Method for removing ink layer from shrink label

Abstract

To provide a method of efficiently removing an ink layer.SOLUTION: There is provided a method of removing an ink layer from a shrink label, comprising the steps of preheating a shrink label including an ink layer, shredding a shrink label 11 after the preheating to fabricate a shrink label piece 71, and removing the ink layer from the shrink label piece 71 by alkaline desorption. A temperature of the preheating is the same as a temperature of the alkaline desorption or higher than the temperature of the alkaline desorption.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for removing an ink layer from a shrink label.

Background Art

[0002] In recent years, plastic products such as polyethylene terephthalate bottles (PET bottles) have been widely used. From the viewpoints of resource conservation and the environment, etc., it is strongly demanded to reuse plastic products such as PET bottles.

[0003] Among plastic products, in particular, the reuse of PET bottles has already been established. However, a shrink label made of plastic and having an ink layer printed for displaying product information or the like may be attached to the body of a PET bottle, but the reuse of this shrink label has not yet been achieved.

[0004] One of the factors that hinders the reuse of shrink labels is that the ink layer cannot be efficiently removed from the shrink labels. If the ink layer cannot be efficiently removed from the shrink label, it is because pellets with useful value cannot be produced from the shrink label.

[0005] For example, Patent Document 1 describes a method in which a heat-shrinkable label is heated and shrunk under non-aqueous immersion conditions and then brought into contact with low-temperature alkaline water to detach and remove the ink layer.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Although it is possible to remove the ink layer by the method described in Patent Document 1, due to the increasing environmental awareness in recent years, a more efficient method for removing the ink layer is desired.

Means for Solving the Problems

[0008] According to the embodiment disclosed herein, there are provided a step of preheating a shrink label provided with an ink layer, a step of crushing the shrink label after the preheating step to produce shrink label pieces, and a step of removing the ink layer from the shrink label pieces by alkali detachment, and the temperature of the preheating is the same as or higher than the temperature of the alkali detachment, and a method for removing the ink layer from the shrink label can be provided.

Advantages of the Invention

[0009] According to the embodiment disclosed herein, a method for removing the ink layer more efficiently than before can be provided.

Brief Description of the Drawings

[0010]

Figure 1

Modes for Carrying Out the Invention

[0011] Figs. 1(a) to (i) show a diagram illustrating an example of the flow of a method for removing an ink layer from a shrink label according to an embodiment. Hereinafter, with reference to Figs. 1(a) to (i), a method for removing an ink layer from a shrink label according to the embodiment will be described.

[0012] <Recovery Step> First, as shown in Fig. 1(a), the PET bottle 10 is recovered in the recovery box 12. Here, a shrink label 11 provided with an ink layer is attached to the body portion of the PET bottle 10. The ink layer is a printing layer for product display and the like.

[0013] As the shrink label 11, for example, a shrink label having an ink layer removable by an alkaline aqueous solution on at least one surface of a heat-shrinkable shrink film (base material) can be used. Examples of the shrink film include polyester films made of polyethylene terephthalate, polyethylene naphthalate, etc.; styrene-based films made of styrene-butadiene block copolymers, etc.; olefin-based films made of olefin resins such as polyethylene and polypropylene; vinyl chloride-based films made of vinyl chloride resins, and the like. These may be foamed films. The shrink film may be single-layer or a laminate of two or more layers. The color of the shrink film is not particularly limited, and may be, for example, milky white or transparent.

[0014] From the viewpoint of shrink adhesion to various containers and the like, the heat shrinkage rate of the shrink film in at least one direction X (main shrinkage direction) is preferably 30% or more, more preferably 50% or more. The thickness of the shrink film can be appropriately selected in consideration of the handleability of the shrink label 11, etc., and can be, for example, about 10 to 100 μm, preferably about 15 to 60 μm. Note that these numerical values of the shrink film are the numerical values of the shrink film used for the production of the shrink label 11 before being attached to a container such as a PET bottle 10.

[0015] The surface of the shrink film may be subjected to a surface treatment such as corona discharge treatment or provided with an anchor coat layer as necessary to enhance the adhesion to the ink layer. The anchor coat layer can be formed by a conventionally known anchor coating agent or the like.

[0016] The ink layer only needs to be soluble or swellable in an alkaline aqueous solution and detachable from the base material, and can be constituted by, for example, either an oil-based ink or an aqueous ink.

[0017] As a method for forming an ink layer on the surface of a shrink film, for example, a method of forming an ink layer on the surface of a shrink film by gravure printing, flexographic printing, screen printing, inkjet printing, or the like can be used. The ink layer may be a single layer or a multilayer. The thickness of the ink layer can be appropriately selected according to the application or the like, and can be, for example, about 0.1 to 100 μm. Further, when the ink layer is a multilayer, the entire ink layer may be alkali-soluble, or at least in its laminated structure, it is sufficient that the ink layer located closest to the shrink film side is alkali-soluble.

[0018] <Compression step> Next, as shown in Fig. 1(b), the recovered PET bottle 10 is compressed with the shrink label 11 attached thereto to obtain a bale 20 with a shrink label.

[0019] <Integration step> Next, as shown in Fig. 1(c), the bale 20 with a shrink label is sent to a recycling factory 30 and integrated.

[0020] <Separation step> Next, as shown in Fig. 1(d), at the recycling factory 30, the shrink label 11 is removed from the PET bottle 10 of the bale 20 with a shrink label, and the PET bottle 10 and the shrink label 11 are separated. The objects to be removed from the PET bottle 10 include normal labels 40 other than the shrink label 11. The PET bottle 10 from which the shrink label 11 and / or the normal label 11 has been separated is reused in the recycling process of existing PET bottles. Examples of the normal label 40 include a shrink label or a non-shrink label having an ink layer that is non-alkali water-detachable.

[0021] <Sorting step> Next, as shown in FIG. 1(e), the shrink label 11 and the normal label 40 are sorted to separate and recover the shrink label 11 from the normal label 40. The normal label 40 separated and recovered from the shrink label 11 is reused, for example, in a thermal recycling process.

[0022] <Preheating step> Next, as shown in FIG. 1(f), the shrink label 11 provided with the ink layer is preheated. The method of preheating the shrink label 11 is not particularly limited as long as it can suppress the amount of shrinkage and curling of the shrink label pieces in the alkali detachment described later. However, the preheating is performed such that the preheating temperature is the same as or higher than the alkali detachment temperature. From the viewpoint of efficiently removing the ink layer from the shrink label pieces in the alkali detachment described later, the preheating temperature is preferably 5°C or higher than the alkali detachment temperature.

[0023] Examples of the method of preheating the shrink label 11 include a method of passing the shrink label 11 through a hot air tunnel 61 or a method of immersing the shrink label 11 in the warm water 60 in a warm water tank 62.

[0024] However, from the viewpoints of the following 1) to 4), it is preferable to use the method of immersing the shrink label 11 in the warm water 60 in the warm water tank 62 as the method of preheating the shrink label 11 rather than the method of passing the shrink label 11 through the hot air tunnel 61.

[0025] 1) When using hot air, the shrink label 11 removed from the PET bottle 10 is blown away by the hot air, making control difficult. 2) The method of immersing in warm water is easier to control the temperature than the method of using hot air. 3) The method of immersing in warm water has a smaller footprint of the device than the method of using hot air. 4) The method of immersing in warm water is less likely to cause uneven shrinkage of the shrink label 11 than the method of using hot air and can shrink uniformly.

[0026] When preheating the shrink label 11 by immersing the shrink label 11 in the warm water 60 in the warm water tank 62, for example, it can be carried out by immersing the shrink label 11 in warm water at about 80°C to 90°C for about 10 seconds to 20 seconds.

[0027] The preheating temperature means the surface temperature of the shrink label 11 during preheating. Therefore, when preheating the shrink label 11 by immersing the shrink label 11 in the warm water 60 in the warm water tank 62, the preheating temperature can be replaced with the temperature of the warm water. Also, when preheating the shrink label 11 by passing the shrink label 11 through the hot air tunnel 61, the preheating temperature can be replaced with the temperature of the hot air.

[0028] <Crushing process> Next, as shown in FIG. 1(g), the preheated shrink label 11 is crushed by a crusher 70 to produce shrink label pieces 71. The method of crushing the preheated shrink label 11 is not particularly limited as long as the size of the shrink label pieces 71 generated after the crushing is smaller than the size of the preheated shrink label 11. For example, the preheated shrink label 11 can be crushed to a size (for example, several cm square) that can efficiently remove the ink layer from the shrink label pieces 71 in the alkali desorption described later.

[0029] <Alkali desorption process> Next, as shown in FIG. 1(h), the ink layer is removed from the shrink label pieces 71 by alkali desorption. The alkali desorption can be carried out, for example, by any one of the following treatments (1) or (2).

[0030] (1) One-tank treatment This treatment can be performed by immersing the shrink label piece 71 in the alkaline aqueous solution 80 in the hot alkaline tank 82 and stirring it. The time required for the treatment varies depending on the stirring speed, the amount of the shrink label piece 71 dropped into the alkaline aqueous solution 80, etc., but is about 30 seconds to 20 minutes. According to this treatment, the shrink film piece 101 and the ink coating 103 can be efficiently separated in the alkaline aqueous solution 80.

[0031] As described above, in this embodiment, the preheating temperature is set to be the same as or higher than the alkaline desorption temperature. The alkaline desorption temperature means the surface temperature of the shrink label piece 71 at the time of alkaline desorption. Therefore, the alkaline desorption temperature can be replaced with the temperature of the alkaline aqueous solution 80 in which the shrink label piece 71 is immersed. From the viewpoint of efficiently removing the ink layer from the shrink label piece 71 in alkaline desorption, the alkaline desorption temperature (the temperature of the alkaline aqueous solution 80) is preferably 65°C or higher. The upper limit of the alkaline desorption temperature is theoretically 100°C, more preferably the alkaline desorption temperature is 85°C or higher and 95°C or lower, and even more preferably the alkaline desorption temperature is 80°C or higher and 90°C or lower.

[0032] The alkaline aqueous solution 80 after removing the ink layer from the shrink label piece 71 may be discarded as waste liquid, or may be reused as the alkaline aqueous solution 80 for alkaline desorption.

[0033] The alkaline aqueous solution 80 is not particularly limited as long as it can remove the ink layer from the shrink label piece 71 by immersing the shrink label piece 71, and is not particularly limited as long as it is an alkaline aqueous solution containing an alkaline substance. For example, an aqueous solution of an alkali metal hydroxide such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), an aqueous solution of an alkali metal carbonate such as sodium carbonate (Na2CO3), an aqueous solution of an alkali metal bicarbonate such as sodium bicarbonate (NaHCO3), or aqueous ammonia can be used.

[0034] The concentration of the alkaline substance in the alkaline aqueous solution 80 can be appropriately selected within a range that does not impair the peelability, operability, workability, etc. of the ink layer. For example, it is about 0.1 to 10% by weight, preferably 0.5 to 5% by weight, and more preferably about 1 to 3% by weight.

[0035] (2) Two-tank treatment In this treatment, the shrink label piece 71 is immersed in the alkaline aqueous solution 80 in the hot alkaline tank 82 for about 30 seconds to 20 minutes, and then the shrink label piece 71 is taken out from the hot alkaline tank 82. The taken-out shrink label piece 71 can be stirred while being immersed in water in a water tank (not shown). The preferable temperature (alkali detachment temperature) and type of the alkaline aqueous solution 80 are the same as those of the alkaline aqueous solution 80 used in the above (1) one-tank treatment. The temperature of the water in the water tank is not particularly limited, but from the viewpoint of avoiding unintentional shrinkage of the shrink label piece 71, it is preferably a temperature lower than the alkali detachment temperature, and from the viewpoint of energy consumption, it is preferably about room temperature (around 27 °C).

[0036] According to this treatment, the shrink label piece 71 is gently immersed in the alkaline aqueous solution 80. Thereby, in the alkaline aqueous solution 80, while suppressing the complete separation of the ink layer from the shrink label piece 71, the adhesion between the two can be reduced. Note that being gently immersed means a state in which the alkaline aqueous solution 80 is not stirred or is stirred very gently so that the complete separation of the above two does not occur. Then, by subsequent immersion in water and stirring, the shrink film piece 101 and the ink coating 103 can be separated in water.

[0037] The alkaline aqueous solution 80 after immersing the shrink label piece 71 may be discarded as waste liquid, or may be reused as the alkaline aqueous solution 80 for alkali desorption. In the case of two-tank treatment, since the change in the characteristics of the alkaline aqueous solution 80 is less than that in one-tank treatment, the alkaline aqueous solution 80 can be reused more efficiently. Examples of the change in the characteristics of the alkaline aqueous solution 80 include the mixing of a large amount of the ink layer.

[0038] <Separation step> Next, as shown in Fig. 1(i), the shrink film piece 91 and the ink coating film 93 are separated. Specifically, for example, the shrink film piece 91 after the ink layer is removed from the shrink label piece by the first net 90 having a relatively large opening is collected, and the ink coating film 93 smaller than the shrink film piece 91 is collected by the second net 92 having a relatively small opening. The ink coating film 93 is a film in which the ink layer removed from the shrink label piece during alkali desorption is finely divided.

[0039] Thereafter, the shrink film piece 91 collected by the first net 90 can be reused as a plastic raw material for manufacturing plastic products such as pellets. Also, by mixing the shrink film piece 91 into the raw material of a new shrink label, it can be reused as a shrink label. On the other hand, the ink coating film 93 collected by the second net 92 can be reused, for example, in a thermal recycling process.

[0040] The method for removing the ink layer from the shrink label of the embodiment includes a step of preheating the shrink label provided with the ink layer, a step of crushing the shrink label after the preheating step to produce shrink label pieces, and a step of removing the ink layer from the shrink label pieces by alkali desorption, and the temperature of the preheating is the same as or higher than the temperature of the alkali desorption.

[0041] The method for removing the ink layer from the shrink label of the embodiment can remove the ink layer from the shrink label more efficiently than before by including at least these configurations.

[0042] That is, in the present embodiment, prior to removing the ink layer from the shrink label by alkali detachment, the shrink label is crushed into shrink label pieces. This is because the ink layer can be efficiently removed from the shrink label by crushing the shrink label and performing alkali detachment in a state where it is made into smaller shrink label pieces.

[0043] However, when shrink label pieces produced by crushing a shrink label that has not been preheated are immersed in an alkaline aqueous solution, the shrink label pieces in the alkaline aqueous solution wind around and curl while shrinking. It is very difficult to remove the ink layer from the curled small shrink label pieces.

[0044] Shrink labels attached to PET bottles or the like have been thermally shrunk once at the time of attachment, but the shrinking ability still remains in the shrink label. Therefore, when the temperature of the alkaline aqueous solution during alkali detachment is high, the shrink label pieces will further thermally shrink. On the other hand, when the temperature of the alkaline aqueous solution is low, the ink layer cannot be efficiently removed from the shrink label pieces.

[0045] Therefore, in the present embodiment, before crushing the shrink label into shrink label pieces, the shrink label is preheated at a temperature equal to or higher than the temperature of alkali detachment to pre-thermally shrink it. Then, the shape of the shrink label can be made, for example, a wavy shape with a small degree of curling.

[0046] Then, the shrink label that has been pre-heated and pre-shrunk is crushed into shrink label pieces. The shrink label pieces obtained by crushing a shrink label with a small degree of curling also have a small degree of curling. Incidentally, if the shrink label is pre-heated after being crushed, the shrink label pieces will curl (be in a wrapped shape) as a whole, which is not suitable for removing the ink layer.

[0047] Thereafter, for such shrink label pieces, alkali desorption is performed at a temperature the same as or lower than the pre-heating temperature. Thereby, even when the temperature of the alkaline aqueous solution during alkali desorption is high, the ink layer can be removed while suppressing the shrinkage of the shrink label pieces during alkali desorption.

[0048] For the above reasons, in this embodiment, it is considered that the ink layer can be removed more efficiently than before.

[0049] In particular, generally, many of the shrink labels 11 removed from containers such as PET bottles 10 have a side length of 10 cm or more. After such a large shrink label 11 is thermally shrunk by pre-heating, it is crushed into several cm squares, preferably 5 cm squares or less, and alkali desorption is performed at 65 °C or higher, preferably 80 °C or higher, more preferably 85 °C or higher, thereby significantly improving the efficiency of removing the ink layer.

[0050] Examples of the shrink label 11 suitable for the method of this embodiment include a shrink label that, after being removed from a container such as a PET bottle 10 and immersed in a warm bath at 95 °C for 10 seconds, has a shrinkage rate of 30% or more, preferably 40% or more, more preferably 50% or more, measured in the radial direction (main shrinkage direction) of the container.

[0051] Also, although vigorous stirring of an alkaline aqueous solution is dangerous, according to this embodiment, since the degree of curling is small, the alkaline aqueous solution can contact the entire surface of the label piece 71 without vigorous stirring, and thus the removal of the ink layer from the shrink label 11 becomes possible.

[0052] <Experimental Example 1> First, using a raw sheet of a PET-based shrink film with a thickness of 50 μm (Hispet (registered trademark) LX-18S manufactured by Mitsubishi Chemical Corporation), a tubular shrink film with a thickness of 50 μm × height (width) of 15 cm × circumference of 24 cm was prepared. A shrink label was created by laminating a first ink layer, a second ink layer, and a third ink layer in this order on the surface of the tubular shrink film. The first ink layer is an alkali-soluble ink layer, and the second ink layer and the third ink layer are non-alkali-soluble ink layers, and the thickness of each ink layer was about 2 μm.

[0053] Specifically, the first ink layer was a resin layer formed by drying an ink containing 56% by weight of ethyl acetate, 8% by weight of isopropyl alcohol, 15% by weight of n-propyl acetate, 3% by weight of nitrocellulose, 15% by weight of an acrylic resin, and 3% by weight of a vinyl chloride-vinyl acetate copolymer. The second ink layer was a resin layer formed by drying the product name "Corras 114 Red KT2" (manufactured by DIC Graphics Co., Ltd.). The third ink layer was a resin layer formed by drying the product name "NT Highlamic (NF) 701 White" (manufactured by Dainichi Seika Kogyo Co., Ltd.).

[0054] Next, a PET bottle with a shrink label was produced by shrinking the shrink label while it was attached to a tubular PET bottle with an outer diameter of 54 mm. At this time, the shrinkage rate of the shrink label was about 30%, and the area of the shrink label after attachment was about 70% of the area of the shrink label before attachment. Then, the shrink label was peeled off from the PET bottle.

[0055] Next, while gently stirring the warm water, the shrink label peeled from the PET bottle was immersed in the warm water at 70°C for 20 seconds for preheating. As a result, the area (length × width) of the shrink label became about 50% of the area of the shrink label before preheating (the area of the shrink label after attachment).

[0056] Next, the preheated shrink label was crushed to produce shrink label pieces in a substantially square shape with a length of 40 mm × a width of 40 mm.

[0057] Thereafter, the shrink label pieces were immersed in a 1.5 wt% NaOH aqueous solution at 70°C for 60 seconds while stirring the NaOH aqueous solution to perform alkali detachment of the ink layer from the shrink film.

[0058] The above steps were performed on 10 shrink label pieces, and the number of shrink label pieces from which the ink layer was removed from the shrink film was confirmed. The results are shown in Table 1.

[0059] As shown in Table 1, in Experimental Example 1, the number of shrink label pieces in which the ink layer remained on the surface of the shrink film after alkali detachment was 0 out of 10. <Experimental Example 2> In Experimental Example 2, the ink layer was removed from the shrink film of the shrink label pieces in the same method and under the same conditions as in Experimental Example 1, except that the temperatures of the warm water and the NaOH aqueous solution were each set to 80°C, and the number of shrink label pieces from which the ink layer was removed was confirmed. The results are shown in Table 1.

[0060] As shown in Table 1, in Experimental Example 1, the number of shrink label pieces in which the ink layer remained on the surface of the shrink film after alkali detachment was 0 out of 10.

[0061] <Experimental Example 3> In Experimental Example 3, the ink layer was removed from the shrink film of the shrink label piece in the same method and under the same conditions as in Experimental Example 1, except that the temperatures of the warm water and the NaOH aqueous solution were each set to 90°C, and the number of shrink label pieces with the ink layer removed was confirmed. The results are shown in Table 1.

[0062] As shown in Table 1, in Experimental Example 3, the number of shrink label pieces with the ink layer remaining on the surface of the shrink film after alkali desorption was 1 out of 10.

[0063] <Experimental Example 4> In Experimental Example 4, the ink layer was removed from the shrink film of the shrink label piece in the same method and under the same conditions as in Experimental Example 1, except that the temperatures of the warm water and the NaOH aqueous solution were each set to 95°C, and the number of shrink label pieces with the ink layer removed was confirmed. The results are shown in Table 1.

[0064] As shown in Table 1, in Experimental Example 4, the number of shrink label pieces with the ink layer remaining on the surface of the shrink film after alkali desorption was 1 out of 10.

[0065] <Experimental Example 5> In Experimental Example 5, the ink layer was removed from the shrink film of the shrink label piece in the same method and under the same conditions as in Experimental Example 1, except that the temperature of the warm water was set to 80°C, and the number of shrink label pieces with the ink layer removed was confirmed. The results are shown in Table 2.

[0066] As shown in Table 2, in Experimental Example 5, the number of shrink label pieces with the ink layer remaining on the surface of the shrink film after alkali desorption was 0 out of 10.

[0067] <Experimental Example 6> In Experimental Example 6, the ink layer was removed from the shrink film of the shrink label piece in the same manner and under the same conditions as in Experimental Example 1, except that the temperature of the warm water was set to 90°C, and the number of shrink label pieces with the ink layer removed was confirmed. The results are shown in Table 2.

[0068] As shown in Table 2, in Experimental Example 6, the number of shrink label pieces with the ink layer remaining on the surface of the shrink film after alkali desorption was 0 out of 10.

[0069] <Experimental Example 7> In Experimental Example 7, the ink layer was removed from the shrink film of the shrink label piece in the same manner and under the same conditions as in Experimental Example 1, except that the temperature of the warm water was set to 90°C and the temperature of the NaOH aqueous solution was set to 85°C, and the number of shrink label pieces with the ink layer removed was confirmed. The results are shown in Table 2.

[0070] As shown in Table 2, in Experimental Example 7, the number of shrink label pieces with the ink layer remaining on the surface of the shrink film after alkali desorption was 0 out of 10.

[0071] <Experimental Example 8> In Experimental Example 8, the ink layer was removed from the shrink film of the shrink label piece in the same manner and under the same conditions as in Experimental Example 1, except that the temperature of the warm water was set to 90°C and the temperature of the NaOH aqueous solution was set to 80°C, and the number of shrink label pieces with the ink layer removed was confirmed. The results are shown in Table 2.

[0072] As shown in Table 2, in Experimental Example 8, the number of shrink label pieces with the ink layer remaining on the surface of the shrink film after alkali desorption was 0 out of 10.

[0073] <Experimental Example 9> In Experimental Example 9, the shrink label piece was immersed in an 80°C aqueous NaOH solution for 10 minutes without stirring, and then the shrink label piece taken out from the aqueous NaOH solution was immersed in water at 27°C (room temperature) for 5 minutes while stirring. Except for this, the ink layer was removed from the shrink film of the shrink label piece in the same method and under the same conditions as in Example 5, and the number of shrink label pieces from which the ink layer was removed was confirmed. The results are shown in Table 2.

[0074] As shown in Table 2, in Experimental Example 9, the number of shrink label pieces in which the ink layer remained on the surface of the shrink film after alkali desorption was 0 out of 10.

[0075] <Experimental Example 10> In Experimental Example 10, the ink layer was removed from the shrink film of the shrink label piece in the same method and under the same conditions as in Experimental Example 1, except that the temperature of the warm water was set to 80°C and the temperature of the aqueous NaOH solution was set to 90°C, and the number of shrink label pieces from which the ink layer was removed was confirmed. The results are shown in Table 3.

[0076] As shown in Table 3, in Experimental Example 10, the number of shrink label pieces in which the ink layer remained on the surface of the shrink film after alkali desorption was 8 out of 10.

[0077] <Experimental Example 11> In Experimental Example 11, the ink layer was removed from the shrink film of the shrink label piece in the same method and under the same conditions as in Experimental Example 1, except that the temperature of the warm water was set to 80°C and the temperature of the aqueous NaOH solution was set to 95°C, and the number of shrink label pieces from which the ink layer was removed was confirmed. The results are shown in Table 3.

[0078] As shown in Table 3, in Experimental Example 11, the number of shrink label pieces in which the ink layer remained on the surface of the shrink film after alkali desorption was 5 out of 10.

[0079] <Experimental Example 12> In Experimental Example 12, the ink layer was removed from the shrink film of the shrink label piece in the same method and under the same conditions as in Experimental Example 1, except that the temperature of the warm water was set to 90°C and the temperature of the NaOH aqueous solution was set to 95°C, and the number of shrink label pieces from which the ink layer was removed was confirmed. The results are shown in Table 3.

[0080] As shown in Table 3, in Experimental Example 12, the number of shrink label pieces in which the ink layer remained on the surface of the shrink film after alkali detachment was 4 out of 10.

[0081] [Table 1]

[0082] [Table 2]

[0083] [Table 3]

[0084] In Tables 1 to 3, Experimental Examples 1 to 9 are examples, and Experimental Examples 10 to 12 are comparative examples. As is clear from the comparison between Experimental Examples 1 to 9 and Experimental Examples 10 to 12, after preheating the shrink label, the shrink label was crushed into shrink label pieces, and in Experimental Examples 1 to 9 where the ink layer was alkali-detached from the shrink label pieces with a NaOH aqueous solution at a temperature lower than the temperature of the preheating warm water, it was confirmed that the ink layer could be removed from more shrink label pieces than in Experimental Examples 10 to 12 where alkali detachment was performed with a NaOH aqueous solution at a temperature higher than the temperature of the preheating warm water.

[0085] Also, as is clear from the comparison between Experimental Examples 1 to 4 and Experimental Examples 5 to 9, in Experimental Examples 5 to 9 where alkali detachment was performed with an aqueous NaOH solution at a temperature lower than the temperature of the preheating warm water, it was confirmed that the ink layer could be removed from more shrink label pieces compared to Experimental Examples 1 to 4 where alkali detachment was performed with an aqueous NaOH solution at the same temperature as the preheating warm water.

[0086] Also, in Experimental Examples 1 to 8 which are Examples, since the time from immersing the shrink label piece in the aqueous NaOH solution until the ink layer was removed from the shrink label piece was about 60 seconds, it was also confirmed that the ink layer could be removed much more efficiently compared to Patent Document 1 which requires immersion for 5 to 30 minutes. Further, in Experimental Example 9 which is an Example, since the ink coating film remaining in the aqueous NaOH solution was extremely small, it was also confirmed that the reuse of the aqueous NaOH solution was easy.

[0087] Although the embodiments and examples have been described as above, it was initially planned to appropriately combine each configuration of the above-described embodiments and examples.

[0088] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0089] 10 PET bottle, 11 Shrink label, 12 Collection box, 20 Label with shrink label, 30 Recycling factory, 40 Normal label, 60 Warm water, 61 Hot air tunnel, 62 Warm water tank, 70 Crusher, 71 Shrink label piece, 80 Alkaline aqueous solution, 82 Hot alkaline tank, 90 First net, 91 Shrink film piece, 92 Second net, 93 Ink coating film.

Claims

1. A step of preheating a shrink label provided with an ink layer; A step of crushing the shrink label after the preheating step to produce shrink label pieces; A step of removing the ink layer from the shrink label pieces by alkali detachment, and A method for removing an ink layer from a shrink label, wherein the temperature of the preheating is the same as or higher than the temperature of the alkali detachment.

2. The method for removing an ink layer from a shrink label according to Claim 1, wherein the temperature of the alkali detachment is 65°C or higher.

3. The method for removing an ink layer from a shrink label according to Claim 1 or Claim 2, wherein the preheating step includes a step of immersing the shrink label in warm water.

4. The method for removing an ink layer from a shrink label according to any one of Claims 1 to 3, wherein the temperature of the preheating is 5°C or higher than the temperature of the alkali detachment.

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