Olefin polymerization catalysts containing amine derivatives

Details Olefin polymerization catalysts containing amine derivatives Olefin polymerization catalysts containing amine derivatives

2001-01-16

2001-08-28

Bell, Mark L. (Department: 1755)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S161000, C526S139000

Reexamination Certificate

active

06281308

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a catalyst for polymerizing olefins. The catalyst contains two polymerization-stable anionic ligands, at least one of which is an amine derivative.
BACKGROUND OF THE INVENTION
Many olefin polymerization catalysts are known, including conventional Ziegler-Natta catalysts. While these catalysts are inexpensive, they exhibit low activity and must be used at high concentrations. As a result, it is sometimes necessary to remove catalyst residues from the polymer, which adds to production costs. Furthermore, Zeigler-Natta catalysts typically produce polymers having high densities and broad molecular weight distributions, properties that are undesirable for some applications such as injection molding. They are also generally poor at controlling polymer density through incorporation of &agr;-olefin comonomers. Unfortunately, when comonomers are used, they are distributed in a non-uniform fashion among the different molecular weights that comprise the molecular weight distribution. Most of the comonomer is incorporated into the low molecular weight polymer molecules; a more uniform incorporation would be desirable.
To improve polymer properties, highly active single-site catalysts. in particular metallocenes, are beginning to replace Zeigler-Natta catalysts. Although more expensive, the new catalysts give polymers with narrow molecular weight distributions, low densities, and good comonomer incorporation.
A metallocene catalyst consists of one or more cyclopentadienyl ring ligands bound to a transition metal in an &eegr;
5
fashion. The cyclopentadienyl ring ligands are polymerization-stable; that is, they remain bound to the metal during the course of the polymerization. One disadvantage of metallocene catalysts is that they tend to produce lower molecular weight polymers at higher temperatures.
Recent attention has focused on developing improved single-site catalysts in which a cyclopentadienyl ring ligand of the metallocene is replaced by a heteroatomic ring ligand. These catalysts may be referred to generally as heterometallocenes.
In particular, U.S. Pat. No. 5,554,775 discloses catalysts containing a boraaryl moiety such as boranaphthalene or boraphenanthrene. Further, U.S. Pat. No. 5,539,124 discloses catalysts containing a pyrrolyl ring, i.e., an “azametallocene.” In addition, PCT Int. Appl. WO 96/34021 discloses azaborolinyl heterometallocenes wherein at least one aromatic ring includes both a boron atom and a nitrogen atom.
Metallocenes and heterometallocenes are much more expensive to produce than the Zeigler-Natta catalysts. Therefore, further research has focused on developing less expensive single-site catalysts that give advantageous polymer properties. One approach is to use readily available organic compounds that can act as polymerization-stable, anionic ligands for transition metals. For example, 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. Other inexpensive organic ligands capable of binding a transition metal may also be available. One example is hydroxylamine derivatives Hughes, et al.,
J. Chem. Soc., Dalton Trans
. (1989) 2389, for example describe the crystal structure of organometallic compounds containing hydroxylamine or hydrazine derivatives bound to a titanium complex in an &eegr;
2
fashion, but they do not describe olefin polymerization catalysts.
In sum, new single-site catalysts are needed. Particularly valuable catalysts would be easily synthesized from readily available starting materials. These catalysts would combine the cost advantages of Zeigler-Natta catalysts with the polymer property advantages of single-site catalysts.
SUMMARY OF THE INVENTION
The invention is a catalyst for polymerizing olefins. The catalyst comprises: (a) an organometallic compound of a Group 3-10 transition metal containing an amine derivative ligand; and (b) an activator such as alumoxane. The amine derivative ligand has the formula RR′N—A
−
or RR′C═N—A
−
where A is O, S, N—R″, or P—R″. Substituents R, R′ and R″ are hydrogen or C
1
-C
20
hydrocarbyl. The Group 3-10 metal also contains other ligands to fill the vacancy of the metal. The additional ligands include polymerization-stable anionic ligands and a ligand X where X is hydride, halide, C
1
-C
20
alkoxy, siloxy, hydrocarbyl, or dialkylamido.
We surprisingly found that catalysts based on amine derivative ligands are true “single-site” catalysts for olefin polymerization: they are highly productive, they incorporate comonomers well, and they give polymers with narrow molecular weight distributions.
DETAILED DESCRIPTION OF THE INVENTION
Catalysts of the invention comprise an activator and an organometallic compound of the formula:
where
M is a Group 3-10 transition metal;
A is O, S, N—R″, or P—R″;
L is a polymerization-stable anionic ligand;
X is hydride, halide, C
1
-C
20
alkoxy, siloxy, hydrocarbyl, or dialkylamido;
R, R′, and R″, which can be same or different, are selected from hydrogen and C
1
-C
20
hydrocarbyl;
and m+n equals the valency of M minus 1.
The transition metal, M, may be any Group 3 to 10 metal or a metal from the lanthanide or actinide series. Preferably, the catalyst contains a Group 4 to 6 transition metal; more preferably, the catalyst contains a Group 4 metal such as titanium or zirconium.
When X is a C
1
-C
20
hydrocarbyl group, it is preferably a group that lacks a hydrogen atom on a carbon that is beta to M. Thus, preferred hydrocarbyl groups include methyl, benzyl, phenyl, neopentyl, or the like.
Catalysts of the invention include a polymerization-stable anionic ligand, L. Suitable L ligands include cyclopentadienyl or substituted cyclopentadienyl 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. Suitable L ligands also include substituted or unsubstituted boraaryl, pyrrolyl, quinolinyl, and pyridinyl groups as described in U S Pat. Nos. 5,554,775, 5,539,124, and 5,637,660, the teachings of which are also incorporated herein by reference. L can also be a substituted or unsubstituted azaborolinyl ligand, such as those described in PCT Int Appl. WO 96/34021. When multiple L ligands are present, they may be the same or different.
Suitable polymerization-stable anionic ligands include amine derivatives of the formula RR′N—A
−
or RR′C═N—A
−
wherein R, R′ and A are as described above. Thus, catalysts of the invention include ones having more than one amine derivative ligand.
The polymerization-stable anionic ligand L and the amine derivative ligand can be bridged. Groups that can be used to bridge the polymerization-stable anionic ligand and the amine derivative include, for example, methylene, ethylene, 1,2-phenylene, and dialkyl silyls. Normally, only a single bridge is used in the organometallic compound. Bridging the ligand changes the geometry around the transtion metal and can improve catalyst activity and other properties, such as comonomer incorporation and thermal stability.
A preferred catalyst comprises an activator and an organometallic compound of the formula:
where
M is a Group 4-6 transition metal, preferably a Group 4 metal;
and L, X, R, R′, m, and n are as described above.
Preferably, X is chlorine, methyl, or benzyl.
Another catalyst of the invention comprises an activator and an organometallic compound of the formula:
where
M is a Group 3-10 transition metal, preferably Groups 4-6 and more preferably Group 4; and
A, L, X, R, R′, m, and n are as described above.
Preferably, X is chlorine, methyl, or benzyl.
A particularly preferred catalyst comprises an activator and an organometallic compound of the formula:
where
Cp is a cyclopentadienyl ligand.
Suitable activators include alumoxanes. Preferred alumoxanes are polymeric aluminum compounds represented by the cyclic formula (R
4
—Al—O)
s
or the

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