Adhesive label

Abstract

To provide an adhesive label which can peel (release) a printed part in a short time by being brought into contact with alkali aqueous solution at low temperature (approximately 70°C), without being peeled from a polyester-based container, and holds the printed part on a label even if the printed part is brought into contact with water for a long time.SOLUTION: An adhesive label has a polyester-based adhesive layer, a polyester-based resin base material, and a peeling coat layer in this order, wherein the peeling coat layer is formed of a composition for peeling coat layer formation containing a polyester-based resin having an acid value of 10 KOHmg / g or more and a crosslinking agent, a content in the composition for peeling coat layer formation of the crosslinking agent is such an amount that a sealing rate of a reactive functional group with the crosslinking agent in the polyester-based resin is 40 to 140 mol%.SELECTED DRAWING: None

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 flakes, 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, carrying 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, when discarding labeled polyester containers, consumers are required to remove the labels from the polyester containers. If consumers have not removed the labels from the polyester containers, recycling companies remove the labels, then crush the polyester containers into flakes, heat-melt them, and recycle them. However, the process of removing labels from polyester containers is extremely cumbersome and time-consuming, and increases recycling costs, resulting in problems of both operational and economic disadvantages. Furthermore, there are cases where the labels remain unremoved.

[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 a pressure-sensitive adhesive label is attached to the adherend, the printed portion becomes an impurity, reducing the recycling efficiency. For this reason, it is necessary to remove the printed portion during washing with an alkaline aqueous solution. When removing the printed portion using an alkaline aqueous solution, it is preferable from the viewpoint of work efficiency that the printed portion can be removed in a short time using an alkaline aqueous solution at a low temperature (about 70°C).

[0009] On the other hand, polyester containers such as PET bottles are sometimes immersed in ice water for long periods of time to cool the beverages etc. contained therein. It is necessary for the label to maintain its functionality even when exposed to water below room temperature for such long periods of time.

[0010] The present invention has been made to solve the above-mentioned problems, and aims to provide an adhesive label that can be detached (peeled off) in a short time by contacting it with a low-temperature (approximately 70°C) alkaline aqueous solution without peeling it from a polyester-based container, and that maintains its functionality as an adhesive label even when in contact with water for a long period of time. [Means for solving the problem]

[0011] The adhesive label according to the present invention, which achieves the above object, comprises a polyester adhesive layer, a polyester resin substrate, 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 comprises a polyester resin having an acid value of 10 KOH mg / g or more and a crosslinking agent, and the content of the crosslinking agent in the composition for forming a release coating layer is an amount such that the blocking rate of functional groups in the polyester resin that are reactive with the crosslinking agent is 40 to 140 mol %. [Effects of the Invention]

[0012] According to the adhesive label of the present invention, the printed portion can be peeled off in a short time in an alkaline aqueous solution at low temperature (about 70°C), and peeling of the print on the adhesive label is suppressed even if the polyester container to which the label is attached is brought into contact with water for a long period of time. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view schematically 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

[0014] One embodiment of the present invention is an adhesive label having, in this order, a polyester-based pressure-sensitive adhesive layer, a polyester-based resin substrate, and a release coating layer, wherein the release coating layer is formed from a composition for forming a release coating layer, which comprises a polyester-based resin having an acid value of 10 KOHmg / g or more and a crosslinking agent, and the content of the crosslinking agent in the composition for forming a release coating layer is an amount such that the blocking rate of the polyester-based resin is 40 to 140 mol%.

[0015] By using a polyester resin with an acid value of 10 KOH mg / g or more as the resin for the release coating layer, the printed portion can be peeled off in a short time in an alkaline aqueous solution at a low temperature (approximately 70°C). The present inventors have found that when a polyester resin with an acid value of 10 KOH mg / g or more is used as the resin for the release coating layer, although normal water resistance is ensured, the printed portion may peel off from the label when the polyester container is immersed in water for a long time to cool it. The present inventors speculate that the cause of this problem lies in the polyester resin with an acid value of 10 KOH mg / g or more. Specifically, they hypothesized that polyester resins with an acid value of 10 KOH mg / g or more are highly hydrophilic due to their high acid value, and that when they come into contact with water for a long time, water penetrates into the release coating layer, resulting in swelling of the release coating layer and a decrease in strength and substrate adhesion. Based on this assumption, the inventors discovered that by crosslinking a polyester resin and controlling the degree of crosslinking, it is possible to achieve both alkali solubility and prevention of detachment of printed areas due to contact with water, thereby completing the present invention.

[0016] 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.

[0017] In this specification, the range "X to Y" means "X or more and Y or less." Unless otherwise specified, operations and measurements of physical properties are carried out under conditions of room temperature (20 to 25°C) and a relative humidity of 45 to 55% RH.

[0018] 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.

[0019] 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 according to JIS Z0237:2022 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 under standard conditions for 24 hours, the adhesive strength is measured according to JIS Z0237:2022. 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).

[0020] The structure of the adhesive label will be described below with reference to FIG.

[0021] FIG. 1 is a schematic cross-sectional view 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 resin substrate (hereinafter also simply referred to as a resin substrate) 16, a polyester 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 an alkaline aqueous solution, 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.

[0022] 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.

[0023] 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-based container (adherend) when it comes into contact with an alkaline aqueous solution, and the polyester-based pressure-sensitive adhesive layer 15 and the resin substrate 16 remain attached to the polyester-based container. Therefore, both the resin substrate 16 and the polyester-based pressure-sensitive adhesive layer 15 can be recycled.

[0024] The concept of "label" includes what are called films, sheets, tapes, etc.

[0025] Each component will be described below.

[0026] <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, or the like.

[0027] The information displayed on the printed portion may be, for example, letters, numbers, illustrations, photographs, graphs, or a combination thereof.

[0028] <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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] The glass transition temperature (Tg) of the urethane-modified polyester resin is, for example, preferably 100°C or lower, and more preferably from -40 to 100°C.

[0035] 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 MC Co., Ltd., and preferably used are Vylon UR-1400 (acid value <1, hydroxyl value 2 to 3, number average molecular weight 40,000, Tg 83°C), UR-8300 (acid value <1, hydroxyl value 3 to 4, number average molecular weight 30,000, Tg 23°C), and UR-6100 (acid value <1, hydroxyl groups 4 to 6, number average molecular weight 25,000, Tg -30°C).

[0036] 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.

[0037] The resin contained in the alkali-insoluble coating layer is preferably a crosslinked product. A crosslinked resin is preferred because it further reduces the solubility in an alkaline aqueous solution. To crosslink the resin, a crosslinking agent may be added to the composition for forming the alkali-insoluble coating layer used to form the alkali-insoluble coating layer. In this case, the crosslinking agent is appropriately selected so as to react with the crosslinkable reactive groups in the resin. In particular, selecting a crosslinking agent that reacts with hydroxyl groups and / or carboxyl groups, which are crosslinkable reactive groups, is preferred because it can crosslink with the hydroxyl groups and / or carboxyl groups of the resin, further reducing the solubility in an alkaline aqueous solution.

[0038] Examples of crosslinking agents that can react with crosslinkable reactive groups (preferably hydroxyl groups and / or carboxyl groups) include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and metal chelate-based crosslinking agents.

[0039] Examples of 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, 1,6,11-undecane triisocyanate, Examples of the polyisocyanate compound include aliphatic diisocyanates such as 1,3,6-hexamethylene triisocyanate, trimethylhexamethylene diisocyanate, and decamethylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate and xylylene diisocyanate; and alicyclic diisocyanates such as isophorone diisocyanate; as well as isocyanate derivatives such as adducts of polyisocyanate compounds and polyol compounds such as trimethylolpropane, biuret compounds and isocyanurate compounds of polyisocyanate compounds, and bifunctional polyisocyanate compounds.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] The above crosslinking agents may be used alone or in combination of two or more.

[0045] 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.

[0046] Considering the ease of recovery of the printed portion and thinness, the thickness of the alkali-insoluble coating layer is preferably 0.05 to 1 μm, and more preferably 0.05 to 0.5 μm.

[0047] The alkali-insoluble coating layer may contain additives such as a catalyst, an ultraviolet absorber, a pigment, and a filler.

[0048] <Detachment Coating Layer 14> The release coating layer is a layer formed from a release coating layer-forming composition containing a polyester resin having an acid value of 10 KOHmg / g or more and a crosslinking agent.

[0049] 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.

[0050] The composition for forming the release coating layer, which is a material for forming the release coating layer, contains a polyester resin having an acid value of 10 KOHmg / g or more.

[0051] (Polyester resin) The acid value of the 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 polyester resin is a value measured in accordance with JIS K 0070:1992. The upper limit of the acid value of the polyester resin is, for example, 150 KOHmg / g or less, and may be 120 KOHmg / g or less.

[0052] The glass transition temperature (Tg) of the polyester resin used in one embodiment of the present invention is preferably 30 to 70° C., more preferably 40 to 70° C., from the viewpoint of improving interlayer adhesion with the resin substrate. In this specification, the glass transition temperature (Tg) of the polyester resin is a value measured in accordance with JIS K 7121:2012, and specifically, a value measured based on the method described below.

[0053] The number average molecular weight (Mn) of the polyester resin is preferably 1,000 to 30,000 from the viewpoint of achieving both water resistance and deinking ability.

[0054] 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 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.

[0055] Examples of the 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.

[0056] 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 polyester resins are also included in the "polyester resin."

[0057] As the alcohol component, a polyhydric alcohol having two or more hydroxyl groups in one molecule can be used.

[0058] 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.

[0059] As the carboxylic acid component, a polybasic acid having two or more carboxyl groups in one molecule can be used.

[0060] 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.

[0061] From the viewpoint of adjusting the acid value within the above range, the polyester-based 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.

[0062] The polyester resin has a reactive functional group capable of crosslinking with a crosslinking agent. Such a reactive functional group is an acid group, and an example of the reactive functional group is a carboxyl group. From the viewpoint of improving the releasability, a polyester resin containing a carboxyl group is preferred.

[0063] When preparing the composition for forming a release coating layer, it is preferable to add a crosslinking agent to the polyester resin in the state of a solution in which the polyester resin is dissolved / dispersed in a solvent.

[0064] The solvent preferably contains at least one selected from water and a water-soluble organic solvent. Here, the water-soluble organic solvent is an organic solvent having a solubility of 20 g or more per 1 g of water at 20° C. In other words, the polyester resin is preferably an aqueous polyester resin that is soluble / dispersible in at least one selected from water and a water-soluble organic solvent.

[0065] 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). These water-soluble organic solvents may be used alone or in combination of two or more. They may also be mixed with water.

[0066] The solid content of the polyester resin in the solvent solution / dispersion of the polyester resin is, for example, 20 to 60 mass %.

[0067] In one embodiment of the present invention, a small amount of an emulsifier, surfactant, or the like may be used to prepare a dispersion in which the polyester resin is dispersed as an emulsion in water and / or a water-soluble organic solvent, as long as the effects of the present invention are not impaired.

[0068] These polyester resin solutions may be commercially available products, such as the Pluscoat Z series manufactured by GOO Chemical Industry Co., Ltd., the PES Resin A series manufactured by Takamatsu Oil & Fat Co., Ltd., the Nichigo Polyester (registered trademark) series manufactured by Mitsubishi Chemical Corporation, and the Aronmelt (registered trademark) PES series manufactured by Toagosei Co., Ltd.

[0069] (Crosslinking agent) Examples of crosslinking agents include epoxy-based crosslinking agents, oxazoline-based crosslinking agents, carbodiimide-based crosslinking agents, isocyanate-based crosslinking agents, metal chelate-based crosslinking agents, and aziridine-based crosslinking agents. Among these, from the viewpoint of the effects of the present invention, the crosslinking agent is preferably at least one selected from the group consisting of epoxy-based crosslinking agents, oxazoline-based crosslinking agents, and carbodiimide-based crosslinking agents. From the viewpoint of ink adhesion after immersion in water, epoxy-based crosslinking agents and / or oxazoline-based crosslinking agents are more preferred, and epoxy-based crosslinking agents are particularly preferred. The crosslinking agents may be used alone or in combination of two or more.

[0070] Examples of epoxy crosslinking agents include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and trimethylolpropanediol. Examples of epoxy crosslinking agents include glycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, diglycidylamine, tetraglycidylxylenediamine, N,N,N',N'-tetraglycidylaminophenylmethane, triglycidyl isocyanurate, mN,N-diglycidylaminophenyl glycidyl ether, N,N-diglycidyltoluidine, N,N-diglycidylaniline, etc. As the epoxy crosslinking agent, a compound having two or more epoxy groups or glycidyl groups in the molecule is preferred.

[0071] Examples of oxazoline-based crosslinking agents include 2,2'-bis-(2-oxazoline), 2,2'-methylene-bis-(2-oxazoline), 2,2'-ethylene-bis-(2-oxazoline), 2,2'-trimethylene-bis-(2-oxazoline), 2,2'-tetramethylene-bis-(2-oxazoline), 2,2'-hexamethylene-bis-(2-oxazoline), 2,2'-octamethylene-bis-(2-oxazoline), and 2,2'-ethylene-bis-(2-oxazoline). Examples of suitable oxazoline crosslinking agents include bis-(4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis-(2-oxazoline), 2,2'-m-phenylene-bis-(2-oxazoline), 2,2'-m-phenylene-bis-(4,4'-dimethyl-2-oxazoline), 2,2'-(1,3-phenylene)-bis-(2-oxazoline), bis-(2-oxazolinylcyclohexane) sulfide, and bis-(2-oxazolinylnorbornane) sulfide. Preferred oxazoline crosslinking agents include compounds having two or more oxazoline groups in the molecule. Examples of such oxazoline crosslinking agents include copolymers of addition-polymerizable 2-oxazolines (e.g., 2-isopropenyl-2-oxazoline) having a substituent with an unsaturated carbon-carbon bond at the second carbon position with other unsaturated monomers. Examples of the copolymer include "Epocross WS-300," "Epocross WS-500," "Epocross WS-700," "Epocross K-2010E," and "Epocross K-2030E" (all trade names, manufactured by Nippon Shokubai Co., Ltd.).

[0072] Examples of carbodiimide crosslinking agents include aromatic polycarbodiimides such as poly(4,4'-diphenylmethanecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(diisopropylphenylcarbodiimide), and poly(triisopropylphenylcarbodiimide); alicyclic polycarbodiimides such as poly(dicyclohexylmethanecarbodiimide); and aliphatic polycarbodiimides such as poly(diisopropylcarbodiimide). Carbodiimide crosslinking agents containing at least two carbodiimide groups are preferred, and commercially available products include, for example, "Carbodilite V-02," "Carbodilite V-02-L2," "Carbodilite SV-02," "Carbodilite V-04," "Carbodilite V-10," "Carbodilite E-02," and "Carbodilite E-05," all manufactured by Nisshinbo Chemical Inc.

[0073] Examples of the isocyanate crosslinking agent include adducts, biurets and isocyanurates of aliphatic diisocyanates such as hexamethylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate and xylylene diisocyanate; and alicyclic diisocyanates such as isophorone diisocyanate.

[0074] The content of the crosslinking agent in the composition for forming a detachment coating layer is an amount that results in a blocking rate of reactive functional groups in the polyester resin with the crosslinking agent of 40 to 140 mol %. By partially crosslinking the reactive functional groups (preferably carboxyl groups) in the polyester resin, it is possible to achieve both improved water resistance (ink adhesion) and improved releasability (deinking ability) with an alkaline aqueous solution.

[0075] The blocking rate of reactive functional groups in a polyester resin with a crosslinking agent (functional group blocking rate) can be calculated as the mole percent of groups in the crosslinking agent that react with the reactive functional groups (e.g., carboxyl groups) relative to the reactive functional groups in the polyester resin. The crosslinking agent is included in the composition for forming a release coating layer so that 40 to 140 mole percent of the reactive functional groups are blocked with groups in the crosslinking agent that react with the reactive functional groups. A functional group blocking rate of 40 to 140 mole percent further enhances both alkali solubility and suppression of print peeling due to prolonged contact with water. The blocking rate of the polyester resin with a crosslinking agent (functional group blocking rate) is preferably 70 to 120 mole percent, more preferably 70 to 110 mole percent, or even 80 to 100 mole percent. Note that not all crosslinking agents react with reactive functional groups in polyester resins, so the amount of crosslinking agent added may exceed 100 mole percent. The blocking rate can be calculated by calculating the number of moles of reactive functional groups in the polyester resin from the acid value of the polyester resin, and then calculating the blocking rate from the number of moles of functional groups in the polyester resin and the crosslinking agent and the amount of addition. Therefore, the reactive functional groups in the polyester resin are preferably acid groups and carboxyl groups.

[0076] The content of the crosslinking agent in the composition for forming a release coating layer may be designed taking into consideration the type of crosslinking agent, the content of the polyester-based resin, etc., so as to achieve the above-mentioned functional group blocking rate. Taking into consideration the effects of the present invention, the content of the crosslinking agent may be, for example, 5 to 300 parts by mass, or 5 to 150 parts by mass, per 100 parts by mass of the polyester-based resin in the composition for forming a release coating layer. Another embodiment of the present invention is a pressure-sensitive adhesive label having, in this order, a polyester-based pressure-sensitive adhesive layer, a polyester-based resin substrate, and a release coating layer, wherein the release coating layer is formed from a composition for forming a release coating layer containing a polyester-based resin having an acid value of 10 KOH mg / g or more and a crosslinking agent, and the content of the crosslinking agent in the composition for forming a release coating layer is 5 to 300 parts by mass per 100 parts by mass of the polyester-based resin.

[0077] (particle) The composition for forming a release coating layer may contain particles for the purpose of improving blocking resistance, etc.

[0078] The particles may be either inorganic or organic. 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, it is preferable that the composition for forming a release coating layer contains silica.

[0079] 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 polyester resin.

[0080] 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.

[0081] (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 polyester resin, crosslinking agent, and particles described above, as long as the effects of the present invention are not impaired.

[0082] <Resin substrate 16> It is necessary to use a polyester film made of the same material as the PET bottle as the adherend, which is compatible with the PET bottle. 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 polyester resin substrate whose composition is close to that of the resin used in the PET bottle. Examples of polyester resin substrates 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 compatible with the resin.

[0083] 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.

[0084] 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 production 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 an extrusion method, a calendar method, a solution coating method, or a casting method.

[0085] 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.

[0086] <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.

[0087] 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.

[0088] [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.

[0089] Among these, it is preferable to contain an aromatic dicarboxylic acid in order to impart cohesive strength.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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).

[0095] [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.

[0096] 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.

[0097] 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 entire polyol component (A2); if the content is too high, production of the polyester resin (A) tends to become difficult.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] Examples of 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.

[0104] 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).

[0105] 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.

[0106] The storage modulus G' 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.

[0107] 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.

[0108] 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.

[0109] <Release liner 30> 1, the release liner 30 has a release substrate 11 and a release agent layer 12. The release liner is an optional member.

[0110] 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 properties due to improved adhesiveness. The surface roughness Ra of the polyester-based pressure-sensitive adhesive side of the release substrate 11 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 11 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 11, the better. However, considering the saturation of the effect and production yield, a surface roughness of 0.01 μm or more is preferred.

[0111] 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).

[0112] 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.

[0113] 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.

[0114] Examples of the paper substrate for laminated paper include glassine paper, wood-free paper, and kraft paper.

[0115] Polyester films include polyethylene terephthalate (PET) and polyethylene ethylenediamine naphthalate (PEN), etc. can be used.

[0116] 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.

[0117] Examples of the release agent constituting the release agent layer include silicone-based release agents, long-chain alkyl-based release agents, fluorine-based release agents, and rubber-based release agents. Among these, silicone-based release agents are preferred. The thickness of the release agent layer is usually about 0.01 to 5 μm.

[0118] <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.

[0119] 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.

[0120] Furthermore, a release coating layer and an alkali-insoluble coating layer can be formed in advance on the resin substrate.

[0121] For each coating layer, a coating layer-forming composition (a composition for forming a detachment coating layer or a composition for forming an alkali-insoluble coating layer, 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, and examples include water, alcohols (e.g., ethanol, isopropanol, etc.), toluene, methyl ethyl ketone, and ethyl acetate. The solvent may be used alone or in combination of two or more.

[0122] Thereafter, the coating layer-forming composition is applied to the resin substrate or the detachment coating layer to form a coating layer (detachment coating layer or alkali-insoluble coating layer). The coating method is not particularly limited, and conventionally known methods can be used, such as a method of 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, for example, a method of applying the coating 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.

[0123] 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.

[0124] <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.

[0125] The present invention encompasses the following aspects and configurations.

[0126] [1] A pressure-sensitive adhesive label having, in this order, a polyester-based pressure-sensitive adhesive layer, a polyester-based resin substrate, and a release coating layer, wherein the release coating layer is formed from a composition for forming a release coating layer, which comprises a polyester-based resin having an acid value of 10 KOHmg / g or more and a crosslinking agent, and the content of the crosslinking agent in the composition for forming a release coating layer is an amount such that the blocking rate of functional groups in the polyester-based resin that are reactive with the crosslinking agent is 40 to 140 mol %.

[0127] [2] The adhesive label according to [1], further comprising an alkali-insoluble coating layer on the release coating layer facing the polyester resin substrate.

[0128] [3] The adhesive label according to [2], wherein the alkali-insoluble coating layer contains a urethane-modified polyester resin.

[0129] [4] The adhesive label according to [2] or [3], wherein the resin contained in the alkali-insoluble coating layer is a crosslinked body.

[0130] [5] The adhesive label according to any one of [1] to [4], wherein the crosslinking agent is at least one selected from the group consisting of epoxy-based crosslinking agents, oxazoline-based crosslinking agents, and carbodiimide-based crosslinking agents.

[0131] [6] The adhesive label according to any one of [1] to [5], wherein the polyester resin has a carboxyl group.

[0132] [7] The adhesive label according to any one of [1] to [6], wherein the blocking rate is 70 to 120 mol %.

[0133] [8] The adhesive label according to any one of [1] to [7], wherein the crosslinking agent is an epoxy-based crosslinking agent and / or an oxazoline-based crosslinking agent.

[0134] [9] A polyester-based container having the adhesive label according to any one of [1] to [8] attached thereto. [Example]

[0135] 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).

[0136] 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 HL") 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").

[0137] 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.

[0138] An aqueous solution (30% solids by mass) of polyester resin (acid value 80 mg KOH / g, carboxyl group-containing, Tg 60°C) and 15 parts by mass (blocking rate 60 mol%) of epoxy crosslinker (Denacol EX-614B, Nagase ChemteX Corporation) were mixed with 100 parts by mass of polyester resin solids to obtain a composition for forming a release coating layer. 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, followed by drying to form a release coating layer.

[0139] 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.

[0140] Example 2 An adhesive label was obtained in the same manner as in Example 1, except that the amount of crosslinking agent added was changed to 20 parts by mass (blocking rate: 80 mol%).

[0141] Example 3 An adhesive label was obtained in the same manner as in Example 1, except that the amount of crosslinking agent added was changed to 25 parts by mass (blocking rate: 100 mol %).

[0142] Example 4 An adhesive label was obtained in the same manner as in Example 1, except that the crosslinking agent in Example 1 was changed to 75 parts by mass (solid content) (blocking rate 60 mol%) of an oxazoline-based crosslinking agent (Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., an aqueous solution with a solid content of 25% by weight).

[0143] Example 5 An adhesive label was obtained in the same manner as in Example 4, except that the amount of crosslinking agent added was changed to 100 parts by mass (blocking rate: 80 mol%).

[0144] Example 6 An adhesive label was obtained in the same manner as in Example 4, except that the amount of crosslinking agent added was changed to 125 parts by mass (blocking rate: 100 mol %).

[0145] Example 7 An adhesive label was obtained in the same manner as in Example 1, except that the crosslinking agent in Example 1 was changed to 126 parts by mass (solid content) (blocking rate 60 mol%) of a carbodiimide-based crosslinking agent (Carbodilite V-02, manufactured by Nisshinbo Chemical Co., Ltd.).

[0146] Example 8 An adhesive label was obtained in the same manner as in Example 7, except that the amount of crosslinking agent added was changed to 168 parts by mass (blocking rate: 80 mol%).

[0147] Example 9 An adhesive label was obtained in the same manner as in Example 7, except that the amount of crosslinking agent added was changed to 210 parts by mass (blocking rate: 100 mol%).

[0148] Example 10 In Example 2, an adhesive label was obtained in the same manner as in Example 2, except that a composition for forming an alkali-insoluble coating layer, which was prepared by mixing 3 parts by mass of a crosslinking agent (hexamethylene diisocyanate) per 100 parts by mass of urethane-modified polyester resin (Vylon UR-8300, manufactured by Toyobo MC Co., Ltd.) and resin solids, and diluting the mixture with toluene, was applied to the obtained release coating layer using a Mayer bar and dried to a dry film thickness of 0.08 μm, thereby forming an alkali-insoluble coating layer.

[0149] (Comparative Example 1) An adhesive label was obtained in the same manner as in Example 1, except that no crosslinking agent was used.

[0150] (Comparative Example 2) 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.

[0151] (Comparative Example 3) An adhesive label was obtained in the same manner as in Example 1, except that the amount of crosslinking agent added was changed to 37 parts by mass (blocking rate: 150 mol%).

[0152] [Evaluation method 1: Deinking] The samples obtained in the examples and comparative examples were printed solid using ink: UV161 J Ink S (manufactured by T&K TOKA) with a printer: RI Tester. The ink was cured by irradiating it with ultraviolet light from a high-pressure mercury lamp, and then cut into samples: 10 mm x 10 mm. Five samples were placed in 1 L of 1.5% by mass sodium hydroxide aqueous 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.

[0153] <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.

[0154] [Evaluation method 2: Initial ink adhesion] Solid printing was performed using UV161 J Ink S (manufactured by T&K TOKA) with a printer: RI Tester. The ink was then cured by irradiating it with ultraviolet light from a high-pressure mercury lamp, and the adhesion to the release coating layer or alkali-insoluble coating layer was evaluated by cellophane tape peeling. Specifically, 100 cross-cuts (10 x 10 squares) were made at 1 mm intervals, and the remaining printed area after the cellophane tape peeling was evaluated according to the following criteria. The results are shown in Table 1.

[0155] <Evaluation criteria> 5: 90-100% remaining 4: 60% or more but less than 90% remaining 3: 40% or more but less than 60% remaining 2: 15% or more but less than 40% remaining 1: 0% or more but less than 15% remaining.

[0156] [Evaluation method 3: Ink adhesion when immersed in water for a long period of time] The samples obtained in the examples and comparative examples were printed solidly using ink: UV161 J Ink S (manufactured by T&K TOKA) with a printer: RI Tester. The ink was cured by irradiating it with ultraviolet light from a high-pressure mercury lamp, and then immersed in tap water at room temperature for 24 hours. Immediately after removal, the ink adhesion was evaluated using cellophane tape peeling. The specific evaluation method and evaluation criteria were the same as those for initial ink adhesion described above. The results are shown in Table 1.

[0157] [Table 1]

[0158] As shown above, the pressure-sensitive adhesive labels of the Examples had excellent deinking properties in alkaline hot water at low temperatures (about 70°C), and maintained ink adhesion even when immersed in water for a long period of time. On the other hand, Comparative Example 1, which used a composition for forming a release coating layer that did not contain a crosslinking agent, had excellent deinking properties in alkaline hot water at low temperatures (about 70°C), but was unable to maintain its initial ink adhesion when immersed in water for a long period of time. Furthermore, Comparative Example 2, which used a polyester resin with an acid value of less than 10 KOH mg / g, resulted in significantly poor deinking properties in alkaline hot water at low temperatures (about 70°C). Furthermore, Comparative Example 3, which had a blocking rate of 150 mol%, showed significantly poor deinking properties in alkaline hot water. [Explanation of symbols]

[0159] 10, 20 adhesive labels, 11 release substrate, 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 release coating layer is formed from a release coating layer-forming composition containing a polyester resin with an acid value of 10 KOH mg / g or more and a crosslinking agent, an amount of the crosslinking agent contained in the composition for forming a detachment coating layer such that a blocking rate of functional groups reactive with the crosslinking agent in the polyester resin is 40 to 140 mol%;

2. The pressure-sensitive adhesive label according to claim 1 , further comprising an alkali-insoluble coating layer on the release coating layer facing the polyester resin substrate.

3. The adhesive label according to claim 2 , wherein the alkali-insoluble coating layer contains a urethane-modified polyester resin.

4. The pressure-sensitive adhesive label according to claim 2 or 3, wherein the resin contained in the alkali-insoluble coating layer is a crosslinked resin.

5. The pressure-sensitive adhesive label according to claim 1 or 2, wherein the crosslinking agent is at least one selected from the group consisting of an epoxy-based crosslinking agent, an oxazoline-based crosslinking agent, and a carbodiimide-based crosslinking agent.

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

7. The adhesive label according to claim 1 or 2, wherein the blocking rate is 70 to 120 mol %.

8. The adhesive label according to claim 1 or 2, wherein the crosslinking agent is an epoxy-based crosslinking agent and / or an oxazoline-based crosslinking agent.

9. A polyester-based container having the adhesive label according to claim 1 or 2 attached thereto.

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