Resin recovery method

Abstract

This resin recovery method is a resin recovery method for recovering a resin from a composite comprising a layer (A) containing a non-hydrolyzable resin (a1) and a layer (B) containing a hydrolyzable resin (b1), the method comprising a step (1) in which the composite is brought into contact with a subcritical fluid to decompose and / or separate the layer (A) and the layer (B), a solid resin (A) comprising a non-hydrolyzable resin (a2) and a solid resin (B) comprising a hydrolyzable resin (b2) are obtained, the non-hydrolyzable resin (a1) and the non-hydrolyzable resin (a2) being the same or having only different molecular weight distributions, and the hydrolyzable resin (b1) and the hydrolyzable resin (b2) being the same or having only different molecular weight distributions.

Description

Technical Field

[0001] This invention relates to a method for recovering resin from a composite containing multiple resins. Background Technology

[0002] With increasing attention to environmental issues and the effective use of resources, there is a growing demand for the reuse of resin products.

[0003] Films and other materials used in the packaging of resin products are typically multilayer films or composites of multiple resins. To reuse these composites, it is necessary to separate and recycle the resins according to their type.

[0004] In Patent Document 1, a laminate of a polyolefin layer and a layer of foreign matter other than polyolefin selected from water-soluble or hydrolyzable foreign matter is treated with water under specific pressure and heated to 200-400°C, thereby dissolving only the foreign matter in the water and recovering the polyolefin.

[0005] In Patent Document 2, a polyolefin resin film containing organic matter other than polyolefin resin is heated to 200-350°C under a specific pressure and then treated with water, thereby hydrolyzing the organic matter other than polyolefin resin and recovering the polyolefin resin.

[0006] In Patent Document 3, supercritical water is used as a solvent to hydrolyze a solid composite material composed of two or more organic polymers. After separating the organic liquid from the organic solid, the organic solid is recovered while the separated organic liquid is separated and recovered according to the material by boiling point separation method.

[0007] In Patent Document 4, the resin layer of the hydrolyzable polymer and the resin layer of the non-hydrolyzable polymer are decomposed and separated through a hydrothermal reaction under specific conditions. The hydrolyzable polymer is hydrolyzed and separated and recovered in the form of monomers, and the non-hydrolyzable polymer is separated and recovered while maintaining its molecular weight.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 8-92411

[0011] Patent Document 2: Japanese Patent Application Publication No. 11-35734

[0012] Patent Document 3: Japanese Patent Application Publication No. 2001-316518

[0013] Patent Document 4: Japanese Patent Application Publication No. 2023-1085 Summary of the Invention

[0014] The problem the invention aims to solve

[0015] In patent documents 1 to 4, non-hydrolyzable resins such as polyolefin resins can be recycled as resins and directly recycled. However, hydrolyzable resins such as polyamide resins are decomposed into monomers and dissolved in water, so they cannot be recycled. Instead, boiling point separation is required to recover the monomers, which is difficult to do due to boiling and other issues.

[0016] The objective of the first aspect of the present invention is to separate and recover the hydrolyzable resin and the non-hydrolyzable resin in resin form from a composite comprising a hydrolyzable resin and a non-hydrolyzable resin.

[0017] The second aspect of the present invention addresses the problem of separating and recovering the hydrolyzable resin in its resin state from a molded body containing the hydrolyzable resin.

[0018] The third aspect of this invention is to separate and recover the non-hydrolyzable resin in its resin state from a molded article containing the non-hydrolyzable resin.

[0019] Solution for solving the problem

[0020] The present invention is, for example, the following [1] to

[14] .

[0021] [1] A resin recovery method, which is a resin recovery method for recovering resin from a composite comprising a layer (A) containing a non-hydrolyzable resin (a1) and a layer (B) containing a hydrolyzable resin (b1).

[0022] The method includes step (1): contacting the aforementioned composite with a subcritical fluid to decompose and / or separate layer (A) and layer (B) to obtain a solid resin (A) composed of a non-hydrolyzable resin (a2) and a solid resin (B) composed of a hydrolyzable resin (b2).

[0023] The aforementioned non-hydrolyzable resin (a1) is the same as the aforementioned non-hydrolyzable resin (a2), or only differs in molecular weight distribution.

[0024] The aforementioned hydrolyzable resin (b1) is the same as the aforementioned hydrolyzable resin (b2), or only differs in molecular weight distribution.

[0025] [2] The resin recycling method according to [1] further includes a recycling step (2): separating and recycling the aforementioned solid resin (A) and the aforementioned solid resin (B) obtained in the aforementioned step (1) by passing them through a filter.

[0026] [3] The resin recycling method according to [1] further includes a recycling step (2): the solid resin (A) and the solid resin (B) obtained in the aforementioned step (1) are separated and recycled by the difference in specific gravity between the solid resin (A) and the solid resin (B).

[0027] [4] According to any one of [1] to [3], in which the number average molecular weight of the hydrolyzable resin (b1) is set as Mn1 and the number average molecular weight of the hydrolyzable resin (b2) is set as Mn2, the ratio of Mn2 to Mn1 (Mn2 / Mn1) is 0.15 or more and Mn2 is 2300 or more.

[0028] [5] The resin recovery method according to any one of [1] to [4], wherein in the aforementioned step (1), the contact time between the aforementioned composite and the aforementioned subcritical fluid is 1 to 60 minutes.

[0029] [6] The resin recycling method according to any one of [1] to [5], wherein the aforementioned non-hydrolyzable resins (a1) and (a2) are polyolefin resins.

[0030] [7] The resin recycling method according to any one of [1] to [6], wherein the aforementioned hydrolyzable resins (b1) and (b2) are polyamide resins or polyester resins.

[0031] [8] According to the resin recycling methods of [1] to [7], the aforementioned composite is waste plastic.

[0032] [9] A resin recycling method, which is a resin recycling method for recovering resin from a molded body containing hydrolyzable resin (b1).

[0033] The method includes a step of contacting the aforementioned molded body with a subcritical fluid to obtain a solid resin (B) composed of a hydrolyzable resin (b2).

[0034] The aforementioned hydrolyzable resin (b1) is the same as the aforementioned hydrolyzable resin (b2) or has a different molecular weight distribution.

[0035]

[10] A resin recycling method, which is a resin recycling method for recovering resin from a molded body containing non-hydrolyzable resin (a1).

[0036] The method includes a step of contacting the aforementioned molded body with a subcritical fluid to obtain a solid resin (A) composed of a non-hydrolyzable resin (a2).

[0037] The aforementioned non-hydrolyzable resin (a1) is the same as or has a different molecular weight distribution than the aforementioned non-hydrolyzable resin (a2).

[0038]

[11] A material recycling product, wherein the raw material contains the aforementioned non-hydrolyzable resin (a2) recovered using the resin recovery method of any one of [1] to [8] and

[10] .

[0039]

[12] A material recycling product, wherein the raw material contains the aforementioned hydrolyzable resin (b2) recovered by any one of the resin recovery methods in [1] to [9].

[0040]

[13] A method for manufacturing a material recycling product, wherein the aforementioned non-hydrolyzable resin (a2) recovered using any one of the resin recycling methods of [1] to [8] and

[10] is used as a raw material for material recycling.

[0041]

[14] A method for manufacturing a material recycling product, wherein the aforementioned hydrolyzable resin (b2) recovered by any one of the resin recycling methods of [1] to [9] is used as a raw material for material recycling.

[0042] The effects of the invention

[0043] According to a first aspect of the present invention, it is possible to separate and recover the hydrolyzable resin and the non-hydrolyzable resin in resin form from a composite comprising the hydrolyzable resin and the non-hydrolyzable resin.

[0044] The second aspect of the present invention enables the separation and recovery of hydrolyzable resin in its resinous state from a molded body containing hydrolyzable resin.

[0045] The third aspect of the present invention enables the separation and recovery of non-hydrolyzable resin in its resin state from a molded article containing non-hydrolyzable resin. Attached Figure Description

[0046] Figure 1 This is an example of an apparatus for performing the resin recovery method of the present invention. Detailed Implementation

[0047] The first aspect of the present invention is a resin recovery method, which is a resin recovery method for recovering resin from a composite comprising a layer (A) containing a non-hydrolyzable resin (a1) and a layer (B) containing a hydrolyzable resin (b1). The method includes the step (1): contacting the aforementioned composite with a subcritical fluid to decompose and / or separate the aforementioned layers (A) and (B) to obtain a solid resin (A) composed of a non-hydrolyzable resin (a2) and a solid resin (B) composed of a hydrolyzable resin (b2), wherein the aforementioned non-hydrolyzable resin (a1) is the same as the aforementioned non-hydrolyzable resin (a2) or only differs in molecular weight distribution, and the aforementioned hydrolyzable resin (b1) is the same as the aforementioned hydrolyzable resin (b2) or only differs in molecular weight distribution.

[0048] In this specification, solid resin refers to resin that is solid at 25°C and 1 atm.

[0049] <Process (1)>

[0050] In step (1), a composite comprising a layer (A) containing a non-hydrolyzable resin (a1) and a layer (B) containing a hydrolyzable resin (b1) is brought into contact with a subcritical fluid. In step (1), layers (A) and (B) are decomposed and / or separated to obtain a solid resin (A) composed of a non-hydrolyzable resin (a2) and a solid resin (B) composed of a hydrolyzable resin (b2).

[0051] Here, "composed of" means excluding components not present in the complex. Preferably, it means excluding substances other than trace amounts of impurities, and more preferably, it means "composed of only".

[0052] A composite is a single entity formed by directly bonding or via adhesives to two or more layers of resin or resin compositions. Examples include laminates and bonded composites. A composite comprises layer (A) and layer (B). Layers (A) and (B) may be adjacent or bonded, or they may not be adjacent. A composite may contain layers other than layers (A) and (B), or other components. For example, in addition to layers (A) and (B), a composite may arbitrarily include inorganic layers.

[0053] Preferably, non-hydrolyzable resin (a1) is the main component in layer (A), and preferably hydrolyzable resin (b1) is the main component in layer (B).

[0054] "In layer (A), non-hydrolyzable resin (a1) is the main component" means that, in all the components of the composition constituting layer (A), non-hydrolyzable resin (a1) is contained in the largest quantity by mass, and in 100% by mass of the composition constituting layer (A), the content of non-hydrolyzable resin (a1) is 50% by mass or more, preferably 70% by mass or more, more preferably 95% by mass or more, and also includes 100% by mass, i.e., layer (A) is composed solely of non-hydrolyzable resin (a1). The same applies to "In layer (B), hydrolyzable resin (b1) is the main component".

[0055] Non-hydrolyzable resins refer to resins in which the bonds are not hydrolyzed or are difficult to hydrolyze. Non-hydrolyzable thermoplastic resins are preferred, such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and other polyethylene resins; polyolefin resins such as polypropylene; tetrafluoroethylene, ethylene / tetrafluoroethylene copolymers, halogenated polyolefins such as polyvinyl chloride, ethylene-vinyl acetate copolymers, acrylic resins, polystyrene resins, acrylonitrile-butadiene-styrene copolymers, and acrylonitrile-styrene copolymers. One or more of these resins may be used. Polyolefin resins are preferred.

[0056] Hydrolyzable resins refer to resins in which at least a portion of the bonds in the resin can be hydrolyzed. As an example, resins having ester bonds, amide bonds, imide bonds, ether bonds, urethane bonds, carbonate bonds, acetal bonds, hemiacetal bonds, ketal bonds, or bonds where some or all of the oxygen atoms are sulfur atoms are preferred. Generally, resins in which at least a portion of the bonds in the main chain can be hydrolyzed are preferred, and hydrolyzable thermoplastic resins are more commonly preferred. Specifically, examples include polyamide resins, polyester resins, polyurethane resins, polycarbonate resins, polyacetal resins, polyether resins, and phenolic resins. One or more of these can be used. Polyamide resins and polyester resins are preferred, and polyamide resins are more preferred.

[0057] Examples of polyamide resins include aliphatic homopolymer polyamide resins, aliphatic copolymer polyamide resins, semi-aromatic homopolymer polyamide resins, semi-aromatic copolymer polyamide resins, aromatic homopolymer polyamide resins, and aromatic copolymer polyamide resins. Monomers used as raw materials for polyamide resins include lactam compounds, aminocarboxylic acids, and combinations of diamines and dicarboxylic acids. Here, a semi-aromatic polyamide resin refers to a polyamide resin whose structural unit is a combination of a diamine and a dicarboxylic acid, where one of the diamine and the dicarboxylic acid is aliphatic and the other is aromatic.

[0058] There are no particular limitations on specific examples of polyamide resins, such as 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.

[0059] Combinations of non-hydrolyzable resin (a1) and hydrolyzable resin (b1) can be listed, with combinations of the above-mentioned resins being preferred, such as combinations of polyolefin resin and polyamide resin, and combinations of polyolefin resin and polyester resin.

[0060] As any inorganic layer, examples include metallic layers that impart gas barrier properties, aroma retention properties, and light reflectivity, as well as hard coatings that impart scratch resistance. There are no particular limitations on metallic layers; examples include layers made of aluminum, silicon, copper-nickel-chromium combinations, gold, palladium, tin, ruthenium, black trivalent chromium, and tin-cobalt alloys. There are also no particular limitations on hard coatings; examples include ceramic layers primarily composed of metal oxides such as alumina, silicon dioxide, zirconium oxide, and titanium dioxide.

[0061] Layers (A), (B), and other components in the composite may appropriately contain functional additives such as dyes, pigments, fibrous reinforcements, particulate reinforcements, plasticizers, antioxidants, heat resistant agents, foaming agents, weather resistant agents, nucleating agents, crystallization promoters, mold release agents, lubricants, antistatic agents, flame retardants, flame retardant auxiliaries, and colorants as any component. These components are preferably added in small quantities as additives, and are not particularly limited. In each layer or the composition constituting the layers, they are preferably 5% by mass or less, more preferably 1% by mass or less.

[0062] In step (1), a composite comprising a layer (A) containing a non-hydrolyzable resin (a1) and a layer (B) containing a hydrolyzable resin (b1) is brought into contact with a subcritical fluid.

[0063] Subcritical fluids are fluids that exist in a liquid state near the critical point and in a region where the temperature and / or pressure is lower than the critical point. They are obtained by pressurizing the fluid in a temperature region above the boiling point. Examples of subcritical fluids include water, alcohols, carbon dioxide, and nitrogen; water is preferred from the viewpoint of having a high ion product.

[0064] Contact refers to maintaining the complex in a subcritical fluid for a certain period of time. There are no particular limitations on the method of contacting the complex with the subcritical fluid; it is usually carried out in a closed system, but can also be done intermittently (batch) or continuously, with continuous operation being preferred. Preferably, it is carried out by adding the complex to a pressure-resistant reaction vessel, heating it, adjusting its own pressure or pressure, and allowing the fluid to circulate at a specified temperature. Examples of reaction vessels include closed reaction vessels such as autoclaves and reaction tubes. There are no particular limitations on the heating method; methods using heaters, molten salt baths, etc., are also possible.

[0065] During contact, the temperature and pressure of the subcritical fluid are not particularly limited as long as a subcritical fluid is generated. When the subcritical fluid is water, the preferred temperatures are 120–374°C and 0.2–22 MPa. When the subcritical fluid is methanol, the preferred temperatures are 85–240°C and 0.2–8 MPa. When the subcritical fluid is ethanol, the preferred temperatures are 95–240°C and 0.2–6 MPa. When the temperature and pressure of the subcritical fluid are within the above ranges, the non-hydrolyzable resin (a2) can be easily recovered while maintaining the molecular weight of the non-hydrolyzable resin (a1), and the recovery rate of the resin as hydrolyzable resin (b1) in the form of hydrolyzable resin (b2) can also be improved.

[0066] The contact time (processing time) is preferably 1 to 60 minutes, more preferably 1 to 30 minutes. When the time is within the above range, the non-hydrolyzable resin (a2) can be easily recycled while maintaining the molecular weight of the non-hydrolyzable resin (a1), and the recovery rate of the resin as hydrolyzable resin (b1) recycled in the form of hydrolyzable resin (b2) can also be improved.

[0067] The temperature, pressure, processing time, and other associated contact-related conditions of these subcritical fluids may be appropriately set according to the type of non-hydrolyzable resin (a1) and / or hydrolyzable resin (b1), with reference to this specification. Preferably, the conditions may be set according to the molecular weight of the desired hydrolyzable resin (b2).

[0068] Contact between the composite and the subcritical fluid can also be carried out by adding acid or alkali, but from the viewpoint of maintaining the molecular weight of the non-hydrolyzable resin (a1) and improving the recovery rate of the resin as a hydrolyzable resin (b1), it is preferable not to add acid or alkali in order to ensure proper decomposition, more preferably to carry out the process under neutral conditions, and even more preferably under conditions of pH 6 to 8.

[0069] Regarding the amount of subcritical fluid used when the composite comes into contact with the subcritical fluid (the amount of subcritical fluid feedstock added to the reaction vessel), the mass ratio of the subcritical fluid to the composite (subcritical fluid / composite) is preferably 0.5 to 500, more preferably 1 to 100, and even more preferably 5 to 20. When this mass ratio is within the above range, layer stripping can be performed smoothly while suppressing the decomposition of the non-hydrolyzable resin.

[0070] In step (1), layers (A) and (B) are decomposed and / or separated. The composite is preferably delaminated. For example, layers (A), (B), and any other layers are delaminated. The treatment liquid after step (1) contains a non-hydrolyzable resin (a2) and a hydrolyzable resin (b2). Moreover, the non-hydrolyzable resin (a1) is not hydrolyzed by the subcritical fluid, but is separated and / or decomposed, at least a portion of which, preferably all of which, becomes a solid resin (A) composed of the non-hydrolyzable resin (a2). The non-hydrolyzable resin (a1) is the same as the non-hydrolyzable resin (a2), or only differs in molecular weight distribution. That is, the two resins are of the same type. In this specification, "same resins or only different molecular weight distribution" means that the resins are of the same type, have the same basic structure, and have the same or different molecular weight distribution. "Same basic structure" means that even if the resins are partially cross-linked, modified, or replaced, as long as the basic properties of the resins remain unchanged, they are considered the same. Different molecular weight distributions (only different molecular weight distributions) mean that the molecular weight changes due to the change in molecular weight caused by process (1), resulting in a change in molecular weight distribution. The same applies below for hydrolyzable resins (b2). That is, those skilled in the art will understand that the various physical properties related to molecular weight are concepts that naturally change with changes in molecular weight.

[0071] Since the non-hydrolyzable resin (a1) is not hydrolyzed, the molecular weight of the non-hydrolyzable resin (a2) and the non-hydrolyzable resin (a1) are maintained at a high rate. The number-average molecular weight of the non-hydrolyzable resin (a2) relative to the number-average molecular weight of the non-hydrolyzable resin (a1) ((number-average molecular weight of non-hydrolyzable resin (a2) Mn4 / number-average molecular weight of non-hydrolyzable resin (a1) Mn3) * 100) is preferably 80% or more, more preferably 85% or more.

[0072] Furthermore, since the non-hydrolyzable resin (a1) is not hydrolyzed, the non-hydrolyzable resin (a2) will not break into fine shapes such as powder, which is also a characteristic. Thus, due to the high molecular weight retention and shape characteristics, the solid resin (A) composed of the non-hydrolyzable resin (a2) is useful as a raw material for material recycling. Additionally, when the non-hydrolyzable resin (a1) melts through contact with a subcritical fluid, because the non-hydrolyzable resin (a1) of the non-hydrolyzable resin (a2) has a high molecular weight retention as described above, the difference in molecular weight between it and the hydrolyzable resin (b2) becomes larger. As a result, sometimes the viscosity difference between the non-hydrolyzable resin (a2) and the hydrolyzable resin (b2) becomes larger. In this case, the viscosity difference can be used to separate the non-hydrolyzable resin (a2) and the hydrolyzable resin (b2).

[0073] In step (1), at least a portion of the hydrolyzable resin (b1) is hydrolyzed by contact with a subcritical fluid, and at least a portion becomes a solid resin (B) composed of hydrolyzable resin (b2). The hydrolyzable resin (b1) and the hydrolyzable resin (b2) are identical, or differ only in their molecular weight distribution. That is, they are of the same type of resin. Preferably, the hydrolyzable resin (b1) and the hydrolyzable resin (b2) differ only in their molecular weight distribution.

[0074] When the number average molecular weight of the hydrolyzable resin (b1) is set as Mn1 and the number average molecular weight of the hydrolyzable resin (b2) is set as Mn2, the ratio of Mn2 to Mn1 (Mn2 / Mn1) is preferably 0.15 or more, and Mn2 is preferably 2300 or more.

[0075] Furthermore, the hydrolyzable resin (b2) is particularly preferably obtained in the form of a fine powder.

[0076] Mn2 / Mn1 represents the retention rate of the molecular weight of hydrolyzable resin (b1) and hydrolyzable resin (b2). Thus, hydrolyzable resin (b2) is a resin obtained by maintaining at least a portion of the molecular weight of hydrolyzable resin (b1).

[0077] The Mn2 value indicates that the hydrolyzable resin (b2) is obtained in the form of a resin. Even after process (1), at least a portion of the hydrolyzable resin (b1) is not decomposed into monomers or oligomers, but remains in the form of a resin.

[0078] Since Mn2 / Mn1 and Mn2 fall within the aforementioned range, the hydrolyzable resin (b1) is recycled in the form of at least a portion of a solid resin (B) having a certain molecular weight. The solid resin (B) can also be used as a raw material for material recycling.

[0079] For Mn2 / Mn1 and Mn2 to be within the aforementioned range, this can be achieved by performing step (1). Preferably, in step (1), this can be achieved by setting the temperature, pressure, and contact time as described above.

[0080] Thus, according to the present invention, by including step (1), both non-hydrolyzable resin and hydrolyzable resin can be recycled in the form of solid resin, which is useful for material recycling. Compared with chemical recycling, which decomposes into monomers during recycling, material recycling simplifies the process of manufacturing new articles and is highly effective as a recycling method.

[0081] In the resin recovery method of the present invention, the recovery rate of the non-hydrolyzable resin (a1) ((mass of non-hydrolyzable resin (a2) / mass of non-hydrolyzable resin (a1)) × 100) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. According to the resin recovery method of the present invention, the non-hydrolyzable resin (a1) can be recovered with a high recovery rate as a non-hydrolyzable resin (a2) that differs only in molecular weight distribution.

[0082] The recovery rate of hydrolyzable resin (b1) ((mass of hydrolyzable resin (b2) / mass of hydrolyzable resin (b1)) × 100) is preferably 10% or more, more preferably 30% or more, further preferably 50% or more, and particularly preferably 80% or more. According to the resin recovery method of the present invention, hydrolyzable resin (b1) can be recovered as hydrolyzable resin (b2), which differs only in molecular weight distribution.

[0083] As shown in the recovery rate above, in step (1), components other than non-hydrolyzable resin (a2) and hydrolyzable resin (b2) are sometimes generated. For example, components such as monomers and dimers that constitute the units of hydrolyzable resin can be listed. In addition, depending on the layers of the composite, components other than non-hydrolyzable resin (a2) and hydrolyzable resin (b2) are sometimes generated.

[0084] <Process (2)>

[0085] The resin recycling method preferably includes a recycling step (2) after step (1).

[0086] The recycling process (2) can be exemplified as follows: Method 1, which separates and recycles the solid resin (A) and solid resin (B) obtained in the aforementioned process (1) by passing them through a filter; and Method 2, which separates and recycles the solid resin (A) and solid resin (B) obtained in the aforementioned process (1) by their specific gravity difference.

[0087] Method 1, which separates and recycles the solid resin (A) and solid resin (B) obtained in the aforementioned process (1) by passing them through a filter, is described below.

[0088] After step (1), the non-hydrolyzable resin (a2) and hydrolyzable resin (b2) contained in the treatment liquid are cooled and preferably obtained in the form of powdered solid resin. Therefore, for example, it is possible to easily separate and recover the non-hydrolyzable resin (a2) as solid resin (A) and the hydrolyzable resin (b2) as solid resin (B) without having to perform a step such as boiling point separation.

[0089] There are no particular restrictions on what kind of filter can be used; for example, filters made of metal, thermoplastic resin, or thermosetting resin can be used.

[0090] There are no particular restrictions on the longitudinal and transverse mesh sizes of the filter. From the viewpoint of facilitating resin separation, it is preferable to use 10 to 100 μm meshes separately, and more preferably 20 to 70 μm meshes.

[0091] The filter can be a single-stage or multi-stage filter. Using filters with different mesh sizes for each stage allows for more efficient separation and is preferred.

[0092] Method 2 for separating and recycling the solid resin (A) and solid resin (B) obtained in the aforementioned process (1) by utilizing the difference in specific gravity is as follows.

[0093] When the specific gravity is in the order of hydrolyzable resin (b2) > subcritical fluid > non-hydrolyzable resin (a2), solid resin (A) and solid resin (B) can be separated according to their specific gravity. Specifically, by cooling in the subcritical fluid, the hydrolyzable resin (b2) that is molten in the subcritical fluid settles and precipitates, while the non-hydrolyzable resin (a2) remains on the surface of the subcritical fluid. These two are then separated.

[0094] Preferably, no other processes other than cooling are included between process (1) and process (2).

[0095] <Pretreatment Process>

[0096] The resin recycling method can have any pretreatment step before step (1).

[0097] As a pretreatment step, a process of pulverizing the composite of molded products can be listed. Including a pulverizing step has the advantage of increasing the contact area with the subcritical fluid. As for the pulverizing unit, there are no particular limitations as long as it is a known pulverizing unit, and examples include jaw crushers, rotary crushers, cone crushers, impact crushers, roller crushers, autogenous mills, pulverizers, stone mills, large paper shredders, ring mills, roller mills, shredders, hammer mills, turbo mills, jet mills, pin mills, centrifugal mills, knife mills, and other mills, crushers, rotoplexes, pulverizers, and ultra-high-speed rotors. Wet pulverization can also be performed. Furthermore, pulverization can be performed while the composite is frozen. Pulverization also includes cutting.

[0098] In addition, as a pretreatment step, a process of melting the composite of the molded article can be listed. By melting the composite at a temperature above the melting temperature of the resin to be recycled, components that do not melt at that temperature can be separated and removed before step (1). As the melting temperature, it is preferably above the melting point of the non-hydrolyzable resin (a1) and the hydrolyzable resin (b1) and below a temperature at which these resins do not undergo thermal degradation. As the melting unit, a melt mixing mill, a mixing extruder, a gear pump, etc. can be listed.

[0099] In addition, as a pretreatment step, a cleaning step for cleaning the composite can be listed. When using waste plastics as the composite, a cleaning step is particularly preferred.

[0100] Regarding the above-mentioned crushing, melting, and cleaning processes, one or more of these processes can be performed. When multiple processes are performed, it is preferable that the melting process is performed immediately before process (1), and more preferably in the order of cleaning, crushing, and melting.

[0101] Post-processing steps

[0102] The resin recycling method may have any post-processing step after step (1) or any step (2).

[0103] As a post-processing step, the drying process of the recovered solid resin (A) and solid resin (B) can be listed.

[0104] In addition, after step (1) or any step (2), a purification step for the recovered solid resin (A) and solid resin (B) may also be included.

[0105] <Materials Recycling>

[0106] As a composite used in resin recycling methods, examples include molded products containing two or more resins. From the perspective of efficient resource utilization, waste plastics (used resin molded products, poorly molded resin molded products, and other waste materials) are preferred. There are no particular limitations on what constitutes waste plastics. Examples include plastic automotive parts (chassis, interior, exterior, window glass, headlight covers, reflectors and other lighting parts, rearview mirrors, displays, seat belts, airbags, airbag covers and other safety mechanisms, tanks, piping, pumps and other fuel system mechanisms, connectors and other electrical wiring mechanisms, gears and other mechanical mechanisms, etc.), electrical equipment (e.g., home appliances, personal computers), plastic parts of portable communication terminals (casings, display parts, circuit boards, antennas, etc.), various optical discs, plastic parts of medical / health devices (artificial dialysis, infusion bags, disposable syringes, physical training equipment, etc.), containers, packaging trays, stationery, toys, furniture, daily necessities, home appliance casings and other molded products, as well as packaging films (including packaging for tablets, powders, liquids and other pharmaceuticals), plastic bags, etc.

[0107] By using solid resins recovered from such composites as raw materials for material recycling, it is possible to contribute to the SDGs (Sustainable Development Goals).

[0108] Specifically, as a method for recycling materials, a method for manufacturing recycled materials using non-hydrolyzable resin (a2) recovered through the aforementioned resin recycling method as a raw material can be provided. In this manufacturing method, non-hydrolyzable resin (a2) can be used as a raw material, and polymerizable monomers and / or other components can be added as needed to obtain recycled materials. Since non-hydrolyzable resin (a1) has a high molecular weight retention rate, it can also be used for recycling without polymerization. Thus, recycled materials containing non-hydrolyzable resin (a2) in the raw material can be obtained.

[0109] Furthermore, as a method for material recycling, specifically, a method for manufacturing recycled materials using hydrolyzed resin (b2) recovered through the aforementioned resin recycling method as a raw material can be provided. In this manufacturing method, hydrolyzed resin (b2) can be used as a raw material, and polymeric monomers and / or other components can be added as needed to obtain the recycled material. According to the aforementioned resin recycling method, at least a portion of the hydrolyzed resin (b1) is recovered in the form of hydrolyzed resin (b2) as a resin. Therefore, compared with chemical recycling, the process of manufacturing new products can be simplified, and the recycling method is highly efficient. Thus, a recycled material containing hydrolyzed resin (b2) in the raw material can be obtained.

[0110] The second aspect of the present invention is a resin recycling method, which is a resin recycling method for recovering resin from a molded body containing hydrolyzable resin (b1). The aforementioned method includes a step of contacting the molded body with a subcritical fluid to obtain a solid resin (B) composed of hydrolyzable resin (b2).

[0111] The aforementioned hydrolyzable resin (b1) is the same as the aforementioned hydrolyzable resin (b2) or has a different molecular weight distribution.

[0112] As a hydrolyzable resin (b1), the resin exemplified in the first aspect of the present invention can be listed.

[0113] The method of contact in the process of contacting the aforementioned molded body with a subcritical fluid to obtain a solid resin (B) composed of hydrolyzable resin (b2) is not particularly limited, and methods similar to the first aspect of the present invention can be cited.

[0114] During contact, the temperature and pressure of the subcritical fluid are not particularly limited as long as a subcritical fluid is generated. When the subcritical fluid is water, the preferred temperatures are 120–374°C and 0.2–22 MPa. When the subcritical fluid is methanol, the preferred temperatures are 85–240°C and 0.2–8 MPa. When the subcritical fluid is ethanol, the preferred temperatures are 95–240°C and 0.2–6 MPa. When the temperature and pressure of the subcritical fluid are within the above ranges, the recovery rate of the resin (b1) as hydrolyzable resin (b2) can be improved.

[0115] The contact time (processing time) is preferably 1 to 60 minutes, more preferably 1 to 30 minutes, and even more preferably 1 to 10 minutes. When the time is within the above range, the recovery rate of the resin as hydrolyzable resin (b1) in the form of hydrolyzable resin (b2) can be improved.

[0116] Furthermore, the pH and the amount of subcritical fluid used are the same as in the first embodiment of the present invention.

[0117] At least a portion of the hydrolyzable resin (b1) is hydrolyzed by a subcritical fluid, and at least a portion of it becomes a solid resin (B) composed of hydrolyzable resin (b2). The hydrolyzable resin (b1) and the hydrolyzable resin (b2) are the same or have different molecular weight distributions. That is, both are of the same type of resin. Preferably, the hydrolyzable resin (b1) and the hydrolyzable resin (b2) have different molecular weight distributions.

[0118] When the number average molecular weight of the hydrolyzable resin (b1) is set as Mn1 and the number average molecular weight of the hydrolyzable resin (b2) is set as Mn2, the ratio of Mn2 to Mn1 (Mn2 / Mn1) is preferably 0.15 or more, and Mn2 is preferably 2300 or more.

[0119] The recovery rate of hydrolyzable resin (b1) ((mass of hydrolyzable resin (b2) / mass of hydrolyzable resin (b1)) × 100) is preferably 10% or more, more preferably 30% or more, further preferably 50% or more, and particularly preferably 80% or more. According to the resin recovery method of the present invention, hydrolyzable resin (b1) can be recovered as hydrolyzable resin (b2), which differs only in molecular weight distribution.

[0120] The third aspect of the present invention is a resin recycling method, which is a resin recycling method for recovering resin from a molded body containing non-hydrolyzable resin (a1).

[0121] The method includes a step of contacting the aforementioned molded body with a subcritical fluid to obtain a solid resin (A) composed of a non-hydrolyzable resin (a2).

[0122] The aforementioned non-hydrolyzable resin (a1) is the same as or has a different molecular weight distribution than the aforementioned non-hydrolyzable resin (a2).

[0123] As a non-hydrolyzable resin (a1), the resin exemplified in the first aspect of the present invention can be listed.

[0124] The contact method in the process of contacting the aforementioned molded body with a subcritical fluid to obtain a solid resin (A) composed of a non-hydrolyzable resin (a2) is not particularly limited, and methods similar to the first aspect of the present invention can be cited.

[0125] The non-hydrolyzable resin (a1) is not hydrolyzed by the subcritical fluid, but is separated and / or decomposed, so that at least a portion, preferably all of it, becomes a solid resin (A) composed of the non-hydrolyzable resin (a2). The non-hydrolyzable resin (a1) and the non-hydrolyzable resin (a2) are the same or have different molecular weight distributions. That is, they are of the same type of resin.

[0126] Since the non-hydrolyzable resin (a1) is not hydrolyzed, the molecular weight of the non-hydrolyzable resin (a2) and the non-hydrolyzable resin (a1) are maintained at a high rate. The number-average molecular weight of the non-hydrolyzable resin (a2) relative to the number-average molecular weight of the non-hydrolyzable resin (a1) ((number-average molecular weight of non-hydrolyzable resin (a2) Mn4 / number-average molecular weight of non-hydrolyzable resin (a1) Mn3) * 100) is preferably 80% or more, more preferably 85% or more.

[0127] The recovery rate of the non-hydrolyzable resin (a1) ((mass of non-hydrolyzable resin (a2) / mass of non-hydrolyzable resin (a1)) × 100) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. According to the resin recovery method of the present invention, the non-hydrolyzable resin (a1) can be recovered with a high recovery rate as a non-hydrolyzable resin (a2) that differs only in molecular weight distribution.

[0128] The second and third embodiments of the present invention may have the same pretreatment and posttreatment steps as the first embodiment of the present invention. The hydrolyzable resin (b2) obtained in the second embodiment of the present invention and the non-hydrolyzable resin (a2) obtained in the third embodiment of the present invention are suitable for material recycling in the same way as in the first embodiment of the present invention.

[0129] Example

[0130] The present invention will now be described in more detail by way of examples and comparative examples, but the present invention is not limited to these examples.

[0131] [Example 1]

[0132] use Figure 1 The manufacturing apparatus performs the following operations.

[0133] The volume of the contents removed from reactor 3 is 50 cm³. 3 In reactor 4, 10 g of pulverized material of a multilayer film (polyamide content 25% by mass%) consisting of a polyamide 6 resin layer, a polyethylene (LDPE) resin layer, and an adhesive layer (number average molecular weight of polyamide 6 resin 15016, number average molecular weight of polyethylene (LDPE) resin 37970) was loaded as a sample. Stainless steel mesh filters (55 μm aperture) were installed at the inlet and outlet of reactor 4.

[0134] After the degassed purified water flows into reactor 4 and the air is vented, the flow path is changed so that the purified water does not pass through reactor 4 via valve operation. That is, in this flow path, the purified water passes through pump 1, heating furnace 2, cooling unit 5', and back pressure valve 6. It should be noted that in order to maintain a certain temperature of the heated purified water, the flow rate is set to a ratio of the total flow rate from the start to the end of the treatment to the mass of the sample of 10.

[0135] Heating begins in reactor 3 and the heater built into furnace 2. If the temperature of reactor 3 and furnace 2 reaches 325°C, reactor 4 is placed inside reactor 3. An operating valve switches the purified water flow path so that purified water flowing from furnace 2 passes through reactor 4. Specifically, in this flow path, purified water passes through pump 1, furnace 2, reactor 4, cooling unit 5, and back pressure valve 6. Additionally, an operating valve adjusts the pressure to convert the purified water to subcritical water.

[0136] The process begins when the temperature inside reactor 4 reaches 325°C, and purified water is continuously circulated for 30 minutes. The purified water flowing through reactor 4 is then discharged outside the system via cooling unit 5. This discharged purified water is continuously collected for 30 minutes. The discharged purified water becomes turbid. After stopping pump 1, reactor 4 is removed from reactor 3 and immersed in cold water for rapid cooling, thus ending the process.

[0137] The turbid purified water was filtered, the solids were recovered, and the recovery rate was calculated. Additionally, the solids inside reactor 4 were recovered, and the recovery rate was calculated.

[0138] The recovered solids were identified by infrared spectroscopy (ATR). The results showed that the solid recovered from the turbid purified water was polyamide 6 resin, and the solid recovered from reactor 4 was polyethylene resin.

[0139] The number average molecular weight of the recovered polyamide 6 resin was 2399.

[0140] [Example 2]

[0141] The process begins when the temperature inside reactor 4 reaches 280°C. Otherwise, the same operation as in Example 1 is performed.

[0142] The recovered solids were identified by infrared spectroscopy (ATR). The results showed that the solid recovered from the turbid purified water was polyamide 6 resin, and the solid recovered from reactor 4 was polyethylene resin.

[0143] The number average molecular weight of the recovered polyamide 6 resin was 2625.

[0144] [Reference Example 1]

[0145] As a sample, 10g of polyamide 6 resin granules (number average molecular weight 14644) was used to replace the 10g of pulverized material of "multilayer film (polyamide content 25% by mass) formed by laminating polyamide 6 resin layer, polyethylene (LDPE) resin layer and adhesive layer". Otherwise, the same operation as in Example 1 was performed.

[0146] The turbid purified water was filtered, the solids were recovered, and the recovery rate was calculated.

[0147] The recovered solids were identified by infrared spectroscopy (ATR). The results showed that the solids recovered from the turbid purified water were polyamide 6 resin.

[0148] The number average molecular weight of the recovered polyamide 6 resin was 2420.

[0149] The results are shown in Table 1.

[0150] [Refer to Examples 2 and 3]

[0151] Internal volume 10cm 3 0.3 g of polyamide 6 resin granules (product name: UBE Nylon 1030B) and 3 cm of water were introduced into a stainless steel reaction tube as a sample. 3The reaction tube was then sealed. It was immersed in a molten salt bath, and subcritical water was prepared at the treatment temperatures listed in Table 1. The granules were then brought into contact with the subcritical water at these temperatures and for the treatment times listed in Table 1. After contact treatment with the subcritical water, the reaction tube was water-cooled, and the treated material was recovered. The treated water was filtered, solids were recovered, and the recovery rate was calculated.

[0152] The recovered solids were identified by infrared spectroscopy (ATR). The results showed that the recovered solids were polyamide 6 resin.

[0153] The results are shown in Table 1.

[0154] [Reference Example 4]

[0155] As a sample, 0.3g of polyethylene terephthalate granules (product name: Bellpet PBK1) was used instead of 0.3g of "polyamide 6 resin granules". The granules were brought into contact with subcritical water at the treatment temperature and treatment time recorded in Table 2. Otherwise, the same operation as in Reference Examples 2 and 3 was performed.

[0156] The recovered solid was identified by infrared spectroscopy (ATR). The results showed that the recovered solid was polyethylene terephthalate.

[0157] The results are shown in Table 2.

[0158] [Refer to Examples 5 and 6]

[0159] As a sample, 0.3g of polyethylene granules (LDPE) (product name: UBE polyethylene F222NH, number average molecular weight 35238) was used instead of 0.3g of "polyamide 6 resin layer granules". The granules were brought into contact with subcritical water at the treatment temperature and treatment time recorded in Table 3. Otherwise, the same operation as in Reference Examples 2 and 3 was performed.

[0160] The recovered solids were identified by infrared spectroscopy (ATR). The results showed that the recovered solids were polyethylene resin.

[0161] The results are shown in Table 3.

[0162] <Calculation of recovery rate of hydrolyzed or non-hydrolyzed resins>

[0163] The resin recovery rate is calculated using the following formula. The unit of resin quantity is mass.

[0164] Recovery rate (%) = Amount of hydrolyzed resin recovered / Amount of hydrolyzed resin in the sample before treatment

[0165] Recovery rate (%) = Amount of non-hydrolyzable resin recovered / Amount of non-hydrolyzable resin in the sample before treatment

[0166] <Determination of the average molecular weight of hydrolyzed polyamide 6 resin>

[0167] For the recovered solid hydrolyzed resin polyamide 6, GPC determination was performed using the following method and conditions to determine the number-average molecular weight Mn2. Similarly, the number-average molecular weight Mn1 of the hydrolyzed resin before treatment was also determined.

[0168] (Determination of number-average molecular weight (GPC))

[0169] GPC device: HLC-8220GPC (manufactured by Tosoh Corporation, detector: RI)

[0170] Columns: Shodex HFIP-LG+HFIP-806M × 2

[0171] Elution buffer: HFIP + 10mM CF3COONa

[0172] Flow rate: 0.8 mL / min

[0173] Column temperature: 40℃

[0174] Sample concentration: 0.05 wt / vol%

[0175] <Determination of the average molecular weight of hydrolyzable polyethylene terephthalate resin>

[0176] The recovered solid hydrolyzed resin was subjected to NMR analysis using the following methods and conditions to determine the number-average molecular weight Mn2. Similarly, the number-average molecular weight Mn1 before treatment was also determined.

[0177] (Determination of number-average molecular weight (NMR))

[0178] NMR apparatus: AL400 manufactured by NEC (Japan Electronics Corporation)

[0179] (1) Quantitative analysis of hydroxyl terminus

[0180] Weigh 30 mg of the sample and dissolve it in 1.0 ml of CDCl3 / HFIP = 1 / 1 (v / v). 1 H-NMR determination.

[0181] (2) Acid-terminal quantification

[0182] Weigh 30 mg of the sample and dissolve it together with 4 mg of triethylamine in 1.0 ml of CDCl3 / HFIP = 1 / 1 (v / v). 1 H-NMR determination.

[0183] The number-average molecular weight is calculated using the following formula. It should be noted that isophthalic acid and diethylene glycol are also present, but they are not included in the calculation due to their trace amounts.

[0184] [Mathematical Expression 1]

[0185]

[0186] <Determination of the average molecular weight of non-hydrolyzable resins>

[0187] For the recovered solid non-hydrolyzable resin, GPC determination was performed using the following method and conditions to determine the number-average molecular weight Mn4. Similarly, the number-average molecular weight Mn3 of the untreated non-hydrolyzable resin was also determined.

[0188] (Determination of number-average molecular weight (GPC))

[0189] High-temperature GPC device: HLC-8321GPC / HT (manufactured by Tosoh Corporation, detector: RI)

[0190] Column: TSKgel guardcolumnHHR(S)+TSKgelGMHHR-H(S)HT×2 columns

[0191] Eluent: o-dichlorobenzene

[0192] Flow rate: 1.0 mL / min

[0193] Column temperature: 145℃

[0194] Sample concentration: 0.1 wt / vol%

[0195] <Calculation of Molecular Weight Retention Rate of Recycled Hydrolyzed Resin>

[0196] The ratio of the number-average molecular weight Mn2 of the recovered hydrolyzed resin to the number-average molecular weight Mn1 of the untreated hydrolyzed resin ([Mn2 / Mn1]×100(%)) was calculated and is shown in Tables 1 and 2.

[0197] <Calculation of Molecular Weight Retention Rate of Recycled Non-Hydrolyzable Resins>

[0198] The ratio of the number average molecular weight Mn4 of the recovered non-hydrolyzable resin to the number average molecular weight Mn3 of the untreated non-hydrolyzable resin ([Mn4 / Mn3]×100(%)) was calculated and is shown in Tables 1 and 3.

[0199] [Table 1]

[0200]

[0201] As shown in Examples 1 and 2, non-hydrolyzable resins were recovered with high molecular weight retention, and hydrolyzable resins were also recovered as resins that can be recycled. Compared with Example 1, which had a processing temperature of 325°C, Example 2, with a processing temperature of 280°C, showed higher recovery rates and molecular weight retention rates for polyethylene resin and polyamide resin.

[0202] As can be seen from Reference Example 1, even when using granules composed solely of hydrolyzable resin, the same molecular weight retention and recovery rate are observed as when using a composite.

[0203] As can be seen from Reference Examples 2 and 3, in the case of polyamide resin, the recovery rate and molecular weight retention rate of the hydrolyzable resin at a treatment temperature of 280°C are significantly higher than those in Reference Example 1. Particularly in Reference Example 3, where the treatment time was 5 minutes, the recovery rate exceeded 90%, and the molecular weight retention rate was also high. From these results, it can be understood that when the composite used in Example 2 is treated at 280°C for 5 minutes, the recovery rate is approximately 90%, and the molecular weight retention rate is approximately 40%.

[0204] [Table 2]

[0205]

[0206] As can be seen from Reference Example 4, when polyethylene terephthalate (PET), which is a hydrolyzable resin, is treated alone with subcritical water, PET can be recovered with a high recovery rate. It is understood that even when treating a composite containing PET and a non-hydrolyzable resin, PET can be recovered with the same high recovery rate as in the Reference Example.

[0207] [Table 3]

[0208]

[0209] As can be seen from Reference Examples 5 and 6, even when the non-hydrolyzable resin is treated alone with subcritical water, the recovery rate and molecular weight retention rate are extremely high. Based on the results of Reference Example 5, it is conceivable that, even when treating a composite containing hydrolyzable resin and polyethylene resin as in Example 2 at a treatment temperature of 280°C, if a longer treatment period of 60 minutes (longer than Example 2) is applied, the molecular weight retention rate of the polyethylene resin will also increase compared to Example 2. Based on the results of Reference Example 6, it is conceivable that, even when treating a composite containing hydrolyzable resin and polyethylene resin as in Example 1 at a treatment temperature of 325°C, if a longer treatment period of 60 minutes (longer than Example 1) is applied, the recovery rate and molecular weight retention rate of the polyethylene resin will not increase compared to Example 1.

[0210] Industrial availability

[0211] The resin recycling method of the present invention can recycle both non-hydrolyzable and hydrolyzable resins as resins, and is therefore useful for recycling non-hydrolyzable and hydrolyzable resins contained in waste plastics as raw materials for material recycling.

[0212] Explanation of reference numerals in the attached figures

[0213] 1 pump

[0214] 2 Heating Furnace

[0215] 3. Reactor

[0216] 4. Reactor

[0217] 5 Cooling Units

[0218] 5' cooling unit

[0219] 6. Back pressure valve.

Claims

1. A resin recovery method, comprising recovering resin from a composite containing a layer (A) of non-hydrolyzable resin (a1) and a layer (B) of hydrolyzable resin (b1). The method includes step (1): contacting the composite with a subcritical fluid to decompose and / or separate layer (A) and layer (B) to obtain a solid resin (A) composed of a non-hydrolyzable resin (a2) and a solid resin (B) composed of a hydrolyzable resin (b2). The non-hydrolyzable resin (a1) is the same as the non-hydrolyzable resin (a2), or only differs in molecular weight distribution. The hydrolyzable resin (b1) is the same as the hydrolyzable resin (b2), or only differs in molecular weight distribution.

2. The resin recycling method according to claim 1, further comprising a recycling step (2): separating and recycling the solid resin (A) and the solid resin (B) obtained in step (1) by passing them through a filter.

3. The resin recycling method according to claim 1 further includes a recycling step (2): separating and recycling the solid resin (A) and the solid resin (B) obtained in step (1) by means of the difference in specific gravity between the solid resin (A) and the solid resin (B).

4. The resin recycling method according to claim 1, wherein, When the number average molecular weight of hydrolyzable resin (b1) is set as Mn1 and the number average molecular weight of hydrolyzable resin (b2) is set as Mn2, the ratio of Mn2 to Mn1, i.e., Mn2 / Mn1, is 0.15 or higher, and Mn2 is 2300 or higher.

5. The resin recycling method according to claim 1, wherein, In the process (1), the composite is brought into contact with the subcritical fluid for 1 to 60 minutes.

6. The resin recycling method according to claim 1, wherein, The non-hydrolyzable resins (a1) and (a2) are polyolefin resins.

7. The resin recycling method according to claim 1, wherein, The hydrolyzable resins (b1) and (b2) are polyamide resins or polyester resins.

8. The resin recycling method according to claim 1, wherein, The composite is made of waste plastic.

9. A resin recycling method, comprising recovering resin from a molded body containing hydrolyzable resin (b1). The method includes a step of contacting the molded body with a subcritical fluid to obtain a solid resin (B) composed of a hydrolyzable resin (b2). The hydrolyzable resin (b1) is the same as the hydrolyzable resin (b2) or has a different molecular weight distribution.

10. A material recycling product comprising, in its raw materials, the non-hydrolyzable resin (a2) recovered by the resin recycling method according to any one of claims 1 to 8.

11. A material recycling product comprising, in its raw materials, the hydrolyzable resin (b2) recovered by the resin recycling method according to any one of claims 1 to 9.

12. A method for manufacturing recycled materials, wherein, The non-hydrolyzable resin (a2) recovered by the resin recovery method according to any one of claims 1 to 8 is used as a raw material for material recycling.

13. A method for manufacturing recycled materials, wherein, The hydrolyzable resin (b2) recovered by the resin recovery method according to any one of claims 1 to 9 is used as a raw material for material recycling.

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