Preparation of homopolymers and copolymers of propene by means of a Ziegler-Natta catalyst system

Polymers of propene are prepared by means of a Ziegler-Natta catalyst system composed of (1) a titanium component based on a finely divided shape-dictating silica gel and containing titanium, magnesium, chlorine and a benzenecarboxylic acid derivative, (2) an aluminum component and (3) a silane component, the titanium component (1) being obtained by (1.1) first preparing (I) a carrier material from (Ia) a silica gel, (Ib) an organomagnesium compound (Ic) a gaseous chlorinating agent and (Id) a specific phthalic acid derivative by (1.1.1) first reacting (Ia) with (Ib), then (1.1.2) passing (Ic) into the product of (1.1.1) together with the phthalic acid derivative (Id) and isolating (I), (1.2) preparing a solid-phase intermediate from (I), (II) an alkanol and (III) titanium tetrachloride by (1.2.1) first reacting (I) with (II), then (1.2.2) introducing (III) into the product resulting from (1.2.1), then (1.3) extracting the solid-phase result from (1.2) with titanium tetrachloride or a titanium tetrachloride/ethylbenzene mixture, and finally (1.4) washing the solid-phase result from (1.3) with a liquid hydrocarbon.

The present invention relates to a process for preparing homopolymers of 
propene and copolymers of propene with minor amounts of other C.sub.2 
-C.sub.12 -, in particular C.sub.2 -C.sub.6 -, .alpha.-monoolefins by 
polymerization, in particular by dry phase polymerization, of the 
monomer(s) at from 20.degree. to 160 .degree. C., in particular at from 
50.degree. to 120.degree. C., under from 1 to 100, in particular from 10 
to 70, bar by means of a Ziegler-Natta catalyst system composed of 
(1) a titanium component based on a finely divided shape-dictating silica 
gel and containing titanium, magnesium, chlorine and a benzenecarboxylic 
acid derivative, 
(2) an aluminum component of the formula 
EQU AlR.sub.3 
where 
R is alkyl of not more than 8, in particular not more than 4, carbon atoms, 
and 
(3) a silane component of the formula 
EQU R.sub.n.sup.1 Si(OR.sup.2).sub.4-n 
where 
R.sup.1 is saturated aliphatic or aromatic hydrocarbyl of not more than 16, 
preferably not more than 10, carbon atoms, 
R.sup.2 is alkyl of not more than 15, preferably not more than 8, in 
particular not more than 4, carbon atoms, and 
n is from 0 to 3, preferably from 0 to 2, in particular 1 or 2, 
with the provisos that the atomic ratio of titanium of titanium component 
(1) : aluminum of aluminum component (2) is from 1:10 to 1:800, in 
particular from 1:20 to 1:200, and the molar ratio of aluminum component 
(2): silane component (3) is from 1:0.01 to 1:0.8, in particular from 
1:0.02 to 1:0.5. 
Polymerization processes of this type are known; they are distinguished 
from other similar processes by the specific form of the catalyst system, 
the prototypes for which may be considered to be the catalyst systems of 
the processes disclosed in European Patent Applications EP-A-0,014,523, 
-0,045,977, -0,171,200 and -0,195,497 and British Patents GB-B-2,101,609 
and -2,101,611. 
The specific forms of the catalyst systems are chosen with certain purposes 
in mind, such as the following: 
The catalyst system should be easily preparable and give a high yield of a 
polymer product which should ideally have a high isotactic index. The 
catalyst system should in addition produce polymers having specific 
morphological properties, for example a uniform particle size and/or a 
reduced level of fines and/or a high bulk density. In addition to these 
parameters, which chiefly concern the control of the polymerization 
system, the workup of the polymers and/or the processing thereof, another 
important objective, in particular in respect of corrosion problems, is a 
low halogen content of the polymer, this being obtainable by increasing 
the polymer yield and/or by means of a catalyst system having a very low 
halogen content. 
Some of these objectives are obtainable in the prior art only by very 
complicated processes or by assigning a lower priority to other 
objectives: 
For instance, European Patent Application EP-A-0,045,977 describes a 
catalyst system consisting of active MgCl.sub.2, TiCl.sub.4 and a phthalic 
acid derivative. However, with silica gel as the shape-dictating carrier 
material the productivity of the catalyst system is no longer 
satisfactory; moreover, the chlorine content of the polymer is 
comparatively high. 
European Patent Applications EP-A-0,014,523 and -0,171,200 and British 
Patents GB-B-2,101,609 and -2,101,611 describe catalyst systems whose 
titanium component is obtained by treating a solid inorganic oxide with an 
organic magnesium compound, a Lewis base and titanium tetrachloride using 
in addition a halogenating agent other than titanium tetrachloride and/or 
an organic compound of the metals boron, aluminum, silicon or tin, a boron 
trihalide or a halogen-containing alcohol. Despite the costly and 
time-intensive procedure, the productivity of the corresponding catalyst 
system is not satisfactory. 
European Patent Application EP-A-0,195,497 describes a catalyst system 
whose titanium component is obtained by treating SiO.sub.2 with an organic 
Mg compound, an alcohol, a Lewis base and TiCl.sub.4. This catalyst system 
likewise has a low productivity. 
The existing processes thus leave something to be desired, in particular as 
regards good productivity and a low chlorine content of the polymer 
combined with high isotacticity and good morphology. 
It is an object of the present invention to provide a titanium component 
which compared with the prior art processes show particularly good 
productivity while giving polymers of low chlorine content, high 
isotacticity and good morphology. 
We have found that this object is achieved by a catalyst system containing 
a titanium component (1) prepared in a particular manner from (I) a 
specific carrier material obtained in a defined manner from (Ia) a 
specific finely divided silica gel, (Ib) a specific organomagnesium 
compound (Ic) a specific gaseous chlorinating agent and (Id) a specific 
phthalic acid derivative, (II) a specific alkanol, and (III) titanium 
tetrachloride. 
The present invention accordingly provides a process for preparing a 
homopolymer of propene or a copolymer of propene with a minor amount of 
another C.sub.2 -C.sub.12 -, in particular C.sub.2 -C.sub.6 -, 
.alpha.-monoolefin by polymerization, in particular by dry phase 
polymerization, of the monomer(s) at from 20.degree. to 160.degree. C., in 
particular at from 50 to 120.degree. C., under from 1 to 100, in 
particular from 20 to 70, bar by means of a Ziegler-Natta catalyst system 
composed of 
(1) a titanium component based on a finely divided shape-dictating silica 
gel and containing titanium, magnesium, chlorine and a benzenecarboxylic 
acid derivative, 
(2) an aluminum component of the formula 
EQU AlR.sub.3 
where 
R is alkyl of not more than 8, in particular not more than 4, carbon atoms, 
and 
(3) a silane component of the formula 
EQU R.sub.n.sup.1 Si(OR.sup.2).sub.4-n 
where 
R.sup.1 is saturated aliphatic or aromatic hydrocarbyl of not more than 16, 
preferably not more than 10, carbon atoms, 
R.sup.2 is alkyl of not more than 15, preferably not more than 8, in 
particular not more than 4, carbon atoms, and 
n is from 0 to 3, preferably from 0 to 2, in particular 1 or 2, 
with the provisos that the atomic ratio of titanium of titanium component 
(1) : aluminum of aluminum component (2) is from 1:10 to 1:800, in 
particular from 1:20 to 1:200, and the molar ratio of aluminum component 
(2) : silane component (3) is from 1:0.01 to 1:0.8, in particular from 
1:0.02 to 1:0.5, which comprises using as the titanium component (1) a 
titanium component obtained by first of all 
(1.1) preparing in a first stage (I) a carrier material from (Ia) a finely 
divided silica gel having a particle diameter of from 1 to 1,000, in 
particular from 10 to 400, .mu.m, a pore volume of from 0.3 to 5, in 
particular from 1 to 3.5, cm.sup.3 /g, a surface area of from 100 to 
1,000, in particular from 200 to 600, m.sup.2 /g, the formula 
SiO.sub.2.aAl.sub.2 O.sub.3, where a is from 0 to 2, in particular from 0 
to 0.5, (Ib) an organomagnesium compound of the formula MgR.sup.3 R.sup.4, 
where R.sup.3 and R.sup.4 are each C.sub.2 -C.sub.10 -alkyl, preferably 
C.sub.4 -C.sub.8 -alkyl, (Ic) a gaseous chlorinating agent of the formula 
ClZ, where Z is Cl or H, preferably H, and (Id) a phthalic acid derivative 
of the formula 
##STR1## 
where X and Y together are oxygen or singly chlorine or C.sub.1 -C.sub.10 
-alkoxy, preferably C.sub.2 C.sub.8 -alkoxy, in particular butoxy, by 
first 
(1 1.1) bringing together in a first substage in a liquid inert 
hydrocarbon, in particular an alkane, with constant mixing at room 
temperature the finely divided silica gel (Ia) and the organomagnesium 
compound (Ib) by using per 10 molar parts of silicon of silica gel (Ia) 
from 1 to 10, in particular from 1.5 to 4, molar parts of the 
organomagnesium compound (Ib), and keeping the mixture at from 20.degree. 
to 140.degree. C., in particular from 60.degree. to 90.degree. C., for 
from 0.5 to 5, in particular from 1 to 2, hours, then 
(1.1.2) introducing into the product obtained from the first substage in a 
second substage with constant mixing at from -20.degree. to +80.degree. 
C., in particular from 0.degree. to +20.degree. C., (i) the gaseous 
chlorinating agent (Ic) using from 2 to 40, in particular from 10 to 20, 
molar parts of chlorinating agent (Ic) per molar part of organomagnesium 
compound (Ib), and (ii) the phthalic acid derivative (Id) using per molar 
part of organomagnesium compound (Ib) from 0.01 to 1, preferably from 0.1 
to 0.4, in particular from 0.20 to 0.35, molar parts of phthalic acid 
derivative (Id) leaving the whole mixture at a temperature within the 
stated range for from 0.5 to 5, in particular from 0.5 to 1, hours and, 
where appropriate, isolating the resulting solid-phase product, i.e. the 
carrier material (I), by removing the liquid phase, and then 
(1.2) preparing in a second stage a solid-phase intermediate from (I) the 
carrier material obtained in the first stage, (II) a C.sub.1 -C.sub.8, 
preferably C.sub.2 -C.sub.6 -alkanol, in particular ethanol, and (III) 
titanium tetrachloride by first 
(1.2.1) bringing together in a first substage in a liquid inert 
hydrocarbon, in particular an alkane, with constant mixing at room 
temperature the carrier material (I) and the alkanol (II) using from 1 to 
5, in particular from 2.5 to 3.5, molar parts of alkanol (II) per molar 
part of magnesium of carrier material (I), and keeping the mixture at from 
20.degree. to 140.degree. C., in particular from 70.degree. to 90.degree. 
C., for from 0.5 to 5, in particular from 1 to 2, hours, then 
(1.2.2) in a second substage introducing the titanium tetrachloride (III) 
with constant mixing at room temperature into the reaction mixture 
resulting from the first substage using from 2 to 20, in particular from 4 
to 8, molar parts of titanium tetrachloride (III) per molar part of 
magnesium of carrier material (I), keeping the mixture at from 10.degree. 
to 150.degree. C., in particular from 90.degree. to 120.degree. C., for 
from 0.5 to 5, in particular from 1 to 2, hours and isolating the 
resulting solid-phase intermediate by removing the liquid phase, then 
(1.3) in a third stage subjecting the solid-phase intermediate obtained 
from the second stage at from 100.degree. to 150.degree. C., in particular 
from 115.degree. to 135.degree. C., for from 0.2 to 8, in particular from 
1 to 6, hours to a single- or multi-stage or preferably continuous 
extraction with titanium tetrachloride or a mixture of titanium 
tetrachloride and an ethylbenzene 10, whose titanium tetrachloride content 
is not less than 2, preferably not less than 5, in particular not less 
than 10% by weight, using for every 10 parts by weight of the solid-phase 
intermediate obtained from the second stage a total of from 10 to 1,000, 
preferably from 20 to 800, in particular from 50 to 300, parts by weight 
of extractant, and finally 
(1.4) in a fourth stage washing the solid-phase product formed in the third 
stage one or more times with a liquid inert hydrocarbon, in particular an 
alkane, and so obtaining titanium component (1). We have found that the 
process according to the invention can be practiced particularly 
successfully if the catalyst system used has a silane component (3) of the 
formula 
EQU R.sub.n.sup.1 Si(OR.sup.2).sub.4-n 
where 
R.sup.1 is phenyl, C.sub.1 -C.sub.4 -alkylphenyl or C.sub.1 -C.sub.5 
-alkyl, 
R.sup.2 is alkyl of not more than 4 carbon atoms, in particular methyl or 
ethyl, and 
n is 1 or 2. 
There now follow specifics concerning the process according to the 
invention: 
The polymerization process as such can be carried out in virtually any form 
customary in the art, for example as a batchwise, cyclic or, in 
particular, continuous process, whether for example as a suspension 
polymerization process or, in particular, as a dry phase polymerization 
process, as long as the novel feature is observed. The possible forms of 
the process, i.e. the technological versions of the polymerization of 
.alpha.-monoolefins by Ziegler-Natta, are well-known from theory and 
practice, so that they require no further observations. 
For completeness it should be mentioned that in the process according to 
the invention it is also possible to regulate the molecular weights of the 
polymers in a conventional manner, for example by means of regulators, in 
particular hydrogen. 
As regards the material side of the novel catalyst system, the details are 
as follows: 
(1) Finely divided silica gel (Ia) to be used for preparing the titanium 
component will in general be an alumosilicate or in particular a silicon 
dioxide, as long as it has the required properties. We have found that the 
commercial carrier material silica gels which meet the stated 
specification are highly suitable. 
The organomagnesium compound (Ib) to be used at the same time can be for 
example dibutylmagnesium, dihexylmagnesium or in particular 
butyloctylmagnesium. 
The gaseous chlorinating agent (Ic) to be used should be very dry and pure; 
it comprises chlorine or in particular hydrogen chloride. 
The above-defined phthalic acid derivative (Id) to be used can be of a 
commercial grade; it should advantageously be very pure. We have found 
that for the purposes of the present invention it is very particularly 
advantageous to use dibutyl phthalate; but it is also possible to use 
other dialkyl phthalates and phthalic anhydride or phthaloyl dichloride. 
The liquid inert hydrocarbon assistant can be a hydrocarbon of the type 
customarily brought together with titanium components for catalyst systems 
of the Ziegler-Natta type without damage to the catalyst system or the 
titanium component thereof. Examples of suitable hydrocarbons are 
pentanes, hexanes, heptanes, gasolines and cyclohexane. 
The alkanols (II) to be used for preparing the titanium component (1) can 
be of the type available commercially. They should advantageously have 
relatively high purities. It is highly advantageous to use for example 
ethanol or n-propyl, i-propyl, n-butyl, i-butyl or tert-butyl alcohols; it 
is particularly advantageous to use ethanol. 
The titanium tetrachloride (III) likewise to be used for preparing the 
titanium component (1) should be of the customary type for Ziegler-Natta 
catalyst systems; the optional ethylbenzene for use in the mixture with 
titanium tetrachloride should be very pure and dry. 
The hydrocarbon to be used in stage (1.4) of the preparation of titanium 
component (1) can likewise be of the customary type; it should 
advantageously be relatively pure. 
The preparation of titanium component (1) is simple and possible for the 
skilled worker without instructions. All that needs to be added in respect 
of stages (1.1), (1.2) and (1.3) is that the solid resulting at each stage 
may advantageously be isolated by filtering off with suction. 
(2) Suitable aluminum components (2) of the stated formula are the 
customary ones which conform to this formula; they are so well-known from 
theory and practice that no further details are required. An outstanding 
representative is for example triethylaluminum. 
(3) The silane component (3) which completes the catalyst system is in 
particular a trialkoxy phenylsilane, a trialkoxy (alkyl), phenylsilane a 
dialkoxydiphenylsilane or a dialkoxydi (alkyl) phenylsilane of the stated 
formula. An outstanding representative is triethoxytoluylsilane; further 
examples are triethoxyethylphenylsilane, dimethoxyditoluylsilane and 
diethoxyditoluylsilane. Dialkoxydialkylsilanes and trialkoxyalkylsilanes 
are also highly suitable. 
The process according to the invention makes it possible to prepare 
homopolymers and copolymers, for example of the binary or ternary type, 
including block copolymers, of propene with minor amounts of other C.sub.2 
-C.sub.12 -.alpha.-monoolefins in an advantageous manner, particularly 
suitable .alpha.-monoolefin comonomers being ethene, 1-butene, 
4-methyl-1-pentene and 1-hexene; but it is also possible to use for 
example n-1-octene, n-1-decene or n-1-dodecene.

EXAMPLE 1 
Preparation of titanium component (1) 
The procedure is that first 
(1.1) a carrier material is prepared in a first stage (I) from (Ia) a 
finely divided silica gel having a particle diameter of from 20 to 45 
.mu.m, a pore volume of 1.75 cm.sup.3 /g, a surface area of 320 m.sup.2 /g 
and the formula SiO.sub.2, (Ib) butyloctylmagnesium, (Ic) hydrogen 
chloride and (Id) di-n-butyl phthalate by first 
(1.1.1) bringing together in a first substage in n-heptane with constant 
mixing by stirring at room temperature the finely divided silica gel (Ia) 
and the organomagnesium compound (Ib) using for every 10 molar parts of 
silicon of silica gel (Ia) 2.5 molar parts of the organomagnesium compound 
(Ib) and keeping the mixture at about 90.degree. C. for 1.5 hours, then 
(1.1.2) in a second substage passing with constant mixing by stirring at 
about 10.degree. C. into the mixture obtained from the first substage (i) 
the gaseous chlorinating agent (Ic) using for every molar part of 
organomagnesium compound (Ib) 10 molar parts of chlorinating agent (Ic) 
and (ii), five minutes after the start of the chlorination, the phthalic 
acid derivative (Id) using for the molar part of organomagnesium compound 
(Ib) 0.3 molar part of phthalic acid derivative (Id), keeping the whole 
mixture at a temperature within the stated range for 1.5 hours, and 
leaving the resulting solid-phase product, i.e. the carrier material (I) 
in the liquid phase, then 
(1.2) in a second stage preparing a solid-phase intermediate from (I) the 
carrier material obtained in the first stage, (II) ethanol and (III) 
titanium tetrachloride by first 
(1.2.1) in a first substage bringing together in n-heptane with constant 
mixing by stirring at room temperature the carrier material (I) and the 
ethanol (II) using 3 molar parts of ethanol (II) per molar part of 
magnesium of carrier material (I) and maintaining the mixture at about 
80.degree. C. for 1.5 hours, then 
(1.2.2) in a second substage introducing the titanium tetrachloride (III) 
with constant mixing by stirring at room temperature into the reaction 
mixture resulting from the first substage using 7 molar parts of titanium 
tetrachloride (III) per molar part of magnesium of carrier material (I), 
maintaining the mixture at about 100.degree. C. for 2 hours with stirring, 
and isolating the resulting solid-phase intermediate by separating off the 
liquid phase by filtering with suction, then 
(1.3) in a third stage subjecting the solid-phase intermediate obtained 
from the second stage at 125.degree. C. for 4 hours to a continuous 
extraction with a mixture of titanium tetrachloride and ethylbenzene 
having a titanium tetrachloride content of 15% by weight, using 100 parts 
by weight of titanium tetrachloride/ethylbenzene mixture for every 10 
parts by weight of the solid-phase intermediate obtained from the second 
stage, then isolating the resulting solid-phase intermediate by filtration 
and finally 
(1.4) in a fourth stage washing the solid-phase product isolated in the 
third stage with n-heptane three times and so obtaining the titanium 
component (1); it contains 4.4% by weight of titanium, 6.5% by weight of 
magnesium and 27.5% by weight of chlorine. 
Polymerization 
A 10-1 capacity steel autoclave equipped with a stirrer is charged with 50 
g of polypropylene powder, 10 mmol of aluminum triethyl (in the form of a 
1-molar solution in n-heptane) as aluminum component (2), 1 mmol of 
triethoxyphenylsilane (in the form of a 1-molar solution in n-heptane) as 
silane component (3), 5 standard liters of hydrogen and finally 120 mg 
(0.11 mmol of titanium) of the above-described titanium component (1) at 
30.degree. C. The reactor temperature is raised to 70.degree. C. in the 
course of 10 minutes, and the reactor pressure is raised to 28 bar at the 
same time by pressurization with gaseous propene. 
The actual polymerization is carried out with constant stirring at 
70.degree. C. under 28 bar over 2 hours, during which consumed monomer is 
continuously replaced by fresh monomer. 
The productivity of catalyst component (1), the heptane-soluble proportion 
(as a measure of the isotacticity) and the particle size distribution of 
the polymer obtained are shown in the Table below. 
EXAMPLE 2 
Example 1 is repeated, except that the silane component (3) used is the 
same molar amount of dimethoxyditoluylsilane. 
The polymerization results thus obtained are again shown in the Table 
below. 
COMISON 
Preparation of titanium component 
Example 1 of European Patent Application EP-A-0,195,497 is carried out. 
The result is a titanium component which contains 3.6% by weight of 
titanium, 4.4% by weight of magnesium and 16% by weight of chlorine. 
Polymerization 
It is carried out as in Example 1 except that the titanium component 
described therein is replaced by the same molar amount of the comparative 
titanium component. 
The polymerization results obtained are again shown in the Table below. 
__________________________________________________________________________ 
Productivity 
Heptane-soluble 
Particle size Chlorine content 
(g of PP/g of 
proportion 
distribution (mm) of product 
catalyst) 
(% by weight) 
&lt;0.25 
0.25-0.5 
0.5-1 
1-2 
&gt;2 (ppm) 
__________________________________________________________________________ 
Example 1 
13,400 2.3 1.3 4.4 64.6 
29.5 
0.1 
20.5 
Example 2 
15,600 1.6 1.1 3.8 50.3 
44.5 
0.3 
17.6 
Comparison 
3,500 4.0 3.0 29.8 54 12.2 
1.0 
46 
__________________________________________________________________________ 
As can be seen from the Table, the catalyst component of the Comparison has 
a significantly lower productivity and stereospecificity than the catalyst 
components of the Examples according to the invention. In addition, the 
chlorine content of the polymer is significantly higher than in the cases 
according to the invention.