Adhesive label

Abstract

To provide a pressure-sensitive adhesive label which enables a polyester container to be recycled without being peeled from the polyester container and enables a printed part to be peeled in a short time in an alkaline aqueous solution at a low temperature (about 70 °C).SOLUTION: A pressure-sensitive adhesive label comprising a polyester-based pressure-sensitive adhesive layer, a polyester resin substrate, and a releasing coat layer in this order, wherein the releasing coat layer is formed from a coat layer-forming composition containing an aqueous polyester resin having an acid number of 10KOHmg / g or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an adhesive label. [Background technology]

[0002] In recent years, there has been a strong demand for the recycling of polyester-based containers due to issues such as environmental pollution and the depletion of petroleum resources. Among polyester-based containers, there is a particular demand for the recycling of polyethylene terephthalate (PET) bottles.

[0003] In material recycling of polyester-based containers, the containers are usually crushed into pellets, then heated and melted to homogenize the entire material, and the resulting recycled resin is used as the material for polyester-based containers.

[0004] Typically, polyester containers such as PET bottles have adhesive labels (also referred to as labels) affixed to their surfaces with various pieces of information. When recycling polyester containers such as labeled PET bottles, if the resin substrate of the label is not compatible with the resin constituting the polyester container, the resin substrate and adhesive constituting the label act as foreign matter, resulting in a problem of reduced mechanical properties of the recycled resin. Therefore, in such cases, it is necessary to peel the label off the polyester container, crush it into pellets, and heat-melt it. However, the process of peeling the label off a polyester container is extremely cumbersome and time-consuming, and increases the recycling processing costs, resulting in problems of both operational and economic disadvantages.

[0005] In this regard, for example, Patent Document 1 listed below discloses an adhesive label comprising a polyester resin substrate that is compatible with a polyester container as an adherend, and a coating layer that is peelable from the substrate by washing and immersing in an alkaline aqueous solution and has printability and is provided on one side of the substrate, and a polyester adhesive layer is provided on the other side.

[0006] With this configuration, the surface coating and ink layer can be easily peeled off by washing and immersing in an alkaline aqueous solution, and by using a polyester-based adhesive made from the same material as resin molded products such as PET bottles, it is possible to recycle molded products such as PET bottles without removing the label. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-10489 Summary of the Invention [Problem to be solved by the invention]

[0008] As mentioned above, when recycling polyester containers such as PET bottles, if an adhesive label is attached to the substrate, the printed portion becomes an impurity, reducing the recycling efficiency. Therefore, the printed portion must be removed during washing with an alkaline aqueous solution. When removing the printed portion using an alkaline aqueous solution, it is preferable for work efficiency that the printed portion can be removed in a short time using an alkaline aqueous solution at a low temperature (approximately 70°C). Furthermore, excellent printability is required when printing information.

[0009] The present invention has been made to solve the above problems, and it is possible to recycle polyester containers without peeling them off from the polyester containers, and to recycle polyester containers at low temperatures (70 An object of the present invention is to provide an adhesive label whose printed portion can be removed (peeled off) in an alkaline aqueous solution at a temperature of about °C in a short time. Another object of the present invention is to provide an adhesive label having excellent printability. [Means for solving the problem]

[0010] In order to achieve the above object, the adhesive label according to the present invention is an adhesive label having a polyester-based resin substrate, a polyester-based adhesive layer, and a release coating layer in this order, wherein the release coating layer is formed from a composition for forming a release coating layer, which contains an aqueous polyester-based resin having an acid value of 10 KOH mg / g or more. [Effects of the Invention]

[0011] The adhesive label of the present invention has a polyester-based resin substrate and a polyester-based adhesive layer, and therefore allows polyester-based containers to be recycled without peeling the adhesive label from the polyester-based container. Furthermore, the adhesive label of the present invention allows the printed portion to be peeled off in a short time in an alkaline aqueous solution at a low temperature (about 70°C). Furthermore, the adhesive label of the present invention has excellent printability. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view illustrating a pressure-sensitive adhesive label according to an embodiment of the present invention. [Figure 2] FIG. 10 is a cross-sectional view illustrating a pressure-sensitive adhesive label according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0014] In this specification, the range "X to Y" means "X or more and Y or less." Unless otherwise specified, operations and physical properties are measured under conditions of room temperature (20 to 25°C) and relative humidity of 45 to 55% RH.

[0015] The adhesive label is attached to a polyester-based container such as a polyethylene terephthalate (PET) bottle. Hereinafter, a PET bottle will be described as an example of an adherend to which the adhesive label is attached. The shape of the adhesive label is not particularly limited, but is generally rectangular when viewed from the stacking direction. The adhesive label may also have a triangular or circular shape. The polyester-based adhesive layer is disposed, for example, on the entire surface of a polyester-based resin substrate.

[0016] Considering adhesion to PET bottles, the adhesive strength of the adhesive label is preferably 3.5 N / 25 mm or more, more preferably 5 N / 25 mm or more, and even more preferably 6.5 N / 25 mm or more. There is no particular upper limit to the adhesive strength of the adhesive label, but it may be 30 N / 25 mm or less, or even 20 N / 25 mm or less. The adhesive strength to the substrate is measured by attaching the polyester adhesive layer side of the adhesive label to a polyethylene terephthalate plate and measuring the adhesive strength after 24 hours in a 180° direction at a test speed of 0.3 m / min according to JIS Z0237:2009 using a tensile tester. More specifically, the adhesive strength to the substrate is measured by the following method: the adhesive label is left to stand under standard conditions (23°C, 50% RH) for 24 hours, the release liner is peeled off, and the polyester adhesive layer side is attached to the polyethylene terephthalate plate. After leaving it for 24 hours under standard conditions, the adhesive strength is measured according to JIS Z0237:2009. Specifically, the adhesive label is peeled off in a 180° direction at a test speed of 0.3 m / min using a tensile tester, and the adhesive strength is measured. The numerical value is converted into peel force per 25 mm of film width (N / 25 mm). do.

[0017] The structure of the adhesive label will be described below with reference to FIG.

[0018] FIG. 1 is a cross-sectional schematic diagram of an adhesive label 10 according to one embodiment. As shown in FIG. 1, the adhesive label 10 according to the embodiment of the present invention has, from top to bottom, a printed portion 13, a release coating layer 14, a polyester-based resin substrate (hereinafter also simply referred to as a resin substrate) 16, a polyester-based adhesive layer 15, and a release liner 30. The release liner 30 is composed of a release agent layer 12 and a release substrate 11 arranged in this order. The release coating layer 14 decomposes and dissolves when it comes into contact with alkaline water, causing the printed portion 13 to detach (peel) from the adhesive label 10. As a result, the detached printed portion 13 floats on the surface, making it easy to collect. The adhesive label 10 may have other functional layers, such as a primer layer, between the layers or on the surface.

[0019] FIG. 2 is a cross-sectional schematic diagram of an adhesive label 20 according to another embodiment. The adhesive label 20 has an alkali-insoluble coating layer 17 between the printed portion 13 and the release coating layer 14 of the adhesive label 10. That is, the alkali-insoluble coating layer 17 is provided on the release coating layer 14 facing the polyester resin substrate 16. The alkali-insoluble coating layer 17 does not dissolve during alkali peeling and remains as resin, so it is released in the form of a film together with the upper printed portion 13. That is, the printed portion does not become small and has a certain size or larger, making it easy to collect. Here, "on the release coating layer" does not only mean that the release coating layer and the alkali-insoluble coating layer are adjacent to each other, but also means that another layer may exist between the release coating layer and the alkali-insoluble coating layer. A preferred embodiment is that the release coating layer and the alkali-insoluble coating layer are adjacent to each other.

[0020] Furthermore, a preferred embodiment has no release coating layer between the resin substrate 16 and the polyester-based pressure-sensitive adhesive layer 15. In one preferred embodiment, the resin substrate 16 and the polyester-based pressure-sensitive adhesive layer 15 are adjacent to each other. Since there is no release coating layer between the resin substrate 16 and the polyester-based pressure-sensitive adhesive layer 15 and the release coating layer 14 is present between the resin substrate 16 and the printed portion 13 or between the resin substrate 16 and the alkali-insoluble coating layer 17, the resin substrate 16 does not peel off from the polyester container (adherend) when it comes into contact with alkaline water, and the polyester-based pressure-sensitive adhesive layer 15 and the resin substrate 16 remain attached to the polyester container. Therefore, both the resin substrate 16 and the polyester-based pressure-sensitive adhesive layer 15 can be recycled.

[0021] The concept of "label" includes what are called films, sheets, tapes, etc.

[0022] Each component will be described below.

[0023] <Print section 13> The printed portion is a layer for displaying information, and is an optional layer in the present invention. There are no particular limitations on how the printed portion is formed, and it can be formed by, for example, flexographic printing, offset printing, letterpress printing, gravure printing, screen printing, etc.

[0024] The information displayed on the printed portion may be, for example, letters, numbers, illustrations, photographs, graphs, or a combination thereof.

[0025] <Alkali-insoluble coating layer> The alkali-insoluble coating layer is a layer disposed below the printed part, and since it does not dissolve during alkali peeling and remains as a resin, the printed part is detached in the form of a film, making it easy to recover the printed part. For this reason, the alkali-insoluble coating layer is preferably disposed on the printed surface.

[0026] The alkali-insoluble coating layer is mainly composed of a resin. Here, "main component" refers to a resin that accounts for 60% by mass or more (upper limit: 100% by mass) of the alkali-insoluble coating layer. The resin is alkali-insoluble. Here, "alkali-insoluble" refers to a resin whose solubility in a 1.5% by mass aqueous sodium hydroxide solution (pH 13.6) at 70°C is 20% by mass or less (lower limit: 0% by mass), preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 1% by mass or less.

[0027] Examples of resins that form the alkali-insoluble coating layer include urethane-modified polyester resins, acrylic acid ester (co)polymers, epoxy resins, and polyamide resins. Among these, urethane-modified polyester resins are preferred as the resin that forms the alkali-insoluble coating layer, as they provide high print adhesion. Furthermore, the resin that forms the alkali-insoluble coating layer preferably has an acid value of 3 KOHmg / g or less, and more preferably 2 KOHmg / g or less, in order to reduce the solubility in alkaline water.

[0028] Specific examples of urethane-modified polyester resins include polymers (polyester urethanes) obtained by reacting various polyisocyanate compounds with polyester polyols having hydroxyl groups at the terminals of polymers obtained by condensation polymerization of polyols and carboxylic acid components.

[0029] Examples of the polyisocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate.

[0030] The number average molecular weight (Mn) of the urethane-modified polyester resin is preferably 2,000 to 100,000, and more preferably 5,000 to 50,000. Here, the number average molecular weight (Mn) is the number average molecular weight measured by gel permeation chromatography (GPC) and converted into polystyrene.

[0031] The glass transition temperature of the urethane-modified polyester resin is, for example, preferably 100°C or lower, and more preferably from -40 to 100°C.

[0032] The urethane-modified polyester resin may be a commercially available product, and examples of commercially available products include the Vylon series (trade name) manufactured by Toyobo Co., Ltd., such as Vylon UR-2300 (number average molecular weight 32,000, Tg 18°C, acid value less than 1 KOH mg / g), Vylon UR-3200 (number average molecular weight 40,000, Tg -3°C, acid value less than 1 KOH mg / g), Vylon UR-3210 (number average molecular weight 40,000, Tg -3°C, acid value less than 1 KOH mg / g), Preferred examples include Byron UR-6100 (number average molecular weight 25,000, Tg -30°C, acid value less than 1 KOH mg / g), Byron UR-8200 (number average molecular weight 25,000, Tg 73°C, acid value less than 1 KOH mg / g), Byron UR-8300 (number average molecular weight 30,000, Tg 23°C, acid value less than 1 KOH mg / g), and Byron UR-8700 (number average molecular weight 32,000, Tg -22°C, acid value less than 1 KOH mg / g).

[0033] The content of the resin in the alkali-insoluble coating layer is preferably 80 to 100% by mass, and more preferably 90 to 99% by mass.

[0034] The resin contained in the alkali-insoluble coating layer is preferably a crosslinked body. When the resin is a crosslinked body, the solubility in alkaline water is further reduced, which is preferable. In order to make the resin a crosslinked body, an alkali-insoluble coating layer for forming the alkali-insoluble coating layer described later is used. A crosslinking agent may be contained in the composition for forming the resin. In this case, a crosslinking agent that reacts with the crosslinkable reactive groups in the resin is appropriately selected. In particular, by selecting a crosslinking agent that reacts with the carboxyl group, which is the crosslinkable reactive group, the carboxyl group remaining in the resin can be crosslinked, which is preferable because the solubility in alkaline water is further reduced.

[0035] Examples of crosslinking agents that can react with a carboxyl group include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and metal chelate-based crosslinking agents.

[0036] Isocyanate crosslinking agents include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methylcaprate, lysine diisocyanate, lysine ester triisocyanate, and 1,6,11-undecane triisocyanate. Examples of the diisocyanate derivatives include aliphatic diisocyanates such as 1,3,6-hexamethylene triisocyanate, trimethylhexamethylene diisocyanate, and decamethylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate and xylene diisocyanate; and alicyclic diisocyanates such as isophorone diisocyanate; as well as adducts of diisocyanate compounds with polyol compounds such as trimethylolpropane, biuret compounds and isocyanurate compounds of diisocyanate compounds, and bifunctional diisocyanate compounds.

[0037] Examples of epoxy crosslinking agents include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, and diglycidylamine.

[0038] Examples of the aziridine crosslinking agent include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethane tri-β-aziridinylpropionate, toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1-(2-methylaziridine), tris-1-(2-methylaziridine)phosphine, and trimethylolpropane tri-β-(2-methylaziridine)propionate.

[0039] Metal chelate crosslinking agents include chelate compounds whose metal atoms are aluminum, zirconium, titanium, zinc, iron, tin, etc., but aluminum chelate compounds are preferred from the viewpoint of performance. Examples of aluminum chelate compounds include diisopropoxyaluminum monooleyl acetoacetate, monoisopropoxyaluminum bisoleyl acetoacetate, monoisopropoxyaluminum monooleate monoethyl acetoacetate, diisopropoxyaluminum monolauryl acetoacetate, diisopropoxyaluminum monostearyl acetoacetate, and diisopropoxyaluminum monoisostearyl acetoacetate.

[0040] Among these, it is preferable that the crosslinking agent is an isocyanate-based crosslinking agent, since high print adhesion can be obtained in the coating layer after crosslinking.

[0041] The above crosslinking agents may be used alone or in combination of two or more.

[0042] The amount of crosslinking agent added is appropriately determined taking into consideration the amount of crosslinkable reactive groups in the resin, and is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the resin.

[0043] The thickness of the alkali-insoluble coating layer is preferably 0.05 to 1 μm, more preferably 0.05 to 0.5 μm, in consideration of ease of recovery of the printed portion and thinness.

[0044] The alkali-insoluble coating layer may contain additives such as a catalyst, an ultraviolet absorber, a pigment, and a filler.

[0045] <Detachment Coating Layer 14> The release coating layer is a layer formed from a coating layer-forming composition containing an aqueous polyester resin having an acid value of 10 KOHmg / g or more.

[0046] From the viewpoint of deinking properties (ability to remove printing ink) when immersed in alkali, the thickness of the release coating layer is preferably 0.01 to 3 μm, more preferably 0.03 to 1 μm, and even more preferably 0.05 to 0.5 μm.

[0047] The composition for forming a release coating layer, which is a material for forming the release coating layer, contains an aqueous polyester resin (hereinafter simply referred to as "aqueous polyester resin") having an acid value of 10 KOHmg / g or more.

[0048] "Aqueous polyester resin" refers to a polyester resin that can be dissolved in an aqueous solvent to form an aqueous solution, or a polyester resin that can be dispersed as an emulsion in an aqueous solvent to form an aqueous dispersion. The use of such an "aqueous" polyester resin makes it possible to reduce the amount of volatile organic compounds emitted during coating. Here, an aqueous solvent refers to one that contains 60% by mass or more of water (up to 100% by mass), preferably 70% by mass or more, more preferably 85% by mass or more, and most preferably 95% by mass or more of aqueous solvent.

[0049] Components other than water contained in the aqueous solvent include water-soluble organic solvents, such as methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, dimethylformamide, methyl cellosolve, tetrahydrofuran, and ethylene glycol mono-t-butyl ether (ETB).

[0050] In one embodiment of the present invention, in order to prepare an aqueous dispersion in which the aqueous polyester resin is dispersed as an emulsion in water, a small amount of an emulsifier, a surfactant, or the like may be used within a range that does not impair the effects of the present invention.

[0051] However, low-molecular-weight components such as emulsifiers and surfactants may be localized in the release coating layer, resulting in reduced adhesion and possibly reduced interlayer adhesion. From the viewpoint of suppressing this phenomenon, in one embodiment of the present invention, the aqueous polyester resin is preferably a self-emulsifying aqueous polyester resin.

[0052] If a self-emulsifying aqueous polyester resin is used, it is possible to form an emulsion without using low molecular weight components such as emulsifiers or surfactants, which can cause a decrease in interlayer adhesion, and therefore the interlayer adhesion of the resulting pressure-sensitive adhesive sheet can be further improved. This means that some kind of hydrophilic group is chemically introduced into the resin skeleton, and the resin itself has emulsifying ability without the need for the addition of an emulsifier or surfactant.

[0053] The acid value of the aqueous polyester resin is 10 KOH mg / g or more, preferably 15 KOH mg / g or more, more preferably 20 KOH mg / g or more, even more preferably 30 KOH mg / g or more, still more preferably 40 KOH mg / g or more, and particularly preferably 50 KOH mg / g or more. In this specification, the acid value of the aqueous polyester resin is measured according to JIS K The values ​​were measured in accordance with 0070:1992.

[0054] The glass transition temperature (Tg) of the aqueous polyester resin used in one embodiment of the present invention is preferably 30 to 55° C., more preferably 33 to 50° C., and even more preferably 36 to 48° C., from the viewpoint of improving interlayer adhesion with the resin substrate. In this specification, the glass transition temperature (Tg) of the aqueous polyester resin is a value measured in accordance with JIS K 7121:2012, and specifically, a value measured based on the method described below.

[0055] The number average molecular weight (Mn) of the aqueous polyester resin is preferably 1,000 to 15,000, more preferably 1,500 to 10,000, and even more preferably 2,000 to 5,000, from the viewpoint of improving the solubility or dispersibility in water and the interlayer adhesion between the primer layer to be formed and the substrate and / or pressure-sensitive adhesive layer. If the Mn of the aqueous polyester resin is in such a range where the molecular weight is relatively low, the solubility or dispersibility in water is sufficiently high, and the coating liquid can be stored stably for a long period of time, which is preferable.

[0056] In the present invention, the number average molecular weight (Mn) is a value calculated as a standard polystyrene as measured by gel permeation chromatography (GPC), and specifically, is a value measured according to the method described below. (1) Number average molecular weight (Mn) Measurements are carried out using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8020") under the conditions below, and the values ​​measured are converted into standard polystyrene equivalents. Columns: TSK guard column HXL-H, TSK gel GMHXL (x2), and TSK gel G2000HXL (all manufactured by Tosoh Corporation). Column temperature: 40°C. Developing solvent: tetrahydrofuran ·Flow rate: 1.0mL / min (2) Glass transition temperature (Tg) Measurements are performed in accordance with JIS K 7121:2012 using a differential scanning calorimeter (manufactured by TA Instruments Japan, product name "DSC Q2000") at a heating rate of 20°C / min.

[0057] Examples of the aqueous polyester resin used in one embodiment of the present invention include copolymers obtained by polycondensation of an alcohol component and a carboxylic acid component, and modified products of such copolymers.

[0058] Examples of modified copolymers include polyurethane-modified polyester resins obtained by reacting hydroxyl groups at the terminals of a copolymer obtained by polycondensation of an alcohol component and a carboxylic acid component with a polyisocyanate compound. In the present invention, such modified aqueous polyester resins are also included in the "aqueous polyester resin."

[0059] As the alcohol component, a polyhydric alcohol having two or more hydroxyl groups in one molecule can be used.

[0060] Specific examples of the alcohol component include ethylene glycol and diethylene glycol. glycols such as ethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 3-methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, neopentyl glycol, and hydroxypivalic acid neopentyl glycol ester; Examples of suitable alcohol components include polylactone diols to which lactones such as bis(hydroxyethyl) terephthalate have been added; polyester diols such as bis(hydroxyethyl) terephthalate; dihydric cyclic alcohols such as 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, spiroglycol, and dihydroxymethyltricyclodecane; ethylene oxide and propylene oxide adducts of bisphenol A; and trihydric or higher polyhydric alcohols such as glycerin, trimethylolpropane, trimethylolethane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, sorbitol, and mannitol. These alcohol components may be used alone or in combination of two or more.

[0061] As the carboxylic acid component, a polybasic acid having two or more carboxyl groups in one molecule can be used.

[0062] Specific examples of the carboxylic acid component include phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, HET acid, maleic acid, and the like. Examples of the carboxylic acid component include dicarboxylic acids and anhydrides thereof, such as cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, and methylhexahydrophthalic acid; tricarboxylic acids and anhydrides thereof, such as trimellitic acid, pyromellitic acid, trimesic acid, methylcyclohexene tricarboxylic acid, hexahydrotrimellitic acid, and tetrachlorohexene tricarboxylic acid; and tetracarboxylic acids and anhydrides thereof, such as 1,2,4,5-cyclohexanetetracarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, and pyromellitic acid. These carboxylic acid components may be used alone or in combination of two or more.

[0063] From the viewpoint of adjusting the acid value within the above range, the aqueous polyester resin used in one embodiment of the present invention preferably has a structural unit derived from a polybasic acid having three or more carboxyl groups in one molecule, and more preferably has a structural unit derived from a tricarboxylic acid or an anhydride of a tricarboxylic acid.

[0064] Furthermore, the aqueous polyester resin used in one embodiment of the present invention is preferably an aqueous polyester resin containing a carboxyl group, from the same viewpoint as above.

[0065] (particle) The composition for forming a release coating layer may contain particles for the purpose of improving blocking resistance, etc.

[0066] The particles may be either inorganic or organic particles as long as they are water-dispersible. Examples of inorganic particles include zirconia, silica, titanium dioxide, kaolin, alumina, and titania. Examples of organic particles include silica, zeolite, calcium carbonate, barium sulfate, magnesium hydroxide, calcium phosphate, glass, mica, and talc. Examples of organic particles include acrylic resin particles such as polymethyl methacrylate, polystyrene particles, styrene-acrylic resin particles, and polycarbonate particles. Of these, silica is preferred.

[0067] The content of the particles in the composition for forming a release coating layer is set appropriately to achieve the desired purpose (for example, improving blocking resistance), and is, for example, 0.1 to 10 parts by mass per 100 parts by mass of the aqueous polyester resin.

[0068] The average particle size of the particles is appropriately set taking into consideration the desired purpose, but for example, for the purpose of improving blocking resistance, it is preferably 0.1 to 1 μm, and more preferably 0.3 to 0.6 μm. In this specification, unless otherwise specified, the average particle size refers to the average particle size on a volume basis, and can be determined, for example, by measuring a particle dispersion using a Coulter Counter particle size distribution analyzer (TA-II model, manufactured by COULTER ELECTRONICS INC.) with a 50 μm aperture.

[0069] (general-purpose additives, other resin components) The composition for forming a release coating layer used in one embodiment of the present invention may contain general-purpose additives such as surfactants in addition to the above-mentioned aqueous polyester resin and particles, as long as the effects of the present invention are not impaired.

[0070] <Resin substrate 16> It is necessary to use a polyester film, which is made of the same material as the PET bottle as the adherend and is compatible with it, as the resin substrate. That is, the resin substrate is a polyester resin substrate. In terms of the quality of the recycled resin, such as its mechanical properties, it is particularly advantageous to use a resin substrate for the polyester film that has a composition similar to that of the resin used in the PET bottle. Examples of resin substrates used in this polyester film include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. One or more of these may be appropriately selected and used depending on the type of resin used in the adherend PET bottle so as to obtain a resin substrate that is compatible with it.

[0071] Here, compatibility means that the resin can be melted at the temperature at which the PET bottle is heated and melted, and is well mixed with the resin substrate of the melted PET bottle, without degrading the properties of the recycled product. If the resin substrate of the PET bottle is a mixture of two or more compatible resins, one of the resins in the mixture that makes up the PET bottle can be used as the resin for resin substrate 16.

[0072] The thickness of the resin substrate 16 is not particularly limited and can be appropriately selected depending on the application, but is generally preferably in the range of 25 to 100 μm. When attaching an adhesive label to a container, a labeling process may be performed using a labeling device to attach the adhesive label to the container, from the perspective of accounting efficiency. By making the thickness of the resin substrate 16 25 μm or more, the adhesive label can be easily released from the release liner 30 during the labeling process. Furthermore, by making the thickness of the resin substrate 16 100 μm or less, the roll length installed in the labeling device can be sufficiently long, reducing the frequency of roll replacement and improving work efficiency. The resin substrate 16 may be obtained by any conventional film-forming method, such as extrusion, calendaring, solution coating, or casting.

[0073] In the present invention, the resin substrate 16 may have a surface layer on one side, if desired, for the purpose of improving adhesion with a coating layer provided thereon and a polyester-based adhesive layer 15 provided on the opposite side. Surface treatments can be applied to one or both sides of the substrate, such as surface roughening treatments using sandblasting or solvent treatment, or surface oxidation treatments such as corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, and ozone or ultraviolet irradiation treatment.

[0074] <Polyester-based pressure-sensitive adhesive layer 15> Next, we will explain the polyester-based pressure-sensitive adhesive layer 15. The polyester-based pressure-sensitive adhesive layer 15 is formed from a polyester-based pressure-sensitive adhesive composition containing a polyester-based resin (A) as a main component.

[0075] The polyester resin (A) used in the present invention can be obtained by copolymerizing copolymerization components containing a polycarboxylic acid component (A1) and a polyol component (A2) as constituent raw materials.

[0076] [Polycarboxylic acid component (A1)] Examples of the polycarboxylic acid component (A1) used in the present invention include: Aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, benzylmalonic acid, diphenic acid, 4,4′-oxydibenzoic acid, and naphthalenedicarboxylic acid; Aliphatic dicarboxylic acids such as malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, thiodipropionic acid, and diglycolic acid; Alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, and adamantanedicarboxylic acid; These may be used alone or in combination of two or more.

[0077] Among these, it is preferable to contain an aromatic dicarboxylic acid in order to impart cohesive strength.

[0078] The content of the aromatic dicarboxylic acid is preferably 50 mol % or less, more preferably 5 to 40 mol %, and particularly preferably 10 to 30 mol %, based on the total polycarboxylic acid component (A1). If the content is too high, the glass transition temperature becomes high, and sufficient adhesive properties tend not to be obtained.

[0079] In order to impart tackiness, it is preferable that the composition contains an aliphatic dicarboxylic acid, and it is particularly preferable that the composition contains an aliphatic dicarboxylic acid having 4 to 12 carbon atoms.

[0080] The content of the aliphatic dicarboxylic acid is preferably 20 mol% or more, more preferably 50 mol% to 95 mol%, and even more preferably 70 to 90 mol%, based on the total polycarboxylic acid component (A1). If the content is too low, the glass transition temperature tends to be high and sufficient adhesive strength tends to be insufficient, while if the content is too high, the adhesive component tends to be reduced, resulting in a decrease in adhesive strength to polar adherends.

[0081] In the present invention, from the viewpoint of a balance of adhesive properties, it is preferable to use an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid in combination as the polycarboxylic acid component (A1), and the content ratio (molar ratio) of the aromatic dicarboxylic acid / aliphatic dicarboxylic acid is preferably from 1 / 99 to 90 / 10, more preferably from 5 / 95 to 49 / 51, and even more preferably from 10 / 9. It is 0~30 / 70.

[0082] In order to increase the number of branching points in the polyester resin (A), a trivalent or higher polycarboxylic acid can be used. Examples of such trivalent or higher carboxylic acids include trimellitic acid, pyromellitic acid, adamantanetricarboxylic acid, and trimesic acid. Among these, trimellitic acid is preferably used because it is relatively less likely to cause gelation. The content of such a trivalent or higher polycarboxylic acid is preferably 10 mol % or less, particularly preferably 0.1 to 5 mol %, based on the total polycarboxylic acid component (A1), in order to increase the cohesive strength of the adhesive. If the content is too high, gelation tends to occur easily during the production of the polyester resin (A).

[0083] [Polyol component (A2)] Examples of the polyol component (A2) used in the present invention include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2,2 and dihydric alcohols such as aliphatic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecane dimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; and aromatic diols such as 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, o-, m-, and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol, and their ethylene oxide and propylene oxide adducts. These may be used alone or in combination of two or more.

[0084] Among these, aliphatic diols and alicyclic diols are preferred because of their excellent reactivity. Particularly preferred aliphatic diols include ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol, and particularly preferred alicyclic diols include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol.

[0085] Furthermore, trihydric or higher polyhydric alcohols can be used to increase the number of branching points in the polyester resin (A), and examples of trihydric or higher polyhydric alcohols include pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, adamantanetriol, etc. The content of such trihydric or higher polyhydric alcohols is preferably 10 mol % or less, particularly preferably 0.1 to 5 mol %, based on the total polyol component (A2); if the content is too high, production of the polyester resin (A) tends to become difficult.

[0086] The blending ratio of the polycarboxylic acid component (A1) to the polyol component (A2) is preferably 1 to 2 equivalents, particularly preferably 1.1 to 1.7 equivalents, of the polyol component (A2) per equivalent of the polycarboxylic acid component (A1). If the content of the polyol component (A2) is too low, the acid value tends to increase, making it difficult to achieve a high molecular weight, while if it is too high, the yield tends to decrease.

[0087] The polyester resin (A) used in the present invention is produced by arbitrarily selecting the polycarboxylic acid component (A1) and the polyol component (A2) and subjecting them to a polycondensation reaction in the presence of a catalyst by a known method.

[0088] The number average molecular weight of the polyester resin (A) used in the present invention is preferably 5,000 to 100,000, more preferably 10,000 to 100,000, and even more preferably 15,000 to 80,000, from the viewpoints of cohesive strength, heat resistance, mechanical strength, adhesiveness, etc.

[0089] The number average molecular weight is the number average molecular weight converted into the molecular weight of standard polystyrene, and is measured by using a high performance liquid chromatography (manufactured by Tosoh Corporation, "HLC-8220 GPC") with two TSK gel GMHXL columns in series.

[0090] Typically, the polyester resin (A) is crosslinked using a crosslinking agent to provide excellent cohesive strength and exhibit excellent performance as a pressure-sensitive adhesive. Examples of such crosslinking agents include polyisocyanate compounds (isocyanate crosslinking agents) and polyepoxy compounds, which have functional groups that react with the hydroxyl and / or carboxyl groups contained in the polyester resin (A). Among these, polyisocyanate compounds are particularly preferred because they can achieve a good balance between initial adhesion, mechanical strength, and heat resistance.

[0091] Examples of such polyisocyanate compounds include polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, and hydrogenated xylylene diisocyanate, as well as isocyanate adducts such as a tolylene diisocyanate adduct of trimethylolpropane, a hexamethylene diisocyanate adduct, and an isophorone diisocyanate adduct. The above polyisocyanate compounds may also be used in which the isocyanate moiety is blocked with phenol, lactam, or the like. These crosslinking agents may be used alone or in combination of two or more.

[0092] The amount of the crosslinking agent to be added can be appropriately selected depending on the molecular weight of the polyester resin (A) and the intended use, but in general, taking into consideration adhesiveness and the like, it is preferable to add 0.5 to 5 parts by mass per 100 parts by mass of the polyester resin (A).

[0093] The polyester-based pressure-sensitive adhesive composition may contain conventionally known additives such as hydrolysis inhibitors, softeners, ultraviolet absorbers, stabilizers, antistatic agents, and tackifiers, as well as other powdery or particulate additives such as inorganic or organic fillers, metal powders, and pigments, within the range that does not impair the effects of the present invention.

[0094] The storage modulus of the polyester-based pressure-sensitive adhesive layer 15 is preferably 1×10 5 ~100×10 5 Pa, more preferably 5×10 5 ~50×10 5 The storage modulus G' of the polyester-based pressure-sensitive adhesive layer 15 is in the range of 100×10 5 On the other hand, if the storage modulus G' of the adhesive layer is 1×10 5 If the storage modulus G' is equal to or greater than Pa, the cohesive force is likely to be ensured. The storage modulus G' of the pressure-sensitive adhesive layer can be adjusted by appropriately changing the type, molecular weight, and compounding ratio of the monomers constituting the polymer (pressure-sensitive adhesive) contained in the pressure-sensitive adhesive layer, the degree of polymerization of the polymer, and, if a crosslinking agent is contained, the amount of crosslinking agent (crosslinking density of the polymer), etc.

[0095] The storage modulus G' of the adhesive layer is determined using a dynamic viscoelasticity analyzer, ARES (manufactured by TA Instruments Japan). A laminate with an adhesive layer 500 μm to 1 mm thick (e.g., 800 μm) formed between two release liners is punched into an 8 mm diameter disk, and the release liners are removed to obtain the adhesive layer sample. Measurements are performed in shear mode at a temperature range of -50°C to 150°C, with a heating rate of 5°C / min and a frequency of 1 Hz. The storage modulus G' (Pa) at 23°C is recorded.

[0096] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but may be, for example, 5 to 100 μm, or 10 to 50 μm.

[0097] <Release liner 30> As shown in FIG. 1, the release liner 30 has a release substrate 11 and a release agent layer 12.

[0098] The surface roughness Ra of the polyester-based pressure-sensitive adhesive side of the release liner is preferably 0.7 μm or less from the viewpoint of improving labeling performance due to improved adhesiveness. The surface roughness Ra of the polyester-based pressure-sensitive adhesive side of the release substrate 12 is preferably 0.5 μm or less, more preferably 0.3 μm or less, and even more preferably 0.1 μm or less. By setting the surface roughness Ra of the polyester-based pressure-sensitive adhesive side of the release substrate 12 to 0.7 μm or less, the irregularities transferred to the pressure-sensitive adhesive layer are reduced, the contact area with the polyester-based container is increased, and the adhesive strength of the polyester-based pressure-sensitive adhesive is improved. This allows for suitable application of adhesive labels to polyester-based containers at high speed using a known labeling device. Note that the smaller the surface roughness Ra of the polyester-based pressure-sensitive adhesive side of the release substrate 12, the better. However, considering the saturation of the effect and production yield, a surface roughness of 0.01 μm or more is preferred.

[0099] The surface roughness Ra (arithmetic mean roughness Ra) can be measured in accordance with ISO 25178 using a scanning white light interference microscope (manufactured by Hitachi High-Tech Science Corporation, VS1550).

[0100] Examples of the release substrate include laminated paper in which a thermoplastic resin such as polyethylene is laminated to a paper substrate, and polyester-based films. The release substrate is preferably a polyester-based film or laminated paper in which a thermoplastic resin is laminated to a paper substrate, because it is easy to control the Ra to the desired value.

[0101] Examples of the laminated thermoplastic resin include olefin-based resins containing α-olefins as monomer components, such as polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer (EVA); polyester-based resins, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); polyvinyl chloride (PVC); vinyl acetate-based resins; polycarbonate (PC); polyphenylene sulfide (PPS); amide-based resins, such as polyamide (nylon) and wholly aromatic polyamide (aramid); thermoplastic polyimide-based resins; and polyether ether ketone (PEEK). These materials may be used alone or in combination. Among these, polyolefins are preferred as the thermoplastic resin, and polyethylene is more preferred. The thickness of the thermoplastic resin laminate layer is, for example, 10 to 40 μm.

[0102] Examples of the paper substrate for laminated paper include glassine paper and wood-free paper.

[0103] Polyester films include polyethylene terephthalate (PET) and polyethylene ethylenediamine naphthalate (PEN), etc. can be used.

[0104] The thickness of the release liner 30 is preferably 25 to 100 μm. By making the thickness of the release liner 30 25 μm or more, the adhesive label has excellent suitability for punching. Furthermore, by making the thickness of the release liner 30 100 μm or less, the release liner has excellent releasability from the polyester adhesive layer during the labeling process.

[0105] Examples of the release agent constituting the release agent 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.

[0106] <Manufacturing method> The method for producing the pressure-sensitive adhesive label of the present invention is not particularly limited, and examples thereof include a method in which an adhesive roll or sheet is produced, and then printing, half-punching, and scrap removal are carried out as necessary to produce the pressure-sensitive adhesive label. Examples of methods for producing an adhesive roll or sheet include (1) a method in which a polyester-based pressure-sensitive adhesive composition is applied to a release liner to form a polyester-based pressure-sensitive adhesive layer, and then this is laminated to a resin substrate, and (2) a method in which a polyester-based pressure-sensitive adhesive composition is applied directly to a resin substrate to form a polyester-based pressure-sensitive adhesive layer, and then a release liner is laminated.

[0107] The method for applying the PSA composition to the resin substrate or release liner is not particularly limited, and the composition can be applied using a known application device such as a roll coater, knife coater, air knife coater, bar coater, blade coater, slot die coater, lip coater, or gravure coater.

[0108] Furthermore, a coating layer or an alkali-insoluble coating layer can be formed in advance on the resin substrate.

[0109] For each coating layer, a coating layer-forming composition (a detachment coating layer-forming composition or an alkali-insoluble coating layer-forming composition, hereinafter collectively referred to as a coating layer-forming composition) is prepared by mixing a resin, an additive as needed, and a solvent. The solvent is appropriately selected depending on the form of the resin. When the resin is an aqueous polyester resin, the solvent is preferably, for example, water or an alcohol (e.g., ethanol, isopropanol, etc.), and more preferably water. One solvent may be used alone, or two or more solvents may be used in combination. When the resin is a urethane-modified polyester resin, the solvent is, for example, toluene, methyl ethyl ketone, or ethyl acetate.

[0110] Thereafter, the coating layer-forming composition is applied to the resin substrate or coating layer to form a coating layer (a release coating layer or an alkali-insoluble coating layer). The coating method is not particularly limited, and a conventionally known method, such as applying the coating layer-forming composition to the resin substrate and drying it to form each coating layer, can be used. The coating method is not particularly limited, and can be, for example, a method of applying the coating layer by appropriately selecting various coating devices such as a blade coater, air knife coater, rod blade coater, bar blade coater, gravure coater, bar coater, multi-stage roll coater, roll coater, reverse roll coater, curtain coater, or spray coater.

[0111] After the coating layer-forming composition is applied, it may be subjected to a drying step. Drying conditions are appropriately set, for example, at 80 to 160° C. for 10 to 60 seconds.

[0112] <Polyester-based containers> The present invention also provides a polyester-based container having the above-mentioned adhesive label attached thereto. The polyester-based container refers to a container made of a polyester-based resin. Examples of polyester-based resins include polyethylene terephthalate. The container can be produced by injection molding, vacuum forming, pressure forming, or the like of the polyester-based resin.

[0113] <Labeling method> Next, a labeling method will be described. Labeling of polyester-based containers with the adhesive label 10 is carried out using a labeling device such as that disclosed in Japanese Patent No. 5,956,220.

[0114] During labeling, the adhesive label 10 attached to the release liner 30 is conveyed, and when the adhesive label is peeled off from the release liner, the release liner is folded back. At this time, the adhesive layer is exposed, and the exposed adhesive layer is attached to the polyester-based container. Here, if the thickness of the resin substrate 16 is too thin or the thickness of the release liner 30 is too thick, even when the release liner 30 is folded back, the polyester-based adhesive layer 15 is difficult to expose, and the adhesive label may not be able to be attached to the polyester-based container. The conveying speed (labeling speed) of the adhesive label 10 of the labeling device is not particularly limited, but is 20 to 150 m / min. [Example]

[0115] Next, the examples will be described. In the examples, the units "parts" or "%" may be used, but unless otherwise specified, they represent "parts by mass" or "% by mass." Furthermore, unless otherwise specified, each operation is carried out at room temperature (25°C).

[0116] Example 1 A polyester-based pressure-sensitive adhesive composition was prepared by adding and mixing 2 parts by mass (solid content) of a crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L") and 40 parts by mass of ethyl acetate to 100 parts by mass (solid content) of a polyester-based resin (manufactured by Mitsubishi Chemical Corporation, product name "NP-110S50EO").

[0117] The obtained polyester-based pressure-sensitive adhesive composition was applied using a knife coater to a release liner (Ra: 0.29 μm, thickness: 88 μm) made of polyethylene-laminated glassine paper coated with a silicone-based release agent so that the film thickness after drying would be 20 μm, and then dried at 90°C for 1 minute to form a polyester-based pressure-sensitive adhesive layer.

[0118] A composition for forming a release coating layer was obtained by mixing 100 parts by mass of a self-emulsifying aqueous polyester resin solution (solid content 25% by mass, viscosity 10 mPa·s (20°C), water solvent, polyester resin: acid value 50 mgKOH / g, carboxyl group-containing, molecular weight 3,000, Tg 46°C) and 1 part by mass of silica (average particle size 0.45 μm) per 100 parts by mass of the aqueous polyester resin solid content. The composition for forming a release coating layer was applied to a 50 μm-thick polyethylene terephthalate film (polyester resin substrate) using a Mayer bar to a dry film thickness of 0.06 μm, and then dried. Onto the obtained release coating layer, a composition for forming an alkali-insoluble coating layer was prepared by mixing 3 parts by mass of a crosslinking agent (hexamethylene diisocyanate) with 100 parts by mass of urethane-modified polyester resin (Vylon UR-8200 manufactured by Toyobo Co., Ltd.) and resin solids, and diluting the mixture with toluene. The composition was applied and dried using a Mayer bar to a dry film thickness of 0.08 μm, forming an alkali-insoluble coating layer.

[0119] An adhesive layer with a release liner laminated thereon was attached to the side of the polyethylene terephthalate film opposite the release coating layer, and the film was left standing for 7 days under standard conditions (23°C, 50% RH) to obtain an adhesive label.

[0120] Example 2 An adhesive label was obtained in the same manner as in Example 1, except that the alkali-insoluble coating layer was not provided.

[0121] Example 3 An adhesive label was obtained in the same manner as in Example 2, except that the composition for forming a release coating layer did not contain silica.

[0122] Example 4 An adhesive label was obtained in the same manner as in Example 1, except that a self-emulsifying aqueous polyester resin solution (solid content 25% by mass, viscosity 10 mPa·s (20°C), solvent: water containing 5% by mass ETB, polyester resin: acid value 47.5 mg KOH / g, contains carboxyl groups, molecular weight 3,000, Tg 52°C) was used.

[0123] (Comparative Example 1) An adhesive label was obtained in the same manner as in Example 1, except that an aqueous polyester resin solution (solid content 25% by mass, viscosity 10 mPa·s (20°C), solvent: water containing 11% by mass ETB, acid value of polyester resin less than 3 mgKOH / g, hydroxyl value 5 mgKOH / g, molecular weight 20,000, Tg 61°C) was used.

[0124] (Comparative Example 2) An adhesive label was obtained in the same manner as in Comparative Example 1, except that no alkali-insoluble coating layer was provided.

[0125] [Evaluation method 1: Printability] A solid print was made using an RI tester and UV161 J Ink S (T&K TOKA) ink. The ink was cured by irradiating it with ultraviolet light from a high-pressure mercury lamp, and then the adhesion to the release coating layer or alkali-insoluble coating layer was evaluated by peeling with cellophane tape. Specifically, 100 crosscuts (10 x 10 squares) were made at 1 mm intervals, and the remaining printed area after peeling with cellophane tape was evaluated according to the following criteria. The results are shown in Table 1.

[0126] <Evaluation criteria> 5:91-100% remaining, 4: 66-90% remaining, 3: 41-65% remaining, 2: 16-40% remaining, 1: 0-15% remaining.

[0127] [Evaluation method 2: Deinking] The samples obtained in the examples and comparative examples were printed solid using an RI tester printer and UV161 J Ink S (manufactured by T&K Toka). The ink was cured by irradiating it with ultraviolet light from a high-pressure mercury lamp, and then cut into 10 mm x 10 mm samples. Five samples were placed in 1 L of a 1.5% by weight aqueous sodium hydroxide solution (pH 13.6) at 70°C and stirred. The time until all five prints peeled was recorded (maximum 15 minutes) and evaluated according to the following criteria. The results are shown in Table 1.

[0128] <Evaluation criteria> 5: All peeled off within 5 minutes 4: It all comes off within 15 minutes 3: Partial peeling after 15 minutes 2: No peeling after 15 minutes, peeling occurs when the printed surface is rubbed immediately after removal 1: No peeling after 15 minutes, and no peeling even when the printed surface is rubbed immediately after removal.

[0129] [Evaluation method 3: Film shape retention] The printed area after the evaluation of deinking property in Evaluation Method 2 was visually inspected, the size (area) of the largest film was measured, and the area relative to the original printed area was evaluated according to the following evaluation criteria. The results are shown in Table 1.

[0130] <Evaluation criteria> 3:81~100%, 2:11~80%, 1:0-10%.

[0131] [Table 1]

[0132] As shown above, the pressure-sensitive adhesive labels of the Examples had excellent printability and excellent deinking properties in low-temperature (approximately 70°C) alkaline warm water. On the other hand, in Comparative Examples 1 and 2, which used a composition for forming a detachable coating layer containing an aqueous polyester resin with an acid value of less than 10 KOH mg / g, no detachment of the printed portion occurred even after 15 minutes of contact with alkaline water. Furthermore, in Example 1, which had an alkali-insoluble coating layer, the printed portion after detachment was in the form of a relatively large film, making it easy to collect.

[0133] In the examples, the blocking resistance was evaluated by the following evaluation method. Sample size: 50mm x 100mm, Sample: Base material alone Ten samples were stacked so that the release coating surface was in contact with the back of the resin substrate, and the samples were placed in an environment of 40°C and 80% RH. , 40g / cm2 Load / left to stand for 7 days. As a result, the blocking resistance was better in the order of Example 1 > Examples 2 and 4 > Example 3. [Explanation of symbols]

[0134] 10, 20 adhesive labels, 11 base material, 12 release agent layer, 13 Printing Department, 14. Detachable coating layer, 15 polyester adhesive layer, 16 Resin substrate, 17 Alkali-insoluble coating layer, 30 release liners.

Claims

1. The film has a polyester-based pressure-sensitive adhesive layer, a polyester-based resin substrate, and a release coating layer in this order, The adhesive label is formed from a composition for forming a release coating layer, which comprises an aqueous polyester resin having an acid value of 10 KOH mg / g or more.

2. 2. The adhesive label according to claim 1, wherein the aqueous polyester resin has a number average molecular weight of 1,000 to 15,000.

3. The adhesive label according to claim 1 or 2, wherein the aqueous polyester resin has a carboxyl group.

4. The pressure-sensitive adhesive label according to any one of claims 1 to 3, further comprising an alkali-insoluble coating layer on the release coating layer facing the polyester resin substrate.

5. The adhesive label according to any one of claims 1 to 4, wherein the alkali-insoluble coating layer is made of a urethane-modified polyester resin.

6. The adhesive label according to claim 4 or 5, wherein the resin contained in the alkali-insoluble coating layer is a crosslinked resin.

7. 7. The adhesive label according to claim 1, further comprising a release liner, the release liner having a surface roughness Ra of 0.7 μm or less on the side of the polyester-based adhesive layer.

8. A polyester-based container having the adhesive label according to any one of claims 1 to 7 attached thereto.

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