Method of preparing metallocene catalyst for polyolefin preparation

Abstract

A method of preparing a high-purity metallocene catalyst capable of providing various selectivities and high activities for polyolefin copolymers, wherein a metallocene compound is formed by reacting a ligand compound with a zirconium compound, and then lithium chloride as a reaction by-product included in the metallocene compound is prepared in a form of a complex compound and effectively removed in a subsequent step of extracting the catalyst, thereby effectively preparing the high-purity metallocene catalyst, is provided.

Claims

1. A method of preparing a metallocene catalyst, the method comprising the steps of: A) forming a metallocene compound by reacting a ligand compound represented by the following Chemical Formula 1 with a zirconium compound comprising chloride in the presence of an alkyl lithium; B) adding a first solvent to the reaction products from step A) including the metallocene compound to form a lithium chloride—the first solvent complex; and C) adding a second solvent to the reaction products from step B) to precipitate the lithium chloride—the first solvent complex, followed by filtration: ##STR00010## wherein R.sub.1 is a C.sub.6-20 aryl substituted with a C.sub.1-20 alkyl; R.sub.2, R.sub.3, and R.sub.4 are each independently hydrogen, a halogen, a C.sub.1-20 alkyl, a C.sub.2-20 alkenyl, a C.sub.1-20 alkylsilyl, a C.sub.1-20 silylalkyl, a C.sub.1-20 alkoxysilyl, a C.sub.1-20 ether, a C.sub.1-20 silylether, a C.sub.1-20 alkoxy, a C.sub.6-20 aryl, a C.sub.7-20 alkylaryl, or a C.sub.7-20 arylalkyl; A is carbon, silicon, or germanium; R.sub.5 is a C.sub.1-20 alkyl substituted with a C.sub.1-20 alkoxy; and R.sub.6 is hydrogen, a C.sub.1-20 alkyl, or a C.sub.2-20 alkenyl, wherein the first solvent is one or more selected from the group consisting of 1,4-dioxane and 1,3-dioxolane, and wherein the second solvent is one or more selected from the group consisting of dichloromethane, chloroform, carbon tetrachloride, benzene, and toluene.

2. The method according to claim 1, wherein the zirconium compound is bis(N,N′-diphenyl-1,3-propanediamido)dichlorozirconium bis(tetrahydrofuran).

3. The method according to claim 1, wherein R.sub.1 is a phenyl substituted with a t-butyl.

4. The method according to claim 1, wherein R.sub.1 is 4-(t-butyl)-phenyl.

5. The method according to claim 1, wherein R.sub.2, R.sub.3, and R.sub.4 are hydrogen.

6. The method according to claim 1, wherein A is silicon.

7. The method according to claim 1, wherein R.sub.5 is 3-(t-butoxy)-propyl, and R.sub.6 is methyl.

8. The method according to claim 1, wherein the first solvent is added and stirred for 1 h or more.

9. The method according to claim 1, wherein the first solvent is removed before step C) by vacuum distillation under conditions of a pressure of 0.5 mbar to 2.0 mbar and a temperature of 30° C. to 45° C.

10. The method according to claim 1, wherein the second solvent is added and filtration is performed, and then the second solvent is removed from the obtained filtrate, followed by recrystallization using one or more solvents selected from the group consisting of dichloromethane and hexane.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The FIGURE is an image showing a size and a distribution of particles produced after performing polymerization processes according to Example 1 and Comparative Example 1 of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(2) Hereinafter, preferred examples will be provided for better understanding of the present invention. However, the following examples are only provided for understanding the present invention more easily, and the content of the present invention is not limited thereby.

EXAMPLES

Example 1

(3) ##STR00009##

(4) Step 1) Preparation of (3-t-butoxypropyl)(methyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)silane

(5) 150 g of 2-methyl-4-(4-t-butylphenyl)-indene was put in a 3 L Schlenk flask, and a toluene/THF (5:1, 715 mL) solution was added thereto and dissolved at room temperature. The solution was cooled to −20° C., and then 240 mL of n-butyllithium solution (n-BuLi, 2.5 M in hexane) was slowly added dropwise and stirred at room temperature for about 15 h. Thereafter, the reaction solution was cooled to −20° C., and 82 g of (3-t-butoxypropyl)dichloromethylsilane and 512 mg of CuCN were slowly added dropwise. The reaction solution was raised to room temperature and stirred for about 15 h, and then 500 mL of water was added thereto. Thereafter, an organic layer was separated and dried over MgSO.sub.4, followed by filtration. A filtrate was distilled under reduced pressure to obtain a yellow oil.

(6) .sup.1H NMR (500 MHz, CDCl.sub.3, 7.26 ppm): −0.09-−0.05; (3H, m), 0.40-0.60; (2H, m), 0.80-1.51; (26H, m), 2.12-2.36; (6H, m), 3.20˜3.28; (2H, m), 3.67-3.76; (2H, m), 6.81-6.83; (2H, m), 7.10-7.51; (14H, m)

(7) Step 2) Preparation of rac-[(3-t-butoxypropylmethylsilanediyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)]zirconium dichloride

(8) Previously prepared (3-t-butoxypropyl)(methyl)bis(2-methyl-4-(4-t-butylphenyl)indenylsilane was put in a 3 L Schlenk flask, and 1 L of toluene/diethylether (volume ratio of 10:1) was added thereto and dissolved at room temperature. The solution was cooled to −20° C., and then 240 mL of an n-butyllithium solution (n-BuLi, 2.5 M in hexane) was slowly added dropwise and stirred at room temperature for about 3 h. Thereafter, the reaction solution was cooled to −20° C., and 92 g of zirconium chloride was added thereto. The reaction solution was raised to room temperature and stirred for about 15 h, and the solvent was removed under reduced pressure. After distillation of all the reaction solvents under reduced pressure, 1,4-dioxane was added in an amount of 750 g, which is about 5 times the weight of 2-methyl-4-(4-t-butylphenyl)-indene, and stirred for about 1 h. The solvent was removed under reduced pressure to obtain a solid mixture of a lithium chloride-1,4-dioxane complex compound and an organometallic compound. About 1 L of dichloromethane was added to a reaction vessel containing the thus-obtained solid mixture, and insoluble inorganic salts, etc. were removed by filtration. A filtrate was dried under reduced pressure, and 300 mL of dichloromethane was added thereto to precipitate crystals. The precipitated crystals were filtered and dried to obtain 80 g of rac-[(3-t-butoxypropylmethylsilanediyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)]zirconium dichloride (yield 31.7%, rac:meso=50:1).

(9) .sup.1H NMR (500 MHz, CDCl.sub.3, 7.26 ppm): 1.19-1.78; (37H, m), 2.33; (3H, s), 2.34; (3H, s), 3.37; (2H, t), 6.91; (2H, s), 7.05-7.71; (14H, m)

(10) The thus-obtained metallocene catalyst was subjected to inductively coupled plasma (ICP-AES) analysis to measure the content of a LiCl reaction impurity. As a result, the content of LiCl was 75 ppm, indicating that the metallocene catalyst having very high purity was prepared by removing the impurity.

(11) Step 3) Preparation of supported catalyst

(12) 3 g of silica was weighed and put in a Schlenk flask, and then 10 mmol of methylaluminoxane (MAO) was added thereto, and allowed to react at 90° C. for about 24 h. After precipitation, an upper layer was removed and a remaining part was washed once with toluene. 60 μmol of rac-[(3-t-butoxypropylmethylsilanediyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)]zirconium dichloride, which is an ansa-metallocene compound prepared in step 2, was dissolved in toluene, and allowed to react at about 70° C. for about 5 h. After the reaction was terminated and precipitation was completed, an upper solution was removed and a remaining reaction product was washed with toluene. The next day, 48 μmol of borate (AB) was dissolved in toluene, and allowed to react at about 70° C. for about 5 h. After the reaction was terminated and precipitation was completed, an upper solution was removed and a remaining reaction product was washed with toluene, and further washed with hexane and then dried under vacuum to obtain 5 g of a silica-supported metallocene catalyst in a solid particle form.

Example 2

(13) 78 g of a metallocene catalyst rac-[(3-t-butoxypropylmethylsilanediyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)]zirconium dichloride (yield 30.9%, rac:meso=50:1) was prepared in the same manner as in Example 1, except that after reaction by addition of zirconium chloride, the reaction solvents were all removed by distillation under reduced pressure and 1,4-dioxane was added in an amount of 1500 g, which is about 10 times the weight of 2-methyl-4-(4-t-butylphenyl)-indene, and then the content of LiCl was measured.

(14) In this regard, the content of LiCl in the produced metallocene catalyst was 30 ppm, indicating that the metallocene catalyst having very high purity was prepared by removing the impurity.

Example 3

(15) 80 g of a metallocene catalyst rac-[(3-t-butoxypropylmethylsilanediyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)]zirconium dichloride (yield 31.7%, rac:meso=50:1) was prepared in the same manner as in Example 1, except that after reaction by addition of zirconium chloride, the reaction solvents were all removed by distillation under reduced pressure and 1,4-dioxane was added in an amount of 2250 g, which is about 15 times the weight of 2-methyl-4-(4-t-butylphenyl)-indene, and then the content of LiCl was measured.

(16) In this regard, the content of LiCl in the produced metallocene catalyst was 50 ppm, indicating that the metallocene catalyst having very high purity was prepared by removing the impurity.

Comparative Example 1

(17) Step 1) Preparation of (3-t-butoxypropyl)(methyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)silane

(18) 150 g of 2-methyl-4-(4-t-butylphenyl)-indene was put in a 3 L Schlenk flask, and a toluene/THF (5:1, 715 mL) solution was added thereto and dissolved at room temperature. The solution was cooled to −20° C., and then 240 mL of n-butyllithium solution (n-BuLi, 2.5 M in hexane) was slowly added dropwise and stirred at room temperature for about 3 h. Thereafter, the reaction solution was cooled to −20° C., and 82 g of (3-t-butoxypropyl)dichloromethylsilane and 512 mg of CuCN were slowly added dropwise. The reaction solution was raised to room temperature and stirred for about 15 h, and then 500 mL of water was added thereto. Thereafter, an organic layer was separated and dried over MgSO.sub.4, followed by filtration. A filtrate was distilled under reduced pressure to obtain a yellow oil.

(19) .sup.1H NMR (500 MHz, CDCl.sub.3, 7.26 ppm): −0.09-−0.05; (3H, m), 0.40-0.60; (2H, m), 0.80-1.51; (26H, m), 2.12-2.36; (6H, m), 3.20˜3.28; (2H, m), 3.67-3.76; (2H, m), 6.81-6.83; (2H, m), 7.10-7.51; (14H, m)

(20) Step 2) Preparation of rac-[(3-t-butoxypropylmethylsilanediyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)]zirconium dichloride

(21) Previously prepared (3-t-butoxypropyl)(methyl)bis(2-methyl-4-(4-t-butylphenyl)indenylsilane was put in a 3 L Schlenk flask, and 1 L of toluene/diethylether (10:1) was added thereto and dissolved at room temperature. The solution was cooled to −20° C., and then 240 mL of n-butyllithium solution (n-BuLi, 2.5 M in hexane) was slowly added dropwise and stirred at room temperature for about 3 h. Thereafter, the reaction solution was cooled to −20° C., and 92 g of zirconium chloride was added thereto. The reaction solution was raised to room temperature and stirred for about 15 h, and the reaction solvent was removed under reduced pressure. Without treatment of a solvent for forming a lithium chloride complex compound, about 1 L of dichloromethane was added, and insoluble inorganic salts, etc. were removed by filtration. A filtrate was dried under reduced pressure, and 300 mL of dichloromethane was added to precipitate crystals. The precipitated crystals were filtered and dried to obtain 80 g of rac-[(3-t-butoxypropylmethylsilanediyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)]zirconium dichloride (yield 31.7%, rac:meso=50:1).

(22) .sup.1H NMR (500 MHz, CDCl.sub.3, 7.26 ppm): 1.19-1.78; (37H, m), 2.33; (3H, s), 2.34; (3H, s), 3.37; (2H, t), 6.91; (2H, s), 7.05-7.71; (14H, m)

(23) The thus-obtained metallocene catalyst was subjected to inductively coupled plasma (ICP-AES) analysis to measure the content of a LiCl reaction impurity. As a result, the content of LiCl was 2110 ppm, indicating that the metallocene catalyst had a high content of impurity.

(24) Step 3) Preparation of supported catalyst

(25) 3 g of silica was weighed and put in a Schlenk flask and then 10 mmol of methylaluminoxane (MAO) was added thereto, and allowed to react at 90° C. for about 24 h. After precipitation, an upper layer was removed and a remaining part was washed once with toluene. 60 μmol of rac-[(3-t-butoxypropylmethylsilanediyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)]zirconium dichloride, which is an ansa-metallocene compound prepared in step 2, was dissolved in toluene, and allowed to react at about 70° C. for about 5 h. After the reaction was terminated and precipitation was completed, an upper solution was removed and a remaining reaction product was washed with toluene. The next day, 48 μmol of borate (AB) was dissolved in toluene, and allowed to react at about 70° C. for about 5 h. After the reaction was terminated and precipitation was completed, an upper solution was removed and a remaining reaction product was washed with toluene, and further washed with hexane and then dried under vacuum, to obtain 5 g of a silica-supported metallocene catalyst in a solid particle form.

Comparative Example 2

(26) A metallocene catalyst was prepared in the same manner as in Example 1, except that after reaction by addition of zirconium chloride, the reaction solvents were all removed by distillation under reduced pressure and tetrahydrofuran (THF) was added, instead of 1,4-dioxane, in an amount of 1500 g, which is about 10 times the weight of 2-methyl-4-(4-t-butylphenyl)-indene, and then the content of LiCl was measured.

(27) In this regard, the content of LiCl in the produced metallocene catalyst was 450 ppm, indicating that the metallocene catalyst had a high content of impurity.

Comparative Example 3

(28) A metallocene catalyst was prepared in the same manner as in Example 1, except that after reaction by addition of zirconium chloride, the reaction solvents were all removed by distillation under reduced pressure and methyl tertiary butyl ether was added, instead of 1,4-dioxane, in an amount of 1500 g, which is about 10 times the weight of 2-methyl-4-(4-t-butylphenyl)-indene, and then the content of LiCl was measured.

(29) In this regard, the content of LiCl in the produced metallocene catalyst was 1730 ppm, indicating that the metallocene catalyst had a high content of impurity.

Comparative Example 4

(30) A metallocene catalyst was prepared in the same manner as in Example 1, except that after reaction by addition of zirconium chloride, the reaction solvents were all removed by distillation under reduced pressure and diethylether (Et.sub.2O) was added, instead of 1,4-dioxane, in an amount of 1500 g, which is about 10 times the weight of 2-methyl-4-(4-t-butylphenyl)-indene, and then the content of LiCl was measured.

(31) In this regard, the content of LiCl in the produced metallocene catalyst was 1850 ppm, indicating that the metallocene catalyst had a high content of impurity.

Comparative Example 5

(32) After reaction by addition of zirconium chloride, the reaction solvents were all removed by distillation under reduced pressure and 1,4-dioxane was added in an amount of about 750 g, which is about 5 times the weight of 2-methyl-4-(4-t-butylphenyl)-indene, and then insoluble solids were filtered and dried to obtain 8 g of rac-[(3-t-butoxypropylmethylsilanediyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)]zirconium dichloride (yield 3.2%).

(33) The thus-obtained metallocene catalyst was subjected to inductively coupled plasma (ICP-AES) analysis to measure the content of a LiCl reaction impurity. As a result, the content of LiCl was 1080 ppm, indicating that the metallocene catalyst had a high content of impurity, and its industrial application was difficult due to a low yield of 3.2%.

Comparative Example 6

(34) 5 g of a metallocene catalyst rac-[(3-t-butoxypropylmethylsilanediyl)-bis(2-methyl-4-(4-t-butylphenyl)indenyl)]zirconium dichloride (yield 2.0%) was prepared in the same manner as in Comparative Example 5, except that after reaction by addition of zirconium chloride, the reaction solvents were all removed by distillation under reduced pressure and 1,4-dioxane was added in an amount of about 1500 g, which is about 10 times the weight of 2-methyl-4-(4-t-butylphenyl)-indene, and then the content of LiCl was measured.

(35) In this regard, the content of LiCl in the produced metallocene catalyst was 1415 ppm, indicating that the metallocene catalyst had a high content of impurity, and its industrial application was difficult due to a low yield of 3.2%.

Comparative Example 7

(36) Preparation of a metallocene catalyst was attempted in the same manner as in Comparative Example 1, except that after reaction by addition of zirconium chloride, the reaction solvents were all removed by distillation under reduced pressure and 1,4-dioxane was added in an amount of about 2250 g, which is about 15 times the weight of 2-methyl-4-(4-t-butylphenyl)-indene. However, all products were dissolved, and thus no organometallic compound was obtained (yield 0%). Also, the content of LiCl could not be measured.

(37) The main process conditions after reaction by addition of zirconium chloride in the preparation processes of the catalysts according to Examples 1 to 3 and Comparative Examples 1 to 7, and the contents of LiCl measured in the produced catalysts, are shown in Table 1 below.

(38) TABLE-US-00001 TABLE 1 Step of forming LiCl Step of selectively extracting complex compound organometallic compound Content of LiCl Amount Amount in catalyst Solvent (ratio) Solvent (ratio) (ppm) Example 1 1,4-Dioxane 5 Dichloromethane 5 75 Example 2 1,4-Dioxane 10 Dichloromethane 5 30 Example 3 1,4-Dioxane 15 Dichloromethane 5 50 Comparative — — Dichloromethane 5 2950 Example 1 Comparative Tetrahydrofuran 10 Dichloromethane 5 450 Example 2 Comparative Methyl t-butyl 10 Dichloromethane 5 1730 Example 3 ether Comparative Diethyl ether 10 Dichloromethane 5 1850 Example 4 Comparative 1,4-Dioxane 5 1,4-Dioxane 5 1080 Example 5 Comparative 1,4-Dioxane 10 1,4-Dioxane 10 1415 Example 6 Comparative 1,4-Dioxane 15 1,4-Dioxane 15 — Example 7

Experimental Example

1) Homopolymerization of Propylene

(39) After vacuum-drying a 2 L stainless reactor at 65° C. and cooling the same, 3.0 mmol of triethylaluminum and about 770 g of propylene were sequentially added thereto at room temperature and with addition of 2 bar of hydrogen.

(40) After stirring the mixture for about 10 minutes, 0.060 g of each of the supported metallocene catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 6 was dissolved in 20 mL of TMA-prescribed hexane, and each of the solutions was added to the reactor under nitrogen pressure. Thereafter, the temperature of the reactor was slowly raised to about 70° C., and then the polymerization was carried out for about 1 h. After the reaction was terminated, unreacted propylene was vented out.

2) Methods of Measuring Physical Properties of Polymers

(41) (1) Catalytic activity: a ratio of the weight of the produced polymer (kg PP) to the amount of the used catalyst (mmol and g of catalyst) was calculated, based on unit time (h).

(42) (2) Melting point (Tm) of polymer: a melting point of the polymer was measured by using a differential scanning calorimeter (DSC, Device Name: DSC 2920, Manufacturer: TA instruments). Specifically, after the polymer was heated to 220° C. and the temperature was maintained for 5 min, the temperature was decreased to 20° C. Thereafter, the temperature was increased again. At this time, the scanning speed of heating and cooling processes was respectively 10° C./min.

(43) (3) Crystallization temperature (Tc) of polymer: a crystallization temperature was determined from a DSC curve which was obtained while decreasing the temperature under the same conditions as in the measurement of the melting point by using DSC.

(44) (4) Melt index (MFR, 2.16 kg): a melt index was measured according to ASTM D1238 at 230° C. with a load of 2.16 kg, and determined as a weight (g) of the polymer melted out for 10 min.

3) Results of Measuring Physical Properties of Polymers

(45) The homopolymerization process conditions of Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 6 using the metallocene-supported catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 6, and results of measuring physical properties of the produced polypropylenes, are shown in Table 2 (homopolymerization) below.

(46) TABLE-US-00002 TABLE 2 Amount polymerization of activity Average supported (kg- particle MFR Polymerization Temperature catalyst Yield PP/g- size (g/10 Tm method (° C.) (mg) (G) cat .Math. h) (μm) min) (° C.) reparation Homo- 70 30 471 15.7 781 12.1 151 Example 1 polymerization Preparation Homo- 70 30 459 15.3 803 11.1 150 Example 2 polymerization Preparation Homo- 70 30 477 15.9 810 13.3 151 Example 3 polymerization Comparative Homo- 70 30 27 0.9 170 87.2 150 Preparation polymerization Example 1 Comparative Homo- 70 30 303 10.1 720 19.2 151 Preparation polymerization Example 2 Comparative Homo- 70 30 75 2.5 255 65.2 151 Preparation polymerization Example 3 Comparative Homo- 70 30 66 2.2 275 59.9 150 Preparation polymerization Example 4 Comparative Homo- 70 30 82 2.7 269 60.1 150 Preparation polymerization Example 5 Comparative Homo- 70 30 77 2.6 275 69.2 151 Preparation polymerization Example 6

(47) Further, scanning electron microscopic (SEM) images showing a size and a distribution of particles produced after performing polymerization processes according to Example 1 and Comparative Example 1 of the present invention are shown in the FIGURE. As shown in the FIGURE, the particle size of the produced polymer was increased to about 25% to inhibit fine powder generation, thereby securing process stability.

(48) As shown in Table 2, Preparation Examples 1 to 3, in which the metallocene compound according to the present invention was used as a supported catalyst, showed the effect of increasing activity upon preparation of polypropylene. In particular, Preparation Examples 1 to 3 showed excellent catalytic activity of 15.3 kg/g.Math.h to 15.9 kg/g.Math.h upon homopolymerization. In contrast, Comparative Preparation Examples 1 to 4, in which the solvent for extracting the LiCl complex compound was not used according to the known method, or the common ether-based solvent was used, showed remarkably low catalytic activity of 0.9 kg/g.Math.h to 2.5 kg/g.Math.h upon random polymerization. Particularly, Preparation Examples 1 to 3 of the present invention remarkably improved purity of the produced metallocene catalysts, as compared with the known method, and therefore the catalytic activities upon polymerization were about 17 times higher than that of Comparative Preparation Example 1 of the known method. As in Comparative Preparation Example 1, when the catalytic activity is low, a larger amount of the catalyst is needed in order to control slurry density in the polymerization process. When the catalytic activity is low, the catalyst reaches its limit, and there is a difficulty in commercial production. In contrast, when the catalytic activity is high as in Preparation Examples 1 to 3 of the present invention, a small amount of the catalyst is needed to control slurry density, and thus it is advantageous in commercial production.

(49) Furthermore, in Preparation Examples 1 to 3 using the high-purity metallocene catalyst according to the present invention, an average particle size of the produced polypropylene was about 3 times larger than those of Comparative Preparation Examples 1 to 6, and in particular, about 4.5 times larger than that of Comparative Preparation Example 1. Accordingly, there is an advantage that long-term production may be stably performed without fouling in a commercial continuous process. As in Comparative Preparation Examples 1, 3, and 4, when the average particle size of the produced polyolefin is significantly small, a possibility of fine powder generation increases or sheets are produced during the process to cause fouling, leading to reduction of overall process efficiency.

(50) Further, in the examples of the present invention, it was confirmed that MFR values were remarkably low, indicating that polypropylene prepared by using the metallocene compound according to the present invention as the supported catalyst has a very high molecular weight.