Method for recovering methyl methacrylate from artificial marble and method for producing methacrylic resin

Abstract

To provide a method that enables efficient recovery of methyl methacrylate from artificial marble.SOLUTION: A method for recovering methyl methacrylate from artificial marble, comprises: step (1) of preparing artificial marble containing a methacrylic resin and aluminum hydroxide; step (2) of pulverizing the artificial marble to obtain pulverized artificial marble; step (3) of heating the pulverized artificial marble with an extruder at a temperature of 350°C or higher and lower than 550°C to generate methyl methacrylate; and step (4), performed after step (2) and before step (3), of washing the pulverized artificial marble with an acid solution to remove aluminum hydroxide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for recovering methyl methacrylate from artificial marble and a method for producing a methacrylic resin. [Background technology]

[0002] In order to reduce the environmental impact, "chemical recycling" is being investigated, in which polymethyl methacrylate is thermally decomposed and depolymerized to isolate and reuse the 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, when it comes to 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, making it a desirable raw material for recovering methyl methacrylate. However, more than half of the components of artificial marble are inorganic, and removing these inorganic components during recycling presents a challenge. Furthermore, the 1% reduction temperature during thermal decomposition of PMMA is approximately 300°C, and thermal decomposition at temperatures below 300°C results in low recovery rates.

[0007] Therefore, an object of the present invention is to provide a method for efficiently recovering methyl methacrylate 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 the recovery rate can be increased by using an extruder to set the pyrolysis temperature to 350°C or higher and lower than 550°C.

[0009] That is, the present invention is as follows. [1] A method for recovering methyl methacrylate from artificial marble, comprising: A step (1) of preparing an artificial marble containing a methacrylic resin and aluminum hydroxide; (2) crushing the artificial marble to obtain crushed artificial marble; (3) heating the crushed artificial marble to 350 ° C or more and less than 550 ° C in an extruder to produce methyl methacrylate; After the step (2) and before the step (3), a step (4) of washing the crushed artificial marble with an acid solution to remove aluminum hydroxide; A method for recovering methyl methacrylate from artificial marble, comprising: [2] The method for recovering methyl methacrylate from artificial marble according to [1], wherein the weight-average molecular weight of the methacrylic resin is 50,000 to 200,000. [3] The method for recovering methyl methacrylate from artificial marble according to [1] or [2], wherein the methacrylic resin is a copolymer of methyl methacrylate and methyl acrylate. [4] The method for recovering methyl methacrylate from artificial marble according to any one of [1] to [3], wherein the acid solution is sulfuric acid. [5] A method for recovering methyl methacrylate from artificial marble according to any one of [1] to [4], further comprising step (5) of mixing the artificial marble with methacrylic resin after step (4), and carrying out step (5) before step (3). [6] The method for recovering methyl methacrylate from artificial marble according to any one of [1] to [5], further comprising a step (6) of cooling the methyl methacrylate obtained in the step (3) to less than 40°C to obtain crude methyl methacrylate. [7] The method for recovering methyl methacrylate from artificial marble according to [6], further comprising a step (7) of distilling the crude methyl methacrylate to remove high-boiling components. [8] A residue recovery tank directly connected to the extruder, the residue recovery tank has a gas outlet line at its top, The method for recovering methyl methacrylate from artificial marble according to any one of [1] to [7], further comprising a step (8) of recovering the methyl methacrylate in gas form from the gas outlet line. [9] A step (P1) of preparing methyl methacrylate obtained by the method for recovering methyl methacrylate according to any one of [1] to [8]; A step (P2) of polymerizing the methyl methacrylate to produce a methacrylic resin; A method for producing a methacrylic resin, comprising: [Effects of the Invention]

[0010] According to the present invention, methyl methacrylate can be efficiently recovered from artificial marble. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a flow diagram of an example of the method for recovering methyl methacrylate from artificial marble according to the present embodiment. [Figure 2] FIG. 2 is a flow diagram of an example of the method for recovering methyl methacrylate from the artificial marble of this embodiment. [Figure 3] FIG. 3 is a flow diagram of an example of the method for recovering methyl methacrylate from the artificial marble of this embodiment. [Figure 4] FIG. 4 is a flow diagram of an example of the method for recovering methyl methacrylate from the artificial marble of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] In this embodiment, the term "methacrylic resin" refers to a polymer of methyl methacrylate, and is a concept that encompasses polymethyl methacrylate.

[0014] 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.

[0015] 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.

[0016] (Method for recovering methyl methacrylate) The method for recovering methyl methacrylate from artificial marble of the present invention comprises: A step (1) of preparing an artificial marble containing a methacrylic resin and aluminum hydroxide; (2) crushing the artificial marble to obtain crushed artificial marble; (3) heating the crushed artificial marble to 350 ° C or more and less than 550 ° C in an extruder to produce methyl methacrylate; After the step (2) and before the step (3), a step (4) of washing the crushed artificial marble with an acid solution to remove aluminum hydroxide; This method for recovering methyl methacrylate from artificial marble includes the steps of: (a) recovering methyl methacrylate from artificial marble; and (b) recovering methyl methacrylate from artificial marble efficiently.

[0017] 1 to 4 are flow diagrams of an example of the method for recovering methyl methacrylate from artificial marble according to this embodiment.

[0018] In the example of Figure 1, the steps are (1) preparing artificial marble containing methacrylic resin, (2) crushing the artificial marble to obtain crushed artificial marble, (4) washing the crushed artificial marble with an acid solution to remove aluminum hydroxide, and (3) heating the crushed artificial marble in an extruder to 350°C or higher but lower than 550°C to produce methyl methacrylate.

[0019] In the example of Figure 2, the process involves the following steps in order: (1) preparing artificial marble containing methacrylic resin; (2) crushing the artificial marble to obtain crushed artificial marble; (4) washing the crushed artificial marble with an acid solution to remove aluminum hydroxide; (5) mixing the artificial marble with methacrylic resin; and (3) heating the crushed artificial marble in an extruder to a temperature of 350°C or higher but lower than 550°C to produce methyl methacrylate.

[0020] In the example of Figure 3, the following steps are carried out in order: (1) preparing artificial marble containing methacrylic resin; (2) crushing the artificial marble to obtain crushed artificial marble; (4) washing the crushed artificial marble with an acid solution to remove aluminum hydroxide; (5) mixing the artificial marble with methacrylic resin; (3) heating the crushed artificial marble to 350°C or higher but less than 550°C in an extruder to produce methyl methacrylate; and (6) cooling the methyl methacrylate to less than 40°C to obtain crude methyl methacrylate.

[0021] In the example of Figure 4, the following steps are carried out in order: (1) preparing artificial marble containing methacrylic resin; (2) crushing the artificial marble to obtain crushed artificial marble; (4) washing the crushed artificial marble with an acid solution to remove aluminum hydroxide; (5) mixing the artificial marble with methacrylic resin; (3) heating the crushed artificial marble to 350°C or higher but less than 550°C in an extruder to produce methyl methacrylate; (6) cooling the methyl methacrylate to less than 40°C to obtain crude methyl methacrylate; and (7) distilling the crude methyl methacrylate to remove high-boiling components.

[0022] Each step of the recovery method of the present invention will be illustrated below.

[0023] Process (1) In step (1), an artificial marble containing a methacrylic resin is prepared. The artificial marble may contain a methacrylic resin.

[0024] ·Methacrylic resin The methacrylic resin may be a known methacrylic resin, and may be a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate monomer and other vinyl monomers.

[0025] 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.

[0026] In one embodiment, the mass proportion of the structural units derived from methyl methacrylate relative to 100 mass% of the methacrylic resin is 80 to 100 mass%.

[0027] Other vinyl monomers copolymerizable with methyl methacrylate affect solubility characteristics and heat resistance. The mass ratio of structural units derived from other vinyl monomers copolymerizable with methyl methacrylate relative to 100% by mass of the methacrylic resin is preferably 0 to 20% by mass. From the viewpoint of thermal decomposition resistance, it is preferably 1% by mass or more. Furthermore, from the viewpoint of mechanical strength, it is preferably 20% by mass or less. It is more preferably 1 to 15% by mass, and even more preferably 3 to 10% by mass. The methacrylic resin may be, for example, a mixture of a methyl methacrylate copolymer containing a crosslinked portion and a non-crosslinked methyl methacrylate copolymer.

[0028] 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.

[0029] The weight-average molecular weight (Mw) of the methacrylic resin is not particularly limited, but is preferably 50,000 to 200,000. By ensuring that Mw is within this range and by washing the artificial marble with an acid solution to reduce the amount of aluminum hydroxide, plasticity is increased and the efficiency of thermal decomposition in the extruder is improved.

[0030] Inorganic fillers The artificial marble may further contain an inorganic filler in addition to the methacrylic resin. In one embodiment, the artificial marble contains a methacrylic resin and an inorganic filler.

[0031] The inorganic filler may be a known inorganic filler, such as calcium carbonate, silica, talc, clay, glass flakes, glass fiber, mica, potassium titanate, alumina, aluminum hydroxide, antimony oxide, zinc compounds, carbon nanotubes, and graphite.

[0032] In one embodiment, the artificial marble comprises aluminum hydroxide.

[0033] In one embodiment, the artificial marble contains a methacrylic resin and an inorganic filler, and the amount of the methacrylic resin is 20 to 95 parts by mass per 100 parts by mass of the total of the methacrylic resin and the inorganic filler.

[0034] Process (2) In step (2), the artificial marble is crushed to obtain crushed artificial marble.

[0035] 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.

[0036] If already crushed artificial marble of the desired size is available, step (2) can be omitted.

[0037] Process (3) In step (3), the crushed artificial marble is heated to 350°C or higher and lower than 550°C in an extruder to produce methyl methacrylate.

[0038] Extruder An example of an extruder is one that can plasticize at least a portion of the raw material to be pyrolyzed, and then depolymerize it into recycled monomers through pyrolysis. Pyrolysis in an extruder is a continuous process, and is superior to the kettle method and fluidized bed method in that it stabilizes the depolymerization process due to a stabilized thermal history and is easier to maintain. While the rotary kiln method, which is also a continuous process, only uses a heat source for pyrolysis, an extruder promotes depolymerization through the heat source and screw shear, allowing for more efficient chemical recycling.

[0039] After extrusion, it is preferable to separate the residue containing undecomposed components such as inorganic components discharged from the outlet of the pyrolysis section of the extruder into a storage tank, and the gas containing recycled methyl methacrylate generated by pyrolysis into a liquid component by cooling and then into a recovery tank, since this facilitates the recycling of inorganic components rather than recycled monomers.

[0040] A method for recycling inorganic components may involve, for example, heating the storage tank or another tank to which the residue containing undecomposed components such as inorganic components in the storage tank, so long as the temperature is high enough to volatilize all organic components and calcinate the inorganic components.

[0041] If the temperature in step (3), i.e., the thermal decomposition temperature, is less than 350°C, the decomposition yield is poor. If the temperature in step (3) exceeds 550°C, methyl methacrylate is decomposed into carbon monoxide, carbon dioxide, etc., and the recovery rate of methyl methacrylate decreases.

[0042] In one embodiment, the pyrolysis temperature is at least 350° C., at least 400° C., at least 450° C., or at least 500° C. In another embodiment, the pyrolysis temperature is less than 550° C., at most 500° C., at most 450° C., or at most 400° C.

[0043] The methyl methacrylate produced in step (3) may be recovered or further treated, for example, by cooling the methyl methacrylate or distilling the crude methyl methacrylate.

[0044] The methyl methacrylate produced in step (3) may be in any form, for example, the methyl methacrylate produced in step (3) may be in a solid form, a liquid form, or a gaseous form.

[0045] The recovery method of this embodiment may further include a step (4) of washing the crushed artificial marble with an acid solution to remove aluminum hydroxide after the step (2) and before the step (3). The recovery method of this embodiment preferably includes the step (4).

[0046] Process (4) In step (4), the crushed artificial marble is washed with an acid solution to remove aluminum hydroxide. The aluminum hydroxide is dissolved in the acid solution and removed.

[0047] The acid solution may include, for example, sulfuric acid, hydrochloric acid, nitric acid, etc. In one embodiment, the acid solution is sulfuric acid.

[0048] The acid solution may be the acid itself or an aqueous solution of the acid.

[0049] When sulfuric acid is used as the acid solution, the concentration of sulfuric acid is preferably 10% to 100%. From the viewpoints of efficiency and safety, it is preferable to use sulfuric acid with a concentration of about 20%.

[0050] In one embodiment, the pH of the acid solution is 4.0 or less, 3.5 or less, 3.0 or less, 2.5 or less, 2.1 or less, 2.0 or less, 1.5 or less, 1.2 or less, 1.0 or less, 0.5 or less, 0.3 or less, or 0.1 or less. In another embodiment, the pH of the acid solution is 0.1 or more, 0.3 or more, 0.5 or more, 1.0 or more, 1.2 or more, 1.5 or more, 2.0 or more, 2.1 or more, 2.5 or more, 3.0 or more, or 3.5 or more.

[0051] The amount of the acid solution can be adjusted appropriately depending on the concentration of aluminum hydroxide in the artificial marble, and is, for example, about 1 to about 10 molar equivalents relative to the aluminum hydroxide in the artificial marble.

[0052] When cleaning artificial marble, it is preferable to mix the artificial marble with an acid solution and heat the mixture to 50°C to 100°C. This temperature range allows aluminum hydroxide to be dissolved efficiently. From the viewpoint of efficiency, a temperature of 60°C or higher is preferable, and 70°C or higher is more preferable. From the viewpoint of safety, a temperature of 90°C or lower is preferable.

[0053] When cleaning the artificial marble, it is preferable to clean it by stirring or shaking.

[0054] The means for separating the solid phase (e.g., containing methacrylic resin) and the liquid phase (e.g., containing aluminum hydroxide) after washing is not particularly limited, and known means such as filtration using a filter or centrifugal sedimentation can be used. By separating the solid phase and the liquid phase, the aluminum hydroxide contained in the liquid phase can be removed.

[0055] The recovery method of the present embodiment may further include a step (5) of mixing the artificial marble obtained after the step (4) with a methacrylic resin.

[0056] Process (5) The artificial marble after step (4) is mixed with methacrylic resin. After removing the aluminum hydroxide after step (4), some aluminum hydroxide may remain in the artificial marble, and the artificial marble may contain a large amount of cross-linking components such as methacrylic resin. Therefore, to ensure the fluidity of the treated object in step (5), methacrylic resin may be added to the artificial marble.

[0057] The weight average molecular weight of the methacrylic resin added in step (5) is preferably 50,000 to 200,000.

[0058] <Extruder configuration> 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 is thermally decomposed, the inorganic filler component has no plasticity, and if there is a long piping distance to the residue tank, there is a possibility of blockage.

[0059] The recovery method of the present embodiment may further include a step (6) of cooling the methyl methacrylate obtained in the step (3) to less than 40° C. to obtain crude methyl methacrylate.

[0060] Process (6) In step (6), the methyl methacrylate obtained in step (3) is cooled to less than 40°C to obtain crude methyl methacrylate. The cooling temperature is preferably less than 35°C, more preferably less than 30°C. Crude methyl methacrylate refers to a composition containing 90% or more methyl methacrylate. Impurities other than methyl methacrylate often include methyl acrylate, n-butyl acrylate, methanol, methyl isobutyrate, methyl propionate, methyl methacrylate oligomers, and methyl methacrylate-methyl acrylate copolymer oligomers.

[0061] The recovery method of the present embodiment may further include a step (7) of distilling the crude methyl methacrylate to remove high-boiling components.

[0062] Process (7) In step (7), the crude methyl methacrylate is distilled to remove high-boiling components. The distillation procedure is not particularly limited, and any known distillation procedure can be used. Examples of high-boiling components include methyl methacrylate oligomers and methyl methacrylate-methyl acrylate copolymer oligomers.

[0063] Depending on the purity and use of the methyl methacrylate obtained in step (3), the methyl methacrylate obtained in step (3) may be recovered, or steps (6) and (7) may be further carried out.

[0064] The recovery method of the present embodiment may further include a step (8) of recovering methyl methacrylate in gas form from a residue recovery tank directly connected to the extruder, the residue recovery tank having a gas outlet line at its top.

[0065] Process (8) In step (8), a residue recovery tank is provided which is directly connected to the extruder, and the residue recovery tank has a gas outlet line at its top, and methyl methacrylate is recovered in gas form from the gas outlet line. Step (8) may be performed after step (3).

[0066] (Method for producing methacrylic resin) The method for producing a methacrylic resin of this embodiment includes a step (P1) of preparing methyl methacrylate obtained by the method for recovering methyl methacrylate of this embodiment; A step (P2) of polymerizing methyl methacrylate to produce a methacrylic resin; Includes.

[0067] The methyl methacrylate polymerized in step (P2) may be at least the methyl methacrylate obtained by the method for recovering methyl methacrylate of the present embodiment. Methyl methacrylate obtained by the method for recovering methyl methacrylate of the present embodiment may be used alone or in combination with commercially available methyl methacrylate.

[0068] The polymerization method is not particularly limited, and known methods such as suspension polymerization, solution polymerization, bulk polymerization, and cast polymerization can be used. [Example]

[0069] 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.

[0070] Example 1 The following steps (1) to (8) were carried out to recover purified methyl methacrylate.

[0071] In step (1), commercially available artificial marble was prepared. The molecular weight of the methacrylic resin in the artificial marble was measured, and it was found to be 150,000. It was also confirmed that 2% by weight of methyl acrylate was copolymerized in the methacrylic resin.

[0072] In step (2), the artificial marble was crushed to obtain crushed artificial marble having a maximum length of 10 mm. The residue heated to 400°C by TGA showed that the aluminum hydroxide content was 50%.

[0073] In step (4), 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 obtain the washed artificial marble. The aluminum hydroxide content in the washed artificial marble was 10%. The aluminum sulfate concentration of the obtained aluminum sulfate aqueous solution was 33%.

[0074] In step (5), 80% by mass of the washed artificial marble and 20% by mass of methacrylic resin were mixed in a dry state.

[0075] In steps (3) and (8), the mixture 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, using an extruder directly connected to a residue recovery tank and equipped with a gas outlet line at the top of the residue tank. The temperature below the inlet was set 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 subjected to depolymerization.

[0076] In step (6), after extrusion, residual components including undecomposed components such as inorganic components discharged from the outlet of the pyrolysis section of the extruder were separated into a storage tank, and the gaseous crude methyl methacrylate generated by pyrolysis was cooled and separated into a liquid component in a recovery tank. The yield of the obtained component including crude methyl methacrylate was 99% based on the weight of the raw materials excluding the inorganic components. The liquid temperature was 10°C.

[0077] In step (7), the crude methyl methacrylate was distilled at a TOP vacuum of 400 hPa or less, a TOP temperature of about 50° C., and a distiller temperature of about 70° C. to remove high-boiling components. The purity of the obtained purified methyl methacrylate was 99.5%.

[0078] (Comparative Example 1) Pyrolysis of artificial marble was carried out in the same manner as in Example 1, except that the temperature of the pyrolysis zone of the extruder was set to 300°C. The yield of the obtained component containing crude methyl methacrylate was 10% based on the weight of the raw materials excluding the inorganic components added. From these results, it was found that pyrolysis hardly progressed at 300°C.

[0079] (Comparative Example 2) Pyrolysis of artificial marble was carried out in the same manner as in Example 1, except that the temperature of the pyrolysis zone of the extruder was set to 590°C. The yield of the obtained component containing crude methyl methacrylate was 55% based on the weight of the raw materials excluding the inorganic components added. From these results, it was found that at 590°C, the pyrolysis of methyl methacrylate itself proceeded further, and the yield did not increase.

[0080] Example 2 The following steps (P1) and (P2) were carried out to produce a methacrylic resin.

[0081] In step (P1), the methyl methacrylate recovered in Example 1 was prepared.

[0082] A mixture was obtained by adding 5 kg of water at 70°C, 130 g of aluminum hydroxide with an average particle size of 23 μm, 0.39 g of sodium lauryl sulfate, and 2.3 g of ethylenediaminetetraacetic acid (EDTA) to a vessel equipped with a stirrer. An appropriate amount of aqueous sodium hydroxide solution was added to the mixture to adjust the pH to the range of 4 to 7, thereby obtaining a suspension.

[0083] In step (P2), 25 kg of water, 3 kg of a suspending agent, and a monomer raw material were charged into a 60 L reactor to obtain a reaction mixture. The composition of this monomer raw material was 15 kg of methyl methacrylate, 5 kg of the methyl methacrylate recovered in Example 1, 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. Next, the mixture containing the polymer was cooled to 50°C, and 20% by mass of sulfuric acid was charged to dissolve the suspending agent. The mixture was then washed, dehydrated, and dried to obtain a methacrylic resin. [Industrial Applicability]

[0084] According to the present invention, methyl methacrylate can be efficiently recovered from artificial marble.

Claims

1. A method for recovering methyl methacrylate from artificial marble, comprising: A step (1) of preparing an artificial marble containing a methacrylic resin and aluminum hydroxide; (2) crushing the artificial marble to obtain crushed artificial marble; (3) heating the crushed artificial marble to 350 ° C or more and less than 550 ° C in an extruder to produce methyl methacrylate; After the step (2) and before the step (3), a step (4) of washing the crushed artificial marble with an acid solution to remove aluminum hydroxide; A method for recovering methyl methacrylate from artificial marble, comprising:

2. The method for recovering methyl methacrylate from artificial marble according to claim 1, wherein the weight average molecular weight of the methacrylic resin is 50,000 to 200,000.

3. The method for recovering methyl methacrylate from artificial marble according to claim 1, wherein the methacrylic resin is a copolymer of methyl methacrylate and methyl acrylate.

4. The method for recovering methyl methacrylate from artificial marble according to claim 1, wherein the acid solution is sulfuric acid.

5. 2. The method for recovering methyl methacrylate from artificial marble according to claim 1, further comprising a step (5) of mixing the artificial marble after the step (4) with a methacrylic resin, and the step (5) is performed before the step (3).

6. 2. The method for recovering methyl methacrylate from artificial marble according to claim 1, further comprising a step (6) of cooling the methyl methacrylate obtained from the step (3) to less than 40°C to obtain crude methyl methacrylate.

7. The method for recovering methyl methacrylate from artificial marble according to claim 6, further comprising a step (7) of distilling the crude methyl methacrylate to remove high-boiling components.

8. A residue recovery tank is directly connected to the extruder, the residue recovery tank has a gas outlet line at its top, 2. The method for recovering methyl methacrylate from artificial marble according to claim 1, further comprising the step (8) of recovering the methyl methacrylate in gas form from the gas outlet line.

9. A step (P1) of preparing methyl methacrylate obtained by the method for recovering methyl methacrylate according to claim 1; A step (P2) of polymerizing the methyl methacrylate to produce a methacrylic resin; A method for producing a methacrylic resin, comprising:

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