JP2024066501A - Adhesive composition and adhesive tape - Google Patents

Abstract

[Problem] To provide a pressure-sensitive adhesive composition that combines excellent high-temperature adhesion and excellent adhesive strength to polyolefins. Also, to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition. [Solution] A pressure-sensitive adhesive composition comprising an acrylic copolymer having a constituent unit derived from an alkyl (meth)acrylate ester, a constituent unit derived from a polar functional group-containing monomer, and a constituent unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond, a tackifier resin T1 which is a terpene resin and has a softening point of more than 120°C and not more than 180°C, and a tackifier resin T2 which is at least one selected from the group consisting of a petroleum resin, a rosin resin, and a xylene resin and has a softening point of more than 120°C and not more than 180°C, wherein the content of the tackifier resin T1 is 5 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the acrylic copolymer, and the content of the tackifier resin T2 is 10 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the acrylic copolymer. [Selected Figure] None

Description

The present invention relates to an adhesive composition. The present invention also relates to an adhesive tape having an adhesive layer containing the adhesive composition.

Adhesive tapes have traditionally been used to assemble parts. For example, adhesive tapes are used to assemble portable electronic devices such as mobile phones and personal digital assistants (PDAs) (for example, Patent Documents 1 and 2).

JP 2009-242541 A JP 2009-258274 A

Adhesive compositions and adhesive tapes used to fasten vehicle parts are required to have adhesive strength to polyolefins such as polypropylene, which are often used in vehicle parts, as well as to steel plates. In addition, since the environment in which they are used can be hot, they need to have sufficient adhesive strength even in high-temperature environments. Conventionally, in order to achieve both adhesive strength to polyolefins and high-temperature adhesion, it was necessary to apply an easy-adhesion treatment such as a primer coating to the polyolefin adherend when laminating the adhesive tape, but from the viewpoint of increasing the number of work processes, it was desired to have no easy-adhesion treatment.

The present invention aims to provide an adhesive composition that combines excellent high-temperature adhesion with excellent adhesive strength to polyolefins. In addition, the present invention aims to provide an adhesive tape having an adhesive layer that contains the adhesive composition.

Disclosure 1 is a pressure-sensitive adhesive composition comprising an acrylic copolymer having a constituent unit derived from an alkyl (meth)acrylate ester, a constituent unit derived from a polar functional group-containing monomer, and a constituent unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond; a tackifier resin T1 which is a terpene resin and has a softening point of more than 120°C and not more than 180°C; and a tackifier resin T2 which is at least one type selected from the group consisting of a petroleum-based resin, a rosin-based resin, and a xylene-based resin and has a softening point of more than 120°C and not more than 180°C, wherein the content of the tackifier resin T1 is 5 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the acrylic copolymer, and the content of the tackifier resin T2 is 10 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the acrylic copolymer.
The present disclosure 2 is the pressure-sensitive adhesive composition of the present disclosure 1, in which the content of a tackifier resin having a softening point of 120° C. or lower is 5 parts by mass or less per 100 parts by mass of the acrylic copolymer.
The present disclosure 3 is the PSA composition according to the present disclosure 1 or 2, wherein the tackifier resin T1 contains a terpene phenol resin.
The present disclosure 4 is a pressure-sensitive adhesive composition according to claim 1, 2, or 3, wherein the tackifier resin T2 contains the petroleum-based resin and the rosin-based resin.
The present disclosure 5 is the pressure-sensitive adhesive composition according to the present disclosure 1, 2, 3, or 4, wherein the content of the petroleum-based resin is 15 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the acrylic copolymer.
The present disclosure 6 is the pressure-sensitive adhesive composition according to the present disclosure 1, 2, 3, 4, or 5, wherein the content of the rosin resin is 15 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the acrylic copolymer.
Disclosure 7 relates to a structural unit derived from an alkyl (meth)acrylate, the alkyl group bonded to the oxygen atom of the ester bond having 1 or more and 4 or less carbon atoms, the content of the structural unit derived from an alkyl (meth)acrylate in which the alkyl group bonded to the oxygen atom of the ester bond has 1 or more and 4 or less carbon atoms is 75% by mass or more and 100% by mass or less, and the structural unit derived from an alkyl (meth)acrylate in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms is 75% by mass or more and 100% by mass or less. or has structural units derived from (meth)acrylic acid alkyl esters in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms, and has structural units derived from (meth)acrylic acid alkyl esters in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms, in which the structural units derived from (meth)acrylic acid alkyl esters have 25 mass% or less of structural units derived from (meth)acrylic acid alkyl esters in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms.
The present disclosure 8 is a pressure-sensitive adhesive tape having a base layer and a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition of the present disclosure 1, 2, 3, 4, 5, 6, or 7.
The present disclosure 9 is the pressure-sensitive adhesive tape of the present disclosure 8, wherein the pressure-sensitive adhesive layer has a gel fraction of 10 mass % or more and 70 mass % or less.
The present disclosure 10 is the pressure-sensitive adhesive tape according to the present disclosure 8 or 9, wherein the base layer has a foamed structure.
The present disclosure 11 relates to a pressure-sensitive adhesive composition, wherein the structural unit derived from the (meth)acrylic acid alkyl ester has a structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms bonded to the oxygen atom of the ester bond is 1 or more and 4 or less, and the content of the structural unit derived from the (meth)acrylic acid alkyl ester in which the number of carbon atoms bonded to the oxygen atom of the ester bond is 1 or more and 4 or less is 75 mass% or more and 100 mass% or less, and the structural unit does not have a structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms bonded to the oxygen atom of the ester bond is 6 or more and 10 or less, or the structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms bonded to the oxygen atom of the ester bond is 6 or more and 10 or less, and the ester and wherein, in the case where the adhesive composition has a structural unit derived from an alkyl (meth)acrylate in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms, the content of the structural unit derived from an alkyl (meth)acrylate in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms is 25 mass% or less, the tackifier resin T2 in the pressure-sensitive adhesive composition comprises the petroleum-based resin and the rosin-based resin, the content of the petroleum-based resin is 15 parts by mass or more and 25 parts by mass or less and the content of the rosin-based resin is 10 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the acrylic copolymer, the gel fraction of the pressure-sensitive adhesive layer is 10% by mass or more and 40% by mass or less, and the thickness of the entire pressure-sensitive adhesive tape is 650 μm or less.
The present invention will be described in detail below.

The present inventors have investigated the composition of the adhesive composition, and have found that the adhesive strength of the adhesive composition is improved by using an acrylic copolymer having a constituent unit derived from an alkyl (meth)acrylate ester, a constituent unit derived from a polar functional group-containing monomer, and a constituent unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond. Furthermore, the present inventors have investigated the use of a combination of specific tackifier resins with high softening points as the tackifier resin to be contained in such an adhesive composition. As a result, they have found an adhesive composition that can achieve both excellent high-temperature adhesion and excellent adhesive strength to polyolefins, and have completed the present invention.

The pressure-sensitive adhesive composition of the present invention contains an acrylic copolymer having a structural unit derived from an alkyl (meth)acrylate ester and a structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond.
In this specification, "(meth)acrylic" means acrylic or methacrylic.
The acrylic copolymer has a structure in which the structural units derived from an olefin polymer having a polymerizable unsaturated double bond at the end are aggregated by interaction to form pseudo-crosslinking points. When the acrylic copolymer has such a structure, the pressure-sensitive adhesive composition exhibits hard properties like a crosslinked pressure-sensitive adhesive composition when strain is small, and the holding power is improved. On the other hand, when a peeling stress is applied and strain becomes large, the pseudo-crosslinking is broken and the molecules of the acrylic copolymer are stretched, so that the pressure-sensitive adhesive composition exhibits high flexibility properties and the adhesive power is improved. In other words, when the pressure-sensitive adhesive composition contains the acrylic copolymer, the adhesive power and holding power of the pressure-sensitive adhesive composition are improved.

The above-mentioned (meth)acrylic acid alkyl esters include, for example, (meth)acrylic acid alkyl esters obtained by dehydration condensation of (meth)acrylic acid and an alcohol having a linear or branched alkyl group having 1 to 24 carbon atoms. Specific examples include methyl (meth)acrylate, ethyl (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, n- Examples of the alkyl esters include octyl, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate. These alkyl (meth)acrylate esters may be used alone or in combination of two or more.

The structural unit derived from the (meth)acrylic acid alkyl ester preferably has a structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 or more and 4 or less. By having a structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 or more and 4 or less, the polarity of the acrylic copolymer becomes greater, and the interaction with the adherend is further enhanced, thereby further improving the adhesive strength of the pressure-sensitive adhesive composition.

In the structural units derived from the (meth)acrylic acid alkyl ester, the number of carbon atoms of the alkyl group bonded to the oxygen atom of the ester bond is 1 to 4, and the content of the structural units derived from the (meth)acrylic acid alkyl ester is preferably 75% by mass. When the content of the structural units derived from the (meth)acrylic acid alkyl ester, the number of carbon atoms of the alkyl group bonded to the oxygen atom of the ester bond is 1 to 4, is 75% by mass or more, the polarity of the acrylic copolymer is increased, and the interaction with the adherend is enhanced, thereby improving the adhesive strength of the pressure-sensitive adhesive composition. In addition, the elastic modulus of the acrylic copolymer is increased, and therefore the adhesive strength and holding power of the pressure-sensitive adhesive composition in a high-temperature environment are further improved. A more preferable lower limit of the content of the structural units derived from the (meth)acrylic acid alkyl ester, the number of carbon atoms of the alkyl group bonded to the oxygen atom of the ester bond is 1 to 4, is 90% by mass.
The upper limit of the content of the structural units derived from an alkyl (meth)acrylate ester in which the alkyl group bonded to the oxygen atom of the ester bond has 1 or more and 4 or less carbon atoms is 100 mass %. In other words, the structural units derived from the alkyl (meth)acrylate ester may be composed only of structural units derived from an alkyl (meth)acrylate ester in which the alkyl group bonded to the oxygen atom of the ester bond has 1 or more and 4 or less carbon atoms.

The structural unit derived from the alkyl (meth)acrylate may have a structural unit derived from an alkyl (meth)acrylate in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms.
In the case of having a structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms of the alkyl group bonded to the oxygen atom of the ester bond is 6 to 10, the preferred upper limit of the content of the structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms of the alkyl group bonded to the oxygen atom of the ester bond is 6 to 10 is 25% by mass. By having a content of the structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms of the alkyl group bonded to the oxygen atom of the ester bond is 6 to 10 or less by 25% by mass or less, the polarity of the acrylic copolymer becomes larger, and the interaction with the adherend becomes stronger, thereby improving the adhesive strength of the pressure-sensitive adhesive composition. In addition, the elastic modulus of the acrylic copolymer becomes larger, thereby improving the adhesive strength and holding power of the pressure-sensitive adhesive composition in a high-temperature environment. A more preferred upper limit of the content of structural units derived from (meth)acrylic acid alkyl esters in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms is 10 mass%, and it is even more preferred that the pressure-sensitive adhesive composition does not have structural units derived from (meth)acrylic acid alkyl esters in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms.

In the acrylic copolymer, the preferred lower limit of the content of the structural units derived from the (meth)acrylic acid alkyl ester is 50% by mass, and the preferred upper limit is 90% by mass. By having the content of the structural units derived from the (meth)acrylic acid alkyl ester within the above range, it is possible to more easily achieve both sufficient flexibility and cohesive strength for the adhesive composition to exert adhesive strength. A more preferred lower limit of the content of the structural units derived from the (meth)acrylic acid alkyl ester is 60% by mass, an even more preferred lower limit is 65% by mass, a more preferred upper limit is 80% by mass, and an even more preferred upper limit is 75% by mass.

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

Examples of the olefin polymer having a polymerizable unsaturated double bond at one end include ethylene-butylene copolymers, ethylene-propylene copolymers, ethylene polymers, propylene polymers, butylene polymers, and the like, each of which has a group having a polymerizable unsaturated double bond at one end or both ends.
These olefin polymers having a polymerizable unsaturated double bond at the terminal may be used alone or in combination of two or more kinds.

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

Examples of the olefin polymer having a (meth)acryloyl group at its terminal include an ethylene macromonomer having a (meth)acryloyl group at one terminal, a propylene macromonomer having a (meth)acryloyl group at one terminal, an ethylene-butylene macromonomer having a (meth)acryloyl group at one terminal, an ethylene-propylene macromonomer having a (meth)acryloyl group at one terminal, etc. Among these, an ethylene-butylene macromonomer having a (meth)acryloyl group at one terminal and an ethylene-propylene macromonomer having a (meth)acryloyl group at one terminal are preferred, since they make it easier to satisfy the glass transition temperature described below and further improve the adhesive strength of the pressure-sensitive adhesive composition.
In this specification, the term "macromonomer" refers to a monomer having a polymerizable functional group and a weight average molecular weight of about 1,000 to 100,000.

In the acrylic copolymer, the preferred lower limit of the content of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal is 5% by mass, and the preferred upper limit is 30% by mass. When the content of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal is 5% by mass or more, the acrylic copolymer forms an appropriate number of pseudo crosslinks, and the adhesive strength and holding power of the pressure-sensitive adhesive composition are further improved. When the content of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal is 30% by mass or less, the cohesive failure of the pressure-sensitive adhesive composition can be further suppressed. The more preferred lower limit of the content of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal is 8% by mass, and even more preferred lower limit is 10% by mass, and even more preferred upper limit is 27% by mass, and even more preferred upper limit is 25% by mass.

The acrylic copolymer has a structural unit derived from a polar functional group-containing monomer.
The acrylic copolymer has a structural unit derived from the polar functional group-containing monomer, and therefore the interaction with the adherend is enhanced, and the adhesive strength and holding power of the adhesive composition are improved. In addition, when the adhesive composition contains a crosslinking agent described below, the acrylic copolymer has a structure crosslinked via the crosslinking agent, and therefore the adhesive strength and holding power of the adhesive composition are improved. By adjusting the degree of crosslinking at this time, the gel fraction of the adhesive layer described below can be adjusted to an appropriate range.

Examples of the constituent units derived from the polar functional group-containing monomer include constituent units derived from carboxy group-containing monomers, constituent units derived from hydroxyl group-containing monomers, constituent units derived from amide group-containing monomers, and constituent units derived from amino group-containing monomers. Among these, from the viewpoint of further improving the adhesive strength and holding power of the pressure-sensitive adhesive composition, it is preferable that the constituent units derived from the polar functional group-containing monomers include at least one constituent unit selected from the group consisting of constituent units derived from carboxy group-containing monomers and constituent units derived from hydroxyl group-containing monomers.
The structural unit derived from these polar functional group-containing monomers may be contained alone or in combination of two or more kinds.

The acrylic copolymer has a structural unit derived from the carboxy group-containing monomer, which enhances the interaction with the adherend, thereby further improving the adhesive strength and holding power of the pressure-sensitive adhesive composition.
Examples of the carboxy group-containing monomer include unsaturated carboxylic acids such as (meth)acrylic acid, (meth)acryloylacetic acid, (meth)acryloylpropionic acid, (meth)acryloylbutyric acid, (meth)acryloylpentanoic acid, crotonic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid.

When the acrylic copolymer has a constituent unit derived from the hydroxyl group-containing monomer, crosslinking of the acrylic copolymer via a crosslinking agent occurs more easily, and the adhesive strength and holding strength of the pressure-sensitive adhesive composition are further improved.
Examples of the hydroxyl group-containing monomer include 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate.

In the acrylic copolymer, the preferred lower limit of the content of the structural unit derived from the hydroxyl group-containing monomer is 0.01% by mass, and the preferred upper limit is 2% by mass. When the content of the structural unit derived from the hydroxyl group-containing monomer is 0.01% by mass or more, crosslinking of the acrylic copolymer via the crosslinking agent occurs more easily, and the adhesive strength and holding power of the pressure-sensitive adhesive composition are further improved. When the content of the structural unit derived from the hydroxyl group-containing monomer is 2% by mass or less, the acrylic copolymer does not become too hard, and the adhesive strength of the pressure-sensitive adhesive composition is further improved. The more preferred lower limit of the content of the structural unit derived from the hydroxyl group-containing monomer is 0.05% by mass, and the more preferred upper limit is 1% by mass.

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

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

In the acrylic copolymer, the preferred lower limit of the total content of the constituent units derived from the polar functional group-containing monomer is 0.1% by mass, and the preferred upper limit is 10% by mass. When the total content of the constituent units derived from the polar functional group-containing monomer is 0.1% by mass or more, the interaction between the acrylic copolymer and the adherend is enhanced, and the adhesive strength and holding power of the pressure-sensitive adhesive composition are further improved. In addition, when the pressure-sensitive adhesive composition contains a crosslinking agent, crosslinking of the acrylic copolymer via the crosslinking agent occurs more easily, and the adhesive strength and holding power of the pressure-sensitive adhesive composition are further improved. When the total content of the constituent units derived from the polar functional group-containing monomer is 10% by mass or less, the acrylic copolymer does not become too hard, and the adhesive strength of the pressure-sensitive adhesive composition is further improved. A more preferred lower limit of the total content of the constituent units derived from the polar functional group-containing monomer is 1% by mass, an even more preferred lower limit is 3% by mass, and a more preferred upper limit is 8% by mass, and an even more preferred upper limit is 6% by mass.

The glass transition temperature (Tg) of the acrylic copolymer is preferably in the range of -100°C or more and 200°C or less, and more preferably -20°C or less. When the glass transition temperature of the acrylic copolymer is -20°C or less, the molecules of the acrylic copolymer are more easily stretched, and the adhesive strength of the pressure-sensitive adhesive composition is further improved. A more preferable upper limit of the glass transition temperature of the acrylic copolymer is -30°C, and a particularly preferable upper limit is -35°C. In addition, when the pressure-sensitive adhesive composition contains a plurality of the acrylic copolymers, it is preferable that the glass transition temperatures of all the acrylic copolymers contained in the pressure-sensitive adhesive composition are -20°C or less.
The glass transition temperature of the acrylic copolymer can be measured by differential scanning calorimetry. More specifically, the glass transition temperature of the acrylic copolymer can be measured by a method conforming to JIS K6240:2011 using a differential scanning calorimeter (manufactured by Seiko Instruments Inc., "220C" or the like) under a nitrogen atmosphere (nitrogen flow, flow rate 50 mL/min) at a measurement temperature of -100°C to 200°C and a temperature rise rate of 10°C/min.

The glass transition temperature of the acrylic copolymer can be adjusted by the type and amount of monomers that are the raw materials for the acrylic copolymer.

The preferred lower limit of the weight average molecular weight (Mw) of the acrylic copolymer is 500,000, and the preferred upper limit is 2,000,000. When the weight average molecular weight of the acrylic copolymer is 500,000 or more, the bulk cohesive strength of the pressure-sensitive adhesive composition is increased, and the adhesive strength and heat resistance of the pressure-sensitive adhesive composition are further improved. When the weight average molecular weight of the acrylic copolymer is 2,000,000 or less, the pressure-sensitive adhesive composition does not become too hard, and the adhesive strength is further improved. The more preferred lower limit of the weight average molecular weight of the acrylic copolymer is 650,000, and the more preferred upper limit is 1,500,000.

The polydispersity of the acrylic copolymer is preferably 1.0 at its lower limit and 6.0 at its upper limit. The polydispersity of the acrylic copolymer within the above range further improves the adhesive strength and holding power of the pressure-sensitive adhesive composition. The polydispersity of the acrylic copolymer is more preferably 1.5 at its lower limit and 4.5 at its upper limit.
The polydispersity refers to the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn).

In this specification, the weight average molecular weight, the number average molecular weight, and the polydispersity can be determined from the molecular weight distribution in terms of polystyrene measured using gel permeation chromatography (GPC). Specifically, for example, they can be determined by measuring under the following conditions using gel permeation chromatography (Waters Corporation, "2690 Separations Module", etc.).
Solvent: Tetrahydrofuran Sample flow rate: 1 mL/min
Detector: Differential refractometer RI
Column: GPC KF-806L (Showa Denko)
Column temperature (measurement temperature): 40°C
Injection volume: 20 μL

The content of the acrylic copolymer in the pressure-sensitive adhesive composition is not particularly limited, but it is preferably greater than 50% by mass in the pressure-sensitive adhesive composition (i.e., it is the main component in the pressure-sensitive adhesive composition). By having the content of the acrylic copolymer greater than 50%, the adhesive strength and holding power of the pressure-sensitive adhesive composition are more likely to be improved.

The pressure-sensitive adhesive composition of the present invention contains a tackifier resin T1 which is a terpene-based resin and has a softening point of more than 120°C and not more than 180°C, and a tackifier resin T2 which is at least one type selected from the group consisting of petroleum-based resins, rosin-based resins, and xylene-based resins and has a softening point of more than 120°C and not more than 180°C.
The tackifier resin T1 has good compatibility with the acrylic copolymer and is therefore easily incorporated into the acrylic copolymer, which can prevent the tackifier resin from inhibiting the formation of pseudo-crosslinks due to the interaction of the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond, thereby improving the adhesive strength of the pressure-sensitive adhesive composition while maintaining the excellent adhesive strength of the acrylic copolymer.
Furthermore, by containing the tackifier resin T2 in the pressure-sensitive adhesive composition, the adhesive strength of the pressure-sensitive adhesive composition to polyolefin is improved.

The softening points of the tackifier resin T1 and the tackifier resin T2 are greater than 120°C and less than or equal to 180°C.
When the softening points of the tackifier resin T1 and the tackifier resin T2 are greater than 120°C, the tackifier resins have excellent heat resistance and improved creep resistance at high temperatures, thereby improving the high-temperature adhesion of the pressure-sensitive adhesive composition. When the softening points of the tackifier resin T1 and the tackifier resin T2 are less than 180°C, the pressure-sensitive adhesive layer does not become too hard, improving the adhesive strength of the pressure-sensitive adhesive composition. The lower limit of the softening points of the tackifier resin T1 and the tackifier resin T2 is preferably 130°C, more preferably 140°C, and the upper limit is preferably 170°C, more preferably 160°C.
In this specification, the softening point of the tackifier resin can be measured by the ring and ball method of JIS K2207.

The terpene resin is a resin obtained by polymerizing a terpene compound.
Examples of the terpene compounds include α-pinene, β-pinene, limonene, dipentene, δ-3-carene, dimethyloctatriene, alloocimene, myrcene, ocimene, linalool, and cosmene.
In addition, the terpene resin may contain other compounds polymerized therein. Among them, the terpene phenol resin obtained by polymerizing the terpene compound and the phenol compound and the hydrogenated terpene phenol resin thereof are preferred. By including the tackifier resin T1 in the terpene phenol resin, the interaction between the pressure-sensitive adhesive composition and the adherend is enhanced, and the adhesive strength of the pressure-sensitive adhesive composition is improved.
Examples of the phenol compound include phenol, cresol, xylenol, propylphenol, norylphenol, methoxyphenol, bromophenol, bisphenol A, bisphenol F, bisphenol S, dihydroxynaphthalene, resorcinol, pyrocatechol, hydroquinone, pyrogallol, 1,2,4-trihydroxybenzene, and phloroglucinol.
The terpene compounds, other compounds, and phenol compounds may each be used alone or in combination of two or more kinds.

Commercially available examples of the above terpene resins with a softening point greater than 120°C and less than or equal to 180°C include YS Resin PX1250 and YS Polystar G150 (both manufactured by Yasuhara Chemical Co., Ltd.).

For 100 parts by mass of the acrylic copolymer, the lower limit of the content of the tackifier resin T1 is 5 parts by mass, and the upper limit is 20 parts by mass. When the content of the tackifier resin T1 is 5 parts by mass or more, the adhesive strength of the adhesive composition is improved. When the content of the tackifier resin T1 is 20 parts by mass or less, the adhesive composition does not become too hard, and the adhesive strength of the adhesive composition is improved. The preferred lower limit of the content of the tackifier resin T1 is 8 parts by mass, more preferably 10 parts by mass, and the preferred upper limit is 17 parts by mass, more preferably 15 parts by mass.

The above-mentioned petroleum resins include, for example, aliphatic petroleum resins, alicyclic petroleum resins, aromatic petroleum resins, and aliphatic saturated hydrocarbon resins and alicyclic saturated hydrocarbon resins obtained by hydrogenating these petroleum resins. Among these, aliphatic saturated hydrocarbon resins and alicyclic saturated hydrocarbon resins obtained by hydrogenating petroleum resins are preferred from the viewpoint of improving the adhesive strength to polyolefins.

Among the above petroleum-based resins with a softening point of more than 120°C and not more than 180°C, commercially available examples include Alcon P-140 (manufactured by Arakawa Chemical Industries Co., Ltd.).

The preferred lower limit of the content of the petroleum-based resin relative to 100 parts by mass of the acrylic copolymer is 15 parts by mass, and the preferred upper limit is 25 parts by mass. When the content of the petroleum-based resin is 15 parts by mass or more, the adhesive strength of the pressure-sensitive adhesive composition to polyolefin is further improved. When the content of the petroleum-based resin is 25 parts by mass or less, the inhibition of pseudo-crosslinking in the acrylic copolymer can be further suppressed, and the adhesive strength of the pressure-sensitive adhesive composition is further improved.

The rosin-based resin is a rosin resin containing a resin acid (for example, abietic acid) as a main component, and a resin that is a derivative of the rosin resin.
Examples of the resin derivative of the rosin resin include disproportionated rosin resin, hydrogenated rosin resin, dimer of resin acid (polymerized rosin resin), and rosin ester resin. The rosin ester resin is obtained by esterifying the rosin resin with alcohol, and examples of the resin include rosin ester, disproportionated rosin ester, hydrogenated rosin ester, and polymerized rosin ester.
Examples of the alcohol include polyhydric alcohols such as ethylene glycol, glycerin, pentaerythritol, etc. In addition, a portion of the hydroxyl groups of the alcohol used in the esterification is not used in the esterification and is contained in the resin, thereby adjusting the hydroxyl value to the above-mentioned range.
In addition, a resin obtained by esterifying a rosin resin is a rosin ester resin, a resin obtained by esterifying a disproportionated rosin resin is a disproportionated rosin ester resin, a resin obtained by esterifying a hydrogenated rosin resin is a hydrogenated rosin ester resin, and a resin obtained by esterifying a polymerized rosin resin is a polymerized rosin ester resin.

Among the above rosin-based resins with a softening point of more than 120°C and not more than 180°C, a commercially available example is Pencel D-160 (manufactured by Arakawa Chemical Industries, Ltd.).

The preferred lower limit of the content of the rosin-based resin relative to 100 parts by mass of the acrylic copolymer is 15 parts by mass, and the preferred upper limit is 25 parts by mass. When the content of the rosin-based resin is 15 parts by mass or more, the adhesive strength of the pressure-sensitive adhesive composition to polyolefin is further improved. When the content of the rosin-based resin is 25 parts by mass or less, the pressure-sensitive adhesive composition does not become too hard, and the adhesive strength of the pressure-sensitive adhesive composition is further improved. The more preferred lower limit of the content of the rosin-based resin is 10 parts by mass, and the more preferred upper limit is 20 parts by mass.

The tackifier resin T2 preferably contains the petroleum-based resin and the rosin-based resin. The petroleum-based resin can greatly improve the adhesive strength of the pressure-sensitive adhesive composition to polyolefin, but is likely to inhibit pseudo-crosslinking by the structural unit derived from the olefin-based polymer having a polymerizable unsaturated double bond at the terminal in the acrylic copolymer, and is likely to reduce the adhesive strength of the pressure-sensitive adhesive composition.
Although the rosin-based resin provides a relatively small improvement in the adhesive strength of the pressure-sensitive adhesive composition to polyolefins, it can suppress the inhibition of pseudo-crosslinking caused by the structural units in the acrylic copolymer derived from the olefin-based polymer having a polymerizable unsaturated double bond at the terminal thereof, and therefore can maintain the adhesive strength of the pressure-sensitive adhesive composition.
Therefore, when the tackifier resin T2 contains the petroleum-based resin and the rosin-based resin, the adhesive composition can further improve the adhesive strength to polyolefin while maintaining sufficient adhesive power.

The xylene-based resin is a resin obtained by reacting and polymerizing m-xylene with formaldehyde in the presence of an acid catalyst.
In addition, other compounds may be polymerized in the xylene resin, and examples of the other compounds include phenolic compounds. Among them, it is preferable that a phenolic compound is polymerized. By polymerizing the phenolic compound in the xylene resin, the polarity of the tackifier resin T2 becomes larger, and the compatibility with the acrylic copolymer becomes better, so that the adhesive strength of the pressure-sensitive adhesive composition is further improved. As the phenolic compound polymerized in the xylene resin, the same phenolic compound as that polymerized in the terpene phenolic resin can be used.
The other compounds may be used alone or in combination of two or more kinds.

The xylene-based resin having a softening point of more than 120°C and not more than 180°C may be a commercially available product, such as GHP-150 (manufactured by Fudow Co., Ltd.).

For 100 parts by mass of the acrylic copolymer, the lower limit of the content of the tackifier resin T2 is 10 parts by mass, and the upper limit is 50 parts by mass. When the content of the tackifier resin T2 is 10 parts by mass or more, the adhesive strength of the pressure-sensitive adhesive composition to polyolefin is improved. When the content of the tackifier resin T2 is 50 parts by mass or less, the pressure-sensitive adhesive composition does not become too hard, and the adhesive force is improved. The preferred lower limit of the content of the tackifier resin T2 is 15 parts by mass, more preferably 20 parts by mass, and the preferred upper limit is 40 parts by mass, more preferably 30 parts by mass.

The pressure-sensitive adhesive composition may contain a tackifier resin different from the tackifier resin T1 and the tackifier resin T2.

The preferred upper limit of the content of the tackifier resin having a softening point of 120°C or less is 5 parts by mass relative to 100 parts by mass of the acrylic copolymer. By making the content of the tackifier resin having a softening point of 120°C or less 5 parts by mass or less, the high temperature adhesion of the pressure-sensitive adhesive composition is further improved. The more preferred upper limit of the content of the tackifier resin having a softening point of 120°C or less is 1 part by mass, and it is most preferred that the pressure-sensitive adhesive composition does not contain a tackifier resin having a softening point of 120°C or less.

The pressure-sensitive adhesive composition preferably contains a crosslinking agent. When the pressure-sensitive adhesive composition contains a crosslinking agent, the acrylic copolymer has a structure crosslinked via the crosslinking agent, and the adhesive strength and holding power of the pressure-sensitive adhesive composition are further improved. By adjusting the degree of crosslinking at this time, the gel fraction of the pressure-sensitive adhesive layer, which will be described later, can be adjusted to an appropriate range.

Examples of the crosslinking agent include epoxy-based crosslinking agents and isocyanate-based crosslinking agents. Among these, isocyanate-based crosslinking agents are preferred because they make it easier to adjust the gel fraction of the adhesive layer (described below) within an appropriate range, and further improve the adhesive strength and holding power of the adhesive tape having the adhesive layer.

The preferred lower limit of the content of the crosslinking agent is 0.1 parts by mass, and the preferred upper limit is 5 parts by mass, relative to 100 parts by mass of the acrylic copolymer. By having the content of the crosslinking agent within the above range, it becomes easier to adjust the gel fraction of the adhesive layer described below within an appropriate range, and the adhesive strength and holding power of the adhesive tape having the adhesive layer are further improved. A more preferred lower limit of the content of the crosslinking agent is 0.5 parts by mass, and a more preferred upper limit is 3 parts by mass.

The above-mentioned adhesive composition may contain conventionally known fine particles and additives, such as inorganic fine particles, conductive fine particles, antioxidants, foaming agents, organic fillers, and inorganic fillers, as necessary.

The present invention also includes a pressure-sensitive adhesive tape having a substrate layer and a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition of the present invention.
The pressure-sensitive adhesive tape of the present invention has a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition, and thus can achieve both high-temperature adhesiveness and adhesive strength to polyolefins.

The preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 10% by mass, and the preferred upper limit is 70% by mass. When the gel fraction of the pressure-sensitive adhesive layer is 10% by mass or more, the bulk cohesive strength of the pressure-sensitive adhesive layer is increased, and the heat resistance and holding power of the pressure-sensitive adhesive tape are further improved. When the gel fraction of the pressure-sensitive adhesive layer is 70% by mass or less, the pressure-sensitive adhesive layer becomes more easily stretched, and the adhesive strength of the pressure-sensitive adhesive tape is further improved. The more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 20% by mass, and even more preferred lower limit is 30% by mass, and the more preferred upper limit is 60% by mass, and even more preferred upper limit is 50% by mass, and even more preferred upper limit is 40% by mass.
The gel fraction of the pressure-sensitive adhesive layer can be measured by the following method.
That is, the pressure-sensitive adhesive layer W ₀ (g) is collected, immersed in 50 mL of ethyl acetate, and shaken with a shaker at 23° C. and 200 rpm for 24 hours. After shaking, the pressure-sensitive adhesive layer that has absorbed and swollen with ethyl acetate is filtered using a metal mesh (opening #200 mesh, mass: W ₁ (g)). The separated pressure-sensitive adhesive layer is dried at 110° C. for 1 hour, and then the mass W ₂ (g) of the pressure-sensitive adhesive layer including the metal mesh is measured. Then, the gel fraction can be measured by a method of calculating the gel fraction from the following formula (1) using the obtained W ₀ , W ₁ , and W ₂ .
Gel fraction (mass%)=100×(W ₂ −W ₁ )/W ₀ (1)
(W ₀ : initial mass of adhesive layer, W ₁ : initial mass of metal mesh, W ₂ : mass of adhesive layer including metal mesh after drying)

The lower limit of the thickness of the pressure-sensitive adhesive layer is preferably 10 μm. When the thickness of the pressure-sensitive adhesive layer is 10 μm or more, the adhesive strength of the pressure-sensitive adhesive tape is further improved. The lower limit of the thickness of the pressure-sensitive adhesive layer is more preferably 30 μm, and even more preferably 50 μm.
There is no particular upper limit to the thickness of the pressure-sensitive adhesive layer, but from the viewpoint of ease of handling of the pressure-sensitive adhesive tape, the upper limit is about 500 μm.

The adhesive tape of the present invention may be a single-sided adhesive tape having the above-mentioned adhesive layer on one side of the above-mentioned base layer, or a double-sided adhesive tape having the above-mentioned adhesive layers on both sides of the above-mentioned base layer.

The substrate used for the substrate layer includes, for example, a sheet made of a resin such as acrylic, olefin, polycarbonate, vinyl chloride, ABS, polyethylene terephthalate (PET), nylon, urethane, polyimide, etc., a sheet having a mesh-like structure, a sheet with holes, a sheet having a foam structure, etc., and from the viewpoint of being more suitable for use in vehicle parts, etc., a sheet having a foam structure is preferred. In other words, from the viewpoint of being more suitable for use in vehicle parts, etc., the substrate layer preferably has a foam structure.

The preferred lower limit of the thickness of the substrate layer is 10 μm, and the preferred upper limit is 2000 μm. When the thickness of the substrate layer is 10 μm or more, the adhesive tape has appropriate stiffness and excellent handleability. When the thickness of the substrate layer is 2000 μm or less, zipping when peeling the adhesive tape from the adherend is easily prevented, and the adhesive strength is further improved. The more preferred lower limit of the thickness of the substrate layer is 50 μm, and the more preferred upper limit is 1000 μm.

The above adhesive tape may further have other layers as long as the effects of the present invention are not impaired.

The method for producing the adhesive tape is not particularly limited, and a conventionally known method can be used. For example, first, the (meth)acrylic acid alkyl ester, the polar functional group-containing monomer, the olefin-based polymer having a polymerizable unsaturated double bond at the end, and other monomers as necessary are copolymerized in a conventional manner to obtain the acrylic copolymer. Next, a solution containing an adhesive composition containing tackifier resin T1, tackifier resin T2, and other additives as necessary is applied to a film that has been subjected to a release treatment, and dried to produce a laminated sheet having an adhesive layer. Then, the laminated sheet produced by the above-mentioned method and a substrate are bonded together to produce an adhesive tape having a substrate layer and an adhesive layer containing the adhesive composition of the present invention.

The preferred upper limit of the thickness of the entire pressure-sensitive adhesive tape is 650 μm. By making the thickness of the entire pressure-sensitive adhesive tape 650 μm or less, it becomes easier to prevent zipping when peeling the pressure-sensitive adhesive tape from the adherend, and the adhesive strength is further improved. The more preferred upper limit of the thickness of the entire pressure-sensitive adhesive tape is 600 μm, and the even more preferred upper limit is 550 μm.
The preferred lower limit of the thickness of the entire pressure-sensitive adhesive tape is 40 μm. By having a thickness of the entire pressure-sensitive adhesive tape of 40 μm or more, the pressure-sensitive adhesive tape can exhibit a sufficient peeling force. The more preferred lower limit of the thickness of the entire pressure-sensitive adhesive tape is 50 μm, and the even more preferred lower limit is 100 μm.

The adhesive tape has a structural unit derived from the (meth)acrylic acid alkyl ester in the adhesive composition, the structural unit having 1 or more and 4 or less carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond, and the content of the structural unit derived from the (meth)acrylic acid alkyl ester in the structural unit having 1 or more and 4 or less carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 75% by mass or more and 100% by mass or less, and does not have a structural unit derived from the (meth)acrylic acid alkyl ester in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms, or has a structural unit derived from the (meth)acrylic acid alkyl ester in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms. In the case where the structural unit is derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 6 to 10, the content of the structural unit derived from the (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 6 to 10 is 25% by mass or less, and the tackifier resin T2 in the pressure-sensitive adhesive composition contains the petroleum-based resin and the rosin-based resin, and the content of the petroleum-based resin is 15 parts by mass or more and 25 parts by mass or less and the content of the rosin-based resin is 10 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the acrylic copolymer, the gel fraction of the pressure-sensitive adhesive layer is 10% by mass or more and 40% by mass or less, and the thickness of the entire pressure-sensitive adhesive tape is preferably 650 μm or less. By having the above-mentioned characteristics of the pressure-sensitive adhesive tape, it is possible to achieve both excellent high-temperature adhesion and excellent adhesive strength to polyolefins.

The pressure-sensitive adhesive tape has a preferred lower limit of 180° peel adhesive strength to SUS at 80°C and a peel speed of 50 mm/min of 10 N/inch or more. When the pressure-sensitive adhesive tape has a 180° peel adhesive strength to SUS at 80°C and a peel speed of 50 mm/min of 10 N/inch or more, the pressure-sensitive adhesive tape has superior high-temperature adhesion. A more preferred lower limit of the 180° peel adhesive strength to SUS at 80°C and a peel speed of 50 mm/min is 15 N/inch.
Although there is no particular upper limit to the 180° peel adhesive strength against SUS at 80° C. and a peel speed of 50 mm/min, the practical limit is about 50 N/inch.
The 180° peel adhesive strength of the above-mentioned pressure-sensitive adhesive tape against SUS at 80° C. and a peel speed of 50 mm/min can be measured by the following method.
That is, the adhesive tape is cut into a flat rectangular shape of 25 mm wide x 75 mm long to prepare a test piece, and then the obtained test piece is laminated to a SUS plate (SUS304 plate washed with ethanol and then wiped dry) by moving a 2 kg rubber roller back and forth at a speed of 300 mm/min. Then, after heating at a temperature of 80°C for 30 minutes, a tensile test is performed using a tensile tester (manufactured by A&D Co., Ltd., "RTI-1310", etc.) under conditions of 80°C, peel speed of 50 mm/min, and peel angle of 180°, and the 180° peel adhesive strength can be measured by a method such as measuring the adhesive strength.

The pressure-sensitive adhesive tape has a preferred lower limit of 10 N/inch for 180° peel adhesion to polypropylene at 80°C and a peel speed of 50 mm/min. When the pressure-sensitive adhesive tape has a 180° peel adhesion to polypropylene of 10 N/inch or more at 80°C and a peel speed of 50 mm/min, the pressure-sensitive adhesive tape has better high-temperature adhesion and adhesive strength to polypropylene. A more preferred lower limit for the 180° peel adhesion to polypropylene at 80°C and a peel speed of 50 mm/min is 15 N/inch.
Although there is no particular upper limit to the 180° peel adhesive strength to polypropylene at 80° C. and a peel speed of 50 mm/min, the practical limit is approximately 50 N/inch.
The 180° peel adhesive strength of the above-mentioned pressure-sensitive adhesive tape against polypropylene at 80°C and a peel speed of 50 mm/min can be measured by, for example, using a polypropylene plate instead of the SUS plate in the measurement of the 180° peel adhesive strength of the above-mentioned pressure-sensitive adhesive tape against SUS at 80°C and a peel speed of 50 mm/min described above.

The uses of the adhesive tape of the present invention are not particularly limited, but since it combines excellent high-temperature adhesion with excellent adhesive strength to polyolefins, it can be suitably used for fixing vehicle parts, etc.

According to the present invention, it is possible to provide a pressure-sensitive adhesive composition that combines excellent high-temperature adhesion with excellent adhesive strength to polyolefins. Furthermore, according to the present invention, it is possible to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer that contains the pressure-sensitive adhesive composition.

FIG. 1 is a schematic diagram showing a method for a retention test.

The following examples further illustrate aspects of the present invention, but the present invention is not limited to these examples.

(Synthesis of Acrylic Copolymers A to D)
In a reactor equipped with a thermometer, a stirrer, and a cooling tube, 300 mL of ethyl acetate and the structural unit monomer shown in Table 1 were added, and the reactor was heated to start reflux. Next, 0.01 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane was added as a polymerization initiator into the reactor, and polymerization was started under reflux. Thereafter, 0.01 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane was added one hour and two hours after the start of polymerization, and further, 0.05 parts by mass of t-hexylperoxypivalate was added four hours after the start of polymerization to continue the polymerization reaction. Then, the polymerization reaction was carried out for a total of 8 hours from the start of polymerization to obtain an ethyl acetate solution containing acrylic copolymers A to D. The ethylene-butylene macromonomer shown in Table 1 is HPVM-L1253 (manufactured by Kraton Polymer Japan, weight average molecular weight 7000).
The molecular weight distribution of the obtained acrylic copolymer was measured in terms of polystyrene using gel permeation chromatography (GPC) (manufactured by Waters, "2690 Separations Module") under the following conditions. The weight average molecular weight (Mw), number average molecular weight (Mn), and polydispersity (Mw/Mn) of the acrylic copolymer were determined from the obtained molecular weight distribution curve.
<GPC Measurement Conditions>
Solvent: Tetrahydrofuran Sample flow rate: 1 mL/min
Detector: Differential refractometer RI
Column: GPC KF-806L (Showa Denko)
Column temperature (measurement temperature): 40°C
Injection volume: 20 μL

(Examples 1 to 25, Comparative Examples 1 to 8)
(1) Preparation of Pressure-Sensitive Adhesive Compositions To the ethyl acetate solutions containing the obtained acrylic copolymers A to D, materials were added in the compositions shown in Tables 2 to 4, and the mixture was stirred to obtain pressure-sensitive adhesive compositions.

(2) Preparation of Adhesive Tape A polyethylene terephthalate film with one side treated for release was prepared. The adhesive composition obtained in "(1) Preparation of Adhesive Composition" above was applied to the release-treated surface of this polyethylene terephthalate film so that the thickness after drying would be 40 μm, and dried at 110° C. for 5 minutes to prepare two laminated sheets having an adhesive layer with a thickness of 40 μm on the release-treated surface of the polyethylene terephthalate film.
Next, sheets of the types and thicknesses shown in Tables 2 to 4 were prepared as substrates. Two of the obtained laminate sheets were laminated, one on each side of the substrate, from the side of the pressure-sensitive adhesive layer, so that the pressure-sensitive adhesive layer was transferred to the substrate and integrated with the substrate, thereby obtaining a pressure-sensitive adhesive tape having a substrate layer and pressure-sensitive adhesive layers on both sides of the substrate layer.

(3) Gel fraction of adhesive layer The adhesive layer W ₀ (g) was collected from the obtained adhesive tape, and the collected adhesive layer was immersed in 50 mL of ethyl acetate and shaken for 24 hours at 23°C and 200 rpm using a shaker. After shaking, the adhesive layer that absorbed and swollen with ethyl acetate was filtered using a metal mesh (opening #200 mesh, mass: W ₁ (g)). The separated adhesive layer was dried for 1 hour under a condition of 110°C, and then the mass W ₂ (g) of the adhesive layer including the metal mesh was measured. Then, the gel fraction was calculated from the obtained W _0, W _1, and W ₂ according to the following formula (1).
Gel fraction (mass%)=100×(W ₂ −W ₁ )/W ₀ (1)
(W ₀ : initial mass of adhesive layer, W ₁ : initial mass of metal mesh, W ₂ : mass of adhesive layer including metal mesh after drying)

<Evaluation>
The adhesive tapes obtained in the Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 2 to 4.

(Room temperature adhesion)
The polyethylene terephthalate film on one side (the side not measured) of the obtained adhesive tape was peeled off, and the surface of the exposed adhesive layer was backed with a 23 μm thick polyethylene terephthalate film (manufactured by Futamura Chemical Co., Ltd., "FE2002"), and then cut into a width of 25 mm x length of 75 mm to prepare a test piece. The obtained test piece was attached to a SUS plate (SUS304 plate washed with ethanol and then wiped dry) by moving a 2 kg rubber roller back and forth at a speed of 300 mm/min to prepare a measurement sample. Next, the prepared measurement sample was left to stand for 20 minutes under an environment of a temperature of 23 ° C. and a relative humidity of 50%, and then a tensile test was performed in accordance with JIS Z0237 using a tensile tester (manufactured by A & D Co., Ltd., "RTI-1310") at 23 ° C., a peel speed of 50 mm/min, and a peel angle of 180 °, and the 180 ° peel adhesion was measured.
The room temperature adhesion of the pressure-sensitive adhesive tape to SUS was evaluated based on the following criteria: when the obtained 180° peel adhesive strength was 20 N/inch or more, it was marked "◎", when it was 15 N/inch or more and less than 20 N/inch, it was marked "◯", when it was 10 N/inch or more and less than 15 N/inch, it was marked "△", and when it was less than 10 N/inch, it was marked "X".
Also, a polypropylene plate was used instead of the SUS plate (a SUS304 plate washed with ethanol and then wiped dry), and the 180° peel adhesive strength against polypropylene was measured in the same manner to evaluate the room temperature adhesive strength of the adhesive tape against polypropylene.

(High temperature adhesion)
The polyethylene terephthalate film on one side (the side not measured) of the obtained adhesive tape was peeled off, and the surface of the exposed adhesive layer was backed with a 23 μm thick polyethylene terephthalate film (manufactured by Futamura Chemical Co., Ltd., "FE2002"), and then cut into a width of 25 mm x length of 75 mm to prepare a test piece. The obtained test piece was attached to a SUS plate (SUS304 plate washed with ethanol and then wiped dry) by moving a 2 kg rubber roller back and forth at a speed of 300 mm/min to prepare a measurement sample. Next, after heating at a temperature of 80°C for 30 minutes, a tensile test was performed using a tensile tester (manufactured by A&D Co., Ltd., "RTI-1310") under the conditions of 80°C, peel speed of 50 mm/min, and peel angle of 180°, and the 180° peel adhesion was measured.
The high temperature adhesion of the pressure-sensitive adhesive tape to SUS was evaluated based on the following criteria: when the obtained 180° peel adhesive strength was 15 N/inch or more, it was marked "◎", when it was 10 N/inch or more and less than 15 N/inch, it was marked "◯", when it was 8 N/inch or more and less than 10 N/inch, it was marked "△", and when it was less than 8 N/inch, it was marked "X".
Also, a polypropylene plate was used instead of the SUS plate (a SUS304 plate washed with ethanol and then wiped dry), and the 180° peel adhesive strength against polypropylene was measured in the same manner to evaluate the high temperature adhesive strength of the adhesive tape against polypropylene.

(Retention Power)
First, the obtained adhesive tape was cut into a width of 25 mm and a length of 60 mm according to JIS Z-1528 to prepare a test piece 1. The test piece 1 was attached to a SUS plate 2 (SUS304 plate washed with ethanol and then wiped dry) having a thickness of 2.0 mm, a width of 50 mm, and a length of 75 mm at 23 ° C., and the adhesive layer on one side of the adhesive tape was laminated by reciprocating a 2 kg rubber roller at a speed of 300 mm / min so that the adhesive area was 25 mm x 25 mm, to prepare a measurement sample. The measurement sample was left to stand at 23 ° C. and a relative humidity of 50%, and then a 1 kg weight 3 was attached to the measurement sample in an environment of 85 ° C. so that a load was applied to the measurement sample in the shear direction. The presence or absence of the test piece 1 falling 24 hours after the load was applied by the weight 3 was measured.
The holding power of the adhesive tape was evaluated by rating it as "◯" when the test piece 1 did not fall and "×" when it did fall.
Even when the evaluation result is "x", the pressure-sensitive adhesive composition of the present invention can achieve both excellent high-temperature adhesion and excellent adhesive strength to polyolefins, and therefore can be used without problems depending on the application.

The substrates used as the substrate layers in Tables 2 to 4 are as follows.
PET sheet (polyethylene terephthalate sheet): manufactured by Toyo Cross Co., Ltd., thickness 23 μm
PE foam (polyethylene foam) (F1): Volara H#07005 (manufactured by Sekisui Chemical Co., Ltd., thickness 500 μm)
PE foam (F2): Volara IF #08008 (manufactured by Sekisui Chemical Co., Ltd., thickness 800 μm)

According to the present invention, it is possible to provide a pressure-sensitive adhesive composition that combines excellent high-temperature adhesion with excellent adhesive strength to polyolefins. Furthermore, according to the present invention, it is possible to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer that contains the pressure-sensitive adhesive composition.

1 Test piece 2 SUS plate 3 1 kg weight

Claims (11)

an acrylic copolymer having a structural unit derived from an alkyl (meth)acrylate ester, a structural unit derived from a polar functional group-containing monomer, and a structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond;
A tackifier resin T1 which is a terpene resin and has a softening point of more than 120° C. and not more than 180° C.; and
The present invention comprises a tackifier resin T2, which is at least one selected from the group consisting of a petroleum-based resin, a rosin-based resin, and a xylene-based resin and has a softening point of more than 120° C. and not more than 180° C.;
The content of the tackifier resin T1 is 5 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the acrylic copolymer,
A pressure-sensitive adhesive composition, characterized in that the content of the tackifier resin T2 is 10 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the acrylic copolymer. The adhesive composition according to claim 1, wherein the content of the tackifier resin having a softening point of 120°C or less is 5 parts by mass or less per 100 parts by mass of the acrylic copolymer. The adhesive composition according to claim 1 or 2, wherein the tackifier resin T1 contains a terpene phenol resin. The adhesive composition according to claim 1 or 2, wherein the tackifier resin T2 contains the petroleum-based resin and the rosin-based resin. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the content of the petroleum-based resin is 15 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the acrylic copolymer. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the content of the rosin-based resin is 15 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the acrylic copolymer. The structural unit derived from the (meth)acrylic acid alkyl ester has a structural unit derived from the (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group bonded to the oxygen atom of the ester bond is 1 or more and 4 or less, and the content of the structural unit derived from the (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group bonded to the oxygen atom of the ester bond is 1 or more and 4 or less is 75 mass % or more and 100 mass % or less, and
3. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the pressure-sensitive adhesive composition does not have any structural units derived from an alkyl (meth)acrylate in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms, or has structural units derived from an alkyl (meth)acrylate in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms and has structural units derived from an alkyl (meth)acrylate in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms, the content of the structural units derived from an alkyl (meth)acrylate in which the alkyl group bonded to the oxygen atom of the ester bond has 6 or more and 10 or less carbon atoms is 25 mass% or less. An adhesive tape having a substrate layer and an adhesive layer containing the adhesive composition according to claim 1 or 2. The adhesive tape according to claim 8, wherein the gel fraction of the adhesive layer is 10% by mass or more and 70% by mass or less. The adhesive tape according to claim 8, wherein the base layer has a foamed structure. In the pressure-sensitive adhesive composition, the structural units derived from an alkyl (meth)acrylate have a structural unit derived from an alkyl (meth)acrylate in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 or more and 4 or less, and the content of the structural units derived from an alkyl (meth)acrylate in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 or more and 4 or less is 75% by mass or more and 100% by mass or less, and
When the composition does not have a structural unit derived from an alkyl (meth)acrylate in which the number of carbon atoms bonded to the oxygen atom of the ester bond is 6 or more and 10 or less, or has a structural unit derived from an alkyl (meth)acrylate in which the number of carbon atoms bonded to the oxygen atom of the ester bond is 6 or more and 10 or less, and has a structural unit derived from an alkyl (meth)acrylate in which the number of carbon atoms bonded to the oxygen atom of the ester bond is 6 or more and 10 or less, the content of the structural unit derived from an alkyl (meth)acrylate in which the number of carbon atoms bonded to the oxygen atom of the ester bond is 6 or more and 10 or less is 25 mass% or less,
In the pressure-sensitive adhesive composition, the tackifier resin T2 contains the petroleum-based resin and the rosin-based resin,
the content of the petroleum-based resin is 15 parts by mass or more and 25 parts by mass or less, and the content of the rosin-based resin is 10 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the acrylic copolymer;
The gel fraction of the pressure-sensitive adhesive layer is 10% by mass or more and 40% by mass or less,
9. The adhesive tape according to claim 8, wherein the adhesive tape has an overall thickness of 650 μm or less.

Images