Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Patent
1993-08-02
1995-07-25
Pal, Asok
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
502103, 502133, B01J 3100
Patent
active
054362130
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a procatalyst composition for an .alpha.-olefin polymerization catalyst, the composition comprising a magnesium dihalide carrier and thereon a compound of tetravalent titanium and an electron donor, the electron donor being a mono- or polyester of an unsaturated polycarboxylic acid in which at least two carboxyl groups are joined to contiguous carbon atoms which form double bonds.
BACKGROUND OF THE INVENTION
.alpha.-olefins are often polymerized using a Ziegler-Natta catalyst system made up of a so-called procatalyst and a cocatalyst. Of these, the procatalyst component is based on a compound of a transition metal belonging to any of Groups IVA-VIII in the Periodic Table of the Elements, and the cocatalyst component is based on an organometallic compound of a metal belonging to any of Groups IA-IIIA in the Periodic Table of the Elements (the groups are defined according to Hubbard, i.e. IUPAC). The catalyst system may also include a carrier on which the transition-metal compound is deposited and an internal electron donor which enhances and modifies the catalytic properties and is deposited on the carrier together with the transition-metal compound. In addition, a separate so-called external electron donor can also be used together with the procatalyst and the cocatalyst.
In the preparation of stereoselective high-yield Ziegler-Natta catalysts on a magnesium dihalide, organic esters are widely used as internal donors to improve the said properties of the catalyst. Publications U.S. Pat. No. 4,522,930, EP-45 977 and FI-70 028 describe an .alpha.-olefin polymerization catalyst obtained by causing a cocatalyst, an external donor and a carrier-based procatalyst to react together. The procatalyst is made up of a titanium compound deposited on a magnesium dihalide carrier and of an internal electron donor. The internal donor may be any of the following (summary of the above state of the art):
Regarding group 2) it is stated that the two carboxyl groups may, or may not, be linked to contiguous carbon atoms which form double bonds. As an example of internal electron donors of the former type, publications FI-70 028 and EP-45 977 mention the compounds di-2-ethyl-hexyl maleate, di-isobutyl maleate, di-isobutyl-3,4-furan-dicarboxylate, di-2-ethyl-hexyl fumarate, 2-ethyl-hexyl fumarate, and 2-ethyl-hexyl monomaleate. In addition, the FI publication states that the esters of maleic, pivalic, carbonic, and phthalic acids are especially advantageous internal donors.
According to Table I of the FI and EP publications, the activity of maleates is, however, only about one-half of the activity of phthalates, and thus there is very little use for them in commercial processes. By the same criteria it can be concluded that the di-butyl-itaconate presented in the table of the US publication is not a practicable internal donor, either.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a maximally active procatalyst composition for a polymerization catalyst. The invention at the same time aims at a procatalyst composition which yields a maximally tactic polymer. A further aim is that the polymer produced should have a suitable morphology, bulk density, and melt index.
These objectives have now been achieved with a procatalyst combination for an .alpha.-olefin polymerization catalyst, the procatalyst combination being is primarily characterized in what is stated in the characterization clause of claim 1. It has thus been realized that, if the electron donor used is a mono- or polyester of an unsaturated polycarboxylic acid in which at least two carboxyl groups are joined to contiguous carbon atoms forming double bonds, at least one of the said carbon atoms of the electron donor, or a carbon atom joined thereto by a double bond, is to be substituted by a hydrocarbon group having 1-20 carbon atoms.
The invention is thus based on the surprising observation that hydrocarbon groups in the vicinity of the carboxyl groups and double bonds in unsaturated polyca
Garoff Thomas
Iiskola Eero
Leinonen Timo
Mills Katriina
Borealis Holding A/S
Pal Asok
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