Adhesive composition, adhesive tape, resin molded body, composite structure, automobile member, and method for producing resin molded body

Abstract

The purposes of the present invention is: to provide an adhesive composition which has excellent adhesive force and holding properties in addition to excellent low dielectric properties; to provide an adhesive tape which has an adhesive layer that contains the adhesive composition; to provide a resin molded body which is molded from a resin composition that comprises the adhesive composition; to provide a composite structure which comprises the adhesive tape; to provide an automobile member which comprises the resin molded body or the composite structure; and to provide a method for producing a resin molded body using the composite structure.　The present invention provides an adhesive composition which contains: an acrylic copolymer that has a constituent unit derived from a (meth)acrylic acid alkyl ester, a constituent unit derived from an olefin-based polymer that has a polymerizable unsaturated double bond at an end thereof, and a constituent unit derived from a polar functional group-containing monomer; and a styrene-based elastomer that contains at least one substance selected from the group consisting of a block copolymer which has a block derived from a styrene-based monomer and a block derived from a conjugated diene-based monomer, and a hydrogenated product of the block copolymer.

Description

Pressure-sensitive adhesive composition, pressure-sensitive adhesive tape, resin molded body, composite structure, automobile component, and method for manufacturing resin molded body

[0001] The present invention relates to a pressure-sensitive adhesive composition. The present invention also relates to a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition. Furthermore, the present invention also relates to a resin molded article molded from a resin composition containing the pressure-sensitive adhesive composition. Furthermore, the present invention also relates to a composite structure including the pressure-sensitive adhesive tape. Additionally, the present invention also relates to an automotive component including the resin molded article or the composite structure. Finally, the present invention also relates to a method for producing a resin molded article using the composite structure.

[0002] BACKGROUND ART Pressure-sensitive adhesive tapes or pressure-sensitive adhesive sheets are widely used in a variety of fields, for example, for assembling portable electronic devices such as mobile phones and personal digital assistants (PDAs), or for fixing in-vehicle electronic device components such as in-vehicle panels to vehicle bodies (e.g., Patent Documents 1 and 2).

[0003] JP 2009-242541 A JP 2009-258274 A

[0004] In recent years, in the field of electronic devices, there has been a demand for transmitting and receiving larger amounts of data at higher speeds, and the practical application of so-called fifth-generation mobile communication systems (5G) has been progressing, which has led to an increase in the frequency of transmission signals. However, an increase in frequency has arisen in the problem of increased attenuation of transmission signals (referred to as "transmission loss"). As pressure-sensitive adhesive compositions and pressure-sensitive adhesive tapes having pressure-sensitive adhesive layers used for assembling electronic devices and fixing components, there is a demand for pressure-sensitive adhesive compositions and pressure-sensitive adhesive tapes with excellent low dielectric properties that can suppress such transmission loss. For example, antennas such as small antenna base stations and vehicle-mounted antennas have been increasingly made into films in recent years. As pressure-sensitive adhesive compositions and pressure-sensitive adhesive tapes used for bonding internal components of such antenna films, bonding antenna films to other components, etc., there is a demand for pressure-sensitive adhesive compositions and pressure-sensitive adhesive tapes with excellent low dielectric properties that can suppress transmission loss and can be suitably used even when the frequency of transmission signals is increased.

[0005] Pressure-sensitive adhesive compositions and pressure-sensitive adhesive tapes for fixing high-frequency communication components are required to have both excellent low dielectric properties and excellent adhesive properties, such as adhesive strength against peeling (adhesive strength) and shear retention. However, with conventional pressure-sensitive adhesive compositions, when the pressure-sensitive adhesive composition is composed of an acrylic copolymer, it is easy to achieve excellent adhesive strength and retention, but it is difficult to achieve low dielectric properties. On the other hand, when the pressure-sensitive adhesive composition is a rubber-based pressure-sensitive adhesive composition containing a rubber-based pressure-sensitive adhesive such as a styrene-based elastomer, it is easy to achieve low dielectric properties, but it is difficult to achieve excellent adhesive strength and retention. Furthermore, when an acrylic copolymer and a rubber-based pressure-sensitive adhesive are to be contained in a pressure-sensitive adhesive composition, the acrylic copolymer has a relatively high polarity while the rubber-based pressure-sensitive adhesive has a relatively low polarity. Therefore, the acrylic copolymer and the rubber-based pressure-sensitive adhesive have low compatibility with each other, making it difficult for the resulting pressure-sensitive adhesive composition to exhibit sufficient adhesive properties. For these reasons, it has been difficult for conventional pressure-sensitive adhesive compositions to achieve both excellent low dielectric properties and excellent adhesive strength and retention.

[0006] An object of the present invention is to provide a pressure-sensitive adhesive composition having excellent low dielectric properties and excellent adhesive strength and retention. Another object of the present invention is to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition. A further object of the present invention is to provide a resin molded article molded from a resin composition containing the pressure-sensitive adhesive composition. A still further object of the present invention is to provide a composite structure including the pressure-sensitive adhesive tape. Additionally, an object of the present invention is to provide an automotive component including the resin molded article or the composite structure. Finally, an object of the present invention is to provide a method for producing a resin molded article using the composite structure.

[0007]

[0010] The present disclosure 1 relates to 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 polymer having a terminal polymerizable unsaturated double bond, and a structural unit derived from a polar functional group-containing monomer, as well as a styrene-based elastomer containing at least one selected from the group consisting of a block copolymer having a block derived from a styrene-based monomer and a block derived from a conjugated diene-based monomer, and a hydrogenated product of the block copolymer.

[0011] The present disclosure 2 relates to the pressure-sensitive adhesive composition of disclosure 1, further containing a crosslinking agent.

[0012] The present disclosure 3 relates to the pressure-sensitive adhesive composition of disclosure 1 or 2, further containing a tackifying resin.

[0013] The present disclosure 4 relates to the pressure-sensitive adhesive composition of disclosure 3, in which the proportion of the total content of the styrene-based elastomer and the tackifying resin in the total content of the acrylic copolymer, the styrene-based elastomer, and the tackifying resin is 20% by mass or more and 70% by mass or less.

[0014] Disclosure 5 is the PSA composition of Disclosure 3 or 4, wherein the proportion of the tackifier resin in the total content of the styrene elastomer and the tackifier resin is 20% by mass or more and 80% by mass or less. Disclosure 6 is the PSA composition of Disclosure 1, 2, 3, 4, or 5, wherein the (meth)acrylic acid alkyl ester comprises at least one selected from the group consisting of n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, and 2-octyl (meth)acrylate. Disclosure 7 is the PSA composition of Disclosure 1, 2, 3, 4, 5, or 6, wherein the content of the structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond in the acrylic copolymer is 5% by mass or more and 55% by mass or less. Disclosure 8 is the PSA composition of Disclosure 1, 2, 3, 4, 5, 6, or 7, further comprising a pigment. Disclosure 9 is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, or 8. Disclosure 10 is the pressure-sensitive adhesive tape of Disclosure 9, in which the pressure-sensitive adhesive layer has a gel fraction of 20% by mass or more and 70% by mass or less. Disclosure 11 is the pressure-sensitive adhesive tape of Disclosures 9 or 10, in which the pressure-sensitive adhesive layer has a foamed structure.Disclosure 12 is the pressure-sensitive adhesive tape of Disclosure 9, 10, or 11 used for bonding to internal components of electrical and electronic devices. Disclosure 13 is a resin molded body molded from a resin composition containing the pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, or 8 and a polyolefin resin. Disclosure 14 is a composite structure comprising the pressure-sensitive adhesive tape of Disclosure 9, 10, 11, or 12 and a member containing a resin including a polyolefin resin. Disclosure 15 is an automotive component comprising the resin molded body of Disclosure 13 or the composite structure of Disclosure 14. Disclosure 16 is a method for producing a resin molded body, the method comprising the steps of forming a resin composition from the composite structure of Disclosure 14 without separating it, and then molding a resin molded body using the resin composition. The present invention will be described in detail below.

[0008] The present inventors have noticed that the use of an acrylic copolymer having structural units derived from a (meth)acrylic acid alkyl ester and structural units derived from an olefin-based polymer having a terminal polymerizable unsaturated double bond in a pressure-sensitive adhesive composition improves compatibility with low-polarity components, and have investigated the inclusion of an acrylic copolymer having the above-mentioned structural units and a rubber-based pressure-sensitive adhesive such as a styrene-based elastomer in a pressure-sensitive adhesive composition. Furthermore, the present inventors have investigated the use of an acrylic copolymer having structural units derived from a (meth)acrylic acid alkyl ester, structural units derived from an olefin-based polymer having a terminal polymerizable unsaturated double bond, and structural units derived from a polar functional group-containing monomer as the acrylic copolymer in a pressure-sensitive adhesive composition having the above-mentioned structure, and have found that a pressure-sensitive adhesive composition having excellent low dielectric properties and excellent adhesive strength and retention properties can be obtained, thereby completing the present invention.

[0009] The pressure-sensitive adhesive composition of the present invention contains an acrylic copolymer (hereinafter sometimes simply referred to as "acrylic copolymer") having structural units derived from a (meth)acrylic acid alkyl ester, structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond, and structural units derived from a polar functional group-containing monomer, and a styrene-based elastomer described below. By containing the acrylic copolymer and the styrene-based elastomer described below, the pressure-sensitive adhesive composition of the present invention has excellent low dielectric properties and excellent adhesive strength and retention. In this specification, "(meth)acrylic" means acrylic or methacrylic.

[0010] The acrylic copolymer has a structural unit derived from a (meth)acrylic acid alkyl ester and a structural unit derived from an olefin-based polymer having a terminal polymerizable unsaturated double bond. The acrylic copolymer has a structure in which structural units derived from an olefin-based polymer having a terminal polymerizable unsaturated double bond, located on the side chains of the acrylic copolymer, aggregate through interaction to form pseudo-crosslinks. Because the acrylic copolymer has such a structure, the pressure-sensitive adhesive composition is hard like a crosslinked pressure-sensitive adhesive composition when strain is small, and exhibits high retention. On the other hand, when peel stress is applied and strain increases, the pseudo-crosslinks are broken, causing the molecules of the acrylic copolymer to elongate, resulting in high flexibility. In other words, when the acrylic copolymer contains a structural unit derived from a (meth)acrylic acid alkyl ester and a structural unit derived from an olefin-based polymer having a terminal polymerizable unsaturated double bond, the resulting pressure-sensitive adhesive composition has sufficient adhesive strength and further improved retention. Furthermore, since olefin polymers having terminal polymerizable unsaturated double bonds have relatively low polarity, the acrylic copolymer has structural units derived from the olefin polymer having terminal polymerizable unsaturated double bonds, resulting in a structure having a high-polarity moiety in the main chain and a low-polarity moiety in the side chain. Therefore, the acrylic copolymer has improved compatibility with low-polarity components in the pressure-sensitive adhesive composition, such as the styrene-based elastomer and tackifier resin described below. As a result, by incorporating the acrylic copolymer and the styrene-based elastomer described below into the pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition can have excellent low dielectric properties, adhesive strength, and retention.

[0011] Examples of the (meth)acrylic acid alkyl ester in the structural unit derived from the (meth)acrylic acid alkyl ester include (meth)acrylic acid alkyl esters having a linear or branched alkyl group having 1 to 24 carbon atoms. Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, n-heptyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and methyl (meth)acrylate. Examples of suitable (meth)acrylates include n-octyl acrylate, isooctyl (meth)acrylate, 2-octyl (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, alkyl (meth)acrylate esters in which the alkyl group has 4 to 8 carbon atoms are preferred, from the viewpoint that the glass transition temperature of the (meth)acrylic copolymer described below easily falls within a suitable range and the adhesive strength of the resulting adhesive composition is further improved, and n-butyl (meth)acrylate is more preferred, from the viewpoint that the retentivity of the resulting adhesive composition is further improved. From the viewpoint of further improving the adhesive strength of the resulting pressure-sensitive adhesive composition, the (meth)acrylic acid alkyl ester more preferably contains at least one selected from the group consisting of n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, and 2-octyl (meth)acrylate. These (meth)acrylic acid alkyl esters may be used alone or in combination of two or more.

[0012] The content of the structural units derived from the (meth)acrylic acid alkyl ester in the acrylic copolymer is preferably 50% by mass at the lower limit and 95% by mass at the upper limit. When the content of the structural units derived from the (meth)acrylic acid alkyl ester is within the above range, the adhesive strength and retention properties of the resulting pressure-sensitive adhesive composition are further improved. The content of the structural units derived from the (meth)acrylic acid alkyl ester is more preferably 60% by mass at the lower limit and 90% by mass at the upper limit, and even more preferably 65% ​​by mass at the lower limit and 85% by mass at the upper limit.

[0013] 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 these, an olefin polymer having a terminal polymerizable unsaturated double bond is preferred from the viewpoint of preventing chemical crosslinking within the molecule and further improving the retention of the resulting pressure-sensitive adhesive composition.

[0014] Examples of the olefin polymer having a terminal polymerizable unsaturated double bond include ethylene-butylene copolymers, ethylene-propylene copolymers, ethylene polymers, propylene polymers, and butylene polymers, each of which has a group containing a polymerizable unsaturated carbon-carbon double bond at one or both terminals. Examples of the group containing a polymerizable unsaturated carbon-carbon double bond include a (meth)acryloyl group, a vinyl ether group, and a styryl group. Of these, a (meth)acryloyl group is preferred because of its excellent copolymerizability with the (meth)acrylic acid alkyl ester.

[0015] Specific examples of the olefin polymer having a terminal polymerizable unsaturated double bond include an ethylene macromonomer having a (meth)acryloyl group at one end, a propylene macromonomer having a (meth)acryloyl group at one end, an ethylene-butylene macromonomer having a (meth)acryloyl group at one end, and an ethylene-propylene macromonomer having a (meth)acryloyl group at one end. Of these, an ethylene-butylene macromonomer having a (meth)acryloyl group at one end and an ethylene-propylene macromonomer having a (meth)acryloyl group at one end are preferred, from the viewpoints of making it easier for the glass transition temperature of the acrylic copolymer described below to fall within a suitable range and further improving the adhesive strength of the resulting pressure-sensitive adhesive composition. These olefin polymers having a terminal polymerizable unsaturated double bond may be used alone, or two or more types may be used in combination. In addition, in this specification, the term "macromonomer" refers to a monomer having a weight-average molecular weight of about 1,000 to 100,000 and having a polymerizable functional group, and the term "(meth)acryloyl" refers to acryloyl or methacryloyl.

[0016] The content of the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond in the acrylic copolymer is preferably 5% by mass or less, and more preferably 55% by mass or less. 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, an appropriate number of pseudo-crosslinks are formed, thereby further improving the adhesive strength and retention of the resulting pressure-sensitive adhesive composition. Furthermore, the acrylic copolymer has a low-polarity moiety in the side chain, which further improves compatibility with low-polarity components in the pressure-sensitive adhesive composition, such as the styrene elastomer and tackifier resin described below. This results in the resulting pressure-sensitive adhesive composition having superior low dielectric properties and further improved adhesive strength and retention. When the content of the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond is 55% by mass or less, the bulk strength of the resulting pressure-sensitive adhesive composition is further improved, thereby further improving the retention of the pressure-sensitive adhesive composition. The more preferred lower limit of the content of the structural unit derived from the olefin polymer having a terminal polymerizable unsaturated double bond is 10% by mass, the more preferred upper limit is 50% by mass, the even more preferred upper limit is 45% by mass, and the even more preferred upper limit is 40% by mass.

[0017] The acrylic copolymer has a structural unit derived from a polar functional group-containing monomer. The acrylic copolymer having the structural unit derived from the (meth)acrylic acid alkyl ester and the structural unit derived from the olefin polymer having a terminal polymerizable unsaturated double bond further has a structural unit derived from a polar functional group-containing monomer, whereby the polar functional groups in the acrylic copolymer interact with each other, resulting in sufficient retention of the pressure-sensitive adhesive composition and further improved adhesive strength.

[0018] 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. Among these, from the viewpoint of further improving the adhesive strength and retention of the resulting pressure-sensitive adhesive composition, it is preferable to include at least one selected from the group consisting of carboxy group-containing monomers and hydroxy group-containing monomers. Specific examples of the carboxy group-containing monomer include unsaturated monocarboxylic acids such as (meth)acrylic acid, (meth)acryloylacetic acid, (meth)acryloylpropionic acid, (meth)acryloylbutyric acid, (meth)acryloylpentanoic acid, and crotonic acid, and dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. Specific examples of the hydroxy group-containing monomer include 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate. Specific examples of the amide group-containing monomer include N-vinyl-2-pyrrolidone, N,N-dimethyl(meth)acrylamide, and N-isopropyl(meth)acrylamide. Specific examples of the amino group-containing monomer include (meth)acryloylmorpholine, dimethylaminoethyl(meth)acrylate, and diethylaminoethyl(meth)acrylate. These polar functional group-containing monomers may be used alone or in combination of two or more.

[0019] The 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 content of the structural units derived from the polar functional group-containing monomer is 0.1% by mass or more, the interaction between the polar functional groups can be further enhanced, thereby further improving the adhesive strength and retention of the pressure-sensitive adhesive composition. When the content of the structural units derived from the polar functional group-containing monomer is 10% by mass or less, the polarity of the acrylic copolymer is further reduced, thereby further improving the low dielectric properties of the resulting pressure-sensitive adhesive composition. Furthermore, the resulting pressure-sensitive adhesive composition does not become too hard, thereby further improving the adhesive strength. Furthermore, when the pressure-sensitive adhesive composition contains a crosslinking agent, when the content of the structural units derived from the polar functional group-containing monomer is within the above range, the acrylic copolymer can form an appropriate crosslinked structure, thereby further improving the retention of the resulting pressure-sensitive adhesive composition. A more preferred lower limit and a more preferred upper limit of the content of the structural units derived from the polar functional group-containing monomer are 1% by mass and 8% by mass, respectively.

[0020] The acrylic copolymer preferably has a glass transition temperature in the range of -100 to 200°C when subjected to differential scanning calorimetry, and all of the glass transition temperatures are -20°C or lower. The acrylic copolymer has glass transition temperatures in the above temperature range, and all of the glass transition temperatures are -20°C or lower. In other words, the acrylic copolymer does not contain a structure with a high glass transition temperature, which makes it easier for the molecules of the acrylic copolymer to stretch, thereby further improving the adhesive strength of the resulting pressure-sensitive adhesive composition. It is more preferable that all of the glass transition temperatures are -30°C or lower, and even more preferably -35°C or lower. The glass transition temperatures can be adjusted by the type of monomer that is the material for the acrylic copolymer. The glass transition temperature can be determined by measuring in a nitrogen atmosphere (nitrogen flow, flow rate 50 mL / min) using a differential scanning calorimeter (for example, "220C" manufactured by Seiko Instruments Inc.) according to a method in accordance with JIS K6240:2011 under conditions of a measurement temperature of -100 to 200°C and a temperature rise rate of 10°C / min.

[0021] 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 (Mw) of the acrylic copolymer is 500,000 or more, the adhesive strength and retention of the resulting pressure-sensitive adhesive composition are further improved. When the weight-average molecular weight (Mw) of the acrylic copolymer is 2,000,000 or less, the resulting pressure-sensitive adhesive composition does not become too hard and has higher adhesive strength. A more preferred lower limit of the weight-average molecular weight (Mw) of the acrylic copolymer is 650,000, 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.

[0022] The polydispersity (weight average molecular weight / number average molecular weight, Mw / Mn) of the acrylic copolymer preferably has a lower limit of 1.0 and an upper limit of 6.0. When the polydispersity (Mw / Mn) of the acrylic copolymer is within the above range, the adhesive strength and retention properties of the resulting pressure-sensitive adhesive composition are further improved. The polydispersity (Mw / Mn) of the acrylic copolymer is more preferably 1.5 and 4.5, respectively.

[0023] In this specification, the terms "weight average molecular weight" and "number average molecular weight" refer to weight average molecular weights measured as polystyrene equivalent molecular weights by gel permeation chromatography (GPC). Specific examples of methods for measuring the weight average molecular weight, number average molecular weight, and polydispersity of the acrylic copolymer include a Waters 2690 Separations Module measuring instrument, a Showa Denko GPC KF-806L column, and ethyl acetate as a solvent, at a sample flow rate of 1 mL / min and a column temperature of 40°C.

[0024] The preferred lower limit of the content of the acrylic copolymer in the pressure-sensitive adhesive composition is 30% by mass, and the preferred upper limit is 50% by mass. When the content of the acrylic copolymer is 30% by mass or more, the adhesive strength and retention of the resulting pressure-sensitive adhesive composition are further improved. When the content of the acrylic copolymer is 50% by mass or less, the resulting pressure-sensitive adhesive composition has even better low dielectric properties. A more preferred lower limit of the content of the acrylic copolymer is 40% by mass, and an even more preferred lower limit is 45% by mass.

[0025] The pressure-sensitive adhesive composition contains a styrene-based elastomer containing at least one selected from the group consisting of a block copolymer having a block derived from a styrene-based monomer and a block derived from a conjugated diene-based monomer, and a hydrogenated product of the block copolymer (hereinafter sometimes referred to as a "hydrogenated block copolymer"). The styrene-based elastomer has low polarity and a small dielectric loss tangent in the high frequency band. Therefore, by including the styrene-based elastomer in the pressure-sensitive adhesive composition, low dielectric properties are improved. In particular, from the viewpoint of a low content of double bonds (unsaturated bonds) and further improving the heat resistance and weather resistance of the resulting pressure-sensitive adhesive composition, it is preferable that the styrene-based elastomer contain a hydrogenated product of the block copolymer. In this specification, the term "hydrogenated product of block copolymer" refers to a block copolymer in which preferably 80% or more, more preferably 90% or more, even more preferably 95% or more, and even more preferably 96% or more of the double bonds (unsaturated bonds) in the repeating units derived from the conjugated diene-based monomer are converted to saturated bonds by hydrogenation. The hydrogenated block copolymer may be a partially hydrogenated product or a completely hydrogenated product. That is, the upper limit of the hydrogenation ratio (hydrogenation rate) may be 100%. The hydrogenation rate is measured by using deuterated chloroform as a solvent and measuring the hydrogenation rate at 20 Hz. １ It can be calculated by measuring the H-NMR spectrum.

[0026] The block copolymer having a block derived from a styrene-based monomer and a block derived from a conjugated diene-based monomer is not particularly limited, as long as it has rubber elasticity at room temperature and has a hard segment portion and a soft segment portion. The block derived from the styrene-based monomer is the hard segment portion, and the block derived from the conjugated diene-based monomer is the soft segment portion. The block copolymer having a block derived from a styrene-based monomer and a block derived from a conjugated diene-based monomer may be linear or branched.

[0027] The block derived from the styrene-based monomer may be any block having a repeating unit derived from the styrene-based monomer, and may also contain a repeating unit derived from another compound such as ethylene. Examples of the styrene-based monomer include alkylstyrene, halogenated styrene, halogen-substituted alkylstyrene, alkoxystyrene, carboxyalkylstyrene, alkyl ether styrene, alkylsilylstyrene, vinylbenzyl dimethoxyphosphide, vinylnaphthalene, vinylanthracene, N,N-diethyl-p-aminoethylstyrene, and vinylpyridine.

[0028] Examples of the alkylstyrene include styrene, methylstyrene, dimethylstyrene, and t-butylstyrene. Examples of the halogenated styrene include chlorostyrene, bromostyrene, and fluorostyrene. Examples of the halogen-substituted alkylstyrene include chloromethylstyrene. Examples of the alkoxystyrene include methoxystyrene and ethoxystyrene. Examples of the carboxyalkylstyrene include carboxymethylstyrene. Examples of the alkyl etherstyrene include vinylbenzyl propyl ether. Examples of the alkylsilylstyrene include trimethylsilylstyrene. Among these, styrene, methylstyrene, and dimethylstyrene are preferred, and styrene is more preferred due to its industrial availability. These styrene-based monomers may be used alone or in combination of two or more.

[0029] The block derived from the conjugated diene monomer has a repeating unit derived from a conjugated diene compound. Examples of the conjugated diene compound include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-octadiene, 1,3-hexadiene, 1,3-cyclohexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, myrcene, and chloroprene. Among these, 1,3-butadiene and isoprene are preferred because of their high polymerization reactivity and industrial availability. These conjugated diene compounds may be used alone or in combination of two or more.

[0030] Examples of hydrogenated block copolymers having a block derived from a styrene monomer and a block derived from a conjugated diene monomer include triblock copolymers such as styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), and styrene-isobutylene-styrene block copolymer (SIBS). Of these, SEBS is preferred from the viewpoint that the resulting pressure-sensitive adhesive composition has appropriate flexibility and superior adhesive strength.

[0031] Examples of the block copolymer having a block derived from a styrene-based monomer and a block derived from a conjugated diene-based monomer include triblock copolymers such as styrene-butadiene-styrene block copolymer (SBS) and styrene-isoprene-styrene block copolymer (SIS). Of these, SIS is preferred from the viewpoint that the resulting pressure-sensitive adhesive composition is more easily stretched and has superior adhesive strength.

[0032] The styrene-based elastomer may contain, in addition to a triblock copolymer of the block derived from the styrene-based monomer and the block derived from the conjugated diene-based monomer, a diblock copolymer of the block derived from the styrene-based monomer and the block derived from the conjugated diene-based monomer. The content of the diblock copolymer in the styrene-based elastomer (hereinafter also referred to as the "diblock ratio") is not particularly limited, but a preferred lower limit is 50% by mass, and a more preferred lower limit is 70% by mass. Having the diblock ratio within this range improves the adhesion of the resulting pressure-sensitive adhesive composition to an adherend and further improves its adhesive strength. The upper limit of the diblock ratio is not particularly limited, but a preferred upper limit is 90% by mass, from the viewpoint of maintaining the cohesive strength of the resulting pressure-sensitive adhesive composition. The diblock ratio can be calculated from the peak area ratio of each copolymer measured by gel permeation chromatography (GPC).

[0033] The content of the block derived from the styrene-based monomer in the styrene-based elastomer (hereinafter sometimes referred to as "styrene content") is not particularly limited, but a preferred upper limit is 20% by mass, and a more preferred upper limit is 16% by mass. When the styrene content is within the above range, the resulting pressure-sensitive adhesive composition does not become too hard, and the adhesion to the adherend is improved, thereby further improving the adhesive strength. Furthermore, the lower limit of the styrene content is not particularly limited, but from the viewpoint of being able to maintain the cohesive strength of the resulting pressure-sensitive adhesive composition, a preferred lower limit is 8% by mass. The styrene content is １ It can be calculated from the peak area ratio of each block measured by H-NMR.

[0034] The weight-average molecular weight (Mw) of the styrene-based elastomer is not particularly limited, but a preferred lower limit is 50,000. When the weight-average molecular weight (Mw) of the styrene-based elastomer is 50,000 or more, the adhesive strength of the resulting pressure-sensitive adhesive composition is further improved, and the resulting pressure-sensitive adhesive composition has even better low dielectric properties. A more preferred lower limit of the weight-average molecular weight of the styrene-based elastomer is 100,000. There is no particular preferred upper limit for the weight-average molecular weight of the styrene-based elastomer, but the larger the weight-average molecular weight of the styrene-based elastomer, the more the adhesive strength of the pressure-sensitive adhesive composition can be increased, but the viscosity of the pressure-sensitive adhesive composition increases and the processability decreases, so the limit is essentially about 600,000.

[0035] The preferred lower limit of the content of the styrene elastomer relative to 100 parts by mass of the acrylic copolymer is 15 parts by mass, and the preferred upper limit is 100 parts by mass. When the content of the styrene elastomer is 15 parts by mass or more, the resulting pressure-sensitive adhesive composition has even better low dielectric properties. When the content of the styrene elastomer is 100 parts by mass or less, the retention properties of the resulting pressure-sensitive adhesive composition are further improved. The more preferred lower limit of the content of the styrene elastomer is 30 parts by mass, and the more preferred upper limit is 70 parts by mass.

[0036] The pressure-sensitive adhesive composition preferably further contains a crosslinking agent. By containing the crosslinking agent in the pressure-sensitive adhesive composition, the acrylic copolymer can form a crosslinked structure in which molecules are chemically crosslinked via the crosslinking agent, thereby further improving the cohesive strength of the resulting pressure-sensitive adhesive composition. As a result, the retentivity of the pressure-sensitive adhesive composition is further improved.

[0037] Examples of the crosslinking agent include epoxy-based crosslinking agents, isocyanate-based crosslinking agents, metal chelate-based crosslinking agents, etc. Among these, isocyanate-based crosslinking agents are preferred from the viewpoint of providing the resulting pressure-sensitive adhesive composition with appropriate flexibility and heat resistance.

[0038] The content of the crosslinking agent relative to 100 parts by mass of the acrylic copolymer is preferably 0.5 parts by mass at the lower limit and 7 parts by mass at the upper limit. When the content of the crosslinking agent is 0.5 parts by mass or more, the acrylic copolymer can appropriately form a crosslinked structure, thereby further improving the cohesive strength of the resulting pressure-sensitive adhesive composition. As a result, the retentivity of the pressure-sensitive adhesive composition is further improved. When the content of the crosslinking agent is 7 parts by mass or less, the resulting pressure-sensitive adhesive composition does not become too hard, and the adhesive strength and retentivity are further improved. A more preferred lower limit of the content of the crosslinking agent is 2 parts by mass, and a more preferred upper limit is 5 parts by mass.

[0039] The pressure-sensitive adhesive composition preferably contains a tackifier resin, which further improves the adhesive strength of the pressure-sensitive adhesive composition.

[0040] The tackifier resin is not particularly limited, but from the viewpoint of low polarity of the tackifier resin and further improving the low dielectric properties of the resulting PSA composition, it is preferable to include a low-hydroxyl value tackifier resin having a hydroxyl value of less than 15 mgKOH / g. The hydroxyl value of the low-hydroxyl value tackifier resin may be 0 mgKOH / g. Examples of the low-hydroxyl value tackifier resin include terpene resins and petroleum resins.

[0041] The tackifier resin may contain a high-hydroxyl value tackifier resin having a hydroxyl value of 15 mgKOH / g or more. Because the high-hydroxyl value tackifier resin has high polarity, it is difficult to dissolve in the low-polarity structural units derived from the olefin-based polymer having a terminal polymerizable unsaturated double bond. As a result, the formation of pseudo-crosslinking points due to interactions between the low-polarity structural units derived from the olefin-based polymer having a terminal polymerizable unsaturated double bond is not inhibited, thereby further improving the adhesive strength of the resulting pressure-sensitive adhesive composition. Examples of the high-hydroxyl value tackifier resin include terpene phenol resins and polymerized rosin ester resins. Furthermore, from the viewpoint of improving the low dielectric properties of the resulting pressure-sensitive adhesive composition due to the low polarity of the tackifier resin, the preferred upper limit of the hydroxyl value of the high-hydroxyl value tackifier resin is 200 mgKOH / g.

[0042] The content of the tackifier resin is not particularly limited, but the preferred lower limit of the content of the low hydroxyl value tackifier resin relative to 100 parts by mass of the acrylic copolymer is 10 parts by mass or more, and the preferred upper limit is 200 parts by mass. When the content of the low hydroxyl value tackifier resin is 10 parts by mass or more, the adhesive strength of the resulting PSA composition is further improved. When the content of the low hydroxyl value tackifier resin is 200 parts by mass or less, the resulting PSA composition does not become too hard, and the adhesive strength and retention are further improved. A more preferred lower limit of the content of the low hydroxyl value tackifier resin is 30 parts by mass, and a more preferred upper limit is 120 parts by mass.

[0043] Furthermore, the preferred upper limit of the content of the high hydroxyl value tackifier resin relative to 100 parts by mass of the acrylic copolymer is 30 parts by mass. When the content of the high hydroxyl value tackifier resin is 30 parts by mass or less, the resulting PSA composition does not become too hard, and the adhesive strength and retention are further improved. Furthermore, the polarity of the resulting PSA composition does not become too high, and the PSA composition has even better low dielectric properties. A more preferred upper limit of the content of the high hydroxyl value tackifier resin is 15 parts by mass. Furthermore, from the viewpoint of improving the low dielectric properties of the PSA composition, it is preferred that the PSA composition does not contain the high hydroxyl value tackifier resin. When the PSA composition contains the high hydroxyl value tackifier resin, a preferred lower limit of the content of the high hydroxyl value tackifier resin is 1 part by mass.

[0044] The proportion of the total content of the styrene-based elastomer and the tackifier resin in the total content of the acrylic copolymer, the styrene-based elastomer, and the tackifier resin is preferably 20% by mass at the lower limit and 70% by mass at the upper limit. When the proportion of the total content of the styrene-based elastomer and the tackifier resin in the total content of the acrylic copolymer, the styrene-based elastomer, and the tackifier resin is within the above range, the resulting PSA composition has further improved low dielectric constant and retention properties. The proportion of the total content of the styrene-based elastomer and the tackifier resin in the total content of the acrylic copolymer, the styrene-based elastomer, and the tackifier resin is more preferably 40% by mass at the lower limit, more preferably 65% ​​by mass at the upper limit, even more preferably 50% by mass, and even more preferably 55% by mass at the lower limit. When the pressure-sensitive adhesive composition does not contain the tackifier resin, the "total content of the acrylic copolymer, the styrene-based elastomer, and the tackifier resin" refers to the total content of the acrylic copolymer and the styrene-based elastomer, and the "total content of the styrene-based elastomer and the tackifier resin" refers to the content of the styrene-based elastomer.

[0045] When the PSA composition contains the tackifier resin, the proportion of the tackifier resin in the total content of the styrene-based elastomer and the tackifier resin is preferably 20% by mass or more at the lower limit and 80% by mass or more at the upper limit. When the proportion of the tackifier resin in the total content of the styrene-based elastomer and the tackifier resin is 20% by mass or more, the retentivity of the resulting PSA composition is further improved. When the proportion of the tackifier resin in the total content of the styrene-based elastomer and the tackifier resin is 80% by mass or less, the resulting PSA composition is not too hard, and the adhesive strength and retentivity of the PSA composition are further improved. The proportion of the tackifier resin in the total content of the styrene-based elastomer and the tackifier resin is more preferably 30% by mass or more at the lower limit and 75% by mass or more at the upper limit, and even more preferably 40% by mass or more at the upper limit and 70% by mass or more at the upper limit.

[0046] The pressure-sensitive adhesive composition preferably further contains expandable particles. By containing expandable particles in the pressure-sensitive adhesive composition, the pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape described below has a foamed structure. As a result, it is possible to impart excellent impact absorption properties to the pressure-sensitive adhesive tape.

[0047] The expandable particles may be, for example, particles that expand when heated, and may be thermally expanded particles. Specific examples include thermal decomposition type foaming agents and thermally expandable microcapsules, and among these, the expandable particles preferably contain thermally expandable microcapsules.

[0048] The thermally expandable microcapsules are particles in which a volatile substance such as a low-boiling point solvent is encapsulated within a resin shell. When heated, the shell resin softens, and the encapsulated volatile substance evaporates or expands. The resulting pressure causes the shell to expand, increasing the particle size. Thus, when heated, the thermally expandable microcapsules become hollow particles with bubbles within the shell. Therefore, in the pressure-sensitive adhesive composition, the expandable particles contain thermally expandable microcapsules, preventing the gas generated from the expandable particles from escaping to the outside of the pressure-sensitive adhesive layer, facilitating the coexistence of an appropriate amount of bubbles within the pressure-sensitive adhesive layer. As a result, the flexibility of the pressure-sensitive adhesive layer formed is improved, and the resulting pressure-sensitive adhesive tape has superior impact resistance.

[0049] The shell resin of the thermally expandable microcapsules is preferably a thermoplastic resin. Examples of the thermoplastic resin include polymers and copolymers of vinyl compounds such as ethylene, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, butadiene, and chloroprene, polyamides such as nylon 6 and nylon 66, and polyesters such as polyethylene terephthalate. Among these, acrylonitrile copolymers are preferred because they are less permeable to encapsulated volatile substances and can easily adjust the average particle size of the expandable particles (described later) within a suitable range.

[0050] Examples of the volatile substance encapsulated in the thermally expandable microcapsules include hydrocarbons having 3 to 7 carbon atoms, such as propane, propylene, butene, normal butane, isobutane, isopentane, neopentane, normal pentane, hexane, and heptane; petroleum ether; methane halides, such as methyl chloride and methylene chloride; and CCl ３ F, CCl ２ F ２ and one or more low-boiling liquids selected from chlorofluorocarbons such as tetramethylsilane, trimethylethylsilane, and the like. Among these, hydrocarbons having 3 to 7 carbon atoms are preferred.

[0051] The average particle size of the expandable particles has a preferred lower limit of 15 μm and a preferred upper limit of 60 μm. When the average particle size of the expandable particles is within the above range, it becomes easier to adjust the balance between the impact resistance and adhesive strength of the resulting pressure-sensitive adhesive tape. The lower limit of the average particle size of the expandable particles is more preferably 20 μm, and the upper limit is more preferably 55 μm, and the even more preferably 25 μm and 50 μm. In this specification, the "average particle size of the expandable particles" refers to the average particle size of unexpanded expandable particles obtained by observing a pressure-sensitive adhesive composition containing the expandable particles. The average particle size of the expandable particles can be obtained by randomly selecting expandable particles using an optical microscope or the like and calculating the average of 10 points.

[0052] The expansion initiation temperature of the expandable particles (also referred to as "expansion initiation temperature") is not particularly limited, but may be, for example, in the temperature range of 95° C. to 150° C. The "expansion initiation temperature of the expandable particles" means the temperature at which the expandable particles start to expand, and can be measured using a thermomechanical analyzer (TMA) or the like.

[0053] Commercially available expandable granules include, for example, Expancel 920DU40 (manufactured by Nippon Phillite Co., Ltd., average particle size 40 μm), Expancel 920DU80 (manufactured by Nippon Phillite Co., Ltd., average particle size 80 μm), EMC-20(B)R (manufactured by Nippon Phillite Co., Ltd., average particle size 20 μm), and Advancel EML101 (manufactured by Sekisui Chemical Co., Ltd., average particle size 50 μm).

[0054] The pressure-sensitive adhesive composition may be colored. By coloring the pressure-sensitive adhesive composition, the resulting pressure-sensitive adhesive composition can be imparted with excellent light-blocking properties, thereby suppressing irradiation of light or ultraviolet light on an adherend to be bonded using the pressure-sensitive adhesive composition, and thereby suppressing deterioration of the adherend due to light or ultraviolet light. Therefore, the resulting pressure-sensitive adhesive composition can be suitably used by bonding it to internal components of electrical and electronic devices.

[0055] When the pressure-sensitive adhesive composition is colored, the pressure-sensitive adhesive composition contains a colorant. Examples of the colorant include pigments and dyes. In particular, from the viewpoint of superior heat resistance, it is preferable that the pressure-sensitive adhesive composition further contains a pigment. Examples of the pigment include carbon black, aniline black, titanium oxide, etc. Among these, carbon black is preferred because it is relatively inexpensive and chemically stable. Examples of the dye include azo dyes, anthraquinone dyes, indigo dyes, etc.

[0056] The content of the colorant relative to 100 parts by mass of the acrylic copolymer is preferably 0.2 parts by mass at the lower limit and 5.0 parts by mass at the upper limit. When the content of the colorant is 0.2 parts by mass or more, the resulting pressure-sensitive adhesive composition can be imparted with sufficient light-blocking properties. When the content of the colorant is 5.0 parts by mass or less, the resulting pressure-sensitive adhesive composition can exhibit sufficient adhesive strength. The lower limit of the content of the colorant is more preferably 0.5 parts by mass, more preferably 4.0 parts by mass at the upper limit, even more preferably 0.8 parts by mass at the lower limit, and even more preferably 3.5 parts by mass at the upper limit.

[0057] The pressure-sensitive adhesive composition may contain conventionally known fine particles and additives, such as inorganic fine particles, antioxidants, organic fillers, and inorganic fillers, as needed.

[0058] The method for producing the pressure-sensitive adhesive composition is not particularly limited, and a conventionally known method 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 (meth)acrylic copolymer. Next, the obtained (meth)acrylic copolymer, the styrene-based elastomer, and, if necessary, the crosslinking agent, the tackifier resin, and other additives are added to obtain the pressure-sensitive adhesive composition.

[0059] The uses of the pressure-sensitive adhesive composition are not particularly limited, but because the pressure-sensitive adhesive composition has excellent adhesive strength and retention, it can be suitably used as a liquid pressure-sensitive adhesive or a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive, which is used for assembling portable electronic devices such as mobile phones and personal digital assistants, or for fixing in-vehicle electronic device components such as in-vehicle panels to vehicle bodies (i.e., for bonding to internal components of electrical and electronic devices). Furthermore, because the pressure-sensitive adhesive composition further has excellent low dielectric properties, it can be even more suitably used as a liquid pressure-sensitive adhesive or a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive, which fixes high-frequency communication components such as small antenna base stations and in-vehicle antennas.

[0060] The present disclosure also provides a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition. The pressure-sensitive adhesive tape may be a non-supported pressure-sensitive adhesive tape that does not have a substrate, or a supported pressure-sensitive adhesive tape in which the pressure-sensitive adhesive layer is formed on a substrate. When the pressure-sensitive adhesive tape is a supported pressure-sensitive adhesive tape, it may be a single-sided pressure-sensitive adhesive tape in which the pressure-sensitive adhesive layer is formed on one side of a substrate, or a double-sided pressure-sensitive adhesive tape in which the pressure-sensitive adhesive layer is formed on both sides. In particular, from the viewpoint of achieving superior low dielectric properties in the resulting pressure-sensitive adhesive tape, it is preferable that the pressure-sensitive adhesive tape be a non-supported pressure-sensitive adhesive tape that does not have a substrate.

[0061] The preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 20% by mass, and the preferred upper limit is 70% by mass. A gel fraction of the pressure-sensitive adhesive layer of 20% by mass or more further improves the cohesive strength of the pressure-sensitive adhesive layer, thereby further improving the retention of the pressure-sensitive adhesive tape when shear stress is applied at high temperatures for a long period of time. A gel fraction of the pressure-sensitive adhesive layer of 70% by mass or less prevents the pressure-sensitive adhesive layer from becoming too hard, thereby further improving the adhesive strength of the resulting pressure-sensitive adhesive tape. A more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 30% by mass, a more preferred upper limit is 65% by mass, an even more preferred lower limit is 40% by mass, and an even more preferred upper limit is 60% by mass.

[0062] The gel fraction of the pressure-sensitive adhesive layer can be measured by the following method. ０(g) The material is scraped off, immersed in 50 mL of tetrahydrofuran, and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, tetrahydrofuran and the adhesive that has absorbed and swollen with tetrahydrofuran are separated using a metal mesh (opening #200 mesh). The separated adhesive is dried at 110°C for 1 hour. The mass of the adhesive including the dried metal mesh is measured, and the gel fraction (mass %) is calculated using the following formula (1). Gel fraction (mass %) = 100 × (W １ -W ２ ) / W ０ (1) (W ０ : initial adhesive mass, W １ : adhesive mass including metal mesh after drying, W ２ : initial mass of the metal mesh)

[0063] Examples of methods for adjusting the gel fraction of the pressure-sensitive adhesive layer include a method for adjusting the degree of crosslinking of the pressure-sensitive adhesive layer and a method for adjusting the amount of crosslinking agent added.

[0064] The thickness of the pressure-sensitive adhesive layer is preferably 5 μm at the lower limit and 100 μm at the upper limit. By having the thickness of the pressure-sensitive adhesive layer within the above range, a pressure-sensitive adhesive tape having excellent adhesive strength, holding power, and handleability can be obtained. The thickness of the pressure-sensitive adhesive layer is more preferably 10 μm at the lower limit and 75 μm at the upper limit.

[0065] The pressure-sensitive adhesive layer preferably has a peak loss tangent (tan δ, hereinafter sometimes simply referred to as "loss tangent") at 40°C or less, measured using a dynamic viscoelasticity measuring device at a measurement frequency of 10 Hz. When the loss tangent of the pressure-sensitive adhesive layer has a peak within the above range, the adhesive strength and holding power of the resulting pressure-sensitive adhesive tape are further improved. The pressure-sensitive adhesive layer more preferably has a peak loss tangent at 35°C or less, and even more preferably at 25°C or less.

[0066] The loss tangent can be obtained by measuring a dynamic viscoelastic spectrum from −100° C. to 200° C. using a viscoelasticity spectrometer (such as “DVA-200” manufactured by IT Measurement & Control Co., Ltd.) under conditions of 5° C. / min and 10 Hz in a slow heating shear deformation mode.

[0067] Examples of methods for adjusting the temperature at which the loss tangent of the pressure-sensitive adhesive layer has a peak include a method of adjusting the composition of the acrylic copolymer and a method of adjusting the amount of tackifier resin added.

[0068] The pressure-sensitive adhesive layer preferably has a foamed structure. When the pressure-sensitive adhesive layer has a foamed structure, the resulting pressure-sensitive adhesive tape can be imparted with better impact resistance, making the pressure-sensitive adhesive tape more suitable for use in bonding to internal components of electric and electronic devices.

[0069] Examples of methods for forming a foamed structure in the pressure-sensitive adhesive layer include a method of incorporating expandable particles into the pressure-sensitive adhesive composition, applying the composition to a release film or the like, and drying by heating to form a foamed structure, a method of forcibly mixing and dispersing a gas into the pressure-sensitive adhesive composition to form a foamed structure, and a method of mixing a liquefied gas into the pressure-sensitive adhesive composition to form a foamed structure. Among these, from the viewpoint that bubbles formed in the pressure-sensitive adhesive layer when the pressure-sensitive adhesive composition is dried at high temperature are easily dispersed and the resulting pressure-sensitive adhesive tape has better impact absorption properties, a method of incorporating expandable particles into the pressure-sensitive adhesive composition, applying the composition to a release film or the like, and drying by heating to form a foamed structure is preferred.

[0070] When the pressure-sensitive adhesive layer has a foamed structure, the deemed density of the pressure-sensitive adhesive layer has a preferred lower limit of 0.59 g / cm ３ and the preferred upper limit is 1.15 g / cm ３ The assumed density of the pressure-sensitive adhesive layer is 0.59 g / cm ３ When the deemed density of the pressure-sensitive adhesive layer is 1.15 g / cm or more, the pressure-sensitive adhesive layer is less likely to cause cohesive failure, and the adhesive strength is further improved. ３ When the deemed density of the pressure-sensitive adhesive layer is 0.65 g / cm or less, the stress relaxation property of the pressure-sensitive adhesive layer is further improved, and the resulting pressure-sensitive adhesive tape can be imparted with better impact absorption properties. ３ , and a more preferable lower limit is 0.70 g / cm ３ , and a more preferable upper limit is 1.05 g / cm ３ , and a more preferable upper limit is 1.00 g / cm３ is.

[0071] The deemed density of the pressure-sensitive adhesive layer can be measured, for example, in accordance with JIS K 7222 or the like using an electronic densimeter (for example, "ED120T" manufactured by Mirage).

[0072] The method for producing the pressure-sensitive adhesive tape is not particularly limited, and a conventionally known method can be used. Specifically, for example, the pressure-sensitive adhesive composition obtained by the above-mentioned method is added to a solvent or the like, and then the mixture is thoroughly stirred to obtain a pressure-sensitive adhesive solution, which is then coated on the release-treated surface of a film that has been subjected to a release treatment, and dried to produce the pressure-sensitive adhesive tape. In addition, the pressure-sensitive adhesive tape produced by the above-mentioned method can also be made into a support-type pressure-sensitive adhesive tape by laminating the pressure-sensitive adhesive tape produced by the above-mentioned method as a pressure-sensitive adhesive layer to a substrate.

[0073] The preferred lower limit of the thickness of the entire pressure-sensitive adhesive tape is 5 μm, and the preferred upper limit is 200 μm. Having the thickness of the entire pressure-sensitive adhesive tape within the above range makes it easier to obtain a pressure-sensitive adhesive tape with appropriate adhesive strength and holding power. The more preferred lower limit of the thickness of the entire pressure-sensitive adhesive tape is 10 μm, and the more preferred upper limit is 100 μm. The thickness of the entire pressure-sensitive adhesive tape does not include the thickness of a film, separator, or the like that protects the outermost pressure-sensitive adhesive layer.

[0074] The applications of the pressure-sensitive adhesive tape are not particularly limited, but because the pressure-sensitive adhesive tape has excellent adhesive strength and retention, it can be suitably used for bonding to internal components of electrical and electronic devices. Specifically, it can be suitably used, for example, for assembling portable electronic devices such as mobile phones and personal digital assistants, or for fixing automotive electronic device components such as automotive panels to vehicle bodies. Furthermore, because the pressure-sensitive adhesive tape also has excellent low dielectric properties, it can be more suitably used for fixing high-frequency communication components such as small antenna base stations and automotive antennas.

[0075] Since the PSA composition has excellent compatibility with low-polarity components, a resin composition produced from at least one of the PSA composition and the PSA tape and a polyolefin resin has excellent performance qualities (e.g., impact resistance) as a resin material and can be more suitably used as a recycled material. That is, the PSA composition and the PSA tape have excellent recyclability with the polyolefin resin.

[0076] The present disclosure also provides a resin molded article molded from a resin composition containing the pressure-sensitive adhesive composition and a polyolefin resin. The resin molded article has high performance and quality as a recycled product.

[0077] The polyolefin resin in the resin molded product is not particularly limited, and examples thereof include thermoplastic olefin resins and thermosetting olefin resins, but thermoplastic olefin resins are preferred from the viewpoint of ease of thermal melting during recycling. Examples of the thermoplastic olefin resin include polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin (EVA), ethylene-ethyl acrylate copolymer resin (EEA), ethylene-methyl methacrylate copolymer resin (EMMA), polyolefin thermoplastic elastomer (TPO), and ethylene propylene rubber (EPDM). Among these, polypropylene is preferred from the viewpoint of ease of recycling.

[0078] The resin molded body can be obtained, for example, by heating and kneading a composite structure including a mixture containing the pressure-sensitive adhesive composition or the pressure-sensitive adhesive tape and a polyolefin resin, or a composite structure including a pressure-sensitive adhesive using the pressure-sensitive adhesive composition or a component containing a resin including a polyolefin resin to which the pressure-sensitive adhesive tape is attached, and then molding the resulting resin composition.

[0079] The apparatus used for heat kneading is not particularly limited, but examples thereof include a blender, kneader, mixing roll, Banbury mixer, plastomill, single-screw or twin-screw extruder, etc. The temperature for heat kneading is not particularly limited, but examples thereof include a temperature range of 180°C to 230°C.

[0080] Examples of methods used for molding the resin composition include methods such as injection molding, extrusion molding, and blow molding, in which a polyolefin resin raw material is heated to flow and easily molded into a molded product of any shape.

[0081] Examples of the resin molded article include resin raw materials, home appliances, stationery, daily necessities, and automobile parts constituting automobile members and materials constituting the automobile parts.

[0082] Examples of the resin raw material in the resin molded body include resin pellets and powder.

[0083] Specific examples of the automotive parts include in-vehicle 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, and the like.

[0084] The present disclosure also provides a composite structure comprising the pressure-sensitive adhesive tape and a member containing a resin including a polyolefin resin (hereinafter, sometimes simply referred to as a "polyolefin resin member"). The composite structure is not particularly limited as long as it comprises the pressure-sensitive adhesive tape and the polyolefin resin member. For example, it may be a structure in which the polyolefin resin member is bonded to another member using the pressure-sensitive adhesive tape. When the composite structure is a structure in which the polyolefin resin member is bonded to another member using the pressure-sensitive adhesive tape, the other member may be a polyolefin resin member or may be something other than a polyolefin resin member, but it is preferable that the other member is also a polyolefin resin member. Furthermore, when the polyolefin resin members are bonded to each other, the polyolefin resin members may be of the same type or different types.

[0085] The polyolefin resin member in the composite structure is not particularly limited as long as it is a member composed of a resin containing a polyolefin resin, and the resin containing a polyolefin resin may be a resin consisting of only a polyolefin resin, or may be a resin containing components other than a polyolefin resin. The resin containing a polyolefin resin may also be a recycled resin obtained by recycling discarded resin members. Examples of the resin containing components other than the polyolefin resin include a resin composition obtained by heating and kneading the pressure-sensitive adhesive composition and the polyolefin resin, and examples of the polyolefin resin member composed of a resin containing components other than the polyolefin resin include the resin molded body.

[0086] Examples of the polyolefin resin in the composite structure include the same polyolefin resins as those in the resin molded body.

[0087] When the composite structure is discarded, it can be recycled as long as the resin composition obtained by collectively producing the composite structure without separating it has excellent performance quality. Recycling the resin composition can reduce the environmental load. Furthermore, recycling the composite structure collectively without separating it is also useful from the viewpoint of improving recycling efficiency.

[0088] A method for improving the performance quality of the resin composition obtained from the composite structure includes, for example, a method of forming the composite structure by bonding the resin molded articles together with the adhesive tape, etc. By such a method, the components in the resin composition obtained from the composite structure can be made more compatible with each other, thereby making it possible to further suppress deterioration in the functionality of the resin composition.

[0089] Specific examples of the composite structure include an automobile part that is the above-mentioned resin molded body bonded together with an adhesive tape, and an automobile part itself that is constructed by bonding together the materials that make up the automobile part using the above-mentioned adhesive tape.

[0090] The present disclosure also provides an automotive component including the resin molded body or the composite structure. Examples of automotive components including the resin molded body include automotive components including the above-described automotive parts. Examples of automotive components including the composite structure include automotive components including a composite structure formed by bonding the above-described automotive parts with the adhesive tape.

[0091] The present disclosure also provides a method for producing a resin molded body, which includes a step of forming a resin composition from the composite structure without separating it, and then molding a resin molded body using the resin composition (hereinafter, sometimes simply referred to as "step (I)").

[0092] The pressure-sensitive adhesive tape in the composite structure has excellent compatibility with low-polarity components, and therefore also has excellent compatibility with polyolefin resins. Therefore, even when the pressure-sensitive adhesive tape and the polyolefin resin member in the composite structure are heated and kneaded together without separating them to produce a resin composition, a resin composition with high performance quality and suppressed functional degradation can be obtained. As a result, resin molded products molded using the resin composition have high performance quality as recycled products. In other words, the method for producing resin molded products makes it practical to recycle the composite structure in one go without the need for separation, thereby improving the recycling efficiency in the manufacturing process. Furthermore, by using the resin composition with excellent performance quality obtained in the manufacturing process, resin molded products useful as recycled products can be produced.

[0093] The "step of forming a resin composition from the composite construct without separating it and then using the resin composition to form a resin molded product" in the above step (I) can be exemplified by a step of generating a resin composition by heating and kneading the composite constructs all at once, and then molding the resulting resin composition to obtain a resin molded product.

[0094] In the above step (I), the apparatus used for heat kneading is not particularly limited, and examples thereof include a blender, kneader, mixing roll, Banbury mixer, plastomill, single-screw or twin-screw extruder, etc. The temperature for heat kneading is not particularly limited, and examples thereof include a temperature range of 180°C to 230°C.

[0095] In the above step (I), examples of the method for molding the resin composition include a method in which the composite components are heated and kneaded together in a single process using a molding method such as injection molding, extrusion molding, or blow molding, and the resulting resin is made to flow by heating and easily molded into a molded product of any shape.

[0096] According to the present invention, a pressure-sensitive adhesive composition having excellent low dielectric properties and excellent adhesive strength and retention can be provided. Furthermore, according to the present invention, a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition can be provided. Furthermore, according to the present invention, a resin molded product molded from a resin composition containing the pressure-sensitive adhesive composition can be provided. Furthermore, according to the present invention, a composite structure including the pressure-sensitive adhesive tape can be provided. Additionally, according to the present invention, an automotive component including the resin molded product or the composite structure can be provided. And, according to the present invention, a method for producing a resin molded product using the composite structure can be provided.

[0097] FIG. 1 is a diagram showing a schematic diagram of a retention test.

[0098] The following examples will explain the present invention in more detail, but the present invention is not limited to these examples.

[0099] (Preparation of Acrylic Copolymer) (Acrylic Copolymer A) A reactor equipped with a thermometer, a stirrer, and a cooling tube was prepared. A mixture of structural unit monomers consisting of 73.9 parts by mass of n-butyl acrylate, 20 parts by mass of an ethylene-butylene macromonomer (an ethylene-butylene macromonomer having a (meth)acryloyl group at one end: manufactured by Kraton Polymers, "HPVM-L1253"), 6.0 parts by mass of acrylic acid, and 0.1 parts by mass of 4-hydroxybutyl acrylate, 0.01 parts by mass of lauryl mercaptan, and 80 parts by mass of ethyl acetate was added to the reactor, and the reactor was heated to initiate reflux. Subsequently, 0.01 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane was added as a polymerization initiator to the reactor, and polymerization was initiated under reflux. Next, 1 hour and 2 hours after the start of polymerization, 0.01 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane was added, and then 4 hours after the start of polymerization, 0.05 parts by mass of t-hexylperoxypivalate was added to continue the polymerization reaction. Then, 8 hours after the start of polymerization, an ethyl acetate solution of acrylic copolymer A was obtained. The weight-average molecular weight and polydispersity of the obtained acrylic copolymer A were measured using a 2690 Separations Module (manufactured by Waters Corporation) as a measuring instrument, a GPC KF-806L (manufactured by Showa Denko KK) as a column, and ethyl acetate as a solvent under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C. The results are shown in Table 1.

[0100] (Acrylic Copolymers B to O) Ethyl acetate solutions of acrylic copolymers B to O were obtained in the same manner as for acrylic copolymer A, except that the mixture of constituent unit monomers was changed as shown in Tables 1 and 2. The weight average molecular weights and polydispersities of the obtained acrylic copolymers B to O were measured in the same manner as for acrylic copolymer A. The results are shown in Tables 1 and 2.

[0101] (Acrylic Copolymers P to Q) Ethyl acetate solutions of acrylic copolymers P to Q were obtained in the same manner as for acrylic copolymer A, except that the amount of ethyl acetate added in the polymerization reaction was changed from 80 parts by mass to the following amounts. The weight average molecular weights and polydispersities of the obtained acrylic copolymers P to Q were measured in the same manner as for acrylic copolymer A. The results are shown in Table 2. <Amount of ethyl acetate added> Acrylic copolymer P: 100 parts by mass Acrylic copolymer Q: 60 parts by mass

[0102]

[0103]

[0104] (Example 1) (1) Preparation of Pressure-Sensitive Adhesive Composition A solution containing a pressure-sensitive adhesive composition was obtained by adding 20 parts by mass of DYNARON 8300P (SEBS, manufactured by ENEOS Materials Corporation) as a styrene-based elastomer, 80 parts by mass of YS Resin PX800 (terpene resin, manufactured by Yasuhara Chemical Co., Ltd.) as a tackifying resin, and 3.0 parts by mass of Coronate L (isocyanate-based crosslinking agent, manufactured by Tosoh Corporation) as a crosslinking agent to 100 parts by mass of the solid content of an ethyl acetate solution of acrylic copolymer A.

[0105] (2) Production of Pressure-Sensitive Adhesive Tape After thoroughly stirring the solution containing the pressure-sensitive adhesive composition obtained in "(1) Preparation of Pressure-Sensitive Adhesive Composition" above, the obtained pressure-sensitive adhesive solution was coated with a doctor knife onto the release-treated surface of a 50 μm polyethylene terephthalate (PET) film, one side of which had been subjected to a release treatment, so that the thickness of the dried film would be 50 μm. The coating solution was dried by heating at 110° C. for 5 minutes to form a pressure-sensitive adhesive layer, and the release-treated surface of a 50 μm-thick release PET film was then superimposed on the formed pressure-sensitive adhesive layer, thereby obtaining a pressure-sensitive adhesive tape with a release PET film.

[0106] (3) Measurement of gel fraction of adhesive layer First, the adhesive of the adhesive layer was ０(g) was scraped off, immersed in 50 mL of tetrahydrofuran, and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, tetrahydrofuran and the PSA that had absorbed the tetrahydrofuran and swollen were separated using a metal mesh (opening #200 mesh). The separated PSA was dried at 110°C for 1 hour. The mass of the PSA including the metal mesh after drying was measured, and the gel fraction (mass %) of the PSA layer was calculated using the following formula (1). The results are shown in Table 3. Gel fraction (mass %) = 100 × (W １ -W ２ ) / W ０ (1) (W ０ : initial adhesive mass, W １ : adhesive mass including metal mesh after drying, W ２ : initial mass of the metal mesh)

[0107] (Examples 2 to 46, Comparative Examples 1 to 8) Pressure-sensitive adhesive tapes were produced in the same manner as in Example 1, except that the formulation of the pressure-sensitive adhesive composition was changed as shown in Tables 3 to 7, and the gel fraction of the pressure-sensitive adhesive layer was measured. The results are shown in Tables 3 to 7. In Examples 41 and 42, the coating solution was dried and a foamed structure was formed, thereby obtaining pressure-sensitive adhesive tapes having a pressure-sensitive adhesive layer with a foamed structure.

[0108] <Evaluation> The pressure-sensitive adhesive tapes obtained in the Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 3 to 7.

[0109] (1) Evaluation of adhesive strength The obtained adhesive tape was cut into a size of 25 mm wide and 50 mm long to prepare a test piece, which was then backed with a 23 μm thick polyethylene terephthalate (PET) film. Next, the backed test piece was attached to a SUS plate (SUS304 plate washed with ethanol and wiped dry), and pressed against the plate by rolling a 2 kg rubber roller back and forth at a speed of 300 mm / min once, and then aged at 23 ° C for 24 hours to obtain a measurement sample. The obtained measurement sample was subjected to a 180 ° peel test in accordance with JIS Z 0237:2009 using a tensile tester (manufactured by A&D Co., Ltd., "Tensilon Universal Material Testing Machine RTI Series") at 23 ° C and a tensile speed of 300 mm / min, and the adhesive strength (N / inch) to SUS at 23 ° C was measured. The obtained adhesive strength to SUS at 23 ° C was evaluated according to the following criteria to evaluate the adhesive strength of the adhesive tape. ◯: The adhesive strength was 10 N / inch or more. Δ: The adhesive strength was 6.0 N / inch or more and less than 10 N / inch. ×: The adhesive strength was less than 6.0 N / inch.

[0110] (2) Evaluation of Retention Ability FIG. 1 shows a schematic diagram of the retention ability test. First, in accordance with JIS Z-1528, the obtained pressure-sensitive adhesive tape was cut to a width of 25 mm and a length of 60 mm to prepare a test piece 2. One side of the test piece 2 was backed with a 23 μm thick polyethylene terephthalate (PET) film 1. The other side of the test piece 2 was attached to a cold-rolled stainless steel plate 3 (SUS304 plate washed with ethanol and wiped dry) 3 having a thickness of 2.0 mm, a width of 50 mm, and a length of 75 mm at 23 ° C., with the test piece 2 being shifted in the lengthwise direction so that it protruded from the end of the SUS304 plate 3. Then, a 2 kg rubber roller was reciprocated once at a speed of 300 mm / min to press the test piece 2 to prepare a measurement sample. The measurement sample was left for 20 minutes in an atmosphere of 23°C and 50% RH, and then a 1 kg weight 4 was attached to the measurement sample in a shear direction in an 80°C environment. The time when the weight 4 was attached was designated as the starting time (0 hours), and a retention test was performed in which the state in which the load by the weight 4 was applied was maintained in an 80°C environment for 24 hours. From the results of the retention test, the retention of the pressure-sensitive adhesive tape was evaluated according to the following criteria: ○: The test piece did not fall. ×: The test piece fell within 24 hours after the start of the retention test. If the evaluation result of the retention test at 80°C is "○", the pressure-sensitive adhesive tape can be used without any problems in practice.

[0111] Furthermore, for those samples that showed an evaluation result of "○" in the above-mentioned retention test at 80°C, a retention test at 120°C was conducted using the same test method as above, except that a 1 kg weight was attached in an environment at 120°C, and a load was applied in the shear direction in an environment at 120°C and the sample was held for 24 hours. From the results of the retention test at 120°C, the retention of the pressure-sensitive adhesive tape was further evaluated according to the following criteria. ○: The test piece did not fall. △: The test piece did not fall within 1 hour after the start of the retention test, but fell within 24 hours. ×: The test piece fell within 1 hour after the start of the retention test. Note that the retention test at 120°C is a test conducted under stricter conditions than the retention test at 80°C, and even if the evaluation result in the retention test at 120°C is "×", as described above, the pressure-sensitive adhesive tape can be used without any problems in practice as long as the evaluation result of the retention test at 80°C is "○". Furthermore, for those for which the evaluation result of the above-mentioned retention test at 80°C was "x", the retention test at 120°C was not carried out and the evaluation result was rated "x".

[0112] (3) Evaluation of low dielectric constant The release PET films on both sides of the obtained adhesive tape were peeled off, and multiple adhesive tapes were laminated until the thickness reached 100 μm to prepare an adhesive layer with a thickness of 100 μm. 50 μm thick polyethylene terephthalate (PET) films were attached to the top and bottom surfaces of the laminated adhesive layer. The obtained laminate of the PET film and adhesive layer was cut into a width of 3 mm and a length of 80 mm, and the dielectric loss tangent (Df) at a frequency of 10 GHz was measured in the TM mode resonator measurement mode using a dielectric constant measuring device (manufactured by AET Corporation, "ADMS01Nc") in accordance with JIS C2565. The dielectric loss tangent at a frequency of 10 GHz of the PET film alone was also measured using the same method. The dielectric loss tangent (Df) value of the adhesive layer alone at a frequency of 10 GHz was calculated using the measured values ​​of the laminate of the PET film and adhesive layer and the measured values ​​of the PET film alone. The dielectric loss tangent (Df) value of the obtained pressure-sensitive adhesive layer alone at a frequency of 10 GHz was used to evaluate the low dielectric properties of the pressure-sensitive adhesive tape according to the following criteria: ∘: The dielectric loss tangent (Df) was 0.015 or less. Δ: The dielectric loss tangent (Df) was greater than 0.015 and less than 0.018. ×: The dielectric loss tangent (Df) was greater than 0.018.

[0113] (4) Evaluation of Compatibility with Polyolefin Resin Compatibility with polyolefin resin was evaluated for Examples 43 to 46 and Comparative Examples 7 and 8. The evaluation method is shown below.

[0114] (i) Preparation of resin molded body derived from resin composition containing adhesive tape 2 g of the adhesive tape obtained in the above-mentioned "(2) Production of 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 using an injection molding machine (HAAKE Minilab 3, manufactured by Thermo Fisher Scientific) under conditions of cylinder temperature 200 ° C., mold temperature 40 ° C., inject press 500 bar / 10 sec, and post press 400 bar / 10 sec, a rectangular test piece (size 80 mm × 10 mm × thickness 4 mm) was prepared as a resin molded body derived from the resin composition containing adhesive tape. 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.

[0115] (ii) Preparation of resin molded body derived from resin composition containing no adhesive tape A strip-shaped test piece was prepared as a resin molded body derived from a resin composition containing no adhesive tape in the same manner as in the above-mentioned "(i) Preparation of resin molded body derived from resin composition containing adhesive tape" except that 0 g of adhesive tape and 200 g of block polypropylene were used.

[0116] (iii) Calculation of Charpy Impact Resistance Performance Reduction Rate The rectangular test pieces obtained in the above-mentioned "(i) Preparation of a resin molded body derived from a resin composition containing a pressure-sensitive adhesive tape" and "(ii) Preparation of a resin molded body derived from a resin composition not containing a pressure-sensitive adhesive tape" were each notched to a depth of 2 mm in accordance with JIS K7111-1 using a notching machine (manufactured by Yasuda Seiki Seisakusho, "Notching Machine No. 189-PNCA"), and impact strength was measured by applying a 2 J impact in the edgewise impact direction with a hammer at 23 ° C using a Charpy impact tester with a thermostatic chamber (manufactured by Yasuda Seiki Seisakusho, "Impact Tester No. 258-L-PC") 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 performance reduction rate (%) was calculated using the following formula. Charpy impact resistance performance reduction rate (%)=100−[(impact strength of resin molded product derived from resin composition containing pressure-sensitive adhesive tape) / (impact strength of resin molded product derived from resin composition not containing pressure-sensitive adhesive tape))×100]

[0117] (iv) Evaluation of Compatibility of Pressure-Sensitive Adhesive Tape with Polyolefin Resin Using the obtained Charpy impact resistance performance reduction rate (%), the compatibility of the pressure-sensitive adhesive tape with the polyolefin resin was evaluated according to the following criteria: ○: The Charpy impact resistance performance reduction rate was less than 7%. ×: The Charpy impact resistance performance reduction rate was 7% or more. When the evaluation is "○", the resin composition obtained by recycling the pressure-sensitive adhesive tape and the polyolefin resin together has excellent quality performance and can be suitably used as a recycled material. Note that even when the evaluation is "×", the pressure-sensitive adhesive tape can be used without any problems depending on the application.

[0118]

[0119]

[0120]

[0121]

[0122]

[0123] According to the present invention, a pressure-sensitive adhesive composition having excellent low dielectric properties and excellent adhesive strength and retention can be provided. Furthermore, according to the present invention, a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition can be provided. Furthermore, according to the present invention, a resin molded product molded from a resin composition containing the pressure-sensitive adhesive composition can be provided. Furthermore, according to the present invention, a composite structure including the pressure-sensitive adhesive tape can be provided. Additionally, according to the present invention, an automotive component including the resin molded product or the composite structure can be provided. And, according to the present invention, a method for producing a resin molded product using the composite structure can be provided.

[0124] 1 Polyethylene terephthalate (PET) film 2 Test piece (adhesive tape) 3 SUS304 plate 4 Weight (1 kg)

Claims

1. A pressure-sensitive adhesive composition comprising: an acrylic copolymer having structural units derived from a (meth)acrylic acid alkyl ester, structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond, and structural units derived from a polar functional group-containing monomer; and a styrene elastomer containing at least one member selected from the group consisting of block copolymers having a block derived from a styrene monomer and a block derived from a conjugated diene monomer, and hydrogenated products of said block copolymers.

2. The pressure-sensitive adhesive composition according to claim 1, further comprising a crosslinking agent.

3. The pressure-sensitive adhesive composition according to claim 1 or 2, further comprising a tackifying resin.

4. The pressure-sensitive adhesive composition according to claim 3, wherein the proportion of the total content of the styrene-based elastomer and the tackifier resin in the total content of the acrylic copolymer, the styrene-based elastomer, and the tackifier resin is 20% by mass or more and 70% by mass or less.

5. The pressure-sensitive adhesive composition according to claim 3 or 4, wherein the proportion of the content of the tackifier resin in the total content of the styrene-based elastomer and the tackifier resin is 20% by mass or more and 80% by mass or less.

6. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, or 5, wherein the (meth)acrylic acid alkyl ester comprises at least one selected from the group consisting of n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, and 2-octyl (meth)acrylate.

7. A pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5 or 6, wherein the content of structural units derived from an olefin polymer having a polymerizable unsaturated double bond at the terminal in the acrylic copolymer is 5% by mass or more and 55% by mass or less.

8. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6 or 7, further comprising a pigment.

9. An adhesive tape having an adhesive layer containing the adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7 or 8.

10. The adhesive tape according to claim 9, wherein the gel fraction of the adhesive layer is 20% by mass or more and 70% by mass or less.

11. The adhesive tape according to claim 9 or 10, wherein the adhesive layer has a foam structure.

12. The adhesive tape according to claim 9, 10 or 11, which is used for adhering to internal components of electrical and electronic devices.

13. A resin molded article formed from a resin composition containing the pressure-sensitive adhesive composition of claim 1, 2, 3, 4, 5, 6, 7 or 8 and a polyolefin resin.

14. A composite structure comprising the adhesive tape according to claim 9, 10, 11 or 12 and a member containing a resin including a polyolefin resin.

15. An automobile component comprising the resin molded article according to claim 13 or the composite structure according to claim 14.

16. A method for producing a resin molded article, comprising the steps of forming a resin composition from the composite structure according to claim 14 without separating it, and then molding the resin molded article using the resin composition.

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