WO2023203980A1 - Procédé de production de bis-(2-hydroxyethyl)téréphtalate et procédé de production de polyéthylène téréphtalate recyclé - Google Patents

Procédé de production de bis-(2-hydroxyethyl)téréphtalate et procédé de production de polyéthylène téréphtalate recyclé Download PDF

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WO2023203980A1
WO2023203980A1 PCT/JP2023/012739 JP2023012739W WO2023203980A1 WO 2023203980 A1 WO2023203980 A1 WO 2023203980A1 JP 2023012739 W JP2023012739 W JP 2023012739W WO 2023203980 A1 WO2023203980 A1 WO 2023203980A1
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terephthalate
hydroxyethyl
bis
bhet
producing
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PCT/JP2023/012739
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English (en)
Japanese (ja)
Inventor
正樹 ▲高▼尾
慧 山原
修司 稲田
博 藤田
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株式会社シンテック
株式会社Jeplan
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Publication of WO2023203980A1 publication Critical patent/WO2023203980A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/03—Preparation of carboxylic acid esters by reacting an ester group with a hydroxy group
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/08—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/48—Separation; Purification; Stabilisation; Use of additives
    • C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/48—Separation; Purification; Stabilisation; Use of additives
    • C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
    • C07C67/54—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation by distillation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
    • C07C69/76—Esters of carboxylic acids having a carboxyl group bound to a carbon atom of a six-membered aromatic ring
    • C07C69/80—Phthalic acid esters
    • C07C69/82—Terephthalic acid esters
    • 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
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
    • C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
    • C08G63/16—Dicarboxylic acids and dihydroxy compounds
    • 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
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
    • C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
    • C08G63/16—Dicarboxylic acids and dihydroxy compounds
    • C08G63/18—Dicarboxylic acids and dihydroxy compounds the acids or hydroxy compounds containing carbocyclic rings
    • C08G63/181—Acids containing aromatic rings
    • C08G63/183—Terephthalic acids
    • 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
    • C08J11/22—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 oxygen-containing compounds
    • C08J11/24—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 oxygen-containing compounds containing hydroxyl groups
    • 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 method for producing highly pure bis-(2-hydroxyethyl) terephthalate from polyester waste, and a method for producing recycled polyethylene terephthalate using such bis-(2-hydroxyethyl) terephthalate.
  • polyester for example, polyethylene terephthalate
  • resin molded products etc.
  • polyester waste manufactured process loss
  • thermal recycling which converts polyester waste including clothing and thread fiber waste into fuel, has the advantage that the combustion heat of polyester waste can be reused.
  • the calorific value of polyester is relatively low, a large amount of polyester waste must be burned in order to utilize the heat of combustion. Therefore, there are problems of loss of polyester raw material and generation of carbon dioxide, which is unfavorable from the viewpoint of resource saving and environmental protection.
  • polyester waste is converted into the raw material monomer bis-(2-hydroxyethyl) terephthalate (hereinafter also referred to as "BHET”) or dimethyl terephthalate (hereinafter also referred to as "DMT”). ), and the recycled BHET or DMT is polycondensed again to produce a new polyester (see Patent Documents 1 to 3). Therefore, there is little deterioration in the quality of polyester due to recycling, making it an excellent closed-loop recycling method.
  • recycled raw materials are mostly used transparent PET bottles, resin scraps, and film scraps that are uncolored and have few impurities.
  • polyester clothing waste contains a variety of stabilizers, antistatic agents, dye-facilitating agents, flame retardants, moisture absorbers, gas barrier agents, etc. that are used to satisfy the required characteristics depending on the clothing application.
  • a chemical recycling method has been proposed in which coloring agents such as dyes and pigments are removed from colored fibrous polyester, and then recycled polyester is obtained again through DMT, which is a raw material monomer (see Patent Documents 4 and 5).
  • the methods described in Patent Documents 4 and 5 are methods for recovering DMT from colored fibrous polyester, and the recycling process is long and requires a large amount of energy, so there are many problems in terms of cost.
  • purified recycled DMT has a major disadvantage in that it cannot be directly used in the polymerization process (terephthalic acid process) that uses terephthalic acid as a raw material, which is currently widespread worldwide.
  • colored polyester waste is depolymerized to obtain a colored depolymerized product containing crude BHET, and the obtained colored depolymerized product is mixed with monoethylene glycol and cooled.
  • a method is disclosed in which BHET is precipitated and then subjected to solid-liquid separation to remove a portion of the dye to obtain high-purity BHET (see Patent Document 6).
  • the mixed medium with the colored depolymerized product is monoethylene glycol
  • the crystal shape of the precipitated BHET becomes finer, and the viscosity of monoethylene glycol at the time of cooling at low temperature becomes high. Become.
  • colored polyester waste is depolymerized to obtain a colored depolymerized product containing crude BHET, and a dye decomposing agent is added to the obtained colored depolymerized product to decolorize it.
  • a method is also disclosed in which a polymer and monoethylene glycol are mixed and cooled to precipitate BHET, and then dye decomposition products and residual dye are removed by solid-liquid separation to obtain high-purity BHET (see Patent Document 7). ).
  • the mixed medium with the decolorizing and depolymerized product is monoethylene glycol, the crystal shape of the precipitated BHET becomes finer and the viscosity of the monoethylene glycol at the time of cooling at a low temperature increases.
  • a method for producing bis-(2-hydroxyethyl) terephthalate which can easily produce bis-(2-hydroxyethyl) terephthalate by efficiently removing pigments, additives, etc.
  • the present invention aims to provide a method for producing recycled polyethylene terephthalate using ethyl terephthalate as a raw material.
  • a method for producing bis-(2-hydroxyethyl) terephthalate involves mixing polyester waste, monoethylene glycol, and a depolymerization catalyst, and depolymerizing the polyester waste to obtain a depolymerized product containing crude bis-(2-hydroxyethyl) terephthalate.
  • the depolymerized product is cooled and a cleaning medium different from that of monoethylene glycol alone is added to transfer at least part of the non-polyester impurities contained in the polyester waste to the cleaning medium.
  • a washing step for removing from the polymerized product; a concentration step for removing low-boiling components containing at least the washing medium from the washed depolymerized product to concentrate crude bis-(2-hydroxyethyl) terephthalate;
  • Bis-(2-hydroxyethyl) terephthalate is recovered from the crude bis-(2-hydroxyethyl) terephthalate by distillation to produce high-purity bis-(2-hydroxyethyl) terephthalate, which is higher in purity than crude bis-(2-hydroxyethyl) terephthalate. hydroxyethyl) terephthalate.
  • colorants such as dyes and pigments, additives, etc. are extracted from polyester waste (especially colored polyester clothing waste, colored PET bottle waste, industrial films containing a large number of additives, etc.). It becomes possible to efficiently decompose and remove agents and the like, and easily produce highly pure bis-(2-hydroxyethyl) terephthalate (BHET).
  • BHET bis-(2-hydroxyethyl) terephthalate
  • high-purity BHET can be easily produced from polyester clothing waste, it is possible to regenerate polyester from polyester clothing waste, which until now was mostly incinerated or landfilled, through raw material monomers. becomes possible.
  • the highly pure recycled BHET produced by the present invention has the great advantage that it can be directly used in a polymerization process using terephthalic acid as a raw material (terephthalic acid process), which is currently widespread worldwide.
  • a method for producing bis-(2-hydroxyethyl) terephthalate in which polyester waste is mixed with monoethylene glycol and a depolymerization catalyst, and the polyester waste is depolymerized to produce crude bis-(2-hydroxyethyl) terephthalate.
  • a depolymerization step to obtain a depolymerized product containing 2-hydroxyethyl) terephthalate, and cooling the depolymerized product and adding a cleaning medium different from that of the monoethylene glycol alone to remove the monoethylene glycol contained in the polyester waste.
  • the cleaning medium contains at least one glycol ether compound having 3 to 12 carbon atoms. how to.
  • the cleaning time per time with the cleaning medium in the cleaning step is 5 The method is ⁇ 120 minutes.
  • the number of times of washing with the washing medium in the washing step is 1 to 8 times. There is a method.
  • the amount of the cleaning medium used per time in the cleaning step is: 1 to 10 parts by weight based on 1 part by weight of the crude bis-(2-hydroxyethyl) terephthalate.
  • the polyester waste contains polyester waste containing 65% by mass or more of polyethylene terephthalate. A method, a thing.
  • the solvent contains water and/or a glycol compound, and the glycol compound has 3 to 3 carbon atoms. 12, and glycols having 2 to 6 carbon atoms.
  • the content of the water and/or glycol compound in the solvent is 85% by mass or more. There is a method.
  • the high-purity bis-(2-hydroxyethyl) terephthalate after the crystallization purification step is )
  • the amount of the ester component remaining in the terephthalate is 1% by mass or less, and the amount of nitrogen atoms remaining in the high purity bis-(2-hydroxyethyl) terephthalate after the crystallization purification step is 10 ppm or less. is, the method.
  • a method for producing recycled polyethylene terephthalate comprising the method for producing bis-(2-hydroxyethyl) terephthalate according to any one of (1) to (14) above.
  • a method comprising the steps of: obtaining ethyl) terephthalate; and obtaining recycled polyethylene terephthalate by polycondensing the bis-(2-hydroxyethyl) terephthalate.
  • FIG. 1 is a flow chart showing a preferred embodiment of the method for producing bis-(2-hydroxyethyl) terephthalate of the present invention.
  • a "process” does not mean only a process that can be distinguished from others, but also a process that is combined with other operations, a process that is actually dispersed into multiple processes, and a process that is '' that include other process elements, and those that can perform operations of multiple steps in one step may belong to the scope of the present invention, as long as they meet the spirit of the invention.
  • FIG. 1 is a flow chart showing a preferred embodiment of the method for producing bis-(2-hydroxyethyl) terephthalate of the present invention.
  • the method for producing bis-(2-hydroxyethyl) terephthalate (BHET) of the present invention can be applied to various polyester wastes such as clothing, PET bottles, films, and resin molded products.
  • BHET bis-(2-hydroxyethyl) terephthalate
  • the present invention is applied to colored polyester clothing waste (colored polyester clothing waste) as the polyester waste.
  • the method for producing BHET of this embodiment includes (1) a depolymerization step, (2) a solid matter removal step, (3) a washing step, (4) a concentration step, (5) a recovery step, and (6) ) a crystallization purification step. Each step will be explained in order below.
  • polyester clothing waste colored with dyes, pigments, and other dyes (coloring dyes) is reacted with monoethylene glycol (hereinafter also referred to as "MEG") and a depolymerization catalyst.
  • MEG monoethylene glycol
  • the colored polyester clothing waste is charged into a tank and mixed, and the colored polyester clothing waste is depolymerized to obtain a depolymerization liquid (liquid depolymerized product) containing colored BHET.
  • polyester constituting polyester clothing include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), as well as polyethylene naphthalate (PEN) and polybutylene naphthalate (PBN). etc.
  • the polyester clothing targeted by the present invention is preferably clothing mainly composed of polyethylene terephthalate (PET) fibers.
  • PET polyethylene terephthalate
  • Such polyester clothing may contain different materials such as nylon, urethane, cotton, and olefin, and stabilizers, antistatic agents, dyeability agents, It may contain various compounds such as flame retardants, moisture absorbers, and gas barrier agents, additives such as titanium oxide used as a matting agent, and solid materials such as zippers, buttons, metals, glass, and sand.
  • the amount of PET (for example, PET fiber) contained in polyester clothing is not particularly limited, but is preferably 65% by mass or more, more preferably 75% by mass or more, and preferably 85% by mass or more. It is more preferable, and particularly preferably 95% by mass or more. Note that the upper limit may be 100% by mass.
  • Pigments used for coloring (dying) polyester clothing are broadly classified into dyes and pigments.
  • the dye include disperse dyes, naphthol dyes, mordant dyes, and vat dyes, but disperse dyes are preferred. This disperse dye is ideal for coloring polyester because it bonds with polyester through intermolecular forces. Further, according to studies conducted by the present inventors, it has been found that the use of the present invention to remove disperse dyes is highly effective.
  • Examples of such disperse dyes include C.I. I. A compound classified as Disperse Black, C.I. I. A compound classified as Disperse Blue, C.I. I. A compound classified as Disperse Red, C.I. I. A compound classified as Disperse Orange, C.I. I. Compound classified as Disperse Yellow, C.I. I. A compound classified as Disperse Green, C.I. I. A compound classified as Disperse Violet, C.I. I. Examples include compounds classified as Disperse Brown.
  • examples of pigments include C.I. I. Compound classified as Pigment Black, C.I. I. A compound classified as Pigment Blue, C.I. I. A compound classified as Pigment Red, C.I. I. Pigment A compound classified as Orange, C.I. I. Compound classified as Pigment Yellow, C.I. I. Compound classified as Pigment Green, C.I. I. A compound classified as Pigment Violet, C.I. I. Examples include compounds classified as Pigment Brown.
  • the form of polyester clothing waste subjected to depolymerization may be in the form of clothing without being cut, in the form of cut flakes, or in the form of granules that have been granulated by some method. However, it is preferably in the form of clothing with a high bulk density. In the form of cut flakes, handling is complicated and the bulk density is low, which may be disadvantageous in depolymerization. A granulated form is advantageous in terms of ease of handling and bulk density, but the cost may increase depending on the method used to make polyester clothing waste into a granular form. There is.
  • polyester clothing waste and MEG in a predetermined ratio are charged into a reaction tank and the polyester clothing waste is depolymerized, the depolymerization reaction is performed with the polyester clothing waste completely immersed in MEG.
  • the bulk density of polyester fibers is between 0.1 and 0.14 g/cm 3 (without compression) in garment form and between 0.08 and 0.1 g/cm 3 (without compression) in flake form. That is, polyester fibers can maintain a higher bulk density when used in the form of clothing. Therefore, even when polyester clothing waste is completely immersed in MEG to efficiently carry out the depolymerization reaction, the amount of MEG used can be reduced.
  • the amount of MEG used is preferably about 4.5 to 7 times the mass of the polyester clothing waste. , more preferably about 5 to 6.5 times.
  • the polyester clothing waste may not be sufficiently immersed in MEG, and the time required for the depolymerization reaction may become longer, or the polyester ( For example, the conversion rate from PET to BHET may become low. In this case, a large amount of polyester oligomer tends to exist in the depolymerization liquid, and the viscosity of the depolymerization liquid tends to increase.
  • depolymerization catalysts include alkali metal hydroxides, alkali metal carbonates, alkali metal fatty acid salts, alkali metal alkoxides, alkaline earth metal hydroxides, alkaline earth metal carbonates, and alkali metals.
  • Examples include earth metal fatty acid salts, alkaline earth metal alkoxides, alkaline earth metal oxides, transition metal hydroxides, transition metal carbonates, transition metal fatty acid salts, transition metal alkoxides, etc.
  • alkali metals include Li, Na, K, etc.
  • examples of alkaline earth metals include Mg, Ca, etc.
  • transition metals include Ti, Zn, Mn, etc.
  • the temperature during depolymerization is preferably about 180 to 210°C, more preferably about 185 to 200°C.
  • the depolymerization time is preferably about 1 to 10 hours, more preferably about 1.5 to 7 hours.
  • the atmospheric pressure during depolymerization is preferably about 60 kPa to 160 kPa.
  • polyester clothing waste often contains foreign matter other than polyester fibers (solid matter insoluble in polyester), so if necessary, these foreign matter can be colored. It is preferable to remove it from the depolymerization solution.
  • Such foreign materials include, for example, foreign materials such as cotton and olefins, solid materials such as zippers, buttons, and metals, and coarse solid materials such as solid materials such as glass and sand that are mixed in during waste collection. These foreign substances can be removed all at once from the colored depolymerization liquid by filtering through a coarse filter with an opening of about 20 to 40 mesh.
  • titanium oxide which is insoluble in polyester
  • polyester clothing may be added to polyester clothing as a matting agent in an amount of about 0.3 to 0.5% by mass.
  • additives that are insoluble in various polyesters are often used in order to satisfy the required properties depending on the clothing use. It is naturally undesirable for these fine solids to be mixed into recycled PET, and depending on the size of these fine solids, they may settle or accumulate inside containers or piping during the process, blocking the flow of liquid. It is preferable to remove these fine solids from the viewpoint of process passability. Specifically, these fine solids can be removed by filtration or hot filtration using a long fiber filter having a size of several ⁇ m to several tens of ⁇ m.
  • colored polyester clothing waste is colored with pigments such as dyes and pigments.
  • the washing step is carried out in order to further increase the purity of the BHET finally obtained when the colored polyester clothing waste is highly colored.
  • a disperse dye most suitable for coloring polyester will be explained as a representative. It is known that when disperse dyes contained in colored polyester clothing waste are mixed into recycled polyester, the recycled polyester becomes colored and, in particular, tends to increase in yellowness. Therefore, when producing BHET from colored polyester clothing waste, it is preferable to perform an operation to previously remove the disperse dye (pigment) contained in the colored polyester clothing waste.
  • Disperse dyes are overwhelmingly compounds with chromophores containing nitrogen atoms, so one way to check the extent to which disperse dyes have been removed is to use a colored depolymerization solution or A method of measuring the amount of nitrogen atoms remaining in BHET (residual amount) can be used.
  • the inventors of the present invention have conducted intensive studies on a method for effectively removing disperse dyes (pigments), and as a result, have discovered the following points. That is, after removing the disperse dye by washing (rinsing) the colored depolymerization liquid and reducing the amount of nitrogen atoms remaining in the colored depolymerization liquid to a predetermined amount or less, each process described below is carried out. It has been found that BHET of higher purity can be easily obtained by performing the following steps. In addition, we have found a substance suitable as a cleaning medium for use in this cleaning.
  • Such a cleaning step can be performed, for example, as follows. That is, first, the colored depolymerization liquid containing MEG that has undergone the above-described depolymerization step and solid matter removal step is cooled to as low a temperature as possible (approximately 90 to 110°C) in a temperature range where fine crystals of BHET and polyester oligomer do not precipitate. ). In this cooling process, the excess MEG in the colored depolymerization liquid may be left as is, but by evaporating and distilling off the excess MEG in the cooling process, the remaining amount of MEG in the colored depolymerization liquid can be reduced. It is preferable to keep it as small as possible.
  • cleaning mixed solution a mixed solution of the cleaning medium and the colored depolymerization liquid is added.
  • the washed solid content (depolymerized product) and the washing medium are subjected to solid-liquid separation, and the disperse dye (pigment) contained in the washing medium is removed from the solid content.
  • the amount of nitrogen atoms in the solid content (heavy liquid content) upon completion of the washing step is preferably 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less. Therefore, if the amount of nitrogen atoms in the solid content cannot be reduced to 300 ppm or less after one cleaning operation, add a new predetermined amount of cleaning medium to the obtained solid content and repeat the cleaning operation again. is preferred.
  • the present inventors have found that a medium containing a glycol ether compound (glycol monoether or glycol diether) is suitable as the cleaning medium used in the above cleaning step.
  • a medium containing a glycol ether compound glycol monoether or glycol diether
  • glycol monoether examples include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, and triethylene glycol monomethyl ether.
  • glycol diether examples include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, Examples include ethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, and dipropylene glycol diethyl ether.
  • the cleaning medium preferably contains at least one glycol ether compound having 3 to 12 carbon atoms. According to studies by the present inventors, it has been found that by using such a cleaning medium, the removal efficiency of disperse dyes (as well as impurities such as additives described below) can be improved.
  • the operation of cooling the colored depolymerization liquid to precipitate BHET or polyester oligomer as a solid content corresponds to a crystallization operation, and a similar method is described in Patent Document 1 mentioned above.
  • the colored depolymerization liquid in this step contains a wide variety of impurities that inhibit the crystallization operation, and the methods described in Patent Documents 6 and 7 mentioned above do not allow crystallization in MEG. becomes. Therefore, the crystal shape of the solid content obtained by the crystallization operation is scaly, and the crystal size is fine crystals of about 10 to 30 ⁇ m. Therefore, solid-liquid separation between the solid content and the cleaning medium tends to become difficult. Furthermore, the pigment component (dye or chromophore) is likely to be trapped between the scale-like crystals, and its removal efficiency is also likely to decrease.
  • the colored depolymerization liquid is cooled in a cleaning medium different from that of MEG alone, and BHET and polyester oligomer are precipitated as solid contents. Therefore, the solid content obtained by the crystallization operation has a needle-like crystal shape and a large crystal size of about 150 to 200 ⁇ m. Therefore, solid-liquid separation between the solid content and the cleaning medium becomes easy. In particular, the dye component is difficult to be incorporated between needle-like crystals, and its removal efficiency is also difficult to decrease.
  • the content of the glycol ether compound in the cleaning medium is preferably 75% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, and 90% by mass or more. It is particularly preferable that the amount is 95% by mass or more, and most preferably 95% by mass or more. Note that the upper limit of the content of the glycol ether compound in the cleaning medium is 100% by mass.
  • a cleaning medium containing a glycol ether compound in such an amount provides extremely good disperse dye (pigment) removal efficiency.
  • This washing step is preferably performed at a temperature of 40°C or lower, more preferably 30°C or lower, and even more preferably 20°C or lower. By performing the cleaning step at such a temperature, it is possible to suitably prevent or reduce loss of BHET due to dissolution in the cleaning medium during the cleaning operation.
  • the viscosity of MEG at 20°C is as high as 20 mPa ⁇ s (20 cp)
  • solid-liquid separation between the solid content and the cleaning medium is difficult. It can be difficult. Therefore, the content of MEG remaining in the solid content tends to be as high as about 50 to 55% by mass (in other words, the extraction rate is as low as 45 to 50% by mass). Therefore, the removal efficiency of the disperse dye is low, and multiple stages of cleaning are required, and at the same time, a large amount of MEG as a cleaning medium is required. Furthermore, the use of a large amount of MEG tends to increase the dissolution loss of BHET.
  • the viscosity at low temperatures is low (for example, the viscosity of glycol ether compounds at 20°C is as low as 1 to 5 mPa ⁇ s (1 to 5 cp)), and the solid content and cleaning medium are low.
  • the content of glycol ether compounds remaining in the solid content is as low as about 15 to 20% by mass (in other words, the extraction rate is as high as 80 to 85% by mass). Therefore, the removal efficiency of the disperse dye is good, the number of cleaning stages can be reduced, and the amount of cleaning medium used can also be reduced. Reducing the amount of glycol ether compound used also leads to a reduction in dissolution loss of BHET.
  • the cleaning medium used in the cleaning process is purified (recovered) by evaporation, distillation, etc. in order to separate the pigment components (dispersed dyes (pigments) or chromophores) contained therein, and then reused.
  • the latent heat of vaporization under atmospheric pressure is quite large, 219 kcal/kg, and a large amount of energy is required for evaporation and distillation operations.
  • the latent heat of vaporization under atmospheric pressure is extremely small at 75 to 90 kcal/kg, and the energy required for evaporation and distillation operations can be significantly reduced, resulting in great cost benefits. It is.
  • the solubility in glycol ether compounds is greater, and the effect of removing disperse dyes contained in colored polyester clothing waste is greater than that of MEG. be.
  • the time for each cleaning with the cleaning medium in the cleaning process is preferably about 5 to 120 minutes, and about 10 to 100 minutes. More preferably, the duration is about 15 to 80 minutes.
  • the number of times of cleaning with the cleaning medium in the cleaning step is preferably about 1 to 8 times, more preferably about 2 to 7 times, and even more preferably about 3 to 6 times. By performing cleaning with the cleaning medium at such a number of times, the efficiency of removing disperse dyes can be sufficiently increased.
  • the amount of cleaning medium used per cleaning step is preferably 1 to 10 parts by mass, and 1.5 to 8 parts by mass per 1 part by mass of crude BHET (solid content: heavy liquid content). It is more preferably 2 to 6 parts by weight, particularly preferably 2.5 to 4 parts by weight. By using the cleaning medium in such an amount, the efficiency of removing disperse dyes can also be sufficiently increased.
  • the depolymerized product washed in the washing step, that is, the solid content (crude BHET and polyester oligomer) from which the pigment components have been separated and removed, is melted by heating, and the depolymerized product in a molten state ( Depolymerization liquid) is obtained. Then, the depolymerization liquid is concentrated by removing low-boiling components having a boiling point lower than that of BHET to obtain crude BHET containing BHET and polyester oligomer as main components. Note that since the obtained crude BHET is a viscous liquid in a molten state, it is also referred to as a crude BHET concentrate.
  • the low boiling point component contains at least a cleaning medium, and may further contain MEG, DEG, and the like.
  • this crude BHET concentrate contains pigment components, polyamide components, polyurethane components, polyester copolymer components, ultrafine titanium oxide of less than 5 ⁇ m and inorganic additives that could not be removed in the solid matter removal step (2). Some impurities may remain.
  • the removal (evaporation/distillation) of the low-boiling components in step (4) can be performed using, for example, various evaporators.
  • various evaporators in order to prevent polymerization of BHET and polyester oligomer during the evaporation operation, it is preferable to carry out the evaporation operation by setting the temperature of the crude BHET concentrate to 130° C. or lower under reduced pressure.
  • an evaporator having a structure (model) such that the residence time of the crude BHET concentrate in the evaporator is 10 minutes or less.
  • Specific examples of the evaporator include a falling film evaporator and a thin film evaporator.
  • the main components are BHET and polyester oligomer, and if necessary, impurities such as remaining pigment components, remaining polyamide components, remaining polyurethane components, remaining polyester copolymer components, remaining titanium oxide, and remaining inorganic additives are removed.
  • BHET is recovered from the contained crude BHET concentrate to obtain high-purity BHET that is purer than the crude BHET concentrate.
  • High purity BHET can be suitably recovered by distillation, preferably distillation under vacuum (reduced pressure) (hereinafter also referred to as "vacuum distillation").
  • the components to be distilled are overwhelmingly BHET, but along with BHET, trace amounts of organic compounds (hereinafter referred to as (Also referred to as "organic compounds having a boiling point.”) may also be distilled out.
  • the amount of the organic compound having these boiling points distilled out is determined by the temperature and pressure (degree of vacuum) during the distillation operation, and the remaining molar concentration of the organic compound having the boiling point in the crude BHET concentrate. Therefore, from the viewpoint of producing BHET with higher purity, it is preferable to remove organic compounds having a boiling point as much as possible in the steps preceding step (5).
  • pigment components (disperse dyes, etc.) have the property of subliming at a temperature lower than the boiling point, so nitrogen atoms remaining in the crude BHET concentrate supplied to this step (5) If the dye component is removed until the amount of BHET becomes 300 ppm or less, it is possible to avoid the problem of a large amount of the dye component being mixed into the high purity BHET obtained in step (5).
  • this simple distillation can be performed according to the conditions such as temperature, pressure, and residence time of the thin film evaporator described in Patent Document 1. .
  • the production amount (recovery amount) tends to decrease due to the decrease in evaporation amount.
  • distillation rectification
  • Distillation accompanied by reflux can easily satisfy the required quality of high-purity BHET by selecting an appropriate reflux ratio.
  • the quality of the high-purity BHET obtained in this step (5) is such that the amount of ester components other than BHET (hereinafter also referred to as "other ester components") remaining in the high-purity BHET is 2.5% by mass. or less (preferably 2% by mass or less), and the amount of nitrogen atoms remaining in the high-purity BHET is preferably 20 ppm or less.
  • other ester components include mono-(2-hydroxyethyl) terephthalate (MHET), diethylene glycol ester, polyester dimer, polyester oligomer, and the like. Note that these components are incorporated into the obtained recycled polyethylene terephthalate when producing the recycled polyethylene terephthalate.
  • the amount (mass %) of other ester components remaining in high-purity BHET shall employ the value (area %) calculated
  • LC-2010AHT high-performance liquid chromatography device
  • the color b value (yellowness) of recycled polyethylene terephthalate produced by polycondensation can be 8 or less, and virgin polyethylene terephthalate It becomes possible to produce recycled polyethylene terephthalate with an average color b value.
  • BHET is recovered from crude BHET (crude BHET concentrate) by distillation to obtain high purity BHET.
  • Organic compounds with a boiling point that have not been completely evaporated and solid substances such as titanium oxide and inorganic additives that do not have a boiling point are discharged from the system as residue from the evaporator. It is preferable that the discharged residue is effectively utilized by separate treatment. That is, it can be said that this step (5) also plays a role as a final separation step for solids that do not have a boiling point.
  • a solvent that has a high ability (solubility) to dissolve the purification target removal materials such as dyes, their decomposition products, chromophores, other ester components remaining in BHET, and other organic compounds with a boiling point.
  • crystallization purification operation By cooling a solution in which high-purity BHET is dissolved in a crystallization solvent, crystals of BHET are precipitated, and the crystallization solvent component containing the crystals and the product to be purified is removed. It is preferable to carry out an operation of solid-liquid separation (hereinafter also referred to as “crystallization purification operation").
  • the BHET manufacturing method of the present invention preferably includes a crystallization purification step after the recovery step.
  • high-purity BHET with increased purity will also be referred to as “crystallization-purified BHET.”
  • the above-mentioned purification target removal material can be removed more efficiently by adjusting the mixing ratio of high purity BHET and crystallization solvent depending on the type of crystallization solvent.
  • the results of a solubility test for the product removed from the purification target conducted by the present inventors revealed that a solvent containing water and/or a glycol compound is suitable as the crystallization solvent.
  • the glycol compound include glycol monoether, glycol diether, and glycol, and one or more of these can be used in combination.
  • glycol monoether examples include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, and triethylene glycol monomethyl ether.
  • glycol diether examples include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, and triethylene glycol.
  • glycol examples include ethylene glycol (monoethylene glycol), diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol. , neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, cyclohexanediol and the like.
  • each of the glycol monoether and the glycol diether preferably has 3 to 12 carbon atoms, more preferably 3 to 10 carbon atoms, and even more preferably 3 to 8 carbon atoms.
  • the number of carbon atoms in the glycol is preferably 2 to 6.
  • the crystallization solvent is at least one glycol selected from the group consisting of water, glycol monoethers or glycol diethers having 3 to 12 carbon atoms, and glycols having 2 to 6 carbon atoms. It is preferable to contain a type compound.
  • a solvent containing water and/or a glycol compound as a crystallization solvent, it is possible to further enhance the removal effect of the purification object removed remaining in high purity BHET.
  • crystallization solvents containing glycol monoether are more preferable from the viewpoint of high ability to remove substances to be purified.
  • the content of water in the crystallization solvent is preferably 100% by mass.
  • the content of the glycol compound in the crystallization solvent is preferably 85% by mass or more, more preferably 90% by mass or more, and 95% by mass or more. It is even more preferable.
  • the upper limit of the content of the glycol compound in the crystallization solvent is 100% by mass.
  • a crystallization solvent containing a glycol compound in such an amount exhibits an extremely good ability to remove a product to be purified. Moreover, such a crystallization solvent is also preferable because it can also dissolve a dye component.
  • the cooling temperature of the solution a lower cooling temperature is preferable from the viewpoint of reducing the amount of high-purity BHET dissolved in the crystallization solvent and increasing the yield of high-purity BHET.
  • the cooling temperature is preferably about 20 to 25°C.
  • slow cooling including natural cooling is preferred from the viewpoint of obtaining BHET crystals of sufficient size.
  • the quality of the crystallized and purified BHET obtained in this step (6) is such that the amount of other ester components remaining in the crystallized and purified BHET is 1% by mass or less (preferably 0.5% by mass or less), It is preferable that the amount of nitrogen atoms remaining in the analytically purified BHET is 10 ppm or less.
  • the number of times the crystallization purification operation is performed is not particularly limited, but if the quality of the crystallized purified BHET obtained in the first operation does not reach the above quality, it is preferable to perform the crystallization purification operation again. According to the present inventors, it has been confirmed that if the crystallization and purification operation is performed at least three times, the quality of the crystallized and purified BHET reaches the above quality regardless of the degree of coloring.
  • the crystallization solvent containing the purification target removed product separated into solid and liquid in the crystallization purification operation is purified by an evaporation operation, distillation operation, etc., and then reused.
  • the product to be purified is preferably recovered as an evaporation residue or distillation residue and treated as industrial waste.
  • the method for crystallizing and purifying high purity BHET of this embodiment is carried out.
  • the method for producing recycled PET of the present invention includes a step of obtaining BHET by the above-described method for producing BHET, and a step of obtaining recycled PET by polycondensing BHET. Therefore, the recycled PET obtained is a polycondensate of BHET.
  • recycled PET When producing recycled PET by polycondensation, recycled PET can be easily produced by mixing BHET and terephthalic acid in an arbitrary ratio.
  • the recycled PET contains a structure derived from BHET in an amount of 50% by mass or more, preferably 65% by mass or more, and 80% by mass or more. It is even more preferable to contain it.
  • the present invention is not limited thereto.
  • the method for producing BHET and the method for producing recycled PET of the present invention may each be replaced with an arbitrary step that exhibits a similar effect, or may be added with an arbitrary desired step.
  • the process of the present invention may be performed batchwise (batch-type), continuously, or a combination thereof.
  • the colored polyester waste applicable to the present invention is also preferably colored PET bottle waste or colored industrial film waste. In the case of colored PET bottle waste or colored industrial film waste, for example, they are crushed and then subjected to a depolymerization step.
  • the processing conditions can be set similarly to the case of colored polyester clothing waste.
  • the polyester waste may be colorless (uncolored).
  • Such colorless polyester waste includes industrial films, packaging materials, etc. containing numerous additives.
  • the additive include inorganic additives such as titanium oxide, silica (silicon oxide), magnesium, and vapor-deposited aluminum. According to studies conducted by the present inventors, it has been found that these additives can also be sufficiently transferred to the cleaning medium and removed in the above-mentioned cleaning step. As mentioned above, one major reason for this is that the crystals of the solids generated during the cleaning process become needle-shaped, making it difficult for fine particles of the additive to be trapped between the crystals. Conceivable. Further, as mentioned above, one factor is considered to be that the viscosity of the cleaning medium at low temperatures is low, which facilitates solid-liquid separation between the inorganic additive and the cleaning medium.
  • the inorganic additive acts as an abrasive that accelerates mechanical wear of the part where the thin film is generated, and has an adverse effect. Therefore, it is preferable to reduce the residual amount of the inorganic additive as much as possible in the steps preceding step (4), from the viewpoint of extending the life of the thin film evaporator. Additionally, these inorganic additives settle in piping and tanks, causing line blockages. Therefore, it is preferable from the viewpoint of stable operation to reduce the residual amount of the inorganic additive as much as possible in the steps preceding step (4).
  • Example A1 Production of high purity BHET, crystallized purified BHET and recycled PET from colored polyester clothing waste (Example A1)
  • Example A1 (1) Depolymerization process First, uncut PET clothing waste colored with black disperse dye, blue disperse dye, red disperse dye, and yellow disperse dye (hereinafter also referred to as "colored clothing waste") is processed. A total of 400 g (total amount of nitrogen atoms contained in colored clothing waste: 3,763 ppm) was prepared for four clothes.
  • the colored depolymerization liquid was filtered while hot to remove coarse solids using a wire mesh strainer with an opening of 30 meshes, to obtain a colored depolymerization liquid from which coarse solids had been removed.
  • coarse solids such as foreign materials other than PET (cotton, olefins), zippers, buttons, metals, glass, sand, etc. were mainly removed.
  • the colored depolymerization liquid was filtered while hot using a 10 ⁇ m stainless steel long fiber filter (Naslon filter) to remove fine solids such as titanium oxide and inorganic additives that are insoluble in polyester of 10 ⁇ m or more.
  • 1,058 g of the remaining colored depolymerization liquid (containing 529 g of BHET) at 105°C was added with 1 diethylene glycol monohexyl ether (carbon atom number: 10) heated to 80°C as a washing medium, 587 g (3 times the mass of crude BHET) was added, and the solution was allowed to cool naturally until the internal temperature reached 20° C. to precipitate BHET crystals. Thereafter, the precipitated solids (crystals) and the cleaning medium containing diethylene glycol monohexyl ether and residual MEG are separated into solid and liquid using a large tabletop centrifuge, and dissolved in diethylene glycol monohexyl ether and residual MEG. The disperse dye was removed. The conditions of the centrifuge were a centrifugal force of 4,000 G and a centrifugation time of 30 minutes.
  • the amount of BHET dissolved in the light liquid fraction (diethylene glycol monohexyl ether and residual MEG) after centrifugation is 101 g, and the amount of BHET dissolved in the light liquid fraction (diethylene glycol monohexyl ether and residual MEG) is 101 g.
  • the total amount) was 535 g, the liquid content (diethylene glycol monohexyl ether and residual MEG) remaining in the heavy liquid fraction was 20% by mass, and the amount of nitrogen atoms remaining in the heavy liquid fraction was 760 ppm.
  • the amount of BHET dissolved in the light liquid fraction after centrifugation is 71 g, and the amount of BHET dissolved in the heavy liquid fraction is 420 g. ) was 15% by mass, and the amount of nitrogen atoms remaining in the heavy liquid fraction was 199 ppm.
  • the amount of BHET dissolved in the light liquid fraction after centrifugation is 47 g, and the amount of BHET dissolved in the heavy liquid fraction is 365 g. ) was 15% by mass, and the amount of nitrogen atoms remaining in the heavy liquid fraction was 64 ppm.
  • the obtained high-purity BHET was subjected to melt polycondensation according to a conventional method to obtain PET (regenerated PET).
  • Example A2 High purity BHET and recycled PET were obtained in the same manner as in Example A1, except that triethylene glycol monobutyl ether (number of carbon atoms: 10) was used as the cleaning medium instead of diethylene glycol monohexyl ether.
  • Example A3 High purity BHET and recycled PET were obtained in the same manner as in Example A1, except that tripropylene glycol monomethyl ether (carbon atoms: 10) was used as the cleaning medium instead of diethylene glycol monohexyl ether.
  • Example A4 High purity BHET and recycled PET were obtained in the same manner as in Example A1, except that ethylene glycol monohexyl ether (number of carbon atoms: 8) was used as the cleaning medium instead of diethylene glycol monohexyl ether.
  • Example A5 High purity BHET and recycled PET were obtained in the same manner as in Example A1, except that ethylene glycol monobutyl ether (carbon atoms: 6) was used as the cleaning medium instead of diethylene glycol monohexyl ether.
  • Example A6 High purity BHET and recycled PET were obtained in the same manner as in Example A1, except that triethylene glycol monohexyl ether (number of carbon atoms: 12) was used as the cleaning medium instead of diethylene glycol monohexyl ether.
  • Example A7 High purity BHET and recycled PET were obtained in the same manner as in Example A1, except that ethylene glycol dimethyl ether (carbon number: 4) was used as the cleaning medium instead of diethylene glycol monohexyl ether.
  • Example A8 High purity BHET and recycled PET were obtained in the same manner as in Example A1, except that ethylene glycol monomethyl ether (carbon number: 3) was used as the cleaning medium instead of diethylene glycol monohexyl ether.
  • Example A9 Except that a mixed solution of 50 parts by mass of ethylene glycol dimethyl ether (number of carbon atoms: 4) and 50 parts by mass of MEG (number of carbon atoms: 2) was used as the cleaning medium instead of diethylene glycol monohexyl ether. High purity BHET and recycled PET were obtained in the same manner as in Example A1.
  • Example A10 The same procedure as in Example A1 was carried out, except that a mixture of 70 parts by mass of ethylene glycol dimethyl ether (carbon atoms: 4) and 30 parts by mass of MEG was used as the cleaning medium instead of diethylene glycol monohexyl ether. High purity BHET and recycled PET were obtained.
  • Example A11 High purity BHET and recycled PET were obtained in the same manner as in Example A1, except that diethylene glycol (number of carbon atoms: 4) was used as the cleaning medium instead of diethylene glycol monohexyl ether.
  • Example A12 High purity BHET and recycled PET were obtained in the same manner as in Example A1, except that triethylene glycol (number of carbon atoms: 6) was used as the cleaning medium instead of diethylene glycol monohexyl ether.
  • Example A1 High purity BHET and recycled PET were obtained in the same manner as in Example A1, except that MEG (number of carbon atoms: 2) was used as the cleaning medium instead of diethylene glycol monohexyl ether. Note that solid-liquid separation in the washing step was difficult compared to each of the Examples.
  • MEG number of carbon atoms: 2
  • Example B1 1 part by mass of high purity BHET obtained in Example A1 and 4 parts by mass of diethylene glycol monohexyl ether (number of carbon atoms: 10) as a crystallization solvent were charged into a 5 L flask, and the internal temperature of the liquid was 80°C. heated until. Thereby, high purity BHET was dissolved in diethylene glycol monohexyl ether to obtain a solution. Thereafter, this solution was allowed to cool naturally to lower the temperature to 20° C. to precipitate BHET crystals.
  • crystallization-purified BHET was obtained by performing the crystallization-purification operation once.
  • the amount of other ester components remaining in the crystallized and purified BHET was 0.4% by mass, and the amount of nitrogen atoms remaining in the crystallized and purified BHET was 5.6 ppm.
  • the obtained crystallized and purified BHET was subjected to melt polycondensation according to a conventional method to obtain PET (regenerated PET).
  • Example B2 Crystallized purified BHET and recycled PET were obtained in the same manner as in Example B1, except that triethylene glycol monobutyl ether (carbon atoms: 10) was used as the crystallization solvent instead of diethylene glycol monohexyl ether.
  • Example B3 Crystallized purified BHET and recycled PET were obtained in the same manner as in Example B1, except that ethylene glycol monohexyl ether (number of carbon atoms: 8) was used as the crystallization solvent instead of diethylene glycol monohexyl ether.
  • Example B4 Crystallized purified BHET and recycled PET were obtained in the same manner as in Example B1, except that ethylene glycol monobutyl ether (carbon atoms: 6) was used as the crystallization solvent instead of diethylene glycol monohexyl ether.
  • Example B5 Crystallized purified BHET and recycled PET were obtained in the same manner as in Example B1, except that ethylene glycol dimethyl ether (carbon atoms: 4) was used as the crystallization solvent instead of diethylene glycol monohexyl ether.
  • Example B6 Crystallized purified BHET and recycled PET were obtained in the same manner as in Example B1, except that ethylene glycol monomethyl ether (number of carbon atoms: 3) was used as the crystallization solvent instead of diethylene glycol monohexyl ether.
  • Example B7 Crystallized purified BHET and recycled PET were obtained in the same manner as in Example B1, except that MEG (number of carbon atoms: 2) was used as the crystallization solvent instead of diethylene glycol monohexyl ether.
  • Example B8 Crystallized purified BHET and recycled PET were obtained in the same manner as in Example B1, except that diethylene glycol (number of carbon atoms: 4) was used as the crystallization solvent instead of diethylene glycol monohexyl ether.
  • Example B9 Crystallized purified BHET and recycled PET were obtained in the same manner as in Example B1, except that water was used as the crystallization solvent instead of diethylene glycol monohexyl ether.
  • Example C1 Depolymerization step 400 g of cut colorless (uncolored) industrial PET film waste (hereinafter also referred to as "colorless film waste”) was prepared.
  • the inorganic additives contained in the colorless flume waste are titanium oxide 3.2g (0.8% by mass), silica 140g (35.0% by mass), magnesium 1,850ppm, and the total amount of nitrogen atoms is 1ppm. there were.
  • diethylene glycol monohexyl ether heated to 80°C was added to 822.6 g of the remaining colorless depolymerization liquid at 105°C (containing 339.7 g of BHET and 143.2 g of inorganic additives) as a washing medium.
  • Number of carbon atoms: 10 1,359 g (4 times the mass of crude BHET) was added, and the solution was allowed to cool naturally until the internal temperature reached 20° C. to precipitate BHET crystals.
  • the precipitated solid content (crystals) and inorganic additives were separated from the cleaning medium containing diethylene glycol monohexyl ether and residual MEG by solid-liquid separation using a large tabletop centrifuge.
  • the conditions of the centrifuge were a centrifugal force of 4,000 G and a centrifugation time of 30 minutes.
  • the amount of BHET dissolved in the light liquid fraction (diethylene glycol monohexyl ether and residual MEG) after centrifugation was 81 g, and the inorganic additive components contained in the light liquid fraction were 1.4 g of titanium oxide,
  • the amount of silica was 63g.
  • the amount of heavy liquid (total amount of solid content and inorganic additives, diethylene glycol monohexyl ether, and residual MEG) is 655 g (including 258.7 g of BHET, 1.8 g of titanium oxide, and 77 g of silica).
  • the liquid content (diethylene glycol monohexyl ether and residual MEG) remaining therein was 48% by mass.
  • the amount of BHET dissolved in the light liquid fraction after centrifugation was 48 g, and the inorganic additive components contained in the light liquid fraction were 0.9 g of titanium oxide and 40 g of silica.
  • the amount of heavy liquid (total amount of solid content and inorganic additives, diethylene glycol monohexyl ether, and residual MEG) is 468 g (including 210.7 g of BHET, 0.9 g of titanium oxide, and 37 g of silica).
  • the liquid content (diethylene glycol monohexyl ether and residual MEG) remaining therein was 47% by mass.
  • titanium oxide was reduced by 72% and silica was reduced by 71% through two washing operations.
  • the obtained high-purity BHET was subjected to melt polycondensation according to a conventional method to obtain PET (regenerated PET).
  • Example C2 High purity BHET and recycled PET were obtained in the same manner as in Example C1, except that ethylene glycol monomethyl ether (carbon number: 3) was used as the cleaning medium instead of diethylene glycol monohexyl ether.
  • Example C1 High purity BHET and recycled PET were obtained in the same manner as in Example C1, except that MEG (number of carbon atoms: 2) was used as the cleaning medium instead of diethylene glycol monohexyl ether. Note that solid-liquid separation in the washing step was difficult compared to Examples C1 and C2.
  • Measurement 2-1 Measurement of the amount of nitrogen atoms The amount of nitrogen atoms remaining in colored clothing waste, solid content after washing, high purity BHET, and crystallized purified BHET was measured using a trace total nitrogen analyzer (manufactured by Mitsubishi Chemical Analytech Co., Ltd., TN-2100H").

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Abstract

La présente invention vise à fournir : un procédé de production de BHET, par lequel le BHET peut être produit d'une manière simple à partir de déchets de PE; et un procédé de production de PET recyclé à l'aide dudit BHET en tant que matière première. Un mode de réalisation de la présente invention concerne par conséquent un procédé de production de BHET. Ce procédé de production comprend : une étape de dépolymérisation pour mélanger des déchets de PE, du MEG et un catalyseur de dépolymérisation, et dépolymériser les déchets de PE pour obtenir un produit de dépolymérisation contenant du BHET brut; une étape de lavage pour refroidir le produit de dépolymérisation, l'ajout d'un milieu de lavage qui est différent du MEG, et le transfert d'au moins certaines impuretés autres que le PE contenu dans le produit de dépolymérisation au milieu de lavage de façon à éliminer ces impuretés du produit de dépolymérisation; une étape de concentration pour éliminer les composants à bas point d'ébullition contenant au moins le milieu de lavage du produit de dépolymérisation lavé de façon à concentrer le BHET brut; et une étape de récupération pour récupérer le BHET à partir du BHET brut concentré au moyen d'une distillation de façon à obtenir un BHET de pureté élevée ayant une pureté supérieure à celle du BHET brut.
PCT/JP2023/012739 2022-04-20 2023-03-29 Procédé de production de bis-(2-hydroxyethyl)téréphtalate et procédé de production de polyéthylène téréphtalate recyclé WO2023203980A1 (fr)

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JP2021191872A (ja) * 2015-12-18 2021-12-16 コンチネンタル ストラクチュラル プラスティックス， インコーポレイテッド 炭素繊維系材料の再利用
JP2020050689A (ja) * 2018-09-21 2020-04-02 日立化成株式会社 処理液及び熱硬化性樹脂硬化物の処理方法
WO2022004359A1 (fr) * 2020-06-29 2022-01-06 株式会社シンテック Procédé de production de bis-(2-hydroxyethyl)téréphtalate et procédé de production de polyéthylène téréphthalate recyclé

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