Method for producing methacrylic resin, methacrylic resin, methacrylic resin composition, and method for producing artificial marble

Abstract

To provide a method that enables production of methacrylic resin from artificial marble.SOLUTION: A method for producing a methacrylic resin (A), comprising: step (1) of pulverizing artificial marble containing a methacrylic resin (B) and aluminum hydroxide (C) to obtain pulverized artificial marble; step (2) of washing the pulverized artificial marble with sulfuric acid to separate a solid phase (D) and an aqueous aluminum sulfate solution (E) as a liquid phase resulting from the washing; and step (3) of performing suspension polymerization using the aqueous aluminum sulfate solution (E) and a polymerizable monomer composition (F) containing methyl methacrylate to produce the methacrylic resin (A).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a methacrylic resin, a methacrylic resin, a methacrylic resin composition, and a method for producing artificial marble. [Background technology]

[0002] From the perspective of reducing the environmental impact, "chemical recycling" is being investigated, in which polymethyl methacrylate is thermally decomposed and depolymerized to isolate and reuse methyl methacrylate.

[0003] For example, Patent Document 1 describes a method for thermally decomposing polymethyl methacrylate (PMMA).

[0004] Furthermore, for example, Patent Document 2 describes a method for recovering methyl methacrylate from artificial marble. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2022-520072 [Patent Document 2] Korean Patent Registration No. 10-0982728 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in chemical recycling of PMMA, it is difficult to secure a large amount of raw material for recycling.On the other hand, artificial marble is easily available in large quantities as scrap material and is a desirable raw material for recovering methyl methacrylate, but more than half of the components of artificial marble are inorganic, and there have been challenges in utilizing the inorganic components during recycling.

[0007] Therefore, an object of the present invention is to provide a method for producing methacrylic resin from artificial marble. [Means for solving the problem]

[0008] In order to solve the above problems, the present inventors have conducted extensive research and have surprisingly found that an aqueous aluminum sulfate solution can be obtained by washing artificial marble containing aluminum hydroxide with sulfuric acid and separating the solid and liquid phases, and that this aqueous aluminum sulfate solution can be used as a suspending agent to polymerize methacrylic resin.

[0009] Furthermore, the present inventors have found that artificial marble can be produced using both methyl methacrylate and inorganic components recovered by pyrolysis of artificial marble.

[0010] That is, the present invention is as follows. [1] A method for producing a methacrylic resin (A), comprising: A step (1) of crushing an artificial marble containing a methacrylic resin (B) and aluminum hydroxide (C) to obtain crushed artificial marble; A step (2) of washing the crushed artificial marble with sulfuric acid to separate a solid phase (D) and a liquid phase of aluminum sulfate aqueous solution (E) produced by washing; a step (3) of carrying out suspension polymerization using the aluminum sulfate aqueous solution (E) and a polymerizable monomer composition (F) containing methyl methacrylate to produce a methacrylic resin (A); A method for producing a methacrylic resin (A), comprising: [2] a step (4) of thermally decomposing the solid phase (D) obtained in the step (2) to obtain methyl methacrylate (G); The method for producing the methacrylic resin (A) according to [1], further comprising a step (5) of mixing the methyl methacrylate (G) with the polymerizable monomer composition (F) of the step (3). [3] A step (6) of adjusting the pH of the aluminum sulfate aqueous solution (E) to 3.0 to 8.0 to prepare a suspension containing aluminum hydroxide; The method for producing the methacrylic resin (A) according to [1] or [2], further comprising using the suspending agent in the step (3). [4] A methacrylic resin obtained by the production method according to any one of [1] to [3]. [5] The methacrylic resin according to [4], which is for injection molding. [6] The methacrylic resin according to [4] or [5], which is for use in artificial marble. [7] A methacrylic resin composition comprising the methacrylic resin according to [5] and a light-diffusing filler, and having light-diffusing properties. [8] A step (A1) of crushing an artificial marble containing a methacrylic resin and aluminum hydroxide to obtain crushed artificial marble; A step (A2) of washing the crushed artificial marble with sulfuric acid and separating the solid phase and aqueous phase produced by washing to obtain an aluminum sulfate aqueous solution; a step (A3) of purifying aluminum hydroxide from the aqueous aluminum sulfate solution; A step (A4) of producing an artificial marble using the aluminum hydroxide; A method for producing artificial marble, comprising: [9] A step (a1) of crushing an artificial marble containing a methacrylic resin and aluminum hydroxide to obtain crushed artificial marble; A step (a2) of washing the crushed artificial marble with sulfuric acid to separate the solid phase and aqueous phase produced by washing; (a3) pyrolyzing the solid phase to produce methyl methacrylate; (a4) a step of producing artificial marble using the methyl methacrylate; A method for producing artificial marble, comprising:

[10] A method for producing artificial marble, characterized by using the methacrylic resin (A) obtained by the production method according to any one of [1] to [3], methyl methacrylate, and aluminum hydroxide. [Effects of the Invention]

[0011] According to the present invention, an aluminum sulfate aqueous solution can be obtained from artificial marble to produce methacrylic resin. Also, according to the present invention, artificial marble can be produced using both methyl methacrylate and inorganic components recovered by pyrolysis of artificial marble. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a flow diagram showing an example of a production flow of the methacrylic resin (A) of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a detailed description will be given of 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.

[0014] In this embodiment, the term "methacrylic resin" refers to a polymer of methyl methacrylate, and is a concept that encompasses polymethyl methacrylate.

[0015] Unless otherwise specified, the materials, components, compounds, resins and solvents described in this specification may be used alone or in combination of two or more.

[0016] In this embodiment, for the sake of convenience in explanation, each step is numbered and expressed as step (1), etc., but this does not mean the order of the steps. (Method for producing methacrylic resin (A)) The method for producing the methacrylic resin (A) of the present invention is as follows: A step (1) of crushing an artificial marble containing a methacrylic resin (B) and aluminum hydroxide (C) to obtain crushed artificial marble; Step (2) of washing the crushed artificial marble with sulfuric acid to separate the solid phase (D) and the liquid phase (E) of aluminum sulfate aqueous solution produced by washing; a step (3) of carrying out suspension polymerization using the aluminum sulfate aqueous solution (E) and a polymerizable monomer composition (F) containing methyl methacrylate to produce a methacrylic resin (A); This method for producing methacrylic resin (A) comprises the steps of: (a) obtaining an aqueous aluminum sulfate solution from artificial marble and producing methacrylic resin;

[0017] Process (1) In step (1), an artificial marble containing a methacrylic resin (B) and aluminum hydroxide (C) is pulverized to obtain a pulverized artificial marble.

[0018] ·Methacrylic resin (B) The methacrylic resin (B) may be a known methacrylic resin, or may be a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate monomer and other vinyl monomers.

[0019] Other vinyl monomers include, for example, alkyl methacrylates having an alkyl group with 2 to 18 carbon atoms, and alkyl acrylates having an alkyl group with 1 to 18 carbon atoms; α,β-unsaturated acids such as acrylic acid and methacrylic acid, unsaturated group-containing dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid, and alkyl esters thereof; aromatic vinyl compounds such as styrene, α-methylstyrene, and styrenes having a substituent on the benzene ring; cyanide vinyl compounds such as acrylonitrile and methacrylonitrile; maleic anhydride, maleimide, N-substituted maleimide, and the like; ethylene glycol di(meth)acrylate, diethylene glycol Examples of suitable acrylates include those obtained by esterifying both terminal hydroxyl groups of ethylene glycol or its oligomers with acrylic acid or methacrylic acid, such as di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate; those obtained by esterifying two alcohol hydroxyl groups with acrylic acid or methacrylic acid, such as neopentyl glycol di(meth)acrylate and di(meth)acrylate; those obtained by esterifying polyhydric alcohol derivatives, such as trimethylolpropane and pentaerythritol, with acrylic acid or methacrylic acid; and polyfunctional monomers, such as divinylbenzene. Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, and 2-ethylhexyl acrylate are preferred from the viewpoints of light resistance, thermal stability, heat resistance, and fluidity.

[0020] In one embodiment, the mass proportion of the structural units derived from methyl methacrylate relative to 100 mass% of the methacrylic resin (B) is 80 to 100 mass%.

[0021] Other vinyl monomers copolymerizable with methyl methacrylate affect solubility and heat resistance. The mass ratio of structural units derived from other vinyl monomers copolymerizable with methyl methacrylate relative to 100 mass% of the methacrylic resin (B) is preferably 0 to 20 mass%. From the viewpoint of thermal decomposition resistance, it is preferably 1 mass% or more. Furthermore, from the viewpoint of mechanical strength, it is preferably 20 mass% or less. It is more preferably 1 to 15 mass%, and even more preferably 3 to 10 mass%. The methacrylic resin (B) may be, for example, a mixture of a methyl methacrylate copolymer containing a crosslinked portion and a non-crosslinked methyl methacrylate copolymer.

[0022] Aluminum hydroxide (C) The artificial marble further contains aluminum hydroxide (C) in addition to the methacrylic resin (B).

[0023] In one embodiment, the amount of the methacrylic resin (B) is 20 to 95 parts by mass relative to 100 parts by mass of the total of the methacrylic resin (B) and aluminum hydroxide (C).

[0024] The artificial marble may contain inorganic fillers other than aluminum hydroxide (C). Examples of inorganic fillers other than aluminum hydroxide (C) include calcium carbonate, silica, talc, clay, glass flakes, glass fiber, mica, potassium titanate, alumina, antimony oxide, zinc compounds, carbon nanotubes, and graphite.

[0025] The method for crushing the artificial marble is not particularly limited, and any known crushing method can be used. The size of the crushed artificial marble is, for example, an average particle size of 50 μm to 1000 μm. From the viewpoint of the efficiency of washing described below, an average particle size of 500 μm or less is preferable. From the viewpoint of the efficiency of solid-liquid separation after washing, an average particle size of 100 μm or more is preferable.

[0026] If already crushed artificial marble of the desired size is available, step (1) can be omitted.

[0027] Process (2) In step (2), the crushed artificial marble is washed with sulfuric acid, and the solid phase (D) and the liquid phase (E) of aluminum sulfate aqueous solution produced by washing are separated.

[0028] The concentration of sulfuric acid is, for example, 10% to 100%. From the viewpoints of efficiency and safety, it is preferable to use sulfuric acid at about 20%.

[0029] The amount of sulfuric acid can be adjusted appropriately depending on the concentration of aluminum hydroxide in the artificial marble, and is, for example, about 1.5 to about 6 molar equivalents relative to the aluminum hydroxide in the artificial marble.

[0030] The temperature when washing the artificial marble can be set as appropriate. The temperature of the sulfuric acid when washing is preferably 50° C. to 80° C. This temperature range allows aluminum hydroxide to be dissolved efficiently.

[0031] When cleaning the artificial marble, it is preferable to clean it by stirring or shaking.

[0032] The means for separating the washed solid phase (D) (e.g., artificial marble containing methacrylic resin (B)) from the liquid phase (E) of aluminum sulfate aqueous solution is not particularly limited, and known means such as filtration and centrifugal sedimentation can be used.

[0033] Process (3) In the step (3), suspension polymerization is carried out using an aqueous aluminum sulfate solution (E) and a polymerizable monomer composition (F) containing methyl methacrylate to produce a methacrylic resin (A).

[0034] The polymerizable monomer composition (F) contains methyl methacrylate. The methyl methacrylate contained in the polymerizable monomer composition (F) is not particularly limited, and may be commercially available methyl methacrylate, methyl methacrylate (G) obtained by thermal decomposition of the solid phase (D) obtained in step (2), or a mixture thereof.

[0035] The methacrylic resin (A) can be produced, for example, using a monomer containing methyl methacrylate, a polymerization initiator, a chain transfer agent, a suspending agent, and the like.

[0036] When free radical polymerization is used, examples of the polymerization initiator that can be used include peroxide-based initiators such as di-t-butyl peroxide, lauryl peroxide, dilauroyl peroxide, t-butylperoxy 2-ethylhexanoate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-bis(t-butylperoxy)cyclohexane, and general azo-based radical polymerization initiators such as azobisisobutyronitrile, azobisisovaleronitrile, and 1,1-azobis(1-cyclohexanecarbonitrile). These radical initiators may also be combined with an appropriate reducing agent to form a redox-based initiator.

[0037] The polymerization initiator may be used in an amount of, for example, 0.001 to 1% by mass relative to 100% by mass of the total mass of the monomers.

[0038] In the method for producing the methacrylic resin (A), when the resin is produced by radical polymerization, a commonly used chain transfer agent can be used to adjust the molecular weight.

[0039] As the chain transfer agent, for example, mercaptans such as n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, 2-ethylhexyl thioglycolate, ethylene glycol dithioglycolate, trimethylolpropane tristhioglycolate, and pentaerythritol tetrakis(thioglycolate) are preferably used.

[0040] The chain transfer agent may be used in an amount of 0.001 to 1% by mass relative to 100% by mass of the total mass of the monomers, and the amount of the chain transfer agent is determined depending on the desired molecular weight.

[0041] In one embodiment, the methacrylic resin comprises polymethyl methacrylate. In another embodiment, the methacrylic resin is polymethyl methacrylate. The methacrylic resin may be a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate monomer with other vinyl monomers.

[0042] Process (4) The method for producing the methacrylic resin (A) of this embodiment may include step (4), in which the solid phase (D) obtained in step (2) is thermally decomposed to obtain methyl methacrylate (G).

[0043] The pyrolysis means is not particularly limited, and examples thereof include an extruder, a kettle-type pyrolysis device, and an externally heated rotary kiln.

[0044] When an extruder is used, a small amount of aluminum hydroxide (C) may remain in the artificial marble after dissolving the aluminum hydroxide (C) in step (2), and the artificial marble may contain a large amount of crosslinking components such as methacrylic resin. Therefore, to ensure the fluidity of the solid phase (D), methacrylic resin may be added to the solid phase (D). The weight-average molecular weight of the added methacrylic resin is preferably 50,000 to 200,000.

[0045] In the present invention, it is preferable that the extruder and the residue recovery tank are directly connected, and the methyl methacrylate-containing composition gas is recovered from the gas outlet line at the top of the residue tank, because when artificial marble containing an inorganic filler such as aluminum hydroxide is thermally decomposed, the inorganic filler has no plasticity, and if the piping to the residue tank is long, the piping may become clogged.

[0046] Process (5) The method for producing the methacrylic resin (A) of this embodiment may include step (5), in which the methyl methacrylate (G) obtained in step (4) is mixed with the polymerizable monomer composition (F) of step (3).

[0047] Process (6) The method for producing the methacrylic resin (A) of this embodiment may include step (6). In step (6), the pH of the aluminum sulfate aqueous solution (E) is adjusted to 3.0 to 8.0 to prepare a suspension containing aluminum hydroxide. The method for adjusting the pH of the aluminum sulfate aqueous solution (E) is not particularly limited, and examples thereof include a method of adding an alkaline substance to the aluminum sulfate aqueous solution (E).

[0048] The alkaline substance is not particularly limited, and for example, an aqueous solution of sodium carbonate, an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, etc. can be used.

[0049] In the method for producing the methacrylic resin (A) of this embodiment, the suspending agent prepared in step (6) may be used in step (3).

[0050] FIG. 1 is a flow diagram showing an example of a production flow for the methacrylic resin (A) of this embodiment. In this example, in step (1), artificial marble containing methacrylic resin (B) and aluminum hydroxide (C) is pulverized. Next, in step (2), the pulverized artificial marble is washed with sulfuric acid and separated into a liquid phase containing an aluminum sulfate aqueous solution (E) and a solid phase (D). Next, in step (4), the solid phase (D) is thermally decomposed to obtain methyl methacrylate (G). Next, in step (3), the aluminum sulfate aqueous solution (E), a polymerizable monomer composition (F) containing methyl methacrylate, and methyl methacrylate (G) are suspension polymerized to produce the methacrylic resin (A).

[0051] Purpose The methacrylic resin obtained by the production method of this embodiment is preferably for injection molding. In particular, measures to reduce environmental impact are required for in-vehicle applications, making this the most suitable application for the methacrylic resin obtained by the production method of this embodiment.

[0052] Methacrylic resin (A) may contain aluminum hydroxide derived from artificial marble, which may cause slight haze during molding. Therefore, methacrylic resin (A) is best suited for coloring and light diffusion applications rather than applications requiring colorless transparency. Light diffusion applications are particularly preferred.

[0053] Another preferred application of the methacrylic resin obtained by the production method of this embodiment is to use the methacrylic resin in the production of artificial marble.

[0054] Furthermore, aluminum hydroxide can be produced from the aluminum sulfate obtained in step (2) and used to produce artificial marble.

[0055] The composition containing methyl methacrylate obtained by pyrolyzing the solid phase obtained in step (2) can be purified and used to produce artificial marble.

[0056] By combining these, it is possible to obtain a methyl methacrylate-containing composition, aluminum hydroxide, and methacrylic resin from artificial marble, and then remanufacture artificial marble, which is most preferable from the perspective of reducing the environmental load.

[0057] (Methacrylic resin composition) In one embodiment, the methacrylic resin composition comprises a methacrylic resin (A) and and a light-diffusing filler, and the methacrylic resin composition has light-diffusing properties.

[0058] Examples of light-diffusing fillers that exhibit light-diffusing performance include inorganic particles such as titanium dioxide, aluminum trioxide, zinc oxide, and barium sulfate; and organic particles such as crosslinked silicone resins, crosslinked methacrylic resins, crosslinked styrene-methyl methacrylate resins, and crosslinked styrene resins.

[0059] The average particle size of the light diffusing filler is, for example, 0.2 to 10 μm.

[0060] The content of the light-diffusing filler in the methacrylic resin composition is, for example, 0.5 to 6 parts by mass relative to 100 parts by mass of the methacrylic resin (A).

[0061] (First embodiment of the method for manufacturing artificial marble) In a first embodiment of the method for producing artificial marble, a step (A1) of crushing an artificial marble containing methacrylic resin and aluminum hydroxide to obtain crushed artificial marble; A step (A2) of washing the crushed artificial marble with sulfuric acid and separating the solid phase and aqueous phase produced by washing to obtain an aluminum sulfate aqueous solution; a step (A3) of purifying aluminum hydroxide from the aqueous aluminum sulfate solution; A step (A4) of producing an artificial marble using the aluminum hydroxide; Includes.

[0062] Step (A1) is the same as step (1) in the method for producing the methacrylic resin (A).

[0063] Step (A2) is the same as step (2) in the method for producing the methacrylic resin (A).

[0064] Step (A3) is the same as step (6) in the method for producing the methacrylic resin (A).

[0065] In step (A4), the aluminum hydroxide from step (A3) can be used to produce artificial marble by a known method for producing artificial marble. For example, the aluminum hydroxide from step (A3), methyl methacrylate, and methacrylic resin can be mixed, and an initiator can be added and heated to produce artificial marble.

[0066] (Second embodiment of the method for manufacturing artificial marble) In a second embodiment of the method for producing artificial marble, a step (a1) of crushing an artificial marble containing methacrylic resin and aluminum hydroxide to obtain crushed artificial marble; A step (a2) of washing the crushed artificial marble with sulfuric acid to separate the solid phase and aqueous phase produced by washing; (a3) pyrolyzing the solid phase to produce methyl methacrylate; (a4) a step of producing artificial marble using the methyl methacrylate; Includes.

[0067] Step (a1) is the same as step (1) in the method for producing the methacrylic resin (A).

[0068] Step (a2) is the same as step (2) in the method for producing the methacrylic resin (A).

[0069] Step (a3) ​​is the same as step (4) in the method for producing the methacrylic resin (A).

[0070] Step (a4) is the same as step (3) in the method for producing the methacrylic resin (A). Step (a4) may be carried out in the same manner as step (A4), except that the methyl methacrylate used in step (A4) is the methyl methacrylate obtained in step (a3).

[0071] (Third embodiment of the method for manufacturing artificial marble) In a third embodiment of the method for producing artificial marble, artificial marble is produced using methacrylic resin (A) obtained by the method for producing methacrylic resin (A) of this embodiment, methyl methacrylate, and aluminum hydroxide. In a known method for producing artificial marble that uses methacrylic resin, methyl methacrylate, and aluminum hydroxide, the methacrylic resin (A) obtained by the method for producing methacrylic resin (A) of this embodiment may be used. [Example]

[0072] 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.

[0073] The raw materials used are as follows: Methyl methacrylate (MMA): Asahi Kasei Chemicals Corporation (containing 2.5 ppm by mass of 2,4-dimethyl-6-t-butylphenol manufactured by Chugai Boeki Co., Ltd. as a polymerization inhibitor) Methyl acrylate (MA): Mitsubishi Chemical Corporation (containing 14 ppm by mass of 4-methoxyphenol manufactured by Kawaguchi Chemical Industry Co., Ltd. as a polymerization inhibitor) n-Octyl mercaptan: Arkema Dilauryl peroxide: manufactured by NOF Corporation 20% sodium carbonate aqueous solution: Taiki Pharmaceutical Co., Ltd. Sodium lauryl sulfate: manufactured by Wako Pure Chemical Industries, Ltd., used as a suspension aid Tetrasodium ethylenediaminetetraacetic acid dihydrate (EDTA): Kishida Chemical Co., Ltd. UV absorber: 2-(2H-benzotriazol-2-yl)-4-methylphenol, manufactured by BASF Japan Ltd., product name "Tinuvin (registered trademark) P" Barium sulfate: Takehara Chemical Industry Co., Ltd., average particle size 5 μm, refractive index 1.64

[0074] Example 1 The methacrylic resin (A) was produced by the following steps.

[0075] ·Process (1) A commercially available artificial marble containing methacrylic resin (B) and aluminum hydroxide (C) was prepared. This artificial marble was heated to 400°C using TGA, and the residue was found to contain 50% aluminum hydroxide. This artificial marble was crushed to obtain crushed artificial marble containing aluminum hydroxide with a maximum length of 10 mm.

[0076] ·Process (2) The crushed artificial marble was mixed with 20% sulfuric acid in a mass ratio of 1:5 and stirred at 80°C for 3 hours, after which the crushed artificial marble was washed with sulfuric acid. The washed artificial marble was filtered to separate the artificial marble (solid phase (D)) and the aluminum sulfate aqueous solution (E) (liquid phase). The aluminum hydroxide content in the artificial marble in the solid phase (D) was 10%. The aluminum sulfate concentration of the resulting aluminum sulfate aqueous solution (E) was 33%.

[0077] 80% by mass of the washed solid phase (D) and 20% by mass of methacrylic resin were dry mixed to obtain a mixture (M).

[0078] ·Process (4) An extruder was prepared, with a direct connection between the extruder and the residue collection tank and a gas outlet line installed above the residue tank. Using this extruder, the mixture (M) was fed into the raw material inlet of a commercially available twin-screw extruder, the flow path of which was filled with nitrogen gas as an inert gas. The temperature below the inlet was adjusted to 250°C, and the mixture was passed through a thermoplastic zone at 300°C and a thermal decomposition zone adjusted to 450°C, where it was depolymerized. After extrusion, the residual components, including undecomposed inorganic components, discharged from the thermal decomposition section outlet of the extruder were separated into a storage tank, and the gaseous crude methyl methacrylate (G) generated by thermal decomposition was cooled and separated into a liquid component in a collection tank. The yield of the resulting crude methyl methacrylate (G)-containing component was 99% based on the weight of the raw materials, excluding the inorganic components, that were fed.

[0079] ·Process(6) 5 kg of water at 70°C, an aqueous aluminum sulfate solution (E), and a 20% aqueous sodium carbonate solution were added to a container equipped with a stirrer, and the pH of the aqueous aluminum sulfate solution (E) was adjusted to a range of 4 to 7. 0.39 g of sodium lauryl sulfate and 2.3 g of EDTA were added to the mixture to prepare a suspension.

[0080] ·Process (3) A 60 L reactor was charged with 25 kg of water, 3 kg of a suspending agent, and a polymerizable monomer composition (F) to obtain a reaction mixture. The composition of the polymerizable monomer composition (F) was 20.5 kg of MMA, 0.42 kg of methyl acrylate, 42 g of dilauroyl peroxide, and 50 g of n-octyl mercaptan. The reaction mixture was stirred and subjected to suspension polymerization at 80°C for 150 minutes. The reaction was then substantially terminated to obtain a polymer. The mixture containing the polymer was then cooled to 50°C, and 20% by mass of sulfuric acid was added to dissolve the suspending agent. The mixture was then washed, dehydrated, and dried to obtain a methacrylic resin (A).

[0081] Example 2 A methacrylic resin composition was produced by the following steps.

[0082] 100 parts by weight of methacrylic resin (A), 2 parts by weight of barium sulfate as a light-diffusing filler, 0.02 parts by weight of an ultraviolet absorber, and other additives were weighed and then placed in a tumbler and mixed to obtain a mixed raw material. The mixed raw material was then placed in a φ26 mm twin-screw extruder. The materials were then melt-kneaded (compounded) at 230°C to produce strands. The strands were then cooled in a water bath. The strands were then cut with a pelletizer to obtain pellets of the methacrylic resin composition. During compounding, a vacuum line was connected to the vent of the extruder, and volatile components such as moisture and monomer components were removed under conditions of -0.08 MPa.

[0083] Example 3 A flat plate-shaped sample was prepared by the following procedure: A mold whose surface (inner surface of the mold cavity) was polished with 8000 grit sandpaper was used. The molding conditions were set as follows: Molding temperature (cylinder temperature): 250℃ Injection speed: 20mm / sec Holding pressure: 70MPa Mold temperature: 65℃

[0084] The obtained pellets of the methacrylic resin composition were placed in an injection molding machine (EC-100SX, manufactured by Shibaura Machine Co., Ltd.) to mold a flat plate sample for evaluation. The dimensions of the flat plate sample are as follows: Plate sample: 100mm x 100mm x 2mm, thickness t = 2mm, length L = 110mm, L / t = 55

[0085] (Evaluation of diffusion rate) The transmittance diffusivity of a 2 mm thick portion of the plate-shaped sample was measured using a spectroscopic variable-angle colorimeter (GC5000, manufactured by Nippon Denshoku Industries Co., Ltd.) to measure the luminance (transmitted light intensity) at angles of 5°, 20°, and 70°, and the diffusivity was calculated using the following formula in accordance with DIN5036. Diffusivity = (transmitted light intensity at 20° + transmitted light intensity at 70°) ÷ (2 × (transmitted light intensity at 5°)) × 100 The sample diffusion rate was over 30%, indicating excellent diffusion performance.

[0086] Example 4 In Example 1, prior to step (3), in step (5), polymerizable monomer composition (F) was mixed with 6.5 kg of methyl methacrylate (G) obtained in step (4). The blending ratio of the polymerizable monomer composition (F) in Example 4 was 14 kg of MMA, 0.42 kg of methyl acrylate, 42 g of dilauroyl peroxide, and 50 g of n-octyl mercaptan. Next, polymerization, washing, dehydration, and drying in step (3) were carried out in the same manner as in Example 1, to obtain a methacrylic resin (A).

[0087] The methacrylic resin (A) obtained in Example 4 was similarly extruded and molded, and the diffusion rate was evaluated. The diffusion rate was 30% or more, indicating excellent diffusion performance.

[0088] Example 5 The artificial marble was manufactured by the following steps.

[0089] The steps of Example 1 were repeated to prepare an aluminum sulfate aqueous solution (E), methyl methacrylate (G), and methacrylic resin (A). Next, 10% sodium hydroxide was added to the aluminum sulfate aqueous solution (E) to precipitate aluminum hydroxide. The mixture was filtered to obtain aluminum hydroxide. Next, 50 parts by mass of the obtained aluminum hydroxide, 30 parts by mass of methyl methacrylate (G), and 20 parts by mass of methacrylic resin (A) were mixed. Next, 0.1 parts of dilauroyl peroxide was added as an initiator to the mixture and mixed. Next, the mixture was heated at 80°C for 3 hours to obtain artificial marble. [Industrial Applicability]

[0090] According to the present invention, an aluminum sulfate aqueous solution can be obtained from artificial marble to produce methacrylic resin. Also, according to the present invention, artificial marble can be produced using both methyl methacrylate and inorganic components recovered by pyrolysis of artificial marble.

Claims

1. A method for producing a methacrylic resin (A), comprising: A step (1) of crushing an artificial marble containing a methacrylic resin (B) and aluminum hydroxide (C) to obtain crushed artificial marble; A step (2) of washing the crushed artificial marble with sulfuric acid to separate a solid phase (D) and a liquid phase of aluminum sulfate aqueous solution (E) produced by washing; a step (3) of carrying out suspension polymerization using the aluminum sulfate aqueous solution (E) and a polymerizable monomer composition (F) containing methyl methacrylate to produce a methacrylic resin (A); A method for producing a methacrylic resin (A), comprising:

2. a step (4) of pyrolyzing the solid phase (D) obtained in the step (2) to obtain methyl methacrylate (G); The method for producing the methacrylic resin (A) according to claim 1, further comprising: a step (5) of mixing the methyl methacrylate (G) with the polymerizable monomer composition (F) of the step (3).

3. a step (6) of adjusting the pH of the aluminum sulfate aqueous solution (E) to 3.0 to 8.0 to prepare a suspension containing aluminum hydroxide; The method for producing the methacrylic resin (A) according to claim 1, further comprising using the suspending agent in the step (3).

4. A methacrylic resin obtained by the production method according to claim 1.

5. The methacrylic resin according to claim 4, which is for injection molding.

6. The methacrylic resin according to claim 4, which is for use in artificial marble.

7. The methacrylic resin according to claim 5, A methacrylic resin composition comprising: a light-diffusing filler; and a light-diffusing filler.

8. A step (A1) of crushing an artificial marble containing a methacrylic resin and aluminum hydroxide to obtain a crushed artificial marble; A step (A2) of washing the crushed artificial marble with sulfuric acid and separating the solid phase and aqueous phase generated by washing to obtain an aluminum sulfate aqueous solution; a step (A3) of purifying aluminum hydroxide from the aqueous aluminum sulfate solution; A step (A4) of producing an artificial marble using the aluminum hydroxide; A method for producing artificial marble, comprising:

9. A step (a1) of crushing an artificial marble containing a methacrylic resin and aluminum hydroxide to obtain a crushed artificial marble; A step (a2) of washing the crushed artificial marble with sulfuric acid to separate the solid phase and the aqueous phase produced by washing; (a3) pyrolyzing the solid phase to produce methyl methacrylate; (a4) a step of producing artificial marble using the methyl methacrylate; A method for producing artificial marble, comprising:

10. A method for producing artificial marble, comprising using the methacrylic resin (A) obtained by the method of claim 1, methyl methacrylate, and aluminum hydroxide.

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