Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
1999-12-13
2002-11-12
Wu, David W. (Department: 1783)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S117000, C556S053000, C526S160000, C526S943000, C526S351000
Reexamination Certificate
active
06479424
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to advantageous ligand systems and fluxional metallocene catalyst components made therefrom which are useful in producing olefin polymers and especially elastomeric propylene polymers.
Recently, a new class of metallocene-based catalyst systems has been described based upon unbridged substituted indenyl structures which have been identified as “fluxional.” These systems are described in the Waymouth et al. U.S. Pat. No. 5,594,080, incorporated by reference herein. Fluxional metallocene components are based on aryl 2-substituted indenyl ligands that ore formed into a metallocene which incorporates a transition metal, including Group 4 (IUPAC Periodic System) metals such as titanium, zirconium, and hafnium. These fluxional catalysts in combination with an anionic co-catalyst such as methylaluminoxane or a borate or borane compound, may be used to produce olefin polymers including elastomeric propylene polymers.
U.S. Pat. No. 5,594,080 describes a series of fluxional catalyst systems which include catalysts prepared from 2-phenylindenyl ligands which form elastomeric propylene polymers. A theory set forth for these Waymouth catalyst systems is that the 2-aryl substituted indenyl ligands rotate about the central metal to form catalysts with differing symmetry. Characteristics of polymerized olefins will depend upon the rotational symmetry state of the catalyst. For example, propylene Will polymerize into isotactic segments when the catalyst is in a “rac” rotational symmetry state, while atactic segments will be formed while the catalyst is in a “meso” rotational symmetry state. Certain Waymouth-type metallocene structures are described in Published PCT Application WO 98/57996, incorporated by reference herein, which has common inventors to this application.
As reported by Waymouth et al., elastomeric polypropylene may be formed by fluxional catalyst systems. However, polymerization activities of the catalyst systems reported by Waymouth et al. remain modest and more active catalysts are needed for commercially-acceptable processes. Further, desirable properties for elastomeric polypropylene include reasonably high molecular weights as indicated by a low melt flow rate (MFR) and suitably high polymer crystallinities which are dependent on isotacticity measured by
13
C NMR, e.g. isotactic pentad content (% m4).
Fluxional catalyst systems have produced a variety “blocky” olefin polymers with advantageous polymer characteristics. A blocky polymer will contain segments of differing compositional microstructures. An example of a blocky polymer is a propylene polymer containing blocks of atactic and isotactic regions which may show plastomeric or elastomeric properties. Other examples of blocky polymers may contain co-monomers within the segments. The broad class of fluxional catalysts and polymers related to this invention are described in Waymouth et al. U.S. Pat. No. 5,594,080. However, in order to make production of polymers made from fluxional catalysts commercially practicable, catalysts with higher polymerization activities coupled with production of suitable polymers are needed. The catalysts described in this invention generally are more active compared to catalysts made with structurally similar ligands under comparable conditions.
SUMMARY OF THE INVENTION
A ligand useful to form a metallocene olefin polymerization catalyst comprises:
wherein at least R
3
and R
4
are substituents having at least a bulk of a t-butyl group and, optionally, wherein R
1
or R
2
may be a bulky substituent group.
BRIEF DESCRIPTION OF THE INVENTION
The present invention is an advantageous metallocene catalyst system based on a ligand system containing bulky substituents at least at the 3 and 5 phenyl positions as shown below:
These bulky substituents are based on tertiary carbon or silicon. Typically these tertiary atoms are substituted with C
1
-C
4
alkyl or substituted (with such as a halide) alkyl. The preferable bulky substituents are t-butyl and trimethylsilyl (TMS). A bulky substituent according to this invention has a spatial bulk (as indicated by steric or van der Waals repulsions) at least as large as a tertiary butyl group.
Optionally, bulky substituents may be placed at the 5 and 6 indenyl positions as shown above. Thus, the ligand systems of this invention contain at least one bulky substituent for groups R
3
and R
4
, and optionally for R
1
and R
2
.
Also, R
1
and R
2
may be connected to form a cycloaliphatic ring system containing 4 to 20 carbon atoms containing tertiary alpha carbon atoms as exemplified by 2-(3,5-di-t-butylphenyl)-5,5,8,8 tetramethyl-5,6,7,8-tetrahydrobenz(f)indene as shown below:
In more preferable ligands, both R
3
and R
4
are bulky and comprise t-butyl or trimethylsilyl (TMS).
Specific examples of ligands include R
3
and R
4
are t-butyl or TMS; R
1
and R
2
are t-butyl or TMS and R
3
and R
4
are t-butyl or TMS; R
3
and R
4
are t-butyl or TMS and R
1
and R
2
are connected to form a cyclohexyl with quaternary alpha carbon atoms; R
1
is t-butyl or TMS and R
3
and R
4
are t-butyl or TMS; and R
1
and R
2
are t-butyl or TMS and R
3
is t-butyl or TMS.
Bis metallocene catalyst components of this invention, especially bis hafnium and zirconium metallocene components, generally show higher olefin polymerization activity than metallocene components formed from structurally similar ligands. Further, polymerizations showing this increased activity typically produce polyolefins with sufficiently low melt flow rates (MFR as measured by ASTM D1238, Condition L) such that hydrogen or other agent may be used to control molecular weight to a useful melt flow range without the polymer transforming into an unsuitable low molecular weight product. Typically polymers formed from the catalysts of this invention without hydrogen have MFR's from below 1 to about 2. Addition of a molecular weight control agent may increase these polymers to a melt flow rate typically from about 1 up to about 100, typically about 1 to 35, and preferably about 2 to about 25. Further, propylene polymer crystallinities are dependent on isotacticity, a measure of which is percent of pentad and longer isotactic runs, measured by percent m4 (% m4), as determined by
13
C nmr techniques. Therefore, isotacticity (m4) is generally indicative of polymer properties. The relationship between polymer properties, crystallinity and isotacticity depends on the polymer structure (blockiness) and propagation statistics. Based on typical materials of this invention, an m4 content less than about 20% typically is an amorphorus gum elastomer which will draw to high elongation, but is very soft and inelastic and exhibits poor recovery and little or no tensile hardening at high strain (>500%) unless the molecular weight is extremely high. A polymer with an m4 content of about 20-25% to 40-45% typically is elastomeric and will exhibit recovery (>80%), hardening at high strain no yielding, and uniform specimen deformation. A polymer with an m4% of about 20 to 25% is borderline between amorphous and elastomeric. A polymer with an m4 content of about 40-45% to about 50-55% typically is plastomeric and will exhibit low to medium recovery (70-80%), strain hardening, low to no yielding, and some non-uniformity of specimen deformation. A polymer with an m4% of about 40 to 45% is borderline between elastomeric and plastomeric. A polymer with an m4 content of about 55 to 80+% typically is a soft polypropylene which is plastic which yields and draws. A polymer with an m4% of about 90 to 100% usually is described as isotactic polypropylene. For propylene polymers made from catalysts of this invention, products in the elastomeric and plastomeric range are preferred; elastomeric properties may be most preferred if elastomeric characteristics are desired.
Metallocene catalyst components may be formed by known techniques. Zirconium and hafnium metallocenes are preferred and hafnium metallocenes are most preferred. The Examples disclose methods for prepar
Ernst Andreas B.
Moore Eric J.
Myers Charles L.
Quan Roger W.
BP Corporation North America Inc.
Harlan R.
Oliver Wallace L.
Wu David W.
LandOfFree
Fluxional catalysts and related ligands containing bulky... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fluxional catalysts and related ligands containing bulky..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fluxional catalysts and related ligands containing bulky... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2967152