Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
C526S124100, C526S351000, C526S348600, C502S104000, C502S115000
FIELD OF THE INVENTION
This invention relates to a method for increasing molecular weight and/or stereoregularity of poly(alpha-olefins) by polymerizing alpha-olefins in the presence of 1) a Ziegler-Natta catalyst system and 2) at least one non-polymerizing olefin which is not polymerizable under the polymerization conditions.
BACKGROUND OF THE INVENTION
Ziegler-Natta catalyst systems are commonly used for polymerization of alpha-olefins.
U.S. Pat. No. 3,732,198 (Whiteley) concerns a method of polymerizing ethylene, at high pressure and temperature, employing a Ziegler-Natta catalyst pretreated with an allylic compound. The reference teaches the use of the allylic compound to suppress free radical polymerization and thereby suppress branching in the resulting polymer.
Isospecific Polymerization of Olefins with Heterogeneous Ziegler-Natta Catalysts,
pp. 185-188 (1985, Springer-Verlag N.Y., Inc.), concerns the addition of acetylene and allene to a Ziegler-Natta reaction mixture to halt polymerization of alpha-olefins. The reference reports that these are polymerizable additives, and therefore long runs of polyacetylene or polyallene are incorporated into the polymer chain. Once the acetylene and/or allene are consumed, polymerization of alpha-olefins resumes at the original rate.
SUMMARY OF THE INVENTION
Briefly, the present invention provides a method of increasing molecular weight and/or stereoregularity of poly(alpha-olefins) by polymerizing alpha-olefins having three or more carbon atoms in the presence of 1) a Ziegler-Natta catalyst system and 2) at least one non-polymerizing olefin which is not polymerizable under the polymerization conditions. The non-polymerizing olefin may then be volatilized or otherwise removed along with any unreacted monomer. The invention further provides a means to temper polymerization rates and reaction temperatures.
What has not been described in the art, and is provided by the present invention, is a method to provide higher molecular weight and/or more stereoregular alpha-olefin polymers, without pretreatment of the catalyst, by addition of a recoverable agent to the monomer stream. This method provides a product polymer having a distinctive molecular weight profile having a bimodal distribution and a distinctive tacticity having increased mmmm pentad content.
In this application:
“cyclic internal olefin” means a compound having a non-aromatic cyclic group wherein at least two carbon atoms of a ring are connected to each other by a double bond, e.g., cyclohexene, methyl cyclohexene, phenyl cyclohexene, and the like;
“alpha-olefin” means a compound of the formula H
C=CHR wherein R is a substituted or unsubstituted alkyl group which may be straight-chain or may contain branches or cycles; and
“substituted” means substituted by conventional substituents which do not substantially interfere with the characteristics of the desired processes or products, e.g., substituents may be alkyl, alkoxy, aryl, phenyl, halo (F, Cl, Br, I), cyano, nitro, etc.
It is an advantage of the present invention to provide alpha-olefin polymers higher molecular weight and/or increased stereoregularity by a convenient means without pretreatment of the catalyst. It is a further advantage of the present invention to provide means to temper polymerization rates and reaction temperatures.
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3M Innovative Properties Company
Dahl Philip Y.
Wu David W.
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