Polymerization catalysts

Details Polymerization catalysts Polymerization catalysts

1999-11-19

2003-01-21

Lu, Caixia (Department: 1713)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Organic compound containing

C502S103000, C502S120000, C502S161000, C526S134000, C526S129000, C526S160000, C526S165000, C526S943000

Reexamination Certificate

active

06509288

ABSTRACT:

The present invention relates to a catalyst system for use in the preparation of substantially terminally unsaturated polyolefins.
Substantially terminally unsaturated polyolefins where the terminal group in the polymer is a vinylidene group have been used as starting materials for the preparation of a variety of compounds for example oil additives, sealants, dispersants, cleaning agents, etc. Such terminally unsaturated polyolefins, especially poly(iso)butenes, have been prepared using various catalysts such as eg boron trifluoride as claimed and described in our EP-A-0145235 and EP-A-0671419. Other processes have been used to produce conventional polymers of 1-olefins using catalysts such as metallocenes alone or in combination with an activator/cocatalyst such as methylaluminoxane. Polyolefins which can be produced by the latter method include homopolymers of propylene, 1-butene, 1-pentene, 1-hexene and 1-octene as well as copolymers of such olefins with one another, in particular copolymers of propylene eg with ethylene. Such polyolefins are characterised by a low molecular weight typically in the range 300-5000.
A particular advantage of such terminally unsaturated polymers is their high degree of reactivity especially towards enophiles such as unsaturated dicarboxylic acid anhydrides which make them particularly suitable for the ene/enophile reactions which enable functionalisation of such polymers into useful products such as lubricating oil additives.
For example EP-A-353935 describes ethylene/alpha-olefin copolymer substituted mono- and dicarboxylic acid lubricant dispersant additives in which the ethylene copolymer is prepared by use of bis(n-butylcyclopentadienyl) zirconium dichloride catalyst and methylaluminoxane (MAO) cocatalyst.
EP-A490454 describes alkenyl succinimides as lube oil additives comprising an alkenyl substituent group derived from a propylene oligomer which is conveniently prepared using as a catalyst a bis(cyclopentadienyl)zirconium compound and cocatalyst MAO.
Similarly, EP-A-268214 describes the use of an alkyl substituted cyclopentadienyl compound of zirconium or hafnilum for the oligomerisation of propylene. A vast number of compounds are listed which include inter alia [(CH3)
5
C
5
]
2
ZrCl
2
. However, all the compounds listed are bis(penta-alkyl substituted cyclopentadiene) derivatives of zirconium or hafnium and these tend to give rise to polymers in which the terminal unsaturated linkage is predominantly a vinyl linkage.
In such prior art preparations the metallocenelcocatalyst systems are used in solution phase with the metallocene/cocatalyst dissolved in or miscible with the liquid reactants or in an inert solvent containing dissolved gaseous reactants.
We have now found that by using specific metallocenelcocatalyst systems, atactic polyolefins and copolymers thereof may be prepared in a range of molecular weights and having a high degree of terminal vinyldene unsaturation.
Thus according to the present invention there is provided a catalyst system suitable for the preparation of substantially terminally unsaturated atactic polymers or copolymers of &agr;-olefins having a molecular weight (Mn) in the range 200-500,000, said catalyst system comprising a metallocene of the formula:
[R
m
CpH
(5−m)
][R
n
CpH
(5−n)
]M(Z)Y
wherein
CpH is a cyclopentadienyl ligand,
Each R represents an alkyl or an aryl substituent on the CpH ligand or two R's may be joined together to form a ring, or the Rs in each CpH group when taken together represents an Si or C bridging group linking two CpH groups wherein said Si or C group may itself be substituted by hydrogen atoms or C1-C3 alkyl groups,
M is a metal selected from hafnium, zirconium and titanium,
Z is selected from a hydrogen atom, a trifluoromethyl sulphonate (hereafter “triflate”), an alkyl and an aryl group,
Y is selected from a 1,3-diketone, a &bgr;-ketoester and a triflate, and each of m and n is same or different and has a value from 0 to 5.
Unless otherwise specified, the terms (co) polymers and (co) polymerisation are used herein and throughout the specification to cover the homopolymerisation and copolymerisation of &agr;-olefins as well as including oligomerisation.
By substantially terminally unsaturated polymers or copolymers is meant polymers or copolymers having ≧60% polymer chains which contain terminal unsaturation.
More specifically, catalysts that may be used to (co)polymerise &agr;-olefins include bis(alkyl cyclopentadienyl) metallocenes wherein R is a suitably a methyl group. Thus, the alkyl substituent on the cyclopentadienyl ligands in the metallocene may be a methyl-; 1,3-dimethyl-; 1,2,4trimethyl-; or tetramethyl-group. Where R represents a substituted or unsubstituted silicon or carbon bridging group linking two CpH ligands, such metallocenes are suitably dimethylsilyl dicyclopentadienyl-zirconium, -hafnium or -titanium compound.
When two R's are joined together the cyclopentadienyl ligand may be represented by indenyl or hydrogenated indenyl.
The metal M in the metallocene may be zirconium, hafnium or titanium. Of these zirconium is preferred.
The group Z in the metallocene catalyst may be a triflate (SO
3
CF
3
) or an alkyl group. Where it is an alkyl group, such a group is preferably a C1-C3 alkyl group.
The group Y in the metallocene is selected from a 1,3-diketonate group,a &bgr;-ketoester anion and a triflate. The diketonate comprises an anion of the formula
[R
1
—C(O)—C(R
2
)—C(O)—R
3
]
−
where R
1
, R
2
and R
3
may be the same or different alkyl or aryl groups or halogenated alkyl groups and in addition R
2
may be a hydrogen atom. The keto-ester anion comprises anions of the formula
[R
1
—C(O)—C(R
2
)—C(O)—OR
3
]
−
where R
1
, R
2
and R
3
may be the same or different alkyl or aryl groups or halogenated alkyl groups and in addition R
2
may be a hydrogen atom.
Preferred anions are those wherein the halogenated alkyl groups are fluorinated alkyl groups in particular hexafluoroacetylacetonate.
Particularly suitably complexes suitable for use with the present invention are:
(C
5
H
5
)
2
Zr(CF
3
COCHCOCF
3
)SO
3
CF
3
(C
5
H
5
)
2
Zr(CF
3
COCHCOCF
3
)CH
3
.
Of these, preferred metallocene catalysts which carry a methyl or a 1,3-dimethyl or a 1,2,4-trimethyl cyclopentadienyl ligands (ie when n is 1-3) give rise to (co)polymers in which the terminal unsaturation is predominantly a vinylidene group eg suitably >97%, preferably >99% vinylidene. However, where the value of each of m and n in these catalysts is 4 or 5, the product may comprise a significant proportion of vinyl terminated groups.
When used as catalysts for (co)polymerising one or more &agr;-olefins, the metallocenes are suitably used in conjunction with a cocatalyst. The cocatalyst may be comprised of an alkylaluminoxane such as eg methyl aluminoxane (hereafter “MAO”) with or without the addition of an alkyl aluminium; the latter is suitably tri-isobutyl aluminium (hereafter “TiBAl”). In a catalyst composition comprising the metallocene catalysts of the present invention and aluminoxanes, the mole ratio of catalyst to co-catalyst is suitably in the range from 3000 to 1:1, preferably in the range from 2000 to 10:1. A reduction in the relative ratios of MAO to the alkyl aluminium used in the catalyst within the ranges specified above would significantly reduce the cost of the process. Furthermore, use of an alkyl aluminium may also improve the reaction rate significantly.
Other suitable co-catalysts are Brønsted acids comprising a cation capable of donating a proton and a compatible non-coordinating anion of general formula
[L-H]
+
[MQ
x
]
−
where L is a neutral Lewis base
H is a hydrogen atom,
M is a metal or metalloid selected from groups V-B, VI-B, VII-B, VIII-B, III-A, IV-A, and V-A of the periodic table, and
Qs are selected independantly from hydrides, dialkyl amido, alkoxide or hydrocarbyl radicals. Preferred activators are trialkyl ammonium salts of tetra-(pentafluorophenylboron).
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