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 that 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, wherein the monomer composition has a color coordinate L* of 94 or more, and a color coordinate b* of 0 to 4.2, and wherein the monomer composition is a recovered product from a polycarbonate-based resin.

2. The monomer composition according to claim 1, wherein the monomer composition has a color coordinate a* of 0.5 or less.

3. The monomer composition according to claim 1 wherein the aromatic diol compound has a purity of 99% or more.

4. 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.

5. The monomer composition according to claim 1, further comprising: impurities other than the aromatic diol compound.

6. The monomer composition according to claim 5, wherein the monomer composition has an impurity ratio of 1.2% or less according to the following mathematical formula:
Impurity ratio={(Total peak area on liquid chromatography−Bisphenol A peak area on liquid chromatography)/Total peak area on liquid chromatography}×100.  [Mathematical Formula]

7. The monomer composition according to claim 1, further comprising: diethyl carbonate as a by-product.

8. 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 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.

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

10. The method for preparing a monomer composition according to claim 8, wherein an amount of the first adsorbent added is 1 part by weight to 1000 parts by weight relative to 100 parts by weight of the second adsorbent added.

11. The method for preparing a monomer composition according to claim 8, wherein the depolymerization reaction of the polycarbonate-based resin is carried out in the presence of a solvent containing ethanol.

12. The method for preparing a monomer composition according to claim 11, wherein a content of the ethanol is 10 to 15 moles relative to 1 mole of the polycarbonate-based resin.

13. The method for preparing a monomer composition according to claim 8, 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.

14. The method for preparing a monomer composition according to claim 8, wherein the separating step comprises: a reduced pressure distillation step of the depolymerization reaction product.

15. The method for preparing a monomer composition according to claim 8, 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.

16. The method for preparing a monomer composition according to claim 8, 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.

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

18. A molded product, comprising: the recycled plastic of claim 17.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0143] 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.

[0144] <Example and Comparative Example: Preparation of Recycled Bisphenol A Monomer Composition>

Example 1

[0145] (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 3 L high-pressure reactor, and the mixture was stirred at 60° C. for 6 hours to proceed a PC depolymerization reaction.

[0146] (2. Neutralization stage) The depolymerization reaction product was cooled to or less, and then the product containing bisphenol A was neutralized using 0.25 mol of 10% hydrochloric acid (HCl) at 20-30° C.

[0147] (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, purified through adsorption for 3 hours, and then filtrated using Celite to remove lignite activated carbon.

[0148] (3-2. Purification-Distillation step) After that, the by-product diethyl carbonate (DEC) was recovered through a low-temperature distillation reducing pressure from 250 mbar and 20-30° C. to 30 mbar and 30° C.

[0149] (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.

[0150] (4-1. Additional purification step—Redissolution step) 16.6 mol of Ethanol was added to the washed material and redissolved.

[0151] (4-2. Additional purification step—Adsorption step) After that, lignite activated carbon as the second adsorbent was added at a ratio of 50 wt. % relative to waste polycarbonate, purified through adsorption for 3 hours, and filtered to remove the lignite activated carbon.

[0152] (4-3. Additional purification step—Recrystallization step) 300 mol of water was added to recrystallize bisphenol A, and the obtained slurry was vacuum filtered at to recover bisphenol A (BPA) crystals.

[0153] (5. Drying step) After that, it was vacuum dried in a convection oven at 40° C. to prepare a recycled bisphenol A monomer composition in which recycled bisphenol A (BPA) was recovered.

Examples 2 to 6, Comparative Examples 1 to 4

[0154] A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that in Example 1, the types of the first adsorbent and the second adsorbent and whether or not they can be used are changed were changed as shown in Table 1 below.

Experimental Example

[0155] The physical properties of the recycled bisphenol A monomer compositions or by-products obtained in the Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 1 below.

[0156] 1. Purity

[0157] 1 wt % of the 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 μm (2.1*50 mm column).

[0158] 2. Color Coordinates (L*, a*, and b*)

[0159] The color coordinates of the recycled bisphenol A monomer compositions were analyzed in reflection mode using HunterLab UltraScan PRO Spectrophotometer.

[0160] 3. Content of Impurities (DMC, DEC, EMC)

[0161] 1 ml of Recycled bisphenol A monomer composition was collected as a sample, liquid chromatography (LC) analysis was performed under the following conditions, and the impurity ratio was calculated according to the following mathematical formula. As a result of measurement using liquid chromatography, all materials except bisphenol A were regarded as impurities.

[0162] <Liquid Chromatography (LC) Conditions> [0163] {circle around (1)} Column: HP-1 (L:30 m, ID:0.32 mm, film:1.05 m) [0164] {circle around (2)} Injection volume: 1 μl [0165] {circle around (3)} Inlet

[0166] Temp.: 260° C., Pressure: 6.92 psi, Total flow: 64.2 ml/min, Split flow: 60 ml/min, spilt ratio: 50:1

[0167] {circle around (4)} Column flow: 1.2 ml/min

[0168] {circle around (5)} Oven temp.: 70° C./3 min-10° C./min-280° C./41 min (Total 65 min)

[0169] {circle around (6)} Detector

[0170] Temp.:280° C., H.sub.2: 35 ml/min, Air: 300 ml/min, He: 20 ml/min

[0171] {circle around (7)} GC Model: Agilent 7890

Impurity ratio={(Total peak area on liquid chromatography−Bisphenol A peak area on liquid chromatography)/Total peak area on liquid chromatography}×100.  [Mathematical Formula]

TABLE-US-00001 TABLE 1 Measurement result of Experimental Example 1 Recycled bisphenol A monomer composition Im- First Second Purity purity Category absorbent absorbent (%) L* a* b* (%) Example 1 Lignite Lignite 99.4 95.3 0.00 3.48 0.6 activated activated carbon carbon Example 2 Anthracite Lignite 99.1 94.8 0.12 3.89 0.9 activated activated carbon carbon Example 3 Coconut Lignite 99.2 95.0 0.34 4.12 0.8 activated activated carbon carbon Example 4 Lignite Anthracite 99.7 96.3 −0.01 2.12 0.3 activated activated carbon carbon Example 5 Anthracite Anthracite 99.3 95.1 0.21 3.44 0.7 activated activated carbon carbon Example 6 Coconut Anthracite 99.0 94.5 0.44 4.03 1.0 activated activated carbon carbon Comparative Lignite — 98.4 93.2 0.89 4.32 1.3 Example 1 activated carbon Comparative — Lignite 98.3 93.1 1.15 5.34 1.7 Example 2 activated carbon Comparative Anthracite — 98.2 92.3 1.21 5.12 1.8 Example 3 activated carbon Comparative Coconut — 98.4 92.4 1.24 5.67 1.6 Example 4 activated carbon
As shown in Table 1, the recycled bisphenol A monomer compositions obtained in Examples 1 to 6 exhibited high purity of 99.0% to 99.7%. Also, the recycled bisphenol A monomer compositions obtained in Examples 1 to 6 exhibited a color coordinates L* of 94.5 to 96.3, a* of −0.01 to 0.44, and b* of 2.12 to 4.12, showing excellent optical properties. In addition, the recycled bisphenol A monomer compositions obtained in Examples 1 to 6 were measured to have a low impurity ratio of 0.3% to 1%. On the other hand, the recycled bisphenol A monomer composition obtained in Comparative Examples 1 to 4 had a purity of 98.2% to 98.4%, which was decreased compared to that of Examples. Further, the recycled bisphenol A monomer compositions obtained in Comparative Examples 1 to 4 exhibited a color coordinate L* of 92.3 to 93.2, a* of 0.89 to 1.24, and b* of 4.32 to 5.67, showing poor optical properties as compared to those of Examples. In addition, the recycled bisphenol A monomer compositions obtained in Comparative Examples 1 to 4 had an impurity ratio of 1.3% to 1.8%, which was higher than in Examples.