Method for recovering substrates and method for recycling substrates

Abstract

To provide a method for recovering ink that recovers ink from a label in a state in which deterioration is suppressed, a method for recovering a base material that removes ink from the base material to recover the base material, a method for recycling a base material, and a method for manufacturing a regenerated base material.SOLUTION: There is provided a method for recovering ink, comprising: steps (S1 to S5) for acquiring a label (11) that is a label having a base material and an ink layer containing ink, and that is separable between the base material and the ink by an alkaline solution; a first alkaline treatment step (S7) for treating the label (11) with the alkaline solution with a first concentration of 0.05 wt.% or more and 0.5 wt.% or less; and a step (S8) for recovering the ink separated in the first alkaline treatment step (S7).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for recovering ink from a label of a plastic product, a method for recovering a substrate, a method for recycling the substrate, and a method for manufacturing a recycled substrate.

Background Art

[0002] Conventionally, plastic products such as bottles made of polyethylene terephthalate (PET) have been widely used as containers for beverages and the like. From the viewpoints of resource saving and environmental protection, etc., it is required to reuse plastic products such as PET bottles.

[0003] Among plastic products, in particular, the reuse of PET bottles as resins, that is, material recycling, has already become widespread. On the other hand, a label on which printing for displaying product information and the like is applied to a plastic substrate may be attached to the body of a PET bottle, but the material recycling of labels is currently slow in spreading.

[0004] In order to reuse a label as material recycling, 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 coat layer (underlayer) soluble in an alkaline aqueous solution, and 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

Summary of the Invention

Problems to be Solved by the Invention

[0006] Labels recovered by the method described in Patent Document 1 are crushed, the ink layer is separated from the substrate, dried, and then reused. It is required that not only the substrate but also the ink be reused.

[0007] The present invention aims to provide an ink recovery method for recovering ink from labels while reducing ink deterioration due to alkaline solutions, a substrate recovery method for recovering substrates by removing ink from substrates constituting labels, a substrate recycling method, and a method for manufacturing recycled substrates. [Means for solving the problem]

[0008] A method for recovering ink according to one aspect of the present invention includes the steps of: obtaining a label having a substrate and an ink layer containing ink, wherein the substrate and the ink can be separated by an alkaline solution; a first alkaline treatment step of treating the label with an alkaline solution having a first concentration of 0.05% by weight or more and 0.5% by weight or less; and recovering the ink separated by the first alkaline treatment step.

[0009] A method for recovering a substrate according to one aspect of the present invention includes a second alkali treatment step of treating the substrate obtained in the first alkali treatment step in the ink recovery method described above with an alkali solution having a second concentration higher than the first concentration, and a recovery step of recovering the substrate that has undergone the second alkali treatment step.

[0010] A method for recycling a substrate according to one aspect of the present invention includes a step of converting the substrate obtained from the recovery step in the above-described method for recovering a substrate into pellets or fluff.

[0011] A method for manufacturing a raw material according to one aspect of the present invention involves manufacturing a recycled material using the pellets or fluff obtained by the above-mentioned step in the material recycling method. [Effects of the Invention]

[0012] According to one aspect of the present invention, ink can be recovered with reduced deterioration due to alkaline solutions. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view of a label according to Embodiment 1 of the present invention. [Figure 2] This is a schematic diagram showing an example of a flow chart for the ink and substrate recovery method according to Embodiment 1. [Figure 3] This is a schematic cross-sectional view of the label relating to a modified example. [Figure 4] This is a schematic cross-sectional view of a label related to an experimental example. [Modes for carrying out the invention]

[0014] The following describes in detail, with reference to the drawings, an example of an embodiment of the present disclosure regarding the recovery method of ink and labels. However, the following description is just one example of the recovery method of ink and substrate according to the present invention, and the technical scope of the present invention is not limited to the illustrated example.

[0015] [Technical concept of the present invention] As mentioned above, there is a need to reuse the ink in addition to the label substrate. However, the inventors have found that when labels are treated with an alkaline solution, the entire pigment contained in the ink, or the surface of the pigment, may deteriorate, hindering the reuse of the ink. The inventors have found that by treating labels with an alkaline solution of a first concentration of 0.5% by weight or less, most of the ink can be recovered from the labels while reducing the deterioration of the pigment. Furthermore, they have found that by treating the substrate from which most of the ink has been removed by treatment with the first concentration alkaline solution with a second concentration alkaline solution that is higher than the first concentration, the remaining ink can be detached from the substrate, and a substrate of good quality can be recovered, thus completing the present invention.

[0016] That is, the ink recovery method according to one aspect of the present invention includes a step of obtaining a label having a base material and an ink layer containing ink, the label being separable between the base material and the ink by an alkaline solution, a first alkali treatment step of treating the label with an alkaline solution having a first concentration of 0.05% by weight or more and 0.5% by weight or less, and a step of recovering the ink separated by the first alkali treatment step.

[0017] The base material recovery method according to one aspect of the present invention includes a second alkali treatment step of treating the base material obtained by the first alkali treatment step in the above-described ink recovery method with an alkaline solution having a second concentration higher than the first concentration, and a step of recovering the base material that has undergone the second alkali treatment step.

[0018] [Embodiment 1] Hereinafter, a specific description will be given based on Embodiment 1. [Label] FIG. 1 shows a schematic cross-sectional view of the label 11 of Embodiment 1. As shown in FIG. 1, the label 11 includes a base material 101, an alkali-soluble underlayer 102 laminated on the base material 101, and an ink layer 103 laminated on the underlayer 102. The label 11 may be a heat-shrinkable label (shrink label) or a label without heat shrinkability. Also, the label 11 may be a stretch label having self-stretchability or a label without self-stretchability. It may be a pouch.

[0019] [Base material] The base material 101 is a substrate containing a resin capable of supporting the underlayer 102 and the ink layer 103. As the resin contained in the base material 101, for example, polyester resins (PET, polyethylene naphthalate, polylactic acid, etc.), polystyrene resins (polystyrene, styrene-butadiene copolymer, etc.), polyolefin resins (polyethylene, polypropylene, etc.), polyvinyl chloride resins, polyamide resins, aramid resins, polyimide resins, polyphenylene sulfide resins, or acrylic resins can be used. The base material 101 may contain one type of these resins or two or more types.

[0020] As the resin contained in the base material 101, it is preferable to use a polyester resin, and among them, it is particularly preferable to use PET. PET is a polyester resin containing terephthalic acid as the main component of the dicarboxylic acid component and ethylene glycol as the main component of the diol component. Further, PET may contain, as other components, for example, dicarboxylic acids such as isophthalic acid, phthalic acid, adipic acid, sebacic acid, or naphthalenedicarboxylic acid, and may contain, for example, diol components such as diethylene glycol, neopentyl glycol, polyalkylene glycol, or 1,4-cyclohexanedimethanol.

[0021] The base material 101 may be, for example, a film having heat shrinkability (shrink film). When the base material 101 is a shrink film, the processability (followability to the container) and the decorativeness of the label 11 can be improved. The base material 101 may also be, for example, a stretch film having self-stretchability.

[0022] The base material 101 may be a single-layer film composed of one layer or a multilayer film composed of two or more layers. Also, the thickness of the base material 101 can be, for example, 5 μm or more and 100 μm or less, but is not particularly limited. The thickness of the base material 101 is more preferably 10 μm or more and 60 μm or less.

[0023] <Underlayer> The base layer 102 is located between the substrate 101 and the ink layer 103 and is a layer containing an alkali-soluble resin. Examples of resins contained in the base layer 102 include acrylic acid copolymer resins. An acrylic acid copolymer resin is a resin that contains acrylic acid and / or methacrylic acid as its main repeating units, and also contains copolymer monomers that can copolymerize with acrylic acid and / or methacrylic acid. Preferably, the acrylic acid copolymer resin is a methacrylic acid-methylmethacrylic acid copolymer. Preferably, the total proportion of acrylic acid and / or methacrylic acid and copolymer monomers in the acrylic acid copolymer resin is 60 mol% or more. In addition to the above-mentioned resins, the base layer 102 may also contain cellulose derivatives, vinyl chloride-vinyl acetate copolymers, esters of acetic acid and lower alcohols such as ethyl acetate and n-propyl acetate.

[0024] The thickness of the underlayer 102 can be, for example, 0.1 μm or more and 5 μm or less, and preferably 0.3 μm or more and 3 μm or less, but is not particularly limited.

[0025] <Ink layer> The ink layer 103 is located on the opposite side of the substrate 101 of the base layer 102 and is a layer containing ink. The ink contained in the ink layer 103 may include, for example, pigments, resins, and additives. Preferably, the ink layer 103 is a design printing layer. The design printing layer is a layer that contains pigments and displays visible patterns or characters. Examples of oil-based inks include those formulated with colorants such as pigments and dyes, binder resins such as acrylic resins, urethane resins, polyester resins, and polyamide resins, and organic solvents, with additives. Examples of water-based inks include those formulated with colorants, water-soluble or water-dispersible binder resins, additives, etc. Examples of additives include lubricants, anti-blocking agents, and anti-settling agents. The ink layer 103 may be provided over the entire surface of the base layer 102, or it may be provided on a part of the base layer 102. Furthermore, the ink layer 103 may be a single layer or a multi-layered layer. The thickness of the ink layer 103 can be, for example, 0.1 μm or more and 30 μm or less, but is not particularly limited.

[0026] [Label manufacturing method] The 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, for example, by forming a film by a method such as inflation, extrusion, or calendering, and if necessary, by subjecting the film to further stretching treatment.

[0027] Next, a base layer 102 is formed on one surface of the substrate 101. The base layer 102 can be formed, for example, by applying a composition containing the resin contained in the base layer 102 to one surface of the substrate 101 and then drying and solidifying it.

[0028] 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 the above-mentioned ink for forming the ink layer 103 to the surface of the base layer 102 and then drying and solidifying it. The ink layer 103 may also be formed by printing, marking, mixing, etc. Known printing methods include gravure printing, flexographic printing, screen printing, inkjet printing, etc. Multiple printing methods may be combined.

[0029] [How to attach the label] The label 11 is attached to a container (for example, a PET bottle), and is wrapped around the container such that the printed side (i.e., the side where the ink layer 103 is located) faces the container. Various methods can be used for wrapping. 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 it once, 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 tube beforehand, placed over the container, and then the label 11 can be shrunk.

[0030] [Method for recovering ink and substrate] Figure 2 is a schematic diagram showing an example of a flow chart of the ink and substrate recovery method according to Embodiment 1. As shown in Figure 2, the ink and substrate recovery method includes a PET bottle recovery step S1, a compression step S2, an accumulation step S3, a label group recovery step S4, a separation step S5, a crushing step S6, a first alkali treatment step S7, a separation step (ink recovery step) S8, a second alkali treatment step S9, and a separation recovery step (substrate recovery step) S10. Steps S1 to S8 correspond to the respective steps in the ink recovery method. The steps of the ink and substrate recovery method will now be described with reference to Figure 2.

[0031] <Bottle collection process> As shown in S1 of Figure 2, used PET bottles (items) 10 are collected in a collection box 12. A label 11 or label 40 having an alkali-soluble base layer 102 and an ink layer 103 is attached to the body of the PET bottle 10. Label 40 is a label in which the base layer is not alkali-soluble, or in which there is no base layer and the ink layer is directly formed on the surface of the substrate, the ink layer is not alkali-soluble and the substrate cannot be separated.

[0032] The article to which 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 label 11 or label 40 is not particularly limited and may be a shrink label, a roll label, a stretch label, or a pouch.

[0033] <Compression process> As shown in S2 of Figure 2, the collected PET bottles 10 are compressed with the labels 11 or 40 attached to form labeled bales 20.

[0034] <Integration Process> As shown in S3 of Figure 2, the labeled bales 20 are collected and sent to the recycling plant 30.

[0035] <Label collection process> As shown in S4 of Figure 2, the label group 50, including the label 11 and label 40 of Embodiment 1, is recovered. At the recycling plant 30, the labels 11 or 40 are removed from the PET bottles 10 of the labeled bale 20, separating the PET bottles 10 from the label group 50 including the labels 11 and 40, and the label group 50 is recovered. The PET bottles 10 are reused, for example, in an existing recycling process.

[0036] <Separation process> Next, as shown in S5 of Figure 2, the labels 11 are separated from the collected label group 50. One method of separation is to mark or indicate on the labels 11 that they are reusable and read this mark. The separated labels 11 are transported to the crusher 70 for the crushing process S6 described below. The separated labels 40 are transported to a thermal recycling plant, for example, and used for thermal recycling.

[0037] <Crushing process> As shown in S6 of Figure 2, the label 11 is crushed by the crusher 70 to produce label pieces 71. In the crushing step S6, prior to removing the ink layer 103 from the label 11 in the subsequent first alkali treatment step S7, the label 11 is crushed into smaller label pieces 71. By performing the first alkali treatment step S7 with the label 11 in the state of smaller label pieces 71, the ink layer 103 can be efficiently removed from the label pieces 71 in the first alkali treatment step S7.

[0038] The method for crushing the label 11 is not particularly limited. In the first alkali treatment step S7 described later, the label 11 is crushed into pieces of a size (for example, several centimeters square) that allows for efficient removal of the ink layer 103 from the label pieces 71.

[0039] Note that the crushing step S6 is not mandatory and can be omitted. In this case, the first alkali treatment step S7 is performed on the label 11. Also, if the label 11 is a shrink label, preheating may be performed before the crushing step S6 to control the amount of curling of the label piece 71, so that the ink layer 103 can be properly removed from the surface of the label piece 71 in the first alkali treatment step S7 described below.

[0040] <First Alkali Treatment Process> As shown in S7 of Figure 2, the underlayer 102 is dissolved by performing a first alkaline treatment on the label piece 71. Specifically, in the first alkaline treatment, an alkaline aqueous solution (first alkaline solution) 80 having a first concentration as the alkaline solution is added to a hot alkaline bath 82 and maintained at a predetermined temperature of 50°C to 95°C. After that, the label piece 71 is immersed in the first alkaline solution 80. At this time, it may be gently stirred. The concentration of the first alkaline solution 80 (first concentration) is 0.05% by weight or more and 0.5% by weight or less. This makes it possible to detach and recover most of the ink layer 103 from the label piece 71 while reducing the deterioration of the entire pigment or the surface of the pigment of the ink. If the first concentration is less than 0.05% by weight, the ink is difficult to detach from the substrate 101 even when physical action is applied (for example, rubbing the label piece 71 with a brush, or bringing the label pieces 71 into contact with each other). On the other hand, if the first concentration is 0.05% by weight or more, the ink layer 103 can be removed by at least physical action. It is even more preferable that the first concentration is 0.1% by weight or more and 0.5% by weight or less. In this case, approximately 100% of the ink layer 103 can be removed by applying physical action as needed. It is particularly preferable that the first concentration is 0.17% by weight or more and 0.5% by weight or less. In this case, approximately 100% of the ink layer 103 can be removed from the substrate 101 without applying physical action.

[0041] The composition of the first alkaline 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 it. For example, the first alkaline solution 80 can be 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. A surfactant may also be added to the first alkaline solution 80 to further improve the desorption of ink from the substrate 101. The concentration of the first alkaline solution 80 may be determined according to its composition.

[0042] The immersion time of the label piece 71 in the first alkaline solution 80 depends on the first concentration, but is preferably 15 minutes or less. In this case, the ink layer 103 can be detached from the label piece 71 while the deterioration of the ink pigment is reduced. The lower the first concentration, the more preferable it is to increase the immersion time. From the viewpoint of further reducing the deterioration of the ink pigment, a shorter immersion time is preferable, and as can be inferred from the experimental examples described later, an immersion time of 14 minutes or less is more preferable, and 12 minutes or less is even more preferable.

[0043] The first alkaline solution 80 is not limited to an alkaline aqueous solution and may contain a solvent other than water. For example, the first alkaline 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. In the first alkaline treatment step S7, instead of immersing the label piece 71 in the first alkaline solution 80, the first alkaline solution 80 may be sprayed onto the label piece 71.

[0044] <Separation process> The label piece 71 is subjected to a first alkali treatment process, and the resulting base material piece, which is most of the ink layer 103 removed from the base material 101 of the label piece 71, is called the base material piece 72. As shown in S8 of Figure 2, the base material piece 72 and the detached pieces 93 generated by the detachment of the ink layer 103 are collected separately in the hot alkali bath 82. For example, the base material piece 72 after the ink layer 103 has detached from the label piece 71 is collected in the first sieve 90 which has a relatively large opening, and the detached pieces 93 of the ink layer 103, which are smaller than the base material piece 72, are collected in the second sieve 92 which has a relatively small opening. The detached pieces 93 collected in the second sieve 92 are reused as ink. As described above, the deterioration of the ink pigment is reduced. If the ink layer 103 contains water-based ink and the water-based ink dissolves in the first alkaline solution 80, in the separation step S8, the water-based ink is agglomerated by solvent evaporation, extraction, etc., instead of sieving, and then separated and recovered by centrifugation, filtration, etc.

[0045] If the ink layer 103 naturally peels off from the substrate 101 without requiring any physical action such as applying running water to the substrate 101, rubbing with fingers or a brush, or rubbing while applying running water, the detached pieces 93 of the ink layer 103 can be collected by sieving without performing any physical treatment. When the first concentration is low, or when physical action is required to peel off the ink layer 103, after the first alkali treatment step S7, the ink layer 103 is peeled off by performing physical treatment such as applying running water, rubbing with fingers or a brush, or rubbing while applying running water, and then sieving is performed.

[0046] The base material pieces 72 are transported to the hot alkali bath 86 for the second alkali treatment step S9 described below. The first alkali solution 80 after the base material pieces 72 and detached pieces 93 have been collected may be disposed of as waste liquid, or it may be reused as the first alkali solution 80 used in another first alkali treatment step S7. Alternatively, its concentration may be adjusted and it may be used as the second alkali solution 84 for the second alkali treatment described below.

[0047] <Second Alkali Treatment Process> As shown in S9 of Figure 2, in the second alkali treatment step, an alkaline aqueous solution (second alkaline solution) 84 having a second concentration higher than the first concentration as an alkaline solution is added to the hot alkali bath 86 and maintained at a predetermined temperature of 50°C to 95°C. After that, the base material pieces 72 recovered in the separation step are immersed in the second alkaline solution 84 and stirred. This removes the ink layer 103 that remained slightly on the base material pieces 72, and base material pieces 91 with almost no ink layer 103 remaining can be obtained. The concentration of the second alkaline solution 84 (second concentration) is preferably 1% by weight or more and 6% by weight or less. Experiments have confirmed that in this case, the ink layer 103 can be efficiently removed from the base material pieces 72. When the second concentration exceeds 6% by weight, it is undesirable from the viewpoint of safety, processing, and cost. The second concentration is more preferably 2% by weight or less, and even more preferably 1.5% by weight or less. Aside from the difference in concentration, the second alkaline solution 84 may have the same composition as the first alkaline solution 80. The second alkaline solution 84 is not limited to an alkaline aqueous solution, and like the first alkaline solution 80, it may contain a solvent other than water as the solvent.

[0048] The immersion time of the base material piece 72 in the second alkaline solution 84 depends on the second concentration, but is preferably 30 seconds to 20 minutes. In this case, the ink layer 103 can be detached from the base material piece 72. The lower the second concentration, the more preferable it is to increase the immersion time. Since the first alkaline treatment step S7 has been performed, the immersion time in the second alkaline solution 84 of the second concentration (corresponding to the concentration of the conventional alkaline treatment) can be reduced, thereby reducing damage to the base material piece 72. From the viewpoint of efficiency and reducing damage to the base material piece 72, a shorter immersion time is preferable. As can be inferred from the experimental examples described later, the immersion time is more preferably 10 minutes or less, even more preferably 5 minutes or less, and particularly preferably 4 minutes or less.

[0049] <Separation and Collection Process> As shown in S10 of Figure 2, the base material pieces 91 and detached pieces 93 are recovered separately from the hot alkaline bath 86. For example, the first sieve 90 collects the base material pieces 91 after the ink layer 103 has detached from the base material pieces 72, and the second sieve 92, which has a smaller opening than the first sieve 90, collects the detached pieces 93 of the ink layer 103 that are smaller than the base material pieces 91. The detached pieces 93 collected by the second sieve 92 could be reused as ink, but considering the possibility of degradation, it is preferable to use them for thermal recycling rather than reusing the ink in the separation and recovery process S10.

[0050] If the ink layer 103 contains water-based ink and the water-based ink dissolves in the second alkaline solution 84, then in the separation and recovery process S10, the water-based ink is agglomerated by solvent evaporation, extraction, etc., instead of sieving, and then separated and recovered by centrifugation, filtration, etc.

[0051] The second alkaline solution 84, after the base material pieces 91 and detached pieces 93 have been collected, can be reused as the second alkaline solution 84 used in another second alkaline treatment step. Since most of the ink has been detached from the first alkaline solution 80 of the first alkaline treatment, the contamination level of the second alkaline solution 84 is low, and it can be reused. It may also be used as the first alkaline solution 80 for the first alkaline treatment by changing its concentration. This suppresses the generation of a large amount of contaminated water with a high concentration of ink, as is the case when alkaline treatment is performed all at once with a conventional high-concentration alkaline aqueous solution.

[0052] [Methods for recycling base materials] The substrate recycling method according to Embodiment 1 includes a step of turning the substrate pieces 91 obtained in the separate collection step S10 of the substrate recovery method described above into pellets or fluffs.

[0053] [Method for manufacturing recycled substrates] The method for manufacturing recycled substrates according to Embodiment 1 involves manufacturing recycled substrates using pellets or fluff obtained by the above-described step in the substrate recycling method. Furthermore, recycled labels can also be manufactured by mixing the substrate pieces 91 into the raw materials for new label substrates.

[0054] [Differentiation] Figure 3 is a schematic cross-sectional view of a modified label 13. The label 13 comprises a substrate 101 and an alkali-soluble ink layer 103 formed on one surface of the substrate 101. The ink layer 103 contains a vehicle resin such as a styrene-acrylic acid copolymer and / or a styrene-maleic acid copolymer, and is formed in the same manner as in Embodiment 1. In the modified label 13, in the first alkali treatment step S7 described above, the ink layer 103 separates from the substrate 101 and dissolves in the first alkali solution 80. In the separation step S8, instead of sieving, the ink is agglomerated by solvent evaporation, extraction, etc., separated by centrifugation, filtration, etc., and recovered. In the second alkali treatment step S9 described above, the ink layer 103 separates from the substrate 101 and dissolves in the second alkali solution 84. The ink dissolved in the second alkaline solution 84 is recovered in the separation and recovery process S10 by coagulation through solvent evaporation, extraction, etc., instead of sieving, and then separated by centrifugation, filtration, etc.

[0055] [summary] As described above, according to the ink recovery method of Embodiment 1, by processing with the first alkaline solution 80 of the first concentration, the ink can be recovered by detaching most of the ink layer 103 from the substrate 101 without affecting the pigment. The recovered ink is less affected by alkali, making it easier to reuse. When the first alkaline treatment step S7 is performed by immersing the label 11 in the first alkaline solution 80, the ink can be detached from the label piece 71 while the deterioration of the ink pigment is reduced. From the viewpoint of detachment efficiency, the immersion time is preferably 15 minutes or less, and more preferably 12 minutes or less. When the first concentration is 0.1% by weight or more and 0.5% by weight or less, approximately 100% of the ink layer 103 can be detached by applying physical action as needed.

[0056] According to the substrate recovery method of Embodiment 1, the treatment using the second alkaline solution 84 of the second concentration allows for the removal of any ink remaining on the substrate piece 72, improving the quality of the reusable substrate piece 91. When the second concentration is 1% by weight or more and 6% by weight or less, the ink can be efficiently removed from the substrate piece 72. When the second alkaline treatment step S9 is performed by immersing the substrate piece 72 for 30 seconds or more and 20 minutes or less, the ink layer 103 can be well removed from the substrate piece 72. Because the first alkaline treatment step S7 has been performed, the treatment time of the second alkaline treatment step S9 can be shortened, resulting in less damage to the substrate piece 72, and the high-concentration second alkaline solution 84 is less likely to be contaminated, making it possible to reuse the solution repeatedly. The immersion time in the second alkaline treatment step S9 is preferably 10 minutes or less, and more preferably 5 minutes or less.

[0057] According to the substrate recycling method of Embodiment 1, high-quality pellets or fluff can be obtained using substrate pieces 91 from which no ink remains.

[0058] According to the manufacturing method of the recycled substrate of Embodiment 1, a recycled substrate of good quality can be manufactured using pellets or fluff obtained from substrate pieces 91 that do not have any ink remaining on them.

[0059] According to the method for recovering ink and substrate, the method for recycling substrate, and the method for manufacturing recycled substrate according to Embodiment 1, the substrate and ink of the label 11 can be reused in a state of good quality, and this can contribute to achieving the Sustainable Development Goals (SDGs).

[0060] [Example of experiment] The following describes the results of an experiment in which the degree of ink detachment from the substrate 101 of label 14 was investigated by varying the concentration of the alkaline solution.

[0061] <label> Label 14 used in the experimental example was prepared as follows. Figure 4 is a schematic cross-sectional view of label 14 related to the experimental example. A PET film with a thickness of 20 μm was prepared as the base material 101. Using a gravure proofing machine, a composition for forming the base layer 102 was applied to one surface of the base material 101 and dried and solidified to form the base layer 102. The composition contains an acrylic acid copolymer resin as a base resin, a cellulose derivative, and a vinyl chloride-vinyl acetate copolymer. Next, using a gravure proofing machine, an ink resin composition containing Etna red as an ink was applied to the base layer 102 and solidified to form the color layer 103a (ink layer). Using a gravure proofing machine, an ink resin composition containing white ink (NT Hi-Lamic (NF) 701 white) was applied to the surface of the color layer 103a and solidified to form the white ink layer 103b. Using a gravure proofing machine, a medium was applied to the surface of the white ink layer 103b and solidified to form an overcoat layer 104. Through these steps, the experimental label 14 (100 mm x 200 mm) was completed. Label pieces were produced by crushing this label 14 into 40 mm x 40 mm pieces.

[0062] <Experiment on ink detachment> In a 500 ml beaker, 300 ml of NaOH aqueous solution, adjusted to the concentrations shown in Table 1 for each experimental example, was added as an alkaline solution. Label pieces were immersed in these NaOH aqueous solutions and gently stirred with a hot stirrer. The time it took for the ink to peel off naturally in the beaker and for the substrate 101 to become transparent was measured. If the ink did not peel off, stirring was continued for 20 minutes, and then the coating layers (color layer 103a, white ink layer 103b, and overcoat layer 104) were lightly rubbed with a finger in running water to check whether the coating layers peeled off or not.

[0063] [Table 1]

[0064] Table 1 shows that when the concentration of the alkaline solution is 0.05% by weight or higher, the ink can be removed by at least physical action, so the alkaline solutions in Experimental Examples 1-4 (concentrations of 0.05% to 0.5% by weight) can be used as the first alkaline solution 80. Furthermore, when the concentration of the first alkaline solution is greater than 0.1% by weight and 0.5% by weight or less, it can be seen that most of the ink can be removed and recovered in about 12 to 15 minutes without applying any physical action. For this reason, it is more preferable that the concentration of the first alkaline solution 80 is greater than 0.1% by weight and 0.5% by weight or less. In addition, if the concentration of the alkaline solution is 0.5% by weight or less, the possibility of deterioration of the ink pigment is low, and even if deterioration occurs, it will be to a minor degree.

[0065] The alkaline solutions in Experimental Examples 5 and 6 have high concentrations of 1% by weight and 1.5% by weight, respectively, and the ink can be detached from the substrate 101 in a short time, so they can be used as the second alkaline solution 84.

[0066] As described above, it was confirmed that when the concentration of the alkaline solution is between 0.05% by weight and 0.5% by weight, at least a portion of the ink can be separated from the label and reused.

[0067] Furthermore, one aspect of this disclosure may be expressed as follows:

[0068] A method for recovering ink according to one aspect of the present invention includes the steps of: obtaining a label having a substrate and an ink layer containing ink, wherein the substrate and the ink can be separated by an alkaline solution; a first alkaline treatment step of treating the label with an alkaline solution having a first concentration of 0.05% by weight or more and 0.5% by weight or less; and recovering the ink separated by the first alkaline treatment step.

[0069] In one embodiment of the present invention, the ink recovery method is such that the first concentration is 0.1% by weight or more and 0.5% by weight or less.

[0070] A method for recovering a substrate according to one aspect of the present invention includes a second alkali treatment step of treating the substrate obtained in the first alkali treatment step in the ink recovery method described above with an alkali solution having a second concentration higher than the first concentration, and a recovery step of recovering the substrate that has undergone the second alkali treatment step.

[0071] In one embodiment of the present invention, the method for recovering a substrate is such that the second concentration may be 1% by weight or more and 6% by weight or less.

[0072] In one embodiment of the present invention, the method for recovering a substrate may be carried out by immersing the substrate in an alkaline solution having the second concentration for 30 seconds to 20 minutes in the second alkali treatment step.

[0073] A method for recycling a substrate according to one aspect of the present invention includes a step of converting the substrate obtained from the recovery step in the above-described method for recovering a substrate into pellets or fluff.

[0074] A method for manufacturing a raw material according to one aspect of the present invention involves manufacturing a recycled material using the pellets or fluff obtained by the above-mentioned step in the material recycling method. [Explanation of Symbols]

[0075] 10 PET bottles Labels 11, 13, and 14 101 Base material 102 Base layer 103 Ink layer 40 labels 50 label groups

Claims

1. A step of obtaining a label having a substrate and an ink layer containing ink, wherein the substrate and the ink can be separated by an alkaline solution, A first alkaline treatment step in which the ink is removed from the substrate using an alkaline solution having a first concentration, A second alkali treatment step involves treating the substrate obtained in the first alkali treatment step with an alkali solution having a second concentration higher than the first concentration, thereby removing any ink remaining on the substrate in the first alkali treatment step from the substrate. A recovery step for recovering the substrate after the second alkali treatment step, A method for recovering a substrate containing [the specified substance].

2. The method for recovering a substrate according to Claim 1, wherein the second concentration is 1% by weight or more and 6% by weight or less.

3. The method for recovering a substrate according to claim 1 or 2, wherein the first concentration is 0.05% by weight or more and 0.5% by weight or less.

4. The method for recovering a substrate according to claim 2, wherein the second alkali treatment step is performed by immersing the substrate in an alkaline solution having the second concentration for 30 seconds to 20 minutes.

5. A method for recycling a substrate, comprising the step of converting the substrate obtained from the recovery step in the substrate recovery method according to claim 1 or 2 into pellets or fluff.

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