Method for recovering inorganic substance from composition containing methacrylic resin and inorganic filler, and method for recovering methyl methacrylate-containing composition from composition containing methacrylic resin and inorganic filler

Abstract

An object of the present invention is to provide a method for recovering an inorganic substance with high purity from a composition containing a methacrylic resin and an inorganic filler regardless of the presence or absence of a crosslinked portion in the methacrylic resin.SOLUTION: A step (1) of preparing a composition (1) containing a methacrylic resin and an inorganic filler, and a step (2) of heating the composition (1) at 200 to 490°C in a system having an oxygen concentration of 0.001 to 9.0% by volume to separate a gas containing methyl methacrylate generated by thermal decomposition of the methacrylic resin and recover an inorganic substance, wherein the methacrylic resin is one or more selected from the group consisting of a methyl methacrylate copolymer (A) containing a crosslinked part and a non-crosslinked methyl methacrylate polymer (B), and the content of the inorganic filler in the composition (1) is 5 to 200 parts by mass with respect to 100 parts by mass of the total of the methacrylic resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for recovering inorganic substances from a composition containing a methacrylic resin and an inorganic filler, and a method for recovering a methyl methacrylate-containing composition from a composition containing a methacrylic resin and an inorganic filler. [Background technology]

[0002] There is a growing need to recycle petroleum-derived synthetic resins in order to reduce environmental impact. Two widely known types of recycling are mechanical recycling, in which the resin is reprocessed by thermal melting, and chemical recycling, in which the monomers obtained by thermal depolymerization are reused.

[0003] Methyl methacrylate copolymers are often used due to their excellent transparency, which allows for design and weather resistance. However, when using them as recycled materials, there are limitations to the extent to which they can be recycled in mechanical recycling due to the need to select compounds such as additives, the presence of impurities that can reduce design, and the deterioration of polymer properties due to thermal history.

[0004] On the other hand, chemical recycling of methyl methacrylate copolymer has the advantage that by depolymerizing it into monomers, the physical properties of the methyl methacrylate copolymer when polymerized using those monomers can be made equivalent to the physical properties of a copolymer made using non-recycled monomers and the physical properties before recycling.

[0005] Methyl methacrylate copolymers are known to be more easily depolymerized than other resins. However, no chemical recycling method is known for cross-linked methyl methacrylate copolymers, especially those containing inorganic fillers. Therefore, a method for recovering methyl methacrylate-containing compositions by chemical recycling is needed to meet social demands for petrochemicals.

[0006] Regarding the recycling method of inorganic fillers in methyl methacrylate copolymers containing inorganic fillers, there are cases where the methyl methacrylate copolymers containing inorganic fillers are crushed and mechanically recycled. In this case, there are issues that the methyl methacrylate copolymers must be plastic, which is not applicable to methyl methacrylate copolymers with crosslinked parts produced by polymerization methods such as cast polymerization, and there are issues that the composition of the recycled material is limited because the ratio of plastic to inorganic components depends on the raw materials.

[0007] Patent Document 1 describes a process in which a plastic molded product containing glass fiber and aluminum hydroxide as inorganic substances is treated with a certain subcritical fluid to decompose the plastic into monomers and oligomers and separate the inorganic substances from the plastic, as well as a process for separating the inorganic substances.

[0008] Patent Document 2 describes a method of recovering boehmite from plastics containing aluminum hydroxide as an inorganic filler by heat treating the plastic at a temperature in the range of 200 to 450°C.

[0009] Patent Document 3 describes a method for recovering aluminum hydroxide from plastics containing the inorganic filler as a flame-retardant filler for thermoplastic or thermosetting resins. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2005-336323 A [Patent Document 2] Patent No. 5006523 [Patent Document 3] JP 2006-297836 A Summary of the Invention [Problem to be solved by the invention]

[0011] Patent Document 1 describes treatment with a subcritical fluid as a method for depolymerizing plastics, but does not describe thermal decomposition. Furthermore, treatment with a fluid is undesirable in terms of the environmental impact of the fluid removal process. Furthermore, while depolymerization of plastics in a subcritical fluid treatment generally results in a high level of impurities, Patent Document 1 does not describe the yield or purity of the decomposition into monomers.

[0012] In Patent Document 2, plastic is depolymerized in an air atmosphere. However, for example, when the plastic is a methyl methacrylate copolymer, the limiting oxygen concentration of methyl methacrylate, the main monomer generated by depolymerization, is 9.4%, which poses a risk of ignition and explosion when heated.

[0013] Patent Document 3 describes a method for regenerating plastics containing aluminum hydroxide by mechanical recycling, but does not describe chemical recycling. Furthermore, in mechanical recycling, the ratio of plastic to inorganic components depends on the raw materials, so there are restrictions on the composition of the recycled material.

[0014] Therefore, an object of the present invention is to provide a method for recovering inorganic substances with high purity from a composition containing a methacrylic resin and an inorganic filler, regardless of whether or not the methacrylic resin has crosslinked moieties.

[0015] Another object of the present invention is to provide a method for recovering a methyl methacrylate-containing composition with high purity from a composition containing a methacrylic resin and an inorganic filler, regardless of whether or not the methacrylic resin has crosslinked moieties. [Means for solving the problem]

[0016] That is, the present invention is as follows.

[0017] First Aspect [1] A method for recovering inorganic matter from a composition containing a methacrylic resin and an inorganic filler, A step (1) of preparing a composition (1) containing a methacrylic resin and an inorganic filler; a step (2) of heating the composition (1) at 200 to 490°C in a system having an oxygen concentration of 0.001 to 9.0% by volume, separating a gas containing methyl methacrylate generated by thermal decomposition of the methacrylic resin, and recovering inorganic substances; Including, the methacrylic resin is at least one selected from the group consisting of a methyl methacrylate copolymer (A) containing a crosslinked portion and a non-crosslinked methyl methacrylate polymer (B); A method for recovering inorganic substances from a composition containing a methacrylic resin and an inorganic filler, wherein the amount of the inorganic filler in the composition (1) is 5 to 200 parts by mass per 100 parts by mass of the total of the methacrylic resins. [2] The inorganic filler is aluminum hydroxide, The step (2) a step (2-1) of heating the composition (1) in the system at 200 to 350°C to separate water vapor from the composition (1); The method for recovering inorganic substances from a composition containing a methacrylic resin and an inorganic filler according to [1], comprising: after step (2-1), step (2-2) of heating the composition (1) in the system at 300 to 490°C to separate the gas. [3] The inorganic filler is aluminum hydroxide, The method for recovering an inorganic substance from a composition containing a methacrylic resin and an inorganic filler according to [1] or [2], wherein the main component of the inorganic substance is boehmite. [4] The method for recovering inorganic substances from a composition containing a methacrylic resin and an inorganic filler according to any one of [1] to [3], wherein the heating in the step (2) is carried out in the same vessel, kiln, or fluidized bed. [5] A method for recovering inorganic substances from a composition containing a methacrylic resin and an inorganic filler according to any one of [1] to [4], wherein the composition (1) is waste artificial marble.

[0018] Second Aspect [6] A method for recovering a methyl methacrylate-containing composition from a composition containing a methacrylic resin and an inorganic filler, comprising: A step (1) of preparing a composition (1) containing a methacrylic resin and an inorganic filler; a step (2) of heating the composition (1) at 200 to 490°C in a system having an oxygen concentration of 0.001 to 9.0% by volume, and separating a gas containing methyl methacrylate generated by thermal decomposition of the methacrylic resin; Including, the methacrylic resin is at least one selected from the group consisting of a methyl methacrylate copolymer (A) containing a crosslinked portion and a non-crosslinked methyl methacrylate polymer (B); A method for recovering a methyl methacrylate-containing composition from a composition containing a methacrylic resin and an inorganic filler, wherein the amount of the inorganic filler in the composition (1) is 5 to 200 parts by mass per 100 parts by mass of the total of the methacrylic resin. [7] The inorganic filler is aluminum hydroxide, The step (2) a step (2-1) of heating the composition (1) in the system at 200 to 350°C to separate water vapor from the composition (1); The method for recovering a methyl methacrylate-containing composition from a composition containing a methacrylic resin and an inorganic filler according to [6], comprising: after step (2-1), step (2-2) of heating the composition (1) in the system at 300 to 490°C to separate the gas. [8] The method for recovering a methyl methacrylate-containing composition from a composition containing a methacrylic resin and an inorganic filler according to [6] or [7], wherein the heating in the step (2) is carried out in the same vessel, kiln, or fluidized bed. [Effects of the Invention]

[0019] According to the present invention, a method for recovering inorganic substances with high purity from a composition containing a methacrylic resin and an inorganic filler, regardless of whether or not crosslinked portions are present in the methacrylic resin, can be provided. Also, according to the present invention, a method for recovering a methyl methacrylate-containing composition with high purity from a composition containing a methacrylic resin and an inorganic filler, regardless of whether or not crosslinked portions are present in the methacrylic resin, can be provided. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram showing the recovery process of a methyl methacrylate-containing composition according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] The following describes in detail an embodiment of the present invention (hereinafter referred to as "the present embodiment"). The present invention is not limited to the following embodiment, and various modifications can be made within the scope of the present invention.

[0022] In this specification, two or more embodiments can be combined in any manner.

[0023] Unless otherwise specified, the materials, monomers, components, compounds, resins, catalysts, and solvents described in this specification may be used alone or in combination of two or more.

[0024] In this specification, the methyl methacrylate copolymer (A) containing a crosslinked portion and the non-crosslinked methyl methacrylate polymer (B) may be referred to as component (A) and component (B), respectively.

[0025] In this specification, the (meth)acryloyl group means one or more groups selected from an acryloyl group and a methacryloyl group.

[0026] As used herein, methyl methacrylate monomer units refer to monomer units derived from methyl methacrylate, and alkyl acrylate monomer units refer to monomer units derived from alkyl acrylate.

[0027] In this specification, the water vapor generated from the inorganic filler may be simply referred to as "water vapor," and the gas containing methyl methacrylate generated by the thermal decomposition of the methacrylic resin may be simply referred to as "gas."

[0028] (First Aspect: Method for Recovering Inorganic Substances from a Composition Containing a Methacrylic Resin and an Inorganic Filler) The first aspect is a method for recovering inorganic matter from a composition containing a methacrylic resin and an inorganic filler, comprising: A step (1) of preparing a composition (1) containing a methacrylic resin and an inorganic filler; a step (2) of heating the composition (1) at 200 to 490°C in a system having an oxygen concentration of 0.001 to 9.0% by volume, separating a gas containing methyl methacrylate generated by thermal decomposition of the methacrylic resin, and recovering inorganic substances; Including, the methacrylic resin is at least one selected from the group consisting of a methyl methacrylate copolymer (A) containing a crosslinked portion and a non-crosslinked methyl methacrylate polymer (B); The method for recovering inorganic substances from a composition containing a methacrylic resin and an inorganic filler is such that the amount of the inorganic filler in the composition (1) is 5 to 200 parts by mass per 100 parts by mass of the methacrylic resin in total.

[0029] Step (1) of the first embodiment In step (1) of the method for recovering inorganic materials according to the present embodiment, a composition (1) containing a methacrylic resin and an inorganic filler is prepared. In the composition (1), the methacrylic resin is at least one selected from the group consisting of a methyl methacrylate copolymer (A) containing a crosslinked portion and a non-crosslinked methyl methacrylate polymer (B); The amount of the inorganic filler in the composition (1) is 5 to 200 parts by mass per 100 parts by mass of the total of (A) and (B).

[0030] The components (A), (B) and inorganic filler of the composition (1) will be described below.

[0031] Component (A) The methyl methacrylate copolymer (A) containing a crosslinked portion (crosslinked portion) of this embodiment has a structure (monomer unit) derived from a methyl methacrylate monomer as a main component, and also contains a structure derived from a monomer having a difunctional or higher functional (meth)acryloyl group for crosslinking. That is, the methyl methacrylate copolymer (A) has a portion crosslinked by a difunctional or higher functional (meth)acryloyl group as a crosslinked portion. Furthermore, the methyl methacrylate copolymer (A) may or may not contain a structure derived from a monomer having a radically polymerizable carbon-carbon double bond as another monomer unit. In one embodiment, the methyl methacrylate copolymer (A) is composed solely of a structure derived from a methyl methacrylate monomer and a structure derived from a monomer having a difunctional or higher functional (meth)acryloyl group.

[0032] The monomer having a bifunctional or higher functional (meth)acryloyl group may be any monomer copolymerizable with methyl methacrylate, and examples thereof include 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 3-methyl-1,5-pentanediol diacrylate, 1,9-nonanediol diacrylate, dimethylol-tricyclodecane diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, 2-methacryloyloxyethyl acid phosphate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol Examples of the acrylic acid acrylate include trimethylolpropane dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, glycerin dimethacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, ethylene oxide adduct of bisphenol A dimethacrylate, ethylene oxide adduct of bisphenol A diacrylate, trimethylolpropane trimethacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, pentaerythritol triacrylate, isocyanuric acid ethylene oxide modified diacrylate, isocyanuric acid ethylene oxide modified triacrylate, and (caprolactone modified) isocyanurate multifunctional acrylate.

[0033] The methacrylic resin in composition (1) is one or more selected from the group consisting of component (A) and component (B). That is, the weight ratio of (A):(B) is 100:0 to 0:100. The methacrylic resin may be component (A) and component (B). In one embodiment, the amount of component (A) is 0 parts by mass or more, 10 parts by mass or more, 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, 50 parts by mass or more, 60 parts by mass or more, 70 parts by mass or more, 80 parts by mass or more, or 90 parts by mass or more, relative to 100 parts by mass of the total of component (A) and component (B). In another embodiment, the amount of component (A) is 100 parts by mass or less, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, or 10 parts by mass or less, relative to 100 parts by mass of the total of components (A) and (B). In yet another embodiment, the methacrylic resin is component (A) alone.

[0034] When composition (1) is derived from artificial marble, from the viewpoint of solvent resistance and mechanical properties, the amount of component (A) is preferably 40 to 100 parts by mass per 100 parts by mass of the total of components (A) and (B).

[0035] (B) Component The non-crosslinked methyl methacrylate polymer (B) of this embodiment is a non-crosslinked methyl methacrylate polymer (B). Component (B) only needs to contain methyl methacrylate monomer units, and may contain alkyl acrylate monomer units in addition to methyl methacrylate monomer units. Component (B) may further contain other monomer units copolymerizable with methyl methacrylate.

[0036] The alkyl group of the alkyl acrylate monomer unit is not particularly limited, and examples thereof include alkyl groups having 1 to 18 carbon atoms. From the viewpoint of availability, the alkyl group is preferably an alkyl group having 1 to 4 carbon atoms.

[0037] The other monomer units may be, for example, vinyl monomers copolymerizable with methyl methacrylate, such as alkyl methacrylates having an alkyl group with 2 to 18 carbon atoms; alkyl acrylates having an alkyl group with 1 to 3 carbon atoms; aromatic vinyl compounds such as styrene, α-methylstyrene, and styrenes having a substituent on the benzene ring; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; maleic anhydride, maleimide, and N-substituted maleimide.

[0038] In one embodiment, component (B) contains only methyl methacrylate monomer units. In another embodiment, component (B) contains only methyl methacrylate monomer units and alkyl acrylate monomer units. In yet another embodiment, component (B) contains methyl methacrylate monomer units and one or more monomer units selected from the group consisting of alkyl acrylate monomer units and other monomer units.

[0039] In one embodiment, the methacrylic resin is the only component (B).

[0040] inorganic filler The size of the inorganic filler of this embodiment is not particularly limited, and from the viewpoint of availability, for example, a size of 100 nm to 10 mm is preferable.

[0041] The form of the inorganic filler is not particularly limited.

[0042] The composition of the inorganic filler is not particularly limited, and examples thereof include calcium carbonate, silica, talc, clay, glass flakes, glass fiber, mica, potassium titanate, alumina, aluminum hydroxide, antimony oxide, zinc compounds, carbon nanotubes, graphite, titanium oxide, barium sulfate, etc. When the object to be thermally decomposed, i.e., composition (1), is derived from artificial marble, it may contain silica or aluminum hydroxide as the inorganic filler. In one embodiment, the inorganic filler is aluminum hydroxide or silica.

[0043] The amount of inorganic filler in composition (1) is 5 to 200 parts by mass per 100 parts by mass of the total methacrylic resin. If the amount of inorganic filler exceeds 200 parts by mass per 100 parts by mass of the total methacrylic resin, the cuttability or crushability of composition (1) will deteriorate due to the high hardness of the inorganic filler. Furthermore, since one of the objects of the present invention is the recycling of inorganic materials, the amount of inorganic filler is set to 5 parts by mass or more per 100 parts by mass of the total methacrylic resin.

[0044] In one embodiment, the amount of the inorganic filler is 5 parts by weight or more, 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, 90 parts by weight or more, 100 parts by weight or more, 110 parts by weight or more, 120 parts by weight or more, 130 parts by weight or more, 140 parts by weight or more, 150 parts by weight or more, 160 parts by weight or more, 170 parts by weight or more, 180 parts by weight or more, or 190 parts by weight or more, based on 100 parts by weight of the total methacrylic resin. In another embodiment, the amount of the inorganic filler is 200 parts by weight or less, 190 parts by weight or less, 180 parts by weight or less, 170 parts by weight or less, 160 parts by weight or less, 150 parts by weight or less, 140 parts by weight or less, 130 parts by weight or less, 120 parts by weight or less, 110 parts by weight or less, 100 parts by weight or less, 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, 60 parts by weight or less, 50 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, 20 parts by weight or less, or 10 parts by weight or less, relative to 100 parts by weight of the total methacrylic resin. In yet another embodiment, the amount of the inorganic filler is 50 to 200 parts by weight or 80 to 150 parts by weight relative to 100 parts by weight of the total methacrylic resin.

[0045] additives The composition (1) may contain additives, such as ultraviolet absorbers, heat stabilizers, light stabilizers, plasticizers, flame retardants, flame retardant aids, curing agents, curing accelerators, antistatic agents, conductivity imparting agents, stress relaxation agents, mold release agents, crystallization accelerators, hydrolysis inhibitors, lubricants, impact imparting agents, friction improvers, compatibilizers, nucleating agents, reinforcing agents, flow adjusters, dyes, sensitizers, colorants, anti-settling agents, anti-sagging agents, fillers, antifoaming agents, light-diffusing fine particles, rust inhibitors, antibacterial agents, anti-fungal agents, antifouling agents, and conductive polymers.

[0046] The form of composition (1) is not particularly limited as long as it can be charged into a pyrolysis apparatus, and examples of the form of composition (1) include box-like, plate-like, block-like, spherical, cylindrical, bead-like, pellet-like, and powder-like forms.

[0047] In one embodiment, composition (1) is artificial marble or artificial marble waste.

[0048] Step (2) of the first embodiment In step (2) of the inorganic material recovery method of this embodiment, composition (1) is heated at 200 to 490°C in a system with an oxygen concentration of 0.001 to 9.0% by volume, and a gas containing methyl methacrylate generated by thermal decomposition of the methacrylic resin is separated to recover the inorganic material.

[0049] Examples of the system for step (2) include a heating device or a pyrolysis device. The oxygen concentration in the system (e.g., in the heating device) is 0.001 to 9.0% by volume. To obtain a high-purity inorganic substance and a methyl methacrylate-containing composition, the oxygen concentration during heating must be within a certain range. In the absence of oxygen, carbonization of organic substances occurs, so the oxygen concentration in the system is 0.001% by volume or more. Furthermore, since the limit oxygen concentration for methyl methacrylate is 9.4% by volume, the oxygen concentration in the system is 9.0% by volume or less to prevent ignition and explosion. If the lower limit of the oxygen concentration is too low, it is difficult to control the oxygen concentration. For these reasons, the oxygen concentration in the system for step (2) is preferably 0.01 to 7% by volume, more preferably 0.1 to 5% by volume. In one embodiment, the oxygen concentration in the system in step (2) is 0.001% by volume or more, 0.01% by volume or more, 0.1% by volume or more, 1% by volume or more, 2% by volume or more, 3% by volume or more, 4% by volume or more, 5% by volume or more, 6% by volume or more, 7% by volume or more, or 8% by volume or more. In another embodiment, the oxygen concentration in the system in step (2) is 9.0% by volume or less, 8% by volume or less, 7% by volume or less, 6% by volume or less, 5% by volume or less, 4% by volume or less, 3% by volume or less, 2% by volume or less, or 1% by volume or less.

[0050] In step (2), composition (1) is heated at 200 to 490°C in a system having an oxygen concentration of 0.001 to 9.0% by volume. In one embodiment, the heating temperature in step (2) is 200°C or higher, 250°C or higher, 300°C or higher, 350°C or higher, 400°C or higher, or 450°C or higher. In another embodiment, the heating temperature in step (2) is 490°C or lower, 450°C or lower, 400°C or lower, 350°C or lower, 300°C or lower, or 250°C or lower. From the viewpoint of increasing the recovery rate of the methyl methacrylate-containing composition obtained by thermal decomposition, the thermal decomposition temperature is preferably 300 to 480°C, more preferably 350 to 450°C.

[0051] The pyrolysis method is not particularly limited, but the kettle method, kiln method and fluidized bed method are preferred in terms of not subjecting the raw material composition (1) to shear and reducing wear on the equipment.

[0052] In one embodiment, the heating in step (2) is carried out in the same vessel, kiln, or fluidized bed.

[0053] In one embodiment, step (2) includes step (2-1) of heating composition (1) in a system at 200 to 350°C and separating water vapor from composition (1), and, after step (2-1), step (2-2) of heating composition (1) in a system at 300 to 490°C and separating gas containing methyl methacrylate generated by thermal decomposition of the methacrylic resin.

[0054] In this embodiment, it is preferable that the inorganic filler is aluminum hydroxide, and step (2) comprises step (2-1) of heating composition (1) in a system at 200 to 350°C and separating water vapor from composition (1), and, after step (2-1), step (2-2) of heating composition (1) in a system at 300 to 490°C and separating gas containing methyl methacrylate generated by thermal decomposition of the methacrylic resin.

[0055] When the inorganic filler is aluminum hydroxide and dehydrates when heated, it can be difficult to separate the water vapor generated from the inorganic filler and the gas containing methyl methacrylate generated by the thermal decomposition of the methacrylic resin in a continuous process such as extrusion. In contrast, even when the inorganic filler is aluminum hydroxide, steps (2-1) and (2-2) make it easy to separate the water vapor and gas. This is because aluminum hydroxide is mostly dehydrated in the range of 200 to 350°C, and methyl methacrylate copolymers depolymerize at around 300°C, generating monomers.

[0056] From the viewpoints of the separation accuracy of the water vapor generated from the inorganic filler (e.g., aluminum hydroxide) and the gas containing methyl methacrylate generated by the thermal decomposition of the methacrylic resin, and of the working efficiency, the temperature in the system in step (2-1) is preferably 205 to 340°C, and more preferably 210 to 330°C.

[0057] In one embodiment, the inorganic filler is aluminum hydroxide and the primary inorganic component is boehmite.

[0058] When the main component (90% by mass or more) of the inorganic substance to be recovered is boehmite or when the inorganic substance is boehmite, boehmite dehydrates at 500°C or higher. Therefore, in order to suppress dehydration from the boehmite and from the viewpoints of the accuracy of separation of water vapor and gas and work efficiency, the temperature in the system of step (2-2) is preferably 320 to 480°C, more preferably 330 to 470°C.

[0059] The thermal decomposition method is not particularly limited, but batch methods such as the kettle method and fluidized bed method are preferred because they make it easy to separate steam and gas. In the case of continuous methods such as the kiln method and extrusion method, steam and gas can be separated by creating a temperature gradient in the heating section.

[0060] In order to improve the accuracy of separation of water vapor and gas, step (2-3) may be included between step (2-1) and step (2-2) as a step in which water vapor and gas are mixed. Regarding the temperature in the system in step (2-3), a value within the temperature range in the system (step 2-1) is set as the minimum temperature in the system in step (2-3), and a value within the temperature range in the system in step (2-2) is set as the maximum temperature in the system in step (2-3). The temperature in the system in step (2-3) is preferably 300 to 380°C, more preferably 310 to 370°C.

[0061] The method for recovering the inorganic substance in step (2) is not particularly limited. For example, when the heating method is a kettle method, the inorganic substance may be recovered by being discharged from the bottom or side of the kettle after the gas has been separated, or by being recovered from the top of the kettle after the interior of the kettle has sufficiently cooled. In the case of a continuous method such as an extrusion method or a kiln method, the inorganic substance may be conveyed to a tank after passing through a heating zone, and the inorganic substance may be recovered by being discharged from the bottom or side of the tank. It is desirable to thoroughly heat the inorganic substance before recovering it to remove as many organic components as possible.

[0062] Examples of inorganic substances recovered by the recovery method of this embodiment include silica, boehmite, calcium carbonate, silica, talc, clay, glass flakes, glass fiber, mica, potassium titanate, alumina, aluminum hydroxide, antimony oxide, zinc compounds, carbon nanotubes, graphites, titanium oxide, barium sulfate, etc. In one embodiment, the inorganic substance recovered is one or more selected from the group consisting of silica and boehmite.

[0063] When the composition (1) is derived from artificial marble, it may contain silica or aluminum hydroxide as an inorganic filler. When the inorganic filler is silica, silica can be recovered as the inorganic substance, and when the inorganic filler is aluminum hydroxide, boehmite can be recovered as the inorganic substance.

[0064] (Second Aspect: Method for Recovering Methyl Methacrylate-Containing Composition from a Composition Containing Methacrylic Resin and Inorganic Filler) A second aspect is a method for recovering a methyl methacrylate-containing composition from a composition containing a methacrylic resin and an inorganic filler, comprising: A step (1) of preparing a composition (1) containing a methacrylic resin and an inorganic filler; a step (2) of heating the composition (1) at 200 to 490°C in a system having an oxygen concentration of 0.001 to 9.0% by volume, and separating a gas containing methyl methacrylate generated by thermal decomposition of the methacrylic resin; Including, the methacrylic resin is at least one selected from the group consisting of a methyl methacrylate copolymer (A) containing a crosslinked portion and a non-crosslinked methyl methacrylate copolymer (B); This is a method for recovering a methyl methacrylate-containing composition from a composition containing a methacrylic resin and an inorganic filler, wherein the amount of the inorganic filler in the composition (1) is 5 to 200 parts by mass per 100 parts by mass of the methacrylic resin in total. A gas containing methyl methacrylate generated by thermal decomposition is separated, and the methyl methacrylate-containing composition contained in the gas or in a gaseous state is recovered.

[0065] Step (1) of the second embodiment In step (1) of the method for recovering a methyl methacrylate-containing composition of this embodiment, a composition (1) containing a methacrylic resin and an inorganic filler is prepared. The composition (1) of the second embodiment is similar to the composition (1) of the first embodiment, and therefore a description thereof will be omitted.

[0066] Another object of the present invention is the recycling of methyl methacrylate-containing compositions. When composition (1) is derived from artificial marble, from the viewpoints of solvent resistance and mechanical properties, the proportion of methyl methacrylate copolymer (A) containing at least crosslinked portions is higher than the proportion of non-crosslinked methyl methacrylate polymer (B). Therefore, the weight ratio of methyl methacrylate copolymer (A) containing crosslinked portions to non-crosslinked methyl methacrylate polymer (B) is preferably A:B=100:0 to 95:5, and practically A:B=100:0 to 90:10 is more preferable.

[0067] Step (2) of the second embodiment In step (2) of the method for recovering a methyl methacrylate-containing composition of this embodiment, composition (1) is heated at 200 to 490°C in a system with an oxygen concentration of 0.001 to 9.0% by volume, and a gas containing methyl methacrylate generated by thermal decomposition of the methacrylic resin is separated to recover the methyl methacrylate-containing composition. Step (2) of the second embodiment is similar to step (2) of the first embodiment, except that the object to be recovered is an inorganic substance or a methyl methacrylate-containing composition, and therefore a detailed description thereof will be omitted. In one embodiment, the separated gas contains a methyl methacrylate-containing composition. In another embodiment, the separated gas is a methyl methacrylate-containing composition.

[0068] Steps (2-1), (2-2) and (2-3) are also similar to step (2) of the first embodiment.

[0069] The method for recovering a methyl methacrylate-containing composition of the second embodiment may further include step (3) of cooling the gas separated in step (2) simultaneously with or after step (2). The cooling temperature is, for example, 5 to 35°C.

[0070] The method for recovering a methyl methacrylate-containing composition of the second embodiment may further include, after step (2), step (4) of purifying the gas separated in step (2). As a purification means, known distillation or the like can be used.

[0071] The separated gas may be recovered as a liquid component by cooling, and the liquid component may be used as a recycled methyl methacrylate-containing composition for polymerization, etc. Alternatively, the decomposition gas may be purified in a gaseous state or in a liquid state after cooling the decomposition gas, and used as a methyl methacrylate-containing composition with a higher purity for polymerization, etc.

[0072] 1 is a flow diagram schematically illustrating an example of a method for recovering a methyl methacrylate-containing composition according to the present embodiment, in which the arrows indicate the flow of the recycling process. [Example]

[0073] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0074] As the composition (1), the following commercially available artificial marbles 1 and 2, component (B), and inorganic filler were used. Artificial marble 1: Contains component (A) and aluminum hydroxide in a mass ratio of 55:45 Artificial marble 2: Contains component (A) and silica in a mass ratio of 50:50 (B) Component: Methacrylic resin, manufactured by Asahi Kasei Corporation, "Delpet (registered trademark) 80N", pellet form inorganic filler Aluminum hydroxide silica

[0075] [Evaluation of the purity of recovered inorganic materials] The recovered inorganic materials obtained in the examples and comparative examples were subjected to X-ray fluorescence analysis to examine the purity of the inorganic components. Sample preparation: Tablets were formed using Al rings. Equipment: Rigaku ZSX-PrimusIV X-ray source: Rh tube X-ray irradiation diameter: 3mmφ

[0076] When composition (1) contained aluminum hydroxide, the purity of the boehmite was investigated by X-ray diffraction analysis. Equipment: Rigaku Ultima-IV X-ray source:Cu-Kα Excitation voltage: 40 kV, current 40 mA Cu-Kβ ray filter: Ni foil Measurement method: θ / 2θ method Slit: DS=1mm, SS=open, vertical slit=10mm 2θ / θ scan: 2θ = 5 to 75° (0.02° / step, 10° / min)

[0077] The purity of the recovered inorganic substance was evaluated according to the following criteria: When the inorganic filler was aluminum hydroxide, the inorganic substance was boehmite, and when the inorganic filler was silica, the inorganic substance was silica. A: 90% or more purity B: Purity of 70% or more and less than 90% C: Less than 70% purity

[0078] [Purity of recovered methyl methacrylate] The purity of methyl methacrylate in the liquid obtained by cooling the gases obtained in the Examples and Comparative Examples was investigated using a gas chromatograph mass spectrometer. Equipment: Agilent7890B / 5977B Column: HP-5MS (L 30 m, I.D 0.250 mm, Film 0.25 μm) Carrier: Helium Detector: MSD Ionization method: EI (electron ionization) Oven temperature: 40℃ (5 min hold) → 20℃ / min → 320℃ (10 min hold) Inlet temperature: 320℃ Mass range: m / z 10-800

[0079] The purity of the recovered methyl methacrylate was evaluated according to the following criteria. A: 85% or more purity B: Purity of 65% or more but less than 85% C: Purity of 50% or more but less than 65% D: Less than 50% purity

[0080] Example 1 Process (1) Artificial marble 1 was crushed to obtain composition (1) which was a crushed product having a maximum length of 10 mm.

[0081] Process (2) Composition (1) was placed into the heating kettle through the raw material inlet, and the raw material inlet was then sealed. The oxygen concentration in the kettle was then adjusted to 1% with a mixed gas containing nitrogen gas as the main component (90% or more). While maintaining this oxygen concentration, composition (1) was heated at 450°C for 3 hours. Next, gas containing methyl methacrylate generated by thermal decomposition was separated from composition (1) and collected. The gas was cooled, and the methyl methacrylate was recovered. Heating of the kettle was stopped, and the kettle was cooled to room temperature. Next, inorganic matter was collected from the kettle.

[0082] Examples 2 to 7 Using artificial marble 1-2, Delpet 80N, and inorganic filler, steps (1) and (2) were carried out in the same manner as in Example 1, except that the types and ratios of component (A), component (B), and inorganic filler were changed as shown in Table 1.

[0083] (Examples 8 to 10) Steps (1) and (2) were carried out in the same manner as in Example 1, except that the heating temperature was changed as shown in Table 1.

[0084] Example 11 The formulation of composition (1) was changed as shown in Table 1, and in step (2-1), a gas mainly containing water vapor was separated from composition (1) at 200°C for 1 hour. Next, in step (2-2), each step was performed in the same manner as in Example 1, except that a gas mainly containing methyl methacrylate was separated from composition (1) at 450°C for 2 hours.

[0085] (Examples 12 to 13) Each step was carried out in the same manner as in Example 11, except that the heating temperatures in steps (2-1) and (2-2) were changed as shown in Table 1.

[0086] (Examples 14 to 16) Steps (1) and (2) were carried out in the same manner as in Example 6, except that the formulation of composition (1) was changed as shown in Table 1.

[0087] (Examples 17 to 18) Steps (1) and (2) were carried out in the same manner as in Example 1, except that mixed gases with different oxygen concentrations were used and the oxygen concentrations were changed as shown in Table 1.

[0088] (Comparative Examples 1 and 2) Steps (1) and (2) were carried out in the same manner as in Example 4, except that the heating temperature was changed as shown in Table 2.

[0089] (Comparative Example 3) Composition (1) was prepared and pyrolyzed in the same manner as in Example 1, except that the heating temperature was changed as shown in Table 2.

[0090] (Comparative Examples 4 to 5) As shown in Table 2, each step was carried out in the same manner as in Example 11, except that the heating temperatures in steps (2-1) and (2-2) were changed.

[0091] (Comparative Example 6) Steps (1) and (2) were carried out in the same manner as in Example 1, except that high-purity nitrogen gas was used and the oxygen concentration was changed to 0%.

[0092] [Table 1]

[0093] [Table 2] [Industrial Applicability]

[0094] According to the present invention, a method for recovering inorganic substances with high purity from a composition containing a methacrylic resin and an inorganic filler, regardless of whether or not crosslinked portions are present in the methacrylic resin, can be provided. Also, according to the present invention, a method for recovering a methyl methacrylate-containing composition with high purity from a composition containing a methacrylic resin and an inorganic filler, regardless of whether or not crosslinked portions are present in the methacrylic resin, can be provided. [Explanation of symbols]

[0095] 1: Raw materials 2:Pyrolysis equipment 3: Cooling section 4: Methyl methacrylate-containing composition recovery section 5: Water-containing composition separation section

Claims

1. A method for recovering inorganic matter from a composition containing a methacrylic resin and an inorganic filler, comprising: A step (1) of preparing a composition (1) containing a methacrylic resin and an inorganic filler; (2) a step of heating the composition (1) at 200 to 490°C in a system having an oxygen concentration of 0.001 to 9.0% by volume, separating a gas containing methyl methacrylate generated by thermal decomposition of the methacrylic resin, and recovering inorganic substances; Including, the methacrylic resin is at least one selected from the group consisting of a methyl methacrylate copolymer (A) containing a crosslinked portion and a non-crosslinked methyl methacrylate polymer (B); A method for recovering inorganic substances from a composition containing a methacrylic resin and an inorganic filler, wherein the amount of the inorganic filler in the composition (1) is 5 to 200 parts by mass per 100 parts by mass of the methacrylic resin in total.

2. the inorganic filler is aluminum hydroxide, The step (2) A step (2-1) of heating the composition (1) in the system at 200 to 350°C to separate water vapor from the composition (1); and (2-2) after step (2-1), heating the composition (1) in the system at 300 to 490°C to separate the gas. A method for recovering inorganic substances from a composition containing a methacrylic resin and an inorganic filler according to claim 1.

3. the inorganic filler is aluminum hydroxide, The method for recovering an inorganic substance from a composition containing a methacrylic resin and an inorganic filler according to claim 1 or 2, wherein the main component of the inorganic substance is boehmite.

4. The method for recovering inorganic substances from a composition containing a methacrylic resin and an inorganic filler according to claim 1 or 2, wherein the heating in the step (2) is carried out in the same vessel, kiln, or fluidized bed.

5. The method for recovering inorganic substances from a composition containing a methacrylic resin and an inorganic filler according to claim 1 or 2, wherein the composition (1) is waste artificial marble.

6. A method for recovering a methyl methacrylate-containing composition from a composition containing a methacrylic resin and an inorganic filler, comprising: A step (1) of preparing a composition (1) containing a methacrylic resin and an inorganic filler; (2) a step of heating the composition (1) at 200 to 490°C in a system having an oxygen concentration of 0.001 to 9.0% by volume, and separating a gas containing methyl methacrylate generated by thermal decomposition of the methacrylic resin; Including, the methacrylic resin is at least one selected from the group consisting of a methyl methacrylate copolymer (A) containing a crosslinked portion and a non-crosslinked methyl methacrylate polymer (B); A method for recovering a methyl methacrylate-containing composition from a composition containing a methacrylic resin and an inorganic filler, wherein the amount of the inorganic filler in the composition (1) is 5 to 200 parts by mass per 100 parts by mass of the total of the methacrylic resins.

7. the inorganic filler is aluminum hydroxide, The step (2) A step (2-1) of heating the composition (1) in the system at 200 to 350°C to separate water vapor from the composition (1); The method for recovering a methyl methacrylate-containing composition from a composition containing a methacrylic resin and an inorganic filler according to claim 6, comprising: after step (2-1), a step (2-2) of heating the composition (1) in the system at 300 to 490°C to separate the gas.

8. The method for recovering a methyl methacrylate-containing composition from a composition containing a methacrylic resin and an inorganic filler according to claim 6 or 7, wherein the heating in step (2) is carried out in the same vessel, kiln, or fluidized bed.

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