Label, and method for removing ink layer from label

Abstract

To provide a label from which an ink layer can be efficiently removed, and a method for removing an ink layer from a label.SOLUTION: A label (11) comprises a substrate (101) and an ink layer (103) on the substrate (101), and the ink layer (103) contains a material that emits light when irradiated with energy rays. When the label (11) is irradiated with energy rays, the ink layer (103) emits light, making it possible to identify and distinguish the label (11) from other labels.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to labels and methods for removing ink layers from labels. [Background technology]

[0002] In recent years, plastic products such as polyethylene terephthalate (PET) bottles have become widely used. From the viewpoints of resource conservation and environmental friendliness, there is a strong demand for the reuse of plastic products such as PET bottles.

[0003] Recycling of plastic products, especially PET bottles, has already been established. However, although plastic labels with an ink layer printed with product information are sometimes attached to the body of the PET bottle, the recycling of labels has not yet been achieved.

[0004] One of the factors hindering the reuse of labels is the inability to fully remove the ink layer from the label. If the ink layer cannot be fully removed from the label, the ink will be mixed into the recycled resin, making it impossible to produce usable recycled products such as pellets from the recycled resin.

[0005] For example, Patent Document 1 describes a plastic label in which a display printing ink layer is formed on a base film via a coating layer that is soluble in an alkaline aqueous solution. In Patent Document 1, the display printing ink layer is alkali-released by dissolving the coating layer of the plastic label in an alkaline aqueous solution. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-240029 Summary of the Invention [Problem to be solved by the invention]

[0007] When labels are actually reused, it is expected that labels whose ink layer can be removed by alkali and labels whose ink layer cannot be removed by alkali will be collected together.

[0008] However, when reusing labels, a technology for separating labels whose ink layer can be removed by alkali from labels whose ink layer cannot be removed by alkali has not yet been established.

[0009] Furthermore, even if alkaline desorption of the ink layer is performed while a mixture of labels whose ink layer can be alkaline desorbed and labels whose ink layer cannot be alkaline desorbed is present, it is necessary to remove the labels whose ink layer cannot be alkaline desorbed after alkaline desorption of the ink layer, so there is a demand for a method for efficiently removing the ink layer. [Means for solving the problem]

[0010] According to the embodiment disclosed herein, a label can be provided that comprises a substrate and an ink layer on the substrate, the ink layer containing a material that emits light when irradiated with energy rays, and that allows the label with the ink layer to be identified and distinguished from other labels by the ink layer emitting light when irradiated with energy rays.

[0011] According to the embodiment disclosed herein, a method for removing an ink layer from a label can be provided, comprising the steps of: recovering a group of labels including the above-mentioned label; irradiating the recovered group of labels with energy rays; separating the labels that have emitted light as a result of being irradiated with the energy rays; and removing the ink layer from the separated labels. [Effects of the Invention]

[0012] According to the embodiments disclosed herein, it is possible to provide a label that allows for efficient removal of an ink layer, and a method for removing an ink layer from a label. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a schematic cross-sectional view of a label according to an embodiment. [Figure 2] 1(a) to 1(i) are diagrams illustrating an example of the flow of a method for removing an ink layer from a label according to an embodiment. [Figure 3] FIG. 10 is a schematic side view illustrating an example of a step of irradiating the collected label group with energy rays. [Figure 4] FIG. 2 is a schematic cross-sectional view of a label of Experimental Example 1. [Figure 5] FIG. 1 is a schematic side view illustrating a method for evaluating the luminescence of a label in Experimental Example 1. [Figure 6] 10 is a schematic cross-sectional view of the labels of Experimental Examples 2 to 4. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] <label> FIG. 1 shows a schematic cross-sectional view of a label of an embodiment. As shown in FIG. 1, the label 11 of the embodiment includes a substrate 101, an alkali-soluble coating layer 102 on the substrate 101, and an ink layer 103 on the coating layer 102. The label 11 of the embodiment may be a heat-shrinkable label (shrink label) or a non-heat-shrinkable label. Furthermore, the label 11 of the embodiment may be a self-stretchable stretch label or a non-self-stretchable label.

[0015] <Base material> The substrate 101 is a base containing a resin capable of supporting the coating layer 102 and the ink layer 103 .

[0016] Examples of resins that can be used in base material 101 include polyester resins (polyethylene terephthalate, polyethylene naphthalate, polylactic acid, etc.), polystyrene resins (polystyrene, styrene-butadiene copolymer, etc.), polyolefin resins (polyethylene, polypropylene, etc.), polyvinyl chloride resins, polyamide resins, aramid resins, polyimide resins, polyphenylene sulfide resins, and acrylic resins. Base material 101 may contain one type of these resins, or may contain two or more types.

[0017] The resin contained in the substrate 101 is preferably a polyester resin, and particularly preferably PET. PET is a polyester resin containing terephthalic acid as the main dicarboxylic acid component and ethylene glycol as the main diol component. PET may also contain other components such as dicarboxylic acids, such as isophthalic acid, phthalic acid, adipic acid, sebacic acid, or naphthalenedicarboxylic acid, and may also contain diol components, such as diethylene glycol, neopentyl glycol, polyalkylene glycol, or 1,4-cyclohexanedimethanol.

[0018] The substrate 101 may be, for example, a heat-shrinkable film (shrink film). When the substrate 101 is a shrink film, the processability (ability to conform to the container) and decorativeness of the label 11 can be improved, and the display area of ​​the label 11 can be further expanded. The substrate 101 may also be, for example, a self-stretchable stretch film.

[0019] The substrate 101 may be a single-layer film made of one layer, or may be a multi-layer film made of two or more layers. The thickness of the substrate 101 can be, for example, 5 μm to 100 μm, but is not particularly limited.

[0020] <Coating layer> The coating layer 102 is located between the substrate 101 and the ink layer 103 and is a layer containing an alkali-soluble resin.

[0021] The coating layer 102 being alkali-soluble means that when a sample in which a coating layer 102 measuring 4 cm x 4 cm is formed on a substrate 101 of any size and an ink layer 103 of any kind is provided on the coating layer 102 is immersed in a 1.5 mass % sodium hydroxide aqueous solution (i.e., 1.5% of the total mass of the sodium hydroxide aqueous solution is sodium hydroxide) at 85°C and stirred at 1500 rpm, 70% or more of the total area of ​​the ink layer 103 will be detached from the sample after an immersion time of 15 minutes.

[0022] The resin contained in the coating layer 102 may be, for example, a resin having the following (1) to (4): (1) A first resin is an acrylic acid copolymer resin having a first glass transition temperature T1; (2) A second resin is an acrylic acid copolymer resin having a second glass transition temperature T2 lower than the T1; (3) The apparent acid value of the coating layer 102 is 40 mgKOH / g or more and 150 mgKOH / g or less; (4) The first resin and the second resin contained in the coating layer 102 occupy 50 to 95% by mass of the entire coating layer 102 in total.

[0023] Resins having the above (1) to (4) have good alkali solubility. Therefore, when the label 11 has the alkali-soluble coating layer 102 between the substrate 101 and the ink layer 103, the ink layer 103 is also released from the label 11 as the coating layer 102 is released from the label 11 by alkali.

[0024] Furthermore, resins having the above (1) to (4) have excellent printability in addition to the alkali solubility described above, which can improve the aesthetic appeal of the ink layer 103 on the coating layer 102.

[0025] As described in (1) and (2) above, the first resin and the second resin are each an acrylic acid copolymer resin. An acrylic acid copolymer resin is a resin that contains acrylic acid and / or methacrylic acid as a main repeating unit and also contains a copolymerizable monomer copolymerizable with the acrylic acid and / or methacrylic acid. The acrylic acid copolymer resin preferably has a total content of acrylic acid and / or methacrylic acid and the copolymerizable monomer of 60 mol % or more in the resin.

[0026] Examples of copolymerizable monomers include (meth)acrylic acid alkyl esters (preferably lower alkyl esters of (meth)acrylic acid) such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and t-butyl (meth)acrylate; hydroxyl group-containing (meth)acrylates such as hydroxyethyl (meth)acrylate; glycidyl group-containing (meth)acrylates such as glycidyl (meth)acrylate; N,N'-dimethyl (meth)acrylamides; Examples of copolymerizable monomers include (meth)acrylamides such as N,N'-diethyl(meth)acrylamide, amino group-containing (meth)acrylates such as dimethylaminoethyl (meth)acrylate, styrenes such as styrene, vinyl toluene, and α-methylstyrene, vinyl esters such as vinyl acetate and vinyl propionate, vinyl halides such as vinyl chloride, vinyl ethers such as methyl vinyl ether, carboxyl group-containing vinyls (excluding (meth)acrylic acid) such as itaconic acid and maleic anhydride, cyano group-containing vinyls such as acrylonitrile and methacrylonitrile, olefins such as ethylene and propylene, and dienes. The copolymerizable monomers can be used alone or in combination of two or more.

[0027] Regarding (1) and (2) above, the Tg of each of the first resin and the second resin can be controlled, for example, by adjusting the mass-average molecular weight (Mm) of the acrylic acid copolymer resin. For example, by making the Mm of the first resin larger than the Mm of the second resin, the first resin and the second resin can be made to have a relationship of T1 > T2. Preferably, the Mm of the first resin is 30,000 or more and 90,000 or less, and the Mm of the second resin is 10,000 or more and less than 30,000.

[0028] With regard to (1) and (2) above, T1, the Tg of the first resin, is preferably 90°C or higher, more preferably 95°C or higher, and particularly preferably 100°C or higher. The upper limit of T1 can be set to, for example, approximately 120°C, in consideration of the physical properties of the acrylic acid copolymer resin. T2, the Tg of the second resin, is preferably less than 80°C, more preferably 75°C or lower, and particularly preferably 65°C or lower. The lower limit of T2 can be set to, for example, approximately 30°C, in consideration of ease of handling. The difference between T1 and T2 is preferably, for example, 20°C or higher, more preferably 30°C or higher, and particularly preferably 40°C or higher. In this case, deterioration in printability can be more effectively suppressed, thereby enabling the cosmetic properties of the ink layer 103 to be particularly improved.

[0029] With regard to the above (3), the apparent acid value of the coating layer 102 refers to the acid value of a mixed resin made up of two or more types of resin contained in the coating layer 102. The apparent acid value of the coating layer 102 can be adjusted by controlling the acid values ​​of the first resin and the second resin. The acid values ​​of the first resin and the second resin can be adjusted, for example, by changing the blending ratio of (meth)acrylic acid and copolymerizable monomer.

[0030] Regarding the above (3), the apparent acid value of the coating layer 102 is more preferably 50 mgKOH / g or more and 130 mgKOH / g or less, and particularly preferably 55 mgKOH / g or more and 125 mgKOH / g or less, which can particularly improve the alkali solubility and printability of the coating layer 102.

[0031] The acid value of the first resin and the acid value of the second resin are each preferably 40 mgKOH / g or more and 150 mgKOH / g or less. In this case, the apparent acid value of the coating layer 102 can be easily set to 40 mgKOH / g or more and 150 mgKOH / g or less as in (3) above. The acid value of the first resin is preferably lower than the acid value of the second resin. The acid value of the first resin is preferably less than 60 mgKOH / g. The acid value of the second resin is preferably 80 mgKOH / g or more.

[0032] Regarding (4) above, the first resin and the second resin in the coating layer 102 preferably account for 70% to 95% by mass, and more preferably 80% to 95% by mass, of the entire coating layer 102. In these cases, it is possible to particularly improve the alkali solubility and printability of the coating layer 102. Furthermore, it is preferable that the content ratio of the first resin and the content ratio of the second resin do not differ significantly. From the viewpoint of improving the synergistic effect of containing two types of resin, the first resin and the second resin, it is preferable that the ratio of the content of the first resin to the content of the second resin (the content of the resin with a relatively large content / the content of the resin with a relatively small content) is 3 or less.

[0033] Whether the coating layer 102 contains an alkali-soluble resin can be confirmed using various analytical techniques. For example, nuclear magnetic resonance (NMR), gas chromatography mass spectrometry (GCMS), or pyrolysis gas chromatography (pyrolysis GCMS) can be used to confirm the presence of a specific content of acrylic acid copolymer resin in the coating layer 102. The acid value of the coating layer 102 can be confirmed, for example, by titrating the coating layer 102. For example, the coating layer 102 can be dissolved in a titration solvent such as a xylene-dimethylformamide mixed solvent, and the acid value can be calculated based on the results of potentiometric titration using a potassium hydroxide solution of a predetermined concentration (e.g., a 0.1 mol / L potassium hydroxide-ethanol solution). Whether the coating layer 102 contains the first and second resins having the above-mentioned Tg can be confirmed, for example, by subjecting the composition used to form the coating layer (described below) to differential scanning calorimetry (DSC). The DSC method can be performed using a DSC6200 manufactured by Seiko Instruments Inc. at a temperature rise rate of 10°C / min. The Mm of the first resin and the Mm of the second resin can be confirmed by, for example, gel permeation chromatography (GPC).

[0034] The first and second resins are preferably methacrylic acid-methyl methacrylic acid copolymers (hereinafter also referred to as "MM copolymers"). In this case, it is possible to significantly improve both the alkali solubility and printability of the coating layer 102. The MM copolymer may be synthesized or commercially available. Commercially available products suitable for the first resin include "DIANAL LR-1941" and "DIANAL BR-87" manufactured by Mitsubishi Rayon Co., Ltd. Commercially available products suitable for the second resin include "JONCRYL JDX-C3000" manufactured by BASF Japan Ltd., "ARUFON UC3000" manufactured by Toa Gosei Co., Ltd., and "BR-605" manufactured by Mitsubishi Rayon Co., Ltd. Among these, it is preferable to use a combination of "DIANAL LR-1941" and "JONCRYL JDX-C3000" as the first and second resins.

[0035] The coating layer 102 may contain other components in addition to the first resin and the second resin. Preferred other components include cellulose derivatives. When the coating layer 102 contains a cellulose derivative, the coating layer 102 can have improved blocking resistance, adhesion, and the like.

[0036] Examples of the cellulose derivative contained in the coating layer 102 include nitrocellulose, acetylcellulose, carboxymethylcellulose or a salt thereof, methylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, cellulose acetate butyrate, and cellulose acetate propionate. Nitrocellulose is preferably used as the cellulose derivative contained in the coating layer 102. In the coating layer 102, the cellulose derivative may be used alone or in combination of two or more types.

[0037] The content of the cellulose derivative in the coating layer 102 is preferably 1% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less, and particularly preferably 8% by mass or more and 12% by mass or less, of the total mass of the coating layer 102. In these cases, the blocking resistance and printability of the coating layer 102 can be improved. The cellulose derivative preferably has a degree of polymerization of 35 to 380, more preferably 45 to 290, and particularly preferably 55 to 110. In these cases, the blocking resistance and printability of the coating layer 102 can be improved.

[0038] Furthermore, the coating layer 102 may contain, for example, a vinyl chloride-vinyl acetate copolymer (hereinafter also referred to as "VV copolymer") as another preferable component. When the coating layer 102 contains the VV copolymer, the adhesion between the substrate 101 and the coating layer 102 can be further improved.

[0039] The content of the VV copolymer in the coating layer 102 is preferably 5 to 20 mass %, more preferably 8 to 18 mass %, and particularly preferably 9 to 12 mass %, of the total mass of the coating layer 3. In these cases, the adhesion and printability of the coating layer 102 can be improved. The VV copolymer in the coating layer 102 preferably has an Mm of 10,000 to 40,000, and more preferably an Mm of 15,000 to 35,000. In these cases, the adhesion of the coating layer 102 is significantly improved.

[0040] The coating layer 102 may further contain a material that emits light when irradiated with energy rays. This allows the labels 11 of the embodiment having the alkali-soluble coating layer 102 to be identified and separated by irradiating the labels 11 with energy rays and causing the coating layer 102 of the labels 11 to emit light.

[0041] The energy rays irradiated onto the label 11 can be, for example, short-wavelength electromagnetic waves such as X-rays or ultraviolet light, visible light, infrared light, near-infrared light, or microwaves. It is preferable to use ultraviolet light as the energy rays irradiated onto the label 11. When ultraviolet light is used as the energy rays irradiated onto the label 11, irradiation with the energy rays tends to induce electronic excitation in the material that emits light.

[0042] As the material that emits light when irradiated with energy rays, for example, a fluorescent pigment or a phosphorescent pigment can be used.

[0043] Fluorescent pigments are pigments that emit light when irradiated with energy rays, but phosphorescent pigments are excluded from the fluorescent pigments.

[0044] Examples of red fluorescent pigments include Y2O2S:Eu, Y2O3:Eu, Y2SiO5:Eu, and Y3AlO 12:Eu, Zn3(PO4)2:Mn, YBO3:Eu, (Y,Gd)BO3:Eu, GdBO3:Eu, ScBO3:Eu, LuBO3:Eu, etc. can be used.

[0045] Examples of blue fluorescent pigments include BaMg2Al 16 O 27 :Eu, Y2SiO5:Ce, CaWO4:Pb, or BaMgAl 14 O 23 :Eu, etc. can be used.

[0046] Examples of green fluorescent pigments include BaMg2Al 16 O 27 :(Eu,Mn), (Ba,Mg)Al 16 O 27 :(Eu,Mn), Zn2SiO4:Mn, BaAl 12 O 19 :Mn, SrAl 13 O 19 :Mn, CaAl 12 O 19 :Mn, YBO3:Tb, BaMgAl 14 O 23 :Mn, LuBO3:Tb, GdBO3:Tb, ScBO3:Tb, or Sr6Si3O3C 14 :Eu, etc. can be used.

[0047] As the fluorescent pigment, for example, one of the above-mentioned types may be used alone, or two or more of the above-mentioned types may be used in combination.

[0048] The phosphorescent pigment is a pigment that emits light when irradiated with energy rays and has phosphorescent properties. Examples of the phosphorescent pigment that can be used include sulfide-based phosphorescent pigments, oxyacid salt-based phosphorescent pigments, and alumina oxide-based phosphorescent pigments.

[0049] Examples of sulfide-based phosphorescent pigments that can be used include calcium sulfide:bismuth (CaS:Bi), calcium strontium sulfide:bismuth (CaSrS:Bi), zinc sulfide:copper (ZnS:Cu), and zinc sulfide:cadmium:copper (ZnCdS:Cu).

[0050] Examples of oxyacid salt phosphorescent pigments that can be used include Zn2SiO4:Mn, (Zn,Be)2SiO4:Mn, Ca3(PO4)2:Ce, and Ca3(PO4)2:(Ce,Mn).

[0051] Examples of alumina oxide phosphorescent pigments that can be used include aluminum oxide-calcium:europium (CaAl2O4:Eu), aluminum oxide-strontium:europium (SrAl2O4:Eu), and aluminum oxide-barium:europium (BaAl2O4:Eu).

[0052] As the phosphorescent pigment, for example, one of the above types may be used alone, or two or more of the above types may be used in combination.

[0053] In addition to the above, the coating layer 102 may contain other components for the purpose of improving printability, etc. For example, when the coating layer 102 contains the first resin, the second resin, the VV copolymer, and the cellulose derivative in predetermined content ratios, the apparent acid value of the coating layer 102 is the sum of the content ratio of each component multiplied by the acid value of each resin.

[0054] The thickness of the coating layer 102 can be, for example, 0.1 μm or more and 5 μm or less, and is preferably 0.3 μm or more and 3 μm or less, but is not particularly limited.

[0055] <Ink layer> The ink layer 103 is located on the coat layer 102 and is a layer containing an ink resin composition. The ink resin composition contained in the ink layer 103 may contain, for example, a pigment, a resin, and an additive. The ink layer 103 is preferably a design print layer. The design print layer is a layer that contains a pigment and displays a visible pattern, letters, etc.

[0056] The ink layer 103 may be provided on the entire surface of the coating layer 102, or on a part of the coating layer 102. The ink layer 103 may be a single layer or may be multi-layered. The thickness of the ink layer 103 may be, for example, about 0.1 μm or more and 100 μm or less, but is not particularly limited.

[0057] The ink layer 103 may further contain a material that emits light when irradiated with energy rays. This allows the label 11 of the embodiment having the alkali-soluble coating layer 102 to be identified and separated by irradiating the label 11 with energy rays and causing the ink layer 103 of the label 11 to emit light.

[0058] <Other layers> The label 11 may further include another layer, such as an overcoat layer, on the ink layer 103. The overcoat layer is a layer for protecting the ink layer 103 from external factors.

[0059] <Label manufacturing method> The label 11 of this embodiment can be manufactured, for example, as follows: First, a substrate 101 is prepared. The substrate 101 can be prepared, for example, by forming a film by a method such as an extrusion method or a calendar method, and then, if necessary, subjecting the film to a stretching treatment.

[0060] Next, the coating layer 102 is formed on one surface of the substrate 101. The coating layer 102 can be formed, for example, by applying a composition containing the resin contained in the coating layer 102 onto one surface of the substrate 101 and then solidifying it.

[0061] Next, an ink layer 103 is formed on the surface of the coat layer 102. The ink layer 103 can be formed, for example, by applying an ink resin composition for forming the ink layer 103 on the surface of the coat layer 102 and then solidifying it.

[0062] When the label 11 further includes another layer such as an overcoat layer, etc., it can be formed by applying a resin composition for forming the other layer on the surface of the ink layer 103 and then solidifying it.

[0063] <Method for Removing Ink Layer from Label> Figs. 2(a) to (i) show a diagram illustrating an example of the flow of a method for removing an ink layer from a label of an embodiment when the label 11 of the embodiment is a shrink label. Hereinafter, a method for removing an ink layer from the label 11 of the embodiment will be described with reference to Figs. 2(a) to (i).

[0064] <PET Bottle Recycling Process> First, as shown in Fig. 2(a), the PET bottle 10 is collected in a collection box 12. Here, on the body portion of the PET bottle 10, a label 11 of the embodiment provided with an ink layer 103 is attached. In the present embodiment, the ink layer 103 is used as a printing layer for product display and the like.

[0065] <Compression Process> Next, as shown in Fig. 2(b), the collected PET bottle 10 is compressed in a state where the label 11 is attached, to obtain a labeled bale 20.

[0066] <Integration Process> Next, as shown in Fig. 2(c), the labeled bale 20 is sent to a recycling factory 30 and integrated.

[0067] <Label Group Collection Process> 2(d), a label group 50 is collected, which includes the labels 11 of the embodiment and the normal labels 40. The label group 50 can be collected, for example, as follows.

[0068] First, at the recycling plant 30, the label 11 of the embodiment and / or the regular label 40 is removed from the PET bottles 10 in the labeled bale 20, and the PET bottles 10 are separated into a label group 50 including the label 11 of the embodiment and the regular label 40, and the label group 50 including the label 11 of the embodiment and the regular label 40 is collected.

[0069] In this embodiment, the normal label 40 is a label in which the coating layer or ink layer is not alkali-soluble and therefore the ink layer cannot be alkali-removed, and which does not contain a material that emits light when irradiated with energy rays.

[0070] Furthermore, the PET bottle 10 from which the label 11 and / or the regular label 40 has been separated can be reused in the existing PET bottle recycling process.

[0071] <Energy beam irradiation and separation process> Next, as shown in Fig. 2(e), the collected label group 50 is irradiated with an energy beam. Fig. 3 shows a schematic side view illustrating an example of the process of irradiating the collected label group 50 with an energy beam. Hereinafter, with reference to Fig. 3, an example of the process of irradiating the collected label group 50 with an energy beam will be described.

[0072] First, the collected label group 50 is carried into the first dark place 201. Next, the label group 50 is irradiated with energy rays 22 from the light source 21 arranged inside the first dark place 201.

[0073] Next, the label group 50 after irradiation with the energy beam 22 is carried out from inside the first dark place 201. Next, the label group 50 carried out from inside the first dark place 201 is carried into inside the second dark place 202.

[0074] At this time, the coating layer 102 of the label 11 of the embodiment after irradiation with the energy rays 22 emits light, and therefore the label 11 of the embodiment appears to glow inside the second dark place 202. On the other hand, the ordinary label 40 does not contain a material that emits light when irradiated with energy rays, and therefore does not appear to glow inside the second dark place 202 even when irradiated with the energy rays 22.

[0075] This makes it possible to separate and collect the labels 11 of the embodiment, which appear to glow in the second dark place 202, from the regular labels 40, which do not appear to glow in the second dark place 202. The regular labels 40, which are collected separately from the labels 11 of the embodiment, are reused, for example, in a thermal recycling process.

[0076] In this embodiment, the label group 50 is irradiated with the energy beam 22 inside the first dark place 201, but the label group 50 does not necessarily have to be irradiated with the energy beam 22 in a dark place.

[0077] <Preheating process> Next, as shown in FIG. 2(f), the shrink label 11 is preheated. The method for preheating the label 11 is not particularly limited as long as it can suppress the amount of shrinkage and curling of the label piece during alkaline desorption, which will be described later. However, it is preferable that the preheating temperature be the same as or higher than the alkaline desorption temperature. From the perspective of efficiently removing the ink layer from the label piece during alkaline desorption, which will be described later, it is preferable that the preheating temperature be at least 5°C higher than the alkaline desorption temperature.

[0078] The label 11 may be preheated, for example, by passing the label 11 through a hot air tunnel 61 or by immersing the label 11 in hot water 60 in a hot water bath 62 .

[0079] However, from the viewpoints of (A) to (D) below, it is preferable to use a method of preheating the label 11 by immersing the label 11 in hot water 60 in a hot water bath 62 rather than passing the label 11 through a hot air tunnel 61. (A) When hot air is used, the label 11 removed from the PET bottle 10 is blown away by the hot air, making it difficult to control. (B) The method of immersing in warm water makes it easier to control the temperature. (C) The warm water immersion method has a smaller footprint. (D) The method of immersing in warm water is less likely to cause uneven shrinkage of the label 11 and allows it to shrink uniformly.

[0080] For example, when preheating the label 11 by immersing the label 11 in hot water 60 in a hot water bath 62, the label 11 can be preheated by immersing the label 11 in hot water of about 80°C to 90°C for about 10 to 20 seconds.

[0081] The preheating temperature refers to the surface temperature of the label 11 during preheating. Therefore, when the label 11 is preheated by immersing it in hot water 60 in a hot water bath 62, the preheating temperature can be replaced with the temperature of the hot water. Also, when the label 11 is preheated by passing it through a hot air tunnel 61, the preheating temperature can be replaced with the temperature of the hot air.

[0082] <Crushing process> Next, as shown in FIG. 1(g), the preheated label 11 is crushed in a crusher 70 to produce label pieces 71. The method for crushing the preheated label 11 is not particularly limited as long as the size of the crushed label pieces 71 is smaller than the size of the preheated label 11. For example, the preheated label 11 can be crushed to a size (e.g., several centimeters square) that allows the ink layer 103 to be efficiently removed from the label piece 71 in the alkali desorption process described below. Note that since the label piece 71 is obtained by crushing the label 11 of the embodiment, it goes without saying that the layer structure of the label piece 71 is the same as that of the label 11 of the embodiment.

[0083] <Alkali removal step> Next, as shown in FIG. 1(h), the ink layer 103 is removed from the label piece 71 by alkaline desorption. Alkaline desorption can be performed, for example, by immersing the label piece 71 in an alkaline aqueous solution 80 at approximately 80°C to 90°C in a hot alkaline bath 82 for 30 seconds to 20 minutes while stirring the hot alkaline bath 82. In this case, the label piece 21 can be easily separated into the substrate 101 and the ink coating film 93 in the hot alkaline bath 82. Alternatively, alkaline desorption can be performed, for example, by immersing the label piece 71 in the alkaline aqueous solution 80 for 30 seconds to 20 minutes, followed by water washing. In this case, the label piece 71 can be easily separated into the substrate 101 and the ink coating film 93 by water washing (for example, in a water bath).

[0084] As described above, in this embodiment, the preheating temperature is set to be the same as or higher than the alkaline desorption temperature. The alkaline desorption temperature refers to the surface temperature of the label piece 71 during alkaline desorption. Therefore, the alkaline desorption temperature can be replaced with the temperature of the alkaline aqueous solution 80 in which the label piece 71 is immersed. From the viewpoint of efficiently removing the ink layer 103 from the label piece 71 during alkaline desorption, the alkaline desorption temperature is preferably 65°C or higher. Theoretically, the upper limit of the alkaline desorption temperature is 100°C, more preferably the alkaline desorption temperature is 85°C or higher and 95°C or lower, and even more preferably the alkaline desorption temperature is 80°C or higher and 90°C or lower.

[0085] The alkaline aqueous solution 80 after the ink layer 103 has been removed from the label piece 71 may be disposed of as waste liquid, or may be reused as the alkaline aqueous solution 80 for alkali removal.

[0086] The alkaline aqueous solution 80 is not particularly limited as long as it is capable of removing the ink layer from the label piece 71 by immersing the label piece 71 in it, and is not particularly limited as long as it is an alkaline aqueous solution containing an alkaline substance. As the alkaline aqueous solution 80, for example, an aqueous solution of an alkali metal hydroxide such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), an aqueous solution of an alkali metal carbonate such as sodium carbonate (Na2CO3), an aqueous solution of an alkali metal hydrogen carbonate such as sodium hydrogen carbonate (NaHCO3), or ammonia water can be used.

[0087] The concentration of the alkaline substance in alkaline aqueous solution 80 can be appropriately selected within a range that does not impair the releasability, operability, or workability of ink layer 103. The concentration of the alkaline substance in alkaline aqueous solution 80 is, for example, about 0.1 to 10% by weight, preferably 0.5 to 5% by weight, and more preferably about 1 to 3% by weight.

[0088] <Process for separating the substrate and the ink film> Next, as shown in Figure 1(i), the substrate 101 and the ink coating film 93 are separated. Separation of the substrate 101 and the ink coating film can be performed, for example, by using a first net 90 with relatively large openings to collect the substrate 101 after the ink layer 103 has been removed, and then using a second net 92 with relatively small openings to collect the ink coating film 93, which is smaller than the substrate 101. In this manner, the ink layer 103 can be removed from the label 11 of this embodiment. The ink coating film 93 is a film formed by finely dividing the ink layer 103 that was removed from the substrate 101 during alkali desorption.

[0089] The substrate 101 collected by the first net 90 can then be reused as a plastic raw material for producing plastic products such as pellets. The substrate 101 can also be mixed into the raw material for new labels, allowing for reuse as labels such as shrink labels. Meanwhile, the ink coating 93 collected by the second net 92 can be reused, for example, in a thermal recycling process.

[0090] The method for removing an ink layer from a label in this embodiment includes the steps of recovering a label group 50 including labels 11 containing a material that emits light when irradiated with energy rays 22, irradiating the recovered label group 50 with energy rays 22, and sorting the labels 11 that have emitted light when irradiated with the energy rays 22.

[0091] Therefore, according to the method for removing an ink layer from a label of the embodiment, by irradiating the label with energy rays 22 to cause it to emit light, a technology can be established that can distinguish labels 11 whose ink layer 103 can be removed by alkaline desorption from ordinary labels 40 whose ink layer 103 cannot be removed by alkaline desorption.

[0092] This allows alkaline release of the ink layer only for labels whose ink layer is alkaline-releasable, and eliminates the need to remove labels whose ink layer is not alkaline-releasable after alkaline release of the ink layer, thereby enabling efficient alkaline release of the ink layer from labels whose ink layer is alkaline-releasable.

[0093] In addition, the method for removing an ink layer from a label in an embodiment includes a step of preheating a label 11 having an ink layer 103, a step of crushing the label 11 after the preheating step to produce label pieces 71, and a step of removing the ink layer 103 from the label pieces 71 by alkaline desorption, and the preheating temperature can be the same as or higher than the alkaline desorption temperature.

[0094] In this case, when the label 11 is a shrink label, the ink layer 103 can be removed from the label 11 more efficiently than before.

[0095] That is, in the method for removing an ink layer from a label of this embodiment, before removing the ink layer 103 from the label 11 by alkaline desorption, the label 11 is crushed into label pieces 71. This is because by crushing the label 11 into smaller label pieces 71 and performing alkaline desorption in that state, the ink layer 103 can be efficiently removed from the label 11.

[0096] When shrink label pieces made by shredding shrink labels that had not been preheated are immersed in an alkaline aqueous solution, the shrink label pieces will shrink while wrapping around and curling in the alkaline solution. It is extremely difficult to remove the ink layer from the curled small pieces of the shrink label.

[0097] Although shrink labels attached to PET bottles and other items are thermally shrunk when attached, they still retain some shrinkage capacity. Therefore, if the temperature of the alkaline aqueous solution is high during alkali removal, the shrink label strip will continue to shrink due to heat. On the other hand, if the temperature of the alkaline aqueous solution is low, the ink layer cannot be efficiently removed from the shrink label strip.

[0098] Therefore, in the method for removing an ink layer from a label of this embodiment, before the shrink label is crushed into shrink label pieces, the shrink label is preheated at a temperature equal to or higher than the alkali desorption temperature to cause it to thermally shrink in advance. This allows the shrink label to have a wavy shape with little curl, for example. If the shrink label is preheated after being crushed, the shrink label pieces will curl (roll up) overall, making them unsuitable for removing the ink layer.

[0099] The shrink label that has been preheated to cause thermal shrinkage is then crushed to produce shrink label pieces. The shrink label pieces obtained by crushing a shrink label with a small degree of curl also have a small degree of curl.

[0100] The shrink label strip can then be subjected to alkali removal at the same temperature as or a lower temperature than that used for preheating. In this case, even if the temperature of the aqueous alkaline solution during alkali removal is high, the ink layer can be removed while suppressing shrinkage of the shrink label strip during alkali removal.

[0101] For the above reasons, it is believed that the method of removing an ink layer from a label of this embodiment can remove the ink layer from the label 11 more efficiently than conventional methods when the label 11 is a shrink label.

[0102] In particular, most shrink labels 11 removed from containers such as PET bottles 10 typically have a side length of 10 cm or more. Labels 11 of this size can be thermally shrunk by preheating, then crushed into pieces of several centimeters square, preferably 5 cm square or less, and subjected to alkali desorption at 65°C or higher, preferably 80°C or higher, and more preferably 85°C or higher, thereby significantly improving the efficiency of removing the ink layer 103.

[0103] An example of a shrink label 11 suitable for the method of this embodiment is a shrink label that, after being removed from a container such as a PET bottle 10 and immersed in a warm bath at 95°C for 10 seconds, has a shrinkage percentage of 30% or more, preferably 40% or more, and more preferably 50% or more, measured in the radial direction (main shrinkage direction) of the container.

[0104] In the above embodiment, the method for removing an ink layer from a label has been described assuming that the label 11 is a shrink label. However, the label 11 used in the embodiment of the method for removing an ink layer from a label does not have to be a shrink label.

[0105] Furthermore, in the above embodiment of the method for removing an ink layer from a label, a case was described in which a label 11 was used in which the material that emits light when irradiated with energy rays is contained only in the coating layer 102. However, in the embodiment of the method for removing an ink layer from a label, the material that emits light when irradiated with energy rays only needs to be contained in at least one layer that constitutes the label 11 (for example, only the coating layer 102, only the ink layer 103, or both the coating layer 102 and the ink layer 103).

[0106] Furthermore, in the above embodiment, when the ink layer 103 is the design print layer described above, it is preferable that only the coat layer 102 contains a material that emits light when irradiated with energy rays. If the ink layer 103 were to be composed of multiple layers (multicolor design print layers), it would be complicated to determine the amount of material that emits light when irradiated with energy rays to be contained in each layer constituting the ink layer 103, and problems such as the need to vary the content of the material that emits light when irradiated with energy rays in each design print layer may arise. Furthermore, when the ink layer 103 is composed of multiple layers (multicolor design print layers), it is preferable that the ink constituting the white layer of the multiple layers constituting the ink layer 103 contains a material that emits light when irradiated with energy rays. In this case, it is easier to confirm that the material that emits light when irradiated with energy rays emits light when irradiated with energy rays.

[0107] Furthermore, in the above embodiment, when the coating layer 102 contains a material that emits light when irradiated with energy rays, it is preferable that the content of the material that emits light when irradiated with energy rays is 5% by mass or more of the entire coating layer 102.

[0108] Furthermore, in the above embodiment, if the ink layer 103 contains a material that emits light when irradiated with energy rays, it is preferable that the content of the material that emits light when irradiated with energy rays is 5% by mass or more of the entire ink layer 103. [Example]

[0109] <Experimental Example 1> (Label Creation) In Experimental Example 1, a label 11 (label of Experimental Example 1) was produced having the configuration shown in the schematic cross-sectional view of Fig. 4. The label of Experimental Example 1 was produced as follows.

[0110] First, a polyethylene terephthalate film (PET film) having a thickness of 20 μm was prepared as the substrate 101. Next, a gravure proofing machine was used to apply a composition for forming the coating layer 102 onto one surface of the PET film, and then the composition was solidified to form the coating layer 102.

[0111] The composition for forming the coating layer 102 was prepared by adding 5 parts by mass of a phosphorescent ink (NT Hilamic (NF) phosphorescent green) to 100 parts by mass of a composition having the composition shown in Table 1 below.

[0112] [Table 1]

[0113] Next, an ink resin composition containing Etna crimson was applied as ink onto the coat 102 layer using a gravure proofing machine, and then solidified to form a color layer 103a.

[0114] Next, using a gravure proofing machine, an ink resin composition containing white ink (NT Hilamic (NF) 701 white) was applied onto the color layer 103a and then solidified to form a white ink layer 103b.

[0115] Thereafter, a gravure proofing machine was used to apply a medium onto the white ink layer 103b and then solidify it to form an overcoat layer 104, thereby completing the label of Experimental Example 1.

[0116] (Evaluation of luminescence) The luminescence of the label of Experimental Example 1 was evaluated by irradiating the label of Experimental Example 1 with ultraviolet light. Figure 5 shows a schematic side view illustrating the method for evaluating the luminescence of the label of Experimental Example 1.

[0117] As shown in Figure 5, the luminescence of the label of Experimental Example 1 was evaluated by irradiating the front surface of the label of Experimental Example 1 with ultraviolet light 22 from light source 21 and evaluating the luminescence from the front side of label 11 in a dark place, and also by irradiating the back surface of the label of Experimental Example 1 with ultraviolet light 22 from light source 21 and evaluating the luminescence from the back side of label 11 (the side on which each layer is formed) in a dark place. The luminescence of the front and back surfaces of the label of Experimental Example 1 was evaluated based on the following evaluation criteria. The results are shown in Table 2.

[0118] (Evaluation criteria for luminescence) A: Strong light was visible to the naked eye B: Normal light emission was visible to the naked eye. C: A weak light emission was visible to the naked eye. D: No visible light was observed

[0119] [Table 2]

[0120] As shown in Table 2, in the label of Experimental Example 1, strong light emission from both the front and back sides was visually confirmed.

[0121] <Experimental Example 2> (Label Creation) In Experimental Example 2, a label 11a (label of Experimental Example 2) was produced having the configuration shown in the schematic cross-sectional view of Fig. 6. The label of Experimental Example 2 was produced as follows.

[0122] First, a 20 μm thick PET film was prepared as the substrate 101. Next, a gravure proofing machine was used to apply a composition for forming the coating layer 102 a onto one surface of the PET film, and then the composition was solidified to form the coating layer 102 a.

[0123] The composition for forming the coating layer 102 consisted solely of the composition shown in Table 1 above, and no phosphorescent ink was added.

[0124] Next, an ink resin composition containing Etna crimson was applied as ink onto the coat 102a layer using a gravure proofing machine, and then solidified to form a color layer 103a.

[0125] Next, using a gravure proofing machine, an ink resin composition containing 100 parts by weight of white ink (NT Hilamic (NF) 701 white) and 5 parts by weight of phosphorescent ink (NT Hilamic (NF) phosphorescent green) was applied onto the color layer 103a layer, and then solidified to form a white ink layer 103c.

[0126] Thereafter, a gravure proofing machine was used to apply a medium onto the white ink 103c and then solidify it to form an overcoat layer 104. In this way, the label of Experimental Example 2 was produced.

[0127] (Evaluation of luminescence) The label of Experimental Example 2 was irradiated with ultraviolet light in the same manner and under the same conditions as the label of Experimental Example 1, and the luminescence of the label of Experimental Example 2 was evaluated in the same manner and with the same evaluation criteria as the label of Experimental Example 1. The results are shown in Table 3.

[0128] [Table 3]

[0129] As shown in Table 3, in the label of Experimental Example 2, weak luminescence was visually confirmed from the front side, and normal luminescence was visually confirmed from the back side.

[0130] <Experimental Example 3> The label of Experimental Example 3 was produced in the same manner and under the same conditions as the label of Experimental Example 2, except that a white ink layer 103c was formed by applying an ink resin composition made by adding 10 parts by weight of phosphorescent ink (NT Hilamic (NF) 701 white) to 100 parts by weight of white ink (NT Hilamic (NF) phosphorescent green) to the color layer 103a layer and then solidifying it.

[0131] Thereafter, the label of Experimental Example 3 was irradiated with ultraviolet light in the same manner and under the same conditions as the labels of Experimental Examples 1 and 2, and the luminescence of the label of Experimental Example 3 was evaluated in the same manner and with the same evaluation criteria as the labels of Experimental Examples 1 and 2. The results are shown in Table 4.

[0132] [Table 4]

[0133] As shown in Table 4, weak light emission was visually confirmed from the front side of the label in Experimental Example 3, and light emission at a normal level or higher was visually confirmed from the back side. In particular, as shown in Table 4, when the ultraviolet light irradiated surface was the back side, strong light emission was visually confirmed from the back side.

[0134] <Experimental Example 4> The label of Experimental Example 4 was produced in the same manner and under the same conditions as the labels of Experimental Examples 2 and 3, except that the white ink layer 103c was formed by applying an ink resin composition made by adding 20 parts by weight of phosphorescent ink (NT Hilamic (NF) luminescent green) to 100 parts by weight of white ink (NT Hilamic (NF) 701 white) onto the color layer 103a layer and then solidifying it.

[0135] Thereafter, the label of Experimental Example 4 was irradiated with ultraviolet light in the same manner and under the same conditions as the labels of Experimental Examples 1 to 3, and the luminescence of the label of Experimental Example 4 was evaluated in the same manner and with the same evaluation criteria as the labels of Experimental Examples 1 to 3. The results are shown in Table 5.

[0136] [Table 5]

[0137] As shown in Table 5, in the label of Experimental Example 4, normal light emission could be visually confirmed from the front side, but strong light emission could be visually confirmed from the back side.

[0138] <Evaluation of luminescence from labels in Experimental Examples 1 to 4> The label of Experimental Example 1, which was produced by incorporating 5 parts by mass of luminescent ink into the coating layer 102, exhibited stronger luminescence from both the front and back sides than the labels of Experimental Examples 2 to 4, which were produced by incorporating 5 to 20 parts by mass of luminescent ink into the white ink layer 103c. This indicates that when sorting labels to remove the ink layer by alkaline desorption, incorporating the luminescent ink into the coating layer between the substrate and the ink layer is preferable to incorporating the luminescent ink into the ink layer on top of the coating layer. Furthermore, when incorporating the luminescent ink into the coating layer, stronger luminescence is obtained with a smaller amount than when incorporating the luminescent ink into the ink layer, allowing for the use of less expensive luminescent ink. This is thought to enable more efficient removal of the ink layer from the label from a cost perspective.

[0139] Although the embodiments and experimental examples have been described above, it is also planned from the beginning that the respective configurations of the above-described embodiments and experimental examples may be appropriately combined.

[0140] The embodiments and experimental examples disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0141] 10 PET bottle, 11, 11a label, 12 collection box, 20 labeled bale, 30 recycling plant, 40 regular label, 50 label group, 60 hot water, 61 hot air tunnel, 62 hot water bath, 70 crusher, 71 label strip, 80 alkaline aqueous solution, 82 hot alkaline bath, 90 first net, 92 second net, 93 ink coating, 101 substrate, 102 coating layer, 103 ink layer, 103a color layer, 103b, 103c white ink layer, 104 overcoat layer, 201 first dark place, 202 second dark place.

Claims

1. A substrate and an ink layer on the substrate, The ink layer contains a material that emits light when irradiated with energy rays, A label in which the ink layer emits light when the label is irradiated with the energy beam, thereby enabling the label having the ink layer to be identified and distinguished from other labels.

2. the ink layer is alkali-soluble, 2. The label according to claim 1, wherein the label having the alkali-soluble ink layer can be identified and separated by irradiating the label with the energy ray, causing the ink layer to emit light.

3. a step of collecting a label group including the label according to claim 1 or claim 2; irradiating the collected label group with energy rays; a step of sorting the labels emitted by irradiating the energy beam; and removing the ink layer from the separated labels.

4. The method for removing an ink layer according to claim 3 , wherein the removing step is a step of removing the ink layer by alkaline desorption.

Images