How to reuse labels

Abstract

To provide a method for reusing labels capable of efficiently separating ink and base materials from labels and efficiently drying the separated base materials.SOLUTION: A method for reusing labels includes: steps (S1 to S5) for acquiring a label (11) having a base material and an ink layer containing ink, and separable between the base material and the ink by an alkaline solution; first crushing step (S6) for crushing the label (11) into label pieces (71) with a first size; separation steps (S7 and S8) for treating the label pieces (71) with the alkaline solution to separate the same into base material pieces (91) and the ink; second crushing step (S9) for crushing the base material pieces (91) into base material pieces (111) with a second size smaller than the first size; and step (S10) for drying the base material pieces (111).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for reusing labels. [Background technology]

[0002] 2. Description of the Related Art 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 reuse 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, labels with product information printed on a plastic substrate are sometimes attached to the body of PET bottles, but material recycling of labels has not been implemented and they are currently limited to thermal recycling.

[0004] To reuse a label, it is preferable to efficiently separate the substrate from the label. For example, Patent Document 1 discloses a label in which a display printing ink layer is formed on a substrate film via a coating layer (underlayer) that is soluble in an alkaline aqueous solution. In this invention, the substrate is separated from the label by dissolving the underlayer in an alkaline aqueous solution. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2003-84670 A Summary of the Invention [Problem to be solved by the invention]

[0006] The collected labels are crushed, the ink is separated from the substrate, and then the labels are dried and reused. In these steps, it is preferable that the separation of the ink and the drying of the substrate are carried out efficiently.

[0007] An object of one aspect of the present invention is to provide a method for reusing labels that can efficiently separate the ink and the substrate from the label and efficiently dry the separated substrate. [Means for solving the problem]

[0008] A label recycling method according to one embodiment of the present invention includes the steps of obtaining a label having a substrate and an ink layer containing ink, the substrate and the ink being separable by an alkaline solution; a first crushing step of crushing the label into label pieces of a first size; a separation step of treating the label pieces with the alkaline solution to separate them into substrate pieces and the ink; a second crushing step of crushing the substrate pieces produced in the separation step into substrate pieces of a second size smaller than the first size; and a drying step of the substrate pieces of the second size produced in the second crushing step. Effect of the Invention

[0009] According to one aspect of the present invention, the ink and the substrate can be efficiently separated from the label, and the separated substrate can be efficiently dried. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view of a label according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a flow of a method for reusing a label according to the first embodiment. [Diagram 3] FIG. 11 is a schematic cross-sectional view of a label according to a modified example. [Figure 4] 10 is a flowchart of a label reuse method according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a label recycling method according to an embodiment of the present disclosure will be described in detail with reference to the drawings. However, the following description is merely an example of the label recycling method according to the present invention, and the technical scope of the present invention is not limited to the illustrated example.

[0012] [Technical Concept of the Present Invention] When reusing a label, it is preferable to efficiently separate the ink of the label from the substrate and to efficiently dry the substrate in order to improve the efficiency of ink recovery and work efficiency. If the label is made small to a certain extent, the surface area increases, and the drying efficiency when drying the substrate improves. However, the present inventors have found a new problem that when the label pieces are made small enough to improve the drying efficiency, the ink becomes difficult to remove in the alkali removal step. In addition, the present inventors have found a new problem that when the ink is separated from the substrate as removed pieces, if the label pieces are crushed too small, even if the ink is removed, the removed pieces cannot be sieved because they are too small, and the ink recovery efficiency decreases.

[0013] The present inventors found these problems through the following experiment. That is, when a label was crushed into small pieces, such as 10 mm square pieces, and the alkali desorption step was performed, the label was sometimes crushed in a twisted state, i.e., with the ink layer wrapped around it. In this case, it was found that during alkali desorption, the ink layer was not removed from the edge of the label, and remained in the label. In addition, if the label is too small, the weight is reduced, and the collision energy between the labels is reduced during the alkali desorption step, which may result in the ink being difficult to remove.

[0014] Furthermore, when the ink particles resulting from the ink layer being separated and broken down by alkaline desorption were sieved through a sieve with a mesh size of 1 mm, many of the particles slipped through the mesh. Therefore, it was necessary to collect the ink particles that slipped through the mesh by evaporating the alkaline solution. If the mesh of the sieve is made finer to solve this problem, the ink particles will clog the sieve, reducing the efficiency of ink collection.

[0015] The inventors have therefore discovered that by crushing the label to a predetermined size (first size) (first crushing) prior to the alkali desorption step and then crushing the base material pieces to a second size smaller than the first size (second crushing), it is possible to efficiently separate the ink and the base material, and also to efficiently dry the separated and crushed base material pieces, thereby completing the present invention.

[0016] That is, a method for recycling a label according to one embodiment of the present invention includes the steps of obtaining a label having a substrate and an ink layer containing ink, the substrate and the ink being separable by an alkaline solution, a first crushing step of crushing the label into label pieces of a first size, a separation step of treating the label pieces with the alkaline solution to separate the substrate pieces and the ink, a second crushing step of crushing the substrate pieces generated in the separation step into substrate pieces of a second size smaller than the first size, and a drying step of drying the substrate pieces of the second size generated in the second crushing step. The present invention is applicable not only to a label having an ink layer laminated on a substrate via an alkali-soluble underlayer, but also to a label having no alkali-soluble underlayer and having an alkali-soluble ink layer laminated on a substrate.

[0017] The longest side of the first size label piece is preferably 20 mm or more and 50 mm or less. Here, the longest side means the longest side among the sides that form the outer edge when the label piece is considered to be a polygon. Since the first size label piece is not necessarily a strict polygon, the straight line parts included in the outer edge of the label piece can be considered as the sides. In addition, when considering a circle circumscribing the label piece, it is preferable that the diameter of this circumscribing circle is 20√2 mm or more and 50√2 mm or less.

[0018] When the first size of the label pieces exceeds 50 mm, the following problems (1) to (5) occur. (1) In the alkali desorption step, the number of label pieces that can be immersed in the alkaline solution at one time decreases, resulting in poor efficiency. (2) The label pieces may become entangled in the stirring blades of the hot alkaline tank 82 described below. (3) When washing the base material pieces after the alkali desorption, the pipe that sends the label pieces from the hot alkaline tank 82 to the washing tank may be clogged with the base material pieces. (4) The label pieces may become entangled with each other. If the label pieces are put into the alkaline solution in an entangled state, it becomes difficult to remove the ink from the entangled parts. (5) Each label piece has large irregularities and bends, and when the label pieces are stirred in the alkali desorption step, there are parts that do not collide with other label pieces because the bends do not open. On the other hand, when the first size is less than 20 mm, as described above, (1) in the alkali desorption step, the ink becomes difficult to remove, and even if the ink is removed, the removed pieces are small, resulting in a decrease in recovery efficiency. (2) There are too many bends (the number of sides increases relatively), so there is a high probability that the ink will not come into contact with the alkaline solution and will not come off.

[0019] When the longest side of the first size label piece is 20 mm or more and 50 mm or less, the ink and the base material can be efficiently separated from the label, the ink can be efficiently recovered, and the above-mentioned problems do not occur.

[0020] The longest side of the second size base material pieces is preferably 5 mm or more and less than 20 mm. When the second size of the base material pieces is 20 mm or more, the base material pieces are bulky and have a small surface area per unit weight, resulting in poor drying efficiency in the drying process. When the second size of the base material pieces is less than 5 mm, the moisture content is high and the drying efficiency is poor. In addition, when centrifugal dehydration is performed before drying, the base material pieces pass through the mesh of the dehydration tank, resulting in poor recovery efficiency.

[0021] When the longest side of the second size base piece is 5 mm or more and less than 20 mm, the base piece is dried efficiently and the above-mentioned problem does not occur.

[0022] [Embodiment 1] A specific description will be given below based on the first embodiment. <label> Fig. 1 shows a schematic cross-sectional view of a label 11 of the first embodiment. As shown in Fig. 1, the label 11 includes a substrate 101, an alkali-soluble underlayer 102 laminated on the substrate 101, and an ink layer 103 laminated on the underlayer 102. The label 11 may be a heat-shrinkable label (shrink label), or may be a label that does not have heat-shrinkable properties. The label 11 may also be a stretch label that has self-stretchability, or may be a label that does not have self-stretchability.

[0023] <Base material> The substrate 101 is a base containing a resin capable of supporting the underlayer 102 and the ink layer 103. Examples of the resin contained in the substrate 101 include polyester-based resins (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.

[0024] The resin contained in the base material 101 is preferably a polyester resin, and more preferably PET. PET is a polyester resin containing terephthalic acid as a main component of the dicarboxylic acid component and ethylene glycol as a main component of the 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.

[0025] The substrate 101 may be, for example, a film having heat shrinkability (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 stretch film having self-stretchability.

[0026] 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 may be, for example, 5 μm or more and 100 μm or less, but is not particularly limited. The thickness of the substrate 101 is more preferably 10 μm or more and 60 μm or less.

[0027] <Underlayer> The underlayer 102 is a layer that is located between the substrate 101 and the ink layer 103 and contains a resin that is alkali-soluble. The underlayer 102 being alkali-soluble means that the underlayer 102 dissolves when immersed in an alkaline solution. For example, when a sample in which a 4 cm×4 cm square underlayer 102 is formed on a substrate 101 of any size and an arbitrary ink layer 103 is 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 103 is detached from the sample in 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 a 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 is preferably such that the total ratio of the acrylic acid and / or methacrylic acid and the copolymerizable monomer in the resin is 60 mol% or more.

[0028] 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.

[0029] <Ink layer> The ink layer 103 is a layer that is located on the opposite side of the base layer 102 from the substrate 101 and contains ink. The ink 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 or characters. Examples of oil-based inks include those that contain additives in a colorant such as a pigment or a dye, a binder resin such as an acrylic resin, a urethane resin, a polyester resin, or a polyamide resin, and an organic solvent. Examples of water-based inks include those that contain a colorant, a water-soluble or water-dispersible binder resin, an additive, and the like. Examples of additives include a lubricant, an anti-blocking agent, and an anti-settling agent. The ink layer 103 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 103 may be a single layer or a multilayer. The thickness of the ink layer 103 can be, for example, about 0.1 μm or more and 30 μm or less, but is not particularly limited.

[0030] <Label manufacturing method> The label 11 of the embodiment can be manufactured, for example, as follows: First, prepare the substrate 101. The substrate 101 can be prepared, for example, by forming a film by a method such as an inflation method, an extrusion method, or a calendar method, and then, if necessary, subjecting the film to a stretching treatment.

[0031] 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 contained in the underlayer 102 to one surface of the substrate 101, and then drying and solidifying the composition.

[0032] Next, an ink layer 103 is formed on the surface of the base layer 102. The ink layer 103 can be formed, for example, by applying an ink composition for forming the ink layer 103 onto the surface of the base layer 102 and then drying and solidifying it. The ink layer 103 may also be formed by printing, lettering, kneading, or the like. Examples of the printing method include gravure printing, flexographic printing, screen printing, inkjet printing, and the like.

[0033] <Method for Reusing Labels> FIG. 2 is a schematic diagram showing an example of the flow of the method for reusing labels according to Embodiment 1. As shown in FIG. 2, the method for separating the ink layer includes a PET bottle collection step S1, a compression step S2, an integration step S3, a label group collection step S4, a separation step S5, a first crushing step S6, an alkali detachment step (separation step) S7, a separation and collection step (separation step) S8, a second crushing step S9, and a drying step S10. Hereinafter, each step of the method for reusing labels will be described with reference to FIG. 2.

[0034] <PET Bottle Collection Step> As shown in S1 of FIG. 2, used PET bottles (articles) 10 are collected in a collection box 12. A label 11 or a label 40 having an alkali-soluble base layer 102 and an ink layer 103 is attached to the body of the PET bottle 10. The label 40 is a label in which the base layer is not alkali-soluble, or the base layer is not present, and the ink layer directly formed on the surface of the base material is not alkali-soluble, and the base material cannot be separated.

[0035] The articles to which the label 11 or the label 40 is attached may be containers other than the PET bottle 10 or various molded articles other than containers. Similarly, the types of the label 11 or the label 40 are not particularly limited, and may be shrink labels, wrap-around labels (roll labels), stretch labels, or the like.

[0036] <Compression Step> As shown in S2 of FIG. 2, the collected PET bottle 10 is compressed with the label 11 or the label 40 attached thereto to obtain a bale 20 with a label.

[0037] <Accumulation process> As shown in S3 of FIG. 2, the labeled bales 20 are collected and sent to a recycling plant 30.

[0038] <Label collection process> 2, a label group 50 including the label 11 of the first embodiment and the label 40 is collected. In the recycling factory 30, the label 11 or the label 40 is removed from the PET bottles 10 in the labeled bale 20, and the PET bottles 10 are separated from the label group 50 including the labels 11 and 40, and the label group 50 is collected. The PET bottles 10 are reused, for example, in an existing recycling process.

[0039] <Separation process> Next, as shown in S5 of Fig. 2, the labels 11 are separated from the collected label group 50. For example, a method of separating the labels 11 may be used in which a description or mark indicating that the labels are reusable is attached to the labels 11 and the mark is read. The separated labels 11 are transported to a crusher 70 for the first crushing step S6 described below. The separated labels 40 are transported to, for example, a thermal recycling plant and reused.

[0040] <First crushing process> 2, the labels 11 are crushed by a crusher 70 to produce label pieces 71. There are no particular limitations on the method of crushing the labels 11, and any method can be used as long as it can produce label pieces 71 of a desired size. As described above, the size (first size) of the label pieces 71 produced by the first crushing step S6 is preferably such that the longest side is 20 mm or more and 50 mm or less.

[0041] <Alkaline removal step> As shown in S7 of FIG. 2, the base layer 102 is detached from the label piece 71 by alkaline detachment. The alkaline detachment is performed, for example, by immersing the label piece 71 in an alkaline aqueous solution 80 as an alkaline solution of about 50° C. to 95° C. in a hot alkaline bath 82 for about 30 seconds to 20 minutes and stirring the inside of the hot alkaline bath 82. In this case, the label piece 71 can be easily separated into a base material piece 91 generated from the base material 101 and a detached piece 93 generated by the ink layer 103 being divided in the hot alkaline bath 82. The alkaline detachment may also be performed, for example, by immersing the label piece 71 in the above-mentioned alkaline aqueous solution 80 for about 30 seconds to 20 minutes and then washing with water. In this case, the label piece 71 can be easily separated into the base material piece 91 and the detached piece 93 by washing with water (for example, in a water bath). A surfactant may be added to the alkaline aqueous solution 80 for the purpose of further improving the detachment property. The alkaline solution is not limited to an alkaline aqueous solution and may contain other solvents.

[0042] The temperature of the alkaline aqueous solution 80 is preferably 65°C or higher. The temperature of the 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 103 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 possible to remove the ink layer 103 from the label piece 71 by immersing the label piece 71 in the alkaline aqueous solution 80. 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 an aqueous ammonia can be used.

[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 103. 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.

[0044] As described above, when the first size in the first crushing step S6 is set to 20 mm or more and 50 mm or less, the edges of the label pieces 71 are less likely to bend, and the ink layer 103 is easily detached from the label pieces 71. The detached pieces 93 of the ink layer 103 have a size that allows them to be efficiently removed by sieving.

[0045] <Sorting and collection process> As shown in S8 of FIG. 2, the base material pieces 91 and the detached pieces 93 in the water tank 86 are collected separately. For example, the base material pieces 91 after the ink layer is detached from the label pieces 71 are collected by a first sieve 90 having a relatively large opening, and the detached pieces 93 smaller than the base material pieces 91 are collected by a second sieve 92 having a relatively small opening. The detached pieces 93 collected by the second sieve 92 can be reused as ink, and can also be reused in the thermal recycling process. When the ink layer 103 contains water-based ink, the ink detached from the label pieces 71 in the alkali detachment process S7 may dissolve and disperse in water. In this case, when collecting the water-based ink, or the water-based ink and the oil-based ink, in the separation and collection process S8, instead of sieving, the ink is coagulated by solvent evaporation, extraction, etc., and separated and collected by centrifugation, filtration, etc. The base material pieces 91 are transported to a crusher 100 for the second crushing step S9 described below.

[0046] <Second crushing process> 2, the base material pieces 91 recovered in the separation and recovery step S8 are crushed by a crusher 100 into base material pieces 111 of a second size smaller than the first size. There are no particular limitations on the method of crushing the base material pieces 91, and any method can be used as long as it can produce base material pieces 111 of a desired size. As described above, it is preferable that the second size has a longest side that is 5 mm or more and less than 20 mm.

[0047] <Drying process> As shown in S10 of FIG. 2, the base material pieces 111 are dried. The base material pieces 111 are dried, for example, by passing through a hot air tunnel 120. Centrifugal dehydration may be performed before drying. As described above, when the second size in the second crushing step S9 is set to 5 mm or more and less than 20 mm, the drying efficiency is good. When centrifugal dehydration is performed, the base material pieces 111 are prevented from passing through the mesh of the dehydration tank. Before drying, the base material pieces 111 may be washed with water and centrifugal dehydration may be performed. The dried base material pieces 111 can be reused as a plastic raw material for the production of plastic products such as pellets. In addition, the base material pieces 111 can be reused as a label by mixing them into the raw material for a new label. In the alkali desorption step S7, the ink is well desorbed from the base material 101, so the base material pieces 111 do not contain ink and are used as a high-quality recycled raw material.

[0048] <Modification> 3 is a schematic cross-sectional view of a label 13 according to a modified example. The label 13 includes a substrate 101 and an alkali-soluble ink layer 103 formed on one surface of the substrate 101. The ink layer 103 contains a water-based ink and is formed in the same manner as in the first embodiment. In the modified label 13, the ink layer 103 dissolves in the alkaline aqueous solution 80 and disappears, and the substrate 101 is separated from the ink layer 103 in the above-mentioned alkali removal step S7. In the separation and recovery step S8, the ink dissolved in the alkaline aqueous solution 80 is coagulated by solvent evaporation, extraction, etc. instead of sieving, and is separated and recovered by centrifugation, filtration, etc.

[0049] <Summary> As described above, in the method for reusing labels 11 according to the first embodiment, the labels 11 are crushed into label pieces 71 of a first size before the alkali desorption step S7, so that the label pieces 71 can be efficiently separated into base material pieces 91 and ink in the alkali desorption step S7. After separation, the base material pieces 91 are crushed into base material pieces 111 of a second size, so that they are efficiently dried in the drying step S10. According to the method for reusing labels according to the first embodiment, it is possible to efficiently reuse the labels 11, which can contribute to the achievement of the Sustainable Development Goals (SDGs).

[0050] [Embodiment 2] Fig. 4 is a flow chart showing a method for reusing the label 11 according to the second embodiment. In the second embodiment, the label 11 is specified as a shrink label, and similarly to the first embodiment, the label 11 includes a substrate 101, a base layer 102, and an ink layer 103. The method for reusing the label 11 according to the second embodiment differs from the method for reusing the label 11 according to the first embodiment in that it includes a preheating step (heating step) before the first crushing step. As shown in Fig. 4, the method for reusing the label 11 includes a PET bottle recovery step S11, a compression step S12, an accumulation step S13, a label group recovery step S14, a separation step S15, a preheating step S16, a first crushing step S17, an alkali release step S18, a separation and recovery step S19, a second crushing step S20, and a drying step S21. The PET bottle collection process S11, compression process S12, accumulation process S13, label group collection process S14, sorting process S15, sorting and collection process S19, second crushing process S20, and drying process S21 are similar to the PET bottle collection process S1, compression process S2, accumulation process S3, label group collection process S4, sorting process S5, sorting and collection process S8, second crushing process S9, and drying process S10 in embodiment 1, so description thereof will be omitted.

[0051] <Preheating process> The method of preheating the label 11 in the preheating step S16 is not particularly limited as long as it can suppress the amount of shrinkage and curling of the label piece 71 in the alkali desorption step S18. In the alkali desorption step S18, the label piece 71 shrinks by a predetermined amount to reduce the volume while suppressing the amount of shrinkage and curling of the label piece 71. This allows the amount of water input into the hot alkali bath 82 to be increased, and the alkali desorption step can be performed efficiently. The preheating temperature (preheating temperature) is preferably higher than the temperature of the alkali treatment in the alkali desorption step S18. For example, when hot water is used, the preheating temperature is preferably 80° C. or higher, and more preferably 90° C. or higher. The preheating temperature is preferably 100° C. or lower, and more preferably 95° C. or lower. The preheating temperature is more preferably higher than the temperature of the alkaline aqueous solution 80 in the alkali desorption step S18. By controlling the preheating temperature and the temperature of the alkaline aqueous solution 80, it is possible to suppress the degree of shrinkage of the label piece 71 in the alkali desorption step S18 and efficiently remove the ink from the label piece 71. It is more preferable that the preheating temperature is 5° C. or more higher than the alkali desorption temperature.

[0052] Examples of methods for preheating the label 11 include passing the label 11 through a hot air tunnel or immersing the label 11 in hot water in a hot water tank. When drying using hot air, the label 11 may be blown away by the hot air, but when immersing the label 11 in hot water, the method of immersing the label 11 in hot water is preferable from the viewpoints that temperature control is easy, a small device is sufficient, and the label 11 shrinks uniformly. When immersing the label 11 in hot water, the label 11 is immersed in hot water at the above-mentioned preheating temperature for about 10 to 20 seconds. When preheating the label 11 by passing the label 11 through a hot air tunnel, the preheating temperature is the temperature of the hot air.

[0053] <First crushing process> As in the first crushing step S6 of the first embodiment, the labels 11 are crushed by a crusher 70 to produce label pieces 71. As in the first embodiment, the first size of the label pieces 71 produced in the first crushing step S17 is preferably such that the longest side is 20 mm or more and 50 mm or less.

[0054] <Alkaline removal step> The alkali desorption step S18 is performed in the same manner as the alkali desorption step S7 in embodiment 1. As described above, the temperature of the alkaline aqueous solution 80 in the hot alkali bath 82 in the alkali desorption step S18 is preferably lower than the temperature in the preheating step S16. As described above, shrinkage of the label piece 71, which makes it difficult to separate the ink layer 103 from, for example, the edge portion, is suppressed.

[0055] As described above, in the method for reusing the label 11 in the second embodiment, the label 11 is crushed into label pieces 71 of a first size before the alkali desorption step S18, as in the first embodiment, so that the label pieces 71 can be efficiently separated into the base material pieces 91 and the ink detached pieces 93 in the alkali desorption step S18. After separation, the base material pieces 91 are crushed into base material pieces 111 of a second size, so that they are efficiently dried in the drying step S21. In the second embodiment, the label 11, which is a shrink label, is subjected to the preheating step S16, and the preheating temperature and the temperature of the alkaline aqueous solution 80 in the alkali desorption step S18 are controlled. Therefore, the degree of shrinkage of the label pieces 71 in the alkali desorption step S18 is controlled, and the base material pieces 91 and the ink detached pieces 93 are efficiently separated from the label pieces 71. Even in cases where the shrink label does not have a base layer and the ink layer 103 is alkali-soluble, the degree of label shrinkage can be controlled by preheating and controlling the preheating temperature and the alkali desorption temperature, and the ink from the label piece 71 dissolves well in the alkaline aqueous solution 80, allowing the base material piece 91 and the ink to be efficiently separated. The label sorting method of embodiment 2 makes it possible to efficiently reuse the labels 11, thereby contributing to the achievement of the Sustainable Development Goals (SDGs). [Explanation of symbols]

[0056] 10 PET bottles 11, 13 Label 101 Base material 102 Base layer 103 Ink layer 40 Label 50 Label Groups

Claims

1. obtaining a label having a substrate and an ink layer containing ink, the substrate and the ink being separable by an alkaline solution; a first crushing step of crushing the label into label pieces of a first size; a separation step of treating the label piece with the alkaline solution to separate the label piece into a base material piece and the ink; a second crushing step of crushing the base material pieces generated in the separation step into base material pieces of a second size smaller than the first size; A step of drying the base material pieces of the second size generated in the second crushing step; How to reuse labels, including:

2. The method for reusing labels according to claim 1 , wherein the longest side of the label piece of the first size is between 20 mm and 50 mm.

3. The method for reusing labels according to claim 1 or 2, wherein the longest side of the base material piece of the second size is 5 mm or more and less than 20 mm.

4. The label is a shrink label, Prior to the first crushing step, The method for reusing a label according to any one of claims 1 to 3, further comprising a heating step of heating the label.

5. The method for recycling a label according to claim 4, wherein the heating step is carried out at a temperature of 80°C or higher.

6. The method for reusing a label according to claim 4 or 5, wherein a temperature of the alkaline solution in the separating step is lower than a heating temperature in the heating step.

Images