Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-12-19
2004-01-27
Lu, Caixia (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S160000, C526S165000, C526S161000, C526S172000
Reexamination Certificate
active
06683150
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for polymerizing propylene with a fluorenyl-indenoindolyl catalyst precursor in the presence of an activator to obtain high molecular weight polypropylene with little or no isotacticity and low levels of syndiotacticity.
BACKGROUND OF THE INVENTION
Polymers of propylene are well known and are characterized by their molecular weight and by the stereoregularity of the monomer units. By “stereoregularity,” we mean whether the recurring units are present in the isotactic, syndiotactic or atactic configuration. These features affect polymer processability and physical properties. Dependent upon the end use application, different properties are desirable.
Catalyst precursors that incorporate a transition metal and an indenoindolyl ligand are known. U.S. Pat. No. 6,232,260 discloses the use of transition metal catalysts based upon indenoindolyl ligands. There is no indication of stereochemical control. Pending application Ser. No. 09/859,332, filed May 17, 2001, discloses a process for the polymerization of propylene in the presence of a Group 3-5 transition metal catalyst that has two non-bridged indenoindolyl ligands wherein the resulting polypropylene has isotactic and atactic stereoblock sequences. Pending application Ser. No. 10/123,774, filed Apr. 16, 2002, discloses a process for the polymerization of ethylene in the presence of a Group 3-10 transition metal catalyst that has two bridged indenoindolyl ligands.
Propylene polymerizations using fluorenyl-cyclopentadienyl and fluorenyl-indenyl catalysts were reported in
Macromol. Rapid Commun
. 20, 284-288 (1999) to give polymers with several different tacticities including some within the desired range. However, the tacticity varied widely with polymerization temperature and no indication of polymer molecular weight was given.
Propylene polymerizations using fluorenyl-indenyl catalysts were reported in
Organometallics
19 3767-3775 (2000) and references cited therein to make a broad range of tacticities. They report that 2-methyl group and 5,6-substitution on the indenyl ligand are necessary requirements to obtain a high enough molecular weight. With these substituents, the level of mmmm pentads was greater than 25%. Without these substituents, they reported one catalyst precursor that gave a lower amount of mmmm pentads, but the highest reported M
w
was 83,000
. J. Am. Chem. Soc
. 121 4348-4355 (1999) gives results for twelve polymerizations with a 2-methyl-5,6-cyclopentyl substituted complex; the amount of mmmm pentads varied from 20 to 72% dependent upon the polymerization temperatures with the amount generally increasing with increasing polymerization temperature. This system was also studied in WO 99/52950 and WO 99/52955 and polymers with mmmm pentads between 25-60% were disclosed.
Macromolecules
35 5742-5743 (2002) studied both the zirconium and hafnium catalysts and reported some advantages using borate activators. However, for any polymerizations done at 20° C. or higher, the amount of mmmm pentads varied from 24-54%.
A bis-fluorenyl catalyst system has been reported in
Organometallics
15 998-1005 (1996) and U.S. Pat. Nos. 5,596,052 and 5,945,496 to give high molecular weight polypropylene, but the pentads were not reported. A subsequent publication by many of the same authors,
Macromol. Chem. Phys
. 202 2010-2028 (2001) indicated that the level of mmmm pentads was about 2%. This subsequent paper reported work done with substituted bis-indenyl systems. A bis-isopropylindenyl system with three different bridging groups is disclosed. One gave a very low M
w
of 9600 and no tacticity was reported. For the other two polymers, one had 15.6% mmmm pentads and the other 25.5%.
Despite the considerable work done in this area, there are very few processes known to produce high molecular weight, low tacticity polypropylene. All processes behave differently and there is often a tradeoff in useful temperature range, activity, polymer properties or process robustness. Therefore, there is a need for a good process to prepare polypropylene with all three of the desired features. Polypropylene with all three features, namely high molecular weight, low isotacticity and low syndiotacticity should have improved properties such as improved transparency, improved flexibility and improved elastic properties.
SUMMARY OF THE INVENTION
The invention is a process to polymerize propylene to give a polymer with high molecular weight and low degrees of isotacticity and syndiotacticity. In particular, the polypropylene has tacticity such that mmmm is 0-20% and rrrr is 0-60%. If a polymer is completely isotactic, it can be too stiff for many applications. The high molecular weight improves strength and mechanical properties. The combination of all three features should give improved mechanical properties, toughness, strength and thermal properties.
The polymerization process is done in the presence of an activator and a fluorenyl-indenoindolyl catalyst precursor.
DETAILED DESCRIPTION OF THE INVENTION
The tacticity of a polymer affects its properties. The term “tacticity” refers to the stereochemical configuration of the polymer. For example, adjacent monomer units can have either like or opposite configuration. If all monomer units have like configuration, the polymer is “isotactic.” If adjacent monomer units have opposite configuration and this alternating configuration continues along the entire polymer chain, the polymer is “syndiotactic.” If the configuration of monomer units is random, the polymer is “atactic.” When two contiguous monomer units, a “diad,” have the same configuration, the diad is called isotactic or “meso” (m). When the monomer units have opposite configuration, the diad is called “racemic” (r). For three adjacent monomer units, a “triad,” there are three possibilities. If the three adjacent monomer units have the same configuration, the triad is designated mm. An rr triad has the middle monomer unit having an opposite configuration from either neighbor. If two adjacent monomer units have the same configuration and it is different from the third monomer, the triad is designated as having mr tacticity. For five contiguous monomer units, a “pentad,” there are ten possibilities. They are mmmm, mmmr, rmmr, mmrr, mrmm, rmrr, mrmr, rrrrr rrrr, and mrrm. A completely syndiotactic polymer would have all rrrr pentads while a completely isotactic polymer would have all mmmm pentads. The configuration can be determined by
13
C nuclear magnetic resonance spectroscopy as described in
Macromolecules
8 687 (1975) and in
Macromolecules
6 925 (1973) and references cited therein. For more information on polymer stereochemistry, see G. Odian,
Principles of Polymerization
, 2
nd
edition, pages 568-580 (1981).
The configuration of the monomer units affects the polymer properties. For example, highly isotactic polypropylene readily forms a crystalline structure and has excellent chemical and heat resistance. The polypropylene made by the process of the invention is characterized in that it has low levels of isotacticity and low levels of syndiotacticity. By low levels of isotacticity, we mean the percent of pentads having mmmm configuration is less than 20%, preferably more than 2% and less than 10%. By low levels of syndiotacticity, we mean the percent of pentads having rrrr is less than 60%, preferably more than 10% and less than 25%. Because of the low levels of syndiotacticity and isotacticity, the polymer is predominantly or even completely amorphous and generally has no melting point. It is transparent, flexible and has good elastic properties.
The polymer has high molecular weight. By high molecular weight, we mean the weight average (M
w
) molecular weight is greater than 65,000 and preferably greater than 100,000. The M
w
can be measured by gel permeation chromatography and affects polymer properties such as elasticity. Generally, the elastic properties such as tensile set and stress recovery improve with increasing molecular weight.
The polymer is prepared by polymeriz
Meverden Craig C.
Nagy Sandor
Tsuie Barbara M.
Equistar Chemicals LP
Lu Caixia
Schuchardt Jonathan L.
Tyrell John
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