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KR-20260063844-A - PREPRATION METHOD OF MONOMER FOR SYNTHESISING RECYCLED PLASTIC, AND MONOMER FOR SYNTHESISING RECYCLED PLASTIC, RECYCLED PLASTIC, MOLDED PRODUCT USING THE SAME

KR20260063844AKR 20260063844 AKR20260063844 AKR 20260063844AKR-20260063844-A

Abstract

The present invention relates to a method for producing a monomer for synthesizing recycled plastic, comprising the steps of: recovering an aromatic diol compound obtained by a depolymerization reaction of a polycarbonate-based resin; melting the aromatic diol compound; crystallizing the melted aromatic diol compound; and obtaining the crystallized aromatic diol compound; and to a monomer for synthesizing recycled plastic using the same, a recycled plastic, and a molded article.

Inventors

  • 이진혁
  • 전병규
  • 홍무호
  • 박태승
  • 김민주

Assignees

  • 주식회사 엘지화학

Dates

Publication Date
20260507
Application Date
20241031

Claims (18)

  1. A step of recovering an aromatic diol compound obtained from the depolymerization reaction of a polycarbonate-based resin; A step of melting the above aromatic diol compound; A step of crystallizing the above-mentioned molten aromatic diol compound; and A step of obtaining the crystallized aromatic diol compound; comprising Method for manufacturing monomers for synthesizing recycled plastics.
  2. In paragraph 1, The step of crystallizing the above-mentioned molten aromatic diol compound is, Cooling the above-mentioned molten aromatic diol compound to a temperature of less than 158°C, Method for manufacturing monomers for synthesizing recycled plastics.
  3. In paragraph 1, Prior to the step of crystallizing the above-mentioned molten aromatic diol compound, The method further comprises the step of melting and purifying the above-mentioned molten aromatic diol compound at a temperature of 130 ℃ to 180 ℃ for 2 to 6 hours. Method for manufacturing monomers for synthesizing recycled plastics.
  4. In paragraph 3, The above melting and purifying step is, A step of cooling the above-mentioned molten aromatic diol compound to form aromatic diol compound crystals; A step of recovering purified aromatic diol compound crystals obtained by partially melting the above aromatic diol compound crystals; and A step comprising melting the crystals of the purified aromatic diol compound; Method for manufacturing monomers for synthesizing recycled plastics.
  5. In paragraph 3, The above melting and purifying step is, A method for manufacturing a monomer for synthesizing recycled plastic, which is repeated 2 to 5 times.
  6. In paragraph 3, The above melting and purifying step is, A method for producing a monomer for synthesizing recycled plastics, wherein purification is carried out by one-stage fractional melt crystallization or multi-stage fractional melt crystallization in a thin film fluid flow type dynamic crystallizer.
  7. In paragraph 1, The crystallized aromatic diol compound having a purity of 99.94% or higher, Method for manufacturing monomers for synthesizing recycled plastics.
  8. In paragraph 1, The yield of the crystallized aromatic diol compound above is 88% or higher, Method for manufacturing monomers for synthesizing recycled plastics.
  9. In paragraph 1, The step of recovering the aromatic diol compound obtained from the depolymerization reaction of the above-mentioned polycarbonate resin is: A step of depolymerizing a polycarbonate-based resin; A step of neutralizing the above depolymerization product by adding acid; A step of removing the water layer from the water layer and organic solvent layer formed in the above neutralization step; and A step of recovering an aromatic diol compound by distilling the above organic solvent layer; comprising Method for manufacturing monomers for synthesizing recycled plastics.
  10. In Paragraph 9, The step of recovering an aromatic diol compound by distilling the above organic solvent layer is, A method for producing a monomer for synthesizing recycled plastic, comprising a multi-stage vacuum distillation step of vacuum distilling the organic solvent layer in three or more stages.
  11. In Paragraph 10, The above multi-stage vacuum distillation step is, A first vacuum distillation step of vacuum distilling the above organic solvent layer at a pressure of 0.12 MPa to 0.45 MPa and a temperature of 48 ℃ to 160 ℃ from a pressure of 0.45 MPa or more and a temperature of 160 ℃ or more; A second vacuum distillation step in which the residual solution of the first vacuum distillation step is pressurized to a pressure of 0.45 MPa or more and a temperature of 125 ℃ or more, and then vacuum distilled at a pressure of 0.009 MPa to 0.45 MPa and a temperature of 42 ℃ to 160 ℃; and A third vacuum distillation step comprising: reducing the residual solution of the second vacuum distillation step to a pressure of 0.0005 MPa or more and a temperature of 155 ℃ or more, and then vacuum distilling it at a pressure of 0.0003 MPa to 0.0005 MPa and a temperature of 42 ℃ to 87 ℃; Method for manufacturing monomers for synthesizing recycled plastics.
  12. In paragraph 1, The depolymerization reaction of the above polycarbonate-based resin is, Characterized by proceeding under a solvent containing ethanol, Method for manufacturing monomers for synthesizing recycled plastics.
  13. In Paragraph 12, The content of the above ethanol is 10 to 15 moles per 1 mole of polycarbonate resin, Method for manufacturing monomers for synthesizing recycled plastics.
  14. In paragraph 1, The depolymerization reaction of the above polycarbonate-based resin is, Characterized by proceeding with a reaction of a base at a content of 0.5 moles or less per 1 mole of polycarbonate resin, Method for manufacturing monomers for synthesizing recycled plastics.
  15. In paragraph 1, Prior to the step of recovering the aromatic diol compound obtained from the depolymerization reaction of the above polycarbonate-based resin, A method further comprising a pretreatment step of passing a polycarbonate-based resin through a filter having a pore diameter of 0.3 μm or less, Method for manufacturing monomers for synthesizing recycled plastics.
  16. A monomer for synthesizing recycled plastic comprising an aromatic diol compound obtained in the method for manufacturing a monomer for synthesizing recycled plastic according to claim 1.
  17. Recycled plastic comprising the reaction product of the monomer and comonomer for the synthesis of recycled plastic of paragraph 16.
  18. A molded article containing recycled plastic of Clause 17.

Description

Preparation method of monomer for synthesizing recycled plastic, and monomer for synthesizing recycled plastic, recycled plastic, and molded product using the same The present invention relates to a method for producing a monomer for synthesizing recycled plastics capable of obtaining high-purity, high-yield aromatic diol compounds through recycling by chemical decomposition of polycarbonate-based resins, and to a monomer for synthesizing recycled plastics using the same, recycled plastics, and molded articles. Polycarbonate is a thermoplastic polymer and a plastic with excellent characteristics, such as excellent transparency, flexibility, and relatively low manufacturing costs. Although polycarbonate is widely used for various purposes, concerns regarding the environment and health during waste disposal have been continuously raised. Currently, physical recycling methods are being used, but as this leads to quality degradation, research on the chemical recycling of polycarbonate is underway. Chemical decomposition of polycarbonate refers to obtaining an aromatic diol compound (e.g., bisphenol A (BPA)) which is a monomer through the decomposition of polycarbonate, and then utilizing it again in polymerization to obtain high-purity polycarbonate. Representative chemical decomposition methods include thermal decomposition, hydrolysis, and alcohol decomposition. Among these, the most common method is alcohol decomposition using base catalysts; however, methanol decomposition has the problem of using methanol, which is harmful to the human body, while ethanol decomposition requires high temperature and pressure conditions and suffers from low yields. In addition, although alcohol decomposition methods using organic catalysts are known, they currently have disadvantages in terms of economics. The invention is described in more detail in the following examples. However, the following examples are merely illustrative of the invention, and the scope of the invention is not limited by the following examples. <Examples, Comparative Examples, and Reference Examples: Preparation of Recycled Bisphenol A Monomers> Example 1 (1. Pretreatment step) A solution in which waste polycarbonate (PC) was dissolved in methylene chloride (MC) (containing 18.73 wt% waste polycarbonate (PC), 78.27 wt% methylene chloride (MC), and 3 wt% other impurities) was recovered as a filter filtrate with a pore diameter of 3.0 μm or less. At this time, the filter filtrate contained 18.76 wt% waste polycarbonate (PC), 78.30 wt% methylene chloride (MC), and 2.94 wt% other impurities. (2. Decomposition Step) The above filtrate was introduced into a 3L high-pressure reactor, ethanol (EtOH), sodium hydroxide (NaOH), and sodium hydrosulfite were introduced, and the atmosphere in the system was replaced with nitrogen to inert the PC depolymerization reaction by stirring at 60°C for 6 hours. At this time, the ingredients were introduced to satisfy a molar ratio of 17 mol of methylene chloride (MC), 11 mol of ethanol (EtOH), and 0.25 mol of sodium hydroxide (NaOH) per 1 mol of waste polycarbonate (PC), and sodium hydrosulfite was introduced at 1% by weight relative to the total reaction solution. (3. Neutralization) The product of the above depolymerization reaction was cooled to 30°C or lower, and then 10% hydrochloric acid (HCl) and water were added to neutralize it to a pH of 7. At this time, the neutralized solution contained 10.33 wt% bisphenol A, 49.53 wt% methylene chloride (MC), 19.30 wt% ethanol (EtOH), 13.03 wt% water, 5.48 wt% diethyl carbonate (DEC), and 2.33 wt% other impurities. (4. Layer Separation) After the water layer and the methylene chloride (MC) layer were formed, the methylene chloride (MC) layer located at the bottom was recovered using a drain device at the bottom of the reactor, and the water layer located at the top was disposed of through a separate solvent recovery process. At this time, the methylene chloride (MC) layer contained 11.99 wt% bisphenol A, 56.76 wt% methylene chloride (MC), 18.70 wt% ethanol (EtOH), 4.61 wt% water, 6.26 wt% diethyl carbonate (DEC), 0.12 wt% phenol, 0.37 wt% 4-tert-butylphenol (PTBP), 0.16 wt% p-isopropenylphenol (IPP), and 1.03 wt% other impurities. (5-1. Distillation - First vacuum distillation) Afterwards, the recovered methylene chloride (MC) layer was introduced into the first distillation section of the distillation column at a pressure of 0.45 MPa and a temperature of 160 ℃, and the pressure was reduced to 0.12 MPa and the temperature was reduced to 48~160 ℃ to distill and remove the methylene chloride (MC), ethanol (EtOH), and water from the methylene chloride (MC) layer, and the residual solution was transferred to the second distillation section. (5-2. Distillation - Second vacuum distillation) Afterwards, in the second distillation section of the distillation column, the residual solution was pressurized to a pressure of 0.45 MPa and a temperature of 125 ℃, then reduced to a pressure o