length of the rafter-jointed portion of the evaluation samples was measured, and a score was assigned based on the following evaluation criteria. Ten measurements were taken for each type of adhesive tape, and the average value was calculated to evaluate its self-adhesion properties. A score of 3 or higher is required to pass.

[0107] (Evaluation Criteria) 5 points: The length of the overlapping section is 5 mm or more. 4. The length of the overlapping section is between 2mm and 5mm. 3. The length of the overlapping section is 1 mm or more but less than 2 mm. 2. The length of the overlapping section is less than 1 mm (adhered only at the ends of the tape). 1 point: The adhesive tape peeled off.

[0108] <Resistance to peeling at the ends> A hexagonal wrench (a hexagonal metal rod) with a side length of 10 mm was wrapped with adhesive tape measuring 12 mm in width and 34 mm in length, and the tape was pressed down with fingers to create an evaluation sample. In this case, the adhesive tape did not cover the entire circumference of the metal rod (the number of turns of the adhesive tape was less than one), and the adhesive tape was applied across all six sides of the hexagonal prism (as shown in Figure 1(1), a condition that scores 5 points according to the evaluation criteria). The evaluation samples were kept at a temperature of 40°C for 3 days. After holding the samples for three days, the condition of the adhesive tape was checked, and a score was assigned based on the following evaluation criteria. Ten measurements were taken for each type of adhesive tape, and the average value was calculated to evaluate its resistance to peeling at the ends. A score of 3 or higher is required to pass.

[0109] (Evaluation Criteria) 5 points: As shown in Figure 1(1), almost no peeling occurred on the adhesive tape. Point 4: As shown in Figure 1(2), peeling occurred at a portion of the end of the adhesive tape. Point 3: As shown in Figure 1(3), peeling occurred in some parts of both ends of the adhesive tape. Two points: As shown in Figure 1(4), a large amount of peeling occurred in the adhesive tape. Point 1: As shown in Figure 1(5), the adhesive tape was only partially stuck in place.

[0110] [Table 1]

[0111] While preferred embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above. That is, other embodiments or various modifications that a person skilled in the art could conceive of within the scope of the invention described in the claims are also understood to fall within the technical scope of this disclosure.

Claims

1. ABA-type triblock copolymer (a) consisting of segment A mainly composed of methacrylic acid ester and segment B mainly composed of acrylic acid ester, ABA-type triblock copolymer (b) consisting of segment A mainly composed of methacrylate ester and segment B mainly composed of acrylic acid ester, A diblock copolymer of type AB (c) consisting of segment A mainly composed of methacrylic acid ester and segment B mainly composed of acrylic acid ester, It contains a tackifying resin (d) with a softening point of 120°C or higher, The aforementioned triblock copolymer (a) does not contain 2-ethylhexyl acrylate as a constituent monomer of segment B. The triblock copolymer (b) has 2-ethylhexyl acrylate as a constituent monomer of segment B. When the total amount of the triblock copolymer (a) and the triblock copolymer (b) is 100 parts by mass, the content of the triblock copolymer (b) is 10 parts by mass or more and 50 parts by mass or less. When the total amount of the triblock copolymer (a) and the triblock copolymer (b) is 100 parts by mass, the content of the diblock copolymer (c) is 60 parts by mass or more and 120 parts by mass or less. When the total amount of the triblock copolymer (a) and the triblock copolymer (b) is 100 parts by mass, the content of the tackifying resin (d) is 45 parts by mass or more and 105 parts by mass or less. An adhesive composition in which the content of the tackifying resin (d) relative to the content of the diblock copolymer (c) [(d) / (c)] is 0.60 or more and 1.80 or less.

2. The adhesive composition according to claim 1, wherein the content of plasticizer (e) is 5 parts by mass or less when the total amount of the triblock copolymer (a) and the triblock copolymer (b) is 100 parts by mass.

3. An adhesive tape comprising a base material and an adhesive layer formed of the adhesive composition according to claim 1 or 2, provided on at least one surface of the base material.

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