Process for making a solid catalyst component for ethylene polymerization and co-polymerization

Abstract

The present invention relates to a process for preparing a solid catalyst component suitable for producing polyethylene and its copolymers, said process comprising the steps of: (a) contacting a dehydrated support having hydroxyl groups with a magnesium compound having the general formula MgR.sup.1R.sup.2; (b) contacting the product obtained in step (a) with modifying compounds (A) and/or (B) and/or (C), wherein: (A) is at least one oxygen and/or nitrogen comprising organic compound; (B) is a compound having the general formula R.sup.11.sub.f(R.sup.12O).sub.gSiX.sub.h, (C) is a compound having the general formula (R.sup.13O).sub.4M, and (c) contacting the product obtained in step (b) with a titanium halide compound having the general formula TiX.sub.4, wherein Ti is a titanium atom and X is a halide atom, wherein an organometallic compound is added either before step (a) and/or after step (c). The invention also relates to a solid catalyst component obtainable by said process. The invention further relates to a process for producing polyethylene and its copolymers in the presence of the solid catalyst component and a co-catalyst.

Claims

1. A process for preparing a solid catalyst component suitable for producing polyethylene and its copolymers, said process comprising the steps of: (a) contacting a dehydrated support having hydroxyl groups with a magnesium compound having the general formula MgR.sup.1R.sup.2, wherein R.sup.1 and R.sup.2 are the same or different and are independently selected from an alkyl group, alkenyl group, alkadienyl group, aryl group, alkaryl group, alkenylaryl group, or alkadienylaryl group; (b) contacting the product obtained in step (a) with modifying compounds (A), (B) and (C), wherein: (A) is an oxygen and/or nitrogen containing organic compound selected from a ketone, carboxylic acid, carboxylic acid ester, acyl halide, aldehyde, alcohol, or aminoketone, (B) is a compound having the general formula R.sup.11.sub.f(R.sup.12O).sub.gSiX.sub.h, wherein f, g and h are each integers from 0 to 4 and the sum of f, g and h is equal to 4 with a proviso that when h is equal to 4 then modifying compound (A) is not an alcohol, Si is a silicon atom, O is an oxygen atom, X is a halide atom and R.sup.11 and R.sup.12 are the same or different and are independently selected from an alkyl group, alkenyl group, alkadienyl group, aryl group, alkaryl group, alkenylaryl group, or alkadienylaryl group; (C) is a compound having the general formula (R.sup.13O).sub.4M, wherein M is a titanium atom, a zirconium atom or a vanadium atom, O is an oxygen atom and R.sup.13 is selected from alkyl group, alkenyl group, alkadienyl group, aryl group, alkaryl group, alkenylaryl group, or alkadienylaryl group; and (c) contacting the product obtained in step (b) with a titanium halide compound having the general formula TiX.sub.4, wherein Ti is a titanium atom and X is a halide atom, wherein an organometallic compound is added before step (a) and/or after step (c).

2. The process according to claim 1 wherein the molar ratio of Mg to hydroxyl groups is from 0.01 to 10.

3. The process according to claim 1 wherein the molar ratio of compound (A) to Mg is from 0.01 to 10 and/or of compound (B) to Mg is from 0.01 to 5 and/or the molar ratio of compound (C) to Mg is from 0.01 to 5.

4. The process according to claim 1 wherein the molar ratio of organometallic compound to magnesium compound is between 0.04 and 0.7 and/or the molar ratio of organometallic compound to titanium halide compound of between is between 0.04 and 0.8.

5. The process according to claim 1 wherein the molar ratio of the organometallic compound to the magnesium compound is between 0.05 and 1.5 and/or the molar ratio of organometallic compound to titanium halide compound is between 0.15 and 1.5.

6. The process according to claim 1 wherein the molar ratio of titanium halide compound to Mg is from 0.01 to 10.

7. The process according to claim 1 wherein the support is silica, alumina, magnesia, thoria, zirconia or mixtures thereof.

8. The process according to claim 1 wherein the support is silica.

9. The process according to claim 1 wherein compound (A) is selected from pentan-2-one, methyl n-propyl ketone, ethyl acetate, n-butyl acetate, acetic acid, isobutyric acid, isobutyraldehyde, ethanoyl chloride, ethanol and sec-butanol and/or 4-methylamino-pent-3-en-2-one, 4-n-butylamino-pent-3-en-2-one, 4-tert-butylamino-pent-3-en-2-one, or 4-cyclohexylamino-pent-3-en-2-one.

10. The process according to claim 1 wherein compound (B) is selected from tetraethoxysilane, n-propyltriethoxysilane, isobutyltrimethoxysilane, dimethyldichlorosilane, n-butyltrichlorosilane, or silicon tetrachloride.

11. The process according to claim 1 wherein compound (C) is selected from titanium tetraethoxide, titanium tetra-n-butoxide, or zirconium tetra-n-butoxide.

12. The process according to claim 1 wherein the total molar ratio of compound (C) and TiX.sub.4 to hydroxyl groups is from 0.05 to 1.0.

13. The process according to claim 1 wherein TiX.sub.4 compound is TiCl.sub.4.

14. A solid catalyst component obtained by the process according to claim 1.

15. A process for producing polyethylene and its copolymers in the presence of the solid catalyst component according to claim 14 and a co-catalyst.

16. The process according to claim 1 wherein the molar ratio of Mg to hydroxyl groups is from 0.01 to 10; the molar ratio of compound (A) to Mg is from 0.01 to 10 and/or of compound (B) to Mg is from 0.01 to 5 and/or the molar ratio of compound (C) to Mg is from 0.01 to 5; the molar ratio of organometallic compound to magnesium compound is between 0.04 and 0.7 and/or the molar ratio of organometallic compound to titanium halide compound is between 0.04 and 0.8; the molar ratio of titanium halide compound to Mg is from 0.01 to 10.

17. The process according to claim 16, wherein compound (A) is selected from pentan-2-one, methyl n-propyl ketone, ethyl acetate, n-butyl acetate, acetic acid, isobutyric acid, isobutyraldehyde, ethanoyl chloride, ethanol and sec-butanol and/or 4-methylamino-pent-3-en-2-one, 4-n-butylamino-pent-3-en-2-one, 4-tert-butylamino-pent-3-en-2-one, or 4-cyclohexylamino-pent-3-en-2-one; compound (B) is selected from tetraethoxysilane, n-propyltriethoxysilane, isobutyltrimethoxysilane, dimethyldichlorosilane, n-butyltrichlorosilane, or silicon tetrachloride; compound (C) is selected from titanium tetraethoxide, titanium tetra-n-butoxide, or zirconium tetra-n-butoxide; and TiX.sub.4 is TiCl.sub.4.

18. A solid catalyst component obtainable by the process according to claim 17.

19. A process for producing polyethylene and its copolymers in the presence of the solid catalyst component according to claim 18 and a co-catalyst.

20. The process according to claim 1, wherein the molar ratio of Mg to hydroxyl groups is from 0.01 to 10; the molar ratio of compound (A) to Mg is from 0.01 to 10; the molar ratio of compound (B) to Mg is from 0.01 to 5; the molar ratio of compound (C) to Mg is from 0.01 to 5; the molar ratio of the organometallic compound to the magnesium compound is between 0.04 and 0.7; the molar ratio of the organometallic compound to the titanium halide compound is between 0.04 and 0.8; and the molar ratio of the titanium halide compound to Mg is from 0.01 to 10.

21. The process according to claim 20, wherein the organometallic compound is added before step (a).

22. The process according to claim 21, wherein the organometallic compound is added after step (c).

Description

EXAMPLES

(1) Silica was purchased from Grace Davison under the trade name of Sylopol 955 (mean particle diameter of 44 microns, a surface area of 303 m.sup.2/g and a pore volume of 1.57 cm.sup.3/g). Prior to use in catalyst preparation the silica was dehydrated by placing it in a vertical column, fluidizing under a nitrogen flow, gradually heating the column to 600 C., and then holding at that temperature for 4 hours, after which the silica was cooled to ambient temperature of about 25 C.

(2) Two procedures were used for the determination of hydroxyl (OH) group content per gram of silica after dehydration:

(3) One of the methods used to determine the hydroxyl group content in silica was based on the method described in J. J. Fripiat and J. Uytterhoeven, J. Phys. Chem. 66, 800, 1962. Dehydrated silica samples were treated with excess methylmagnesium iodide solution in tetrahydrofuran. To a flask connected to a digital pressure transducer were added 2.0 g of silica and 10.0 cm.sup.3 of decahydronaphthalene. 2.0 cm.sup.3 of a 3.0 molar solution of methylmagnesium iodide in tetrahydrofuran was then added to the flask and the content of the flasks was stirred for 30 minutes. All compounds additions were conducted under nitrogen atmosphere. The silica hydroxyl groups reacted with methylmagnesium iodide, producing an equal mole amount of methane; as a result, the pressure in the flask increased. The difference in initial pressure and pressure after reaction at a given temperature was measured and the resulted value was used to calculate the silica hydroxyl group content.

(4) Another method used to determine the hydroxyl group content in silica was by .sup.1H NMR spectroscopy on a Bruker 600 MHz NMR spectrometer, using a 5 mm probe at room temperature with deuterated tetrahydrofuran as solvent. Dehydrated silica samples were treated with excess benzyl magnesium chloride solution in tetrahydrofuran. 0.2 g of silica and 3.0 g of the benzyl magnesium chloride solution with a concentration of 1.0 wt. % were added into a vial under a nitrogen atmosphere. The vial was stirred for 30 minutes. The silica hydroxyl groups reacted with benzylmagnesium chloride producing an equal mole amount of toluene. The amount of the produced toluene was determined by .sup.1H NMR spectroscopy and the silica hydroxyl group content was calculated based on the amount of toluene produced.

(5) All the dehydrated silica samples employed in the examples were found to contain 0.90 to 1.00 mmol hydroxyl groups per gram of silica by both of the above silica hydroxyl group content analysis procedures.

(6) Gel permeation chromatography (GPC) analysis was conducted on a Polymer Lab PL-220 instrument at 160 C. using a flow rate of 1.0 cm.sup.3/min and 1,2,4-trichlorbenzene as the solvent in order to determine the number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) of the polymer resin.

(7) Melt index (MI) of the polymer resin was measured according to ASTM D1238 at a temperature of 190 C. and a load of 2.16 kg or 21.6 kg.

(8) Polymer density was measured using a density gradient column according to ASTM D2389.

(9) Bulk density was measured according to ASTM D1895.

(10) % Fines of the polymer was measured according to ASTM D1921.

Example 1

(11) Synthesis of the Solid Catalyst Components X and X2

(12) 2.5 g of Sylopol 955 silica which had been dehydrated at 600 C. for 4 hours under a nitrogen flow was placed in a 40 cm.sup.3 flask. 15 cm.sup.3 of iso-pentane was added to slurry the silica, then 1.79 mmol of di-n-butylmagnesium was added to the flask and the resultant mixture was stirred for 60 minutes at a temperature of 35 C. Then, 2.51 mmol of pentan-2-one, was added to the flask and the resultant mixture was stirred for 60 minutes at a temperature of 35 C. Then, 0.25 mmol of tetraethoxysilane was added to the flask and the resultant mixture was stirred for 30 minutes at a temperature of 35 C. Next, 0.06 mmol of tetraethylorthotitanate was added to the flask and the resultant mixture was stirred for 30 minutes at a temperature of 35 C. Subsequently, 1.75 mmol of titanium tetrachloride was added to the flask and the resultant mixture was stirred for 30 minutes at a temperature of 35 C. Finally, the slurry was dried using a nitrogen purge at 70 C. for 60 minutes to yield a free-flowing solid product.

(13) For the preparation of solid catalyst component X2 the process above for the preparation of solid catalyst component X was repeated but 0.16 mmol ethylaluminum dichloride was added before the addition of di-n-butylmagnesium. The resultant mixture was stirred for 30 minutes at a temperature of 35 C. before the addition of di-n-butylmagnesium.

(14) Synthesis of the Solid Catalyst Component X3

(15) 2.5 g of Sylopol 955 silica which had been dehydrated at 600 C. for 4 hours under a nitrogen flow was placed in a 40 cm.sup.3 flask. 15 cm.sup.3 of iso-pentane was added to slurry the silica, then 1.79 mmol of di-n-butylmagnesium was added to the flask and the resultant mixture was stirred for 60 minutes at a temperature of 35 C. Then, 3.5 mmol of pentan-2-one, was added to the flask and the resultant mixture was stirred for 60 minutes at a temperature of 35 C. Then, 0.25 mmol of tetraethoxysilane was added to the flask and the resultant mixture was stirred for 30 minutes at a temperature of 35 C. Next, 0.06 mmol of tetraethylorthotitanate was added to the flask and the resultant mixture was stirred for 30 minutes at a temperature of 35 C. Subsequently, 1.75 mmol of titanium tetrachloride was added to the flask and the resultant mixture was stirred for 30 minutes at a temperature of 35 C. Finally, 0.33 mmol ethylaluminum dichloride was added and the resultant mixture was stirred for 30 minutes at a temperature of 35 C. The slurry was dried using a nitrogen purge at 70 C. for 60 minutes to yield a free-flowing solid product.

Example 2

(16) Gas Phase Polymerization

(17) A gas phase autoclave reactor with a volume of 1.6 liters was purged with nitrogen at 120 C. for 45 minutes followed by a pressure purge with monomer three times. The reactor was then allowed to cool to room temperature. Ethylene/hydrogen (ratio 0.015) was introduced to the reactor such as to raise the reactor pressure to 20.7 bar and the reactor temperature was raised to 85 C. Then, 1.0 mmol of triethylaluminum was injected into the reactor. This was followed by injection of 60.0 mg of the solid catalyst components X, X2 and

(18) X3, respectively, after being slurried in 20 cm.sup.3 of iso-pentane. Polymerization was carried out for 1 hour, with ethylene/hydrogen supplied on demand to maintain the total reactor pressure at 20.0 bar. Polymers obtained were analyzed see table 1 below.

(19) TABLE-US-00001 TABLE 1 Catalyst component X X2 X3 Mn/g/mol 24331 24842 21768 Mw/g/mol 93000 85911 78026 MWD 3.79 3.45 3.5 MI 21.6 Kg 65.9 88.1 117.6

(20) One can see that with solid catalyst components X2 and X3, which rely on the addition of an organometallic compound before step (a) or after step (c) molecular weight can be decreased, MWD is narrower and MI can be increased versus solid catalyst components X.