Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-12-14
2004-03-30
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, C526S170000, C526S348200, C526S348300
Reexamination Certificate
active
06713582
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for producing polymers of &agr;-olefins, e.g., 1-hexene, 1-octene, 1-decene, 1-dodecene, and the like, comprising a minor amount of a bulky olefinic comonomer, e.g., norbornylene, vinyl cyclohexane, and the like, in the presence of a metallocene catalyst. The invention also relates to the resulting polymers and to lubricant compositions in which the polymer functions as a viscosity modifier.
2. Description of the Related Art
Catalytic oligomerization of olefins is a known technique for manufacturing hydrocarbon basestocks useful as lubricants. Efforts to improve upon the performance of natural mineral oil based lubricants by the synthesis of oligomeric hydrocarbon fluids have been the subject of important research and development in the petroleum industry for several decades, leading to recent commercial production of a number of superior poly(&agr;-olefin) synthetic lubricants (hereinafter referred to as “PAO”). These materials are primarily based on the oligomerization of &agr;-olefins, such as C
2
-C
20
olefins. Industrial research effort on synthetic lubricants has generally focused on fluids exhibiting useful viscosities over a wide range of temperature, i.e., improved viscosity index (VI), while also showing lubricity, thermal, and oxidative stability and pour point equal to or better than mineral oil. These newer synthetic lubricants provide lower friction and hence increase mechanical efficiency across the full spectrum of mechanical loads and do so over a wider range of operating conditions than mineral oil lubricants.
Well known structural and physical property relationships for high polymers as contained in the various disciplines of polymer chemistry have pointed the way to &agr;-olefins as a fruitful field of investigation for the synthesis of oligomers with the structure thought to be needed to confer improved lubricant properties thereon. Owing largely to studies on the polymerization of propene and vinyl monomers, the mechanism of the polymerization of &agr;-olefins and the effect of that mechanism on polymer structure is reasonably well understood, providing a strong resource for targeting on potentially useful oligomerization methods and oligomer structures. Building on that resource, oligomers of &agr;-olefins from 2 to 20 carbon atoms have been prepared with commercially useful synthetic lubricants from, e.g., 1-decene oligomerization.
A significant problem in the manufacture of synthetic lubricants is the production of lubricants in a preferred viscosity range in good yield without excessive catalyst deactivation. Frequently, it is difficult to directly produce lower viscosity range lubes without incurring lower yields due to the production of non-lubricant range materials. Methods to control molecular weight of lubricants in the oligomerization step are sought after in the art to overcome the problems in the manufacture of, particularly, lower viscosity lubricants.
Janiak, C. et al.,
Journal of Molecular Catalysis A: Chemical
, 166:193-201 (2001) provide a full literature and patent account of work describing the vinyl polymerization to homo-polynorbornene. The interest in vinyl homo-polynorbornene is driven by its dielectric and mechanical properties for the technical application as an interlevel dielectric in microelectronics applications. The norbornene/olefin copolymerization is covered to some extent for comparison the metal catalysts are presented and important polymer product properties are emphasized.
U.S. patent application Ser. No. 09/637,791, filed Aug. 11, 2000 now abandoned, discloses a liquid polyalphaolefin homo- or copolymer, preferably 1-decene, which is substantially amorphous and obtained by a polymerization process employing hydrogen and a particular type of metallocene catalyst. Additionally, a liquid polyalphaolefin homo- or copolymer containing from 2 to about 12 carbon atoms possess a unique combination of properties, i.e., low molecular weight (M
w
), low polydispersity index (M
w
/M
n
), controllable kinematic viscosity (Kv
100
), low Iodine Number (I
2
) and low glass transition temperature (T
g
) and are substantially amorphous. These liquid polyalphaolefin homo- or copolymers are useful for manufacturing a variety of products including lubricating oils in which the polyalphaolefin functions as a viscosity modifier.
SUMMARY OF THE INVENTION
The present invention is directed to a process for polymerizing &agr;-olefins, such as (but not limited to) 1-hexene, 1-octene, 1-decene, and 1-dodecene, to form low molecular weight oligomers and polymers having viscosities suitable for synthetic lubricant applications wherein the process does not require the use of a secondary hydrogenation step to achieve a saturated polymer. The polymerization is carried out in the presence of minor amounts of a bulky olefinic comonomer, such as norbornene (preferred), vinyl cyclohexane, and the like, so that viscosities as low as 20 cSt can be achieved while containing levels of unsaturation (as measured by iodine number determination) at the limits of the test method.
The monomers are polymerized in the presence of a Kaminsky-type “metallocene” catalyst, which provides for stereochemical control during polymerization. Examples of suitable catalysts include, but not limited to, rac-Et(Ind)
2
ZrCl
2
, rac-Et(IndH
4
)
2
ZrCl
2
, rac-Me
2
Si(Ind)
2
ZrCl
2
, rac-Me
2
Si(IndH
4
)
2
ZrCl
2
, Me
2
Si(Cp-9-Flu)ZrCl
2
, Me
2
C(Cp-9-Flu)ZrCl
2
, and especially (C
6
H
5
)
2
C(Cp-9-Flu)ZrCl
2
. These catalysts are commonly used in the polymerization of alphaolefins in conjunction with an alkylaluminum activator, such as methylaluminoxane (MAO), and, possibly, an organoboron activator.
The poly(&agr;-olefin) (PAO) obtained possesses excellent clarity, substantially improved viscosity index, and low temperature properties. By inclusion of both a bulky olefinic comonomer and hydrogen into the polymerization, unsaturation levels are further improved over the inclusion of hydrogen alone in metallocene polymerization, and the need for subsequent hydrogenation of the PAO to remove unsaturation is virtually eliminated.
The PAO formed by this process affords an iodine number of 3 or less for the viscosity range of 40-100 cSt, which is currently commercially available via a different process that involves hydrogenation. This represents both a saving of time and a reduction in production costs from the established production of commercial PAO.
More particularly, the present invention is directed to a process for the preparation of a poly(&agr;-olefin) copolymer comprising polymerizing at least one &agr;-olefin and at least one bulky olefin in the presence of hydrogen and a catalytically effective amount of catalyst comprising the product obtained by combining a metallocene procatalyst with a cocatalyst, the metallocene procatalyst being at least one compound of general formula:
(Cp
1
R
1
m
)R
3
(Cp
2
R
2
p
)MX
q
wherein Cp
1
of ligand (Cp
1
R
1
m
) and Cp
2
of ligand (Cp
2
R
2
p
) are the same or different cyclopentadienyl rings, R
1
and R
2
each is, independently, hydrogen or a hydrocarbyl, halocarbyl, heterocarbyl, hydrocarbyl-substituted organometalloid or halocarbyl-substituted organometalloid group containing up to about 20 carbon atoms, m is 0 to 5, p is 0 to 5 and two R
1
and/or R
2
substituents on adjacent carbon atoms of the cyclopentadienyl ring associated therewith can be joined together to form a ring containing from 4 to about 20 carbon atoms, R
3
is a bridging group bridging Cp
1
with Cp
2
, M is a transition metal having a valence of from 3 to 6, each X is a non-cyclopentadienyl ligand and is, independently, halogen or a hydrocarbyl, oxyhydrocarbyl, halocarbyl, hydrocarbyl-substituted organometalloid, oxyhydrocarbyl-substituted organometalloid or halocarbyl-substituted organometalloid group containing up to about 20 carbon atoms, and q is equal to the valence of M minus 2, the cocatalyst being an aluminoxane and it being provided that ligand (Cp
1
R
1
m
) is dif
DiMaio Anthony
Matan Thomas P.
Lu Caixia
Reitenbach Daniel
Uniroyal Chemical Company, Inc.
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