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
2002-11-04
2004-03-02
Wood, Elizabeth (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, C502S114000, C502S115000, C502S118000, C502S129000, C502S132000, C502S133000, C502S134000, C502S150000, C502S152000, C502S153000, C502S154000, C502S155000, C502S162000, C585S010000, C585S012000, C585S506000, C585S507000, C526S096000, C526S097000, C526S098000, C526S099000, C526S103000, C526S117000, C526S135000, C526S154000, C526S172000, C526S943000
Reexamination Certificate
active
06699813
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a catalyst composition that is formed by combining a nickel-containing compound with a lanthanide-based catalyst composition.
BACKGROUND OF THE INVENTION
Catalyst systems based on lanthanide metals, in particular neodymium, are known to be useful for polymerizing conjugated diene monomers. These catalyst systems are advantageously more active in aliphatic solvents, which are environmentally preferred, than in aromatic solvents. They are also often highly stereospecific and can produce cis-1,4-polydienes or trans-1,4-polydienes depending on the catalyst compositions. For example, lanthanide-based catalyst systems including a neodymium compound, an alkylating agent, and a source of halogen are particularly useful for producing cis-1,4-polydienes from various conjugated diene monomers such as 1,3-butadiene, isoprene, and 1,3-pentadiene. These catalyst systems are also capable of copolymerizing different types of conjugated diene monomers to give stereoregular cis-1,4-copolymer.
The cis-1,4-polydienes produced with a lanthanide-based catalyst have a linear backbone structure and exhibit good green strength and excellent viscoelastic properties. The linear backbone structure is believed to improve the tensile properties and abrasion and fatigue resistance, and to reduce hysteresis loss of rubber compounds. Therefore, these cis-1,4-polydienes are particularly suitable for use in tire components such as sidewall and tread.
Low molecular weight polydienes, such as low molecular weight cis-1,4-polydienes, made with lanthanide-based catalysts are also useful in rubber compounds. They can be blended with high molecular weight cis-1,4-polybutadiene to improve a variety of properties such as fracture resistance, snow traction, wet traction, and rolling resistance. Therefore, there is a demand for low or moderately high molecular weigh polydienes.
The molecular weight of polydienes produced with lanthanide-based catalysts can be controlled by varying the amount of catalyst used or adjusting the amounts of co-catalyst concentrations within the catalyst system. As a result, polydienes having a wide range of molecular weights can be produced with lanthanide-based catalyst systems. In general, the molecular weight of the polydienes can be reduced by increasing the catalyst and co-catalyst concentrations. Very high catalyst and co-catalyst concentrations, however, are required to produce low molecular weight polydienes such as liquid polydienes, which results in very high catalyst costs. In addition, the use of high catalyst levels necessitates the removal of catalyst residues from the polymer because these residues can cause subsequent adverse effects, such as retardation of the sulfur cure rate. The removal of catalyst residues from polymer (also referred to as de-ashing) is time-consuming and adds to manufacturing costs.
One approach to these problems is to use a molecular weight regulator without raising catalyst levels. Unfortunately, traditional molecular weight regulators such as &agr;-olefins and nonconjugated dienes are ineffective in polymerizations that are catalyzed by lanthanide-based catalyst systems. In addition, the use of molecular weight regulators in Ziegler-Natta catalyst systems generally results in decrease in catalyst activity. Furthermore, the use of molecular weight regulators often adversely affects the polymer microstructure such as cis-1,4-linkage content.
Therefore, there is a need to develop a new method of regulating the molecular weight of polydienes produced with lanthanide-based catalyst systems. There is also a need to develop an improved lower-cost lanthanide-based catalyst composition for producing low molecular weight polydienes, in particular low molecular weight cis-1,4-polydienes.
SUMMARY OF THE INVENTION
It has been unexpectedly discovered that nickel compounds can be used as very efficient molecular weight regulators in conjugated diene polymerizations that are catalyzed by lanthanide-based catalyst systems.
The present invention provides a catalyst composition that is the combination of or the reaction product of ingredients comprising (a) an lanthanide compound, (b) an alkylating agent, (c) a nickel-containing compound, and optionally (d) a halogen-containing compound, with the proviso that the halogen-containing compound must be present where none of the lanthanide compound, the alkylating agent, and the nickel-containing compound contain a labile halogen atom.
The present invention also includes a process for lowering the molecular weight of polydienes prepared with a lanthanide-based catalyst system, the process comprising polymerizing conjugated dienes with a lanthanide-based catalyst system that is formed by combining (a) a lanthanide compound, (b) an alkylating agent, (c) a nickel-containing compound, and optionally (d) a halogen-containing compound, with the proviso that the halogen-containing compound must be present where none of the lanthanide compound, the alkylating agent, and the nickel-containing compound contain a labile halogen atom.
The present invention further includes a process for forming conjugated diene polymers comprising the step of polymerizing conjugated diene monomers in the presence of a catalytically effective amount of a catalyst composition formed by combining (a) an lanthanide compound, (b) an alkylating agent, (c) a nickel-containing compound, and optionally (d) a halogen-containing compound, with the proviso that the halogen-containing compound must be present where none of the lanthanide compound, the alkylating agent, and the nickel-containing compound contain a labile halogen atom.
The addition of one or more nickel-containing compounds to lanthanide-based catalyst compositions for polymerizing cis-1,4-polydienes advantageously provides a method by which the molecular weights of the resulting polydienes can be easily regulated without significantly deteriorating catalyst activity and polymer microstructure. As a result, low molecular weight polydienes can be produced in high yields with low catalyst levels after relatively short polymerization times.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
This invention is directed toward a method of regulating the molecular weights of polydienes by using a lanthanide-based composition that is modified with a nickel-containing compound. Various types of lanthanide-based compositions can be employed to catalyze the polymerization of dienes to produce polydienes. One type of lanthanide-based composition comprises a lanthanide compound, an alkylating agent, and a halogen-containing compound. When the lanthanide compound or the alkylating agent contain a halogen atom, the halogen-containing compound is optional. Another type of lanthanide-based composition comprises a lanthanide compound and an aluminoxane. Still another type of lanthanide-based composition comprises a lanthanide compound, an alkylating agent, and a non-coordinating anion or non-coordinating anion precursor.
In one embodiment, the catalyst composition is formed by combining (a) a lanthanide compound, (b) an alkylating agent, (c) a nickel-containing compound, and (d) a halogen-containing compound. Where the lanthanide compound, alkylating agent, or nickel-containing compound contains a labile halogen atom, the need for an additional compound containing a labile halogen atom is optional. Therefore, the catalyst system may be formed by combining (a) a lanthanide compound, (b) an alkylating agent, and (c) a nickel-containing compound, with the proviso that at least one of the lanthanide compound, the alkylating agent, or the nickel-containing compound includes a labile halogen atom. In addition to the catalyst ingredients (a), (b), (c), and (d), other organometallic compounds or Lewis bases can also be added, if desired.
Various lanthanide compounds or mixtures thereof can be employed as ingredient (a) of the catalyst composition. Preferably, these compounds are soluble in hydrocarbon solvents such as aromatic hydrocarbons, aliphatic hydrocarbons, or cyclo
Lawson David
Luo Steven
Masaki Koji
Ozawa Yoichi
Bridgestone Corporation
Reginelli Arthur M.
Wood Elizabeth
LandOfFree
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