JP7777959B2 - adhesive labels - Google Patents

Description

The present invention relates to adhesive labels.

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.

When recycling polyester containers, the containers are typically crushed into pellets, then heated and melted to homogenize the entire material, and the resulting recycled resin is used as the material for polyester containers.

Typically, polyester containers such as PET bottles have adhesive labels (also referred to as "labels") affixed to their surface that carry 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 that makes up the polyester container, the resin substrate and adhesive that make up 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 recycling processing costs, resulting in problems that are both operationally and economically disadvantageous.

In this regard, for example, Patent Document 1 below discloses an adhesive label comprising a polyester resin substrate that is compatible with the polyester container to be adhered, a coating layer that can be peeled from the substrate by washing and immersing in an alkaline aqueous solution and has printability, and a polyester adhesive layer that is provided on the opposite side.

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.

Japanese Patent Application Laid-Open No. 2000-10489

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 recycling efficiency. For this reason, 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 at a low temperature (around 70°C). Furthermore, excellent printability is required when printing information.

The present invention was invented to solve the above-mentioned problems, and aims to provide an adhesive label that allows polyester containers to be recycled without being peeled off from the polyester container, and whose printed portion can be removed (peeled off) in a short time in an alkaline aqueous solution at a low temperature (approximately 70°C). Another aim of the present invention is to provide an adhesive label with excellent printability.

To achieve the above object, the adhesive label of the present invention is an adhesive label having a polyester resin substrate, a polyester adhesive layer, and a release coating layer in this order, with the release coating layer being formed from a release coating layer-forming composition containing an aqueous polyester resin with an acid value of 10 KOH mg/g or more.

The adhesive label of the present invention has a polyester-based resin substrate and a polyester-based adhesive layer, making it possible to recycle polyester-based containers without removing the adhesive label from the polyester-based container. Furthermore, the adhesive label of the present invention allows the printed portion to be removed in a short time using an alkaline aqueous solution at a low temperature (approximately 70°C). Furthermore, the adhesive label of the present invention has excellent printability.

1 is a cross-sectional view schematically illustrating a pressure-sensitive adhesive label according to an embodiment of the present invention. FIG. 10 is a cross-sectional view illustrating a pressure-sensitive adhesive label according to another embodiment of the present invention.

Embodiments of the present invention will now be described with reference to the accompanying drawings. Note that in the description of the drawings, identical elements will be given the same reference numerals, and duplicate explanations will be omitted. Also, the dimensional proportions in the drawings have been exaggerated for the sake of explanation, and may differ from the actual proportions.

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 at room temperature (20-25°C) and a relative humidity of 45-55% RH.

The adhesive label is affixed to a polyester-based container such as a polyethylene terephthalate (PET) bottle. Below, we will explain using a PET bottle as an example of the adherend to which the adhesive label is affixed. 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 be triangular or circular. The polyester-based adhesive layer is disposed, for example, over the entire surface of the polyester-based resin substrate.

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 it after 24 hours in a 180° direction at a test speed of 0.3 m/min using a tensile tester in accordance with JIS Z0237:2009. More specifically, the adhesive strength to the substrate is measured using the following method: the adhesive label is left to stand for 24 hours under standard conditions (23°C, 50% RH), the release liner is removed, and the polyester adhesive layer side is attached to the polyethylene terephthalate plate. After leaving the film under standard conditions for 24 hours, 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 to the peel force per 25 mm of film width (N/25 mm).

The structure of the adhesive label will be explained below with reference to Figure 1.

Figure 1 is a schematic cross-sectional view of an adhesive label 10 according to one embodiment. As shown in Figure 1, the adhesive label 10 according to an 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 the 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.

Figure 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 located 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 as a film together with the upper printed portion 13. In other words, the printed portion does not break down into small pieces and maintains a certain size, making it easy to recover. 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.

A preferred embodiment does not have a release coating layer between the resin substrate 16 and the polyester-based pressure-sensitive adhesive layer 15. In one suitable embodiment, the resin substrate 16 and the polyester-based pressure-sensitive adhesive layer 15 are adjacent to each other. 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 exists between the resin substrate 16 and the printed portion 13, or between the resin substrate 16 and the alkali-insoluble coating layer 17. This prevents the resin substrate 16 from peeling off from the polyester container (adherend) when it comes into contact with alkaline water, and the polyester-based pressure-sensitive adhesive layer 15 and resin substrate 16 remain attached to the polyester container. This makes it possible to recycle both the resin substrate 16 and the polyester-based pressure-sensitive adhesive layer 15.

The concept of "label" includes things called films, sheets, tapes, etc.

Each component is explained below.

<Printing 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.

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

<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.

The alkali-insoluble coating layer is primarily composed of a resin. "Main component" here 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. "Alkali-insoluble" here refers to a resin that dissolves in a 1.5% by mass aqueous solution of sodium hydroxide (pH 13.6) at 70°C in an amount of 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.

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, as this reduces solubility in alkaline water.

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

Examples of polyisocyanate compounds include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate.

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 polystyrene-equivalent number average molecular weight measured by gel permeation chromatography (GPC).

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

Commercially available urethane-modified polyester resins may be used. 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).

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

The resin contained in the alkali-insoluble coating layer is preferably crosslinked. A crosslinked resin is preferred because it further reduces solubility in alkaline water. To crosslink the resin, a crosslinking agent can be added to the alkali-insoluble coating layer-forming composition described below. In this case, a crosslinking agent that reacts with the crosslinkable reactive groups in the resin is appropriately selected. In particular, selecting a crosslinking agent that reacts with carboxyl groups, which are crosslinkable reactive groups, is preferred because it can crosslink the carboxyl groups remaining in the resin, further reducing solubility in alkaline water.

Crosslinking agents that can react with carboxyl groups include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and metal chelate-based crosslinking agents.

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 diisocyanate compounds 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 isocyanate derivatives such as adducts of diisocyanate compounds and polyol compounds such as trimethylolpropane, biuret and isocyanurate diisocyanate compounds, and bifunctional diisocyanate compounds.

Examples of epoxy-based 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.

Examples of aziridine-based crosslinking agents 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.

Metal chelate crosslinking agents include chelate compounds containing metal atoms such as aluminum, zirconium, titanium, zinc, iron, and tin, with aluminum chelate compounds being preferred from the standpoint 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.

Among these, it is preferable that the crosslinking agent be an isocyanate-based crosslinking agent, as this will result in high print adhesion in the coating layer after crosslinking.

The above crosslinking agents may be used alone or in combination with two or more types.

The amount of crosslinking agent added is set appropriately taking into account the amount of crosslinkable reactive groups in the resin, but is preferably 0.01 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of resin.

The thickness of the alkali-insoluble coating layer is preferably 0.05 to 1 μm, and more preferably 0.05 to 0.5 μm, taking into consideration ease of recovery of the printed area and thin film properties.

The alkali-insoluble coating layer may contain additives such as catalysts, UV absorbers, pigments, and fillers.

<Detachable 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 KOH mg/g or more.

From the perspective of deinking ability (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.

The release coating layer-forming composition, which is the 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 KOH mg/g or more.

"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. Using such an "aqueous" polyester resin makes it possible to reduce volatile organic compound emissions during coating. Here, an aqueous solvent refers to one that contains 60% or more water by mass (up to 100% by mass), preferably 70% or more by mass, more preferably 85% or more by mass, and most preferably 95% or more by mass of water.

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

In one embodiment of the present invention, to prepare an aqueous dispersion in which the aqueous polyester resin is dispersed as an emulsion in water, small amounts of emulsifiers, surfactants, etc. may be used as long as the effects of the present invention are not impaired.

However, low-molecular-weight components such as emulsifiers and surfactants may become localized in the release coating layer, reducing adhesion and possibly causing a decrease in interlayer adhesion. To prevent this phenomenon, in one embodiment of the present invention, the aqueous polyester resin is preferably a self-emulsifying aqueous polyester resin.

Self-emulsifying aqueous polyester resins can form emulsions without using low-molecular-weight components such as emulsifiers and surfactants, which can reduce interlayer adhesion, and therefore can further improve the interlayer adhesion of the resulting pressure-sensitive adhesive sheet. The term "self-emulsifying" means that some kind of hydrophilic group has been chemically introduced into the resin skeleton, and the resin itself has emulsifying properties, without the need for the addition of emulsifiers or surfactants.

The acid value of the aqueous polyester resin is 10 KOHmg/g or more, preferably 15 KOHmg/g or more, more preferably 20 KOHmg/g or more, even more preferably 30 KOHmg/g or more, still more preferably 40 KOHmg/g or more, and particularly preferably 50 KOHmg/g or more. In this specification, the acid value of the aqueous polyester resin is a value measured in accordance with JIS K 0070:1992.

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 according to the method described below.

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 solubility or dispersibility in water and interlayer adhesion between the formed primer layer and the substrate and/or pressure-sensitive adhesive layer. This relatively low molecular weight range for the aqueous polyester resin results in sufficiently high solubility and dispersibility in water, enabling the coating liquid to be stored stably for long periods of time, which is preferable.

In the present invention, the value of 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 based on 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 following conditions, and the values measured are converted into standard polystyrene equivalents.
Column: "TSK guard column HXL-H", "TSK gel GMHXL (x2)", "TSK gel G2000HXL" (all manufactured by Tosoh Corporation)
Column temperature: 40°C
Developing solvent: tetrahydrofuran Flow rate: 1.0 mL/min
(2) Glass transition temperature (Tg)
Measurement is performed in accordance with JIS K 7121:2012 using a differential scanning calorimeter (manufactured by TA Instruments Japan, product name "DSC Q2000") at a temperature rise rate of 20°C/min.

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.

Examples of modified copolymers include polyurethane-modified polyester resins obtained by reacting the hydroxyl groups at the ends 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 term "aqueous polyester resin."

The alcohol component can be a polyhydric alcohol having two or more hydroxyl groups in one molecule.

Specific alcohol components include glycols such as ethylene glycol, diethylene 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 neopentyl glycol hydroxypivalate. Examples include polylactone diols obtained by adding lactones such as ε-caprolactone to these glycols; 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.

A polybasic acid having two or more carboxyl groups in one molecule can be used as the carboxylic acid component.

Specific carboxylic acid components include, for example, dicarboxylic acids such as 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, fumaric acid, itaconic acid, cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, and methylhexahydrophthalic acid. Examples of suitable carboxylic acids include carboxylic acids and their anhydrides; tricarboxylic acids such as trimellitic acid, pyromellitic acid, trimesic acid, methylcyclohexene tricarboxylic acid, hexahydrotrimellitic acid, and tetrachlorohexene tricarboxylic acid and their anhydrides; and tetracarboxylic acids 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 and their anhydrides. These carboxylic acid components may be used alone or in combination of two or more.

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 contains structural units derived from a polybasic acid having three or more carboxyl groups per molecule, and more preferably contains structural units derived from a tricarboxylic acid or a tricarboxylic acid anhydride.

Furthermore, for the same reasons as above, the aqueous polyester resin used in one embodiment of the present invention is preferably an aqueous polyester resin containing a carboxyl group.

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

The particles may be either inorganic or organic, as long as they are water-dispersible. Examples of inorganic particles include zirconia, silica, titanium dioxide, kaolin, alumina, titania, 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. Among these, silica is preferred.

The content of particles in the composition for forming the release coating layer is set appropriately to achieve the desired purpose (e.g., improved blocking resistance), but is, for example, 0.1 to 10 parts by mass per 100 parts by mass of the aqueous polyester resin.

The average particle size of the particles is set appropriately taking into consideration the desired purpose; for example, if the goal is to improve 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, 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 (Model TA-II, manufactured by COULTER ELECTRONICS INC.) with a 50 μm aperture.

(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.

<Resin substrate 16>
It is necessary to use a polyester film, which is 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 PET bottle as the adherend, so as to obtain a resin substrate that is compatible with it.

Here, compatibility means that the material melts at the temperature at which the PET bottle is heated and melted, is well mixed with the resin base material of the molten PET bottle, and does not degrade the properties of the recycled product. Furthermore, if the resin base material that makes up the PET bottle is a mixture of two or more compatible resins, one of the resins from the mixture that makes up the PET bottle can be used as the resin for resin base material 16.

The thickness of the resin substrate 16 is not particularly limited and can be selected appropriately 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 in which the adhesive label is attached to the container using a labeling device, 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. This resin substrate 16 may be obtained by any conventional film-forming method, such as extrusion, calendaring, solution coating, or casting.

In the present invention, the resin substrate 16 can be surface-treated on one or both sides as desired to improve adhesion to the coating layer provided thereon and to the polyester-based pressure-sensitive adhesive layer 15 provided on the opposite side. Examples of surface treatment methods include surface roughening treatments such as sandblasting or solvent treatment, or surface oxidation treatments such as corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, and ozone/ultraviolet irradiation treatment.

<Polyester-based pressure-sensitive adhesive layer 15>
Next, a description will be given of 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.

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

[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.

Among these, it is preferable to include an aromatic dicarboxylic acid in order to impart cohesive strength.

The content of such 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 will be high, and sufficient adhesive performance will tend to be unavailable.

Furthermore, in order to impart a tacky feel, it is preferable to include an aliphatic dicarboxylic acid, and it is particularly preferable to include an aliphatic dicarboxylic acid having 4 to 12 carbon atoms.

The content of such 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 this content is too low, the glass transition temperature tends to be high and sufficient adhesive strength cannot be obtained. If this content is too high, the adhesive component tends to be reduced, resulting in reduced adhesive strength to polar substrates.

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

In order to increase the number of branching points in the polyester resin (A), trivalent or higher polycarboxylic acids can also be used. Examples of such trivalent or higher polycarboxylic acids include trimellitic acid, pyromellitic acid, adamantanetricarboxylic acid, and trimesic acid. Among these, trimellitic acid is preferred because it is relatively less likely to cause gelation. The content of such trivalent or higher polycarboxylic acids is preferably 10 mol % or less, and 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 more easily during the production of the polyester resin (A).

[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 ethylene oxide and propylene oxide adducts thereof. These can be used alone or in combination of two or more.

Among these, aliphatic diols and alicyclic diols are preferred due to their excellent reactivity. Particularly preferred aliphatic diols are ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol, and preferred alicyclic diols are 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol.

Trihydric or higher polyhydric alcohols can also be used to increase the number of branching points in the polyester resin (A). Examples of trihydric or higher polyhydric alcohols include pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, and adamantanetriol. The content of such trihydric or higher polyhydric alcohols is preferably 10 mol % or less, and 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.

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

The polyester resin (A) used in the present invention is produced by subjecting the polycarboxylic acid component (A1) and polyol component (A2) selected from the above to a polycondensation reaction in the presence of a catalyst using a known method.

From the viewpoints of cohesive strength, heat resistance, mechanical strength, adhesiveness, etc., 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.

The number average molecular weight indicated above is the number average molecular weight converted to standard polystyrene molecular weight and is measured using high performance liquid chromatography (Tosoh Corporation, "HLC-8220 GPC") with two TSK gel GMHXL columns in series.

Typically, crosslinking the polyester resin (A) with a crosslinking agent results in excellent cohesive strength and excellent performance as an adhesive. Examples of such crosslinking agents include polyisocyanate compounds (isocyanate-based crosslinking agents) and polyepoxy compounds, which are compounds having functional groups that react with the hydroxyl and/or carboxyl groups contained in the polyester resin (A). Of these, polyisocyanate compounds are particularly preferred because they provide a good balance of initial adhesion, mechanical strength, and heat resistance.

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 the tolylene diisocyanate adduct, hexamethylene diisocyanate adduct, and isophorone diisocyanate adduct of trimethylolpropane. The above polyisocyanate compounds can also be used in which the isocyanate moiety is blocked with phenol, lactam, or the like. These crosslinking agents can be used alone or in combination.

The amount of crosslinking agent to be added can be selected appropriately depending on the molecular weight of the polyester resin (A) and the intended use, but typically, taking into account adhesiveness and other factors, it is preferable to use 0.5 to 5 parts by mass per 100 parts by mass of polyester resin (A).

The polyester-based pressure-sensitive adhesive composition can contain conventional additives such as hydrolysis inhibitors, softeners, UV absorbers, stabilizers, antistatic agents, and tackifiers, as well as other powdery or particulate additives such as inorganic or organic fillers, metal powders, and pigments, provided that the effects of the present invention are not impaired.

The storage modulus of the polyester-based pressure-sensitive adhesive layer 15 is preferably in the range of 1×10 ⁵ to 100×10 ⁵ Pa, more preferably 5×10 ⁵ to 50×10 ⁵ Pa, at 23°C and a frequency of 1 Hz. If the storage modulus G' of the polyester-based pressure-sensitive adhesive layer 15 is 100×10 ⁵ Pa or less, adhesive strength is likely to be ensured. On the other hand, if the storage modulus G' of the pressure-sensitive adhesive layer is 1×10 ⁵ Pa or more, cohesive strength 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, as well as the degree of polymerization of the polymer, and if a crosslinking agent is contained, the amount of the crosslinking agent (crosslinking density of the polymer), etc.

The storage modulus G' of the adhesive layer is determined using an ARES dynamic viscoelasticity measuring device (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 out into a disk with a diameter of 8 mm, 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, a heating rate of 5°C/min, and a frequency of 1 Hz, and the storage modulus G' (Pa) at 23°C is recorded.

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

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

From the perspective of improving labeling performance due to improved adhesiveness, the surface roughness Ra of the polyester adhesive side of the release liner is preferably 0.7 μm or less. The surface roughness Ra of the polyester 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. Thus, by setting the surface roughness Ra of the polyester adhesive side of the release substrate 12 to 0.7 μm or less, the irregularities transferred to the adhesive layer are reduced, the contact area with the polyester container is increased, and the adhesive strength of the polyester adhesive is improved. This allows for optimal application of adhesive labels to polyester containers at high speeds using known labeling equipment. Note that the smaller the surface roughness Ra of the polyester adhesive side of the release substrate 12, the better. However, considering the saturation of the effect and production yield, a roughness of 0.01 μm or more is preferable.

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

Examples of release substrates include laminated paper, which is a paper substrate laminated with a thermoplastic resin such as polyethylene, or polyester film. Because it is easier to control the Ra to the desired value, it is preferable that the release substrate be a polyester film or laminated paper, which is a paper substrate laminated with a thermoplastic resin.

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.

Examples of paper substrates for laminated paper include glassine paper and fine paper.

Polyester-based films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) can be used.

The thickness of the release liner 30 is preferably 25 to 100 μm. A release liner 30 with a thickness of 25 μm or more provides excellent suitability for the cutting process of adhesive labels. Furthermore, a release liner 30 with a thickness of 100 μm or less provides excellent releasability of the release liner from the polyester-based adhesive layer during the labeling process.

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

<Manufacturing method>
[0023] 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 the pressure-sensitive 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.

The method for applying the pressure-sensitive adhesive composition to the resin substrate or release liner is not particularly limited, and application can be performed using known coating devices such as a roll coater, knife coater, air knife coater, bar coater, blade coater, slot die coater, lip coater, or gravure coater.

In addition, a coating layer or an alkali-insoluble coating layer can be formed on the resin substrate in advance.

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, optional additives, and a solvent. The solvent is selected appropriately depending on the type of resin. When the resin is a water-based polyester resin, the solvent is preferably water or an alcohol (e.g., ethanol, isopropanol, etc.), with water being more preferred. 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.

The coating layer-forming composition is then 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 any conventionally known method can be used, such as applying the coating layer-forming composition to the resin substrate and drying it to form each coating layer. The coating method is not particularly limited, and can be performed using an appropriate coating device, 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.

After the coating layer-forming composition has been applied, it may be subjected to a drying process. Drying conditions are set appropriately, but for example, drying at 80 to 160°C for 10 to 60 seconds.

<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.

<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.

During labeling, the adhesive label 10 attached to the release liner 30 is conveyed, and the release liner 30 is folded back as the adhesive label is peeled off from the release liner. At this time, the adhesive layer is exposed, and the exposed adhesive layer is attached to the polyester container. If the resin substrate 16 is too thin or the release liner 30 is too thick, the polyester adhesive layer 15 may not be easily exposed even when the release liner 30 is folded back, and the adhesive label may not be able to be attached to the polyester container. The conveying speed (labeling speed) of the adhesive label 10 in the labeling device is not particularly limited, but is generally 20 to 150 m/min.

The following examples are provided. In the examples, the terms "parts" and "%" may be used, but unless otherwise specified, they represent "parts by mass" or "% by mass." Furthermore, unless otherwise specified, all operations were performed at room temperature (25°C).

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").

The resulting 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 would have a dry thickness of 20 μm, and then dried at 90°C for 1 minute to form a polyester-based pressure-sensitive adhesive layer.

100 parts by weight of a self-emulsifying aqueous polyester resin solution (25% solids by weight, 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 weight of silica (average particle size 0.45 μm) were mixed for every 100 parts by weight of aqueous polyester resin solids to obtain a composition for forming a detachment coating layer. The composition for forming a detachment coating layer was applied to a 50 μm-thick polyethylene terephthalate film (polyester resin substrate) using a Meyer bar and dried to a dry film thickness of 0.06 μm. An alkali-insoluble coating layer-forming composition was prepared by mixing 3 parts by mass of a crosslinking agent (hexamethylene diisocyanate) for every 100 parts by mass of urethane-modified polyester resin (Vylon UR-8200, manufactured by Toyobo Co., Ltd.) and resin solids, and then diluting it with toluene. This composition was then applied to the resulting release coating layer using a Mayer bar and dried to a dry film thickness of 0.08 μm, forming an alkali-insoluble coating layer.

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 to stand for 7 days under standard conditions (23°C, 50% RH) to obtain an adhesive label.

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.

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

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 of ETB, polyester resin: acid value 47.5 mgKOH/g, containing carboxyl groups, molecular weight 3,000, Tg 52°C) was used.

(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 of 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.

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

[Evaluation Method 1: Printability]
A solid print was made using a printer: RI Tester, and ink: UV161 J Black S (manufactured by T&K Toka). 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 cellophane tape peeling. Specifically, 100 crosscuts (10 squares x 10 squares) were made at 1 mm intervals, and the remaining printed area after cellophane tape peeling was evaluated according to the following evaluation criteria. The results are shown in Table 1.

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

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

<Evaluation criteria>
5: Completely peeled off within 5 minutes; 4: Completely peeled off within 15 minutes; 3: Partial peeling within 15 minutes; 2: No peeling within 15 minutes, but peeled off when the printed surface was rubbed immediately after removal; 1: No peeling within 15 minutes, but did not peel off even when the printed surface was rubbed immediately after removal.

[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.

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

As shown above, the pressure-sensitive adhesive labels of the Examples not only had excellent printability but also 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 took on a relatively large film shape, making it easy to recover.

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

10, 20 adhesive labels,
11 base material,
12 release agent layer,
13 Printing Department,
14. Detachable coating layer,
15 polyester-based pressure-sensitive adhesive layer,
16 resin substrate,
17 alkali-insoluble coating layer,
30 release liner.

Claims (7)

The film has a polyester-based pressure-sensitive adhesive layer, a polyester-based resin substrate, and a release coating layer in this order,
the release coating layer is formed from a release coating layer-forming composition containing an aqueous polyester resin with an acid value of 10 KOH mg/g or more,
The pressure-sensitive adhesive label further comprises an alkali-insoluble coating layer on the release coating layer facing the polyester resin substrate . The adhesive label according to claim 1, wherein the number average molecular weight of the aqueous polyester resin is 1,000 to 15,000. The adhesive label according to claim 1 or 2, wherein the aqueous polyester resin has a carboxyl group. The adhesive label according to any one of claims 1 to 3 , wherein the alkali-insoluble coating layer is made of a urethane-modified polyester resin. The pressure-sensitive adhesive label according to any one of claims 1 to 4 , wherein the resin contained in the alkali-insoluble coating layer is a crosslinked resin. The adhesive label according to any one of claims 1 to 5 , 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. A polyester-based container having the adhesive label according to any one of claims 1 to 6 attached thereto.