WO2023074438A1 - 熱可塑性樹脂の製造方法 - Google Patents

熱可塑性樹脂の製造方法 Download PDF

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Publication number
WO2023074438A1
WO2023074438A1 PCT/JP2022/038587 JP2022038587W WO2023074438A1 WO 2023074438 A1 WO2023074438 A1 WO 2023074438A1 JP 2022038587 W JP2022038587 W JP 2022038587W WO 2023074438 A1 WO2023074438 A1 WO 2023074438A1
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Prior art keywords
polyamide
caprolactam
oligomer
water
solid
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PCT/JP2022/038587
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English (en)
French (fr)
Japanese (ja)
Inventor
浩平 山下
昌佑 高橋
昌史 加藤
美帆子 西村
公哉 加藤
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Toray Industries Inc
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Toray Industries Inc
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Application filed by Toray Industries Inc filed Critical Toray Industries Inc
Priority to CN202280068837.2A priority Critical patent/CN118103438A/zh
Priority to EP22886766.9A priority patent/EP4424758A4/en
Priority to US18/697,715 priority patent/US20250282925A1/en
Priority to JP2022569546A priority patent/JPWO2023074438A1/ja
Priority to KR1020247010247A priority patent/KR20240095408A/ko
Publication of WO2023074438A1 publication Critical patent/WO2023074438A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
    • C07D201/02—Preparation of lactams
    • C07D201/12—Preparation of lactams by depolymerising polyamides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C08J11/14—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with steam or water
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
    • C07D201/16—Separation or purification
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D223/00—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom
    • C07D223/02—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings
    • C07D223/06—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D223/08—Oxygen atoms
    • C07D223/10—Oxygen atoms attached in position 2
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
    • C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
    • C08G69/08—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from amino-carboxylic acids
    • C08G69/14—Lactams
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C08J11/18—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material
    • C08J11/28—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic compounds containing nitrogen, sulfur or phosphorus
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2377/00—Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Derivatives of such polymers
    • C08J2377/02—Polyamides derived from omega-amino carboxylic acids or from lactams thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

  • the present invention is a method for producing a thermoplastic resin from waste polyamide 6 resin composition moldings via ⁇ -caprolactam, which achieves both resource recycling and reduction of greenhouse gas emissions, and comprises a polyamide 6 resin composition.
  • the present invention relates to a method for producing a thermoplastic resin using high-purity ⁇ -caprolactam obtained by depolymerizing a product waste by using only a small amount of water having a high specific heat capacity and a high heat of vaporization.
  • Patent Literature 1 discloses a method of producing hydrocarbons by a process including pyrolysis and steam cracking of waste plastics. Although these methods have the advantage of being able to convert mixed waste plastics into pyrolysis oil, they require cracking at a high temperature of 800°C or higher in order to convert the pyrolysis oil into secondary raw materials such as plastic monomers.
  • the ⁇ -caprolactam recovery method disclosed in Patent Document 2 is a high-yield reaction with a depolymerization yield of polyamide 6 of 80% or more, the depolymerization reaction takes a long time. Furthermore, since a large amount of superheated steam, about 10 times that of polyamide 6 fiber, is required, this technology remains a problem in achieving both the recycling of fossil resources and the reduction of greenhouse gas emissions. In addition, since this method uses phosphoric acid as a catalyst, the reaction is susceptible to impurities, such as catalyst deactivation due to additives contained in plastics and adhering impurities in waste plastics.
  • the ⁇ -caprolactam recovery methods disclosed in Patent Documents 3 and 4 use only water for the depolymerization reaction, and do not use a catalyst such as phosphoric acid. There is an advantage that reaction deactivation due to does not occur.
  • a large amount of water which has a specific heat capacity of 4.2 kJ/kg K and a heat of vaporization of 2,250 kJ/kg, is about 10 times that of polyamide 6. , a large amount of energy is required for the depolymerization reaction and recovery of ⁇ -caprolactam from a low-concentration ⁇ -caprolactam aqueous solution.
  • thermodynamic equilibrium point of ⁇ -caprolactam produced by depolymerization and the linear oligomer produced by hydrolytic ring-opening of ⁇ -caprolactam shifted to the side of the linear oligomer simply by reducing the amount of water used. It is considered to be
  • the present invention has the following configurations. 1. Production of a thermoplastic resin by obtaining ⁇ -caprolactam by the following steps (a) and (b) using waste (A) of resin moldings containing at least polyamide 6 as a raw material, and polymerizing the raw material containing ⁇ -caprolactam Method. (a) At least one of water (B) heated to 290° C. or higher and 350° C. or lower or polyamide 6 oligomer aqueous solution (B1) heated to 290° C. or higher and 350° C.
  • step (b) of adding and contacting one of them; step (b) of separating the reaction mixture obtained in step (a) into a solid matter and an aqueous solution containing ⁇ -caprolactam by solid-liquid separation (I);
  • the waste (A) of the resin molding is added to water (B) heated to 290° C. or higher and 350° C. or lower, or water (B) heated to 290° C. or higher and 350° C. or lower, Item 1.
  • the method for producing a thermoplastic resin according to Item 1 wherein the step of further adding and contacting the polyamide 6 oligomer aqueous solution (B1) heated to 290°C or higher and 350°C or lower. 3.
  • the reaction mixture is separated into a non-melt and an aqueous solution containing at least ⁇ -caprolactam and polyamide 6 oligomer by solid-liquid separation (b1), and obtained in the step (b1).
  • step (b2) step of separating the obtained filtrate into polyamide 6 oligomer and ⁇ -caprolactam aqueous solution by solid-liquid separation.
  • a polyamide 6 oligomer aqueous solution (B1) obtained by mixing the polyamide 6 oligomer separated in the step (b) or step (b2) with water and heating to 290° C. or higher and 350° C. or lower is used in step (a).
  • the method for producing a thermoplastic resin according to any one of items 1 to 3, characterized by: 5.
  • the aqueous solution of polyamide 6 oligomer (B1) is an extract obtained in a step of hot water extraction of polyamide 6 oligomer from polyamide 6, which is a product of polyamide 6 production, according to items 1 to 4.
  • the mass ratio of water to the polyamide 6 in the waste (A) of the resin molding, or the total mass of the polyamide 6 and the polyamide oligomer in the water and the waste (A) of the resin molding Production of the thermoplastic resin according to any one of items 1 to 5, wherein the product of X and Y is 2,000 or less when the ratio is X:1 and the reaction temperature is Y ° C. Method.
  • the present invention uses only a small amount of water having a high specific heat capacity and heat of vaporization or an aqueous solution of a polyamide 6 oligomer containing water as a solvent to depolymerize the waste of a polyamide 6 resin composition molded body while saving energy.
  • a method for producing a thermoplastic resin using ⁇ -caprolactam can be provided.
  • the present invention is a method for producing a thermoplastic resin in which ⁇ -caprolactam is obtained by using waste (A) of resin moldings containing at least polyamide 6 as a raw material, and the ⁇ -caprolactam-containing raw material is polymerized.
  • Polyamide 6 used in the present invention is a polyamide resin mainly composed of 6-aminocaproic acid and/or ⁇ -caprolactam. Other monomers may be copolymerized to the extent that the object of the present invention is not impaired.
  • main raw material means that a total of 50 mol% or more of 6-aminocaproic acid-derived units or ⁇ -caprolactam-derived units is contained in a total of 100 mol% of the monomer units constituting the polyamide resin. means It is more preferable to contain 6-aminocaproic acid-derived units or ⁇ -caprolactam-derived units in an amount of 70 mol% or more, more preferably 90 mol% or more.
  • Other monomers to be copolymerized include, for example, amino acids such as 11-aminoundecanoic acid, 12-aminododecanoic acid and para-aminomethylbenzoic acid, lactams such as ⁇ -lyrolactam, tetramethylenediamine, pentamethylenediamine, Hexamethylenediamine, 2-methylpentamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-/2,4,4-trimethylhexamethylenediamine, 5-methylnona Aliphatic diamines such as methylenediamine, aromatic diamines such as metaxylylenediamine and paraxylylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1-amino-3 -aminomethyl-3,5,5-trimethylcyclohexane, bis
  • polyamides 6 may be added with polymerization degree modifiers, terminal group modifiers, and the like.
  • polymerization degree modifiers and terminal group modifiers include acetic acid and benzoic acid.
  • the degree of polymerization of the polyamide 6 of the present invention is not particularly limited, but the relative viscosity measured at 25 ° C. in a 98% concentrated sulfuric acid solution with a resin concentration of 0.01 g / mL is in the range of 1.5 to 5.0. is preferred. When the relative viscosity is in such a preferable range, the reaction efficiency with a small amount of water tends to be high, so it can be exemplified preferably.
  • Polyamide 6 of the present invention may contain a cyclic oligomer represented by the following formula (a).
  • the amount of the cyclic oligomer represented by the following formula (a) contained in polyamide 6 is not particularly limited, but is preferably 2.0% by mass or less, more preferably 1.8% by mass or less, and 1.5% by mass. It is more preferably exemplified that it is not more than mass %.
  • m is an integer of 2-4.
  • the cyclic oligomer represented by the following formula (a) melts and volatilizes, causing line clogging and the like.
  • the present invention uses waste resin moldings containing at least polyamide 6 as a raw material.
  • any waste of the resin molded body containing at least polyamide 6 may be used.
  • the waste of resin moldings containing polyamide 6 includes polyamide 6 products, industrial waste generated in the process of manufacturing polyamide 6 products, and waste after use of polyamide 6 products.
  • Polyamide 6 products include textile structures for clothing such as used clothes, uniforms, sportswear and innerwear; industrial textile structures such as curtains, carpets, ropes, nets, belts and sheets; Examples include electronic molded parts, aircraft parts, industrial machine parts, film products, extrusion molded products, in-situ polymerized molded products, RIM molded products, and the like. Furthermore, product scraps, pellet scraps, lump-like scraps, and cutting scraps generated during the cutting process are also subject to waste.
  • the waste (A) of the resin molding of the present invention can further contain an alkali metal halide within a range that does not impair the purpose of the present invention.
  • alkali metal halides include alkali metal halides such as lithium iodide, sodium iodide, potassium iodide, lithium bromide, sodium bromide, potassium bromide, lithium chloride, sodium chloride and potassium chloride. , and two or more of these can be used in combination.
  • potassium iodide is preferable from the viewpoint of easy availability, excellent dispersibility in polyamide 6, higher reactivity with radicals, and improved retention stability at high temperatures.
  • alkali metal halides can be used in combination with Group 11 metal halides such as copper (I) iodide, copper (I) bromide, and copper (I) chloride to further improve the retention stability at high temperatures. It is more preferably used for
  • alkali metal halides are preferably blended in an amount of 0.01 to 1 part by mass with respect to 100 parts by mass of polyamide 6 in the waste (A) of resin moldings.
  • the content of the alkali metal halide is more preferably 0.02 to 0.5 parts by mass, more preferably 0.03 to 0.4 parts by mass.
  • the waste (A) of the resin molding of the present invention may contain a fibrous filler.
  • a fibrous filler herein may be any filler having a fibrous shape. Specifically, glass fibers, polyacrylonitrile (PAN)-based and pitch-based carbon fibers, stainless steel fibers, metal fibers such as aluminum fibers and brass fibers, polyester fibers, organic fibers such as aromatic polyamide fibers, gypsum fibers, ceramics Fibers, asbestos fibers, zirconia fibers, alumina fibers, silica fibers, titanium oxide fibers, silicon carbide fibers, rock wool, potassium titanate whiskers, silicon nitride whiskers, wollastonite, fibrous and whisker fillers such as alumina silicate, nickel , copper, cobalt, silver, aluminum, iron, and alloys thereof. You may contain 2 or more types of these.
  • the content of the fibrous filler is preferably 1 to 200 parts by mass with respect to 100 parts by mass of the waste (A) of resin moldings
  • the waste (A) of the resin molding of the present invention is further compounded with fillers other than fibrous fillers, thermoplastic resins other than polyamide 6, various additives, etc., within a range that does not impair the purpose of the present invention. be able to.
  • Fillers other than fibrous fillers may be either organic fillers or inorganic fillers, and examples include non-fibrous fillers, and two or more of these fillers may be blended.
  • non-fibrous fillers examples include talc, wollastonite, zeolite, sericite, mica, kaolin, clay, pyrophyllite, bentonite, asbestos, alumina silicate, non-swelling silicates such as calcium silicate, Li-type fluorine Swellable layered silicates such as teniolite, Na-type fluoroteniolite, Na-type tetrasilicon fluoromica, swelling mica of Li-type tetrasilicon fluoromica, silicon oxide, magnesium oxide, alumina, silica, diatomaceous earth, zirconium oxide, titanium oxide, Metal oxides such as iron oxide, zinc oxide, calcium oxide, tin oxide and antimony oxide, metal carbonates such as calcium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, dolomite and hydrotalcite, calcium sulfate and barium sulfate metal hydroxides such as metal sulfates, magnesium hydroxide, calcium hydroxide, aluminum
  • Organic onium ions include, for example, ammonium ions, phosphonium ions, and sulfonium ions.
  • additives include N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamide), tetrakis[methylene-3-(3',5'-di- Phenolic compounds such as t-butyl-4'-hydroxyphenyl)propionate]methane, phosphorus compounds, mercaptobenzimidazole compounds, dithiocarbamic acid compounds, sulfur compounds such as organic thioacid compounds, N,N'- Thermal stabilizers such as amine compounds such as di-2-naphthyl-p-phenylenediamine and 4,4'-bis( ⁇ , ⁇ -dimethylbenzyl)diphenylamine, isocyanate compounds, organic silane compounds, organic titanate compounds , organic borane compounds, coupling agents such as epoxy compounds, polyalkylene oxide oligomer compounds, thioether compounds, ester compounds, plasticizers such as organic phosphorus compounds, crystal nuclei such as
  • thermoplastic resins other than polyamide 6 contained in the waste (A) of resin moldings include polyamide resins other than polyamide 6, polyester resins, polyolefin resins, modified polyphenylene ether resins, polysulfone resins, polyketone resins, poly Etherimide resin, polyarylate resin, polyethersulfone resin, polyetherketone resin, polythioetherketone resin, polyetheretherketone resin, polyimide resin, polyamideimide resin, polyethylene tetrafluoride resin, polyphenylene sulfide resin, etc. . You may mix
  • the amount of the thermoplastic resin other than polyamide 6 is preferably 30 parts by mass or less per 100 parts by mass of polyamide 6 in the waste (A) of the resin moldings of the present invention.
  • ⁇ -caprolactam is obtained by using waste (A) of a resin molding containing at least polyamide 6 as a raw material, and the raw material containing ⁇ -caprolactam is polymerized to produce a thermoplastic resin. The method.
  • thermoplastic resin here may be any thermoplastic resin obtained by polymerizing a raw material containing ⁇ -caprolactam, for example, polyamide 6 containing ⁇ -caprolactam as a main raw material, or As a raw material, copolymers of monomers other than ⁇ -caprolactam or block copolymers with polyalkylene glycol such as polyethylene glycol may be used.
  • Examples of monomers other than ⁇ -caprolactam include amino acids such as 11-aminoundecanoic acid, 12-aminododecanoic acid, and para-aminomethylbenzoic acid; lactams such as ⁇ -lyrolactam; methylenediamine, 2-methylpentamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-/2,4,4-trimethylhexamethylenediamine, 5-methylnonamethylene Aliphatic diamines such as diamines, aromatic diamines such as metaxylylenediamine and paraxylylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1-amino-3- aminomethyl-3,5,5-trimethylcyclohexane, bis(4-aminocyclohexyl)methane, bis(3-methyl-4
  • the ⁇ -caprolactam-derived unit is preferably contained in a total of 50 mol% or more, more preferably 70 mol% or more, and 90 mol% or more. is more preferred.
  • the present invention relates to a method for depolymerizing waste resin moldings containing at least polyamide 6, polyamide 6 is preferable as the thermoplastic resin from the viewpoint of repeated recycling of fossil resources.
  • the degree of polymerization of the thermoplastic resin of the present invention is not particularly limited. A range is preferred. When the relative viscosity of the thermoplastic resin is in such a preferable range, it tends to be possible to achieve both strength, rigidity, and toughness, which are characteristics of the thermoplastic resin obtained using ⁇ -caprolactam as a main raw material. be able to.
  • the polyamide 6 oligomer used in the present invention is a polyamide 6 oligomer containing 6-aminocaproic acid and/or ⁇ -caprolactam as a main component.
  • Other monomers may be included as long as the object of the present invention is not impaired.
  • "mainly constituting” means that the unit derived from 6-aminocaproic acid or the unit derived from ⁇ -caprolactam in the total 100 mol% of the monomer units constituting the polyamide 6 oligomer is 50 mol% or more in total. means to contain It is more preferable to contain 6-aminocaproic acid-derived units or ⁇ -caprolactam-derived units in an amount of 70 mol% or more, more preferably 90 mol% or more.
  • polyamide 6 oligomer examples include, for example, amino acids such as 11-aminoundecanoic acid, 12-aminododecanoic acid, and para-aminomethylbenzoic acid, lactams such as ⁇ -laurolactam, tetramethylenediamine, and pentamethylene.
  • Diamine Diamine, hexamethylenediamine, 2-methylpentamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-/2,4,4-trimethylhexamethylenediamine, 5- Aliphatic diamines such as methylnonamethylenediamine, aromatic diamines such as metaxylylenediamine and paraxylylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1-amino -3-aminomethyl-3,5,5-trimethylcyclohexane, bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, Alicyclic diamines such as bis(aminopropyl)piperazine and
  • the number average molecular weight of the polyamide 6 oligomer of the present invention is not particularly limited, but the number average molecular weight is preferably in the range of 100 to 5000, more preferably in the range of 200 to 3000, and in the range of 200 to 2000. One is particularly preferable and can be exemplified. When the molecular weight of the polyamide 6 oligomer is within such a preferable range, the solubility in water tends to be high, and the polyamide 6 oligomer aqueous solution (B1) used in the present invention tends to be easily prepared.
  • the number average molecular weight here was calculated by GPC analysis using 1,1,1,3,3,3-hexafluoro-2-propanol as a solvent. Showa Denko GPC-HFIP805 was used as the column, and PMMA was used as the standard substance.
  • composition of the polyamide 6 oligomer used in the present invention is not particularly limited, but the content of the linear polyamide 6 oligomer of 2 to 12-mer contained in the polyamide 6 oligomer is preferably 90% by mass or more. I can give an example. More preferably, the amount of the linear 2-12-mer oligomer is 93% by mass or more, and particularly preferably 95% by mass or more.
  • the solubility in water is increased, and the terminal carboxylic acid concentration of the polyamide 6 oligomer is As the temperature increases, the reaction between polyamide 6 and water is accelerated, and the efficiency of ⁇ -caprolactam production tends to increase.
  • the amount of linear 2- to 12-mer oligomers in the polyamide 6 oligomer was quantitatively analyzed by high-performance liquid chromatography using an aqueous formic acid solution and an acetonitrile formic acid solution as eluents.
  • the method for preparing the polyamide 6 oligomer used in the present invention is not particularly limited.
  • a polyamide 6 oligomer prepared by the same method as that for synthesizing the fatty acid-based polyamide 6 resin may be used.
  • when producing ⁇ -caprolactam by adding a resin composition containing at least polyamide 6 and at least one of water heated to 290° C. or higher and 350° C. or lower or an aqueous solution of polyamide 6 oligomer it is obtained as a by-product.
  • Polyamide 6 oligomers may be used.
  • waste (A) of a resin molding containing polyamide 6 as a resin composition containing polyamide 6, water (B) heated to 290 ° C. or higher and 350 ° C.
  • waste (A) of resin moldings containing polyamide 6 is brought into contact with water (B) heated to 290° C. or higher and 350° C. or lower.
  • Polyamide 6 oligomer obtained as a by-product in the production of ⁇ -caprolactam, or waste (A) of resin moldings containing at least polyamide 6, water heated to 290 ° C. or higher and 350 ° C. or lower or polyamide 6 oligomer It is preferable to use a polyamide 6 oligomer recovered as a by-product when producing ⁇ -caprolactam by adding at least one of the aqueous solutions.
  • the polyamide 6 oligomer aqueous solution (B1) used in the present invention is prepared by heating and mixing the polyamide 6 oligomer and water.
  • Water used for preparing the aqueous polyamide 6 oligomer aqueous solution (B1) is not particularly limited, and tap water, ion-exchanged water, distilled water, well water, etc. can be used. From the viewpoint of , ion-exchanged water and distilled water are preferably used.
  • the concentration of the polyamide 6 oligomer in the polyamide 6 oligomer aqueous solution (B1) used in the present invention is any concentration as long as the polyamide 6 oligomer is dissolved in water when heated to 290 ° C. or higher and 350 ° C. or lower. However, it is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.
  • concentration of the polyamide 6 oligomer is within these preferred ranges, the solubility in water when preparing the aqueous polyamide 6 oligomer solution (B1) is increased, and the aqueous polyamide 6 oligomer solution (B1) can be prepared at a lower temperature. It becomes possible.
  • an extract containing polyamide 6 oligomer obtained in a step of hot water extraction of polyamide 6 oligomer from polyamide 6, which is a product of polyamide 6 production can be used as polyamide 6 oligomer aqueous solution (B1).
  • a polyamide 6 resin obtained by polymerizing ⁇ -caprolactam contains, as impurities, unreacted monomers produced in the polymerization equilibrium reaction and polyamide 6 oligomers. Therefore, in order to remove these, pellets after polymerization are supplied to a hot water extraction tower, and unreacted monomers and polyamide 6 oligomers are extracted and removed by hot water extraction.
  • aqueous solution (B1) of the present invention is also exemplified as a preferable form from the viewpoint of industrial waste reduction. can.
  • the non-melting substance in the present invention may be any non-melting substance contained in the waste (A) of resin moldings containing at least polyamide 6.
  • the waste (A) of the resin molding is depolymerized by adding at least one of water (B) heated to 290° C. or higher and 350° C. or lower or an aqueous polyamide 6 oligomer solution (B1). It is present as a solid state in the reaction mixture when carried out.
  • fillers such as fibrous fillers, non-fibrous fillers, and elastomers used in producing resin molded articles containing polyamide 6, and waste resin molded articles containing polyamide 6 ( Examples include metal parts and rubber parts included in A).
  • non-melt materials are in a solid state when depolymerization of polyamide 6 is performed by adding at least one of water (B) heated to 290 ° C. or higher and 350 ° C. or lower or an aqueous polyamide 6 oligomer solution (B1). Since it remains in the reaction mixture, it can be separated from ⁇ -caprolactam and polyamide 6 oligomer by solid-liquid separation.
  • thermoplastic resin composition of the present invention the waste (A) of the resin molding is treated with water (B) heated to 290 ° C. or higher and 350 ° C. or lower or 290 ° C. or higher and 350 ° C.
  • the water (B) used here or the water in the polyamide 6 oligomer aqueous solution (B1) is not particularly limited, and tap water, ion-exchanged water, distilled water, well water, etc. can be used. From the viewpoint of suppressing side reactions, ion-exchanged water and distilled water are preferably used.
  • step (a) water (B) heated to 290°C or higher and 350°C or lower or water in polyamide 6 oligomer aqueous solution (B1) heated to 290°C or higher and 350°C or lower serves as a reaction substrate.
  • the pressure of water reaches 22.1 MPa and the temperature reaches 374.2° C., it becomes neither a liquid nor a gas. This point is called the critical point of water, and hot water at a temperature and pressure lower than the critical point is called subcritical water.
  • the water used in the present invention is subcritical water
  • the polyamide 6 oligomer aqueous solution is subcritical water in which the polyamide 6 oligomer is dissolved.
  • the temperature of the water (B) and the polyamide 6 oligomer aqueous solution (B1) of the present invention is preferably 300° C. or higher and 340° C. or lower, more preferably 320° C. or higher and 340° C. or lower. By being in such a preferable range, there is a tendency that corrosion of equipment during the reaction can be suppressed.
  • the pressure of the water is preferably higher than the saturated vapor pressure.
  • Water may be in a liquid state, a gaseous state such as water vapor, or both. preferably higher than
  • the upper limit of water pressure is not particularly limited, but can be exemplified as 20 MPa or less. Such a pressure range tends to increase the ionic product of water, which is preferable.
  • a method of pressurizing and sealing the inside of a pressure vessel is used to bring the water into such a pressure range.
  • a gas may be sealed in addition to the water (B) or the polyamide 6 oligomer aqueous solution (B1).
  • gases include air, argon, and nitrogen. From the viewpoint of suppressing side reactions such as oxidation reactions, it is preferable to use nitrogen or argon.
  • the degree of gas pressurization is not particularly limited because it is set to a target pressure, but 0.3 MPa or more can be mentioned.
  • the amount of water used in the water (B) and the aqueous polyamide 6 oligomer aqueous solution (B1) to be used is not particularly limited, but the mass ratio of the water (B) and the polyamide 6 in the waste (A) of the resin molding, the water ( B) and the sum of the water in the aqueous polyamide 6 oligomer solution (B1) and the mass ratio of the sum of the polyamide 6 and the polyamide 6 oligomer, or the sum of the water, the polyamide 6 and the polyamide 6 oligomer in the aqueous polyamide 6 oligomer solution (B1) It is preferable to adjust the amount of water used so that the product of X and Y is 2,000 or less, where the mass ratio of is X:1 and the reaction temperature is Y°C.
  • the product of X and Y is preferably 1,600 or less, more preferably 1,300 or less, and particularly preferably 1,200 or less.
  • the lower limit of the product of X and Y is not particularly limited, but is preferably 300 or more, more preferably 320 or more, and particularly preferably 340 or more.
  • the present invention aims to achieve both the recycling of fossil resources and the reduction of greenhouse gas emissions by recovering ⁇ -caprolactam from waste resin moldings containing polyamide 6 through energy saving, and producing thermoplastic resin therefrom. It is about how to Water has a specific heat capacity of 4.3 kJ/kg K and a heat of vaporization of 2,250 kJ/kg, which are extremely high compared to other organic solvents. When the product is within these preferred ranges, both the production efficiency of ⁇ -caprolactam and energy saving can be achieved.
  • the product of X, Y and Z is 60,000 or less. More preferably 40,000 or less, still more preferably 30,000 or less, and particularly preferably 20,000 or less.
  • the lower limit of the product of X, Y and Z is not particularly limited, but it is preferably 5,000 or more, more preferably 8,000 or more, and particularly preferably 9,000 or more.
  • the method of the reaction by adding at least one of the waste (A) of the resin molding and water (B) or the polyamide 6 oligomer aqueous solution (B1) and bringing them into contact is known as a batch system or a continuous system.
  • Various reaction methods can be adopted. For example, batch type autoclaves, vertical/horizontal reactors, and vertical/horizontal reactors equipped with compression mechanisms such as cylinders in addition to agitators and heating functions. mentioned.
  • it is a continuous type, it is an extruder equipped with a heating function, a tubular reactor, a tubular reactor equipped with a mixing mechanism such as a baffle, a line mixer, a vertical or horizontal reactor, and a vertical reactor equipped with a stirrer.
  • the atmosphere in the production is desirably a non-oxidizing atmosphere, preferably an inert atmosphere such as nitrogen, helium, or argon, and a nitrogen atmosphere is preferable from the viewpoints of economy and ease of handling.
  • step (b) In the present invention, the reaction mixture containing the polyamide 6 oligomer obtained in step (a) and the ⁇ -caprolactam aqueous solution is separated into solids and the ⁇ -caprolactam aqueous solution by solid-liquid separation (I).
  • step (b) a step of Here, the solid matter includes the above-mentioned unmelted matter and precipitated polyamide 6 oligomer.
  • the temperature at which the solid-liquid separation (I) is performed may be in any temperature range as long as the solids and the ⁇ -caprolactam aqueous solution can be separated. The following temperatures are preferred.
  • the temperature at which the solid-liquid separation (I) is performed is preferably 95° C. or lower, and more preferably 90° C. or lower.
  • the temperature at which the solid-liquid separation (I) is performed is more preferably 80° C. or lower, more preferably 60° C. or lower, and 50 ° C. or less can be particularly preferably exemplified.
  • the lower limit temperature for solid-liquid separation (I) is not particularly limited, but is preferably 10°C or higher, more preferably 15°C or higher, and even more preferably 20°C or higher.
  • the waste (A) of the resin molding contains a non-melted material, the non-melted material exists as a solid, and by performing solid-liquid separation (I) at a temperature at which the polyamide 6 oligomer dissolves in water, as a solid component Most non-melts can be separated.
  • the resin molding waste (A) does not contain non-melting substances, ⁇ -caprolactam is soluble in water in the above temperature range, but polyamide 6 oligomer tends to be less soluble in water. Therefore, by performing solid-liquid separation (I) in the above preferred temperature range, most of the polyamide 6 oligomer can be separated as a solid component, and high-purity ⁇ -caprolactam can be recovered.
  • the method for performing solid-liquid separation (I) is not particularly limited, and known methods can be employed. Sedimentation separation, a method combining these methods, and the like can be employed. A decanter separation method in which sedimentation is separated before the filtration operation is also a preferred method.
  • the filter used for the filtration operation should be stable under the conditions for solid-liquid separation (I), and for example, a filter sieve or a sintered plate can be suitably used.
  • the mesh diameter or pore diameter of this filter can be adjusted over a wide range depending on the viscosity, pressure, temperature, size of non-melted matter, purity of the resulting filtrate (content of solids), etc. of the reaction mixture to be filtered. can. In particular, it is effective to select the mesh diameter or pore diameter according to the size in the reaction mixture of the non-molten material recovered as the solid phase component by the solid-liquid separation (I).
  • the filter medium used for solid-liquid separation (I) using the polyamide 6 oligomer as the filtered product must be able to separate the polyamide 6 oligomer and pass a solution containing at least ⁇ -caprolactam and water.
  • a filter medium having a thickness in the range of 1 ⁇ m, more preferably in the range of 5 ⁇ m to 0.1 ⁇ m, and even more preferably in the range of 1 ⁇ m to 0.1 ⁇ m can be exemplified.
  • the polyamide 6 oligomer that permeates the filter medium tends to decrease, and the purity of ⁇ -caprolactam is high when water is removed from the filtrate and ⁇ -caprolactam is recovered. tend to become Moreover, the recovery rate of the polyamide 6 oligomer recovered by the solid-liquid separation (I) tends to be high, which is preferable.
  • the filter examples include a method using a filter such as a sieve, a method using a centrifugal separator, a method using a centrifugal filter, a method using a vibrating screen, a method using a pressure filter, and a method using a suction filter. Examples include, but are not limited to.
  • the mother liquor adhering to the solid content separated into solid and liquid by the solid-liquid separation (I) of the present invention is washed with water heated to the temperature at which the solid-liquid separation (I) was performed, and substantially the mother liquor is removed. It is preferable to avoid sticking.
  • non-oxidizing atmosphere is an atmosphere in which the oxygen concentration in the gas phase is 5% by volume or less, preferably 2% by volume or less, and more preferably an atmosphere substantially free of oxygen, that is, an inert gas atmosphere such as nitrogen, helium, or argon. Among these, it is preferable to carry out under a nitrogen atmosphere from the viewpoint of economy and ease of handling.
  • the solid-liquid separation (I) of the present invention is performed by separately reheating the reaction mixture obtained in the step (a) to the temperature at which the solid-liquid separation (I) is performed, and (a) A method of performing solid-liquid separation (I) by cooling to a temperature at which solid-liquid separation (I) is performed after the step can be exemplified.
  • the method of performing solid-liquid separation (I) by cooling to the temperature at which solid-liquid separation (I) is performed after the step (a) can be mentioned.
  • seed crystals may be added to facilitate precipitation of the polyamide 6 oligomer.
  • Seed crystals can be added at the start of cooling or during cooling. Since the seed crystals used here are preferably crystals of the same material as the polyamide 6 oligomer, it is preferable to use polyamide 6 or polyamide 6 oligomer as the seed crystal. The use of these seed crystals promotes precipitation of polyamide 6 oligomers, and tends to increase the purity of ⁇ -caprolactam recovered by solid-liquid separation (I).
  • the wet cake-like polyamide 6 oligomer recovered as a solid phase component by solid-liquid separation (I) contains water, it can be used as a raw material for an aqueous polyamide 6 oligomer aqueous solution (B1) in a wet cake-like state without performing a drying treatment.
  • aqueous polyamide 6 oligomer aqueous solution (B1) in a wet cake-like state without performing a drying treatment.
  • the polyamide 6 oligomer recovered by solid-liquid separation (I) as a raw material without going through the drying process in this way, the amount of industrial waste can be reduced and the energy required for the drying process can be omitted.
  • the reaction mixture obtained in step (a) is combined with non-melting substances and at least ⁇ -caprolactam and an aqueous solution containing polyamide 6 oligomer by solid-liquid separation (b1), and the filtrate obtained in step (b1) is separated into polyamide 6 oligomer and ⁇ -caprolactam aqueous solution by solid-liquid separation (b2 ) step and preferably performed.
  • Solid-liquid separation of the unmelted material in the step (b1) reduces the amount of polyamide 6 oligomer that is treated as industrial waste together with the unmelted material, and further facilitates the utilization of polyamide 6 oligomer as a raw material, which is preferable.
  • the temperature at which step (b1) is performed may be any temperature range as long as it is possible to separate the non-melt into a solid phase and the polyamide 6 oligomer and ⁇ -caprolactam into a liquid phase.
  • the depolymerization reaction of the waste (A) of the resin moldings is carried out at 290° C. or higher and 350° C. or lower, so the temperature is preferably below these temperatures.
  • the present inventors investigated the dissolution behavior and precipitation behavior of the polyamide 6 oligomer in water in the present invention, and found that the temperature at which the polyamide 6 oligomer dissolves in water is 100 ° C.
  • the temperature at which polyamide 6 oligomer once melted precipitates is less than 100°C.
  • the difference between the temperature at which the polyamide 6 oligomer dissolves in water and the temperature at which the polyamide 6 oligomer precipitates occurs because the polyamide 6 oligomer is in a supercooled state in a temperature range of less than 100 ° C. and equal to or higher than the temperature at which the polyamide 6 oligomer precipitates. It's for.
  • a polyamide 6 oligomer crystal nucleus is generated, and the generated crystal nucleus grows to a size sufficient for precipitation, and the polyamide 6 oligomer precipitates.
  • step (b1) is more preferably carried out in a temperature range below the boiling point under normal pressure, more preferably at 95° C. or lower, and even more preferably at 90° C. or lower.
  • the lower limit temperature for performing the step (b1) can include the temperature at which the polyamide 6 oligomer is in a supercooled state. Specifically, it is preferably 50 ° C. or higher, more preferably 60 ° C. or higher. More preferably, the temperature is 70° C. or higher.
  • the step (b1) in such a preferable temperature range, 97% or more, preferably 98% or more, more preferably 99% or more of ⁇ -caprolactam and polyamide 6 oligomer can be recovered as liquid phase components, (b1) It tends to be possible to reduce recovery loss in the process.
  • the reaction mixture prepared in the step (a) is reheated to a temperature at which the polyamide 6 oligomer dissolves, and then cooled to a temperature at which the step (b1) is performed to perform solid-liquid separation.
  • a method of cooling to the temperature at which step (b1) is performed and performing solid-liquid separation preferably the reaction mixture in step (a)
  • a method of cooling to the temperature for performing the step (b1) and performing solid-liquid separation may be mentioned.
  • the unmelted matter in the reaction mixture obtained in the step (a) can be separated as filtered matter, preferably 95% or more of the unmelted matter contained in the mixture , more preferably 97% or more, more preferably 99% or more, can be recovered as a solid content.
  • aqueous solution containing ⁇ -caprolactam and polyamide 6 oligomer adheres to the non-melt filtered product separated in step (b1), such filtered product is washed with fresh water. As a result, the amounts of ⁇ -caprolactam and polyamide 6 oligomer remaining in the filtrate can be reduced.
  • the washing of the filtrate with fresh water is carried out in a temperature range below the boiling point under normal pressure, preferably in a temperature range of 95°C or below, more preferably 90°C or below.
  • Recovery method of ⁇ -caprolactam There is no particular limitation on the recovery method of ⁇ -caprolactam from the filtrate obtained by the solid-liquid separation (I) of the present invention, and any method can be employed. For example, by subjecting the aqueous ⁇ -caprolactam solution obtained by solid-liquid separation (I) to a distillation operation, ⁇ -caprolactam with high purity can be recovered by separating it from water and polyamide 6 oligomer. Further, if the water-insoluble component is precipitated by cooling the ⁇ -caprolactam aqueous solution recovered by the solid-liquid separation (I), it can be separated in advance by a known method such as solid-liquid separation and subjected to distillation separation. .
  • Methods for obtaining ⁇ -caprolactam of even higher purity include a method of precision distillation of recovered ⁇ -caprolactam, a method of vacuum distillation with the addition of a trace amount of sodium hydroxide, a method of activated carbon treatment, an ion exchange treatment method, and a recycling method. It can be combined with a purification method such as a method of crystallization. These methods can efficiently remove impurities that are difficult to separate by distillation.
  • thermoplastic resin obtained by conventionally known methods, for example, a method of thermally melt-polymerizing ⁇ -caprolactam in the presence of a small amount of water, and heating ⁇ -caprolactam and a copolymer component in the presence of a small amount of water.
  • thermoplastic resin composition A method of melt-polymerizing ⁇ -caprolactam, a method of heat-melt-polymerizing a block copolymer component such as polyethylene glycol with ⁇ -caprolactam in the presence of a small amount of water, and the like. Further, the thermoplastic resin thus obtained is optionally melt-kneaded with a fibrous filler and various additives to produce a thermoplastic resin composition, which is then subjected to a generally known method such as injection molding or extrusion molding. Various molded articles such as sheets and films can be obtained by the method.
  • thermoplastic resin of the present invention and its molded articles can be used for various purposes such as electric/electronic parts, building materials, various containers, daily necessities, household goods and sanitary goods, taking advantage of their excellent properties.
  • it is preferably used for aircraft parts and electric/electronic parts that require toughness and rigidity.
  • aircraft-related parts such as landing gear pods, winglets, spoilers, edges, rudders, elevators, failings, and ribs
  • electrical and electronic parts such as generators, motors, transformers, and current transformers.
  • the melting point of polyamide 6 is measured by differential scanning calorimeter analysis, in which the temperature of the polyamide is lowered from the molten state to 30 ° C. at a rate of 20 ° C./min in a nitrogen gas atmosphere, and then the temperature is raised by 20 ° C./min.
  • the temperature of the endothermic peak that appears when the temperature is increased to the melting point +40°C at a high speed.
  • the temperature of the endothermic peak with the highest peak intensity was taken as the melting point.
  • the pellets were extracted with 20 times the amount of hot water at 98° C. to recover an extract containing unreacted caprolactam and polyamide 6 oligomer.
  • the total amount of unreacted caprolactam and polyamide 6 oligomer in the extract was 0.5% by mass, and polyamide 6 oligomer was 0.1% by mass.
  • Example 1 Collect used non-reinforced polyamide 6 fastener parts (polyamide 6 content ratio is 99% by mass or more), put it in a crusher with a screen of 7 mm diameter, obtain crushed products with an average particle size of 6 mm, visually Removal of identifiable contaminants was performed. 20.0 g of the crushed product and 60.0 g of deionized water were placed in a SUS316L autoclave equipped with a stirrer, a bottom plug valve and a glass filter (average opening 10 ⁇ m) at the bottom. Since the content of polyamide 6 in the fastener part is 99% by mass or more, the mass ratio (X:1) of water to polyamide 6 is 3:1.
  • the reaction vessel was purged with nitrogen, sealed under a nitrogen pressure of 0.5 MPa, and then reacted at 320° C. for 15 minutes while stirring at 200 rpm.
  • the ultimate pressure during the reaction was 10.5 MPa. Since the reaction temperature Y ° C. is 320 ° C., the product of X and Y is 960, and since the residence time at the reaction temperature of 320 ° C. is 15 minutes, the product of X, Y and Z is 14,400. .
  • the internal temperature was cooled to 50°C, and the bottom plug valve was opened while maintaining the temperature at 50°C to perform solid-liquid separation (I).
  • the filtrate obtained by solid-liquid separation (I) was subjected to vacuum drying at 50° C. for 12 hours to recover 2.7 g of solid content.
  • the obtained solid content was analyzed by high-performance liquid chromatography under the conditions described above. As a result, it was found to be a polyamide 6 oligomer containing 96.5% by mass of linear 2- to 12-mers. Since this polyamide 6 oligomer has a high purity, it can be further utilized as a raw material for depolymerization. Further, the filtrate obtained by solid-liquid separation (I) was subjected to high-performance liquid chromatography measurement, and the amount of ⁇ -caprolactam contained in the filtrate was 15.0 g. The rate was 75.2%.
  • the recovered filtrate is heated to 55°C under reduced pressure of 30 mmHg to distill and separate water to obtain a concentrated ⁇ -caprolactam aqueous solution, which is further distilled under reduced pressure of 5 mmHg at a heating temperature of 150 to 170°C.
  • ⁇ -caprolactam was recovered.
  • the concentration and distillation yield of ⁇ -caprolactam was 95.8%.
  • the HPLC impurity content of the distilled ⁇ -caprolactam was 0.48%, and the quality was such that it could be used as a raw material for polymerization of polyamide 6.
  • polymerization was carried out using the obtained ⁇ -caprolactam as a starting material.
  • Example 2 Used mobile phone casings made of glass fiber reinforced polyamide 6 (polyamide 6 content in the resin is 99% by mass or more, glass fiber content in the resin composition is 45% by mass) are collected and screens with a diameter of 7 mm are used. A crushed product with an average particle diameter of 6 mm was obtained, and contaminants that could be visually confirmed were removed. 36.4 g of the crushed product and 60.0 g of deionized water were placed in a SUS316L autoclave equipped with a stirrer, a bottom plug valve and a glass filter (average opening 10 ⁇ m) at the bottom.
  • the mass ratio of water to polyamide 6 (X: 1 ) is 3:1.
  • the reaction vessel was purged with nitrogen, sealed under a nitrogen pressure of 0.5 MPa, and then reacted at 340° C. for 15 minutes while stirring at 200 rpm. Since the reaction temperature Y ° C. is 340 ° C., the product of X and Y is 1,020, and since the residence time at the reaction temperature of 340 ° C. is 15 minutes, the product of X, Y and Z is 15,300. is.
  • the internal temperature was cooled to 50° C., and the bottom plug valve was opened while maintaining the temperature at 50° C. to perform solid-liquid separation (I) of the unmelted material.
  • solid-liquid separation (I) was performed while introducing nitrogen into the autoclave at 0.3 MPa. Furthermore, about 3 times the amount (mass) of deionized water is introduced into the autoclave and the filtrate is rinsed and washed at 50°C three times, and the filtrate and the wet filtrate are collected. bottom.
  • the amount of ⁇ -caprolactam contained in the filtrate was 14.4 g. It was 71.9%. Further, the recovered filtrate is heated to 55°C under reduced pressure of 30 mmHg to distill and separate water to obtain a concentrated ⁇ -caprolactam aqueous solution, which is further distilled under reduced pressure of 5 mmHg at a heating temperature of 150 to 170°C. ⁇ -caprolactam was recovered. The concentration and distillation yield of ⁇ -caprolactam was 95.8%.
  • the HPLC impurity content of the distilled ⁇ -caprolactam was 0.48%, and the quality was such that it could be used as a raw material for polymerization of polyamide 6.
  • polymerization was carried out using the obtained ⁇ -caprolactam as a starting material. 10 g of ⁇ -caprolactam, 2.2 mg of benzoic acid and 10.0 g of deionized water were weighed out in a test tube. After the test tube was placed in the autoclave and the inside of the autoclave was replaced with nitrogen, the jacket temperature was set to 250° C. and heating was started. After the internal pressure reached 1.0 MPa, the internal pressure was maintained at 1.0 MPa for 3 hours.
  • the internal pressure was released to normal pressure over 1.5 hours, and heating was stopped when the internal temperature reached 228°C.
  • the polymer was recovered from the test tube and crushed.
  • the crushed polymer was treated in hot water at 95° C. for 15 hours to extract and remove unreacted monomers and low polymers.
  • Example 3 Used mobile phone casings made of glass fiber reinforced polyamide 6 (polyamide 6 content in the resin is 99% by mass or more, glass fiber content in the resin composition is 45% by mass) are collected and screens with a diameter of 7 mm are used. A crushed product with an average particle diameter of 6 mm was obtained, and contaminants that could be visually confirmed were removed. 36.4 g of the crushed product and 60.0 g of deionized water were placed in a SUS316L autoclave equipped with a stirrer, a bottom plug valve and a glass filter (average opening 10 ⁇ m) at the bottom.
  • the mass ratio of water to polyamide 6 (X: 1 ) is 3:1.
  • the reaction vessel was purged with nitrogen, sealed under a nitrogen pressure of 0.5 MPa, and then reacted at 340° C. for 15 minutes while stirring at 200 rpm. Since the reaction temperature Y ° C. is 340 ° C., the product of X and Y is 1,020, and since the residence time at the reaction temperature of 340 ° C. is 15 minutes, the product of X, Y and Z is 15,300. .
  • step (b1) After completion of the reaction, the internal temperature was cooled to 90°C, and the bottom plug valve was opened while the temperature was kept at 90°C to separate the non-melted glass fibers by solid-liquid separation (step (b1)). .
  • step (b1) solid-liquid separation
  • solid-liquid separation was performed while introducing nitrogen into the autoclave at 0.3 MPa.
  • the filtrate was rinsed with deionized water heated to 90° C. in an amount (mass) about 3 times that of the filtrate, and the filtrate and the wet filtrate were recovered.
  • the filtrate obtained in the step (b1) was cooled to an internal temperature of 25° C. and subjected to solid-liquid separation using a glass filter with an average mesh size of 10 to 16 ⁇ m (step (b2)). Furthermore, the filtered residue was rinsed three times with deionized water heated to 25° C. in an amount about three times the amount of the filtered residue, and the filtrate and the wet filtered residue were recovered.
  • the amount of ⁇ -caprolactam contained in the filtrate was 14.1 g
  • the yield relative to polyamide 6 in the crushed product used as the raw material was 70.0 g. was 5%.
  • the recovered filtrate is heated to 55°C under reduced pressure of 30 mmHg to distill and separate water to obtain a concentrated ⁇ -caprolactam aqueous solution, which is further distilled under reduced pressure of 5 mmHg at a heating temperature of 150 to 170°C.
  • ⁇ -caprolactam was recovered.
  • the concentration and distillation yield of ⁇ -caprolactam was 95.8%.
  • the HPLC impurity content of the distilled ⁇ -caprolactam was 0.48%, and the quality was such that it could be used as a raw material for polymerization of polyamide 6.
  • polymerization was carried out using the obtained ⁇ -caprolactam as a starting material.
  • the wet filter cake obtained in the step (b1) was vacuum-dried at 50°C for 12 hours to recover 16.2 g of glass fibers.
  • 1.0 g of the collected glass fiber was weighed into a crucible, treated in an air atmosphere for 3 hours in an electric furnace heated to 600° C., and the amount of organic matter adhering to the collected glass fiber was evaluated from the weight reduction. The mass reduction was 1.3% by mass, indicating that the recovered glass fibers were high-purity glass fibers with a small amount of adhered organic matter.
  • the wet filtrate obtained in step (b2) was vacuum-dried at 50° C. for 12 hours to recover 2.0 g of the solid content of solid-liquid separation (I).
  • the obtained solid content was analyzed by high-performance liquid chromatography under the conditions described above. As a result, it was found to be a polyamide 6 oligomer containing 97.6% by mass of linear 2- to 12-mer oligomers. Since this polyamide 6 oligomer has a high purity, it can be further utilized as a raw material for depolymerization.
  • Example 4 Used mobile phone casings made of glass fiber reinforced polyamide 6 (polyamide 6 content in the resin is 99% by mass or more, glass fiber content in the resin composition is 45% by mass) are collected and screens with a diameter of 7 mm are used. A crushed product with an average particle diameter of 6 mm was obtained, and contaminants that could be visually confirmed were removed. 32.7 g of the crushed product and 27.8 g of deionized water were weighed into an autoclave made of SUS316L equipped with a stirrer, a bottom plug valve and a glass filter (average mesh opening of 10 ⁇ m) at the bottom, and further described in Example 3.
  • the internal temperature was cooled to 90° C., and the bottom plug valve was opened while maintaining the temperature at 90° C. to perform solid-liquid separation ((b1) step).
  • solid-liquid separation was performed while introducing nitrogen into the autoclave at 0.3 MPa.
  • the filtrate was rinsed with deionized water heated to 90° C. in an amount (mass) about 3 times that of the filtrate, and the filtrate and the wet filtrate were collected.
  • the filtrate obtained in step (b1) was cooled to an internal temperature of 30° C. and subjected to solid-liquid separation using a glass filter with an average mesh size of 10 to 16 ⁇ m (step (b2)). Furthermore, the filtered residue was rinsed three times with deionized water heated to 30° C. in an amount about three times the amount of the filtered residue, and the filtrate and the wet filtered residue were recovered.
  • the amount of ⁇ -caprolactam contained in the filtrate was 13.8 g, and the yield relative to polyamide 6 in the crushed product used as the raw material was 76.7. %Met.
  • Example 3 Comparison with Example 3 reveals that the yield of ⁇ -caprolactam relative to polyamide 6 is increased by using an aqueous polyamide 6 oligomer solution when reacting polyamide 6 with water. Further, the recovered filtrate is heated to 55°C under reduced pressure of 30 mmHg to distill and separate water to obtain a concentrated ⁇ -caprolactam aqueous solution, which is further distilled under reduced pressure of 5 mmHg at a heating temperature of 150 to 170°C. ⁇ -caprolactam was recovered. The concentration and distillation yield of ⁇ -caprolactam was 95.8%. The HPLC impurity content of the distilled ⁇ -caprolactam was 0.48%, and the quality was such that it could be used as a raw material for polymerization of polyamide 6.
  • step (b2) was vacuum-dried at 50° C. for 12 hours to recover 2.0 g of the solid content of solid-liquid separation (I).
  • the obtained solid content was analyzed by high-performance liquid chromatography under the conditions described above. As a result, it was found to be a polyamide 6 oligomer containing 97.8% by mass of linear 2- to 12-mer oligomers. Since this polyamide 6 oligomer has a high purity, it can be further utilized as a raw material for depolymerization.
  • Example 1 the solid-liquid separation (I) can significantly reduce the polyamide component that will be treated as industrial waste among the 6 components of the raw material polyamide. It can be seen that it is excellent as a method for cyclical use.
  • Example 5 Collect used non-reinforced polyamide 6 fastener parts (polyamide 6 content ratio is 99% by mass or more), put it in a crusher with a screen of 7 mm diameter, obtain crushed products with an average particle size of 6 mm, visually Removal of identifiable contaminants was performed. 45.0 g of the crushed product and 135.0 g of deionized water were placed in a SUS316L autoclave equipped with a stirrer, a bottom plug valve and a glass filter (average opening 10 ⁇ m) at the bottom. Since the content of polyamide 6 in the fastener part is 99% by mass or more, the mass ratio (X:1) of water to polyamide 6 is 3:1.
  • the reaction vessel was purged with nitrogen, sealed under a nitrogen pressure of 5.0 MPa, and then reacted at 320° C. for 15 minutes while stirring at 200 rpm.
  • the ultimate pressure during the reaction was 19.6 MPa.
  • the reaction temperature Y ° C. is 320 ° C.
  • the product of X and Y is 960.
  • the residence time at the reaction temperature of 320 ° C. is 15 minutes, the product of X, Y and Z is 14, 400.
  • the internal temperature was cooled to 50°C, and the bottom plug valve was opened while maintaining the temperature at 50°C to perform solid-liquid separation (I).
  • the filtrate obtained by solid separation (I) was subjected to vacuum drying at 50° C. for 12 hours, and 4.8 g of solid-liquid content was recovered.
  • the obtained solid content was analyzed by high-performance liquid chromatography under the conditions described above. As a result, it was found to be a polyamide 6 oligomer containing 97.1% by mass of linear 2-12-mers. Since this polyamide 6 oligomer has a high purity, it can be further utilized as a raw material for depolymerization. Further, the filtrate obtained by solid-liquid separation (I) was measured by high-performance liquid chromatography, and the amount of ⁇ -caprolactam contained in the filtrate was 37.4 g. The rate was 83.0%.
  • Example 2 Comparison with Example 1 reveals that the yield of ⁇ -caprolactam obtained tends to improve by increasing the pressure during the reaction to a pressure higher than the saturated vapor pressure. Further, the recovered filtrate is heated to 55°C under reduced pressure of 30 mmHg to distill and separate water to obtain a concentrated ⁇ -caprolactam aqueous solution, which is further distilled under reduced pressure of 5 mmHg at a heating temperature of 150 to 170°C. ⁇ -caprolactam was recovered. The concentration and distillation yield of ⁇ -caprolactam was 95.8%. The HPLC impurity content of the distilled ⁇ -caprolactam was 0.48%, and the quality was such that it could be used as a raw material for polymerization of polyamide 6.
  • the crushed polymer was treated in hot water at 95° C. for 15 hours to extract and remove unreacted monomers and low polymers.
  • Example 6 Used mobile phone casings made of glass fiber reinforced polyamide 6 (polyamide 6 content in the resin is 99% by mass or more, glass fiber content in the resin composition is 45% by mass) are collected and screens with a diameter of 7 mm are used. A crushed product with an average particle diameter of 6 mm was obtained, and contaminants that could be visually confirmed were removed. 68.0 g of the crushed product and 112.0 g of deionized water were placed in a SUS316L autoclave equipped with a stirrer, a bottom plug valve and a glass filter (average opening 10 ⁇ m) at the bottom.
  • the mass ratio of water to polyamide 6 (X: 1 ) is 3:1.
  • the reaction vessel was purged with nitrogen, sealed under a nitrogen pressure of 5.0 MPa, and then reacted at 320° C. for 15 minutes while stirring at 200 rpm. The ultimate pressure during the reaction was 19.8 MPa.
  • the reaction temperature Y ° C. is 320 ° C.
  • the product of X and Y is 960
  • the residence time at the reaction temperature of 320 ° C. is 15 minutes
  • the product of X, Y and Z is 14,400. .
  • step (b1) After completion of the reaction, the internal temperature was cooled to 90°C, and the bottom plug valve was opened while the temperature was kept at 90°C to separate the non-melted glass fibers by solid-liquid separation (step (b1)). .
  • step (b1) solid-liquid separation
  • solid-liquid separation was performed while introducing nitrogen into the autoclave at 0.3 MPa.
  • the filtrate was rinsed with deionized water heated to 90° C. in an amount (mass) about 3 times that of the filtrate, and the filtrate and the wet filtrate were recovered.
  • the filtrate obtained in the step (b1) was cooled to an internal temperature of 25° C. and subjected to solid-liquid separation using a glass filter with an average mesh size of 10 to 16 ⁇ m (step (b2)). Furthermore, the filtered residue was rinsed three times with deionized water heated to 25° C. in an amount about three times the amount of the filtered residue, and the filtrate and the wet filtered residue were recovered. As a result of high-performance liquid chromatography measurement of the filtrate obtained in the step (b2), the amount of ⁇ -caprolactam contained in the filtrate was 29.9 g. was 0%.
  • the recovered filtrate is heated to 55°C under reduced pressure of 30 mmHg to distill and separate water to obtain a concentrated ⁇ -caprolactam aqueous solution, which is further distilled under reduced pressure of 5 mmHg at a heating temperature of 150 to 170°C.
  • ⁇ -caprolactam was recovered.
  • the concentration and distillation yield of ⁇ -caprolactam was 95.8%.
  • the HPLC impurity content of the distilled ⁇ -caprolactam was 0.48%, and the quality was such that it could be used as a raw material for polymerization of polyamide 6.
  • polymerization was carried out using the obtained ⁇ -caprolactam as a starting material.
  • 1.0 g of the collected glass fiber was weighed into a crucible, treated in an air atmosphere for 3 hours in an electric furnace heated to 600° C., and the amount of organic matter adhering to the collected glass fiber was evaluated from the weight reduction. The mass reduction was 1.2% by mass, indicating that the recovered glass fibers were high-purity glass fibers with a small amount of adhered organic matter.
  • step (b2) was vacuum-dried at 50° C. for 12 hours to recover 3.6 g of the solid content of solid-liquid separation (I).
  • the obtained solid content was analyzed by high-performance liquid chromatography under the conditions described above. As a result, it was found to be a polyamide 6 oligomer containing 97.4% by mass of linear 2- to 12-mer oligomers. Since this polyamide 6 oligomer has a high purity, it can be further utilized as a raw material for depolymerization.
  • Example 7 Collect used non-reinforced polyamide 6 fastener parts (polyamide 6 content ratio is 99% by mass or more), put it in a crusher with a screen of 7 mm diameter, obtain crushed products with an average particle size of 6 mm, visually Removal of identifiable contaminants was performed. 30.0 g of the crushed product and 60.0 g of deionized water were placed in a SUS316L autoclave equipped with a stirrer, a bottom plug valve and a glass filter (average opening 10 ⁇ m) at the bottom. Since the content of polyamide 6 in the fastener part is 99% by mass or more, the mass ratio (X:1) of water to polyamide 6 is 2:1.
  • the reaction vessel was purged with nitrogen, sealed under a nitrogen pressure of 0.5 MPa, and then reacted at 320° C. for 15 minutes while stirring at 200 rpm. Since the reaction temperature Y ° C. is 320 ° C., the product of X and Y is 640, and the residence time at the reaction temperature of 320 ° C. is 15 minutes, so the product of X, Y and Z is 9,600. .
  • the internal temperature was cooled to 50°C, and the bottom plug valve was opened while maintaining the temperature at 50°C to perform solid-liquid separation (I). At the stage when the filtration rate decreased, solid-liquid separation (I) was performed while introducing nitrogen into the autoclave at 0.3 MPa.
  • the filtrate obtained by solid-liquid separation (I) was subjected to vacuum drying at 50° C. for 12 hours to recover 6.5 g of solid content.
  • the obtained solid content was analyzed by high-performance liquid chromatography under the conditions described above. As a result, it was found to be a polyamide 6 oligomer containing 97.5% by mass of linear 2- to 12-mers. Since this polyamide 6 oligomer has high purity, it can be further utilized as a raw material for depolymerization. Further, the filtrate obtained by solid-liquid separation (I) was subjected to high-performance liquid chromatography measurement, and the amount of ⁇ -caprolactam contained in the filtrate was 19.5 g. The rate was 65.0%.
  • the recovered filtrate is heated to 55°C under reduced pressure of 30 mmHg to distill and separate water to obtain a concentrated ⁇ -caprolactam aqueous solution, which is further distilled under reduced pressure of 5 mmHg at a heating temperature of 150 to 170°C.
  • ⁇ -caprolactam was recovered.
  • the concentration and distillation yield of ⁇ -caprolactam was 95.8%.
  • the HPLC impurity content of the distilled ⁇ -caprolactam was 0.48%, and the quality was such that it could be used as a raw material for polymerization of polyamide 6.
  • polymerization was carried out using the obtained ⁇ -caprolactam as a starting material.
  • Example 8 Collect used non-reinforced polyamide 6 fastener parts (polyamide 6 content ratio is 99% by mass or more), put it in a crusher with a screen of 7 mm diameter, obtain crushed products with an average particle size of 6 mm, visually Removal of identifiable contaminants was performed. 60.0 g of the crushed product and 120.0 g of deionized water were charged into a SUS316L autoclave equipped with a stirrer, a bottom plug valve, and a glass filter (average opening 10 ⁇ m) at the bottom. Since the content of polyamide 6 in the fastener part is 99% by mass or more, the mass ratio (X:1) of water to polyamide 6 is 2:1.
  • the reaction vessel was purged with nitrogen, sealed under a nitrogen pressure of 5.0 MPa, and then reacted at 320° C. for 15 minutes while stirring at 200 rpm.
  • the ultimate pressure during the reaction was 19.6 MPa.
  • the reaction temperature Y ° C. is 320 ° C.
  • the product of X and Y is 640
  • the residence time at the reaction temperature of 320 ° C. is 15 minutes
  • the product of X, Y and Z is 9,600. is.
  • the internal temperature was cooled to 50°C, and the bottom plug valve was opened while maintaining the temperature at 50°C to perform solid-liquid separation (I).
  • the filtrate obtained by solid-liquid separation (I) was subjected to vacuum drying at 50° C. for 12 hours to recover 9.2 g of solid content.
  • the obtained solid content was analyzed by high-performance liquid chromatography under the conditions described above. As a result, it was found to be a polyamide 6 oligomer containing 97.1% by mass of linear 2-12-mers. Since this polyamide 6 oligomer has a high purity, it can be further utilized as a raw material for depolymerization. Further, the filtrate obtained by solid-liquid separation (I) was measured by high-performance liquid chromatography, and the amount of ⁇ -caprolactam contained in the filtrate was 45.0 g. The rate was 75.0%.
  • Example 7 shows that the yield of ⁇ -caprolactam obtained by increasing the pressure during the reaction to a pressure higher than the saturated vapor pressure tends to improve. Further, the recovered filtrate is heated to 55°C under reduced pressure of 30 mmHg to distill and separate water to obtain a concentrated ⁇ -caprolactam aqueous solution, which is further distilled under reduced pressure of 5 mmHg at a heating temperature of 150 to 170°C. ⁇ -caprolactam was recovered. The concentration and distillation yield of ⁇ -caprolactam was 95.8%. The HPLC impurity content of the distilled ⁇ -caprolactam was 0.48%, and the quality was such that it could be used as a raw material for polymerization of polyamide 6.
  • Example 9 Used mobile phone casings made of glass fiber reinforced polyamide 6 (polyamide 6 content in the resin is 99% by mass or more, glass fiber content in the resin composition is 45% by mass) are collected and screens with a diameter of 7 mm are used. A crushed product with an average particle diameter of 6 mm was obtained, and contaminants that could be visually confirmed were removed. 60.0 g of the crushed product and 48.9 g of deionized water were weighed into a SUS316L autoclave equipped with a stirrer, a bottom plug valve, and a glass filter (average opening of 10 ⁇ m) at the bottom, and further described in Example 3.
  • the internal temperature was cooled to 90° C., and the bottom plug valve was opened while maintaining the temperature at 90° C. to perform solid-liquid separation ((b1) step).
  • solid-liquid separation was performed while introducing nitrogen into the autoclave at 0.3 MPa.
  • the filtrate was rinsed with deionized water heated to 90° C. in an amount (mass) about 3 times that of the filtrate, and the filtrate and the wet filtrate were recovered.
  • the filtrate obtained in step (b1) was cooled to an internal temperature of 50° C. and subjected to solid-liquid separation using a glass filter with an average mesh size of 10 to 16 ⁇ m (step (b2)). Furthermore, the filtered residue was rinsed three times with deionized water heated to 50° C. in an amount about three times the amount of the filtered residue, and the filtrate and the wet filtered residue were recovered.
  • the amount of ⁇ -caprolactam contained in the filtrate was 27.1 g, and the yield relative to polyamide 6 in the crushed product used as the raw material was 82.0. %Met.
  • Example 4 By comparison with Example 4, it can be seen that the yield of ⁇ -caprolactam obtained tends to be improved by increasing the pressure during the reaction to a pressure higher than the saturated vapor pressure. Further, the recovered filtrate is heated to 55°C under reduced pressure of 30 mmHg to distill and separate water to obtain a concentrated ⁇ -caprolactam aqueous solution, which is further distilled under reduced pressure of 5 mmHg at a heating temperature of 150 to 170°C. ⁇ -caprolactam was recovered. The concentration and distillation yield of ⁇ -caprolactam was 95.8%. The HPLC impurity content of the distilled ⁇ -caprolactam was 0.48%, and the quality was such that it could be used as a raw material for polymerization of polyamide 6.
  • ⁇ -caprolactam 10.0 g of ⁇ -caprolactam, 2.2 mg of benzoic acid and 10.0 g of deionized water were weighed out in a test tube. After the test tube was placed in the autoclave and the inside of the autoclave was replaced with nitrogen, the jacket temperature was set to 250° C. and heating was started. After the internal pressure reached 1.0 MPa, the internal pressure was maintained at 1.0 MPa for 3 hours. Thereafter, the internal pressure was released to normal pressure over 1.5 hours, and heating was stopped when the internal temperature reached 228°C. After the polymerization was completed, the polymer was taken out from the test tube and crushed.
  • the crushed polymer was treated in hot water at 95° C. for 15 hours to extract and remove unreacted monomers and low polymers.
  • the wet filter cake obtained in the step (b1) was vacuum-dried at 50° C. for 12 hours to recover 27.1 g of glass fibers.
  • 1.0 g of the collected glass fiber was weighed into a crucible, treated in an air atmosphere for 3 hours in an electric furnace heated to 600° C., and the amount of organic matter adhering to the collected glass fiber was evaluated from the weight reduction.
  • step (b2) The mass reduction was 1.4% by mass, indicating that the recovered glass fibers were high-purity glass fibers with a small amount of adhered organic matter.
  • the wet filtrate obtained in step (b2) was vacuum-dried at 50° C. for 12 hours to recover 6.3 g of the solid content of solid-liquid separation (I).
  • the obtained solid content was analyzed by high-performance liquid chromatography under the conditions described above. As a result, it was found to be a polyamide 6 oligomer containing 97.9% by mass of linear 2- to 12-mer oligomers. Since this polyamide 6 oligomer has a high purity, it can be further utilized as a raw material for depolymerization.
  • Example 10 Here, the hot water extract in the PA6 production process obtained by the method described in Reference Example 1 was concentrated until the concentration of unreacted ⁇ -caprolactam and polyamide 6 oligomer reached 5.8% by mass, and used as a depolymerization raw material. Examples used are described. Used mobile phone casings made of glass fiber reinforced polyamide 6 (polyamide 6 content in the resin is 99% by mass or more, glass fiber content in the resin composition is 45% by mass) are collected and screens with a diameter of 7 mm are used. A crushed product with an average particle diameter of 6 mm was obtained, and contaminants that could be visually confirmed were removed.
  • the reaction temperature Y ° C. is 320 ° C.
  • the product of X and Y is 1,050
  • the residence time at the reaction temperature of 320 ° C. is 15 minutes
  • the product of X, Y and Z is 15,740. be.
  • the internal temperature was cooled to 90° C., and the bottom plug valve was opened while maintaining the temperature at 90° C. to perform solid-liquid separation ((b1) step).
  • solid-liquid separation was performed while introducing nitrogen into the autoclave at 0.3 MPa.
  • the filtrate was rinsed with deionized water heated to 90° C. in an amount (mass) about 3 times that of the filtrate, and the filtrate and the wet filtrate were recovered.
  • the filtrate obtained in step (b1) was cooled to an internal temperature of 50° C. and subjected to solid-liquid separation using a glass filter with an average mesh size of 10 to 16 ⁇ m (step (b2)). Furthermore, the filtered residue was rinsed three times with deionized water heated to 50° C. in an amount about three times the amount of the filtered residue, and the filtrate and the wet filtered residue were recovered.
  • the amount of ⁇ -caprolactam contained in the filtrate was 13.6 g, and the yield relative to polyamide 6 in the crushed product used as the raw material was 75.6. %Met.
  • the extract in the polyamide 6 polymerization process can also be used as the polyamide 6 oligomer aqueous solution without any problem.
  • the recovered filtrate is heated to 55°C under reduced pressure of 30 mmHg to distill and separate water to obtain a concentrated ⁇ -caprolactam aqueous solution, which is further distilled under reduced pressure of 5 mmHg at a heating temperature of 150 to 170°C.
  • ⁇ -caprolactam was recovered.
  • the concentration and distillation yield of ⁇ -caprolactam was 95.8%.
  • the HPLC impurity content of the distilled ⁇ -caprolactam was 0.48%, and the quality was such that it could be used as a raw material for polymerization of polyamide 6.
  • ⁇ -caprolactam 10.0 g of ⁇ -caprolactam, 2.2 mg of benzoic acid and 10.0 g of deionized water were weighed out in a test tube. After the test tube was placed in the autoclave and the inside of the autoclave was replaced with nitrogen, the jacket temperature was set to 250° C. and heating was started. After the internal pressure reached 1.0 MPa, the internal pressure was kept at 1.0 MPa for 3 hours. Thereafter, the internal pressure was released to normal pressure over 1.5 hours, and heating was stopped when the internal temperature reached 228°C. After the polymerization was completed, the polymer was taken out from the test tube and crushed.
  • the crushed polymer was treated in hot water at 95° C. for 15 hours to extract and remove unreacted monomers and low polymers.
  • the wet filter cake obtained in the step (b1) was vacuum-dried at 50° C. for 12 hours to recover 14.7 g of glass fibers.
  • 1.0 g of the collected glass fiber was weighed into a crucible, treated in an air atmosphere for 3 hours in an electric furnace heated to 600° C., and the amount of organic matter adhering to the collected glass fiber was evaluated from the weight reduction.
  • step (b2) was vacuum-dried at 50° C. for 12 hours to recover 1.8 g of the solid content of solid-liquid separation (I).
  • the obtained solid content was analyzed by high-performance liquid chromatography under the conditions described above. As a result, it was found to be a polyamide 6 oligomer containing 97.4% by mass of linear 2- to 12-mer oligomers. Since this polyamide 6 oligomer has a high purity, it can be further utilized as a raw material for depolymerization.
  • Example 11 Here, the hot water extract in the PA6 production process obtained by the method described in Reference Example 1 was concentrated until the total concentration of unreacted ⁇ -caprolactam and polyamide 6 oligomer was 6.5% by mass, and the depolymerized raw material
  • An example used for Used mobile phone casings made of glass fiber reinforced polyamide 6 (polyamide 6 content in the resin is 99% by mass or more, glass fiber content in the resin composition is 45% by mass) are collected and screens with a diameter of 7 mm are used. A crushed product with an average particle diameter of 6 mm was obtained, and contaminants that could be visually confirmed were removed.
  • the internal temperature was cooled to 90° C., and the bottom plug valve was opened while maintaining the temperature at 90° C. to perform solid-liquid separation ((b1) step).
  • solid-liquid separation was performed while introducing nitrogen into the autoclave at 0.3 MPa.
  • the filtrate was rinsed with deionized water heated to 90° C. in an amount (mass) about 3 times that of the filtrate, and the filtrate and the wet filtrate were recovered.
  • the filtrate obtained in step (b1) was cooled to an internal temperature of 50° C. and subjected to solid-liquid separation using a glass filter with an average mesh size of 10 to 16 ⁇ m (step (b2)). Furthermore, the filtered residue was rinsed three times with deionized water heated to 50° C. in an amount about three times the amount of the filtered residue, and the filtrate and the wet filtered residue were recovered.
  • the amount of ⁇ -caprolactam contained in the filtrate was 14.9 g, and the yield relative to polyamide 6 in the crushed product used as the raw material was 75.3. %Met.
  • the recovered filtrate is heated to 55°C under reduced pressure of 30 mmHg to distill and separate water to obtain a concentrated ⁇ -caprolactam aqueous solution, which is further distilled under reduced pressure of 5 mmHg at a heating temperature of 150 to 170°C.
  • ⁇ -caprolactam was recovered.
  • the concentration and distillation yield of ⁇ -caprolactam was 95.7%.
  • the HPLC impurity content of the distilled ⁇ -caprolactam was 0.39%, and the quality was such that it could be used as a raw material for polymerization of polyamide 6.
  • polymerization was carried out using the obtained ⁇ -caprolactam as a starting material.
  • step (b2) was subjected to vacuum drying at 50° C. for 12 hours to recover 1.7 g of solid content in solid-liquid separation (I).
  • the obtained solid content was analyzed by high-performance liquid chromatography under the conditions described above. As a result, it was found to be a polyamide 6 oligomer containing 97.9% by mass of linear 2- to 12-mer oligomers. Since this polyamide 6 oligomer has a high purity, it can be further utilized as a raw material for depolymerization.

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WO2025205744A1 (ja) * 2024-03-28 2025-10-02 東レ株式会社 熱可塑性ポリマー由来成分の回収方法、回収装置、解重合中間体組成物、解重合反応組成物、およびリサイクルモノマーの製造方法、製造装置
WO2025233341A1 (en) * 2024-05-07 2025-11-13 Basf Se Separation of plastic solvolysis mixtures from filler components
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WO2026023530A1 (ja) * 2024-07-23 2026-01-29 東レ株式会社 不溶性原料およびポリアミドまたはポリエステルの分離方法、リサイクルモノマー、およびポリマー

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