Adhesive sheet

Abstract

To provide an adhesive sheet in which the adhesive layer has low adhesive strength to other adherends, the adhesive layers can be firmly bonded together, the adhesive layer is not destroyed even when peeled off after being bonded once, and sufficient adhesive strength is maintained even when re-bonded. [Solution] An adhesive sheet comprising a substrate containing a vinyl chloride resin and a plasticizer, an intermediate layer containing methyl methacrylate-grafted natural rubber, and an adhesive layer on the intermediate layer, the adhesive layer comprising an adhesive containing a rubber component containing natural rubber, methyl methacrylate-grafted natural rubber, and a plasticizer, wherein the swelling degree of the rubber component relative to the plasticizer is 1.5 to 4.5 times. [Selection diagram] None

Description

Technical Field

[0001] The present invention relates to an adhesive sheet suitable for bundling and protecting long articles.

Background Art

[0002] In order to bundle electric wires and wirings of buildings and the like, a bundling tape made of polyvinyl chloride as a base material is used. After bundling the electric wires and wirings, the tape is repeatedly wound in a spiral shape to impart electrical insulation, heat resistance, flame retardancy, abrasion resistance, etc. together with bundling. However, since the method of repeatedly winding the tape in this way takes a lot of man-hours, in recent years, in order to reduce man-hours, a method of tying a single sheet and fixing it with a strongly adhesive tape such as a double-sided tape has increased, and a sheet provided with a double-sided tape for that purpose is known (Patent Documents 1 and 2).

[0003] In many cases, this double-sided adhesive tape is provided with a release paper in order to prevent the adhesive layer and the base material from adhering to each other before use. When using, it is necessary to peel off the release paper, but there is a problem that the work of peeling off this release paper takes time and the release paper after peeling becomes waste. Therefore, as an adhesive sheet that does not use release paper, a sheet having an adhesive layer that fuses by heat (Patent Document 3), a tape or sheet that bonds adhesive layers together with a pressure-sensitive adhesive (Patent Documents 4 and 5) are known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method described in Patent Document 3, the operation of pressing with a heat sealer occurs, which prolongs the working time, and it cannot be used when the heat resistance of the object to be protected is low. In addition, the adhesive tape described in Patent Document 4 has too high an adhesive force on the adhesive surface, making it difficult to handle and having poor workability. The adhesive sheet using natural rubber graft-polymerized with methyl methacrylate described in Patent Document 5 can be bonded together due to the adhesiveness between the adhesive surfaces, and the adhesive force to other adherends is low and easy to handle. However, since the adhesive force is low, there is a risk of peeling in applications that require high adhesive force such as electrical wiring. In addition, when the adhesive tape is misapplied during construction, it is required to be able to peel it off without destroying the adhesive layer (so-called peelability) and to exhibit the same adhesive force even when reattached (so-called re-adhesiveness). However, in the adhesive sheet described in Patent Document 5, when trying to peel it off after once pasting, a defect occurs in which the adhesive layer peels off from the base material, so-called anchor defect, and thus peeling and re-adhesion cannot be performed.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive sheet having a low adhesive force of the adhesive layer to other adherends, capable of firmly bonding the adhesive layers together, not destroying the adhesive layer even when peeled off after once bonding, and exhibiting sufficient adhesive force even when reattached.

Means for Solving the Problems

[0007] As a result of intensive studies, the present inventors have found that the above problems can be solved by an adhesive sheet having a specific configuration, and have completed the present invention.

[0008] That is, the present invention is as follows. (1) An adhesive sheet comprising an intermediate layer containing methyl methacrylate grafted natural rubber (B) on a base material containing a vinyl chloride resin and a plasticizer (A), and an adhesive layer made of an adhesive containing natural rubber (C1), a rubber component (C) containing methyl methacrylate grafted natural rubber (C2), and a plasticizer (A) on the intermediate layer, wherein the degree of swelling of the rubber component (C) with respect to the plasticizer (A) is 1.5 to 4.5 times. (2) The adhesive sheet according to (1), wherein the content of the plasticizer (A) in 100% by mass of the adhesive is 5 to 35% by mass. (3) The adhesive sheet according to (1) or (2), wherein the methyl methacrylate / natural rubber ratio of the rubber component (C) is 3 / 97 to 30 / 70% by mass. (4) The adhesive sheet according to any one of (1) to (3), further containing 100 parts by mass or less of a synthetic rubber in the intermediate layer with respect to 100 parts by mass of the methyl methacrylate grafted natural rubber (B) contained in the intermediate layer. (5) The adhesive sheet according to any one of (1) to (4), wherein the gel fraction of the rubber component (C) is 50 to 100% by mass. (6) The adhesive sheet according to any one of (1) to (5), wherein the plasticizer (A) contained in the base material and the adhesive layer is diisononyl phthalate (DINP). (7) The adhesive sheet according to any one of (1) to (6), which is for bundling and protecting electric wires.

Advantages of the Invention

[0009] According to the adhesive sheet of the present invention, the adhesive force of the adhesive layer to other adherends is low, and the adhesive layers can be firmly bonded to each other, so that it can be adhered only to the target site and is easy to handle. In addition, even if it is peeled off after being bonded once, the adhesive layer is not damaged, and sufficient adhesive force is exhibited even when re-bonded, so that construction defects due to misbonding can be prevented. Thereby, for example, in the field of electrical work, it can be suitably used for bundling and protecting long articles such as electric wires and wirings.

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications as long as the effects of the present invention are not inhibited.

[0011] The adhesive sheet of this embodiment includes a base material, an intermediate layer on the base material, and an adhesive layer on the intermediate layer. The intermediate layer plays a role of closely adhering the base material and the adhesive layer. The adhesive layer is a pressure-sensitive adhesive layer that is adhered by being bonded with a small pressure by hand or the like. The adhesive layer can wrap a long article or the like with the adhesive surface on the inside, and by bonding the adhesive surfaces together, the adhesive force is developed between the adhesive layers, and the long article or the like can be bundled.

[0012] <Base material> For the purpose of bundling long articles and protecting them from various environments, the base material must have electrical insulation, heat resistance, flame retardancy, and must be able to achieve both strength and flexibility. Therefore, it is essential to use a vinyl chloride-based resin. Examples of the vinyl chloride-based resin include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, etc. These may be used alone or in combination of two or more. Among these, polyvinyl chloride is preferred because of its excellent flexibility, stretchability, and moldability, and can be used generally and inexpensively.

[0013] The degree of polymerization of polyvinyl chloride is not particularly limited, but preferably 500 to 4000, more preferably 800 to 3000, and even more preferably 1000 to 2000, so that particularly good processability can be obtained.

[0014] The base material contains a plasticizer to impart flexibility, extensibility, and processability. As the plasticizer, phthalate plasticizers, isophthalate plasticizers, terephthalate plasticizers, adipate plasticizers and their polyester plasticizers, phosphate plasticizers, trimellitate plasticizers, epoxy plasticizers, etc. can be used. Specific examples of the plasticizer include DINP (diisononyl phthalate), DHP (diheptyl phthalate), DOP (di-2-ethylhexyl phthalate), n-DOP (di-n-octyl phthalate), DIDP (diisodecyl phthalate), DOIP (di-2-ethylhexyl isophthalate), DOTP (di-2-ethylhexyl terephthalate), BBP (benzyl butyl phthalate), TOTM (tri-2-ethylhexyl trimellitate), DOA (di-2-ethylhexyl adipate), TCP (tricresyl phosphate), BOA (benzyl octyl adipate), polyester-based (adipic acid-propylene glycol-based polyester, adipic acid-butylene glycol-based polyester, phthalic acid-propylene glycol-based polyester), DPCP (diphenyl cresyl phosphate), diisodecyl adipate, epoxidized soybean oil, epoxidized linseed oil, chlorinated paraffin, etc. These may be used alone or in combination of two or more. Preferably, it is a phthalate plasticizer that is inexpensive and has a high plasticizing effect, and more preferably DINP.

[0015] The content of the plasticizer (A) in the base material is preferably 20 to 100 parts by mass, more preferably 30 to 80 parts by mass, and still more preferably 40 to 60 parts by mass with respect to 100 parts by mass of the vinyl chloride-based resin. When the plasticizer is 20 parts by mass or more, the extensibility is improved, which is advantageous when bending the protected object after covering the long protected object. When the plasticizer is 100 parts by mass or less, the abrasion resistance is improved, and it is less likely that the protected object will be damaged by abrasion.

[0016] The plasticizer (A) in the base material must be one that is difficult to dissolve the adhesive described later and can cause swelling. If the adhesive is soluble in the plasticizer (A), when the plasticizer that has oozed out from the base material migrates to the adhesive, the adhesive will dissolve and the structure cannot be maintained. Also, if the adhesive is not easily swollen by the plasticizer (A), the plasticizer that has oozed out from the base material remains on the surface layer of the adhesive surface, greatly inhibiting the adhesive force.

[0017] In the base material, fillers, modifiers, and other additives can be blended as long as they do not inhibit the effects of the present invention. Examples of other additives include colorants, stabilizers, antioxidants, ultraviolet absorbers, lubricants, etc.

[0018] Examples of the filler include aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, triphenyl phosphate, ammonium polyphosphate, polyphosphoric acid amide, zirconium oxide, magnesium oxide, zinc oxide, titanium oxide, molybdenum oxide, guanidine phosphate, hydrotalcite, snakeite, zinc borate, anhydrous zinc borate, zinc metaborate, barium metaborate, antimony oxide, antimony trioxide, antimony pentoxide, red phosphorus, talc, alumina, silica, boehmite, bentonite, sodium silicate, calcium silicate, calcium sulfate, calcium carbonate, magnesium carbonate, carbon black. These can be selected alone or in combination of two or more. Preferably, they are talc, alumina, silica, calcium silicate, calcium sulfate, calcium carbonate, magnesium carbonate, and more preferably calcium carbonate with excellent economic efficiency. The filler may be obtained by pulverizing a natural product, or may be obtained by neutralizing and precipitating an aqueous solution or the like. It may also be one with a functional group introduced by a surface treatment agent or the like. As the surface treatment agent, fatty acids, rosin acids, lignin acids, quaternary ammonium salts, etc. can be used.

[0019] Examples of the modifier include vinyl chloride-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, chlorinated polyethylene, chlorinated polyvinyl chloride, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene-styrene copolymer, methyl methacrylate-butadiene-styrene copolymer, acrylonitrile-butadiene copolymer, methyl methacrylate-butyl acrylate copolymer, thermoplastic polyurethane, polyester-based thermoplastic elastomer, and the like. These may be used alone or in combination of two or more.

[0020] The contents of the filler, modifier, and other additives are not particularly limited and can be blended as long as the effects of the present invention are not impaired. For example, it can be more than 0 part by mass and 50 parts by mass or less with respect to 100 parts by mass of the above resin.

[0021] Examples of the method for molding the base material include a method of obtaining a composition obtained by melt-kneading a mixture of a resin, a plasticizer, a filler, a modifier, and other additives. The melt-kneading method is not particularly limited, but various mixers and kneaders equipped with heating devices such as a twin-screw extruder, continuous and batch kneaders, rolls, and Banbury mixers can be used. The composition is mixed so as to be uniformly dispersed, and the resulting mixture is formed into a base material by a conventional molding method such as a calender method, a T-die method, or an inflation method. A calender molding machine is preferable as the molding machine in terms of productivity, color change, shape uniformity, etc. As the roll arrangement method in calender molding, for example, known methods such as an L-type, an inverse L-type, and a Z-type can be adopted, and the roll temperature is usually set to 150 to 200°C, preferably 155 to 190°C.

[0022] The thickness of the base material varies depending on the purpose of use and application, etc., but is preferably 50 to 2000 μm, more preferably 100 to 1000 μm.

[0023] <Intermediate layer> The intermediate layer uses natural rubber graft-polymerized with methyl methacrylate (hereinafter referred to as "methyl methacrylate-grafted natural rubber"). Since methyl methacrylate-grafted natural rubber has an affinity with polyvinyl chloride-based resin and natural rubber, by using this, a base material made of polyvinyl chloride-based resin and an adhesive layer made of natural rubber can be adhered. If there is no intermediate layer, after the adhesive surfaces are bonded together, so-called anchor failure occurs, where peeling occurs at the interface between the base material layer and the adhesive layer during peeling.

[0024] It is essential that methyl methacrylate-grafted natural rubber (B) is copolymerized with methyl methacrylate, but other (meth)acrylic acid-based monomers excluding methyl methacrylate, such as methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, acrylonitrile, etc. may be copolymerized.

[0025] The methyl methacrylate / natural rubber ratio in methyl methacrylate-grafted natural rubber (B) is preferably 10 / 90 to 30 / 70% by mass, more preferably 20 / 80 to 60 / 40% by mass, and still more preferably 30 / 70 to 50 / 50% by mass. When natural rubber that is not graft-polymerized with methyl methacrylate is used for the intermediate layer, after the adhesive surfaces are bonded together, so-called anchor failure occurs, where peeling occurs at the interface between the base material layer and the adhesive layer during peeling.

[0026] In the intermediate layer, synthetic rubber can be added as needed. By adding an appropriate synthetic rubber, the peelability can be further improved, and the adhesive force between the adhesive surfaces after re-peeling can be maintained at a high level. Examples of the synthetic rubber include butadiene rubber, isoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, methyl methacrylate-butadiene rubber, isobutylene rubber (butyl rubber), chloroprene rubber, acrylic rubber, thermoplastic elastomers (such as ethylene-propylene rubber, ethylene-propylene-diene rubber, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, etc.), acrylic rubber, urethane rubber, and the like. In particular, it is preferable to add acrylic rubber (ACM), acrylonitrile-butadiene rubber (NBR), and methyl methacrylate-butadiene rubber (MBR). The addition amount of the synthetic rubber is preferably 100 parts by mass or less with respect to 100 parts by mass of methyl methacrylate graft natural rubber (B).

[0027] The intermediate layer may contain additives such as surfactants, viscosity modifiers, anti-aging agents, plasticizers, and fillers as long as the effects of the present invention are not inhibited. When containing additives, the content thereof is not particularly limited and can be 50% by mass or less in the adhesive layer.

[0028] As the method for forming the intermediate layer, a conventionally known method can be used. For example, it can be formed by a method of coating on one side of a substrate by a method such as a forward rotation roll method, a reverse roll method, a gravure roll method, a spray method, a kiss roll method, a bar method, a knife method, a comma method, a lip die method, or the like.

[0029] From the viewpoints of the adhesive force between the substrate and the adhesive layer and the maintenance of the structure of the intermediate layer, the thickness of the intermediate layer is preferably 0.1 to 3.0 μm, more preferably 0.2 to 2.0 μm, and still more preferably 0.3 to 1.0 μm.

[0030] <Adhesive> The adhesive that constitutes the adhesive layer must contain a rubber component (C) and a plasticizer (A). The rubber component (C) must contain natural rubber (C1) and methyl methacrylate grafted natural rubber (C2). By using natural rubber (C1), the adhesive force between the adhesive surfaces can be high, and the adhesive force with the surface on the opposite side of the adhesive surface (self-back adhesive force) can be kept low. Also, by using an appropriate amount of methyl methacrylate grafted natural rubber (C2), the adhesion to the intermediate layer is improved and the peelability is improved, so that re-adhesion of the adhesive surface becomes possible.

[0031] As a specific example of natural rubber (C1), unmodified natural rubber is most preferable, but natural rubber crosslinked with a sulfur-based compound, an organic peroxide-based compound, etc., or natural rubber depolymerized by mastication or treatment with an organic peroxide agent may also be used. Also, those from which impurities have been removed by centrifugation, defatting, protein-removing agent treatment, etc. of latex may be used. However, those copolymerized with other monomers described later are not included herein.

[0032] Methyl methacrylate grafted natural rubber (C2) is obtained by graft copolymerizing methyl methacrylate onto natural rubber. The graft monomer may be one type or a copolymer of the above-mentioned plurality of types.

[0033] The rubber component (C) may contain other synthetic rubbers as necessary. Specific examples of synthetic rubbers include butadiene rubber, isoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, methyl methacrylate butadiene rubber, isobutylene rubber (butyl rubber), chloroprene rubber, acrylic rubber, thermoplastic elastomers (ethylene-propylene rubber, ethylene-propylene-diene rubber, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer), etc.

[0034] The ratio of methyl methacrylate to natural rubber in the rubber component (C) is preferably 3 / 97 to 30 / 70% by mass, more preferably 3 / 97 to 24 / 76% by mass, and still more preferably 3 / 97 to 18 / 82% by mass. When the ratio of methyl methacrylate is at least the above lower limit value, it can be peeled off uniformly between the adhesive surfaces during peeling, and the adhesive force between the adhesive surfaces during re-adhesion can be maintained. When the ratio of methyl methacrylate is at most the above upper limit value, the adhesive force (self-back adhesive force) between the surface opposite to the adhesive surface and the other surface can be lowered.

[0035] The rubber component (C) must be difficult to dissolve in and not swell with respect to the plasticizer (A). If the rubber component (C) has high solubility in the plasticizer (A), when the plasticizer exuded from the base material migrates to the rubber component (C), the rubber component (C) dissolves and the structure cannot be maintained. Further, if the rubber component (C) does not swell with the plasticizer (A), the plasticizer exuded from the base material remains on the surface layer of the adhesive surface, greatly inhibiting the adhesive force.

[0036] It is essential that the degree of swelling of the rubber component (C) with respect to the plasticizer (A) is 1.5 to 4.5 times, preferably 2.0 to 4.0 times, and still more preferably 2.3 to 3.7 times. When the degree of swelling is less than 1.5 times, the plasticizer (A) cannot be completely absorbed by the rubber component (C), bleeds out on the surface of the adhesive layer, and the adhesive force decreases. When the degree of swelling exceeds 4.5 times, the plasticizer (A) in the base material easily migrates to the rubber component (C), and the tack increases. The degree of swelling can be measured, for example, by the following method. Sampling method of the rubber component (C): Press Benkot M-1 (manufactured by Asahi Kasei Corporation) impregnated with toluene against the adhesive surface side of the adhesive sheet to wipe off the adhesive. Add 1 part by mass of the obtained adhesive to 100 parts by mass of ethanol, set an Erlenmeyer flask with a stopper in a constant temperature water bath (50 °C ± 2 °C), and stir with a stirrer at a rotation speed of 600 / min for 2 hours. After stirring, cool the Erlenmeyer flask with a stopper to 23 °C or lower with ice water, and filter the whole amount through a 270-mesh wire mesh whose weight has been previously measured for the sample. Heat the insoluble matter after filtration at 150 °C for 10 minutes to obtain the rubber component (C). Swelling degree measurement: For 1.00 g of the rubber component (C) collected by the above method, 100 g of the plasticizer (A) is added with a whole pipette. After inserting the rotor, it is sealed. A conical flask with a stopper is set in a constant temperature water bath (50 °C ± 2 °C) and stirred with a stirrer at a rotation speed of 600 / min for 2 hours. After stirring, the conical flask with a stopper is cooled to 23 °C or lower with ice water, and the whole amount is filtered through a 270-mesh wire mesh whose weight has been previously measured (let the weight of the wire mesh before filtration be W1 (g)). The weight of the wire mesh after filtration is measured (let the weight of the wire mesh after filtration be W2 (g)), and the swelling degree of the rubber component (C) with respect to the plasticizer (A) is calculated from the following formula. Swelling degree = (W2 - W1) / 1.00

[0037] The insoluble matter ratio (gel fraction) of the rubber component (C) is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and still more preferably 70 to 100% by mass. When the gel fraction is 50% by mass or more, stickiness of the adhesive layer is less likely to occur. The insoluble matter ratio can be measured by the following two methods, and either one can be selected. Measurement method 1: The wire mesh obtained by the measurement of the swelling degree above is heated in an explosion-proof oven at the boiling point of the plasticizer (A) + 30 °C for 1 hour, and then the weight of the wire mesh is measured (let the weight of the wire mesh after drying be W3 (g)). Using W1 to W3 obtained by the measurement of the swelling degree above, it is calculated from the following formula. Gel fraction (% by mass) = [(W3 - W1) / (W2 - W1)] × 100 Measurement method 2: Approximately 1 μg of the filtrate in the above swelling degree measurement is measured for the mass X (μg) of the rubber component in the filtrate using LC-MS, and it is calculated from the following formula. Gel fraction (% by mass) = (1 - X) × 100

[0038] The swelling degree and gel fraction of the rubber component (C) can be adjusted by the component ratio of natural rubber (C1) and methyl methacrylate grafted natural rubber (C2), the component ratio of methyl methacrylate of methyl methacrylate grafted natural rubber and natural rubber, the modified state of natural rubber (presence or absence of crosslinking, mastication, depolymerization, defatting treatment, deproteinization treatment), addition of other rubber components, etc.

[0039] It is essential to use the plasticizer (A) as the test solvent for measuring the swelling degree of the rubber component (C). However, the following solvents may be used instead of the plasticizer (A) as the test solvent for the gel fraction. Solvents that can be used: aromatic hydrocarbons such as benzene, toluene, o-xylene, m-xylene, p-xylene, aliphatic hydrocarbons such as hexane, heptane, octane, alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, 1,2-dimethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, halogenated hydrocarbons such as methyl chloride, methylene chloride, chloroform, carbon tetrachloride, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ethers such as diethyl ether, dibutyl ether, cyclic ethers such as tetrahydrofuran, aliphatic carboxylic acid esters such as ethyl acetate, butyl acetate, adipic acid diester, aromatic carboxylic acid esters such as benzoic acid ester, phthalic acid diester, trimellitic acid triester, aprotic polar solvents such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO)

[0040] The method for forming the pressure-sensitive adhesive sheet can be obtained, for example, by applying a solution, emulsion or dispersion of an adhesive containing an elastomer mixed with a tackifier, fillers such as inorganic fine particles, a plasticizer, a surfactant, a viscosity modifier, an antioxidant, and other additives to one side of a substrate via a primer layer (intermediate layer), drying it in a drying oven, and then winding it up in a roll shape. Examples of the coating method include the positive rotation roll method, the reverse roll method, the gravure roll method, the spray method, the kiss roll method, the bar method, the knife method, the comma method, the lip die method, etc. Also, from the viewpoints of safety and environmental load, it is preferable to use an emulsion or dispersion with water as the form of the above-mentioned adhesive.

[0041] The pressure-sensitive adhesive sheet of the present invention may be aged for a predetermined time or heat-treated at a predetermined temperature for the purposes of stress relaxation during winding, improving the adhesion between the intermediate layer and the pressure-sensitive adhesive layer, and enhancing the affinity between the components of the pressure-sensitive adhesive layer. The aging or heat treatment is preferably performed at a time and temperature at which the performance of the pressure-sensitive adhesive sheet is sufficiently stable. In particular, in the case of the pressure-sensitive adhesive sheet of the present invention, it is preferably performed at a temperature equal to or higher than the softening point or glass transition point of the intermediate layer and the pressure-sensitive adhesive layer. The temperature in the heat treatment of the pressure-sensitive adhesive sheet is preferably 100°C or higher and 130°C or lower, and the time is preferably 1 hour or longer and 6 hours or shorter.

[0042] The plasticizer contained in the pressure-sensitive adhesive layer must contain the same components as the plasticizer (A) in the base material. A pressure-sensitive adhesive layer without a plasticizer has insufficient adhesiveness and does not exhibit the adhesive force when the pressure-sensitive adhesive layers are bonded together. Further, when the plasticizer contained in the pressure-sensitive adhesive layer is a component different from the plasticizer (A) in the base material, the constituent components of the plasticizer change during storage and the performance is not stable. Examples of the method for providing a pressure-sensitive adhesive layer containing a plasticizer include a method of forming a pressure-sensitive adhesive layer in which a rubber component and a plasticizer are previously mixed on the intermediate layer, a method of forming a pressure-sensitive adhesive layer composed of a rubber component without a plasticizer on the intermediate layer and then further applying a plasticizer, and a method of forming a pressure-sensitive adhesive layer composed of a rubber component without a plasticizer on the intermediate layer and then transferring the plasticizer in the base material to the pressure-sensitive adhesive layer by heat treatment or the like.

[0043] The content of the plasticizer (A) in the pressure-sensitive adhesive is preferably 5 to 35% by mass, more preferably 10 to 30% by mass, and still more preferably 15 to 25% by mass based on 100% by mass of the pressure-sensitive adhesive. When the plasticizer (A) is 5% by mass or more, the adhesive surfaces are sufficiently adhered and the adhesive force between the adhesive surfaces becomes high. Further, when the plasticizer (A) is 35% by mass or less, the tack of the adhesive surface can be suppressed low.

[0044] The pressure-sensitive adhesive may contain a tackifier as necessary. However, since a pressure-sensitive adhesive containing a tackifier is sticky and not very suitable for use as a pressure-sensitive adhesive sheet, it is preferably less than 20% by mass based on 100% by mass of the pressure-sensitive adhesive. Examples of the tackifier include rosin resin, hydrogenated rosin resin, rosin ester resin, rosin-modified phenol resin, phenol resin, alkylphenol resin, terpene resin, terpene phenol resin, coumarone resin, indene resin, coumarone-indene resin, coumarone-indene-styrene resin, styrene resin, xylene resin, styrene-maleic acid resin, aliphatic petroleum resin, alicyclic petroleum resin, aromatic petroleum resin, aliphatic / aromatic copolymerized petroleum resin, and the like. These may be used alone or in combination of two or more.

[0045] The pressure-sensitive adhesive may contain inorganic fine particles as necessary. A pressure-sensitive adhesive containing an appropriate amount of inorganic fine particles can reduce the self-back adhesive force while maintaining the adhesiveness between the adhesive surfaces to a certain extent. Specific examples of the inorganic fine particles include silica, talc, alumina, sodium silicate, calcium silicate, calcium sulfate, calcium carbonate, magnesium carbonate, magnesium oxide, zinc oxide, titanium oxide, boehmite, bentonite, hydrotalcite, etc. Among them, silica, alumina, and calcium carbonate, which are excellent in processability and safety, are preferred, and more preferably calcium carbonate, which is excellent in economy. The fine particles may be used alone or in combination of two or more. The content of the inorganic fine particles is preferably 50% by mass or less, more preferably 1 to 25% by mass, based on 100% by mass of the pressure-sensitive adhesive. If the content of the inorganic fine particles exceeds 50% by mass, the adhesive force may be reduced, so 50% by mass or less is preferred.

[0046] The pressure-sensitive adhesive may contain a surfactant, a viscosity modifier, an antioxidant, and other additives within a range that does not inhibit the adhesive performance. The content ratio of these additives in the pressure-sensitive adhesive is not particularly limited, but is preferably 20% by mass or less based on 100% by mass of the pressure-sensitive adhesive layer.

[0047] The thickness of the adhesive layer is preferably 3 to 100 μm, more preferably 10 to 50 μm, from the viewpoints of the manifestation of adhesive force and the maintenance of the structure of the adhesive layer. By setting the thickness of the adhesive layer to 3 μm or more, the adhesive force can be sufficiently manifested. Further, by setting the thickness of the adhesive layer to 100 μm or less, the structure of the adhesive layer can be sufficiently maintained, and the cohesive failure of the adhesive is less likely to occur.

[0048] The adhesive force between the adhesive surfaces of the adhesive sheet is preferably 8 N or more, more preferably 10 N or more, and still more preferably 12 N or more at a width of 15 mm. Note that the higher the adhesive force between the adhesive layers, the better. The method for measuring the adhesive force between the adhesive surfaces is as follows. Prepare two test pieces with a width of 15 mm and a length of 120 mm, bond the adhesive layers of the test pieces in an area of 15 mm × 100 mm at 23°C, reciprocate once at a speed of 5 mm per second with a pressure roller of 2 kg load, and then leave it for 20 minutes. Next, measure the load when the two test pieces are peeled off at a peeling speed of 300 mm / min at 23°C. The peeling direction of the test piece is such that the angle formed by the two test pieces after peeling is 180°.

[0049] The self-back adhesive force of the adhesive sheet is preferably 0.1 N or less, more preferably 0.05 N or less, and still more preferably 0.03 N or less at a width of 50 mm. Note that the lower the self-back adhesive force, the better. The method for measuring the self-back adhesive force is as follows. Prepare two test pieces with a width of 15 mm and a length of 120 mm, bond the adhesive surface of the test piece and the surface on the opposite side of the adhesive surface (self-back) in an area of 15 mm × 100 mm at 23°C, reciprocate once at a speed of 5 mm per second with a pressure roller of 2 kg load, and then leave it for 20 minutes. Next, measure the load when the two test pieces are peeled off at a peeling speed of 300 mm / min at 23°C. The peeling direction of the test piece is such that the angle formed by the two test pieces after peeling is 180°.

[0050] The probe tack of the adhesive surface of the adhesive sheet is 2 preferably 3 N / cm or less, more preferably 2.5 N / cm or less 2More preferably, it is 2 N / cm or less. 2 It is 3 N / cm or less. 2 When it is 3 N / cm or less, it is less likely to stick to a long article such as an electric wire when focusing and protecting the long article. Note that a lower probe tack is better. The probe tack is measured using a probe tack tester (NS PROBE TACK TESTER manufactured by Nichiban Co., Ltd.) in accordance with ASTM D 2979. After contacting a cylindrical probe with a diameter of 5 mm at a speed of 1 cm / second in an environment of 23°C, it is contacted for 0.02 seconds, and the load when peeling off at a speed of 1 cm / second is measured.

[0051] The ball number of the ball tack on the adhesive surface of the adhesive sheet is preferably 5 or less, more preferably 3 or less, and even more preferably 1 or less. When it is 5 or less, it is less likely to stick to a long article such as an electric wire when focusing and protecting the long article. Note that a lower ball tack is better. The ball tack is determined in accordance with JIS Z 0237 using a ball tack tester (PI-1201 tester manufactured by Sangyo Co., Ltd.) with an inclination angle of 30 degrees to obtain the ball number of the steel ball that stops within the measurement part.

[0052] The adhesive sheet preferably has a 100% tensile modulus of 5 to 50 MPa, more preferably 10 to 40 MPa, and even more preferably 15 to 30 MPa in accordance with JIS K 6251. When it is 5 MPa or more, the structure after bundling is fixed to a certain extent, so the bundling is not likely to loosen. When it is 50 MPa or less, it is advantageous when deforming the bundled object because it maintains appropriate flexibility even after bundling.

[0053] The adhesive sheet preferably has a breaking strength of 10 to 200 MPa, more preferably 15 to 100 MPa, and even more preferably 20 to 40 MPa in accordance with JIS K 6251. When the breaking strength is 10 MPa or more, the mechanical durability of the bundled object is improved. When the breaking strength is 200 MPa or less, the workability when cutting the sheet into a predetermined size is improved.

[0054] The adhesive sheet preferably has an elongation at break of 50 to 500% according to JIS K 6251, more preferably 100 to 300%, and still more preferably 150 to 250%. When the elongation at break is 50% or more, the mechanical durability of the binding object is improved. When the elongation at break is 500% or less, the workability when cutting the sheet into a predetermined size is improved.

[0055] The adhesive sheet preferably has a volume resistivity of 1×10 10 Ωcm or more according to JIS K 6271, more preferably 1×10 11 Ωcm or more, and still more preferably 1×10 12 Ωcm or more. When the volume resistivity is the above-described value or more, the electrical insulation of the binding object is improved.

[0056] The adhesive sheet of the present invention can protect the surface and inside of the object to be protected from mechanical damage and abrasion, and can also be used as a sheet for insulating from electricity and blocking irradiation such as sunlight. In particular, it can be suitably used as a sheet for binding and protecting by bonding the adhesive surfaces together after coating long articles such as electric wires and wiring.

Examples

[0057] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The raw materials of the base material, primer (intermediate layer), and adhesive used in the present invention are shown in Table 1.

[0058] [Example 1] (Production of base material) To 100 parts by mass of polyvinyl chloride (TH-1000, manufactured by Taiyo Vinyl Co., Ltd.) as a vinyl chloride resin, 40 parts by mass of DINP (manufactured by Jay Plus Co., Ltd.) as a plasticizer was blended, and an appropriate amount of a stabilizer, lubricant, and filler was blended. After kneading for 10 minutes on a two-roll mill at a roll temperature of 170°C, a base material with a thickness of 400 μm was obtained.

[0059] (Production of methyl methacrylate graft natural rubber) As the methyl methacrylate grafted natural rubber, 0.3 kg of methyl methacrylate as a monomer was added to 1.4 kg of natural rubber emulsion (manufactured by Revertex), and after adding a redox initiator (0.07 kg of benzoyl peroxide and 0.07 kg of tetraethylenepentamine), 0.02 kg of surfactant, and pure water, emulsion polymerization was carried out to obtain a graft polymerization rubber emulsion (MG50). The composition of the methyl methacrylate grafted natural rubber used in the examples is shown in Table 2.

[0060] (Preparation of Adhesive Emulsion) An adhesive emulsion (A-1) was obtained by mixing 80 g of methyl methacrylate grafted natural rubber (MG50), 20 g of natural rubber emulsion (manufactured by Revertex), and 20 g of a 50% emulsion of DINP (manufactured by Jayplus). The composition of the adhesive used in the examples is shown in Table 3.

[0061] (Preparation of Adhesive Sheet) 100 parts by mass of methyl methacrylate grafted rubber (MG50) was applied as an emulsion for primer (intermediate layer) on the surface of the above substrate, and dried at 100 °C for 1 minute to form a primer layer (intermediate layer) with a thickness of 1 μm on the surface of the substrate. Next, an emulsion adhesive (A-1) was applied on the surface of the primer layer (intermediate layer), and dried at 110 °C for 1 minute using an oven to form an adhesive sheet having a three-layer structure of a substrate with a thickness of 400 μm / an intermediate layer with a thickness of 1 μm / an adhesive layer with a thickness of 30 μm. After winding this adhesive sheet into a roll shape, heat treatment was performed at 110 °C for 2 hours. The configuration and physical properties of the adhesive sheet used in the examples are shown in Table 4.

[0062] (Examples 2 to 19, Comparative Examples 1 to 10) An adhesive sheet was obtained in the same manner as in Example 1, except that the type and thickness of the methyl methacrylate grafted natural rubber emulsion, emulsion adhesive, and the composition of the substrate in Example 1 were changed. The composition of the methyl methacrylate grafted natural rubber used in the examples and comparative examples is shown in Table 2, the composition of the adhesive is shown in Table 3, and the configuration and physical properties of the adhesive sheet are shown in Tables 4 to 6.

[0063] [Qualitative Analysis of Plasticizers in Substrate and Adhesive] Bencot M-1 (manufactured by Asahi Kasei Corporation) impregnated with toluene was pressed against the adhesive side of the adhesive sheet to scrape off the adhesive, separating the substrate and the adhesive. GC-MS analysis was performed on each of the substrate and the adhesive, and since diisononyl phthalate (DINP) was detected in both, it was confirmed that the substrate and the adhesive contain DINP as a plasticizer.

[0064] [Sampling and Evaluation of Rubber Component (C)] Bencot M-1 impregnated with toluene was pressed against the adhesive side of the adhesive sheet to scrape off the adhesive. To 100 parts by mass of ethanol, 1 part by mass of the obtained adhesive was added, and an Erlenmeyer flask with a stopper was set in a constant temperature water bath (50 °C ± 2 °C) and stirred at 600 / min for 2 hours with a stirrer. After stirring, the Erlenmeyer flask with a stopper was cooled to 23 °C or lower with ice water, and the entire amount was filtered through a 270-mesh wire netting whose weight had been previously measured. The insoluble matter after filtration was heated at 150 °C for 10 minutes to obtain the rubber component (C). For the obtained rubber component, the <methyl methacrylate / natural rubber ratio> and <gel fraction> were measured by the following methods, and the results are shown in Tables 3 to 6. Also, the results of <swelling degree> and <plasticizer content in the adhesive layer> are shown in Tables 3 to 6.

[0065] <Methyl Methacrylate / Natural Rubber Ratio> Approximately 10 mg of the sample of the rubber component (C) was impregnated with 800 μL of deuterated chloroform. When it swelled without completely dissolving in the chloroform solution, ultrasonic treatment was performed to obtain a measurement sample. The obtained 1 Using the peak area derived from methyl methacrylate at 3.2 to 3.9 ppm and the specific peak area derived from natural rubber at 4.6 to 5.6 ppm in 1H-NMR, the weight ratio of methyl methacrylate / natural rubber was calculated.

[0066] <Swelling Degree> Approximately 1.00 g of the rubber component (C) sample (weight measured to two decimal places) was taken into a 200-ml conical flask with a stopper. Approximately 100 g of the plasticizer DINP (weight measured to the nearest whole number) was added as a solvent using a whole pipette. After inserting a rotor, the flask was sealed. The conical flask with a stopper was set in a constant-temperature water bath (50 ± 2°C) and stirred at 600 rpm for 2 hours using a stirrer. After stirring, the conical flask with a stopper was cooled to 23°C or lower with ice water, and the entire sample was filtered through a 270-mesh wire mesh whose weight had been pre-measured (the weight of the wire mesh before filtration was designated as W1 [g]). The weight of the wire mesh after filtration was measured (the weight of the wire mesh after filtration was designated as W2 [g]). The swelling degree of the rubber component (C) with respect to the plasticizer (A) was calculated using the following formula. Swelling degree = (W2 - W1) / 1.00

[0067] <Gel fraction> Bencot M-1 (manufactured by Asahi Kasei Corporation) impregnated with toluene was pressed against the adhesive side of the adhesive sheet to wipe off the adhesive. 1 part by mass of the obtained adhesive was added to 100 parts by mass of ethanol. The conical flask with a stopper was set in a constant-temperature water bath (50°C ± 2°C) and stirred at 600 rpm for 2 hours using a stirrer. After stirring, the conical flask with a stopper was cooled to 23°C or lower with ice water, and the entire sample was filtered through a 270-mesh wire mesh whose weight had been pre-measured. The filtered component was heated at 150°C for 10 minutes to remove moisture, then added to a conical flask with a stopper containing 100 g of toluene. After inserting a rotor, the flask was sealed. The conical flask with a stopper was set in a constant-temperature water bath (50°C ± 2°C) and stirred at 600 rpm for 2 hours using a stirrer. After stirring, the conical flask with a stopper was cooled to 23°C or lower with ice water, and the entire sample was filtered through a 270-mesh wire mesh whose weight had been pre-measured (the weight of the wire mesh before filtration was W1 (g), and the weight of the wire mesh after filtration was W2 (g)). After heating at 150°C for 1 hour, the weight of the wire mesh was measured. (The weight of the wire mesh after drying was designated as W3 (g)). Using W1 to W3 obtained from the above measurements, the following formula was used for calculation. Gel fraction (mass%) = [(W3 - W1) / (W2 - W1)] × 100

[0068] <Plasticizer content in the adhesive layer> Bencot M-1 impregnated with heavy chloroform was pressed against the adhesive side of the adhesive sheet to wipe off the adhesive. The adhesive was impregnated with 800 μL of heavy chloroform. When it did not dissolve in the chloroform solution, ultrasonic treatment was performed to obtain a measurement sample. For the 1 1H-NMR spectrum of the above adhesive, the 1 1H-NMR spectra of the rubber component obtained in advance and the plasticizer identified by GC-MS were compared, and the plasticizer content in the adhesive layer was quantified from the peak area ratio of the adhesive rubber component and the plasticizer.

[0069] Test pieces required for each evaluation were cut out from the above adhesive sheet, and <probe tack>, <adhesive force between adhesive surfaces>, <peelability>, <re-adhesiveness>, and <self-back adhesive force> were measured as evaluation methods. The evaluation results are shown in Tables 3 to 6.

[0070] <probe tack> According to ASTM D 2979, using a probe tack tester (NS PROBE TACK TESTER manufactured by Nichiban Co., Ltd.), a cylindrical probe with a diameter of 5 mm was brought into contact at a speed of 1 cm / second in an environment of 23°C, then brought into contact for 0.02 seconds, and the load when peeling off at a speed of 1 cm / second was measured. Those with a probe tack of 4 N or less were considered qualified, and those exceeding it were considered unqualified.

[0071] <adhesive force between adhesive layers> Two test pieces with a width of 15 mm and a length of 120 mm were prepared. In an environment of 23°C, the adhesive layers of the test pieces were bonded together with an area of 15 mm × 100 mm, and after reciprocating once at a speed of 5 mm per second with a pressure roller with a load of 2 kg, they were left for 20 minutes. Next, the load when the test pieces were peeled off at a speed of 300 mm / minute in an environment of 23°C was measured. The peeling direction of the test pieces was such that the angle formed by the two test pieces after peeling was 180°. The adhesive force between the adhesive layers was considered qualified if it was 5 N or more, and unqualified if it was less.

[0072] <peelability> After measuring the adhesive force between the adhesive layers, the adhesive surface of the sample was visually observed. When the adhesive surface peeled off over the entire interface and remained on the intermediate layer side in the same state as before bonding, it was marked as "○". When the adhesive surface peeled off over the entire interface but the adhesive surface became rough and whitened, it was marked as "△". When a part or all of one-sided adhesive peeled off from the intermediate layer side and the adhesive moved to the other side, it was marked as "×". For the evaluation of peelability, "○" and "△" were considered qualified, and "×" was considered unqualified.

[0073] <Re-adhesiveness> Among the samples for which peelability was evaluated, for those that were "○" or "△", the adhesive force between the adhesive surfaces was measured. A value of 5 N or more was considered qualified, and those below it were considered unqualified.

[0074] <Self-back adhesive force> Two test pieces with a width of 50 mm and a length of 120 mm were prepared. In a 23°C environment, the adhesive surface of the test piece and the surface on the opposite side of the adhesive surface (self-back surface) were bonded over an area of 15 mm × 100 mm, and after reciprocating once at a speed of 5 mm per second with a pressure roller of 2 kg load, it was left for 20 minutes. Next, the load when the test piece was peeled off at a speed of 300 mm / min in a 23°C environment was measured. The peeling direction of the test piece was set so that the angle formed by the two test pieces after peeling was 180°. The self-back adhesive force was considered qualified when it was 0.1 N or less, and those exceeding it were considered unqualified.

[0075]

Table 1

[0076]

Table 2

[0077]

Table 3

[0078]

Table 4

[0079]

Table 5

[0080]

Table 6

Claims

1. An adhesive sheet comprising an intermediate layer containing methyl methacrylate grafted natural rubber (B) on a base material containing a vinyl chloride resin and a plasticizer (A), and an adhesive layer comprising a rubber component (C) containing natural rubber (C1) and methyl methacrylate grafted natural rubber (C2) and a plasticizer (A) on the intermediate layer, wherein the plasticizer (A) is one or more plasticizers selected from the group consisting of DINP (diisononyl phthalate), DHP (diheptyl phthalate), DOP (di-2-ethylhexyl phthalate), n-DOP (di-n-octyl phthalate), DIDP (diisodecyl phthalate), DOI (di-2-ethylhexyl isophthalate), DOTP (di-2-ethylhexyl terephthalate), BBP (benzyl butyl phthalate), TOTM (tri-2-ethylhexyl trimellitate), DOA (di-2-ethylhexyl adipate), TCP (tricresyl phosphate), BOA (benzyl octyl adipate), adipic acid-propylene glycol polyester, adipic acid-butylene glycol polyester, phthalic acid-propylene glycol polyester, DPCP (diphenyl cresyl phosphate), diisodecyl adipate, epoxidized soybean oil, epoxidized a mmani oil, and chlorinated paraffin, the degree of swelling of the rubber component (C) with respect to the plasticizer (A) is determined by the following steps: (a) 1 part by mass of the adhesive obtained from the adhesive surface side of the adhesive sheet is added to 100 parts by mass of ethanol, (b) In a conical flask with a stopper, at 50 °C ± 2 °C, (a) is stirred with a stirrer at a rotation speed of 600 / min for 2 hours, (c) The conical flask with a stopper is cooled to 23 °C or lower with ice water, (d) The sample is filtered through a 270-mesh wire mesh whose weight has been previously measured, (e) The insoluble matter after filtration is heated at 150 °C for 10 minutes to obtain the rubber component (C), (f) 100 g of the plasticizer (A) is added to 1.00 g of the rubber component (C), (g) In a sealed conical flask with a stopper, at 50 ± 2 °C, (f) is stirred with a stirrer at a rotation speed of 600 / min for 2 hours, (h) The conical flask with a stopper is cooled to 23 °C or lower with ice water, (i) The sample is filtered through a 270-mesh wire mesh whose weight has been previously measured (let the weight of the wire mesh before filtration be W1 (g)), (j) The weight of the wire mesh after filtration is measured (let the weight of the wire mesh after filtration be W2 (g)), Formula (k): The swelling degree is calculated by swelling degree = (W2 - W1) / 1.00 to calculate the swelling degree of the plasticizer (A) with respect to the rubber component (C). When measured by a method including, it is 1.5 to 4.5 times. Adhesive sheet.

2. The adhesive sheet according to claim 1, wherein the content of the plasticizer (A) in 100% by mass of the adhesive is 5 to 35% by mass.

3. The adhesive sheet according to claim 1 or 2, wherein the methyl methacrylate / natural rubber ratio of the rubber component (C) is 3 / 97 to 30 / 70% by mass.

4. The adhesive sheet according to any one of claims 1 to 3, further containing 100 parts by mass or less of synthetic rubber in the intermediate layer with respect to 100 parts by mass of the methyl methacrylate graft natural rubber (B) contained in the intermediate layer.

5. The adhesive sheet according to any one of claims 1 to 4, wherein the gel fraction of the rubber component (C) is 50 to 100% by mass.

6. The adhesive sheet according to any one of claims 1 to 5, wherein the plasticizer (A) contained in the base material and the adhesive layer is diisononyl phthalate (DINP).

7. The adhesive sheet according to any one of claims 1 to 6, which is for bundling and protecting electric wires.

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