Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
lOS99~77
The present inventlon relatee to a proces~ for the
polymerization Or alpha-olefins, particularly ethylene, b~
~eans Or a catalyst system constituted by an aluminium alkyl
and the combination Or a tran6ition metal chloride and
titanium trichloride finely dispersed on a material having a
high superricial area; a further aspect Or the invention cQncerns
the cataIytic system employed as ~ell as the method ror preparing
8uch a catalyst.
It 18 ~no~n that titaniu~ halides, ~hich are active
rro~ a catalytic point Or vie~, are employed in the lo~ pressure
polymerizatlon Or alpha-oleiin~. Theso are prepared by reducing
titaniu~ tetrahalides ~ith alu~inium aIkyl or alkyl-halldo
, co~pounds. Ihe rea¢tion i8 generally oarried out w der ~n
i ~nert atmosphere and in the presen¢e of an inert sol~ent. The
1 catslyst thus obtained~ is then used togethor ~ith metal alkyl
co~pounds ior the polymerization Or alpha-oleiins in suspe~slon
~ ln an organic solvent, under reasonable preasures of the monomer.
¦ ~o~ever~ the~e tltaniu~ halides are impure because of
the presence Or alu~inium compounds and do not sho~ a very high
¢atal~tic activit~ 80 that the rinal polymer needs espensive
shing operations in order to re~oie the catalytic r0~iduale.
~ ethods have been recentl~ proposed, according to
~h~ch the titanium h~lides are supported carried on inorganlc
substances 80 as to obt~n pol~merization catal~sts having an
' i~proved errecti~eness. For instance, use may be made Or
i,~ carrièrs such as ~agneslum oxide or hydroxide; howe~er~ it is
to be ~oted that the catalytic activity o~ the titanium compound,
, ~ .
oarried on tbese materials, highly varies according to the
chemical nature oi the sur~ace thereor; therefore, such compounds
~0 must,in many case~, undergo trestments with Grignard reagents,
aluminlu~ alkyl compounds or hydrogen, in order to improve their
errectivene~s. ~ '
~ .
-- 1 .
` ~ lOS997~
The subject invention proposes to provide an improved
process for the polymerization of alpha-olefins, wherein use
is made of a catalytic system which has a high activity and
does not need any preliminary treatment of the carrier.
The catalytic system utili.zed, which constitutes a
further aspect of the present invention, comprises the following
two components:
a) an aluminum compound represented by the formula
AlR3 or AlRXY3 x in which R is an alkyl, aryl or cycloalkyl
radical, Y is a halogen or hydrogen, and x is a number between
~ 1 and 2;
; b) the combination product of titanium trichloride
and an isostructural chloride of another transition metal
selected from the group consisting of V, Mn, Co and Fe, the
product being supported on a carrier having a high superficial
area and selected from the oxides of elements belonging to
Groups II to IV of the Periodic Table, the weight ratio between
components (a) and (b) ranging from 4 to 78.
The component (b) of the catalytic system of the
invention is very stable from a chemical point of view since the
titanium trichloride and transition metal chloride are iso-
structural; moreover, it contains titanium in its optimum valence
: state, which provides for the best catalytic activity.
The component (b) is advantageously prepared by
impregnating the carrier, previously dehydrated by a thermal
treatment, with a low valence derivative of the other transition
metal, preferably a transition metal derivative in the zero
valence state such as a carbonyl metal derivative, dissolved in a
hydrocarbon solvent, refluxing the impregnated carrier with
titanium tetrachloride and, finally, removing excess of this
latter from the carrier.
The zero val.ence transition metal derivative may contain
ligands of a type different from the carbonyl one, for instance
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`-`` lOS9977
.
allyl, cyclopentadienilic olefinic, nitrosyl groups, and the like.
During the process, volatile substances are developed
and, in particular, carbon` monoxide in the case where use is
made of carbonyl metal compounds; the oxidation of the metal
and the simultaneous reduction of titanium tetrachloride to
`
i trichloride occur according to the following reaction
,
M (CO)p + n TiC14 ) MCln.n TiC13+ p CO
wherein p represents the carbonyl number and n the valence
state taken by the transition metal M during its oxidation by
lo titanium tetrachloride.
The transition metal which is selected among V, Mn, Fe
and Co is advantageously used in an amount ranging from 0.1 to 10%
by weight with respect to the weight of the carrier, preferably
from 1 to 3% by weight.
The material employed as carrier is preferably selected
~ among silica, silica-alumina, ZnO2, MnO, TiO2 and CaO.
-~ As mentioned above, pretreatments are not necessary
since the activity of the catalytic systems of the invention is
high and homogeneous, even if the chemical nature of the carrier
; 20 undergoes changes; however, such carriers can also be subjected
to pretreatments with Grignard reagents or aluminium alkyl-
halides so as to further increase the performances thereof.
The activities observed in polymerization are anyhow
higher than those obtained by means of carriers treated only
with TiC14, the other conditions remaining the same.
The catalysts of the invention show a good behaviour
in the presence of hydrogen and, in the case of the ethylene
polymerization, give rise to a narrow molecular weight distri-
bution.
The polymerization reaction is carried out according
to known procedures, at temperatures comprised from 0 to 200C
and at pressures ranging from 0.1 to 50 atmospheres. It is
performed in steel autoclave equipped with an anchor stirrer
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~` ~05997 7
when the operations are carried out at pressures higher than
the atmospheric one. The catalyst is introduced together with
the solvent and the metal alkyl compound.
The autoclave being thermostated at the polymerization
temperature, H2 and then ethylene are introduced therein under
pressure at the desired pressure ratio. The reaction is generally
~` stopped by adding alcohol into the autoclave.
With peculiar reference to the Examples hereinafter
reported, the solvent, the organic metal compound (Al(-C4Hg)3
in concentration equal to 0.2~ by volume) and the transition
element compound combination, previously prepared as specified
in each example, are introduced into the autoclave, thermostated
at 85C. The ethylene pressure was kept constant for the whole
test which was carried out over six hours. The procedures
described in the following examples will refer to these working
conditions (standard polymerization). The polymers obtained are
dried under vacuum up to a constant weight before evaluating
the yields as polymer.
The examples which will now follow are given only
to illustrate the subject invention which must not be considered
as being limited thereto. In these examples, the designations
"MF2 16" and "MF21 6" stand for the Melt Flow index under a
charge of 2.16 kg and of 21.6 kg, respectively, according to
ASTM-D 1236-65T.
EXAMPLE 1
100 g of "Low Alumina" SiO2/A12O3, SA = 400 m /g,
were refluxed in boiling xylene in order to azeotropically
remove water. The product, dried, filtered under nitrogen
and washed with hexane, was added with 3 g of tetracarbonyl-
vanadium cyclopentadienyl, V (CO)4 Cp, in 200 ml of hexane.This solvent was removed by means of a rotating evaporator
and the yellow material obtained, which was air sensitive, was
~059~
refluxed~ after having been suspended in 200 ml of ~iC14~ over
~lx hours. During this time~ the material became dark violet. It
~as then filtered, repeatedly washed ~ith hexane and dried under
~acuum.
The analysis ~howed the following composition
Ti 7.3%
V 0.40%
Cl 12.54%
240 mg of this ¢atalyst were ~mployed in the et~ylene polymerization
at the partial pre~sure~ of H2- 13 atm; and C2H4= 8 atm.
500 g of polyethylene were obtained having MF21 6' 1
[ ~ 135C = 4.6
decaline
d ~g and containing 36 ppm of Ti+ r, in which the ~i content was
about 33 ppm.
EXAMP~E 2
The same SiO2- A1203 employed in example 1 was refluxed in
~ ~ thc same conditions with only titanium tetrachloride.
;~ ~fter the same treatment~ the ~hite material obta~ne~
hich ~a~ air sen~it~ve , ga~e the following anslysi~
Ti 4.10~
Cl 7.98%
224 mg of this cataly~t gave, in the ~ame polymerization
co~ditions a~ describea in example 1, 60 g of polymer having ~F21 6=
135C = 6.6 dl/g and a Ti content equal to 150 ppm.
decaline
EXAMPIE 3
25 g of SiO2 ( > 9g%), SA = 400 m2/g, were dehgdrated~
through an azeotropic distillation with xylene, treated with 0.55 g
V(CO)4 Cp in he~ane (50ml3 and then refluxed, after having re-
~3D mo~ed the hydrocarbon solvent~ in liquid TiC14 (50ml)~ as described
in example 1. ~he colour of the catalyst thus obtained was dar~
~iolet. The analy~is showed the following composition:
-- 5 --
10599~7
Ti 4.65
V 0.40~
- C1 8.24%
105 mg of the cstalyst obtained were used in a standard
polymerization at relative pregsures H2/C2H4 = 10/10 atm, 102 g
of polyethylene were obtained having MF21 6 = 0 3 and Ti+V con-
tent equal to 52 ppm, in which the Ti content Wa8 46 ppm.
EXAMPIE 4
85 g of SiO2/A1203 of the same type employed in examples
1 and 2 were dried in muffle at 400C over 24 hours and then
impregnated with 4.0 g of E~ln2 (C0)10 in 200 ml of hexane.
- The solvent ~a9 removed by means of a rotating evaporation
~, and the orange-yellow solid obtained was refluxed in boiling Ti
C14 over 6 hours.
1 The re~ulting violet material was filtered, washed with hexane
and dried under vacuum; it showed the follo~ing analysis
~i 5.73%
~n 1.35%
. .,
Cl 12.60%
169 mg of this product were employed in a standard polymeri-
zation test at 13 atm. of H2 and 8 atm. of C2H4, and produced
i 151 g of polyethylene having MF2 16 = 0-350, 21~21 6 = 15.684,
MF21.6/~2.j6 = 44~ [ ~ = 3.3 dl/g and 79 ppm of Mn + Ti, in
which the Ti oontent was 64 ppm.
EXAMPIE 5
416 mg of the product described in example 4 ~ere employed
in a standard polymerization at relative pressures H2/C2H4 =
10/5 atm.3and produced 55 g of polyethyle1ne Ohaving ~F2 16 = 5.16,
21.6 1 .6, ~F21.6/ r.l~2,16 = 41~ ~1 Decaline = 1-6
dl~g and Ti + Mn content equal to 229 ppm in ~hich the Ti conten~
was 185 ppm.
,
059 9
EX-AMPIE 6
260 mg of the product employed in example 4 were employed in
a standard polymerization by replacing Al(i-C4Hg)3 with AlEt2Cl
and working at relative pre~sures H2/C2H4 equal to 10/10 atm~h3~s.
120 g Qf polymer were obtain~e3d50hcaving MF2.16 135, 21.6
=8.727, MF2~ 6/MF2.16 = 64~ L~ decaline = 3.5 dl/g and a
Ti + Mn content equal to 153 ppm, in which the Ti content ~as 124
ppm.
EXAMPIE 7
25 g of a finely powdered i`IgO, dried in muffle at 400C over
one night, were reacted ~ith 1-5 g of Co2 (CO)g in 100 ml of hexa-
ne. The solvent was then removed by means of a rotating evapora-
tor and the residual was refluxed under nitrogen in TiC14 (100 ml~
over 8 hours.
A violet po~der ~as obtalned after hot filtration, wnich was
repeatedly wa~hed with hexane and dried under vacuum; it sho~ed
the following composition
Ti 3.70%
Co 1.55%
Cl 31.15~
31 mg of the product thus obtained ~ere employed in a standard
~polymerization at 10 H2 atmospheres and 10 C2H4 atmospheres.
250 g of polyethylene were obtained having r~F2 16 = 0.869,
~;~ MF21.6 = 34.97~ MP21.6/M~2.16 = 40.2,~ d~x~ine = 1.92 dl/g and a
~; ~ Ti ~ Co content equal to 6.5 ppm, in which the ~i content ~as 4.6
ppm.
EXAMPIE 8
A ~ample of commercial MgO was hydrated in water at 80C for
4 hours and then dried in muffle at 400C in air for 24 hours.
20 mg of the MgO 90 treated were impregnated ~lith V(CO)4 Cp
~1.2 g) in hexane (100 ml) and the solvent was removed by means of
a rotating evaporator. The dry residual was then refluxed in boi-
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- ` ~0599~7
.. . .
ling TiC14 (100 ml) over 4 hours. A violet product was obtained,
which was filtered, washed and vaccum dried; it sho~ed the fol-
lowing composition
Ti 3~1%
V 0.58%
i Cl 35.23%
; .
20 mg of this catalyst were employed in a standard polymeri-
zation at relative pressure~ H2/C2H4 = 10/10 atm. 235 g of polye-
` thylene were obtained havi135Mc2.16 1. 3~ 21.6
- ~ 1.6/~F2.16 ' 40-8-t~ decaline = 1.90 dl/g and contai-
ning 3.3 ppm of Ti + V, in which the Ti content was 2.8 ppm.
EX~MPIE 9
20g of MgO, treated according to the procedure of example 8,
were refluxed in boilitng TiC14 (100 ml) over 4 hours.
A white solid was then filtered, which was wa~hed and vac-
, . . .
, ~; ~ uum dried, it showed the following composition
~ ~ Ti 1.43%
: ! Cl 31.62%
42 mg of this catalyst were employed for the ~ake of compari-
son, in a standard polymerization carried out as described in ex-
nmple 8. 81 g of polyethylene were obtained having MF2 16 = 1.81,
MF21.6 = 44~ MF21.6/MF2.16 = 36-3~ [~J decaline = 2.73 dl/g
i.~
and a Ti content equal to 7.4 ppm.
EXA~PIE 10
25 g of SiO2, of the same type employed in example 3, were
dehydrated b~ mean~ of an azeotropic distillation with xylene and
reacted nith 2 ml of Al~tC12 in hexane (100 ml). The suspension
was then added with V (CO)4 Cp (1.Og) and then the solvent was re-
moved by means of a rotating evaporator. ~he re~ulting product
was refluxed in boiling TiC14 over 6 hours. After filtration,
washing with hexane and vacuum drying, the viol-t ob~ained product
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. - .
` lOS9977
had the following composition
~i 2.97%
V 0.86%
Al 1.90%
Cl 8.59%
192 mg o~ the catalyst thus obtained ~ere used in a standard
polymerization at relative pressures H2/C~H4 e~ual to 10/10 atm.
96 g of polyethylene were obtained, having M~2 16=.335~MF21 6=
14.1,MF21.6/MF2.16=42.1[~]= 2.63 dl/g and ~i+V content equal to
80 ppm, in which the ~i content wa~ 60 ppm
EXAMPIE 11
25g of SiO2 = A1203 of the same type employed in e~ample 1,
drled over one night in a stove at 200C, ~as treated ~ith an
ether solution of chlorobutyl Grignard (10 ml, solution 1/1 ml)
in 10 ml of exane. The solvent Wa9 evaporated by means of a ro-
tating evaporator and then 1.2 g V (C0)4 Cp was sdded in 100 ml of
hexane.
After the removal of the solvent, the dry product was re-
fluxed in boiling ~iC14 over 6 hours. A violet solid ~as then
flltered, washed and dried; it showed the following composition:
Ti 9,20%
V 0.74%
~g 1.07%
Cl 21.85%
212 mg of this product ~ere employed in a standard polyme-
rization with 7.5 atm. of ethylene and lS H2 atm., and produced
325 g of polyethylene having M~2 16= 1.014, MF~l 6= 45~44~
MF21 6/MF2 16 = 45~44~L ~(~ = 2-0 dl/g and containing 65 ppm
of Ti + V, in which the ~i content was 61 ppm.
,
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