Method for separating and recovering plastic film, and method for producing recycled plastic pellets

Abstract

The method for separating and recovering a plastic film having at least an ink layer includes step 1 of crushing the plastic film, step 2 of immersing the plastic film in a cleaning liquid, and step 3 of separating the ink layer from the plastic film by stirring the crushed plastic film in a rinsing liquid containing at least a water-soluble solvent. The present invention also provides a method for producing recycled plastic pellets, which comprises recovering the plastic crushed material separated by steps 1 to 3, melting the recovered material, and molding it with a molding machine.

Description

[Technical field]

[0001] The present invention relates to a method for separating and recovering plastic films, and a method for producing recycled plastic pellets using crushed plastic material recovered by said method. [Background technology]

[0002] Currently, the recycling rate of plastic waste, which is separated and collected, is 9% of the plastic produced worldwide. Of the 91% of plastic that has become garbage, 12% has been incinerated, and 79% has been landfilled or leaked into the environment (Non-Patent Document 1). One of the reasons for this continued low recycling rate is the difficulty of the separation and collection system. In order to recycle plastic, it is necessary to separate and collect waste plastics that are integrated with different plastic materials such as polyethylene (PE) and polypropylene (PP) by material. However, many plastic products, including laminated films, are made of different plastic materials that are bonded and laminated, making it difficult to separate and collect them by material. Therefore, there is a strong demand for the construction of a recycling system that can easily separate and collect waste plastic.

[0003] In addition, recycled plastic products are difficult to turn back into the same product from a cost perspective, and basically deteriorate every time they are recycled, so they are inevitably reborn as products of lower quality. One reason for the deterioration in quality of recycled plastic is that inks and pigments are mixed into the plastic as impurities. However, since many plastic products have printing on their surfaces, it is difficult to decolorize them during the recycling process, and as a result, recycled plastic products are colored. Recycled plastics that contain pigments and inks not only have significantly lower commercial value due to the coloring, but also end up as plastics that have deteriorated physically due to the impurities, so there is a demand for recycling methods that can produce high-quality recycled plastics.

[0004] In response to these issues, Patent Document 1 proposes a recycling method in which the aluminum layer is dissolved from crushed multilayer film using an alkali, the multilayer film is separated based on differences in specific gravity, and then the valuable components are separated and recycled by selectively melting the film in a solvent. Patent Document 2 proposes a process in which printed film is crushed, the ink is removed, and the film is rinsed and dried, but both processes are long and complicated.

[0005] Furthermore, Patent Document 3 provides a method for removing ink from a printed, rolled film using a solvent and a non-abrasive cloth, and Patent Document 4 provides a method for removing ink from a printed, rolled film using a solvent, a brush, and a wiper blade, but these methods merely involve removing the ink from a rolled film to produce an unprinted film.

[0006] In particular, in recent years, with the diversification of packaging materials, there is an increasing demand for high functionality of packaging materials, improved adhesion of ink films to plastic substrates, and high design of printed matter, which has led to a diversification of packaging materials and ink types, and at the same time, peeling off the ink layer has become more difficult. For example, in a laminated film in which multiple films are laminated, or in a laminate in which an ink layer is provided on a film and then another film is laminated with an adhesive layer, in the case of a laminated film in which an ink layer is provided between multiple films (reverse printing), it is necessary to separate the multiple films to remove the ink layer, making peeling off the ink layer more difficult. There is a demand for a method that can peel off the ink layer from plastic films with such diverse configurations. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Science Advances 19 Jul 2017:Vol. 3, no. 7, e1700782 [Patent documents]

[0008] [Patent Document 1] JP 2006-205160 A [Patent Document 2] Special Publication No. 2015-520684 [Patent Document 3] Special Publication No. 2016-509613 [Patent Document 4] Special Publication No. 2018-514384 Summary of the Invention [Problem to be solved by the invention]

[0009] In the conventional techniques, the separation of laminated films is carried out by a process of dry crushing the laminated films, followed by a process of deinking or separation, which is a general process that is long and complicated. In addition, the conventional techniques make it difficult to recycle laminated films with a wide variety of compositions, which reduces the quality and commercial value of recycled plastics.

[0010] Therefore, the problem that the present invention aims to solve is to provide a method for easily separating and recovering a wide variety of plastic films having at least an ink layer, and a method for producing high-quality recycled plastic pellets using the crushed plastic material recovered by said method. [Means for solving the problem]

[0011] As a result of extensive research to solve the above-mentioned problems, the inventors have discovered an easy method for regenerating plastic laminates into high-quality recycled raw materials, which includes step 1 of crushing a plastic film, step 2 of immersing the plastic film in a cleaning liquid, and step 3 of separating the ink layer from the plastic film by agitating the crushed plastic film in a rinsing liquid.

[0012] In other words, the present invention provides a method for separating and recovering a plastic film having at least an ink layer, which comprises step 1 of crushing the plastic film, step 2 of immersing the plastic film in a cleaning liquid, and step 3 of separating the ink layer from the plastic film by stirring the crushed plastic film in a rinsing liquid containing at least a water-soluble solvent.

[0013] The present invention also provides a method for producing recycled plastic pellets, which comprises recovering the crushed plastic material separated by the above-described method in single layers, melting the recovered material, and molding it with a molding machine. Effect of the Invention

[0014] According to the present invention, a wide variety of plastic films having at least an ink layer can be separated into single layers, and crushed single-layer films can be easily recovered, separated, and reused. According to the method of the present invention, not only plastic films having an ink layer exposed on the film surface (front-printed), but also plastic laminates having various configurations such as laminated films having an ink layer between multiple films (reverse-printed) can be separated into single layers, and the ink layer can be easily peeled off. In other words, regardless of the type of plastic laminate, the film can be separated into single layers, and the ink layer can be easily separated (peeled off), which makes it easier to separate and recover plastic laminates, and the recovered plastic can be reused as high-quality recycled plastic raw material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <About step 1> The method for separating and recovering a plastic film of the present invention includes a step 1 of crushing the plastic film. In the step 1, the method for crushing the plastic film is not particularly limited, and can be performed by a known method. The crushing may be performed in an air atmosphere in the absence of liquid such as a solvent, or in water or a cleaning solution. When crushing is performed in an air atmosphere, a dry crusher can be used. When crushing is performed in water or a cleaning solution, a wet crusher that can perform crushing and pressure feeding at the same time can be used. When a wet crusher is used, the plastic film can be efficiently crushed, and the laminated plastic film can be peeled off into each layer.

[0016] By crushing the plastic film in step 1, it becomes easier to completely peel off the plastic film into a single layer in the below-described steps 2 and 3. In step 1, it is sufficient that the plastic film is crushed, and the crushed plastic film may be in a state in which at least a part of the edge or the like is partially peeled off, and each layer may be completely peeled off, or each layer may not be peeled off.

[0017] The long sides of the plastic film crushed in step 1 are preferably 1 mm to 30 mm, more preferably 1 mm to 20 mm, and even more preferably 1 mm to 10 mm. When the length is within the above range, the time required for the treatment liquid to penetrate from the end faces of the fluff to the center is shortened in step 2 of immersing the plastic film in a cleaning liquid, making it easier to completely peel off the plastic film into a single layer.

[0018] In order to reduce the time required for the treatment solution to penetrate from the end face to the center of the fluff, it is more preferable that holes or slits are made in the crushed plastic film. The diameter of the hole or the length of the slit is preferably 0.5 mm or more, more preferably 0.8 mm or more, and even more preferably 1.0 mm or more.

[0019] (Dry crusher) The dry crusher used in step 1 is not particularly limited, and any known technology for crushing solids or cutting films can be applied, such as a jaw crusher, impact crusher, cutter mill, stamp mill, ring mill, roller mill, jet mill, hammer mill, colloid mill, rotary cutter, mycolloider, masscolloider, ball mill, power mill, pin mill, airflow crusher (jet mill), shear friction crusher, cutter crusher, impact crusher (hammer mill, ball mill), roll crusher, homogenizer, ultrasonic crusher, etc. In order to prevent the substrate or ink layer from softening due to frictional heat during crushing and the cross section of the laminate from fusing, it is preferable to perform crushing or crushing in a cooled state of the laminate or crushing device.

[0020] The dry crusher can be preferably used for separating and recovering films in both plastic films in which an ink layer is exposed on the film surface (surface printing) and laminated films in which an ink layer is provided between multiple films (reverse printing). The ink layer applied to the plastic film is a printed ink layer for providing display such as a product name and decorativeness, and is often printed with organic solvent-based printing ink, water-based ink, or active energy ray curable ink using a gravure printer, flexographic printer, offset printer, inkjet printer, etc. In plastic films provided with such ink layers, the film and the printed surface are not completely separated when a dry crusher is used in step 1, but in the present invention, the film and the printed surface can be completely separated in steps 2 and 3 described below. In the case of a laminated film in which an ink layer is provided between multiple films (reverse printing), in addition to the dry crusher, a wet crusher is preferably used to improve the separability of the ink layer provided between the films.

[0021] (Wet crusher) The wet crusher used in step 1 is not particularly limited, but is preferably a wet crusher that can crush, disperse, mix, and pump solids in a liquid at the same time. Specifically, it is preferable to use a crusher that has a mechanism for crushing solids in a liquid by shear force and / or friction force, and is also preferable to use a crusher that has a mechanism for crushing and pumping plastic films. Examples of such wet crushers include a wet crushing pump, a colloid mill, an attritor, and a beater.

[0022] (Wet fracturing pump) It is preferable that the wet crushing pump has a mechanism for crushing the solids using fixed blades and rotating blades while pumping the solids in the liquid. A more preferable mechanism is a three-stage crushing mechanism using a combination of four parts: cutting blades, crushing impeller, shroud ring, and grid.

[0023] The wet-type crushing pump crushes plastic films in three stages. The plastic film is roughly cut by the fixed blade cutting edge and the inlet edge of the rotating blade crushing impeller, then it is stirred and pumped by the axial-flow crushing impeller, and some of the plastic film is cut by hitting the blade of the shroud ring of the fixed blade. The laminated film that passes through the crushing impeller is further crushed and stirred between the grids, passes through the grid, is pressurized by the pressurizing impeller, and is pumped to the next process.

[0024] The pumping speed is not particularly limited, but considering the peeling and separation efficiency when peeling off the ink layer and separating the plastic film into each layer, it is recommended to use a pumping speed of 0.03 m 3 The upper limit of the pumping speed is not particularly limited, and is preferably a standard operating speed of the device, for example, 1.4 m 3 / min is sufficient to remove the ink and separate the plastic film into single layers.

[0025] The shape of the grid is not particularly limited. Since the grid aperture affects the size of the crushed laminate film, the grid aperture is preferably 0.1 to 50 mm, and more preferably 1 to 20 mm in consideration of the crushing efficiency and the size of the crushed laminate film.

[0026] Specific examples of wet fracturing pumps include the KD series from Husqvarna Zenoah, the Suncutta series from Nikuni, the Disintegrator series from Furukawa Industrial Machinery Systems, the Incrusher series and Refiner from Aikawa Iron Works, the Scatter from Sanwa Hydrotech, and the Trigonal from Nippon Coke Company.

[0027] (Colloid Mill) The colloid mill used in this invention is a machine used to reduce particle size in a dispersion system where particles are suspended in a liquid. A colloid mill consists of a rotor and a stator combination, where the rotor rotates at high speed against the fixed stator. The high speed rotation generates high levels of shear, which is used to reduce the particle size in the liquid.

[0028] The crushing section of the colloid mill is made up of a combination of a toothed, truncated cone-shaped rotor and a stator, and the rotor and stator are tapered so that they become narrower as they approach the discharge port. The laminated film is crushed by repeatedly applying strong shear, compression, and impact in the ring-shaped gap that narrows as it approaches the discharge port.

[0029] Specific colloid mills are not particularly limited as long as they are dispersing machines generally called colloid mills, and examples include the Colloid Mill MK series from IKA Corporation, the WCM series from Iwaki Corporation, the PUC Colloid Mill series from Mountec Corporation, and the Cavitron from Eurotech Corporation.

[0030] (grinder) The grinding machine preferably has a mechanism for crushing solid matter placed between a pair of upper and lower millstones by shear or friction while rotating them in liquid, and is preferably capable of grinding solid matter into a fine powder while flowing water through it.

[0031] The size of the crushed material can be adjusted by adjusting the distance between the upper and lower pair of millstones, but it is usually finely ground to 500 μm or less, preferably 300 μm or less, and more preferably 200 μm or less. By reducing the size of the crushed material in this way, each layer of the plastic film is separated into a single layer, and the storage space for the crushed material can be reduced, making inventory management easier. In addition, when producing recycled plastic from the crushed material, it can be put into a kneader without passing through a compressor or the like, so the process can be simplified. On the other hand, the lower limit of the size of the crushed material is preferably 10 μm or more, preferably 30 μm or more, and more preferably 50 μm or more in order to facilitate recovery.

[0032] The rotation speed and water flow speed are not particularly limited.

[0033] A specific example of the grinding machine is the Supermass Colloider manufactured by Masuko Sangyo Co., Ltd.

[0034] As described above, the wet crusher can be preferably used when separating and recovering a laminated plastic film in which an ink layer is provided between a plurality of films (reverse printing).

[0035] In most cases, the reverse-printed laminated plastic film is provided with a printed ink layer for displaying the trade name and providing decorativeness in addition to the adhesive. The ink layer is often printed with an organic solvent-based printing ink, a water-based ink, or an active energy ray curable ink using a gravure printer, a flexographic printer, an offset printer, an inkjet printer, or the like. In the case of a plastic film provided with such an ink layer, in order to peel and remove the ink layer more efficiently, the plastic film may be crushed in a cleaning solution containing a cleaning component or a peeling component in water. By crushing the plastic film in a cleaning solution containing a cleaning component or a peeling component in water, the ink layer provided on the plastic film can be peeled and removed and the plastic film can be separated into single layers at the same time. For example, the inks most commonly used for plastic laminated films, including those for food packaging, are gravure ink and flexographic ink, but in a wet crushing process using a cleaning solution, the printing ink layer can also be peeled off, making it efficient. In addition, the laminated film may have a metal foil or vapor-deposited film such as aluminum laminated thereon, but in the present invention, the metal foil or vapor-deposited film can also be peeled off or dissolved. As already described above, the layers constituting the plastic film may be peeled off into single layers by crushing in water, or a part of the crushed plastic film may be partially peeled off. In addition, the ink layer provided on the plastic film does not need to be completely removed from the plastic film in step 1, and may be partially attached, or may not be removed from the ink layer.

[0036] When a wet-type crusher is used in step 1, crushing may be performed using water as a solvent, or a cleaning liquid in which water contains a cleaning or peeling component such as an inorganic base or a surfactant, or other components. The cleaning liquid may be water containing one or a suitable combination of two or more of the following components:

[0037] (Inorganic Bases) The aqueous cleaning solution usable in step 1 may be water containing an inorganic base. Specific examples of the inorganic base include sodium hydroxide and potassium hydroxide. These inorganic bases are contained in a concentration of 0.1 to 10% by weight, more preferably 0.1 to 5% by weight, based on the total amount of the aqueous cleaning solution. The pH is preferably 10 or higher.

[0038] (Surfactant) Water containing a surfactant can be used as the aqueous cleaning liquid that can be used in step 1. The surfactant is not particularly limited, and any known surfactant can be used, including, for example, anionic surfactants, nonionic surfactants, amphoteric surfactants, and cationic surfactants.

[0039] 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 alkylol amides, alkyl alkanol amides, acetylene glycol, oxyethylene adducts of acetylene glycol, polyethylene glycol polypropylene glycol block copolymers, and the like. Among these, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid alkylol amides, acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers.

[0040] In the present invention, the aqueous cleaning liquid preferably contains 50% by weight or more of water and 0.01% by weight to 5% by weight of a polyoxyalkylene alkyl ether surfactant containing at least one compound represented by general formula (1).

[0041] R 1 -O-[CH2-CH(X 1 )-O]n 1 -H (1) In general formula (1), R 1 represents a linear or branched alkyl group, an alkenyl group, or an octylphenol group; n 1 represents the average number of moles added, and X 1 represents hydrogen or a short chain alkyl group.

[0042] More preferably, R 1 A linear or branched alkyl or alkenyl group having 10 or more carbon atoms is preferred. The more carbon atoms there are, the better the ink removability, and this is preferred. Specific numbers of carbon atoms include a decyl group having 10 carbon atoms, a lauryl group having 12 carbon atoms, a tridecyl group having 13 carbon atoms, a myristyl group having 14 carbon atoms, a cetyl group having 16 carbon atoms, and an oleyl group and a stearyl group having 18 carbon atoms.

[0043] Specific products include the Noigen series, DSK NL-Dash series, and DKS-NL series manufactured by Daiichi 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. These are nonionic surfactants represented by the general formula (1). 1 This applies when the number of carbon atoms represented by is 10 or more, but is not limited to this.

[0044] The HLB value of the polyoxyalkylene alkyl ether surfactant represented by the general formula (1) is not particularly limited. The HLB value here means a value that indicates the degree of affinity of the surfactant to water and oil (a water-insoluble organic compound), and is defined by the Griffin method (HLB value = 20 x sum of formula weights of hydrophilic parts / molecular weight).

[0045] Among the nonionic surfactants represented by the general formula (1), R 1Specific surfactants with 10 or more carbon atoms and an HLB value of less than 12.5, as indicated by the above, from Daiichi Kogyo Seiyaku Co., Ltd., are Noigen XL-41, Noigen LF-40X, Noigen TDS-30, Noigen TDS-50, Noigen TDS-70, Noigen TDX-50, Noigen SD-30, Noigen SD-60, DKS NL-15, DKS NL-30, DKS NL-40, DKS NL-50, DKS NL-60, DKS NL-70, Noigen ET-83, Noigen ET-102, DSK Dash400, DSK Dash403, DSK Dash404, DSK Dash408, Noigen LP-55, Noigen LP-70, Noigen ET-65, Noigen ET-95, Noigen ET-115, Noigen ET-69, Noigen ET-89, Noigen ET-109, Noigen ET-129, Noigen ET-149, NOF Corporation's 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-507, Nonion H Examples of such coating agents include, but are not limited to, T-510, Nonion HT-512, and those manufactured by Kao Corporation such as Emulgen 102KG, Emulgen 103, Emulgen 104P, Emulgen 105, Emulgen 106, Emulgen 108, Emulgen 210P, Emulgen 404, Emulgen 408, Emulgen 409PV, Emulgen 705, and Emulgen 707, and those manufactured by Lion Corporation such as Leox CL-30, Leox CL-40, Leox CL-50, Leox CL-60, Leocal NL-30C, Leocal TD-50, Leocal TD-70, Leocal SC-50, and Leocal SC-70.

[0046] Among the nonionic surfactants represented by the general formula (1), specific surfactants in which R1 represents a linear or branched alkyl or alkenyl group having 10 or more carbon atoms and an HLB value of 12.5 or more are listed by Daiichi Kogyo Seiyaku Co., Ltd. as NOIGEN XL-61, NOIGEN XL-6190, NOIGEN XL-70, NOIGEN XL-80, NOIGEN XL-100, NOIGEN XL-140, NOIGEN XL-160, XL-400D, NOIGEN XL-1 000, Noigen LF-60X, Noigen LF-80X, Noigen LF-100X, Noigen TDS-80, Noigen TDS-100, Noigen TDS-120, Noigen TDS-200D, Noigen TDS-500F, Noigen TDX-80, Noigen TDX-80D, Noigen TDX-100D, Noigen TDX-120D, Noigen SD-70, Noigen SD-80, Noigen SD-110, Noigen 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, Noigen ET-160, Noigen ET-170, Noigen ET-190, DSK Dash410, Noigen LP-80, Noigen LP-100, Noigen LP-180, Noigen ET-135, Noigen ET-165, Noigen ET-159, Noigen ET-189, NOF Corporation's 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 I D-206, Nonion ID-209, Dispanol TOC, Nonion HT-515, Nonion HT-518, Kao's products include Emulgen 109P, 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 the Emulgen 2025G and Lion's Leox CL-90, Leox CL-230, Leocal TD-90, Leocal TD-90D, Leocal TDA-90-25, Leocal TDN-90-80, Leocal TD-120, Leocal TD-200, Leocal TDA-400-75, Leocal SC-80, Leocal SC-90, Leocal SC-120, Leocal SC-150, Leocal SC-200, Leocal SC-300, and Leocal SC-400 can be mentioned, but are not limited to these.

[0047] In general formula (1), R 1 When is an octylphenol group, octylphenol ethoxylates are preferred.

[0048] Specific examples of such products include, but are not limited to, the TRITON (registered trademark) series from Dow Chemical Company, the Igepal CA series from Rhodia Corporation, the Nonidet P series from Shell Chemicals, and the Nikkol OP series from Nikko Chemicals.

[0049] Specifically, the amphoteric surfactant is preferably a betaine-type amphoteric surfactant, and more preferably contains an amphoteric surfactant having an alkylcarboxybetaine skeleton or an alkylamidecarboxybetaine skeleton containing at least one compound represented by general formula (2a).

[0050] R1-R2-N + (CH3)2CH2COO - (2a) (In general formula (2a), R1 represents hydrogen or C(=O)R3-NH- (R3 represents a linear or branched alkyl or alkenyl group), and R2 represents an alkylene group or an alkenylene group.) In general formula (2a), R1 preferably represents a hydrogen atom. The compound represented by general formula (2a) is preferably an amphoteric surfactant having an alkylcarboxybetaine skeleton represented by general formula (2a-1).

[0051] C n H 2n+1 N + (CH3)2CH2COO - (2a-1) (In general formula (2a-1), n ​​represents the average number of moles added.) In formula (2a-1), n ​​is preferably 8 or more, more preferably 10 or more, and even more preferably 11 or more.

[0052] Specific products that fall under the general formula (2a) include Nissan Anon BDF (registered trademark)-R, Nissan Anon BDF (registered trademark)-SF, Nissan Anon BDC-SF, and Nissan Anon BDL-SF manufactured by NOF Corporation, Amogen CB-H and Amogen HB-C manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Rekabion B-200 and Rekabion B-300 manufactured by New Japan Chemical Co., Ltd., and Obazoline CAB-30 and Obazoline ISAB manufactured by Toho Chemical Industry Co., Ltd. Specific examples of products corresponding to the general formula (1a-1) include, but are not limited to, Amogene S, Amogene SH, and Amogene K manufactured by Daiichi Kogyo Seiyaku Co., Ltd.; Anhitor 20BS, Anhitor 24B, and Anhitor 86B manufactured by Kao Corporation; Nissan Anon BF, Nissan Anon BL, and Nissan Anon BL-SF manufactured by NOF Corporation; Rekabion A-100, Rekabion A-200, and Rekabion A-700 manufactured by New Japan Chemical Co., Ltd.; and Obazoline LB and Obazoline LB-SF manufactured by Toho Chemical Co., Ltd.

[0053] In addition, the betaine-type amphoteric surfactant may be one having an imidazolinium betaine skeleton. Specific examples of such products include Nissan Anon GLM-R and Nissan Anon GLM-R-LV manufactured by NOF Corporation, and Amphitol 20Y-B manufactured by Kao Corporation, but are not limited to these.

[0054] The amphoteric surfactant may be a surfactant represented by the following general formula (2b).

[0055] R4-(NHC2H4) nb-N(R5)2(2b) (In the general formula (2b), R4 represents a linear or branched alkyl group or alkenyl group, nb represents an integer of 0 to 5, and R5 represents hydrogen, -CH2COONa, or -CH2COOH, but two R5s may be the same or different, and at least one R5 represents -CH2COONa.) In general formula (2b), R4 preferably represents a linear alkyl group, and R4 preferably has 8 or more carbon atoms, more preferably 10 or more carbon atoms, and even more preferably 12 or more carbon atoms.

[0056] Specific examples of products that correspond to the general formula (2b) include Nissan Anon LG-R and Nissan Anon LA manufactured by NOF Corporation, but are not limited to these.

[0057] The amphoteric surfactant may be an amine oxide surfactant represented by the following general formula (2c).

[0058] R6-N + (CH3)2O - (2c) (In the general formula (2c), R6 represents a linear or branched alkyl group or an alkenyl group.) In general formula (2c), R6 is preferably R4 in general formula (2b) represents a linear alkyl group, and the number of carbon atoms in R4 is preferably 8 or more, more preferably 10 or more, and even more preferably 12 or more.

[0059] Specific examples of products that correspond to the general formula (2c) include Amogene AOL manufactured by Daiichi Kogyo Seiyaku Co., Ltd. and Amphitol 20N manufactured by Kao Corporation, but are not limited to these.

[0060] Specifically, the cationic surfactant is preferably a cationic surfactant having a quaternary ammonium skeleton, and more preferably contains a cationic surfactant having a quaternary ammonium skeleton that contains at least one compound represented by general formula (3a).

[0061] R1-N + (R2R3)-R4 (3a) (In general formula (3a), R1 represents a linear or branched alkyl group, or a linear or branched alkenyl group, -CH2- in the alkyl or alkenyl group may be replaced by -C(=O)-, -NH-, or -C(=O)-NH-; R2 and R3 represent a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkenyl group; R4 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 or alkenyl group may be replaced by a carboxy group or a phenyl group.) In general formula (3a), R1 is preferably a long-chain alkyl group or alkenyl group in order to further improve the releasability of the ink, specifically, it is preferably an alkyl group or alkenyl group having 8 to 30 carbon atoms, preferably an alkyl group having 10 to 25 carbon atoms, and preferably an alkyl group or alkenyl group having 12 to 22 carbon atoms. The alkyl group or alkenyl group may be linear or branched, but is preferably linear, and more preferably a linear alkyl group.

[0062] In R1, at least one or more -CH2- in the alkyl group or alkenyl group may be substituted with -C(=O)-, -NH-, or -C(=O)-NH-. Among these, it is preferable that at least one or more -CH2- in the alkyl group or alkenyl group is substituted with -C(=O)-NH- or -NH-C(=O), it is preferable that one -CH2- in the alkyl group is substituted with -C(=O)-NH- or -NH-C(=O), and it is more preferable that R1 has an amidopropyl skeleton.

[0063] R2 and R3 each preferably represent a linear or branched alkyl group or a linear or branched alkenyl group, more preferably a linear or branched alkyl group, particularly preferably a linear alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group.

[0064] R4 is preferably a linear or branched alkyl group, a linear or branched alkenyl group, or a phenyl group, more preferably a linear or branched alkyl group, and the terminal -CH3 in the alkyl or alkenyl group is preferably substituted with a carboxy group or a phenyl group.

[0065] R4 preferably has 1 to 8 carbon atoms, more preferably 1 to 5 carbon atoms, even more preferably 1 to 3 carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0066] When R4 represents a methyl group, it is preferable that R2 and R3 also represent methyl groups and general formula (3a) represents an alkyltrimethylammonium skeleton.

[0067] In addition, when R4 represents an ethyl group, the terminal -CH3 in the ethyl group is preferably substituted with a carboxy group or a phenyl group. In other words, R4 preferably represents -CH2-(C(=O)OH or represents a benzyl group. The compound represented by general formula (3a) is preferably a cationic surfactant having a quaternary ammonium skeleton represented by general formula (3a-1).

[0068] C n H 2n+1 N + (CH3)2R4 (3a-1) (In the general formula (3a-1), n ​​represents the average number of moles added, and R4 has the same meaning as R4 in the general formula (3a) described in claim 3.) In the general formula (3a-1a), the number of carbon atoms represented by n is preferably 8 or more. The greater the number of carbon atoms (exceeding 8), the better the ink removability, and this is preferred. Specific numbers of carbon atoms include an octyl group having 8 carbon atoms, a nonyl group having 9 carbon atoms, a decyl group having 10 carbon atoms, an undecyl group having 11 carbon atoms, a lauryl group having 12 carbon atoms, a tridecyl group having 13 carbon atoms, a myristyl group having 14 carbon atoms, a pentadecyl group having 15 carbon atoms, a cetyl group having 16 carbon atoms, and an oleyl group and stearyl group having 18 carbon atoms.

[0069] The preferred groups for R4 are the same as those in formula (3a). These cationic surfactants having a quaternary ammonium skeleton are preferably of the quaternary ammonium skeleton salt type formed with a halogen, and Cl - It is preferable to form a salt with Br - It is preferable to form a salt with I - It is preferable that the quaternary ammonium skeleton salt that forms a salt with a halogen promotes hydrolysis of the ink film due to the nucleophilic action of the halogen, and is therefore considered to improve the peelability of the ink.

[0070] Among these, alkyltrimethylammonium chloride type, dialkyldimethylammonium chloride type, and alkylbenzalkonium chloride type compounds are preferred.

[0071] Specific products corresponding to the general formula (3a) or (3a-1) include 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 manufactured by NOF Corporation, Catiogen TML, Catiogen TMP, Catiogen TMS, Catiogen DDM-PG, Catiogen BC-50, and Catiogen TBB manufactured by Daiichi Kogyo Co., Ltd., and Coatamine 24P, Coatamine 86P Conc, Coatamine 86P Conc, and Coatamine 86P Conc, manufactured by Kao Corporation. Examples of these 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 Lipoguard 2HP-80. Examples include, but are not limited to, Poguard 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, and the like.

[0072] The cationic surfactant preferably contains at least one compound represented by a primary or secondary alkanolamine skeleton, and more preferably contains at least one compound represented by a monoalkanolamine skeleton. The primary monoalkanolamine is preferably a lower alkanol having 1 to 4 carbon atoms, and specific examples thereof include monoethanolamine, 2-aminoisobutanol, etc., and the secondary monoalkanolamine is N-methylethanolamine, 2-ethylaminoethanol, isopropanolamine, etc., but substances other than those exemplified can also be used as appropriate. Furthermore, these monoalkanolamine compounds can be used alone or in appropriate combination of two or more, and can also be used by mixing with water. These cationic surfactants having a monoalkanolamine skeleton are preferably monoalkanolamine salts formed with halogens, and Cl - It is preferable to form a salt with

[0073] These surfactants can be used alone or in combination of two or more. The amount of the surfactant added is preferably 5% by weight or less, and more preferably 2% by mass or less, based on the total amount of the aqueous cleaning solution. The lower limit of the surfactant is not particularly limited and may be 0% by mass, but when a surfactant is contained, it is preferably 0.1% by mass or more.

[0074] (non-water-soluble alcohol) Water containing a water-insoluble primary alcohol can be used as a cleaning liquid in step 1. The water-insoluble primary alcohol is preferably contained in an amount of 20% by weight or less relative to the water.

[0075] 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, decan-1-ol, undecane-1-ol, dodecane-1-ol, tridecane-1-ol, tetradecane-1-ol, pentadecane-1-ol, hexadecan-1-ol, heptadecane-1-ol, octadecane-1-ol, and nonadecan-1-ol. Examples of such amines include 1-methyl-1-phenylpropane, ...

[0076] (Non-water-soluble glycol ether organic solvent) A water-insoluble glycol ether-based organic solvent may be contained in water as the cleaning liquid usable in step 1. The water-insoluble glycol ether-based organic solvent is preferably an aqueous cleaning liquid containing 20% ​​by weight or less of the water.

[0077] Examples of the water-insoluble glycol ether organic solvent include aromatic glycol ethers.

[0078] (Aromatic glycol ether solvent) As a cleaning liquid that can be used in step 1, water containing an aromatic glycol ether solvent can be used. Examples of 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 ester glycol ethers 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 them, ethylene glycol monophenyl ether (phenoxyethanol) is more preferable.

[0079] (Water-soluble alcohol) As a cleaning liquid that can be used in step 1, water containing a water-soluble primary alcohol can be used. Examples of the water-soluble primary alcohol include methanol, ethanol, and propan-1-ol, and an arbitrary mixture of these can also be used as an industrial alcohol. The water-soluble primary alcohol is preferably contained in an amount of 20% by weight or more relative to the water.

[0080] (Water-soluble glycol ether organic solvent) A water-soluble glycol ether-based organic solvent may be added to water as a cleaning liquid that can be used in step 1. The water-soluble glycol ether-based organic solvent is preferably an aqueous cleaning liquid that contains 20% by weight or more of the water.

[0081] An example of the water-soluble glycol ether organic solvent is alkylene glycol alkyl ether.

[0082] (Water-soluble alkylene glycol alkyl ether solvent) R 1 -O-[CH2-CH(X)-O]n 1 -R 2 (4) (In general formula (4), R 1 represents an alkyl group having one or more carbon atoms, R 2 represents an alkyl group having one or more carbon atoms or hydrogen, 1 represents an integer of 1 to 3, and X represents hydrogen or a methyl group. Among the alkylene glycol alkyl ethers represented by the general formula (4), water-soluble alkylene glycol alkyl ethers are more preferred.

[0083] Examples of the alkylene glycol alkyl ether represented by the 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 monobutyl 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 alkylene glycol alkyl ethers can be used alone or in appropriate combination of two or more, and can also be used by mixing with water. There is no particular problem if the content of alkylene glycol alkyl ether is 20% by weight or more, but when water is the medium, it is preferably 30% by weight or more, and most preferably 40% by weight or more. On the other hand, the upper limit may be 100% by weight, but it is preferable to use water as the medium from the viewpoint of environmental impact and safety.

[0084] Among the water-soluble alkylene glycol alkyl ethers represented by the general formula (4), the alkylene glycol monoalkyl ethers represented by the general formula (5) are more preferred.

[0085] R 2 -O-[CH2-CH(X)-O]n 2 -H (5) (In general formula (5), R 2 represents an alkyl group having one or more carbon atoms, 2 represents an integer of 1 to 3, and X represents hydrogen or a methyl group. Examples of the water-soluble alkylene glycol alkyl ether represented by general formula (5) include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl 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, 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.

[0086] Furthermore, in an aqueous cleaning solution containing a water-soluble alkylene glycol alkyl ether represented by the general formula (5), the water content is much higher than 50% by weight, and therefore the aqueous cleaning solution can maintain its stripping properties. 2 is an alkyl group having 3 or more carbon atoms, n 2 1~3, X 2 is preferably hydrogen or a methyl group.

[0087] Specific examples 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, propylene glycol monobutyl ether, etc. These alkylene glycol alkyl ethers can be used alone or in appropriate combination of two or more, and can also be used by mixing with water.

[0088] Among these, diethylene glycol monobutyl ether, ethylene glycol mono-tert-butyl ether, and propylene glycol monopropyl ether are particularly preferred from the standpoints of environmental characteristics, flammability, and antifoaming properties.

[0089] (Water-soluble monoalkanolamine organic solvent) A water-soluble alkanolamine organic solvent may be contained in water as a cleaning liquid that can be used in step 1. The water-soluble alkanolamine organic solvent is preferably an aqueous cleaning liquid containing 20% ​​by weight or more of the water.

[0090] The primary or secondary monoalkanolamine having a boiling point of 150 to 200° C. may be contained in an amount of 10% by weight to 50% by weight based on the total amount of the cleaning liquid.

[0091] Examples of primary monoalkanolamines include monoethanolamine, 2-aminoisobutanol, isopropanolamine, etc., and examples of secondary monoalkanolamines include N-methylethanolamine, 2-ethylaminoethanol, dimethylaminoethanol, etc., but primary and secondary monoalkanolamines other than those exemplified can also be used as appropriate as long as they have a boiling point within the range of 150 to 200° C. Furthermore, these monoalkanolamine compounds can be used alone or in appropriate combination of two or more, and can also be used by mixing with water.

[0092] (Antifoaming agent) The water used in step 1 may contain an antifoaming agent. In step 1, a large amount of bubbles may be generated during the stirring and crushing steps, and if the bubbles remain, they may overflow during the plastic film recovery step. In addition, in the plastic film crushing step, if a large amount of bubbles are caught in the cleaning liquid, the plastic substrate may not be crushed to the desired size.

[0093] Compounds commonly used as defoaming agents include water-soluble organic solvents and nonionic surfactants with an HLB value in the range of 1 to 3, but silicone compounds are particularly preferred because of their high defoaming ability. Among these, emulsion-type and self-emulsifying silicone compounds are preferred.

[0094] Specific examples of self-emulsifying defoamers include X-50-1176, KS-530, and KS-537 manufactured by Shin-Etsu Chemical Co., Ltd., and examples of emulsion defoamers include KM-7750D, KM-7752, and KM-98 manufactured by Shin-Etsu Chemical Co., Ltd., and FS Antifoam 025, FS Antifoam 80, FS Antifoam 92, FS Antifoam 93, DKQ1-1183, and DKQ1-1247 manufactured by Nagase Chemspec Corporation, but are not limited to these.

[0095] The antifoaming agent may be used alone or in combination of two or more kinds. The content of the antifoaming agent in the cleaning liquid usable in step 1 is preferably in the range of 0.01 to 5 wt %, more preferably in the range of 0.02 to 4 wt %, and further preferably in the range of 0.03 to 3 wt %.

[0096] (liquid temperature) The temperature of the water or cleaning solution used in step 1 is not particularly limited as long as the liquid state can be maintained, but it is usually preferable to carry out the step at a liquid temperature of 15 to 90°C. When using an aqueous cleaning solution in which a surfactant or the like has been added to water, it is preferable to adjust the liquid temperature according to the type of surfactant. The optimal temperature at which the cleaning effect is excellent varies depending on the type of surfactant, but is, for example, preferably 40°C or higher, preferably 65°C or higher, and preferably 85°C or higher. On the other hand, when it is desired to improve the crushability of the plastic film, i.e., to crush the plastic film into smaller pieces, it is preferable that the liquid temperature is not too high, and therefore, it is preferably 40° C. or less, preferably 30° C. or less, and more preferably 20° C. or less. The smaller the size of the plastic film after crushing, the larger the cross-sectional area becomes, so that in step 2, each layer constituting the plastic film becomes easier to swell into a single layer.

[0097] <About step 2> The method for separating and recovering plastic films of the present invention includes step 2 of immersing the plastic film crushed in step 1 in a cleaning solution. In step 2, each layer constituting the plastic film and the ink layer can be easily swollen.

[0098] (Soaking time) In step 2, the immersion time is preferably a time for which the crushed plastic film is sufficiently swollen, and specifically, is preferably 30 minutes or more. More specifically, it is within the range of 30 minutes to 48 hours. If the lower limit is less than 30 minutes, it becomes difficult to achieve sufficient swelling in step 2. On the other hand, if the upper limit exceeds 48 hours, the separation and recovery of the present invention takes too much time. Note that swelling of the plastic film means that the ink layer provided on the plastic film, and if an adhesive layer is present, the adhesive layer and / or the ink layer swell, and the cross-sectional thickness of the plastic film increases.

[0099] The immersion time can be adjusted appropriately by combining the liquid temperature and agitation described below. The higher the liquid temperature, the shorter the immersion time. When building a practical recycling system, it is preferable to increase the liquid temperature and set the upper limit of the immersion time to about 4 hours. For example, if the immersion is performed at room temperature, sufficient swelling can be achieved by immersing for 24 hours or more. If the liquid temperature is 40°C, sufficient swelling can be achieved by immersing for 16 hours. If the liquid temperature is 75°C, sufficient swelling can be achieved by immersing for 2 hours.

[0100] (temperature) In step 2, the temperature of the cleaning liquid is not particularly limited as long as the liquid state can be maintained. If the liquid temperature is room temperature, heating is not required, which is preferable since it contributes to reducing CO2 emissions. On the other hand, if efficiency is prioritized as a practical recycling system, a method of shortening the immersion time while heating the liquid temperature is also preferable. That is, it is usually preferable to carry out the process at a liquid temperature of 15 to 90°C. When using an aqueous cleaning liquid in which a surfactant or the like is added to water, it is preferable to adjust the liquid temperature according to the type of surfactant. The optimal temperature at which the cleaning effect is excellent varies depending on the type of surfactant, but is preferably 40°C or higher, preferably 50°C or higher, and preferably 60°C or higher. The upper limit of the liquid temperature is not particularly limited as long as the liquid state can be maintained, but is usually preferably 90°C or lower.

[0101] On the other hand, when it is desired to improve the crushability of the plastic film, that is, to crush the plastic film into smaller pieces, it is preferable that the liquid temperature is not too high, and therefore, it is preferably 40° C. or less, preferably 30° C. or less, and more preferably 20° C. or less. The smaller the size of the plastic film after crushing, the larger the cross-sectional area becomes, so that each layer constituting the plastic film becomes easier to separate into single layers in step 3, and the ink layer becomes easier to peel off and decolorize.

[0102] (stir) In step 2, stirring is not essential and is optional, but stirring allows for more efficient swelling. It is preferable to keep the stirring speed at a level that does not easily cause foaming or the like even without adding an antifoaming agent.

[0103] The equipment and method for stirring when stirring are not particularly limited, and known methods can be used. Specifically, there are devices equipped with a motor with stirring blades that can stir the cleaning liquid in a container, devices equipped with a device that generates ultrasonic waves, devices that can shake the container, wet crushers, etc. The wet crusher can be the same as the crusher described in step 1.

[0104] (Cleaning solution) The washing liquid used in step 2 may be the same as that used when using the wet crusher in step 1. Specifically, it is preferable that the washing liquid contains water and the inorganic base described in step 1, and it is also preferable to use a washing liquid containing water and the inorganic base described in step 1 and further containing the surfactant described in step 1.

[0105] The cleaning solution used in step 2 preferably contains an appropriate amount of an organic solvent. As the organic solvent, for example, it is preferable to use a water-soluble solvent that is miscible with water, and specifically, the water-soluble solvent preferably contains one or more water-soluble alcohols or water-soluble solvents having a flash point of 21° C. or higher. By using a water-soluble solvent in the cleaning solution, hydroxide ions generated from the inorganic base contained in the cleaning solution are less likely to be hydrated, so that the nucleophilicity of the hydroxide ions is increased, and the reaction for peeling the ink layer can be advanced in a hydrophobic field environment, which is effective for peeling the ink film.

[0106] The water-soluble solvent having a flash point of 21°C or higher is preferably a water-soluble organic solvent that falls under the second and third petroleum classes defined in the Fire Service Act, such as diethylene glycol butyl ether, propylene glycol propyl ether, or 3-methoxy-3-methyl-1-butanol.

[0107] Examples of water-soluble alcohols include alcohols specified in the Fire Service Act, such as methanol, ethanol, 1-propyl alcohol, and 2-propyl alcohol, which may be used alone or in combination.

[0108] The organic solvent may preferably contain the water-insoluble alcohol or water-insoluble glycol ether organic solvent described in the above step 1. Among them, butan-1-ol, benzyl alcohol, and ethylene glycol monophenyl ether (phenoxyethanol) are particularly preferred.

[0109] In step 2, the plastic film crushed in step 1 is sufficiently swollen, so that the plastic film can be easily peeled off completely into a single layer in step 3. In particular, when the plastic film has an ink layer, it can be difficult to decolorize the plastic depending on the type of ink and the configuration of the plastic film, but in the present invention, by carrying out steps 1 and 2, at least a part of each layer of the plastic film is peeled off or a base that facilitates peeling is created, and in step 3 described below, the plastic film is separated into single layers and the ink layer is peeled off, so that the ink layer can be easily peeled off regardless of the type of ink or the configuration of the plastic film.

[0110] In particular, from the viewpoint of peelability of the ink layer, it is preferable for the cleaning solution used in step 2 to contain a large amount of water-soluble solvent in the cleaning solution; specifically, the water-soluble solvent is preferably 30% by mass or more, preferably 40% by mass or more, preferably 50% by mass or more, preferably 60% by mass or more, preferably 70% by mass or more, preferably 80% by mass or more, preferably 90% by mass or more, and preferably 95% by mass or more.

[0111] In particular, the cleaning solution used in step 2 includes inorganic bases, specifically sodium hydroxide and potassium hydroxide. These inorganic bases are preferably contained at a concentration of 0.1 to 10% by weight, more preferably 0.1 to 5% by weight, based on the total amount of the ink cleaning solution. The pH is preferably 10 or more, more preferably 11 or more, and more preferably 12 or more. Since sodium hydroxide is poorly soluble in organic solvents, it is preferable to use a cationic surfactant in combination when sodium hydroxide is used. Specifically, a cleaning 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 can be used. On the other hand, when potassium hydroxide is used, it is not necessary to use a cationic surfactant in combination because it is easily soluble in organic solvents. Specifically, a cleaning solution containing potassium hydroxide and a water-soluble alcohol or an aromatic glycol ether solvent can be used.

[0112] Furthermore, the cleaning solution used in step 2 may contain water. By containing water in the cleaning solution in step 2, the operational stability and environmental stability in step 2 can be improved.

[0113] In addition, the cleaning solution used in step 2 may contain a surfactant. The surfactant is not particularly limited, and known surfactants can be used, such as anionic surfactants, nonionic surfactants, amphoteric surfactants, cationic surfactants, etc. Specific types of these surfactants can be the same as those described as surfactants that can be contained in water in step 1. In the cleaning solution of step 2, the surfactant may be used alone or in combination of two or more kinds. The amount of the surfactant added is preferably 5% by weight or less, and more preferably 2% by mass or less, based on the total amount of the cleaning solution. The lower limit of the surfactant is not particularly limited and may be 0% by mass, but when a surfactant is contained, it is preferably 0.01% by mass or more.

[0114] <About step 3> The method for separating and recovering a plastic film of the present invention includes, after steps 1 and 2, a step 3 of agitating the crushed and swollen plastic film in a rinsing liquid to separate the plastic film.

[0115] (Rinse) The rinse liquid used in step 3 contains at least a water-soluble solvent. Specifically, the water-soluble solvent preferably contains one or more water-soluble alcohols or water-soluble solvents having a flash point of 21° C. or higher. The use of a water-soluble solvent in the rinse liquid is effective in peeling off the ink film on the surface of the plastic film piece after step 3.

[0116] The water-soluble solvent having a flash point of 21° C. or more is preferably a water-soluble solvent among organic solvents that fall under the second and third petroleum classes defined in the Fire Service Act. Specific examples of the second and third petroleum classes include 3-methoxy-3-methyl-1-butanol, diethylene glycol monobutyl ether, and propylene glycol propyl ether.

[0117] Examples of water-soluble alcohols include alcohols specified in the Fire Service Act. Specific examples of alcohols include methanol, ethanol, 1-propyl alcohol, 2-propyl alcohol, etc., and industrial ethanol containing these may be used alone or in combination.

[0118] It may also contain a cleaning liquid used when using the wet crusher in step 1. For example, it may preferably contain the water-insoluble alcohol or water-insoluble glycol ether organic solvent described in step 1 as the organic solvent. Among them, butan-1-ol, benzyl alcohol, and ethylene glycol monophenyl ether (phenoxyethanol) are particularly preferred.

[0119] In particular, from the viewpoint of peelability of the ink layer, the rinsing liquid used in step 3 preferably contains a large amount of so-called water-soluble solvents, including alcohols, in the cleaning liquid; specifically, the water-soluble solvent is preferably 30% by mass or more, preferably 40% by mass or more, preferably 50% by mass or more, preferably 60% by mass or more, preferably 70% by mass or more, preferably 80% by mass or more, preferably 90% by mass or more, and preferably 95% by mass or more.

[0120] In step 3, when a rinse solution mainly made of a water-soluble solvent containing an alcohol without intentionally mixing water is used, an inorganic salt can be used.

[0121] (Inorganic salts) The inorganic salt used in the present invention may be any salt that can be used as a grinding aid, and is not particularly limited. However, from the viewpoint of removing the inorganic salt in a later step, it is preferable that the inorganic salt is water-soluble to the extent that 10 g or more dissolves in 100 g of water at room temperature. It is also preferable that the inorganic salt is insoluble to the extent that only 10 mg or less dissolves in 100 g of the above-mentioned water-soluble organic solvent at room temperature, and it is more preferable that the inorganic salt is substantially insoluble in the organic solvent. Specifically, sodium chloride, potassium chloride, calcium chloride, sodium sulfate, potassium sulfate, aluminum sulfate, etc. are mentioned, and sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate are more preferable. The above-mentioned inorganic salts can be used alone or in combination of two or more kinds.

[0122] When an inorganic salt is used as a grinding aid, the amount of the inorganic salt is preferably 100 to 2000 mass %, more preferably 300 to 1500 mass %, relative to 100 of the plastic film. The amount of the rinsing liquid is 5000 to 50000 mass %, preferably 10000 to 40000 mass %, relative to 100 of the plastic film. The more the amount of inorganic salt relative to the plastic film, the higher the peeling effect of the ink layer, and the smaller the amount of solvent in this case, the higher the effect.

[0123] When an inorganic salt is used as a grinding aid, the treatment temperature is preferably 1500° C. or lower, particularly preferably 20 to 100° C. The treatment time is preferably about 10 minutes to 3 hours.

[0124] The device for kneading the mixture of the plastic film pieces, inorganic salt (grinding aid), and water-soluble organic solvent that has been through step 2 may be any device capable of mechanically grinding the plastic film pieces, and a specific example is a kneader. In addition, a paint shaker, a paint conditioner, a batch type kneader such as Kawata's Super Mixer, Nippon Coke's FM Mixer, Attritor, and Inoue Seisakusho's Trimix, and a continuous kneader such as Asada Iron Works' KCK Mill can also be used. Devices other than these can also be used.

[0125] (stir) In step 3, the equipment and method for stirring when stirring are not particularly limited, and known methods can be used. Specifically, examples include an apparatus equipped with a motor with stirring blades that can stir the cleaning liquid in a container, an apparatus equipped with a device that generates ultrasonic waves, an apparatus that can shake the container, a kneader, a wet crusher, etc. The wet crusher may be the same as the crusher described in step 1.

[0126] Step 3 preferably includes a step of passing the plastic film crushed in step 1 through a clearance of 30 mm or less. The clearance is more preferably 20 mm or less, and even more preferably 10 mm or less. By passing through a clearance of 10 mm or less, a high shear force can be applied to the plastic film, which has the effect of, for example, rubbing off the ink from a plastic film where an ink layer is provided exposed, or applying a shear stress to a plastic film where an ink layer is provided between multiple films, and can promote peeling of the laminate.

[0127] Since the wet crusher has a crushing mechanism using fixed blades and rotating blades, the clearance can be easily controlled by the operating conditions. The narrower the clearance, the higher the shear force that can be applied to the plastic film, but the narrower the clearance, the more likely the plastic film will become clogged and the faster the temperature of the water or cleaning liquid will rise, so it is preferable that the clearance is 0.1 mm or more.

[0128] Specifically, the clearance through which the plastic film passes is provided by a method of providing a clearance of a predetermined size or less and applying high shear. For example, the size gap between the inner wall of the tank of the treatment tank in which the plastic film and / or water are stirred and the stirring blade is controlled to a predetermined size or less, a baffle plate is installed at a distance of a predetermined size or less from the tank wall, the plastic film and / or water is designed to pass through a screen having holes with a diameter of a predetermined size or less, the plastic film and / or water is passed between two rolls with a gap of a predetermined size or less, the laminate is sandwiched between the media using a ball mill or the like to collide with each other, and the gap between the rotary blade and the fixed blade is controlled to a predetermined size or less by providing a fixed blade on the outside of the rotary blade as in a homogenizer.

[0129] The shear rate in step 3 is 2,000 s -1 The higher the shear rate, the greater the effect of rubbing off the ink from the plastic film and the greater the effect of applying shear stress to the plastic film in which the ink layer is provided between multiple films, so there is no upper limit.

[0130] The shear rate (D) is defined by the following formula. D=v / Δy v: flow velocity (m / s), calculated as v = π × R × (n / 60) π: Pi R: diameter of the rotary blade (m) n: Rotating blade speed (rpm) Δy: Clearance (m), here referring to the gap (m) between the rotating blade and the fixed blade.

[0131] The larger the diameter of the fixed blade of the wet crusher, the higher the flow rate, so the larger the fixed blade of the wet crusher is, the more preferable it is. The narrower the clearance, the higher the shear rate, so the narrower the clearance, the more preferable it is.

[0132] The blade design of the fixed blade and the rotary blade is preferably such that at least some of the blades are arranged in a radial direction, and the blades arranged in a radial direction are preferably inclined at an angle of 2 to 60 degrees from the radial direction, more preferably 5 to 45 degrees.

[0133] When a plurality of blades are arranged on the rotary blade, the blade width of the rotary blade is preferably 0.5 to 5.0 mm, the groove width between the blades is preferably 0.5 to 5.0 mm, and the blade height is preferably 1.0 to 5.0 mm.

[0134] The Froude number (Fr) of stirring in step 3 is preferably 10 or more. The faster the Froude number of stirring, the greater the effect of rubbing off the ink from the plastic film and the greater the effect of applying shear stress to the plastic film in which the ink layer is provided between multiple films, so there is no upper limit.

[0135] The Froude number (Fr) of stirring is defined by the following formula: Fr = {(n / 60) 2}×R / g n: Rotating blade speed (rpm) R: diameter of the rotary blade (m) g:Gravity acceleration=9.8(m / s 2 ) Since step 3 is a step of peeling off adhesive and ink layers from the plastic film swollen in water, it is preferable to use a wet crusher that can provide high shear force and / or high friction force. Examples of such wet crushers include the KD series from Husqvarna Zenoah, the Suncutter series from Nikuni, the Disintegrator series from Furukawa Industrial Machinery Systems, the Ink Crusher series and Refiner from Aikawa Iron Works, the Scatter from Sanwa Hydrotech, the Trigonal from Nippon Coke Company, the alkali cleaning / cleaning deinking equipment from Nippon Seam, and the Scissors Cutter series cleaning and crushing machines.

[0136] Since the purpose of step 3 is to remove ink particles remaining on the surface layer of the plastic film, known dispersing equipment using media such as beads or rods can be used. Examples of dispersing equipment with media include dispersers, dispersing equipment with stirring blades such as turbine blades, paint shakers, roll mills, ball mills, vibration mills, attritors, sand mills, and bead mills.

[0137] The diameter of the media used is preferably 0.5 to 20 mm, more preferably 1 to 10 mm, and further preferably 2 to 5 mm. Materials of the media include steel, zirconia, alumina, glass, etc., and can be appropriately selected depending on the properties of the rinsing liquid selected. If the media diameter is less than 0.2 mm, it is difficult to handle and difficult to recover the media, and if it exceeds 5 mm, it is easy to handle. The residence time in the disperser is preferably 1 to 30 minutes.

[0138] Examples of the media-containing dispersing machine include Star Mill manufactured by Ashizawa Finetech Co., Ltd., MSC-MILL, SC-MILL, and Attritor MA01SC manufactured by Mitsui Mining Co., Ltd., Apex Mill manufactured by Hiroshima Metal & Machinery Co., Ltd., Vibration Mill manufactured by Chuo Kakoki Co., Ltd., Nano Grain Mill, Pico Grain Mill, Pure Grain Mill, Mega Capper Grain Mill, Cera Power Grain Mill, Dual Grain Mill, AD Mill, Twin AD Mill, Basket Mill, and Twin Basket Mill manufactured by Asada Iron Works, and Apex Mill, Ultra Apex Mill, and Super Apex Mill manufactured by Kotobuki Industries Co., Ltd.

[0139] The stirring time in step 3 is not particularly limited as long as the entire plastic film can be rinsed with the rinse liquid. Although it varies depending on the stirring equipment and method used, in order to thoroughly rinse, it is preferably 1 minute or more, more preferably 3 minutes or more, and more preferably 5 minutes or more. On the other hand, the upper limit of the stirring time is not particularly limited, but it is preferably 60 minutes or less, and more preferably 30 minutes or less.

[0140] (Ink removal rate) The ink removal rate of the plastic film after step 3 is preferably 50% or more, more preferably 75% or more, and particularly preferably 90% or more.

[0141] Ink removability is measured as follows.

[0142] After the third step, the film is washed and dried, and the ink removal rate of the printed portion is determined by calculating the area through image processing of a photograph taken with an optical microscope, and then calculating the ink removal rate using the following formula. The ink removal rate is preferably 50% or more, more preferably 75% or more, and particularly preferably 90% or more. Ink removal rate (%) = (1 - ink-adhered area after cleaning / ink-adhered area before cleaning) x 100 (Surface roughness) The surface roughness of the plastic film pieces after step 3 is preferably 0.7 μm or more. By using the above-mentioned wet crushing equipment to make the surface roughness of the crushed material 0.7 μm or more, the plastic film laminate can be separated into single layers, and not only the ink layer provided on the surface of the plastic film laminate but also the ink layer provided between the laminates can be removed, so that the collected crushed material is suitable as a raw material for producing high-quality recycled plastic.

[0143] The surface roughness of the crushed material is preferably 0.7 μm or more, more preferably 0.8 μm or more, and even more preferably 0.9 μm or more. On the other hand, the upper limit is not particularly limited and can be appropriately adjusted depending on the conditions of the wet crushing equipment.

[0144] The surface roughness of the film is determined by measuring the surface roughness Sa of a 500 μm x 600 μm area using a white light interference microscope manufactured by Ryoka Systems Co., Ltd. Sa is not a value determined from a cross section like Ra, but is a value that indicates the entire area of ​​the surface, so it has a wider evaluation range and can evaluate the overall surface roughness.

[0145] (Size of film piece) The size of the plastic film pieces after step 3 is preferably 20 mm or less in the long side direction, more preferably 10 mm or less, and even more preferably 5 mm or less. Also, the length in the short side direction is preferably 20 mm or less, preferably 10 mm or less, preferably 5 mm or less, and preferably 3 mm or less. There is no particular lower limit on the size of the crushed material, but if it is too small, recovery is reduced, so the length in the long side direction is preferably 1 mm or more. (Surface area ratio of film pieces after process 1 and process 3) If the surface area of ​​the film after step 1 is 1, the surface area after step 3 is preferably at least 1 or less, more preferably 0.9 or less, and even more preferably 0.8 or less. Since step 3 is a step for washing the film surface, the smaller the film is during washing than its original size, the better the film has been rubbed and washed.

[0146] (Collection equipment) The crushed plastic material separated into single layers in step 3 can be collected as a single layer. The equipment and method for collecting the crushed plastic material are not particularly limited, but for example, a filter, a centrifuge, an automatic scraping bar screen, an inclined wire screen, a rotating drum screen, etc. can be used.

[0147] (Plastic film) The plastic film separated and recovered by the present invention is a plastic film having at least an ink layer. Any plastic film can be separated and recovered, including plastic films with an ink layer exposed on the film surface (front-printed), laminated films with an ink layer provided between multiple films (reverse-printed), single-layer films and laminated films generally distributed as packaging materials for food packaging and daily necessities, and plastic films with various types of resin layers discarded by recycling. In other words, the separation and recovery method of the present invention is characterized in that it does not require re-sorting and can be treated together.

[0148] Furthermore, for containers such as PET bottles, shrink labels, which are laminated films formed into a cylindrical shape, are used to display the product name, etc., and to add decorativeness. When recycling, consumers often peel off the shrink label and discard the PET bottle body and the shrink label separately. However, with the separation and recovery method of the present invention, even if the PET bottle body and the shrink label are integrated, the shrink label can be separated from the PET bottle body, and the shrink label can be separated into each single-layer film.

[0149] A laminated film laminated with a reactive adhesive often has an adhesive layer made of the reactive adhesive laminated between at least two resin film layers or metal foil or vapor-deposited film layers. Specifically, in the laminated film, if the resin film layer is represented as (F), the metal foil layer of the metal foil or vapor-deposited film layer is represented as (M), and the adhesive layer of the reactive adhesive or the like is represented as (AD), the following configurations are considered as specific embodiments of the laminated film, but are of course not limited thereto. (F) / (AD) / (F), (F) / (AD) / (F) / (AD) / (F), (F) / (AD) / (M) / (AD) / (F), (F) / (AD) / (M), (F) / (AD) / (M) / (F), (F) / (AD) / (F) / (AD) / (M) / (AD) / (F), (F) / (AD) / (M) / (AD) / (F) / (AD) / (F), (M) / (AD) / (F) / (AD) / (M), (AD) / (F) / (AD) / (M), (AD) / (F) / (AD) / (F) / (AD), etc.

[0150] (Coat layer) The outermost surface of the laminated film structure may have a functional coating layer. The coating layer may be colorless or colored. The coating layer may be provided in contact with the substrate, or may be provided via an inorganic deposition layer or the like in contact with the substrate. The coating layer may be in a form in which different coating layers are laminated. There is no particular restriction on the thickness of the coating layer, but it is preferably 0.1 μm or more and 100 μm or less, more preferably 0.1 μm or more and 10 μm or less, and even more preferably 1 μm or more and 5 μm or less.

[0151] Functional coating layers are formed for various purposes. Representative functions are wide-ranging, including hard coating, silicone-based peeling, IR cut, waterproof and moisture-proof, antibacterial, UV cut, heat dissipation, photocatalysis, weather resistance, anti-fogging, fingerprint and stain resistance, self-repair, water and oil repellency, etc.

[0152] The laminated film which is the subject of this separation and recovery method may further have a paper layer, an oxygen absorbing layer, an anchor coat layer, an ink layer, a removable primer layer provided to facilitate the peeling of the ink, etc.

[0153] (Primer layer) The printing ink is printed on a resin film that will become the base film layer (F1) of the laminated film, and then the reactive adhesive is applied to the printed surface, which is then laminated with another base film (F1), a sealant layer (F2), a metal foil, or a metal foil layer (M) of a vapor-deposited film layer to form a laminated film. In a laminated film having this layer structure, a primer layer can be preferably provided on the base film layer (F1) that will become the printed surface. The primer layer preferably contains a resin having an acidic group, since it is easily dissolved or hydrolyzed by an alkaline solution, and the laminated film that has been printed with the ink and then laminated with the adhesive can be easily separated into a single layer film.

[0154] The primer may be provided on the sealant layer (F2), or may be provided on both F1 and F2. When the primer is provided on both F1 and F2, the films can be more easily separated into a single layer film.

[0155] For the primer layer, a resin having an acidic group or a low molecular weight compound can be used alone. In addition, a resin having an acidic group or a low molecular weight compound can be mixed with a resin having no acidic group. Examples of the resin having an acidic group include resins having an acid value such as rosin-modified maleic acid resins and rosin-modified fumaric acid resins, radical copolymers such as (meth)acrylic resins, styrene-(meth)acrylic resins, styrene-(anhydride)maleic acid resins, and terpene-(anhydride)maleic acid resins, which are copolymerized with polymerizable monomers having an acidic group, such as polymerizable monomers having a carboxyl group, such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, cinnamic acid, or their acid anhydrides, polymerizable monomers having a sulfonic acid group, such as sulfonated styrene, and polymerizable monomers having a sulfonamide group, such as vinylbenzenesulfonamide, and acid-modified polyolefin resins, which can be used singly or in a mixture of a plurality of them.

[0156] The primer layer may be made by mixing a resin having a low acid value and film-forming properties at room temperature with one or more low molecular weight compounds having an acidic group.

[0157] Examples of low molecular weight compounds having an acidic group 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 singly or in combination.

[0158] 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, mellitic 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 pyruvic acid 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 singly or in combination.

[0159] The resin having film-forming properties at room temperature includes various synthetic resins, such as polyester, polyvinyl chloride, copolymers of vinyl chloride and other unsaturated double bond-containing monomers, homopolymers of (meth)acrylic acid esters, copolymers of (meth)acrylic acid esters and other unsaturated double bond-containing monomers, copolymers of polystyrene or styrene monomers and other unsaturated double bond-containing monomers, ketone-formaldehyde condensates and hydrogenated products thereof, polyfunctional epoxy resins, polyvinyl acetals, polyurethanes, etc. These can be used alone or in combination of one or more selected from these. Examples of polyfunctional epoxy compounds include bisphenol A novolac epoxy resins, bisphenol F novolac epoxy resins, bisphenol S novolac epoxy resins, biphenyl epoxy resins, and naphthalene epoxy resins.

[0160] When a single or multiple low molecular weight compounds having acidic groups are mixed with the resin having a low acid value and film-forming properties at room temperature, the amount of the compound added may be appropriately determined within a range that does not impair the printability or coatability of the primer solution, but is preferably in the range of 0.5 to 50% by weight, more preferably 1.0 to 30% by weight, based on the solid content of the primer solution.

[0161] When the printed material is, for example, polypropylene (PP), the film-forming resin is preferably at least one thermoplastic resin that is solid at 50°C and is selected from the group consisting of ketone-formaldehyde condensates and hydrogenated products thereof, polyester, vinyl chloride-vinyl acetate copolymer, and polyvinyl acetal, which have good adhesion to PP. Examples of such ketone-formaldehyde condensates and hydrogenated products thereof include the TEGO (registered trademark) VariPlus series (SK,A) from Evonik Degussa Japan Ltd. Examples of vinyl chloride-vinyl acetate copolymers include the Solvine (registered trademark) series (Solvine AL, etc.) manufactured by Nissin Chemical Industry Co., Ltd.; and examples of polyvinyl acetals include the S-LEC (registered trademark) series (S-LEC KS-10, etc.) manufactured by Sekisui Chemical Co., Ltd.

[0162] To form a primer layer on a substrate, a solution prepared using each of the above components is applied to the substrate and dried. The amount of coating is about 0.1 to 5 μm (dry thickness), but if it is less than 0.1, it is difficult to apply uniformly, and if it exceeds 5 μm, it is uneconomical and not practical. Coating is performed by a normal coating method, such as gravure, letterpress, flexography, roll coater, reverse coater, spray method, etc. The formation of the primer layer and printing thereon may be performed continuously (in-line), or the formation of the primer layer and printing may be performed separately.

[0163] When printing is performed immediately after in-line primer coating using a printer such as roll-to-roll, the printed surface may stick to the back surface of the substrate, a phenomenon known as blocking, depending on the resolubility of the resin used in the primer layer in the ink solvent and the glass transition point (Tg) of the resin itself. To prevent such blocking, transparent particles with a particle size of 0.1 μm to 10 μm such as silica or titanium oxide may be mixed into the primer solvent as an anti-blocking agent at a ratio of about 0.005 to 5% of the total amount of primer.

[0164] In addition, in order to prevent blocking, the resin solution with a high acid value used in the primer may be neutralized with ammonia or the like before application, thereby preventing re-dissolution in the solvent contained in the printing ink.

[0165] The acid value of the compound having an acidic group is not particularly limited, but is preferably 50 mgKOH / g or more, more preferably 100 mgKOH / g or more, and even more preferably 150 mgKOH / g or more.

[0166] In the case of laminated films using the aforementioned primer layer, if the printing design is based on white, the ink layer will mostly consist of white ink, and the film laminated with the adhesive may be difficult to peel off at low temperatures or with a low-concentration alkaline solution. In such cases, the peelability of the ink layer can be improved by introducing a medium layer used in printing ink between the primer layer and the white ink layer, or between the white ink layer and the adhesive layer.

[0167] In the present invention, when the laminate film is a laminate film laminated with a reactive adhesive, it is preferable that the reactive adhesive contains a compound having an acidic group. Also, when the laminate film is a laminate film laminated with a reactive adhesive and has an ink layer and / or a primer layer, it is preferable that at least one layer of the reactive adhesive, the ink layer, and the primer layer contains a compound having an acidic group. If any one of the layers contains a compound having an acidic group, separation and recovery proceeds more easily.

[0168] Among these, it is preferable that any of the components of the reactive adhesive has an ester bond, since it is easily dissolved or hydrolyzed by an alkaline solution, and the adhesive can be easily separated into a monolayer film in a short time in the above steps 2 and 3. Specific examples of the reactive adhesive having any of the components thereof having an ester bond include reactive adhesives containing either or both of a polyol composition having a polyol compound such as a polyester polyol, a polyether ester polyol, a polyester (polyurethane) polyol, or an acrylic polyol having an ester bond, and a polyisocyanate composition having a polyisocyanate compound that is a reaction product between the polyol compound having an ester bond and the above various polyisocyanates.

[0169] In addition to the polyol composition and the polyisocyanate composition, a reactive adhesive to which a resin having an acidic group or a low molecular weight compound is added can also be preferably used. As the resin having an acidic group or the low molecular weight compound, any resin or low molecular weight compound can be used without any particular limitation as long as it can be easily mixed with the polyol composition or the polyisocyanate composition, which are the main components of the reactive adhesive (in this case, a solvent described below may be used as necessary), and has an acid value.

[0170] Examples of the resin having an acidic group include resins having an acid value such as rosin-modified maleic acid resin and rosin-modified fumaric acid resin; radical copolymer resins such as (meth)acrylic resin, styrene-(meth)acrylic resin, styrene-maleic acid (anhydride) resin, and terpene-maleic acid (anhydride) resin, which are copolymerized with polymerizable monomers having an acidic group, such as polymerizable monomers having a carboxyl group, such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, cinnamic acid, or acid anhydrides thereof; polymerizable monomers having a sulfonic acid group, such as sulfonated styrene; and polymerizable monomers having a sulfonamide group, such as vinylbenzenesulfonamide; and acid-modified polyolefin resins. These may be used singly or in combination.

[0171] Examples of low molecular weight compounds having an acidic group include saturated fatty acids, unsaturated fatty acids, hydroxy acids, aromatic carboxylic acids, dicarboxylic acids, tricarboxylic acids, oxocarboxylic acids, carboxylic acid derivatives, and acid anhydrides, and these can be used singly or in combination.

[0172] 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, mellitic 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 pyruvic acid 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 singly or in combination.

[0173] The acid value of the resin or low molecular weight compound having an acidic group is not particularly limited, but is preferably 150 mgKOH / g or more.

[0174] As described above, the alkaline solution used in this separation and recovery method is presumed to act on the interface between the laminated film and the adhesive or printing ink, significantly reducing the adhesive strength, thereby causing interfacial peeling. On the other hand, since the solubility of the alkaline solution itself is high, the non-crosslinked printing ink layer also dissolves. Even if the printing ink layer itself is crosslinked, the present invention causes interfacial peeling, so it is presumed that efficient separation and recovery can be performed in a short time.

[0175] (Ink layer) The ink layer is, for example, a printing ink printed with an organic solvent-based printing ink, a water-based ink, or an active energy ray curable ink using a gravure printing machine, a flexographic printing machine, an offset printing machine, an inkjet printing machine, or the like. It may be an ink layer printed in multicolor using a plurality of ink types. In the present invention, the ink layer can be peeled off regardless of the type of ink by going through steps 1 and 2.

[0176] Printing inks to which resins or low molecular weight compounds having acidic groups have been added can also be preferably used. The resins or low molecular weight compounds having acidic groups can be used without any particular limitation as long as they can be easily mixed with the binder resin or organic solvent, which are the main components of the printing ink, and have an acid value.

[0177] As the resin or low molecular weight compound having an acidic group, the compounds described in the primer layer can be used.

[0178] The printing ink preferably contains the resin or low molecular weight compound having an acidic group. The amount of the compound added may be appropriately determined within a range that does not impair the printability of the printing ink, but is preferably in the range of 0.5 to 50% by weight, more preferably 1.0 to 30% by weight, based on the solid content of the printing ink.

[0179] The location where the ink layer is provided is not particularly limited. For example, the ink layer may be provided on the outermost layer of the laminated film, or may be provided between the resin film layer (F) and the adhesive layer (AD). When the ink layer is provided between the resin film layer (F) and the adhesive layer (AD) (reverse printing), the ink layer and the adhesive layer are more strongly bonded, making it more difficult to peel off the ink layer, but the method of the present invention can effectively peel off the ink layer even in the reverse printing configuration.

[0180] The ink layer may be a layer that displays any design, pattern, letter, symbol, etc., for the purpose of providing decoration or aesthetics, or displaying the contents, expiration date, manufacturer or seller, etc. The ink layer may be a solid ink layer that does not have a design, pattern, letter, symbol, etc. The method of forming the ink layer is not particularly limited, and the ink layer may be formed using a known pigment and / or dye. The ink layer may be formed preferably using a printing ink containing a pigment and / or dye. The ink layer may have a single layer structure or a multi-layer structure. The thickness of the ink layer is preferably 0.1 to 10 μm, more preferably 1 to 5 μm.

[0181] The ink layer may contain a pigment derivative and / or a resin-type dispersant as a dispersant for the colorant. These may be used alone, but it is preferable to use them in combination, since this improves the dispersion stability and the stability over time.

[0182] For example, when the plastic film has a structure of (F1) / INK / (AD) / (M) / (F2) or (F1) / INK / (AD) / (F2), the ink layer is present between the layers that make up the plastic film, and the ink layer and adhesive layer are more strongly bonded, making it difficult to separate them into a single layer and remove the ink layer. However, if the F2 film is partially peeled off in step 1, or F2 is crushed into a state in which it can be easily peeled off, the remaining layer structure can be easily peeled off in step 2, and the ink layer can be removed.

[0183] The resin film layer (F) can be classified according to the required role, and functions as a base film layer (F1) or a sealant layer (F2) that becomes a heat-sealed portion when forming a packaging material.

[0184] Examples of resin films that can be used as the base film layer (F1) include polyolefin films such as low-density polyethylene, high-density polyethylene, linear low-density polyethylene, OPP (biaxially oriented polypropylene), and CPP (non-oriented polypropylene), polyester films such as polyethylene terephthalate (PET) and polybutylene terephthalate, polyamide films such as nylon 6, nylon 6,6, and metaxylene adipamide (N-MXD6), biodegradable films such as polylactic acid, polyacrylonitrile films, poly(meth)acrylic films, polystyrene films, polycarbonate films, saponified ethylene-vinyl acetate copolymer (EVOH) films, polyvinyl alcohol films, and K-coats such as polyvinylidene chloride, as well as films containing pigments. Transparent deposition films in which alumina or silica is deposited on these films may also be used.

[0185] The surface of the film material may be subjected to various surface treatments such as flame treatment, corona discharge treatment, or chemical treatment using a desorption primer.

[0186] As the flexible polymer film to be the sealant layer (F2), preferred are polyolefin-based films such as polyethylene film, polypropylene film, ethylene-vinyl acetate copolymer, ionomer resin, EAA resin, EMAA resin, EMA resin, EMMA resin, biodegradable resin film, etc. In terms of generic names, CPP (unoriented polypropylene) film, VMCPP (aluminum-deposited unoriented polypropylene film), LLDPE (linear low-density polyethylene), LDPE (low-density polyethylene), HDPE (high-density polyethylene), VMLDPE (aluminum-deposited non-low-density polyethylene film) film, films containing these pigments, etc. The surface of the film may be subjected to various surface treatments such as flame treatment, corona discharge treatment, or chemical treatment such as desorption primer.

[0187] The thickness of the plastic film is preferably 5 μm or more and 200 μm or less, more preferably 10 μm or more and 100 μm or less, and further preferably 10 μm or more and 50 μm or less.

[0188] From the viewpoint of reuse as a recycled material, the base material is polyethylene, biaxially oriented polypropylene, etc. It is preferred that the film comprises a polyolefin resin such as Pyrene.

[0189] Examples of the metal foil layer (M) include foils of metals having excellent ductility, such as gold, silver, copper, zinc, iron, lead, tin and alloys thereof, steel, stainless steel, and aluminum.

[0190] The paper layer may be natural paper, synthetic paper, etc. The first and second sealant layers may be formed of the same materials as the sealant layers described above.

[0191] Other layers may contain known additives and stabilizers, such as antistatic agents, non-reactive adhesive layers, adhesion enhancing coating agents, plasticizers, lubricants, antioxidants, and the like.

[0192] <Particle size distribution of desorbed ink components> The median diameter (D50) of the ink components that have been removed is preferably 1 μm or more. By making the median diameter of the ink layer components that have been removed 1 μm or more, it is possible to suppress the ink components that have been removed from reattaching to the substrate, and to obtain a colorless recycled material. The median diameter of the ink components that have been removed is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and particularly preferably 20 μm or more.

[0193] The span value A of the detached ink component represents the particle size distribution width of the detached ink layer component, and the larger the value, the wider the particle size distribution width, and the more likely it is to contain fine ink layer components that are easily redeposited on the substrate. The span value A is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less. A span value of 10 or less is preferable because it can suppress redepositing of the detached ink layer.

[0194] In the present invention, the volume-based median diameter (D50) and span value A of the ink layer components detached from the plastic substrate layer are measured by a laser diffraction particle size distribution measuring device. The span value A is expressed by the following formula.

[0195] A = (D90-D10) / D50 D10: Cumulative 10% diameter of volume-based particle size distribution obtained by laser diffraction particle size distribution measurement of the desorbed ink components D90: Cumulative 90% diameter of volumetric particle size distribution obtained by laser diffraction particle size distribution measurement of the detached ink layer components <Manufacturing method of molding material> The recycled plastic film pieces recovered by the above-mentioned method for producing recycled plastic film are melt-kneaded to produce pellets for molding. In the melt-kneading process, various additives are added as necessary, and the mixture is mixed using a Henschel mixer, a tumbler, a disperser, or the like, and then mixed or dispersed using a kneader, a roll mill, a twin-screw extruder, a single-screw extruder, a rotor-type twin-screw kneader, or the like. This produces a recycled resin, which is a resin composition. The shape of the recycled resin is not particularly limited, and may be pellet-like, powder-like, granular, or bead-like. In the melt-kneading process, a twin-screw extruder is preferably used. The molding material may further contain a master batch. The master batch is not particularly limited as long as it has compatibility with the recycled resin, and generally, a mixture of a thermoplastic resin such as a polyethylene resin or a polypropylene resin and a colorant can be used. The thermoplastic resin contained in the master batch may be used alone or in combination of two or more types. The master batch may contain, within the scope not impairing the effects of the present invention, a metallic soap of an alkali metal, an alkaline earth metal, or zinc, hydrotalcite, a nonionic surfactant, a cationic surfactant, an anionic surfactant, an amphoteric surfactant, an antistatic agent, a flame retardant such as a halogen-based, phosphorus-based, or metal oxide, a lubricant such as ethylene bisalkyl amide, an antioxidant, an ultraviolet absorber, a filler, or a peroxide.

[0196] <Molded object> The molding material obtained by the above-mentioned manufacturing method is heated and molded to obtain a molded body. The heat molding method is not particularly limited, and examples thereof include injection molding, extrusion molding, blow molding, and compression molding. The molding material produced using the plastic substrate recovered by the separation and recovery method of the present invention is of high quality because the ink layer is detached and the reattachment of the adhesive component is suppressed, and can be used in various fields such as home appliances, stationery, automobile parts, toys, sports goods, medical use, and building and construction materials.

[0197] Additives that can be used in the manufacturing process of the recycled pellets obtained by the manufacturing method of recycled plastic film include at least one antioxidant selected from the group consisting of phenols and phosphorus-based antioxidants, at least one lubricant selected from fatty acid amides, alkylene fatty acid amides, metal soaps, and esters, hindered amine weather stabilizers, waxes having an acid value of 5 mg KOH / g or less, at least one antistatic agent selected from fatty acid sulfonates and fatty acid esters, and at least one peroxide selected from organic peroxides for modifying polypropylene. Examples of phenol-based antioxidants include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, 2,2'-methylene-bis-(4-methyl-6-t-butylphenol), 2,2'-methylene-bis-(4-ethyl-6-t-butylphenol), 4,4'-thiobis-(3-methyl-6-t-butylphenol), 4,4'-butylidene-bis-(3-methyl-6-t-butylphenol), 3,9-bis[{1,1-dimethyl-2-{β-(3-t-butyl-4-hydroxy-5-methyl 1,1,3-tris-(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-{methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate}methane, and bis{(3,3'-bis-4'-hydroxy-3'-t-butylphenyl)butyric acid}glycol ester.

[0198] Examples of phosphorus-based antioxidants include triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, 4,4'-butylidene-bis-(3-methyl-6-t-butylphenyl-di-tridecyl) phosphite, cyclic neopentane tetrayl bis(octadecyl phosphite), trisdiphenyl phosphite, diisodecylpentaerythritol diphosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, cyclic neopentane tetrayl bis(2,4-di 2,2-methylenebis(4,6-t-butylphenyl)octylphosphite, cyclic neopentanetetraylbis(2,6-di-t-methylphenyl)phosphite, and 2,2-methylenebis(4,6-t-butylphenyl)octylphosphite.

[0199] These antioxidants may be used alone or in combination of two or more. The amount of the antioxidant added is preferably 0.01 to 1 mass%, more preferably 0.03 to 0.5 mass%, based on the mass of the molding material. An amount of 0.01 mass% or more is preferable in terms of antioxidant properties, and an amount of 1 mass% or less is preferable in terms of processability.

[0200] Examples of fatty acid amide-based lubricants include aliphatic monocarboxylic acid amides such as lauric acid amide, palmitic acid amide, oleic acid amide, stearic acid amide, erucic acid amide, behenic acid amide, ricinoleic acid amide, and hydroxystearic acid amide; N-substituted aliphatic monocarboxylic acid amides such as N-oleyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl oleic acid amide; aliphatic biscarboxylic acid amides such as methylene bisstearic acid amide and ethylene bisstearic acid amide; N,N'-ethylene bis-oleyl amide, N,N'-ethylene bisstearic acid amide, and N,N'-methylene bisstearic acid amide.

[0201] Examples of metal soap-based lubricants include metal salts of higher fatty acids such as calcium stearate, magnesium stearate, barium stearate, zinc stearate, aluminum stearate, lithium stearate, calcium laurate, magnesium laurate, barium laurate, zinc laurate, aluminum laurate, and lithium laurate, as well as calcium hydroxystearate, magnesium hydroxystearate, barium hydroxystearate, zinc hydroxystearate, aluminum hydroxystearate, and lithium hydroxystearate.

[0202] These lubricants may be used alone or in combination of two or more. The amount of the lubricant added is preferably 0.01 to 1 mass%, more preferably 0.03 to 0.5 mass%, based on the mass of the molding material. An amount of 0.01 mass% or more is preferable in terms of activity, and an amount of 1 mass% or less is preferable in terms of processability.

[0203] Examples of the hindered amine weathering stabilizer include dimethyl succinate-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{{2,2,6,6-tetramethyl-4-piperidyl)imino}], N ,N'-bis(3-aminopropyl)ethylenediamine-2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazine condensate, bis(2,2,6,6-tetramethyl-4-piperidyl)separate, and bis(1,2,2,6,6-pentamethyl-4-piperidyl) 2-(3,5-di-t-4-hydroxybenzyl)-2-n-butylmalonate.

[0204] Examples of waxes having an acid value of 5 mgKOH / g or less include natural waxes and synthetic waxes. Examples of natural waxes include vegetable waxes such as carnauba wax, rice wax, and Japan wax; animal waxes such as beeswax, lanolin, and spermaceti; mineral waxes such as montan wax, ozokerite, and ceresin; and petroleum waxes such as paraffin wax, microcrystalline wax, and petrolatum. Examples of synthetic waxes include semi-synthetic waxes and fully synthetic waxes. Semi-synthetic waxes are natural waxes or natural wax-like materials that have been modified by chemical treatments such as esterification, amidation, and neutralization with an acidic wax. Examples of synthetic waxes include synthetic hydrocarbons such as polyethylene waxes, polypropylene waxes, and polystyrene waxes.

[0205] These waxes having an acid value of 5 mgKOH / g or less may be used alone or in combination of two or more kinds. The amount of wax having an acid value of 5 mgKOH / g or less added is preferably 0.5 to 50 mass%, more preferably 1 to 30 mass%, based on the mass of the molding material. An amount of 0.5 mass% or more is preferable in terms of fluidity adjustment, and an amount of 50 mass% or less is preferable in terms of processability.

[0206] Examples of the anionic surfactant-based antistatic agent include carboxylates such as alkali metal salts of higher fatty acids; sulfates such as higher alcohol sulfates and higher alkyl ether sulfates; sulfonates such as alkylbenzene sulfonates, alkyl sulfonates and paraffin sulfonates; and phosphates such as higher alcohol phosphates.

[0207] Examples of nonionic surfactants include polyethylene glycol-type nonionic surfactants such as higher alcohol ethylene oxide adducts, fatty acid ethylene oxide adducts, higher alkylamine ethylene oxide adducts, and polypropylene glycol ethylene oxide adducts; polyhydric alcohol-type nonionic surfactants such as fatty acid esters of polyethylene oxide or glycerin, fatty acid esters of pentaerythritol, fatty acid esters of sorbitol or sorbitan, alkyl ethers of polyhydric alcohols, and fatty amides of alkanolamines.

[0208] These antistatic agents may be used alone or in combination of two or more kinds. The amount of the antistatic agent added is preferably 0.05 to 1 mass %, more preferably 0.1 to 0.5 mass %, based on the mass of the molding material. An amount of 0.05 mass % or more is preferable in terms of antistatic properties, and an amount of 1 mass % or less is preferable in terms of transparency and low bleeding properties.

[0209] Examples of organic peroxides include dicumyl peroxide, di(2-t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3.

[0210] These organic peroxides may be used alone or in combination of two or more kinds, and may also be used after dilution with an inorganic filler.

[0211] In order to improve the physical properties of the recycled pellets obtained by the method for producing recycled plastic film, they may be melt-kneaded with at least one of an acid-modified polypropylene and a thermoplastic elastomer having a melting point of 130° C. or higher.

[0212] The modification of the physical properties of recycled pellets means changing the physical properties of the plastic pellets that are the raw material for the plastic film before being recycled.

[0213] The properties that can be modified are varied and include, but are not limited to, tensile strength, flexural strength, elongation at break, tensile modulus, flexural modulus, and yield stress.

[0214] Examples of commercially available acid-modified thermoplastic elastomers include maleic anhydride-modified isoprene rubber such as LIR-403 manufactured by Kuraray Co., Ltd., modified isoprene rubber such as LIR-410 manufactured by Kuraray Co., Ltd., carboxy-modified nitrile rubber such as Clynac 110, 221, and 231 manufactured by Polycer Co., Ltd., maleic anhydride-modified polybutene such as Nippon Oil Corporation's Nisseki Polybutene, ethylene methacrylic acid copolymers such as Nucrel manufactured by Mitsui DuPont Polychemicals Co., Ltd., ethylene methacrylic acid copolymers such as Yukalon manufactured by Mitsubishi Chemical Corporation, maleic anhydride-modified ethylene-propylene rubber such as Toughmer M (MA8510) manufactured by Mitsui Chemicals Co., Ltd. and TX-1215 manufactured by Mitsui Chemicals Co., Ltd., Examples of maleic anhydride-modified ethylene-butene rubbers include maleic anhydride-modified ethylene-butene rubbers such as I Chemicals' Tufmer M (MH7020); maleic anhydride-modified polyethylenes such as Mitsui DuPont Polychemicals' HPR series (maleic anhydride-modified EEA); Atofina's Bondine (maleic anhydride-modified EEA); Asahi Kasei's Tuftec (maleic anhydride-modified SEBS, M1943); Kraton Polymers' Kraton (maleic anhydride-modified SEBS, FG1901X); Asahi Kasei's Tufprene (maleic anhydride-modified SBS, 912); Kuraray's Septon (maleic anhydride-modified SEPS); Japan Polyolefins' Rexpearl (maleic anhydride-modified EEA, ET-182G, 224M, 234M); and Nippon Paper Chemicals' Aurouren (maleic anhydride-modified EEA, 200S, 250S).

[0215] A particularly suitable example of the acid-modified thermoplastic elastomer is a maleic anhydride-modified styrene-ethylene-butadiene-styrene copolymer. Commercially available acid-modified styrene-ethylene-butylene-styrene block copolymers include Tuftec M1911, Tuftec M1913, and Tuftec M1943 manufactured by Asahi Kasei Chemicals Corporation.

[0216] Examples of commercially available thermoplastic elastomers that are not acid-modified include ethylene methacrylic acid copolymers such as Nucrel manufactured by DuPont-Mitsui Polychemicals, ethylene methacrylic acid copolymers such as Yukalon manufactured by Mitsubishi Chemical Corporation, α-olefin copolymers such as Tafmer manufactured by Mitsui Chemicals, Inc., SEBS such as Tuftec manufactured by Asahi Kasei Corporation, SBS manufactured by Kuraray such as Tufprene manufactured by Asahi Kasei Corporation, SEPS such as Septon, and EEA such as Rexpearl manufactured by Japan Polyolefins Co., Ltd.

[0217] For example, when a single-screw or twin-screw extruder is used in the melt-kneading step, general melt-kneading conditions can be used. The kneading temperature is preferably 180 to 260°C, more preferably 190 to 250°C, and even more preferably 200 to 240°C. If the temperature is below 180°C, melt-kneading is difficult, and if the temperature is above 260°C, the physical properties of the produced recycled pellets are significantly reduced. The screw rotation is preferably 50 to 500 rpm, more preferably 180 to 400 rpm, and even more preferably 100 to 300 rpm. If the rotation speed is too low, it is difficult to produce uniform recycled pellets during melting, and if it is too high, the physical properties of the produced recycled pellets are significantly reduced due to the heat generated during kneading.

[0218] The melt mass flow rate (MFR) of the recycled pellets is preferably 2 to 50 g / 10 min, more preferably 3 to 40 g / 10 min, and more preferably 5 to 30 g / 10 min. By having the melt mass flow rate within the above range, a regenerated mold material suitable for various molding processes such as injection molding and extrusion molding can be provided.

[0219] (Decolorization evaluation of recycled pellets) The plastic film pieces that had been subjected to steps 1 to 3 in sequence were extruded at 200°C using a twin-screw extruder and pelletized to obtain recycled pellets. The recycled pellets were then hot-pressed at 200°C using a heat press to produce a pressed plate with a thickness of 1 mm. The pressed plate was measured for color value L using a spectrophotometer (X-rite, X-riteeXact). * , a * , b *The raw material pellets of the plastic film were also subjected to a similar hot pressing process to create a press plate with a thickness of 1 mm, and the color difference ΔE was calculated using the following formula. ΔE=((L * xL * y) 2 +(a * xa * y) 2 +(b * x-b * y) 2 ) 1 / 2 x: Raw material pellets y: Recycled pellets ΔE is preferably 30 or less, more preferably 20 or less, more preferably 10 or less, and even more preferably 5 or less. The recycled pellets have been decolorized by the washing process to the extent that there is no color difference between the recycled pellets and the raw pellets, and they are highly useful as recycled pellets. In addition, since many molded products are melt-kneaded with a master batch containing a colorant, a ΔE of 30 or less is sufficient for use as long as the desired color tone can be obtained.

[0220] When the recycled pellets are made into a film having a thickness of about 100 μm, the total light transmittance is preferably 30% or more, more preferably 50% or more, and even more preferably 70% or more. The higher the total light transmittance, the more the ink has been decolorized by the washing process, and the more useful the recycled pellets are.

[0221] (a mix of recycled and virgin pellets) In the melt-kneading process of the plastic film from which the ink layer has been removed, it can be mixed with virgin plastic pellets at any ratio depending on the purpose. For example, the mixing ratio of the recycled pellets to the virgin pellets in terms of weight is 99.5:0.5 to 50:50. From the viewpoint of recyclability, it is preferable to make the ratio of the recycled pellets as high as possible.

[0222] The virgin plastic pellets used in this case may be at least one type of polypropylene selected from block polymers, random polymers, and homopolymers. They may also be selected from acid-modified polypropylene, thermoplastic elastomers, and polyethylene using a metallocene catalyst, and at least one type of these may be mixed and used.

[0223] An example of a specific embodiment of the method for separating and recovering plastic films of the present invention will be described below.

[0224] (1) Process 1: Crushing plastic film First, the plastic film is sequentially fed into a dry crusher or a wet crusher (hereinafter simply referred to as a crusher) to produce crushed plastic material. At this time, the plastic film may be cut into plastic pieces, for example, about 20 cm square or 30 cm square, and then fed into the crusher. By passing through this cutting process, the crushing in the crusher in the next process can be performed more efficiently. For the cutting, a known crusher can be used, for example, an impact crusher such as a hammer crusher or a rotary crusher, a shredder, a cutter, etc. are included. The size and shape of the plastic film to be fed are not particularly limited, but the maximum length of the plastic pieces is, for example, preferably 50 cm or less, preferably 30 cm or less, preferably 20 cm or less, and preferably 10 cm or less.

[0225] When a screen or mesh is used in the dry crusher in step 1, the hole diameter is preferably 30 mm or less, more preferably 20 mm or less, and even more preferably 10 mm or less. When a 10 mm screen or mesh is used, the size of the crushed film pieces is 0.5 to 10 mm on the long side. The smaller the crushed film size is, the more effective the immersion in the cleaning solution in step 2 is, so in step 1, the smaller the crushed film size is, the more preferable it is.

[0226] When a wet crusher is used in step 1, the laminated film roll is cut into pieces of about 20 cm square or 30 cm square, and the laminated film is drawn into the crushing section by the suction of the crusher and crushed into pieces of about 1 to 20 mm or 5 to 20 mm, and then transported to the next process in 0.03 m pieces. 3 / min. At this time, the film fed in is subjected to high shear when it is crushed, so that at least a part of each layer constituting the laminated film is easily separated into single layers. If an ink layer is provided on the laminated film, the ink layer is also easily peeled off and removed from the film by the high shear caused by crushing, so it is preferable that at least a part of the ink layer is peeled off.

[0227] Even if the object to be crushed is not a laminated film roll but individual film bags collected from the market, they can be fed into the crusher in the same condition as they are collected.

[0228] When the plastic film is pulverized into powder form using a grinder as the crusher, it is preferable to use a laminated film roll cut into small pieces of about 5 mm square. The plastic film crushed by the grinder is pulverized to about 10 to 500 μm.

[0229] The number of times of the crushing step in the step 1 may be one or several.

[0230] (2) Step 2: Immersing the plastic film in a cleaning solution In step 2, the plastic crushed material crushed in step 1 may be immersed in the cleaning solution by leaving it to stand, or may be immersed and stirred as necessary using a known stirring device such as a homodisper or a wet crusher similar to that in step 1. If the crushed plastic film is front-printed, the ink layer on the front side is made to swell sufficiently, and if it is a laminated film including reverse printing, the ink layer and adhesive layer are made to swell completely.

[0231] The liquid temperature and stirring time during immersion in the cleaning liquid are not particularly limited, and can be appropriately adjusted depending on various conditions such as the material of the cleaning liquid used and the structure of the plastic film.

[0232] (3) A process of separating the plastic film by stirring the crushed plastic film in a rinsing liquid. After swelling the plastic crushed material in steps 1 and 2, the plastic film is stirred in a rinsing liquid to separate the plastic film. After separation, the rinsing liquid contains the separated single layer films and residues of adhesives, printing inks, metal foils, etc., floating or dissolved in the liquid. These are removed from the rinsing liquid and then separated and recovered.

[0233] As an example of a specific method, for example, in flotation separation, plastics with a light specific gravity such as polyolefins such as polypropylene and polyethylene (floating matter) are separated from heavy materials such as condensation synthetic films such as polyester and nylon, which have a higher specific gravity than polyolefins, or metal foils, and the heavy materials are removed. Next, if necessary, the recovered plastics are washed and dehydrated in a washing and dehydration process, and plastics with different specific gravities are separated by centrifugation. For example, plastics can be separated into plastics separated that contain vinyl chloride resins, polyethylene terephthalate, etc., which sink in water and have a specific gravity of 1 or more, and plastics separated that contain olefin-based resins such as polyethylene and polypropylene, which do not contain vinyl chloride resin. Further separation is possible by appropriately changing the specific gravity by changing the blending ratio of the liquid used in the flotation separation, for example, water to an organic solvent or salt.

[0234] After rough separation and recovery using gravity separation, more advanced separation may be performed using electrostatic separation that takes advantage of the inherent charging properties of plastics.

[0235] One example of a specific method is to separate a mixture of plastics by dropping it between parallel plate electrodes to which a voltage is applied, which is charged in advance. This method can separate combinations of plastics with small specific gravity differences that are difficult to separate by gravity separation.

[0236] In step 3, a known stirring device such as a homodisper, a wet crusher similar to that in step 1, a paint shaker, a paint conditioner, a so-called mixer, a kneader, or a kneader may be used. Devices other than these may also be used.

[0237] (4) Recovery and reuse of cleaning solution (Step 4) The water, washing liquid, and rinsing liquid used in steps 1 to 3 are supplied to one or more recycle machines selected from a filter, a centrifuge, and an ultrafilter to recover them, and are reused after removing solid matter. While the wet crushing step and the gravity separation step are performed in steps 1 to 3, the water, washing liquid, or the washing liquid recycling step can be continuously operated to separate solid matter from the water, washing liquid, and rinsing liquid.

[0238] (5) Drying of plastic separations (step 5) In order to remove residual moisture from the plastic film recovered in step 3, the film pieces are dried by one or more methods selected from reduced pressure heating drying, hot air drying, and pressurized compression drying. As a pre-treatment for producing recycled pellets described later, after or during drying of the recovered film pieces, briquettes may be produced using a pressurized compressor such as a Nippon Seam Co., Ltd. pressurized dehydrator, a Oike Iron Works Co., Ltd. pellet mill, or an Elcom Co., Ltd. Stella briquette machine. When the plastic film is pulverized into powder form using a grinder as a wet crusher, the crushed material is pulverized to about 10 to 500 μm, and the density of the crushed material is high, so the pressurized compression step can be omitted. The density varies depending on the material constituting the crushed material, but a higher density is preferable because it is easier to handle in a kneader. Specifically, in a dry state, it is preferably 0.03 kg or more, more preferably 0.05 kg or more, more preferably 0.2 kg or more, and even more preferably 0.3 kg or more.

[0239] (6) Preparation of recycled pellets (Step 6) The film pieces or briquettes dried in step 5 are fed into a single-screw and twin-screw extruder to produce recycled pellets. When the film pieces are fed directly into the extruder without going through the pressurized compression step, a phenomenon called bridging, in which ink pieces clog the inlet, is likely to occur. In order to avoid bridging, the film pieces may be pressurized in the feeder section or pushed in with air. In addition, the feeder section may use two screws that rotate in opposite directions, or a side feeder may be used to push in. The kneader conditions are not particularly limited, but it is preferable to operate at 180 to 260°C in order not to significantly deteriorate the resin performance before recycling. EXAMPLES

[0240] The contents and effects of the present invention will be described in more detail below with reference to examples. The films, printing inks, reactive adhesives, and organic solvents used as raw materials in each example and comparative example are also shown below. (Film used for laminated film) OPP: Biaxially oriented polypropylene film 20μm CPP: Non-oriented polypropylene film 35μm (Printing ink) INK1: DIC Graphics Glossa 507 Primary Indigo S2 INK2: DIC Graphics Finart R507 Primary Blue INK3: DIC Graphics Finart R794 White S (Reactive adhesive) AD1: Solvent-based adhesive Dick Dry LX-401A and SP-60 two-part adhesive (ether-based adhesive) AD2: Solvent-free adhesive Dick Dry 2K-SF-400A and HA-400B, two-component adhesive (ester adhesive) (Laminated Film Manufacturing Method) The laminated film was produced by printing on the target film using the printing method described below, and then laminating the target film using the lamination method described below. The film layer structure, reactive adhesive, and printing ink types were combined as shown in Table 1.

[0241] (Printing method) For the printing inks, gravure inks, each ink was spread on the film "Film 1" using a proofer.

[0242] (Lamination method) The reactive adhesive "AD" was applied to the surface of the printing ink-laid film "Film1" using a laminator to a coating weight of 3 g / m2 solid content, and then laminated to the film "Film2". The laminated film was subjected to an aging reaction at 40°C for 72 hours. The laminated films "LAM1" to "LAM2" shown in Table 1 were obtained. Note that blanks indicate that no configuration was present.

[0243] [Table 1]

[0244] (Step 1: Crushing step) Print 1 and LAM 1 and 2 were placed in a dry crusher equipped with a screen with a hole diameter of 10 mm, and crushed until the short side of the crushed film was approximately 5 to 10 mm and the long side was approximately 10 to 20 mm.

[0245] (Process 2 Soaking process) PRO_A: Gently immersed in cleaning solution at 40°C for 16 hours. PRO_B: Placed in a cleaning solution at 75°C for 120 minutes and stirred at 500 rpm using a three-one motor.

[0246] (Cleaning solution) Water, the solvents shown in Table 2, and 2% by weight of potassium hydroxide were mixed to prepare the cleaning solution shown in Table 3. The cleaning solution composition was calculated by adding the ingredients vertically, and water was added to make up to 100% if the amount was less than 100%.

[0247] [Table 2]

[0248] [Table 3]

[0249] (Step 3 Stirring separation step) PRO_V: 50 g of the plastic film obtained in step 2 was used in 1000 mL of "diethylene glycol normal butyl ether" used as a rinsing liquid. A vibration mill manufactured by Chuo Kakoki Co., Ltd. was used as the equipment, and stainless steel rods with a diameter of 19 mm were used as the media. The rod filling rate was set to 30%, and the mill was operated for 10 minutes. PRO_W: 10 g of the plastic film obtained in step 2 was used in 300 mL of city water, and the blender was a Mighty Blender manufactured by Osaka Gas Chemicals, operated at 19,000 rpm for 5 minutes. PRO_X: 10 g of the plastic film obtained in step 2 was used in 300 mL of "normal propyl alcohol:water = 60:40 liquid" used as a rinse solution, and the Mighty Blender manufactured by Osaka Gas Chemicals was used and operated at 19,000 rpm for 5 minutes. PRO_Y: 10 g of the plastic film obtained in step 2 was used, and the equipment was operated for 30 minutes using a paint conditioner in 300 mL of "normal propyl alcohol containing 150 g of sodium chloride" used as a rinse solution. PRO_Z: 10 g of the plastic film obtained in step 2 was used, and the equipment was operated for 30 minutes in a paint conditioner in a solution containing 100 mL of "diethylene glycol normal butyl ether" used as the rinsing liquid and 400 g of zirconia balls with a diameter of 4.8 mm.

[0250] (Decolorization evaluation of recycled pellets) The results in Tables 4 to 6 show the state of ink removal from the plastic film. The pieces of plastic film that had been subjected to steps 1 to 3 in sequence were extruded at 200°C using a twin-screw extruder to produce recycled pellets. The recycled pellets obtained were hot-pressed at 200°C using a heat press to produce a pressed plate with a thickness of 1 mm. The pressed plate was measured for color value L using a spectrophotometer (X-rite, X-riteeXact). *, a * , b * The raw material pellets of the plastic film (non-recycled product, Prime Polymer's F-300SP) were also subjected to the same heat press process, and the color difference ΔE was determined. ◎: ΔE is 10 or less ○: ΔE is 20 or less △: ΔE is 30 or less ×: ΔE is 31 or more The marks ◎, ◯, and △ indicate a range in which there is no practical problem.

[0251] [Table 4]

[0252] [Table 5]

[0253] Comparative examples are shown in Table 6. Blank spaces in the table indicate that no experiment was carried out.

[0254] [Table 6]

[0255] From these results, it was found that the examples of the present invention were able to peel off the plastic film, and also peel off the ink layer present between the layers of the plastic film.

Claims

1. A method for separating and recovering a plastic film having at least an ink layer, comprising: A step 1 of crushing the plastic film; A step 2 of immersing the plastic film in a cleaning solution; A process 3 of separating the ink layer from the plastic film by stirring the crushed plastic film in a rinsing liquid containing at least a water-soluble solvent. having A method for separating and recovering plastic films, wherein the step 3 comprises agitating the plastic films using a medium that assists in grinding the plastic films.

2. A method for separating and recovering plastic films as described in claim 1, wherein the media is beads, rods, or inorganic salts that are present in an insoluble state in the rinse solution.

3. 3. The method for separating and recovering a plastic film according to claim 1 or 2, wherein the cleaning solution contains (a) a water-soluble solvent and (b) an inorganic base.

4. 3. The method for separating and recovering a plastic film according to claim 1 or 2, wherein in step 2, the plastic film is immersed in a cleaning liquid to swell the ink layer.

5. A method for separating and recovering plastic films as described in claim 1 or 2, wherein the plastic film is a laminate having at least a plastic film layer and another layer selected from a plastic film layer, a vapor deposition film layer and a metal foil layer, and the ink layer is between the plastic film layer and the other layer.

6. The method for separating and recovering a plastic film according to claim 1 or 2, wherein in step 1, the plastic film after shredding is shredded to have a long side of 1 mm or more and 30 mm or less.

7. A method for producing recycled plastic pellets, comprising recovering the crushed plastics separated by the method according to claim 1 or 2, melting the recovered material, and molding the material in a molding machine.

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