Recycled material production method, label, and container with label

Abstract

The present invention separates a printing layer from a substrate resin layer in a label in which the printing layer does not separate from the substrate resin layer when an adhesion layer is dissolved.　This recycled material production method comprises: immersing a label 10, which includes a substrate resin layer 21 and a printing layer 22 provided to the substrate resin layer 21 and has had all or a portion of an adhesion layer 30 on a surface thereof removed therefrom, in an alkaline solution that includes a surfactant, thereby separating the printing layer 22 from the substrate resin layer 21; and obtaining a recycled material that is derived from the substrate resin layer 21 from which the printing layer 22 has been separated.

Description

Method for producing recycled material, label, and labeled container

[0001] The present disclosure relates to a method for producing a recycled material, a label, and a labeled container.

[0002] Japanese Patent No. 6210991 (Patent Document 1) discloses a conventional cylindrical shrink label. The cylindrical shrink label includes a heat-shrinkable label base material, and a joint formed by forming the label base material into a cylindrical shape, overlapping edges of the base material with each other, and performing solvent welding on the overlapping edges. At the joint, a resin layer soluble in a hot alkaline aqueous solution is formed on at least one of the overlapping edges. Patent Document 1 discloses that in a labeled container equipped with the cylindrical shrink label, the label does not peel off from the container during distribution and use, and when discarded, the joint is peeled off by treatment with a hot alkaline aqueous solution, so that the label can be easily peeled off from the container.

[0003] Japanese Patent No. 6210991

[0004] In order to obtain a recycled material derived from the base resin layer of a label, it is conceivable to peel the label off the container and further remove the printed layer provided on the base resin layer of the label. However, when peeling the label off the container, the treatment liquid for dissolving the adhesive layer (for example, the joint formed of the resin layer in Patent Document 1) may cause the printed layer to detach from the base resin layer. If the printed layer detaches when the label is peeled off the container, the printed layer will adhere to the container. If the container is intended to be used repeatedly (a so-called returnable container such as a bottle), adhesion of the printed layer to the container is not preferable.

[0005] Here, if the printed layer is physically or chemically firmly provided on the base resin layer, it may be possible to suppress detachment of the printed layer from the base resin layer caused by the above-mentioned treatment liquid. However, in this case, it can be difficult to detach the printed layer from the base resin layer in the subsequent process.

[0006] This disclosure has been made in view of the above-mentioned problems, and its purpose is to provide a method for manufacturing recycled materials, a label, and a labeled container that can detach the printed layer from the base resin layer in a label in which the printed layer does not detach from the base resin layer when the adhesive layer is dissolved.

[0007] This disclosure relates to the following examples [1] to [6].

[0008] [1] A method for manufacturing recycled material, comprising: immersing a label, which includes a base resin layer and a printed layer provided on the base resin layer, and after a part or all of the adhesive layer on the surface has been removed, in an alkaline solution containing a surfactant to detach the printed layer from the base resin layer; and obtaining recycled material derived from the base resin layer from which the printed layer has been detached.

[0009] [2] A label comprising a label body and an adhesive layer, wherein the adhesive layer is provided on the label body, and the adhesive layer is configured to dissolve when the label is immersed in a first alkaline solution, and the label body comprises a base resin layer and a printing layer, the printing layer is provided on the base resin layer, and the printing layer is configured not to detach from the base resin layer when the label body is immersed in the first alkaline solution, and to detach from the base resin layer when the label body is immersed in a second alkaline solution containing a surfactant.

[0010] [3] The label according to [2], wherein the adhesive layer is configured to dissolve when the label is immersed in the first alkaline solution comprising 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less, and less than 0.1 parts by weight of a first surfactant as an optional component, and the printing layer is configured so as not to detach from the base resin layer when the label body is immersed in the first alkaline solution comprising 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less, and less than 0.1 parts by weight of a first surfactant as an optional component, and the label body is configured to detach from the base resin layer when immersed in the second alkaline solution comprising 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less, and 0.5 parts by weight or more of a second surfactant.

[0011] [4] The label according to [3], wherein the adhesive layer is configured to dissolve when the label is immersed in the first alkaline solution which does not contain a surfactant.

[0012] [5] The label according to any one of [2] to [4], wherein the printed layer is configured not to detach from the base resin layer when the temperature is below 80°C.

[0013] A labeled container comprising a label as described in any of [6], [2] to [5], and a bottle-shaped container, wherein the label is a tubular shrink label attached to the container, and the adhesive layer adheres one end and the other end of the tubularly curved label body to each other.

[0014] According to this disclosure, a method for manufacturing recycled materials, a label, and a labeled container can be provided that allow the printed layer to be detached from the base resin layer in a label in which the printed layer does not detach from the base resin layer when part or all of the adhesive layer is dissolved.

[0015] This is a flow chart showing a method for manufacturing recycled material according to one embodiment of the present disclosure. This is a diagram showing a labeled container. This is a cross-sectional view of the labeled container in Figure 2, taken in the direction of the arrow III-III. This is a partial cross-sectional view showing an enlarged view of area IV in Figure 3. This is a schematic cross-sectional view showing the label body immediately after processing in step S2. This is a schematic cross-sectional view showing the label body immediately after processing in step S3.

[0016] Hereinafter, a method for manufacturing recycled materials and a label according to one embodiment of this disclosure will be described with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and their descriptions will not be repeated.

[0017] Figure 1 is a flowchart showing a method for manufacturing recycled material according to one embodiment of the present disclosure. As shown in Figure 1, the method for manufacturing recycled material according to one embodiment of the present disclosure comprises: recovering a labeled container (step S1); separating the label from the container by dissolving part or all of the adhesive layer of the label (step S2); detaching the printing layer from the base resin layer of the label (step S3); and obtaining recycled material derived from the base resin layer (step S4).

[0018] <Step S1> Figure 2 shows a labeled container with a cylindrical shrink label attached. As shown in Figure 2, in step S1, the labeled container 1 is collected. The collected labeled container 1 comprises a container 5 and a label 10.

[0019] Container 5 may be a so-called returnable container or a one-way container. A returnable container is a container that can be reused in its original shape. A returnable container may be a glass bottle or a synthetic resin bottle. A returnable bottle, for example, is collected after being distributed to the market, washed, and then reused. A one-way container is a disposable container that is not reused in its original shape. A one-way container may be a glass bottle. A one-way bottle, for example, is collected after being distributed to the market, crushed, and reused as a raw material for recycled material made into cullet. A one-way container may be a resin container such as a PET bottle. From the viewpoint of reducing the environmental burden in reuse, it is sometimes preferable that container 5 be a returnable container, as this allows for relatively low energy consumption for reuse. The method for manufacturing recycled material according to this embodiment is particularly useful when container 5 is a returnable container, as will be described later. Container 5 according to this embodiment is a glass bottle that serves as a returnable container.

[0020] The label 10 is attached to the container 5. Depending on the method of attachment, the label 10 can be classified into shrink labels, wrap labels, stretch labels, tack labels, etc. Shrink labels are attached to the container by heat shrinkage. Wrap labels are attached by wrapping them around the container, adhering one end of the label to the surface of the container, and then overlapping the other end with the first end and adhering or fusing it. Stretch labels are formed in a tubular shape and are attached to the container by self-stretching. Tack labels are attached to the container by using an adhesive such as a pressure-sensitive adhesive. The above classification of labels 10 is not particularly limited, but if the shape of the container 5 is relatively complex, it is preferable that the label 10 be a tubular shrink label. When the label 10 is a shrink label, the label 10 can provide a high degree of decorative appeal to the container 5.

[0021] Figure 3 is a cross-sectional view of the labeled container shown in Figure 2, viewed in the direction of the arrow III-III. Figure 4 is a partial cross-sectional view showing an enlarged view of region IV in Figure 3. As shown in Figures 3 and 4, the label 10 comprises a label body 20 and an adhesive layer 30.

[0022] In this embodiment, the label body 20 is placed on the surface of the container 5. The label body 20 is attached to the container 5. The label body 20 includes one end 20A located on one side in the direction along the outward-facing surface, and the other end 20B located on the opposite side. The adhesive layer 30 is provided on the label body 20. In this embodiment, the one end 20A and the other end 20B overlap via the adhesive layer 30. In Figure 3, the outer surface of the other end 20B and the inner surface of the one end 20A are overlapped via the adhesive layer 30 to form a lap seal, but the inner surface of the other end 20B and the inner surface of the one end 20A may overlap via the adhesive layer 30 to form a fin seal, or the outer surface of the other end 20B and the outer surface of the one end 20A may overlap via the adhesive 30 to form a seal. In all cases, the overlap width may be 3 mm or more and 15 mm or less. Furthermore, fine perforations penetrating the label body 20 may be provided at one end 20A, or at both one end 20A and the other end 20B. The effect of providing these perforations will be described later. Note that in wrap-around labels and tack labels, one end 20A and the other end 20B do not necessarily have to overlap.

[0023] The label body 20 includes a base resin layer 21 and a printing layer 22. The thickness of the base resin layer 21 is, for example, 5 μm or more and 200 μm or less, preferably 10 μm or more and 100 μm or less.

[0024] The base resin layer 21 may be a label base material that mainly contains a thermoplastic resin or is substantially composed of a thermoplastic resin. Examples of thermoplastic resins include polyester films made of polyester resins such as polyethylene terephthalate resin, polyethylene naphthalate resin, and polylactic acid resin; polystyrene films made of polystyrene resins such as styrene-butadiene block copolymer; polyolefin films made of olefin resins such as polyethylene and polypropylene; and polyvinyl chloride films made of vinyl chloride resin.

[0025] If the label 10 is a shrink label, the base resin layer 21 may be a heat-shrinkable label base material that mainly contains a thermoplastic resin or is substantially made of a thermoplastic resin. Specifically, it is a film in which the above-mentioned thermoplastic resin is substantially uniaxially stretched to impart heat shrinkability in the stretching direction. When a shrink label formed into a tube is attached to a container, the stretching direction is the circumferential direction of the tube, and the width direction (lateral direction) of the film before it is processed into a tube. Among these, polystyrene films (OPS films) stretched mainly in one direction, polyethylene terephthalate films (PET films) stretched mainly in one direction, multilayer films made by laminating polystyrene resin and polyethylene terephthalate resin (for example, a two-type three-layer film of PET / PS / PET, etc.), olefin films (particularly preferred are COC / PP / COC films made by laminating cyclic olefin resin and polypropylene resin). These may also be foamed films. The shrinkage rate of these heat-shrinkable films in the stretching direction is, for example, 30% to 75% when immersed in 90°C hot water for 10 seconds. The preferred PET film for shrinking is a polyethylene terephthalate film containing amorphous components, which is a glycol-modified polyethylene terephthalate resin in which a portion of the ethylene glycol component is replaced with other diol components such as cyclohexanedimethanol, neopentyl glycol, or diethylene glycol, or a polyethylene terephthalate resin modified by replacing the dicarboxylic acid component with isophthalic acid, adipic acid, etc. The label substrate may be a single layer or a laminate of two or more layers. The label substrate is not limited to transparent; for example, it may be milky white or other colored.

[0026] The printed layer 22 is provided on the base resin layer 21. The printed layer 22 is provided on one surface of the base resin layer 21, but it may also be provided on both surfaces of the base resin layer 21. The printed layer 22 and the container 5 are not bonded to each other. The thickness of the printed layer 22 is not particularly limited, but may be, for example, 0.1 μm or more and 10 μm or less. The printed layer 22 may be a single layer or a multilayer layer. Depending on its function, the printed layer 22 may be a design printed layer, a base printed layer, a surface coating layer, etc., and these may be provided as a single layer or in appropriate combinations, and the area in which each layer is provided may also be appropriately selected. Depending on its purpose, the area in which the printed layer 22 is formed may also be appropriately selected. Details of the configuration of the printed layer 22 will be explained further after the method for manufacturing the recycled material is described.

[0027] The adhesive layer 30 is provided on the label body 20. The adhesive layer 30 adheres one end 20A and the other end 20B of the cylindrically curved label body 20 to each other. In the case of wrap-around labels and tack labels, the adhesive layer 30 may adhere the label body 20 to the container 5. The thickness of the adhesive layer 30 is not particularly limited, but is preferably 0.01 μm to 10 μm, more preferably 0.05 μm to 3 μm, and particularly preferably 0.1 μm to 1 μm. The adhesive layer 30 may adhere a bonding tape member to the label substrate, or the tape member itself may form the adhesive layer. Further details of the adhesive layer 30 will be explained after the method for manufacturing the recycled material is described.

[0028] <Step S2> Next, step S2 will be described (see Figure 1). In step S2, the adhesive layer 30 of the label 10 is dissolved. Specifically, the labeled container 1, which is equipped with the label 10, is immersed in the first alkaline solution. Here, the adhesive layer 30 is configured to dissolve in part or all when the label 10 is immersed in the first alkaline solution. Therefore, when the labeled container 1 is immersed in the first alkaline solution, part or all of the adhesive layer 30 dissolves. If fine perforations are made in one or both of the label body 20 portions of one end 20A or the other end 20B as described above, the first alkaline solution can be made to penetrate more easily. As part or all of the adhesive layer 30 dissolves, one end 20A and the other end 20B are separated from each other. Then, in the labeled container 1, the label body 20 is separated from the container 5, and the label body 20 (i.e., the label 10 from which part or all of the adhesive layer 30 on the surface has been removed) can be recovered. Meanwhile, container 5 is washed with the first alkaline solution and can be reused as a returnable container.

[0029] The first alkaline solution is not particularly limited as long as it is a strongly alkaline liquid. For example, the first alkaline solution is an aqueous solution in which an alkaline component is dissolved in an amount of 0.05% to 2.0% by weight. As the alkaline component, alkali metal hydroxides such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), alkali metal carbonates such as sodium carbonate (Na2CO3), alkali metal bicarbonates such as sodium bicarbonate (NaHCO3), or aqueous ammonia can be used. In step S2, it is also preferable to immerse the label 10 (labeled container 1) in the first alkaline solution at 80°C or higher. By immersing the label 10 (labeled container 1) in such a relatively high-temperature first alkaline solution, the adhesive layer 30 having the components described later can be dissolved in a shorter time. In particular, in the case of shrink labels, when heated to 80°C or higher, the label substrate shrinks due to thermal stress, which acts in a direction that separates one end 20A from the other end 20B, causing the adhesive layer to begin to dissolve and peel off easily. In step S2, the time for immersing the label 10 (labeled container 1) in the first alkaline solution varies depending on the type of label and the processing temperature. However, if a shrink label is to be peeled from the container, it is preferable to immerse it for 1 minute or less, and even for labels other than shrink labels, it is preferable to immerse it for 3 minutes or less. In order to dissolve and remove the adhesive layer 30, it may be immersed for 5 minutes or more, and if it is necessary to dissolve and remove it completely, it may be immersed for 10 minutes or more.

[0030] Furthermore, the first alkaline solution may contain a surfactant from the viewpoint of cleaning the container 5 in step S2. However, from the viewpoint of suppressing the detachment of the printed layer 22, it is preferable that the surfactant content in the first alkaline solution is lower than the surfactant content in the second alkaline solution. If the first alkaline solution contains a surfactant, it is preferable that the first alkaline solution contains less than 0.1 parts by weight of a first surfactant per 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less. This allows the container 5 to be cleaned well in step S2. If the first alkaline solution contains a surfactant, it is sufficient that the first alkaline solution contains 0.001 parts by weight or more of a first surfactant per 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less. Furthermore, from the viewpoint of suppressing the detachment of the printed layer 22 in step S1, it is preferable that the first alkaline solution does not contain a surfactant.

[0031] Conventional known surfactants can be used for the first surfactant. The first surfactant may be an ionic surfactant (anionic surfactant, cationic surfactant, or amphoteric surfactant), or a nonionic surfactant, and multiple components from these may be used in combination. However, from the viewpoint of suppressing the detachment of the printed layer 22 in step S2, it is preferable that the first surfactant is different from the second surfactant described later.

[0032] Therefore, in this embodiment, the adhesive layer 30 is configured to dissolve when the label 10 is immersed in a first alkaline solution containing 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less, and less than 0.1 parts by weight of a first surfactant as an optional component. Here, dissolution means that the adhesive strength is weakened to the extent that the label can be peeled off, that is, to the extent that it can be easily peeled off by dissolution. Furthermore, the adhesive layer 30 is configured to dissolve when immersed in a first alkaline solution at 80°C or higher. The adhesive layer 30 may be configured not to dissolve when immersed in a first alkaline solution at a temperature below 80°C. The specific components of the adhesive layer 30 will be described later.

[0033] Figure 5 is a schematic cross-sectional view showing the label body immediately after the processing in step S2. As shown in Figure 5, the printing layer 22 is configured so as not to detach from the base resin layer 21 when the label body 20 is immersed in the first alkaline solution. For this reason, the base resin layer 21 and the printing layer 22 remain laminated together. Although not shown, the adhesive layer 30 may not be completely dissolved and may remain partially. For example, when the label 10 is immersed in the first alkaline solution, 50% to 90% or more of the adhesive layer 30 before immersion may remain on the surface of the label body 20.

[0034] Therefore, the printing layer 22 is configured not to substantially detach from the base resin layer 21 when the label body 20 is immersed in a first alkaline solution containing 100 parts by weight of an aqueous sodium hydroxide solution and less than 0.1 parts by weight of a first surfactant as an optional component. Furthermore, the printing layer 22 may be configured not to detach from the base resin layer 21 when the temperature is below 80°C. The specific configuration of the printing layer 22 will be described later.

[0035] The method for manufacturing recycled material according to this embodiment may further include between step S2 and step S3 a step of washing and drying the label body 20, or a step of cutting the label body 20 to break it into smaller pieces.

[0036] <Step S3> Next, step S3 will be described. Figure 6 is a schematic cross-sectional view showing the label body immediately after the process in step S3. As shown in Figures 5 and 6, the label (i.e., the label body 20), after some or all of the adhesive layer 30 on the surface has been removed, is immersed in a second alkaline solution containing a surfactant to detach the printing layer 22 from the base resin layer 21. Note that, as described above, if some of the adhesive layer 30 remains on the label body 20 after step S2, the adhesive layer 30 is removed almost completely by the second alkaline solution.

[0037] The second alkaline solution contains a strongly alkaline liquid and a surfactant. The strongly alkaline liquid is, for example, an aqueous solution in which the alkaline component is dissolved in an amount of 0.05% to 2.0% by weight. As the alkaline component, alkali metal hydroxides such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), alkali metal carbonates such as sodium carbonate (Na2CO3), alkali metal bicarbonates such as sodium bicarbonate (NaHCO3), or aqueous ammonia can be used.

[0038] The type of the second surfactant is not particularly limited, but the second surfactant may be an ionic surfactant (anionic surfactant, cationic surfactant, or amphoteric surfactant), or a nonionic surfactant, and multiple components from these may be used in combination. Among these, it is preferable that the surfactant includes a nonionic surfactant. The nonionic surfactant may be a polyethylene glycol type nonionic surfactant or a polyhydric alcohol type nonionic surfactant, but it is preferable that the second surfactant is a polyethylene glycol type nonionic surfactant.

[0039] Furthermore, the above-mentioned nonionic surfactant may be an aqueous solution containing at least one component selected from the group consisting of, for example, polyoxyethylene hydrogenated castor oil, cumylphenol polyethylene glycol, polyoxyethylene alkyl ether, polyoxyalkylene alkenyl ether, polyoxyethylene distyleninated phenyl ether, polyoxyalkylene, alkenyl ether sucrose fatty acid ester, alkyl glycoside, polyoxyethylene-polyoxypropylene block copolymer, polyoxyethylene ether of glycerin ester, fatty acid alkylolamide, and glycerin fatty acid ester. The total concentration of these components in the aqueous solution is preferably 0.5% by weight or more, and more preferably 1.0% by weight or more. There is no particular upper limit to the concentration of these components in the aqueous solution. The total concentration of these components in the aqueous solution may be 10.0% by weight or less.

[0040] Furthermore, in step S3, it is also preferable to immerse the label (i.e., the label body 20) after part or all of the adhesive layer 30 on the surface has been removed in a second alkaline solution at 80°C or higher. Immersing the label body 20 in such a relatively high-temperature second alkaline solution allows for more reliable detachment of the printed layer 22, which has the components described later, from the base resin layer 21. In addition, in step S3, the period for which the label body 20 is immersed in the second alkaline solution is preferably 5 minutes or more, and more preferably 10 minutes or more, from the viewpoint of more reliable detachment of the printed layer 22. Alternatively, this period may be 30 minutes or less. Before step S3, the label body 20 may be crushed and cut into pieces of, for example, about 5 to 30 mm in size, and this fragmentation improves the detachment efficiency of the printed layer 22.

[0041] Therefore, the printing layer 22 is configured to detach from the base resin layer 21 when the label body 20 is immersed in a second alkaline solution containing a surfactant. The printing layer 22 is configured to detach from the base resin layer 21 when the label body 20 is immersed in a second alkaline solution containing 100 parts by weight of an aqueous sodium hydroxide solution and 0.5 parts by weight or more of a second surfactant. The specific configuration of the printing layer 22 will be described later.

[0042] <Step S4> Next, step S4 will be described. In step S4, recycled material derived from the base resin layer 21 from which the printed layer 22 has been removed is obtained. Specifically, the base resin layer 21 from which the printed layer 22 has been removed may be used as recycled material as is, or the base resin layer 21 from which the printed layer 22 has been removed may be washed with water and dried, and then molded into pellets by melt extrusion to obtain pelletized recycled material.

[0043] <Specific configuration of the printed layer and adhesive layer> The configuration of the printed layer 22 and adhesive layer 30 is not limited as long as the printed layer 22 is configured so as not to substantially detach from the base resin layer 21 in step S2 described above, and as long as the above-described processing is possible in steps S2 and S3. More specifically, the configuration of the printed layer 22 and adhesive layer 30 is designed as follows.

[0044] The printing layer 22 is preferably one that dissolves or swells in a second alkaline solution containing a surfactant and is detachable from the base resin layer 21. The printing layer 22 is formed of, for example, oil-based ink (solvent-based ink) or water-based ink. The printing layer 22 may be composed of ultraviolet curable ink. As the oil-based ink, for example, one obtained by blending additives into a colorant such as a pigment or a dye, a binder resin, and an organic solvent may be used. As the water-based ink, one obtained by blending water and a colorant with a water-soluble or water-dispersible binder resin, additives, or the like may be used. As the ultraviolet curable ink, one obtained by blending additives such as a colorant, an ultraviolet curable monomer, an ultraviolet curable oligomer, a resin, a photopolymerization initiator, and a sensitizer may be used. Ultraviolet curable ink is generally a solvent-free ink. Examples of the additives include lubricants, anti-blocking agents, matting agents, and anti-settling agents.

[0045] As a method for forming the printing layer 22 on the surface of the base resin layer 21, for example, a method of forming the printing layer 22 on a film by gravure printing, flexographic printing, screen printing, offset printing, liquid toner printing, powder toner printing, inkjet printing, or the like can be used. When the printing layer 22 is a multilayer, the layer in contact with the base resin layer 21 is preferably a printable layer or an anchor layer that can be dissolved or swollen in a treatment solution and removed. In this case, the entire printing layer 22 can be removed from the film base material along with the removal of the anchor layer in contact with the base resin layer 21. From the viewpoint of easy removal, the anchor layer is preferably formed of either water-based ink or oil-based ink. When the printing layer 22 is a multilayer, all layers may be removable with the treatment solution.

[0046] The adhesive layer 30 may be tacky in the case of a tack label, and may be heat-sensitive adhesive in the case of a wrap-around label, etc. In the case of a tubular shrink label, the adhesive layer 30 may be fixed to one end 20A and the other end 20B of the label body 20. A preferred example of the resin constituting the adhesive layer 30 is a resin with a high acid value within a range that does not impair adhesion to one end 20A and the other end 20B of the label body 20. From the viewpoint of solubility in the second alkaline solution, the acid value (mg-KOH / g-resin) of the entire resin constituting the adhesive layer 30 is preferably at least 10, more preferably 20 or more, and particularly preferably 25 or more. Furthermore, from the viewpoint of adhesion between one end 20A and the other end 20B of the label body 20 during use, the acid value is preferably 200 or less, more preferably 150 or less, and particularly preferably 100 or less. The acid value can be calculated based on the results of potentiometric titration using a potassium hydroxide solution of a predetermined concentration (e.g., a 0.1 mol / L potassium hydroxide-ethanol solution) after dissolving the resin in a titration solvent (e.g., a mixed solvent of xylene and dimethylformamide).

[0047] Furthermore, if the label 10 is a tubular shrink label, the resin constituting the adhesive layer 30 is formed by applying a sealing solvent containing the resin constituting the adhesive layer 30 between one end 20A and the other end 20B of the label body 20. Conventional known sealing solvents can be used, and suitable examples include tetrahydrofuran (THF), 1,3-dioxolane, dioxane, n-hexane, cyclohexane, methylcyclohexane, methyl ethyl ketone (MEK), acetone, methyl isobutyl ketone (MIBK), methyl acetate, methanol, isopropyl alcohol, etc. Of these, THF, MEK, and 1,3-dioxolane are particularly preferred.

[0048] The adhesive layer 30 may be composed of a base resin that is soluble in the above-mentioned sealing solvent and insoluble in a first alkaline solution, and a thermally alkali-soluble resin that is soluble in the first alkaline solution, or may be composed only of the thermally alkali-soluble resin that is soluble in the first alkaline solution. The base resin is preferably a resin that dissolves in a sealing solvent and exhibits adhesiveness; for example, urethane-based resins, acrylic-based resins, polyamide-based resins, vinyl chloride-vinyl acetate-based resins, polyester-based resins, cellulose-based resins, or resins of the same type as those constituting the base resin layer 20 can be used, with urethane-based resins, acrylic-based resins, and polyamide-based resins being preferred. Here, the expression "insoluble in the first alkaline solution" means that the resin does not dissolve even when immersed in the first alkaline solution for 20 minutes. The thermally alkali-soluble resin is preferably a resin that is soluble in the sealing solvent and has an acid value of 80 to 500; for example, a styrene-maleic acid copolymer having an acid value of 80 to 500 or a carboxyl group-containing acrylic resin can be used. When the base resin and the thermally alkali-soluble resin are mixed, the mixing ratio is preferably determined such that the acid value of the entire resin constituting the adhesive layer 30 falls within the above-mentioned range. Although it varies depending on the acid value and other factors, the content of the thermally alkali-soluble resin is, for example, 5% by weight to 70% by weight based on the total weight of the resin constituting the adhesive layer 30. The combined use of the base resin and the thermally alkali-soluble resin improves the adhesive strength between one end 20A and the other end 20B of the label body 20 during use.

[0049] Hereinafter, the present disclosure will be described more specifically with reference to experimental examples, but the present disclosure is not limited to these examples.

[0050] <Experimental Example 1> [Sample Preparation] First, the sample was prepared as follows. A 30 μm thick heat-shrinkable PET film was printed with oil-based red ink in a grid pattern on the film surface using gravure printing, and then a solid layer of white ink was printed on top to form a shrink label. The above shrink label was cut into label pieces averaging 25 mm square. A first alkaline solution (1.5 wt% sodium hydroxide aqueous solution) was placed in a 500 mL beaker, and then five of the above label pieces were added. After stirring for 10 minutes while maintaining the temperature of the first alkaline solution at 85°C, the label pieces were filtered through a mesh to obtain the sample. The printed layer of the sample did not detach from the PET film.

[0051] [Immersion Test in Second Alkaline Solution] Next, a second alkaline solution (1.5 wt% alkaline aqueous solution) containing 1 wt% surfactant was placed in a 500 mL beaker, and then the above sample was added. The mixture was stirred while maintaining the temperature of the second alkaline solution at 85°C. During stirring, the process from the start of stirring until the detachment of the printed layer was completed was visually evaluated. In Experimental Example 1, a cumylphenol polyethylene glycol aqueous solution (nonionic surfactant) was used as the surfactant.

[0052] <Experimental Examples 2-9> In Experimental Examples 2-9, the same samples as in Experimental Example 1 were used, and the immersion test in the second alkaline solution was carried out in the same manner except for the type of surfactant. In Experimental Examples 2-8, the surfactants used were, respectively, a commercially available dish soap (a mixture of cationic, anionic, and nonionic surfactants), sodium lauryl sulfate (anionic surfactant), ammonium polyoxyethylene distyrenated ether sulfate (anionic surfactant), sodium dodecylbenzenesulfonate (anionic surfactant), sodium alkylnaphthalene sulfonate (anionic surfactant), polyoxyethylene alkyl ether (nonionic surfactant), polyoxyethylene distyrenated phenyl ether (nonionic surfactant), and a mixture of sodium alkylnaphthalene sulfonate (anionic surfactant) and polyoxyethylene alkyl ether (nonionic surfactant).

[0053] <Visual Evaluation Results of Detachment in Experimental Examples 1-9> In each of Experimental Examples 1-9, the time taken for the white ink portion and the color ink portion of the printed layer to detach after the start of stirring was visually evaluated and the results are shown in Table 1 below. The evaluation criteria in Table 1 are as follows: E (Excellent): The printed layer was almost completely detached before 10 minutes had elapsed since the start of stirring. G (Good): The printed layer was almost completely detached after 10 minutes and before 15 minutes had elapsed since the start of stirring. A (Average): The printed layer was detached after 15 minutes had elapsed since the start of stirring, by stirring more vigorously.

[0054]

[0055] As shown in Table 1 above, in Experimental Examples 1 to 9, it was confirmed that the printed layer was removed by treatment with the second alkaline solution containing a surfactant. Furthermore, in Experimental Examples 1 to 9, it was confirmed that the printed layer was not removed by treatment with the first alkaline solution.

[0056] <Experimental Example 10> A shrink label made of a 30 μm thick heat-shrinkable PET film was attached to the body of a 400 ml glass bottle, and an experiment was conducted to see if the ends would peel off at the center seal (the area where one end of the label body is bonded to the other by an adhesive layer) using a first alkaline solution. Specifically, first, an adhesive was prepared by dissolving 8 parts by weight of styrene-maleic anhydride copolymer (Clay Valley, SMA17352P) and 5 parts by weight of carboxyl group-containing acrylic resin (BASF, "JDX-C3000A") as a heat-alkali soluble resin in 100 parts by weight of the organic solvent 1,3-dioxolane. This adhesive was applied between one end and the other end of the label body, and a cylindrical shrink label was prepared by sealing the two ends together via the adhesive. The prepared shrink label was fitted onto the body of a glass bottle and heat-shrinked to attach it. When a glass bottle with a shrink label attached was immersed in the same first alkaline solution as used in Experimental Example 1 at a temperature of 85°C for 1 minute, one end and the other end of the center seal separated from each other, and the shrink label peeled off (detached) from the glass bottle.

[0057] <Experimental Example 11> A glass bottle with a shrink label attached was prepared in the same manner as in Experimental Example 10, except that an adhesive containing only 8 parts by weight of a carboxyl group-containing acrylic resin (BASF's "JDX-C3000A") was used as the heat-alkali-soluble resin. When this glass bottle was immersed in the first alkaline solution under the same conditions as in Experimental Example 10, one end and the other end of the center seal separated from each other, and the shrink label peeled off the glass bottle.

[0058] <Experimental Example 12> A glass bottle with a shrink label attached was prepared in the same manner as in Experimental Example 10, except that an adhesive containing only 15 parts by weight of styrene-maleic anhydride copolymer (Clay Valley, SMA17352P) was used as the heat-alkali-soluble resin. When this glass bottle was immersed in the first alkaline solution under the same conditions as in Experimental Example 10, one end and the other end of the center seal separated from each other, and the shrink label peeled off the glass bottle.

[0059] As described above, in experimental examples 10 to 12, it was confirmed that the adhesive layer dissolved upon treatment with the first alkaline solution.

[0060] As described above, a method for manufacturing recycled material according to one embodiment of the present disclosure comprises a base resin layer 21 and a printed layer 22 provided on the base resin layer 21, and immersing the label 10, after a part or all of the adhesive layer 30 on the surface has been removed, in an alkaline solution containing a surfactant to detach the printed layer 22 from the base resin layer 21, and obtaining recycled material derived from the base resin layer 21 from which the printed layer 22 has been detached.

[0061] According to the above configuration, by immersing the label 10, after part or all of the adhesive layer 30 has been removed, in an alkaline solution containing a surfactant, the printed layer 22 can be detached from the base resin layer 21, even if the printed layer 22 does not detach from the base resin layer 21 when part or all of the adhesive layer 30 is dissolved.

[0062] A label 10 according to one embodiment of the present disclosure comprises a label body 20 and an adhesive layer 30. The adhesive layer 30 is provided on the label body 20. The adhesive layer 30 is configured to dissolve when the label 10 is immersed in a first alkaline solution. The label body 20 includes a base resin layer 21 and a printing layer 22. The printing layer 22 is provided on the base resin layer 21. The printing layer 22 is configured not to detach from the base resin layer 21 when the label body 20 is immersed in a first alkaline solution. The printing layer 22 is configured to detach from the base resin layer 21 when the label body 20 is immersed in a second alkaline solution containing a surfactant.

[0063] According to the above configuration, after part or all of the adhesive layer 30 is removed from the label body 20 by an alkaline solution, the printed layer 22 can be detached from the base resin layer 21 by immersing the label body 20 in an alkaline solution containing a surfactant. Therefore, a label 10 can be provided in which the printed layer 22 does not detach from the base resin layer 21 when part or all of the adhesive layer 30 is dissolved, and in which the printed layer 22 can be detached from the base resin layer 21.

[0064] In a label 10 according to one embodiment of the present disclosure, the adhesive layer 30 is configured to dissolve when the label 10 is immersed in a first alkaline solution containing 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less, and less than 0.1 parts by weight of a first surfactant as an optional component. The printing layer 22 is configured so as not to detach from the base resin layer 21 when the label body 20 is immersed in a first alkaline solution containing 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less, and less than 0.1 parts by weight of a first surfactant as an optional component. The printing layer 22 is configured to detach from the base resin layer 21 when the label body 20 is immersed in a second alkaline solution containing 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less, and 0.5 parts by weight or more of a second surfactant.

[0065] According to the above configuration, the printed layer 22 is configured not to detach from the base resin layer 21 when immersed in a sodium hydroxide aqueous solution with relatively little or no surfactant, thereby ensuring that the printed layer 22 does not detach when the adhesive layer 30 is dissolved by the first alkaline solution. At the same time, by using a sodium hydroxide aqueous solution with a relatively large amount of surfactant in the second alkaline solution, the printed layer 22 can be more reliably detached from the base resin layer 21.

[0066] In a label 10 according to one embodiment of the present disclosure, the printed layer 22 is configured not to detach from the base resin layer 21 when the temperature is below 80°C.

[0067] According to the above configuration, the adhesive layer 30 can be prevented from detaching from the base resin layer 21 in situations unintended by the user, while the printed layer 22 can be detached from the base resin layer 21 by raising the temperature of the second alkaline solution to 80°C or higher.

[0068] In the above-described embodiments and examples, the combinatorial configurations may be combined with each other.

[0069] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than the foregoing description, and all modifications are intended to be within the meaning and scope of the equivalents of the claims.

[0070] 1 Labeled container, 5 Container, 10 Label, 20 Label body, 20A One end, 20B Other end, 21 Base resin layer, 22 Printing layer, 30 Adhesive layer.

Claims

1. A method for manufacturing recycled material, comprising: immersing a label, which includes a base resin layer and a printed layer provided on the base resin layer, and after a part or all of the adhesive layer on the surface has been removed, in an alkaline solution containing a surfactant to detach the printed layer from the base resin layer; and obtaining recycled material derived from the base resin layer from which the printed layer has been detached.

2. A label comprising a label body and an adhesive layer, wherein the adhesive layer is provided on the label body, and the adhesive layer is configured to dissolve when the label is immersed in a first alkaline solution, and the label body comprises a base resin layer and a printing layer, the printing layer is provided on the base resin layer, and the printing layer is configured not to detach from the base resin layer when the label body is immersed in the first alkaline solution, and to detach from the base resin layer when the label body is immersed in a second alkaline solution containing a surfactant.

3. The label according to claim 2, wherein the adhesive layer is configured to dissolve when the label is immersed in the first alkaline solution comprising 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less, and less than 0.1 parts by weight of a first surfactant as an optional component, and the printing layer is configured so as not to detach from the base resin layer when the label body is immersed in the first alkaline solution comprising 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less, and less than 0.1 parts by weight of a first surfactant as an optional component, and the label body is configured to detach from the base resin layer when immersed in the second alkaline solution comprising 100 parts by weight of an aqueous sodium hydroxide solution in which sodium hydroxide is dissolved at a concentration of 0.05% by weight or more and 2.0% by weight or less, and 0.5 parts by weight or more of a second surfactant.

4. The label according to claim 3, wherein the adhesive layer is configured to dissolve when the label is immersed in the first alkaline solution which does not contain a surfactant.

5. The label according to claim 2, wherein the printed layer is configured not to detach from the base resin layer when the temperature is below 80°C.

6. A labeled container comprising a label according to any one of claims 2 to 5 and a bottle-shaped container, wherein the label is a tubular shrink label attached to the container, and the adhesive layer adheres one end and the other end of the tubularly curved label body to each other.

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