JP7377997B1 - Adhesive composition and adhesive sheet or tape - Google Patents

Abstract

An object of the present invention is to provide an acrylic-rubber mixed adhesive that has excellent high-temperature and low-temperature properties and can adhere to polyolefin materials, which are difficult to adhere to. SOLUTION: This is an adhesive composition containing a (meth)acrylic copolymer, natural rubber, a tackifying resin, and a chlorinated polyolefin. [Selection diagram] None

Description

The present invention relates to an adhesive composition and an adhesive sheet or tape.

Plastic materials (particularly polyolefin materials containing polyolefins such as polypropylene and polyethylene) are adherends that are less adhesive than metal materials. Here, a method has been proposed in which a tackifying resin is added as an acrylic pressure-sensitive adhesive capable of adhering to polyolefin materials that are difficult to adhere to (for example, Patent Document 1).

Patent No. 6850182

An object of the present invention is to provide an acrylic pressure-sensitive adhesive containing a (meth)acrylic copolymer that has excellent high-temperature properties and low-temperature properties and can adhere to polyolefin materials that are difficult to adhere to.

The present inventors have discovered that by further blending a chlorinated polyolefin into an adhesive composition containing a (meth)acrylic copolymer, rubber, and a tackifying resin, and selecting natural rubber as the rubber, The present invention has been completed by discovering that the above problems can be solved. Specifically, the details are as follows.
The present invention (1) is a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer and a tackifier resin, which further contains a chlorinated polyolefin and natural rubber.
The present invention (2) is the pressure-sensitive adhesive composition according to the invention (1), wherein the pressure-sensitive adhesive composition is irradiated with energy rays.
The present invention (3) is an adhesive sheet having an adhesive layer formed from the adhesive composition of the invention (1) or (2).

According to the present invention, it is possible to provide an acrylic pressure-sensitive adhesive that has excellent high-temperature properties and low-temperature properties and is capable of adhering to polyolefin materials that are difficult to adhere to.

The pressure-sensitive adhesive composition according to the present embodiment is an acrylic rubber made by blending a (meth)acrylic copolymer (A), natural rubber (B), a tackifier resin (C), and a chlorinated polyolefin (D). It is a mixed adhesive composition. The adhesive composition will be described in detail below. The adhesive composition (components, composition, physical properties), the method for producing the adhesive composition, and its uses will be described in detail below.

≪Adhesive composition≫
<Ingredients>
{(meth)acrylic copolymer (A)}
(monomer component)
The (meth)acrylic polymer can be obtained by polymerizing a monomer composition containing a (meth)acrylic acid alkyl ester having an alkyl group of 2 to 18 carbon atoms as a main component. Here, the number of carbon atoms in the alkyl group in the (meth)acrylic acid alkyl ester is preferably 2 to 14, more preferably 4 to 12, in order to improve adhesiveness with the polyolefin material. be. The monomer composition may optionally contain a functional group-containing unsaturated monomer or an unsaturated monomer copolymerizable with a (meth)acrylic acid alkyl ester or a functional group-containing unsaturated monomer. You may do so. Further, the (meth)acrylic acid alkyl ester may be used alone or in combination of two or more.

Here, the (meth)acrylic acid alkyl ester is typically a compound represented by the following formula.

^Formula : _H2C = ^CR1COOR2

Here, in the formula, R ¹ is a hydrogen atom or a methyl group, and R ² is a linear or branched alkyl group having 1 to 18 carbon atoms. Specific examples of ^R2 include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, n-pentyl group, neopentyl group, and isoamyl group. , n-hexyl group, n-heptyl group, octyl group, 2-ethylhexyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group group, hexadecyl group, heptadecyl group, octadecyl group, etc.

Examples of the (meth)acrylic acid alkyl ester represented by the formula include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, and (meth)acrylate. Butyl, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, neopentyl (meth)acrylate, isoamyl (meth)acrylate, (meth)acrylate ) hexyl acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, (meth)acrylic acid Isononyl, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate , hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, dicyclo (meth)acrylate Examples include pentanyl, dicyclopentenyl (meth)acrylate, isobornyl (meth)acrylate, and 1-adamantyl (meth)acrylate. In addition, high Tg monomers having a Tg of 10 to 250°C, such as methyl methacrylate (Tg: 105°C), cyclohexyl acrylate (Tg: 15°C), cyclohexyl methacrylate (Tg: 66°C), acrylic acid 3, 3,5-trimethylcyclohexyl (Tg: 52°C), dicyclopentanyl methacrylate (Tg: 175°C), dicyclopentanyl acrylate (Tg: 120°C), dicyclopentenyl acrylate (Tg: 120°C) Isobornyl methacrylate (Tg: 173°C), isobornyl acrylate (Tg: 97°C), 1-adamantyl methacrylate (Tg: 250°C), 1-adamantyl acrylate (Tg: 153°C), etc. may be used.

Next, examples of the functional group-containing unsaturated monomer include carboxyl group-containing unsaturated monomers. Here, examples of the carboxyl group-containing unsaturated monomer include unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and cinnamic acid, monomethyl itaconate, and itaconic acid. unsaturated dicarboxylic acid monoesters such as acid monobutyl, 2-acryloyloxyethyl phthalic acid, unsaturated tricarboxylic acid monoesters such as 2-methacryloyloxyethyl trimellitic acid, 2-methacryloyloxyethyl pyromellitic acid, and carboxyethyl acrylate. (β-carboxyethyl acrylate, etc.), carboxyalkyl acrylates such as carboxypentyl acrylate, acrylic acid dimers, acrylic acid trimers, and unsaturated dicarboxylic anhydrides such as itaconic anhydride, maleic anhydride, fumaric anhydride, etc. It will be done. Furthermore, the functional group-containing unsaturated monomers include, for example, hydroxyl group-containing unsaturated monomers such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate, and (meth) Acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-methylol Unsaturated monomers containing amide groups such as (meth)acrylamide, N-methylolpropane (meth)acrylamide, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, (meth)acrylic Amino group-containing unsaturated monomers such as t-butylaminoethyl acid, glycidyl group-containing unsaturated monomers such as glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, and (meth)acrylonitrile. Cyano group-containing unsaturated monomers, maleimide group-containing monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, N-methylitaconimide, N-ethylitaconimide , N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide and other itaconimide group-containing monomers, and N-(meth)acryloyloxymethylene. Succinimide group-containing monomers such as succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyoctamethylene succinimide, N-vinylpyrrolidone, N-(1-methyl (vinyl)pyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, (meth ) Vinyl group-containing heterocyclic compounds such as acryloylmorpholine, styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, Unsaturated monomers containing sulfonic acid groups such as (meth)acryloyloxynaphthalenesulfonic acid, unsaturated monomers containing phosphoric acid groups such as 2-hydroxyethyl acryloyl phosphate, and functional compounds such as 2-methacryloyloxyethyl isocyanate. and other monomers such as N-vinylcarboxylic acid amide.

Next, examples of the unsaturated monomer include vinyl ester group-containing monomers such as vinyl acetate, aromatic unsaturated monomers such as styrene and vinyltoluene, cyclopentyl di(meth)acrylate, and isobornyl (meth)acrylate. (meth)acrylic acid alicyclic hydrocarbon ester monomers such as (meth)acrylic acid alicyclic hydrocarbon ester monomers, alkoxy group-containing unsaturated monomers such as (meth)acrylic acid methoxyethyl, (meth)acrylic acid ethoxyethyl, ethylene, propylene, isoprene, butadiene, isobutylene. olefinic monomers such as vinyl ethers, vinyl ether monomers such as vinyl ethers, halogen atom-containing unsaturated monomers such as vinyl chloride, and heterocyclic or halogen atom-containing monomers such as tetrahydrofurfuryl (meth)acrylate and fluorine (meth)acrylate. acrylic acid ester monomers and polyfunctional monomers {for example, (mono- or poly)ethylene glycol di(meth)acrylate such as ethylene glycol di(meth)acrylate, and (mono- or poly)ethylene glycol di(meth)acrylate such as propylene glycol di(meth)acrylate. Examples include poly)alkylene glycol di(meth)acrylate and polyhydric alcohol (meth)acrylic acid ester divinylbenzene.

(monomer composition)
Next, preferred amounts of each monomer component in the monomer composition will be explained. First, the blending ratio of the (meth)acrylic acid alkyl ester is preferably 60 to 99.5 parts by mass, and 70 to 99 parts by mass, based on 100 parts by mass of the total amount of the monomer composition. is more suitable. Further, the blending ratio of the functional group-containing unsaturated monomer is preferably 0.5 to 20 parts by weight, and 1 to 10 parts by weight, based on 100 parts by weight of the total amount of the monomer composition. It is preferable that When the amount of the functional group-containing unsaturated monomer is within this range, the cohesive force, high temperature properties, initial tack, and low temperature properties are further improved.

(Weight average molecular weight)
The weight average molecular weight Mw of the (meth)acrylic polymer is preferably 200,000 to 1,500,000, more preferably 300,000 to 1,200,000 in terms of standard polystyrene determined by gel permeation chromatography (GPC). , more preferably from 650,000 to 1,000,000. When the molecular weight is within this range, the cohesive force and high temperature properties are further improved, and the manufacturing process becomes easier.

(process)
The (meth)acrylic copolymer can be produced by copolymerizing the above-mentioned monomer composition. For example, the monomer composition described above is subjected to a radical reaction in the presence of a polymerization initiator. Here, the method for polymerizing the monomer composition described above is a conventionally known method, such as solution polymerization method (boiling point polymerization method or constant temperature polymerization method), emulsion polymerization method, suspension polymerization method, bulk polymerization method, etc. It is. Here, the polymerization initiator is not particularly limited, and examples thereof include organic peroxides, azo compounds, and the like. Examples of the organic peroxides include dilauroyl peroxide, dibenzoyl peroxide, 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-Butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2 -ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compound include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. The polymerization initiators may be used alone or in combination of two or more.

{Natural rubber (B)}
The natural rubber preferably has a weight average molecular weight (weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC)) of 100,000 to 700,000, and one that has a weight average molecular weight of 250,000 to 700,000. It is more preferable, and even more preferable is one in the range of 300,000 to 650,000. It is preferable that the weight average molecular weight is within this range because cohesive force, high temperature properties, and compatibility with the acrylic copolymer are better. The natural rubber can be produced by, for example, physically or chemically cutting ordinary natural rubber by a known method.

{Tackifying resin (C)}
The tackifier resin is not particularly limited, and examples include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic/aromatic copolymers, and alicyclic copolymers. , coumaron-indene resin, terpene resin, aromatic modified terpene resin, terpene phenol resin, rosin resin such as disproportionated rosin, rosin ester, maleic acid modified rosin, polymerized rosin, and phenolic resin. and xylene-based resins. These resins may be hydrogenated resins. Further, the tackifying resin may be used alone or in combination. Here, the softening point of at least one type of tackifying resin is preferably 100°C or higher, more preferably 130°C or higher, even more preferably 150°C or higher, It is particularly suitable that the temperature is 170°C or lower. When the softening point is within this range, excellent results are obtained in cohesive force, high temperature properties, initial tack, and low temperature properties. Further, it is preferable to use a combination of tackifying resins having different softening points rather than using them alone.

{Chlorinated polyolefin (D)}
As the chlorinated polyolefin, from the viewpoint of adhesive strength with the polyolefin material, a polyolefin having a chlorine content of 10 to 50% by mass is preferred, and a chlorine content of 15 to 30% by mass is more preferred. For example, polyethylene, polypropylene, polymethylpentene, polybutene, ethylene/propylene copolymer, propylene/butene copolymer, ethylene/vinyl acetate copolymer, ethylene/propylene/butene, each having a chlorine content within the above range. copolymers, cyclic polyolefins, and the like. Moreover, the chlorinated polyolefin may be modified with an acidic functional group by block polymerization or graft polymerization of an acid component such as a carboxylic acid. Examples of the acid component used for modification include carboxylic acids such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride, or their anhydrides. From the viewpoint of compatibility with the acrylic copolymer and adhesiveness with the polyolefin material, it is preferable to use a modified material. Further, the weight average molecular weight of the chlorinated polyolefin is preferably from 5,000 to 300,000.

{Other ingredients}
The acrylic-rubber mixed adhesive according to this embodiment may contain known additives such as fillers, antioxidants, ultraviolet absorbers, softeners, oils, surface conditioners, crosslinking agents, etc., as necessary. It's okay. Moreover, as a rubber component, synthetic rubber may be contained in addition to natural rubber. Examples of synthetic rubber include isoprene rubber, butadiene rubber, chloroprene rubber, butyl rubber, polyisobutylene, styrene-butadiene rubber, ethylene-propylene rubber, nitrile rubber, silicone rubber, or styrene-isoprene-styrene block copolymer, styrene-butadiene. - Thermoplastic elastomers such as styrene block copolymers, styrene-ethylene-butylene-styrene block copolymers, styrene-ethylene-propylene-styrene block copolymers can also be used.

<Formulation>
Various essential components {(meth)acrylic copolymer (A), natural rubber (B), tackifier (C), chlorinated polyolefin (D)} in the acrylic-rubber mixed adhesive according to the present embodiment The blending ratio will be explained.

(B/A)
The mass ratio (B/A) of natural rubber (B) to the (meth)acrylic copolymer is preferably 10/90 to 90/10, more preferably 20/80 to 60/40. and 25/75 to 50/50 is more preferable.

(C/A+B)
The mass ratio (C/A+B) of the tackifier (C) to the total mass of the (meth)acrylic copolymer (A) and natural rubber (B) is preferably 0.2 to 1.5. It is preferable, 0.3 to 1.2 is more preferable, and 0.5 to 1.0 is even more preferable.

(D/A+B)
The mass ratio (D/A+B) of the chlorinated polyolefin (D) to the total mass of the (meth)acrylic copolymer (A) and natural rubber (B) is preferably 0.002 to 0.15. The range is preferably 0.005 to 0.1, and even more preferably 0.01 to 0.05.

<Physical properties>
The physical properties of the acrylic-rubber mixed adhesive according to this embodiment will be explained.

(15℃ adhesive strength)
The 15° C. adhesive strength of the acrylic-rubber mixed adhesive according to the present embodiment is preferably 8 N/10 mm or more, more preferably 10 N/10 mm or more. Here, the adhesive strength is a value measured by the method below.
[Adhesive force measurement method]
The surface of an automotive PP material (a composite material made of homopolypropylene, ethylene propylene copolymer, etc.) is thoroughly cleaned with isopropanol (hereinafter referred to as IPA). In an atmosphere of 15°C, a double-sided adhesive tape (10 mm width x 70 mm length) with a release liner removed is applied to the surface of an automotive PP material, and the release liner on the opposite side of the applied double-sided tape is peeled off. The exposed adhesive surface is lined with a PET film (thickness 25 μm, 12 mm width x 90 mm), and it is crimped once with a 2 kg rubber roll. After leaving it in an atmosphere of 15°C for 12 hours, the end of the tape was peeled off, and the tape was peeled in a 180° direction using a tensile tester at a speed of 50 mm/min. Measure the force (N/10mm). Note that the measured value of the adhesive force is an integrated average value.

(23℃ adhesive strength)
The 23° C. adhesive strength of the acrylic-rubber mixed adhesive according to the present embodiment is preferably 8 N/10 mm or more, more preferably 10 N/10 mm or more. The adhesive strength was measured in the same way as the test method described in [Adhesive Strength Measurement] above, except that the atmospheric temperature at the time of pasting, leaving, and measurement was 23°C, and the standing time after pasting was 24 hours. It is.

(80℃ adhesive strength)
The 80° C. adhesive strength of the acrylic-rubber mixed adhesive according to the present embodiment is preferably 2 N/10 mm or more, more preferably 4 N/10 mm or more. The adhesive strength was measured using the above-mentioned [Adhesive Strength Measurement] except that the atmospheric temperature at the time of pasting and leaving was 23°C, the standing time after pasting was 24 hours, and the atmospheric temperature at the time of measurement was 80°C. The test method is the same as that described in ].

(80℃ shear force)
The 80° C. shear force of the acrylic-rubber mixed adhesive according to the present embodiment is preferably 0.10 MPa or more, more preferably 0.15 MPa or more. Here, the shearing force is a value measured by the following method.
[Shear force measurement]
Prepare two sheets of PP material for automobiles adjusted to a width of 27 mm and a length of 100 mm, and thoroughly wash the surface of the PP material for automobiles with IPA. In an atmosphere of 23°C, apply double-sided adhesive tape (25 mm x 25 mm) with the release liner removed to the lengthwise end of the PP material for automobiles, making sure that the double-sided tape does not protrude. Peel off the release liner on the other side. The other PP material for automobiles is attached to the exposed adhesive surface in the same manner, and the material is pressed back and forth once with a 5 kg rubber roll. After being left in an atmosphere of 23°C for 24 hours, the distance between the fixing jigs was set to 130 mm using a tensile testing machine, and the test specimen was pulled at a tension speed of 50 mm/min, and the maximum load (N) until the specimen broke was 80 Measured in a °C atmosphere. Note that the obtained maximum load (N) is proportionally converted into shear force (MPa) per unit area.

≪Production method of acrylic-rubber mixed adhesive≫
The acrylic-rubber mixed pressure-sensitive adhesive according to this embodiment is prepared by combining a (meth)acrylic copolymer (A), natural rubber (B), a tackifier resin (C), and a chlorinated polyolefin (D) using a well-known method. It can be produced by mixing. For example, an example of a method for manufacturing a tape to which an acrylic-rubber mixed adhesive is applied will be described. First, (meth)acrylic polymer (A), natural rubber (B), tackifying resin (C), chlorinated polyolefin (D), and other additives are added to a solvent, mixed and stirred until uniform, Prepare an adhesive solution. This adhesive solution is applied to the surface of a silicone-treated release liner, and the solvent in the solution is removed by drying to form an adhesive layer. Next, foamed polyolefin is bonded to the surface of the adhesive layer. A double-sided pressure-sensitive adhesive tape is manufactured by again bonding the opposite side of the foamed polyolefin bonded to the pressure-sensitive adhesive layer to the surface of the pressure-sensitive adhesive layer. Note that pressure may be applied to the manufactured double-sided adhesive tape through a laminator to improve the adhesion between the adhesive layer and the foamed polyolefin.

Here, when preparing the acrylic-rubber mixed adhesive according to the present embodiment, it is preferable to irradiate it with energy rays. Here, the term "energy ray" refers to electromagnetic waves or charged particle beams that have energy quanta. Examples include ultraviolet rays, radiation, and electron beams. Here, the ultraviolet rays can be irradiated using, for example, an ultraviolet source such as an electrodeless lamp, a high-pressure mercury lamp, a metal halide lamp, or a UV-LED. The electron beam is generated by, for example, an electron beam accelerator. Here, among energy beams, electron beams are preferable. In the case of electron beam irradiation, the irradiation dose is preferably 1 to 500 kGy, more preferably 5 to 350 kGy, and even more preferably 10 to 200 kGy.

≪Applications≫
The acrylic-rubber mixed adhesive according to the present embodiment can be used, for example, in the form of a product (eg, a tape, a sheet) to which the adhesive is applied. The acrylic-rubber mixed adhesive has excellent adhesion even to polyolefin materials that are difficult to adhere to, and has excellent adhesive durability even in harsh environments. Therefore, it can be used in various fields such as automobiles, aircraft, ships, electronic devices, electronic device housings, home appliances, infrastructure structures, lifeline building materials, and general building materials. Particularly suitable adherends are adhesive sheets for automotive vehicles such as adhesive sheets for automobile exteriors and adhesive sheets for automobile interiors, and adhesive sheets for fixing members and films made of polyolefin materials. Further, the support such as an adhesive sheet or an adhesive tape is not particularly limited, and examples thereof include foamed polyolefin. Further, the support may be a single base material or a combination of multiple base materials. In addition, the adhesive sheet or adhesive tape may have an adhesive on one side or both sides.

The present invention will be specifically described below with reference to Examples. Note that the present invention is not limited to the examples at all.

≪Polymerization of (meth)acrylic copolymer≫
A mixed solution consisting of 76 parts by weight of 2-ethylhexyl acrylate, 20 parts by weight of n-butyl acrylate, 4 parts by weight of acrylic acid, and 100 parts by weight of ethyl acetate was charged into a flask equipped with a stirrer, a condenser, a thermometer, and a nitrogen inlet tube. While purging with nitrogen, the temperature was raised to 80°C, and a solution of 0.5 parts by weight of lauroyl peroxide dissolved in 10 parts by weight of ethyl acetate was added dropwise, and the mixture was heated for 8 hours to obtain 50% acrylic polymer A-2. Ta. The polymer had a glass transition temperature T g of -63.0° C. and a weight average molecular weight of 740,000. According to the method described above, a composition was prepared so as to have the Tg shown below, and acrylic polymers A-1 and A-3 were polymerized and used as the acrylic copolymer of the adhesive tape. The glass transition temperature Tg of the polymer was calculated by the following formula based on the glass transition temperature (° C.) of the homopolymer of each component (weight fraction) (literature value).
1/Tg=W1/Tg1+W2/Tg2+...
Tg: Glass transition temperature of copolymer Tg1: Glass transition temperature of homopolymer of monomer Tg1 constituting the copolymer (literature value)
W1: Weight fraction of monomer Tg1 constituting the copolymer Tg2: Glass transition temperature of homopolymer of monomer Tg2 constituting the copolymer (literature value)
W2: Weight fraction of monomer Tg2 constituting the copolymer

≪Molecular weight adjustment of natural rubber≫
45 g of natural rubber (Pale Crepe No. 1) was put into a small mixer (capacity 60 cc, blade shape Sigma type) of Laboplast Mill (Model 4C150, Toyo Seiki Seisakusho), and the mixture was heated at a rotation speed of 40 rpm and a heating temperature of 135°C. High temperature mastication was performed for 30 minutes to obtain natural rubber B-1 having a weight average molecular weight of 380,000 (weight average molecular weight/number average molecular weight = 2.6). According to the above method, only the heating temperature was changed and high temperature mastication was performed to obtain natural rubber B-2 and natural rubber B-3. The heating temperature when preparing natural rubber B-2 was 120°C, and the heating temperature when preparing natural rubber B-3 was 180°C.

≪Preparation of adhesive composition≫
According to the compositions in Tables 1 to 3, various raw materials were added to a predetermined amount of toluene solvent, mixed and dissolved, and the solid content concentration was adjusted to 40%, and then applied to a release liner and dried at 100 ° C. for 5 minutes. An adhesive layer with a thickness of 60 μm was formed. Subsequently, a double-sided adhesive tape was produced by laminating a foamed polyolefin (trade name: Borara XL-P#08007, Sekisui Chemical Co., Ltd.), which had been corona-treated on both sides, and an adhesive layer. Thereafter, EB irradiation (acceleration voltage 150 kV, irradiation dose 60 kGy or 80 kGy) was performed in a nitrogen atmosphere to obtain test tapes according to Examples and Comparative Examples. Here, the raw materials are as follows.

Acrylic polymer A-1: weight average molecular weight 740,000 (weight average molecular weight/number average molecular weight = 3.8), Tg -55.2°C
Acrylic polymer A-2: Weight average molecular weight 740,000 (weight average molecular weight/number average molecular weight = 15.3), Tg -63.0°C
Acrylic polymer A-3: Weight average molecular weight 600,000 (weight average molecular weight/number average molecular weight = 3.7), Tg -55.2°C
Natural rubber B-1: Weight average molecular weight 380,000 (weight average molecular weight/number average molecular weight = 2.6)
Natural rubber B-2: Weight average molecular weight 610,000 (weight average molecular weight/number average molecular weight = 3.6)
Natural rubber B-3: Weight average molecular weight 350,000 (weight average molecular weight/number average molecular weight = 3.3)
Synthetic rubber b-1: Chloroprene rubber (Skyprene 580, Tosoh Corporation)
Synthetic rubber b-2: SEBS (Krayton G1657MS, Kraton Corporation)
Synthetic rubber b-3: SBS (Krayton D1102, Kraton Corporation)
Tackifying resin C-1: Polymerized rosin ester (Pensel D160, Arakawa Chemical Industry Co., Ltd.) (softening point 150-165°C)
Tackifying resin C-2: Polymerized rosin ester (Pensel D135, Arakawa Chemical Industry Co., Ltd.) (softening point 130-140°C)
Tackifying resin C-3: Polymerized rosin ester (Pensel D125, Arakawa Chemical Industry Co., Ltd.) (softening point 120-130°C)
Tackifying resin C-4: Terpene phenol resin (YS Polyster U130, Yasuhara Chemical Co., Ltd.) (softening point 130±5°C)
Tackifying resin C-5: Terpene resin (YS Resin PX1150N, Yasuhara Chemical Co., Ltd.) (softening point 115 ± 5°C)
Chlorinated polyolefin D-1: Acid-modified chlorinated polyolefin (Super Chron 3228S, Nippon Paper Industries Co., Ltd.) (chlorine content 28% by mass)
Chlorinated polyolefin D-2: Acid-modified chlorinated polyolefin (Super Chron 930S, Nippon Paper Industries Co., Ltd.) (chlorine content 21% by mass)

≪Evaluation≫
The tapes according to Examples and Comparative Examples were evaluated for 15°C adhesive strength, 23°C adhesive strength, 80°C adhesive strength, and 80°C shear force. The results are shown in Tables 1 to 3. Note that the failure mode described in each column indicates the visually observed state of the sample after the test. The "support" is the destruction of the foamed polyolefin, ie the adhesive layer is still adhered to the automotive PP material. "Aggregation" means cohesive failure of the adhesive, in which the adhesive layer is destroyed, that is, the automobile PP material and the foamed polyolefin are separated by the destroyed adhesive layer. "Interface" means that the adhesive layer has peeled off from the surface of the automotive PP material, that is, no adhesive remains on the surface of the adherend. In addition, when the destruction mode is written together, it indicates that the destruction mode was a mixture of both. Here, the comprehensive evaluation criteria for Examples and Comparative Examples are as follows.
<Comprehensive judgment criteria>
A: 23°C adhesive strength 10N or more, 80°C adhesive strength 4N or more, 80°C shear force 0.15 MPa or more, 15°C adhesive strength 10N or more B: 23°C adhesive strength 8N or more, 80°C adhesive strength 2N or more, 80°C shear Force 0.10MPa or more, 15℃ adhesive force 8N or more C: 15℃ adhesive force less than 8N

Claims (2)

In an adhesive composition containing a (meth)acrylic copolymer and a tackifying resin,
further comprising chlorinated polyolefin and natural rubber;
The adhesive composition is irradiated with energy rays.
An adhesive composition characterized by: An adhesive sheet or tape having an adhesive layer formed from the adhesive composition according to claim 1.