Method for separating labels and recovering substrates from labels

Abstract

To provide a label that can easily classify a re-usable label, a method for separating the label, and a method for recovering a base material from the label.SOLUTION: A label (11) includes: a base material (101); a separation layer (102) laminated on the base material (101), the separation layer being separable from the base material (101); an ink layer (105) located in the opposite side of the separation layer (102) to the side where the base material (101) is located, the ink layer including ink; a heat generation unit (104) for generating heat by being irradiated with an energy line.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a label, a method for sorting the label, and a method for recovering the substrate from the label. [Background technology]

[0002] Conventionally, plastic products such as polyethylene terephthalate (PET) bottles have been widely used as beverage containers, etc. From the viewpoints of resource conservation and environmental protection, there is a demand for the recycling of plastic products such as PET bottles.

[0003] Among plastic products, the reuse of PET bottles as resin, i.e., material recycling, is already widespread. On the other hand, plastic labels printed with product information are sometimes attached to the body of PET bottles, but material recycling of these labels has not been implemented and they are currently only thermally recycled.

[0004] To reuse labels as a material recycler, it is necessary to efficiently remove the ink from the label. For example, Patent Document 1 discloses a 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, and the ink is alkaline-desorbed from the label by dissolving the coating layer in an alkaline aqueous solution. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-240029 Summary of the Invention [Problem to be solved by the invention]

[0006] It is possible to remove ink from labels using the method described in Patent Document 1. However, before carrying out the ink removal process, it is necessary to separate labels that can remove ink, i.e., labels that have the above-mentioned coating layer, from labels that cannot remove ink.

[0007] An object of one aspect of the present invention is to provide labels that can be easily separated into reusable labels, a method for separating labels, and a method for recovering substrates from labels. [Means for solving the problem]

[0008] A label according to one embodiment of the present invention comprises a substrate, a separation layer laminated to the substrate and separable from the substrate, an ink layer containing ink and located on the opposite side of the separation layer from the substrate side, and a heat generating portion located on the opposite side of the separation layer from the substrate side and containing a material that generates heat when irradiated with energy rays. [Effects of the Invention]

[0009] According to one aspect of the present invention, reusable labels can be easily separated. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view of a label according to a first embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing an example of the flow of a label sorting method and a base material separation method according to the first embodiment. [Figure 3] FIG. 10 is a schematic side view showing an example of a step of irradiating the collected label group with energy rays. [Figure 4] FIG. 10 is a schematic cross-sectional view of a label according to a first modified example. [Figure 5] FIG. 10 is a schematic cross-sectional view of a label according to a second modification. [Figure 6] FIG. 10 is a schematic cross-sectional view of a label according to a third modified example. [Figure 7] FIG. 10 is a schematic cross-sectional view of a label according to a fourth modified example. [Figure 8] FIG. 13 is a schematic cross-sectional view of a label according to a fifth modified example. [Figure 9] FIG. 10 is a schematic cross-sectional view of a label according to a second embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional view of a label according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, labels, a label sorting method, and a method for recovering substrates from labels according to embodiments of the present disclosure will be described in detail with reference to the drawings. However, the following description is merely an example of the labels, the label sorting method, and the method for recovering substrates from labels according to the present invention, and the technical scope of the present invention is not limited to the illustrated examples.

[0012] [Embodiment 1] <label> FIG. 1 shows a schematic cross-sectional view of a label 11 according to a first embodiment. As shown in FIG. 1, the label 11 includes a substrate 101, an alkali-soluble base layer (separation layer) 102 laminated on the substrate 101, and an ink layer 105 laminated on the base layer 102. The label 11 may be a heat-shrinkable label (shrink label) or a non-heat-shrinkable label. The label 11 may also be a self-stretchable stretch label or a non-self-stretchable label. As described below, the ink layer 105 includes a heat-generating portion 104 containing a material (heat-generating material) that generates heat upon irradiation with energy rays, and a non-heat-generating portion 103 that does not contain the heat-generating material and does not generate heat. As shown in FIG. 1, the heat-generating portion 104 having a predetermined width is formed on the surface of the base layer 102, and the non-heat-generating portion 103 is formed to surround the heat-generating portion 104. The heat-generating portion 104 may be formed in a hole or recess formed in the non-heat-generating portion 103. 1 corresponds to the back side of label 11, and label 11 is used by facing the back side toward the surface of a container such as a PET bottle, for example, to cover the surface. As will be described later, label 11 may have ink layer 105 formed on the front side of substrate 101. Non-heat-generating portion 103 may be generally transparent.

[0013] <Base material> The substrate 101 is a base containing a resin capable of supporting the underlayer 102 and the ink layer 105. Examples of the resin contained in the substrate 101 include polyester-based resins (polyethylene terephthalate (PET), polyethylene naphthalate, polylactic acid, etc.), polystyrene-based resins (polystyrene, styrene-butadiene copolymer, etc.), polyolefin-based resins (polyethylene, polypropylene, etc.), polyvinyl chloride-based resins, polyamide-based resins, aramid-based resins, polyimide-based resins, polyphenylene sulfide-based resins, and acrylic-based resins. The substrate 101 may contain one type of these resins, or may contain two or more types.

[0014] 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.

[0015] 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. The substrate 101 may also be, for example, a self-stretchable stretch film.

[0016] 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 or more and 100 μm or less, but is not particularly limited.

[0017] <Underlayer> The underlayer 102 is located between the substrate 101 and the ink layer 105 and contains an alkali-soluble resin. The alkali-solubility of the underlayer 102 means that the underlayer 102 dissolves when immersed in an alkaline aqueous solution. For example, when a sample of a 4 cm × 4 cm underlayer 102 formed on a substrate 101 of any size and an ink layer 105 provided on the underlayer 102 is immersed in a 1.5% by mass aqueous sodium hydroxide solution at 85°C and stirred at 1500 rpm, 70% or more of the total area of the ink layer 105 is removed from the sample after 15 minutes of immersion. An example of the resin contained in the underlayer 102 is an acrylic acid copolymer resin. The acrylic acid copolymer resin is a resin that contains acrylic acid and / or methacrylic acid as the main repeating unit and also contains a copolymerizable monomer copolymerizable with the acrylic acid and / or methacrylic acid. The acrylic acid copolymer resin is preferably a methacrylic acid-methyl methacrylic acid copolymer. The acrylic acid copolymer resin preferably has a total ratio of acrylic acid and / or methacrylic acid and the copolymerizable monomer of 60 mol % or more in the resin.

[0018] The thickness of the underlayer 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.

[0019] <Ink layer> The ink layer 105 is located on the opposite side of the base layer 102 from the substrate 101 and is a layer containing ink. The ink contained in the ink layer 105 may contain, for example, a pigment, a resin, and an additive. The ink layer 105 is preferably a design print layer. The design print layer is a layer containing a pigment and displaying a visible pattern, character, or the like. The ink layer 105 may be provided on the entire surface of the base layer 102, or may be provided on a part of the base layer 102. The ink layer 105 may be a single layer or multiple layers. The thickness of the ink layer 105 can be, for example, approximately 0.1 μm or more and 30 μm or less, but is not particularly limited. As described above, the ink layer 105 includes the heat-generating portion 104 and the non-heat-generating portion 103 other than the heat-generating portion 104.

[0020] <Heat generating part> The ink constituting the heat generating portion 104 contains a material that generates heat when irradiated with energy rays.

[0021] [Energy rays] Examples of energy rays include short-wavelength electromagnetic waves such as X-rays or ultraviolet light, visible light, infrared light, near-infrared light, and microwaves. The present inventors have investigated labels that can be distinguished by detecting heat generation by including a base layer that can be removed with an alkaline solution and a material that generates heat when irradiated with energy rays. Conventionally, labels have been distinguished by detecting color development upon irradiation with energy rays such as ultraviolet light. However, because the degree of luminescence is not very strong, a large amount of luminescent material must be included in the label, or a high-performance camera is required. In contrast, when using the above-mentioned heat-generating material, only a small amount is required, and a high-performance camera is not required. In particular, it is preferable to use a material that absorbs energy rays in the microwave range as the heat-generating material. Materials used in conventional design printing are less likely to generate heat when irradiated with energy rays in the microwave range. Therefore, using a material that absorbs energy rays in the microwave range as the heat-generating material allows for highly accurate distinction between reusable labels and labels that are not suitable for reuse.

[0022] [Heat-generating materials] Examples of heat-generating materials that absorb energy rays in the microwave range include aluminum pigments, carbon black, and conductive polymers such as polythiophene conductive polymers. Aluminum pigments and carbon black, in particular, significantly absorb microwaves, allowing the heat-generating portion 104 to generate heat effectively, enabling the reusable labels 11 to be easily separated. From the perspective of generating heat with a small amount of energy, it is preferable to use a material with a dielectric loss factor of 10 or greater. Carbon black, with a dielectric loss factor of 100 or greater, is more preferable as a heat-generating material because it more significantly absorbs microwaves. Furthermore, carbon black has excellent light resistance, so it does not fade before the label 11 is collected, unlike the aforementioned ultraviolet-emitting materials. Microwaves can reach the heat-generating portion 104 regardless of whether the label 11 is facing up or down during transportation, so the orientation of the label 11 does not affect microwave absorption. Carbon black, being black, can be used for JAN codes, product labels, product descriptions, recycling marks, photoelectric tube marks, and other markings without compromising design aesthetics. When the heat generating portion 104, which is part of the label 11, generates heat, this can be easily detected by thermography, so the area of the heat generating portion 104 in a plan view can be small. Therefore, the cost of the heat generating portion 104, such as printing costs, is low.

[0023] <Label manufacturing method> The label 11 of the 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.

[0024] Next, the underlayer 102 is formed on one surface of the substrate 101. The underlayer 102 can be formed, for example, by applying a composition containing the resin, solvent, etc. contained in the underlayer 102 to one surface of the substrate 101 and then drying and solidifying the composition.

[0025] Next, non-heat-generating portions 103 and heat-generating portions 104 are formed on the surface of base layer 102 as ink layer 105. Ink layer 105 contains, for example, ink for forming non-heat-generating portions 103 and a heat-generating material, and can be formed by applying ink for forming heat-generating portions 104 to the surface of base layer 102, followed by drying and solidification. Non-heat-generating portions 103 and heat-generating portions 104 may be formed by printing, imprinting, kneading, etc. Examples of printing methods include well-known methods such as gravure printing, flexographic printing, screen printing, and inkjet printing. Multiple printing methods may also be combined.

[0026] The non-heat-generating portions 103 and the heat-generating portions 104 may be formed at once on the surface of the base layer 102, for example, by printing, or they may be formed separately. When the non-heat-generating portions 103 and the heat-generating portions 104 are formed separately, the non-heat-generating portions 103 may be formed first on the surface of the base layer 102, and then the heat-generating portions 104 may be formed on the surface of the base layer 102 where the non-heat-generating portions 103 are not formed, or the heat-generating portions 104 may be formed first on the surface of the base layer 102, and then the non-heat-generating portions 103 may be formed.

[0027] <How to attach the label> The label 11 is attached to a container (e.g., a PET bottle) and is wrapped around the container so that the printed surface (i.e., the side where the ink layer 105 is located) faces the container. Various wrapping methods can be used. For example, if the label 11 is a wrap-around label, one end of the label 11 can be attached to the container and wrapped around the container, and the other end can be attached to the surface of the other end. If the label 11 is a shrink label, the label 11 can be formed into a cylindrical shape in advance, placed over the container, and then shrunk.

[0028] <How to separate labels and recover substrate> Fig. 2 is a schematic diagram showing an example of the flow of the label sorting method and substrate recovery method according to embodiment 1. As shown in Fig. 2, the ink layer separation method includes a bottle recovery step S1, a compression step S2, an accumulation step S3, a label group recovery step S4, an energy ray irradiation / separation step (a step of irradiating energy rays and a step of separating labels) S5, a crushing step S6, an alkali release step S7, and a step of separating the substrate and the ink coating film (a step of separating the substrate: hereinafter referred to as the separation step) S8. Hereinafter, each step of the label sorting method and substrate recovery method will be described with reference to Fig. 2. Steps S1 to S5 relate to the label sorting method, and steps S4 to S6 relate to the substrate recovery method.

[0029] <Bottle collection process> As shown in S1 of Fig. 2, used PET bottles (items) 10 are collected in a collection box 12. A label 11 having an alkali-soluble base layer 102 and an ink layer 105 (heat-generating portion 104), or a label 40 not including the heat-generating portion 104, is attached to the body of the PET bottle 10.

[0030] The article to which the label 11 or label 40 is attached may be a container other than the PET bottle 10 or various molded products other than containers. Similarly, the type of the label 11 or label 40 is not particularly limited, and may be a shrink label, a wrap label (roll label), a stretch label, or the like.

[0031] <Compression process> As shown in S2 of FIG. 2, the collected PET bottles 10 are compressed with the labels 11 or 40 attached to them to form labeled bales 20.

[0032] <Accumulation process> As shown in S3 of FIG. 2, the labeled bales 20 are collected and sent to a recycling plant 30.

[0033] <Label collection process> As shown in S4 of Figure 2, a label group 50 including the label 11 of embodiment 1 and labels 40 that do not include the heat-generating portion 104 is collected. At the recycling plant 30, the label 11 or label 40 is removed from the PET bottles 10 in the labeled bale 20, separating the PET bottles 10 from the label group 50 including the label 11 and label 40, and the label group 50 is collected. The label 40 is assumed to be a label that does not include the heat-generating portion 104 and does not include an alkali-soluble base layer 102 or ink layer 105 that can be separated from the substrate 101. The PET bottles 10 are reused, for example, in an existing recycling process.

[0034] <Energy beam irradiation and separation process> Next, as shown in S5 of Fig. 2, microwaves as energy rays are irradiated onto the collected label group 50. Fig. 3 shows a schematic side view of an example of the step of irradiating energy rays onto the collected label group 50. Hereinafter, with reference to Fig. 3, an example of the step of irradiating microwaves onto the collected label group 50 will be described.

[0035] First, the collected label group 50 is carried into the microwave irradiation area 201. A microwave irradiation unit 21 is arranged in the microwave irradiation area 201. Microwaves 22 are irradiated from the microwave irradiation unit 21 onto the label group 50. Since the label 11 includes the heat-generating portion 104, it generates heat when irradiated with microwaves. Since the label 40 does not include the heat-generating portion 104, it does not generate heat.

[0036] Next, the group of labels 50 irradiated with microwaves 22 is carried out of the microwave irradiation area 201 and carried into the thermography area 202. A thermography camera 24 is disposed in the thermography area 202 and is connected to an image processing device 25. The thermography camera 24 may be, for example, an infrared camera, and the image processing device 25 may be, for example, a PC (personal computer). The thermography camera 24 captures images of the group of labels 50 being conveyed. The image processing device 25 acquires the image data from the thermography camera 24, processes the images, and displays the temperature distribution of each label 11 or label 40 on a display. When the labels 11 are conveyed on the conveyor, microwave absorption and heat generation are not affected regardless of whether the labels 11 are facing front or back, so there is no need to consider the orientation of the labels 11.

[0037] After microwave irradiation, the heat-generating portion 104 of the label 11 generates heat, which is displayed as a red portion on the display of the image processing device 25. The label 40 does not contain any material that generates heat when microwaves are irradiated, and therefore does not have any red portions. This makes it possible to separate the label 11 from the label 40 and collect them separately. Based on the temperature distribution image, the labels 11 are separated manually or by a robot and transported to the crusher 70 described below. The separated labels 40 are transported to, for example, a thermal recycling plant and reused. The microwave irradiation area 201 and the thermography area 202 may be the same area. That is, image data may be acquired by the thermography camera 24 while irradiating the label group 50 with microwaves 22.

[0038] <Crushing process> As shown in S6 of Fig. 2, the label 11 is crushed by a crusher 70 to produce label pieces 71. In the crushing step S6, prior to removing the ink layer 105 from the label 11 in the subsequent alkali desorption step S7, the label 11 is crushed into smaller label pieces 71. By performing the alkali desorption step S7 in this state where the label 11 is broken into smaller label pieces 71, the ink layer 105 can be efficiently removed from the label pieces 71 in the alkali desorption step S7.

[0039] There is no particular limitation on the method for crushing the labels 11. In the alkali desorption step S7 described below, the labels 11 are crushed into pieces of a size (for example, several centimeters square) that allows the ink layer 105 to be efficiently removed from the label pieces 71.

[0040] The crushing step S6 is not essential and can be omitted. In this case, the alkali desorption step S7 is carried out on the labels 11. If the labels 11 are shrink labels, preheating may be carried out before the crushing step S6 to reduce the amount of curling of the label pieces 71, so that the ink layer 105 is properly desorbed from the surface of the label pieces 71 in the alkali desorption step S7 described below.

[0041] <Alkali removal step> As shown in S7 of FIG. 2, the ink layer 105 is removed from the label piece 71 by alkaline desorption. Alkaline desorption is 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 approximately 30 seconds to 20 minutes while stirring the hot alkaline bath 82. In this case, the label piece 71 can be easily separated into the substrate 101 and the ink coating film 93 formed from the ink layer 105 in the hot alkaline bath 82. Alternatively, alkaline desorption may be performed by immersing the label piece 71 in the alkaline aqueous solution 80 for approximately 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 (e.g., in a water bath). A surfactant may be added to the alkaline aqueous solution 80 to further improve the desorption properties.

[0042] The temperature of the alkaline aqueous solution 80 is preferably 65°C or higher. The temperature for alkali desorption is preferably 100°C or lower, more preferably 85°C to 95°C, and even more preferably 80°C to 90°C. The alkaline aqueous solution 80 after removing the ink layer 105 from the label piece 71 may be disposed of as waste liquid or may be reused as the alkaline aqueous solution 80 for alkali desorption. The alkaline aqueous solution 80 is not particularly limited as long as it is capable of removing the ink layer 105 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. Examples of the alkaline aqueous solution 80 that can be used include 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 (NaCO), an aqueous solution of an alkali metal bicarbonate such as sodium bicarbonate (NaHCO), and ammonia water.

[0043] The concentration of the alkaline substance in the alkaline aqueous solution 80 can be appropriately selected within a range that does not impair the releasability, operability, or workability of the ink layer 105 and the heat generating portion 104. The concentration of the alkaline substance in the alkaline aqueous solution 80 is, for example, about 0.1 to 10% by weight, preferably about 0.5 to 5% by weight, and more preferably about 1 to 3% by weight. The alkaline aqueous solution 80 may contain a solvent other than water. For example, the alkaline aqueous solution 80 may contain, in addition to water, a glycol-based solvent or a high-boiling-point solvent (e.g., a polymer alcohol-based solvent) as a solvent.

[0044] <Separation process> As shown in S8 of Figure 2, the film pieces 91 and ink coating film 93 in the water tank 86 are separated and collected. For example, a first sieve 90 with relatively large openings collects the film pieces 91 after the ink layer has been detached from the label pieces 71, and a second sieve 92 with relatively small openings collects the ink coating film 93, which is smaller than the film pieces 91. The ink coating film 93 is a film formed by finely dividing the ink layer 105 removed from the label pieces 71 in the alkali detachment step S7.

[0045] The film pieces 91 collected by the first sieve 90 can then be reused as plastic raw materials for producing plastic products such as pellets. The film pieces 91 can also be reused as labels by mixing them into the raw materials for new labels. Meanwhile, the ink coating 93 collected by the second sieve 92 can be reused, for example, in a thermal recycling process.

[0046] In addition, if the ink coating film 93 detached from the label piece 71 in the alkali detachment process S7 contains water-based ink, in the separation process S8, instead of sieving, the ink is coagulated by solvent evaporation, extraction, etc., and then separated and recovered by centrifugation, filtration, etc.

[0047] <Variation 1> FIG. 4 is a schematic cross-sectional view of a label 13 according to Modification 1. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals, and detailed descriptions thereof will be omitted. This also applies to Modifications 2 to 5 described below. The label 13 includes a substrate 101 and an alkali-soluble base layer 102 formed on one surface of the substrate 101. A heat-generating portion 104 is formed on the surface of the base layer 102 opposite the substrate 101. The heat-generating portion 104 has a certain area in a plan view and is formed by coating, printing, imprinting, kneading, or the like. A non-heat-generating portion 103 is formed so as to cover the surface of the heat-generating portion 104 and the surface of the base layer 102. The label 13 is manufactured by forming the heat-generating portion 104 on the surface of the base layer 102, and then forming the non-heat-generating portion 103. The heat-generating portion 104 is covered and protected by the non-heat-generating portion 103. The heat-generating portion 104 and the non-heat-generating portion 103 form an ink layer 105. In the case of label 13, the surface of heat generating portion 104 is not exposed, so there is no risk of heat generating portion 104 falling off (breaking off) due to external factors. Also, because heat generating portion 104 is covered by non-heat generating portion 103, heat is less likely to escape to the outside when it is generated, and heat generation can be detected well, allowing labels 13 to be separated.

[0048] <Variation 2> 5 is a schematic cross-sectional view of label 14 according to variant example 2. Heat-generating portion 104 of label 14 is formed in a recess that is recessed toward base layer 102 from the surface of non-heat-generating portion 103 that is not in contact with base layer 102. Unlike label 11, the thickness of heat-generating portion 104 is thinner than the thickness of non-heat-generating portion 103. If heat-generating portion 104 has a black color such as carbon black, the area in which heat-generating portion 104 is formed can be limited to an area in which heat generation can be detected, thereby reducing the impact of non-heat-generating portion 103 on the design.

[0049] <Variation 3> 6 is a schematic cross-sectional view of label 15 according to modification 3. Heat-generating portion 104 of label 15 is formed on the surface of non-heat-generating portion 103 that is not in contact with base layer 102. In the case of label 15, after non-heat-generating portion 103 is formed over the entire surface of base layer 102, heat-generating portion 104 can be easily formed in spot-like positions at will.

[0050] <Variation 4> 7 is a schematic cross-sectional view of a label 16 according to Modification 4. The heat generating portion 104 of the label 16 is formed on the surface of the substrate 101 that is not in contact with the underlayer 102. In the case of the label 16, the heat generating portion 104 can be easily formed at any position on the surface of the substrate 101.

[0051] <Variation 5> 8 is a schematic cross-sectional view of a label 17 according to Variation 5. In label 17, base layers 102 are formed on both sides of substrate 101. Heat-generating portions 104 are formed on the surface of base layer 102 that is exposed on the outermost surface of label 17. In the case of label 17, the base layer 102 on the side where heat-generating portions 104 are formed can also be separated from the substrate by alkali desorption or the like, and the substrate 101 can be reused in a state where it does not contain the non-heat-generating portions 103 and the ink layer 105 of the heat-generating portions 104.

[0052] <Effects> As described above, the labels 11, 13 to 17 (hereinafter referred to as labels 11, etc.) of embodiment 1 include a heat-generating portion 104. Therefore, by detecting heat generation, reusable labels 11, etc. can be easily separated. Heat generation can be effectively detected by thermography. The base material 101 of the separated labels 11, etc. can be separated from the non-heat-generating portion 103 and the heat-generating portion 104 by removing the base layer 102, allowing the base material 101 to be reused. When the heat-generating portion 104 is contained in the ink layer 105, a visible image or character can be displayed by the heat-generating portion 104. When the energy rays are microwaves, the label 11, etc. contains a material that absorbs energy rays in the microwave range and generates heat, allowing it to be clearly distinguished from labels that do not contain this material. When carbon black or aluminum pigment is used as the heat-generating material, these materials significantly absorb microwaves, so the heat-generating portion 104 generates heat effectively, allowing reusable labels to be easily separated. If the dielectric loss factor of the heat-generating material is 10 or greater, even a small amount of the heat-generating material can generate a detectable amount of heat.

[0053] According to the method for separating labels 11 etc. of embodiment 1, it is possible to easily separate labels 11 etc. that have generated heat by irradiating them with energy rays in the energy ray irradiation / separation step S5, and to easily separate labels 11 etc. that can separate the base material 101. In the energy ray irradiation / separation step S5, it is possible to easily detect labels 11 that have generated heat using thermography.

[0054] According to the method for recovering the substrate from labels 11, etc. of embodiment 1, the substrate 101 can be separated from labels 11, etc. that have been detected as reusable based on heat generation using the above-mentioned method for separating labels 11, etc., and can be reused effectively.

[0055] According to the method for separating labels 11 and the like and the method for separating the base material from labels 11 and the like of embodiment 1, it is possible to reuse labels 11 and the like, thereby contributing to the achievement of the Sustainable Development Goals (SDGs).

[0056] The above label 11 etc. has been described as having the ink layer 105 on the back side (the side of the label that contacts the container), but the ink layer 105 may also be on the front side.

[0057] [Embodiment 2] FIG. 9 is a schematic cross-sectional view of a label 18 according to embodiment 2. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and detailed descriptions thereof are omitted. In the label 18, an alkali-soluble base layer 108 is formed on the front side of the substrate 101 (the side of the label opposite the side that contacts the container). The base layer 108 includes a non-heat-generating portion 106, which is a base layer that does not contain a heat-generating material, and a heat-generating portion 107, which is a base layer that contains a heat-generating material. The composition of the non-heat-generating portion 106 is the same as that of the above-described base layer 102. The heat-generating portion 107 is formed in a hole or recess provided in the non-heat-generating portion 106. The heat-generating portion 107 contains the same heat-generating material as the above-described heat-generating portion 104 and is alkali-soluble. The non-heat-generating portion 106 and the heat-generating portion 107 may be formed on the surface of the substrate 101 by printing or the like. Alternatively, one of the non-heat-generating portion 106 and the heat-generating portion 107 may be formed on the surface of the substrate 101 after the other has been formed. Alternatively, a composition containing the heat-generating material of the heat-generating portion 107 may be mixed with a composition for forming the non-heat-generating portion 106, and the mixture may be applied to the surface of the substrate 101, solidified, and dried to form the base layer 108. An ink layer 109 is formed on the surface of the base layer 108. The composition of the ink layer 109 is the same as the composition of the non-heat-generating portion 103 described above, and the ink layer 109 is formed on the surface of the base layer 108 in the same manner as the non-heat-generating portion 103. Because the base layer 108 includes the heat-generating portion 107, the ink layer 109 can be formed with fewer design restrictions based on the heat-generating portion 107.

[0058] [Embodiment 3] FIG. 10 is a schematic cross-sectional view of a label 19 according to a third embodiment. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and detailed descriptions thereof will be omitted. The label 19 includes a substrate 101 and an alkali-soluble ink layer 112 formed on one surface of the substrate 101. The ink layer 112 includes a non-heat-generating portion 110 and a heat-generating portion 111 containing a heat-generating material. The heat-generating portion 111 having a predetermined width is formed on the surface of the substrate 101, and the non-heat-generating portion 110 is formed so as to surround the heat-generating portion 111. The heat-generating portion 111 may be formed in a hole or recess formed in the non-heat-generating portion 110. The non-heat-generating portion 110 and the heat-generating portion 111 contain a vehicle resin, such as a styrene-acrylic acid copolymer and / or a styrene-maleic acid copolymer. The non-heat-generating portion 110 and the heat-generating portion 111 are formed in the same manner as the non-heat-generating portion 103 and the heat-generating portion 104 described above. According to the third embodiment, in the above-described alkali desorption step, the ink layer 112 dissolves in the alkaline aqueous solution and disappears, and the substrate 101 is separated from the ink layer 112. That is, the substrate 101 can be separated from the ink layer 112 without having the underlayer 102 as a separation layer. [Example]

[0059] The results of examining the material for the heat generating portion 104 will be described below. <Evaluation of ink shrinkage> A PET film was prepared as the substrate 101. Using a gravure proofing machine, ink containing Samples 1 to 10 shown in Table 1 below was applied to the substrate 101 layer and then solidified to form an ink layer. The heat-generating materials and imaginary parts of the complex relative permittivity (dielectric loss coefficients) of Samples 1 to 10 are shown in Table 1. Here, the ink layer corresponds to the heat-generating part 104.

[0060] The substrate 101 layer on which each ink layer was formed was cut into 50 mm x 50 mm pieces and irradiated with microwaves in a microwave oven for 10 seconds to evaluate shrinkage. The shrinkage evaluation is as follows. High shrinkage means that the microwaves are well absorbed and heat is generated. Rating A: The shrink film shrinks to its maximum shrinkage rate, or some of the film melts. Rating B: The shrink film shrunk (however, the shrinkage rate was less than the maximum shrinkage rate) Rating C: Did not shrink

[0061] [Table 1]

[0062] From Table 1, it can be seen that when the ink compositions of Samples 1 to 4 containing carbon black with a dielectric loss factor of 100 or more were applied to the substrate 101, they shrunk well, i.e., they absorbed a large amount of microwaves and generated heat well. When the ink compositions of Samples 1 to 4 containing carbon black with a dielectric loss factor of 10 or less were applied to the substrate 101, they did not shrink. It can be seen that when the composition of Sample 9 containing an aluminum pigment with a dielectric loss factor of 10 or more was applied to the substrate 101, they shrunk well and generated heat well. When the composition of Sample 10 containing an aluminum pigment with a dielectric loss factor of less than 10 was applied to the substrate 101, they did not shrink.

[0063] From the above, it can be seen that materials for the heat generating part 104 include carbon black, aluminum pigment, and silver ink, and that it is preferable to use a material with a dielectric loss coefficient of 10 or more. When carbon black is selected as the material for the heat generating part 104, carbon black with a dielectric loss coefficient of 100 or more is more preferable.

[0064] <Summary> The label according to aspect 1 of the present invention comprises a substrate, a separation layer laminated to the substrate and separable from the substrate, an ink layer containing ink located on the opposite side of the separation layer from the substrate, and a heat generating portion containing a material that generates heat when irradiated with energy rays.

[0065] According to the above configuration, since the label is provided with a heat generating portion containing a material that generates heat when irradiated with energy rays, the heat generation can be detected and the reusable labels can be easily separated. By separating the separation layer from the substrate by an alkaline desorption treatment or the like, the substrate of the separated label can be separated from the heat generating portion and reused.

[0066] In the label according to the second aspect of the present invention, the heat generating portion is included in the ink layer.

[0067] According to the above configuration, the heat generating portion is included in the ink layer, so that a visible pattern or character can be displayed. The heat generating portion and the portion other than the heat generating portion can be formed simultaneously by printing, etc. The entire ink layer may be the heat generating portion.

[0068] In the label according to a third aspect of the present invention, the heat generating portion is included in the separation layer.

[0069] According to the above-mentioned configuration, since the heat generating portion is contained in the separation layer, the ink layer can be formed with less design restrictions due to the heat generating portion. This can also be applied when the separation layer and the ink layer are formed in this order on the front side of the substrate (the side opposite to the side that contacts the container of the label).

[0070] A label according to a fourth aspect of the present invention comprises a substrate, an ink layer laminated on the substrate and containing ink that is separable from the substrate, and a heat generating portion contained in the ink layer and containing a material that generates heat when irradiated with energy rays.

[0071] According to the above-mentioned configuration, the heat generating portion can be separated from the ink layer including the heat generating portion without using a separation layer.

[0072] In a label according to a fifth aspect of the present invention, the energy rays are microwaves.

[0073] There are only a limited number of materials that can absorb energy rays in the microwave range. According to the above configuration, by including a material that absorbs energy rays in the microwave range and generates heat, the label can be clearly distinguished from labels that do not include this material.

[0074] In a label according to a sixth aspect of the present invention, the material has a dielectric loss coefficient of 10 or more.

[0075] According to the above configuration, even if the amount of material is small, a large amount of microwaves is absorbed and heat is generated.

[0076] In a label according to a seventh aspect of the present invention, the material is carbon black or aluminum pigment.

[0077] Carbon black or aluminum pigments significantly absorb microwaves, so that the heating portion heats up well and the reusable labels can be easily separated.

[0078] A label sorting method according to aspect 8 of the present invention includes a step of collecting a group of labels including any of the labels described above, a step of irradiating the collected group of labels with the energy beam, and a step of sorting the labels including the heat-generating portion that has been heated by irradiating the energy beam.

[0079] According to the above configuration, by detecting the labels that have generated heat as a result of being irradiated with energy rays, it is possible to easily separate the labels from which the base material can be separated.

[0080] In the label sorting method according to a ninth aspect of the present invention, the heated labels are detected using thermography in the sorting step.

[0081] With this configuration, the image of the heated part turns red, making it easy to detect heated labels. If only a part of the label is heated, it can be detected by thermography, so there is no need to provide a heated part on the entire label, and separable labels can be produced inexpensively.

[0082] A method for recovering substrates from labels according to aspect 10 of the present invention includes the steps of recovering a group of labels including the above-described labels, irradiating the recovered group of labels with the energy ray, separating the labels including the heat-generating portion that has been heated by irradiating the energy ray, and separating the substrates from the labels separated by the separating step.

[0083] According to the above configuration, the base material can be separated from the separated labels and reused. [Explanation of symbols]

[0084] 10 PET bottles 11, 13, 14, 15, 16, 17, 18, 19 Labels 101 Base material 102, 108 Base layer 103, 110 Non-heat-generating part 104, 107, 111 Heat generating part 105, 109 Ink layer 106 Non-heat-generating portion (non-heat-generating portion of the base layer) 21 Microwave irradiation unit 22 Microwave 24 Thermography Camera 25 Image processing device 40 Labels 50 Label Groups

Claims

1. A substrate, a separation layer laminated on the substrate and separable from the substrate; an ink layer containing ink, the ink layer being located on the side of the separation layer opposite to the substrate; a heat generating portion including a material that generates heat when irradiated with microwaves; collecting a group of labels including a label comprising: irradiating the collected label group with microwaves; a sorting step of sorting the labels including the heat-generating portions that have generated heat by irradiating the microwaves; Label sorting methods, including:

2. A substrate, an ink layer that is laminated on the substrate and contains ink that is separable from the substrate; a heat generating portion that is included in the ink layer and includes a material that generates heat when irradiated with microwaves; collecting a group of labels including a label comprising: irradiating the collected label group with microwaves; a sorting step of sorting the labels including the heat-generating portions that have generated heat by irradiating the microwaves; Label sorting methods, including:

3. 3. The label sorting method according to claim 1, wherein the heated labels are detected using thermography in the sorting step.

4. A substrate, a separation layer laminated on the substrate and separable from the substrate; an ink layer containing ink, the ink layer being located on the side of the separation layer opposite to the substrate; a heat generating portion including a material that generates heat when irradiated with microwaves; collecting a group of labels including a label comprising: irradiating the collected label group with microwaves; a sorting step of sorting the labels including the heat-generating portions that have generated heat by irradiating the microwaves; and separating the substrate from the labels separated in the separating step.

5. A substrate, an ink layer that is laminated on the substrate and contains ink that is separable from the substrate; a heat generating portion that is included in the ink layer and includes a material that generates heat when irradiated with microwaves; collecting a group of labels including a label comprising: irradiating the collected label group with microwaves; a sorting step of sorting the labels including the heat-generating portions that have generated heat by irradiating the microwaves; and separating the substrate from the labels separated in the separating step.

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