Classifications

• • 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
  • 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
  • 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
  • C08G69/16—Preparatory processes
• • 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
  • C08G69/46—Post-polymerisation treatment
• • 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 depolymerizing polyamide 6 that achieves both the cyclical use of fossil resources and the reduction of greenhouse gas emissions.
• the present invention relates to a recycling method for depolymerizing polyamide 6 using an aqueous solution having a high purity and recovering high-purity ⁇ -caprolactam at a high yield.
• 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 method for recovering ⁇ -caprolactam disclosed in Patent Document 2 is a high-yield reaction with a depolymerization yield of polyamide 6 of 80% or more, but requires a long time for the depolymerization reaction. Furthermore, since a large amount of superheated steam, which is about 10 times that of nylon 6 fiber, is required, this technology remains a problem in achieving both fossil resource recycling and global warming 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 present inventors conducted depolymerization experiments using polyamide 6 containing a potassium salt as a raw material under the same and similar conditions as the method described in Patent Document 2. As a result, it was found that the ⁇ -caprolactam yield was greatly reduced. Found. It is believed that this is due to the deactivation of the phosphoric acid catalysis by the potassium salt.
• 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
• a resin composition (A) containing at least polyamide 6 is contacted with an aqueous polyamide 6 oligomer aqueous solution (C) heated to 290 ° C. or more and 350 ° C. or less, or a resin composition (A) containing at least polyamide 6 and 290 ° C. or more 350
• a method for producing ⁇ -caprolactam characterized by adding water (B) heated to 290° C. or higher and 350° C. or lower in addition to an aqueous polyamide 6 oligomer aqueous solution (C) heated to 0° C. or lower and bringing them into contact. 2.
• the polyamide 6 oligomer aqueous solution (C) is further added.
• the method for producing ⁇ -caprolactam according to item 1 characterized in that the addition of 3.
• the method for producing ⁇ -caprolactam according to item 1 or 2 wherein the polyamide 6 oligomer used in the polyamide 6 oligomer aqueous solution (C) is a polyamide 6 oligomer that is a by-product in the method for producing ⁇ -caprolactam. . 4. 4.
• the present invention can produce ⁇ -caprolactam with high yield and high selectivity even when using a small amount of water having a high specific heat capacity, so energy consumption is low.
• a method for producing ⁇ -caprolactam can be provided.
• Resin composition (A) In the present invention, when water (B) heated to 290° C. or higher and 350° C. or lower is added and brought into contact with a resin composition (A) containing at least polyamide 6, an aqueous polyamide 6 oligomer solution (C) is further added.
• a method for producing ⁇ -caprolactam characterized by 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 resin composition (A) of the present invention can further contain an alkali metal halide within a range that does not impair the object 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 per 100 parts by mass of polyamide 6.
• 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 resin composition (A) 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 resin composition (A).
• the resin composition (A) of the present invention may further contain fillers other than fibrous fillers, thermoplastic resins other than polyamide 6, and various additives within a range that does not impair the object of the present invention.
• 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 resin composition (A) include polyamide resins other than polyamide 6, polyester resins, polyolefin resins, modified polyphenylene ether resins, polysulfone resins, polyketone resins, and polyetherimide resins. , polyarylate resin, polyether sulfone resin, polyether ketone resin, polythioether ketone resin, polyether ether ketone resin, polyimide resin, polyamideimide resin, tetrafluoropolyethylene resin, polyphenylene sulfide resin, and the like. 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 thermoplastic resin (A) of the present invention.
• the resin composition (A) containing polyamide 6 of the present invention may be waste of resin moldings containing at least polyamide 6.
• 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 method for producing ⁇ -caprolactam of the present invention comprises contacting a resin composition (A) containing at least polyamide 6 with an aqueous polyamide 6 oligomer solution (C) heated to 290° C. or more and 350° C. or less, Or in addition to the resin composition (A) containing at least polyamide 6 and the polyamide 6 oligomer aqueous solution (C) heated to 290 ° C. or higher and 350 ° C. or lower, water (B) heated to 290 ° C. or higher and 350 ° C. or lower is added.
• the polyamide 6 oligomer as used herein 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 in a total of 100 mol% of the monomer units constituting the polyamide 6 oligomer, 6-aminocaproic acid-derived units or ⁇ -caprolactam-derived units total 50 mol% or more. 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 1,4-bis(3-aminopropyl
• 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 (B) 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.
• a polyamide 6 oligomer obtained as a by-product may be used.
• the resin composition (A) containing at least polyamide 6 and the polyamide 6 oligomer aqueous solution (C) heated to 290 ° C. or more and 350 ° C.
• the polyamide 6 oligomer aqueous solution (C) heated to 350 ° C. or higher it is obtained as a by-product when producing ⁇ -caprolactam by contacting water (B) heated to 290 ° C. or higher and 350 ° C. or lower.
• Polyamide 6 oligomers may be used. From the viewpoint of reducing industrial waste when producing ⁇ -caprolactam, a resin containing at least polyamide 6, which is a by-product when producing ⁇ -caprolactam by contact with water heated to 290° C. or higher and 350° C. or lower.
• a resin composition containing at least polyamide 6, or a by-product in the production of ⁇ -caprolactam by contacting the composition (A) with an aqueous polyamide 6 oligomer aqueous solution (C) heated to 290° C. or higher and 350° C. or lower (C) ) and the polyamide 6 oligomer aqueous solution (C) heated to 290 ° C. or higher and 350 ° C. or lower, and further brought into contact with water (B) heated to 290 ° C. or higher and 350 ° C. or lower to produce ⁇ -caprolactam. It is preferred to use biorecoverable polyamide 6 oligomers.
• the polyamide 6 oligomer aqueous solution (C) used in the present invention is prepared by heating and mixing the polyamide 6 oligomer and water.
• the water used for preparing the aqueous polyamide 6 oligomer aqueous solution (C) is not particularly limited, and tap water, ion-exchanged water, distilled water, well water, etc. can be used. From the point of view, ion-exchanged water and distilled water are preferably used.
• the concentration of the polyamide 6 oligomer in the polyamide 6 oligomer aqueous solution (C) used in the present invention may be 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. , 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 (C) is increased, and the aqueous polyamide 6 oligomer solution (C) can be prepared at a lower temperature. It becomes possible.
• the extract containing the polyamide 6 oligomer in the step of hot-water extracting the polyamide 6 oligomer from the polyamide 6 produced during production of the polyamide 6 can also be used as the polyamide 6 oligomer aqueous solution (C).
• polyamide 6 resin obtained by polymerizing ⁇ -caprolactam contains unreacted monomers and polyamide 6 oligomers generated in the polymerization equilibrium reaction as impurities.
• the unreacted monomers and polyamide 6 oligomer are extracted and removed by hot water extraction by supplying to a hot water extraction tower.
• the use of the extract in the step of hot water extraction of the polyamide 6 oligomer from the polyamide 6 during production of the polyamide 6 as the polyamide 6 oligomer aqueous solution (C) of the present invention can also be exemplified as a preferred embodiment.
• the method for producing ⁇ -caprolactam of the present invention comprises a resin composition (A) containing at least polyamide 6 and an aqueous polyamide 6 oligomer solution (C) heated to 290°C or higher and 350°C or lower. or in addition to the resin composition (A) containing at least polyamide 6 and the polyamide 6 oligomer aqueous solution (C) heated to 290 ° C. or higher and 350 ° C. or lower, and further heated to 290 ° C. or higher and 350 ° C. or lower water (B ) is added.
• a pressure of 22.1 MPa and a temperature of 374.2° C. it becomes neither liquid nor 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.
• this subcritical water is water, it has the characteristics of (i) a low dielectric constant and (ii) a high ionic product. is dependent on and can be controlled.
• the low dielectric constant makes it an excellent solvent for organic compounds, even though it is water, and the high ion product increases the concentration of hydrogen ions and hydroxide ions, resulting in an excellent hydrolytic action.
• the temperature of the water (B) and the polyamide 6 oligomer aqueous solution (C) 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 water when the aqueous polyamide 6 oligomer solution (C) or the aqueous polyamide 6 oligomer solution (C) and water (B) are used in combination is preferably higher than the saturated vapor pressure.
• Water may be in a liquid state, a gaseous state such as water vapor, or both. higher than the pressure is preferred.
• 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 polyamide 6 oligomer aqueous solution (C), or the polyamide 6 oligomer aqueous solution (C) and water (B).
• gases include air, argon, Nitrogen and the like can be mentioned, but nitrogen and argon are preferably used from the viewpoint of suppressing side reactions such as oxidation reactions.
• the degree of pressurization of the gas 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 method for producing ⁇ -caprolactam of the present invention is not particularly limited. It is preferable to adjust the amount of water used so that the product of Y is 2,000 or less. More preferably, the product of X and Y is 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 relates to energy-saving production of ⁇ -caprolactam from a polyamide 6 resin composition for the purpose of achieving both the recycling of fossil resources and the reduction of greenhouse gas emissions.
• 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.
• the product of is within these ranges, both efficiency in producing ⁇ -caprolactam and energy saving can be achieved.
• the residence time at the reaction temperature Y° C. is Z minutes, the condition that the product of X, Y and Z is 60,000 or less can be preferably exemplified. More preferably 40,000 or less, still more preferably 30,000 or less, and particularly preferably 20,000 or less.
• the condition is preferably 5,000 or more, more preferably 8,000 or more, and particularly preferably 9,000 or more. can.
• the inventors have found that by setting the product and the product of X, Y and Z within the above range, the by-production of linear oligomers can be suppressed and the production efficiency of ⁇ -caprolactam can be greatly improved, leading to the present invention.
• ⁇ -caprolactam of the present invention various known reaction methods such as batch method and continuous method can be employed.
• 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.
• Type/horizontal reactors, towers, and the like 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.
• Method for recovering ⁇ -caprolactam The method for recovering ⁇ -caprolactam of the present invention is not particularly limited, and any method can be employed.
• the ⁇ -caprolactam aqueous solution is obtained by distilling it together with water after the depolymerization reaction is completed.
• an ⁇ -caprolactam aqueous solution can be obtained as the reaction progresses.
• the resulting ⁇ -caprolactam aqueous solution is separated from water by distillation, whereby ⁇ -caprolactam with high purity can be recovered.
• the recovered aqueous solution of ⁇ -caprolactam contains water-insoluble components, they 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.
• Polyamide 6 and Molded Articles Thereof According to the method for producing ⁇ -caprolactam described in the present invention, ⁇ -caprolactam with high purity can be obtained, so that it can be used as a raw material for polymerization of polyamide 6.
• Polyamide 6 can be produced by a generally known method of thermally melt-polymerizing ⁇ -caprolactam in the presence of a small amount of water.
• the polyamide 6 obtained in this way is melt-kneaded with fibrous fillers and various additives as necessary to produce a polyamide 6 resin composition, and injection molding, extrusion molding, etc.
• Various molded articles such as sheets and films can be obtained by the method.
• the polyamide 6 of the present invention and its molded articles can be used for various purposes such as electric/electronic parts, building members, various containers, daily necessities, household goods and sanitary goods, taking advantage of their excellent properties. In particular, 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. , voltage regulators, rectifiers, resistors, inverters, relays, power contacts, switches, circuit breakers, switches, knife switches, multi-pole rods, motor cases, TV housings, laptop housings and internal parts, CRT display housings and Internal parts, printer housings and internal parts, mobile terminal housings and internal parts such as mobile phones, mobile personal computers, handheld mobile devices, IC and LED compatible housings, capacitor base plates, fuse holders, various gears, various cases, electronics such as cabinets Parts, connectors, connectors for SMT, card connectors, jacks, coils, coil bobbins, sensors, LED lamps, sockets, resistors, relays, relay cases, reflectors, small switches, power supply parts, coil bobbins, capacitors, variable condenser cases, optical pickups Chassis
• the solution viscosity ⁇ r was measured at 25° C. using a 0.01 g/mL solution of 98% concentrated sulfuric acid.
• the melting point is measured by using a differential scanning calorimeter, in a nitrogen gas atmosphere, the temperature of the polyamide is lowered from the molten state to 30 ° C. at a temperature decrease rate of 20 ° C./min, and then the temperature is increased by 20 ° C./min.
• the temperature of the endothermic peak that appears when the temperature is raised to °C was taken as the temperature. However, when two or more endothermic peaks were detected, the temperature of the endothermic peak with the highest peak intensity was taken as the melting point.
• the amount of the cyclic dimer to tetramer oligomer is obtained by pulverizing polyamide 6, passing through a JIS standard sieve of 24 mesh, collecting polyamide 6 powder that is impermeable to 124 mesh, and adding 20 g of the polyamide 6 powder to 200 mL of methanol. Extraction was performed using a time Soxhlet extractor, and the cyclic oligomer contained in the extract was quantitatively analyzed using high performance liquid chromatography. The measurement conditions are as follows.
• the ⁇ -caprolactam yield calculated by high performance liquid chromatography measurement of the recovered reaction mixture was 78%.
• a 10-fold amount (mass) of methanol was added to the resulting reaction mixture, stirred to form a slurry, and then filtered through a glass filter (average pore size: 10 to 16 ⁇ m) to obtain a solid content.
• the filtrate was vacuum-dried at 50° C. for 12 hours to obtain polyamide 6. An oligomer was obtained.
• High-performance liquid chromatography analysis of the obtained polyamide 6 oligomer revealed that the linear 2- to 12-mer oligomer content was 95.8% by mass.
• Example 1 17.6 g of polyamide 6 (PA6-A) and 25.5 g of deionized water were weighed into a SUS316L autoclave equipped with a stirrer, and 36.9 g of an aqueous solution of polyamide 6 oligomer having a concentration of 6.5% by mass was added.
• the mass ratio (X:1) of water to polyamide 6 and polyamide 6 oligomer is 3:1.
• the polyamide 6 oligomer used here is the polyamide 6 oligomer described in Reference Example 4.
• 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.
• the reaction mixture was recovered by cooling to room temperature. Since the reaction temperature Y° C. is 320° C., the product of X and Y is 960. 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 amount of ⁇ -caprolactam produced was 15.8 g, calculated by high-performance liquid chromatography measurement of the recovered reaction mixture, and the yield relative to polyamide 6 (PA6-A) used in the reaction was 89.8%. Further, the reaction mixture recovered by the above reaction is subjected to distillation separation of water at a reduced pressure of 30 mmHg and a heating temperature of 55° C.
• a reaction mixture was prepared by carrying out the reaction under the same conditions as in Example 1. About 10 times the amount (mass) of methanol was added to the resulting reaction mixture, stirred to form a slurry, and then filtered through a glass filter (average pore size 10 to 16 ⁇ m) to recover the solid content. Furthermore, methanol is added in an amount about 5 times the amount of the collected solids, stirred to form a slurry, and the operation of filtering through a glass filter is repeated 4 times. A polyamide 6 oligomer was recovered.
• Example 2 17.6 g of polyamide 6 (PA6-A) and 25.5 g of deionized water were weighed into a SUS316L autoclave equipped with a stirrer, and the polyamide 6 oligomer prepared by the method described in Reference Example 5 was used to give a concentration of 6.0. 36.9 g of an aqueous polyamide 6 oligomer solution adjusted to 5% by mass was added. Weight ratio of water to polyamide 6 and polyamide 6 oligomer (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 320° C. for 15 minutes while stirring at 200 rpm.
• the reaction mixture was recovered by cooling to room temperature. Since the reaction temperature Y° C. is 320° C., the product of X and Y is 960. 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 amount of ⁇ -caprolactam produced was 15.7 g, calculated by high-performance liquid chromatography measurement of the recovered reaction mixture, and the yield relative to polyamide 6 (PA6-A) used in the reaction was 89.2%.
• PA6-A polyamide 6
• Example 3 25.1 g of PA6-B prepared in Reference Example 1 and 25.5 g of deionized water were weighed into a SUS316L autoclave equipped with a stirrer, and 36.9 g of an aqueous solution of polyamide 6 oligomer having a concentration of 6.5% by mass was added. .
• the mass ratio (X:1) of water to polyamide 6 and polyamide 6 oligomer is 3:1.
• the polyamide 6 oligomer used here is the polyamide 6 oligomer described in Reference Example 4.
• 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.
• the reaction mixture was recovered by cooling to room temperature. Since the reaction temperature Y ° C. is 340 ° C., the product of X and Y is 1,020, and the residence time at the reaction temperature of 340 ° C. is 15 minutes, so the product of X, Y and Z is 15,300. be.
• the amount of ⁇ -caprolactam produced calculated from high-performance liquid chromatography measurement of the recovered reaction mixture was 15.0 g, and the yield of PA6-B used in the reaction relative to polyamide 6 in PA6-B was 85.4%. .
• Example 4 25.1 g of PA6-C described in Reference Example 2 and 25.5 g of deionized water were weighed into a SUS316L autoclave equipped with a stirrer, and 36.9 g of an aqueous polyamide 6 oligomer solution having a concentration of 6.5% by mass was added. bottom.
• the mass ratio (X:1) of water to polyamide 6 and polyamide 6 oligomer is 3:1.
• the polyamide 6 oligomer used here is the polyamide 6 oligomer described in Reference Example 4.
• 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 reaction mixture was recovered by cooling to room temperature. Since the reaction temperature Y ° C. is 320 ° C., the product of X and Y is 960, and the residence time at the reaction temperature of 320 ° C. is 15 minutes, so the product of X, Y and Z is 14,400. .
• the amount of ⁇ -caprolactam produced calculated by high-performance liquid chromatography measurement of the recovered reaction mixture was 14.9 g, and the yield relative to polyamide 6 in PA6-C used in the reaction was 84.8%.
• Example 5 A reaction mixture was prepared by carrying out the reaction under the same conditions as in Example 1 except that PA6-D described in Reference Example 3 was used instead of PA6-A.
• the yield of ⁇ -caprolactam calculated by high-performance liquid chromatography of the recovered reaction mixture was 15.7 g, and the yield relative to polyamide 6 in PA6-D used in the reaction was 89.2%.
• Example 7 39.6 g of polyamide 6 (PA6-A) and 57.4 g of deionized water were weighed into a SUS316L autoclave equipped with a stirrer, and the polyamide 6 oligomer prepared by the method described in Reference Example 4 was used to give a concentration of 6.0. 83.0 g of an aqueous polyamide 6 oligomer solution adjusted to 5% by mass was added. Weight ratio of water to polyamide 6 and polyamide 6 oligomer (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 19.7 MPa.
• the reaction mixture was recovered by cooling to room temperature. Since the reaction temperature Y° C. is 320° C., the product of X and Y is 960. 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 amount of ⁇ -caprolactam produced was 36.9 g calculated by high-performance liquid chromatography measurement of the recovered reaction mixture, and the yield relative to polyamide 6 (PA6-A) used in the reaction was 93.2%.
• PA6-A polyamide 6
• Example 8 26.4 g of polyamide 6 (PA6-A) and 25.5 g of deionized water were weighed into a SUS316L autoclave equipped with a stirrer, and the polyamide 6 oligomer prepared by the method described in Reference Example 4 was used to give a concentration of 9.5. 36.9 g of an aqueous polyamide 6 oligomer solution adjusted to 8% by mass was added. Weight ratio of water to polyamide 6 and polyamide 6 oligomer (X:1 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.
• the reaction mixture was recovered by cooling to room temperature. Since the reaction time Y° C. is 320° C., the product of X and Y is 640. Since the residence time at the reaction temperature of 320° C. is 15 minutes, the product of X, Y and Z is 9,600.
• the amount of ⁇ -caprolactam produced was 18.8 g as calculated by high-performance liquid chromatography measurement of the recovered reaction mixture, and the yield relative to polyamide 6 (PA6-A) used in the reaction was 71.0%.
• Example 9 52.6 g of polyamide 6 (PA6-A) and 51.0 g of deionized water were weighed into a SUS316L autoclave equipped with a stirrer, and the polyamide 6 oligomer prepared by the method described in Reference Example 4 was used to give a concentration of 9.0. 73.8 g of an aqueous polyamide 6 oligomer solution adjusted to 8% by mass was added. Weight ratio of water to polyamide 6 and polyamide 6 oligomer (X:1 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 19.8 MPa.
• the reaction mixture was recovered by cooling to room temperature. Since the reaction time Y°C is 320°C, the product of XtoY 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 amount of ⁇ -caprolactam produced was 45.1 g calculated by high-performance liquid chromatography measurement of the recovered reaction mixture, and the yield relative to polyamide 6 (PA6-A) used in the reaction was 85.7%.
• PA6-A polyamide 6
• 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 10 The hot water extract in the PA6 production process obtained by the method described in Reference Example 6 was concentrated until the concentration of unreacted caprolactam and polyamide 6 oligomer reached 6.5% by mass, and the solution using the resulting concentrated solution Polymerization was carried out. 17.6 g of polyamide 6 (PA6-A) and 25.5 g of deionized water were weighed into a SUS316L autoclave equipped with a stirrer, and 36.9 g of the concentrate was added. The mass ratio (X:1) of water to polyamide 6 and polyamide 6 oligomer is 3.3:1. The reaction vessel was purged with nitrogen, sealed under a nitrogen pressure of 0.5 MPa, and then reacted at 320° C.
• the reaction mixture was recovered by cooling to room temperature. Since the reaction temperature Y° C. is 320° C., the product of X and Y is 1056. Since the residence time at the reaction temperature of 320° C. is 15 minutes, the product of X, Y and Z is 15,840.
• the amount of ⁇ -caprolactam produced was 14.8 g calculated by high-performance liquid chromatography measurement of the recovered reaction mixture, and the yield relative to polyamide 6 (PA6-A) used in the reaction was 84.1%.
• Example 11 The hot water extract in the PA6 production process obtained by the method described in Reference Example 6 was concentrated until the total concentration of unreacted caprolactam and polyamide 6 oligomer was 6.5% by mass, and the obtained concentrate was used. Depolymerization was carried out. 20.0 g of polyamide 6 (PA6-A) and 65.0 g of the concentrate were added to a SUS316L autoclave equipped with a stirrer. The mass ratio (X:1) of water to polyamide 6 and polyamide 6 oligomer is 2.9:1. 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 reaction mixture was recovered by cooling to room temperature. Since the reaction temperature Y° C. is 320° C., the product of X and Y is 928. Since the residence time at the reaction temperature of 320° C. is 15 minutes, the product of X, Y and Z is 13,920.
• the amount of ⁇ -caprolactam produced was 15.7 g, calculated by high-performance liquid chromatography measurement of the recovered reaction mixture, and the yield relative to polyamide 6 (PA6-A) used in the reaction was 78.5%.

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