Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-06-08
2003-04-08
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S128000, C526S169000, C526S335000, C526S136000, C526S348000, C502S117000, C502S121000, C502S162000
Reexamination Certificate
active
06545107
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a catalyst composition for polymerizing conjugated dienes such as 1,3-butadiene.
BACKGROUND OF THE INVENTION
Syndiotactic 1,2-polybutadiene is a high-vinyl polybutadiene 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. Due to its stereoregular structure, syndiotactic 1,2-polybutadiene is a crystalline thermoplastic resin, but it 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, and molybdenum for preparing 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: (1) a catalyst system comprising a cobalt compound, a phosphine compound, an organoaluminum compound, and water and (2) a catalyst system comprising a cobalt compound, an organoaluminum compound, and carbon disulfide. 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; halogenated solvents present toxicity problems.
The second cobalt catalyst system uses carbon disulfide. 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 use 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 molybdenum-containing compounds, such as the combination of molybdenum acetylacetonate and triethylaluminum, are also known 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 molybdenum-based catalyst systems have no industrial utility.
U.S. Pat. No. 3,336,280 discloses a process for polymerizing 1,3-butadiene to rubbery 1,2-polybutadiene by using a catalyst system comprising molybdenum pentachloride, a trialkylaluminum compound, and a promoter compound selected from the group consisting of ethers, amines, amides, and alkylideneamines. U.S. Pat. No. 3,451,987 describes a process for preparing amorphous 1,2-polybutadiene by polymerizing 1,3-butadiene in the presence of a catalyst system comprising a molybdenum halide or oxyhalide and a dialkylaluminum alkoxide. Japanese Pat. No. 75,154,389 (See
Chemical Abstracts
1976, Vol. 84, 151913k) discloses a process that produces rubbery 1,2-polybutadiene by polymerizing 1,3-butadiene in the presence of a catalyst system consisting of molybdenum pentachloride, an organoaluminum compound, and phenol. U.S. Pat. No. 4,912,182 discloses a process for synthesizing high vinyl polybutadiene by polymerizing 1,3-butadiene in the presence of a catalyst system comprising a molybdenum-containing compound prepared by modifying molybdenum pentachloride, molybdenum trichloride, or molybdenum tetrachloride with an alkyl carboxylic acid or an aryl carboxylic acid, and an aluminum-containing compound prepared by modifying a trialkylaluminum compound with 2-allylphenol. These molybdenum-based catalyst systems, however, produce amorphous atactic 1,2-polybutadiene, which has no crystallinity.
Because syndiotactic 1,2-polybutadiene is a useful product 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 (a) an molybdenum-containing compound (b) a silyl phosphonate, and (c) an organoaluminum compound.
The present invention also includes a catalyst composition formed by a process comprising the steps of combining (a) a molybdenum-containing compound, (b) a silyl phosphonate, and (c) an organoaluminum compound.
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) a molybdenum-containing compound, (b) a silyl phosphonate, and (c) an organoaluminum compound.
Advantageously, the catalyst composition of the present invention does not contain carbon disulfide. Therefore, the toxicity, objectionable smell, dangers, and expense associated with the use of carbon disulfide are eliminated. In addition, 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. Further, the molybdenum-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 nonhalogenated solvents such as aliphatic and cycloaliphatic hydrocarbons.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The present invention is directed toward a catalyst composition that can be employed to synthesize syndiotactic 1,2-polybutadiene. It has now been found that 1,3-butadiene can be efficiently polymerized into syndiotactic 1,2-polybutadiene by using this molybdenum-based catalyst composition. Other conjugated dienes can likewise be polymerized.
The catalyst composition of the present invention is formed by combining (a) a molybdenum-containing compound, (b) a silyl phosphonate, and (c) an organoaluminum compound. In addition to these three catalyst ingredients (a), (b), and (c), other organometallic compounds or Lewis bases can also be added, if desired.
Various molybdenum-containing compounds or mixtures thereof can be employed as ingredient (a). Molybdenum-containing compounds that are soluble in a hydrocarbon solvents such as aromatic hydrocarbons, aliphatic hydrocarbons, or cycloaliphatic hydrocarbons are preferred. Hydrocarbon-insoluble molybdenum-containing compounds, howev
Brumbaugh Dennis R.
Hayes Michael W.
Luo Steven
Bridgestone Corporation
Choi Ling-Sui
Palmer Meredith E.
Reginelli Art
Wu David W.
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