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, which comprises an aromatic diol compound, wherein an impurity ratio according to the following Equation 1 is 1.2% or less, wherein the aromatic diol compound yield according to the following Equation 2 is more than 65%, and wherein the monomer composition for synthesizing recycled plastic is recovered from a polycarbonate-based resin:
Impurity ratio={(Total peak area on liquid chromatography−Bisphenol A peak area on liquid chromatography)/Total peak area on liquid chromatography}×100,  [Equation 1]
Yield (%)=W.sub.1/W.sub.0  [Equation 2] in Equation 2, W.sub.0 is the mass of the aromatic diol compound obtained during 100% decomposition of polycarbonate-based resin, and W.sub.1 is the mass of the aromatic diol compound actually obtained.

2. The monomer composition for synthesizing recycled plastic according to claim 1 wherein: the monomer composition for synthesizing recycled plastic has a color coordinate L* of 94 or more.

3. The monomer composition for synthesizing recycled plastic according to claim 1 wherein: the monomer composition for synthesizing recycled plastic has a color coordinate a* of 0.5 or less.

4. The monomer composition for synthesizing recycled plastic according to claim 1 wherein: the monomer composition for synthesizing recycled plastic has a color coordinate b* of 0 to 4.2.

5. The monomer composition for synthesizing recycled plastic according to claim 1 wherein: the monomer composition for synthesizing recycled plastic has an aromatic diol compound purity of 99% or more.

6. The monomer composition for synthesizing recycled plastic according to claim 1 wherein: the monomer composition for synthesizing recycled plastic contains diethyl carbonate as a by-product, and the diethyl carbonate is recovered from the polycarbonate-based resin.

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 base so that the pH of a depolymerization reaction product is 12 or more; adding water after the addition of base to separate a carbonate precursor from the depolymerization reaction product; and adding an acid so that the pH of the depolymerization reaction product from which the carbonate precursor has been separated is 4 or less.

8. The method for preparing a monomer composition for synthesizing recycled plastic according to claim 7 wherein: in the step of adding a base so that the pH of the depolymerization reaction product is 12 or more, an aromatic diol compound contained in the depolymerization reaction product is converted into a salt of the aromatic diol compound.

9. The method for preparing a monomer composition for synthesizing recycled plastic according to claim 7 wherein: in the step of adding water after the addition of base to separate a carbonate precursor from the depolymerization reaction product, a water layer containing a salt of the aromatic diol compound and an organic solvent layer containing diethyl carbonate are separated.

10. The method for preparing a monomer composition for synthesizing recycled plastic according to claim 7 wherein: in the step of adding an acid so that the pH of the depolymerization reaction product from which the carbonate precursor has been separated is 4 or less, a salt of the aromatic diol compound contained in the depolymerization reaction product is converted into the aromatic diol compound.

11. The method for preparing a monomer composition for synthesizing recycled plastic according to claim 7 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 for synthesizing recycled plastic according to claim 11 wherein: the 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 for synthesizing recycled plastic 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.

14. The method for preparing a monomer composition for synthesizing recycled plastic according to claim 7 wherein: after the step of adding an acid so that the pH of the depolymerization reaction product from which the carbonate precursor has been separated is 4 or less, the method further comprises a purification step of the depolymerization reaction product from which the carbonate precursor has been separated.

15. The method for preparing a monomer composition for synthesizing recycled plastic according to claim 14 wherein: the purification step of the depolymerization reaction product from which the carbonate precursor has been separated 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 for synthesizing recycled plastic according to claim 14 wherein: the purification step of the depolymerization reaction product from which the carbonate precursor has been separated comprises, an adsorption purification step for the depolymerization reaction product from which the carbonate precursor has been separated.

17. The method for preparing a monomer composition for synthesizing recycled plastic according to claim 14 wherein: the purification step of the depolymerization reaction product from which the carbonate precursor has been separated comprises, a washing step for the depolymerization reaction product from which the carbonate precursor has been separated.

18. A recycled plastic comprising a reaction product of the monomer composition for synthesizing recycled plastic of claim 1 and a comonomer.

19. A molded product comprising the recycled plastic of claim 18.

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.

Example and Comparative Example: Preparation of Recycled Bisphenol A Monomer Composition

Example 1

[0144] (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.

[0145] (2. Basifying step) The product of the depolymerization reaction was cooled to 30° C. or less, and then the product containing bisphenol A was basified with 2 mol of 40% sodium hydroxide (NaOH) until it reached a pH of 14.

[0146] (3. Layer separation step) After that, water was further added to form a water layer and a methylene chloride (MC) layer. The methylene chloride (MC) layer located on the lower side was removed using a separatory funnel, and the water layer located on the upper side was recovered.

[0147] (4. Acidifying step) The recovered water layer was acidified by adding 10% HCl and water until it reached a pH of 1 to 2. Then, bisphenol A was recovered by filtration through vacuum filtration.

[0148] (5-1. Additional purification step—Redissolution step) Bisphenol A was added to 16.6 mol of ethanol and redissolved.

[0149] (5-2. Additional purification step—Adsorption step) After that, lignite activated carbon as the 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.

[0150] (5-3. Additional purification step—Recrystallization step) 300 mol of water was added to recrystallize bisphenol A, and then the obtained slurry was vacuum filtered at 20˜30° C. to recover bisphenol A (BPA) crystals.

[0151] (6. 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.

Example 2

[0152] A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that the following (Washing step) was added between (4. Acidifying step) and (5-1. Additional purification step—Redissolution step) of Example 1.

[0153] (Washing step) Primary washing was performed using methylene chloride (MC) of once the mass of used PC at 20˜30° C., followed by vacuum filtration. The filtrate was secondarily washed using water of three times the mass of PC used at a temperature of 50° C.

Example 3

[0154] A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that (5-2. Additional purification step—Adsorption step) of Example 1 was not performed.

Comparative Example 1

[0155] A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that the following (Distillation step) was performed instead of (3. Layer separation step) and (4. Acidifying step) of Example 1.

[0156] (Distillation step) After that, the product lowered to pH 2 was subjected to a low-temperature distillation reducing pressure from 250 mbar and 20˜30° C. to 30 mbar and 30° C.

Experimental Example

[0157] 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.

[0158] 1. Purity

[0159] 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).

[0160] 2. Color Coordinates (L*, a*, and b*)

[0161] The color coordinates of the recycled bisphenol A monomer compositions were analyzed in reflection mode using HunterLab UltraScan PRO Spectrophotometer.

[0162] 3. Yield

[0163] The weight of BPA produced when the polycarbonate used in the reaction was 100% decomposed was measured, and the weight of the obtained BPA was measured, and the yield of BPA was calculated according to the following Equation 2.

Yield (%)=W.sub.1/W.sub.0  [Equation 2]

[0164] in Equation 2, W.sub.0 is the mass of the aromatic diol compound obtained during 100% decomposition, and W.sub.1 is the mass of the aromatic diol compound actually obtained. Specifically, when about 100 g of polycarbonate was decomposed, the mass of BPA obtained during 100% decomposition in theory is 89 g. If the mass of the actually obtained BPA is 80 g, the yield is 80/89*100=90%.

[0165] 4. Impurity Ratio

[0166] 1 ml of the recycled bisphenol A monomer composition was collected as a sample, subjected to ion chromatography (IC) analysis under the following conditions, and the impurity ratio was determined according to the following Equation 1. As a result of measurement using liquid chromatography, all materials except bisphenol A were regarded as impurities.

[0167] <Liquid Chromatography (LC) Conditions> [0168] {circle around (1)} Column: HP-1(L:30 m, ID:0.32 mm, film:1.05 m) [0169] {circle around (2)} Injection volume: 1 [0170] {circle around (3)} Inlet [0171] Temp.: 260° C., Pressure: 6.92 psi, Total flow: 64.2 ml/min, [0172] Split flow: 60 ml/min, spilt ratio: 50:1 [0173] {circle around (4)} Column flow: 1.2 ml/min [0174] {circle around (5)} Oven temp.: 70° C./3 min-10° C./min-280° C./41 min (Total 65 min) [0175] {circle around (6)} Detector [0176] Temp.:280° C., H.sub.2: 35 ml/min, Air: 300 ml/min, He: 20 ml/min [0177] {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,  [Equation 1]

TABLE-US-00001 TABLE 1 Measurement result of Experimental Example 1 Purity Yield Impurity Category (%) L* a* b* (%) (%) Example 1 99.3 96.4 0.12 1.82 72 0.7 Example 2 99.7 97.1 0.01 1.57 68 0.3 Example 3 99.1 95.9 0.25 2.24 73 0.9 Comparative 99.1 96.0 0.34 2.49 65 0.9 Example 1

[0178] As shown in Table 1, the recycled bisphenol A monomer compositions obtained in Examples 1 to 3 exhibited high purity of 99.1% to 99.7%. Also, the recycled bisphenol A monomer compositions obtained in Examples 1 to 3 exhibited a color coordinates L* of 95.9 to 97.1, a* of 0.01 to 0.25, and b* of 1.57 to 2.24, showing excellent optical properties. In addition, the recycled bisphenol A monomer compositions obtained in Examples 1 to 3 were measured to have a high BPA yield of 68% to 73%. Further, the recycled bisphenol A monomer compositions obtained in Examples 1 to 3 were measured to have a low impurity ratio of 0.3% to 0.9%. On the other hand, the recycled bisphenol A monomer composition obtained in Comparative Example 1 exhibited a color coordinate L* of 96.0, a* of 0.34, and b* of 2.49, showing poor optical properties as compared to those of Examples. In addition, the recycled bisphenol A monomer compositions obtained in Comparative Example 1 was measured to have a BPA yield of 65%, which was lower than in Examples.