Removal method and method for manufacturing recycled film

Abstract

The present invention provides a removal method that can sufficiently remove the printed layer from a film through barrel polishing, and a method for manufacturing recycled film using the film obtained through this removal method. [Solution] The removal method is a method for removing a printed layer from a film containing a printed layer. The film is manufactured for packaging goods. When the film is used for packaging goods, the film thickness is a first thickness. This removal method includes a heating step of heating the film so that the film thickness becomes a second thickness which is greater than the first thickness due to thermal shrinkage, and a stirring step of stirring the thermally shrunk film and an abrasive in a barrel.

Description

Technical Field

[0001] The present invention relates to a removal method and a method for manufacturing a recycled film.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2024-122485 (Patent Document 1) discloses a method for removing a coating layer from a laminated film. In this method for removing a coating layer, for example, barrel polishing is performed to remove the coating layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the printing layer on the film is removed through barrel polishing as disclosed in the above Patent Document 1, a situation may occur where the film adheres to the inner wall surface of the barrel or the films adhere to each other. In a state where such a situation is likely to occur, the printing layer cannot be sufficiently removed from the film through barrel polishing.

[0005] The present invention has been made to solve such problems, and an object thereof is to provide a removal method capable of sufficiently removing a printing layer from a film through barrel polishing, and a method for manufacturing a recycled film using the film obtained through the removal method.

Means for Solving the Problems

[0006] A removal method according to a certain aspect of the present invention is a method for removing a printed layer from a film containing a printed layer. The film is manufactured for packaging goods. When the film is used for packaging goods, the film has a first thickness. This removal method includes a heating step of heating the film so that the film shrinks due to heat, resulting in a second thickness which is greater than the first thickness, and a stirring step of stirring the heat-shrunk film and an abrasive in a barrel.

[0007] In this removal method, the film is heated to a second thickness, which is thicker than the first thickness, and then the film and abrasive are stirred in the barrel. Therefore, with this removal method, the film and abrasive are stirred in the barrel while the film has a certain degree of stiffness, which suppresses the film from sticking to the inner wall of the barrel and from sticking to each other. As a result, this removal method suppresses the occurrence of situations where the printed layer on the film is not sufficiently removed.

[0008] The above removal method may further include a cutting step, which occurs after the heating step and before the stirring step, in which the film is cut so that it is divided into multiple film pieces, and in the stirring step, the multiple heat-shrunk film pieces may be introduced into the barrel as the heat-shrunk film.

[0009] If the film is cut before the heating process, the size of each film piece after heat shrinkage will vary depending on the original film material. In this removal method, the film is cut after the heating process and before the stirring process. Therefore, with this removal method, since the film is cut after heat shrinkage, it is possible to suppress the occurrence of variations in the size of each film piece.

[0010] In the removal method described above, the shortest portion of each of the multiple film pieces may be longer than the longest portion of the abrasive material.

[0011] According to this removal method, the shortest part of each film piece is longer than the longest part of the abrasive, thus improving the efficiency of removing the printed layer from the film compared to the case where the shortest part of each film piece is shorter than the longest part of the abrasive.

[0012] In the above removal method, the abrasive material may include a first abrasive material and a second abrasive material, and the longest portion of the second abrasive material may be longer than the longest portion of the first abrasive material.

[0013] This removal method allows for the efficient removal of the printed layer with a relatively large second abrasive, while simultaneously removing any remaining fine printed layers from the uneven areas of the film with a relatively small first abrasive.

[0014] The above removal method may further include a recovery step after the stirring step, in which the multiple film pieces are recovered by separating the multiple film pieces from the abrasive material using a mesh.

[0015] With this removal method, the abrasive material passes through the mesh while multiple film fragments get caught in the mesh, making it easy to recover multiple film fragments.

[0016] In the above removal method, the shortest portion of each of the multiple film pieces may be longer than the longest portion of the mesh.

[0017] According to this removal method, the shortest part of each of the multiple film pieces is longer than the longest part of the mesh, making it difficult for the film pieces to pass through the mesh, thus allowing for the efficient collection of multiple film pieces.

[0018] A method for manufacturing a recycled film according to another aspect of the present invention includes the steps of manufacturing a film from which the printing layer has been removed by using the above-described removal method, and manufacturing a recycled film by using the film from which the printing layer has been removed.

[0019] According to the method for manufacturing this recycled film, since the recycled film is manufactured by using a film from which the printing layer has been sufficiently removed, a high-quality recycled film can be manufactured.

Effects of the Invention

[0020] According to the present invention, it is possible to provide a removal method capable of sufficiently removing the printing layer from the film through barrel polishing, and a method for manufacturing a recycled film using the film obtained through the removal method.

Brief Description of the Drawings

[0021] [Figure 1] It is a diagram schematically showing the configuration of a resource recycling system. [Figure 2] It is a plan view schematically showing an example of a printed film. [Figure 3] It is a diagram schematically showing the III-III cross section of FIG. 2. [Figure 4] It is a diagram for explaining the configuration of a printing layer removing device. [Figure 5] It is a diagram schematically showing a part of a net included in a barrel polishing unit. [Figure 6] It is a flowchart showing an example of the manufacturing procedure of a recycled film. [Figure 7] It is a flowchart showing each process performed in step S100 of FIG. 6. [Figure 8] It is a diagram schematically showing a cross section of an example of the manufactured recycled film.

Modes for Carrying Out the Invention

[0022] Hereinafter, embodiments according to one aspect of the present invention (hereinafter, also referred to as "the present embodiment") will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated. Also, for ease of understanding, each drawing is schematically drawn with appropriate omissions or exaggerations of the subject.

[0023] [1. Configuration of the resource recycling system, etc.] In recent years, marine pollution caused by plastic waste has become a global problem. Resource recycling is attracting attention as a means of addressing this issue.

[0024] Figure 1 is a schematic diagram showing the configuration of a resource recycling system S1 that uses a method for manufacturing recycled film according to this embodiment. Referring to Figure 1, in the resource recycling system S1, for example, a resin film with a pattern printed on it (hereinafter also referred to as "printed film") is recycled and a new film is manufactured. The pattern consists of, for example, a design, letters, symbols (e.g., a barcode), or a combination thereof. The printed film is a packaging material such as a heat-shrinkable film or label that can be used for food, beverages, pharmaceuticals / medical products, cosmetics, toiletries, or industrial / agricultural products. Below, we will describe the case of recycling waste heat-shrinkable film, which is a typical printed film.

[0025] Figure 2 is a schematic plan view showing an example of a printed film. Figure 3 is a schematic view showing the III-III cross-section of Figure 2. Referring to Figures 2 and 3, the printed film 40, which is an example of a material to be recycled in the resource recycling system S1, is, for example, a film that has been used to package a product and then recovered from the market. The printed film 40 may have been heat-shrunk once, for example, when it is attached to the product. The printed film 40 includes a resin layer 42 and a printed layer 44 formed on the resin layer 42.

[0026] In the manufacturing process of the printed film 40, a heat-shrinkable film that is not yet heat-shrinkable and has not yet had a design printed on it is first produced. The heat-shrinkable film before the design is printed on it is composed of, for example, only a resin layer 42. This heat-shrinkable film may be heat-shrinkable mainly in the horizontal axis direction (width direction) for use as a tubular label. The heat shrinkage rate (main shrinkage direction) of this heat-shrinkable film is appropriately selected considering ease of attachment to containers, etc., when used as a label, but for example, when this heat-shrinkable film is immersed in 90°C hot water for 10 seconds, it is preferably 30% or more, and more preferably 50% or more. The design is printed (formation of the printed layer 44 on the resin layer 42) by, for example, oil-based ink or water-based ink using an intaglio plate (gravure plate, etc.), a relief plate (flexographic plate, etc.), a planar plate (offset plate, etc.), or a stencil plate, or by digital printing such as an inkjet method. The materials subject to recycling in resource recycling system S1 do not necessarily have to be printed film that has been used to package a product; they may also be printed film that has never been used to package a product.

[0027] As described above, the printed film 40 includes a resin layer 42 and a printed layer 44. In this example, the resin layer 42 is a heat-shrinkable film. The printed layer 44 is composed of, for example, a coloring component (colorant) such as ink that forms a pattern. In this example, the item to be packaged (product) is placed on the printed layer 44 side. That is, at the time of packaging with the printed film 40, the printed layer 44 was located on the inside. The printed layer 44 may be a single layer or a multi-layer layer. The thickness of the printed layer 44 is appropriately selected depending on the application, but can be, for example, about 0.1 to 20 μm. An inner coat layer may be provided on the printed layer 44, and an overcoat layer or another printed layer may be provided on the resin layer 42 (on the opposite side from the printed layer 44). The inner coat layer is formed, for example, to improve the slipperiness between the item to be packaged or the mounting device and the inner surface of the tubular label (a tubular label formed by bonding both ends of the printed film). The overcoat layer is formed, for example, to reduce scratching of the outer surface of the label. The inner coat layer and the overcoat layer are each formed, for example, during the printing process of the design.

[0028] The resin layer 42 may consist of a single layer or multiple laminated layers. The resin layer 42 may include layers mixed with different types of resins, or it may include multiple layers, each containing a different type of resin. The overall thickness of the resin layer 42 can be appropriately selected depending on the application, but is preferably 10 μm to 60 μm, more preferably 12 μm to 50 μm, and even more preferably 15 μm to 35 μm. When the thickness of the resin layer 42 is within the above range, excellent heat shrinkability, excellent convertibility for printing or center sealing, or excellent mounting properties can be obtained. In addition, each layer constituting the resin layer 42 may contain components other than resin. Each layer may contain metal components such as aluminum, inorganic components such as silicon dioxide or aluminum oxide, antiblocking agents, additives, etc. Examples of additives include heat stabilizers, antioxidants, ultraviolet absorbers, light stabilizers, lubricants, antistatic agents, flame retardants, antibacterial agents, and fluorescent whitening agents.

[0029] Examples of resin types contained in each layer include polyolefin resins, polystyrene resins, polyamide resins, and polyester resins. Examples of polyolefin resins include polypropylene, polyethylene, and cyclic polyolefin resins. Examples of polypropylene resins include binary or ternary random copolymers with propylene as the main component and ethylene, butene, and α-olefin as copolymer components. Specifically, α-olefins are preferably composed of ethylene, 1-butene, 1-hexene, 1-octene, etc., and may contain two or more types of α-olefins. Furthermore, polypropylene resins may be mixtures of different propylene-α-olefin random copolymers. Examples of polyethylene resins include branched low-density polyethylene resins, linear low-density polyethylene resins, high-density polyethylene resins, ethylene-vinyl acetate copolymers, ionomer resins, or mixtures thereof. Also, copolymers of ethylene and α-olefins are used. Examples of α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. The copolymer may be a random copolymer or a block copolymer. Examples of cyclic olefin resins include (a) copolymers of ethylene or propylene with cyclic olefins (e.g., norbornene and its derivatives, or tetracyclododecene and its derivatives), (b) ring-opened polymers of the cyclic olefin or copolymers with α-olefins, (c) hydrogenated polymers of (b), and (d) graft-modified products of (a) to (c) using unsaturated carboxylic acids and their derivatives. The above-mentioned cyclic olefins are not particularly limited, and specific examples include norbornene, 6-methylnorbornene, 6-ethylnorbornene, 5-propylnorbornene, 6-n-butylnorbornene, 1-methylnorbornene, 7-methylnorbornene, 5,6-dimethylnorbornene, 5-phenylnorbornene, and 5-benzylnorbornene.Examples of polystyrene resins include homopolymers of styrene monomers and copolymers consisting of styrene monomers and other monomers (conjugated dienes, aliphatic unsaturated carboxylic acid esters, etc.). Specifically, these include aromatic vinyl hydrocarbon-conjugated diene copolymers, mixed resins of aromatic vinyl hydrocarbon-conjugated diene copolymers and aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymers, and rubber-modified impact-resistant polystyrene. More specifically, these include styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-isoprene-butadiene copolymers, styrene-acrylic copolymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene copolymers, general-purpose polystyrene (GPPS), and highly branched polystyrene. Examples of polyamide resins include aliphatic polyamides, aromatic polyamides, amorphous polyamides, and polyamide elastomers. Examples of the above-mentioned aliphatic polyamides include aliphatic nylon and its copolymers, specifically polycapramide (nylon-6), poly-ω-aminoheptanoic acid (nylon-7), poly-ω-aminononanoic acid (nylon-9), polyundecaneamide (nylon-11), polylauryl lactam (nylon-12), polyethylenediamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-4,6), polyhexamethylene adipamide (nylon-6,6), polyhexamethylene sevacamide (nylon-6,10), polyhexamethylene dodecamide (nylon-6,12), polyoctamethylene adipamide (nylon-8,6), polydecamethylene adipamide (nylon-10,8), etc. Examples of polyester resins include those obtained by condensation polymerization of a dicarboxylic acid component and a diol component. The types of dicarboxylic acid components mentioned above are not particularly limited, and examples include terephthalic acid, o-phthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, octyl succinic acid, cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, fumaric acid, maleic acid, itaconic acid, decamethylenecarboxylic acid, their anhydrides, and lower alkyl esters.The types of diol components listed above are not particularly limited, and include ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, neopentyl glycol (2,2-dimethylpropane-1,3-diol), 1,2-hexanediol, 2,5- Examples include aliphatic diols such as hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, and polytetramethylene ether glycol; 2,2-bis(4-hydroxycyclohexyl)propane; alkylene oxide adducts of 2,2-bis(4-hydroxycyclohexyl)propane; and alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol.

[0030] Referring again to Figure 1, the resource recycling system S1 includes a printing layer removal device 10, a resin raw material manufacturing device 20, and a film manufacturing device 30. The printing layer removal device 10 is configured to remove the printing layer from, for example, printed film recovered from the market, printed film before being used for product packaging, the selvage portion (the end portions in the width direction of the printed film, on which information for confirming the printing status of the printed film is printed) that has been cut from printed film before being used for product packaging and recovered in roll form, or waste printed film generated during the manufacturing process such as test print films. The history of the printed film from which the printing layer is removed by the printing layer removal device 10 is not particularly limited and may include, for example, unused products, intermediate processed products, leftover products, defective products, prototypes, discarded products, etc. The printing layer removal device 10 removes, for example, the printing layer 44, the inner coat layer, and the overcoat layer (hereinafter also referred to as "printing layer 44, etc.") from the printed film 40. The printing layer removal device 10 will be described in detail later.

[0031] The resin raw material manufacturing apparatus 20 is configured to manufacture resin raw materials using the printed film 40 from which the printed layer 44 and the like have been removed by the printed layer removal apparatus 10. The film manufacturing apparatus 30 is configured to manufacture films using the resin raw materials manufactured by the resin raw material manufacturing apparatus 20.

[0032] Figure 4 is a diagram illustrating the configuration of the print layer removal device 10. As shown in Figure 4, the print layer removal device 10 includes a heating unit 100, a cutting unit 110, a barrel polishing unit 120, and a washing and drying unit 130.

[0033] The heating unit 100 is configured to heat the printed film 40. When the printed film 40 is heated and shrinks due to the heat, the thickness of the printed film 40 increases. When the printed film 40 is used for packaging a product and its thickness is a first thickness, the heating unit 100 heats the printed film 40 so that its thickness becomes a second thickness, which is greater than the first thickness. The heating unit 100 may heat the printed film 40 by, for example, immersing it in hot water, blowing hot air onto it, or transporting it in a space kept at a high temperature.

[0034] The cutting unit 110 is configured to cut the printed film 40 after it has been heated and heat-shrunk in the heating unit 100. When the printed film 40 is cut, it is divided into a plurality of film pieces FS1. The shape of each of the plurality of film pieces FS1 is, for example, a rectangle. If the shape of the film pieces FS1 is square, the film pieces FS1 are relatively less likely to bend, and if the shape of the film pieces FS1 is rectangular, the film pieces are relatively less likely to stick together. The cutting unit 110 includes, for example, a blade configured to cut the printed film 40, and cuts the printed film 40 with the blade so that it is divided into a plurality of film pieces FS1.

[0035] The barrel polishing unit 120 is configured to perform barrel polishing on multiple film pieces FS1 manufactured after cutting by the cutting unit 110. The barrel polishing unit 120 includes a barrel (barrel container) 122 with a space formed inside. A solution containing, for example, multiple film pieces FS1, multiple abrasives PA1, PA2, and a surfactant and warm water is introduced into the barrel 122. The amount of each introduced varies depending on the barrel polishing method, but for example, when using a rotating barrel, it is preferable to have a volume ratio of approximately 0.01 to 1 film piece and 3 to 4 abrasives per 1 part solution, with a small amount of abrasives protruding above the solution surface, as this allows for efficient polishing. In this state, as the barrel 122 rotates or vibrates, the multiple film pieces FS1 and abrasives PA1, PA2 are agitated within the barrel 122, and barrel polishing is performed by friction generated when the film pieces FS1 and abrasives PA1, PA2 come into contact. Regarding the rotation speed, for example, when using a rotating barrel, increasing the rotation speed improves polishing efficiency. However, beyond a certain speed, the movement of the abrasive material and film pieces cannot keep up adequately, so an efficient rotation speed should be set appropriately. Through barrel polishing, the printed layer 44 of each film piece FS1 is removed from the resin layer 42. The abrasive materials PA1 and PA2 are of different sizes. In this example, the longest part L5 of the abrasive material PA2 is longer than the longest part L4 of the abrasive material PA1 (see Figure 5). The length of the longest part L4 of the abrasive material PA1 is preferably 1% to 70% of the longest part L5 of the abrasive material PA2, more preferably 3% to 50%, and even more preferably 5% to 30%. This allows for efficient removal of the printed layer 44 with the relatively large abrasive material PA2, while also allowing for the removal of fine printed layers 44 remaining on the uneven parts of each film piece FS1 with the relatively small abrasive material PA1. It can also be expected to reduce the adhesion of the film pieces FS1 to the inner surface of the barrel 122.

[0036] Examples of barrel polishing performed in the barrel polishing unit 120 include rotary barrel polishing, centrifugal barrel polishing, fluid barrel polishing, vibratory barrel polishing, gyro polishing, and reciprocating polishing. As abrasives PA1 and PA2, known abrasives such as ceramic media, metal media, and plastic media can be used. It is preferable to use aluminum oxide abrasives because they have high hardness and toughness and are relatively inexpensive. The materials of abrasives PA1 and PA2 may be the same or different. The shapes of abrasives PA1 and PA2 are not particularly limited, such as spherical, prismatic, or polyhedral shapes, but for example, abrasive PA2 may be a regular tetrahedron or other shape with acute angles, and abrasive PA1 may be small spheres (beads).

[0037] Figure 5 is a schematic diagram showing a portion of the mesh 125 contained in the barrel polishing unit 120. Referring to Figure 5, after stirring in the barrel 122, the mesh 125 is used to separate the multiple film pieces FS1 and the abrasives PA1 and PA2. The mesh 125 has multiple mesh openings H1. The length L2 of the shortest part of each film piece FS1 is longer than the length L1 of the longest part of each mesh opening H1. On the other hand, the lengths L4 and L5 of the longest parts of the abrasives PA1 and PA2, respectively, are shorter than the length L6 of the shortest part of the mesh opening H1. Therefore, when the contents of the barrel 122 are released toward the mesh 125, the abrasives PA1 and PA2 and the solution pass through the mesh openings H1, while the multiple film pieces FS1 remain on the mesh 125. This allows for the recovery of the multiple film pieces FS1. Furthermore, when the printed film 40 is cut after heat shrinkage, shavings of the printed film 40 and film pieces smaller than the film piece FS1 may be generated, and these may be included in the contents of the barrel 122.

[0038] Furthermore, the length L2 of the shortest portion of each film piece FS1 is longer than the length L5 of the longest portion of the abrasive PA2. The length L5 of the longest portion of the abrasive PA2 is preferably 3% to 70%, more preferably 4% to 50%, and even more preferably 5% to 30% of the length L2 of the shortest portion of the film piece FS1. As a result, since the shortest portion of each film piece FS1 is longer than the longest portion of the abrasive PA2, the removal efficiency of the printed layer 44 on the film piece FS1 can be improved compared to the case where the shortest portion of each film piece FS1 is shorter than the longest portion of the abrasive PA2.

[0039] Referring again to Figure 4, the washing and drying unit 130 is configured to, for example, spray a washing solution such as water onto the film piece FS1 that has undergone barrel polishing. This washes away any remaining debris on the film piece FS1. The washing and drying unit 130 is also configured to, for example, blow hot air onto the film piece FS1 after washing. This dries the surface of the film piece FS1. Finally, the film piece FS1, consisting only of the resin layer 42 from which the printing layer 44 and the like have been removed, is recovered.

[0040] In the printing layer removal device 10, the heating unit 100, cutting unit 110, barrel polishing unit 120, and washing / drying unit 130 may be configured as an integrated line or as separate devices. Furthermore, the transport of the printed film 40 or film pieces FS1 between the heating unit 100, cutting unit 110, barrel polishing unit 120, and washing / drying unit 130 may be carried out by machinery such as a belt conveyor or by human hands.

[0041] Referring again to Figure 1, the recycled film produced by the film manufacturing apparatus 30 is printed on again. That is, printed film 40 is produced again. A portion of the produced printed film 40 is put back into the resource recycling system S1. Resource recycling is achieved by repeating this cycle.

[0042] [2. Manufacturing procedure for recycled film] Figure 6 is a flowchart illustrating an example of the manufacturing procedure for recycled film. Each step shown in this flowchart begins with the collection of film waste materials, such as printed film 40. The film waste materials may include various types of film with various types of printing. However, the film waste materials do not necessarily have to include various types of film with various types of printing; for example, they may include only one type of film. For example, only one predetermined type of film may be recycled as film waste materials from the waste materials collected from a factory, etc.

[0043] Referring to Figure 6, the collected film waste is subjected to a process to remove the printed layer (step S100). In step S100, barrel polishing is performed.

[0044] Figure 7 is a flowchart showing the steps performed in step S100 of Figure 6. Referring to Figure 7, the heating unit 100 heats the collected film waste (step S200). The heat treatment method in the heating step is not particularly limited as long as it is a heat treatment method that causes a predetermined thermal shrinkage of the film waste. As the heat treatment method in the heating step, for example, a method of passing through a heated liquid, a method of passing through a heated roll, a method of passing through a hot air tunnel, a method of applying superheated steam, etc. may be appropriately selected. As each film waste shrinks due to the heat, the thickness of each film waste becomes thicker than the thickness when used for product packaging. The thermal shrinkage rate (main shrinkage direction) of the film waste in the heating step is preferably 30 to 85%, more preferably 40 to 80%, and even more preferably 50 to 75%. Furthermore, it is preferable that the thickness of the film waste becomes 1.3 times or more through the heat treatment in the heating step, more preferably 2 times or more, even more preferably 2.5 times or more, and even more preferably 3 times or more.

[0045] The cutting unit 110 cuts the heat-shrinkable film waste (step S210). This divides the printed film 40 into multiple film pieces FS1, for example. If the printed film 40 were cut before the heating process, the size of the heat-shrinkable film pieces FS1 would vary depending on the material of the original film. In this embodiment, the film waste is cut after the heating process and before the stirring process (barrel polishing process). Therefore, according to this embodiment, since the printed film 40 is cut after heat shrinkage, it is possible to suppress variations in the size of each film piece FS1. The size of the film piece FS1 is determined appropriately according to the specifications of the barrel polishing unit 120, but for example, the length L2 of the shortest part of the film piece FS1 is preferably 15 mm or more, and more preferably 20 mm or more.

[0046] The barrel polishing unit 120 performs barrel polishing on multiple film pieces FS1 (step S220). That is, the multiple film pieces FS1 and the polishing materials PA1 and PA2 are agitated in the barrel 122. Thus, in this embodiment, barrel polishing of the film waste is performed after the film waste has become thicker through the heating process. The reason why the barrel polishing process is performed after the heating process will be explained next.

[0047] Generally, when the printed layer of a printed film is removed through barrel polishing, the printed film may stick to the inner wall of the barrel, or the printed films may stick to each other. In conditions where such situations are likely to occur, the printed layer may not be sufficiently removed from the printed film through barrel polishing.

[0048] In this embodiment, for example, the printed film 40 is heated so that its thickness becomes a second thickness greater than the first thickness, and then the printed film 40 (film pieces FS1) and abrasives PA1 and PA2 are stirred in the barrel 122. Therefore, according to this embodiment, since the film pieces FS1 and abrasives PA1 and PA2 are stirred in the barrel 122 while each film piece FS1 has a certain degree of stiffness, it is possible to suppress the occurrence of the film pieces FS1 sticking to the inner wall surface of the barrel 122 and the film pieces FS1 sticking to each other. As a result, according to this embodiment, it is possible to suppress the occurrence of situations in which the printed layer 44 on the film pieces FS1 is not sufficiently removed.

[0049] The barrel polishing unit 120 discharges the contents of the barrel 122 onto the mesh 125, thereby separating the multiple film pieces FS1 from the abrasives PA1 and PA2 (step S230). Subsequently, the washing and drying unit 130 washes the film pieces FS1 (step S240) and dries them (step S250). This completes the process of creating multiple film pieces FS1 from which the printed layer 44 has been removed.

[0050] Referring again to Figure 6, once the removal of the printing layer is completed in step S100, recycled raw materials are produced by granulating the film waste after the removal of the printing layer (step S110). Step S110 is carried out, for example, by a resin raw material manufacturing apparatus 20. The resin raw material manufacturing apparatus 20 can be implemented, for example, by various known apparatuses capable of granulating film waste. In step S110, the film waste after the removal of the printing layer is processed into granules. Examples of granulation methods include melt granulation and compression granulation. In melt granulation, the melt-kneaded film waste is extruded, and the extruded film waste is water-cooled and cut at the die outlet, thereby processing the film waste into granules. In compression granulation, the film waste is compressed and molded, thereby processing the film waste into granules. In step S110, additives (for example, heat stabilizers, antioxidants, UV absorbers, light stabilizers, lubricants, antistatic agents, flame retardants, antibacterial agents, fluorescent whitening agents, virgin raw materials, antiblocking agents) may be added to the film waste. Granulation in step S110 increases the bulk density of the film waste, reducing the space required for storage of the film waste.

[0051] In step S110, once the recycled raw materials are produced, the film manufacturing apparatus 30 performs a film formation process for the recycled film (step S120). In addition, the resin raw materials used in the production of the recycled film may also include biomass-derived raw materials or chemically recycled raw materials.

[0052] [3. An example of recycled film] Figure 8 is a schematic diagram showing a cross-section of an example of a recycled film to be manufactured. As shown in Figure 8, the recycled film 50 includes an intermediate layer 52 and adjacent layers 51 and 53. In the recycled film 50, the intermediate layer 52 is sandwiched between the adjacent layers 51 and 53. In the recycled film 50, the intermediate layer 52 is made of a resin material containing virgin material and recycled material. Each of the adjacent layers 51 and 53 is made of virgin material. Each of the adjacent layers 51 and 53 may also contain recycled material. An adhesive layer may be provided between the intermediate layer 52 and the adjacent layers 51 and 53.

[0053] Examples of resin types that make up the virgin raw materials contained in each layer include polyolefin resins, polystyrene resins, polyamide resins, and polyester resins. Examples of polyolefin resins include polypropylene, polyethylene, and cyclic polyolefin resins. Examples of polypropylene resins include binary or ternary random copolymers with propylene as the main component and ethylene, butene, and α-olefin as copolymer components. Specifically, α-olefins are preferably composed of ethylene, 1-butene, 1-hexene, 1-octene, etc., and may contain two or more types of α-olefins. Furthermore, polypropylene resins may be mixtures of different propylene-α-olefin random copolymers. Examples of polyethylene resins include branched low-density polyethylene resins, linear low-density polyethylene resins, high-density polyethylene resins, ethylene-vinyl acetate copolymers, ionomer resins, or mixtures thereof. Also, copolymers of ethylene and α-olefins are used. Examples of α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. The copolymer may be a random copolymer or a block copolymer. Examples of cyclic olefin resins include (a) copolymers of ethylene or propylene with cyclic olefins (e.g., norbornene and its derivatives, or tetracyclododecene and its derivatives), (b) ring-opened polymers of the cyclic olefin or copolymers with α-olefins, (c) hydrogenated polymers of (b), and (d) graft-modified products of (a) to (c) using unsaturated carboxylic acids and their derivatives. The above-mentioned cyclic olefins are not particularly limited, and specific examples include norbornene, 6-methylnorbornene, 6-ethylnorbornene, 5-propylnorbornene, 6-n-butylnorbornene, 1-methylnorbornene, 7-methylnorbornene, 5,6-dimethylnorbornene, 5-phenylnorbornene, and 5-benzylnorbornene.Examples of polystyrene resins include homopolymers of styrene monomers and copolymers consisting of styrene monomers and other monomers (conjugated dienes, aliphatic unsaturated carboxylic acid esters, etc.). Specifically, these include aromatic vinyl hydrocarbon-conjugated diene copolymers, mixed resins of aromatic vinyl hydrocarbon-conjugated diene copolymers and aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymers, and rubber-modified impact-resistant polystyrene. More specifically, these include styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-isoprene-butadiene copolymers, styrene-acrylic copolymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene copolymers, general-purpose polystyrene (GPPS), and highly branched polystyrene. Examples of polyamide resins include aliphatic polyamides, aromatic polyamides, amorphous polyamides, and polyamide elastomers. Examples of the above-mentioned aliphatic polyamides include aliphatic nylon and its copolymers, specifically polycapramide (nylon-6), poly-ω-aminoheptanoic acid (nylon-7), poly-ω-aminononanoic acid (nylon-9), polyundecaneamide (nylon-11), polylauryl lactam (nylon-12), polyethylenediamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-4,6), polyhexamethylene adipamide (nylon-6,6), polyhexamethylene sevacamide (nylon-6,10), polyhexamethylene dodecamide (nylon-6,12), polyoctamethylene adipamide (nylon-8,6), polydecamethylene adipamide (nylon-10,8), etc. Examples of polyester resins include those obtained by condensation polymerization of a dicarboxylic acid component and a diol component. The types of dicarboxylic acid components mentioned above are not particularly limited, and examples include terephthalic acid, o-phthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, octyl succinic acid, cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, fumaric acid, maleic acid, itaconic acid, decamethylenecarboxylic acid, their anhydrides, and lower alkyl esters.The types of diol components listed above are not particularly limited, and include ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, neopentyl glycol (2,2-dimethylpropane-1,3-diol), 1,2-hexanediol, 2,5- Examples include aliphatic diols such as hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, and polytetramethylene ether glycol; 2,2-bis(4-hydroxycyclohexyl)propane; alkylene oxide adducts of 2,2-bis(4-hydroxycyclohexyl)propane; and alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol.

[0054] [4. Features] As described above, in the resource recycling system S1 according to this embodiment, the printed film 40 is heated so that its thickness becomes a second thickness which is greater than the first thickness, and then the film pieces FS1 and abrasives PA1 and PA2 are stirred in the barrel 122. Therefore, with the resource recycling system S1, the film pieces FS1 and abrasives PA1 and PA2 are stirred in the barrel 122 while each film piece FS1 has a certain degree of stiffness, so that the film pieces FS1 do not stick to the inner wall surface of the barrel 122, and the film pieces FS1 do not stick to each other. As a result, with the resource recycling system S1, the occurrence of insufficient removal of the printed layer 44 from each film piece FS1 can be suppressed. Furthermore, recycled raw materials can be manufactured using films that have undergone such processing, and recycled films 50 with less foreign matter contamination originating from the printed layer 44 can be manufactured using such recycled raw materials. The recycled film 50 can be used, for example, as packaging material such as packaging bags or cylindrical labels that are used to cover containers by joining both ends together to form a tube.

[0055] [5. Other Embodiments] The concept of the above embodiments is not limited to those described above. Examples of other embodiments to which the concept of the above embodiments can be applied will be described below.

[0056] <5-1> In the above embodiment, the printed film 40 was heated and then cut. However, this order is not necessarily limited. The printed film 40 may be cut and divided into a plurality of film pieces FS1, and then the plurality of film pieces FS1 may be heated.

[0057] <5-2> In the above embodiment, abrasives PA1 and PA2 were used as abrasives for barrel polishing. However, it is not always necessary to use two types of abrasives in barrel polishing. One type of abrasive may be used, or three or more types may be used.

[0058] <5-3> Furthermore, in the above embodiment, the printed film 40 was divided into multiple film pieces FS1 by cutting the film waste after heat shrinkage in the heating process. However, the film waste may be cut first, and then the film pieces may be heat-shrunk by the heating process.

[0059] <5-4> Furthermore, in the above embodiment, after the heating step, a stirring step was performed in which the film piece FS1 and the abrasives PA1 and PA2 were stirred in the barrel 122. However, in order to prevent curling of the film piece FS1 (such as the edges being rolled up), the heating step may be performed by gradually increasing the temperature, or by heating while sandwiching film waste and film pieces (hereinafter referred to as "film waste, etc."). Alternatively, the film waste, etc. after heating may be nipped with a cooling roll to keep the film pieces flat.

[0060] <5-5> Furthermore, in the above embodiment, after the heating step, a stirring step was performed in which the film piece FS1 and the abrasives PA1 and PA2 were stirred in the barrel 122. However, a soaking step may be provided between the heating step and the stirring step in which the film waste material is immersed in at least one of the soaking solutions, such as an alkaline aqueous solution, a surfactant, and a solvent. The soaking step makes it easier to peel off the printed layer, and the printed layer can be efficiently removed in the stirring step. In the soaking step, it is preferable to leave the film waste material undisturbed in the soaking solution to prevent the printed layer from peeling off and contaminating the soaking solution. The heating step and the soaking step may also be performed simultaneously. The soaking time should be adjusted as appropriate depending on the type and temperature of the soaking solution used, the material of the film and printed layer, etc.

[0061] Embodiments of the present invention have been described illustratively above. That is, a detailed description and accompanying drawings have been disclosed for illustrative purposes. Therefore, some of the components described in the detailed description and accompanying drawings may not be essential for solving the problem. Consequently, the mere fact that these non-essential components are described in the detailed description and accompanying drawings does not mean that they should be immediately assumed to be essential.

[0062] Furthermore, the above embodiments are merely illustrative in every respect of the present invention. The above embodiments can be improved or modified in various ways within the scope of the present invention. For example, at least a part of the configuration of one embodiment may be combined with at least a part of the configuration of any other embodiment. In other words, in carrying out the present invention, specific configurations can be appropriately adopted depending on the embodiment. [Explanation of Symbols]

[0063] 10 Printed layer removal device, 20 Resin raw material manufacturing device, 30 Film manufacturing device, 40 Printed film, 42 Resin layer, 44 Printed layer, 50 Recycled film, 51, 53 Adjacent layers, 52 Intermediate layer, 100 Heating unit, 110 Cutting unit, 120 Barrel polishing unit, 122 Barrel, 125 Mesh, 130 Washing and drying unit, FS1 Film piece, H1 Mesh size, PA1, PA2 Abrasive material, S1 Resource recycling system.

Claims

1. A removal method for removing a printed layer from a film containing a printed layer, The aforementioned film is manufactured for the purpose of packaging products. When the film is used to package the product, the thickness of the film is the first thickness. A heating step of heating the film so that the film shrinks due to heat, resulting in a second thickness that is greater than the first thickness, A removal method comprising a stirring step of stirring the heat-shrinked film and abrasive material in a barrel.

2. The process further includes a cutting step, which occurs after the heating step and before the stirring step, in which the film is cut so that it is divided into a plurality of film pieces. The removal method according to claim 1, wherein in the stirring step, the plurality of heat-shrunk film pieces are introduced into the barrel as the heat-shrunk film.

3. The removal method according to claim 2, wherein the shortest portion of each of the plurality of film pieces is longer than the longest portion of the abrasive material.

4. The abrasive material includes a first abrasive material and a second abrasive material. The removal method according to any one of claims 1 to 3, wherein the longest portion of the second abrasive is longer than the longest portion of the first abrasive.

5. The removal method according to claim 2 or 3, further comprising a recovery step of recovering the plurality of film pieces by separating the plurality of film pieces and the abrasive material using a mesh after the stirring step.

6. The removal method according to claim 5, wherein the shortest portion of each of the plurality of film pieces is longer than the longest portion of the mesh.

7. A step of manufacturing a film from which the printed layer has been removed by using the removal method described in any one of claims 1 to 3, A method for manufacturing a recycled film, comprising the step of manufacturing a recycled film by using a film from which the printing layer has been removed.

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