JP2024049285A - System for regenerating methyl (meth)acrylate and method for regenerating methyl (meth)acrylate - Google Patents

Abstract

[Problem] A regeneration system and method for preventing ignition and explosion in a connecting pipe. [Solution] The regeneration system includes a pyrolysis device 10 for pyrolyzing scraps of a molded body of a (meth)acrylic resin composition, the pyrolysis device having an input section 12 for inputting the scraps and a gas extraction section 14 for extracting a gas containing methyl (meth)acrylate produced by pyrolysis of the (meth)acrylic resin composition, and a gas treatment device 30 connected to the gas extraction section by a connecting pipe 20 and comprising a purifier for purifying the gas extracted through the connecting pipe and a cooler for cooling the gas, the connecting pipe including one or more pipe bodies 22A, and a cooling section 24 for cooling the gas flowing through the pipe body in at least a partial region of the pipe body, the pyrolysis device being an extruder, and satisfying the following formula (1): 0.6≦D2.5/A2.0≦25 (1) (A: inner diameter of the connecting pipe, D: inner diameter of the cylinder of the extruder) [Selected Figure] FIG. 1

Description

The present invention relates to a system for regenerating methyl (meth)acrylate and a method for regenerating methyl (meth)acrylate.

Polymethyl(meth)acrylate (PMMA), a polymer made from methyl(meth)acrylate (MMA), has excellent transparency and weather resistance. Therefore, polymethyl(meth)acrylate is widely used as a material for components that make up automobile parts, signboards, display devices, etc.

In response to the recent rise in resource prices and growing awareness of environmental issues, products (molded articles) containing polymethyl(meth)acrylate used for the various applications described above are being collected and recycled.

Methods for recycling polymethyl(meth)acrylate include, for example, material recycling, in which the recovered molded bodies are subjected to a molding process again to produce new molded bodies; chemical recycling, in which the recovered molded bodies are heat-treated to thermally decompose (depolymerize) the polymethyl(meth)acrylate to recover the methyl(meth)acrylate, and the recovered methyl(meth)acrylate (sometimes called regenerated MMA) is used to produce new molded bodies; and thermal recycling, in which the recovered molded bodies are burned as fuel, and the combustion energy is used directly as a heat source and even to generate electricity.

Polymethyl (meth)acrylate can be recycled by chemical recycling because it is possible to recover methyl (meth)acrylate in high yields by heating at a relatively low temperature of about 300°C and reduce impurities.

In chemical recycling, for example, a known embodiment is to supply acrylic resin scrap to a twin-screw extruder having a sealed cylinder, heat it to 400-600°C for thermal decomposition, and suck in the decomposition gas discharged from the tip of the twin-screw extruder through a residue tank using the negative pressure effect of a cooler and a vacuum pump, and condense the decomposition gas in the cooler to form liquid monomers (see Patent Document 1). Another known heat treatment method is to supply a synthetic polymer material to a cylinder, continuously heat it in the cylinder, and extract and concentrate the low-molecular-weight gaseous pyrolysate obtained by the heating (see Patent Document 2).

Japanese Patent Application Laid-Open No. 11-106427 U.S. Pat. No. 3,959,357

However, with the techniques disclosed in Patent Documents 1 and 2, when the decomposition gas and gaseous pyrolysates discharged outside the cylinder after the heat treatment are discharged to the outside through a connecting tube connected to the cylinder, the decomposition gas and gaseous pyrolysates may leak from the connecting tube. In particular, when the connecting tube includes multiple pipe sections that are connected by connecting sections such as flange connections or threaded connections, the decomposition gas and gaseous pyrolysates may leak from the connecting sections. Here, since the decomposition gas and gaseous pyrolysates are usually flammable, there is a risk that the leaked gas may ignite and explode in some cases.

The inventors conducted extensive research to solve the above problems, and discovered that the above problems could be solved by providing a connecting pipe with a specific configuration for use in drawing the gas produced by pyrolysis out of the pyrolysis device, which led to the completion of the present invention.

That is, the present invention provides the following [1] to [14].
[1] A pyrolysis device for pyrolyzing scraps of a molded body obtained by molding a (meth)acrylic polymer composition containing a (meth)acrylic polymer, the pyrolysis device having an input section for inputting the scraps and a gas discharge section for discharging a gas containing methyl (meth)acrylate produced by pyrolysis of the (meth)acrylic resin composition;
a gas treatment device connected to the gas extraction section by a connecting pipe, the gas treatment device including at least one selected from the group consisting of a purifier for purifying the gas extracted through the connecting pipe and a cooler for cooling the gas,
The connecting pipe includes one or more pipe bodies, and has a cooling section in at least a portion of the pipe body for cooling the gas flowing through the pipe body.
[2] The connecting pipe includes two or more of the pipe main bodies, and has at least one connection portion formed by joining the two or more pipe main bodies together in the middle of the entire length of the connecting pipe, and the cooling portion is provided in at least a part of a region from the gas discharge portion to the connection portion located closest to the gas discharge portion,
The regeneration system according to claim 1, wherein the connection is a flange connection or a threaded connection.
[3] The regeneration system according to [2], wherein the ratio of the extension length of the cooling section from the connection section located closest to the gas outlet section to the gas outlet section to the entire length of the connecting pipe is 5% to 50% when the entire length of the connecting pipe is 100%.
[4] The regeneration system according to any one of [1] to [3], wherein the cooling unit is a functional unit capable of cooling the gas to a temperature equal to or higher than the boiling point and lower than the ignition point of the gas.
[5] The regeneration system according to any one of [1] to [4], wherein the cooling unit includes a double-pipe heat exchanger through which a medium can circulate.
[6] The regeneration system according to [5], wherein the medium used in the double-pipe heat exchanger is at least one selected from the group consisting of water, air, oil, molten salt and steam.
[7] The regeneration system according to any one of [1] to [6], wherein the pyrolysis device is a device that pyrolyzes the scrap under a pressure of 0.005 MPa to 1.5 MPa.
[8] The regeneration system according to any one of [1] to [7], wherein the pyrolysis device is an extruder, a kneader, or a fluidized bed heater.
[9] The regeneration system according to [8], wherein the pyrolysis device is an extruder.
[10] The reproducing system according to [9], which satisfies the following formula (1):

0.6≦D2.5/A2.0≦25 (1)

(In the above formula (1),
A represents the inner diameter of the connecting pipe,
D represents the inner diameter of the cylinder of the extruder.
[11] A pyrolysis step of pyrolyzing the scrap at a pressure of 0.005 MPa to 1.5 MPa using a pyrolysis device by using the regeneration system according to any one of claims 1 to 10;
a recovery step of extracting and recovering the gas from the gas extraction section of the thermal decomposition apparatus, the recovery step including a cooling section for cooling the gas circulating within the tubular body, the cooling section including one or more tubular bodies, and extracting and recovering the gas while cooling the gas in at least a portion of the tubular body.
[12] The regeneration method according to [11], wherein the recovery step is a recovery step in which the gas is extracted and recovered while being cooled by the cooling section provided in at least a portion of the region from the gas extraction section to the connection section located closest to the gas extraction section, the recovery step including at least one of the pipe bodies and a connection section formed by joining the pipe bodies together in the middle of the entire length of the connecting pipe, the connection section being a flange connection section or a threaded connection section.
[13] The method for recycling according to [11] or [12], wherein the scrap has a water content of less than 1%.
[14] The recycling method according to any one of [11] to [13], wherein the aluminum content in the scrap is 0 to 50 mass%.

According to the present invention, it is possible to effectively prevent ignition and explosion in the connecting pipe for discharging the gas generated by pyrolysis in the pyrolysis device from the pyrolysis device, in particular, ignition and explosion caused by the connection part of the connecting pipe.

FIG. 1 is a schematic diagram showing the configuration of a playback system according to the present invention.

The following describes in detail an embodiment of the present invention with reference to the drawings. Note that each drawing merely shows the shape, size, and arrangement of the components in a schematic manner to allow the invention to be understood. The present invention is not limited to the following description, and each component can be modified without departing from the gist of the present invention. In the drawings, duplicated descriptions of identical components denoted by the same reference numerals may be omitted.

1. Playback System The playback system of this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing an example of the configuration of the playback system.

As shown in FIG. 1, the recycling system 1 of the present embodiment includes a pyrolysis device 10 for pyrolyzing scraps of a molded body obtained by molding a (meth)acrylic resin composition containing a (meth)acrylic polymer, the pyrolysis device 10 having an input section 12 for inputting the scraps and a gas extraction section 14 for extracting a gas containing methyl (meth)acrylate produced by pyrolysis of the (meth)acrylic resin composition;
a gas treatment device 30 connected to the gas extraction section 14 by a connecting pipe 20 and including at least one selected from the group consisting of a purifier for purifying the gas extracted through the connecting pipe 20 and a cooler for cooling the gas;
The connecting pipe 20 includes a tubular pipe body 22A, and has a cooling section 24 in at least a portion of the pipe body 22A for cooling the gas flowing within the pipe body 22A by contacting the outer surface of the pipe body 22A or passing through the inside of the pipe body 22A.

(Explanation of terms)
"(Meth)acrylic" includes acrylic, methacrylic, and combinations thereof.

A "(meth)acrylic polymer composition" is a composition that contains a (meth)acrylic polymer as a main component and may further contain other components.

"(Meth)acrylic polymer" is a polymer having monomer units derived from a monomer having a (meth)acrylic group.

Here, examples of the (meth)acrylic polymer include a (meth)acrylic homopolymer containing only monomer units derived from an alkyl (meth)acrylate having an alkyl group with 1 to 4 carbon atoms; and a (meth)acrylic copolymer having 85% by mass or more and less than 100% by mass of monomer units derived from an alkyl (meth)acrylate having an alkyl group with 1 to 4 carbon atoms, and more than 0% by mass and 15% by mass or less of monomer units derived from other vinyl monomers copolymerizable with the monomer units derived from an alkyl (meth)acrylate having an alkyl group with 1 to 4 carbon atoms.

The "alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms" refers to a compound represented by, for example, CH ₂ ═C(CH ₃ )COOR (wherein R is an alkyl group having 1 to 4 carbon atoms).

A vinyl monomer copolymerizable with an alkyl (meth)acrylate having an alkyl group with 1 to 4 carbon atoms is a monomer that is copolymerizable with an alkyl methacrylate having an alkyl group with 1 to 4 carbon atoms and has a vinyl group.

Examples of alkyl (meth)acrylates having an alkyl group with 1 to 4 carbon atoms include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, sec-butyl methacrylate, and isobutyl methacrylate. The alkyl methacrylate having an alkyl group with 1 to 4 carbon atoms is preferably methyl methacrylate.

Examples of vinyl monomers copolymerizable with alkyl (meth)acrylates having an alkyl group with 1 to 4 carbon atoms include methacrylic acid 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 with 1 to 4 carbon atoms); methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, Examples of such monomers include acrylic acid esters such as 2-hydroxypropyl acrylate and monoglycerol acrylate; unsaturated carboxylic acids or anhydrides thereof such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride and itaconic anhydride; 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.

As a method for producing a (meth)acrylic polymer, for example, an alkyl (meth)acrylate having an alkyl group with 1 to 4 carbon atoms and, if necessary, a vinyl monomer copolymerizable with the alkyl (meth)acrylate having an alkyl group with 1 to 4 carbon atoms may be polymerized by a method such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization.

The "other components" that the (meth)acrylic polymer composition may contain include, for example, any suitable conventionally known mold release agent, polymerization regulator, polymerization initiator, ultraviolet absorber, and colorant that may be added to produce a molded article having specific properties.

"Scrap" is usually a used molded body that is produced by molding a methyl (meth)acrylate polymer composition into various shapes by any suitable injection molding process known in the art, and is collected as waste after being used for a specific purpose, and is a molded body adjusted to a shape and size that can be used as a raw material in the recycling system of the present invention. "Scrap" may also be a molded body that is made by collecting defective products during molding and adjusting them to a shape and size that can be used as a raw material in the recycling system of the present invention, or it may be a molded body that is made by collecting scraps generated during molding or in later processes such as polishing and adjusting them to a shape and size that can be used as a raw material in the recycling system of the present invention.

"Residue containing undecomposed components" may include components produced by thermal decomposition such as methyl (meth)acrylate.

The components that may make up the playback system 1 of this embodiment are described in detail below.

(1) Pyrolysis Device The recycling system 1 of the present embodiment includes a pyrolysis device 10. The pyrolysis device 10 can be any device having a suitable configuration known in the art, provided that it is capable of pyrolyzing scraps of a molded body obtained by molding a (meth)acrylic resin composition containing a (meth)acrylic polymer to generate a gas containing methyl (meth)acrylate and a residue containing undecomposed components.

In this embodiment, examples of the pyrolysis device 10 include an extruder, a kneader, and a fluidized bed heater.

In this embodiment, the pyrolysis device 10 is preferably an extruder. Suitable examples of the extruder that is the pyrolysis device 10 include twin-screw extruders such as a twin-screw co-rotating extruder and a twin-screw counter-rotating extruder.

In this embodiment, an example of a kneader that can be suitably used as the pyrolysis device 10 is the device described in U.S. Pat. No. 10,301,235.

In this embodiment, an example of a fluidized bed heater that can be suitably used as the pyrolysis device 10 is the device described in JP 2009-112902 A.

An example of the configuration of the pyrolysis device 10 will be described below by taking the configuration of a twin-screw extruder as an example.
The pyrolysis device 10, which is a twin-screw extruder, includes a pyrolysis section 11 for heat-treating scrap as a raw material. The pyrolysis section 11 corresponds to, for example, a cylinder for moving the raw material in the extension direction of the twin-screw extruder while heat-treating the raw material therein, and a screw disposed inside the cylinder.

In this embodiment, the pyrolysis device 10 is configured as a twin-screw extruder, i.e., the pyrolysis section 11. For example, components such as the cylinder and screw can be of any suitable configuration known in the art.

In this embodiment, it is preferable to determine the size of the inner diameter of the cylinder of the twin-screw extruder taking into consideration the size of the inner diameter of the tube section 22, i.e., the tube section main body 22A, which will be described later (details will be described later).

The pyrolysis section 11 is provided with an input section 12 for supplying scrap, which is the raw material, to the pyrolysis section 11. The input section 12 has a configuration equivalent to a hopper (feeder) in a twin-screw extruder. The hopper, which is the input section 12, is usually provided near the upstream end of the cylinder, which is the pyrolysis section 11, so that the raw material can be supplied into the cylinder, which is the pyrolysis section 11.

The pyrolysis section 11 is provided with one or more gas extraction sections (vents) 14 for extracting gas containing methyl (meth)acrylate produced by pyrolysis. The arrangement (position) of the one or more gas extraction sections 14 is not particularly limited, and any suitable arrangement corresponding to the design can be adopted. For example, from the viewpoint of improving the efficiency of extracting the generated gas, the gas extraction section 14 is preferably provided near the downstream end of the pyrolysis section 11 on the opposite side to the input section 12 already described, and on the upper end side of the pyrolysis section 11. When two or more gas extraction sections 14 are provided, it is preferable to arrange them so that they are aligned at a predetermined interval (e.g., equal intervals) on the upper end side of the pyrolysis section 11.

The pyrolysis device 10 has a residue discharge section 16 provided in the pyrolysis section 11. The residue discharge section 16 is a functional section for discharging residue containing undecomposed components generated in the pyrolysis section 11. The residue discharge section 16 is preferably provided near the downstream end of the pyrolysis section 11.

In this embodiment, the pyrolysis device 10 is preferably a device capable of pyrolyzing scrap under a pressure of 0.005 MPa to 1.5 MPa, from the viewpoint of preventing air from leaking into the system and preventing decomposition gas (gas generated by pyrolysis) from leaking out of the system.

(2) Connecting Pipe The regeneration system 1 of this embodiment includes a connecting pipe 20 for functionally connecting the pyrolysis device 10, which has already been described, to the gas treatment device 30, the details of which will be described later.

The connecting pipe 20 includes a pipe section 22 that guides (circulates) the gas containing methyl (meth)acrylate from the pyrolysis device 10 to the gas treatment device 30.

In this embodiment, the tube section 22 has a tubular tube body 22A and a cooler 24 that cools the gas flowing through the tube body 22A, i.e., the connecting tube 20, by contacting the outer surface of the tube body 22A or passing through the inside of the tube body 22A.

In this embodiment, the shape, material, etc. of the tubular body 22A are not particularly limited, provided that the gas containing methyl (meth)acrylate produced in the pyrolysis device 10 can be drawn out of the pyrolysis device 10 and introduced into the gas treatment device 30. Any suitable stainless steel piping or the like that has been conventionally known can be used as the tubular body 22.

In this embodiment, it is preferable to determine the size of the inner diameter of the tube section 22, i.e., the tube section main body 22A, taking into consideration the size of the inner diameter of the cylinder of the twin-screw extruder that is the pyrolysis device 10 (details will be described later).

The cooling section 24 is a functional section for adjusting the temperature of the gas containing methyl (meth)acrylate discharged from the pyrolysis device 10, and is a functional section that can cool the temperature of the gas containing methyl (meth)acrylate flowing through the tube main body 22A, i.e., the connecting tube 20, and further through the tube main body 22A, to a temperature equal to or higher than the boiling point and lower than the ignition point of the gas containing methyl (meth)acrylate.

In the regeneration system 1 of this embodiment, the connecting pipe 20 includes two or more pipe bodies 22A as shown in FIG. 1, and may have at least one connection portion 22B formed by joining two or more pipe bodies 22A together midway through the entire length of the connecting pipe 20.

The number of connection parts 22B, the spacing between two or more connection parts 22B, and the form of the connection parts 22B are not particularly limited. The connection parts 22B can be in any suitable form depending on the design of the playback system 1.

In this embodiment, the connection portion 22B is specifically assumed to be, for example, a flange connection portion or a screw connection portion.

From the viewpoint of more effectively preventing ignition and explosion, the cooling section 24 is preferably provided in at least a portion of the area from the gas extraction section 14 of the pyrolysis device 10 to the connection section 22B located closest to the gas extraction section 14, and more preferably provided so as to cover the entire area from the gas extraction section 14 to the connection section 22B located closest to the gas extraction section 14.

In this way, by locating the cooling section 24 closer to the gas extraction section 14, the gas containing methyl (meth)acrylate can be cooled immediately after it is extracted from the pyrolysis device 10, which makes it possible to more effectively prevent ignition and explosion.

The manner in which the cooling unit 24 is installed is not particularly limited, provided that it can effectively adjust the temperature of the gas containing methyl (meth)acrylate flowing through the tube body 22A. The cooling unit 24 can be installed, for example, so as to seamlessly cover the outer periphery of the tube body 22A.

The ratio of the extension length of the cooling section 24 from the connection section 22B located closest to the gas extraction section 14 to the gas extraction section 14 to the total length of the connecting pipe 20 is preferably 5% to 50%, and more preferably 5% to 15%, when the total length of the connecting pipe 20 is taken as 100%, from the viewpoint of effectively preventing ignition and explosion. With such a ratio, a sufficient cooling effect can be obtained.

Any suitable configuration known in the art can be used as the cooling unit 24. Specifically, the cooling unit 24 includes, for example, a double-pipe heat exchanger through which a medium (coolant) can circulate.

In this embodiment, it is preferable to use a double-pipe heat exchanger as the cooling section 24.

In the cooling section 24, which is the double-pipe heat exchanger already described, the medium that can be used to cool the gas containing methyl (meth)acrylate is preferably at least one selected from the group consisting of water, air, oil, molten salt, and water vapor.

Examples of oils that can be suitably used as a medium (coolant) in the cooling section 24 include methylphenyl silicone oil, dimethyl silicone oil, liquid paraffin, and a mixture of diphenyl and diphenyl oxide.

An example of a molten salt that can be suitably used as a medium (coolant) in the cooling section 24 is a mixture of an alkali nitrate and a nitrite.

In the pyrolysis device 10 and the connecting pipe 20 of the regeneration system 1 of this embodiment, it is preferable that the following formula (1) is satisfied, on the premise that the pyrolysis device 10 is the extruder already described.

0.6≦D2.5/A2.0≦25 (1)

In the formula (1),
A represents the inside diameter of the connecting tube,
D represents the inner diameter of the cylinder of the extruder.

If the extruder and connecting pipe of the pyrolysis device 10 are designed to satisfy the above formula (1), the amount of undecomposed components entrained in the pyrolysis gas and heading toward the connecting pipe is reduced, preventing clogging (blockage) of the connecting pipe due to undecomposed components, and allowing the pyrolysis of scraps by the pyrolysis device 10 to be carried out more safely.

According to the regeneration system 1 of this embodiment, the connecting pipe 20 is equipped with a cooling section 24, so that it is possible to effectively prevent ignition and explosion caused by gas containing methyl (meth)acrylate flowing through the pipe body 22A, and in particular, ignition and explosion caused by gas containing methyl (meth)acrylate leaking from the connection section 22B.

(3) Residue Storage Device The residue storage device 40 is connected to the pyrolysis device 10 by any suitable piping (connecting pipe) known in the art. Specifically, the residue discharge section 16 of the pyrolysis device 10 and the storage tank 42 of the residue storage device 40 are connected by a connecting pipe. The form of this connecting pipe is not particularly limited. This connecting pipe may have the same configuration as the pipe body 22A already described, and the size, material, etc. can be any suitable configuration taking into consideration the requirements required for the regeneration system 1, etc.

(4) Gas Treatment Device In this embodiment, the regeneration system 1 includes a gas treatment device 30 connected to the gas discharge section 14 of the pyrolysis device 10 via the connecting pipe 20 already described. The gas treatment device 40 is a functional unit for treating the gas discharged from the gas discharge section 14, which is a gas containing methyl (meth)acrylate produced by pyrolysis of the scrap input into the pyrolysis device 10.

In this embodiment, the gas processing device 30 may be any suitable device known in the art that is selected in accordance with the required processing, which is determined by taking into consideration the composition, temperature, etc. of the gas that may be generated by the pyrolysis process by the pyrolysis device 10.

The gas processing device 30 may be, for example, a purifier for purifying the gas extracted from the pyrolysis device 10, or a cooler for cooling the gas extracted from the pyrolysis device 10. In this embodiment, it is preferable to use, as the gas processing device 300, a gas processing device including at least one type selected from the group consisting of a purifier and a cooler.

2. Regeneration method The regeneration method of methyl (meth)acrylate of this embodiment is a regeneration method of methyl (meth)acrylate using the regeneration system 1 already described, and includes a pyrolysis step of pyrolyzing scrap at a pressure of 0.005 MPa to 1.5 MPa by the pyrolysis device 10, and a recovery step of extracting and recovering gas from the gas extraction section 14 of the pyrolysis device 10, which includes one or more tubular bodies 22A and includes a cooling section for cooling the gas that is in contact with the outer surface of the tubular body 22A or that passes through the inside of the tubular body 22A and flows through the tubular body 22A while being cooled and extracted from at least a partial region of the tubular body 22A.

In the regeneration method of this embodiment, since water significantly reduces the purity of methyl (meth)acrylate after purification, the water content in the "scrap of the molded body obtained by molding the (meth)acrylic polymer composition containing the (meth)acrylic polymer" is preferably less than 1%.

In addition, in the recycling method of this embodiment, the aluminum content in the scrap is preferably 0 to 50 mass %, and more preferably 0 to 10 mass %, from the standpoint of equipment protection and decomposition efficiency.

The "boiling point" temperature of the assumed "temperature above the boiling point and below the ignition point of the gas containing methyl (meth)acrylate" is about 100°C, so the "boiling point" temperature is above this temperature, and the "ignition point" temperature is about 421°C, so the gas containing methyl (meth)acrylate can be discharged from the pyrolysis device 10 while adjusting the cooling conditions (temperature of the refrigerant, flow rate, etc.) by the cooling unit 24 so that the temperature is below this temperature. The temperature of the gas after being cooled by the cooling unit 24, taking into account the "temperature above the boiling point and below the ignition point of the gas containing methyl (meth)acrylate", is preferably, for example, 200°C to 410°C, and more preferably 300°C to 400°C.

The methyl (meth)acrylate regenerated and recovered by the regeneration method of this embodiment (sometimes referred to as regenerated methyl (meth)acrylate or recovered methyl (meth)acrylate) may unavoidably contain impurities such as methyl isobutyrate, methyl propionate, and methyl acrylate. Regenerated methyl (meth)acrylate that may contain such impurities (before carrying out a purification process, etc.) may be referred to as a methyl (meth)acrylate product.

The steps included in the method for regenerating methyl (meth)acrylate according to this embodiment will be described in detail below. Note that the following description will be given assuming an example in which an extruder is used as the pyrolysis device 10.

(1) Pyrolysis Step The pyrolysis step is a step in which scrap is pyrolyzed (depolymerized) by the pyrolysis device 10 to generate a gas containing methyl (meth)acrylate and a residue containing undecomposed components.

In this embodiment, the conditions for carrying out the pyrolysis process (e.g., pressure (MPa), cylinder temperature (°C), screw rotation speed (rpm), scrap supply amount (raw material supply rate) (kg/hour)) are not particularly limited. The conditions for carrying out the pyrolysis process can be any suitable conditions, taking into consideration, for example, the properties and composition of the scrap to be treated.

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

The cylinder temperature in the pyrolysis process of this embodiment is usually set to 400°C to 500°C from the viewpoint of pyrolysis efficiency, and is preferably 450°C to 470°C when the scrap is pure polymethyl(meth)acrylate, for example.

The screw rotation speed in the pyrolysis step of this embodiment is usually set to 500 rpm to 1500 rpm from the viewpoint of stable operation of the extruder, and is preferably set to 500 rpm to 1000 rpm when the scrap is pure polymethyl(meth)acrylate, for example.

The scrap supply rate in the pyrolysis process of this embodiment varies depending on the cylinder diameter, but is usually between 10 kg/hour and 5,000 kg/hour. For example, if the cylinder diameter is 47 mm, the rate is preferably between 40 kg/hour and 90 kg/hour.

(2) Recovery Step The recovery step is a step of extracting and recovering gas from the gas extraction section 14 of the thermal decomposition apparatus 10.

In the regeneration method of this embodiment, the recovery process specifically includes one or more pipe bodies 22A, and is a process of extracting and recovering gas while cooling it using a cooling section 24 that cools the gas flowing through the pipe body 22A, in contact with the outer surface of the pipe body 22A or passing through the inside of the pipe body 22A, from at least a partial area of the pipe body 22A.

If the recovery process is performed in this manner, it is possible to effectively prevent ignition and explosion in components related to the gas generated by pyrolysis that are located downstream of the pyrolysis device 10, such as the connecting pipe 20, particularly the connection part 22B.

In the regeneration method of this embodiment, the recovery process is preferably a recovery process in which the gas is extracted and recovered while being cooled by a cooling section 24 provided in at least a portion of the region from the gas extraction section 14 to the connection section 22B located closest to the gas extraction section 14, the connection section 22B including two or more pipe section bodies 22A and formed by joining two or more pipe section bodies 22A together midway through the entire length of the connecting pipe 20, and at least one connection section 22B being a flange connection section or a threaded connection section.

In this embodiment, the recovery process may include any suitable processing process (e.g., purification process, cooling process) using the gas processing device 30 (e.g., a purifier, a cooler) already described.

In this embodiment, the conditions for carrying out the recovery process are not particularly limited. The conditions for carrying out the recovery process can be any suitable conditions, taking into consideration, for example, the properties, composition, temperature, etc. of the gas extracted from the gas extraction section 14 of the pyrolysis device 10.

(3) Storage Step The storage step is a step in which the residue containing the uncracked components produced in the pyrolysis step is discharged from the residue discharge section 16 of the pyrolysis device 10 and introduced into the residue storage device 40 for storage.

Specifically, the storage process can be a process in which the residue containing undecomposed components is drawn out of the pyrolysis device 10 using, for example, any suitable pump known in the art via a connecting pipe (piping) that connects the residue discharge section 16 of the pyrolysis device 10 to the storage tank 42 of the residue storage device 40, and introduced into the storage tank 42, and then stored in the storage tank 42.

According to the method for regenerating methyl (meth)acrylate in this embodiment, the gas containing methyl (meth)acrylate extracted from the thermal decomposition device 10 is cooled by the cooling section 24 provided in the connecting pipe 20 to a temperature preferably equal to or higher than the boiling point and lower than the ignition point, so that ignition and explosion caused by the configuration located downstream of the thermal decomposition device 10, particularly the connection part, can be prevented, and methyl (meth)acrylate can be regenerated more safely and efficiently.

REFERENCE SIGNS LIST 1 Regeneration system 10 Pyrolysis device 11 Pyrolysis section 12 Feeding section 14 Gas extraction section 16 Residue discharge section 20 Connecting pipe 22 Pipe section 22A Pipe section main body 22B Connection section 24 Cooling section 30 Gas treatment device 40 Residue storage device 42 Storage tank

Claims (11)

A pyrolysis apparatus for pyrolyzing scraps of a molded body obtained by molding a (meth)acrylic polymer composition containing a (meth)acrylic polymer, the pyrolysis apparatus having an input section for inputting the scraps and a gas extraction section for extracting a gas containing methyl (meth)acrylate produced by pyrolysis of the (meth)acrylic resin composition;
a gas treatment device connected to the gas extraction section by a connecting pipe, the gas treatment device including at least one selected from the group consisting of a purifier for purifying the gas extracted through the connecting pipe and a cooler for cooling the gas,
The connecting pipe includes one or more pipe bodies, and has a cooling portion in at least a partial region of the pipe body for cooling the gas flowing through the pipe body,
The pyrolysis device is an extruder,
The following formula (1)
0.6≦ ^D2.5 / ^A2.0 ≦25 (1)
(In the above formula (1),
A represents the inner diameter of the connecting pipe,
D represents the inner diameter of the cylinder of the extruder.
A methyl (meth)acrylate regeneration system that satisfies the above requirements. The regeneration system of claim 1, wherein the connection is a flange connection or a threaded connection. The regeneration system according to claim 2, wherein the ratio of the extension length of the cooling section from the connection section located closest to the gas extraction section to the gas extraction section to the total length of the connecting pipe is 5% to 50% when the total length of the connecting pipe is 100%. The regeneration system according to any one of claims 1 to 3, wherein the cooling unit is a functional unit capable of cooling the gas to a temperature equal to or higher than the boiling point and lower than the ignition point. The regeneration system according to any one of claims 1 to 3, wherein the cooling unit includes a double-pipe heat exchanger through which a medium can circulate. The regeneration system according to claim 5, wherein the medium used in the double-pipe heat exchanger is at least one selected from the group consisting of water, air, oil, molten salt, and water vapor. The regeneration system according to any one of claims 1 to 3, wherein the pyrolysis device is a device that pyrolyzes the scrap under a pressure of 0.005 MPa to 1.5 MPa. A pyrolysis step of pyrolyzing the scrap at a pressure of 0.005 MPa to 1.5 MPa using a pyrolysis device by using the regeneration system according to any one of claims 1 to 3;
a recovery step of extracting and recovering the gas from the gas extraction section of the thermal decomposition apparatus, the recovery step including a cooling section for cooling the gas circulating within the tubular body, the cooling section including one or more tubular bodies, and extracting and recovering the gas while cooling the gas in at least a portion of the tubular body. The regeneration method according to claim 8, wherein the connection is a flange connection or a threaded connection. The method of claim 8, wherein the scrap contains less than 1% water. The recycling method according to claim 8, wherein the aluminum content in the scrap is 0 to 50 mass %.

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