Adhesive agent, adhesive tape, polyolefin resin molded body, composite structure, automobile member, and method for manufacturing polyolefin resin molded body

Abstract

The present invention relates to an adhesive agent formed from an adhesive agent composition containing an acrylic copolymer, the acrylic copolymer including a constituent unit (i) derived from an alkyl (meth)acrylate, a constituent unit (ii) derived from an olefin polymer having a terminal polymerizable unsaturated double bond, and a constituent unit (iii) derived from a polar functional group-containing monomer, 5 mass% or more of the copolymer is constituted by the constituent unit (ii), and said adhesive agent satisfying at least one of the following first, second, and third configurations. First configuration: (1) 0 to 30 mass% of the polymer is constituted by a constituent unit (i-1) having a C1-4 alcohol-derived alkyl group, and (2) the gel fraction of the adhesive agent is 10 to 90 mass%. Second configuration: (1) More than 10 mass% to 60 mass% or less of the copolymer is constituted by the constituent unit (i-1), and (2) the gel fraction of the adhesive agent is 55 mass% or less. Third configuration: (1) The SP value of the copolymer is 9.30 (cal / cm3)1 / 2 to 9.95 (cal / cm3)1 / 2, and (2) the gel fraction of the adhesive agent is 10 to 55 mass%.

Description

Adhesive, adhesive tape, polyolefin resin molded body, composite structure, automobile component, and method for manufacturing polyolefin resin molded body

[0001] The present invention relates to a pressure-sensitive adhesive and a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive.The present invention also relates to a polyolefin resin molded product containing the pressure-sensitive adhesive and a polyolefin resin.The present invention further relates to a composite structure including the pressure-sensitive adhesive tape and a member containing a polyolefin resin to which the pressure-sensitive adhesive tape is attached.Furthermore, the present invention also relates to an automotive member.In addition, the present invention relates to a method for producing a polyolefin resin molded product.

[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] Because automotive components can be used in high-temperature environments, adhesives and tapes used to secure automotive components must have excellent holding performance even at high temperatures. Furthermore, adhesives and tapes used to secure automotive components must have excellent holding performance against not only steel plates but also polyolefin resins such as polypropylene, which are commonly used in automotive components. However, many conventional adhesives and tapes generally have poor holding performance against polyolefin resins, and there is still a demand for adhesives and tapes with excellent holding performance against polyolefin resins.

[0005] 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.

[0006] The present invention aims to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive tape that have excellent holding properties at high temperatures for polyolefin resins such as polypropylene and adherends containing polyolefin resins, and that can be recycled together with polyolefin resins such as polypropylene. Another object of the present invention is to provide a polyolefin resin molded product containing the pressure-sensitive adhesive and a polyolefin resin. A further object of the present invention is to provide a composite structure comprising the pressure-sensitive adhesive tape and a polyolefin resin-containing member to which the pressure-sensitive adhesive tape is attached. A further object of the present invention is to provide an automotive member comprising the polyolefin resin molded product or the composite structure. Another object of the present invention is to provide a method for producing a polyolefin resin molded product that can further reduce the environmental impact of production by recycling the pressure-sensitive adhesive tape and the polyolefin resin-containing member together.

[0007] Disclosure 1 provides a pressure-sensitive adhesive formed from a pressure-sensitive adhesive composition containing an acrylic copolymer having a structural unit derived from a (meth)acrylic acid alkyl ester, a structural unit derived from an olefin-based polymer having a terminal polymerizable unsaturated double bond, and a structural unit derived from a polar functional group-containing monomer, wherein the acrylic copolymer contains 5 mass% or more of the structural unit derived from the olefin-based polymer having a terminal polymerizable unsaturated double bond, and the pressure-sensitive adhesive 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 9.95 (cal / cm) ３ ) １／２(2) the gel fraction of the PSA is 10% by mass or more and 55% by mass or less. Disclosure 2 is the PSA of Disclosure 1, wherein the structural units derived from the polar functional group-containing monomer include at least one selected from the group consisting of structural units derived from a carboxy group-containing monomer and structural units derived from a hydroxyl group-containing monomer. Disclosure 3 is the PSA of Disclosure 2, wherein the structural units derived from the polar functional group-containing monomer include structural units derived from the hydroxyl group-containing monomer.

[0013] Disclosure 4 is the PSA of Disclosure 3, wherein the structural units derived from the (meth)acrylic acid alkyl ester comprise 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 having an alcohol-derived alkyl group with 7 or more carbon atoms in the acrylic copolymer is 5% to 90% by mass, the structural units derived from the polar functional group-containing monomer do not comprise structural units derived from the carboxy group-containing monomer, or the structural units derived from the polar functional group-containing monomer comprise 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. Disclosure 5 is the PSA of Disclosure 1, 2, 3, or 4, wherein the PSA composition further comprises a tackifier resin. Disclosure 6 is the pressure-sensitive adhesive of Disclosure 5, wherein the content of the tackifier resin per 100 parts by mass of the acrylic copolymer is 40 parts by mass or less. Disclosure 7 is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive of Disclosures 1, 2, 3, 4, 5, or 6. Disclosure 8 is the pressure-sensitive adhesive tape of Disclosure 7, further having a substrate, the substrate containing a polyolefin resin. Disclosure 9 is the pressure-sensitive adhesive tape of Disclosures 7 or 8, wherein the 180° peel strength from polypropylene at 23°C is 5.0 N / 25 mm or more. Disclosure 10 is a polyolefin resin molded product containing the pressure-sensitive adhesive of Disclosures 1, 2, 3, 4, 5, or 6 and a polyolefin resin.Disclosure 11 is a composite structure comprising the pressure-sensitive adhesive tape of Disclosure 7, 8, or 9 and a member comprising a polyolefin resin to which the pressure-sensitive adhesive tape is attached. Disclosure 12 is an automotive component comprising the polyolefin resin molded body of Disclosure 10 or the composite structure of Disclosure 11. Disclosure 13 is a method for producing a polyolefin resin molded body, comprising a step of molding, without separation, a composite structure comprising a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive and a member comprising a polyolefin resin to which the pressure-sensitive adhesive tape is attached. The present invention is described in detail below. Note that matters common to the first, second, and third structures of Disclosure 1 are not particularly specified.

[0008] 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 by using a pressure-sensitive adhesive or pressure-sensitive adhesive tape that is highly compatible with polyolefin resins such as polypropylene. The present inventors have investigated using a pressure-sensitive adhesive formed from a pressure-sensitive adhesive composition containing an acrylic copolymer having a specific structure as a pressure-sensitive adhesive that is highly compatible with polyolefin resins such as polypropylene, and adjusting the polarity of the acrylic copolymer and the gel fraction of the pressure-sensitive adhesive to specific ranges. As a result, they have found that a pressure-sensitive adhesive and a pressure-sensitive adhesive tape can be obtained that have excellent retention performance for polyolefin resins such as polypropylene and polyolefin resin-containing adherends at high temperatures, and that can be recycled all at once with polyolefin resins such as polypropylene, thereby completing the present invention.

[0009] The pressure-sensitive adhesive of the present invention is 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 electron beam, etc.).

[0010] 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.

[0011] 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.

[0012] Examples of (meth)acrylic acid alkyl esters in which the alkyl group derived from the alcohol has 7 or more carbon atoms include 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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 of the present invention exhibits hard properties like a crosslinked pressure-sensitive adhesive when the strain applied to the pressure-sensitive adhesive is small, and its holding performance is improved. On the other hand, when peel stress is applied and the strain increases, the pseudo-crosslinks are broken and the molecules of the acrylic copolymer are stretched, 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 of the present invention has improved holding performance and further improves adhesive strength. In addition, the structural units derived from olefin polymers having terminal polymerizable unsaturated double bonds have low polarity, and the adhesive of the present invention has improved wettability due to a reduced interfacial free energy with polyolefin resins such as polypropylene. As a result, the adhesive of the present invention has excellent retention performance for polyolefin resins such as polypropylene and adherends containing polyolefin resins. Furthermore, the acrylic copolymer has improved compatibility with polyolefin resins such as polypropylene, so that polyolefin resin molded articles obtained by recycling the adhesive of the present invention and polyolefins such as polypropylene together have excellent quality. As a result, the adhesive of the present invention can be recycled together with polyolefin resins such as polypropylene.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] The 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 acrylic copolymer forms an appropriate number of pseudo-crosslinks, thereby improving the holding performance and adhesive strength of the pressure-sensitive adhesive of the present invention. Furthermore, the pressure-sensitive adhesive of the present invention has improved wettability due to a decrease in the interfacial free energy with polyolefin resins such as polypropylene. As a result, the pressure-sensitive adhesive of the present invention has excellent holding performance for polyolefin resins such as polypropylene and adherends containing polyolefin resins. Furthermore, the improved compatibility of the acrylic copolymer with polyolefin resins such as polypropylene ensures that polyolefin resin molded articles obtained by recycling the pressure-sensitive adhesive of the present invention and polyolefin resins such as polypropylene together have excellent quality. As a result, the pressure-sensitive adhesive of the present invention can be recycled together with polyolefin resins such as polypropylene. The lower limit of the content of the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond is preferably 10% by mass, and more preferably 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 pressure-sensitive adhesive of the present invention 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.

[0023] The acrylic copolymer 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 of the present invention and 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.

[0024] 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.

[0025] 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.

[0026] Examples of the hydroxyl group-containing monomer include 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate.

[0027] 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.

[0028] Examples of the amino group-containing monomer include (meth)acryloylmorpholine, 2-dimethylaminoethyl (meth)acrylate, and 2-diethylaminoethyl (meth)acrylate.

[0029] 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.

[0030] 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.

[0031] 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 enhancing the cohesive strength of the pressure-sensitive adhesive of the present invention 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 pressure-sensitive adhesive of the present invention does not become too hard and has sufficient initial adhesive strength. A more preferred lower limit of the total content of the structural units derived from the polar functional group-containing monomer is 1% by mass, an even more preferred lower limit is 3% by mass, and an even more preferred upper limit is 8% by mass.

[0032] 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.

[0033] 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.

[0034] The weight-average molecular weight (Mw) of the acrylic copolymer preferably has a lower limit of 500,000 and an 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 of the present invention 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 of the present invention does not become too hard, and the initial adhesive strength is further improved. A more preferred lower limit of the weight-average molecular weight of the acrylic copolymer is 550,000, a more preferred upper limit is 1,500,000, an even more preferred lower limit is 800,000, and an even more preferred upper limit is 1,200,000.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] The glass transition temperature of the acrylic copolymer can be adjusted by changing the type and content of the monomers that are the raw materials for the acrylic copolymer.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] The pressure-sensitive adhesive of the present invention 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 in which the carbon number of the alkyl group derived from an alcohol is 1 to 4, or the structural units derived from the (meth)acrylic acid alkyl ester contain 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 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 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, it exhibits excellent retention performance at high temperatures and excellent retention performance for polyolefin resins such as polypropylene and adherends containing polyolefin resins. In addition, it becomes possible to recycle the pressure-sensitive adhesive together with polyolefin resins such as polypropylene. Furthermore, it exhibits excellent adhesive strength at high temperatures.

[0045] 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 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 mass%. In the first configuration, by having 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 being 30 mass% or less, the interfacial free energy of the pressure-sensitive adhesive of the present invention with a polyolefin resin such as polypropylene is reduced, thereby improving wettability, and as a result, the pressure-sensitive adhesive exhibits excellent retention performance at high temperatures to polyolefin resins such as polypropylene and to adherends containing polyolefin resins. Furthermore, the polyolefin resin molded article obtained by recycling the pressure-sensitive adhesive of the present invention and a polyolefin resin such as polypropylene together is of excellent quality, making it possible to recycle the pressure-sensitive adhesive of the present invention together with a polyolefin resin such as polypropylene. When the first structure 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 preferred 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 27% by mass, and more preferably 20% by mass. When the first structure 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 preferred 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 5% by mass, and more preferably 10% by mass.

[0046] 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.

[0047] In the first configuration, the gel fraction of the pressure-sensitive adhesive of the present invention has a lower limit of 10% by mass and an upper limit of 90% by mass. When the gel fraction of the pressure-sensitive adhesive of the present invention is 10% by mass or more in the first configuration, the pressure-sensitive adhesive of the present invention has excellent cohesive strength and improved retention performance at high temperatures. When the gel fraction of the pressure-sensitive adhesive of the present invention is 90% by mass or less, compatibility with polyolefin resins such as polypropylene is improved. Furthermore, the pressure-sensitive adhesive of the present invention does not become too hard and has sufficient initial adhesive strength. In the first configuration, the preferred lower limit of the gel fraction of the pressure-sensitive adhesive of the present invention is 20% by mass, and the preferred upper limit is 85% by mass, more preferably 25% by mass, more preferably 80% by mass, even more preferably 40% by mass, and even more preferably 70% by mass. In this specification, the gel fraction is measured by the following method, etc. That is, when the pressure-sensitive adhesive is 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)

[0048] 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.

[0049] In the first aspect, the pressure-sensitive adhesive composition preferably further contains a crosslinking agent. In the first aspect, 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 of the present invention, making it easier to adjust the gel fraction to the above-mentioned range. As a result, the high-temperature retention performance of the pressure-sensitive adhesive of the present invention is further improved.

[0050] In the first aspect, 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 of the present invention to within the above-mentioned range.

[0051] 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. In the first 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 of the present invention within the above range, and the retention performance at high temperatures is further improved. In the first configuration, 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.

[0052] In the second configuration, the structural unit derived from the (meth)acrylic acid alkyl ester comprises a structural unit derived from a (meth)acrylic acid alkyl ester, the carbon number of which is from 1 to 4. In the second configuration, the structural unit derived from the (meth)acrylic acid alkyl ester comprises a structural unit derived from a (meth)acrylic acid alkyl ester, the carbon number of which is from 1 to 4. This increases the polarity of the acrylic copolymer, thereby increasing the cohesive strength of the pressure-sensitive adhesive of the present invention and improving the retention performance at high temperatures.

[0053] 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 in the acrylic copolymer is 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 enhancing the cohesive strength of the pressure-sensitive adhesive of the present invention and improving its retention performance at high temperatures. 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 pressure-sensitive adhesive of the present invention with polyolefin resins such as polypropylene is reduced, thereby improving wettability. As a result, the pressure-sensitive adhesive of the present invention exhibits excellent retention performance with polyolefin resins such as polypropylene and adherends containing polyolefin resins. Furthermore, polyolefin resin molded articles obtained by recycling the pressure-sensitive adhesive of the present invention and polyolefin resins such as polypropylene together are of excellent quality, and therefore the pressure-sensitive adhesive of the present invention can be recycled together with polyolefin resins such as polypropylene. In the second configuration, the content of structural units derived from a (meth)acrylic acid alkyl ester in which the alkyl group derived from the alcohol has 1 to 4 carbon atoms is preferably 14% by mass at the lower limit, 56% by mass at the upper limit, 20% by mass at the more preferred lower limit, and 50% by mass at the more preferred upper limit.

[0054] 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.

[0055] In the second configuration, the pressure-sensitive adhesive of the present invention has a gel fraction of 55% by mass or less. By having the pressure-sensitive adhesive of the present invention have a gel fraction of 55% by mass or less, compatibility with polyolefin resins such as polypropylene is improved. In the second configuration, the gel fraction of the pressure-sensitive adhesive of the present invention 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, since a smaller gel fraction of the pressure-sensitive adhesive of the present invention is preferable, the lower limit is not limited, and may be, for example, 0% by mass.

[0056] In the second aspect, examples of methods for adjusting the gel fraction of the pressure-sensitive adhesive of the present invention 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.

[0057] 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. In the second configuration, by containing the crosslinking agent in an amount of 1.5 parts by mass or less, the gel fraction of the pressure-sensitive adhesive of the present invention can be easily adjusted within the above-mentioned range. As a result, the pressure-sensitive adhesive of the present invention has excellent retention performance for polyolefin resins such as polypropylene and adherends containing polyolefin resins, and also has excellent quality after being recycled together with the polyolefin resin. 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. Furthermore, in the second configuration, since a smaller content of the crosslinking agent is preferable, the lower limit is not limited, but it is preferably greater than 0 parts by mass.

[0058] In the second configuration, examples of the crosslinking agent include the same crosslinking agents as those in the first configuration.

[0059] 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.

[0060] In the third configuration, the gel fraction of the pressure-sensitive adhesive of the present invention has a lower limit of 10% by mass and an upper limit of 55% by mass. In the third configuration, when the gel fraction of the pressure-sensitive adhesive is 10% by mass or more, the pressure-sensitive adhesive of the present invention has excellent cohesive strength and improved retention performance at high temperatures. In the third configuration, when the gel fraction of the pressure-sensitive adhesive of the present invention is 55% by mass or less, compatibility with polyolefin resins such as polypropylene is improved. Furthermore, when the gel fraction of the pressure-sensitive adhesive is 55% by mass or less, the pressure-sensitive adhesive of the present invention does not become too hard and has sufficient initial adhesive strength. The preferred lower limit of the gel fraction of the pressure-sensitive adhesive of the present invention 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.

[0061] 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.

[0062] 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 of the present invention. This makes it easier to adjust the gel fraction within the above-mentioned range, and further improves the high-temperature retention performance of the pressure-sensitive adhesive of the present invention.

[0063] In the third configuration, the crosslinking agent may be the same as the crosslinking agent in the first configuration.

[0064] 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 of the present invention within the above range, and the retention performance at high temperatures is further improved. In addition, the compatibility of the pressure-sensitive adhesive of the present invention with polyolefin resins such as polypropylene is improved. A more preferred lower limit of the content of the crosslinking agent is 0.05 parts by mass, and a more preferred upper limit is 1.0 parts by mass.

[0065] In the third aspect, 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 In the third aspect, since the SP value of the acrylic copolymer is within the above range, the interfacial free energy between the pressure-sensitive adhesive of the present invention and polyolefin resins such as polypropylene is reduced, thereby improving wettability, and as a result, the pressure-sensitive adhesive of the present invention has excellent retention performance for polyolefin resins such as polypropylene and adherends containing polyolefin resins. Furthermore, since the polyolefin resin molded article obtained by recycling the pressure-sensitive adhesive of the present invention and polyolefin resins such as polypropylene together is of excellent quality, the pressure-sensitive adhesive of the present invention can be recycled together with polyolefin resins such as polypropylene. A preferred lower limit of the SP value of the acrylic copolymer is 9.36 (cal / cm３ ) １／２ , the preferred 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 copolymer.

[0066] 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 In the first or second configuration, when the SP value of the acrylic copolymer is within the above range, the interfacial free energy between the pressure-sensitive adhesive of the present invention and polyolefin resins such as polypropylene is reduced, thereby improving wettability, and as a result, the pressure-sensitive adhesive of the present invention has better retention performance for polyolefin resins such as polypropylene and adherends containing polyolefin resins. Furthermore, since the polyolefin resin molded article obtained by recycling the pressure-sensitive adhesive of the present invention and polyolefin resins such as polypropylene together has better quality, the pressure-sensitive adhesive of the present invention can be recycled together with polyolefin resins such as polypropylene. 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 / cm３ ) １／２ , and a more preferable upper limit is 9.70 (cal / cm ３ ) １／２ is.

[0067] 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.

[0068] The pressure-sensitive adhesive composition may further contain a tackifier resin. When the pressure-sensitive adhesive composition contains a tackifier resin, the adhesive strength of the pressure-sensitive adhesive of the present invention is further improved.

[0069] 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.

[0070] 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 and Arcon P140 (both 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.).

[0071] 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.

[0072] 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.

[0073] 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.

[0074] The pressure-sensitive adhesive of the present invention is contained in a pressure-sensitive adhesive layer constituting a pressure-sensitive adhesive tape. A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive of the present invention also constitutes one aspect of the present invention.

[0075] The thickness of the pressure-sensitive adhesive layer preferably has a lower limit of 5 μm and an upper limit of 500 μm. When the thickness of the pressure-sensitive adhesive layer is 5 μm or more, good adhesion to the adherend is likely to be obtained. When the thickness of the pressure-sensitive adhesive layer is 500 μm or less, high productivity is likely to be obtained during the production of the pressure-sensitive adhesive tape. A more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 10 μm, a more preferred upper limit is 300 μm, an even more preferred lower limit is 20 μm, and an even more preferred upper limit is 200 μm. In this specification, the thickness can be measured using a dial thickness meter (such as the "ABS Digimatic Indicator" manufactured by Mitutoyo Corporation).

[0076] The pressure-sensitive adhesive tape of the present invention may be a non-support type having no substrate, or a supported type having a substrate. When the pressure-sensitive adhesive tape of the present invention is a non-support type having no substrate, the pressure-sensitive adhesive tape of the present invention can be more easily recycled together with the polyolefin resin. On the other hand, when the pressure-sensitive adhesive tape of the present invention is a supported type having a substrate, the pressure-sensitive adhesive tape of the present invention can be more easily processed.

[0077] When the pressure-sensitive adhesive tape of the present invention has a substrate, it may be a single-sided pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer on one side of the substrate, or a double-sided pressure-sensitive adhesive tape having the pressure-sensitive adhesive layers on both sides of the substrate.

[0078] The substrate preferably contains a polyolefin resin, which improves compatibility between the substrate and an adherend containing a polyolefin resin, making it easier to recycle the substrate and the adherend containing a polyolefin resin together.

[0079] The substrate may contain only one type of resin, or may contain two or more types of resins. When the substrate contains two or more types of resins, it is preferable that the polyolefin resin is the main component of all resins contained in the substrate. Here, "being 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 resins, if the content ratio of the polyolefin resin in the resins is 50% by mass or more, the entire pressure-sensitive adhesive tape of the present invention will have better compatibility with an adherend containing a polyolefin resin, making it easier to recycle the pressure-sensitive adhesive tape of the present invention and the adherend containing a polyolefin resin together. The lower limit of the content ratio of the olefin resin is more preferably 70% by mass, and even more preferably 90% by mass. The higher the content ratio of the polyolefin resin, the better, and the upper limit may be 100% by mass (i.e., all resins contained in the substrate are polyolefin resins).

[0080] 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.). Examples of the biaxially oriented PE films include BOPE films (manufactured by Seiwa Film Group Co., Ltd.). 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 (manufactured by Sekisui Chemical Co., Ltd.).

[0081] 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 pressure-sensitive adhesive tape can be easily processed. The more preferred lower limit of the thickness of the substrate is 5 μm, and even more preferred is 10 μm. 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 pressure-sensitive adhesive tape of the present invention can be more easily recycled together with the polyolefin resin. The more preferred upper limit of the thickness of the substrate is 300 μm, and even more preferred is 100 μm.

[0082] The pressure-sensitive adhesive tape of the present invention may further have other layers as long as the effects of the present invention are not impaired.

[0083] As a method for producing the pressure-sensitive adhesive tape of the present invention, 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. Alternatively, the pressure-sensitive adhesive tape of the present invention can 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.

[0084] The preferred lower limit of the 180° peel strength of the pressure-sensitive adhesive tape of the present invention from a polypropylene plate at 23°C is 1.0 N / 25 mm. When the 180° peel strength of the pressure-sensitive adhesive tape of the present invention from a polypropylene plate at 23°C is 1.0 N / 25 mm or more, the pressure-sensitive adhesive tape of the present invention has superior adhesive strength to polypropylene. Furthermore, when the material is pressed in the recycling of a composite structure described below, peeling of the pressure-sensitive adhesive tape from a member containing a polyolefin resin can be more effectively prevented, thereby improving the efficiency of recycling of the composite structure described below. As a result, recycling can be performed on a large scale. The more preferred lower limit of the 180° peel strength of the pressure-sensitive adhesive tape of the present invention from a polypropylene plate at 23°C is 1.5 N / 25 mm, an even more preferred lower limit is 1.8 N / 25 mm, an even more preferred lower limit is 5.0 N / 25 mm, a particularly preferred lower limit is 7.0 N / 25 mm, and an especially preferred lower limit is 9.0 N / 25 mm. The 180° peel strength of the pressure-sensitive adhesive tape of the present invention from a polypropylene plate at 23°C can be measured by the following method, etc. That is, first, the pressure-sensitive adhesive tape of the present invention is cut into a width of 25 mm x 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 moving 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 rate of 300 mm / min, and the pressure-sensitive adhesive tape is peeled from the polypropylene plate, whereby measurement can be performed. When the pressure-sensitive adhesive tape is a double-sided pressure-sensitive adhesive tape, the pressure-sensitive adhesive layer on one side (the side not being measured) is attached and backed to a 23 μm-thick polyethylene terephthalate (PET) film so as to prevent air from entering, and then the tape is cut into a width of 25 mm x length of 100 mm to prepare a test piece.

[0085] 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. The more preferred lower limit of the overall thickness of the pressure-sensitive adhesive tape of the present invention is 20 μm, and even more preferred lower limit is 30 μm. Furthermore, the preferred upper limit of the overall thickness of the pressure-sensitive adhesive tape of the present invention is 700 μm. When the overall thickness of the pressure-sensitive adhesive tape of the present invention is 700 μm or less, the pressure-sensitive adhesive tape of the present invention can be more easily recycled together with the polyolefin resin. The more preferred upper limit of the overall thickness of the pressure-sensitive adhesive tape of the present invention is 500 μm, and even more preferred upper limit is 300 μm.

[0086] The uses of the pressure-sensitive adhesive of the present invention and the pressure-sensitive adhesive tape of the present invention are not particularly limited, and they can be used, for example, to fix parts in electronic devices, vehicles, houses, building materials, etc. In particular, they have excellent holding performance at high temperatures for polyolefin resins such as polypropylene and adherends containing polyolefin resins, and are therefore preferably used to fix interior components and on-board components of a vehicle. Specifically, the material can be suitably used for fastening, for example, automotive panels, cushioning materials, sound-absorbing materials, water-stopping materials, vibration-damping materials, 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, blinkers, stop lamps and the like, 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 conditioning modules, or parts that constitute these. Furthermore, since the pressure-sensitive adhesive of the present invention and the pressure-sensitive adhesive tape of the present invention have excellent compatibility with polyolefin resins, polyolefin resin molded articles obtained by recycling the pressure-sensitive adhesive of the present invention or the pressure-sensitive adhesive tape of the present invention together with polyolefin resins have excellent material quality. Therefore, the pressure-sensitive adhesive of the present invention and the pressure-sensitive adhesive tape of the present invention can be recycled together with polyolefin resins such as polypropylene, and the polyolefin resin molded articles obtained by recycling are useful as reused products.

[0087] A polyolefin resin molded product containing the pressure-sensitive adhesive of the present invention and a polyolefin resin also constitutes one aspect of the present invention. The polyolefin resin molded product of the present invention, even if it contains a resin obtained by recycling the pressure-sensitive adhesive and polyolefin resin, is excellent in quality and useful as a recycled product. As described above, the polyolefin resin molded product of the present invention refers to a product that can be obtained by recycling the pressure-sensitive adhesive of the present invention or the pressure-sensitive adhesive tape of the present invention and a polyolefin resin all at once. This 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 polyolefin resin raw materials include home appliances, stationery, daily necessities, and vehicle parts that constitute automotive components. The "pressure-sensitive adhesive of the present invention" in the polyolefin resin molded product of the present invention may be derived from the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape. Furthermore, if the pressure-sensitive adhesive tape of the present invention has a substrate containing a polyolefin resin, the polyolefin resin recycled together with the pressure-sensitive adhesive tape to obtain the polyolefin resin molded product is different from the polyolefin resin-containing substrate contained in the pressure-sensitive adhesive tape of the present invention.

[0088] Examples of the polyolefin resin in the polyolefin resin molded body include thermoplastic olefin resins and thermosetting olefin resins. Among these, thermoplastic olefin resins are preferred from the viewpoint of facilitating thermal melting during recycling. Examples of the thermoplastic olefin resin in the polyolefin resin molded body include polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin (EVA), ethylene-ethyl acrylate copolymer resin (EEA), ethylene-methyl methacrylate copolymer resin (EMMA), polyolefin-based thermoplastic elastomer (TPO), and ethylene propylene rubber (EPDM).

[0089] The polyolefin resin molded article of the present invention can be obtained, for example, by collectively heating and kneading a mixture containing the above-mentioned pressure-sensitive adhesive or the above-mentioned pressure-sensitive adhesive tape and a polyolefin resin, or a composite structure comprising a member containing the above-mentioned pressure-sensitive adhesive or the above-mentioned pressure-sensitive adhesive tape and a polyolefin resin, 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.

[0090] The present invention also provides a composite structure comprising the pressure-sensitive adhesive tape of the present invention and a member containing a polyolefin resin to which the pressure-sensitive adhesive tape is attached. The composite structure of the present invention allows the pressure-sensitive adhesive tape of the present invention and the polyolefin resin to be recycled together, thereby reducing the environmental load.

[0091] Examples of the polyolefin resin in the composite structure of the present invention include the polyolefin resin in the polyolefin resin molded article described above. The polyolefin resin may be a resin obtained by recycling, or the polyolefin resin molded article described above may be used. Among these, it is preferable to use the polyolefin resin molded article described above from the viewpoint of further reducing the environmental load.

[0092] The composite structure of the present invention is not particularly limited as long as it is a composite structure obtained by adhering the above-mentioned pressure-sensitive adhesive tape to a member containing a polyolefin resin. Examples of the composite structure 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 parts, floor carpet parts, pillar garnishes, armrests, interior lamps, room mirror housings, assist grips, and air conditioning modules, which are adhered together with the above-mentioned pressure-sensitive adhesive tape, and automobile parts themselves formed by adhering the components constituting these parts with the above-mentioned pressure-sensitive adhesive tape.

[0093] An automobile component comprising the polyolefin resin molded body of the present invention or the composite structure 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.

[0094] The present invention also includes a method for producing a polyolefin resin molded product, which includes a step of molding, without separation, a composite structure comprising an adhesive tape having an adhesive layer containing an adhesive, and a member comprising a polyolefin resin to which the adhesive tape is attached. The method for producing a polyolefin resin molded product of the present invention includes a step (hereinafter sometimes referred to as "step (I)") of molding, without separation, a composite structure comprising an adhesive tape having an adhesive layer containing an adhesive, and a member comprising a polyolefin resin to which the adhesive tape is attached (hereinafter sometimes simply referred to as "the composite structure in step (I)"), and since the adhesive tape and the member comprising a polyolefin resin are recycled together, the environmental load in production can be further reduced.

[0095] The method for producing a polyolefin resin molded product of the present invention includes the above-mentioned step (I). The adhesive tape having an adhesive layer containing an adhesive in the above-mentioned step (I) is preferably one that has high compatibility with polyolefin resins. When the adhesive tape having an adhesive layer containing the above-mentioned adhesive has high compatibility with polyolefin resins, the quality of the polyolefin resin obtained through the above-mentioned step (I) is superior, and the obtained polyolefin resin molded product becomes more useful as a recycled product. Examples of adhesive tapes having an adhesive layer containing the above-mentioned adhesive include those similar to the adhesive tape of the present invention described above.

[0096] The composite structure in step (I) is not particularly limited as long as it is a polyolefin resin-containing member to which the adhesive tape in step (I) has been attached. Examples of polyolefin resins used in the composite structure in step (I) include thermoplastic olefin resins and thermosetting olefin resins. Among these, thermoplastic olefin resins are preferred from the viewpoint of facilitating thermal melting in step (I). Examples of thermoplastic olefin resins include polyethylene, polypropylene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), polyolefin-based thermoplastic elastomer (TPO), and ethylene propylene rubber (EPDM). Furthermore, the polyolefin resin used in the composite structure in step (I) may be a recycled resin or a polyolefin resin molded product obtained by the production method of the present invention. In particular, the use of the above-described polyolefin resin molded product is preferred from the viewpoint of further reducing the environmental impact. Specific examples of the composite structure in step (I) include those similar to the composite structure of the present invention described above.

[0097] Examples of the step of molding without separation in the above step (I) include a step of heating and kneading the composite constructs in the above step (I) 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.

[0098] The polyolefin resin molded article obtained by the production method of the present invention is a reused product obtained by recycling adhesive tape and polyolefin resin together, and is useful from the viewpoint of reducing environmental impact. The polyolefin resin molded article obtained by the production method of the present invention includes not only molded articles made 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 made using the polyolefin resin raw materials include home appliances, stationery, daily necessities, and vehicle parts that constitute automobile components.

[0099] According to the present invention, it is possible to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive tape that have excellent holding performance at high temperatures for polyolefin resins such as polypropylene and adherends containing polyolefin resins, and that can be recycled together with polyolefin resins such as polypropylene. The present invention also provides a polyolefin resin molded product containing the pressure-sensitive adhesive and a polyolefin resin. Furthermore, the present invention also provides a composite structure comprising the pressure-sensitive adhesive tape and a member containing polyolefin resin to which the pressure-sensitive adhesive tape is attached. Furthermore, the present invention also provides an automotive member containing the polyolefin resin molded product or the composite structure. Additionally, the present invention also provides a method for producing a polyolefin resin molded product, which can further reduce the environmental impact of production by recycling the pressure-sensitive adhesive tape and the member containing polyolefin resin together.

[0100] FIG. 2 is a diagram schematically showing a method for evaluating the holding performance of a pressure-sensitive adhesive tape on SUS.

[0101] The following examples will explain the present invention in more detail, but the present invention is not limited to these examples.

[0102] (Synthesis of Acrylic Copolymers A to U) A reactor equipped with a thermometer, a stirrer, and a cooling tube was charged with 100 parts by mass of ethyl acetate, 40 parts by mass of cyclohexane, and a mixture of the structural unit monomers in the proportions shown in Table 1. 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 solutions containing acrylic copolymers A to U, respectively. Regarding acrylic copolymer F, the polymerization reaction was carried out by changing the amounts of ethyl acetate to 90 parts by mass and cyclohexane to 40 parts by mass. Furthermore, the weight average molecular weight (Mw) of the obtained acrylic copolymer was measured using gel permeation chromatography (GPC) (Waters, "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 refractometer RI Column: GPC KF-806L (Showa Denko KK) Column temperature (measurement temperature): 40°C Injection volume: 20 μL

[0103] 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

[0104] (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") 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.

[0105] (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.

[0106]

[0107] (Example 1) (Preparation of Pressure-Sensitive Adhesive Composition) A solution containing a pressure-sensitive adhesive composition was obtained by adding 0.5 parts by mass of Desmodur L-75(C) (manufactured by Covestro) as a crosslinking agent to 100 parts by mass of the solid content of the solution of acrylic copolymer A.

[0108] (Preparation of adhesive tape) The obtained solution containing the adhesive composition was thoroughly stirred, and then coated with a doctor knife onto the release-treated surface of a 50 μm-thick release polyethylene terephthalate (PET) film, one side of which had been release-treated. The coating solution was then dried by heating at 110° C. for 10 minutes, thereby forming an adhesive layer (50 μm thick) containing an adhesive formed from the adhesive composition. Furthermore, a 25 μm-thick release PET film, one side of which had been release-treated, was prepared, and the formed adhesive layer and the release-treated surface were overlapped to obtain an adhesive tape with a release PET film.

[0109] (Measurement of gel fraction) 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 ３(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. ４ The weight (g) of the sample was measured, and the gel fraction was calculated using the following formula (2). The results are shown in Table 2. Gel fraction (mass%) = 100 × (W ４ -W ３ ) / 0.1 (2) (W ３ : mass of metal mesh, W ４ : Mass of adhesive after drying (including metal mesh)

[0110] (Measurement of 180° peel force against SUS at 23°C) The release PET film on one side of the obtained pressure-sensitive adhesive tape (the side of the pressure-sensitive adhesive layer not being measured) was peeled off, and the exposed pressure-sensitive adhesive layer was attached to a 23 μm-thick polyethylene terephthalate (PET) film while preventing air from getting in. The film was then cut to a width of 25 mm and a length of 100 mm to prepare a test piece. The obtained test piece was bonded to a SUS plate (a SUS304 plate that had been washed with ethanol and then wiped dry) by moving a 2 kg rubber roller back and forth at a speed of 300 mm / min, 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 ("RTI-1310" manufactured by A&D Co., Ltd.) under conditions of 23°C, 50% RH, and a peel rate of 300 mm / min, and the pressure-sensitive adhesive tape was peeled from the SUS plate to measure the 180° peel strength against SUS at 23°C. The results are shown in Table 2.

[0111] (Measurement of 180° peel strength from polypropylene at 23° C.) The 180° peel strength from polypropylene at 23° C. was measured in the same manner using a polypropylene plate ("RPP 1350" manufactured by Takiron C. Co., Ltd.) instead of the SUS plate (SUS304 plate washed with ethanol and then wiped dry), and the results are shown in Table 2.

[0112] (Examples 2 to 14, 16, 19 to 38, Comparative Examples 1 to 6) Pressure-sensitive adhesive compositions and pressure-sensitive adhesive tapes were obtained and measurements were carried out in the same manner as in Example 1, except that in the above-mentioned "(Preparation of Pressure-sensitive Adhesive Composition)", the compositions were changed to those shown in Tables 2 to 5. The results are shown in Tables 2 to 5.

[0113] (Examples 15 and 17) (Preparation of Pressure-Sensitive Adhesive Composition) 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 Table 3.

[0114] (Preparation of adhesive tape) A 50 μm thick adhesive layer was formed in the same manner as in Example 1, and then a substrate shown in Table 3 was prepared, and the formed adhesive layer was bonded to one side of the substrate. Further, an adhesive layer having the same composition and thickness was formed, bonded to the other side of the substrate, and aged for 48 hours in an environment of 40° C. and 50% RH, thereby obtaining an adhesive tape having a substrate and 50 μm thick adhesive layers on both sides of the substrate.

[0115] The gel fraction, 180° peel strength from SUS at 23° C., and 180° peel strength from polypropylene at 23° C. were measured in the same manner as in Example 1. The results are shown in Table 3.

[0116] (Example 18) (Preparation of Pressure-Sensitive Adhesive Composition) A solution containing a pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the composition was changed as shown in Table 3.

[0117] (Preparation of adhesive tape) In the same manner as in Example 1, an adhesive layer having a thickness of 50 μm was formed, and then a substrate shown in Table 3 was prepared. The formed adhesive layer was attached to one side of the substrate, and the substrate was left to cure for 48 hours in an environment of 40° C. and 50% RH, thereby obtaining an adhesive tape having a substrate and an adhesive layer on one side of the substrate.

[0118] Measurement of the gel fraction, the 180° peel strength from SUS at 23°C, and the 180° peel strength from polypropylene at 23°C were carried out in the same manner as in Example 1. The results are shown in Table 3. In measuring the 180° peel strength from SUS at 23°C and the 180° peel strength from polypropylene at 23°C in Example 18, the pressure-sensitive adhesive tape obtained without backing with a 23 μm-thick polyethylene terephthalate (PET) film was cut as is to a width of 25 mm and a length of 100 mm to prepare a test piece.

[0119] <Evaluation> The pressure-sensitive adhesive tapes obtained in the Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 2 to 5.

[0120] (Compatibility with Polypropylene) (1) Preparation of Polypropylene Molded Product Containing Pressure-Sensitive Adhesive Tape 2 g of the pressure-sensitive adhesive tape obtained in the above-mentioned "(Preparation of Pressure-Sensitive Adhesive Tape)" and 198 g of block polypropylene (Novatec PP BC10HRF, manufactured by Japan Polypropylene Corporation) were heated and kneaded using a Plastomill under conditions of 200 ° C. and 50 rpm. 7 g of the resin composition obtained by heating and kneading was weighed out, and an injection molding machine (HAAKE Minilab 3, manufactured by Thermo Fisher Scientific) was used under 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 produced as a polypropylene molded product containing the pressure-sensitive adhesive tape for evaluating Charpy impact resistance performance. The plastomill used was a HAAKE RheoDrive 16OS (manufactured by Thermo Fisher Scientific) with a roller rotor Rheomix 3000 OS (manufactured by Thermo Fisher Scientific) connected to the mixer section.

[0121] (2) Preparation of polypropylene molded body containing no adhesive tape A strip-shaped test piece was prepared as a polypropylene molded body containing no adhesive tape for evaluating Charpy impact resistance performance in the same manner as in the above-mentioned "(1) Preparation of polypropylene molded body containing adhesive tape" except that 0 g of adhesive tape and 200 g of block polypropylene were used.

[0122] (3) Evaluation of Charpy Impact Resistance The rectangular test pieces obtained in the above-mentioned "(1) Preparation of Polypropylene Molded Body Containing Pressure-Sensitive Adhesive Tape" and "(2) Preparation of Polypropylene Molded Body Not Containing Pressure-Sensitive Adhesive Tape" 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. Then, using a Charpy impact tester with a thermostatic chamber (manufactured by Yasuda Seiki Seisakusho, "Impact Tester No. 258-L-PC"), a 2 J impact was applied in the edgewise impact direction with a hammer 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 polypropylene molded body containing pressure-sensitive adhesive tape) / (impact strength of polypropylene molded body not containing pressure-sensitive adhesive tape))×100] Using the obtained Charpy impact resistance reduction rate (%), the compatibility of the pressure-sensitive adhesive tape with polypropylene was evaluated according to the following criteria. ○: The Charpy impact resistance reduction rate was less than 5%. △: The Charpy impact resistance reduction rate was 5% or more and less than 7% ×: The Charpy impact resistance reduction rate was 7% or more. If the evaluation is "○" or "△", the pressure-sensitive adhesive tape of the present invention can be recycled together with polyolefin resins such as polypropylene, and the better the evaluation, the easier the recycling becomes.

[0123] (Holding Performance at High Temperatures) (1) Holding Performance to SUS 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 to prevent air intrusion. The tape was then cut into 25 mm-wide strips and bonded to a SUS plate (a SUS304 plate washed with ethanol and then wiped dry) by rolling a 2 kg rubber roller back and forth at a speed of 300 mm / min. The adhesive tape of Example 18 was not backed, and the adhesive tape was bonded to the SUS plate using the method described above. Next, a slit was made in the adhesive tape so that the adhesive area was 25 mm x 25 mm, and the tape was left to stand at 23°C for 20 minutes to prepare a test sample. The prepared test sample was placed in an 80°C oven and heated for another 20 minutes. After that, a 500 g weight was hung from the tape and a load was applied in the shear direction under conditions of 80°C and 50% RH, as shown in FIG. 1 . The amount of displacement (movement) (mm) from the cut position one hour after the load was applied was measured with a scale magnifier. Using the obtained amount of displacement (mm), the holding performance of the adhesive tape against SUS at high temperatures was evaluated according to the following criteria: ○: The amount of displacement was 0 mm or more and less than 5 mm. △: The amount of displacement was 5 mm or more and less than 25 mm. ×: The amount of displacement was 25 mm or more, and the adhesive tape fell off.

[0124] (2) Holding performance against polypropylene Test samples were prepared in the same manner as in the above-mentioned "(1) Holding performance against SUS" except that the pressure-sensitive adhesive tape was attached to a polypropylene plate (manufactured by Takiron C.I., "RPP 1350") instead of an SUS plate, and the holding performance of the pressure-sensitive adhesive tape against polypropylene at high temperatures was evaluated.

[0125]

[0126]

[0127]

[0128]

[0129] According to the present invention, it is possible to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive tape that have excellent holding performance at high temperatures for polyolefin resins such as polypropylene and adherends containing polyolefin resins, and that can be recycled together with polyolefin resins such as polypropylene. The present invention also provides a polyolefin resin molded product containing the pressure-sensitive adhesive and a polyolefin resin. Furthermore, the present invention also provides a composite structure comprising the pressure-sensitive adhesive tape and a member containing polyolefin resin to which the pressure-sensitive adhesive tape is attached. Furthermore, the present invention also provides an automotive member containing the polyolefin resin molded product or the composite structure. Additionally, the present invention also provides a method for producing a polyolefin resin molded product, which can further reduce the environmental impact of production by recycling the pressure-sensitive adhesive tape and the member containing polyolefin resin together.

[0130] 1. Adhesive tape 2. SUS304 plate 3. 500g weight

Claims

1. An adhesive formed from an adhesive composition containing an acrylic copolymer having structural units derived from an alkyl (meth)acrylate ester, structural units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal, and structural units derived from a monomer containing a polar functional group, The acrylic copolymer contains 5% by mass or more of constituent units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminus. An adhesive characterized by satisfying 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 The following: (2) The gel fraction of the adhesive is 10% by mass or more and 55% by mass or less.

2. The adhesive according to claim 1, wherein 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 carboxyl group-containing monomer and a constituent unit derived from a hydroxyl group-containing monomer.

3. The adhesive according to claim 2, wherein the constituent unit derived from the polar functional group-containing monomer includes the constituent unit derived from the hydroxyl group-containing monomer.

4. The constituent units derived from the (meth)acrylate alkyl ester include constituent units derived from the (meth)acrylate alkyl ester having 7 or more carbon atoms in the alcohol-derived alkyl group, and the content of the constituent units derived from the (meth)acrylate alkyl ester having 7 or more carbon atoms in the alcohol-derived alkyl group 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 adhesive according to claim 3.

5. The adhesive composition further comprises a tackifying resin, as described in claim 1, 2, 3, or 4.

6. The adhesive according to claim 5, wherein the content of the tackifying resin is 40 parts by mass or less per 100 parts by mass of the acrylic copolymer.

7. An adhesive tape having an adhesive layer containing the adhesive described in claim 1.

8. Furthermore, it has a base material, The substrate contains a polyolefin resin. The adhesive tape according to claim 7.

9. The adhesive tape according to claim 7 or 8, wherein the 180° peel strength of the adhesive tape on polypropylene at 23°C is 5.0 N / 25 mm or more.

10. A polyolefin resin molded article containing the adhesive described in claim 1 and a polyolefin resin.

11. A composite structure comprising the adhesive tape described in claim 7 and a member containing a polyolefin resin to which the adhesive tape is attached.

12. An automotive component comprising a polyolefin resin molded body according to claim 10, or a composite structure according to claim 11.

13. A method for manufacturing a polyolefin resin molded article, comprising a step of molding a composite structure without separating the composite structure, which comprises an adhesive tape having an adhesive layer containing an adhesive agent and a member containing a polyolefin resin to which the adhesive tape is attached.