Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
2000-02-16
2002-01-01
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S103000, C502S152000, C502S155000, C502S167000, C502S169000, C556S012000, C556S051000, C556S052000, C556S410000, C564S238000, C564S271000, C564S272000, C564S321000, C564S429000, C564S442000
Reexamination Certificate
active
06335303
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a polymerization catalyst composition and to its use in the polymerization of alkenes (olefins), in particular alpha olefins. The present invention relates to methods of making a series of organic compounds, the methods for making metal-containing catalyst systems employing these organic compounds, and a polymerization process for employing the catalysts. In particular, the present invention relates to polymerization catalysts containing electron-withdrawing amide ligands.
BACKGROUND OF THE INVENTION
The use of metal-containing compounds as catalysts for the polymerization of small organic molecules to high molecular weight polymer is an area of intense interest.
Polymerization processes of olefins, such as the production of polyethylene from ethene, whereby homogeneous catalyst systems of the Ziegler-Natta type are used, are well known. Several factors are important in determining the utility of a particular catalyst system. Firstly, the system must show good catalytic activity, that is, each molecule of catalyst should be capable of joining together many hundreds, thousands or even millions of monomer units before it is subject to deactivation. Secondly, the catalyst should provide good control over the molecular weight of the resultant polymer chain and give a narrow molecular weight distribution of polymer chains. Thirdly, the catalyst should provide good control over the molecular architecture of the polymer which it produces. In the polymerization of propylene, for example, the catalyst may be capable of aligning all of the pendant methyl groups onto the same side of the polymer chain (isotactic), while another catalyst may constrain them to alternate in a left-right-left-right sequence as the polymer chain is formed (syndiotactic).
Fourthly, the catalyst should, if desired, allow the incorporation into the polymer chain of two or more different monomer types and the formation of co-polymers containing monomers of widely differing structures.
The polymerization of hydrocarbon monomers containing a double bond (i.e. alkenes, or olefins) is one of the largest volume processes carried out by the chemical industry. The field of olefin polymerization is dominated by the use of catalysts containing the Group IV metals (titanium, zirconium and hafnium) and to a lesser extent chromium and vanadium. In recent years, the use of Group IV metal catalysts containing one or, more usually, two cyclopentadienyl-type ligands (such as the complex depicted in I) has become extremely important due to their high catalytic activity, and extremely good control over both molecular weight distribution and molecular architecture of the resulting polymer.
These catalysts are being investigated extensively by major chemical companies. However, a drawback of these catalyst systems is their inability to co-polymerize olefins with many of the readily-available co-monomers desired by industry (e.g. vinyl chloride, carbon monoxide). In many cases the co-monomers are oxygen-containing species which coordinate very strongly to the metal center and prevent the coordination and polymerization of the olefin.
Thus a considerable amount of work is being focused upon developing alternatives to the bis-cyclopentadienyl ligand system for the early transition metals and lanthanides. One option which has been explored is to employ diimine ligands on a transition metal center (II), and this type of complex has been found to be extremely useful for the co-polymerization of olefins with olefinic esters.
Another possibility which has been investigated is to replace one or both of the cyclopentadienyl ligands with a bulky oxygen-donor ligand such as an aryloxide (as shown in III and IV).
However, previous work has shown that the introduction of these relatively electron-donating ligands in place of cyclopentadienyl ligands greatly attenuates the catalytic activity of a metal center (see Clark et al.,
Organometallics
1996, 15, 949 and Butcher et al.,
Organometallics
1996, 15, 1488). This is believed to be a result of build-up of electron density at the metal center which reduces the electrophilicity of the metal.
In order to counteract this undesirable effect, the present catalyst system was developed involving: (i) changing the ligand donor atom from oxygen to nitrogen, which has only one rather than two lone pairs capable of donation to a metal center; (ii) placing highly electron-withdrawing groups onto the nitrogen atom to further reduce the amount of electron density donated to the metal center; and, (iii) as catalytic activity for olefin polymerization has been reported to be increased by linking or “tying-back” two ligands to form a single bidentate ligand (see Fendrick et al.,
Organometallics
1988, 7, 1828), this principle was applied and two amine ligands are linked together to form a single ligand containing two —NH groups:
While a few recent patents and papers have described the use of such “tied-back” bis-amine ligands in the formulation of olefin polymerization catalysts, the substituents employed on the nitrogen atoms were alkyl or aryl groups, which serve to provide steric bulk but do not greatly influence the electronic characteristics of the ligand. For example, in WO 92/12162 there are disclosed catalyst systems for the polymerization of alpha olefins, comprising as a first component an amido transition metal compound of the general formula (A)
wherein M is zirconium, hafnium or titanium, N is a nitrogen atom having three substituents, X is any univalent anionic ligand, R is a hydrocarbyl, T is a covalent hydrocarbyl bridging group containing a Group 14 or 16 element such as a silicon radical, y is 1 or 0 and z is 2−y, and as a second component alumoxane. The disclosed effect of this group of catalysts is the production of solid stereoregular polyolefins having a molecular weight well in excess of 100,000.
In WO 96/27439 there are disclosed catalyst systems for the oligomerization of ethene to higher olefins, comprising as a first component a compound represented by the general formula (B)
wherein M is zirconium, hafnium or titanium; each N is a three coordinate nitrogen atom; each Y is Si, Ge or Sn; each X is, independently, a hydride or R; each R is, independently, a hydrocarbyl one or more carbon atoms of which may be substituted by an element selected from Si, O, P, N and S; Q is a neutral Lewis base and m is a number from 0 to 2; or a dimer thereof. The disclosed effect of this group of catalysts is the production of olefins having a chain length within the range of 4 to 24 carbon atoms.
The present invention combines the concept of the bis-amine ligand with the use of electron-withdrawing or electron-donating substituents so as to influence the electronic as well as the steric character of the ligand.
DETAILED DESCRIPTION OF THE INVENTION
There has now been found a number of novel catalyst compositions based on bridged or unbridged amido transition metal or lanthanide compounds which are effective in the polymerization of alpha olefins to high molecular weight polymers. These catalyst compositions are distinguished from the prior art by the ability to greatly affect the electrophilicity of the metal center by introducing electron-withdrawing substituents directly onto the nitrogen atoms. Compared to the best catalyst compositions based on metallocenes, these novel compositions are distinguished by the ease of preparation of the complexes from readily available precursors.
The present invention is useful for performing polymerization reactions—most notably the polymerization of olefins, such as ethylene and propylene, but is also applicable to the polymerization of cyclic carbonate monomers to form polycarbonates. The focal point of the invention is a catalyst system which utilizes electron-withdrawing amide ligands attached to a transition or lanthanide metal center.
The present invention also provides classes of bridged bis-amine ligands which are C
2
-symmetric (chiral), which may be produced either by placing an inherently chi
Click Damon R.
Watkin John G.
Bell Mark L.
Cottrell Bruce H.
Pasterczyk J.
The Regents of the University of California
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