CHROMIUM-BASED CATALYST COMPONENT COMPRISING A MODIFIED INORGANIC OXIDE SUPPORT

Abstract

The present invention relates to a catalyst component comprising an inorganic oxide supported chromium, wherein said inorganic oxide support has been modified by a metal halide modifier, preferably aluminum trichloride or aluminum trichloride hexahydrate. The present invention also relates to a process for obtaining such a catalyst component, a catalyst system comprising said catalyst component and a process for the polymerization of olefins using said catalyst system.

Claims

1. A process for preparing an inorganic oxide-supported chromium catalyst component, said process comprises: 1) providing an inorganic oxide support; 2) modifying said support by a metal halide modifier, wherein said step of modifying comprising the sub steps of: 2a) contacting said support provided in step 1) with said metal halide modifier to obtain an intermediate product; and 2b) applying a heat treatment to said intermediate product obtained in step 2a) at a temperature between 400 and 800° C. to obtain a metal-modified support; 3) contacting said metal-modified support obtained in step 2b) with a silyl chromate compound to obtain the catalyst component.

2. The process according to claim 1, wherein said inorganic oxide is silica.

3. The process according to claim 1, wherein said metal halide of step 2a) and said silyl chromate of step 3) are used in such amounts that the resulting catalyst component comprises, in wt. % based on the total weight of the catalyst component, between 0.1 and 7.0 metal from modifier and between 0.1 and 3.0 chromium.

4. The process according to claim 1, wherein aluminum trichloride (AlCl.sub.3) or aluminum trichloride hexahydrate (AlCl.sub.3(H.sub.2O).sub.6) is used as the metal halide in step 2a).

5. The process according to claim 1, wherein bis-triphenyl silyl chromate is used as the silyl chromate in step 3).

6. The process according to claim 2, wherein said metal-modified support obtained in step 2b) is a metal-oxo-chloride modified silica in case that aluminum trichloride is used or wherein said metal-modified support obtained in step 2b) is a metal-oxo modified silica in case that aluminum trichloride hexahydrate is used.

7. A catalyst component comprising an inorganic oxide supported chromium, characterized in that said inorganic oxide support has been modified by a metal halide modifier, wherein said catalyst component comprises in wt. % based on the total weight of the catalyst component, between 0.1 and 7.0 metal, and between 0.1 and 3.0 chromium.

8. A catalyst component according to claim 7 wherein said metal is selected from the group consisting of aluminum, boron, gallium, zinc, copper, thallium, indium, vanadium, chromium, and iron.

9. The catalyst component according to claim 8 that is obtainable by the process comprising 1) providing an inorganic oxide support; 2) modifying said support by a metal halide modifier, wherein said step of modifying comprising the sub steps of: 2a) contacting said support provided in step 1) with said metal halide modifier to obtain an intermediate product; and 2b) applying a heat treatment to said intermediate product obtained in step 2a) at a temperature between 400 and 800° C. to obtain a metal-modified support; 3) contacting said metal-modified support obtained in step 2b) with a silyl chromate compound to obtain the catalyst component.

10. A polymerization catalyst system comprising the catalyst component according to claim 8.

11. The polymerization catalyst system according to claim 10, wherein said co-catalyst is an alkyl aluminum alkoxide.

12. A process of preparing a polyolefin by contacting at least one olefin with a polymerization catalyst system according to claim 10 under polymerization conditions.

13. The process according to claim 12, wherein the olefin is ethylene or a mixture of ethylene and a comononer.

14. A polyethylene obtainable by the process of claim 13.

15. A polyethylene according to claim 14, having a high load melt index between 1 and 20.

Description

DESCRIPTION OF THE DRAWINGS

[0087] FIGS. 1-15 are GPC traces obtained for examples 1-15 respectively.

DETAILED DESCRIPTION OF THE INVENTION

[0088] The present invention is described below in more detail. All embodiments described with respect to one aspect are also applicable to the other aspects of the invention, unless otherwise stated.

[0089] The present invention is involved with the modification of a support for a silyl chromate catalyst component or—stated otherwise—the addition of a second metal active site (e.g. aluminum) beside chromate. This additional secondary metal aluminum active site changes the behaviour of the primary chromium active site of the catalyst component.

[0090] As stated above the present process for preparing a polymerization catalyst component, comprising three steps. Each of which will be described in more detail below.

Step 1) Inorganic Oxide Support

[0091] The first step in the preparation of the catalyst component consist in a step of providing an inorganic oxide support. During the remainder of this detailed description silica will be used as example of the inorganic support, although the invention is not limited thereto.

[0092] The inorganic support used for the present invention is preferably silicon dioxide or silica (SiO.sub.2).

[0093] The silica that is useful as support according to the present invention may have a surface area (SA) larger than 150 m.sup.2/g and pore volume (PV) larger than 0.8 cm3/g. Examples of a suitable support for the preparation of silyl chromate based catalyst are the commercially available silica grades from W. R. Grace & co. (USA) being 955W and 4802, from PQ corp. (USA), being ES70, ES70W, MS3050, MS3040, from Asahi Glass Co. (Japan) being M302F, H302F, H202F.

[0094] According to a further optional embodiment of the invention—preferably when a non-hydrate metal modifier is used—water and other volatile compounds are removed from the support before it is modified. This can e.g. be carried out by heat activation of the support in a stream of an inert gas. An example of a suitable inert gas is nitrogen.

[0095] The inorganic oxide support is preferably provided in the form of particles.

[0096] Preferably, the particles have a size of between 10 and 100 micrometre. The particle size distribution of the particles is preferably between 42 and 50, more preferably between 45 and 47, as measured by ATSM D-4464-10. It can also be measured by ISO 13320:2009.

[0097] Surface area of the inorganic oxide support is preferably between 100 and 1000 m.sup.2/gram and more preferably between 250 to 500 m.sup.2/gram, even more preferably between 300 and 320 m.sup.2/gram, as measured by a static volumetric measurement technique according to ASTM (D-3663-03).

[0098] The pore volume (or porosity or void fraction) of the inorganic oxide support is preferably between 0.5 and 3.5 milliliters/gram, more preferably between 1.4 and 1.6 ml/gram, as measured by a static volumetric measurement technique according to ASTM (D-4222-03).

Step 2) Modification of Support

[0099] The second step in the preparation of the catalyst component relates to the modification of the inorganic support. More precisely, the surface of the particles is modified by means of a metal modifier, wherein the metal is selected from Group 13 or the Periodic Table of elements and chromium, iron, vanadium, copper and zinc (viz. aluminum, boron, gallium, zinc, copper, thallium, indium, vanadium, chromium, and iron). Most preferably, said metal modifier is an aluminum modifier. Said metal modifier is preferably a monohalide, dihalide or trihalide of said metal, wherein the halide is selected from fluoride, chloride, bromide and iodide. Most preferably, said metal modifier only has halide ligands. In other words, the number of halide ligands is the same as the oxidation state of the metal. Preferably, all halide ligands are the same. When a metal halide is used (being an aluminum metal modifier) and silica is used as the support, the metal (e.g. aluminum) halide reacts with silanol (Si—OH) groups that are present at the surface of the silica particles. This step comprises two sub steps being, firstly contacting the support with the modifier and secondly applying a heat treatment.

[0100] According to the present invention non-limiting examples of suitable modifiers are the following. It should be noted that in the description of the present invention boron is considered to be a “metal” in the context of a “metal modifier”: aluminum trichloride, aluminum tribromide, aluminum triiodide, aluminum trifluoride, boron trichloride, boron tribromide boron triiodide, boron trifluoride, gallium trichloride, gallium tribromide, gallium triiodide, gallium trifluoride, zinc dichloride, zinc dibromide, zinc diiodide, zinc difluoride, copper dichloride, copper dibromide, copper diiodide, copper difluoride, copper chloride, copper bromide, copper iodide, copper fluoride, thallium trichloride, thallium tribromide, thallium triiodide, thallium trifluoride, thallium chloride, thallium bromide, thallium iodide, thallium fluoride, indium trichloride, indium tribromide, indium triiodide, indium trifluoride, vanadium trichloride, vanadium tribromide, vanadium triiodide, vanadium trifluoride, chromium trichloride, chromium dichloride, chromium tribromide, chromium dibromide, iron dichloride, iron trichloride, iron tribromide, iron dichloride, iron triiodide, iron diiodide, iron trifluoride, iron difluoride. Each of these can be used in a non-hydrate or hydrate form. A combination of two or more modifiers, either non-hydrate, hydrate or both may also be used. Most preferably aluminum trichloride in either a non-hydrate or hexahydrate form.

Step 2a) Metal Halide Modifier Added to Support

[0101] This step is related to the addition of a metal halide to the support.

[0102] The modifier can be added to the support in a number of ways. For example, the support can be suspended in a solvent to which the modifier is added as such. Or a solution of the modifier can be made prior to contact with the support in suspension. It is preferred that a solution of modifier is used. More preferably, the solvents used for the suspension of the support and the solution of the modifier are similar or even the same.

[0103] Preferably, metal trihalides (e.g. aluminum trihalide) are used as the modifier, because it was found by the present inventors that during the step of heat treatment one or two halides are lost and the remaining halide(s) provide the metal-oxo or metal-oxo-chloride structure (for a hexahydrate and non-hydrate respectively) that will bond to the chromium and lower its acidity. The most preferred modifier is aluminum trichloride non-hydrate or aluminum trichloride hexahydrate.

[0104] The amount of metal halide used can be selected based on the percentage metal that is desired in the modified support. This can be used to tune the properties of the final catalyst component.

[0105] Preferably, the metal loading from the modifier (the amount of modifier metal present in the modified silica) is between 0.05 and 5.0 wt. %, preferably between 0.1 or even 0.4 and 1.2 wt. %, more preferably 0.8 wt. %. the present inventors have found that for an non-hydrate aluminum halide modifier when the amount of aluminum loading exceeded 5.0 wt. % the productivity dropped by 90% which is undesirable.

[0106] In an embodiment, the metal modifier is a non-hydrate aluminum and the aluminum loading (the amount of aluminum present in the modified silica) is between 0.05 and 5.0 wt. %, preferably between 0.1 or even 0.4 and 1.2 wt. %, more preferably 0.8 wt. %.

[0107] In an embodiment, the metal modifier is a hydrate aluminum and the aluminum loading (the amount of aluminum present in the modified silica) is between 0.1 and 5.0 wt. %, preferably between 0.4 and 1.2 wt. %, more preferably 0.8 wt. %.

[0108] Suitable solvents for both preparing the support suspension as a solution of the modifier are solvents having a boiling point above 50° C., preferably above 60° C. Solvents when using a non-hydrate modifier are preferably ethers (e.g. dibutyl ether, tetrahydrofuran, dioxane), chlorinated alkanes (e.g. chloroform), acetates (e.g. ethyl acetate), hydrocarbon solvents, more preferably selected from the group of alkanes (e.g. hexane, heptane, octane), aromatics (e.g. benzene, toluene). Preferably, the solvent is dibutylether when using a non-hydrate modifier.

[0109] Solvents when using a hydrate modifier are preferably polar solvents. Most preferably, the solvent is water when using a hydrate modifier.

[0110] The reaction is preferably carried out at a temperature between 30° C. and 70° C., more preferably 40° C. and 50° C.

[0111] The reaction mixture of silica and solvent is preferably premixed under stirring to provide a stable suspension before the modifier is added. This ensures an even distribution of the metal-oxo(-chloride) groups over the silica surface. Preferably, the stirring speed during premixing is between 200 and 600 ppm, more preferably between 300 and 500 rpm, such as between 350 and 450 rpm or 400 rpm.

[0112] Preferably, a solution of modifier contains between 5 and 40 wt. %, preferably between 10 and 30 wt. %, more preferably between 15 and 25 wt. % of modifier based on the total weight of the solution. When the solution is more diluted insufficient reaction will occur with the support. When the solution is more concentrated there might be a less homogeneous distribution of the metal-oxo(-chloride) groups over the silica surface. The solution of modifier is preferably added over a period of time to the silica suspension. For example, over a period of between 1 and 20 minutes, preferably between 5 and 15 minutes, more preferably between 8 and 12 minutes.

[0113] The total mixture (suspension of silica and solution of modifier) is mixed at a temperature of 30° C. and 70° C., more preferably 40° C. and 50° C. The temperature is preferably the same as for the preparation of the suspension of support above.

[0114] The duration of this reaction step is preferably between 10 minutes and 3 hours, more preferably between 30 minutes and 2 hours, such as 1 hour.

[0115] Preferably, the stirring speed during mixing is between 200 and 600 ppm, more preferably, between 300 and 500 rpm, such as between 350 and 450 rpm or 400 rpm. Preferably, the speed of mixing is the same as during the step of premixing the support and solvent.

[0116] Upon completion of the modification reaction, the solvent may be partially or completely removed. This removal may be by any known techniques, e.g. by filtration, decantation or by evaporation, preferably vacuum evaporation (e.g. rotary evaporation) but evaporation by heating is also possible. Preferably, the solvent is completely removed.

Step 2b) Heat Treatment

[0117] The second sub step in this modification process is a heat treatment or thermal treatment. This heat treatment ensures that a metal-oxo(-halide) is formed, bound to the silica surface.

[0118] The heat treatment is carried out at a temperature between 400 and 800° C. Preferably, the heat treatment is carried out at temperatures between 500 and 700° C., more preferably between 550° C. and 650° C., even more preferably between 580 and 620° C.

[0119] The heat treatment is preferably carried out for a period of between 30 minutes and 10 hours, more preferably between 1 and 5 hours, even more preferably between 2 and 4 hours.

[0120] The heat treatment is for example carried out in a fluidized bed furnace. The heat treatment is preferably carried out in an atmosphere of air. The heat treatment is preferably carried out at ambient pressure. However the use of either elevated pressure (e.g. until 1.0 bar) or reduced pressure (e.g. until −1.0 bar) is also possible.

[0121] After the heat treatment, preferably the solid support is cooled to room temperature under an inert atmosphere (viz. an atmosphere without oxygen, e.g. a nitrogen atmosphere) and subsequently stored in an inert atmosphere.

[0122] After this step the solid, modified support may be subjected to analysis to determine the amount of aluminum that is present. The method of analysis is discussed in the Example section below.

[0123] The modification step 2) (combination of 2a) and 2b) leads to the addition of either metal-oxo-halide or metal-oxo to the silica support. This has been found by the present inventors to increases the acidity of the support, which becomes more electron withdrawing. If was found by the present inventors, that the presence of aluminum-oxo(-chloride) creates another active site in addition to chromium for the production of high molecular weight HDPE polymer chains resulting in e.g. bimodal resin (see Examples 12 and 13) with broad molecular weight distribution due to the dual character of the active site. Preferably, a MWD of above 35 or even above 50 is obtained. By tuning the percentage of aluminum-oxo(-chloride) present on the support, MW, MWD and crystallinity can be controlled. By adding more modifier to modify the solid support, the higher the MWD will be. However, simultaneously a decrease in productivity is observed for the non-hydrate modifier. A balance between a high MWD and a sufficiently high productivity should be sought. The present inventors also found that when using a hexahydrate aluminum chloride, aluminum-oxo species are formed with lead to the production of monomodal HDPE with a higher productivity (see Examples 14 and 15).

Step 3) Chromation of Modified Support

[0124] During this step the active site chromium is added to the support. A silyl chromate is added to the modified support obtained from step 2). The silyl chromate may be added in an amount that is sufficient to obtain the desired chromium content. For example, the silyl chromate may be added in a weigh ratio of silyl chromate to support of 1:100 to 1:5, preferably between 1:60 and 1:10, such as between 1:10 and 1:30.

[0125] The silyl chromate compounds suitable for the present invention have one or more groups of the following formula:

—[Si(R).sub.2—O—Cr(═O).sub.2—O]—

wherein R can be any hydrocarbyl group having from 1 to about 14 carbon atoms.

[0126] Among the preferred compounds—in other words preferred silyl chromate compounds—containing said groups are the bis-trihydrocarbyl-silyl-chromates of the following formula:

Si(R).sub.3—O—Cr(═O).sub.2—O—Si(R).sub.3

wherein R is any hydrocarbyl group containing from 1 to about 14 carbon atoms, preferably from about 3 to about 10 carbon atoms. R can e.g. be an alkyl, alkylaryl, aryl, aralkyl group, preferably an aryl group because these are the most stable. Examples of the R groups are the following: methyl, ethyl, propyl, iso-propyl, iso-butyl, n-pentyl, isopentyl, hexyl, 2-methyl-pentyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, dodecyl, tridecyl, tetradecyl, benzyl, phenetyl, p-methylbenzyl, phenyl, tolyl, xylyl, naphtyl, ehtylphenyl, methylnapthyl, dimethylnaphtyl, and others. Examples of more preferred silyl chromates are the following: bis-trimethyl-silyl-chromate, bis-triethyl-silyl-chromate, bis-tributyl-silyl-chromate, bis-triisopentyl-silyl-chromate, bis-tri-2-ethylhexyl-silyl-chromate, bis-tridecyl-silyl-chromate, bis-tri(tetradecyl)-silyl-chromate, bis-tribenzyl-silyl-chromate, bis-triphenetyl-silyl-chromate, bis-triphenyl-silyl-chromate, bis-tritolyl-silyl-chromate, bis-trixylyl-silyl-chromate, bis-trinaphtyl-silyl-chromate, bis-triethylphenyl-silyl-chromate, bis-trimethylnaphtyl-silyl-chromate, polydiphenylsilyl-chromate, polydiethylsilyl-chromate and the like.

[0127] Most preferred are the trisaryl-silyl-chromates because of their stability at room temperature and even under ambient air for up to several hours.

[0128] Suitable solvents for this step are solvents having a boiling point above room temperature (23° C.). Solvents are preferably hydrocarbon solvents, more preferably selected from the group of alkanes (e.g. isopentane, hexane, heptane, octane), aromatics (e.g. benzene, toluene), chlorinated alkanes (e.g. chloroform). Preferably, the solvent is isopentane.

[0129] The reaction mixture of modified silica and solvent is preferably premixed under stirring to provide a stable suspension before the silyl chromate is added. This ensures an even distribution of the chromate active sites over the silica surface. Preferably, the stirring speed during premixing is between 200 and 600 ppm, more preferably between 300 and 500 rpm, such as between 350 and 450 rpm or 400 rpm.

[0130] The reaction of step 3) is preferably carried out at room temperature (23° C.). Elevated temperatures up to 40 or 50° C. are also possible.

[0131] The total mixture (suspension of modified silica and chromate) is mixed for a duration of preferably between 10 minutes and 3 hours, more preferably between 30 minutes and 2 hours, such as 1 hour.

[0132] Preferably, the stirring speed during mixing is between 200 and 600 ppm, more preferably between 300 and 500 rpm, such as between 350 and 450 rpm or 400 rpm. Preferably, the speed of mixing is the same as during the step of premixing the modified support and solvent.

[0133] At the end of this step 3) a catalyst component is obtained. Preferably, the catalyst component comprises in wt. % based on the total weight of the catalyst component: [0134] Aluminum or other modifier-metal: between 0.05 and 7.0 wt. % [0135] Chromium: between 0.1 and 3.0 wt. %

[0136] The obtained catalyst component may be used as such (in a solvent) or may be isolated as a solid. It may be further washed, preferably with the solvent also used during the reaction; and then stored and further used as a suspension in said inert solvent. Alternatively, the product may be dried, preferably partly dried, preferably slowly and under mild conditions; e.g. at ambient temperature and pressure.

Preparation of the Catalyst System

[0137] After step 3) has been carried out and a catalyst component is being prepared a co-catalyst may be added to obtain a catalyst system. A co-catalyst is present in order to increase the activity of the catalyst component formed.

[0138] Examples of co-catalyst are alkyl aluminum alkoxides having a formula of:

R.sub.2—Al—OR.sub.2

wherein R.sub.2 can be an alkyl group having one to 12 carbon atoms, e.g. methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, hexyl, cyclohexyl, heptyl, cycloheptyl, and wherein OR.sub.2 can be an alkoxy or aryloxy group, wherein R.sub.2 can be selected from the same group as cited above, but may also be an aryl group having 6 to 20 carbon atoms, e.g. phenyl, tolyl, xylyl, mesityl, benzyl, phenyl and naphthyl. The R.sub.2 groups can be the same or different. The most preferred co-catalyst is diethylaluminum ethoxide (Et.sub.2AlEtO, known as DELOX).

[0139] Preferably, said co-catalyst is added prior to the polymerization reaction to a suspension of said catalyst component. Preferably, said co-catalyst is added in form of a solution. Said co-catalyst may also be added during the polymerization.

Ratio of Metals in Catalyst Component

[0140] The amount of chromium in the catalyst component is generally at least 0.1% by weight. The amount of chromium in the catalyst component is generally at most 1.2% by weight.

[0141] When an aluminum-based co catalyst is used, the molar ratio of aluminum (co-catalyst) to chromium (catalyst component) ranges between 0.1:1 and 25:1, preferably 0.1:1 and 10:1.

[0142] The loading of chromium (weight percentage wt. %) in the final catalyst component preferably ranges between 0.1 and 1.2.

Polymerization Process

[0143] The polymerization process can be carried out in different manners, for example under high pressure, in solution, in slurry and in gas phase. It can be carried out continuously or batch wise. A person skilled in the art will be able to determine the optimal conditions.

[0144] During the polymerization process, preferably, a solvent is present, also being described in more detail below. In addition, the olefin that is used, is described in more detail below.

[0145] It is preferred to carry out the polymerization process in the absence of moisture and oxygen. The catalyst component is present in an amount of 50 to 700 mg (total amount of catalyst), preferably between 250 mg and 500 mg.

[0146] The polymerization pressure is preferably between 1 and 40 bar, more preferably between 15 and 20 bar.

[0147] The polymerization temperature is preferably between 70 and 120° C., more preferably between 90 and 105° C.

[0148] The duration of polymerization is preferably between 30 and 90 minutes, more preferably between 50 and 70 minutes, such as 1 hour.

[0149] During the polymerization a water scavenger may be present. An example of water scavengers is triethyl aluminum (TEAL).

[0150] Hydrogen may the present during the polymerization in order to control the molecular weight (Mw) for different MWD values of the resulting polymer

[0151] The polyethylene obtained with the process according to the invention is suited to be applied in the production of large size blow molded articles (such as closed-head shipping containers, fuel tanks, and containers for industrial use) and high molecular weight film applications. Preferably, the polyethylene obtained has a HLMI value of between 1 and 20.

Co-Catalyst

[0152] During polymerization a reducing agent is preferably present. The presence of such a reducing agent is known in the field. A person skilled in the art will be able to determine which reducing agents, as well as the amount, based on the circumstances of the polymerization.

[0153] As co-catalyst preferably structures corresponding to the following formula are used:

M(R′).sub.a(R″).sub.b

[0154] Wherein M is a metal selected from the group, consisting of aluminum, gallium and magnesium and is preferably aluminum. [0155] each R′ independently is a saturated or unsaturated hydrocarbon group containing from about 1 to 20 carbon atoms. R′ can be an alkyl, aryl, aralkyl, alkenyl, cycloalkyl. Suitable examples of group R are methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, hexyl, cyclohexyl, heptyl, cycloheptyl, allyl, propenyl, phenyl, tolyl, xylyl, mesityl, benzyl, phenyl and naphthyl; [0156] each R″ independently is either R′ or H; [0157] a is an integer selected from 1, 2, or 3 and b is either 0, 1, or 2 on the proviso that a+b equals the valence of metal M.

[0158] It is preferred that M is aluminum. It is preferred that R′ is alkyl. Even more preferred are compounds wherein a is 3 and b is 0. Examples of suitable co-catalysts are trialkyl aluminum compounds, such as: trimethyl aluminum, triethyl aluminum (TEAL), tripropyl aluminum, tri-isobutyl aluminum (TIBA), tri-n-butyl aluminum; dialkyl aluminum hydrides, such as diethyl aluminum hydride, methyl-ethyl-aluminum hydride; tri aryl aluminum, such as triphenyl aluminum. Other examples are trialkyl gallium compounds, such as: trimethyl gallium, triethyl gallium, tripropyl gallium, tri-isobutyl gallium, tri-n-butyl gallium; dialkyl gallium hydrides, such as diethyl gallium hydride, methyl-ethyl-gallium hydride; tri aryl gallium, such as triphenyl gallium. Other examples are dialkyl magnesium compounds, such as: dimethyl magnesium, diethyl magnesium, dipropyl magnesium, di-isobutyl magnesium, di-n-butyl magnesium monoalkyl magnesium hydrides, such as ethyl magnesium hydride, methyl magnesium hydride; di aryl magnesium, such as diphenyl magnesium.

Olefin

[0159] The olefin used in the polymerization according to the invention may be selected from ethylene or a combination of ethylene and a co-monomer, selected from mono- and di-olefins containing from 3 to 10 carbon atoms, such as for example branched or straight olefins selected from the following group propylene, butylene, pentene, hexene, heptene, octene, nonene, decene and/or butadiene. According to a preferred embodiment of the invention the olefin is ethylene.

Solvent

[0160] The solvents or inert diluent or dispersant used during the polymerization may be selected from the group consisting liquefied ethane, propane, isobutene, n-butane, isopentane, n-hexane, other hexanes including cyclohexane, isooctane, paraffinic mixtures of alkanes having from 8 to t12 carbon atoms. The solvent is preferably isopentane.

[0161] The present invention will be further elucidated with the following examples without being limited hereto.

EXAMPLES

Step of Preparation of Modified Silica

[0162] [Step 2a]

[0163] Firstly, 50 g of silica (Silica 955 of Grace) was transferred into 500 mL round bottom flask. Dibutylether (250 ml, dried) was added as a solvent at room temperature. The mixture was then heated to a temperature of 50° C. and stirred at a stirring speed of 400 rpm.

[0164] Separately, a solution was prepared of either 2.16 g of AlCl.sub.3 in 10 mL of dibutylether as the solvent (for Examples 1-11) or of 17.3 g of AlCl.sub.3 in 10 mL of dibutylether as the solvent (for Examples 12-13) or AlCl.sub.3(H.sub.2O).sub.6 in 10 ml of water as the solvent (for Examples 14-15). This aluminum modifier solution was added slowly over a period of 10 minutes to the silica mixture. The resulting mixture was stirred for a period of 1 h at a temperature 50° C. and with a stirring speed of 400 rpm. Upon completion of the modification reaction, the solvent—dibutylether and optionally water—was removed by evaporation using vacuum.

[Step 2b]

[0165] Subsequently, the modified silica was subjected to a heat treatment (calcined) at a temperature of 600° C. under an air atmosphere during a period of 3 hours. The resulting solid product, being the modified silica contained either 0.8 wt. % (for Examples 1-11) or 4.5 wt. % (for Examples 12-13) of 0.1 wt. % (for Examples 14-15) of aluminum in the form of aluminum-oxo-chloride for examples 1-13 and aluminum-oxo for Examples 14-15.

Step of Preparing the Catalyst

[0166] In 100 mL round bottom flask, a predetermined amount (as disclosed in Table 1) of a silyl chromate (bis-triphenyl silylchromate) and a predetermined amount (as disclosed in Table 1) of modified silica prepared in the previous step were added to 40 mL of isopentane. The resulting mixture was stirred at room temperature (23° C.) for 1 hour at a stirring speed of 300 rpm. Then, a predetermined amount (as disclosed in Table 1) of diethyl aluminum ethoxide (Et.sub.2AlEtO, known as DELOX or DEALE) was added slowly to the mixture and stirred for 5 minutes (stirring speed of 300 rpm). This mixture is then ready for injection into the polymerization reactor to prepare the polymer. It should be noted that DELOX is used only as a co-catalyst. It does not form part of the catalyst component but does form part of the catalyst system. DELOX is added in the form of a 0.7 wt. % solution in isopentane.

[0167] The aluminum, magnesium and chromium content (loading) of the resulting catalyst components were tested by the following method: ICP (inductively coupled plasma) analysis.

IPC Method

[0168] An amount of about 0.1 g of sample was weighed in a 50 mL centrifuge tube inside a glove box. This sample was subsequently removed from the glove box. Then 5 mL of concentrated nitric acid (HNO.sub.3) is slowly added to the sample and stirred by using vortex mixture for about one minute. Inside a fume hood the lid of the centrifuge tube is opened to allow any fumes to escape from the sample. The opened centrifuge tube is left inside the fume hood occasional stirring for about one hour. Then, the sample was diluted to 50 mL by using deionized water. A blank was prepared in the same way except for the presence of the sample. In addition, standard were prepared for each of the different metals, said samples having concentrations of 0 mg/L, 1 mg/L, 5 mg/L, and 10 mg/L using valid certified individual element Mg, Ti and Al from a stock of 1000 mg/L. Sample analysis is performed by using a Thermo ICP system (Instrument ID: ICP-2). The instrument was standardized by using above mentioned standards. QC check standard (5 mg/L from different batch of the certified standard) is run to verify the calibration. A suitable dilution were made for the sample analyzed against the standard. The results will be reported for each element in %

[0169] The aluminum loading is the result of the metal halide modification of the inorganic oxide support. When an aluminum halide modifier is used it should be noted that the co-catalyst does not play in role in the aluminum content of the catalyst component.

[0170] The flow index is determined by HLMI (High Load Melt Index) Test Method ASTM D 1238 Condition F measured at 190° C. under a load of 21.6 kg and the results are given in g/10 minutes.

[0171] Polymer molecular weight and its distribution (MWD) were determined by Gel Permeation Chromatography (GPC) using a Polymer Labs 220 gel permeation chromatograph. The chromatograms were run at 150° C. using 1,2,4-trichlorobenzene as the solvent with a flow rate of 0.9 ml/min. The refractive index detector is used to collect the signal for molecular weights. The software used is Cirrus from PolyLab for molecular weights from GPC. The calibration of the HT-GPC uses a Hamielec type calibration with broad standard and fresh calibration with each sample set.

Example 1 (Comparative)

[0172] A standard silica 955W from W. R. Grace was used. This was subsequently contacted in an amount of 250 mg with 8.9 mg bis-triphenyl silylchromate and 0.2 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 0.29 wt. % and an aluminum content of 0 wt. % since no aluminum modification of the silica is carried out in this comparative example.

Example 2

[0173] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 250 mg with 17.8 mg bis-triphenyl silylchromate and 0.4 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 1 wt. % and an aluminum content of 0.8 wt. %.

Example 3

[0174] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 250 mg with 17.8 mg bis-triphenyl silylchromate and 0.7 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 1 wt. % and an aluminum content of 0.8 wt. %.

Example 4

[0175] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 250 mg with 17.8 mg bis-triphenyl silylchromate and 1.0 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 1 wt. % and an aluminum content of 0.8 wt. %.

Example 5

[0176] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 250 mg with 17.8 mg bis-triphenyl silylchromate and 1.3 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 1 wt. % and an aluminum content of 0.8 wt. %.

Example 6

[0177] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 250 mg with 17.8 mg bis-triphenyl silylchromate and 1.7 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 1 wt. % and an aluminum content of 0.8 wt. %.

Example 7

[0178] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 500 mg with 33 mg bis-triphenyl silylchromate and 1.3 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 1 wt. % and an aluminum content of 0.8 wt. %.

Example 8

[0179] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 500 mg with 33 mg bis-triphenyl silylchromate and 1.52 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 1 wt. % and an aluminum content of 0.8 wt. %.

Example 9

[0180] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 500 mg with 33 mg bis-triphenylsilylchromate and 1.7 ml of a solution of diethylaluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 1 wt. % and an aluminum content of 0.8 wt. %.

Example 10

[0181] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 500 mg with 33 mg bis-triphenyl silylchromate and 2.0 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 1 wt. % and an aluminum content of 0.8 wt. %.

Example 11

[0182] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 500 mg with 33 mg bis-triphenyl silylchromate and 2.5 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 1 wt. % and an aluminum content of 0.8 wt. %.

Example 12

[0183] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 500 mg with 30 mg bis-triphenyl silylchromate and 0.7 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 0.9 wt. % and an aluminum content of 4.5 wt. %.

Example 13

[0184] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 500 mg with 30 mg bis-triphenyl silylchromate and 0.25 ml of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane). The catalyst component of the resulting catalyst system had a chromium content of 0.9 wt. % and an aluminum content of 4.5 wt. %.

Example 14

[0185] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 250 mg with 8.9 mg bis-triphenyl silylchromate in 40 mL of isopentane. Then 0.2 mL of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane) was added and stirred for 5 minutes. The catalyst component of the resulting catalyst system had a chromium content of 0.29 wt. % and an aluminum content of 0.1 wt. %.

Example 15

[0186] A modified silica prepared as discussed above was used. This was subsequently contacted in an amount of 250 mg with 8.9 mg bis-triphenyl silylchromate in 40 mL of isopentane. Then 0.35 mL of a solution of diethyl aluminum ethoxide (7 wt. % in isopentane) was added and stirred for 5 minutes. The catalyst component of the resulting catalyst system had a chromium content of 0.29 wt. % and an aluminum content of 0.1 wt. %.

Ethylene Polymerization

[0187] The polymerization reaction was carried out in a stirred autoclave reactor. The reaction is carried out in 1 L of deoxygenated isopentane in the presence of an alkyl aluminum water scavenger, viz. 0.1 ml (1 M) of triethylaluminum, also known as TEAL). The polymerization reaction in the presence of the catalyst components 1-15 was conducted at 100° C. and 20 bars (290 psi) of total pressure. Ethylene polymerization was carried out for 1 hour, with ethylene supplied on demand to maintain the total reactor pressure at 20 bar. Upon completion of the polymerization, the reactor was vented and cooled to ambient temperature to recover the polymer.

[0188] The results are shown in Table 1.

[0189] In Table 1 Mw is the weight-average molecular weight. M.sub.w is related to strength properties (tensile, impact resistance). M.sub.n is the number-average molecular weight; M.sub.n is related to brittleness, and flow properties. PDI is the polydispersity index or molecular weight distribution. Productivity relates to the effectiveness of the catalyst component in olefin polymerization. Polymer bulk density is defined as the weight per unit volume of polymer.

TABLE-US-00001 Example Nr. 1 2 3 4 5 6 7 8 Type of Silica.sup.#1 ST MD MD MD MD MD MD MD amount (mg) 250 250 250 250 250 250 500 500 Silyl chromate (mg) 8.9 17.8 17.8 17.8 17.8 17.8 33.0 33.0 Al wt. % 0 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Cr wt. % 0.29 1 1 1 1 1 1 1 Detox (7 wt. %) (ml) 0.2 0.4 0.7 1.0 1.3 1.7 1.3 1.52 Productivity.sup.#2 0.98 1.38 1.05 1.1 0.72 0.7 1.01 1.13 Mw.sup.#3 227,000 417,000 493,000 470,000 475,000 625,000 474,000 416,000 PDI 15 27.8 35.2 24.7 30.4 28.5 29.5 27.73 Mn.sup.#4 15,000 15,000 14,000 19,000 15,000 22,000 16,000 15,000 PBD.sup.#5 40 40 38 38 35 39 40 43 HLMI (21.5 kg).sup.#6 27.01 3.53 2.15 2.31 1.64 1.40 2.90 3.45 FIG. (drawings) 1 2 3 4 5 6 7 8 Example Nr. 9 10 11 12 13 14 15 Type of Silica.sup.#1 MD MD MD MD MD MD MD amount (mg) 500 500 500 500 500 500 500 Silyl chromate (mg) 33.0 33.0 33.0 30.0 30.0 8.9 8.9 Al wt. % 0.8 0.8 0.8 4.5 4.5 0.1 0.1 Cr wt. % 1 1 1 0.9 0.9 0.29 0.29 Detox (7 wt. %) (ml) 1.7 2.0 2.5 0.7 0.25 0.2 0.35 Productivity.sup.#2 0.81 0.73 0.85 0.20 0.31 2.7 1.4 Mw.sup.#3 378,000 355,000 631,000 850,007 679,381 185,000 223,000 PDI 22.2 22 33.2 46.1 54.86 12.3 14 Mn.sup.#4 17,000 16,000 19,000 18,404 12,384 15,000 16,000 PBD.sup.#5 40 43 42 41 38 43 39 HLMI (21.6 kg).sup.#6 2.35 2.45 1.74 0.43 0.57 26.79 14.87 FIG. (drawings) 9 10 11 12 13 14 15 .sup.#1ST is standard silica, being Grace 955W, MD is silica modified as disclosed in the Examples of the present invention .sup.#2productivity is measured in kilograms of polymer per gram of catalyst per hour .sup.#3the unit of M.sub.w is gram per mole .sup.#4the unit of M.sub.n is gram per mole .sup.#5the unit of polymer bulk density is grams per 100 millilitres .sup.#6the unit of HLMI is the mass of polymer, in grams

[0190] Thus, it has been shown that the catalyst component according to the present invention modified using an aluminum chloride modifier (Examples 2-13) is able to provide a polymer having a high molecular weight and high molecular weight distribution. Moreover, it has been shown that the catalyst component according to the present invention modified using an aluminum chloride hexahydrate modifier (Examples 14 and 15) provides a monomodal polymer with an very large increase in productivity while maintaining a similar molecular weight and molecular weight distribution.

[0191] Thus, one or more of the objections of the present invention are achieved by the present catalyst component.

[0192] More embodiments are disclosed in the appended claims.