JP7706319B2 - Separation method - Google Patents

Description

The present invention relates to a method for sorting labels.

Conventionally, plastic products such as PET (polyethylene terephthalate) bottles have been widely used. From the perspective of resource conservation and environmental protection, there is a demand for the reuse of plastic products such as PET bottles and labels attached to PET bottles. In order to recycle these plastic products, it is necessary to separate the items such as PET bottles (particularly containers) and the labels and recycle them separately.

As disclosed in Patent Document 1, gravity separation and wind sorting are known as methods for separating objects and labels. In the gravity separation method, a crushed object containing a mixture of crushed objects and labels is placed in water, and the crushed object is separated into labels that float on the water (those with a specific gravity of less than 1.0) and objects that sink in the water (those with a specific gravity of 1.0 or more). In the wind sorting method, wind is blown onto the crushed object to blow away the relatively light labels, separating the crushed object into relatively light labels and heavy objects.

JP 2005-335288 A

However, with the specific gravity separation method, when the label has a specific gravity of 1.0 or more, the label sinks in the water together with the item, making it impossible to separate the item from the label. Also, with the winnowing separation method, as PET bottles have become lighter and thinner in recent years, the item flies away along with the label, making it impossible to accurately separate the item from the label. For this reason, there has been a demand for technology that can accurately separate the item from the label.

One aspect of the present invention aims to realize a sorting method that can more accurately separate items and labels.

In order to solve the above problem, a label sorting method according to one embodiment of the present invention is a method for separating labels from articles, and includes a crushing process for crushing the labels and the articles into label pieces and article pieces, an immersion process for immersing the label pieces and the article pieces in a liquid, and a bubbling process for generating bubbles in the liquid and attaching the bubbles to the label pieces and the article pieces.

According to the method, in the bubbling step, air bubbles are attached to the label pieces and the object pieces immersed in the liquid, so that the label pieces, which are thinner and have a smaller mass (weight) than the object pieces, tend to float in the liquid. Therefore, the label pieces can be made to float to the liquid surface by the buoyancy of the air bubbles, while the object pieces, which are thicker and have a larger mass than the label pieces, remain submerged in the liquid. This makes it possible to separate the object and the label even if the label could not be separated by the conventional gravity separation method. In addition, if the bubbling step is performed without crushing the label and the object, the label and the object may interfere with each other, and the object may prevent the label from floating up. In the crushing step, the label and the object are crushed into label pieces and bottle pieces, so that the object pieces do not hinder the label pieces from floating up. As a result, the label pieces tend to float, and the label and the object can be accurately separated.

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

According to the above method, air bubbles can be attached to the label pieces and the bottle pieces in the same way during the bubbling process. Therefore, even if the label and the object have a higher specific gravity than the liquid submerged in the liquid during the immersion process, the label and the object can be suitably separated.

In the separation method, the bubbling step may involve vibrating the liquid or supplying air into the liquid via a bubble generating section.

This method effectively creates air bubbles in the liquid, which can then be attached to the label piece and the article piece.

In the sorting method, the labels and the items may be crushed into label pieces and item pieces each having a size of 5 mm to 20 mm in the crushing step.

This method makes it possible to prevent the label pieces and the article pieces from interfering with each other when they float or sink in the liquid. This allows the labels and the articles to be separated in an optimal manner.

In the sorting method, the article with the label attached may be crushed in the crushing step.

According to the above method, by crushing the item with the label attached, the label and the item can be separated while being crushed. Therefore, the process of peeling (separating) the label from the item and the process of crushing the label and the item can be carried out simultaneously, and the process of peeling the label from the item can be omitted.

According to one aspect of the present invention, a sorting method can be realized that can more accurately separate items and labels.

FIG. 2 is a schematic diagram showing an example of a flow of a label sorting method according to the first embodiment of the present invention. 1A to 1C are schematic diagrams illustrating a method for generating bubbles in a bubbling process. FIG. 4 is a schematic diagram showing an example of a flow of a method for removing an ink layer according to a second embodiment of the present invention.

[Embodiment 1]
FIG. 1 is a schematic diagram showing an example of a flow of a method S100 for separating labels 11 according to the first embodiment of the present invention. The method S100 for separating labels 11 is a method for separating labels 11 from PET bottles 10 (articles). As shown in FIG. 1, the method S100 for separating labels includes a bottle collecting step S1, a compression step S2, a stacking step S3, and a separation step S4. Each step of the method S100 for separating labels 11 will be described below with reference to FIG. 1. Note that in the method S100 for separating labels, the bottle collecting step S1, the compression step S2, and the stacking step S3 may be omitted.

In this embodiment, 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 types of labels such as a wrap-around label (roll label) and a stretch label. In addition, the article to which the label 11 is attached is not limited to a PET bottle 10, and may be any item that can be used with the label 11 attached, such as a container other than the PET bottle 10 or various molded products other than containers.

<Bottle collection process>
1, a used PET bottle 10 is collected in a collection box 12. A label 11 having an ink layer containing ink is attached to the body of the PET bottle 10.

<Compression process>
Next, as shown in S2 of FIG. 1, the collected PET bottles 10 with the labels 11 attached are compressed to form labeled bales 20.

<Collection process>
Next, as shown in S3 of FIG. 1, the labeled bales 20 are sent to a recycling plant 30 and accumulated.

<Separation process>
The separating step S4 is a step of separating and separating the labels 11 from the PET bottles 10. The separating step S4 includes a crushing step S41, an immersion step S42, and a bubbling step S43.

<Crushing process>
1, in the crushing step S41, the labeled bale 20, i.e., the PET bottle 10 with the label 11 attached thereto, is crushed into label fragments 71 and bottle fragments 72 (item fragments). In the crushing step S41, the label fragments 71 and the bottle fragments 72 are crushed to have approximately the same size.

Because the label 11 is a shrink label, the label 11 and the PET bottle 10 are not adhered to each other. Therefore, the label 11 and the PET bottle 10 are separated by crushing the labeled bale 20 in the crushing process S41. This makes it possible to omit the process of peeling the label 11 off the PET bottle 10 by hand or the like. After the crushing process S41, the individual label pieces 71 and bottle pieces 72 are mixed together.

In addition, when the label 11 is a wrap-around label, the label 11 and the PET bottle 10 are partially adhered to each other. Therefore, after crushing, some of the bottle fragments 72 may have label fragments 71 attached thereto. Although the amount of bottle fragments 72 with such label fragments 71 attached thereto is small, the bottle fragments 72 with the label fragments 71 attached thereto may be collected after the bubbling process S43 described below, for example, and separated into the label fragments 71 and the bottle fragments 72.

In the crushing step S41, the label 11 and the PET bottle 10 are crushed into label pieces 71 and bottle pieces 72, each of which is, for example, 5 mm square or more and 20 mm square or less. Here, a 5 mm square refers to an external shape of 5 mm length x 5 mm width. However, the label pieces 71 and bottle pieces 72 are not limited to this external shape, and may have any shape that does not cause the label pieces 71 and bottle pieces 72 to interfere with each other in the bubbling step S43. The same applies to a 20 mm square.

If the label piece 71 and the bottle piece 72 are too large, the label piece 71 and the bottle piece 72 will overlap in the water W in a later process, and will interfere with each other as the label piece 71 and the bottle piece 72 float and sink. Also, if the label piece 71 and the bottle piece 72 are too small, the label piece 71 will be difficult to handle, and for example, when recovering ink from the label piece 71, it will be difficult to recover the ink.

Therefore, by crushing the label 11 and the PET bottle 10 to the above size, it is possible to prevent the label pieces 71 and the bottle pieces 72 from interfering with each other when they float or sink in the water W, and the label pieces 71 become easier to handle. The optimal size for the label pieces 71 and the bottle pieces 72 is approximately 10 mm square.

The method for 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. In addition, in this embodiment, the labeled bale 20 is crushed, but the PET bottle 10 with the label 11 attached may be crushed without being compressed.

<Soaking process>
1, in the immersion step S42, the label piece 71 and the bottle piece 72 are immersed in liquid. Specifically, the label piece 71 and the bottle piece 72 are placed in water W contained in a water tank 50, and the label piece 71 and the bottle piece 72 are immersed in the water W. If the label piece 71 and the bottle piece 72 are made of PET with a specific gravity of about 1.4, for example, in the immersion step S42, both the label piece 71 and the bottle piece 72 are submerged in the water W.

The liquid in which the label piece 71 and the bottle piece 72 are immersed is not limited to water W. Any liquid with a specific gravity of approximately 1.0 will suffice. A surfactant may also be added to the water W. Adding a surfactant to the water W makes it easier to generate bubbles B in the bubbling step S43 described below, and/or makes it harder for the generated bubbles B to break, thereby making it easier for the label piece 71 to float.

In addition, for example, if label pieces with a specific gravity of less than 1.0 are mixed in, the label pieces will float to the water surface in the immersion process S42. Therefore, in the immersion process S42, the label pieces with a specific gravity of less than 1.0 can be separated from the label pieces 71 and bottle pieces 72. The separation of label pieces with a specific gravity of less than 1.0 will be described later.

<Bubbling process>
In the bubbling process S43, with the label piece 71 and the bottle piece 72 submerged in the water W, air bubbles B are generated in the water W, and the air bubbles B are attached to the label piece 71 and the bottle piece 72. It is desirable that the diameter of the air bubbles B is 0.5 mm or more and 1.0 mm or less. If the diameter of the air bubbles B is too small, sufficient buoyancy cannot be obtained, while if the diameter of the air bubbles B is too large, the air bubbles B are difficult to attach to the label piece 71 and the bottle piece 72. By setting the diameter of the air bubbles B to 0.5 mm or more and 1.0 mm or less, the air bubbles B can be attached to the label piece 71 and the bottle piece 72 in the same manner.

In the bubbling process S43, the temperature of the water W is not particularly limited, and can be, for example, around room temperature (23°C or higher and 27°C or lower). In addition, the weight of the label pieces 71 and bottle pieces 72 relative to the weight of the water W is desirably 1 part by weight or higher and 5 parts by weight or lower per 100 parts by weight of water. Furthermore, the water depth is not particularly limited, and it is sufficient that it is deep enough so that the floating label pieces 71 and the non-floating bottle pieces 72 do not coexist.

The method of generating bubbles B in the bubbling process S43 is not particularly limited. For example, bubbles B may be generated by supplying air into the water W through a bubble generating unit. FIG. 2 is a schematic diagram illustrating a method of generating bubbles B in the bubbling process S43. Specifically, as shown in FIG. 2, bubbles B may be generated in the water W by submerging the outlet of the air pump 51 in the water W of the water tank 50 and attaching a porous member 52 such as a sponge to the outlet as a bubble generating unit. In addition, a stirrer may be used as the bubble generating unit, and microbubbles may be generated as bubbles B by supplying air while rotating the water W at high speed inside the stirrer. In this case, it is desirable to supply the amount of air at 100 mL/min or more and 200 mL/min or less for 1 L of water W. Also, bubbles B may be generated by vibrating the water W. Specifically, bubbles B may be generated by vibrating the water tank 50 to vibrate the water W. In this case, it is desirable to vibrate the water tank 50 back and forth five times in five seconds with a vibration amplitude of 15 cm. Also, bubbles B may be generated by stirring the water W while the label piece 71 and the bottle piece 72 are submerged in the water W. The time for generating bubbles B is, for example, about 30 seconds to 1 minute.

In the bubbling process S43, air bubbles B are generated in the water W, causing the air bubbles B to adhere 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, rises to the surface of the water W, while the bottle piece 72, which is thicker and has a larger mass than the label piece 71, remains submerged in the water W. The label piece 71 and the bottle piece 72 are both made of PET and have the same specific gravity, but the label piece 71 is thinner than the bottle piece 72, so its mass is smaller. Therefore, when the air bubbles B adhere to the label piece 71 and the bottle piece 72 in the same way, the buoyancy of the air bubbles B causes the label piece 71, which has a smaller mass than the bottle piece 72, to rise to the surface of the water W, while the bottle piece 72 remains submerged in the water W.

In the bubbling process S43, the label pieces 71 floating in the water W are collected with a net or the like. This makes it possible to separate the label pieces 71 and bottle pieces 72 into the label pieces 71 and bottle pieces 72, even though the label pieces 71 and bottle pieces 72 have a higher specific gravity than the water W that was submerged in the water W in the immersion process S42 and could not be separated by conventional specific gravity separation methods.

When the air bubbles B are generated by an air pump, the immersion step S42 and the bubbling step S43 may be performed simultaneously. Specifically, the label pieces 71 and the bottle pieces 72 may be immersed in the water W of the water tank 50 while the air bubbles B are being generated in the water W. This allows the immersion step S42 to be omitted, and the label 11 and the PET bottle 10 to be separated more efficiently.

The water W in the water tank 50 may be gently stirred with a stirrer or the like. In this case, the label pieces 71 that have sunk to the bottom of the water tank 50 are stirred with the stirrer once, which makes it easier for bubbles to adhere to the label pieces 71 and makes them easier to separate.

This method also makes it possible to accurately separate labels from items, improving recycling efficiency. This will contribute to achieving the Sustainable Development Goals (SDGs).

(Modification)
In the first embodiment, a method for separating label pieces 71 and bottle pieces 72 made of PET with a specific gravity of 1.0 or more has been described. However, by using the present invention, not only can label pieces 71 and bottle pieces 72 made of materials with a specific gravity of 1.0 or more be separated, but also label pieces made of materials with a specific gravity of less than 1.0 can be separated individually. Below, as a modified example, a method for separating label pieces 71 and bottle pieces 72 made of PET, and PP label pieces made of PP (polypropylene) with a specific gravity of about 0.9 will be described.

In this modified example, in the bottle recovery process S1, the labels 11 include not only labels made of PET but also PP labels made of PP. The compression process S2 and accumulation process S3 are the same as in the first embodiment, and in the crushing process S41, label pieces 71, bottle pieces 72, and PP label pieces are formed.

In this modification, in the immersion step S42, the label pieces 71, bottle pieces 72, and PP label pieces are immersed in water W and left to stand. As a result, of the label pieces 71, bottle pieces 72, and PP label pieces, the label pieces 71 and bottle pieces 72 with a specific gravity of 1.0 or more sink, and the PP label pieces with a specific gravity of less than 1.0 rise to the surface of the water W. At this stage, the PP label pieces floating on the water W are collected with a net or the like. Thereafter, as described in the first embodiment, the label pieces 71 and bottle pieces 72 are separated by the bubbling step S43. This allows the label pieces 71, bottle pieces 72, and PP label pieces to be separated from one another. As a result, the different materials can be separated for recycling, improving the quality of the recycled products.

The method for separating the label pieces 71 and bottle pieces 72 from the PP label pieces is not limited to the above. For example, separation may be performed using a conventional winnowing method.

[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 a flow of a method for removing an ink layer according to embodiment 2 of the present invention. For convenience of explanation, the same reference numerals are given to members having the same functions as those described in embodiment 1, and the description thereof will not be repeated.

If the label 11 has an ink layer on which product information or the like is printed, the label 11 can be effectively reused by removing the ink layer. The sorting method S100 according to the first embodiment of the present invention can also be used as a method for removing the ink layer.

As shown in FIG. 3, the ink layer removal method according to this embodiment includes the label 11 separation method S100 described above. S1 to S4 shown in FIG. 3 are the same as S1 to S4 shown in FIG. 1. Therefore, below, each step from S5 onwards of the ink layer removal method will be described with reference to FIG. 3.

<Preheating step>
As shown in S5 of Fig. 3, if the label piece 71 is a shrink label piece 71a, for example, the label piece 71 separated in the previous step S4 is preheated. Preheating the shrink label piece 71a reduces the amount of shrinkage and curling of the label piece 71 during alkali release, which will be described later, and facilitates separation between the ink layer and the label substrate, thereby improving the efficiency of alkali release. Methods for preheating the shrink label piece 71a include, for example, passing the shrink label piece 71a through a hot air tunnel 61, or immersing the shrink label piece 71a in hot water 60 in a hot water bath 62. Note that if the label piece 71 separated in the previous step S4 is a label other than a shrink label, such as a roll label or stretch label, the preheating step is not necessary.

<Alkaline removal step>
3, the alkali-soluble ink layer is removed from the label piece 71 by alkaline desorption. This treatment can be performed by immersing the label piece 71 in an alkaline aqueous solution 80 in a hot alkaline bath 82 and stirring the solution. The alkaline aqueous solution 80 after the ink layer has been removed from the label piece 71 may be disposed of as waste liquid, or may be reused as the alkaline aqueous solution 80 for alkaline desorption.

<Separation/recovery process>
3, the film piece 91 and the ink coating 93 are separated and collected. Specifically, for example, a first net 90 having a relatively large opening collects the film piece 91 from which the ink layer has been removed from the label piece 71, and a second net 92 having a relatively small opening collects the ink coating 93, which is smaller than the film piece 91. The ink coating 93 is a film formed by finely dividing the ink layer removed from the label piece 71 during alkali desorption.

The film pieces 91 captured by the first net 90 can then be reused, for example as plastic raw material for the production of plastic products such as pellets. Meanwhile, the ink coating 93 captured by the second net 92 can be reused, for example, in a thermal recycling process.

An embodiment of the present invention will be described below. In this embodiment, a simulation experiment of the sorting method S100 for the labels 11 according to the present invention was carried out, and the results were verified.

In this embodiment, first, the printed PET label and PET bottle were cut to a predetermined size (crushing step S41). The cut sizes were 5 mm square, 10 mm square, and 20 mm square.

Next, a 500 ml container containing 300 ml of water was prepared, and a few drops of surfactant were added. Furthermore, 3 g of PET label pieces and 3 g of PET bottle pieces of each size were placed in the container (immersion process S42), and bubbles of different diameters were generated in this state (bubbling process S43). The bubble sizes were small, medium, and large, with small bubbles being bubbles with a diameter of more than 0 mm and 0.5 mm or less, medium bubbles being bubbles with a diameter of more than 0.5 mm and 1.0 mm or less, and large bubbles being bubbles with a diameter of more than 1.0 mm.

After closing the lid of the container, the container was shook 20 times back and forth over 10 seconds with an amplitude of 5 cm to generate small bubbles inside the container. After closing the lid of the container, the container was shook 5 times back and forth over 5 seconds with an amplitude of 15 cm to generate medium bubbles inside the container. After closing the lid of the container, the container was shook 2 times back and forth over 3 seconds with an amplitude of 30 cm to generate large bubbles inside the container.

After the air bubbles were generated, the lid of the container was opened and the state of separation of the PET label and PET bottle was visually inspected and evaluated according to the following criteria according to the size of the cut and the size of the air bubbles. Specifically, if a large amount of the label floated and the bottle did not float, it was rated as A; if part of the label floated and the bottle did not float, it was rated as B; and if the label did not float at all, it was rated as C. The evaluation results are shown in Table 1.

As shown in Table 1, it was confirmed that the PET label pieces and PET bottle pieces can be separated most efficiently when the PET label pieces and PET bottle pieces are 10 mm square and air bubbles are generated within the bubbles. In addition, when the PET label pieces and PET bottle pieces are 5 mm square or 10 mm square, it was confirmed that the PET label pieces and PET bottle pieces can be separated regardless of whether small, medium or large air bubbles are generated. In addition, when the PET label pieces and PET bottle pieces are 20 mm square, it was confirmed that the PET label pieces and PET bottle pieces can be separated if they are within the bubbles.

The inventors also conducted a similar test in which the cut size of the PET label and PET bottle was 10 mm square, and bubbles with a diameter of 0.5 mm to 1.0 mm (inside the bubbles) were generated without adding a surfactant. As a result, it was confirmed that part of the label floated, but the bottle did not float.

This example confirmed that the label sorting method of the present invention makes it possible to separate labels and bottles.

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

10 PET bottles (items)
11 Label 52 Porous member (air bubble generating portion)
71 Label piece 72 Bottle piece (article piece)
B Air bubbles S4 Separation step S41 Crushing step S42 Immersion step S43 Bubbling step S100 Separation method W Water (liquid)

Claims (3)

A method for separating labels from PET bottles , comprising the steps of:
a crushing step of crushing the label and the PET bottle , the label including the first label having a specific gravity of less than 1.0 and the second label having a specific gravity of 1.0 or more , into a first label piece, a second label piece, and a bottle piece;
an immersion step of immersing the first label piece, the second label piece, and the bottle piece in water to which a surfactant has been added ;
a collection step of collecting the first label piece floating on the surface of the water containing the surfactant;
a bubbling step in which, after the collecting step, the water containing the surfactant in which the second label piece and the bottle piece are submerged is stirred, and air bubbles are generated in the water containing the surfactant , so that the air bubbles adhere to the second label piece and the bottle piece;
Including ,
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 each having a side length of 5 mm or more and 20 mm or less,
A fractionation method , wherein the diameter of the bubbles generated in the bubbling step is 0.5 mm or more and 1.0 mm or less . The separation method according to claim 1 , wherein in the bubbling step, the water to which the surfactant has been added is vibrated, or air is supplied into the water via a bubble generating unit. 3. The method according to claim 1, wherein the PET bottles with the labels attached thereto are crushed in the crushing step.

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