Composite structure, polyolefin resin molded body, motor vehicle member, and method for producing polyolefin resin molded body

Abstract

The purpose of the present invention is to provide a composite structure in which an adhesive member and a member to be bonded can be recycled together. Another purpose of the present invention is to provide a polyolefin resin molded body formed from said composite structure. Another purpose of the present invention is to provide a motor vehicle member containing said composite structure or said polyolefin resin molded body. Another purpose of the present invention is to provide a method for producing a polyolefin resin molded body using said composite structure. The present invention is a composite structure comprising an adhesive member and a member to be bonded. The adhesive member has an adhesive agent formed from an adhesive composition. The adhesive composition contains an acrylic copolymer having a constituent unit derived from an alkyl (meth)acrylate ester and a constituent unit derived from an olefin-based polymer having a polymerizable unsaturated double bond at a terminal. The member to be bonded includes a member that contains a polyolefin resin.

Description

Composite structure, polyolefin resin molded body, automobile component, and method for manufacturing polyolefin resin molded body

[0001] The present invention relates to a composite structure. The present invention also relates to a polyolefin resin molded article obtained from the composite structure. The present invention further relates to an automobile member. In addition, the present invention also relates to a method for producing a polyolefin resin molded article.

[0002] Conventionally, adhesive tapes having an adhesive layer containing an adhesive have been widely used to fix components in electronic components, vehicles, houses, and building materials (e.g., Patent Documents 1 to 3). Specifically, adhesive tapes have been 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.

[0003] JP 2015-052050 A JP 2015-021067 A JP 2015-120876 A

[0004] In recent years, efforts to address environmental issues have led to the desire to recover and reuse (recycle) resources once used, and automobiles are also being recycled. Automobile recycling is typically performed by removing reusable and easily removable parts, such as engines, doors, catalysts, and plastic parts, from scrapped automobiles, dismantling the automobile, pressing the automobile, shredding the pressed materials, and separating metals such as iron. Automobile shredder residue (ASR) remaining after separating metals such as iron contains resins, metals, paper, wood, and the like. From the perspective of improving automobile recycling efficiency, it is desirable to reuse ASR as well, and particularly desirable to reuse the resins contained in large amounts in ASR. However, because the resins contained in ASR contain a mixture of various resins derived from numerous components, such as automobile parts and adhesives used to secure automobile parts, resins obtained by direct recycling are often of poor quality. Furthermore, if resin separation is performed to improve quality, it is difficult to separate and recover the resins, requiring a great deal of time and expense. As a result, the resins in ASR are not currently being fully reused. Furthermore, the resin parts removed before pressing contain a mixture of many different resins derived from various materials, such as adhesives, and are therefore not currently being fully reused.

[0005] An object of the present invention is to provide a composite structure that allows for the simultaneous recycling of a pressure-sensitive adhesive member and an adherend member. Another object of the present invention is to provide a polyolefin resin molded product molded from the composite structure. A further object of the present invention is to provide an automotive component that includes the composite structure or the polyolefin resin molded product. Additionally, an object of the present invention is to provide a method for producing a polyolefin resin molded product using the composite structure.

[0006] Disclosure 1 is a composite structure including a pressure-sensitive adhesive member and an adherend member, wherein the pressure-sensitive adhesive member has a pressure-sensitive adhesive formed from a pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition containing an acrylic copolymer having structural units derived from a (meth)acrylic acid alkyl ester and structural units derived from an olefin-based polymer having a terminal polymerizable unsaturated double bond, and the adherend member is a composite structure including a member containing a polyolefin resin. Disclosure 2 is the composite structure of Disclosure 1, wherein two or more adherend members are bonded together by the pressure-sensitive adhesive member. Disclosure 3 is the composite structure of Disclosure 1 or 2, wherein the polyolefin resin in the adherend member contains a polypropylene-based block copolymer. Disclosure 4 is the composite structure of Disclosure 1, 2, or 3, wherein the adherend member contains at least one colorant selected from the group consisting of pigments and dyes. The present disclosure 5 is a composite structure according to the present disclosure 1, 2, 3, or 4, wherein, in the pressure-sensitive adhesive composition, the content of the structural unit derived from the olefin polymer having a terminal polymerizable unsaturated double bond in the acrylic copolymer is 5 mass% or more, and the composite structure satisfies at least one constitution selected from the group consisting of the following first constitution, second constitution, and third constitution:First configuration: (1) the structural units derived from the (meth)acrylic acid alkyl ester do not contain structural units derived from a (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms, or the structural units derived from the (meth)acrylic acid alkyl ester contain structural units derived from a (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms, and the content of structural units derived from the (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms in the acrylic copolymer is 30% by mass or less, and (2) the gel fraction of the pressure-sensitive adhesive is 10% by mass or more and 90% by mass or less. Second configuration: (1) the structural units derived from the (meth)acrylic acid alkyl ester contain structural units derived from a (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms in the acrylic copolymer, and the content of structural units derived from the (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms in the acrylic copolymer is more than 10% by mass and 60% by mass or less, and (2) the gel fraction of the pressure-sensitive adhesive is 55% by mass or less. Third configuration: (1) The SP value of the acrylic copolymer is 9.30 (cal / cm). ３ ) １／２ More than 9.95 (cal / cm ３ ) １／２and (2) the gel fraction of the pressure-sensitive adhesive is 10% by mass or more and 55% by mass or less. Disclosure 6 is the composite construct of Disclosures 1, 2, 3, 4, or 5, wherein the acrylic copolymer has a constituent unit derived from a polar functional group-containing monomer, and the constituent unit derived from the polar functional group-containing monomer includes at least one selected from the group consisting of a constituent unit derived from a carboxy group-containing monomer and a constituent unit derived from a hydroxyl group-containing monomer. Disclosure 7 is the composite construct of Disclosure 6, wherein the constituent unit derived from the polar functional group-containing monomer includes a constituent unit derived from the hydroxyl group-containing monomer. The present disclosure 8 is the composite structure of the present disclosure 7, wherein the structural units derived from the (meth)acrylic acid alkyl ester include structural units derived from a (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 7 or more carbon atoms, the content of the structural units derived from the (meth)acrylic acid alkyl ester in the acrylic copolymer being 5% by mass or more and 90% by mass or less, the structural units derived from the polar functional group-containing monomer do not include structural units derived from the carboxy group-containing monomer, or the structural units derived from the polar functional group-containing monomer include structural units derived from the carboxy group-containing monomer, the content of the structural units derived from the carboxy group-containing monomer in the acrylic copolymer is 8% by mass or less, and the content of the structural units derived from the hydroxyl group-containing monomer in the acrylic copolymer is 0.01% by mass or more. The present disclosure 9 is the composite structure of the present disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the PSA contains a tackifier resin. Disclosure 10 is the composite structure of Disclosure 9, wherein the content of the tackifier resin per 100 parts by mass of the acrylic copolymer is 40 parts by mass or less. Disclosure 11 is the composite structure of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the PSA member is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the PSA. Disclosure 12 is the composite structure of Disclosure 11, wherein the pressure-sensitive adhesive layer has a thickness of 5 μm or more and 75 μm or less. Disclosure 13 is the composite structure of Disclosures 11 or 12, wherein the pressure-sensitive adhesive tape does not have a substrate.Disclosure 14 is the composite structure of Disclosures 11 or 12, wherein the pressure-sensitive adhesive tape has a substrate, and the substrate contains a polyolefin resin. Disclosure 15 is the composite structure of Disclosures 11, 12, 13, or 14, wherein the pressure-sensitive adhesive tape has a 180° peel strength from a polypropylene plate at 23°C of 5.0 N / 25 mm or more. Disclosure 16 is the composite structure of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, wherein the content of the pressure-sensitive adhesive member in the composite structure is 0.1% by mass or more and 3.0% by mass or less. Disclosure 17 is the composite structure of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, wherein a primer layer is provided between the adherend and the pressure-sensitive adhesive member. Disclosure 18 is the composite structure of Disclosure 17, wherein the primer forming the primer layer is at least one selected from the group consisting of a polyolefin-based primer, a urethane-based primer, and a metal alkoxide-based primer. Disclosure 19 is a polyolefin resin molded body molded from the composite structure of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18. Disclosure 20 is an automotive component comprising the composite structure of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, or the polyolefin resin molded body of Disclosure 19. The present disclosure 21 is a method for producing a polyolefin resin molded article, comprising a step of molding, without separating, the composite structure of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18. The present invention will be described in detail below.

[0007] The present inventors have focused on the fact that resins used in automobiles contain a high proportion of polyolefin resins such as polypropylene, and have investigated ways to suppress deterioration in the quality of resins obtained by recycling all of the resins used in automobiles at once.The present inventors have found that, in a composite structure having a pressure-sensitive adhesive member and an adherend, a member containing a polyolefin resin is selected as the adherend, and the pressure-sensitive adhesive of the adhesive member is an acrylic copolymer having a specific composition, and as a result, a composite structure can be obtained in which the adherend and the pressure-sensitive adhesive member can be recycled at once, thereby completing the present invention.

[0008] The composite structure of the present invention comprises an adhesive member and an adherend. The composite structure of the present invention allows the adhesive member and adherend to be recycled together, thereby reducing the environmental impact. From the viewpoint of ease of handling in the recycling process, the composite structure of the present invention preferably has two or more adherends bonded together with the adhesive member. The two or more adherends may be the same or different. Two or more adherends that are different means that at least one of the material and shape of the adherends is different.

[0009] The adherend member includes a member containing a polyolefin resin. In this specification, the term "polyolefin resin" refers to any resin having structural units derived from olefins, and may also refer to a copolymer having structural units other than those derived from olefins. Examples of copolymers having structural units other than those derived from olefins include polyolefin rubber and polyolefin block copolymers.

[0010] Examples of the polyolefin resin in the adherend include thermoplastic olefin resins and thermosetting olefin resins. Among these, thermoplastic olefin resins are preferred from the viewpoint of ease of thermal melting during recycling. Examples of the thermoplastic olefin resin include polyethylene, polypropylene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), polyolefin thermoplastic elastomer (TPO), ethylene propylene rubber (EPDM), and polypropylene block copolymers. Among these, from the viewpoint of further improving the impact resistance of the adherend, it is preferable that the polyolefin resin in the adherend contains a polypropylene block copolymer. Examples of the polypropylene block copolymer include copolymers in which ethylene is copolymerized with a propylene block.

[0011] In the adherend, the preferred lower limit of the content of the olefin-derived structural units in the polyolefin resin is 50% by mass. A preferred lower limit of 50% by mass or more of the olefin-derived structural units further improves the quality of the resin obtained by recycling the composite structure of the present invention, making it easier to recycle the composite structure of the present invention in bulk. A more preferred lower limit of the content of the olefin-derived structural units is 75% by mass, and an even more preferred lower limit is 90% by mass. Furthermore, in the adherend, the higher the content of the olefin-derived structural units in the polyolefin resin, the more preferred, and it may even be 100% by mass. In the adherend, it is most preferred that the polyolefin resin is composed only of structural units derived from the olefin.

[0012] Examples of the olefin-derived structural units in the polyolefin resin of the adherend include propylene-derived structural units, ethylene-derived structural units, isoprene-derived structural units, butadiene-derived structural units, butylene-derived structural units, etc. Among these, from the viewpoint of facilitating the collective recycling of the composite structure of the present invention, it is preferable that the olefin-derived structural units include propylene-derived structural units.

[0013] In the adherend member, examples of the polyolefin resin composed only of structural units derived from the olefin include polypropylene, polyethylene, polyisoprene, cyclic olefin, cyclic olefin copolymer, polybutadiene, polybutylene, etc. Among these, from the viewpoint of facilitating the collective recycling of the composite structure of the present invention, it is preferable that the polyolefin resin contains polypropylene.

[0014] The adherend may contain one type of resin or two or more types of resin. When the adherend contains two or more types of resin, it is preferable that the polyolefin resin be the main component of all resins in the adherend. The preferred lower limit of the content of the polyolefin resin in all resins is 50% by mass. When the content of the olefin resin is 50% by mass or more, the quality of the resin obtained by recycling the composite structure of the present invention is further improved, making it easier to recycle the composite structure of the present invention in bulk. When the adherend contains two or more types of resin, the more preferred lower limit of the content of the olefin resin is 70% by mass, and even more preferred is 90% by mass. The higher the content of the polyolefin resin, the better, and it may even be 100% by mass (i.e., all resins contained in the adherend are polyolefin resins).

[0015] The adherend may contain at least one selected from the group consisting of pigments and dyes. Even if the composite structure contains at least one selected from the group consisting of pigments and dyes, the composite structure of the present invention can be recycled collectively without any problems.

[0016] The adherend is preferably surface-treated. Surface-treated adherends improve adhesion between the adhesive and the adherend, preventing the adhesive from peeling off from the adherend during cutting or crushing in the recycling process of the composite structure of the present invention, improving handling. As a result, the composite structure of the present invention can be easily recycled in bulk.

[0017] Examples of the surface treatment include a method of acid-modifying the surface of the adherend to make it highly polar, a method of corona-treating the surface of the adherend, etc. A specific example of a method of acid-modifying the surface of the adherend is coating the surface of the adherend with maleic acid-modified polypropylene.

[0018] The composite structure of the present invention is not particularly limited as long as it comprises the above-mentioned adhesive member such as a liquid adhesive or adhesive tape and the above-mentioned adherend member containing a polyolefin resin. Specific examples include automobile parts such as fenders, door outer panels (door outers), 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 tail lamps, turn signals, stop lamps, etc., 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, room mirror housings, assist grips, air conditioner modules, etc., bonded together with a liquid adhesive or adhesive tape, or parts themselves formed by bonding together the components constituting these parts with a liquid adhesive or adhesive tape.

[0019] The pressure-sensitive adhesive member has a pressure-sensitive adhesive formed from a pressure-sensitive adhesive composition. Methods for forming the pressure-sensitive adhesive from the pressure-sensitive adhesive composition include, for example, a method of heating the pressure-sensitive adhesive composition, and a method of irradiating the pressure-sensitive adhesive composition with ultraviolet light or an electron beam. In the method for forming the pressure-sensitive adhesive, the degree of crosslinking and gel fraction of the pressure-sensitive adhesive can be adjusted by adjusting the conditions (e.g., heating temperature, irradiation intensity of ultraviolet light or an electron beam, etc.).

[0020] The pressure-sensitive adhesive composition contains an acrylic copolymer. The acrylic copolymer has structural units derived from a (meth)acrylic acid alkyl ester. In this specification, "(meth)acrylic" means acrylic or methacrylic.

[0021] The structural unit derived from the alkyl (meth)acrylate may include a structural unit derived from an alkyl (meth)acrylate in which the alkyl group derived from an alcohol has 7 or more carbon atoms. The upper limit of the number of carbon atoms in the alkyl group in the structural unit derived from an alkyl (meth)acrylate in which the alkyl group derived from an alcohol has 7 or more carbon atoms is preferably 15. In this specification, the term "alcohol-derived alkyl group" refers to an alkyl group bonded to an oxygen atom of an ester bond in the alkyl (meth)acrylate. The alcohol-derived alkyl group is preferably linear or branched.

[0022] Examples of (meth)acrylic acid alkyl esters in which the alkyl group derived from the alcohol has 7 or more carbon atoms include isoheptyl (meth)acrylate, n-heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate. Among these, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, and n-heptyl (meth)acrylate are preferred from the viewpoint of further improving adhesive strength to polyolefin resins such as polypropylene. These alkyl (meth)acrylates may be used alone or in combination of two or more.

[0023] The content of the structural units derived from the (meth)acrylic acid alkyl ester in which the alcohol-derived alkyl group has 7 or more carbon atoms in the acrylic copolymer is preferably 5% by mass at the lower limit and 90% by mass at the upper limit. When the content of the structural units derived from the (meth)acrylic acid alkyl ester in which the alcohol-derived alkyl group has 7 or more carbon atoms is within the above range, the affinity with the polyolefin resin is further improved. The content of the structural units derived from the (meth)acrylic acid alkyl ester in which the alcohol-derived alkyl group has 7 or more carbon atoms is more preferably 30% by mass at the lower limit and 75% by mass at the upper limit.

[0024] The structural unit derived from the alkyl (meth)acrylate may include a structural unit derived from an alkyl (meth)acrylate in which the alkyl group derived from an alcohol has 5 or 6 carbon atoms.

[0025] Examples of the (meth)acrylic acid alkyl esters in which the alkyl group derived from the alcohol has 5 carbon atoms include n-pentyl (meth)acrylate, isopentyl (meth)acrylate, etc. Examples of the (meth)acrylic acid alkyl esters in which the alkyl group derived from the alcohol has 6 carbon atoms include n-hexyl (meth)acrylate, isohexyl (meth)acrylate, etc.

[0026] The content of the structural units derived from the (meth)acrylic acid alkyl ester in the acrylic copolymer is preferably 20% by mass at the lower limit and 90% by mass at the upper limit. Having a content of the structural units derived from the (meth)acrylic acid alkyl ester of 20% by mass or more makes it easier to maintain the performance of the adhesive, and also allows the polymerization reaction during production to proceed efficiently. Having a content of the structural units derived from the (meth)acrylic acid alkyl ester of 90% by mass or less makes it easier to maintain the quality of the polyolefin resin obtained when recycled together with the polyolefin resin. The content of the structural units derived from the (meth)acrylic acid alkyl ester is more preferably 30% by mass at the lower limit, more preferably 85% by mass at the upper limit, even more preferably 40% by mass at the lower limit, and even more preferably 80% by mass at the upper limit.

[0027] The acrylic copolymer has structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond. Because the acrylic copolymer has structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond, when a pressure-sensitive adhesive is formed, the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond in the side chain of the acrylic copolymer aggregate through interaction, forming a structure in which pseudo-intermolecular crosslinks are formed. Because the acrylic copolymer has such a structure, the pressure-sensitive adhesive exhibits hard properties like a crosslinked pressure-sensitive adhesive when strain applied to the pressure-sensitive adhesive is small, improving retention performance. On the other hand, when peel stress is applied and strain increases, the pseudo-crosslinks are broken and the acrylic copolymer molecules stretch, so the pressure-sensitive adhesive of the present invention exhibits high flexibility and further improves adhesive strength. In other words, because the acrylic copolymer has structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond, the pressure-sensitive adhesive exhibits improved retention performance and further improves adhesive strength. This improves the adhesion between the PSA member and the adherend, preventing peeling of the PSA member from the adherend during cutting or pulverization in the recycling process of the composite structure of the present invention, thereby improving handleability. As a result, the composite structure of the present invention can be recycled in bulk. Furthermore, the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond have low polarity, and the acrylic copolymer has improved compatibility with polyolefin resins such as polypropylene. This results in a polyolefin resin molded product obtained by recycling the PSA and polyolefins such as polypropylene in bulk with superior quality. As a result, the composite structure of the present invention can be recycled in bulk. Furthermore, the improved compatibility of the acrylic copolymer with polyolefin resins such as polypropylene improves wettability, resulting in the PSA having superior retention performance for polyolefin resins such as polypropylene and adherends containing polyolefin resins.

[0028] The olefin polymer having a terminal polymerizable unsaturated double bond may have a polymerizable unsaturated double bond at one terminal or at both terminals. Among them, an olefin polymer having a terminal polymerizable unsaturated double bond is preferred from the viewpoint of facilitating the formation of an appropriate number of pseudo-crosslinks.

[0029] Examples of the olefin polymer having a terminal polymerizable unsaturated double bond include ethylene-butylene copolymers, ethylene-propylene copolymers, ethylene polymers, propylene polymers, butylene polymers, etc., which have a group having a polymerizable unsaturated double bond at one or both terminals. These olefin polymers having a terminal polymerizable unsaturated double bond may be used alone or in combination of two or more.

[0030] Examples of the group having a polymerizable unsaturated double bond include a (meth)acryloyl group, a vinyl ether group, and a styryl group. Among these, a (meth)acryloyl group is preferred because of its excellent copolymerizability with the (meth)acrylic acid alkyl ester. In this specification, "(meth)acryloyl" means acryloyl or methacryloyl.

[0031] Examples of olefin polymers having a (meth)acryloyl group at their termini include an ethylene macromonomer having a (meth)acryloyl group at one terminus, a propylene macromonomer having a (meth)acryloyl group at one terminus, an ethylene-butylene macromonomer having a (meth)acryloyl group at one terminus, and an ethylene-propylene macromonomer having a (meth)acryloyl group at one terminus. Among these, an ethylene-butylene macromonomer having a (meth)acryloyl group at one terminus and an ethylene-propylene macromonomer having a (meth)acryloyl group at one terminus are preferred, as they make it easier to satisfy the glass transition temperature described below and further improve the adhesive strength of the pressure-sensitive adhesive of the present invention. In this specification, the term "macromonomer" refers to a monomer having a polymerizable functional group and a weight-average molecular weight of approximately 1,000 to 100,000.

[0032] The preferred lower limit of the content of the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond in the acrylic copolymer is 5% by mass. When the content of the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond is 5% by mass or more, the compatibility of the acrylic copolymer with polyolefin resins such as polypropylene is improved. As a result, polyolefin resin molded articles obtained by recycling the pressure-sensitive adhesive and polyolefin resins such as polypropylene together are of excellent quality. As a result, the composite structure of the present invention can be recycled together more easily. Furthermore, an appropriate number of pseudo-crosslinks are formed in the acrylic copolymer, further improving the adhesive strength and retention performance of the pressure-sensitive adhesive. Furthermore, the wettability of the pressure-sensitive adhesive is improved by reducing the interfacial free energy with polyolefin resins such as polypropylene. As a result, the pressure-sensitive adhesive has better retention performance for polyolefin resins such as polypropylene and adherends containing polyolefin resins. A more preferred lower limit of the content of the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond is 10% by mass, and an even more preferred lower limit is 20% by mass. Furthermore, the preferred upper limit of the content of the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond is 50% by mass. By having the content of the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond be 50% by mass or less, cohesive failure of the PSA can be further suppressed. The preferred upper limit of the content of the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond is 45% by mass, and even more preferably 40% by mass.

[0033] The acrylic copolymer preferably has a structural unit derived from a polar functional group-containing monomer. The acrylic copolymer has a structural unit derived from a polar functional group-containing monomer, which increases the polarity of the acrylic copolymer, thereby increasing the cohesive strength of the pressure-sensitive adhesive and further improving its retention performance at high temperatures. Furthermore, when the pressure-sensitive adhesive of the present invention contains a crosslinking agent described below, the acrylic copolymer has a structure crosslinked via the crosslinking agent, further improving the adhesive strength and retention performance of the pressure-sensitive adhesive of the present invention.

[0034] Examples of the polar functional group-containing monomer include carboxy group-containing monomers, hydroxy group-containing monomers, amide group-containing monomers, and amino group-containing monomers. In particular, from the viewpoint of further improving the adhesive strength and retention performance of the pressure-sensitive adhesive of the present invention, the polar functional group-containing monomer preferably includes at least one selected from the group consisting of carboxy group-containing monomers and hydroxy group-containing monomers, and more preferably includes a hydroxy group-containing monomer. That is, the structural unit derived from the polar functional group-containing monomer preferably includes at least one selected from the group consisting of structural units derived from carboxy group-containing monomers and structural units derived from hydroxy group-containing monomers, and more preferably includes a structural unit derived from a hydroxy group-containing monomer. These polar functional group-containing monomers may be used alone, or two or more may be used in combination.

[0035] Examples of the carboxy group-containing monomer include unsaturated carboxylic acids such as (meth)acrylic acid, (meth)acryloylacetic acid, (meth)acryloylpropionic acid, (meth)acryloylbutyric acid, (meth)acryloylpentanoic acid, crotonic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, and 2-carboxyethyl (meth)acrylate.

[0036] Examples of the hydroxyl group-containing monomer include 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate.

[0037] Examples of the amide group-containing monomer include N-vinyl-2-pyrrolidone, N-vinylcaprolactam, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N-isopropyl(meth)acrylamide.

[0038] Examples of the amino group-containing monomer include (meth)acryloylmorpholine, 2-dimethylaminoethyl (meth)acrylate, and 2-diethylaminoethyl (meth)acrylate.

[0039] The content of the structural units derived from the hydroxyl group-containing monomer in the acrylic copolymer is preferably 0.01% by mass at the lower limit and 6% by mass at the upper limit. When the content of the structural units derived from the hydroxyl group-containing monomer is 0.01% by mass or more, crosslinking via the crosslinking agent in the acrylic copolymer is more likely to occur, thereby improving the adhesive strength and retention performance of the pressure-sensitive adhesive. When the content of the structural units derived from the hydroxyl group-containing monomer is 6% by mass or less, the pressure-sensitive adhesive does not become too hard, and the adhesive strength of the pressure-sensitive adhesive is further improved. A more preferred lower limit of the content of the structural units derived from the hydroxyl group-containing monomer is 0.03% by mass, an even more preferred lower limit is 0.05% by mass, and an even more preferred upper limit is 3% by mass.

[0040] The content of the structural units derived from the carboxy group-containing monomer in the acrylic copolymer is preferably 0.1% by mass at the lower limit and 8% by mass at the upper limit. When the content of the structural units derived from the carboxy group-containing monomer is 0.1% by mass or more, the cohesive strength of the PSA is further improved, and the adhesive strength and retention performance are further improved. When the content of the structural units derived from the carboxy group-containing monomer is 8% by mass or less, the PSA does not become too hard, and a good balance between adhesive strength and retention performance is achieved. A more preferred lower limit of the content of the structural units derived from the carboxy group-containing monomer is 0.3% by mass, a more preferred upper limit is 6% by mass, an even more preferred upper limit is 5% by mass, and an even more preferred upper limit is 2.5% by mass. Note that, from the viewpoint of affinity with polyolefin resins, the acrylic copolymer does not need to have structural units derived from the carboxy group-containing monomer.

[0041] The total content of the structural units derived from the polar functional group-containing monomer in the acrylic copolymer is preferably 0.1% by mass at the lower limit and 10% by mass at the upper limit. When the total content of the structural units derived from the polar functional group-containing monomer is 0.1% by mass or more, the polarity of the acrylic copolymer is increased, thereby increasing the cohesive strength of the PSA and further improving its retention performance at high temperatures. Furthermore, the polymerization reaction is more likely to proceed smoothly. When the total content of the structural units derived from the polar functional group-containing monomer is 10% by mass or less, the PSA does not become too hard and has sufficient initial adhesive strength. The lower limit of the total content of the structural units derived from the polar functional group-containing monomer is more preferably 1% by mass, even more preferably 3% by mass, and even more preferably 8% by mass.

[0042] The acrylic copolymer preferably has the following constitutional units derived from the (meth)acrylic acid alkyl ester: the alkyl group derived from the alcohol has 7 or more carbon atoms; the content of the constitutional units derived from the (meth)acrylic acid alkyl ester: the alkyl group derived from the alcohol has 7 or more carbon atoms; the content of the constitutional units derived from the (meth)acrylic acid alkyl ester: the alkyl group derived from the alcohol has 7 or more carbon atoms is 5% by mass or more and 90% by mass or less; the polar functional group-containing monomer does not contain a constitutional unit derived from the carboxy group-containing monomer; or the constitutional units derived from the polar functional group-containing monomer include a constitutional unit derived from the carboxy group-containing monomer; the content of the constitutional units derived from the carboxy group-containing monomer in the acrylic copolymer is 5% by mass or less; and the content of the constitutional units derived from the hydroxyl group-containing monomer in the acrylic copolymer is 0.01% by mass or more. The acrylic copolymer has such a constitution, which makes it possible to introduce moderately flexible chemical crosslinks.

[0043] The acrylic copolymer may contain the structural unit derived from the alkyl (meth)acrylate, the structural unit derived from the olefin polymer having a terminal polymerizable unsaturated double bond, and the structural unit derived from the polar functional group-containing monomer, but may also contain structural units derived from other monomers in addition to these structural units.

[0044] The weight-average molecular weight (Mw) of the acrylic copolymer has a preferred lower limit of 500,000 and a preferred upper limit of 2,000,000. When the weight-average molecular weight of the acrylic copolymer is 500,000 or more, the cohesive strength of the pressure-sensitive adhesive is increased, and the retention performance at high temperatures is further improved. When the weight-average molecular weight of the acrylic copolymer is 2,000,000 or less, the pressure-sensitive adhesive does not become too hard, and the initial adhesive strength is further improved. The weight-average molecular weight of the acrylic copolymer has a more preferred lower limit of 550,000, a more preferred upper limit of 1,500,000, an even more preferred lower limit of 800,000, and an even more preferred upper limit of 1,200,000.

[0045] The ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the acrylic copolymer (polydispersity: Mw / Mn) is preferably 1.0 at its lower limit and 10.0 at its upper limit. The polydispersity of the acrylic copolymer within the above range further improves the adhesive strength and retention performance of the pressure-sensitive adhesive of the present invention. The polydispersity of the acrylic copolymer is more preferably 1.5 at its lower limit and 9.0 at its upper limit, more preferably 2.0 at its lower limit and 8.0 at its upper limit.

[0046] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) refer to the weight average molecular weight measured in gel permeation chromatography (GPC) in terms of standard polystyrene. Specifically, the acrylic copolymer is diluted to 0.1% by mass with tetrahydrofuran (THF), and the diluted solution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm). The obtained filtrate is supplied to a gel permeation chromatograph (Waters, "2690 Separations Module", etc.), and GPC measurement is performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40 ° C., and the polystyrene-equivalent molecular weight of the acrylic copolymer is measured to determine the weight average molecular weight (Mw) and number average molecular weight (Mn). As the column, for example, a GPC KF-806L (Showa Denko KK) or the like is used, and as the detector, for example, a differential refractometer or the like can be used. Furthermore, the polydispersity (Mw / Mn) can be obtained by using the weight average molecular weight (Mw) and number average molecular weight (Mn) thus obtained.

[0047] Examples of methods for adjusting the weight-average molecular weight of the acrylic copolymer include a method of changing the concentration of a polymerization initiator or a monomer during the polymerization reaction, a method of adding a small amount of a chain transfer agent such as dodecyl mercaptan, and a method of changing the type of polymerization reaction solvent to control chain transfer to the solvent.

[0048] The glass transition temperature (Tg) of the acrylic copolymer is preferably in the range of -100°C or higher and 200°C or lower, with a more preferred upper limit of -20°C. When the glass transition temperature of the acrylic copolymer is -20°C or lower, the molecules of the acrylic copolymer are more easily stretched, thereby further improving the adhesive strength of the pressure-sensitive adhesive of the present invention. A more preferred upper limit of the glass transition temperature of the acrylic copolymer is -25°C, and an even more preferred upper limit is -30°C. When the acrylic copolymer has multiple glass transition temperatures, it is more preferred that all of the glass transition temperatures are -20°C or lower. When the pressure-sensitive adhesive of the present invention contains multiple acrylic copolymers, it is more preferred that all of the acrylic copolymers have glass transition temperatures of -20°C or lower. In this specification, the glass transition temperature can be measured by differential scanning calorimetry. More specifically, the measurement can be performed in a nitrogen atmosphere (nitrogen flow, flow rate 50 mL / min) using a differential scanning calorimeter (manufactured by Seiko Instruments Inc., "220C" or the like) according to a method in accordance with JIS K6240:2011, under conditions of a measurement temperature of -100°C to 200°C and a temperature rise rate of 10°C / min.

[0049] The glass transition temperature of the acrylic copolymer can be adjusted by changing the type and content of the monomers that are raw materials for the acrylic copolymer.

[0050] The preferred lower limit of the content of the acrylic copolymer in the pressure-sensitive adhesive of the present invention is 40% by mass. When the content of the acrylic copolymer is 40% by mass or more, the adhesive strength of the pressure-sensitive adhesive of the present invention is further improved. The more preferred lower limit of the content of the acrylic copolymer is 50% by mass, and even more preferred is 55% by mass. The content of the acrylic copolymer may be 100% by mass, but the preferred upper limit is 90% by mass, more preferably 80% by mass, and even more preferably 70% by mass.

[0051] The polymerization method for synthesizing the acrylic copolymer may be a conventionally known method in which a raw material monomer mixture is subjected to a radical reaction in the presence of a polymerization initiator, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization, etc. Among these, solution polymerization is preferred because of its ease of synthesis.

[0052] When solution polymerization is used as the polymerization method, examples of the reaction solvent include ethyl acetate, toluene, methyl ethyl ketone, methyl sulfoxide, ethanol, acetone, diethyl ether, cyclohexane, etc. These reaction solvents may be used alone or in combination of two or more.

[0053] Examples of the polymerization initiator include organic peroxides and azo compounds. Examples of the organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

[0054] The pressure-sensitive adhesive of the present invention preferably satisfies at least one constitution selected from the group consisting of the following first constitution, second constitution, and third constitution: First constitution: (1) the structural units derived from the (meth)acrylic acid alkyl ester do not contain structural units derived from a (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms, or the structural units derived from the (meth)acrylic acid alkyl ester contain structural units derived from a (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms, and the content of the structural units derived from the (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms in the acrylic copolymer is 30% by mass or less, and (2) the gel fraction of the pressure-sensitive adhesive is 10% by mass or more and 90% by mass or less. Second configuration: (1) the structural units derived from the (meth)acrylic acid alkyl ester include structural units derived from a (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from an alcohol is 1 to 4, and the content of the structural units derived from the (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from an alcohol is 1 to 4 in the acrylic copolymer is more than 10% by mass and 60% by mass or less, and (2) the gel fraction of the pressure-sensitive adhesive is 55% by mass or less. Third configuration: (1) the SP value of the acrylic copolymer is 9.30 (cal / cm ３ ) １／２ More than 9.95 (cal / cm ３ ) １／２(2) The gel fraction of the pressure-sensitive adhesive is 10% by mass or more and 55% by mass or less. When the pressure-sensitive adhesive of the present invention satisfies at least one configuration selected from the group consisting of the first, second, and third configurations, the pressure-sensitive adhesive member has excellent holding performance and adhesive strength at high temperatures, and excellent holding performance for polyolefin resins such as polypropylene and adherends containing polyolefin resins. This further improves adhesion between the pressure-sensitive adhesive member and the adherend, preventing peeling of the pressure-sensitive adhesive member from the adherend during cutting or crushing in the recycling process of the composite structure of the present invention, thereby improving handleability. As a result, the composite structure of the present invention can be recycled in bulk more easily.

[0055] In the first configuration, the structural units derived from the (meth)acrylic acid alkyl ester do not contain structural units derived from a (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms, or the structural units derived from the (meth)acrylic acid alkyl ester contain structural units derived from a (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms, and the preferred upper limit of the content of structural units derived from the (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms in the acrylic copolymer is 30% by mass. By limiting the content of structural units derived from the (meth)acrylic acid alkyl ester having an alcohol-derived alkyl group with 1 to 4 carbon atoms to 30% by mass or less, the polyolefin resin molded article obtained by recycling the pressure-sensitive adhesive and a polyolefin resin such as polypropylene together can be of superior quality, making it easier to recycle the composite structure of the present invention together. The reduced interfacial free energy between the pressure-sensitive adhesive and the polyolefin resin such as polypropylene improves wettability, resulting in superior retention of the pressure-sensitive adhesive to polyolefin resins such as polypropylene and adherends containing polyolefin resins at high temperatures. When the first composition contains structural units derived from a (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from the alcohol is 1 to 4, the upper limit of the content of structural units derived from a (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from the alcohol is 1 to 4 is preferably 27% by mass, and more preferably 20% by mass. Furthermore, when the first composition contains structural units derived from a (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from the alcohol is 1 to 4, the lower limit of the content of structural units derived from a (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from the alcohol is 1 to 4 is preferably 5% by mass, and more preferably 10% by mass.

[0056] In the first aspect, examples of the (meth)acrylic acid alkyl ester in which the alkyl group derived from the alcohol has 1 to 4 carbon atoms include (meth)acrylic acid alkyl esters obtained by dehydration condensation of (meth)acrylic acid with an alcohol having a linear or branched alkyl group having 1 to 4 carbon atoms. Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, and isobutyl (meth)acrylate. Of these, methyl (meth)acrylate is preferred from the viewpoint of further improving the polarity of the acrylic copolymer, and butyl (meth)acrylate is preferred from the viewpoint of further improving the compatibility of the acrylic copolymer with polyolefin resins such as polypropylene. These (meth)acrylic acid alkyl esters may be used alone or in combination of two or more.

[0057] In the first configuration, the preferred lower limit of the gel fraction of the pressure-sensitive adhesive is 10% by mass, and the preferred upper limit is 90% by mass. In the first configuration, when the gel fraction of the pressure-sensitive adhesive is 10% by mass or more, the pressure-sensitive adhesive has excellent cohesive strength, and the pressure-sensitive adhesive member has improved retention performance at high temperatures. When the gel fraction of the pressure-sensitive adhesive is 90% by mass or less, compatibility with polyolefin resins such as polypropylene is improved. Furthermore, the pressure-sensitive adhesive does not become too hard, and the pressure-sensitive adhesive member has sufficient initial adhesive strength. A more preferred lower limit of the gel fraction of the pressure-sensitive adhesive is 20% by mass, a more preferred upper limit is 85% by mass, an even more preferred lower limit is 25% by mass, an even 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. In this specification, the gel fraction is measured by the following method, etc. That is, when the pressure-sensitive adhesive is W ０ (g) The sample is collected, immersed in 50 mL of tetrahydrofuran (THF), and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, the sample is passed through a metal mesh (opening #200 mesh, mass: W １(g)) was used to filter out the THF and the adhesive that had absorbed the THF and swollen, and the adhesive that had absorbed the THF and swollen was dried at 110°C for 1 hour, and then the mass W of the adhesive that included the metal mesh was measured. ２ (g) is measured, and the gel fraction is calculated using the following formula (1): Gel fraction (mass%) = 100 × (W ２ -W １ ) / W ０ (1) (W ０ : initial mass of adhesive, W １ : mass of metal mesh, W ２ : Mass of adhesive after drying (including metal mesh)

[0058] In the first configuration, examples of methods for adjusting the gel fraction of the pressure-sensitive adhesive to fall within the above-mentioned range include, but are not limited to, changing the type or content of the crosslinking agent contained in the pressure-sensitive adhesive composition, and adjusting the illuminance or irradiation time of the electron beam or ultraviolet light used when irradiating with an electron beam or ultraviolet light to form the pressure-sensitive adhesive.

[0059] In the first aspect, the pressure-sensitive adhesive composition preferably further contains a crosslinking agent. When the pressure-sensitive adhesive composition contains a crosslinking agent, the acrylic copolymer is crosslinked via the crosslinking agent to form a crosslinked structure, thereby increasing the gel fraction of the pressure-sensitive adhesive, making it easier to adjust the gel fraction to within the above-mentioned range. As a result, the retention performance of the pressure-sensitive adhesive member at high temperatures is further improved.

[0060] In the first configuration, examples of the crosslinking agent include epoxy-based crosslinking agents, isocyanate-based crosslinking agents, etc. Among these, isocyanate-based crosslinking agents are preferred from the viewpoint of making it easier to adjust the gel fraction of the pressure-sensitive adhesive within the above-mentioned range.

[0061] In the first configuration, the preferred lower limit of the content of the crosslinking agent relative to 100 parts by mass of the acrylic copolymer is 0.01 parts by mass, and the preferred upper limit is 10 parts by mass. By having the content of the crosslinking agent within this range, it becomes easier to adjust the gel fraction of the pressure-sensitive adhesive within the above-mentioned range, and the retention performance of the pressure-sensitive adhesive member at high temperatures is further improved. The more preferred lower limit of the content of the crosslinking agent is 0.1 parts by mass, and the more preferred upper limit is 2 parts by mass.

[0062] In the second configuration, the structural units derived from the (meth)acrylic acid alkyl ester include structural units derived from a (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from an alcohol is from 1 to 4. When the structural units derived from the (meth)acrylic acid alkyl ester include structural units derived from a (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from an alcohol is from 1 to 4, the polarity of the acrylic copolymer increases, thereby increasing the cohesive force of the pressure-sensitive adhesive and improving the holding performance of the pressure-sensitive adhesive at high temperatures.

[0063] In the second configuration, the content of structural units derived from a (meth)acrylic acid alkyl ester in which the alcohol-derived alkyl group has 1 to 4 carbon atoms is preferably greater than 10% by mass and not more than 60% by mass. In the second configuration, when the content of structural units derived from a (meth)acrylic acid alkyl ester in which the alcohol-derived alkyl group has 1 to 4 carbon atoms is greater than 10% by mass, the polarity of the acrylic copolymer is increased, thereby increasing the cohesive strength of the PSA and further improving the holding performance of the PSA at high temperatures. In the second configuration, when the content of structural units derived from a (meth)acrylic acid alkyl ester in which the alcohol-derived alkyl group has 1 to 4 carbon atoms is 60% by mass or less, the interfacial free energy of the PSA with polyolefin resins such as polypropylene is reduced, thereby improving wettability. As a result, the PSA has better holding performance for polyolefin resins such as polypropylene and adherends containing polyolefin resins. In addition, since the polyolefin resin molded article obtained by recycling the pressure-sensitive adhesive of the present invention and a polyolefin resin such as polypropylene together has excellent quality, it is more preferable to recycle the composite structure of the present invention together with the polyolefin resin such as polypropylene. A more preferred lower limit of the content of structural units derived from the (meth)acrylic acid alkyl ester in which the alkyl group derived from the alcohol has 1 to 4 carbon atoms is 14% by mass, a more preferred upper limit is 56% by mass, an even more preferred lower limit is 20% by mass, and an even more preferred upper limit is 50% by mass.

[0064] In the second configuration, examples of the (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from the alcohol is 1 or more and 4 or less include the same as the (meth)acrylic acid alkyl ester in the first configuration described above.

[0065] In the second configuration, the pressure-sensitive adhesive has a gel fraction of 55% by mass or less. In the second configuration, a gel fraction of 55% by mass or less of the pressure-sensitive adhesive improves compatibility with polyolefin resins such as polypropylene. The gel fraction of the pressure-sensitive adhesive is preferably 45% by mass or less (especially less than 45% by mass), more preferably 30% by mass or less (especially less than 30% by mass), and most preferably 10% by mass or less (especially less than 10% by mass). Furthermore, in the second configuration, a smaller gel fraction of the pressure-sensitive adhesive of the present invention is preferable, so the lower limit is not limited, and it may be 0% by mass or more.

[0066] In the second configuration, examples of methods for adjusting the gel fraction of the pressure-sensitive adhesive within the above-mentioned range include, but are not limited to, a method of changing the type or content of a crosslinking agent contained in the pressure-sensitive adhesive composition, and a method of adjusting the illuminance or irradiation time of electron beams or ultraviolet rays used when irradiating with electron beams or ultraviolet rays to form the pressure-sensitive adhesive.

[0067] In the second configuration, the pressure-sensitive adhesive composition preferably does not contain a crosslinking agent, or contains a crosslinking agent, and the content of the crosslinking agent relative to 100 parts by mass of the acrylic copolymer is preferably 1.5 parts by mass or less. By containing the crosslinking agent in an amount of 1.5 parts by mass or less, the gel fraction of the pressure-sensitive adhesive can be easily adjusted within the above-mentioned range. As a result, the pressure-sensitive adhesive exhibits excellent retention performance for polyolefin resins such as polypropylene and adherends containing polyolefin resins, and the composite structure of the present invention exhibits excellent quality after being recycled in bulk. In the second configuration, when a crosslinking agent is contained, the upper limit of the content of the crosslinking agent is more preferably 1.0 part by mass, even more preferably 0.5 parts by mass, and even more preferably 0.2 parts by mass. In the second configuration, when a crosslinking agent is contained, a smaller content of the crosslinking agent is preferable, so the lower limit is not limited, but it is preferably greater than 0 parts by mass.

[0068] In the second configuration, the crosslinking agent may be the same as the crosslinking agent in the first configuration.

[0069] In the first configuration, when the structural units derived from the (meth)acrylic acid alkyl ester do not include a structural unit derived from the (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from the alcohol is 1 to 4, the acrylic copolymer has the structural unit derived from the (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from the alcohol is 5 or more as the structural unit derived from the (meth)acrylic acid alkyl ester. Furthermore, in the first configuration, when the structural units derived from the (meth)acrylic acid alkyl ester include a structural unit derived from the (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from the alcohol is 1 to 4, and in the second configuration, the structural unit derived from the (meth)acrylic acid alkyl ester may have a structural unit derived from the (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from the alcohol is 5 or more.

[0070] In the third configuration, the gel fraction of the pressure-sensitive adhesive preferably has a lower limit of 10% by mass and an upper limit of 55% by mass. In the third configuration, a gel fraction of the pressure-sensitive adhesive of 10% by mass or more provides excellent cohesive strength and improves the retention performance of the pressure-sensitive adhesive member at high temperatures. In the third configuration, a gel fraction of the pressure-sensitive adhesive of 55% by mass or less provides improved compatibility with polyolefin resins such as polypropylene. Furthermore, a gel fraction of the pressure-sensitive adhesive of 55% by mass or less prevents the pressure-sensitive adhesive from becoming too hard, providing the pressure-sensitive adhesive member with sufficient initial adhesive strength. The preferred lower limit of the gel fraction of the pressure-sensitive adhesive is 20% by mass, the preferred upper limit is 52% by mass, the more preferred lower limit is 30% by mass, and the more preferred upper limit is 50% by mass.

[0071] In the third configuration, examples of methods for adjusting the gel fraction of the pressure-sensitive adhesive within the above-mentioned range include, but are not limited to, changing the type or content of a crosslinking agent contained in the pressure-sensitive adhesive composition, or adjusting the illuminance or irradiation time of electron beams or ultraviolet rays used when irradiating with electron beams or ultraviolet rays to form the pressure-sensitive adhesive.

[0072] In the third configuration, the pressure-sensitive adhesive composition preferably further contains a crosslinking agent. In the third configuration, the pressure-sensitive adhesive composition contains a crosslinking agent, which forms a crosslinked structure in which the acrylic copolymer is crosslinked via the crosslinking agent, thereby increasing the gel fraction of the pressure-sensitive adhesive, making it easier to adjust the gel fraction within the above-mentioned range, and further improving the retention performance of the pressure-sensitive adhesive member at high temperatures.

[0073] In the third configuration, the crosslinking agent may be the same as the crosslinking agent in the first configuration.

[0074] In the third configuration, the preferred lower limit of the content of the crosslinking agent relative to 100 parts by mass of the acrylic copolymer is 0.01 parts by mass, and the preferred upper limit is 1.5 parts by mass. In the third configuration, by having the content of the crosslinking agent within the above range, it becomes easier to adjust the gel fraction of the pressure-sensitive adhesive within the above range, and the retention performance of the pressure-sensitive adhesive member at high temperatures is further improved. The more preferred lower limit of the content of the crosslinking agent is 0.05 parts by mass, and the more preferred upper limit is 1.0 parts by mass.

[0075] In the third configuration, the SP value of the acrylic copolymer has a lower limit of 9.30 (cal / cm ３ ) １／２ and the upper limit is 9.95 (cal / cm ３ ) １／２ When the SP value of the acrylic copolymer is within the above range, the interfacial free energy between the pressure-sensitive adhesive and polyolefin resin such as polypropylene is reduced, thereby improving wettability, and as a result, the pressure-sensitive adhesive member has better retention performance for polyolefin resin such as polypropylene or an adherend containing polyolefin resin. In addition, a polyolefin resin molded article obtained by recycling the pressure-sensitive adhesive and polyolefin resin such as polypropylene together has excellent quality, making it easier to recycle the composite structure of the present invention together. A more preferred lower limit of the SP value of the acrylic copolymer is 9.36 (cal / cm ３ ) １／２ , and a more preferable upper limit is 9.80 (cal / cm ３ )１／２ , and a more preferable lower limit is 9.45 (cal / cm ３ ) １／２ , and a more preferable upper limit is 9.70 (cal / cm ３ ) １／２ In this specification, the "SP value" is also called the solubility parameter, and is an index that can represent the ease of solubility, calculated using the Fedors method (R.F. Fedors, Polym. Eng. Sci., 14(2), 147-154 (1974)) (unit: (cal / cm ３ ) １／２ The SP value of the acrylic polymer can be calculated as a weighted average based on the SP values ​​and content ratios of the respective structural unit monomers contained in the acrylic polymer.

[0076] In the first or second configuration, the SP value of the acrylic copolymer has a preferred lower limit of 9.30 (cal / cm ３ ) １／２ and the preferred upper limit is 9.95 (cal / cm ３ ) １／２ When the SP value of the acrylic copolymer is within the above range, the interfacial free energy between the pressure-sensitive adhesive and polyolefin resin such as polypropylene is reduced, thereby improving wettability, and as a result, the pressure-sensitive adhesive member has better retention performance for polyolefin resin such as polypropylene or an adherend containing a polyolefin resin. In addition, a polyolefin resin molded article obtained by recycling the pressure-sensitive adhesive and polyolefin resin such as polypropylene together has better quality, making it easier to recycle the composite structure of the present invention together. A more preferred lower limit of the SP value of the acrylic copolymer is 9.36 (cal / cm ３ ) １／２ , and a more preferable upper limit is 9.80 (cal / cm ３ ) １／２ , and a more preferable lower limit is 9.45 (cal / cm ３ ) １／２ , and a more preferable upper limit is 9.70 (cal / cm ３ ) １／２ is.

[0077] Examples of a method for adjusting the SP value of the acrylic copolymer include a method for adjusting the type and content ratio of the monomers constituting the acrylic copolymer. Specifically, for example, the SP value of the acrylic copolymer can be increased by a method for increasing the content ratio of structural units derived from (meth)acrylic acid alkyl esters in which the carbon number of the alkyl group derived from alcohol is 1 to 4 in the acrylic copolymer, and the SP value of the acrylic copolymer can be decreased by a method for increasing the content ratio of structural units derived from (meth)acrylic acid alkyl esters in which the carbon number of the alkyl group derived from alcohol is 5 or more in the acrylic copolymer.

[0078] The PSA composition may further contain a tackifier resin, which further improves the adhesive strength of the PSA.

[0079] Examples of the tackifying resin include rosin resins, terpene resins, terpene phenol resins, aromatic-modified terpene resins, petroleum resins, and styrene resins. Among these, from the viewpoint of ensuring good wettability to the adherend, it is preferable that the tackifying resin be at least one selected from the group consisting of rosin resins, terpene resins, terpene phenol resins, and petroleum resins. These tackifying resins may be used alone or in combination of two or more.

[0080] Examples of the rosin resins include Pencel D-135, Superester A-125, and Pine Crystal KE359 (all manufactured by Arakawa Chemical Industries, Ltd.), Pentalyn C (manufactured by Eastman Chemical Co.), and SYLVALITE 2115 (manufactured by Kraton). Examples of the terpene resins include YS Resin PX1250, YS Resin PX1150, and YS Resin PX1000 (all manufactured by Yasuhara Chemical Co.), and SYLVARES 3125 (manufactured by Kraton). Examples of the terpene phenol resins include YS Polystar G150, YS Polystar T160, YS Polystar T145, YS Polystar TH130, YS Polystar UH115, YS Polystar K125, and YS Polystar U130 (all manufactured by Yasuhara Chemical Co., Ltd.), SYLVARES 1150, and SYLVARES TP7042 (all manufactured by Kraton Corporation). Examples of the aromatic modified terpene resins include YS Polystar TO125 (manufactured by Yasuhara Chemical Co., Ltd.). Examples of the petroleum resins include Arcon P125, Arcon P140 (manufactured by Arakawa Chemical Industries, Ltd.), Quintone RX110 (manufactured by Nippon Zeon Co., Ltd.), Petrocol 130 (manufactured by Tosoh Corporation), and Petrotack 100V (manufactured by Tosoh Corporation). Examples of the styrene resin include YS Resin SX100 (manufactured by Yasuhara Chemical Co., Ltd.).

[0081] The upper limit of the content of the tackifier resin relative to 100 parts by mass of the acrylic copolymer is preferably 40 parts by mass. When the content of the tackifier resin is 40 parts by mass or less, the PSA of the present invention is likely to maintain wettability to the adherend. The content of the tackifier resin is more preferably 30 parts by mass or less (particularly less than 30 parts by mass), and even more preferably 20 parts by mass or less. Furthermore, the lower limit of the content of the tackifier resin may be 0 parts by mass relative to 100 parts by mass of the acrylic copolymer, but is preferably 5 parts by mass, more preferably 10 parts by mass, and even more preferably 15 parts by mass.

[0082] The pressure-sensitive adhesive composition may contain conventionally known fine particles and additives, such as inorganic fine particles, conductive fine particles, antioxidants, foaming agents, organic fillers, and inorganic fillers, as needed.

[0083] The method for producing the pressure-sensitive adhesive of the present invention is not particularly limited, and conventionally known methods can be used. For example, first, the (meth)acrylic acid alkyl ester, the olefin-based polymer having a terminal polymerizable unsaturated double bond, the polar functional group-containing monomer, and, if necessary, other monomers are copolymerized by a conventional method to obtain the acrylic copolymer. Next, the obtained acrylic copolymer is added to, if necessary, a crosslinking agent, a tackifying resin, and other additives to obtain a pressure-sensitive adhesive composition. The obtained pressure-sensitive adhesive composition is then thoroughly stirred and mixed, and then heated or irradiated with ultraviolet light or electron beams, or the like, to obtain a pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition.

[0084] The pressure-sensitive adhesive in the pressure-sensitive adhesive member may be used as a liquid pressure-sensitive adhesive or a liquid adhesive, or as a pressure-sensitive adhesive in a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer. That is, the composite structure of the present invention may be bonded to the adherend using a liquid adhesive or a pressure-sensitive adhesive tape. From the viewpoint of processability, the pressure-sensitive adhesive member preferably includes a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive. The composite structure of the present invention may include one or more types of pressure-sensitive adhesive members. When two or more types of pressure-sensitive adhesive members are present, a liquid adhesive and a pressure-sensitive adhesive tape may be used in combination. When two or more types of pressure-sensitive adhesive members are present, it is sufficient that at least one of the pressure-sensitive adhesive members contains the pressure-sensitive adhesive, but it is preferable that all of the pressure-sensitive adhesive members contain the pressure-sensitive adhesive. When the pressure-sensitive adhesive member contains a liquid adhesive, the liquid adhesive may be applied in a layer or in a specific spot. In particular, applying the liquid adhesive in a layer is preferable from the viewpoint of adhesion to the adherend.

[0085] When the PSA member includes the PSA tape, the thickness of the PSA layer in the PSA tape preferably has a lower limit of 5 μm and an upper limit of 75 μm. When the PSA layer has a thickness of 5 μm or more, the PSA tape can achieve good adhesion to the adherend, thereby improving the adhesive strength between the PSA member and the adherend, and further suppressing peeling of the PSA member from the adherend when recycling the composite structure of the present invention. As a result, it becomes more practical to recycle the composite structure of the present invention in its entirety. When the PSA layer has a thickness of 75 μm or less, compatibility with polyolefin resins is improved, improving the practicality of recycling. The PSA layer thickness more preferably has a lower limit of 10 μm, a more preferably upper limit of 70 μm, an even more preferably lower limit of 20 μm, and an even more preferably upper limit of 65 μm. In this specification, thickness can be measured using a dial thickness meter (such as the "ABS Digimatic Indicator" manufactured by Mitutoyo Corporation).

[0086] When the pressure-sensitive adhesive member includes the pressure-sensitive adhesive tape, the pressure-sensitive adhesive tape may be a non-support type pressure-sensitive adhesive tape that does not have a substrate, or a supported type pressure-sensitive adhesive tape that has a substrate. When the pressure-sensitive adhesive tape of the present invention is a non-support type pressure-sensitive adhesive tape that does not have a substrate, the composite structure of the present invention can be recycled as a whole. On the other hand, when the pressure-sensitive adhesive tape is a supported type pressure-sensitive adhesive tape that has a substrate, the pressure-sensitive adhesive tape can be processed more easily.

[0087] When the pressure-sensitive adhesive tape has a substrate, it may be a single-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on one side of the substrate, or a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of the substrate.

[0088] When the pressure-sensitive adhesive tape has a substrate, the substrate preferably contains a polyolefin resin, which improves compatibility with the adherend, making it easier to recycle the composite structure of the present invention as a whole.

[0089] In the substrate, the content of the olefin-derived structural units in the polyolefin resin is preferably 70% by mass at its lower limit. By setting the content of the olefin-derived structural units at a preferred lower limit of 70% by mass, the substrate has better compatibility with adherends containing polyolefin resins, making it easier to recycle the composite structure of the present invention in one go. A more preferred lower limit for the content of the olefin-derived structural units is 80% by mass, and an even more preferred lower limit is 90% by mass. Furthermore, in the substrate, the content of the olefin-derived structural units in the polyolefin resin is preferably as high as possible, and may be as high as 100% by mass. In the substrate, it is most preferred that the polyolefin resin is composed solely of structural units derived from the olefin.

[0090] Examples of the olefin-derived structural units in the polyolefin resin in the substrate include propylene-derived structural units, ethylene-derived structural units, isoprene-derived structural units, butadiene-derived structural units, butylene-derived structural units, etc. Among these, from the viewpoint of facilitating the collective recycling of the substrate and the adherend containing the polyolefin resin, it is preferable that the olefin-derived structural units include propylene-derived structural units.

[0091] When the polyolefin resin in the substrate contains a structural unit derived from propylene, the preferred lower limit of the content of the structural unit derived from propylene in the polyolefin resin is 50% by mass.When the content of the structural unit derived from propylene is 50% by mass or more, the substrate has better compatibility with the adherend containing the polyolefin resin, and it becomes easier to recycle the substrate and the adherend containing the polyolefin resin together.A more preferred lower limit of the content of the structural unit derived from propylene is 70% by mass, and an even more preferred lower limit is 90% by mass.Furthermore, the content of the structural unit derived from propylene in the substrate is preferably as high as possible, and may be 100% by mass.

[0092] In the base material, examples of the polyolefin resin composed only of structural units derived from the olefin include polypropylene, polyethylene, polyisoprene, cyclic olefin, cyclic olefin copolymer, polybutadiene, polybutylene, etc. Among these, from the viewpoint of facilitating the collective recycling of the composite structure of the present invention, it is preferable that the polyolefin resin contains polypropylene.

[0093] The substrate may contain only one type of resin, or may contain two or more types of resin.When the substrate contains two or more types of resin, it is preferable that the polyolefin resin is the main component of all resins contained in the substrate.Incidentally, "the main component of all resins contained in the substrate" means that the content ratio of the polyolefin resin in all resins contained in the substrate is 50% by mass or more.When the substrate contains two or more types of resin, when the content ratio of the polyolefin resin in the resin is 50% by mass or more, when the substrate contains two or more types of resin, the more preferred lower limit of the content ratio of the polyolefin resin is 70% by mass, and even more preferred lower limit is 90% by mass.In addition, the higher the content ratio of the polyolefin resin, the more preferred, and its upper limit may be 100% by mass (i.e., all resins contained in the substrate are polyolefin resins).

[0094] The substrate may contain at least one colorant selected from the group consisting of pigments and dyes. Even if the substrate contains at least one colorant selected from the group consisting of pigments and dyes, the composite structure of the present invention can be recycled in its entirety without any problems. Examples of substrates containing the colorant include PP craft film (manufactured by Acrisande Co., Ltd.).

[0095] The shape of the substrate is not particularly limited, but from the viewpoint of ease of handling as an adhesive tape, it preferably includes at least one selected from the group consisting of a film, a sheet, a nonwoven fabric, a foam, and a net.

[0096] Examples of substrates containing 50% by mass or more of the polyolefin resin include OPP films, biaxially oriented PE films, CPP films, olefin fiber nonwoven fabrics, and olefin foams. Examples of the OPP films include Pylen Film P2261 (manufactured by Toyobo Co., Ltd.) and Torayfan BO #60-2548 (manufactured by Toray Industries, Inc.). Examples of the biaxially oriented PE films include BOPE Film (manufactured by Seiwa Film Group Co., Ltd.) and Torayfan NO (manufactured by Toray Industries, Inc.). Examples of the CPP films include ET20 (manufactured by Okamoto Corporation). Examples of the olefin fiber nonwoven fabrics include All Olefin Paper-20 (manufactured by Nippon Paper Papylia Co., Ltd.). Examples of the olefin foams include Softlon S, Lightlon #41, and WL006 (all manufactured by Sekisui Chemical Co., Ltd.). An example of a net containing the olefin resin is Conwed Net (manufactured by ENEOS Techno Materials). Examples of substrates containing 50% by mass or more of the polyolefin resin include EVA film, cycloolefin copolymer film, cycloolefin polymer film, nonwoven fabric containing an olefin resin, and polypropylene kraft film. An example of the EVA film is Suntec EF1522.1 (manufactured by Asahi Kasei Corporation). An example of the cycloolefin copolymer film is F Film (manufactured by Gunze Co., Ltd.). An example of the cycloolefin polymer film is ZenonFilm (manufactured by Nippon Zeon Co., Ltd.). An example of the nonwoven fabric containing an olefin resin is Splitop (manufactured by Maeda Kosen Co., Ltd.). An example of the polypropylene kraft film is PP kraft film (manufactured by Acrisande Co., Ltd.).

[0097] The substrate preferably has at least one melting point and glass transition temperature of 100°C or higher. When the substrate has at least one melting point and glass transition temperature of 100°C or higher, the heat resistance of the PSA member is further improved. It is more preferable that the substrate has both a melting point and a glass transition temperature of 100°C or higher. When the substrate has a melting point or glass transition temperature that cannot be measured, it is preferable that the measurable melting point or glass transition temperature is 100°C or higher. When the substrate has multiple melting points or multiple glass transition temperatures, it is preferable that at least one of the melting points or glass transition temperatures is 100°C or higher, and it is more preferable that all of the melting points or glass transition temperatures of the substrate are 100°C or higher.

[0098] From the above viewpoints, the lower limit of the melting point of the substrate is preferably 100°C, more preferably 120°C, and even more preferably 150°C. Furthermore, from the viewpoint of ease of melting during recycling of the composite structure of the present invention, the upper limit of the melting point of the substrate is preferably 200°C, more preferably 180°C. The melting point of the substrate can be measured, for example, by the following method. That is, the substrate is subjected to differential scanning calorimetry (DSC) using a differential scanning calorimeter (DSC-7020, manufactured by Hitachi High-Tech Science Corporation, etc.) under measurement conditions of a nitrogen atmosphere, a heating rate of 10°C / min, and a measurement temperature of 30°C to 500°C, and the melting point of the substrate can be measured by reading the temperature showing the endothermic peak from the obtained differential scanning calorimetry curve.

[0099] From the above viewpoints, the lower limit of the glass transition temperature of the substrate is preferably 100°C, more preferably 120°C, and even more preferably 150°C. Furthermore, from the viewpoint of ease of melting during recycling of the composite structure of the present invention, the upper limit of the glass transition temperature of the substrate is preferably 200°C, more preferably 180°C, and even more preferably 150°C. The glass transition temperature of the substrate can be measured, for example, by the following method. That is, the substrate is subjected to differential scanning calorimetry (DSC) using a differential scanning calorimetry (DSC) device (manufactured by Hitachi High-Tech Science Corporation, "DSC-7020" or the like) under measurement conditions of a nitrogen atmosphere, a heating rate of 10°C / min, and a measurement temperature of -50°C to 300°C, and the midpoint of the displacement is read from the obtained differential scanning calorimetry curve, thereby measuring the glass transition temperature of the substrate.

[0100] The preferred upper limit of the gel fraction of the substrate is 10% by mass. When the gel fraction of the substrate is 10% by mass or less, it becomes easier to recycle the composite structure of the present invention in one go. The more preferred upper limit of the gel fraction of the substrate is 5% by mass, and the even more preferred upper limit is 0% by mass. The gel fraction of the substrate can be measured by the following method. That is, ３ (g) is immersed in 50 mL of xylene and shaken in a shaker at 115°C and 200 rpm for 24 hours. After shaking, the xylene and the substrate that has absorbed and swollen with the xylene are filtered out using a metal mesh (opening #200 mesh). The substrate that has absorbed and swollen with the xylene is then vacuum-dried, and the mass W of the substrate is then measured. ４ (g) was measured, and the gel fraction was calculated using the following formula (2): Gel fraction (mass%) = 100 × W ４ / W ３ (2) (W ３ : initial mass of the substrate, W ４ : mass of substrate after drying)

[0101] The preferred lower limit of the thickness of the substrate is 1 μm. When the thickness of the substrate is 1 μm or more, the adhesive tape can have good processability. The more preferred lower limit of the thickness of the substrate is 5 μm, and even more preferred is 10 μm. Furthermore, the preferred upper limit of the thickness of the substrate is 500 μm. When the thickness of the substrate is 500 μm or less, the adhesive tape can have good processability. Furthermore, it becomes easier to recycle the substrate together with the composite structure of the present invention. The more preferred upper limit of the thickness of the substrate is 300 μm, and even more preferred is 200 μm.

[0102] The pressure-sensitive adhesive tape may further have other layers within the range that does not impair the effects of the present invention.

[0103] As a method for producing the above-mentioned pressure-sensitive adhesive tape, for example, a pressure-sensitive adhesive tape without a substrate can be produced by coating a solution of the pressure-sensitive adhesive composition obtained by the above-mentioned method on the release-treated surface of a release film that has been subjected to a release treatment, drying the solution, or the like, to form a pressure-sensitive adhesive layer. Alternatively, a pressure-sensitive adhesive tape with a substrate can be produced by laminating the pressure-sensitive adhesive tape produced by the above-mentioned method as a pressure-sensitive adhesive layer to a substrate. The pressure-sensitive adhesive tape of the present invention can also be produced by thoroughly mixing the solution of the pressure-sensitive adhesive composition obtained by the above-mentioned method, coating the solution on the release-treated surface of a release film that has been subjected to a release treatment, heating or irradiating with ultraviolet rays or electron beams, or the like, and then drying the mixture to form a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition.

[0104] When the pressure-sensitive adhesive member includes the pressure-sensitive adhesive tape, the 180° peel strength of the pressure-sensitive adhesive tape from a polypropylene plate at 23°C is preferably 1.0 N / 25 mm at a minimum. When the 180° peel strength of the pressure-sensitive adhesive tape from a polypropylene plate at 23°C is 1.0 N / 25 mm or more, the adhesion between the pressure-sensitive adhesive member and the adherend is further improved, and peeling of the pressure-sensitive adhesive member from the adherend during cutting or crushing in the recycling process of the composite structure of the present invention is prevented, thereby improving handleability. As a result, the composite structure of the present invention can be recycled in bulk. The 180° peel strength of the pressure-sensitive adhesive tape from a polypropylene plate at 23°C is more preferably 1.5 N / 25 mm at a minimum, even more preferably 1.8 N / 25 mm at a minimum, even more preferably 5.0 N / 25 mm at a minimum, particularly preferably 7.0 N / 25 mm at a minimum, and especially preferably 9.0 N / 25 mm at a minimum. The 180° peel strength of the pressure-sensitive adhesive tape from the polypropylene plate at 23°C can be measured by the following method. Specifically, the pressure-sensitive adhesive tape of the present invention is first cut into a width of 25 mm and a length of 100 mm to prepare a test piece, and the obtained test piece is bonded to a polypropylene plate (e.g., "RPP 1350" manufactured by Takiron C.I.) by rolling a 2 kg rubber roller back and forth at a speed of 300 mm / min to prepare a measurement sample. The obtained measurement sample is subjected to a 180° peel test in accordance with JIS Z0237 using a tensile tester (e.g., "RTI-1310" manufactured by A&D Co., Ltd.) under conditions of 23°C, 50% RH, and a peel speed of 300 mm / min, and the pressure-sensitive adhesive tape is peeled from the polypropylene plate, whereby measurement can be performed. When the adhesive tape is a double-sided adhesive tape, the adhesive layer on one side (the side not being measured) is attached to a polyethylene terephthalate (PET) film having a thickness of 23 μm so as to prevent air from getting in, and then the film is cut to a width of 25 mm and a length of 100 mm to prepare a test piece.

[0105] The preferred lower limit of the overall thickness of the pressure-sensitive adhesive tape of the present invention is 10 μm. When the overall thickness of the pressure-sensitive adhesive tape of the present invention is 10 μm or more, the process of applying the pressure-sensitive adhesive tape of the present invention to an adherend becomes easier. A more preferred lower limit of the overall thickness of the pressure-sensitive adhesive tape of the present invention is 20 μm, and an even more preferred lower limit is 30 μm. Furthermore, a preferred upper limit of the overall thickness of the pressure-sensitive adhesive tape of the present invention is 1000 μm. When the thickness of the pressure-sensitive adhesive tape of the present invention is 1000 μm or less, the tape has good processability. Furthermore, it becomes easier to recycle the pressure-sensitive adhesive tape together with the composite structure of the present invention. A more preferred upper limit of the overall thickness of the pressure-sensitive adhesive tape of the present invention is 500 μm, and an even more preferred upper limit is 300 μm.

[0106] The composite structure of the present invention preferably has a primer layer between the adherend and the adhesive member, as long as the effects of the present invention are not impaired. By having a primer layer between the adherend and the adhesive member, the adherend and the adhesive member are more firmly bonded. As a result, the composite structure of the present invention can better prevent the adhesive tape from peeling off from the polyolefin resin-containing member when pressing the material for recycling, making it easier to recycle the adhesive member and the adherend together without separating them.

[0107] The shape of the primer layer is not particularly limited, but it is preferably the same shape as the adhesive interface between the adherend and the pressure-sensitive adhesive member, which allows the adherend and the pressure-sensitive adhesive member to be more firmly bonded together.

[0108] Examples of primers that form the primer layer include urethane-based primers, polyolefin-based primers, acrylic-based primers, and metal alkoxide-based primers. Among these, from the viewpoint of more firmly adhering the adherend and the adhesive member, it is preferable to include at least one selected from the group consisting of urethane-based primers, polyolefin-based primers, and metal alkoxide-based primers. Furthermore, from the viewpoint of making it easier to recycle the composite structure of the present invention in one go, polyolefin-based primers are more preferred.

[0109] The urethane primer is a primer having a urethane bond, and a specific example thereof is K-500 (manufactured by 3M). The polyolefin primer is a primer having a structural unit derived from olefin, and a specific example thereof is Surflen P-1000 (manufactured by Mitsubishi Chemical Corporation). Among these, primers containing chlorinated polypropylene are preferred, and examples of primers containing chlorinated polypropylene include Hardlen 13-LP (manufactured by Toyobo MC Co., Ltd.). The acrylic primer is a primer having a (meth)acryloyl group, and a specific example thereof is Polyment NK-350 (manufactured by Nippon Shokubai Co., Ltd.). The metal alkoxide primer is a primer having a metal alkoxide group, and a specific example thereof is AP111 (manufactured by 3M).

[0110] The primer layer can be formed by the following method: The primer layer can be formed by directly applying the primer onto the surface of the adherend with a brush or the like and then drying.

[0111] The composite structure of the present invention can be produced, for example, by producing an adhesive tape by the above-mentioned method and fixing a member containing a polyolefin resin with the produced adhesive tape. The composite structure of the present invention can also be produced by spot-coating an adhesive material onto the surface of a member containing a polyolefin resin.

[0112] A polyolefin resin molded product molded from the composite structure of the present invention is also one aspect of the present invention. The polyolefin resin molded product of the present invention is excellent in quality and useful as a recycled product, even if it contains a resin recycled from the above-mentioned pressure-sensitive adhesive material and the above-mentioned adherend containing a polyolefin resin. The polyolefin resin molded product of the present invention is obtained by recycling the above-mentioned composite structure, and the polyolefin resin molded product of the present invention includes not only molded products using polyolefin resin raw materials obtained by recycling, but also polyolefin resin raw materials obtained by recycling. Examples of the polyolefin resin raw materials include polyolefin resin pellets and polyolefin resin powder. Examples of molded products using the above-mentioned polyolefin resin raw materials include vehicle parts that constitute home appliances, stationery, daily necessities, and automotive components.

[0113] The polyolefin resin molded article of the present invention can be obtained, for example, by heating and kneading the above-mentioned composite components all at once, and then molding the resulting resin. The apparatus used for heating and kneading is not particularly limited, and examples thereof include a blender, kneader, mixing roll, Banbury mixer, plastomill, single-screw or twin-screw extruder, etc. Examples of molding methods include injection molding, extrusion molding, blow molding, or other molding methods in which a polyolefin resin raw material is heated to flow and easily molded into a molded article of any shape.

[0114] An automobile component comprising the composite structure of the present invention or the polyolefin resin molded body of the present invention is also one aspect of the present invention. The automobile component of the present invention can be recycled in bulk, thereby reducing the environmental impact. Examples of automobile components comprising the polyolefin resin molded body include automobile components comprising vehicle parts made of the polyolefin resin molded body. Examples of automobile components comprising the composite structure include automobile components in which vehicle parts containing polyolefin resin are bonded together with adhesive tape.

[0115] The present invention also includes a method for producing a polyolefin resin molded product, which includes a step of molding the composite structure of the present invention without separating it. The method for producing a polyolefin resin molded product of the present invention recycles the composite structure in one go, thereby further reducing the environmental load during production.

[0116] Examples of the process for molding the composite structure without separating it include a process of heating and kneading the composite structure all at once, and then molding the resulting resin. The apparatus used for heating and kneading is not particularly limited, and examples include a blender, kneader, mixing roll, Banbury mixer, plastomill, single-screw or twin-screw extruder, etc. Examples of the molding method include a method in which a polyolefin resin raw material is heated to flow using a molding method such as injection molding, extrusion molding, or blow molding, and easily molded into a molded product of any shape.

[0117] The polyolefin resin molded article obtained by the manufacturing method of the present invention is a reused product obtained by recycling a pressure-sensitive adhesive material and a material containing a polyolefin resin together, and is useful from the viewpoint of reducing environmental impact. Note that the polyolefin resin molded article obtained by the manufacturing method of the present invention includes not only molded articles using polyolefin resin raw materials, but also polyolefin resin raw materials. Examples of the polyolefin resin raw materials include polyolefin resin pellets and polyolefin resin powder. Examples of molded articles using the polyolefin resin raw materials include home appliances, stationery, daily necessities, and vehicle parts that constitute automobile components.

[0118] According to the present invention, a composite structure can be provided in which a pressure-sensitive adhesive member and a substrate can be recycled together. Furthermore, according to the present invention, a polyolefin resin molded product molded from the composite structure can be provided. Furthermore, according to the present invention, an automotive component including the composite structure or the polyolefin resin molded product can be provided. Additionally, according to the present invention, a method for producing a polyolefin resin molded product using the composite structure can be provided.

[0119] FIG. 1 is a diagram showing a schematic diagram of a retention test at high temperature.

[0120] The following examples will explain the present invention in more detail, but the present invention is not limited to these examples.

[0121] (Preparation of Styrenic Elastomer-Containing Film) As the composition for forming the styrene-based elastomer-containing film, polypropylene ("PL500A" manufactured by SunAllomer Corporation) and SEBS block copolymer ("DYNARON 8300P" manufactured by ENEOS Materials Corporation) were used in a mass ratio of 9:1. The polypropylene and SEBS block copolymer were fed into a twin-screw extruder for extrusion molding and melt-kneaded at 200°C, followed by extrusion molding to form a styrene-based elastomer-containing film having a thickness of 100 μm. Furthermore, the obtained styrene-based elastomer-containing film was subjected to differential scanning calorimetry (DSC) measurement using a differential scanning calorimeter ("DSC-7020" manufactured by Hitachi High-Tech Science Corporation) under the following measurement conditions: a nitrogen atmosphere, a heating rate of 10°C / min, and a measurement temperature of 30°C to 500°C. The endothermic peak temperature was read from the obtained differential scanning calorimetry curve, and the melting point of the styrene-based elastomer-containing film was found to be 160°C.

[0122] Example 1 Synthesis of Acrylic Copolymer 100 parts by mass of ethyl acetate, 40 parts by mass of cyclohexane, and a monomer mixture having the content ratios shown in Table 1 were added to a reactor equipped with a thermometer, a stirrer, and a cooling tube. Nitrogen gas was then blown in to expel dissolved oxygen, and the reactor was heated to 60°C under a nitrogen gas flow. Subsequently, 0.1 parts by mass of azobisisobutyronitrile was added as a polymerization initiator to the reactor, and polymerization was initiated at a constant temperature of 60°C. Thereafter, 4 hours after the start of polymerization, 0.5 parts by mass of t-hexyl peroxypivalate was added to continue the polymerization reaction. The polymerization reaction was then carried out for a total of 6 hours from the start of polymerization, yielding a solution containing an acrylic copolymer. Furthermore, the weight average molecular weight (Mw) of the obtained acrylic copolymer was measured using gel permeation chromatography (GPC) (Waters Corporation, "2690 Separations Module") under the following conditions. The results are shown in Table 1. <GPC measurement conditions> Solvent: tetrahydrofuran Sample flow rate: 1 mL / min Detector: differential refractive index RI Column: GPC KF-806L (Showa Denko KK) Column temperature (measurement temperature): 40°C Injection volume: 20 μL

[0123] (Measurement of Glass Transition Temperature of Acrylic Copolymer) The glass transition temperature of the obtained acrylic copolymer was measured by differential scanning calorimetry using a differential scanning calorimeter (manufactured by Seiko Instruments Inc., "220C" or the like) under a nitrogen atmosphere (nitrogen flow, flow rate 50 mL / min) at a measurement temperature of -100°C to 200°C and a heating rate of 10°C / min in accordance with JIS K6240:2011. The results are shown in Table 1.

[0124] (Calculation of SP Value of Acrylic Copolymer) Using the Fedors method (R.F. Fedors, Polym. Eng. Sci., 14(2), 147-154 (1974)), the SP value of the acrylic copolymer was calculated as a weighted average based on the SP values ​​and content ratios of the structural unit monomers contained in the acrylic copolymer. The results are shown in Table 1.

[0125] (Preparation of Pressure-Sensitive Adhesive Member) A solution containing a pressure-sensitive adhesive composition was obtained by adding 10 parts by mass of Pencel D-135 (manufactured by Arakawa Chemical Industries, Ltd.) as a tackifier resin and 0.5 parts by mass of Desmodur L-75(C) (manufactured by Covestro) as a crosslinking agent to 100 parts by mass of the solids content of the obtained acrylic copolymer solution. After thoroughly stirring the obtained solution containing the pressure-sensitive adhesive composition, it was coated with a doctor knife onto the release-treated surface of a 50 μm-thick release polyethylene terephthalate (PET) film that had been release-treated on one side, and heated at 110°C for 10 minutes to dry the coating solution, thereby forming a pressure-sensitive adhesive layer (thickness 50 μm) containing Pressure-Sensitive Adhesive A formed from the pressure-sensitive adhesive composition. Furthermore, a 25 μm-thick release PET film that had been release-treated on one side was prepared, and the formed pressure-sensitive adhesive layer was overlapped with the release-treated surface to obtain a pressure-sensitive adhesive tape with a release PET film as a pressure-sensitive adhesive member.

[0126] (Measurement of gel fraction of adhesive) 0.1 g of adhesive was sampled from the adhesive layer of the obtained adhesive tape, immersed in 50 mL of tetrahydrofuran (THF), and shaken in a shaker at a temperature of 23°C and 200 rpm for 24 hours. After shaking, the adhesive was passed through a metal mesh (opening #200 mesh, mass: W ４ (g)) was used to filter out the THF and the adhesive that had absorbed the THF and swollen, and the adhesive that had absorbed the THF and swollen was dried at 110°C for 1 hour, and then the mass W of the adhesive that included the metal mesh was measured. ５ The weight (g) of the sample was measured, and the gel fraction was calculated using the following formula (3). The results are shown in Table 1. Gel fraction (mass%) = 100 × (W ５ -W ４ ) / 0.1 (3) (W ４ : mass of metal mesh, W ５ : Mass of adhesive after drying (including metal mesh)

[0127] (Measurement of 180° peel strength of adhesive tape against polypropylene at 23 ° C.) The obtained adhesive tape was cut into a size of 25 mm wide and 100 mm long, and then the release PET film on one side of the obtained adhesive tape was peeled off and attached to a 23 μm thick polyethylene terephthalate (PET) sheet so as not to trap air, to prepare a test piece. A polypropylene plate (manufactured by Takiron C.I., "RPP 1350") was washed with ethanol and wiped dry, and then a 2 kg rubber roller was run back and forth at a speed of 300 mm / min to prepare a test piece, which was then bonded to prepare a measurement sample. The obtained measurement sample was subjected to a 180° peel test in accordance with JIS Z0237 using a tensile tester (manufactured by A & D, "RTI-1310") under conditions of 23 ° C., 50% RH, and a peel speed of 300 mm / min, and the 180° peel strength was measured by peeling the adhesive tape from the polypropylene plate. The results are shown in Table 2.

[0128] (Measurement of slippage in a retention test of adhesive tape against a polypropylene plate at high temperatures) The release PET film on one side of the obtained adhesive tape was peeled off, and the tape was attached to a 23 μm-thick polyethylene terephthalate (PET) sheet without allowing air to enter. The tape was then cut into 25 mm-wide strips. A 50 mm-wide, 75 mm-long polypropylene plate (manufactured by Takiron C.I., "RPP 1350") was washed with ethanol and wiped dry. The cut adhesive tape was then attached to the polypropylene plate by rolling a 2 kg rubber roller back and forth at a speed of 300 mm / min, producing the measurement sample shown in FIG. 1 . The prepared measurement sample was placed in an oven at 80°C and heated for a further 20 minutes. After heating at 80°C and 50% RH, a 500 g weight was hung from the plate and a load was applied in the shear direction as shown in FIG. 1 . The slippage (movement) (mm) from the cut position one hour after the load was applied was measured using a scale magnifier. The results are shown in Table 2.

[0129] (Preparation of Composite Structure) The release film on one side of the adhesive tape obtained by the above-mentioned "(Preparation of Adhesive Member)" was peeled off, and a 2 mm thick block polypropylene (Novatec PP BC10HRF, manufactured by Japan Polypropylene Corporation) containing a polyolefin resin was bonded to the exposed adhesive layer, and the adhesive was pressed by reciprocating once using a 2 kg rubber roller at a speed of 300 mm / min. Furthermore, the release film on the other side of the adhesive tape to which the block polypropylene had been bonded was peeled off, and the same block polypropylene was similarly bonded to the exposed adhesive layer and pressed together, followed by aging in an environment of 23 °C and 50% RH to prepare a composite structure. The size of the adhesive tape was determined so that the content ratio of the adhesive member in the composite structure satisfied the values ​​listed in Table 2.

[0130] (Calculation of the content ratio of the adhesive member in the composite structure) The mass W of the adhesive tape measured during the above-mentioned "(preparation of the adhesive member)" ６ (g) and the mass W of the composite structure measured during the above-mentioned "(preparation of the composite structure)" ７ The content (mass%) of the PSA material in the composite structure was calculated using the following formula (4) using the weight (g) of the PSA material in the composite structure. The results are shown in Table 2. Content (mass%) of the PSA material in the composite structure = (W ７ / W ６ ) x 100 (4)

[0131] (Examples 2 and 28) (Synthesis of Acrylic Copolymer) A polymerization reaction was carried out in the same manner as in Example 1, except that the composition of the monomer mixture was changed to that shown in Table 1, to obtain a solution containing an acrylic copolymer. The weight average molecular weight (Mw) of the obtained acrylic copolymer was measured using gel permeation chromatography (GPC) (manufactured by Waters, "2690 Separations Module") under the following conditions. The results are shown in Table 1.

[0132] (Preparation of Pressure-Sensitive Adhesive Member) A solution containing a pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the composition was as shown in Tables 2 and 4. A pressure-sensitive adhesive layer having a thickness of 50 μm was formed in the same manner as in Example 1, and then a substrate shown in Tables 2 and 4 was prepared. The formed pressure-sensitive adhesive layer was attached to one side of the substrate, and the resulting mixture was aged for 48 hours in an environment of 40° C. and 50% RH, thereby obtaining a pressure-sensitive adhesive tape having a substrate and a pressure-sensitive adhesive layer having a thickness shown in Tables 2 and 4 on one side of the substrate as a pressure-sensitive adhesive member.

[0133] (Preparation of Composite Structure) The release film on one side of the adhesive tape obtained by the above-mentioned "(Preparation of Adhesive Member)" was peeled off, and the adherend shown in Tables 2 and 4 was attached to the exposed adhesive layer, and the laminate was pressed together by moving it back and forth once at a speed of 300 mm / min using a 2 kg rubber roller, and then cured in an environment of 23°C and 50% RH to prepare a composite structure. At this time, the size of the adhesive tape was determined so that the content ratio of the adhesive member in the composite structure satisfied the numerical values ​​shown in Tables 2 and 4.

[0134] The above-mentioned "(Measurement of the glass transition temperature of the acrylic copolymer)", "(Calculation of the SP value of the acrylic copolymer)", "(Measurement of the gel fraction)", "(Measurement of the 180° peel force of the pressure-sensitive adhesive tape from polypropylene at 23°C)", "(Measurement of the amount of slippage in a retention test against a polypropylene plate at high temperature)", and "(Calculation of the content ratio of the pressure-sensitive adhesive member in the composite construct)" were carried out in the same manner as in Example 1, except that in the measurements of "(Measurement of the 180° peel force of the pressure-sensitive adhesive tape from polypropylene at 23°C)" and "(Measurement of the amount of slippage in a retention test against a polypropylene plate at high temperature)", the pressure-sensitive adhesive tape obtained without backing with a 23 μm-thick polyethylene terephthalate (PET) film was cut as is to prepare a test piece having a width of 25 mm and a length of 100 mm. The results are shown in Tables 1 to 4.

[0135] (Examples 3, 11, 23-24, 39, Comparative Example 2) (Synthesis of Acrylic Copolymer) A polymerization reaction was carried out in the same manner as in Example 1, except that the composition of the monomer mixture was changed to that shown in Table 1, to obtain a solution containing an acrylic copolymer. Furthermore, the weight average molecular weight (Mw) of the obtained acrylic copolymer was measured using gel permeation chromatography (GPC) (manufactured by Waters, "2690 Separations Module") under the following conditions. The results are shown in Table 1.

[0136] (Preparation of Pressure-Sensitive Adhesive Members) Solutions containing pressure-sensitive adhesive compositions were obtained in the same manner as in Example 1, except that the compositions were changed as shown in Tables 2 to 6. After forming pressure-sensitive adhesive layers with the thicknesses shown in Tables 2 to 6 in the same manner as in Example 1, substrates shown in Tables 2 to 6 were prepared, and the formed pressure-sensitive adhesive layer was bonded to one side of the substrate. Furthermore, pressure-sensitive adhesive layers with the same compositions and thicknesses were formed and bonded to the other side of the substrate, and the resulting mixture was aged in an environment of 40°C and 50% RH for 48 hours, thereby obtaining pressure-sensitive adhesive tapes having a substrate as a pressure-sensitive adhesive member and pressure-sensitive adhesive layers with the thicknesses shown in Tables 2 to 6 on both sides of the substrate.

[0137] (Preparation of Composite Structure) Composite structures were prepared in the same manner as in Example 1, except that the adherends were as shown in Tables 2 to 6. At this time, the size of the adhesive tape was determined so that the content ratio of the adhesive member in the composite structure satisfied the values ​​shown in Tables 2 to 6.

[0138] The above-mentioned "(Measurement of glass transition temperature of acrylic copolymer)", "(Calculation of SP value of acrylic copolymer)", "(Measurement of gel fraction)", "(Measurement of 180° peel force of pressure-sensitive adhesive tape against polypropylene at 23°C)", "(Measurement of displacement in retention test against polypropylene plate at high temperature)", and "(Measurement of content ratio of pressure-sensitive adhesive member relative to composite construct as 100%)" were carried out in the same manner as in Example 1. The results are shown in Tables 1 to 6.

[0139] Example 4 Synthesis of Acrylic Copolymer A polymerization reaction was carried out in the same manner as in Example 1, except that the composition of the monomer mixture was changed to that shown in Table 1, to obtain a solution containing an acrylic copolymer. The weight average molecular weight (Mw) of the obtained acrylic copolymer was measured using gel permeation chromatography (GPC) (manufactured by Waters, "2690 Separations Module") under the following conditions. The results are shown in Table 1.

[0140] (Preparation of adhesive member) In the same manner as in Examples 2 and 28, except that the adhesive composition was as shown in Table 1 and the substrate was as shown in Table 2, an adhesive tape having a substrate and an adhesive layer having a thickness of 50 μm on one side of the substrate was obtained as an adhesive member.

[0141] (Preparation of Composite Structure) A 2 mm thick block polypropylene (manufactured by Japan Polypropylene Corporation, "Novatec PP BC10HRF") was prepared as an adherend containing a polyolefin resin. A urethane primer (manufactured by 3M, "K-500") was applied to the surface of the adherend in the shape of an adhesive tape to be bonded, and then dried to form a primer layer on the side of the adherend to which the adhesive member was bonded. The release film of the adhesive tape obtained in the above-described "(Preparation of Adhesive Member)" was peeled off, and the adherend was attached to the exposed adhesive layer so that the primer layer overlapped. The laminate was then pressed and integrated by reciprocating once using a 2 kg rubber roller at a reciprocating speed of 300 mm / min, and then aged in an environment of 23 ° C. and 50% RH to produce a composite structure having a primer layer. At this time, the size of the adhesive tape was determined so that the content ratio of the adhesive member in the composite structure satisfied the values ​​listed in Table 2.

[0142] The above-mentioned "(Measurement of the glass transition temperature of the acrylic copolymer)", "(Calculation of the SP value of the acrylic copolymer)", "(Measurement of the gel fraction)", "(Measurement of the 180° peel strength of the pressure-sensitive adhesive tape against polypropylene at 23°C)", "(Measurement of the amount of slippage in a retention test against a polypropylene plate at high temperature)", and "(Measurement of the content ratio of the pressure-sensitive adhesive member, assuming the composite construct to be 100%)" were performed in the same manner as in Example 1, except that in the measurements of "(Measurement of the 180° peel strength of the pressure-sensitive adhesive tape against polypropylene at 23°C)" and "(Measurement of the amount of slippage in a retention test against a polypropylene plate at high temperature)", the pressure-sensitive adhesive tape was cut into a width of 25 mm and a length of 100 mm without being backed with a 23 μm-thick polyethylene terephthalate (PET) film. The results are shown in Tables 1 and 2.

[0143] (Example 5) (Synthesis of acrylic copolymer) A polymerization reaction was carried out in the same manner as in Example 1, except that the composition of the monomer mixture was changed to that shown in Table 1, to obtain a solution containing an acrylic copolymer. Furthermore, the weight average molecular weight (Mw) of the obtained acrylic copolymer was measured using gel permeation chromatography (GPC) (manufactured by Waters, "2690 Separations Module") under the following conditions. The results are shown in Table 1.

[0144] (Preparation of Pressure-Sensitive Adhesive Member) Except that the compositions of the pressure-sensitive adhesives were as shown in Table 2 and the substrates were as shown in Table 2, pressure-sensitive adhesive tapes having a substrate and a pressure-sensitive adhesive layer with a thickness of 50 μm on both sides of the substrate were obtained as pressure-sensitive adhesive members in the same manner as in Examples 3, 11, 23 to 24, and 39 and Comparative Example 2.

[0145] (Preparation of Composite Structure) A 2 mm thick block polypropylene (Novatec PP BC10HRF manufactured by Japan Polypropylene Corporation) containing a polyolefin resin was prepared as an adherend. A urethane primer (K-500 manufactured by 3M Corporation) was applied to the surface of the adherend in the shape of an adhesive tape to be bonded, and then dried to form a primer layer on the side of the adherend to which the adhesive member was bonded. The release film on one side of the adhesive tape obtained by the above-mentioned "(Preparation of Adhesive Member)" was peeled off, and the adherend was bonded to the exposed adhesive layer so that the primer layer overlapped. The adhesive was then pressed by reciprocating once using a 2 kg rubber roller at a speed of 300 mm / min. Furthermore, the release film on the other side of the adhesive tape to which the adherend was bonded was peeled off, and a block polypropylene having a similar primer layer was similarly bonded to the exposed adhesive layer, pressure-bonded, and integrated, followed by aging in an environment of 23 ° C. and 50% RH to prepare a composite structure. At this time, the size of the adhesive tape was determined so that the content ratio of the adhesive member in the composite structure would satisfy the values ​​shown in Table 2.

[0146] The above-mentioned "(Measurement of glass transition temperature of acrylic copolymer)", "(Calculation of SP value of acrylic copolymer)", "(Measurement of gel fraction)", "(Measurement of 180° peel force of pressure-sensitive adhesive tape against polypropylene at 23°C)", "(Measurement of displacement in retention test against polypropylene plate at high temperature)", and "(Calculation of content ratio of pressure-sensitive adhesive member in composite construct)" were carried out in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0147] (Examples 6 to 10, 12 to 22, 25 to 27, 33 to 38, Comparative Examples 1 and 3) Pressure-sensitive adhesive members and composite structures were produced and measured in the same manner as in Example 1, except that in the above-mentioned "(Synthesis of acrylic copolymer)", the composition of the monomer mixture was as shown in Table 1, in the above-mentioned "Preparation of pressure-sensitive adhesive member", the composition of the pressure-sensitive adhesive layer and the thickness of the pressure-sensitive adhesive layer were changed as shown in Tables 1 to 6, and in the above-mentioned "Preparation of composite structure", the adherend was changed as shown in Tables 2 to 6. The results are shown in Tables 1 to 6.

[0148] Examples 29 to 32 Synthesis of Acrylic Copolymers Solutions containing acrylic copolymers were obtained by carrying out a polymerization reaction in the same manner as in Example 1, except that the composition of the monomer mixture was changed to that shown in Table 1. The weight average molecular weight (Mw) of the obtained acrylic copolymers was measured using gel permeation chromatography (GPC) (manufactured by Waters, "2690 Separations Module") under the following conditions. The results are shown in Table 1.

[0149] (Preparation of Adhesive Member) An adhesive tape having an adhesive layer with a thickness of 50 μm was obtained as an adhesive member in the same manner as in Example 1, except that the composition of the adhesive was changed as shown in Tables 4 and 5.

[0150] (Preparation of Composite Structure) A 2 mm thick block polypropylene (Novatec PP BC10HRF manufactured by Japan Polypropylene Corporation) containing a polyolefin resin was prepared as an adherend. The primers shown in Tables 4 and 5 were applied to the surface of the adherend in the shape of the adhesive tape to be bonded, and then dried to form a primer layer on the side of the adherend to which the adhesive was to be bonded. The release film on one side of the adhesive tape obtained in the above-described "(Preparation of Adhesive Member)" was peeled off, and the adherend was bonded to the exposed adhesive layer so that the primer layer overlapped. A 2 kg rubber roller was used for pressure-bonding, moving back and forth once at a speed of 300 mm / min. Furthermore, the release film on the other side of the adhesive tape to which the adherend was bonded was peeled off, and a block polypropylene having a similar primer layer was similarly bonded to the exposed adhesive layer, pressure-bonded, and integrated, followed by aging in an environment of 23°C and 50% RH to prepare a composite structure. At this time, the size of the adhesive tape was determined so that the content ratio of the adhesive member in the composite structure would satisfy the values ​​shown in Tables 4 and 5.

[0151] The above-mentioned "(Measurement of glass transition temperature of acrylic copolymer)", "(Calculation of SP value of acrylic copolymer)", "(Measurement of gel fraction)", "(Measurement of 180° peel force of pressure-sensitive adhesive tape against polypropylene at 23°C)", "(Measurement of displacement in retention test against polypropylene plate at high temperature)", and "(Calculation of content ratio of pressure-sensitive adhesive member in composite construct)" were carried out in the same manner as in Example 1. The results are shown in Tables 1, 4 and 5.

[0152] The monomers shown in Table 1 are as follows: MA: methyl acrylate BA: n-butyl acrylate n-Hex: n-hexyl acrylate n-HA: n-heptyl acrylate 2OA: 1-methylheptyl acrylate 2EHA: 2-ethylhexyl acrylate LA: lauryl acrylate EBm: ethylene-butylene macromonomer (manufactured by Kraton Polymer Japan, "HPVM-L1253", weight average molecular weight: 7000) AAc: acrylic acid 4HBA: 4-hydroxybutyl acrylate

[0153]

[0154] <Evaluation> The composite structures obtained in the examples and comparative examples were evaluated as follows. The results are shown in Tables 2 to 6.

[0155] (Recyclability) (1) Preparation of molded body molded from composite structure After 200 g of the obtained composite structure was shredded, it was heated and kneaded using a plastomill at 200 ° C. and 50 rpm. 7 g of the resin composition obtained by heating and kneading was weighed out, and using an injection molding machine (manufactured by Thermo Fisher Scientific, "HAAKE Minilab 3"), under the conditions of a cylinder temperature of 200 ° C., a mold temperature of 40 ° C., an injection press of 500 bar / 10 sec, and a post press of 400 bar / 10 sec, a rectangular test piece (size 80 mm × 10 mm × thickness 4 mm) was prepared as a molded body molded from the composite structure for Charpy impact resistance performance evaluation. A HAAKE RheoDrive 16OS (manufactured by Thermo Fisher Scientific Inc.) was used as the plastomill, and a roller rotor Rheomix 3000 OS (manufactured by Thermo Fisher Scientific Inc.) was connected to the mixer section. Note that for the composite structure of Comparative Example 3, heat mixing was performed at 260°C, and test pieces were prepared by injection molding with a cylinder temperature of 260°C and a mold temperature of 90°C.

[0156] (2) Preparation of molded body from the adherend alone Strip-shaped test pieces were prepared as molded bodies from the adherend alone for evaluating Charpy impact resistance performance in the same manner as in "(1) Preparation of molded body from composite structure" above, except that 200 g of the adherend used in each example and comparative example was used instead of 200 g of the composite structure. Note that for the adherend of Comparative Example 3, the test piece was prepared by heating and kneading at 260 ° C, and the cylinder temperature during injection molding was set to 260 ° C and the mold temperature was set to 90 ° C.

[0157] (3) Evaluation by Charpy Impact Resistance The strip-shaped test pieces obtained in the above-mentioned "(1) Preparation of a molded body molded from a composite structure" and "(2) Preparation of a molded body molded from a single adherend member" were each notched to a depth of 2 mm using a notching machine (manufactured by Yasuda Seiki Seisakusho, "Notching Machine No. 189-PNCA") in accordance with JIS K7111-1. A 2J impact was applied in the edgewise impact direction with a hammer using a thermostatic chamber-equipped Charpy impact tester (manufactured by Yasuda Seiki Seisakusho, "Impact Tester No. 258-L-PC") at 23 ° C., and the impact strength was measured. The impact strength was measured by repeating the measurement five times, and the average of the three values ​​obtained excluding the maximum and minimum values ​​was used. Based on the obtained impact strength value, the Charpy impact resistance degradation rate (%) was calculated using the following formula. Charpy impact resistance reduction rate (%)=100−[((impact strength of molded body molded from the composite structure) / (impact strength of molded body molded from the single adherend member))×100] Using the obtained Charpy impact resistance reduction rate (%), the recyclability of the composite structure of the present invention was evaluated according to the following criteria. ◎: The Charpy impact resistance reduction rate was 5.0% or less. ○: The Charpy impact resistance reduction rate was more than 5.0% and 7.0% or less. ×: The Charpy impact resistance reduction rate was more than 7.0%. If the evaluation is "◎" or "◯", the composite structure of the present invention can be recycled together with polyolefin resins such as polypropylene, and the better the evaluation, the easier it can be recycled.

[0158]

[0159]

[0160]

[0161]

[0162]

[0163] According to the present invention, a composite structure can be provided in which a pressure-sensitive adhesive member and a substrate can be recycled together. Furthermore, according to the present invention, a polyolefin resin molded product molded from the composite structure can be provided. Furthermore, according to the present invention, an automotive component including the composite structure or the polyolefin resin molded product can be provided. Additionally, according to the present invention, a method for producing a polyolefin resin molded product using the composite structure can be provided.

[0164] 1. Adhesive tape 2. Polypropylene plate 3. 500g weight

Claims

1. A composite structure comprising an adhesive member and a adherend member, The adhesive member has an adhesive formed from an adhesive composition, The adhesive composition contains an acrylic copolymer having structural units derived from an alkyl (meth)acrylate ester and structural units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal end. The adherend includes a member containing polyolefin resin. A composite structure characterized by the following features.

2. The composite structure according to claim 1, wherein two or more of the adherends are bonded together by the adhesive member.

3. The composite structure according to claim 1 or 2, wherein the polyolefin resin in the adherend comprises a polypropylene-based block copolymer.

4. The composite structure according to claim 1 or 2, wherein the adherend contains at least one coloring agent selected from the group consisting of pigments and dyes.

5. In the adhesive composition, the content of constituent units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal in the acrylic copolymer is 5% by mass or more. A composite structure according to claim 1 or 2, which satisfies at least one configuration selected from the group consisting of the first configuration, the second configuration, and the third configuration described below. First configuration: (1) The constituent units derived from the alkyl (meth)acrylate do not include constituent units derived from the alkyl (meth)acrylate whose alkyl group has 1 to 4 carbon atoms, or the constituent units derived from the alkyl (meth)acrylate include constituent units derived from the alkyl (meth)acrylate whose alkyl group has 1 to 4 carbon atoms, and the content of constituent units derived from the alkyl (meth)acrylate whose alkyl group has 1 to 4 carbon atoms in the acrylic copolymer is 30% by mass or less. (2) The gel fraction of the adhesive is 10% by mass or more and 90% by mass or less. Second configuration: (1) The constituent units derived from the alkyl (meth)acrylate include constituent units derived from the alkyl (meth)acrylate, wherein the alkyl group derived from the alcohol has 1 to 4 carbon atoms, and the content of the constituent units derived from the alkyl (meth)acrylate, wherein the alkyl group derived from the alcohol has 1 to 4 carbon atoms, in the acrylic copolymer is greater than 10% by mass and 60% by mass or less; (2) The gel fraction of the adhesive is 55% by mass or less. Third component: (1) The SP value of the acrylic copolymer is 9.30 (cal / cm²). ３ ) １／２ 9.95 (cal / cm) ３ ) １／２ (2) The gel fraction of the adhesive is 10% by mass or more and 55% by mass or less.

6. The acrylic copolymer has constituent units derived from a monomer containing a polar functional group, The composite structure according to claim 1 or 2, wherein the constituent unit derived from the polar functional group-containing monomer includes at least one selected from the group consisting of constituent units derived from carboxyl group-containing monomers and constituent units derived from hydroxyl group-containing monomers.

7. The composite structure according to claim 6, wherein the constituent unit derived from the polar functional group-containing monomer includes the constituent unit derived from the hydroxyl group-containing monomer.

8. The constituent units derived from the alkyl (meth)acrylate include constituent units derived from the alkyl (meth)acrylate having an alcohol-derived alkyl group with 7 or more carbon atoms, and the content of the constituent units derived from the alkyl (meth)acrylate having an alcohol-derived alkyl group with 7 or more carbon atoms in the acrylic copolymer is 5% by mass or more and 90% by mass or less. The constituent units derived from the polar functional group-containing monomer do not include the constituent units derived from the carboxyl group-containing monomer, or the constituent units derived from the polar functional group-containing monomer include the constituent units derived from the carboxyl group-containing monomer, and the content ratio of the constituent units derived from the carboxyl group-containing monomer in the acrylic copolymer is 8% by mass or less. The acrylic copolymer contains 0.01% by mass or more of the constituent units derived from the hydroxyl group-containing monomer. The composite structure according to claim 7.

9. The adhesive is a composite structure according to claim 1 or 2, comprising a tackifying resin.

10. The composite structure according to claim 9, wherein the content of the tackifying resin is 40 parts by mass or less per 100 parts by mass of the acrylic copolymer.

11. The composite structure according to claim 1 or 2, wherein the adhesive member is an adhesive tape having an adhesive layer containing the adhesive.

12. The composite structure according to claim 11, wherein the thickness of the adhesive layer is 5 μm or more and 75 μm or less.

13. The adhesive tape is a composite structure according to claim 11, which does not have a base material.

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

15. The composite structure according to claim 11, wherein the 180° peel force of the adhesive tape on a polypropylene plate at 23°C is 5.0 N / 25 mm or more.

16. The composite structure according to claim 1 or 2, wherein the content ratio of the adhesive member in the composite structure is 0.1% by mass or more and 3.0% by mass or less.

17. The composite structure according to claim 1 or 2, having a primer layer between the adherend and the adhesive member.

18. The composite structure according to claim 17, wherein the primer forming the primer layer is at least one selected from the group consisting of polyolefin-based primers, urethane-based primers, and metal alkoxide-based primers.

19. A polyolefin resin molded article formed from the composite structure described in claim 1.

20. An automotive component comprising the composite structure described in claim 1, or the polyolefin resin molded body described in claim 19.

21. A method for producing a polyolefin resin molded article, comprising the step of molding the composite structure described in claim 1 or 2 without separating the components.