Gas phase olefin polymerization process

Details Gas phase olefin polymerization process Gas phase olefin polymerization process

1999-07-09

2002-08-20

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...

C526S129000, C526S130000, C526S134000, C526S161000, C526S172000, C526S901000, C526S067000, C526S068000, C526S069000, C526S070000

Reexamination Certificate

active

06437062

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a polymerisation process in particular to a gas phase process for the polymerisation of olefins using a catalyst system comprising an activated metallocene complex.
BACKGROUND OF THE INVENTION
Catalysts based on metallocene complexes have been widely used for the polymerisation of olefins. These complexes are used in catalyst systems typically comprising a bis(cyclopentadienyl) transition metal as the complex and a cocatalyst. Such bis (Cp) transition metal complexes are referred to as metallocenes and are typically based on titanium or zirconium metals and when used are cocatalysed with aluminium compounds such as aluminoxanes. When used in gas phase processes such bis (Cp) metallocene systems may be supported on silica. Such catalyst systems are described in EP 129368 and EP 206794.
More recently another type of transition metal complex has been used to prepare olefin polymers. Such complexes have a single cyclopentadienyl ring ligand and a hetero atom bonded to the metal atom and may also be used in conjunction with aluminoxanes. These complexes are referred to as having a ‘constrained geometry’ and are described in EP 420436 and EP 416815.
Similar catalyst systems are taught in EP 418044 and WO 92/00333. In these systems the catalyst system comprises a mono(cyclopentadienyl) heteroatom metal complex and an ionic activator compound and such systems have been referred to as ionic mono(cyclopentadienyl) catalysts. Typical ionic activators for such systems may be exemplified by borates.
WO 95/00526 describes titanium or zirconium complexes in which the transition metal is in the +2 formal oxidation state. The complex also comprises a neutral, conjugated or non-conjugated diene ligand which forms a &pgr;-complex with the metal. Such complexes are rendered catalysts by combination with an activating cocatalyst for example aluminoxanes, boranes or borates. When used in a gas phase polymerisation process such catalysts are also suitably supported on silica.
Another type of catalyst system is described in WO 96/04290. Here the metallocene complex is represented by a bis(Cp) complex but which also comprises conjugated dienes which may be associated with the metal as a &pgr;-complex or &sgr;-complex.
Metallocene complexes have been disclosed as suitable for use in processes for the polymerisation of olefins in the gas phase. For example EP 206794, EP 696293, EP 719289, EP 802202, EP 659773, EP 593083 and EP 739360 disclose the use of metallocene complexes in the gas phase.
SUMMARY OF THE INVENTION
We have now surprisingly found that in gas phase processes using activated metallocene catalyst systems an improvement in catalytic activity may be obtained by the injection of an inert liquid into the reactor.
In particular we found that the use of lower alkanes are particularly suitable for this purpose.
Thus according to the present invention there is provided a process for the polymerisation of olefins in the gas phase said process being carried out in the presence of a catalyst system comprising (a) a metallocene and (b) an activator characterised in that a lower alkane is added to the gas phase reactor operating in non-condensed mode.
The alkane is added preferably directly to the reactor.
DESCRIPTION OF PREFERRED EMBODIMENTS
Titanium (II) or zirconium (II) complexes are particularly suitable as the metallocene for use in the process of the present invention. Such complexes are disclosed in the aforementioned WO 95/00526 which is incorporated herein by reference. The complexes have the general formula:
wherein:
R′ each occurrence is independently selected from hydrogen, hydrocarbyl, silyl, germyl, halo, cyano, and combinations thereof, said R′ having up to 20 non hydrogen atoms, and optionally, two R′ groups (where R′ is not hydrogen, halo or cyano) together form a divalent derivative thereof connected to adjacent positions of the cyclopentadienyl ring to form a fused ring structure;
X is a neutral &eegr;
4
- bonded diene group having up to 30 non-hydrogen atoms, which forms a &eegr;-complex with M;
Y is —O—, —S—, —NR*—, —PR*—;
M is titanium or zirconium in the +2 formal oxidation state;
Z* is SiR*
2
, CR*
2
, SiR*
2
SiR*
2
, CR*
2
CR*
2
, CR*═CR*, CR*
2
SiR*
2
, or GeR*
2
; wherein:
R* each occurrence is independently hydrogen, or a member selected from hydrocarbyl, silyl, halogenated alkyl, halogenated aryl, and combinations thereof, said R* having up to 10 non-hydrogen atoms, and optionally, two R* group from Z* (when R* is not hydrogen), or an R* group from Z* and an R* group from Y form a ring system.
Most preferred complexes are amidosilane or amidoalkanediyl complexes wherein the metal is titanium.
Highly preferred diene groups are 1,4-diphenyl-1,3-butadiene, 1,3-pentadiene, 1,4-dibenzyl-1,3-butadiene, 3-methyl-1,3-pentadiene.
Illustrative but not limiting examples of complexes preferred are (tert-butylamido) (tetramethyl-&eegr;5-cyclopentadienyl) dimethyl silane titanium (II) 1,4-diphenyl-1,3 -butadiene,
(tert-butylamido) (tetramethyl-&eegr;5-cyclopentadienyl) dimethyl silane titanium (II) 1,3-pentadiene,
(tert-butylamido) (2-methylindenyl) dimethylsilanetitanium (II) 1,4-diphenyl-1,3-butadiene.
These complexes are rendered catalytically active by combination with an activating cocatalyst. Suitable cocatalysts include aluminoxanes, especially methylaluminoxane (MAO) or strong Lewis acids eg tri (hydrocarbyl) boron compounds or halogenated derivatives.
A particularly preferred activator is tris (pentafluorophenyl) boron.
Other complexes suitable for use in the process of the present invention are those in which the metal is in a higher valency state. Such complexes are disclosed in EP 416815 and EP 491842 both of which are incorporated herein by reference. The complexes have the general formula:
wherein:
Cp* is a single &eegr;5-cyclopentadienyl or &eegr;5-substituted cyclopentadienyl group optionally covalently bonded to M through —Z—Y— and corresponding to the formula:
 wherein R each occurrence is hydrogen or a moiety selected from halogen, alkyl, aryl, haloalkyl, alkoxy, aryloxy, silyl groups, and combinations thereof of up to 20 non-hydrogen atoms, or two or more R groups together form a fused ring system;
M is zirconium, titanium or hafnium bound in an &eegr;5 bonding mode to the cyclopentadienyl or substituted cyclopentadienyl group and is in a valency state of +3 or +4.
X each occurrence is hydride or a moiety selected from halo, alkyl, aryl, silyl, germyl, aryloxy, alkoxy, amide, siloxy, and combinations thereof (e.g. haloalkyl, haloaryl, halosilyl, alkaryl, aralkyl, silylalkyl, aryloxyaryl, and alkyoxyalkyl, amidoalkyl, amidoaryl) having up to 20 non-hydrogen atoms, and neutral Lewis base ligands having up to 20 non-hydrogen atoms;
n is 1 or 2 depending on the valence of M;
Z is a divalent moiety comprising oxygen, boron, or a member of Group 14 of the Periodic Table of the Elements;
Y is a linking group covalently bonded to the metal comprising nitrogen, phosphorus, oxygen or sulfur, or optionally Z and Y together form a fused ring system.
Most preferred complexes are those wherein Y is a nitrogen or phosphorus containing group corresponding to the formula (—NR
1
) or (—PR
1
) wherein R
1
is C
1
-C
10
alkyl or C
6
-C
10
aryl and wherein Z is SiR″
2
, CR″
2
, SiR″
2
SiR″
2
, CR″═CR″ or GeR″
2
in which R″ is hydrogen or hydrocarbyl.
Most preferred complexes are those wherein M is titanium or zirconium.
Illustrative, but not limiting examples of suitable complexes are (tert-butylamido) (tetramethyl-&eegr;5-cyclopentadienyl) dimethyl silanetitanium dimethyl, (tert-butylamido) dibenzyl (tetramethyl-&eegr;5-cyclopendienyl) silane zirconium dibenzyl, (benzylamido) dimethyl (tetramethyl-&eegr;5-cyclopentadienyl) silane titanium dichloride, (phenylphosphido) dimethyl (tetramethyl-&eegr;5-cyclopentadienyl) silane zirconium dibenzyl and the like.
These complexes are rendered catalytically active by combination

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