Method for producing styrene monomer

Abstract

The present invention addresses the problem of providing a method for producing a styrene monomer capable of suppressing a decrease in the amount of styrene produced per unit time. The present invention is a method for producing a styrene monomer, the method comprising: a mixed solution preparation step for preparing a mixed solution in which a solvent and a styrene-based resin composition containing a styrene-based polymer containing styrene monomer units are mixed; a purification step for purifying the mixed solution by means of a purification means; a devolatilization step in which the purified liquid mixture is devolatilized to produce a fluid; and a first pyrolysis step for generating a first pyrolysis liquid by pyrolyzing the fluid.

Description

Technical Field

[0001] The present invention relates to a method for producing styrene monomer. Background Art

[0002] In recent years, in line with the SDGs (Sustainable Development Goals), there has been a growing demand for technologies to recycle plastic materials such as polystyrene resins. Among these methods, mechanical recycling, which aims to reuse polystyrene resins without temporarily reducing them to styrene monomers, and chemical recycling, which temporarily reduces them to styrene monomers, have attracted significant attention as polystyrene resin recycling methods.

[0003] Regarding the mechanical recycling of polystyrene resins, a technique is known, for example, as described in Patent Document 1. Patent Document 1 discloses a technique in which polystyrene resin waste is dissolved in a good solvent such as cymene, p-xylene, toluene, or ethylbenzene, and after removing insoluble matter, the mixture is mixed with a poor solvent such as heptane to precipitate and recover the polystyrene resin components.

[0004] Patent Document 2 discloses a technique for recovering polystyrene resin without reducing the molecular weight of the polystyrene waste by dissolving polystyrene waste in limonene or an organic solvent having a boiling point of less than 200° C., removing insoluble matter, and then performing vacuum heating and devolatilization.

[0005] On the other hand, regarding the chemical recycling of polystyrene resins, a technique is known, for example, as described in Patent Document 3. Patent Document 3 discloses a technique in which waste polystyrene resin is heat-melted and introduced into a tubular pyrolysis device, where the molten polystyrene resin is further pyrolyzed at a high temperature to obtain styrene monomer.

[0006] Similarly, Patent Document 4 discloses a technique in which a polystyrene resin is heat-melted at a high temperature using a twin-screw extruder and then thermally decomposed to obtain a styrene monomer.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: International Publication No. 2023 / 082009;

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2000-334738;

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2001-40136;

[0012] Patent document 4: Japanese Patent Application Laid-Open No. 2021-134281. Summary of the Invention

[0013] Conventional mechanical recycling technologies for styrene resins involve dissolving polystyrene waste once using two or more organic solvents to remove foreign matter, followed by precipitation or devolatilization using a poor solvent, thereby recovering high-quality recycled polystyrene resin. However, when recycled polystyrene resin is used for food hygiene applications, it has been confirmed that the purity of the recycled polystyrene resin is insufficient depending on the intended use. Consequently, there is a need to remove impurities that meet various standards depending on the intended use.

[0014] Furthermore, all of the aforementioned existing chemical recycling technologies for styrene resins involve a pyrolysis step for polystyrene waste. This pyrolysis step is currently virtually unavoidable when converting polymers to monomers through chemical recycling. Therefore, Patent Documents 3 and 4 disclose mechanisms for removing pyrolysis residues or solid residues generated during pyrolysis.

[0015] However, polystyrene waste is often not composed solely of pure polystyrene resin. It contains other resins, such as polyolefin resins used in packaging, and sometimes inevitably contains inorganic substances such as metal powder. Furthermore, it has been confirmed that during the pyrolysis process of reducing polystyrene waste to styrene monomer, these other resins and inorganic substances exhibit different decomposition behaviors from the polystyrene resin, resulting in more than just pyrolysis residue.

[0016] Specifically, in the gas generated by pyrolysis, low-fluidity liquid or solid is produced at a temperature lower than the pyrolysis temperature. Therefore, in addition to the pyrolysis residue containing carbides and inorganic substances produced during pyrolysis, it is confirmed that new problems such as blockage of the piping connecting the pyrolysis device or each device or reduction in the continuous operation of the pyrolysis process have also arisen.

[0017] Therefore, an object of the present disclosure is to suppress a decrease in the production amount of styrene during the average operation time during long-term operation.

[0018] The present inventors have conducted intensive research to solve the above-mentioned problems and have found that, by liquefying a styrene resin composition containing a styrene polymer including styrene monomer units by adding a solvent, purifying and devolatilizing the mixed liquid and then pyrolyzing the fluid obtained to obtain a first pyrolysis liquid, clogging of piping caused by residues produced in the pyrolysis step or gases generated by pyrolysis can be suppressed, and reduction in the production amount of styrene during the average operating time during long-term operation can be suppressed, thereby completing the present invention.

[0019] That is, the present disclosure is as follows.

[0020] [1] A method for producing styrene monomer, comprising:

[0021] a mixed liquid preparation step of preparing a mixed liquid by mixing a styrene-based resin composition and a solvent, wherein the styrene-based resin composition contains a styrene-based polymer including styrene monomer units;

[0022] a purification step, purifying the mixed solution through a purification unit;

[0023] a devolatilization step of devolatilizing the purified mixed liquid to produce a fluid; and

[0024] In the first pyrolysis step, the fluid is pyrolyzed to generate a first pyrolysis liquid containing styrene monomer.

[0025] [2] The method for producing a styrene monomer according to [1], wherein:

[0026] The method further includes a recovery step of distilling the first pyrolysis liquid to recover styrene monomer.

[0027] [3] The method for producing a styrene monomer according to [1], wherein:

[0028] The solvent is one or more selected from the group consisting of toluene, methyl ethyl ketone, and ethylbenzene.

[0029] [4] The method for producing a styrene monomer according to any one of [1] to [3], wherein

[0030] In the fluid, the styrene-based polymer accounts for 10% by mass or more and 100% by mass or less relative to 100% by mass of the total amount of the fluid.

[0031] [5] The method for producing a styrene monomer according to any one of [1] to [4], wherein

[0032] In the purified mixed liquid, the styrene-based polymer accounts for 5% by mass or more and 100% by mass or less relative to 100% by mass of the total amount of the purified mixed liquid.

[0033] [6] The method for producing a styrene monomer according to any one of [1] to [5], wherein

[0034] In the mixed liquid, the styrene-based polymer accounts for 5% by mass or more relative to 100% by mass of the total amount of the mixed liquid.

[0035] [7] The method for producing a styrene monomer according to any one of [1] to [6], wherein

[0036] In the mixed liquid preparation step, the ambient temperature for mixing the styrene resin composition and the solvent is 0° C. or higher.

[0037] [8] The method for producing a styrene monomer according to any one of [1] to [7], wherein

[0038] The devolatilization step is performed under reduced pressure.

[0039] [9] The method for producing a styrene monomer according to any one of [1] to [8], wherein

[0040] The first pyrolysis step is performed under reduced pressure.

[0041]

[10] The method for producing a styrene monomer according to any one of [1] to [9], wherein

[0042] The method further includes an analysis step of analyzing the first pyrolysis liquid.

[0043]

[11] The method for producing a styrene monomer according to any one of [1] to

[10] , wherein

[0044] In the first pyrolysis step, pyrolysis steam containing styrene monomer is cooled to produce a first pyrolysis liquid.

[0045]

[12] The method for producing a styrene monomer according to any one of [1] to

[11] , wherein

[0046] The styrene resin composition contains 20% by mass or less of inclusions.

[0047]

[13] The method for producing a styrene monomer according to any one of [1] to

[12] , wherein

[0048] further comprising a second pyrolysis step,

[0049] The second pyrolysis step is to distill the first pyrolysis liquid to separate it into a first fraction containing styrene monomer and a second fraction having a lower styrene monomer concentration than the first fraction, then separate the first fraction into a third fraction having a higher styrene monomer concentration than the first fraction and a fourth fraction having a lower styrene monomer concentration than the first fraction, and then pyrolyze the fourth fraction again to generate a second pyrolysis liquid.

[0050]

[14] The method for producing a styrene monomer according to

[13] , wherein:

[0051] further comprising a recycling process,

[0052] In the recycling step, the second pyrolysis liquid is distilled to separate into a fifth fraction containing styrene monomer and a sixth fraction having a lower styrene monomer concentration than the fifth fraction, and then the styrene monomer is recovered from the fifth fraction.

[0053]

[15] The method for producing a styrene monomer according to

[14] , wherein:

[0054] The recycling step further includes a step (I) of recovering styrene monomer by using the fifth fraction as a part of the first pyrolysis liquid and a step (II) of recovering styrene monomer by distilling the fifth fraction separately from the first pyrolysis liquid.

[0055]

[16] The method for producing a styrene monomer according to any one of [1] to

[15] , wherein

[0056] The first pyrolysis step is a step of heating the fluid to obtain pyrolysis vapor containing styrene monomer and then cooling the pyrolysis vapor to generate the first pyrolysis liquid. The concentration of the adhesion inducer contained in the first pyrolysis liquid is less than 0.2% by mass.

[0057]

[17] The method for producing a styrene monomer according to any one of [1] to

[16] , wherein

[0058] The devolatilization step is a step of devolatilizing the mixed liquid using a flash drum, a flash tank polymer heater, a twin-screw devolatilizer, a thin film evaporator, or an extruder to produce the fluid.

[0059]

[18] The method for producing a styrene monomer according to any one of [1] to

[17] , wherein

[0060] The purification unit is one or more units selected from the group consisting of filtration, decantation, centrifugal separation, centrifugal sedimentation, spiral decanter, strainer, screening mesh or filter.

[0061]

[19] The method for producing a styrene monomer according to any one of [1] to

[18] , wherein

[0062] The purification unit is a purification mechanism that combines centrifugal separation and filtration.

[0063] According to the present disclosure, a method for suppressing a decrease in the production amount of styrene in the average operation time during long-term operation can be provided.

[0064] According to the present disclosure, a method for helping to extend the continuous operation time can be provided.

[0065] According to the present disclosure, it is possible to provide a method for reducing by-products in the pyrolysis liquid obtained in the pyrolysis step, reducing the load of the subsequent distillation step, and enabling continuous operation without requiring complex maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is a flowchart showing an example of the method for producing a styrene monomer from a styrene-based resin composition according to the present embodiment.

[0067] Figure 2 This is a flowchart showing another example of the method for producing a styrene monomer from a styrene-based resin composition according to the present embodiment.

[0068] Figure 3 This is a schematic diagram showing an example of a pyrolysis apparatus used in the method for producing a styrene monomer from a styrene-based resin composition according to the present embodiment.

[0069] Figure 4 This is a flowchart showing another example of the method for producing a styrene monomer from a styrene-based resin composition according to the present embodiment.

[0070] Figure 5 This is a schematic diagram showing an example of a styrene monomer production apparatus according to the present embodiment.

[0071] Figure 6 is shown in the use of C1P connection via the connection section Figure 3 In the case of producing styrene monomer by using the pyrolysis device 10 and the liquefaction device L, a photograph of the state of the glass tube, that is, the connection portion C1P, before producing styrene monomer is shown. Figure 6 This is a photograph showing the state of the glass tube, ie, the connection portion C1P, before the production of styrene monomer in Comparative Example 5.

[0072] Figure 7 is shown in the use of C1P connection via the connection section Figure 3 This is a photograph of the state of the glass tube, ie, the connecting portion C1P, during the production of styrene monomer in Comparative Example 5, when styrene monomer was produced using the pyrolysis apparatus 10 and the liquefaction apparatus L.

[0073] Figure 8 is shown in the use of C1P connection via the connection section Figure 3 This is a photograph of the state of the glass tube, ie, the connection portion C1P, immediately after the production of styrene monomer in Comparative Example 5, when styrene monomer was produced using the pyrolysis apparatus 10 and the liquefaction apparatus L. DETAILED DESCRIPTION

[0074] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. However, the present invention is not limited to the following description and can be carried out with various modifications within the scope of the gist of the invention.

[0075] [Method for producing styrene monomer]

[0076] The method for producing a styrene monomer disclosed herein is a method for pyrolyzing a styrene resin composition containing a styrene polymer comprising styrene monomer units. Furthermore, the styrene polymer may be a resin comprising used, discarded, or abandoned styrene monomer units. Specifically, the method for producing a styrene monomer of this embodiment includes: a mixed liquid preparation step of preparing a mixed liquid of a styrene resin composition and a solvent; a purification step of purifying the mixed liquid by a purification unit; a devolatilization step of devolatilizing the purified mixed liquid to produce a fluid; and a first pyrolysis step of pyrolyzing the fluid to generate a first pyrolysis liquid comprising styrene monomer.

[0077] This can not only suppress the generation of pyrolysis residues containing carbides and inorganic substances during pyrolysis, but also suppress factors that reduce the continuous operability of the pyrolysis process, such as clogging of the pyrolysis device or the pipes connecting the devices.

[0078] In addition, the method for producing styrene monomer preferably further comprises a recovery step of distilling the first pyrolysis liquid to recover the styrene monomer. This allows production of styrene monomer with high purity.

[0079] Below, refer to Figure 1 and Figure 2 After the overall description of the method for producing styrene monomers according to the present embodiment, each step (S1) to (S10) will be described in detail. Figure 4 The flowchart shown.

[0080] Figure 1 : is a flow chart showing an example of a method for producing a styrene monomer from a styrene resin composition according to the present embodiment. Figure 1 The process of the present invention is shown as follows: a mixed liquid preparation step (S1) of preparing a mixed liquid obtained by mixing a styrene resin composition as a raw material and a solvent; a purification step (S2) of purifying the mixed liquid to concentrate the styrene polymer contained in the mixed liquid; a devolatilization step (S3) of devolatilizing the purified mixed liquid to prepare a fluid after distilling off a specified amount of the solvent; a first pyrolysis step (S4) of pyrolyzing the fluid to generate a first pyrolysis liquid containing styrene monomer; and a recovery step (S5) of recovering styrene monomer from the first pyrolysis liquid, which is set as needed.

[0081] Figure 2 This is a flowchart showing another example of the method for producing a styrene monomer from a styrene-based resin composition according to the present embodiment.

[0082] In more detail, Figure 2 The invention shows a mixed liquid preparation step (S1) of preparing a mixed liquid obtained by mixing a styrene resin composition as a raw material and a solvent; a purification step (S2) of purifying the mixed liquid to concentrate the styrene polymer contained in the mixed liquid; a devolatilization step (S3) of devolatilizing the purified mixed liquid to prepare a fluid after distilling off a predetermined amount of the solvent; a first pyrolysis step (S4) of pyrolyzing the fluid to generate a first pyrolysis liquid containing styrene monomer; a first distillation step (S6) of distilling the first pyrolysis liquid to separate it into a first fraction containing styrene monomer and a second fraction having a lower styrene monomer concentration than the first fraction; and a separation step (S7) of separating the first pyrolysis liquid into a first fraction containing styrene monomer and a second fraction having a lower styrene monomer concentration than the first fraction. A second distillation step (S7) is to be set up for distilling the first fraction and separating it again into a third fraction containing styrene monomer and a fourth fraction with a lower styrene monomer concentration than the third fraction; a second pyrolysis step (S8) is to pyrolyze the fourth fraction again to generate a second pyrolysis liquid; a third distillation step (S9) is to be set up as needed for distilling the second pyrolysis liquid and separating it into a fifth fraction containing styrene monomer and a sixth fraction with a lower styrene monomer concentration than the fifth fraction; a recycling step (S10) is to be set up as needed for recovering styrene monomer from the fifth fraction; and a recovery step (S5) is to be set up as needed for recovering styrene monomer from the first pyrolysis liquid.

[0083] Figure 4 : is a flow chart showing another example of the method for producing a styrene monomer from a styrene resin composition according to the present embodiment. Figure 4The figure shows a preparation step of preparing a styrene resin composition as a raw material; a mixed liquid preparation step (S1) of preparing a mixed liquid in which a solvent is added to the styrene resin composition as a raw material; a purification step (S2) of purifying the mixed liquid to concentrate the styrene polymer contained in the mixed liquid, thereby removing impurities and the like contained in the styrene resin composition as a raw material; a devolatilization step (S3) of devolatilizing the purified mixed liquid to prepare a fluid after distilling off a predetermined amount of the solvent; a first pyrolysis step (S4) of pyrolyzing the fluid to generate a first pyrolysis liquid containing styrene monomer; and a recovery step (S5) of recovering styrene monomer from the first pyrolysis liquid, which is provided as needed. In addition, the devolatilization step (S3) may also include, as needed, a step of recovering the solvent distilled off from the purified mixed liquid and purifying the solvent by distillation (=solvent recovery purification step). Moreover, the regenerated solvent purified by the solvent recovery purification step may also be reused in the mixed liquid preparation step (S1). Furthermore, the residue obtained in the solvent recovery and purification step, excluding the purified regenerated solvent, is discharged and can be used as fuel in the first pyrolysis step ( S4 ).

[0084] Furthermore, the light fraction or heavy fraction (light oil, heavy oil) obtained in the recovery step (S5), which is a component other than styrene monomer, can also be used as fuel in the first pyrolysis step (S4). This is expected to increase the yield of the obtained styrene monomer.

[0085] Hereinafter, each step will be described.

[0086] (Mixed solution preparation step: S1)

[0087] The method for producing a styrene monomer according to the present embodiment includes a step of preparing a mixed solution of a styrene resin composition and a solvent. This step achieves the effect of concentrating the styrene polymer by utilizing the solubility of the solvent.

[0088] Solvents

[0089] The solvent of this embodiment preferably dissolves the styrene polymer in the styrene resin composition. Thus, it is possible to separate the styrene polymer into a component that dissolves in the solvent and a component that is insoluble or poorly soluble in the solvent. As a result, the styrene polymer can be concentrated.

[0090] In this embodiment, the solubility parameter (SP value ((cal / cm 3 ) 1 / 2) is preferably 8.0 or greater and less than 11.0, more preferably 8.3 or greater and less than 10.5, and even more preferably 8.6 or greater and less than 10.0. When the solubility parameter of the solvent is within the above range, it is easy to selectively dissolve styrene-based polymers (e.g., polystyrene, styrene-(meth)acrylic acid copolymer, etc.).

[0091] Preferred solvents for this embodiment include the following. The SP values ​​of the corresponding solvents are shown in parentheses. The solvent is preferably an organic solvent. Specifically, the organic solvent may include one or more solvents selected from the group consisting of acetone (9.9), chloroform (9.3), methyl ethyl ketone (9.3), benzene (9.2), tetrahydrofuran (9.1), toluene (8.9), ethylbenzene (8.8), and styrene (9.3). The solvent may be a single solvent or a mixed solvent of two or more solvents.

[0092] The solubility parameter (SP value) specified in the present embodiment is calculated using a function of cohesive energy density represented by the following formula (1).

[0093] SP value ((cal / cm 3 ) 1 / 2 )=(△E / V) 1 / 2 (1)

[0094] (In the above formula (1), ΔE represents the intermolecular cohesive energy (heat of vaporization), V represents the total volume of the mixed liquid, and ΔE / V represents the cohesive energy density.)

[0095] In addition, the heat amount change ΔHm due to mixing is expressed by the following formula (2) using the SP value.

[0096] △Hm=V(δ1-δ2)·Φ1·Φ2 (2)

[0097] (In the above formula (2), δ1 represents the SP value of the solvent, δ2 represents the SP value of the solute, Φ1 represents the volume fraction of the solvent, and Φ2 represents the volume fraction of the solute.)

[0098] According to the above formulas (1) and (2), the closer the values ​​of δ1 and δ2 are, the smaller ΔHm is, and the smaller the Gibbs free energy is. Therefore, the affinity between substances with a small difference in SP value becomes higher.

[0099] The above SP values ​​are SP values ​​obtained using the Hilderbrand method (including the Hansen method) and are based on reference values ​​("Polymer handbook 4 thEdition" "J. Brandrup, EHImmergut, EAGrulke" WILEY-INTERSCENCE).

[0100] The solvent of this embodiment is preferably an organic solvent, or a mixed solvent obtained by mixing two or more organic solvents. In addition, the number of carbon atoms of each component constituting the organic solvent is more preferably 8 or less, and the number of carbon atoms is further preferably 1 or more and 8 or less.

[0101] By setting the number of carbon atoms of the organic solvent to 8 or less, the solubility of the styrene-based polymer can be ensured while suppressing the boiling point of the solvent itself from becoming higher. In addition, in the devolatilization process of devolatilizing the purified mixed liquid containing the styrene-based polymer to prepare a fluid, the amount of residual solvent in the fluid can be suppressed to a low level.

[0102] In addition, by using a carbon atom number of 1 to 8 and a solubility parameter (SP value ((cal / cm 3 ) 1 / 2 ) is an organic solvent having a solubility difference of 8.0 or more and less than 11.0, thereby being able to promote the selective separation of the inclusions and / or adhesion inducers described later and the styrene-based polymer and / or styrene monomer described later by utilizing the solubility difference of each component in the organic solvent.

[0103] The content of the solvent in this embodiment is preferably 5 to 95% by mass, more preferably 35 to 90% by mass, and even more preferably 50 to 80% by mass relative to the entire mixed liquid.

[0104] When the mixing amount of the solvent is within the above range, separation into a component containing the styrene-based polymer dissolved in the solvent and components other than the styrene-based polymer can be easily achieved.

[0105] <Styrene resin composition>

[0106] The styrene resin composition used in the method for producing styrene monomer in this embodiment only needs to contain a styrene polymer containing styrene monomer units. The lower limit of the content of the styrene polymer contained in the styrene resin composition used as a raw material for the method for producing styrene monomer can be preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, and further preferably 80% by mass or more relative to the whole styrene resin composition.

[0107] On the other hand, the upper limit of the content of the styrene-based polymer may be 50% by mass, 60% by mass, 70% by mass, 80% by mass, or 100% by mass or less relative to the entire styrene-based resin composition.

[0108] When the content of the styrene polymer in the styrene resin composition is within the above range, the yield of the pyrolysis liquid generated in the pyrolysis step described later increases, thereby achieving an effect of increasing the yield of the styrene monomer in the recovery step.

[0109] The styrene resin composition of this embodiment may further include used, discarded or abandoned materials, pre-consumer materials such as factory recyclates, post-consumer materials such as market recyclates, long-term inventory pellets, or non-standard pellets. In addition, the styrene resin composition may further include additives such as a phosphorus-based flame retardant, liquid paraffin, a stabilizer, or a colorant.

[0110] The styrene resin composition may also contain foreign matter. The styrene resin composition of the present embodiment is preferably a used, discarded or discarded material, that is, the styrene resin composition is preferably a recycled polystyrene resin composition. In the case where the styrene resin composition of the present embodiment is a recycled polystyrene resin composition, the styrene resin composition may contain foreign matter as an admixture from recycling. As such inclusions, for example, other resins other than styrene polymers (for example, olefin resins such as polyethylene resins and polypropylene resins), inorganic substances (for example, metal powder or silica), pigments, pigments, particles, attachments or foreign matter, etc. may be included.

[0111] In more detail, the foreign matter in this specification may also include other resins such as olefin resins, polyether resins, polyester resins or polyamide resins that do not actually contain styrene monomer units. Furthermore, it may be a mixed resin in which the product of these other resins or other resins such as olefin resins, polyether resins, polyester resins, polyamide resins and styrene polymers comprising styrene monomer units are stacked. In other aspects of the styrene resin composition of the present embodiment, it may also be a composition in which a cellulose-based (paper label, etc.) represented by paper, a thermosetting resin represented by a phenolic resin, polyurethane resin, epoxy resin, melamine resin, or styrene polymers comprising styrene monomer units are mixed. Further, fillers such as inorganic materials such as silicate minerals and glass represented by talc and carbon fibers, glass fibers, and cellulose fibers used in fiber-reinforced plastics may also be included. In addition, metals represented by aluminum or iron or SUS may also be included.

[0112] The upper limit of the amount of foreign matter contained in the styrene resin composition used as a raw material in the method for producing styrene monomer is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and even more preferably 20% by mass or less, relative to the total mass of the styrene resin composition. Furthermore, the lower limit of the amount of foreign matter contained in the styrene resin composition is preferably 0% by mass or more, more preferably greater than 0% by mass, relative to the total mass of the styrene resin composition.

[0113] In particular, the method for producing styrene monomer according to this embodiment is particularly advantageous when using post-consumer materials that generate residues during pyrolysis. However, even if the styrene resin composition according to this embodiment is a virgin polystyrene resin composition containing unused styrene polymers, or a pre-consumer material such as factory recyclate, it may contain the aforementioned additives, or other resins or inorganic substances mixed in during processing. Therefore, the method for producing styrene monomer according to this embodiment is advantageous as a method for producing styrene monomer from such virgin polystyrene resin compositions or pre-consumer materials while suppressing the generation of pyrolysis residues.

[0114] Styrene polymers

[0115] The styrene resin composition that can be used in the present embodiment contains a styrene polymer comprising a styrene monomer unit. Moreover, the styrene resin composition or styrene polymer can be a used-up, discarded or discarded material. Moreover, as long as the styrene polymer has a styrene monomer unit, it is preferably a polymer obtained by polymerizing a styrene monomer unit with one or more of other vinyl monomer units and rubber-like polymers that can be copolymerized with the styrene monomer as needed. In other words, the styrene polymer included in the styrene resin composition is preferably a polymer with a styrene monomer unit, more preferably a polymer that must include a styrene monomer unit and includes monomer units of other vinyl monomers and / or rubber-like polymers that can be copolymerized with the styrene monomer unit as any component. The preferred embodiment of the styrene polymer of the present embodiment is not particularly limited, specifically, for example, a rubber-modified styrene resin or a styrene copolymer resin in which particles of a rubber-like polymer are dispersed in a polymer matrix containing polystyrene, a polystyrene polymer (polystyrene and / or polystyrene-unsaturated carboxylic acid polymer, etc.) can be cited.

[0116] In the styrene polymer contained in the styrene resin composition that can be used in this embodiment, the lower limit of the content of styrene monomer units is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more relative to the entire styrene polymer (100% by mass). On the other hand, the upper limit of the content of styrene monomer units can be 50% by mass, 60% by mass, 70% by mass, 80% by mass, or 100% by mass.

[0117] -Polystyrene-

[0118] In the present embodiment, polystyrene refers to a polymer comprising a styrene monomer unit and, as required, other styrene-based monomer units. As the monomer constituting the polystyrene, in addition to styrene, other styrene-based monomers can be cited as other arbitrary components. Other styrene-based monomers can include α-methylstyrene, α-methyl-p-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene and styrene derivatives such as tert-butylstyrene or bromostyrene and indene. These monomers can use one or more than two. Polystyrene, within the scope of not damaging the effect of the present invention, does not exclude further containing monomer units other than the above-mentioned monomer units, and is typically composed of styrene monomer units.

[0119] -Rubber modified styrene resin-

[0120] In this embodiment, the rubber-modified styrene resin is a material in which particles of a rubber-like polymer are dispersed in a styrene-based polymer (e.g., polystyrene) serving as a matrix phase, and has a sea-island structure in which the matrix phase serves as a sea phase and the particles of the rubber-like polymer (=rubber-like polymer particles) serve as island phases. The rubber-modified styrene resin can be produced by polymerizing a styrene monomer (and, if necessary, other styrene-based monomers and unsaturated carboxylic acid-based monomers) in the presence of a rubber-like polymer.

[0121] In addition, the unsaturated carboxylic acid-based monomers include (meth)acrylic acid monomers and (meth)acrylic acid ester monomers.

[0122] The styrene monomer constituting the rubber-modified styrene resin of the present embodiment and other styrene monomers added as needed are the same as the styrene monomer of the polystyrene described above, and therefore their description is omitted here.

[0123] The rubber-like polymer particles included in the rubber-modified styrene-based resin of this embodiment may, for example, contain a resin containing styrene monomer units obtained from the above-mentioned styrene monomer inside the rubber-like polymer particles, and / or a resin containing styrene monomer units may be grafted onto the surface of the rubber-like polymer particles. More specifically, the rubber-like polymer particles may contain polystyrene and / or a polystyrene-unsaturated carboxylic acid polymer. Similarly, polystyrene and / or a polystyrene-unsaturated carboxylic acid polymer may be grafted onto the surface of the rubber-like polymer particles.

[0124] As the rubbery polymer, for example, rubber components such as polybutadiene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, and acrylonitrile-butadiene copolymer can be used. Among them, the rubbery polymer is preferably polybutadiene or styrene-butadiene copolymer. As polybutadiene, both high-cis polybutadiene with a high cis content and low-cis polybutadiene with a low cis content can be used. In addition, as the structure of the styrene-butadiene copolymer, both random structures and block structures can be used. These rubbery polymers can be used alone or in combination. In addition, saturated rubber obtained by hydrogenating butadiene-based rubber can be used.

[0125] Examples of such rubber-modified styrene-based resins include HIPS (high impact polystyrene), ABS resin (acrylonitrile-butadiene-styrene copolymer), AAS resin (acrylonitrile-acrylic rubber-styrene copolymer), and AES resin (acrylonitrile-ethylene propylene rubber-styrene copolymer).

[0126] When the rubber-modified styrene-based resin is a HIPS-based resin, high-cis polybutadiene in which 90 mol% or more consists of cis-1,4 bonds is particularly preferred in these rubbery polymers. Within this high-cis polybutadiene, preferably 6 mol% or less consists of vinyl-1,2 bonds, and particularly preferably 3 mol% or less consists of vinyl-1,2 bonds.

[0127] It should be noted that the content of compounds having a cis-1,4 structure, a trans-1,4 structure or a vinyl 1,2 structure as isomers related to the constituent units of the above-mentioned high-cis polybutadiene can be calculated by measuring using an infrared spectrophotometer and performing data processing using the Morero method (D. Morero, A. Santambrogio, L. Porri, F. Ciampelli, Chem, Ind. 41, 758 (1959)).

[0128] The high-cis polybutadiene can be easily obtained by a known production method, for example, by polymerizing 1,3-butadiene using a catalyst containing an organoaluminum compound and a cobalt compound or a nickel compound.

[0129] The content of the rubber-like polymer contained in the rubber-modified styrene-based resin is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, based on 100% by mass of the total amount of the rubber-modified styrene-based resin.

[0130] In addition, in this disclosure, the content of the rubber-like polymer contained in the rubber-modified styrene-based resin is a value calculated using pyrolysis gas chromatography.

[0131] The average particle size of the rubber-like polymer particles contained in the rubber-modified styrene-based resin is preferably 0.5 to 4.0 μm, more preferably 0.8 to 3.5 μm.

[0132] In addition, in this disclosure, the average particle size of the rubber-like polymer particles contained in the rubber-modified styrene-based resin is measured by the following method.

[0133] The ultrathin sections of 75nm were made by utilizing the rubber-modified styrene resin after osmium tetroxide staining, and the photo of 10000 times of magnification was taken using an electron microscope. In the photo, the particles dyed black were rubber-like polymers (a). The area average particle size was calculated using the following mathematical formula (N1) by the photo, and the average particle size of the rubber-like polymer particles was used. For this determination, the photo was input into a scanner at a resolution of 200dpi, and the particle analysis software of image analysis device IP-1000 (manufactured by Asahi Kasei Group) was used to measure the particle size.

[0134] Average particle size = ΣniDri 3 / ΣniDri 2 (N1)

[0135] (In the above mathematical formula (N1), ni is the number of rubbery polymer particles having a particle size Dri, and the particle size Dri is the particle size calculated as the equivalent circle diameter from the area of ​​the particles in the photograph.)

[0136] The reduced viscosity of the rubber-modified styrene-based resin (which is an indicator of the molecular weight of the rubber-modified styrene-based resin) is preferably in the range of 0.50 to 0.85 dL / g, more preferably in the range of 0.55 to 0.80 dL / g.

[0137] In addition, in this disclosure, the reduced viscosity of the rubber-modified styrene-based resin is a value measured under the conditions of 30° C. and a concentration of 0.5 g / dL in a toluene solution.

[0138] -Styrene copolymer resin-

[0139] In the present embodiment, the styrene copolymer resin refers to a resin comprising a styrene monomer unit and an unsaturated carboxylic acid monomer unit copolymerizable with the styrene monomer. In the styrene copolymer resin involved in the present embodiment, when the total content of the styrene monomer unit and the unsaturated carboxylic acid monomer unit is set to 100% by mass, the content of the styrene monomer unit is preferably 69 to 98% by mass, more preferably 74 to 96% by mass, and even more preferably in the range of 77 to 92% by mass.

[0140] In addition, the unsaturated carboxylic acid-based monomer of the present embodiment includes an unsaturated carboxylic acid monomer (for example, a (meth)acrylic acid monomer) and an unsaturated carboxylic acid ester monomer (for example, a (meth)acrylic acid ester monomer).

[0141] In the styrene-based copolymer resin of the present embodiment, when the total content of the styrene monomer unit, the unsaturated carboxylic acid monomer unit, and the unsaturated carboxylic acid ester monomer unit in the styrene-based copolymer resin is set to 100% by mass, the content of the unsaturated carboxylic acid monomer unit is preferably 2 to 16% by mass, more preferably 4 to 14% by mass, and further preferably 8 to 13% by mass.

[0142] In this embodiment, when the total content of the styrene monomer unit, the unsaturated carboxylic acid monomer unit, and the unsaturated carboxylic acid ester monomer unit is 100 mass %, the content of the unsaturated carboxylic acid ester monomer unit is preferably 0 to 15 mass %, more preferably 1 to 12 mass %, and even more preferably 2 to 10 mass %.

[0143] In this embodiment, the contents of the styrene monomer unit, the unsaturated carboxylic acid monomer unit (e.g., methacrylic acid monomer unit), and the unsaturated carboxylic acid ester monomer unit (e.g., methyl methacrylate monomer unit) in the styrene copolymer resin can be determined by proton nuclear magnetic resonance ( 1 The integrated ratio of the spectrum measured by a H-NMR (spectral) analyzer was obtained.

[0144] In the present embodiment, the styrene-based copolymer resin does not exclude the monomer units containing styrene monomer units and unsaturated carboxylic acid monomers (such as unsaturated carboxylic acid monomer units and unsaturated carboxylic acid ester monomer units) as an example of other monomers within the scope of not damaging the effect of the present invention. However, the styrene-based copolymer resin of the present invention is preferably typically composed of styrene monomer units, unsaturated carboxylic acid monomer units, and / or unsaturated carboxylic acid ester monomer units.

[0145] The styrene-based copolymer resin of the present embodiment may further contain other styrene-based monomers in addition to the styrene monomer.

[0146] The unsaturated carboxylic acid monomer constituting the styrene-based copolymer resin of the present embodiment is not particularly limited, and examples thereof include (meth)acrylic acid (methacrylic acid and / or acrylic acid), maleic anhydride, maleic acid, fumaric acid, and itaconic acid.

[0147] The unsaturated carboxylic acid ester monomer constituting the styrene-based copolymer resin of the present embodiment is not particularly limited, and examples thereof include (meth)acrylates (e.g., methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and cyclohexyl (meth)acrylate). These unsaturated carboxylic acid ester monomers may be used alone or in combination of two or more.

[0148] Suitable styrene-based copolymer resins for the present embodiment include styrene-methacrylic acid copolymers, styrene-methyl methacrylate copolymers, styrene-methacrylic acid-methyl methacrylate copolymers, styrene-acrylic acid copolymers, styrene-methyl acrylate copolymers, styrene-acrylic acid-methyl acrylate copolymers, styrene-methyl methacrylate-butyl methacrylate copolymers, styrene-butyl methacrylate copolymers, and styrene-maleic anhydride copolymers.

[0149] In this embodiment, the weight average molecular weight (Mw) of the styrene copolymer resin is preferably 100,000 to 350,000, more preferably 120,000 to 300,000, and even more preferably 140,000 to 240,000. The weight average molecular weight (Mw) is a value obtained by gel permeation chromatography in terms of standard polystyrene.

[0150] In this embodiment, the polymerization method of the styrene-based polymer resin is not particularly limited. For example, as a free radical polymerization method, bulk polymerization or solution polymerization can be appropriately adopted. The polymerization method mainly includes a polymerization step of polymerizing the polymerization raw materials (monomer components) and a devolatilization step of removing volatile components such as unreacted monomers and polymerization solvent from the polymer product.

[0151] -Optional ingredients-

[0152] The styrene resin composition of the present embodiment may contain, in addition to the styrene polymer and the inclusions contained as needed, any additional components such as conventionally known additives and processing aids as needed, within the scope that does not impair the effects of the present invention. Examples of such additives and processing aids include antioxidants, weathering agents, lubricants, antistatic agents, and fillers.

[0153] Examples of the antioxidant include phenol-based compounds, phosphorus-based compounds, and sulfide-based compounds.

[0154] As the weathering agent, an ultraviolet absorber or the like can be used.

[0155] As the lubricant, fatty acid amide, fatty acid ester, fatty acid, fatty acid metal salt system, etc. can be used.

[0156] As the antistatic agent, cationic, anionic, nonionic, amphoteric, fatty acid partial esters such as glycerol fatty acid monoester, and the like can be used.

[0157] As the filler, talc, calcium carbonate, barium sulfate, carbon fiber, glass fiber, cellulose fiber, mica, wallastonite, whisker, etc. can be used.

[0158] The styrene resin composition of the present embodiment may contain, in addition to the above-mentioned additives and processing aids, an anti-blocking agent, a colorant, an anti-frost agent, a surface treatment agent, an antibacterial agent, an anti-die drool agent (anti-die drool agents such as silicone oils described in Japanese Patent Application Laid-Open No. 2009-120717, monoamide compounds of higher aliphatic carboxylic acids, and monoester compounds obtained by reacting higher aliphatic carboxylic acids with mono- to trivalent alcohol compounds). The total content of the optional added ingredients such as additives and processing aids in the styrene resin composition may preferably be 0% to 6% by mass, more preferably 0.05% to 5% by mass.

[0159] <Preferred embodiment of styrene resin composition>

[0160] A preferred embodiment of the styrene resin composition that serves as a raw material for the method for producing a styrene monomer according to the present embodiment is one in which the total content of the styrene polymer and any added components is 50 to 100% by mass, the content of impurities is 1 to 30% by mass, and the styrene resin composition can be a recycled styrene resin composition containing a styrene polymer that is used, discarded, or discarded and recycled.

[0161] By using a recycled styrene-based resin composition containing a styrene-based polymer that has been used, discarded, or recycled as a raw material for a production method, it is possible to reduce environmental load.

[0162] <Preferred Form of Mixed Liquid>

[0163] As a preferred embodiment of the mixed liquid obtained by the mixed liquid preparation process of this embodiment, the total content of the styrene-based polymer, the solvent and any added components can be preferably 50 to 100 mass% relative to the entire mixed liquid, more preferably 50 mass% or more and less than 100 mass%, and the content of inclusions is preferably 0 to 30 mass%, more preferably more than 0 mass% and less than 10 mass%.

[0164] <Mixing or kneading conditions in the mixed solution preparation process>

[0165] The mixed solution of this embodiment only needs to contain a styrene resin composition and a solvent, wherein the styrene resin composition contains a styrene polymer, and the styrene polymer contains styrene monomer units. The dispersion state of the solvent in the styrene resin composition is not particularly limited, and can be preliminarily mixed using a known mixing mechanism or kneading mechanism before or during the purification step described below.

[0166] The mixing mechanism or kneading mechanism for mixing the styrene resin composition and the solvent is not particularly limited, and is preferably a method for uniformly mixing the components in the mixed solution, and may be melt mixing or melt kneading as required. Specific examples of the mixing or kneading mechanism include a magnetic stirrer, a Three-One Motor stirrer, a single screw extruder, a twin screw extruder, a screw extruder, an open roll mill, a kneader, a Banbury mixer, or an internal mixer.

[0167] The mixing or kneading time in the mixed solution preparation step is preferably about 1 to 240 minutes, more preferably 1 to 120 minutes, further preferably 2 to 120 minutes, and even more preferably 5 to 120 minutes.

[0168] The temperature of the mixing environment in the mixed solution preparation process is preferably 0 to 260° C., more preferably 10 to 100° C., and even more preferably 20 to 80° C. Further, in the case of mixing, the pressure in the mixing mechanism (or in the mixing device) is preferably such that the pressure difference between atmospheric pressure and the pressure is within ±500 hPa, more preferably within ±300 hPa. In addition, as needed, the mixing mechanism (or in the mixing device) can be replaced with an inert gas. Specific examples of the inert gas include nitrogen, argon, carbon dioxide, and the like.

[0169] <Preparation process>

[0170] In the method for producing styrene monomer disclosed herein, for example, a preparatory step of preparing a raw material, i.e., a styrene resin composition, may be further included before the mixed solution preparation step. Examples of the preparatory step include a step of recycling waste plastics containing styrene resins generated by the market or consumers (post-consumer products) and reusing them as a raw material, i.e., a styrene resin composition (post-consumer), and / or a step of recycling products such as scraps from manufacturing before they are circulated to consumers or the market (pre-consumer products) and reusing them as a raw material, i.e., a styrene resin composition (pre-consumer).

[0171] As a preparation process for preparing a styrene resin composition using post-consumer products and / or pre-consumer products, a method preferably includes a pulverization process of pulverizing waste plastics containing styrene resins, a washing process of washing the pulverized waste plastics, or a sorting process of sorting the pulverized waste plastics.

[0172] On the other hand, as a preparation step for preparing a styrene-based resin composition using materials such as pre-consumer raw pellets, a method including a pulverization step of pulverizing the raw material containing the styrene-based resin is preferred.

[0173] (Purification step: S2)

[0174] The method for producing styrene monomer according to the present embodiment includes a purification step of purifying the mixed liquid prepared in the mixed liquid preparation step by passing it through a purification unit, thereby removing impurities that may be mixed in the mixed liquid.

[0175] The purification mentioned here refers to a process of removing impurities, mixed materials and other inclusions from the styrene resin composition so that the concentration of the styrene polymer contained in the mixed liquid after the purification step is higher than the concentration of the styrene polymer contained in the mixed liquid before the purification step.

[0176] The purification unit in this embodiment is not particularly limited as long as it is an apparatus that can accommodate the mixed liquid, and a known purification mechanism can be used to perform preliminary purification before or simultaneously with the devolatilization step described below.

[0177] As the purification mechanism, there is no particular limitation, but a unit that purifies each component in the mixed solution uniformly is preferred. As a specific example of the purification mechanism, filtration, decantation, centrifugation, centrifugal sedimentation, spiral decanter, filter, screen or filter, etc. can be cited. The purification mechanism can be a separate unit, or it can be a unit combining two or more. Among them, a purification mechanism that can be continuously processed (for example, centrifugation, filtration, spiral decanter, filter, screen or filter) is preferred, and a purification mechanism that combines centrifugation and filtration is more preferred. Thus, by removing the foreign matter that may be mixed into the mixed solution by centrifugation, the time efficiency of the filtration (for example, the processing speed) can be improved. Regarding the time required for purification, as the time from the time the mixed solution is added to the purification unit to the time the purified mixed solution obtained by the purification unit is obtained, for example, preferably about 1 second to 240 minutes.

[0178] The centrifugal separation used in this embodiment preferably uses a centrifuge. Moreover, the centrifuge is a device that has a rotating body (basket) with holes or slits on the side surface, and generates centrifugal force by rotating the rotating body to separate solids and liquids or separate substances with different specific gravities. The centrifuge preferably performs centrifugal separation within a range of centripetal acceleration of 200 to 20,000 G. Moreover, the rotating body preferably has a cross-sectional shape in the vertical direction including its rotation axis having a roughly cylindrical or roughly truncated cone-shaped profile. The lighter-specific-gravity agglomerates contained in the mixed liquid are supplied to the interior of the rotating body of the centrifuge and are centrifuged, thereby becoming floating components, gathering on the side of the rotating body close to the rotation axis, and being separated from the remaining mixed liquid.

[0179] As the centrifugal separator, for example, a disc centrifuge or a screw decanter centrifuge is preferable.

[0180] In this embodiment, to efficiently remove foreign matter that may be present in the mixed liquid, a filter (e.g., a bag made of nonwoven fabric or a resin sheet, etc.) as described below may be placed along the inner wall of the centrifuge's rotor. By placing the bag made of nonwoven fabric or a resin sheet along the inner wall of the rotor, a dual effect of centrifugal sedimentation and centrifugal filtration can be achieved. Thus, foreign matter accumulated within the rotor can be removed from the rotor along with the filter, nonwoven fabric, or resin sheet bag.

[0181] The filtration used in this embodiment is preferably filtration using a filter. The filter may contain a filter aid on the filter surface and / or inside the filter. From the viewpoint of reducing scratches and particles, the mesh size of the filter is preferably less than 1 / 10 of the average particle size of the filter aid, more preferably less than 1 / 20, and further preferably less than 1 / 30. From the viewpoint of preventing leakage of the aid, the upper limit of the mesh size of the filter is preferably less than 10 μm, more preferably less than 5 μm, and further preferably less than 3 μm. In addition, from the viewpoint of increasing the overnight speed of the filter, the lower limit of the mesh size of the filter is preferably greater than 0.1 μm, more preferably greater than 0.2 μm, and further preferably greater than 0.3 μm.

[0182] Examples of the filter material include filter paper, polyethylene, polypropylene, polyethersulfone, polyphenylene sulfide, cellulose acetate, nylon, polycarbonate, plastics such as Teflon (registered trademark), ceramics, and metal mesh.

[0183] The shape of the filter is not particularly limited, but is preferably a sheet-shaped, cylindrical, disc-shaped, or pleated-shaped filter from the viewpoints of ease of handling and reduction of scratches and particles.

[0184] The conditions for filtration using the filter are not particularly limited. From the perspective of improving filtration accuracy and productivity, the pressure difference during filtration is preferably 0.008 to 10 MPa, more preferably 0.05 to 1 MPa. In addition, from the perspective of improving filtration accuracy and productivity, the number of filter stages is preferably 1 to 5, more preferably 1 to 3. In addition, from the perspective of improving filtration accuracy and productivity, the filtration speed is preferably 0.1 L / (min·m 2 ) or more, more preferably 5 L / (min·m 2 )above.

[0185] In addition, when a filter cloth is used as a filter, the air permeability (ventilation rate) of the filter can be 1 or more and 3000 cm 3 / cm 2 min or less, preferably more than 1 and less than 3000 cm 3 / cm 2 min, more preferably 20 or more and less than 2500 cm 3 / cm 2 ·min.

[0186] The material of the filter cloth is preferably a material with low solubility in the solvent (for example, 100 parts by mass of solvent is added to 1 weight of the filter cloth, immersed at 40°C for 1 hour, solid-liquid separation is performed, the filter cloth is recovered as a solid component, and the weight when vacuum-dried at an ambient temperature of 100°C for 1 hour shows a weight change of less than 10% compared with the initial weight of the filter cloth), and is made of metal, nylon, fluororesin (polytetrafluoroethylene, etc.), PPS, PAEK (polyaryletherketone), polyester, polypropylene, polyethylene, and more preferably stainless steel, nylon, fluororesin (polytetrafluoroethylene, etc.), PPS, and PAEK.

[0187] The filter cloth may be woven in a plain weave, a damask weave (also called a twill weave), or a satin weave, preferably a damask weave.

[0188] In the purified mixed liquid obtainable by the purification unit, the content of the styrene-based polymer in the mixed liquid is preferably 5 mass % to 100 mass %, more preferably 5 mass % to 50 mass %, based on the entire purified mixed liquid.

[0189] In addition, in the purified mixed liquid obtained by the purification unit, the content of inclusions in the mixed liquid is preferably 30% by mass or less, and more preferably 20% by mass or less, relative to the total content of the purified mixed liquid. It should be noted that the content of inclusions in the purified mixed liquid is the value obtained by subtracting the total content of the styrene polymer and the content of the solvent from the mixed liquid. Furthermore, the purified mixed liquid may contain other resins that do not substantially contain styrene monomer units, such as olefin resins, polyether resins, polyester resins, or polyamide resins.

[0190] In the purification process or purification unit of this embodiment, an auxiliary agent (so-called filter aid) such as diatomaceous earth, perlite, powdered silica, powdered activated carbon, or aluminum silicate may be added to the mixed liquid prepared in the mixed liquid preparation step as needed to improve purification efficiency. These auxiliary agents not only improve the removal efficiency of inclusions (e.g., pigments, other resins, or other inorganic substances) in the purification unit, or the removal efficiency of particles that are difficult to remove without the auxiliary agents, but also help remove and / or reduce chemical substances that are not needed in the production and recovery of styrene monomer from the mixed liquid by utilizing the chemical and / or physical adsorption effects of the auxiliary agents in the mixed liquid, as well as by utilizing the inclusion and / or loading of the auxiliary agent aggregates in the mixed liquid. The inclusion and / or loading of the auxiliary agent aggregates in the mixed liquid includes the effect of surrounding specific components in the mixed liquid with aggregates of the auxiliary agent particles, thereby creating a condition that prevents them from diffusing into the mixed liquid.

[0191] The additive is preferably in a granular form. In this case, the volume average particle size (D50) of the additive is preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm. The average particle size (D50) of the additive is measured using a laser diffraction particle size analyzer (manufactured by Shimadzu Corporation, trade name "SALD-2300"), and the volume average particle size D50 is determined from the 50% value of the obtained particle size distribution.

[0192] The amount of the additive added to the purification unit is preferably 50% by mass or less, more preferably 0.001% by mass or more and 45% by mass or less, and even more preferably 0.1% by mass or more and 30% by mass or less, relative to the total weight of the mixed solution. It should be noted that the amount of the additive relative to the total weight of the inclusions in the mixed solution is preferably 100% by mass or less, more preferably 0.01% by mass or more and 50% by mass or less, and even more preferably 0.1% by mass or more and 40% by mass or less.

[0193] As the method for adding the auxiliary agent, the auxiliary agent described later can be added to the mixing or kneading in the mixed solution preparation process as the so-called body-feed method. In addition, the auxiliary agent can also be added to the mixed solution purified by the purification unit. In this case, the mixing method of the auxiliary agent added to the mixed solution and the mixing method of the mixed solution containing the auxiliary agent are not particularly limited. It is preferred that the various components in the mixed solution are uniformly mixed, and it can also be melt mixing or melt kneading as needed. As a specific example of the mixing or kneading mechanism, a magnetic stirrer, a Three-One Motor stirrer, a single screw extruder, a twin screw extruder, a screw extruder, an open roll mill, a kneader, a Banbury mixer or a closed mixer can be cited.

[0194] The time for mixing or kneading the purified mixed liquid with the auxiliary agent is preferably about 1 to 240 minutes, more preferably 1 to 120 minutes, further preferably 2 to 120 minutes, and even more preferably 5 to 120 minutes.

[0195] The temperature at which the purified mixed solution mixed or kneaded with the auxiliary agent is mixed or kneaded is preferably 0 to 260° C., more preferably 10 to 100° C., and even more preferably 20 to 80° C. Furthermore, in the case of mixing, the pressure in the mixing mechanism (or in the mixing device) is preferably such that the pressure difference between atmospheric pressure and the pressure is preferably within ±500 hPa, more preferably within ±300 hPa. In addition, as needed, the mixing mechanism (or the mixing device) can be replaced with an inert gas. Specific examples of the inert gas include nitrogen, argon, carbon dioxide, and the like.

[0196] Alternatively, as a different method for adding the auxiliary agent, a method can be employed in which the auxiliary agent or a dispersion of the auxiliary agent is added to the interior or exterior of the purification mechanism, and then the mixed solution is contacted with the auxiliary agent to perform purification. The dispersion is preferably a liquid at room temperature and pressure that facilitates uniform dispersion of the auxiliary agent. The solvent is preferably selected from the solvents of this embodiment, and examples of the solvent include one or more solvents selected from the group consisting of acetone, chloroform, methyl ethyl ketone, benzene, tetrahydrofuran, toluene, ethylbenzene, and styrene. The solvent may be a single solvent or a mixture of two or more solvents.

[0197] In this case, specific examples of the purification mechanism include filtration, decantation, centrifugation, centrifugal sedimentation, a spiral decanter, or a filter. The time required for purification, which is the time from the injection of the mixed solution into the purification unit to which the auxiliary agent or a dispersion of the auxiliary agent has been added in advance to the inside or the outer surface of the purification unit until the purified mixed solution is obtained by the purification unit, is preferably about 1 second to 240 minutes, for example.

[0198] (Devolatile process: S3)

[0199] The method for producing a styrene monomer according to the present embodiment includes a devolatilization step of devolatilizing the solvent component (including the solvent and the solvent contained in the raw material styrene resin composition) contained in the mixed liquid purified in the purification step to obtain a fluid.

[0200] This has the effect of volatilizing low molecular weight components and distilling off the solvent.

[0201] In this specification, the product obtained by subjecting the purified mixed liquid to a devolatilization step is referred to as a fluid.

[0202] The devolatilization step of this embodiment is not particularly limited as long as it is a step using an apparatus that can accommodate the mixed liquid, and a known devolatilization apparatus can be used to perform preliminary devolatilization before or simultaneously with the pyrolysis step described below.

[0203] The devolatilization step is not particularly limited, but preferably uniformly removes volatile components from the purified mixed liquid. Specific examples of the devolatilization step include conventional devolatilization devices such as flash drums, flash tank polymer heaters, twin-screw devolatilizers, thin-film evaporators, and extruders. Among these, devolatilization devices with a small retention area are preferred.

[0204] The temperature of the devolatilization treatment in the devolatilization step (e.g., the temperature inside the devolatilizer) is generally about 100 to 280° C., more preferably 190 to 260° C. The pressure of the devolatilization treatment (e.g., the pressure inside the devolatilizer) is generally about 0.13 to 5.0 kPa, preferably 0.13 to 4.5 kPa, more preferably 0.13 to 4.0 kPa.

[0205] Preferred devolatilization steps in this embodiment include, for example, a method in which the purified mixed liquid is heated at 100 to 280° C. in a devolatilizer while reducing the pressure in the devolatilizer to remove volatile components, and a method in which volatile components are removed using an extruder or the like provided for the purpose of removing volatile components.

[0206] For example, if the viscosity of the fluid needs to be adjusted, residual solvent may be included as a result of the devolatilization process, or solvent may be added using the mixing mechanism or kneading mechanism described above to adjust the viscosity. In this case, the added solvent may be preheated, and the temperature of the prepared fluid is preferably about 50 to 280°C, more preferably 190 to 260°C.

[0207] In the fluid, the content of the solvent in the fluid is preferably 90% by mass or less, and more preferably 50% by mass or less, based on the entire fluid.

[0208] Furthermore, in the fluid, the content of the styrene-based polymer in the fluid is preferably 10% by mass or more and 100% by mass or less, and more preferably 50% by mass or more and 100% by mass or less, relative to the entire fluid.

[0209] The content of foreign substances that may be contained in the fluid obtained in the devolatilization step is a value obtained by subtracting the total content of the styrene-based polymer and the content of the solvent from the fluid.

[0210] <Solvent recovery and purification process>

[0211] The method for producing styrene monomer according to this embodiment may, as needed, include a step of recovering the solvent component removed by distillation from the purified mixed liquid in the devolatilization step (S3) to purify the solvent by distillation (=solvent recovery and purification step). Furthermore, the solvent purified in the solvent recovery and purification step (=so-called regenerated solvent) can be reused in the mixed liquid preparation step (S1). Furthermore, the residue obtained in the solvent recovery and purification step, excluding the purified regenerated solvent, can be discharged and used as fuel in the first pyrolysis step (S4).

[0212] The distillation method can appropriately adopt known distillation conditions depending on the type of solvent used.

[0213] (First Pyrolysis Step: S4)

[0214] The method for producing styrene monomer of this embodiment includes a first pyrolysis step of pyrolyzing the fluid prepared in the devolatilization step. Thus, by using a fluid containing a high concentration of styrene-based polymers, the fluid is thermally decomposed into a high concentration of styrene monomer.

[0215] The fluid may contain a styrene resin composition containing a styrene polymer comprising styrene monomer units. The fluid may be pre-pyrolyzed before or during the first pyrolysis step. Furthermore, the aforementioned optional additives may be added to the fluid as needed before and / or during the pyrolysis step.

[0216] In the fluid, the content of the styrene-based polymer in the fluid is preferably 10% by mass or more and 100% by mass or less, and more preferably 50% by mass or more and 100% by mass or less, based on the entire fluid.

[0217] As a method for pyrolyzing a fluid according to this embodiment, a first pyrolysis step may be performed in which, for example, after the pyrolysis device is filled with the fluid, the fluid is heated in an environment (e.g., the temperature inside the pyrolysis device) at a temperature of 400 to 800°C, preferably 450 to 600°C, and more preferably 450 to 580°C. Furthermore, in this case, the temperature of the fluid being filled is approximately 50 to 280°C, more preferably 190 to 260°C. Furthermore, a first pyrolysis step may be performed in which the pyrolysis device is previously heated and filled with the fluid. In this case, the temperature inside the pyrolysis device, when the pyrolysis device is previously heated, is 400 to 800°C, preferably 450 to 600°C, and the temperature of the fluid being filled is approximately 50 to 280°C, more preferably 190 to 260°C. Since the pyrolysis temperature of styrene-based polymers (e.g., polystyrene, rubber-modified polystyrene-based resins, and styrene-based copolymer resins) is approximately 330-380°C, by setting the temperature range of the pyrolysis device above, the majority of the generated pyrolysis steam can be converted into pyrolysis products of the styrene-based polymer. Furthermore, by subjecting the fluid to this first pyrolysis step, other resins such as polyolefin-based resins that may be included in the raw material styrene-based resin composition containing the styrene-based polymer, which contains styrene monomer units, can be removed.

[0218] In this embodiment, the first pyrolysis step can be performed under reduced pressure or normal pressure, but is preferably performed under reduced pressure. The reaction pressure in the first pyrolysis step is preferably 1 to 100 kPa, more preferably 2 to 50 kPa, and even more preferably 3 to 30 kPa.

[0219] Since the first pyrolysis step needs to be performed at a temperature at which the raw material is heated and evaporated to form a gasified raw material, performing this step under reduced pressure can achieve the effect of suppressing the generation of by-products during decomposition.

[0220] The pyrolysis device of this embodiment can use a known pyrolysis device. For example, the pyrolysis device of this embodiment includes: a pyrolysis device connected for introducing the fluid, a raw material supply pump for supplying the fluid, and a heating mechanism (such as a hot plate, electric heating wire, or hot air furnace) provided on the periphery of the pyrolysis device. A storage tank may also be provided in which the fluid is stored before being connected to the pyrolysis device.

[0221] The type of pyrolysis apparatus used in the first pyrolysis step is not particularly limited, and a known method can be used. For example, a general pyrolysis method such as an externally heated rotary kiln pyrolysis apparatus or a fluidized bed pyrolysis apparatus can be used.

[0222] Furthermore, if necessary, a device for supplying a polymerization inhibitor may be used to intermittently or continuously supply the polymerization inhibitor to suppress the polymerization reaction of the polymerizable components contained in the pyrolysis liquid.

[0223] As an example of the pyrolysis device of this embodiment, there is Figure 3 The device shown.

[0224] Specifically, the pyrolysis device 10 includes a cylindrical pyrolysis section 1 having an opening 2 and an outlet 3 provided at each end thereof, and a pyrolysis furnace 5 surrounding the pyrolysis section 1. Furthermore, the outlet 3 is fluidically connected to a liquefaction device L for cooling pyrolysis steam via a connection portion C1P (e.g., a tubular body such as a glass tube).

[0225] Moreover, in Figure 3In one example of the pyrolysis furnace 5 shown, a tubular pyrolysis section 1 is covered by the pyrolysis furnace 5 (more specifically, the furnace wall of the pyrolysis furnace 5), and a cavity is formed between the pyrolysis furnace wall and the tubular pyrolysis section 1, and a structure having various heating units is provided in the cavity. As the heating unit, for example, a heating unit that can control the temperature within a specified range by supplying a heat medium (heating gas) into the cavity of the pyrolysis furnace 5 can be cited. If the inlet for the heat medium (heating gas) fed into the cavity of the pyrolysis furnace 5 is provided near the opening 2 for supplying the fluid, the ambient temperature to which the resin composition supplied to the pyrolysis section 1 through the opening is too high and can be heated rapidly, which is preferred from the viewpoint of suppressing the formation of pyrolysis residues.

[0226] When a fluid is supplied from the opening 2, the raw material composition moves along the process flow direction (direction of the arrow) inside the cylindrical pyrolysis section 1 heated by the pyrolysis furnace 5, and is converted into pyrolysis steam. The raw material composition flows from the discharge port 3 through the connection portion C1P (e.g., a tubular body) in the form of pyrolysis steam to the liquefaction device L, which cools the pyrolysis steam to prepare a (first) pyrolysis liquid.

[0227] Furthermore, in the pyrolysis apparatus 10 of this embodiment, in order to regulate the amount of pyrolysis steam generated within the cylindrical pyrolysis section 1 and discharge it to the outside, the cylindrical pyrolysis section 1 may be provided with a vent hole (not shown) and a pipe body through which the pyrolysis steam flowing out of the vent hole (not shown) can be ventilated. This pipe body may extend, for example, to the vicinity of the outlet 3 of the pyrolysis section 1. Thus, as needed, the pyrolysis steam flowing out of the vent hole (not shown) can be recovered through the pipe body, which is equipped with a valve or the like.

[0228] In this specification, "pyrolysis" refers to chemical decomposition of organic matter or the like by heating in the absence of oxygen or the like.

[0229] Furthermore, in the first pyrolysis step, the fluid may be heated to generate a first pyrolysis liquid. More specifically, it is preferred that in the first pyrolysis step, the pyrolysis vapor containing the styrene monomer is cooled to generate the first pyrolysis liquid. Specifically, the pyrolysis vapor generated by heating the fluid using the pyrolysis device is cooled to generate the first pyrolysis liquid containing the styrene monomer. The temperature at which the pyrolysis vapor is cooled may preferably be above -30°C and the boiling point T of the styrene monomer is preferably within the range of 100°C. sb (°C) or lower, more preferably -20°C to 80°C.

[0230] As a result, olefin hydrocarbon compounds (such as ethylene or propylene) having a boiling point of -30°C or less will not be liquefied or will be difficult to liquefy in most cases, and thus low-boiling-point monomers, which are decomposition products of other resins such as polyolefin resins that may be contained in the styrene resin composition, can be effectively removed. sb The fraction below 0.1°C can be stored separately and used as a combustion raw material for the pyrolysis device.

[0231] Furthermore, the pyrolysis steam generated by heating the fluid in the first pyrolysis step is cooled to the boiling point T of the styrene monomer. sb (℃) or higher and 450℃ or lower to obtain the first pyrolysis liquid, i.e., the high boiling point component, which is liquefied by the liquefaction device and then dripped into the pyrolysis device again, thereby returning to the pyrolysis device and performing the pyrolysis process again. In addition, the generated pyrolysis steam can be cooled to -30℃ or higher and the boiling point T of the styrene monomer by the liquefaction device. sb (°C) or lower, and is obtained as a part of the second pyrolysis liquid described later.

[0232] As a method for cooling the pyrolysis steam, a liquefaction device is preferably used. A known liquefaction device can be used as the liquefaction device. For example, various heat removal solvents such as water that can be cooled to the cooling temperature, or cooling pipes that utilize the heat removal effect of heat removal elements composed of metals and other inorganic materials can be used.

[0233] Furthermore, as needed, a reforming device for reforming the components of the pyrolysis steam (for example, including dechlorination, adsorption of odorous or coloring components, removal of acidic or alkaline components, heating treatment, etc.) may be fluidly connected between the pyrolysis device and the liquefaction device.

[0234] Furthermore, if necessary, an analysis step of analyzing the first pyrolysis liquid may be provided. In this analysis step, properties such as the concentration of styrene monomer in the first pyrolysis liquid, the temperature of the first pyrolysis liquid, and the viscosity of the first pyrolysis liquid may be evaluated.

[0235] <Cooling pipe attachment>

[0236] During research into the method for producing styrene monomer according to this embodiment, it was confirmed that deposits sometimes form on the cooling pipes during the cooling process in the first pyrolysis step. Such deposits on the cooling pipes reduce the thermal efficiency of the pyrolysis apparatus, resulting in reduced pyrolysis efficiency, potentially leading to blockage of piping and reduced processing capacity. Furthermore, when the pyrolysis vapor generated during the pyrolysis of the fluid in the first pyrolysis step is cooled to produce the first pyrolysis liquid, there is a concern that such deposits could reduce cooling efficiency.

[0237] In the method for producing styrene monomer according to the present embodiment, since the amount of foreign matter contained in the fluid reaching the first pyrolysis step is substantially reduced, it is considered that the amount of matter adhering to the cooling pipe is reduced.

[0238] In this embodiment, the first pyrolysis step preferably involves heating the fluid to obtain pyrolysis vapor containing styrene monomer, and then cooling the pyrolysis vapor using a liquefaction device to generate a first pyrolysis liquid. More specifically, the pyrolysis vapor containing styrene monomer generated by heating the fluid at a predetermined temperature and a predetermined pressure using a pyrolysis device is cooled to generate a first pyrolysis liquid containing styrene monomer. The temperature at which the pyrolysis vapor is cooled may preferably be above -30°C and the boiling point T of the styrene monomer may be less than 0. sb (°C) or lower, more preferably -20°C to 80°C.

[0239] As the first pyrolysis step, for example, using Figure 3 In the case of a pyrolysis device, the outlet 3 is fluidly connected to the liquefaction device. Therefore, it has been confirmed that when the generated pyrolysis vapor containing styrene monomer is injected into the liquefaction device, deposits may be generated inside the pipe (also called cooling pipe or heat exchange inner wall) in the liquefaction device from the connection portion (so-called connecting pipe) where the pyrolysis device and the liquefaction device are fluidly connected (see Figure 7 or Figure 8 Therefore, an investigation into this deposit revealed that a high concentration of a specific component (hereinafter referred to as an adhesion inducer) in the resulting first pyrolysis liquid resulted in an increase in the amount of deposits deposited on the inner walls of the cooling pipe or heat exchanger (including the connection portion connecting the pyrolysis unit and the liquefaction unit to the pipe within the liquefaction unit). Furthermore, it was confirmed that the amount of adhesion inducers and deposits deposited on the inner walls of the cooling pipe or heat exchanger decreased when the type of solvent used and the conditions of the purification process were set to specified levels.

[0240] In more detail, when using Figure 3 When the styrene monomer of this embodiment is produced by using the pyrolysis device 10 shown and the liquefaction device L connected to the pyrolysis unit 1 of the pyrolysis device 10 via the connection portion C1P (glass tube), Figure 6 The image shows that the connecting portion C1P (glass tube) is transparent before the start of the first pyrolysis process. However, during the pyrolysis operation, the connecting portion C1P (glass tube) becomes blurred, and a thin film of milky white attachment is observed on the inner wall of the connecting portion C1P (see Figure 7 ). In addition, during the pyrolysis operation, it was confirmed that the black substance Res adhered to the entire surface of the connecting portion C1P and the inner wall of the liquefaction device L, and was close to being blocked (refer to Figure 8 ).

[0241] In this embodiment, the first pyrolysis step is a step of heating the fluid to obtain pyrolysis vapor containing styrene monomer and then cooling the pyrolysis vapor to generate the first pyrolysis liquid. The concentration of the adhesion inducer contained in the first pyrolysis liquid is preferably less than 0.2% by mass.

[0242] As described above, during the investigation of deposits on the inner wall surfaces of cooling pipes or heat exchangers, it was confirmed that there is a certain correlation between the amount of deposits on the inner wall surfaces of cooling pipes or heat exchangers and the amount of deposits contained in the first pyrolysis liquid. However, by setting the concentration of the deposits contained in the first pyrolysis liquid to less than 0.2% by mass, the amount of deposits on the inner wall surfaces of cooling pipes or heat exchangers can be reduced. In addition, as shown in the Examples and Comparative Examples described below, if the concentration of the deposits contained in the first pyrolysis liquid is less than 0.2% by mass, then Figure 6 As shown in the image, the glass tube of the connecting portion C1P remains transparent, and no thin film of milky white deposits is confirmed on the inner wall of the cooling tube or the heat exchanger. On the other hand, if the concentration of the adhesion inducer contained in the first pyrolysis liquid is 0.2% by mass or more, as shown in FIG. Figure 7 As shown, the glass tube of the connection portion C1P was confirmed to be turbid, or a thin film of milky white deposits was observed on the inner walls of the cooling tube and heat exchanger. Furthermore, when the system was operated with the deposits adhered to the inner walls, it was confirmed that black material Res adhered to the entire surface of the inner walls of the connection portion C1P and the liquefaction unit L, approaching clogging.

[0243] The concentration of the adhesion inducer contained in the first pyrolysis liquid may be 0 to less than 0.2 mass %, preferably more than 0 mass % and less than 0.19 mass %, and more preferably more than 0 mass % and less than 0.18 mass % relative to the entire first pyrolysis liquid.

[0244] However, from the viewpoint of long-term operation, the amount of the adhesion inducer in the first pyrolysis liquid is preferably less than 0.2% by mass.

[0245] The "adhesion inducer" in this specification refers to the pyrolysis components of inclusions, which may be inorganic salts (especially substances containing elements from periods 2 to 5 within groups 1 to 17 of the periodic table), or low-molecular organic compounds with a melting point of 100°C or less and a molecular weight (or number average molecular weight) of 10 to 1000 (especially substances with a melting point of 40°C or less as a monomer compound), polyethylene, polypropylene, polyacetal (especially polyoxymethylene), polyamide (especially polyamide 6, polyamide 66), polyvinyl chloride, polyester (especially polyethylene terephthalate, polybutylene terephthalate), polyether, polyphenylene ether (especially modified polyphenylene ether) and other resins, especially resins with a weight average molecular weight (Mw) of less than 100,000.

[0246] (Recovery process: S5)

[0247] The method for producing a styrene monomer according to the present embodiment preferably includes, as necessary, a recovery step of recovering the styrene monomer from the first pyrolysis liquid containing the styrene monomer produced in the first pyrolysis step.

[0248] Thus, styrene monomer is recovered via the pyrolysis liquid from which foreign substances and low-volatile substances (solvent, olefin-based hydrocarbon-based compounds, etc.) are removed in the devolatilization step.

[0249] Furthermore, it is more preferred that the recovery step recover the styrene monomer from the first pyrolysis liquid containing styrene monomer by distillation. In other words, for example, the recovery step is preferably a distillation recovery step in which the styrene monomer is recovered from the first pyrolysis liquid containing styrene monomer by distillation. The distillation recovery step is preferably performed in two or more stages using two or more distillation towers. Furthermore, it is preferred that an inert gas (e.g., nitrogen, a rare gas, etc.) from an inert gas supply source be filled into these two or more distillation towers, and distillation be performed while replacing the air inside the distillation towers with the inert gas.

[0250] The distillation temperature in the distillation recovery step is preferably, for example, in the range of 50 to 200°C, and more preferably in the range of 50 to 150°C. For example, in the distillation recovery step, when the first pyrolyzed liquid is distilled in two stages using two distillation columns, the distillation temperature of the first distillation in the two stages is, for example, in the range of 50 to 200°C, and preferably in the range of 50 to 150°C. Furthermore, the distillation temperature of the second distillation in the two stages is, for example, in the range of 50 to 200°C, and preferably in the range of 50 to 150°C.

[0251] The pressure of the distillation environment in the distillation recovery step (for example, the pressure in the distillation column) is preferably 10 to 70 Torr, more preferably 20 to 60 Torr.

[0252] When the first pyrolysis liquid is distilled under the above-mentioned distillation conditions, it is separated into a fraction containing styrene monomer at a high concentration (so-called light component) and a fraction having a lower styrene monomer concentration than this fraction (so-called heavy component).

[0253] For example, in the distillation recovery step, when the first pyrolyzed liquid is distilled in two stages using two distillation towers, components with lower boiling points (e.g., including toluene, etc.) become light components in the first distillation tower, while components with higher boiling points (e.g., including styrene monomer, etc.) become heavy components. Preferably, after the light components are exhausted, the heavy components are distilled again in the second distillation tower to separate them into a fraction containing a high concentration of styrene monomer and a fraction with a lower styrene monomer concentration than the fraction, thereby recovering the styrene monomer. It should be noted that a polymerization inhibitor may be used in the distillation recovery step to prevent polymerization of the styrene monomer.

[0254] The first pyrolysis liquid only needs to contain styrene monomer, and preliminary pyrolysis can be performed before or simultaneously with the recovery process. Furthermore, during the first pyrolysis process and / or in the recovery process after the first pyrolysis process, any additional components can be added to the fluid as needed to suppress the polymerization reaction of the generated styrene monomer.

[0255] In this embodiment, as a method for recovering styrene monomer, a known recovery method can be used. For example, a distillation tower is fluidly connected to the distillation tower, and the distillation tower distills the first pyrolysis liquid, which can separate low-boiling point components such as benzene or toluene from crude styrene monomer (styrene monomer with a purity of less than 90%). Furthermore, in order to improve the purity of the separated crude styrene monomer, the distillation tower can also be fluidly connected to a distillation tower that distills the crude styrene monomer. Moreover, as needed, a dechlorination device that dechlorinates the components in the pyrolysis liquid can also be fluidly connected between the pyrolysis device and the distillation tower.

[0256] (First Distillation Step (S6))

[0257] The method for producing styrene monomer according to this embodiment preferably distills the first pyrolysis liquid, as needed, to separate it into a first fraction containing styrene monomer and a second fraction having a lower styrene monomer concentration than the first fraction. This allows the recovery of the second fraction containing styrene monomer at a lower concentration, or the recovery of the first fraction containing styrene monomer, styrene dimer, and styrene trimer at a higher concentration than the second fraction. The ability to recover the fraction containing a higher concentration of styrene monomer can improve the yield of styrene monomer.

[0258] That is, when the styrene resin composition is pyrolyzed in the first pyrolysis step, styrene dimers and styrene trimers may be contained as by-products in the first pyrolysis liquid. Therefore, if these styrene dimers and styrene trimers can be effectively utilized, the yield of styrene monomer can be increased.

[0259] As a method for separating the first pyrolysis liquid into a first fraction containing styrene monomer, styrene dimer, and styrene trimer and a second fraction having a lower styrene monomer concentration than the first fraction by distillation, distillation using a distillation column is preferred.

[0260] Therefore, the method for producing styrene monomer of the present embodiment preferably includes a first distillation step as needed, in which the first pyrolysis liquid is distilled to separate into a first fraction containing styrene monomer, styrene dimer, and styrene trimer and a second fraction having a lower styrene monomer concentration than the first fraction.

[0261] This first distillation step is preferably performed in one or more stages using one or more distillation columns. Furthermore, it is preferred that these one or more distillation columns be filled with an inert gas (e.g., nitrogen, a rare gas, etc.) from an inert gas supply source, and distillation be performed while the air inside the distillation column is replaced with the inert gas.

[0262] The distillation temperature in the first distillation step is preferably, for example, in the range of 50 to 200° C., more preferably 50 to 150° C. For example, in the first distillation step, when the first pyrolyzed liquid is distilled in a single stage using a single distillation column, the distillation temperature in the single stage of distillation is, for example, in the range of 50 to 200° C., preferably 50 to 150° C.

[0263] The pressure of the distillation environment in the first distillation step (for example, the pressure in the distillation column) is preferably 10 to 70 Torr, more preferably 20 to 60 Torr.

[0264] If the first pyrolysis liquid is distilled under the above-mentioned distillation conditions, it is separated into a first fraction (so-called high-boiling-point component) containing styrene monomer, styrene dimer and styrene trimer and a second fraction (so-called low-boiling-point component) having a lower styrene monomer concentration than the first fraction.

[0265] The difference between the styrene monomer concentration in the first fraction and the styrene monomer concentration in the second fraction is preferably such that the styrene monomer concentration in the first fraction is approximately twice or more the styrene monomer concentration in the second fraction.

[0266] For example, in the first distillation step, when the first pyrolyzed liquid is distilled in a single stage using a single distillation column, components with relatively low boiling points (such as toluene) become low-boiling-point components in the distillation column, while styrene monomer and styrene dimers / trimers become high-boiling-point components. Note that a polymerization inhibitor may be used in the first distillation step to prevent polymerization of the styrene monomer.

[0267] (Second Distillation Step (S7))

[0268] The method for producing styrene monomer of the present embodiment is preferably, as needed, to distill the first fraction and separate it into a third fraction containing styrene monomer and a fourth fraction having a styrene monomer concentration lower than that of the third fraction. Thus, styrene monomer can be recovered from the third fraction containing styrene monomer at a high concentration. Alternatively, a fourth fraction containing styrene dimer and styrene trimer at a high concentration compared to the third fraction can be recovered. Thus, since the fraction containing styrene monomer at a high concentration can be recovered, the yield of styrene monomer can be improved. In addition, in the first pyrolysis step, when the styrene resin composition is pyrolyzed, styrene dimer and styrene trimer etc. can also be included in the first pyrolysis solution as by-products. Therefore, as long as these styrene dimers and styrene trimers can be effectively utilized, the yield of styrene monomer can be improved.

[0269] As a method for separating the first fraction into a fourth fraction containing styrene dimers and styrene trimers and a third fraction having a higher styrene monomer concentration than the fourth fraction by distillation, distillation using a distillation column is preferred.

[0270] Therefore, the method for producing styrene monomer according to the present embodiment preferably includes, if necessary, a second distillation step in which the first fraction is distilled to separate into a fourth fraction containing styrene dimers and styrene trimers and a third fraction having a higher styrene monomer concentration than the fourth fraction.

[0271] In this second distillation step, it is preferred to use one or more distillation columns and perform the distillation in one or more stages. Furthermore, it is preferred to fill these one or more distillation columns with an inert gas (e.g., nitrogen, a rare gas, etc.) from an inert gas supply source, and to perform distillation while replacing the air inside the distillation column with the inert gas.

[0272] The distillation temperature in the second distillation step is preferably, for example, 50 to 200°C, more preferably 50 to 150°C. For example, when the fourth fraction is distilled in a single stage of a single distillation column in the second distillation step, the distillation temperature in the single stage is, for example, 50 to 200°C, preferably 50 to 150°C. The pressure of the distillation environment in the second distillation step (e.g., the pressure within the distillation column) is preferably 10 to 70 Torr, more preferably 20 to 60 Torr.

[0273] When the first fraction is distilled under the above-described distillation conditions, it is separated into a fourth fraction (so-called high-boiling-point component) containing styrene dimers and styrene trimers and a third fraction (so-called low-boiling-point component) having a higher styrene monomer concentration than the first fraction.

[0274] The difference between the styrene monomer concentration in the third fraction and the styrene monomer concentration in the fourth fraction is preferably such that the styrene monomer concentration in the third fraction is approximately twice or more the styrene monomer concentration in the fourth fraction.

[0275] For example, in the second distillation step, when the fourth fraction is distilled in one stage using one distillation column, components with relatively low boiling points (such as styrene monomer) become low-boiling-point components, and styrene dimers / trimers become high-boiling-point components in the distillation column.

[0276] In addition, in order to prevent the polymerization of the styrene monomer in the second distillation step, a polymerization inhibitor may be used.

[0277] Note that, since the fraction having the highest purity of styrene monomer is the third fraction, it is preferred to recover the third fraction as styrene monomer.

[0278] (Second Pyrolysis Step (S8))

[0279] The method for producing styrene monomer according to this embodiment preferably further includes, if necessary, a second pyrolysis step of further pyrolyzing the fourth fraction to produce a second pyrolysis liquid. This allows the pyrolysis of the fourth fraction containing styrene dimers and styrene trimers to further produce styrene monomer, thereby increasing the yield of styrene monomer.

[0280] As a method for pyrolyzing the fourth fraction according to this embodiment, for example, a second pyrolysis step can be performed. In this second pyrolysis step, after the fourth fraction is filled into a pyrolysis apparatus, the fourth fraction is heated in an environment (e.g., the temperature within the pyrolysis apparatus) set to 300-700°C, preferably 320-600°C, and more preferably 350-500°C. In this case, the temperature of the filled fourth fraction is approximately 0-300°C, preferably 25-280°C, more preferably 25-250°C, and even more preferably 25-150°C. Furthermore, the second pyrolysis step can be performed by filling the preheated pyrolysis apparatus with the fourth fraction.

[0281] In this case, if the pyrolysis device is preheated, the temperature within the pyrolysis device is 300-700°C, preferably 320-600°C, and more preferably 350-500°C. The temperature of the fourth fraction to be charged is approximately 0-300°C, preferably 25-280°C, more preferably 25-250°C, and even more preferably 25-150°C. Since the styrene dimers and styrene trimers contained in the fourth fraction have a pyrolysis temperature of approximately 200-700°C at atmospheric pressure, by setting the temperature range of the pyrolysis device above, most of the generated pyrolysis steam can be converted into pyrolysis products of styrene dimers and styrene trimers. This can thereby increase the yield of styrene monomer.

[0282] In this embodiment, the second pyrolysis step can be carried out under reduced pressure or normal pressure, preferably under reduced pressure. Specifically, the reaction pressure in the second pyrolysis step is preferably 1 to 202 kPa, more preferably 7 to 101 kPa, further preferably 20 to 101 kPa, and even more preferably 20 to 80 kPa.

[0283] In the second pyrolysis step, since it is required to be performed at a temperature at which the raw material is heated and evaporated to become a gasified raw material, performing the step under reduced pressure can achieve the effect of reducing by-products due to decomposition.

[0284] Furthermore, in the second pyrolysis step, when the fourth fraction is heated to generate the second pyrolysis liquid, the pyrolysis vapor is preferably cooled to generate the second pyrolysis liquid. Specifically, the pyrolysis vapor generated by heating the fourth fraction in the pyrolysis apparatus is cooled to generate the second pyrolysis liquid containing styrene monomer. The temperature at which the pyrolysis vapor is cooled is preferably at least -30°C and below the boiling point Tsb (°C) of the styrene monomer, more preferably between -20°C and 80°C.

[0285] The cooling can be carried out by the same known method as in the first pyrolysis step.

[0286] (Third Distillation Step (S9))

[0287] In the method for producing styrene monomer of this embodiment, the second pyrolysis liquid is preferably distilled as needed to separate into a fifth fraction containing styrene monomer and a sixth fraction having a lower styrene monomer concentration than the fifth fraction. This can improve the yield of styrene monomer.

[0288] As a method of distilling the second pyrolysis liquid to separate it into a fifth fraction containing styrene monomer and a sixth fraction having a lower styrene monomer concentration than the fifth fraction, distillation using a distillation column is preferred.

[0289] Therefore, the method for producing styrene monomer according to the present embodiment preferably includes, if necessary, a third distillation step in which the second pyrolysis liquid is distilled to separate into a fifth fraction containing styrene monomer and a sixth fraction having a lower styrene monomer concentration than the fifth fraction.

[0290] In the third distillation step, distillation is preferably performed at least once in one or more distillation towers (so-called one-stage or more distillation). Furthermore, it is preferred that the distillation towers be filled with an inert gas (e.g., nitrogen, a rare gas, etc.) from an inert gas supply source, and distillation be performed while replacing the air inside the distillation tower with the inert gas.

[0291] The distillation temperature in the third distillation step is preferably, for example, in the range of 50 to 200°C, and more preferably in the range of 50 to 150°C.

[0292] The pressure of the distillation environment in the third distillation step (for example, the pressure in the distillation column) is preferably 8 to 70 Torr, more preferably 9 to 60 Torr.

[0293] When the second pyrolysis liquid is distilled under the above-mentioned distillation conditions, it is separated into a fifth fraction (so-called low-boiling-point component) containing styrene monomer and a sixth fraction (so-called high-boiling-point component) having a lower styrene monomer concentration than the fifth fraction.

[0294] The difference between the styrene monomer concentration in the fifth fraction and the styrene monomer concentration in the sixth fraction is preferably such that the styrene monomer concentration in the fifth fraction is approximately twice or more the styrene monomer concentration in the sixth fraction.

[0295] In addition, in order to prevent the polymerization of the styrene monomer in the third distillation step, a polymerization inhibitor may be used.

[0296] (Recycling Step (S10))

[0297] The method for producing styrene monomer according to the present embodiment preferably further includes, if necessary, a recycling step of recovering the styrene monomer from the fifth fraction.

[0298] Preferred recycling steps include, for example, step (I) of recovering styrene monomer by treating the fifth fraction as a part of the first pyrolysis liquid and step (II) of recovering styrene monomer by distilling the fifth fraction separately from the first pyrolysis liquid.

[0299] The step (I) of recovering styrene monomer by using the fifth fraction as a part of the first pyrolysis liquid is as described in the above column (recovery step: S5).

[0300] In addition, the contents of the above-mentioned (first distillation step: S6) and / or (second distillation step: S7) and / or (third distillation step: S9) columns are cited for the step (II) of recovering styrene monomer by distilling the fifth fraction separately from the first pyrolysis liquid.

[0301] (Apparatus for producing styrene monomer)

[0302] The present invention discloses a device for producing styrene monomer, comprising: a dissolver for preparing a mixed liquid, wherein the mixed liquid is a mixture of a styrene-based resin composition and a solvent, wherein the styrene-based resin composition contains a styrene-based polymer including styrene monomer units; a purification unit for purifying the mixed liquid; a devolatilization device for devolatilizing the purified mixed liquid to produce a fluid; a pyrolysis device for pyrolyzing the fluid; and a liquefaction device for cooling pyrolysis vapor obtained by the pyrolysis device to generate a first pyrolysis liquid.

[0303] Below, refer to Figure 5 , an example of a production apparatus for styrene monomer is described. Figure 5 This is an apparatus having the method for producing a styrene monomer according to this embodiment.

[0304] Specifically, the apparatus for producing styrene monomer of the present embodiment comprises a dissolver 15 as a recessed device filled with and mixed with a styrene resin composition 12 as a raw material, a filter aid 13 as needed, and a solvent 11; a purification unit 17 for purifying a mixed liquid prepared by the dissolver 15; a devolatilization device 20 for devolatilizing the mixed liquid purified by the purification unit 17 to prepare a fluid; and a pyrolysis device 10 ( Figure 3 ), through the pyrolysis device 10 ( Figure 3 ) is cooled to generate a liquefaction device L ( Figure 3 ) a fluidly connected device.

[0305] An example of producing styrene monomer using the apparatus for producing styrene monomer is as follows.

[0306] The raw materials, namely the styrene resin composition 12, and the filter aid 13 added as needed, are filled into a dissolver 15, which serves as a recessed device, via a hopper 14. The solvent 11 is then also filled into the dissolver 15, which serves as a recessed device. A rotating shaft S is mounted in the dissolver 15, with a stirring blade attached to one end of the rotating shaft, and a motor (M) as a power source attached to the other end of the rotating shaft. Thus, as the rotating shaft S rotates, a mixed liquid is prepared in the dissolver 15, comprising the raw materials, namely the styrene resin composition 12, the filter aid 13 added as needed, and the solvent 11. Furthermore, since the dissolver 15 is fluidically connected to a purification unit 17 via a pipe attached to the bottom or side of the dissolver 15, the mixed liquid prepared in the dissolver 15 is pumped to the purification unit 17 by a pump 16. An example of the purification unit 17 is a centrifuge having a filter installed within the rotating body. This removes impurities from the mixed liquid, which is then discharged to the outside as an impurity cake 18. On the other hand, the mixed liquid from which impurities have been removed is filled into the tank 19. Since the mixed liquid is fluidically connected to the devolatilizer 20 via a pipe body installed in the tank 19, the purified mixed liquid filled into the tank 19 is pumped to the devolatilizer 20 by the pump 16. Thereafter, the solvent and the like are distilled off in the devolatilizer 20 to generate a fluid. The fluid is then pumped to, for example, Figure 3 The pyrolysis device shown in the figure performs a first pyrolysis step (S4) and a recovery step (S5) of recovering styrene monomer from the first pyrolysis liquid.

[0307] Example

[0308] [Measurement and evaluation methods]

[0309] The physical properties of the resin compositions obtained in the respective Examples and Comparative Examples were measured and evaluated according to the following methods.

[0310] <Evaluation Method for Solvents in the Mixed Liquid Preparation Process>

[0311] The solubility of the solvent and the styrene resin composition in the mixed solution preparation process of this embodiment can be evaluated using GPPS particles. 1.0 g of GPPS particles and solvent were added to a 100 mL screw bottle at a specified mass % concentration using various solvents. When mixed and liquefied for 1 hour using an oscillator at 25°C, the case where the solid content with a long side of 5 mm or more remained was marked as unsuitable for mixed liquefaction "×", and the case where the solid content with a long side of 5 mm or more did not remain was marked as suitable for mixed liquefaction "0". Table 1-1 shows the type of solvent and mass % and whether it can be mixed and liquefied.

[0312] <Pyrolysis Apparatus and Procedures Used in Examples and Comparative Examples>

[0313] "Examples 1 to 21"

[0314] In Examples 1-21 and Comparative Examples 1-5, pyrolysis experiments were conducted using a small, simple experimental reactor (a small laboratory pyrolysis apparatus). However, the size of the apparatus is not particularly limited, provided it does not detract from the desired experimental purpose. The details are as follows.

[0315] The styrene resin composition containing a styrene polymer containing styrene monomer units is loaded into a SUS reaction vessel, which is arranged in a pouring heater, and a SUS cover with a branch pipe is installed. After being bolted with a wrench, a special adapter with an O-ring is installed on the branch pipe, and a glass Liebig condenser, a distillation adapter with a branch pipe equipped with a decompression hose, and a pyrolysis liquid recovery eggplant flask are coated with silicone grease and installed. In addition, a three-way cock is installed on the branch pipe equipped with the decompression hose, and a nitrogen balloon and a vacuum pump are connected. The temperature is monitored by thermocouples installed in the pouring heater and in the container. The refrigerant is delivered at -10°C, the vacuum pump is set to 34hPa for decompression, the output of the pouring heater is adjusted, pyrolysis is performed at 450°C, and the pyrolysis liquid is recovered in the eggplant flask by liquefying with the Liebig condenser into which the refrigerant has flowed.

[0316] <Residue rate>

[0317] In the method for producing styrene monomer according to this embodiment, the residue rate (A) can be calculated from the crude residue rate (B) calculated from the weight ratio of the styrene resin composition charged to the pyrolysis apparatus to the solid matter remaining after pyrolysis, the thermal weight loss rate (C) measured under a nitrogen atmosphere, and the thermal weight loss rate (D) measured under an air atmosphere. The residue rate (A), the crude residue rate (B), the thermal weight loss rate (C), and the thermal weight loss rate (D) are expressed as follows.

[0318] At this time, a residue rate (A) of 0.4% or less is considered "excellent," and a residue rate of 0.35% or less is considered "good." If the residue rate (A) is greater than 0.5%, the thermal efficiency of the pyrolysis apparatus decreases, leading to a decrease in pyrolysis efficiency, which may cause clogging of piping, etc., and a decrease in processing capacity. It should be noted that when the weight of the solid matter remaining after pyrolysis of the charged styrene resin composition becomes zero, the crude residue rate (B) becomes 0, and the thermal weight loss rate (C) and the thermal weight loss rate (D) are considered to be 0.

[0319] Residue rate (A) = (coarse residue rate (B) × (thermal weight loss rate (C) - thermal weight loss rate (D)) + coarse residue (B) × (thermal weight loss rate (D)) / 100

[0320] <Thermogravimetric weight loss (%)>

[0321] Thermogravimetric weight loss (%) was measured using a Shimadzu TGA apparatus (TGA-50) with a TA60-WS. A 10 mg sample of the crude residue obtained in the pyrolysis experiment was collected in a deep-bottomed aluminum pan and measured under a 20 mL / min nitrogen or dry air flow, with a temperature increase of 20°C / min from 25°C to 550°C, and then maintained at 550°C for 60 minutes. Thermogravimetric weight loss (C) and (D) were calculated based on the ratio of the difference between the weight at 25°C (the starting point of the measurement) and the weight at the end point of the measurement, held at 550°C for 60 minutes after the temperature increase.

[0322] Thermal weight loss rate (C) % = "remaining weight in the deep bottom aluminum pan after measurement under nitrogen conditions" / "sample weight in the deep bottom aluminum pan before measurement" × 100

[0323] Thermal weight loss rate (D) % = "remaining weight in the deep-bottomed aluminum pan after measurement under air conditions" / "sample weight in the deep-bottomed aluminum pan before measurement" × 100

[0324] <Evaluation method for deposits>

[0325] The first pyrolysis step of this embodiment is a step in which a mixed liquid obtained by mixing a styrene resin composition containing a styrene monomer unit as a raw material and a solvent is purified, and the fluid obtained by devolatilization is heated to obtain pyrolysis vapor containing styrene monomers, and then the pyrolysis vapor is cooled to generate a first pyrolysis liquid. At this time, if thick deposits are confirmed on the inner wall surface of the heat exchanger (the so-called cooling pipe surface) of the liquefaction device that cools the pyrolysis vapor, it is marked with an "×" (for example, Figure 8 If the deposits are small and thin, mark them with △ (e.g. Figure 7 If no attachment is found, mark it as 0 (for example Figure 6 The presence or absence of attachments is recorded in Tables 1-2 to 1-5.

[0326] Deposits in the cooling pipes reduce the thermal efficiency of the pyrolysis device, thereby reducing the overall pyrolysis efficiency of the device, leading to concerns about clogging of piping and reduced processing capacity. Furthermore, when cooling the pyrolysis vapor generated during the pyrolysis of the fluid in the first pyrolysis step to obtain the first pyrolysis liquid, there is a concern that the deposits may reduce the cooling efficiency.

[0327] <Quantitative Method for Determining Adhesion Inducers in the First Pyrolysis Solution>

[0328] In this embodiment and comparative example, the adhesion inducer in the first pyrolysis liquid was quantified by the following steps.

[0329] The first pyrolysis liquid obtained by the pyrolysis experiment of the styrene resin composition is heated for 30 minutes in such a manner that the internal temperature of the first pyrolysis liquid is 60°C. Then, 10 g of the liquid is taken out from the heated first pyrolysis liquid and cooled in a refrigerator at 0°C for 1 hour. The cooled liquid is filtered under reduced pressure using a PTFE membrane filter (T100A047A) produced by Toyo Filter Paper Co., Ltd. and recovered. Then, the filtrate is washed with MEK (1 mL) cooled to 0°C. In addition, the washed filtrate is dried at 60°C for 30 minutes in a vacuum dryer, and the dry weight of the filtrate is weighed. The mass concentration of the adhesion inducer is calculated based on the dry weight ratio of the weighed first pyrolysis liquid 10 g and the filtrate.

[0330] It should be noted that when investigating deposits on the inner wall surface of the heat exchanger (so-called cooling tube surface), it was confirmed that there was a certain correlation between the deposits and the components (=deposition inducers) contained in the first pyrolysis liquid.

[0331] When the amount of adhesion inducers in the first pyrolysis liquid obtained in the first pyrolysis step was between 0 and less than 0.2 wt%, no adhesion was observed in the liquefaction unit that cools the pyrolysis vapor immediately after the first pyrolysis liquid was generated. On the other hand, when the amount of adhesion inducers in the first pyrolysis liquid was between 0.2 wt% and less than 0.45 wt%, thin film-like adhesion was observed on the inner wall surface of the heat exchange unit that cools the pyrolysis vapor immediately after the first pyrolysis liquid was generated. Furthermore, when the amount of adhesion inducers in the first pyrolysis liquid was greater than 0.45 wt%, significant adhesion was observed.

[0332] Furthermore, in the first pyrolysis step, after heating the fluid to obtain pyrolysis vapor containing styrene monomer, the pyrolysis vapor is cooled to generate the first pyrolysis liquid. When this step is continuously operated for one week without decomposition and cleaning, the presence of thick deposits on the inner wall surface of the heat exchanger of the liquefaction device that cools the pyrolysis vapor is marked with an ×, the presence of trace, thin-film deposits is marked with a △, and the absence of deposits is marked with an O. These are recorded as the items indicating the presence or absence of deposits (after one week of operation) in Tables 1-2 to 1-5.

[0333] When the first pyrolysis step was operated continuously for one week without decomposition and cleaning, and the amount of adhesion inducers in the first pyrolysis liquid was between 0 and less than 0.15 wt%, no adhesion was observed in the liquefaction unit that cools the pyrolysis vapor during the first pyrolysis liquid generation step. However, when the amount of adhesion inducers in the first pyrolysis liquid was between 0.15 wt% and less than 0.35 wt%, thin film-like adhesion was observed on the inner wall surface of the heat exchange unit that cools the pyrolysis vapor during the first pyrolysis liquid generation step. Furthermore, when the amount of adhesion inducers in the first pyrolysis liquid was greater than 0.35 wt%, significant adhesion was observed.

[0334] The materials used in Examples and Comparative Examples are as follows.

[0335] <GPPS>

[0336] GPPS 680 manufactured by PS Japan Corporation was used.

[0337] <Post-consumer material: Polystyrene material A>

[0338] A styrene resin composition recovered from household appliances was used and had a weight average molecular weight (Mw) of 110,000.

[0339] <Recycled and sorted materials: Polystyrene material B>

[0340] The styrene resin composition was used, which was separated as polystyrene from waste plastics collected by the container recycling method. The weight average molecular weight (Mw) was 110,000.

[0341] <Recycled and sorted material: Polystyrene material C>

[0342] The styrene resin composition was used, which was separated as polystyrene from waste plastics collected in the market. The weight average molecular weight (Mw) was 100,000.

[0343] <Recycled and sorted materials: Polystyrene material D>

[0344] The styrene resin composition was used, which was separated as polystyrene from waste plastics collected in the market. The weight average molecular weight (Mw) was 105,000.

[0345] Polyethylene

[0346] SGF4960 manufactured by Braskem S.A. was used.

[0347] <Polypropylene>

[0348] MA3 produced by Japan Polypropylene Corporation (JPP) was used.

[0349] (Example 1)

[0350] Toluene was added to GPPS (99 parts by mass) and polyethylene (1 part by mass) in a manner such that the concentration (solid content concentration) became 10% by mass, and the mixture was stirred to prepare a mixed solution. Next, the mixed solution was subjected to suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B to purify the mixed solution. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (1). The fluid (1) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas containing styrene monomer generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C, thereby obtaining a first pyrolysis liquid (1) containing styrene monomer.

[0351] Table 1-2 shows the crude residue rate (B), weight loss rate (C), and weight loss rate (D) in the container used for pyrolysis, and the residue rate (A) calculated therefrom.

[0352] (Example 2)

[0353] Toluene was added to GPPS (99 parts by mass) and polypropylene (1 part by mass) in a manner such that the concentration was 10% by mass (solid content concentration), and the mixture was stirred to prepare the mixture. Next, the mixture was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixture was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (2). The fluid (2) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (2).

[0354] Table 1-2 shows the crude residue rate (B), weight reduction rates (C) and (D) in the container used for pyrolysis, and the residue rate (A) calculated therefrom.

[0355] (Example 3)

[0356] Toluene was added to GPPS (99 parts by mass) and talc (1 part by mass) in a manner such that the concentration (solid content concentration) was 10% by mass, and the mixture was stirred to prepare a mixed solution. Subsequently, the mixed solution was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (3). The fluid (3) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (3).

[0357] Table 1-2 shows the crude residue rate (B), weight reduction rates (C) and (D) in the container used for pyrolysis, and the residue rate (A) calculated from these.

[0358] (Example 4)

[0359] Methyl ethyl ketone was added to GPPS (99 parts by mass) and talc (1 part by mass) in a manner such that the concentration was 10% by mass (solid content concentration) and stirred to prepare a mixed solution. Subsequently, the mixed solution was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (4). The fluid (4) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (4). The crude residue rate (B), weight reduction rate (C) and (D) in the container used in the pyrolysis, and the residue rate (A) calculated from these are shown in Table 1-2.

[0360] (Example 5)

[0361] Toluene was added to polystyrene material A (100 parts by mass) and stirred to prepare a mixed solution. The slurry was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified slurry was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (5). The fluid (4) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (5). The crude residue rate (B) in the container used for the decomposition, the weight loss rates (C) and (D) analyzed by TGA analysis, and the residue rate (A) calculated from these are shown in Table 1-2.

[0362] (Example 6)

[0363] Toluene was added to polystyrene material B (100 parts by mass) and stirred to prepare a mixed solution. The slurry was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified slurry was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (6). The fluid (6) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (6). The crude residue rate (B), weight reduction rate (C) and (D) in the container used for the decomposition, and the residue rate (A) calculated therefrom are shown in Table 1-2.

[0364] (Example 7)

[0365] MEK was added to polystyrene material B (100 parts by mass) in a manner such that the concentration was 10% by mass and stirred to prepare a mixed solution. The slurry was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified slurry was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (7). The fluid (7) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (7). The crude residue rate (B), weight reduction rate (C) and (D) in the container used for the decomposition, and the residue rate (A) calculated therefrom are shown in Table 1-2.

[0366] (Example 8)

[0367] Toluene was added to polystyrene material B (100 parts by mass) in a manner such that the concentration became 10% by mass and the mixture was stirred to prepare a mixed solution. Radiolite (trade name) #100 (diatomaceous earth) manufactured by Showa Chemical Industry Co., Ltd. was added in an amount of 4% by mass relative to the weight of the mixed solution and stirred to prepare a mixed solution containing diatomaceous earth. The mixed solution containing diatomaceous earth was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution containing diatomaceous earth was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (8). The fluid (8) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (8). Table 1-2 shows the crude residue rate (B), weight reduction rates (C) and (D) in the container used for decomposition, and the residue rate (A) calculated therefrom.

[0368] (Example 9)

[0369] A mixed solution was prepared by adding MEK to polystyrene material B (100 parts by mass) at a concentration of 10% by mass and stirring. Radiolite #100 (diatomaceous earth) manufactured by Showa Chemical Industry Co., Ltd. was added at 4% by mass relative to the weight of the mixed solution and stirred to prepare a mixed solution containing diatomaceous earth. The mixed solution containing diatomaceous earth was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution containing diatomaceous earth was devolatilized in a vacuum dryer at 160°C and 40hPa to obtain a fluid (9). The fluid (9) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (9). The crude residue rate (B), weight loss rate (C) and (D) in the container used for decomposition, and the residue rate (A) calculated therefrom are shown in Table 1-2.

[0370] (Example 10)

[0371] Ethylbenzene was added to GPPS (99 parts by mass) and polyethylene (1 part by mass) in a manner such that the concentration (solid content concentration) became 10% by mass, and the mixture was stirred to prepare a mixed solution. Next, the mixed solution was subjected to suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B to purify the mixed solution. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (10). The fluid (10) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas containing styrene monomer generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (10) containing styrene monomer.

[0372] Table 1-3 shows the crude residue rate (B), weight loss rate (C), and weight loss rate (D) in the container used for pyrolysis, and the residue rate (A) calculated therefrom.

[0373] (Example 11)

[0374] A mixed solution was prepared by adding ethylbenzene so as to make GPPS (99 parts by mass) and polypropylene (1 part by mass) into a concentration of 10% by mass (solid content concentration). The mixture was then purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (11). The fluid (11) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (11).

[0375] Table 1-3 shows the crude residue rate (B), weight reduction rates (C) and (D) in the container used for pyrolysis, and the residue rate (A) calculated therefrom.

[0376] (Example 12)

[0377] Ethylbenzene was added to GPPS (99 parts by mass) and talc (1 part by mass) in a manner such that the concentration was 10% by mass (solid content concentration), and the mixture was stirred to prepare a mixed solution. Next, the mixed solution was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (12). The fluid (12) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (12).

[0378] Table 1-3 shows the crude residue rate (B), weight reduction rates (C) and (D) in the container used for pyrolysis, and the residue rate (A) calculated therefrom.

[0379] (Example 13)

[0380] Ethylbenzene was added to polystyrene material A (100 parts by mass) and stirred to prepare a mixed solution. The mixed solution was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (13). The fluid (13) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (13). The crude residue rate (B) in the container used for decomposition, the weight loss rate (C) and (D) analyzed by TGA analysis, and the residue rate (A) calculated from these are shown in Table 1-3.

[0381] (Example 14)

[0382] Ethylbenzene was added to polystyrene material B (100 parts by mass) in such a manner that the concentration was 10% by mass and stirred to prepare a mixed solution, and suction filtration was performed using a Kiriyama funnel and Kiriyama filter paper 5B to purify the mixed solution. Thereafter, the purified slurry was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (14). The fluid (14) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (14). The crude residue rate (B), weight reduction rate (C) and (D) in the container used for the decomposition, and the residue rate (A) calculated therefrom are shown in Table 1-3.

[0383] (Example 15)

[0384] A mixed solution was prepared by adding ethylbenzene to polystyrene material B (100 parts by mass) at a concentration of 10% by mass and stirring. Radiolite #100 (diatomaceous earth) manufactured by Showa Chemical Industry Co., Ltd. was added at 4% by mass relative to the weight of the mixed solution and stirred to prepare a mixed solution containing diatomaceous earth. The mixed solution containing diatomaceous earth was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution containing diatomaceous earth was devolatilized in a vacuum dryer at 160°C and 40hPa to obtain a fluid (15). The fluid (15) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (15). The crude residue rate (B), weight loss rate (C) and (D) in the container used for decomposition, and the residue rate (A) calculated therefrom are shown in Tables 1-3.

[0385] (Example 16)

[0386] Ethylbenzene was added to polystyrene material C (100 parts by mass) in a manner such that the concentration was 10% by mass and stirred to prepare a mixed solution, and suction filtration was performed using a Kiriyama funnel and Kiriyama filter paper 5B to purify the mixed solution. Subsequently, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (16). The fluid (16) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight reduction rate (C) and (D) in the container used for the decomposition, and the residue rate (A) calculated therefrom are shown in Table 1-4.

[0387] (Example 17)

[0388] Ethylbenzene was added to polystyrene material C (100 parts by mass) in a manner such that the concentration became 10% by mass and the mixture was stirred to prepare a mixed solution. Radiolite #100 (diatomaceous earth) manufactured by Showa Chemical Industry Co., Ltd. was added in an amount of 4% by mass relative to the weight of the mixed solution and stirred to prepare a mixed solution containing diatomaceous earth. The mixed solution containing diatomaceous earth was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution containing diatomaceous earth was devolatilized in a vacuum dryer at 160°C and 40hPa to obtain fluid (17). The fluid (17) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight loss rate (C) and (D) in the container used for the decomposition, and the residue rate (A) calculated therefrom are shown in Table 1-4.

[0389] (Example 18)

[0390] Ethylbenzene was added to polystyrene material D (100 parts by mass) in a manner such that the concentration was 10% by mass and stirred to prepare a mixed solution. The mixed solution was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (18). The fluid (18) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight reduction rate (C) and (D) in the container used for the decomposition, and the residue rate (A) calculated therefrom are shown in Table 1-4.

[0391] (Example 19)

[0392] Ethylbenzene was added to polystyrene material D (100 parts by mass) in a manner such that the concentration was 10% by mass and the mixture was stirred to prepare a mixed solution. Radiolite #100 (diatomaceous earth) manufactured by Showa Chemical Industry Co., Ltd. was added at 4% by mass relative to the weight of the mixed solution and stirred to prepare a mixed solution containing diatomaceous earth. The mixed solution containing diatomaceous earth was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution containing diatomaceous earth was devolatilized in a vacuum dryer at 160°C and 40hPa to obtain a fluid (19). The fluid (19) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight loss rate (C) and (D) in the container used for the decomposition, and the residue rate (A) calculated therefrom are shown in Tables 1-4.

[0393] (Example 20)

[0394] Styrene monomer was added to GPPS (99 parts by mass) and polyethylene (1 part by mass) in a manner such that the concentration (solid content concentration) became 10% by mass and stirred to prepare a mixed solution. Next, the mixed solution was subjected to suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B to purify the mixed solution. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (20). The fluid (20) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas containing styrene monomer generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (20) containing styrene monomer.

[0395] Table 1-4 shows the crude residue rate (B), weight loss rate (C), and weight loss rate (D) in the container used for pyrolysis, and the residue rate (A) calculated therefrom.

[0396] (Example 21)

[0397] Styrene monomer was added to GPPS (99 parts by mass) and polypropylene (1 part by mass) in a manner such that the concentration was 10% by mass (solid content concentration) and the mixture was stirred to prepare a mixed solution. Subsequently, the mixed solution was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (21). The fluid (21) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (21).

[0398] Table 1-4 shows the crude residue rate (B), weight reduction rates (C) and (D) in the container used for pyrolysis, and the residue rate (A) calculated therefrom.

[0399] (Example 22)

[0400] Styrene monomer was added to GPPS (99 parts by mass) and talc (1 part by mass) in a manner such that the concentration was 10% by mass (solid content concentration) and stirred to prepare a mixed solution. Subsequently, the mixed solution was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (22). The fluid (22) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (22).

[0401] Table 1-4 shows the crude residue rate (B), weight reduction rates (C) and (D) in the container used for pyrolysis, and the residue rate (A) calculated therefrom.

[0402] (Example 23)

[0403] A mixed solution was prepared by adding styrene monomer so that the polystyrene material A (100 parts by mass) had a concentration of 10% by mass (solid content concentration), and stirring was performed. The mixed solution was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (23). The fluid (23) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the first pyrolysis (23) was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (23). The crude residue rate (B) in the container used for decomposition, the weight loss rates (C) and (D) analyzed by TGA analysis, and the residue rate (A) calculated from these are shown in Table 1-4.

[0404] (Example 24)

[0405] A mixed solution was prepared by adding styrene monomer in such a manner that the polystyrene material B (100 parts by mass) had a concentration of 10% by mass and stirring. The mixed solution was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (24). The fluid (24) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (24). The crude residue rate (B), weight reduction rate (C) and (D) in the container used for the decomposition, and the residue rate (A) calculated therefrom are shown in Table 1-4.

[0406] (Example 25)

[0407] A mixed solution was prepared by adding styrene monomer so that the polystyrene material B (100 parts by mass) had a concentration of 10% by mass and stirring. Radiolite #100 (diatomaceous earth) manufactured by Showa Chemical Industry Co., Ltd. was added at 4% by mass relative to the weight of the mixed solution and stirred to prepare a mixed solution containing diatomaceous earth. The mixed solution containing diatomaceous earth was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution containing diatomaceous earth was devolatilized in a vacuum dryer at 160°C and 40hPa to obtain a fluid (25). The fluid (25) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (25). The crude residue rate (B), weight loss rate (C) and (D) in the container used for decomposition, and the residue rate (A) calculated therefrom are shown in Tables 1-4.

[0408] (Example 26)

[0409] A mixed solution was prepared by adding styrene monomer in such a manner that the polystyrene material C (100 parts by mass) had a concentration of 10% by mass and stirring. The mixed solution was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (26). The fluid (26) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (26). The crude residue rate (B), weight reduction rate (C) and (D) in the container used for the decomposition, and the residue rate (A) calculated therefrom are shown in Table 1-4.

[0410] (Example 27)

[0411] Styrene monomer was added to polystyrene material C (100 parts by mass) in a manner such that the concentration was 10% by mass and the mixture was stirred to prepare a mixed solution. Radiolite #100 (diatomaceous earth) manufactured by Showa Chemical Industry Co., Ltd. was added at 4% by mass relative to the weight of the slurry and stirred to prepare a mixed solution containing diatomaceous earth. The mixed solution containing diatomaceous earth was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized in a vacuum dryer at 160°C and 40hPa to obtain a fluid (27). The fluid (27) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (27). The crude residue rate (B), weight loss rate (C) and (D) in the container used for decomposition, and the residue rate (A) calculated therefrom are shown in Tables 1-4.

[0412] (Example 28)

[0413] A mixed solution was prepared by adding styrene monomer in such a manner that the polystyrene material D (100 parts by mass) became 10% by mass and stirring. The mixed solution was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution was devolatilized using a vacuum dryer at 160°C and 40hPa to obtain a fluid (28). The fluid (28) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (28). The crude residue rate (B), weight reduction rate (C) and (D) in the container used for the decomposition, and the residue rate (A) calculated therefrom are shown in Table 1-4.

[0414] (Example 29)

[0415] A mixed solution was prepared by adding styrene monomer so that the polystyrene material D (100 parts by mass) had a concentration of 10% by mass and stirring. Radiolite #100 (diatomaceous earth) manufactured by Showa Chemical Industry Co., Ltd. was added at 4% by mass relative to the weight of the mixed solution and stirred to prepare a mixed solution containing diatomaceous earth. The mixed solution containing diatomaceous earth was purified by suction filtration using a Kiriyama funnel and Kiriyama filter paper 5B. Thereafter, the purified mixed solution containing diatomaceous earth was devolatilized in a vacuum dryer at 160°C and 40hPa to obtain a fluid (29). The fluid (29) recovered by devolatilization was pyrolyzed at 450°C and 34hPa, and the gas generated by the pyrolysis was condensed using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (29). The crude residue rate (B), weight loss rate (C) and (D) in the container used for decomposition, and the residue rate (A) calculated therefrom are shown in Tables 1-4.

[0416] (Example 30)

[0417] Styrene monomer was added to polystyrene material B (100 parts by mass) in a manner such that the concentration was 10% by mass and stirred to prepare a mixed solution. Radiolite #100 (diatomaceous earth) manufactured by Showa Chemical Industry Co., Ltd. was added in an amount of 4% by mass relative to the weight of the slurry and stirred to prepare a mixed solution containing diatomaceous earth. The mixture was filtered using a pressure filter with an air permeability of 1000 cm 3 / cm 2 The diatomaceous earth-containing mixed liquid was purified by pressure filtration using a 2 / 2 woven nylon filter cloth of 1.500 psi and nitrogen at 0.2 MPa. The purified diatomaceous earth-containing mixed liquid was then devolatilized at 160°C and 40 hPa to obtain a fluid (30). Figure 3 The pyrolysis apparatus described in the invention pyrolyzes the fluid (30) recovered by devolatilization at 450°C and 34 hPa, and condenses the gas generated by the pyrolysis using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (30). The crude residue rate (B), weight loss rate (C) and (D) in the apparatus used for the decomposition, and the residue rate (A) calculated therefrom were 0.35%, and the content of adhesion inducers in the first pyrolysis liquid was 0.02 wt%.

[0418] Then, the first pyrolysis liquid (30) was distilled in a first distillation step at 60°C and 53 Torr, and the obtained second fraction was distilled in a second distillation step at 100°C and 22 Torr to obtain styrene monomer as a third fraction.

[0419] The yield of the total styrene monomer recovered by distillation in the process was 55%.

[0420] (Example 31)

[0421] Ethylbenzene was added to polystyrene material D (100 parts by mass) to give a concentration of 10% by mass and stirred to prepare a mixed solution. 3 / cm 2 The mixture was purified by pressure filtration using a nylon 2 / 2 woven filter cloth at 0.2 MPa under nitrogen. The purified mixture was then devolatilized at 160°C and 40 hPa to obtain a fluid (31). Figure 3 The pyrolysis apparatus described in the invention pyrolyzes the fluid (31) recovered by devolatilization at 450°C and 34 hPa, and condenses the gas generated by the pyrolysis using a cooling pipe cooled at -10°C, thereby obtaining a first pyrolysis liquid (31). The crude residue rate (B), weight reduction rate (C) and (D) in the apparatus used for decomposition, and the residue rate (A) calculated therefrom were 0.34%, and the content of adhesion inducers in the first pyrolysis liquid was 0.02 wt%.

[0422] (Example 32)

[0423] Toluene was added to prepare a mixed solution by stirring so that GPPS (99 parts by mass) and polyethylene (1 part by mass) were 10% by mass (solid content concentration). 3 / cm 2 The mixture was purified by pressure filtration using a nylon 2 / 2 woven filter cloth at 0.2 MPa under nitrogen. The purified mixture was then devolatilized at 160°C and 40 hPa to obtain a fluid (32). Figure 3 The pyrolysis apparatus described in the invention pyrolyzes the fluid (32) recovered by devolatilization at 450°C and 34 hPa, and condenses the gas generated by the pyrolysis using a cooling pipe cooled at -10°C, thereby obtaining a first pyrolysis liquid (32). The crude residue rate (B), weight reduction rate (C) and (D) in the apparatus used for decomposition, and the residue rate (A) calculated therefrom were 0.05%, and the content of adhesion inducers in the first pyrolysis liquid was 0.01 wt%.

[0424] (Example 33)

[0425] Ethylbenzene was added to polystyrene material B (100 parts by mass) to give a concentration of 10% by mass and stirred to prepare a mixed solution. Radiolite #100 (diatomaceous earth) manufactured by Showa Chemical Industry Co., Ltd. was added to the mixed solution at a concentration of 4% by mass relative to the weight of the mixed solution and stirred to prepare a mixed solution containing diatomaceous earth. The mixture was filtered using a pressure filter with an air permeability of 1000 cm 3 / cm 2 The diatomaceous earth-containing mixed liquid was purified by pressure filtration using a nylon 2 / 2 woven filter cloth at 0.2 MPa under nitrogen. The purified diatomaceous earth-containing mixed liquid was then devolatilized at 160°C and 40 hPa to obtain a fluid (33). Figure 3 The pyrolysis apparatus described in the invention performs a first pyrolysis step on the devolatilized recovered fluid (15) under the conditions of 450°C and 34hPa to pyrolyze the fluid, and condenses the gas generated by the pyrolysis using a cooling pipe cooled at -10°C to obtain a first pyrolysis liquid (33).

[0426] Then, the first pyrolysis liquid (33) was distilled at 60°C and 53 Torr in the first distillation step, and the obtained second fraction was distilled at 100°C and 22 Torr in the second distillation step, thereby obtaining styrene monomer as the third fraction. On the other hand, the fourth fraction other than the third fraction was subjected to the second pyrolysis step. Specifically, the SUS reaction container filled with the fourth fraction was placed in a pouring heater, and a SUS cover with a branch pipe was installed and bolted with a wrench. A special adapter with an O-ring was installed on the branch pipe, and silicone grease was applied to the condenser, the distillation adapter with the branch pipe equipped with a decompression hose, and the receiving container for pyrolysis liquid recovery. Then, a three-way cock was installed on the branch pipe equipped with a decompression hose, and a nitrogen balloon and a vacuum pump were connected. In addition, the temperature was monitored by thermocouples installed in the pouring heater and in the container.

[0427] The refrigerant is delivered at -10°C, the vacuum pump is set to 700hPa to reduce the pressure, the output of the pouring heater is adjusted, the second pyrolysis process is carried out at 450°C, and the second pyrolysis liquid is prepared in the receiving container by liquefying it with a condenser into which the refrigerant flows. The prepared second pyrolysis liquid is heated from 50°C to 80°C at 13hPa with an increment of 5°C every 5 minutes using a distiller, and the low-boiling fraction (fifth fraction) is distilled off. On the other hand, the high-boiling fraction (sixth fraction) is discharged to the outside. It should be noted that the low-boiling fraction (fifth fraction) is added to the above-mentioned first pyrolysis liquid as needed for reuse.

[0428] The crude residue rate (B), weight loss rate (C) and (D) in the container of the device used for decomposition, and the residue rate (A) calculated therefrom were 0.05%, and the content of the adhesion inducer in the first pyrolysis liquid was 0.01 wt%.

[0429] The yield of the total styrene monomer recovered by distillation in the process was 70%.

[0430] (Comparative Example 1)

[0431] A mixture of GPPS (99 parts by mass) and polyethylene (1 part by mass) was prepared and thermally decomposed at 450°C and 34 hPa without dissolving it in a solvent and without undergoing purification or devolatilization. The decomposition gas was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight loss rates (C) and (D) in the vessel used for the decomposition, and the residue rate (A) calculated from these are shown in Tables 1-5.

[0432] (Comparative Example 2)

[0433] A mixture of GPPS (99 parts by mass) and polypropylene (1 part by mass) was prepared and thermally decomposed at 450°C and 34 hPa without dissolving it in a solvent and without undergoing purification or devolatilization. The decomposition gas was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight loss rates (C) and (D) in the vessel used for the decomposition, and the residue rate (A) calculated from these are shown in Tables 1-5.

[0434] (Comparative Example 3)

[0435] GPPS (99 parts by mass) and talc (1 part by mass) were mixed and thermally decomposed at 450°C and 34 hPa without undergoing purification or devolatilization. The decomposition gas was condensed using a cooling tube cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight loss rates (C) and (D) within the vessel used for decomposition, and the residue rate (A) calculated from these are shown in Tables 1-5.

[0436] (Comparative Example 4)

[0437] Polystyrene material A (100 parts by mass) was thermally decomposed at 450°C and 34 hPa without dissolving it in a solvent and without undergoing a purification or devolatilization step. The decomposition gas was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B) in the container used for decomposition, the weight loss rates (C) and (D) obtained by analysis, and the residue rate (A) calculated from these are shown in Tables 1-5.

[0438] (Comparative Example 5)

[0439] Similar to the styrene monomer production apparatus used in Examples 30 to 33, a connection Figure 3 Styrene monomer was produced using a pyrolysis unit 10 and a liquefaction unit L. Polystyrene material B (100 parts by mass) was pyrolyzed at 450°C and 34 hPa without dissolving it in a solvent and without undergoing purification or devolatilization steps. The decomposition gas was condensed in a liquefaction unit cooled at -10°C to obtain a decomposed liquid. The crude residue rate (B), weight loss rates (C) and (D) within the container used for the decomposition, and the residue rate (A) calculated from these are shown in Tables 1-5.

[0440] In addition, the state of the connecting portion C1P of the glass tube before the production of the styrene monomer in Comparative Example 5 is shown in FIG. Figure 6 Furthermore, the state of the connecting portion C1P of the glass tube in the process of manufacturing styrene monomer is shown in FIG. Figure 7 Furthermore, the state of the connecting portion C1P of the glass tube immediately after the styrene monomer is produced is shown in FIG. Figure 8 . Figures 6-8 These photos show the state of the glass tube over time. From these photos, it can be confirmed that the transparent glass tube is obscured by a thin film of milky white deposits, and eventually, the black substance Res adheres to the entire surface of the connecting portion C1P and the inner wall of the liquefaction device L, approaching clogging.

[0441] (Comparative Example 6)

[0442] A mixture of GPPS (90 parts by mass) and polystyrene material B (10 parts by mass) was thermally decomposed at 450°C and 34 hPa without dissolving it in a solvent and without undergoing purification or devolatilization steps. The decomposition gas was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight loss rates (C) and (D) within the container used for the decomposition, and the residue rate (A) calculated from these are shown in Tables 1-5.

[0443] (Comparative Example 7)

[0444] A mixture of GPPS (75 parts by mass) and polystyrene material B (25 parts by mass) was thermally decomposed at 450°C and 34 hPa without dissolving it in a solvent and without undergoing purification or devolatilization steps. The decomposition gas was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight loss rates (C) and (D) within the container used for the decomposition, and the residue rate (A) calculated from these are shown in Tables 1-5.

[0445] (Comparative Example 8)

[0446] A mixture of GPPS (50 parts by mass) and polystyrene material B (50 parts by mass) was thermally decomposed at 450°C and 34 hPa without dissolving it in a solvent and without undergoing purification or devolatilization steps. The decomposition gas was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight loss rates (C) and (D) within the container used for the decomposition, and the residue rate (A) calculated from these are shown in Tables 1-5.

[0447] (Comparative Example 9)

[0448] A mixture of GPPS (30 parts by mass) and polystyrene material B (70 parts by mass) was thermally decomposed at 450°C and 34 hPa without dissolving it in a solvent and without undergoing purification or devolatilization steps. The decomposition gas was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight loss rates (C) and (D) within the decomposition vessel used, and the residue rate (A) calculated from these are shown in Tables 1-5.

[0449] (Comparative Example 10)

[0450] A mixture of GPPS (15 parts by mass) and polystyrene material B (85 parts by mass) was thermally decomposed at 450°C and 34 hPa without dissolving it in a solvent and without undergoing purification or devolatilization steps. The decomposition gas was condensed using a cooling pipe cooled at -10°C to obtain a decomposition liquid. The crude residue rate (B), weight loss rates (C) and (D) within the decomposition vessel used, and the residue rate (A) calculated from these are shown in Tables 1-5.

[0451] Table 1-1

[0452] solvent GPPS (mass %) Is it suitable for slurrying? Toluene 5 ○ Toluene 10 ○ Toluene 20 ○ Toluene 30 ○ Toluene 40 ○ Ethylbenzene 10 ○ Ethylbenzene 20 ○ Ethylbenzene 30 ○ Ethylbenzene 40 ○ Styrene 10 ○ Styrene 20 ○ Styrene 30 ○ Styrene 40 ○ Methyl ethyl ketone 10 ○ Methyl ethyl ketone 20 ○ Methyl ethyl ketone 30 ○ Methyl ethyl ketone 40 ○ Tetrahydrofuran 10 ○ Methanol (MeOH) 10 ×

[0453]

[0454]

[0455]

[0456]

[0457] The experimental results in Tables 1-2 to 1-5 confirm that the method for producing styrene monomer in this embodiment produces less deposits adhering to the inner walls of the cooling pipes or heat exchangers, or less residue, than the method for producing styrene monomer in the comparative example. Therefore, it is believed that since clogging of the piping caused by residues or gases generated by pyrolysis can be suppressed, a decrease in the amount of styrene produced per unit time can be suppressed.

Claims

1. A method for producing styrene monomer, wherein: include: a mixed liquid preparation step of preparing a mixed liquid by mixing a styrene-based resin composition and a solvent, wherein the styrene-based resin composition contains a styrene-based polymer including styrene monomer units; a purification step, purifying the mixed solution through a purification unit; a devolatilization step of devolatilizing the purified mixed liquid to produce a fluid; as well as The first pyrolysis step pyrolyzes the fluid to generate a first pyrolysis liquid.

2. The method for producing styrene monomer according to claim 1, wherein The method further includes a recovery step of distilling the first pyrolysis liquid to recover styrene monomer.

3. The method for producing styrene monomer according to claim 1, wherein The solvent is one or more selected from the group consisting of toluene, methyl ethyl ketone, and ethylbenzene.

4. The method for producing styrene monomer according to claim 1, wherein In the fluid, the styrene-based polymer accounts for 10% by mass or more and 100% by mass or less relative to 100% by mass of the total amount of the fluid.

5. The method for producing a styrene monomer according to claim 1 or 2, wherein: In the purified mixed liquid, the styrene-based polymer accounts for 5% by mass or more and 100% by mass or less relative to 100% by mass of the total amount of the purified mixed liquid.

6. The method for producing a styrene monomer according to claim 1 or 2, wherein: In the mixed liquid, the styrene-based polymer accounts for 5% by mass or more relative to 100% by mass of the total amount of the mixed liquid.

7. The method for producing a styrene monomer according to claim 1 or 2, wherein: In the mixed liquid preparation step, the ambient temperature for mixing the styrene resin composition and the solvent is 0° C. or higher.

8. The method for producing a styrene monomer according to claim 1 or 2, wherein: The devolatilization step is performed under reduced pressure.

9. The method for producing a styrene monomer according to claim 1 or 2, wherein: The first pyrolysis step is performed under reduced pressure.

10. The method for producing a styrene monomer according to claim 1 or 2, wherein: The method further includes an analysis step of analyzing the first pyrolysis liquid.

11. The method for producing a styrene monomer according to claim 1 or 2, wherein: In the first pyrolysis step, pyrolysis steam containing styrene monomer is cooled to produce a first pyrolysis liquid.

12. The method for producing a styrene monomer according to claim 1 or 2, wherein: The styrene resin composition contains 20% by mass or less of inclusions.

13. The method for producing a styrene monomer according to claim 1 or 2, wherein: further comprising a second pyrolysis step, In the second pyrolysis step, the first pyrolysis liquid is distilled to separate into a first fraction containing styrene monomer and a second fraction having a lower styrene monomer concentration than the first fraction. After the first fraction is separated into a third fraction having a higher styrene monomer concentration than the first fraction and a fourth fraction having a lower styrene monomer concentration than the first fraction, the fourth fraction is pyrolyzed again to generate a second pyrolysis liquid.

14. The method for producing styrene monomer according to claim 13, wherein further comprising a recycling process, In the recycling step, the second pyrolysis liquid is distilled to separate into a fifth fraction containing styrene monomer and a sixth fraction having a lower styrene monomer concentration than the fifth fraction, and then the styrene monomer is recovered from the fifth fraction.

15. The method for producing styrene monomer according to claim 14, wherein The recycling step further includes a step (I) of recovering styrene monomer by using the fifth fraction as a part of the first pyrolysis liquid and a step (II) of recovering styrene monomer by distilling the fifth fraction separately from the first pyrolysis liquid.

16. The method for producing styrene monomer according to claim 1, wherein The first pyrolysis step is a step of heating the fluid to obtain pyrolysis vapor containing styrene monomer and then cooling the pyrolysis vapor to generate the first pyrolysis liquid. The concentration of the adhesion inducer contained in the first pyrolysis liquid is less than 0.2% by mass.

17. The method for producing styrene monomer according to claim 1, wherein The devolatilization step is a step of devolatilizing the mixed liquid using a flash drum, a flash tank polymer heater, a twin-screw devolatilizer, a thin film evaporator, or an extruder to produce the fluid.

18. The method for producing styrene monomer according to claim 1, wherein The purification unit is one or more units selected from the group consisting of filtration, decantation, centrifugal separation, centrifugal sedimentation, spiral decanter, filter, screen or filter.

19. The method for producing styrene monomer according to claim 18, wherein The purification unit is a purification mechanism that combines centrifugal separation and filtration.

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