Magnesium chloride particles with a truncated structure, catalytic component supported on these particles, polyolefins obtained by employing this catalytic component, procedures for manufacturing these products

Porous particles of MgCl.sub.2 which have essentially the shape of two truncated right cones connected by their larger bases, which truncated cones are incurved towards the axis of symmetry perpendicular to the bases, at the intersection of the envelope of the truncated cones with two orthogonal planes passing through the said axis of symmetry. These particles are impregnated with a transition metal compound and employed as a catalytic component in the polymerization of olefins. The resultant polyolefins, especially polyethylene, polypropylene and their copolymers, are comprised of particles with a distinctive structure.

BACKGROUND OF THE INVENTION 
The present invention pertains to particles of magnesium chloride 
(MgCl.sub.2) with a novel shape as well as to the procedure for 
manufacturing these particles. These MgCl.sub.2 particles can be employed 
as a catalytic support, especially in the catalytic components of the 
Ziegler-Natta type. The polyolefins obtained by means of polymerization of 
olefins in the presence of the catalytic component containing this 
MgCl.sub.2 also have a distinctive structure. These catalytic components 
and the polyolefins obtained in the presence of these components are also 
part of the invention. 
SUMMARY OF THE INVENTION 
When viewed under a microscope, the MgCl.sub.2 in accordance with the 
invention is comprised of porous particles which have the shape of two 
truncated right cones connected by their larger bases, which truncated 
cones are incurved towards the axis of symmetry perpendicular to the 
bases, at the intersection of the envelope of the truncated cones with two 
orthogonal planes passing through the said axis of symmetry. The two 
truncated cones are generally essentially identical and symmetrical and 
such that the ratio D:h of the largest diameter "D" of the bases to the 
total height "h" of the two connected truncated cones is between 1 and 2, 
and more especially between 1.4 and 1.7. The usual D:d ratio of the 
largest diameter "D" of the particle to the largest diameter "d" of the 
small base of the truncated cones is between 2 and 4, and more especially 
between 2.5 and 3.5. The invention also comprises catalytic components 
embodying the MgCl.sub.2 particles, polyoloefins obtained utilizing such 
catalytic components, and the process of making such products.

DETAILED DESCRIPTION 
The four incurvations on each of the two truncated cones, separated from 
each other essentially by 90.degree., referring to FIGS. 1 and 2, can be 
defined in relation to the largest radius "R" of the larger base of the 
truncated cones and to the distance "E" separating the center of this 
larger base of the truncated cone on this base from the point of maximum 
incurvation. This ratio R:E is generally between 1.1 and 1.5 and more 
especially between 1.2 and 1.4. These incurvations usually follow the two 
truncated cones from the larger base to the smaller base. Under these 
conditions, the ratio r:e can be between 1.1 and 1.5 and more especially 
between 1.2 and 1.4, "r" being the largest radius of one of the two 
smaller bases of the truncated cones and "e" representing the distance 
separating the center of this smaller base from the point of maximum 
incurvation on this same base. 
These MgCl.sub.2 particles have a rough and furrowed surface which assures 
excellent porosity. This porosity is generally between 0.5 and 3.5cm.sup.3 
/g, preferably between 1.5 and 2.5cm.sup.3 /g; it can be estimated that in 
these particles the pores with radii between 5 and 100 nm represent up to 
50% of the porous volume. Their specific surface area is usually between 
100 and 400m.sup.2 /g, preferably between 200 and 300m.sup.2 /g. 
The size of the MgCl.sub.2 particles is generally between 10 and 100.mu.m, 
providing a narrow granulometric distribution. The D90:D10 range of 
granulometric distribution is usually lower than 4 and more generally 
lower than 3; D90 and D10 being the diameters smaller than which are 90% 
and 10% by weight of the particles, respectively. 
These particles are obtained by precipitation with 1,4-dioxane of 
MgCl.sub.2 in solution in alcohol, with the said solution being emulsified 
in a dispersant medium; the recovered MgCl.sub.2 particles are then 
treated so as to totally eliminate the 1,4-dioxane. 
The MgCl.sub.2 to be treated is first put into solution in an alcohol under 
the usual dissolution conditions at a concentration equal to at most the 
limit of saturation at the temperature of the subsequent treatment of the 
solution. The alcohol employed is preferably a monoalcohol containing from 
1 to 20 carbon atoms; n-butanol is the most highly recommended. 
The solution of MgCl.sub.2 in alcohol is emulsiifed in a dispersant medium, 
which is a liquid that is a nonsolvent of and inert in relation to the 
solution, at a temperature than can range from room temperature to 
100.degree. C. Although it is not necessary, the emulsion can be prepared 
in the presence of a surface-active agent, preferably a nonionic 
surface-active agent. The liquid dispersant is preferably selected from 
among the heavy hydrocarbons with at least eight carbon atoms in their 
molecule, such as the paraffin oils with a viscosity at 20.degree. C. 
between 0.1 and 1 Pa.s. In the emulsion, the volume ratio of the 
dispersant medium to the alcohol phase, represented by the solution of 
MgCl.sub.2 in alcohol, is usually between 1 and 5, preferably between 2 
and 4. As is known by the person skilled in this field, the agitation must 
be sufficient so as to maintain the alcohol phase in the form of droplets 
in the dispersant medium. As long as this condition is observed, the 
agitation conditions do not seem to be critical because, in particular, of 
a better stability of the emulsion at the procedure temperatures than at 
higher temperatures. 
To this emulsion is added the precipitation agent which is 1,4-dioxane. The 
1,4-dioxane is preferably added to the emulsion under agitation so as to 
assure immediate crystallization of the MgCl.sub.2. The rate of 
introduction of the 1,4-dioxane does not appear to be critical; the 
1,4-dioxane may be added as quickly as possible or allowed to flow slowly 
into the emulsion. The temperature of the 1,4-dioxane at the time of its 
introduction into the dispersion is also not critical. In contrast, so as 
to assure excellent precipation of MgCl.sub.2, it is recommended that two 
volumes of 1,4-dioxane be employed per volume of alcohol solution and to 
avoid allowing the temperature of the reaction medium to drop below around 
20.degree. C. 
The precipated MgCl.sub.2 is in the form of particles as previously 
defined. This MgCl.sub.2 is recovered in the form of a MgCl.sub.2, 
1,4-dioxane complex containing generally on the order of 67% by weight of 
dioxane and 33% by weight of MgCl.sub.2. This complex must be treated so 
as to totally eliminate the 1,4-dioxane from the MgCl.sub.2. In fact, it 
is known that for certain applications of MgCl.sub.2, the presence of 
1,4-dioxane is harmful, particularly when MgCl.sub.2 is employed as a 
support for a Ziegler-type catalytic component for polymerization; in 
fact, 1,4-dioxane has a catalyst-poisoning effect. 
This dioxane can be eliminated from the MgCl.sub.2 by any of the known 
means such as heating under vacuum for a sufficient length of time such 
as, for example, at 200.degree.-208.degree. C. under a vacuum between 1 
and 2 kPa, or by hot fluidization of the complex at, for example, 
400.degree. C. under an inert gas stream. 
A particularly noteworthy means of eliminating the 1,4-dioxane from the 
MgCl.sub.2 is comprised of treating the complex obtained with an aluminum 
compound selected from among the nonhalogenated aluminoxanes, the 
nonhalogenated aluminosiloxanes or the AlR.sub.3 alkylaluminums in which R 
represents an alkyl radical containing from 1 to 20 carbon atoms. The 
1,4-dioxane removed from the MgCl.sub.2 forms a complex with the aluminum 
compound. In order to achieve this, the MgCl.sub.2 1,4-dioxane complex is 
suspended in an inert liquid which is a solvent of the aluminum compound 
and the new complex formed: aluminum compound--1,4-dioxane after addition 
of the said aluminum complex. The inert liquid used for suspending the 
MgCl.sub.2 complex can be, for example, selected from among the saturated 
or unsaturated hydrocarbons such as hexane, heptane, benzene, toluene, the 
partially or completely chlorinated compounds with a larger dipole moment 
such as CH.sub.2 Cl.sub.2,C.sub.2 H.sub.4 Cl.sub.2,CCl.sub.4,C.sub.2 
Cl.sub.4 or orthodichloro-benzene, or from among the aromatic compounds 
having hydrocarbon groups and/or at least one chlorine atom. This 
treatment with the aluminum compound can be carried out under agitation at 
room temperature or under hot conditions, possibly under pressure so as to 
accelerate the reaction. The treatment temperature is not critical; this 
temperature is only limited by the boiling point of the inert liquid 
employed as a suspension agent. It is recommended that in the suspension 
an amount of aluminum compound be employed such that the molar ratio 
Al:1,4-dioxane be equal to or greater than 2. The excess of the aluminum 
is limited only by economic issues and the ease of washing. Rather than 
employing a large excess of the aluminum compound in the suspension, it is 
preferable for total elimination of the 1,4-dioxane to carry out multiple 
treatments of the MgCl.sub.2 with the aluminum compound. After the usual 
washings and rinsings for elimination of the final traces of the complex 
of the aluminum compound and 1,4-dioxane and possibly drying, the 
MgCl.sub.2 recovered is essentially pure and contains more than 24% by 
weight of Mg; it also preserves the previously defined shape and 
characteristics. 
When the MgCl.sub.2 particles are intended for use as a transition-metal 
support of Ziegler-Natta type catalytic components, it can be of value to 
not totally eliminate the aluminum compound which was used in the final 
treatment for eliminating the 1,4-dioxane. 
X-ray observation of the MgCl.sub.2 obtained shows a crystalline product 
with certain diffraction peaks, including the peak located at circa 
0.181-0.184 nm (nanometer) that is characteristic of MgCl.sub.2 as well as 
three additional peaks located at circa 0.75-0.85 nm, 0.70-0.75 nm and 
0.50-0.52 nm. These measurements were carried out using PHILIPS equipment 
with the following characteristics: 
scatter band of 1.degree. 
convergence aperture of 0.1.degree. 
nickel filter 
normal focal tube made of copper 
PW 1130 generator 
PW 1050/25 goniometer 
acceleration voltage=50 KV 
emission intensity=30 mA 
goniometer rotation rate: 1.degree. (2 )/minute 
By means of its novel structure, the MgCl.sub.2 obtained has all of the 
same advantages as MgCl.sub.2 with a spherical shape, while reducing its 
drawbacks. In order to obtain good pourability, as measured in accordance 
with the standard ASTM D-1895, of the MgCl.sub.2 and, more particularly, 
of the final polymer or copolymer, when the MgCl.sub.2 is employed as a 
catalytic support, research was focused on the particle structures of 
MgCl.sub.2. The spherical shape was particularly investigated in the case 
of catalysis such that the final polymer or copolymer particle, which 
essentially reproduces the support particle in a homothetic manner, would 
have this pourability quality. The disadvantage of this sphericity is that 
it facilitates the accumulation of electrostatic charges in the reactors 
and conduits, thereby causing, in particular, the adhesion of powder to 
the walls. The structure of the MgCl.sub.2 in accordance with the 
invention makes it possible to reduce this type of disadvantage. 
A Ziegler-type catalytic component can be obtained by combining the 
MgCl.sub.2 in accordance with the invention with a transition metal 
compound. Thus, for example, this type of component can be obtained by 
deposition on the MgCl.sub.2 of a titanium and/or vanadium compound which 
is preferably halogenated and, more specifically, of TiCl.sub.4, 
TiCl.sub.3, VCl.sub.4, VCl.sub.3 or VOCl.sub.3. This catalytic compound 
combined with a cocatalyst selected from among the organometallic 
compounds of metals I to III on the Periodic Table and, more specifically, 
the aluminum compounds, is employed as a catalyst of the polymerization or 
copolymerication of linear or branched olefins such as ethylene, 
propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 1,3 butadiene 
and 1,9-decadiene. 
At least one electron donor may be added during the preparation of the 
catalytic component and/or the cocatalyst. The electron donors may be 
selected, for example, from among the Lewis acids, the esters of 
oxygenated acids, the ketones, aldehydes, ethers, amines, amides, the 
silicon compounds such as the silanes, and the phosphorus compounds such 
as the phosphines and the phosphoramides; the preferred electron donors 
being the alkylated esters or polyesters of aromatic acids, the alkyl 
mono- or diethers, the alkoxysilanes and the alkylalkoxysilanes. 
The catalyst obtained from a component prepared from the MgCl.sub.2 of the 
invention is suitable for all types of polymerization of olefins: at high 
or low pressure, in suspension, in gas phase or mass polymerization. 
The catalytic component obtained from the MgCl.sub.2 in accordance with the 
invention is also comprised of particles which, when viewed under a 
microscope, have the shape essentially of two truncated right cones 
connected by their larger bases, which truncated cones are incurved 
towards the axis of symmetry perpendicular to the bases, at the 
intersection of the envelope of the truncated cones with two orthogonal 
planes passing through the said axis of symmetry. The two truncated cones 
are generally essentially identical and symmetrical such that the ratio 
D:H of the largest diameter "D" of the bases to the total height "h" of 
the two connected truncated cones is between 1 and 2 and, more especially, 
between 1.4 and 1.7. The usual ratio of the largest diameter "D" of the 
component particle to the largest diameter "d" of the small bases of the 
truncated cones is between 2 and 4 and, more especially, between 2.5 and 
3.5. The four incurvations on each of the two truncated cones, separated 
from each other essentially by 90.degree., can be defined in relation to 
the largest radius "R" of the larger base of the truncated cones and to 
the distance "E" separating the center of this large base of the truncated 
cones from the point of maximum incurvation on this same base. This ratio 
R:E is generally between 1.1 and 1.5 and, more especially, between 1.2 and 
1.4. These incurvations, which are much more accentuated at the large 
bases than at the small bases of the truncated cones, usually follow each 
truncated cone from the larger base to the smaller base. Under these 
condition, the ratio r:e can be between 1.1 and 1.5 and, more especially, 
between 1.2 and 1.4, with "r" being the largest radius of one of the two 
small bases of the truncated cones and "e" representing the distance 
separating the center of this small base from the point of maximum 
incurvation on this same base. 
These catalytic component particles have an essentially smooth surface; the 
porosity of these particles is generally between 1 and 3 cm.sup.3 /g and, 
preferably, between 1.5 and 2.5 cm.sup.3 /g. Their specific surface area 
is usually between 100 and 400 m.sup.2 /g and, preferably, between 200 and 
300 m.sup.2 /g. 
The size of the catalytic component particles is generally between 4 and 
100.mu.m for a narrow granulometric distribution. The D90:D10 range of 
granulometric distribution, as previously defined, is usually lower than 4 
and more generally lower than 3. 
The catalytic component can advantageously be prepared by impregnation, in 
a known manner, of the previously described MgCl.sub.2 particles by a 
transition metal compound which is liquid or in solution and which has one 
or more halogen atoms, particularly chlorine atoms. Prior to this 
impregnation or at least at the same time, it can be advisable to carry 
out the deposition of at least one organic compound selected from among 
the previously mentioned electron donors. 
The resultant catalytic composition, combined with a conventional 
cocatalyst, usually selected from among the organic aluminum compounds 
such as the aluminoxanes, the aluminosiloxanes, the compounds with Al-R-Al 
bonds in which R represents an alkyl group, or of formula AlXqR's in which 
X represents Cl or OR' with R' designating a C.sub.1 to C.sub.16, 
preferably a C.sub.1 to C.sub.12, alkyl radical while q and s are numbers 
such that 1&lt;s&lt;3, 0&lt;q&lt;2 with q+s=3, form a catalyst which is suitable for 
the polymerization of olefins and, more specifically, of ethylene, 
propylene, 1-butene, 4-methyl-1-pentene and 1-hexene or their mixtures. 
The possibility is not excluded of combining with the cocatalyst an 
electron donor such as previously defined. The catalytic component and the 
cocatalyst are combined in proportions such that the molar ratio of the 
aluminum contained in the cocatalyst to the transition metal of the said 
component is between 0.5 and 1000, preferably between 1 and 400. 
The polymerization of the previously mentioned olefins or, in general, 
C.sub.2 to C.sub.12 olefins singly or in mixtures, by means of the 
previously defined catalytic system can be implemented in solution or in 
suspension in an inert liquid medium and notably in an aliphatic 
hydrocarbon such as n-heptane, n-hexane, isohexane, isobutane or mass 
polymerization can be carried out in at least one of the olefins to be 
polymerized which is maintained in the liquid or hypercritical state. 
The operating conditions, notably the temperatures, pressures, amounts of 
catalytic system, for these liquid-phase polymerizations are those which 
are usually recommended for the similar cases involving supported or 
unsupported conventional catalytic systems of the Ziegler-Natta type. 
For example, for polymerization carried out in suspension or in solution in 
an inert liquid medium, one can operate at temperatures up to 250.degree. 
C. and under pressures ranging from atmospheric pressure to 250 bar. In 
the case of polymerization in a liquid propylene medium, the temperatures 
can go as high as the critical temperature and the pressures can be 
between atmospheric pressure and the critical pressure. For mass 
polymerization or mass copolymerization of ethylene leading to 
polyethylenes or to a predominately ethylene-containing copoylmers, one 
can operate at temperatures between 130.degree. and 350.degree. C. and a 
pressures randing from 200 to 3500 bar. 
The catalytic system obtained by combination of the transition metal 
component according to the invention witha a cocatalyst and possibly an 
electron donor as previously defined, can also be used for the gas-phase 
polymerization of the previously mentioned olefins or olefins mixtures. 
Specifically, gas-phase polymerization can be carried out with contact of 
the said catalytic system with a mixture of ethylene or propylene and one 
or more C.sub.2 to C.sub.12 olefins such as ethylene, propylene, 1-butene, 
1-hexene, 4-methyl-1-pentene and 1-octene, which contains when it is in 
contact with the catalytic system a molar proportion of C.sub.2 to 
C.sub.12 comonomers between 0.1 and 90%, preferably between 1 and 60%. 
The gas-phase polymerization of the olefin or olefins in contact with the 
catalytic system can be carried out in any reactor that allows gas-phase 
polymerization, particularly in an agitated and/or fluided bed reactor. 
The implementation conditions for the gas-phase polymerization notably 
temperature, pressure, injection of the olefin or olefins into the 
agitated and/or fluidized bed reactor, control of the polymerization 
temperature and pressure, are similar to those recommended in the prior 
art for the gas-phase polymerization of olefins. Operations are generally 
carried out at a temperature below the melting point Tf of the polymer or 
copolymer to be synthesized, more specifically between +20.degree. C. and 
(Tf -5).degree. C., and under a pressure such that the olefin or olefins, 
and possibly the other hydrocarbon monomers present in the reactor, are 
essentially in vapor phase. 
The solution, suspension, mass, or gas-phase polymerization can be carried 
out in the presence of a chain-transfer agent so as to control the 
melt-flow index of the polymer or copolymer to be produced. The preferred 
chain-transfer agent is hydrogen which is used in an amount which can be 
as high as 90%, preferably between 0.1 and 60%, of the total volume of the 
olefins and hydrogen brought into the reactor. 
The transition metal component in accordance with the invention can also be 
used for the preparation of an active prepolymer, which can be used alone 
or in combination with a cocatalyst selected from the previously defined 
aluminum compounds. 
The said active prepolymer is obtained by bringing into contact one or more 
C.sub.2 to C.sub.12 alpha-olefins with a catalytic system formed by 
combining the transition metal component according to the invention with a 
cocatalyst selected from among the compounds that were previously 
mentioned for this purpose and employed in the previously specified 
proportions, with the said C.sub.2 to C.sub.12 olefin or olefins being 
used in an amount representing 2 to 500 grams, perferably 2 to 100 grams, 
of C.sub.2 to C.sub.12 olefin or olefins per gram of the transition metal 
component. 
The catalytic component in accordance with the invention is particularly 
valuable in the polymerization or copolymerization of ethylene or 
propylene or their mixtures with each other or with another olefin in that 
it makes it possible to obtain polymers or copolymers with novel 
structures to the extent, obviously, that the polymerization temperature 
is lower than the melting point of the polymer formed. 
When viewed under a microscope, the polyethylene or the copolymers of 
ethylene generally with more than 80% by weight of ethylene and at least 
one other olefin, usually a C.sub.3 to C.sub.12 olefin, have the 
appearance of particles which are pierced centrally and comprised of a 
succession of agglometrates attached to each other and arranged in a 
ring-like manner. These particles have an average size between 300 and 
1000.mu.m and are comprised of agglomerates of a size generally between 50 
and 400 .mu.m, more specifically between 200 and 2000 .mu.m. The polymer 
or copolymer obtained, which has a narrow granulometric distribution 
usually between 3 and 4, has a high apparent density, measured according 
to the standard ASTM D1895 Method A, benerally between 0.35 and 0.40 
g/cm.sup.3. The pourability of the powders is also high with values that 
are usually lower than or equal to 20 seconds, according to the standard 
ASTM D1895. 
When viewed under a microscope, the polypropylene or the copolymers of 
propylene and ethylene or at least one other C.sub.4 to C.sub.12 olefin, 
generally with more than 80% by weight of propylene, have the form of 
particles comprised of two truncated right cones connected by their larges 
bases, which truncated cones are incurved towards the axis of symmetry 
perpendicular to the bases, at the intersection of the envelope of the 
truncated cones with two orthogonal planes passing through the said axis 
of symmetry. The two truncated cones are generally essentially identical 
and symmetrical and such that the ratio D:h of the largest diameter "D" of 
the bases to the total height "h" of the two connected truncated cones is 
between 1 and 2, more specifically between 1.4 and 1.7. The usual ratio 
D:d of the largest diameter "D" of the particle to the largest diameter 
"d" of the small bases of the truncated cones is between 2 and 4, more 
specifically between 2.5 and 3.5. The four incurvations on each of the two 
truncated cones, separated from each other essentially by 90%, can be 
defined in relation to the largest radius "R" of the larger base of the 
truncated cone and to the distance "E" separating the center of this 
larger base of the truncated cones from the point of maximum incurvation 
on this same base. This ratio R:E is generally between 1.1 and 1.5, more 
specifically between 1.2 and 1.4. These incurvations usually follow the 
two truncated cones from the larger base to the smaller base. Under these 
conditions, the ratio r:e can be between 1.1 and 1.5, more specifically 
between 1.2 and 1.4, with "r" being the smallest radius of one of the two 
small bases of the truncated cones and "e" representing the distance 
separating the center of this small base from the point of maximum 
incurvation on this same base. Attached FIGS. 1 and 2 show a front view 
and a top view of and are representative of this polypropylene and its 
copolymers. 
These propylene and propylene copolymer particles, the size of which is 
generally between 200 and 500 .mu.m for a narrow granulometric 
distribution, have a specific surface area between 0.1 and 3 m.sub.2 /g. 
The D90:D10 range of granulometric distribution is usually lower than 4, 
more generally lower than 3. The apparent densities of the propylene 
polymers or copolymers are particularly high and generally between 0.45 
and 0.55 g/cm.sup.3. The pourability of the powders is usually between 20 
and 25 seconds. 
The particles of polypropylene and its copolymers obtained from a 
MgCl.sub.2 component and/or support as previously described are generally 
essentially homothetic to the particles of the MgCl.sub.2 component and/or 
support. 
The D90:D10 range of granulometric distribution is determined by means of a 
MALVERN 1600 laser granulometer. The specific surface area is measured by 
isothermal physical absorption of nitrogen at the temperature of liquid 
nitrogen, BET method, on a QUANTASORB device. The porous volume is 
determined by intrusion of mercury under pressure with an ERBASCIENCE 1500 
porosimeter. 
The following examples illustrate the invention without, however, limiting 
it. 
EXAMPLE 1 
Into an agitated reactor thermostated at 40.degree. C. and purged with dry 
nitrogen are introduced 50 mL of a solution of MgCl.sub.2 in n-butanol 
such that the BuOH:MgCl.sub.2 molar ratio is 10. One then adds 200 mL of a 
paraffin oil with a viscosity of 0.2 Pa.s measured at 20.degree. C. 
Agitation is brought to a speed such that the linear speed at the end of a 
blade is 120 m/s. The biphasic mixture is left under agitation for 5 
minutes and then 125 mL of 1,4-dioxane is added quickly and all at once. 
Precipitation of the MgCl.sub.2, 1,4-dioxane complex is immediate. After 
filtration, washing with hexane and drying under a nitrogen stream, one 
recovers circa 14 g of a white pulverized powder with very good 
pourability, the particles of which have a morphology corresponding to 
FIGS. 3 and 4. The composition of the solid prepared in this manner is 67% 
1,4-dioxane and 33% MgCl.sub.2. The average largest diameter of the 
particles is 27 .mu.m and the D90:D10 ratio is 3.6. The specific surface 
area measured by BET is 4 m.sup.2 /g and the porosity is 1.1 cm.sup.3 /g. 
5.8 g of this composition is treated with a solution of triethylaluminum in 
1,2-dichloroethane such that the Al:1,4-dioxane molar ratio is 2 and the 
concentration in aluminum is 1 mole per liter. After filtration, washing 
and drying of the solid, one obtains a powder at least 80% of the 
structure of which corresponds to that in FIGS. 3 and 4. The mean diameter 
of the particles is 15 .mu.m. The porosity is 2.16 cm.sup.3 /g for a 
specific surface area of 272 m.sup.2 /g, the mean D:h ratio=1.5 and the 
D:d ratio=2.5 with R:E=1.2 and r:e=1.2. The D90:D10 ratio=3.5. The 
MgCl.sub.2 contains 24.5% Mg. 
This powder is taken up in 50 mL of a solution of dioctyl phthalate in 
1,2-dichloroethane at 0.2 mole for 2 hours at 80.degree. C. After 
filtration, 50 mL of pure TiCl.sub.4 is added to the MgCl.sub.2. After 2 
hours under agitation at 80.degree. C., a new filtration is carried out 
and the solid is taken up in 50 mL of a solution of 1,2-dichloroethane 
containing 1 mole of TiCl.sub.4 for 30 minutes at 80.degree. C. under 
agitation. After filtration, this treatment with dilute TiCl.sub.4 is 
carried out again. After filtration, washing with hexane and drying, one 
obtains 1.9g of catalytic component containing 69%, 23.8% and 0.9% by 
weight of chlorine, magnesium and titanium, respectively. The structure of 
the component particles obtained corresponds to those of FIGS. 5 and 6. 
The mean diameter of the particles is 15 .mu.m and the range of the 
granulometric distribution is 3.4. On average, the particles have the 
following characteristics: D:h=1.5, D:d=2.5, R:E=1.2 and r:e=1.2. Their 
mean porosity is 2.2 cm.sup.3 /g for a specific surface area of 290 
m.sup.2 /g. 
Into a stainless steel reactor are introduced 1.2 L of hydrogen, 600 g of 
liquid propylene, 1.3 g of triethylaluminum and 0.1 molar equivalent in 
relation to the aluminum of cyclohexylmethyldimethoxysilane. 20 mg of the 
prior catalytic component is added. The reactor is kept under agitation 
for 1 hour at 70.degree. C. 
One recovers 172 g of polypropylene with good pourability, the structure of 
the particles of which corresponds to that shown in FIG. 8. The mean 
diameter of the polymer particles is 270 .mu.m and the range of 
granulometric distribution is 2.6. The level of fine particles smaller 
than 10 .mu.m is 0.2 %. The apparent density is 0.46 g/cm.sup.3 and the 
pourability is 21 seconds. The level of polymer insoluble in boiling 
heptane is 95.1%. The melt-flow index measured according to the standard 
ASTM D1238 Method L is 4. 
EXAMPLE 2 
A MgCl.sub.2 powder is prepared under the conditions of Example 1 except 
that the operation is carried out at 65.degree. C. rather than 40.degree. 
C. 14 g of powder is finally obtained and treated with a solution of 
triethylaluminum in 1,2-dichloroethane under the same conditions as in 
Example 1. The final structure of the particles corresponds to that shown 
in FIGS. 3 and 4. The mean diameter of the particles is 35 m and the range 
of their granulometric distribution is 3.8. The porosity=1.7 cm.sup.3 /g, 
the specific surface area=229 m.sup.2 /g, D:h=1.6, D:d=3, R:E=1.3, 
r:e=1.3, Mg =24.3%. The powder obtained is put into suspension in 50 mL of 
pure TiCl.sub.4 for 3 hours at 80.degree. C. After filtration, washing 
with hexane and drying, the catalytic component obtained contains 23.5%, 
1.4% and 71.3% by weight of magnesium, titanium and chlorine, 
respectively. The structure of the particles of the resultant component 
corresponds to that of FIGS. 5 and 6. The mean diameter of the particles 
is 30 .mu.m and the range of the granulometric distribution is 3.3. On 
average the particles have the following characteristics: D:h=1.6, D:d=3, 
R:E=1.3, and r:e=1.3. Their mean porosity is 1.53 cm.sup.3 /g for a 
specific surface area of 207 m.sup.2 /g. 
Into a stainless steel reactor, one introduces under nitrogen 2 liters of 
hexane, 10 mM of triisobutylaluminum and 10 mg of the preceding catalytic 
component. The temperature is brought to 86.degree. C. The reaction medium 
is put under a pressure of 0.4 MPa of hydrogen. The reactor is fed with a 
mixture of ethylene and of 1-butene at 1% 1-butene. The monomer pressure 
is 0.6 MPa. After three hours of reaction, one recovers 173 g of 
ethylene-butene copolymer with very good pourability, the structure of the 
particles of which corresponds to that shown in FIG. 9. The mean diameter 
of the polymer particles is 500 .mu.m and the range of granulometric 
distribution is 3.8. The apparent density is 0.35 g/cm.sup.3 and the 
pourability is 19 seconds. The melt-flow indices measured according to the 
standard ASTM D1238 Methods E and F are 1 and 34, respectively. 
EXAMPLE 3 
With all other conditions corresponding to those of Example 1, 240 mL of 
butanol solution of MgCl.sub.2 and 1150 mL of paraffin oil are employed. 
The linear agitation speed at the end of the blade is 280 m/s and the 
operating temperature is 90.degree. C. 700 mL of 1,4-dioxane is added. One 
obtains 66 g of powder, the structure of the particles of which correspons 
to that shown in FIGS. 3 and 4. The mean diameter of the particles is 15 
.mu.m and the range of granulometric distribution is 3.5. The porosity=2.1 
Cm.sup.3 /g, the specific surface area=217 m.sup.2 /g, D:h=1.5, D:d=3, 
R:E=1.2 and r:e=1.2 
EXAMPLE 4 
Use is again made of the catalytic component as described in Example 2. 
The homopolymerization of ethylene is carried out under the same conditions 
as those of Example 2, except with regard to the partial pressures of 
hydrogen and ethylene which are 0.47 MPa and 0.63 MPa, respectively. After 
2 hours of reaction, 53 g of polyethylene are recovered. The structure of 
the particles corresponds to that shown in FIG. 7. 
The mean diameter is 640 microns. The range of granulometric distribution 
is 3.4. The apparent density is 0.37 g/cm.sup.3 and the pourability is 20 
seconds. 
The melt-flow indices measured according to the standard ASTM D1238 Methods 
E and F are 3.5 and 108, respectively. 
EXAMPLE 5 
The catalytic component described in Example 1 is employed in the 
copolymerization of propylene and ethylene. Into a stainless steel reactor 
purged with nitrogen are introduced in order: 1.2 liters of hydrogen, 600 
g of liquid propylene, 1.3 g of triethylaluminum and 0.1 molar equivalent 
in relation to the aluminum of cyclohexylmethyldimethoxysilane. Twenty mg 
of the catalytic component is then added and the temperature is raised to 
70.degree. C. 
As soon as the reaction temperature reaches 70.degree. C., ethylene at a 
flow rate of 10 Nl/min is introduced into the reactor for 1 hour. 
After degassing the reactor, 160 g of propyleneethylene copolymer is 
recovered. 
The structure of the particles corresponds to that of FIG. 10. The mean 
diameter is 330 .mu.m and the range of granulometric distribution is 3.6. 
The level of fine particles smaller than 100 .mu.m is 1%. 
The apparent density is 0.43 g/cm.sup.3 and the pourability is 25 seconds. 
The melt-flow index of the copolymer measured according to the standard 
ASTM D1238 Method L is 2.5. The level of copolymer insoluble in boiling 
heptane is 82%. Infrared analysis of the level of ethylene in the 
copolymer yielded a value of 3.5 % by weight. 
While the invention has been described in connection with a preferred 
embodiment, it is not intended to limit the scope of the invention to the 
particular form set forth, but on the contrary, it is intended to cover 
such alternatives, modifications, and equivalents as may be included with 
the spirit of the invention as defined by the appended claims.