Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-09-18
2001-05-29
Bell, Mark L. (Department: 1755)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
active
06239236
ABSTRACT:
The present invention relates to catalyst components for the polymerization of olefins, to the catalysts obtained therefrom and to the use of said catalysts in the polymerization of olefins CH
2
═CHR in which R is hydrogen or a hydrocarbyl radical with 1-12 carbon atoms. In particular the present invention relates to catalyst components, suitable for the stereospecific polymerization of olefins, comprising titanium, Mg, halogen and an electron donor compound selected from cyanoesters having a particular formula. Said catalyst components when used in the polymerization of olefins, and in particular of propylene, are characterized by an excellent response to hydrogen and are also capable to give polymers with very broad molecular weight distribution.
Many patent applications have been filed in the field of the so-called high-yield polymerization catalysts, in particular regarding the catalysts for the polymerization of propylene. Tipically, said catalysts comprise a solid catalyst component, constituted by a magnesium dichloride on which are supported a titanium compound and an internal electron donor compound (usually an ester of a phthalic acid), an Al-alkyl compound and an external donor (usually a silicon compound). The above catalyst systems, although capable of providing propylene polymers with high stereoregularity and in high yields , are also characterized by a poor capability of response to hydrogen. In other words, very high concentrations of hydrogen, used as molecular weight regulator, are necessary in order to obtain polymers with low molecular weight. The low molecular weight polymers are requested in applications where high fluidity in the molten state and good mechanical properties are necessary. The production of webs for non-woven fabrics, which is carried out by melt blown or spun bonded processes, is an example of such applications. In some cases, the molecular weights required for the propylene polymers are so low that, to produce them, the prior art catalyst systems would require a pressure of hydrogen well above the operative limit of conventional bulk polymerization plants. In these cases, such low molecular weight polymers are obtained by visbreaking of the high molecular weight polymers at high temperatures (200°-300° C.) and in the presence of free radical generators such as organic peroxides.
Moreover, the propylene polymers obtained with the above mentioned catalyst systems usually have a narrow molecular weight distribution (MWD) as compared for example with polyolefins prepared by using the conventional catalysts comprising a titanium trichloride based catalyst component. The narrow MWD causes a worsening of the processability of the polymers which involves a decrease of the quality of the products in applications such as molding or thermoforming. One of the approaches that have been tried to broaden the MWD comprises carrying out the polymerization in at least two steps under different polymerization conditions. However, these multisteps processes require a more complicated and sophisticated polymerization operation which increases the cost of the polymerization process.
Accordingly, there is still a need of a polymerization catalyst system with a good response to hydrogen and also capable of producing polymers with broad MWD.
It has now surprisingly been found that if specific cyanoesters are used as internal donor, catalyst components capable to give an excellent response to hydrogen are obtained. Very surprisingly said catalyst components, differently from what is known in the art, couple this feature with the capability of producing polymers with broad molecular weight distribution.
It is therefore an object of the present invention to provide a solid catalyst component for the polymerization of olefins CH
2
═CHR in which R is hydrogen or a hydrocarbyl radical with 1-12 carbon atoms, comprising Ti, Mg, halogen and an electron donor compound selected from cyanoesters of formula (I):
wherein R
1
is a C
1
-C
20
linear or branched alkyl, alkenyl, cycloalkyl, cycloalkylalkyl, alkylcycloalkyl, aryl, arylalkyl or alkylaryl group; n is 0, 1, 2 or 3; R
2
, R
3
, R
4
and R
5
are independently selected from hydrogen or C
1
-C
20
linear or branched alkyl, alkenyl, cycloalkyl, cycloalkylalkyl, alkylcycloalkyl, aryl, arylalkyl or alkylaryl groups; two or more of R
2
and R
3
, and R
4
and R
5
, can be joined to form a cycle.
Preferably R
1
is a C
1
-C
4
linear alkyl group. In particular, R
1
is preferably selected from methyl or ethyl.
Among the compounds of formula (I) particularly preferred are those compounds in which n is 0. In this case one particularly preferred class is that in which one of R
2
or R
3
is hydrogen and the other is selected from C
1
-C
20
linear or branched alkyl, alkenyl, cycloalkyl, cycloalkylalkyl, alkylcycloalkyl, aryl, arylalkyl or alkylaryl group and in particular from C
1
-C
8
branched alkyl groups. Specific examples of preferred compounds of this latter class are methyl 2-i-butyl-cyanoacetate, ethyl 2-i-butyl-cyanoacetate, ethyl 2-i-propyl-cyanoacetate, ethyl 2-(1,2-dimethyl-propyl)-cyanoacetate, ethyl 2-t-butyl-cyanoacetate.
Among the compounds in which n is 0 particularly preferred is the class in which both R
2
and R
3
are selected from C
1
-C
20
linear or branched alkyl, alkenyl, cycloalkyl, cycloalkylalkyl, alkylcycloalkyl, aryl, arylalkyl or alkylaryl groups in which R
2
and R
3
can also form a cycle. Particularly preferred are the compounds in which both R
2
and R
3
, equal or different to each other, are selected from C
1
-C
8
linear or branched alkyl or aryl groups. Specific examples of preferred compounds of this class are ethyl 2,2-di-n-butyl-cyanoacetate, ethyl 2-i-butyl-2-n-butyl-cyanoacetate, ethyl 2,2-di-i-butyl-cyanoacetate, ethyl 2-i-butyl-2-i-propyl-cyanoacetate, ethyl 2,2-di-i-propyl-cyanoacetate, ethyl 2,2-di-benzyl ethyl-cyanoacetate.
As explained above, the catalyst component comprises, in addition to the above electron donor, Ti, Mg and halogen. In particular, the catalyst component comprises a titanium compound, having at least a Ti-halogen bond, and the above mentioned electron donor compound supported on a Mg halide. The magnesium halide is preferably MgCl
2
in active form that is widely known from the patent literature as a support for Ziegler-Natta catalysts. U.S. Pat. No. 4,298,718 and U.S. Pat. No. 4,495,338 were the first to describe the use of these compounds in Ziegler-Natta catalysis. It is known from these patents that the magnesium dihalides in active form used as support or co-support in components of catalysts for the polymerization of olefins are characterized by X-ray spectra in which the most intense diffraction line that appears in the spectrum of the non-active halide is diminished in intensity and is replaced by a halo whose maximum intensity is displaced towards lower angles relative to that of the more intense line.
The preferred titanium compounds used in the catalyst component of the present invention are TiCl
4
and TiCl
3
, furthermore, also Ti-haloalcoholates of formula Ti(OR)
n-y
X
y
, where n is the valence of titanium and y is a number between 1 and n, can be used.
The preparation of the solid catalyst component can be carried out according to several methods.
According to one of these methods, the magnesium dichloride in an anhydrous state and the electron donor compound of formula (I) are milled together under conditions in which activation of the magnesium dichloride occurs. The so obtained product can be treated one or more times with an excess of TiCl
4
at a temperature between 80 and 135° C. This treatment is followed by washings with hydrocarbon solvents until chloride ions disappeared. According to a further method, the product obtained by co-milling the magnesium chloride in an anhydrous state, the titanium compound and the electron donor compound of formula (I) is treated with halogenated hydrocarbons such as 1,2-dichloroethane, chlorobenzene, dichloromethane etc. The treatment is carried out for a time between 1 and 4 hours and a
Balbontin Giulio
Gulevich Yuri V.
Morini Giampiero
Bell Mark L.
Bryan Cave LLP
Montell Technology Company B.V.
Pasterczyk J.
Stiefel Maurice B.
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