Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-03-08
2002-11-05
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...
C526S074000, C526S124900, C526S134000, C526S141000, C526S147000, C526S161000, C526S172000, C526S156000, C526S904000
Reexamination Certificate
active
06476165
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for polymerizing olefins in the presence of a supported single-site catalyst, an optional activator, and a fatty amine additive. The support is treated with an effective amount of an organoboron compound. The combination of an organoboron treated support and fatty amine surprisingly increases the activity of the catalyst.
BACKGROUND OF THE INVENTION
Many olefin polymerization catalysts are known, including conventional Ziegler-Natta catalysts. To improve polymer properties, highly active single-site catalysts, in particular metallocenes, are beginning to replace Ziegler-Natta catalysts. Although more expensive, the new catalysts give polymers with narrow molecular weight distributions and good comonomer incorporation, which allows easier production of low-density polymers.
Recent attention has focused on developing improved single-site catalysts that contain a heteroatomic ring ligand. In particular, U.S. Pat. No. 5,554,775 discloses single-site catalysts containing a boraaryl moiety such as boranaphthalene or boraphenanthrene. U.S. Pat. No. 5,539,124 discloses catalysts containing a pyrrolyl ring, i.e., an “azametallocene.” Further, U.S. Pat. No. 5,637,660 discloses catalysts in which a cyclopentadienyl moiety of a metallocene is replaced by a readily available quinolinyl or pyridinyl ligand. U.S. Pat. No. 5,902,866 discloses azaborolinyl heterometallocenes wherein at least one aromatic ring includes both a boron atom and a nitrogen atom. Additionally, PCT Intl. Appl. No. 99/24446 discloses catalysts containing an indenoindolyl ligand which contains both indene and indole units within the same ring system.
Single-site catalysts are typically soluble in the polymerization reaction medium and are therefore valuable for solution processes. However, for gas-phase, slurry, and bulk monomer processes, it is useful to immobilize the catalyst on a carrier or support in order to control polymer morphology. One disadvantage is that the supported catalysts typically give decreased activity compared to unsupported catalysts. Another disadvantage is that supported catalysts tend to cause reactor fouling and/or sheeting. Reactor fouling results in many serious problems including poor heat transfer, poor particle morphology, and forced reactor shutdown.
To solve these problems, a number of process and catalyst modifications have been disclosed. Copending appl. Ser. No. 09/318,008, filed May 25, 1999, now U.S. Pat. No. 6,211,311 , discloses pre-treating the support with a chemical modifier to improve heterometallocene catalyst activity and shelf-life. For supporting Ziegler-Natta catalysts, support modifications with organomagnesiums, organosilanes, and organoboranes are disclosed in U.S. Pat. Nos. 4,508,843, 4,530,913, and 4,565,795. Metallocene catalyst support modification with organosilanes and aluminum, zinc, or silicon compounds is taught in U.S. Pat. Nos. 4,808,561 and 5,801,113.
Methods to reduce reactor fouling have also been disclosed. Copending appl. Ser. No. 09/301,802, filed Apr. 29, 1999, now U.S. Pat. No. 6,201,076, discloses the use of fatty amine additives to reduce reactor fouling in olefin polymerization with supported heterometallocenes. For olefin polymerization using metallocenes, EP 811,638 teaches the addition of an antistatic agent to the polymerization reactor to reduce static buildup that can lead to fouling or sheeting. PCT Intl. Appl. Nos. WO 96/11960 and WO 96/11961 disclose catalyst systems formed by combining a metallocene, an activator, and an amine surface modifier applied to a support. Both references teach that the surface modifier must be added to the support during catalyst preparation in order to reduce reactor fouling.
In sum, new olefin polymerization processes that would prevent reactor fouling and increase catalyst activity with supported single-site catalysts are needed. Particularly valuable processes would use readily available additives that can be fed directly to the reactor.
SUMMARY OF THE INVENTION
The invention is a polymerization process. The process comprises polymerizing an olefin in the presence of a support, a single-site catalyst, an optional activator, and a fatty amine. The support is chemically treated with an organoboron compound. The single-site catalyst contains a polymerization-stable, heteroatomic ligand. The fatty amine is added directly to the polymerization reactor.
We surprisingly found that the addition of fatty amine, when added directly to the reactor, in combination with organoboron modification of the support increases catalyst activity compared to comparable runs without the addition of fatty amine.
DETAILED DESCRIPTION OF THE INVENTION
The process of the invention comprises polymerizing an olefin in the presence of a support that has been chemically treated with an organoboron compound, a single-site catalyst, optionally an activator, and a fatty amine. The single-site catalyst contains a polymerization-stable, heteroatomic ligand. The fatty amine is added directly to the polymerization reactor.
Single-site catalysts useful in the invention contain at least one anionic, polymerization-stable, heteroatomic ligand. Suitable heteroatomic ligands include substituted or unsubstituted boraaryl, pyrrolyl, quinolinyl, pyridinyl, and azaborolinyl groups as described in U.S. Pat. Nos. 5,554,775, 5,539,124, 5,637,660, and 5,902,866 the teachings of which are also incorporated herein by reference. Substituted or unsubstituted indenoindolyl ligands, such as those described in PCT Intl. Appl. No. 99/24446 can also be used. The polymerization-stable ligands may also include cyclopentadienyl (substituted or unsubstituted) anions such as those described in U.S. Pat. Nos. 4,791,180 and 4,752,597, the teachings of which are incorporated herein by reference.
The polymerization-stable anionic ligands can be bridged. Groups that can be used to bridge the polymerization-stable anionic ligands include, for example, methylene, ethylene, 1,2-phenylene, and dialkyl silyls. Normally, only a single bridge is used in the single-site catalyst. Bridging the ligand changes the geometry around the transition metal and can improve catalyst activity and other properties, such as comonomer incorporation and thermal stability.
The single-site catalyst includes a transition or lanthanide metal. Preferably, the metal is from Groups 3 to 10 of the Periodic Table. More preferred catalysts include a Group 4 to 6 transition metal; most preferably, the catalyst contains a Group 4 metal such as titanium or zirconium.
The single-site catalyst usually includes at least one other ligand. Preferably, the other ligand is hydride, halide, C
1
-C
20
alkoxy, siloxy, hydrocarbyl, or dialkylamido. More preferably, the ligand is hydride, chloride, bromide, C
1
-C
8
alkoxy, C
3
-C
18
trialkylsiloxy, methyl, phenyl, benzyl, neopentyl, or C
2
-C
6
dialkylamido. Particularly preferred are hydrocarbyl groups that do not undergo &bgr;-hydrogen elimination reactions (e.g., olefin formation with loss of M-H); examples of preferred hydrocarbyl groups are methyl, phenyl, benzyl, neopentyl, and the like.
An activator is preferably used to convert the metal complex to a cationically active species. Suitable activators include alumoxanes. Preferred alumoxanes are polymeric aluminum compounds represented by the cyclic formula (R
1
—Al—O)
s
or the linear formula R
1
(R
1
—Al—O)
s
AlR
1
wherein R
1
is a C
1
-C
5
alkyl group and s is an integer from 1 to about 20. Preferably, R
1
is methyl and s is from about 4 to about 10. Exemplary alumoxane activators are (poly)methylalumoxane (MAO), ethylalumoxane, and diisobutylalumoxane. Optionally, the activator is a trialkyl or triaryl aluminum compound, which preferably has the formula AlR
2
3
where R
2
denotes a C
1
-C
20
hydrocarbyl.
Suitable activators also include neutral boron and aluminum compounds, including substituted or unsubstituted trialkyl or triaryl boron or aluminum derivatives, such as tris(perfluorophenyl)boron, and ionic borates such as tri(n-butyl)ammonium t
Carroll Kevin M.
Equistar Chemicals LP
Rabago R.
Wu David W.
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