Method for separating and recovering plastic films and method for producing recycled plastic pellets

Abstract

The present invention relates to a method for separating and recovering plastic films having at least an ink layer, the method comprising: a step 1 of crushing a plastic film; a step 2 of immersing the plastic film in a cleaning liquid; and a 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. Further, the present invention also provides a method for producing recycled plastic pellets, the method configured so that the crushed plastic material separated by the process of steps 1-3 is recovered and the recovered material is melted and then molded by a molding machine.

Description

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

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

[0002] Currently, the recycling rate for plastic waste, which is the result of separate collection, is only 9% of all plastic produced worldwide. Of the 91% of plastic waste, 12% is incinerated, and 79% is disposed of in landfills or leaks into the environment (Non-Patent Document 1). One of the reasons for this persistently low recycling rate is the difficulty of implementing separate collection systems. To recycle plastics, waste plastics that contain different plastic materials, such as polyethylene (PE) and polypropylene (PP), must be separated and collected separately. However, many plastic products, including laminated films, are made of different plastic materials bonded together, making it difficult to separate and collect each material. Therefore, there is a strong demand for a recycling system that can easily separate and collect waste plastics.

[0003] Furthermore, it is difficult to recycle recycled plastic products into the same product due to cost considerations, and they generally deteriorate each time they are recycled, resulting in products of lower quality. One reason for the decline in quality of recycled plastic is the presence of inks and pigments as impurities in the plastic. However, many plastic products have printing on their surfaces, making it difficult to decolorize them during the recycling process, resulting in colored recycled plastic products. Recycled plastics containing pigments and inks not only have significantly lower commercial value due to the coloring, but also tend to become plastics with physically degraded properties due to the impurities. Therefore, a recycling method that produces high-quality recycled plastic is needed.

[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 alkali, the multilayer film is separated based on differences in specific gravity, and then the film is selectively melted in a solvent to separate and recycle valuable components. Patent Document 2 proposes a process in which printed film is crushed, the ink is removed, 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 has been an increasing demand for high functionality in packaging materials, improved adhesion of ink films to plastic substrates, and sophisticated design of printed materials. This 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 together, or in a laminate in which an ink layer is formed on a film and then laminated with another film, etc., via an adhesive layer, in the case of a laminated film in which the ink layer is formed between multiple films (reverse printing), removing the ink layer requires separating the multiple films, making peeling off the ink layer even more difficult. A method that can peel off the ink layer from such plastic films with diverse configurations is desired.

[0007] Science Advances 19 Jul 2017:Vol. 3, no. 7, e1700782

[0008] Japanese Patent Application Laid-Open No. 2006-205160 Special Publication No. 2015-520684 Special Publication No. 2016-509613 Special Publication No. 2018-514384

[0009] In the prior art, the separation of laminated films involves a dry crushing process followed by a deinking or separation process, which is a common, long and complicated process. Furthermore, the prior art methods 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 that have at least an ink layer, and a method for producing high-quality recycled plastic pellets using crushed plastic material recovered by this method.

[0011] As a result of extensive research to solve the above-mentioned problems, the inventors have discovered a simple 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 solution, and step 3 of separating the ink layer from the plastic film by agitating the crushed plastic film in a rinse solution.

[0012] That is, 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 solution, and step 3 of separating the ink layer from the plastic film by stirring the crushed plastic film in a rinse solution 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 plastics separated by the above-described method in layers, melting the recovered materials, and molding them in a molding machine.

[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, sorted, and reused. The method of the present invention can separate plastic laminates into single layers and easily peel off the ink layer, not only for plastic films in which the ink layer is exposed on the film surface (surface-printed), but also for plastic laminates of various configurations, such as laminate films in which the ink layer is provided between multiple films (reverse-printed). 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 simplifies the separation and recovery method of plastic laminates and allows the recovered plastic to be reused as high-quality recycled plastic raw material.

[0015] <Regarding Step 1> The method for separating and recovering plastic film of the present invention includes Step 1 of crushing the plastic film. In Step 1, the method for crushing the plastic film is not particularly limited, and can be performed by a known method. Crushing may be performed in an air atmosphere in the absence of a 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 can be used, which can crush and pressure-feed simultaneously. When a wet crusher is used, the plastic film can be crushed efficiently, and the laminated plastic film can be peeled into each layer.

[0016] By crushing the plastic film in step 1, it becomes easier to completely peel off the plastic film into single layers 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. If the length is within the above range, the time required for the treatment solution to penetrate from the edge surfaces of the fluff to the center can be shortened in step 2 of immersing the plastic film in a cleaning solution, making it easier to completely peel the plastic film into a single layer.

[0018] In order to shorten the time it takes for the treatment solution to penetrate from the edge of the fluff to the center, it is more preferable that holes or slits be made in the shredded 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 known techniques 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, microcolloider, mass colloider, 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, which would cause the cross section of the laminate to fuse, it is preferable that the crushing and crushing be carried out in a cooled state.

[0020] The dry crusher can be preferably used to separate and recover films for both plastic films in which an ink layer is exposed on the film surface (surface-printed) and laminate films in which an ink layer is provided between multiple films (reverse-printed). The ink layer applied to the plastic film is a printed ink layer for providing display such as a trade name or decorativeness, and is often printed with organic solvent-based printing ink, water-based ink, or active energy ray-curable ink using a gravure printing machine, flexographic printing machine, offset printing machine, inkjet printing machine, or the like. In plastic films provided with such ink layers, the film and the printed surface do not completely separate when a dry crusher is used in step 1. However, 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 laminate films in which an ink layer is provided between multiple films (reverse-printed), in addition to the dry crusher, a wet crusher is preferably used to enhance 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 a wet crusher that can crush, disperse, mix, and pump-feed solids in a liquid simultaneously is preferred. Specifically, a crusher having a mechanism for crushing solids in a liquid by shear force and / or friction force is preferred, and a crusher having a mechanism for crushing and pumping plastic films is also preferred. Examples of such wet crushers include a wet crushing pump, a colloid mill, an attritor, and a beater.

[0022] (Wet-type crushing pump) The wet-type crushing pump preferably has a mechanism for crushing the solids using fixed blades and rotary blades while pumping the solids in a liquid, and a more preferred mechanism is one that crushes the solids in three stages using a combination of four parts: cutting blades, a crushing impeller, a shroud ring, and a grid.

[0023] The wet-type crushing pump crushes plastic film in three stages. The plastic film is roughly cut by the fixed blade cutting edges and the inlet edge of the rotary blade crushing impeller, then stirred and pressure-fed by the axial-flow crushing impeller, with some of the plastic film hitting the blades of the shroud ring of the fixed blade and being cut. 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 pressure impeller, and is pressure-fed 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 0.03 m ３ The upper limit of the pumping speed is not particularly limited, and is preferably a standard operating speed of the apparatus, for example, 1.4 m / min. ３ / min is sufficient to peel off the ink and separate the plastic film into single layers.

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

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

[0027] (Colloid Mill) The colloid mill used in the present invention is a machine used to reduce the particle size in a dispersion system in which particles are suspended in a liquid. A colloid mill consists of a rotor and a stator combination, and the rotor rotates at high speed relative to 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 consists of a toothed, truncated cone-shaped rotor and a stator, and the rotor and stator are tapered so that they narrow as they approach the discharge outlet. 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 outlet.

[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 grinder preferably has a mechanism for crushing solid material placed between the millstones by shearing or friction while rotating a pair of upper and lower millstones in a liquid, and is preferably capable of crushing solid material into a fine powder while flowing water.

[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 pulverized 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. Furthermore, when producing recycled plastic from the crushed material, it can be fed into a kneader without going through a compressor or the like, thereby simplifying the process. On the other hand, the lower limit of the crushed material size is preferably 10 μm or more, preferably 30 μm or more, and more preferably 50 μm or more, to facilitate recovery.

[0032] There are no particular limitations on the rotation speed or water flow rate.

[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, reverse-printed laminated plastic films are provided with an adhesive and a printed ink layer for displaying product names and other information or for providing decorative features. The ink layer is often printed using a gravure printing machine, flexographic printing machine, offset printing machine, inkjet printing machine, or the like, with an organic solvent-based printing ink, a water-based ink, or an active energy ray-curable ink. In plastic films provided with such an ink layer, the plastic film may be crushed in a cleaning solution containing water and a cleaning component or a peeling component to more efficiently peel and remove the ink layer. By crushing the plastic film in a cleaning solution containing water and a cleaning component or a peeling component, the ink layer formed on the plastic film can be peeled and removed and the plastic film separated into single layers simultaneously. For example, gravure ink and flexographic ink are the inks most commonly used for plastic laminated films, including those used for food packaging. A wet crushing process using a cleaning solution is efficient because it can also peel off the printed ink layer. In addition, the laminated film may have a metal foil or vapor-deposited film such as aluminum laminated thereon, and in the present invention, the metal foil or vapor-deposited film can also be peeled or dissolved. As already mentioned above, by crushing in water, each layer constituting the plastic film may be peeled off into a single layer, 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 remain partially attached, or may not be removed from the ink layer.

[0036] When a wet crusher is used in step 1, crushing may be carried out using water as a solvent, or a washing liquid obtained by adding a washing or peeling component such as an inorganic base or a surfactant, or other component to water. The washing liquid may be water containing one or a suitable combination of two or more of the following components:

[0037] (Inorganic Base) 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 weight 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 known surfactants can be used, for example, anionic surfactants, nonionic surfactants, amphoteric surfactants, cationic surfactants, etc.

[0039] Typical examples of nonionic surfactants include polyoxyalkylene alkyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, fatty acid alkylolamides, alkylalkanolamides, 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 alkylolamides, acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers are mentioned.

[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-[CH ２ -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, as represented by the formula (I) above, is preferred. The greater the number of carbon atoms, exceeding 10, the better the ink removability, and this is preferred. Specific examples of the number 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 products include nonionic surfactants represented by the general formula (1), such as R １ The present invention is applicable when the number of carbon atoms represented by the formula (I) is 10 or more, but is not limited thereto.

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

[0045] Among the nonionic surfactants represented by the general formula (1), R １ Specific surfactants having 10 or more carbon atoms and an HLB value of less than 12.5, as indicated by the formula (I), 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 Dash 408, 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, and 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 a coating agent include, but are not limited to, T-510, Nonion HT-512, and Kao Corporation's 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 Lion Corporation's Rheox CL-30, Rheox CL-40, Rheox CL-50, Rheox CL-60, Rheocol NL-30C, Rheocol TD-50, Rheocol TD-70, Rheocol SC-50, and Rheocol SC-70.

[0046] Furthermore, among the nonionic surfactants represented by 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 Dai-ichi 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, and 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, and Nonion I D-206, Nonion ID-209, Dispanol TOC, Nonion HT-515, Nonion HT-518, and Kao Corporation 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, and Emulgen 2020G-HA.Examples of Emulgen 2025G manufactured by Lion Corporation include Rheox CL-90, Rheox CL-230, Rheocol TD-90, Rheocol TD-90D, Rheocol TDA-90-25, Rheocol TDN-90-80, Rheocol TD-120, Rheocol TD-200, Rheocol TDA-400-75, Rheocol SC-80, Rheocol SC-90, Rheocol SC-120, Rheocol SC-150, Rheocol SC-200, Rheocol SC-300, and Rheocol SC-400, but are not limited to these.

[0047] In general formula (1), R １ When is an octylphenol group, octylphenol ethoxylate is 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, 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 alkylamidocarboxybetaine skeleton containing at least one compound represented by general formula (2a).

[0050] R1-R2-N ＋ (CH ３ ) ２ CH ２ COO － (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 ＋(CH ３ ) ２ CH ２ COO － (2a-1) (In general formula (2a-1), n ​​represents the average number of moles added.) In general formula (2a-1), n ​​is preferably 8 or more, more preferably 10 or more, and even more preferably 11 or more.

[0052] Specific products corresponding to 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 Dai-ichi Kogyo Seiyaku Co., Ltd., Rekabion B-200 and Rekabion B-300 manufactured by New Japan Chemical Co., Ltd., and Obazolin CAB-30 and Obazolin 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, Amogen S, Amogen S-H, and Amogen K manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; Amphitol 20BS, Amphitol 24B, and Amphitol 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 Obazolin LB and Obazolin LB-SF manufactured by Toho Chemical Co., Ltd.

[0053] Furthermore, the betaine-type amphoteric surfactant may be one having an imidazolinium betaine skeleton, and 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 also be a surfactant represented by the following general formula (2b):

[0055] R4-(NHC ２ H ４ ) ｎｂ -N(R5) ２(2b) (In the general formula (2b), R4 represents a linear or branched alkyl or alkenyl group, nb represents an integer of 0 to 5, and R5 represents hydrogen, —CH ２ COONa or -CH ２ COOH, but two R5s may be the same or different, and at least one R5 is -CH ２ 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 corresponding to 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 also be an amine oxide surfactant represented by the following general formula (2c).

[0058] R6-N ＋ (CH ３ ) ２ O － (2c) (In general formula (2c), R6 represents a linear or branched alkyl group or alkenyl group.) In general formula (2c), R6 represents a linear alkyl group, and in general formula (2b), R4 preferably 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 fall under 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, for example, a cationic surfactant having a quaternary ammonium skeleton containing at least one compound represented by general formula (3a).

[0061] R1-N ＋(R2R3)-R4 (3a) (In the general formula (3a), R1 represents a linear or branched alkyl group or a linear or branched alkenyl group, and —CH ２ - may be substituted 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 -CH ３ may be substituted with 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 enhance ink releasability, specifically an alkyl group or alkenyl group having 8 to 30 carbon atoms is preferred, an alkyl group having 10 to 25 carbon atoms is preferred, or an alkyl group or alkenyl group having 12 to 22 carbon atoms is preferred. The alkyl group or alkenyl group may be linear or branched, but is preferably linear, and is more preferably a linear alkyl group.

[0062] R1 is an alkyl or alkenyl group having at least one —CH ２ - may be substituted with -C(=O)-, -NH- or -C(=O)-NH-. Among these, at least one -CH ２ - is preferably substituted with -C(=O)-NH- or -NH-C(=O), and one -CH ２ It is preferable that - 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 preferably represents a linear or branched alkyl group, a linear or branched alkenyl group, or a phenyl group, and more preferably represents a linear or branched alkyl group. ３ 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 preferred that R2 and R3 also represent methyl groups, and general formula (3a) represents an alkyltrimethylammonium skeleton.

[0067] When R4 represents an ethyl group, the terminal —CH ３ is preferably substituted with a carboxy group or a phenyl group. ２ It is preferable that the compound represented by general formula (3a) represents —(C(═O)OH or 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 ＋ (CH ３ ) ２ R4 (3a-1) (In general formula (3a-1), n ​​represents the average number of moles added, and R4 has the same meaning as R4 in general formula (3a) described in claim 3.) In 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 a stearyl group, each 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 quaternary ammonium skeleton salts formed with halogens. － It is preferable to form a salt with Br － It is preferable to form a salt with I, and more preferably I － It is preferable that the quaternary ammonium skeleton salt that forms a salt with a halogen accelerates the hydrolysis of the ink film due to the nucleophilic action of the halogen, and is therefore thought to improve the removability 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), manufactured by NOF Corporation, 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, and Nissan Cation F. ２ -50R, Nissan Cation M ２-100R, manufactured by Daiichi Kogyo Co., Ltd., Catiogen TML, Catiogen TMP, Catiogen TMS, Catiogen DDM-PG, Catiogen BC-50, and Catiogen TBB, manufactured by Kao Corporation, Cortamine 24P, Cortamine 86P Concentrate, Cortamine 60W, Cortamine 86W, Sanisole C, and Sanisole B-50, and manufactured by Lion Corporation, Lipoguard C-50, Lipoguard T-28, Lipoguard T-30, Lipoguard T-50, Lipoguard T-800, Lipoguard 16-29, Lipoguard 16-50E, and Lipoguard 18-63. , Lipoguard 22-80, Lipoguard CB-50, Lipoguard 210-80E, Lipoguard 2C-75, Lipoguard 2HP-75, Lipoguard 2HP flakes, Lipoguard 2HT-75, Lipoguard 2HT flakes, Lipoguard 20-751, 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, but are not limited to these.

[0072] Furthermore, 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. Primary monoalkanolamines are preferably lower alkanols having 1 to 4 carbon atoms, and specific examples thereof include monoethanolamine and 2-aminoisobutanol. Secondary monoalkanolamines include N-methylethanolamine, 2-ethylaminoethanol, and isopropanolamine, but substances other than those listed above can also be used as appropriate. These monoalkanolamine compounds can be used alone or in appropriate combinations of two or more, and can also be used by mixing with water. These monoalkanolamine skeleton cationic surfactants are preferably monoalkanolamine salts formed by forming salts 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 surfactant added is preferably 5% by weight or less, and more preferably 2% by weight or less, based on the total amount of the aqueous cleaning solution. The lower limit of the surfactant content is not particularly limited and may be 0% by weight, but when a surfactant is contained, it is preferably 0.1% by weight or more.

[0074] (Water-insoluble alcohol) A solution containing a water-insoluble primary alcohol in water can be used as the 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, pentadecan-1-ol, hexadecan-1-ol, heptadecan-1-ol, octadecane-1-ol, and nonadecan-1-ol. ethanol, icosan-1-ol, heneicosan-1-ol, docosan-1-ol, tricosan-1-ol, tetracosan-1-ol, pentacosan-1-ol, hexacosan-1-ol, heptacosan-1-ol, octacosan-1-ol, nonacosan-1-ol, triacontan-1-ol, policosanol, 2-methylpropan-1-ol, and benzyl alcohol, among which butan-1-ol and benzyl alcohol are preferred.

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

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

[0078] (Aromatic Glycol Ether Solvent) The cleaning liquid usable in step 1 may be water containing an aromatic glycol ether solvent. 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. Of these, ethylene glycol monophenyl ether (phenoxyethanol) is more preferred.

[0079] (Water-soluble alcohol) A cleaning solution usable in step 1 may be water containing a water-soluble primary alcohol. Examples of water-soluble primary alcohols include methanol, ethanol, and propan-1-ol, and industrial alcohols containing any mixture of these may also be used. The water-soluble primary alcohol is preferably present in an amount of 20% by weight or more relative to the amount of water.

[0080] (Water-soluble glycol ether organic solvent) A water-soluble glycol ether organic solvent may be added to water as the cleaning liquid usable in step 1. The cleaning liquid is preferably an aqueous cleaning liquid containing 20% ​​by weight or more of the water-soluble glycol ether organic solvent relative to the water.

[0081] Examples of the water-soluble glycol ether organic solvent include alkylene glycol alkyl ethers.

[0082] (Water-soluble alkylene glycol alkyl ether solvent) R １-O-[CH ２ -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 general formula (4), water-soluble alkylene glycol alkyl ethers are more preferred.

[0083] Examples of the alkylene glycol alkyl ether represented by general formula (4) include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol methyl ethyl ether, ethylene glycol methyl propyl ether, ethylene glycol ethyl propyl ether, ethylene glycol 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 suitable 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), alkylene glycol monoalkyl ethers represented by the general formula (5) are more preferred.

[0085] R ２ -O-[CH ２ -CH(X)-O]n２ -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 liquid containing a water-soluble alkylene glycol alkyl ether represented by general formula (5), the removability can be maintained even in a composition in which the water content is formulated at a rate significantly exceeding 50% by weight. ２ is an alkyl group having 3 or more carbon atoms, n ２ is 1 to 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 in terms of environmental friendliness, flammability, and antifoaming properties.

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

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

[0091] Examples of primary monoalkanolamines include monoethanolamine, 2-aminoisobutanol, and isopropanolamine, while examples of secondary monoalkanolamines include N-methylethanolamine, 2-ethylaminoethanol, and dimethylaminoethanol, but primary and secondary monoalkanolamines other than those exemplified above 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 combinations 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 foam may be generated during the stirring and crushing steps, and if the foam remains, the foam may overflow during the plastic film recovery step. Furthermore, in the plastic film crushing step, if a large amount of foam is entrained 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, with emulsion-type and self-emulsifying silicone compounds being particularly 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 thereto.

[0095] The amount of the defoaming agent in the cleaning solution usable in step 1 is preferably in the range of 0.01 to 5% by weight, more preferably in the range of 0.02 to 4% by weight, and even more preferably in the range of 0.03 to 3% by weight.

[0096] (Liquid Temperature) The liquid temperature of the water or cleaning liquid used in step 1 is not particularly limited as long as it can maintain a liquid state, but it is usually preferable to perform 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 depending on the type of surfactant. The optimal temperature for excellent cleaning effect varies depending on the type of surfactant, but is 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 40°C or lower is preferable, 30°C or lower is preferable, and 20°C or lower is preferable. The smaller the size of the plastic film after crushing, the larger the cross-sectional area, and therefore it becomes easier for each layer constituting the plastic film to swell into a single layer in step 2.

[0097] <Regarding Step 2> The method for separating and recovering plastic films of the present invention includes Step 2 of immersing the plastic film shredded 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] (Immersion Time) In step 2, the immersion time is preferably a time that allows the shredded plastic film to swell sufficiently, and specifically, is preferably 30 minutes or more. More specifically, it is in 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 process of the present invention takes too long. 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 ink layer, swell, increasing the cross-sectional thickness of the plastic film.

[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 required. When building a practical recycling system, it is preferable to set the upper limit of the immersion time to about 4 hours while increasing the liquid temperature. For example, when immersion is performed at room temperature, sufficient swelling can be achieved by immersion for 24 hours or more. Furthermore, when the liquid temperature is 40°C, sufficient swelling can be achieved by immersion for 16 hours. Furthermore, when the liquid temperature is 75°C, sufficient swelling can be achieved by immersion for 2 hours.

[0100] (Temperature) In step 2, the temperature of the cleaning liquid is not particularly limited as long as it can be kept in a liquid state. If the liquid temperature is kept at room temperature, heating is not required, so CO ２ This is preferable as it can contribute to reducing emissions. On the other hand, when efficiency is prioritized as a practical recycling system, a method of shortening the immersion time while increasing 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 depending on the type of surfactant. The optimum temperature for excellent cleaning effect 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. There is no particular limit to the upper limit of the liquid temperature as long as the liquid state can be maintained, but usually 90°C or lower is preferable.

[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 preferably 20° C. or less. The smaller the size of the plastic film after crushing, the larger the cross-sectional area becomes, and therefore, in step 3, it becomes easier for the layers constituting the plastic film to separate into single layers, and it also becomes easier to peel off and decolorize the ink layer.

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

[0103] The equipment and method for stirring are not particularly limited, and known methods can be used. Specific examples include a device equipped with a motor equipped with stirring blades that can stir the cleaning solution in a container, a device equipped with a device that generates ultrasonic waves, a device that can shake the entire container, and a wet crusher. The wet crusher can be the same as the crusher described in step 1.

[0104] (Washing Liquid) The washing liquid used in step 2 can be the same as the washing liquid used when using the wet crusher in step 1. Specifically, it preferably 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, increasing the nucleophilicity of the hydroxide ions and allowing the reaction of peeling the ink layer to proceed in a hydrophobic environment, which is effective in peeling the ink film.

[0106] The water-soluble solvent having a flash point of 21°C or higher is preferably a water-soluble solvent among organic solvents that fall under the second and third petroleum categories specified in the Fire Service Act, and preferred examples thereof include diethylene glycol butyl ether, propylene glycol propyl ether, and 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 step 1. Among these, 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 swelled, which allows the plastic film to be easily peeled off completely into single layers 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. However, in the present invention, by carrying out steps 1 and 2, at least a portion 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 the releasability of the ink layer, it is preferable that the cleaning liquid used in step 2 contains a large amount of water-soluble solvent 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.

[0111] Furthermore, the cleaning solution used in step 2 in particular includes inorganic bases, specifically sodium hydroxide and potassium hydroxide. These inorganic bases are preferably contained at a concentration of 0.1 to 10 wt % relative to the total amount of the ink cleaning solution, more preferably 0.1 to 5 wt %. The pH is preferably 10 or higher, more preferably 11 or higher, and even more preferably 12 or higher. Because sodium hydroxide is poorly soluble in organic solvents, it is preferable to use a cationic surfactant in combination with sodium hydroxide when using sodium hydroxide. Specific examples include cleaning solutions containing sodium hydroxide, a cationic surfactant, a water-insoluble aromatic glycol ether solvent, and a water-soluble alcohol or water-soluble alkanolamine solvent. On the other hand, because potassium hydroxide is readily soluble in organic solvents, it is not necessary to use a cationic surfactant in combination with potassium hydroxide. Specific examples include cleaning solutions containing potassium hydroxide and a water-soluble alcohol or aromatic glycol ether solvent.

[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] Furthermore, the cleaning solution used in step 2 may contain a surfactant. The surfactant is not particularly limited, and known surfactants can be used, including, for example, anionic surfactants, nonionic surfactants, amphoteric surfactants, and cationic surfactants. 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, a surfactant can be used alone or in combination of two or more types. The amount of surfactant added is preferably 5% by weight or less, and more preferably 2% by weight 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 weight, but when a surfactant is contained, it is preferably 0.01% by weight or more.

[0114] <Regarding Step 3> The method for separating and recovering plastic films of the present invention includes Step 3, in which, after Steps 1 and 2, the crushed and swollen plastic film is stirred in a rinse solution to separate the plastic film.

[0115] (Rinse liquid) 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. Using 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 higher 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, and 2-propyl alcohol. Industrial ethanol containing these may be used alone or in combination.

[0118] It may also contain the 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 these, butan-1-ol, benzyl alcohol, and ethylene glycol monophenyl ether (phenoxyethanol) are particularly preferred.

[0119] In particular, from the viewpoint of the releasability of the ink layer, the rinse 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 containing a water-soluble solvent as the main component, including alcohols without intentionally blending water, is used, an inorganic salt can be used.

[0121] (Inorganic Salt) The inorganic salt used in the present invention may be any salt usable as a grinding aid, and is not particularly limited. However, from the viewpoint of removing the inorganic salt in a subsequent step, it is preferably water-soluble to the extent that 10 g or more dissolves in 100 g of water at room temperature. Furthermore, it is preferably 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 more preferably is substantially insoluble in the organic solvent. Specific examples include sodium chloride, potassium chloride, calcium chloride, sodium sulfate, potassium sulfate, and aluminum sulfate, with sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate being more preferred. The above-mentioned inorganic salts may be used alone or in combination of two or more.

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

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

[0124] The device for kneading the mixture of plastic film pieces, inorganic salt (grinding aid), and water-soluble organic solvent that has undergone step 2 can be any device that can mechanically grind 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 a Super Mixer manufactured by Kawata Corporation, an FM Mixer or Attritor manufactured by Nippon Coke Company, or a Trimix manufactured by Inoue Seisakusho Co., Ltd., or a continuous kneader such as a KCK Mill manufactured by Asada Iron Works Co., Ltd., can also be used. Other devices can also be used.

[0125] (Agitation) In step 3, the equipment and method for agitation when agitating are performed are not particularly limited, and known methods can be used. Specific examples include an apparatus equipped with a motor with an agitator blade that can agitate the cleaning liquid in a container, an apparatus equipped with a device that generates ultrasonic waves, an apparatus that can shake the entire container, a kneader, a wet crusher, etc. The wet crusher that can be used 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, scraping off ink from a plastic film with an exposed ink layer or applying shear stress to a plastic film with an ink layer formed between multiple films, thereby facilitating peeling of the laminate.

[0127] Since the wet crusher has a crushing mechanism using fixed blades and rotary blades, the clearance can be easily controlled by its operating conditions. The narrower the clearance, the higher the shear force that can be applied to the plastic film. However, the narrower the clearance, the more likely the plastic film will clog and the faster the temperature of the water or cleaning liquid will rise. Therefore, the clearance is preferably 0.1 mm or more.

[0128] Specifically, the clearance through which the plastic film passes can be set by a method of providing a clearance of a predetermined size or less and applying high shear. For example, the clearance can be set by controlling the size gap between the inner wall of a treatment tank that stirs the plastic film and / or water and the stirring blade to a predetermined size or less, installing a baffle plate at a distance of a predetermined size or less from the tank wall, designing the plastic film and / or water to pass through a screen with holes of a diameter of a predetermined size or less, passing the plastic film and / or water between two rolls with a gap of a predetermined size or less, using a ball mill or the like to sandwich the laminate between the media, or providing a fixed blade on the outside of a rotary blade as in a homogenizer and controlling the gap between the rotary blade and the fixed blade to a predetermined size or less.

[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) referred to here is defined by the following formula: D = v / Δy, where v is the flow rate (m / s) and is calculated as v = π × R × (n / 60), π is the circumference constant, R is the diameter of the rotary blade (m), n is the rotation speed of the rotary blade (rpm), and Δy is the clearance (m), which here refers to the gap (m) between the rotary blade and the fixed blade.

[0131] The larger the diameter of the fixed blades of the wet crusher, the higher the flow rate, so the larger the fixed blades of the wet crusher, the more preferable it is, and 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 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 rotary blade has multiple blades arranged thereon, 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 where 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: Rotary blade rotation speed (rpm) R: Rotary blade diameter (m) g: Gravitational acceleration = 9.8 (m / s ２ Since step 3 is a step of peeling off adhesive, ink layers, etc. from a 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, and the alkali cleaning / cleaning / deinking equipment and cleaning / crushing Scissors Cutter series from Nippon Seam.

[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, dispersers having stirring blades such as turbine blades, paint shakers, roll mills, ball mills, vibration mills, attritors, sand mills, and bead mills.

[0137] The spherical diameter of the media used is preferably 0.5 to 20 mm, more preferably 1 to 10 mm, and even more preferably 2 to 5 mm. Materials for the media include steel, zirconia, alumina, and glass, and can be appropriately selected depending on the properties of the selected rinse solution. Media diameters of less than 0.2 mm are difficult to handle and difficult to recover, while media diameters of more than 5 mm are easy to handle. The residence time in the disperser is preferably 1 to 30 minutes.

[0138] Examples of the media-containing disperser 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., a 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 solution. While this varies depending on the stirring equipment and method used, it is preferably 1 minute or more, more preferably 3 minutes or more, and even more preferably 5 minutes or more to ensure sufficient rinsing. On the other hand, the upper limit of the stirring time is not particularly limited, but 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 film has been subjected to step 3, it is washed and dried. The ink removal rate of the printed portion is then determined by calculating the area through image processing of a photograph taken using 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 washing / ink-adhered area before washing) 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 wet crushing equipment described above to increase the surface roughness of the crushed material to 0.7 μm or more, the plastic film laminate can be separated into single layers. Furthermore, not only the ink layer on the surface of the plastic film laminate but also the ink layer between the laminates can be removed. Therefore, the recovered 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, there is no particular upper limit and it can be adjusted appropriately 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 × 600 μm area using a white light interference microscope manufactured by Ryoka Systems Co., Ltd. Unlike Ra, Sa is not a value determined from a cross section, but rather a value that indicates the entire in-plane area, so it has a wider evaluation range and can evaluate the overall surface roughness.

[0145] (Size of Film Pieces) 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. The length of the short side direction is preferably 20 mm or less, more preferably 10 mm or less, more preferably 5 mm or less, and even more 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 decreases, so the length of the long side direction is preferably 1 mm or more. (Surface Area Ratio of Film Pieces After Step 1 and Step 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 in which the film surface is washed, the smaller the film is during washing compared to its original size, the better the film has been rubbed and washed.

[0146] (Recovery Equipment) The crushed plastic material separated into single layers in step 3 can be recovered layer by layer. The equipment and method for recovering 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 rotary drum screen, etc. can be used.

[0147] (Plastic Film) The plastic film to be separated and recovered by the present invention is a plastic film having at least an ink layer. Plastic films that can be separated and recovered include, without particular limitation, plastic films with an exposed ink layer on the film surface (surface printing), laminated films with an ink layer between multiple films (reverse printing), single-layer films and laminated films that are generally distributed as packaging materials for food packaging and household goods, and plastic films with various types of resin layers discarded through recycling. That is, the separation and recovery method of the present invention is characterized by the fact that they can be treated together without the need for special re-sorting.

[0148] Furthermore, shrink labels, which are laminated films formed into a cylindrical shape, are used on containers such as PET bottles to display product names and add decorative features. When recycling, consumers often peel off the shrink label and discard the PET bottle body and shrink label separately. However, the separation and recovery method of the present invention makes it possible to separate the shrink label from the PET bottle body even when the PET bottle body and shrink label are integrated, and to separate the shrink label 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 possible as specific embodiments of the laminated film, but of course, are not limited to these. (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] (Coating Layer) A functional coating layer may be present on the outermost surface of the laminated film structure. 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 vapor deposition layer or the like in contact with the substrate. The coating layer may be in the form of a laminate of different coating layers. There are no particular restrictions 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 a variety of purposes, including hard coating, silicone-based peeling, IR blocking, waterproof and moisture-proofing, antibacterial properties, UV blocking, heat dissipation, photocatalysis, weather resistance, anti-fogging, fingerprint and stain resistance, self-repellency, and water and oil repellency.

[0152] The laminated film that is the target 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 removal of the ink, etc.

[0153] (Primer Layer) The printing ink is printed on a resin film that will become the base film layer (F1) in the laminate 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) that is a vapor-deposited film layer to form a laminate film. In a laminate film having this layer structure, a primer layer can also 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 in an alkaline solution. This makes it possible to easily separate the laminate film, which has been printed with ink and then laminated with an adhesive, into single-layer films.

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

[0155] The primer layer can be formed using a resin or a low molecular weight compound having an acidic group alone. Alternatively, a resin or a low molecular weight compound having an acidic group can be mixed with a resin not having an acidic group. Examples of resins 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-maleic acid (anhydride) resins, and terpene-maleic acid (anhydride) 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 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 resins can be used singly or in combination.

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

[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, and 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 resins capable of forming films at room temperature include various synthetic resins, such as polyesters, polyvinyl chloride, copolymers of vinyl chloride and other unsaturated double bond-containing monomers, (meth)acrylic acid ester homopolymers, copolymers of (meth)acrylic acid esters and other unsaturated double bond-containing monomers, polystyrene, copolymers of 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 an acidic group 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 determined appropriately 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 printing substrate is, for example, polypropylene (PP), the film-forming resin is preferably at least one thermoplastic resin that is solid at 50°C and that has good adhesion to PP and is selected from the group consisting of ketone-formaldehyde condensates and hydrogenated products thereof, polyesters, vinyl chloride-vinyl acetate copolymers, and polyvinyl acetals. Examples of such ketone-formaldehyde condensates and hydrogenated products include the TEGO® VariPlus series (SK, AP, etc.) manufactured by Evonik Degussa Japan Co., Ltd.; examples of polyesters include the Vylon® series (Vylon 200, etc.) manufactured by Toyobo Co., Ltd.; examples of vinyl chloride-vinyl acetate copolymers include the Solbin® series (Solbin AL, etc.) manufactured by Nissin Chemical Industry Co., Ltd.; and examples of polyvinyl acetals include the S-LEC® 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 the above components is applied to the substrate and dried. The application amount is approximately 0.1 to 5 μm (dry thickness), but if it is less than 0.1 μm, it is difficult to apply uniformly, and if it exceeds 5 μm, it is uneconomical and therefore not practical. Conventional application methods, such as gravure, letterpress, flexography, roll coater, reverse coater, and spray method, are used for application. The formation of the primer layer and printing thereon can be performed continuously (in-line), or the formation of the primer layer and printing can be performed separately.

[0163] When printing is performed immediately after in-line primer coating using a printer such as a roll-to-roll printer, 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 temperature (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 in an amount of about 0.005 to 5% of the total amount of primer.

[0164] Furthermore, 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-solubility 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 be mostly white ink, and the film laminated with adhesive may be difficult to peel off at low temperatures or with low-concentration alkaline solutions. In such cases, the peelability of the ink layer can be improved by introducing a medium layer, which is used in printing inks, 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. When any layer contains a compound having an acidic group, separation and recovery proceeds more easily.

[0168] Among these, it is preferable that one 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 single-layer film in a short time in steps 2 and 3. Specific examples of reactive adhesives having one of the components of the reactive adhesive having an ester bond include reactive adhesives containing either or both of a polyol composition having a polyol compound such as a polyester polyol, polyether ester polyol, polyester (polyurethane) polyol, or acrylic polyol having an ester bond, and a polyisocyanate composition having a polyisocyanate compound that is a reaction product of the polyol compound having an ester bond with one of the various polyisocyanates.

[0169] In addition to the polyol composition and the polyisocyanate composition, reactive adhesives to which a resin having an acidic group or a low molecular weight compound is added can also be preferably used. The resin having an acidic group or the 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 resins and rosin-modified fumaric acid resins; radical copolymer resins such as (meth)acrylic resins, styrene-(meth)acrylic resins, styrene-maleic acid (anhydride) resins, and terpene-maleic acid (anhydride) resins obtained by copolymerizing 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, and 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 mentioned 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 their adhesive strength and causing interfacial delamination. Meanwhile, the alkaline solution itself has a high solubility, so the uncrosslinked printing ink layer also dissolves. Even if the printing ink layer itself is crosslinked, the present invention causes interfacial delamination, so it is presumed that efficient separation and recovery can be performed in a short time.

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

[0176] Printing inks containing resins or low molecular weight compounds having acidic groups 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] The resins and low molecular weight compounds having an acidic group may be the same as those described in the primer layer.

[0178] The printing ink preferably contains the resin or low molecular weight compound having an acidic group. The amount of the resin or low molecular weight compound added may be determined appropriately 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 laminate 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 firmly bonded, making peeling of the ink layer more difficult. However, the method of the present invention can effectively peel off the ink layer even in a reverse printing configuration.

[0180] The ink layer can be a layer that displays any design, pattern, letter, symbol, etc. for the purpose of adding decoration or aesthetic appeal, or indicating the contents, expiration date, manufacturer or seller, etc. The ink layer may be a solid ink layer that does not have any design, pattern, letter, symbol, etc. The method for forming the ink layer is not particularly limited, and the ink layer can be formed using known pigments and / or dyes. The ink layer can preferably be formed using printing ink containing pigments and / or dyes. 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 their combined use is preferred because it further improves dispersion stability and 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 single layers and remove the ink layer. However, if the F2 film is partially peeled off in step 1, or if F2 is crushed into a state that makes it easy to peel 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 vapor-deposited films obtained by vapor-depositing alumina, silica, or the like onto 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] Preferred flexible polymer films for the sealant layer (F2) include polyethylene films, polypropylene films, polyolefin films such as ethylene-vinyl acetate copolymers, ionomer resins, EAA resins, EMAA resins, EMA resins, EMMA resins, and biodegradable resin films. Examples of generic names include CPP (non-oriented polypropylene) films, VMCPP (aluminum-vapor-deposited non-oriented polypropylene film), LLDPE (linear low-density polyethylene), LDPE (low-density polyethylene), HDPE (high-density polyethylene), VMLDPE (aluminum-vapor-deposited non-low-density polyethylene film), and films containing these pigments. The film surface may be subjected to various surface treatments, such as flame treatment, corona discharge treatment, or chemical treatment using a release primer or the like.

[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 even more preferably 10 μm or more and 50 μm or less.

[0188] From the viewpoint of reuse as a recycled substrate, the substrate preferably contains a polyolefin resin film such as polyethylene or biaxially oriented polypropylene.

[0189] Examples of the metal foil layer (M) include foils of metals with 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 made of natural paper, synthetic paper, etc. The first and second sealant layers may be made of the same material as the sealant layer described above.

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

[0192] <Particle size distribution of detached ink components> The median diameter (D50) of the detached ink components is preferably 1 μm or more. By having the median diameter of the detached ink layer components be 1 μm or more, it is possible to suppress the detached ink components from reattaching to the substrate, and to obtain a colorless recycled material. The median diameter of the detached ink components 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 likely to re-adhere to 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 re-adhesion 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 using a laser diffraction particle size distribution analyzer. The span value A is expressed by the following formula:

[0195] A = (D90 - D10) / D50, where D10 is the cumulative 10% diameter of the volume-based particle size distribution obtained by laser diffraction particle size distribution measurement of the detached ink component. D90 is the cumulative 90% diameter of the volume-based particle size distribution obtained by laser diffraction particle size distribution measurement of the detached ink layer component. <Method for Manufacturing Molding Material> Molding pellets can be produced by melt-kneading recycled plastic film pieces recovered by the above-described recycled plastic film manufacturing method. In the melt-kneading process, various additives are added as needed, and the mixture is mixed using a Henschel mixer, tumbler, disperser, etc., followed by mixing and dispersion using a kneader, roll mill, twin-screw extruder, single-screw extruder, rotor-type twin-screw kneader, etc. This produces a recycled resin, which is a resin composition. The shape of the recycled resin is not particularly limited and may be in the form of pellets, powder, granules, or beads. A twin-screw extruder is preferably used for the melt-kneading process. The molding material may further contain a masterbatch. The masterbatch is not particularly limited as long as it is compatible with the recycled resin. 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 masterbatch may be used alone or in combination of two or more. The masterbatch may contain, within the scope of the present invention, a metal soap of an alkali metal, 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 bisalkylamide, an antioxidant, an ultraviolet absorber, a filler, or a peroxide, as long as the effects of the present invention are not impaired.

[0196] <Molded Products> Molded products can be obtained by heat molding the molding material obtained by the above-described production method. The heat molding method is not particularly limited, and examples thereof include injection molding, extrusion molding, blow molding, and compression molding. Molded products produced using plastic substrates recovered by the separation and recovery method of the present invention are of high quality because the ink layer has been detached and re-adhesion of adhesive components has been suppressed. They can be used in a variety of fields, such as home appliances, stationery, automotive parts, toys, sporting goods, medical applications, and building and construction materials.

[0197] Additives that can be used in the manufacturing process of recycled pellets obtained by the manufacturing method of recycled plastic film include at least one antioxidant selected from the group consisting of phenolic and phosphorus-based antioxidants, at least one lubricant selected from fatty acid amides, alkylene fatty acid amides, metal soaps, and esters, hindered amine-based weather stabilizers, waxes with 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 phenolic 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 phenyl)propionyloxy}ethyl}2,4,8,10-tetraoxaspiro]5,5-undecane, 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 neopentanetetraylbis(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 neopentanetetraylbis(2,4-di 2,2-methylenebis(4,6-t-butylphenyl) phosphite, cyclic neopentanetetraylbis(2,6-di-t-methylphenyl) phosphite, and 2,2-methylenebis(4,6-t-butylphenyl) octyl phosphite.

[0199] These antioxidants may be used alone or in combination of two or more. The amount of 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 preferred in terms of antioxidant properties, and an amount of 1 mass% or less is preferred in terms of processability.

[0200] Examples of fatty acid amide 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-oleylamide, 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 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 preferred in terms of activity, and an amount of 1 mass% or less is preferred 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 with an acid value of 5 mgKOH / g or less include natural waxes and synthetic waxes. Examples of natural waxes include plant-based waxes such as calidrilla wax, carnauba wax, rice wax, and Japan wax; animal-based 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 obtained by modifying natural waxes or natural wax-like materials through chemical treatments such as esterification, amidation, and neutralization with acidic waxes. Examples of synthetic waxes include synthetic hydrocarbons such as polyethylene-based waxes, polypropylene-based waxes, and polystyrene-based 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. 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 preferred in terms of fluidity adjustment, and an amount of 50 mass% or less is preferred in terms of processability.

[0206] Examples of anionic surfactant-based antistatic agents 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 sorbit 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. 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 preferred in terms of antistatic properties, and an amount of 1 mass % or less is preferred 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, or may be used after being diluted 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] Modifying 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 include, but are not limited to, tensile strength, flexural strength, elongation at break, tensile modulus, flexural modulus, and yield stress.

[0214] 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 Corporation, maleic anhydride-modified polybutene such as Nippon Oil Corporation's Nisseki Polybutene, ethylene methacrylic acid copolymer such as Nucrel manufactured by DuPont-Mitsui Polychemicals, ethylene methacrylic acid copolymer such as Yukalon manufactured by Mitsubishi Chemical Corporation, maleic anhydride-modified ethylene-propylene rubber such as Tafmer M (MA8510) manufactured by Mitsui Chemicals, Inc. and TX-1215 manufactured by Mitsui Chemicals, Inc., and Examples of the maleic anhydride-modified polyethylene include maleic anhydride-modified ethylene-butene rubber such as Tafmer M (MH7020) manufactured by I Chemicals, Inc., HPR series (maleic anhydride-modified EEA) manufactured by DuPont-Mitsui Polychemicals, Bondine (maleic anhydride-modified EEA) manufactured by Atofina, Tuftec (maleic anhydride-modified SEBS, M1943) manufactured by Asahi Kasei Corporation, Kraton (maleic anhydride-modified SEBS, FG1901X) manufactured by Kraton Polymers, Tufprene (maleic anhydride-modified SBS, 912) manufactured by Asahi Kasei Corporation, Septon (maleic anhydride-modified SEPS) manufactured by Kuraray Co., Ltd., Rexpearl (maleic anhydride-modified EEA, ET-182G, 224M, 234M) manufactured by Japan Polyolefins Co., Ltd., and Aurouren (maleic anhydride-modified EEA, 200S, 250S) manufactured by Nippon Paper Chemicals Co., Ltd.

[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 non-acid-modified thermoplastic elastomers 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 Co., Ltd. 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 process, conventional 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. Melt-kneading is difficult at temperatures below 180°C, while the physical properties of the recycled pellets produced are significantly reduced at temperatures above 260°C. 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, while if it is too high, the heat generated during kneading significantly reduces the physical properties of the recycled pellets produced.

[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 even more preferably 5 to 30 g / 10 min. By ensuring that the melt mass-flow rate is within the above range, a recycled material suitable for various molding processes such as injection molding and extrusion molding can be provided.

[0219] (Evaluation of decolorization 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 hot-pressed at 200°C using a heat press to prepare 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 prepare a press plate with a thickness of 1 mm, and the color difference ΔE was calculated using the following formula: ΔE = ((L ＊ x-L ＊ y) ２ + (a ＊ x-a ＊ y) ２ +(b ＊ x-b ＊ y) ２ ) １／２ x: raw 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 in the washing process to the extent that their color is indistinguishable from that of the raw pellets, and are therefore highly useful as recycled pellets. Furthermore, since many molded products are melt-kneaded with a masterbatch 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 formed into a film having a thickness of about 100 μm, the total light transmittance thereof 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] (Mixing recycled pellets with virgin pellets) In the melt-kneading process of the plastic film from which the ink layer has been removed, virgin plastic pellets can be mixed at any ratio depending on the purpose. For example, the mixing ratio of recycled pellets to virgin pellets, calculated by weight, is 99.5:0.5 to 50:50. From the viewpoint of recyclability, it is preferable to increase the ratio of recycled pellets as much 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 polypropylenes, thermoplastic elastomers, and polyethylenes using metallocene catalysts, 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 of Shredding Plastic Film First, plastic films are 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, crushing in the crusher in the next process can be carried out 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, or the like. The size and shape of the plastic film to be fed are not particularly limited, but the maximum length of the plastic pieces is preferably, for example, 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, the more effective the immersion in the cleaning solution in step 2, and therefore the smaller the crushed film size in step 1, 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 suction of the crusher and crushed into pieces of about 1 to 20 mm or 5 to 20 mm, and then sent to the next step in 0.03 m pieces. ３ The film is pumped at a rate of 1 / min. At this time, the high shear force that the film receives when it is crushed causes at least a portion of each layer constituting the laminate film to be easily separated into single layers. If the laminate film has an ink layer, the high shear force caused by crushing also makes the ink layer easily peeled and removed from the film, and it is preferable that at least a portion of the ink layer is peeled off.

[0227] Even if the object to be shredded is not a laminated film roll but individual film bags collected from the market, they can be fed into the shredder in the same state as when they were collected.

[0228] When a plastic film is pulverized into powder using an attritor as a 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 attritor is pulverized to about 10 to 500 μm.

[0229] The crushing step in step 1 may be carried out once or in several steps.

[0230] (2) Step 2 of Immersing Plastic Film in Cleaning Solution In step 2, the crushed plastic material crushed in step 1 may be immersed in the cleaning solution by being left to stand, or may be immersed and stirred as necessary using a known stirring device such as a Homo Disper or a wet crusher similar to that used in step 1. If the crushed plastic film is front-printed, the ink layer on the surface 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 sufficiently.

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

[0232] (3) Step 3: Separating the Plastic Film by Agitating the Shredded Plastic Film in a Rinse Solution After swelling the plastic film in steps 1 and 2, the plastic film is agitated in a rinse solution to separate the plastic film. After separation, the rinse solution contains the separated single-layer films and residues of adhesives, printing inks, metal foils, etc., floating or dissolved therein. These are removed from the rinse solution and then separated and recovered.

[0233] As an example of a specific method, for example, in flotation separation, plastics with low specific gravity, such as polyolefins such as polypropylene and polyethylene, are separated from heavy materials such as condensation synthetic films such as polyester and nylon, or metal foils, which have a higher specific gravity than polyolefins, and the heavy materials are removed. If necessary, the recovered plastics are then further 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 containing vinyl chloride resins and polyethylene terephthalate, which sink in water with a specific gravity of 1 or more, and plastics containing olefin-based resins such as polyethylene and polypropylene, which do not contain vinyl chloride resin. Further separation is possible by changing the specific gravity by appropriately changing the blending ratio of the liquid used in the flotation separation, such as water to an organic solvent or salt.

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

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

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

[0237] (4) Recovery and reuse of cleaning solution (Step 4) The water, cleaning solution, and rinse solution used in Steps 1 to 3 are recovered by supplying them to one or more recycling machines selected from a filter, a centrifuge, and an ultrafilter, and then reused after removing solids. While the wet crushing step and the gravity separation step are performed in Steps 1 to 3, the water, cleaning solution, or the cleaning solution recycling step can be continuously operated to separate solids from the water, cleaning solution, and rinse solution.

[0238] (5) Drying of Separated Plastics (Step 5) The plastic film recovered in Step 3 is dried by one or more methods selected from reduced-pressure heat drying, hot air drying, and pressurized compression drying to remove residual moisture. As a pretreatment for producing recycled pellets (described below), briquettes may be produced after or during the drying of the recovered film pieces using a pressurized compressor such as a Nippon Seam compression dehydrator, a Oike Iron Works pellet mill, or an Elcom Stella or briquette machine. When the plastic film is pulverized into powder using a wet grinder, the crushed material is crushed to a size of approximately 10 to 500 μm. Since the crushed material has a high density, 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 when feeding it into a kneader. Specifically, a dry weight of 0.03 kg or more is preferred, 0.05 kg or more is more preferred, 0.2 kg or more is more preferred, and 0.3 kg or more is even more preferred.

[0239] (6) Preparation of Recycled Pellets (Step 6) The film pieces or briquettes dried in Step 5 are fed into a single-screw or twin-screw extruder to prepare recycled pellets. When film pieces are fed directly into the extruder without the pressure compression step, a phenomenon known as bridging, in which ink pieces clog the inlet, is likely to occur. To avoid bridging, the film pieces may be pressurized in the feeder section or pushed in with air. Alternatively, the feeder section may use two counter-rotating screws, or a side feeder may be used to push in the film. The kneader conditions are not particularly limited, but it is preferable to operate the kneader at 180 to 260°C to avoid significant deterioration of the resin performance before recycling.

[0240] The contents and effects of the present invention will be explained 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. (Films used in laminated film) OPP: biaxially oriented polypropylene film 20 μm CPP: unoriented polypropylene film 35 μm (Printing inks) INK1: Glossa 507 primary blue S2 manufactured by DIC Graphics INK2: Finart R507 primary blue manufactured by DIC Graphics INK3: Finart R794 white S manufactured by DIC Graphics (Reactive adhesives) AD1: solvent-based adhesive Dickdry LX-401A and SP-60 two-component adhesive (ether-based adhesive) AD2: solventless adhesive Dickdry 2K-SF-400A and HA-400B two-component adhesive (ester-based 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 laminating method described below. The layer structure of the film, the reactive adhesive, and the type of printing ink were combined as shown in Table 1.

[0241] (Printing Method) Each gravure ink used as printing ink was applied to the film "Film 1" using a proofer.

[0242] (Lamination method) The reactive adhesive "AD" was applied to the printing ink-drawn surface of the film "Film 1" using a laminator to a coating amount of 3 g / m2 solid content, and then laminated to the film "Film 2". 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 blank spaces indicate that no configuration was present.

[0243]

[0244] (Step 1: Crushing Step) Print 1 and LAMs 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 about 5 to 10 mm and the long side was about 10 to 20 mm.

[0245] (Step 2, Immersion Step) PRO_A: Gently immersed in a 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, a solvent shown in Table 2, and 2 wt% 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 any amounts less than 100%.

[0247]

[0248]

[0249] (Step 3, Stirring and 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 rinse solution, and a vibration mill manufactured by Chuo Kakoki Co., Ltd. was used as the equipment, with a stainless steel rod having a diameter of 19 mm as the media, and the rod filling rate was 30%, and the operation was carried out 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 equipment was a Mighty Blender manufactured by Osaka Gas Chemicals, and the operation was carried out for 5 minutes at 19,000 rpm. 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, with a Mighty Blender manufactured by Osaka Gas Chemicals, and the operation was carried out for 5 minutes at 19,000 rpm. 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 liquid. PRO_Z: 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 a solution consisting of 100 mL of "diethylene glycol normal butyl ether" used as a rinse liquid and 400 g of zirconia balls with a diameter of 4.8 mm.

[0250] (Evaluation of decolorization of recycled pellets) The results in Tables 4 to 6 show the state of ink removal from the plastic film. Pieces of plastic film that had been sequentially subjected to steps 1 to 3 were extruded at 200°C using a twin-screw extruder to produce recycled pellets. The obtained recycled pellets 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 for the plastic film (non-recycled F-300SP manufactured by Prime Polymer Co., Ltd.) were also subjected to the same hot pressing 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 Note that ◎, ○, and △ are in the range where there is no problem in practical use.

[0251]

[0252]

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

[0254]

[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: 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.

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

3. A 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 solution to swell the ink layer.

4. 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.

5. A method for separating and recovering plastic films as described in claim 1 or 2, wherein in step 1, the long sides of the crushed plastic film are crushed to 1 mm or more and 30 mm or less.

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

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