Adhesives, adhesive tapes, polyolefin resin molded articles, and composite structures

Abstract

The present invention provides an adhesive that has excellent adhesion to polyolefin resins such as polypropylene and adherends containing polyolefin resins, and that can be recycled together with polyolefin resins such as polypropylene. It also provides an adhesive tape having an adhesive layer containing the adhesive. Furthermore, it provides a polyolefin resin molded article formed from a resin composition containing the adhesive and a polyolefin resin. In addition, it provides a composite structure comprising the adhesive tape and a member containing polyolefin resin to which the adhesive tape is attached. [Solution] An adhesive formed from an adhesive composition containing an elastomer with a saturated hydrocarbon chain as the main chain and a tackifying resin, wherein the shear storage modulus of the adhesive at 30°C, as measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz, is 6.00 × 10⁻⁶. 5 The adhesive is less than Pa, and the adhesive has a glass transition temperature of more than -5°C, as measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz and a measurement temperature range of -50°C to 150°C.

Description

[Technical Field]

[0001] The present invention relates to an adhesive and an adhesive tape having an adhesive layer containing the adhesive. The present invention also relates to a polyolefin resin molded article formed from a resin composition containing the adhesive and a polyolefin resin. Furthermore, the present invention relates to a composite structure comprising the adhesive tape and a member containing a polyolefin resin to which the adhesive tape is attached. [Background technology]

[0002] Adhesive tapes having an adhesive layer containing an adhesive have been widely used to fix components in electronic devices, vehicles, houses, and building materials (for example, Patent Documents 1 to 3). Specifically, for example, adhesive tapes are used to adhere a cover panel for protecting the surface of a portable electronic device to a touch panel module or a display panel module, or to adhere a touch panel module to a display panel module. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-052050 [Patent Document 2] Japanese Patent Publication No. 2015-021067 [Patent Document 3] Japanese Patent Publication No. 2015-120876 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Adhesives and tapes used to fasten automotive components require adhesive strength not only to steel plates but also to polyolefin resins such as polypropylene, which are commonly used in automotive components. However, conventional adhesives and tapes generally have low adhesive strength to polyolefin resins, and there is still a need for adhesives and tapes with superior adhesive strength to polyolefin resins.

[0005] In recent years, as an effort to address environmental issues, there has been a growing desire to recover and reuse (recycle) resources that have been used once, and automobile recycling is also being carried out. Generally, automobile recycling involves removing reusable parts such as engines, doors, catalytic converters, and plastic parts from scrapped vehicles, dismantling the vehicles, pressing the materials, shredding the pressed material, and then separating the metals such as iron. Automobile Shredder Residue (ASR), which remains after separating metals such as iron, contains resins, metals, paper, wood, etc. From the perspective of improving the efficiency of automobile recycling, it is desirable to reuse ASR as well, and in particular, it is desirable to reuse the resins that are largely contained in ASR. However, because the resins contained in ASR are a mixture of many types derived from various sources such as automobile parts and adhesives used to fix automobile parts, the resin obtained by recycling it as is is often of poor quality. Furthermore, attempting to separate the resins to improve quality is difficult and requires a great deal of time and expense for resin separation and collection. For this reason, the resins in ASR are not currently being reused sufficiently. Furthermore, the resin parts removed before pressing are currently not being fully reused because they contain a mixture of various resins derived from numerous sources such as adhesives.

[0006] The present invention aims to provide an adhesive that has excellent adhesion to polyolefin resins such as polypropylene and adherends containing polyolefin resins, and that can be recycled together with polyolefin resins such as polypropylene. The present invention also aims to provide an adhesive tape having an adhesive layer containing the adhesive. Furthermore, the present invention aims to provide a polyolefin resin molded article containing the adhesive and a polyolefin resin. In addition, the present invention aims to provide a composite structure comprising the adhesive tape and a member containing a polyolefin resin to which the adhesive tape is attached. [Means for solving the problem]

[0007] Disclosure 1 is an adhesive formed from an adhesive composition containing an elastomer having a saturated hydrocarbon chain as its main chain and a tackifying resin, wherein the shear storage modulus of the adhesive at 30°C, as measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz, is 6.00 × 10⁻⁶. 5 The adhesive is less than Pa, and the above adhesive is an adhesive whose glass transition temperature, as measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz and a measurement temperature range of -50°C to 150°C, is greater than -5°C. Disclosure 2 is the adhesive of Disclosure 1, wherein the adhesive has a loss loss tangent of less than 1.00 at 120°C, as measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz. Disclosure 3 is an adhesive according to Disclosure 1 or 2, wherein the elastomer having the saturated hydrocarbon chain as its main chain includes a styrene-based elastomer. Disclosure 4 is an adhesive of Disclosure 3 in which the styrene-based elastomer is a hydrogenated styrene-based elastomer. Disclosure 5 is an adhesive of Disclosure 4 in which the hydrogenated styrene elastomer includes a hydrogenated ABA-type linear block copolymer. Disclosure 6 is an adhesive of Disclosure 5 in which the hydrogenated styrene-based elastomer comprises a styrene-ethylene-butylene-styrene copolymer. Disclosure 7 is an adhesive according to Disclosure 1, 2, 3, 4, 5, or 6, wherein the tackifying resin comprises at least one selected from the group consisting of petroleum resins and terpene resins. Disclosure 8 is the adhesive of Disclosure 7, wherein the content of the tackifying resin per 100 parts by mass of the elastomer having the saturated hydrocarbon chain as the main chain is 40 parts by mass or more. Disclosure 9 is an adhesive according to Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the adhesive composition contains a softening agent. Disclosure 10 is an adhesive of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, which does not have a foamed structure. Disclosure 11 is an adhesive tape having an adhesive layer containing the adhesive of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. Disclosure 12 is an adhesive tape according to Disclosure 11, wherein the thickness of the adhesive layer is 10 μm or more. Disclosure 13 is an adhesive tape according to Disclosure 11 or 12, wherein the adhesive tape has a base material, and the base material contains a polyolefin resin. Disclosure 14 is a polyolefin resin molded article formed from a resin composition containing an adhesive of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 and a polyolefin resin. Disclosure 15 is a composite structure comprising an adhesive tape according to Disclosure 11, 12, or 13 and a member containing a polyolefin resin to which the adhesive tape is attached. The present invention will be described in detail below.

[0008] The inventors focused on the fact that polyolefin resins such as polypropylene are frequently used in automobiles and investigated how to suppress the deterioration of resin quality even when recycling all the resins used in automobiles together by using adhesives and adhesive tapes with high compatibility with polyolefin resins such as polypropylene. The inventors investigated using an adhesive formed from an adhesive composition containing an elastomer having a specific structure as an adhesive with high compatibility with polyolefin resins such as polypropylene, and adjusting the shear storage modulus and glass transition temperature of the adhesive to a specific range. As a result, they found that it is possible to obtain an adhesive that has excellent adhesive strength to polyolefin resins such as polypropylene and adherends containing polyolefin resins, and that can be recycled together with polyolefin resins such as polypropylene (i.e., without separating or dismantling the adhesive from the polyolefin resin), thus completing the present invention. Furthermore, since automotive components can be used in high-temperature environments, adhesives and adhesive tapes used to fix automotive components require excellent holding performance at high temperatures. The adhesive of the present invention tends to have excellent holding performance at high temperatures, making it useful in this respect as well.

[0009] The adhesive of the present invention is formed from an adhesive composition. Methods for forming an adhesive from an adhesive composition include, for example, heating the adhesive composition or irradiating the adhesive composition with ultraviolet light or an electron beam. Furthermore, by adjusting the conditions (for example, the heating temperature, the irradiation intensity of ultraviolet light or an electron beam, etc.) in the method of forming the adhesive, the degree of crosslinking and the gel fraction of the adhesive can be adjusted. The adhesive of the present invention may use the above-mentioned uncrosslinked adhesive composition as is, or it may use the crosslinked product of the above-mentioned adhesive composition.

[0010] The above adhesive composition contains an elastomer having a saturated hydrocarbon chain as the main chain. Since the elastomer having a saturated hydrocarbon chain as the main chain has a low polarity, the interfacial free energy of the adhesive composition containing the elastomer having a saturated hydrocarbon chain as the main chain with a polyolefin resin such as polypropylene is reduced, and the wettability of the adhesive of the present invention with respect to a polyolefin resin such as polypropylene is improved. As a result, the adhesive of the present invention has improved adhesive strength with respect to a polyolefin resin such as polypropylene or an adherend containing a polyolefin resin. Therefore, the adhesive of the present invention contains an elastomer having a saturated hydrocarbon chain as the main chain and a tackifier resin described later, and by adjusting the shear storage modulus of the adhesive at 30°C and the glass transition temperature of the adhesive described later to the ranges described later, it is possible to have excellent adhesive strength with respect to a polyolefin resin such as polypropylene or an adherend containing a polyolefin resin. In addition, since the elastomer having a saturated hydrocarbon chain as the main chain has improved compatibility with a polyolefin resin such as polypropylene, the polyolefin resin molded body obtained by recycling the adhesive of the present invention and a polyolefin resin such as polypropylene together has excellent quality. Therefore, it is practically possible to recycle the adhesive of the present invention and a polyolefin resin such as polypropylene together, and the polyolefin resin molded body obtained by recycling is useful as a recycled product.

[0011] The elastomer having a saturated hydrocarbon chain as the main chain is not particularly limited as long as it has a saturated hydrocarbon chain as the main chain and is a high molecular compound having rubber elasticity at room temperature. In this specification, the "main chain" means a structure excluding side chains and terminals in a high molecular compound, that is, a structure excluding the terminals in the longest chain in a high molecular compound.

[0012] Examples of elastomers having the above-mentioned saturated hydrocarbon chain as the main chain include styrene-based elastomers and ethylene-α-olefin copolymer elastomers. Among these, styrene-based elastomers are preferred from the viewpoint of obtaining an adhesive with superior adhesive strength when incorporated into an adhesive composition.

[0013] The above-mentioned styrene-based elastomer may be a hydrogenated styrene-based elastomer obtained by hydrogenating the styrene-based elastomer (hereinafter, at least one compound selected from the group consisting of styrene-based elastomers and hydrogenated styrene-based elastomers may be referred to as a "styrene-based elastomer compound species"). The above-mentioned styrene-based elastomer is more preferably a hydrogenated styrene-based elastomer, from the viewpoint of further reducing polarity and further improving compatibility with polyolefin resins such as polypropylene. In this specification, "hydrogenated styrene elastomer" means a styrene elastomer in which, of the double bonds (unsaturated bonds) of the elastomer having the saturated hydrocarbon chain as its main chain, preferably 80% or more, more preferably 90% or more, even more preferably 95% or more, even more preferably 96% or more, and usually 100% or less, are converted to saturated bonds by hydrogenation. The hydrogenated styrene elastomer may be a partially hydrogenated or fully hydrogenated product. The hydrogenation ratio (hydrogenation rate) is determined using deuterated chloroform as a solvent at 20 Hz. 1 This can be calculated by measuring the H-NMR spectrum.

[0014] Examples of the styrene-based elastomer compounds mentioned above include block copolymers containing blocks derived from styrene monomers and having hard segment portions and soft segment portions. Specifically, examples include ABA-type linear block copolymers having a structure represented by formula ABA and their hydrogenated products, and formula (AB) n Examples include radial block copolymers having a structure represented by C and hydrogenated products thereof. A: Block of the hard segment portion B: Block of the soft segment portion C: Components derived from coupling agents n: an integer greater than or equal to 3. In particular, from the viewpoint of making it easier to satisfy the appropriate range for the shear storage modulus at 30°C, the glass transition temperature of the adhesive described later, the loss tangent at 120°C, and the gel fraction of the adhesive described later, the styrene-based elastomer compound species preferably includes the ABA-type linear block copolymer, and among these, the hydrogenated styrene-based elastomer preferably includes a hydrogenated product of the ABA-type linear block copolymer.

[0015] The styrene-based elastomers mentioned above specifically include, for example, block copolymers having blocks derived from styrene monomers and blocks derived from conjugated diene monomers, and block copolymers having blocks derived from styrene monomers and blocks derived from α-olefin monomers. In particular, from the viewpoint of obtaining an adhesive with superior adhesive strength when included in an adhesive composition, it is preferable to include block copolymers having blocks derived from styrene monomers and blocks derived from conjugated diene monomers. In a block copolymer derived from a styrene monomer and a block derived from a conjugated diene monomer, the block derived from the styrene monomer is the hard segment portion (A above), and the block derived from the conjugated diene monomer is the soft segment portion (B above).

[0016] The block derived from the styrene monomer described above may be any block having repeating units derived from a styrene monomer, and may also contain repeating units derived from other compounds such as ethylene and 1,3-butadiene (which is converted to an ethylene-butylene structure by hydrogenation). Examples of the styrene monomers mentioned above include alkylstyrene, halogenated styrene, halogen-substituted alkylstyrene, alkoxystyrene, carboxyalkylstyrene, alkyl ether styrene, alkylsilyl styrene, vinyl benzyl dimethoxy phosphide, vinyl naphthalene, vinyl anthracene, N,N-diethyl-p-aminoethylstyrene, vinylpyridine, and the like.

[0017] Examples of the alkylstyrenes mentioned above include styrene, methylstyrene, dimethylstyrene, and t-butylstyrene. Examples of the above-mentioned halogenated styrenes include chlorostyrene, bromostyrene, and fluorostyrene. Examples of halogen-substituted alkylstyrenes include chloromethylstyrene. Examples of the above-mentioned alkoxystyrene include methoxystyrene and ethoxystyrene. Examples of the above-mentioned carboxyalkylstyrene include carboxymethylstyrene. Examples of the above-mentioned alkyl ether styrene include vinyl benzylpropyl ether. Examples of the alkylsilylstyrene mentioned above include trimethylsilylstyrene. Among these, styrene, methylstyrene, and dimethylstyrene are preferred, with styrene being the most preferred due to its ease of industrial availability. These aromatic alkenyl compounds may be used individually or in combination of two or more.

[0018] The block derived from the above-mentioned conjugated diene monomer has repeating units derived from the conjugated diene monomer. The block derived from the above-mentioned conjugated diene monomer may not have repeating units derived from the styrene monomer. Examples of the above-mentioned conjugated diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-octadiene, 1,3-hexadiene, 1,3-cyclohexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, myrcene, chloroprene, and the like. Among these, 1,3-butadiene and isoprene are preferred due to their high polymerization reactivity and ease of industrial availability. These conjugated diene monomers may be used individually or in combination of two or more.

[0019] Furthermore, the block derived from the above-mentioned conjugated diene monomer may have, for example, a constituent unit derived from 2,5-dihydrofuran-2,5-dione.

[0020] Examples of the hydrogenated styrene-based elastomer having the structure represented by the above formula ABA include styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), and styrene-isobutylene-styrene block copolymer (SIBS). In particular, it is preferable that the hydrogenated styrene-based elastomer contains SEBS, as this makes it easier to satisfy the appropriate range for the shear storage modulus at 30°C, the glass transition temperature of the adhesive, the loss tangent at 120°C, and the gel fraction of the adhesive, as described later.

[0021] Examples of styrene-based elastomers having the structure represented by the above formula ABA include styrene-isoprene-styrene block copolymer (SIS) and styrene-butadiene-styrene block copolymer (SBS). In particular, it is preferable that the above styrene-based elastomer contains SIS, as this makes it easier to satisfy the appropriate range for the shear storage modulus at 30°C, the glass transition temperature of the adhesive, the loss tangent at 120°C, and the gel fraction of the adhesive, which will be described later.

[0022] The styrene-based elastomer may contain, in addition to a triblock copolymer of a block derived from the styrene-based monomer and a block derived from the conjugated diene monomer, a diblock copolymer of a block derived from the styrene-based monomer and a block derived from the conjugated diene monomer. The content of the diblock copolymer in the styrene-based elastomer (hereinafter also referred to as the "diblock ratio") is not particularly limited, but a preferred lower limit is 5% by mass, and a more preferred lower limit is 10% by mass. When the diblock ratio is within the above range, the adhesion of the adhesive of the present invention to the adherend is further improved, and the adhesive strength to the polyolefin resin is further enhanced. Furthermore, while the upper limit of the above-mentioned diblock ratio is not particularly limited, a preferred upper limit is 80% by mass from the viewpoint of maintaining the cohesive force of the adhesive of the present invention. The diblock ratio can be calculated from the peak area ratio of each copolymer measured by gel permeation chromatography (GPC).

[0023] The percentage of blocks derived from the styrene monomer in the above-mentioned styrene-based elastomer (hereinafter sometimes referred to as "styrene content") is not particularly limited, but a preferred upper limit is 40% by mass, and a more preferred upper limit is 30% by mass. When the above-mentioned styrene content is within the above range, the adhesive of the present invention does not become too hard, and as a result of improved adhesion to the adherend, the adhesive strength to polyolefin resin is further improved. Furthermore, while the lower limit of the styrene content is not particularly limited, a preferred lower limit is 3% by mass, from the viewpoint of maintaining the cohesive force of the adhesive of the present invention. The styrene content is as follows: 1 It can be calculated from the peak area ratio of each block measured by 1H-NMR.

[0024] The weight-average molecular weight (Mw) of the elastomer having the saturated hydrocarbon chain as its main chain is not particularly limited, but a preferred lower limit is 50,000 and a preferred upper limit is 600,000. Having the weight-average molecular weight (Mw) of the elastomer having the saturated hydrocarbon chain as its main chain within the above range further improves the adhesive strength of the adhesive of the present invention to polyolefin resins. A more preferred lower limit for the weight-average molecular weight of the elastomer having the saturated hydrocarbon chain as its main chain is 100,000 and a more preferred upper limit is 500,000.

[0025] In this specification, "weight-average molecular weight" refers to the weight-average molecular weight measured as polystyrene-equivalent molecular weight by gel permeation chromatography (GPC). Specifically, the weight-average molecular weight of elastomers with the above saturated hydrocarbon chain as the main chain can be measured by the GPC method in the following way. Specifically, first, a solution of an elastomer with a saturated hydrocarbon chain as the main chain dissolved in tetrahydrofuran (THF) is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to obtain a GPC test solution. Next, the GPC system (Waters Corporation, "ACQUITY") TM Advanced Polymer Chromatography TM System), GPC column (Waters Corporation, "HSPgel") TMGPC measurements will be performed using an HR MB-M (6.0 mm × 150 mm) column and a differential refractive index detector (Waters, "2414"). The sample injection volume will be 20 mg / mL, the solution volume 10 μL, the flow rate 0.5 mL / min, and the column temperature 40°C. The analysis software will be Empower3, which is included with the instrument. Polystyrene (peak top molecular weights: 2.11 million, 1.09 million, 427,000, 190,000, 37,900, 18,100, 5,970, 2,420, 500) (Tosoh Corporation) will be used as the standard. GPC measurements will be performed using the polystyrene standard, and a calibration curve will be created using the analysis software to convert the eluted amount to the polystyrene molecular weight. The analysis will then be performed, and the weight-average molecular weight will be calculated from the GPC elution volume using this calibration curve.

[0026] The preferred lower limit and preferred upper limit of the content of the elastomer having the saturated hydrocarbon chain as the main chain in the above adhesive composition is 20% by mass. Having the content of the elastomer having the saturated hydrocarbon chain as the main chain within this range makes it easier to adjust the shear storage modulus of the adhesive at 30°C within a suitable range, and further improves the adhesive strength to the polyolefin resin. A more preferred lower limit for the elastomer having the saturated hydrocarbon chain as the main chain is 30% by mass, a more preferred upper limit is 80% by mass, an even more preferred lower limit is 40% by mass, and an even more preferred upper limit is 70% by mass.

[0027] The above adhesive composition contains a tackifying resin. The inclusion of a tackifying resin in the above adhesive composition improves the adhesive strength of the adhesive of the present invention. Therefore, the adhesive of the present invention contains an elastomer with the above saturated hydrocarbon chain as the main chain and a tackifying resin, and by adjusting the shear storage modulus at 30°C and the glass transition temperature of the adhesive, which will be described later, to the range described later, it is possible to obtain an adhesive that has excellent adhesion to polyolefin resins such as polypropylene and adherends containing polyolefin resins.

[0028] The tackifying resin preferably includes at least one selected from petroleum resins and terpene resins. By including at least one selected from petroleum resins and terpene resins in the tackifying resin, the interfacial free energy of the adhesive composition with polyolefin resins such as polypropylene is reduced, thereby improving the wettability of the adhesive of the present invention with polyolefin resins such as polypropylene. As a result, the adhesive of the present invention exhibits improved adhesion to polyolefin resins such as polypropylene and adherends containing polyolefin resins. Furthermore, because the compatibility of the adhesive of the present invention with polyolefin resins such as polypropylene is further improved, the polyolefin resin molded articles obtained by recycling the adhesive of the present invention and polyolefin resins such as polypropylene together are of superior quality, making it more practical to recycle the adhesive of the present invention together with polyolefin resins such as polypropylene.

[0029] Examples of the above petroleum resins include C5 petroleum resins, hydrogenated C5 petroleum resins, alicyclic saturated hydrocarbon resins, C9 petroleum resins, hydrogenated C9 petroleum resins, hydrogenated C9 aromatic resins, and hydrogenated α-methylstyrene resins. Among these, hydrogenated C5 petroleum resins, hydrogenated C9 petroleum resins, hydrogenated C9 aromatic resins, and hydrogenated α-methylstyrene resins, which do not have carbon-carbon double bonds (unsaturated bonds), are preferred from the viewpoint that the shear storage modulus at 30°C, the glass transition temperature, the loss tangent at 120°C, and the gel fraction of the adhesive of the present invention, as described later, will more easily satisfy an appropriate range.

[0030] Examples of the above-mentioned petroleum resins include Alcon P-100 and Alcon P-120 (both manufactured by Arakawa Chemical Industries, Ltd.).

[0031] Examples of the terpene resins mentioned above include resins obtained by polymerizing terpene compounds and hydrogenated versions of such resins. Specific examples of the terpene compounds include α-pinene, β-pinene, limonene, dipentene, δ-3-carene, dimethyloctatriene, allocimene, myrcene, linalool, ocimene, and cosmene.

[0032] Examples of the terpene resins mentioned above include YS Resin PX1250, YS Resin PX1000, and YS Resin PX800 (all manufactured by Yasuhara Chemical Co., Ltd.).

[0033] The above-mentioned tackifying resin may also contain resins other than the above-mentioned petroleum resin and terpene resin.

[0034] The preferred lower limit of the softening point of the tackifying resin is 80°C, and the preferred upper limit is 150°C. A softening point of 80°C or higher for the tackifying resin improves the heat resistance of the adhesive of the present invention, resulting in superior adhesion and retention performance to polyolefins such as polypropylene at high temperatures. A softening point of 150°C or lower for the tackifying resin prevents the adhesive from becoming too hard, resulting in improved adhesion to the substrate and enhanced adhesion to polyolefin resins. A more preferred lower limit of the softening point of the tackifying resin is 90°C, a more preferred upper limit is 140°C, an even more preferred lower limit is 100°C, and an even more preferred upper limit is 130°C. The softening point of the above-mentioned tackifying resin can be measured by a method in accordance with JIS K2207.

[0035] In the above adhesive composition, the preferred lower limit of the content of the tackifying resin per 100 parts by mass of the elastomer having the saturated hydrocarbon chain as the main chain is 40 parts by mass. The tackiness of the adhesive of the present invention is further improved when the content of the tackifying resin is 40 parts by mass or more. A more preferred lower limit for the content of the tackifying resin is 50 parts by mass, an even more preferred lower limit is 60 parts by mass, and an even more preferred lower limit is 75 parts by mass. Furthermore, the preferred upper limit for the content of the tackifying resin is 150 parts by mass. By having a content of 150 parts by mass or less of the tackifying resin, even if the adhesive composition contains the tackifying resin, the shear storage modulus of the adhesive at 30°C, the glass transition temperature of the adhesive, the loss tangent of the adhesive at 120°C, and the gel fraction of the adhesive, as described later, tend to stay within an appropriate range, thereby further improving the heat resistance of the adhesive of the present invention. A more preferred upper limit for the content of the tackifying resin is 130 parts by mass, an even more preferred upper limit is 120 parts by mass, and an even more preferred lower limit is 100 parts by mass.

[0036] Regarding the analysis of the type and content of the above-mentioned tackifying resin, the following methods can be used. Specifically, the above-mentioned adhesive composition is dissolved in tetrahydrofuran, and only the dissolved sol is extracted. The composition can then be analyzed by measuring and analyzing the sol components using methods such as gel permeation chromatography (GPC), infrared absorption spectroscopy (IR), and gas chromatography-mass spectrometry (GC-MS).

[0037] Preferably, the above adhesive composition further contains a softening agent. The inclusion of a softening agent in the adhesive composition makes it easier to adjust the shear storage modulus of the adhesive at 30°C to a more appropriate range, thereby improving the adhesive strength to polyolefin resins such as polypropylene.

[0038] Examples of the above-mentioned softening agents include polybutene, polybutadiene, n-butene-isobutylene copolymer, polyisoprene, and paraffinic oils. In particular, from the viewpoint of superior compatibility with elastomers having saturated hydrocarbon chains as the main chain, it is preferable that the above-mentioned softening agent contains polybutene or polybutadiene.

[0039] In the above adhesive composition, the preferred upper limit of the content of the softener per 100 parts by mass of the elastomer having the saturated hydrocarbon chain as the main chain is 100 parts by mass. By having a softener content of 100 parts by mass or less, the adhesive of the present invention has improved heat resistance and superior adhesive strength and holding performance at high temperatures. A more preferred upper limit of the softener content is 70 parts by mass, and an even more preferred upper limit is 50 parts by mass. Furthermore, the content of the softening agent may be 0 parts by mass, but from the viewpoint of making it easier to adjust the shear storage modulus of the adhesive at 30°C, which will be described later, to a more appropriate range by including the softening agent in the adhesive composition, a preferred lower limit is 10 parts by mass, and a more preferred lower limit is 20 parts by mass.

[0040] Preferably, the above adhesive composition further contains a crosslinking aid. By including a crosslinking aid in the above adhesive composition, the shear storage modulus at 30°C, the glass transition temperature of the adhesive, the loss tangent at 120°C, and the gel fraction of the adhesive, as described later, are more likely to meet appropriate ranges, thereby further improving the heat resistance of the adhesive of the present invention.

[0041] Examples of the crosslinking aids mentioned above include (meth)acrylic monomers and triallyl isocyanurate. By including these crosslinking aids in the adhesive composition, the shear storage modulus at 30°C, the glass transition temperature, the loss tangent at 120°C, and the gel fraction of the adhesive, as described later, are more likely to meet appropriate ranges, thereby further improving the heat resistance of the adhesive of the present invention. In this specification, "(meth)acrylic" means acrylic or methacrylic.

[0042] Examples of the (meth)acrylic monomers mentioned above include (meth)acrylic acid esters, which are commonly used as monomers constituting (meth)acrylic copolymers. The number of functional groups of the (meth)acrylic monomer is not particularly limited and may be bifunctional, trifunctional, tetrafunctional, pentafunctional, hexafunctional, etc. Examples of the above (meth)acrylic monomers include ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. Among these, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate are preferred from the viewpoint of good compatibility with elastomers having the above saturated hydrocarbon chain as the main chain and easier crosslinking of the adhesive composition. These (meth)acrylic monomers may be used individually or in combination of two or more.

[0043] In the above adhesive composition, the preferred lower limit of the content of the crosslinking aid per 100 parts by mass of the elastomer having the saturated hydrocarbon chain as the main chain is 1.0 part by mass, and the preferred upper limit is 20 parts by mass. When the content of the crosslinking aid is 1.0 part by mass or more, the shear storage modulus at 30°C, the glass transition temperature of the adhesive, the loss tangent at 120°C, and the gel fraction of the adhesive, as described later, are more likely to meet appropriate ranges, and the heat resistance of the adhesive of the present invention is further improved. When the content of the crosslinking aid is 20 parts by mass or less, the crosslinking aid does not bleed out, and the adhesive strength of the adhesive of the present invention is further improved. A more preferred lower limit for the content of the crosslinking aid is 2.0 parts by mass, a more preferred upper limit is 15 parts by mass, an even more preferred lower limit is 3.0 parts by mass, and an even more preferred upper limit is 10 parts by mass.

[0044] The above adhesive composition may optionally contain conventionally known fine particles and additives such as inorganic fine particles, conductive fine particles, antioxidants, foaming agents, organic fillers, and inorganic fillers.

[0045] The method for producing the adhesive of the present invention is not particularly limited, and conventionally known methods can be used. For example, first, an elastomer having the above saturated hydrocarbon chain as the main chain, a tackifier resin, and, if necessary, a crosslinking aid and other additives are added to obtain an adhesive composition. Then, after sufficiently stirring and mixing the obtained adhesive composition, heating, irradiating with ultraviolet rays or electron beams, etc. are performed to obtain an adhesive formed from the adhesive composition.

[0046] The adhesive of the present invention has a shear storage modulus at 30°C (hereinafter, may also be simply referred to as "the shear storage modulus of the adhesive at 30°C") measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz of less than 6.00×10 5 Pa. Since the shear storage modulus of the above adhesive at 30°C is less than 6.00×10 5 Pa, the wettability of the above adhesive is improved, and the adhesive of the present invention has excellent adhesive strength to polyolefins such as polypropylene. Therefore, the adhesive of the present invention contains an elastomer having a saturated hydrocarbon chain as the main chain and a tackifier resin described later, and by adjusting the shear storage modulus of the adhesive at 30°C and the glass transition temperature of the adhesive described later to the ranges described later, it can have excellent adhesive strength to polyolefin resins such as polypropylene and adherends containing polyolefin resins. The preferable upper limit of the shear storage modulus of the above adhesive at 30°C is 5.00×10 5 Pa, a more preferable upper limit is 4.00×10 5 Pa, and an even more preferable upper limit is 3.50×10 5 Pa. Also, the preferable lower limit of the shear storage modulus of the above adhesive at 30°C is 5.00×10 4 Pa. Since the shear storage modulus of the above adhesive at 3 at 30°C is 5.00×10 4 Pa or more, the adhesive of the present invention has better heat resistance and is more excellent in adhesive strength and holding performance to polyolefins such as polypropylene at high temperatures. The more preferable lower limit of the shear storage modulus of the above adhesive at 30°C is 1.00×10 5Pa, a more preferable lower limit is 1.50 × 10 5 Pa, and a more preferable lower limit is 2.00 × 10⁻⁶ 5 It is Pa.

[0047] Specific methods for adjusting the shear storage modulus of the above-mentioned adhesive at 30°C include, for example, changing the type of elastomer having the saturated hydrocarbon chain as the main chain, adjusting the type and content of the tackifying resin, using a tackifying resin with a softening point in a specific range, and adding a softener to the above-mentioned adhesive composition.

[0048] The adhesive of the present invention has a glass transition temperature (hereinafter sometimes simply referred to as "glass transition temperature of the adhesive") exceeding -5°C, as measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz and a measurement temperature range of -50°C to 150°C. Because the glass transition temperature of the adhesive exceeds -5°C, the adhesive of the present invention exhibits excellent adhesion to polyolefins such as polypropylene. Therefore, the adhesive of the present invention contains an elastomer with a saturated hydrocarbon chain as the main chain and a tackifying resin described later, and by adjusting the shear storage modulus at 30°C and the glass transition temperature of the adhesive described later to the range described later, it is possible to obtain an adhesive with excellent adhesion to polyolefin resins such as polypropylene and adherends containing polyolefin resins. The preferred lower limit for the above adhesive is -4°C, a more preferred lower limit is -3°C, and an even more preferred lower limit is 0°C. Furthermore, the preferred upper limit for the glass transition temperature of the above adhesive is 15°C. A glass transition temperature of 15°C or lower allows the adhesive to exhibit superior tackiness at the moment of application, making the application process easier. A more preferred upper limit for the glass transition temperature of the above adhesive is 13°C, and an even more preferred upper limit is 10°C. In this specification, the "glass transition temperature" refers to the temperature at which a maximum of loss tangent (tanδ) obtained by dynamic viscoelasticity measurement occurs, specifically the temperature at which a maximum due to micro-Brownian motion appears. Furthermore, if there are multiple maximums of loss tangent, in this specification, the "glass transition temperature" refers to the temperature at which the lowest-temperature maximum of loss tangent appears among the maximums of loss tangent in the range of -50°C to 150°C.

[0049] Specific methods for adjusting the glass transition temperature of the above-mentioned adhesive include, for example, changing the type of elastomer having the saturated hydrocarbon chain as the main chain, adjusting the type and content of the tackifying resin, using a tackifying resin with a softening point in a specific range, and adding a softener to the above-mentioned adhesive composition.

[0050] The adhesive of the present invention preferably has a loss tangent at 120°C (hereinafter sometimes simply referred to as "the loss tangent of the adhesive at 120°C") of less than 1.00, as measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz. Having a loss tangent of less than 1.00 at 120°C of the above adhesive improves the heat resistance of the adhesive of the present invention, resulting in superior adhesion and retention performance to polyolefins such as polypropylene at high temperatures. A more preferable upper limit for the loss tangent of the above adhesive at 120°C is 0.90, and an even more preferable upper limit is 0.80. Furthermore, a preferred lower limit for the loss tangent of the above adhesive at 120°C is 0.20. When the loss tangent of the above adhesive at 120°C is 0.20 or higher, the wettability of the adhesive is further improved, and the adhesive strength to polyolefin resins such as polypropylene or adherends containing polyolefin resins is further improved. A more preferred lower limit for the loss tangent of the above adhesive at 120°C is 0.30, and an even more preferred lower limit is 0.40.

[0051] Specific methods for adjusting the loss tangent of the above-mentioned adhesive at 120°C include, for example, changing the type of elastomer with a saturated hydrocarbon chain as the main chain, adjusting the type and content of the tackifying resin, using a tackifying resin with a softening point in a specific range, and adding a softener to the above-mentioned adhesive composition.

[0052] The shear storage modulus at 30°C, the glass transition temperature of the adhesive, and the loss tangent at 120°C of the adhesive are measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz. Specifically, first, the adhesive of the present invention is applied to the release surface of a release film such as a release PET film to create a dried adhesive sheet. Then, the adhesive sheets are stacked to create a laminate consisting only of adhesive with a thickness of approximately 1 mm, and the laminate is cut to a width of 6 mm and a length of 10 mm to obtain a test specimen. Next, the obtained test specimen is subjected to dynamic viscoelasticity measurement using a dynamic viscoelasticity measuring device in shear mode, under nitrogen atmosphere conditions, with a measurement temperature range of -50°C to 150°C, a heating rate of 5°C / min, a measurement frequency of 10 Hz, and a strain of 0.08%. An example of the above-mentioned dynamic viscoelasticity measuring device is the DVA-200 (manufactured by IT Measurement Control Co., Ltd.). Furthermore, if the adhesive tape of the present invention, as described later, consists only of an adhesive layer, a measurement sample may be prepared by laminating the adhesive layer obtained by peeling off a release PET film or the like that protects the adhesive layer.

[0053] The adhesive of the present invention has a preferred lower limit of gel fraction of 3% by mass and a preferred upper limit of 70% by mass. When the gel fraction of the adhesive of the present invention is 3% by mass or more, the cohesive force of the adhesive of the present invention is increased and the retention performance at high temperatures is further improved. When the gel fraction of the adhesive of the present invention is 70% by mass or less, the adhesive of the present invention does not become too hard and has sufficient initial adhesive strength. Furthermore, when the gel fraction of the adhesive of the present invention is 70% by mass or less, the compatibility with polyolefin resins such as polypropylene is further improved. A more preferred lower limit of gel fraction of the adhesive of the present invention is 5% by mass, a more preferred upper limit is 60% by mass, an even more preferred lower limit is 10% by mass, and an even more preferred upper limit is 50% by mass. The gel fraction of the adhesive of the present invention is measured by the following method or the like. Specifically, W0 (g) of the adhesive is taken, immersed in 50 mL of tetrahydrofuran (THF), and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, the THF and the adhesive that has absorbed THF and swollen are filtered off using a metal mesh (mesh size #200, mass: W1 (g)). The adhesive that has absorbed THF and swollen is dried at 110°C for 1 hour, and the mass W2 (g) of the adhesive containing the metal mesh is measured. The gel fraction is then calculated using the following formula (1). Gel fraction (mass %) = 100 × (W2 - W1) / W0(1) (W0: initial mass of adhesive, W1: mass of metal mesh, W2: mass of adhesive after drying (including metal mesh))

[0054] Methods for adjusting the gel fraction of the adhesive of the present invention to the above-mentioned range include, for example, changing the type and amount of crosslinking aid contained in the adhesive composition, or adjusting the irradiance and irradiation time of the electron beam or ultraviolet light irradiated to form the adhesive of the present invention.

[0055] The adhesive of the present invention preferably does not have a foamed structure. By not having a foamed structure, the parts to which the adhesive is bonded together are less likely to shift and adhere more strongly. In order for the adhesive of the present invention to not have a foamed structure, it is sufficient not to generate air bubbles in the process of mixing the adhesive composition, coating, and forming the film, and it is preferable that the adhesive composition does not contain a foaming agent. In this specification, "having no foamed structure" means "having no bubbles visible to the naked eye."

[0056] The adhesive of the present invention is preferably contained in the adhesive layer that constitutes the adhesive tape. An adhesive tape having an adhesive layer containing the adhesive of the present invention is also one of the present inventions.

[0057] The preferred lower limit for the thickness of the adhesive layer is 10 μm. A thickness of 10 μm or more of the adhesive layer makes it easier to obtain good adhesion to the adherend and further improves the adhesive strength to the polyolefin resin. A more preferred lower limit for the thickness of the adhesive layer is 20 μm, an even more preferred lower limit is 30 μm, and an even more preferred lower limit is 50 μm. Furthermore, the preferred upper limit for the thickness of the adhesive layer is 800 μm. Having an adhesive layer thickness of 800 μm or less makes it easier to achieve high productivity during the production of adhesive tapes. A more preferred upper limit for the thickness of the adhesive layer is 700 μm, an even more preferred upper limit is 600 μm, an even more preferred upper limit is 400 μm, and a particularly preferred upper limit is 200 μm. In this specification, thickness can be measured using a dial thickness gauge (such as the "ABS Digimatic Indicator" manufactured by Mitutoyo Corporation).

[0058] The adhesive tape of the present invention may be a non-support type adhesive tape without a base material, or a support type adhesive tape having a base material. If the adhesive tape of the present invention is a non-support type adhesive tape without a base material, it becomes easier to recycle the adhesive tape with polyolefin resin. On the other hand, if the adhesive tape of the present invention is a support type adhesive tape having a base material, it becomes easier to process the adhesive tape of the present invention.

[0059] If the adhesive tape of the present invention has a base material, it may be a single-sided adhesive tape having the adhesive layer on one side of the base material, or a double-sided adhesive tape having adhesive layers on both sides of the base material.

[0060] The above-mentioned base material preferably contains a polyolefin resin. The inclusion of a polyolefin resin in the base material improves its compatibility with the polyolefin resin, making it easier to recycle the adhesive tape and the adherend containing the polyolefin resin together.

[0061] The above-mentioned substrate may contain only one type of resin, or it may contain two or more types of resins. When the above-mentioned substrate contains two or more types of resins, it is preferable that the polyolefin resin is the main component of all the resins contained in the above-mentioned substrate. Note that "the main component of all the resins contained in the above-mentioned substrate" means that the content ratio of the polyolefin resin in the total resins contained in the above-mentioned substrate is 50% by mass or more. When the above-mentioned base material contains two or more types of resins (i.e., when the content of the above-mentioned polyolefin resin in the resin contained in the base material is 50% by mass or more), the entire adhesive tape of the present invention becomes more compatible with adherends containing polyolefin resin, and it becomes easier to recycle the adhesive tape of the present invention and the adherend containing polyolefin resin together. Furthermore, the higher the content of the above-mentioned polyolefin resin, the better. A more preferable lower limit for the content of the above-mentioned polyolefin resin is 70% by mass, and an even more preferable lower limit is 90% by mass. It may also be 100% by mass (i.e., all the resin contained in the base material is polyolefin resin).

[0062] Examples of substrates containing 50% by mass or more of the above-mentioned polyolefin resin include OPP film, biaxially oriented PE film, CPP film, olefin fiber nonwoven fabric, and olefin foam. Examples of the OPP film mentioned above include Pyrene film P2261 (manufactured by Toyobo Co., Ltd.). Examples of the biaxially oriented PE film mentioned above include BOPE film (manufactured by Sewa Film Group Co., Ltd.). Examples of the above-mentioned CPP film include ET20 (manufactured by Okamoto Co., Ltd.). Examples of the olefin fiber nonwoven fabrics mentioned above include All-Olefin Paper-20 (manufactured by Nippon Paper Industries Co., Ltd.). Examples of the olefin foam mentioned above include Softlon S (manufactured by Sekisui Chemical Co., Ltd.).

[0063] The preferred lower limit for the thickness of the above-mentioned substrate is 1 μm. A substrate thickness of 1 μm or more allows the adhesive tape to obtain better processability. A more preferred lower limit for the thickness of the above-mentioned substrate is 5 μm, an even more preferred lower limit is 10 μm, and an even more preferred lower limit is 20 μm. Furthermore, the preferred upper limit for the thickness of the above-mentioned substrate is 500 μm. Having a substrate thickness of 500 μm or less makes it easier to recycle the adhesive tape of the present invention together with the polyolefin resin. A more preferred upper limit for the thickness of the above-mentioned substrate is 300 μm, an even more preferred upper limit is 100 μm, and an even more preferred upper limit is 50 μm.

[0064] The adhesive tape of the present invention may have other layers, as long as they do not impair the effects of the present invention.

[0065] The adhesive tape of the present invention can be manufactured, for example, by forming an adhesive layer by coating a solution of the adhesive composition obtained by the method described above onto the release surface of a release film that has been subjected to a release treatment, and then drying it. Alternatively, it can be manufactured by heating and melting the raw materials of a solvent-free adhesive composition and mixing them uniformly, and then applying a hot-melt coating to the release surface of a release film that has been subjected to a release treatment, thereby forming an adhesive layer. Furthermore, the adhesive tape of the present invention can also be manufactured by thoroughly mixing the solution of the adhesive composition obtained by the method described above, coating it onto the release surface of a release film that has undergone a release treatment, heating it, irradiating it with ultraviolet light or an electron beam, and then drying it to form an adhesive layer containing the adhesive formed from the adhesive composition. Furthermore, by using the adhesive tape manufactured by the method described above as an adhesive layer and bonding it to a substrate, an adhesive tape having a substrate can also be created.

[0066] The thickness of the adhesive tape of the present invention has a preferred lower limit of 10 μm. A thickness of 10 μm or more makes it easier to apply the adhesive tape to a substrate. A more preferred lower limit for the thickness of the adhesive tape of the present invention is 20 μm, an even more preferred lower limit is 30 μm, and an even more preferred lower limit is 50 μm. Furthermore, the preferred upper limit for the thickness of the adhesive tape of the present invention is 700 μm. Having an overall thickness of 700 μm or less makes it easier to recycle the adhesive tape together with the polyolefin resin. A more preferred upper limit for the thickness of the adhesive tape of the present invention is 500 μm, and an even more preferred upper limit is 300 μm. In this specification, the term "thickness of the adhesive tape" does not include the thickness of the separator, such as a release PET film, that protects the outermost adhesive layer of the adhesive tape.

[0067] The applications of the adhesive and adhesive tape of the present invention are not particularly limited, but they can be used, for example, to fix parts in electronic devices, vehicles, houses, building materials, etc. In particular, because they have excellent adhesive strength to polyolefin resins such as polypropylene and adherends containing polyolefin resins, they are suitably used to fix interior components and on-board parts of vehicles. Specifically, it can be suitably used to fix, for example, in-vehicle panels, cushioning materials, sound-absorbing materials, waterproofing materials, vibration-damping materials, fenders, door outer panels (door outer panels), back doors, bonnets (front hoods, engine hoods), trunk lids, bumpers, wheel covers, caps, mudguards, bumper unders, spoilers such as side sill spoilers and rear spoilers, fender liners, engine under covers, housings for taillights, turn signals, and stop lamps, air intake pipes, air cleaner cases, resonators, front end modules, cooling fans, fan shrouds, instrument panels, console boxes, glove boxes, steering wheels, shift levers, accelerator pedals, door trims, seats, headrests, ceiling members, floor carpet members, pillar garnishes, armrests, interior lamps, rearview mirror housings, assist grips, air conditioning modules, or components that make up these. Furthermore, since the adhesive and adhesive tape of the present invention have excellent compatibility with polyolefin resins, the polyolefin resin molded articles formed from a resin composition obtained by recycling the adhesive and adhesive tape of the present invention together with polyolefin resins have superior material quality. Therefore, the adhesive and adhesive tape of the present invention can be recycled together with polyolefin resins such as polypropylene, and the polyolefin resin molded articles obtained by recycling are useful as recycled products.

[0068] A polyolefin resin molded article formed from a resin composition containing the adhesive of the present invention and a polyolefin resin is also one of the present inventions. The polyolefin resin molded article of the present invention is of excellent quality and useful as a recycled product, even when molded from a resin composition made from recycled adhesive and polyolefin resin. As described above, the polyolefin resin molded article of the present invention refers to an article that can be obtained by molding a resin composition obtained by recycling the adhesive or adhesive tape of the present invention and the polyolefin resin together, and includes not only molded articles using the polyolefin resin raw material of the resin composition obtained by recycling, but also the polyolefin resin raw material of the resin composition obtained by recycling. Examples of the polyolefin resin raw materials mentioned above include polyolefin resin pellets and polyolefin resin powder. Examples of molded products using the polyolefin resin raw materials include home appliances, stationery, daily necessities, and vehicle parts. Furthermore, the "adhesive of the present invention" in the polyolefin resin molded article of the present invention may be derived from the adhesive layer of the adhesive tape. Also, if the adhesive tape has a base material containing polyolefin resin, the polyolefin resin recycled together with the adhesive tape in order to obtain the polyolefin resin molded article of the present invention means that it is different from the base material containing polyolefin resin that is present in the adhesive tape of the present invention.

[0069] Examples of the polyolefin resins mentioned above include thermoplastic olefin resins and thermosetting olefin resins. Among these, thermoplastic olefin resins are preferred from the viewpoint of easier thermal melting during recycling. Examples of the thermoplastic olefin resins mentioned above include polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin (EVA), ethylene-ethyl acrylate copolymer resin (EEA), ethylene-methyl methacrylate copolymer resin (EMMA), polyolefin-based thermoplastic elastomer (TPO), and ethylene propylene rubber (EPDM).

[0070] The polyolefin resin molded article of the present invention can be obtained, for example, by heating and kneading a composite structure comprising a mixture containing the above-mentioned adhesive or adhesive tape and polyolefin resin, or a member containing polyolefin resin to which the above-mentioned adhesive or adhesive tape is attached, and then molding the resulting resin composition. The apparatus used for heating and kneading is not particularly limited, but examples include blenders, kneaders, mixing rolls, Banbury mixers, plast mills, single-screw or twin-screw extruders, etc. The molding method can be a method in which the polyolefin resin raw material is heated and made to flow using a molding method such as injection molding, extrusion molding, or blow molding, and easily molded into a molded article of any shape.

[0071] A composite structure comprising the adhesive tape of the present invention and a member containing a polyolefin resin to which the adhesive tape is attached is also one of the present inventions. The composite structure of the present invention makes it practically possible to recycle the adhesive tape and the polyolefin resin together, thereby reducing the environmental burden.

[0072] The composite structure of the present invention is not particularly limited as long as it comprises the adhesive tape and a member containing polyolefin resin to which the adhesive tape is attached. For example, a composite structure in which a member containing polyolefin resin and other members are bonded and fixed together with the adhesive tape can be used. In the case where the composite structure of the present invention is a composite structure in which a member containing polyolefin resin and other members are bonded and fixed together with the adhesive tape as described above, the other members may be members containing polyolefin resin or members other than members containing polyolefin resin. However, from the viewpoint of further reducing the environmental burden, it is preferable that the other members also contain polyolefin resin. Furthermore, when bonding components containing polyolefin resin together, the components containing the polyolefin resin may be of the same type or may be different.

[0073] Examples of polyolefin resin-containing components in the composite structure of the present invention include the polyolefin resin-containing components in the polyolefin resin molded articles described above. The polyolefin resin may also be a resin obtained through recycling, and the polyolefin resin molded articles described above may be used as the polyolefin resin-containing components. In particular, from the viewpoint of further reducing the environmental burden, the polyolefin resin-containing components are preferably the polyolefin resin molded articles described above.

[0074] The composite structure of the present invention is not particularly limited as long as it is a member containing polyolefin resin to which the above adhesive tape is attached, but examples include automotive parts such as fenders, door outer panels (door outer panels), back doors, bonnets (front hoods, engine hoods), trunk lids, bumpers, wheel covers, caps, mudguards, bumper unders, spoilers such as side sill spoilers and rear spoilers, fender liners, engine under covers, housings such as taillights, turn signals and stop lamps, air intake pipes, air cleaner cases, resonators, front end modules, cooling fans, fan shrouds, instrument panels, console boxes, glove boxes, steering wheels, shift levers, accelerator pedals, door trims, seats, headrests, ceiling members, floor carpet members, pillar garnishes, armrests, interior lamps, rearview mirror housings, assist grips, air conditioning modules, or parts that constitute these. [Effects of the Invention]

[0075] The present invention provides an adhesive that has excellent adhesion to polyolefin resins such as polypropylene and adherends containing polyolefin resins, and that can be recycled together with polyolefin resins such as polypropylene. Furthermore, the present invention provides an adhesive tape having an adhesive layer containing the adhesive. Moreover, the present invention provides a polyolefin resin molded article formed from a resin composition containing the adhesive and a polyolefin resin. In addition, the present invention provides a composite structure comprising the adhesive tape and a member containing a polyolefin resin to which the adhesive tape is attached. [Brief explanation of the drawing]

[0076] [Figure 1] This diagram schematically illustrates a retention test used to evaluate the retention performance of adhesive tape on polypropylene. [Modes for carrying out the invention]

[0077] The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0078] (Synthesis of radial hydrogenated styrene elastomer A) 4000 g of degassed and dehydrated cyclohexane, 200 g of 1,3-butadiene monomer, 3.0 g of n-butyllithium (n-BuLi), and tetrahydrofuran (THF) were added in an autoclave in a molar ratio of n-BuLi / THF = 40. Polymerization was then carried out at the polymerization initiation temperature of 40°C for 40 minutes, followed by the addition of 100 g of styrene monomer and polymerization for 60 minutes (aromatic alkenyl polymer block (A)). Subsequently, 700 g of 1,3-butadiene monomer was added and polymerization was carried out for 150 minutes (styrene-based block copolymer with diblock structure (AB)). A coupling reaction was carried out on a diblock styrene-based block copolymer (AB) by adding 0.25 molars of tetrachlorosilane (SiCl4) to the polymer ends as a coupling agent, yielding a styrene-based block copolymer with a styrene content of 10% by mass. This copolymer was diluted with purified and dried cyclohexane to adjust the polymer concentration to 5% by mass, and then subjected to the hydrogenation reaction.

[0079] In the hydrogenation reaction, first, 1000 g of the copolymer solution was placed in a thoroughly dried 2 L autoclave equipped with a stirrer, degassed under reduced pressure, and then hydrogenated, and maintained at 90°C under stirring. Next, 50 mL of cyclohexane solution containing 0.2 mmol of di-p-trilbis(η-cyclopentadienyl)titanium and 10 mL of cyclohexane solution containing 0.108 mmol of n-butyllithium (n-BuLi) were mixed at 0°C and 2.0 kg / cm³. 2 The mixture was mixed under hydrogen pressure and added to the copolymer solution in an autoclave. The hydrogenation reaction was started with a hydrogen gas supply pressure of 0.7 MPa-Gauge and a reaction temperature of 80°C under stirring. Once hydrogen absorption was complete, the reaction solution was returned to room temperature and atmospheric pressure and withdrawn from the reaction vessel to obtain radial hydrogenated styrene elastomer (AB) 4C. The resulting radial hydrogenated styrene elastomer (AB) 4C is 1 ¹H-NMR analysis revealed that more than 95% of the butadiene units and less than 5% of the styrene units were hydrogenated.

[0080] The obtained radial hydrogenated styrene elastomer (AB) 4C was dissolved in tetrahydrofuran (THF), and the resulting solution was filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to obtain the GPC test solution. And then there's the GPC system (Waters Corporation, "ACQUITY") TM Advanced Polymer Chromatography TM System), GPC column (Waters Corporation, "HSPgel") TM GPC measurements were performed using an HR MB-M (6.0 mm × 150 mm) column and a differential refractive index detector. The sample injection volume was 10 μL of a 20 mg / mL solution, the flow rate was 0.5 mL / min, and the column temperature was 40°C. Empower3, the software included with the instrument, was used for the analysis. Polystyrene (peak top molecular weights: 2.11 million, 1.09 million, 427,000, 190,000, 37,900, 18,100, 5,970, 2,420, 500) (manufactured by Tosoh Corporation) was used as the standard. GPC measurements were performed using polystyrene as a standard sample. A calibration curve was created using analysis software to convert the eluted amount to the polystyrene molecular weight, and the analysis was performed. The weight-average molecular weight (Mw) was then calculated from the GPC eluted volume using this calibration curve. The weight-average molecular weight was 300,000.

[0081] (Synthesis of (meth)acrylic copolymer B (weight-average molecular weight: 450,000)) In a reactor equipped with a thermometer, stirrer, and condenser, 140 parts by mass of ethyl acetate, 28 parts by mass of 2-ethylhexyl acrylate, 68 parts by mass of n-butyl acrylate, 3.8 parts by mass of acrylic acid, and 0.2 parts by mass of 4-hydroxybutyl acrylate were added. Then, nitrogen gas was blown in to expel dissolved oxygen, and the reactor was heated to 60°C under nitrogen gas flow. Subsequently, 0.1 parts by mass of azobisisobutyronitrile was added to the reactor as a polymerization initiator, and polymerization was started at a constant temperature of 60°C. After that, 0.5 parts by mass of t-hexyl peroxypivalate was added 4 hours after the start of polymerization to continue the polymerization reaction. The polymerization reaction was carried out for a total of 6 hours from the start of polymerization to obtain an ethyl acetate solution containing (meth)acrylic copolymer B. (Example 1) (Making adhesive tape) A solution containing an adhesive composition was obtained by adding 100 parts by mass of DYNARON 8300P (manufactured by ENEOS Material, weight-average molecular weight: 200,000) as an elastomer with saturated hydrocarbon chains as the main chain, 50.0 parts by mass of Alcon P100 (manufactured by Arakawa Chemical Industries, Ltd.) as a tackifying resin, and 300 parts by mass of toluene as a solvent to a container. After thoroughly stirring the obtained solution containing the adhesive composition, it was coated onto the release-treated surface of a 50 μm thick release polyethylene terephthalate (PET) film with one side treated with a release agent using a doctor knife, and the coating solution was dried by heating at 110°C for 10 minutes to form an adhesive layer (50 μm thick) containing the adhesive formed from the adhesive composition (an adhesive without a foamed structure). Furthermore, a 25 μm thick release PET film with one side treated with a release agent was prepared, and the formed adhesive layer and the release-treated surface were placed on top of it to obtain an adhesive tape with a release PET film attached.

[0082] (Measurement of shear storage modulus of adhesive at 30°C) Multiple adhesive layers were prepared by peeling off the release PET films from both sides of the adhesive tape with the obtained release PET film. These layers were stacked to create a laminate consisting only of the adhesive layer with a thickness of 1 mm, and the laminate was cut to a width of 6 mm and a length of 10 mm to obtain test specimens. Next, the obtained test specimens were subjected to dynamic viscoelasticity measurement using a dynamic viscoelasticity measuring device (IT Measurement Control Co., Ltd., "DVA-200") in shear mode under nitrogen atmosphere, measurement temperature range -50°C to 150°C, heating rate 5°C / min, measurement frequency 10 Hz, and strain 0.08%, thereby measuring the shear storage modulus of the adhesive at 30°C. The results are shown in Table 1.

[0083] (Measurement of the glass transition temperature of adhesives) The glass transition temperature of the adhesive was measured by performing dynamic viscoelasticity measurements using the same method as described above for "(Measurement of shear storage modulus of adhesive at 30°C)". The results are shown in Table 1.

[0084] (Measurement of loss tangent of adhesive at 120°C) The loss tangent of the adhesive at 120°C was measured by performing dynamic viscoelasticity measurements using the same method as described above for "(Measurement of shear storage modulus of adhesive at 30°C)". The results are shown in Table 1.

[0085] (Measurement of gel fraction of adhesive) 0.1 g of adhesive was taken from the adhesive layer of the obtained adhesive tape, immersed in 50 mL of tetrahydrofuran (THF), and shaken for 24 hours at a temperature of 23°C and 200 rpm using a shaker. After shaking, the THF and the adhesive that had absorbed THF and swollen were filtered off using a metal mesh (mesh size #200, mass: W1 (g)). The adhesive that had absorbed THF and swollen was dried at 110°C for 1 hour, and the mass W2 (g) of the adhesive containing the metal mesh was measured. The gel fraction was calculated using the following formula (2). The results are shown in Table 1. Gel fraction (mass%) = 100 × (W2 - W1) / 0.1 (2) (W1: Mass of metal mesh, W2: Mass of adhesive after drying (including metal mesh))

[0086] (Examples 2-6, 12-16, Comparative Examples 4-6) In the "(Preparation of Adhesive Tape)" described above, an adhesive tape having an adhesive layer containing an adhesive without a foamed structure was obtained in the same manner as in Example 1, except that the composition of the adhesive composition was as shown in Tables 1-2 and 4, and measurements were performed. The results are shown in Tables 1-2 and 4.

[0087] (Examples 7-11, 17-26, Comparative Examples 2-3) In the "(Preparation of Adhesive Tape)" described above, a laminate was prepared by forming an adhesive layer and layering a release PET film in the same manner as in Example 1, except that the composition of the adhesive composition was as shown in Tables 1 to 4. The obtained laminate was then further irradiated with an electron beam at the acceleration voltage and irradiation energy shown in Tables 1 to 4, using an electron beam irradiation device (NHV Corporation, "EBC300-60"), on the adhesive layer on one side of the laminate through the release PET film (EB irradiation), thereby obtaining an adhesive tape having an adhesive layer containing an adhesive without a foamed structure. The measurements were performed in the same manner as in Example 1, and the results are shown in Tables 1 to 4.

[0088] (Comparative Example 1) To 100 parts by mass of the solid content of the ethyl acetate solution of (meth)acrylic copolymer B prepared by the method described above, the tackifying resin and crosslinking agent shown in Table 4 were added and thoroughly stirred to obtain a solution containing the adhesive composition. Using this solution, an adhesive tape having an adhesive layer containing an adhesive without a foamed structure was prepared in the same manner as in Example 1. The measurements were performed in the same manner as in Example 1, and the results are shown in Table 4.

[0089] <Rating> The adhesive tapes obtained in the examples and comparative examples were evaluated as follows. The results are shown in Tables 1 to 4.

[0090] (Adhesion to polyolefin resins) A 25 μm thick release PET film (the side not to be measured) was peeled off one side of the obtained adhesive tape. The exposed adhesive layer was then attached to a 23 μm thick polyethylene terephthalate (PET) film, ensuring no air was trapped inside. The tape was then cut to a width of 10 mm and a length of 100 mm to prepare a test specimen. The adhesive layer exposed by peeling off the release PET film from the obtained test specimen was then bonded to a polypropylene board (Takiron CI Co., Ltd., "RPP 1350") that had been washed with ethanol and then wiped dry. A 2 kg rubber roller was used to press the tape back and forth once at a speed of 300 mm / min to prepare a measurement sample. A 90° peel test was performed on the obtained measurement sample using a tensile testing machine (A&D Co., Ltd., "RTI-1310") in accordance with JIS Z 0237, under conditions of 23°C, 50% RH, and a peeling speed of 300 mm / min. The 90° peel force (N / 10 mm) was measured by peeling the adhesive tape from the polypropylene board. The adhesive strength of the adhesive tape to polyolefin resin was evaluated according to the following criteria. • ○: The 90° peel force on the polypropylene sheet was 2.5 N / 10 mm or more. • ×: The 90° peel force on the polypropylene sheet was less than 2.5 N / 10 mm.

[0091] (Compatibility with polyolefin resins) (1) Preparation of polypropylene molded articles derived from resin compositions containing adhesive tape 2 g of the adhesive tape obtained in the above-mentioned "(Preparation of Adhesive Tape)" and 198 g of block polypropylene (Novatec PP BC10HRF, manufactured by Nippon Polypropylene Co., Ltd.) were heated and kneaded using a Plastmill at 200°C and 50 rpm. 7 g of the resin composition obtained by heating and kneading was weighed out, and strip-shaped test pieces (size 80 mm × 10 mm × thickness 4 mm) were prepared as polypropylene molded articles derived from the resin composition containing the adhesive tape for Charpy impact resistance evaluation using an injection molding machine (HAAKE Minilab3, manufactured by Thermo Fisher Scientific) under the conditions of cylinder temperature 200°C, mold temperature 40°C, inject press 500 bar / 10 sec, and post press 400 bar / 10 sec. For the plast mill, we used a HAAKE RheoDrive 16OS (manufactured by Thermo Fisher Scientific), and connected a Rheomix 3000 OS roller rotor (manufactured by Thermo Fisher Scientific) to the mixer section.

[0092] (2) Preparation of polypropylene molded articles derived from resin compositions that do not contain adhesive tape Strip-shaped test pieces were prepared as polypropylene molded articles derived from a resin composition that does not contain adhesive tape for Charpy impact resistance evaluation, in the same manner as described in "(1) Preparation of polypropylene molded articles derived from a resin composition containing adhesive tape" above, except that 0g of adhesive tape and 200g of block polypropylene were used.

[0093] (3) Evaluation of Charpy impact resistance The strip-shaped test pieces obtained in the above-mentioned "(1) Preparation of polypropylene molded articles derived from resin compositions containing adhesive tape" and "(2) Preparation of polypropylene molded articles derived from resin compositions not containing adhesive tape" were each notched to a depth of 2 mm using a notching machine (Yasuda Seiki Seisakusho Co., Ltd., "Notching Machine No. 189-PNCA") in accordance with JIS K7111-1. The impact strength was then measured by applying a 2 J impact in the edgewise impact direction with a hammer at a constant temperature chamber equipped with a Charpy impact tester (Yasuda Seiki Seisakusho Co., Ltd., "Impact Tester No. 258-L-PC") at a temperature of 23°C. The impact strength was measured by repeating the measurement five times and using the average of the three values ​​obtained, excluding the maximum and minimum values. Based on the obtained impact strength values, the Charpy impact resistance degradation rate (%) was calculated using the following formula. Charpy impact resistance degradation rate (%) = 100 - [((Impact strength of polypropylene molded article derived from resin composition containing adhesive tape) / (Impact strength of polypropylene molded article derived from resin composition not containing adhesive tape)) × 100]

[0094] The obtained Charpy impact resistance degradation rate (%) was used to evaluate the compatibility of the adhesive tape with polyolefin resin according to the following criteria. ○: The Charpy impact resistance degradation rate was less than 10%. ×: The Charpy impact resistance degradation rate was 10% or more. If the evaluation is "○", then the adhesive tape of the present invention can be practically recycled together with polyolefin resins such as polypropylene.

[0095] (Holding performance at high temperatures) (1) Retention performance for polypropylene (1-1) Holding performance at 40°C The 25 μm thick release PET film was peeled off one side of the obtained adhesive tape, and it was attached to a 23 μm thick polyethylene terephthalate (PET) film, ensuring no air was trapped inside. The tape was then cut into 10 mm wide strips and bonded to a polypropylene board (Takiron CI Co., Ltd., "RPP 1350") that had been washed with ethanol and then wiped dry, by running a 2 kg rubber roller back and forth at a speed of 300 mm / min once. Next, cuts were made in the adhesive tape so that the bonding area was 10 mm x 10 mm, and the test sample was prepared by letting it stand at 23°C for 20 minutes. The prepared test sample was placed in a 40°C oven and heated for another 20 minutes. Then, under conditions of 40°C and 50% RH, a 150 g weight 4 was suspended from the PET film 1 as shown in Figure 1 to apply a load in the shear direction, and this state was maintained for 24 hours in a holding test. During the retention test, we observed whether or not the adhesive tape fell. If the adhesive tape fell, we measured the time from the start of the retention test until the tape fell, and evaluated the retention performance at 40°C according to the criteria described later.

[0096] (1-2) Holding performance at 80°C The evaluation of the holding performance at 80°C was performed using the same method as described in "(1-1) Holding performance at 40°C" above, except that the prepared test sample was placed in an 80°C oven and heated for a further 20 minutes, followed by a holding test in which the sample was held under load for 1 hour at 80°C and 50% RH.

[0097] (2) Retention performance against SUS Except for using a test sample made by attaching adhesive tape to a SUS304 plate instead of a polypropylene plate (manufactured by Takiron CI Co., Ltd., "RPP 1350"), and conducting a holding test in which the applied load was maintained for 24 hours, the holding performance against SUS was evaluated using the same method as described in "(1-2) Holding performance at 80°C".

[0098] (3) Evaluation The retention performance in the above-mentioned "(1-1) Retention performance at 40°C", "(1-2) Retention performance at 80°C", and "(2) Retention performance against SUS" was evaluated according to the following criteria, and the retention performance of the adhesive tape at high temperatures was assessed. • ○: The adhesive tape did not fall, or the time the adhesive tape remained in place was 1 hour or more. •△: The adhesive tape fell for more than 10 minutes but less than 1 hour. • ×: The adhesive tape was left in place for less than 10 minutes. Even if any of the above evaluations result in "×", the adhesive and adhesive tape of the present invention can still be used without problems depending on the application.

[0099] [Table 1]

[0100] [Table 2]

[0101] [Table 3]

[0102] [Table 4] [Industrial applicability]

[0103] The present invention provides an adhesive that has excellent adhesion to polyolefin resins such as polypropylene and adherends containing polyolefin resins, and that can be recycled together with polyolefin resins such as polypropylene. Furthermore, the present invention provides an adhesive tape having an adhesive layer containing the adhesive. Moreover, the present invention provides a polyolefin resin molded article formed from a resin composition containing the adhesive and a polyolefin resin. In addition, the present invention provides a composite structure comprising the adhesive tape and a member containing a polyolefin resin to which the adhesive tape is attached. [Explanation of Symbols]

[0104] 1 PET film 2 Adhesive tape 3 Polypropylene sheet 4. 150g weight

Claims

1. The adhesive is formed from an adhesive composition containing an elastomer with a saturated hydrocarbon chain as its main chain and a tackifying resin. The adhesive has a shear storage modulus of 6.00 × 10 at 30°C, as measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz. ５ It is less than Pa, The aforementioned adhesive has a glass transition temperature exceeding -5°C, as measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz and a measurement temperature range of -50°C to 150°C. An adhesive characterized by the following features.

2. The adhesive according to claim 1, wherein the loss tangent at 120°C, as measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz, is less than 1.

00.

3. The adhesive according to claim 1 or 2, wherein the elastomer having the saturated hydrocarbon chain as its main chain includes a styrene-based elastomer.

4. The adhesive according to claim 3, wherein the styrene-based elastomer comprises a hydrogenated styrene-based elastomer.

5. The adhesive according to claim 4, wherein the hydrogenated styrene elastomer comprises a hydrogenated A-B-A type linear block copolymer.

6. The adhesive according to claim 5, wherein the hydrogenated styrene elastomer comprises a styrene-ethylene-butylene-styrene copolymer.

7. The adhesive according to claim 1 or 2, wherein the tackifying resin comprises at least one selected from the group consisting of petroleum resins and terpene resins.

8. The adhesive according to claim 7, wherein the content of the tackifying resin relative to 100 parts by mass of the elastomer having the saturated hydrocarbon chain as the main chain is 40 parts by mass or more.

9. The adhesive according to claim 1 or 2, wherein the adhesive composition contains a softening agent.

10. The adhesive according to claim 1 or 2, which does not have a foamed structure.

11. An adhesive tape having an adhesive layer containing the adhesive according to claim 1 or 2.

12. The adhesive tape according to claim 11, wherein the thickness of the adhesive layer is 10 μm or more.

13. The adhesive tape has a base material, The substrate contains a polyolefin resin. The adhesive tape according to claim 11.

14. A polyolefin resin molded article formed from a resin composition containing the adhesive described in claim 1 or 2 and a polyolefin resin.

15. A composite structure comprising the adhesive tape described in claim 11 and a member containing a polyolefin resin to which the adhesive tape is attached.

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