Adhesive tape and method for manufacturing adhesive tape

Abstract

The present invention provides: an adhesive tape in which anchoring fractures are suppressed; and a method for manufacturing the same. An adhesive tape according to an embodiment of the present invention includes, in the following order: a base material containing an olefin resin; a first adhesive agent layer containing an olefin resin; and a second adhesive agent layer containing a styrene elastomer. A method for manufacturing an adhesive tape according to an embodiment of the present invention is a method for manufacturing an adhesive tape which includes, in the following order: a base material containing an olefin resin; a first adhesive agent layer containing an olefin resin; and a second adhesive agent layer containing a styrene elastomer. Said method includes: hot-melt application, to the base material, of an adhesive agent composition which forms the first adhesive agent layer; and hot-melt application, to the first adhesive agent layer, of an adhesive agent composition which forms the second adhesive agent layer.

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] Packaging containers such as bags are known that have a fastener attached to the opening so that the bag can be resealed after removing part of the contents, such as food or detergent. The process of attaching a fastener to a bag is complicated and increases manufacturing costs, so alternative bags with a resealable function have been studied. As an example of a bag with a resealable function, a bag with a resealable portion has been proposed (for example, Patent Document 1).

[0003] Another known method is to use adhesive tape to secure the opening of a packaging container so that it does not open when the container is resealed. The adhesive tape used for resealing is required to be both resealable and easy to open. However, even if the adhesive tape has suitable adhesive properties at the time of manufacture, its adhesive strength increases over time, which may damage the packaging container when it is opened. Furthermore, when the container is reopened, the adhesive tape may lose its anchorage, making it difficult to reuse the adhesive tape.

[0004] JP 2014-15244 A

[0005] The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a pressure-sensitive adhesive tape that is inhibited from causing anchor failure.

[0006] A pressure-sensitive adhesive tape according to an embodiment of the present invention comprises, in this order, a substrate containing an olefin-based resin, a first pressure-sensitive adhesive layer containing an olefin-based resin, and a second pressure-sensitive adhesive layer containing a styrene-based elastomer. In one embodiment, the olefin-based resin contained in the substrate comprises a propylene-based resin. In one embodiment, the propylene-based resin content in the olefin-based resin contained in the substrate is 40% by weight to 100% by weight. In one embodiment, the first pressure-sensitive adhesive layer has a thickness of 5 μm to 30 μm. In one embodiment, the second pressure-sensitive adhesive layer has a thickness of 5 μm to 50 μm. In one embodiment, a release treatment is performed on the surface of the substrate on which the first pressure-sensitive adhesive layer is not formed. In one embodiment, the olefin-based resin contained in the first pressure-sensitive adhesive layer comprises a propylene-based resin. In one embodiment, the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer further comprises a tackifier, and the content of the tackifier is 20% by weight to 60% by weight. In one embodiment, the second pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition including a styrene-isoprene block copolymer, an olefin-based elastomer, and a tackifier. In one embodiment, the styrene-isoprene block copolymer has a styrene content of 10% by weight to 25% by weight. In one embodiment, the styrene-isoprene block copolymer includes a diblock copolymer. In one embodiment, the tackifier content is 2% by weight to 40% by weight. In one embodiment, the tackifier includes a hydrogenated petroleum resin. In one embodiment, the pressure-sensitive adhesive composition forming the second pressure-sensitive adhesive layer further includes an oil. In one embodiment, the oil content is 5% by weight to 30% by weight. In one embodiment, the adhesive strength of the second pressure-sensitive adhesive layer to a stainless steel plate is 0.05 N / 25 mm to 15 N / 25 mm. In one embodiment, the difference in melt viscosity at 160°C between the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition forming the second pressure-sensitive adhesive layer is 50,000 mPa s or less.In one embodiment, the second pressure-sensitive adhesive layer has at least two portions with different adhesive strengths, including a strong adhesive portion and a weak adhesive portion. In one embodiment, the difference in adhesive strength between the strong adhesive portion and the weak adhesive portion to a stainless steel plate is 1 N / 25 mm to 10 N / 25 mm. In another aspect of the present invention, there is provided a method for producing a pressure-sensitive adhesive tape having, in this order, a substrate containing an olefin-based resin, a first pressure-sensitive adhesive layer containing an olefin-based resin, and a second pressure-sensitive adhesive layer containing a styrene-based elastomer. This production method includes hot-melt coating a pressure-sensitive adhesive composition that forms the first pressure-sensitive adhesive layer onto the substrate, and hot-melt coating a pressure-sensitive adhesive composition that forms the second pressure-sensitive adhesive layer onto the first pressure-sensitive adhesive layer. In one embodiment, the production method includes simultaneously hot-melt coating the pressure-sensitive adhesive composition that forms the first pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition that forms the second pressure-sensitive adhesive layer. In one embodiment, the second adhesive layer has at least two portions with different adhesive strengths, including a strong adhesive portion and a weak adhesive portion, and the method comprises pattern-coating an adhesive composition that forms each portion.

[0007] According to an embodiment of the present invention, an adhesive tape in which anchor failure is suppressed can be provided. Therefore, an adhesive tape having an adhesive layer with high adhesive strength can be provided. Furthermore, even in the case of an adhesive tape having an adhesive layer whose adhesive strength may increase during storage, anchor failure during peeling can be suppressed. Therefore, the adhesive tape can be suitably used in applications in which application and peeling are repeated.

[0008] It is a schematic cross-sectional view of an adhesive tape according to one embodiment of the present invention. It is a schematic cross-sectional view of an adhesive tape according to another embodiment of the present invention. It is a schematic cross-sectional view of an adhesive tape according to yet another embodiment of the present invention. It is a schematic cross-sectional view showing a usage mode of the adhesive tape shown in FIG.

[0009] A. Overall Configuration of the Pressure-Sensitive Adhesive Tape The pressure-sensitive adhesive tape of an embodiment of the present invention has, in this order, a substrate containing an olefin-based resin, a first pressure-sensitive adhesive layer containing an olefin-based resin (hereinafter also referred to as an olefin-based pressure-sensitive adhesive layer), and a second pressure-sensitive adhesive layer containing a styrene-based elastomer (hereinafter also referred to as a styrene-based pressure-sensitive adhesive layer). By having the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer in this order, a pressure-sensitive adhesive tape with excellent storage stability and suppressed anchor failure can be provided. Pressure-sensitive adhesive tapes having a pressure-sensitive adhesive layer containing a styrene-based elastomer increase their adhesive strength during storage, which can result in anchor failure between the substrate and the pressure-sensitive adhesive layer. The pressure-sensitive adhesive tape of an embodiment of the present invention has a pressure-sensitive adhesive layer containing an olefin-based resin between a substrate containing an olefin-based resin and a pressure-sensitive adhesive layer containing a styrene-based elastomer. With this configuration, anchor failure between the substrate and the pressure-sensitive adhesive layer upon peeling can be suppressed even when stored in a state where the tape is attached to an adherend. Therefore, the pressure-sensitive adhesive tape may be reapplied and used. Therefore, it can be suitably used as a resealing sealant that is repeatedly sealed and unsealed.

[0010] The first and second pressure-sensitive adhesive layers may be formed over the entire surface of one side of the substrate, or may be formed over only a portion of the substrate. Fig. 1A is a schematic cross-sectional view of a pressure-sensitive adhesive tape according to one embodiment of the present invention. The pressure-sensitive adhesive tape 100 shown in Fig. 1A has a substrate 10, a first pressure-sensitive adhesive layer 20 containing an olefin-based resin, and a second pressure-sensitive adhesive layer 30 containing a styrene-based elastomer. In the illustrated example, the first pressure-sensitive adhesive layer 20 and the second pressure-sensitive adhesive layer 30 are formed over a portion of the substrate. Extensions extending in the planar direction from the first pressure-sensitive adhesive layer 20 and the second pressure-sensitive adhesive layer 30 of the substrate 10 can serve as handles when using the pressure-sensitive adhesive tape 100.

[0011] In one embodiment, the second adhesive layer of the pressure-sensitive adhesive tape has at least two portions with different adhesive strengths, including a strong adhesive portion and a weak adhesive portion. The pressure-sensitive adhesive tape of the present invention can suppress anchor failure even when portions with different adhesive strengths are provided in the second adhesive layer that comes into contact with the adherend. Therefore, for example, the pressure-sensitive adhesive tape can have a portion whose adhesive strength is adjusted to match the surface characteristics of the portion to be applied to the adherend. In one embodiment, the pressure-sensitive adhesive tape has a strong adhesive portion with higher adhesive strength and a weak adhesive portion with lower adhesive strength than the strong adhesive portion. The pressure-sensitive adhesive tape 101 shown in FIG. 1B has a substrate 10, a first adhesive layer 20, a strong adhesive portion 31, and a weak adhesive portion 32. In the illustrated example, one strong adhesive portion and one weak adhesive portion are formed, but two or more strong adhesive portions and / or two or more weak adhesive portions may be formed depending on the application. The second adhesive layer may also be formed using three or more adhesive compositions with different adhesive strengths. The strong adhesive portion and the weak adhesive portion may be formed continuously on the substrate, or may be formed with any appropriate gap therebetween. The adhesive tape 102 shown in FIG. 1C has a substrate 10, a first adhesive layer 20, a strong adhesive portion 31, and a weak adhesive portion 32. In this illustrated example, the adhesive tape 102 has a gap between the strong adhesive portion 31 and the weak adhesive portion 32. This configuration allows for an adhesive tape in which the adhesive layer is formed only in the necessary portion to match the attachment portion of the adherend. The strong adhesive portion and the weak adhesive portion may also be patterned. For example, they may be arranged in a striped pattern, a checkerboard pattern, or a dot pattern. A typical example is a striped pattern in which the strong adhesive portion and the weak adhesive portion are alternately arranged. In the illustrated example, the first adhesive layer 20 is formed only between the strong adhesive portion 31, the weak adhesive portion 32, and the substrate 10, but the first adhesive layer 20 may also be formed in the gap portion. In practice, a release liner is temporarily and releasably attached to the adhesive layer until use.

[0012] The thickness of the olefin-based pressure-sensitive adhesive layer is preferably 5 μm to 30 μm. The thickness of the olefin-based pressure-sensitive adhesive layer is more preferably 10 μm or more, and even more preferably 15 μm or more. Furthermore, the thickness of the olefin-based pressure-sensitive adhesive layer is more preferably 25 μm or less, and even more preferably 20 μm or less. By ensuring that the thickness of the olefin-based pressure-sensitive adhesive layer is within the above range, it is possible to provide a pressure-sensitive adhesive tape in which anchor failure is suppressed even when the adhesive strength of the second pressure-sensitive adhesive layer is high.

[0013] The thickness of the styrene-based pressure-sensitive adhesive layer is preferably 5 μm to 50 μm. The thickness of the styrene-based pressure-sensitive adhesive layer is more preferably 10 μm or more, and even more preferably 15 μm or more. The thickness of the styrene-based pressure-sensitive adhesive layer is more preferably 40 μm or less, even more preferably 30 μm or less, still more preferably 25 μm or less, and particularly preferably 20 μm or less. When the thickness of the styrene-based pressure-sensitive adhesive layer is within the above range, it can exhibit appropriate adhesiveness to the adherend.

[0014] The adhesive strength of the styrene-based pressure-sensitive adhesive layer to a stainless steel plate (i.e., the adhesive strength of the pressure-sensitive adhesive tape) is preferably 0.05 N / 25 mm to 15 N / 25 mm. The adhesive strength of the styrene-based pressure-sensitive adhesive layer is more preferably 10 N / 25 mm or less, even more preferably 6 N / 25 mm or less, and particularly preferably 4 N / 25 mm or less. The adhesive strength of the styrene-based pressure-sensitive adhesive layer to a stainless steel plate is more preferably 0.1 N / 25 mm or more, even more preferably 0.2 N / 25 mm or more, even more preferably 0.3 N / 25 mm or more, even more preferably 0.5 N / 25 mm or more, even more preferably 1 N / 25 mm or more, particularly preferably 2 N / 25 mm or more, and most preferably 3 N / 25 mm or more. By having the adhesive strength to a stainless steel plate in the above range, appropriate adhesive strength to the adherend can be exerted. In this specification, the adhesive strength to a stainless steel plate refers to the value measured in a 90° peel test at a peel rate of 300 mm / min against a SUS plate. Generally, the adhesive strength of an adhesive tape is determined by the width of the tape used as a sample. Therefore, the adhesive strength can be calculated appropriately based on the width of the adhesive tape.

[0015] The difference in melt viscosity at 160°C between the pressure-sensitive adhesive composition forming the olefin-based pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition forming the styrene-based pressure-sensitive adhesive layer is preferably 50,000 mPa·s or less, more preferably 40,000 mPa·s or less, even more preferably 30,000 mPa·s or less, particularly preferably 20,000 mPa·s or less, and most preferably 10,000 mPa·s or less. The smaller the difference in melt viscosity at 160°C between the pressure-sensitive adhesive composition forming the olefin-based pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition forming the styrene-based pressure-sensitive adhesive layer, the more preferable it is, for example, 0 mPa·s or more, preferably 0 mPa·s to 5,000 mPa·s. When the difference in melt viscosity at 160°C between the pressure-sensitive adhesive composition forming the olefin-based pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition forming the styrene-based pressure-sensitive adhesive layer is within the above range, it may be possible to simultaneously form the olefin-based pressure-sensitive adhesive layer and the styrene-based pressure-sensitive adhesive layer by simultaneous hot-melt coating. In this specification, the melt viscosity at 160°C refers to the melt viscosity measured at 160°C using a viscometer (for example, Model: DVE Viscometer, spindle: LV, manufactured by Brookfield).

[0016] When the second pressure-sensitive adhesive layer has at least two portions with different adhesive strengths, the difference in adhesive strength between the portions can be set to any appropriate value depending on the application, etc. The difference in adhesive strength to a stainless steel plate between the portions with different adhesive strengths is preferably 1 N / 25 mm to 10 N / 25 mm. The difference in adhesive strength between the portions with different adhesive strengths is more preferably 1.5 N / 25 mm or more, even more preferably 2 N / 25 mm or more, even more preferably 2.5 N / 25 mm or more, even more preferably 3 N / 25 mm or more, particularly preferably 4 N / 25 mm or more, and most preferably 4.5 N / 25 mm or more. Furthermore, the difference in adhesive strength to a stainless steel plate between the portions with different adhesive strengths is more preferably 9 N / 25 mm or less, even more preferably 8 N / 25 mm or less. By having the difference in adhesive strength within the above range, a pressure-sensitive adhesive tape with easy-open properties can be provided. The adhesive strength to a stainless steel plate is as described above.

[0017] The adhesive tape (total thickness) can be set to any appropriate thickness. For example, it is 20 μm to 200 μm, preferably 30 μm to 150 μm, and more preferably 40 μm to 130 μm. If the thickness of the adhesive tape is within the above range, it can be suitably used for various applications.

[0018] Each component will be described in detail below.

[0019] B. Substrate The substrate is a resin substrate containing an olefin-based resin. Any appropriate olefin-based resin can be used as the olefin-based resin. Specific examples include homopolymers and copolymers of two or more olefins. The olefin is preferably an olefin having 2 to 20 carbon atoms. Examples of such α-olefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 4-methyl-1-pentene. Propylene-based resins are preferably used because they can provide adhesive tape with properties such as breaking strength and resistance to elongation, are low cost, and can be supplied stably. The propylene-based resin may be homopolypropylene, block polypropylene, or random polypropylene. Only one type of olefin-based resin may be used, or two or more types may be used in combination.

[0020] The content of the propylene resin in the olefin resin is preferably 40% by weight to 100% by weight. The content of the propylene resin in the olefin resin is more preferably 50% by weight or more, even more preferably 80% by weight or more, particularly preferably 85% by weight or more, and most preferably 90% by weight or more. In one embodiment, the content of the propylene resin is more preferably 95% by weight or less, even more preferably 90% by weight or less. When the content of the propylene resin is in the above range, it is possible to provide a pressure-sensitive adhesive tape having physical properties suitable for a pressure-sensitive adhesive tape, such as breaking strength and resistance to elongation. In yet another embodiment of the present invention, the content of the propylene resin is preferably 90% by weight to 100% by weight. When the content of the propylene resin is in the above range, anchor failure of the pressure-sensitive adhesive tape can be further suppressed.

[0021] The substrate may contain any appropriate resin other than an olefin-based resin. Examples of resins other than an olefin-based resin include synthetic rubber-based resins such as styrene-isoprene block copolymer (SIS) and styrene-butadiene block copolymer (SBS), polyester-based resins such as polyethylene terephthalate (PET), and polyamide-based resins. These resins are used in an amount of less than 50% by weight relative to 100% by weight of the resin contained in the substrate.

[0022] The substrate may contain any other appropriate components in addition to the resin. Examples of such additives include antioxidants, ultraviolet absorbers, light stabilizers, fluorescent agents, colorants, etc. These additives can be used in any appropriate amount.

[0023] The substrate may be subjected to a surface treatment such as corona discharge treatment on the surface on which the adhesive layer is formed. The surface of the substrate opposite to the surface on which the adhesive layer is formed may also be subjected to a release treatment. By performing the release treatment, it is possible to prevent the substrate and the adhesive layer from sticking together when the adhesive tapes are stacked, and it may be possible to store the adhesive tape in a roll form. The release treatment can be performed by any appropriate method. For example, it can be performed by applying a silicone-based release agent.

[0024] The thickness of the substrate can be set to any appropriate thickness, for example, 10 μm to 100 μm, preferably 20 μm to 90 μm, and more preferably 30 μm to 80 μm.

[0025] C. First Pressure-Sensitive Adhesive Layer The first pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing an olefin-based resin. The pressure-sensitive adhesive composition containing an olefin-based resin is a hot-melt pressure-sensitive adhesive. The pressure-sensitive adhesive composition containing an olefin-based resin contains an olefin-based resin and a tackifier.

[0026] C-1. Olefin-Based Resin Any appropriate olefin-based resin can be used as the olefin-based resin. Preferred examples of the olefin-based resin include homopolymers of α-olefins and copolymers of two or more types of α-olefins. Preferred α-olefins are α-olefins having 2 to 20 carbon atoms. Examples of such α-olefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 4-methyl-1-pentene. Preferably, an olefin-based resin containing propylene as the α-olefin is used.

[0027] In one embodiment, the propylene-containing olefin-based resin preferably has a propylene ratio of 40% by weight or more, more preferably 50% by weight or more, even more preferably 75% by weight or more, and particularly preferably 85% by weight or more. The propylene ratio of the propylene-containing olefin-based resin is most preferably 85% by weight to 100% by weight. The propylene ratio of the olefin-based resin may be 100% by weight, i.e., a propylene homopolymer. When the propylene ratio is within the above range, the adhesion between the substrate and the first pressure-sensitive adhesive layer can be further improved. Furthermore, for example, when a propylene-based resin is used as the substrate, the effect of improving adhesion can be further exerted. In this specification, the propylene ratio refers to the content ratio of propylene units in the structural units contained in the copolymer.

[0028] In one embodiment, the olefin resin used in the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer preferably has a low melting point. For example, the melting point of the olefin resin is, for example, 120°C or lower, preferably 110°C or lower. In this specification, the melting point refers to the temperature of the maximum endothermic peak obtained by differential scanning calorimetry (DSC). In one embodiment, the olefin resin used in the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer preferably has a low weight-average molecular weight. For example, an olefin resin having a weight-average molecular weight of 10,000 to 500,000 is used as the olefin resin. In one embodiment, the olefin resin used in the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer preferably has a low density. For example, the density of the olefin resin is 0.90 g / cm ３ The following is the result.

[0029] The content of the olefin resin in the olefin-based pressure-sensitive adhesive composition is preferably 20% by weight to 70% by weight, more preferably 25% by weight to 65% by weight, even more preferably 30% by weight to 60% by weight, and particularly preferably 40% by weight to 60% by weight.

[0030] Commercially available olefin resins may be used, such as some of the "Rextac" (registered trademark) series manufactured by REXTAC, LLC (e.g., REXTAC RT 2788, REXTAC RT 2730, etc.) and some of the "VISTAMAX" series manufactured by ExxonMobil Corporation (e.g., VISTAMAX 8780, VISTAMAX 8380, etc.).

[0031] C-2. Tackifier Any appropriate resin can be used as the tackifier. Specific examples include natural resins such as terpene resins and rosin resins, and synthetic resins such as petroleum resins, hydrogenated petroleum resins, styrene resins, coumarone-indene resins, phenolic resins, and xylene resins. Examples of petroleum resins include aliphatic petroleum resins, alicyclic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins of an alicyclic component and an aromatic component, and copolymerized petroleum resins of an alicyclic component and an aliphatic component. Hydrogenated petroleum resins are preferably used. The use of hydrogenated petroleum resins improves compatibility with olefin resins, thereby improving the heat stability of the hot-melt pressure-sensitive adhesive composition. Only one tackifier may be used, or two or more tackifiers may be used in combination.

[0032] The tackifier content in 100 wt% of the olefin-based pressure-sensitive adhesive composition is preferably 2 wt% to 60 wt%. The olefin-based pressure-sensitive adhesive composition more preferably contains 50 wt% or less of the tackifier, even more preferably 45 wt% or less, and particularly preferably 40 wt% or less. A tackifier content within the above range can provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer with sufficient initial adhesive strength. A tackifier content greater than 60 wt% may leave adhesive residue on the adherend. Furthermore, the adherend may be damaged during peeling. Furthermore, the hot-melt pressure-sensitive adhesive composition preferably contains 25 wt% or more of the tackifier, more preferably 30 wt% or more, and even more preferably 35 wt% or more. A tackifier content within the above range can provide a hot-melt pressure-sensitive adhesive composition with adequate adhesive strength to the adherend. In one embodiment, the tackifier content in 100 wt% of the olefin-based pressure-sensitive adhesive composition is preferably 35 wt% to 45 wt%.

[0033] C-3. Other Components The hot-melt pressure-sensitive adhesive of the present invention may contain any appropriate other components as long as the effects of the present invention are not impaired. Examples of such other components include liquid paraffin, antioxidants, UV absorbers, light stabilizers, fluorescent agents, colorants, and the like. Such other components may be used alone or in combination of two or more. The content of the other components is such that the content of the olefin resin and the content of the tackifier fall within the above-mentioned ranges.

[0034] D. Second PSA Layer The second PSA layer is formed from a PSA composition containing a styrene-based elastomer. The PSA composition containing a styrene-based elastomer is a hot melt PSA. The PSA composition containing a styrene-based elastomer contains a styrene-based elastomer and a tackifier.

[0035] In one embodiment, the storage modulus G' at 25°C of the second pressure-sensitive adhesive layer (substantially a pressure-sensitive adhesive composition containing a styrene-based elastomer) is preferably 0.2 MPa or less, more preferably 0.15 MPa or less, even more preferably 0.12 MPa or less, and particularly preferably 0.1 MPa or less. When the storage modulus G' at 25°C is within the above range, a pressure-sensitive adhesive composition with even better adhesiveness can be obtained. The storage modulus G' at 25°C is preferably 0.01 MPa or more. The storage modulus of the second pressure-sensitive adhesive layer may be set to any appropriate value depending on the adherend of the pressure-sensitive adhesive tape. In one embodiment, the storage modulus of the second pressure-sensitive adhesive layer is preferably 0.12 MPa to 0.16 MPa, and in another embodiment, preferably 0.05 MPa to 0.08 MPa. The storage modulus G' (25°C) of the pressure-sensitive adhesive layer can be determined by dynamic viscoelasticity measurement. Specifically, a disk-shaped sample having a thickness of approximately 1 mm and a diameter of 7.9 mm is prepared by any appropriate method using the pressure-sensitive adhesive layer to be measured (or the pressure-sensitive adhesive sheet in the case of a substrate-less pressure-sensitive adhesive sheet). This sample is sandwiched and fixed between parallel plates, and dynamic viscoelasticity measurement is performed using a viscoelasticity tester (for example, manufactured by TA Instruments, product name: DISCOVERY HR-3 HYBRID RHEOMETER or an equivalent) under the following conditions, whereby the storage modulus G' (25°C) can be determined. Measurement mode: shear mode Temperature range: -40°C to 120°C Heating rate: 3°C / min Measurement frequency: 1.6 Hz

[0036] D-1. Styrene-based elastomer The hot melt pressure-sensitive adhesive composition preferably contains 2 wt% to 80 wt% of a styrene-based elastomer relative to 100 wt% of the hot melt pressure-sensitive adhesive composition. The styrene-based pressure-sensitive adhesive composition more preferably contains 10 wt% to 75 wt%, even more preferably 20 wt% to 70 wt%, particularly preferably 30 wt% to 65 wt%, and most preferably 40 wt% to 60 wt% of a styrene-based elastomer. By ensuring that the content of the styrene-based elastomer is within the above range, a pressure-sensitive adhesive composition with sufficient initial adhesive strength can be provided.

[0037] The styrene content of the styrene elastomer can be set to any appropriate value. The styrene content of the styrene elastomer is preferably 10% by weight or more, more preferably 12% by weight or more, and even more preferably 14% by weight or more. If the styrene content of the styrene elastomer is less than 10% by weight, the initial adhesive strength may be excessively high, and adhesive residue may occur upon peeling. The styrene content of the styrene elastomer is preferably 25% by weight or less, more preferably 20% by weight or less, and even more preferably 18% by weight or less. If the styrene content of the styrene elastomer exceeds 25% by weight, the adhesive strength may become too high over time.

[0038] The melt flow rate (MFR) of the styrene elastomer is preferably 5 g / 10 min to 40 g / 10 min, more preferably 10 g / 10 min to 30 g / 10 min, and even more preferably 20 g / 10 min to 30 g / 10 min. Having an MFR within the above range improves the coatability of the hot-melt PSA composition, enabling a good PSA layer to be formed by hot-melt coating, as described below. In this specification, MFR refers to a value measured at 200°C and 5 kg using the method specified in ISO 1133.

[0039] Any appropriate elastomer can be used as the styrene-based elastomer. Examples include styrene-isoprene block copolymer (SIS), styrene-butadiene block copolymer (SBS), styrene-ethylenebutylene block copolymer (SEBS), styrene-ethylenepropylene block copolymer (SEPS), styrene-ethyleneethylenepropylene block copolymer (SEEPS), and styrene-butadiene-butene-styrene block copolymer (SBBS). These may be used alone or in combination of two or more. Preferably, styrene-isoprene block copolymer (hereinafter also referred to as SIS) can be used.

[0040] The SIS preferably contains a diblock copolymer, which makes it possible to adjust the initial adhesive strength to an appropriate value and also improve the wettability of the pressure-sensitive adhesive composition.

[0041] The content of the SIS diblock copolymer in the SIS is preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 30% by weight or more. By having the content of the SIS diblock copolymer in the above range, the initial adhesive strength can be adjusted to an appropriate value, and the wettability of the pressure-sensitive adhesive composition can also be improved. The content of the SIS diblock copolymer in the SIS is preferably 80% by weight or less, more preferably 50% by weight or less, even more preferably 40% by weight or less, and particularly preferably 35% by weight or less. When the content of the SIS diblock copolymer is within the above range, adhesive residue on the adherend can be prevented.

[0042] D-2. Tackifiers PSA compositions containing styrene-based elastomers preferably contain 2 wt% to 40 wt% of a tackifier. PSA compositions containing styrene-based elastomers more preferably contain 30 wt% or less of a tackifier, even more preferably 20 wt% or less, particularly preferably 10 wt% or less, and most preferably 8 wt% or less. A tackifier content within the above range can provide a PSA composition capable of forming a PSA layer with sufficient initial adhesive strength. A tackifier content greater than 40 wt% can leave adhesive residue on the adherend. Furthermore, the adherend can be damaged during peeling. PSA compositions containing styrene-based elastomers preferably contain 4 wt% or more of a tackifier, more preferably 6 wt% or more. A tackifier content within the above range can provide a hot-melt PSA composition with adequate adhesive strength to the adherend.

[0043] Any appropriate resin can be used as the tackifier. Specific examples include natural resins such as terpene resins and rosin resins, as well as synthetic resins such as petroleum resins, hydrogenated petroleum resins, styrene resins, coumarone-indene resins, phenolic resins, and xylene resins. Examples of petroleum resins include aliphatic petroleum resins, alicyclic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins of an alicyclic component and an aromatic component, and copolymerized petroleum resins of an alicyclic component and an aliphatic component. Hydrogenated petroleum resins are preferably used. The use of hydrogenated petroleum resins improves compatibility with styrene elastomers and olefin elastomers, thereby improving the heat stability of the hot-melt pressure-sensitive adhesive composition. Only one tackifier may be used, or two or more tackifiers may be used in combination.

[0044] In one embodiment, the PSA composition contains a tackifier having a softening point of less than 90°C (hereinafter referred to as a tackifier Ｕ９０ It is preferable that the tackifier contains a tackifier. Ｕ９０ By using the tackifier, the adhesive strength of the adhesive composition can be improved. Ｕ９０ The softening point of the tackifier may be room temperature or lower. Ｕ９０ The tackifiers may be used alone or in combination of two or more. Preferably, two or more tackifiers are used. Ｕ９０ Two or more tackifiers are used in combination. Ｕ９０ By using these in combination, the adhesive strength of the pressure-sensitive adhesive composition can be further improved.

[0045] The softening point of a tackifier is defined as a value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at the lowest possible temperature and carefully filled into a ring placed on a flat metal plate, avoiding the formation of bubbles. After cooling, the raised portion of the ring, including the top edge, is cut off with a slightly heated knife. Next, a holder (ring stand) is placed in a glass container (heating bath) with a diameter of at least 85 mm and a height of at least 127 mm, and glycerin is poured into it to a depth of at least 90 mm. Next, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in the glycerin without touching each other, and the glycerin temperature is maintained at 20°C ± 5°C for 15 minutes. Next, the steel ball is placed in the center of the surface of the sample in the ring and placed in its fixed position on the holder. Next, keeping the distance from the top of the ring to the glycerin surface at 50 mm, place a thermometer, align the center of the thermometer's mercury bulb with the center of the ring, and heat the container. The flame of the Bunsen burner used for heating should be aimed midway between the center of the bottom and the edge of the container, ensuring even heating. After heating begins and reaching 40°C, the rate of increase in bath temperature must be 5.0 ± 0.5°C per minute. The sample gradually softens, flows down the ring, and finally touches the bottom plate, at which point the temperature is read and considered the softening point. Two or more samples should be measured at the same time, and the average value should be used.

[0046] tackifier Ｕ９０ As the tackifier, among the tackifiers exemplified above, those having a softening point of less than 90°C can be used. Ｕ９０ Preferably, the resin comprises a hydrocarbon-based resin.

[0047] tackifier Ｕ９０Examples of hydrocarbon resins that can be preferably used as the binder include various hydrocarbon resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (such as styrene-olefin copolymers), aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins. Hydrogenated hydrocarbon resins are more preferred. Only one type of hydrocarbon resin may be used, or two or more types may be used in combination.

[0048] tackifier Ｕ９０ The tackifier may contain another tackifier in addition to the hydrocarbon resin. As the other tackifier, any appropriate tackifier having a softening point of less than 90°C may be used from among the tackifiers exemplified above. One type of the other tackifier may be used, or two or more types may be used in combination. Tackifier Ｕ９０ may contain, for example, a hydrocarbon resin and a terpene resin.

[0049] The tackifier may be two or more types of tackifiers. Ｕ９０ and at least one tackifier having a softening point of 90° C. or higher. When the PSA composition further contains a tackifier having a softening point of 90° C. or higher, the cohesive strength of the PSA composition can be improved.

[0050] As the tackifier having a softening point of 90°C or higher, any appropriate tackifier can be selected from the tackifiers exemplified above that have a softening point of 90°C or higher. One type of tackifier having a softening point of 90°C or higher may be used, or two or more types may be used in combination. The tackifier having a softening point of 90°C or higher may include at least one selected from a hydrocarbon resin and a terpene tackifying resin (for example, a terpene phenol resin).

[0051] Two or more tackifiers Ｕ９０When using at least one tackifier having a softening point of 90°C or higher, the total content of the tackifiers relative to 100 parts by weight of the adhesive composition is preferably 30 parts by weight or higher, more preferably 35 parts by weight or higher, even more preferably 40 parts by weight or higher, and particularly preferably 45 parts by weight or higher. If the total content of these tackifiers relative to the adhesive composition is within the above range, an adhesive composition with higher adhesive strength can be prepared. The total content of the tackifiers relative to 100 parts by weight of the adhesive composition is preferably 70 parts by weight or lower, more preferably 65 parts by weight or lower, and even more preferably 60 parts by weight or lower.

[0052] Two or more tackifiers Ｕ９０ and at least one tackifier having a softening point of 90°C or higher, the proportion of the tackifier in the total content of the tackifiers Ｕ９０ The total content of the tackifier is preferably 50% by weight or more, more preferably 60% by weight or more, and even more preferably 65% ​​by weight or more. Ｕ９０ The total content of the tackifier is preferably 85% by weight or less, more preferably 80% by weight or less, and even more preferably 75% by weight or less. Ｕ９０ When the total content is within the above range, the adhesive strength of the pressure-sensitive adhesive composition can be further improved.

[0053] D-3. Oil The PSA composition containing a styrene-based elastomer preferably further contains an oil. By including an oil, the wettability of the PSA composition containing a styrene-based elastomer can be improved. Any appropriate oil can be used as the oil. Examples include process oil, naphthenic oil, paraffinic oil, and vulcanization oil. Preferably, paraffinic oil can be used. Only one type of oil may be used, or two or more types may be used in combination.

[0054] The oil can be used in any appropriate amount. A PSA composition containing a styrene-based elastomer preferably contains 5 wt % to 30 wt % of oil. A PSA composition containing a styrene-based elastomer more preferably contains 25 wt % or less of oil, and even more preferably contains 20 wt % or less. If the oil content is high, adhesive residue may occur on the adherend. A PSA composition containing a styrene-based elastomer more preferably contains 5 wt % or more of oil, even more preferably contains 10 wt % or more, and particularly preferably contains 15 wt % or more. When the oil content is within the above range, a PSA composition with excellent wettability can be obtained.

[0055] D-4. Olefin-Based Elastomer In one embodiment, the PSA composition containing a styrene-based elastomer further contains an olefin-based elastomer. By including both a styrene-based elastomer and an olefin-based elastomer, the adhesive strength to the adherend can be appropriately adjusted. For example, a PSA layer that combines resealability and easy opening can be formed for use in a resealable sealant. The PSA composition containing a styrene-based elastomer preferably contains 2 wt% to 50 wt% of the olefin-based elastomer. The olefin-based elastomer content is more preferably 5 wt% or more, even more preferably 10 wt% or more, particularly preferably 15 wt% or more, and most preferably 20 wt% or more. By including an olefin-based elastomer in the above range, the adhesive strength to the adherend can be appropriately adjusted. For example, a PSA composition that combines resealability and easy opening can be provided. The olefin-based elastomer content is preferably 40 wt% or less, more preferably 35 wt% or less, and even more preferably 30 wt% or less. In one embodiment, the content of the olefin-based elastomer is preferably 5% by weight to 25% by weight, more preferably 10% by weight to 20% by weight. By having the content of the olefin-based elastomer in this range, the initial adhesive strength can be adjusted to an appropriate value. Furthermore, the heat stability of the pressure-sensitive adhesive composition can be improved.

[0056] The density of the olefin-based elastomer is preferably 0.830 g / cm ３More preferably, it is 0.835 g / cm ３ More preferably, it is 0.840 g / cm ３ More preferably, it is 0.845 g / cm ３ The density of the olefin elastomer is preferably 0.890 g / cm ３ or less, more preferably 0.885 g / cm ３ More preferably, it is 0.880 g / cm or less. ３ or less, and particularly preferably 0.875 g / cm ３ When the density of the olefin-based elastomer is within the above range, it is possible to provide a PSA composition that can achieve both resealability and easy-openability.

[0057] The viscosity of the olefin elastomer at 190° C. is preferably 1,500 mPa·s to 6,500 mPa·s, more preferably 2,000 mPa·s to 6,000 mPa·s, and even more preferably 3,000 mPa·s to 5,000 mPa·s. When the viscosity of the olefin elastomer is within the above range, the resulting composition can be suitably used as a hot-melt pressure-sensitive adhesive composition.

[0058] Any appropriate olefin-based elastomer can be used as the olefin-based elastomer. Preferably, an α-olefin-based elastomer can be used. Specific examples of the α-olefin-based elastomer include at least one elastomer selected from ethylene-based elastomers, propylene-based elastomers, and 1-butene-based elastomers. The olefin-based elastomer may be a homopolymer of the above α-olefin-based elastomer, a copolymer of two or more α-olefin-based elastomers, or a copolymer of an α-olefin-based elastomer and another monomer component. A single olefin-based elastomer may be used, or two or more olefin-based elastomers may be used in combination. A propylene-based elastomer is preferred. The use of a propylene-based elastomer can improve the heat stability of the hot-melt pressure-sensitive adhesive composition. In this specification, the terms ethylene-based elastomer, propylene-based elastomer, and 1-butene-based elastomer refer to elastomers whose primary components are ethylene, propylene, or 1-butene, respectively. In this specification, the term "main component" refers to the monomer component that accounts for the largest proportion of the components that make up the elastomer.

[0059] In one embodiment, the propylene-based elastomer comprises a copolymer of propylene and ethylene. By including a copolymer of propylene and ethylene, the initial adhesive strength can be adjusted to an appropriate value. When a copolymer of propylene and ethylene is used as the propylene-based elastomer, the ethylene content in the propylene-based elastomer is preferably 5 wt% to 20 wt%, more preferably 7 wt% to 15 wt%. By having the ethylene content in the propylene-based elastomer in the above range, a PSA composition that can achieve both resealability and easy-openability can be provided.

[0060] The softening point of the α-olefin elastomer is preferably less than 100° C., more preferably not more than 98° C., and even more preferably not more than 96° C. The softening point is, for example, not less than 30° C. When the softening point is within the above range, the resulting composition can be suitably used as a hot-melt pressure-sensitive adhesive composition.

[0061] D-5. Other Additives The PSA composition containing a styrene-based elastomer may further contain any other appropriate additives as needed. Examples include antioxidants, UV absorbers, light stabilizers, fluorescent agents, colorants, etc. These additives may be used alone or in combination of two or more. The other additives are used in any appropriate amount within the range in which the effects of the present invention can be obtained, so that the total amount of the styrene-based elastomer, tackifier, optional olefin-based elastomer, and oil is 100% by weight.

[0062] As described above, in one embodiment, the second pressure-sensitive adhesive layer has two or more portions with different adhesive strengths. As described above, the adhesive strength to an adherend can be adjusted by further adding an olefin-based elastomer to a pressure-sensitive adhesive composition containing a styrene-based elastomer. Therefore, for example, a difference in adhesive strength can be imparted by increasing the content of the olefin-based elastomer in the pressure-sensitive adhesive composition forming the portion with low adhesive strength compared to the pressure-sensitive adhesive composition forming the portion with high adhesive strength. Furthermore, portions with different adhesive strengths may be formed by adjusting the content of the tackifier in the pressure-sensitive adhesive composition forming each portion.

[0063] E. Method for Producing a Pressure-Sensitive Adhesive Tape One embodiment of the present invention provides a method for producing a pressure-sensitive adhesive tape having, in this order, a substrate containing an olefin-based resin, a first pressure-sensitive adhesive layer containing an olefin-based resin, and a second pressure-sensitive adhesive layer containing a styrene-based elastomer. This method includes hot-melt coating a pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer onto the substrate, and hot-melt coating a pressure-sensitive adhesive composition forming the second pressure-sensitive adhesive layer onto the first pressure-sensitive adhesive layer. By hot-melt coating the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive composition onto the substrate, it is possible to form pressure-sensitive adhesive layers by applying multiple pressure-sensitive adhesives, including those with different adhesive strengths. This widens the range of substrate options because the type and melt viscosity of the pressure-sensitive adhesive are not affected. Furthermore, solvent-free coating can reduce environmental impact. Furthermore, the pressure-sensitive adhesive composition used can be easily changed, reducing material loss during design changes and facilitating the production of a wide variety of products on a single production line. Furthermore, the PSA composition forming the first PSA layer and the PSA composition forming the second PSA layer can be easily coated at a relatively low temperature range of about 140°C to 160°C. Therefore, the PSA layers can be formed by hot melt coating without adversely affecting the substrate. In this specification, hot melt coating refers to discharging a molten PSA composition from a nozzle and coating it.

[0064] The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be formed by forming the first pressure-sensitive adhesive layer on a substrate and then forming the second pressure-sensitive adhesive layer on the first pressure-sensitive adhesive layer, or by simultaneously applying the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition forming the second pressure-sensitive adhesive layer to the substrate. In one embodiment, the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition forming the second pressure-sensitive adhesive layer are simultaneously hot-melt coated. Simultaneous hot-melt coating can improve productivity. In addition, the anchoring property of the second pressure-sensitive adhesive layer to the first pressure-sensitive adhesive layer can be improved.

[0065] As described above, in one embodiment, the pressure-sensitive adhesive tape has at least two portions with different adhesive strengths. Even when the second pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape has portions with different adhesive strengths, the first pressure-sensitive adhesive layer, the second pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer having at least two portions with different adhesive strengths can be simultaneously formed by hot-melt coating. The pressure-sensitive adhesive layers can be formed by any appropriate method. For example, pressure-sensitive adhesive layers can be simultaneously formed by pattern-coating the pressure-sensitive adhesive composition using an apparatus equipped with multiple slot applicators. An example of such a slot applicator is the TrueCoat Slot Applicator manufactured by Nordson. By forming the pressure-sensitive adhesive layers by pattern coating, for example, a pressure-sensitive adhesive tape with any gap between the pressure-sensitive adhesive layers can be more easily produced.

[0066] F. Uses of the Pressure-Sensitive Adhesive Tape The pressure-sensitive adhesive tape of the present invention can be used for any suitable use. In one embodiment, the pressure-sensitive adhesive tape of the present invention can be used as a resealing seal material.

[0067] Fig. 2 is a schematic cross-sectional view showing a use mode of a pressure-sensitive adhesive tape according to an embodiment of the present invention. In the illustrated example, the pressure-sensitive adhesive tape 101 shown in Fig. 1B is used as a resealing sealant for an adherend 200. In the illustrated example, the pressure-sensitive adhesive tape 101 is fixed to the adherend 200 by the strong adhesive portion 31, and the weak adhesive portion 32 is adhered to the adherend 200 to reseal the tape. The pressure-sensitive adhesive composition containing the styrene-based elastomer can achieve both resealability and easy-openability by further containing an olefin-based elastomer. Therefore, when the pressure-sensitive adhesive tape 101 is used as a resealing sealant, it can achieve both the ability to seal the adherend 200 and the easy-openability at the time of opening.

[0068] In one embodiment, the pressure-sensitive adhesive tape can be suitably used as a resealing sealant. In one embodiment, the pressure-sensitive adhesive tape can be suitably used in packaging materials having a printed portion. Packaging materials may have a printed portion to display necessary information. When a packaging material has a printed portion, the adhesive strength of the pressure-sensitive adhesive tape may increase over time depending on the composition of the ink used for printing and the paint (e.g., lacquer) used to protect the printed surface, making it difficult to easily peel the tape. This tendency may be more pronounced when a nitrocellulose-based lacquer is applied to the printed surface. The pressure-sensitive adhesive tape according to an embodiment of the present invention can achieve both resealability and easy opening, even when used in packaging materials having a printed surface to which a nitrocellulose-based lacquer is applied.

[0069] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The evaluation methods used in the examples are as follows. Unless otherwise specified, parts mean parts by weight, and % means % by weight.

[0070] Example 1 The materials listed in Table 1 were mixed to prepare pressure-sensitive adhesive compositions for forming a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer. An unstretched PP film (thickness: 80 μm) with a release treatment applied to the surface opposite to the pressure-sensitive adhesive composition-coated surface was used as the substrate. Using a TrueCoat Slot applicator (manufactured by Nordson), a pressure-sensitive adhesive composition (a pressure-sensitive adhesive composition containing an olefin-based resin) for forming the first pressure-sensitive adhesive layer and a pressure-sensitive adhesive composition (a pressure-sensitive adhesive composition containing a styrene-based elastomer) for forming the second pressure-sensitive adhesive layer were simultaneously laminate-coated onto the non-release-treated surface of the substrate to obtain a pressure-sensitive adhesive tape. The coating temperature was 160°C, and the line speed was 100 m / min. The thickness of the first pressure-sensitive adhesive layer was 15 μm, and the thickness of the second pressure-sensitive adhesive layer was 30 μm. The resulting pressure-sensitive adhesive tape was evaluated as follows.

[0071]

[0072] [Examples 2 to 13, 18 to 26 and Comparative Examples 1 to 9] Pressure-sensitive adhesive tapes were prepared in the same manner as in Example 1, except that the substrate, the pressure-sensitive adhesive compositions forming the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer, and the thickness of each layer were changed as shown in Tables 2 to 4.

[0073] 1. Adhesive Strength The pressure-sensitive adhesive tapes of the Examples and Comparative Examples were cut to a width of 25 mm to prepare samples with an adhesive area of ​​25 mm wide and 50 mm long. SUS304 plates were used as adherends. The samples were pressed onto the SUS plate surface with two reciprocating strokes under a 2 kg load to achieve the above adhesive area (25 mm x 50 mm). After 30 minutes at room temperature (23°C), the samples were peeled at a 90° angle at a peel rate of 300 mm / min to measure adhesive strength. An AR-1000 tester manufactured by Cheminstruments was used for the measurements. The obtained adhesive strength was converted to N / 25 mm, and the average value of three samples was used as the adhesive strength of that sample. 2. Anchor Failure After the above adhesive strength test, the SUS plate surface was visually observed. If no adhesive residue was observed, the anchor strength was evaluated as ○ (good), and the average value of the measurement results was used as the adhesive strength. The surface of the SUS plate after the adhesive strength test was visually observed, and if any adhesive residue was found, it was marked as anchor failure, and the adhesive strength could not be measured, so it was indicated as anchor failure. 3. Method for Measuring Storage Modulus G' Using Styrene 2, 7, and 8, disc-shaped punched samples with a thickness of approximately 1 mm and a diameter of 7.9 mm were prepared. The prepared samples were then sandwiched and fixed between parallel plates, and dynamic viscoelasticity measurements were performed using a viscoelasticity tester (for example, manufactured by TA Instruments, product name: DISCOVERY HR-3 HYBRID RHEOMETER) under the following conditions to determine the storage modulus G' (25°C). Measurement mode: shear mode Temperature range: -40°C to 120°C Heating rate: 3°C / min Measurement frequency: 1.6 Hz

[0074]

[0075]

[0076]

[0077] Examples 14 to 17 Two types of adhesive compositions with different adhesive strengths were used as the adhesive composition forming the second adhesive layer. Using a Nordson TrueCoat Slot applicator, adhesive tapes were obtained in which the second adhesive layer A and the second adhesive layer B were pattern-coated on the first adhesive layer. The adhesive composition forming the first adhesive layer, the adhesive composition forming the second adhesive layer A, and the adhesive composition forming the second adhesive layer B were simultaneously laminate-coated on the non-release-treated side of the substrate. The pattern coating was as follows: second adhesive A: 17 mm width, second adhesive B: 8 mm width, and second adhesive A / B gap: 1 mm width. Coating was performed at a coating temperature of 160°C and a line speed of 100 m / min. The second adhesive layer A of the adhesive tapes obtained in Examples 14 to 17 was attached to a packaging material (printed film) used to package commercially available products. After application, the tape was left to stand at room temperature (23°C) for 30 minutes, and then the second pressure-sensitive adhesive layer A was peeled off from the printed film, and the surface of the adherend after peeling was visually observed. Evaluation was performed on three sample specimens. For the pressure-sensitive adhesive tapes of Examples 14 to 17, all three samples could be peeled off without leaving any adhesive residue on the adherend. Furthermore, no peeling of the printed portion on the surface of the printed film was observed when the pressure-sensitive adhesive tape was peeled off. Furthermore, the second pressure-sensitive adhesive layer A of the pressure-sensitive adhesive tape after peeling was re-applied to the printed film. The pressure-sensitive adhesive tape adhered sufficiently to the printed film and was re-adherable.

[0078] Examples 27 to 32 The materials listed in Table 1 were mixed to prepare pressure-sensitive adhesive compositions for forming a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer. An unstretched PP film (thickness: 80 μm) with a release treatment applied to the side opposite to the pressure-sensitive adhesive composition-coated surface was used as the substrate. Using a TrueCoat Slot applicator (manufactured by Nordson), the pressure-sensitive adhesive composition for forming the first pressure-sensitive adhesive layer was applied to the non-release-treated side of the substrate to form a pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer), which was then stored at 23°C for 24 hours. Next, the pressure-sensitive adhesive composition for forming the second pressure-sensitive adhesive layer was laminated onto the first pressure-sensitive adhesive layer to obtain a pressure-sensitive adhesive tape. The coating temperature was 160°C, and the line speed was 100 m / min. The thickness of the first pressure-sensitive adhesive layer was 15 μm, and the thickness of the second pressure-sensitive adhesive layer was 15 μm. The resulting pressure-sensitive adhesive tape was used for the above-mentioned evaluations.

[0079] The pressure-sensitive adhesive tape according to an embodiment of the present invention can suppress anchor failure even when it has a pressure-sensitive adhesive layer with high adhesive strength, and therefore can be used even for pressure-sensitive adhesive tapes having a pressure-sensitive adhesive layer whose adhesive strength may increase during storage.

[0080] REFERENCE SIGNS LIST 100 Adhesive tape 101 Adhesive tape 102 Adhesive tape 10 Base material 20 First adhesive layer 30 Second adhesive layer 31 Strong adhesive portion 32 Weak adhesive portion

Claims

1. An adhesive tape having, in this order, a base material containing an olefin resin, a first adhesive layer containing an olefin resin, and a second adhesive layer containing a styrene elastomer.

2. The adhesive tape according to claim 1, wherein the olefin resin contained in the base material contains a propylene resin.

3. The adhesive tape according to claim 2, wherein the content of the propylene resin in the olefin resin contained in the base material is 40% by weight to 100% by weight.

4. The adhesive tape according to claim 1, wherein the thickness of the first adhesive layer is 5 μm to 30 μm.

5. The adhesive tape according to claim 1, wherein the thickness of the second adhesive layer is 5 μm to 50 μm.

6. The adhesive tape according to claim 1, wherein a release treatment is performed on the surface of the base material where the first adhesive layer is not formed.

7. The adhesive tape according to claim 1, wherein the olefin resin contained in the first adhesive layer contains a propylene resin.

8. The adhesive tape according to claim 1, wherein the adhesive composition forming the first adhesive layer further contains a tackifier, and the content of the tackifier is 20% by weight to 60% by weight.

9. The adhesive tape according to claim 1, wherein the second adhesive layer is formed of an adhesive composition containing a styrene-isoprene block copolymer, an olefin elastomer, and a tackifier.

10. The adhesive tape according to claim 9, wherein the styrene content of the styrene-isoprene block copolymer is 10% by weight to 25% by weight.

11. The adhesive tape according to claim 9, wherein the styrene-isoprene block copolymer contains a diblock copolymer.

12. The adhesive tape according to claim 9, wherein the content of the tackifier is 2% by weight to 40% by weight.

13. The adhesive tape according to claim 9, wherein the tackifier contains a hydrogenated petroleum resin.

14. The adhesive tape according to claim 9, wherein the adhesive composition forming the second adhesive layer further contains oil.

15. The adhesive tape according to claim 14, wherein the content of the oil is 5% by weight to 30% by weight.

16. The adhesive tape according to claim 1, wherein the adhesive force of the second adhesive layer to a stainless steel plate is 0.05 N / 25 mm to 15 N / 25 mm.

17. The pressure-sensitive adhesive tape according to claim 1, wherein the difference in melt viscosity at 160° C. between the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition forming the second pressure-sensitive adhesive layer is 50,000 mPa·s or less.

18. The pressure-sensitive adhesive tape according to claim 1, wherein the second pressure-sensitive adhesive layer has at least two portions with different adhesive forces, including a strong adhesive portion and a weak adhesive portion.

19. The pressure-sensitive adhesive tape according to claim 18, wherein the difference in adhesive force to a stainless steel plate between the strong adhesive portion and the weak adhesive portion is 1 N / 25 mm to 10 N / 25 mm.

20. A method for manufacturing a pressure-sensitive adhesive tape, which sequentially has a base material containing an olefin resin, a first pressure-sensitive adhesive layer containing an olefin resin, and a second pressure-sensitive adhesive layer containing a styrene-based elastomer, comprising: hot melt coating the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer onto the base material; hot melt coating the pressure-sensitive adhesive composition forming the second pressure-sensitive adhesive layer onto the first pressure-sensitive adhesive layer.

21. The manufacturing method according to claim 20, including simultaneously hot melt coating the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition forming the second pressure-sensitive adhesive layer.

22. The second pressure-sensitive adhesive layer has at least two portions with different adhesive forces, including a strong adhesive portion and a weak adhesive portion, The manufacturing method according to claim 20 or 21, including pattern coating the pressure-sensitive adhesive composition forming each portion.