Method for treating composite

Abstract

A hydrolyzable resin and a filler are each efficiently recovered from a composite containing hydrolyzable resin and filler.　The present invention is a method for treating a composite that contains a hydrolyzable resin (a1) and a filler, the method comprising: a contact step (1) for bringing the composite into contact with a subcritical fluid to obtain a contact liquid; a treatment step (2) for maintaining the state of contact between the composite and subcritical fluid in the contact liquid for a certain period of time to obtain a treatment liquid containing a hydrolyzable resin (a2) in which a portion or all of the hydrolyzable resin (a1) has undergone decomposition and / or separation; a separation step (3) for separating the hydrolyzable resin (a2) and the filler from the treatment liquid; and a recovery step (4) for individually recovering the separated hydrolyzable resin (a2) and filler.

Description

Composite processing method

[0001] The present invention relates to a composite treatment method for composites containing resin and fillers.

[0002] In recent years, with growing concern for environmental issues and the efficient use of resources, there has been a demand for the reuse of plastic products. Among plastic products, the reuse of products containing only plastic (for example, PET bottles) is becoming increasingly practical.

[0003] Some resin products contain fillers for various purposes, such as improving strength, durability, and weather resistance, imparting special functions like conductivity, flame retardancy, and sliding properties, and reducing costs. Resin products containing resin and fillers (hereinafter sometimes referred to as composites) cannot be reused unless the resin and fillers are separated, but efficient separation of resin and fillers is technically difficult, so reuse has not progressed much. Furthermore, some composites are difficult to burn, making incineration difficult and leaving landfill as the only option. Given this situation, there is a need for technology to reuse composites.

[0004] Patent Document 1 describes a method for recovering reinforcing fibers from fiber-reinforced plastic by a first heat treatment step of heat-treating the fiber-reinforced plastic in a superheated steam atmosphere, a second heat treatment step of heat-treating the fiber-reinforced plastic heat-treated in the first heat treatment step in a non-superheated steam atmosphere, and an ultrasonic step of applying ultrasonic waves to the fiber-reinforced plastic heat-treated during the second heat treatment step.

[0005] Patent Document 2 describes an apparatus for recycling a hydrolyzable resin composition containing a hydrolyzable resin (e.g., polyamide, PET, etc.) and additives (e.g., inorganic fibers such as glass fibers and carbon fibers). The apparatus comprises an extruder for hydrolyzing the hydrolyzable resin contained in the hydrolyzable resin composition to obtain a depolymer, and a vaporizer for thermally decomposing the depolymer to vaporize monomers. The extruder has a first inlet for introducing the hydrolyzable resin composition, a second inlet for introducing water, and a screw for mixing the hydrolyzable resin composition with water.

[0006] Patent Document 3 describes a method for producing recycled monomers by contacting a composition containing a polymer (such as polyamide or PET) with subcritical water. In this method, the conditions are set such that X and the product X, Y, and Z (X, Y, Z) satisfy a predetermined range, where Mp°C is the melting point of the polymer measured by a differential scanning calorimeter, X°C is the reaction temperature, Y minutes is the reaction time, and Z is the mass ratio of water to polymer (Z:1). Patent Document 3 also states that the composition may contain fibrous fillers such as glass fibers.

[0007] Patent Document 4 describes a composite film made by laminating aluminum foil and resin (for example, polyethylene, polyamide, PET, etc.) being treated under subcritical and / or supercritical conditions in the presence of water, separated, and the aluminum foil being recovered in a metallic state.

[0008] Patent Document 5 describes a method of contacting and reacting fiber-reinforced plastic with supercritical or subcritical water in a reactor to separate and recover the fibers for reuse. Thermoplastic and thermosetting plastics are described as examples of plastics. Patent Document 5 describes a method of decomposing organic polymer components such as thermoplastics or thermosetting plastics in fiber-reinforced plastic waste to a low molecular weight level.

[0009] Japanese Patent Publication No. 2024-022821, Japanese Patent Publication No. 2023-137802, Japanese Patent Publication No. 2024-003803, Japanese Patent Publication No. 2010-227740, Japanese Patent Publication No. Hei 10-087872

[0010] The method described in Patent Document 1 requires numerous steps, including heat treatment with superheated steam, heat treatment with non-superheated steam, and ultrasonic treatment. Furthermore, the method described in Patent Document 1 does not place much emphasis on resin recovery, and it is assumed that some of the resin will be thermally decomposed. The recycling apparatus described in Patent Document 2 decomposes the resin contained in the resin composition into monomers by hydrolysis and thermal decomposition, and does not consider material recycling in the resin state. The method for producing recycled monomers described in Patent Document 3 decomposes the resin into monomers and then chemically recycles it, and does not consider material recycling in the resin state. The method described in Patent Document 4 recovers only aluminum foil, and does not consider resin recycling. The method described in Patent Document 5 recovers fibers and low molecular weight (liquid oligomer) derived from plastic, and does not consider material recycling in the resin state.

[0011] The present invention aims to efficiently recover a hydrolyzable resin and a filler from a composite containing a hydrolyzable resin and a filler.

[0012] [1] A method for processing a composite containing a hydrolyzable resin (a1) and a filler, comprising: a contact step (1) of bringing the composite into contact with a subcritical fluid to obtain a contact liquid; a processing step (2) of maintaining the state in which the composite and the subcritical fluid are in contact in the contact liquid for a certain period of time to obtain a processing liquid containing a hydrolyzable resin (a2) from which part or all of the hydrolyzable resin (a1) has been decomposed and / or separated; a separation step (3) of separating the hydrolyzable resin (a2) and the filler from the processing liquid; and a recovery step (4) of individually recovering the separated hydrolyzable resin (a2) and the filler. [2] The composite processing method of [1], wherein the separation step (3) is a step of separating the hydrolyzable resin (a2) and the filler through a filter. [3] The composite processing method of [1] or [2], wherein no stirring operation is performed in the processing step (2). [4] A composite processing method from any one of [1] to [3], wherein the contact step (1), the processing step (2), and the separation step (3) are performed within a single system. [5] A composite processing method from any one of [1] to [4], wherein the processing liquid contains the hydrolyzable resin (a2) dissolved in the subcritical fluid. [6] A composite processing method from any one of [1] to [5], wherein, when the number average molecular weight of the hydrolyzable resin (a1) is Mn1 and the number average molecular weight of the hydrolyzable resin (a2) is Mn2, the Mn retention rate (100 × Mn2 / Mn1), which is the percentage of Mn2 to Mn1, is 15% or more, and Mn2 is 2300 or more. [7] A composite processing method from any one of [1] to [6], wherein in the processing step (2), the holding time for the composite and the subcritical fluid to be in contact is 1 to 60 minutes. [8] A composite treatment method from any one of [1] to [7], wherein the subcritical fluid is subcritical water. [9] A composite treatment method from any one of [1] to [8], wherein the hydrolyzable resin (a1) and the hydrolyzable resin (a2) are polyamide resin or polyester resin.

[10] A composite treatment method from any one of [1] to [9], wherein the filler is glass fiber, carbon fiber and / or carbon black particles.

[11] A composite treatment method from any one of [1] to

[10] , wherein the composite is waste plastic.

[12] A material recycled product containing the hydrolyzable resin (a2) recovered by any composite processing method of [1] to

[11] as a raw material.

[13] A material recycled product containing the filler recovered by any composite processing method of [1] to

[11] as a raw material.

[14] A method for manufacturing a material recycled product, in which material recycling is performed using the hydrolyzable resin (a2) recovered by any composite processing method of [1] to

[11] as a raw material.

[15] A method for manufacturing a material recycled product, in which material recycling is performed using the filler recovered by any composite processing method of [1] to

[11] as a raw material.

[0013] According to the present invention, it is possible to efficiently recover the hydrolyzable resin and the filler from a composite containing the hydrolyzable resin and the filler, respectively.

[0014] This is an example of an apparatus for performing the composite processing method of the present invention. This is an example of a preferred embodiment of a reactor used in the composite processing method of the present invention.

[0015] The present invention relates to a method for processing a composite containing a hydrolyzable resin (a1) and a filler, comprising: a contact step (1) of bringing the composite into contact with a subcritical fluid to obtain a contact liquid; a processing step (2) of maintaining the state in which the composite and the subcritical fluid are in contact in the contact liquid for a certain period of time to obtain a processing liquid containing a hydrolyzable resin (a2) from which part or all of the hydrolyzable resin (a1) has been decomposed and / or separated; a separation step (3) of separating the hydrolyzable resin (a2) and the filler from the processing liquid; and a recovery step (4) of individually recovering the separated hydrolyzable resin (a2) and the filler.

[0016] In this invention, "resin" refers to a material with a number-average molecular weight of 1,000 or more, and is a distinctly different concept from monomers and oligomers with a number-average molecular weight of less than 1,000.

[0017] First, the composite material and its components to be treated by the above composite material treatment method will be described. A composite material is a member that includes at least a portion of a region (A) in which a hydrolyzable resin (a1) and a filler are bonded together directly or via other components (e.g., adhesive, dispersant, etc.) to form a single unit, or in which the filler is dispersed with the hydrolyzable resin (a1) as a matrix. Preferably, the composite material consists only of region (A), but it may further include other regions (B) that do not contain at least one of the hydrolyzable resin (a1) and the filler. For example, the composite material may be a laminate comprising one or more layered regions (A) and one or more other layered regions (B).

[0018] The composite is preferably composed mainly of a hydrolyzable resin (a1) or a filler. "Main component" refers to the component that is present in the greatest quantity by mass in the composite. More preferably, one of the hydrolyzable resin (a1) or the filler is the main component, and the other is the second most abundant component.

[0019] The total content of hydrolyzable resin (a1) and filler relative to 100% by mass of all components constituting the composite is preferably 70% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more. The above total content may also be 100% by mass (i.e., the composite consists of hydrolyzable resin (a1) and filler). "Consists of" means that it does not contain anything other than trace amounts of impurities, and preferably means "consists only of".

[0020] The hydrolyzable resin (a1) content is preferably 30 to 99% by mass, more preferably 50 to 90% by mass, and even more preferably 65 to 80% by mass, relative to 100% by mass of all components constituting the composite. The filler content is preferably 1 to 70% by mass, more preferably 10 to 50% by mass, and even more preferably 20 to 35% by mass, relative to 100% by mass of all components constituting the composite. Hydrolyzable resin (a2) and filler tend to be easily recovered efficiently from such composites.

[0021] Hydrolyzable resins are resins in which at least a portion of the bonds in the resin are hydrolyzed. For example, resins having ester bonds, amide bonds, imide bonds, ether bonds, urethane bonds, carbonate bonds, acetal bonds, hemiacetal bonds, ketal bonds, hemiketal bonds, or bonds in which some or all of the oxygen atoms contained in these bonds are replaced with sulfur atoms are preferred. Generally, it is preferable that the resin has bonds in which at least a portion of the main chain in the resin is hydrolyzed, and hydrolyzable thermoplastic resins are preferred. Specifically, examples include polyamide resins, polyester resins, polyurethane resins, polycarbonate resins, polyacetal resins, polyether resins, phenolic resins, etc. These may be one type or two or more types. Among these, polyamide resins or polyester resins are preferred, and polyamide resins are more preferred.

[0022] Examples of polyamide resins include aliphatic homopolyamide resins, aliphatic copolymer polyamide resins, semi-aromatic homopolyamide resins, semi-aromatic copolymer polyamide resins, aromatic homopolyamide resins, and aromatic copolymer polyamide resins. Examples of monomers used as raw materials for polyamide resins include lactam compounds, aminocarboxylic acids, and combinations of diamines and dicarboxylic acids. Here, semi-aromatic polyamide resin refers to a polyamide resin in which a combination of diamines and dicarboxylic acids is used as the constituent unit, with one of the diamines and dicarboxylic acids being aliphatic and the other being aromatic.

[0023] There are no particular limitations on specific examples of polyamide resins, but examples include polyamide 410, polyamide 6, polyamide 56, polyamide 66, polyamide 610, polyamide 612, polyamide 11, polyamide 12, polyamide 56 / 6, polyamide 6 / 66, polyamide 6 / 12, polyamide 6 / 66 / 12, polyamide 9T, polyamide 6T, polyamide 6I, polyamide MXD6, polyamide 66 / 6T, polyamide 6T / 6, polyamide 66 / 6I, polyamide 6I / 6, polyamide 12 / 6T, polyamide 66 / 6T / 6I, polyamide 66 / 6 / 6I, polyamide 6T / 6I, polyamide 6T / M5T, etc.

[0024] Examples of polyester resins include aliphatic homopolyester resins, aliphatic copolymer polyester resins, aromatic polyester resins, and aromatic copolymer polyester resins. Examples of monomers for polyester resins include combinations of glycols and dicarboxylic acids.

[0025] Specific examples of polyester resins include polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polyethylene isophthalate (PEI), PET / PEI copolymer, polybutylene naphthalate (PBN), polyethylene naphthalate (PEN), polylactic acid (PLA), polyglycolic acid (PGA), and polyester elastomers.

[0026] A filler is a substance that, when observed under a microscope in a cross-section of the composite, is found to be immiscible with the surrounding resin and possesses a specific shape (e.g., particulate, flake-like, fibrous, etc.). In the composite, the filler exists dispersed in a hydrolyzable resin (a1) that functions as a base resin or binder, for example. Examples of fillers include fibrous fillers and particulate fillers. Examples of fibrous fillers include inorganic fibrous fillers and organic fibrous fillers. Examples of particulate fillers include inorganic particulate fillers and organic fibrous fillers. The filler may also be an organic-inorganic composite filler, a combination of inorganic and organic materials. These may be one type or two or more types.

[0027] Examples of inorganic fibrous fillers include carbon fibers, glass fibers, carbon nanotubes, ceramic fibers, and metal fibers. Examples of carbon fibers include PAN-based carbon fibers and pitch-based carbon fibers. Examples of glass fibers include E-glass fibers, S-glass fibers, C-glass fibers, ECR-glass fibers, and AR-glass fibers. Examples of ceramic fibers include silica fibers, silica-alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, and potassium titanate fibers. Examples of metal fibers include stainless steel fibers, aluminum fibers, titanium fibers, copper fibers, and brass fibers. Examples of organic fibrous fillers include aramid fibers, fluororesin fibers, acrylic fibers, and cellulose fibers.

[0028] Examples of inorganic particulate fillers include glass beads, talc particles, kaolin particles, wollastonite particles, silica particles, alumina (aluminum oxide) particles, zirconia particles, diatomaceous earth, clay particles, gypsum particles, red iron oxide particles, graphite particles, carbon black particles, calcium carbonate particles, titanium dioxide particles, zinc oxide particles, copper particles, stainless steel particles, aluminum hydroxide particles, dolomite particles, mica powder, silicon carbide particles, glass powder, carbon particles, barium sulfate particles, boron nitride particles, and silicon nitride particles. Examples of organic particulate fillers include wood powder, pulp powder, and resin particles (e.g., fluororesin particles, melamine resin particles, acrylic resin particles, etc.).

[0029] The above composite processing method is applicable to composites containing any type of filler. However, there is a strong need for reuse of relatively expensive or highly versatile fillers, for example. In addition, inorganic fibrous fillers or inorganic particulate fillers are less likely to decompose in subcritical fluids and therefore tend to be easier to recover efficiently. Considering these points comprehensively, inorganic fibrous fillers or inorganic particulate fillers are preferred as fillers, glass fibers, carbon fibers, talc, or alumina are more preferred, and glass fibers are even more preferred. Composites containing glass fibers are used in various fields, for example, as fiber-reinforced plastics (FRP), but efficient recycling has been difficult with conventional reuse technologies. In contrast, the above composite processing method enables efficient reuse of composites containing glass fibers.

[0030] In addition, composites containing glass fibers and other fillers (for example, inorganic particulate fillers such as carbon black particles), and composites containing carbon fibers, which have seen increasing use in recent years, are also suitable for treatment using the above composite treatment method. In summary, glass fibers, carbon fibers, and / or carbon black particles are preferred as fillers.

[0031] Furthermore, the composite may include a layered filler. In this case, it is preferable to consider it as a separate concept from a composite having region (A) and an arbitrary region (B). Examples of the layered filler include inorganic layers, which will be described later. As the inorganic layer, a metal layer is preferred, and an aluminum layer is more preferred. A composite comprising a layered filler may, for example, comprise at least one hydrolyzable resin (a1) layer and at least one inorganic layer, or it may have at least one inorganic layer on the surface or inner surface of the hydrolyzable resin (a1), which has a shape other than a layer. In this case, the composite may further comprise other layers other than the hydrolyzable resin (a1) layer and the inorganic layer (for example, other resin layers that do not contain hydrolyzable resin (a1)).

[0032] Inorganic layers include metal layers that provide gas barrier properties, aroma retention, and light reflectivity, and hard coat layers that provide scratch resistance. There are no particular restrictions on the metal layers, but examples include layers of aluminum, silicon, copper-nickel-chromium combinations, gold, palladium, tin, ruthenium, black trivalent chromium, and tin-cobalt alloys. There are no particular restrictions on the hard coat layers, but examples include ceramic layers mainly composed of metal oxides such as alumina, silica, zirconia, and titania.

[0033] An example of a composite treatment method comprising a layered filler can be expressed as follows. The same applies even if the hydrolyzable resin (a1) is in a shape other than a layer. A composite treatment method comprising a layer containing a hydrolyzable resin (a1) and an inorganic layer, comprising: a contact step (1) of bringing the composite into contact with a subcritical fluid to obtain a contact liquid; a treatment step (2) of maintaining the state in which the composite and the subcritical fluid are in contact in the contact liquid for a certain period of time to obtain a treatment liquid containing a hydrolyzable resin (a2) from which part or all of the hydrolyzable resin (a1) has been decomposed and / or separated; a separation step (3) of separating the hydrolyzable resin (a2) and the filler from the treatment liquid; and a recovery step (4) of individually recovering the separated hydrolyzable resin (a2) and the filler.

[0034] The composite may further contain a non-hydrolyzable resin as an optional component. The non-hydrolyzable resin may be included together with the hydrolyzable resin (a1) and the filler in region (A), or it may be included in other regions (B).

[0035] A non-hydrolyzable resin is a resin in which the bonds in the resin are not hydrolyzed or are difficult to hydrolyze. A non-hydrolyzable thermoplastic resin is preferred, and a resin in which some or all of the bonds in the main chain are not hydrolyzed or are difficult to hydrolyze is more preferred. Examples include polyethylene resins such as low-density polyethylene (LDPE) resin, linear low-density polyethylene (LLDPE) resin, and high-density polyethylene (HDPE) resin, polyolefin resins such as polypropylene resin, halogenated polyolefins such as tetrafluoroethylene, ethylene / tetrafluoroethylene copolymer, and polyvinyl chloride, ethylene vinyl acetate copolymer, acrylic resin, polystyrene resin, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, etc. These may be used alone or in combination of two or more.

[0036] The composite may have, for example, as another region (B), a non-hydrolyzable resin layer containing a non-hydrolyzable resin. The composite may also have, as another region (B), an inorganic layer.

[0037] Examples of the inorganic layer include a metal layer that imparts gas barrier properties, fragrance retention properties, light reflection properties, etc., and a hard coat layer that imparts scratch resistance. There is no particular limitation on the metal layer. Examples include layers of aluminum, silicon, a combination of copper-nickel-chromium, gold, palladium, tin, ruthenium, black trivalent chromium, tin cobalt alloy, etc. There is no particular limitation on the hard coat layer. Examples include layers of ceramics mainly composed of metal oxides such as alumina, silica, zirconia, and titania.

[0038] The composite may optionally contain functional additives such as dyes, pigments, plasticizers, antioxidants, heat-resistant agents, foaming agents, weather-resistant agents, crystal nucleating agents, crystallization accelerators, mold release agents, lubricants, antistatic agents, flame retardants, flame retardant aids, colorants, etc. These may be contained together with the hydrolyzable resin (a1) and the filler in region (A), or may be contained in another region (B). These are preferably components that are blended in small amounts as additives. Although not particularly limited, with respect to 100% by mass of all the components constituting the composite, the content ratio thereof is preferably 5% by mass or less, and more preferably 1% by mass or less.

[0039] <Contact step (1)> In the contact step (1), the composite and the subcritical fluid are brought into contact to obtain a contact liquid. In the contact step (1), "contact" means bringing the subcritical fluid into contact with at least a part of the surface of the composite. In the contact step (1), it is preferable to bring the subcritical fluid into contact with 50% or more of the surface area of the composite, and more preferably to bring the subcritical fluid into contact with the entire surface of the composite. In the contact step (1), methods such as supplying the subcritical fluid to a container containing the composite, introducing the composite into a container filled with the subcritical fluid, or previously bringing a fluid that is not in the subcritical state into contact with the composite and then bringing the fluid into the subcritical state can be applied.

[0040] The subcritical fluid is a fluid that exists in a liquid state in a region near the critical point and at a temperature and / or pressure lower than the critical point, and is obtained by pressurizing the fluid in a temperature range above the boiling point. Examples of the type of fluid include water, alcohol, carbon dioxide, nitrogen, etc., and water is preferable from the viewpoint of having a high ionic product. That is, as the subcritical fluid, subcritical water is preferable.

[0041] There are no particular limitations on the method of bringing the composite and the subcritical fluid into contact, but it is usually carried out in a sealed state, and can be done in a batch or continuous manner, but continuous is preferred. Preferably, the composite is placed in a pressure-resistant reaction vessel, heated to adjust the self-pressure or pressure, and the fluid is circulated at a predetermined temperature. Examples of reaction vessels include sealed reaction vessels, such as autoclaves and reaction tubes. There are no particular limitations on the heating method, but examples include methods using heaters and molten salt baths.

[0042] When contacting the subcritical fluid, there are no particular restrictions on the temperature and pressure as long as a subcritical fluid is generated. However, if the subcritical fluid is water, 120 to 374°C and 0.2 to 22 MPa are preferred. If the subcritical fluid is methanol, 85 to 240°C and 0.2 to 8 MPa are preferred. If the subcritical fluid is ethanol, 95 to 240°C and 0.2 to 6 MPa are preferred. When the temperature and pressure of the subcritical fluid are within the above ranges, the recovery rate of the hydrolyzable resin (a2), which is a resin derived from the hydrolyzable resin (a1), can be increased. It is preferable that the hydrolyzable resin (a2) has the property of dissolving in the subcritical fluid.

[0043] <Processing step (2)> In processing step (2), the composite and the subcritical fluid are kept in contact in the contact liquid for a certain period of time to obtain a processing liquid containing hydrolyzable resin (a2) from which part or all of the hydrolyzable resin (a1) has been decomposed and / or separated. In processing step (2), the composite is decomposed and / or separated, and filler released from hydrolyzable resin (a1) and hydrolyzable resin (a2), which is a resin derived from hydrolyzable resin (a1), are produced.

[0044] In processing step (2), it is preferable that the entire composite is decomposed and / or separated, but in some cases, a portion of the composite may remain without decomposing and / or separating, resulting in relatively large composite residue. Since the composite residue is difficult to dissolve or disperse in the processing solution, it is recovered separately. In the above composite processing method, it is desirable that the temperature, pressure, reaction time, etc., be set so as to minimize the generation of composite residue.

[0045] The processing liquid contains at least a hydrolyzable resin (a2) and may further contain a filler. Preferably, the processing liquid contains a hydrolyzable resin (a2) dissolved in a subcritical fluid. In such a processing liquid, the filler is contained in the solid component and the hydrolyzable resin (a2) is contained in the liquid component, so the filler and the hydrolyzable resin (a2) can be easily separated in the separation step (3) described later.

[0046] In addition, the treatment solution may further contain monomers or oligomers produced by the decomposition of the hydrolyzable resin (a1), optional components that may be present in the composite, and other components. The components in the treatment solution may be dissolved in the subcritical fluid or dispersed in the subcritical fluid. The treatment solution may be, for example, a solution, suspension, or slurry.

[0047] In processing step (2), the preferred holding time (reaction time) for the composite and the subcritical fluid to be in contact is 1 to 60 minutes. When the reaction time falls within this range, the recovery rate of hydrolyzable resin (a2), which is derived from hydrolyzable resin (a1), can be increased.

[0048] Contact between the composite and the subcritical fluid can be carried out by adding an acid or base, but from the viewpoint of facilitating the recovery of hydrolyzable resin (a2), which is derived from hydrolyzable resin (a1), it is preferable not to add an acid or base in order to moderate the decomposition reaction rate, and more preferably under neutral conditions, and even more preferably under pH 6 to 8 conditions.

[0049] When the composite is brought into contact with the subcritical fluid, the amount of subcritical fluid used (the amount of subcritical fluid charged into the reaction vessel) is preferably such that the mass ratio of subcritical fluid to the composite (subcritical fluid / composite) is 0.5 to 500, more preferably 1 to 100, and even more preferably 5 to 20. When the mass ratio is within the above range, the composite can be processed smoothly.

[0050] In the processing step (2), at least a portion of the hydrolyzable resin (a1) is hydrolyzed by a subcritical fluid, resulting in a resin in which at least a portion consists of hydrolyzable resin (a2). Hydrolyzable resin (a1) and hydrolyzable resin (a2) are either identical or have different molecular weight distributions. That is, the types of resins are the same. It is preferable that hydrolyzable resin (a1) and hydrolyzable resin (a2) have different molecular weight distributions.

[0051] When the number average molecular weight of hydrolyzable resin (a1) is Mn1 and the number average molecular weight of hydrolyzable resin (a2) is Mn2, it is preferable that the Mn retention rate (100 × Mn2 / Mn1), which is the percentage of Mn2 to Mn1, is 15% or more, and that Mn2 is 2300 or more. The Mn retention rate is more preferably 35% or more, even more preferably 50% or more, particularly preferably 70% or more, and most preferably 90% or more. The Mn2 is more preferably 4000 or more, even more preferably 5000 or more, particularly preferably 10000 or more, and most preferably 13000 or more.

[0052] The fact that Mn2 is the aforementioned value is preferable in terms of material recycling of the hydrolyzable resin (a2). Even after going through the processing step (2), at least a portion of the hydrolyzable resin (a1) remains as resin without being decomposed into monomers or oligomers.

[0053] Since the Mn2 and Mn retention rates are within the aforementioned ranges, the hydrolyzable resin (a1) is recovered as a resin having a certain molecular weight, at least a portion of it. This resin can also be used as a raw material for material recycling.

[0054] The Mn2 and Mn retention rates can be set within the above ranges by performing processing step (2). Preferably, this can be achieved by using the above-mentioned preferred temperature, pressure, and reaction time in processing step (2).

[0055] In processing step (2), at least a portion of the hydrolyzable resin (a1) that was bound to the filler in the composite, or the hydrolyzable resin (a1) as a matrix in which the filler was dispersed, is decomposed and / or separated, and at least a portion of the filler contained in the composite is released. At least a portion (preferably all) of the released filler is recovered in the recovery step (4) described later without being hydrolyzed by the subcritical fluid. Since processing step (2) does not involve heat treatment, mechanical treatment, or chemical treatment with chemicals other than the subcritical fluid on the filler, less damaged filler (preferably undamaged filler) can be recovered in the recovery step (4).

[0056] In processing step (2), stirring may be performed to improve processing efficiency, but it is preferable not to stir in order to avoid damaging the filler material. In particular, if a batch process is used in processing step (2), it is preferable not to stir. Furthermore, if the filler material is a fibrous filler, it is preferable not to stir in processing step (2) in order to suppress the breakage of the fibers.

[0057] Thus, the above composite processing method, by having processing step (2), allows for the recovery of the hydrolyzable resin (a2) as a resin and the recovery of the filler in the recovery step (4) described later, making it useful for material recycling. Compared to chemical recycling, which decomposes the resin into monomers during recovery, material recycling simplifies the process of manufacturing new products and is a highly effective recycling method.

[0058] <Separation Step (3)> In separation step (3), the hydrolyzable resin (a2) and the filler are separated from the processing solution. Methods for separating the hydrolyzable resin (a2) and the filler include, for example, a method that uses the difference in specific gravity or the difference in solubility or dispersibility in the processing solution to precipitate only one component from the processing solution, a method that uses the differences in adsorption capacity, charge, mass, hydrophobicity, etc. of the two to perform chromatography, and a method that uses the difference in size of the two to separate them by passing them through a filter.

[0059] The separation step (3) is preferably a step of separating the hydrolyzable resin (a2) and the filler through a filter. Here, the size of the hydrolyzable resin (a2) and the filler varies depending on the type of filler and the degree of decomposition of the hydrolyzable resin (a2). For example, if the filler is a fibrous filler, the filler can be collected by the filter and the hydrolyzable resin (a2) can be passed through the filter. Also, if the filler is minute, the hydrolyzable resin (a2) can be collected by the filter and the filler can be passed through the filter. Separation by filter is efficient in that the cost and energy required for processing are relatively low.

[0060] There are no particular restrictions on the type of filter; for example, metal, thermoplastic, or thermosetting resin filters can be used.

[0061] The vertical and horizontal mesh sizes of the filter are not particularly limited and are determined by the size of the hydrolyzable resin (a2) and the packing material. However, from the viewpoint of facilitating separation, a mesh size of 1 to 100 μm is preferred for each, and a mesh size of 20 to 70 μm is more preferred. The filter may be a single stage or multiple stages. Using filters with different mesh sizes for each stage in a multiple-stage process allows for more effective separation and is therefore preferable.

[0062] <Recovery Process (4)> In recovery process (4), the hydrolyzable resin (a2) and the filler separated in separation process (3) are recovered separately. In the above composite processing method, by recovering the hydrolyzable resin (a2) and the filler separately at once, it is possible to reuse resources more effectively compared to known processing methods that recover only the resin or known processing methods that recover only the filler.

[0063] In the recovery step (4), for example, the packing material collected by the filter is recovered. The recovered packing material can be used as a raw material for material recycling, which will be described later. In addition, in the recovery step (4), for example, the treatment of the treatment liquid from which the packing material has been removed is performed to evaporate volatile components or to reduce the solubility or dispersibility of the hydrolyzable resin (a2), thereby recovering the hydrolyzable resin (a2). As a method for recovering the hydrolyzable resin (a2), a method that utilizes the property that subcritical fluids have high dissolving power and can dissolve even substances that do not dissolve in a non-subcritical state is preferred. Specifically, a method in which the hydrolyzable resin (a2) is dissolved in the treatment liquid in the treatment step (2), and the treatment liquid is returned to a non-subcritical state in the recovery step (4) to precipitate the hydrolyzable resin (a2) in the treatment liquid is preferred. The recovered hydrolyzable resin (a2) can be used as a raw material for material recycling, which will be described later.

[0064] In the above composite processing method, the recovery rate of the filler (100 × mass of recovered filler / mass of filler contained in the composite) is preferably 50% or more, more preferably 70% or more, and even more preferably 90% or more.

[0065] In the above composite processing method, the recovery rate of the hydrolyzable resin (a2) ((mass of hydrolyzable resin (a2) / mass of hydrolyzable resin (a1)) × 100) is preferably 10% or more, more preferably 30% or more, even more preferably 50% or more, and particularly preferably 80% or more. According to the above composite processing method, the hydrolyzable resin (a2) can be efficiently recovered from the composite.

[0066] <Pre-treatment step> The above composite processing method may include an optional pre-treatment step before the contact step (1). An example of a pre-treatment step is a step of crushing the composite of the molded product. Having a crushing step has the advantage of increasing the contact area with the subcritical fluid. The crushing means is not particularly limited as long as it is a known crushing means, but examples include mills such as joke crushers, gyratory crushers, cone crushers, impact crushers, roll crushers, self-sharpening crushers, stamp mills, millstone crushers, pulverizers, large shredders, ring mills, roll mills, cutter mills, hammer mills, turbo mills, jet mills, pin mills, centrifugal mills, chopper mills, crushers, Rotoplex, Pulverizer, Ultrarotor, etc. Crushing may be done wet. The composite can also be crushed while frozen. Crushing also includes cutting.

[0067] Furthermore, a pretreatment step may be a step of melting the composite of the molded product. By melting the composite at a temperature above the melting point of the resin to be recovered, components that do not melt at that temperature can be separated and removed before the contact step (1). The melting temperature is preferably above the melting point of the hydrolyzable resin (a1) and is such that these resins do not undergo thermal degradation. Examples of melting means include a melting kneader, a kneading extruder, a gear pump, etc.

[0068] <Specific aspects of the composite processing method> Another pre-treatment step is a step of kneading the composite of the molded product. By kneading the composite in the pre-treatment step, the filler can be efficiently pulverized while the hydrolyzable resin (a1) is in a molten state. Examples of kneading means include a melt kneader and a kneading extruder. Furthermore, the kneaded material can be further refined using a pelletizer or the like, if necessary.

[0069] Furthermore, a pretreatment step may include a washing step for washing the composite. Having a washing step is particularly preferable when waste plastic is used as the composite.

[0070] The above-mentioned grinding, melting, and washing steps can be selected from one or more of these steps. When multiple steps are selected from these, it is preferable to perform the melting step immediately before the contact step (1), and it is more preferable to perform them in the order of washing, grinding, and melting.

[0071] <Post-processing steps> The composite processing method may include optional post-processing steps after the recovery step (4). Examples of post-processing steps include drying the recovered hydrolyzable resin (a2) and filler. Alternatively, the method may include purifying the recovered hydrolyzable resin (a2) and filler after the recovery step (4).

[0072] As a specific example of the above-described composite processing method, the continuous composite processing method shown in Figure 1 will be explained. However, this method is merely one example of the above-described composite processing method and is not limited in any way. First, in Figure 1, the pulverized composite material is packed into the reactor 4, which has been removed from the reactor 3. Then, after the air inside is discharged by flowing the degassed fluid into the reactor 4, the flow path is changed by valve operation so that the fluid does not pass through the reactor 4 (pump 1, heating furnace 2, cooling means 5', back pressure valve 6). Heating of the heaters in the reactor 3 and heating furnace 2 is started, and when the fluid reaches a predetermined temperature at which it can become subcritical, the reactor 4 is set inside the reactor 3, and the valve is operated to switch the flow path so that the fluid that has left the heating furnace 2 passes through the reactor 4 (pump 1, heating furnace 2, reactor 4, cooling means 5, back pressure valve 6). Then, the pressure is adjusted by operating the valve so that the fluid becomes a subcritical fluid (corresponding to contact step (1)). When the reactor 4 reaches the predetermined temperature, the process is considered to have started (corresponding to process step (2)), and the processed liquid discharged from the reactor 4 is collected for a predetermined time. After that, the heater heating of the reactor 3 and the heating furnace 2 is stopped, and the reactor 4 is slowly cooled to end the process. The processed liquid generated in the reactor 4 during process step (2) is subjected to a separation step (3) and a recovery step (4) by a predetermined method. For example, if a filter is installed at the outlet of the reactor 4, the packing material is collected in the filter when the processed liquid is discharged from the reactor 4. On the other hand, hydrolyzable resin (a2) that dissolves in the subcritical fluid or is atomized to a size that is not collected by the filter passes through the filter and is discharged in the discharged liquid (separation step (3)). After that, the heater heating of the reactor 3 and the heating furnace 2 is stopped, and the slowly cooled reactor 4 is removed from the reactor 3 to end the process. After completion, the packing material is recovered from inside the reactor 4, and the hydrolyzable resin (a2) is recovered from the processed liquid discharged from the reactor 4 (recovery step (4)). However, various methods can be used for the separation step (3) and the recovery step (4) depending on the type of composite.

[0073] In a continuous composite processing method, it is preferable to perform the contact step (1), processing step (2), and separation step (3) within a single system. The continuous composite processing method shown in Figure 1 allows a series of steps to be performed within a single system by using the filter. By performing a series of steps continuously within a single system in this way, the operating rate of the equipment can be increased and the composite can be processed efficiently.

[0074] An example of a preferred embodiment of the reactor 4 in Figure 1 is the reactor 40 in Figure 2. The reactor 40 in Figure 2 has a substantially cylindrical structure with a hollow section that penetrates from one end to the other. The hollow section of the reactor 40 has an inlet channel I with a relatively small diameter that serves as the fluid inlet, a cavity C with a relatively large diameter that is the site where the fluid processing takes place, and an outlet channel O with a relatively small diameter that serves as the fluid outlet. Inside the cavity C, a flow straightening member 42 installed on the inlet side, a composite T to be processed, a mesh 44 for supporting the composite T, and a filter 46 installed on the outlet side are arranged. The flow straightening member 42 straightens the flow of the subcritical fluid that enters the cavity C, reducing reaction unevenness during processing. The flow straightening member 42 is composed of, for example, a pair of meshes arranged opposite each other and a number of beads fixed by being sandwiched between these meshes. The material of the beads is not particularly limited as long as it does not react with the subcritical fluid, but examples include stainless steel and alumina. The diameter of the beads is, for example, 1 to 10 mm. The support mesh 44 is a support member that prevents the composite T from coming into contact with the inner wall of the reactor 40. The support mesh 44 ensures that the entire surface of the composite T comes into contact with the subcritical fluid, reducing uneven reaction during processing. As described above, the filter 46 collects the packing material generated during the processing of the composite T. The filter 46 is, for example, a mesh. The mesh used for the rectifier member 42, the support mesh 44, and the filter 46 may be the same mesh or different meshes. The mesh opening is, for example, 20 to 100 μm. The material of the mesh is not particularly limited as long as it does not react with the subcritical fluid, but examples include stainless steel and alumina.

[0075] <Material Recycling> Examples of composites used in the composite processing method include molded products containing hydrolyzable resin (a1) and fillers, but from the viewpoint of effective resource utilization, waste plastics (waste such as used resin molded products, defective resin molded products, and scraps) are preferred. There are no particular limitations on waste plastics, but examples include plastic automobile parts (chassis, interior, exterior, window glass, lighting parts such as headlamp covers and reflectors, side mirrors, display parts, safety mechanisms such as safety belts, airbags and airbag covers, fuel system mechanisms such as tanks, pipes and pumps, electrical wiring mechanisms such as connectors, mechanical mechanisms such as gears, etc.), plastic parts of electrical equipment (e.g., home appliances, personal computers) and mobile communication terminals (casings, display parts, electrical circuit boards, antennas, etc.), various optical discs, plastic parts of medical and health equipment (hemodialysis, infusion bags, disposable syringes, physical training equipment, etc.), various molded products such as containers, packaging trays, stationery, toys, furniture, daily necessities, and home appliance casings, as well as packaging films (including packaging for pharmaceuticals such as tablets, powders, and liquids), and shopping bags.

[0076] By using the resin or filler recovered from such composites as raw materials for material recycling, we can contribute to the SDGs (Sustainable Development Goals).

[0077] As a specific example of material recycling, a method for manufacturing material recycled products can be described, in which material recycling is performed using the hydrolyzable resin (a2) recovered in the recovery process (4) as a raw material. In this manufacturing method, a material recycled product can be obtained by using the hydrolyzable resin (a2) as a raw material, and, if necessary, by additional polymerization of monomers and / or mixing it with other components. Since the hydrolyzable resin (a2) has a relatively high Mn retention rate, it can also be used for recycling without polymerization. In this way, a material recycled product containing hydrolyzable resin (a2) as a raw material can be obtained.

[0078] Another method of material recycling involves a method for manufacturing recycled materials, in which the filler recovered by the composite processing method described above is used as a raw material. In this manufacturing method, the filler is used as a raw material and, if necessary, mixed with other components such as resin to obtain recycled materials. In this way, recycled materials containing filler as a raw material can be obtained.

[0079] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0080] [Example 1] Internal volume 10 cm ３ In a stainless steel reaction tube, 0.3 g of glass fiber reinforced polyamide 6 resin pellets (manufactured by UBE Corporation, product name: 1015GC6), with a glass fiber content of 30% by mass of the total mass, and 3 cm³ of water were added as the sample. ３ A reaction tube was introduced and sealed. This reaction tube was placed in a molten salt bath, and the temperature of the molten salt bath was raised to the treatment temperature shown in Table 1. Then, with the time to reach the treatment temperature set to 0 min, the pellets were brought into contact with subcritical water for the treatment time shown in Table 1. The solid components after treatment were filtered to separate and recover the polyamide 6 resin residue (PA6) and glass fibers (GF), and the recovery rates were calculated. The results are shown in Table 1.

[0081] [Reference Examples 1 and 2] As samples, 0.3 g of polyamide 6 resin pellets (manufactured by UBE Corporation, product name: UBE Nylon 1030B) were used instead of glass fiber reinforced polyamide 6 resin pellets. The procedure was the same as in Example 1, except that the pellets were brought into contact with subcritical water at the processing temperature and processing time listed in Table 1. The results are shown in Table 1.

[0082] [Reference Example 3] Instead of 0.3 g of "polyamide 6 resin pellets" as the sample, 0.3 g of polyethylene terephthalate pellets (manufactured by Bell Polyester Products Co., Ltd., product name: Bellpet® PBK1) was used, and the procedure was the same as in Reference Example 1, except that the pellets were brought into contact with subcritical water at the treatment temperature and treatment time shown in Table 2. The recovered solid was identified by infrared spectroscopy (ATR method). As a result, the recovered solid was identified as polyethylene terephthalate. The results are shown in Table 2.

[0083] <Calculation of Recovery Rate of Hydrolyzable Resin> The recovery rate of the resin was calculated using the following formula. The unit of resin amount is mass. Recovery rate (%) = Amount of hydrolyzable resin recovered / Amount of hydrolyzable resin in the sample before treatment

[0084] <Measurement of the average molecular weight of hydrolyzable resin polyamide 6> The recovered solid hydrolyzable resin polyamide 6 was measured by GPC using the following method and conditions to determine its number-average molecular weight Mn2. Similarly, the number-average molecular weight Mn1 of the hydrolyzable resin before treatment was also measured.

[0085] (Measurement of number-average molecular weight (GPC)) GPC instrument: HLC-8220GPC (manufactured by Tosoh Corporation, detector: RI) Column: Shodex HFIP-LG + HFIP-806M x 2 Eluent: HFIP + 10 mM CF ３ COONa Flow rate: 0.8 mL / min Column temperature: 40°C Sample concentration: 0.05 wt / vol%

[0086] <Measurement of the average molecular weight of hydrolyzable resin polyethylene terephthalate> The recovered solid hydrolyzable resin was measured by NMR using the method and conditions described below to determine the number-average molecular weight Mn2 shown in Table 2. Similarly, the number-average molecular weight Mn1 before treatment was also measured.

[0087] (Measurement of number-average molecular weight (NMR)) NMR apparatus: JEOL "AL400" (1) Weigh 30 mg of the hydroxyl-terminated sample and measure CDCl ３ / HFIP = 1 / 1 (v / v) dissolved in 1.0 ml, １1H-NMR measurement was performed. (2) 30 mg of the acid-terminated quantitative sample was weighed, and 4 mg of triethylamine and CDCl ３ / HFIP = 1 / 1 (v / v) 1.0 ml and dissolved, １ and 1H-NMR measurement was performed.

[0088] The number average molecular weight was calculated according to the following formula. Although isophthalic acid and diethylene glycol were also present in the sample, they were not included in the calculation because they were in trace amounts.

[0089]

[0090] N: Degree of polymerization of monomers in one molecule S ａ : Integral value of ethylene glycol in the main chain １ 1H-NMR spectra: δ 4.70 (4, s, backbone -OCH ２ -) S ｂ : Integral value of terminal ethylene glycol １ [[ID=U23]]1H-NMR spectra: δ 4.00 (4, s, backbone HOCH ２ -) S ｃ : Integral value of terephthalic acid in the main chain １ 1H-NMR spectra: δ 8.09 (4, s, backbone aromatic H) S ｄ : Integral value of terminal terephthalic acid １ 1H-NMR spectra: δ 7.97 (4, s, end-group aromatic H)

[0091] <Calculation of the recovery rate of the recovered filler> The recovery rate of the filler (glass fiber) was calculated by the following formula. The unit of the filler amount is mass. Recovery rate (%) = Amount of recovered glass fiber / Amount of glass fiber in the sample before treatment

[0092] The above results are shown in Tables 1 and 2 below.

[0093]

[0094] According to Example 1, it was found that the filler was recovered with a high recovery rate, and the hydrolyzable resin was also recovered as a material-cycleable resin. From Reference Example 1, it was found that even when pellets consisting only of hydrolyzable resin were used, the molecular weight retention rate and recovery rate were similar to those when a composite was used. From Reference Example 2, it was found that in the case of polyamide resin, a processing time of 5 minutes resulted in a much higher recovery rate and molecular weight retention rate of the hydrolyzable resin than in Reference Example 1. From these results, it can be understood that when the composite used in Example 1 was processed at 250°C for 5 minutes, the recovery rate was approximately 90%, and the molecular weight retention rate was approximately 90%.

[0095]

[0096] Reference Example 3 shows that even when polyethylene terephthalate is treated alone with subcritical water as a hydrolyzable resin, polyethylene terephthalate is recovered with a high recovery rate. From the trends in Example 1 and Reference Examples 1 and 2, it can be understood that even when treating a composite containing polyethylene terephthalate and a filler, polyethylene terephthalate can be recovered with a high recovery rate similar to that in Reference Example 3.

[0097] [Example 2] In Example 2, the apparatus shown in Figure 1 was used. As reactor 4, a stainless steel reaction tube with an internal volume of 60 mL having the same structure as reactor 40 shown in Figure 2 was used. The rectifier member of the stainless steel reaction tube had a pair of meshes arranged opposite each other and a plurality of alumina balls with a diameter of 3 mm fixed between these meshes. The meshes of each part of the stainless steel reaction tube (corresponding to the rectifier member 42, mounting mesh 44, and filter 46) were all SUS mesh with an opening of 50 μm.

[0098] As a sample, a resin handle (Joe Prince Takeshita Co., Ltd.'s "Resin Two-Hole Handle") containing 6% polyamide, 30% by mass of glass fiber, and 0.2% by mass of carbon black particles was used. First, as a pretreatment, the resin handle was pulverized. One pulverized piece of the pulverized resin handle (approximately 7 mm x 10 mm x 13 mm) was placed in the stainless steel reaction tube.

[0099] Using the apparatus shown in Figure 1, degassed purified water was introduced into the reactor 4 and then discharged. Subsequently, the flow path was changed by operating the valves of the apparatus to prevent the purified water from passing through the reactor 3. The flow rate of the purified water was set so that the mass ratio of the sample PA mass to the total flow rate of purified water from the start to the end of the process was 1:520. Next, the heater heating of the reactor 3 and the heating furnace 2 was started, and when the temperature of the reactor 3 reached 250°C, the reactor 4 was set inside the reactor 3. Next, the valves of the apparatus were operated to switch the flow path so that the purified water that had left the heating furnace 2 would pass through the reactor 4. The valves of the apparatus were also operated to adjust the pressure to 15 MPa, setting the purified water to be subcritical water.

[0100] The process was considered to have started when the temperature inside reactor 4 reached 245°C, and during the process, the cloudy treated water discharged from reactor 4 was collected for 45 minutes. The temperature of the treated water discharged from reactor 4 was within the range of approximately 250 ± 5°C. After that, the flow of liquid in the device was stopped, and reactor 4 was removed to terminate the process.

[0101] The treated water was filtered to recover the solid (polyamide resin). The recovery rate, molecular weight retention rate, and number-average molecular weight of the recovered solid were measured according to the above-described methods: <Calculation of Recovery Rate of Hydrolyzable Resin> and <Measurement of Average Molecular Weight of Hydrolyzable Resin Polyamide 6>. Furthermore, the residue inside reactor 4 was removed, filtered, and the solid (carbon black particles and glass fibers) was recovered. The recovery rate of the recovered solid was calculated according to the formula: "Recovery Rate (mass%) = Total Mass of Recovered Filler / Mass of Filler in Pre-Treatment Sample". The results are shown in Table 3 below.

[0102] Furthermore, the recovered treated water was cloudy white, confirming the absence of carbon black particles. Therefore, it was determined that the carbon black particles present in the sample were entangled with the glass fibers, forming a single mass, and were recovered as residue within reactor 4.

[0103]

[0104] [Example 3] In Example 3, a 3D printer filament containing 6% polyamide and 20% by mass of carbon fiber (PolyMide PA6-CF, manufactured by Polymaker) was used as the sample. As a pretreatment, the filament was cut into lengths of several millimeters using a strand cutter to form pellets. 2.2 g of the cut filament was placed in the stainless steel reaction tube. In Example 3, the same procedures as in Example 2 were followed for the rest of the process, and the results were measured. The results are shown in Table 4 below.

[0105] [Example 4] In Example 4, a laminated sheet was used as the sample, which was formed by bonding a 200 μm thick polyamide 6 sheet (manufactured by UBE Corporation, product name: UBE Nylon 1030B) and an 11 μm thick aluminum foil (manufactured by Monotaro Co., Ltd., "Aluminum Foil") by heat pressing. As a pretreatment, the laminated sheet was kneaded using a kneader and then pulverized to form chips several centimeters in size. 2.0 g of the pulverized laminated sheet was placed in the stainless steel reaction tube. In Example 4, the processing was carried out in the same manner as in Example 2 in other respects, and the results were measured. The results are shown in Table 4 below.

[0106]

[0107] Examples 2 to 4 showed that in various composites, the fillers were recovered with a high recovery rate, and the hydrolyzable resins were also recovered as resins that could be material-cycled.

[0108] The composite processing method of the present invention makes it possible to efficiently recover the hydrolyzable resin and the filler from a composite containing the hydrolyzable resin and the filler, respectively.

[0109] 1. Pump 2. Heating furnace 3. Reactor 4. Reactor 5, 5' Cooling means 6. Back pressure valve

Claims

1. A method for processing a composite containing a hydrolyzable resin (a1) and a filler, comprising: a contact step (1) of bringing the composite into contact with a subcritical fluid to obtain a contact liquid; a processing step (2) of maintaining the state in which the composite and the subcritical fluid are in contact in the contact liquid for a certain period of time to obtain a processing liquid containing a hydrolyzable resin (a2) from which part or all of the hydrolyzable resin (a1) has been decomposed and / or separated; a separation step (3) of separating the hydrolyzable resin (a2) and the filler from the processing liquid; and a recovery step (4) of individually recovering the separated hydrolyzable resin (a2) and the filler.

2. The composite processing method according to claim 1, wherein the separation step (3) is a step of separating the hydrolyzable resin (a2) and the filler through a filter.

3. The composite processing method according to claim 1, wherein no stirring operation is performed in the processing step (2).

4. The composite processing method according to claim 1, wherein the contact step (1), the processing step (2), and the separation step (3) are performed within a single system.

5. The composite treatment method according to claim 1, wherein the treatment liquid contains the hydrolyzable resin (a2) dissolved in the subcritical fluid.

6. The composite treatment method according to claim 1, wherein, when the number average molecular weight of the hydrolyzable resin (a1) is Mn1 and the number average molecular weight of the hydrolyzable resin (a2) is Mn2, the Mn retention rate (100 × Mn2 / Mn1), which is the percentage of Mn2 to Mn1, is 15% or more, and Mn2 is 2300 or more.

7. The composite processing method according to claim 1, wherein the time for which the composite and the subcritical fluid are in contact in the processing step (2) is 1 to 60 minutes.

8. The composite treatment method according to claim 1, wherein the subcritical fluid is subcritical water.

9. The composite treatment method according to claim 1, wherein the hydrolyzable resin (a1) and the hydrolyzable resin (a2) are polyamide resin or polyester resin.

10. The composite treatment method according to claim 1, wherein the filler is glass fiber, carbon fiber and / or carbon black particles.

11. The composite processing method according to claim 1, wherein the composite is waste plastic.

12. A material recycled product comprising the hydrolyzable resin (a2) recovered by the composite processing method according to any one of claims 1 to 11 as a raw material.

13. A material recycled product comprising the filler recovered by the composite processing method according to any one of claims 1 to 11 as a raw material.

14. A method for manufacturing a material recycled product, wherein the hydrolyzable resin (a2) recovered by the composite processing method described in any one of claims 1 to 11 is used as a raw material for material recycling.

15. A method for manufacturing a material recycled product, wherein material recycling is performed using the filler recovered by the composite processing method described in any one of claims 1 to 11 as a raw material.

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