Method for producing resin composition molded body

Abstract

A method for producing a resin composition molded body according to the present disclosure comprises: preparing a plastic waste containing a low melting point resin having a melting point in the range of 80°C to less than 190°C and a non-low melting point resin that is a high melting point resin or a thermosetting resin having a melting point of 190°C or higher; pulverizing the plastic waste to obtain a resin composition powder; adding at least one of a low melting point resin-containing powder and a non-low melting point resin-containing powder prepared in advance to the resin composition powder, and mixing to obtain a resin composition powder mixture adjusted so that the ratio of the content of the low melting point resin to the content of the non-low melting point resin falls within a predetermined range; and molding the resin composition powder mixture to obtain a resin composition molded body.

Description

Method for producing molded resin composition

[0001] The present disclosure relates to a method for producing a resin composition molded article.

[0002] Woody resin composition molded articles, 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 articles 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 articles has been investigated (see, for example, Patent Document 1 and Non-Patent Document 1).

[0003] The use of plastic waste, including waste plastics, as a resin raw material for resin composition molded articles has been investigated. For example, in a method for producing a resin composition molded article containing slag, the use of a high-melting point plastic and a low-melting point plastic classified from two or more different types of plastic waste has been investigated (Patent Document 2). Furthermore, the use of a pulverized mixture of plastic waste mixed with a plastic binder and molded into a molded article has also been investigated.

[0004] Japanese Patent Publication No. 2001-353707 Korean Patent Publication No. 10-2022-0002779 Japanese Patent Publication No. 7-227849

[0005] 2020 Plastic Product Production, Disposal, Recycling, and Treatment Material Flow Diagram, Plastic Waste Management Institute, https: / / www.pwmi.or.jp / flow_pdf / flow2020.pdf

[0006] The use of plastic waste, including waste plastics, as a resin raw material for resin composition molded products promotes resource circulation and reduces CO2 emissions from incineration of waste. ２This is desirable from the perspective of significantly contributing to the reduction of waste emissions. However, conventionally, only low-melting-point resins that are easily thermoformable are separated and recovered from plastic waste and utilized. Because the separated and recovered low-melting-point resins are thermoformable, they are utilized 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 a high proportion of non-low-melting-point resins, such as high-melting-point resins and thermosetting resins, making thermoforming difficult. For this reason, waste plastic residues are rarely utilized for anything 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, according to the inventor's research, there is a problem in that the blending ratio of low-melting-point resins to non-low-melting-point resins contained in plastic waste varies depending on the location and time of generation of the plastic waste. If the blending ratio of low-melting-point resins to non-low-melting-point resins contained in plastic waste varies, it becomes difficult to consistently produce resin composition molded articles by thermoforming. However, separating plastic waste into low-melting-point resins and non-low-melting-point resins is a complicated process, and requires equipment for the separation.

[0007] The present disclosure aims to provide a method for producing a resin composition molded product that can effectively utilize plastic waste containing a low-melting point resin and a non-low-melting point resin as a molding raw material without separating the low-melting point resin and the non-low-melting point resin, even if the blending ratio of the resins (low-melting point resin and non-low-melting point resin) is different.

[0008] The present disclosure relates to a method for producing a resin composition molded body, which includes preparing plastic waste containing a low-melting-point resin having a melting point within a range of 80°C or higher but lower than 190°C and a non-low-melting-point resin which is a high-melting-point resin or a thermosetting resin having a melting point of 190°C or higher, pulverizing the plastic waste to obtain a resin composition powder, adding 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 and mixing them to obtain a resin composition powder mixture adjusted so that the ratio of the content of the low-melting-point resin to the content of the non-low-melting-point resin is within a predetermined range, and molding the resin composition powder mixture to obtain a resin composition molded body.

[0009] 1 is a block diagram of a resin composition molded body manufacturing system that can be used in a method for manufacturing a resin composition molded body according to an embodiment of the present disclosure; FIG. 2 is a flow diagram of a method for manufacturing a resin composition molded body according to an embodiment of the present disclosure; FIG. 3 is a model of a fountain flow in a mold that can be used in a method for manufacturing a resin composition molded body according to an embodiment of the present disclosure.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following embodiments, a woody resin composition formed body containing wood flour will be used as an example of a resin composition formed body, and a method for producing the same will be described.

[0011] 1 is a block diagram of a resin composition molded body manufacturing system that can be used in a resin composition molded body manufacturing method 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.

[0012] 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 crusher 16, a storage tank 17, and a weighing tank 18.

[0013] Plastic waste includes low-melting-point resins with melting points in the range of 80°C to less than 190°C, and non-low-melting-point resins, which are mixtures of high-melting-point resins with melting points of 190°C or higher and thermosetting resins, or both. Plastic waste may also contain substances other than synthetic resins. The substances other than synthetic resins may be inorganic or organic. Examples of inorganic substances include magnetic substances, 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 substances include iron, cobalt, and nickel. Examples of non-magnetic metals include aluminum. Examples of organic substances include oils and fats, food residue, and surfactants.

[0014] Examples of low-melting-point resins include polystyrene (PS), acrylonitrile-butadiene-styrene resin (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.

[0015] Plastic waste refers to any one or a mixture of two or more wastes including, for example, waste plastics derived from municipal waste, waste plastics derived from industrial waste, and waste plastics derived 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.

[0016] The ignition residue of plastic waste may be in the range of 0.5% by mass or more and 10% by mass or less. 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 in a crucible. The sample is kept at 600°C for two hours in a high-temperature electric furnace to completely burn off organic components including synthetic resins. After cooling, the weight of the remaining sample is divided by the weight before heating to determine the ignition residue as a percentage.

[0017] 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 plastics derived from municipal waste may be waste plastic residue. Waste plastic residue is the residue remaining after separating and recovering a portion of the resin contained in waste plastic derived from municipal waste, for example, 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% by mass or more of the low-melting-point resin contained in the waste plastic, alternatively, 5% by mass to 95% by mass, alternatively, 5% by mass to 50% by mass, or alternatively, 5% by mass to 15% by mass. The proportion of the sum of PP and PE in the separated and recovered low-melting point resin may be 20% by mass or more, may be in the range of 50% by mass or more and 100% by mass or less, or may be in the range of 70% by mass or more and 100% by mass or less.

[0018] Waste plastic derived from industrial waste is waste plastic generated as a result of business activities. Examples of waste plastic derived from industrial waste include off-spec products and surplus production. Waste plastic derived from marine plastic waste is waste plastic that accumulates in the ocean when plastic products are directly dumped into the sea or when plastic products discarded on land are washed into the sea via rivers or lakes. Examples of plastic products include plastic fragments, PET bottles, fishing gear, etc. Waste plastic derived from marine plastic waste includes microplastics that are 5 mm or smaller in size due to the degradation of plastic products caused by the effects of waves and ultraviolet rays.

[0019] The content of low-melting point resin and non-low-melting point resin in the synthetic resin contained in the plastic waste is not particularly limited. 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.

[0020] 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% by mass to 95% by mass or less, or in the range of 35% by mass to 90% by mass or less. 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 in any of the following ranges: 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 total content of PE and PP relative to the total amount of low-melting point resin may be 90% by mass or less, or in the range of 20% by mass to 80% by mass. The content of the non-low melting point resin in the synthetic resin may be, for example, 5% by mass or more, in the range of 5% by mass to 75% by mass or less, or in the range of 10% by mass to 65% by mass or less. 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 the range of 1 / 3 to 5.00 in mass ratio, or in the range of 0.71 to 3.00 in mass ratio. The low melting point resin / non-low melting point resin content ratio may be less than 4.00 in mass ratio, or in the range of 1 / 3 to 3.00 in mass ratio. The 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 the range of 0.01 to 100 in mass ratio, or in the range of 0.05 to 50 in mass ratio. The content of the thermosetting resin in the synthetic resin may be, for example, 0% by mass or more, or may be in the range of 1% by mass to 10% by mass, and 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 to 90% by mass.

[0021] 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. The plastic waste used in each production unit may have, for example, a standard deviation of the content of low-melting-point resin of 1% by mass or more, in the range of 1% by mass to 23% by mass or less, or in the range of 2% by mass to 12% by mass or less.

[0022] The crusher 11 is a device that crushes plastic waste to obtain plastic fragments. For example, a uniaxial crusher can be used as the crusher 11. The size of the plastic fragments 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.

[0023] 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.

[0024] The non-magnetic metal separator 13 is a device for removing and recovering 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.

[0025] 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 grinding function can be used as the washer 14. The wet grinding washer may be one that grinds the plastic pieces in water. For the grinding function of the plastic pieces, a grinder that has a fixed blade and a rotary blade and grinds the plastic pieces by sandwiching them between the fixed blade and the rotary blade can be used. By using the wet grinding washer to grind the plastic pieces into coarse plastic particles and wash them at the same time, it is possible to more efficiently remove deposits that are attached to the coarse plastic particles.

[0026] The compressing machine 15 is a device that compresses the coarse plastic particles to remove moisture adhering to the coarse plastic particles and reduce the volume thereof, thereby obtaining coarse plastic powder. A screw-type compressing machine equipped with a screw inside a barrel having 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, the barrel, and the coarse plastic particles, and a portion of the low-melting-point resin of the coarse plastic particles melts, causing the coarse plastic particles to fuse together, thereby reducing the volume of the coarse plastic particles.

[0027] The pulverizer 16 is a device that pulverizes the coarse plastic powder to produce a fine resin composition powder. The pulverizer 16 may be a fine pulverizer (cutter mill), a hammer mill, or a pin mill. The fine pulverizer (cutter mill) is equipped with 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.

[0028] A sieve may be disposed 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. As the sieve, for example, a sieve with a mesh size in the range of 1 to 3 mm can be used. The sieve mesh size may be 3 mm, 2 mm, or 1 mm. If the sieve mesh size is, 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, which may easily cause the sieve to become clogged.

[0029] 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.

[0030] The resin composition powder supply unit 10 can produce resin composition powder from plastic waste by a method including, for example, a crushing process, a magnetic substance removal process, a non-magnetic metal removal process, a water washing process, a volume reduction process, and a pulverization process.

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

[0032] The magnetic substance removal process is a process for removing and recovering magnetic substances contained in plastic fragments. The magnetic substance removal process is performed using a magnetic separator 12. By performing the magnetic substance removal process, magnetic substances mixed in plastic fragments can be reliably removed. By removing the magnetic substances, it is possible to prevent the negative effect of magnetic substances remaining inside the crusher during the crushing process, which causes wear and damage to the blades inside the crusher and gradually reduces the crushing efficiency of the crusher. In particular, by performing the magnetic substance removal process after the plastic waste is converted into plastic fragments in the crushing process, 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 is a process for removing and recovering non-magnetic metals contained in plastic pieces. The non-magnetic metal removal process is performed using a non-magnetic metal separator 13.

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

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

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

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

[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 grinder 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 an opening of 20 to 50 mm. The opening 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), a hammer mill, or a pin mill can be used as the crusher 23. One type of crusher 23 may be used alone, or two or more types may be used in combination.

[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 sieve mesh size 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. 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 the resin composition molded product 10 using an optical microscope and measuring the particle diameter of the wood flour.

[0045] The storage tank 24 is a tank that temporarily stores the wood powder generated by the crusher 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 to be 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 is a powder made of a resin having a melting point equal to or higher than the melting point of the low-melting-point resin contained in plastic waste. The low-melting-point resin powder contains 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 singly or in combination of two or more. When multiple low-melting-point resins are contained, the melting point of the low-melting-point resin refers to the lowest melting point of the multiple low-melting-point resins. 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 pulverizing plastic waste containing 60% by mass or more of 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. The low-melting-point resin powder can be, for example, waste materials such as shrink film (PE), cable ties (PP), and polystyrene foam (PS) that have been used for packaging, bundling, and curing products, crushed to 3 mm or less. Also usable is recycled plastics (PP, PE, PS) collected and produced in accordance with the Containers and Packaging Recycling Law, 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 42.

[0050] The non-low melting point resin powder is a powder made of a resin having a melting point equal to or higher than the melting point of the low melting point resin contained in plastic waste. The non-low melting point resin powder includes a non-low melting point resin. Examples of non-low melting point resins include PET, PA6, PBT, PPS, PEEK, PI, PU, ​​and PF. The non-low melting point resins may be used singly or in combination of two or more. When multiple types of non-low melting point resins are contained, the melting point of the non-low melting point resin refers to the lowest melting point of the multiple types of non-low melting point resins. 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 pulverizing plastic waste containing 60% by mass or more of a non-low melting point resin. The non-low melting point resin powder may pass through a sieve with a mesh size of 3 mm. As the non-low melting point resin powder, for example, recycled raw materials such as PET waste materials used as egg containers or food packaging materials, crushed to 3 mm or less, can be used.

[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 supply unit 50 stores additives to be added to the resin composition molded article as desired. The additive supply unit 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 the 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 the wood flour and the resin component, 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 for temporarily storing the additive. The metering tank 52 is a tank for measuring the additive sent from the storage tank 51 and temporarily storing a predetermined amount of the additive. The storage tank 51 and the metering tank 52 may be provided one for each type of additive, or one for an additive mixture containing two or more types of additives.

[0055] The molded body production section 60 produces a resin composition molded body. The molded body production section 60 includes 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, for example, 150°C or higher when PE is included. 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 method for producing a resin composition molded product using the resin composition molded product production system 100 will be described. Fig. 2 is a flow diagram of the method for producing a resin composition molded product according to one embodiment of the present disclosure. The method for producing a resin composition molded product according to this embodiment includes an analysis step S1, a mixing step S2, and a molding step S3.

[0060] The analysis step S1 is a step of analyzing the composition of the resin composition powder. The ratio of the content of the low-melting point resin to the content of the 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.

[0062] The resin composition powder is immersed in a heavy liquid as a sample powder. The amount of floating material rising to the surface of the heavy liquid and the amount of sediment that settles are then measured. The floating material is scooped out of the heavy liquid. The sediment is recovered by filtering the heavy liquid after all of the floating material has been scooped out. The recovered floating material and sediment are washed with water, dried, and the amounts of floating material and sediment are measured. The amount of floating material 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 heavy liquid can be, for example, 1.08 to 1.13. The heavy liquid may be, for example, an organic solvent such as ethylene glycol or an aqueous solution of an inorganic salt such as a sodium chloride solution. To prevent floating due to buoyancy of the sample powder, the particle size of the sample powder may be 3 mm or less. Furthermore, if air bubbles are present in the sample powder, resin powder that would otherwise settle in the heavy liquid may float to the surface. By stirring under appropriate conditions or adding a surfactant to the heavy liquid, it is possible to prevent air bubbles from adhering, thereby improving analytical accuracy.

[0063] The mixing step S2 is a step of obtaining a raw material mixture by mixing the resin composition powder, at least one of a low-melting-point resin-containing powder and a non-low-melting-point resin-containing powder, wood flour, and additives. The mixing step S2 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.

[0064] In the mixing step S2, the mixing ratio of the resin composition powder and the 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 S1. 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 S2 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.

[0065] The molding step S3 is a step in which the raw material mixture obtained in the mixing step S2 is molded to obtain a wood resin composition molded body. The molding step S3 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.

[0066] FIG. 3 illustrates a model of a fountain flow in a mold 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. 3 , a molten material powder mixture 300 flowing within a mold 200 forms a fountain flow 301, flows from a flow front 302 to the inner surface of the mold 200, and solidifies to form a skin layer 310. The flow velocity of the molten material 300 within the mold 200 differs between the center of the mold 200 and the vicinity of the inner surface. The difference in flow velocity of the molten material 300 within the mold 200 varies depending on conditions such as the viscosity of the molten material 300 and the lubricity of the mold 200 and the molten material 300. A large difference in flow velocity of the molten material 300 makes it difficult to uniformly discharge the molten material 300 from the mold 200, resulting in defects in the shape of the resulting molded article. This can particularly occur in the case of profile extrusion (with complex cross-sectional shapes and varying wall thicknesses) for sashes and the like, leading to warpage and poor cross-sectional dimensional accuracy.

[0067] The viscosity of the molten material 300 varies significantly depending on the component ratio of the low-melting-point resin and the non-low-melting-point resin. In this embodiment, the content ratio of the low-melting-point resin and the non-low-melting-point resin in the resin composition powder is determined in the analysis step S1, and the content of the low-melting-point resin and the non-low-melting-point resin is adjusted to an appropriate component ratio in the mixing step S2, so that the viscosity of the molten material 300 can be maintained stably. This improves moldability during extrusion. This makes it possible to apply plastic waste to shapes that are difficult to mold, such as sashes, and further expands the scope of effective use of plastic waste.

[0068] In the molding step S3, 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.

[0069] 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 an opening of 1 mm.

[0070] The resin composition formed body obtained as described above contains wood flour and has a texture similar to that of wood, and can therefore 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.

[0071] In the method for producing a resin composition molded body of this embodiment, a resin composition powder derived from plastic waste is mixed with at least one of a low-melting-point resin-containing powder and a non-low-melting-point resin-containing powder, and the resulting mixture is molded to obtain a resin composition molded body. Therefore, even if the blending ratio of the low-melting-point resin to the non-low-melting-point resin contained in the plastic waste is different, it is possible to stably produce a resin composition molded body using the plastic waste as a raw material without separating the low-melting-point resin from the non-low-melting-point resin. Therefore, this embodiment provides a method for producing a resin composition molded body that can effectively utilize plastic waste whose blending ratio of resins (low-melting-point resin and non-low-melting-point resin) is unknown.

[0072] In the method for producing a resin composition molded body of this embodiment, the content of the low-melting point resin and non-low-melting point resin in the resin composition powder is measured in the analysis step S1, and the amount of the low-melting point resin-containing powder and non-low-melting point resin-containing powder to be added to the resin composition powder is adjusted based on the measured content values ​​obtained, thereby making it possible to produce a resin composition molded body more stably.

[0073] In the method for producing a resin composition molded product according to this embodiment, the content of the low-melting point resin and the non-low-melting point resin in the resin composition powder can be measured in the analysis step S1 by immersing the sample powder (resin composition powder) in a heavy liquid, measuring the amount of material that rises to the surface of the heavy liquid and the amount of material that sinks, and using the amount of material that rises to the surface as the content of the low-melting point resin and the amount of material that sinks as the content of the non-low-melting point resin. This method allows the content of the low-melting point resin and the non-low-melting point resin to be measured quickly and accurately. Furthermore, by setting the specific gravity of the heavy liquid to 1.08 to 1.13, the content of the low-melting point resin and the non-low-melting point resin can be measured more accurately.

[0074] In the method for producing a resin composition molded body of this embodiment, by adjusting the amounts of low-melting point resin-containing powder and non-low-melting point resin-containing powder added to the resin composition powder derived from plastic waste in the mixing step S2 so that the ratio of the content of low-melting point resin to the content of non-low-melting point resin contained in the resin composition powder mixture is within a range of 1 / 3 to 5 in mass ratio, it is possible to obtain a resin composition molded body that is less likely to break during molding and has excellent water resistance.

[0075] In the method for producing a resin composition molded article of this embodiment, when the resin composition powder derived from plastic waste is passed through a sieve with a mesh size of 3 mm, 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 production of the resin composition molded article, thereby further improving the water resistance of the obtained resin composition molded article.

[0076] 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, so that when the resin composition powder contains a small amount of low-melting point resin, it is easy to adjust the amount of the low-melting point resin-containing powder added. 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, so that when the resin composition powder contains a small amount of non-low-melting point resin, it is easy to adjust the amount of the non-low-melting point resin-containing powder added.

[0077] 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.

[0078] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited thereto. In this embodiment, the content of the low-melting point resin and the non-low-melting point resin in the resin composition powder derived from plastic waste is measured in the analysis step S1, but the analysis step S1 is not an essential configuration. For example, if the content of the low-melting point resin and the non-low-melting point resin in the plastic waste is known, the analysis step S1 may be omitted. Furthermore, if the analysis result in the analysis step S1 indicates that it is unnecessary to add the low-melting point resin powder and the non-low-melting point resin powder to the resin composition powder, the mixing step may be omitted. Furthermore, in this embodiment, the content of the low-melting point resin and the non-low-melting point resin in the resin composition powder is measured in the analysis step S1. However, the content of the non-low-melting point resin may be determined by measuring only the low-melting point resin and subtracting the content of the low-melting point resin from the resin composition powder, or the content of the non-low-melting point resin may be determined by measuring only the non-low-melting point resin and subtracting the content of the non-low-melting point resin from the resin composition powder. Furthermore, in this embodiment, in the analysis step S1, the contents of the low-melting point resin and the non-low-melting point resin in the resin composition powder are measured using the difference in specific gravity, but the measurement method is not limited to this. For example, DSC (differential scanning calorimetry), GC-MS (gas chromatography-mass spectrometry), infrared absorption spectroscopy, and elemental analysis (CHN coder) may also 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.

[0079] In this embodiment, the resin composition powder stored in the storage tank 17 of the resin composition powder supply unit 10 is used as the sample powder in the analysis step S1, but the sample powder is not limited to this. For example, the sample powder may be coarse plastic powder pulverized by the washer 14, or plastic pieces before being coarsely pulverized. Furthermore, when the coarse plastic powder or plastic pieces are used as the sample powder, the coarse plastic powder or plastic pieces may be mixed with wood powder and then finely pulverized.

[0080] In this embodiment, the molding step S3 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.

[0081] In addition, in this embodiment, a woody resin composition formed body containing wood flour has been described as an example of a resin composition formed body, but it need not contain wood flour and may contain a resin composition powder derived from plastic waste. In addition, 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.

[0082] The present disclosure will be described in more detail below based on examples. The present disclosure is not limited to these examples. The following materials were used in these examples.

[0083] Resin composition powders A to D: Resin composition powders obtained using waste plastic residues derived from municipal waste. The compositions of the resin composition powders are shown in Table 1 below. The production method of the resin composition powders and the method for analyzing the composition are as follows.

[0084] (Method for producing resin composition powder) Four types of bale-shaped waste plastic residues derived from general waste were prepared as plastic waste. The content of non-low melting point resins contained in the four types of waste plastics prepared was measured, and the standard deviation was calculated to be 22.2 mass%. The bale-shaped waste plastic residues were prepared by separating and recovering low melting point resins (polyethylene, polypropylene, polystyrene) from plastic waste collected as recyclable waste in accordance with the Containers and Packaging Recycling Law, and compressing the waste plastic residue after the low melting point resins were separated and recovered into a bale. The waste plastic residues contained PP, PE, PS, PA6, and PET.

[0085] First, bale-shaped waste plastic residue was placed in a crusher and crushed. The resulting crushed material was then passed through a high-magnetic pulley-type magnetic separator with a magnetic force of 20,000 gauss on the belt surface to remove iron-containing materials. The crushed material from which the iron-containing materials had been removed was then crushed in a single-axis coarse crusher until it passed through a 50 mm mesh sieve, yielding plastic fragments. The magnetic materials contained in the resulting plastic fragments were removed and recovered using a hanging magnetic separator and a pulley-type magnetic separator. Next, non-magnetic metals contained in the plastic fragments were removed and recovered using a non-magnetic metal separator. Next, the plastic fragments were crushed and washed using a wet crusher / washer until they passed through a 12 mm mesh sieve, yielding coarse plastic particles. The coarse plastic particles obtained from the wet crusher / washer were then compressed and dehydrated using a volume-reducing press / dehydrator to reduce their volume, yielding coarse plastic powder with a moisture content of 0.5% by mass. Finally, the plastic coarse powder was pulverized using a cutter mill type pulverizer until it passed through a sieve with 1 mm openings, thereby obtaining resin composition powders A to D.

[0086] (Method for analyzing the composition of resin composition powder) 500 mL of clean water and 100 g of sodium chloride were stirred and mixed until the sodium chloride was dissolved, to obtain a sodium chloride aqueous solution. A commercially available liquid detergent (product name: NANOX Detergent for Odor, manufactured by Lion Corporation) was diluted 100 times to obtain a surfactant aqueous solution. 4.4 mL of the surfactant aqueous solution was added to the sodium chloride aqueous solution, and the mixture was stirred and mixed to prepare a sodium chloride aqueous solution (heavy liquid) for composition analysis.

[0087] A sodium chloride aqueous solution for composition analysis was stirred using a magnetic stirrer at a strength sufficient to create a vortex, and 60 g of the resin composition powder was added to the vortex. After stirring for 5 minutes, the magnetic stirrer was turned off and the solution was allowed to stand for 10 minutes. The entire amount of the floating material that had risen to the surface of the sodium chloride aqueous solution after standing was scooped out. After scooping out the entire amount of the floating material, the sodium chloride aqueous solution was filtered using filter paper to recover the sediment that had settled or floated in the sodium chloride aqueous solution. The recovered floating material and sediment were thoroughly washed with tap water and then dried overnight at 40°C using a dryer. The weights of the floating material and sediment after drying were measured. The content of the floating material was defined as the content of low-melting-point resins (PP, PE, PS) and the content of the sediment as the content of non-low-melting-point resins (PA6, PET), and the low-melting-point resin content / non-low-melting-point resin content ratio was calculated using the following formula. The results are shown in Table 1 below. Low melting point resin content / non-low melting point resin content ratio=weight of low melting point resin / weight of non-low melting point resin

[0088]

[0089] Low-melting-point resin powder: A powder obtained by mixing three raw materials, namely, low-density polyethylene (Suntech LD M1920, manufactured by Asahi Kasei Corporation), polypropylene (J106G, manufactured by Prime Polymer Co., Ltd.), and polystyrene (GPPS HF77, manufactured by PS Japan Co., Ltd.), at 33.3% by mass each, and pulverizing the mixture until it passed through a sieve with 3 mm openings was used.

[0090] Non-low melting point resin powder: PET powder obtained by pulverizing PET waste until it passes through a sieve with 3 mm openings.

[0091] Wood flour: Wood flour obtained by crushing waste wood until it passes through a sieve with 300 mm openings.

[0092] Additives: A mixture containing 3 parts by mass of pigment, 3 parts by mass of compatibilizer (maleic anhydride-modified polypropylene-based compatibilizer), 1 part by mass of lubricant, and 1 part by mass of weather-resistant material.

[0093] [Example 1] A low melting point resin powder was added to resin composition powder A in a ratio of low melting point resin content / non-low melting point resin content of 1.40, and mixed using a mixer to obtain a resin composition powder mixture.

[0094] 60 parts by mass of the obtained resin composition powder mixture, 30 parts by mass of wood flour, and 10 parts by mass of additives were mixed using a heat mixer at 150° C. The obtained mixture was molded using an extruder equipped with a mold A having a rectangular cross section with a thickness of 30 mm and a width of 300 mm, to obtain a plate-shaped resin composition molded product.

[0095] The moldability and water resistance of the obtained resin composition molded articles were evaluated by the following methods. The results are shown in Table 3 below, along with the composition of the resin composition molded article calculated from the composition of the resin composition powder and the blending amounts of each raw material.

[0096] (Moldability) The appearance of the obtained resin composition molded article was visually observed to judge moldability. A resin composition molded article having two or fewer cracks with a length of 1 mm or more at the end in the width direction was rated as "A", a resin composition molded article having three or more cracks was rated as "B", and a resin composition molded article having a large end defect was rated as "C".

[0097] (Water Resistance) The resin composition molded body was immersed in warm water adjusted to 60°C. Every day, the resin composition molded body was taken out of the warm water, and the thickness of the resin composition molded body was measured. The rate of change in thickness of the resin composition molded body relative to the thickness of the resin composition molded body on the previous day was calculated using the following formula (1). Rate of change in thickness of resin composition molded body (%) = (thickness of resin composition molded body - thickness of resin composition molded body on the previous day) / thickness of resin composition molded body on the previous day × 100 (1)

[0098] When the change rate in thickness of the resin composition molded body became 0.5% or less, it was determined that the expansion rate of the resin composition molded body due to water absorption had reached equilibrium, and the equilibrium expansion rate of the thickness of the resin composition molded body was calculated using the following formula (2). The thickness of the resin composition molded body was determined as the average of the thicknesses at five locations: the center of the plane and the portions near each of the four corners. Equilibrium expansion rate (%) = {(Tf - Ti) / Ti} × 100 (2) In the above formula, Tf (unit: mm) is the thickness of the resin composition molded body when the change rate in thickness became 0.5% or less, and Ti (unit: mm) is the thickness of the resin composition molded body before immersion in warm water. The water resistance was evaluated as "A" when the equilibrium expansion rate was 10% or less, "B" when it was more than 10% and 20% or less, and "C" when it was more than 20%.

[0099] Examples 2 to 8 Resin composition powders were prepared in the same manner as in Example 1, except that the additive resin powders shown in Table 2 below were added to the resin composition powders shown in Table 2 in proportions such that the low-melting-point resin content / non-low-melting-point resin content ratio was the value shown in Table 2. Using the obtained resin composition powder mixture, a plate-shaped resin composition molded product was prepared in the same manner as in Example 1. In Examples 6 to 8, the mold used for the extruder was mold B, which had a rectangular cross-section and was 30 mm thick and 120 mm wide. The moldability and water resistance of the obtained resin composition molded products were evaluated in the same manner as in Example 1. The results are shown in Table 3 below.

[0100] Reference Examples 1 to 5 The resin composition powder shown in Table 3 below was used, and plate-shaped resin composition molded articles were produced in the same manner as in Example 1, except that 60 parts by mass of the resin composition powder, 30 parts by mass of wood flour, and 10 parts by mass of additives were mixed at 150°C using a heat mixer. In Reference Example 5, the mold used for the extruder was mold B, which had a rectangular cross-section and was 30 mm thick and 120 mm wide. The moldability and water resistance of the obtained resin composition molded articles were evaluated in the same manner as in Example 1. The results are shown in Table 3 below.

[0101]

[0102]

[0103] The results in Table 3 show that raw material powder mixtures prepared by adding at least one of a low-melting-point resin-containing powder and a non-low-melting-point resin-containing powder to a resin composition powder derived from plastic waste and mixing them have improved moldability, enabling the stable production of resin composition molded bodies. The resin composition molded bodies obtained in Reference Examples 1 and 2 had reduced water resistance. This was because the low-melting-point resin content was low, and the highly water-absorbent wood flour was not sufficiently coated with the low-melting-point resin, resulting in the wood flour absorbing water. Furthermore, the resin composition molded body obtained in Reference Example 3 had the same composition as the resin composition molded body obtained in Example 7, but the molded body quality was inferior. This was because the mold B used in Example 7 was 120 mm wide, while the mold A used in Reference Example 3 was 300 mm wide, resulting in a large difference in the flow rate of the molten raw material powder mixture within the mold. The resin composition molded bodies obtained in Reference Examples 4 and 5 had reduced moldability. This is because the content of the low-melting-point resin in the raw material powder mixture was high, which reduced the viscosity of the molten raw material powder mixture and increased the fluidity of the molten raw material powder mixture in the mold, resulting in a large difference in flow rate of the molten raw material powder mixture between the two ends that contact the inner surface of the mold and the central part that does not contact the inner surface of the mold. The moldability of the resin composition molded product obtained in Reference Example 4 was lower than that of the resin composition molded product obtained in Reference Example 5. This is because the mold A used in Reference Example 4 had a width of 300 mm, which increased the difference in flow rate of the molten raw material powder mixture in the mold.

[0104] Aspects of the present disclosure are set forth below.

[0105] (Appendix 1) A method for producing a resin composition molded body, comprising: preparing plastic waste containing a low-melting-point resin having a melting point in the range of not less than 80°C but less than 190°C, and a non-low-melting-point resin which is a mixture of one or both of a high-melting-point resin and a thermosetting resin having a melting point of not less than 190°C; pulverizing the plastic waste to obtain a resin composition powder; 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, thereby obtaining a resin composition powder mixture in which the ratio of the content of the low-melting-point resin to the content of the non-low-melting-point resin is adjusted to be within a predetermined range; and molding the resin composition powder mixture to obtain a resin composition molded body.

[0106] (Appendix 2) The method for producing a resin composition molded body described in Appendix 1, comprising measuring the content of at least one of the low melting point resin and the non-low melting point resin in the plastic waste, and adjusting the amount of the low melting point resin-containing powder and the non-low melting point resin-containing powder to be added to the resin composition powder based on the measured content value obtained.

[0107] (Appendix 3) The method for producing a resin composition molded body according to Appendix 2, wherein the method for measuring the content of the low melting point resin and the non-low melting point resin in the plastic waste comprises immersing a sample powder obtained by pulverizing the plastic waste in a heavy liquid, measuring the amount of matter that rises to the surface of the heavy liquid and the amount of matter that sinks, and defining the amount of matter that rises as the content of the low melting point resin and the amount of matter that sinks as the content of the non-low melting point resin.

[0108] (Appendix 4) The method for producing a resin composition molded article according to Appendix 3, wherein the heavy liquid has a specific gravity of 1.08 to 1.13.

[0109] (Appendix 5) The method for producing a resin composition molded article according to appendix 3 or 4, wherein the heavy liquid is an aqueous sodium chloride solution.

[0110] (Appendix 6) The method for producing a resin composition molded product according to any one of Appendices 1 to 5, wherein the amounts of the low-melting point resin-containing powder and the non-low-melting point resin-containing powder added to the resin composition powder are adjusted so that the mass ratio of the content of the non-low-melting point resin to the content of the low-melting point resin contained in the resin composition powder mixture is within a range of 1 / 3 to 5.

[0111] (Appendix 7) The method for producing a resin composition molded article according to any one of Appendices 1 to 6, wherein the resin composition powder is passed through a sieve having an opening of 3 mm.

[0112] (Appendix 8) The method for producing a resin composition molded article according to any one of Appendices 1 to 7, wherein the low-melting-point resin-containing powder contains 60 mass % or more of a low-melting-point resin.

[0113] (Appendix 9) The method for producing a resin composition molded article according to any one of Appendices 1 to 8, wherein the powder containing a non-low melting point resin contains 60 mass % or more of a non-low melting point resin.

[0114] (Appendix 10) The method for producing a resin composition molded body according to any one of Appendices 1 to 9, 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.

[0115] (Appendix 11) The method for producing a resin composition molded product according to any one of Appendices 1 to 10, wherein the production units of the resin composition molded product 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 1 mass% or more.

[0116] (Appendix 12) The method for producing a resin composition molded article according to Appendix 11, wherein the standard deviation of the content of the low-melting point resin is 2% by mass or more.

[0117] (Appendix 13) The method for producing a resin composition molded article according to any one of Appendices 1 to 12, wherein the resin composition molded article is molded by extrusion molding the resin composition powder.

[0118] (Appendix 14) The method for producing a resin composition molded product according to Appendix 13, wherein the molding temperature of the extrusion molding is lower than the melting point of the non-low melting point resin contained in the resin composition powder by −10° C.

[0119] (Appendix 15) A method for producing a resin composition molded body, comprising: preparing plastic waste containing a low-melting-point resin having a melting point in the range of 80°C or more but less than 190°C; and a non-low-melting-point resin which is a high-melting-point resin or a thermosetting resin having a melting point of 190°C or more; pulverizing the plastic waste to obtain a resin composition powder; measuring the content of at least one of the low-melting-point resin and the non-low-melting-point resin in the plastic waste; and molding the resin composition powder to obtain a resin composition molded body.

[0120] (Appendix 16) A method for producing a resin composition molded body according to Appendix 15, comprising adding at least one of a powder containing a low melting point resin and a powder containing a non-low melting point resin to the resin composition powder based on a measured value of the content of at least one of the low melting point resin and the non-low melting point resin in the plastic waste, and adjusting the ratio of the content of the low melting point resin to the content of the non-low melting point resin to be within a predetermined range, thereby obtaining a resin composition molded body, or by molding the resin composition powder as it is to obtain a resin composition molded body.

[0121] 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, 200...Mold, 300...Melt, 301...Fountain flow, 302...Flow front, 310...Skin layer

Claims

1. A method for producing a resin composition molded body, comprising the steps of: 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 which is a mixture of one or both of a high-melting point resin and a thermosetting resin having a melting point of 190°C or higher; pulverizing the plastic waste to obtain a resin composition powder; adding at least one of a low-melting point resin-containing powder and a non-low-melting point resin-containing powder which have been previously prepared to the resin composition powder and mixing them to obtain a resin composition powder mixture in which the ratio of the content of the low-melting point resin to the content of the non-low-melting point resin is adjusted to be within a predetermined range; and molding the resin composition powder mixture to obtain a resin composition molded body.

2. A method for producing a resin composition molded body as described in claim 1, comprising measuring the content of at least one of the low melting point resin and the non-low melting point resin in the plastic waste, and adjusting the amount of the low melting point resin-containing powder and the non-low melting point resin-containing powder to be added to the resin composition powder based on the measured content value obtained.

3. A method for producing a resin composition molded body as described in claim 2, wherein the method for measuring the content of the low melting point resin and the non-low melting point resin in the plastic waste comprises immersing a sample powder obtained by pulverizing the plastic waste in a heavy liquid, measuring the amount of the floating matter rising to the surface of the heavy liquid and the amount of the sediment that sinks, and defining the amount of the floating matter as the content of the low melting point resin and the amount of the sediment as the content of the non-low melting point resin.

4. The method for producing a resin composition molded article according to claim 3, wherein the specific gravity of the heavy liquid is 1.08 to 1.

13.

5. The method for producing a resin composition molded article according to claim 3 or 4, wherein the heavy liquid is an aqueous sodium chloride solution.

6. A method for producing a resin composition molded body described in any one of claims 1 to 5, wherein the amounts of the low melting point resin-containing powder and the non-low melting point resin-containing powder added to the resin composition powder are adjusted so that the mass ratio of the content of the non-low melting point resin to the content of the low melting point resin contained in the resin composition powder mixture is within the range of 1 / 3 to 5.

7. A method for producing a resin composition molded product according to any one of claims 1 to 6, wherein the resin composition powder is passed through a sieve having an opening size of 3 mm.

8. A method for producing a resin composition molded body according to any one of claims 1 to 7, wherein the low-melting point resin-containing powder contains 60 mass% or more of a low-melting point resin.

9. A method for producing a resin composition molded article according to any one of claims 1 to 8, wherein the powder containing a non-low melting point resin contains 60 mass% or more of a non-low melting point resin.

10. A method for producing a resin composition molded body described in any one of claims 1 to 9, comprising adding a previously prepared cellulose-based material powder to and mixing the resin composition powder to obtain a cellulose-based material-containing resin composition powder mixture, and molding the cellulose-based material-containing resin composition powder mixture.

11. A method for producing a resin composition molded body described in any one of claims 1 to 10, 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 1 mass% or more.

12. A method for producing a resin composition molded article according to any one of claims 1 to 11, wherein the resin composition molded article is molded by extrusion molding the resin composition powder.

13. The method for producing a resin composition molded product according to claim 12, wherein the molding temperature of the extrusion molding is lower than the melting point of the non-low melting point resin contained in the resin composition powder by -10°C.

14. A method for producing a resin composition molded body, comprising: preparing plastic waste containing a low-melting point resin having a melting point in the range of 80°C or more but less than 190°C, and a non-low-melting point resin which is a high-melting point resin having a melting point of 190°C or more or a thermosetting resin; pulverizing the plastic waste to obtain a resin composition powder; measuring the content of at least one of the low-melting point resin and the non-low-melting point resin in the plastic waste; and molding the resin composition powder to obtain a resin composition molded body.

15. A method for producing a resin composition molded body as described in claim 1413, comprising adding at least one of a low melting point resin-containing powder and a non-low melting point resin-containing powder prepared in advance to the resin composition powder based on a measured value of the content of at least one of the low melting point resin and the non-low melting point resin in the plastic waste, and adjusting the ratio of the content of the low melting point resin to the content of the non-low melting point resin to be within a predetermined range to obtain a resin composition molded body, or molding the resin composition powder as it is to obtain a resin composition molded body.

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