EP2041149A2

EP2041149A2 - Supported metallocene catalyst systems free of aluminoxane and perfluorophenylborate activators

Info

Publication number: EP2041149A2
Application number: EP07747942A
Authority: EP
Inventors: Sergei Mikhailovich Aldoshin; Natalia Mikhailovna Bravaya; Andrei Nikolaevich Panin; Olga Mikhailovna Chukanova; Abbas Razavi
Original assignee: Total Petrochemicals Research Feluy SA; Institute of Problems of Chemical Physics of Russian Academy of Sciences; Institute of Problems of Chemcial Physics RAS (IPCP RAS)
Current assignee: Total Petrochemicals Research Feluy SA; Institute of Problems of Chemical Physics of Russian Academy of Sciences; Institute of Problems of Chemcial Physics RAS (IPCP RAS)
Priority date: 2006-05-26
Filing date: 2007-05-23
Publication date: 2009-04-01
Also published as: EA200802394A1; WO2007139440A2; WO2007139440A3

Abstract

The present invention discloses a class of supported metallocene catalyst systems that can be activated without aluminoxane or perfluorophenylborate.

Description

SUPPORTED METALLOCENE CATALYST SYSTEMS FREE OF ALUM1NOXANE AND PERFLUOROPHENYLBORATE ACTIVATORS

5 The present invention relates to the field of supported metallocene catalyst systems that are very active in the homo- or co-polymerisation of ethylene and propylene without addition of aluminoxane or perfluorophenylborate as activating agents.

The polymerisation of olefins in the presence of metallocene complexes has mostly 10 been described in homogeneous catalysis. In that type of polymerisation, the catalyst, the olefin monomer and the resulting polymer are all present in the same liquid phase, typically a solvent.

Homogeneous catalyst systems are however not adapted to suspension or gas 15 phase polymerisation. These processes nevertheless offer many advantages such as for example, the preparation of a polymer in granular form having a defined particles size distribution.

The most commonly employed activating agents in metallocene catalysis are 20 aluminoxane and perfluorophenylborates. The activators are costly and in homogeneous versions of the catalysts produce polymers that have a poor morphology, therefore incompatible with high yield processes in suspension or gas phase polymerisation. The catalytic system, i.e. the metallocene complex and its activator, must be supported on a solid support in order to be used in these 25 polymerisation processes.

The most typical technique was to support onto solid supports, homogeneous -— ^■ - activatoτs^~such^~as^~methyϊalurπoxane^~ (MAO)ras^"descriBed ^"foTexample By^~CfiierT(X Polym. ScL, Part A : Pol. Chem., 1991, 29, 1603.), or by Collins (Macromolecules, 30 1992, 25, 1780), or by Soga (Makromol. Chem., 1993, 194, 1745) or by Kaminsky (Makromol. Chem. Rapid Commun., 1993, 14, 239) or such as perfluoroarylborates as described for example in US-A-5643847 or such as perfluoroarylaluminates. The metallocene complex was then added to the impregnated support. It has been observed however that the activity of supported metallocene catalyst systems activated with such activating agents decreased very rapidly.

Polymers obtained with these systems had high apparent densities but 5 unfortunately, they had irregular grain size.

These catalytic systems using supported activators were also less active than equivalent homogeneous systems and the polymer properties were thereby degraded. 10

Alternatively, solid activating supports were developed: they are described for example in Marks (J. Am. Chem. Soc, 1998, 720, 13533).

In another approach, Panin et al. (A.N. Panin, Z.M. Dzhabieva, P.M. Nedorezova, 15 V.I. Tsetkova, S. L. Saratovskikh, O.N. Babkina, N. M. Bravaya, in J. Polym. Sci.: Part A: Polym. Chem., 39, 1915, 2001) or by Babkina et al. (O.N. Babkina, N. M. Bravaya, P.M. Nedorezova, S.L. Saratovskikh, and V.I. Tsetkova in Kinet. Catal. 43, 341 , 2002) have tested aluminium alkyls in the activation of dimethylated zirconocenes bearing a substituent at 2-position of indenyl ring. These 20 homogeneous catalyst systems were active in homogeneous polymerisation of ethylene or propylene under specific conditions.

There is thus a need to develop new activating agents for producing catalyst systems that are very active in heterogeneous homo- or co-polymerisation of 25 ethylene and alpha-olefins.

It is an aim of the present invention to provide active supported metallocene ^{■"" "} catalyst system that do^~not require^" alαminoxane or perfluoroph&nylbOrates; ^"

30 It is another aim of the present invention to provide active supported metallocene catalyst system for homo-polymerising ethylene or alpha-olefins. It is also an aim of the present invention to provide active supported metallocene catalyst system for co-polymerising ethylene with alpha-olefins or propylene with ethylene or higher alpha-olefins.

It is yet another aim of the present invention to provide an active supported metallocene catalyst system that maintains a good activity.

It is a further aim of the present invention to provide a method for supporting and activating metallocene catalyst systems without aluminoxane and perfluorophenylborates.

It is yet a further aim of the present invention to prepare polymers having good morphology.

Any one of those aims has been at least partially fulfilled by the present invention.

Accordingly, the present invention provides an active supported catalyst system comprising: - a support; - an activating agent of general formula

AIR*₃

wherein each R* is the same or different and is selected from alkoxy or alkyl groups having from 1 to 12 carbon atoms; - an olefin;

- and a dialkylated metallocene catalyst component of general formula I

^" RV (R^aR^blnd)-₂ M Q₂ ^" (I)

or of formula Il

R"s (R^aR^blnd) ZR^C M Q₂ (II) wherein - lnd is an indenyl or hydogenated indenyl;

- R^a and R^b are each independently selected from hydrogen or hydrocarbyl having from 1 to 20 carbon atoms, with the restriction that R^a and R^b are not simultaneously hydrogen; - R" is an optional structural bridge between the two indenyls imparting stereorigidity to the complex;

- s is 0 if the bridge is absent and 1 if the bridge is present

- M is a metal Group 4 of the Periodic Table;

- each Q is independently selected from alkyl having from 1 to 6 carbon atoms unsubstituted or substituted with benzene;

- Z is an heteroatom selected from N₁ O or P;

- R^c is a bulky substituent on the heteroatom that has at least 3 carbon atoms.

Preferably, substituents R^a and R^b on the indenyl are in positions 2 and/or 4 and they are alkyl having from 1 to 12 carbon atoms or aryl having from 3 to 8 carbon atoms. If there is only one substituent it is more preferably at position 2. Among the most preferred substituents, one can cite methyl, t-butyl, unsubstituted or substituted phenyl.

The type of bridge between the ligands in the present catalyst component is not particularly limited. Typically R" comprises an alkylidene group having from 1 to 20 carbon atoms, a germanium group (e.g. a dialkyl germanium group), a silicon group (e.g. a dialkyl silicon group), a siloxane group (e.g. a dialkyl siloxane group), an alkyl phosphine group or an amine group. Preferably, the substituent on the bridge comprises a silicon atom or a hydrocarbyl radical having at least one carbon, such as a substituted or unsubstituted ethylenyl radical, for example -CH₂-CH₂- (Et). Most preferably R" is Et, Me₂Si or Ph₂C.

In a preferred embodiment according to the present invention, M is selected from zirconium, titanium or hafnium. More preferably M is zirconium.

Preferably both Q are the same, more preferably they are methyl, unsubstituted or substituted with benzene. Preferably, Z is nitrogen.

Preferably, the activating agent is an aluminiumalkyl. Especially suitable aluminiumalkyl are trialkylaluminium, the most preferred being triisobutylaluminium (TIBAL).

The preferred support is porous mineral oxide advantageously chosen from silica, alumina and mixtures thereof. Preferably it is silica.

The porous mineral oxide particles preferably have at least one of the following characteristics:

- they include pores having a diameter ranging from 7.5 to 30 nm;

- they have a porosity ranging from 1 to 4 cm³ /g; - they have a specific surface area ranging from 100 to 1000 m² /g; and

- they have an average diameter ranging from 1 to 100 μm.

Without being bound by a theory, it is speculated that both trialkylaluminium and olefin participate in the initiation process according to the following reaction scheme.

L₂ M Q₂ + Al R"₃ < L₂ M Q₂ . AI R"₃

olefin / coordination vacancy

L₂ M Q₂ . Al R"₃ L₂ M⁴

— ^x L₂M-t- <Q-——Q-AΓ- RV -- --

wherein L is the ligand. 7 000256

6

In the most preferred embodiment according to the present invention, each indenyl carries two substituents. The resulting metallocene complex with trialkylaluminum is therefore not a very tight complex and the olefin further helps dissociate the complex.

The presence and position of substituents in the vicinity of the transition metal and/or polarity of the olefin have an influence on the level of initiation of the resulting catalyst system. Substituents in positions 2 and/or 4 and/or olefins having a high polarity are preferred.

The dialkylation of the metallocene was carried out using a conventional method such as described for example by Girardello et al. (M.A. Girardello, M.S. Eisen, CL. Stren in J. Am. Chem. Soc. 117, 12114, 1995.) Alkyllithium was added dropwise at a temperature of about - 80 ⁰C to the dihalogenated metallocene and the system was heated slowly to a temperature of at least 20 ⁰C. Dialkylated metallocene was then separated out.

The present invention also discloses a process for preparing an active supported metallocene catalyst system that comprises the steps of: a) adding alkyl aluminium to a porous mineral oxide support in an amount of at least 3.10^'3 mol per gram of support; b) adding of toluene solution of dialkylated metallocene component to the impregnated support under stirring; c) drying to obtain a powder.

The present invention further discloses a process for homo- or co-polymerising ethylene or alpha-olefins that comprises the steps of: ^._ — _aj adding alkyraluminiunτtσasolventirτaιτamount to reacrra concentration of at least 3.10^'3 mol per litre; b) adding the monomer into the solution of step a) until a constant concentration is obtained; c) adding the optional comonomer; d) adding the active supported catalyst component of the present invention in powder form; e) maintaining under polymerization conditions; f) retrieving a homo- or co-polymer.

List of Figures.

Figure 1 represents, for catalyst C4, the catalyst productivity expressed in kg of ethylene/propylene copolymer per mol of Zr per minute as a function of the amount of triisobutyl-aluminium (TIBAL) expressed in 10^"3 mol/g used for silica treatment.

Figure 2 represents, for catalyst C4, the catalyst productivity expressed in g of ethylene/propylene copolymer per g of support Siθ₂ per 10 minutes as a function of zirconium loading expressed in 10^'5 mol/g.

Figure 3 represents, for catalyst C4, the catalyst productivity expressed in kg of ethylene/propylene copolymer per mol of Zr per minute as a function of the amount of triisobutyl-aluminium (TIBAL) used as cocatalyst expressed in 10^"2 mol/L.

Figure 4 represents, for catalyst C4, the catalyst productivity expressed in kg of ethylene/propylene copolymer per mol of Zr as a function of polymerisation time expressed in minutes and for different polymerisation temperatures. It shows that supported metallocen catalyst systems exhibit stable copolymerisation kinetics even at high polymerisation temperature.

Figure 5 represents, for catalyst C4, the catalyst productivity expressed in kg of ethylene/propylene^* copolymer per morof Zr per miπute^~as rs f uπctiorrof propylene^""" concentration expressed in mol/L and for an ethylene pressure of 11 bars. The activities for ethylene and for propylene homopolymerisation are also indicated on the figure. δ

Figure 6 represents, for catalyst C4 with TIBAL as cocatalyst, the copolymer yield expressed in kg of ethylene/propylene copolymer per mol of Zr as a function of polymerisation time expressed in minutes. For comparison, the yields obtained in the homoplymerisation of ethylene and of propylene are also indicated.

The solvents that can be used in the present invention are aliphatic solvents.

The amount of aluminium alkyl used to treat the support must be of at least 3.10-³ mol per gram of support as can be seen on figure 1. Any additional amount of aluminium alkyl does not improve the productivity of the final supported catalyst system.

The total amount of aluminium in the catalyst system, coming from the activating agent, is selected to give a Al/M ratio of from 10 to 1000, preferably from 50 to 500 and more preferably of about 80 to 300.

The amount of catalyst component loaded on the support has a direct influence on the catalyst productivity that increase linearly with increasing catalyst loading as can be seen on figure 2.

The aluminium alkyl cocatalyst used for activating the metallocene component is preferably used in an amount ranging from 5 to 15.10^'3 mol/L as can be seen on figure 3. Too small or too large amounts lead to reduced catalyst productivity.

The productivity of the metallocene catalyst system in heterogeneous copolymerisation is increasing with increasing temperature as can be seen on figure 4 and the catalyst system exhibits very stable kinetics at temperatures ranging- of 20^~to 80 °C7prefeτably fronrr 30 tσ70^{" α}C: Thrs^~is^~ oppσsitertσ^~* homogeneous copolymerisation that exhibits a decrease of activity at increased polymerisation temperatures.

The catalyst productivity in the copolymerisation of ethylene and propylene also shows a clear dependence upon the relative amounts of monomer and comonomer in the feed. This dependence is illustrated in figure 5: the propylene concentration is varied while the concentration of ethylene remains unchanged. The preferred concentration ratio of monomer to comonomer is of from 1 to 0.5 mol/mol, more preferably of about 0.7 mol/mol it ethylene is the monomer .

The heterogeneous catalyst systems of the present invention are more active in copolymerisation than in homoplymerisation under other similar conditions: this is illustrated in figure 6.

The active supported metallocene catalyst system of the present invention is very active in heterogeneous homo- or co-polymerisation of ethylene with alpha-olefins or of propylene with ethylene or higher alpha-olefins.

The polymerisation temperature can range from -100 up to 200 ⁰C. Preferably it is of from 20 to 80 ⁰C and the polymerisation time varies between a few minutes and . several hours, preferably from 3 minutes to 2 hours.

The preferred monomers are ethylene and propylene. The comonomers for ethylene are preferably propylene and hexene-1. The comonomers for propylene are preferably ethylene and hexene-1.

Examples.

Several polymerisations were carried out with the catalyst systems according to the present invention.

The catalyst components were selected as follows: C1^~ = rac-Et(lnd)2ZrMe2 ^{~~ " ~~}

C2 = rac-Et(2-Me-lnd)₂ZrMe₂ C3 = rac-Me₂Si(lnd)₂ZrMe₂

C4 = rac-Me₂Si(2-Me-lnd)₂ZrMe₂

C5 = rac-Me₂Si(2-Me,4-Ph-lnd)₂ZrMe₂

C6 = (2-Ph-lnd)₂ZrMe₂ C7 = Ph₂C(Cp-FIu)HfMe₂ C8 = Me₂C(Cp-FIu)HfMe₂ C9 = Ph₂C(Cp-FIu)ZrMe₂

wherein lnd is an indenyl, Cp is a cyclopentadienyl, Flu is a fluorenyl, Me is a methyl and Ph is a phenyl.

Example 1

Preparation of immobilised catalyst.

All the procedures for synthesising supported catalyst systems were made under dry argon atmosphere or under vacuum. Purified toluene was refluxed over LiAIH₄ and stored over 4 A molecular sieves before usage. Silica was pumped out for 4 to 6 hours at a temperature ranging from 90 to100 °C. The desirable amount of TIBAL as solution in toluene was poured onto the silica and the suspension was kept under mixing at a temperature of 20 ⁰C for a period of time of 3 hour. The amount of TIBAL on the support was of between 3.10^'3 and 4.10^"3 mol of TIBAL per gram of support. The suspension was then filtered out and washed three times with dry toluene. The dimethylated zirconocene catalyst component was added to the SiO₂/TIBA suspension as a solution in toluene. Suspension was kept under stirring for a period of time of 1 hour at a temperature of 20 °C. Toluene was slowly removed by pumping while simultaneous stirring the suspension. The supported catalyst system was transferred as powder into a glass vial under dry argon atmosphere and the vials was sealed.

Several catalyst components were deposited on a silica support, activated with

TIBAL and tested in the homopolymerisation of ethylene and of propylene and in the copolymerisation of ethylene with propylene or hexene and of propylene with ethylene or hexene.

Homo- and co-polymerisation reactions. The homo- or co-polymerisation of ethylene and/or propylene was carried in a 200 mL stainless steel reactor. 60 mL of heptane were used as solvent. The polymerisation conditions are summarised in Table I and the results are summarized in Table II.

TABLE I.

TABLE II.

* Ph₃CB(CeFs)₄ was used as cocatalyst in addition to TIBAL, with a B/Zr ratio of 1/1 for the copolymerisation of ethylene and propylene with the cyclopentadienyl- fluorenyl based catalyst system. It was active when used with a usual activating agent but not active at all when used with TIBAL alone.

Prepolvmerisation.

Additional examples were carried out with catalyst component C4 with a prepolymerisation step prior to the copolymerisation of ethylene and propylene. The prepolymerisation and copolymerisation conditions are reported in Table III and the results are reported in Table IV.

TABLE

Run Catalyst Zr.10⁵ Tl BA.10³ C3H6 C2H4/C3H6 T t ^** rπol/g- mol/L mol/b- - mol/mol*— °e- min

1 C4 4 10 1.4 1/0 - 0.61 50 15 - 30 2 C4 4 10 0.2 1/0 - 3.8 50 30 - 30 3 C4 4 10 2.5 0/1 -0.3 50 25 - 10 TABLE IV.

mol/mol* : the two ratios refer respectively to the ethylene to propylene molar ratios in prepolymerisation and in polymerisation. t** : the two times refer respectively to the prepolymerisation and to the polymerisation times.

Y# : the two numbers refer respectively to the yields in prepolymerisation and in polymerization.

It can be concluded that all types of substituted indenyl complexes, bridged or unbridged, showed activity in the homo- or co-polymerisation of ethylene and propylene, the best results being obtained with the complex having a bridge and steric hindrance.

Claims

1. An active supported catalyst system comprising: - a support; - an activating agent of general formula

- and a dialkylated metallocene catalyst component of general formula I

R"s (R^aR^blnd)₂ M Q₂ (I)

or of formula Il

R"s (R^aR^blnd) ZR^C M Q₂ (II) wherein

- lnd is an indenyl or hydogenated indenyl; - R^a and R^b are each independently selected from hydrogen or hydrocarbyl having from 1 to 20 carbon atoms, with the restriction that R^a and R^b are not simultaneously hydrogen;

- R" is an optional structural bridge between the two indenyls imparting stereorigidity to the complex; - s is 0 if the bridge is absent and 1 if the bridge is present

- M is a metal Group 4 of the Periodic Table;

- each Q is independently selected from alkyl having from 1 to 6 carbon atoms unsubstifuted Or substitϋtelfwitrT benzene;^{"" ~ ~}

- Z is an heteroatom selected from N, O or P; - R^c is a bulky substituent on the heteroatom that has at least 3 carbon atan activating agent of general formula

2. The active catalyst system of claim 1 wherein substituents R^a and R^b on the indenyl are in positions 2 and/or 4 and they are alkyl having from 1 to 12 carbon atoms or aryl having from 3 to 8 carbon atoms.

3. The active catalyst system of claim 1 or claim 2 wherein the bridge R" is present.

4. The active catalyst system of claim 3 wherein the bridge is Et₁ Me₂Si or Ph₂C

5. The active catalyst system of any one of the preceding claims wherein the Q's are the same and are methyl groups.

6. The active catalyst system of any one of the preceding claims wherein M is zirconium.

7. The active catalyst system of any one of the preceding claims wherein Z is N.

8. The active catalyst system of any one of the preceding claims wherein the activating agent is an aluminium alkyl.

9. The active catalyst system of claim 8 wherein the alkylating agent is triisobutylaluminium.

10. A process for preparing an active supported catalyst system that comprises the steps of: a)^~addiπg^*alky|-aluminium tGra^~porσαsrmineral oxidσ support in an amount of at least 3.10^"3 mol per gram of support; b) adding of toluene solution the dialkylated metallocene component of any one of claims 1 to 9 to the impregnated support under stirring; c) drying to obtain a powder.

11. A process for homo- or co-polymerising ethylene or alpha-olefins that comprises the steps of: a) adding alkyl aluminium to a solvent in an amount to reach a concentration of at least 3.10^'3 mol per litre; b) adding the monomer into the solution of step a) until a constant concentration is obtained; c) adding the optional comonomer; d) adding the active supported catalyst component of the present invention in powder form; e) maintaining under polymerization conditions; f) retrieving a homo- or co-polymer.

12. The process of claim 11 wherein the monomer and/or comonomer are selected from ethylene, propylene or hexene.