Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1998-08-26
2000-06-13
Teskin, Fred
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
526126, 526134, 526153, 526160, 526161, 526165, 526346, C08F 4649, C08F 1206
Patent
active
060751045
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for polymerizing vinylidene aromatic monomers, such as styrene, to produce polymers having a high degree of syndiotacticity using a catalyst composition comprising a Group 4 metal complex and a catalyst adjuvant. The resulting polymers may be usefully employed in the preparation of solid objects and articles such as a moldings, films, sheets and foamed objects by molding, casting or the like process.
In U.S. Pat. No. 4,680,353 there is disclosed a process for the preparation of polymers of vinylidene aromatic monomers having a stereoregular structure of high syndiotacticity, by the use of Group 4 metal coordination catalysts and an alumoxane cocatalyst.
In U.S. Pat. No. 5,066,741 there are disclosed certain cationic metal compounds formed by reacting a Group 4 metal complex with ammonium or phosphonium salts of Bronsted acids containing a non-coordinating compatible anion or with cationic oxidizers containing a noncoordinating compatible anion. The complexes are usefully employed as catalysts in the polymerization of polymers of vinylidene aromatic monomers having a stereoregular structure of high syndiotacticity.
In U.S. Pat. No. 5,374,696, certain Group 4 metal complexes wherein the metal is in the +3 oxidation state and their use as addition polymerization catalysts are disclosed. For the teachings contained therein.
According to the present invention there is now provided a novel process for preparing polymers of vinylidene aromatic monomers having a high degree of syndiotacticity. The process comprises contacting at least one polymerizabie vinylidene aromatic monomer under polymerization conditions with a catalyst composition comprising:
Cp is a single .eta..sup.5 -cyclopentadienyl or .eta..sup.5 -substituted cyciopentadienyl group, the substituted cyclopentadienyl group being optionally also bonded to M through a substituent X;
M is a metal of Group 4 or the Lanthanide Series of the Periodic Table;
X each occurrence is an inert anionic ligand of up to 20 nonhydrogen atoms and optionally X and Cp are joined together;
X' is an inert, neutral donor ligand;
m and p are independently 0 or 1;
n is an integer greater than or equal to 1; and
the sum of m and n is equal to the oxidation state of the metal; the formula:
R is C.sub.1-20 hydrocarbyl, and
n is 1 or 2.
Compared to polymerization processes utilizing a similar catalyst composition that lacks the aforementioned adjuvant, the present process achieves a significantly improved conversion of monomer and greater efficiency in use, thereby permitting a reduction in the quantity of metal complex employed. In addition the molecular weight of the resulting product is desirably reduced compared to the polymer molecular weight obtained in the absence of such adjuvant. In addition the present adjuvants may be combined with the use of hydrogen to further improve the conversion and reduce the molecular weight of the resulting polymer product.
All reference to the Periodic Table of the Elements herein shall refer to the Periodic Table of the Elements, published and copyrighted by CRC Press, Inc., 1989. Also, any reference to a Group or Series shall be to the Group or Series as reflected in this Periodic Table of the Elements, utilizing the IUPAC system for numbering groups.
As used herein, the term "syndiotactic" refers to polymers having a stereoregular structure of greater than 50 percent syndiotactic of a racemic triad as determined by .sup.13 C nuclear magnetic resonance spectroscopy. Such polymers may be usefully employed in the preparation of articles and objects (for example, via compression molding, injection molding or other suitable technique) having an extremely high resistance to deformation due to the effects of temperature.
Preferred adjuvants used herein include methylsilane, dimethylsilane, phenylsilane and diphenylsilane. Most preferred are phenylsilane and diphenylsilane which due to the fact that they are liquids are readily measured and handled in the polymerization process.
With respect to the metal co
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Borodychuk Karen K.
Newman Thomas H.
Teskin Fred
The Dow Chemical Company
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