Recycling methods for styrene resins

Abstract

To provide a recycling method for recovering a styrene monomer by pyrolyzing a flame-retardant styrene in terms of resin composition, which does not cause corrosive gas, reduces combustion residues, and has a high styrene monomer recovery rate.SOLUTION: A recycling method for recovering a styrene monomer from a styrenic resin is provided, including a step (1) for preparing a mixture that comprises a styrenic resin material (A) comprising the styrenic resin, blended with an NOR hindered amine compound (B) and a step (2) for pyrolyzing the mixture.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a recycling method for recovering styrene monomer from a styrene-based resin. [Background technology]

[0002] Styrenic resins are used in a wide range of applications due to their excellent moldability, dimensional stability, and impact resistance. In particular, flame-retardant polystyrene resin compositions are used in a wide range of applications, including home appliances and office equipment, and are used in exterior components, transparent parts, and other components that require design.

[0003] In recent years, environmental and resource depletion issues have led to increased demand for the recycling of materials, and material recycling efforts are being promoted. While material recycling is being implemented, materials that are heavily soiled or have undergone significant resin degradation cannot be recycled, and chemical recycling is expected to be the next step. For styrene-based resins, chemical recycling has been developed to recover styrene monomer through thermal decomposition, but flame-retardant polystyrene resins in particular face challenges such as increased corrosive gases and combustion residues, as well as a decrease in styrene monomer yield, making chemical recycling unfeasible.

[0004] For example, Patent Document 1 discloses a technology for recovering styrene monomers from styrene resins, and Patent Document 2 discloses a flame retardant technology in which a specific NOR-type hindered amine compound is blended. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-2088 [Patent Document 2] Special Publication No. 2002-507238 Summary of the Invention [Problem to be solved by the invention]

[0006] However, Patent Document 1 only proposes removing the combustion residue using processing equipment because the residual solid content in the residue of styrene-based resins has a negative impact on chemical recycling, and does not describe anything about the materials. Furthermore, there is a problem that equipment is required to remove the residual solid content generated by the combustion of styrene-based resins, which makes the equipment complex and expensive. Furthermore, Patent Document 2 only describes technology related to flame retardancy, and does not describe anything about the thermal decomposition of styrene-based resins.

[0007] Therefore, an object of the present invention is to provide a recycling method that suppresses or prevents the generation of corrosive gases in recycling in which a styrene-based resin is thermally decomposed to recover styrene monomer, reduces combustion residues that become solids remaining during the thermal decomposition of a styrene-based resin, and allows styrene monomer to be easily obtained with a high styrene monomer recovery rate. [Means for solving the problem]

[0008] As a result of intensive research to solve the above problems, the present inventors have found that a recycling method can be obtained in which the generation of corrosive gases is suppressed or prevented, combustion residues are reduced, the styrene monomer recovery rate is high, and styrene monomer can be easily obtained by thermally decomposing a material containing a NOR-type hindered amine compound and a styrene resin, and have completed the present invention.

[0009] That is, the present invention is as follows. [1] A recycling method for recovering styrene monomer from styrene-based resin, A step (1) of preparing a mixture by blending a NOR type hindered amine compound (B) with a styrene-based resin material (A) containing the styrene-based resin; and (2) thermally decomposing the mixture.

[0010] [2] The content of the NOR type hindered amine compound (B) in the mixture is preferably 0.1 to 5.0 parts by mass per 100 parts by mass of the styrene resin material (A).

[0011] [3] The styrene-based resin material (A) is preferably a styrene-based resin including a rubber-modified styrene-based resin.

[0012] [4] The mixture preferably further contains 0.1 to 30 parts by mass of a phosphorus-based flame retardant (C) relative to 100 parts by mass of the styrene-based resin material (A).

[0013] [5] The styrene-based resin material (A) is preferably a post-consumer material. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a recycling method in which a styrene-based resin is thermally decomposed to recover styrene monomer, which does not generate corrosive gases or suppresses the generation of corrosive gases, reduces combustion residues that become residual solids, and achieves a high recovery rate of styrene monomer. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following describes in detail an embodiment of the present invention (hereinafter referred to as "the present embodiment"); however, the present invention is not limited to the following description and can be implemented in various modifications within the scope of its gist.

[0016] [How to recycle styrene resin] The method for recycling a styrene-based resin according to the present embodiment is a method for recovering styrene monomer from a styrene-based resin. The styrene-based resin may be a used, discarded, or to-be-discarded styrene-based resin. That is, the method for recycling a styrene-based resin includes a step (1) of preparing a mixture by blending a NOR-type hindered amine compound (B) with a styrene-based resin material (A) containing the styrene-based resin, and a step (2) of thermally decomposing the mixture. If necessary, a phosphorus-based flame retardant (C) may be blended into the mixture in the step (1) or the step (2). This allows no or suppressed generation of corrosive gases during the thermal decomposition of the styrene-based resin or the styrene-based resin material (A), reduces combustion residues that become residual solids, and enables easy production of styrene monomer with a high recovery rate.

[0017] Each step will be described in detail below. (Process (1)) The recycling method of the present embodiment for recovering styrene monomer from a styrene-based resin includes a step (1) of preparing a mixture of a styrene-based resin material (A) containing a styrene-based resin and a NOR-type hindered amine compound (B). The mixture in this embodiment may contain a styrene-based resin material (A) containing a styrene-based resin and a NOR-type hindered amine compound (B). The dispersion state of the NOR-type hindered amine compound (B) in the styrene-based resin material (A) is not particularly limited. Premixing may be performed using a known mixing or kneading mechanism before or during step (2), which will be described later. The mixing or kneading mechanism is not particularly limited, and a method that uniformly mixes the components in the mixture is preferred. Melt mixing or melt kneading may also be used, if necessary. Specific examples of the mixing or kneading mechanism include a single-screw extruder, a twin-screw extruder, a screw-type extruder, an open roll, a kneader, a Banbury mixer, and an internal mixer. The mixing or kneading time is preferably about 1 to 10 minutes. Furthermore, the temperature condition for melt kneading is preferably 180 to 260°C. Furthermore, when melt-kneading, it is preferable to reduce the pressure inside the kneading mechanism (or inside the kneading device), and the vacuum pressure is preferably 500 mmHg or more. Note that the vacuum pressure refers to the pressure difference between atmospheric pressure and the pressure inside the kneading mechanism, and can be reduced through a vent or the like. In the mixture of this embodiment, the NOR type hindered amine compound (B) is preferably blended in an amount of 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, and even more preferably 0.3 to 3 parts by mass, relative to the styrene type resin material (A) (100 parts by mass). More specifically, in the mixture of this embodiment, the NOR type hindered amine compound (B) is preferably blended in an amount of 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, and even more preferably 0.3 to 3 parts by mass, relative to the styrene type resin (100 parts by mass).

[0018] <Styrene-based resin material (A): Component (A)> In the method for recycling styrene-based resins of this embodiment, the styrene-based resin material (A) is a pre-consumer material such as a factory-collected product, a post-consumer material such as a market-collected product, or in some cases, long-term inventory pellets, non-standard pellets, etc. Furthermore, the styrene-based resin material (A) is a flame-retardant styrene-based resin containing a phosphorus-based flame retardant, and may contain liquid paraffin, stabilizers, colorants, etc. It can also be used for products in which other resins such as olefin-based resins or polyether-based resins are laminated, or for mixed resins in which other resins such as olefin-based resins or polyether-based resins are mixed. This recycling method is particularly useful for rubber-modified styrene-based resins that produce residues during thermal decomposition, and is more environmentally friendly for post-consumer materials.

[0019] The styrene resin contained in the styrene resin material (A) usable in this embodiment may be a used, discarded, or discarded styrene resin. The styrene resin may contain styrene monomer units, and is preferably a resin obtained by polymerizing styrene monomer units and, if necessary, one or more selected from other vinyl monomer units copolymerizable with the styrene monomer and rubbery polymer (a). In other words, the styrene resin is preferably a polymer containing styrene monomer units, and more preferably a polymer that essentially contains styrene monomer units and optionally contains other vinyl monomers copolymerizable with the styrene monomer units and / or monomer units of rubbery polymer (a). The preferred form of the styrene-based resin in this embodiment is not particularly limited, but specific examples include a rubber-modified styrene-based resin in which particles of a rubber-like polymer (a) are dispersed in a polymer matrix containing polystyrene, a polystyrene-based polymer (polystyrene and / or polystyrene-unsaturated carboxylic acid polymer, etc.), or a styrene-based copolymer resin. The styrene-based resin contained in the styrene-based resin material (A) usable in this embodiment may contain 50% by mass or more of styrene-based monomer units relative to the entire styrene-based resin (100% by mass), preferably 60% by mass or more, and more preferably 70% by mass or more. In this embodiment, the styrene-based resin contained in the styrene-based resin material (A) may contain 70% by mass or more of the styrene-based resin relative to the entire styrene-based resin material (A) (100% by mass), preferably 75% by mass or more, and more preferably 80% by mass or more.

[0020] <<Polystyrene>> In this embodiment, polystyrene refers to a homopolymer obtained by polymerizing a styrene-based monomer, and a commonly available one can be appropriately selected and used. Examples of styrene-based monomers constituting polystyrene include, in addition to styrene, α-methylstyrene, α-methyl-p-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, and t-butylstyrene, as well as styrene derivatives such as bromostyrene and indene. Styrene is particularly preferred from an industrial perspective. One or more of these styrene-based monomers can be used. While polystyrene may contain further monomer units other than the above-mentioned styrene-based monomer units as long as the effects of the present invention are not impaired, polystyrene typically consists of styrene-based monomer units.

[0021] <<Rubber-modified styrene resin>> In this embodiment, the rubber-modified styrene-based resin is a resin in which particles of a rubber-like polymer (a) are dispersed in a styrene-based resin matrix, and can be produced by polymerizing a styrene-based monomer in the presence of the rubber-like polymer (a).

[0022] Examples of styrene-based monomers constituting the rubber-modified styrene-based resin of this embodiment include, in addition to styrene, α-methylstyrene, α-methyl-p-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, t-butylstyrene, and styrene derivatives such as bromostyrene and indene. Styrene is particularly preferred. These styrene-based monomers can be used alone or in combination.

[0023] The rubber-like polymer (a) contained in the rubber-modified styrene-based resin of this embodiment may, for example, contain a resin containing a styrene monomer unit obtained from the above-mentioned styrene-based monomer inside the rubber-like polymer (a), and / or may be a rubber-like polymer (a) having a resin containing a styrene monomer unit grafted onto the surface thereof.

[0024] Examples of the rubbery polymer (a) that can be used include rubber components such as polybutadiene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, and acrylonitrile-butadiene copolymer. The rubber component may also contain polystyrene and / or polystyrene-unsaturated carboxylic acid polymers. Among these, polybutadiene or styrene-butadiene copolymer is preferred as the rubbery polymer (a). Both high-cis polybutadiene with a high cis content and low-cis polybutadiene with a low cis content can be used as the polybutadiene. The styrene-butadiene copolymer can have either a random structure or a block structure. One or more of these rubbery polymers (a) can be used. Saturated rubbers obtained by hydrogenating butadiene rubbers can also be used.

[0025] Examples of such rubber-modified styrene resins include HIPS (high impact polystyrene), ABS resin (acrylonitrile-butadiene-styrene copolymer), AAS resin (acrylonitrile-acrylic rubber-styrene copolymer), and AES resin (acrylonitrile-ethylene propylene rubber-styrene copolymer).

[0026] When the rubber-modified styrene resin is a HIPS resin, the particularly preferred rubber polymer (a) is a high-cis polybutadiene having 90 mol % or more of cis-1,4 bonds. In the high-cis polybutadiene, vinyl-1,2 bonds are preferably 6 mol % or less, and particularly preferably 3 mol % or less.

[0027] The content of isomers having a cis-1,4 structure, a trans-1,4 structure, or a vinyl-1,2 structure as structural unit isomers of the high-cis polybutadiene can be measured using an infrared spectrophotometer and calculated by processing the data by the Morello method.

[0028] The high-cis polybutadiene can be easily obtained by a known production method, for example, by polymerizing 1,3-butadiene using a catalyst containing an organoaluminum compound and a cobalt or nickel compound.

[0029] The content of the rubber-like polymer (a) in the rubber-modified styrene-based resin is preferably 3 to 20 mass% and more preferably 5 to 15 mass% relative to the total amount of the rubber-modified styrene-based resin (100 mass%). If the content of the rubber-like polymer (a) is less than 3 mass%, the impact resistance of the styrene-based resin may be reduced. If the content of the rubber-like polymer (a) is more than 20 mass%, the flame retardancy may be reduced.

[0030] In the present disclosure, the content of the rubber-like polymer (a) contained in the rubber-modified styrene-based resin is a value calculated using pyrolysis gas chromatography.

[0031] The average particle size of the rubbery polymer (a) contained in the rubber-modified styrene-based resin is preferably 0.5 to 4.0 μm, more preferably 0.8 to 3.5 μm, from the viewpoint of impact resistance and flame retardancy.

[0032] In the present disclosure, the average particle size of the rubber-like polymer (a) contained in the rubber-modified styrene-based resin can be measured by the following method. An ultrathin section with a thickness of 75 nm is prepared from a rubber-modified styrene-based resin stained with osmium tetroxide, and a photograph is taken at a magnification of 10,000 times using an electron microscope. In the photograph, the black-stained particles are the rubber-like polymer (a). From the photograph, the following mathematical formula (N1): Average particle diameter=ΣniDri 3 / ΣniDri 2 (N1) (In the above formula (N1), ni is the number of rubber polymer (a) particles having a particle diameter Dri, and the particle diameter Dri is the particle diameter calculated as a circle-equivalent diameter from the area of ​​the particle in the photograph.) The area-average particle diameter is calculated by the above equation, and is taken as the average particle diameter of the rubber-like polymer (a). This measurement is carried out by scanning a photograph at a resolution of 200 dpi and using particle analysis software of an image analyzer IP-1000 (manufactured by Asahi Kasei Corporation).

[0033] The reduced viscosity of the rubber-modified styrene resin (which is an index of the molecular weight of the rubber-modified styrene resin) is preferably in the range of 0.50 to 0.85 dL / g, more preferably 0.55 to 0.80 dL / g. If it is less than 0.50 dL / g, there is a risk of reduced impact strength, and if it exceeds 0.85 dL / g, there is a risk of reduced moldability due to reduced fluidity.

[0034] In the present disclosure, the reduced viscosity of the rubber-modified styrene-based resin is a value measured in a toluene solution at 30° C. and a concentration of 0.5 g / dL.

[0035] The method for producing the rubber-modified styrenic resin is not particularly limited, but it can be produced by bulk polymerization (or solution polymerization) in which a styrenic monomer (and a solvent) is polymerized in the presence of the rubber-like polymer (a), or by bulk-suspension polymerization in which the reaction transitions to suspension polymerization during the course of the reaction, or by emulsion graft polymerization in which a styrenic monomer is polymerized in the presence of a rubber-like polymer (a) latex. In bulk polymerization, the resin can be produced by continuously supplying a mixed solution of the rubber-like polymer (a) and the styrenic monomer, and optionally an organic solvent, an organic peroxide, and / or a chain transfer agent, to a polymerization apparatus consisting of a complete mixing reactor or a tank reactor and multiple tank reactors connected in series.

[0036] <Styrene copolymer resin> In this embodiment, the styrene-based copolymer resin refers to a resin containing a styrene-based monomer unit and another monomer (e.g., an unsaturated carboxylic acid-based monomer unit) copolymerizable with the styrene-based monomer. For example, when the other monomer is an unsaturated carboxylic acid-based monomer unit, the styrene-based copolymer resin according to the present invention preferably has a styrene-based monomer unit content of 69 to 98% by mass, more preferably 74 to 96% by mass, and even more preferably 77 to 92% by mass, when the total content of the styrene-based monomer unit and the unsaturated carboxylic acid-based monomer unit is taken as 100% by mass. By setting the content to 69% by mass or more, the fluidity of the resin can be improved. On the other hand, by setting the content of the styrene-based monomer unit to 98% by mass or less, it becomes difficult to obtain a desired amount of an unsaturated carboxylic acid-based monomer unit (described below), which is an example of the other monomer, and it becomes difficult to obtain the effects described below of these monomer units.

[0037] The unsaturated carboxylic acid monomer in this embodiment includes an unsaturated carboxylic acid monomer and an unsaturated carboxylic acid ester monomer.

[0038] In a preferred styrene-based copolymer resin of this embodiment, the unsaturated carboxylic acid monomer unit plays a role in improving heat resistance. When the total content of the styrene-based monomer units, unsaturated carboxylic acid monomer units, and unsaturated carboxylic acid ester monomer units in the styrene-based copolymer resin is taken as 100% by mass, the content of the unsaturated carboxylic acid monomer units is preferably 2 to 16% by mass, more preferably 4 to 14% by mass, and even more preferably 8 to 13% by mass. By setting the content to 2% by mass or more, the dispersibility of component (B) can be improved and heat resistance can be further improved. On the other hand, by setting the content to 16% by mass or less, when the flame-retardant styrene-based resin composition of this embodiment is used as a masterbatch, excellent dispersibility in the styrene-based resin can be exhibited, improving flame retardancy, and further improving molded appearance, resin flowability, and mechanical properties.

[0039] Generally, styrene-methacrylic acid-based resins including styrene-methacrylic acid-methyl methacrylate copolymer resins, which are one form of the styrene-based copolymer resins of the present invention, are mostly produced on an industrial scale by radical polymerization. However, in this embodiment, in order to suppress the gelation reaction in the devolatilization step, various alcohols can be added to the polymerization system to carry out the polymerization.

[0040] The unsaturated carboxylic acid ester monomer can be used to suppress the dehydration reaction of the unsaturated carboxylic acid monomer through intermolecular interaction with the unsaturated carboxylic acid monomer and to improve the mechanical strength of the resin, and further contributes to improving resin properties such as weather resistance and surface hardness.

[0041] In this embodiment, when the total content of the styrene-based monomer units, unsaturated carboxylic acid monomer units, and unsaturated carboxylic acid ester monomer units is taken as 100% by mass, the content of the unsaturated carboxylic acid ester monomer units is preferably 0 to 15% by mass, more preferably 1 to 12% by mass, and even more preferably 2 to 10% by mass. By setting the content to 15% by mass or less, the fluidity of the resin can be improved and water absorption can be suppressed. Furthermore, by setting the lower limit of the content of the unsaturated carboxylic acid ester monomer units to 0% by mass, heat resistance can be improved and costs can be reduced, but from the above-mentioned perspective, the content of the unsaturated carboxylic acid ester monomer units can also be set to more than 0% by mass.

[0042] In addition, when an unsaturated carboxylic acid monomer and an unsaturated carboxylic acid ester monomer unit are bonded adjacent to each other, a dealcoholization reaction may occur under certain conditions when a high-temperature, high-vacuum devolatilizer is used, resulting in the formation of a six-membered cyclic acid anhydride. The styrene-based copolymer resin of the present embodiment may contain this six-membered cyclic acid anhydride, but since this reduces fluidity, it is preferable that the amount of the six-membered cyclic acid anhydride produced is as small as possible.

[0043] In the present embodiment, the contents of the styrene-based monomer unit (for example, styrene monomer unit), the unsaturated carboxylic acid monomer unit (for example, methacrylic acid monomer unit), and the unsaturated carboxylic acid ester monomer unit (for example, methyl methacrylate monomer unit) in the styrene-based copolymer resin can be determined by proton nuclear magnetic resonance ( 1 It can be calculated from the integral ratio of the spectrum measured by a H-NMR spectrometer.

[0044] In the present embodiment, the styrene-based copolymer resin may further contain monomer units other than the styrene-based monomer units and unsaturated carboxylic acid-based monomer units (e.g., unsaturated carboxylic acid monomer units and unsaturated carboxylic acid ester monomer units), which are examples of other monomers, within a range that does not impair the effects of the present invention. However, the styrene-based copolymer resin in the present invention is typically preferably composed of styrene-based monomer units, unsaturated carboxylic acid monomer units, and / or unsaturated carboxylic acid ester monomer units.

[0045] The styrene-based monomer constituting the styrene-based copolymer resin of this embodiment is not particularly limited, but examples thereof include styrene, α-methylstyrene, α-methyl-p-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, t-butylstyrene, bromostyrene, and styrene derivatives such as indene. From an industrial viewpoint, styrene is preferred as the styrene-based monomer. These styrene-based monomers can be used alone or in combination of two or more.

[0046] The unsaturated carboxylic acid monomer constituting the styrene-based copolymer resin of this embodiment is not particularly limited, but examples thereof include methacrylic acid, acrylic acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, etc. As the unsaturated carboxylic acid monomer, methacrylic acid is preferred because it has a significant effect of improving heat resistance, is liquid at room temperature, and has excellent handleability. These unsaturated carboxylic acid monomers can be used alone or in combination of two or more.

[0047] The unsaturated carboxylic acid ester monomer constituting the styrene copolymer resin of this embodiment is not particularly limited, but examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and cyclohexyl (meth)acrylate. As the (meth)acrylic acid ester monomer, methyl (meth)acrylate is preferred because it has little effect on the deterioration of heat resistance. These unsaturated carboxylic acid ester monomers can be used alone or in combination of two or more.

[0048] Suitable styrene copolymer resins for this embodiment include styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-methacrylic acid-methyl methacrylate copolymer, styrene-acrylic acid copolymer, styrene-methyl acrylate copolymer, styrene-acrylic acid-methyl acrylate copolymer, styrene-methyl methacrylate-butyl methacrylate copolymer, styrene-butyl methacrylate copolymer, and styrene-maleic anhydride copolymer.

[0049] In this embodiment, the weight-average molecular weight (Mw) of the styrene copolymer resin is preferably 100,000 to 350,000, more preferably 120,000 to 300,000, and even more preferably 140,000 to 240,000. When the weight-average molecular weight (Mw) is 100,000 to 350,000, a resin with an excellent balance between mechanical strength and fluidity is obtained, and the amount of gel contamination is also reduced. The weight-average molecular weight (Mw) is a value obtained by gel permeation chromatography in terms of standard polystyrene.

[0050] In the present embodiment, the polymerization method for the styrene-based alkoxy group polymerized resin is not particularly limited, but for example, bulk polymerization or solution polymerization can be suitably adopted as a radical polymerization method. The polymerization method mainly comprises a polymerization step of polymerizing polymerization raw materials (monomer components) and a devolatilization step of removing volatile components such as unreacted monomers and polymerization solvent from the polymerization product.

[0051] An example of a method for polymerizing a styrene copolymer resin that can be used in this embodiment will be described below.

[0052] When the polymerization raw materials are polymerized to obtain a styrene copolymer resin, a polymerization initiator and a chain transfer agent are typically contained in the polymerization raw material composition.

[0053] Examples of polymerization initiators used in the polymerization of styrene copolymer resins include organic peroxides, such as peroxyketals such as 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)cyclohexane, and n-butyl-4,4-bis(t-butylperoxy)valerate; dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide; diacyl peroxides such as acetyl peroxide and isobutyryl peroxide; peroxydicarbonates such as diisopropyl peroxydicarbonate; peroxyesters such as t-butyl peroxyacetate; ketone peroxides such as acetylacetone peroxide; and hydroperoxides such as t-butyl hydroperoxide. Among these, 1,1-bis(t-butylperoxy)cyclohexane is preferred from the viewpoints of decomposition rate and polymerization rate.

[0054] Examples of the chain transfer agent used in the polymerization of the styrene copolymer resin include α-methylstyrene linear dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-octyl mercaptan.

[0055] Solution polymerization using a polymerization solvent can be used as a polymerization method for styrene copolymer resins, if necessary. Examples of polymerization solvents include aromatic hydrocarbons, such as ethylbenzene, and dialkyl ketones, such as methyl ethyl ketone. These solvents can be used alone or in combination. Other polymerization solvents, such as aliphatic hydrocarbons, can be added to the aromatic hydrocarbons as long as they do not reduce the solubility of the polymerization product. These polymerization solvents are preferably used in an amount not exceeding 25 parts by weight per 100 parts by weight of the total monomers. If the amount of polymerization solvent exceeds 25 parts by weight per 100 parts by weight of the total monomers, the polymerization rate tends to decrease significantly and the mechanical strength of the resulting resin tends to decrease significantly. Adding the polymerization solvent at a ratio of 5 to 20 parts by weight per 100 parts by weight of the total monomers before polymerization facilitates uniform quality and is also preferable in terms of controlling the polymerization temperature.

[0056] In this embodiment, the apparatus used in the polymerization step for obtaining the styrene-based copolymer resin is not particularly limited and may be appropriately selected according to the polymerization method of the styrene-based resin. For example, when bulk polymerization is employed, a polymerization apparatus using one or a plurality of completely mixed reactors connected in series can be used. Also, there is no particular limitation on the devolatilization step. When bulk polymerization is adopted, the polymerization is carried out until the unreacted monomer finally becomes preferably 50% by mass or less, more preferably 40% by mass or less, and the volatile components such as such unreacted monomers are removed by a known method for devolatilization treatment. More specifically, for example, ordinary devolatilization apparatuses such as a flash drum, a twin-screw devolatilizer, a thin-film evaporator, and an extruder can be used, but a devolatilization apparatus with less residence parts is preferred. The temperature of the devolatilization treatment is usually about 190 to 280°C, and from the viewpoint of suppressing the formation of a six-membered cyclic acid anhydride due to the adjacency of an unsaturated carboxylic acid monomer (for example, methacrylic acid) and an unsaturated carboxylic acid ester monomer (for example, methyl methacrylate), 190 to 260°C is more preferred. The pressure of the devolatilization treatment is usually about 0.13 to 4.0 kPa, preferably 0.13 to 3.0 kPa, and more preferably 0.13 to 2.0 kPa. As the devolatilization method, for example, a method of removing volatile components by reducing the pressure under heating and a method of removing through an extruder or the like designed for the purpose of removing volatile components are desirable.

[0057] <NOR type hindered amine compound (B): Component (B)> The content of the NOR type hindered amine compound (B) in the mixture of this embodiment is preferably 0.1 to 5 parts by mass, more preferably 0.3 to 3 parts by mass, and even more preferably 0.5 to 2.0 parts by mass, relative to 100 parts by mass of the component (A). When the content of the NOR type hindered amine compound (B) is 0.1 part by mass or more, the combustion residue generated when the styrene-based resin is thermally decomposed can be reduced, and the styrene monomer can be recovered in a high yield. The component (B) may be added directly as an additive, or a compound already contained in the styrene-based resin or the styrene-based resin material (A) can also be used. Furthermore, a recycled material containing the NOR type hindered amine compound (B), such as a post-consumer material, can also be used. In this case, it is not necessary to add another styrene-based resin when recycling. The content of the NOR type hindered amine compound can be quantified by dissolving it in THF solvent and then performing gravimetric analysis using a gas chromatograph.

[0058] In addition, component (B) stabilizes the radical decomposition products from the styrene-based resin during thermal decomposition, resulting in a high recovery rate of styrene monomer and no residue. Furthermore, when the styrene-based resin or styrene-based resin material (A) contains a phosphorus-based flame retardant (C), it reacts with the phosphorus flame retardant decomposition products and reduces phosphorus-derived residues. On the other hand, such an effect is not observed in the case of N-methyl-type hindered amine compounds or NH-type hindered amine compounds.

[0059] The NOR type hindered amine compound (B) used in this embodiment is not particularly limited as long as it has an N-alkoxyl group (>N-OR) structure. Specific examples of the NOR type hindered amine compounds (B) include those described in JP-A No. 2002-507238, WO 2005 / 082852, WO 2008 / 003605, etc.

[0060] Furthermore, the NOR type hindered amine compound (B) is preferably a polymeric type. The polymeric type is generally an oligomeric or polymeric compound. The polymeric type can reduce mold deposits during molding processing and has excellent flame retardancy and heat resistance.

[0061] The oligomeric or polymeric NOR type hindered amine compound (B) preferably has 2 to 100 repeating units, and more preferably 5 to 80 repeating units.

[0062] Specific examples of the NOR type hindered amine compound (B) that can be used in this embodiment include the following compounds: 1-cyclohexyloxy-2,2,6,6-tetramethyl-4-octadecylaminopiperidine; 2,2,6,6-tetramethyl-4-piperidyl)sebacate; 2,4-bis[(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)butylamino]-6-(2-hydroxyethylamino)-s-triazine; bis(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidine- 4-yl)adipate; an oligomeric compound which is a condensation product of 4,4'-hexamethylenebis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-[(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl)butylamino]-s-triazine end-capped with 2-chloro-4,6-bis(dibutylamino)-s-triazine; an oligomeric compound which is a condensation product of 4,4'-hexamethylenebis(amino-2,2,6,6-tetramethylpiperidine) and 2-chloro-4,6-bis(dibutylamino)-s-triazine end-capped with 2-chloro-4,6-bis(dibutylamino)-s-triazine; Oligomeric compounds that are condensation products of end-capped 2,4-dichloro-6-[(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)butylamino]-s-triazine; 2,4-bis[(1-cyclohexyloxy-2,2,6,6-piperidin-4-yl)-6-chloro-s-triazine]; peroxidized 4-butylamino-2,2,6,6-tetramethylpiperidine, 2,4,6-trichloro-s-triazine, cyclohexane, and N,N'-ethane-1,2-diylbis(1,3-propanediol). amine) (N,N',N'''-tris{2,4-bis[(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)n-butylamino]-s-triazin-6-yl}-3,3'-ethylenediiminodipropylamine); bis(1-undecanoxy-2,2,6,6-tetramethylpiperidin-4-yl)carbonate; 1-undecyloxy-2,2,6,6-tetramethylpiperidin-4-one; bis(1-stearyloxy-2,2,6,6-tetramethylpiperidin-4-yl)carbonate.

[0063] The NOR hindered amine compound (B) of the present embodiment may be a commercially available product, and examples thereof include FlamestabNOR116FF, TINUVIN NOR371, TINUVIN XT850FF, TINUVIN XT855FF, and TINUVIN PA123 manufactured by BASF, and LA-77Y, LA-81, and FP-T80 manufactured by ADEKA Corporation. In the present embodiment, the NOR type hindered amine compound (B) may be used alone or in combination of two or more.

[0064] <Phosphorus-based flame retardant (C): Component (C)> In step (1) or step (2) of this embodiment, the styrene-based resin material (A) or the mixture may contain a phosphorus-based flame retardant (C). The content of the phosphorus-based flame retardant (C) is preferably 0.1 to 30 parts by mass, more preferably 2 to 20 parts by mass, and even more preferably 3 to 15 parts by mass, relative to 100 parts by mass of the styrene-based resin material (A). If the content exceeds 30 parts by mass, the amount of residue increases, making frequent removal necessary during recycling. The phosphorus-based flame retardant (C) may be already contained in the styrene-based resin or the styrene-based resin material (A), or may be blended with the styrene-based resin material (A) or the mixture in step (1) or step (2) of this embodiment. The content of the NOR-type hindered amine compound can be quantified by dissolving it in a THF solvent and then performing gravimetric analysis using a gas chromatograph. The former styrene-based resin or styrene-based resin material (A) containing the phosphorus-based flame retardant (C) is used for flame retardant applications, including pre-consumer materials such as factory-recovered products and post-consumer materials such as market-recovered products. In some cases, long-term inventory pellets and non-standard pellets are also included. By using it in combination with a NOR-type hindered amine compound (B), it is possible to suppress or prevent the generation of corrosive gases from the phosphorus flame retardant and reduce the amount of residue left behind during thermal decomposition of the styrene-based resin material (A). In particular, when a phosphonate ester compound and / or a phosphinic acid compound is used as the phosphorus-based flame retardant (C), residue reduction can be even more effective.

[0065] The phosphorus-based flame retardant (C) that can be used in this embodiment is not particularly limited, and those obtained by conventionally known methods or commercially available products can be used. The phosphorus-based flame retardant (C) is preferably a phosphate ester compound, a phosphazene compound, a phosphonic acid compound (including, for example, phosphonic acid esters), or a phosphinic acid compound (including, for example, phosphinic acid salt compounds). These may be used alone or in combination of two or more. Among them, phosphate ester compounds, phosphonic acid ester compounds, and phosphinic acid compounds that are highly compatible with styrene-based resins are most preferred.

[0066] --Phosphate ester compounds-- The phosphoric acid ester compound is preferably an aromatic phosphoric acid ester compound, such as a monomeric phosphoric acid ester compound, trimethyl phosphate (TMP), triethyl phosphate (TEP), triphenyl phosphate (TPP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), or cresyl diphenyl phosphate (CDP), or an aromatic condensed phosphoric acid ester compound, which is a reaction product of phosphorus oxychloride, a divalent phenolic compound, and phenol (or an alkylphenol), such as resorcinol bis-dixylenyl phosphate, resorcinol bis-diphenyl phosphate, bisphenol A bis-diphenyl phosphate (BADP), bisphenol A bis-dicresyl phosphate, biphenol bis-diphenyl phosphate, or biphenol bis-dixylenyl phosphate. Among these, triphenyl phosphate (TPP), tricresyl phosphate (TCP), resorcinol bis-dixylenyl phosphate, resorcinol bis-diphenyl phosphate, bisphenol A bis-diphenyl phosphate (BADP), biphenol bis-diphenyl phosphate, and biphenol bis-dixylenyl phosphate are preferred, triphenyl phosphate (TPP), resorcinol bis-dixylenyl phosphate, and resorcinol bis-diphenyl phosphate are more preferred, and resorcinol bis-dixylenyl phosphate is even more preferred.

[0067] Furthermore, from the viewpoints of heat resistance and reduction of mold deposits during molding, the phosphate ester compound is preferably a condensed phosphate ester compound, and in particular, an aromatic condensed phosphate ester compound represented by the following chemical formula (1) is preferred. [ka] (In the above chemical formula (1), R 1 ~R 5 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or a halogen atom; R 1 ~R 5 may be the same or different. n is an integer of 0 to 30, preferably an integer of 0 to 10. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an amyl group, a tert-amyl group, a hexyl group, a 2-ethylhexyl group, an n-octyl group, a nonyl group, and a decyl group. Examples of the cycloalkyl group include a cyclohexyl group. Examples of the aryl group include a phenyl group, a cresyl group, a xylyl group, a 2,6-xylyl group, a 2,4,6-trimethylphenyl group, a butylphenyl group, and a nonylphenyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom.

[0068] Furthermore, among the above-mentioned phosphate ester compounds, from the viewpoint of achieving both flame retardancy and transparency, phosphate ester compounds represented by the following compounds (1-1), (1-2), or (1-3) are preferred, compounds (1-2) or (1-3) are more preferred, and compound (1-2) is even more preferred. As compound (1-2) (resorcinol bis-dixylenyl phosphate), for example, PX-200 manufactured by Daihachi Chemical Industry Co., Ltd. can be used, and as compound (1-3) (resorcinol bis-diphenyl phosphate), for example, CR-733S manufactured by Daihachi Chemical Industry Co., Ltd. can be used. [ka]

[0069] -Phosphazene compounds- Examples of phosphazene compounds include 1,1,3,3,5,5-hexa(methoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(ethoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(n-propoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(iso-propoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(n-butoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(iso-butoxy)cyclotriphosphazene, and 1,1,3,3,5,5-hexa(phenoxy)cyclotriphosphazene. Cyclotriphosphazene, 1,1,3,3,5,5-hexa(p-tolyloxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(m-tolyloxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(o-tolyloxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(4-ethylphenoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(4-n-propylphenoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(4-isopropylphenoxy)cyclotriphosphazene, 1,1 ,3,3,5,5-hexa(4-t-butylphenoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(4-t-octylphenoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(2,3-dimethylphenoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(2,4-dimethylphenoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(2,5-dimethylphenoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(2,6-dimethylphenoxy)cyclotriphosphazene, 1, 3,5-tris(methoxy)-1,3,5-tris(phenoxy)cyclotriphosphazene, 1,3,5-tris(ethoxy)-1,3,5-tris(phenoxy)cyclotriphosphazene, 1,3,5-tris(n-propoxy)-1,3,5-tris(phenoxy)cyclotriphosphazene, 1,3,5-tris(iso-propoxy)-1,3,5-tris(phenoxy)cyclotriphosphazene, 1,3,5-tris(n-butoxy)-1,3,5-tris(phenoxy)cyclotriphosphazene, 1,3,5-tris(iso-butoxy)-1,3,5-Tris(phenoxy)cyclotriphosphazene, 1,3,5-tris(methoxy)-1,3,5-tris(p-tolyloxy)cyclotriphosphazene, 1,3,5-tris(methoxy)-1,3,5-tris(m-tolyloxy)cyclotriphosphazene, 1,3,5-tris(methoxy)-1,3,5-tris(o-tolyloxy)cyclotriphosphazene, 1,3,5-tris(ethoxy)-1,3,5-tris(p-tolyloxy)cyclotriphosphazene Sphazene, 1,3,5-tris(ethoxy)-1,3,5-tris(m-tolyloxy)cyclotriphosphazene, 1,3,5-tris(ethoxy)-1,3,5-tris(o-tolyloxy)cyclotriphosphazene, 1,3,5-tris(n-propoxy)-1,3,5-tris(p-tolyloxy)cyclotriphosphazene, 1,3,5-tris(n-propoxy)-1,3,5-tris(m-tolyloxy)cyclotriphosphazene, 1,3,5- Tris(n-propoxy)-1,3,5-tris(o-tolyloxy)cyclotriphosphazene, 1,3,5-tris(iso-propoxy)-1,3,5-tris(p-tolyloxy)cyclotriphosphazene, 1,3,5-tris(n-butoxy)-1,3,5-tris(p-tolyloxy)cyclotriphosphazene, 1,3,5-tris(iso-butoxy)-1,3,5-tris(p-tolyloxy)cyclotriphosphazene, 1,3,5-tris(meth Examples of suitable cyclophosphazenes include 1,3,5-tris(4-t-butylphenoxy)cyclotriphosphazene, 1,3,5-tris(methoxy)-1,3,5-tris(4-t-octylphenoxy)cyclotriphosphazene, 1,3,5-tris(n-propoxy)-1,3,5-tris(4-t-butylphenoxy)cyclotriphosphazene, and 1,3,5-tris(n-propoxy)-1,3,5-tris(4-t-octylphenoxy)cyclotriphosphazene.

[0070] Among these, 1,1,3,3,5,5-hexa(methoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(ethoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(phenoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(p-tolyloxy)cyclotriphosphazene, 1,3,5-tris(methoxy)-1,3,5-tris(phenoxy)cyclotriphosphazene, and 1,3,5-tris(ethoxy)cyclotriphosphazene are preferred. 1,1,3,3,5,5-hexa(ethoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(phenoxy)cyclotriphosphazene, and 1,3,5-tris(ethoxy)-1,3,5-tris(phenoxy)cyclotriphosphazene are more preferred, and 1,1,3,3,5,5-hexa(ethoxy)cyclotriphosphazene, 1,1,3,3,5,5-hexa(phenoxy)cyclotriphosphazene, and 1,3,5-tris(ethoxy)-1,3,5-tris(phenoxy)cyclotriphosphazene is even more preferred.

[0071] -phosphonic acid ester- Examples of phosphonate esters include those represented by the following chemical formula (2). [ka] (In the above chemical formula (2), R 6 ~R 10 are each independently a hydrogen atom or an optionally substituted monovalent hydrocarbon group, and R 6 ~R 10 may be the same or different. In this specification, the monovalent hydrocarbon group may be either linear (either straight chain or branched chain) or cyclic (either monocyclic, fused polycyclic, bridged ring, or spiro ring), and examples thereof include cyclic hydrocarbon groups having a side chain. In addition, the hydrocarbon group may be either saturated or unsaturated. Examples of the hydrocarbon group include an alkyl group, a cycloalkyl group, an allyl group, an aryl group, an alkylaryl group, and an arylalkyl group.

[0072] Specific examples of the phosphonate ester represented by the above chemical formula (2) include compounds represented by the following formulae (2-1) to (2-8). [ka]

[0073] -Phosphinic acid compounds- Examples of phosphinic acid compounds include 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 10-benzyl-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Examples of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide that can be used include HCA manufactured by Sanko Co., Ltd., and examples of 10-benzyl-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide that can be used include BCA manufactured by Sanko Co., Ltd.

[0074] -Phosphinate compounds- The phosphinate compound is preferably represented by the following general formula (i) and contains at least one phosphinate selected from phosphinates and diphosphinates, and more preferably the phosphinate accounts for 70 mass % or more of the total phosphinate compound (100 mass %). The following general formula (i): [ka] [In the above formula (i), R i1 and R i2 are each independently unsubstituted or one or more hydrogen atoms are substituted by R i3 a linear or branched alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 6 to 14 carbon atoms, which may be substituted by The substituent R i3 is represented by the following formula (ii): [ka] "In the above formula (ii), Rii1 are each independently a linear or branched alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms, and * represents a bond to another atom. M i is at least one selected from the group consisting of calcium ions, magnesium ions, aluminum ions, zinc ions, bismuth ions, manganese ions, sodium ions, potassium ions, and protonated nitrogen bases, and p + is M i represents the ionic valence of the compound, and is a positive integer of 1 to 3, and m i1 is a positive integer between 1 and 3, and n - represents a negative integer of -1, -2, or -3, r is a positive integer of 1 to 3, and |p + ×r|=|n - ×m i1 | Also, R i1 and R ii1 If there are multiple of each, i1 and R ii1 may be the same or different.] Therefore, the phosphinate compound in this embodiment may contain 30 mass % or less of a known flame retardant other than the phosphinate represented by general formula (i) relative to the entire phosphinate compound (100 mass %). In the above formula (i), M i "p" represents the ionic valence of + The absolute value of the product of " and "r" is "n - " and "m i1 " is equal to the absolute value of the product. In (i) above, p + is preferably 1 or 2. i1 is preferably 1 or 2. - is preferably -1 or -2. r is preferably 1 or 2.

[0075] In this embodiment, a preferred phosphinate is represented by the following general formula (iii): [ka] [In the above formula (iii), R 11 and R 12 are each independently a linear or branched alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms, and M 1 is at least one selected from the group consisting of calcium ions, magnesium ions, aluminum ions, zinc ions, bismuth ions, manganese ions, sodium ions, potassium ions, and protonated nitrogen bases, and a + is M 1 represents the ionic valence, is an integer of 1 to 3, and m 1 is an integer between 1 and 3, and a=m 1 R 11 and R 12 If there are multiple of each, 11 and R 12 may be the same or different.

[0076] In this embodiment, a preferred diphosphinate salt is represented by the following general formula (iv): [ka] [In the above formula (iv), R 21 and R 22 are each independently a linear or branched alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms, and L 23 is a linear or branched alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 10 carbon atoms, an alkylarylene group having 6 to 14 carbon atoms, or an arylalkylene group having 6 to 14 carbon atoms, and M 2 is at least one selected from the group consisting of calcium ions, magnesium ions, aluminum ions, zinc ions, bismuth ions, manganese ions, sodium ions, potassium ions, and protonated nitrogen bases; b + is M 2 represents the ionic valence, is an integer of 1 to 3, and m 2is an integer of 1 to 3, q ​​is an integer of 1 or 2, and b×q=2m 2 R 21 and R 12 If there are multiple of each, 21 and R 22 may be the same or different.

[0077] In the above formulas (i), (ii), (iii), and (iv), examples of the linear or branched alkyl group having 1 to 6 carbon atoms include linear alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, or a hexyl group, and branched alkyl groups such as an isopropyl group, an isobutyl group, a s-butyl group, a t-butyl group, an isoamyl group, or a t-amyl group. In the above formulas (i), (ii), (iii) and (iv), the aryl group having 6 to 10 carbon atoms may have a monocyclic structure or a fused ring structure, for example, a phenyl group or a naphthyl group. In the above formula (iv), examples of the linear or branched alkylene group having 1 to 10 carbon atoms include groups in which one hydrogen atom has been removed from the above linear or branched alkyl group having 1 to 6 carbon atoms. In the above formula (iv), examples of the arylene group having 6 to 10 carbon atoms include groups in which one hydrogen atom has been removed from the above aryl group having 6 to 10 carbon atoms. In the above formula (i), examples of the aralkyl group having 6 to 14 carbon atoms include a benzyl group, a phenylethyl group, a phenylpropyl group, a phenylbutyl group, a methylphenyl group, an ethylphenyl group, a propylphenyl group, a butylphenyl group, a methylnaphthyl group, an ethylnaphthyl group, and a tert-butylnaphthyl group. In the above formula (iv), examples of the alkylarylene group having 6 to 14 carbon atoms include a methylphenylene group, an ethylphenylene group, a tert-butylphenylene group, a methylnaphthylene group, an ethylnaphthylene group, and a tert-butylnaphthylene group. In the above formula (iv), examples of the arylalkylene group having 6 to 14 carbon atoms include a phenylmethylene group, a phenylethylene group, a phenylpropylene group, and a phenylbutylene group. In the above formula (iii), R 11 and R 12 is preferably each independently a linear alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. In the above formula (iii), M 1 is preferably calcium, magnesium, aluminum, or zinc. 1 represents the ionic valence, which is 2 or 3. In the above formula (iv), R 21 and R 22 is preferably each independently a linear alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. In the above formula (iv), L 23 are each preferably independently a linear alkylene group having 1 to 6 carbon atoms or an arylene group having 6 to 10 carbon atoms. In the above formula (iv), M 2 is preferably calcium, magnesium, aluminum, or zinc. 2 represents the ionic valence, which is 2 or 3. Phosphinate compounds have excellent electrical properties, making them suitable for flame-retardant materials that require insulation. They also have excellent hydrolysis properties, making them suitable for use in high-temperature, high-humidity environments, and are highly recyclable.

[0078] The phosphinate salts used in the present embodiment are produced in an aqueous solution using, among others, phosphinic acid and a metal carbonate, metal hydroxide or metal oxide, and are essentially monomeric compounds, but depending on the reaction conditions and circumstances, also include polymeric phosphinate salts with a condensation degree of 1 to 3.

[0079] Such phosphinate salts are not particularly limited, and examples thereof include calcium dimethylphosphinate, magnesium dimethylphosphinate, aluminum dimethylphosphinate, zinc dimethylphosphinate, calcium ethylmethylphosphinate, magnesium ethylmethylphosphinate, aluminum ethylmethylphosphinate, zinc ethylmethylphosphinate, calcium diethylphosphinate, magnesium diethylphosphinate, aluminum diethylphosphinate, zinc diethylphosphinate, calcium methyl-n-propylphosphinate, magnesium methyl-n-propylphosphinate, aluminum methyl-n-propylphosphinate, zinc methyl-n-propylphosphinate, calcium methanedi(methylphosphinate), magnesium methanedi(methylphosphinate), aluminum methanedi(methylphosphinate), zinc methanedi(methylphosphinate), calcium benzene-1,4-(dimethylphosphinate), benzene-1,4- Examples include magnesium (dimethylphosphinate), aluminum benzene-1,4-(dimethylphosphinate), zinc benzene-1,4-(dimethylphosphinate), calcium methylphenylphosphinate, magnesium methylphenylphosphinate, aluminum methylphenylphosphinate, zinc methylphenylphosphinate, calcium diphenylphosphinate, magnesium diphenylphosphinate, aluminum diphenylphosphinate, and zinc diphenylphosphinate. Calcium dimethylphosphinate, aluminum dimethylphosphinate, zinc dimethylphosphinate, calcium ethylmethylphosphinate, aluminum ethylmethylphosphinate, aluminum ethylbutylphosphinate, aluminum dibutylphosphinate, zinc ethylmethylphosphinate, calcium diethylphosphinate, aluminum diethylphosphinate, and zinc diethylphosphinate are preferred. Commercially available phosphinate compounds (b) are not particularly limited, and examples thereof include Exolit (registered trademark) OP1230, OP1240, OP1311, OP1312, OP930, and OP935 manufactured by Clariant Japan K.K.

[0080] In this embodiment, the phosphinate compound is preferably granular. When the phosphinate compound is granular, the average particle size of the phosphinate compound is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 20 μm or less, from the viewpoint of improving the mechanical strength and appearance of a molded article obtained by molding the flame-retardant resin composition of this embodiment. It is preferable to use a powder of the phosphinate compound (b) pulverized to this particle size. The particle size is preferably more than 0.5 μm and 20 μm, more preferably more than 1 μm and 20 μm or less. Using a powder with a preferred particle size is particularly preferable because it not only exhibits high flame retardancy but also significantly increases impact strength. The average particle size of the granular phosphinate compound is measured based on the volumetric particle size measured using a laser diffraction / scattering particle size analyzer. The value is measured using a 3% aqueous isopropanol solution as the dispersant for the phosphinate compound. Specifically, the average particle size can be determined by using a laser diffraction / scattering particle size analyzer LA-910 (manufactured by Horiba, Ltd.) to perform a blank measurement using a 3% aqueous isopropanol solution as the dispersant, followed by adding a measurement sample to achieve a specified transmittance (95% to 70%). The sample is dispersed in the dispersant by irradiating it with ultrasound for 1 minute.

[0081] <Optional addition ingredients> In addition to the components (A) to (C) described above, the styrene-based resin material (A) or mixture of this embodiment may contain optional additives, processing aids, and other known additives, as needed, within the range that does not impair the effects of the present invention. Examples of such additives and processing aids include antioxidants, weathering agents, lubricants, antistatic agents, and fillers.

[0082] Examples of the antioxidant include phenolic compounds, phosphorus compounds, and thioether compounds.

[0083] Examples of the phenolic antioxidant include 2,6-di-tert-butyl-p-cresol, 2,6-diphenyl-4-octadecyloxyphenol, distearyl(3,5-di-tert-butyl-4-hydroxybenzyl)phosphonate, 1,6-hexamethylenebis[(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid amide], 4,4'-thiobis(6-tert-butyl-m-cresol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylene Bis(4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis(6-tert-butyl-m-cresol), 2,2'-ethylidenebis(4,6-di-tert-butylphenol), 2,2'-ethylidenebis(4-sec-butyl-6-tert-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl)isocyanurate, 1,3,5-tris(3 ,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene, 2-tert-butyl-4-methyl-6-(2-acryloyloxy-3-tert-butyl-5-methylbenzyl)phenol, stearyl [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate methyl ester ] methane, thiodiethylene glycol bis[(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,6-hexamethylene bis[(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis[3,3-bis(4-hydroxy-3-tert-butylphenyl)butylic acid] glycol ester, bis[2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl] terephthalate, 1,3,5-tris[(3,Examples of suitable bis(3-tert-butyl-4-hydroxyphenyl)propionyloxyethyl)isocyanurate include 3,9-bis[1,1-dimethyl-2-{(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane, and triethylene glycol bis[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate]. These may be used alone or in combination of two or more.

[0084] Examples of the phosphorus-based antioxidant include tris(2,4-di-tert-butylphenyl)phosphite, trisnonylphenyl phosphite, tris[2-tert-butyl-4-(3-tert-butyl-4-hydroxy-5-methylphenylthio)-5-methylphenyl]phosphite, tridecyl phosphite, octyldiphenyl phosphite, di(decyl)monophenyl phosphite, di(tridecyl)pentaerythritol diphosphite, and di(nonylphenyl)pentaerythritol diphosphite. tetra(tridecyl)isopropylidenediphenol diphosphite, bis(2,4-tert-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, bis(2,4,6-tri-tert-butylphenyl)pentaerythritol diphosphite, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, tetra(tridecyl)isopropylidenediphenol diphosphite, tetra(tridecyl)-4,4'-n- Butylidenebis(2-tert-butyl-5-methylphenol) diphosphite, hexa(tridecyl)-1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane triphosphite, tetrakis(2,4-di-tert-butylphenyl)biphenylene diphosphonite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 2,2'-methylenebis(4,6-tert-butylphenyl)-2-ethylhexylphospha phosphite, 2,2'-methylenebis(4,6-tert-butylphenyl)-octadecyl phosphite, 2,2'-ethylidenebis(4,6-di-tert-butylphenyl)fluorophosphite, tris(2-[(2,4,8,10-tetrakis-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]ethyl)amine, phosphite of 2-ethyl-2-butylpropylene glycol and 2,4,6-tri-tert-butylphenol, etc. These may be used alone or in combination of two or more.

[0085] Examples of the thioether antioxidant include dialkyl thiodipropionates such as dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiodipropionate, and pentaerythritol tetra(β-alkylmercaptopropionate) esters. These may be used alone or in combination of two or more.

[0086] As the weatherproofing agent, an ultraviolet absorber or the like can be used. Examples of the ultraviolet absorber include 2-hydroxybenzophenones such as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 5,5'-methylenebis(2-hydroxy-4-methoxybenzophenone); 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, and 2-(2'-hydroxy-3'-tert-butylphenyl)-5-chlorobenzotriazole. 2-(2'-hydroxyphenyl)benzotriazoles such as 2-(2'-hydroxy-5'-tert-octylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole, 2,2'-methylenebis(4-tert-octyl-6-(benzotriazolyl)phenol), and 2-(2'-hydroxy-3'-tert-butyl-5'-carboxyphenyl)benzotriazole; phenyl salicylate Benzoates such as resorcinol monobenzoate, 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate, 2,4-di-tert-amylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate, and hexadecyl-3,5-di-tert-butyl-4-hydroxybenzoate; substituted oxanilides such as 2-ethyl-2'-ethoxyoxanilide and 2-ethoxy-4'-dodecyloxanilide; and ethyl-α-cyano-β,β-diphenylacrylate. and triaryltriazines such as 2-(2-hydroxy-4-octoxyphenyl)-4,6-bis(2,4-di-tert-butylphenyl)-s-triazine, 2-(2-hydroxy-4-methoxyphenyl)-4,6-diphenyl-s-triazine, and 2-(2-hydroxy-4-propoxy-5-methylphenyl)-4,6-bis(2,4-di-tert-butylphenyl)-s-triazine. These may be used alone or in combination of two or more.

[0087] As the lubricant, fatty acid amides, fatty acid esters, fatty acids, fatty acid metal salts, etc. can be used.

[0088] Examples of the aliphatic amide lubricant include stearic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, ethylene biserucic acid amide, ethylene bislauric acid amide, etc. These may be used alone or in combination of two or more.

[0089] Examples of the aliphatic ester lubricants include methyl laurate, methyl myristate, methyl palmitate, methyl stearate, methyl oleate, methyl erucate, methyl behenate, butyl laurate, butyl stearate, isopropyl myristate, isopropyl palmitate, octyl palmitate, coconut fatty acid octyl ester, octyl stearate, tallow fatty acid octyl ester, lauryl laurate, stearyl stearate, behenyl behenate, cetyl myristate, esters of linear, unbranched saturated monocarboxylic acids having 28 to 30 carbon atoms (hereinafter abbreviated as montanic acid) and ethylene glycol, esters of montanic acid and glycerin, ... Examples include esters of montanic acid and butylene glycol, esters of montanic acid and trimethylolethane, esters of montanic acid and trimethylolpropane, esters of montanic acid and pentaerythritol, glycerin monostearate, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, sorbitan trioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, etc. These may be used alone or in combination of two or more.

[0090] Specific examples of saturated fatty acids among the above-mentioned fatty acid-based lubricants include lauric acid (dodecanoic acid), isodecanoic acid, tridecylic acid, myristic acid (tetradecanoic acid), pentadecylic acid, palmitic acid (hexadecanoic acid), margaric acid (heptadecanoic acid), stearic acid (octadecanoic acid), isostearic acid, tuberculostearic acid (nonadecanoic acid), 2-hydroxystearic acid, arachidic acid (icosanoic acid), behenic acid (docosanoic acid), lignoceric acid (tetradocosanoic acid), cerotic acid (hexadocosanoic acid), montanic acid (octadocosanoic acid), and melissic acid, and particularly include lauric acid, palmitic acid, stearic acid, behenic acid, 12-hydroxystearic acid, and montanic acid.

[0091] Specific examples of unsaturated fatty acids among the fatty acid-based lubricants include myristoleic acid (tetradecenoic acid), palmitoleic acid (hexadecenoic acid), oleic acid (cis-9-octadecenoic acid), elaidic acid (trans-9-octadecenoic acid), ricinoleic acid (octadecadienoic acid), vaccenic acid (cis-11-octadecenoic acid), linoleic acid (octadecadienoic acid), linolenic acid (9,11,13-octadecatrienoic acid), elestearic acid (9,11,13-octadecatrienoic acid), gadoleic acid (icosanoic acid), erucic acid (docosanoic acid), nervonic acid (tetradocosanoic acid), etc. These may be used alone or in combination of two or more.

[0092] Examples of the fatty acid metal salt lubricant include lithium salts, calcium salts, magnesium salts, and aluminum salts of the fatty acids of the fatty acid lubricant. These may be used alone or in combination of two or more.

[0093] The antistatic agent may be a cationic, anionic, nonionic, amphoteric, or fatty acid partial ester such as glycerin fatty acid monoester. Specific examples include alkyltrimethylammonium salts, dialkyldimethylammonium salts, benzalkonium salts, N,N-bis(2-hydroxyethyl)-N-(3-dodecyloxy-2-hydroxypropyl)methylammonium methosulfate, (3-laurylamidopropyl)trimethylammonium methylsulfate, stearamidopropyldimethyl-2-hydroxyethylammonium nitrate, stearamidopropyldimethyl-2-hydroxyethylammonium phosphate, cationic polymers, alkyl sulfonates, alkylbenzene sulfonates, sodium alkyldiphenylether disulfonate, alkyl nitrate ester salts, phosphorus Acid alkyl ester salts, alkyl phosphate amine salts, stearic acid monoglyceride, pentaerythritol fatty acid esters, sorbitan monopalmitate, sorbitan monostearate, diglycerin fatty acid esters, alkyldiethanolamines, alkyldiethanolamine fatty acid monoesters, alkyldiethanolamides, polyoxyethylene dodecyl ethers, polyoxyethylene alkylphenyl ethers, polyethylene glycol monolaurate, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyether block copolymers, cetyl betaine, hydroxyethyl imidazoline sulfate, etc. These may be used alone or in combination of two or more.

[0094] As the filler, talc, calcium carbonate, barium sulfate, carbon fiber, mica, wollastonite, whisker, etc. can be used.

[0095] In addition to the additives and processing aids described above, the mixture of this embodiment may contain optional components such as antiblocking agents, colorants, antiblooming agents, surface treatment agents, antibacterial agents, and anti-seizure agents (such as silicone oils described in JP 2009-120717 A, monoamide compounds of higher aliphatic carboxylic acids, and monoester compounds obtained by reacting higher aliphatic carboxylic acids with monohydric to trihydric alcohol compounds). The total content of optional components such as additives and processing aids in the mixture may be 0.05 to 5% by mass.

[0096] The mixture of this embodiment may consist essentially of components (A), (B), and any optional additional components, or may consist of only components (A), (B), (A), (C), or (A), (C), and any optional additional components.

[0097] The phrase "consisting essentially of only components (A), (B), and (C) and any optional additional components" means that 95 to 100 mass % (preferably 98 to 100 mass %) of the mixture is components (A), (B), and (C), or components (A), (B), and (C) and any optional additional components.

[0098] The mixture of this embodiment may contain inevitable impurities in addition to components (A) to (C) and optional additional components, as long as the effects of the present invention are not impaired.

[0099] (Process (2)) The recycling method of the present embodiment for recovering styrene monomer from a styrene-based resin includes a step (2) of thermally decomposing a mixture of a styrene-based resin material (A) containing a styrene-based resin and a NOR-type hindered amine compound (B). The mixture may contain a styrene-based resin material (A) containing a styrene-based resin and a NOR-type hindered amine compound (B), and if necessary, premixing may be performed using the mixing mechanism or kneading mechanism described above before or during step (2). In addition, in step (1) and / or step (1), a phosphorus-based flame retardant (C) may be added to the mixture or the styrene-based resin material (A) as needed. In the present embodiment, a preferred method for pyrolyzing the mixture is, for example, to carry out a pyrolysis step in which the mixture is filled into a pyrolysis furnace and then heated to a temperature of 400 to 800° C., preferably 450 to 600° C. The pyrolysis vapor generated in this step may be cooled to a temperature of not less than the boiling point of the styrene monomer and not more than 180° C. to liquefy the high-boiling point component and drop it again into the pyrolysis furnace, thereby recovering the styrene monomer again. By setting the temperature of the pyrolysis furnace within the above range, other resins such as polyolefin resins that may be contained in the raw styrene resin material (A) can be removed. That is, the thermal decomposition temperature of polystyrene is approximately 330 to 380°C, while the thermal decomposition temperature of polyolefin resins (e.g., polyethylene, polypropylene) is approximately 400 to 450°C. Therefore, by setting the temperature in the pyrolysis furnace to 400 to 800°C, most of the generated pyrolysis steam can become the pyrolysis products of the styrene resin. In addition, the pyrolysis furnace of this embodiment can be a known pyrolysis furnace. For example, the pyrolysis furnace of this embodiment includes a raw material storage tank capable of storing the raw material styrene resin material (A) and NOR-type hindered amine compound (B), a pyrolysis furnace fluidly connected to the raw material storage tank, a raw material supply pump that supplies the raw material in the raw material storage tank to the pyrolysis furnace, and a heating mechanism (such as a hot plate) provided on the periphery of the pyrolysis furnace. Furthermore, if necessary, a polymerization inhibitor supply device may be used to intermittently or continuously supply a polymerization inhibitor to suppress the polymerization reaction of the styrene monomer produced. The pyrolysis furnace in this embodiment may be fluidly connected to an atmospheric rectification column capable of rectifying pyrolysis vapor supplied from the pyrolysis furnace and separating low-boiling components such as benzene or toluene from crude styrene monomer (styrene monomer having a purity of 90% or less). Furthermore, the atmospheric rectification column may be fluidly connected to a vacuum distillation column that vacuum distills the crude styrene monomer to increase the purity of the separated crude styrene monomer. If necessary, a dechlorination device that dechlorinates components in the pyrolysis vapor generated by pyrolysis may be fluidly connected between the pyrolysis furnace and the atmospheric rectification column. In the present invention, the mechanism for pyrolyzing a mixture containing a styrene-based resin material (A) and a NOR-type hindered amine compound (B) may be, as described above, for example, a pyrolysis mechanism having a pyrolysis furnace, an atmospheric rectification column, and a vacuum distillation column. This mechanism can recover styrene monomer and provide a method for recycling styrene-based resins. The recycling method of recovering styrene monomer from a styrene-based resin of this embodiment may include a step (3) of recovering styrene monomer from pyrolysis vapor generated by the pyrolysis in the above step (2). Hereinafter, an example of a process for pyrolyzing a mixture containing a styrene-based resin material (A) and a NOR-type hindered amine compound (B) and recovering styrene monomer from the pyrolysis vapor generated by the pyrolysis will be described. A mixture containing a styrene-based resin material (A), a NOR-type hindered amine compound (B), and an optional phosphorus-based flame retardant (C) is premixed using the mixing or kneading mechanism described above, and then charged into a pyrolysis furnace and heated to a temperature of 400 to 800°C. The mixture is then thermally decomposed in the pyrolysis furnace, and the resulting pyrolysis vapor passes through an optional dechlorination device and is then supplied to an atmospheric rectification column. The dechlorination device is filled with a metal powder, such as iron powder or an iron-based catalyst, and chlorine-containing substances contained in the pyrolysis vapor can be removed by adsorption with the metal powder. The atmospheric rectification column then rectifies the pyrolysis vapor supplied from the pyrolysis furnace, recovering low-boiling components such as benzene or toluene from the top of the column, recovering crude styrene monomer (styrene monomer with a purity of 90% or less) from the center of the column, and recovering high-boiling components such as styrene dimer or styrene trimer from the bottom of the column. The crude styrene monomer recovered from the center of the atmospheric rectification column is recovered in a crude styrene monomer recovery vessel via a condenser and a dechlorination device, a portion of which is refluxed to the atmospheric rectification column, and the remainder is supplied to a vacuum distillation column. Then, by performing vacuum distillation in the vacuum distillation column at 110°C or less, high-purity styrene monomer (purity of 99.5% or more) can be recovered.

[0100] <Preferable embodiment of the method for recycling styrene-based resin> In the method for recycling styrene-based resins according to this embodiment, a product, crushed product, or pellets is heated and subjected to electromagnetic waves to undergo thermal decomposition, and the vaporized gas is collected to recover styrene monomer. The NOR hindered amine compound (B) may be added before heating, or may be contained in the product, crushed product, or pellets as the styrene-based resin material (A). The heating temperature during thermal decomposition is 400°C to 800°C, preferably 450°C to 600°C. The vaporized gas is recovered as a gas or as a liquid after cooling, and then styrene monomer is produced by distillation or other methods. The NOR hindered amine compound (B) is decomposed and does not remain as a residue in the pyrolysis furnace, and does not affect the impurities of the styrene monomer. Furthermore, when a phosphorus-based flame retardant (C) is contained in the styrene-based resin material (A), it generally remains as acid value phosphorus as a residue in the heating furnace. However, the presence of the NOR hindered amine compound (B) significantly reduces the amount of residue. This is thought to be because, during thermal decomposition, the NOR type hindered amine compound (B) reacts with the phosphorus compound to form a gas. Phosphorus-based flame retardants (C) may generate corrosive gases such as phosphine gas, but the reaction with the NOR type hindered amine compound (B) can suppress or prevent the generation of corrosive gases.

[0101] [Evaluation of recycled materials] <Corrosive gases> Typical examples of the corrosive gas in the method for recycling a styrene-based resin according to the present embodiment include halogen-based gases and phosphinic acid-based gases, and it is necessary that the corrosive gas does not corrode iron at the temperature at which the styrene-based resin generates gas.

[0102] <Residue amount> The amount of residue in the styrene-based resin recycling method of this embodiment can be determined by thermogravimetric analysis (TGA) under a nitrogen atmosphere, and is preferably 1% or less, more preferably 0.8% or less. If it is more than 1%, the thermal efficiency of the pyrolysis furnace may decrease and pipes may become clogged.

[0103] <Styrene monomer recovery rate> The styrene monomer recovery rate in the styrene-based resin recycling method of this embodiment is preferably 40% or more, more preferably 45% or more. If the styrene monomer recovery rate is lower than 40%, profitability is low and the styrene monomer may become low in purity.

[0104] [Recycled styrene resin made from recycled styrene monomer] The styrene monomer recovered by the recycling of this embodiment can be used in bulk polymerization or solution polymerization, which are common methods for producing styrene-based resins, to produce recycled styrene-based resins. [Example]

[0105] Hereinafter, the embodiments of the present invention will be described in more detail based on examples and comparative examples, but the present invention is not limited to these examples in any way.

[0106] "Measurement and evaluation methods" The physical properties of the resin compositions obtained in the examples and comparative examples were measured and evaluated according to the following methods.

[0107] (1) Measurement of corrosive gases Five grams of each of the pellet-like mixtures (1) to (19) prepared in the Examples and Comparative Examples and a 10 x 10 x 1 mm iron plate were placed in a glass Petri dish, sealed, and then heated in an oven at 400°C for one hour. After 24 hours, the presence or absence of rust on the surface of the iron plate was visually inspected.

[0108] (2) Measurement of combustion residue amount The pellet-shaped mixtures (1) to (19) prepared in the examples and comparative examples were subjected to thermogravimetric analysis (TGA) to measure the amount of residue at 550°C under conditions of a heating rate of 10°C / hour in a nitrogen atmosphere. The amount of combustion residue is calculated as follows: (weight of pellet-shaped mixture after thermal decomposition) / (charge weight of pellet-shaped mixture)×100(%).

[0109] (3) Measurement of styrene monomer ratio The pellet-shaped mixtures (1) to (19) prepared in the examples and comparative examples were measured at 550°C under a nitrogen atmosphere using pyrolysis gas chromatography / mass spectrometry, and evaluated as the ratio of the styrene monomer peak area to the total peak area of ​​styrene monomer, styrene dimer, and styrene trimer.

[0110] The materials used in the examples and comparative examples are as follows. <hips> A rubber-modified styrenic resin made of high-impact polystyrene (HIPS) with an MFR of 7.0 was used. The HIPS used polybutadiene as the rubbery polymer, and the content of the rubbery polymer was 8.6% by mass. The average particle size of the high-impact polystyrene (HIPS) was 1.5 μm.

[0111] <HIPS containing NOR-type hindered amine compound (B) (NOR-HIPS-1)> A rubber-modified styrenic resin made of polystyrene (HIPS) with an MFR of 8.2 containing 3% by mass of the NOR-type hindered amine compound B1 described below was used. The HIPS used polybutadiene as the rubbery polymer, and the content of the rubbery polymer was 8.5% by mass. The average particle size of the high-impact polystyrene (HIPS) was 1.5 μm. After adding 0.2 parts by mass of Irganox 1076 and Irgafos 168 to this HIPS, they were premixed, and the obtained premix was mixed together. Using a twin-screw extruder (manufactured by Toshiba Machine Co., Ltd., TEM-26SS), melt extrusion was carried out in the range of 220 °C (screw rotation speed was 150 rpm, discharge rate was 10 kg / hr) to produce pellets.

[0112] <HIPS containing NOR-type hindered amine compound (B) (NOR-HIPS-2)> A rubber-modified styrenic resin made of high-impact polystyrene (HIPS) with an MFR of 6.2 containing 1% by mass of the NOR-type hindered amine compound B1 described below and 5% by mass of the phosphonate ester described below was used. The HIPS used polybutadiene as the rubbery polymer, and the content of the rubbery polymer was 8.5% by mass. The average particle size of the high-impact polystyrene (HIPS) was 1.5 μm. The manufacturing method was the same as that of NOR-HIPS-1.

[0113] <HIPS containing NOR-type hindered amine compound (B) (NOR-HIPS-3)> A rubber-modified styrene resin, which is high-impact polystyrene (HIPS) with an MFR of 8.5 containing 1% by mass of the NOR-type hindered amine compound B1 described below and 5% by mass of the phosphate ester described below, was used. The HIPS used polybutadiene as the rubber-like polymer, and the content of the rubber-like polymer was 8.5% by mass. The average particle size of the high-impact polystyrene (HIPS) was 1.5 μm. The manufacturing method was the same as that of NOR-HIPS-1.

[0114] <HIPS Containing NOR-Type Hindered Amine Compound (B) (NOR-HIPS-4)> A rubber-modified styrene resin, which is high-impact polystyrene (HIPS) with an MFR of 8.1 containing 1% by mass of the NOR-type hindered amine compound B1 described below and 5% by mass of the phosphinic acid-based compound described below, was used. The HIPS used polybutadiene as the rubber-like polymer, and the content of the rubber-like polymer was 8.5% by mass. The average particle size of the high-impact polystyrene (HIPS) was also 1.5 μm. The manufacturing method was the same as that of NOR-HIPS-1.

[0115] <HIPS Containing NOR-Type Hindered Amine Compound (B) (NOR-HIPS-5)> A rubber-modified styrene resin, which is high-impact polystyrene (HIPS) with an MFR of 3.8 containing 1% by mass of the NOR-type hindered amine compound B1 described below and 20% by mass of aluminum phosphinate, was used. The HIPS used polybutadiene as the rubber-like polymer, and the content of the rubber-like polymer was 7% by mass. The average particle size of the high-impact polystyrene (HIPS) was 1.5 μm. The manufacturing method was the same as that of NOR-HIPS-1.

[0116] <Post-consumer Material> High-impact polystyrene recovered from household appliances was used. It had an MFR of 5.6, a rubber-like polymer content of 7.5% by mass, and an average particle size of 1.6 μm.

[0117] <Component (B)> NOR-type hindered amine compound B1 (also referred to as NOR-HALS-B1 in Tables 1 and 2) [BASF, Flamestat NOR116FF, NOR-type polymer type] NOR-type hindered amine compound B2 (also referred to as NOR-HALS-B2 in Tables 1 and 2) [ADEKA CORPORATION, ADK STAB LA-81 NOR type]

[0118] <(C) component> Phosphonate ester compound [Marubishi Yuka Kogyo Co., Ltd., Nonene 73] Phosphate ester: Resorcinol bis-dixylenyl phosphate [PX-200, manufactured by Daihachi Chemical Industry Co., Ltd.] Phosphinic acid compound [HCA, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, manufactured by Sanko Co., Ltd.] Aluminum phosphinate "Exolit OP1230 manufactured by Clariant Japan"

[0119] <Additives> (phenolic antioxidant) Stearyl [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] [BASF, Irganox 1076] (phosphorus antioxidant) Tris(2,4-di-tert-butylphenyl)phosphite [BASF, Irgafos168]

[0120] [Example 1-1] The recovered styrene-based material or styrene-based resin material (A) was premixed with the above-mentioned HIPS and the NOR-type hindered amine compound (B) NOR-HALS-B1 in the composition ratios shown in Table 1 to prepare a pellet-shaped mixture (1). The pellet-shaped mixture was then thermally decomposed at approximately 550°C under a nitrogen atmosphere using the thermal decomposition apparatus described in JP 2021-134281 A to recover styrene monomer. The purity of the styrene monomer was 98%, and the recovery rate of styrene monomer was 55%. The amount of combustion residue, which constitutes the remaining solid content generated by the thermal decomposition of the recovered styrene-based resin (A-1), was 0.5%. [Example 1-2] The pellet-shaped mixture (1) prepared in Example 1-1 was evaluated according to the procedures described in the above "Measurement of Corrosive Gases," "Measurement of Combustion Residue Amount," and "Measurement of Styrene Monomer Ratio." The results are shown in Table 1. As shown in Table 1, it was confirmed that the values ​​of the combustion residue amount and styrene monomer ratio were roughly the same as when the pyrolysis apparatus of Example 1-1 was used, and the measurement results of the corrosive gases were also the same. Therefore, for Examples 2 to 12 and Comparative Examples 1 to 7, the pyrolysis apparatus of Example 1-1 was not used, and the pellet-shaped mixtures (2) to (19) obtained in each Example and Comparative Example were evaluated as they were according to the procedures described in the above "Measurement" columns. [Examples 2 to 7] The components were premixed in the composition ratios shown in Table 1, and the resulting premixes were mixed together and melt-extruded (screw rotation speed: 150 rpm, extrusion rate: 10 kg / hr) at a temperature range of 180°C to 230°C using a twin-screw extruder (Toshiba Machine Co., Ltd., TEM-26SS) to prepare pellet-shaped mixtures (2) to (7), which were evaluated according to the procedures in the measurement section above. [Examples 8 to 12] Pellet-shaped mixtures (8) to (12) containing the styrene-based resin material (A) and the NOR-type hindered amine compound (B) in the composition ratios shown in Table 1 were evaluated as they were according to the procedures in the measurement section above. [Comparative Examples 1 to 2] Pellet-shaped mixtures (13) and (14) containing the styrene-based resin material (A) and the NOR-type hindered amine compound (B) in the composition ratios shown in Table 2 were evaluated as they were according to the procedures in the measurement section above. [Comparative Examples 3 to 7] The components were premixed at the composition ratios shown in Table 2, and the resulting premixes were mixed together in one batch. Using a twin-screw extruder (Toshiba Machine Co., Ltd., TEM-26SS), the mixtures were melt-extruded (screw rotation speed: 150 rpm, extrusion rate: 10 kg / hr) at a temperature range of 180°C to 230°C to produce pellet-shaped mixtures (15) to (19), which were evaluated according to the procedures in the measurement section above.

[0121] [Table 1]

[0122] [Table 2]

[0123] Examples 1 to 12 showed no generation of corrosive gases, small amounts of combustion residues, and high styrene monomer ratios, as shown in Table 1. Regardless of whether melt mixing was performed or not, the generation of corrosive gases, the amount of combustion residues, and the styrene monomer ratio were all good, and good results were also obtained for materials containing a phosphorus-based flame retardant (C). On the other hand, in Comparative Examples 1 and 2, as shown in Table 2, when the NOR type hindered amine compound (B) was not contained, the amount of combustion residue exceeded 1%. In addition, in Comparative Example 3, as shown in Table 2, when the amount of the NOR type hindered amine compound (B) was large, the amount of combustion residue increased and the styrene monomer ratio also decreased. Similarly, for Comparative Examples 4 to 7, as shown in Table 2, when the NOR-type hindered amine compound (B) was not present and the phosphorus-based flame retardant (C) was contained, the amount of combustion residue increased, the styrene monomer ratio decreased, and corrosive gases were generated. [Industrial Applicability]

[0124] The object of the present invention is to provide a recycling method for a styrene-based resin that suppresses or prevents the generation of corrosive gases during recycling, in which a styrene-based resin is thermally decomposed to recover styrene monomer, and that reduces combustion residues that become solids remaining during the thermal decomposition of the styrene-based resin, thereby achieving a high recovery rate of styrene monomer.< / hips>

Claims

1. A recycling method for recovering styrene monomer from a styrene-based resin, comprising: a step (1) of preparing a mixture by blending a NOR-type hindered amine compound (B) with a styrene-based resin material (A) containing the styrene-based resin, which is a rubber-modified styrene-based resin; (2) pyrolyzing the mixture at a temperature of 450°C or higher and 800°C or lower; and a step (3) of recovering styrene monomer from the pyrolysis vapor obtained in the step (2), a content of the NOR-type hindered amine compound (B) in the mixture is more than 0 parts by mass and not more than 5.0 parts by mass per 100 parts by mass of the styrene-based resin material (A).

2. A recycling method for recovering styrene monomer as described in claim 1, wherein 95 to 100 mass% of the mixture is composed of the styrene-based resin material (A) and the NOR-type hindered amine-based compound (B).

3. 3. The recycling method for recovering styrene monomer according to claim 1, wherein the mixture further contains 0.1 to 30 parts by mass of a phosphorus-based flame retardant (C) relative to 100 parts by mass of the styrene-based resin material (A).

4. The method for recycling styrene monomers according to any one of claims 1 to 3, wherein the styrene-based resin material (A) is a post-consumer material.

5. 5. The method for recycling styrene monomer recovery according to claim 1, wherein the amount of residue in the mixture as measured by thermogravimetric analysis (TGA) under a nitrogen atmosphere is 1% or less.

6. The recycling method for recovering styrene monomer according to any one of claims 1 to 5, wherein a peak area ratio of the styrene monomer to a total peak area of ​​the styrene monomer, styrene dimer and styrene trimer in the pyrolysis vapor is 45% or more.

7. The method for recycling styrene monomer according to any one of claims 1 to 6, wherein the mixture further contains an antioxidant.

8. The recycling method for recovering styrene monomer described in claim 1, wherein the mixture is a mixture containing the styrene-based resin material (A) and the NOR-type hindered amine compound (B) or a mixture containing the styrene-based resin material (A), the NOR-type hindered amine compound (B), and a phosphorus-based flame retardant (C), and 95 to 100 mass % of the mixture is composed of the styrene-based resin material (A), the NOR-type hindered amine compound (B), and the phosphorus-based flame retardant (C).

9. the mixture is any one of a mixture containing the styrene-based resin material (A) and the NOR hindered amine compound (B), a mixture containing the styrene-based resin material (A), the NOR hindered amine compound (B), and a phosphorus-based flame retardant (C), a mixture containing the styrene-based resin material (A), the NOR hindered amine compound (B), and an additive component, and a mixture containing the styrene-based resin material (A), the NOR hindered amine compound (B), a phosphorus-based flame retardant (C), and an additive component; the additive component is an antioxidant, 2. The recycling method for recovering styrene monomer according to claim 1, wherein a total content of the styrene-based resin material (A), the NOR-type hindered amine compound (B), the phosphorus-based flame retardant (C), and the additive components accounts for 95 to 100% by mass of the mixture.

10. The method for recycling styrene monomers according to claim 1, wherein the average particle size of the rubber-like polymer (a) contained in the rubber-modified styrene-based resin is 0.5 to 4.0 μm.

11. A recycling method for recovering styrene monomer as described in claim 1, wherein the content of rubber-like polymer (a) contained in the rubber-modified styrene-based resin is 3 to 20 mass % relative to 100 mass % of the total amount of the rubber-modified styrene-based resin.

Images