Method for preparing polycarbonate

Abstract

The present invention provides a method for preparing a polycarbonate by removing a solvent from a polycarbonate polymerization solution without impairing the physical properties of the polycarbonate.

Claims

1. A method for preparing a polycarbonate, comprising the steps of: 1) adding an antioxidant, and a hydrolysis-resistant agent having an epoxy-fused aliphatic ring, to a polycarbonate polymerization solution; and 2) spraying steam at a temperature higher than a boiling point of removing a solvent in the polycarbonate polymerization solution onto the polycarbonate polymerization solution to evaporate the solvent to yield a solid polycarbonate.

2. The method for preparing a polycarbonate of claim 1, wherein the solvent of the polycarbonate polymerization solution is methylene chloride, or chlorobenzene.

3. The method for preparing a polycarbonate of claim 1, wherein at least two types of antioxidants are added.

4. The method for preparing a polycarbonate of claim 1, wherein the antioxidant comprises a phosphite-based antioxidant, and a hindered phenol-based antioxidant.

5. The method for preparing a polycarbonate of claim 1, wherein the antioxidant is added in an amount of 100 ppmw to 1,000 ppmw relative to the polycarbonate in the polycarbonate polymerization solution.

6. The method for preparing a polycarbonate of claim 1, wherein the hydrolysis-resistant agent is added in an amount of 100 ppmw to 1,000 ppmw relative to the polycarbonate in the polycarbonate polymerization solution.

7. The method for preparing a polycarbonate of claim 1, wherein the temperature of the steam is 210 C. to 230 C.

8. The method for preparing a polycarbonate of claim 1, wherein the pressure of the steam is 17 to 23 kgf/cm.sup.2.

9. The method for preparing a polycarbonate of claim 1, wherein the prepared polycarbonate has a YI value of 1.0 or less as measure according to ASTM D1925.

10. The method for preparing a polycarbonate of claim 1, wherein the prepared polycarbonate has a reduction in weight average molecular weight of 400 g/mol or less after allowing it to stand for 168 hours at 85 C. and 85% relative humidity.

11. The method for preparing a polycarbonate of claim 1, wherein the prepared polycarbonate has a reduction in impact strength at room temperature (measured at 23 C. according to ASTM D256 ( inch, Notched Izod)) of 100 J/m after allowing it to stand for 168 hours at 85 C. and 85% relative humidity.

12. The method for preparing a polycarbonate of claim 1, wherein a steam ejector is used for spraying the steam onto polycarbonate polymerization solution.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) Below, preferred examples are provided to aid in the understanding of the present invention. However, the following examples are provided only for illustration of the invention, and should not be construed as limiting the scope of the present invention thereto.

Preparation Example: Polycarbonate Polymerization Solution

(2) 978.4 g of bisphenol A (BPA), 1,620 g of a 32% aqueous NaOH solution, and 7,500 g of distilled water were added to a 20 L glass reactor, and after confirming that BPA was completely dissolved under a nitrogen atmosphere, 3,670 g of methylene chloride and 18.3 g of p-tert-butylphenol (PTBP) were added and mixed. 3,850 g of methylene chloride in which 542.5 g of triphosgene (TPG) was dissolved was added dropwise thereto for 1 hour. At this time, the pH was maintained at 12 using an aqueous NaOH solution. After completion of the dropwise addition, the mixture was aged for 15 minutes, and 195.7 g of triethylamine was dissolved in methylene chloride and added to the mixture. After 10 minutes, the pH was adjusted to 3 with a 1N hydrochloric acid aqueous solution, and the resultant was washed with distilled water three times to obtain 8,645 g of a polycarbonate polymerization solution. The weight of the polycarbonate dissolved in the polycarbonate polymerization solution was 1,125 g, and the concentration thereof was about 13% by weight.

Example 1

(3) 0.2250 g of IR1010, 0.3374 g of PEP-36, and 0.2250 g of C-2021P were mixed to 4,975 g of the polycarbonate polymerization solution prepared in the Preparation Example. Steam (temperature: 220 C., pressure: 20 kgf/cm.sup.2) was sprayed onto the mixed solution using a steam ejector to obtain a solid polycarbonate.

Example 2

(4) 0.1688 g of IR1010, 0.3936 g of PEP-36, and 0.2250 g of C-2021P were mixed to 4,975 g of the polycarbonate polymerization solution prepared in the Preparation Example. Steam (temperature: 220 C., pressure: 20 kgf/cm.sup.2) was sprayed onto the mixed solution using a steam ejector to obtain a solid polycarbonate.

Example 3

(5) 0.2250 g of IR1010, 0.3374 g of DP9228, and 0.2250 g of C-2021P were mixed to 4,975 g of the polycarbonate polymerization solution prepared in the Preparation Example. Steam (temperature: 220 C., pressure: 20 kgf/cm.sup.2) was sprayed onto the mixed solution using a steam ejector to obtain a solid polycarbonate.

Example 4

(6) 0.1688 g of IR1010, 0.3936 g of DP9228, and 0.2250 g of C-2021P were mixed to 4,975 g of the polycarbonate polymerization solution prepared in the Preparation Example. Steam (temperature: 220 C., pressure: 20 kgf/cm.sup.2) was sprayed onto the mixed solution using a steam ejector to obtain a solid polycarbonate.

Comparative Example 1

(7) 0.5623 g of P-168 was mixed to 4,975 g of the polycarbonate polymerization solution prepared in the Preparation Example. Steam (temperature: 220 C., pressure: 20 kgf/cm.sup.2) was sprayed onto the mixed solution using a steam ejector to obtain a solid polycarbonate.

Comparative Example 2

(8) 0.2250 g of IR1010 and 0.3374 g of PEP-36 were mixed to 4,975 g of the polycarbonate polymerization solution prepared in the Preparation Example. Steam (temperature: 220 C., pressure: 20 kgf/cm.sup.2) was sprayed onto the mixed solution using a steam ejector to obtain a solid polycarbonate.

Comparative Example 3

(9) 0.2250 g of IR1010, 0.3374 g of PEP-36, and 0.2250 g of ADR4370 were mixed to 4,975 g of the polycarbonate polymerization solution prepared in the Preparation Example. Steam (temperature: 220 C., pressure: 20 kgf/cm.sup.2) was sprayed onto the mixed solution using a steam ejector to obtain a solid polycarbonate.

Experimental Example

(10) 0.050 part by weight of tris (2,4-di-tert-butylphenyl) phosphite, 0.010 part by weight of octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 0.030 part by weight of pentaerythritol tetrastearate were added to each solid polycarbonate prepared in Examples and Comparative Examples, pelletized using a 30 mm twin-screw extruder provided with a vent, and then injection-molded at a cylinder temperature of 300 C. and a mold temperature of 80 C. using an N-20C injection molding device from JSW, Ltd., to manufacture each molded specimen.

(11) The properties of the above specimens were measured by the following methods, and the results are shown in Table 1 below.

(12) 1) YI (Yellow Index): Specimen (length/width/thickness=60 mm/40 mm/3 mm) was injection-molded at 300 C., and then YI (Yellow Index) of the specimen was measured using Color-Eye 7000A (X-Rite) according to ASTM D1925. Meanwhile, the measurement conditions for YI (Yellow Index) were as follows: Measurement temperature: Room temperature (23 C.) Aperture size: Large area of view Measurement method: Transmittance was measured in spectral range (360 nm to 750 nm)

(13) 2) Reduction in weight average molecular weight (AMw) and reduction in impact strength at room temperature (Notched Izod Impact): The weight average molecular weight (Mw.sub.0) was measured by calibrating according to the PC standard using Agilent 1200 series. Further, the impact strength at room temperature (NII.sub.0) was measured at 23 C. according to ASTM D256 ( inch, Notched Izod). Subsequently, the specimen was allowed to stand for 168 hours at 85 C. and 85% relative humidity using a thermo-hygrostat (JEIO TECH, TH-KE), and then the weight average molecular weight (Mw.sub.1) and the impact strength at room temperature (NII.sub.1) were measured in the same manner, and the difference therebetween (Mw.sub.0-Mw.sub.1 and NII.sub.0-NII.sub.1) was each measured.

(14) The results are shown in Table 1 below.

(15) TABLE-US-00001 TABLE 1 Hydrolysis- resistant Antioxidant (ppmw) agent (ppmw) Mw NII P-168 IR1010 PEP-36 DP9228 C-2021P ADR4370 YI (g/mol) (J/m ) Ex. 1 200 300 200 0.94 310 5 Ex. 2 150 350 200 0.92 370 5 Ex. 3 200 300 200 0.83 350 5 Ex. 4 150 350 200 0.81 390 6 Comparative 500 1.02 840 31 Ex. 1 Comparative 200 300 0.94 2,600 190 Ex. 2 Comparative 200 300 200 1.07 380 6 Ex. 3 The following antioxidants and hydrolysis-resistant agents were used. P-168: Tris(2,4-ditert-butylphenyl)phosphite (IRGAFOS 168) IR1010: [3-[3-(4-hydroxy-3,5-ditert-butyl-phenyl)propanoyloxy]-2,2-bis[3-(4-hydroxy-3,5-ditert-butyl- phenyl)propanoyloxymethyl[propyl] 3-(4-hydroxy-3,5-ditert-butyl-phenyl)propanoate PEP-36: Bis(2,6-di-ter-butyl-4-methylphenyl)pentaerythritol-diphosphite DP9228: bis(2,4-dicumylphenyl)pentaerythritol diphosphite C-2021P: 3,4-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate ADR4370: JONCRYL ADR-4370