Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-01-27
2001-12-18
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...
C502S104000, C502S120000, C502S152000, C526S165000, C526S172000, C526S348000, C526S943000, C526S161000, C526S348500, C526S348200, C526S348600
Reexamination Certificate
active
06331601
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a supported single-site catalyst and a process for making it. The transition metal of the catalyst is tethered through a bridged, bidentate ligand that is covalently bound to the support. The invention also relates to an olefin polymerization process that uses the supported catalyst.
BACKGROUND OF THE INVENTION
Metallocene and non-metallocene single-site catalysts (hereinafter all referred to as single-site catalysts) provide olefin polymers with narrow is molecular weight distribution, reduced low molecular weight extractables, enhanced incorporation of a-olefin comonomers, low density, and controlled content and distribution of long-chain branching. Because of these unique properties, the polymers often outperform polyolefins prepared with Ziegler-Natta catalysts.
Polymerization of an olefin with a single-site catalyst is usually conducted in solution. Solution polymerizations are easy to control, and they can be carried out under a broad range of process conditions. However, solution polymerizations require polymer products to be soluble in process solvents. For this reason, solution polymerization is usually suitable for making very low density polyethylene (VLDPE), plastomers, or elastomers that are soluble in hydrocarbons. Solution polymerization is usually not suitable for making polymers with poor solubility in hydrocarbons, such as high-density polyethylene (HDPE) or polypropylene (PP).
HDPE, PP and other olefin polymers of higher density and crystallinity are usually made in a continuous slurry, fluidized-bed gas phase, or bulk polymerization. In these polymerization processes, the catalyst and the polymer products are neither soluble in the process solvent nor in the monomer at the reaction temperature employed. Smooth and continuous operation of the slurry or gas phase process requires the catalyst particles not to clog or clump, and not to foul the reactor wall, the agitator blades, or the distributor plates. While Ziegler-Natta catalysts are commonly used in slurry and gas phase processes, single-site catalysts are generally not used because they are soluble either in the process solvent or in the monomer.
The importance of non-solution processes for making polyolefins has sparked efforts to immobilize single-site catalysts while retaining their “single-site” nature. Because the perception exists that the supported single-site catalyst can be leached from the support in the reaction solvent employed, one approach to immobilizing the metallocene complex is to covalently bind it to the support (see, e.g., liskola et al.,
Macromolecules
30 (1997) 2853, or Lee et al.,
Macromol. Rapid Commun
. 18 (1997) 427). Another method is to synthesize an amine-functional support by reacting partly hydroxylated silica with 3-aminopropyltrimethoxysilane, and then reacting the support with (
5
Me
5
)TiCl
3
to give a tethered metallocene catalyst (see Uozumi et al.,
Macromol. Rapid Commun
. 18 (1997) 9). Amine-functionalized polystyrene has also been used to make supported imidovanadium catalysts useful for ethylene polymerization (Chen et al.,
J. Chem. Soc., Chem. Commun
. (1998) 1673).
“Constrained geometry” or “open architecture” catalysts are known (see, e.g., U.S. Pat. No. 5,026,798 and EP 416,815). These unsupported catalysts comprise a metal complex of a cyclopentadienyl ring and a heteroatom bridged by a covalent group, for example, Me
2
Si(C
5
Me
4
)(N-tBu)TiCl
2
. These catalysts are highly active, and they enhance incorporation of long-chain &agr;-olefin into ethylene polymers.
New single-site catalysts are needed. Especially needed are supported single-site catalysts that can be used in non-solution olefin polymerizations without sacrificing their “single-site” character. Preferably, the catalysts would remain anchored to the support throughout the polymerization and would avoid reactor fouling. Valuable catalysts would have high activity and would give polyolefins with narrow molecular weight distribution, good long-chain &agr;-olefin incorporation, and a controlled degree of long-chain branching. Ideally, the catalysts would be easy and inexpensive to prepare with readily available reagents.
SUMMARY OF THE INVENTION
The invention is a process for making a supported single-site catalyst in which the metal component is tethered through a bridged, bidentate ligand that is covalently bound to the support.
The process comprises two steps. First, an amine-functionalized support, Q—NH
2
, reacts with a ligand compound of the formula X—A—L, in which X is a leaving group, A is a linking group, and L is a polymerization-stable pi-bonded ancillary ligand that is covalently bonded to the linking group. This gives a supported ligand of the formula: Q—NH—A—L. In step two, the supported ligand reacts with a transition or lanthanide metal compound to produce a tethered catalyst of the structure:
where M is a Group 3 to 10 transition or lanthanide metal, Y is a ligand selected from the group consisting of halide, alkoxy, siloxy, dialkylamino, C
1
-C
10
alkyl, C
6
-C
15
aryl, and C
7
-C
15
aralkyl or alkaryl, and n is the number of Y groups and equals the valence of M minus 2.
The supported catalyst maintains its “single-site” nature: it has high reactivity and produces olefin polymers with narrow molecular weight distribution. Moreover, the supported single-site catalyst of the invention is stable in the olefin polymerization process. It is not leached from the support during the polymerization, and it does not cause reactor fouling.
DETAILED DESCRIPTION OF THE INVENTION
Supported catalysts of the invention are reaction products of a supported ligand and a transition metal compound. In step one of the process, the supported ligand is prepared from an amine-functionalized support.
Amine-functionalized supports useful in the invention have one or more primary amino groups and have the general structure Q—NH
2
in which Q is an inorganic solid or a polymer support. Suitable inorganic solids include silica, alumina, magnesia, titania, or the like, or mixtures thereof. Silica is preferred. Suitable polymer supports include polyolefins, polystyrenes, polyacrylates, polyurethanes, or the like. Amine functionality is introduced by any suitable method. Some amine-functionalized supports, such as aminomethylated polystyrene, are commercially available. Example 1 below illustrates a way to introduce primary amine functionality into a silica by reacting calcined silica with 3-aminopropyltrimethoxysilane. Other methods for making amine-functionalized supports are described in U.S. Pat. Nos. 5,846,943 and 5,886,186, the teachings of which are incorporated herein by reference
The amine-functionalized support reacts with a ligand compound of the formula X—A—L to give a supported ligand of formula Q—NH—A—L. In the first formula, X is a leaving group. By “leaving group,” we mean an anionic group that can be displaced in a nucleophilic substitution reaction by the primary amine-containing support. Examples include halide, alkoxy, siloxy, dialkylamino, and the like. Halides, especially, bromide, chloride, and iodide, are preferred.
Suitable “linking groups” (A) are bivalent groups that can form a bridge between the polymerization-stable ligand and the amine group of the support. Suitable linking groups include, for example, Si(R)
2
, CH
2
, CHR, C(R)
2
, or the like. Particularly preferred is Si(R)
2
.
The linking group is covalently bonded to a polymerization-stable pi-bonded ancillary ligand (L). L is most preferably a substituted or unsubstituted cyclopentadienyl (Cp′) group with zero to four substituents (alkyl, aryl, aralkyl, alkoxy, halide, etc.), at least one of which is preferably methyl. Suitable L groups include, but are not limited to, isolobal analogues to the cyclopentadienyl ligand, such as substituted or unsubstituted boratabenzene ligands (boratabenzenes, boratanaphthalenes, borataanthracenes, etc.) bonded to A through a carbon atom or a group attached to the boron atom, pyrrole and indole ligands, open pentadienyl and cyclic
Equistar Chemicals LP
Lu Caixia
Schuchardt Jonathan L.
Wu David W.
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