Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
  • C08L77/02—Polyamides derived from omega-amino carboxylic acids or from lactams thereof
• • 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
  • 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
  • C08J11/14—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
  • 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
  • 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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2207/00—Properties characterising the ingredient of the composition
  • C08L2207/20—Recycled plastic
• • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/141—Feedstock
  • Y02P20/143—Feedstock the feedstock being recycled material, e.g. plastics
• • 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 relates to a resin made of chemically recycled nylon 6 and a method for producing the same.
• Polyamide is a material that is widely used in textile and resin products, clothing, and industrial applications, and with growing interest in sustainability, including the SDGs (Sustainable Development Goals), reuse through recycling is on the rise.
• SDGs Stustainable Development Goals
• Known methods for recycling polyamide include thermal recycling, material recycling, and chemical recycling.
• the chemical recycling method is an industrially useful recycling method, as it breaks down polyamide resin into its raw monomers, which are then recovered and reused as raw materials for polymers.
• nylon 6 one of the polyamides, is produced from petroleum-derived ⁇ -caprolactam
• the polymerization reaction is an equilibrium reaction, so it is common for an extraction process to be carried out after polymerization to remove the monomer and oligomer components.
• it is common to depolymerize and reuse the recovered monomer and oligomer components in order to reduce raw material losses and the burden on wastewater, and nylon 6 has an advantage over other polyamides in that it can utilize this recovery and reuse cycle.
• Patent Document 1 describes a method for chemically recycling dustproof clothing
• Patent Document 2 describes a method for chemically recycling clothing products made from nylon 6 fibers.
• this method it is assumed that chemical recycling will be carried out from the product design stage onwards, and it is described that by making nylon 6 the main material in the product, it is possible to minimize the mixing of impurities from other resins such as polyurethane and polyester, thereby obtaining highly pure monomer raw material.
• Patent Document 3 also describes a method for recycling nylon 6 clothing products, in which the content of water repellent and titanium oxide is limited to a certain amount or less, thereby avoiding equipment troubles and recovering the monomer ⁇ -caprolactam during depolymerization. It describes how depolymerization can be achieved without clogging the distillation line by regulating the mixture ratio of substances that inhibit the depolymerization process that returns nylon products to the raw material ⁇ -caprolactam.
• Patent Document 4 describes a method for recycling nylon 6 products that contain one or more resin components as impurities by pre-treating them in an alkaline aqueous solution.
• Patent Documents 1 and 2 are designed to limit the use of resins and materials other than nylon 6.
• the quality of the ⁇ -caprolactam obtained by chemical recycling is high in purity, the products to which it can be applied are limited in the first place, and it must be recovered without being mixed with other products, making chemical recycling extremely limited. Furthermore, it cannot be applied to the chemical recycling of general nylon 6 products already available on the market.
• Patent Document 3 focuses on substances that inhibit the depolymerization of nylon 6 products and limits their ratio, thereby increasing the purity of the quality of ⁇ -caprolactam.
• Patent Document 4 makes it possible to chemically remove resins other than nylon 6 that reduce the quality of ⁇ -caprolactam after depolymerization.
• the other eluted components must be discharged as waste liquid, which places a heavy burden on the wastewater treatment process, making it difficult to expand the volume and difficult to apply in industrial applications.
• the objective of the present invention is to provide a regenerated nylon 6 resin and a method for producing the same that have a similar color tone to nylon products produced from ⁇ -caprolactam that are not obtained through recycling, when chemically recycling nylon 6 products that are already available in large quantities on the market on an industrial scale.
• the present invention employs the following configuration.
• the nylon 6 resin according to (1) above which contains a substance other than nylon 6 having a peak in the region of 6.5 ppm to 13.0 ppm in 1 H NMR, the substance having a benzene ring structure.
• a method for producing a nylon 6 resin according to (1) or (2) above comprising depolymerizing a raw material nylon 6 recovered product to recover ⁇ -caprolactam, purifying the ⁇ -caprolactam, and polymerizing the ⁇ -caprolactam, wherein a ratio of polyester resin in the nylon 6 recovered product is 5 mass% or less.
• the present invention makes it possible to provide chemically recycled nylon 6 resin that has a color tone equivalent to that of so-called virgin nylon 6 resin that has not been chemically recycled.
• the nylon 6 resin of the present invention is made of chemically recycled nylon 6, and contains 1 mass % or less of peaks other than nylon 6 in the region of 6.5 ppm to 13.0 ppm in 1 H NMR.
• the nylon 6 resin of the present invention is preferably 95 mass % or more of nylon 6, more preferably 97 mass % or more, and even more preferably 99 mass % or more.
• the nylon 6 resin of the present invention is suitable for having a relative viscosity in a 98% sulfuric acid solution in the range of 2.0 to 4.0.
• This nylon 6 resin may contain additives such as titanium oxide and heat stabilizers to the extent that they do not impede the purpose of the present invention.
• the nylon 6 resin of the present invention contains 1% by mass or less of peaks other than nylon 6 in the region of 6.5 ppm to 13.0 ppm in 1 H NMR.
• the peaks other than nylon 6 are more preferably 0.7% by mass or less, and even more preferably 0.5% by mass or less, while the lower limit is preferably 0.1% by mass or more. That is, it is preferable that the peaks other than nylon 6 are contained in the range of 0.1% by mass or more to 1% by mass in the region of 6.5 ppm to 13.0 ppm in 1 H NMR.
• the region of 6.5 ppm to 13.0 ppm in 1 H NMR is a peak where multiple bonds and hydrogen atoms bonded to aromatics that affect the color tone of the resin can be confirmed, and if the peaks contained in this region are 1% by mass or less, a nylon 6 resin with good color tone can be obtained.
• substances other than nylon 6 that can be confirmed by peaks in the above region include those having a benzene ring structure, and it is particularly desirable to control the content of substances containing a benzene ring structure. If a large amount of benzene ring structure is contained, the color tone of the obtained nylon 6 resin may be deteriorated.
• An example of a substance having a benzene ring structure is terephthalic acid.
• the 1 H NMR in the present invention may be measured by any method.
• the resin pellets are dissolved in deuterated HFIP (hexafluoroisopropanol) (containing TMS (tetramethylsilane)), and 1 H NMR is measured.
• Other deuterated solvents may be used as long as they dissolve nylon 6.
• the integral ratio is calculated from the peaks assigned to each component to calculate the amount of the component.
• the amount of the component other than nylon 6 in the present invention is calculated from the ratio of the 4H peak area derived from terephthalic acid at 8 to 8.5 ppm and the 2H peak area derived from nylon 6 at 3 to 3.5 ppm.
• the peaks are not limited to the above peaks as long as they are not interfered with by other peaks and can be identified.
• the method for producing the nylon 6 resin of the present invention includes depolymerizing a nylon 6 recycled product to recover ⁇ -caprolactam, purifying the ⁇ -caprolactam, and polymerizing the ⁇ -caprolactam, and the ratio of polyester resin in the nylon 6 recycled product is 5 mass% or less.
• the nylon 6 recycled product is pre-consumer scrap and/or post-consumer scrap. Although not limited to the following, for example, pre-consumer scrap is washed away scrap from the spinning process, thread breakage scrap, and extrusion scrap, and post-consumer scrap is recovered clothing products, fishing nets, ropes, etc.
• the depolymerization carried out in the present invention may be carried out by any method.
• the nylon 6 recovered product is melted by heating and depolymerized.
• a catalyst may be used in this process, and the process may be carried out in the absence (dry process) or presence (wet process) of water.
• the pressure during depolymerization may be reduced, normal, or increased.
• the depolymerization temperature is preferably 100°C to 400°C, more preferably 200°C to 350°C, and even more preferably 220°C to 300°C. If the temperature is too low, the nylon 6 recovered product will not melt, and the depolymerization rate will be slow. If the temperature is too high, the nylon 6 monomer (i.e., ⁇ -caprolactam) will decompose, resulting in a decrease in the purity of the recovered ⁇ -caprolactam.
• an acid catalyst or a base catalyst is used.
• acid catalysts include phosphoric acid, boric acid, sulfuric acid, organic acids, organic sulfonic acids, solid acids, and salts thereof.
• base catalysts include alkali hydroxides, alkali salts, alkaline earth hydroxides, alkaline earth salts, organic bases, and solid bases.
• Preferred examples include phosphoric acid, boric acid, organic acids, alkali hydroxides, and alkali salts. More preferred examples include phosphoric acid, sodium phosphate, potassium phosphate, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate.
• the amount of catalyst used is preferably 0.01% to 50% by mass based on the nylon 6 recovered product. More preferably, it is 0.01% to 20% by mass, and even more preferably, it is 0.5% to 10% by mass. If the amount of catalyst is too small, the reaction rate will be slow, and if it is too large, there will be many side reactions and the catalyst cost will increase, which will be economically disadvantageous.
• the amount of water is preferably 0.1 to 50 times by mass relative to the amount of the recovered nylon 6 product. More preferably, it is 0.5 to 20 times by mass, and even more preferably, it is 1 to 10 times by mass. If the amount of water is too small, the reaction rate will be slow, and if it is too large, the concentration of the recovered aqueous solution of ⁇ -caprolactam will be low.
• the nylon 6 recovered product to be depolymerized should preferably have less other resin components such as polyurethane and polyester. Resin components other than nylon 6 are preferably 5% by mass or less, more preferably 3% by mass or less, with a lower limit of 1% by mass or more, relative to the nylon 6 recovered product. If nylon 6 recovered products to which other resins remain attached or attached are decomposed by depolymerization, the purity of the recovered ⁇ -caprolactam will decrease, and the recovery rate of ⁇ -caprolactam may decrease due to an increase in the viscosity of the molten raw material during depolymerization and catalyst deactivation.
• the ratio of polyester resin in the nylon 6 recovered product is set to 5% by mass or less.
• the ratio of polyester resin is preferably 3% by mass or less, and more preferably 1% by mass or more. In other words, the ratio of polyester resin is preferably 1% by mass or more and 5% by mass or less.
• the method for recovering ⁇ -caprolactam in the present invention is not particularly limited, and any method may be used.
• the generated ⁇ -caprolactam is distilled from the depolymerization reaction apparatus by vacuum distillation and recovered. After the depolymerization reaction is completed, ⁇ -caprolactam may be extracted by vacuum distillation. It may be continuously extracted as the depolymerization reaction progresses.
• wet depolymerization is performed, the generated ⁇ -caprolactam is distilled together with water from the depolymerization reaction apparatus, and an aqueous ⁇ -caprolactam solution is recovered. After the depolymerization reaction is completed, ⁇ -caprolactam may be extracted by vacuum distillation. It may be continuously extracted as the depolymerization reaction progresses.
• Methods for purifying the recovered ⁇ -caprolactam include, for example, subjecting the recovered ⁇ -caprolactam to precision distillation, vacuum distillation with the addition of a small amount of sodium hydroxide, treatment with activated carbon, ion exchange treatment, and recrystallization, and these purification methods can be combined.
• the degree of coloration of ⁇ -caprolactam obtained by the depolymerization performed in the present invention is measured by placing a 50% by mass aqueous solution of ⁇ -caprolactam in a 10 mm long quartz cell and measuring the transmittance at a wavelength of 290 nm based on water using a spectrophotometer.
• the higher the transmittance the lower the degree of coloration.
• a low degree of coloration of ⁇ -caprolactam can lighten the color tone of nylon 6 resin.
• the transmittance of a 50% by mass aqueous solution of ⁇ -caprolactam is preferably 30% or more, and more preferably 50% or more. Since a higher transmittance is preferable, there is no particular upper limit.
• the polymerization method of the present invention may be any method.
• a stainless steel autoclave (polymerization reactor) is charged with an aqueous solution of recovered and purified ⁇ -caprolactam with a concentration of 80 to 95% by mass, and the inside of the polymerization reactor is sealed with nitrogen.
• the temperature is raised over 1 to 3 hours until the internal pressure of the polymerization reactor becomes 0.8 to 1.2 MPa, and the polymerization reaction is carried out at 240 to 260°C for 1 to 2 hours while maintaining the pressure.
• the pressure in the polymerization reactor is then released, and polymerization is carried out for another 1 to 2 hours under a nitrogen stream.
• the resulting polymer is extruded in a strand shape and cooled/cut to obtain pellets.
• the resulting pellets are then transferred to a normal pressure vessel equipped with hot water in an amount 5 to 20 times the amount of pellets, and allowed to remain at a water temperature of 90 to 100°C for 12 to 24 hours to extract unreacted monomer or oligomer components, followed by dehydration treatment.
• ⁇ Measuring method ⁇ ⁇ Transmittance> The obtained ⁇ -caprolactam and purified water were mixed to obtain a 50% by mass aqueous solution of ⁇ -caprolactam, which was then placed in a 10 mm long quartz cell and the transmittance at a wavelength of 290 nm relative to water was measured using a spectrophotometer, and the result was expressed as a color tone.
• ⁇ Amount of Peak Components Other Than Nylon 6> 1 mg of the resin pellets was dissolved in 0.4 mL of deuterated HFIP, and 1 H NMR was measured using an ECA-400 manufactured by JEOL Ltd. The amount of components other than nylon 6 in the region of 6.5 ppm to 13.0 ppm was calculated from the peaks assigned to each component.
• Example 1 420 g of recycled nylon 6 product containing 21 g of polyester resin and 16.8 g of a 75 mass % aqueous phosphoric acid solution containing phosphoric acid as a depolymerization catalyst were charged into a depolymerization apparatus, and the mixture was heated to 260° C. in a nitrogen atmosphere. The nitrogen was stopped, and superheated steam was blown into the depolymerization apparatus at an introduction rate of 500 g/hour to start the reaction. The reaction was carried out at 260° C. for 10 hours, and the steam containing ⁇ -caprolactam continuously distilled from the depolymerization apparatus was recovered and cooled to obtain an aqueous ⁇ -caprolactam solution.
• the resulting aqueous ⁇ -caprolactam solution was concentrated by distilling off water with an evaporator at about 70° C. under reduced pressure of 3.3 kPa, and then transferred to a 1000 ml Huben flask. 5.3 g of a 40% by mass aqueous solution of sodium hydroxide was added thereto, and the mixture was further concentrated under reduced pressure conditions of about 100° C. and 3.3 kPa. Then, ⁇ -caprolactam was distilled under reduced pressure conditions of about 160° C. and 0.7 kPa to obtain 335 g of purified ⁇ -caprolactam. The transmittance of a 50% by mass aqueous solution of ⁇ -caprolactam was 37%.
• the molten nylon 6 was extruded from the bottom of the polymerization vessel into a gut shape, cooled with water, and cut into pellets using a pelletizer. Low molecular weight impurities were extracted from the pellets with hot water to obtain nylon 6 resin pellets obtained by chemical recycling.
• the resin pellets thus obtained were measured for the amount of substances having peaks other than those of nylon 6 in the region of 6.5 ppm to 13.0 ppm, and for color tone YI. The results are shown in Table 1.
• Example 2 Example 3, Comparative Example 1
• Example 2 Example 2, Example 3, Comparative Example 1
• Example 1 The procedure of Example 1 was repeated except that polymerization was carried out using virgin ⁇ -caprolactam as the raw material.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
• Polyamides (AREA)

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• 2023
  • 2023-11-16 EP EP23897520.5A patent/EP4628521A1/en active Pending
  • 2023-11-16 WO PCT/JP2023/041252 patent/WO2024116869A1/ja not_active Ceased
  • 2023-11-16 KR KR1020257017624A patent/KR20250113412A/ko active Pending
  • 2023-11-16 CN CN202380082272.8A patent/CN120265682A/zh active Pending
  • 2023-11-16 JP JP2023572952A patent/JPWO2024116869A1/ja active Pending
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