A method for removing a functional layer from a plastic film having a functional layer, and a method for producing recycled plastic pellets.

Abstract

To provide a method for efficiently and effectively removing a functional layer from a plastic film having a functional layer. [Solution] A method for removing a functional layer from a plastic film having a functional layer, comprising: (A) a step of wet-shredding the plastic film; and (B) a step of washing the shredded plastic film after step (A) using a washing device comprising a cylindrical rotating tank having a plurality of discharge holes and conveying blades on its inner surface and rotatable about a central axis as a rotation axis, and a discharge unit that discharges a washing liquid toward the inner surface of the rotating tank, wherein step (B) comprises supplying the shredded material into the rotating tank from one end of the rotating tank, conveying the shredded material from one end of the rotating tank to the other end by rotating the rotating tank, and washing the shredded material by spraying a washing liquid onto the shredded material while it is being conveyed.

Description

[Technical Field]

[0001] This disclosure relates to a method for removing a functional layer from a plastic film having a functional layer, and a method for producing recycled plastic pellets. [Background technology]

[0002] Plastic films that make up plastic products are typically equipped with functional layers, such as ink layers, hard coat layers, and silicone coating layers, to impart functionality. However, if components derived from these functional layers are mixed into recycled plastic raw materials, it can cause problems such as unintended discoloration, the generation of off-odors during the production of recycled plastic pellets, and a decrease in product properties. Therefore, there is a need for recycling methods for plastic products that do not involve the mixing of these components.

[0003] To address the above issues, Patent Document 1 discloses a method for removing ink, which includes the steps of processing a printed film, crushing it, removing ink from the film, rinsing the film, recovering the cleaning solution, recovering the pigment, and drying the film. Patent Document 2 also discloses a batch-type processing apparatus comprising a processing tank for alkaline processing a laminate containing a resin substrate and a printed layer (ink layer), a filter through which a liquid containing the printed layer detached from the laminate passes, and an extraction mechanism for extracting the liquid that has passed through the filter to the outside of the processing tank, as well as a method for recovering a resin substrate using the processing apparatus. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2015-520684 [Patent Document 2] Japanese Patent Publication No. 2022-090235 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, conventional methods such as those disclosed in Patent Document 1 do not always provide sufficient ink removal. Furthermore, methods for removing the printed layer using batch-type processing equipment, such as those disclosed in Patent Document 2, require a lot of time because the processing liquid is circulated through a filter many times to remove the printed layer in the processing tank, which presents challenges in terms of productivity.

[0006] Therefore, one aspect of this disclosure aims to provide a method for efficiently and effectively removing a functional layer from a plastic film having a functional layer. Another aspect of this disclosure aims to provide a method for producing recycled plastic pellets using plastic film fragments or processed materials recovered through the above method. [Means for solving the problem]

[0007] Some aspects of this disclosure provide the following [1] to [9].

[0008] [1] A method for removing a functional layer from a plastic film having a functional layer, (A) A step of wet-shredding the plastic film, (B) A cleaning device comprising a cylindrical rotating tank having a plurality of discharge holes and conveying blades on its inner surface and rotatable about its central axis as a rotation axis, and a discharge section that discharges cleaning liquid toward the inner surface of the rotating tank, to clean the crushed plastic film that has undergone the process of (A), including the step of cleaning the crushed plastic film that has undergone the process of (A), A method comprising the steps of (B) above: supplying the crushed material into the rotating tank from one end of the rotating tank; conveying the crushed material from one end of the rotating tank to the other end by rotating the rotating tank; and washing the crushed material by spraying the washing liquid onto the crushed material while it is being conveyed.

[0009] [2] The method according to [1], wherein in step (B) above, the cleaning liquid is discharged such that the impact force index I, which can be determined by the following formula (I), is between 13 and 1100. Impact force index I = Q·√P·(1 / r) 2 ...(I) [Q represents the discharge flow rate of the cleaning fluid (unit: L / min), P represents the discharge pressure of the cleaning fluid (unit: MPa), and r represents the distance (unit: m) from the discharge port of the discharge unit to the inner surface of the rotating tank.]

[0010] [3] The method according to [1] or [2], wherein the discharge pressure P of the cleaning solution in step (B) is 0.15 to 15 MPa.

[0011] [4] The method according to any one of [1] to [3], wherein the value Vf / d obtained by dividing the amount Vf supplied per minute of the crushed material into the rotating tank in step (B) by the inner diameter d of the rotating tank is 0.04 to 0.5 kg / (min·cm).

[0012] [5] The method according to any one of [1] to [4], wherein the rotational speed of the rotating tank in step (B) is 3 to 50 rpm.

[0013] [6] The method according to any one of [1] to [5], wherein the minimum width of the discharge hole is 0.1 to 5 mm.

[0014] [7] The method according to any one of [1] to [6], wherein the average size Sa of the plastic film pieces in the crushed material is 2 to 10 mm.

[0015] [8] The method according to any one of [1] to [7], further comprising the step of wetting the plastic film with a liquid containing water, a surfactant, and an inorganic base before step (A).

[0016] [9] A method for producing recycled plastic pellets, comprising forming plastic film fragments or processed materials recovered through any of the methods described in [1] to [8] into pellets. [Effects of the Invention]

[0017] According to one aspect of this disclosure, a method for efficiently and effectively removing a functional layer from a plastic film having a functional layer can be provided. According to another aspect of this disclosure, a method for producing recycled plastic pellets using plastic film fragments or processed materials recovered through the above method can be provided. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic external side view showing an example of a washing apparatus for washing crushed material used in the method of the present disclosure. [Figure 2] Figure 1 is a schematic internal side view of the cleaning apparatus. [Figure 3] This is a schematic cross-sectional view along line AA in Figure 1. [Modes for carrying out the invention]

[0019] The following describes exemplary embodiments of this disclosure. However, this disclosure is not limited in any way to the embodiments described below. In this specification, numerical ranges indicated using "~" indicate a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. Unless otherwise explicitly stated, the units of the numbers before and after "~" are the same. The upper and lower limits described individually can be combined in any way. In addition, specific compounds, products, etc. are given as examples below, but other substances may also be used as appropriate. In this specification, "(meth)acrylic" means at least one of acrylic and the corresponding methacrylic.

[0020] <Method for removing the functional layer> One embodiment of the present disclosure is a method for removing a functional layer from a plastic film having a functional layer (hereinafter also simply referred to as "plastic film") (hereinafter also simply referred to as "removal method"), and includes the steps of (A) and (B) below. (A) Process of wet-shredding the above plastic film (B) A cleaning device comprising a cylindrical rotating tank having multiple discharge holes and conveying blades on its inner surface and rotatable around its central axis, and a discharge section that discharges cleaning liquid toward the inner surface of the rotating tank, to clean the crushed plastic film that has undergone the process described in (A) above.

[0021] In the above removal method, step (B) comprises supplying crushed material into the rotating tank from one end of the rotating tank, transporting the crushed material from one end of the rotating tank to the other end by rotating the rotating tank, and cleaning the crushed material by spraying a cleaning solution onto the crushed material while it is being transported.

[0022] According to the above removal method, the functional layer can be efficiently and effectively removed from the plastic film, and plastic film pieces that do not have a functional layer or have a sufficiently small amount of functional layer attached can be recovered. Therefore, the above removal method can be suitably used as a process for producing high-quality recycled plastic raw materials (e.g., recycled plastic pellets).

[0023] The reason why the above removal method can efficiently and effectively remove the functional layer from the plastic film is as follows:

[0024] In the wet shredding process, shear force is applied to the functional layer of the plastic film and the plastic film is agitated. As a result of the friction between the films due to the shear force and agitation, and contact between the liquid and the functional layer, the separation (peeling) of the functional layer from the plastic film progresses. Since this separated functional layer is easily reattached to the plastic film, it is necessary to remove the reattached functional layer again. In contrast, in the above removal method, in step (B), a washing process is performed on the shredded material using a washing device having the above characteristics. In this washing process, by spraying washing liquid onto the shredded material in the rotating tank of the washing device, the functional layer that has reattached to the plastic film is separated (peeled) again and introduced into the discharge hole along with the washing liquid, thus preventing the functional layer from reattaching to the plastic film. Furthermore, since this washing process is a continuous process in which the transport and washing of the shredded material are performed simultaneously, the processing time is shorter compared to a batch process, and when compared over a certain processing time, the functional layer can be removed more efficiently than in a batch process.

[0025] In the following, the cleaning equipment used in step (B) will be described with reference to the drawings, and then each step of the removal method described above will be explained in detail. In the drawings, the same or equivalent parts are denoted by the same reference numerals, and redundant explanations are omitted.

[0026] Figure 1 is a schematic external side view showing an example of a washing apparatus for washing crushed material. The washing apparatus 100 shown in Figure 1 comprises a rotating tank 10 and a washing liquid supply pipe 20 introduced into the rotating tank 10. The rotating tank 10 is a cylindrical wedge wire screen extending along a central axis R, and is rotatable about the central axis R as the axis of rotation. The rotating tank 10 is formed by arranging a large number of wedge wires 10a extending in the direction of the central axis R in parallel along the circumferential direction, and bundling them together with a plurality of reinforcing members 10b.

[0027] Figure 2 is a schematic internal side view of the cleaning device 100 shown in Figure 1. As shown in Figure 2, the rotating tank 10 has a plurality of discharge holes 12 for discharging cleaning fluid and a conveying blade 14 on its inner circumferential surface. The discharge holes 12 are gaps (slits) between adjacent wedge wires 10a, and a plurality of them are provided across the entire inner circumferential surface. The conveying blade 14 is provided in a continuous spiral shape from one end to the other on the inner circumferential surface of the rotating tank 10. Also, as shown in Figure 2, the cleaning fluid supply pipe 20 has a discharge section 22 for discharging cleaning fluid. The discharge section 22 discharges the cleaning fluid supplied from the cleaning fluid supply pipe 20 toward the inner circumferential surface of the rotating tank 10. A plurality of discharge sections 22 are arranged in the axial direction (direction along the central axis R) of the rotating tank 10.

[0028] Figure 3 is a schematic cross-sectional view along line AA in Figure 1. As shown in Figure 3, the wedge wire 10a has a triangular cross-section, and the vertices of the triangle are arranged so that they face outward. Also, as shown in Figure 3, the conveying blades 14 have a predetermined height and are provided to protrude from the inner surface toward the central axis R. In Figure 3, d represents the inner diameter of the rotating tank 10, and r represents the distance from the discharge port 22a of the discharge section 22 to the inner surface of the rotating tank 10.

[0029] Although not shown in the diagram, both ends of the rotating tank 10 (both ends in the axial direction) are open. The opening at one end is a supply port for supplying (injecting) the material to be processed, and the opening at the other end is a discharge port for discharging the material to be processed. When the material to be processed (crushed material) is supplied into the rotating tank 10 from one end (supply port), the material is conveyed by the conveying blades 14 as the rotating tank 10 rotates, contacting the inner surface of the rotating tank 10, and is also washed by the washing liquid discharged from the discharge section 22, and then discharged from the other end (discharge port) of the rotating tank 10.

[0030] The cleaning equipment used in process (B) has been described above using cleaning equipment 100 as an example, but the cleaning equipment used in process (B) is not limited to the above.

[0031] The rotating tank may be made by forming a mesh screen into a cylindrical shape. In this case, the gaps (openings) in the mesh screen become the discharge holes.

[0032] The size of the rotating tank can be changed as appropriate. The axial length of the rotating tank may be, for example, 1000 to 6000 mm. The perimeter of the cross-section of the rotating tank may be, for example, 1200 to 5600 mm. The inner diameter d of the rotating tank may be, for example, 400 to 1800 mm.

[0033] The shape of the cross-section perpendicular to the central axis of the rotating tank is preferably perfectly circular (circularity of 1), but it may also be approximately circular with a circularity less than 1. The closer the circularity of the cross-sectional shape of the rotating tank is to 1, the less likely the crushed material supplied to the rotating tank is to accumulate, and the better the discharge from the washing device tends to be. The circularity referred to here is defined by the following formula. Roundness = 4π × (Area of ​​cross-section) / (Perimeter of cross-section) 2

[0034] The discharge holes provided on the inner circumferential surface of the rotating tank only need to have the function of discharging the cleaning fluid, and may be through holes penetrating from the inner circumferential surface to the outer circumferential surface of the rotating tank, or they may not be through holes. The opening shape of the discharge holes is not particularly limited and may be circular, elliptical, rectangular, polygonal, etc.

[0035] The minimum width of the discharge hole may be, for example, 0.05 to 5 mm, and is preferably 0.1 to 5 mm from the viewpoint of increasing the recovery rate of plastic film fragments and from the viewpoint of better removing the functional layer. When the minimum width of the discharge hole is 0.1 mm or more, functional layer fragments washed away by the cleaning solution are more easily introduced into the discharge hole, and the removal of functional layer fragments tends to improve. On the other hand, when the minimum width of the discharge hole is 5 mm or less, plastic film fragments are less easily introduced into the discharge hole, and the recovery rate of plastic film fragments tends to improve. From the viewpoint of further better removal of the functional layer, the minimum width of the discharge hole may be 0.3 mm or more, 0.5 mm or more, or 1 mm or more, and from the viewpoint of further increasing the recovery rate of plastic film fragments, it may be 2 mm or less, 1 mm or less, or 0.7 mm or less. From these perspectives, the minimum width of the discharge hole may be 0.1-2 mm, 0.1-1 mm, 0.1-0.7 mm, 0.3-2 mm, 0.3-1 mm, 0.3-0.7 mm, 0.5-2 mm, or 1-2 mm. The minimum width of the discharge hole is equal to the diameter of a virtual circle inscribed in the opening of the discharge hole (the opening on the inner circumferential surface side). For example, if the rotating tank is formed of a wedge wire screen, the mesh opening of the wedge wire screen (the minimum width of the gap between the wedge wires) becomes the minimum width of the discharge hole. Also, for example, if the rotating tank is formed of a mesh screen, the mesh opening of the mesh screen becomes the minimum width of the discharge hole.

[0036] The conveying blades only need to have the function of conveying the crushed material from one end of the rotating tank to the other while keeping it in contact with the inner surface of the rotating tank as the tank rotates. The size, shape, number, and arrangement angle of the conveying blades can be changed as appropriate, taking into consideration the size of the device, the processing volume, the processing conditions, etc.

[0037] The discharge section only needs to be capable of spraying a cleaning solution onto the crushed material. A commonly known spray nozzle can be used for the discharge section. For example, flat, full-cone, hollow-cone, solid, and fine-atoming spray nozzles can be used. The distance from the discharge port to the inner surface of the rotating tank can be adjusted by changing the nozzle length. The distance r from the discharge port to the inner surface of the rotating tank is, for example, 0.1 to 0.7 m.

[0038] The number of discharge nozzles can be appropriately selected according to the size of the rotary tank. A larger number of discharge nozzles tends to increase the frequency with which the cleaning solution is sprayed onto the crushed material, thereby improving the removal of functional layer fragments. On the other hand, if there are too many discharge nozzles, the amount of cleaning solution consumed increases, thus increasing processing costs. From a cost-effectiveness standpoint, the number of discharge nozzles may be, for example, 1 to 20, 2 to 8, or 3 to 5 per meter in the axial direction of the rotary tank. If there are multiple discharge nozzles, they may be arranged at equal intervals or at uneven intervals. Also, the discharge angles and discharge directions of the multiple discharge nozzles may be the same or different.

[0039] As the cleaning device described above, a known solid-liquid separation device known as a drum screen can be applied. A specific example of a cleaning device is the TS drum screen manufactured by Toyo Screen Industry Co., Ltd. Alternatively, as a cleaning device, a known drum screen can be modified by separately introducing a cleaning liquid supply pipe having a discharge section inside the drum screen.

[0040] (Process:(A)) In step (A), the plastic film (plastic film having a functional layer) is wet-crushed. Wet crushing is a process in which the plastic film is crushed in the presence of a liquid while being agitated (for example, with the liquid encompassed with the plastic film). In this specification, "crushing" means breaking down a solid (film) into small pieces using a crusher or the like, and terms such as pulverization, decomposition, and shredding are also included in "crushing".

[0041] (A) is the process by which a shredded plastic film is obtained. The shredded product includes plastic film pieces from which part or all of the functional layer has been separated by wet shredding, and part or all of the functional layer separated from the plastic film (hereinafter also referred to as "functional layer pieces").

[0042] [Plastic film] A plastic film having a functional layer comprises at least a resin film layer and a functional layer provided on the resin film layer.

[0043] Plastic film refers to, for example, waste plastic film (so-called discarded plastic film). The plastic film can be used in any way without particular limitations, including films commonly distributed for food packaging and household goods packaging, and discarded films with various types of resin film layers. These can also be used in combination. Plastic film can also be used cut from rolls of plastic film.

[0044] The plastic film may be either a laminated film having a functional layer on its outermost surface, or a laminated film in which the functional layer is provided between multiple resin film layers. When the plastic film is a laminated film having a functional layer on its outermost surface, the removal of the functional layer is improved. Examples of laminated films having a functional layer on their outermost surface and laminated films in which the functional layer is provided between multiple resin film layers include front-printed films and back-printed films, which are commonly used for food packaging and the like.

[0045] - Resin film layer - Resin film layers can be classified by their required function into categories such as the base film layer (F1) and the sealant layer (F2), which serves as the heat-sealing area when forming packaging materials.

[0046] Examples of resin films that form the base film layer (F1) include polyolefin films composed of low-density polyethylene, high-density polyethylene, linear low-density polyethylene, OPP (biaxially oriented polypropylene), CPP (unoriented polypropylene), etc.; polyester films composed of polyethylene terephthalate (PET), polybutylene terephthalate, etc.; polyamide films composed of nylon 6, nylon 6,6, metaxylene adipamide (N-MXD6), etc.; biodegradable films composed of polylactic acid, etc.; polyacrylonitrile films; poly(meth)acrylic films; polystyrene films; polycarbonate films; ethylene-vinyl acetate copolymer saponified (EVOH) films; polyvinyl alcohol films; and triacetylcellulose films. These films may contain pigments. A vapor-deposited layer may be formed on the surface of these films by vapor-depositing metals such as aluminum and copper, titanium oxide, alumina, silica, etc. Various surface treatments, such as flame treatment, corona discharge treatment, or chemical treatments such as desorption primers, may be performed on the surface of these films.

[0047] The resin film that forms the sealant layer (F2) is, for example, a flexible polymer film. Examples of flexible polymer films include polyolefin films such as polyethylene film, polypropylene film, and ethylene-vinyl acetate copolymer film, as well as films composed of ionomer resin, EAA resin, EMAA resin, EMA resin, EMMA resin, biodegradable resin, etc. As the resin film, films known by common names such as CPP (unoriented polypropylene) film, VMCPP (aluminum-deposited unoriented polypropylene) film, LLDPE (linear low-density polyethylene) film, LDPE (low-density polyethylene) film, HDPE (high-density polyethylene) film, and VMLDPE (aluminum-deposited low-density polyethylene) film can also be used. These films may contain pigments. Various surface treatments such as flame treatment, corona discharge treatment, or chemical treatment with desorption primer may be performed on the surface of these films.

[0048] From the perspective of reuse as a recycled base material for general consumer use, the resin film layer preferably includes a film made of polyolefin such as polyethylene or polypropylene (polyolefin film), and more preferably includes a polypropylene film. On the other hand, from the perspective of reuse as a recycled base material for industrial use, the resin film layer preferably includes a film made of polyolefin such as polyethylene or polypropylene (polyolefin film), or a film made of polyester such as polyethylene terephthalate (polyester film). The polyolefin may be a stretched film (e.g., uniaxially stretched or biaxially stretched film) or an unstretched film.

[0049] The thickness of the resin film layer is preferably 5 to 1000 μm, and more preferably 10 to 500 μm.

[0050] -Functional Layer- The functional layer may be, for example, an ink layer. The ink layer is a layer containing ink and may have the function of displaying any picture, pattern, character, symbol, etc., for the purpose of decoration or aesthetic appeal, or for displaying contents, expiration date, manufacturer, or seller information. The ink layer may also be a solid ink layer without pictures, patterns, characters, or symbols. In the removal method of this embodiment, it is preferable that the functional layer is an ink layer from the viewpoint of easily obtaining better removal performance.

[0051] The ink layer is formed by printing using, for example, a gravure printer, flexographic printer, offset printer, or inkjet printer. That is, the ink used to form the ink layer may be gravure printing ink, flexographic printing ink, offset printing ink, or inkjet printing ink. Among these, from the viewpoint of being easy to remove using the method of this embodiment, it is preferable that the ink forming the ink layer is gravure ink.

[0052] The ink used to form the above-mentioned ink layer may be, for example, an organic solvent-type printing ink, a water-based ink, or an active energy ray-curing ink. The ink layer may be formed from one type of ink, or from multiple types of ink. That is, the ink layer may be a single-color printing ink layer, or a multi-color printing ink layer.

[0053] The ink, for example, contains a binder resin and an organic solvent as its main components. The ink may also contain a pigment and / or dye as a coloring agent. The ink may also contain a pigment derivative and / or a resin-type dispersant as a dispersant for the coloring agent. These materials may be used individually or in combination. Using a pigment derivative and a resin-type dispersant in combination improves dispersion stability and stability over time.

[0054] The ink may contain a compound having an acidic group from the viewpoint of functional layer removal. The compound having an acidic group can be used without particular limitations. Preferably, the compound having an acidic group is a compound (for example, a resin or a low molecular weight compound) that can be easily mixed with the main components of the ink, such as the binder resin or organic solvent.

[0055] Examples of resins having acidic groups include resins with acid values ​​such as rosin-modified maleic acid resin and rosin-modified fumaric acid resin; polymerizable monomers having carboxyl groups such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, cinnamic acid, or their acid anhydrides; polymerizable monomers having sulfonic acid groups such as sulfonated styrene; (meth)acrylic resins obtained by copolymerizing polymerizable monomers having acidic groups (for example, polymerizable monomers having sulfonamide groups such as vinylbenzenesulfonamide); radical copolymers such as styrene-(meth)acrylic resin, styrene-(anhydride)maleic acid resin, terpene-(anhydride)maleic acid resin, and acid-modified polyolefin resins. These can be used individually or in combination of multiple types.

[0056] Examples of low molecular weight compounds containing acidic groups include saturated fatty acids, unsaturated fatty acids, hydroxy acids, aromatic carboxylic acids, dicarboxylic acids, tricarboxylic acids, oxocarboxylic acids, carboxylic acid derivatives, and acid anhydrides. These can be used individually or in combination.

[0057] Examples of saturated fatty acids include lauric acid, myristic acid, palmitic acid, margaric acid, and stearic acid. Examples of unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and sorbic acid. Examples of hydroxy acids include lactic acid, malic acid, and citric acid. Examples of aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, melitic acid, and cinnamic acid. Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, and maleic acid. Examples of tricarboxylic acids include aconitic acid. Examples of oxocarboxylic acids include pyruvate and oxaloacetic acid. Examples of carboxylic acid derivatives include amino acids and nitrocarboxylic acids. Examples of acid anhydrides include trimellitic anhydride and pyromellitic anhydride. These can be used individually or in combination.

[0058] The content of the acidic compound can be appropriately determined within a range that does not impair the printability of the ink, but it is preferably in the range of 0.5 to 50% by mass, and more preferably in the range of 1.0 to 30% by mass, relative to the solid content of the ink.

[0059] The ink layer may be a single-layer or multi-layer structure. The thickness of the ink layer is preferably 0.1 to 10 μm, and more preferably 1 to 5 μm.

[0060] The functional layer may be a layer other than the ink layer, and may be a functional coating layer formed for purposes such as hard coating, silicone-based release, IR cut, waterproofing and moisture resistance, antibacterial properties, UV cut, heat dissipation, photocatalysis, weather resistance, anti-fogging, fingerprint resistance, self-healing, water and oil repellency, etc. Examples of functional coating layers include hard coating layers, adhesive layers, release layers, decorative layers, light-shielding layers, UV-shielding layers, easy-adhesion layers (primer layers), antistatic layers, refractive index adjusting layers, oligomer encapsulation layers, etc. These functional coating layers may be colorless or colored.

[0061] Functional coating layers can be formed by coating the surface of a resin film layer with surface modifiers, coating agents used as electronic materials, etc. Examples of surface modifiers include hard coating agents, self-healing coating agents, anti-fingerprint and anti-fouling coating agents, anti-fogging coating agents, silicone-based release agents, non-silicone-based release agents, waterproof and moisture-proof coating agents, water-repellent and oil-repellent coating agents, photocatalytic coating agents, weather-resistant coating agents, and IR-cut coating agents. Examples of coating agents used as electronic materials include optical adhesives, polyimide varnishes, liquid crystal alignment film materials, electromagnetic wave shielding coating agents, fine wiring pastes, antistatic coating agents, high refractive index coating agents, and optical lens coating agents.

[0062] The functional coating layer may be a metal layer formed from a metallic material. The metal layer may be a layer made of metal foil, or a metal vapor-deposited layer formed by the deposition of metal or metal oxide. Examples of metal foils include foils of metals with excellent malleability, such as gold, silver, copper, zinc, iron, lead, tin and their alloys, steel, stainless steel, and aluminum. Examples of metal vapor-deposited layers include layers made of one or more materials such as aluminum, aluminum oxide, silica, and zinc oxide.

[0063] The functional coating layer may be an oxygen-absorbing layer, an anchor coating layer, or a delamination primer layer provided to facilitate the removal of the ink layer (for example, a layer containing the acidic compound described above).

[0064] The functional coating layer may be a single layer or a laminate of different types of layers. For example, the functional coating layer may have a layer formed of one of the above-mentioned coating agents and the above-mentioned metal vapor deposition layer. In this case, the layer formed of one of the above-mentioned coating agents may be provided via a metal vapor deposition layer in contact with the resin film layer.

[0065] The functional layer removed by the removal method of this embodiment is preferably located in contact with a resin film layer, and more preferably in contact with a polyolefin film. Furthermore, as described above, the functional layer removed by the removal method of this embodiment is preferably located on the outermost surface of the plastic film (i.e., the outermost layer). The plastic film may have functional layers on its outermost surface and between multiple resin film layers, but the removal method of this embodiment is more suitable for removing the functional layer located on the outermost surface of the plastic film. Therefore, the removal method of this embodiment is preferably a method for removing the functional layer located on the outermost surface of the plastic film.

[0066] The plastic film may further have layers other than the resin film layer and functional layer described above (such as a paper layer made of natural paper or synthetic paper).

[0067] The thickness of the plastic film is preferably 5 to 200 μm, more preferably 10 to 100 μm, and even more preferably 10 to 50 μm.

[0068] The average size Sp of a plastic film may be, for example, 5 to 100 mm. The average size Sp is the average value of the sizes of individual plastic films. The size of an individual plastic film refers to the length of the longest line segment within the surface of the plastic film. For example, if the plastic film is triangular, the length of the longest side; if the plastic film is a polygon with four or more sides, the length of the longest diagonal; and if the plastic film is circular, the length of the longest diameter. The average size Sp is determined by randomly selecting 30 plastic films from the entire plastic film, measuring their average size, and calculating the average of the 30 measured sizes.

[0069] The average size Sp of the plastic film may be 7 mm or more, 15 mm or more, 30 mm or more, or 40 mm or more, from the viewpoint of increasing the recovery rate of plastic film fragments and from the viewpoint of better removing the functional layer. The average size Sp of the plastic film may be 80 mm or less or 60 mm or less, from the viewpoint of better removing the functional layer. From the above viewpoint, the average size Sp of the plastic film may be 7 to 80 mm, 15 to 60 mm, 30 to 60 mm, or 40 to 60 mm.

[0070] A plastic film having a desired average size Sp may be obtained, for example, by crushing a plastic film with a size larger than the desired average size Sp.

[0071] [liquid] The liquid in step (A) may be, for example, water, or a liquid containing water and a cleaning component (hereinafter referred to as "cleaning component-containing liquid"). From the viewpoint of suppressing equipment deterioration (corrosion, etc.), the pH of the liquid is preferably 12.0 or less, more preferably 8.0 or less, and even more preferably water. If the wetting step described later is not performed, using a cleaning component-containing liquid as the liquid tends to remove the functional layer more effectively.

[0072] Examples of cleaning components include inorganic bases and surfactants. One or more cleaning components can be used individually or in appropriate combinations. The cleaning components may be selected according to the type of functional layer, and materials known as functional layer stripping components can also be used. In one embodiment, the cleaning component-containing liquid preferably contains an inorganic base and a surfactant.

[0073] -Inorganic bases- Examples of inorganic bases include sodium hydroxide and potassium hydroxide. The inorganic base may be included in the cleaning component-containing solution at a concentration of 0.1 to 10% by mass relative to the total volume of the cleaning component-containing solution, and more preferably at a concentration of 0.1% to 5% by mass. The pH of the cleaning component-containing solution using the inorganic base is preferably 10 or higher, and may be 11 or higher or 12 or higher.

[0074] - Surfactants - The surfactant is not particularly limited, and any known surfactant can be used. Examples of surfactants include anionic surfactants, nonionic surfactants, amphoteric surfactants, and cationic surfactants. Surfactants can be used alone or in mixtures of two or more types. The amount of surfactant added is preferably 5% by mass or less, and more preferably 2% by mass or less, based on the total amount of the cleaning component-containing liquid. There is no particular lower limit to the amount of surfactant added. The amount of surfactant added may be 0% by mass, but if a surfactant is used, it is preferably 0.1% by mass or more.

[0075] Examples of nonionic surfactants include polyoxyalkylene alkyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, fatty acid alkylolamides, alkyl alkanolamides, acetylene glycols, oxyethylene adducts of acetylene glycols, and polyethylene glycol polypropylene glycol block copolymers. Among these, polyoxyethylene nonylphenyl ethers, polyoxyethylene octylphenyl ethers, polyoxyethylene dodecylphenyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid alkylolamides, acetylene glycols, oxyethylene adducts of acetylene glycols, and polyethylene glycol polypropylene glycol block copolymers are preferably used.

[0076] In one embodiment, a cleaning agent-containing solution is preferably used, which contains 50% by mass or more of water and 0.01% to 5% by mass of a polyoxyalkylene alkyl ether surfactant containing at least one compound represented by the following general formula (1). R 1 -O-[CH2-CH(X 1 )-O]n 1 -H (1)

[0077] In general formula (1), R 1 n represents a linear or branched alkyl group, alkenyl group, or octylphenol group, 1 represents the average number of moles added, X 1 represents hydrogen or a short-chain alkyl group. Here, a short-chain alkyl group refers to an alkyl group having 1 to 7 carbon atoms.

[0078] R in General Formula (1) 1 is preferably a linear or branched alkyl or alkenyl group having 10 or more carbon atoms. As the number of carbon atoms increases beyond 10, the removability of the functional layer (particularly the removability of an ink layer) tends to improve. 1 Preferable specific examples of R include decyl groups having 10 carbon atoms, lauryl groups having 12 carbon atoms, tridecyl groups having 13 carbon atoms, myristyl groups having 14 carbon atoms, cetyl groups having 16 carbon atoms, oleyl groups having 18 carbon atoms, and stearyl groups.

[0079] The HLB value of the polyoxyalkylene alkyl ether surfactant containing the compound represented by General Formula (1) is not particularly limited. The HLB value may be, for example, 12.5 or more, or may be less than 12.5. The HLB value as used herein is a value indicating the degree of affinity of a surfactant for water and oil (water-insoluble organic compounds), and is defined by the Griffin method (HLB value = 20 × total formula weight of hydrophilic portions / molecular weight).

[0080] Commercially available products may be used as the polyoxyalkylene alkyl ether surfactant. For example, among the Neugen series, DKS NL-Dash series, and DKS-NL series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., the Nonion series manufactured by NOF Corporation, the Emulgen series manufactured by Kao Corporation, and the Leox series, Leocol series, and Lionol series manufactured by Lion Corporation, those containing a compound in which the number of carbon atoms of the group represented by R in General Formula (1) 1 is 10 or more can be used.

[0081] Among polyoxyalkylene alkyl ether surfactants, R in General Formula (1) 1Products containing compounds in which the group indicated by has 10 or more carbon atoms and an HLB value of less than 12.5 include, for example, Daiichi Kogyo Seiyaku Co., Ltd.'s products: Neugen XL-41, Neugen LF-40X, Neugen TDS-30, Neugen TDS-50, Neugen TDS-70, Neugen TDX-50, Neugen SD-30, Neugen SD-60, DKS NL-15, DKS NL-30, DKS NL-40, DKS NL-50, DKS NL-60, DKS NL-70, Neugen ET-83, Neugen ET-102, DKS NL-Dash400, DKS NL-Dash403, DKS NL-Dash404, DKS NL-Dash408, Neugen LP-55, Neugen LP-70, Neugen ET-65, Neugen ET-95, Neugen ET-115, Neugen ET-69, Neugen ET-89, Neugen ET-109, Neugen ET-129, Neugen ET-149, NOF Corporation products: Nonion K-204, Persoft NK-60, Nonion P-208, Nonion P-210, Nonion E-202, Nonion E-202S, Nonion E-205, Nonion E-205S, Nonion S-202, Nonion S-207, Nonion EH-204, Nonion ID-203, Nonion HT-505, Nonion HT- Examples include 507, Nonion HT-510, Nonion HT-512, and from Kao Corporation, Emulgen 102KG, Emulgen 103, Emulgen 104P, Emulgen 105, Emulgen 106, Emulgen 108, Emulgen 210P, Emulgen 404, Emulgen 408, Emulgen 409PV, Emulgen 705, Emulgen 707, and from Lion Corporation, Leox CL-30, Leox CL-40, Leox CL-50, Leox CL-60, Leox NL-30C, Leox TD-50, Leox TD-70, Leox SC-50, Leox SC-70.

[0082] Among polyoxyalkylene alkyl ether surfactants, R in general formula (1) 1Products containing a compound whose alkyl or alkenyl group has 10 or more carbon atoms and has an HLB value of 12.5 or higher include, for example, the following products from Daiichi Kogyo Seiyaku Co., Ltd.: Neugen XL-61, Neugen XL-6190, Neugen XL-70, Neugen XL-80, Neugen XL-100, Neugen XL-140, Neugen XL-160, XL-400D, Neugen XL-1000, and Neugen LF-6. 0X, Neugen LF-80X, Neugen LF-100X, Neugen TDS-80, Neugen TDS-100, Neugen TDS-120, Neugen TDS-200D, Neugen TDS-500F, Neugen TDX-80, Neugen TDX-80D, Neugen TDX-100D, Neugen TDX-120D, Neugen SD-70, Neugen SD-80, Neugen SD-110, Neugen SD-150, DKS NL-80, DKS NL-90, DKS NL-100, DKS NL-110, DKS NL-180, DKS NL-250, DKS NL-450F, DKS NL-600F, Neugen ET-160, Neugen ET-170, Neugen ET-190, DKS Dash410, Neugen LP-80, Neugen LP-100, Neugen LP-180, Neugen ET-135, Neugen ET-165, Neugen ET-159, Neugen ET-189, NOF Corporation products: Nonion K-220, Nonion K-230, Nonion K-2100W, Persoft NH-90C, Persoft NK-100, Persoft NK-100C, Nonion P-210, Nonion P-213, Nonion E-212, Nonion E-215, Nonion E-230, Nonion S-215, Nonion S-220, Nonion B-250, Nonion ID-20 6. Nonion ID-209, Dispanol TOC, Nonion HT-515, Nonion HT-518, Kao Corporation products: Emulgen 109P, Emulgen 110, Emulgen 120, Emulgen 123P, Emulgen 130K, Emulgen 147, Emulgen 150, Emulgen 220, Emulgen 320P, Emulgen 350, Emulgen 420, Emulgen 430, Emulgen 709, Emulgen 1108, Emulgen 1118S-70, Emulgen 1135S-70, Emulgen 1150S-60, Emulgen 4085, Emulgen 2020G-HA,Examples of Emulgen 2025G from Lion Corporation include Leox CL-90, Leox CL-230, Leocol TD-90, Leocol TD-90D, Leocol TDA-90-25, Leocol TDN-90-80, Leocol TD-120, Leocol TD-200, Leocol TDA-400-75, Leocol SC-80, Leocol SC-90, Leocol SC-120, Leocol SC-150, Leocol SC-200, Leocol SC-300, and Leocol SC-400. Examples from Nikko Chemicals include NIKKOL BL-2, NIKKOL BL-4.2, NIKKOL BL-9EX, NIKKOL BL-21, and NIKKOL BL-25.

[0083] Among the compounds represented by general formula (1), R 1 As a compound in which the group is an octylphenol group, octylphenol ethoxylate is preferred. Examples of products containing octylphenol ethoxylate include Dow Chemical's TRITON® series, Rhodia's Igepal CA series, Shell Chemicals' Nonidet P series, and Nikko Chemicals' Nikkol OP series.

[0084] As the amphoteric surfactant, betaine-type amphoteric surfactants are preferred, and more preferably, amphoteric surfactants having an alkylcarboxybetaine skeleton or an alkylamidecarboxybetaine skeleton containing at least one compound represented by the following general formula (2a). R 1 -R 2 -N + (CH3)2CH2COO - (2a)

[0085] In general formula (2a), R 1 is hydrogen or C(=O)R 3 -NH-(R 3 R represents a linear or branched alkyl or alkenyl group. 2 R represents an alkylene group or an alkenylene group. In general formula (2a), R 1 It is preferable that this represents a hydrogen atom.

[0086] The compound represented by general formula (2a) is preferably an amphoteric surfactant having an alkylcarboxybetaine skeleton represented by the following general formula (2a-1). C n H 2n+1 N + (CH3)2CH2COO - (2a-1)

[0087] In general formula (2a-1), n ​​represents the average number of moles added. In general formula (2a-1), n ​​is preferably 8 or greater, more preferably 10 or greater, and even more preferably 11 or greater.

[0088] Specific products that fall under the category of amphoteric surfactants containing compounds represented by general formula (2a) include, for example, Nissan Anon BDF(registered trademark)-R, Nissan Anon BDF(registered trademark)-SF, Nissan Anon BDC-SF, and Nissan Anon BDL-SF from NOF Corporation; Amogen CB-H and Amogen HB-C from Daiichi Kogyo Seiyaku Co., Ltd.; Rikabion B-200 and Rikabion B-300 from Shin Nippon Rika Co., Ltd.; and Obazolin CAB-30 and Obazolin ISAB from Toho Chemical Industry Co., Ltd. Furthermore, specific products that fall under the category of amphoteric surfactants containing compounds represented by general formula (2a-1) include, for example, Amogen S, Amogen SH, and Amogen K from Daiichi Kogyo Seiyaku Co., Ltd.; Anchitol 20BS, Anchitol 24B, and Anchitol 86B from Kao Corporation; Nissan Anon BF, Nissan Anon BL, and Nissan Anon BL-SF from NOF Corporation; Rikabion A-100, Rikabion A-200, and Rikabion A-700 from Shin Nippon Rika Co., Ltd.; and Obazolin LB and Obazolin LB-SF from Toho Chemical Co., Ltd.

[0089] As a betaine-type amphoteric surfactant, an amphoteric surfactant having an imidazolinium betaine skeleton can also be used. Specific products that fall under the category of amphoteric surfactants having an imidazolinium betaine skeleton include, for example, Nissan Anon GLM-R and Nissan Anon GLM-R-LV from NOF Corporation, and Anchitol 20Y-B from Kao Corporation.

[0090] The amphoteric surfactant may also be a surfactant represented by the following general formula (2b). R 4 -(NHC2H4) nb -N(R 5 )2(2b)

[0091] In general formula (2b), R 4 represents a linear or branched alkyl or alkenyl group, nb represents an integer from 0 to 5, and R 5 R represents hydrogen, -CH2COONa, or -CH2COOH, but there are two R values. 5 They may be the same or different, and at least one R 5 represents -CH2COONa. In general formula (2b), R 4 R preferably represents a linear alkyl group. 4 The number of carbon atoms is preferably 8 or more, more preferably 10 or more, and even more preferably 12 or more.

[0092] Specific products that fall under the category of amphoteric surfactants containing compounds represented by general formula (2b) include, for example, Nissan Anon LG-R and Nissan Anon LA, manufactured by NOF Corporation.

[0093] The amphoteric surfactant may also be an amine oxide type surfactant represented by the following general formula (2c). R 6 -N + (CH3)2O - (2c)

[0094] In general formula (2c), R 6R represents a linear or branched alkyl or alkenyl group. In general formula (2c), R 6 It is preferable that R represents a linear alkyl group. 6 The number of carbon atoms in the group represented is preferably 8 or more, more preferably 10 or more, and even more preferably 12 or more.

[0095] Specific products that fall under the category of amphoteric surfactants containing compounds represented by general formula (2c) include, for example, Amogen AOL from Daiichi Kogyo Seiyaku Co., Ltd. and Amhitol 20N from Kao Corporation.

[0096] As cationic surfactants, cationic surfactants with a quaternary ammonium skeleton are preferred, and more preferably, cationic surfactants with a quaternary ammonium skeleton containing at least one compound represented by the following general formula (3a). R 1 -N + (R 2 R 3 )-R 4 (3a)

[0097] In general formula (3a), R 1 R represents a linear or branched alkyl group, or a linear or branched alkenyl group, and the -CH2- in the alkyl group or alkenyl group may be substituted with -C(=O)-, -NH-, or -C(=O)-NH-. 2 and R 3 R represents a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkenyl group, and the -CH2- in the alkyl group or alkenyl group may be substituted with -O-. 4 represents a hydrogen atom, a linear or branched alkyl group, a linear or branched alkenyl group, or a phenyl group, and the terminal -CH3 in the alkyl group or alkenyl group may be substituted with a carboxyl group or a phenyl group.

[0098] In general formula (3a), R 1To further improve the removeability of the functional layer (especially the ink layer), it is preferable that the group is a long-chain alkyl or alkenyl group. Specifically, R 1 The alkyl or alkenyl group is preferably an alkyl group having 8 to 30 carbon atoms, more preferably an alkyl group having 10 to 25 carbon atoms, and even more preferably an alkyl or alkenyl group having 12 to 22 carbon atoms. The alkyl or alkenyl group may be linear or branched, but it is preferably linear. 1 It is more preferable that the alkyl group is a straight chain.

[0099] In general formula (3a), R 1 At least one -CH2- in the alkyl or alkenyl group shown may be substituted with -C(=O)-, -NH-, or -C(=O)-NH-. In particular, it is preferable that at least one -CH2- in the alkyl or alkenyl group is substituted with -C(=O)-NH- or -NH-C(=O), and it is preferable that one -CH2- in the alkyl group is substituted with -C(=O)-NH- or -NH-C(=O), R 1 It is more preferable that it contains an amidopropyl skeleton.

[0100] In general formula (3a), R 2 and R 3 The group is preferably a linear or branched alkyl group or a linear or branched alkenyl group, more preferably a linear or branched alkyl group, even more preferably a linear alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group.

[0101] In general formula (3a), R 4 The group is preferably a linear or branched alkyl group, a linear or branched alkenyl group, or a phenyl group, and more preferably a linear or branched alkyl group. Furthermore, the terminal -CH3 in the alkyl group or alkenyl group is preferably substituted with a carboxyl group or a phenyl group.

[0102] In general formula (3a), R4 The number of carbon atoms is preferably 1 to 8, more preferably 1 to 5, even more preferably 1 to 3, and particularly preferably 1 or 2.

[0103] In general formula (3a), R 4 If R represents a methyl group, 2 and R 3 It is preferable that R also represents a methyl group, and that the general formula (3a) shows an alkyltrimethylammonium skeleton. 4 When R represents an ethyl group, it is preferable that the terminal -CH3 in the ethyl group is substituted with a carboxyl group or a phenyl group. In other words, R 4 It is preferable that -CH2-(C(=O)OH or a benzyl group be represented.

[0104] The compound represented by general formula (3a) is preferably a cationic surfactant containing a quaternary ammonium skeleton compound represented by the following general formula (3a-1). C n H 2n+1 N + (CH3)2R 4 (3a-1)

[0105] In the general formula (3a-1), n ​​represents the average number of moles added, and R 4 R in general formula (3a) 4 It has the same meaning as R. 4 The preferred group is the same as in general formula (3a).

[0106] In general formula (3a-1), the average number of moles added represented by n is preferably 8 or greater. The higher the average number of moles added represented by n (exceeding 8), the more likely it is that the removeability of the functional layer (especially the ink layer) will improve. n H 2n+1Specific examples of groups represented by include the octyl group (8 carbon atoms), the nonyl group (9 carbon atoms), the decyl group (10 carbon atoms), the undecyl group (11 carbon atoms), the lauryl group (12 carbon atoms), the tridecyl group (13 carbon atoms), the myristyl group (14 carbon atoms), the pentadecyl base group (15 carbon atoms), the cetyl group (16 carbon atoms), the oleyl group (18 carbon atoms), and the stearyl group.

[0107] From the viewpoint of improving the removeability of the functional layer (especially the ink layer), the quaternary ammonium skeleton compound is preferably a quaternary ammonium skeleton salt type that forms a salt with a halogen, and Cl - , Br - or I - It is more preferable that the quaternary ammonium skeleton salt form a salt with a halogen. Among these, alkyltrimethylammonium halide, dialkyldimethylammonium halide, and alkylbenzalkonium halide compounds are preferred, and alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, and alkylbenzalkonium chloride compounds are more preferred. The above quaternary ammonium skeleton salts that form a salt with a halogen are thought to contribute to improving the removeability of the functional layer (especially the ink layer) because the nucleophilic action of the halogen promotes hydrolysis of the functional layer (especially the ink layer).

[0108] Specific products that fall under the category of cationic surfactants containing compounds represented by general formula (3a) (including compounds represented by general formula (3a-1)) include, for example, Nissan Cation MA, Nissan Cation SA, Nissan Cation BB, Nissan Cation FB, Nissan Cation PB-300, Nissan Cation ABT2-500, Nissan Cation AB, Nissan Cation AB-600, Nissan Cation VB-M Flake, Nissan Cation VB-F, Nissan Cation 2-DB-500E, Nissan Cation 2-DB-800E, Nissan Cation 2ABT, Nissan Cation 2-OLR, Nissan Cation F2-50R, and Nissan Cation M2-100R from NOF Corporation; Catiogen TML, Catiogen TMP, Catiogen TMS, Catiogen DDM-PG, Catiogen BC-50, and Catiogen TBB from Daiichi Kogyo Co., Ltd.; and Cotamin 24P and Cotamin from Kao Corporation. Examples include Min 86P Concentrate, Cortamin 60W, Cortamin 86W, Sanizol C, and Sanizol B-50. Lion Corporation products include Lipoguard C-50, Lipoguard T-28, Lipoguard T-30, Lipoguard T-50, Lipoguard T-800, Lipoguard 16-29, Lipoguard 16-50E, Lipoguard 18-63, Lipoguard 22-80, Lipoguard CB-50, Lipoguard 210-80E, Lipoguard 2C-75, Lipoguard 2HP-75, and Lipo Examples include LipoGuard 2HP Flake, LipoGuard 2HT-75, LipoGuard 2HT Flake, LipoGuard 20-75L, LipoGuard 41-50, TMAC-50, TPAH-40, TBAB-50A, TBAB-100A, TBAH-40, LipoGuard PH-100, BTMAC-50, BTMAC-100A, BTEAC-50, BTEAC-100A, BTBAC-50A, etc., and from Toho Chemical Industry Co., Ltd., examples include Kachinaru SPC-20V-S.

[0109] Cationic surfactants preferably contain at least one compound having a primary or secondary alkanolamine skeleton, and more preferably contain at least one compound having a monoalkanolamine skeleton (monoalkanolamine compounds).

[0110] As primary monoalkanolamines, lower alkanols having 1 to 4 carbon atoms are preferred. Specifically, examples include monoethanolamine and 2-aminoisobutanol. As secondary monoalkanolamines, examples include N-methylethanolamine, 2-ethylaminoethanol, and isopropanolamine. These monoalkanolamine compounds can be used individually or in appropriate combinations of two or more, and can also be used mixed with water. These monoalkanolamine compounds are preferably in the form of monoalkanolamine salts that form salts with halogens, and Cl - It is preferable to form a salt with this.

[0111] In one embodiment, the cleaning component-containing liquid may contain, as a cleaning component, organic solvents such as water-soluble or water-insoluble alcohols, water-soluble or water-insoluble glycol ether-based organic solvents, or water-soluble monoalkanolamine-based organic solvents. The organic solvent may contain compounds corresponding to the above-mentioned surfactants, and such compounds are included in the cleaning component-containing liquid as surfactants and organic solvents.

[0112] - Non-water-soluble alcohols - Examples of water-insoluble alcohols include water-insoluble primary alcohols. It is preferable that the water-insoluble primary alcohol be present in an amount of 20% by mass or less relative to water.

[0113] Examples of water-insoluble primary alcohols include butan-1-ol, pentan-1-ol, hexane-1-ol, heptan-1-ol, octan-1-ol, nonan-1-ol, decane-1-ol, undecane-1-ol, dodecane-1-ol, tridecane-1-ol, tetradecane-1-ol, pentadecane-1-ol, hexadecane-1-ol, heptadecane-1-ol, and octadecane-1-ol. Examples include nonadecan-1-ol, eicosan-1-ol, heneicosan-1-ol, docosan-1-ol, tricosan-1-ol, tetracosan-1-ol, pentacosan-1-ol, hexacosan-1-ol, heptacosan-1-ol, octacosan-1-ol, nonacosan-1-ol, triacontan-1-ol, policosanol, 2-methylpropane-1-ol, and benzyl alcohol. Among these, butan-1-ol and benzyl alcohol are preferred.

[0114] -Water-soluble alcohols- Examples of water-soluble alcohols include alcohols specified in the Fire Service Act. Specific examples of water-soluble alcohols include methanol, ethanol, 1-propyl alcohol, 2-propyl alcohol, etc., and mixtures of these can also be used as industrial alcohols. Water-soluble alcohols are preferably water-soluble primary alcohols. It is preferable that the water-soluble alcohols are present in an amount of 20% by mass or more relative to water.

[0115] -Non-water-soluble glycol ether-based organic solvent- Examples of water-insoluble glycol ether-based organic solvents include water-insoluble aromatic glycol ether solvents and water-insoluble ester-based glycol ether solvents. Examples of water-insoluble aromatic glycol ether solvents include ethylene glycol monophenyl ether (phenoxyethanol), ethylene glycol monobenzyl ether, ethylene glycol dibenzyl ether, diethylene glycol monophenyl ether, diethylene glycol diphenyl ether, and propylene glycol monophenyl ether. Examples of water-insoluble ester-based glycol ether solvents include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-butyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate. Among these, ethylene glycol monophenyl ether (phenoxyethanol) is preferred. It is preferable that the water-insoluble glycol ether-based organic solvent be contained in an amount of 20% by mass or less relative to water.

[0116] -Water-soluble glycol ether-based organic solvent- Examples of water-soluble glycol ether-based organic solvents include water-soluble alkylene glycol alkyl ether solvents. It is preferable that the water-soluble glycol ether-based organic solvent be present in an amount of 20% by mass or more relative to water.

[0117] As the water-soluble alkylene glycol alkyl ether solvent, a compound represented by the following general formula (4) (water-soluble alkylene glycol alkyl ether) is preferably used. R 1 -O-[CH2-CH(X)-O] n1 -R 2 (4)

[0118] In general formula (4), R 1 R represents an alkyl group having 1 or more carbon atoms. 2represents an alkyl group or hydrogen atom with one or more carbon atoms, n1 represents an integer from 1 to 3, and X represents a hydrogen atom or a methyl group.

[0119] Examples of compounds represented by general formula (4) include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol methyl ethyl ether, ethylene glycol methyl propyl ether, ethylene glycol ethyl propyl ether, ethylene glycol-tert-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl propyl ether, diethylene glycol ethyl propyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol dimethyl ether, and propylene glycol diethyl ether. These compounds can be used individually or in combination of two or more as appropriate, and can also be used mixed with water.

[0120] The content of the compound represented by general formula (4) in the cleaning component-containing solution may be 20% by mass or more, preferably 30% by mass or more, and more preferably 40% by mass or more when water is the medium.

[0121] Among the compounds represented by general formula (4), the compound represented by the following general formula (5) (water-soluble alkylene glycol monoalkyl ether) is even more preferred. R 2-O-[CH2-CH(X)-O] n2 -H (5)

[0122] In general formula (5), R 2 represents an alkyl group having one or more carbon atoms, n2 represents an integer from 1 to 3, and X represents a hydrogen or methyl group.

[0123] Examples of compounds represented by general formula (5) include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol tert-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether.

[0124] Furthermore, when the water content in the cleaning agent-containing solution significantly exceeds 50% by mass, the effect of improving peelability is easily obtained, and as a water-soluble alkylene glycol monoalkyl ether, R in general formula (5) is used. 2It is preferable to use a compound in which is an alkyl group having 3 or more carbon atoms, n2 is 1 to 3, and X is hydrogen or a methyl group. Examples of such compounds include ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol tert-butyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether. These compounds can be used individually or in appropriate combinations of two or more, and can also be used mixed with water. Among these, diethylene glycol monobutyl ether, ethylene glycol mono-tert-butyl ether, and propylene glycol monopropyl ether are particularly preferred in terms of environmental properties, flammability, and defoaming properties.

[0125] -Water-soluble monoalkanolamine-based organic solvents- As water-soluble monoalkanolamine organic solvents, primary to secondary monoalkanolamine compounds are preferably used. Examples of primary monoalkanolamine compounds include monoethanolamine, 2-aminoisobutanol, and isopropanolamine. Examples of secondary monoalkanolamine compounds include N-methylethanolamine, 2-ethylaminoethanol, and dimethylaminoethanol. The boiling points of these monoalkanolamine compounds are preferably 150 to 200°C. These monoalkanolamine compounds can be used individually or in appropriate combinations of two or more, and can also be used mixed with water.

[0126] It is preferable that the water-soluble monoalkanolamine-based organic solvent be contained in an amount of 20% by mass or more relative to the water. Primary to secondary monoalkanolamines with a boiling point of 150 to 200°C may be contained in an amount of 10% to 50% by mass relative to the total amount of the cleaning component-containing liquid.

[0127] As a cleaning agent, a water-soluble solvent with a flash point of 21°C or higher can also be used. The water-soluble solvent with a flash point of 21°C or higher is preferably a water-soluble solvent among organic solvents that fall under Class II and Class III petroleum as defined in the Fire Service Act, for example, diethylene glycol butyl ether, propylene glycol propyl ether, and 3-methoxy-3-methyl-1-butanol are preferred.

[0128] The cleaning component-containing liquid preferably contains a water-soluble solvent among the above organic solvents. From the viewpoint of improving the removal efficiency of the functional layer, the water-soluble solvent content is preferably 30% by mass or more, based on the total amount of the cleaning component-containing liquid, and may be 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0129] In one embodiment, the cleaning component-containing liquid preferably contains an inorganic base and an organic solvent, and more preferably contains an inorganic base and a water-soluble solvent. When the cleaning component-containing liquid contains a water-soluble solvent in addition to the inorganic base, the hydroxide ions generated from the inorganic base are less likely to be hydrated, thus increasing the nucleophilicity of the hydroxide ions, and allowing for better separation (peeling) of the functional layer (especially the ink layer) from the plastic film in a hydrophobic environment.

[0130] Since sodium hydroxide is poorly soluble in organic solvents, it is preferable to use a cationic surfactant in combination when using sodium hydroxide and an organic solvent. A cleaning component-containing solution containing sodium hydroxide, an organic solvent, and a cationic surfactant may, for example, be a cleaning component-containing solution containing sodium hydroxide, a cationic surfactant, a water-insoluble aromatic glycol ether solvent, and a water-soluble alcohol or a water-soluble alkanolamine solvent.

[0131] Since potassium hydroxide is readily soluble in organic solvents, it is not necessary to use cationic surfactants in combination when using potassium hydroxide. A cleaning solution containing potassium hydroxide and an organic solvent may be, for example, a cleaning solution containing potassium hydroxide and a water-soluble alcohol or aromatic glycol ether solvent.

[0132] In one embodiment, the cleaning component-containing liquid may also contain an antifoaming agent. As the antifoaming agent, a water-soluble organic solvent, a nonionic surfactant with an HLB value in the range of 1 to 3, etc., may be used, or a silicone-based compound may be used. Silicone-based compounds are preferred in terms of their high antifoaming ability, and among them, emulsion-type or self-emulsifying silicone-based compounds are more preferred. These antifoaming agents may be used individually or in combination of two or more.

[0133] Specific examples of self-emulsifying defoaming agents include Shin-Etsu Chemical's X-50-1176, KS-530, and KS-537. Specific examples of emulsion-type defoaming agents include Shin-Etsu Chemical's KM-7750D, KM-7752, and KM-98, and Nagase Chemspec's FS Antifoam 025, FS Antifoam 80, FS Antifoam 92, FS Antifoam 93, DKQ1-1183, and DKQ1-1247, among others. However, the list is not limited to these.

[0134] The amount of defoaming agent may be, for example, 0.01 to 5% by mass, 0.02 to 4% by mass, or 0.03 to 3% by mass, based on the total amount of the cleaning component-containing liquid.

[0135] [Wet crushing process] Wet crushing can be carried out using known apparatus and methods. Specific examples of apparatus include devices equipped with a motor with stirring blades that can agitate the washing liquid in a container, devices equipped with ultrasonic wave generators, devices that can shake the container, and wet crushers that can crush and pump simultaneously. More specifically, examples include the KD series from Husqvarna Zenoah, the San Cutter series from Nikuni, the Disintegrator series from Furukawa Industrial Systems, the Incrusher series and Refiners from Aikawa Iron Works, the Scatter from Sanwa Hydrotech, the Trigonal from Nippon Coke Co., Ltd., the alkaline washing and deinking equipment from Nippon Seam Co., Ltd., and the Scissors Cutter series of washing and crushing machines.

[0136] As a wet crushing apparatus, a wet crusher is preferred, and a wet crusher that can simultaneously crush, disperse, mix, and pump solids in a liquid is more preferred. Specifically, a crusher having a mechanism for crushing solids in a liquid by shear force and / or frictional force is preferred, and a crusher having a mechanism that can crush and pump plastic film in addition to the above mechanism is more preferred. Examples of such wet crushers include wet crushing pumps, colloid mills, grinders, and beaters.

[0137] A wet crushing pump preferably has a mechanism that crushes solid material by fixed blades and rotating blades while pumping the solid material in a liquid. A more preferred mechanism is one that performs three stages of crushing using a combination of four parts: a cutting blade, a crushing impeller, a shroud ring, and a grid.

[0138] When using a wet crushing pump with the above-described more preferable mechanism, the plastic film is roughly cut, for example, by the cutting edge of a fixed blade and the edge of the inlet of the rotating crushing impeller, then agitated and pumped by an axial-flow type crushing impeller, and some of the plastic film is cut by contact with the blade portion of the shroud ring of the fixed blade. The film that passes through the crushing impeller becomes film fragments, which are further crushed and agitated between the film and the grid, and then pressurized by a pressure impeller and pumped through the grid to the next process. The pumping speed at this time is not particularly limited, but for example, 0.03 m3 It may be greater than / min. There is no particular upper limit to the pumping speed, and it is not limited to the standard operating speed of the equipment (e.g., 1.4m / min). 3 It may also be ( / min). The shape of the grid used in the wet pump of the above mechanism is not particularly limited. The diameter of the grid may be, for example, 5 to 100 mm.

[0139] Specific examples of wet crushing pumps include the KD series from Husqvarna Zenoah, the San Cutter series from Nikuni, the Disintegrator series from Furukawa Industrial Systems, the Incrusher series and refiners from Aikawa Iron Works, the Scatter from Sanwa Hydrotech, and the Trigonal from Nippon Coke Co., Ltd.

[0140] A colloidal mill is a machine used to reduce particle size in dispersions where particles are suspended in a liquid. A colloidal mill consists of a rotor and a stator, with the rotor rotating at high speed relative to the stationary stator. The high level of shear generated by the high-speed rotation reduces the particle size in the liquid.

[0141] The crushing section of the colloid mill consists of a combination of a toothed, frustoconical rotor and a stator, both of which are tapered, narrowing as they approach the discharge port. The laminated film is crushed by repeatedly applying strong shear, compression, and impact within a ring-shaped gap that narrows as it approaches the discharge port.

[0142] While specific colloid mills are not limited to any disperser generally referred to as a colloid mill, examples include IKA's MK series colloid mill, Iwaki's WCM series, Mountec's PUC colloid mill series, and Eurotech's Cavitron.

[0143] A beating machine is a machine that has a beating mechanism. Here, "beating" refers to the operation of mechanically beating and loosening an object to be processed in the presence of a liquid. Examples of specific beating machines include the double disc refiner, single disc refiner, and double conifer manufactured by Aikawa Iron Works Co., Ltd.

[0144] Step (A) includes, for example, (A-1) supplying a plastic film and a liquid to a processing space, (A-2) performing a wet crushing process in the processing space, and (A-3) discharging the crushed material and liquid from the processing space. In step (A-1), the plastic film and the liquid may be supplied to the processing space almost simultaneously. Specifically, for example, when supplying the plastic film to the processing space, the liquid may be encombusted with the plastic film.

[0145] The ratio (V2 / V1) of the volume of liquid V2 to the volume of plastic film V1 supplied to the processing space may be 0.43 to 99 from the viewpoint of better removing the functional layer. If the ratio (V2 / V1) is 0.43 or higher, re-adhesion of the functional layer separated (peeled) from the plastic film is unlikely, and if the ratio (V2 / V1) is 99 or lower, separation (peeling) of the functional layer due to friction between plastic films is likely to progress. From the viewpoint of even better removing the functional layer, the ratio (V2 / V1) may be 0.7 to 90, 1.5 to 70, or 10 to 50. When the above processes (A-1) to (A-3) are carried out in parallel and continuously, the ratio (V2 / V1) may be calculated from the volume of plastic film supplied to the processing space per unit time and the volume of liquid supplied to the processing space per unit time. The volume of plastic film can be calculated by the Archimedes method.

[0146] The process in (A-2) preferably includes passing the plastic film through a clearance of 30 mm or less. This process is carried out, for example, in the processing space described above. In this process, the plastic film is crushed by passing through the clearance while encompassing a liquid. The clearance is more preferably 20 mm or less, and even more preferably 10 mm or less. By passing the plastic film through a clearance of 10 mm or less, a high shear force can be applied to the plastic film. Therefore, by setting the clearance to 10 mm or less, for example, the effect of scraping off the functional layer from a plastic film in which the functional layer is exposed (such as a surface-printed plastic film) or the effect of applying shear stress to a plastic film in which the functional layer is provided between multiple films (such as a back-printed film) can be obtained, and the functional layer can be removed more effectively.

[0147] When a wet shredder has a mechanism that shreds using fixed and rotating blades, the clearance can be easily controlled depending on the operating conditions. A narrower clearance allows for a higher shear force to be applied to the plastic film. On the other hand, a narrower clearance makes clogging of the plastic film more likely, and the temperature of the liquid (water, cleaning solution, etc.) rises more rapidly. Therefore, a clearance of 0.1 mm or more is preferable.

[0148] Methods for providing a predetermined clearance for the plastic film to pass through include, for example, controlling the size gap between the inner wall of the tank in the processing tank for agitating the plastic film and the agitator blade to be less than or equal to a predetermined size; installing baffles at a distance of less than or equal to a predetermined size from the tank wall; designing a screen through which the plastic film passes with holes of less than or equal to a predetermined size; passing the plastic film between two rolls with a gap of less than or equal to a predetermined size; sandwiching the plastic film between ball mills or the like to cause the media to collide; and controlling the gap between the rotating blades and the fixed blades to be less than or equal to a predetermined size, as in a homogenizer, by providing fixed blades on the outside of the rotating blades.

[0149] The step (A-2) is a plastic film at 2000s -1 or higher shear rate, and it is preferable to include a shearing step. This step may be a step of passing the plastic film through a clearance of 30 mm or less. That is, the step (A-2) is a plastic film with a shear rate of 2000s -1 may include a step of passing the plastic film through a clearance of 30 mm or less so as to achieve the above. The higher the shear rate, the higher the effect of scraping off the functional layer from the plastic film and the effect of applying shear stress to the plastic film. The upper limit of the shear rate is not particularly limited, and for example, it may be 500000s -1 .

[0150] Note that the shear rate (D) as used herein is defined, for example, by the following formula. D=v / Δy v: flow velocity (unit: m / s), calculated as v=π×R×(n / 60) π: pi R: diameter of the rotary blade (unit: m) n: rotation speed of the rotary blade (unit: rpm) Δy: clearance (unit: m), which refers herein to the gap between the rotary blade and the fixed blade.

[0151] The larger the diameter of the fixed blade of a wet crusher, the higher the flow velocity, so the larger the size of the fixed blade of a wet crusher, the more preferable it is. On the other hand, the narrower the clearance, the higher the shear rate, so the narrower the clearance, the more preferable it is.

[0152] As for the blade design of the fixed blade and the rotary blade, a shape in which at least a part of the blades are arranged in the radial direction is preferable. The blades arranged in the radial direction are preferably inclined by 2 to 60° from the radial direction, and more preferably inclined by 5 to 45°.

[0153] When a plurality of blades are arranged in parallel on the rotary blade, the blade width of the rotary blade is preferably 0.5 to 5.0 mm, the groove width between adjacent blades is preferably 0.5 to 5.0 mm, and the blade height is preferably 1.0 to 5.0 mm.

[0154] The stirring fluid number (Fr) is preferably 10 or higher. A faster stirring fluid number enhances the effect of scraping the ink layer off the plastic film piece and applying shear stress to the plastic film piece. There is no particular upper limit to the stirring fluid number (Fr), but it may be 16, for example.

[0155] The Froude number (Fr) used here is defined by the following formula. Fr={(n / 60) 2} × R / g n: Rotational speed of the blade (unit: rpm) R: Diameter of the rotating blade (unit: m) g: Gravitational acceleration = 9.8 (unit: m / s²) 2 )

[0156] The average size Sa of the plastic film fragments in the crushed material obtained by wet crushing may be, for example, 0.3 to 65 mm, but is preferably 2 to 10 mm from the viewpoint of increasing the recovery rate of plastic film fragments and from the viewpoint of better removing the functional layer. When the average size Sa of the plastic film fragments is 2 mm or more, the proportion of plastic film fragments introduced into the discharge hole decreases in step (B) described later, and the recovery rate of plastic film fragments tends to improve. On the other hand, when the average size Sa of the plastic film fragments is 10 mm or less, even if the plastic film fragments are wet with a liquid such as water which has high surface tension, the adhesion force between the film fragments does not increase, and it tends to be easier to remove the functional layer present on the surfaces in contact with the film fragments. From the viewpoint of further increasing the recovery rate of plastic film fragments, the average size Sa of the plastic film fragments in the crushed material may be 2.2 mm or more, 2.5 mm or more, or 3.5 mm or more, and from the viewpoint of even better removing the functional layer, it may be 5 mm or less, 4 mm or less, or 3 mm or less. From these perspectives, the average size Sa of plastic film fragments in the crushed material may be 2.2-10 mm, 2.2-5 mm, 2.2-4 mm, 2.2-3 mm, 2.5-10 mm, 2.5-5 mm, 3.5-10 mm, or 3.5-5 mm. The average size Sa of plastic film fragments in the crushed material can be changed by adjusting the conditions of the wet crushing process (e.g., the clearance and shear rate described above). The method for measuring the average size Sa of plastic film fragments is the same as the method for measuring the average size of the plastic film described above.

[0157] The ratio (Sa / Sp) of the average size Sa of plastic film fragments in the crushed material to the average size Sp of the plastic film may be 0.8 or less, 0.7 or less, 0.3 or less, or 0.2 or less from the viewpoint of better removal of the functional layer. The ratio (Sa / Sp) may be 0.01 or more, 0.04 or more, 0.07 or more, or 0.1 or more from the viewpoint of increasing the recovery rate of plastic film fragments. From the above viewpoint, the ratio (Sa / Sp) may be 0.01 to 0.8, 0.04 to 0.7, 0.04 to 0.3, 0.04 to 0.2, 0.07 to 0.2, or 0.1 to 0.2.

[0158] The average particle size of the functional layer fragments in the crushed material obtained by wet crushing may be 0.001 to 0.5 mm. If the average particle size of the functional layer fragments is 0.001 mm or more, the functional layer fragments adhering to the plastic film fragments will be easier to remove in step (B). Also, if the average particle size of the functional layer fragments is 0.5 mm or less, the functional layer fragments will be easier to discharge through the discharge holes in step (B). The average particle size of the functional layer fragments refers to the particle size of the functional layer fragments (D50) at 50% of the cumulative value (by volume) measured by a laser diffraction particle size analyzer or a dynamic light scattering particle size analyzer.

[0159] (Process:(B)) In step (B), the crushed plastic film material that has gone through step (A) is washed using the washing device described above. Step (B) comprises supplying the crushed material into the rotating tank from one end (supply port), conveying the crushed material from one end to the other by rotating the rotating tank, and washing the crushed material by spraying a washing solution onto the crushed material while it is being conveyed. As a result, the plastic film pieces in the crushed material are washed, and the washed plastic film pieces (plastic film pieces that do not have a functional layer or have a sufficiently small amount of functional layer attached) are discharged from the discharge port of the rotating tank. The supply of the crushed material, the rotation of the rotating tank, and the washing of the crushed material may be performed simultaneously.

[0160] The amount of crushed material supplied may be adjusted as appropriate, taking into account the size of the rotating tank. For example, the amount of crushed material supplied to the rotating tank per minute, Vf, divided by the inner diameter d of the rotating tank (Vf / d), may be 0.02 to 0.8 kg / (min·cm). From the viewpoint of more efficiently removing the functional layer, Vf / d may be 0.04 kg / (min·cm) or more, 0.1 kg / (min·cm) or more, or 0.2 kg / (min·cm) or more, and from the viewpoint of better removing the functional layer, it may be 0.5 kg / (min·cm) or less. From these viewpoints, Vf / d may be 0.04 to 0.5 kg / (min·cm), 0.1 to 0.5 kg / (min·cm), or 0.2 to 0.5 kg / (min·cm).

[0161] The rotational speed of the rotary tank may be adjusted as appropriate, taking into consideration the conveying speed of the crushed material. The rotational speed of the rotary tank may be, for example, 2 to 80 rpm. From the viewpoint of more efficiently removing the functional layer, the rotational speed of the rotary tank may be 3 rpm or more, 5 rpm or more, or 20 rpm or more, and from the viewpoint of more effectively removing the functional layer, it may be 50 rpm or less, 30 rpm or less, or 20 rpm or less. From these viewpoints, the rotational speed of the rotary tank may be 3 to 50 rpm, 3 to 30 rpm, 3 to 20 rpm, 5 to 50 rpm, 5 to 30 rpm, 5 to 20 rpm, or 20 to 80 rpm.

[0162] The cleaning solution may be, for example, water, or a liquid containing water and a cleaning component. As the cleaning component, the cleaning components exemplified in step (A) above can be used, and the preferred examples of cleaning components are the same as the examples of preferred cleaning components shown in step (A) above.

[0163] The washing time for the crushed material may be, for example, 2 seconds to 2 minutes, or 2 seconds to 30 seconds from the viewpoint of further improving efficiency. Here, the washing time for the crushed material refers to the time taken from when the crushed material is supplied to the rotating tank until it is washed and discharged as plastic film pieces. The washing time for the crushed material can be adjusted by the rotation speed of the rotating tank, the size of the rotating tank, the design of the conveying blades, etc.

[0164] In step (B), the cleaning solution may be discharged such that the impact force index I, calculated by the following formula (I), is between 10 and 1200. Impact force index I = Q·√P·(1 / r) 2 ...(I) [In equation (I), Q represents the discharge flow rate of the cleaning fluid (unit: L / min), P represents the discharge pressure of the cleaning fluid (unit: MPa), and r represents the distance from the discharge port of the discharge section to the inner surface of the rotating tank (unit: m).]

[0165] The above impact force index is a numerical value that represents the degree of impact force exerted by the discharged washing liquid on the crushed material, and is derived as follows.

[0166] First, the impact force F0 of the cleaning fluid near the discharge port is expressed as the product of the mass flow rate m of the cleaning fluid and the discharge velocity v0 (the velocity of the cleaning fluid immediately after discharge) (m·v0), and the mass flow rate m of the cleaning fluid is expressed as the product of the density ρ of the cleaning fluid and the volumetric flow rate Q (ρ·Q). Furthermore, using Bernoulli's theorem, the relationship between the discharge pressure P of the cleaning fluid and the discharge velocity v0 is expressed by the following equation (II). And since the density ρ of the cleaning fluid is approximately constant, the impact force F0 can be expressed as the following equation (III) using the constant C and the variables Q and P. v0 = √(2P / ρ) ···(II) [In equation (II), v0 represents the discharge velocity of the cleaning solution, P represents the discharge pressure of the cleaning solution, and ρ represents the density of the cleaning solution.] F0 = C·Q·√P ···(III) [In equation (III), F0 represents the impact force of the cleaning fluid near the discharge port, C represents a constant, Q represents the volumetric flow rate of the cleaning fluid, and P represents the discharge pressure of the cleaning fluid.]

[0167] Further, when the distance from the discharge port to the crushed material increases, the velocity v(t) of the cleaning liquid (liquid droplets), which is a variable of time t immediately after discharge (hereinafter simply referred to as "v"), decreases under the influence of air resistance and the like, and the impact force of the cleaning liquid also decreases accordingly. The air resistance F applied to the discharged cleaning liquid A is proportional to the square of the velocity v of the cleaning liquid, so the air resistance F A can be expressed as -k·v 2 using the air resistance constant k. In this case, the equation of motion representing the relationship between the force acting on the cleaning liquid and the acceleration of the cleaning liquid is represented by the following differential equation (IV). m·(dv / dt)=-k·v 2 ···(IV) [In formula (IV), v and k have the same definitions as above, m represents the mass flow rate of the cleaning liquid, and t represents the time elapsed since immediately after discharge.] By solving this differential equation, the velocity v of the cleaning liquid can be expressed by the following formula (V). v=v0 / {1+(k·v0·t / m)} ···(V) [In formula (V), v, v0, k, t and m have the same definitions as above.] In this case, it is convenient to express that the kinetic energy of the cleaning liquid affected by air resistance is inversely proportional to the square of the distance from the discharge port.

[0168] In this case, the relationship between the impact force F0 of the cleaning liquid near the discharge port and the impact force F of the cleaning liquid near the crushed material (the impact force exerted by the discharged cleaning liquid on the crushed material) R can be approximated by the following formula (VI). F R =F0·α / R 2 ···(VI) [In formula (VI), F R represents the impact force of the cleaning liquid near the crushed material, F0 represents the impact force of the cleaning liquid near the discharge port, α represents a constant, and R represents the distance from the discharge port to the crushed material.]

[0169] Since the height of the crushed material is sufficiently small compared to the distance from the discharge port to the crushed material and can be ignored, the impact force F of the washing liquid near the crushed material can be calculated from equations (III) and (VI) above. R This can be expressed by the following equation (VII). F R =C·Q·√P·α / r 2 ...(VII) [F in equation (VII) R C, Q, P, and α are equivalent to those described above, and r represents the distance from the discharge port of the discharge section to the inner surface of the rotating tank.

[0170] From equation (VII) above, it can be seen that the impact force exerted by the discharged washing liquid on the crushed material is related to three variables: Q, P, and r. That is, Q, P, and r are related to the impact force on the order of 1st, 0.5th, and -2nd power, respectively. From these relationships, equation (I) above can be derived.

[0171] When the impact force index I is 10 or higher, the functional layer tends to be removed more effectively, and when the impact force index I is 1200 or lower, the recovery rate of plastic film fragments tends to improve. From the viewpoint of further better removal of the functional layer, the impact force index I may be 13 or higher, 16 or higher, 20 or higher, 25 or higher, 30 or higher, 50 or higher, or 100 or higher, and from the viewpoint of further increasing the recovery rate of plastic film fragments, it may be 1100 or lower, 800 or lower, or 300 or lower. From these viewpoints, the impact force index I may be 13-1100, 16-1100, 20-1100, 25-1100, 30-1100, 50-1100, 100-1100, 13-800, 13-300, 16-300, 20-300, or 25-300. The above impact force index I is the impact force index of the cleaning liquid discharged from a single discharge port. When there are multiple discharge nozzles with different impact force index I for the cleaning fluid (for example, when there are multiple discharge nozzles with different discharge flow rates Q and / or discharge pressures P), it is sufficient that the impact force index I of the cleaning fluid discharged from at least one nozzle be within the above range, but it is preferable that the impact force index I of the cleaning fluid discharged from all nozzles be within the above range.

[0172] The discharge flow rate (volume flow rate) Q of the cleaning fluid, the discharge pressure P of the cleaning fluid, and the distance r from the discharge port of the discharge section to the inner surface of the rotating tank can be appropriately adjusted so that the impact force index I falls within the above range.

[0173] The discharge flow rate Q of the cleaning solution may be, for example, 4 to 10 L / min. The above discharge flow rate Q is the discharge flow rate at a single discharge port. If there are multiple discharge ports with different discharge flow rates Q, it is sufficient that the discharge flow rate Q of at least one discharge port is within the above range, but it is preferable that the discharge flow rate Q of all discharge ports is within the above range.

[0174] The discharge pressure P of the cleaning solution may be, for example, 0.1 to 20 MPa. From the viewpoint of better removal of the functional layer, the discharge pressure P of the cleaning solution may be 0.15 MPa or higher, 0.25 MPa or higher, 1 MPa or higher, or 10 MPa or higher, and from the viewpoint of increasing the recovery rate of plastic film fragments, it may be 15 MPa or lower, 10 MPa or lower, or 1 MPa or lower. From these viewpoints, the discharge pressure P of the cleaning solution may be 0.15 to 15 MPa, 0.15 to 10 MPa, 0.15 to 1 MPa, 0.25 to 15 MPa, 0.25 to 10 MPa, 0.25 to 1 MPa, 1 to 15 MPa, or 10 to 15 MPa. The above discharge pressure P is the discharge pressure at one discharge section. If there are multiple discharge sections with different discharge pressures P, it is sufficient that the discharge pressure P of at least one discharge section is within the above range, but it is preferable that the discharge pressure P of all discharge sections is within the above range.

[0175] The removal method of the above embodiment may include the following steps (C) to (E) in addition to steps (A) and (B) above. (C) A final washing process for the recovered plastic film pieces that have been washed in step (B). (D) A drying step for the plastic film pieces that have been washed in step (B) or step (C) (drying step) (E)(B) is a process of separating and recovering the cleaning solution from the mixture of functional layer pieces and cleaning solution discharged from the discharge hole in step (B). (F) A step (rough crushing step) to be performed before step (A) by crushing the plastic film to be used in step (A) to produce a plastic film of the desired average size Sp. (G) A step (wetting step) in which the plastic film to be used in step (A) is wetted with a liquid containing water, a surfactant and an inorganic base (hereinafter also referred to as the "wetting solution") before step (A). (H)(C), (F), and / or (G) process for recovering the liquid used in the process.

[0176] (Process:(C)) In step (C), for example, the plastic film pieces that have been cleaned in step (B) may be stirred in a rinsing solution to perform a final cleaning of the plastic film pieces. This step makes it possible to remove any fragments of the functional layer that remain on the film surface if the functional layer could not be completely removed in steps (A) and (B). As the rinsing solution in step (C), the liquid exemplified in step (A) or the cleaning solution exemplified in step (B) may be used. Furthermore, the stirring equipment and stirring method in step (C) are not particularly limited, and known equipment (for example, the stirring equipment exemplified in step (G) described later) and known methods may be used. In addition, known dispersion equipment using media such as beads (bead mill, etc.) may be used. As media, salt, glass beads, metal beads (steel beads, zirconia beads, alumina beads, etc.) may be used. The material of the media can be appropriately selected depending on the properties of the rinsing solution chosen. The diameter of the spheres of the media used may be, for example, 0.5 to 20 mm. The equipment residence time in process (C) may be, for example, 1 to 30 minutes.

[0177] (Process:(D)) In step (D), the plastic film pieces washed in step (B) or (C) are dried to remove any remaining moisture. Drying may be carried out by one or more methods selected from vacuum heating drying, hot air drying, and pressure compression drying. In addition, as a pretreatment for producing recycled pellets as described later, briquettes may be produced in step (D) after or during drying using a pressurized compressor such as a GENIUS press dewatering machine, a Miike Iron Works pellet mill, or an Elcom Stella or briquette machine.

[0178] (Process:(E)) In step (E), for example, the mixture containing the functional layer fragments and cleaning solution discharged in step (B) may be supplied to one or more recycling machines selected from a filter, centrifuge, and ultrafilter to separate the solid material such as the functional layer fragments from the cleaning solution. In step (E), the separated solid material is also recovered separately from the cleaning solution. The separated and recovered cleaning solution and solid material may be reused.

[0179] (Process:(F)) In step (F), the plastic film is crushed by a known method. The crushing may be carried out under dry conditions (for example, in an air atmosphere where no liquid such as water is present) or under wet conditions (for example, in a liquid such as water). In the case of dry conditions, a dry crusher can be used. In the case of wet conditions, the wet crusher described above can be used. If crushing is carried out dry, there is no need to intentionally mix liquid into the next step (step (A)), making it easy to control the concentration and composition of the liquid used in the next step, and consequently, it is also easy to control the removeability of the functional layer. Therefore, it is preferable to carry out crushing under dry conditions. From this viewpoint, when crushing is carried out under wet conditions, it is preferable to dry the plastic film after crushing it before proceeding to the next step (step (A)). Crushing may be carried out in several stages. In one embodiment, if the above removal method includes step (G) (wetting step), the plastic film may be crushed to the desired average size Sp before step (G).

[0180] While not particularly limited, any known technology for crushing solids or shredding films can be applied, such as jaw crushers, impact crushers, cutter mills, stamp mills, ring mills, roller mills, jet mills, hammer mills, colloid mills, rotary cutters, mycoloiders, mascoloiders, ball mills, power mills, pin mills, air-flow crushers (jet mills), shear friction crushers, cutter crushers, impact crushers (hammer mills, ball mills), roll crushers, homogenizers, ultrasonic crushers, etc. It is preferable to perform crushing while the plastic film or crushing device is cooled, in order to prevent the resin film layer or functional layer from softening due to frictional heat during crushing and the cross-section of the plastic film from fusing together.

[0181] (Process:(G)) In step (G), the plastic film is moistened with a wetting solution. Here, "moistened" means bringing the plastic film into contact with the wetting solution and making it wet. By performing step (G), each layer constituting the plastic film (especially the functional layer) can be swollen, which improves the removeability of the functional layer in step (A). The effect of step (G) on improving the removeability of the functional layer is particularly noticeable when the liquid used in step (A) does not contain cleaning components (for example, water).

[0182] As the surfactant, the surfactants exemplified in step (A) above can be used, and the preferred examples of surfactants are the same as the preferred examples of surfactants shown in step (A). As the inorganic base, the inorganic bases exemplified in step (A) above can be used, and the preferred examples of inorganic bases are the same as the preferred examples of inorganic bases shown in step (A).

[0183] The above wetting solution may further contain water-soluble or water-insoluble alcohols, water-soluble or water-insoluble glycol ether-based organic solvents, water-soluble monoalkanolamine-based organic solvents, and other organic solvents, as well as an antifoaming agent. Specific examples of these are the same as those shown in step (A) above.

[0184] Methods for wetting a plastic film with a wetting solution include, for example, immersing the plastic film in the wetting solution, applying a cleaning solution to the plastic film using a spray, brush, roller, etc., or dropping the wetting solution onto the plastic film. When the wetting process involves immersing the plastic film in a wetting solution, the wetting solution can also be called an "immersion solution."

[0185] If step (G) is a step of immersing the plastic film in a wetting solution, the immersion may be performed while the film is standing still, but the functional layer of the plastic film can be swollen more efficiently by stirring the wetting solution and the plastic film simultaneously with the immersion. It is preferable to keep the stirring speed at a speed that does not easily cause foaming, etc., even without adding an antifoaming agent. The stirring device and stirring method are not particularly limited, and known devices and methods can be used. Examples of usable devices include a device equipped with a motor with stirring blades that can stir the washing solution in the container, a device equipped with a device that generates ultrasonic waves, a device that can shake the container, a wet crusher, etc. In addition, devices in which the contents are mixed by a rotating mechanism, such as a mixing tank with a stirring shaft, a planetary mixer, a Henschel mixer, a continuous kneader, an extruder, a screw feeder, a Ribocone, a Nauter mixer, a PV mixer, etc., and devices in which the tank itself rotates to mix the contents, such as a ball mill, a pot mill, an FV dryer, a conical dryer, a tumbler, etc., can also be used. As a wet crusher, one similar to the crusher exemplified in step (F) above (coarse crushing step) can be used. Known agitators such as homodispersers can also be used.

[0186] The temperature of the wetting solution used in step (G) is not particularly limited as long as it is at a temperature at which the wetting solution can remain in a liquid state, but is preferably 15 to 90°C. The temperature of the wetting solution is preferably adjusted according to the type of surfactant. The optimal temperature varies depending on the type of surfactant, but is usually preferably 40°C or higher (e.g., 40 to 90°C), and may also be 50°C or higher or 60°C or higher. If efficiency is prioritized as a practical recycling system, it is also preferable to shorten the contact time between the wetting solution and the plastic film (wetting time) while heating the wetting solution.

[0187] In step (G), the contact time between the wetting solution and the plastic film (wetting time) is preferably the time required for the adhesion between the functional layer and the resin film layer to be reduced by the wetting solution, and is preferably 10 seconds or more (for example, 10 seconds to 48 hours). If step (G) is a step of immersing the plastic film in the wetting solution, the wetting time (immersion time) can be appropriately adjusted by combining the liquid temperature and stirring. The higher the liquid temperature, the shorter the wetting (immersion time) can be, and the more sufficiently the functional layer of the plastic film can be swollen.

[0188] If the functional layer is formed from a non-curable composition, the functional layer can be dissolved in the solvent, making it easier to obtain the effect of improved removalability of the functional layer by step (G).

[0189] (Process:(H)) In step (H), if any of the above steps (C), (F) (coarse crushing step), and (G) (wetting step) are carried out, the liquids used in these steps (water, wetting solution, rinsing solution, etc.) are treated so that they can be reused. Specifically, for example, the above liquids are supplied to one or more recycling machines selected from a filter, centrifuge, and ultrafilter to remove solid matter and then reused.

[0190] Each step in the removal method of the above embodiment is an independent step, but they may be performed individually or sequentially.

[0191] If the above removal method is a method for removing a functional layer provided on the outermost surface of a plastic film, the removeability of the functional layer can also be evaluated by calculating the area of ​​the functional layer attached to the outermost surface of the film piece (functional layer attachment area) using an optical microscope. Furthermore, the removeability of the functional layer can also be evaluated by quantifying phenomena that reflect the spectral properties specific to the material forming the functional layer, obtained from various spectroscopic analyses such as IR spectra, Raman spectra, X-ray fluorescence, NIR, visible light transmittance, haze meters, and spectrophotometers, and comparing the quantitative values.

[0192] <Method for manufacturing recycled plastic pellets> Another embodiment of the present disclosure is a method for producing recycled plastic pellets, in which plastic film fragments or processed materials recovered through the above-described removal method are formed into pellets. Here, the processed materials of the plastic film fragments refer to, for example, materials obtained by crushing, melting and kneading, etc., the plastic film fragments obtained by the removal method of the above embodiment.

[0193] The method for forming plastic film pieces or processed materials therein into pellets is not particularly limited and may be a known method. For example, first, various additives, a masterbatch (generally a mixture of a thermoplastic resin such as polyethylene resin or polypropylene resin and a colorant), etc., as needed, are added to the plastic film pieces or processed materials therein, and the mixture is mixed using a Henschel mixer, tumbler, disper, etc. Then, the resulting mixture is melt-kneaded using a kneader, roll mill, twin-screw extruder, single-screw extruder, rotor-type twin-screw kneader, etc., and formed into pellets to produce recycled plastic pellets.

[0194] The recycled plastic pellets obtained by the above manufacturing method may be recycled plastic pellets that do not contain components (inks, coatings, etc.) derived from the functional layer of the plastic film used as the material, or whose content is sufficiently reduced. Therefore, by using the above recycled plastic pellets as a material, high-quality recycled plastic products can be manufactured. Accordingly, the above recycled plastic pellets can be used in a variety of fields, such as home appliances, stationery, automobile parts, toys, sporting goods, medical supplies, and building materials. Furthermore, a functional layer may be added again to the film manufactured using the above recycled plastic pellets. The type of functional layer may be the same as that which was added before recycling, or it may be different. When the above recycled plastic pellets are used for multilayer film applications, a multilayer film may be made in which the core layer is a film derived from recycled plastic pellets and the surface layers (front and back) are films derived from virgin pellets. The recycled plastic product may be, for example, a molded body obtained by heat molding (e.g., injection molding, extrusion molding, blow molding, compression molding, etc.) the above recycled plastic pellets. [Examples]

[0195] The contents of this disclosure will be described in more detail below using examples and comparative examples, but this disclosure is not limited to the following examples.

[0196] <Plastic film> In the examples and comparative examples, stretched polypropylene (OPP) film having a functional layer (ink layer) prepared in the following preparation example 1 was used as the plastic film.

[0197] <Example 1> Gravure ink (DIC Graphics Glossa 507 primary color cyan S2) was spread onto an OPP film (30 μm thick) using a proofer, printing the ink across the entire surface of the OPP film and forming an ink layer. This resulted in an OPP film having an ink layer as a functional layer.

[0198] <Examples 1-82 and Comparative Example 1> The above OPP film was processed by the following rough crushing process, wetting process, and processes (A) and (B) to obtain processed film pieces.

[0199] (Coarse crushing process) The OPP film prepared in Example 1 was dry-crushed (coarsely crushed) so that it had a polygonal shape with an average size Sp of approximately 50 mm.

[0200] (Wetting process) Aqueous solutions containing 2% by mass of sodium hydroxide (immersion solutions S1 to S15) were prepared. The additives shown in Table 1 were added to immersion solutions S1 to S15 in an amount that equaled 1% by mass based on the total volume of the aqueous solution.

[0201] [Table 1]

[0202] Next, the plastic film after the coarse crushing treatment described above was immersed in the immersion solution at 80°C for 1 hour. The combinations of plastic film and immersion solution used in each example are shown in Tables 2 to 6. After that, the plastic film was removed from the immersion solution and rinsed with water. Rinsing was continued until the pH of the rinse water was 10 or less.

[0203] (Process:(A)) A wet shredding process was performed on the plastic film that had been processed in the above wetting process. The apparatus and processing method for the wet shredding process were as specified in the conditions M1, M2, or M3 below. [Condition M1] • Equipment: Nikuni Cutter C125H (Grid mesh size = 8mmΦ) • Processing method: Operate the above device at 50Hz and add 0.05ml of water. 3The plastic film was sequentially fed into the apparatus from the inlet side while being circulated at a rate of / min. The ratio of the volume of water supplied (V2 / V1) to the volume of plastic film supplied (V1) was 87.4. The fluff-shaped crushed material that came out of the outlet was collected. [Condition M2] • Equipment: Nippon Seam PFS-40 washing and grinding machine (grid mesh size = 5mmΦ) Processing method: The above apparatus was operated at a rotational speed of 600 rpm, and the plastic film was sequentially fed in from the inlet side of the apparatus while supplying water at a rate of 15 L / min. The ratio of the volume of water supplied (V2 / V1) to the volume of plastic film supplied (V1) was 3.0. The fluff-shaped crushed material that came out of the outlet was collected. [Condition M3] The conditions were the same as in M1 above, except that the grid mesh size was set to 30 mmΦ. The ratio of the volume of water supplied (V2 / V1) to the volume of plastic film supplied (V1) was 87.4. The fluff-shaped crushed material that came out of the outlet was collected.

[0204] In Examples 1-82 and Comparative Example 1, the average size Sa of the plastic film fragments in the recovered crushed material was as shown in Tables 2-6.

[0205] (Process:(B)) A washing treatment was performed on the crushed plastic film material that had undergone the process described in (A) above. The crushed material was sequentially fed into the rotating tank of the washing device from the inlet (supply port) side, and the plastic film fragments discharged from the outlet (discharge port) side were collected. In the process described in (B), the discharge pressure P (unit: MPa), discharge flow rate Q (unit: L / min) of the washing liquid, the rotation speed of the rotating tank (unit: rpm), the amount of crushed material supplied to the rotating tank per minute Vf (unit: kg / h), the value obtained by dividing the supply amount Vf by the inner diameter d of the rotating tank Vf / d (unit: kg / min·cm), the distance r (unit: m) from the discharge port of the discharge section to the inner surface of the rotating tank, and the impact force index I calculated by the above formula (I) were the values ​​shown in Tables 2 to 5. The washing treatment time for the crushed material in Examples 1 to 82 ranged from 4 seconds to 30 seconds.

[0206] [Examples 1-73] The following were used as the washing equipment and washing liquid for washing the crushed material. Device body: Drum screen model 0306 (product name, manufactured by Toyo Screen Industry Co., Ltd.) Screen mesh opening: 0.5mm Discharge section: Flat-type spray nozzle (four nozzles installed at 20cm intervals) Cleaning solution: Water

[0207] [Examples 74-77] The crushed material was washed using the same washing apparatus and washing solution as in Examples 1 to 73, except that a screen with a mesh opening of 1 mm was used.

[0208] [Example 78] The crushed material was washed using the same washing apparatus and washing solution as in Examples 1 to 73, except that a screen with a mesh opening of 0.05 mm was used.

[0209] [Examples 79-82] As the cleaning solution, an aqueous solution containing 0.6% by mass of NOF Corporation's surfactant F2-50R was used instead of water. The same cleaning apparatus as in Examples 1 to 73 was used.

[0210] (Drying Step) The fluffed plastic film pieces collected in step (B) were dried using a hot air dryer at 80°C for 2 hours to obtain treated film pieces.

[0211] [Comparative Example 1] Instead of the cleaning treatment using a cleaning device, the fluffed crushed product obtained after step (A) was immersed in water and stirred at room temperature for 1 hour to perform rinse cleaning. After rinse cleaning, the fluffed crushed product was collected and dried to obtain treated film pieces. <Examples 83 to 86> The OPP film produced in Production Example 1 was treated by the following rough crushing step and the following steps (A) and (B) to obtain treated film pieces. Specifically, in Examples 83 to 86, the functional layer of the OPP film was removed without performing the swelling step described above.

[0213] (Rough Crushing Step) The OPP film produced in Production Example 1 was dry-crushed (roughly crushed) into polygonal pieces having an average size Sp of about 50 mm.

[0214] (Step (A)) Wet crushing treatment was performed on the plastic film treated in the rough crushing step described above.

[0215] [Example 83] Wet crushing treatment was performed under the same conditions as the above M2, except that an aqueous solution containing 0.1% by mass of DKS NL-Dash408, a surfactant manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., was used instead of water as the liquid circulated in the wet crushing apparatus.

[0216] [Example 84] Wet crushing treatment was performed under the same conditions as the above M2, except that an aqueous solution containing 0.1% by mass of F2-50R, a surfactant manufactured by NOF Corporation, was used instead of water as the liquid circulated in the wet crushing apparatus.

[0217] [Example 85] The wet crushing treatment was carried out under the same conditions as M2 above, except that an aqueous solution containing 0.1% by mass of Kao Corporation's surfactant Emulgen 108 was used as the liquid flowing through the wet crushing apparatus instead of water.

[0218] [Example 86] The wet crushing treatment was carried out under the same conditions as M2 above, except that an aqueous solution containing 0.1% by mass of Kao Corporation's surfactant Emulgen 120 was used as the liquid flowing through the wet crushing apparatus instead of water.

[0219] In Examples 83-86, the average size Sa of the plastic film fragments in the recovered crushed material was as shown in Table 5.

[0220] (Process:(B)) The crushed plastic film material that had undergone the process described in (A) above was subjected to a washing treatment under the same conditions as in Example 1. The crushed material was sequentially fed into the rotating tank of the washing device from the inlet (supply port) side, and the plastic film fragments discharged from the outlet (discharge port) side were collected.

[0221] (drying process) The fluff-shaped plastic film pieces recovered in step (B) were dried using a hot air dryer at 80°C for 2 hours to obtain treated film pieces.

[0222] <Recovery Rate> The recovery rate of plastic film fragments in step (B) of Examples 1 to 86 was determined using the following formula. The results are shown in Tables 2 to 5. Plastic film fragment recovery rate (%) = [Amount of plastic film fragments recovered per 10 minutes (unit: kg)] / [Design value of the amount of plastic film fragments supplied to the rotating tank per 10 minutes (unit: kg)] × 100

[0223] <Rating> [L * a* b * L* expressed in the color system * value] The coloring of the treated film pieces of Examples 1 to 86 and Comparative Example 1 was evaluated by L* * a* * b* * L* value (brightness index) expressed in the L*a*b* color system * . The L* * value was measured by the following method.

[0224] First, the treated film piece was press-molded at a temperature equal to or higher than the softening point to obtain a flat plate-shaped molded article (thickness: 30 µm). Next, the L* * value of the obtained molded article was measured in accordance with JIS Z 8722. For the measurement of the L* * value, a spectrophotometer (manufactured by Nippon Denshoku Industries Co., Ltd., product name: SE6000) was used. PPCPAPER HighWhite (product name, manufactured by Otsuka Corporation Co., Ltd.) was used as the base, and the measured value of co-extruded multilayer film (product name: Differen T2160T, manufactured by DIC Corporation) was used as a reference. A larger L* * value indicates better removability of the functional layer. The results are shown in Tables 2 to 6.

[0225]

Table 2

[0226]

Table 3

[0227]

Table 4

[0228]

Table 5

[0229]

Table 6

[0230] 10...rotating tank, 10a...wedge wire, 10b...reinforcement material, 12...discharge hole, 14...conveyor blades, 20...cleaning liquid supply pipe, 22...discharge section, 22a...discharge port, 100...cleaning device, R...central axis.

Claims

1. A method for removing a functional layer from a plastic film having a functional layer, (A) A step of wet-shredding the plastic film, (B) A cleaning device comprising a cylindrical rotating tank having a plurality of discharge holes and conveying blades on its inner surface and rotatable about its central axis as a rotation axis, and a discharge section that discharges cleaning liquid toward the inner surface of the rotating tank, to clean the crushed plastic film that has undergone the process of (A), A method comprising the steps of (B) above: supplying the crushed material into the rotating tank from one end of the rotating tank; conveying the crushed material from one end of the rotating tank to the other end by rotating the rotating tank; and washing the crushed material by spraying the washing liquid onto the crushed material while it is being conveyed.

2. The method according to claim 1, wherein in step (B) above, the cleaning liquid is discharged such that the impact force index I, which can be determined by the following formula (I), is between 13 and 1100. Impact force index I = Q * √P * (1 / r) ２ ... (I) [Q represents the discharge flow rate of the cleaning fluid (unit: L / min), P represents the discharge pressure of the cleaning fluid (unit: MPa), and r represents the distance (unit: m) from the discharge port of the discharge unit to the inner surface of the rotating tank.]

3. The method according to claim 1, wherein the discharge pressure P of the cleaning solution in step (B) is 0.15 to 15 MPa.

4. The method according to claim 1, wherein the value Vf / d obtained by dividing the amount Vf supplied per minute of the crushed material into the rotating tank in step (B) by the inner diameter d of the rotating tank is 0.04 to 0.5 kg / (min·cm).

5. The method according to claim 1, wherein the rotational speed of the rotating tank in step (B) is 3 to 50 rpm.

6. The method according to claim 1, wherein the minimum width of the discharge hole is 0.1 to 5 mm.

7. The method according to claim 1, wherein the average size Sa of the plastic film pieces in the crushed material is 2 to 10 mm.

8. The method according to claim 1, further comprising the step of wetting the plastic film with a liquid containing water, a surfactant, and an inorganic base before step (A).

9. A method for producing recycled plastic pellets, comprising forming plastic film fragments or processed materials thereof, recovered via the method described in any one of claims 1 to 8, into pellets.

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