Method for recycling and regenerating peeling sheets

Abstract

The method for recycling release sheets includes: step S1 of supplying a resin sheet laminate to a user company, wherein the resin sheet laminate includes an adhesive sheet and a release sheet having a substrate made of resin material; step S3 of recycling the used release sheets using a recycling container; and step S5 of sorting and inspecting the contents within the recycling container. Step S5 includes analytical tests that analyze the structure of the contents using visible light, infrared light, or ultrasound.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a recycling method for peeling sheets. Background Technology

[0002] In recent years, with the increasing awareness of environmental protection, the reuse or recycling of various products, from industrial products to daily necessities, has been widely advocated. Since the enactment of the Plastics Resource Recycling Promotion Law, the recycling and regeneration of resin products has received particular attention. For example, research is underway on the reuse of resin substrates used in the manufacturing process of laminates containing polarizing plates (e.g., see Patent Document 1).

[0003] In recycling, efficient material recovery and sorting are crucial. Research is also underway on establishing recycling systems for printing materials (e.g., see Patent Document 2).

[0004] Patent Document 1: Japanese Patent Publication No. 2015-118388

[0005] Patent Document 2: Japanese Patent Publication No. 2017-139008 Summary of the Invention

[0006] -The technical problem the invention aims to solve-

[0007] In recent years, efforts have been made not only to recycle resin materials, but also to develop closed-loop recycling, which involves recycling resin materials from used products and reusing them as materials for the same products. In closed-loop recycling, since the recycled resin materials need to maintain a quality close to that of unused materials, the introduction of foreign matter during the recycling of used materials can cause even greater problems.

[0008] As a form of closed-loop recycling, attempts have begun to explore recycling the release fins from used labels with adhesive layers and release tabs, regenerating them into resin materials for reuse in the manufacture of release fins. While labels come in a wide variety of types and materials, one type of release fin can be used for multiple labels; therefore, recycling release fins allows for effective recycling. However, because closed-loop recycling of release fins is a new initiative, its implementation methods are not yet fully mature.

[0009] The purpose of this invention is to provide a method for recycling and regenerating a stripping sheet and a stripping sheet suitable for the method. This method for recycling and regenerating a stripping sheet can efficiently regenerate the stripping sheet and remove foreign matter with high precision.

[0010] - Technical solutions used to solve technical problems -

[0011] The method for recycling release sheets disclosed in this specification includes: supplying a resin sheet laminate to a user company, the resin sheet laminate including an adhesive sheet and a release sheet, the adhesive sheet having an adhesive layer, the release sheet having a substrate made of resin material, the release sheet being bonded to the adhesive sheet and having a first side with a release agent layer and a second side opposite to the first side; using a recycling container to recycle used release sheets peeled off from the resin sheet laminate from the user company in any shape selected from roll sheets and single sheets; storing the structure of the release sheets in the storage section of an analysis system having a storage section, an irradiation section, a detection section, and a judgment section; classifying and inspecting the contents of the recycling container recovered from the user company; removing foreign matter that is determined by the classification inspection to be not the used release sheet from the contents of the recycling container; and regenerating the used release sheets into resin raw materials. The step of classifying and inspecting the contents within the recycling container includes: the detection unit detecting visible light, infrared light, or ultrasonic waves reflected or transmitted from the contents after being irradiated by the irradiation unit; the step of analyzing the structure of the contents based on the visible light, infrared light, or ultrasonic waves detected by the detection unit; the step of comparing the analyzed structure with the structure of the release liner stored in the storage unit; and the step of determining that any rolls or single sheets in the contents whose structure is inconsistent with the structure of the stored release liner are not the used release liner.

[0012] -The effects of the invention-

[0013] According to the recycling method disclosed in this specification, since the structural inspection of the stripping sheet using visible light, infrared light or ultrasound can be used for classification inspection, efficient recycling of the used stripping sheet can be achieved. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view showing a resin sheet laminate, which includes an example of a release sheet suitable for a method of recycling release sheets according to a first embodiment of this disclosure.

[0015] Figure 2 This is observed from the side that is in contact with the adhesive layer. Figure 1 A top view of the peeling process shown;

[0016] Figure 3This is a cross-sectional view showing a resin sheet laminate, which includes another example of a release sheet suitable for the recycling method of the release sheet involved in the first embodiment.

[0017] Figure 4 This is a flowchart illustrating a method for recycling and regenerating the stripping sheet according to the first embodiment;

[0018] Figure 5 This is a block diagram showing the inspection system used in the cyclic regeneration method according to the first embodiment;

[0019] Figure 6 This is a flowchart showing the detailed steps involved in sorting and inspecting the contents. Detailed Implementation

[0020] (First Implementation)

[0021] Figure 1 This is a cross-sectional view showing a resin sheet laminate including a release liner. Figure 2 This is a top view of the release sheet viewed from the side in contact with the adhesive layer. Figure 3 This is a cross-sectional view showing another example of the release strips. These release strips 10, 10A are suitable for the cyclic regeneration method involved in the first embodiment.

[0022] Figure 4 This is a flowchart illustrating the method for recycling and regenerating the stripping sheet according to the first embodiment. Figure 5 This is a block diagram illustrating the analysis system used in the recycling method of this embodiment.

[0023] In the recycling method of this embodiment, the regeneration is recovered from Figure 1 The release tab 10 is peeled off from the resin sheet laminate 20 shown, or the release tab 10A is peeled off from the resin sheet laminate 20A. The resin sheet laminate 20 includes an adhesive sheet 15 and a release tab 10. The adhesive sheet 15 has a substrate sheet 7 and an adhesive layer 5 disposed on one side of the substrate sheet 7. The release tab 10 is attached to the adhesive layer 5.

[0024] The release sheet 10 has a first surface 6 on which a release agent layer 3 is formed, and a second surface 8 opposite to the first surface 6. A three-dimensional shape 4 is formed on at least one of the first surface 6 and the second surface 8, and the release sheet 10 has a substrate 1 made of resin material. Here, "three-dimensional shape" refers to a three-dimensional shape relative to a plane, such as a concave portion, a convex portion, or a combination of concave and convex portions. The "three-dimensional shape" is not particularly limited as long as it is a three-dimensional shape. The substrate 1 is sheet-like. Figure 1 and Figure 2The diagram shows an example where the three-dimensional shape 4 is a concave, frustum-shaped recess. A raised pattern is formed on the first surface 6, and a reverse raised pattern is formed on the adhesive layer 5. This raised pattern is formed by repeatedly arranging the recesses at regular intervals in a two-dimensional direction. The reverse raised pattern corresponds to the raised pattern and is formed by multiple protrusions 13 divided by a grid-like groove 11. The raised pattern formed on the first surface 6 can also be described as being formed by grid-like protrusions 9.

[0025] With this structure, air is discharged from the groove 11 when the adhesive sheet 15 is attached to the substrate, so that the adhesive sheet 15 can be attached to the substrate without entraining air.

[0026] Even such as Figure 3 Release sheets that do not have a three-dimensional shape and have a flat release surface, such as the release sheet 10A shown for the resin sheet laminate 20A, can also be regenerated by this recycling method.

[0027] The substrate sheet 7 can be formed from one or more materials selected from resin sheets, paper, and synthetic paper, or it can be a laminate of these materials. When the adhesive sheet 15 is a label or the like, an easy-adhesive layer for improving adhesion to ink can be formed on at least one of the surfaces of the substrate sheet 7 that are in contact with the adhesive layer 5 and the surface opposite to that surface.

[0028] The size of the raised and recessed pattern formed on the release sheet 10 is not particularly limited. The height of the three-dimensional shape 4 is, for example, 5 μm to 100 μm, the longitudinal length and the transverse length are 20 μm to 1000 μm, and the spacing between adjacent three-dimensional shapes 4 is approximately 20 μm to 1000 μm. As long as a pattern of grooves 11 that serve as air passages can be formed on the adhesive layer 5, air entrainment can be effectively reduced when the adhesive sheet 15 is bonded, which is therefore preferred.

[0029] The adhesive layer 5 can also be formed using one or more adhesives selected from polyurethane, acrylic, silicone, polyester, and rubber. As an adhesive, plant-derived adhesives can be used, or plant-derived thickeners can be added.

[0030] The substrate 1 of the release sheets 10 and 10A can be made of any recyclable resin material. There are no particular limitations on the resin material, but polyester resin, especially polyethylene terephthalate (PET), is preferred due to its high versatility and mature recycling technology. The substrate 1 can be transparent or white, but from a reuse perspective, it can be left uncolored with inks or the like. When the substrate 1 is formed of a porous resin material, it is white. Compared to using a transparent general resin film, the amount of resin material used can be reduced because the substrate 1 is porous. For example, KAMISHINE (registered trademark) manufactured by Toyobo Co., Ltd. can be used as the substrate 1. From an environmental perspective, the substrate 1 can also contain biomass polyester containing plant-derived materials.

[0031] Release agent layer 3 contains a release agent containing silicone resin, fluororesin, etc. Figure 1 In the example shown, the release agent layer 3 is formed in the shape of the three-dimensional shape 4. The thickness of the release agent layer 3 is generally less than 5 μm. An antistatic layer may also be provided on the second surface 8 and / or the first surface 6 of the substrate 1.

[0032] Figure 5 The analysis system 30 shown includes, for example, a storage unit 21, an analysis device 25, and a judgment unit 27. The storage unit 21 can store structural information such as the thickness and material of each layer of the peeling sheets 10 and 10A. The analysis device 25 analyzes the structure of the object under inspection in the form of a roll of sheet or a single sheet.

[0033] The analysis apparatus 25 includes an irradiation unit 24 and a detection unit 22. The irradiation unit 24 irradiates the object under inspection with visible light, infrared light, or ultrasound, while the detection unit 22 detects reflected light or transmitted light from the object under inspection and analyzes the layer structure, thickness, and constituent materials of the object. The type of analysis apparatus 25 is not particularly limited, but an apparatus capable of detecting structural differences in the object under inspection with sufficient accuracy is preferred. When infrared light is used in the analysis apparatus 25, it can be a dispersive analysis apparatus or a Fourier transform (FT-IR) analysis apparatus. By using a Fourier transform analysis apparatus 25, analysis can be performed with high accuracy and high speed.

[0034] The judgment unit 27 compares the structural information of the release sheets 10 and 10A read from the storage unit 21 with the structure of the object to be inspected analyzed by the analysis device 25. If the structure of the object to be inspected matches the structure of the release sheets 10 and 10A, it determines that the rolled sheet or single sheet is the release sheet 10 or 10A. If the structure of the object to be inspected does not match the structure of the release sheets 10 and 10A, it determines that the rolled sheet or single sheet is not the release sheet 10 or 10A. In this step, each rolled sheet and each single sheet is judged to be a foreign object.

[0035] At least one of the storage unit 21 and the judgment unit 27 can be disposed within the analysis device 25 or externally. The analysis device 25 can be a handheld analysis device that can be moved around, or a fixed-position analysis device. When using a fixed-position analysis device 25, for example, it is possible to continuously inspect objects transported by a conveyor such as a conveyor belt. When used for continuous inspection, the analysis performed by the analysis device 25 is preferably completed, for example, within one second. When the analysis device 25 is a handheld analysis device, it can be used even when the analysis takes several seconds to tens of seconds. Furthermore, by using it close to the object being inspected, reflected or transmitted light can be detected more reliably, thus improving the analysis accuracy.

[0036] according to Figure 4 The steps shown involve the recycling of release sheets 10 and 10A. First, in step S1, the resin sheet laminates 20 and 20A are supplied or sold to a user company, or sold to a processing company for further processing before being supplied to the user company. The processing company prints on the surface of the adhesive sheet 15, or performs die-cutting or semi-cutting on the adhesive sheet 15. Additionally, the user company sometimes performs printing or other processing itself.

[0037] Next, in step S2, the company using the resin sheet laminate 20, 20A or the processed product supplied with the resin sheet laminate 20, 20A peels the adhesive sheet 15 off the release sheet 10, 10A and uses it. The company stores and accumulates the used release sheets 10, 10A after peeling, rather than discarding them.

[0038] In step S3, a recycling container is used to recover a specified amount of used peeling sheets 10, 10A from the utilizing enterprise in any shape selected from rolled sheets and single sheets. The length of the rolled sheets, the size of the single sheets, and the presence of cut sections are not particularly limited.

[0039] In step S4, the storage unit 21 stores the structure of the release sheets 10 and 10A. Specifically, it stores the layer structure of the release sheets 10 and 10A, the material and thickness of each layer, etc. This step can be performed at any time as long as it is before the subsequent classification and inspection.

[0040] In step S5, the contents of the recycling container are sorted and inspected. Sorting and inspection S5 includes analytical testing, in which the structure of the contents is analyzed using visible light, infrared light, or ultrasound to determine whether the contents are peeling flakes 10 and 10A. Details of the analytical testing are provided below. Figure 6 As shown in the image.

[0041] First, in step S5A, the structure of the contents within the recycling container is analyzed sequentially for each roll of sheet or each single sheet. The analysis results from the analysis device 25 are sent to the judgment unit 27.

[0042] Next, in steps S5B and S5C, the determination unit 27 compares the structure of the contents with the structure of the release sheets 10 and 10A stored in the storage unit 21. The determination unit 27 determines that rolls or single sheets in the contents with a structure inconsistent with the structure of the stored release sheets 10 and 10A are not used release sheets 10 and 10A. Rolls or single sheets with a structure consistent with the structure of the release sheets 10 and 10A are determined to be used release sheets 10 and 10A.

[0043] If the object to be inspected is determined not to be a used stripper sheet 10 or 10A, it is classified as a foreign object in step S5D. According to this method, stripper sheets with different shapes but the same sheet structure, such as stripper sheet 10 and stripper sheet 10A, can be easily detected. Therefore, even when there are multiple stripper sheets to be recycled, reliable classification is possible. On the other hand, in cases where classification using the optical properties of visible light is difficult, such as when stripper sheets 10 and 10A are white, accurate classification based on the sheet structure can be performed using infrared light or ultrasound.

[0044] It should be noted that when the wettability of the first side 6 of the release sheet 10 or 10A is less than that of the second side 8, and the wettability of both sides is known, a wettability test can be performed in the classification inspection S5. For example, a dyne pen can be used to perform the wettability test, the wettability of which is greater than that of the first side 6 and less than that of the second side 8. As a specific example, when the wettability of the first side of the release sheet 10 or 10A is less than 30 dyn / cm (=30 mN / m) and the wettability of the second side is 40 dyn / cm (=40 mN / m), the ink of the 40 dyn / cm dyne pen is applied to both sides of the contents (roll sheet or single sheet). If, after five seconds, both sides repel the ink, or if neither side repels the ink, it can be easily determined that the contents are not the release sheet 10 or 10A. It should be noted that whether ink is rejected can be confirmed visually, or by connecting a camera or other device to an analytical apparatus.

[0045] The sub-step 5A, which involves performing a wettability test and analyzing the contents using light or ultrasound, can either be performed or only one of these tests can be performed. It is possible to appropriately select which result, the wettability test result or the analytical test result, is prioritized for judgment. For example, if the results of the analytical test and the wettability test are consistent, the judgment is made according to that result; if the results are inconsistent, the predetermined result of either the analytical test or the wettability test can be prioritized for judgment. Furthermore, if the results are inconsistent, it can be determined that it is not a release liner 10 or 10A. The judgment unit of the analytical apparatus can also use both the analytical test result and the wettability test result for judgment.

[0046] The wettability test can be applied without relying on the color or transparency of the release sheets 10 and 10A. Therefore, when the release sheets 10 and 10A are opaque and difficult to classify by optical properties, the results of the wettability test are preferred. Furthermore, in analytical tests using visible light, infrared light, or ultrasound, it is difficult to determine the presence or absence of the release agent layer 3, but the wettability test easily identifies this. Therefore, by using the wettability test in conjunction with other methods, even if resin sheets with the same composition as the substrate 1 of the release sheets 10 and 10A but without the release agent layer 3 are mixed into the contents of the recycling container, the possibility of mistaking the resin sheets without the release agent layer 3 as used release sheets 10 and 10A can be reduced, significantly improving the reliability of classification inspection without incurring high costs.

[0047] It should be noted that the wettability test can be performed after or before the analysis test using visible light, infrared light, or ultrasound. When the wettability test is performed first, even if the results indicate that the contents are not used release diaphragms 10 or 10A, it is preferable to perform the analysis test using visible light, infrared light, or ultrasound rather than omitting it. By performing these two tests, the type of foreign matter detected in step S5 can be easily determined, and by recording the inspection results in a storage device or similar device, it is easy to establish countermeasures to prevent foreign matter contamination. However, if the wettability test indicates that the contents are not used release diaphragms 10 or 10A, the analysis test may not be performed. Furthermore, when the wettability test is performed after the analysis test, the wettability test can be performed regardless of the analysis test results, or the decision to perform the wettability test can be made based on the analysis test results.

[0048] In resin sheet laminates 20 and 20A, there is sometimes a structure in which multiple release tabs 10 and 10A are connected by a connecting tape. In this case, the connecting tape can be easily classified based on the difference in material between the connecting tape and the release tabs 10 and 10A. When the object to be inspected is a roll of sheet material, only a portion may need to be inspected.

[0049] Next, in Figure 4 In step S6 shown, when a foreign object is determined to be a foreign object rather than a used peeling sheet 10 or 10A during the sorting inspection, the foreign object is removed from the contents of the recycling container.

[0050] In step S7, the contents may also be pretreated as needed. For example, the used release sheets 10, 10A may be washed with warm water or alkaline water to remove the release agent layer 3 and / or antistatic layer, and then heated and melted after being cut to an appropriate size to form granules. If there are no particular problems, granules may also be formed without removing the release agent layer 3. As a pretreatment, the surfaces of the used release sheets 10, 10A may be ground. There are methods for grinding both sides of the used release sheets 10, 10A simultaneously and methods for grinding only one side, but in the case of grinding only one side, as long as the above-mentioned wetting test using ink is performed, it is possible to determine which side 6 has the release agent layer 3 formed on, and therefore the release agent layer 3 can be easily removed.

[0051] In step S8, the used release sheets 10 and 10A are recycled into resin raw materials. The recycling method is not particularly limited, and various methods can be used depending on the resin composition of the release sheet 10. The recycled resin raw materials can be reused in the production of release sheets. When producing release sheets, recycled raw materials can be used alone or mixed with unused raw materials. Considering environmental impact, it is preferable that the substrate of newly produced release sheets contains at least 10% by mass of recycled resin raw materials. Release sheets 10 and 10A may also contain resin raw materials recycled from used release sheets, i.e., resin raw materials obtained through so-called closed-loop recycling. It is preferable to use materials obtained through closed-loop recycling because this directly conserves petroleum resources.

[0052] In the method of this embodiment, the adhesive sheet 15 included in the resin sheet laminate 20, 20A does not necessarily have to have a substrate sheet 7. It can also be configured to not have a substrate sheet but be sandwiched between two release sheets 10 or two release sheets 10A. Alternatively, the resin sheet laminate 20 can be sold in step S1 such that a release agent layer 3 is provided on both sides of the substrate 1 and a release sheet 10 is provided only on one side of the so-called substrate-free adhesive sheet 15. In this case, the resin sheet laminate 20 can also be provided in a roll form, which is formed by winding the back side (second side) of the release sheet 10 in contact with the side of the adhesive layer 5 opposite to the release sheet 10.

[0053] It should be noted that the process can also be carried out continuously after receiving the stripping sheets recovered from the utilizing enterprise in step S3. Figure 4 The storage process (step S4), inspection process (step S5), and foreign matter removal process (step S6) are shown. Alternatively, steps S4 and S5 can be performed as a receiving inspection of the peeling sheets recovered from the utilizing company. In this case, it is also possible to reject the peeling sheet if it is found to contain foreign matter exceeding the permissible range.

[0054] The recycling method according to this embodiment can detect and remove foreign objects with high precision and efficiency.

[0055] -Industry Applicability-

[0056] The method for recycling the release liner disclosed herein is useful in the field of environmentally friendly adhesive sheets such as labels.

[0057] - Symbol Explanation -

[0058] 1. Substrate

[0059] 3. Release agent layer

[0060] 4. Three-dimensional shape

[0061] 5 adhesive layer

[0062] 7. Substrate sheet

[0063] 9. Protruding part

[0064] 10, 10A release tablets

[0065] 11 slots

[0066] 13 convex part

[0067] 15 Adhesive Sheets

[0068] 20, 20A resin sheet laminate

[0069] 21 Storage Department

[0070] 22 Testing Department

[0071] 24 Irradiation Department

[0072] 25 Analytical apparatus

[0073] 27 Judgment Department

[0074] 30. Analysis System.

Claims

1. A method for the recycling and regeneration of a release slab, characterized in that: The method for recycling the stripper includes: The step of supplying a resin sheet laminate to a user enterprise, the resin sheet laminate comprising an adhesive sheet and a release sheet, the adhesive sheet having an adhesive layer, the release sheet having a substrate made of resin material, the release sheet being bonded to the adhesive sheet and having a first side having a release agent layer formed thereon and a second side opposite to the first side; The step of using recycling containers to recycle used peeling sheets peeled off from the resin sheet laminate from the utilizing enterprise in any shape selected from roll sheets and single sheets; The step of classifying and inspecting the contents of the recycling container recovered from the utilization enterprise to determine whether the contents of the recycling container are the used stripping sheets; When the object is determined to be a foreign object rather than the used peeling sheet in the determination step, the step of removing the foreign object from the contents of the recovery container; and The step of regenerating the used release sheets into resin raw materials. The determination step includes an analytical test, in which an analytical system having a storage unit, an irradiation unit, a detection unit, and a determination unit is used, and visible light, infrared light, or ultrasound is used to determine whether the contents are the used release liner. The analytical experiment includes: The sub-step of detecting visible light, infrared light, or ultrasonic waves reflected from or transmitted through the contents after being irradiated by the irradiation unit; and In the determination unit, a sub-step is taken to determine whether the contents are the used peeling sheet by confirming whether the detection result of the detection unit is consistent with the structure of the peeling sheet pre-stored in the storage unit. The resin sheet laminate has a connecting tape that links the release sheets together. The judgment step includes classifying the connecting tape from the used peeling sheets based on the detection results of the detection unit. The removal step includes removing the connecting tape.

2. The method for recycling and regenerating the release slab according to claim 1, characterized in that: The peeling sheet includes a peeling sheet having a flat shape and a peeling sheet having irregularities formed on the first surface.

3. The method for recycling and regenerating the release slab according to claim 1, characterized in that: The analysis system has a handheld analysis device that includes the irradiation unit and the detection unit.

4. The method for recycling and regenerating the release slab according to claim 1, characterized in that: The first side of the release liner has less wettability than the second side. The determination step includes a wettability test. The wettability test includes a coating step, a detection step, and a judgment step. In the coating step, an ink with wettability greater than that of the first side and less than that of the second side is applied to both sides of the contents. In the detection step, it is detected whether the coated ink is repelled. In the judgment step, based on the detection results of the detection step, it is determined whether the contents are the used release liner. In the determination step, if the contents are determined not to be the used release tablet in the wettability test, the contents are determined not to be the used release tablet regardless of the determination result in the analytical test.

5. The method for recycling and regenerating the release slab according to claim 1, characterized in that: The substrate of the release liner is made of polyester resin.

6. The method for recycling the stripping sheet according to any one of claims 1 to 5, characterized in that: The substrate of the release sheet contains more than 10% by mass of recycled resin raw materials.

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