Resealable label

Abstract

The present invention provides a resealable label that maintains resealability in low-temperature environments such as refrigerators and freezers, while also offering excellent resealability against condensation. [Solution] A resealable label having a base material and an adhesive layer, wherein the adhesive layer is formed from an adhesive composition comprising a rubber-based adhesive containing a styrene copolymer and a tackifying resin, and the content of the tackifying resin in the adhesive composition is 25% by mass or more.

Description

Technical Field

[0001] The present invention relates to a resealable label.

Background Art

[0002] Food products are sometimes sold in a state of being contained in bag-shaped or box-shaped packages such as so-called pillow types and gusset types. In these packages, there is a form in which a so-called flap label having a resealing function is provided so as to cover the outlet for taking out the contents. In such a package, after taking out the contents, even if there is something left inside, the outlet can be sealed, so that it is possible to take out the contents again later.

[0003] A resealable label having a resealing function such as a flap label is required to maintain its adhesiveness even after repeated use. As an adhesive composition used in such a label having resealability, in Patent Document 1, (meth)acrylate (a1) and styrene (a2) are contained in a mass ratio of (meth)acrylate (a1):styrene (a2) = 85:15 to 99:1, and an emulsion containing a styrene-acrylic copolymer (A) having a glass transition temperature in the range of -60°C to 30°C, a latex emulsion containing natural rubber (B), and an aqueous medium are contained, and the styrene-acrylic copolymer (A) is the main component in the total amount of solids in the adhesive composition. An adhesive composition is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When storing food packaging in a refrigerator or freezer, or when storing refrigerated or frozen foods, moisture often adheres to the surface of the packaging due to condensation after being removed from the refrigerator or freezer and left for a short time. However, conventional resealable labels have not provided sufficient resealability against packaging with moisture on the surface (condensation surface).

[0006] Therefore, the present invention aims to provide a resealable label that maintains resealability in low-temperature environments such as refrigerators and freezers, while also exhibiting excellent resealability against condensation. [Means for solving the problem]

[0007] The present invention provides the following:

[0008] (1) A resealable label having a base material and an adhesive layer, wherein the adhesive layer is formed from an adhesive composition comprising a rubber-based adhesive containing a styrene copolymer and a tackifying resin, and the content of the tackifying resin in the adhesive composition is 25% by mass or more.

[0009] (2) The resealable label described in (1), which has an adhesive strength of 3N / 25mm or more in the condensation surface test.

[0010] (3) A resealable label as described in (1) or (2), having an adhesive strength of 5 N / 25 mm or more in low-temperature tests.

[0011] (4) A resealable label as described in any one of (1) to (3), having a storage modulus of elasticity of 500 Pa or more at 100°C.

[0012] (5) A resealable label according to any one of (1) to (4), wherein the softening point of the tackifying resin is 110°C or lower.

[0013] (6) The resealable label according to any one of (1) to (5), wherein the adhesive composition contains a plasticizer.

[0014] (7) The resealable label according to (6), wherein the content of the plasticizer is 5 to 50% by mass in the adhesive composition.

[0015] (8) The resealable label according to (6) or (7), wherein the plasticizer is a petroleum-based plasticizer.

[0016] (9) The resealable label according to any one of (1) to (8), wherein the adhesive composition is of the hot-melt type.

[0017] (10) The resealable label according to any one of (1) to (9), which is attached to a food package.

[0018] (11) The resealable label according to any one of (1) to (10), which is used for a package stored in a refrigerator or a freezer.

[0019] (12) The resealable label according to any one of (1) to (11), which is a flap label.

Advantages of the Invention

[0020] According to the resealable label of the present invention, while maintaining the resealability in a low-temperature environment such as in a refrigerator or a freezer, even if condensation occurs on the package after taking out the package stored in the refrigerator or the freezer, the adhesiveness to the condensation surface is excellent.

Brief Description of the Drawings

[0021] [Figure 1] It is a schematic cross-sectional view of the resealable label of an embodiment of the present invention. [Figure 2] It is a schematic view showing a state where the bag-shaped package is sealed again with the resealable label shown in FIG. 1 after rounding the bag-shaped package. [Figure 3] It is a schematic view showing a bag-shaped package with an opening sealed by the resealable label shown in FIG. 1. [Figure 4] It is a view when taking out the contents of the bag-shaped package with the resealable label of FIG. 3.

Modes for Carrying Out the Invention

[0022] The first embodiment of the present invention is a resealable label having a base material and an adhesive layer, wherein the adhesive layer is formed from an adhesive composition containing a rubber-based adhesive containing a styrene copolymer and an adhesion promoter resin, and in the adhesive composition, the content of the adhesion promoter resin is 25% by mass or more. With such a configuration, a resealable label is obtained that maintains resealability in a low-temperature environment such as inside a refrigerator or freezer and has excellent resealability to a frozen surface. Here, for the resealability, it is required not only to be able to simply seal the opening of the adherend (such as a package), but also to have no or few peeling marks (so-called glue residue) on the adherend during peeling. Generally, adhesiveness and glue residue are in a trade-off relationship and it is difficult to achieve both. Also, even a resealable label that has good adhesiveness at room temperature and little glue residue after peeling does not maintain good adhesiveness and little glue residue after peeling even after repeated use at low temperature or on a frozen surface. According to the configuration of the present embodiment, a resealable label having good adhesiveness and little glue residue after peeling can be obtained even after repeated use at low temperature or on a frozen surface. In the present embodiment, as the adhesive of the adhesive layer, a rubber-based adhesive is selected, and it is considered that the above effects are achieved by the content balance of the styrene copolymer and the adhesion promoter resin.

[0023] Note that a resealable label is a label that is used for sealing or temporarily fixing a package such as a container or a bag, and is used (resealed) after being pasted on and peeled from the package and then pasted again.

[0024] Hereinafter, embodiments of the present invention will be described while referring to the attached drawings.

[0025] Figure 1 is a cross-sectional view showing a resealable label 20. The resealable label 20 has a base material 21 and an adhesive layer 22. A release liner to protect the adhesive layer until use may be laminated on the side of the adhesive layer 22 opposite to the base material 21. In the following description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. Also, the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios.

[0026] The adhesive strength (hereinafter also simply referred to as condensation surface adhesive strength) in the condensation surface test of resealable labels is preferably 3N / 25mm or higher, and more preferably 5N / 25mm or higher. A condensation surface adhesive strength above the above lower limit ensures sufficient adhesion for resealing even when condensation droplets are present on the surface of the packaging after it has been removed from a refrigerator or freezer. While there is no particular need to set an upper limit for the adhesive strength in the condensation surface test of resealable labels, it is preferably 20N / 25mm or lower. A condensation surface adhesive strength below the above upper limit allows for peeling with appropriate force. Furthermore, peeling of the printed surface of the packaging is reduced. The condensation surface adhesive strength can be controlled by the mass ratio of rubber-based adhesive (especially styrene copolymer) to tackifying resin, and the softening point of the tackifying resin. A higher mass ratio of tackifying resin to rubber-based adhesive tends to increase the condensation surface adhesive strength. A lower softening point of the tackifying resin also tends to increase the condensation surface adhesive strength. The adhesion strength of the condensation surface is a value measured according to the room-temperature condensation surface adhesion strength test described in the following example.

[0027] The adhesive strength of a resealable label in a low-temperature test (hereinafter also simply referred to as low-temperature adhesive strength) is preferably 5N / 25mm or higher, more preferably 7N / 25mm or higher, and even more preferably 9N / 25mm or higher. A low-temperature adhesive strength above the above lower limit ensures sufficient adhesion for resealing even when stored in a refrigerator or freezer. While there is no particular need to set an upper limit for the low-temperature adhesive strength of a resealable label, it is preferably 20N / 25mm or lower. A low-temperature adhesive strength below the above upper limit allows for peeling with appropriate force, and also reduces peeling of the printed surface of the packaging. Low-temperature adhesive strength can be controlled by the mass ratio of rubber-based adhesive to tackifying resin, the softening point of the tackifying resin, etc. A higher mass ratio of tackifying resin to rubber-based adhesive tends to increase low-temperature adhesive strength. A lower softening point of the tackifying resin also tends to increase low-temperature adhesive strength. Note that the low-temperature adhesive strength is a value measured according to the low-temperature adhesive strength test described in the following examples, for example.

[0028] The following describes the components that make up each label. In this specification, "X~Y" indicating a range means "X or more and Y or less". Unless otherwise specified, operations and measurements of physical properties are performed under room temperature (20~25°C) / relative humidity of 45~55%RH. In this specification, "(meth)acrylic acid" refers to "acrylic acid and / or methacrylic acid". In the following description, the labels of the present invention may be simply referred to as "labels". The concept of "label" includes films, sheets, tapes, etc.

[0029] <Base material> The substrate is not particularly limited and includes resin substrates; so-called synthetic paper made of resin; metal foils such as copper, aluminum, and stainless steel; composite sheet substrates made by laminating metal foil and plastic film; vapor-deposited substrates with aluminum, silica, etc.; nonwoven fabric substrates; or paper substrates. As resin substrates, for example, films made of at least one resin selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyvinyl chloride, polystyrene, polyurethane, polycarbonate, polyamide, polyimide, polyetherimide, poly(meth)acrylic acid ester, polybutene, polybutadiene, polymethylpentene, acrylic urethane, ethylene vinyl acetate copolymer, ethylene(meth)acrylic acid copolymer, ethylene(meth)acrylic acid ester copolymer, ABS resin, ionomer resin, and various thermoplastic elastomers, or single or multiple laminated films selected from these can be used. The paper substrate is not particularly limited and includes, for example, fine paper, kraft paper, glassine paper, coated paper, art paper, cast coated paper, impregnated paper, foamed paper, thermal paper, dust-free paper, parchment paper, rayon paper, recycled paper, and water-resistant paper containing a wet-strengthening agent (for example, the water-resistant paper described in Japanese Patent No. 7424723). The paper substrate may also be a laminate formed by stacking two or more layers of these materials.

[0030] In particular, the base material is preferably a resin base material, synthetic paper, or water-resistant paper, as these have high base material strength and are less likely to tear even when used on a condensed substrate.

[0031] Various types of information, such as letters, numbers, symbols, and figures, may be recorded on the surface of the substrate (the side facing the adhesive layer).

[0032] Furthermore, the substrate may have a printable coating layer on its surface.

[0033] The thickness of the substrate is not particularly limited, but is preferably 10 μm to 200 μm, more preferably 20 μm to 150 μm, and even more preferably 30 μm to 100 μm. Such a thickness provides good handling during application.

[0034] <Adhesive layer> The storage modulus of the adhesive layer is preferably 500 Pa or higher, more preferably 500 to 50,000 Pa, even more preferably 5,000 to 30,000 Pa, and particularly preferably 10,000 to 25,000 Pa at 100°C. A storage modulus of the adhesive layer above the lower limit ensures minimal adhesive residue even when used at low temperatures or on condensation surfaces. Conversely, a storage modulus below the upper limit makes it easier to maintain adhesive strength even at low temperatures or on condensation surfaces. Note that 100°C is the temperature at which the adhesive initially flows, and a higher storage modulus at this temperature indicates better cohesiveness of the adhesive layer and reduced wettability. The storage modulus of the adhesive layer can be controlled by the mass ratio of rubber-based adhesive to tackifying resin, the plasticizer content in the adhesive composition, etc. A lower mass ratio of tackifying resin to rubber-based adhesive tends to increase the storage modulus of the adhesive layer. Furthermore, the lower the plasticizer content in the adhesive composition, the higher the storage modulus tends to be. The storage modulus is a value measured according to the example below.

[0035] The thickness of the adhesive layer (film thickness after drying) is typically 1 to 100 μm, preferably 5 to 50 μm.

[0036] The adhesive layer is formed from an adhesive composition.

[0037] The adhesive composition may be a solvent-type containing a solvent or a solvent-free type (so-called hot melt type), but due to considerations for the environment, a solvent-free type is preferred, and also because it eliminates the need for solvent removal steps, and from the viewpoint of the effects of the present invention, the adhesive composition is preferably of the hot melt type.

[0038] The adhesive composition includes a rubber-based adhesive and a tackifying resin, and preferably includes a plasticizer for ease of handling and coating properties.

[0039] (Rubber-based adhesive) The rubber-based adhesive contains a styrene copolymer as the rubber resin. Other rubber resins besides the styrene copolymer may include natural rubber resins or other copolymers. Alternatively, the rubber-based adhesive may not contain any rubber resins other than the styrene copolymer. Preferably, the rubber-based adhesive consists substantially of only the styrene copolymer. Here, "substantially consisting solely of the styrene copolymer" means that the rubber-based adhesive may contain 0.01% by mass or less of other rubber resins other than the styrene copolymer, and may contain 0.005% by mass or less, and particularly preferably contains 0% by mass of other rubber resins.

[0040] The content of the rubber-based adhesive is preferably 10% by mass or more and 60% by mass or less in the adhesive composition, more preferably 20% by mass or more and 50% by mass or less, even more preferably 25% by mass or more and 45% by mass or less, and even more preferably 30% by mass or more and 40% by mass or less.

[0041] Styrene copolymers are copolymers of styrene and other comonomers.

[0042] Examples of styrene-based copolymer block copolymers include styrene-isoprene block copolymers such as styrene-isoprene block copolymer (SI) and styrene-isoprene-styrene block copolymer (SIS); styrene-butadiene random copolymers such as styrene-butadiene rubber (SBR); styrene-butadiene block copolymers such as styrene-butadiene-styrene copolymer (SBS), styrene-butadiene-styrene-butadiene copolymer (SBSB), and styrene-butadiene-butylene-styrene copolymer (partially hydrogenated styrene-butadiene-styrene copolymer; SBBS); styrene-isobutylene-styrene block copolymer (SIBS); styrene-ethylene / butylene-styrene copolymer (SEBS); styrene-ethylene / propylene-styrene (SEPS) copolymer; and styrene-ethylene-ethylene / propylene-styrene (SEEPS) copolymer. Styrene-based copolymers may be used individually or in combination of two or more types. Among these, the styrene copolymer is preferably a styrene-isoprene block copolymer and / or a styrene-butadiene block copolymer, and more preferably a styrene-isoprene-styrene copolymer (SIS) and / or a styrene-butadiene-styrene copolymer (SBS), because it is easy to impart tackiness to the material.

[0043] The styrene monomer content in the styrene copolymer is preferably 15% by mass or more and 50% by mass or less, and more preferably 20% by mass or more and 45% by mass or less, of the monomers constituting the styrene copolymer. A styrene content above the lower limit is preferable because it provides excellent cohesive force and reduces the likelihood of adhesive residue on the adherend, while a styrene content below the upper limit is preferable because it ensures sufficient adhesive strength when resealing.

[0044] The styrene copolymer may be a single structure such as a linear, branched, or multi-branched structure, or it may be a mixture of different structures. When a styrene resin rich in linear structures is used in the adhesive layer, excellent adhesive performance can be provided. On the other hand, a branched or multi-branched structure with styrene blocks at the molecular ends can adopt a pseudo-crosslinked structure, providing excellent cohesive force and thus high holding power. For this reason, styrene resins may be mixed and used according to the required properties. In one preferred embodiment, the styrene copolymer has a branched structure.

[0045] The mass-average molecular weight (Mw) of the styrene copolymer is preferably 50,000 to 500,000, and more preferably 100,000 to 400,000.

[0046] In this specification, "mass-average molecular weight (Mw)" is a value calculated on a standard polystyrene basis by gel permeation chromatography (GPC).

[0047] The mass-average molecular weight (Mw) is measured, for example, using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8020") under the following conditions, and is expressed in terms of standard polystyrene equivalent. (Measurement conditions) • Column: A series of "TSK guard column HXL-H", "TSK gel GMHXL" (2 pieces), and "TSK gel G2000HXL" (all manufactured by Tosoh Corporation) linked together. Column temperature: 40°C • Developing solvent: tetrahydrofuran ·Flow rate: 1.0mL / min.

[0048] The styrene copolymer content is preferably 10% by mass or more and 60% by mass or less in the adhesive composition, more preferably 20% by mass or more and 50% by mass or less, even more preferably 25% by mass or more and 45% by mass or less, and even more preferably 30% by mass or more and 40% by mass or less.

[0049] Furthermore, if the adhesive composition contains a plasticizer, the amount of styrene copolymer is preferably 10 to 60 parts by mass, more preferably 20 to 50 parts by mass, even more preferably 25 to 45 parts by mass, and even more preferably 30 to 40 parts by mass, based on 100 parts by mass of the total of the styrene copolymer, tackifying resin, and plasticizer.

[0050] Furthermore, the content of the styrene copolymer in the adhesive composition is more preferably 25% by mass or more and 70% by mass or less, but may be 30% by mass or more and 70% by mass or less, or 30% by mass or more and 60% by mass or less.

[0051] The styrene copolymer content being within the above range results in excellent resealability on condensation surfaces and under low-temperature storage conditions.

[0052] (Adhesive-forming resin) The tackifying resin is not particularly limited, and examples include rosin-based resins, alicyclic petroleum resins, terpene-based resins, and styrene-based resins. From the viewpoint of the effects of the present invention, the tackifying resin is preferably at least one selected from the group consisting of rosin-based resins and alicyclic petroleum resins (preferably C5 / C9 petroleum resins), and rosin-based resins are more preferred. The tackifying resin may be used alone or in combination of two or more types.

[0053] Furthermore, tackifying resins are components that supplementarily improve the adhesive strength of the adhesive layer, and are oligomers with a mass-average molecular weight (Mw) of typically less than 10,000, and are distinct from the rubber-based adhesives mentioned above.

[0054] The tackifying resin content is 25% by mass or more in the adhesive composition. If the tackifying resin content is less than 25% by mass in the adhesive composition, the resealability on condensation surfaces and under low-temperature storage conditions will be significantly reduced. Preferably, the tackifying resin content is 25% by mass or more and 60% by mass or less in the adhesive composition, and more preferably 30% by mass or more and 55% by mass or less.

[0055] Furthermore, if the adhesive composition contains a plasticizer, the amount of tackifying resin is preferably 25 parts by mass or more, more preferably 25 parts by mass or more and 60 parts by mass or less, and even more preferably 30 parts by mass or more and 55 parts by mass or less, based on 100 parts by mass of the total of the rubber-based adhesive, tackifying resin, and plasticizer.

[0056] Furthermore, the mass ratio of styrene copolymer to tackifying resin is preferably styrene copolymer:tackifying resin = 1:0.5 to 2.5, and more preferably styrene copolymer:tackifying resin = 1:0.75 to 2, from the viewpoint of condensation surface and resealability under low-temperature storage.

[0057] Furthermore, the content of the tackifying resin relative to the total amount of solids in the adhesive composition is preferably 30% by mass or more, more preferably 30% by mass or more and 70% by mass or less, and may be 35% by mass or more and 70% by mass or less, or 40% by mass or more and 70% by mass or less.

[0058] The tackifying resin content being within the above range results in excellent resealability on condensation surfaces and under low-temperature storage conditions.

[0059] The softening point of the tackifying resin is preferably 140°C or lower, more preferably 110°C or lower, even more preferably 70-110°C, and particularly preferably 85-100°C. Having a softening point within the above range provides superior resealability on condensation surfaces and under low-temperature storage conditions. The softening point is measured by the ring-and-ball method described in JIS K5902-1969 or JIS K2207-1996. When using multiple types of tackifying resins, the softening point is the sum of the softening points of each resin multiplied by their respective blending mass ratios. For example, if 50% by mass of tackifying resin A with a softening point a°C and 50% by mass of tackifying resin B with a softening point b°C are used, the softening point of the tackifying resin (°C) = (a × 50 / 100 + b × 50 / 100).

[0060] Examples of rosin resins that can be used include gum rosin, wood rosin, tall oil rosin, and rosin derivatives such as polymerized rosin, disproportionated rosin, hydrogenated rosin, reinforced rosin, rosin esters, polymerized rosin esters, rosin phenol, disproportionated rosin esters, and hydrogenated rosin esters. Polyhydric alcohols that can be used for esterification include ethylene glycol, diethylene glycol, glycerin, and pentaerythritol. In addition, one or more of these can be used in combination.

[0061] Rosin-based resins may be used alone or in combination of two or more types.

[0062] Petroleum resins are obtained by polymerizing diolefins and monoolefins in the fractions of cracked oil, which are by-products of the production of ethylenes by steam cracking of petroleum products, using known methods. C5 petroleum resins are those made from C5 fractions such as isoprene, 1,3-pentadiene, cyclopentene, and cyclopentadiene, while C9 petroleum resins are those made from C9 fractions such as styrene, vinyltoluene, α-methylstyrene, indene, alkylindene, and dicyclopentadiene.

[0063] Examples of alicyclic petroleum resins include alicyclic hydrocarbon resins obtained by cyclizing and then polymerizing C5 petroleum resins, polymers of cyclic diene compounds (such as cyclopentadiene, dicyclopentadiene, ethylidene norbornene, dipentene, ethylidenebicycloheptene, vinylcycloheptene, tetrahydroindene, vinylcyclohexene, and limonene) or their hydrogenated products, and alicyclic hydrocarbon resins obtained by hydrogenating the aromatic rings of C9 petroleum resins or C5 / C9 resins.

[0064] Alicyclic petroleum resins may be used alone or in combination of two or more types.

[0065] Examples of terpene resins include terpene resins, terpene phenol resins, aromatically modified terpene resins, and hydrogenated terpene resins obtained by hydrogenating these, with aromatically modified terpene resins being preferred.

[0066] Terpene resins may be used individually or in combination of two or more types.

[0067] Examples of styrene-based resins include monopolymers of α-methylstyrene, monopolymers of styrene monomers, copolymers of α-methylstyrene and styrene monomers, and copolymers of α-methylstyrene, styrene monomers, and other monomers.

[0068] Styrene resins may be used alone or in combination of two or more types.

[0069] (Plasticizer) Adhesive compositions preferably contain plasticizers, from the viewpoint of coating properties and other factors.

[0070] The plasticizer is not particularly limited, and conventionally known plasticizers can be used. Examples include petroleum-based plasticizers; natural oils such as castor oil or tall oil; dialkyl dibasic acids such as dibutyl phthalate, dioctyl phthalate or dibutyl adipate; and low molecular weight liquid polymers such as liquid polybutene or liquid polyisoprene.

[0071] Among these, it is preferable that the plasticizer be a petroleum-based plasticizer, as this further enhances the effects of the present invention, is particularly stable against heat and ultraviolet light, and allows for the creation of an adhesive composition with excellent hue. Furthermore, an embodiment in which the plasticizer is solely a petroleum-based plasticizer is also a preferred embodiment.

[0072] Furthermore, petroleum-based plasticizers can be used in combination with other plasticizers. In this case, it is preferable to use petroleum-based plasticizers at a concentration of 60% or more, 70% or more, 80% or more, or 90% or more (up to a maximum of 100% by mass) of the total amount of plasticizers (100% by mass).

[0073] Examples of petroleum-based plasticizers include paraffinic process oils, naphthenic process oils, and aromatic process oils. Petroleum-based plasticizers may be used alone or in combination of two or more. In particular, naphthenic process oils are preferred as petroleum-based plasticizers because they have excellent compatibility with other components and good adhesive properties.

[0074] The plasticizer content is preferably 5% by mass or more and 50% by mass or less in the adhesive composition, more preferably 10% by mass or more and 45% by mass or less, even more preferably 10% by mass or more and 30% by mass or less, and particularly preferably 15% by mass or more and 25% by mass or less. When the plasticizer content is above the lower limit, the coating properties of the adhesive composition are good, and when the plasticizer content is below the upper limit, sufficient adhesive strength is ensured to allow for resealing.

[0075] Furthermore, if the adhesive composition contains a plasticizer, the amount of the plasticizer is preferably 5 to 50 parts by mass, more preferably 10 to 45 parts by mass, even more preferably 10 to 30 parts by mass, and even more preferably 15 to 25 parts by mass, based on 100 parts by mass of the total of the styrene copolymer, tackifying resin, and plasticizer.

[0076] <Removable Liner> A release liner is an optional component provided to protect the adhesive layer and is peeled off from the adhesive label when it is applied to the substrate. In this case, a release agent is usually provided on the adhesive layer side of the release liner to facilitate its removal from the adhesive layer.

[0077] The material of the release substrate constituting the release liner is not particularly limited, and known materials can be used. Examples include resin materials and paper. Examples of resin materials include polyester and polyolefin. Examples of paper include kraft paper, fine paper, glassine paper, and laminated paper laminated with a thermoplastic resin such as polyethylene.

[0078] The thickness of the release liner is preferably 25 μm or more and 100 μm or less.

[0079] Examples of release agents that make up the release agent layer include silicone-based release agents, long-chain alkyl-based release agents, fluorine-based release agents, and rubber-based release agents. Among these, silicone-based release agents are preferred. The thickness of the release agent layer is usually about 0.01 to 5 μm.

[0080] <Manufacturing method> One example of a method for manufacturing a resealable label is to apply a heated hot-melt adhesive composition onto a release liner, and then laminate a substrate onto the resulting adhesive layer. Alternatively, an adhesive layer may be formed on the substrate beforehand, and then the release liner may be laminated onto it.

[0081] If the adhesive composition is of the hot-melt type, it is preferable that it is heated to melt when applied to the release liner or substrate, and the melting temperature (coating temperature) is, for example, 120 to 210°C or 130 to 190°C.

[0082] The method of coating the adhesive composition is not particularly limited, and it can be coated using known coating equipment such as a roll coater, knife coater, air knife coater, bar coater, blade coater, slot die coater, lip coater, or gravure coater.

[0083] <How to use> Figure 2 shows one method of using the resealing label 20 shown in Figure 1. As shown in Figure 2, the bag-shaped packaging 11, which is configured in a roughly rectangular shape, can contain, for example, frozen food. After removing a predetermined amount of the contents of the bag-shaped packaging 11, the bag-shaped packaging 11 can be rolled up from the top to the bottom and the resealing label 20 can be attached near the opening to reseal the bag-shaped packaging 11 (see Figure 2).

[0084] Furthermore, as shown in Figure 3, the resealing label 20 may cover the opening 212 of the bag-shaped packaging 210 to seal the bag-shaped packaging 210. A resealing label with this configuration is also called a flap label. That is, one embodiment of the present invention is a flap label having a base material and an adhesive layer, wherein the adhesive layer is formed from an adhesive composition comprising a rubber-based adhesive containing a styrene copolymer and a tackifying resin, and the content of the tackifying resin in the adhesive composition is 25% by mass or more. Before initial opening, the bag-shaped packaging is provided with a perforated or other type of cut portion 211 for forming an opening, and when opened for the first time, the cut portion 211 adheres to the flap label side, forming an opening 212. With the opening 212 formed, the contents of the bag-shaped packaging 210 can be removed. After removing a predetermined amount of the contents from the bag-shaped packaging 210, the bag-shaped packaging 210 can be resealed by reattaching the resealing label 20 to the bag-shaped packaging 210 near the opening 212, as shown in Figure 3.

[0085] As described above, the resealable label of one embodiment of the present invention is a resealable label for packaging, and since it has excellent adhesion and repeated resealability even when used in a refrigerator or freezer, it is preferable to use it on packaging stored in a refrigerator or freezer.

[0086] Furthermore, the resealable label is preferably one that is affixed to packaging (food packaging) containing food, which is often used in refrigerators and freezers. Examples of food include frozen foods such as frozen noodles, frozen rice, frozen fried foods, frozen processed meat products, and frozen dairy products; and refrigerated foods such as confectionery, bread, noodles, pickles, miso, ham, bacon, sausages, processed chicken products, cooked foods, and cheese. [Examples]

[0087] Next, we will describe the examples. In the examples, the units "parts" or "%" may be used, but unless otherwise specified, they represent "parts by mass" or "mass%". Also, unless otherwise specified, each operation is carried out at room temperature (25°C).

[0088] [Example 1] In a stainless steel container with heating and stirring functions, 40 parts by mass of styrene-isoprene-styrene copolymer (SIS, styrene content 20%, styrene-isoprene block content 80%, mass-average molecular weight 150,000), 35 parts by mass of rosin ester resin (Kraton SYLVALITE RE100L, softening point: 98°C) as a tackifying resin, and 25 parts by mass of naphthenic process oil as a plasticizer were added. The mixture was stirred and kneaded while maintaining a temperature of 170°C to prepare a hot-melt adhesive composition as a homogeneous molten mixture. Next, the prepared hot-melt adhesive composition was melt-coated onto a glassine paper release liner using a die coater to form an adhesive layer with a thickness of 16 μm. Subsequently, a synthetic paper with a thickness of 80 μm (Yupo Corporation, Yupo Tack® base paper SGS80) was laminated onto the formed adhesive layer to create a resealable label.

[0089] [Examples 2-3, Comparative Example 2] A resealable label was obtained in the same manner as in Example 1, except that the adhesive composition had the composition shown in Table 1. In Example 2, a C5 / C9 petroleum resin (DX390N, manufactured by Zeon Corporation, softening point: 93°C) was used as the tackifying resin instead of rosin ester resin.

[0090] [Comparative Example 1] An acrylic adhesive composition with a solid content of 30% by mass was prepared by mixing 100 parts by mass of an acrylic copolymer (monomer composition: 2-ethylhexyl acrylate / methyl acrylate / glycidyl methacrylate / acrylic acid / silane coupling agent = 65 / 30 / 1.5 / 1 / 0.4), 5 parts by mass of an aziridine crosslinking agent, and 20 parts by mass of toluene as a solvent. The obtained adhesive composition was applied to a glassine paper release liner using a roll knife coater to a coating thickness of 16 μm after drying, and dried at 90°C for 2 minutes to form an adhesive layer. Next, a synthetic paper with a thickness of 80 μm (Yupo Corporation, Yupo Tack® base paper SGS80) was laminated onto the adhesive layer to produce a resealable label.

[0091] [Methods for measuring various physical properties] 1.Normal temperature condensation surface adhesion Measurements were performed in accordance with JIS Z0237:2022. Specifically, adhesive sheets prepared in each example and comparative example were cured for 7 days under conditions of 23°C and 50%RH to obtain samples. These samples were cut to a width of 25 mm, the release liner was peeled off, and the adhesive surface of the exposed adhesive layer was attached to a condensed polyethylene board (2 mm thick), and pressed down once back and forth with a 2000 g roller. Subsequently, the sheets were peeled off at a peeling speed of 300 mm / min and a peeling angle of 180° under conditions of 23°C and 50%RH, and the adhesive strength on the condensed surface at room temperature was measured. The measurement results are shown in Table 1.

[0092] The polyethylene boards with condensation were prepared by evenly spraying 0.20g of water onto the surface of a polyethylene board (70mm x 150mm) that had been left standing in a 23°C, 50% RH environment.

[0093] 2. Low-temperature adhesion Using the same procedure as for the adhesion strength test on a condensation surface at room temperature, the adhesive sheet was cured for 7 days under conditions of 23°C and 50% RH to prepare a sample for the low-temperature adhesion strength test. This sample was cut to a width of 25 mm and left to stand in a 5°C environment for 24 hours. Then, under the same environment, the release liner was peeled off, and the exposed adhesive layer was attached to a polyethylene board (2 mm thick) that had been stored at 5°C for 24 hours, and pressed down once back and forth with a roller weighing 2000 g. Then, under the same environment, it was peeled off at a peeling speed of 300 mm / min and a peeling angle of 180°, and the low-temperature adhesion strength was measured. The measurement results are shown in Table 1.

[0094] 3. Storage modulus In each example and comparative example, release paper was placed on the adhesive layer formed, and a substrate-less adhesive sheet was prepared by sandwiching the adhesive between the release papers. The release liner was peeled off this substrate-less adhesive sheet, and the exposed adhesive was laminated to a thickness of 600 μm. The laminate was punched out into a disc shape with a diameter of 8 mm, and the sample was obtained after removing the release liner. The storage modulus of this sample was measured using a Modular Compact Rheometer MCR302 (fixture: PP8, measurement conditions: shear strain γ 0.1-0.01%, frequency f 1 Hz, temperature sweep from -40°C to 120°C), and the storage modulus G'(Pa) at 100°C was recorded.

[0095] [Evaluation method 1: Resealability (low-temperature condensation surface adhesion)] Using the same procedure as for the adhesion strength of a condensed surface at room temperature, the adhesive sheets prepared in each example and comparative example were cured for 7 days under conditions of 23°C and 50% RH to obtain samples. These samples were cut to a width of 25 mm, and the release liner was peeled off in a 5°C environment. The adhesive surface of the exposed adhesive layer was attached to a condensed polyethylene board (2 mm thick) and pressed down once back and forth with a 2000 g roller. Subsequently, the adhesive strength was measured by peeling it off at a peeling speed of 300 mm / min and a peeling angle of 180° in the same environment. The peeled sample was pressed down with a roller using the same procedure to a newly prepared condensed polyethylene board, and the low-temperature condensed surface adhesion strength was measured repeatedly three times. The results of the third measurement and the condition of the polyethylene board to which the sample was attached were evaluated according to the evaluation criteria below. The results are shown in Table 1. The adhesive strength is preferably 3 to 10 N / 25 mm.

[0096] (Evaluation Criteria) A: There is no adhesive residue on the polyethylene plate after the sample has been removed. B: There is a small amount of adhesive residue on the polyethylene plate after the sample has been removed. C: There is adhesive residue on the polyethylene plate after the sample has been removed.

[0097] The polyethylene boards that had condensed on them were prepared by evenly spraying 0.20g of water onto the surface of a polyethylene board (70mm x 150mm) that had been left standing in a 5°C environment.

[0098] [Evaluation Method 2: Resealability (Test using packaging)] Using the same procedure as for the adhesive strength on a condensation surface at room temperature, the adhesive sheets prepared in each example and comparative example were cured for 7 days under conditions of 23°C and 50% RH to obtain samples. These samples were cut to a width of 25 mm, and the adhesive surface of the exposed adhesive layer was attached to a polyethylene frozen food packaging bag, spanning both the folded and unfolded sections of the opening. The bag was then stored at -20°C for 24 hours. After removing the bag from the -20°C environment, the sample was peeled off, left to stand at 23°C and 50% RH for 5 minutes, and then reattached to the same location. The packaging bag was stored in the same environment for a further 240 hours, and the condition of the adhesive label was observed and evaluated according to the evaluation criteria below. The results are shown in Table 1.

[0099] (Evaluation Criteria) A: The adhesive state is maintained, and there is no adhesive residue on the packaging after peeling. B: The adhesive state is maintained, and there is a small amount of adhesive residue on the packaging after peeling. C: The adhesive is not being maintained and has come off.

[0100] [Table 1] As shown above, the resealable labels of the examples were excellent for repeated use on low-temperature and condensation-prone surfaces. On the other hand, the resealable labels of Comparative Example 1, which used an acrylic adhesive in the adhesive layer, and Comparative Example 2, which used a rubber-based adhesive and had a tackifying resin content of 20% by mass in the adhesive composition, were inferior for repeated use on low-temperature and condensation-prone surfaces. However, the resealable labels of Comparative Examples 1 and 2 had no problems with repeated use at room temperature. [Explanation of Symbols]

[0101] 11, 210 Bag-shaped packaging, 20 resealable labels, 21 Base material, 22 Adhesive layer, 211 Cut section, 212 opening.

Claims

1. A resealable label having a base material and an adhesive layer, The adhesive layer is formed from an adhesive composition comprising a rubber-based adhesive containing a styrene copolymer and a tackifying resin. A resealable label wherein the adhesive composition contains 25% by mass or more of the tackifying resin.

2. The resealable label according to claim 1, wherein the adhesive strength in a condensation surface test is 3 N / 25 mm or more.

3. A resealable label according to claim 1 or 2, wherein the adhesive strength in low-temperature tests is 5 N / 25 mm or more.

4. The resealable label according to claim 1 or 2, wherein the storage modulus of the adhesive layer at 100°C is 500 Pa or more.

5. The resealable label according to claim 1 or 2, wherein the softening point of the tackifying resin is 110°C or lower.

6. The resealable label according to claim 1, wherein the adhesive composition comprises a plasticizer.

7. The resealable label according to claim 6, wherein the content of the plasticizer is 5 to 50% by mass in the adhesive composition.

8. The resealable label according to claim 6 or 7, wherein the plasticizer is a petroleum-based plasticizer.

9. The resealable label according to claim 1 or 2, wherein the adhesive composition is of the hot-melt type.

10. A resealable label according to claim 1 or 2, which is affixed to a food package.

11. A resealable label according to claim 1 or 2, for use on packaging stored in a refrigerator or freezer.

12. A resealable label according to claim 1 or 2, which is a flap label.

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