Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
2000-09-27
2002-04-30
Wu, David W. (Department: 1713)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C526S160000, C526S943000
Reexamination Certificate
active
06380125
ABSTRACT:
TECHNICAL FIELD
The invention relates to catalysts, catalyst systems and processes for production of alternating copolymers of ethylene and alpha olefins, and to novel classes of atactic and isotactic alternating copolymers of ethylene and alpha olefins, which copolymers will include a wide range of crystallinity and exhibit commercially useful properties.
BACKGROUND
The copolymerization of ethylene with alpha olefins using transition metal catalysts is well known. Metallocene catalysts have recently proven useful for olefin copolymerization as copolymers produced with metallocene catalysts tend to have more random comonomer distributions and better compositional homogeneity than copolymers produced with heterogeneous catalysts (H. H. Brintzinger, D. Fischer, R. Mülhaupt, B. Rieger, R. M. Waymouth,
Angew. Chem., Int. Ed. Engl.
1995, 34, 1143). The properties of olefin copolymers depend on not only the relative amounts of the comonomers but on the sequence distribution of the comonomers along the polymer chain and, for copolymers containing alpha olefins, on the stereochemistry of the copolymers. While metallocene catalysts have proven useful for the synthesis of olefin copolymers with random distributions of comonomers along the chain there is a need for catalyst systems which can produce olefin copolymers with a specific non-random comonomer distribution.
Atactic alternating copolymers are known. Chien et al reported that achiral bridged bis flourenyl metallocenes yield very low r
1
r
2
values for ethylene/propylene copolymerization, although they do not report any production of alternating copolymers (Yu, Z.; Marquez, M.; Rausch, M. D.; Chien, J. C.,
J. Polym. Sci. Part A: Polym. Chem.
1995, 33, p 2795-2801). Galimberti report the synthesis of elastomeric ethylene/propylene copolymers with alternating structures in the presence of achiral bridged bisflourenyl metallocenes (Galimberti, M. Resconi, L.; Albizzati, E. Eur. Pat. Appl. EP 632,066, Jan. 4, 1995). In addition, Uozumi et al. report that achiral bis indenyl catalysts yield alternating ethylene/octene copolymers. (Uozumi, T.; Miyazawa, K.; Sano, T.; Soga, K.,
Macromol. Rapid, Commun.
1997, 18, p. 883-889. Since all of these catalysts are achiral any resulting polymers would be atactic.
Crystalline alternating copolymers are known for comomoners that are not readily homopolymerized. For example, Natta reported that using a VCl
4
/AlR
3
catalyst cyclopentene can be copolymerized with ethylene to give crystalline (and probably isotactic) alternating ethylene/cyclopentene copolymers (Natta, G.; Dall'Asta, G.; Mazzanti, G.; Pasquon, I.; Valvassori, A.; Zambelli, A.,
Makromol. Chem.
1962, 54, p. 95-101.) Harrington reports that crystalline copolymers of ethylene/cyclic olefins can be prepared with bridged monocyclopentadienyl-amido metallocenes (Harrington, B. A. PCT WO 96/40806, Dec. 19, 1996). Harrington does not report the tacticity of the copolymers produced. Xu reports that crystalline isotactic alternating ethylene/stryrene copolymers can be prepared with certain bridged monocyclopentadienyl-amido metallocenes (Xu, G.
Macromolecules,
1998, 31, 2395,2402.)
Thus there is a need for catalysts systems that are able to readily copolymerize alpha olefins and ethylene to give alternating isotactic ethylene/alpha olefin copolymers.
THE INVENTION
Summary, Objects and Advantages
It is among the objects and advantages of the invention to provide methods of selecting metallocene catalyst symmetries for production of two novel classes of copolymers of ethylene with alpha olefins which have alternating structures, a first class of atactic alternating copolymers and a second class of isotactic alternating copolymers, which copolymers exhibit a wide range of crystallinity and accordingly a wide range of interesting and useful properties. It is another object and advantage of the invention to provide methods of making and use of a class of fluorenyl bridged metallocene catalysts, which by appropriate selection of ligand substituents in accord with the teachings of the invention may be symmetric or assymetric, resulting in atactic, or isotactic or atactic, respectively, alternating copolymers of ethylene with alpha olefins which exhibit a wide range of commercially useful properties. It is still another object and advantage of the invention to provide a novel class of bridged fluorenyl metallocene catalysts which in assymetric structural form interconvert between states during polymerization of ethylene with alpha olefins to produce alternating isotactic or atactic copolymers. Still other objects and advantages will be evident from a detailed consideration of the specification, formulas, schemes, and claims of this application, and from the inherent characteristics and properties of the polymers described herein and which are produceable from the catalysts hereof in accord with the processes herein described.
The invention is directed to novel processes and catalysts for the production of alternating copolymers of ethylene and alpha olefins. A degree of alternation of up to 83% is easily obtained and higher degrees of alternation with these polymerization systems are indicated. Another aspect of this invention are processes for producing novel classes of isotactic or atactic alternating copolymers of ethylene and alpha olefins, the presence or not and degree of tacticity of which is controlled by the symmetry (or assymetry) of at least one of the ligands.
In a broad aspect, the invention relates to catalysts and processes for the alternating copolymerization of ethylene and alpha olefins. The catalyst systems of the present invention encompass bridged metallocene complexes in the presence of a cocatalyst. Exemplary metallocene components comprise bridged cyclopentadienyl-flourenyl complexes of the general formula:
in which: M is a Group 3, 4 or 5 Transition metal, a Lanthanide or an Actinide; X and X′ are the same or different uninegative ligands, such as but not limited to hydride, halogen, hydrocarbyl, halohydrocarbyl, amine, amide, or borohydride substituents (preferably halogen, alkoxide, or C
1
to C
7
hydrocarbyl); L is a substituted or unsubstituted cyclopentadienyl (Cp) or indenyl ligand; Flu is a substituted or unsubstituted fluorenyl ligand; and Y is a bridging group. Exemplary preferred Transition Metals include Titanium, Hafnium, Vanadium, and, most preferably, Zirconium. An exemplary Group 3 metal is Yttrium, a Lanthanide is Samarium, and an Actinide is Thorium.
The ligand L may be any mononuclear or polynuclear hydrocarbyl or silahydrocarbyl ring, typically at least a mono-substituted cyclopentadienyl ring. Preferably L has the formula:
where R
1
is a substituted or unsubstituted alkyl, alkylsilyl or aryl substituent of 1 to about 30 carbon atoms, and R
2
-R
4
are the same or different hydrogen or substituted or unsubstituted alkyl, alkylsilyl or aryl substituents of 1 to about 30 carbon atoms, and any adjacent pair of R
1
-R
4
may be connected in a ring.
A particularly preferred group of bridged Cp-fluorenyl complexes have the general formula:
where M is a transition metal such as Ti, Hf, or Zr, R
1
and R
2
may be the same or different alkyl, alkylsilyl, or aryl, or substituted alkyl, alkylsilyl or aryl substituents of 1 to about 30 carbon atoms, or a ring thereof, and Y may be a bridging group preferably selected from a C
1
-C
4
alkylidene radical and Ge, Si, P, B, or In radicals.
In a first aspect of the invention we have found surprisingly that when the Cp ligand is symmetric, e.g., R
1
=R
2
=a primary alkyl group such as a methyl group and Y=(CH
3
)
2
C or (CH
3
)
2
Si, that atactic alternating copolymers of ethylene and alpha olefins are formed.
In a second aspect of the invention we have found that when the Cp ligand is assymetric, e.g., R
1
=a primary or secondary alkyl and R
2
=H, and Y=(CH
3
)
2
C or (CH
3
)
2
Si, alternating, isotactic ethylene/alpha olefin copolymers are formed.
While not wishing to be bound by theory, we presently beli
LeClerc Margrete K.
Waymouth Robert
Dulin, Esq. Jacques M.
Harlan R.
Innovation Law Group
The Board of Trustees of the Leland Stanford Junior University
Wu David W.
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