Note: Descriptions are shown in the official language in which they were submitted.
37~;
The present inventioll relates to a catalytic s~vstem
useful for the po]ymerization of alpha-olefins, particularly
ethylene, to a method for preparing the same and to a polymeriza-
tio~ process employiny such a catalyst.
It is known that alpha-olefins may be polymerized by
means of catalytic systems consisting of a combination ofa
titanium compound and a metal organic aluminium compound.
Such catalytic systems however do not present a
satisfactory activity.
The Applicants have -t~ought -that a satisfactory acti-
vity could be obtained if the titanium compound of such catalytic
systems is dispersed over a carrier having a high surface area.
The so obtained compound could be employed under the usual
conditions, for polymerizing alpha-olefins at low pressure.
The Applicants have used silica, alumina or silica-
alumina with a high surface area as catalyst carrier. It has
been noted, however, that the catalyst activity of the titanium
compound dispersed on such materials varies widely according to
the chemical nature of the surface of the carriers. In particu-
lar, some catalysts show such a low polymerization activity thatthey must be subjected to a specific treatment before being
used, such as, for instance, with an organo-metallic compound of
aluminium or magnesium, and more particularly with a metal alkyl
chloride. Said compounds react with the surface hydroxyls of the
carrier, thus preventing hydrolysis of the titanium compound
that is dispersed. `~
Such a method of activation of the catalysts however
entails some disadvantages deriving from the use of solutions
of said aluminium and magnesium compounds, which are expensive
and must be manipulated with great care. Furthermore, in the
case of the magnesium alkyl-halides, they must be usually prepa-
red in ether solvents, which present, in addition to their
high costs, the considerable disadvantage that they must be
prepared in a very pure state, and they are tied to the carrier
~L~698~
in an irreversible way, after the actiVatincJ trea-tment.
The present invention proposes a process ~or the
polymeri~ation o~ alpha-olefins, by using a catal~tic system
which has a high activity and remains unimpaired in time.
The catalytic system, according to the present
invention, consists of two components, which are:
1) an aluminium compound chosen among those of formula
AlR3 or AlRXY3_ , wherein R is a lower alkyl radical,
Y is an halogen or hydrogen atom and x is a number between 1
an~ 2, and
2) a titanium compound finely dispersecl over a carrier
having a high surface area, which carrier has been previously
treated with a magnesium inorganic compound of the formula:
~gX2.nH2O wherein X represents a halide and n a number ranging
from 0 to 6, in which catalysts the amount of magnesium dispersed
on the carrier is ranging from O.l to 10~ by weight and the
molar ratio of aluminium to titanium is ranging from 20 to 75~
The magnesium inorganic compound which is a magnesium -
halide, is dispersed over the carrier in a watery medium. After
removing the water, the carrie~ is subsequently subjected to an
activation treatment, by heating under vacuum at a temperature
ranging between 200 and 250C. The obtained product is -then re-
fluxed in liquid titanium tetrachloride, filtered, washed with
a hydrocarbon solvent and finally dried under vacuum.
When compared to the known techniques for the treatment
of a carrier with magnesium organic compound, the method accord- `
ing to the present invention presents the advantage that any
easily available and water soluble magnesium compound, not neces-
sarily pure, can be used without resorting to expensive and non
removable solvent.
The catalytic system according to the invention shows
a good response to hy~rogen (in particular to a Mg/q'i ratio
between 0.5 and 2 on the carrier) and allows or the obtention
-- 2 --
8~
o:E high yield of powder free, a~l(l polyetllylene with high bulk
density (10% of the particles obt~ine~ have ~ diameter below
200 y).
The carriers that can be used according to the
invention, can be chosen amon~ SiO2, SiO2/A12O3, A12O3, MgO,
TiO2, Zro2 and the rare earths oxides, whereas the magnesium
compound is chosen among the maynesium inorganic compounds of
the formula MgX2 . n H2O, wherein X represents a halide and n
is a number ranging from 0 to 6. The amount of magnesium dispersed
on t~e carrier may vary between 0.1 and 10~ by weight and
preferably between l and 5% by weight.
The polymerization reaction, when using the so obtained
ca-talyst system, is carried out according to the usual method, at
temperatures ranging from 0 to 200C and under pressures varying
from 0.1 to 50 atmospheres.
When operating above the atmospheric pressure, the
polymerization is carried out in a steel autoclave, provided with
an anchor stirrer. The catalyst is introduced together with the
solvent and the alkyl metal. The autoclave, which has a tempera-
ture control set, is first pressurized with H2 at the polymeriza-
tion temperature and afterwards with ethylene (or another olefin)at the required pressure ratio. The reaction is stopped by adding
alcohol in the autoclave.
The present invention will be now better understood
with particular reference to the following non-restrictive
examples o~ polymerization wherein, in every case, khe polymeriza-
tion reaction was carried out in the presence of 1 liter of
n-hexane as solvent, 2 cm 3 of Al i-But3 as aluminium organic
compound and a given amount of the hereinafter defined titanium
compound dispersed on a carrier, in a pressure vessel at a
temperature of ~5C.
EXAMPLE 1
10 y of SiO2, grade 56, produced by Davidson
- 3 -
~ t7~
Petrochemicals, haviny a surEace area of 285 m /g, a diame-ter o
pores of 168 A, and a volume oF pores o~ 1. 20 cm3/g, we~ 8U5-
pended in a water solution (50 ml) of Mg C12 . 6 H2O (2,5 g).
The water was removed in a rotating evaporator and the product
obtained, dried under vacuum Eor 4 hours at 170C, was refluxed
in TiC14 (100 ml) for 4 hours. The product was filtered undex
nitrogen on a sintered glass filter, washed on the filter with
petroleum ether and dried under vacuum for 4 hours.
The product obtained had the following composition
Ti= 4,72
Mg~ 2,12%
Cl-14,28%
251 mg of this product were used as dispersed titanium compound
for the polymerization of ethylene (PH ~ 10 atm, PC2H4
After 2 hours, 116 g of polyethylene were obtained, with a MF2 16
1 015 a MF 1 6 of 39-56~ a RMF21 6/MF2.~6
Index according to the PSTM Ru'es). The so obta~ed polyethylene
contained 98 ppm of Ti, had a bulk density of 0.295 g/cm , and
showed less than 10~ of particles with a diameter of 200 ~.
10 g of the same type of SiO2 were refluxed after
drying under vacuum for 4 hours at 175C, in liquid TiC14, without
any pre-treatment.
The product after filtration, washing with hexane and
drying, had the following composition
Ti- 4.85%
Cl _7.98~
30A mg of this product, were used as dispersed titanium compound
for the polymerization of ethylene under a pressure of 10 atm
H2 and 10 atm C2H4. After 5 hours, 36 g of polymer were obtained
having a MF2.16 of , a MF21.6 of 2-08, a MF2 16/~F2 16 o
and containing 410 ppm of Ti.
E~AMPLE 2
312 mg of the same product prepared as described in the
4 -
` ~L0~98~i~6
previous example, were used for the polymerization of ethylene
ith P ~ 15 km and P ~ 5 atm After 5 hours, 455 y of
polymer were obtained, with a MF2 16 of 6-32, a MF21 6 of 230.1
MF21 6/MF2 16 f 36-4~ arld a Content of 27 ppm o~ Ti
EX~MPI.E 3
10 g of SiO2 of the same type as used in example 1 were
treated, in the same way as previously described, with 3~5 g of
MgC12 . 6 H2O and activated under vacuum at 200c for 4 hours.
After refluxing in TiC14 (100 ml), this product was
filtered and washed with benzene, according to the conventional
procedures. The vacuum dried product had the following composition
Ti -4.61
Mg- 2.84
Cl-16.18%
235 mg of this product yielded in a 5 hour polymerization test,
H2 C2H4=lo atm, 427 g of polymer with a
MF of 2.63, a MF21 6 of 91-50~ a RMF2 16 j MF 16
and a content of 25 ppm of Ti.
EXAMPLE 4
10 g of SiO2 of the same type as used in example 1
were impregnated by a treatment of the same type as previously
described, with 10 g of MgC12 6 H2O.
After activation for 2 hours under vacuum at 200 C, the
product was refluxed in TiC14, hot filtered, repeatedly washed
with hexane, and finally dried under vacuum. When tested, this
product had the following composition
Ti- 15.08%
Mg ~ 3.95%
Cl =35.37%
205 mg of this product yielded, in a 2 hours polymerization
reaction, 370 g of polymer having a MF2 16 of 2-41, a MF21 6 f
. ~
.
MF21 6 / 2 16 f 42 4 and containing ~3
EXAMPhE S
10 g SiO2 (grade 951, supplied by Davidson Petrochemi-
cals having a surface area of 600 m2/g, a diameter of pores of
67 ~, and a volume of pores of 1 cm3/g were trea'ed in a water
solution of MgC12 . 6 H2O (2.2 g).
After a treatment similar to that described in example
1, the product, activated under vacuum at 200C for 4 hours and
treated according to the normal procedures with TiC14 boiling
for 4 hours, had the following composition
Ti = 8.12%
Mg = 1.82~
Cl -13.83%
264 mg of this product were used for the polymerization of ethy-
lene with PH _ 10 atm and PC ~1 -10 atm and a residence time of
2 hours. 120 g of polymer were obtained, having a MF2 16 f
2-40, a MF21 6 of 75.56, and a RMF of 30.8, and
containing 178 ppm of Ti.
EXAMPLE 6
226 mg of the product prepared as described in example
5, were used in a standard polymeri~ation, identical to that
described in example 4, but with a residence time of 5 hours.
354 g of polymer were obtained, with a MF of 0.15, a MF21 6
21.6/MF2.16 of 37.5 and a Ti content of
52 ppm.
EXAMæLE 7
2 A]2O3 (SiO2 =87%, A12O3= 13%, surf~ce
area =400 m2/g) were treated as described in example 1.
After activation at 200C under vacuurn, for 30', the
product was refluxed in TiCl~ (100 ml). The produc-t obtained
after washing and treatment as already described, had the
;~ 6 -
10~ 6
following composi-tion
Ti ~ 7.50
Mg = 1.10
Cl -19.70~
312 mg of this product were used for the polymerization of
ethylene during 2 hours, with PH c 10 atm, PC H - 10 atm, 62 g
of polymer was obtained, having a MF2 16 of 0.62, a MF21 6 of
MF21 6/MF2.16 of 43.2 and con-taining 382 ppm of Ti
EXAMPLE 8
15 g of Sio2/A12O3, the same one as used in example
7 but dried for 20 hours at 450, were treated with 1 g of
MgC12 anhydrous in 25 ml H2O.
The product obtained, previously dried on a rotating
evaporator, was placed into an oven at 350 and treated for 6
hours with a slow stream of gaseous HCl.
The product obtained after the usual treatment with
TiC14 (100 ml) at reflux, iltration and washing with benzene
and drying under vacuum, had the following composition
Ti ~ 3.8%
- Cl= 13.6
Mg = 0.15~
251 mg of this product were used for the polymerization of
ethylene at PH ~ 5 atm, PC H ~ 10 atm. After 6 hours, 414 g of
polymer were obtained, with a MF2 16 of -~, a MF21 6 of 4-54 and
MF21 6/MF2 16 f 45-4 and a Ti content of 2 ppm.
EXAMPLE 9
10 g of SiO2/A12O3 of the same type as used in example
7, were treated with MgC12 . 6 ~l2O (1.6 y) in an aqueous
vehicle. The water was removed firstly on a rotaring evaporator
under vacuum at the room ternperature, and then hy azeotrope
distillation with xylene.
-- 7 ~
:
. - : -. . :
The so obtained product was re1uxed in TiC14 (200 ml),
filtered, washed and vacuum dried. At -the end of the above
operations, i-t had the following composition
Ti -- 8.5%
Mg = 1.1%
Cl -18.95~
155 mg of this product was used in a standard polymerization.
After 2 hours with PH _10 atm, PC2H4
were obtained, with a MF2 16 of 0 47~ a M~21 6 of 20-35 and a
MF21.6/~F2.16 of 44.4 and a ~i content of 347 ppm.
EXAMPLE 10
62 mg of the product used in example 9 were used in a
standard polymerization. After 6 hours with PH ~ 8 atm,
PC H = 10 atm, 247 g of polymer were obtained, having a MF2 16
f 0 09 a MF of 5.56 and a RMF21 6/MF2 16
containing 22 ppm of Ti.
EXAMPLE 11
10 g of SiO2 . A12O3 of the same type as used in
example 7, were treated with 2.5 g of MgC12 . 6 H2O according to
the procedure described in example 8. The product had the
following composition
Ti ~ 8.41%
; Mg - 1.94%
Cl -23.62%
157 mg of this product were used in a standard polymerization
After 2 hours with PH = 10 atm, PC H ~ 10 atm, 45 g of polymer
were obtained, having a MF2 16 of 0.928, a MF21 6 of 39-35 and
MF21 6/MF2 16 f 42-4~ and containing 294 ppm of Ti
EXAMPLE 12
. ,
10 y of SiO2 . A12O3 of the same type as used in
example 7, were treated with MgC12 . 6 H2O (4 g) and finally with
- 8 -
:
6~7~
TiC14 according to the procedure described in ex~mple 8.
The product had the following composition
Ti = 8.59%
Mg = 2.85%
Cl -26.69~
250 mg of this product were used .in a standard polymerization,
h PH2 10 atm, and PC H ~ 10 atm. After 2 hours, 106 g
polymer were obtained, having a MF2 16 of 1-316~ a MF21 6 f
MF21 6/MF 2 16 f 37-5 and containing 203 ppm in Ti
.~ ~`'
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