Adhesive tape and adhesive tape manufacturing method

Abstract

The present invention addresses the problem of providing an adhesive tape which is unlikely to exhibit adhesive bleed or to become detached over a long period of time, and which has high adhesive force in a low-temperature environment.　One embodiment of the present invention is an adhesive tape comprising: a base material layer containing a polyvinyl chloride resin; and a rubber-based adhesive agent layer provided on at least one surface of the base material layer. The rubber-based adhesive agent layer contains 25-45 mass% of a rubber component, 5-25 mass% of a (meth)acrylic polymer, and 40-60 mass% of a tackifier. The rubber component is at least one selected from the group consisting of natural rubber, modified natural rubbers, and styrene-butadiene rubbers. The glass transition temperature of the (meth)acrylic polymer is 45°C or higher.

Description

Adhesive tape and method for manufacturing adhesive tape

[0001] The present invention relates to an adhesive tape and a method for producing an adhesive tape.

[0002] Adhesive tapes are used to bundle multiple electric wires in electrical work, automotive components, indoor and outdoor exterior components, repair components, etc. High adhesive strength is required for adhesive tapes used to bundle such electric wires.

[0003] A known method for improving the adhesive strength of adhesive tapes is to use a pressure-sensitive adhesive composition in which a tackifier resin is blended with a pressure-sensitive adhesive. Such pressure-sensitive adhesive compositions generate large amounts of volatile organic compounds (VOCs) because the pressure-sensitive adhesive and the tackifier resin are made compatible in an organic solvent. This poses a problem of significant environmental impact.

[0004]

[0003] Meanwhile, adhesive tapes for electric wires, which are placed in environments prone to high temperatures, are required to have high heat resistance in addition to the adhesive strength described above. When an adhesive tape with low heat resistance is used, a problem occurs in which the ends of the adhesive tape wrapped around the electric wire peel off. To improve the heat resistance of adhesive tapes, a method using a crosslinked adhesive composition (e.g., Patent Document 1) is known. However, such crosslinking treatment is generally carried out in an organic solvent such as toluene, and therefore still poses a problem of environmental load due to VOCs.

[0005] Japanese Patent Application Laid-Open No. 2002-256242

[0006] In view of the above-mentioned circumstances, the present inventors have investigated an adhesive tape that has a low environmental impact during production and high adhesive strength. When an adhesive tape obtained by a production method using, for example, an aqueous latex is used for the above-mentioned applications, the adhesive strength of the adhesive tape may decrease after several years of use, causing peeling, or the adhesive components may deteriorate and become sticky. Furthermore, when used in a harsh environment (for example, a low-temperature environment), the adhesive strength may be insufficient.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide an adhesive tape that is resistant to peeling and stickiness over a long period of time and has high adhesive strength even in a low-temperature environment.

[0008] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using specific components as adhesives and optimizing the composition, and have thus completed the present invention.

[0009] The present invention provides the following: [1] A pressure-sensitive adhesive tape comprising a base layer containing a polyvinyl chloride resin and a rubber-based pressure-sensitive adhesive layer provided on at least one surface of the base layer, wherein the rubber-based pressure-sensitive adhesive layer contains 25 to 45% by mass of a rubber component, 5 to 25% by mass of a (meth)acrylic polymer, and 40 to 60% by mass of a tackifier, the rubber component being at least one selected from the group consisting of natural rubber, modified natural rubber, and styrene-butadiene rubber, and the (meth)acrylic polymer having a glass transition temperature of 45°C or higher. [2] The pressure-sensitive adhesive tape according to [1], wherein the content of structural units derived from alkyl (meth)acrylate in a total of 100% by mass of monomer units constituting the (meth)acrylic polymer is 60% by mass or higher. [3] The pressure-sensitive adhesive tape according to [1] or [2], wherein the modified natural rubber is a graft copolymer of natural rubber and alkyl (meth)acrylate. [4] The pressure-sensitive adhesive tape according to any of [1] to [3], wherein the tackifier contains a petroleum resin. [5] The pressure-sensitive adhesive tape according to any one of [1] to [4], wherein the rubber-based pressure-sensitive adhesive layer has a storage modulus of 0.25 to 0.45 MPa at 23°C. [6] The pressure-sensitive adhesive tape according to any one of [1] to [5], wherein the rubber-based pressure-sensitive adhesive layer has a thickness of 10 to 40 μm. [7] The pressure-sensitive adhesive tape according to any one of [1] to [6], wherein the pressure-sensitive adhesive tape has an adhesive strength of 1.8 to 4.0 N / 10 mm at 23°C, measured according to a method in accordance with JIS Z0237:2000. [8] The pressure-sensitive adhesive tape according to any one of [1] to [7], wherein the pressure-sensitive adhesive tape is used for bundling electric wires. [9] A method for producing the pressure-sensitive adhesive tape according to any one of [1] to [8], comprising a pressure-sensitive adhesive layer-forming step of forming the rubber-based pressure-sensitive adhesive layer on at least one surface of the base layer, wherein the pressure-sensitive adhesive layer-forming step comprises applying an aqueous latex containing a rubber-based pressure-sensitive adhesive composition to at least one surface of the base layer.

[0010] According to the present invention, it is possible to provide an adhesive tape that is resistant to peeling and stickiness over a long period of time and has high adhesive strength even in a low-temperature environment.

[0011] The present invention will be described in detail below. The present invention is not limited to these descriptions. The features of the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently. Furthermore, elements of the following embodiments that are not defined in the claims are optional elements and can be omitted.

[0012] <Explanation of Terms> In this specification, for example, the expression "A to B" means greater than or equal to A and less than or equal to B. In this specification, for example, the expression "within a range between any two of the exemplified numerical values" means greater than or equal to A and less than or equal to B when the exemplified numerical values ​​are A and B (A<B).

[0013] 1. Pressure-sensitive adhesive tape The pressure-sensitive adhesive tape according to the present embodiment comprises a base layer and a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer according to the present embodiment is provided on at least one surface of the base layer. Typically, the pressure-sensitive adhesive layer according to the present embodiment is preferably provided on one surface (one side) of the base layer. Furthermore, in the pressure-sensitive adhesive tape according to the present embodiment, the pressure-sensitive adhesive layer may be provided directly on at least one surface of the base layer, or the pressure-sensitive adhesive layer may be provided via another layer (for example, a primer layer described below).

[0014] 1.1 Base Material Layer The base material layer according to this embodiment contains a polyvinyl chloride resin, and is preferably formed from a resin composition containing a polyvinyl chloride resin.

[0015] 1.1.1 Polyvinyl Chloride Resin The average degree of polymerization of the polyvinyl chloride resin according to this embodiment is preferably 500 to 2000, more preferably 1000 to 2000, and even more preferably 1000 to 1500. The average degree of polymerization of the polyvinyl chloride resin may be, for example, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, or 2000, or may be within a range between any two of the values ​​exemplified here. Two or more polyvinyl chloride resins with different average degrees of polymerization may also be used. When the lower limit of the average degree of polymerization of the polyvinyl chloride resin is within this range, the polymer chains become entangled, and when a resin composition is prepared, the content of the plasticizer described below falls within a suitable range, improving the tensile elongation of the pressure-sensitive adhesive tape. When the upper limit of the average degree of polymerization of the polyvinyl chloride resin falls within this range, the resin is likely to gel and has excellent film-forming properties.

[0016] In the base layer according to this embodiment, when the resin composition is taken as 100% by mass, the content of the polyvinyl chloride resin is preferably 40% by mass or more, and more preferably 50% by mass or more.

[0017] 1.1.2 Plasticizer The resin composition forming the base layer according to this embodiment preferably further contains a plasticizer. The plasticizer according to this embodiment is not particularly limited as long as it can impart flexibility to the base layer. Examples of plasticizers according to this embodiment include carboxylic acid ester plasticizers, polyester plasticizers, epoxy plasticizers, and phosphoric acid plasticizers. These plasticizers may be used alone or in combination of two or more. Preferred plasticizers according to this embodiment are carboxylic acid ester plasticizers and polyester plasticizers. Furthermore, from the viewpoint of cost, preferred plasticizers according to this embodiment are carboxylic acid ester plasticizers.

[0018] 1.1.2.1 Carboxylic Acid Ester-Based Plasticizers Examples of carboxylic acid ester-based plasticizers according to this embodiment include phthalic acid esters, isophthalic acid esters, trimellitic acid esters, adipic acid esters, and terephthalic acid esters. Phthalic acid esters and trimellitic acid esters are preferred as plasticizers according to this embodiment. When such types of plasticizers are used, the melt viscosity of the resin composition tends to decrease, making it easier to achieve a uniform thickness during film formation and reducing the likelihood of pinholes occurring in the substrate layer. Furthermore, from the viewpoint of cost, phthalic acid esters are preferred as plasticizers according to this embodiment.

[0019] Examples of phthalate esters according to this embodiment include diisononyl phthalate (DINP), diheptyl phthalate (DHP), di-2-ethylhexyl phthalate (DOP), di-n-octyl phthalate (n-DOP), and diisodecyl phthalate (DIDP). Preferred plasticizers according to this embodiment are diesters of phthalic acid and alcohols having 9 to 10 carbon atoms, such as diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP). Such types of plasticizers have an excellent plasticizing effect on polyvinyl chloride resins, and can reduce bleed-out.

[0020] An example of the trimellitic ester according to the present embodiment is trioctyl trimellitate (TOTM). When the plasticizer is of this type, the resin composition has excellent heat resistance.

[0021] Examples of the adipic acid ester according to the present embodiment include diisononyl adipate (DINA) and dioctyl adipate (DOA). When the plasticizer is of such a type, the resin composition has excellent flexibility and film-forming properties.

[0022] 1.1.2.2 Polyester-Based Plasticizers Examples of polyester-based plasticizers according to this embodiment include polyesters of dibasic acids and glycols. Examples of dibasic acids include phthalic acid, adipic acid, and sebacic acid. Examples of glycols include 1,2-propanediol and butanediol. With these types of plasticizers, the molecular weight of the plasticizer is relatively large, resulting in low volatility of the resin composition, and the polarity of the plasticizer is relatively high, resulting in excellent oil resistance.

[0023] In the substrate layer according to this embodiment, when the resin composition is taken as 100% by mass, the plasticizer content is preferably 15 to 50% by mass, and more preferably 20 to 45% by mass. The plasticizer content in the resin composition may be, for example, 15, 20, 25, 30, 35, 40, 45, or 50% by mass, or may be within a range between any two of the values ​​exemplified here. When the plasticizer content is equal to or greater than the lower limit, the resin composition attains an appropriate hardness during kneading, improving the film-forming properties of the substrate. When the plasticizer content is equal to or less than the upper limit, the strength of the pressure-sensitive adhesive tape is improved.

[0024] 1.1.3 Filler The base layer according to this embodiment may further contain a filler. The filler according to this embodiment is not particularly limited as long as it can increase the weight of the base layer and improve its hardness. The filler according to this embodiment is preferably an inorganic filler. This type of filler makes it easier to achieve both the reinforcing effect and flexibility of the base layer. Examples of fillers according to this embodiment include calcium carbonate, aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, triphenyl phosphite, ammonium polyphosphate, polyphosphate amide, zirconium oxide, magnesium oxide, zinc oxide, titanium oxide, molybdenum oxide, guanidine phosphate, hydrotalcite, smectite, zinc borate, zinc borate anhydrous, zinc metaborate, barium metaborate, antimony oxide, antimony pentoxide, red phosphorus, mica, talc, alumina, silica, boehmite, bentonite, sodium silicate, calcium silicate, calcium sulfate, and magnesium carbonate. These fillers may be used alone or in combination of two or more.

[0025] 1.1.4 Other Additives The substrate layer according to this embodiment may contain other additives as needed, provided that the effects of the present invention are not impaired. Examples of other additives include colorants (including pigments such as carbon black), stabilizers, lubricants, elastomers, antioxidants, and UV absorbers.

[0026] 1.1.4.1 Stabilizers Examples of stabilizers according to this embodiment include metal soaps (metal-based composite stabilizers). The inclusion of a stabilizer such as a metal soap facilitates improved thermal stability of the base layer. Examples of metal-based composite stabilizers include fatty acid calcium, fatty acid zinc, and fatty acid barium. Examples of fatty acid components of metal-based composite stabilizers include lauric acid, stearic acid, and ricinoleic acid. Specific examples of such metal-based composite stabilizers include calcium laurate, calcium stearate, calcium laurate, zinc laurate, zinc ricinoleate, zinc stearate, barium laurate, barium stearate, and barium ricinoleate. These may be used alone, or two or more may be used in combination. From the viewpoint that the thermal stability effect is more likely to be enhanced by combining them, a Ca—Zn-based metal stabilizer containing fatty acid calcium and fatty acid zinc is preferably used. The content of the metal-based composite stabilizer according to this embodiment is preferably 0.1 to 10% by mass, and more preferably 1 to 5% by mass, when the resin composition is taken as 100% by mass.

[0027] 1.1.4.2 Lubricants Examples of lubricants according to this embodiment include higher fatty acids such as stearic acid and palmitic acid; higher alcohols such as palmityl alcohol and stearyl alcohol; metal salts of higher fatty acids such as calcium stearate, zinc stearate, barium stearate, aluminum stearate, magnesium stearate, and sodium palmitate; higher fatty acid esters such as butyl stearate and glyceryl monostearate; and higher fatty acid amides such as oleic acid amide, stearic acid amide, and erucic acid amide. Here, "higher" refers to a group having 9 or more carbon atoms, preferably 9 to 30 carbon atoms. These may be used alone, or two or more may be used in combination. Among these, stearic acid is preferred from the viewpoint of film-forming properties of the substrate. The content of the lubricant according to this embodiment is preferably 0.01 to 5.0% by mass, and more preferably 0.1 to 1.0% by mass, based on 100% by mass of the resin composition.

[0028] 1.1.4.3 Elastomer The elastomer according to this embodiment is preferably a thermoplastic elastomer. Examples of thermoplastic elastomers include urethane elastomers, olefin elastomers, chlorinated polyethylene elastomers, ethylene vinyl acetate elastomers, polyester elastomers, styrene elastomers, and polyamide elastomers. These may be used alone or in combination of two or more. Of these, chlorinated polyethylene is preferred from the viewpoint of tensile elongation at low temperatures (e.g., −5°C or lower). The content of the lubricant according to this embodiment is preferably 0.1 to 15% by mass, and more preferably 1.0 to 10% by mass, based on 100% by mass of the resin composition.

[0029] 1.1.5 Thickness of the Base Material Layer The thickness of the base material layer according to this embodiment is preferably 250 μm or less, more preferably 100 to 250 μm, and even more preferably 120 to 200 μm. The thickness of the base material layer may be, for example, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, or 250 μm, or may be within a range between any two of the values ​​exemplified here. The thickness of the base material layer can be measured using a method in accordance with JIS C2107:2011. Specifically, it can be the average value measured at multiple measurement points using a gauge. The thickness of the base material layer may be measured on the base material layer before the pressure-sensitive adhesive layer is formed, or it may be measured on the base material layer from which the pressure-sensitive adhesive layer has been removed using a solvent after the production of the pressure-sensitive adhesive tape. When the thickness of the base material layer is equal to or greater than the lower limit, the strength of the pressure-sensitive adhesive tape is improved. If the thickness of the substrate layer is equal to or less than the upper limit, the repulsive force when the substrate is wound around an electric wire or the like is reduced.

[0030] 1.2 Pressure-sensitive adhesive layer The pressure-sensitive adhesive layer according to this embodiment is a rubber-based pressure-sensitive adhesive layer. The rubber-based pressure-sensitive adhesive layer according to this embodiment contains a rubber component, a (meth)acrylic polymer, and a tackifier.

[0031] 1.2.1 Rubber Component The rubber-based pressure-sensitive adhesive layer according to this embodiment preferably further contains a rubber component. Examples of the rubber component according to this embodiment include natural rubber, synthetic rubber, and modified natural rubber (a graft copolymer of natural rubber with at least one selected from the above-mentioned synthetic rubbers and alkyl (meth)acrylates). Examples of the rubber component according to this embodiment include natural rubber, styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene-styrene block copolymer (SBS), hydrogenated products of the above-mentioned styrene-based block copolymers (SIPS, SEBS), styrene-butadiene rubber (SBR), synthetic rubber such as polyisoprene rubber (IR), polyisobutylene (PIB), and butyl rubber (IIR), as well as graft copolymers of natural rubber with at least one selected from the above-mentioned synthetic rubbers and alkyl (meth)acrylates. These rubber components may be used alone or in combination of two or more. The rubber component according to this embodiment contains at least one selected from the group consisting of natural rubber, modified natural rubber, and styrene-butadiene rubber (SBR), preferably two or more, and particularly preferably all three. The use of such a rubber component allows for a PSA layer with excellent balance of adhesive properties. The rubber component according to this embodiment preferably contains modified natural rubber. It is particularly preferable to use a graft copolymer of natural rubber and alkyl (meth)acrylate as the modified natural rubber. The use of modified natural rubber provides excellent compatibility of the rubber component with the (meth)acrylic polymer.

[0032] The rubber component content in the rubber-based pressure-sensitive adhesive layer according to this embodiment is 25 to 45% by mass, preferably 30 to 40% by mass. The rubber component content in the rubber-based pressure-sensitive adhesive layer may be, for example, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, or 45% by mass, or may be within a range between any two of the values ​​exemplified herein. When the rubber component content is equal to or greater than the lower limit, the storage modulus of the pressure-sensitive adhesive layer becomes appropriate, the adhesive strength of the pressure-sensitive adhesive tape improves, and the pressure-sensitive adhesive tape becomes less susceptible to peeling over a long period of time. When the rubber component content is equal to or less than the upper limit, the pressure-sensitive adhesive tape becomes less susceptible to deterioration even during long-term storage, and becomes less susceptible to peeling over a long period of time.

[0033] The rubber-based pressure-sensitive adhesive layer according to the present embodiment preferably contains a natural rubber component. The content of the natural rubber component in the rubber-based pressure-sensitive adhesive layer according to the present embodiment may be, for example, 1 to 20% by mass, preferably 2 to 15% by mass, and more preferably 5 to 12% by mass. The content of the natural rubber component in the rubber-based pressure-sensitive adhesive layer may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20% by mass, or may be within a range between any two of the values ​​exemplified here. When the content of the natural rubber component is equal to or greater than the lower limit, the pressure-sensitive adhesive tape has superior adhesive strength even at low temperatures (e.g., −5°C or below). When the content of the natural rubber component is equal to or less than the upper limit, the pressure-sensitive adhesive tape is resistant to peeling over a long period of time. In this specification, the term "natural rubber component" includes natural rubber and the natural rubber portion of modified natural rubber, and the "natural rubber component content" refers to the sum of the natural rubber content and the value calculated from the natural rubber content in the modified natural rubber. It is particularly preferable to use a natural rubber component and a synthetic rubber component in combination as the rubber component in this embodiment. The combined use of a synthetic rubber component improves the compatibility of the rubber component with the (meth)acrylic polymer, thereby further improving the adhesive strength of the pressure-sensitive adhesive tape.

[0034] 1.2.2 (Meth)acrylic Polymer The (meth)acrylic polymer according to this embodiment is a polymer containing structural units derived from alkyl (meth)acrylate. The alkyl (meth)acrylate according to this embodiment is preferably methyl (meth)acrylate, with methyl methacrylate being particularly preferred. The alkyl group of the alkyl (meth)acrylate according to this embodiment preferably has 18 or less carbon atoms, more preferably 1 to 8, and even more preferably 1 to 3. When the alkyl group of the alkyl (meth)acrylate has a carbon number within this range, the glass transition temperature of the (meth)acrylic polymer increases, thereby further improving the adhesive strength of the pressure-sensitive adhesive tape. The (meth)acrylic polymer according to this embodiment may, for example, contain structural units derived from alkyl (meth)acrylate in a total of 100% by mass of the constituent monomer units of 60% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The (meth)acrylic polymer according to this embodiment may contain structural units derived from glycidyl (meth)acrylate, in addition to structural units derived from alkyl (meth)acrylate.

[0035] The glass transition temperature of the (meth)acrylic polymer according to this embodiment is 45°C or higher, preferably 55°C or higher, and more preferably 60°C or higher. The upper limit of the glass transition temperature of the (meth)acrylic polymer according to this embodiment can be, for example, 150°C. The glass transition temperature of the (meth)acrylic polymer according to this embodiment is preferably 45 to 150°C, more preferably 55 to 110°C, and even more preferably 60 to 110°C. The glass transition temperature of the (meth)acrylic polymer may be, for example, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 130, 140, or 150°C, or may be within a range between any two of the values ​​exemplified here. The glass transition temperature of the (meth)acrylic polymer in the pressure-sensitive adhesive layer can be measured by isolating the (meth)acrylic polymer from the pressure-sensitive adhesive layer. The glass transition temperature of the (meth)acrylic polymer can be measured, for example, by a method in accordance with JIS K 7121:2012, specifically by differential scanning calorimetry (DSC). Furthermore, when a plurality of types of (meth)acrylic polymers are contained in the pressure-sensitive adhesive layer, the "glass transition temperature of the (meth)acrylic polymer" can be calculated as follows. For example, when a% by mass of (meth)acrylic polymer A having a glass transition temperature X and b% by mass of (meth)acrylic polymer B having a glass transition temperature Y are contained in 100% by mass of (meth)acrylic polymer (a + b = 100), the "glass transition temperature of the (meth)acrylic polymer" in the present application can be calculated by the following formula: X × (a / 100) + Y × (b / 100). When the glass transition temperature of the (meth)acrylic polymer is equal to or higher than the lower limit, the adhesive strength of the pressure-sensitive adhesive tape is improved, and further, even when the pressure-sensitive adhesive tape is used for a long period of time, the side surfaces are less likely to become sticky. When the glass transition temperature of the (meth)acrylic polymer is equal to or lower than the upper limit, compatibility is improved and workability is improved.

[0036] The content of the (meth)acrylic polymer in the rubber-based pressure-sensitive adhesive layer according to this embodiment is 5 to 25% by mass, preferably 7 to 22% by mass, and more preferably 10 to 20% by mass. The content of the (meth)acrylic polymer in the rubber-based pressure-sensitive adhesive layer may be, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25% by mass, or may be within a range between any two of the values ​​exemplified herein. When the content of the (meth)acrylic polymer is equal to or greater than the lower limit, the adhesive strength of the pressure-sensitive adhesive tape is improved, resulting in a pressure-sensitive adhesive tape that is less likely to peel over a long period of time. When the content of the (meth)acrylic polymer is equal to or less than the upper limit, the hardness of the rubber-based pressure-sensitive adhesive layer becomes appropriate, further improving the adhesive strength of the pressure-sensitive adhesive tape. Furthermore, the pressure-sensitive adhesive tape exhibits excellent adhesive strength even at low temperatures (e.g., −5°C or lower).

[0037] 1.2.3 Tackifier The rubber-based pressure-sensitive adhesive layer according to this embodiment preferably contains a tackifier. The tackifier according to this embodiment can be selected taking into consideration the softening point and compatibility with each component. Examples of tackifiers according to this embodiment include emulsions of terpene resins, rosin resins, hydrogenated rosin resins, coumarone-indene resins, styrene-based resins, petroleum resins, terpene-phenol resins, xylene-based resins, and other aliphatic hydrocarbon resins or aromatic hydrocarbon resins. These tackifiers may be used alone or in combination of two or more. The tackifier according to this embodiment preferably contains a petroleum resin, and it is particularly preferable to use a petroleum resin and a terpene-phenol resin in combination.

[0038] The tackifier content in the rubber-based pressure-sensitive adhesive layer according to this embodiment is 40 to 60% by mass, preferably 45 to 55% by mass, and more preferably 48 to 53% by mass. The tackifier content in the rubber-based pressure-sensitive adhesive layer may be, for example, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, or 60% by mass, or may be within a range between any two of the values ​​exemplified herein. When the tackifier content is within this range, the storage modulus of the rubber-based pressure-sensitive adhesive layer becomes appropriate, resulting in a pressure-sensitive adhesive tape that is less likely to peel over a long period of time. When the tackifier content is equal to or greater than the lower limit, the adhesive strength of the pressure-sensitive adhesive tape is improved, resulting in a pressure-sensitive adhesive tape that is less likely to peel over a long period of time. Furthermore, when the tackifier content is equal to or less than the upper limit, the pressure-sensitive adhesive tape is less likely to become sticky on the side surfaces even after long-term use.

[0039] The glass transition temperature of the tackifier in the rubber-based pressure-sensitive adhesive layer according to this embodiment is preferably 40 to 150°C. The glass transition temperature of the tackifier in the pressure-sensitive adhesive layer can be measured in the same manner as the glass transition temperature of the (meth)acrylic polymer in the pressure-sensitive adhesive layer described above. When the glass transition temperature of the tackifier in the rubber-based pressure-sensitive adhesive layer is in this range, the adhesive strength of the pressure-sensitive adhesive tape is further improved.

[0040] 1.2.4 Thickness of the Pressure-Sensitive Adhesive Layer The thickness of the pressure-sensitive adhesive layer according to this embodiment is preferably 10 to 40 μm, more preferably 15 to 35 μm, and even more preferably 20 to 35 μm. The thickness of the pressure-sensitive adhesive layer may be, for example, 10, 15, 20, 25, 30, 35, or 40 μm, or may be within a range between any two of the values ​​exemplified herein. The thickness of the pressure-sensitive adhesive layer can be measured, for example, by measuring the thickness of the pressure-sensitive adhesive tape using a method in accordance with JIS C2107:2011 and calculating the difference (absolute value) between the thickness of the pressure-sensitive adhesive tape and the thickness of the base layer measured using the above-mentioned method. When the thickness of the pressure-sensitive adhesive layer is equal to or greater than the lower limit, the adhesive strength of the pressure-sensitive adhesive tape is further improved. When the thickness of the pressure-sensitive adhesive layer is equal to or less than the upper limit, the pressure-sensitive adhesive tape is easily unwound when used in a roll, resulting in excellent tape unfoldability.

[0041] 1.2.5 Storage Modulus of Pressure-Sensitive Adhesive Layer The storage modulus of the rubber-based pressure-sensitive adhesive layer according to this embodiment at 23°C is, for example, 0.15 MPa or more, preferably 0.25 to 0.45 MPa, and more preferably 0.30 to 0.40 MPa. The storage modulus of the rubber-based pressure-sensitive adhesive layer at 23°C may be, for example, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, or 0.45 MPa, or may be within a range between any two of the values ​​exemplified here. The storage modulus of the rubber-based pressure-sensitive adhesive layer at 23°C can be measured, for example, by scraping off 0.1 g of the rubber-based pressure-sensitive adhesive layer from the pressure-sensitive adhesive tape and forming it into a sheet with a thickness of 1 mm using a dynamic modulus measuring device under the following conditions. Measurement start temperature: -60°C Measurement end temperature: 120°C Heating rate: 4°C / min Frequency: 1 Hz When the storage modulus at 23°C of the rubber-based pressure-sensitive adhesive layer is not less than the lower limit, the adhesive strength of the pressure-sensitive adhesive tape is further improved, and the pressure-sensitive adhesive tape is less likely to peel over a long period of time. When the storage modulus at 23°C of the rubber-based pressure-sensitive adhesive layer is not more than the upper limit, the adhesive strength of the pressure-sensitive adhesive tape is further improved. Furthermore, when the storage modulus at 23°C of the rubber-based pressure-sensitive adhesive layer is not more than the upper limit, the repulsive force when wrapped around an electric wire or the like is reduced, and the pressure-sensitive adhesive tape is less likely to peel over a long period of time.

[0042] 1.3 Other Layers The pressure-sensitive adhesive tape according to this embodiment may further include other layers as long as the effects of the present invention are not impaired. The pressure-sensitive adhesive tape according to this embodiment may further include a primer layer between the substrate layer and the pressure-sensitive adhesive layer for the purpose of improving the adhesion between the substrate layer and the pressure-sensitive adhesive layer.

[0043] The primer for the primer layer according to this embodiment preferably contains a mixture of a graft polymer obtained by graft-polymerizing methyl methacrylate onto natural rubber and an acrylonitrile-butadiene copolymer. Furthermore, a particularly preferred primer is one in which the above mixture is further mixed with a (meth)acrylic polymer used in the rubber-based pressure-sensitive adhesive layer. The mixing ratio of the mixture to the (meth)acrylic polymer can be, for example, 1:0.1 to 1:10, or 1:1 to 1:5. Such a primer composition brings the polarities of the primer layer and the pressure-sensitive adhesive layer closer, making peeling between the primer layer and the pressure-sensitive adhesive layer less likely to occur.

[0044] The graft polymer according to this embodiment is preferably one obtained by graft polymerizing 70 to 40% by mass of natural rubber with 30 to 60% by mass of methyl methacrylate. When the lower limit of the methyl methacrylate content is within this range, adhesion to the substrate layer is excellent and delamination is unlikely to occur. When the upper limit of the methyl methacrylate content is within this range, the primer itself is less likely to harden and is more likely to follow the deformation of the substrate layer, making delamination less likely to occur.

[0045] As the acrylonitrile-butadiene copolymer according to this embodiment, a medium nitrile type (25 to 30% by mass of acrylonitrile, 75 to 70% by mass of butadiene), a medium-high nitrile type (31 to 35% by mass of acrylonitrile, 69 to 65% by mass of butadiene), or a high nitrile type (36 to 43% by mass of acrylonitrile, 64 to 57% by mass of butadiene) can be used. These may be used alone or in combination of two or more. The content of the acrylonitrile-butadiene copolymer is preferably 25 to 300 parts by mass relative to 100 parts by mass of the graft polymer.

[0046] 2. Method for Producing Pressure-Sensitive Adhesive Tape The pressure-sensitive adhesive tape according to this embodiment can be produced, for example, by laminating a pressure-sensitive adhesive layer on at least one surface of a base layer. Specifically, the method for producing the pressure-sensitive adhesive tape according to this embodiment includes a base layer-forming step and a pressure-sensitive adhesive layer-forming step.

[0047] 2.1 Base Material Layer Forming Step The method for producing a pressure-sensitive adhesive tape according to this embodiment includes a base material layer forming step in which a base material layer is formed using a polyvinyl chloride resin or a resin composition containing a polyvinyl chloride resin. The resin composition according to this embodiment can be produced by melt-kneading a polyvinyl chloride resin, a plasticizer, and other additives in a mixer or the like so as to uniformly disperse them. The base material layer according to this embodiment can be produced by forming a polyvinyl chloride resin or a resin composition into a predetermined thickness using a calendar molding machine or the like. The temperature at this time can be set as desired depending on the components in the resin composition, and can be set, for example, to 100 to 200°C.

[0048] 2.2 Primer Layer Forming Step The method for producing a pressure-sensitive adhesive tape according to this embodiment preferably further includes a primer layer forming step. In this embodiment, the primer layer forming step involves, for example, applying a primer to at least one surface of the substrate layer, and then thoroughly removing the solvent (e.g., moisture) in a drying oven. Examples of primer application methods include gravure, spray, kiss roll, bar, and knife methods.

[0049] 2.3 Pressure-Sensitive Adhesive Layer Formation Step The pressure-sensitive adhesive tape manufacturing method according to this embodiment includes a pressure-sensitive adhesive layer formation step of forming a rubber-based pressure-sensitive adhesive layer on at least one surface of the substrate layer. When the above-described primer layer formation step is included, the pressure-sensitive adhesive layer formation step refers to forming a rubber-based pressure-sensitive adhesive layer on at least one surface of the substrate layer via a primer layer. In the pressure-sensitive adhesive layer formation step according to this embodiment, it is preferable to coat at least one surface of the substrate with an aqueous latex containing a rubber-based pressure-sensitive adhesive composition. Since all components of the rubber-based pressure-sensitive adhesive layer according to this embodiment are soluble in water, an aqueous solvent can be used. The use of an aqueous latex reduces residual solvent, which can occur when organic solvents are used, thereby suppressing adverse effects on the human body and reducing environmental impact. Examples of coating methods for the aqueous latex include the comma method, lip die method, gravure method, roll method, and slot die method. After coating the aqueous latex, the solvent (water) is thoroughly removed in a drying oven to obtain a pressure-sensitive adhesive tape.

[0050] 3. Characteristics of the Adhesive Tape The adhesive tape according to this embodiment is resistant to peeling over a long period of time. To make an adhesive tape resistant to peeling over a long period of time, it is necessary for the adhesive strength to be high and for the adhesive strength to be maintained over a long period of time. In this specification, "resistant to peeling over a long period of time" means that the tape has high adhesive strength even when used after long-term storage, and by extension, that the adhesive strength can be maintained over a long period of time after the start of use (e.g., wrapping).

[0051] 3.1 Adhesive Strength (Normal Condition, to SUS) The adhesive strength (normal condition, to SUS) of the pressure-sensitive adhesive tape according to this embodiment is preferably 1.6 N / 10 mm or more, more preferably 1.8 N / 10 mm or more, even more preferably 1.9 N / 10 mm or more, and particularly preferably 2.0 N / 10 mm or more. Furthermore, the adhesive strength (normal condition, to SUS) of the pressure-sensitive adhesive tape according to this embodiment is preferably 4.0 N / 10 mm or less. The adhesive strength (normal condition, to SUS) of the pressure-sensitive adhesive tape according to this embodiment is preferably 1.8 to 4.0 N / 10 mm, more preferably 1.9 to 3.5 N / 10 mm, and even more preferably 2.0 to 3.0 N / 10 mm. The adhesive strength (normal condition, to SUS) can be measured, for example, using a SUS plate as the test plate at 23°C using a method in accordance with JIS Z0237:2000. When the adhesive strength (normal, to SUS) of the adhesive tape is at least the lower limit, the adhesive strength is excellent and the tape can be suitably used in operating machinery or components for machinery. When the adhesive strength (normal, to SUS) of the adhesive tape is at most the upper limit, the tape becomes easy to unwind when used in a roll, the adhesive tape has excellent unfoldability, and workability is improved. Methods for improving the adhesive strength (normal, to SUS) of the adhesive tape include, for example, increasing the rubber component in the rubber-based adhesive layer, increasing the content of a tackifier, and using a (meth)acrylic polymer with a higher glass transition temperature.

[0052] 3.2 Adhesive Strength (Normal, to SUS, after storage at 60°C for 10 days) The adhesive strength of the pressure-sensitive adhesive tape according to this embodiment (normal, to SUS, after storage at 60°C for 10 days) is preferably 1.6 N / 10 mm or more, more preferably 1.7 N / 10 mm or more, and even more preferably 1.8 N / 10 mm or more. Furthermore, the adhesive strength of the pressure-sensitive adhesive tape according to this embodiment (normal, to SUS, after storage at 60°C for 10 days) is preferably 4.0 N / 10 mm or less. The adhesive strength of the pressure-sensitive adhesive tape according to this embodiment (normal, to SUS, after storage at 60°C for 10 days) is preferably 1.6 to 4.0 N / 10 mm, more preferably 1.7 to 3.0 N / 10 mm, and even more preferably 1.8 to 2.5 N / 10 mm. The adhesive strength (normal, to SUS, after storage at 60°C for 10 days) can be measured, for example, after storing the adhesive tape in an atmosphere at 60°C for 10 days, in the same manner as in the above-mentioned adhesive strength (normal, to SUS). When the adhesive strength of the adhesive tape (normal, to SUS, after storage at 60°C for 10 days) is equal to or greater than the lower limit, the adhesive tape has excellent adhesive strength and is resistant to peeling over a long period of time (for example, several years). When the adhesive strength of the adhesive tape (normal, to SUS, after storage at 60°C for 10 days) is equal to or less than the upper limit, the tape becomes easy to unwind when used in a roll, resulting in excellent unfoldability of the adhesive tape and improved workability. Methods for improving the adhesive strength of a pressure-sensitive adhesive tape (normal, against SUS, after storage at 60°C for 10 days) include, for example, adjusting the rubber component content in the rubber-based pressure-sensitive adhesive layer, increasing the (meth)acrylic polymer content, increasing the amount of tackifier, and using a (meth)acrylic polymer with a higher glass transition temperature; particularly, reducing the rubber component content (particularly natural rubber and modified natural rubber), increasing the (meth)acrylic polymer content, and using a (meth)acrylic polymer with a higher glass transition temperature are included.

[0053] 4. Method of Use The pressure-sensitive adhesive tape according to this embodiment can be used to bind electric wires. Accordingly, one embodiment of the present invention is a pressure-sensitive adhesive tape for bundling electric wires. The pressure-sensitive adhesive tape according to this embodiment can be used in various mechanical devices, such as automobiles, aircraft, trains, factory automation equipment, home appliances, office automation equipment, medical equipment, communications equipment, and play equipment, or in components for such mechanical devices. The pressure-sensitive adhesive tape according to this embodiment is resistant to peeling over long periods of time and can be used favorably even in harsh environments, and is therefore particularly favorable for use in moving mechanical devices, such as automobiles, aircraft, trains, factory automation equipment, home appliances, and play equipment, or in components for such mechanical devices.

[0054] The present invention will be described in more detail below with reference to examples. Note that the examples described below are representative examples of the present invention and should not be construed as narrowing the scope of the present invention.

[0055] <Base layer formation step> 55 parts by mass of polyvinyl chloride resin, 36 parts by mass of plasticizer, 3.5 parts by mass of stabilizer, 0.5 parts by mass of lubricant, and 5 parts by mass of elastomer were melt-kneaded in a Banbury mixer so as to be uniformly dispersed to form a resin composition. The obtained resin composition was then calendered at a roll temperature of 173°C to form a base layer.

[0056] <Primer layer forming step> A primer was gravure coated on one side of each substrate layer, and the moisture was thoroughly removed in a drying oven to form a primer layer. The thickness of the primer layer after drying was 0.3 μm.

[0057] <Adhesive Formation Step> A rubber-based adhesive composition having the formulation shown in Tables 1 to 3 was dissolved in water to prepare an aqueous latex containing the rubber-based adhesive composition. The aqueous latex containing the rubber-based adhesive composition was applied onto a primer layer using the comma method (i.e., the aqueous latex containing the rubber-based adhesive composition was applied to one side of the substrate layer via the primer layer), and the moisture was thoroughly removed in a drying oven to prepare an adhesive tape. The adhesive tapes of Examples and Comparative Examples prepared in this manner were subjected to the tests and evaluations described below, and the results are shown in Tables 1 to 3. The thicknesses of the substrate layer and the adhesive layer were measured using a thickness gauge (manufactured by Mitutoyo Corporation) according to a method in accordance with JIS C2107:2011 (n=5).

[0058] The components used to obtain the resin composition are as follows. Polyvinyl chloride resin: Polyvinyl chloride resin 1300: "TH-1300" manufactured by Taiyo Vinyl Corporation, average degree of polymerization 1300 Plasticizer: TOTM: "TOTM" manufactured by J-Plus Corporation, trioctyl trimellitate Stabilizer: Metal-based composite stabilizer: "OW-5200" manufactured by Sakai Chemical Industry Co., Ltd. Lubricant: Stearic acid: "Sakura stearate" manufactured by NOF Corporation Elastomer: Chlorinated polyethylene: "ELASLENE (registered trademark) 301MA" manufactured by Resonac Corporation

[0059] The ingredients used in preparing the primer layer are as follows: Primer: A mixed emulsion of a graft polymer latex obtained by graft polymerizing methyl methacrylate onto natural rubber and an acrylonitrile-butadiene copolymer emulsion ("KT4612A" manufactured by E-Tech Co., Ltd.) and a (meth)acrylic polymer ("E277" manufactured by Toyochem Co., Ltd.) in a 1:2 ratio.

[0060] The components used in preparing the pressure-sensitive adhesive layer are as follows. In the tables, "SBR" means "styrene-butadiene rubber" and "Tg" means "glass transition temperature." The formulations shown in Tables 1 to 3 are values ​​converted into solid content. Rubber components: Natural rubber: "HA LATEX" manufactured by Resitex Co., Ltd. Modified natural rubber: "MG-40S" manufactured by Resitex Co., Ltd., a graft copolymer of natural rubber and methyl methacrylate, natural rubber component content 70% by mass SBR-1 (styrene-butadiene rubber 1): "T-093A" manufactured by JSR Corporation SBR-2 (styrene-butadiene rubber 2): "0533" manufactured by JSR Corporation SBR-3 (styrene-butadiene rubber 3): "KT-4615B" manufactured by E-TEC Co., Ltd.

[0061] (Meth)acrylic polymer: A-1: ​​"E277" manufactured by Toyochem Co., Ltd., 100% content of structural units derived from methyl (meth)acrylate (alkyl group carbon number: 1), glass transition temperature: 91 ° C. A-2: "AE162" manufactured by E-Tech Co., Ltd., 100% content of structural units derived from alkyl (meth)acrylate, glass transition temperature: 92 ° C. A-3: "AE703" manufactured by E-Tech Co., Ltd., 100% content of structural units derived from alkyl (meth)acrylate, glass transition temperature: 54 ° C. A-4: "TOCRYL (registered trademark) BCX-8104" manufactured by artience Co., Ltd., 100% content of structural units derived from alkyl (meth)acrylate, glass transition temperature: 29 ° C.

[0062] Tackifier: Petroleum resin-1: "AP-1100" manufactured by Arakawa Chemical Industries, Ltd., glass transition temperature 60°C Petroleum resin-2: "AP-2100" manufactured by Arakawa Chemical Industries, Ltd., glass transition temperature 50°C Terpene-phenol resin: "E200" manufactured by Arakawa Chemical Industries, Ltd., glass transition temperature 98°C

[0063] <Adhesion strength (normal, to SUS)> Using a SUS plate as the test plate, measurement was performed in an environment of 23° C. according to a method conforming to JIS Z0237: 2000. For the measurement, a tabletop precision universal testing machine ("Autograph (registered trademark) AGS-1kNX" manufactured by Shimadzu Corporation) was used, and the average value of measurements taken multiple times (n=5) was calculated.

[0064] <Adhesive Strength (Normal Condition, Against SUS, After Storage at 60° C. for 10 Days)> After storing the pressure-sensitive adhesive tape in an atmosphere at 60° C. for 10 days, the adhesive strength was measured in the same manner as described above.

[0065] <Storage modulus of adhesive layer> 0.1 g of the rubber-based adhesive layer was scraped off from the adhesive tape and formed into a sheet with a thickness of 1 mm to prepare a sample for measuring storage modulus. This sample was measured using a dynamic modulus measuring device ("ARES" manufactured by TA Instruments Japan Co., Ltd.) under the following conditions: Measurement start temperature: -60°C Measurement end temperature: 120°C Heating rate: 4°C / min Frequency: 1 Hz

[0066] <Wire Winding Properties> Ten heat-resistant automotive wires ("AVX050" manufactured by Sumitomo Wiring Systems, Ltd.) cut to a length of 800 mm and four heat-resistant automotive wires ("AVX085" manufactured by Sumitomo Wiring Systems, Ltd.) cut to a length of 800 mm were prepared. These 14 wires were bundled together and both longitudinal ends were secured together with adhesive tape to facilitate winding. Then, the adhesive tape (19 mm wide) of each Example or Comparative Example was wrapped around the wires in a half-wrap manner with the adhesive layer facing inward to prepare an evaluation sample. Here, "half-wrap winding" refers to wrapping the adhesive tape around the wire so that half of the width of the adhesive tape overlaps half of the width of the already-wrapped adhesive tape. Each evaluation sample was evaluated according to the following criteria. A: No peeling was observed. B: Minor peeling (peel distance from the end less than 1.0 mm) was observed. C: Peeling was observed (peel distance from the end was 1.0 mm or more).

[0067] <Low-temperature adhesion> A test was conducted in the same manner as in the "wire winding property" above, except that the test environment was -10°C. Each evaluation sample was evaluated according to the following criteria. A: No peeling was observed. B: Minor peeling was observed (peel distance from the end less than 1.0 mm). C: Peeling was observed (peel distance from the end 1.0 mm or more).

[0068] <Long-term storage stability> After storing the adhesive tape in an atmosphere of 40°C for 100 days, a test was conducted in the same manner as in the "wire winding property" described above. Each evaluation sample was evaluated according to the following criteria. (Sticky side) A: No stickiness on the side of the tape that interfered with work. B: Slight stickiness on the side of the tape that interfered with work. C: Stickiness on the side of the tape that interfered with work. (Peeling) A: No peeling was observed. B: Minor peeling (peeling distance from the end less than 1.0 mm) was observed. C: Peeling (peeling distance from the end 1.0 mm or more) was observed.

[0069]

[0070]

[0071]

[0072] From the results in Tables 1 and 2, it can be seen that the Examples according to the present invention were pressure-sensitive adhesive tapes that were excellent in low-temperature adhesion and long-term storage stability, and were resistant to peeling and stickiness over long periods of time, and had high adhesive strength in low-temperature environments. On the other hand, from the results in Table 3, it can be seen that the Comparative Examples that did not satisfy the configuration of the present invention were inferior in at least one of low-temperature adhesion and long-term storage stability.

Claims

1. An adhesive tape comprising a substrate layer containing polyvinyl chloride resin and a rubber-based adhesive layer provided on at least one surface of the substrate layer, wherein the rubber-based adhesive layer contains 25 to 45 mass% of a rubber component, 5 to 25 mass% of a (meth)acrylic polymer, and 40 to 60 mass% of a tackifier, the rubber component being at least one selected from the group consisting of natural rubber, modified natural rubber, and styrene-butadiene rubber, and the glass transition temperature of the (meth)acrylic polymer being 45°C or higher.

2. The adhesive tape according to claim 1, wherein the content of structural units derived from alkyl (meth)acrylate is 60% by mass or more out of a total of 100% by mass of monomer units constituting the (meth)acrylic polymer.

3. The adhesive tape according to claim 1, wherein the modified natural rubber is a graft copolymer of natural rubber and alkyl (meth)acrylate.

4. The adhesive tape according to claim 1, wherein the tackifier contains a petroleum resin.

5. The adhesive tape according to claim 1, wherein the rubber-based adhesive layer has a storage modulus at 23°C of 0.25 to 0.45 MPa.

6. The adhesive tape according to claim 1, wherein the thickness of the rubber-based adhesive layer is 10 to 40 μm.

7. The adhesive tape according to claim 1, wherein the adhesive strength of the adhesive tape measured at 23°C according to a method in accordance with JIS Z0237:2000 is 1.8 to 4.0 N / 10 mm.

8. The adhesive tape according to any one of claims 1 to 7, which is used for bundling electrical wires.

9. A method for producing an adhesive tape according to any one of claims 1 to 7, comprising an adhesive layer forming step of forming the rubber-based adhesive layer on at least one surface of the base layer, the adhesive layer forming step comprising applying an aqueous latex containing a rubber-based adhesive composition to at least one surface of the base layer.

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