MONOMER COMPOSITION FOR SYNTHESIZING RECYCLED PLASTIC, PREPARATION METHOD THEREOF, RECYCLED PLASTIC, AND MOLDED PRODUCT USING THE SAME

Abstract

The present disclosure relates to a monomer composition for synthesizing recycled plastic which contains a high-purity aromatic diol compound recovered through recycling by chemical decomposition of a polycarbonate-based resin, a method for preparing the same, and a recycled plastic, and molded product using the same.

Claims

1. A monomer composition for synthesizing recycled plastic, comprising: an aromatic diol compound; and diethyl carbonate as a by-product, wherein the monomer composition is a recovered product from a polycarbonate-based resin, and wherein a recovery rate of diethyl carbonate according to the following mathematical formula is 82% or more:
Recovery rate of diethyl carbonate={(Number of moles of diethyl carbonate recovered)/(Number of moles of diethyl carbonate in entire by-product mixture)}×100.  [Mathematical Formula]

2. The monomer composition according to claim 1, wherein the monomer composition has a color coordinate L* of 96.1 or more.

3. The monomer composition according to claim 1, wherein the monomer composition has a color coordinate a* of 0.4 or less.

4. The monomer composition according to claim 1, wherein the monomer composition has a color coordinate b* of 2.5 or less.

5. The monomer composition according to claim 1, wherein the monomer composition has an aromatic diol compound purity of 96% or more.

6. The monomer composition according to claim 1, wherein the aromatic diol compound is one or more selected from the group consisting of bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfoxide, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)ketone, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3-chlorophenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, and 1,1-bis(4-hydroxyphenyl)-1-phenylethane.

7. A method for preparing a monomer composition for synthesizing recycled plastic, the method comprising the steps of: depolymerizing a polycarbonate-based resin; adding a first adsorbent to a depolymerization reaction product to perform an adsorption purification and then removing the first adsorbent; separating a carbonate precursor from the depolymerization reaction product; and purifying the depolymerization reaction product from which the carbonate precursor has been separated, wherein the purifying step comprises: a step of washing the depolymerization reaction product from which the carbonate precursor has been separated; and a step of adding a second adsorbent to the depolymerization reaction product from which the carbonate precursor has been separated to perform an adsorption purification and then removing the second adsorbent.

8. The method for preparing a monomer composition according to claim 7, wherein the first adsorbent and the second adsorbent are the same or different from each other, and each independently include at least one activated carbon selected from the group consisting of a plant-based activated carbon, a coal-based activated carbon, a petroleum-based activated carbon, and a waste activated carbon.

9. The method for preparing a monomer composition according to claim 7, wherein an amount of the first adsorbent added is 1 part by weight to 1000 parts by weight based on 100 parts by weight of the second adsorbent added.

10. The method for preparing a monomer composition according to claim 7, wherein the washing step comprises: a step of washing the depolymerization reaction product from which the carbonate precursor has been separated with a first solvent at a temperature of 10° C. or more and 30° C. or less; and a step of washing the depolymerization reaction product from which the carbonate precursor has been separated with a second solvent at a temperature of 40° C. or more and 80° C. or less.

11. The method for preparing a monomer composition according to claim 10, wherein the first solvent is an organic solvent.

12. The method for preparing a monomer composition according to claim 10, wherein the second solvent is water.

13. The method for preparing a monomer composition according to claim 10, wherein a difference value between the temperature of the step of washing with the second solvent at a temperature of 40° C. or more and 80° C. or less, and the temperature of the step of washing with the first solvent at a temperature of 10° C. or more and 30° C. or less is 20° C. or more and 50° C. or less.

14. The method for preparing a monomer composition according to claim 7, wherein the depolymerization reaction of the polycarbonate-based resin is carried out in the presence of a solvent containing ethanol.

15. The method for preparing a monomer composition according to claim 7, wherein the depolymerization reaction of the polycarbonate-based resin is carried out by reacting a base in an amount of 0.5 moles or less relative to 1 mole of the polycarbonate-based resin.

16. The method for preparing a monomer composition according to claim 7, wherein the separating step comprises: a reduced pressure distillation step of the depolymerization reaction product.

17. The method for preparing a monomer composition according to claim 7, wherein after the step of adding a second adsorbent to the depolymerization reaction product from which the carbonate precursor has been separated to perform an adsorption purification and then removing the second adsorbent, the purifying step further comprises a recrystallization step of the depolymerization reaction product from which the carbonate precursor has been separated.

18. The method for preparing a monomer composition according to claim 7, further comprising: a neutralization reaction step of the depolymerization reaction product with an acid, before the step of adding a first adsorbent to the depolymerization reaction product to perform an adsorption purification and then removing the first adsorbent.

19. A recycled plastic, comprising: a reaction product of the monomer composition of claim 1 and a comonomer.

20. A molded product, comprising: the recycled plastic of claim 19.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0139] Hereinafter, the present disclosure will be explained in detail with reference to the following examples. However, these examples are for illustrative purposes only, and the scope of the present disclosure is not limited thereto.

EXAMPLE

Example 1

[0140] (1. Decomposition step) 1 mol of Pretreated waste polycarbonate (PC) was dissolved in 17 mol of methylene chloride (MC), and then added together with 11 mol of ethanol (EtOH) and 0.25 mol of sodium hydroxide (NaOH) to a 3L high-pressure reactor, and the mixture was stirred at 60° C. for 6 hours to proceed a PC depolymerization reaction. [0141] (2. Neutralization stage) The depolymerization reaction product was cooled to 30° C. or less, and then the product containing bisphenol A was neutralized using 0.25 mol of 10% hydrochloric acid (HCl) at 20-30° C. [0142] (3-1. Purification-Adsorption step) After that, the product whose pH has been lowered to less than 2 was passed through an adsorption tower in which lignite activated carbon was added as a first adsorbent in a ratio of 50 wt. % relative to waste polycarbonate, and purified through adsorption. [0143] (3-2. Purification-Distillation step) After that, the by-product diethyl carbonate (DEC) was separated and recovered through a low-temperature distillation reducing pressure from 250 mbar and 20-30° C. to 30 mbar and 30° C. [0144] (3-3. Purification-Washing step) After that, the residue from which diethyl carbonate (DEC) was removed was primarily washed using methylene chloride (MC) (1 time the mass of PC used) at 20 to 30° C., and vacuum filtered. The filtrate was secondarily washed using water (three times the mass of PC used) at a temperature of 50° C. [0145] (4-1. Additional purification step—Redissolution step) 16.6 mol of Ethanol was added to the washed material and redissolved. [0146] (4-2. Additional purification step—Adsorption step) After that, lignite activated carbon as the second adsorbent was put into an adsorption tower at a ratio of 50 wt. % relative to waste polycarbonate, passed through it, and purified through adsorption. [0147] (4-3. Additional purification step—Recrystallization step) After that, 300 mol of water was slowly added while stirring to recrystallize bisphenol A, and then filtered to obtain a solid. [0148] (5. Drying step) After that, it was dried in a vacuum oven at 30-50° C. to prepare a recycled bisphenol A monomer composition.

Examples 2 to 10

[0149] A recycled bisphenol A monomer composition and a recycled plastic were prepared in the same manner as in Example 1, except that in Example 1, the conditions of each step were changed as shown in Table 1 below.

TABLE-US-00001 TABLE 1 (4- (4-3. 1. Additional (3-3. Additional purification Purification- purification step- Washing step) step- Recrys- (1. Decompositon step) First Second First Second Redissolution tallization Category PC(eq) MC(eq) NaOH(eq) EtOH(eq) adsorbent adsorbent washing washing step) step) Exam- 1 17 0.25 11 Lignite Lignite MC/ Water/ EtOH/ Water/300 ple 1 activated activated 20~30° C. 50° C. 16.6 mol eq carbon carbon mol eq Exam- 1 17 0.25 11 Lignite Lignite MC/ Water/ EtOH/ Water/300 ple 2 carbon carbon 20~30° C. 20~30° C. 16.6 mol eq activated activated mol eq Exam- 1 17 0.25 11 Lignite Lignite MC/ Water/ EtOH/ Water/300 ple 3 activated activated 20~30° C. 70° C. 16.6 mol eq carbon carbon mol eq Exam- 1 17 0.25 11 Lignite Lignite Water/ MC/ EtOH/ Water/300 ple 4 activated activated 50° C. 20~30° C. 16.6 mol eq carbon carbon mol eq Exam- 1 20 0.25 11 Lignite Lignite MC/ Water/ EtOH/ Water/300 ple 5 activated activated 20~30° C. 50° C. 16.6 mol eq carbon carbon mol eq Exam- 1 17 0.25 12.5 Lignite Lignite MC/ Water/ EtOH/ Water/300 ple 6 activated activated 20~30° C. 50° C. 16.6 mol eq carbon carbon mol eq Exam- 1 17 0.25 8.5 Lignite Lignite MC/ Water/ EtOH/ Water/300 ple 7 activated activated 20~30° C. 50° C. 16.6 mol eq carbon carbon mol eq Exam- 1 17 0.25 11 Lignite Lignite MC/ Water/ EtOH/ Water/300 ple 8 activated activated 20~30° C. 50° C. 5.5 mol eq carbon carbon mol eq Exam- 1 17 0.25 11 Lignite Lignite MC/ Water/ EtOH/ Water/300 ple 9 activated activated 20~30° C. 50° C. 11.1 mol/eq carbon carbon mol eq Exam- 1 17 0.25 11 Lignite Lignite MC/ Water/ EtOH/ Water/325 ple 10 activated activated 20~30° C. 50° C. 16.6 mol eq carbon carbon mol eq

COMPARATIVE EXAMPLE

Comparative Example 1

[0150] A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that (4-2. Additional purification step—Adsorption step) was not performed in Example 1.

Comparative Example 2

[0151] A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that (3-1. Purification-Adsorption step) was not performed in Example 1.

Comparative Example 3

[0152] A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that in the (3-3. Purification-Washing step) of Example 1, the residue from which diethyl carbonate (DEC) has been removed was subjected to a primary washing using methylene chloride (MC) (20 times the mass of PC used) at 20-30° C., and the secondary washing was not performed.

Comparative Example 4

[0153] A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that (3-3. Purification-Washing step) was not performed in Example 1.

Experimental Example

[0154] The physical properties of the recycled bisphenol A monomer composition or by-products obtained in Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 2 below.

[0155] 1. Purity

[0156] 1 wt % of Recycled bisphenol A monomer composition was dissolved in acetonitrile (ACN) solvent under normal pressure and 20 to 30° C. conditions, and then the purity of bisphenol A (BPA) was analyzed by ultraperformance liquid chromatography (UPLC) on a Waters HPLC system using ACQUITY UPLC® BEH C18 1.7 In (2.1*50 mm column).

[0157] 2. Color Coordinates (L*, a*, and b*)

[0158] The color coordinates of the recycled bisphenol A monomer composition were analyzed in reflection mode using HunterLab UltraScan PRO Spectrophotometer.

[0159] 3. Recovery Rate of by-Product (DEC)

[0160] The percentage ratio of the number of moles of recovered DEC to the number of moles of DEC in the diethyl carbonate (DEC) by-product mixture containing MC, EtOH, and water separated in the distillation step was determined according to the following mathematical formula.

Recovery rate of diethyl carbonate={(Number of moles of diethyl carbonate recovered)/(Number of moles of diethyl carbonate in entire by-product mixture)}×100.  [Mathematical Formula]

[0161] Specifically, the number of moles of DEC in the by-product mixture can be measured by measuring the number of moles of DEC produced through a gas chromatography-flame ionization detector (GC-FID) device for the mixed solution immediately after depolymerization. The number of moles of recovered DEC can be that in which the number of moles of a by-product solution was measured for DEC by the same method through gas chromatography-flame ionization detector (GC-FID) device.

TABLE-US-00002 TABLE 2 Measurement result of Experimental Example 1 DEC Recovery rate Category Purity (%) L* a* b* (%) Example 1 99.72 98.91 −0.06 1.49 89.2 Example 2 99.13 96.91 −0.01 1.53 88.1 Example 3 99.14 97.12 0.06 1.56 87.9 Example 4 97.29 96.19 0.33 2.21 85.1 Example 5 96.82 97.82 0.31 1.82 87.1 Example 6 99.85 98.82 −0.05 1.48 88.8 Example 7 96.13 97.11 0.02 1.55 88.1 Example 8 97.11 96.92 0.26 2.10 86.2 Example 9 97.85 96.98 0.21 1.62 88.5 Example 10 99.12 97.11 0.11 1.51 87.6 Comparative 96.12 96.01 0.11 2.62 81.2 Example 1 Comparative 96.87 94.12 0.55 3.11 77.1 Example 2 Comparative 96.97 95.11 0.45 2.79 79.2 Example 3 Comparative 95.81 94.19 0.41 3.02 76.6 Example 4

[0162] As shown in Table 1, the recycled bisphenol A monomer compositions obtained in Examples 1 to 10 exhibited high purities of 96.13% to 99.85%. Also, the recycled bisphenol A monomer compositions obtained in Examples 1 to 10 exhibited color coordinates L* of 96.19 to 98.91, a* of −0.06 to 0.33, and b* of 1.48-2.21, showing excellent optical properties. In addition, the recycled bisphenol A monomer compositions obtained in Examples 1 to 10 were measured to have high DEC recovery rates of 85.1% to 89.2%. On the other hand, the recycled bisphenol A monomer compositions obtained in Comparative Examples 1 to 4 exhibited purities of 95.81% to 96.97%, which was decreased as compared to Examples. Further, the recycled bisphenol A monomer compositions obtained in Comparative Examples 1 to 4 exhibited color coordinates L* of 94.12 to 96.01, a* of 0.11 to 0.55, and b* of 2.62 to 3.11, showing poor optical properties as compared to Examples. Furthermore, the recycled bisphenol A monomer compositions obtained in Comparative Examples 1 to 4 had DEC recovery rates of 76.6% to 81.2%, which were lower than those of Examples.