GAS PHASE POLYMERISATION OF ETHYLENE

Abstract

The invention relates to a process for the production of polyethylene by gas phase polymerisation of ethylene in the presence of a supported chromium oxide based catalyst which is modified with an amino alcohol wherein the molar ratio of amino alcohol:chromium ranges between 0.5:1 and 1.5:1 wherein the support is silica having a surface area (SA) between 250 m2/g and 400 m2/g and a pore volume (PV) between 1.1 cm3/g and less than 2.0 cm3/g.

Claims

1. A process for the production of polyethylene by gas phase polymerisation of ethylene in the presence of a supported chromium oxide based catalyst composition which is modified with an amino alcohol wherein the molar ratio of amino alcohol:chromium ranges between 0.5:1 and 1.5:1, wherein the support is silica having a surface area (SA) between 450 m.sup.2/g and 550 m.sup.2/g and a pore volume (PV) between 1.7 cm.sup.3/g and 2.0 cm.sup.3/g and wherein the catalyst comprises a titanium compound.

2. The process according to claim 1 characterised in that the amount of chromium in the supported catalyst is 0.1% by weight and 0.5% by weight.

3. The process according to claim 1, characterised in that the molar ratio of amino alcohol:chromium ranges between 0.7:1 and 1.5:1.

4. The process according to claim 1, characterised in that the molar ratio of amino alcohol:chromium ranges between 1:1 and 1.3:1.

5. The process according to claim 1, characterised in that the amino alcohol has the formula ##STR00002## wherein the R groups may be, independently of one other the same or different, a C.sub.1-C.sub.10 alkyl group, and R.sup.1 is a C.sub.3-C.sub.8 cycloalkyl group or a C.sub.4-C.sub.16 alkyl substituted cycloalkyl group.

6. The process according to claim 5 characterised in that the amino alcohol is 4-(cyclohexylamino) pentan-2-ol or 4-[(2-methylcyclohexyl) amino]pentan-2-ol.

7. The process according to claim 1, characterised in that the titanium compound a compound according to the formulas Ti (OR.sup.1).sub.nX.sub.4-n and Ti (R.sup.2).sub.nX.sub.4-n, wherein R.sup.1 and R.sup.2 represent an (C.sub.1-C.sub.20) alkyl group, (C.sub.1-C.sub.20) aryl group or (C.sub.1-C.sub.20) cycloalkyl group, X represents a halogen atom, and n represents a number satisfying 0n4.

8. Polyethylene obtained with the process according to claim 1, characterised in that the polyethylene has a high-load melt index (HLMI)5 g/10 min and 10 g/10 min (according to ISO 1133); M.sub.w/M.sub.n20 and 30 (according to size exclusion chromatography (SEC) measurement); and a density 945 kg/m.sup.3 and 965 kg/m.sup.3 (according to IS01183).

9. An article prepared using the products obtained with the process according to claim 1.

10. Container, jerry can or intermediate bulk container prepared using the products obtained with the process according to claim 1.

11. The process according to claim 1 characterised in that the amount of chromium in the supported catalyst is 0.1% by weight and 0.5% by weight, the molar ratio of amino alcohol:chromium ranges between 1:1 and 1.3:1, and the amino alcohol has the formula ##STR00003## wherein the R groups may be, independently of one other the same or different, a C.sub.1-C.sub.10 alkyl group, and R.sup.1 is a C.sub.3-C.sub.8 cycloalkyl group or a C.sub.4-C.sub.16 alkyl substituted cycloalkyl group.

12. The process according to claim 11 characterised in that the titanium compound is a compound according to the formulas Ti (OR.sup.1).sub.nX.sub.4-n and Ti (R.sup.2).sub.nX.sub.4-n, wherein R.sup.1 and R.sup.2 represent an (C.sub.1-C.sub.20) alkyl group, (C.sub.1-C.sub.20) aryl group or (C.sub.1-C.sub.20) cycloalkyl group, X represents a halogen atom, and n represents a number satisfying 0n4.

Description

EXAMPLES

Example I

[0038] Catalyst I

[0039] To a 3 L three-necked round bottom flask, equipped with a condenser and a mechanical stirrer 200 g of silica average particle size of 35 micrometres, a pore volume of 1.85 ml/g and a surface area of 490 m2/g dried at 200 C. for 3 hours. 4.3 g of Chromium acetate hydroxide were added to the silica then slurried in 250 cm.sup.3 of Methanol (100%), which was stirred at 70 C. for 30 minutes. After wards drying ethanol solvent took place at 85 C. with nitrogen purge. The dried chromium salt on silica powder was cooled down to room temperature then slurried with 250 cm.sup.3 of iso-pentane, to be followed by the addition of 39 cm.sup.3 of 100% Ti(OC.sub.2H.sub.5).sub.4 (tetra ethoxy titanium) which was allowed to mix for 30 minutes at 45 C. then drying the solvent at 75 C. with nitrogen purge. For the chromium catalyst activation the dried catalyst powder was placed in the calciner and the following sequence was followed: [0040] Ramp from ambient to 150 C. in 3 hours under N2 flow then hold for 10 minutes [0041] Ramp from 150 C. to 450 C. in 3 hours [0042] At 450 C. switch from N2 to 02 flow [0043] Ramp from 450 C. to 759 C. in 3 hours under 02 [0044] Hold at 759 C. for 3 hours [0045] Cool to room temperature then switch to N2 purge. [0046] Elemental analysis: 0.35 wt % Cr and 2.9 wt % Ti

[0047] Catalyst II

[0048] Catalyst I Treated with 4-(Cyclohexylamino) Pentan-2-Ol

[0049] 5 grams of previously activated catalyst was placed in a 40 cm.sup.3 flask. 30 cm.sup.3 of isopentane was added to slurry the activated catalyst, then a 0.1 M isopentane solution of 2-(cyclohexylamino)-4-pentanol was added to the flask and the resultant mixture agitated. It then stood for 60 minutes at a temperature of 50 C. The slurry was dried under vacuum or using a nitrogen purge at a temperature of 50 C. The modified catalyst was stored under nitrogen until use. The catalyst was pale green in color. The mole ratio of 4-(cyclohexylamino) pentan-2-ol to chromium was calculated to be 1.2:1.

Comparative Example A

[0050] Catalyst A

[0051] To a three-necked round bottom flask, equipped with a condenser and a mechanical stirrer 200 g of dried silica with 0.5% Cr average particle size of 45 micrometres, a pore volume of 1.5 ml/g and a surface area of 300 m.sup.2/g at 200 C. slurried with 250 cm.sup.3 of iso-pentane, to be followed by the addition of 65 cm.sup.3 of tetraethoxy titanium Ti(OC.sub.2H.sub.5).sub.4 (100%). The contents were mixed at 35 C. for another 60 minutes followed by drying the solvent at 85 C. with nitrogen purge. For the chrome catalyst activation the dried catalyst powder was placed in the calciner and was activated in air at 825 C. for 4 hours.

[0052] Elemental analysis: 0.5 wt % Cr and 3.8 wt % Ti

[0053] Catalyst B (According to WO2012045426):

[0054] Catalyst a Treated with 4-(Cyclohexylamino) Pentan-2-Ol

[0055] 5 grams of previously activated catalyst was placed in a 40 cm.sup.3 flask. 30 cm.sup.3 of isopentane was added to slurry the activated catalyst, then a 0.1M isopentane solution of 4-(cyclohexylamino)pentan-2-ol was added to the flask and the resultant mixture agitated. It then stood for 60 minutes at a temperature of 50 C. The slurry was dried under vacuum or using a nitrogen purge at a temperature of 50 C. The modified catalyst was stored under nitrogen until use. The catalyst was pale green in color. The mole ratio of 2-(cyclohexylamino)-4-pentanol to chromium was calculated to be 1.2:1.

Example II

[0056] Ethylene Polymerisation

[0057] An autoclave with a volume of 2 liters was purged with nitrogen at 150 C. for 30 minutes. After cooling the autoclave to 90 C., one liter of isopentane was introduced to the reactor and then the reactor was pressurized up to 20 bar with ethylene. Then 0.1 ml of TEAL solution (1M) was injected into the reactor to scavenge the impurities, followed by 0.20 g of the solid Catalyst II after being slurried in 20 cm.sup.3 of isopentane. The reactor temperature was raised to 100 C. Ethylene polymerization was carried out for 1 hour, with ethylene supplied on demand to maintain the total reactor pressure at 20 bars. Upon completion of the polymerization, the reactor was vented and cooled to ambient temperature to recover the polymer.

[0058] 346 grams of polyethylene were recovered giving a catalyst productivity of 1,730 g PE/g cat h at 200 psig.

[0059] The characteristics of the obtained polyethylene: [0060] weight average molecular weight: 325,000 [0061] number average molecular weight: 13,000 [0062] molecular weight distribution: 25 [0063] resin bulk density: 460 kg/m.sup.3.

Comparative Example B

[0064] Ethylene Polymerisation

[0065] An autoclave with a volume of 2 liters was purged with nitrogen at 150 C. for 30 minutes. After cooling the autoclave to 90 C., one liter of isopentane was introduced to the reactor and then the reactor was pressurized up to 20 bar with ethylene. Then 0.1 ml of TEAL solution (1 M) was injected into the reactor to scavenge the impurities, followed by 0.20 g of the solid Comparative Catalyst B after being slurried in 20 cm.sup.3 of isopentane. The reactor temperature was raised to 100 C. Ethylene polymerization was carried out for 1 hour, with ethylene supplied on demand to maintain the total reactor pressure at 20 bars. Upon completion of the polymerization, the reactor was vented and cooled to ambient temperature to recover the polymer.

[0066] 232 grams of polyethylene were recovered giving a catalyst productivity of 1,160 g PE/g cat h at 200 psig.

[0067] The characteristics of the obtained polyethylene: [0068] weight average molecular weight: 265,000 [0069] number average molecular weight: 12,045 [0070] molecular weight distribution: 22 [0071] resin bulk density: 350 kg/m.sup.3.

[0072] Picture 1 shows the polymer obtained with the comparative catalyst B.

[0073] Pictures 2 and 3 show the polymer obtained with the catalyst II (different magnifications).