Method for manufacturing recycled synthetic resin, method for manufacturing molded products, and method for recycling discarded resin.

Abstract

Provided is a method which is for producing a recycled synthetic resin and by which filtration can be carried out continuously for a long time at a high treatment speed even when a waste resin is used, and a high-quality synthetic resin can be obtained. The method for producing a recycled synthetic resin includes: a mixing step for mixing a waste thermoplastic resin, a radically polymerizable monofunctional monomer, and a filter aid (A) to obtain a mixture (1); a filtration step for filtering the mixture (1) using a filter medium coated with a filter aid (B) in advance to obtain a filtrate mixture (2); and a polymerization step for polymerizing the radically polymerizable monofunctional monomer in the filtrate mixture (2) to synthesize a polymer, wherein the content of the filter aid (A) in the mixture (1), the coating amount of the filter aid (B) on the filter medium, and the filtration resistance in the filtration step are within predetermined ranges.

Description

[Technical Field]

[0001] The present invention relates to a method for producing recycled synthetic resin, a method for producing molded products, and a method for recycling discarded resin. [Background technology]

[0002] Various synthetic resins are present in discarded plastics from factories and households. Among these, polystyrene and other synthetic resins are used in many fields, including food packaging trays, cases for electrical appliances and information equipment, insulation materials, and cushioning materials, and they also account for a large proportion of discarded plastics. Therefore, recycling the large quantities of discarded polystyrene and other synthetic resins as resources is a significant technical challenge, and various recycling methods have been proposed.

[0003] Discarded plastics may contain foreign substances such as colorants, color fixatives, paper dust, and inorganic materials. In other words, synthetic resins such as polystyrene in discarded plastics may contain foreign substances. Therefore, it is necessary to remove these foreign substances during the recycling process, and several technologies for doing so are known.

[0004] For example, Patent Document 1 discloses a method for removing a colorant from a foamed polystyrene resin containing a colorant, which involves dissolving the resin in a predetermined organic solvent, then adding an adsorbent to separate the colorant contained in the resin using the adsorbent, and then removing the organic solvent.

[0005] Furthermore, for example, Patent Document 2 discloses a process for recycling thermoplastic polymer waste, in which a mixture of thermoplastic polymer waste dissolved in a solvent is heated and cooled to obtain a supernatant and waste residue, and the supernatant is separated from the solid waste residue by operations such as filtration. [Prior art documents] [Patent Documents]

[0006] Patent Document 1 Japanese Patent Application Laid-Open No. 04-215804 Patent Document 2 Japanese Patent Application Laid-Open No. 2022-505818 Summary of the Invention Problems to be Solved by the Invention

[0007] However, since the above-described conventional technology only performs filtration under normal conditions, there is a risk that the filtrate will come into direct contact with the filter medium, and the filtration resistance may become excessively high. Such problems can have an adverse effect on the filtration processing speed and long-term continuous operation. Furthermore, since the technology described in Patent Document 1 actively removes the organic solvent used to remove the coloring agent, there is still room for improvement in terms of environmental impact.

[0008] Therefore, an object of the present invention is to provide a method for producing a recycled synthetic resin that can continuously perform filtration for removing foreign substances contained in the resin at a high processing speed for a long time even when using a discarded resin, and can obtain a high-quality synthetic resin. Another object of the present invention is to provide a method for producing a molded product using the recycled synthetic resin obtained by the above production method. Another object of the present invention is to provide a method for recycling a discarded resin that can continuously perform filtration for removing foreign substances contained in the discarded resin at a high processing speed for a long time and can obtain a high-quality recycled synthetic resin. Means for Solving the Problems

[0009] As a result of intensive studies, the present inventors have found that the above problems can be solved by using a radically polymerizable monofunctional monomer and using a filter aid in a predetermined mode and amount when performing filtration to remove foreign substances, and thus have arrived at the present invention. The gist of the present invention for solving the above problems is as follows.

[0010] [1] A method for producing a regenerated synthetic resin, comprising: a mixing step of mixing a discarded thermoplastic resin, a radically polymerizable monofunctional monomer, and a filter aid (A) to obtain a mixture (1); a filtering step of filtering the mixture (1) using a filter medium pre-coated with a filter aid (B) to obtain a filtrate mixture (2); a polymerization step of polymerizing the radically polymerizable monofunctional monomer in the filtrate mixture (2) to synthesize a polymer and obtaining a regenerated synthetic resin containing the thermoplastic resin and the polymer; and the proportion of the filter aid (A) in the mixture (1) is 1% by mass or more and 15% by mass or less; the coating amount of the filter aid (B) on the filter medium is 0.5 kg / m 2 or more and 5.0 kg / m 2 or less; the filtration resistance in the filtration step is 2.0×10 12 m -1 or less. A method for producing a regenerated synthetic resin, characterized by the above.

[0011] [2] The method for producing a regenerated synthetic resin according to [1], wherein the filter aid (A) and the filter aid (B) are each independently one or more selected from diatomaceous earth, perlite, cellulose fiber, clay, activated carbon, alumina, silica, aluminosilicate, and zeolite.

[0012] [3] The method for producing a regenerated synthetic resin according to [1] or [2], wherein the discarded thermoplastic resin is discarded polystyrene and the radically polymerizable monofunctional monomer is a styrene monomer.

[0013] [4] A method for producing a molded article, characterized by molding the regenerated synthetic resin obtained by the production method according to any one of [1] to [3] to obtain a molded article.

[0014] [5] A method for recycling discarded resin, A mixing step involves mixing discarded thermoplastic resin, a radically polymerizable monofunctional monomer, and a filter aid (A) to obtain a mixture (1), and The filtration step involves filtering the mixture (1) using a filter material that has been pre-coated with a filter aid (B) to obtain a filtrate mixture (2), Polymerization step: Polymerizing the radical polymerizable monofunctional monomer in the filtrate mixture (2) to synthesize a polymer, thereby obtaining the thermoplastic resin and a regenerated synthetic resin containing the polymer. Includes, The proportion of the filter aid (A) in the mixture (1) is 1% by mass or more and 15% by mass or less. The amount of the filter media coated with the filter aid (B) is 0.5 kg / m 2 More than 5.0kg / m 2 The following: The filtration resistance in the aforementioned filtration process is 2.0 × 10 12 m -1 The following is: A method for recycling discarded resin, characterized by the features described above. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a method for producing recycled synthetic resin that allows for continuous filtration at a high processing speed for a long period of time to remove foreign matter contained in discarded resin, and that enables the production of high-quality synthetic resin. Furthermore, according to the present invention, it is possible to provide a method for manufacturing molded products using recycled synthetic resin obtained by the above manufacturing method. Furthermore, according to the present invention, it is possible to provide a method for recycling discarded resin that allows for continuous filtration to remove foreign matter contained in the discarded resin at a high processing speed for a long period of time, and that enables the acquisition of high-quality recycled synthetic resin. [Brief explanation of the drawing]

[0016] [Figure 1]It is a schematic diagram of a polymerization apparatus according to an aspect that can be used in a polymerization process.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the present invention will be exemplified and described in detail based on its embodiments.

[0018] <Method for Producing Recycled Synthetic Resin> A method for producing a recycled synthetic resin according to an embodiment of the present invention (hereinafter, may be referred to as "the method for producing a synthetic resin of the present embodiment") includes a mixing step of mixing a discarded thermoplastic resin, a radically polymerizable monofunctional monomer, and a filter aid (A) to obtain a mixture (1); a filtering step of filtering the mixture (1) using a filter medium pre-coated with a filter aid (B) to obtain a filtrate mixture (2); and a polymerization step of polymerizing the radically polymerizable monofunctional monomer in the filtrate mixture (2). And the method for producing a synthetic resin of the present embodiment is characterized in that the proportion of the filter aid (A) in the mixture (1) is 1% by mass or more and 15% by mass or less; the coating amount of the filter aid (B) on the filter medium is 0.5 kg / m 2 or more and 5.0 kg / m 2 or less; the filtration resistance in the filtration step is 2.0×10 12 m -1 or less; in the polymerization step, a radically polymerizable monofunctional monomer is polymerized to synthesize a polymer, and a recycled synthetic resin containing the thermoplastic resin and the polymer is obtained.

[0019] In the synthetic resin manufacturing method of this embodiment, since filtration is performed using a filter aid, foreign matter contained in the discarded resin can be effectively removed. Furthermore, in the synthetic resin manufacturing method of this embodiment, since filter aids (A) and (B) are used in predetermined forms and amounts, the filtered material is less likely to come into direct contact with the filter material during filtration, and the filtration characteristics can be improved by significantly reducing the filtration resistance (cake resistance + filter material resistance). Moreover, in the synthetic resin manufacturing method of this embodiment, a new polymer is synthesized by polymerizing a radically polymerizable monofunctional monomer in the polymerization step, and the regenerated synthetic resin finally obtained can be composed of the resin from which foreign matter has been removed by filtration (derived from the discarded resin) and the newly synthesized polymer. Therefore, according to the synthetic resin manufacturing method of this embodiment, even when using discarded resin, filtration to remove foreign matter contained in the resin can be performed continuously for a long period of time at a high processing speed, and high-quality synthetic resin can be obtained.

[0020] (Mixing process) The mixing step in this embodiment involves mixing discarded thermoplastic resin, a radically polymerizable monofunctional monomer, and a filter aid (A) to obtain a mixture (1). Note that discarded thermoplastic resin typically contains foreign substances such as colorants, colorants, paper dust, and inorganic materials; therefore, the mixture (1) obtained in the mixing step may also contain these foreign substances.

[0021] In obtaining mixture (1), only the discarded thermoplastic resin, the radically polymerizable monofunctional monomer, and the filter aid (A) may be mixed, or other materials other than those described above may be further mixed. Examples of other materials include virgin thermoplastic resin (i.e., thermoplastic resin that has not been discarded).

[0022] The mixture (1) obtained in the mixing step preferably contains the discarded thermoplastic resin dissolved in the radically polymerizable monofunctional monomer. Furthermore, in the mixing step, it is preferable to heat and / or stir in order to promote such dissolution. Heating can be performed using a heater such as an oil heater or a steam heater. Stirring can be performed using an impeller, for example. The heater and impeller are not particularly limited, and known ones can be used.

[0023] [Discarded thermoplastic resin] In the method for producing the synthetic resin of this embodiment, discarded thermoplastic resin is mixed in to obtain mixture (1). This mixing of discarded thermoplastic resin can be carried out using only thermoplastic resin (discarded thermoplastic resin), or it can be carried out using a composition containing thermoplastic resin. Examples of compositions containing thermoplastic resin include discarded plastics discharged from factories or households (hereinafter sometimes referred to as "discarded plastics").

[0024] Waste plastics, including packaging materials, are typically collected at facilities equipped with recycling equipment for recycling into raw materials. These waste plastics often consist of a mixture of plastic films, molded plastics, and other materials. Furthermore, collected waste plastics are often printed on to improve visibility during distribution. Plastic films and similar materials often have layers of inorganic vapor-deposited materials such as paper, metal foil, alumina, or silica added to provide functionality. In other words, waste plastics often contain impurities such as colorants, colorants, paper dust, metal foil, or inorganic vapor-deposited layers, which are part of the printing raw materials. In this regard, the synthetic resin manufacturing method of this embodiment allows for the achievement of the desired objective even when such waste plastics are mixed to obtain mixture (1).

[0025] Examples of thermoplastic resins that make up the discarded thermoplastic resin include styrene resins, (meth)acrylic resins, vinyl resins, etc. These thermoplastic resins may be used individually or in combination of two or more types.

[0026] Styrene-based resins refer to resins obtained by polymerization using at least styrene as a monomer. Examples of styrene-based resins include resins obtained by polymerizing substantially only styrene (i.e., polystyrene), and resins obtained by copolymerizing styrene with a comonomer copolymerizable with styrene.

[0027] Examples of comonomers copolymerizable with styrene include aromatic vinyls other than styrene, such as methylstyrene (α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, etc.), ethylstyrene, propylstyrene, butylstyrene, chlorostyrene, and bromostyrene; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate; unsaturated fatty acids such as (meth)acrylic acid, maleic acid, and fumaric acid; unsaturated di-fatty acid anhydrides such as maleic anhydride and itaconic anhydride; and unsaturated di-fatty acid imides such as N-phenylmaleimide. These comonomers may be used individually or in combination of two or more.

[0028] Furthermore, in addition to those described above, there are various variations of styrene-based resins, such as resins in which a rubbery polymer is graft polymerized and dispersed in particulate form on a continuous phase made of the styrene-based resin described above; resins in which a rubbery polymer is graft polymerized and dispersed in particulate form on a continuous phase made of a copolymer of styrene and a highly branched macromonomer; copolymers of styrene and a highly branched macromonomer; and so on. Any variation of styrene-based resin can be used in this embodiment.

[0029] Examples of (meth)acrylic resins include polymers or copolymers of radically polymerizable monofunctional monomers mainly composed of (meth)acrylic acid esters. Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, iso-octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, iso-nonyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, and the like. Furthermore, examples of (meth)acrylic resins include those obtained by copolymerizing the above-mentioned (meth)acrylic acid esters with aromatic vinyl monomers other than styrene used in the aforementioned styrene resins, or monomers having a vinyl group used in the vinyl resins described later.

[0030] Examples of vinyl resins include homopolymers of monomers having vinyl groups, and copolymers of monomers having vinyl groups and comonomers copolymerizable with said monomers. Specifically, examples of vinyl resins include homopolymers or copolymers using vinyl chloride or vinyl acetate.

[0031] Examples of polymers using vinyl chloride (vinyl chloride resins) include polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene chloride, chlorinated polyethylene, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl isobutyl ether copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, vinyl chloride-styrene copolymer, vinyl chloride-isobutylene copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-styrene-maleic anhydride terpolymer, vinyl chloride-styrene-acrylonitrile copolymer, vinyl chloride-butadiene copolymer, vinyl chloride-isoprene copolymer, vinyl chloride-chlorinated propylene copolymer, vinyl chloride-vinylidene chloride-vinyl acetate terpolymer, vinyl chloride-maleic acid ester copolymer, vinyl chloride-methacrylate ester copolymer, vinyl chloride-acrylonitrile copolymer, vinyl chloride-various vinyl ether copolymers, and blends thereof. Furthermore, blends of the aforementioned vinyl chloride resins with chlorine-free synthetic resins (for example, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl (meth)acrylate copolymer, polyester, etc.) can also be used.

[0032] Polymers using vinyl acetate (vinyl acetate resins) include homopolymers of vinyl acetate monomers and copolymers of vinyl acetate monomers with unsaturated monomers copolymerizable with the monomer. Examples of unsaturated monomers include long-chain (meth)acrylic monomers represented by alkyl (meth)acrylate monomers such as n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, and stearyl (meth)acrylate; hydroxyl group-containing (meth)acrylic monomers represented by 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 1'4-butanediol mono(meth)acrylate, and (poly)ethylene glycol mono(meth)acrylate; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; vinyl monomers such as styrene, acrylonitrile, and vinyl chloride; and ethylene.

[0033] Among the materials mentioned above, the thermoplastic resin constituting the discarded thermoplastic resin is preferably a styrene-based resin, and more preferably polystyrene. Styrene-based resins, especially polystyrene, are used in many fields, such as food packaging trays, cases for electrical appliances or information equipment, insulation materials, and cushioning materials, and moreover, they account for a large proportion of waste plastics. Therefore, using waste plastics containing polystyrene can contribute to further improving the recycling rate.

[0034] The proportion of discarded thermoplastic resin in the total amount of mixture (1) is not particularly limited, but is preferably 0.1% by mass or more and 50% by mass or less. If the above proportion is 0.1% by mass or more, the processing efficiency of the discarded thermoplastic resin and, consequently, the recycling rate can be improved. Furthermore, if the above proportion is 50% by mass or less, the insolubility of the resin in mixture (1) can be suppressed, and pressure abnormalities in the subsequent polymerization process can be suppressed, making operation easier. From a similar viewpoint, the above proportion is more preferably 5% by mass or more, even more preferably 10% by mass or more, even more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0035] [Radical polymerizable monofunctional monomers] In the method for producing the synthetic resin of this embodiment, a radically polymerizable monofunctional monomer is mixed to obtain mixture (1).

[0036] Examples of radically polymerizable monofunctional monomers include aromatic vinyls such as styrene, methylstyrene (α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, etc.), ethylstyrene, propylstyrene, butylstyrene, chlorostyrene, and bromostyrene; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate; unsaturated fatty acids such as (meth)acrylic acid, maleic acid, and fumaric acid; unsaturated di-fatty acid anhydrides such as maleic anhydride and itaconic anhydride; unsaturated di-fatty acid imides such as N-phenylmaleimide; and monomers having a vinyl group other than those mentioned above. These radically polymerizable monofunctional monomers may be used individually or in combination of two or more.

[0037] Regarding suitable combinations of discarded thermoplastic resin and radically polymerizable monofunctional monomer, it is preferable that the radically polymerizable monofunctional monomer is a monomer constituting the discarded thermoplastic resin. Furthermore, it is more preferable that the discarded thermoplastic resin is discarded polystyrene and the radically polymerizable monofunctional monomer is a styrene monomer. In these cases, there are advantages in terms of improved filtration characteristics and the quality of the resulting recycled synthetic resin.

[0038] Furthermore, the above-mentioned radical polymerizable monofunctional monomer is preferably a naphtha-derived monomer from the viewpoint of suppressing the deterioration of the physical properties of the resulting regenerated synthetic resin.

[0039] The above-mentioned radical polymerizable monofunctional monomer is preferably capable of dissolving discarded thermoplastic resin. Furthermore, it is preferable that the radical polymerizable monofunctional monomer passes through the filter material in the filtration step described later. In other words, it is preferable that the radical polymerizable monofunctional monomer is liquid during the filtration step described later. Based on these considerations, an appropriate radical polymerizable monofunctional monomer can be selected.

[0040] The proportion of radically polymerizable monofunctional monomers in the total amount of mixture (1) is not particularly limited, but is preferably 50% by mass or more and 98% by mass or less. If the above proportion is 50% by mass or more, the insolubility of the discarded thermoplastic resin in mixture (1) can be suppressed, and pressure abnormalities can be suppressed in the subsequent polymerization process, making operation easier. Furthermore, if the above proportion is 98% by mass or less, the processing efficiency of the discarded thermoplastic resin and, consequently, the recycling rate can be improved. From a similar viewpoint, the above proportion is more preferably 60% by mass or more, even more preferably 65% ​​by mass or more, even more preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0041] [Filtration aid (A)] In the method for producing the synthetic resin of this embodiment, a filter aid (A) is mixed in to obtain mixture (1). The filter aid (A) is typically a solid.

[0042] The filter aid (A) is not particularly limited, but it is preferably one or more selected from diatomaceous earth, perlite, cellulose fiber, clay, activated carbon, alumina, silica, alumina silicate, and zeolite. In this case, the filtration characteristics (processing speed, long-term operation, etc.) can be further improved.

[0043] The permeability of the filter aid (A) is preferably 0.03 darcy or more and 4.50 darcy or less. If the permeability of the filter aid (A) is 0.03 darcy or more, the cake resistance is further reduced and the filtration processing speed can be further increased. Also, if the permeability of the filter aid (A) is 4.50 darcy or less, the effect of removing foreign matter contained in the discarded resin can be further enhanced. From a similar viewpoint, the permeability of the filter aid (A) is more preferably 0.80 darcy or more, even more preferably 1.25 darcy or more, even more preferably 1.50 darcy or more, and even more preferably 4.00 darcy or less, even more preferably 3.50 darcy or less, and even more preferably 3.00 darcy or less.

[0044] In this specification, "transmission rate" for filtration aids (filtration aid (A) and filtration aid (B)) is determined using Darcy's formula. Specifically, for a thickness of 1 cm and an area of ​​1 cm²... 2 A packed bed of filter aids is subjected to a pressure difference of 1 atmosphere, and a fluid with a viscosity of 1 cp flows at a rate of 1 cm³ / s. 3 When flowing at a certain flow rate, the transmittance is defined as 1 darcy.

[0045] The proportion of filter aid (A) in the total amount of mixture (1) must be between 1% by mass and 15% by mass. If the above proportion is less than 1% by mass, the cake resistance may increase during filtration, potentially reducing the filtration rate. Conversely, if the above proportion exceeds 15% by mass, the cake resistance may increase, potentially reducing the filtration rate. From a similar viewpoint, the proportion of filter aid (A) in the total amount of mixture (1) is preferably 1.0% by mass or more, preferably 1.5% by mass or more, more preferably 2% by mass or more, preferably 10% by mass or less, more preferably 6% by mass or less, and even more preferably 4% by mass or less.

[0046] (filtration process) In this embodiment, the filtration step is a step of filtering the mixture (1) obtained in the mixing step. Such filtration must be performed using a filter material that has been pre-coated with a filter aid (B), and by such filtration, a filtrate mixture (2) is obtained.

[0047] [Filter media] The filter material used in the filtration process is not particularly limited and includes, for example, filter paper, ceramic filters, glass filters, membrane filters, polytetrafluoroethylene (PTFE) filter cloth, polyphenylene sulfide (PPS) filter cloth, polypropylene (PP) filter cloth, polyester filter cloth, nylon filter cloth, etc.

[0048] [Filtration aid (B)] Filtration aid (B) is used to coat the filter media beforehand. Filtration aid (B) is typically a solid.

[0049] The filter aid (B) is not particularly limited, but it is preferably one or more selected from diatomaceous earth, perlite, cellulose fiber, clay, activated carbon, alumina, silica, alumina silicate, and zeolite. In this case, the filtration characteristics (processing speed, long-term operation, etc.) can be further improved. Furthermore, the filter aid (B) and the filter aid (A) described above may be the same or different.

[0050] The permeability of the filter aid (B) coated on the filter media is preferably 0.03 darcy or more and 2.00 darcy or less. If the permeability of the filter aid (B) is 0.03 darcy or more, the filter media resistance, taking the coating into account, is further reduced, and the filtration rate can be further increased. Also, if the permeability of the filter aid (B) is 2.00 darcy or less, the possibility of the filtered material directly contacting the filter media during filtration is sufficiently reduced, and continuous filtration over a long period of time can be performed more reliably. From a similar viewpoint, the permeability of the filter aid (B) is more preferably 0.10 darcy or more, even more preferably 0.30 darcy or more, even more preferably 0.50 darcy or more, and more preferably 1.50 darcy or less, even more preferably 1.00 darcy or less, and even more preferably 0.80 darcy or less.

[0051] [Coating of filter media] In this embodiment, filtration is performed using a filter medium that has been pre-coated with the filter aid (B). In this regard, the operation of coating the filter medium with the filter aid (B) can be performed prior to the filtration process. Alternatively, commercially available filter medium coated with the filter aid (B) can be used.

[0052] The method for coating the filter media with the filter aid (B) is not particularly limited. For example, the filter aid (B) can be coated onto the filter media by sending a mixture of the filter aid (B) dispersed in a solvent into a filtration device equipped with a filter media and performing filtration. The filtration device can be the same as the one used in a later filtration step. Furthermore, it is preferable to use the same radical polymerizable monofunctional monomer as used in this embodiment as the solvent for dispersing the filter aid (B).

[0053] The amount of filter media coated with filter aid (B) is 0.5 kg / m². 2 More than 5.0kg / m 2 The following is required: The above coating amount is 0.5 kg / m 2If the amount is less than 5.0 kg / m³, there is a higher possibility that the filtered material will come into direct contact with the filter media during filtration, which may prevent continuous filtration for extended periods. 2 If the coating is too high, the resistance of the filter media, taking the coating into account, may increase, potentially reducing the filtration rate. From a similar perspective, the amount of filter aid (B) coating on the filter media should be 0.8 kg / m³. 2 The above is preferable, and 1.0 kg / m 2 The above is more preferable, 1.2 kg / m 2 The above is even more preferable, and also 4.0 kg / m 2 The following is preferable: 3.5 kg / m 2 The following is more preferable: 3.0 kg / m 2 The following is even more preferable.

[0054] [filtration] The filtration method is not particularly limited and includes, for example, natural filtration, reduced pressure filtration, pressure filtration, centrifugal filtration, and cross-flow filtration. Furthermore, filtration may be carried out continuously or in batches.

[0055] The temperature of the mixture (1) during filtration is preferably such that polymerization of the radically polymerizable monofunctional monomer does not proceed. Furthermore, considering the viscosity suitable for filtration, the temperature of the mixture (1) during filtration is preferably between 20°C and 70°C.

[0056] In this embodiment, the filtration resistance in the filtration process is 2.0 × 10⁻⁶ 12 m -1 The following applies. This enables efficient filtration that yields high-quality filtrate. The filtration resistance can be expressed as the sum of the cake resistance and filter media resistance, which will be described later. Furthermore, this filtration resistance is caused by a combination of factors such as the type and amount of filter aid (A) used; the type of filter media used; the type, amount, mixing ratio, and coating amount of filter aid (B) used; and can be achieved by appropriately selecting these factors.

[0057] Furthermore, the cake resistance in the filtration process is 1.0 × 10⁻⁶ 10 m-1 The above 1.0 × 10 12 m -1 The following is preferable. If the cake resistance is within the above range, it is possible to achieve a good balance between foreign matter removal performance and filtration characteristics (processing speed, long-term operation, etc.). This cake resistance is caused by a combination of factors such as the type and amount of filter aid (A) used; the type of filter media used; the type, amount, mixing ratio, and coating amount of filter aid (B); so it is preferable to select these appropriately.

[0058] Furthermore, the filter media resistance in the filtration process is 1.0 × 10⁻⁶ 9 m -1 The above 1.0 × 10 12 m -1 The following is preferable. If the filter media resistance is within the above range, it is possible to balance the prevention of direct contact of the filtered material with the filter media and the filtration characteristics (processing speed, long-term operation, etc.). This filter media resistance is caused by a combination of factors such as the type, amount, and mixing ratio of the filter aid (B), and the amount of coating; the type of filter media used; therefore, it is preferable to select these appropriately.

[0059] The filtration mixture (2) obtained in the filtration step typically contains the thermoplastic resin and radically polymerizable monofunctional monomer mixed in the mixing step. Alternatively, the filtration mixture (2) may consist only of the thermoplastic resin and radically polymerizable monofunctional monomer. On the other hand, the filter aid (A) mixed in the mixing step is typically separated as a cake (filtered residue) in the filtration step. Furthermore, if there is any thermoplastic resin that has not dissolved in mixture (1), such thermoplastic resin can also be separated as a cake (filtered residue) in the filtration step.

[0060] (Polymerization process) In this embodiment, the polymerization step is a step of polymerizing the radically polymerizable monofunctional monomer in the filtrate mixture (2) obtained in the filtration step to synthesize a polymer. Through this polymerization step, a regenerated synthetic resin is finally obtained.

[0061] In this polymerization process, the thermoplastic resin mixed in the mixing process is essentially not involved, and a radically polymerizable monofunctional monomer is polymerized as the sole monomer to synthesize a new polymer. Therefore, the final recycled synthetic resin can consist of the thermoplastic resin (derived from discarded thermoplastic resin) from which impurities have been removed by filtration, and the newly synthesized polymer. As a result, the resulting recycled synthetic resin is of equivalent or even higher quality than recycled resin obtained by conventional recycling methods.

[0062] The polymerization method is not particularly limited, and known methods can be used. The polymerization method is also not particularly limited, and examples include bulk polymerization, suspension polymerization, and solution polymerization. Polymerization may be carried out continuously or in batches, but from the viewpoint of manufacturing efficiency, continuous polymerization is preferred.

[0063] In the polymerization process, radical polymerization initiators can be used without particular limitation. Examples of such radical polymerization initiators include peroxyketals such as 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)butane, and 2,2-bis(4,4-di-butylperoxycyclohexyl)propane; hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide; dialkyl peroxides such as di-t-butyl peroxide, dicumyl peroxide, and di-t-hexyl peroxide; benzoyl peroxide; and disinamoyl peroxide. Examples include diacyl peroxides such as phosphate; peroxyesters such as t-butyl peroxybenzoate, di-t-butyl peroxyisophthalate, and t-butyl peroxyisipropyl monocarbonate; and azo compounds such as N,N'-azobisisobutylnitrile, N,N'-azobis(cyclohexane-1-carbonnitrile), N,N'-azobis(2-methylbutyronitrile), N,N'-azobis(2,4-dimethylvaleronitrile), and N,N'-azobis[2-(hydroxymethyl)propionitrile]. These radical polymerization initiators may be used individually or in combination of two or more.

[0064] In the polymerization process, a chain transfer agent may be added to the polymerization reaction system to prevent the molecular weight of the synthesized polymer from becoming excessively large. Examples of chain transfer agents include monofunctional chain transfer agents having one chain transfer group and polyfunctional chain transfer agents having multiple chain transfer groups. Examples of monofunctional chain transfer agents include alkyl mercaptans and thioglycolic acid esters. Examples of polyfunctional chain transfer agents include polyhydric alcohols in which the hydroxyl group has been esterified with thioglycolic acid or 3-mercaptopropionic acid. Examples of the above polyhydric alcohols include ethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, and sorbitol.

[0065] In the polymerization process, long-chain alcohols, polyoxyethylene alkyl ethers, polyoxyethylene lauryl ethers, polyoxyoleyl ethers, polyoxyethylene alkenyl ethers, etc., can be used to suppress gel formation in the resulting regenerated synthetic resin.

[0066] In the polymerization process, an organic solvent may be added to the polymerization reaction system to reduce the viscosity of the polymer product. Examples of such organic solvents include toluene, ethylbenzene, xylene, acetonitrile, benzene, chlorobenzene, dichlorobenzene, anisole, cyanobenzene, dimethylformamide, N,N-dimethylacetamide, and methyl ethyl ketone.

[0067] The polymerization process can be carried out, for example, using a polymerization apparatus capable of continuous polymerization as shown in Figure 1. Specifically, referring to Figure 1, the filtrate mixture (2) is sent to a stirred reactor 2 by pump 1. The filtrate mixture (2) sent to the stirred reactor 2 is then sent to a circulating polymerization line (I) by pump 3, and then circulated within the circulating polymerization line (I) by pump 7. This circulating polymerization line (I) consists of three reactors 4, 5, and 6. The filtrate mixture (2) after circulation (at least partially polymerized) is sent to a non-circulating polymerization line (II). This non-circulating polymerization line (II) consists of three reactors 8, 9, and 10. After being sent to the non-circulating polymerization line (II), the polymerization reaction product is discharged by pump 11.

[0068] The polymerization reaction product discharged by pump 11 may be sent to a defoliation tank to volatilize unreacted radical polymerizable monofunctional monomers. In this case, two defoliation tanks can be connected, and it is preferable to adjust the first defoliation tank to a reduced pressure of approximately 4.0 kPa and the second defoliation tank to a reduced pressure of approximately 1.3 kPa.

[0069] In the polymerization apparatus shown in Figure 1, radical polymerizable monofunctional monomers may be further added to the filtrate mixture (2) between the stirred reactor 2 and the circulating polymerization line (I), or a solvent such as an organic solvent may be added, as needed. Also, in the polymerization apparatus shown in Figure 1, radical polymerizable monofunctional monomers may be further added to the filtrate mixture (2) between the circulating polymerization line (I) and the non-circulating polymerization line (II), or a solvent such as an organic solvent may be added.

[0070] <Method for manufacturing molded products> A method for manufacturing a molded product according to one embodiment of the present invention (hereinafter sometimes referred to as "the method for manufacturing a molded product of this embodiment") is characterized by obtaining a molded product by molding the recycled synthetic resin obtained by the manufacturing method described above.

[0071] According to the manufacturing method of the molded product of this embodiment, since the molding is performed using high-quality synthetic resin (recycled synthetic resin) obtained by the synthetic resin manufacturing method described above, it is possible to obtain a molded product of equivalent or higher quality than that obtained by conventional methods.

[0072] The shape of the molded product manufactured by the manufacturing method of this embodiment is not particularly limited and can be changed as appropriate depending on the purpose.

[0073] In the molding process, only the recycled synthetic resin obtained by the synthetic resin manufacturing method described above may be used as the resin raw material, or the said synthetic resin may be used in combination with other resins. The other resins are not particularly limited, but for example, they may be the same as the thermoplastic resin that constitutes the discarded thermoplastic resin and / or the polymer synthesized in the polymerization process. These other resins may be a single type or a combination of two or more types.

[0074] In the molding process, lubricants, antistatic agents, antioxidants, heat stabilizers, UV absorbers, dyes, plasticizers, etc., can be used as long as they do not impair the physical properties of the recycled synthetic resin.

[0075] In the molding process, molded products may be obtained directly using resin raw materials. Alternatively, in the molding process, intermediate molding materials such as pellets may be first produced using recycled synthetic resin or other resin raw materials, and then molded products may be manufactured using these intermediate molding materials.

[0076] Specifically, in the molding process, intermediate molding materials such as pellets can be obtained by melting and kneading the resin material and then extruding it. These operations can be carried out using equipment such as a kneader, roll mill, single-screw extruder, twin-screw extruder, or rotor-type twin-screw kneader. Next, the obtained intermediate molding materials such as pellets can be heated and molded to obtain a final molded product. The method of heating and molding is not particularly limited and includes, for example, injection molding, extrusion molding, blow molding, and compression molding.

[0077] <Methods for recycling discarded resin> A method for recycling discarded resin according to one embodiment of the present invention (hereinafter sometimes referred to as "the recycling method of this embodiment") includes a mixing step of mixing discarded thermoplastic resin, a radically polymerizable monofunctional monomer, and a filter aid (A) to obtain a mixture (1); a filtering step of filtering the mixture (1) using a filter material pre-coated with a filter aid (B) to obtain a filtrate mixture (2); and a polymerization step of polymerizing the radically polymerizable monofunctional monomer in the filtrate mixture (2). The method for producing the synthetic resin according to this embodiment is such that the proportion of the filter aid (A) in the mixture (1) is 1% by mass or more and 15% by mass or less; and the amount of the filter aid (B) coating on the filter material is 0.5 kg / m 2 More than 5.0kg / m 2 The following conditions must be met: the filtration resistance in the filtration process is 2.0 × 10⁻⁶ 12 m -1 The following is a characteristic feature: in the polymerization step, a radically polymerizable monofunctional monomer is polymerized to synthesize a polymer, and a regenerated synthetic resin containing the thermoplastic resin and the polymer is obtained.

[0078] Each step of the regeneration method of this embodiment is typically the same as the synthetic resin manufacturing method of this embodiment described above. Therefore, for a detailed explanation of the regeneration method of this embodiment, the description of the synthetic resin manufacturing method of this embodiment described above can be used as a reference. Furthermore, according to the regeneration method of this embodiment, filtration to remove foreign matter contained in the discarded resin can be performed continuously for a long period of time at a high processing speed, and high-quality regenerated synthetic resin can be obtained. [Examples]

[0079] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0080] (Mixing process) As a mixing step, each material, such as thermoplastic resin, was stirred and mixed in a tank equipped with stirring blades in the compositions shown in Tables 1, 2, and 3 to obtain mixture (1). At this time, the discarded thermoplastic resin was dissolved in a radically polymerizable monofunctional monomer.

[0081] (Coating of filter media) Prior to the filtration process, the filter media was coated with a filter aid (B) as appropriate. Specifically, a predetermined amount of filter aid (B) with the compositions shown in Tables 1, 2, and 3 was prepared, and the filter aid (B) was suspended in a solvent in a tank with a stirring blade, separate from the tank mentioned above. The solvent used at this time was the same as that used in the mixing process for the radically polymerizable monofunctional monomer. The resulting suspension was then filtered using a pump into a filtration apparatus equipped with a filter media (manufactured by Mitsubishi Chemical Machinery Ltd., Schneider Filter, filter media (filter cloth): made of PPS, filtration area: 0.2 m²). 2 The liquid was pumped into the container and pressure filtration was performed at a pressure of 0.1 MPa. In this way, the filter media was coated with filter aid (B). The amount of filter aid (B) coated in each example was (kg / m³). 2 The results are shown in Tables 1, 2, and 3.

[0082] (filtration process) Next, the mixture (1) obtained in the mixing step was pumped into the aforementioned filtration apparatus at room temperature (approximately 25°C) and subjected to pressurized filtration at a pressure of 0.4 MPa. This removed foreign matter and other contaminants from the mixture (1), yielding the filtrate mixture (2).

[0083] (Polymerization process) The filtrate mixture (2) was placed in the polymerization apparatus shown in Figure 1, and the radical polymerizable monofunctional monomers in the filtrate mixture (2) were polymerized by continuous polymerization. Subsequently, the mixture was subjected to a defoliation tank to appropriately volatilize the unreacted radical polymerizable monofunctional monomers, thereby obtaining a regenerated synthetic resin containing the thermoplastic resin blended during the mixing process and a polymer formed by the polymerization of the radical polymerizable monofunctional monomers blended during the mixing process. In the polymerization process, perbutyl Z (manufactured by NOF Corporation) was used as a radical polymerization initiator.

[0084] Then, during the series of operations described above, the following measurements and evaluations were performed. The results are shown in Tables 1, 2, and 3, respectively.

[0085] <Filter media resistance> In the filtration process for coating with filter aid (B), the amount of filtrate per unit time and the viscosity of the obtained filtrate were measured. In particular, viscosity was measured using the Electro Magnetically Spinning Method (EMS) under the following conditions. (conditions) Measurement device model number: EMS-1000S (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) Spherical probe: Made of aluminum, 2mm in diameter (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) Sample volume: 300 μL Probe rotation speed: 1000 rpm

[0086] Then, using these measurements, the filter media resistance (R m (Unit: m) -1 )(filter media resistance considering coating) is given by the following formula:

number

[0087] <Cake Resistance> During the filtration process, the amount of filtrate per unit time and the viscosity of the obtained filtrate mixture (2) were measured. In particular, the viscosity was measured under the same conditions as above. These measured values ​​were then compared with the filter media resistance (R) described above. m Using the values ​​related to ), the cake resistance (R c (Unit: m) -1 ) is expressed as follows:

number

[0088] <Filtration resistance> The filtration resistance was calculated as the sum of the cake resistance and filter media resistance mentioned above.

[0089] <Whether or not the filtered material comes into direct contact with the filter media> After the filtration process, it was visually confirmed whether the filtered material was in direct contact with the filter media. If the filtered material was not in direct contact with the filter media, it could be determined that filtration could be performed continuously for a long period of time.

[0090] <Filtration completion time> During the filtration process, the time required to obtain 5 L of filtrate mixture (2) was measured. A smaller measurement indicates a higher filtration rate. In the table, examples where the filtration completion time is indicated as "-" indicate that the filtrate mixture could not be obtained because the filtered material came into direct contact immediately after the start of filtration.

[0091] <Total light transmittance of synthetic resins> The total light transmittance of the synthetic resin obtained in the polymerization process was measured using a HAZE Meter NDH7000II (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7361-1.

[0092] <Recycling rate> The recycling rate in each example was calculated by taking the mass of the discarded thermoplastic resin as a and the mass of the polymerized radical polymerizable monofunctional monomer as b, and then calculating {a / (a+b)} × 100.

[0093] [Table 1]

[0094] [Table 2]

[0095] [Table 3]

[0096] Diatomaceous earth A... Manufactured by Showa Chemical Industry Co., Ltd., "Radiolight #100", Transmittance: 0.05 darcy Diatomaceous earth B... Manufactured by Showa Chemical Industry Co., Ltd., "Radiolight #300", Transmittance: 0.11 darcy Diatomaceous earth C... Manufactured by Showa Chemical Industry Co., Ltd., "Radiolight #600", Transmittance: 1.10 darcy Diatomaceous earth D... Manufactured by Showa Chemical Industry Co., Ltd., "Radiolight #800", Transmittance: 1.84 darcy Diatomaceous earth E... Manufactured by Showa Chemical Industry Co., Ltd., "Radiolight #900", Transmittance: 3.29 darcy Diatomaceous earth F... Manufactured by Daikalite Co., Ltd., "Daikalite Speedex", Transmittance: 1.80 darcy Perlite A... Manufactured by Mitsui Kinzoku Perlite Co., Ltd., "RocaHelp 419", Transmittance: 0.09 darcy Perlite B... Manufactured by Mitsui Kinzoku Perlite Co., Ltd., "RocaHelp 439", Transmittance: 0.45 darcy Perlite C... Manufactured by Mitsui Kinzoku Perlite Co., Ltd., "RocaHelp 4189", Transmittance: 1.69 darcy Perlite D... Manufactured by Showa Chemical Industry Co., Ltd., "Topco No. 38", Transmittance: 1.66 darcy

[0097] PS...Polystyrene PMMA...Polymethyl methacrylate St-BA...Styrene-butyl acrylate copolymer St-MA...Styrene-methacrylic acid copolymer

[0098] Tables 1 and 2 show that in the embodiments according to the present invention, there is no direct contact of the filtered material with the filter media, and the filtration completion time is short, allowing filtration to be performed continuously for a long period of time at a high processing speed. In contrast, Table 3 shows that in the comparative examples, there is direct contact of the filtered material with the filter media, or the filtration completion time is long, or both. [Industrial applicability]

[0099] According to the present invention, it is possible to provide a method for producing recycled synthetic resin that allows for continuous filtration at a high processing speed for a long period of time to remove foreign matter contained in discarded resin, and that enables the production of high-quality synthetic resin. Furthermore, according to the present invention, it is possible to provide a method for manufacturing molded products using recycled synthetic resin obtained by the above manufacturing method. Furthermore, according to the present invention, it is possible to provide a method for recycling discarded resin that allows for continuous filtration to remove foreign matter contained in the discarded resin at a high processing speed for a long period of time, and that enables the acquisition of high-quality recycled synthetic resin. [Explanation of symbols]

[0100] 1: Pump 2: Stirred reactor 3: Pump 4, 5, 6: Reactors 7: Pump 8,9,10: Reactor 11: Pump (I): Circulating polymerization line (II): Non-circulating polymerization line

Claims

1. A method for producing recycled synthetic resin, A mixing step involves mixing discarded thermoplastic resin, a radically polymerizable monofunctional monomer, and a filter aid (A) to obtain a mixture (1), and The filtration step involves filtering the mixture (1) using a filter material that has been pre-coated with a filter aid (B) to obtain a filtrate mixture (2), A polymerization step is performed to polymerize the radical polymerizable monofunctional monomer in the filtrate mixture (2) to synthesize a polymer, thereby obtaining a regenerated synthetic resin containing the thermoplastic resin and the polymer. Includes, The proportion of the filter aid (A) in the mixture (1) is 1% by mass or more and 15% by mass or less. The amount of the filter media coated with the filter aid (B) is 0.5 kg / m ２ 5.0kg / m or more ２ The following: The filtration resistance in the aforementioned filtration process is 2.0 × 10 １２ I understand －１ The following: The permeability of the filter aid (B) is 0.10 darcy or higher. In the polymerization step, the radical polymerizable monofunctional monomer is polymerized as the sole monomer to synthesize a polymer. A method for producing recycled synthetic resin, characterized by the following:

2. The method for producing a recycled synthetic resin according to claim 1, wherein the filtration aid (A) and the filtration aid (B) are each independently selected from one or more of the following: diatomaceous earth, perlite, cellulose fiber, clay, activated carbon, alumina, silica, alumina silicate, and zeolite.

3. A method for producing a recycled synthetic resin according to claim 1 or 2, wherein the discarded thermoplastic resin is discarded polystyrene, and the radical polymerizable monofunctional monomer is a styrene monomer.

4. A method for producing a molded product, characterized by molding a recycled synthetic resin obtained by the manufacturing method described in claim 1 or 2 to obtain a molded product.

5. A method for recycling discarded resin, A mixing step involves mixing discarded thermoplastic resin, a radically polymerizable monofunctional monomer, and a filter aid (A) to obtain a mixture (1), and The filtration step involves filtering the mixture (1) using a filter material that has been pre-coated with a filter aid (B) to obtain a filtrate mixture (2), A polymerization step is performed to polymerize the radical polymerizable monofunctional monomer in the filtrate mixture (2) to synthesize a polymer, thereby obtaining a regenerated synthetic resin containing the thermoplastic resin and the polymer. Includes, The proportion of the filter aid (A) in the mixture (1) is 1% by mass or more and 15% by mass or less. The amount of the filter media coated with the filter aid (B) is 0.5 kg / m ２ 5.0kg / m or more ２ The following: The filtration resistance in the aforementioned filtration process is 2.0 × 10 １２ I understand －１ The following: The permeability of the filter aid (B) is 0.10 darcy or higher. In the polymerization step, the radical polymerizable monofunctional monomer is polymerized as the sole monomer to synthesize a polymer. A method for recycling discarded resin, characterized by the features described above.

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