Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
1998-10-05
2001-02-06
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S155000, C502S162000, C502S165000, C502S166000, C502S167000, C502S168000, C502S169000, C502S171000, C502S172000
Reexamination Certificate
active
06184171
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to catalyst compositions suitable for olefinic polymerization and to methods of forming polyolefinic products using the subject catalyst composition. More particularly, the present invention is directed to heterogeneous catalyst composition comprising a cation component derived from at least one bidentate or tridentate transition metal compound which is activated by an ionic metal or metalloid, silane-modified inorganic oxide support, as fully described herein below. The subject compositions have been found useful in catalyzing olefinic and acetylenic polymerization to provide high molecular weight homopolymers and functionalized copolymers.
Ziegler-Natta and metallocene-alumoxane type catalyst systems are well known in the art as being useful for the polymerization of olefins. Recently, metallocene ionic-pair type of catalyst has been developed which can provide polymer products having improved properties compared to conventional catalyst systems.
Ziegler-Natta type catalysts have long been the conventional system used in olefinic polymerization processes. The transition metal catalyst and the activator (e.g., trialkyl aluminum) may be introduced into the reaction zone on a support. These supports are normally inorganic oxides. Silica, as a support for Ziegler-Natta type catalysts, has been widely used in commercial polyethylene processes, as described in Macromol. Symp., 1995, 89, 563.
Over the past decade, single-site olefin polymerization catalyst systems have been developed. These systems typically use a Group IV-B metallocene compound (compounds having at least one cyclodienyl group coordinated by the pi-bond to a transition metal as, for example cyclopentadienyl and bis(cyclopentadienyl) transition metal compounds) and an ionic activator. U.S. Pat. No. 5,241,025 teaches the use of a catalyst system comprising a Group III-A element compound. This compound has a cation capable of donating a proton which irreversibly reacts with a ligand of the Group IV-B metal compound and an anion which is bulky and non-coordinatable with the Group IV transition metal cation produced upon the reaction of the metallocene and activator compound. Similarly, U.S. Pat. No. 5,198,401 teaches that ionic catalyst compositions can be prepared by combining two components, bis(cyclopentadienyl) Group IV-B metal complex containing at least one ligand which will combine irreversibly with the second component or at least a portion thereof such as a cation portion thereof. The combination of the two components produces an ionic catalyst composition comprising a cationic bis(cyclopentadienyl) Group IV-B metal complex which has a formal coordination number 3 and a 4+ valence charge and the aforementioned non-coordinating anion. Both of the above U.S. Patents are directed to homogeneous metallocene polyolefin catalyst systems. Use of these catalyst systems in slurry reactors, can result in reactor fouling, poor productivities, poor polymer bulk densities, and poor polymer morphologies.
A supported ion pair catalyst system is taught in WO 94/03506. The support, which had been modified with an alkyl aluminum reagent, is treated with a solution of a metallocene catalyst and an anionic activator, and the solvent is removed. The resulting catalyst system provided a heterogeneous ion pair catalyst system of low activity. This system is taught to be useful in slurry reaction processes. Such processes are highly desired as they combine the advantages of homogeneous catalysis and the ease of particle forming associated with slurry and heterogeneous polymerization processes. However, because there is no direct chemical bond between the catalyst ion pair and the support, resolubilization of the catalyst is possible and would cause the system to be unsuitable for slurry reaction processes.
Activators which are widely used are aluminum compounds selected from an alumoxane or an aluminum compound having the formula AlR
3
wherein each R is independently selected from a C
1
-C
20
hydrocarbyl or C
1
-C
20
hydrocarbyloxy group and preferably selected from alumoxanes and tris(C
1
-C
4
hydrocarbyl) aluminum compounds. The alumoxanes are most preferred. These compounds are oligimers or polymeric aluminum oxy compounds containing chains of alternating aluminum and oxygen atoms and whereby the aluminum atoms carry a substituent such as an alkyl group. Alumoxanes are normally formed by the reaction of water and an aluminum alkyl, which may, in addition to the alkyl group, contain halide or alkoxide groups, as disclosed in U.S. Pat. No. 4,542,119 and EP-A-338,044. The most preferred alumoxane is methylalumoxane (MAO). Due to the unstable and pyrophoric nature of alumoxanes, one must use a high degree of care in handling systems using these activators.
More recently, several patents (U.S. Pat. Nos. 5,516,737; 5,529,965; 5,595,950; and 5,625,015) disclose the use of silica supported metallocene/aluminum alkyl activated systems for slurry and gas phase heterogeneous olefin polymerization processes. However, these systems, like others which use MAO and the like as activator, have known disadvantages of requiring high molar ratios of aluminum to metallocene in order to achieve a catalyst composition of suitable reactivity, although such systems still produce undesirable low molecular weight polymer product.
WO 93/11172 discloses the use of certain polyanionic transition metal catalyst compositions. The anionic moiety is composed of a plurality of metal or metalloid atom containing non-coordinating anionic groups which are chemically bonded to a core component, such as silica, via a hydrocarbyl moiety. The transition metal catalyst is generally of the metallocene type. This catalyst system has certain disadvantages. Firstly, the anionic metal or metalloid component is taught to be bonded to the support substrate by dehydrohalogenation of a halogen containing metal/metalloid precursor with hydroxyl groups of the support. Small amounts of halogen by-product and/or precursor remain in the product. These materials can poison the catalyst system. Further, the reference teaches that the metalloid precursors, 4, 5 and 6 (See FIG. 1 of WO '172) may be reacted with the hydroxylated substrate, such as silica, alumina or metal oxide to bond the metalloid to the substrate. This produces an equivalence of HCl which may be liberated or produce an ammonium halide which will poison the resultant catalyst system and, thereby, achieves a system of low activity. Still further, the reference teaches that the support should be made substantially free of residual hydroxyl groups which are known to be located on the silica surface. Such groups are also known to reduce the activity of the intended catalyst. Removal of all of the hydroxyl groups is difficult. Still further, WO 93/11172 teaches that one must avoid exposing its catalyst to high concentrations of functional (especially oxygen containing functional) groups as such groups can poison the catalyst system. Finally, the catalyst system taught by WO 93/11172 and WO 97/19959 has low catalytic activity, is sensitive to oxygen and oxygen containing groups and provides polymer products having low polydispersity (narrow molecular weight distribution). Polymer products having these properties are difficult to process (e.g., extrude) by known techniques.
It would be desirable to provide a heterogeneous catalyst composition and a polymerization process capable of producing olefinic polymers at good catalyst efficiencies. It would be further desirable to provide a heterogeneous catalyst composition suitable for use in slurry and heterogeneous gas phase polymerization processes. Still further, it would be desirable to provide a heterogeneous catalyst composition capable of producing olefinic polymers having a sufficiently high polydispersity value, that is, to provide a polymer product of desired broad molecular weight distribution and of high weight average molecular weight. Still further, it would be desirable to provide a heterogeneous ca
Bell Mark L.
Maggio Robert A.
Pasterczyk J.
Troffkin Howard J.
W.R. Grace & Co. -Conn
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