Slurry polymerization process using an unsupported...

Details Slurry polymerization process using an unsupported... Slurry polymerization process using an unsupported...

1999-11-15

2001-05-22

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...

C526S126000, C526S127000, C526S161000, C526S943000, C526S160000, C526S348600, C526S336000, C502S155000

Reexamination Certificate

active

06235853

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a slurry process for the copolymerization of ethylene and an alpha olefin using a catalyst system comprising a combination of an unsupported phosphinimine-cyclopentadienyl catalyst and a cocatalyst.
BACKGROUND OF THE INVENTION
Several different polymerization processes are commercially employed for the preparation of ethylene polymers, including those known to persons skilled in the art as “high pressure”, “gas phase”, “solution” and “slurry”.
This invention relates to a slurry polymerization process. In a conventional slurry polymerization process, a “supported” catalyst (i.e. a catalyst which is deposited on a support) is used to initiate ethylene polymerization in a hydrocarbon diluent. The hydrocarbon diluent does not completely dissolve the resulting polymer, thereby creating a slurry of dispersed polymer particles (hence the term “slurry” process). The so-called “Phillips” slurry process for ethylene polymerization is widely reported to use a catalyst consisting of a chromium complex deposited on a metal oxide (such as silica or alumina) and isobutane as the diluent.
A slurry polymerization process which uses a phosphinimine-cyclopentadienyl catalyst in a conventional form (i.e. in supported form) for the preparation of ethylene polymers is disclosed in a copending and commonly assigned patent application (Stephen et al).
We have now discovered that an unsupported phosphinimine-cyclopentadienyl type catalyst may be advantageously used in a slurry polymerization process, thereby eliminating the need to prepare the catalyst in supported form and allowing simple, inexpensive catalyst addition systems to be utilized.
SUMMARY OF THE INVENTION
The present invention provides a slurry process for the copolymerization of ethylene comprising contacting ethylene and at least one other comonomer in a slurry polymerization reactor in the presence of a hydrocarbon diluent, characterized in that said copolymerization is catalyzed by a combination of 1) a phosphinimine catalyst defined by the formula:
wherein
Cp is selected from the group consisting of unsubstituted cyclopentadienyl, substituted cyclopentadienyl, unsubstituted indenyl, substituted indenyl, unsubstituted fluorenyl and substituted fluorenyl;
Pl is a phosphinimine ligand defined by the formula:
wherein each R
1
is independently selected from the group consisting of (a) a hydrogen atom, (b) a halogen atom, (c) C
1-20
hydrocarbyl radicals which are unsubstituted by or further substituted by a halogen atom, (d) a C
1-8
alkoxy radical, (e) a C
6-10
aryl or aryloxy radical, (f) an amido radical (which may be substituted), (g) a silyl radical of the formula:
 —Si—(R
2
)
3
wherein each R
2
is independently selected from the group consisting of hydrogen, a C
1-8
alkyl or alkoxy radical, C
6-10
aryl or aryloxy radicals, and (h) a germanyl radical of the formula:
Ge—(R
2
)
3
wherein R
2
is as defined above; M is a metal selected form the group consisting of titanium, hafnium and zirconium; X is an activatable ligand; n is 1 or 2; and 2) a cocatalyst, with the proviso that said phosphinimine catalyst is unsupported.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Part 1. Description of Catalysts
The catalyst used in the first reactor of the process of this invention is an organometallic complex of a group 4 metal which is characterized by having one phosphinimine ligand (where the term phosphinimine is defined in section 1.2 below) and one cyclopentadienyl ligand (as described in section 1.3 below).
Any such organometallic having a phosphinimine ligand which displays catalytic activity for ethylene polymerization may be employed. Preferred catalysts are defined by the formula:
wherein M is a transition metal selected from Ti, Hf and Zr (as described in section 1.1 below); Pl is a phosphinimine ligand (as described in section 1.2 below); Cp is a cyclopentadienyl-type ligand (as described in section 1.3 below); X is an activatable ligand which is most preferably a simple monanionic ligand such as alkyl or a halide (as described in section 1.4 below); and n is 1 or 2 depending upon the valence of the metal M and the valence of the activatable ligand(s) as described in section 1.4.
The most preferred first catalysts are group 4 metal complexes in the highest oxidation state. For example, a catalyst may be a cyclopentadienyl (phosphinimine) complex of titanium, zirconium or hafnium having two additional, monoanionic ligands. It is particularly preferred that the catalyst contains one phosphinimine ligand, one cyclopentadienyl ligand and two chloride or alkyl ligands.
1.1 Metals
The first catalyst is an organometallic complex of a group 4 metal. The preferred metals are titanium, hafnium or zirconium with titanium being most preferred.
1.2 Phosphinimine Ligand
The first catalyst must contain a phosphinimine ligand which is covalently bonded to the metal. This ligand is defined by the formula:
wherein each R
1
is independently selected from the group consisting of a hydrogen atom, a halogen atom, C
1-20
hydrocarbyl radicals which are unsubstituted by or further substituted by a halogen atom, a C
1-8
alkoxy radical, a C
6-10
aryl or aryloxy radical, an amido radical, a silyl radical of the formula:
 —Si—(R
2
)
3
wherein each R
2
is independently selected from the group consisting of hydrogen, a C
1-8
alkyl or alkoxy radical, C
6-10
aryl or aryloxy radicals, and a germanyl radical of the formula:
Ge—(R
2
)
3
wherein R
2
is as defined above.
The preferred phosphinimines are those in which each R
1
is a hydrocarbyl radical. A particularly preferred phosphinimine is tri-(tertiary butyl) phosphinimine (i.e. where each R
1
is a tertiary butyl group).
1.3 Cyclopentadienyl Ligands
As used herein, the term cyclopentadienyl-type ligand is meant to convey its conventional meaning, namely a ligand having a five carbon ring which is bonded to the metal via eta-5 bonding. Thus, the term “cyclopentadienyl-type” includes unsubstituted cyclopentadienyl, substituted cyclopentadienyl, unsubstituted indenyl, substituted indenyl, unsubstituted fluorenyl and substituted fluorenyl. An exemplary list of substituents for a cyclopentadienyl ligand includes the group consisting of C
1-10
hydrocarbyl radical (which hydrocarbyl substituents are unsubstituted or further substituted); a halogen atom, C
1-8
alkoxy radical, a C
6-10
aryl or aryloxy radical; an amido radical which is unsubstituted or substituted by up to two C
1-8
alkyl radicals; a phosphido radical which is unsubstituted or substituted by up to two C
1-8
alkyl radicals; silyl radicals of the formula —Si—(R)
3
wherein each R is independently selected from the group consisting of hydrogen, a C
1-8
alkyl or alkoxy radical C
6-10
aryl or aryloxy radicals; germanyl radicals of the formula Ge—(R)
3
wherein R is as defined directly above.
1.4 Activatable Ligand
The term “activatable ligand” refers to a ligand which may be activated by a cocatalyst, (or “activator”), to facilitate olefin polymerization. Exemplary activatable ligands are independently selected from the group consisting of a hydrogen atom, a halogen atom, a C
1-10
hydrocarbyl radical, a C
1-10
alkoxy radical, a C
5-10
aryl oxide radical; each of which said hydrocarbyl, alkoxy, and aryl oxide radicals may be unsubstituted by or further substituted by a halogen atom, a C
1-8
alkyl radical, a C
1-8
alkoxy radical, a C
6-10
aryl or aryloxy radical, an amido radical which is unsubstituted or substituted by up to two C
1-8
alkyl radicals; a phosphido radical which is unsubstituted or substituted by up to two C
1-8
alkyl radicals.
The number of activatable ligands depends upon the valency of the metal and the valency of the activatable ligand. The preferred first catalyst metals are group 4 metals in their highest oxidation state (i.e. 4
+
) and the preferred activatable ligands are monoanionic (such as a halide—especially chloride or an alkyl—especially methyl). Thus, the preferred first catalyst contains a phosphinimine ligand, a cyclopentadienyl ligand a

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