Shrink labels and methods for sorting shrink labels

Abstract

Provided are a shrink label and a shrink lable segregation method, with which it is possible to improve segregation accuracy.　A shrink label (11) comprises a heat-shrinkable substrate (101), and a coating film (110) on the substrate (101). The coating film (110) has a light producing layer (110a) including a light storing pigment, and the light emission time period of the light storing pigment after heat-shrinking of the shrink label (11) can be configured to be longer than the light emission time period of the light storing pigment before heat-shrinking of the shrink label (11).

Description

Technical Field

[0001] The present disclosure relates to shrink labels and a method for sorting shrink labels.

Background Art

[0002] In recent years, plastic products such as polyethylene terephthalate bottles (PET bottles) have been widely used. From the viewpoints of resource conservation and environmental protection, etc., it is strongly required to recycle plastic products such as PET bottles.

[0003] Among plastic products, the recycling of PET bottles in particular has already been established. However, a plastic shrink label having an ink layer printed for displaying product information or the like may be attached to the body of a PET bottle, but recycling of the shrink label has not yet been achieved.

[0004] One of the factors inhibiting the recycling of shrink labels is that the coating film such as the ink layer cannot be sufficiently removed from the shrink label. If the coating film cannot be sufficiently removed from the shrink label, the coating film may be mixed into the recycled resin regenerated from the shrink label, and it may not be possible to produce recycled products such as pellets having a useful value from the recycled resin.

[0005] Therefore, for example, Patent Document 1 describes a plastic label in which a display printing ink layer is formed on a base film through a coat layer soluble in an alkaline aqueous solution. In Patent Document 1, the display printing ink layer is alkali-desorbed by dissolving the coat layer of the plastic label in an alkaline aqueous solution.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] When shrink labels are actually recycled, it is expected that labels with removable coatings and labels with non-removable coatings will be collected together.

[0008] However, when recycling shrink labels, a technology for separating labels whose coating can be removed from those whose coating cannot be removed has not yet been established.

[0009] Even if a technology is established to separate shrink labels with removable coatings from labels with non-removable coatings, if the accuracy of this separation is poor, it will be impossible to produce usable recycled products. [Means for solving the problem]

[0010] According to the embodiments disclosed herein, a shrink label is provided comprising a heat-shrinkable substrate and a coating film on the substrate, wherein the coating film has a light-emitting layer containing a phosphorescent pigment, and the light-emitting time of the phosphorescent pigment after the heat shrinkage of the shrink label is made longer than the light-emitting time of the phosphorescent pigment before the heat shrinkage of the shrink label.

[0011] According to the embodiments disclosed herein, a method for separating shrink labels is provided, comprising the steps of: collecting a group of labels including the above-mentioned shrink labels; heat-shrinking the shrink labels; irradiating the group of labels after heat-shrinking with energy rays; and separating the shrink labels that have emitted light due to the irradiation with energy rays. [Effects of the Invention]

[0012] The embodiments disclosed herein provide shrink labels and methods for sorting shrink labels that can improve sorting accuracy. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view of an example of a shrink label according to an embodiment. [Figure 2] Figures (a) to (i) illustrate an example of a flow chart of the method for separating shrink labels and removing the coating from shrink labels according to the embodiment. [Figure 3] This is a schematic cross-sectional view of another example of a shrink label according to the embodiment. [Figure 4] This is a schematic side view illustrating an example of the process of irradiating a group of labels with energy rays. [Figure 5] These are schematic cross-sectional views of the shrink labels from Experimental Examples 1-9. [Figure 6] These photographs show the luminescence of phosphorescent pigments in both shrunk and non-shrunk materials 5 seconds after irradiation with ultraviolet light. [Figure 7] These photographs show the luminescence of phosphorescent pigments in both shrunk and non-shrunk materials 10 seconds after irradiation with ultraviolet light. [Figure 8] These photographs show the luminescence of phosphorescent pigments in both shrunk and non-shrunk materials 15 seconds after irradiation with ultraviolet light. [Figure 9] These photographs show the luminescence of phosphorescent pigments in both shrunk and non-shrunk materials 20 seconds after irradiation with ultraviolet light. [Figure 10] These photographs show the luminescence of phosphorescent pigments in both shrunk and non-shrunk materials 25 seconds after irradiation with ultraviolet light. [Figure 11] These photographs show the luminescence of phosphorescent pigments in both shrunk and non-shrunk materials 30 seconds after irradiation with ultraviolet light. [Figure 12] These photographs show the luminescence of phosphorescent pigments in both shrunk and non-shrunk materials 35 seconds after irradiation with ultraviolet light. [Figure 13]This is a photograph showing the luminescence of the phosphorescent pigments of the shrinkage products and non-shrinkage products 40 seconds after ultraviolet light irradiation. [Figure 14] This is a photograph showing the luminescence of the phosphorescent pigments of the shrinkage products and non-shrinkage products 45 seconds after ultraviolet light irradiation. [Figure 15] This is a photograph showing the luminescence of the phosphorescent pigments of the shrinkage products and non-shrinkage products 50 seconds after ultraviolet light irradiation. [Figure 16] This is a photograph showing the luminescence of the phosphorescent pigments of the shrinkage products and non-shrinkage products 55 seconds after ultraviolet light irradiation. [Figure 17] This is a photograph showing the luminescence of the phosphorescent pigments of the shrinkage products and non-shrinkage products 60 seconds after ultraviolet light irradiation. [Figure 18] This is a photograph showing the luminescence of the phosphorescent pigments of the shrinkage products and non-shrinkage products 65 seconds after ultraviolet light irradiation. [Figure 19] This is a photograph showing the luminescence of the phosphorescent pigments of the shrinkage products and non-shrinkage products 70 seconds after ultraviolet light irradiation.

Embodiments for Carrying Out the Invention

[0014] <Shrink Label> FIG. 1 shows a schematic cross-sectional view of an example of the shrink label of the embodiment. As shown in FIG.​​​​​​​​​Examples of resins that can be included in the 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 such as nylon, aramid resins, polyimide resins, polyphenylene sulfide resins, or acrylic resins. The base material 101 may contain one of these resins, or it may contain two or more of them.

[0017] The resin contained in the base material 101 is preferably a polyester resin, and among these, PET is preferred. This is because a PET recycling system has already been established. PET is a polyester resin that contains terephthalic acid as the main component of the dicarboxylic acid component and ethylene glycol as the main component of the diol component. In addition, 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 base material 101 is a heat-shrinkable film (shrink film). Such a base material 101 can improve the processability (conformability to the container) and decorative properties of the shrink label 11, and also make it possible to further increase the display area of ​​the shrink label 11.

[0019] The substrate 101 may be a single-layer film consisting of one layer, or a multilayer film consisting 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 film> The coating film 110 is a film provided on the substrate 101. The coating film 110 has at least an emissive layer 110a containing a phosphorescent pigment (not shown). When energy rays are irradiated onto the coating film 110 of the shrink label 11, the phosphorescent pigment in the emissive layer 110a emits light.

[0021] In the embodiment of the shrink label 11, it is possible to make the luminescence time of the phosphorescent pigment in the light-emitting layer 110a after the shrink label 11 has been heat-shrinked longer than the luminescence time of the phosphorescent pigment before the shrink label 11 has been heat-shrinked. Therefore, by applying the embodiment of the shrink label 11 to the target shrink label and irradiating the shrink label 11 with energy rays after heat-shrinking, the luminescence time of the phosphorescent pigment in the light-emitting layer 110a can be made longer, thereby improving the accuracy of sorting the target shrink label.

[0022] The composition of the coating film 110 of the shrink label 11 in the embodiment is not particularly limited. The coating film 110 may have other layers 110b in addition to the light-emitting layer 110a, as long as it has at least one light-emitting layer 110a. Other layers 110b may include, for example, an anchor coat layer, a color ink layer, a front and back medium, or a matte varnish.

[0023] <Luminous layer> The light-emitting layer 110a contains a phosphorescent pigment and a binder resin. The light-emitting layer 110a is a layer formed by applying a resin composition for a light-emitting layer containing a phosphorescent pigment and a binder resin, and then drying and curing it.

[0024] Phosphorescent pigments are pigments that emit light when irradiated with energy rays and possess phosphorescent properties. Examples of phosphorescent pigments include sulfide-based phosphorescent pigments, oxyacid-based phosphorescent pigments, and alumina oxide-based phosphorescent pigments.

[0025] Examples of sulfide-based phosphorescent pigments that can be used include calcium sulfide:bismuth-based (CaS:Bi), calcium sulfide-strontium sulfide:bismuth-based (CaSrS:Bi), zinc sulfide:copper-based (ZnS:Cu), or zinc sulfide-cadmium sulfide:copper-based (ZnCdS:Cu).

[0026] Examples of oxyacid-based phosphorescent pigments that can be used include Zn2SiO4:Mn, (Zn,Be)2SiO4:Mn, Ca3(PO4)2:Ce, or Ca3(PO4)2:(Ce,Mn).

[0027] Examples of alumina oxide-based phosphorescent pigments that can be used include aluminum-calcium oxide: europium type (CaAl2O4:Eu), aluminum-strontium oxide: europium type (SrAl2O4:Eu), or aluminum-barium oxide: europium type (BaAl2O4:Eu).

[0028] As for 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.

[0029] As the binder resin, for example, acrylic resins, urethane resins, or polyolefin resins can be used. The binder resin may also contain coloring pigments and may contain any additives such as fillers, lubricants, or stabilizers.

[0030] In particular, if the light-emitting layer 110a contains a colored pigment such as white, yellow, or red, the light-emitting layer 110a can have both luminescence in the dark (described later) and color display properties under visible light, thereby becoming one of the color layers that constitute the design. With such a light-emitting layer 110a, the reduction in the number of colors that can be used in the printing manufacturing process can be suppressed compared to the case where the light-emitting layer 110a simply has luminescence but no color display properties.

[0031] <Other layers> As described above, the other layer 110b may include, for example, an anchor coat layer, a color ink layer, a front and back medium, or a matte varnish.

[0032] <Method for manufacturing shrink labels> The shrink label 11 of the embodiment can be manufactured, for example, as follows. First, a base material 101 is prepared. The base material 101 can be prepared by forming a film by methods such as extrusion, inflation, tubularization, or calendering, and if necessary, by subjecting the film to further stretching treatment.

[0033] Next, a coating film 110 is formed on at least one surface of the substrate 101. For example, if the coating film 110 consists of an anchor coat layer, an emissive layer 110a, and a color ink layer in that order from the substrate 101 side, the coating film 110 is formed, for example, by first applying an anchor coat layer resin composition, which is a precursor to the anchor coat layer, to one surface of the substrate 101 and drying and curing it to form the anchor coat layer. Next, an emissive layer 110a is formed by applying an emissive layer resin composition, which is a precursor to the emissive layer 110a, to the anchor coat layer and drying and curing it. Next, a color ink layer can be formed by applying a color ink layer resin composition, which is a precursor to the color ink layer, to the emissive layer 110a and drying and curing it. As a result, a coating film 110 is formed in which the anchor coat layer, the emissive layer 110a, and the color ink layer are laminated in that order from the substrate 101 side.

[0034] The resin composition for the light-emitting layer includes, for example, a binder resin and a phosphorescent pigment along with a solvent. The light-emitting layer 110a is formed when the solvent is removed from the light-emitting layer resin composition by drying or other means and the composition hardens.

[0035] The phosphorescent pigment content in the light-emitting layer 110a is preferably 0.052% by weight or more, more preferably 0.26% by weight or more, and even more preferably 0.5% by weight or more, based on the total weight of the light-emitting layer 110a. In this case, the emission of light from the phosphorescent pigment after irradiating the shrink label 11 with energy rays tends to be clearly visible.

[0036] The phosphorescent pigment content in the light-emitting layer 110a is preferably 71.4% by weight or less, more preferably 9.2% by weight or less, and even more preferably 4.9% by weight or more. In this case, the amount of phosphorescent pigment used tends to be reduced, which tends to allow for the production of shrink labels 11 at a lower cost. In addition, since the amount of other pigments that can be added to the light-emitting layer 110a increases relatively, the light-emitting layer 110a can also be used as a color ink layer that emits colors for design.

[0037] <Method for sorting shrink labels and method for removing coating from shrink labels> Figures 2(a) to 2(i) illustrate an example of a flow chart for the method of separating the shrink labels 11 and removing the coating 110 from the shrink labels 11 according to the embodiment. The method of separating the shrink labels 11 and removing the coating 110 from the shrink labels 11 according to the embodiment will be described below with reference to Figures 2(a) to 2(i).

[0038] <Bottle collection process> First, as shown in Figure 2(a), bottles 10 such as PET bottles are collected in the collection box 12. Here, a shrink label 11 is attached to the body of the bottle 10.

[0039] The shrink label 11 used here, for example, as shown in the schematic cross-sectional view of Figure 3, has a coating film 110 placed on one surface of a substrate 101. The coating film 110 comprises, from the substrate 101 side, an alkali-soluble coating layer 102, an emissive layer 110a on the coating layer 102, and a color ink layer 103 on the emissive layer 110a. The coating film 110 is soluble in an alkaline aqueous solution (hereinafter also referred to as "alkali-soluble"). Examples of alkali-soluble coating films 110 include cases where the coating layer 102 in contact with the substrate 101 is alkali-soluble, cases where the coating layer 102 and the emissive layer 110a are alkali-soluble, and cases where the coating layer 102, the emissive layer 110a, and the color ink layer 103 are all alkali-soluble.

[0040] If the coating layer 102 is alkali soluble, the resin included in the coating layer 102 can be, for example, a resin having the following (1) to (4). (1) Contains a first resin which is an acrylic acid copolymer resin having a first glass transition temperature T1; (2) Contains a second resin which is an acrylic acid copolymer resin having a second glass transition temperature T2 lower than T1; (3) The apparent acid value of the coating layer 102 is between 40 mg KOH / g and 150 mg KOH / g; (4) The first resin and the second resin contained in the coating layer 102 together account for 50 to 95% by mass of the entire coating layer 102.

[0041] The light-emitting layer 110a contains a phosphorescent pigment. The light-emitting layer 110a may also contain, for example, other coloring pigments, a binder resin, and additives. If the light-emitting layer 110a is alkali-soluble, the light-emitting layer 110a may use, for example, a resin having the properties of (1) to (4) described above as the binder resin.

[0042] The color ink layer 103 may include, for example, a coloring pigment, a binder resin, and additives. If the color ink layer 103 is alkali soluble, the light-emitting layer 110a may use, for example, a resin having the properties of (1) to (4) above as the binder resin.

[0043] The aforementioned base material 101 is the target of sorting, i.e., the shrink label, but the collected bottles 10 naturally also include bottles 10 with the regular labels 40 described later attached.

[0044] <Compression process> Next, as shown in Figure 2(b), the collected bottles 10 are compressed with the label 11 or a regular label 40 attached to them to form a labeled bale 20.

[0045] <Integration Process> Next, as shown in Figure 2(c), the labeled bales 20 are sent to the recycling plant 30 for collection.

[0046] <Label collection process> Next, as shown in Figure 2(d), the label group 50, which includes the shrink label 11 of the embodiment and the regular label 40, is recovered. The recovery of the label group 50 can be carried out, for example, as follows.

[0047] First, at the recycling plant 30, the shrink labels 11 of the embodiment and / or regular labels 40 are removed from the bottles 10 of the labeled bale 20, separating the label group 50, which includes the shrink labels 11 of the embodiment and the regular labels 40, from the bottles 10, and the label group 50, which includes the shrink labels 11 of the embodiment and the regular labels 40, is recovered.

[0048] In this embodiment, the standard label 40 is a label in which the coating film 110 is not alkali-soluble and does not include the light-emitting layer 110a. This is because this embodiment aims to both separate the shrink labels 11 and remove the coating film 110 from the shrink labels 11. In other embodiments, if the sole purpose is to separate the shrink labels 11, the shrink labels 11 in those embodiments only need to have the light-emitting layer 110a.

[0049] Furthermore, the bottle 10 from which the shrink label 11 and / or regular label 40 have been separated is recycled in the existing bottle recycling process.

[0050] <Heat shrinkage process> Next, as shown in Figure 2(e), the shrink label 11 of the embodiment is heat-shrinked by heating the label group 50, which includes the shrink label 11 of the embodiment and the ordinary label 40. Methods for heat-shrinking the shrink label 11 of the embodiment include, for example, passing the label group 50 through a hot air tunnel 61 or immersing the label group 50 in hot water 60 in a hot water bath 62. Alternatively, the shrink label 11 of the embodiment can be irradiated with steam or infrared light.

[0051] However, from the viewpoints of (A) to (D) below, it is preferable to use the method of immersing the label group 50 in the hot water 60 in the hot water bath 62 as a method for heat-shrinking the shrink label 11 of the embodiment, rather than the method of passing the label group 50 through the hot air tunnel 61. (A) If hot air is used, the label group 50 removed from the bottle 10 will be blown away by the hot air, making it difficult to control. (B) The method of immersing in hot water makes temperature control easier. (C) The method of immersing in hot water results in a smaller equipment footprint. (D) The method of immersing in hot water is less likely to cause uneven shrinkage of the shrink label 11 and allows for uniform shrinkage.

[0052] For example, when heating the shrink labels 11 by immersing the label group 50 in hot water 60 in a hot water bath 62, this can be done, for example, by immersing the label group 50 in hot water at about 80°C to 90°C for about 10 to 20 seconds.

[0053] The shrinkage rate of the shrink label 11 is preferably 30% or more, and more preferably 50% or more. When the shrink label 11 is shrunk to a shrinkage rate of 30% or more, and especially 50% or more, and then irradiated with energy rays, the luminescence time of the phosphorescent pigment tends to be extended.

[0054] The shrinkage rate of the shrink label 11 is expressed as a percentage of the difference between the length of the shrink label 11 before shrinkage and the length after shrinkage in the main shrinkage direction of the shrink label 11, relative to the length of the shrink label 11 before shrinkage in the main shrinkage direction of the shrink label 11.

[0055] Here, the shrink label 11 is unwound from the roll in an unshrunk state, cut to a predetermined length, wrapped around the body of a bottle 10 such as a PET bottle, and then heat-shrinked to be attached to the bottle 10. In this context, "the length of the shrink label 11 before shrinkage in the main shrinkage direction" refers to the length of the shrink label 11 in the main shrinkage direction in an unshrunk state as it is unwound from the roll.

[0056] Furthermore, "the length of the shrink label 11 after shrinkage in the main shrinkage direction" refers to the length of the shrink label 11 in the main shrinkage direction after it has been further heat-shrunk in the heat shrinkage process described above, starting from the state in which it was heat-shrunk when wrapped around the body of the bottle 10.

[0057] <Energy ray irradiation and sorting process> Next, as shown in Figure 2(f), the label group 50, including the heat-shrunk shrink labels 11, is irradiated with energy rays. Figure 4 shows a schematic side view illustrating an example of the process of irradiating the label group 50 with energy rays. The following describes an example of the process of irradiating the label group 50 with energy rays, referring to Figure 4.

[0058] First, the label group 50, including the heat-shrunk shrink labels 11, is brought into the first dark place 201. Next, the label group 50 is irradiated with energy rays 22 from a light source 21 located inside the first dark place 201.

[0059] Next, the label group 50, after irradiation with energy rays 22, is removed from inside the first dark room 201. Then, the label group 50 removed from inside the first dark room 201 is brought into the second dark room 202.

[0060] At this time, since the coating layer 102 of the shrink label 11 of the embodiment continues to emit light after irradiation with the energy rays 22, the shrink label 11 of the embodiment appears to glow inside the second dark place 202. On the other hand, the normal label 40 does not contain an emissive layer 110a, so even if it is irradiated with the energy rays 22, it does not appear to glow inside the second dark place 202.

[0061] This makes it possible to separate and collect the shrink label 11 of the embodiment that glows inside the second dark place 202 from the normal label 40 that does not glow inside the second dark place 202.

[0062] In particular, in the shrink label 11 of the embodiment, as described above, it is possible to make the luminescence time of the phosphorescent pigment after the shrink label 11 has been heat-shrinked longer than the luminescence time of the phosphorescent pigment before the shrink label 11 has been heat-shrinked, thereby improving the sorting accuracy of the shrink label 11 of the embodiment.

[0063] The regular labels 40, which are collected separately from the shrink labels 11 of the embodiment, are recycled, for example, in a thermal recycling process.

[0064] In this embodiment, the label group 50 was irradiated with energy rays 22 inside the first dark place 201, but the irradiation of the label group 50 with energy rays 22 does not necessarily have to be done in the dark.

[0065] <Crushing process> Next, as shown in Figure 2(g), the separated and recovered shrink labels 11 are crushed by a crusher 70 to produce shrink label pieces 71. The method of crushing the shrink labels 11 is not particularly limited as long as the size of the shrink label pieces 71 produced after crushing is smaller than the size of the shrink labels 11 before crushing.

[0066] The shrink label 11 can be crushed into pieces of a size (for example, several centimeters square) that allows for efficient removal of the color ink layer 103 from the shrink label piece 71 during the alkali desorption process described later. It goes without saying that the layer structure of the shrink label piece 71 is the same as that of the shrink label 11 in the embodiment, since the shrink label piece 71 is obtained by crushing the shrink label 11 of the embodiment.

[0067] <Alkali desorption process> Next, as shown in Figure 2(h), the color ink layer 103 is removed from the shrink label piece 71 by alkaline desorption. Alkaline desorption can be performed, for example, by immersing the shrink label piece 71 in an alkaline aqueous solution 80 at about 80°C to 90°C in a hot alkaline bath 82 for about 30 seconds to 20 minutes and stirring the contents of the hot alkaline bath 82. For example, if the coating layer 102 is alkali soluble, the coating layer 102 will dissolve in the hot alkaline bath 82, and the shrink label piece 71 can be easily separated into the base material 101 and the ink film 93 (consisting of the light-emitting layer 110a and the color ink layer 104). Alternatively, alkaline desorption can also be performed, for example, by immersing the shrink label piece 71 in the above-mentioned alkaline aqueous solution 80 for about 30 seconds to 20 minutes and then washing it with water. In this case, the shrink label piece 71 can be easily separated into the base material 101 and the ink film 93 by washing it with water (for example, in a water bath).

[0068] The alkaline aqueous solution 80 is not particularly limited as long as it is possible to remove the color ink layer 103 from the shrink label piece 71 by immersing 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 bicarbonate such as sodium bicarbonate (NaHCO3), or ammonia water can be used.

[0069] The concentration of the alkaline substance in the alkaline aqueous solution 80 can be appropriately selected within a range that does not impair the desorption ability, operability, or workability of the color ink layer 103. The concentration of the alkaline substance in the 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. The alkaline aqueous solution 80 may also contain any surfactant.

[0070] The alkaline aqueous solution 80 remaining after removing the color ink layer 103 from the shrink label piece 71 may be disposed of as waste liquid, or it may be recycled as an alkaline aqueous solution 80 for alkali desorption.

[0071] <Separation process between substrate and ink coating> Next, as shown in Figure 2(i), the substrate 101 and the ink film 93 are separated. Separation of the substrate 101 and the ink film can be performed, for example, by collecting the substrate 101 after the color ink layer 103 has been removed using a first mesh 90 having a relatively large opening, and collecting the ink film 93, which is smaller than the substrate 101, using a second mesh 92 having a relatively small opening. The ink film 93 is a film formed by finely fragmenting the color ink layer 103 that was removed from the substrate 101 during alkali desorption.

[0072] As a result, the coating 110 can be removed from the shrink label 11 of the embodiment.

[0073] Subsequently, the substrate 101 collected by the first mesh 90 can be recycled, for example, as a plastic raw material for the manufacture of plastic products such as pellets. Alternatively, the substrate 101 can be mixed into the raw material for new labels and recycled as labels such as shrink labels. Meanwhile, the ink film 93 collected by the second mesh 92 can be recycled, for example, in a thermal recycling process.

[0074] According to the embodiments described in detail above, the target shrink labels can be sorted with high precision. Furthermore, if the coating 110 is alkali soluble, the substrate 101 of the shrink label 11 and the coating 110 can be separated, making it possible to recycle the substrate 101.

[0075] Furthermore, when the color ink layer 103 contains phosphorescent pigment, it is preferable that it be contained within the white ink layer that constitutes the design printing layer. In particular, the white ink layer tends to be located on the outside of the multilayer structure compared to other color ink layers, which has the advantage of making the luminescence easier to see. In addition, the white ink layer is often filled in as a solid color, in which case it is easy to confirm the luminescence. [Examples]

[0076] <Experimental Examples 1-9> In Experimental Examples 1-9, shrink labels 11 (the shrink labels for Experimental Examples 1-9) with the configuration shown in the schematic cross-sectional view of Figure 5 were prepared. After thermally shrinking the shrink labels for Experimental Examples 1-9, they were irradiated with energy rays, and the presence or absence of luminescence from the phosphorescent pigment was visually confirmed. The results are shown in Table 1.

[0077] First, a polyethylene terephthalate film (PET film) with a thickness of 20 μm was prepared as the base material 101.

[0078] Next, using a gravure proofing machine, a resin composition for the light-emitting layer, which serves as a precursor for the light-emitting layer 110a, was applied to one surface of the PET film, then dried and cured to form the light-emitting layer 110a.

[0079] For the luminescent layer resin composition, NT Hi-Lamic (NF) 701 White was mixed with NT Hi-Lamic (NF) Phosphorescent Green in the proportions shown in Table 1 below.

[0080] Next, a resin composition for the white ink layer, which serves as a precursor for the white ink layer 104, was applied to the light-emitting layer 110a and then cured to form the white ink layer 104. This resulted in the creation of shrink labels for Experimental Examples 1 to 9, in which a coating film 100 was arranged on the substrate 101, with a light-emitting layer 110a of approximately 1 μm thickness and a white ink layer 104 of approximately 1 μm thickness stacked in that order.

[0081] Furthermore, NT Hi-Lamic (NF) 701 White was used as the resin composition for the white ink layer.

[0082] The shrink labels in Experimental Examples 1-9 were prepared using the same method and under the same conditions, except that the mixing ratio of NT Hi-Lamic (NF) 701 White and NT Hi-Lamic (NF) Phosphorescent Green in the resin composition for the luminescent layer was changed as shown in Table 1.

[0083] The values ​​in the "Weight of NT Hi-Lamic (NF) 701 White (g)" column of Table 1 indicate the amount of NT Hi-Lamic (NF) 701 White used in the preparation of the luminescent layer resin compositions for Experimental Examples 1-9. The values ​​in the "Weight of NT Hi-Lamic (NF) Phosphorescent Green (g)" column of Table 1 indicate the amount of NT Hi-Lamic (NF) Phosphorescent Green used in the preparation of the luminescent layer resin compositions for Experimental Examples 1-9. The values ​​in the "Total Weight of Resin Composition for Luminescent Layer" column of Table 1 indicate the weight of the resin composition used in Experimental Examples 1-9. The values ​​in the "Phosphorescent Pigment (Weight %)" column of Table 1 indicate the percentage (weight %) of the phosphorescent pigment relative to the total weight of the cured luminescent layer 110a of the resin composition for the luminescent layer in Experimental Examples 1-9. In the "Presence or Absence of Luminescence" column of Table 1, "Yes" indicates that luminescence was present, and "No" indicates that luminescence was absent. The shrinkage rate of each shrink label was approximately 60%.

[0084] [Table 1]

[0085] As shown in Table 1, the luminescence of the phosphorescent pigment after heat shrinkage could be visually confirmed in all of the shrink labels from Experimental Examples 1 to 9. Therefore, the luminescence of the phosphorescent pigment after heat shrinkage could be confirmed at least within the numerical range shown in the "Phosphorescent Pigment (Weight %)" column of Table 1.

[0086] <Experimental Example 10> In Experimental Example 10, two shrink labels 11 (the shrink labels of Experimental Example 10) were prepared in the same manner as in Experimental Examples 1 to 9, except that the content of phosphorescent pigment relative to the total weight of the luminescent layer 110 after drying and curing was set to 4.9% by weight. Then, the following was investigated to see if there was a difference in the luminescence time of the phosphorescent pigment after irradiation with energy rays between the shrink labels of Experimental Example 10 that were heat-shrunk and those that were not.

[0087] First, the heat shrinkage of the shrink label in Experiment Example 10 was performed by immersing one of the shrink labels in 90°C hot water. Hereafter, the heat-shrunk shrink label from Experiment Example 10 will be referred to as the "shrinkable product," and the shrink label from Experiment Example 10 that was not heat-shrunk will be referred to as the "unshrinkable product."

[0088] Next, energy irradiation was performed using an ECS-1511U manufactured by iGraphics Co., Ltd., by irradiating ultraviolet light from the substrate 101 side of both the shrinkable and non-shrinkable materials. Here, the lamp intensity of the ultraviolet light was set to 1 kW.

[0089] Then, after irradiating both the shrinkable and non-shrinkable samples with ultraviolet light, each was placed in a dark box, and the luminescence of the phosphorescent pigment was photographed using the camera of an iPhone 8 at 5-second intervals for 70 seconds. The results are shown in Figures 6 to 19.

[0090] Figure 6 is a photograph showing the luminescence of the phosphorescent pigment in both the shrinkable and non-shrinkable samples 5 seconds after irradiation with ultraviolet light, and Figure 7 is a photograph showing the luminescence of the phosphorescent pigment in both the shrinkable and non-shrinkable samples 10 seconds after irradiation with ultraviolet light.

[0091] Furthermore, Figure 8 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 15 seconds after irradiation with ultraviolet light, and Figure 9 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 20 seconds after irradiation with ultraviolet light.

[0092] Furthermore, Figure 10 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 25 seconds after irradiation with ultraviolet light, and Figure 11 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 30 seconds after irradiation with ultraviolet light.

[0093] Furthermore, Figure 12 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 35 seconds after irradiation with ultraviolet light, and Figure 13 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 40 seconds after irradiation with ultraviolet light.

[0094] Furthermore, Figure 14 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 45 seconds after irradiation with ultraviolet light, and Figure 15 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 50 seconds after irradiation with ultraviolet light.

[0095] Furthermore, Figure 16 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 55 seconds after irradiation with ultraviolet light, and Figure 17 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 60 seconds after irradiation with ultraviolet light.

[0096] Furthermore, Figure 18 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 65 seconds after irradiation with ultraviolet light, and Figure 19 is a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 70 seconds after irradiation with ultraviolet light.

[0097] As shown in Figure 11 (a photograph showing the luminescence of the phosphorescent pigment in the shrunk and non-shrunk samples 30 seconds after irradiation with ultraviolet light), the phosphorescent pigment in the non-shrunk sample ceased to emit light 30 seconds after irradiation with ultraviolet light, while the phosphorescent pigment in the shrunk sample still emitted light 30 seconds after irradiation with ultraviolet light.

[0098] As shown in Figure 16 (a photograph showing the luminescence of the phosphorescent pigment in the shrinkable and non-shrinkable samples 55 seconds after irradiation with ultraviolet light), it was confirmed that the luminescence of the phosphorescent pigment disappeared 55 seconds after irradiation with ultraviolet light.

[0099] As described above, the embodiments and experimental examples have been explained, but it was also planned from the outset that the various configurations of the embodiments and experimental examples described above could be combined as appropriate.

[0100] The embodiments and experimental examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope of the claims are intended to be included. [Explanation of Symbols]

[0101] 10 Bottle, 11 Shrink label, 12 Collection box, 20 Labeled bale, 21 Light source, 22 Energy rays, 30 Recycling plant, 40 Regular label, 50 Label group, 60 Hot water, 61 Hot air tunnel, 62 Hot water bath, 70 Crusher, 71 Shrink label piece, 80 Alkaline aqueous solution, 82 Hot alkaline bath, 90 First mesh, 92 Second mesh, 93 Ink film, 101 Substrate, 102 Coating layer, 103 Color ink layer, 104 White ink layer, 110 Coating film, 110a Luminescent layer, 110b Other layers, 201 First dark place, 202 Second dark place.

Claims

1. A heat-shrinkable base material, A shrink label comprising a coating film on the substrate, The aforementioned coating film has a color ink layer containing color ink, The aforementioned color ink layer includes a white ink layer placed as the outermost layer of the coating film. The aforementioned white ink layer contains a phosphorescent pigment. A shrink label in which, when the heat shrinkage rate of the shrink label is 30% or more, it is possible to make the luminescence time of the phosphorescent pigment after the heat shrinkage of the shrink label longer than the luminescence time of the phosphorescent pigment before the heat shrinkage of the shrink label.

2. The shrink label according to claim 1, wherein the white ink layer is a solid print layer.

3. A process for recovering the label group including the shrink label, The process of heat-shrinking the aforementioned shrink label, A step of irradiating the group of labels with energy rays after the shrink labels have been heat-shrunk, A method for separating shrink labels, comprising the step of separating the shrink labels that have emitted light by being irradiated with the aforementioned energy rays, The aforementioned shrink label is A heat-shrinkable base material, The coating film on the substrate, The aforementioned coating film has a light-emitting layer containing a phosphorescent pigment, A method for sorting shrink labels, which makes it possible to make the luminescence time of the phosphorescent pigment after the shrink label has been heat-shrinked longer than the luminescence time of the phosphorescent pigment before the shrink label has been heat-shrinked, when the heat shrinkage rate of the shrink label is 30% or more.

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