Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
2002-04-04
2004-04-20
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
C556S465000
Reexamination Certificate
active
06723865
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to aromatic silane compounds and to Ziegler-Natta catalyst systems which use said aromatic silane compounds as electron donors for the production of olefin polymers. The olefin polymers produced with such catalyst systems exhibit a desirable stereoblock content of from about 7 to about 25%.
Polymer stereoblock content can affect the physical properties of the polymer itself and those of products prepared therefrom, particularly films manufactured from such polyolefins and blends of such polyolefins with elastomeric materials, regardless of whether they are mechanically blended from pre-produced polyolefins and elastomeric materials or reactor blended by first producing such a polyolefin then producing the elastomeric material in the presence of the polyolefin.
Organosilane compounds have been used in catalysts (1) as an internal electron donor in a solid catalyst component comprising a halogen-containing titanium compound supported on an activated magnesium dihalide compound and (2) as an external electron donor in combination with an aluminum-alkyl co-catalyst. Typically the organosilane compounds have Si—OR, Si—OCOR or Si—NR
2
groups, where R is alkyl, alkenyl, aryl, arylalkyl or cycloalkyl having 1 to 20 atoms. Such compounds are described in U.S. Pat. Nos. 4,180,636; 4,242,479; 4,347,160; 4,382,019; 4,435,550; 4,442,276; 4,473,660; 4,530,912 and 4,560,671, where they are used as internal electron donors in the solid catalyst component; and in U.S. Pat. Nos. 4,472,524, 4,522,930, 4,560,671, 4,581,342, 4,657,882 and European patent application Nos. 45976 and 45977, where they are used as external electron donors with the aluminum-alkyl co-catalyst.
Conventional propylene homopolymers, obtained by using external electron donors known in the state of the art, show a high degree of cristallinity, which determines the physical properties of the polymers, such as high melting temperature, high glass temperature and high &Dgr;H
fus
. These physical properties, while necessary in some applications, are often disadvantageous in fiber and film applications, where lower bonding temperatures are required, for instance in producing laminate structures.
Hence, there is the need for external electron donor compounds which allow propylene polymers to be obtained having a relatively high degree of stereoblocks, at the same time at acceptable polymerization yields.
SUMMARY OF THE INVENTION
It has been surprisingly found that a novel class of substituted aromatic silane compounds can be used as external electron donors for olefin polymerization catalyst systems, in order to produce propylene polymers having a stereoblock content of from about 7 to about 25%.
In one aspect, the present invention concerns an aromatic silane compound useful as electron donor compound in an olefin polymerization catalyst, having formula (I):
wherein
R
1
is selected from the group consisting of linear or branched C
1-26
alkyl, C
2-26
alkenyl, C
1-26
alkoxy, C
2-26
alkoxyalkyl, C
7-26
arylalkyl, C
3-26
cycloalkyl and C
4-26
cycloalkoxy groups, optionally containing one or more halogen atoms;
R
2
is an aromatic ring having at least one substituent in the ortho position selected from C
1-10
hydrocarbon groups; and
R
3
and R
4
, the same or different from each other, are selected from the group consisting of a linear or branched C
1-10
alkyl and C
3-10
cycloalkyl groups.
In another aspect, the present invention concerns a catalyst system for the polymerization of olefins comprising:
(A) an aromatic silane compound having formula (I):
wherein
R
1
is selected from the group consisting of linear or branched C
1-26
alkyl, C
2-26
alkenyl, C
1-26
alkoxy, C
2-26
alkoxyalkyl, C
7-26
arylalkyl, C
3-26
cycloalkyl and C
4-26
cycloalkoxy groups, optionally containing one or more halogen atoms;
R
2
is an aromatic ring having at least one substituent in the ortho position; and
R
3
and R
4
, the same or different from each other, are selected from the group consisting of a linear or branched C
1-10
alkyl and C
3-10
cycloalkyl groups;
(B) an aluminum alkyl compound; and
(C) a solid catalyst component comprising Mg, Ti, halogen and an electron donor compound.
In another aspect, this invention concerns a process for the polymerization of alpha-olefins carried out in the presence of the catalyst system described above, to produce a polyolefin having a stereoblock content of from about 7 to about 25%, and preferably from 12 to 20%.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The inventors have discovered that organosilanes having an aromatic ring substituted in the ortho position can produce, in conjunction with the catalyst systems described below, polyolefin resins having a stereoblock content of from about 7 to about 25%.
The aromatic silane compounds of the present invention have the following formula (I):
wherein R
1
, R
2
, R
3
and R
4
have the meanings reported above.
In one preferred embodiment of the present invention, R
1
is a linear or branched C
1-18
alkyl or C
3-18
cycloalkyl, and even more preferably R
1
is a linear C
1-5
alkyl or a branched C
3-8
alkyl.
R
2
is an aromatic ring having at least one substituent in the ortho position selected from C
1-10
hydrocarbon groups. Depending on the stereoblock content desired, R
2
may preferably be a non-heterocyclic aromatic system, and most preferably a mono-substituted phenyl ring system, a di-substituted phenyl ring system, or a mono-substituted naphthyl ring system. By “substituent in the ortho position”, it is meant that at least one of the two aromatic ring atoms adjacent to the aromatic ring atom that is bound to the silicon atom must be substituted.
The groups R
3
and R
4
, the same or different from each other, are preferably C
1-10
alkyl, and even more preferably are methyl or ethyl.
Illustrative examples of aromatic silanes which conform to formula (I) include the following:
(2-ethylphenyl)-3,3-dimethylbutyl-dimethoxysilane;
(2-ethylphenyl)-3-methylbutyl-dimethoxysilane;
(2-ethylphenyl)-propyl-dimethoxysilane;
(2-ethylphenyl)-3,3,3trifluoropropyl-dimethoxysilane;
(2-methylphenyl)-propyl-dimethoxysilane; and
(2,6-dimethylphenyl)-propyl-dimethoxysilane.
The aromatic silanes of the present invention may be prepared from readily available starting materials using conventional synthesis methods and equipment well known to those of ordinary skill in the art. Aromatic silanes where the aromatic ring system is an ortho-substituted phenyl group may be prepared by the reaction between the appropriate 2-phenylmagnesium bromide and the appropriate alkyl-trialkoxysilane, as illustrated in Example 2. Alternatively, such ortho-substituted aromatic silanes may be prepared by first reacting the appropriate 2-bromobenzene with an alkyl lithium reagent, such as n-butyl lithium, to generate the corresponding 2-phenyl lithium, which is then allowed to react with the appropriate alkyl-trialkoxysilane, as illustrated in Example 3.
The organosilanes of the present invention are useful as the external electron donor in an olefin polymerization catalyst system. More particularly, the present invention concerns a catalyst system for the polymerization of olefins comprising:
(A) an aromatic silane compound having formula (I):
wherein
R
1
is preferably a linear or branched C
1-18
alkyl or C
3-18
cycloalkyl, and even more preferably R
1
is a linear C
1-5
alkyl;
R
2
is an aromatic ring having at least one substituent in the ortho position;
R
3
and R
4
, the same or different from each other, are preferably C
1-10
alkyl groups, and even more preferably are methyl or ethyl;
(B) an aluminum alkyl compound; and
(C) a solid catalyst component comprising Mg, Ti, halogen and an electron donor compound as essential elements.
In said aromatic silane compound (A), R
1
is preferably selected from the group consisting of linear or branched C
1-18
alkyl, C
1-18
alkoxyl and C
3-18
cycloalkyl groups, and even more preferably R
1
is selected from the group consisting of linear C
1-5
alkyl and branched C
3-
Evain Eric J.
Stewart Constantine A.
Barts Samuel
Basell Poliolefine Italia S.p.A.
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