Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-04-05
2001-11-20
Wood, Elizabeth D. (Department: 1755)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S092000, C526S093000, C526S100000, C526S136000, C526S139000, C526S169100, C526S127000, C526S128000, C526S171000, C526S335000, C502S152000, C502S153000, C502S154000, C502S155000, C502S158000, C502S162000
Reexamination Certificate
active
06320004
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an iron-based catalyst composition for polymerizing conjugated dienes and the polymeric compositions therefrom.
BACKGROUND OF THE INVENTION
Polymers prepared by polymerizing conjugated dienes are useful. For example, 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 from syndiotactic 1,2-polybutadiene. It can also be blended into and co-cured with natural or synthetic rubbers in order to improve the properties thereof. 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, iron, 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.
Two cobalt-based catalyst systems are known for preparing syndiotactic 1,2-polybutadiene. The first comprises a cobalt compound, a phosphine compound, an organoaluminum compound, and water. This catalyst system 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 catalyst system comprises a cobalt compound, an organoaluminum compound, and carbon disulfide. Because carbon disulfide has a low flash point, obnoxious smell, high volatility, and toxicity, it 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 melting temperature of about 200-210° C., which makes it difficult to process. Although the melting temperature of the syndiotactic 1,2-polybutadiene produced with this cobalt catalyst system can be reduced by employing a catalyst modifier, the use of this catalyst modifier has adverse effects on the catalyst activity and polymer yields.
Syndiotactic 1,2-polybutadiene compositions that have multiple melting temperatures are also useful. Syndiotactic 1,2-polybutadiene compositions that have a relatively high melting temperature are generally characterized by having better mechanical properties than syndiotactic 1,2-polybutadiene compositions having relatively low melting temperatures. On the other hand, syndiotactic 1,2-polybutadiene having relatively low melting temperatures are known to mix well, especially during mechanical kneading with elastomers. Syndiotactic 1,2-polybutadiene compositions that have multiple melting temperatures benefit from both of these advantages.
Because conjugated diene polymers are useful, and the catalysts known heretofore in the art have many shortcomings, there is a need for improved catalyst compositions. Also, because syndiotactic 1,2-polybutadiene compositions having multiple melting temperatures are useful, there is likewise a need to develop a catalyst composition and process for preparing these compositions.
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 a iron-containing compound, an organomagnesium compound, and a silyl phosphonate.
The present invention also includes a catalyst composition formed by a process comprising the steps of combining a iron-containing compound, an organomagnesium compound, and a silyl phosphonate.
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 iron-containing compound, an organomagnesium compound, and a silyl phosphonate.
Advantageously, the catalyst compositions of this invention have very high catalytic activity and stereoselectivity for polymerizing 1,3-butadiene into syndiotactic 1,2-polybutadiene. This activity and selectivity, among other advantages, allows syndiotactic 1,2-polybutadiene to be produced in high yields with low catalyst levels after relatively short polymerization times. Significantly, syndiotactic 1,2-polybutadiene having one or more melting temperatures can be prepared without a melting temperature modifier. In addition, the catalyst composition of this invention does not contain carbon disulfide. Further, the iron-containing compounds that are utilized in the catalyst composition of this invention 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 non-halogenated solvents such as aliphatic and cycloaliphatic hydrocarbons.
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Syndiotactic 1,2-Polybutadiene with Co-CS2Catalyst System I. Preparation Properties and Application of Highly Crystalline Syndiotactic 1,2-Polybutadiene, II. Catalyst for Stereospecific Polymerization of Butadiene to Syndiotactic 1,2-Polybutadiene, III.1H and13C-NMR Study of Highly Syndiotactic 1,2-Polybutadiene and IV Mechanism of Syndiotactic Polymerization of Butadiene with Cobalt Compounds-Organoaluminum-CS2,Journal of Polymer Science: Polymer Chemistry Edition, by H. Ashitaka et al., vol. 21, pp. 1853-1860 and 1951-1995, (1983) No month.
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Bridgestone Corporation
Burleson David G.
Reginelli Arthur M.
Wood Elizabeth D.
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