Method for producing molded article

Abstract

The present invention provides a method for producing a molded article capable of achieving excellent extensibility by recovering a recycled plastic from a multilayer body that has a plastic film layer and a functional layer. This method for producing a molded article includes: an immersion step in which a multilayer body that has a plastic base material layer and a functional layer is immersed in an alkali-containing desorption liquid; a shaking step in which the multilayer body after immersion is shaken in the presence of water using a specific continuous shaking device that is provided with a dispersion medium in a container so as to obtain a recycled plastic; an extrusion step in which the recycled plastic or a composition that contains the recycled plastic is melted and kneaded at a specific temperature, and extruded; a take-up step in which the extruded melt-kneaded material is taken as a strand; and a molding step in which molding is performed using the strand.

Description

Molded product manufacturing method

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

[0002] Currently, the amount of waste plastic that is separated and collected (recycling rate) is 9% of all plastic produced worldwide. Of the 91% of waste plastic that is not separated and collected, 12% is incinerated, and 79% is landfilled or leaks into the environment (Non-Patent Document 1). One of the reasons for this persistently low recycling rate is the difficulty of implementing a separate collection system.

[0003] Specifically, in order to recycle plastics, it is necessary to separate and collect waste plastics that contain different types of plastic materials, such as polyethylene (PE) and polypropylene (PP), into individual materials. However, in many plastic products, including laminated films, different types of plastic materials are bonded together, making it difficult to separate and collect each material. Therefore, there is a strong demand for the development of a recycling system that can easily separate and collect waste plastics.

[0004] In addition, from a cost perspective, it is difficult to return recycled plastic products to the same product as before recycling. Furthermore, plastic products generally deteriorate every time they are recycled. Therefore, recycled plastic products inevitably lose quality.

[0005] In this regard, one reason for the decline in quality of recycled plastics is the presence of ink or pigments as impurities in the plastic. In particular, many plastic products have printed surfaces, making them difficult to decolorize during the recycling process. Furthermore, plastic films that make up plastic products typically have various functional layers, such as hard coat layers, adhesive layers, and removable primer layers, in addition to ink layers (printed layers). However, components derived from these functional layers can also cause unintended coloration.

[0006] As a result, recycled plastic products are often discolored. Not only does this significantly reduce the commercial value of such recycled plastic products, but the impurities can also cause deterioration in physical properties such as tensile strength. Therefore, a method for producing high-quality recycled plastic products is needed.

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

[0008] Furthermore, Patent Document 2 proposes a method for removing ink from a printed plastic film. Specifically, Patent Document 2 discloses a method in which the printed plastic film is treated with a plunger, then crushed in a crusher, the ink on the film is removed in a predetermined washing system, and the treated plastic film is then rinsed and dried.

[0009] Science Advances 19 Jul 2017:Vol. 3, no. 7, e1700782

[0010] JP 2006-205160 A JP 2015-520684 A

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

[0012] Furthermore, Patent Documents 1 and 2 mainly focus only on removing layers formed on plastic films, and do not consider improving the physical properties, such as the extensibility, of recycled plastic products (molded products).

[0013] Therefore, the present invention aims to provide a method for manufacturing a molded product that can recover recycled plastic from a laminate having a plastic substrate layer and a functional layer, and obtain a molded product with excellent extensibility.

[0014] The present inventors have conducted extensive research and found that the above-mentioned problems can be solved by using a laminate including a plastic substrate layer and a functional layer as a raw material and performing a predetermined process, which led to the invention. The gist of the present invention that solves the above-mentioned problems is as follows.

[0015] [1] A method for producing a molded product, comprising recovering recycled plastic from a laminate comprising a plastic substrate layer and a functional layer, and using the recycled plastic to produce a molded product, the method comprising: an immersion step of immersing the laminate in a release liquid containing an alkali; an agitation step of shaking the immersed laminate in the presence of water using a continuous agitation device comprising a dispersion medium in a container to obtain 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 molten mixture as strands; and a molding step of molding using the strands, wherein the continuous agitation device used in the agitation step has a container with a filling rate of dispersion medium 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.

[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 carried out 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.

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

[0019] [5] The method according to [4], wherein the rinse solution contains a water-soluble solvent.

[0020] According to the present invention, a method for manufacturing a molded product can be provided that recovers recycled plastic from a laminate having a plastic substrate layer and a functional layer, and enables the production of a molded product with excellent extensibility.

[0021] The present invention will be described in detail below by way of example based on embodiments thereof.

[0022] <Method for Producing Molded Articles> A method for producing a molded article according to one embodiment of the present invention (hereinafter sometimes referred to as the "method of the present embodiment") is a method for producing a molded article, in which recycled plastic is recovered from a laminate including a plastic substrate layer and a functional layer, and the recycled plastic is used to produce a molded article. The method of the present embodiment is characterized by including the following steps: an immersion step of immersing the laminate in a release liquid containing an alkali; a shaking step of shaking the immersed laminate in the presence of water using a continuous shaking device equipped with a dispersion medium in a container, thereby obtaining 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 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 dispersion medium 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 intensive research by the present inventors, it was found that recycled plastic suitable as a material for molded articles can be obtained by using a laminate comprising a plastic substrate layer and a functional layer as the processing target, and by carrying out the prescribed immersion and shaking steps, as in the method of this embodiment. It was also found that by carrying out the prescribed extrusion, pull-up, and molding steps using such recycled plastic, molded articles with excellent extensibility can be obtained. It is presumed that this improvement in extensibility is due to specific changes in the crystalline structure and higher-order structure of the plastic substrate layer (and thus the recycled plastic) caused by appropriately carrying out the prescribed shaking step and optimizing the melt-kneading temperature in the extrusion step.

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

[0025] (Laminate as Treatment Target) In the method of this embodiment, a laminate including at least a plastic substrate layer and a functional layer is used as a treatment target.

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

[0027] The laminate used in this embodiment may be, for example, a plastic film that has become waste (waste plastic film). The laminate is not particularly limited, and plastic films that are generally distributed as packaging materials for food packaging or daily necessities, films having various types of discarded plastic substrates, etc. may be used. The laminate may be used alone or in combination of two or more types.

[0028] The laminate used in this embodiment may include only one plastic substrate layer, or may include two or more plastic substrate layers. When the laminate includes two or more plastic substrate layers, the plastics constituting these plastic substrate layers may be the same or different from each other.

[0029] The laminate used in this embodiment may include only one functional layer, or may include two or more functional layers. When the laminate includes two or more functional layers, these functional layers may be the same as or different from each other.

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

[0031] [Plastic Substrate Layer] As described above, the laminate used in this embodiment includes a plastic substrate layer. The plastic substrate layer refers to a layer-like member containing plastic as the main constituent resin.

[0032] Specific examples of the plastic substrate layer include polyolefin films made of polyolefin; polyester films made of polyethylene terephthalate (PET), polybutylene terephthalate, etc.; polyamide films made of nylon 6, nylon 6,6, metaxylene adipamide (N-MXD6), etc.; biodegradable films made of polylactic acid, etc.; polyacrylonitrile films; poly(meth)acrylic films; polystyrene films; polycarbonate films; saponified ethylene-vinyl acetate copolymer (EVOH) films; polyvinyl alcohol films; and triacetyl cellulose films.

[0033] More specific examples of the polyolefin include polyethylenes such as low-density polyethylene, high-density polyethylene, and linear low-density polyethylene; polypropylenes such as OPP (biaxially oriented polypropylene) and CPP (non-oriented polypropylene); propylene-ethylene copolymers; and ethylene-butene-propylene copolymers.

[0034] In particular, from the viewpoint of versatility and ease of recovery of the final molded product, the plastic substrate layer preferably contains a polyolefin as a main constituent resin, and more preferably contains a polypropylene such as OPP or CPP as a 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 is 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, and 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 examples thereof include a printing layer (also referred to as an ink layer), an adhesive layer, a removable primer layer, and a functional coating layer. The laminate may include one type of these functional layers alone, or two or more types in combination.

[0038] The functional layer (printing layer, adhesive layer, removable primer layer, functional coating layer, etc.) can contain a resin having an acidic group or a low molecular weight compound having an acidic group. The functional layer can also contain a resin not having an acidic group in addition to the resin having an acidic group or the low molecular weight compound having an acidic group.

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

[0040] 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.

[0041] Saturated fatty acids include lauric acid, myristic acid, palmitic acid, margaric acid, and stearic acid. Unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and sorbic acid. Hydroxy acids include lactic acid, malic acid, and citric acid. Aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, mellitic acid, and cinnamic acid. Dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, and maleic acid. Tricarboxylic acids include aconitic acid. Oxocarboxylic acids include pyruvic acid and oxaloacetic acid. Carboxylic acid derivatives include amino acids and nitrocarboxylic acids. Acid anhydrides include trimellitic anhydride and pyromellitic anhydride.

[0042] -Printed Layer- The laminate used in this embodiment can 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 design, pattern, letter, symbol, etc. is displayed for the purpose of providing decoration or aesthetic appeal, or for displaying the contents, expiration date, manufacturer or seller, etc. Alternatively, the printed layer may be a layer on which no design, pattern, letter, symbol, etc. is displayed (i.e., a layer with no gaps, a solid layer).

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

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

[0045] The print layer may be located on the outermost surface of the laminate, or 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 may be any adhesive that can be used in a general-purpose lamination method. Examples of lamination methods include dry lamination or wet lamination using a solvent-based lamination adhesive, and non-solvent lamination using a solvent-free lamination adhesive.

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

[0048] The adhesive layer is usually formed by applying an adhesive layer composition (solution) to the surface to be formed and drying it.

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

[0050] -Removable Primer Layer- The laminate used in this embodiment can have a removable primer layer as a functional layer. In this case, recyclability can be improved and the quality of the recycled plastic can be improved. The removable primer layer can be easily removed from other layers by treatment with a solution (removal liquid) containing an alkali.

[0051] The removable primer layer in the laminate is preferably in contact with the plastic substrate layer. The removable primer layer in the laminate is preferably bonded to and sandwiched between the plastic substrate layer and a functional layer other than the removable primer layer (e.g., a printing layer, an adhesive layer, a functional coating layer, etc.). This can further improve recyclability and the quality of the recycled plastic.

[0052] The removable primer layer is usually formed by applying a composition (solution) for a removable primer layer to a surface to be formed, and drying it.

[0053] Furthermore, the removable primer layer (and the removable primer layer composition) may contain a resin that has film-forming properties at room temperature. Examples of resins that have film-forming properties at room temperature include polyester; 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 or hydrogenated products thereof; polyfunctional epoxy resins; polyvinyl acetal; urethane resins; and the like. Examples of polyfunctional epoxy resins include bisphenol A novolac epoxy resins, bisphenol F novolac epoxy resins, bisphenol S novolac epoxy resins, biphenyl epoxy resins, and naphthalene epoxy resins. These resins that have film-forming properties at room temperature may be used alone or in combination of two or more.

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

[0055] The urethane resin is a general term for a polymer compound having a urethane bond (—NHCOO—). The urethane resin can be obtained, for example, by reacting an aromatic polyester polyol with a polyisocyanate and, if necessary, a chain extender or the like.

[0056] In another embodiment, the removable primer layer preferably contains polyvinyl alcohol. Such a removable primer layer can be formed using, for example, a composition for a removable primer layer 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 is the raw material for the synthetic fiber vinylon.

[0058] Examples of the aqueous medium include water and organic solvents miscible with water. The aqueous medium may be used alone or in combination of two or more. Examples of the organic solvent 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 can be provided with a functional coating layer as a functional layer. The functional coating layer can be provided on the laminate for purposes such as hard coating, silicone-based release, IR cut, waterproof and moisture-proof, antibacterial, UV cut, heat dissipation, photocatalysis, weather resistance, anti-fogging, fingerprint and stain resistance, self-repair, and water and oil repellency. Specific examples of the functional coating layer include a hard coating layer, an adhesive layer, a release layer, a decorative layer, a light-shielding layer, an ultraviolet-shielding layer, an antistatic layer, a refractive index adjustment layer, and an oligomer sealing layer. These functional coating layers may be colorless or colored.

[0060] The functional coating layer can be formed by applying various coating agents to the surface to be formed, such as surface modifiers such as hard coating agents, self-healing coating agents, anti-fingerprint and anti-fouling coating agents, anti-fog 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, optical pressure-sensitive adhesives, polyimide varnishes, liquid crystal alignment film materials, electromagnetic wave shielding coating agents, fine wiring pastes, antistatic coating agents, high refractive index coating agents, optical lens coating agents, etc. The thickness of these functional coating layers 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.

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

[0062] The functional coating layer may be a single layer, or may be a multilayer consisting of the same or different functional coating layers. For example, the functional coating layer may be a multilayer consisting of a layer formed using the various coating agents and the metal vapor deposition layer. In this case, the layer formed using the various coating agents may be provided on 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] (Pretreatment Step) In the method of this embodiment, there is no particular limitation, and a pretreatment step of crushing the above-mentioned laminate may be performed prior to the immersion step. By performing such a pretreatment step, the processing efficiency of each subsequent step is improved, and the recycled plastic can be recovered more efficiently from the laminate. More specifically, by performing such a pretreatment step, the recycled plastic can be recovered as film pieces in the subsequent step. The method of crushing the laminate is not particularly limited, and known methods can be used. Furthermore, the laminate can be crushed in an air atmosphere in the absence of liquids such as solvents, and in this case, a known dry crusher can be suitably used.

[0065] When the pretreatment step is carried out, the laminate can be crushed so that the short and long sides are preferably 1 mm to 30 mm, more preferably 1 mm to 20 mm.

[0066] (Immersion Step) In the method of the present embodiment, the immersion step involves immersing the above-described laminate in a release solution containing an alkali, thereby causing the laminate to swell.

[0067] [Removal Solution] Examples of the alkali in the removal solution include sodium hydroxide, lithium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogencarbonate, ammonium, etc. Among these, sodium hydroxide or potassium hydroxide is preferred as the alkali, and sodium hydroxide is more preferred.

[0068] The concentration of the alkali in the desorption liquid is, for example, preferably 0.1% by mass to 10% by mass, more preferably 0.1% by mass to 5% by mass, as a proportion of the total amount of the desorption liquid.

[0069] The pH of the desorption liquid is preferably 10 or more, more preferably 11 or more, and even more preferably 12 or more.

[0070] The desorption liquid may contain water, which can improve operational stability and environmental stability.

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

[0072] The desorption liquid 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 desorption liquid are less likely to be hydrated, thereby increasing the nucleophilicity of the ions. As a result, recycled plastics can be recovered more efficiently.

[0073] [Stirring] In the immersion step, stirring is preferably performed, although not essential. In this case, the laminate can be swollen more efficiently. The stirring device and stirring conditions are not particularly limited, and known devices can be appropriately used. For example, immersion with stirring can be performed using a container equipped with a motor-driven stirring blade, a container equipped with a means for generating ultrasonic waves, a container equipped with a shaking means, or the like.

[0074] [Immersion Temperature] The immersion temperature (temperature of the release solution during immersion) is not particularly limited as long as the release solution can be kept in a liquid state, and can be, for example, 15 to 90°C. However, a higher immersion temperature is preferable because it allows the immersion time to be shortened. Specifically, the preferred immersion temperature is 40°C or higher, 50°C or higher, or 60°C or higher, although this differs depending on the composition of the release solution.

[0075] [Immersion Time] In the immersion step, the immersion time is preferably a time sufficient to swell the laminate, specifically, 30 minutes or more. From the viewpoint of processing efficiency, the immersion time is preferably 48 hours or less. When the immersion temperature is room temperature, an immersion time of 24 hours can sufficiently swell the laminate. When the immersion temperature is, for example, 40°C, an immersion time of 16 hours can sufficiently swell the laminate. When the immersion temperature is, for example, 75°C, an immersion time of 120 minutes can sufficiently swell the laminate. Furthermore, the immersion time can be appropriately adjusted by combining the presence or absence of stirring and the immersion temperature as described above.

[0076] (Cleaning Step) After the immersion step, the laminate may be contaminated with a release solution containing an alkali. Therefore, in the method of the present embodiment, a cleaning step of cleaning the laminate may be carried out after the immersion step, without any particular limitation, in order to remove the adhering alkali. Water is usually used to clean the laminate.

[0077] (Shaking step) In the method of the present embodiment, the laminate after the immersion step is shaken in the presence of water using a continuous shaker equipped with a dispersion medium in a container. By such shaking, recycled plastic derived from the plastic substrate layer of the laminate is produced, and the recycled plastic is obtained.

[0078] Shaking can be carried out using a continuous shaking device equipped with a dispersion medium such as rods or beads, etc. Examples of continuous shaking devices equipped with such dispersion media include a paint shaker, a ball mill, a vibration mill, an attritor, and a bead mill.

[0079] When a rod is used as the dispersion medium, examples of the material of the rod include steel, zirconia, alumina, and stainless steel. The diameter of the rod is preferably 12 mm or more, and is preferably 35 mm or less, more preferably 24 mm or less, and even more preferably 19 mm or less. When the diameter of the rod is 12 mm or more, the rod is easy to handle and can prevent problems such as twisting within the device. When the diameter of the rod is 35 mm or less, the rod can be sufficiently contacted with the laminate within a predetermined time, preventing a decrease in productivity.

[0080] When beads are used as the dispersion medium, examples of the material of the beads include steel, zirconia, alumina, stainless steel, and glass. The diameter (sphere diameter) of the beads is preferably 0.5 mm or more, more preferably 5 mm or more, and even more preferably 10 mm or more, and is preferably 35 mm or less, more preferably 30 mm or less, and even more preferably 25 mm or less. Beads with a diameter of 0.5 mm or more are easy to handle and can prevent the beads from becoming mixed with the laminate (or film pieces) to be processed, making it difficult to recover the beads. Beads with a diameter of 35 mm or less can ensure a sufficient number of contacts with the laminate within a given time period, thereby preventing a decrease in productivity.

[0081] The continuous shaking device used in the shaking process requires that the filling rate of the dispersion medium in the container be 30 vol% or more and 80 vol% or less. If the filling rate of the dispersion medium is less than 30 vol%, the crystalline structure and higher-order structure of the plastic substrate layer cannot be specifically changed, and there is a risk that the extensibility of the final molded product cannot be improved. Furthermore, if the filling rate of the dispersion medium exceeds 80 vol%, sufficient energy cannot be imparted to the laminate, and there is a risk that the desired recycled plastic cannot be obtained. From the same perspective, the filling rate of the dispersion medium in the container is preferably 35 vol% or more, and preferably 70 vol% or less, and more preferably 60 vol% or less.

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

[0083] In the shaking step using a continuous shaker, 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 be 2000 g / min or less, 1500 g / min or less, or 1000 g / min or less. In this case, specific changes in the crystal structure and higher-order structure of the plastic substrate layer can be more effectively brought about while maintaining high productivity and processing efficiency.

[0084] In the shaking step using a continuous shaker, the ratio of the laminate to water can be, for example, 50 g or more, 100 g or more, or 120 g or more of the laminate per 1 L of water, or 400 g or less, 300 g or less, or 200 g or less of the laminate per 1 L of water. In this case, specific changes in the crystal structure and higher-order structure of the plastic substrate layer can be more effectively brought about while maintaining high productivity and processing efficiency.

[0085] The recycled plastic produced in the shaking step can be recovered prior to the subsequent extrusion step. The recovery method is not particularly limited, and examples thereof include common methods such as gravity separation in a liquid such as water. It is also preferable to thoroughly remove moisture from the recovered recycled plastic prior to the subsequent extrusion step.

[0086] (Rinsing step) Substances not intended for recovery, such as functional layers, may remain on or adhere to the surface of the recycled plastic obtained in the shaking step. Therefore, the method of the present embodiment preferably further includes a rinsing step of washing the recycled plastic with a rinse liquid after the shaking step (and before the extrusion step).

[0087] The cleaning with the rinse solution may be accompanied by stirring. The stirring device and stirring conditions are not particularly limited, and known devices can be appropriately used. For example, immersion with stirring can be performed using a container equipped with a motor-driven stirring blade, a container equipped with a means for generating ultrasonic waves, a container equipped with a shaking means, or the like.

[0088] The washing with the rinse solution can be carried out using an apparatus equipped with a dispersion medium such as rods or beads, etc. The apparatus equipped with such a dispersion medium is the same as that described above in the shaking step.

[0089] The rinse liquid preferably contains a water-soluble solvent. Examples of water-soluble solvents include water-soluble alcohols and water-soluble solvents having 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 having 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 the water-soluble solvent in the rinse liquid is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, and still more preferably 90% by mass or more.

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

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

[0093] The recycled plastic content of the entire resin raw material subjected to 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 entire resin raw material subjected to the extrusion process. From the same perspective, 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 subjected to the extrusion process consists solely of the recycled plastic).

[0094] The composition to be subjected to the extrusion step may contain appropriate amounts of metal soaps of alkali metals, alkaline earth metals, or zinc; 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 oxide flame retardants; lubricants such as ethylene bisalkylamides; antioxidants; ultraviolet absorbers; fillers; colorants; peroxides, etc., within limits that do not impair the effects of the present invention.

[0095] The melt-kneading temperature in the extrusion process must be between 40°C and 120°C, which is the melting point of the recycled plastic. If the melt-kneading temperature is not 40°C or higher, which is the melting point of the recycled plastic, the crystalline structure and higher-order structure of the recycled plastic cannot be specifically changed, and there is a risk that the extensibility of the finally obtained molded product cannot be improved. Furthermore, if the melt-kneading temperature is not 120°C or lower, which is the melting point of the recycled plastic, there is a risk that the extensibility of the finally obtained molded product cannot be improved due to overheating.

[0096] When a single-screw extruder or a twin-screw extruder is used, the screw rotation speed is preferably 50 rpm or more and 500 rpm or less. If the screw rotation speed is 50 rpm or more, a more uniform melt-kneaded product can be obtained. Furthermore, if the screw rotation speed is 500 rpm or less, a significant decrease in the physical properties of the melt-kneaded product can be suppressed. From the same viewpoint, the screw rotation speed is more preferably 100 rpm or more, even more preferably 180 rpm or more, and more preferably 400 rpm or less, even more preferably 300 rpm or less.

[0097] The feeding rate of the resin raw material during extrusion is preferably 5 kg / h or more and 100 kg / h or less. If the feeding rate is 5 kg / h or more, the resin pressure during extrusion increases, and a better kneaded state can be formed. Furthermore, if the feeding rate is 100 kg / h or less, device malfunctions such as clogging can be suppressed. From the same viewpoint, the feeding rate of the resin raw material during extrusion is more preferably 50 kg / h or less, and even more preferably 30 kg / h or less.

[0098] The resin pressure during extrusion is preferably 1 MPa or more and 30 MPa or less. If the resin pressure is 1 MPa or more, a better kneaded state can be formed. Furthermore, if the resin pressure is 30 MPa or less, device malfunctions such as clogging can be suppressed. From the same viewpoint, the resin pressure during extrusion is more preferably 25 MPa or less, and even more preferably 20 MPa or less.

[0099] (Taking Step) In the method of the present embodiment, the melt-kneaded material extruded in the extrusion step is taken up as a strand in the taking step. The taking step can be performed using the same device as the extrusion step. That is, a series of operations in the extrusion step and the taking step can be performed using the same device.

[0100] The take-up speed of the strand in the take-up step is preferably 8 m / min or more and 50 m / min or less. If the take-up speed of the strand is 8 m / min or more, specific changes in the crystalline structure and higher-order structure of the recycled plastic can be more effectively brought about, and the extensibility of the finally obtained molded product can be further improved. Furthermore, if the take-up speed of the strand is 50 m / min or less, the occurrence of defects such as wire breakage can be suppressed. From the same viewpoint, the take-up speed of the strand in the take-up step is more preferably 30 m / min or less.

[0101] (Molding step) In the method of the present embodiment, the strand is molded in the molding step. A molded product is finally obtained by this molding step. In the molding step, pellets obtained by cutting the strand with a pelletizer or the like may be used for molding.

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

[0103] In the molding step, the strands or pellets can be heat-molded. The heat-molding method is not particularly limited, and examples thereof include injection molding, extrusion molding, blow molding, and compression molding.

[0104] The heating temperature during heat molding is preferably 180°C or higher, 190°C or higher, or 200°C or higher, and is 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 20°C or higher and 60°C or lower. If the mold temperature is 20°C or higher, the fluidity of the molten resin can be maintained, and poor filling and the generation of bubbles can be prevented. Furthermore, if the mold temperature is 60°C or lower, the cooling rate of the molten resin can be maintained appropriately, and the shrinkage rate after molding can be suppressed. From the same 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. Furthermore, if the molding time is 45 seconds or less, productivity can be maintained at a good level. From the same viewpoint, the molding time is more preferably 20 seconds or more, even more preferably 25 seconds, and more preferably 40 seconds or less, even more preferably 35 seconds or less.

[0107] The holding pressure during heat molding is preferably 20 MPa or more and 100 MPa or less. If the holding pressure is 20 MPa or more, the quality of the molded product and therefore its surface can be improved. Furthermore, if the holding pressure is 100 MPa or less, release defects can be suppressed. From the same viewpoint, the holding pressure during heat molding is more preferably 30 MPa or more, even more preferably 40 MPa or more, and more preferably 70 MPa or less, and even more preferably 60 MPa or less.

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

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

[0110] <Preparation of Composition for Removable Primer Layer (1)> 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) were mixed and reacted to prepare polyol (a) (aromatic polyester polyol).

[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-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the mixture was reacted at 75° C. for 8 hours under a nitrogen stream to obtain a urethane resin (1).

[0112] Next, the urethane resin (1) was diluted with isopropyl alcohol so that the solid content concentration of the urethane resin (1) became 10%, thereby obtaining a composition for a removable primer layer (1).

[0113] <Preparation of Composition for Removable Primer Layer (2)> 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 were mixed to obtain a composition for removable primer layer (2).

[0114] <Preparation of Composition for Removable Primer Layer (3)> 10 parts by mass of PVA-2 (polyvinyl alcohol, manufactured by Nippon Vinyl Acetate & 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 were mixed to obtain a composition for removable primer layer (3).

[0115] <Preparation of Composition for Removable Primer Layer (4)> 10 parts by mass of PVA-3 (polyvinyl alcohol, manufactured by Nippon Vinyl Acetate & 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 were mixed to obtain a composition for removable primer layer (4).

[0116] <Preparation of Composition for Removable Primer Layer (5)> 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 were mixed to obtain a composition for removable primer layer (5).

[0117] <Preparation of Adhesive Layer Composition> The adhesive layer composition was prepared by mixing DICDRY (registered trademark) LX-510 manufactured by DIC Corporation and DICDRY (registered trademark) KW-75 manufactured by DIC Corporation in a mass ratio of LX-510:KW-75=9:1, and then diluting the mixture with ethyl acetate as a solvent (a polyurethane-based two-component curing laminating adhesive).

[0118] <Preparation of composition for printing layer (white)> As the composition for the printing layer (white), a urethane-based laminating ink (Finart R794 White S, manufactured by DIC Corporation) was used, the viscosity of which was adjusted to 15 seconds (25°C) using a Zahn Cup #3 manufactured by Rigo Co., Ltd.

[0119] <Preparation of composition for printing layer (indigo)> For the composition for the printing layer (indigo), a surface printing gravure ink (Glossa 507 Primary Indigo S2, manufactured by DIC Graphics) was used, with its viscosity adjusted to 15 seconds (25°C) using a Zahn Cup #3 manufactured by Rigo Co., Ltd.

[0120] <Preparation of Laminate (LAM1)> The composition for the printing layer (white) was tightly coated onto PP1 as a plastic substrate using a gravure printing machine equipped with a gravure plate with a plate depth of 43 μm. Then, the coating was passed through an oven at 70°C to dry and harden the coating, forming a printing layer (white) on PP1. Next, the composition for the adhesive layer was applied onto the printing layer (white) in an amount (solid content) of 4 g / m ２The adhesive layer composition was applied using an RDS Mayer coating bar so that the adhesive layer composition was uniform. Next, the solvent in the adhesive layer composition was evaporated using a dryer. Meanwhile, the removable primer layer (1) composition was applied tightly (solidly) to PP2 as a plastic substrate layer using a gravure printing machine. Next, the composition was dried at 90°C for 1 minute to form a removable primer layer (1) on PP2. Next, the plastic substrate layers were bonded together so that the adhesive composition on PP1 and the removable primer layer (1) on PP2 were in contact. Then, aging was performed at 40°C for 5 days to obtain a laminate (LAM1) having a layer structure of "PP1 / printed layer (white) / adhesive layer / detachable primer layer (1) / PP2".

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

[0122] <Preparation of Laminate (LAM3)> A composition for a removable primer layer (1) was tightly applied onto PP1 as a plastic substrate layer using a gravure printing machine. The applied composition was then dried at 90°C for 1 minute to form a removable primer layer (1) on PP1. A composition for a printing layer (white) was then applied onto the removable primer layer (1) without any gaps using a gravure printing machine equipped with a gravure plate with a plate depth of 43 μm. The resulting mixture was then passed through an oven at 70°C to dry and cure, forming a printing layer (white) on the removable primer layer (1). A composition for an adhesive layer was then applied onto the printing layer (white) in an amount (solid content) of 4 g / m. ２The adhesive layer composition was applied using an RDS Mayer coating bar so that the adhesive layer composition was uniform. Next, the solvent in the adhesive layer composition was volatilized using a dryer. Meanwhile, the removable primer layer (1) composition was tightly coated on PP2 as a plastic substrate layer using a gravure printing machine. Next, the coating was dried at 90°C for 1 minute to form a removable primer layer (1) on PP2. Next, the plastic substrate layers were bonded together so that the adhesive composition on PP1 and the removable primer layer (1) on PP2 were in contact. Then, aging was performed at 40°C for 5 days to obtain a laminate (LAM3) having a layer structure of "PP1 / Removable primer layer (1) / Printing layer (white) / Adhesive layer / Removable primer layer (1) / PP2".

[0123] <Preparation of Laminate (LAM4)> A composition for a removable primer layer (1) was tightly applied onto PET1 as a plastic substrate layer using a gravure printing machine. The applied composition was then dried at 90°C for 1 minute to form a removable primer layer (1) on PET1. A composition for a printing layer (white) was then applied onto the removable primer layer (1) without any gaps using a gravure printing machine equipped with a gravure plate with a plate depth of 43 μm. The resulting mixture was then passed through an oven at 70°C to dry and cure, forming a printing layer (white) on the removable primer layer (1). A composition for an adhesive layer was then applied onto the printing layer (white) in an amount (solid content) of 4 g / m. ２ The adhesive composition was applied using an RDS Meyer coating bar so that the adhesive layer composition was formed as follows: Next, the solvent in the adhesive layer composition was evaporated using a dryer. Next, PP2 was laminated as a plastic substrate layer to the adhesive composition on PET1. Then, aging was carried out 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] <Preparation of Laminate (LAM5)> A composition for a removable primer layer (1) was tightly applied onto PP1 as a plastic substrate layer using a gravure printing machine. The applied composition was then dried at 90°C for 1 minute to form a removable primer layer (1) on PET1. A composition for a printing layer (white) was then applied onto the removable primer layer (1) without any gaps using a gravure printing machine equipped with a gravure plate with a plate depth of 43 μm. The resulting mixture was then passed through an oven at 70°C to dry and cure, forming a printing layer (white) on the removable primer layer (1). A composition for an adhesive layer was then applied onto the printing layer (white) in an amount (solid content) of 4 g / m. ２ The adhesive layer composition was applied using an RDS Meyer coating bar so that the adhesive layer composition was formed as follows: Next, the solvent in the adhesive layer composition was evaporated using a dryer. Next, PP3 was laminated to the adhesive composition on PP1 as a plastic substrate layer. Then, aging was carried out at 40°C for 5 days to obtain a laminate (LAM5) having a layer structure of "PP1 / removable primer layer (1) / printed layer (white) / adhesive layer / PP3".

[0125] <Preparation of Laminate (LAM6)> A composition for a removable primer layer (2) was applied to PP1 as a plastic substrate layer in an amount (solid content) of 0.5 g / m ２ The coating was applied without gaps using a gravure printing machine equipped with a gravure plate with a plate depth of 22 μm so that the coating was uniform. The coating was then dried by passing through an oven at 70°C. The coating was then left at room temperature for one day to form a removable primer layer (2) on PP1. An adhesive layer composition was then applied onto the removable primer layer (2). PP2 was then attached as a plastic substrate layer to the adhesive layer composition on PP1. Aging was then performed at 40°C for three days to obtain a laminate (LAM6) having a layer structure of "PP1 / removable primer layer (2) / adhesive layer / PP2."

[0126] <Preparation of Laminate (LAM7)> A composition for a removable primer layer (3) was applied to PE1 as a plastic substrate layer in an amount (solid content) of 0.5 g / m ２The composition was tightly coated using a gravure printing machine equipped with a gravure plate with a plate depth of 22 μm so that the thickness of the PE1 was uniform. The composition was then dried by passing through an oven at 70°C. This was then left at room temperature for one day to form a removable primer layer (3) on PE1. A composition for a printing layer (white) was then coated tightly onto this removable primer layer (3) using a gravure printing machine equipped with a gravure plate with a plate depth of 43 μm. This was then dried and cured by passing through an oven at 70°C to form a printing layer (white) on the removable primer layer (3). An adhesive layer composition was then coated onto this printing layer (white). PE1 was then bonded to the adhesive layer composition on PE1 as a plastic substrate layer. Aging was then performed at 40°C for three days to obtain a laminate (LAM7) having a layer structure of "PE1 / removable primer layer (3) / printing layer (white) / adhesive layer / PE1."

[0127] <Preparation of Laminate (LAM8)> A composition for a removable primer layer (4) was applied to PET1 as a plastic substrate layer in an amount (solid content) of 0.5 g / m ２ The coating was applied without gaps using a gravure printing machine equipped with a gravure plate with a plate depth of 22 μm so that the coating was uniform. The coating was then passed through an oven at 70°C for drying. The coating was then left at room temperature for one day to form a removable primer layer (4) on PET1. A composition for an adhesive layer was then applied onto the removable primer layer (4). Meanwhile, the composition for a removable primer layer (4) was applied without gaps to PP2 as a plastic substrate layer using a gravure printing machine. The coating was then passed through an oven at 70°C for drying. The coating was then left at room temperature for one day to form a removable primer layer (4) on PP2. The plastic substrate layers were then bonded together so that the adhesive layer composition on PET and the removable primer layer (4) on PP2 were in contact. Aging was then performed for three days at 40°C to obtain a laminate (LAM8) having a layer structure of "PET1 / detachable primer layer (4) / adhesive layer / detachable primer layer (4) / PP2."

[0128] <Preparation of Laminate (LAM9)> A composition for a removable primer layer (5) was applied to PP1 as a plastic substrate layer in an amount (solid content) of 0.5 g / m２ The composition was tightly coated using a gravure printing machine equipped with a gravure plate with a plate depth of 22 μm so that the resulting coating was uniform. The coating was then dried by passing through an oven at 70°C. This was then left at room temperature for one day to form a removable primer layer (5) on PP1. A composition for a printing layer (white) was then tightly coated onto this removable primer layer (5) using a gravure printing machine equipped with a gravure plate with a plate depth of 43 μm. This was then dried and cured by passing through an oven at 70°C to form a printing layer (white) on the removable primer layer (5). An adhesive layer composition was then coated onto this printing layer (white). PP3 was then bonded to the adhesive layer composition on PP1 as a plastic substrate layer. Aging was then performed at 40°C for three days to obtain a laminate (LAM9) having a layer structure of "PP1 / removable primer layer (5) / printing layer (white) / adhesive layer / PP3."

[0129] <Preparation of Laminate (Surface Printed Material, Pri1)> The composition for the printing layer (indigo) was tightly coated onto PP2 as a plastic substrate layer using a gravure printing machine equipped with a gravure plate with a plate depth of 43 μm. The coating was then dried and cured by passing through an oven at 70°C to form a printing layer (indigo) on PP2. In this way, a laminate (Pri1) having a layer structure of "PP2 / printed layer (indigo)" was obtained.

[0130] <Preparation of Laminate (Surface Printed Material, Pri2)> A composition for a removable primer layer (1) was tightly applied onto PE1, which served as a plastic substrate layer, using a gravure printer. This was then dried at 90°C for 1 minute to form a removable primer layer (1) on PE1. Next, a composition for a printing layer (indigo) was applied onto this removable primer layer (1) without any gaps using a gravure printer equipped with a gravure plate with a plate depth of 43 μm. This was then dried and cured by passing through an oven at 70°C to form a printing layer (indigo) on the removable primer layer (1). In this way, a laminate (Pri2) having a layer structure of "PE1 / removable primer layer (1) / printing layer (indigo)" was obtained.

[0131] The layer structure of each laminate produced is shown in Table 1.

[0132]

[0133] <Production of Molded Articles> (Pretreatment Step) Each of the produced laminates was placed in a dry crusher fitted with a screen having a hole diameter of 10 mm and through which cooling water was flowed, and pretreated so that the short side dimensions were approximately 5 to 10 mm and the long side dimensions were approximately 10 to 20 mm.

[0134] (Immersion Step) The laminate after the pretreatment step was subjected to the following immersion step (A) or immersion step (B). Immersion step (A): A release liquid selected from release liquids (1) to (4) shown in Table 2 was used as the release liquid, and 2 kg of the laminate was placed in 15 L of the release liquid. The laminate was then immersed in the release liquid at 40°C for 16 hours. Immersion step (B): A release liquid selected from release liquids (1) to (4) shown in Table 2 was used as the release liquid, and 2 kg of the laminate was placed in 15 L of the release liquid. The laminate was then immersed in the release liquid at 75°C for 120 minutes while stirring at 300 rpm using a Three-One Motor.

[0135]

[0136] Alkali: sodium hydroxide Surfactant (1): Dai-ichi Kogyo Seiyaku Co., Ltd.'s "DKS NL Dash 403", polyalkyl alkylene lauryl ether, HLB value = 6.5 Surfactant (2): Dai-ichi Kogyo Seiyaku Co., Ltd.'s "DKS NL Dash 408", polyalkyl alkylene lauryl ether, HLB value = 12.5 Surfactant (3): NOF Corporation's "M2-100R", cationic surfactant

[0137] (Washing Step) After the immersion step, the laminate was showered with water to wash off the alkali until the pH fell within the range of 7 to 12, and then the laminate was placed in a colander and lightly dehydrated.

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

[0139] (Rinsing step) The recycled plastic film pieces obtained in the shaking step were washed with a rinse solution. Specifically, 1 kg of the recycled plastic film pieces was placed in 10 L of diethylene glycol methyl ether as a rinse solution, and the mixture was stirred using a Three-One motor (rotation speed: 500 rpm) for 30 minutes.

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

[0141] (Extrusion Process and Take-Up Process) 0.3% of an antioxidant (Irganox 1010) was blended into the recycled plastic film pieces after the shaking and rinsing processes. A twin-screw extruder "KZW" (L / D = 45) manufactured by Technovel Corporation was used as the extrusion device. The film pieces were fed into the twin-screw extruder at a rate of 10 kg / h with a screw rotation speed of 300 rpm, melt-kneaded, and then extruded. The resin pressure during this process was 1 to 2 MPa. The extruded melt-kneaded product was taken up as a strand and pelletized. The melt-kneading temperature (actual temperature measured during extrusion) and strand take-up speed used in each example are shown in Tables 3 to 5.

[0142] (Molding step) The obtained pellets were injection molded using an injection molding machine "MS100" manufactured by Sodick Corporation to produce 4 mm thick dumbbell test pieces (molded products). The injection molding conditions were an injection temperature (heating temperature) of 200°C, a mold temperature (cooling temperature) of 40°C, a pressing pressure of 90 MPa, a holding pressure of 50 MPa, and a molding time (cooling time) of 30 seconds. A 1B mold specified in JIS K 7139 was used as the mold.

[0143] <Measurements and Evaluations> In the series of operations described above, the following measurements and evaluations were carried out. The results are shown in Tables 3 to 5.

[0144] (Releasability) After the shaking and rinsing processes, the area of ​​peeled off portions relative to the total area of ​​the recycled plastic film pieces was measured. The measured peeled off area was scored according to the following criteria. The higher the score, the better the releasability. 1 point: peeled off area is less than 10% 2 points: peeled off area is 10% or more but less than 50% 3 points: peeled off area is 50% or more but less than 100% 4 points: peeled off area is 100%

[0145] (Strand Diameter) After cooling, the strand taken up in the take-up step was measured for diameter at five points. The five measured values ​​were averaged and rounded to the nearest whole number.

[0146] (Elongation at break of molded product) Dumbbell test pieces (molded products) obtained by injection molding were elongated at a rate of 100 mm / min in accordance with JIS K6301 to measure the elongation at break. The number of measurements was 10 per level, and the average value of 6 points, excluding the two highest and two lowest measured values, was used. The larger this value, the higher the extensibility.

[0147]

[0148]

[0149]

[0150] It can be seen from Tables 3 to 5 that in the examples according to the present invention, molded articles were produced by carrying out the specified steps, and the obtained molded articles had superior elongation properties compared to the comparative examples.

[0151] According to the present invention, a method for manufacturing a molded product can be provided that recovers recycled plastic from a laminate having a plastic substrate layer and a functional layer, and enables the production of a molded product with excellent extensibility.

Claims

1. A method for producing a molded product, in which recycled plastic is recovered from a laminate comprising a plastic substrate layer and a functional layer, and the recycled plastic is used to produce a molded product, comprising: an immersion step in which the laminate is immersed in a release liquid containing an alkali; a shaking step in which the immersed laminate is shaken in the presence of water using a continuous shaking device equipped with a dispersing medium in a container to obtain recycled plastic; an extrusion step in which the recycled plastic or a composition containing the recycled plastic is melt-kneaded and extruded; a withdrawal step in which the extruded molten mixture is taken up as strands; and a molding step in which the strands are molded using the strands; wherein the continuous shaking device used in the shaking step has a container with a dispersing medium filling rate 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.

2. The method according to claim 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.

3. The method according to claim 1 or 2, wherein the molding step is carried out 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 liquid after the shaking step.

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

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