KR100332016B1 - Polyolefin Production Method and Polyolefin Catalyst - Google Patents

Abstract

The present invention comprises alumoxanes and the same transition metals and is selected from mono, di, and tri-cyclopentadienyls and substituted cyclopentadienyls of the transition metals, at least one being bridged and at least one being bridged Non-supported catalyst-component comprising at least two metallocenes, and a catalyst system composed of a co-catalyst and at least one type of olefin in contact with the polymerization mixture in a reaction mixture under polymerization conditions to have a multimodal or at least bimodal molecular weight distribution. Provided are methods for producing polyolefins.

Description

Method for producing polyolefin and polyolefin catalyst

The present invention relates to a process for the preparation of polyolefins having a bimodal or multimodal molecular weight distribution. The invention also relates to a polyolefin polymerization catalyst system. The present invention also relates to a process for producing a polyolefin polymerization catalyst system.

Polyolefins with a multimodal molecular weight distribution (MWD) can be converted into articles by extrusion, thermoforming, rotational molding, etc., and have advantages over typical polyolefins without a multimodal molecular weight distribution. Polyolefins having a multimodal molecular weight distribution can be processed more easily. That is, they are processed at lower throughput and at higher throughputs while at the same time these polymers are preferred because their melt flow rate instability is reduced resulting in improved properties for applications such as high strength films.

Many methods for producing polyolefins having a multimodal molecular weight distribution are known, but each method has disadvantages. Polyolefins having a multimodal molecular weight distribution can be prepared using two distinctly distinct catalysts, each producing a polyolefin having a different molecular weight distribution, in the same reactor, but it is difficult to control the inflow of the catalyst, and the produced polymer particles The size of the is not uniform, so that the polymer may separate during storage and transport, resulting in a non-uniform product. In addition, polyolefins having a bimodal molecular weight distribution can be prepared by continuously polymerizing in two separate reactors or by kneading polymers having different molecular weight distributions during processing, all of which increase the capital cost.

EP 0128045 discloses a process for the preparation of polyethylenes having a broad molecular weight distribution and / or a multimodal molecular weight distribution. Polyethylene is obtained directly from a single polymerization process in the presence of an aluminoxane and a catalyst system containing at least two metallocenes, each having a different propagation and termination rate constant.

There are limitations to known methods for preparing polyolefins having a bimodal molecular weight distribution or polymodal molecular weight distribution. Even under ideal conditions, the gel permeation chromatography curve does not show a clear bimodal molecular weight distribution of the polyolefin. The molecular weight distribution and shear rate and catalyst activity of the polymers disclosed in known methods are relatively poor. In addition, known metallocene catalyst systems for producing bimodal molecular weights use aluminoxanes as cocatalysts during polymerization, but severely foul the reactor interior, making it nearly impossible to use such types of catalysts in a continuous process. .

Thus, it is not surprising that none of the known methods for producing polyolefins of multimodal molecular weight distribution from a single polymerization process in the presence of a catalyst system comprising two or more metallocenes have been developed on an industrial scale.

It is an object of the present invention to provide a novel process for producing polyolefins having a multimodal molecular weight distribution. Another object of the present invention is to provide a novel high activity polymerization catalyst system. It is another object of the present invention to provide a novel process for preparing the polymerization catalyst system of the present invention.

According to the invention, polyolefins having bimodal or polymodal molecular weight distributions contain at least one olefin in the reaction mixture under polymerization conditions, (a) containing alumoxane and the same transition metal and mono-, di- and A supported catalyst component comprising at least two metallocenes selected from tricyclopentadienyl and substituted cyclopentadienols, at least one bridged and at least one unbridged, and (b) a cocatalyst It is prepared by contacting with the containing catalyst system.

Although alumoxane can be used as a promoter, Applicants have found that it is not necessary to use alumoxane as a promoter during the polymerization process for the production of polyolefins according to the process of the invention. Also, using alumoxane as a promoter during the polymerization can foul the reactor.

According to a preferred embodiment of the invention, the general formula MR _x (wherein M is a metal selected from Al, B, Zn, Li and Mg, each R is the same or different and has a halide or carbon atom of 1 to 12 One or more cocatalysts selected from phosphorus alkoxy or alkyl groups, wherein x is from 1 to 3). Particularly suitable cocatalysts are trialkylaluminums selected from trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum or tri-n-octylaluminum, most preferred is triisobutylaluminum.

According to the present invention, the range and average molecular weight of the molecular weight distribution can be adjusted by selecting the catalyst system. In a preferred embodiment of the invention, this control is also carried out by introducing an amount of hydrogen during the polymerization. In another preferred embodiment of the present invention, comonomers are used for such control purposes, examples of which can be used as such comonomers are 1-olefins such as 1-butene, 1-hexene, 1-octene, 4-methyl-pentene and the like. Included, most preferred is 1-hexene.

The polymerization process can be carried out under slurry phase polymerization conditions, which was unexpectedly found to be a substantial advantage of the process of the invention. Slurry phase polymerization can be carried out under well known operating conditions, but it is preferred to work for 10 minutes to 4 hours at a temperature of about 20 to 125 ° C. and a pressure of about 0.1 to 5.6 MPa.

Another advantage of the present invention is that a continuous reactor can be used to carry out the polymerization. Such continuous reactor is preferably a loop reactor. During the polymerization process, the olefin monomer (s), catalyst system, promoter and diluent are mixed and introduced into the reactor.

Another advantage of the present invention is that the bulk density of the polymer obtained by the process of the present invention is particularly high. Bulk density is an important feature of polymers. The bulk density, usually expressed in grams per cm 3, should be relatively high. If the bulk density is too low, the polymer tends to be fluffed and causes problems with plugging and handling in the product delivery system. Low volume density represents a problem in fluff packaging and extrusion processes. This is particularly important in continuous or semicontinuous polymerization where plugging of the withdrawal outlet or other points in the polymerization system can cause serious inhibition problems in the production schedule.

According to the present invention, the relative amounts of hydrogen and olefins introduced into the polymerization reactor when using hydrogen are about 0.001 to 15 mole percent hydrogen and 85 to 99.999 mole percent olefins based on the total amount of hydrogen and olefins present. It is preferable that it is 0.2-3 mol% of hydrogen, and 97-99.8 mol% of olefin.

The polymerization reaction is preferably carried out in the diluent at a temperature at which the polymer remains in a suspended solid phase in the diluent. Examples of the diluent include isobutane, n-hexane, n-heptane, methylcyclohexane, n-pentane, n-butane, n-decane, cyclohexane, and the like. Preferred diluent is isobutane.

The olefin monomers used in the process of the present invention for producing polyolefins having bimodal or polymodal molecular weight distributions in which each polymer particle contains both high and low molecular weight polymer molecules include ethylene and mono-1-olefins (alpha olefins). It is preferred to select from mono-1-olefins having 2 to 10 carbon atoms, preferably for example 4-methyl-1-pentene. More preferably these mono-1-olefins are selected from the group consisting of ethylene, propylene and mixtures thereof, with ethylene being most preferred.

According to the present invention, the supported catalyst component used in the process for producing a polyolefin having a polymodal molecular weight distribution is at least two bridged with alumoxane, at least one bridged, at least one bridged and comprising the same transition metal. As long as metallocene is included, it can be manufactured by any known method.

Known methods for preparing this type of catalyst are disclosed in European Patent No. O 2 O6794, which is incorporated herein by reference. The patent discloses a catalyst component comprising a reaction product of one or more metallocenes and alumoxanes in the presence of a support material and provides a supported metallocene-alumoxane reaction product as the sole catalyst component.

The metallocenes used in the process of the present invention are cyclopentadienyl derivatives of Group 4b, 5b or 6b metals of the periodic table and include mono-, di- and tricyclopentadienyl derivatives of transition metals and derivatives thereof It is an organometallic coordination compound. Particular preference is given to metallocenes of Group 4b and 5b metals such as titanium, zirconium, hafnium and vanadium.

Preferred metallocenes can be represented by the following general formulas (I), (II) and (III).

Wherein Cp is a cyclopentadienyl ring, M is a 4b, 5b or 6b transition metal, R is a hydrocarbyl group or hydrocarboxyl group having 1 to 20 carbon atoms, X is halogen, m is 1 to 3, n is 0 to 3, q is 0 to 3, and m + the sum of n + q is equal to the oxidation state of the metal, and (C ₅ R _'k) is a cyclopentadienyl or substituted cyclopentadienyl Dienyl, each R 'is the same or different and is hydrogen or a hydrocarbyl radical such as an alkyl, alkenyl, aryl, alkylaryl, or arylalkyl radical having 1 to 20 carbon atoms or two carbon atoms combined ₄ to form a C ₆ ring, R "is C ₁ to C ₄ alkylene radical, a dialkyl germanium or silicon or siloxane, or two (C ₅ R _'k) alkyl phosphine to the bridging ring or amine radical And Q is aryl, alkyl, alke having 1 to 20 carbon atoms , Hydrocarbyl radicals such as alkylaryl or aryl alkyl radicals, hydrocarboxy radicals having 1 to 20 carbon atoms, or halogen, which may be the same or different and Q 'is an alkylidene group having 1 to about 20 carbon atoms , s is 0 or 1, g is 0, 1 or 2, s is 0 when g is 0, k is 4 when s is 1 and k is 5 when s is 0.

Examples of hydrocarbyl radicals include methyl, ethyl, propyl, butyl, amyl, isoamyl, hexyl, isobutyl, heptyl, octyl, nonyl, decyl, cetyl, 2-ethylhexyl, phenyl and the like.

Examples of the halogen atoms include chlorine, bromine, fluorine and iodine, and chlorine is preferable among these halogen atoms.

Examples of hydrocarboxy radicals include methoxy, ethoxy, propoxy, butoxy, amyloxy and the like.

Examples of the alkylidene group include methylidene, ethylidene and propylidene.

According to a preferred embodiment of the invention, the catalyst component is deposited on a support

At least one metallocene is not bridged and is selected from the general formula (Cp) ₂ MX ₂ , wherein each Cp is the same or different and is substituted from substituted or unsubstituted cyclopentadienyl, indenyl or fluoryl, M is zirconium, titanium or hafnium, and X is the same or different and is a hydrocarbyl radical or halogen such as an aryl, alkyl, alkenyl, alkylaryl or arylalkyl group having 1 to 20 carbon atoms;

At least one metallocene is bridged and is selected from the general formula R ″ (Cp) ₂ MX ₂ , wherein each Cp is the same or different and is substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl And M is zirconium, titanium or hafnium, X is the same or different and is a hydrocarbyl radical or halogen such as an aryl, alkyl, alkenyl, alkylaryl, or aryl alkyl radical having 1 to 20 carbon atoms, R " Is a C ₁ to C ₄ alkylene radical, dialkyl germanium or silicon or siloxane, or an alkyl phosphine or amine radical bridging two (Cp) rings).

Preferably, in the above formula, Cp in unbridged metallocene is substituted or unsubstituted cyclopentadienyl or indenyl, M is zirconium, titanium or hafnium, X is C1 or CH ₃ , bridged metal In Rosen Cp is substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl, M is zirconium, titanium or hafnium, X is Cl or CH ₃ and R '' is an ethylene radical or silicon.

Preferably, the unbridged metallocene is bis (cyclopentadienyl) zirconium dichloride and the bridged metallocene is ethylene-bis (indenyl) zirconium dichloride,

The molar ratio of unbridged metallocene to bridged metallocene may be wide, and according to the invention limiting the molar ratio is merely a range of molecular weight distribution (MWD) and the degree of bimodality required for the resulting polymer. )to be. Preferably, the mole ratio of unbridged metallocene to bridged metallocene is 10: 1 to 1:10, preferably 5: 1 to 1: 5, more preferably 4: 1 to 2: 1. .

The alumoxanes used in the process of the invention are well known and preferably comprise oligomeric linear and / or cyclic alkyl alumoxanes represented by the following general formulas (I) and (II):

Oligomeric linear alumoxanes and

Oligomocyclic Cycloalumoxanes

Wherein n is 1 to 40, preferably 10 to 20, m is 3 to 40, preferably 3 to 20, and R is a C ₁ to C ₈ alkyl group, preferably methyl.

In general, when preparing alumoxane from, for example, aluminum trimethyl and water, a mixture of linear and cyclic compounds is obtained.

The support used in the process of the present invention may be any solid, and in particular may be a porous support such as talc, an inorganic oxide and a dendritic support material such as polyolefin. Preferably, the support material is a finely ground inorganic oxide. Suitable inorganic oxides preferably used by the present invention include Group 2a, 3a, 4a or 4b metal oxides such as silica, alumina and mixtures thereof. Other inorganic oxides that can be used alone or in admixture with silica or alumina include magnesia, titania, zirconia and the like. However, other suitable support materials may be used, such as finely divided functionalized polyolefins such as finely divided polyethylene. Preferably, the support is silica having a surface area of 200 to 600 m 2 / g and a pore volume of 0.5 to 3 ml / g.

The amount of alumoxane and metallocenes usefully used in the preparation of solid phase supported catalysts can vary widely. Preferably the molar ratio of aluminum to transition metal is from 1: 1 to 100: 1, preferably from 5: 1 to 50: 1.

The order of addition of metallocene and alumoxane to the support material may vary. According to one preferred embodiment of the present invention, alumoxane dissolved in a suitable inert hydrocarbon solvent is added to the support material slurried in the same or different suitable hydrocarbon solution, followed by addition of a mixture of two or more metallocenes to the slurry. .

According to another preferred embodiment of the invention, the supported catalyst component is prepared by mixing a bridged metallocene alumoxane supported catalyst with an unbridged metallocene alumoxane supported catalyst.

Preferred solvents include mineral oils and various hydrocarbons which are liquid at the reaction temperature and do not react with each component. Examples of useful solvents include alkanes such as pentane, isopentane, hexane, heptane, octane and nonane; Cycloalkanes such as cyclopentane and cyclohexane and aromatics such as benzene, toluene, ethylbenzene and diethylbenzene.

Preferably, the support material is slurried in toluene and the metallocene and alumoxane are dissolved in toluene before adding to the support material.

Example

1. Preparation of catalyst (A)

The support used is silica with a surface area of 322 m 2 / g (GRACE 952). The silica was dried in a high vacuum on a schlenk line for 3 hours to remove the physically absorbed water and further treated, then suspended in toluene and reacted with methyl alumoxane (MAO) at reflux for 3 hours. . Finally, it was cooled and washed three times with toluene to remove unreacted MAO. A solution of two corresponding metallocenes in toluene was added to the treated silica and the mixture was stirred for 1 hour. The supernatant was filtered off and the residual solid was washed three times with toluene and dried under vacuum. Three minutes before the catalyst was introduced into the reaction zone, 1 ml of 25% by weight triisobutylaluminum (TIBAL) in toluene was added. All polymerization reactions were carried out in 2 L Buchi reactors in 1 L of isobutane as diluents.

2. Polymerization Procedure (A)

A suspension of supported catalyst was introduced to the reactor under isobutane pressurization. The polymerization reaction was initiated by pressurizing the reactor to a pressure of 30 bar ethylene. Ethylene pressurization was maintained during the entire polymerization reaction. The polymerization reaction was stopped by cooling the reactor and letting out ethylene. The polymer was recovered and analyzed. The catalyst type, polymerization conditions and polymer properties are shown in Table 1.

3. Preparation of catalyst (B)

The two supports used are the same MAO supported silica as prepared in method (A) above.

(a) A solution of (Cp) ₂ ZrCl _{2 in} toluene was deposited on the first support by stirring the resulting suspension for 1 hour at room temperature. The supernatant was filtered off and the remaining solid component was washed three times with toluene and dried under vacuum.

(b) A solution of (Ind) ₂ ZrCl _{2 in} toluene was deposited on the second support by stirring the resulting suspension at room temperature for 1 hour. The supernatant was filtered off and the remaining solid was washed three times with toluene and then dried under vacuum.

(c) The two types of supported metallocenes (a) and (b) obtained, respectively, were mixed in a weight ratio of 2: 1 ((a) :( b)).

4. Polymerization Procedure (B)

The capacity of the reactor used in all examples is 35 liters and stirred continuously. This continuous reactor is first charged with isobutane at a pressure of 40 bar. Next, as shown in FIG. 1, a suspension of supported catalyst (1), isobutane (2), TIBAL (3), hexene (4), ethylene (5) and hydrogen (6) are continuously introduced into the reactor. Let's do it. The polymer was recovered in (9). All polymers were analyzed by gel permeation chromatography (GPC-WATERS MILLIPORE) and differential scanning calorimetry (DSC). Graphs are shown in FIGS. 2-20 (FIGS. 2-20 correspond to Examples 5-23 in Table 2, respectively). "D" represents Mw / Mn ratio (MWD) and "D '"Represents the Mz / Mw ratio and" A "represents the area under the curve. The polymerization conditions and polymer properties are shown in Table 2.

TABLE 1

TABLE 2

1 is a reaction scheme in accordance with an example of the present invention.

2 to 20 are graphs obtained from the polymers corresponding to Examples 2 to 23 in Table 2.

Claims (15)

In a catalyst system for use in the production of a polyolefin having a bimodal or polymodal molecular weight distribution, with or without a supported catalyst component, wherein the supported catalyst component contains the same transition metal as alumoxane and is of the general formula At least one metallocene bridged and at least one non-bridged, molar ratio of unbridged metallocene to bridged metallocene, 10: 1 to 1:10. Catalytic system characterized in that: Wherein Cp is a cyclopentadienyl ring, M is a 4b, 5b or 6b transition metal, R is a hydrocarbyl group or hydrocarboxyl group having 1 to 20 carbon atoms, X is halogen, m is 1 to 3, n is 0 to 3, q is 0 to 3, and m + the sum of n + q is equal to the oxidation state of the metal, and (C ₅ R _'k) is a cyclopentadienyl or substituted cyclopentadienyl Dienyl, each R 'is the same or different and is a hydrocarbyl radical such as hydrogen, an alkyl, alkenyl, aryl, alkylaryl, or arylalkyl radical having 1 to 20 carbon atoms, or two carbon atoms combined ₄ to form a C ₆ ring, R "is C ₁ to C ₄ alkylene radical, a dialkyl germanium or silicon or siloxane, or two (C ₅ R _'k) alkyl phosphine to the bridging ring or amine radical And Q is aryl, alkyl, alkenyl, alkyl having 1 to 20 carbon atoms Hydrocarbyl radicals such as aryl or aryl alkyl radicals, hydrocarboxy radicals having 1 to 20 carbon atoms, or halogens, which may be the same or different from each other, Q 'is an alkylidene group having 1 to about 20 carbon atoms, s is 0 or 1, g is 0, 1 or 2, s is 0 when g is 0, k is 4 when s is 1, k is 5 when s is 0. The compound of claim 1, wherein the general formula MR _x , wherein M is a metal selected from Al, B, Zn, Li, and Mg, each R is the same or different, and a halide or alkoxy having 1 to 12 carbon atoms, or And at least one cocatalyst selected from an alkyl group and x is from 1 to 3). 3. The catalyst system of claim 2, wherein the promoter is trialkyl aluminum selected from trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum and tri n-octylaluminum. The method according to any one of claims 1 to 3, The unbridged metallocene is selected from the general formula (Cp) ₂ MX ₂ , wherein each Cp is the same or different, substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl, and M is Zirconium, titanium or hafnium, X is the same or different and is a hydrocarbyl radical or halogen, such as an aryl, alkyl, alkenyl, alkylaryl or aryl alkyl radical having 1 to 20 carbon atoms, The bridged metallocene is selected from the general formula R ″ (Cp) ₂ MX ₂ , wherein each Cp is the same or different and is selected from substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl, M Is zirconium, titanium or hafnium, X is the same or different and is a hydrocarbyl radical or halogen such as an aryl, alkyl, alkenyl, alkyl aryl, or aryl alkyl radical having 1 to 20 carbon atoms, and R ″ is C _{A 1-} C ₄ alkylene radical, dialkyl germanium or silicon or siloxane, or an alkyl phosphine or amine radical bridging two (Cp) rings). 5. The compound of claim 4, wherein in the general formula of the unbridged metallocene, Cp is substituted or unsubstituted cyclopentadienyl or indenyl, M is zirconium, titanium or hafnium, X is Cl or CH ₃ , bridged In the general formula of the metallocene, Cp is substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl, M is zirconium, titanium or hafnium, X is Cl or CH ₃ and R '' is an ethylene radical or silicon Catalytic system characterized in that. 6. The catalyst system of claim 5, wherein the unbridged metallocene is bis (cyclopentadienyl) zirconium dichloride and the bridged metallocene is ethylenebis (daleyl) zirconium dichloride. A process for producing a polyolefin having a bimodal or polymodal molecular weight distribution, the method comprising the step of contacting a promoter-containing catalyst system according to claim 1 with at least one olefin in a polymerization reaction zone under polymerization conditions. 8. The catalyst system of claim 7, wherein the catalyst system is of the general formula MR _x , wherein M is a metal selected from Al, B, Zn, Li, and Mg, each R is the same or different, and has a halide or carbon number of 1-12. And at least one cocatalyst selected from alkoxy or an alkyl group, x being from 1 to 3). 9. The process of claim 8 wherein the promoter is trialkylaluminum selected from trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum or tri-n-octylaluminum. The process according to claim 7, wherein the polymerization reaction comprises isobutane, n-hexane, n-heptane, methylcyclohexane, n-pentane, n-butane, n-decane and cyclohexane. Characterized in that it is carried out in a diluent. 10. The process according to any of claims 7 to 9, characterized in that 0.001 to 15 mole percent hydrogen is introduced into the polymerization reaction zone, based on the total amount of hydrogen and olefins present. The method according to any one of claims 7 to 9, Unbridged metallocene is selected from the general formula (Cp) ₂ MX ₂ , wherein each Cp is the same or different and is substituted from substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl, and M is Zirconium, titanium or hafnium, X is the same or different and is a hydrocarbyl radical or halogen such as an aryl, alkyl, alkenyl, alkylaryl or aryl alkyl radical having 1 to 20 carbon atoms, The bridged metallocene is selected from the general formula R ″ (Cp) ₂ MX ₂ , wherein each Cp is the same or different and is selected from substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl, M Is zirconium, titanium or hafnium, X is the same or different and is a hydrocarbyl radical or halogen such as an aryl, alkyl, alkenyl, alkyl aryl, or aryl alkyl radical having 1 to 20 carbon atoms, and R ″ is C ₁ -C ₄ alkylene radical, dialkyl germanium or silicon or siloxane, or an alkyl phosphine or amine radical bridging two (Cp) rings). 13. The compound of claim 12, wherein in the general formula of the unbridged metallocene, Cp is substituted or unsubstituted cyclopentadienyl or indenyl, M is zirconium, titanium or hafnium, x is Cl or CH ₃ , bridged In the general formula of the metallocene, Cp is substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl, M is zirconium, titanium or hafnium, X is Cl or CH ₃ and R '' is an ethylene radical or silicon Method characterized by that. The method of claim 13 wherein the unbridged metallocene is bis (cyclopentadienyl) zirconium dichloride and the bridged metallocene is ethylenebis (indenyl) zirconium dichloride. A process for preparing a supported catalyst component for the production of polyolefins having a bimodal or polymodal molecular weight distribution, comprising adding an alumoxane dissolved in an inert, suitable hydrocarbon solvent to a support material slurried in a suitable inert hydrocarbon liquid and then in an inert solvent. Adding a mixture of dissolved unbridged metallocene and bridged metallocene dissolved in an inert solvent to the slurry; Wherein said unbridged metallocene solution and bridged metallocene solution are separately added to an alumoxane to form a metallocene alumoxane supported catalyst and then mixed together.