JP7795056B2 - Labeled containers and how to recycle labeled containers - Google Patents

Description

The present invention relates to a labeled container.

Currently, there are a variety of plastic products on the market. Many of these plastic products have labels attached to them that display product information. For example, many polyethylene terephthalate (PET) bottles filled with beverages have labels attached to the outside of the PET bottle that display the beverage inside.

In recent years, there has been a strong demand for the reuse of plastic containers from environmental and other perspectives. For example, recycling systems for PET bottles with the above-mentioned labels attached have already been established and are widely used. Specifically, the labels are first removed from the PET bottles, and then the delabeled PET bottles are subjected to a recycling process. For example, Patent Document 1 (JP 2013-527813 A) discloses a device for continuously removing labels from multiple PET bottles.

Special table number 2013-527813

However, removing the labels is a complicated process and is one of the factors hindering the efficient reuse of plastic containers.

The present invention was made in consideration of the above-mentioned problems, and the object of the present invention is to provide a labeled container that allows for efficient reuse.

Labeled containers come in two types: one where the label is glued to the plastic container, and one where the label is placed over the container. Removing the label from the former tends to be more complicated than the latter. This is because, when peeling the glued label off the container, depending on the amount of force used, part of the label may remain on the surface of the container. Therefore, the inventors decided to focus on realizing efficient reuse of labeled containers with labels glued to them.

Labels with functions such as product display have a printed layer that enables that function. If such labels are subjected to a recycling process together with containers, it becomes difficult to produce highly usable resin pellets. This is because the pigments contained in the printed layer affect the physical properties and color of the resin pellets. For this reason, in order to regenerate highly usable resin pellets from labeled containers, it is necessary to reliably separate the label from the container. However, after extensive research, the inventors have made a major shift in thinking when it comes to labeled containers with labels attached, and have discovered that more efficient reuse can be achieved even if part of the label remains on the surface of the container. The embodiments of the present invention listed below were completed in this way.

A labeled container according to one embodiment of the present invention is a labeled container with a label attached thereto. The container is a polyester-based container, and the label has a base layer having opposing first and second surfaces, an adhesive layer that adheres the first surface of the base layer to the container, a bonding layer laminated on the second surface of the base layer, and a printed layer located on the opposite side of the bonding layer from the base layer. The base layer is a polyester-based film, the adhesive layer is a polyester-based adhesive, and the bonding layer is soluble in at least one of warm water and an alkaline solution.

In the labeled container described above, the bonding layer is soluble in at least one of warm water and alkaline solution. Therefore, by simply bringing the labeled container into contact with warm water or alkaline solution, the bonding layer and the printing layer located on the opposite side of the substrate layer from the bonding layer can be easily separated from the labeled container.

Furthermore, in the past, in order to recycle a container, the label and container had to be completely separated, as mentioned above, and great care had to be taken when peeling the label off the labeled container. In contrast, with the labeled container described above, the bonding layer and printing layer can be removed from the container even if part of the label remains on the surface of the container. Because the base layer and adhesive layer are made of the same material (polyester resin) as the container, they can be subjected to the recycling process together with the container.

In this way, the labeled containers described above can be recycled appropriately without requiring excessive care in the tedious task of removing the labels from the labeled containers. Therefore, the labeled containers described above can be reused efficiently.

In the above-mentioned labeled container, the bonding layer is preferably insoluble in hot water but soluble in alkaline solution. This sufficiently prevents unintended layer separation of the label, while enabling efficient reuse when recycled using alkaline solution.

In the labeled container described above, the label preferably has a support layer that supports the printed layer and is located on the opposite side of the adhesive layer from the base layer. This allows the support layer to support the printed layer even after the printed layer is separated from the base layer, thereby preventing the printed layer from dispersing finely in warm water or an alkaline solution.

In the above-mentioned labeled container, a printing layer is preferably located between the carrier layer and the bonding layer. With such a labeled container, the carrier layer can function as a protective layer for the printing layer.

The present invention provides labeled containers that allow for efficient reuse.

FIG. 1 is a side view showing one embodiment of a labeled container according to the first embodiment. FIG. 2 is a cross-sectional view showing an example of a layered structure of the label according to the first embodiment. FIG. 3 is a partial cross-sectional view showing a state in which a part of the label is separated from the labeled container according to the first embodiment. FIG. 4 is a cross-sectional view showing the layered structure of the label according to the second embodiment. FIG. 5 is a cross-sectional view showing the layered structure of the label according to the third embodiment. FIG. 6 is a side view showing another example of a labeled container.

In this specification, a numerical range expressed as "lower limit A to upper limit B" means a range between lower limit A and upper limit B. When multiple such numerical ranges are separately listed, any lower limit and any upper limit can be selected to set "any lower limit to any upper limit." The dimensions, scale, and shapes of layers and components shown in each figure may differ from the actual ones. An example of the present disclosure will now be described with reference to the drawings.

First Embodiment
[Container with label]
1 is a perspective view showing one embodiment of a labeled container according to the present invention. In FIG. 1, the labeled container 1 comprises a container 10, a label 20, and a cap 30.

[container]
The container 10 has an internal space for containing food, beverages, medicine, or other items. The label 20 is adhered to the outer surface of the container 10. The cap 30 covers the opening of the container 10, thereby closing off the internal space defined by the container 10.

The configuration of the labeled container 1 is not limited to this, and it is sufficient that the internal space of the container 10 can contain an object to be contained and that the label 20 displays product information, etc. For example, instead of the cap 30, the internal space may be closed by another closure member such as a spout, zipper, or lid seal, or it may not be closed. Other shapes of the labeled container 1 include a bowl shape.

Furthermore, the position where the label 20 is attached on the labeled container 1 is not particularly limited. For example, as shown in Figure 6, a portion of the label 20 may not be adhered to the surface of the container 10 (a portion of the label 20 may be separated from the container 10). In Figure 6, the label 20 is attached to the body portion of the container 10, but it may also be adhered to the shoulder portion of the container 10 or the cap 30 so that a portion of it is separated from the surface of the container 10. Furthermore, the shape of the label 20 is not particularly limited.

In this embodiment, the container 10 is a polyester-based container. A polyester-based container is a container whose main component is a polyester-based resin. The term "main component" refers to a material that accounts for 50% or more of the total weight of the container 10. Preferred polyester-based resins include polylactic acid, polyethylene terephthalate (PET), polybutylene terephthalate, etc.

[cap]
The cap 30 covers the opening of the container 10 to close the internal space of the container 10. The labeled container 1 of this embodiment may or may not have the cap 30, as described above. If the labeled container 10 has the cap 30, it is preferable that the cap 30 be made primarily of polyester resin. In this case, the cap 30 can be provided together with the container 10 in a recycling system without being removed from the container 10.

[label]
The label 20 is adhered to the outer surface of the container 10 and functions to display product information and the like. FIG. 2 is a cross-sectional view showing an example of the laminated structure of a label according to this embodiment. Referring to FIG. 2, the label 20 includes a base layer 21 having a first surface 21a and a second surface 21b facing each other, an adhesive layer 22 that bonds the first surface 21a of the base layer 21 to the container 10, a bonding layer 23 laminated on the second surface 21b of the base layer 21, and a printing layer 24 located on the opposite side of the bonding layer 23 from the base layer 21. The shape of the label 20 is not particularly limited, as long as it displays the intended display within an area observed from the outside. FIG. 1 shows a substantially rectangular label 20. The thickness of the label 20 is also not particularly limited, as long as it has the rigidity, flexibility, and other properties required for the label 20, and is, for example, 20 to 170 μm, preferably 20 to 120 μm, and more preferably 30 to 100 μm.

(Base material layer)
The base layer 21 is the basic skeleton of the label 20 and functions as a carrier for the other layers to be laminated on it. In other words, the shape of the base layer 21 determines the overall shape of the label 20. The thickness of the base layer 21 can be, for example, 10 to 80 μm. This allows the base layer 21 to function as a carrier while preventing the label 20 from becoming unnecessarily thick.

The base layer 21 is a polyester film. A polyester film is a film whose main component is a polyester resin. Preferred polyester resins include polylactic acid, polyethylene terephthalate (PET), and polybutylene terephthalate. The base layer 21 is preferably made of the same polyester resin material as the container 10. For example, if the container 10 is a PET container, the base layer 21 is preferably a PET film, and if the container 10 is a polylactic acid container, the base layer 21 is preferably a polylactic acid film. If the container 10 and the base layer 21 are made of the same material, the recyclability is further improved.

(Adhesive layer)
The adhesive layer 22 bonds the first surface 21a of the base layer 21 to the container 10. That is, the adhesive layer 22 is interposed between the container 10 and the base layer 21, bonding the container 10 and the label 20 to each other. The adhesive strength of the adhesive layer 22 to the container 10 and the label 20 is preferably 5 N/25 mm or more, and more preferably 20 N/25 mm or more. This prevents the label 20 from unintentionally peeling off.

Furthermore, when reusing the labeled container 10 of the present disclosure, excessive care is not required when peeling off the label 20. If the label 20 needs to be completely peeled off from the container 10 in order to reuse the labeled container 20, the adhesive strength must be carefully adjusted. In contrast, with the labeled container 10 of the present disclosure, such careful adjustment is not necessary.

In this specification, adhesive strength refers to a value measured using a method conforming to JIS Z 0237 180-degree peeling. Specifically, the adhesive strength refers to the maximum strength measured when a laminate consisting of a first member (container) and a second member (substrate layer) bonded together is cut into a 100 mm x 25 mm piece, and the first member is peeled off at 180 degrees at a rate of 300 mm/min at a temperature of 23±2°C, a humidity of 50±5% RH.

The adhesive layer 22 is a polyester-based adhesive. A polyester-based adhesive is an adhesive whose main component is a polyester-based resin. Preferred polyester-based resins include polylactic acid, polyethylene terephthalate (PET), polybutylene terephthalate, etc. The adhesive layer 22 is preferably made of the same polyester-based adhesive as the container 10. For example, if the container 10 is a PET-based container, the adhesive layer 22 is preferably a PET-based adhesive, and if the container 10 is a polylactic acid-based container, the adhesive layer 22 is preferably a polylactic acid-based adhesive. If the container 10 and the adhesive layer 22 are made of the same material, the recyclability is further improved.

(bonding layer)
The bonding layer 23 is laminated on the second surface 21b of the base material layer 21. That is, the bonding layer 23 is interposed between the base material layer 21 and another layer located on the opposite side of the base material layer 21 from the bonding layer 23, and bonds and fixes the base material layer 21 and the other layer to each other. In this embodiment, the bonding layer 23 fixes the base material layer 21 and the printing layer 24.

The bonding layer 23 also has the property of being soluble in at least one of warm water and alkaline solutions. Specifically, if a laminated structure (length x width: 1 cm x 1 cm) having a bonding layer sandwiched between two layers is immersed in 85°C water and agitated for 15 minutes, and the two layers separate, the bonding layer is considered to be soluble in warm water. Similarly, if a laminated structure (length x width: 1 cm x 1 cm) having a bonding layer sandwiched between two layers is immersed in an alkaline solution (1.5 wt% NaOH aqueous solution) at 85°C and agitated for 15 minutes, and the two layers separate, the bonding layer is considered to be soluble in alkaline solutions. The agitation speed depends on the agitation volume, but can be, for example, approximately 1000 rpm.

Possible cases in which the bonding layer 23 may become soluble include when the bonding layer 23 dissolves in at least one of warm water and alkaline solution, reducing (losing) the bonding ability of the bonding layer 23 itself to adjacent layers, when moisture penetrates (enters) the interface between the bonding layer 23 and adjacent layers, causing the bonding layer 23 to peel away from the other layers, and when the bonding layer 23 swells, reducing (losing) the bonding ability of the bonding layer itself.

The bonding layer 23 in this embodiment is preferably a base layer. The base layer is a layer in which a resin composition containing at least a binder resin is solidified through a drying process or the like, thereby adhering other layers in contact with it. In other words, the base layer does not have the adhesive properties of an adhesive layer (described below). The resin composition may further contain a solvent, additives, etc., as needed.

When the bonding layer 23 is a base layer, it is preferable that the base layer further contains a curing agent in addition to the binder resin. This can improve the water resistance of the bonding layer 23.

From the perspective of recyclability, the binder resin is preferably a polyester-based resin. The curing agent is selected depending on the type of binder resin, but preferred are carbodiimide-based curing agents, aziridine-based curing agents, isocyanate-based curing agents, and oxazoline-based curing agents. For example, if the binder resin is a resin with carboxyl groups, it is preferable to use a carbodiimide-based curing agent as the curing agent, and if the binder resin is a resin with sulfonic acid groups, it is preferable to use an isocyanate-based curing agent as the curing agent.

When the curing agent in the above resin composition is a carbodiimide-based curing agent and the binder resin is a polyester-based resin, the solids ratio (X:Y) of the curing agent (X) to the binder resin (Y) in the undercoat layer is preferably 100:4 to 100:30, more preferably 100:10 to 100:30, and particularly preferably 100:20 to 100:30. In this case, the bonding layer 23 itself has good water resistance, adhesion to the base layer 21, and solubility in alkaline solutions. In this specification, water resistance refers to resistance to water at room temperature (23°C).

(Printing layer)
The printed layer 24 is located on the opposite side of the base material layer 21 from the bonding layer 23. In Fig. 2, the printed layer 24 is adjacent to the bonding layer 23. The printed layer 24 is a layer formed with one or more types of ink, and displays visible product markings, etc. The printed layer 24 may be formed on the entire surface of the base material layer 21, or may be formed on only a part of the base material layer 21.

The ink that constitutes the printing layer 24 is not particularly limited, and examples include oil-based ink, water-based ink, and UV-curable ink. In particular, from the perspective of environmental compatibility, the ink that constitutes the printing layer 24 is preferably water-based ink or UV-curable ink. Of these, UV-curable ink is preferred for the ink that constitutes the printing layer 24. This is because it does not contain organic solvents and dries quickly. UV-curable ink also has high decorative properties.

[Manufacturing method of labeled containers]
The labeled container 1 described above can be produced by appropriately combining conventionally known methods.

An example of a manufacturing method for a labeled container 1 in which the bonding layer 23 is a base layer is described below. First, a substrate laminate is prepared, which is composed of a base layer 21 made of a polyester film, an adhesive layer 22 made of a polyester adhesive, and a release paper laminated in this order. Next, a resin composition that will serve as the bonding layer 23 (base layer) is applied to one side of the base layer 21 (the second side 21b, the side without the adhesive layer 22 and release paper), and a drying process is performed as necessary to form the bonding layer 23 (base layer). There are no particular restrictions on the method for applying the resin composition, and conventionally known methods can be used.

Next, a printing layer 24 is formed on the surface of the bonding layer 23 opposite the surface that contacts the base layer 21. There are no particular restrictions on the method for forming the printing layer 24, and any conventionally known method can be used. Finally, if necessary, the base layer 21 on the release paper is punched into a label shape and unnecessary portions are removed from the release paper. This produces a label 20 equipped with a release paper. Next, the label 20 is removed from the release paper, and the exposed adhesive surface (adhesive layer 22) is adhered to the surface of the container 10. In this way, a labeled container 1 is produced. Furthermore, by forming a laminate as described above on a long piece of release paper, a continuous label strip can also be produced in which multiple labels 20 are adhered continuously along the longitudinal direction of the release paper.

The manufacturing method of the label 20 is not limited to the above. For example, the bonding layer 23 and the printing layer 24 may be formed in sequence on the base material layer 21 using the same method as above, and then a polyester-based adhesive may be applied to the exposed surface (first surface 21a) of the base material layer 21 to form the adhesive layer 22.

[How to reuse labeled containers]
After being used by a consumer or the like, the labeled container 1 is brought into contact with warm water or an alkaline solution after the label 20 has been removed, thereby dissolving the bonding layer 23. This dissolving process can be easily carried out, for example, by immersing the labeled container 1 in a bath containing warm water or an alkaline solution and stirring the water.

As a result, the bonding layer 23 dissolves in warm water or an alkaline solution, and as a result, the bonding layer 23 and each layer located farther away from the container 10 are separated from the container 10. Figure 3 is a partial cross-sectional view showing a state in which part of the label has been separated from a labeled container according to this embodiment, and shows the labeled container 1 after the labeled container 1 has been subjected to a dissolving process. Note that the labeled container 1 does not need to undergo the peeling process described above.

The labeled container shown in Figure 3 (hereinafter also referred to as the "solubilized container") consists of a container 10, an adhesive layer 22, and a base layer 21, all of which are made of polyester-based resin. Therefore, the solubilized container can be subjected to a recycling process, for example, in an already established reuse system.

[effect]
According to the labeled container 1 described above, the bonding layer 23 is soluble in at least one of hot water and alkaline solution. Therefore, the bonding layer 23 and the printing layer 24 located on the opposite side of the substrate layer 21 from the bonding layer 23 can be easily separated from the labeled container 1 by simply contacting the labeled container 1 with hot water or alkaline solution. The solubilized container from which a portion of the label 20 has been separated in this manner can be directly subjected to a recycling process. Therefore, the labeled container 1 described above can be efficiently reused without excessive care being taken during the peeling process. In particular, when the bonding layer 23 is the above-described base layer, it can be soluble in alkaline solution.

It is also worth noting that, while in the past, the label 20 was discarded, with the labeled container 1 described above, the base layer 21, which makes up the majority of the label 20, and the adhesive layer 22 that bonds the base layer 21 to the container 10 can also be subjected to the recycling process.

In labeled containers 1, it is preferable that the bonding layer 23 is insoluble in hot water but soluble in alkaline solutions. This is because, while situations in which labeled containers 1 are immersed in alkaline solutions are not anticipated except during recycling processes, it is conceivable that labeled containers 1 may be unintentionally immersed in hot water. In other words, if the bonding layer 23 were soluble in hot water, it is possible that the layers of the label 20 would separate at an unintended time.

A particularly preferred configuration of the labeled container 1 includes a container 10 made of a PET film, an adhesive layer 22 made of a PET adhesive, a base layer 21 made of a PET film, and a base layer (bonding layer 23) containing a binder resin made of a carbodiimide curing agent and a polyester resin. In this configuration, the adhesion between the base layer 21 and the bonding layer 23, the water resistance of the bonding layer 23, the alkali solubility of the bonding layer 23, and the adhesion between the bonding layer 23 and the printed layer 24 are all excellent. This prevents unintended layer separation of the label 20 and facilitates separation of the label 20 through alkali dissolution treatment. Furthermore, the bonding layer 23 is not soluble in hot water, preventing unintended separation of the label 20. Unintended separation of the label 20 occurs, for example, when the labeled container 1 comes into contact with hot water that is not intended for dissolution treatment, resulting in separation of the label 20.

Second Embodiment
A labeled container according to the second embodiment will be described with reference to Fig. 4. Fig. 4 shows a label 20A which further comprises a carrier layer 25 in addition to the label 20 according to the first embodiment. That is, in the labeled container according to the second embodiment, in addition to the configuration of the labeled container according to the first embodiment, the label further comprises a carrier layer.

[Container with label]
The label 20A has a configuration in which a carrier layer 25 is further provided compared to the label 20. The carrier layer 25 is located on the opposite side of the bonding layer 23 from the base material layer 21. Furthermore, a printing layer 24 is located between the carrier layer 25 and the bonding layer 23.

[Support layer]
The support layer 25 is a layer that supports the printed layer 24. In other words, the printed layer 24 is not capable of forming a layer by itself, but rather uses a solid layer such as a film as a carrier, and can form a layer shape on the surface of the carrier, and the support layer 25 is a layer that functions as a carrier for such printed layer 24. Furthermore, the support layer 25 is preferably at least one of a film having a specific gravity lower than that of water or an alkaline aqueous solution, and a heat-shrinkable film. For example, the support layer 25 is preferably a polyolefin film such as polyethylene or polypropylene, and in particular, a polypropylene film is preferred. In this case, the support layer 25 can have a specific gravity lower than that of water or an alkaline aqueous solution. In addition to the polyolefin films, examples of heat-shrinkable films include polystyrene films.

There are no particular restrictions on the thickness of the carrier layer 25. Since it is sufficient for the carrier layer 25 to function as a carrier for the printing layer 24, it is preferable that the thickness be smaller than the thickness of the base layer 21, which is the base material of the label, and can be 10 to 30 μm. This is to avoid unnecessarily increasing the total amount of material for the label 20. The carrier layer 25 may have the same shape as the base layer 21, or it may have a different shape, for example, a shape smaller than the base layer 21.

[Joining layer]
In this embodiment, the bonding layer 23 may be, for example, the above-mentioned base layer or an adhesive layer. The adhesive layer is a layer made of an adhesive agent and adheres a layer in contact with it by virtue of its own adhesiveness.

When the bonding layer 23 is an adhesive layer, the adhesive strength of the adhesive layer is preferably 2 to 25 N/25 mm. This is to prevent unintended separation of the label 20A. Examples of adhesives that have excellent adhesion to the base layer 21 made of polyester resin and are soluble in at least one of warm water and alkaline solution include acrylic emulsion adhesives.

[Manufacturing method of labeled containers]
A labeled container having the label 20A can be manufactured by appropriately combining conventionally known methods.

This section describes an example of a method for manufacturing a labeled container according to this embodiment, in which the bonding layer 23 is a base layer. First, a substrate laminate is prepared as in the first embodiment, and the bonding layer 23 and the printing layer 24 are formed on the second surface 21b of the substrate layer 21 of the substrate laminate. Next, an adhesive (not shown) is used to bond the printing layer 24 to the carrier layer 25 using a known lamination method. Examples of the adhesive include UV-curable adhesives, solvent-based adhesives, and hot-melt adhesives. This produces a label 20A equipped with a release paper. Next, the release paper is removed from the label 20A, and the exposed adhesive surface (adhesive layer 22) is adhered to the surface of the container 10. This completes the manufacturing process for a labeled container equipped with the label 20A. Note that the adhesive layer 22 may be formed by applying a polyester-based adhesive to the exposed surface (first surface 21a) of the substrate layer 21 without using a substrate laminate, and the manufacturing method for the label web is the same as in the first embodiment.

An example of a method for manufacturing a labeled container according to this embodiment, in which the bonding layer 23 is an adhesive layer, is described below. First, a substrate laminate is prepared as in the first embodiment, and an adhesive is applied to the second surface 21b of the substrate layer 21 of the substrate laminate to form the bonding layer 23 (adhesive layer). For ease of handling, it is preferable to attach a second release paper to the surface of the bonding layer 23 (adhesive layer). Next, a carrier layer 25 is prepared, and a printing layer 24 is formed on one surface of the carrier layer 25. The method for forming the printing layer 24 is not particularly limited, and any conventionally known method can be used. Next, the second release paper is removed from the bonding layer 23 (adhesive layer), and the carrier layer 25 is adhered to the exposed bonding layer 23. The layers are laminated so that the printing layer 24 is positioned between the bonding layer 23 and the carrier layer 25. This produces a label 20A equipped with a release paper. Next, the release paper is removed from the label 20A, and the exposed adhesive surface (adhesive layer 22) is adhered to the surface of the container 10. In this manner, a labeled container having the label 20A is manufactured. Note that the adhesive layer 22 may be formed by applying a polyester adhesive to the exposed surface (first surface 21a) of the base material layer 21 without using the base material laminate, and the manufacturing method of the continuous label is the same as in the first embodiment.

[effect]
The labeled container according to this embodiment can achieve the effects of the labeled container 1 according to the first embodiment, as well as the effects of the carrier layer 25. Specifically, the carrier layer 25 is a film that functions as a carrier itself. In other words, the adhesive layer 22 and the printing layer 24 are layers that can only maintain their shape on the surface of another layer that has a certain shape, whereas the base layer 21 and the carrier layer 25 can maintain their own certain shape by themselves.

Thus, the above-mentioned dissolving process causes the printed layer 24 to separate from the container 10, but with the label 20A, the printed layer 24 can exist in hot water or an alkaline solution while supported by the support layer 25. Therefore, in addition to the effects of the labeled container 1 with the label 20 described above, a labeled container equipped with the label 20A can also prevent the printed layer 24 from dispersing into fine particles in hot water or an alkaline solution.

In addition, in label 20A, the printing layer 24 is protected from external factors by the support layer 25, thereby preventing unintentional damage to the printing layer 24.

Furthermore, the support layer 25 is preferably a film with a specific gravity lower than that of water or an alkaline aqueous solution. In this case, the container 10, adhesive layer 22, and substrate 21 are made of polyester resin, which has a specific gravity higher than that of water or an alkaline aqueous solution. Therefore, the support layer 25 carrying the printing layer 24 and the container 10 to which the adhesive layer 22 and substrate layer 21 are attached can be easily separated by gravity separation in water or an alkaline solution.

The carrier layer 25 may also be, for example, a heat-shrinkable film. In this case, the carrier layer 25 can be shrunk in warm water or an alkaline solution, so as to roll up the printed layer 24. The printed layer 24 rolled up in the shrunken and curled carrier layer 25 comes into contact with warm water or an alkaline solution less frequently. This further significantly prevents the printed layer 24 from dispersing finely in warm water or an alkaline solution. It is also expected that the thermal shrinkage of the carrier layer 25 will make it easier for the base layer 21 and the printed layer 24 to separate.

Furthermore, if the support layer 25 has a specific gravity smaller than that of water or an alkaline aqueous solution and is heat-shrinkable, both easy separation by specific gravity separation and significant suppression of dispersion of the printing layer 24 are possible.

As in the first embodiment, the bonding layer 23 is preferably insoluble in hot water and soluble in an alkaline solution. In this embodiment, the bonding layer 23 may be the base layer described above or an adhesive layer. When the bonding layer 23 is a base layer, a preferred base layer is one containing a carbodiimide curing agent and a binder resin made of a polyester resin, as in the first embodiment. When the bonding layer 23 is an adhesive layer, a preferred adhesive layer is one having an adhesive strength of 2 to 25 N/25 mm.

Third Embodiment
A labeled container according to the third embodiment will be described with reference to Fig. 5. Fig. 5 discloses a label 20B which further comprises a carrier layer 25 in addition to the label 20 according to the first embodiment. That is, in the labeled container according to the third embodiment, in addition to the configuration of the labeled container according to the first embodiment, the label further comprises a carrier layer. Furthermore, the labeled container according to the third embodiment differs from the configuration of the labeled container according to the second embodiment in the arrangement of the printing layer and the carrier layer.

[Container with label]
The label 20B has a configuration in which a carrier layer 25 is further provided compared to the label 20. The carrier layer 25 is located on the opposite side of the bonding layer 23 from the base material layer 21. The carrier layer 25 is further located between the printing layer 24 and the bonding layer 23. The carrier layer 25 is the same as the carrier layer 25 according to the second embodiment. As in the second embodiment, the bonding layer 23 is preferably a base layer or an adhesive layer. The other configurations are the same as those of the first embodiment.

[Manufacturing method of labeled containers]
A labeled container having the label 20B can be manufactured by appropriately combining conventionally known methods.

An example of a method for manufacturing a labeled container according to this embodiment, in which the bonding layer 23 is a base layer, is described below. First, a substrate laminate is prepared as in the first embodiment, and a bonding layer 23 (base layer) is formed on the second surface 21b of the substrate layer 21 of the substrate laminate. Meanwhile, a carrier layer 25 is prepared, and a printing layer 24 is formed on one surface of the carrier layer 25. The method for forming the printing layer 24 is not particularly limited, and a conventionally known method can be used. Next, the bonding layer 23 (base layer) and the carrier layer 25 are bonded together using a known lamination method using an optional adhesive. Examples of the optional adhesive include UV-curable adhesives, solvent-based adhesives, and hot-melt adhesives. The printing layer 24 formed on the carrier layer 25 is positioned so that it is not positioned between the bonding layer 23 and the carrier layer 25, i.e., is positioned on the exposed surface of the label 20B. This produces a label 20B equipped with a release liner. Next, the release paper is removed from the label 20B, and the exposed adhesive surface (adhesive layer 22) is adhered to the surface of the container 10. In this manner, a labeled container equipped with the label 20B is manufactured. Note that the adhesive layer 22 may be formed by applying a polyester adhesive to the exposed surface (first surface 21a) of the base material layer 21 without using the base material laminate, and the manufacturing method of the continuous label is the same as in the first embodiment.

An example of a method for manufacturing a labeled container according to this embodiment, in which the bonding layer 23 is an adhesive layer, is described below. First, an adhesive is applied to one surface of the support layer 25 to form the bonding layer 23 (adhesive layer). For ease of handling, it is preferable to attach a release paper to the exposed surface of the bonding layer 23. Next, a printing layer 24 is formed on the surface of the support layer 25 where the bonding layer 23 is not formed. There are no particular restrictions on the method for forming the printing layer 24, and any conventionally known method can be used. Next, a substrate laminate is prepared, and the bonding layer 23 (adhesive layer) is adhered to one surface (second surface 21b) of the substrate layer 21 (the release paper is removed before adhesion). This produces a label 20B equipped with a release paper. Next, the release paper is removed from the label 20B, and the exposed adhesive surface (adhesive layer 22) is adhered to the surface of the container 10. This completes the manufacturing of a labeled container equipped with the label 20B. It should be noted that the adhesive layer 22 may be formed by applying a polyester adhesive to the exposed surface (first surface 21a) of the base layer 21 without using a base laminate, and the manufacturing method of the continuous label is the same as in the first embodiment.

[effect]
In addition to the effects of the labeled container 1 of the first embodiment, the labeled container of this embodiment also has the effect of enabling easy separation by gravity separation and/or preventing the printed layer 24 from being finely dispersed in warm water or alkaline solution.

In this embodiment, as in the second embodiment, the bonding layer 23 may be the above-mentioned base layer or an adhesive layer. When a base layer or an adhesive layer is used as the bonding layer 23, the same effects as those of the labeled container according to the second embodiment can be achieved.

The present invention will be further described in detail below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

<Evaluation method>
Using the samples prepared in each example, evaluations were carried out according to the following evaluation methods.

[Adhesion evaluation]
Adhesion was evaluated by the following method. Specifically, for each of the labels of Examples 1 to 8, a 24 mm wide adhesive tape (manufactured by Nichiban Co., Ltd., product name "Cellotape (registered trademark)") was firmly attached to the surface of the printed layer under standard conditions (23°C, 1 atmosphere, 50% RH), and then the adhesive tape was peeled off in a 180-degree direction. The surface of the adhesive tape after peeling was visually observed and evaluated according to the following criteria.
AA: No ink deposits were observed on the adhesive tape, and no ink peeling was observed.
A: Ink deposits were found on the adhesive tape, and the ink peeled area ratio of the sample piece was less than 3%.
B: Ink deposits were found on the adhesive tape, and the ink peeled area rate of the sample piece was 3% or more. The ink peeled area was calculated using the formula: (total area of areas where ink has peeled off/area of the ink layer before the tape was applied) x 100.

[Water resistance evaluation]
Each label was immersed in water at room temperature (approximately 23°C) for 24 hours, then removed from the water and allowed to stand for 1 minute and then for 10 minutes, after which the above-mentioned peel resistance test was carried out and evaluated according to the following criteria.
AA: No ink deposits were observed on the adhesive tape, and no ink peeling was observed.
A: A large amount of ink deposits was observed on the adhesive tape, and the ink peeled area ratio of the sample piece was less than 3%.
B: A large amount of ink deposits was observed on the adhesive tape, and the ink peeled area ratio of the sample piece was 3% or more but less than 10%.
C: A large amount of ink deposits was observed on the adhesive tape, and the ink peeled area rate of the sample piece was 10% or more. The ink peeled area was calculated using the formula (total area of areas where ink has peeled off/area of the ink layer before the tape was applied) x 100.

[Alkali desorption test]
Each sample (10 mm x 10 mm) was immersed in a 1.5 wt % NaOH aqueous solution at 85°C and stirred at 600 rpm for 15 minutes. The sample was then removed from the NaOH aqueous solution and allowed to stand for 5 minutes, after which the detachment of the printed layer was visually observed and evaluated according to the following criteria.
A: No printed layer was visually observed on the surface of the sample.
B: A printed layer was visually observed on the surface of the sample.

[Hot water desorption evaluation]
Each sample (10 mm x 10 mm) was immersed in warm water at 85°C and stirred at 600 rpm for 15 minutes. The sample was then removed from the warm water and allowed to stand for 5 minutes, after which the detachment of the printing layer was visually observed and evaluated according to the following criteria.
A: No printed layer was visually observed on the surface of the sample.
B: A printed layer was visually observed on the surface of the sample.

<Study 1: Alkali-soluble underlayer>
[Example 1]
A polyester film (38 μm thick, manufactured by Toyobo Co., Ltd., "E5100") was prepared as the base layer. A base layer material (resin composition) containing a carbodiimide curing agent (curing agent) and a polyester resin (binder resin) was prepared as the bonding layer material. Specifically, a polyester resin aqueous dispersion (manufactured by Mitsubishi Chemical Corporation, "WR-961") and a carbodiimide curing agent (manufactured by Nisshinbo Chemical Inc., "Carbodilite E-03A") were mixed at a solid content ratio (weight ratio) of 100:10 to prepare a resin composition. The resin composition was then solid-printed onto the base layer using a bar coater and dried (100°C, 20 seconds). The bonding layer formed on the base layer had a thickness of approximately 1 μm.

Next, a printed layer was formed on the bonding layer. Specifically, UV-curable ink ("AF Indigo" manufactured by T&K TOKA Corporation) was printed solidly on the bonding layer using a flexo coater and cured by UV irradiation. The thickness of the printed layer formed on the bonding layer was approximately 1 μm.

In this manner, a label of Example 1 (except that it did not have an adhesive layer on one side of the base layer) was produced, and then cut into 10 mm x 10 mm pieces to produce several samples.

[Example 2]
The labels and samples of Example 2 were prepared in the same manner as in Example 1, except that the resin composition of the bonding layer material was a mixture of binder resin and carbodiimide-based curing agent in a solid content ratio (weight ratio) of 100:20.

[Example 3]
The label and sample of Example 3 were prepared in the same manner as in Example 1, except that the resin composition of the bonding layer material was made up of a binder resin and a carbodiimide-based curing agent in a solid content ratio (weight ratio) of 100:30.

[Example 4]
Except for changing the material for the bonding layer, the label and sample of Example 4 were produced in the same manner as in Example 1. Specifically, a resin composition was prepared in which a polyester resin aqueous dispersion ("WR-961" manufactured by Mitsubishi Chemical Corporation) and a carbodiimide curing agent ("XL-732" manufactured by Stahl Polymers) were mixed in a solid content ratio (weight ratio) of 100:4.

[Example 5]
Except for the addition of a medium ink as a printing layer, the label and sample of Example 5 were produced in the same manner as in Example 2. Specifically, a UV-curable varnish ("FTV varnish" manufactured by T&K TOKA Corporation) was printed solidly on the ink layer consisting of the indigo ink using a flexo coater and then cured by UV irradiation.

[Example 6]
The label and sample of Example 2 were produced in the same manner as in Example 1, except that the resin composition for the bonding layer material contained a binder resin and a carbodiimide curing agent in a weight ratio (based on solid content) of 100:0. That is, a resin composition consisting only of the binder resin was used as the bonding layer material.

The evaluation results are shown in Table 1. Referring to Table 1, it was confirmed that each of the labels of Examples 1 to 6 had high alkali releasability while maintaining sufficient adhesion and water resistance after 1 minute. Furthermore, it was confirmed that each of the labels of Examples 1 to 5 had high alkali releasability while maintaining sufficient adhesion, water resistance after 1 minute, and water resistance after 10 minutes. Therefore, it was confirmed that each of the labels of Examples 1 to 6 had the function of a label while allowing the ink layer to be easily removed by contact with an alkaline solution. It was also confirmed that each sample did not have hot water releasability.

<Study 2: Hot water desorbable base layer>
[Example 7]
The label and sample of Example 7 were produced in the same manner as in Example 1, except that a resin composition consisting solely of a polyester resin aqueous dispersion ("WR901S20WO" manufactured by Mitsubishi Chemical Corporation) was used as the bonding layer material.

[Example 8]
The label and sample of Example 8 were produced in the same manner as in Example 7, except that "WR905S20WO" manufactured by Mitsubishi Chemical Corporation was used.

The evaluation results are shown in Table 2. Referring to Table 2, it was confirmed that the labels of Examples 7 and 8 had sufficient adhesion and water resistance after 10 minutes, while also having high hot water releasability. Therefore, it was confirmed that the labels of Examples 7 and 8 function as labels, while allowing the ink layer to be easily removed by contact with hot water. It was also confirmed that none of the samples had alkaline releasability.

<Study 3>
A labeled container model was produced using the label of Example 1. Specifically, a 10 mm x 10 mm polyester film (thickness 100 μm, manufactured by Toyobo Co., Ltd., "E5100") was used as the container. An adhesive was applied to the exposed surface of the base layer of the label of Example 1, and this was adhered to the polyester film. The laminate produced in this manner was used as a labeled container model. A polyester adhesive was used as the adhesive material, and it was applied to the surface of the base layer using a gravure printing machine so that the adhesive layer would have a thickness of 20 μm after drying.

When an alkali release test was conducted using the manufactured model, no printed layer was observed on the surface of the polyester film used as a container, and only the film base layer was visible.

1 Container with label, 10 Container, 20 Label, 21 Base layer, 21a First surface, 21b Second surface, 22 Adhesive layer, 23 Bonding layer, 24 Printing layer, 25 Carrier layer, 30 Cap.

Claims (7)

A labeled container to which a label is attached,
The container is a polyester-based container,
The label has a base layer having a first surface and a second surface facing each other, an adhesive layer that bonds the first surface of the base layer and the container to each other, a bonding layer that is laminated on the second surface of the base layer, and a printing layer that is located on the opposite side of the bonding layer from the base layer,
the substrate layer is a polyester film that is insoluble in hot water and alkaline solutions,
the adhesive layer is a polyester adhesive that is insoluble in hot water and alkaline solutions,
A labeled container, wherein the bonding layer is soluble in at least one of warm water and an alkaline solution. The labeled container according to claim 1, wherein the bonding layer is insoluble in hot water and soluble in an alkaline solution. The labeled container according to claim 1 or 2, wherein the polyester container, the polyester film, and the polyester adhesive are primarily composed of the same type of polyester resin. The labeled container according to claim 3, wherein the homogeneous polyester resin is polyethylene terephthalate. The labeled container according to any one of claims 1 to 4, wherein the label has a support layer that supports the printing layer and is located on the opposite side of the bonding layer from the base layer. The labeled container according to claim 5, wherein the printing layer is located between the carrier layer and the bonding layer. 2. A method for recycling a labeled container according to claim 1, comprising:
providing a labeled container;
A step of treating the labeled container with an alkali to remove the bonding layer, thereby separating the printed layer from the labeled container;
recycling the labeled container from which the printed layer has been separated;
A method for recycling labeled containers, including: