Method for producing recycled synthetic resin, method for producing molded product, and method for recycling waste 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

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

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

[0002] Various synthetic resins are present in discarded plastics discharged from factories or households. Among them, synthetic resins such as polystyrene are used in many fields, such as food packaging trays, cases for electrical appliances or information devices, insulation materials, and cushioning materials, and they also account for a large proportion of discarded plastics. Therefore, recycling the large amounts of discarded synthetic resins such as polystyrene as resources is an important technical challenge, and various recycling methods have been proposed.

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

[0004] For example, Patent Document 1 discloses a method for removing a colorant from an expanded polystyrene resin containing the colorant, in which the resin is dissolved in a predetermined organic solvent, an adsorbent is then added, the colorant contained in the resin is separated by the adsorbent, and the organic solvent is then removed.

[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 a waste residue, and the supernatant is separated from the solid waste residue by an operation such as filtration.

[0006] Japanese Patent Application Publication No. 04-215804 Special Publication No. 2022-505818

[0007] However, in the above-mentioned conventional technology, since filtration is performed only under normal conditions, there is a risk that the filtered material may come into direct contact with the filter material and that the filtration resistance may become excessively high. Such problems may adversely affect 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 colorant, there is room for improvement in terms of environmental impact.

[0008] Therefore, an object of the present invention is to provide a method for producing recycled synthetic resin, which can perform filtration to remove foreign matter contained in discarded resin continuously at a high processing speed for a long period of time, even when using discarded resin, and can produce high-quality synthetic resin. Another object of the present invention is to provide a method for producing molded articles using the recycled synthetic resin obtained by the above-mentioned production method. Another object of the present invention is to provide a method for recycling discarded resin, which can perform filtration to remove foreign matter contained in the discarded resin continuously at a high processing speed for a long period of time, and can produce high-quality recycled synthetic resin.

[0009] The present inventors have conducted extensive research and found that the above-mentioned problems can be solved by using a radical polymerizable monofunctional monomer and by using a filter aid in a specific manner and in a specific amount when filtering to remove foreign matter, and have thus come up with the present invention. The gist of the present invention that solves the above-mentioned problems is as follows.

[0010] [1] A method for producing a recycled 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 filtration step of filtering the mixture (1) using a filter medium previously 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) to synthesize a polymer and obtain a recycled synthetic resin containing the thermoplastic resin and the polymer, wherein a 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) coated on the filter medium is 0.5 kg / m２ 5.0kg / m or more ２ The filtration resistance in the filtration step is 2.0 × 10 or less. １２ m －１ A method for producing recycled synthetic resin, characterized in that:

[0011] [2] 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, alumina silicate, and zeolite. [1] The method for producing a regenerated synthetic resin.

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

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

[0014] [5] A method for recycling a discarded 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 filtration step of filtering the mixture (1) using a filter medium previously 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) to synthesize a polymer and obtain a recycled synthetic resin containing the thermoplastic resin and the polymer, wherein 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 coating amount of the filter aid (B) on the filter medium is 0.5 kg / m ２ 5.0kg / m or more ２ The filtration resistance in the filtration step is 2.0 × 10 or less. １２ m －１ A method for regenerating discarded resin, characterized in that:

[0015] According to the present invention, a method for producing recycled synthetic resin can be provided, which can perform filtration to remove foreign matter contained in discarded resin continuously at a high processing speed for a long period of time, even when using discarded resin, and can produce high-quality synthetic resin. Furthermore, according to the present invention, a method for producing molded articles can be provided using the recycled synthetic resin obtained by the above-mentioned production method. Furthermore, according to the present invention, a method for recycling discarded resin can be provided, which can perform filtration to remove foreign matter contained in discarded resin continuously at a high processing speed for a long period of time, and can produce high-quality recycled synthetic resin.

[0016] FIG. 1 is a schematic diagram of one embodiment of a polymerization apparatus that can be used in the polymerization process.

[0017] The present invention will be described in detail below by way of example based on embodiments thereof.

[0018] <Method for producing recycled synthetic resin> A method for producing recycled synthetic resin according to one embodiment of the present invention (hereinafter sometimes referred to as the "method for producing synthetic resin according to this embodiment") comprises 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 filtration step of filtering the mixture (1) using a filter material previously 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). In the method for producing synthetic resin according to this embodiment, 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 coating amount of the filter aid (B) on the filter material is 0.5 kg / m ２ 5.0kg / m or more ２ the filtration resistance in the filtration step is 2.0 × 10 or less; １２ m －１ In the polymerization step, a polymer is synthesized by polymerizing a radically polymerizable monofunctional monomer, and the thermoplastic resin and a recycled synthetic resin containing the polymer are 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, the filter aid (A) and the filter aid (B) are each used in a predetermined manner and in a predetermined amount, so that the filtered material is less likely to come into direct contact with the filter material during filtration, and the filtration resistance (cake resistance + filter material resistance) can be significantly reduced, thereby improving filtration characteristics. Furthermore, in the synthetic resin manufacturing method of this embodiment, a radically polymerizable monofunctional monomer is polymerized in the polymerization step to newly synthesize a polymer, and the final recycled synthetic resin can be composed of a 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 at a high processing speed for a long period of time, and a high-quality synthetic resin can be obtained.

[0020] (Mixing step) In the present embodiment, the mixing step is a step of mixing the discarded thermoplastic resin, the radical polymerizable monofunctional monomer, and the filter aid (A) to obtain a mixture (1). In addition, the discarded thermoplastic resin may usually contain foreign matter such as colorants, color formers, paper powder, inorganic substances, etc., so the mixture (1) obtained in the mixing step may also contain these foreign matter.

[0021] To obtain the mixture (1), only the discarded thermoplastic resin, the radical 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., non-discarded thermoplastic resin).

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

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

[0024] Waste plastics, including packaging materials, are typically collected at facilities with recycling equipment to be recycled into recycled raw materials. These waste plastics often contain a mixture of plastic film, molded plastic, and other materials. Collected waste plastics are often printed to enhance visibility during distribution. Furthermore, films, such as plastic films, are often laminated with paper, metal foil, or inorganic vapor-deposited layers such as alumina or silica to provide functionality. In other words, waste plastics are often in the form of a composition containing foreign matter, such as colorants, color formers, paper powder, and inorganic substances derived from metal foil or inorganic vapor-deposited layers, which are printing materials. In this regard, the synthetic resin manufacturing method of the present embodiment can achieve the desired objective even when such waste plastics are mixed to obtain the mixture (1).

[0025] Examples of the thermoplastic resin constituting the discarded thermoplastic resin include styrene-based resins, (meth)acrylic-based resins, vinyl-based resins, etc. These thermoplastic resins may be used alone or in combination of two or more.

[0026] The styrene-based resin refers to a resin obtained by polymerizing at least styrene as a monomer, and examples of the styrene-based resin include a resin obtained by polymerizing substantially only styrene (i.e., polystyrene) and a resin obtained by copolymerizing styrene and a comonomer copolymerizable with styrene.

[0027] Examples of comonomers copolymerizable with styrene include aromatic vinyls other than styrene, such as methylstyrene (a-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 difatty acid anhydrides, such as maleic anhydride and itaconic anhydride; and unsaturated difatty acid imides, such as N-phenylmaleimide. These comonomers may be used alone or in combination of two or more.

[0028] In addition to the above-mentioned styrene-based resins, there are various variations, such as a resin obtained by graft-polymerizing a rubber polymer onto a continuous phase of the above-mentioned styrene-based resin and dispersing it in particulate form; a resin obtained by graft-polymerizing a rubber polymer onto a continuous phase of a copolymer of styrene and a multibranched macromonomer and dispersing it in particulate form; a copolymer of styrene and a multibranched macromonomer; etc. Any of these variations of styrene-based resins can be used in this embodiment.

[0029] Examples of (meth)acrylic resins include polymers or copolymers of radically polymerizable monofunctional monomers containing (meth)acrylic acid esters as the main component. 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, and phenoxyethyl (meth)acrylate. Further, examples of the (meth)acrylic resin include those obtained by copolymerizing the above-mentioned (meth)acrylic acid esters with aromatic vinyl monomers other than styrene used in the above-mentioned styrene-based resins, or monomers having a vinyl group used in the below-mentioned vinyl-based resins.

[0030] Examples of vinyl resins include homopolymers of monomers having a vinyl group, copolymers of a monomer having a vinyl group and a comonomer copolymerizable with the monomer, etc. Specific 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-methacrylic acid ester copolymer, vinyl chloride-acrylonitrile copolymer, vinyl chloride-various vinyl ether copolymers, and blends thereof. Also usable are blends of the vinyl chloride resins described above with chlorine-free synthetic resins (e.g., acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, ethylene-vinyl acetate copolymers, ethylene-ethyl (meth)acrylate copolymers, polyesters, etc.).

[0032] Examples of polymers using vinyl acetate (vinyl acetate resins) include homopolymers of vinyl acetate monomers and copolymers of vinyl acetate monomers and unsaturated monomers copolymerizable with said monomers. Examples of unsaturated monomers include long-chain (meth)acrylic monomers typified 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 typified 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 above-mentioned materials, the thermoplastic resin constituting the discarded thermoplastic resin is preferably a styrene-based resin, and more preferably polystyrene. Styrene-based resins, particularly polystyrene, are used in many fields, such as food packaging trays, cases for electrical appliances or information devices, heat insulating materials, and cushioning materials, and also account for a large proportion of discarded plastics. Therefore, using discarded 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 proportion is 0.1% by mass or more, the processing efficiency of discarded thermoplastic resin and therefore the recycling rate can be improved. Furthermore, if the proportion is 50% by mass or less, insolubility of the resin in mixture (1) can be suppressed, and pressure abnormalities can be suppressed in the subsequent polymerization step, making operation easier. From the same viewpoint, the proportion is more preferably 5% by mass or more, even more preferably 10% by mass or more, and more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0035] [Radical Polymerizable Monofunctional Monomer] In the method for producing a synthetic resin according to the present embodiment, a radical polymerizable monofunctional monomer is mixed to obtain the mixture (1).

[0036] Examples of radically polymerizable monofunctional monomers include aromatic vinyls such as styrene, methylstyrene (a-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 difatty acid anhydrides such as maleic anhydride and itaconic anhydride; unsaturated difatty 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 alone or in combination of two or more.

[0037] Regarding a suitable combination of a discarded thermoplastic resin and a 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 this case, it is advantageous in terms of improving the filtration characteristics and the quality of the resulting recycled synthetic resin.

[0038] Moreover, the radically polymerizable monofunctional monomer is preferably a monomer derived from naphtha, from the viewpoint of suppressing deterioration in the physical properties of the resulting recycled synthetic resin.

[0039] The radical polymerizable monofunctional monomer is preferably capable of dissolving the discarded thermoplastic resin. In addition, the radical polymerizable monofunctional monomer is preferably passed through a filter material in the filtration process described below. In other words, the radical polymerizable monofunctional monomer is preferably in a liquid state during the filtration process described below. Based on these points, an appropriate radical polymerizable monofunctional monomer can be selected.

[0040] The proportion of the radically polymerizable monofunctional monomer 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 proportion is 50% by mass or more, insolubility of the discarded thermoplastic resin in mixture (1) can be suppressed, and pressure abnormalities can be suppressed in the subsequent polymerization step, making operation easier. Furthermore, if the proportion is 98% by mass or less, the processing efficiency of the discarded thermoplastic resin and, ultimately, the recycling rate can be improved. From the same viewpoint, the proportion is more preferably 60% by mass or more, even more preferably 65% ​​by mass or more, and more preferably 95% by mass or less, and even more preferably 90% by mass or less.

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

[0042] The filter aid (A) is not particularly limited, but is preferably one or more selected from diatomaceous earth, pearlite, 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 can be further reduced, and the filtration processing speed can be further increased. In addition, 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 improved. From the same viewpoint, the permeability of the filter aid (A) is more preferably 0.80 darcy or more, more preferably 1.25 darcy or more, even more preferably 1.50 darcy or more, and 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, the "permeability" of the filter aids (filter aid (A) and filter aid (B)) is calculated using Darcy's formula. Specifically, the permeability is calculated by the Darcy formula for a filter having a thickness of 1 cm and an area of ​​1 cm. ２ A fluid with a viscosity of 1 cp flows at a rate of 1 cm per second through a packed bed of filter aid. ３ When the flow rate is 1 darcy, the permeability is defined as 1 darcy.

[0045] The proportion of the filter aid (A) in the total amount of the mixture (1) must be 1% by mass or more and 15% by mass or less. If the proportion is less than 1% by mass, the cake resistance increases during filtration, and the filtration processing speed may decrease. If the proportion is more than 15% by mass, the cake resistance may increase and the filtration processing speed may decrease. From the same viewpoint, the proportion of the filter aid (A) in the total amount of the mixture (1) is preferably 1.0% by mass or more, preferably 1.5% by mass or more, more preferably 2% by mass or more, and preferably 10% by mass or less, more preferably 6% by mass or less, and even more preferably 4% by mass or less.

[0046] (Filtration step) In this embodiment, the filtration step is a step of filtering the mixture (1) obtained in the mixing step. This filtration needs to be performed using a filter material pre-coated with the filter aid (B), and a filtrate mixture (2) is obtained by this filtration.

[0047] [Filter Material] The filter material used in the filtration step is not particularly limited, and examples thereof include filter paper, ceramic filters, glass filters, membrane filters, polytetrafluoroethylene (PTFE) filter cloth, polyphenylene sulfide (PPS) filter cloth, polypropylene (PP) filter cloth, polyester filter cloth, and nylon filter cloth.

[0048] [Filter Aid (B)] The filter aid (B) is used to coat the filter medium in advance, and is typically a solid.

[0049] As filter aid (B), there is no particular limitation, but it is preferably one or more selected from diatomaceous earth, pearlite, cellulose fiber, clay, activated carbon, alumina, silica, alumina silicate and zeolite.In this case, it can further improve filtration characteristics (processing speed, long-term operation etc.).In addition, filter aid (B) and above-mentioned filter aid (A) can be the same or different.

[0050] The permeability of the filter aid (B) coated on the filter material 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 material resistance added with coating can be further reduced, and the filtration processing speed can be further increased.In addition, if the permeability of the filter aid (B) is 2.00 darcy or less, the possibility that the filtered material directly contacts the filter material during filtration can be sufficiently reduced, and long-term continuous filtration can be more reliably performed.From the same viewpoint, the permeability of the filter aid (B) is more preferably 0.10 darcy or more, more preferably 0.30 darcy or more, more preferably 0.50 darcy or more, more preferably 1.50 darcy or less, more preferably 1.00 darcy or less, and more preferably 0.80 darcy or less.

[0051] [Coating of filter material] In this embodiment, use the filter material that is coated with filter aid (B) in advance to filter.In this respect, before the filtration process, can carry out the operation of coating filter aid (B) on filter material.Or can use the commercially available filter material that is coated with filter aid (B).

[0052] The method of coating the filter aid (B) on the filter material is not particularly limited.For example, the mixed solution obtained by dispersing the filter aid (B) in a solvent is sent into a filter device equipped with a filter material, and then filtering is performed, so that the filter aid (B) can be coated on the filter material.As the filter device, the filter device used in the subsequent filtration step can be used.In addition, as the solvent for dispersing the filter aid (B), it is preferable to use the same one as the radical polymerizable monofunctional monomer used in this embodiment.

[0053] The coating amount of the filter aid (B) on the filter medium is 0.5 kg / m ２ 5.0kg / m or more ２ The coating amount must be 0.5 kg / m or less. ２ If the coating amount is less than 5.0 kg / m, the filtered material may come into direct contact with the filter material during filtration, which may make it impossible to perform filtration continuously for a long period of time. ２ From the same viewpoint, the coating amount of the filter aid (B) on the filter medium is 0.8 kg / m or less. ２ More than 1.0 kg / m is preferable. ２ More preferably, 1.2 kg / m or more ２ More preferably, 4.0 kg / m ２ Preferably less than 3.5 kg / m ２ More preferably, 3.0 kg / m or less ２ The following is even more preferred:

[0054] [Filtration] The filtration method is not particularly limited, and examples thereof include natural filtration, reduced pressure filtration, pressure filtration, centrifugal filtration, and cross-flow filtration. Filtration may be carried out continuously or batchwise.

[0055] The temperature of the mixture (1) during filtration is preferably a temperature at which the polymerization of the radically polymerizable monofunctional monomer does not proceed. Also, taking into consideration the viscosity suitable for filtration, the temperature of the mixture (1) during filtration is preferably 20° C. or higher and 70° C. or lower.

[0056] In this embodiment, the filtration resistance in the filtration step is 2.0 × 10 １２ m －１ The following is the result. This allows for efficient filtration to obtain high-quality filtrate. Note that, the filtration resistance can be expressed as the sum of the cake resistance and the filter resistance described below. In addition, this filtration resistance is caused by factors such as the type and amount of the filter aid (A) used; the type of filter material used; the type, amount, compounding ratio and coating amount of the filter aid (B) used; and so on, so it can be achieved by appropriately selecting these factors.

[0057] The cake resistance in the filtration process is 1.0 x 10 １０ m －１ Above 1.0 x 10 １２ m －１ Preferably, it is less than 1 / 2. If cake resistance is within the above range, it can achieve a good balance between the removal performance of foreign matter and filtration characteristics (processing speed, long-term operation, etc.). This cake resistance is caused by factors such as the type and amount of filter aid (A) used; the type of filter material used; the type, amount, compounding ratio and coating amount of filter aid (B) etc. in a complex manner, so it is preferable to select these factors appropriately.

[0058] The filter resistance in the filtration process is 1.0 x 10 ９ m －１ Above 1.0 x 10 １２ m －１ Preferably, the resistance of filter material is below the above range.If the resistance of filter material is within the above range, it can prevent the direct contact of filtered material with filter material and achieve a good balance with filtration characteristics (processing speed, long-term operation etc.).This resistance of filter material is caused by the type, amount, compounding ratio and coating amount of filter aid (B) and the type of filter material used; etc., in a complex manner, so it is preferable to select these factors appropriately.

[0059] The filtered mixture (2) obtained in the filtration step typically contains the thermoplastic resin and the radical polymerizable monofunctional monomer mixed in the mixing step. The filtered mixture (2) can also consist of only the thermoplastic resin and the radical polymerizable monofunctional monomer. Meanwhile, the filter aid (A) mixed in the mixing step is typically separated as a cake (filtered product) in the filtration step. Furthermore, if there is any thermoplastic resin that has not been completely dissolved in the mixture (1), this thermoplastic resin can also be separated as a cake (filtered product) in the filtration step.

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

[0061] In this polymerization process, the thermoplastic resin mixed in the mixing process is not substantially involved, and the radically polymerizable monofunctional monomer is polymerized as the only monomer to synthesize a new polymer. Therefore, the final recycled synthetic resin can be composed of thermoplastic resin (derived from discarded thermoplastic resin) from which foreign matter has been removed by filtration and the newly synthesized polymer. Therefore, the resulting recycled synthetic resin is of the same or higher quality as recycled resin obtained by conventional recycling methods.

[0062] The polymerization method is not particularly limited, and known methods can be used. The polymerization system is also not particularly limited, and examples thereof include bulk polymerization, suspension polymerization, and solution polymerization. The polymerization may be carried out continuously or batchwise, but from the viewpoint of production efficiency, it is preferable to carry out the polymerization continuously.

[0063] In the polymerization step, a radical polymerization initiator can be used without any 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; dicinnamoyl peroxide; peroxyesters such as t-butylperoxybenzoate, di-t-butylperoxyisophthalate, and t-butylperoxyisopropyl monocarbonate; and azo compounds such as N,N'-azobisisobutylnitrile, N,N'-azobis(cyclohexane-1-carbonitrile), 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 alone or in combination of two or more.

[0064] In the polymerization step, 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 the chain transfer agent include monofunctional chain transfer agents having one chain transfer group and polyfunctional chain transfer agents having multiple chain transfer groups. Examples of the monofunctional chain transfer agent include alkyl mercaptans and thioglycolic acid esters. Examples of the polyfunctional chain transfer agent include polyhydric alcohols in which hydroxy groups are esterified with thioglycolic acid or 3-mercaptopropionic acid. Examples of the polyhydric alcohols include ethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, and sorbitol.

[0065] In the polymerization step, 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 recycled synthetic resin.

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

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

[0068] The polymerization reaction product discharged by the pump 11 may be supplied to a devolatilizing tank to volatilize unreacted radically polymerizable monofunctional monomers. In this case, two devolatilizing tanks may be connected together, and it is preferable to adjust the pressure of the first devolatilizing tank to about 4.0 kPa and the second devolatilizing tank to about 1.3 kPa.

[0069] In the polymerization apparatus shown in Figure 1, if necessary, a radical polymerizable monofunctional monomer 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. In addition, in the polymerization apparatus shown in Figure 1, a radical polymerizable monofunctional monomer 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 a molded product> 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 according to this embodiment") is characterized in that the recycled synthetic resin obtained by the above-described manufacturing method is molded to obtain a molded product.

[0071] According to the method for manufacturing a molded product of this embodiment, molding is performed using high-quality synthetic resin (recycled synthetic resin) obtained by the above-mentioned synthetic resin manufacturing method, so that molded products of equal or higher quality than those obtained by conventional methods can be obtained.

[0072] The shape of the molded product produced by the molded product production method of this embodiment is not particularly limited, and can be changed appropriately depending on the purpose.

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

[0074] In the molding process, lubricants, antistatic agents, antioxidants, heat stabilizers, ultraviolet absorbers, dyes, plasticizers, etc. can be used within the range that does not impair the physical properties of the recycled synthetic resin.

[0075] In the molding process, a molded product may be obtained directly from the resin raw material, or alternatively, an intermediate molding material such as pellets may be prepared from the resin raw material such as recycled synthetic resin, and then the intermediate molding material may be used to manufacture a molded product.

[0076] Specifically, in the molding process, an intermediate molding material such as pellets can be obtained by melt-kneading and extruding a resin material. This series of operations can be performed using, for example, a kneader, a roll mill, a single-screw extruder, a twin-screw extruder, a rotor-type twin-screw kneader, or the like. The obtained intermediate molding material such as pellets can then be heat-molded to finally obtain a molded product. The heat-molding method is not particularly limited, and examples include injection molding, extrusion molding, blow molding, and compression molding.

[0077] <Method 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") comprises 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 material previously 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 synthetic resin manufacturing method of this 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; and the coating amount of the filter aid (B) on the filter material is 0.5 kg / m ２ 5.0kg / m or more ２ the filtration resistance in the filtration step is 2.0 × 10 or less; １２ m －１ In the polymerization step, a polymer is synthesized by polymerizing a radically polymerizable monofunctional monomer, and the thermoplastic resin and a recycled synthetic resin containing the polymer are obtained.

[0078] The steps of the recycling method of this embodiment are typically the same as those of the synthetic resin manufacturing method of this embodiment described above. Therefore, the details of the recycling method of this embodiment can be explained using the explanation of the synthetic resin manufacturing method of this embodiment described above. Furthermore, according to the recycling method of this embodiment, filtration to remove foreign matter contained in discarded resin can be performed continuously at a high processing speed for a long period of time, and high-quality recycled synthetic resin can be obtained.

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

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

[0081] (Coating of filter material) Prior to the filtration step, the filter aid (B) was appropriately coated on the filter material. Specifically, first, a predetermined amount of filter aid (B) having the composition shown in Table 1, Table 2, and Table 3 was prepared, and the filter aid (B) was suspended in a solvent in a tank having a stirring blade other than the above-mentioned tank. The solvent used at this time was the same as the radical polymerizable monofunctional monomer used in the mixing step. The obtained suspension was pumped into a filtration device equipped with a filter material (manufactured by Mitsubishi Chemical Engineering Co., Ltd., Schneider filter, filter material (filter cloth): made of PPS, filtration area: 0.2 m ２ The solution was sent into a filter medium (filtering chamber) and pressure-filtered at a pressure of 0.1 MPa. In this way, the filter aid (B) was coated on the filter medium. At this time, the coating amount (kg / m) of the filter aid (B) in each example was ２ ) are shown in Tables 1, 2 and 3.

[0082] (Filtration step) Next, the mixture (1) obtained in the mixing step was pumped into the above-mentioned filtration device at room temperature (about 25°C) and subjected to pressure filtration at a pressure of 0.4 MPa. This removed foreign matter and the like from the mixture (1), and a filtrate mixture (2) was obtained.

[0083] (Polymerization step) The filtrate mixture (2) was introduced into the polymerization apparatus shown in Figure 1, and the radical polymerizable monofunctional monomer in the filtrate mixture (2) was polymerized by continuous polymerization. The mixture was then passed through a devolatilization tank to appropriately volatilize unreacted radical polymerizable monofunctional monomer, thereby obtaining a recycled synthetic resin containing the thermoplastic resin blended during the mixing step and a polymer formed by polymerization of the radical polymerizable monofunctional monomer blended during the mixing step. In the polymerization step, Perbutyl Z (manufactured by NOF Corporation) was used as the radical polymerization initiator.

[0084] During the above-described series of operations, the following measurements and evaluations were carried out, and the results are shown in Tables 1, 2, and 3, respectively.

[0085] <Filter Resistance> In the filtration for coating the filter aid (B), the amount of filtrate per unit time and the viscosity of the obtained filtrate were measured. In particular, the viscosity was measured by the Electromagnetically Spinning Method (EMS) under the following conditions. (Conditions) Measuring device model number: EMS-1000S (Kyoto Electronics Manufacturing Co., Ltd.) Spherical probe: Aluminum, 2 mmφ (Kyoto Electronics Manufacturing Co., Ltd.) Sample amount: 300 μL Probe rotation speed: 1000 rpm

[0086] These measurements were used to calculate the filter resistance (R ｍ ) (unit: m －１ ) (filter medium resistance including coating) is calculated using the following formula: [In the formula, ΔP １ is the filtration pressure during filtration (filter aid (B) coating), and μ １ is the viscosity of the filtrate during filtration (filter aid (B) coating), and u １ is the filtration rate per unit area during filtration (coated with the filter aid (B)). ]. In the comparative example in which the filter aid (B) coating is not performed, the filter material resistance (R ｍ ) was measured.

[0087] <Cake Resistance> In 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 measurement was carried out under the same conditions as above. These measured values ​​and the above filter medium resistance (R ｍ ) and the cake resistance (R ｃ ) (unit: m －１ ) into the following formula: [In the formula, ΔP ２ is the filtration pressure during filtration (filtration process), and μ ２ is the viscosity of the filtrate during filtration (filtration process), and u ２ is the filtration rate per unit area during filtration (filtration process).

[0088] <Filtration Resistance> The filtration resistance was calculated as the sum of the cake resistance and the filter medium resistance.

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

[0090] <Filtration Completion Time> In the filtration step, the time required to obtain 5 L of filtrate mixture (2) was measured. A smaller measured value indicates a higher filtration processing speed. In the examples in the table where the filtration completion time is indicated as "-", the filtered material came into direct contact immediately after the start of filtration, so a filtrate mixture was not obtained.

[0091] <Total Light Transmittance of Synthetic Resin> The total light transmittance of the synthetic resin obtained in the polymerization step 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 determined by calculating {a / (a+b)}×100, where a is the mass of the discarded thermoplastic resin and b is the mass of the polymerized radical polymerizable monofunctional monomer.

[0093]

[0094]

[0095]

[0096] Diatomaceous earth A... "Radiolite #100", manufactured by Showa Chemical Industry Co., Ltd., transmittance: 0.05 darcy Diatomaceous earth B... "Radiolite #300", manufactured by Showa Chemical Industry Co., Ltd., transmittance: 0.11 darcy Diatomaceous earth C... "Radiolite #600", manufactured by Showa Chemical Industry Co., Ltd., transmittance: 1.10 darcy Diatomaceous earth D... "Radiolite #800", manufactured by Showa Chemical Industry Co., Ltd., transmittance: 1.84 darcy Diatomaceous earth E... "Radiolite #900", manufactured by Showa Chemical Industry Co., Ltd., transmittance: 3.29 darcy Diatomaceous earth F... "Dicalite Speedex", manufactured by Dicalite Corporation, transmittance: 1.80 darcy Perlite A... "Rocahelp 419", manufactured by Mitsui Kinzoku Perlite Co., Ltd., transmittance: 0.09 darcy Perlite B: "ROCAHELP 439" manufactured by Mitsui Kinzoku Perlite Co., Ltd., transmittance: 0.45 darcy. Perlite C: "ROCAHELP 4189" manufactured by Mitsui Kinzoku Perlite Co., Ltd., transmittance: 1.69 darcy. Perlite D: "TOPCO No. 38" manufactured by Showa Chemical Industry Co., Ltd., transmittance: 1.66 darcy.

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

[0098] From Tables 1 and 2, it can be seen that in the examples according to the present invention, the filtered material did not come into direct contact with the filter medium and the filtration completion time was short, so filtration could be carried out continuously for a long period of time at a high processing speed.In contrast, from Table 3, it can be seen that in the comparative examples, the filtered material came into direct contact with the filter medium, or the filtration completion time was long, or both.

[0099] According to the present invention, a method for producing recycled synthetic resin can be provided, which can perform filtration to remove foreign matter contained in discarded resin continuously at a high processing speed for a long period of time, even when using discarded resin, and can produce high-quality synthetic resin. Furthermore, according to the present invention, a method for producing molded articles can be provided using the recycled synthetic resin obtained by the above-mentioned production method. Furthermore, according to the present invention, a method for recycling discarded resin can be provided, which can perform filtration to remove foreign matter contained in discarded resin continuously at a high processing speed for a long period of time, and can produce high-quality recycled synthetic resin.

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

Claims

1. A method for producing a recycled 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 filtration step of filtering the mixture (1) using a filter medium previously 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) to synthesize a polymer and obtain a recycled synthetic resin containing the thermoplastic resin and the polymer, wherein 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 coating amount of the filter aid (B) on the filter medium is 0.5 kg / m ２ 5.0kg / m or more ２ The filtration resistance in the filtration step is 2.0 × 10 or less. １２ m －１ A method for producing recycled synthetic resin, characterized in that:

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

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

4. A method for producing a molded product, comprising molding the recycled synthetic resin obtained by the method of claim 1 or 2 to obtain a molded product.

5. A method for recycling discarded resin, comprising: a mixing step of mixing a discarded thermoplastic resin, a radical polymerizable monofunctional monomer, and a filter aid (A) to obtain a mixture (1); a filtration step of filtering the mixture (1) using a filter medium previously coated with a filter aid (B) to obtain a filtrate mixture (2); and a polymerization step of polymerizing the radical polymerizable monofunctional monomer in the filtrate mixture (2) to synthesize a polymer and obtain a recycled synthetic resin containing the thermoplastic resin and the polymer, wherein 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 coating amount of the filter aid (B) on the filter medium is 0.5 kg / m ２ 5.0kg / m or more ２ The filtration resistance in the filtration step is 2.0 × 10 or less. １２ m －１ A method for regenerating discarded resin, characterized in that: