JP7657130B2 - Method for recovering ink, method for recovering substrate, method for recycling substrate, and method for manufacturing recycled substrate - Google Patents

Description

The present invention relates to a method for recovering ink from labels of plastic products, a method for recovering substrates, a method for recycling substrates, and a method for manufacturing recycled substrates.

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

Reusing PET bottles as resin, in other words, material recycling, is already widespread among plastic products. On the other hand, labels with product information printed on a plastic substrate are sometimes attached to the body of a PET bottle, but material recycling of labels has not yet taken off.

To reuse labels as part of 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 coating layer (underlayer) that is soluble in an alkaline aqueous solution, and the substrate is separated from the label by dissolving the underlayer in an alkaline aqueous solution.

JP 2003-84670 A

The labels recovered by the method described in Patent Document 1 are crushed, the ink layer is separated from the substrate, and then dried and reused. There is a demand to reuse not only the substrate but also the ink.

The present invention aims to provide an ink recovery method that recovers ink from labels while reducing deterioration of the ink caused by alkaline solutions, a substrate recovery method that removes ink from substrates that constitute labels and recovers the substrate, a substrate recycling method, and a method for manufacturing recycled substrates.

The ink recovery method according to one aspect 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 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.

The method for recovering a substrate according to one embodiment of the present invention includes a second alkaline treatment step in which the substrate obtained by the first alkaline treatment step in the above-described ink recovery method is treated with an alkaline solution having a second concentration higher than the first concentration, and a recovery step in which the substrate that has been subjected to the second alkaline treatment step is recovered.

A method for recycling a substrate according to one embodiment of the present invention includes a step of converting the substrate obtained from the recovery step in the substrate recovery method described above into pellets or fluff.

The method for producing raw substrate according to one aspect of the present invention produces recycled substrate using the pellets or fluff obtained by the above steps in the substrate recycling method.

According to one aspect of the present invention, it is possible to recover ink that has been reduced in deterioration due to alkaline solutions.

1 is a schematic cross-sectional view of a label according to a first embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a flow of a method for recovering ink and a substrate according to the first embodiment. FIG. 11 is a schematic cross-sectional view of a label according to a modified example. FIG. 13 is a schematic cross-sectional view of a label according to an experimental example.

The following describes in detail an embodiment of the ink and label recovery method, which is an example of the present disclosure, with reference to the drawings. However, the following description is an example of the ink and substrate recovery method according to the present invention, and the technical scope of the present invention is not limited to the illustrated example.

[Technical Concept of the Present Invention]
As described above, there is a demand for reusing the ink in addition to the substrate of the label. However, the present inventor has found that when the label is treated with an alkaline solution, the entire pigment contained in the ink or the surface of the pigment may be altered, which may cause problems in reusing the ink. The present inventor has found that by treating the label with an alkaline solution having a first concentration of 0.5% by weight or less, most of the ink can be recovered from the label with reduced alteration of the pigment. The present inventor has also found that by treating the substrate from which most of the ink has been removed by treatment with an alkaline solution having a second concentration higher than the first concentration, the remaining ink can be detached from the substrate, and a substrate having good quality can be recovered, thereby completing the present invention.

That is, the ink recovery method according to one aspect of the present invention includes a step 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 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 a step of recovering the ink separated by the first alkaline treatment step.

The method for recovering a substrate according to one embodiment of the present invention includes a second alkaline treatment step in which the substrate obtained by the first alkaline treatment step in the above-described ink recovery method is treated with an alkaline solution having a second concentration higher than the first concentration, and a step of recovering the substrate that has been subjected to the second alkaline treatment step.

[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 a label without heat-shrinkability. The label 11 may be a stretch label with self-stretchability or a label without self-stretchability. It may also be a pouch.

<Substrate>
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.

The resin contained in the substrate 101 is preferably a polyester resin, and more 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.

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.

The substrate 101 may be a single-layer film consisting of one layer, or may be a multilayer film consisting 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. It is more preferable that the thickness of the substrate 101 is 10 μm or more and 60 μm or less.

<Base layer>
The undercoat layer 102 is located between the substrate 101 and the ink layer 103, and is a layer containing an alkali-soluble resin. Examples of the resin contained in the undercoat layer 102 include acrylic acid copolymer resins. 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 copolymer monomer that can be copolymerized 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 copolymer monomer in the resin of 60 mol % or more. In addition to the above-mentioned resins, the undercoat layer 102 may contain cellulose derivatives, vinyl chloride-vinyl acetate copolymers, esters of acetic acid and lower alcohols such as ethyl acetate and n-propyl acetate, and the like.

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

<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.

[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.

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

Next, the 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 ink described above 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 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 be combined.

[How to attach the label]
The label 11 is attached to a container (e.g., a PET bottle) and is wrapped around the container, for example, so that the printed surface (i.e., the side on which the ink layer 103 is located) faces the container. Various wrapping methods can be used. For example, when the label 11 is a wrap-around label, one end of the label 11 is attached to the container and wrapped around the container, and the other end is attached to the surface of the one end. When the label 11 is a shrink label, the label 11 is formed into a cylindrical shape in advance, and then the label 11 is shrunk by covering the container.

[Method of recovering ink and substrate]
Fig. 2 is a schematic diagram showing an example of a flow of the ink and substrate recovery method according to the first embodiment. As shown in Fig. 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 (a step of recovering ink) S8, a second alkali treatment step S9, and a separation recovery step (a recovery step of recovering substrates) S10. The steps S1 to S8 correspond to the respective steps in the ink recovery method. Hereinafter, each step of the ink and substrate recovery method will be described with reference to Fig. 2.

<Bottle collection process>
As shown in S1 of Fig. 2, a used PET bottle (item) 10 is 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. The label 40 is a label in which the base layer is not alkali-soluble, or in the case where the label does not have a base layer and the ink layer is formed directly on the surface of the base material, the ink layer is not alkali-soluble and the base material cannot be separated.

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, a pouch, etc.

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

<Collection process>
As shown in S3 of FIG. 2, the labeled bales 20 are accumulated and sent to a recycling plant 30.

<Label collection process>
2, a label group 50 including the label 11 of embodiment 1 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.

<Sorting process>
Next, as shown in S5 of Fig. 2, the labels 11 are separated from the collected label group 50. For example, the separation method may be a method in which a description or mark indicating that the labels 11 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 crushing step S6 described below. The separated labels 40 are transported to, for example, a thermal recycling plant and used for thermal recycling.

<Crushing process>
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 103 from the label 11 in the subsequent first alkali treatment step S7, the label 11 is crushed into smaller label pieces 71. In this way, by carrying out the first alkali treatment step S7 with the label 11 in a state of being in the form 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.

The method for crushing the labels 11 is not particularly limited. The labels 11 are crushed into pieces of a size (e.g., several centimeters square) that allows the ink layer 103 to be efficiently removed from the label pieces 71 in the first alkali treatment step S7 described below.

The crushing step S6 is not essential and can be omitted. In this case, the first alkali treatment step S7 is carried out on the label 11. If the label 11 is a shrink label, preheating may be carried out before the crushing step S6 to control the amount of curling of the label piece 71, so that the ink layer 103 is satisfactorily detached from the surface of the label piece 71 in the first alkali treatment step S7 described below.

<First alkali treatment step>
As shown in S7 of FIG. 2, the label piece 71 is subjected to a first alkali treatment to dissolve the undercoat layer 102. Specifically, in the first alkali treatment, an alkaline aqueous solution (first alkaline solution) 80 having a first concentration as an alkaline solution is charged into a hot alkaline bath 82 and maintained at a predetermined temperature of 50° C. to 95° C. Then, the label piece 71 is immersed in the first alkaline solution 80. At this time, the solution may be gently stirred. The concentration (first concentration) of the first alkaline solution 80 is 0.05% by weight or more and 0.5% by weight or less. This makes it possible to remove and recover most of the ink layer 103 from the label piece 71 while reducing deterioration of the entire pigment of the ink or the surface of the pigment. When the first concentration is less than 0.05% by weight, the ink is difficult to remove from the substrate 101 even when a physical action (for example, rubbing the label piece 71 with a brush or bringing the label pieces 71 into contact with each other) is applied. On the other hand, when the first concentration is 0.05% by weight or more, the ink layer 103 can be detached by at least applying a physical action. It is more preferable that the first concentration is 0.1% by weight or more and 0.5% by weight or less. In this case, substantially 100% of the ink layer 103 can be detached by applying a physical action as necessary. 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, substantially 100% of the ink layer 103 can be detached from the substrate 101 without applying a physical action.

The composition of the first alkaline solution 80 is not particularly limited as long as the ink layer 103 can be removed from the label piece 71 by immersing the label piece 71 in the first alkaline 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 (Na ₂ CO ₃ ), an aqueous solution of an alkali metal hydrogen carbonate such as sodium hydrogen carbonate (NaHCO ₃ ), or an aqueous ammonia solution can be used as the first alkaline solution 80. A surfactant may be further added to the first alkaline solution 80 in order to improve the release of the ink from the substrate 101. The concentration of the first alkaline solution 80 may be determined according to the composition of the first alkaline solution 80.

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 with less deterioration of the ink pigment. The lower the first concentration, the longer the immersion time is preferable. From the viewpoint of further reducing deterioration of the ink pigment, a shorter immersion time is preferable, and as can be inferred from the experimental example described below, an immersion time of 14 minutes or less is more preferable, and 12 minutes or less is even more preferable.

The first alkaline solution 80 is not limited to an alkaline aqueous solution, and may contain a solvent other than water as a solvent. 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 polymeric 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 label piece 71 may be sprayed with the first alkaline solution 80.

<Sorting process>
The label piece 71 is subjected to the first alkali treatment process, and the base material piece generated by removing most of the ink layer 103 from the base material 101 of the label piece 71 is called the base material piece 72. As shown in S8 of FIG. 2, the base material piece 72 in the hot alkali bath 82 and the detached piece 93 generated by the detachment of the ink layer 103 are separately collected. For example, the base material piece 72 after the ink layer 103 is detached from the label piece 71 is collected by a first sieve 90 having a relatively large opening, and the detached piece 93 of the ink layer 103 smaller than the base material piece 72 is collected by a second sieve 92 having a relatively small opening. The detached piece 93 collected by the second sieve 92 is reused as ink. As described above, the deterioration of the pigment of the ink is reduced. If the ink layer 103 contains an aqueous ink that dissolves in the first alkaline solution 80, in the separation step S8, the aqueous ink is coagulated by solvent evaporation, extraction, etc. instead of sieving, and then separated and recovered by centrifugation, filtration, etc.

When the ink layer 103 naturally peels off from the substrate 101 without the need for physical actions such as applying running water to the substrate 101, rubbing with a finger 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 a physical action is required to peel off the ink layer 103, such as when the first concentration is low, the ink layer 103 is peeled off after the first alkali treatment step S7 by performing a physical treatment such as applying running water, rubbing with a finger or a brush, or rubbing while applying running water, and then sieving is performed.

The substrate pieces 72 are transported to a hot alkaline tank 86 for carrying out the second alkaline treatment step S9 described below. The first alkaline solution 80 after the substrate pieces 72 and detached pieces 93 have been collected may be disposed of as waste liquid, or may be reused as the first alkaline solution 80 used in another first alkaline treatment step S7. The concentration may also be adjusted and used as the second alkaline solution 84 described below for the second alkaline treatment.

<Second Alkali Treatment Step>
As shown in S9 of FIG. 2, in the second alkali treatment step, an alkaline aqueous solution (second alkaline solution) 84 having a second concentration higher than the first concentration is charged into a hot alkaline tank 86 as an alkaline solution and maintained at a predetermined temperature of 50° C. to 95° C. Thereafter, the base material pieces 72 recovered in the separation step are immersed in the second alkaline solution 84 and stirred. As a result, the ink layer 103 remaining slightly on the base material pieces 72 is detached, and base material pieces 91 with almost no ink layer 103 remaining can be obtained. The concentration (second concentration) of the second alkaline solution 84 is preferably 1% by weight or more and 6% by weight or less. In this case, it has been confirmed by experiments that the ink layer 103 can be efficiently detached from the base material pieces 72. And, if the second concentration exceeds 6% by weight, it is not preferable from the viewpoints 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. Except for the different 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, may contain a solvent other than water as a solvent.

The immersion time of the substrate piece 72 in the second alkaline solution 84 depends on the second concentration, but is preferably 30 seconds or more and 20 minutes or less. In this case, the ink layer 103 can be detached from the substrate piece 72. The lower the second concentration, the longer the immersion time is preferable. Since the substrate piece 72 has been subjected to the first alkaline treatment step S7, 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 to reduce damage to the substrate piece 72. From the viewpoint of efficiency and reduction of damage to the substrate piece 72, a shorter immersion time is preferable. As can be inferred from the experimental example 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.

<Sorting and collection process>
As shown in S10 of Fig. 2, the base material pieces 91 and the detached pieces 93 in the hot alkali bath 86 are collected separately. For example, a first sieve 90 collects the base material pieces 91 after the ink layer 103 has been detached from the base material pieces 72, and a second sieve 92 having smaller openings 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 may be reused as ink, but considering the possibility of denaturation, it is preferable that in the separation and recovery step S10, the ink is not reused but rather used for thermal recycling.

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

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 to be used in another second alkaline treatment step. Since most of the ink has been detached from the first alkaline solution 80 in the first alkaline treatment, the second alkaline solution 84 is less contaminated and can be used repeatedly. The concentration may be changed and used as the first alkaline solution 80 for the first alkaline treatment. This prevents the generation of a large amount of contaminated water with a high alkaline concentration containing ink, as occurs when alkaline treatment is performed all at once with a conventional high-concentration alkaline aqueous solution.

[Method of recycling substrate]
The method for recycling a substrate according to the first embodiment includes a step of converting the substrate pieces 91 obtained in the sorting and recovery step S10 in the substrate recovery method described above into pellets or fluff.

[Method of manufacturing recycled substrate]
The method for producing the recycled substrate according to the first embodiment produces the recycled substrate using the pellets or fluff obtained by the above-mentioned steps in the above-mentioned method for recycling the substrate. It is also possible to produce a recycled label by mixing the substrate pieces 91 into the raw material for a new label substrate.

[Modification]
FIG. 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 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 the first embodiment. In the modified label 13, in the first alkali treatment step S7, the ink layer 103 is separated from the substrate 101 and dissolved in the first alkali solution 80. In the separation step S8, the ink dissolved in the first alkali solution 80 is aggregated by solvent evaporation, extraction, etc. instead of sieving, and is separated and recovered by centrifugation, filtration, etc. In the second alkali treatment step S9, the ink layer 103 is separated from the substrate 101 and dissolved in the second alkali solution 84. In the separation and recovery step S10, the ink dissolved in the second alkaline solution 84 is coagulated by solvent evaporation, extraction, or the like instead of sieving, and then separated and recovered by centrifugation, filtration, or the like.

[summary]
As described above, according to the ink recovery method of the first embodiment, the ink can be recovered by removing most of the ink layer 103 from the substrate 101 without affecting the pigment by treatment using the first alkaline solution 80 of the first concentration. The recovered ink is less affected by the alkali, so it is easy to reuse it thereafter. When the first alkaline treatment step S7 is performed by immersing the label 11 in the first alkaline solution 80, the ink can be removed from the label piece 71 in a state where the deterioration of the ink pigment is less likely to occur. From the viewpoint of the removal 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, the ink layer 103 can be removed by approximately 100% by applying a physical action as necessary.

According to the substrate recovery method of the first embodiment, the ink remaining in the substrate piece 72 can be removed by treatment with the second alkaline solution 84 of the second concentration, and the quality of the substrate piece 91 to be reused is improved. 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 to 20 minutes or less, the ink layer 103 can be satisfactorily removed from the substrate piece 72. Since the substrate piece 72 has been subjected to the first alkaline treatment step S7, the treatment time of the second alkaline treatment step S9 can be shortened, there is little damage to the substrate piece 72, and the high concentration second alkaline solution 84 is less likely to be contaminated, so this solution can be reused repeatedly. The immersion time in the second alkaline treatment step S9 is preferably 10 minutes or less, more preferably 5 minutes or less.

According to the substrate recycling method of embodiment 1, it is possible to obtain high-quality pellets or fluff using substrate pieces 91 on which no ink remains.

According to the manufacturing method of the recycled substrate of the first embodiment, a high-quality recycled substrate can be manufactured using pellets or fluff obtained from the substrate pieces 91 on which no ink remains.

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 good quality state, thereby contributing to the achievement of the Sustainable Development Goals (SDGs).

[Experimental Example]
The following describes the results of an experiment in which the concentration of the alkaline solution was changed to examine the degree of ink detachment from the substrate 101 of the label 14 described below.

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

<Ink removal experiment>
In a 500 ml beaker, 300 ml of an aqueous NaOH solution adjusted to the concentration of each experimental example in Table 1 below was added as an alkaline solution, and the label pieces were immersed in the aqueous NaOH solution and gently stirred with a hot stirrer. The time until the ink naturally peeled off in the beaker and the substrate 101 became transparent was measured. If the ink did not peel off, stirring was continued until 20 minutes had elapsed, 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 confirm whether the coating layers peeled off or not.

From Table 1, when the concentration of the alkaline solution is 0.05% by weight or more, the ink can be removed by at least applying a physical action, so the alkaline solutions of Experimental Examples 1 to 4 (concentration 0.05% by weight to 0.5% by weight) can be used as the first alkaline solution 80. Also, when the concentration of the first alkaline solution is greater than 0.1% by weight and less than 0.5% by weight, it can be seen that most of the ink can be removed and recovered in about 12 to 15 minutes without applying a physical action. From this, it is more preferable that the concentration of the first alkaline solution 80 is greater than 0.1% by weight and less than 0.5% by weight. Also, if the concentration of the alkaline solution is less than 0.5% by weight, the possibility of the ink pigment deteriorating is low, and even if it does deteriorate, the degree of deterioration is minor.

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

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

REFERENCE SIGNS LIST 10 PET bottle 11, 13, 14 Label 101 Substrate 102 Base layer 103 Ink layer 40 Label 50 Label group

Claims (7)

obtaining a label having a substrate and an ink layer containing an ink, the substrate and the ink being separable by an alkaline solution;
a first alkali treatment step of treating the label with an alkali solution having a first concentration of 0.05% by weight or more and 0.5% by weight or less;
recovering the ink separated by the first alkali treatment;
A method for recovering ink comprising the steps of: The ink recovery method according to claim 1, wherein the first concentration is 0.1% by weight or more and 0.5% by weight or less. 3. The ink recovery method according to claim 1, further comprising: a second alkali treatment step of treating the base material obtained by the first alkali treatment step with an alkali solution having a second concentration higher than the first concentration;
a recovery step of recovering the base material that has been subjected to the second alkali treatment step;
A method for recovering a substrate comprising the steps of: The method for recovering a substrate according to claim 3, wherein the second concentration is 1% by weight or more and 6% by weight or less. The method for recovering a substrate according to claim 3 or 4, wherein the second alkaline treatment step is performed by immersing the substrate in an alkaline solution having the second concentration for 30 seconds or more and 20 minutes or less. A method for recycling a substrate, comprising a step of forming the substrate obtained in the recovery step of the substrate recovery method according to any one of claims 3 to 5 into pellets or fluff. A method for producing a recycled substrate, comprising the steps of: producing a recycled substrate using the pellets or fluff obtained by the steps of the substrate recycling method described in claim 6.

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