Separation method

Abstract

To realize a sorting method capable of further accurately sorting articles and labels.SOLUTION: A sorting method (S100) for sorting labels (11) and PET bottles (10) includes: crushing step (S41) for crushing the labels (11) and the PET bottles (10) into label pieces (71) and bottle pieces (72); immersing step (S42) for immersing the label pieces (71) and the bottle pieces (72) in water (W); and bubbling step (S43) for generating bubbles (B) in the water (W) to allow the bubbles (B) to adhere to the label pieces (71) and the bottle pieces (72).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for separating labels.

Background Art

[0002] Conventionally, plastic products such as PET (polyethylene terephthalate) bottles have been widely used. From the viewpoints of resource saving and environmental protection, etc., it is required to reuse plastic products such as PET bottles and labels attached to PET bottles. In order to recycle these plastic products, it is necessary to separate articles (especially containers) such as PET bottles and labels and recycle them separately.

[0003] As separation methods for separating articles and labels, as disclosed in Patent Document 1, a specific gravity separation method and a pneumatic separation method are known. The specific gravity separation method puts a crushed body in which crushed articles and labels are mixed into water, and separates the crushed body into labels that float in water (those with a specific gravity of less than 1.0) and articles that sink in water (those with a specific gravity of 1.0 or more). The pneumatic separation method separates the crushed body into labels with relatively small mass and articles with large mass by blowing air onto the crushed body to blow off the labels with relatively small mass.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the specific gravity separation method, in the case of labels with a specific gravity of 1.0 or more, the labels sink in water together with the articles, and there is a problem that they cannot be separated from the articles and the labels. Further, in the winnowing separation method, in recent years, since PET bottles have become lighter and thinner, there is a problem that the articles fly away together with the labels and the articles and the labels cannot be accurately separated. Therefore, there has been a demand for a technology for accurately separating articles and labels.

[0006] One aspect of the present invention aims to realize a separation method capable of more accurately separating an article and a label.

Means for Solving the Problems

[0007] In order to solve the above problems, a label separation method according to one aspect of the present invention is a separation method for separating a label and an article, including a crushing step of crushing the label and the article into label pieces and article pieces, a dipping step of dipping the label pieces and the article pieces in a liquid, and a bubbling step of generating bubbles in the liquid and attaching the bubbles to the label pieces and the article pieces.

[0008] According to the above method, in the bubbling step, by attaching bubbles to the label pieces and the article pieces immersed in the liquid, the label pieces, which are thinner and have a smaller mass (weight) than the article pieces, are more likely to float in the liquid. For this reason, the label pieces can be floated to the liquid surface by the buoyancy of the bubbles, and the article pieces, which are thicker and have a larger mass than the label pieces, remain sunk in the liquid. As a result, even labels that could not be separated by the conventional specific gravity separation method can be separated from the articles and the labels. Further, if the bubbling step is performed without crushing the label and the article, the label and the article may interfere with each other and the article may prevent the label from floating. In the crushing step, by crushing the label and the article into label pieces and bottle pieces, it is possible to prevent the article pieces from preventing the floating of the label pieces. As a result, the label pieces are more likely to float, and the label and the article can be accurately separated.

[0009] In the above separation method, the diameter of the bubbles may be 0.5 mm or more and 1.0 mm or less.

[0010] According to the above method, in the bubbling step, bubbles can be similarly attached to the label piece and the bottle piece. Therefore, even for a label and an article having a specific gravity greater than that of the liquid immersed in the liquid in the immersion step, the label and the article can be suitably separated.

[0011] In the above separation method, in the bubbling step, the liquid may be vibrated or air may be supplied into the liquid through a bubble generating portion.

[0012] According to the above method, bubbles can be suitably generated in the liquid and attached to the label piece and the article piece.

[0013] In the above separation method, in the crushing step, the label and the article may be crushed into the label pieces and the article pieces having a size of 5 mm square or more and 20 mm square or less.

[0014] According to the above method, when the label pieces and the article pieces float and sink in the liquid, it is possible to avoid interference with each other. Thereby, the label and the article can be suitably separated.

[0015] In the above separation method, in the crushing step, the article with the label attached thereto may be crushed.

[0016] According to the above method, by crushing the article with the label attached thereto, the label and the article can be separated while being crushed. Therefore, the step of peeling (separating) the label from the article and the step of crushing the label and the article can be carried out simultaneously, and the step of peeling the label from the article can be omitted.

Advantages of the Invention

[0017] According to one aspect of the present invention, it is possible to realize a separation method capable of more accurately separating an article and a label.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0019] 〔Embodiment 1〕 FIG. 1 is a schematic diagram showing an example of the flow of the sorting method S100 of the label 11 according to Embodiment 1 of the present invention. The sorting method S100 of the label 11 is a sorting method for separating the label 11 and the PET bottle 10 (article). As shown in FIG. 1, the label sorting method S100 includes a bottle collection step S1, a compression step S2, an accumulation step S3, and a sorting step S4. Hereinafter, with reference to FIG. 1, each step of the sorting method S100 of the label 11 will be described. In the label sorting method S100, the bottle collection step S1, the compression step S2, and the accumulation step S3 may be omitted.

[0020] In the present embodiment, an example will be described in which the label 11 is a shrink label made of PET (polyethylene terephthalate) and the article to which the label 11 is attached is a PET bottle 10. Note that the label 11 is not limited to a shrink label, and may be various labels such as a wrap-around label (roll label) and a stretch label. Further, the article to which the label 11 is attached is not limited to the PET bottle 10, and may be any article that is used with the label 11 attached, such as a container other than the PET bottle 10 or various molded products other than containers.

[0021] <Bottle Collection Step> First, as shown in S1 of FIG. 1, the used PET bottle 10 is collected in the collection box 12. A label 11 having an ink layer containing ink is attached to the body of the PET bottle 10.

[0022] <Compression step> Next, as shown in S2 of FIG. 1, the collected PET bottle 10 with the label 11 attached is compressed to obtain the labeled bale 20.

[0023] <Accumulation step> Next, as shown in S3 of FIG. 1, the labeled bale 20 is sent and accumulated to the recycling factory 30.

[0024] <Separation step> The separation step S4 is a step of separating and sorting the label 11 and the PET bottle 10. The separation step S4 includes a crushing step S41, a dipping step S42, and a bubbling step S43.

[0025] <Crushing step> In the crushing step S41, as shown in S41 of FIG. 1, the labeled bale 20, that is, the PET bottle 10 with the label 11 attached, is crushed into label pieces 71 and bottle pieces 72 (article pieces). In the crushing step S41, the label pieces 71 and the bottle pieces 72 are crushed to have substantially the same size.

[0026] Since the label 11 is a shrink label, the label 11 and the PET bottle 10 are not adhered. Therefore, by crushing the labeled bale 20 in the crushing step S41, the label 11 and the PET bottle 10 are separated. Thereby, the step of peeling and separating the label 11 from the PET bottle 10 by human hands or the like can be omitted. After the crushing step S41, the individual label pieces 71 and bottle pieces 72 are mixed.

[0027] When the label 11 is a winding label, the label 11 and the PET bottle 10 are partially adhered to each other. Therefore, when crushed, the label pieces 71 may adhere to some of the bottle pieces 72. Although the amount of the bottle pieces 72 with the adhered label pieces 71 is small, for example, after the bubbling step S43 described later, the bottle pieces 72 with the adhered label pieces 71 may be collected and separated into the label pieces 71 and the bottle pieces 72.

[0028] In the crushing step S41, the label 11 and the PET bottle 10 are crushed into label pieces 71 and bottle pieces 72 having, for example, a size of about 5 mm square or more and 20 mm square or less. Here, the 5 mm square indicates an outer shape having a length × width of 5 mm × 5 mm. However, the label pieces 71 and the bottle pieces 72 are not limited to this outer shape, and in the bubbling step S43, any shape may be used as long as the label pieces 71 and the bottle pieces 72 do not interfere with each other. The same applies to the 20 mm square.

[0029] If the label pieces 71 and the bottle pieces 72 are too large, in subsequent steps, the label pieces 71 and the bottle pieces 72 may overlap in the water W, and when the label pieces 71 and the bottle pieces 72 float and sink, the label pieces 71 and the bottle pieces 72 may interfere with each other. On the other hand, if the label pieces 71 and the bottle pieces 72 are too small, it becomes difficult to handle the label pieces 71. For example, when recovering ink from the label pieces 71, it becomes difficult to recover the ink.

[0030] Therefore, by crushing the label 11 and the PET bottle 10 to the above-described size, it is possible to avoid interference between the label pieces 71 and the bottle pieces 72 when they float and sink in the water W, and it becomes easier to handle the label pieces 71. The size of the label pieces 71 and the bottle pieces 72 is optimally about 10 mm square.

[0031] The method of crushing the label 11 and the PET bottle 10 is not particularly limited. For example, as shown in S41 of FIG. 1, the labeled bale 20 may be crushed using a crusher 70. Further, in the present embodiment, the labeled bale 20 is crushed, but the PET bottle 10 with the label 11 attached may be crushed without being compressed.

[0032] <Immersion process> In the immersion process S42, as shown in S42 of FIG. 1, the label piece 71 and the bottle piece 72 are immersed in a liquid. Specifically, the label piece 71 and the bottle piece 72 are put into the water W contained in the water tank 50, and the label piece 71 and the bottle piece 72 are immersed in the water W. When the label piece 71 and the bottle piece 72 are made of PET having a specific gravity of about 1.4, for example, in the immersion process S42, both the label piece 71 and the bottle piece 72 sink in the water W.

[0033] Note that the liquid for immersing the label piece 71 and the bottle piece 72 is not limited to the water W. Any liquid having a specific gravity of about 1.0 may be used. Also, a surfactant may be added to the water W. By adding the surfactant to the water W, it becomes easier to generate the bubbles B in the bubbling process S43 described later, and / or the generated bubbles B are less likely to break, so that the label piece 71 is more likely to float.

[0034] Also, for example, when label pieces having a specific gravity of less than 1.0 are mixed, the label pieces float on the water surface in the immersion process S42. Therefore, in the immersion process S42, the label pieces having a specific gravity of less than 1.0 can be separated from the label piece 71 and the bottle piece 72. Note that the separation of the label pieces having a specific gravity of less than 1.0 will be described later.

[0035] <Bubbling process> In the bubbling process S43, with the label piece 71 and the bottle piece 72 sunk in the water W, bubbles B are generated in the water W and the bubbles B are attached to the label piece 71 and the bottle piece 72. The diameter of the bubbles B is preferably 0.5 mm or more and 1.0 mm or less. If the diameter of the bubbles B is too small, sufficient buoyancy cannot be obtained. On the other hand, if the diameter of the bubbles B is too large, it is difficult for the bubbles B to attach to the label piece 71 and the bottle piece 72. By setting the diameter of the bubbles B to 0.5 mm or more and 1.0 mm or less, the bubbles B can be attached to the label piece 71 and the bottle piece 72 in the same manner.

[0036] In the bubbling step S43, the temperature of the water W is not particularly limited and can be, for example, about room temperature (23°C or higher and 27°C or lower). Also, the weight of the label piece 71 and the bottle piece 72 relative to the weight of the water W is desirably 1 part by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the water. Furthermore, the water depth is not particularly limited, and it is sufficient if there is a depth such that the floating label piece 71 and the non-floating bottle piece 72 are not mixed.

[0037] The method of generating the bubbles B in the bubbling step S43 is not particularly limited. For example, the bubbles B may be generated by supplying air into the water W through a bubble generation part. FIG. 2 is a schematic diagram for explaining the method of generating the bubbles B in the bubbling step S43. Specifically, as shown in FIG. 2, the discharge port of the air pump 51 is submerged in the water W of the water tank 50, and a porous member 52 such as a sponge is attached to the discharge port as a bubble generation part, whereby the bubbles B may be generated in the water W. Also, a stirring device may be used as the bubble generation part, and microbubbles may be generated as the bubbles B by supplying air while swirling the water W at high speed inside the stirring device. In this case, the amount of air supplied is desirably 100 mL / min or more and 200 mL / min or less with respect to 1 L of the capacity of the water W. Also, the bubbles B may be generated by vibrating the water W. Specifically, the water W may be vibrated by applying vibration to the water tank 50. In this case, it is desirable to apply vibration to the water tank 50 at a swing width of 15 cm and reciprocate 5 times in 5 seconds. Also, the bubbles B may be generated by stirring the water W with the label piece 71 and the bottle piece 72 submerged in the water W. The time for generating the bubbles B is, for example, about 30 seconds or more and 1 minute or less.

[0038] In the bubbling step S43, bubbles B are generated in water W to attach the bubbles B to the label piece 71 and the bottle piece 72. As a result, the label piece 71, which is thinner and has a smaller mass than the bottle piece 72, floats on the water surface of water W, and the bottle piece 72, which is thicker and has a larger mass than the label piece 71, remains submerged in water W. Since both the label piece 71 and the bottle piece 72 are made of PET, their specific gravities are the same, but the label piece 71 is thinner than the bottle piece 72, so its mass is smaller. Therefore, when the bubbles B are similarly attached to the label piece 71 and the bottle piece 72, due to the buoyancy of the bubbles B, the label piece 71 with a smaller mass than the bottle piece 72 floats on the water surface of water W, and the bottle piece 72 remains submerged in water W.

[0039] In the bubbling step S43, the label piece 71 floating on water W is collected with a net or the like. As a result, even the label piece 71 and the bottle piece 72, which have a specific gravity greater than that of water W and sank in water W in the immersion step S42 and could not be separated by the conventional specific gravity separation method, can be separated into the label piece 71 and the bottle piece 72.

[0040] When generating the bubbles B with an air pump, the immersion step S42 and the bubbling step S43 may be performed simultaneously. Specifically, the label piece 71 and the bottle piece 72 may be put into water W in a state where the bubbles B are being generated in the water W of the water tank 50. As a result, the immersion step S42 can be omitted, so that the separation of the label 11 and the PET bottle 10 can be performed more efficiently.

[0041] Also, the water W in the water tank 50 may be gently stirred with a stirrer or the like. In this case, when the label piece 71 sunk to the bottom of the water tank 50 is once stirred by the stirrer, bubbles are likely to adhere to the label piece 71, making it easier to separate.

[0042] Also, according to such a method, it is possible to accurately separate the label and the article, and improve the efficiency of recycling. Thereby, it can contribute to the achievement of the sustainable development goals (SDGs).

[0043] (Modification example) In Embodiment 1, a method for separating the label piece 71 and the bottle piece 72 made of PET with a specific gravity of 1.0 or more was described. However, by using the present invention, not only the separation of the label piece 71 and the bottle piece 72 made of a material with a specific gravity of 1.0 or more, but also the case including a label piece made of a material with a specific gravity of less than 1.0 can be separately separated. As a modification example below, a method for separating the label piece 71 made of PET, the bottle piece 72, and the PP label piece made of PP (polypropylene) with a specific gravity of about 0.9 will be described.

[0044] In this modification example, in the bottle collection step S1, the label 11 includes not only a label made of PET but also a PP label made of PP. The compression step S2 and the accumulation step S3 are the same as those in Embodiment 1. In the crushing step S41, the label piece 71, the bottle piece 72, and the PP label piece are formed.

[0045] In this modification example, in the immersion step S42, the label piece 71, the bottle piece 72, and the PP label piece are immersed in water W and left standing. As a result, among the label piece 71, the bottle piece 72, and the PP label piece, the label piece 71 and the bottle piece 72 with a specific gravity of 1.0 or more sink, and the PP label piece with a specific gravity of less than 1.0 floats on the water surface of the water W. At this stage, the PP label piece floating on the water W is collected with a net or the like. Then, as described in Embodiment 1, the label piece 71 and the bottle piece 72 are separated by the bubbling step S43. As a result, the label piece 71, the bottle piece 72, and the PP label piece can be separated respectively. As a result, since sorting can be performed for each different material and recycling can be carried out, the quality of the recycled product can be improved.

[0046] Note that the method for separating the label piece 71 and the bottle piece 72 from the PP label piece is not limited to the above. For example, separation may be performed using a conventional air classification method.

[0047] 〔Embodiment 2〕 Another embodiment of the present invention will be described below with reference to FIG. 3. FIG. 3 is a schematic diagram showing an example of the flow of the method for removing the ink layer according to Embodiment 2 of the present invention. For the sake of convenience of explanation, members having the same functions as those described in Embodiment 1 are denoted by the same reference numerals, and the description thereof will not be repeated.

[0048] When the label 11 has an ink layer on which a product display or the like is printed, the label 11 can be effectively reused by removing the ink layer. The sorting method S100 according to Embodiment 1 of the present invention can also be used in the method for removing the ink layer.

[0049] As shown in FIG. 3, the method for removing the ink layer according to the present embodiment includes the above-described sorting method S100 of the label 11. S1 to S4 shown in FIG. 3 are the same as S1 to S4 shown in FIG. 1. Therefore, hereinafter, with reference to FIG. 3, each step after S5 of the method for removing the ink layer will be described.

[0050] <Preheating step> As shown in S5 of FIG. 3, for example, when the label piece 71 is the shrink label piece 71a, the label piece 71 sorted in S4 of the previous step is preheated. By preheating the shrink label piece 71a, the amount by which the label piece 71 shrinks and curls during the subsequent alkali detachment can be suppressed, and the separation between the ink layer and the label base material becomes easier, so that the alkali detachment efficiency can be increased. Examples of the method for preheating the shrink label piece 71a include a method of passing the shrink label piece 71a through a hot air tunnel 61 or a method of immersing the shrink label piece 71a in the warm water 60 in a warm water tank 62. When the label piece 71 sorted in S4 of the previous step is a label other than a shrink label, for example, a wound label or a stretch label, the preheating step is unnecessary.

[0051] <Alkali detachment step> Next, as shown in S6 of FIG. 3, the alkali-soluble ink layer is removed from the label piece 71 by alkali detachment. This treatment can be performed by immersing the label piece 71 in the alkali aqueous solution 80 in the hot alkali tank 82 and stirring it. The alkali aqueous solution 80 after removing the ink layer from the label piece 71 may be discarded as waste liquid, or may be reused as the alkali aqueous solution 80 for alkali detachment.

[0052] <Separation / Recovery Step> Next, as shown in S7 of FIG. 3, the film piece 91 and the ink coating film 93 are separated and recovered. Specifically, for example, the film piece 91 after the ink layer is removed from the label piece 71 is collected by the first net 90 having a relatively large opening, and the ink coating film 93 smaller than the film piece 91 is collected by the second net 92 having a relatively small opening. The ink coating film 93 is a film obtained by finely dividing the ink layer removed from the label piece 71 during alkali detachment.

[0053] Thereafter, the film piece 91 collected by the first net 90 can be reused as a plastic raw material for manufacturing plastic products such as pellets. 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.

Example

[0054] An example of the present invention will be described below. In this example, for the sorting method S100 of the label 11 according to the present invention, a simulation experiment of the sorting method S100 was performed and the results were verified.

[0055] In this example, first, the printed PET label and the PET bottle were cut into predetermined sizes (crushing step S41). The cutting sizes were 5 mm square, 10 mm square, and 20 mm square.

[0056] Next, a 500 ml container filled with 300 ml of water was prepared, and several drops of surfactant were added. Further, 3 g of PET label pieces and 3 g of PET bottle pieces of each size were put into the container (immersion step S42), and bubbles of different diameters were generated in that state (bubbling step S43). The sizes of the bubbles were classified as small bubbles, medium bubbles, and large bubbles. Small bubbles were defined as bubbles with a diameter greater than 0 mm and less than or equal to 0.5 mm, medium bubbles were defined as bubbles with a diameter greater than 0.5 mm and less than or equal to 1.0 mm, and large bubbles were defined as bubbles with a diameter greater than 1.0 mm.

[0057] After closing the lid of the container, small bubbles were generated in the container by shaking the container back and forth 20 times for 10 seconds with an amplitude of 5 cm. After closing the lid of the container, medium bubbles were generated in the container by shaking the container back and forth 5 times for 5 seconds with an amplitude of 15 cm. After closing the lid of the container, large bubbles were generated in the container by shaking the container back and forth 2 times for 3 seconds with an amplitude of 30 cm.

[0058] After generating the bubbles, the lid of the container was opened, and the separation state of the PET label and the PET bottle was visually observed and evaluated according to the following criteria according to the cutting size and the size of the bubbles. Specifically, when a large amount of labels floated and the bottles did not float, it was rated as A; when a part of the labels floated and the bottles did not float, it was rated as B; when the labels did not float, it was rated as C. The evaluation results are shown in Table 1.

[0059]

Table 1

[0060] As shown in Table 1, when the PET label pieces and the PET bottle pieces were 10 mm square and medium bubbles were generated, it was confirmed that the PET label pieces and the PET bottle pieces could be separated most efficiently. Also, when the PET label pieces and the PET bottle pieces were 5 mm square or 10 mm square, it was confirmed that the PET label pieces and the PET bottle pieces could be separated regardless of whether small bubbles, medium bubbles, or large bubbles were generated. Also, when the PET label pieces and the PET bottle pieces were 20 mm square, it was confirmed that the PET label pieces and the PET bottle pieces could be separated if they were medium bubbles.

[0061] In addition, the inventor conducted the same test when the sizes of the cutting of the PET label and the PET bottle were 10 mm square and bubbles with a diameter of 0.5 mm or more and 1.0 mm or less (in the foam) were generated without adding a surfactant. As a result, it was confirmed that a part of the label floated and the bottle did not float.

[0062] According to this example, it was confirmed that the label and the bottle can be separated by the separation method of the label according to the present invention.

[0063] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Explanation of Signs

[0064] 10 PET bottle (article) 11 Label 52 Porous member (bubble generating part) 71 Label piece 72 Bottle piece (article piece) B Bubble S4 Separation process S41 Crushing process S42 Immersion process S43 Bubbling process S100 Separation method W Water (liquid)

Claims

1. A separation method for separating labels and PET bottles, comprising: a crushing step of crushing the labels and the PET bottles including a first label having a specific gravity of less than 1.0 and a second label having a specific gravity of 1.0 or more into first label pieces, second label pieces, and bottle pieces; a dipping step of dipping the first label pieces, the second label pieces, and the bottle pieces in water added with a surfactant; a collecting step of collecting the first label pieces floating on the water surface of the water added with the surfactant; after the collecting step, a bubbling step of stirring the water added with the surfactant in which the second label pieces and the bottle pieces have sunk, generating bubbles in the water added with the surfactant, and attaching the bubbles to the second label pieces and the bottle pieces; and in the crushing step, the first label, the second label, and the PET bottle are crushed into the first label pieces, the second label pieces, and the bottle pieces having a size of 5 mm square or more and 20 mm square or less; a separation method, wherein the diameter of the bubbles generated in the bubbling step is 0.5 mm or more and 1.0 mm or less.

2. The separation method according to claim 1, wherein in the bubbling step, the water added with the surfactant is vibrated or air is supplied into the water through a bubble generating portion.

3. The separation method according to claim 1 or 2, wherein in the crushing step, the PET bottle with the label attached is crushed.

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