JP7718136B2 - adhesive labels - Google Patents

Description

The present invention relates to an adhesive label. More specifically, it relates to an adhesive label that is attached to an adherend such as a container, and then does not peel off when exposed to room temperature water, but can be easily peeled off from the adherend when exposed to warm or hot water.

Adhesive labels are used in a wide range of applications, including commercial, office, process control, logistics management, and home use. A commonly used adhesive sheet has an adhesive layer on one side of a surface substrate, with the adhesive layer sandwiched between the surface substrate and a release sheet. Recently, adhesive labels without a release sheet have also been developed, in which a release agent or mold release agent is applied to one side of the surface substrate, and an adhesive layer is then applied and laminated on the other side.

Paper, film, metal foil, or the like is used as the surface substrate. Release sheets are often coated with a release agent or mold release agent such as a silicone compound or a fluorine compound. Examples of release sheet substrates include laminated paper, in which a resin film such as polyethylene is laminated onto high-density base paper such as glassine paper, clay-coated paper, kraft paper, or high-quality paper; and resin-coated paper, in which a coating layer composed primarily of a pigment and a water-soluble polymer such as polyvinyl alcohol or starch is applied to kraft paper or high-quality paper. Among these, polyethylene-laminated laminated paper is the most widely used. Adhesives that can be used include rubber-based, acrylic-based, and vinyl ether-based emulsions, as well as various solvent- and solvent-free adhesives.

One use of such adhesive labels is as a management label for plastic containers used as returnable boxes in various logistics departments. Plastic containers are generally made of molded polypropylene or polyethylene resins, due to their ease of molding, durability, chemical resistance, etc. Adhesive labels with printed or inscribed information necessary for logistics management are affixed to one or more surfaces of these plastic containers. However, they are fundamentally required to remain in place until the container is transported to its destination, i.e., to have strong adhesive properties to the surface of the substrate.
The information on the adhesive label is read by a computer, but when a plastic container is reused, there are problems such as the computer misreading the information if a new management label is affixed over a previously used adhesive label.
Therefore, when reusing the product, it is necessary to remove the adhesive label that was firmly attached to the product.

Recently, there has been an accelerating movement away from plastic as a measure to combat environmental issues, and stainless steel trays and containers are beginning to be used in place of plastic containers. These also use adhesive labels for management and display purposes, but just like plastic containers, they require adhesive labels that can both firmly adhere to the substrate and be easily removed from the substrate.

In recent years, when plastic containers and the like are reused, they are washed in automatic washing machines. However, as mentioned above, the adhesive strength of the adhesive labels is so strong that they cannot be removed by washing, and so the labels must be removed by hand, which is costly and time-consuming. Adhesive labels that can be removed by washing in an automatic washing machine have also been proposed (Patent Documents 1 and 2).

Japanese Patent Application Publication No. 9-114382 Japanese Patent Application Laid-Open No. 2001-89722

The adhesive labels in Patent Documents 1 and 2 use an adhesive whose adhesive strength weakens when it comes into contact with water, so they peel off even when water at room temperature or condensation is present. This invention provides an adhesive label that adheres firmly when attached, maintains its adhesion even when water at room temperature is present, and can be easily removed with warm or hot water.

The present invention is as follows.
(1) A pressure-sensitive adhesive label having at least a surface substrate and a pressure-sensitive adhesive layer formed on one surface of the surface substrate,
The surface substrate is a paper substrate having a Stockigt sizing degree of 25 seconds or more,
The adhesive label is characterized in that when the adhesive label is attached to a water-impermeable substrate and immersed in water at 20°C for 300 seconds, the adhesive label does not peel off from the substrate, but when immersed in warm water at 60°C for 300 seconds, the adhesive label peels off from the substrate.
(2) When a test sheet is prepared by laminating 25 g/ ^m2 of the adhesive forming the adhesive layer on a polyethylene terephthalate film having a thickness of 50 μm, the adhesive strength of the test sheet to a SUS plate is 60 to 800 N/m,
The adhesive label according to (1) is characterized in that when the test sheet is attached to a SUS plate and immersed in water at 20°C for 300 seconds, the test sheet does not peel off from the SUS plate, but when immersed in warm water at 60°C for 300 seconds, the test sheet peels off from the SUS plate.
(3) When a test sheet is prepared by laminating 25 g / m ² of the adhesive forming the adhesive layer on a polyethylene terephthalate film having a thickness of 50 μm, the adhesive strength of the test sheet to a SUS plate is 60 to 800 N / m,
An adhesive label according to (1) or (2), characterized in that when the test sheet is attached to a polypropylene plate and immersed in water at 20°C for 300 seconds, the test sheet does not peel off from the polypropylene plate, and when immersed in warm water at 60°C for 300 seconds, the adhesive label peels off from the polypropylene plate.
(4) The adhesive label according to any one of (1) to (3), wherein the surface substrate is a paper substrate having a Stockigt sizing degree of 30 seconds or more.
(5) The adhesive label according to any one of (1) to (4), wherein the adhesive layer contains an acrylic emulsion adhesive.

The pressure-sensitive adhesive label of the present invention is a pressure-sensitive adhesive label having at least a surface substrate and a pressure-sensitive adhesive layer formed on one surface of the surface substrate.
The surface substrate must be a paper substrate having a Stoeckigt sizing degree of 25 seconds or more as specified in JIS P 8122:2004. It is preferably 30 seconds or more, more preferably 40 seconds or more. The upper limit is not particularly limited, but is about 500 seconds. By using such a surface substrate, when hot or warm water is applied, moisture penetrates from the surface of the paper substrate into the interior of the paper substrate, rather than reducing the strength of the paper substrate due to moisture penetration from the surface of the paper substrate into the interior of the paper substrate. This allows the adhesive label to be peeled off without destroying the paper substrate. If the paper substrate is destroyed, a portion of the paper substrate may remain on the adherend, or a portion of the adhesive may remain on the adherend.

The pressure-sensitive adhesive label of the present invention is required to not peel off from an adherend that is impermeable to water when the pressure-sensitive adhesive label is immersed in water at 20° C. for 300 seconds while attached to the adherend, and to peel off from the adherend when immersed in warm water at 60° C. for 300 seconds. This enables the pressure-sensitive adhesive label to not peel off in room temperature water, cold water, condensed water, or the like, which are not intended for peeling, but to peel off when warm water or hot water is applied for the purpose of peeling.
In order to control the peelability by changing the water temperature, it is necessary to use a paper substrate having the specific Stockigt sizing degree mentioned above, and to use an adhesive whose adhesive strength at the interface between the adhesive layer and the adherend decreases when warm water is applied.

The adhesive is not particularly limited as long as, when made into an adhesive label and attached to a water-impermeable substrate, the adhesive label does not peel off from the substrate when immersed in 20°C water for 300 seconds, and peels off from the substrate when immersed in 60°C warm water for 300 seconds.

The adhesive preferably has an adhesive strength to SUS plate of 60 to 800 N/m, more preferably 100 to 600 N/m. The adhesive strength here refers to the adhesive strength of a test sheet to SUS plate when 25 g/m2 of adhesive is laminated onto a 50 μm thick polyethylene terephthalate sheet, creating a test sheet. The adhesive strength is a value in accordance with JIS-Z-0237. An adhesive strength of 60 N/m or more ensures sufficient adhesion to the adherend, while an adhesive strength of 800 N/m or less ensures stable peeling when warm water is applied.

Furthermore, among adhesives that satisfy the above adhesive strength, an adhesive is preferred that does not peel off from the SUS plate when the test sheet is attached to the SUS plate and immersed in water at 20°C for 300 seconds, and that peels off from the SUS plate when immersed in warm water at 60°C for 300 seconds.
The use of such an adhesive in an adhesive label makes the label preferable when used on an adherend such as a container made of SUS etc. Note that "peeling of the test sheet" does not only mean that the test sheet floats up from the SUS plate, but also includes peeling when a slight water flow is generated while the SUS plate is immersed or when the SUS plate is shaken.

Furthermore, among adhesives that satisfy the above-mentioned adhesive strength, an adhesive is preferred that, when the test sheet is attached to a polypropylene plate and immersed in water at 20°C for 300 seconds, the test sheet does not peel off from the polypropylene plate, but when immersed in warm water at 60°C for 300 seconds, the test sheet peels off from the polypropylene plate.
The use of such an adhesive in an adhesive label makes the label preferable when used on an adherend such as a container of polypropylene, etc. Note that "peeling of the test sheet" does not only mean that the test sheet floats up from the polypropylene plate, but also that the test sheet peels off when the test sheet is immersed in water and the SUS plate is gently shaken.

It is preferable to use an adhesive that does not peel off when immersed in water at 20°C and peels off when immersed in warm water at 60°C for 300 seconds on both the SUS plate and the polypropylene plate, as this will exhibit good adhesive strength and peelability for many materials.
The pressure-sensitive adhesive label of the present invention is not limited to use on SUS plates or polypropylene plates, but can be applied to various materials as long as the adherend is water-impermeable. If the adherend is water-permeable, water may penetrate into the adherend during peeling, potentially destroying the adherend and making it difficult to separate the pressure-sensitive adhesive label.

The adhesive can be selected from a variety of emulsion, solvent, or solventless adhesives, such as rubber-based, acrylic-based, or vinyl ether-based adhesives, as long as they satisfy the above requirements. Among these, emulsion-type adhesives are preferred because they provide excellent hydrophilicity at the interface between the adherend surface and the adhesive layer. Acrylic emulsion-type adhesives are also particularly preferred because their adhesive strength and hydrophilicity are easy to control. An acrylic emulsion-type adhesive will be described below as a representative example.

The components that make up the acrylic emulsion-type pressure-sensitive adhesive preferably contain a hydrophilic component. Examples include ethylenically unsaturated carboxylic acid-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, monoalkyl maleic acid, monoalkyl itaconic acid, and monoalkyl fumaric acid; alkoxyalkyl (meth)acrylates such as methoxyethyl acrylate and ethoxyethyl acrylate; carboxylic acid-modified rosin esters; caprolactone adducts of (meth)acrylic acid; hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, (meth)acrylamide, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate; and other hydrophilic monomers that can be copolymerized with these monomers. These monomers are preferably contained in an amount of approximately 5 to 20% by weight in the pressure-sensitive adhesive composition. A content of 5% by weight or more enhances the hydrophilicity of the pressure-sensitive adhesive, while a content of 20% by weight or less enhances adhesive strength.

Further, as components constituting the pressure-sensitive adhesive, in addition to the above-mentioned hydrophilic monomers, copolymerizable monomers that impart tack to the pressure-sensitive adhesive include butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, etc.
Furthermore, components that adjust adhesive performance include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, cyclohexyl (meth)acrylate, glycidyl (meth)acrylate, vinyl acetate, vinyl propionate, vinyl chloride, styrene, ethylene, etc.
These compounds can be used as appropriate in consideration of the balance of adhesive performance of the adhesive, but it is more preferable to use butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, methyl (meth)acrylate, or vinyl acetate in terms of adhesiveness, cohesive strength, etc. of the adhesive.

When producing the copolymer to obtain the adhesive, at least one of (poly)alkylene glycol di(meth)acrylate, (poly)alkylene glycol mono(meth)acrylate, (poly)ethylene glycol, and (poly)propylene glycol may be added. Producing the copolymer in the presence of these compounds can increase the hydrophilicity of the adhesive and increase its molecular weight.

The method for producing the copolymer is not particularly limited, and it can be produced by known methods such as solution polymerization in the presence of water, a solvent, a chain transfer agent, a polymerization initiator, etc., or emulsion polymerization in an aqueous system in the presence of an emulsifier, a chain transfer agent, a polymerization initiator, a dispersant, etc.

Polymerization initiators used during polymerization include, for example, persulfates such as potassium persulfate and ammonium persulfate; azo compounds such as 2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile); peroxides such as hydrogen peroxide, benzoyl peroxide and lauryl peroxide; and so-called redox polymerization initiators consisting of a combination of ammonium persulfate with sodium sulfite or sodium acid sulfite. The amount of polymerization initiator used is typically 0.2 to 2% by mass, and more preferably 0.3 to 1% by mass, of the total amount of monomers used in the polymerization.

Examples of chain transfer agents added during copolymerization include alkyl mercaptans such as octyl mercaptan, nonyl mercaptan, decyl mercaptan, dodecyl mercaptan, and N-dodecyl mercaptan; thioglycolic acid esters such as octyl thioglycolate, nonyl thioglycolate, 2-ethylhexyl thioglycolate, and 2-ethylhexyl β-mercaptopropionate; and 2,4-diphenyl-4-methyl-1-pentene and 1-methyl-4-isopropylidene-1-cyclohexene. Thioglycolic acid esters, 2,4-diphenyl-4-methyl-1-pentene, and 1-methyl-4-isopropylidene-1-cyclohexene are particularly preferred, as the resulting copolymers have a low odor. The amount of chain transfer agent used is adjusted to approximately 0.001 to 3% by mass of the total monomers to be polymerized. Organic solvents such as methanol, ethanol, and isopropyl alcohol can also be used.

The monomer concentration during polymerization is typically 30 to 70% by mass, and preferably 40 to 60% by mass. The polymerization reaction is typically carried out at a temperature of 60 to 100°C for 2 to 8 hours. Additionally, wetting agents, leveling agents, thickeners, antifoaming agents, preservatives, etc. can be added as appropriate.

By adding a crosslinking agent to an acrylic emulsion-type pressure-sensitive adhesive, the strength of the pressure-sensitive adhesive layer can be increased while maintaining hydrophilicity. When the pressure-sensitive adhesive layer has a high film strength, the pressure-sensitive adhesive layer is maintained during peeling, allowing for smooth peeling without leaving adhesive residue on the adherend.
Examples of the crosslinking agent include epoxy-based crosslinking agents such as ethylene glycol diglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, and pentaerythritol polyglycidyl ether; isocyanate-based crosslinking agents such as 1,2-ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,2,4-trimethyl-1,6-hexamethylene diisocyanate; and aluminum metal chelate-based crosslinking agents such as aluminum tris(acetylacetate), aluminum tris(ethylacetoacetate), aluminum acetoacetate aluminum diisopropylate, and aluminum monoacetylacetonate bis(ethylacetoacetate).

When these crosslinking agents are added, they are used in the range of 0.1 to 1.5 parts by mass relative to 100% by mass of the adhesive composition. Adding a crosslinking agent has the effect of improving peel resistance due to strong adhesion to the adherend, but adding too much will increase the crosslink density of the adhesive, weakening the adhesive strength of the resulting adhesive and making it less practical. Of these crosslinking agents, epoxy-based crosslinking agents in particular make it difficult for the adhesive layer to separate after crosslinking, improving peelability in warm water.

A hydrophilic plasticizer can be added to acrylic emulsion adhesives to adjust the adhesive's physical properties and prevent discoloration and deterioration over time. The addition of a hydrophilic plasticizer can also increase the adhesive's hydrophilicity and improve its releasability with warm water.
Examples of hydrophilic plasticizing substances include alkanolamines such as triethanolamine, tripropanolamine, triisopropanolamine, N-methyldiethanolamine, and N,N-dibutylethanolamine; sugar alcohols such as glycerin, sorbitol, mannitol, dulcite, idite, erythritol, arabitol, and adonite; copolymers of polyethylene oxide or polypropylene oxide with polyhydric alcohols such as glycerin, xylitol, trioxyisobutane, and sorbitol; polyether polyols such as polyethylene glycol and polypropylene glycol; copolymers of ethylene oxide and propylene oxide; and nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, and polyoxyethylene polyoxypropylene glycol.
Taking into consideration the adhesiveness and peelability in warm water, these substances are added in an amount of 10% by weight or less, more preferably in the range of 0.5 to 10% by weight, based on 100% by weight of the adhesive. Among these hydrophilic plasticizing substances, alkanolamines and nonionic surfactants are particularly preferred, as they can produce adhesives with good adhesion and storage stability.

When attached to a water-impermeable substrate, the adhesive label will not peel off from the substrate when immersed in 20°C water for 300 seconds, but will peel off from the substrate when immersed in 60°C warm water for 300 seconds. An adhesive that satisfies this requirement can be obtained by, for example, using a known adhesive and adjusting the hydrophilicity, adhesiveness, etc., using a crosslinking agent or hydrophilic plasticizing substance, as described above.

As mentioned above, the surface substrate is a paper substrate with a Stockigt sizing degree of 25 seconds or more. However, other paper substrates such as art paper, coated paper, cast paper, kraft paper, thermal paper, inkjet paper, impregnated paper, and kraft paper can also be used. Even if the paper substrate is high-quality paper with a Stockigt sizing degree of less than 25 seconds, the Stockigt sizing degree can be adjusted to 25 seconds or more by applying a coating liquid primarily composed of natural or synthetic resins and/or pigments, such as casein, dextrin, starch and its derivatives, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, and acrylic ester copolymer.

The typical adhesive label configuration is an adhesive sheet in which an adhesive is coated on one side of the surface substrate, with the adhesive sandwiched between the surface substrate and a release sheet. However, it can also be a tape-like product in which a release agent is coated on the heat-sensitive layer side of thermal paper, or a release-removing printable layer is provided on the printing surface of printing paper such as art paper or coated paper, with an adhesive layer provided on the opposite side, without the use of a release sheet. There are no particular limitations on the release sheet, and any known release sheet can be used.

The adhesive layer may be applied directly to the surface substrate, or may be applied to a release sheet and then laminated to the surface substrate, thereby transferring the adhesive layer to the surface substrate. Known coating methods can be used, such as reverse roll coaters, knife coaters, air knife coaters, bar coaters, slot die coaters, lip coaters, and reverse gravure coaters. The amount of adhesive applied after drying is adjusted to a range of approximately 5 to 50 g/ ^m² . A coating amount of 5 g/m² or ^more ensures sufficient adhesive strength to the adherend, while a coating amount of 50 g/m² or ^less ensures stable peeling.

The present invention will be explained in more detail below using examples, but of course the present invention is not limited to these. Furthermore, all parts, ratios, coating amounts, etc. in the examples are expressed by solid weight unless otherwise specified.

"Surface base material"
Surface substrate A: commercially available coated printing paper (basis weight 84.9 g/m ² , Stockigt sizing degree 17 seconds)
Surface substrate B: commercially available coated printing paper (basis weight 84.9 g/m ² , Stockigt sizing degree 36 seconds)
Surface substrate C: commercially available coated printing paper (basis weight 89 g/m ² , Stockigt sizing degree 209 seconds)
Surface substrate D: commercially available thermal recording paper (basis weight 76 g/m ² , Stockigt sizing degree 43 seconds)

"Production of adhesive 1"
An emulsified monomer mixture was prepared by mixing 75 parts of methoxyethyl acrylate, 20 parts of an acrylic acid caprolactone adduct (trade name: Aronix M-5300, manufactured by Toagosei Co., Ltd.), 220 parts of 2-ethylhexyl acrylate, 45 parts of acrylic acid, 20 parts of vinyl acetate, 20 parts of methyl (meth)acrylate, 6 parts of an anionic emulsifier (trade name: Emal NC-35, manufactured by Kao Corporation), and 150 parts of ion-exchanged water.

Next, 150 parts of ion-exchanged water, 3 parts of potassium peroxide, and 3 parts of octyl mercaptan were charged into a flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen inlet tube, and a thermometer, and the temperature was raised to 80°C while purging with nitrogen, after which 1/6 of the emulsified monomer mixture was added dropwise. When the reaction rate reached 90%, the remaining monomer mixture was added dropwise over 3 hours to carry out polymerization. After completion of the dropwise addition, the mixture was aged at 80°C for 3 hours to complete the reaction.
Next, 2 parts of triethanolamine, 3 parts of a nonionic surfactant (trade name: Emulgen 810, manufactured by Kao Soap Co., Ltd.), and 28 parts of an ethylene-vinyl acetate-acrylic copolymer (trade name: Sumikaflex S-3110, manufactured by Sumitomo Chemical Co., Ltd.) were added to 100 parts of this copolymer, and the mixture was stirred vigorously to obtain an acrylic emulsion-type pressure-sensitive adhesive. 0.5 parts of diglycerol polyglycidyl ether (trade name: Denacol EX-421, manufactured by Nagase Chemicals Co., Ltd.) was added as a crosslinking agent to 100 parts of the acrylic emulsion-type pressure-sensitive adhesive obtained by the above method to produce a pressure-sensitive adhesive.

"Production of adhesive 2"
An adhesive was produced in the same manner as in the production of adhesive 1, except that diglycerol polyglycidyl ether was not added.

"Production of adhesive 3"
An adhesive was produced in the same manner as in the production of adhesive 1, except that the amount of diglycerol polyglycidyl ether added was changed to 0.1 part.

"Production of adhesive 4"
An adhesive was produced in the same manner as in the production of adhesive 1, except that the amount of diglycerol polyglycidyl ether added was changed to 1.5 parts.

"Adhesive 5"
A commercially available removable acrylic adhesive (product name: ATR-715, manufactured by Saiden Chemical Industries, Ltd.) was prepared.

"Adhesive 6"
A commercially available medium-tack acrylic adhesive (product name: BPS1109, manufactured by Toyochem Co., Ltd.) was prepared.

"Creating a test sheet"
Each of PSA 1 to 5 was coated onto a polyethylene-laminated release paper so that the coating weight after drying was 25 g/ ^m² , dried, and then laminated to a 50 μm-thick polyethylene terephthalate film (product name: E5100/manufactured by Toyobo Co., Ltd.) to form a PSA layer, thereby obtaining a test sheet with a release paper. Evaluations were performed by peeling off the release paper to expose the PSA layer. The obtained test sheets were subjected to the following evaluations, and the results are shown in Table 1.

"Adhesion"
The adhesive strength to the SUS plate was measured in accordance with JIS-Z-0237 .

"20℃ water immersion test"
After the test sheet was attached to the SUS plate and left for 24 hours, it was immersed in water at 20° C. and the condition of the test sheet was visually evaluated.
After the test sheet was attached to the polypropylene plate and left for 24 hours, it was immersed in water at 20° C. and the condition of the test sheet was visually evaluated.
(Evaluation criteria)
⊚: The test sheet did not float even after 300 seconds had passed, and no water penetrated from the periphery of the test sheet.
○: The test sheet did not float even after 300 seconds, but a small amount of water infiltrated from the periphery of the test sheet.
△: After 300 seconds, the test sheet was slightly lifted.
×: Test sheet peeled off within 300 seconds

"60°C water immersion test"
After the test sheet was attached to the SUS plate and left for 24 hours, it was immersed in water at 60° C. and the condition of the test sheet was visually evaluated.
After the test sheet was attached to the polypropylene plate and left for 24 hours, it was immersed in water at 60° C. and the condition of the test sheet was visually evaluated.
(Evaluation criteria)
⊚: The test sheet peeled off within 180 seconds. ○: The test sheet peeled off within more than 180 seconds and 300 seconds.
△: The test sheet has not peeled off after 300 seconds, but peels off when lightly stirred. ×: The test sheet has not lifted even after 300 seconds, and does not peel off when lightly stirred.

Comparative Example 1
(Preparation of adhesive labels)
The obtained adhesive 1 was applied to a commercially available polyethylene laminated release paper so as to have a dry weight of 25 g/m ² , and after drying, it was attached to the surface substrate A to obtain an adhesive label.

Example 1
(Preparation of adhesive labels)
The obtained adhesive 1 was applied to a commercially available polyethylene laminated release paper so as to have a dry weight of 25 g/m ² , and after drying, it was attached to the surface substrate B to obtain an adhesive label.

Example 2
(Preparation of adhesive labels)
The obtained adhesive 1 was applied to a commercially available polyethylene laminated release paper so as to have a dry weight of 25 g/m ² , and after drying, it was attached to the surface substrate C to obtain an adhesive label.

Example 3
(Preparation of adhesive labels)
The obtained adhesive 1 was applied to a commercially available polyethylene laminated release paper so as to have a dry weight of 25 g/m ² , and after drying, it was attached to a surface substrate D to obtain an adhesive label.

Example 4
(Preparation of adhesive labels)
The obtained adhesive 2 was applied to a commercially available polyethylene laminated release paper so as to have a dry weight of 25 g/m ² , and after drying, it was attached to the surface substrate B to obtain an adhesive label.

Example 5
(Preparation of adhesive labels)
The obtained adhesive 3 was applied to a commercially available polyethylene laminated release paper so as to have a dry weight of 25 g/m ² , and after drying, it was attached to the surface substrate B to obtain an adhesive label.

Example 6
(Preparation of adhesive labels)
The obtained adhesive 4 was applied to a commercially available polyethylene laminated release paper so as to have a dry weight of 25 g/m ² , and after drying, it was stuck to the surface substrate B to obtain an adhesive label.

Comparative Example 2
(Preparation of adhesive labels)
The obtained adhesive 5 was applied to a commercially available polyethylene laminated release paper so as to have a dry weight of 25 g/m ² , and after drying, it was stuck to the surface substrate B to obtain an adhesive label.

Comparative Example 3
(Preparation of adhesive labels)
The obtained adhesive 6 was applied to a commercially available polyethylene laminated release paper so as to have a dry weight of 25 g/m ² , and after drying, it was attached to the surface substrate B to obtain an adhesive label.

The resulting adhesive labels were evaluated as follows:

"20℃ water immersion test"
A SUS plate, a polypropylene plate, and a glass plate were prepared as adherends, and after adhering an adhesive label, the plate was left for 24 hours, immersed in water at 20° C., and the state of the adhesive label was visually evaluated.
(Evaluation criteria)
⊚: The adhesive label did not come off even after 300 seconds had passed, and no water penetrated from around the label.
○: The adhesive label did not lift even after 300 seconds, but a small amount of water penetrated from the periphery of the label.
△: After 300 seconds, the adhesive label was slightly lifted.
×: Adhesive label peels off within 300 seconds (60°C water immersion test)
A SUS plate, a polypropylene plate, and a glass plate were prepared as adherends, and after adhering an adhesive label, the plates were left for 24 hours, immersed in water at 60° C., and the state of the adhesive label was visually evaluated.
(Evaluation criteria)
⊚: The adhesive label peeled off within 180 seconds. ○: The adhesive label peeled off within more than 180 seconds and 300 seconds.
△: The adhesive label has not peeled off after 300 seconds, but the adhesive label peels off when the adherend is shaken. ×: The adhesive label has not lifted even after 300 seconds, and the adhesive label does not peel off when the adherend is shaken.

As such, the adhesive label of the present invention exhibits sufficient adhesion to the adherend, does not peel off when exposed to water at 20°C, and is easily peeled off when exposed to warm water. Furthermore, the adherend is not limited to SUS plate, and can be applied to a variety of other materials, including metal containers, plastic containers, and glass containers.

Claims (5)

A pressure-sensitive adhesive label having at least a surface substrate and a pressure-sensitive adhesive layer formed on one surface of the surface substrate,
The surface substrate is a paper substrate having a Stockigt sizing degree of 25 seconds or more,
An adhesive label characterized in that when the adhesive label is attached to a water-impermeable adherend and immersed in water at 20°C for 300 seconds, the adhesive label does not peel off from the adherend, but when immersed in warm water at 60°C for 300 seconds, the adhesive label peels off from the adherend,
the pressure-sensitive adhesive layer contains an acrylic emulsion-type pressure -sensitive adhesive and a hydrophilic plasticizing substance,
The adhesive label has an additive amount in the adhesive layer of 0.5 to 10% by weight relative to 100% by weight of the adhesive.
When a test sheet is prepared by laminating 25 g/ ^m2 of the adhesive forming the adhesive layer onto a polyethylene terephthalate film having a thickness of 50 μm, the adhesive strength of the test sheet to an SUS plate in accordance with JIS-Z-0237 is 60 to 800 N/m,
2. The adhesive label according to claim 1, wherein the adhesive is such that when the test sheet is attached to a stainless steel plate and immersed in water at 20°C for 300 seconds, the test sheet does not peel off from the stainless steel plate, but when immersed in warm water at 60°C for 300 seconds, the test sheet peels off from the stainless steel plate. When a test sheet is prepared by laminating 25 g/ ^m2 of the adhesive forming the adhesive layer onto a polyethylene terephthalate film having a thickness of 50 μm, the adhesive strength of the test sheet to an SUS plate in accordance with JIS-Z-0237 is 60 to 800 N/m,
3. The adhesive label according to claim 1, wherein the adhesive is such that when the test sheet is attached to a polypropylene plate and immersed in water at 20°C for 300 seconds, the test sheet does not peel off from the polypropylene plate, but when immersed in warm water at 60°C for 300 seconds, the test sheet peels off from the polypropylene plate. The adhesive label according to any one of claims 1 to 3, wherein the surface substrate is a paper substrate having a Stockigt sizing degree of 30 seconds or more. 5. The adhesive label according to claim 1, wherein the hydrophilic plasticizing substance is at least one selected from the following hydrophilic plasticizing substances:
(hydrophilic plasticizing substance)
Nonionic surfactants selected from alkanolamines such as triethanolamine, tripropanolamine, triisopropanolamine, N-methyldiethanolamine, and N,N-dibutylethanolamine; sugar alcohols such as glycerin, sorbitol, mannitol, dulcite, idite, erythritol, arabitol, and adonite; copolymers of polyethylene oxide or polypropylene oxide with polyhydric alcohols such as glycerin, xylitol trioxyisobutane, and sorbitol; polyether polyols such as polyethylene glycol and polypropylene glycol; copolymers of ethylene oxide and propylene oxide; polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene polyoxypropylene glycols.