Catalyst system and process for the production of polyethylenes

Abstract

The present invention relates to a catalyst system for the production of polyethylene comprising: I) the reaction product obtained by reacting a) a hydrocarbon solution comprising: i. a magnesium-containing compound selected from an organic oxygen-containing magnesium compound and/or a halogen-containing magnesium compound; and ii. an organic oxygen-containing titanium compound wherein the molar ratio of magnesium:titanium is lower than 3:1; and b) an organo aluminium halide having the formula AlR.sub.nX.sub.3-n in which R is a hydrocarbon moiety containing 1-10 carbon atoms, X is a halogen and 0<n<3; II) an aluminium compound having the formula AlR.sub.3, in which R is a hydrocarbon moiety containing 1-10 carbon atoms; and III) one or more of an electron donor selected from the group of 1,2-dialkoxy hydrocarbon compounds wherein the molar ratio of supplied organo aluminium halide I)b) to supplied titanium in I)a) in the preparation of I) is between 5.0 and 7.0; and the molar ratio of the electron donor III) to the titanium present in the reaction product I) is between 0.05 and 0.40 The production of polyethylene using said catalyst system results in a reduction of formation of ethane and a reduction of the hexane-extractable content of the polyethylene.

Claims

1. A catalyst system for the production of polyethylene comprising: I) the reaction product obtained by reacting a) a hydrocarbon solution comprising: i. a magnesium-containing compound selected from an organic oxygen-containing magnesium compound and/or a halogen-containing magnesium compound; and ii. an organic oxygen-containing titanium compound wherein the molar ratio of magnesium:titanium is lower than 3:1; and b) an organo aluminium halide having the formula AlR.sub.nX.sub.3-n in which R is a hydrocarbon moiety containing 1-10 carbon atoms, X is a halogen and 0<n<3; II) an aluminium compound having the formula AlR.sub.3, in which R is a hydrocarbon moiety containing 1-10 carbon atoms; and III) an electron donor selected from the group of 1,2-dialkoxy hydrocarbon compounds wherein the molar ratio of supplied organo aluminium halide I)b) to supplied titanium in I)a) in the preparation of I) is between 5.0 and 7.0; and the molar ratio of the one or more of an electron donor III) to the titanium present in the reaction product I) is between 0.05 and 0.40.

2. The catalyst system according to claim 1 wherein the electron donor III) comprises an external electron donor.

3. The catalyst system according to claim 1, for the production of polyethylene wherein the production of polyethylene is performed in a slurry polymerisation process.

4. The catalyst system according to claim 1, wherein the electron donor is selected from the group of 1,2-dialkoxy hydrocarbon compounds represented by the formula (I): ##STR00003## wherein C.sub.1-C.sub.2 is a connecting group consisting of 2 carbon atoms which are in the sp.sup.3 and/or sp.sup.2 hybridisation form and wherein the substituents R and R are hydrocarbon groups with 1-10 carbon atoms and may be the same or different and may optionally be substituted with other heteroatom-containing groups.

5. The catalyst according to claim 1, wherein the electron donor is selected from the group of 1,2-dialkoxy hydrocarbon compounds of formula (II) or (III): ##STR00004## wherein the substituents R are selected from hydrocarbon groups with 1-10 carbon atoms or hydrogen and may be the same or different and may optionally be substituted with other heteroatom-containing groups, and may join with one or more of other substituents R to form cyclic groups.

6. The catalyst system according to claim 1, wherein the electron donor is selected from 1,2-dimethoxybenzene, 1,2,4-trimethoxybenzene, 1,2-diethoxybenzene, 2,3-dimethoxytoluene, 1-allyl-3,4-dimethoxybenzene, 1,2-dimethoxyethane, 1,2-dimethoxy cyclohexane, 1,2-dimethoxypropane, 1,2-dimethoxybutane, or 2,3-dimethoxybutane.

7. A process for the production of a polyethylene, the process comprising polymerizing ethylene in the presence of the catalyst system according to claim 1 to produce a polyethylene, wherein the polyethylene has a density of 935 kg/m.sup.3 and 975 kg/m.sup.3 as measured in accordance with ISO 1183-1 (2012), method A.

8. The process according to claim 7 wherein the polyethylene is a multimodal polyethylene.

9. The process for the production of polyethylene according to claim 7, wherein the process is a multi-stage slurry polymerisation process comprising at least two stages.

10. The process according to claim 9 wherein ingredient I) and II) of the catalyst system are introduced in the first stage of said multi-stage polymerisation process, and wherein ingredient III) is introduced in any of the stages of said multi-stage slurry polymerisation process.

11. The process according to claim 7, wherein the polyethylene has a melt flow rate of greater than or equal to 60.0 g/10 min, as determined in accordance with ISO 1133-1 (2011), at a temperature of 190 C. and a load of 21.6 kg.

12. The process according to claim 7, wherein the polyethylene has a hexane-extractable content of less than 2.00 wt %.

13. The process according to claim 12, wherein the hexane-extractable content is less than 1.50 wt %.

14. The process according to claim 7, wherein a fraction of ethane formed during polymerization is lower than 0.25 volume percent.

15. The process according to claim 7, wherein a fraction of ethane formed during polymerization is lower than 0.30 volume percent; wherein the polyethylene has a hexane-extractable content is less than 2.00 wt %; and wherein the polyethylene has a melt flow rate of greater than or equal to 60.0 g/10 min, as determined in accordance with ISO 1133-1 (2011), at a temperature of 190 C. and a load of 21.6 kg.

16. The process according to claim 15, wherein the hexane-extractable content is less than 1.50 wt %.

17. The process according to claim 15, wherein a fraction of ethane formed during polymerization is lower than 0.25 volume percent.

18. The catalyst system according to claim 1, wherein: the magnesium-containing compound is magnesium ethoxide; the organic oxygen-containing titanium compound is Ti(OC.sub.4H.sub.9).sub.4, the molar ratio of magnesium:titanium is equal to or greater than 1.5:1 and lower than 3:1; the organo aluminium halide having the formula AlR.sub.nX.sub.3-n is ethyl aluminium dichloride; the aluminium compound having the formula AlR.sub.3 is trietyl aluminium or triisobutyl aluminium; and the electron donor is selected from the group consisting of 1,2-dimethoxybenzene and 1-allyl-3,4-dimethoxybenzene.

Description

EXAMPLES

(1) Experiment I: Preparation of Ingredient I) of the Catalyst System

(2) Experiment IA: Preparation of Ingredient I)a)

(3) Under a nitrogen atmosphere, 132.5 g of granular Mg(OC.sub.2H.sub.5).sub.2 and 199 ml of Ti(OC.sub.4H.sub.9).sub.4, both at a temperature of 25 C. were introduced into a 2 l round bottom flask equipped with a reflux condenser and a stirrer. Under gentle stirring, the mixture was heated to 180 C., and subsequently stirred for 90 min. A clear liquid was obtained. The contents of the round bottom flask were cooled to 120 C., and subsequently diluted with 1318 g hexane. The contents of the round bottom flask were cooled to 67 C. The temperature was maintained at 67 C. for 120 min, and subsequently cooled down to 25 C. The resulting solution was stored under nitrogen atmosphere. Analysis of the solution showed a titanium concentration of 0.29 mol/l.

(4) Experiment IB: Preparation of Ingredient I)

(5) 311 ml hexane and 149 ml of the solution obtained from experiment IA, both at a temperature of 25 C., were introduced into a 1.0 l glass reactor equipped with baffles, a reflux condenser and a stirrer. The reactor was stirred at a stirring speed of 1400 rpm. In a separate Schlenk flask, 75 ml of a 50 wt % solution of ethyl aluminium dichloride in hexane was added to 43 ml hexane. The resulting solution was introduced into the glass reactor gradually over a period of 15 min using a peristaltic pump. The Schlenk flask was rinsed with 45 ml of hexane, and the contents of the flask were also added to the glass reactor. Subsequently, the contents of the glass reactor were refluxed for 120 min, after which the contents of the glass reactor were cooled down to 25 C. A suspension was obtained. The suspension was transferred under nitrogen to a glass filter of grade P16 in accordance with ISO 4793 (1980) to separate the solid material. The obtained solid material was subjected to 3 washings, using 500 ml of hexane for each washing. Subsequent to washing, the solid material was suspended in 500 ml hexane and stored under nitrogen atmosphere. Analysis of the solid material showed the solid material to comprise 10.1 wt % titanium compared to the total weight solid material.

(6) Experiment IC: Preparation of Ingredient I)a)

(7) Under a nitrogen atmosphere, 100.0 g of granular Mg(OC.sub.2H.sub.5).sub.2 and 150 ml of Ti(OC.sub.4H.sub.9).sub.4, both at a temperature of 25 C. were introduced into a 2 l round bottom flask equipped with a reflux condenser and a stirrer. Under gentle stirring, the mixture was heated to 180 C., and subsequently stirred for 90 min. A clear liquid was obtained. The contents of the round bottom flask were cooled to 120 C., and subsequently diluted with 1480 ml hexane. The contents of the round bottom flask were cooled to 67 C. The temperature was maintained at 67 C. for 120 min, and subsequently cooled down to 25 C. The resulting solution was stored under nitrogen atmosphere. Analysis of the solution showed a titanium concentration of 0.25 mol/l.

(8) Experiment ID: Preparation of Ingredient I)

(9) 262 ml hexane and 162 ml of the solution obtained from experiment IC, both at a temperature of 25 C., were introduced into a 1.0 l glass reactor equipped with baffles, a reflux condenser and a stirrer. The reactor was stirred at a stirring speed of 1400. In a separate Schlenk flask, 98 ml of a 50 wt % solution of ethyl aluminium dichloride in hexane was added to 56 ml hexane. The resulting solution was introduced into the glass reactor gradually over a period of 15 min using a peristaltic pump. The Schlenk flask was rinsed with 45 ml of hexane, and the contents of the flask were also added to the glass reactor. Subsequently, the contents of the glass reactor were refluxed for 120 min, after which the contents of the glass reactor were cooled down to 25 C. A suspension was obtained. The suspension was transferred under nitrogen to a glass filter of grade P16 in accordance with ISO 4793 (1980) to separate the solid material. The obtained solid material was subjected to 3 washings, using 500 ml of hexane for each washing. Subsequent to washing, the solid material was suspended in 500 ml hexane and stored under nitrogen atmosphere. Analysis of the solid material showed the solid material to comprise 11.1 wt % titanium compared to the total weight solid material.

(10) Experiment II: Polymerisation

Examples 1-5 and Comparative Examples 6-8

(11) Polymerisation was carried out in a 20 l autoclave reactor. 10 l hexane as diluent was fed to the reactor. The reactor was heated to 85 C. The reactor comprised a headspace in which the reactants were dosed in gaseous form. Ethylene was fed to obtain an ethylene partial pressure of the gas in the headspace of the reactor of 1.6 bar. Hydrogen was fed in such quantity as to ensure a hydrogen to ethylene ratio by volume of 0.50 v/v. 1-Butene was fed in such quantities as to ensure a 1-butene to ethylene ratio by volume of 0.07 v/v. 8 mmol of a cocatalyst as presented in table 1 was added to the reactor. A quantity of a solution of an electron donor as presented in table 1 was added in order to obtain a donor:Ti ratio as presented in table 1. A quantity of the slurry obtained in experiment I containing 10 mg of the ingredient I) as indicated in table 1 was dosed. The temperature was maintained at 85 C., and the pressure was kept constant by feeding ethylene. The hydrogen to ethylene ratio by volume was maintained at 0.50 v/v by feeding hydrogen. The 1-butene to ethylene ratio by volume was maintained at 0.07 v/v by feeding 1-butene. The ethylene uptake was monitored to calculate the quantity of polymer produced during the reaction. The reaction was stopped after 120 min by depressurizing the reactor to atmospheric conditions, and the reactor contents were cooled to 30 C., after which the reactor contents were passed over a polyamide filter cloth having a pore size of 25 m. The polymer powder was collected and subsequently dried.

(12) In table 1, the catalyst composition using in the polymerisation experiments are presented.

(13) TABLE-US-00001 TABLE 1 Catalyst Ingredient I) from Al:Ti Electron Donor:Ti Example experiment ratio donor ratio Cocatalyst 1 IB 6.0 DMB 0.10 TiBA 2 IB 6.0 ME 0.10 TiBA 3 IB 6.0 ME 0.10 TEA 4 IB 6.0 DMB 0.05 TiBA 5 IB 6.0 DMB 0.50 TiBA 6 IB 6.0 TiBA 7 ID 8.5 DMB 0.25 TiBA 8 ID 8.5 TiBA

(14) In table 1, the Al:Ti ratio represents the molar ratio of supplied titanium in the preparation of ingredient I) of the catalyst system of the present invention to the aluminium halide in ingredient I).

(15) DMB=1,2 dimethoxybenzene

(16) ME=methyl eugenol (1-allyl-3,4-dimethoxybenzene)

(17) TiBA=tri isobutyl aluminium

(18) TEA=triethyl aluminium

(19) The donor:Ti ratio represents the molar ratio of the electron donor III) to the titanium present in I).

(20) In table 2, features of the polymers produced and the polymerisation process in examples 1-5 and comparative examples 6-8 are presented.

(21) TABLE-US-00002 TABLE 2 Hexane- extractable Ethane MFR(5) MFR(21.6) Density content formation Example (g/10 min) (g/10 min) (kg/m.sup.3) (wt %) (v %) 1 8.1 72.2 943 0.94 0.20 2 10.9 94.4 945 0.98 0.19 3 10.3 88.5 945 0.65 0.19 4 13.1 110.5 944 0.65 0.17 5 5.6 49.8 942 6 13.4 118.2 943 0.86 0.20 7 4.26 40.8 938 2.02 0.17 8 11.4 113.6 942 4.30 0.38

(22) MFR(5) represents the melt mass flow rate as determined in accordance with ISO 1133-1 (2011), at a temperature of 190 C. and a load of 5.0 kg.

(23) MFR(21.6) represents the melt mass flow rate as determined in accordance with ISO 1133-1 (2011), at a temperature of 190 C. and a load of 21.6 kg.

(24) The density is determined in accordance with ISO 1183-1 (2012), method A.

(25) The wt % hexane-extractable content is determined according to the aforementioned method.

(26) The v % of ethane formation is determined according to the aforementioned method.

(27) Examples 1-5, compared to comparative examples 6-8, demonstrate that only by selecting a catalyst system according to the present invention, in which the molar ratio of supplied titanium in I)a) to the aluminium halide I)b) is between 5.0 and 7.0; and the molar ratio of the electron donor III) to the titanium present in I) is between 0.05 and 0.40, result in a reduction of hexane-extractable content formation and ethane formation, whilst resulting in a polymer product having desired melt flow rate as reflected by MFR(5) and MFR(21.6), as well as a desired density.