Removal method and method for manufacturing recycled film

Abstract

The present invention provides a removal method that can efficiently remove a functional layer from a film containing a functional layer, and a method for manufacturing recycled film using the said removal method. [Solution] The removal method involves removing the functional layer from a film containing the functional layer. The film is transported from upstream to downstream. A first heating mechanism and a second heating mechanism located downstream of the first heating mechanism are provided in the film transport path. The removal method includes the steps of: producing a heat-shrinkable film by heating the film with the first heating mechanism and the film with the second heating mechanism; and removing the functional layer from the heat-shrinkable film. The temperature of the first heating mechanism is lower than the temperature of the second heating mechanism.

Description

Technical Field

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

Background Art

[0002] JP-A-2010-89434 (Patent Document 1) discloses a resin recycling apparatus. In this resin recycling apparatus, the resin is softened through heating, and the surface layer of the softened resin is flattened. Thereafter, the surface layer of the flattened resin is removed, and the resin with the surface layer removed is recycled (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Many film products are provided with functional layers such as printing layers. Therefore, many film waste materials also contain foreign substances such as colorants. When manufacturing a recycled film using film waste materials, the foreign substances contained in the film waste materials affect the quality of the recycled film. In order to suppress the influence of the foreign substances contained in the film waste materials on the quality of the recycled film, it is conceivable to remove the functional layer from the film waste materials in advance. However, it is not always easy to efficiently remove the functional layer. The above Patent Document 1 does not disclose a solution to such a problem.

[0005] The present invention has been made to solve such problems, and an object thereof is to provide a removal method capable of efficiently removing a functional layer from a film containing the functional layer, and a method for manufacturing a recycled film using the removal method.

Means for Solving the Problems

[0006] A removal method according to a certain aspect of the present invention removes a functional layer from a film containing a functional layer. The film is transported from upstream to downstream. A first heating mechanism and a second heating mechanism located downstream of the first heating mechanism are provided in the film transport path. The removal method includes the steps of producing a heat-shrunk film by heating the film with the first heating mechanism and the film with the second heating mechanism, and removing the functional layer from the heat-shrunk film. The temperature of the first heating mechanism is lower than the temperature of the second heating mechanism.

[0007] The present inventors have found that when a film containing a functional layer is rapidly heated at a high temperature, numerous wrinkles and other defects occur in the film due to thermal shrinkage. When numerous wrinkles and other defects occur in the film, it becomes difficult to efficiently remove the functional layer. In this removal method, the temperature of the first heating mechanism is lower than the temperature of the second heating mechanism, which is located downstream of the first heating mechanism. Therefore, this removal method suppresses rapid thermal shrinkage of the film at a high temperature, thereby suppressing the occurrence of wrinkles and other defects in the film after thermal shrinkage. As a result, this removal method allows for more efficient removal of the functional layer from the film after thermal shrinkage.

[0008] In this removal method, the film after heat shrinkage may be stretched in the direction of film transport.

[0009] This removal method stretches the film in the direction of film transport after heat shrinkage, thus further suppressing the occurrence of wrinkles and other defects in the film after heat shrinkage.

[0010] In this removal method, the stretching ratio of the film in the film transport direction may be less than 2 times, and the thickness of the film may become 2 times or more after heating the film by the first heating mechanism and the second heating mechanism.

[0011] In this removal method, the film is heated by a first heating mechanism and then by a second heating mechanism, resulting in the film's thickness more than doubling. Therefore, with this removal method, for example, when the functional layer is removed physically, the film is less likely to break after heat shrinkage, thus allowing for more efficient removal of the functional layer from the heat-shrunk film.

[0012] In this removal method, the functional layer may include a printed layer, the film may include a printed portion where a printed layer is formed and a transparent portion where a printed layer is not formed, and in the film, the printed portion and the transparent portion may be formed alternately in the direction of film transport.

[0013] Generally, the degree of thermal shrinkage differs between the printed area and the transparent area. Therefore, if a film containing both printed and transparent areas shrinks rapidly due to heat, wrinkles are likely to form. This removal method suppresses the rapid thermal shrinkage of the film at high temperatures, thus preventing wrinkles and other issues from forming in the film after thermal shrinkage, even if the printed and transparent areas are formed alternately.

[0014] In this removal method, in the step of removing the functional layer from the heat-shrunk film, the heat-shrunk film may be subjected to physical treatment in order to remove the functional layer from the heat-shrunk film.

[0015] In this removal method, the shrinkage rate of the film at the temperature of the first heating mechanism may be less than 47%.

[0016] According to this removal method, the shrinkage rate of the film at the temperature of the first heating mechanism is less than 47%, and rapid thermal shrinkage of the film is suppressed, thereby suppressing the occurrence of wrinkles and other defects in the film after thermal shrinkage.

[0017] In this removal method, there may be no other heating mechanism between the first heating mechanism and the second heating mechanism, and the difference between the shrinkage rate of the film at the temperature of the first heating mechanism and the shrinkage rate of the film at the temperature of the second heating mechanism may be less than 47%.

[0018] According to this removal method, the difference between the shrinkage rate of the film at the temperature of the first heating mechanism and the shrinkage rate of the film at the temperature of the second heating mechanism is less than 47%, and the rapid thermal shrinkage of the film is suppressed. Therefore, the generation of wrinkles and the like in the film after thermal shrinkage can be suppressed.

[0019] A method for manufacturing a recycled film according to another aspect of the present invention includes a step of manufacturing a film from which a functional layer has been removed by using the above removal method, and a step of manufacturing a recycled film by using the film from which the functional layer has been removed.

[0020] In this method for manufacturing a recycled film, the removal of the functional layer in the film after thermal shrinkage is performed more efficiently. Therefore, according to this method for manufacturing a recycled film, a recycled film can be efficiently manufactured by using a film from which the functional layer has been efficiently removed.

Effects of the Invention

[0021] According to the present invention, it is possible to provide a removal method capable of efficiently removing a functional layer from a film including the functional layer, and a method for manufacturing a recycled film using the removal method.

Brief Description of the Drawings

[0022] [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 front view schematically showing a part of the configuration of a film heating device. [Figure 5] It is a diagram schematically showing the configuration of a printing layer removing device. [Figure 6] It is a perspective view schematically showing the configuration of a first removing mechanism. [Figure 7] It is a perspective view schematically showing the configuration of a second removing mechanism. [Figure 8] It is a flowchart showing an example of the manufacturing procedure of a recycled film. [Figure 9] It is a diagram schematically showing a cross-section of an example of the recycled film to be manufactured. [Embodiments for Carrying Out the Invention]

[0023] 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.

[0024] [1. Configuration of Resource Recycling System, etc.] FIG. 1 is a diagram schematically showing the configuration of a resource recycling system S1 that uses the method for manufacturing a recycled film according to the present embodiment. Referring to FIG. 1, in the resource recycling system S1, for example, a resin film printed with a pattern (hereinafter, also referred to as a "printed film") is recycled to produce a new film. The pattern is composed of, for example, a pattern, characters, symbols (e.g., barcodes), or a combination thereof. The printed film is, for example, a packaging material such as a heat-shrinkable film or a label that can be used for food, beverages, pharmaceuticals, medical products, cosmetics, toiletries, or industrial and agricultural supplies. Hereinafter, the case of recycling waste materials of a heat-shrinkable film, which is a typical printed film, will be described.

[0025] Figure 2 is a schematic plan view showing an example of a printed film. In this example, the printed film 40 is a heat-shrinkable film with a printed layer, in its pre-heat-shrink state. The printed film 40 is a long film having a longitudinal direction and a width direction. The longitudinal direction is the conveying direction (MD (Machine Direction)) during film manufacturing by roll-to-roll, and the width direction is the direction perpendicular to the conveying direction (TD (Transversal Direction)).

[0026] The printed film 40 is managed in a roll for storage and handling purposes. The printed film 40 may be heat-shrinkable mainly in the horizontal direction (width direction) for use as a tubular label, for example. The heat shrinkage rate (main shrinkage direction) of the resin layer 42 (see Figure 3) is appropriately selected considering ease of attachment to containers, etc., when used as a label, but for example, it is preferably 30% or more, and more preferably 50% or more, when immersed in 90°C hot water for 10 seconds.

[0027] As shown in Figure 2, the printed film 40 includes a product section 400 and selvage sections 410A and 410B. The selvage sections 410 are located adjacent to each end of the product section 400 in the width direction. A design is printed on both the product section 400 and the selvage sections 410. Printing on the film is performed, for example, by using a gravure printing plate.

[0028] The product section 400 is used for packaging plastic containers, glass containers, paper containers, etc. The product section 400 includes a printed section P1 and a transparent section P2. In the product section 400, the printed section P1 and the transparent section P2 are formed alternately in the MD. A design is printed on the printed section P1, and no design is printed on the transparent section P2. The length of the transparent section P2 in the MD is, for example, 0.5 cm or more and 10 cm or less. Information for confirming the printing status of the product section 400 is printed on each of the ear sections 410A and 410B. The ear sections 410 are cut and wound before shipment of the product section 400. This forms a wound body of the product section 400 and the ear sections 410.

[0029] The printed film (product section 400) with the design printed on it is attached to the outer circumference of the container body as a label. Methods of attaching it to the container include, for example, wrapping the label around the container, and forming a cylindrical label (hereinafter also referred to as "cylindrical label") by bonding both ends of the printed film with the side where the design is formed facing inward, and then heat-shrinking the cylindrical label after placing it over the container to make the label adhere tightly to the outer circumference of the container body. A cylindrical label is manufactured, for example, by the following method: A long roll of printed film is slit to the width of each design, a solvent or the like is applied to one end of the TD of the printed film, and the other end is overlapped and bonded together (center seal) to obtain a long roll of cylindrical label. One cylindrical label is obtained by cutting the long roll of cylindrical label, and one cylindrical label is attached to the container.

[0030] Figure 3 is a schematic diagram showing the III-III cross-section of Figure 2. As shown in Figure 3, 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 object to be packaged is placed on the printed layer 44 side. That is, when packaging is performed with the printed film 40, the printed layer 44 is 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, etc., 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 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 of the inner surface of the tubular label between the object to be packaged and the mounting device. The overcoat layer is formed, for example, to reduce scratches on the outer surface of the label. The inner coat layer and the overcoat layer are formed, for example, during the printing process of the design. Each of the inner coat layer, the printed layer, and the overcoat layer is included in the "functional layer" in this invention.

[0031] 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 40 μm. When the thickness of the resin layer 42 is within the above range, excellent heat shrinkability, excellent convertibility such as printing and 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, 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.

[0032] 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 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.

[0033] Referring again to Figure 1, the resource recycling system S1 includes a film heating device 5, a printing layer removal device 10, a resin raw material manufacturing device 20, and a film manufacturing device 30. The film heating device 5 is configured to heat and shrink film waste materials (hereinafter also referred to as "film waste") by heating, for example, used printed film or labels, selvages cut from printed film and recovered in roll form, or waste printed film generated during the manufacturing process of test print films. The film heating device 5 will be described in detail later.

[0034] The printing layer removal device 10 is configured, for example, to remove the printing layer from film waste. When removing the printing layer from a cylindrical label, it is desirable to open the cylindrical label in advance by peeling off the center seal or the like to make it into a film in order to remove the printing layer efficiently. The history of the printed film 40 from which the printing layer is removed by the printing layer removal device 10 is not particularly limited and may be, for example, unused, intermediate processed, leftover, defective, prototype, or discarded. 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.

[0035] 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.

[0036] Figure 4 is a schematic front view showing part of the configuration of the film heating device 5. Referring to Figure 4, in the film heating device 5, the printed film 40 is conveyed from upstream to downstream. The film heating device 5 includes a plurality of heating rolls 50 and a plurality of backup rolls 51. Each of the plurality of heating rolls 50 is configured to heat the printed film 40 so that the printed film 40 shrinks due to heat. Each of the plurality of backup rolls 51 is configured to press the heat-shrunk printed film 40 against the corresponding heating roll 50. The printed film 40, fed out from a feed roll (not shown), shrinks due to heat upon contact with each heating roll 50.

[0037] In the film heating device 5, the following sets are arranged in the order from upstream to downstream in the transport direction of the printed film 40: a set including a heating roll 50A and a backup roll 51A, a set including a heating roll 50B and a backup roll 51B, a set including a heating roll 50C and a backup roll 51C, and a set including a heating roll 50D and a backup roll 51D.

[0038] In the film heating device 5, with respect to two adjacent heating rolls 50 in the conveying direction, the temperature of the downstream heating roll 50 is equal to or greater than the temperature of the upstream heating roll 50. That is, in the film heating device 5, the heating temperature of the printed film 40 gradually increases. The temperature of the heating roll 50A, which is the first to heat the printed film 40, is preferably such that the thermal shrinkage rate (hereinafter also simply referred to as "shrinkage rate") when the printed film 40 is immersed in hot water at that temperature for 10 seconds is less than 47%, and more preferably such that the shrinkage rate is 34% or less. Furthermore, with respect to two adjacent heating rolls 50 in the conveying direction, it is preferable that the difference between the shrinkage rate of the printed film 40 at the temperature of the downstream heating roll 50 and the shrinkage rate of the printed film 40 at the temperature of the upstream heating roll 50 is less than 47%, more preferably that the difference between the shrinkage rate of the printed film 40 at the temperature of the downstream heating roll 50 and the shrinkage rate of the printed film 40 at the temperature of the upstream heating roll 50 is 38% or less, and even more preferably that the difference between the shrinkage rate of the printed film 40 at the temperature of the downstream heating roll 50 and the shrinkage rate of the printed film 40 at the temperature of the upstream heating roll 50 is 29% or less.

[0039] The present inventors have found that when a printed film 40 is rapidly heated at a high temperature, numerous wrinkles and other defects occur in the printed film 40 due to thermal shrinkage. When the printed film 40 is rapidly heated at a high temperature, for example, numerous wrinkles extending along the medium-dimension (MD) and edge irregularities occur at both ends of the TD. Edge irregularities refer to the distortion of the shape of the printed film 40 at its edges due to folds or other causes. When numerous wrinkles and other defects occur in the printed film 40, it becomes difficult to efficiently remove the printed layer 44 and the like. In the film heating device 5, the temperature of the upstream heating roll 50 is lower than the temperature of the downstream heating roll 50. Therefore, the film heating device 5 suppresses rapid thermal shrinkage of the printed film 40 at a high temperature, thereby suppressing the occurrence of wrinkles and other defects in the printed film 40 after thermal shrinkage. As a result, the resource recycling system S1 allows for more efficient removal of the printed layer 44 and the like from the printed film 40 after thermal shrinkage.

[0040] Furthermore, in the printed film 40, the printed portion P1 and the transparent portion P2 are formed alternately in the transport direction of the printed film 40. Generally, the degree of thermal shrinkage differs between the printed portion P1 and the transparent portion P2. Therefore, for example, if a film containing the printed portion P1 and the transparent portion P2 shrinks rapidly due to heat, wrinkles are likely to occur. With the film heating device 5, rapid thermal shrinkage of the printed film 40 at high temperatures is suppressed, so even if the printed portion P1 and the transparent portion P2 are formed alternately in the printed film 40, the occurrence of wrinkles and the like in the printed film 40 after thermal shrinkage can be suppressed.

[0041] Furthermore, in the film heating device 5, with respect to two adjacent heating rolls 50 in the transport direction, the rotation speed of the downstream heating roll 50 is equal to or greater than the rotation speed of the upstream heating roll 50. As a result, in the film heating device 5, the printed film 40 is stretched in the transport direction of the printed film 40. The stretching ratio of the printed film 40 is preferably 1.0 times or more and less than 2 times, more preferably 1.1 times or more and 1.8 times or less, and even more preferably 1.2 times or more and 1.5 times or less. By stretching the printed film 40, the occurrence of wrinkles and the like in the printed film 40 is further suppressed.

[0042] The film heating device 5 is not limited to the method of sandwiching the printed film 40 between heating rolls 50, as long as it is a heating method that causes a predetermined thermal shrinkage of the printed film 40. For example, methods such as immersion in hot water, passing through a hot air tunnel, or applying superheated steam may be appropriately selected. A separate mechanism may be provided to suppress curling and wrinkles in the film that occur after the printed film 40 has been thermally shrunk, and to make it substantially flat. It is preferable for the film heating device 5 and the printing layer removal device 10, etc. to be arranged on a continuous transport path, but the process is not limited to this. For example, after the printed film 40 has been thermally shrunk by the independent film heating device 5, the printed film 40 may be processed by the printing layer removal device 10, etc. on a separate transport path.

[0043] In the resource recycling system S1, the printed film 40 is heated and thermally shrinks before the printed layer 44 and other components are removed from the printed film 40. Therefore, with the resource recycling system S1, the printed film 40 becomes thicker before the printed layer 44 and other components are removed, so even if tension is applied to the printed film 40 for transport, it is possible to suppress the occurrence of the printed film 40 breaking as the printed layer 44 and other components are removed. As a result, with the resource recycling system S1, the printed layer 44 and other components can be continuously removed while transporting a long length of printed film 40, thus enabling efficient removal of the printed layer 44 and other components from the printed film 40. Furthermore, with the resource recycling system S1, the length of the printed film 40 in the width direction is shortened due to the thermal shrinkage of the printed film 40, so it is possible to suppress an increase in the size of the printed layer removal device 10. From the viewpoint of the above effects, the thermal shrinkage rate (main shrinkage direction) of the printed film 40 in the film heating device 5 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 printed film 40 doubles or more through heating in the film heating device 5, and even more preferably 2.5 times or more.

[0044] Figure 5 is a schematic diagram showing the configuration of the printing layer removal device 10. In the printing layer removal device 10, the printed film 40 is transported from upstream to downstream. The printing layer removal device 10 includes a first removal mechanism 110, a second removal mechanism 120, and a third removal mechanism 130. In the printing layer removal device 10, the first removal mechanism 110, the second removal mechanism 120, and the third removal mechanism 130 are arranged in this order from upstream to downstream along the transport path of the printed film 40. Each of the first removal mechanism 110, the second removal mechanism 120, and the third removal mechanism 130 is configured to perform a physical treatment on the printed film 40 after heat shrinkage.

[0045] Figure 6 is a schematic perspective view showing the configuration of the first removal mechanism 110. Referring to Figure 6, the first removal mechanism 110 includes a plurality (e.g., 6) transport rolls 112 and a plurality (e.g., 3) metal files 114. The plurality of transport rolls 112 and the plurality of metal files 114 are arranged alternately from upstream to downstream along the transport path of the printed film 40. Each of the plurality of transport rolls 112 is configured to transport the printed film 40 from upstream to downstream. Each of the plurality of metal files 114 is in contact with the printed layer 44 of the transported printed film 40. Each of the plurality of metal files 114 is configured to roughen or remove the printed layer 44 of the printed film 40. As the printed film 40 is transported with the metal files 114 in contact with the printed layer 44 of the printed film 40, the printed layer 44 of the printed film 40 is roughened or removed. Each of the multiple metal files 114 may rotate, for example, while in contact with the printed layer 44 of the printed film 40. The debris from the removal of the printed layer 44 generated in this process is collected and discarded, for example, by a suction mechanism (not shown).

[0046] Figure 7 is a schematic perspective view showing the configuration of the second removal mechanism 120. Referring to Figure 7, the second removal mechanism 120 includes a plurality (e.g., 10) transport rolls 122, a plurality (e.g., 3) polishing rolls 124, and a polishing roll 126. The plurality of polishing rolls 124, 126 and the plurality of transport rolls 122 are arranged alternately from upstream to downstream along the transport path of the printed film 40. Each of the plurality of transport rolls 122 is configured to transport the printed film 40 from upstream to downstream. Each of the plurality of polishing rolls 124 and polishing rolls 126 is made of, for example, ceramic. Each of the plurality of polishing rolls 124 is configured to roughen or remove the printed layer 44 of the printed film 40 while rotating in contact with the printed layer 44 of the printed film 40. The polishing roll 126 is configured to roughen or remove the overcoat layer of the printed film 40 while rotating in contact with the overcoat layer of the printed film 40. The waste from the printed layer 44 generated during this process is collected and discarded, for example, by a suction mechanism (not shown).

[0047] Referring again to Figure 5, the third removal mechanism 130 is configured to transport the printed film 40 from upstream to downstream and to perform wet blasting on both sides of the printed film 40. In the third removal mechanism 130, media (abrasive material) and liquid (e.g., water) are sprayed onto both sides of the printed film 40. Note that the treatment performed on the printed film 40 by the third removal mechanism 130 does not necessarily have to be wet blasting; it may be simple blasting. If blasting is performed, the film may be washed after the treatment. By performing blasting, it is possible to remove any remaining printed layer 44 in recessed areas such as wrinkles on the printed film 40 that could not be reached by polishing rolls, etc. The removed debris of the printed layer 44 generated during blasting is sucked up together with the media and liquid by, for example, a suction mechanism (not shown), and the removed debris is separated and discarded by a cyclone particle separator (not shown), while the media and liquid are reused in blasting.

[0048] In this way, the printed layer removal device 10 applies physical processing to the printed film 40 in multiple stages. By making the coarseness of the physical removal process progressively finer, in the order of the first removal mechanism 110, the second removal mechanism 120, and the third removal mechanism 130, a large portion of the printed layer 44 can be removed in the earlier stages, and any remaining printed layer 44 in recesses or other areas of the film can be removed with high precision in the later stages. Therefore, the printed layer removal device 10 can remove the printed layer 44 from the printed film 40 with higher precision. The transport speed of the printed layer removal device 10 is adjusted as appropriate depending on the capabilities of each removal mechanism, but is preferably, for example, around 3 m / min to 500 m / min. In addition, the printed layer removal device 10 applies a wet blast treatment to the printed film 40 at the end. Therefore, the printed layer removal device 10 can also wash away any remaining debris on the surface of the printed film 40 from the previous process through the wet blast treatment. Furthermore, in the second removal mechanism 120, physical treatment is applied to both sides of the printed film 40 after heat shrinkage. Therefore, with the printed layer removal device 10, for example, if an overcoat layer is formed on the printed film 40, both the printed layer 44 and the overcoat layer can be removed from the printed film 40. The overcoat layer may contain (meth)acrylic acid ester resins that can cause haze reduction in recycled film, but since this method can remove the overcoat layer together with the printed layer 44, this effect can be reduced.

[0049] 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.

[0050] [2. Manufacturing procedure for recycled film] Figure 8 is a flowchart illustrating an example of the manufacturing procedure for recycled film. Each step shown in this flowchart begins with the film waste material being collected. The film waste material may include various types of film with various types of printing. However, the film waste material does not necessarily have to include various types of film with various types of printing; for example, it may include only one type of film. For example, only one predetermined type of film may be recycled as film waste material from the waste material collected from a factory or the like.

[0051] Referring to Figure 8, the collected film waste is subjected to heat treatment (step S100). In step S100, the heating temperature of the film waste is gradually increased to suppress the occurrence of rapid thermal shrinkage of the film waste. After heating the film waste, the printed layer is removed (for example, by physical deinking) (step S110). In step S110, the printed layer is removed by mechanical action such as rubbing, scraping, or peeling. In step S110, both chemical and physical removal may be used. In step S110, the printed layer 44, etc., is removed from the printed film 40 by using, for example, the printed layer removal device 10. In step S110, the printed layer is removed, and recycled raw materials are produced from the film waste after the printed layer removal, allowing a large amount of recycled raw materials to be used in the production of recycled film.

[0052] In step S110, once the removal of the printed layer is complete, recycled raw materials are produced by granulating the film waste after the removal of the printed layer (step S120). Step S120 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 S120, the film waste after the removal of the printed 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 S120, 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 S120 increases the bulk density of the film waste, reducing the space required for storage of the film waste.

[0053] In step S120, once the recycled raw materials are produced, the film manufacturing apparatus 30 performs a film formation process on the recycled film (step S130). 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.

[0054] [3. An example of recycled film] Figure 9 is a schematic diagram showing a cross-section of an example of a recycled film to be manufactured. As shown in Figure 9, the recycled film 60 includes an intermediate layer 62 and adjacent layers 61 and 63. In the recycled film 60, the intermediate layer 62 is sandwiched between the adjacent layers 61 and 63. In the recycled film 60, the intermediate layer 62 is made of resin material containing virgin material and recycled material. Each of the adjacent layers 61 and 63 is made of virgin material. Neither of the adjacent layers 61 and 63 contains recycled material. An adhesive layer may be provided between the intermediate layer 62 and the adjacent layers 61 and 63.

[0055] 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 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.

[0056] [4. Features] As described above, in the resource recycling system S1, the temperature of the upstream heating roll 50 is lower than the temperature of the downstream heating roll 50. Therefore, with the resource recycling system S1, rapid thermal shrinkage of the printed film 40 at high temperatures is suppressed, and thus the occurrence of wrinkles and other defects in the printed film 40 after thermal shrinkage can be suppressed. As a result, with the resource recycling system S1, the functional layer on the printed film 40 after thermal shrinkage can be removed more efficiently.

[0057] [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.

[0058] <5-1> In the above embodiment, the printing layer removal device 10 physically removed the printing layer 44, etc., from the printed film 40. However, the printing layer removal device 10 does not necessarily need to physically remove the printing layer 44, etc., from the printed film 40. The printing layer removal device 10 may, for example, chemically remove the printing layer 44, etc., from the printed film 40. That is, the printing layer removal device 10 may, for example, remove the printing layer 44, etc., from the film by spraying alkaline water onto the printing layer 44, etc., of the printed film 40.

[0059] <5-2> Furthermore, in the above embodiment, the printed film 40 was conveyed by roll to roll. However, the printed film 40 does not necessarily have to be conveyed by roll to roll. The printed film 40 may be in sheet form, for example, and each sheet of printed film 40 may be conveyed from upstream to downstream by a conveying device such as a belt conveyor.

[0060] <5-3> Furthermore, in the above embodiment, the first removal mechanism 110 included a plurality of metal files 114. However, the configuration of the first removal mechanism 110 for physically treating the printed layer 44 of the printed film 40 is not limited to this. For example, the first removal mechanism 110 may be provided with a blade whose tip is sharp like a cutting edge instead of the metal files 114. The blade may also be fixed or rotate like an electric planer. Moreover, a grinding wheel may be provided instead of the metal files 114.

[0061] <5-4> Furthermore, in the above embodiment, the printing layer removal device 10 included a first removal mechanism 110, a second removal mechanism 120, and a third removal mechanism 130. However, the printing layer removal device 10 does not necessarily have to include all of the first removal mechanism 110, the second removal mechanism 120, and the third removal mechanism 130. On the other hand, additional steps may be provided to perform removal with even higher precision. For example, another removal mechanism for removing the printing layer 44 may be provided upstream of the film heating device 5. The type of mechanism that performs the removal process is not limited as long as it can perform the desired removal process. Known devices other than the files, polishing rolls, and blasts described in the above embodiment, such as metal rotating brushes, rotating blades, scrapers, belt sanders, etc., can be used individually or in combination.

[0062] <5-5> Furthermore, in the above embodiment, physical processing was performed on both sides of the printed film 40 in each of the second removal mechanism 120 and the third removal mechanism 130. However, physical processing is not necessarily required on both sides of the printed film 40 in each of the second removal mechanism 120 and the third removal mechanism 130. For example, physical processing may be performed only on the side of the printed film 40 on which the printed layer 44 is formed.

[0063] 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.

[0064] 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. [Examples]

[0065] The following describes embodiments of the present invention. However, the present invention is not limited to the embodiments described below.

[0066] [1. Examples and Comparative Examples] Printed films with printed designs were used to prepare heat-shrinkage-treated printed films for Examples 1-20 and Comparative Example 1-4. The printed films used in Examples 1-16 and Comparative Example 1-3 included both a printed area and a transparent area, with the printed area having a length of 11.6 cm and the transparent area having a length of 0.6 cm. The printed films used in Examples 17-20 and Comparative Example 4 also included both a printed area and a transparent area, with the printed area having a length of 14.3 cm and the transparent area having a length of 4.1 cm.

[0067] The thickness of the printed films used in the preparation of Examples 1-20 and Comparative Examples 1-4 was 40 μm. The moist heat shrinkage rates of the printed films used in the preparation of Examples 1-20 and Comparative Examples 1-4 at different temperatures were 18% at 70°C, 34% at 75°C, 47% at 80°C, 56% at 85°C, 64% at 90°C, 68% at 95°C, and 72% at 100°C. Each moist heat shrinkage rate was measured by cutting the printed film into 10 cm squares and immersing the 10 cm squares of printed film in warm water at each temperature for 10 seconds.

[0068] In Examples 1-20 and Comparative Example 1-4, at least one of the following differed: the number of heating rolls used for heat shrinkage, the set temperature, the heating distance, and the stretching ratio. The number of heating rolls, the set temperature, the heating distance, and the stretching ratio in each of Examples 1-20 and Comparative Example 1-4 are shown in Tables 1, 2, and 3 below.

[0069] [Table 1] [Table 2] [Table 3]

[0070] [2. Evaluation details] Wrinkles and edge irregularities were evaluated by observing the appearance of the printed films after heat shrinkage in Examples 1-20 and Comparative Examples 1-4.

[0071] <Wrinkle evaluation> The wrinkles in the printed film after heat shrinkage were evaluated according to the following criteria. 0: There are countless deep, creased wrinkles. 1: There are still some deep, creased wrinkles remaining. 2: There are countless fine, creased wrinkles. 3: There are countless shallow wrinkles. 4: There are still some shallow wrinkles remaining. 5: The surface has irregularities. 6: There is some degree of unevenness due to the pattern. 7: There are no wrinkles.

[0072] <Evaluation of edge irregularity> The edge irregularities of the printed film after heat shrinkage were evaluated according to the following criteria. 0: The bend at the end is large, and the end is also significantly meandering. 1: The edges are folded wide and have a fine, wavy texture. 2: The fold at the edge is narrow, and the edge is finely wavy. 3: The fold at the edge is narrow, and there is no waviness or other distortion at the edge. 4: No edge irregularities exist.

[0073] [3. Evaluation Results] The results of the evaluations of the printed films after heat shrinkage in Examples 1-20 and Comparative Examples 1-4 are shown in Tables 4, 5, and 6 below.

[0074] [Table 4] [Table 5] [Table 6] We were able to confirm that gradually increasing the heating temperature of the printed film improved wrinkles and edge irregularities in the printed film after heat shrinkage. Furthermore, we were able to confirm that stretching the printed film in MD during heating further improved wrinkles and edge irregularities in the printed film after heat shrinkage. [Explanation of Symbols]

[0075] 5 Film heating device, 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 Heating roll, 51 Backup roll, 60 Recycled film, 61, 63 Adjacent layers, 62 Intermediate layer, 110 First removal mechanism, 112, 122 Conveyor rolls, 114 Metal file, 120 Second removal mechanism, 124, 126 Polishing rolls, 130 Third removal mechanism, 400 Product section, 410 Edge section, P1 Printed section, P2 Transparent section, S1 Resource recycling system.

Claims

1. A removal method for removing a functional layer from a film containing a functional layer, The aforementioned film is transported from upstream to downstream. A first heating mechanism and a second heating mechanism located downstream of the first heating mechanism are provided in the film transport path. A process for manufacturing a heat-shrunk film by heating the film with the first heating mechanism and the film with the second heating mechanism, The step includes removing the functional layer from the film after heat shrinkage, A removal method wherein the temperature of the first heating mechanism is lower than the temperature of the second heating mechanism.

2. The removal method according to claim 1, wherein the heat-shrunk film is stretched in the direction of film transport.

3. The stretching ratio of the film in the transport direction of the film is less than 2 times, The removal method according to claim 2, wherein the thickness of the film doubles or more after heating the film by the first heating mechanism and heating the film by the second heating mechanism.

4. The functional layer includes a printing layer, The film includes a printed portion on which the printed layer is formed and a transparent portion on which the printed layer is not formed. The removal method according to claim 2 or 3, wherein the film is formed with alternating printed portions and transparent portions in the direction of transport of the film.

5. The removal method according to any one of claims 1 to 3, wherein in the step of removing the functional layer from the heat-shrunk film, the heat-shrunk film is subjected to a physical treatment in order to remove the functional layer from the heat-shrunk film.

6. The removal method according to any one of claims 1 to 3, wherein the shrinkage rate of the film at the temperature of the first heating mechanism is less than 47%.

7. If no other heating mechanism exists between the first heating mechanism and the second heating mechanism, The removal method according to any one of claims 1 to 3, wherein the difference between the shrinkage rate of the film at the temperature of the first heating mechanism and the shrinkage rate of the film at the temperature of the second heating mechanism is less than 47%.

8. A step of manufacturing a film from which the functional 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 functional layer has been removed.

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