Philips catalysts reduced with organic compounds and possessing

Details Philips catalysts reduced with organic compounds and possessing Philips catalysts reduced with organic compounds and possessing

1998-05-07

2000-11-14

Seidleck, James J.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

526104, 526113, 526352, 502256, 502438, C08F 424, B01J 2002

Patent

active

061471712

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to catalyst systems which are suitable for polymerizing ethylene and 1-alkenes and comprise as active constituents catalyst with organic compounds selected from the group of linear C.sub.4 -C.sub.10 - or cyclic C.sub.3 -C.sub.10 -alkenes with at least one internal C.dbd.C double bond, of 1,3-butadiene, of C.sub.2 -C.sub.10 -alkynes and of C.sub.1 -C.sub.10 -aldehydes, group or of the second subgroup of the Periodic Table of the Elements.
The present invention furthermore relates to a process for preparing the catalyst systems defined at the outset by loading a porous inorganic solid with a chromium compound, oxidizing the solid obtainable in this way, and treating the oxidized solid with a reducing agent, to a process for preparing poly(1-alkenes) by polymerizing 1-alkenes in the presence of a reduced Phillips catalyst system, and to the poly(1-alkenes) obtainable by polymerizing 1-alkenes in the presence of the catalyst system defined at the outset.
Olefin polymerization catalysts based on oxidized chromium compounds which are fixed on porous solids, called Phillips catalysts, are known and are employed in particular for polymerizing ethylene or copolymerizing ethylene with 1-alkenes. The polymers are important starting materials for preparing all types of sheets and shaped articles.
Granular Phillips catalysts obtained by oxidation are generally not polymerization-active within a certain timespan, usually a few minutes, even if they are already in contact with the monomer. The polymerization starts only after an induction period, and the catalyst granules can become surrounded with a protective polymer sheath.
However, during the induction period, very many unprotected catalyst granules are crushed by the shear forces prevailing in the polymerization reactor. This catalyst abrasion leads to the polymer containing unwanted polymer fine dust.
In addition, especially in gas-phase fluidized bed reactors, it is found that the crushed catalyst is carried out of the fluidized bed into the circulating gas system and only there starts to polymerize, which in turn leads to unwanted deposits of polymer in condensers etc.
The induction period can be shortened so that the catalyst granules can be covered more quickly with a protective polymer sheath if the catalysts obtained by oxidation are reduced with carbon monoxide (Inorg. Nucl. Chem. Lett. (1968), 4, 393) or with hydrogen (J. Polym. Sci., Part A1, (1970), 8, 2637).
However, the disadvantages of both methods are that the reducing agents have to be employed in large excess, and their reaction products, carbon dioxide and water, are catalyst poisons. Furthermore, the high toxicity of carbon monoxide and the great explosiveness of hydrogen lead to considerable safety costs in industrial polymerization.
It is an object of the present invention to overcome the abovementioned disadvantages and to provide in particular catalyst systems for 1-alkene polymerization which have a short induction period and can be prepared straightforwardly.
We have found that this object is achieved by the catalyst systems defined at the outset, a process for preparing these catalyst systems, a process for preparing poly(1-alkenes) using the defined catalyst systems, and the poly(1-alkenes).
The precursor for the catalyst systems according to the invention is, as a rule, a conventional Phillips catalyst prepared by oxidation, as described, for example, in DE-A 25 40 279 or EP-A 0 429 937.
Described simply, it is generally obtained by impregnating a carrier substance with a chromium-containing solution, such as chromium(III) nitrate in water or methanol, chromium(III) acetate in water or methanol, or chromium(VI) oxide in water, evaporating the solvent and heating the solid under oxidizing conditions, for example in an oxygen-containing atmosphere, at 400 to 1000.degree. C. This oxidation can take place in the presence of suitable fluorinating agents, for example ammonium hexafluorosilicate.
The carrier material is normally a porous inorganic solid, which may a

REFERENCES:
patent: 4173548 (1979-11-01), Pullukat et al.
patent: 4284527 (1981-08-01), Pullukate et al.
patent: 4368302 (1983-01-01), Downs
JMS-Rev. Macromol. Chem. Phys., 153-199 (1989).
Jrl. of Poly. Sci, Part A-1, vol., 8, 2637-2752 (1970).
Inorg. Nucl. Chem. Lts, vol. 4, 393-397, 1968.

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