Method for producing resin film

Abstract

To provide a method for producing a resin film having a specific gravity of less than 1 from a film label.SOLUTION: The method for producing a resin film comprises the following steps: preparing, as a starting material, at least either a film label that comprises an ink layer and a resin layer or a resin bottle to which the film label is fitted; recovering a thermoplastic resin having a specific gravity of less than 1 from the starting material; and obtaining a resin film having a specific gravity of less than 1 by means of extrusion molding from feedstock containing the recovered thermoplastic resin. The step of recovering a thermoplastic resin having a specific gravity of less than 1 comprises the following steps: dividing the starting material or the resin layer into individual pieces; separating the ink layer from the film label or each piece of the film label, thereby obtaining the resin layer or pieces of the resin layer from which the ink layer has been removed; and subjecting the starting material, the resin layer or the pieces thereof to gravity separation, thereby recovering the starting material, the resin layer or the pieces thereof having a specific gravity of less than 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a resin film. [Background technology]

[0002] Patent Document 1 discloses a technique for obtaining high-purity pellets when recycling labeled plastic bottles into pellets. More specifically, it discloses a thermoplastic polymer label from which the ink layer can be easily removed, a method for removing ink from a thermoplastic polymer label, and a method for recycling the label and bottle from which the ink has been removed. The ink layer on the label disclosed in Patent Document 1 can be easily removed by immersing it in alkaline warm water. The thermoplastic resin of the label from which the ink layer has been removed is separated and sorted by specific gravity and used to produce recycled pellets.

[0003] Furthermore, Patent Document 2 discloses a laminated film from which the ink layer can be separated by immersion in water. This laminated film has a resin layer containing polyvinyl alcohol between a resin film and a printed layer printed with ink. According to Patent Document 2, when this laminated film is immersed in water, the single-layer film and ink of each layer separate in the water, allowing each separated material to be sorted and recovered according to specific gravity.

[0004] As described above, removing the ink layer from labels made of thermoplastic resin allows for more accurate gravity separation of the thermoplastic resin. Some printing inks contain components with relatively high specific gravities, such as titanium oxide. Labels with such ink layers laminated on them may be separated as having a high specific gravity, regardless of the type of thermoplastic resin, which can have an undesirable effect on the purity of the recycled pellets. It is expected that the use of technologies such as those disclosed in Patent Documents 1 and 2 will lead to the active reuse of plastic bottles containing labels. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-333952 [Patent Document 2] International Publication No. 2021 / 090690 Summary of the Invention [Problem to be solved by the invention]

[0006] Among the thermoplastic resins separated and recovered from labels and bottles, resins with a specific gravity of more than 1, such as polyester, are recycled into labels and bottles after recovery, repeating the cycle from resources to products. However, for thermoplastic resins with a specific gravity of less than 1, such a cycle has not yet been considered, and they tend to be discarded after being separated and recovered.

[0007] The present disclosure aims to provide a method for recovering a thermoplastic resin having a specific gravity of less than 1 from at least one of a film label having an ink layer and a resin layer and a resin bottle to which the film label is attached, and using the recovered thermoplastic resin to produce a resin film having a specific gravity of less than 1. [Means for solving the problem]

[0008] A method for producing a resin film according to one aspect of the present disclosure includes the following. The method includes preparing at least one of a film label having an ink layer and a resin layer, and a resin bottle with the film label attached, as a starting material, recovering a thermoplastic resin having a specific gravity of less than 1 from the starting material, and using the recovered thermoplastic resin as a raw material to extrude a resin film having a specific gravity of less than 1. Furthermore, recovering the thermoplastic resin having a specific gravity of less than 1 includes the following: dividing the starting material or the resin layer, separating the ink layer from the film label or the film label pieces to obtain a resin layer or resin layer pieces from which the ink layer has been removed, and separating the starting material, the resin layer, or the pieces thereof by specific gravity to recover the starting material, the resin layer, or the pieces thereof having a specific gravity of less than 1.

[0009] In the above-mentioned method for producing a resin film, recovering the thermoplastic resin having a specific gravity of less than 1 may include, in this order, dividing the starting material into individual pieces, separating the ink layer from the individual pieces of the film label to obtain individual pieces of the resin layer from which the ink layer has been removed, separating the individual pieces of the resin layer by specific gravity, and recovering the individual pieces of the resin layer having a specific gravity of less than 1.

[0010] The method for producing a resin film may further include laminating an ink layer on the extruded resin film to produce a film label having an ink layer and a resin layer.

[0011] In the above-mentioned method for manufacturing a resin film, the produced film label may be used as a starting material, and the steps of recovering a thermoplastic resin having a specific gravity of less than 1 and incorporating the recovered thermoplastic resin into the raw material to produce a resin film having a specific gravity of less than 1 may be repeated one or more times.

[0012] In the above-mentioned method for manufacturing a resin film, obtaining the resin layer or individual pieces of the resin layer from which the ink layer has been removed may include separating the ink layer by immersing the film label or individual pieces of the film label in an alkaline aqueous solution.

[0013] The method for producing a resin film may further include neutralizing the resin layer or the individual pieces of the resin layer after immersion in the alkaline aqueous solution.

[0014] In the above-mentioned method for producing a resin film, obtaining the resin layer or individual pieces of the resin layer from which the ink layer has been removed may include separating the ink layer by immersing the film label or individual pieces of the film label in water.

[0015] In the above-mentioned method for producing a resin film, obtaining the resin layer or individual pieces of the resin layer from which the ink layer has been removed may include washing the resin layer or individual pieces of the resin layer from which the ink layer has been separated.

[0016] The above-mentioned method for producing a resin film may further include drying the recovered thermoplastic resin having a specific gravity of less than 1 between recovering the thermoplastic resin having a specific gravity of less than 1 and extruding the resin film having a specific gravity of less than 1. [Effects of the Invention]

[0017] According to the above-mentioned aspects, there is provided a method for recovering a thermoplastic resin having a specific gravity of less than 1 from at least one of a film label having an ink layer and a resin layer and a resin bottle to which the film label is attached, and using the recovered thermoplastic resin to produce a resin film having a specific gravity of less than 1. The produced resin film can be reused as a film label having an ink layer. This allows for the circulation of the thermoplastic resin having a specific gravity of less than 1 contained in the film label or resin bottle. [Brief explanation of the drawings]

[0018] [Figure 1] 3 is a flowchart showing the flow of a manufacturing method according to the first embodiment. [Figure 2] 10 is a flowchart showing the flow of a manufacturing method according to a second embodiment. [Figure 3] 10 is a flowchart showing the flow of a manufacturing method according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, several embodiments of a resin film manufacturing method according to the present disclosure will be described. In this manufacturing method, a thermoplastic resin with a specific gravity of less than 1 is recovered from a film label or a resin bottle containing the same, and a resin film with a specific gravity of less than 1 is manufactured using the recovered thermoplastic resin. The resin bottle is typically a PET bottle primarily composed of polyethylene terephthalate (PET). The manufactured resin film is suitable as a base film for a film label to be attached to the resin bottle, and can be recycled as a film label for a resin bottle, including a PET bottle, by undergoing processing such as printing. In other words, according to this manufacturing method, film labels can be manufactured as recycled products in a cyclical manner from a film label as a starting material.

[0020] [First embodiment] FIG. 1 is a flowchart showing the flow of a resin film manufacturing method according to a first embodiment. As shown in FIG. 1, the resin film manufacturing method includes a step of preparing a starting material, followed by subsequent steps S1 to S5. Steps S1 to S4 involve recovering a thermoplastic resin with a specific gravity of less than 1 from the starting material, and then extruding the recovered thermoplastic resin into a resin film with a specific gravity of less than 1. Step S5 involves forming an ink layer of printing ink on the manufactured resin film to manufacture a film label (recycled product) that is primarily attached to a PET bottle. The recycled film label can be reused as the starting material and subjected to new steps S1 to S5. Note that the order of steps S1, S2, S2A, S2B, and S3 in FIG. 1 can be changed as appropriate. Therefore, the method of the first embodiment shown in FIG. 1 will be described in detail below, followed by detailed descriptions of other embodiments in which the order of the steps is different.

[0021] <1. Starting materials> The starting raw material that is the starting point of the circulation in the resin film manufacturing method shown in Figure 1 includes a film label. The film label is configured as a label by forming a printing layer on a resin film (resin layer) whose main component is a thermoplastic resin. The film label may or may not be heat-shrinkable. This film label may be a used product, an unused product, an intermediate processed product, a product discarded during the manufacturing process, etc., and its history is not particularly limited.

[0022] Resin films are broadly classified into olefin-based films, styrene-based films, and ester-based films based on their main component. Olefin-based films contain olefin-based resins such as polyethylene, polypropylene, cyclic polyolefins, and petroleum resins. Olefin-based films are primarily composed of at least one of polyethylene and polypropylene, both of which have a specific gravity of less than 1, and typically have an overall specific gravity of less than 1.

[0023] Styrene-based films are mainly composed of polystyrene (specific gravity 1.03 to 1.06), and usually have an overall specific gravity of more than 1. Ester-based films are mainly composed of polyethylene terephthalate (specific gravity 1.25 to 1.40), and usually have an overall specific gravity of more than 1. Therefore, the pieces recovered as thermoplastic resin with a specific gravity of less than 1 in the gravity separation step (S3) described below are derived from the olefin-based film among the above resin films.

[0024] The film label may be removed from the PET bottle or may be attached to the PET bottle. That is, the starting material may be a film label alone, a PET bottle with a film label attached, or a mixture of these. A typical PET bottle has a container body made of polyethylene terephthalate (PET), and the cap and cap ring attached to the container body are made of polyethylene or polypropylene. These cap and ring portions are also separated from the olefin-based film in the gravity separation step (S3) described below, and can be recovered as resources. The recovered cap and ring portions may be included in the raw material for the resin film. Like the film label, the PET bottles used as the starting material may be used as products, unused bottles, intermediate processed products, discarded products during the manufacturing process, etc., and their history is not particularly limited.

[0025] <2.Singulation process> Step S1 is a singulation step in which the starting material is singulated to obtain two or more separated pieces. Hereinafter, the pieces obtained in step S1 may be referred to as pieces (P1). By performing the singulation step prior to the ink separation step described below, separation of the ink layer in the ink separation step is promoted. When the starting material is a film label alone removed from a PET bottle, the film label is singulated in step S1. There are no particular limitations on the method for singulating the film label, and it can be performed using a known slitter, shredder, cutter, or the like. There are no particular limitations on the size of the pieces.

[0026] When the starting material includes a film label attached to a PET bottle, the PET bottle is separated into individual pieces together with the film label in step S1. The method for separating labeled PET bottles is not particularly limited, and can be performed using a known grinder, cutter, or shredder. Most of the film label peels off from the PET bottle during the process of separating the bottle along with the film label. This results in individual pieces of the PET bottle and individual pieces of the film label. The size of these pieces is not particularly limited, but it is preferable that the size of the pieces is such that the container body and the ring portion attached to the neck of the container body can be separated. Furthermore, when separating PET bottles together with the film label, the individual pieces of the film label may be selected from the resulting pieces, and the selected individual pieces of the film label may be sent to the ink layer separation process described below. The method for separating the individual pieces of the film label is not particularly limited, and examples include blowing away the individual pieces of the film label using wind force and collecting the individual pieces of the film label using vibration.

[0027] <3. Ink layer separation process> Step S2 is an ink layer separation step in which the ink layer is separated from the film label pieces to obtain resin layer pieces from which the ink layer has been removed. Hereinafter, the pieces including the resin layer pieces obtained in step S2 will also be referred to as pieces (P2).

[0028] Because film labels contain an ink layer, their overall specific gravity is often greater than that of the resin film itself, which serves as the base film. Printing inks contain components with relatively high specific gravities, often resulting in an overall specific gravity exceeding 1. For example, white ink contains titanium oxide, which has a relatively high specific gravity of 3.9 to 4.1. Therefore, simply dividing the film label into individual pieces may result in inadequate separation of thermoplastic resins with specific gravities less than 1 from thermoplastic resins with specific gravities greater than 1 in the subsequent gravity separation process. This tendency is particularly pronounced when the resin film is thin, as the ink layer accounts for a large proportion of the overall film label's specific gravity. By performing step S2 before step S3, a large amount of thermoplastic resin with a specific gravity less than 1 can be efficiently recovered.

[0029] The method for separating the ink layer is not particularly limited, and known methods can be appropriately adopted. For example, a method of immersing the pieces (P1) in an alkaline aqueous solution, a method of immersing the pieces (P1) in water, a method using a film cleaning device (deinking device), etc. are included. The pieces (P1) may be pieces of film labels sorted before step S2, or may be pieces of film labels including pieces of PET bottles.

[0030] Film labels are also known that have been devised to make the ink layer easier to remove using the above-mentioned methods. For example, there is a film label that has an intermediate layer that dissolves or swells in alkaline warm water between the ink layer and a base layer made of a thermoplastic resin (see Patent Document 1). When this film label is immersed in a 3% NaOH solution at 90°C for a certain period of time or more, the ink layer is peeled off from the base layer together with the intermediate layer, and the ink layer can be removed as a result. The intermediate layer is composed of a resin composition that swells or dissolves in alkaline warm water.

[0031] In addition, as disclosed in JP 2001-350411 A, there are also film labels in which the ink layer swells or dissolves in an alkaline aqueous solution, making it easy to separate from the resin film. The ink layer of this film label can also be removed by immersing it in a 3% NaOH solution at 60°C for a certain period of time.

[0032] Another example is a film label having a layer containing polyvinyl alcohol (PVA) as an intermediate layer between a resin film and an ink layer (see Patent Document 2). When this film label is immersed in water at 20°C to 50°C, the PVA swells, causing the ink layer to peel off from the resin film together with the PVA, making it possible to remove the ink layer.

[0033] The above-mentioned methods may be combined as appropriate. For example, the individual pieces (P1) may be immersed in water, then removed, and then further immersed in an alkaline aqueous solution. Conversely, the individual pieces (P1) may be immersed in an alkaline aqueous solution, then removed, and then further immersed in water.

[0034] In this manner, an individual piece (P2) including an individual piece of the resin layer from which the ink layer has been removed is obtained.

[0035] <4. Neutralization process> Step S2A can be provided between steps S2 and S3 as needed. Step S2A is a neutralization step in which the individual pieces (P2) after immersion in the alkaline aqueous solution in step S2 are immersed in an acidic aqueous solution to neutralize the alkalinity. The acidic aqueous solution is not particularly limited, but an acetic acid aqueous solution, for example, can be used. When an alkaline aqueous solution is used in step S2, providing this step S2A can save the amount of water used in the washing step described below.

[0036] <5. Cleaning process> Step S2B can be provided between steps S2 and S3 as needed. Step S2B is a washing step in which the alkaline aqueous solution adhering to the individual pieces (P2) is washed with water after the individual pieces (P1) have been immersed in the alkaline aqueous solution in step S2. Step S2B can be provided instead of or in addition to step S2A.

[0037] <6. Specific gravity separation process> Step S3 is a gravity separation step in which the individual pieces (P2) obtained in step S2 are separated into those composed of a thermoplastic resin having a specific gravity of less than 1 and those composed of a thermoplastic resin having a specific gravity of more than 1. Methods for gravity separation include, but are not limited to, liquid separation methods and wind separation methods. However, gravity separation using water is preferred because it is simple yet allows for accurate separation. That is, when the individual pieces (P2) are placed in water, the individual pieces of thermoplastic resin having a specific gravity of less than 1 (hereinafter also referred to as "individual pieces (P3)") rise to the water surface, while the individual pieces of thermoplastic resin having a specific gravity of more than 1 (hereinafter also referred to as "individual pieces (P4)") sink into the water. To ensure accuracy in gravity separation, the water into which the individual pieces (P2) are placed is preferably at a temperature of 20°C or higher, more preferably 30°C or higher, and preferably 55°C or lower, and more preferably 45°C or lower.

[0038] As described above, the olefin-based film, cap, and ring fragments rise to the surface of the water as fragments (P3). On the other hand, fragments of the styrene-based film, ester-based film, polyethylene terephthalate (container body), and overcoat components of the ink layer sink to the water as fragments (P4). The fragments (P3) and (P4) separated by specific gravity in this way can be separately collected.

[0039] The individual pieces (P3) may be further separated into olefin-based film-derived pieces and cap and ring-derived pieces by a known method using wind power, vibration, or the like, and the olefin-based film-derived pieces may be sent to the subsequent step S4. Furthermore, among the collected individual pieces (P4), both the polyethylene terephthalate pieces and the ester-based film pieces can be used to produce recycled pellets. The recycled pellets are used, for example, as raw materials for producing PET bottle container bodies again. For this reason, step S3 may include a step of collecting the individual pieces (P4) and again introducing them into liquids of different specific gravities for further specific gravity separation in order to separate the styrene-based film from the ester-based film and polyethylene terephthalate.

[0040] <7. Drying process> The pieces (P3) recovered in step S3 preferably undergo step S3A before the extrusion molding step (S4) described below. Step S3A is a drying step in which moisture is removed from the pieces (P3) recovered in step S3. The drying method is not particularly limited, and drying can be performed using a hot air dryer, vacuum dryer, or fan. The drying temperature is preferably 30°C or higher, more preferably 40°C or higher, and preferably 90°C or lower, and more preferably 80°C or lower. By setting the drying temperature below the above temperature, fusion of the olefin-based resin can be prevented. Furthermore, by setting the drying temperature above the above temperature, the drying time can be shortened. Furthermore, when the pieces (P3) include pieces of the olefin-based film, cap, and ring portions, the pieces derived from the olefin-based film and the pieces derived from the cap and ring portions may be separated while drying the pieces (P3) in step S3. This separation can be performed using the known method already described.

[0041] By removing moisture from the pieces (P3) in the drying process, manufacturing defects such as the formation of bubbles in the resin film extruded in step S4 can be avoided. Furthermore, when pieces derived from olefin-based films are selected and sent to step S4, the resin film extruded in step S4 will be uncolored or almost uncolored. This means that there are fewer restrictions on its use as a base film, allowing for the production of higher quality film labels.

[0042] <8. Extrusion molding process> Step S4 is a step of feeding the individual pieces (P3) to an extruder, melt-kneading them, and then extrusion-molding them to obtain a resin film with a specific gravity of less than 1. Although not limited thereto, in this embodiment, the resin film is stretched after extrusion and configured as a film having heat shrinkability.

[0043] The individual pieces (P3) may be kneaded alone, but are preferably kneaded together with other raw material compositions (hereinafter also referred to as "additional raw materials") that are not recycled raw materials. Furthermore, the extrusion may be co-extrusion. That is, the resin film may be single-layered or multi-layered, and is configured so that the overall specific gravity is less than 1 by adjusting the blending of the thermoplastic resin derived from the individual pieces (P3) (hereinafter also referred to as "recycled raw material (P3)") and the additional raw materials and the balance of the thickness of each layer. When the co-extrusion method is a T-die method, the lamination method may be a feed block method, a multi-manifold method, or a method combining these.

[0044] When the resin film has a multilayer structure, the recycled material (P3) is preferably contained in the inner layer. In this embodiment, an olefin-based resin is combined as an additional material, and a three-layer resin film is co-extruded, comprising a base layer and adjacent layers laminated adjacent to both sides of the base layer. The adjacent layers contain the additional material, and the base layer contains the recycled material (P3) and the additional material. The base layer preferably contains 1% by mass or more of the recycled material (P3) relative to 100% by mass of the total thermoplastic resin constituting the base layer, more preferably 5% by mass or more, more preferably 60% by mass or less, and even more preferably 40% by mass or less. By blending an appropriate amount of the recycled material (P3) in the base layer, the thermal shrinkage rate of the resin film is within a more preferable range, while natural shrinkage is suppressed. In addition, the rigidity of the resin film is improved. These favorable effects are thought to be due in part to the fact that the recycled material (P3) reduces the crystallinity of the resin.

[0045] Examples of the olefin resin used as an additional raw material include ethylene resin, propylene resin, cyclic olefin resin, petroleum resin, and a mixed resin of at least two of these. These resins can be used in both the base layer and the adjacent layer. Each resin will be described below.

[0046] [Ethylene-based resin] Examples of ethylene-based resins include branched low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ionomer resin, and mixtures thereof. Of these, linear low-density polyethylene is preferred.

[0047] Linear low-density polyethylene is a copolymer of ethylene and an α-olefin. Specific examples of the α-olefin include 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene, and the linear low-density polyethylene may contain two or more types of α-olefins. The specific gravity of the linear low-density polyethylene is usually 0.910 to 0.940.

[0048] Commercially available linear low-density polyethylene resins such as those mentioned above include Evolue (manufactured by Prime Polymer Co., Ltd.), Yumerit (manufactured by Ube Maruzen Polyethylene Co., Ltd.), and Novatec (manufactured by Japan Polyethylene Co., Ltd.).

[0049] [Propylene-based resin] When imparting heat shrinkability to a resin film, the propylene-based resin is preferably a binary or ternary random copolymer containing propylene as the main component and an α-olefin as a copolymerization component. The proportion of the α-olefin as a copolymerization component is preferably 1 to 10 mol %. The propylene-based resin may also be a mixture of different propylene-α-olefin random copolymers. The α-olefin is as described above. The specific gravity of the propylene-based resin is usually 0.900 to 0.910. The propylene-based resin may also contain long-chain branched polypropylene, a propylene-based elastomer, etc.

[0050] Commercially available propylene-based resins such as those mentioned above include Adsyl (manufactured by Basell), Novatec (manufactured by Japan Polypropylene), Waymax (manufactured by Japan Polypropylene), and Tafmer (manufactured by Mitsui Chemicals).

[0051] [Cyclic olefin resin] Cyclic olefin resins can reduce the crystallinity of resin films, increase the heat shrinkage rate, and also improve stretchability during production. Examples of cyclic olefin resins include (a) random copolymers of ethylene or propylene with cyclic olefins, (b) ring-opening polymers of the cyclic olefins or copolymers with α-olefins, (c) hydrogenated products of the polymers of (b), and (d) graft-modified products of (a) to (c) with unsaturated carboxylic acids and their derivatives.

[0052] The cyclic olefin is not particularly limited, and examples thereof include norbornene, 6-methylnorbornene, 6-ethylnorbornene, 5-propylnorbornene, 6-n-butylnorbornene, 1-methylnorbornene, 7-methylnorbornene, 5,6-dimethylnorbornene, 5-phenylnorbornene, 5-benzylnorbornene, and the like, and norbornene and its derivatives. Further examples thereof include tetracyclododecene, 8-methyltetracyclo-3-dodecene, 8-ethyltetracyclo-3-dodecene, 5,10-dimethyltetracyclo-3-dodecene, and the like, and tetracyclododecene and its derivatives. The α-olefin is as described above.

[0053] Commercially available products of the above-mentioned cyclic olefin resins include APEL (manufactured by Mitsui Chemicals, Inc.), TOPAS COC (manufactured by Polyplastics Co., Ltd.), and ZEONOR (manufactured by Zeon Corporation).

[0054] [Petroleum resin] Petroleum resins are resins obtained by polymerizing C5 or C9 fractions produced by thermal cracking of naphtha, or mixtures of these, as well as hydrogenated products thereof. Among these, hydrogenated alicyclic hydrocarbon resins with partially or completely hydrogenated alicyclic structures are preferred from the viewpoints of suppressing softening of resin films at temperatures below 100°C and ensuring transparency and rigidity. Furthermore, polymerized products obtained by purifying single or multiple components of C5 or C9 fractions can also be used.

[0055] Commercially available petroleum resins such as those mentioned above include, for example, Imave (manufactured by Idemitsu Kosan Co., Ltd.), Alcon (manufactured by Arakawa Chemical Industries Co., Ltd.), and Regalite (manufactured by Eastman Co., Ltd.).

[0056] In addition, additives such as antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, lubricants, antistatic agents, flame retardants, antibacterial agents, fluorescent brighteners, and colorants may be added to the resin film as needed.

[0057] The resin film of this embodiment is extruded, taken up on a take-up roll, cooled and solidified, and then stretched uniaxially or biaxially. The stretching method may be, for example, a roll stretching method, a tenter stretching method, or a combination thereof. The stretching temperature is, but is not limited to, preferably 65°C or higher, more preferably 70°C or higher, and preferably 120°C or lower, and more preferably 115°C or lower. The stretching ratio in the main shrinkage direction is, but is not limited to, preferably 3 times or higher, more preferably 4 times or higher, and preferably 7 times or lower, and more preferably 6 times or lower.

[0058] In step S4, a resin film containing recycled raw material (P3) and having a specific gravity of less than 1 is produced. In the next step S5, an ink layer is laminated onto this resin film, which can be suitably used as a film label for a PET bottle. However, the present invention is not limited to this, and the film can also be used as a film label for containers other than PET bottles, or as a packaging material as is.

[0059] <9. Ink layer lamination process> Step S5 is a step of laminating an ink layer using a printing ink on the resin film produced in step S4. The method of laminating the ink layer is not particularly limited. For example, an adjacent layer may be printed and an ink layer may be laminated on the surface of the adjacent layer. In this case, the printing ink used to form the printed layer is preferably one that easily swells or dissolves in an alkaline aqueous solution, such as the ink described above. Alternatively, the adjacent layer may not be printed, and a printed thermoplastic resin film with an ink layer formed thereon may be separately prepared and laminated on the adjacent layer. In this case, from the viewpoint of easily separating the ink layer and the resin film by specific gravity later, it is preferable to provide an intermediate layer between the printed thermoplastic resin film and the adjacent layer, the intermediate layer being made of a resin composition that easily swells or dissolves in water or an alkaline aqueous solution.

[0060] In any of the above cases, the printing method is not particularly limited, and known methods such as offset printing, gravure printing, flexographic printing, inkjet printing, screen printing, etc. An overcoat layer may be laminated on the ink layer as appropriate.

[0061] In step S5, for example, a rolled resin film is sequentially unwound while ink layers are sequentially laminated to obtain a sheet of film labels in which many film labels are connected. The obtained sheet is slit to an appropriate width, and both ends are sealed to produce a tubular film label. The sealing method is not particularly limited, and known methods such as heat sealing, ultrasonic sealing, adhesive sealing, and organic solvent sealing can be used.

[0062] The cylindrical film label thus produced is attached to a PET bottle and heated together with the bottle, causing the film label to thermally shrink and adhere closely to the PET bottle so as to conform to the outer shape of the bottle. In this way, a PET bottle with a film label attached is produced. The heating method is not particularly limited, and may be hot air or steam.

[0063] The recycled film labels that have been through steps S1 to S5 can be distributed together with PET bottles. After that, they can be used as starting materials again. It is preferable that the cycle from starting materials to recycled products be repeated two or more times.

[0064] [Second embodiment] 2 is a flowchart showing the flow of a manufacturing method according to a second embodiment. The manufacturing method for a resin film according to the second embodiment shares with the first embodiment the steps involved in the process from the starting material to the recovery of a thermoplastic resin having a specific gravity of less than 1, but the order in which the steps are carried out differs from that of the first embodiment. Below, a description of the configuration common to the first embodiment will be omitted, and differences from the first embodiment will be mainly described.

[0065] Step S21 is an ink layer separation step in which the ink layer is separated from the starting film label to obtain a resin layer from which the ink layer has been removed. The method for performing step S21 is the same as step S2, but differs from the first embodiment in that it is performed on undivided film labels. For this reason, from the standpoint of efficiency, it is preferable to prepare a single film label as the starting material. The manufacturing method according to the second embodiment may further include step S21A, which is a neutralization step, and step S21B, which is a washing step, after step S21. Steps S21A and S21B are the same as steps S2A and S2B, respectively, in the first embodiment.

[0066] The subsequent step S22 is a singulation step in which the resin layer (which may include PET bottles) obtained in step S21 is singulated, and is the same as step S1 in the first embodiment. By performing the singulation step after the ink layer separation step, machines such as grinders, cutters, crushers, shredders, and slitters are prevented from being contaminated by the printing ink. By step S22, individual pieces of the resin layer (which may include individual pieces of PET bottles) are obtained.

[0067] Steps S23 to S25 following step S22 are performed on the individual pieces obtained in step S22, and are the same as steps S3 to S5 in the first embodiment, so a description thereof will be omitted.

[0068] [Third embodiment] 3 is a flowchart showing the flow of a manufacturing method according to a third embodiment. The resin film manufacturing method according to the third embodiment shares the steps from the starting material to the recovery of a thermoplastic resin having a specific gravity of less than 1 with the first and second embodiments, but the order in which the steps are carried out differs from these embodiments. Below, a description of the configuration common to the first embodiment will be omitted, and differences from the first embodiment will be mainly described.

[0069] Step S31 is a singulation step in which the starting material is singulated to obtain two or more separated pieces, and is the same as step S1 in the first embodiment. The following step S32 is a specific gravity separation step in which the pieces obtained in step S31 are separated into pieces with a specific gravity of less than 1 and pieces with a specific gravity of more than 1. The method of performing step S32 is the same as step S3 in the first embodiment, but differs from the first embodiment in that it is performed prior to the ink layer separation step. Step S32 separates the olefin-based film label pieces, cap pieces, and ring portion pieces from the styrene-based film label pieces, ester-based film label pieces, and container body pieces among the pieces of the starting material. Pieces with a specific gravity of less than 1 may be sent together to the subsequent step S33, or the olefin-based film label pieces may be specifically selected using the known method already exemplified and sent to step S33.

[0070] The following step S33 is an ink layer separation step in which the ink layer is separated from an individual piece of an olefin-based film label having a specific gravity of less than 1 to obtain an individual piece of a resin layer from which the ink layer has been removed. The method for performing step S33 is the same as step S3 in the first embodiment. Step S33 obtains an individual piece of a resin layer composed mainly of an olefin-based resin. By performing step S32 before step S33, the separated ink layer is prevented from adhering to the individual pieces of the PET bottle container body. The manufacturing method according to the third embodiment may further include, after step S33, step S33A, which is a neutralization step, step S33B, which is a washing step, and step S33C, which is a drying step. Steps S33A, S33B, and S33C are the same as steps S2A, S2B, and S3A, respectively. The following steps S34 and S35 are the same as steps S4 and S5, respectively. Therefore, their description will be omitted.

[0071] <10. Features> According to the resin film manufacturing method of this embodiment, a resin film with a specific gravity of less than 1 contained in a film label can be reused through a relatively simple process. In particular, by reproducing a resin film with a specific gravity of less than 1 from this resin film, a cycle is established from film label to film label. Furthermore, by using recycled materials, the heat shrinkability, rigidity, and natural shrinkability of the olefin-based resin film can be made favorable.

[0072] <11. Variations> Although several embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the present disclosure. For example, the following modifications are possible. Furthermore, the gist of the following modifications can be combined as appropriate.

[0073] <11-1> In the second embodiment, the order of performing step S22 (singulation step) and step S23 (gravity separation step) may be reversed. That is, step S23 may be performed after step S21 (ink layer separation step), step S21A (neutralization step), and step S21B (washing step), and then step S22 may be performed.

[0074] <11-2> In the third embodiment, step S32 (gravity separation step) may be performed prior to step S31 (singulation step). That is, step S31 and step S33 (ink layer separation step) may be performed after step S32. In this case, either step S31 or step S33 may be performed first. When step S32 is followed by step S33, step S33A (neutralization step), and step S33B (washing step), the order of the subsequent step S31 and step S33C (drying step) may also be changed as appropriate.

[0075] <11-3> In the first to third embodiments and their modifications, the neutralization step, washing step, and drying step may be omitted as appropriate, or may be added as appropriate between the steps. Furthermore, in the first to third embodiments and their modifications, when the starting materials include PET bottles, the selection of raw materials derived from film labels may be added as appropriate between the steps in addition to the above-mentioned timing.

[0076] <11-4> When the resin film produced in the extrusion molding step has a multilayer structure having two or more layers, the extrusion molding step may include forming an intermediate layer between a first layer and a second layer different from the first layer, the intermediate layer being composed of a resin composition that easily swells or dissolves in water or an alkaline aqueous solution. In this case, the intermediate layer may be co-extruded with the first and second layers, or the first and second layers may be extruded separately, and the resin composition that forms the intermediate layer may be laminated on the surface of one of the layers, and the first and second layers may be laminated so as to sandwich the layer.

[0077] <Additional Notes> From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0078] (Configuration 1) A method for manufacturing a resin film, comprising: preparing at least one of a film label having an ink layer and a resin layer, and a resin bottle to which the film label is attached, as a starting material; recovering a thermoplastic resin having a specific gravity of less than 1 from the starting material; and extruding a resin film having a specific gravity of less than 1 using the recovered thermoplastic resin as a raw material. Note that recovering the thermoplastic resin having a specific gravity of less than 1 includes: slicing the starting material or the resin layer; separating the ink layer from the film label or the film label pieces to obtain the resin layer or the resin layer pieces from which the ink layer has been removed; and separating the starting material, the resin layer, or the pieces thereof by specific gravity to recover the starting material, the resin layer, or the pieces thereof, each having a specific gravity of less than 1; and the extruded resin film having a specific gravity of less than 1 is composed primarily of an olefin-based resin. [Example]

[0079] Examples of the present disclosure will be described in detail below, but the present disclosure is not limited to these examples.

[0080] <1. Preparation of Examples and Reference Examples> The raw materials shown in Table 1 were blended in the proportions (unit: mass%) shown in Table 1 as raw materials for the base layer and the adjacent layers laminated adjacent to both sides of the base layer to prepare resin compositions for the base layer and adjacent layers. In the examples, recycled raw materials with a specific gravity of less than 1 were blended into the raw materials for the base layer. This recycled raw material is a material obtained from a resin film that was once manufactured as an olefin-based film, and is known to contain polypropylene, polyethylene, cyclic olefin copolymer (COC), and petroleum resin. Raw materials other than the recycled raw materials are commercially available, non-recycled raw materials, and the following products were used. COC1: TOPAS (registered trademark), manufactured by Polyplastics Co., Ltd. COC2: TOPAS (registered trademark), manufactured by Polyplastics Co., Ltd. LLDPE: Evolue (registered trademark), manufactured by Prime Polymer Co., Ltd. Random PP copolymer: Adsyl®, manufactured by LyondellBasell Petroleum resin: Alcon, manufactured by Arakawa Chemical Industries, Ltd. [Table 1]

[0081] The above resin composition was melted separately for the base layer and the adjacent layer, co-extruded through a T-die, and cooled and solidified using a roll cooled to 30°C to produce an unstretched resin film. This was stretched 5 times using a tenter-type stretching machine at 90°C to produce a three-layer resin film. The thickness of the entire resin film, the thickness of the base layer, and the thickness of the adjacent layer were the same in the examples and reference examples. The specific gravity of the resin film in the reference example was 0.94.

[0082] <2. Evaluation> The resin films according to the above Examples and Reference Examples were evaluated as follows.

[0083] <2-1. Shrinkage rate> Three samples each measuring 100 mm in the main shrinkage (TD) direction and 100 mm in the secondary shrinkage (MD) direction were cut out from any location of the resin films of the Examples and Reference Examples. Each sample was immersed in warm water for 10 seconds, then removed and immersed in 20°C water for 10 seconds, and then removed again. The length L (mm) of each sample in the TD direction was then measured, and the shrinkage rate (%) in the TD direction was calculated according to the following formula. For the resin films of the Examples and Reference Examples, the average value of the shrinkage rates of each sample was taken as the heat shrinkage rate. Shrinkage rate (%) = {(100-L) / 100} x 100 The hot water used was 70°C, 80°C, and 90°C, and three of the above samples were prepared for each temperature, and the shrinkage rate was calculated. <2-2. Natural shrinkage rate> Three samples measuring 100 mm in the MD direction and 100 mm in the TD direction were cut out from any location of the resin films according to the Examples and Reference Examples. Each sample was left to stand for 7 days in a low-temperature incubator (IL-82, manufactured by Yamato Scientific Co., Ltd.) adjusted to 40°C, and then the length L (mm) of each sample in the TD direction was measured. The natural shrinkage rate (%) in the TD direction of each sample was calculated using the same formula as for the shrinkage rate. The average natural shrinkage rate of each sample for the resin films according to the Examples and Reference Examples was taken as the natural shrinkage rate.

[0084] <2-3.Young's Modulus> Three samples each measuring 250 mm in MD × 5 mm in TD and three samples each measuring 250 mm in TD × 5 mm in MD were cut out from any location of the resin film according to the Examples and Reference Examples. The Young's modulus (GPa) in MD and TD of these samples was measured using a Strograph (VE-1D, manufactured by Toyo Seiki Seisakusho, Ltd.) according to the method of ASTM D882.

[0085] <3. Evaluation Results> The evaluation results are shown in Table 2 below. [Table 2]

[0086] As can be seen from Table 2, the examples containing recycled materials had higher Young's modulus and improved rigidity in both the MD and TD directions compared to the reference examples. Furthermore, the examples had slightly higher shrinkage at 80°C and 90°C compared to the reference examples, while the natural shrinkage was suppressed, demonstrating favorable performance compared to the reference examples. [Explanation of symbols]

[0087] S1~S5, S21~S25, S31~S35 Process (Step)

Claims

1. preparing at least one of a film label having an ink layer and a resin layer and a resin bottle to which the film label is attached as a starting material; recovering a thermoplastic resin having a specific gravity of less than 1 from the starting material; extruding a resin film having a specific gravity of less than 1 using the recovered thermoplastic resin as a raw material; Equipped with The recovery of the thermoplastic resin having a specific gravity of less than 1 includes: singulating the starting material or the resin layer; Separating the ink layer from the film label or the piece of the film label to obtain the resin layer or the piece of the resin layer from which the ink layer has been removed; gravity-separating the starting material, the resin layer, or individual pieces thereof to recover the starting material, the resin layer, or individual pieces thereof having a specific gravity of less than 1; Including, A method for manufacturing a resin film.

2. The recovery of the thermoplastic resin having a specific gravity of less than 1 includes: singulating the starting material; Separating the ink layer from the individual pieces of the film label to obtain individual pieces of the resin layer from which the ink layer has been removed; and recovering the resin layer pieces having a specific gravity of less than 1 by subjecting the resin layer pieces to specific gravity separation in this order. The method for producing the resin film according to claim 1 .

3. laminating an ink layer on the extruded resin film to produce a film label having an ink layer and a resin layer; Further provided with The method for producing the resin film according to claim 1 or 2.

4. The produced film label is used as the starting material, and the steps of recovering a thermoplastic resin having a specific gravity of less than 1 and incorporating the recovered thermoplastic resin into a raw material to produce a resin film having a specific gravity of less than 1 are repeated one or more times. The method for producing a resin film according to claim 3 .

5. obtaining the resin layer or the piece of the resin layer from which the ink layer has been removed includes separating the ink layer by immersing the film label or the piece of the film label in an alkaline aqueous solution; The method for producing the resin film according to any one of claims 1 to 4.

6. neutralizing the resin layer or pieces of the resin layer after immersion in the alkaline aqueous solution; Further provided with The method for producing a resin film according to claim 5 .

7. obtaining the resin layer or the piece of the resin layer from which the ink layer has been removed includes separating the ink layer by immersing the film label or the piece of the film label in water; The method for producing the resin film according to any one of claims 1 to 6.

8. Obtaining the resin layer or the individual pieces of the resin layer from which the ink layer has been removed includes washing the resin layer or the individual pieces of the resin layer from which the ink layer has been separated. The method for producing a resin film according to any one of claims 1 to 7.

9. drying the recovered thermoplastic resin having a specific gravity of less than 1 between recovering the thermoplastic resin having a specific gravity of less than 1 and extruding the resin film having a specific gravity of less than 1; Further provided with The method for producing a resin film according to any one of claims 1 to 8.

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