Thermal decomposition system of methacrylic resin composition and method for producing reproduced methyl methacrylate

Abstract

To provide a thermal decomposition system of a methacrylic resin composition which removes moisture in thermal decomposition gas in thermal decomposition of a methacrylic resin composition, and can efficiently obtain methyl methacrylate.SOLUTION: A thermal decomposition system of a methacrylic resin composition includes a thermal decomposition part for thermally decomposing a methacrylic resin composition, a distillation part for distilling thermal decomposition gas generated in the thermal decomposition part, and a moisture removal part having an adsorption material or an absorption material, and the absorption material absorbs the moisture in the thermal decomposition gas from the distillation part, and the absorption material absorbs the moisture in the thermal decomposition gas from the distillation part. A method for producing reproduced methyl methacrylate includes: a thermal decomposition step (1) of thermally decomposing a methacrylic resin composition; a distillation step (2) of distilling thermal decomposition gas generated in the step (1); and a moisture removal step (3) of removing the moisture in the thermal decomposition gas generated in the step (2) with an adsorption material or an absorption material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a system for pyrolysis of methacrylic resin compositions and a method for producing recycled methyl methacrylate. [Background technology]

[0002] Methacrylic resins obtained by polymerizing monomers containing methyl methacrylate have excellent transparency and weather resistance, and are therefore widely used as materials for components constituting automobile parts, signboards, display devices, etc.

[0003] Due to the recent rise in resource prices and growing awareness of environmental issues, there has been a growing trend to collect and recycle products (molded bodies) containing methacrylic resins used for various purposes as described above.

[0004] Methods for recycling molded bodies containing methacrylic resin include, for example, material recycling, in which recovered molded bodies are subjected to a molding process again to produce new molded bodies; chemical recycling, in which recovered molded bodies are thermally decomposed (depolymerized) to recover the pyrolyzed monomers, and new molded bodies are produced using these monomers; and thermal recycling, in which recovered molded bodies are burned and the combustion energy obtained is used as a direct heat source or as electricity converted by a generator.

[0005] By heating methacrylic resin at a relatively low temperature of around 300 to 500°C, the pyrolysis product, monomer, can be recovered in high yield. For this reason, methacrylic resin is suitable for chemical recycling.

[0006] One application of methacrylic resin compositions is artificial marble, which is a composition containing methacrylic resin and inorganic filler. Artificial marble is produced from a large amount of scrap material during production or molding, making it suitable for recovery and recycling. However, thermal decomposition of artificial marble generates water, which has a boiling point close to that of methyl methacrylate, making it difficult to remove by distillation.

[0007] Patent Document 1 describes a method for recovering methyl methacrylate from artificial marble. Patent Document 2 describes a method for adsorbing impurities before a gas treatment device for pyrolysis gas as a regeneration system for (meth)acrylic polymers. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Registration No. 10-0982728 [Patent Document 2] Patent No. 7460843 Summary of the Invention [Problem to be solved by the invention]

[0009] Patent Document 1 describes that water is separated using a flowing water separator, but the actual extent of water removal is unclear.

[0010] Patent Document 2 describes a method for removing impurities including water, but it is unclear whether this method can remove all of the water generated during thermal decomposition, such as in the case of artificial marble.

[0011] Therefore, an object of the present invention is to provide a thermal decomposition system for a methacrylic resin composition that removes moisture in the pyrolysis gas during the thermal decomposition of a methacrylic resin composition and efficiently obtains methyl methacrylate.

[0012] Another object of the present invention is to provide a method for removing moisture in pyrolysis gas during the pyrolysis of a methacrylic resin composition and efficiently producing recycled methyl methacrylate. [Means for solving the problem]

[0013] The present invention is as follows. [1] a thermal decomposition section for thermally decomposing the methacrylic resin composition; a distillation section for distilling the pyrolysis gas generated in the pyrolysis section; a moisture removal unit having an adsorbent or absorbent material; Including, A system for thermally decomposing a methacrylic resin composition, wherein the adsorbent adsorbs moisture in the pyrolysis gas from the distillation section, and the absorbent absorbs moisture in the pyrolysis gas from the distillation section. [2] The thermal decomposition system for a methacrylic resin composition according to [1], wherein the adsorbent or absorbent is alumina or zeolite. [3] The thermal decomposition system for a methacrylic resin composition according to [1] or [2], wherein the methacrylic resin composition contains an inorganic filler. [4] The thermal decomposition system for a methacrylic resin composition according to any one of [1] to [3], wherein the methacrylic resin composition is an artificial marble containing the inorganic filler. [5] The thermal decomposition system for a methacrylic resin composition according to [3] or [4], wherein the inorganic filler is aluminum hydroxide. [6] the pyrolysis section is an extruder, The thermal decomposition system for a methacrylic resin composition according to any one of [1] to [5], wherein the extruder thermally decomposes a mixture of a methacrylic resin and crushed artificial marble. [7] a thermal decomposition step (1) of thermally decomposing a methacrylic resin composition; a distillation step (2) of distilling the pyrolysis gas generated in the pyrolysis step (1); a moisture removal step (3) of removing moisture in the pyrolysis gas generated in the distillation step (2) using an adsorbent or absorbent; 1. A method for producing recycled methyl methacrylate monomer, comprising: [8] The method for producing a recycled methyl methacrylate monomer according to [7], wherein the methacrylic resin composition contains an inorganic filler. [9] The method for producing recycled methyl methacrylate monomer according to [7] or [8], wherein the methacrylic resin composition is an artificial marble containing the inorganic filler.

[10] The method for producing a recycled methyl methacrylate monomer according to [8] or [9], wherein the inorganic filler is aluminum hydroxide.

[11]

[10] The method for producing recycled methyl methacrylate monomer according to

[10] , further comprising a crushing step (4) of crushing the artificial marble containing aluminum hydroxide and an acid washing step (5) of acid washing the crushed artificial marble before the thermal decomposition step (1). [Effects of the Invention]

[0014] A thermal decomposition system for a methacrylic resin composition can be provided that removes moisture from the pyrolysis gas produced during the thermal decomposition of the methacrylic resin composition to efficiently produce methyl methacrylate.A method for efficiently producing recycled methyl methacrylate can be provided that removes moisture from the pyrolysis gas produced during the thermal decomposition of the methacrylic resin composition. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of the configuration of a pyrolysis system according to the present disclosure. [Figure 2] FIG. 2 is a diagram schematically illustrating another example of the configuration of the pyrolysis system of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention (hereinafter also referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following embodiment, and various modifications can be made within the scope of the gist thereof.

[0017] In the present disclosure, methacrylic resin refers to a polymer whose main component is a structural unit derived from methyl methacrylate. "Mainly composed of" means that the polymer contains 80% by mass or more of structural units derived from methyl methacrylate.

[0018] The methacrylic resin may contain, in addition to structural units derived from methyl methacrylate, 0 to 20% by mass of units derived from vinyl monomers copolymerizable with methyl methacrylate.

[0019] Examples of vinyl monomers copolymerizable with methyl methacrylate include methacrylate esters such as cyclohexyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, and monoglycerol methacrylate (excluding alkyl methacrylates having an alkyl group having 1 to 4 carbon atoms); methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and monoglycerol methacrylate. Examples of suitable monomers include acrylic acid esters such as dimethylpropyl acrylate and monoglycerol acrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, and itaconic anhydride, or their acid anhydrides; nitrogen-containing monomers such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, diacetone acrylamide, and dimethylaminoethyl methacrylate; epoxy group-containing monomers such as allyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate; and styrene-based monomers such as styrene and α-methylstyrene.

[0020] In the present disclosure, the methacrylic resin composition may consist solely of methacrylic resin, or may contain a methacrylic resin composition and a component other than the methacrylic resin. The component other than the methacrylic resin may include a polymer other than the methacrylic resin, such as polyvinyl chloride, polyolefin, or polyester, or an additive. The additive may include a filler, a colorant, an ultraviolet inhibitor, or a mold release agent.

[0021] (artificial marble) In the present disclosure, the methacrylic resin composition may be an artificial marble further containing an inorganic filler in addition to the methacrylic resin. In one embodiment, the artificial marble contains the methacrylic resin and the inorganic filler.

[0022] 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.

[0023] In one embodiment, the artificial marble comprises aluminum hydroxide.

[0024] 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.

[0025] Artificial marble is generally made of a methacrylic resin composition containing aluminum hydroxide. Aluminum hydroxide generates water when heated, so it is suitable for the present invention, which has a moisture adsorption or absorption facility.

[0026] It is preferable to crush the artificial marble, mix it with a methacrylic resin composition that does not contain inorganic substances, and then perform pyrolysis using an extruder as the pyrolysis section. This is because the artificial marble contains a large amount of inorganic substances, and when an extruder is used, the plasticity is low and there is a possibility of clogging.

[0027] 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.

[0028] If already crushed artificial marble of the desired size is available, the crushing step can be omitted.

[0029] It is preferable that the artificial marble containing aluminum hydroxide is crushed, washed with acid, and then pyrolyzed. The artificial marble crushed as described above is washed with an acid solution to remove aluminum hydroxide. The aluminum hydroxide is dissolved in the acid solution and removed.

[0030] The acid solution may include, for example, sulfuric acid, hydrochloric acid, nitric acid, etc. In one embodiment, the acid solution is sulfuric acid.

[0031] The acid solution may be the acid itself or an aqueous solution of the acid.

[0032] 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%.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] When cleaning the artificial marble, it is preferable to clean it by stirring or shaking.

[0037] 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.

[0038] The recovery method of the present embodiment may further include a step of mixing the acid-washed artificial marble with a methacrylic resin composition that does not contain inorganic substances.

[0039] The acid-washed artificial marble is mixed with methacrylic resin. Even after the aluminum hydroxide is removed from the acid-washed artificial marble, some aluminum hydroxide may remain, and the artificial marble may contain a large amount of cross-linking components such as methacrylic resin. Therefore, to ensure the fluidity of the processed material during the extrusion process, methacrylic resin may be added to the artificial marble.

[0040] The weight average molecular weight of the methacrylic resin composition containing no inorganic substance is preferably 50,000 to 200,000.

[0041] <Methacrylic resin composition thermal decomposition system> One embodiment of the present disclosure comprises: a thermal decomposition section for thermally decomposing the methacrylic resin composition; a distillation section for distilling the pyrolysis gas generated in the pyrolysis section; a moisture removal unit having an adsorbent or absorbent material; Including, The adsorbent adsorbs moisture in the pyrolysis gas from the distillation section, and the absorbent absorbs moisture in the pyrolysis gas from the distillation section, in a pyrolysis system for a methacrylic resin composition.

[0042] 1 is a diagram illustrating an example of the configuration of a pyrolysis system according to the present disclosure. In the example of FIG. 1, the pyrolysis system 1 includes a raw material supply unit 10, a heat separation unit 20, a distillation unit 30, a residue tank 40, and a moisture removal unit 50.

[0043] 2 is a diagram schematically illustrating another example of the configuration of the pyrolysis system of the present disclosure. In the example of Fig. 2, the pyrolysis system 1 includes a raw material supply section 10, an extruder 21 as a heat dividing section, a distillation section 30, a residue tank 40, and a moisture removal section 50.

[0044] The pyrolysis system of the present disclosure performs a regeneration process of methyl methacrylate by thermally decomposing a methacrylic resin composition. That is, the pyrolysis system of the present disclosure can obtain methyl methacrylate from the methacrylic resin composition. The pyrolysis system of the present disclosure has excellent operational efficiency because it can remove moisture from the pyrolysis gas without interrupting the pyrolysis process of the raw material.

[0045] (pyrolysis section) The thermal decomposition unit thermally decomposes the methacrylic resin composition. The thermal decomposition unit includes a thermal decomposition machine having a raw material inlet for introducing raw materials including the methacrylic resin composition and a gas outlet for extracting pyrolysis gas.

[0046] In the present disclosure, the thermal decomposition section includes a thermal decomposition machine. Examples of the thermal decomposition machine include an extruder, a kneader, and a fluidized bed heater. In an embodiment of the present disclosure, the thermal decomposition machine preferably includes an extruder.

[0047] An extruder refers to a device equipped with a mechanism that rotates a screw disposed inside a cylindrical member (cylinder) to melt raw materials introduced from the upstream side of the cylinder and transport them downstream. In an embodiment of the present disclosure, a kneader that can be suitably used as a thermal cracker is, for example, the device described in U.S. Pat. No. 10,301,235. In an embodiment of the present disclosure, a fluidized bed heater that can be suitably used as a thermal cracker is, for example, the device described in Japanese Patent Laid-Open No. 2009-112902.

[0048] In the present disclosure, it is preferable to use an extruder as the pyrolyzer. By using an extruder as a device (pyrolyzer) for pyrolyzing the methacrylic resin composition, the pyrolysis treatment can be carried out efficiently.

[0049] The type of extruder included in the pyrolysis section is not particularly limited, and a known twin-screw extruder or single-screw extruder can be used. From the viewpoint of efficiently performing pyrolysis of the raw materials including the methacrylic resin composition, the extruder is preferably a twin-screw extruder such as a twin-screw co-rotating extruder or a twin-screw counter-rotating extruder.

[0050] As components of the extruder such as a cylinder and a screw, known components can be used without any particular limitation.

[0051] The pyrolysis machine is provided with a raw material inlet and a gas outlet, in this order from the upstream side in the flow direction of the raw material. The configurations of the raw material inlet and the gas outlet are not particularly limited, and known configurations can be used without any particular limitation.

[0052] When the pyrolyzer is an extruder, its raw material inlet is not particularly limited as long as it is in a state suitable for feeding raw materials containing a methacrylic resin composition into the cylinder of the extruder. From the viewpoint of the recovery efficiency of pyrolysis gas, the raw material inlet is preferably located near the upstream end of the pyrolyzer. The raw material inlet is preferably oriented upward in the direction of gravity.

[0053] The gas outlet of the pyrolyzer is not particularly limited as long as it has a configuration suitable for extracting the pyrolysis gas of the methacrylic resin composition from the pyrolyzer. From the viewpoint of the recovery efficiency of the pyrolysis gas, the gas outlet is preferably located near the downstream end of the pyrolyzer. The gas outlet is preferably oriented upward in the direction of gravity.

[0054] When the thermal cracker is an extruder, it is preferred that a residue tank is directly connected to the outlet of the extruder and that a gas vent port is disposed at the top of the residue tank.

[0055] The material of the thermal cracker is not particularly limited, and known materials can be used without any particular limitations.

[0056] An impurity gas outlet for discharging impurity gas may be provided between the raw material inlet and the gas outlet of the pyrolysis machine. This prevents impurities contained in the raw material introduced through the raw material inlet from being mixed into the pyrolysis gas. As a result, impurities can be more reliably removed in the moisture removal section described below.

[0057] From the viewpoint of suppressing mixing of the impurity gas and the pyrolysis gas, the pyrolyzer may be capable of independently adjusting the temperature of the region between the raw material inlet and the impurity gas outlet and the temperature of the region between the impurity gas outlet and the gas outlet. That is, the temperature of the region between the raw material inlet and the impurity gas outlet and the temperature of the region between the impurity gas outlet and the gas outlet can be set to different temperatures. It is preferable that the temperature of the region between the impurity gas outlet and the gas outlet be set to a temperature higher than the temperature of the region between the raw material inlet and the impurity gas outlet.

[0058] For example, the temperature of the region between the raw material inlet and the impurity gas outlet may be adjusted to be equal to or higher than the temperature at which the impurity gas is generated and lower than the thermal decomposition initiation temperature of the (meth)acrylic polymer, and the temperature of the region between the impurity gas outlet and the gas withdrawal port may be adjusted to be equal to the thermal decomposition initiation temperature of the (meth)acrylic polymer.

[0059] By adjusting the temperature of the region between the raw material inlet and the impurity gas outlet so that it is equal to or higher than the temperature at which the impurity gas is generated and lower than the thermal decomposition starting temperature of the (meth)acrylic polymer, it is possible to selectively generate and remove the impurity gas from the raw material in this region, thereby effectively preventing the impurity gas generated from the raw material being transported inside the pyrolyzer from being mixed into the pyrolysis gas. As a means for adjusting the temperature of the thermal cracker, any known means can be used without any particular limitation.

[0060] In order to prevent impurity gas from being mixed into the pyrolysis gas, the pyrolyzer may have a sealing member disposed between the impurity gas outlet and the gas extraction port. When the pyrolyzer is an extruder, the sealing member is provided around the axis of the extruder's screw. The sealing member can, for example, prevent impurity gas remaining in the cylinder without being discharged from the impurity gas outlet from moving to the gas extraction port. Examples of the sealing member include the introduction of a screw element. Examples of the screw element include a seal ring, an element with a reverse flight structure, and an element with a reverse kneading structure. These elements form a resin pool by retaining or reversing the flow of the resin, thereby making it easier for the impurity gas to be discharged from the impurity gas extraction port. As the sealing member, an appropriate commercially available product may be used in consideration of the size and material.

[0061] The pyrolyzer may include components other than those described above. For example, the pyrolyzer may further include a residue discharge port. The residue discharge port discharges the residue containing undecomposed components generated in the pyrolysis treatment of the raw material containing the (meth)acrylic polymer to the outside of the pyrolyzer. The residue discharge port is preferably provided near the downstream end of the pyrolyzer. The orientation of the residue discharge port is preferably horizontal or downward in the direction of gravity.

[0062] The conditions for carrying out the thermal decomposition of the raw material using a thermal decomposition machine are not particularly limited, and can be set in consideration of the properties, composition, etc. of the raw material to be treated.

[0063] The pressure in the thermal decomposition step is preferably 0.005 MPa to 1.5 MPa, more preferably 0.01 MPa to 0.3 MPa, from the viewpoint of preventing air from leaking into the system and decomposition gas from leaking out of the system.

[0064] From the viewpoint of thermal decomposition efficiency, the temperature of the thermal decomposition section in the thermal decomposition step (for example, the cylinder temperature of the extruder) can usually be set to 400° C. to 500° C. When the raw material is a pure (meth)acrylic polymer, the temperature is preferably 450° C. to 470° C.

[0065] The screw rotation speed of the extruder in the thermal decomposition step can usually be set to 500 rpm to 1500 rpm from the viewpoint of stable operation of the extruder, and is preferably 500 rpm to 1000 rpm when the raw material is a pure methacrylic resin composition.

[0066] The amount of raw material supplied in the pyrolysis step varies depending on the scale of the pyrolysis section (for example, the diameter of the cylinder of the extruder), but is usually 10 kg / hour to 5,000 kg / hour. For example, when the cylinder diameter is 47 mm, the amount is preferably 40 kg / hour to 90 kg / hour.

[0067] (Distillation section) In the distillation section, the pyrolysis gas generated in the pyrolysis section is distilled. The distillation section is not particularly limited and can be selected from known means. For example, the distillation column described in International Publication No. 2020 / 261720 can be used.

[0068] (moisture removal section) The moisture removal section includes an adsorbent or absorbent. The adsorbent adsorbs moisture in the pyrolysis gas from the distillation section. The absorbent absorbs moisture in the pyrolysis gas from the distillation section.

[0069] The moisture removal unit includes, for example, a pipe through which the pyrolysis gas flows and an adsorbent or absorbent disposed inside the pipe. By configuring the moisture removal unit in this manner, moisture in the purified methyl methacrylate (MMA) discharged from the distillation unit can be removed.

[0070] The type of adsorbent contained in the moisture removal unit is not particularly limited and can be selected depending on the type, concentration, etc. of impurities to be removed. Examples of adsorbents include alumina, calcium oxide, calcium carbonate, iron oxide, iron hydroxide, carbon, and zeolite. Examples of adsorbents include a composite of iron oxide and carbon, a composite of metallic iron and carbon, a composite of iron oxide, metallic iron, and carbon, a composite of calcium oxide and carbon, a composite of iron oxide, calcium carbonate, and carbon, a composite of iron oxide, calcium oxide, and carbon, a composite of metallic iron, calcium carbonate, and carbon, a composite of metallic iron, calcium oxide, and carbon, a composite of iron oxide, metallic iron, calcium carbonate, and carbon, a composite of iron oxide, metallic iron, calcium oxide, and carbon, a composite of iron oxide, metallic iron, calcium oxide, and carbon, a composite of iron oxide, metallic iron, calcium carbonate, and carbon, a composite of iron oxide, metallic iron, calcium oxide, and carbon, and a composite of iron oxide, metallic iron, calcium carbonate, calcium oxide, and carbon.

[0071] The adsorbent is preferably alumina or zeolite.

[0072] From the viewpoint of increasing the efficiency of removing impurities from the pyrolysis gas passing through the removal section, it is preferable that the adsorbent has a large contact area with the pyrolysis gas, and from this viewpoint, the adsorbent is preferably in a particulate form.

[0073] A specific example of the absorbent is an aqueous solution containing a reducing agent and a base. By bringing this aqueous solution into contact with the pyrolysis gas, impurities in the pyrolysis gas can be absorbed.

[0074] Preferably, the base is selected from the group consisting of sodium hydroxide, sodium carbonate and sodium bicarbonate (NaHCO3).

[0075] Preferably, the reducing agent is selected from the group consisting of sodium sulfite, hydrogen peroxide, sodium thiosulfate and sodium bisulfite (or hydrogen sulfite) (NaHSO3).

[0076] The adsorbent or absorbent contained in the moisture removing section may be one type alone or a combination of two or more types.

[0077] If the raw material supplied to the thermal cracking section contains chlorine and water, the reaction between the chlorine and water may generate hydrochloric acid. Therefore, the section of the connecting section from the gas outlet of the thermal cracker to the distillation section and the section from the distillation section to the water removal section are preferably made of a material with excellent corrosion resistance. Examples of such materials include titanium, zirconium, tantalum, and nickel alloys.

[0078] Since pyrolysis gas contains polymerizable substances, there is a risk of tube blockage due to the polymerizable substances. By installing a pressure gauge between the pyrolysis section and the distillation section, it is possible to predict the occurrence of tube blockage due to the polymerization of polymerizable substances by the generation of a pressure difference, and tube replacement can be carried out in a planned manner.

[0079] (Raw material supply department) The raw material supply unit supplies raw material to the pyrolysis unit. The method of supplying raw material to the pyrolysis unit is not particularly limited and can be selected from known methods. The raw material supply unit may include a processing device for processing the raw material, such as crushing, a detector for detecting foreign matter contained in the raw material, a measuring device for controlling the amount of raw material input, etc.

[0080] (residue tank) The residue tank stores the residue discharged from the thermal decomposition section. The method for storing the residue is not particularly limited and can be selected from known methods. The residue tank may also be equipped with a processing device or the like for processing the residue into a disposable state.

[0081] In the present invention, it is preferable that the extruder and the residue tank are directly connected and the methyl methacrylate-containing composition gas is recovered from the gas outlet at the top of the residue tank. This is because when artificial marble containing an inorganic filler such as aluminum hydroxide is thermally decomposed as a methacrylic resin composition, the inorganic filler has no plasticity, and if the piping to the residue tank is long, the piping may become clogged.

[0082] <Method for producing recycled methyl methacrylate> One embodiment of the present disclosure comprises: a thermal decomposition step (1) of thermally decomposing a methacrylic resin composition; a distillation step (2) of distilling the pyrolysis gas generated in the pyrolysis step (1); a moisture removal step (3) of removing moisture in the pyrolysis gas generated in the distillation step (2) using an adsorbent or absorbent; A method for producing recycled methyl methacrylate, comprising:

[0083] According to the production method of the present disclosure, it is possible to efficiently carry out a regeneration process of a methacrylic resin composition while suppressing the inclusion of moisture in the pyrolysis gas obtained by thermally decomposing the methacrylic resin composition.

[0084] The pyrolysis in the pyrolysis step (1) is the same as the pyrolysis in the pyrolysis section described in the pyrolysis system.

[0085] The distillation in the distillation step (2) is similar to the distillation in the distillation section described in the thermal cracking system, and for example, the distillation process described in WO 2020 / 261720 can be used.

[0086] The moisture removal in the moisture removal step (3) is similar to the moisture removal by an adsorbent or absorbent in the moisture removal section described in the thermal decomposition system.

[0087] According to the manufacturing method of the present disclosure, the methacrylic resin composition contained in the raw material is thermally decomposed to be recycled into a methyl methacrylate composition, which can be used, for example, as a raw material monomer for methyl methacrylate polymer.

[0088] The regenerated methyl methacrylate composition obtained by the production method of the present disclosure may be a mixture of methyl methacrylate and unavoidably contained compounds other than methyl methacrylate (e.g., methyl isobutyrate, methyl propionate, methyl acrylate, etc.). In this case, the compounds other than methyl methacrylate in the mixture may or may not be removed.

[0089] In one embodiment of the manufacturing method of the present disclosure, the methacrylic resin composition contains an inorganic filler.

[0090] In one embodiment of the manufacturing method of the present disclosure, the methacrylic resin composition is an artificial marble containing an inorganic filler.

[0091] In one embodiment of the manufacturing method of the present disclosure, the inorganic filler is aluminum hydroxide.

[0092] In one embodiment of the manufacturing method of the present disclosure, the method further includes a crushing step (4) of crushing the aluminum hydroxide-containing artificial marble and an acid washing step (5) of washing the crushed artificial marble with acid before the thermal decomposition step (1). The crushing step (4) and the acid washing step (5) may be performed simultaneously, or the acid washing step (5) may be performed after the crushing step (4). [Explanation of symbols]

[0093] 1: Pyrolysis system 10: Raw material supply department 20: Pyrolysis section 21: Extruder 30: Distillation section 40: Residue tank 50: Moisture removal section

Claims

1. a thermal decomposition section for thermally decomposing the methacrylic resin composition; a distillation section for distilling the pyrolysis gas generated in the pyrolysis section; a moisture removal unit having an adsorbent or absorbent material; Including, A system for thermally decomposing a methacrylic resin composition, wherein the adsorbent adsorbs moisture in the pyrolysis gas from the distillation section, and the absorbent absorbs moisture in the pyrolysis gas from the distillation section.

2. The thermal decomposition system for a methacrylic resin composition according to claim 1, wherein the adsorbent or absorbent is alumina or zeolite.

3. The thermal decomposition system for a methacrylic resin composition according to claim 1 or 2, wherein the methacrylic resin composition contains an inorganic filler.

4. The thermal decomposition system for a methacrylic resin composition according to claim 3, wherein the methacrylic resin composition is an artificial marble containing the inorganic filler.

5. The thermal decomposition system for a methacrylic resin composition according to claim 4, wherein the inorganic filler is aluminum hydroxide.

6. the pyrolysis section is an extruder, The pyrolysis system for a methacrylic resin composition according to claim 4, wherein the extruder pyrolyzes a mixture of methacrylic resin and crushed artificial marble.

7. a thermal decomposition step (1) of thermally decomposing a methacrylic resin composition; a distillation step (2) of distilling the pyrolysis gas generated in the pyrolysis step (1); a moisture removal step (3) of removing moisture from the pyrolysis gas generated in the distillation step (2) using an adsorbent or absorbent; A method for producing regenerated methyl methacrylate, comprising:

8. The method for producing recycled methyl methacrylate according to claim 7, wherein the methacrylic resin composition contains an inorganic filler.

9. The method for producing recycled methyl methacrylate according to claim 8, wherein the methacrylic resin composition is an artificial marble containing the inorganic filler.

10. 10. The method for producing recycled methyl methacrylate according to claim 9, wherein the inorganic filler is aluminum hydroxide.

11. 11. The method for producing recycled methyl methacrylate according to claim 10, further comprising a crushing step (4) of crushing the artificial marble containing aluminum hydroxide and an acid washing step (5) of acid washing the crushed artificial marble before the thermal decomposition step (1).

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