Recycling method of resin composition

Abstract

To provide a recycling method of a resin composition which reduces a production amount of a nitrogen atom-containing compound, in decomposition oil obtained by decomposing a waste polyolefin resin containing an acrylonitrile-based polymer.SOLUTION: A recycling method of a resin composition includes a decomposition treatment step of decomposing a resin composition containing a polyolefin-based polymer and an acrylonitrile-based polymer, in the presence of an acidic compound or an acid donor compound, and obtaining decomposition oil, and a separation step of obtaining two or more fractions having different boiling points, from the obtained decomposition oil, wherein the method includes a control step of controlling a content ratio of the acidic compound or the acid doner compound in the resin composition in the decomposition treatment step, using an arbitrary analysis value of a process liquid after the separation step.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for recycling a resin composition. More specifically, the present invention relates to a method for recycling a resin composition, which comprises subjecting a resin composition containing a polyolefin polymer and an acrylonitrile polymer to a decomposition treatment to obtain a decomposition oil, and then obtaining a desired fraction from the obtained decomposition oil by a distillation purification method or the like. [Background technology]

[0002] Polyolefin polymers such as high-density polyethylene (HDPE) and polypropylene (PP) are widely used in a variety of applications, including automobiles, home appliances, daily necessities, and containers, due to their excellent flexibility, impact resistance, chemical resistance, heat resistance, and moldability.

[0003] In addition, acrylonitrile polymers such as acrylonitrile-styrene resin (AS resin), acrylonitrile-ethylene-propylene-diene-styrene resin (AES resin), and acrylonitrile-butadiene-styrene resin (ABS resin) are widely used in home appliances, precision instruments, automotive materials, building materials, housing products, etc. because of their excellent mechanical strength properties, dimensional stability, processability, and colorability.

[0004] In recent years, from the perspectives of environmental protection and sustainability, reprocessing waste plastics, including polyolefin-based polymers and acrylonitrile-based polymers, and reusing them as new products and materials has become an important issue, which is expected to reduce environmental impact and resource waste. Known methods for reprocessing waste plastics include the material recycling method and the chemical recycling method.

[0005] In the material recycling method, thermoplastic resins are heated to soften them and then remolded. Although the material recycling process is generally simple, it is difficult to physically separate different materials such as metals and chlorine-containing compounds, and the resulting remolded products have insufficient physical properties, limiting their uses. On the other hand, chemical recycling involves chemically converting thermoplastic resins back into their raw materials, which are then refined and resynthesized. Chemical recycling processes are generally complex, so the cost of obtaining recycled products is high on a one-time basis, but the physical properties of the recycled products are excellent.

[0006] A method has been reported in which waste polyolefin resin is recovered from containers, packaging materials, molded products, etc. that contain polyolefin polymers such as high-density polyethylene (HDPE) as a primary component, and the recovered waste polyolefin resin is chemically recycled. This method involves reusing the decomposition oil obtained by decomposing the waste polyolefin resin, and the fraction obtained by separating and refining the decomposition oil by distillation, as raw materials for new chemical products.

[0007] As a method for chemically recycling polyolefin resin to obtain decomposition oil, for example, Patent Document 1 discloses a technology in which a polyolefin resin composition is melted and thermally decomposed using a thermal decomposition tank, and the obtained decomposition oil is separated, purified, and reused. Furthermore, Patent Documents 2 and 3 disclose a technique in which a polyolefin resin composition is catalytically pyrolyzed in the presence of a catalyst, and the resulting cracked oil is separated, refined, and reused. Furthermore, Patent Document 4 and Non-Patent Document 1 disclose a technology in which plastic waste, such as waste polyolefin resins such as polyethylene and polypropylene, is hydrothermally decomposed using supercritical water as a reaction medium, and the resulting decomposition oil is separated, refined, and reused. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-154510 [Patent Document 2] Japanese Patent Application Publication No. 9-302358 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-37518 [Patent Document 4] Japanese Patent Application Publication No. 10-67991 [Non-patent literature]

[0009] [Non-Patent Document 1] Environmental Resource Engineering, VOl.52, p5-13(2005) Summary of the Invention [Problem to be solved by the invention]

[0010] However, in the sorting process of waste plastics, due to the limitations of the sorting technology, impurity plastics other than polyolefin-based polymers, for example, plastics containing heteroatoms such as nitrogen, oxygen, and chlorine, such as the above-mentioned acrylonitrile-based polymers, may be mixed in as impurities.If it is difficult to completely remove these contaminated plastics, the waste plastics containing trace amounts of these impurity plastics will be subjected to chemical recycling.

[0011] According to the investigations of the present inventors, when waste polyolefin resin contains acrylonitrile-based polymers, the waste polyolefin resin is decomposed to obtain cracked oil, and the fraction obtained from the resulting cracked oil by distillation purification contains nitrogen-containing compounds that are presumed to be derived from the decomposition products of the acrylonitrile-based polymers.As a result, when the obtained fraction is thermally decomposed (cracking), NOx gum derived from these nitrogen-containing compounds is produced, which accumulates in or blocks the deep-freezing system (chiller system), causing operational problems.

[0012] An object of the present invention is to solve the above-mentioned problems, that is, to provide a method for recycling a resin composition, which comprises subjecting a resin composition containing a polyolefin polymer and an acrylonitrile polymer to a cracking treatment to obtain a cracked oil, and further separating and purifying the obtained cracked oil to obtain a desired fraction, in which the content of nitrogen-containing compounds is reduced. [Means for solving the problem]

[0013] As a result of extensive investigations aimed at solving the above-mentioned problems, the present inventors have found that when a resin composition containing a polyolefin polymer and an acrylonitrile polymer is decomposed in the presence of an acidic compound or an acid donor compound, the content of the acidic compound or acid donor compound in the resin composition in the decomposition treatment step can be controlled within a predetermined range, thereby making it possible to reduce the content of nitrogen-containing compounds in a desired fraction separated and purified from the resulting cracked oil.

[0014] That is, the present invention provides the following.

[0015] [1] A decomposition step in which a resin composition containing a polyolefin polymer and an acrylonitrile polymer is decomposed in the presence of an acidic compound or an acid donor compound to obtain a decomposed oil; A method for recycling a resin composition, comprising a separation step of obtaining two or more fractions having different boiling points from the obtained cracked oil, A method for recycling a resin composition, comprising a control step of controlling the content ratio of the acidic compound or the acid donor compound in the resin composition in the decomposition treatment step using any analytical value of the process solution in the separation step or later.

[0016] [2] The method for recycling a resin composition according to [1], wherein the two or more fractions having different boiling points in the separation step include a hydrocarbon-containing composition (1) mainly composed of hydrocarbon compounds having a boiling point at atmospheric pressure of 25°C or more and 210°C or less, and a hydrocarbon-containing composition (2) mainly composed of hydrocarbon compounds having a boiling point at atmospheric pressure of more than 210°C and 480°C or less.

[0017] [3] The method for recycling a resin composition according to [2], wherein the process liquid is the hydrocarbon-containing composition (1) or the hydrocarbon-containing composition (2).

[0018] [4] The method for recycling a resin composition according to [3], wherein an arbitrary analytical value of the process liquid is the total content of nitrogen atoms contained in the hydrocarbon-containing composition (1) or the hydrocarbon-containing composition (2).

[0019] [5] The method for recycling a resin composition according to any one of [1] to [4], wherein the decomposition treatment in the decomposition treatment step comprises thermally decomposing the resin composition in a molten state at a decomposition treatment pressure in the range of -0.1 MPaG or more and 10 MPaG or less.

[0020] [6] The decomposition treatment step includes decomposing the resin composition in a molten state by acting a supercritical fluid or a subcritical fluid on the resin composition, The method for recycling a resin composition according to any one of [1] to [4], wherein the control step includes controlling the pH of the supercritical fluid or near-supercritical fluid in the decomposition treatment step within a predetermined range using any analytical value of the process solution.

[0021] [7] The method for recycling a resin composition according to [6], wherein the pH is controlled to be within a range of 5 to 8 in the controlling step.

[0022] [8] The method for recycling a resin composition according to [6] or [7], comprising controlling the pH in the decomposition treatment step so that the total content of nitrogen atoms contained in the hydrocarbon-containing composition (1) or the hydrocarbon-containing composition (2) is equal to or less than a predetermined value.

[0023] [9] The method for recycling a resin composition according to [8], wherein the predetermined value is 40 ppm by mass.

[0024]

[10] The method for recycling a resin composition according to any one of [4] to [9], wherein the nitrogen atoms are at least nitrogen atoms contained in a decomposition product of the acrylonitrile polymer.

[0025]

[11] The method for recycling a resin composition according to any one of [1] to

[10] , wherein the acid donor compound is at least one selected from polyvinyl chloride, polyvinylidene chloride, and polyethylene terephthalate.

[0026]

[12] The method for recycling a resin composition according to any one of [1] to

[11] , wherein the acidic compound is at least one selected from inorganic acids and organic acids.

[0027]

[13] The method for recycling a resin composition according to any one of [1] to

[12] , wherein the polyolefin polymer is at least one selected from a polyethylene polymer and a polypropylene polymer.

[0028]

[14] The method for recycling a resin composition according to any one of [1] to

[13] , wherein the resin composition contains 60.0% by mass or more and 99.9% by mass or less of the polyolefin-based polymer and 0.1% by mass or more and 40.0% by mass or less of the acrylonitrile-based polymer, relative to 100% by mass of the total mass of the resin composition.

[0029]

[15] The method for recycling a resin composition according to any one of [1] to

[14] , wherein the resin composition is decomposed in the presence of 0.01 to 10.0 parts by mass of the acidic compound or the acid donor compound relative to 100 parts by mass of the resin composition. [Effects of the Invention]

[0030] According to the present invention, a resin composition containing a polyolefin polymer and an acrylonitrile polymer is cracked to obtain a cracked oil, and the cracked oil is then separated and purified to obtain a desired fraction, and the content of nitrogen-containing compounds in the fraction can be reduced. As a result, the product quality of the obtained fraction can be improved, and the above-mentioned problems can be solved. Furthermore, since the content of nitrogen-containing compounds in wastewater generated in the process of obtaining the cracked oil can be reduced, the load on the wastewater treatment process when the wastewater is decomposed using a known wastewater treatment method such as a chemical treatment method such as a coagulation sedimentation method or an activated sludge method can be reduced. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention will be described in detail below, but the present invention is not limited to the following description and can be practiced with any modifications within the scope of the gist of the present invention.

[0032] Unless otherwise specified, in this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits, and "A to B" means A or more and B or less. In this specification, "A or B" means "A," "B," and "A and B," unless otherwise specified. For example, "including A or B" means "including A," "including B," and "including A and B," unless otherwise specified. In this specification, "mass %" refers to the content ratio of a specified component contained in a total amount of 100 mass %, and "mass %" refers to the content ratio of a specified component contained in a total amount of 100 mass %. "mass %" and "weight %" have the same meaning. "Optional" or "optionally" means that the subsequently described circumstance may or may not occur, and thus the description includes both the occurrence and non-occurrence of the circumstance. All steps described herein can be performed in any suitable order unless otherwise stated herein or clearly contradicted by context.

[0033] <Method for Reusing Resin Composition> The method for recycling a resin composition of the present invention includes a cracking process in which a resin composition containing a polyolefin-based polymer described below and an acrylonitrile-based polymer described below (hereinafter referred to as the "resin composition of the present invention") is cracked in the presence of an acidic compound or an acid donor compound (hereinafter referred to as the "acidic compound, etc.") described below to obtain cracked oil, and a separation process in which two or more fractions having different boiling points described below are obtained from the obtained cracked oil. Furthermore, the method for recycling a resin composition of the present invention includes a control step of controlling the content ratio of the acidic compounds, etc. in the resin composition in the decomposition treatment step using any analytical value of the process liquid after the separation step.

[0034] In the decomposition treatment, the resin composition of the present invention is decomposed preferably in a molten state, so that the polyolefin-based polymer contained in the resin composition can be decomposed into its constituent raw materials, such as olefins, and the acrylonitrile-based polymer can be decomposed into its constituent raw materials, such as lactams.

[0035] The embodiment of the "decomposition treatment" in the present invention is not particularly limited as long as it is a method that can decompose the resin composition in the present invention, preferably in a molten state, to obtain a decomposed oil. For example, known thermal decomposition treatments, known decomposition treatments using supercritical fluids or subcritical fluids such as hydrothermal decomposition treatments, and known catalytic pyrolysis treatments can be used.

[0036] The "cracked oil" refers to an oil or oily substance obtained by cracking the resin composition of the present invention. The "cracked oil" can contain, in addition to the hydrocarbon-containing composition (1) and the hydrocarbon-containing composition (2) described below, non-volatile heavy components generated by polymerization or the like during the cracking process, and residues containing metal components derived from additives to the resin composition of the present invention. The hydrocarbon-containing composition (1) and the hydrocarbon-containing composition (2) (hereinafter referred to as "hydrocarbon-containing composition (1) or (2)") can be reused as polymerization raw materials for new polyolefin polymers. On the other hand, the residues contain a large amount of impurities and have no application as products, so they are generally discarded.

[0037] The term "thermal decomposition treatment" refers to a thermochemical decomposition treatment of organic substances under the influence of temperature alone under conditions that are substantially free of oxygen and do not supply oxygen from the outside. The pressure in the thermal cracking treatment is usually in the range of -0.1 to 10 MPaG (gauge pressure), preferably in the range of -0.05 to 1.0 MPa, as this provides excellent operability and a good color for the resulting cracked oil. Furthermore, those skilled in the art can appropriately optimize the thermal cracking treatment temperature, residence time in the thermal cracking treatment device, type of thermal cracking treatment device, and the like, and perform the thermal cracking treatment.

[0038] The apparatus for carrying out the pyrolysis treatment is not particularly limited, and known pyrolysis treatment apparatuses can be used. Examples of known pyrolysis treatment apparatuses include single- or twin-screw extruder-type reactors; kiln-type reactors such as gas-heated kilns and electrically heated kilns; agitator-equipped tank-type reactors; tank-type reactors; tubular reactors; fluidized-bed reactors; and fixed-bed reactors. Among these, twin-screw extruder-type reactors and kiln-type reactors are preferred due to their excellent productivity. Furthermore, steam, thermal oil / gas, electricity, microwaves, combustion gas, and the like can be used as heat sources.

[0039] The "decomposition treatment using a supercritical fluid or a subcritical fluid" refers to a thermochemical decomposition treatment of organic substances by utilizing the high reactivity of a supercritical fluid that is neither liquid nor gaseous, or a subcritical fluid close to a supercritical state, which is obtained by adjusting the temperature and pressure. When water is used as the fluid, thermal decomposition (hydrothermal decomposition) occurs in the presence of water. Specifically, when water is used, the temperature and pressure are controlled, and the water is heated to preferably 100 to 700°C, more preferably 150 to 500°C, to perform hydrothermal decomposition treatment by utilizing the high reactivity of supercritical water or subcritical water.

[0040] The term "supercritical fluid" refers to a state in which a solvent such as methanol or water, or a gas such as CO2, is at a temperature and pressure higher than its critical point, and is a fluid whose density is higher than that of a normal gas and whose molecular momentum is similar to that of a gas. The "subcritical fluid" is a fluid in which a solvent such as methanol or water, or a gas such as CO2, is in a temperature range near the critical point but lower than the critical temperature, and its reactivity is similar to that of a supercritical fluid. As the supercritical fluid or sub-supercritical fluid, it is preferable to use water in a supercritical state or a sub-critical state from the viewpoint of economic efficiency and the efficiency of the decomposition treatment. The definitions of "supercritical state" and "subcritical state" are the same as the definitions of "supercritical fluid" and "subcritical fluid" described above, respectively.

[0041] The term "catalytic pyrolysis" refers to the thermochemical decomposition of organic substances in the presence of a known pyrolysis catalyst under conditions that are substantially oxygen-free and without external oxygen supply, at a high temperature range, under the influence of the pyrolysis catalyst and temperature. Specifically, examples include a method in which waste plastics are melted and pyrolyzed using a known heating means such as an extruder, and the resulting melt or vapor, or both, are brought into contact with a pyrolysis catalyst to lighten the waste plastics. Examples of the thermal decomposition catalyst include inorganic solid acid oxide particles such as silica-alumina, silica-titania, silica-zirconia, alumina-magnesia, alumina-zirconia, alumina-titania, bentonite, kaolinite, and zeolite.

[0042] The "two or more fractions having different boiling points" can include a hydrocarbon-containing composition (1) whose main component is a hydrocarbon-based compound whose boiling point at atmospheric pressure is 25°C or more and 210°C or less, and a hydrocarbon-containing composition (2) whose main component is a hydrocarbon-based compound whose boiling point at atmospheric pressure is more than 210°C and 480°C or less. The phrase "mainly composed of" means that the hydrocarbon-containing composition (1) or (2) contains the above-mentioned hydrocarbon compound in an amount of 50 mass % or more, preferably 60 mass % or more, and more preferably 70 mass % based on the total mass of the hydrocarbon-containing composition. The hydrocarbon-containing composition (1) refers to a hydrocarbon-containing composition primarily composed of hydrocarbon compounds having a boiling point of 25°C to 210°C under atmospheric pressure, among the components contained in the pyrolysis oil. Examples of the hydrocarbon compounds include one or more saturated and unsaturated hydrocarbons having 4 to 12 carbon atoms. Specific examples include compounds containing normal paraffins, isoparaffins, olefins, aromatics, and naphthenes. The hydrocarbon compounds may contain oxygen, nitrogen, and chlorine atoms in their molecules. The hydrocarbon-containing composition (2) refers to a hydrocarbon-containing composition primarily composed of hydrocarbon compounds having a boiling point of more than 210°C and not more than 480°C under atmospheric pressure, among the components contained in the pyrolysis oil. Examples of the hydrocarbon compounds include one or more saturated and unsaturated hydrocarbons having 13 to 33 carbon atoms. Specific examples include compounds containing normal paraffins, isoparaffins, olefins, aromatics, and naphthenes. The hydrocarbon compounds may contain oxygen, nitrogen, and chlorine atoms in their molecules.

[0043] The method for recycling a resin composition of the present invention includes a control step of controlling the content ratio of acidic compounds and the like in the resin composition in the decomposition treatment step within a predetermined range using any analytical value of the process liquid obtained in the separation step and thereafter. By including this control step, the quality of the hydrocarbon-containing composition (1) or the hydrocarbon-containing composition (2), for example, the content of nitrogen-containing compounds in the hydrocarbon-containing composition (1) or the hydrocarbon-containing composition (2), can be efficiently controlled and reduced.

[0044] In the present invention, the "nitrogen atom" mainly refers to a nitrogen atom contained in a decomposition product of the acrylonitrile polymer and / or a compound derived from the decomposition product, and specifically, The term "nitrogen atom" refers to a nitrogen atom contained in a decomposition product of a nitrile compound that is a raw material for an acrylonitrile polymer and / or a nitrile compound, a nitrogen-containing heterocyclic compound, or ammonia that is presumed to be derived from the decomposition product. The "nitrogen atom" also includes nitrogen atoms contained in compounds other than the above-mentioned compounds, such as additives that are already contained in the resin composition and the acidic compound containing a nitrogen atom.

[0045] The process liquid is a process liquid from the separation step onward, and is not particularly limited as long as its composition and properties are related to the content of nitrogen-atom-containing compounds in the hydrocarbon-containing composition (1) or (2). For example, the obtained hydrocarbon-containing composition (1) or (2) itself, a purified product obtained by purifying the hydrocarbon-containing composition (1) or (2) using a known separation and purification means such as distillation, liquid-liquid separation, crystallization, or the like, or the process wastewater generated during the purification can be used. In this way, by using the analytical values ​​of the process liquid from the separation step onward, the content ratio of acidic compounds, etc. in the resin composition in the decomposition treatment step can be controlled within a predetermined range, and the amount of nitrogen-atom-containing compounds produced in the obtained hydrocarbon-containing composition (1) or (2) can be more efficiently controlled and reduced.

[0046] Furthermore, the arbitrary analytical value of the process solution is not particularly limited as long as it is related to the content of nitrogen-containing compounds in the hydrocarbon-containing composition (1) or (2). For example, the total content of nitrogen atoms contained in the resulting hydrocarbon-containing composition (1) or (2) or the purity and quality of a purified product obtained by purifying the hydrocarbon-containing composition (1) or (2) can be used. Furthermore, information on the type and content ratio of residual specific compounds in treated wastewater obtained by subjecting the above-mentioned process wastewater to activated sludge treatment can also be used as the arbitrary analytical value of the process solution. This makes it possible to more efficiently control and reduce the formation of nitrogen-containing compounds in the resulting hydrocarbon-containing composition (1) or (2).

[0047] In the decomposition step, as one embodiment for decomposing the resin composition in a molten state, a decomposition treatment using a known supercritical fluid or subcritical fluid can be used. In this case, in the control step, the pH of the supercritical fluid or subcritical fluid can be controlled within a predetermined range using any analytical value of the process liquid after the separation step. By controlling the pH to be within the predetermined range, the content ratio of the acidic compound, etc. in the resin composition in the decomposition step can be controlled within the predetermined range. In this case, the pH range of the supercritical fluid or subcritical fluid is not particularly limited as long as the content of nitrogen-containing compounds contained in the two or more fractions with different boiling points, specifically the hydrocarbon-containing composition (1) or (2), can be controlled to a predetermined value or less. For example, it can be controlled to a pH range of 5 to 8. The lower limit of the pH is not particularly limited, and from the viewpoint of efficiently controlling and reducing the production of nitrogen-containing compounds in the resulting cracked oil, a pH of 5 or more is preferred, a pH of 5.5 or more is more preferred, and a pH of 6 or more is even more preferred. On the other hand, the upper limit of the pH is not particularly limited, and, similar to the lower limit, from the viewpoint of efficiently controlling and reducing the production of nitrogen-containing compounds in the resulting cracked oil, a pH of 8 or less is preferred, a pH of 7.8 or less is more preferred, and a pH of 7.5 or less is even more preferred. The above upper and lower limits can be combined arbitrarily.

[0048] A specific method for controlling the pH within a predetermined range is to adjust the total content of the acidic compounds and the like in the supercritical fluid or the sub-supercritical fluid.

[0049] According to the investigations of the present inventors, it is presumed that the nitrogen-containing compounds contained in the hydrocarbon-containing composition (1) or (2) of the present invention are derived from decomposition products of acrylonitrile polymers. The present inventors have found that the generation of nitrogen-containing compounds in the hydrocarbon-containing composition (1) or (2) of the present invention can be efficiently suppressed by decomposing the resin composition in the presence of an acidic compound or the like.

[0050] When the hydrocarbon-containing composition (1) or (2) of the present invention contains a nitrogen atom-containing compound, the following problems arise. This nitrogen atom-containing compound is mixed into the lower olefin products such as propylene obtained by thermal decomposition (cracking) of the hydrocarbon-containing composition (1) or (2), and reduces the performance of the catalyst used to polymerize the lower olefins such as propylene. Even if the nitrogen-containing compounds are removed from the hydrocarbon-containing composition (1) or (2), the removed nitrogen-containing compounds are contained in the aqueous waste liquid, and this aqueous waste liquid must be decomposed using known wastewater treatment methods such as chemical treatment methods such as coagulation sedimentation or activated sludge methods, which increases the load on the wastewater treatment process. However, according to the method for recycling a resin composition of the present invention, it is possible to solve the above-mentioned problems.

[0051] In the method for recycling a resin composition according to the present invention, one embodiment of the decomposition treatment includes a method in which a resin composition containing the polyolefin-based polymer and the acrylonitrile-based polymer and the acidic compound are melt-mixed and then decomposed.

[0052] In another embodiment of the decomposition treatment in the method for recycling a resin composition of the present invention, the content of acidic compounds and the like in the resin composition is controlled in the decomposition treatment step so that the nitrogen atom content (hereinafter referred to as "nitrogen atom content") in the resulting hydrocarbon-containing composition (1) or (2) is equal to or less than a predetermined value. This solves the above-mentioned problems that occur when the hydrocarbon-containing composition (1) or (2) is thermally decomposed (cracking).

[0053] The predetermined value of the nitrogen atom content is not particularly limited, and is generally preferably 40 ppm by mass, more preferably 30 ppm by mass, even more preferably 20 ppm by mass, particularly preferably 10 ppm by mass, and most preferably 5 ppm by mass, relative to the total mass of each of the hydrocarbon-containing compositions (1) and (2). Alternatively, no nitrogen atoms may be contained (nitrogen atom content is 0 ppm by mass). The nitrogen atom content can be analyzed by the method described in the Examples section below.

[0054] As described above, examples of the method for decomposing the resin composition of the present invention include a method for thermally decomposing the resin composition in the presence of an acidic compound or the like, and a method for decomposing the resin composition by allowing a supercritical fluid or a subcritical fluid to act on the resin composition.

[0055] The method for thermally decomposing the resin composition of the present invention in the presence of an acidic compound or the like is not particularly limited, and examples thereof include the following method (1-1) or (1-2). Method (1-1): A method in which an acidic compound or the like is melt-kneaded with the resin composition of the present invention using a known melting means such as a single-screw extruder or a twin-screw extruder, while being decomposed. Method (1-2): A method in which the resin composition of the present invention, the acidic compound, etc. are melt-mixed and decomposed using a known reactor such as a kiln-type reactor, a tank-type reactor, a tubular reactor, a fluidized-bed reactor, or a fixed-bed reactor.

[0056] The method for decomposing the resin composition of the present invention by allowing a supercritical fluid or a subcritical fluid to act on it is not particularly limited, and examples thereof include the following methods (2-1) to (2-3). Method (2-1): A method in which the resin composition of the present invention and the acidic compound, etc. are melt-mixed using a known melting means such as a single-screw extruder or a twin-screw extruder, and then a solvent such as methanol or water or a gas such as CO2 is allowed to act on the resin composition using a reactor for decomposition treatment under high temperature and high pressure at which the solvent or the gas forms a supercritical fluid or subcritical fluid. Method (2-2): A method in which the resin composition of the present invention, the acidic compound, etc., and a solvent such as methanol or water capable of forming a supercritical fluid or a sub-supercritical fluid, or a gas such as CO2, are reacted with the resin composition using a known melt mixing means such as a single-screw extruder or a twin-screw extruder under high temperature and pressure at which the solvent or the gas forms a supercritical fluid or a sub-critical fluid. Method (2-3): A method in which the resin composition of the present invention, the acidic compound, etc., and a solvent such as methanol or water capable of forming a supercritical fluid or a near-supercritical fluid, or a gas such as CO2, are charged into a reactor for decomposition treatment, and then the supercritical fluid or near-supercritical fluid is allowed to act on the resin composition under high temperature and pressure conditions at which the solvent or the gas is brought into a supercritical state or a near-supercritical state.

[0057] In the method (2-1) or (2-3), the reactor used for the decomposition treatment may be either a batch type or a continuous type. The reactor shape may be, for example, a pipe type, a cylindrical vertical type, or a horizontal type. The means for dispersing the resin composition in a molten state in high-temperature, high-pressure water in the present invention is not particularly limited, and examples thereof include static dispersion means using a packing such as a partition or a static mixer, and / or forced dispersion means using an insert that performs a reciprocating or rotating motion, such as an agitator, a mixer, or a reciprocating or rotating motion. These dispersion means may be used singly or in combination.

[0058] Furthermore, one embodiment of the method for decomposition treatment by the action of a supercritical fluid or a subcritical fluid includes a method in which the acidic compound or the like is present in a supercritical fluid or a sub-supercritical fluid so that the nitrogen atom content in the resulting hydrocarbon-containing composition (1) or (2) is a predetermined value or less (referred to as "Embodiment A"). Another embodiment of the method for decomposition treatment by acting with a supercritical fluid or a subcritical fluid is a method in which any analytical value of the process liquid after the separation step is used to control the content ratio of the acidic compound or the like in the resin composition or in the supercritical fluid or sub-supercritical fluid before acting with the resin composition (referred to as "Embodiment B").

[0059] In embodiment A, the amount of the acidic compound, etc. required to make the nitrogen atom content in the resulting hydrocarbon-containing composition (1) or (2) not more than a predetermined value is optimally determined based on the volume and residence time in the reactor, the type and amount of the resin composition of the present invention charged, the reaction temperature of the decomposition treatment, etc. Specifically, depending on the combination of production conditions used in the decomposition treatment, the amount or content ratio of the acidic compound, etc. that makes the nitrogen atom content in the resulting hydrocarbon-containing composition (1) or (2) not more than a predetermined value can be determined experimentally or calculated by simulation.

[0060] On the other hand, in embodiment B, the content ratio of the acidic compound, etc. in the resin composition may be controlled within a predetermined range using any analytical value of the process liquid after the separation step, or the content ratio of the acidic compound, etc. in the resin composition may be controlled within a predetermined range by controlling the content ratio of the acidic compound, etc. in the supercritical fluid or sub-supercritical fluid before mixing with the resin composition. The method for controlling the content ratio of the acidic compound and the like is not particularly limited, and can be appropriately selected by a person skilled in the art in this field according to well-known techniques. For example, there can be mentioned methods for controlling the internal volume and residence time in the reactor, the type and charged amount of the resin composition of the present invention, the reaction temperature of the decomposition treatment, etc.

[0061] In the method for recycling a resin composition of the present invention, the lower limit of the specific amount of the acidic compound or the like to be added is not particularly limited, but is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, even more preferably 0.5 part by mass or more, and particularly preferably 1.0 part by mass or more, relative to 100 parts by mass of the resin composition of the present invention. On the other hand, the upper limit of the specific blend amount of the acidic compound etc. is not particularly limited, but is preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 3.0 parts by mass or less, and particularly preferably 2.0 parts by mass or less, relative to 100 parts by mass of the resin composition of the present invention. The upper and lower limits can be combined in any combination. For example, in Embodiment A and Embodiment B, the specific amount of the acidic compound or the like is preferably 0.01 parts by mass or more and 10.0 parts by mass or less, more preferably 0.1 parts by mass or more and 5.0 parts by mass or less, even more preferably 0.5 parts by mass or more and 3.0 parts by mass or less, and particularly preferably 1.0 parts by mass or more and 2.0 parts by mass or less, relative to 100 parts by mass of the resin composition of the present invention.

[0062] In the method for recycling a resin composition of the present invention, the upper limit of the nitrogen atom content contained in the resulting hydrocarbon-containing composition (1) or (2) is not particularly limited, but can be preferably 40 ppm by mass or less, based on the total mass of the hydrocarbon-containing composition (1) or (2). This nitrogen atom content is more preferably 30 ppm by mass or less, even more preferably 20 ppm by mass or less, particularly preferably 10 ppm by mass or less, and most preferably 5 ppm by mass or less. On the other hand, the lower limit of the nitrogen atom content contained in the resulting hydrocarbon-containing composition (1) or (2) is not particularly limited, but from the viewpoint of economic efficiency, such as the production cost required to reduce the nitrogen atom content, it can be 1 ppm by mass or more, preferably 2 ppm by mass or more, based on the total mass of the hydrocarbon-containing composition (1) or (2). The above upper and lower limits can be combined arbitrarily. The nitrogen atom content can be analyzed by the method described in the Examples section below.

[0063] The cracked oil obtained by the above-described method for recycling a resin composition of the present invention can be reused as a polymerization raw material for a new polyolefin polymer.

[0064] In the method for recycling a resin composition of the present invention, the reaction temperature for decomposing the resin composition of the present invention varies depending on the types and content ratios of the polyolefin polymer and acrylonitrile polymer contained in the resin composition, but is usually 250°C to 500°C, preferably 250°C to 475°C. If the temperature is lower than 250°C, a long reaction time is required to ensure a high monomer recovery rate, which leads to an increase in the size of the equipment and a decrease in productivity. If the temperature exceeds 500°C, the monomer recovery rate drops significantly. The reaction pressure for decomposition treatment is Pressure at which solvents such as methanol and water, which can form supercritical fluids or near-supercritical fluids, and gases such as CO2, can remain in liquid form. In order to ensure the solubility of the polyolefin polymer and acrylonitrile polymer in the resin composition of the present invention, and the hydrocarbon-containing composition (1) or (2) obtained by decomposing the polyolefin polymer, in a supercritical fluid or a near-supercritical fluid, the density of the supercritical fluid or the near-supercritical fluid is 0.2 g / cm 3 Pressure above The higher the reaction temperature, the higher the pressure required. There is no upper limit on the pressure for decomposition treatment due to the reaction, but from the viewpoint of equipment, a pressure of 50 MPa or less is practical.

[0065] In the method for recycling a resin composition of the present invention, the mass ratio of a solvent such as methanol or water, or a gas such as CO2, capable of forming a supercritical fluid or near-supercritical fluid, to the polyolefin polymer in the resin composition of the present invention, which is supplied to the reactor, is in the range of 0.5 to 20, preferably 1 to 15. The amount of the solvent or gas required for the decomposition treatment of the polyolefin polymer must be sufficient to completely dissolve the hydrocarbon-containing composition (1) or (2) produced by the decomposition treatment. For example, when the polyolefin polymer is polypropylene, a mass ratio of less than 0.5 will result in the production of propylene, a monomer, that cannot be completely dissolved in the supercritical fluid or near-supercritical fluid. On the other hand, a mass ratio exceeding 20 has the advantage of allowing the decomposition treatment to proceed rapidly, but it is undesirable because it leads to an increase in the size of the reactor, high-temperature and high-pressure supercritical fluid or near-supercritical fluid production equipment, wastewater treatment equipment, and the like, and to an increase in the energy required for treatment.

[0066] In the method for recycling a resin composition of the present invention, the optimum residence time in the reactor is determined depending on the type of polyolefin polymer in the resin composition and the reaction temperature. Since the reactor size increases in proportion to the residence time, the residence time is usually 60 minutes or less, but from the viewpoint of the equipment difficulty in adjusting the reaction, the residence time is 1 second or more. From the viewpoint of the yield of the raw material olefin, the residence time is preferably 40 minutes or less and 10 seconds or more, and more preferably 30 minutes or less and 20 seconds or more.

[0067] The hydrocarbon-containing composition (1) or (2) obtained by the method for recycling a resin composition of the present invention can be recovered by passing it through a solid-liquid separation section, where solids or insoluble matters are separated and removed from the aqueous solution after the reaction, as needed, and then reducing the pressure and carrying out conventional separation and purification operations such as crystallization and distillation.

[0068] (Resin composition) The resin composition in the present invention is a resin composition containing a polyolefin polymer described later and an acrylonitrile polymer described later.

[0069] The lower limit of the content of the polyolefin polymer in the resin composition of the present invention is not particularly limited, but can usually be set to 60.0 mass% or more, preferably 70.0 mass% or more, more preferably 80.0 mass% or more, even more preferably 85.0 mass% or more, and particularly preferably 90.0 mass% or more, relative to 100% total mass of the resin composition. On the other hand, the lower limit of the content of the polyolefin polymer is not particularly limited, and from the viewpoint of economic efficiency such as the production cost required to highly purify the resin composition, it can usually be set to 99.9 mass% or less, preferably 99.0 mass% or less, more preferably 98.0 mass% or less, even more preferably 97.5 mass% or less, and particularly preferably 97.0 mass% or less, relative to the total mass of the resin composition. The upper and lower limits can be combined arbitrarily. For example, the content of the polyolefin polymer in the resin composition of the present invention can be 60.0% by mass or more and 99.9% by mass or less, preferably 70.0% by mass or more and 99.0% by mass or less, more preferably 80.0% by mass or more and 98.0% by mass or less, still more preferably 85.0% by mass or more and 97.5% by mass or less, and particularly preferably 90.0% by mass or more and 97.0% by mass or less.

[0070] The lower limit of the content of the acrylonitrile polymer in the resin composition of the present invention is not particularly limited, but can usually be set to 0.1 mass% or more, preferably 0.5 mass% or more, more preferably 1.0 mass% or more, even more preferably 2.0 mass% or more, and particularly preferably 3.0 mass% or more, relative to 100% of the total mass of the resin composition. On the other hand, the lower limit of the content of the acrylonitrile polymer is not particularly limited, and from the viewpoint of economic efficiency such as the production cost required to highly purify the resin composition, it can usually be set to 40.0 mass% or less, preferably 30.0 mass% or less, more preferably 20.0 mass% or less, even more preferably 15.0 mass% or less, and particularly preferably 10.0 mass% or less, relative to the total mass of the resin composition. The upper and lower limits can be combined arbitrarily. For example, the content of the acrylonitrile polymer in the resin composition of the present invention can be 0.1% by mass or more and 40.0% by mass or less, preferably 0.5% by mass or more and 30.0% by mass or less, more preferably 1.0% by mass or more and 20.0% by mass or less, still more preferably 2.0% by mass or more and 15.0% by mass or less, and particularly preferably 3.0% by mass or more and 10.0% by mass or less.

[0071] (Polyolefin polymer) Examples of polyolefin polymers used in the present invention include ethylene resins such as high-density polyethylene, low-density polyethylene, linear very low-density polyethylene, polypropylene (homopolypropylene, block copolymer polypropylene, random copolymer polypropylene, etc.), polybutene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-maleic anhydride copolymer, and ionomer resins (e.g., ethylene-methacrylic acid copolymer ionomer resin, etc.). These may be used alone or as a mixture of two or more. Among the above polyolefin polymers, polyethylene polymers and polypropylene polymers, particularly polyethylene polymers, are preferably used.

[0072] The origin of these polyolefin polymers is not particularly limited, and examples thereof include polyolefin films or polyolefin sheets, such as those used in recycled bottles, transparent packaging such as Saran Wrap, and shopping bags, and polyolefin fibers.

[0073] The shape of these polyolefin-based polymers is not particularly limited, and they may be prepared by pretreatment such as separation from other materials and washing in a conventional manner prior to the decomposition treatment of the present invention, and then into granular, fibrous or flake form. Alternatively, commercially available products may be used as they are, or may be processed into any shape suitable for handling by compression, cutting, crushing or the like and then used.

[0074] (Acrylonitrile polymer) The acrylonitrile polymer used in the present invention is not particularly limited, and known acrylonitrile polymers can be used. Specific examples include acrylonitrile homopolymers and copolymers of acrylonitrile and vinyl monomers, as disclosed in JP-A-2000-302989. Examples of vinyl monomers copolymerizable with acrylonitrile include alkyl acrylates, alkyl methacrylates, acrylic acid, methacrylic acid, methacrylonitrile, acrylamide, vinyl bromide, vinyl fluoride, vinyl acetate, vinylidene bromide, styrene, ethylene, and propylene. However, the vinyl monomers are not particularly limited as long as they are copolymerizable with acrylonitrile, and two or more vinyl monomers can be used in combination. These may be used alone or in combination.

[0075] (acidic compound) The acidic compound used in the present invention is not particularly limited, and at least either an inorganic acid or an organic acid can be used. As the inorganic acid or organic acid, for example, a compound having a carboxylic acid group, a phosphoric acid group, or a sulfonic acid group, or an ester thereof, or other known acidic compound can be appropriately selected and used.

[0076] More specifically, examples of the acidic compound include known Bronsted acids such as hydrochloric acid, nitric acid, boric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid, adipic acid, ascorbic acid, aspartic acid, azelaic acid, adenosine phosphate, benzoic acid, formic acid, valeric acid, citric acid, glycolic acid, glutamic acid, glutaric acid, cinnamic acid, succinic acid, acetic acid, tartaric acid, oxalic acid, p-toluenesulfinic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, nicotinic acid, picolinic acid, phthalic acid, terephthalic acid, propionic acid, benzenesulfinic acid, benzenesulfonic acid, malonic acid, and maleic acid; and esters thereof, as disclosed in JP 2021-161333 A. Among these acidic compounds, phosphorous acid, sulfonic acids, and esters thereof are preferred, and phosphorous acid, p-toluenesulfonic acid, methyl p-toluenesulfonate, and butyl p-toluenesulfonate are more preferred. Among these, at least one selected from hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, and phosphoric acid is preferred. These can be used alone or in combination of two or more.

[0077] (acid donor compound) The acid donor compound used in the present invention is not particularly limited, and may be any compound that generates the above-mentioned acidic compound upon decomposition, specifically at least one selected from polyvinyl chloride, polyvinylidene chloride, and polyethylene terephthalate. Among these, polyvinyl chloride is preferred because it is commercially available at low cost. These can be used alone or in combination of two or more. [Example]

[0078] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these examples.

[0079] [raw materials] The abbreviations for the raw materials used in the following examples and comparative examples are as follows. PE-1: Polyolefin polymer (high-density polyethylene) (product name: Cat. No. 547999, manufactured by Sigma-Aldrich) ABS: acrylonitrile polymer (product name: Denka ABS GR-2000, manufactured by Denka Company Ltd.) PVC-1: Polyvinyl chloride (product name: Cat. No. 8500-30463, manufactured by GL Sciences)

[0080] [Method for measuring nitrogen atom content] The nitrogen atom content in the hydrocarbon-containing composition (1) or (2) obtained in the examples and comparative examples was measured using a gas chromatograph (GC apparatus) (apparatus name: Agilent 6890, manufactured by Agilent; column used: nonpolar column BPX-5 manufactured by SGE, inner diameter 0.32 mm, length 60 m, film thickness 0.25 μm; detector: chemiluminescence nitrogen detector (product name: NCD SIEVERS 255)) according to the following procedure. 1.0 μL of the hydrocarbon-containing composition (1) or (2) obtained in the examples and comparative examples was injected into a GC device, held at 50° C. for 5 minutes, and then heated to 300° C. at a heating rate of 10° C. / min. Based on the peak area of ​​the obtained gas chromatogram, a calibration curve prepared in advance, and a relationship between boiling point and GC retention time prepared in advance, the nitrogen content of each of the components in the boiling range corresponding to hydrocarbon-containing composition (1) (boiling point of 25°C or more and 210°C or less) and the components in the boiling range corresponding to hydrocarbon-containing composition (2) (boiling point of more than 210°C and 480°C or less) was calculated, and the numerical values ​​were evaluated as the nitrogen atom content (unit: mass ppm) relative to the total mass of hydrocarbon-containing composition (1) or (2), respectively. The calibration curve and the relationship between boiling point and GC retention time were prepared using acetonitrile, pyridine, aniline, toluidine, and quinoline as nitrogen-containing compounds with known boiling points.

[0081] [Example 1] A 50 mL batch autoclave was charged with 2.77 g of PE-1 (high-density polyethylene) as a polyolefin polymer, 0.10 g of ABS as an acrylonitrile polymer, 0.033 g of PVC-1 as an acid donor compound, and 33 mL of water. After purging the autoclave with nitrogen, the autoclave was sealed and the temperature inside the autoclave was raised to 450°C using an electric furnace. The internal pressure of the autoclave was then increased to 25 MPa to form supercritical water. The decomposition reaction of the mixture of PE-1, ABS, and PVC-1 in the supercritical water was continued for 25 minutes while maintaining this temperature and pressure. During the decomposition reaction, the pH of the mixture of supercritical water, PE-1, ABS, and PVC-1 in the autoclave was 7.3. During the decomposition reaction, the contents of the autoclave were heated and melted without stirring, and the resulting decomposition products were mixed by natural convection or other means. The reactor was then cooled to room temperature (25°C), and the contents of the autoclave were recovered to obtain cracked oil and an aqueous waste liquid. The nitrogen atom contents in the hydrocarbon-containing composition (1) and the hydrocarbon-containing composition (2) evaluated by the above analytical method were 0.0 ppm by mass and 19.0 ppm by mass, respectively.

[0082] [Comparative Example 1] The reaction was carried out under the same conditions as in Example 1, except that no acidic substance (PVC-1) was used and PE-1 and ABS were used in the proportions shown in Table 1, to obtain cracked oil and aqueous waste liquid. During the cracking reaction, the pH of the supercritical water in the autoclave was 9.4. The obtained cracked oil was evaluated using the same analytical method as in Example 1, and the results are shown in Table 1.

[0083] [Table 1]

[0084] In Example 1, a resin composition containing a polyolefin polymer and an acrylonitrile polymer was decomposed with a supercritical fluid in the presence of an acid donor compound. Therefore, the nitrogen atom content in the hydrocarbon-containing composition (1) and the hydrocarbon-containing composition (2) obtained after the treatment was low, and the content of nitrogen-containing compounds was also low. On the other hand, in Comparative Example 1, a resin composition containing a polyolefin polymer and an acrylonitrile polymer was decomposed with a supercritical fluid without using an acidic compound or the like. Therefore, compared to Example 1, the nitrogen atom content and the nitrogen atom-containing compound content in the hydrocarbon-containing composition (1) and the hydrocarbon-containing composition (2) obtained after the treatment were high.

[0085] From the above results, it can be seen that when a resin composition containing a polyolefin polymer and an acrylonitrile polymer is decomposed to obtain a hydrocarbon-containing composition (1) or (2), the nitrogen atom content in the resulting hydrocarbon-containing composition (1) or (2) can be analyzed, and based on this value, the content of the acidic compounds and the like in the resin composition in the decomposition treatment step can be controlled within a predetermined range, for example, the pH of the supercritical fluid or the near-supercritical fluid in the decomposition treatment step can be controlled within a predetermined range, for example, a pH range of 5 to 8, thereby obtaining a hydrocarbon-containing composition (1) or (2) with a reduced content of nitrogen atom-containing compounds, which can be expected to be reused as a polymerization raw material for a new polyolefin polymer.

Claims

1. a decomposition step of decomposing a resin composition containing a polyolefin polymer and an acrylonitrile polymer in the presence of an acidic compound or an acid donor compound to obtain a decomposed oil; and A method for recycling a resin composition, comprising a separation step of obtaining two or more fractions having different boiling points from the obtained cracked oil, A method for recycling a resin composition, comprising a control step of controlling the content ratio of the acidic compound or the acid donor compound in the resin composition in the decomposition treatment step using any analytical value of the process solution in the separation step or later.

2. 2. The method for recycling a resin composition according to claim 1, wherein the two or more fractions having different boiling points in the separation step include a hydrocarbon-containing composition (1) mainly composed of a hydrocarbon-based compound having a boiling point at atmospheric pressure of 25°C or more and 210°C or less, and a hydrocarbon-containing composition (2) mainly composed of a hydrocarbon-based compound having a boiling point at atmospheric pressure of more than 210°C and 480°C or less.

3. The method for recycling a resin composition according to claim 2, wherein the process liquid is the hydrocarbon-containing composition (1) or the hydrocarbon-containing composition (2).

4. The method for recycling a resin composition according to claim 3, wherein the arbitrary analytical value of the process liquid is the total content of nitrogen atoms contained in the hydrocarbon-containing composition (1) or the hydrocarbon-containing composition (2).

5. The decomposition treatment in the decomposition treatment step includes thermally decomposing the resin composition in a molten state at a decomposition treatment pressure in the range of -0.1 MPaG or more and 10 MPaG or less. The method for recycling a resin composition according to claim 1.

6. the decomposition treatment step includes decomposing the resin composition in a molten state by acting a supercritical fluid or a subcritical fluid on the resin composition, 2. The method for recycling a resin composition according to claim 1, wherein the control step includes controlling the pH of the supercritical fluid or near-supercritical fluid in the decomposition treatment step within a predetermined range using any analytical value of the process solution.

7. The method for recycling a resin composition according to claim 6, wherein the pH is controlled to be within a range of 5 to 8 in the controlling step.

8. 7. The method for recycling a resin composition according to claim 6, further comprising controlling the pH in the decomposition treatment step so that the total content of nitrogen atoms contained in the hydrocarbon-containing composition (1) or the hydrocarbon-containing composition (2) is equal to or less than a predetermined value.

9. The method for recycling a resin composition according to claim 8, wherein the predetermined value is 40 ppm by mass.

10. 5. The method for recycling a resin composition according to claim 4, wherein the nitrogen atoms are at least nitrogen atoms contained in a decomposition product of the acrylonitrile polymer.

11. The method for recycling a resin composition according to claim 1, wherein the acid donor compound is at least one selected from the group consisting of polyvinyl chloride, polyvinylidene chloride, and polyethylene terephthalate.

12. The method for recycling a resin composition according to claim 1 , wherein the acidic compound is at least either an inorganic acid or an organic acid.

13. The method for recycling a resin composition according to any one of claims 1 to 12, wherein the polyolefin polymer is at least one selected from a polyethylene polymer and a polypropylene polymer.

14. The method for recycling a resin composition according to any one of claims 1 to 12, wherein the resin composition contains 60.0 mass% or more and 99.9 mass% or less of the polyolefin-based polymer and 0.1 mass% or more and 40.0 mass% or less of the acrylonitrile-based polymer, relative to 100% of the total mass of the resin composition.

15. The method for recycling a resin composition according to any one of claims 1 to 12, wherein the decomposition treatment is performed in the presence of 0.01 parts by mass or more and 10.0 parts by mass or less of the acidic compound or the acid donor compound relative to 100 parts by mass of the resin composition.

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