Method for producing resin composition molded article and method for producing resin composition powder for producing resin composition molded article

Abstract

To provide a method for producing a resin composition molded article, enabling effective use of waste plastic including low-melting-point resin and non-low-melting-point resin.SOLUTION: A method for producing a resin composition molded article is provided, comprising: preparing waste plastic including at least one selected from waste plastic residue derived from general waste, waste plastic derived from industrial waste, and waste plastic derived from marine plastic waste, the plastic waste including resin having a low-melting-point in a range from 80°C or higher and 190°C or lower, a high-melting-point resin having a melting point of 190°C higher, and a thermosetting resin; performing removal treatment and water washing treatment on the plastic waste or crushed material obtained by crushing the plastic waste; obtaining resin composition powder by pulverizing the plastic waste after the water washing treatment or the crushed material; and obtaining a resin composition molded article by molding the resin composition powder.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a resin composition molded article and a method for producing a resin composition powder for use in producing a resin composition molded article. [Background technology]

[0002] Woody resin composition molded products, in which a powder of a cellulose-based material such as wood flour is dispersed in a resin, are also called wood plastics. While they have a texture similar to that of wood, they offer advantages over wood, such as resistance to corrosion, cracking, and splintering, and are lightweight. For this reason, woody resin composition molded products are widely used as building materials and other materials. The use of low-melting-point resins, such as waste-derived polypropylene, as the resin for woody resin composition molded products has been investigated (see, for example, Patent Document 1, Patent Document 2, and Non-Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-353707 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-66952 [Non-patent literature]

[0004] [Non-Patent Document 1] 2020 Plastic Product Production, Disposal, Recycling, and Treatment Material Flow Chart, Plastic Waste Management Institute, https: / / www.pwmi.or.jp / flow_pdf / flow2020.pdf Summary of the Invention [Problem to be solved by the invention]

[0005] Using plastic waste, including waste plastics, as a resin raw material for resin composition molded products is desirable from the perspective of promoting resource circulation and significantly contributing to reducing CO2 emissions from waste incineration. However, conventional practice has been to separate and recover only low-melting-point resins, which are easily thermoformable, from plastic waste. Because the separated and recovered low-melting-point resins are thermoformable, they are used as recycled resins for material recycling. On the other hand, the waste plastic residue remaining after the low-melting-point resins are separated and recovered contains an increased proportion of non-low-melting-point resins, such as high-melting-point resins and thermosetting resins, making thermoforming difficult. For this reason, waste plastic residue is difficult to utilize other than thermal recycling. Consequently, the material recycling rate of plastic waste in Japan is low. In recent years, there has been an increasing demand for increasing the material recycling rate of plastic waste. However, the inventors' research has revealed a problem: waste plastic residues derived from municipal waste, industrial waste, and marine plastic waste are difficult to thermoform due to the presence of inorganic substances such as magnetic materials, and organic substances such as oils and fats, food residues, and surfactants. Inorganic matter can damage manufacturing equipment used to produce resin composition molded articles and may hinder the continuous production of resin composition molded articles. Organic matter can serve as a nutrient source for microorganisms such as mold and bacteria, potentially promoting their proliferation, so it is important to reduce the amount of contamination. Because organic matter has a high affinity with waste plastics, a process is required to reduce the amount of organic matter adhering to waste plastics to a level that will suppress microbial proliferation.

[0006] The present disclosure aims to provide a method for producing a resin composition molded product that can effectively utilize plastic waste containing low-melting point resins and non-low-melting point resins, even if it contains inorganic substances such as magnetic materials or organic substances such as oils and fats, food residues, and surfactants. [Means for solving the problem]

[0007] The present disclosure relates to a method for producing a resin composition molded body, which comprises preparing plastic waste containing at least one of waste plastic residue derived from municipal waste, waste plastic derived from industrial waste, and waste plastic derived from marine plastic waste, the plastic waste containing a low-melting-point resin having a melting point in the range of 80°C or higher but lower than 190°C, and a non-low-melting-point resin including at least one of a high-melting-point resin and a thermosetting resin having a melting point of 190°C or higher, performing a process for removing magnetic substances and a water-washing process on the plastic waste or crushed material obtained by crushing the plastic waste, pulverizing the plastic waste or crushed material after the water-washing process to obtain a resin composition powder, and molding the resin composition powder to obtain a resin composition molded body. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram of a resin composition molded article manufacturing system that can be used in a method for manufacturing a resin composition molded article according to an embodiment of the present disclosure. FIG. [Figure 2] FIG. 1 is a flow diagram of a method for producing a resin composition powder for producing a resin composition molded article according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a flow diagram of a method for producing a resin composition molded article according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following embodiment, a woody resin composition molded body containing wood powder will be used as an example of a resin composition molded body, and a method for producing the same will be described.

[0010] FIG. 1 is a block diagram of a resin composition molded article production system that can be used in a method for producing a resin composition molded article according to an embodiment of the present disclosure. As shown in FIG. 1, the resin composition molded body manufacturing system 100 includes a resin composition powder supply unit 10, a wood powder supply unit 20, a low melting point resin powder supply unit 30, a non-low melting point resin powder supply unit 40, an additive supply unit 50, and a molded body manufacturing unit 60.

[0011] The resin composition powder supply unit 10 produces and stores resin composition powder for producing resin composition molded articles from plastic waste. The resin composition powder supply unit 10 includes a plastic waste crusher 11, a magnetic separator 12, a non-magnetic metal separator 13, a washer 14, a compression volume reducer 15, a pulverizer 16, a storage tank 17, and a weighing tank 18.

[0012] Plastic waste includes low-melting-point resins with melting points between 80°C and 190°C, and non-low-melting-point resins, which are mixtures of high-melting-point resins with melting points above 190°C and thermosetting resins, or both. Plastic waste may also contain substances other than synthetic resins. These substances may be inorganic or organic. Examples of inorganic substances include magnetic materials, non-magnetic metals, glass, pebbles, metals, shells, sand, and other inorganic materials, as well as desiccants such as silica gel and iron-based oxygen absorbers. Examples of magnetic materials include iron, cobalt, and nickel. Examples of non-magnetic metals include aluminum. Examples of organic materials include oils and fats, food residue, and surfactants.

[0013] Examples of low-melting-point resins include polystyrene (PS), acrylonitrile-butadiene-styrene (ABS), polyethylene (PE), polymethyl methacrylate (PMMA), polycarbonate (PC), polypropylene (PP), polyamide 12 (PA12), and polyacetal (POM). The melting point of high-melting-point resins may be 340°C or lower. Examples of high-melting-point resins include polyethylene terephthalate (PET), polyamide 6 (PA6), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and polyether ether ketone (PEEK). Thermosetting resins are resins after curing. Examples of thermosetting resins include polyimide (PI), polyurethane (PU), and phenolic resin (PF). The low-melting-point resin and non-low-melting-point resin contained in plastic waste may be one type or two or more types.

[0014] Plastic waste refers to any one or a mixture of two or more of the following waste materials: waste plastic residues from municipal waste, waste plastics from industrial waste, and waste plastics from marine plastic waste. Plastic refers to molded products made of synthetic resin. For example, plastic waste refers to waste containing 50% or more by mass of waste plastic. The waste plastic content of plastic waste may be, for example, in the range of 50% to 100% by mass, in the range of 50% to 99.5% by mass, or in the range of 50% to 70% by mass.

[0015] The ignition residue of the plastic waste may be in the range of 0.5% by mass to 10% by mass. The ignition residue is a value measured, for example, by the following method. (Method for measuring ignition residue) The weight of the sample before heating is measured while it is still in the crucible. It is then heated in a high-temperature electric furnace at 600°C for two hours to completely burn off the organic components, including synthetic resins. After cooling, the remaining weight of the sample is divided by the weight before heating to determine the ignition residue as a percentage.

[0016] Municipal waste refers to waste other than industrial waste and marine plastic waste, including household waste discarded from ordinary households. Examples of waste plastics derived from municipal waste include plastics used as product containers and packaging materials. Waste plastic residue is the residue remaining after separating and recovering a portion of the resins contained in waste plastic derived from municipal waste, such as the residue remaining after separating and recovering a portion of the low-melting-point resin. The low-melting-point resin to be separated and recovered may include, for example, at least one of PP, PE, and PS, or may include both PP and PE. Waste plastic residue may be the residue remaining after separating and recovering 5% or more, 5% to 95% or less, 5% to 50% or less, or 5% to 15% or less of the low-melting-point resin contained in the waste plastic. The sum of PP and PE may account for 20% or more, 50% to 100% or less, or 70% to 100%.

[0017] Industrial waste plastic is waste plastic generated as a result of business activities. Examples of industrial waste plastic include non-standard products and surplus production. Marine plastic waste is waste plastic that accumulates in the ocean when plastic products are directly dumped into the ocean or when plastic products discarded on land are washed into the ocean via rivers and lakes. Examples of plastic products include plastic fragments, PET bottles, and fishing gear. Marine plastic waste includes microplastics, which are plastic products that have deteriorated due to the effects of waves and ultraviolet rays and are now 5 mm or smaller in size.

[0018] There are no particular restrictions on the content of low-melting-point resin and non-low-melting-point resin in the synthetic resin contained in the plastic waste. The content of low-melting-point resin may be, for example, in the range of 3% by mass to 95% by mass. The content of non-low-melting-point resin may be, for example, in the range of 5% by mass to 97% by mass. The ratio of the content of low-melting-point resin to non-low-melting-point resin (low-melting-point resin / non-low-melting-point resin content ratio) may be, for example, in the range of 1 / 3 to 5.00 by mass. The content of low-melting-point resin may be 80% by mass or less, or 70% by mass or less. The content of low-melting-point resin may be in any of the ranges of 5% by mass to 80% by mass, 25% by mass to 80% by mass, 25% by mass to 75% by mass, or 30% by mass to 70% by mass. The content of non-low-melting-point resin may be 20% by mass or more, or 30% by mass or more. The content of the low-melting-point resin may be within any of the ranges of 20% to 95% by mass, 20% to 75% by mass, 25% to 75% by mass, or 30% to 70% by mass. The low-melting-point resin / non-low-melting-point resin content ratio may be less than 4.00 by mass, or within the range of 1 / 3 to 3.00 by mass.

[0019] When the plastic waste is waste plastic residue, the content of low-melting-point resin in the synthetic resin contained in the waste plastic residue may be, for example, 95% by mass or less, for example, in the range of 25% to 95% by mass, or 35% to 90% by mass. The total content of PE, PP, and PS in the synthetic resin contained in the waste plastic residue may be 80% by mass or less, or 70% by mass or less. The total content of PE, PP, and PS may be within any of the following ranges: 5% to 80% by mass, 25% to 80% by mass, 25% to 75% by mass, or 30% to 70% by mass. The total content of PE and PP relative to the total amount of low-melting-point resin may be 90% by mass or less, or within the range of 20% to 80% by mass. The content of non-low-melting-point resin in the synthetic resin may be, for example, 5% by mass or more, 5% to 75% by mass, or 10% to 65% by mass. The ratio of the content of the low-melting-point resin to the non-low-melting-point resin in the synthetic resin (low-melting-point resin / non-low-melting-point resin content ratio) may be, for example, in a mass ratio range of 1 / 3 to 5.00, or in a mass ratio range of 0.71 to 3.00. The mass ratio of the low-melting-point resin / non-low-melting-point resin may be less than 4.00, or in a mass ratio range of 1 / 3 to 3.00. The mass ratio of the content of the thermosetting resin to the high-melting-point resin contained in the non-low-melting-point resin in the synthetic resin (thermosetting resin / high-melting-point resin) may be, for example, in a mass ratio range of 0.01 to 100, or in a mass ratio range of 0.05 to 50. The content of the thermosetting resin in the synthetic resin may be, for example, 0% by mass or more, or in a mass ratio range of 1% by mass to 10% by mass. The content of the high melting point resin in the synthetic resin may be, for example, 5% by mass or more, or may be in the range of 10% by mass or more and 90% by mass or less.

[0020] The form of the plastic waste is not particularly limited, and may be, for example, bale-like or block-like. When the production units (lots) of resin composition molded products are divided according to the type of plastic waste, the plastic waste used in each production unit may be generated at different locations or times. For example, the plastic waste used in each production unit may have a standard deviation of 2% by mass or more in the content of low-melting-point resin, and may be in the range of 2% by mass or more and 23% by mass or less.

[0021] The crusher 11 is a device that crushes plastic waste to obtain plastic pieces. For example, a uniaxial crusher can be used as the crusher 11. The size of the plastic pieces obtained by the crusher 11 is not particularly limited, but may be, for example, a size that passes through a sieve with a mesh size of 20 to 50 mm. The mesh size of the sieve may be 50 mm, 40 mm, or 30 mm.

[0022] The magnetic separator 12 is a device that removes and recovers magnetic materials contained in plastic pieces. As the magnetic separator 12, for example, a hanging type magnetic separator, a pulley type magnetic separator, a drum type magnetic separator, or a roll type magnetic separator can be used. Examples of magnetic materials include iron, stainless steel, and ferrite. The magnetic separator 12 may be used alone or in combination of two or more types.

[0023] The non-magnetic metal separator 13 is a device that removes and recovers non-magnetic metals contained in plastic pieces. Examples of non-magnetic metals include aluminum, copper, zinc, and brass. An eddy current separator can be used as the non-magnetic metal separator 13.

[0024] The washer 14 is a device that washes and removes deposits such as detergent, food stains, and oil stains that are attached to the plastic pieces. A wet grinding washer with a crushing function can be used as the washer 14. The wet grinding washer may be one that crushes the plastic pieces in water. For the crushing function of the plastic pieces, a crusher that has a fixed blade and a rotary blade and crushes the plastic pieces by sandwiching them between the fixed blade and the rotary blade can be used. By using the wet grinding washer to crush the plastic pieces into coarse plastic particles and washing them at the same time, it is possible to more efficiently remove deposits that are attached to the coarse plastic particles.

[0025] The compressing machine 15 is a device that compresses the coarse plastic particles to remove moisture adhering to the coarse plastic particles and reduce their volume, thereby obtaining coarse plastic powder. A screw-type compressing machine equipped with a screw inside a barrel with a drainage hole can be used as the compressing machine 15. By using a screw-type compressing machine, moisture is removed by frictional heat between the screw, barrel, and coarse plastic particles, and a portion of the low-melting-point resin in the coarse plastic particles melts, causing the coarse plastic particles to fuse together, thereby reducing the volume of the coarse plastic particles.

[0026] The pulverizer 16 is a device that pulverizes the coarse plastic powder to produce a fine resin composition powder. As the pulverizer 16, a fine pulverizer (cutter mill), a hammer mill, or a pin mill can be used. The fine pulverizer (cutter mill) is a device that has a fixed blade and a rotary blade and pulverizes plastic pieces by sandwiching them between the fixed blade and the rotary blade. The pulverizer 16 may be used alone or in combination of two or more types.

[0027] A sieve may be provided at the outlet of the pulverizer 16 for the resin composition powder. The pulverizer 16 may be configured to retain, for example, coarse-sized coarse plastic powder inside the pulverizer 16 and discharge only the fine resin composition powder that passes through the sieve to the outside. The sieve may have a mesh size of 1 to 3 mm, for example. The sieve may have a mesh size of 3 mm, 2 mm, or 1 mm. If the sieve has a mesh size of, for example, 500 μm or less, the heat generated by pulverizing the coarse plastic powder may melt the pulverized low-melting-point resin, and the molten resin may solidify on the surface of the sieve, potentially causing the sieve to become clogged.

[0028] The storage tank 17 is a tank that temporarily stores the resin composition powder produced by the pulverizer 16. The measuring tank 18 is a tank that measures the resin composition powder sent from the storage tank 17 and temporarily stores a predetermined amount of the resin composition powder.

[0029] The resin composition powder supply unit 10 can produce a resin composition powder from plastic waste, for example, as follows: Fig. 2 is a flow diagram of a method for producing a resin composition powder for producing a resin composition molded article according to one embodiment of the present disclosure.

[0030] The method for producing the resin composition powder of this embodiment includes a crushing step S11, a magnetic substance removal step S12, a non-magnetic metal removal step S13, a water washing step S14, a volume reduction step S15, and a pulverization step S16.

[0031] The crushing step S11 is a step of crushing plastic waste to obtain plastic pieces. The crushing step S11 is performed using a crusher 11.

[0032] The magnetic substance removal process S12 is a process for removing and recovering magnetic substances contained in plastic fragments. The magnetic substance removal process S12 is performed using a magnetic separator 12. By performing the magnetic substance removal process S12, magnetic substances mixed in the plastic fragments can be reliably removed. By removing the magnetic substances, it is possible to prevent the magnetic substances from remaining inside the crusher in the crushing process S16, which would cause wear and tear on the blades inside the crusher and gradually reduce the crushing efficiency of the crusher. In particular, by performing the magnetic substance removal process S12 after the plastic waste is converted into plastic fragments in the crushing process S11, molded bodies such as push-type pumps used in hand soap and shampoo containers are crushed, and metal magnetic materials such as spring materials and screw materials used in the molded bodies can be more reliably removed.

[0033] The non-magnetic metal removal process S13 is a process for removing and recovering non-magnetic metals contained in the plastic pieces. The non-magnetic metal removal process S13 is performed using a non-magnetic metal separator 13.

[0034] The water washing process S14 is a process for washing and removing any adhering matter (especially organic matter) adhering to the plastic pieces by washing them with water. In the water washing process S14, the plastic pieces may be pulverized into coarse plastic particles, while the adhering matter adhering to the coarse plastic particles is washed and removed. The water washing process S14 is carried out using a washer 14. By carrying out the water washing process S14, adverse effects such as reduced pulverization efficiency due to melting and adhering of organic matter such as detergent, food stains, and oil stains to the blades inside the pulverizer in the pulverizer process S16, or clogging of the sieve of the pulverizer due to melting and adhering of organic matter to the sieve of the pulverizer can be prevented. Furthermore, the amount of organic matter mixed in the resulting resin composition powder is reduced, making it less susceptible to the growth of microorganisms.

[0035] The volume reduction step S15 is a step of removing moisture adhering to the coarse plastic particles and reducing their volume to obtain coarse plastic powder. The volume reduction step S15 is performed using a compression volume reduction machine 15.

[0036] The pulverization step S16 is a step in which the plastic coarse powder is pulverized to obtain a resin composition powder. In the method for producing a resin composition powder of this embodiment, in the pulverization step S16, the low melting point resin and the non-low melting point resin contained in the plastic waste are pulverized simultaneously without being separated. The pulverization step S16 is performed using a pulverizer 16. The resin composition powder obtained by pulverization is sent to a storage tank 17.

[0037] If the plastic waste is in bale or lump form, the bale or lump plastic waste may be crushed using a crusher before the crushing step S11. Furthermore, the plastic waste may contain various bulky magnetic waste items, such as batteries, lighters, spray cans, razors, and syringe needles. Therefore, the bulky magnetic waste items may be removed and collected using a magnetic separator before the crushing step S11.

[0038] The wood powder supply unit 20 produces and stores wood powder to be used as a raw material for resin composition molded bodies from waste wood. The wood powder supply unit 20 has a crusher 21, a magnetic separator 22, a pulverizer 23, a storage tank 24, and a measuring tank 25.

[0039] Examples of waste wood that can be used include waste construction wood, thinned wood, and sawdust.

[0040] The crusher 21 is a device that crushes waste wood to obtain wood chips. For example, a uniaxial crusher can be used as the crusher 21. The size of the wood chips obtained by the crusher 21 is not particularly limited, but may be, for example, a size that passes through a sieve with openings of 20 to 50 mm. The openings of the sieve may be 50 mm, 40 mm, or 30 mm.

[0041] The magnetic separator 22 is a device that removes and recovers magnetic materials contained in wood pieces. As the magnetic separator 22, for example, a hanging type magnetic separator, a pulley type magnetic separator, a drum type magnetic separator, or a roll type magnetic separator can be used. Examples of magnetic materials include nails and bolts. The magnetic separator 22 may be used alone or in combination of two or more types.

[0042] The crusher 23 is a device that crushes wood pieces to generate fine wood powder. A fine crusher (cutter mill), hammer mill, or pin mill can be used as the crusher 23. The crusher 23 may be used alone or in combination of two or more types.

[0043] A sieve may be provided at the wood powder outlet of the pulverizer 23. The pulverizer 16 may be configured to retain, for example, coarse-sized plastic coarse powder inside the pulverizer 16 and discharge only the fine resin composition powder that passes through the sieve to the outside. As the sieve, for example, a sieve with a mesh size in the range of 300 μm to 3 mm can be used. The mesh size of the sieve may be 2 mm, 1 mm, or 500 μm.

[0044] The particle size of the wood flour is not particularly limited, but among particles with a major axis of 1.0 mm or more, the content of particles with a major axis of 3.0 mm or more may be 35% by number or less, or 20% by number or less. Furthermore, the content of particles with a major axis of less than 2.0 mm may be 30% by number or more, or 50% by number or less. The content of these particles can be determined by observing a cross section of a resin composition molded product using an optical microscope and measuring the particle size of the wood flour.

[0045] The storage tank 24 is a tank that temporarily stores the wood powder generated by the grinder 23. The measuring tank 25 is a tank that measures the wood powder sent from the storage tank 24 and temporarily stores a predetermined amount of wood powder.

[0046] The low-melting-point resin powder supplying section 30 stores the low-melting-point resin powder used as a raw material for the resin composition molded article as needed. The low-melting-point resin powder supplying section 30 has a storage tank 31 and a measuring tank 32.

[0047] The low-melting-point resin powder includes a low-melting-point resin. Examples of low-melting-point resins include PS, ABS, PE, PMMA, PC, PP, PA12, and POM. The low-melting-point resins may be used alone or in combination. The low-melting-point resin powder may also contain a non-low-melting-point resin. The low-melting-point resin content of the low-melting-point resin powder may be, for example, 60% by mass or more, or 80% by mass or more. The low-melting-point resin powder may be obtained by crushing plastic waste containing 60% by mass or more of a low-melting-point resin. The low-melting-point resin powder may be one that passes through a sieve with a mesh size of 3 mm. Examples of low-melting-point resin powder include waste materials such as shrink film (PE), cable ties (PP), and polystyrene foam (PS) used for packaging, bundling, and curing products, crushed to 3 mm or less. Recycled plastics (PP, PE, PS) collected and produced in accordance with the Containers and Packaging Recycling Law may also be crushed to 3 mm or less.

[0048] The storage tank 31 is a tank for temporarily storing the low-melting-point resin powder. The measuring tank 32 is a tank for measuring the low-melting-point resin powder sent from the storage tank 31 and temporarily storing a predetermined amount of the low-melting-point resin powder.

[0049] The non-low melting point resin powder supply unit 40 stores the non-low melting point resin powder used as a raw material for the resin composition molded article as needed. The non-low melting point resin powder supply unit 40 has a storage tank 41 and a measuring tank .

[0050] The non-low melting point resin powder includes a non-low melting point resin. Examples of the non-low melting point resin include PET, PA6, PBT, PPS, PEEK, PI, PU, ​​and PF. The non-low melting point resin may be used alone or in combination of two or more. The non-low melting point resin powder may contain a non-low melting point resin. The content of the non-low melting point resin in the non-low melting point resin powder may be, for example, 60% by mass or more, or 80% by mass or more. The non-low melting point resin powder may be obtained by crushing plastic waste containing 60% by mass or more of a non-low melting point resin. The non-low melting point resin powder may be one that passes through a sieve with a mesh size of 3 mm. Recycled materials such as PET waste used as egg containers or food packaging materials crushed to 3 mm or less can be used as the non-low melting point resin powder.

[0051] The storage tank 41 is a tank for temporarily storing the non-low melting point resin powder. The measuring tank 42 is a tank for measuring the non-low melting point resin powder sent from the storage tank 41 and temporarily storing a predetermined amount of the non-low melting point resin powder.

[0052] The additive supplying section 50 stores additives to be added to the resin composition molded article as desired. The additive supplying section 50 includes a storage tank 51 and a measuring tank 52.

[0053] Additives that can be used include various additives commonly used in conventional resin composition molded products, such as pigments, compatibilizers for improving the affinity between resin and wood flour, fillers, lubricants, weathering agents, heat stabilizers, foaming agents, and antistatic agents. Pigments are used to color the resin composition molded product. Examples of pigments that can be used include inorganic pigments, organic pigments, and mixtures thereof. Compatibilizers are used to increase the adhesion between wood flour and resin components, improving the strength and water resistance of the resin composition molded product. Examples of compatibilizers that can be used include maleic anhydride-modified polypropylene compatibilizers. Lubricants are added to improve the sliding properties with the mold. Examples of lubricants that can be used include oxidized polyolefin wax, acid-modified polyolefin wax, calcium stearate, and zinc stearate. Examples of weathering agents that can be used include ultraviolet absorbers (UVA), light absorbers (HALS), and antioxidants.

[0054] The storage tank 51 is a tank that temporarily stores the additive. The measuring tank 52 is a tank that measures the additive sent from the storage tank 51 and temporarily stores a predetermined amount of the additive. One storage tank 51 and one measuring tank 52 may be provided for each type of additive, or one may be provided for an additive mixture in which two or more types of additives are mixed.

[0055] The molded body production section 60 produces a resin composition molded body. The molded body production section 60 has a mixer 61, a storage tank 62, and an extruder 63.

[0056] The mixer 61 is a device that mixes a resin composition powder, which is a raw material for the resin composition molded body, at least one of a low-melting-point resin-containing powder and a non-low-melting-point resin-containing powder, wood flour, and additives to obtain a raw material mixture. A heater mixer, for example, can be used as the mixer 61. By using the heater mixer to mix the raw materials while heating, a mixture in which the raw materials are uniformly dispersed can be obtained. The heating temperature of the heater mixer varies depending on the resins contained in the raw material mixture, but may be in the range of 100 to 150°C, for example, when the resin with the lowest melting point is PE.

[0057] The storage tank 62 is a tank for temporarily storing the raw material mixture, and supplies a predetermined amount of the raw material mixture to the extruder 63.

[0058] The extruder 63 is a device that molds the raw material mixture into a predetermined shape. Examples of the extruder 63 that can be used include a single-screw extruder and a twin-screw extruder. The molding temperature of the extruder 63 varies depending on factors such as the type and content of the low-melting-point resin contained in the raw material mixture, but is 150°C or higher when PE is included, for example. On the other hand, wood flour decomposes and gasifies at temperatures above 190°C, which can cause bubbles to form in the resin composition molded product, so the molding temperature is preferably below 190°C.

[0059] Next, a description will be given of a method for producing a resin composition molded article using the resin composition molded article production system 100. Fig. 3 is a flow diagram of the method for producing a resin composition molded article according to one embodiment of the present disclosure. The method for producing a resin composition molded article of this embodiment includes an analyzing step S21, a mixing step S22, and a molding step S23.

[0060] The analysis step S21 is a step of analyzing the composition of the resin composition powder. The ratio of the content of low-melting-point resin to the content of non-low-melting-point resin in the resin composition powder can be used as the composition of the resin composition powder. The resin composition powder (sample powder) to be analyzed may be, for example, the resin composition powder stored in the storage tank 17 of the resin composition powder supply unit 10.

[0061] The content of the low-melting point resin and the content of the non-low-melting point resin in the resin composition powder can be analyzed by, for example, separating the low-melting point resin and the non-low-melting point resin by utilizing the difference in specific gravity between them, and then measuring the content of each of the separated resins. In this embodiment, the analysis was performed as follows. The resin composition powder is immersed in an aqueous sodium chloride solution as a sample powder. Next, the amount of floating matter rising to the surface of the aqueous sodium chloride solution and the amount of sediment that sinks are measured. The floating matter is scooped out of the aqueous sodium chloride solution. The sediment is recovered by filtering the aqueous sodium chloride solution after all of the floating matter has been scooped out. The recovered floating matter and sediment are washed with water and then dried, and the amounts of the floating matter and sediment are measured. The amount of floating matter is the content of the low-melting-point resin, and the amount of sediment is the content of the non-low-melting-point resin. The specific gravity of the aqueous sodium chloride solution can be, for example, 1.08 to 1.13.

[0062] The mixing step S22 is a step of mixing the resin composition powder, at least one of the low-melting-point resin-containing powder and the non-low-melting-point resin-containing powder, wood flour, and additives to obtain a raw material mixture. The mixing step S22 is performed by mixing the raw materials sent from the measuring tanks 18, 25, 32, 42, and 52 using a mixer 61. The obtained raw material mixture is sent to a storage tank 62.

[0063] In the mixing step S22, the mixing ratio of the resin composition powder and the low-melting-point resin-containing powder and / or the non-low-melting-point resin-containing powder is adjusted based on the ratio of the low-melting-point resin content to the non-low-melting-point resin content of the resin composition powder obtained in the analysis step S21. The total content of the low-melting-point resin and the non-low-melting-point resin in the raw material mixture obtained in the mixing step S22 may be, for example, in the range of 50 to 90 mass%. The wood flour content may be, for example, in the range of 5 to 40 mass%. The additive content may be, for example, in the range of 5 to 40 mass%. The ratio of the wood flour content to the low-melting-point resin content (wood flour / low-melting-point resin content ratio) may be 5.0 or less. Furthermore, the ratio of the low-melting-point resin content to the non-low-melting-point resin content of the resin composition powder mixture may be, by mass, in the range of 1 / 3 to 5, or in the range of 1 / 3 to 1.40.

[0064] The molding step S23 is a step in which the raw material mixture obtained in the mixing step S22 is molded to obtain a wood resin composition molded body. The molding step S23 is carried out by extruding the raw material mixture sent from the storage tank 62 using an extruder 63. By extrusion molding, the low-melting-point resin in the resin composition powder melts, resulting in a wood resin composition molded body in which a non-low-melting-point resin and wood flour are dispersed in the low-melting-point resin. There are no particular restrictions on the shape of the wood resin composition molded body, and it may be, for example, a plate-like shape.

[0065] In the molding step S23, the molding temperature of the raw material mixture is preferably less than 10°C below the melting point of the non-low-melting-point resin contained in the raw material mixture. For example, if the melting point of the non-low-melting-point resin is 250°C, the molding temperature is preferably less than 240°C. By leaving the non-low-melting-point resin unmelted in the woody resin composition molded body, the non-low-melting-point resin is dispersed in islands within the molded body and behaves like a filler. Because the non-low-melting-point resin has a higher elastic modulus than the low-melting-point resin, the island-like dispersion of the non-low-melting-point resin can reinforce the low-melting-point resin, which has a sea-like and low elastic modulus. As a result, the resin composition molded body as a whole has high elasticity and strength. Furthermore, in blended systems containing wood flour, molding at a temperature above 200°C may carbonize the wood flour, so molding at a temperature below 190°C is desirable. The molding temperature of the raw material mixture is preferably at least 5 to 10°C above the melting point of the low-melting-point resin. The molding temperature of the raw material mixture may be, for example, in the range of 160°C or higher and 190°C or lower. The melting point of the non-low melting point resin means the lowest temperature among the melting points of the multiple types of non-low melting point resins contained in the raw material mixture. The melting point of the low melting point resin means the highest temperature among the melting points of the multiple types of low melting point resins contained in the raw material mixture.

[0066] From the viewpoint of improving the elasticity and strength of the resin composition molded article, the resin composition powder is preferably fine, and more preferably passes through a sieve with 1 mm openings.

[0067] The woody resin composition formed body obtained as described above contains wood flour and has a texture similar to that of wood, so it can be used as a wood substitute. The resin composition formed body can be used, for example, as a civil engineering material, a building material, or a gardening material. Examples of civil engineering materials include paving materials. Examples of building materials include flooring materials, particularly bathroom flooring materials, roofing materials, wall materials, handrails, sashes, wood decks, fences, etc. Examples of gardening materials include flower beds.

[0068] In the method for producing a resin composition molded product of this embodiment configured as described above, plastic waste containing a low-melting point resin and a non-low-melting point resin is crushed in a crushing step S11 to obtain crushed material, and the crushed material is then subjected to a magnetic substance removal treatment step S12, a non-magnetic metal removal treatment step S13, and a water washing treatment step S14, followed by a pulverization step S16, thereby efficiently removing inorganic matter, oils and fats, food residues, surfactants, and other organic matter mixed in the plastic waste. Therefore, the method for producing a resin composition molded product of this embodiment allows for the industrially stable production of a resin composition molded product using plastic waste containing a low-melting point resin and a non-low-melting point resin.

[0069] In the method for producing a resin composition molded product of this embodiment, by using a fine grinder (cutter mill) as the grinder 16 in the grinding step S16, it is possible to industrially produce a resin composition powder derived from plastic waste more efficiently. Furthermore, in the method for producing a resin composition molded product of this embodiment, if the resin composition powder derived from plastic waste has been passed through a sieve with 3 mm mesh, the non-low melting point resin is fine, so that the non-low melting point resin can be coated with a molten low melting point resin during the production of the resin composition molded product. This further improves the water resistance of the resulting resin composition molded product. Furthermore, in the method for producing a resin composition molded product of this embodiment, after the water-washing treatment step S14, a compression volume reducer 15 is used in the volume reduction treatment step S15 to remove water and fuse plastic coarse particles together to reduce the volume, thereby improving the grinding efficiency in the grinding step S16.

[0070] In the method for producing a resin composition molded article of this embodiment, when waste plastic residue derived from municipal waste is used as the plastic waste, the resin composition of the waste plastic residue is prone to change. Therefore, when using a resin composition powder derived from waste plastic residue, at least one of a low-melting-point resin-containing powder and a non-low-melting-point resin-containing powder prepared in advance may be added and mixed to obtain a resin composition powder mixture, which may then be molded. This allows the contents of the low-melting-point resin and non-low-melting-point resin in the resin composition powder mixture to be adjusted, thereby enabling the stable production of resin composition molded articles.

[0071] In the method for producing a resin composition molded product of this embodiment, when the low-melting-point resin-containing powder added to the resin composition powder derived from plastic waste contains 60% by mass or more of the low-melting-point resin, the low-melting-point resin content of the low-melting-point resin-containing powder is high, making it easier to adjust the amount of the low-melting-point resin-containing powder added when the resin composition powder contains a small amount of low-melting-point resin. Also, in the method for producing a resin composition molded product of this embodiment, when the non-low-melting-point resin-containing powder added to the resin composition powder derived from plastic waste contains 60% by mass or more of the non-low-melting-point resin, the non-low-melting-point resin content of the non-low-melting-point resin-containing powder is high, making it easier to adjust the amount of the non-low-melting-point resin-containing powder added when the resin composition powder contains a small amount of non-low-melting-point resin.

[0072] In the method for producing a resin composition molded article of this embodiment, wood flour is added to and mixed with a resin composition powder derived from plastic waste to obtain a wood-flour-containing resin composition powder mixture, and the wood flour-containing resin composition powder mixture is molded to obtain a resin composition molded article having a texture similar to that of wood. Instead of wood flour, a cellulose-based material powder such as pulp powder can be used. The particle size of the wood flour correlates with the water resistance of the resulting resin composition molded article, and finer wood flour particle size tends to improve the water resistance of the resin composition molded article. From the perspective of improving the water resistance of the resin composition molded article, the wood flour is preferably passed through a sieve with a mesh size of 300 μm to 3 mm, and more preferably passed through a sieve with a mesh size of 500 μm.

[0073] In the method for producing a resin composition powder for producing a resin composition molded product of this embodiment, plastic waste is crushed in a crushing step S11 to obtain crushed material, and the crushed material is then subjected to a magnetic substance removal treatment step S12, a non-magnetic metal removal treatment step S13, and a water washing treatment step S14, followed by pulverization, thereby efficiently removing inorganic matter, oils and fats, food residues, surfactants, and other organic matter mixed in the plastic waste. Therefore, according to the method for producing a resin composition powder of this embodiment, a resin composition powder that can be used for producing a resin composition molded product can be industrially and stably produced using waste plastic residues derived from municipal waste or waste plastics derived from industrial waste.

[0074] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited thereto. For example, in this embodiment, plastic waste is crushed in the crushing step S11, but the crushing step S11 may be omitted depending on the shape of the plastic waste. In this embodiment, non-magnetic metals contained in the plastic fragments are removed and recovered in the non-magnetic metal removal treatment step S13, but the non-magnetic metal removal treatment step S13 may be omitted, for example, if the amount of non-magnetic metal contained in the plastic fragments is small. In the method for producing a resin composition powder of this embodiment, the plastic coarse particles after washing in the water washing treatment step S14 are reduced in volume in the volume reduction treatment step S15, but the washed plastic coarse particles may be crushed in the crushing step S16 without being reduced in volume.

[0075] In this embodiment, the content of low-melting point resin and non-low-melting point resin in the resin composition powder derived from plastic waste is measured in the analysis step S21, but the analysis step S21 is not an essential component. For example, if the content of low-melting point resin and non-low-melting point resin in the plastic waste is known, the analysis step S21 may be omitted. Furthermore, in this embodiment, the content of low-melting point resin and non-low-melting point resin in the resin composition powder is measured in the analysis step S21. However, it is also possible to measure only the low-melting point resin and subtract the content of the low-melting point resin from the resin composition powder to determine the content of the non-low-melting point resin, or to measure only the non-low-melting point resin and subtract the content of the non-low-melting point resin from the resin composition powder to determine the content of the low-melting point resin. Furthermore, in this embodiment, the content of low-melting point resin and non-low-melting point resin in the resin composition powder is measured using the difference in specific gravity in the analysis step S21, but the measurement method is not limited thereto. For example, DSC (differential scanning calorimetry), GC-MS (gas chromatography-mass spectrometry), infrared absorption spectroscopy, and elemental analysis (CHN coder) may be used. When DSC is used, the content of the non-low melting point resin may be measured, and the amount obtained by subtracting the content of the non-low melting point resin from the content of the resin composition powder may be used as the content of the low melting point resin.

[0076] In this embodiment, the molding step S23 is performed by extrusion molding, but the molding method for the resin composition molded body is not limited to this. The molding method for the resin composition molded body may be any method that melts the low-melting-point resin of the resin composition powder to form a molten resin composition. The molding method for the resin composition molded body may be, for example, injection molding, press molding, cast molding, or laminate molding using a 3D printer.

[0077] In this embodiment, the coarse plastic powder is crushed in crusher 16, and the wood chips are crushed in crusher 23. However, the coarse plastic powder and the wood chips may be crushed simultaneously using the same crusher to produce a powder mixture containing a resin composition powder and wood flour. While the resin composition molded body has been described using a wood-based resin composition molded body containing wood flour as an example, it does not have to contain wood flour, as long as it contains a resin composition powder derived from plastic waste. Furthermore, in this embodiment, waste wood is used as the raw material for the wood flour, but the raw material for the wood flour is not limited to waste wood. [Example]

[0078] The present disclosure will be described in more detail below based on examples. The present disclosure is not limited to these examples. In these examples, wastes 1 to 4, general waste, and recycled resins were used as plastic waste, each containing the amounts of low-melting-point resin and non-low-melting-point resin shown in Table 1 below. Wastes 1 to 4 are waste plastic residues derived from general waste that remain after separating and recovering low-melting-point resin from general waste. The ratio of low-melting-point resin content to non-low-melting-point resin content of wastes 1 to 4 is lower than that of general waste. This makes material recycling difficult. Material recycling is particularly difficult for wastes with a low-melting-point resin content / non-low-melting-point resin content ratio of less than 1.00. Recycled resin is low-melting-point resin separated and recovered from general waste. Recycled resin has a high ratio of low-melting-point resin content to non-low-melting-point resin content, and is therefore used for material recycling.

[0079] [Table 1]

[0080] [Example 1] (Production of resin composition powder) Waste 1 was fed into a crusher and crushed. The crushed material obtained was passed through a high-magnetic pulley-type magnetic separator with a magnetic force of 2000 gauss on the belt surface to remove iron-containing materials. Next, the crushed material from which the iron-containing materials had been removed was crushed in a uniaxial coarse crusher until it passed through a 50 mm mesh sieve, obtaining plastic fragments (crushing process). The magnetic substances contained in the obtained plastic fragments were removed and recovered using a hanging magnetic separator and a pulley-type magnetic separator (magnetic substance removal process). Next, the non-magnetic metals contained in the plastic fragments were removed and recovered using a non-magnetic metal separator (non-magnetic metal removal process). Next, the plastic fragments were crushed and washed using a wet crushing and washing machine until they passed through a 12 mm mesh sieve, obtaining coarse plastic particles (water washing process). Next, the coarse plastic particles obtained in the wet grinding and washing machine were compressed and dehydrated using a volume reduction and compression dehydrator to reduce the volume, obtaining a coarse plastic powder with a moisture content of 0.5% by mass (volume reduction process). Finally, the coarse plastic powder was pulverized using a cutter mill-type pulverizer until it passed through a sieve with 2 mm openings (pulverization process). In this way, a resin composition powder was obtained. Table 2 below shows whether or not the magnetic substance removal process, non-magnetic metal removal process, water washing process, and volume reduction process were performed, as well as the opening diameter of the sieve used in the pulverization process.

[0081] In the grinding process, the long-term stability of the processing capacity of the cutter mill type grinder was evaluated by the following method, and the results are shown in Table 2 below.

[0082] (Long-term processing capacity stability) The grinding process is carried out continuously for 12 hours, and the degree of decline in grinding capacity is evaluated. The raw materials are fed into the cutter mill-type grinder by adjusting the current value of the grinder's main shaft motor to be constant. The weight of the resin composition powder obtained in the 30 minutes from 30 minutes after the start of operation to 1 hour after the start of operation is defined as the initial processing amount. The weight of the resin composition powder obtained in the 30 minutes from 11 hours 30 minutes after the start of operation to 12 hours after the start of operation is measured, and the obtained weight is converted into a percentage of the initial processing amount, and the obtained value is defined as the processing capacity maintenance rate. A processing capacity maintenance rate of 90% or more is defined as "A," a rate of 70% or more but less than 90% is defined as "B," and a rate of less than 70% is defined as "C." The blades of the cutter mill-type grinder are re-sharpened for each example and comparative example and used for evaluation.

[0083] (Wood flour production) The waste wood was fed into a crusher and crushed in a uniaxial coarse crusher until it passed through a sieve with 50 mm openings, yielding wood chips (crushing process). The magnetic materials contained in the obtained wood chips were removed and recovered using a hanging magnetic separator and a pulley magnetic separator (magnetic material removal process). Next, the wood chips were crushed using a cutter mill-type crusher until they passed through a sieve with 1 mm openings (crushing process). In this way, wood powder was obtained. The opening diameters of the sieves used in the crushing process are shown in Table 2 below.

[0084] (Method of manufacturing resin composition molded article) 60 parts by mass of resin composition powder, 30 parts by mass of wood powder, and 10 parts by mass of additives (a mixture containing pigment, compatibilizer, inorganic filler, lubricant, and weathering agent) were mixed at 150°C using a heat mixer. The resulting mixture was molded using an extruder equipped with a rectangular cross-sectional mold 30 mm thick and 300 mm wide to obtain a plate-shaped resin composition molded product. The composition of the resulting resin composition molded product is shown in Table 3 below.

[0085] The resulting resin composition molded articles were evaluated for bending strength, water resistance, and mildew resistance by the following methods, and the results are shown in Table 3 below.

[0086] (bending strength) The bending strength (three-point bending) of a full-scale specimen is measured in accordance with Method B specified in JIS A 5741:2016 (Wood-plastic recycled composite materials). A bending strength of 20 MPa or more is assigned an "S" grade, 15 MPa or more but less than 20 MPa an "A" grade, 10 MPa or more but less than 15 MPa an "B" grade, and less than 10 MPa an "C" grade.

[0087] (water resistance) The sample is immersed in warm water adjusted to 60°C. Every day, the sample is taken out of the warm water and the thickness of the sample is measured. The rate of change in thickness compared to the thickness of the sample on the previous day is calculated using the following formula (1). Sample thickness change rate (%) = (sample thickness - previous day's sample thickness) / previous day's sample thickness × 100 (1)

[0088] When the change in thickness of the sample becomes 0.5% or less, the expansion rate of the sample due to water absorption is considered to have reached equilibrium, and the equilibrium expansion rate of the sample thickness is calculated using the following formula (2): The sample thickness was calculated as the average of the thicknesses at five points: the center of the plane and the areas near each of the four corners. Equilibrium expansion rate (%) = {(Tf-Ti) / Ti} × 100 (2) In formula (2), Tf (unit: mm) is the thickness of the resin composition molded body when the rate of change in thickness becomes 0.5% or less, and Ti (unit: mm) is the thickness of the resin composition molded body before immersion in hot water. Water resistance is rated as "S" if the equilibrium expansion rate is 5% or less, "A" if it is 10% or less, "B" if it is more than 10% but less than 20%, and "C" if it is more than 20%.

[0089] (Mold resistant) The area of ​​the sample where mycelia have grown after two weeks is measured according to Method A specified in Appendix A (Testing of Plastic Products) of JIS Z 2911:2018 (Testing Methods for Mold Resistance). Mold resistance is rated as "A" if the growth area is less than 25%, "B" if it is 25% or more but less than 50%, and "C" if it is 50% or more.

[0090] [Examples 2 to 16, Comparative Examples 1 to 3] Resin composition powder and wood flour were produced in the same manner as in Example 1, except that the conditions for producing the resin composition powder and wood flour were changed as shown in Table 2, and resin composition molded articles were produced using the obtained resin composition powder and wood flour. Table 2 shows the processing capacity and long-term stability of the grinder used in producing the resin composition powder, and Table 3 shows the bending strength, water resistance, and mold resistance of the obtained resin composition molded articles.

[0091] [Comparative Example 4 and Reference Example 1] The plastic waste listed in Table 2 was used instead of waste 1, and instead of performing a water washing process and a volume reduction process on the plastic pieces after the non-magnetic metal removal process, the plastic pieces were granulated and then the resulting granules were cooled by spraying water (granulation-water spraying process), and the resulting granules were crushed using a cutter mill-type crusher until they could pass through a sieve with 2 mm openings (crushing process). Except for this, a resin composition powder and wood flour were produced in the same manner as in Example 1, and a resin composition molded body was produced using the resulting resin composition powder and wood flour.

[0092] [Reference example 2] A resin composition powder and wood flour were produced in the same manner as in Example 1, except that recycled resin was used instead of waste 1, and the processes from the magnetic substance removal process to the volume reduction process were not carried out, and the waste was pulverized using a cutter mill-type pulverizer until it passed through a sieve with 2 mm openings (pulverization process).The obtained resin composition powder and wood flour were used to produce a resin composition molded body.

[0093] [Table 2]

[0094] [Table 3]

[0095] The results shown in Tables 2 and 3 indicate that resin composition powders obtained in Examples 1 to 16, which were subjected to the magnetic material removal treatment, non-magnetic metal removal treatment, water washing treatment, and volume reduction treatment, can be used to obtain resin composition molded articles with excellent bending strength, water resistance, and mold resistance. In particular, the resin composition molded articles obtained in Examples 2 and 11, in which the sieve used in the pulverizer to produce the resin composition powder had a mesh size of 1 mm, and in Examples 8 and 16, in which the sieve used in the pulverizer to produce the resin composition powder had a mesh size of 500 μm, exhibited improved bending strength. This is because the use of resin composition powder that passed through a sieve with a mesh size of 1 mm or 500 μm resulted in the dispersion of fine, non-low-melting-point resin particles in the resin composition molded article in an island-like pattern. These results indicate that, from the perspective of bending strength of the resin composition molded article, it is preferable that the resin composition powder be fine, i.e., that the resin composition powder be finely ground. On the other hand, finely ground resin composition powder tends to reduce the processing capacity and long-term stability of the pulverizer, and therefore, it is preferable that the sieve mesh size be 1 mm or larger when using a cutter mill-type pulverizer. Furthermore, the resin composition molded bodies obtained in Examples 4 and 12, in which the sieve used in the mill to produce the wood flour had a mesh size of 500 μm, exhibited improved water resistance. This is because the use of fine wood flour that passed through a sieve with a mesh size of 500 μm as the wood flour, which is a water absorption factor in the water resistance test, allows the wood flour to be efficiently mixed and dispersed in the low-melting-point resin, thereby suppressing changes in water absorption in the resin composition molded body. The results of Examples 1 to 16 confirmed that waste plastic residues that were previously thermally recycled can be used for material recycling by carrying out the magnetic substance removal process, non-magnetic metal removal process, water washing process, and volume reduction process according to the present disclosure.

[0096] In contrast, Comparative Example 1, in which the water-washing treatment step and the volume-reducing treatment step were not performed, exhibited a decrease in the long-term stability of the crusher's processing capacity. This was because organic matter, such as detergent, food stains, and oil stains, was not removed and mixed into the crusher, melting and adhering to the cutters inside the crusher, reducing the crushing efficiency, and the organic matter melting and adhering to the crusher's sieve, clogging it. Furthermore, the resin composition molded product obtained in Comparative Example 1 exhibited a decrease in water resistance. This was due to the incorporation of organic matter into the resin composition molded product. Comparative Example 2, in which the magnetic substance removal treatment step and the non-magnetic metal removal treatment step were not performed, exhibited a decrease in the long-term stability of the crusher's processing capacity. This was due to the magnetic substances and non-magnetic metals being mixed into the crusher without being removed, causing wear on the cutters inside the crusher. Comparative Example 3, in which the magnetic substance removal treatment step, non-magnetic metal removal treatment step, water-washing treatment step, and volume-reducing treatment step were not performed, exhibited a significant decrease in the long-term stability of the crusher's processing capacity. This is because organic matter, magnetic materials, and non-magnetic metals were not removed and were mixed into the pulverizer. In Comparative Example 4 and Reference Example 1, in which a granulation-water sprinkling process was performed instead of a water washing process and a volume reduction process, the pulverizer's long-term processing capacity stability decreased, and the mold resistance of the resulting resin composition molded body decreased. This is because the organic matter contained in the plastic waste could not be removed in the granulation-water sprinkling process. On the other hand, in Reference Example 2, which used recycled resin, a resin composition molded body excellent in bending strength, water resistance, and mold resistance was obtained, even without performing each of the processes from the magnetic material removal process to the volume reduction process.

[0097] Aspects of the present disclosure are set forth below. (Appendix 1) A method for producing plastic waste containing at least one of waste plastic residues derived from municipal waste, waste plastics derived from industrial waste, and waste plastics derived from marine plastic waste, the method comprising preparing plastic waste containing a low-melting-point resin having a melting point in the range of 80°C or higher but lower than 190°C, and a non-low-melting-point resin including at least one of a high-melting-point resin and a thermosetting resin having a melting point of 190°C or higher; The plastic waste or crushed material obtained by crushing the plastic waste is subjected to a magnetic substance removal treatment and a water washing treatment, pulverizing the plastic waste or the crushed material after the water washing treatment to obtain a resin composition powder; A method for producing a resin composition molded article, comprising molding the resin composition powder to obtain a resin composition molded article.

[0098] (Appendix 2) Attachment 1: The method for producing a resin composition molded article according to Appendix 1, wherein the ignition residue of the plastic waste is in the range of 0.5% by mass to 10% by mass.

[0099] (Appendix 3) A method for producing a resin composition molded body described in Appendix 1 or 2, wherein the content of the low-melting point resin in the synthetic resin contained in the waste plastic residue derived from municipal waste and the waste plastic derived from marine plastic waste is 95% by mass or less, and the content of the non-low-melting point resin in the synthetic resin is 5% by mass or more.

[0100] (Appendix 4) A method for producing a resin composition molded body described in any one of Appendix 1 to 3, wherein the content of the low-melting point resin in the synthetic resin contained in the waste plastic residue derived from municipal waste and the waste plastic derived from marine plastic waste is in the range of 5% by mass or more and 80% by mass or less.

[0101] (Appendix 5) 5. A method for producing a resin composition molded body according to any one of claims 1 to 4, wherein the waste plastic residue derived from municipal waste is the residue remaining after separating and recovering a portion of the low-melting point resin contained in the waste plastic contained in the municipal waste.

[0102] (Appendix 6) The method for producing a resin composition molded body described in Appendix 5, wherein the waste plastic residue derived from municipal waste is the residue remaining after separating and recovering 5% by mass or more of the low-melting point resin contained in the waste plastic contained in the municipal waste.

[0103] (Appendix 7) 7. The method for producing a resin composition molded body according to any one of claims 1 to 6, wherein the waste plastic residue derived from municipal waste contains at least one of polyethylene and polypropylene, and the total content of the polyethylene and polypropylene relative to the total amount of the low-melting point resin is 90 mass% or less.

[0104] (Appendix 8) A method for producing a resin composition molded body described in any one of Appendices 1 to 7, wherein the content of the high-melting point resin in the synthetic resin contained in the waste plastic residue derived from general waste is in the range of 10% by mass or more and 90% by mass or less.

[0105] (Appendix 9) A method for producing a resin composition molded body described in any one of Appendices 1 to 8, wherein the content of the thermosetting resin in the synthetic resin contained in the waste plastic residue derived from municipal waste is in the range of 0% by mass or more and 20% by mass or less.

[0106] (Appendix 10) A method for producing a resin composition molded body described in any one of Appendix 1 to 9, wherein the ratio of the content of the thermosetting resin to the high-melting point resin in the waste plastic residue derived from general waste is in the range of 0.01 or more and 100 or less in mass ratio.

[0107] (Appendix 11) A method for producing a resin composition molded body described in any one of Appendices 1 to 10, wherein the ratio of the content of the low-melting point resin to the non-low-melting point resin in the waste plastic residue derived from general waste (low-melting point resin / non-low-melting point resin content ratio) is less than 4.00 by mass.

[0108] (Appendix 12) 12. The method for producing a resin composition molded body according to any one of claims 1 to 11, wherein the production units of the resin composition molded body are divided according to the type of the plastic waste, and the standard deviation of the content of the low-melting point resin in the plastic waste used in each production unit is 2% by mass or more.

[0109] (Appendix 13) 13. The method for producing a resin composition molded body according to any one of claims 1 to 12, wherein the magnetic substance removal treatment is carried out on crushed material obtained by crushing the plastic waste.

[0110] (Appendix 14) 14. The method for producing a resin composition molded article according to any one of claims 1 to 13, further comprising the step of performing a non-magnetic metal removal treatment between the magnetic substance removal treatment and the water washing treatment.

[0111] (Appendix 15) 15. The method for producing a resin composition molded article according to any one of claims 1 to 14, wherein the crushed material is crushed using a fine crusher.

[0112] (Appendix 16) 16. The method for producing a resin composition molded product according to any one of claims 1 to 15, wherein the crushed material is pulverized under conditions that allow the resin composition powder to pass through a sieve with a mesh size of 3 mm.

[0113] (Appendix 17) 17. A method for producing a resin composition molded body according to any one of claims 1 to 16, wherein the plastic waste is crushed into coarse plastic particles by a water washing treatment, and any deposits adhering to the coarse plastic particles are washed away.

[0114] (Appendix 18) 18. The method for producing a resin composition molded product according to any one of claims 1 to 17, wherein the resin composition molded product is molded by extrusion molding the resin composition powder.

[0115] (Appendix 19) The crushed material after the water washing treatment is dehydrated using a compressing machine, 19. The method for producing a resin composition molded article according to any one of claims 1 to 18, wherein the crushed product after the dehydration treatment is pulverized.

[0116] (Appendix 20) 20. The method for producing a resin composition molded product according to any one of claims 1 to 19, further comprising adding and mixing at least one of a low-melting-point resin-containing powder and a non-low-melting-point resin-containing powder that have been prepared in advance to the resin composition powder to obtain a resin composition powder mixture, and molding the resin composition powder mixture.

[0117] (Appendix 21) 21. The method for producing a resin composition molded article according to claim 20, wherein the low-melting-point resin-containing powder contains 60% by mass or more of a low-melting-point resin.

[0118] (Appendix 22) 21. The method for producing a resin composition molded article according to claim 20, wherein the powder containing a non-low melting point resin contains 60 mass % or more of a non-low melting point resin.

[0119] (Appendix 23) 23. A method for producing a resin composition molded body according to any one of claims 1 to 22, comprising adding a cellulose-based material powder prepared in advance to the resin composition powder and mixing them to obtain a cellulose-based material-containing resin composition powder mixture, and molding the cellulose-based material-containing resin composition powder mixture.

[0120] (Appendix 24) 24. The method for producing a resin composition molded product according to any one of Appendices 1 to 23, wherein the resulting resin composition molded product has a bending strength of 20 MPa or more as measured in accordance with Method B specified in JIS A 5741:2016.

[0121] (Appendix 25) A method for producing a resin composition molded product according to any one of Appendices 1 to 24, wherein the area of ​​the mycelium-grown portion of the obtained resin composition molded product after two weeks, as measured by Method A specified in Appendix A of JIS Z 2911:2018, is less than 25% of the total area.

[0122] (Appendix 26) A method for producing a resin composition powder for use in producing resin composition molded products, comprising: preparing plastic waste containing at least one of waste plastic residues derived from municipal waste, waste plastics derived from industrial waste, and waste plastics derived from marine plastic waste, the plastic waste containing a low-melting-point resin having a melting point in the range of 80°C or higher but lower than 190°C, and a non-low-melting-point resin containing one or both of a high-melting-point resin having a melting point of 190°C or higher and a thermosetting resin; subjecting the plastic waste or crushed material obtained by crushing the plastic waste to a treatment for removing magnetic substances and a water-washing treatment; and pulverizing the plastic waste or crushed material after the water-washing treatment to obtain a resin composition powder. [Explanation of symbols]

[0123] 10...resin composition powder supply section, 11...crusher, 12...magnetic separator, 13...non-magnetic metal separator, 14...washer, 15...compression volume reducer, 16...crusher, 17...storage tank, 18...measuring tank, 20...wood powder supply section, 21...crusher, 22...magnetic separator, 23...crusher, 24...storage tank, 25...measuring tank, 30...low melting point resin powder supply section, 31...storage tank, 32...measuring tank, 40...non-low melting point resin powder supply section, 41...storage tank, 42...measuring tank, 50...additive supply section, 51...storage tank, 52...measuring tank, 60...molded body production section, 61...mixer, 62...storage tank, 63...extruder, 100...resin composition molded body production system

Claims

1. A method for producing plastic waste comprising at least one of waste plastic residue derived from municipal waste, waste plastic derived from industrial waste, and waste plastic derived from marine plastic waste, the method comprising preparing plastic waste containing a low-melting-point resin having a melting point in the range of 80°C or higher but lower than 190°C, and a non-low-melting-point resin including at least one of a high-melting-point resin and a thermosetting resin having a melting point of 190°C or higher; The plastic waste or crushed material obtained by crushing the plastic waste is subjected to a magnetic substance removal treatment and a water washing treatment, pulverizing the plastic waste or the crushed material after the water washing treatment to obtain a resin composition powder; A method for producing a resin composition molded article, comprising molding the resin composition powder to obtain a resin composition molded article.

2. 2. A method for producing a resin composition molded body according to claim 1, wherein the content of the low-melting point resin in the synthetic resin contained in the waste plastic residue derived from municipal waste and the waste plastic derived from marine plastic waste is in the range of 5% by mass or more and 80% by mass or less.

3. 3. The method for producing a resin composition molded body according to claim 1, wherein the waste plastic residue derived from municipal waste is a residue remaining after separating and recovering a portion of a low-melting point resin contained in the waste plastic contained in the municipal waste.

4. 4. The method for producing a resin composition molded body according to claim 1, wherein the ratio of the content of the non-low melting point resin in the waste plastic residue derived from general waste to the content of the non-low melting point resin in the waste plastic residue derived from general waste is less than 4.00 in mass ratio.

5. 5. The method for producing a resin composition molded body according to claim 1, wherein the production units of the resin composition molded body are divided according to the type of the plastic waste, and the standard deviation of the content of low-melting point resin in the synthetic resin contained in the plastic waste used in each production unit is 2 mass% or more.

6. The method for producing a resin composition molded article according to claim 1 , wherein the magnetic substance removal treatment is carried out on crushed material obtained by crushing the plastic waste.

7. The method for producing a resin composition molded article according to claim 1 , further comprising the step of removing non-magnetic metals between the step of removing the magnetic material and the step of washing with water.

8. The method for producing a resin composition molded article according to claim 1 , wherein the crushed material is crushed using a fine grinder.

9. The method for producing a resin composition molded article according to claim 1 , wherein the crushed material is pulverized under conditions that allow the resin composition powder to pass through a sieve with a mesh size of 3 mm.

10. The method for producing a resin composition molded article according to any one of claims 1 to 9, wherein the plastic waste is pulverized into coarse plastic particles in a water washing treatment, and any deposits adhering to the coarse plastic particles are washed away.

11. The method for producing a resin composition molded article according to claim 1 , wherein the resin composition molded article is molded by extrusion molding the resin composition powder.

12. The crushed material after the water washing treatment is dehydrated using a compression volume reducer, The method for producing a resin composition molded article according to claim 1 , wherein the crushed product after the dehydration treatment is pulverized.

13. At least one of a low-melting-point resin-containing powder and a non-low-melting-point resin-containing powder that have been prepared in advance is added to and mixed with the resin composition powder to obtain a resin composition powder mixture; The method for producing a resin composition molded article according to claim 1 , further comprising molding the resin composition powder mixture.

14. A cellulose-based material powder prepared in advance is added to and mixed with the resin composition powder to obtain a cellulose-based material-containing resin composition powder mixture; The method for producing a resin composition molded article according to claim 1 , further comprising molding the cellulose-based material-containing resin composition powder mixture.

15. The method for producing a resin composition molded product according to any one of claims 1 to 14, wherein the resulting resin composition molded product has a bending strength of 20 MPa or more as measured in accordance with Method B specified in JIS A 5741:2016.

16. The method for producing a resin composition molded product according to any one of claims 1 to 15, wherein the area of ​​the mycelium-grown portion of the resin composition molded product after two weeks, as measured by Method A specified in Annex A of JIS Z 2911:2018, is less than 25% of the total area.

17. A method for producing plastic waste comprising at least one of waste plastic residue derived from municipal waste, waste plastic derived from industrial waste, and waste plastic derived from marine plastic waste, the method comprising preparing plastic waste containing a low-melting-point resin having a melting point in the range of 80°C or higher but lower than 190°C, and a non-low-melting-point resin including at least one of a high-melting-point resin and a thermosetting resin having a melting point of 190°C or higher; The plastic waste or crushed material obtained by crushing the plastic waste is subjected to a magnetic substance removal treatment and a water washing treatment, The method for producing a resin composition powder for producing a resin composition molded article includes pulverizing the plastic waste or the crushed material after the water washing treatment to obtain a resin composition powder.

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