Waste plastic raw material, plastic decomposition oil and manufacturing method of plastic decomposition oil

Abstract

To provide a waste plastic raw material capable of reducing organic oxygen-containing components excluding CO and CO2 contained in obtained decomposition oil in chemical recycling of waste polyolefin resin.SOLUTION: A waste plastic raw material to be used for manufacturing plastic decomposition oil contains a polyolefin polymer, and also at least one of an oxygen-containing compound (A) having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring, and an oxygen-containing compound (B) excluding the oxygen-containing compound (A), having a conjugated structure in which an oxygen atom is conjugated with an aromatic ring. The waste plastic raw material is such that: the content ratio of the oxygen-containing compound (A) is 0.40 mass% or less in terms of the oxygen atom bonded to the aromatic ring based on the total mass of the waste plastic raw material; and the content ratio of the oxygen-containing compound (B) is 2.50 mass% or less in terms of the oxygen atom excluding the oxygen atom bonded to the aromatic ring, having the conjugated structure with the aromatic ring.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to waste plastic raw materials, plastic decomposition oil, and a method for producing plastic decomposition oil. [Background technology]

[0002] In recent years, from the perspectives of environmental protection and sustainability, reprocessing waste plastics, including polyolefin polymers such as high-density polyethylene (HDPE) and polypropylene (PP), 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 reusing waste plastics include material recycling and chemical recycling.

[0003] 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.

[0004] 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, and the cost of obtaining recycled products is high on a one-time basis, but the physical properties of the recycled products are superior.

[0005] BACKGROUND ART Known methods for recovering waste polyolefin resin from various molded articles, such as containers and packaging materials, primarily composed of polyolefin polymers such as high-density polyethylene (HDPE), and chemically recycling the recovered waste polyolefin resin include, specifically, methods in which decomposition oil obtained by decomposing polyolefin polymers and fractions separated and purified from the decomposition oil by distillation are reused as raw materials for new chemical products.

[0006] As a method for chemically recycling polyolefin resins to obtain cracked oil, for example, Patent Document 1 discloses a technology in which polyolefin resins are melted and thermally decomposed in a thermal decomposition tank, and the resulting light oil component is reused. Furthermore, Patent Documents 2 and 3 disclose a technique in which a polyolefin resin is catalytically pyrolyzed in the presence of a catalyst, and the resulting cracked oil is purified and reused. Furthermore, Patent Document 4 discloses a technology in which waste polyolefin resins such as polyethylene and polypropylene are hydrothermally decomposed using supercritical water as a reaction medium, and the resulting decomposition oil is purified and reused. Furthermore, Non-Patent Documents 1 and 2 report that when waste materials or biomass materials containing compounds containing oxygen atoms are pyrolyzed to obtain cracked oil, organic oxygen-containing components, CO, and CO are produced. [Prior art documents] [Patent documents]

[0007] [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]

[0008] [Non-Patent Document 1] Japanese J.Multiphase Flow,Vol13(2), p101-108(1999) [Non-patent document 2] Energy Fuels, Vol24, p5686-5695(2010) Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the process of separating waste polyolefin resin for chemical recycling from waste plastics, due to the limitations of the separation technology, the waste may contain additives such as resins containing oxygen atoms in the polymer structure, such as polyethylene terephthalate resins, polyurethane resins, polycarbonate resins, acrylic resins, ABS resins, and polyamide resins, and plasticizers and heat stabilizers containing oxygen atoms in the molecule, such as ether compounds, ester compounds, amide compounds, epoxy compounds, alkoxysilane compounds, phenolic compounds, and phthalic acid compounds, and these additives may not be completely removed. As a result, waste polyolefin resins containing trace amounts of the above-mentioned oxygen-containing compounds, i.e., compounds containing oxygen atoms in their structure, are used for chemical recycling.

[0010] According to the studies of the present inventors, it has been found that the cracked oil obtained from such waste polyolefin resin contains carbon monoxide (CO), carbon dioxide (CO2), and organic oxygen-containing components other than CO and CO2 (hereinafter also referred to as "organic oxygen-containing components"), which are produced by the decomposition of the oxygen-containing compounds, and that some of these organic oxygen-containing components are difficult to remove efficiently. It has also been found that when these unremoved organic oxygen-containing components are contained in the cracked oil, the following problems arise. (1) If the obtained cracked oil contains a large amount of organic oxygen-containing components, these must be removed using known refining reaction conditions such as distillation or crystallization, which increases the burden on the manufacturing process. (2) When the organic oxygen-containing component is methanol, the methanol is contaminated into products such as lower olefins obtained by thermal cracking of the cracked oil, and this methanol reduces the performance of the catalyst used in polymerizing the lower olefins to produce polyolefin polymers. (3) When the organic oxygen-containing component is an organic acid, the organic acid corrodes the thermal decomposition device. (4) When using the steam cracking method, a considerable amount of organic oxygen-containing components is mixed into the process wastewater, which must be decomposed using known wastewater treatment methods such as chemical treatment methods such as coagulation and sedimentation or activated sludge, which increases the load on the wastewater treatment process.

[0011] Therefore, waste plastic raw materials to be subjected to chemical recycling generate CO and / or CO2 during thermal decomposition, but it is required to reduce the above-mentioned organic oxygen-containing components. However, the prior art, Patent Documents 1-4, and Non-Patent Documents 1-2 did not provide detailed information on the relationship between the types of oxygen-containing compounds in waste plastic raw materials and the amounts of CO, CO2, and organic oxygen-containing components produced. Therefore, it was not known whether there was a correlation between the content of oxygen-containing compounds in waste plastic raw materials and the amount of organic oxygen-containing components produced in the resulting cracked oil. In other words, there was no mention of suppressing the production of organic oxygen-containing components in the chemical recycling of waste polyolefin resin containing oxygen-containing compounds, and no technology for producing plastic cracked oil from waste plastic raw materials that produces a low amount of organic oxygen-containing components was previously known.

[0012] The present invention aims to solve these problems. That is, an object of the present invention is to provide a waste plastic raw material that can reduce organic oxygen-containing components other than CO and CO contained in plastic decomposition oil obtained during chemical recycling, for example, chemical recycling of polyolefin polymers containing oxygen-containing compounds. Another object of the present invention is to provide plastic cracked oil with a reduced content of organic oxygen-containing components other than CO and CO2. Another object of the present invention is to provide a method for producing plastic decomposition oil that can reduce the generation of organic oxygen-containing components other than CO and CO2 in the resulting plastic decomposition oil. [Means for solving the problem]

[0013] As a result of extensive research into solving the above-mentioned problems, the inventors have discovered that the above-mentioned problems can be solved by reducing the content of oxygen-containing compounds having specific structures contained in waste plastic raw materials to be subjected to chemical recycling to a threshold value or less.

[0014] That is, the present invention provides the following. [1] Waste plastic raw materials used in the production of plastic decomposition oil, The composition contains a polyolefin polymer, and The composition further comprises at least one of an oxygen-containing compound (A) having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring, and an oxygen-containing compound (B) other than the oxygen-containing compound (A) having a conjugated structure in which an oxygen atom is conjugated with the aromatic ring, A waste plastic raw material, wherein the content of the oxygen-containing compound (A) is 0.40 mass% or less in terms of oxygen atoms bonded to aromatic rings, and the content of the oxygen-containing compound (B) is 2.50 mass% or less in terms of oxygen atoms having a conjugated structure with aromatic rings other than oxygen atoms bonded to aromatic rings, relative to the total mass of the waste plastic raw material. [2] The waste plastic raw material according to [1], wherein the oxygen-containing compound (A) contains at least one chemical structure selected from the group consisting of an aromatic hetero five-membered ring structure in which the hetero atom is oxygen, an aromatic hetero six-membered ring structure in which the hetero atom is oxygen, and a phenol structure or a phenol derivative structure. [3] The waste plastic raw material according to [1] or [2], wherein the oxygen-containing compound (B) comprises a compound having an aromatic ester structure in which an ester bond is bonded to an aromatic ring on the carbonyl group side. [4] The waste plastic raw material according to any one of [1] to [3], wherein the waste plastic raw material further contains biomass. [5] The waste plastic raw material according to any one of [1] to [4], wherein the polyolefin polymer is contained in an amount of 60 mass % or more based on the total mass of the waste plastic raw material. [6] Plastic decomposition oil, which is a decomposition product of the waste plastic raw material according to any one of [1] to [5]. [7] A method for producing plastic decomposition oil, comprising decomposing waste plastic raw materials to obtain plastic decomposition oil, determining whether or not the content of an oxygen-containing compound (A) having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring and the content of an oxygen-containing compound (B) other than the oxygen-containing compound (A) having a conjugated structure in which an oxygen atom is conjugated with an aromatic ring, contained in the waste plastic raw material (P1), exceed a predetermined value relative to the total mass of the waste plastic raw material (P1); the predetermined value of the oxygen-containing compound (A) is 0.40 mass% in terms of oxygen atoms bonded to aromatic rings, the predetermined value of the oxygen-containing compound (B) is 2.50 mass% in terms of oxygen atoms having a conjugated structure with the aromatic ring other than oxygen atoms bonded to the aromatic ring, In the judgment, when the content ratio of at least one of the oxygen-containing compound (A) and the oxygen-containing compound (B) exceeds the predetermined value, (i) further mixing other plastics (P3) with the waste plastic raw material (P1), and reducing the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) contained in the resulting waste plastic raw material (P4) to the predetermined values ​​or less relative to the total mass of the waste plastic raw material (P4), and then decomposing the waste plastic raw material (P4); or (ii) removing a portion of the waste plastic raw material (P1), and reducing the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) contained in the resulting waste plastic raw material (P2) to the predetermined values ​​or less relative to the total mass of the waste plastic raw material (P2), and then decomposing the waste plastic raw material (P2); or In the determination, if the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) do not exceed the predetermined value, (iii) decomposing the waste plastic raw material (P1); A method for producing plastic decomposition oil. [8] The method for producing plastic decomposition oil according to [7], wherein the oxygen-containing compound (A) contains at least one chemical structure selected from the group consisting of an aromatic hetero five-membered ring structure in which the heteroatom is oxygen, an aromatic hetero six-membered ring structure in which the heteroatom is oxygen, and a phenol structure or a phenol derivative structure. [9] The method for producing plastic decomposition oil according to [7] or [8], wherein the waste plastic raw material (P1) contains an oxygen component.

[10] The method for producing plastic decomposition oil according to any one of [7] to [9], wherein the waste plastic raw material (P1) contains 60 mass% or more of polyolefin polymers relative to the total mass of the waste plastic raw material (P1).

[11] The method for producing plastic decomposition oil according to any one of [7] to [9], wherein the waste plastic raw material (P4) contains 60 mass% or more of a polyolefin polymer relative to the total mass of the waste plastic raw material (P4).

[12] The method for producing plastic decomposition oil according to any one of [7] to [9], wherein the waste plastic raw material (P2) contains 60 mass% or more of a polyolefin polymer relative to the total mass of the waste plastic raw material (P2). [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a waste plastic raw material that can reduce the content of organic oxygen-containing components contained in the plastic decomposition oil obtained during chemical recycling, for example, during chemical recycling of polyolefin-based polymers containing oxygen-containing compounds. Furthermore, according to the present invention, it is possible to provide plastic decomposition oil with a reduced content of organic oxygen-containing components. Furthermore, according to the present invention, a method for producing plastic decomposition oil can be provided that can reduce the generation of organic oxygen-containing components in the resulting plastic decomposition oil. [Brief explanation of the drawings]

[0016] [Figure 1]1 is a graph showing the relationship between the content of oxygen-containing compound (A) in the waste plastic raw material (equivalent to the amount of oxygen atoms bonded to aromatic rings) (unit: mass%) and the ratio (unit: %) of the amount of oxygen atoms in the organic oxygen-containing components of the cracked oil and aqueous phase to the total recovered amount of decomposition products (cracked oil and aqueous phase). [Figure 2] 1 is a flowchart showing an example of the operation of the method for producing plastic decomposition oil of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] 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.

[0018] 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, "% by mass" indicates the content of a given component in a total amount of 100% by mass. "Optional" or "optionally" means that the subsequently described situation may or may not occur, and includes both cases where the situation occurs and cases where it does not occur. In this specification, the content of the oxygen-containing compound (A) contained in the waste plastic raw material is the amount converted into oxygen atoms bonded to aromatic rings, and the content of the oxygen-containing compound (B) contained in the waste plastic raw material is the amount converted into oxygen atoms having a conjugated structure with aromatic rings other than oxygen atoms bonded to aromatic rings.

[0019] In the context of the waste plastic raw materials of this invention, "waste plastic" refers to used plastic products and plastic materials, specifically plastic materials that have been used once and can be reused, recycled, or disposed of after being discarded, and that produce plastic decomposition oil (pyrolysis oil) through chemical recycling. Furthermore, "biomass" refers to organic matter derived from living organisms that produces pyrolysis oil through chemical recycling, and includes organic matter from plants, animals, microorganisms, etc., specifically wood and agricultural residues, food waste, compost, livestock excrement, and even organic matter obtained from microorganisms.

[0020] All steps described herein can be performed in any suitable order unless otherwise stated herein or clearly contradicted by context.

[0021] 1. Waste plastic raw materials One embodiment of the present invention relates to waste plastic raw materials. The waste plastic raw material according to this embodiment is a waste plastic raw material used for producing plastic decomposition oil, that is, a waste plastic raw material to be subjected to chemical recycling (chemically recycled raw material). The waste plastic raw material according to this embodiment includes a polyolefin polymer. The waste plastic raw material according to this embodiment further includes at least one of an oxygen-containing compound (A) having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring, and an oxygen-containing compound (B) other than the oxygen-containing compound (A) having a conjugated structure in which an oxygen atom is conjugated with the aromatic ring.

[0022] According to the present invention, it has been discovered that, in plastic decomposition oil obtained by decomposition treatment of waste plastic raw materials, specific oxygen-containing compounds (A) and (B) contained in the waste plastic raw materials are more likely to remain as organic oxygen in the plastic decomposition oil than other oxygen-containing compounds. This has made it possible to set the conditions required for the waste plastic raw materials that are the raw materials for producing plastic decomposition oil of the desired quality. More specifically, in the waste plastic raw material according to this embodiment, by setting the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) to be equal to or less than a threshold value, when the waste plastic raw material is decomposed to obtain plastic decomposition oil, it is possible to reduce the content of organic oxygen-containing components in the obtained plastic decomposition oil. Specifically, in the waste plastic raw material according to this embodiment, the content ratio of the oxygen-containing compound (A) is 0.40 mass% or less, and the content ratio of the oxygen-containing compound (B) is 2.50 mass% or less, relative to the total mass of the waste plastic raw material. The oxygen-containing compound (A), the oxygen-containing compound (B) and the organic oxygen-containing component will be described in detail below.

[0023] In the waste plastic raw material of this embodiment, the upper limit of the content of the oxygen-containing compound (A) is 0.40 mass% or less, preferably 0.30 mass% or less, more preferably 0.20 mass% or less, even more preferably 0.15 mass% or less, particularly preferably 0.08 mass% or less, and most preferably 0.04 mass% or less, relative to the total mass of the waste plastic raw material, from the viewpoint of reducing the amount of organic oxygen-containing components produced in the obtained plastic decomposition oil. On the other hand, the lower limit of the content of the oxygen-containing compound (A) is not particularly limited, and the oxygen-containing compound (A) may be substantially absent (0 mass%). From the viewpoint of economic efficiency, such as the production cost required to reduce the oxygen atoms having a conjugated structure with an aromatic ring, the content of the oxygen-containing compound (A) can be 0.001 mass% or more, preferably 0.002 mass% or more, more preferably 0.003 mass% or more, even more preferably 0.004 mass% or more, particularly preferably 0.005 mass% or more, and most preferably 0.006 mass% or more.

[0024] The upper and lower limits of the content of the oxygen-containing compound (A) can be arbitrarily combined. That is, the content of the oxygen-containing compound (A) contained in the waste plastic raw material of this embodiment is not particularly limited, and may be 0 mass%, 0.001 mass% to 0.40 mass%, 0.002 mass% to 0.30 mass%, 0.003 mass% to 0.20 mass%, 0.004 mass% to 0.15 mass%, 0.005 mass% to 0.08 mass%, or 0.006 mass% to 0.04 mass%.

[0025] In the waste plastic raw material of this embodiment, the upper limit of the content of the oxygen-containing compound (A) can be set to 0.40 parts by mass or less per 100 parts by mass of the total mass of the polyolefin-based polymer contained in the waste plastic raw material, from the viewpoint of reducing the amount of organic oxygen-containing components produced in the obtained plastic decomposition oil, and is preferably 0.30 parts by mass or less, more preferably 0.20 parts by mass or less, even more preferably 0.15 parts by mass or less, particularly preferably 0.08 parts by mass or less, and most preferably 0.04 parts by mass or less. On the other hand, the lower limit of the content of the oxygen-containing compound (A) is not particularly limited, and the oxygen-containing compound (A) may not be substantially contained. From the viewpoint of economic efficiency, such as the production cost required to reduce the oxygen atoms having a conjugated structure with an aromatic ring, the content may be 0.001 part by mass or more, preferably 0.002 part by mass or more, more preferably 0.003 part by mass or more, even more preferably 0.004 part by mass or more, particularly preferably 0.005 part by mass or more, and most preferably 0.006 part by mass or more, relative to 100 parts by mass of the total mass of the polyolefin polymer.

[0026] The upper and lower limits of the content of the oxygen-containing compound (A) can be arbitrarily combined. That is, the content of the oxygen-containing compound (A) contained in the waste plastic raw material of this embodiment may be 0 part by mass, 0.001 to 0.40 parts by mass, 0.002 to 0.30 parts by mass, 0.003 to 0.20 parts by mass, 0.004 to 0.15 parts by mass, 0.005 to 0.08 parts by mass, or 0.006 to 0.04 parts by mass, relative to 100 parts by mass of the total mass of the polyolefin-based polymer.

[0027] In the waste plastic raw material of this embodiment, the upper limit of the content of the oxygen-containing compound (B) is 2.50 mass% or less, preferably 2.00 mass% or less, more preferably 1.00 mass% or less, even more preferably 0.50 mass% or less, particularly preferably 0.20 mass% or less, and most preferably 0.10 mass% or less, relative to the total mass of the waste plastic raw material, from the viewpoint of reducing the amount of organic oxygen-containing components produced in the obtained plastic decomposition oil. On the other hand, the lower limit of the content of the oxygen-containing compound (B) is not particularly limited, and the oxygen-containing compound (B) may be substantially absent (0 mass%). From the viewpoint of economic efficiency, such as the production cost required to reduce the oxygen atoms having a conjugated structure with an aromatic ring, the content of the oxygen-containing compound (B) can be 0.01 mass% or more, preferably 0.02 mass% or more, more preferably 0.03 mass% or more, even more preferably 0.05 mass% or more, particularly preferably 0.06 mass% or more, and most preferably 0.08 mass% or more.

[0028] The upper and lower limits of the content of the oxygen-containing compound (B) can be arbitrarily combined. That is, the content of the oxygen-containing compound (B) contained in the waste plastic raw material of this embodiment is not particularly limited, and may be 0 mass%, 0.01 mass% to 2.50 mass%, 0.02 mass% to 2.00 mass%, 0.03 mass% to 1.00 mass%, 0.05 mass% to 0.50 mass%, 0.06 mass% to 0.20 mass%, or 0.08 mass% to 0.10 mass%.

[0029] In the waste plastic raw material of this embodiment, the upper limit of the content of the oxygen-containing compound (B) can be set to 2.50 parts by mass or less per 100 parts by mass of the total mass of the polyolefin-based polymer contained in the waste plastic raw material, from the viewpoint of reducing the amount of organic oxygen-containing components produced in the obtained plastic decomposition oil, and is preferably 2.00 parts by mass or less, more preferably 1.00 parts by mass or less, even more preferably 0.50 parts by mass or less, particularly preferably 0.20 parts by mass or less, and most preferably 0.10 parts by mass or less. On the other hand, the lower limit of the content of the oxygen-containing compound (B) is not particularly limited, and the oxygen-containing compound (B) may not be substantially contained. From the viewpoint of economic efficiency, such as the production cost required to reduce the oxygen atoms having a conjugated structure with an aromatic ring, the content may be 0.01 parts by mass or more, preferably 0.02 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, particularly preferably 0.06 parts by mass or more, and most preferably 0.08 parts by mass or more, relative to 100 parts by mass of the total mass of the polyolefin polymer.

[0030] The upper and lower limits of the content of the oxygen-containing compound (B) can be arbitrarily combined. That is, the content of the oxygen-containing compound (B) contained in the waste plastic raw material of this embodiment may be 0 part by mass, 0.01 to 2.50 parts by mass, 0.02 to 2.00 parts by mass, 0.03 to 1.00 parts by mass, 0.05 to 0.50 parts by mass, 0.06 to 0.20 parts by mass, or 0.08 to 0.10 parts by mass, relative to 100 parts by mass of the total mass of the polyolefin-based polymer.

[0031] In the waste plastic raw material of this embodiment, at least one of the content of the oxygen-containing compound (A) and the content of the oxygen-containing compound (B) is not 0% by mass (0 parts by mass). The method for measuring the content ratio of the oxygen-containing compound (A) and the content ratio of the oxygen-containing compound (B) contained in the waste plastic raw material of the present invention will be described in detail later.

[0032] The method for controlling the content ratio of the oxygen-containing compound (A) and the oxygen-containing compound (B) contained in the waste plastic raw material is not particularly limited, and examples thereof include a method of mixing two or more types of waste plastics having different content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B), a method of removing waste plastics having a high content ratio of at least one of the oxygen-containing compound (A) and the oxygen-containing compound (B), and a method of diluting the waste plastics by blending them with waste oil such as waste cooking oil or waste lubricating oil.

[0033] The waste plastic raw material according to this embodiment may contain an oxygen-containing compound other than the oxygen-containing compound (A) and the oxygen-containing compound (B). In the waste plastic raw material of this embodiment, the upper limit of the oxygen atom concentration in the waste plastic raw material is preferably 5.00 mass% or less, more preferably 3.00 mass% or less, even more preferably 2.00 mass% or less, and particularly preferably 1.50 mass% or less, relative to the total mass of the waste plastic raw material, from the viewpoint of reducing the amount of organic oxygen-containing components produced in the obtained plastic decomposition oil. On the other hand, the lower limit of the oxygen atom concentration in the waste plastic raw material is not particularly limited, and the waste plastic raw material may be substantially free of the oxygen-containing compound (A) (0 mass%). From the viewpoint of economic efficiency such as production cost, the lower limit of the oxygen atom concentration in the waste plastic raw material can be set to 0.001 mass% or more, preferably 0.005 mass% or more, more preferably 0.01 mass% or more, even more preferably 0.03 mass% or more, and particularly preferably 0.05 mass% or more. The method for measuring the concentration of oxygen atoms contained in the waste plastic raw material of the present invention will be described later.

[0034] The waste plastic raw material of this embodiment contains a polyolefin polymer as waste plastic. The lower limit of the content of the polyolefin polymer contained in the waste plastic raw material of this embodiment is not particularly limited, and can be 60 mass% or more, preferably 70 mass% or more, more preferably 80 mass% or more, even more preferably 85 mass% or more, and particularly preferably 90 mass% or more, relative to 100% of the total mass of the waste plastic raw material. 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 costs required to highly purify the waste plastic raw material, it can be 99% by mass or less, preferably 98% by mass or less, more preferably 96% by mass or less, even more preferably 94% by mass or less, and particularly preferably 92% by mass or less, relative to 100% of the total mass of the waste plastic raw material. The upper and lower limits of the content of the polyolefin polymer can be combined arbitrarily. That is, the content of the polyolefin polymer contained in the waste plastic raw material of this embodiment is not particularly limited, and can be 60% by mass or more and 99% by mass or less, preferably 70% by mass or more and 98% by mass or less, more preferably 80% by mass or more and 96% by mass or less, even more preferably 85% by mass or more and 94% by mass or less, and particularly preferably 90% by mass or more and 92% by mass or less, relative to 100% of the total mass of the waste plastic raw material.

[0035] The waste plastic raw material of the present invention can further contain biomass. When biomass is subjected to chemical recycling as a waste plastic raw material, pyrolysis oil is produced, just like fossil fuels such as petroleum, coal, and natural gas. As a result, consumption of natural resources can be reduced and carbon dioxide emissions can be reduced compared to fossil fuels. In addition, the amount of waste can be reduced, mitigating the burden on the environment. Specific examples of biomass include disposable chopsticks, paper, textile products such as clothing, and food waste.

[0036] The waste plastic raw material of the present invention may be either recycled used products from the market or process waste generated during the manufacturing process of a product before it is released to the market. Examples of used products include home appliances, automobiles, containers and packaging, daily necessities, and miscellaneous goods. Examples of process waste include waste generated during the manufacturing process of products such as bags, films, sheets, and molded products from plastics.

[0037] <Organic oxygen-containing components> The organic oxygen-containing component in the present invention (hereinafter also simply referred to as "organic oxygen-containing component") is a decomposition product produced by decomposition of the oxygen-containing compound (A) and the oxygen-containing compound (B) contained in the waste plastic raw material. In the present invention, the oxygen-containing compound (A) is a compound having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring. Examples include a compound having an aromatic hetero five-membered ring structure in which the hetero atom is oxygen, a compound having an aromatic hetero six-membered ring structure in which the hetero atom is oxygen, and a compound having a phenol structure or a phenol derivative structure. In the present invention, the oxygen-containing compound (B) is a compound other than the oxygen-containing compound (A) that has a conjugated structure in which an oxygen atom is conjugated with an aromatic ring. Examples include a compound having an aromatic ester structure in which an ester bond is bonded to the aromatic ring on the carbonyl group side. Some organic oxygen-containing components contained in plastic decomposition oil are difficult to efficiently remove using known decomposition and purification methods. As a result, these unremoved organic oxygen-containing components may contaminate plastic decomposition oil or products derived from it, resulting in a deterioration in product quality. Furthermore, a significant amount of organic oxygen-containing components may be contaminated into process wastewater, necessitating decomposition treatment using known wastewater treatment methods, such as chemical treatment methods like coagulation and sedimentation or activated sludge, which increases the load on the wastewater treatment process. Furthermore, when the organic oxygen-containing components are organic acids, such as phenols or benzoic acid, there is also the problem of increased corrosion of pyrolysis equipment, which performs the cracking process.

[0038] <Oxygen-containing compounds (A)> The oxygen-containing compound (A) in the present invention is a compound having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring. According to the studies of the present inventors, it has been confirmed that oxygen-containing compounds (A) having such a structure are difficult to decompose into CO and / or CO when decomposed using a chemical recycling method, and are decomposed into organic oxygen-containing components that maintain the conjugated structure. Therefore, the lower the content of oxygen-containing compounds (A) in the waste plastic raw material, the lower the amount of organic oxygen-containing components produced in the resulting plastic decomposition oil. Therefore, by setting the content of oxygen-containing compounds (A) in the waste plastic raw material to a predetermined value or less, the content of organic oxygen-containing components in the plastic decomposition oil can be reduced.

[0039] Examples of the oxygen-containing compound (A) include compounds having at least one chemical structure selected from the group consisting of an aromatic five-membered heterocyclic structure in which the heteroatom is oxygen, an aromatic six-membered heterocyclic structure in which the heteroatom is oxygen, and a phenol structure or a phenol derivative structure. By selecting such an oxygen-containing compound (A) and controlling its content to a predetermined value or less, the content of organic oxygen-containing components in the plastic decomposition oil can be reduced more efficiently. The oxygen-containing compound (A) contained in the waste plastic raw material may be one type or two or more types.

[0040] The compound having an aromatic hetero five-membered ring structure in which the heteroatom is oxygen is not particularly limited, and examples thereof include compounds having a furan ring, a benzofuran ring, an isobenzofuran ring, an oxazole ring, a benzoxazole ring, a benzisoxazole ring, etc.

[0041] The compound having an aromatic hetero six-membered ring structure in which the heteroatom is oxygen is not particularly limited, and examples thereof include compounds having a coumarin ring, a chromone ring, a phenoxazine ring, a xanthene ring, a chromene ring, etc.

[0042] The compound having a phenol structure or a phenol derivative structure is not particularly limited, and examples thereof include compounds having a phenol skeleton, cresol skeleton, hydroquinone skeleton, naphthol skeleton, catechol skeleton, resorcinol skeleton, eugenol skeleton, phenolphthalein skeleton, salicylic acid skeleton, benzenediol skeleton, etc. Examples of the compound having a phenol structure or a phenol derivative structure include phenolic antioxidants such as dibutylhydroxytoluene (BHT), phenol resins, polycarbonate resins, polyphenylene oxide, polyether ether ketone, etc.

[0043] <Oxygen-containing compounds (B)> The oxygen-containing compound (B) in the present invention is a compound other than the oxygen-containing compound (A) that has a conjugated structure in which an oxygen atom is conjugated with an aromatic ring. That is, the oxygen-containing compound (B) is a compound that does not contain an oxygen atom bonded to an aromatic ring, but contains an oxygen atom other than an oxygen atom bonded to an aromatic ring that has a conjugated structure with the aromatic ring. A compound that contains both an oxygen atom bonded to an aromatic ring and an oxygen atom other than an oxygen atom bonded to an aromatic ring that has a conjugated structure with the aromatic ring is classified as the oxygen-containing compound (A). According to the studies of the present inventors, it has been confirmed that oxygen-containing compounds (B) having such structures can also be decomposed into organic oxygen-containing components that maintain the conjugated structure when decomposed using a chemical recycling method. Therefore, the lower the content of oxygen-containing compounds (B) in the waste plastic raw material, the lower the amount of organic oxygen-containing components produced in the resulting plastic decomposition oil tends to be. Therefore, by setting the content of oxygen-containing compounds (B) contained in the waste plastic raw material to a predetermined value or less, the content of organic oxygen-containing components in the plastic decomposition oil can be reduced.

[0044] Examples of the oxygen-containing compound (B) include compounds having an aromatic ester structure in which an ester bond is bonded to an aromatic ring on the carbonyl group side. By selecting such an oxygen-containing compound (B) and adjusting its content to a predetermined value or less, the content of organic oxygen-containing components in the plastic decomposition oil can be more efficiently reduced. The oxygen-containing compound (B) contained in the waste plastic raw material may be one type or two or more types.

[0045] Examples of the aromatic ring in a compound having an aromatic ester structure in which an ester bond is bonded to the aromatic ring on the carbonyl group side include a benzene ring and a naphthalene ring. The compound having an aromatic ester structure in which an ester bond is bonded to an aromatic ring on the carbonyl group side is not particularly limited, and examples thereof include polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and phthalate plasticizers such as di-2-ethylhexyl phthalate, diisononyl phthalate, dibutyl phthalate, diisodecyl phthalate, and di-n-octyl phthalate.

[0046] <Polyolefin polymer> Examples of polyolefin polymers contained in the waste plastic raw material of this embodiment 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). These may be used alone or in combination. As the polyolefin polymer contained in the waste plastic raw material, polyethylenes are particularly preferred. The origin of these polymers is not particularly limited, and examples thereof include polyolefin films or polyolefin sheets, such as those used in recycled bottles, transparent packaging, and shopping bags, and polyolefin fibers. The form of these polymers is not particularly limited, and they may be used in the form of granules, threads, or flakes after pretreatment such as separation from other materials and washing by a conventional method prior to the decomposition treatment of the present invention, or they may be used as is or after processing into any shape suitable for handling by compression, cutting, or the like.

[0047] 2. Plastic decomposition oil Another embodiment of the present invention relates to a plastic cracking oil. The plastic decomposition oil of the present invention refers to an oil or oily substance that is a decomposition product of the waste plastic raw material according to the above-described embodiment. Alternatively, the plastic decomposition oil of the present invention refers to an oil or oily substance obtained by the method for producing plastic decomposition oil of the present invention described below.

[0048] 3. Manufacturing method of plastic decomposition oil Yet another embodiment of the present invention relates to a method for producing plastic cracking oil. The method for producing plastic decomposition oil of the present invention includes subjecting waste plastic raw materials to a decomposition treatment to obtain plastic decomposition oil. 2 shows a flow chart illustrating an example of the operation of the method for producing plastic decomposition oil of the present invention. Each operation will be explained below.

[0049] Specifically, the following operations (1) and (2-a) or (1) and (2-b) are included. (1) Determine whether the content of oxygen-containing compound (A) having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring, and the content of oxygen-containing compound (B) other than oxygen-containing compound (A) having a conjugated structure in which an oxygen atom is conjugated with an aromatic ring, contained in waste plastic raw material (P1) to be subjected to decomposition treatment, exceed a predetermined value relative to the total mass of the waste plastic raw material (P1). In the judgment of (2-a)(1), if the content ratio of at least one of the oxygen-containing compound (A) and the oxygen-containing compound (B) exceeds the predetermined value, (i) Mixing the waste plastic raw material (P1) with other plastics (P3), and reducing the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) contained in the resulting waste plastic raw material (P4) to the predetermined values ​​or less relative to the total mass of the waste plastic raw material (P4), and then decomposing the waste plastic raw material (P4), or (ii) A portion of the waste plastic raw material (P1) is removed, and the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) contained in the resulting waste plastic raw material (P2) are each set to the above-mentioned predetermined values ​​or less relative to the total mass of the waste plastic raw material (P2), and then the waste plastic raw material (P2) is subjected to a decomposition treatment. or, In the judgment of (2-b)(1), if the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) do not exceed the predetermined values, (iii) The waste plastic raw material (P1) is decomposed and treated.

[0050] In making the determination in (1) or in measuring the content of the oxygen-containing compound (A) in the waste plastic raw material before the decomposition treatment in (2-a), the sampling method for the waste plastic raw material is not particularly limited, and a person skilled in the art can appropriately select and use a known statistical sampling method in accordance with common technical knowledge. For example, analytical samples can be taken from a large amount of waste plastic (or the bales if the waste plastic is baled) by a random sampling method or a two-stage sampling method in accordance with JIS Z 7302-1. The specific embodiment of the random sampling method is not limited, and a person skilled in the art can use known random sampling methods by optimizing the conditions appropriately according to common technical knowledge. For example, when the amount of waste plastic raw material is about 200 to 300 kg, the amount is reduced to about 20 kg by the quartering method, and this is collected as a sample for analysis. Furthermore, the collected analytical sample (approximately 20 kg) can be pulverized by a person skilled in the art using a known pulverizer appropriately selected according to the shape, size, hardness, etc. of the sample, in accordance with common technical knowledge. If necessary, the analytical sample can be pulverized while being cooled using liquid nitrogen. Furthermore, the crushed analytical sample can be reduced to approximately 1 g using the incremental reduction method in accordance with JIS Z 8833:2011, and then analyzed.

[0051] The content of the oxygen-containing compound (A) (equivalent to the amount of oxygen atoms bonded to aromatic rings) contained in the waste plastic raw materials (P1) to (P4) (hereinafter simply referred to as "waste plastic raw materials") can be measured by the following procedure using pyrolysis gas chromatography / mass spectrometry (pyrolysis GC / MS method) and elemental analysis.

[0052] First, the content of oxygen atoms in the waste plastic raw material is measured using elemental analysis.

[0053] Next, the molecular structure of the oxygen-containing compound (A) contained in the waste plastic raw material is identified using pyrolysis gas chromatography / mass spectrometry (pyrolysis GC / MS method), and the content ratio of the oxygen-containing compound (A) contained in the waste plastic raw material is measured. Specifically, in structural analysis by pyrolysis GC / MS, the conjugated structure portion in the oxygen-containing compound (A) is not pyrolyzed, and components (fragments) having the conjugated structure are detected in a mass spectrum, thereby confirming that the oxygen-containing compound (A) is contained in the waste plastic raw material. For example, the presence of the oxygen-containing compound (A) can be confirmed by detecting a peak of a specific pyrolysis product derived from the oxygen-containing compound (A) (for example, phenol when the oxygen-containing compound (A) is a phenolic resin) in the MS spectrum.

[0054] Furthermore, the content of the oxygen-containing compound (A) in the waste plastic raw material is measured using a gas chromatogram obtained by the pyrolysis GC / MS method, and the content of the oxygen-containing compound (A) in the waste plastic raw material is calculated based on this content. Specifically, for the oxygen-containing compound (A), the content ratio of the oxygen-containing compound (A) contained in the waste plastic raw material is calculated using a calibration curve of the oxygen-containing compound (A) prepared in advance using the gas chromatogram obtained by the pyrolysis GC / MS method. When preparing the calibration curve, a mixture in which silica (SiO2) and / or calcium carbonate (CaCO3) is blended at 0.01 to 0.04% by mass is used as a standard sample for the oxygen-containing compound (A). After setting the heating furnace temperature of the pyrolysis apparatus to a temperature at which the oxygen-containing compound (A) is sufficiently pyrolyzed (for example, about 600°C when the oxygen-containing compound (A) is a phenolic resin), a calibration curve is created based on the peak area of the pyrolyzate characteristic of the oxygen-containing compound (A). As the "pyrolyzate characteristic of the oxygen-containing compound (A)", for example, when the oxygen-containing compound (A) is a phenolic resin, phenol; when it is a polycarbonate resin, bisphenol A; when it is a polyphenylene oxide, 2,6-xylenol; when it is a polyether ether ketone, a calibration curve can be created using the peak of phenol. As the main components of the waste plastic raw material other than the oxygen-containing compound (A), when it is a polyethylene resin, 1-hexene; when it is a polypropylene resin, a calibration curve can be created using the peak of 2,4-dimethyl-1-heptene.

[0055] Note that an example of the measurement conditions for the pyrolysis GC / MS method is shown below. The following measurement conditions can be appropriately optimized by those skilled in the art according to well-known techniques.

[0056] <Pyrolysis Conditions> Pyrolysis apparatus: Multi-shot Pyrolyzer EGA / PY-3030D (manufactured by Frontier Lab Co., Ltd.) Thermal extraction temperature: 350°C Pyrolysis temperature: 600°C Sample amount: Approximately 0.4 mg <GC / MS Measurement Conditions> [[ID=​​​Single quadrupole mass spectrometer: Agilent 5977B (Agilent Technologies) (GC conditions) Ionization method: Electron ionization method (EI method) Column: GC capillary column BPX-5 (manufactured by SGE, inner diameter 0.25 mm x length 30 m x film thickness 0.25 μm) Carrier gas: Helium, flow rate 1.0 mL / min (constant flow) Heating conditions (350°C hot extraction): 40°C (hold time 2 minutes) → Heat at 20°C / minute → 320°C (hold time 14 minutes) Heating conditions (600°C pyrolysis): 40°C (holding time 2 minutes) → Heating at 20°C / minute → 320°C (holding time 44 minutes) Inlet temperature: 320℃ Split ratio: 1:100 (MS conditions) Transfer line temperature: 250℃ Ion source temperature: 230℃ Quadrupole temperature: 150℃ Scan mode: m / z = 29 to 800 Measurement mode: SIM (m / z = 64, 113, 122, 128)

[0057] Next, the content of the oxygen-containing compound (A) in terms of oxygen atoms can be calculated based on the content of the oxygen-containing compound (A) in the waste plastic raw material and the content of oxygen atoms in the waste plastic raw material measured by elemental analysis. Specifically, when a component (fragment) having a conjugated structure is detected by pyrolysis GC / MS, the content of oxygen atoms measured by the above elemental analysis method can be evaluated as being derived from a component having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring. Based on this evaluation, the content of the oxygen-containing compound (A) in terms of oxygen atoms can be calculated.

[0058] The content of the oxygen-containing compound (B) contained in the waste plastic raw material (equivalent to the amount of oxygen atoms having a conjugated structure with the aromatic ring other than the oxygen atoms bonded to the aromatic ring) can also be measured in the same manner as the content of the oxygen-containing compound (B). As the "thermal decomposition product characteristic of the oxygen-containing compound (B)", for example, a calibration curve can be prepared using the peak of benzoic acid when the oxygen-containing compound (B) is polyethylene terephthalate, or the peak of 2-naphthalenecarboxylic acid when the oxygen-containing compound (B) is polyethylene naphthalate.

[0059] When the waste plastic raw material contains multiple types of oxygen-containing compounds (A) and oxygen-containing compounds (B) and other polymers, the content ratios of these components can be calculated using pyrolysis GC / MS. Specifically, the content ratios of the polymers can be calculated from the peak intensity ratios derived from each component on the gas chromatogram obtained by pyrolysis GC / MS.

[0060] The spectra obtained by pyrolysis GC / MS from each polymer can be found in known literature or in known MS spectrum databases.

[0061] <Waste plastic raw materials> In the production method of the present invention, waste plastic raw materials are decomposed to obtain plastic decomposition oil. The waste plastic raw materials to be decomposed in the manufacturing method of the present invention are the waste plastic raw material (P4) in (i) of (2-a) above, the waste plastic raw material (P2) in (ii) of (2-a) above, and the waste plastic raw material (P1) in (2-b) above. Hereinafter, these waste plastic raw materials to be decomposed will be collectively referred to as "waste plastic raw material (P)".

[0062] In the waste plastic raw material (P) of the present invention, in order to reduce the content of organic oxygen-containing components in the resulting plastic decomposition oil, it is necessary that the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) do not exceed predetermined values. The "predetermined value" of the oxygen-containing compound (A) is 0.40 mass% in terms of oxygen atoms bonded to aromatic rings. The "predetermined value" of the oxygen-containing compound (B) is 2.50 mass% in terms of oxygen atoms having a conjugated structure with aromatic rings other than oxygen atoms bonded to aromatic rings.

[0063] The upper limit of the content of the oxygen-containing compound (A) contained in the waste plastic raw material (P) (equivalent to the amount of oxygen atoms bonded to aromatic rings) is 0.40 mass% or less, preferably 0.30 mass% or less, more preferably 0.20 mass% or less, even more preferably 0.15 mass% or less, particularly preferably 0.08 mass% or less, and most preferably 0.04 mass% or less, relative to the total mass of the waste plastic raw material, from the viewpoint of reducing the amount of organic oxygen-containing components produced in the obtained plastic decomposition oil. On the other hand, the lower limit of the content of the oxygen-containing compound (A) contained in the waste plastic raw material (P) is not particularly limited, and the oxygen-containing compound (A) may be substantially absent (0 mass%). From the viewpoint of economic efficiency, such as the production cost required to reduce oxygen atoms having a conjugated structure with an aromatic ring, the content of the oxygen-containing compound (A) can be 0.001 mass% or more, preferably 0.002 mass% or more, more preferably 0.003 mass% or more, even more preferably 0.004 mass% or more, particularly preferably 0.005 mass% or more, and most preferably 0.006 mass% or more.

[0064] The upper and lower limits of the content of the oxygen-containing compound (A) can be arbitrarily combined. That is, the content of the oxygen-containing compound (A) contained in the waste plastic raw material (P) is not particularly limited and may be 0 mass%, 0.001 mass% to 0.40 mass%, 0.002 mass% to 0.30 mass%, 0.003 mass% to 0.20 mass%, 0.004 mass% to 0.15 mass%, 0.005 mass% to 0.08 mass%, or 0.006 mass% to 0.04 mass%.

[0065] The waste plastic raw material (P) may contain a polyolefin-based polymer. In this case, the upper limit of the content of the oxygen-containing compound (A) contained in the waste plastic raw material (P) can be set to 0.40 parts by mass or less, preferably 0.30 parts by mass or less, more preferably 0.20 parts by mass or less, even more preferably 0.15 parts by mass or less, particularly preferably 0.08 parts by mass or less, and most preferably 0.04 parts by mass or less, per 100 parts by mass of the total mass of the polyolefin-based polymer, from the viewpoint of reducing the amount of organic oxygen-containing components produced in the obtained plastic decomposition oil. On the other hand, the lower limit of the content of the oxygen-containing compound (A) is not particularly limited, and the oxygen-containing compound (A) may not be substantially contained. From the viewpoint of economic efficiency, such as the production cost required to reduce the oxygen atoms having a conjugated structure with an aromatic ring, the content may be 0.001 part by mass or more, preferably 0.002 part by mass or more, more preferably 0.003 part by mass or more, even more preferably 0.004 part by mass or more, particularly preferably 0.005 part by mass or more, and most preferably 0.006 part by mass or more, relative to 100 parts by mass of the total mass of the polyolefin polymer.

[0066] The upper and lower limits of the content of the oxygen-containing compound (A) can be arbitrarily combined. That is, the content of the oxygen-containing compound (A) contained in the waste plastic raw material (P) may be 0 part by mass, 0.001 to 0.40 parts by mass, 0.002 to 0.30 parts by mass, 0.003 to 0.20 parts by mass, 0.004 to 0.15 parts by mass, 0.005 to 0.08 parts by mass, or 0.006 to 0.04 parts by mass, relative to 100 parts by mass of the total mass of the polyolefin-based polymer.

[0067] The upper limit of the content of oxygen-containing compound (B) contained in waste plastic raw material (P) (equivalent to the amount of oxygen atoms having a conjugated structure with aromatic rings other than oxygen atoms bonded to aromatic rings) is 2.50 mass% or less, preferably 2.00 mass% or less, more preferably 1.00 mass% or less, even more preferably 0.50 mass% or less, particularly preferably 0.20 mass% or less, and most preferably 0.10 mass% or less, relative to the total mass of waste plastic raw material, from the viewpoint of reducing the amount of organic oxygen-containing components produced in the obtained plastic decomposition oil. On the other hand, the lower limit of the content of the oxygen-containing compound (B) contained in the waste plastic raw material (P) is not particularly limited, and the oxygen-containing compound (B) may be substantially absent (0 mass%). From the viewpoint of economic efficiency, such as the production cost required to reduce oxygen atoms having a conjugated structure with an aromatic ring, the content of the oxygen-containing compound (B) can be 0.01 mass% or more, preferably 0.02 mass% or more, more preferably 0.03 mass% or more, even more preferably 0.05 mass% or more, particularly preferably 0.06 mass% or more, and most preferably 0.08 mass% or more.

[0068] The upper and lower limits of the content of the oxygen-containing compound (B) can be arbitrarily combined. That is, the content of the oxygen-containing compound (B) contained in the waste plastic raw material (P) is not particularly limited and may be 0 mass%, 0.01 mass% to 2.50 mass%, 0.02 mass% to 2.00 mass%, 0.03 mass% to 1.00 mass%, 0.05 mass% to 0.50 mass%, 0.06 mass% to 0.20 mass%, or 0.08 mass% to 0.10 mass%.

[0069] When the waste plastic raw material (P) contains a polyolefin-based polymer, the upper limit of the content of the oxygen-containing compound (B) contained in the waste plastic raw material (P) can be set to 2.50 parts by mass or less per 100 parts by mass of the total mass of the polyolefin-based polymer, from the viewpoint of reducing the amount of organic oxygen-containing components produced in the obtained plastic decomposition oil, and is preferably 2.00 parts by mass or less, more preferably 1.00 parts by mass or less, even more preferably 0.50 parts by mass or less, particularly preferably 0.20 parts by mass or less, and most preferably 0.10 parts by mass or less. On the other hand, the lower limit of the content of the oxygen-containing compound (B) is not particularly limited, and the oxygen-containing compound (B) may not be substantially contained. From the viewpoint of economic efficiency, such as the production cost required to reduce the oxygen atoms having a conjugated structure with an aromatic ring, the content may be 0.01 parts by mass or more, preferably 0.02 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, particularly preferably 0.06 parts by mass or more, and most preferably 0.08 parts by mass or more, relative to 100 parts by mass of the total mass of the polyolefin polymer.

[0070] The upper and lower limits of the content of the oxygen-containing compound (B) can be arbitrarily combined. That is, the content of the oxygen-containing compound (B) contained in the waste plastic raw material (P) may be 0 part by mass, 0.01 to 2.50 parts by mass, 0.02 to 2.00 parts by mass, 0.03 to 1.00 parts by mass, 0.05 to 0.50 parts by mass, 0.06 to 0.20 parts by mass, or 0.08 to 0.10 parts by mass, relative to 100 parts by mass of the total mass of the polyolefin-based polymer.

[0071] When carrying out the production method of the present invention, it is necessary that the content ratio of the oxygen-containing compound (A) and the oxygen-containing compound (B) in the waste plastic raw material (P) to be subjected to the decomposition treatment does not exceed a predetermined value. In a certain waste plastic raw material (P1), when the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) do not exceed predetermined values, the waste plastic raw material (P1) can be used for decomposition treatment to produce plastic decomposition oil of the desired quality ((2-b) above).

[0072] On the other hand, if at least one of the oxygen-containing compound (A) and oxygen-containing compound (B) content ratios in a certain waste plastic raw material (P1) exceeds a predetermined value, when the waste plastic raw material (P1) is subjected to a decomposition process, it is not possible to produce a plastic decomposition oil of the desired quality. Therefore, it is necessary to adjust the content ratios of the oxygen-containing compound (A) and oxygen-containing compound (B) in the waste plastic raw material (P1). The following aspects can be mentioned as a method for adjusting the content ratio of the oxygen-containing compound (A) and the oxygen-containing compound (B) in the waste plastic raw material, particularly as a method for adjusting the content ratio of the oxygen-containing compound (A) and the oxygen-containing compound (B) so that it does not exceed a predetermined value. (i) A method of further mixing other plastics (P3) with waste plastic raw materials ((i) of (2-a) above). (ii) A method of removing a portion of the waste plastic raw material ((2-a)(ii) above).

[0073] (i) A method of mixing other plastics (P3) with waste plastic raw materials One method for reducing the content of oxygen-containing compounds (A) in waste plastic raw material (P1) is to reduce the content of oxygen-containing compounds (A) in the entire waste plastic raw material by mixing it with another plastic (P3) that has a lower content of oxygen-containing compounds (A) than the waste plastic raw material (P1), in particular, a content of oxygen-containing compounds (A) that is lower than a predetermined value. Another method for reducing the content of the oxygen-containing compound (B) in the waste plastic raw material (P1) is to mix another plastic (P3) having a lower content of the oxygen-containing compound (B) than the waste plastic raw material (P1), in particular, a content of the oxygen-containing compound (B) lower than a predetermined value, thereby reducing the content of the oxygen-containing compound (B) in the entire waste plastic raw material.

[0074] The plastic (P3) may be a waste plastic raw material, or a virgin plastic product or plastic material, as long as the content of the oxygen-containing compound (A) and the oxygen-containing compound (B) is smaller than that of the waste plastic raw material (P1), particularly if the content of the oxygen-containing compound (A) and the oxygen-containing compound (B) is smaller than a predetermined value. Alternatively, a waste plastic raw material, a virgin plastic product or a plastic material that is substantially free of the oxygen-containing compound (A) and the oxygen-containing compound (B) may be used. From the viewpoint of chemical recycling, it is preferable to use a waste plastic raw material in which the content ratio of the oxygen-containing compound (A) and the oxygen-containing compound (B) is smaller than a predetermined value, or a waste plastic raw material that is substantially free of the oxygen-containing compound (A) and the oxygen-containing compound (B).

[0075] (ii) A method for removing a portion of waste plastic raw materials As a method for reducing the content of the oxygen-containing compound (A) in the waste plastic raw material (P1), there can be mentioned a method of removing a portion of the waste plastic raw material (P1) having a high content of the oxygen-containing compound (A), in particular, a portion having a content of the oxygen-containing compound (A) greater than a predetermined value. In addition, as a method for reducing the content ratio of the oxygen-containing compound (B) in the waste plastic raw material (P1), there can be mentioned a method of removing a portion of the waste plastic raw material (P1) having a high content ratio of the oxygen-containing compound (B), in particular, a portion having a content ratio of the oxygen-containing compound (B) greater than a predetermined value.

[0076] In many cases, the distribution of components in waste plastic raw materials is not uniform. In such cases, some of the waste plastic raw materials may have a high proportion of oxygen-containing compound (A), while other parts may have a low proportion of oxygen-containing compound (A). Similarly, some of the waste plastic raw materials may have a high proportion of oxygen-containing compound (B), while other parts may have a low proportion of oxygen-containing compound (B). In such cases, by removing the parts with a high proportion of either or both of oxygen-containing compound (A) and oxygen-containing compound (B), the proportion of either or both of oxygen-containing compound (A) and oxygen-containing compound (B) in the entire waste plastic raw material can be reduced and adjusted so that it does not exceed a predetermined value.

[0077] Waste plastic raw materials (P) can contain either waste plastic or biomass. When waste plastic or biomass is subjected to chemical recycling as waste plastic raw materials, pyrolysis oil is produced, just like fossil fuels such as petroleum, coal, and natural gas. As a result, consumption of natural resources can be reduced and carbon dioxide emissions can be reduced compared to fossil fuels. In addition, the amount of waste can be reduced, easing the burden on the environment. Specific examples of biomass include disposable chopsticks, paper, textile products such as clothing, and food waste.

[0078] The waste plastic raw material (P1) can contain a polyolefin polymer as the waste plastic. In particular, the lower limit of the content of polyolefin polymers contained in the waste plastic raw material (P) to be subjected to decomposition treatment is not particularly limited, and is preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 80 mass% or more, particularly preferably 85 mass% or more, and particularly preferably 90 mass% or more, relative to 100% of the total mass of the waste plastic raw material (P). 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 costs required to highly purify the waste plastic raw material, it is preferably 99% by mass or less, more preferably 98% by mass or less, even more preferably 96% by mass or less, particularly preferably 94% by mass or less, and particularly preferably 92% by mass or less, relative to 100% by total mass of the waste plastic raw material (P). The above upper and lower limits can be combined arbitrarily, and may be, for example, 60 to 99 mass %, 70 to 98 mass %, 80 to 96 mass %, 85 to 94 mass %, or 90 to 92 mass %.

[0079] The waste plastic raw material (P1) may contain oxygen-containing compounds other than the oxygen-containing compound (A) and the oxygen-containing compound (B). In particular, the upper limit of the oxygen atom concentration contained in the waste plastic raw material (P) to be subjected to decomposition treatment is preferably 5.00 mass% or less, more preferably 3.00 mass% or less, even more preferably 2.00 mass% or less, and particularly preferably 1.50 mass% or less, relative to the total mass of the waste plastic raw material, from the viewpoint of reducing the amount of organic oxygen-containing components produced in the resulting plastic decomposition oil. On the other hand, the lower limit of the oxygen atom concentration contained in the waste plastic raw material (P) is not particularly limited, and it is also possible for the waste plastic raw material (P) to contain substantially no oxygen-containing compound (A) (0 mass%). From the viewpoint of economic efficiency such as production cost, the lower limit of the oxygen atom concentration in the waste plastic raw material can be set to 0.001 mass% or more, preferably 0.005 mass% or more, more preferably 0.01 mass% or more, even more preferably 0.03 mass% or more, and particularly preferably 0.05 mass% or more.

[0080] Details of the oxygen-containing compound (A), the oxygen-containing compound (B), the polyolefin polymer, and the organic oxygen-containing component are as explained above in "1. Waste plastic raw material."

[0081] <Method for decomposing waste plastic raw materials> The embodiment of the decomposition process for waste plastics in the present invention is not particularly limited as long as it is a method that can decompose waste plastic raw materials and obtain plastic decomposition oil, and for example, known thermal decomposition processes, known decomposition processes using supercritical fluids or subcritical fluids such as hydrothermal decomposition processes, and known contact pyrolysis processes can be used.

[0082] "Pyrolysis 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 thermal decomposition treatment is carried out at a pressure in the range of -0.1 to 10 MPaG (gauge pressure), preferably -0.05 to 1.0 MPa, which provides excellent operability and a good color for the resulting plastic decomposition oil. Furthermore, those skilled in the art can appropriately optimize the thermal decomposition treatment temperature, residence time in the thermal decomposition treatment device, type of thermal decomposition treatment device, and the like, and perform the thermal decomposition treatment.

[0083] The apparatus for carrying out the pyrolysis treatment is not particularly limited, and known pyrolysis treatment apparatuses can be used. Examples include reactors such as single-screw or twin-screw extruder reactors; kiln-type reactors such as gas-heated kilns and electrically heated kilns; agitator-equipped tank reactors; tank reactors; tubular reactors; fluidized-bed reactors; and fixed-bed reactors. Steam, thermal oil / gas, electricity, microwaves, and combustion gases are used as heat sources. Twin-screw extruder reactors and kiln-type reactors are preferred because of their excellent productivity.

[0084] "Decomposition treatment using a supercritical fluid or a subcritical fluid" refers to a thermochemical decomposition treatment of an organic substance by adjusting the temperature and pressure to utilize the high reactivity of a supercritical fluid that is neither liquid nor gaseous, or a subcritical fluid close to a supercritical state. 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 may be controlled to heat the water to 100 to 700°C, preferably 150 to 500°C, and the hydrothermal decomposition treatment may be performed by utilizing the high reactivity of the supercritical water or subcritical water.

[0085] A "supercritical fluid" refers to a state in which solvents such as methanol or water, or gases such as CO2, are at a temperature and pressure higher than their critical point.The fluid has a higher density than normal gases and the momentum of its molecules is similar to that of gases. Furthermore, a "subcritical fluid" is a fluid 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 economy and the efficiency of the decomposition treatment.

[0086] "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, due to the influence of the pyrolysis catalyst and temperature. For example, waste plastics are melted and pyrolyzed using a known heating means such as an extruder, and the resulting melt, vapor, or both are then contacted with a pyrolysis catalyst to lighten the resulting mixture. Examples of pyrolysis catalysts include inorganic solid acid oxide particles such as silica-alumina, silica-titania, silica-zirconia, alumina-magnesia, alumina-zirconia, alumina-titania, bentonite, kaolinite, and zeolite.

[0087] The method for thermally decomposing waste plastic raw materials in the present invention is not particularly limited, and examples thereof include the following method (1-1) or (1-2). Method (1-1): A method in which the waste plastic raw material of the present invention is melted and kneaded while being decomposed using a known melting means such as a single-screw extruder or a twin-screw extruder. Method (1-2): A method in which the waste plastic raw material of the present invention is melted and 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.

[0088] In the present invention, the method for decomposing raw waste plastic material 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 waste plastic raw material of the present invention is melted 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 waste plastic raw material using a reactor for decomposition treatment under high temperature and pressure at which the solvent or gas forms a supercritical fluid or subcritical fluid. Method (2-2): A method in which a known melt mixing means such as a single-screw extruder or a twin-screw extruder is used to act on the waste plastic raw material of the present invention with a solvent such as methanol or water, or a gas such as CO2, which is capable of forming the waste plastic raw material and a supercritical fluid or sub-supercritical fluid, under high temperature and pressure at which the solvent or gas forms a supercritical fluid or sub-critical fluid. Method (2-3): A method in which the waste plastic raw material of the present invention 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 charged into a reactor for decomposition treatment, and then the supercritical fluid or sub-supercritical fluid is allowed to act on the waste plastic raw material under high temperature and pressure conditions at which the solvent or gas is brought into a supercritical state or a sub-supercritical state.

[0089] In the method (2-1) or (2-3), the reactor used for the decomposition treatment may be of a batch type or a continuous type. The reactor shape may be, for example, a pipe type, or a cylindrical vertical or horizontal type. The means for dispersing the waste plastic raw material in a molten state in high-temperature, high-pressure water in the present invention is not particularly limited, and may include, for example, static dispersing means using a packing such as a partition or a static mixer, and / or forced dispersing means using an insert that performs a reciprocating or rotating motion. One or more of a single type of dispersing means may be used, or multiple types of dispersing means may be used in combination.

[0090] In the method for producing plastic decomposition oil of the present invention, the reaction temperature for decomposing waste plastic raw materials varies depending on the type and content of the polyolefin polymer contained in the waste plastic raw materials, but is usually 250°C or higher and 450°C or lower, preferably 250°C or higher and 370°C or lower. 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 450°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 in the waste plastic raw material of the present invention and the plastic decomposition oil obtained by decomposing the polyolefin polymer in a supercritical fluid or a sub-supercritical fluid, the density of the supercritical fluid or the sub-supercritical fluid is 0.2 g / cm 3 The higher the reaction temperature, the higher the pressure required. There is no upper limit on the pressure for decomposition treatment in terms of reaction, but from the viewpoint of equipment, a pressure of 50 MPa or less is practical.

[0091] In the method for producing plastic decomposition oil of the present invention, the weight 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 waste plastic raw material, which is supplied to the reactor, is preferably in the range of 2 to 10, more preferably in the range of 3 to 7. When the ratio is equal to or greater than the above lower limit, the amount of solvent or gas required for hydrolysis of the polyolefin polymer is likely to be sufficient to completely dissolve the plastic decomposition oil produced by the decomposition treatment. For example, when the polyolefin polymer is polypropylene, a weight ratio of 2 or greater ensures that the produced monomer, propylene, can be completely dissolved in the supercritical fluid or near-supercritical fluid. On the other hand, a weight ratio of 10 or less ensures that the decomposition treatment proceeds sufficiently quickly, which is unlikely to lead 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, or other equipment, or to an increase in the energy required for treatment.

[0092] In the method for producing plastic decomposition oil of the present invention, the optimum residence time in the reactor is determined by the type of polyolefin polymer in the waste plastic raw material and the reaction temperature. Since the reactor size increases in proportion to the residence time, the residence time is usually 20 minutes or less, but due to the difficulty of equipment for regulating the reaction, it is 1 second or more. From the viewpoint of the yield of raw material olefin, the residence time is preferably 10 minutes or less and 10 seconds or more, and more preferably 5 minutes or less and 20 seconds or more. The plastic decomposition oil obtained by the plastic decomposition oil manufacturing method of the present invention can be recovered by passing it through a solid-liquid separation section, where solids or insoluble matter are separated and removed from the aqueous solution after the reaction, if necessary, and then reducing the pressure and carrying out conventional separation and purification operations such as crystallization and distillation. [Example]

[0093] The present invention will be explained in more detail below by way of experimental examples in place of working examples, but the present invention is not limited to these experimental examples.

[0094] The compounds used in the experimental examples are as follows: PE: High-density polyethylene (Product name: Cat. No. 547999, manufactured by Sigma-Aldrich)

[0095] Oxygen-containing plastic (1): Polyester resin represented by the following general formula (trade name: Bellpet (registered trademark) IP121B, manufactured by Bell Polyester Products Co., Ltd.)

[0096] [ka]

[0097] Oxygen-containing plastic (2): Polyurethane resin represented by the following general formula (trade name: Elastollan (registered trademark) C95A10, manufactured by BASF)

[0098] [ka]

[0099] Oxygen-containing plastic (3): Nylon 66 resin represented by the following general formula (trade name: Amilan (registered trademark) CM3001-N, manufactured by Toray Industries, Inc.)

[0100] [ka]

[0101] Oxygen-containing plastic (4): Nylon 6 resin represented by the following general formula (trade name: Nylon-6, Cat. No. 181110 (registered trademark), manufactured by Sigma-Aldrich)

[0102] [ka]

[0103] Oxygen-containing plastic (5): Polycarbonate resin represented by the following general formula (trade name: Iupilon S-3000R N113, manufactured by Mitsubishi Engineering-Plastics Corporation)

[0104] [ka]

[0105] Oxygen-containing plastic (6): Phenolic resin represented by the following general formula (trade name: Sumicon PM, manufactured by Sumitomo Bakelite Co., Ltd.)

[0106] [ka]

[0107] Oxygenated biomass-derived materials: Commercially available paper products containing polysaccharides represented by the following general formula:

[0108] [ka]

[0109] Oxygen-containing resin additive (1): bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (trade name: B3924, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0110] [ka]

[0111] Oxygen-containing resin additive (2): stearic acid amide (product name: S0075, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0112] [ka]

[0113] Oxygen-containing resin additive (3): 2-(5-tert-butyl-2-hydroxyphenyl)benzotriazole (trade name: H0719, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0114] [ka]

[0115] Oxygen-containing resin additive (4): dibutylhydroxytoluene (trade name: D0228, manufactured by Tokyo Chemical Industry Co., Ltd.; referred to as “BHT” in Table 1)

[0116] [ka]

[0117] Of the above compounds, the oxygen-containing plastic (1) is the oxygen-containing compound (B), and the oxygen-containing plastics (5) and (6) and the oxygen-containing resin additives (3) and (4) are the oxygen-containing compound (A).

[0118] <Evaluation method> (1) Evaluation of waste plastic raw materials (1-1) Method for measuring the content of oxygen-containing compounds (A) in waste plastic raw materials (equivalent to the amount of oxygen atoms bonded to aromatic rings) The molecular structures of the oxygen-containing plastics (1) to (6), oxygen-containing biomass-derived materials, and oxygen-containing resin additives (1) to (4) used in the examples and comparative examples are known, so the content of oxygen-containing compound (A) in the waste plastic raw material (equivalent to the amount of oxygen atoms bonded to aromatic rings) was calculated using the oxygen atom concentration in the waste plastic calculated using the "(1-3) Method for measuring oxygen atom concentration in waste plastic raw material" described below and the following formula (I).

[0119]

number

[0120] If the molecular structure of the oxygen-containing plastics and oxygen-containing resin additives in the waste plastics is unknown, the molecular structure can be identified by pyrolysis GC / MS analysis.

[0121] (1-2) Method for measuring the content of oxygen-containing compounds (B) in waste plastic raw materials (the amount of oxygen atoms that have a conjugated structure with aromatic rings other than oxygen atoms bonded to aromatic rings) The molecular structures of the oxygen-containing plastics (1) to (6), oxygen-containing biomass-derived materials, and oxygen-containing resin additives (1) to (4) used in the examples and comparative examples are known, so the content of oxygen-containing compound (B) in the waste plastic raw material (equivalent to the amount of oxygen atoms having a conjugated structure with an aromatic ring, other than oxygen atoms bonded to an aromatic ring) was calculated using the oxygen atom concentration in the waste plastic calculated using the "(1-3) Method for measuring oxygen atom concentration in waste plastic raw material" described below and the following formula (II).

[0122]

number

[0123] (1-3) Method for measuring oxygen atom concentration in waste plastic raw materials (1-3(a)) Oxygen-containing plastics First, oxygen analysis was performed on the oxygen-containing plastics (1) to (6) used in the examples and comparative examples using an elemental analyzer (device name: Vario EL cube, manufactured by Elemental) to measure the oxygen atom content (unit: mass %). Next, the content (unit: mass %) of oxygen atoms contained in the oxygen-containing plastic was calculated from the obtained value of the oxygen atom content. The measurement conditions were a fractionating column temperature of 1170°C and a measurement mode of "O (oxygen)." Benzoic acid was used as the standard substance, and the analytical value was the average of three measured values. Next, the oxygen atom concentration in the waste plastic raw material was calculated using the obtained content converted to oxygen atoms and the following formula (III).

[0124]

number

[0125] (1-3(b)) Oxygen-containing resin additives For the oxygen-containing resin additives (1) to (4) used in the examples and comparative examples, the content (unit: mass%) of oxygen atoms contained in the oxygen-containing resin additive was calculated from the molecular formula of the additive component, and the oxygen atom concentration in the waste plastic raw material was calculated using the following formula (IV).

[0126]

number

[0127] (2) Evaluation of decomposition gas The production rates of CO and / or CO2 in the decomposition product gases obtained in the Examples and Comparative Examples were measured according to the following method.

[0128] (2-1) Method for measuring the rate of CO and / or CO2 produced in decomposition product gas First, the "number of oxygen atoms in raw materials" used in the examples and comparative examples was measured using the "(2-1-1) method for measuring the number of oxygen atoms in raw materials" described below. Furthermore, the "number of oxygen atoms of CO and / or CO in decomposition product gases" obtained in the examples and comparative examples was measured using the "(2-1-2) method for measuring the number of oxygen atoms of CO and / or CO in decomposition product gases" described below. Next, the production ratio of CO and / or CO2 in the decomposition product gas obtained in the examples and comparative examples was calculated using the following formula (V).

[0129]

number

[0130] In other words, when the production ratio of CO and / or CO2 is 1.00, it means that all of the oxygen components in the raw material have been quantified as CO and / or CO2.

[0131] (2-1-1) Method for measuring the number of oxygen atoms in raw materials (2-1-1(a)) Oxygen-containing plastics The oxygen-containing plastics (1) to (6) used in the examples and comparative examples were subjected to oxygen analysis using an elemental analyzer (device name: Vario EL cube, manufactured by Elemental) to measure the oxygen atom content (unit: mass %). Next, the content (unit: mass %) of oxygen atoms contained in the oxygen-containing plastic was calculated from the obtained value of the oxygen atom content. The measurement conditions were a fractionating column temperature of 1170°C and a measurement mode of "O (oxygen)." Benzoic acid was used as the standard substance, and the analytical value was the average of three measured values.

[0132] Next, the number of oxygen atoms in the raw material was calculated using the obtained content converted to oxygen atoms and the following formula (VI).

[0133]

number

[0134] (2-1-1(b)) Oxygen-containing resin additives For the oxygen-containing resin additives (1) to (4) used in the examples and comparative examples, the content (unit: mass%) of oxygen atoms contained in the oxygen-containing resin additive was calculated from the molecular formula of the additive component, and the number of oxygen atoms in the raw material was calculated using the following formula (VII).

[0135]

number

[0136] (2-1-2) Method for measuring the number of oxygen atoms of CO and / or CO2 in decomposition product gas The concentrations of CO and / or CO2 in the decomposition product gases obtained in the Examples and Comparative Examples were quantified using gas chromatography (GC) under the following measurement conditions. <Measurement conditions> Measurement equipment: Gas chromatograph (GC-2014, manufactured by Shimadzu Corporation) Detector: Thermal conductivity detector (TCD) Detector temperature: 310℃ Column: Shincarbon-ST (product name, manufactured by Shinwa Chemical Industry Co., Ltd., inner diameter 3 mm x length 2 m) Column temperature: 40°C (hold time: 5 minutes) → Heat at 10°C / min → 300°C (hold time: 15 minutes) Carrier gas: Argon ·Inlet temperature: 100℃ ·Injection volume: 1mL Next, the number of oxygen atoms of CO and / or CO in the decomposition product gas was calculated using the volume of the decomposition product gas obtained in the examples and comparative examples, the obtained concentration of CO and / or CO, and the following formula (VIII).

[0137]

number

[0138] (3) Evaluation of cracked oil and aqueous phase (3-1) Calculation method for the generation rate of organic oxygen-containing components Since no oxygen-containing gas components other than CO or CO2 were detected, it was determined that all oxygen-containing decomposition products other than CO or CO2 were contained in the decomposition oil and aqueous phase as organic oxygen-containing components. Therefore, the production ratio of organic oxygen-containing components in the plastic decomposition oil and aqueous phase obtained in the Examples and Comparative Examples was calculated using the following formula (IX).

[0139]

number

[0140] (3-2) Method for calculating the ratio of the oxygen atom amount of organic oxygen-containing components to the total recovered amount of decomposition products Since no oxygen-containing gas components other than CO or CO2 were detected, it was assumed that all oxygen-containing decomposition products other than CO or CO2 were contained in the cracked oil and aqueous phase as organic oxygen-containing components. Therefore, the oxygen atom weight (unit: mg) of the organic oxygen-containing components in the cracked oil and aqueous phase obtained in the examples and comparative examples was calculated using the following formula (X). Next, the ratio (unit: mass %) of the oxygen atom amount of the organic oxygen-containing component to the total recovered amount of the decomposition products obtained in the Examples and Comparative Examples was calculated using the following formula (XI).

[0141]

number

[0142] [Example 1] A batch autoclave with a capacity of 50 mL was charged with 2.8 g (100 parts by mass) of PE (high-density polyethylene), 0.087 g (3.1 parts by mass) of oxygen-containing plastic (1), and 30 mL of water. After replacing the atmosphere in the autoclave with nitrogen, the autoclave was sealed and the temperature inside the autoclave was raised to 450 ° C using an electric furnace, and the internal pressure was set to 25 MPa. The reaction was continued for 25 minutes while maintaining this temperature and pressure. The reactor was then cooled to room temperature, and the contents were recovered to obtain cracked oil and an aqueous phase. Table 3 shows the production rates of organic oxygen-containing components and CO and / or CO2 in the cracked oil and aqueous phase, calculated according to the above-mentioned measurement methods.

[0143] [Examples 2 to 12, Comparative Examples 1 to 3] In Example 1, the oxygen-containing plastic (1) was replaced with an oxygen-containing compound or an oxygen-containing resin additive, and the type and amount of the oxygen-containing compound or the oxygen-containing resin additive were changed as shown in Tables 1 and 2. The decomposition treatment was carried out under the same conditions as in Example 1 to obtain a decomposed oil and an aqueous phase. The evaluation results of the obtained decomposed oil and aqueous phase are shown in Table 3.

[0144] [Table 1]

[0145] [Table 2]

[0146] [Table 3]

[0147] For Examples 1 to 12 and Comparative Examples 2 to 3, the relationship between the content of the oxygen-containing compound (A) in the waste plastic raw material (equivalent to the amount of oxygen atoms bonded to aromatic rings) (unit: mass%) and the ratio (unit: %) of the amount of oxygen atoms in the organic oxygen-containing components in the cracked oil and aqueous phase to the total recovered amount of decomposition products (cracked oil and aqueous phase) is shown in Figure 1.

[0148] It can be seen from Tables 1 to 3 and FIG. 1 that in the waste plastic raw materials of Examples 1 to 12, the oxygen atom weights of the organic oxygen-containing components in the cracked oil and aqueous phase are small. On the other hand, in the waste plastic raw material of Comparative Example 1, the content of oxygen-containing compound (B) other than oxygen-containing compound (A) having a conjugated structure in which an oxygen atom is conjugated with an aromatic ring (calculated as oxygen atoms having a conjugated structure with an aromatic ring other than oxygen atoms bonded to an aromatic ring) exceeded 2.50 mass% relative to the total mass of the waste plastic raw material, so the amount of oxygen atoms in the organic oxygen-containing components of the cracked oil and aqueous phase was large. Also, in the waste plastic raw materials of Comparative Examples 2 and 3, the content of oxygen-containing compound (A) having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring (calculated as oxygen atoms bonded to the aromatic ring) exceeded 0.40 mass% relative to the total mass of the waste plastic raw material, so the amount of oxygen atoms in the organic oxygen-containing components of the cracked oil and aqueous phase was large.

[0149] That is, in Example 1, the content of the polyester resin, which is the oxygen-containing compound (B), was below a predetermined value, so the oxygen atomic weight of the organic oxygen-containing components in the cracked oil and aqueous phase was small. Furthermore, in the commercially available paper product containing polysaccharide in Example 2, the polyurethane resin in Example 3, the nylon 66 resin in Example 4, the nylon 6 resin in Example 5, the bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate in Example 6, and the stearic acid amide in Example 7, the oxygen atoms bonded to the aromatic ring did not have a conjugated structure with the aromatic ring, so the oxygen atomic weight of the organic oxygen-containing components in the cracked oil and aqueous phase was small. Furthermore, in Examples 8 to 12, the content of dibutylhydroxytoluene (BHT) or phenol resin, which is the oxygen-containing compound (A), was below a predetermined value, so the oxygen atomic weight of the organic oxygen-containing components in the cracked oil and aqueous phase was small.

[0150] On the other hand, in Comparative Example 1, the content of the polyester resin, which is the oxygen-containing compound (B), exceeded the predetermined value, so the oxygen atom weight of the organic oxygen-containing component in the cracked oil and aqueous phase was large. In Comparative Example 2, the polycarbonate resin was the oxygen-containing compound (A), and in Comparative Example 3, the phenol resin was the oxygen-containing compound (A), and both exceeded the predetermined value, so the production ratio of the organic oxygen-containing component in the cracked oil and aqueous phase was large.

[0151] The reason for the above results is presumably that the oxygen-containing raw material (A), which has a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring, and the oxygen-containing compound (B), other than the oxygen-containing compound (A), which has a conjugated structure in which an oxygen atom is conjugated with an aromatic ring, have strong carbon-oxygen bonds and are therefore less likely to be thermally decomposed under the thermal decomposition conditions, and therefore are less likely to undergo a decomposition reaction to CO and / or CO2.

[0152] Therefore, by using waste plastic raw materials in which the content ratio of oxygen-containing raw material (A) having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring (equivalent to the amount of oxygen atoms bonded to the aromatic ring) and the content of oxygen-containing compound (B) other than oxygen-containing compound (A) having a conjugated structure in which an oxygen atom is conjugated with an aromatic ring are kept below a specified value, it is possible to obtain high-quality plastic decomposition oil with few residual organic oxygen components, and it is expected that the load on wastewater treatment can be reduced and corrosion of thermal decomposition equipment, etc. can be suppressed.

Claims

1. A waste plastic raw material used for producing plastic decomposition oil, The composition contains a polyolefin polymer, and The composition further comprises at least one of an oxygen-containing compound (A) having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring, and an oxygen-containing compound (B) other than the oxygen-containing compound (A) having a conjugated structure in which an oxygen atom is conjugated with the aromatic ring, The content of the oxygen-containing compound (A) is 0.40 mass% or less, calculated as oxygen atoms bonded to aromatic rings, relative to the total mass of the waste plastic raw material, and the content of the oxygen-containing compound (B) is 2.50 mass% or less, calculated as oxygen atoms having a conjugated structure with aromatic rings other than oxygen atoms bonded to aromatic rings.

2. 2. The waste plastic raw material according to claim 1, wherein the oxygen-containing compound (A) comprises at least one chemical structure selected from the group consisting of an aromatic hetero five-membered ring structure in which the heteroatom is oxygen, an aromatic hetero six-membered ring structure in which the heteroatom is oxygen, and a phenol structure or a phenol derivative structure.

3. 3. The waste plastic raw material according to claim 1, wherein the oxygen-containing compound (B) comprises a compound having an aromatic ester structure in which an ester bond is bonded to an aromatic ring on the carbonyl group side.

4. The waste plastic material according to claim 1 or 2, further comprising biomass.

5. The waste plastic raw material according to claim 1 or 2, wherein the polyolefin polymer is contained in an amount of 60 mass% or more based on the total mass of the waste plastic raw material.

6. A plastic decomposition oil, which is a decomposition product of the waste plastic raw material according to claim 1 or 2.

7. A method for producing plastic decomposition oil, comprising decomposing waste plastic raw materials to obtain plastic decomposition oil, determining whether or not the content ratio of an oxygen-containing compound (A) having a conjugated structure in which an oxygen atom bonded to an aromatic ring is conjugated with the aromatic ring, and the content ratio of an oxygen-containing compound (B) other than the oxygen-containing compound (A) having a conjugated structure in which an oxygen atom is conjugated with an aromatic ring, contained in the waste plastic raw material (P1), exceed a predetermined value relative to the total mass of the waste plastic raw material (P1); the predetermined value of the oxygen-containing compound (A) is 0.40 mass% in terms of oxygen atoms bonded to aromatic rings, the predetermined value of the oxygen-containing compound (B) is 2.50 mass% in terms of oxygen atoms having a conjugated structure with the aromatic ring other than oxygen atoms bonded to the aromatic ring, In the determination, when the content ratio of at least one of the oxygen-containing compound (A) and the oxygen-containing compound (B) exceeds the predetermined value, (i) further mixing other plastics (P3) with the waste plastic raw material (P1), and reducing the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) contained in the resulting waste plastic raw material (P4) to the predetermined values ​​or less relative to the total mass of the waste plastic raw material (P4), and then decomposing the waste plastic raw material (P4); or (ii) removing a portion of the waste plastic raw material (P1), and reducing the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) contained in the obtained waste plastic raw material (P2) to the predetermined values ​​or less relative to the total mass of the waste plastic raw material (P2), and then decomposing the waste plastic raw material (P2); or In the determination, if the content ratios of the oxygen-containing compound (A) and the oxygen-containing compound (B) do not exceed the predetermined value, (iii) decomposing the waste plastic raw material (P1); A method for producing plastic decomposition oil.

8. 8. The method for producing plastic decomposition oil according to claim 7, wherein the oxygen-containing compound (A) contains at least one chemical structure selected from the group consisting of an aromatic hetero five-membered ring structure in which the heteroatom is oxygen, an aromatic hetero six-membered ring structure in which the heteroatom is oxygen, and a phenol structure or a phenol derivative structure.

9. The method for producing plastic decomposition oil according to claim 7, wherein the waste plastic raw material (P1) contains an oxygen component.

10. The method for producing plastic decomposition oil according to any one of claims 7 to 9, wherein the waste plastic raw material (P1) contains 60 mass% or more of a polyolefin polymer relative to the total mass of the waste plastic raw material (P1).

11. The method for producing plastic decomposition oil according to any one of claims 7 to 9, wherein the waste plastic raw material (P4) contains 60 mass% or more of a polyolefin polymer relative to the total mass of the waste plastic raw material (P4).

12. The method for producing plastic decomposition oil according to any one of claims 7 to 9, wherein the waste plastic raw material (P2) contains 60 mass% or more of a polyolefin polymer relative to the total mass of the waste plastic raw material (P2).

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