Manufacturing method for molded products

Abstract

To provide a method for manufacturing a molded article capable of obtaining the molded article excellent in stretchability by recovering a recycled plastic from a laminate having a plastic film layer and a functional layer.SOLUTION: A method for producing a molded article, comprising an immersion step of immersing a laminate comprising a plastic substrate layer and a functional layer in a releasing liquid containing an alkali, a shaking step of shaking the immersed laminate in the presence of water using a continuous shaking apparatus comprising a dispersion medium in a container to obtain a recycled plastic, an extrusion step of melt-kneading and extruding the recycled plastic or a composition containing the recycled plastic, a take-up step of taking up the extruded melt-kneaded product as a strand, and a molding step of molding the strand.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a molded product.

Background Art

[0002] Currently, the amount of waste plastic that is separately collected (recycling rate) is 9% of the plastic produced globally. As for the breakdown of the 91% of waste plastic that was not separately collected, 12% was incinerated, 79% was landfilled, or leaked into the environment (Non-Patent Document 1). One of the reasons for the continued low recycling rate is the difficulty of the separate collection system.

[0003] Specifically, in order to recycle plastic, it is necessary to separate and collect waste plastic in which different plastic materials such as polyethylene (PE) and polypropylene (PP) are integrated, by material. However, in many plastic products including laminated films, different plastic materials are adhered to each other, making it difficult to separate and collect them by material. Therefore, there is a strong demand for the construction of a recycling system that can easily separate and collect waste plastic.

[0004] In addition, from the perspective of cost, it is difficult for recycled plastic products to return to the same products as before recycling. Moreover, plastic products basically deteriorate every time they are recycled. Therefore, the quality of recycled plastic products has to decline.

[0005] In this regard, one reason why the quality of recycled plastic deteriorates is the presence of ink or pigment as an impurity in the plastic. In particular, many plastic products have printing applied to their surface, making it difficult to decolorize them during the recycling process. Furthermore, the plastic film that makes up plastic products generally has various functional layers in addition to the ink layer (printing layer), such as a hard coat layer, adhesive layer, and detachable primer layer. However, components derived from these functional layers can also cause unintended discoloration.

[0006] As a result, recycled plastic products are often colored. Such recycled plastic products not only have significantly lower commercial value due to the coloring, but their physical properties, such as elasticity, can also deteriorate due to impurities. Therefore, there is a need for methods to produce high-quality recycled plastic products.

[0007] For example, Patent Document 1 proposes a method for recycling multilayer film waste containing plastic and aluminum layers. Specifically, Patent Document 1 discloses a recycling method in which, for crushed multilayer film, the aluminum layer is dissolved in alkali, the remaining crushed material is separated by the difference in specific gravity, and then selectively heated and dissolved in an organic solvent, thereby separating the valuable components.

[0008] Furthermore, Patent Document 2 proposes a method for removing ink from printed plastic films. Specifically, Patent Document 2 discloses a method in which a printed plastic film is processed with a plunger, then crushed with a crusher, then the ink on the film is removed in a predetermined washing system, then the processed plastic film is rinsed, and then dried. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] Science Advances 19 Jul 2017:Vol. 3, no. 7, e1700782 [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2006-205160 [Patent Document 2] Special Publication No. 2015-520684 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] However, the methods described in Patent Documents 1 and 2 are both lengthy, complex, and involve many steps. Furthermore, the method described in Patent Document 1 is limited to the removal of the aluminum layer, and the method described in Patent Document 2 is limited to the removal of the ink. Therefore, it is difficult to remove various functional layers using these methods.

[0012] Furthermore, Patent Documents 1 and 2 focus primarily on the removal of layers formed on plastic films, and do not address improving the physical properties of recycled plastic products (molded articles), such as their extensibility.

[0013] Therefore, the object of the present invention is to provide a method for manufacturing a molded article that can recover recycled plastic from a laminate comprising a plastic substrate layer and a functional layer, and obtain a molded article with excellent stretchability. [Means for solving the problem]

[0014] The inventors, after diligent research, discovered that the above problems could be solved by using a laminate comprising a plastic substrate layer and a functional layer as raw material and going through a predetermined process, leading to the present invention. The gist of the present invention, which solves the above problems, is as follows.

[0015] [1] A method for manufacturing a molded product, which comprises recovering recycled plastic from a laminate comprising a plastic substrate layer and a functional layer, and manufacturing a molded product using the recycled plastic, the method comprising: an immersion step of immersing the laminate in a stripping liquid containing an alkali; a shaking step of obtaining recycled plastic by shaking the immersed laminate in the presence of water using a continuous shaking device provided with a dispersion medium in a container; an extrusion step of melt-kneading and extruding the recycled plastic or a composition containing the recycled plastic; a take-up step of taking up the extruded melt-kneaded product as a strand; a molding step of molding using the strand; comprising: the filling rate of the dispersion medium in the container of the continuous shaking device used in the shaking step is 30 vol% or more and 80 vol% or less; the melt-kneading temperature in the extrusion step is 40°C or more and 120°C or less than the melting point of the recycled plastic; A method for manufacturing a molded product, characterized by the above.

[0016] [2] The method according to [1], wherein the take-up speed of the strand in the take-up step is 8 m / min or more and 50 m / min or less.

[0017] [3] The method according to [1] or [2], wherein the molding step is performed using a mold, the mold temperature is 20°C or more and 60°C or less, and the molding time is 10 seconds or more and 45 seconds or less.

[0018] [4] The method according to any one of [1] to [3], further comprising a rinsing step of rinsing the recycled plastic with a rinsing liquid after the shaking step.

[0019] [5] The method according to [4], wherein the rinsing liquid contains a water-soluble solvent. [Advantages of the Invention]

[0020] According to the present invention, it is possible to provide a method for manufacturing a molded article that allows for the recovery of recycled plastic from a laminate comprising a plastic substrate layer and a functional layer, thereby obtaining a molded article with excellent stretchability. [Modes for carrying out the invention]

[0021] The present invention will be described in detail below based on its embodiments.

[0022] <Method for manufacturing molded products> A method for manufacturing a molded article according to one embodiment of the present invention (hereinafter sometimes referred to as "the method of this embodiment") is a method for manufacturing a molded article that recovers recycled plastic from a laminate comprising a plastic substrate layer and a functional layer, and manufactures a molded article using the recycled plastic. The method of this embodiment is characterized by comprising: an immersion step of immersing the laminate in a desorption liquid containing alkali; a shaking step of obtaining recycled plastic by shaking the immersed laminate in the presence of water using a continuous shaking device equipped with dispersed media in a container; an extrusion step of melting and kneading the recycled plastic or a composition containing the recycled plastic and extruding it; a take-up step of taking up the extruded molten mixture as strands; and a molding step of molding using the strands. Furthermore, the method of this embodiment is further characterized in that the continuous shaking device used in the shaking step has a filling rate of the dispersed media in the container of 30 vol% or more and 80 vol% or less, and the melt-kneading temperature in the extrusion step is 40°C or more and 120°C or less, which is the melting point of the recycled plastic.

[0023] As a result of diligent research by the inventors, it has been found that by using a laminate comprising a plastic substrate layer and a functional layer as the object to be processed, as in the method of this embodiment, and by performing predetermined immersion and shaking steps, it is possible to obtain recycled plastic suitable as a molded product material. Furthermore, it has been found that by performing predetermined extrusion, take-up, and molding steps using such recycled plastic, it is possible to obtain molded products with excellent extensibility. This improvement in extensibility is presumed to be due to the specific changes in the crystalline structure and higher-order structure of the plastic substrate layer (and thus the recycled plastic) caused by appropriately performing the predetermined shaking step and optimizing the melt-kneading temperature in the extrusion step.

[0024] Furthermore, the method of this embodiment is not limited to printed layers, but can also be used as a processing target even if it is a laminate in which various functional layers described later are provided on a plastic substrate layer, and a desired molded product can be manufactured.

[0025] (Laminate as the target of processing) In the method of this embodiment, a laminate comprising at least a plastic substrate layer and a functional layer is used as the object to be processed.

[0026] The laminate used in this embodiment is, for example, a non-roll form plastic film. Alternatively, the laminate can be cut from a roll form plastic film.

[0027] The laminate used in this embodiment may be, for example, a waste plastic film (discarded plastic film). The laminate is not particularly limited, and can be a plastic film that is commonly distributed as packaging material for food or household goods, or a film with various types of discarded plastic substrates. The laminate may be used alone or in combination of two or more types.

[0028] Furthermore, the laminate used in this embodiment may have only one plastic substrate layer, or it may have two or more. When the laminate has two or more plastic substrate layers, the plastics constituting these plastic substrate layers may be the same, or they may be different from one another.

[0029] Furthermore, the laminate used in this embodiment may have only one functional layer or two or more functional layers. If the laminate has two or more functional layers, these functional layers may be identical or different.

[0030] The laminate used in this embodiment may be, for example, a laminate having a functional layer on its outermost surface. The laminate used in this embodiment may be, for example, a laminate in which a functional layer is provided between a plurality of plastic substrate layers.

[0031] [Plastic substrate layer] As described above, the laminate used in this embodiment comprises a plastic substrate layer. The plastic substrate layer refers to a layered member that contains plastic as its main constituent resin.

[0032] Examples of plastic substrate layers include: polyolefin films composed of polyolefins; polyester films composed of polyethylene terephthalate (PET), polybutylene terephthalate, etc.; polyamide films composed of nylon 6, nylon 6,6, metaxylene adipamide (N-MXD6), etc.; biodegradable films composed of polylactic acid, etc.; polyacrylonitrile films; poly(meth)acrylic films; polystyrene films; polycarbonate films; ethylene-vinyl acetate copolymer saponified (EVOH) films; polyvinyl alcohol films; triacetylcellulose films, etc.

[0033] More specifically, the above-mentioned polyolefins include polyethylene such as low-density polyethylene, high-density polyethylene, and linear low-density polyethylene; polypropylene such as OPP (biaxially oriented polypropylene) and CPP (unoriented polypropylene); propylene-ethylene copolymer; ethylene-butene-propylene copolymer; and the like.

[0034] In particular, from the viewpoint of the versatility and ease of recovery of the final molded product, the plastic substrate layer preferably contains polyolefin as the main constituent resin, and more preferably contains polypropylene such as OPP or CPP as the main constituent resin. That is, the plastic substrate layer is preferably a polyolefin film, and more preferably a polypropylene film.

[0035] The thickness of the plastic substrate layer is not particularly limited, but is preferably, for example, 5 μm or more, or 10 μm or more, and also preferably, for example, 500 μm or less, 200 μm or less, 100 μm or less, or 50 μm or less.

[0036] The plastic substrate layer is preferably in contact with the functional layer in the laminate. Furthermore, the plastic substrate layer is preferably located on the outermost surface of the laminate.

[0037] [Functional Layer] As described above, the laminate used in this embodiment includes a functional layer. The functional layer is not particularly limited and includes, for example, a printing layer (also called an ink layer), an adhesive layer, a detachable primer layer, a functional coating layer, etc. The laminate may have one of these functional layers alone, or two or more in combination.

[0038] Functional layers (printing layers, adhesive layers, detachable primer layers, functional coating layers, etc.) may contain resins having acidic groups or low-molecular-weight compounds having acidic groups. In addition, the above functional layers may contain resins that do not have acidic groups, in addition to resins having acidic groups or low-molecular-weight compounds having acidic groups.

[0039] Examples of resins having acidic groups include rosin-modified maleic acid resins, rosin-modified fumaric acid resins, and polymer resins obtained by copolymerizing polymerizable monomers having acidic groups. Examples of polymerizable monomers having acidic groups include polymerizable monomers having carboxyl groups such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, cinnamic acid, or their acid anhydrides, polymerizable monomers having sulfonic acid groups such as sulfonated styrene, and polymerizable monomers having sulfonamide groups such as vinylbenzenesulfonamide. Specific examples of the above polymer resins include (meth)acrylic resins, styrene-(meth)acrylic resins, styrene-(anhydride)maleic acid resins, and terpene-(anhydride)maleic acid resins.

[0040] Examples of low molecular weight compounds containing acidic groups include saturated fatty acids, unsaturated fatty acids, hydroxy acids, aromatic carboxylic acids, dicarboxylic acids, tricarboxylic acids, oxocarboxylic acids, carboxylic acid derivatives, and acid anhydrides.

[0041] Examples of saturated fatty acids include lauric acid, myristic acid, palmitic acid, margaric acid, and stearic acid, while examples of unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and sorbic acid. Examples of hydroxy acids include lactic acid, malic acid, and citric acid. Examples of aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, melitic acid, and cinnamic acid. Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, and maleic acid. Examples of tricarboxylic acids include aconitic acid. Examples of oxocarboxylic acids include pyruvate and oxaloacetate. Examples of carboxylic acid derivatives include amino acids and nitrocarboxylic acids. Examples of acid anhydrides include trimellitic anhydride and pyromellitic anhydride.

[0042] -Print layer- The laminate used in this embodiment may include a printed layer as a functional layer. The printed layer is typically a layer containing ink. The printed layer may be a layer on which any picture, pattern, character, and symbol is displayed for the purpose of decoration or aesthetic appeal, or for displaying contents, expiration date, and manufacturer or seller information. Alternatively, the printed layer may be a layer on which no picture, pattern, character, or symbol is displayed (i.e., a layer without gaps, a solid layer).

[0043] The printed layer is formed by printing using, for example, a gravure printer, a flexographic printer, an offset printer, or an inkjet printer. That is, the ink used to form the printed layer may be gravure ink, flexographic ink, offset ink, or inkjet ink.

[0044] The ink may be, for example, an organic solvent-based printing ink, a water-based ink, or an active energy ray-curing ink. The ink contained in the printing layer may be a single type or a combination of two or more types. Furthermore, the printing layer may be a single-color printing layer or a multi-color printing layer.

[0045] The printed layer may be located on the outermost surface of the laminate, or it may be sandwiched between other layers.

[0046] -Adhesive layer- The laminate used in this embodiment may include an adhesive layer as a functional layer. The adhesive constituting the adhesive layer can be any adhesive that can be used in a general-purpose lamination method. Examples of lamination methods include dry lamination and wet lamination using solvent-type laminating adhesives, and non-solvent lamination using solvent-free laminating adhesives.

[0047] Examples of the adhesives mentioned above include vinyl resins, (meth)acrylic resins, polyamide resins, polyester resins, polyether resins, polyurethane resins, epoxy resins, and rubber resins. Such adhesives may be one-component or two-component types, and may be curing or non-curing types.

[0048] The adhesive layer is typically formed by applying an adhesive layer composition (solution) to the surface to be bonded and allowing it to dry.

[0049] The adhesive layer is preferably sandwiched between other layers in the laminate (plastic substrate layer; functional layer other than the adhesive layer; etc.).

[0050] -Desorbable primer layer- The laminate used in this embodiment may include a detachable primer layer as a functional layer. In this case, recyclability can be improved, and the quality of recycled plastic can be improved. The detachable primer layer can be easily detached from other layers by treatment with an alkali-containing solution (detachment solution).

[0051] In a laminate, the deleasable primer layer is preferably in contact with the plastic substrate layer. Furthermore, it is preferable that the deleasable primer layer in the laminate is bonded to and sandwiched between the plastic substrate layer and other functional layers (e.g., a printing layer, an adhesive layer, a functional coating layer, etc.). In this case, recyclability can be further improved, and the quality of recycled plastic can be further enhanced.

[0052] A detachable primer layer is typically formed by applying a detachable primer layer composition (solution) to the surface to be formed and allowing it to dry.

[0053] Furthermore, the detachable primer layer (and composition for the detachable primer layer) may contain a resin that forms a film at room temperature. Examples of resins that form a film at room temperature include polyester; polyvinyl chloride; copolymers of vinyl chloride and other unsaturated double-bond-containing monomers; homopolymers of (meth)acrylic acid esters; copolymers of (meth)acrylic acid esters and other unsaturated double-bond-containing monomers; polystyrene; copolymers of styrene monomer and other unsaturated double-bond-containing monomers; ketone-formaldehyde condensates or their hydrogenated products; polyfunctional epoxy resins; polyvinyl acetal; urethane resins; and the like. Examples of polyfunctional epoxy resins include bisphenol A novolac type epoxy resin, bisphenol F novolac type epoxy resin, bisphenol S novolac type epoxy resin, biphenyl type epoxy resin, and naphthalene type epoxy resin. These resins that form a film at room temperature may be used individually or in combination of two or more types.

[0054] In one embodiment, the detachable primer layer preferably contains a urethane resin. Such a detachable primer layer can be formed, for example, using a detachable primer layer composition containing a urethane resin and an aqueous medium.

[0055] Furthermore, urethane resin is a general term for polymer compounds having urethane bonds (-NHCOO-). The above-mentioned urethane resin can be obtained, for example, by reacting an aromatic polyester polyol with a polyisocyanate and, if necessary, a chain extender.

[0056] In another embodiment, the detachable primer layer preferably contains polyvinyl alcohol. Such a detachable primer layer can be formed, for example, using a detachable primer layer composition containing polyvinyl alcohol and an aqueous medium.

[0057] Polyvinyl alcohol is a colorless powder obtained by saponifying polyvinyl acetate. It is also a water-soluble thermoplastic resin and a raw material for the synthetic fiber vinylon.

[0058] Examples of the aqueous medium include water and organic solvents that are miscible with water. The aqueous medium may be used alone or in combination of two or more. Examples of organic solvents that are miscible with water include alcohols such as methanol, ethanol, n-propanol, and isopropanol; ketones such as acetone and methyl ethyl ketone; polyalkylene glycols such as ethylene glycol, diethylene glycol, and propylene glycol; alkyl ethers of polyalkylene glycols; and N-methyl-2-pyrrolidone.

[0059] - Functional coating layer - The laminate used in this embodiment may include a functional coating layer as a functional layer. The functional coating layer may be provided on the laminate for purposes such as hard coating, silicone-based release, IR cut, waterproofing and moisture resistance, antibacterial properties, UV cut, heat dissipation, photocatalysis, weather resistance, anti-fogging, fingerprint resistance, self-healing, and water and oil repellency. Specifically, examples of functional coating layers include hard coating layers, adhesive layers, release layers, decorative layers, light-shielding layers, ultraviolet shielding layers, antistatic layers, refractive index adjusting layers, and oligomer encapsulation layers. These functional coating layers may be colorless or colored.

[0060] Functional coating layers can be formed by applying various coating agents, such as hard coating agents, self-healing coating agents, anti-fingerprint and anti-fouling coating agents, anti-fogging coating agents, silicone-based release agents, non-silicone-based release agents, waterproof and moisture-proof coating agents, water-repellent and oil-repellent coating agents, photocatalytic coating agents, weather-resistant coating agents, IR-cut coating agents, and other surface modifiers, optical adhesives, polyimide varnishes, liquid crystal alignment film materials, electromagnetic wave shielding coating agents, fine wiring pastes, antistatic coating agents, high refractive index coating agents, and optical lens coating agents, to the surface to be formed. The thickness of these functional coating layers is preferably 0.1 μm to 100 μm, more preferably 0.1 μm to 10 μm, and even more preferably 1 μm to 5 μm.

[0061] The functional coating layer may be a layer formed of a metallic material (metal layer). The metal layer may be a metal foil, or a metal vapor-deposited layer formed by the deposition of a metal or metal oxide. Examples of metal foils include foils of metals with excellent malleability such as gold, silver, copper, zinc, iron, lead, tin and their alloys, steel, stainless steel, and aluminum. Examples of metal vapor-deposited layers include layers containing aluminum, aluminum oxide, silica, zinc oxide, etc.

[0062] The functional coating layer may be a single layer or a multilayer consisting of multiple identical or different functional coating layers. For example, the functional coating layer may be a multilayer consisting of a layer formed using the above-mentioned various coating agents and the above-mentioned metal vapor deposition layer. In this case, the layer formed using the above-mentioned various coating agents may be provided in the laminate via a metal vapor deposition layer in contact with the plastic substrate layer.

[0063] Next, each step constituting the method of this embodiment will be described.

[0064] (Pre-treatment process) The method of this embodiment is not particularly limited, and a pretreatment step of crushing the laminate described above may be performed prior to the immersion step. Performing such a pretreatment step increases the processing efficiency of each subsequent step, and allows for more efficient recovery of recycled plastic from the laminate. More specifically, by performing such a pretreatment step, the recycled plastic can be recovered as film pieces in a later step. The method of crushing the laminate is not particularly limited, and known methods can be used. Furthermore, the crushing of the laminate can be performed in an air atmosphere where no liquid such as a solvent is present, and in that case, a known dry crusher can be suitably used.

[0065] When performing a pretreatment step, the laminate can be crushed so that the dimensions in the short side direction and the long side direction are preferably 1 mm to 30 mm, more preferably 1 mm to 20 mm.

[0066] (Soaking process) In the method of this embodiment, the aforementioned laminate is immersed in a desorption solution containing alkali as an immersion step. This allows the laminate to swell.

[0067] [Separated liquid] Examples of alkalis in the eluent include sodium hydroxide, lithium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and ammonium. Among these, sodium hydroxide or potassium hydroxide is preferred as the alkali, with sodium hydroxide being more preferred.

[0068] The alkali concentration in the eluent is preferably 0.1% to 10% by mass, and more preferably 0.1% to 5% by mass, as a percentage of the total volume of the eluent.

[0069] The pH of the eluent is preferably 10 or higher, preferably 11 or higher, and more preferably 12 or higher.

[0070] The eluent may contain water. In this case, operational stability and environmental stability can be improved.

[0071] The eluent may contain a surfactant. The surfactant is not particularly limited, and known surfactants can be used. Examples of surfactants include anionic surfactants, nonionic surfactants, amphoteric surfactants, and cationic surfactants. The surfactant may be used alone or in combination of two or more. When a surfactant is used, the concentration of the surfactant in the eluent is preferably 0.01% to 5% by mass, and more preferably 2% by mass or less, as a percentage of the total eluent.

[0072] The eluent may contain an appropriate amount of organic solvent. Examples of organic solvents include water-soluble alcohols and water-soluble solvents with a flash point of 21°C or higher. Examples of water-soluble alcohols include methanol, ethanol, 1-propyl alcohol, and 2-propyl alcohol. Examples of water-soluble solvents with a flash point of 21°C or higher include diethylene glycol methyl ether, diethylene glycol butyl ether, propylene glycol propyl ether, and 3-methoxy-3-methyl-1-butanol. By using the above-mentioned water-soluble organic solvent, ions such as hydroxide ions generated from the alkali in the eluent become less susceptible to hydration, thus increasing the nucleophilicity of these ions. As a result, recycled plastics can be recovered more efficiently.

[0073] [Stirring] While not essential, stirring is preferable during the immersion process. This allows for more efficient swelling of the laminate. The stirring device and stirring conditions are not particularly limited, and known devices can be appropriately adopted. For example, immersion with stirring can be performed using a container equipped with a motor-driven stirring blade, a container equipped with means for generating ultrasonic waves, or a container equipped with a shaking means.

[0074] [Soaking temperature] The immersion temperature (temperature of the desorbed liquid during immersion) is not particularly limited as long as the liquid state of the desorbed liquid is maintained, but can be, for example, 15 to 90°C. However, a higher immersion temperature is preferable because it allows for a shorter immersion time. Specifically, the preferred immersion temperature varies depending on the composition of the desorbed liquid, but is 40°C or higher, 50°C or higher, or 60°C or higher.

[0075] [Soaking time] In the immersion process, the immersion time is preferably such that the laminate is sufficiently swollen, and specifically, it is preferably 30 minutes or more. Furthermore, from the viewpoint of processing efficiency, the immersion time is preferably 48 hours or less. Also, if the immersion temperature is room temperature, the laminate can be sufficiently swollen with an immersion time of 24 hours. Furthermore, if the immersion temperature is, for example, 40°C, the laminate can be sufficiently swollen with an immersion time of 16 hours. Furthermore, if the immersion temperature is, for example, 75°C, the laminate can be sufficiently swollen with an immersion time of 120 minutes. In addition, the immersion time can be appropriately adjusted depending on the combination of whether or not stirring is performed and the immersion temperature as described above.

[0076] (Washing process) After the immersion process, the laminate may have alkali-containing desorbing solution adhering to it. Therefore, in the method of this embodiment, although not particularly limited, a washing step may be performed after the immersion process to wash the laminate in order to remove the adhering alkali. Water can usually be used for washing the laminate in this way.

[0077] (Shaking process) In the method of this embodiment, as a shaking step, the laminate after the immersion step is shaken in the presence of water using a continuous shaking device equipped with dispersed media in a container. This shaking generates recycled plastic derived from the plastic substrate layer of the laminate, and the recycled plastic is obtained.

[0078] Shaking can be performed using a continuous shaking device equipped with a dispersion medium such as rods or beads. Examples of such continuous shaking devices equipped with a dispersion medium include paint shakers, ball mills, vibratory mills, attritors, and bead mills.

[0079] When using rods as the dispersion medium, the material of the rods can be steel, zirconia, alumina, stainless steel, etc. The diameter of the rods is preferably 12 mm or more, more preferably 35 mm or less, more preferably 24 mm or less, and even more preferably 19 mm or less. A rod diameter of 12 mm or more makes handling easier and helps suppress problems such as twisting within the device. Furthermore, a rod diameter of 35 mm or less ensures sufficient contact with the laminate within a predetermined time, thereby suppressing a decrease in productivity.

[0080] When beads are used as a dispersion medium, the material of the beads can be steel, zirconia, alumina, stainless steel, or glass. The diameter (sphere diameter) of the beads is preferably 0.5 mm or more, more preferably 5 mm or more, even more preferably 10 mm or more, preferably 35 mm or less, more preferably 30 mm or less, and even more preferably 25 mm or less. If the diameter of the beads is 0.5 mm or more, they are easy to handle and it is possible to suppress the difficulty in recovering the beads due to them getting mixed with the laminate (or film piece) to be processed. Also, if the diameter of the beads is 35 mm or less, it is possible to ensure a sufficient number of contacts with the laminate within a predetermined time and suppress a decrease in productivity.

[0081] The continuous shaking device used in the shaking process requires that the filling rate of the dispersed media in the container be between 30 vol% and 80 vol%. If the filling rate of the dispersed media is less than 30 vol%, it may not be possible to specifically change the crystalline structure and higher-order structure of the plastic substrate layer, and the extensibility of the final molded product may not be improved. Furthermore, if the filling rate of the dispersed media exceeds 80 vol%, it may not be possible to provide sufficient energy to the laminate, and the desired recycled plastic may not be obtained. From a similar viewpoint, the filling rate of the dispersed media in the container is preferably 35 vol% or more, preferably 70 vol% or less, and more preferably 60 vol% or less.

[0082] In a shaking process using a continuous shaking device, the residence time of the material to be processed can be, for example, 10 seconds or more, 20 seconds or more, or 30 seconds or more, and can also be 10 minutes or less, 5 minutes or less, or 2 minutes or less. In this case, specific changes in the crystalline structure and higher-order structure of the plastic substrate layer can be brought about more effectively while maintaining high productivity and processing efficiency.

[0083] In the shaking process using a continuous shaking device, the processing speed of the laminate can be, for example, 100 g / min or more, 200 g / min or more, or 300 g / min or more, and can also be 2000 g / min or less, 1500 g / min or less, or 1000 g / min or less. In this case, while maintaining high productivity and processing efficiency, it is possible to more effectively bring about specific changes in the crystalline structure and higher-order structure of the plastic substrate layer.

[0084] In a shaking process using a continuous shaking device, the ratio of laminate to water can be, for example, 50g or more, 100g or more, or 120g or more of laminate per liter of water, or 400g or less, 300g or less, or 200g or less. In this case, specific changes in the crystalline structure and higher-order structure of the plastic substrate layer can be brought about more effectively while maintaining high productivity and processing efficiency.

[0085] Furthermore, the recycled plastic generated in the shaking process can be recovered prior to the subsequent extrusion process. The recovery method is not particularly limited and can be any conventional method, such as specific gravity separation in a liquid such as water. In addition, it is preferable to thoroughly remove moisture from the recovered recycled plastic prior to the subsequent extrusion process.

[0086] (Rinsing process) Non-recoverable substances, such as functional layers, may remain on and adhere to the surface of the recycled plastic obtained in the shaking process. Therefore, it is preferable that the method of this embodiment further includes a rinsing step in which the recycled plastic is washed with a rinsing solution after the shaking process (and before the extrusion process).

[0087] Washing with rinsing solution may be accompanied by agitation. The agitation device and agitation conditions are not particularly limited, and known devices can be appropriately adopted. For example, immersion with agitation can be performed using a container equipped with a motor-driven agitator, a container equipped with means for generating ultrasonic waves, or a container equipped with a shaking means.

[0088] Washing with a rinsing solution can be performed using a device equipped with a dispersion medium such as rods or beads. Such a device equipped with a dispersion medium is the same as that described in the shaking process.

[0089] The rinsing solution preferably contains a water-soluble solvent. Examples of water-soluble solvents include water-soluble alcohols and water-soluble solvents with a flash point of 21°C or higher. Examples of water-soluble alcohols include methanol, ethanol, 1-propyl alcohol, and 2-propyl alcohol. Examples of water-soluble solvents with a flash point of 21°C or higher include diethylene glycol methyl ether, diethylene glycol butyl ether, propylene glycol propyl ether, and 3-methoxy-3-methyl-1-butanol.

[0090] From the viewpoint of improving cleaning efficiency, the proportion of water-soluble solvent in the rinsing solution is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, and even more preferably 90% by mass or more.

[0091] (Extrusion process) In the method of this embodiment, the extrusion step involves melting and kneading the recycled plastic obtained in the shaking step, or a composition containing the recycled plastic, and then extruding it. The extrusion step can be carried out using equipment such as a kneader, roll mill, single-screw extruder, twin-screw extruder, or rotor-type twin-screw kneader. Among these, a twin-screw extruder is preferred from the viewpoint of processing efficiency.

[0092] In the extrusion process, only recycled plastic obtained in the shaking process, or a composition containing the recycled plastic and other resins, can be used as the resin raw material. Preferably, the other resins are those compatible with the recycled plastic, and specifically, thermoplastic resins (virgin thermoplastic resins) such as polyethylene resin and polypropylene resin. These other resins may be used individually or in combination of two or more.

[0093] The recycled plastic content in the total resin raw material used in the extrusion process is preferably 50% by mass or more. In this case, the recycling rate is at a sufficiently high level. The recycled plastic content refers to the proportion of recycled plastic in the total resin raw material used in the extrusion process. From a similar viewpoint, the recycled plastic content is more preferably 60% by mass or more, even more preferably 75% by mass or more, and even more preferably 90% by mass or more. It is also preferable that the recycled plastic content is 100% by mass (i.e., the resin raw material used in the extrusion process consists only of recycled plastic).

[0094] The composition used in the extrusion process may contain appropriate amounts of alkali metal, alkaline earth metal, or zinc metal soap; hydrotalcite; surfactants such as nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants; antistatic agents; flame retardants such as halogen-based, phosphorus-based, or metal oxides; lubricants such as ethylenebisalkylamide; antioxidants; ultraviolet absorbers; fillers; colorants; peroxides, etc., to the extent that they do not impede the effects of the present invention.

[0095] The melt-mixing temperature in the extrusion process must be between 40°C and 120°C above the melting point of the recycled plastic. If the melt-mixing temperature is not above 40°C above the melting point of the recycled plastic, it may not be possible to specifically change the crystalline structure and higher-order structure of the recycled plastic, and the extensibility of the final molded product may not be improved. Furthermore, if the melt-mixing temperature is not below 120°C above the melting point of the recycled plastic, it may not be possible to improve the extensibility of the final molded product due to overheating.

[0096] When using a single-screw or twin-screw extruder, the screw rotation speed is preferably 50 rpm or more and 500 rpm or less. A screw rotation speed of 50 rpm or more allows for the acquisition of a more uniform molten mixture. Furthermore, a screw rotation speed of 500 rpm or less can suppress a significant decrease in the physical properties of the molten mixture. From a similar viewpoint, a screw rotation speed of 100 rpm or more is more preferable, 180 rpm or more is even more preferable, 400 rpm or less is even more preferable, and 300 rpm or less is even more preferable.

[0097] The feeding rate of the resin raw material during extrusion is preferably between 5 kg / h and 100 kg / h. If the feeding rate is 5 kg / h or higher, the resin pressure during extrusion increases, allowing for a better mixing state to be formed. If the feeding rate is 100 kg / h or lower, equipment malfunctions such as clogging can be suppressed. From a similar viewpoint, the feeding rate of the resin raw material during extrusion is more preferably 50 kg / h or lower, and even more preferably 30 kg / h or lower.

[0098] The resin pressure during extrusion is preferably between 1 MPa and 30 MPa. A resin pressure of 1 MPa or higher allows for a better mixing state. Furthermore, a resin pressure of 30 MPa or lower can suppress equipment malfunctions such as clogging. From a similar viewpoint, the resin pressure during extrusion is more preferably 25 MPa or lower, and even more preferably 20 MPa or lower.

[0099] (Collection process) Furthermore, in the method of this embodiment, the molten mixture extruded in the extrusion process is taken up as strands in the take-up process. The take-up process can be carried out using the same equipment as the extrusion process. That is, the series of operations for the extrusion process and the take-up process can be carried out using the same equipment.

[0100] The strand take-up speed in the take-up process is preferably 8 m / min or more and 50 m / min or less. If the strand take-up speed is 8 m / min or more, it can more effectively bring about specific changes in the crystalline structure and higher-order structure of the recycled plastic, and the extensibility of the final molded product can be further improved. If the strand take-up speed is 50 m / min or less, the occurrence of defects such as wire breakage can be suppressed. From a similar viewpoint, it is more preferable that the strand take-up speed in the take-up process is 30 m / min or less.

[0101] (molding process) In the method of this embodiment, the molding process involves molding using the strand. This molding process ultimately yields a molded product. Alternatively, the molding process may also involve using pellets obtained by cutting the strand with a pelletizer or the like.

[0102] The final shape of the molded product is not particularly limited and can be modified as appropriate depending on the purpose.

[0103] In the molding process, the strands or pellets can be heat-molded. The heat molding method is not particularly limited and includes, for example, injection molding, extrusion molding, blow molding, compression molding, etc.

[0104] The heating temperature during heat molding is preferably 180°C or higher, 190°C or higher, or 200°C or higher, and also preferably 260°C or lower, 250°C or lower, or 240°C or lower.

[0105] In the case of heat molding using a mold (such as injection molding), the mold temperature is preferably between 20°C and 60°C. If the mold temperature is 20°C or higher, the fluidity of the molten resin can be maintained, preventing filling defects and the generation of air bubbles. If the mold temperature is 60°C or lower, the cooling rate of the molten resin can be appropriately maintained, suppressing the shrinkage rate after molding. From a similar viewpoint, the mold temperature is more preferably 30°C or higher, and more preferably 50°C or lower.

[0106] The molding time during heat molding is preferably 10 seconds or more and 45 seconds or less. If the molding time is 10 seconds or more, a good molded product can be obtained by sufficient cooling. Also, if the molding time is 45 seconds or less, productivity can be maintained well. From a similar viewpoint, the molding time is more preferably 20 seconds or more, even more preferably 25 seconds, even more preferably 40 seconds or less, and even more preferably 35 seconds or less.

[0107] The holding pressure during heat molding is preferably between 20 MPa and 100 MPa. A holding pressure of 20 MPa or higher can improve the quality of the molded product and its surface. Furthermore, a holding pressure of 100 MPa or lower can suppress mold release defects. From a similar viewpoint, a holding pressure of 30 MPa or higher is more preferable, 40 MPa or higher is even more preferable, 70 MPa or lower is even more preferable, and 60 MPa or lower is even more preferable. [Examples]

[0108] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples. In addition, unless otherwise specified, "%" in the compositions of the following examples means "mass%".

[0109] <Preparation of the plastic substrate layer> The following materials were prepared as the plastic substrate layer. PP1...Polypropylene film, manufactured by Toyobo Co., Ltd., "P2161", thickness: 20 μm, melting point of the constituent polypropylene: 165°C PE1...Polyethylene film, manufactured by Futamura Chemical Co., Ltd., "PE3K-H", thickness: 25 μm, melting point of the constituent polyethylene: 125°C PET1...Polyethylene terephthalate film, manufactured by Toyobo Co., Ltd., "E5100", thickness: 12 μm, melting point of the constituent polyethylene terephthalate: 260°C PP2...Polypropylene film, manufactured by Toyobo Co., Ltd., "P1128", thickness: 30 μm, melting point of the constituent polypropylene: 145°C PP3...Polypropylene film, manufactured by Toray Industries, Inc., "VM-CPP", Thickness: 30 μm, Melting point of constituent polypropylene: 145°C

[0110] <Preparation of composition for detachable primer layer (1)> Polyol (a) (aromatic polyester polyol) was prepared by mixing 0.32 g of terephthalic acid (TPA), 0.32 g of isophthalic acid (IPA), 0.13 g of ethylene glycol (EG), and 0.23 g of diethylene glycol (DEG) and reacting them.

[0111] Next, 0.74 g of polyol (a), 0.20 g of isophorone diisocyanate, and 0.06 g of 2,2'-dimethylolpropionic acid were charged into a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, and the mixture was reacted at 75°C for 8 hours under a nitrogen stream to obtain urethane resin (1).

[0112] Next, the urethane resin (1) was diluted with isopropyl alcohol to a solid content concentration of 10% to obtain a composition for a detachable primer layer (1).

[0113] <Preparation of composition for detachable primer layer (2)> A composition for a detachable primer layer (2) was obtained by mixing 10 parts by mass of PVA1 (polyvinyl alcohol, PVA-A, weight-average molecular weight: 48,000), 45.0 parts by mass of water, and 45.0 parts by mass of ethanol.

[0114] <Preparation of composition for detachable primer layer (3)> A composition for a detachable primer layer (3) was obtained by mixing 10 parts by mass of PVA-2 (polyvinyl alcohol, manufactured by Nippon Vinegar Bi-Poval Co., Ltd., J-POVAL JF-05, weight-average molecular weight: 22,000), 0.5 parts by mass of polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd.), 44.5 parts by mass of water, and 45.0 parts by mass of ethanol.

[0115] <Preparation of composition for detachable primer layer (4)> A composition for a detachable primer layer (4) was obtained by mixing 10 parts by mass of PVA-3 (polyvinyl alcohol, manufactured by Nippon Vinegar Bi-Poval Co., Ltd., J-POVAL JF-17, weight-average molecular weight: 75,000), 1.0 part by mass of polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd.), 44.0 parts by mass of water, and 45.0 parts by mass of ethanol.

[0116] <Preparation of composition for detachable primer layer (5)> A composition for a detachable primer layer (5) was obtained by mixing 10 parts by mass of PVA-4 (polyvinyl alcohol, manufactured by Kuraray Co., Ltd., KURARAY POVAL 60-98, weight-average molecular weight: 106,000), 3.0 parts by mass of polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd.), 42.0 parts by mass of water, and 45.0 parts by mass of ethanol.

[0117] <Preparation of adhesive layer composition> As the adhesive layer composition, DICDRY® LX-510 and DICDRY® KW-75, both manufactured by DIC Corporation, were mixed in a mass ratio of LX-510:KW-75 = 9:1, and further diluted with ethyl acetate as a solvent (a polyurethane-based two-component curing laminate adhesive).

[0118] <Preparation of composition for the printing layer (white)> For the printing layer (white), a urethane-based laminate ink (Finato R794 White S, manufactured by DIC Corporation) was used, with its viscosity adjusted to 15 seconds (25°C) using a Zaan Cup #3 manufactured by Rigosha.

[0119] <Preparation of composition for the printing layer (blue)> For the printing layer (blue), a gravure ink for surface printing (DIC Graphics, Glossa 507 primary color blue S2) was used, with its viscosity adjusted to 15 seconds (25°C) using a Zaan cup #3 manufactured by Rigosha.

[0120] <Fabrication of the laminate (LAM1)> A white printing layer composition was applied seamlessly onto a PP1 plastic substrate using a gravure printing press equipped with a gravure plate with a plate depth of 43 μm. The mixture was then dried and cured by passing it through a 70°C oven to form a white printing layer on the PP1. Next, an adhesive layer composition was applied to this white printing layer at a solid content of 4 g / m². 2 The mixture was coated using an RDS Mayer coating bar. Next, the solvent in the adhesive layer composition was evaporated using a dryer. Meanwhile, the composition for the detachable primer layer (1) was applied evenly (solidly) onto the PP2 plastic substrate layer using a gravure printing machine. Next, it was dried at 90°C for 1 minute to form the detachable primer layer (1) on the PP2. Then, the plastic substrate layers were bonded together so that the adhesive composition on PP1 and the detachable primer layer (1) on PP2 were in contact. Finally, aging was performed at 40°C for 5 days to obtain a laminate (LAM1) having the layer structure of "PP1 / printed layer (white) / adhesive layer / detachable primer layer (1) / PP2".

[0121] <Fabrication of the laminate (LAM2)> A laminate (LAM2) was obtained in the same manner as LAM1, except that PE1 was used instead of PP1 and PE1 was used instead of PP2, and the layer structure was "PE1 / printed layer (white) / adhesive layer / detachable primer layer (1) / PE1".

[0122] <Fabrication of the laminate (LAM3)> A composition for the detachable primer layer (1) was applied seamlessly to the PP1 plastic substrate layer using a gravure printing press. Next, it was dried at 90°C for 1 minute to form the detachable primer layer (1) on the PP1. Then, a composition for the printable layer (white) was applied seamlessly onto this detachable primer layer (1) using a gravure printing press equipped with a gravure plate with a plate depth of 43 μm. Next, it was dried and cured by passing it through a 70°C oven to form the printable layer (white) on the detachable primer layer (1). Finally, an adhesive layer composition was applied to this printable layer (white) at a coating rate (solid content) of 4 g / m². 2 The coating was applied using an RDS Mayer coating bar. Then, the solvent in the adhesive layer composition was evaporated using a dryer. On the other hand, the composition for the detachable primer layer (1) was applied without gaps onto the PP2 plastic substrate layer using a gravure printing machine. Next, it was dried at 90°C for 1 minute to form the detachable primer layer (1) on the PP2. Then, the plastic substrate layers were bonded together so that the adhesive composition on PP1 and the detachable primer layer (1) on PP2 were in contact. Finally, aging was performed at 40°C for 5 days to obtain a laminate (LAM3) having a layer structure of "PP1 / detachable primer layer (1) / printed layer (white) / adhesive layer / detachable primer layer (1) / PP2".

[0123] <Fabrication of the laminate (LAM4)> A composition for a detachable primer layer (1) was applied seamlessly to a PET1 plastic substrate layer using a gravure printing press. Next, it was dried at 90°C for 1 minute to form a detachable primer layer (1) on the PET1. Then, a composition for a printable layer (white) was applied seamlessly onto this detachable primer layer (1) using a gravure printing press equipped with a gravure plate with a plate depth of 43 μm. Finally, it was dried and cured by passing it through a 70°C oven to form a printable layer (white) on the detachable primer layer (1). Finally, an adhesive layer composition was applied to this printable layer (white) at a coating rate (solid content) of 4 g / m². 2The material was coated using an RDS Mayer coating bar. Next, the solvent in the adhesive layer composition was evaporated using a dryer. Then, PP2, which serves as the plastic substrate layer, was bonded to the adhesive composition on PET1. Finally, aging was performed at 40°C for 5 days to obtain a laminate (LAM4) having a layer structure of "PET1 / detachable primer layer (1) / printed layer (white) / adhesive layer / PP2".

[0124] <Fabrication of the laminate (LAM5)> A composition for the detachable primer layer (1) was applied seamlessly to PP1, a plastic substrate layer, using a gravure printing press. Next, it was dried at 90°C for 1 minute to form the detachable primer layer (1) on PET1. Then, a composition for the printable layer (white) was applied seamlessly onto this detachable primer layer (1) using a gravure printing press equipped with a gravure plate with a plate depth of 43 μm. Next, it was dried and cured by passing it through a 70°C oven to form the printable layer (white) on the detachable primer layer (1). Finally, an adhesive layer composition was applied to this printable layer (white) at a coating rate (solid content) of 4 g / m². 2 The material was coated using an RDS Mayer coating bar. Next, the solvent in the adhesive layer composition was evaporated using a dryer. Then, PP3, which serves as the plastic substrate layer, was bonded to the adhesive composition on PP1. Finally, aging was performed at 40°C for 5 days to obtain a laminate (LAM5) having a layer structure of "PP1 / detachable primer layer (1) / printed layer (white) / adhesive layer / PP3".

[0125] <Fabrication of the laminate (LAM6)> On the PP1 plastic substrate layer, a composition for a detachable primer layer (2) is applied at a coating rate (solid content) of 0.5 g / m². 2To achieve this, the material was coated without gaps using a gravure printing press equipped with a gravure plate with a plate depth of 22 μm. Next, it was dried by passing it through a 70°C oven. Then, it was left at room temperature for one day to form a detachable primer layer (2) on PP1. Next, an adhesive layer composition was applied onto this detachable primer layer (2). Then, PP2, which serves as a plastic substrate layer, was bonded to the adhesive layer composition on PP1. Finally, aging was performed at 40°C for three days to obtain a laminate (LAM6) having a layer structure of "PP1 / detachable primer layer (2) / adhesive layer / PP2".

[0126] <Fabrication of the laminate (LAM7)> On the PE1 plastic substrate layer, a composition for a detachable primer layer (3) is applied at a rate (solid content) of 0.5 g / m². 2 To achieve this, the material was coated without gaps using a gravure printing press equipped with a gravure plate with a plate depth of 22 μm. Next, it was dried by passing it through a 70°C oven. Then, it was left at room temperature for one day to form a detachable primer layer (3) on PE1. Next, the composition for the printing layer (white) was coated without gaps onto this detachable primer layer (3) using a gravure printing press equipped with a gravure plate with a plate depth of 43 μm. Next, it was dried and cured by passing it through a 70°C oven to form a printing layer (white) on the detachable primer layer (3). Next, the composition for the adhesive layer was applied onto this printing layer (white). Next, PE1 as a plastic substrate layer was bonded to the adhesive layer composition on PE1. Then, it was aged at 40°C for three days to obtain a laminate (LAM7) having a layer structure of "PE1 / detachable primer layer (3) / printing layer (white) / adhesive layer / PE1".

[0127] <Fabrication of the laminate (LAM8)> On the PET1 plastic substrate layer, a composition for a detachable primer layer (4) is applied at a rate (solid content) of 0.5 g / m². 2The material was coated without gaps using a gravure printing press equipped with a gravure plate with a plate depth of 22 μm. Next, it was dried by passing it through a 70°C oven. Then, it was left at room temperature for one day to form a detachable primer layer (4) on PET1. Next, the adhesive layer composition was applied on this detachable primer layer (4). Meanwhile, the detachable primer layer (4) composition was coated without gaps on PP2, which is a plastic substrate layer, using a gravure printing press. Next, it was dried by passing it through a 70°C oven. Then, it was left at room temperature for one day to form a detachable primer layer (4) on PP2. Next, the plastic substrate layers were bonded together so that the adhesive layer composition on PET and the detachable primer layer (4) on PP2 were in contact. Then, it was aged at 40°C for three days to obtain a laminate (LAM8) having the layer structure of "PET1 / detachable primer layer (4) / adhesive layer / detachable primer layer (4) / PP2".

[0128] <Fabrication of the laminate (LAM9)> On the PP1 plastic substrate layer, the composition for the detachable primer layer (5) is applied at a coating rate (solid content) of 0.5 g / m². 2 To achieve this, the material was coated without gaps using a gravure printing press equipped with a gravure plate with a plate depth of 22 μm. Next, it was dried by passing it through a 70°C oven. Then, it was left at room temperature for one day to form a detachable primer layer (5) on PP1. Next, the composition for the printing layer (white) was coated without gaps onto this detachable primer layer (5) using a gravure printing press equipped with a gravure plate with a plate depth of 43 μm. Next, it was dried and cured by passing it through a 70°C oven to form a printing layer (white) on the detachable primer layer (5). Next, the composition for the adhesive layer was applied onto this printing layer (white). Next, PP3, which serves as a plastic substrate layer, was bonded to the adhesive layer composition on PP1. Then, it was aged at 40°C for three days to obtain a laminate (LAM9) having a layer structure of "PP1 / detachable primer layer (5) / printing layer (white) / adhesive layer / PP3".

[0129] <Preparation of laminated material (surface-printed material, Pri1)> A composition for the printing layer (blue) was applied seamlessly onto a PP2 plastic substrate layer using a gravure printing press equipped with a gravure plate with a plate depth of 43 μm. The mixture was then dried and cured by passing it through a 70°C oven to form the printing layer (blue) on the PP2. In this way, a laminate (Pri1) having a "PP2 / printing layer (blue)" structure was obtained.

[0130] <Preparation of laminated material (surface-printed material, Pri2)> A composition for the detachable primer layer (1) was applied seamlessly onto PE1, a plastic substrate layer, using a gravure printing press. Next, it was dried at 90°C for 1 minute to form the detachable primer layer (1) on PE1. Then, a composition for the printing layer (blue) was applied seamlessly onto this detachable primer layer (1) using a gravure printing press equipped with a gravure plate with a plate depth of 43 μm. Finally, it was dried and cured by passing it through a 70°C oven to form the printing layer (blue) on the detachable primer layer (1). In this way, a laminate (Pri2) having a layer structure of "PE1 / detachable primer layer (1) / printing layer (blue)" was obtained.

[0131] Table 1 shows the layer structure of each laminate created.

[0132] [Table 1]

[0133] <Manufacturing of molded products> (Pre-treatment process) Each of the fabricated laminates was placed in a dry crusher fitted with a 10mm diameter screen and cooled with water, and pre-treated so that the dimensions were approximately 5-10mm in the short direction and 10-20mm in the long direction.

[0134] (Soaking process) The laminate after the pretreatment process was subjected to either the following immersion process (A) or immersion process (B). Immersion process (A): A desorbing solution was selected from desorbing solutions (1) to (4) shown in Table 2, and 2 kg of laminate was placed in 15 L of the desorbing solution. The laminate was then immersed in the desorbing solution at 40°C for 16 hours. Immersion process (B): A desorbing solution was selected from desorbing solutions (1) to (4) shown in Table 2, and 2 kg of laminate was placed in 15 L of the desorbing solution. The laminate was then immersed in the desorbing solution at 75°C for 120 minutes while stirring at 300 rpm using a three-one motor.

[0135] [Table 2]

[0136] Alkali: Sodium hydroxide Surfactant (1): "DSK NL Dash 403" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., polyalkylalkylene lauryl ether, HLB value = 6.5 Surfactant (2): "DSK NL Dash 408" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., polyalkylalkylene lauryl ether, HLB value = 12.5 Surfactant (3): NOF Corporation, "M2-100R", cationic surfactant

[0137] (Washing process) After the immersion process, the laminate was rinsed with water using a shower until the pH was within the range of 7 to 12 to remove the alkali, and then lightly dehydrated by placing it in a colander.

[0138] (Shaking process) Next, the laminate was subjected to the following shaking process (a), shaking process (b), or shaking process (c) to obtain recycled plastic film pieces. Shaking process (a): A continuous vibratory mill manufactured by Chuo Kakoki Co., Ltd. was used as the continuous shaking device. 2 kg of laminate was used, and the ratio of laminate to water was adjusted to 150 g / 1 L. The vibratory mill used was equipped with dispersion media in the container. A 19 mm diameter rod was used as the dispersion media, and the filling rate of the dispersion media in the container was set to 15 vol%. The amount of water flowing in was adjusted so that the introduced laminate was discharged from the machine in 1 minute, and the laminate was shaken. The processing speed of the laminate at this time was 500 g / min. Shaking process (b): A continuous vibratory mill manufactured by Chuo Kakoki Co., Ltd. was used as the continuous shaking device. 2 kg of laminate was used, and the ratio of laminate to water was adjusted to 150 g / 1 L. The vibratory mill used was equipped with dispersion media in the container. A 19 mm diameter rod was used as the dispersion media, and the filling rate of the dispersion media in the container was set to 35 vol%. The amount of water flowing in was adjusted so that the introduced laminate was discharged from the machine in 1 minute, and the laminate was shaken. The processing speed of the laminate at this time was 500 g / min. Shaking process (c): A continuous vibratory mill manufactured by Chuo Kakoki Co., Ltd. was used as the continuous shaking device. 2 kg of laminate was used, and the ratio of laminate to water was adjusted to 150 g / 1 L. The vibratory mill used was equipped with dispersion media in the container. A 19 mm diameter rod was used as the dispersion media, and the filling rate of the dispersion media in the container was set to 60 vol%. The amount of water flowing in was adjusted so that the introduced laminate was discharged from the machine in 1 minute, and the laminate was shaken. The processing speed of the laminate at this time was 500 g / min.

[0139] (Rinsing process) The recycled plastic film pieces obtained in the shaking process were washed with a rinsing solution. Specifically, 1 kg of recycled plastic film pieces were placed in 10 L of diethylene glycol methyl ether as the rinsing solution, and a stirring operation (rotation speed: 500 rpm) using a three-one motor was performed for 30 minutes.

[0140] After the shaking and rinsing processes, the recycled plastic film pieces were subjected to specific gravity separation in water using a water-tank specific gravity separation apparatus manufactured by Nippon Seam Co., Ltd. During this process, polyolefin resins, specifically polypropylene and polyethylene (recycled plastic film pieces), floated, while the other components settled. The floating film pieces were collected and centrifuged at 500 rpm to remove moisture. They were then dried at 60°C for one day.

[0141] (Extrusion process and take-up process) An antioxidant (Irganox 1010) at a concentration of 0.3% was added to the recycled plastic film pieces after the shaking and rinsing processes. A twin-screw extruder "KZW" (L / D=45) manufactured by Technovel Co., Ltd. was used as the extrusion device. The film pieces were fed into the twin-screw extruder at a speed of 10 kg / h with a screw rotation speed of 300 rpm, and after melt-mixing, they were extruded. The resin pressure at that time was 1 to 2 MPa. The extruded melt-mixed material was taken up as strands and also pelletized. The melt-mixing temperature (measured temperature during extrusion) and strand take-up speed used in each example are shown in Tables 3 to 5.

[0142] (molding process) Using the obtained pellets, a 4mm thick dumbbell test piece (molded product) was produced by injection molding using the "MS100" injection molding machine manufactured by Sodick Co., Ltd. The injection molding conditions were as follows: injection temperature (heating temperature) 200°C, mold temperature (cooling temperature) 40°C, indentation pressure 90 MPa, holding pressure 50 MPa, and molding time (cooling time) 30 seconds. A mold of type 1B as specified in JIS K 7139 was used.

[0143] <Measurement and Evaluation> The following measurements and evaluations were performed during the series of operations described above. The results are shown in Tables 3 to 5.

[0144] (Peelability) The area of ​​the peeled portion relative to the total surface area was measured for the recycled plastic film pieces after the shaking and rinsing processes. A score was assigned to the measured peeled area according to the following criteria. A higher score indicates superior peelability. 1 point... Peeling area is less than 10% 2 points... Peeling area is 10% or more but less than 50% 3 points... Peeling area is 50% or more but less than 100% 4 points... 100% of the peeling area

[0145] (Strand diameter) After the strands were taken up during the take-up process and cooled, their diameter was measured at five different points. The five measurements were averaged and rounded to the nearest tenth.

[0146] (Elongation at the fracture point of molded products) Dumbbell test specimens (molded products) obtained by injection molding were stretched at a speed of 100 mm / min in accordance with JIS K6301, and the elongation at the breaking point was measured. Ten measurements were taken for each level, and the average of the six measurements was used, after excluding the two highest and two lowest measurements. A higher value indicates higher extensibility.

[0147] [Table 3]

[0148] [Table 4]

[0149] [Table 5]

[0150] Tables 3 to 5 show that in the embodiments according to the present invention, molded products are manufactured by performing a predetermined process, and the resulting molded products exhibit superior extensibility compared to the comparative examples. [Industrial applicability]

[0151] According to the present invention, it is possible to provide a method for manufacturing a molded article that allows for the recovery of recycled plastic from a laminate comprising a plastic substrate layer and a functional layer, thereby obtaining a molded article with excellent stretchability.

Claims

1. A method for manufacturing a molded product, comprising recovering recycled plastic from a laminate comprising a plastic substrate layer and a functional layer, and manufacturing a molded product using the recycled plastic, An immersion step in which the laminate is immersed in a desorption solution containing alkali, An optional cleaning step for cleaning the laminate after the immersion step, A shaking step is performed to obtain recycled plastic by shaking the laminate obtained in the immersion step or the washing step in the presence of water using a continuous shaking device equipped with dispersed media in a container. An extrusion step of melting and kneading the recycled plastic or a composition containing the recycled plastic and extruding it, The process involves taking up the extruded molten mixture as strands, and A molding process in which the strand is used to form the object, Includes, The continuous shaking device used in the shaking process has a filling rate of 30 vol% to 80 vol% of the dispersed media in the container, the dispersed media is a rod with a diameter of 12 mm to 35 mm, or a bead with a spherical diameter of 0.5 mm to 35 mm, and the residence time of the laminate in the shaking process is 10 seconds to 10 minutes. The melt-kneading temperature in the extrusion process is between 40°C and 120°C above the melting point of the recycled plastic. A method for manufacturing molded products, characterized by the following.

2. The method according to claim 1, wherein the strand pulling speed in the pulling process is 8 m / min or more and 50 m / min or less.

3. The method according to claim 1 or 2, wherein the molding step is performed using a mold, the mold temperature is 20°C or higher and 60°C or lower, and the molding time is 10 seconds or higher and 45 seconds or lower.

4. The method according to claim 1 or 2, further comprising a rinsing step of washing the recycled plastic with a rinsing solution after the shaking step.

5. The method according to claim 4, wherein the rinse solution contains a water-soluble solvent.

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