Catalyst and process for olefin polymerization

Details Catalyst and process for olefin polymerization Catalyst and process for olefin polymerization

2001-10-09

2004-05-04

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...

C526S130000, C526S126000, C526S172000, C526S943000, C526S352000, C502S103000

Reexamination Certificate

active

06730756

ABSTRACT:

The present invention relates to improvements in and relating to olefin polymerization, in particular metallocene-catalysed ethylene homo- or copolymerization.
Olefin polymerization may be catalysed by a wide range of catalytic materials. Within the past fifteen or so years however there has been great interest in the so-called metallocene or single site catalysts in which the catalytically active metal (usually a transition metal or lanthanide) is &eegr;-liganded by one or more, e.g. 1, 2 or 3, &eegr;-ligands, for example cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, etc. ligands. Such catalysts have been described widely in the patents and patent applications of companies such as Hoechst, Exxon, Dow, BASF, Montell, Fina and Mitsui.
Most commonly, the metallocene catalysts described in the literature are of formula A
where M is the catalytically active metal, Hal is a halide such as chloride, each L is an &eegr;-ligand, c is 0 or 1 and R*, when present, is a bridging group the linking two &eegr;-ligands L together.
Metallocene catalysts are commonly used together with a co-catalyst or catalyst activator, frequently a boron compound or an aluminoxane, for example methylaluminoxane (MAO).
Despite the extensive research that has gone into the development of metallocene olefin-polymerization catalysts over recent years, there is still a need for metallocene catalyst systems with improved properties, e.g. in terms of activity and ability to produce olefin homo- and copolymers having desired characteristics (for example molecular weight distribution, rheology, molecular structure, etc.).
It has now been found that the use of supported metallocene-amides gives rise to just such improved properties.
Thus viewed from one aspect the present invention provides a heterogeneous olefin polymerization catalyst comprising a porous particulate support material having impregnated therein a metallocene catalyst (hereinafter a “metallocene-amide”) the metal atom whereof is bound to an amide group which is not bound to a &eegr;-ligand of the metallocene, or the reaction product of a said metallocene catalyst and a co-catalyst.
Conveniently, the metallocene amide is of formula I
(L)
n
MX
a
(NR
2
)
b
  (I)
where n is 1, 2 or 3; a is 0, 1, 2, 3 or 4; b is 1, 2, 3, 4 or 5; n+a+b is the total coordination number for M; M is a catalytically active transition metal or lanthanide; each L, which may be the same or different, is a &eegr;-ligand, optionally linked via a bridging group R* to a second group L or to a metal-coordinating group X; each X is a metal coordinating group; and each R, which may be the same or different is a hydrocarbyl group or two groups R, together with the intervening nitrogen, are an optionally substituted, nitrogen bound heterocyclic group, where R (or a heterocyclic group NR
2
) may contain heteroatoms such as Si, N, P, B, O, S, etc.
In a preferred embodiment, the metallocene-amide is of formula II
(where each L is a &eegr;-ligand, M is a group 3 to 8 transition metal or a lanthanide, Hal is a halide, c is 0 or 1, R*, where present, is a bridging group linking two &eegr;-ligands L, and each R, which may be the same or different, is a hydrocarbyl group containing up to 8 carbons or the two R groups together with the intervening nitrogen form a heterocyclic group having up to 9 ring atoms, and R or NR
2
may contain other heteroatoms as mentioned above) or the reaction product of a metallocene of formula I and a co-catalyst.
In the metallocene-amide present in the catalysts according to the invention, the catalytically active metal is preferably zirconium, hafnium or titanium, and such metallocene-amides may be referred to below as zirconocene-amides, hafnocene-amides and titanocene amides.
In the heterogeneous catalyst of the invention, the porous support may be any porous, substantially inert support, such as an inorganic oxide or salt or an organic material, e.g. a metal or pseudometal oxide or halide or an organic polymer, for example silica, alumina, zirconia, silica-alumina, magnesium chloride titanium dioxide, magnesium oxide, aluminium phosphate or an acrylate, methacrylate, polyethylene, polypropylene, polystyrene, or styrene-divinylbenzene polymer. Particularly preferably the support is a fine-grained inorganic oxide such as an inorganic oxide of an element of Group 2(A), 3(B) or 4 of the Periodic Table (Hubbard), most preferably silica, alumina or a mixture or derivative of these.
The support present in the catalyst of the invention is preferably dry. In general, metal oxide supports also contain surface hydroxyl groups which may react with metallocenes or aluminoxanes. Therefore the support can be dehydrated or dehydroxylated before use. Such treatment may be either a thermal treatment or a reaction between the surface hydroxyl groups of the support and a reagent contacted with it. Thus the porous support material is preferably heat treated (calcined) before impregnation, e.g. at a temperature of 200 to 1100° C., preferably 400 to 900° C., for 0.5 to 50 hours, preferably 5 to 20 hours. Such heat treatment is preferably effected in a dry, non-reducing atmosphere, such as oxygen, air or nitrogen. The particle size before heat treatment is preferably in the range 1 to 200 &mgr;m, more preferably 5 to 40 &mgr;m, the porosity is preferably in the range 0.2 to 3.5 mL/g (more preferably at least 0.9 mL/g) and the surface area is preferably in the range 20 to 1000 m
2
/g (BET method). Examples of suitable support materials include Grace 955W silica from WR Grace & Co., Sylopol 2109 and Sylopol 55SJ (silicas from Grace Davison), and ES70F and MD747JR (silicas from Crosfield).
The porous support is preferably impregnated with both the metallocene-amide and a co-catalyst, either sequentially or more preferably simultaneously. Where impregnation is simultaneous, the porous support will conveniently become impregnated with the reaction product of the metallocene-amide and the co-catalyst. Preferred as co-catalysts are the aluminoxanes, in particular the C
1-10
alkylaluminoxanes, most particularly methylaluminoxane (MAO).
Such aluminoxanes may be used as the sole co-catalyst or alternatively may be used together with other co-catalysts. Thus besides or in addition to aluminoxanes, other cation complex forming catalyst activators may be used. In this regard mention may be made of the silver and boron compounds known in the art. What is required of such activators is that they should react with the metallocene-amide to yield an organometallic cation and a non-coordinating anion (see for example the discussion on non-coordinating anions J
−
in EP-A-617052 (Asahi)).
Aluminoxane co-catalysts are described by Hoechst in WO94/28034. These are linear or cyclic oligomers having up to 40, preferably 3 to 20, —[Al(R″)O]— repeat units (where R″ is hydrogen, C
1-10
alkyl (preferably methyl) or C
6-18
aryl or mixtures thereof).
Where a co-catalyst is used, it may be used separately but more preferably it is also loaded onto the porous support material. In this event it is preferred to allow the catalyst and the co-catalyst to react in a liquid phase and to load the reaction product onto the support. If used separately, the cocatalyst may for example be added into the polymerization reactor together with the supported metallocene-amide.
The support impregnation according to the invention is preferably effected by contacting the support with the metallocene-amide and/or co-catalyst in a liquid, or less preferably a gaseous form, e.g. in solution in an organic solvent. The volume of liquid used is preferably 0.5 to 2.0, more preferably 0.8 to 1.5, especially 0.9 to 1.1, times the pore volume of the support material. Most preferably the volume of liquid is such that an essentially dry mixing occurs, i.e. it is preferred to use a quantity insufficient to form a slurry with the support material.
The loading of porous support materials with catalysts is described at length in WO95/12622 (Borealis), U.S. Pat. No. 5,332,706 (Mobil), EP-A-2

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