Activating agents for hafnium-based metallocene components

Abstract

The present invention discloses an active metallocene catalyst system prepared with a hafnium-based metallocene catalyst system and an activating agent comprising an aluminoxane and a sterically hindered Lewis base.

Claims

1. A method comprising: preparing a metallocene catalyst system by combining a hafnium-based metallocene catalyst component and an activating agent; wherein the hafnium-based metallocene catalyst component is of formula II
R (FluR.sub.m)X Hf Q.sub.2(II) wherein Flu is a fluorenyl ring; wherein each R is the same or different and is hydrogen or a hydrocarbyl radical containing from 1 to 20 carbon atoms; wherein m is an integer from 0 to 8; wherein each Q is a hydrocarbyl radical having from 1 to 20 carbon atoms, a hydrocarboxy radical having from 1 to 20 carbon atoms or a halogen and can be the same or different from each other; wherein X is a hetero atom ligand with one or two lone pair electrons and is selected from group 16; and wherein R is a structural bridge between Flu and X; wherein the activating agent has a low or no co-ordinating capability and comprises an aluminoxane and a Lewis base, and wherein the activating agent comprises a ratio of Lewis base to total aluminum of from 0.5:1 to 0.9:1; and wherein prior to the combining of the hafnium-based metallocene catalyst component and the activating agent, forming the activating agent by: mixing the aluminoxane with the Lewis base; and reacting the aluminoxane and the Lewis base for a period of time sufficient to reach equilibrium, wherein aluminum alkyl present in the activating agent is neutralized by the Lewis base.

2. The method of claim 1, wherein the period of time sufficient to reach equilibrium ranges from 30 minutes to 2 hours.

3. The method of claim 1, wherein the activating agent comprises a ratio of Lewis base to total aluminum of from 0.55:1 to 0.75:1.

4. The method of claim 1, wherein the Lewis base is a compound of formula R*.sub.a-c E (G-R*.sub.b-1).sub.c or of formula R*(G-R*.sub.b-1).sub.c wherein G is a group 15 or 16 element of the Periodic Table, b is equal to the valency of G, E is a group 14 or 15 element of the Periodic Table, a is the coordination number of E, c is an integer from 1 to 4, at most equal to a and each R* is independently a hydrogen or an unsubstituted or substituted hydrocarbyl.

5. The method of claim 1, wherein the Lewis base is N,N-dimethylaniline, ethylamine; diethylamine; trimethylamine; triphenylamine; triphenylphosphine; hexamethylphosphorus triamide; diethylether; ethanol; phenol; thiophenol, 2,6-di-t-butyl-4-methylphenol; tetraethoxysilane; phenyltriethoxysilane; diphenyidiethoxysilane; triphenylethoxysilane; or diethyldiethoxysilane.

6. The method of claim 1, wherein the Lewis base is a phenol.

7. The method of claim 6, wherein the phenol is a sterically hindered phenol.

8. The method of claim 6, wherein the phenol is a multi-substituted phenol.

9. The method of claim 1, wherein the hafnium-based metallocene catalyst component and the activating agent are combined with a support material.

10. The method of claim 9, wherein the activating agent is contacted with the support material prior to the hafnium-based metallocene catalyst component.

11. The method of claim 9, wherein combining the hafnium-based metallocene catalyst component and the activating agent with the support material comprises: providing the activating agent dissolved in an inert hydrocarbon solvent; providing the support material slurried in the same inert hydrocarbon solvent as the activating agent or in another inert hydrocarbon solvent; adding the activating agent to the support material; after adding the activating agent to the support material, adding the hafnium-based metallocene catalyst component to the activating agent and the support material.

12. The method of claim 1, wherein R is an alkylidene group having from 1 to 20 carbon atoms, a germanium group, a silicon group, a siloxane group, an alkyl phosphine group, or an amine group.

13. The method of claim 1, wherein R is a hydrocarbyl radical having at least one carbon.

14. The method of claim 1, wherein R is CH.sub.2CH.sub.2, Ph.sub.2C, or Me.sub.2Si.

15. The method of claim 1, wherein Q is a halogen.

16. The method of claim 15, wherein Q is Cl.

17. The method of claim 1, wherein X is oxygen or sulphur.

18. The method of claim 1, wherein the hafnium-based metallocene catalyst component is a bridged cyclopentadienyl-fluorenyl complex that has a Cs or Cl symmetry.

19. The method of claim 1, wherein the metallocene catalyst system has a ratio Al/Hf of from 100 to 5000.

20. The method of claim 1, wherein the metallocene catalyst system has a ratio Al/Hf of from 500 to 2000.

21. A method comprising: mixing an aluminoxane containing aluminum alkyl with a Lewis base, wherein the Lewis base is a multi-substituted phenol; reacting the aluminoxane and the Lewis base for a period of time sufficient to reach equilibrium, wherein the aluminum alkyl is neutralized by the Lewis base, to obtain an activating agent comprising the aluminoxane and the Lewis base; combining a hafnium-based metallocene catalyst component and the activating agent; wherein the hafnium-based metallocene catalyst component is of formula II
R (FluR.sub.m)X Hf Q.sub.2(II) wherein Flu is a fluorenyl ring; wherein each R is the same or different and is hydrogen or a hydrocarbyl radical containing from 1 to 20 carbon atoms; wherein m is an integer from 0 to 8; wherein each Q is a hydrocarbyl radical having from 1 to 20 carbon atoms, a hydrocarboxy radical having from 1 to 20 carbon atoms or a halogen and can be the same or different from each other; wherein X is a hetero atom ligand with one or two lone pair electrons and is selected from group 16; and wherein R is a structural bridge between Flu and X; wherein the activating agent has a low or no co-ordinating capability, and wherein the activating agent comprises a ratio of Lewis base to total aluminum of from 0.55:1 to 0.75:1.

Description

LIST OF FIGURES

(1) FIG. 1 represents schemes describing the formation of internal and terminal vinilydene unsaturations in a growing polymer chain.

(2) FIG. 2 represents the .sup.1H NMR spectra of polypropylene samples prepared with Me.sub.2C(3-.sup.tBu-Cp)(Flu)MCl.sub.2 wherein M is Zr (2a) or Hf (2b)

EXAMPLES

(3) Polymerisation of Propylene with PH.sub.2C(Cp)(Flu)MCl.sub.2.

(4) Metal M was selected as Zr and Hf respectively. All polymerisation reactions were carried out at a temperature of 50 C. and with a 0.4M solution of C.sub.3H.sub.6 in toluene. The activating agents were respectively methylaluminoxane (MAO) or a mixture MAO/phenol. When MAO was used as activating agent, the ratio [Al]/[M] was of 1.10.sup.3 and when the mixture MAO/phenol was used as activating agent, the ratio [Al]/[M] was of (1.0 to 1.5). 10.sup.3 and the ratio [phenol]/[Al] was of 0.6, wherein [Al] represents the total amount of aluminium. The results are displayed in Table I, they include the productivities expressed in kg.sub.PP/{[C.sub.3H.sub.6]*mol.sub.Hf*h} and polymer properties of active site enantioselectivity a, fractional abundance of skipped insertions P.sub.sk and viscosity-average molecular mass Mv determined in tetralin at 135 C.

(5) TABLE-US-00001 TABLE I Activating Productivity * 10.sup.3 Metal agent kg.sub.PP/{[C.sub.3H.sub.6] * mol.sub.Hf * h} P.sub.sk Mv* Zr MAO 1.1 0.978 0.072 81000 Zr MAO/phenol 2.4 0.983 0.054 410000 Hf MAO 0.06 0.948 0.119 16000 Hf MAO/phenol 2.1 0.941 0.082 610000

(6) It can be seen that the addition of phenol to MAO increases the productivity of both catalyst systems, but the effect was dramatically larger for Hf-based catalyst system than for Zr-based catalyst system. The molecular weight of polypropylene prepared with the hafnium-based catalyst system activated with the mixture MAO/phenol was also considerably larger than that prepared with the zirconium-based catalyst system, all other polymerisation parameters being the same.

(7) Polymerisation of Propylene with Me.sub.2C(3-R-Cp)(Flu)MCl.sub.2

(8) A first set of polymerisations was carried out with metal M selected as hafnium and with substituent R on the cyclopentadienyl selected as methyl and tert-butyl respectively. All polymerisation reactions were carried out at a temperature of 50 C. and with a 0.4 M solution of propene in toluene. When MAO was used as activating agent, the ratio [Al]/[M] was of 7.10.sup.2 and when the mixture MAO/phenol was used as activating agent the ratio [Al]/[M] was of 6.10.sup.2 and the ratio [phenol]/[Al] was of 0.6. The results are reported in Table II.

(9) TABLE-US-00002 TABLE II Activating Productivity * 10.sup.3 Metal agent R kg.sub.PP/{[C.sub.3H.sub.6] * mol.sub.Hf * h} Hf MAO Me 14 Hf MAO/phenol Me 90 Hf MAO t-Bu Hf MAO/phenol t-Bu 33

(10) Additional polymerisations were carried out with metal M selected as hafnium or zirconium and with substituent R on the cyclopentadienyl ring selected as methyl. The polymerisation temperature and propene partial pressure were selected as indicated in Table III. The polymer properties of enantioselectivity at site i, .sub.i (i=1 or 2), of conditional probability P.sub.ij of monomer insertion at site j after a previous insertion at site i (i=1 or 2 and j=1 or 2) are also displayed in Table III. In all polymerisation reactions, the catalyst system was activated with a mixture MAO/phenol having a ratio [phenol]/[Al] of 0.6.

(11) TABLE-US-00003 TABLE III Pressure Temp. C.sub.3H.sub.6 Metal C. bars .sub.1 P.sub.12 .sub.2 P.sub.21 Zr 25 1 0.98 0.9 0.44 1 Zr 25 8 0.99 0.97 0.44 1 Hf 25 1 0.95 0.82 0.5 1 Hf 25 8 0.95 0.98 0.52 1 Zr 50 1 0.97 0.66 0.43 1 Zr 50 8 0.98 0.9 0.45 1 Hf 50 1 0.91 0.66 0.56 1 Hf 50 4 0.956 0.82 0.51 1

(12) At a polymerisation temperature of 25 C., the polymers obtained all had a hemiisotactic-like structure and they all exhibited a weak tendency of the growing chain to back skip to the less hindered coordination site upon diluting the monomer. The enantioselectivity of the more open coordination site was lower for the hafnocene (95%) than for the zirconocene (98%) and it was not sensitive to monomer concentration.

(13) At a polymerisation temperature of 50 C., the enantioselectivity of the more open coordination site decreased with decreasing monomer concentration for the hafnocene, whereas it remained unaltered for the zirconocene.

(14) Without wishing to be bound by a theory, this behaviour might be the result of growing chain epimerisation.

(15) The present inventors have reported in European patent application EP-03102060 that the catalyst systems based on catalyst component Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrCl.sub.2 generated polypropylene with an unprecedently high level of internal chain unsaturations. These internal chain unsaturations were attributed to -H elimination followed by allylic chain activation as summarised in FIG. 1.

(16) The hafnocenes of the present invention did not exhibit the tendency to produce internal unsaturations. Their NMR spectrum indicated on the contrary a majority of terminal unsaturations. The .sup.1H NMR spectra in the olefinic region of 400 MHz were recorded for the polymer samples prepared in toluene with Me.sub.2C(3-.sup.tBu-Cp)(Flu)MCl.sub.2 wherein M is Zr or Hf. They are represented in FIGS. 2a and 2b respectively. It can be seen from these spectra that the samples prepared with the zirconocene (2a) have truly internal vinylidene unsaturations, whereas those prepared with the hafnocene (2b) show the two peaks characteristic of terminal vinylidene unsaturations and additionally a complex pattern at 5.0-5.1 ppm that could represent a terminal vinyl.