Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-01-24
2003-09-23
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S128000, C526S185000, C526S194000, C526S351000
Reexamination Certificate
active
06624264
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to alkoxysilacycloalkanes, to the process for their preparation and to their use as electron-donor in processes for the polymerization or copolymerization of olefins like propylene or ethylene.
BACKGROUND OF THE INVENTION
A polyolefin which has an excessively high content of heptane-solubles may have a tendency to stick and is therefore difficult to convey and, as a result, is not very suitable for industrial applications. In addition, in the alimentary field, the presence of solubles in a polyolefin which is intended to come into contact with foodstuffs is deemed to be undesirable. For these reasons, for example, isotactic polypropylene preferably has a heptane-insolubles content (denoted by HI, from the expression “heptane-insoluble”) higher than 80% by weight.
Patent Application EP 250229 teaches that the use of certain silanes during the polymerization of olefins allows the hexane-solubles content of the polyolefin obtained to be reduced.
The paper by R. West, Journal of the American Chemical Society (1954) 76, 6012, describes a method for the preparation of 1,1-dimethoxysilacyclohexane. This preparation involves numerous stages and the intermediate formation of a chlorosilacycloalkane which is particularly tricky to handle and easily degradable.
The process of the present invention is particularly simple, involves raw materials which are easily available and relatively stable and does not involve any chlorosilacycloalkane. The stability of the materials used reduces the risk of side reactions, thereby tending in the direction of better purity of the products which are finally prepared.
The presence of alkoxysilacycloalkanes in the environment for the polymerization or copolymerization of at least one olefin is reflected in an appreciable increase in the polyolefin yield and in an appreciable increase in the HI of the said polyolefin. In addition, the alkoxysilacycloalkane acts as a morphology protector in the suspension and gas-phase polymerization or copolymerization processes. This means that, in the case of these so-called heterogeneous processes, the polymer or copolymer formed is a better morphological replica of the initial solid catalytic component if an alkoxysilacycloalkane is introduced as an external electron-donor into the polymerization or copolymerization environment.
The process according to the invention includes the stage of reaction between an alkylenedimagnesium dibromide of formula Br—Mg—A—Mg—Br in which A is a divalent alkylene radical optionally substituted, for example by an alkyl radical containing, for example, from 1 to 6 carbon atoms, the said alkylene radical containing from 4 to 7 carbon atoms, the optional substituent(s) being excluded, and a tetraalkoxysilane of formula (OR
1
) (OR
2
) (OR
3
) (OR
4
)Si in which R
1
, R
2
, R
3
and R
4
, which may be identical or different, denote linear or branched, saturated and/or unsaturated hydrocarbon radicals which may include a ring.
The radicals R
1
, R
2
, R
3
and R
4
preferably are alkyl radicals containing from 1 to 6 carbon atoms.
The reaction may be carried out in a solvent which preferably exhibits a Lewis base character, as is the case with ethers. The solvent may, for example, be diethyl ether.
The quantity of inert solvent which is employed may, for example, be such that, assuming the reaction yield to be equal to 100%, the alkoxysilacycloalkane formed is encountered again in a concentration of between 0.05 and 2 moles/liter.
The reaction may be carried out, for example, between 0 and 50° C. for 10 min to 12 hours, if appropriate under pressure if the volatility of the species used makes this necessary, bearing in mind the temperature chosen. Since the reaction is generally exothermic, it is preferable to bring the dibromide and the tetraalkoxysilane into contact gradually and with stirring so as to retain control of the temperature of the mixture. The reaction results in the formation of at least one alkoxysilacycloalkane of formula
in which X and Y denote groups forming part of the group of the radicals R
1
, R
2
, R
3
and R
4
and in which A retains the meaning given above. The ring of the alkoxysilacycloalkane therefore contains a silicon atom and a number of carbon atoms equal to the number of carbon atoms which the alkylene radical A contained, the optional substituents of the said alkylene radical being excluded.
The alkoxysilacycloalkanes in the case of which A is an alkylene radical containing at least one alkyl substituent are also a subject-matter of the present invention.
By way of example, Table 1 below mentions some alkoxysilacycloalkanes which can be prepared by the process according to the invention, by reaction of tetramethoxysilane with an alkylenedimagnesium dibromide, depending on the nature of the divalent alkylene radical A included in the alkylenedimagnesium dibromide.
TABLE 1
Nature of A
Alkoxysilacycloalkane formed
tetramethylene
1,1-dimethoxysilacyclopentane
1-methyltetramethylene
1,1-dimethoxy-2-methylsilacyclopentane
1-ethyltetramethylene
1,1-dimethoxy-2-ethylsilacyclopentane
1-n-propyltetramethylene
1,1-dimethoxy-2-n-
propylsilacyclopentane
1-isopropyltetramethylene
1,1-dimethoxy-2-
isopropylsilacyclopentane
1-n-butyltetramethylene
1,1-dimethoxy-2-n-
butylsilacyclopentane
pentamethylene
1,1-dimethoxysilacyclohexane
1-methylpentamethylene
1,1-dimethoxy-2-methylsilacyclohexane
1-ethylpentamethylene
1,1-dimethoxy-2-ethylsilacyclohexane
1-n-propylpentamethylene
1,1-dimethoxy-2-n-
propylsilacyclohexane
1-isopropylpentamethylene
1,1-dimethoxy-2-
isopropylsilacyclohexane
1-n-butylpentamethylene
1,1-dimethoxy-2-n-butylsilacyclohexane
2,3-dimethyltetramethylene
1,1-dimethoxy-3,4-
dimethylsilacyclopentane
1,4-dimethyltetramethylene
1,1-dimethoxy-2,5-
dimethylsilacyclopentane
hexamethylene
1,1-dimethoxysilacycloheptane
The reaction also gives rise to the formation of BrMgOZ in which Z is a radical forming part of the group of the radicals R
1
, R
2
, R
3
and R
4
. This BrMgOZ, considered as being a by-product in the context of the present invention, is generally solid and can, in this case, be removed for example by filtration. After evaporation of the optional solvent employed and of any excess reactants, the alkoxysilacycloalkane may be purified by distillation, preferably at reduced pressure, for example between 1 and 1×10
3
mbar.
The alkylenedimagnesium dibromide of formula Br—Mg—A—Mg—Br may be prepared, for example, by reaction between a dibromoalkane of formula Br—A—Br and magnesium in the presence of a solvent, for example an ether like diethyl ether, for example between 0 and 50° C., if appropriate under pressure if the volatility of the species used demands this, bearing in mind the temperature chosen.
The alkoxysilacycloalkanes capable of being obtained by the process according to the invention may be used as an electron-donor in the polymerization or copolymerization of at least one olefin. For example, the silacycloalkane may be introduced within a solid catalytic component of the Ziegler-Natta type and may act as an internal electron-donor.
It is also possible to employ it as an external electron-donor in an environment for the polymerization or copolymerization of at least one olefin, so as to reduce the hexane-solubles content of the polymer or copolymer finally prepared.
In the case of this latter application (external electron-donor) it is preferred to employ an alkoxysilacycloalkane of formula (I) in which X and Y denote methyl radicals.
The alkoxysilacycloalkane preferably contains at least one alkyl substituent positioned alpha to the silicon atom. Particularly high HI values are obtained when the alkyl substituent contains at least two carbon atoms. An excellent compromise of properties (very high HI and generally high yield) is obtained when the alkyl substituent contains 2 or 3 carbon atoms, as is the case with 1,1-dimethoxy-2-ethylsilacyclopentane, 1,1-dimethoxy-2-n-propylsilacyclopentane, 1,1-dimethoxy-2-isopropylsilacyclopentane, 1,1-dimethoxy-2-ethylsilacyclohexane, 1,1-dimethoxy-2-n-prop
Barthel Valerie
Batt-Coutrot Delphine
Brun Claude
Brusson Jean-Michel
Coutrot Philippe
Atofina
Moore Margaret G.
Smith , Gambrell & Russell, LLP
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