Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-11-12
2001-04-03
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S169100, C526S335000, C502S117000, C502S121000, C502S155000
Reexamination Certificate
active
06211313
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to a catalyst composition for use in polymerizing conjugated dienes. More particularly, the present invention is directed toward an iron-based catalyst composition that is formed by combining an iron-containing compound, a hydrogen phosphite, and an aluminoxane. Advantageously, the iron-based catalyst composition of this invention can be used to polymerize 1,3-butadiene into syndiotactic 1,2-polybutadiene.
BACKGROUND OF THE INVENTION
Syndiotactic 1,2-polybutadiene is a crystalline thermoplastic resin that has a stereoregular structure in which the side chain vinyl groups are located alternately on the opposite sides in relation to the polymeric main chain. Syndiotactic 1,2-polybutadiene is a unique material that exhibits the properties of both plastics and rubber, and therefore it has many uses. For example, films, fibers, and various molded articles can be made utilizing syndiotactic 1,2-polybutadiene. It can also be blended into and co-cured with natural or synthetic rubbers.
Syndiotactic 1,2-polybutadiene can be made by solution, emulsion, or suspension polymerization. Generally, syndiotactic 1,2-polybutadiene has a melting temperature within the range of about 195° C. to about 215° C., but due to processability considerations, it is generally desirable for syndiotactic 1,2-polybutadiene to have a melting temperature of less than about 195° C.
Various transition metal catalyst systems based on cobalt, titanium, vanadium, chromium, and molybdenum for the preparation of syndiotactic 1,2-polybutadiene have been reported. The majority of these catalyst systems, however, have no practical utility because they have low catalytic activity or poor stereoselectivity, and in some cases they produce low molecular weight polymers or partially crosslinked polymers unsuitable for commercial use.
The following two cobalt-based catalyst systems are well known for the preparation of syndiotactic 1,2-polybutadiene on a commercial scale: (1) a catalyst system containing cobalt bis(acetylacetonate), triethylaluminum, water, and triphenylphosphine (U.S. Pat. Nos. 3,498,963 and 4,182,813), and (2) a catalyst system containing cobalt tris(acetylacetonate), triethylaluminum, and carbon disulfide (U.S. Pat. No. 3,778,424). These cobalt-based catalyst systems also have serious disadvantages.
The first cobalt catalyst system referenced above yields syndiotactic 1,2-polybutadiene having very low crystallinity. Also, this catalyst system develops sufficient catalytic activity only when halogenated hydrocarbon solvents are used as the polymerization medium, and halogenated solvents present toxicity problems.
The second cobalt catalyst system referenced above uses carbon disulfide as one of the catalyst components. Because of its low flash point, obnoxious smell, high volatility, and toxicity, carbon disulfide is difficult and dangerous to use, and requires expensive safety measures to prevent even minimal amounts escaping into the atmosphere. Furthermore, the syndiotactic 1,2-polybutadiene produced with this cobalt catalyst system has a very high melting temperature of about 200-210° C., which makes it difficult to process the polymer. Although the melting temperature of the syndiotactic 1,2-polybutadiene produced with this cobalt catalyst system can be reduced by employing a catalyst modifier as a fourth catalyst component, the presence of this catalyst modifier has adverse effects on the catalyst activity and polymer yields. Accordingly, many restrictions are required for the industrial utilization of these cobalt-based catalyst systems.
Coordination catalyst systems based on iron-containing compounds, such as the combination of iron(III) acetylacetonate and triethylaluminum, have been known for some time, but they have shown very low catalytic activity and poor stereoselectivity for the polymerization of conjugated dienes. The product mixture often contains oligomers, low molecular weight liquid polymers, and partially crosslinked polymers. Therefore, these iron-based catalyst systems have no industrial utility.
Because syndiotactic 1,2-polybutadiene is useful and the catalysts known heretofore in the art have many shortcomings, it would be advantageous to develop a new and significantly improved catalyst composition that has high catalytic activity and stereoselectivity for polymerizing 1,3-butadiene into syndiotactic 1,2-polybutadiene.
SUMMARY OF THE INVENTION
In general, the present invention provides a catalyst composition that is the combination of or the reaction product of ingredients comprising an iron-containing compound, a hydrogen phosphite, and an aluminoxane.
The present invention also provides a catalyst composition formed by a process comprising the step of combining an iron-containing compound, a hydrogen phosphite compound, and an aluminoxane.
The present invention also provides a process for preparing 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 an iron-containing compound, a hydrogen phosphite, and an aluminoxane.
The present invention also provides a process for preparing syndiotactic 1,2-polybutadiene, comprising the step of polymerizing 1,3-butadiene in the presence of a catalytically effective amount of a catalyst composition formed by combining an iron-containing compound, a hydrogen phosphite, and an aluminoxane.
The present invention also provides a conjugated diene polymer that is prepared by polymerizing conjugated diene monomers with a catalyst composition formed by a process comprising the step of combining an iron-containing compound, a hydrogen phosphite, and an aluminoxane.
The present invention further provides a syndiotactic 1,2-polybutadiene polymer that is prepared by polymerizing 1,3-butadiene with a catalyst composition formed by a process comprising the step of combining an iron-containing compound, a hydrogen phosphite, and an aluminoxane.
Advantageously, the catalyst composition of the present invention has very high catalytic activity and stereoselectivity for polymerizing conjugated diene monomers such as 1,3-butadiene. This activity and selectivity, among other advantages, allows syndiotactic 1,2-polybutadiene to be produced in very high yields with low catalyst levels after relatively short polymerization times. Significantly, the catalyst composition of this invention is very versatile and capable of producing syndiotactic 1,2-polybutadiene with a wide range of melting temperatures without the need for a catalyst modifier that may have adverse effects on the catalyst activity and polymer yields. In addition, the catalyst composition of this invention does not contain carbon disulfide. Therefore, the toxicity, objectionable smell, dangers, and expense associated with the use of carbon disulfide are eliminated. Further, the catalyst composition of this invention is iron-based, and iron compounds are generally stable, inexpensive, relatively innocuous, and readily available. Furthermore, the catalyst composition of this invention has high catalytic activity in a wide variety of solvents including the environmentally-preferred nonhalogenated solvents such as aliphatic and cycloaliphatic hydrocarbons.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The present invention is generally directed toward an iron-based catalyst composition, methods of using this catalyst composition for polymerizing conjugated dienes, and the resulting polymers. It has now been found that conjugated dienes can be efficiently polymerized with an iron-based catalyst composition including an iron-containing compound, a hydrogen phosphite, and an aluminoxane. In particular, 1,3-butadiene can be efficiently polymerized into syndiotactic 1,2-polybutadiene by using this catalyst composition.
The catalyst composition of the present invention is formed by combining (a) an iron-containing compound, (b) a hydrogen phosphite, and (c) an aluminoxane. In addition to the three catalyst ingredients (a)
Bridgestone Corporation
Burleson David G.
Reginelli Arthur M.
Teskin Fred
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