Method for producing recycled material

Abstract

The purpose is to provide a method for producing a recycled material that is capable of suppressing re-adhesion of an ink layer to a plastic label while reducing the amount of water used in a water washing step.　The method for producing a recycled material includes: a) a step for immersing a plastic label having an ink layer in a treatment solution to remove the ink layer from the plastic label; b) after the step a, a step for deliquoring the plastic label so that the treatment solution content of the plastic label is 30 mass% or less; c) after the step b, a step for washing the plastic label with water; and d) after the step c, a step for obtaining a first recycled material derived from the plastic label.

Description

Manufacturing methods for recycled materials

[0001] The present invention relates to a method for producing recycled materials from recovered plastic labels.

[0002] In recent years, plastic products such as polyethylene terephthalate bottles (PET bottles) have been widely used. From the viewpoints of resource conservation and environmental considerations, there is a demand for recycling plastic products such as PET bottles. Furthermore, plastic labels (hereinafter also referred to as "plastic labels") are sometimes attached to the body of PET bottles. Plastic labels typically have an ink layer printed thereon to display product information, etc. There is a movement to reuse these plastic labels in the same way as PET bottles.

[0003] When recycling plastic labels, the ink layer is usually removed from the plastic label and the plastic label is cut into pieces, which are then melt-kneaded and pelletized. Patent Document 1 discloses a removal solution that efficiently removes the ink layer from plastic labels.

[0004] JP 2023-51162 A

[0005] The inventors have discovered that even if an ink layer can be efficiently removed from a plastic label, the next problem is the re-adhesion of the ink layer to the plastic label. Washing the plastic label with a large amount of water is considered as a method for preventing such re-adhesion, but this method has the problem of not being able to sufficiently prevent re-adhesion. Another problem is that the amount of water used in the washing process increases.

[0006] An object of the present invention is to provide a method for producing recycled materials that can reduce the amount of water used in the washing step while suppressing the re-adhesion of an ink layer to a plastic label.

[0007] The present invention relates to the following examples [1] to [4]. [1] A method for producing a recycled material, comprising: a) a step of immersing a plastic label having an ink layer in a treatment solution to remove the ink layer from the plastic label; b) a step of draining the treatment solution after step a so that the content of the treatment solution in the plastic label is 30 mass% or less; c) a step of rinsing the plastic label with water after step b; and d) a step of obtaining a first recycled material derived from the plastic label after step c. [2] The production method according to [1], wherein the pH of the plastic label subjected to step b is greater than 11.5 and the pH of the plastic label subjected to step c is 11.5 or less. [3] The production method according to [1] or [2], further comprising: e) a step of cutting the plastic label, wherein step e is performed at least before step a. [4] The manufacturing method according to any one of [1] to [3], wherein the step b includes a process of applying centrifugal force to the plastic label.

[0008] [5] The manufacturing method according to any one of [1] to [4], further comprising: f) a step of obtaining a second recycled material derived from the ink layer. [6] The manufacturing method according to [5], wherein the step f comprises: f1) a first recovery step of recovering the ink layer in the processing solution used in step a after step a. [7] The manufacturing method according to [5] or [6], wherein the step f comprises: f2) a second recovery step of recovering the ink layer in the processing solution drained in step b. [8] The manufacturing method according to any one of [5] to [7], wherein the step f comprises: f3) a third recovery step of recovering the ink layer in a solution containing water used for washing with water in step c.

[0009] According to the manufacturing method of the present invention, it is possible to manufacture a recycled material that can reduce the amount of water used in washing and can suppress the re-adhesion of the ink layer to the plastic label.

[0010] Fig. 1 is a diagram showing a flow of a method for producing a recycled material according to a first embodiment. Fig. 2 is a diagram showing an example of an apparatus configuration that can be used to perform the method for producing a recycled material shown in Fig. 1. Fig. 3 is a diagram showing a flow of a method for producing a recycled material according to a second embodiment.

[0011] The present invention is a method for producing recycled materials, and includes the following steps a, b, c, and d: a) a step of immersing a plastic label having an ink layer in a treatment solution to remove the ink layer from the plastic label; b) a step of draining the treatment solution after step a so that the treatment solution content of the plastic label is 30% by mass or less; c) a step of washing the plastic label with water after step b; and d) a step of obtaining a first recycled material derived from the plastic label after step c.

[0012] Various raw materials are used for the label substrate of plastic labels. In the manufacturing method of recycled materials, it is preferable to obtain recycled materials for each raw material. To achieve this, it is preferable to have a sorting step in which plastic labels contained in recovered labels are sorted by raw material. The sorting step may be performed before step a or after step c.

[0013] The method for producing a recycled material of the present invention may further include the following step e): e) cutting the plastic label. Step e is performed at least before step a, and may be performed at a timing other than before step a.

[0014] The method for producing a recycled material of the present invention may further include the following step f): f) obtaining a second recycled material derived from the ink layer.

[0015] <Plastic Labels> In this invention, recycled materials are produced using recovered labels. Recovered labels include plastic labels. Furthermore, the plastic labels in the recovered labels are not limited to those peeled off from PET bottles and other materials. They may also include printed plastic films (label substrates, as described below) that are discarded from factories as defective products due to poor printing or scrap materials during the plastic label manufacturing process and then recovered. There are various types of plastic labels. Plastic labels can be classified, for example, by their application (attachment method, attachment target), size, and raw materials. Plastic labels can also be classified into shrink labels, wrap labels, stretch labels, tack labels, and other labels based on their attachment method. Shrink labels are attached to containers by heat shrinkage. Heat-shrinkable cap seals that seal the opening of a container by heat shrinkage are also included in shrink labels. Wrap labels are attached by wrapping them around the container and gluing or fusing the label edge. Stretch labels are attached to containers by self-stretching. Tack labels are attached to containers by affixing them to the container using an adhesive such as a pressure-sensitive adhesive. Plastic labels also include those made of heat-shrinkable film (overwrap film with product designs printed on it) that covers cup containers for instant noodles and the like, labels that are wrapped around containers for prepared foods such as natto, and labels used to seal bundles or collections of goods or to tie around clothing. Examples of label recovery items include shrink labels and wrap-around labels.

[0016] A plastic label usually has a label substrate and an ink layer provided on at least one surface of the label substrate, but ink layers may also be provided on both surfaces of the label substrate.

[0017] The ink layer is not particularly limited as long as it is detachable from the label substrate, but it is preferably one that dissolves or swells in the treatment solution and is detachable from the label substrate. The ink layer may be formed, for example, with an oil-based ink (solvent-based ink) or a water-based ink. The ink layer may also be composed of a UV-curable ink. Oil-based inks may be those containing additives in addition to a colorant such as a pigment or dye, a binder resin, and an organic solvent. Water-based inks may be those containing water and a colorant, a water-soluble or water-dispersible binder resin, additives, etc. UV-curable inks may be those containing additives such as a colorant, a UV-curable monomer, a UV-curable oligomer, a resin, a photopolymerization initiator, and a sensitizer. UV-curable inks are typically solvent-free inks. Additives include lubricants, anti-blocking agents, matting agents, and anti-settling agents.

[0018] The ink layer can be formed on the surface of the label substrate by, for example, gravure printing, flexographic printing, screen printing, offset printing, liquid toner printing, powder toner printing, or inkjet printing, which involves forming an ink layer on a film. The ink layer may be a single layer or multiple layers. The thickness of the ink layer can be selected appropriately depending on the application, and can be, for example, approximately 0.1 μm to 10 μm. Depending on its function, the ink layer may be a design printing layer, a base printing layer, a surface coating layer, or the like, which is provided as a single layer or in appropriate combination, and the area in which each layer is provided can also be selected appropriately. The area in which the ink layer is formed can be selected appropriately depending on its purpose.

[0019] When the ink layer is multilayered, the layer in contact with the label substrate is preferably an ink layer or anchor layer that can be removed by dissolving or swelling with a processing solution. In this case, the entire ink layer can be removed from the film substrate along with the removal of the anchor layer in contact with the label substrate. From the viewpoint of ease of removal, the anchor layer is preferably formed of either a water-based ink or an oil-based ink. When the ink layer is multilayered, all layers may be removable with a processing solution.

[0020] In plastic labels, ink layers are provided for purposes such as decoration and product display. Depending on their function, ink layers include design printing layers, undercoating layers, and surface coating layers, which are provided as single layers or in appropriate combinations. Each layer constituting the ink layer may be provided over the entire surface of the label substrate, or may be provided only on a portion depending on its purpose.

[0021] The label substrate for plastic labels is mainly made of a thermoplastic resin. Examples of thermoplastic resins include polyester films made of polyester resins such as polyethylene terephthalate resins, polyethylene naphthalate resins, and polylactic acid resins; polystyrene films made of polystyrene resins such as styrene-butadiene block copolymers; polyolefin films made of olefin resins such as polyethylene and polypropylene; and polyvinyl chloride films made of vinyl chloride resins. The thickness of the label substrate is, for example, 5 to 200 μm, and preferably 10 to 100 μm.

[0022] The label substrate for shrink labels is typically a heat-shrinkable label substrate made of a thermoplastic resin. Examples of thermoplastic resins are as described above. Among these, preferred are unidirectionally stretched polystyrene-based films (OPS films), polyethylene terephthalate-based films (PET films), coextruded films with a PET / PS / PET structure formed by laminating polystyrene-based resin and polyethylene terephthalate-based resin, and olefin-based films (especially COC / PP composite films formed from a composite material of a cyclic olefin-based resin and a polypropylene-based resin). These may also be foamed films. The shrinkable PET film is preferably a polyethylene terephthalate-based film (PETG film) made from a glycol-modified polyethylene terephthalate-based resin in which a portion of the ethylene glycol component is replaced with other diol components, such as cyclohexanedimethanol, neopentyl glycol, or diethylene glycol. The other diol components preferably account for 10% or more, more preferably 15% or more, of the total diol components. The label substrate may be a single layer or a laminate of two or more layers. The color of the label substrate is not particularly limited and may be, for example, milky white or transparent. The heat shrinkage rate (when immersed in 90°C hot water for 10 seconds) of the label substrate in at least one direction (the main shrinkage direction) is preferably 30% or more, more preferably 50% or more, from the viewpoint of shrink adhesion to various containers. Furthermore, the heat shrinkage rate (when immersed in 90°C hot water for 10 seconds) in the direction perpendicular to the main shrinkage direction of the label substrate is preferably -5 to 15%. Note that negative values ​​for the heat shrinkage rate indicate expansion. The thickness of the label substrate can be selected appropriately taking into consideration the handleability of the shrink label, but can be, for example, 10 to 100 μm, and preferably 15 to 60 μm. Note that the thicknesses listed above are values ​​for the label substrate used to prepare the shrink label before it is attached to a container.

[0023] The label substrate for a wrap-around label is primarily made of a thermoplastic resin. Examples of thermoplastic resins are as described above. Among these, polyethylene terephthalate-based films (PET films, particularly biaxially oriented PET films) and biaxially oriented polypropylene-based films (OPP films) made of polypropylene-based resins are preferred. The PET film for a wrap-around label is preferably a PET film made of unmodified polyethylene terephthalate-based resin or a PET film made of polyethylene terephthalate-based resin modified with less than 10%, more preferably 6% or less of a diol component, a dicarboxylic acid component, or both. These may also be foamed films. The label substrate may be a single layer or a laminate of two or more layers. The label substrate for a wrap-around label is preferably non-heat-shrinkable, and its heat shrinkage rate (when immersed in 90°C hot water for 10 seconds) is, for example, 5% or less, preferably 3% or less. The thickness of the label substrate is, for example, 8 to 100 μm, preferably 10 to 60 μm.

[0024] The label substrate for stretch labels is made of a polyolefin resin film. Among these, polyethylene resin films are particularly preferred. The label substrate for tack labels can be the same films as those exemplified for wrap-around labels. The label substrate for the overlap film is a heat-shrinkable biaxially oriented film made of polypropylene, polyethylene, or the like, with a thickness of approximately 6 to 30 μm. The label substrate for the strapping or banding labels can be the same films as those exemplified for wrap-around labels.

[0025] A preferred embodiment of the manufacturing method of the present invention will be described below, but the present invention is not limited thereto.

[0026] First Embodiment [Method for Producing Recycled Material] Fig. 1 is a diagram showing the flow of a method for producing a recycled material according to this embodiment. As shown in Fig. 1, the method for producing a recycled material according to this embodiment includes, in order, a sorting step S10, a cutting step S20 (corresponding to "step e"), an ink layer removing step S30 (corresponding to "step a"), a first deliquifying step S40 (corresponding to "step b"), a water-washing step S50 (corresponding to "step c"), a second deliquifying step S60, a drying step S70, and a pelletizing step S80 (corresponding to "step d").

[0027] In this embodiment, recycled materials are produced using recovered labels. The recovered labels include multiple plastic labels. The plastic labels included in the recovered labels typically have a label substrate and an ink layer on at least one surface of the label substrate. By subjecting the "plastic labels" to a cutting process S20 described below, the plastic labels are cut into "label pieces." By subjecting the "label pieces" to an ink layer removal process S30 described below, the ink layer is removed to form "label substrate pieces." In this specification, regardless of the processing situation, the object to be processed is referred to as a "plastic label," and the term "plastic label" may be used as a concept that also encompasses "label pieces" and "label substrate pieces."

[0028] <Sorting Step (S10)> In the sorting step S10, the plastic labels contained in the recovered labels are sorted. For example, they are sorted by the type of resin used in the label base material. The sorting method is not particularly limited, but examples include a method of sorting based on the infrared spectrum obtained by irradiating the labels with infrared light, a method of sorting using differences in specific gravity, a visual sorting method, and a method of sorting by imaging or visual inspection based on pre-registered information such as label design and material type.

[0029] The sorting step S10 is not essential and can be omitted. If the sorted recovered labels are to be used, the sorting step S10 is not necessary. The sorting step S10 may also be performed at a different timing, for example, after the drying step S70.

[0030] <Cutting Step (S20)> In the cutting step S20, plastic labels contained in the recovered labels are cut to produce label pieces. The cutting method in the cutting step S20 is not limited, and examples thereof include a method of crushing using a known crusher. Examples of known crushers include impact crushers such as hammer crushers and rotary crushers, shredders, cutters, and the like. The size and shape of the label pieces obtained are not limited, but the maximum length of the label pieces is preferably, for example, 50 mm or less, more preferably 30 mm or less, and even more preferably 20 mm or less. The average length of the label pieces may be, for example, 5 mm to 40 mm, or 10 mm to 30 mm.

[0031] <Ink Layer Removal Step (S30)> In the ink layer removal step S30, the ink layer is removed from the label piece. There are no limitations on the method for removing the ink layer, and it can be removed by a known method.

[0032] The ink layer removal step S30 is a step of bringing the label piece into contact with a treatment solution. The treatment solution is selected to dissolve or swell at least a portion of the ink layer of the label piece, and preferably to dissolve or swell all of the ink layer contained in the label piece.

[0033] In the ink layer removal step S30, for example, label pieces are placed in the treatment solution in the solution tank and stirred. The stirring speed and time vary depending on factors such as the amount of label pieces added, but are typically between 30 seconds and 20 minutes. The temperature of the treatment solution at this time can be normal temperature (approximately 15°C to 25°C), room temperature (1°C to 30°C), a temperature higher than normal temperature, or a high temperature (e.g., 70°C to 95°C, 75°C to 90°C).

[0034] The treatment solution is alkaline, for example, with a pH of 11 to 14, preferably greater than 11.5 and less than 13.5, and more preferably 12 to 13. The treatment solution preferably contains a component that dissolves or swells the aqueous ink layer and the oil-based ink layer at room temperature. In other words, the treatment solution preferably contains both a component that dissolves or swells the aqueous ink layer and a component that dissolves or swells the oil-based ink layer. By using such a treatment solution, ink layers on label pieces can be efficiently removed, regardless of whether they are aqueous or oil-based ink layers. Furthermore, all of the aqueous and oil-based ink layers contained in the label pieces can be simultaneously dissolved or swelled, allowing the ink layers to be separated and removed from the label pieces. Therefore, even if label pieces in recovered labels contain both aqueous and oil-based ink layers, both can be removed simultaneously. Furthermore, if the label pieces in the recovered labels contain an ultraviolet-curable ink layer as an ink layer, it is preferable that the treatment solution further contains a component that dissolves or swells the ultraviolet-curable ink layer.

[0035] Examples of the treatment solution include a solution containing at least one component selected from the group consisting of an alkaline component, a surfactant, a glycol-based solvent (e.g., glycol ether), and a high-boiling-point solvent (e.g., polymeric alcohol). The treatment solution preferably contains an alkaline component, and more preferably a solution containing an alkaline component and a surfactant. The treatment solution preferably contains water as a solvent component. The water content of the solvent component of the treatment solution is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. The treatment solution may contain components other than those listed above. The surfactant may be an ionic surfactant (anionic surfactant, cationic surfactant, or zwitterionic surfactant) or a nonionic surfactant, or a combination of these components may be used. Examples of the alkaline component include alkali metal hydroxides such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), alkali metal carbonates such as sodium carbonate (NaCO), alkali metal bicarbonates such as sodium bicarbonate (NaHCO), and ammonia water. The concentration of the alkaline component in the treatment solution can be appropriately selected within a range that does not impair the releasability, operability, workability, etc. of the ink layer, and is, for example, 0.1 to 10% by mass, preferably 0.5 to 5% by mass, and more preferably 1 to 4% by mass. By bringing the treatment solution into contact with the ink layer or label, the water-based ink layer and / or oil-based ink layer can be dissolved or swelled at room temperature.

[0036] The treatment solution may also be a mixture of an aqueous ink remover containing a component that dissolves or swells the aqueous ink layer and an oil-based ink remover containing a component that dissolves or swells the oil-based ink layer, which makes it easy to produce a treatment solution that contains both a component that dissolves or swells the aqueous ink layer and a component that dissolves or swells the oil-based ink layer.

[0037] The aqueous ink remover is not particularly limited as long as it dissolves or swells the aqueous ink layer at room temperature. The aqueous ink remover may be, for example, a commercially available aqueous ink remover for removing aqueous ink, or may be a commercially available agent (removal agent, cleaning agent, etc.) for purposes other than removing aqueous ink.

[0038] As such an aqueous ink remover, for example, a product named "Ventilation Fan Range Cleaner PRO" (manufactured by Rinrei Co., Ltd.) can be suitably used. Table 1 below shows an example of the composition and components of an aqueous ink remover (product named "Ventilation Fan Range Cleaner PRO") that can be suitably used in producing the treatment solution 80.

[0039]

[0040] As shown in Table 1, the aqueous ink remover can contain, for example, water, a glycol-based solvent (glycol ether), an amphoteric surfactant (alkyl betaine), sodium hydroxide, potassium hydroxide, a sequestering agent, and the like.

[0041] The oil-based ink remover is not particularly limited as long as it dissolves or swells the oil-based ink layer at room temperature. The oil-based ink remover may be, for example, a remover for oil-based ink that is commercially available for removing oil-based ink, or may be a chemical (remover, cleaner, etc.) that is commercially available for purposes other than removing oil-based ink.

[0042] A suitable example of such an oil-based ink remover solution is "PAINTSOLV-W," a product manufactured by Infinity Co., Ltd. Table 2 below shows an example of the composition and components of an oil-based ink remover (product name "PAINTSOLV-W") that can be suitably used to produce a treatment solution.

[0043] As shown in Table 2, the oil-based ink remover can contain, for example, a high-boiling point solvent (polymer alcohol-based solvent), a nonionic surfactant (lauryl glucoside), and the like.

[0044] By mixing an aqueous ink remover containing the components shown in Table 1 with an oil-based ink remover containing the components shown in Table 2 in a ratio of, for example, 1:9, it is possible to suitably produce a treatment solution that dissolves or swells the ink layer at room temperature.

[0045] By performing the above-described process, the processing solution contains both the label substrate fragments and the ink layer, from which the label substrate fragments are collected. The method for collecting the label substrate fragments is not limited. For example, the label substrate fragments after the ink layer has been removed can be collected using a mesh with relatively large openings, and the ink layer can be collected using a mesh with relatively small openings. Alternatively, the label substrate fragments can be collected using a mesh, and the ink layer that passes through the mesh and settles (precipitates) in the processing solution can be collected. In this case, a precipitant may be added to precipitate the ink layer, making it easier to separate from the processing solution. When collecting the label substrate fragments, it is difficult to collect only the label substrate fragments, and often a portion of the ink layer is collected along with the label substrate fragments. The inventors recognized the problem of the ink layer collected together with the label substrate fragments re-adhering to the label substrate fragments. To solve this problem, they developed the present invention, which includes a subsequent first dewatering step S40.

[0046] <First draining step (S40)> In the first draining step S40, a draining process is performed on the label substrate pieces collected in the ink layer removing step S30 so that the content of the treatment solution is 30% by mass or less, preferably 25% by mass or less. The content of the treatment solution is calculated by using the difference between the mass (W1) of the collected label substrate and the mass (W2) of the label substrate after thorough washing and drying as the content of the treatment solution. Specifically, the content of the treatment solution was calculated using the following formula (1): Treatment solution content (%) = (1 - (W1 - W2) / W1) x 100 (1)

[0047] The first draining step S40 is not limited to any method that can reduce the content of the processing solution in the label substrate pieces, and the draining process can be performed by, for example, placing the label substrate pieces in a centrifuge and rotating them to apply centrifugal force to the label substrate pieces, placing the label substrate pieces in a conveying path having a screw and conveying the label substrate pieces while the screw slams them against the wall, compressing the collected label substrate pieces, or a combination of these methods. The method using a centrifuge is preferably used.

[0048] In this embodiment, by having the first draining process S40 after the ink layer removal process S30, it is possible to reduce the amount of water used in the subsequent water washing process S50 while suppressing the re-adhesion of the ink layer on the label substrate piece.

[0049] In this embodiment, by performing a deliquoring process in the first deliquoring step S40 so that the content of the treatment solution in the label substrate piece is 30% by mass or less, the treatment solution and ink layer adhering to the label substrate piece can be removed in the ink layer removal step S30, and it is therefore presumed that even if the amount of water used in the subsequent water washing step S50 is reduced, adhesion of the ink layer can be suppressed and a sufficiently cleaned label substrate piece can be obtained. On the other hand, it is presumed that it is difficult to remove the ink layer that may adhere to the label substrate piece only in the subsequent water washing step S50 without going through the first deliquoring step S40, and therefore it is presumed that even if the amount of water used in the water washing step S50 is increased, the ink layer adhering to the label substrate piece cannot be sufficiently removed.

[0050] The pH of the label substrate pieces that have undergone the first deliquoring step S40, as measured by the following method, is preferably 11.5 or less, more preferably less than 11.0, and even more preferably 10.5 or less. The pH of the label substrate pieces is determined by drying the label substrate pieces without washing them after collection, immersing 10 g of the dried label substrate pieces in 50 g of water, and measuring the pH of the water sampled.

[0051] In this embodiment, in the first deliquifying step S40, deliquifying is performed so that the content of the treatment solution in the label substrate pieces is 30% by mass or less, thereby making it possible to set the pH of the label substrate pieces to 11.5 or less. The content of the treatment solution in the label substrate pieces subjected to the first deliquifying step S40 is expected to vary depending on the method for collecting the label substrate pieces, but if the label substrate pieces are simply collected by a method such as filtration without applying external force, the content will usually be more than 30% by mass. Furthermore, the pH of the label substrate pieces subjected to the first deliquifying step S40, measured by the above method, will usually be more than 11.5, although it will vary depending on the treatment solution used in the ink removal step S30. The label pieces that have undergone the first deliquifying step S40 are then subjected to the water washing step S50.

[0052] <Water-Rinsing Step (S50)> In the water-rinsing step S50, the label substrate pieces that have been dewatered in the first dewatering step S40 are subjected to a water-rinsing treatment. The method for rinsing the label substrate pieces is not particularly limited, and they can be washed by, for example, placing the label substrate pieces in a water tank and stirring them, stirring the label substrate pieces with a water flow, placing the label substrate pieces in a tank with a mesh at the bottom and then pouring water over them from above, or placing the label in a tank with a screw at the bottom and then pouring water over them from above. The temperature of the water in the water tank is not particularly limited, but from the perspective of energy consumption, it can be set to, for example, about room temperature (around 27°C). In the water-rinsing step (S50), the film pieces are washed so that the pH of the film pieces after the second dewatering step (S60) and the drying step (S70) is preferably 9.5 or less, more preferably 9.0 or less, and even more preferably 8.5 or less.

[0053] <Second Deliquoring Step (S60)> After the water-washing step S50, a second deliquoring step S60 is carried out to deliquore water adhering to the film pieces. The second deliquoring step S60 is not limited as long as it is a method that reduces the content of the treatment solution in the label substrate pieces, and the deliquoring process can be carried out by, for example, a method of putting the label substrate pieces into a centrifuge and rotating them to apply centrifugal force to the label substrate pieces, a method of putting the label substrate pieces into a conveying path having a screw and conveying the label substrate while the screw strikes it against the wall, a method of blowing air, or a combination of these methods.

[0054] <Drying Step (S70)> After the second deliquoring step S60, the label substrate pieces are dried to reduce the content of the treatment solution in the label substrate pieces in the drying step S70. The method for the drying step S70 is not particularly limited, but the label substrate pieces can be dried by, for example, reduced pressure heat drying, hot air drying, heat drying (by radiant heat such as hot air or infrared rays, or by self-heating due to microwaves, etc.), reduced pressure heat drying, pressurized compression drying, etc.

[0055] <Pelletizing Step (S80)> After the drying step S70, the label substrate pieces are fed into a single-screw or twin-screw extruder and melt-kneaded to produce pellets in the pelletizing step S80. The melt-kneading conditions are not particularly limited, but melt-kneading at a temperature of 130°C to 280°C is preferred to prevent deterioration of the resin performance before recycling.

[0056] In this embodiment, a process for obtaining pellets as the first recycled material (pelletization process S80) has been described, but such a process may also be a process for obtaining a first recycled material other than pellets, and examples of first recycled materials other than pellets include the film pieces themselves obtained through the drying process S70, a compressed body obtained by compressing the film pieces, etc.

[0057] <Other Steps> The method for producing recycled material according to this embodiment may include steps other than those described above, and the cutting step S20 is not limited to being performed before the ink layer removing step S30. For example, it may be performed between the ink layer removing step S30 and the first deliquifying step S40, between the first deliquifying step S40 and the water-washing step S50, between the water-washing step S50 and the second deliquifying step S60, or between the second deliquifying step S60 and the drying step S70, or it may be performed multiple times. By performing the cutting step S20 before the ink layer removing step S30, the ink layer removing step S30 can be performed efficiently.

[0058] [Recycled Material Manufacturing Apparatus] FIG. 2 is a diagram showing an example of an apparatus configuration that can sequentially perform the ink layer removal step S30, the first draining step S40, and the water washing step S50 in the recycled material manufacturing method shown in FIG.

[0059] The apparatus 100 shown in FIG. 2 comprises a processing solution tank 110, a drainer 120, a conveying path 130 with a screw, and a water washing tower 140. The processing solution tank 110 contains a processing solution 111 and an agitator 112. Label pieces 113 are agitated in the processing solution 111 by the agitator 112 to perform the ink layer removal step S30. The drainer 120 applies centrifugal force to the label substrate pieces by rotation, subjecting them to the first draining step S40. After the first draining step S40, the label substrate pieces have a processing solution content of 30% by mass or less. The label substrate pieces are then transported by the screw in the conveying path 130 to the top of the water washing tower 140. In the conveying path 130, the label substrate pieces are showered with water. The label substrate pieces are then led from above into the water washing tower 140 and transported downward while being showered with water. That is, the water washing step S50 is carried out in the conveying path 130 and the water washing tower 140. In the apparatus 100 shown in Fig. 2, a crushing blade is provided in the water washing tower 140, and the label substrate pieces are further crushed while being washed with water.

[0060] Second Embodiment [Method for Producing Recycled Material] Fig. 3 is a diagram showing the flow of the method for producing a recycled material of this embodiment. As shown in Fig. 3, the main flow of the method for producing a recycled material of this embodiment includes, in order, a sorting step S10, a cutting step S20 (a step corresponding to "step e"), an ink layer removing step S30 (a step corresponding to "step a"), an ink layer separating step S35, a first liquid-removing step S40 (a step corresponding to "step b"), a water-washing step S50 (a step corresponding to "step c"), an ink layer separating step S55, a second liquid-removing step S60, a drying step S70, and a pelletizing step S80 (a step corresponding to "step d"). In the above manufacturing method, the separating step S10, cutting step S20, ink layer removing step S30, first draining step S40, water washing step S50, second draining step S60, drying step S70, and pelletizing step S80 are the same steps as those in the flow of the manufacturing method of recycled materials shown in FIG. 1, and therefore will not be described here.

[0061] In the ink layer separating step S35, the processing solution containing the ink layer may be sent to a first ink layer recovering step S91, where the ink layer contained in the processing solution is recovered. In the first draining step S40, the drained processing solution may be sent to a second ink layer recovering step S92, where the ink layer contained in the processing solution is recovered. In the ink layer separating step S55, the processing solution containing the ink layer may be sent to a third ink layer recovering step S93, where the ink layer contained in the processing solution is recovered. In the second draining step S60, the drained processing solution may be sent to a fourth ink layer recovering step S94, where the ink layer contained in the processing solution is recovered.

[0062] The ink layers recovered in the first ink layer recovery process S91, the second ink layer recovery process S92, the third ink layer recovery process S93, and the fourth ink layer recovery process S94 are subjected to the ink material manufacturing process S95 (a process corresponding to "process f"), where a second recycled material derived from the ink layers can be obtained.

[0063] In this embodiment, it is not essential to include all of the first ink layer recovery step S91, the second ink layer recovery step S92, the third ink layer recovery step S93, and the fourth ink layer recovery step S94, but it is sufficient to include at least one of these steps. The first ink layer recovery step S91 is located upstream in the flow, and therefore can recover a large amount of ink layer, so it is preferable to include this step S91.

[0064] <First Ink Layer Recovery Step (S91)> The first ink layer recovery step S91 is a step of recovering the ink layer from the processing solution containing the ink layer separated in the ink layer separation step S35. The ink layer separation step S35 separates the label substrate piece and the ink layer from the processing solution containing the label substrate piece and the ink layer obtained in the ink layer removal step S30. As described in the ink layer removal step S30, the ink layer separation step S35 may involve collecting the label substrate piece with a mesh having openings and separating the label substrate piece from the processing solution containing the ink layer that has passed through the mesh. The processing solution containing the ink layer that has passed through the mesh is sent to the first ink layer recovery step S91. In the first ink layer recovery step S91, the ink layer is recovered from the processing solution containing the ink layer. In the first ink layer recovery step S91, for example, the ink layer may be collected and recovered by passing the treatment solution through a mesh having smaller openings than the mesh used in the ink layer separation step S35 to collect the label substrate pieces, or the ink layer that has settled (precipitated) in the treatment liquid tank may be collected and recovered.

[0065] The ink layer removing step S30, the ink layer separating step S35, and the first ink layer recovering step S91 may be different steps or may partially overlap, and it is possible to determine which step some of the processes belong to. For example, the processing solution containing the ink layer may be obtained in the ink layer removing step S30 or in the ink layer separating step S35. For example, the process of collecting the ink layer from the processing solution containing the ink layer may be performed in the ink layer separating step S35 or in the first ink layer recovering step S91.

[0066] The ink layer removal step S30 is a step of contacting the label strip with a treatment solution, and this contacting step may be performed multiple times using different treatment solutions. For example, it may be performed twice using two alkaline treatment solutions with different pH values. The higher the pH of the treatment solution, the better the ink layer removal performance, but the more likely the recovered ink layer is to be denatured. Therefore, by increasing the pH of the second treatment solution compared to the first treatment solution, a less denatured ink layer can be recovered from the first treatment solution, and an even larger ink layer can be recovered from the second treatment solution, thereby improving recovery efficiency. If the ink layer removal step S30 involves contacting the label strip with a treatment solution multiple times, the treatment solution may be recovered and sent to the first ink layer recovery step S91 after each contacting step.

[0067] <Second ink layer recovery step (S92)> The second ink layer recovery step S92 is a step in which the processing solution drained from the label substrate piece in the first draining step S40 is recovered and the ink layer contained in this processing solution is recovered. In the second ink layer recovery step S92, for example, the processing solution may be passed through a mesh having openings smaller than the ink layer contained in the processing solution to capture and recover the ink layer, or the ink layer that has settled (precipitated) in a processing liquid tank may be captured and recovered.

[0068] <Third Ink Layer Recovery Step (S93)> The third ink layer recovery step S93 is a step of recovering an ink layer from the treatment solution containing the ink layer separated in the ink layer separation step S55. The ink layer separation step S55 recovers a solution containing water used in the water washing step S50, and sends this solution to the third ink layer recovery step S93. In the third ink layer recovery step S93, for example, the treatment solution may be passed through a mesh having openings smaller than the ink layer contained in the solution to capture and recover the ink layer, or the ink layer that has settled (precipitated) in a treatment liquid tank may be captured and recovered.

[0069] <Fourth ink layer recovery step (S94)> The fourth ink layer recovery step S94 is a step in which the processing solution drained from the label substrate piece in the second draining step S60 is recovered and the ink layer contained in this processing solution is recovered. In the fourth ink layer recovery step S94, for example, the processing solution may be passed through a mesh having openings smaller than the ink layer contained in the processing solution to capture and recover the ink layer, or the ink layer that has settled (precipitated) in a processing liquid tank may be captured and recovered.

[0070] <Ink Material Manufacturing Step (S95)> The ink layers recovered in the first ink layer recovery step S91, the second ink layer recovery step S92, the third ink layer recovery step S93, and the fourth ink layer recovery step S94 are sent to the ink material manufacturing step S95. In the ink material manufacturing step S95, materials contained in the ink layers (second recycled materials) can be recovered. An example of the second recycled material is titanium dioxide, a white-white pigment contained in the ink layers. Known methods can be used to recover titanium dioxide from ink layers containing various materials. An example of a known method is the method described in Japanese Patent No. 7162710. Japanese Patent No. 7162710 describes a method of obtaining titanium dioxide by calcining an ink layer.

[0071] The present invention will be explained in more detail below by showing test examples, but the present invention is not limited to these examples.

[0072] [Preparation of Samples] Samples 1 and 2 were prepared as follows.

[0073] <Sample 1> A shrink label was formed by gravure printing an alkali-soluble coating layer on a 30 μm-thick polyester film, followed by gravure printing of oil-based color ink and white ink. The shrink label was cut into label pieces with an average size of 25 mm square. 150 L of treatment solution (1.5% alkaline aqueous solution) was placed in a 300 L kettle, and then 8 kg of the label pieces were added. The treatment solution was stirred for 15 minutes while maintaining the temperature at 80°C, and the label pieces were filtered through a mesh to produce Sample 1. The treatment solution content of Sample 1 was 250% by mass.

[0074] <Sample 2> A label piece obtained in the same manner as in the preparation of Sample 1 was subjected to a deliquoring process using a centrifuge (first deliquoring process) to obtain Sample 2. The content of the treatment solution in Sample 2 was 20% by mass.

[0075] [Water Washing Process] The entire amounts of Sample 1 and Sample 2 were placed in separate cylindrical 1 mm square mesh containers with a diameter of 400 mm and a height of 500 mm. Sample 1 and Sample 2 were then washed by showering them with washing water from above at a flow rate of 0.2 L / sec. A portion of the washed label strip was allowed to air dry, and then 10 g of the washed label strip was weighed out on an electronic balance into a beaker and mixed with 50 g of water. The pH of the mixed water was measured. For Sample 1 and Sample 2, the amount of washing water used in the washing process was increased by a predetermined amount, and the pH was measured. The pH measurement results are shown in Table 3. For Sample 1, washing was completed after 500 L of washing water was used, and for Sample 2, washing was completed after 50 L of washing water was used.

[0076]

[0077] [Visual Evaluation] The presence or absence of an ink layer on the surface after the water washing step was visually evaluated for Sample 1 and Sample 2. Although Sample 1 had been washed with 500 L of washing water, adhesion of an ink layer to the surface was confirmed. Although Sample 2 had only been washed with 50 L of washing water, adhesion of an ink layer to the surface was not confirmed.

[0078] The results shown in Table 3 show that for label pieces, by having the first dewatering step (Sample 2), the amount of cleaning water used in the water washing step to achieve a predetermined pH (for example, pH 9.5 or less) can be significantly reduced compared to when the first dewatering step is not performed (Sample 1), and staining of the surface caused by the ink layer can be suppressed.

[0079] 110 Processing solution tank, 111 Processing solution, 112 Agitator blade, 113 Label strip, 120 Deliquoring machine, 130 Conveying path, 140 Water washing tower.

Claims

1. A method for producing recycled materials, comprising: a) a step of immersing a plastic label having an ink layer in a treatment solution to remove the ink layer from the plastic label; b) a step of draining the treatment solution after step a so that the treatment solution content of the plastic label is 30% by mass or less; c) a step of washing the plastic label with water after step b; and d) a step of obtaining a first recycled material derived from the plastic label after step c.

2. The manufacturing method of claim 1, wherein the pH of the plastic label subjected to step b is greater than 11.5, and the pH of the plastic label subjected to step c is 11.5 or less.

3. The manufacturing method according to claim 1 or 2, further comprising the step of: e) cutting the plastic label, wherein step e is carried out at least before step a).

4. The manufacturing method according to claim 1 or 2, wherein step b includes applying centrifugal force to the plastic label.

5. The method of claim 1, further comprising the step of: f) obtaining a second recycled material derived from the ink layer.

6. The manufacturing method according to claim 5, wherein step f comprises: f1) a first recovery step, after step a, of recovering the ink layer in the processing solution used in step a.

7. The manufacturing method according to claim 5 or 6, wherein step f comprises: f2) a second recovery step of recovering the ink layer in the processing solution drained in step b.

8. The manufacturing method according to claim 5 or 6, wherein step f comprises: f3) a third recovery step of recovering the ink layer in a solution containing water used for washing in step c).

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