Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
1995-12-15
2001-04-24
Lipman, Bernard (Department: 1713)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S126000, C502S127000, C526S123100, C526S125800, C526S351000, C526S352000, C526S352200
Reexamination Certificate
active
06221801
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a new solid catalyst component for the polymerization of olefins, making it possible to synthesize polyolefins with broadened molecular mass distributions.
BACKGROUND OF THE INVENTION
The present invention also relates to a process for the manufacture of the said solid catalyst component and to a process for the polymerization of olefins in the presence of the said solid catalyst component.
For the manufacture of polyolefin films it is preferable to have available polyolefins exhibiting broadened molecular masses. The polyolefin intended to be converted into film must preferably contain molecules of high molecular mass because these are the molecules that ensure the continuity of the film and prevent its tearing when it is stretched. A polyolefin contains molecules of high molecular mass if the ratio of the z-average molecular mass (denoted by Mz) to the weight-average molecular mass (denoted by Mw) is high. If the polyolefin contained only molecules of high molecular mass, its conversion into film would become difficult, given the high temperatures needed for its manufacture. This is why it is preferable that the polyolefin should also contain molecules of low molecular mass. A polyolefin contains molecules of low molecular mass if the ratio of the weight-average molecular mass (de noted by Mw) to the number-average molecular mass (denoted by Mn) is high and for example higher than 5.5.
It is desirable, moreover, to improve the filmability further by reducing the crystallinity of the polyolefin.
In fact, the reduction in crystallinity is reflected, on the one hand, in a lowering of the modulus of elasticity, which decreases the stiffness of the film and improves its resistance to stresses during stretching or in its final use, and, on the other hand, in a reduction in the effect of temperature on the rheological properties of the material being stretched, and this makes it easier to control the quality of the final product.
A polyolefin is less crystalline if it has a high solubility in heptane. For the film application, therefore, preference is given to a polyolefin exhibiting a low value of insolubility in heptane (represented by HI, from the expression “heptane-insoluble”), for example lower than 97% by weight and, better, lower than 94% by weight.
However, this value must not be too low because otherwise the polymer is tacky and consequently becomes difficult to transport. This value is preferably higher than 80% by weight and, still more preferably, higher than 90% by weight.
The synthesis of polyolefins containing molecules of high mass and molecules of low mass at the same time, if appropriate exhibiting an HI that is appropriate in the sense referred to above, using a productive process, that is to say in which the product efficiency is as high as possible and, in the case of propylene polymerization, is at least 20 000 grams of polymer per gram of solid catalyst component per hour, is particularly difficult without resorting to mixing subsequent to the manufacture of the polyolefins.
Patent Application EP 0385 765 A2 teaches that it is possible to broaden the molecular mass distribution of polypropylene by introducing two kinds of silanes into the polymerization mixture. This document describes polymerizations in the presence of catalyst components containing 2.5% by weight of titanium and 13.8% by weight of diisobutyl phthalate.
Patent Application EP 0350170 teaches that highly isotactic polypropylene can be obtained by polymerization of propylene in the presence of a solid catalyst component containing 2.2% by weight of titanium and in the presence of a silane as an external electron-donor.
Patent Application WO 91/14718 shows that polypropylene with a broadened molecular mass distribution can be obtained by carrying out the polymerization with the aid of a number of reactors mounted in cascade.
DESCRIPTION OF THE INVENTION
The present invention relates to a solid catalyst component for the polymerization of olefins which makes it possible to obtain polymers or copolymers exhibiting a high Mz/Mw, generally higher than 3, and a high Mw/Mn, generally higher than 5.5. In addition, when they originate from at least one monomer containing at least three carbon atoms, these polymers or copolymers generally exhibit an HI ranging from 85 to 97% by weight and capable of ranging even from 90 to 94% by weight. In addition, the solid catalyst component according to the invention exhibits a high activity. These objectives are attained without it being necessary to introduce two silanes during the polymerization and without it being necessary to resort to a number of reactors mounted in cascade.
The solid catalyst component according to the invention includes magnesium, titanium and halogen, preferably chlorine, atoms and includes a diester of phthalic acid in which the hydrocarbon groups in the ester functional groups, which may be identical or different, are saturated, linear or branched and contain from one to eight carbon atoms, the titanium being in an at least partially halogenated, preferably chlorinated, form and in an oxidation state of three and/or four, and is characterized in that the titanium is present therein in a proportion of at least 2.5% by weight and in that the diester of phthalic acid is present therein in a proportion of less than 7% by weight.
The titanium content preferably ranges from 3 to 5% by weight.
The diester content is preferably higher than 2% by weight and, better, ranges from 3 to 6% by weight.
The diester of phthalic acid may be chosen, for example, from the following compounds: diethyl phthalate, diisobutyl phthalate, di-n-butyl phthalate, dihexyl phthalate and dioctyl phthalate.
The preferred diesters are dibutyl phthalates.
It is not ruled out for the catalyst component according to the invention to contain a Lewis base not forming part of the class of the diesters entering within the composition of the catalyst component according to the invention. This Lewis base may be a liquid or solid organic compound known for entering within the composition of the catalyst components of Ziegler-Natta type. This Lewis base may be chosen from aliphatic or aromatic carboxylic acids and their alkyl esters, aliphatic or cyclic ethers, ketones, vinyl esters, acrylic derivatives, in particular alkyl acrylates or alkyl methacrylates, and alcohols. Particularly suitable as a Lewis base are compounds such as methyl para-toluate, ethyl benzoate, ethyl or butyl acetate, ethyl ether, ethyl para-anisate, tetrahydrofuran, dioxane, acetone, methyl isobutyl ketone, vinyl acetate, methyl methacrylate, ethanol and butanol. This Lewis base may be present in the catalyst component according to the invention in a proportion of 0.01 to 8% by weight. Tetrahydrofuran (THF) is a preferred Lewis base.
Tetrahydrofuran is preferably present in a proportion of 0.3 to 1% by weight in the solid catalyst component according to the invention.
Any known techniques for manufacturing solid catalyst components of Ziegler-Natta type, containing magnesium, halogen and titanium atoms and an ester of phthalic acid, may be adapted for the synthesis of the catalyst component according to the invention, so long as these processes can be modified in respect of the quantity of the titanium derivative which is introduced and in respect of the quantity of ester of phthalic acid which is introduced, so as to obtain the contents of titanium and of the diester of phthalic acid characterizing the solid catalyst component according to the invention. By employing the techniques which are known in their principle in order to produce catalyst components of Ziegler-Natta type, a person skilled in the art can produce the catalyst component according to the invention after having carried out a few routine tests concerning essentially the quantity of the titanium derivative and the quantity of the diester of phthalic acid to be used, so as to arrive at the solid catalyst component according to the invention. The solid catalyst component is preferably ba
Brusson Jean-Michel
Duranel Laurent
Appryl S.N.C.
Lipman Bernard
Smith , Gambrell & Russell, LLP
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