CA1085813A - Catalytic element containing titanium chloride for use especially for the polymerization of alpha- olefins - Google Patents

Abstract

A B S T R A C T

The invention relates to catalytic elements of formula TiC13 (A1C13)x (E, TiC14)y in which x is comprised between 0.08 and 0.19, E is an ether such that the complex (E, TiC14) is soluble at 55°C in titanium tetrachloride or an aromatic hydrocarbon and y is between 0.0003 and 0.03, having, in their X-ray diffraction spectrum, lines corresponding to planes of lattice distance 1.755 .ANG., 2.665 .ANG. and 5.81 .ANG. and whereof the dimension of the crystallites along the axis of symmetry corresponding to the lattice distance 5.81 .ANG. is between 190 .ANG. and 260 .ANG.. The catalytic elements of the present invention are useful in polymerizing .alpha.-olefins.

Description

~858~L~

The present invention relates to catalytic elements for the polymerization of ~-olefins, a method for the prepa-ration of these catalytic elements and a method for the polymerization of ~-olefins from systems including these catalytic elements.
The polymerization of a-olefins in the presence of a catalytic system comprising on the one hand, a solid compo-sition of titanium trichloride TiC13 and possibly syn-crystallized aluminium chloride AlC13 and on the other hand, an organo-aluminic activating compound is well known. The chemical formula and physical structure of the TiC13 - AlC13 composition are decisive factors for the performances of yield and stereospecificity of the methods for the polymerization of ~-olefins using such systems. Several methods for the physical and chemical treatment of the TiC13 - AlC13 compositions have thus been proposed for improving these performances. Thus, British Patent No. 1,087,314 describes grinding together, at-a temperature less than 80, the mixed titanium and aluminium chloride TiC13, --AlC13 and a monoether present at a rate of 0.03 to 1 mole/mole TiC13. On the other hand, British Patent No. 1,370,559 describes the treatment of the mixed chloride at ; a temperature of between 0C and 80C, with an ether added at the rate of 1 to 5 moles/mole TiC13, followed by a reaction with titanium tetrachloride at a temperature of between - 30C
and ~ 135C and preferably between 40C and 70C, a reaction which is advantageously carried out in the presence of an inert diluent, preferably an aliphatic hydrocarbon. This method makes it possible to increase the catalytic activlty from 40%
to 55% and to achieve stereospecificity, measured by the rate of polymer insoluble in hexane, of 95% to 96% for polypropyl-ene. Finally, French Patent No. 2,151,113 describes the reaction at a temperature of between 30 and 100C, necessarily in a hydrocarbon, of the ground mixed chloride with an ether present at the rate of 0.006 to 0.7 moles/mole TiC13. This method makes it possible to increase the catalytic activity from 40% to 70% and to achieve stereospecificity, measured by the rate of polymer insoluble in hexane, of 97% to 99% for ; polypropylene.
These methods improve the yield and stereospecificity of the methods for the polymerization of ~-olefins, but on the one hand, they are dependent upon the presence of a hydrocarbon diluent which makes the treatment intricate and long-drawn and on the other hand, they lead to polymers having an isotacticity, which is still insufficient for numerous applications. The object of the invention is therefore to propose a simplified physico-chemical treatment of the TiC13 - AlC13 compositions used in catalytic systems for the polymerization of ~-olefins, whilst improving the yield and stereospecificity of this polymerization.
It has been found that super-active and superstereo-specific catalytic elements may be prepared in the absence of a hydrocarbon diluent and at temperatures greater than those currently used in the prior art. These catalytic elements :~
fulfil the formula: TiC13 (AlC13)x (E, TiC14)y in which x is comprised between 0.08 and 0.19, preferably between 0.09 and 0.14, E is a compound chosen from diisoamyl ether and di-n-butyl ether and y is between 0.003 and 0.03. In their X-ray diffraction spectrum, they have lines corresponding to the ;-o o o planes of lattice distance 1.755 A, 5.81 A and 2.665 A and the dimension of the crystallites along the axis of symmetry corre-o o sponding to the lattice distance 5.81 A is between l90A and : 260A. The method of preparation of the catalytic elements according to the invention consists of reacting, on the one hand, the mixed titanium and aluminium chloride TiC13 - AlC13 of crystalline form ~ (acoording to the classification adopted by the Journal of Polymer Science - 51 - 403) pre-activated by grinding and, on the other hand, a complex of titanium tetra-chloride and of a compound chosen From diisoamyl ether and di-n-butyl ether, said complex being in solution in titanium tetrachloride or an aromatic hydrocarbon and the reaction temperature being between 55 and 130C, preferably between 70 and 115C. This method makes it possible to increase the yield of the polymerizations carried out by means of these catalytic systems, in a more substantial manner than known methods, since the improvement may reach 125% in the case of propylene and most frequently makes the stage of eliminating the catalytic residues useless. On the other hand, it makes it possible to achieve a stereospecificity, measured by the rate of polymer which is insoluble in heptane, of 91 to 97% for polyp~opylene.
It also has the advantage of reduc;ng the number and duration of treatment operations and therefore of reducing the cost price of the catalytic elements.
The mixed chloride TiC13, - AlC13 of crystalline form used in the method according to the invention is a product of disorderly crystalline structure obtained in known manner by grinding. The conditions of this grinding have no influence on the working up or the advantage of the method according to the invention.
The complex used in the method according to the invention is of the type 1:1 formed between titanium tetra-chloride TiC14 and a compound chosen from diisoamyl ether (D.I.A.E.) and di-n-butyl ether (D.N.B.E.). The choice of the ether is of peculiar importance, since it has been found that 35E~3 diethylether, diphenylether, diisopropylether and methyltertio-butylether are not so convenient for the working up of the process according to the invention. The molar ratio TjAl or DNB~ is currently between 0.05 and 1, and the complex is in solution either in titanium tetrachloride or in an aromatic hydrocarbon such as toluene. On the other hand, the molar ratio TjAl or TDjBl is generally between 0.05 and 8 and the molar ratio TTic13 between 0.1 and 3.
In the method according to the invention, the re-10 action temperature between the mixed chloride of form ~ and the complex is comprised between 55 and 130C and preferably between 70 and 115C. Contrary to the two-stage method of British Patent No. 1,370,559, in which the total duration of treatment, outside the intermediate operation of washing, is never less than 75 minutes, the method according to the in-vention offers the advantage of a duration of treatment of between 1 and 60 minutes and preferably between 2 and 15 minutes.
The treatment of the invention makes it possible to 20 increase the specific surface of the catalytic elements in a ratio equal to 3.5 and substantially higher than methods of the prior art. For example, this ratio is equal to 2.5 in British Patent No. 1,370,559. This comparison of relative values is most significant, since it is known that the absolute values of specific surfaces are strongly influenced by the nature of the reference catalytic element and by the conditions of measure-ment. On the other hand, the microporosity of catalytic elements is multiplied by a factor of about 5 by the treatment according to the invention. This fact is particularly 30 important in the initial phase of polymerization where the polymer crystallizing in the micropores promotes the process of fracturing of the crystalline system, followed by the formation of new active sites.
The catalytic elements of the invention are used to polymerize ~-olefins jointly with an activating compound of formula AlRnX3 n in which:
- R is a hydrocarbon radical comprising 1 to 8 carbon atoms and chosen from alkyl, aryl, cycloalkyl, arylalkyl and alkylaryl radicals.
- X is a halogen atom or trialkyl-siloxy group.
- n is any number such that 0 < n ~ 3.
Trialkylaluminiums and monohalogenodialkylaluminiums constitute effective activating compounds. The molar ratio of the activating compound to the catalytic element of the invention is in known manner between 0.5 and 10 and may be determined depending on the ~-olefin to be polymerized and ; other operating conditions, using prior knowledge of the man skilled in the art.
The catalytic elements oF the invention and the activating compound constitute catalytic systems suitable for the polymerization of ~-olefins at pressures of between 1 and

2,500 atmospheres and at temperatures of between 0 and 350C.
The polymerization method according to the invention as above-defined will thus be preferably used with ~-olefins comprising 2 to 8 carbon atoms, such as ethylene, propylene, l-butene, 4-methyl-pentene, l-hexene and vinylcyclohexene. By extension, the method of polymerization according to the invention may be used for the preparation of copolymers of two of these ~- ;
olefins as well as with diolefins such as butadiene, isoprene, ethylidenenorbornene, dicyclopentadiene, 4-vinyl-cyclohexene.
The choice of the conditions as regards temperature and pressure in each case is within the scope of a man skilled in ~5~13 the art: thus, the aforesaid ~-olefins may all be polymerized at a temperature of 0 to 120C under 1 to 50 atmospheres and ethylene may also be polymerized at a temperature of 120 to 350C at a very high pressure of 300 to 27500 atmospheres. In the latter case, the catalytic elements of the invention may be advantageously grinded with magnesium chloride before being used.
The polymerization method according to the invention may use any one of known techniques continuously or discontinu-ously: the solution method, suspended method in a diluent, mass polymerization in the liquid or gaseous phase. For the polymerization of ethylene at very high pressure, an autoclave or tubular reactor may be used. In known manner, the molecular weight of the polymer may be adjusted by maintaining a certain pressure of hydrogen in the reaction medium. The isotacticity of polymers obtained by means of the catalytic systems of the invention may be further increased by the introduction to the reaction medium of known additives such as furfural, 2-pyrrole-aldehyde, 2-N-methylpyrrole aldehyde (British Patent No.
1,410,106), hydrazine and l,l-dimethylhydrazine (U.S. Patent No. 3,907,761) ethyl benzoate, hexamethylphosphorotriamide, cycloheptatriene and trimethylphosphine. Also in known manner, the catalyst may be pre-polymerized with an a-olefin in a jclfin ratio of 0.5 to 30 to prevent decantation in the injection circuits of the polymerization autoclave reactors.
As explained above, the activity of the catalytic elements of the present invention is not only greater than that of commercial catalysts, but also greater than that of com-mercial catalysts treated according to methods of the prior art. In order to compare the activity of catalytic systems used in different polymerization processes and in particular in ~0~i8~3 processes of varying duration carried out at different pressures, it is well known to express said ~ activity in grams of polymer per gram of TiC13 contained in the catalytic system, per hour and per atmosphere. In the case of poly-propylene, it has thus been found that a commercial catalyst having an activity of 58 achieved an activity of 89 when treated according to the method of British Patent No. 1,370,559 and an activity of 120 when treated according to the method of the invention. Finally, ageing of the catalytic elements according to the invention is characterized by a slight reduction in activity and by retention or improvement of the stereospecificity, contrary to commercial catalysts which enjoy an improvement of the activity and a sudden decrease of the stereospecificity which renders them unsuitable for producing numerous qualities of polymers.
The following examples serve to illustrate the invention and in no case to limit the latter. Diisoamylether and di-n-butylether may thus be replaced by any ether able to form with TiC14 a complex soluble at 55C in titanium tetra-0 chloride or an aromatic hydrocarbon.EXAMPLE 1 A mixed titanium and aluminium chloride TiC13 - AlCl sold by TOHO TITANIUM under the trade name TAC~l91 is placed in suspension, in a pyrex glass container, in titanium tetra-chloride, in the presence of diisoamyl ether (DIAE). The molar ratios of the constituents of the suspension are TjAl = 1 and TDjAl = 0.15. The titanium tetrachloride is used without special purification, whereas the ether has been dried using a molecular sieve and distilled over calcium hydride. The sus-pension stirred with a magnetized rod is rapidly heated to thetemperature T for a duration of 15 minutes. At the end of the ~LV85~3 operation, the catalytic element is separated, then washed three times at 20C by being placed in suspension in heptane at a concentration of 0.25 to 2 moles/litre and immediately acti-vated by monochlorodiethylaluminium in a molar ratio 1:1 in order to stabilize its structure. The heptane used has been de-gasified by bubbling through nitrogen, dried on a molecular sieve column and distilled over lithium aluminohydride, whereas the activator has not been subjected to special purification.
The dry and purified heptane, the catalytic system and the propene purified over activated alumina and a molecular sieve are introduced successively into a 0.5 litre flask which is dry and has been purged by means of nitrogen, until atmos-pheric pressure is reached at 60C. This pressure is kept constant during polymerization by the introduction of gaseous propylene. After 1 hour of polymerization, the contents of the flask are poured onto a Bachner filter without de-activation of the catalyst and without washing. The polypropylene powder retained by the filter is dried to give a constant weight by evaporation of the solvent. The soluble parts are recovered and dried to give a constant weight. The rate of insoluble polymer is determined by taking into account the activating agent carried over with the soluble parts. In Table I, the catalytic activity ~ is expressed in grams of polypropylene per gram of TiC13, per hour and per atmosphere and the stereo-specificity ~ is expressed as a percentage of insoluble matter in heptane at 60C.

TABLE I

Test 1 ~ 3 4 5 6 7 8 rc 55 65 75 35 95 105 115 ~ 58 77 105 113 115 106 99 90 _ __ 94~0 83.590.5 93.9 95.0 95.3 94.9 93.9 Test 1 corresponds to the commercial reference product which has not undergone any treatment. Furthermore, the specific surface measured by means of a PERKIN-ELMER 212 D
adsorptometer calibrated according to BS standard 4359/1 is 69m2/9 for test 4 against only 21m2/9 for test 1. The porosi-ty, defined by the ~olume of micropores of diameter less than 200 A and measured by means of a CARL0 ERBA mercury porosi-meter9 is 0.115cm3/g for test 4 against only 0.023cm3/g for -~
test 1. The crystalline structure of the catalytic elements corresponding to tests 5 and 6 has been determined by means of the X-ray diffraction spectrum and compared with that of the reference product (test 1). The characteristic lines of this 3 spectrum correspond to planes of lattice distance 5.81 A and 1.755 A and make it possible to calculate by the Scherrer formula the dimensions of crystallites along the hexagonal axis of symmetry (c) and in the direction at right-angles to this axis (a) (Journal of Catalysis - 28 - 351). The results of these measure~ents are given in Table II.

35~3~q~

TA~LE II

Test 5 6 c (A) 308 210 228 a ~A~ 412 520 490 The mixed titanium and aluminium chloride TAC 191 is treated according to the same sequence of operations as in tests 2 to 8 and the polymerization test of propylene is also carried out under identical conditions. Nevertheless, the s TiC13 and TiC14 and the durations t have been modified and are given in Table III.
TABLE III

Test TC TiC13 ~ [ t/mins _ _ : 9 95 0.5 0.075 15 92 92.6

3 0.45 15 97 93.7 11 95 1 1 15 108 93.8 12 g5 0.075 0.15 15 110 93.8 13 95 1 0.15 6 92 95.0 ~:
14 100 2 116 94.1 The mixed titanium and aluminium chloride TAC 191 is treated under the conditions of tests 2 to 8 replacing the diisoarnyl ether by di-n-butyl ether (DNBE) and at a temperature ; T of 95C. The polymerization test of propylene is carried out as in tests 2 to 8. A catalytic activity ~ of 85 and a stereospecificity ~ of 91.1 are measured.

3S8~3 The titanium and aluminium chloride TAC 191 is placed in suspension in the presence of diisoamyl ether in a mixture of titanium tetrachloride and toluene, the ratio of volume _iC14 being equal to 0.7. Toluene is used which has been toluene de-gasified by bubbling through nitrogen, dried on a molecular sieve column and distilled over lithium aluminohydride. The treatment is then carried out at 85C under the conditions of tests 2 to 8, with the exception of the duration which is increased to 60 minutes. At the end of the polymerization test of propylene, carried out as in the preceding examples, a cata-lytic activity ~ of 120 and a stereospecificity ~ of 92.0 are measured.

The catalytic element prepared under the conditions of Test 5 of Example 1 is used jointly with an activating agent of formula Al(C8~l17)3 to polymerize ethylene at a temperature of 260C and at a pressure of 1500 atmospheres. The activating agent is used in an atomic ratio ATl equal to 3 and the resi-dence time in the stirred autoclave reactor is 34 seconds.Under these conditions, the catalytic yield is 2.7 kg polymer per milliatom oF titanium. The polyethylene thus obtained has a volume of 0.940g/cm a melt index (measured according to ASTM
1238-62T standard) of 0.5 and a mean molecular mass by weight of 96000. The rate of l-butene measured in the re-cycling circuits is 2.4% by weight.

The catalytic element prepared under the conditions of Test 5 of Example 1 is ground for two hours with magnesium chloride then used jointly with the tri-n-octylaluminium acti-vating agent to polymerize the ethylene in an autoclave reactor ilq~8~i89~3 provided with agitation means at a temperature of 260C and at a pressure of 1200 atmospheres. The activating agent is used in a quantity such that the atomic ratio Al is equal to 3.
; Under these conditions, the catalytic yield is 5.5 kg polymer per milliatom of titanium. The polyethylene obtained has a mass of 0.962 g/cm and a mean molecular mass by weight of 93,000. The rate of l-butene measured in the re-cycling circuits is 2.2% by weight.

The catalytic elements according to Tests 1, 5 and 6 of Example 1 are used jointly with the monochlorodiethyl-aluminium activating agent to polymerize the l-butene at 60C
in solution in methylcyclohexane, the pressure of the l-butene being equal to 0.75 atmospheres and the total pressure to 1.075 atmospheres. Table IV hereafter gives the results of the cata-lytic activity ~ in grams of l-polybutene per gram of TiC13, per hour and per atmosphere, the isotacticity ~ measured by the rate of polymer insoluble in boiling diethyl ether and recalls the preparation temperature T of the catalyt;c elements used.
TABLE IV

Test TC ~ ~ ~

_ 83.7 94.8 16 85 112.7 97.0 17 95 117 97.7 L~ The mixed titanium and aluminium chloride TAC 191 is treated with di-n-butyl ether according to the sequence of operations of Example 1 at a temperature of 85C, with the exception of the washing operation, which is carried out at 5~L3 20C by placing the latter in suspension in a non-inert diluent such as toluene. The molar ratios TiC13 and TiCl~ are varied as given in Table V, which gives the results oF polymerization of l-butene in solution carried out according to the conditions of Example 7. Test 15 could constitute a comparison reference.
TABLE V

TiC13 ¦ ri cl 4 ~ a ~ ¦

18 1 0.15 81 97.7 19 1 1 109 97.2 ~:

The catalytic element prepared under the conditions of Test 5 of Example 1 is used jointly with the monochloro- `
diethylaluminium activator for mass-polymerizing l-butene. 40 litres of monomer are introduced into a 50 litre reactor pro-vided with agitation means comprising a helical band and purged by means of n;trogen and the monomer is heated to the chosen polymerization temperature. The l-butene used comprises 100 ppm l,3-butadiene and, after drying by means of a molecular screen and filtration on glass wool, 6 ppm water. A solution comprising 10 millimoles/litre of activating agent in methyl-cyclohexane under hydrogen is introduced into the reactor, then hydrogen is introduced up to the desired partial pressure and finally a suspension of the catalytic element of the invention in methylcyclohexane, under nitrogen. After the end of polymerization, the polybutene solution is sent to the washing reactor, where it is firstly put in contact with 250 ml iso-propanol for 30 minutes, then washed twice with 20 litres of water at 60C for 30 minutes. A solution of a mixture of anti-oxidizing and stabilizing agent is then introduced with stirring. The polybutene solution is sent to a 30 litre reactor where the l-butene evaporates and the polymer crystal-lizes. It is dried in a ventilated oven a~ 55C, then ground and granulated.
The melt index of the polymer obtained is measured according to the ASTM 1238-62T standard and its isotacticity is measured by the rate of insoluble polymer in boiling diethyl ether. The dynamometric properties under traction are deter-mined according to IS0 527 standard with sheets moulded at 180C by compression and left for 8 days.
The results of tests 20 to 26, in which the partial hydrogen pressure PH2 expressed in atmospheres and the polymer-i~ation temperature Tl are varied, are given in Table VI. The flow threshold SF and the braking strength RR are expressed in kg/cm , the elongation on braking AR and the isotacticity a are expressed as a percentage, the melt index IF in 9/10 mins, the catalytic activity ~ in grams of l-polybutene per gram of TiC13 and per hour.
TABLE VI
:
20Test 20 21 22 23 24 25 26 TlC 50 60 60 60 60 70 80 PH2 1 0.1 0.3 1 2 0.2 0.5 ;
~ 1050 1235 1680 1660 1590 1840 2505 IF 2.75 0.14 0.9 4.6 25 1.3 28 ~ 97.7 97.8 98.5 97.5 97.5 97.9 93.2 ~151S8~3 The catalytic element corresponding to Test 1 oF
Example 1 is used jointly with the monochlorodiethylaluminium activator for mass-polymerizing l-butene under the operating conditions of Example 9. Test 29 was carried out with the addition of furfural to the reaction medium at the rate of 0.3 millimoles per litre of l-butene. The additive is introduced into the reactor in the form of a solution of 200 millimoles per litre in methylcyclohexane of furfural having a purity greater than 99% and dried on a molecular screen and stored in a dark place. In Table VII~ showing the results, the symbols have the same significance as in Example 9.
TABLE VII
,, ; Test T~C pH2 IF SFRR AR

27 60 0. 2 9751.6 95.8 157221 1 75 28 60 0.7 1014 9 87.8 128208 223 29 60 0.7 12564.9 97.6 207285 25 Tests 20, 23 and 26 of Example 9 are reproduced by adding furfural to the reaction medium, in a concentration C
expressed in millimoles per litre of l-butene. The corre-sponding results are given in Table VIII where the polymer-ization temperature Tl is recalled.
TABLE VIII `-Test T~~C C _ a SF RR AR

0.1945 99.2 _ _ 31 60 0.31920 97.1 212 400 320 32 80 0.12260 97.0 __ ~s~

The catalytic element prepared under the conditions of Test 19 is used jointly with the monochlorodiethylaluminium activating agent in order to polymerize l-butene under the conditions of Test 21 and in the presence of 0.1 millimole per litre of l-butene in the reaction medium. The results obtained are:
= 1225 and ~ = 99.6 The catalytic element prepared under the conditions of Test 5 is used jointly with an activating system constituted by monochlorodiethylaluminium and/or triethylaluminium in the concentrations given in Table IX hereafter in order to polymer-ize l-butene under the conditions of Example 7. An additive, whose nature and concentration are also given, is possibly added to the reaction medium.
~ TABLE IX :
.~
:~ Al(C2H5)3 Al(C2H5)2 Cl Additive :: :
Test Name m-mole/l ~ ~
_ m-mole/l m-mole/l _ .; 33 2.45 11.75 furfural 0.3 148.694.9 .. 3~ 5 0 triene 5 190 88.6 0 Ethyl 1.5 311 85.1 Benzoate : 36 5 0 Ethyl 0.6 668 80.6 :~
Benzoate The statistical copolymerization of l-butene and ethylene is carried out at 60C under the operating conditions of Example 9. Table X hereafter gives the molar proportion of ethylene, as well as the partial hydrogen pressure and the results obtained such as the activity, isotacticity and break-ing strength of the resultant copolymer. Tests 37 and 38 use the catalytic elements prepared in Tests 1 and 5 respectively.
TABLE X

Test % C2H4 PH2 RR
_ 37 0.78 0.8 1040 94.4 313 38 0.93 0.7 1450 98.2 384 0.1 millimole furfural per litre of mixture of mono-mers is added to a 4 litre autoclave reactor having mechanical agitation means, heated to 60C and containing a quantity b of liquid l-butene and a quantity p of liquid propene. Then, polymerization takes place at 60C for 1 hour, under a partial ; hydrogen pressure of 0.5 bar and by means of a catalytic system comprising 10 millimoles/litre monochlorodiethylaluminium acti-vating agent and 1 millimole/litre of the element prepared under the conditions of Test 5 of Example 1. The copolymer obtained is deactivated by isopropyl alcohol, then washed with water at 75C, dried and weighed. The catalytic activity ~ is 2Q thus measured in g/gTiC13/hour, the isotacticity a determined by dissolution in boiling diethyl ether, the melt index according to ASTM 1238-62T standard and the molar rate P of the propene sequence by infrared spectrometry. These results are given in Table XI.

1q)~5~3~3 TABLE XI

Test b (kg) p (k9) ~ % ~.I P %
; ~
39 3.85 0.08 1 170 99.5 22 1.5 3.91 0.175 1 210 98.5 2.4 5.6 41 3.21 0.31 1 110 96.4 3.9 17.7 ;; In a 4 litre autoclave reactor, provided with mechanical agitation means heated to 65C and containing 1.4 litre l-butene, 0.7 litre propene and 0.7 litre methylcyclo-hexane, polymerization is carried out for 2 hours under a partial hydrogen pressure of 0.5 bar and by means of a cata-lytic system comprising 10 millimoles/litre monochlorodiethyl- ;
aluminium activating agent and 0.2 millimoles/litre of the element prepared under the conditions of Test 5 of Example 1.
The copolymer obtained is de-activated by isopropanol, washed with water at 75C, dried and weighed. Its main properties, determined as previously, are as follows:
~ - 990 g/gTiC13/hr ~ - 39%
MI - 67 P = 55%

_ 1~ -

Claims (13)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. Catalytic elements of the formula TiC13 (A1C13)X
(E, TiC14)y in which x is comprised between 0.08 and 0.19, E is an ether selected from diisoamyl ether (DIAE) or di-n-butyl ether (DNBE) which form the complex (E, TiC14) soluble at 55°C in titanium tetrachloride or an aromatic hydrocarbon and y is between 0.003 and 0.03, having, in their X-ray dif-fraction spectrum, lines corresponding to planes of lattice distance 1.755 .ANG., 2.665 .ANG. and 5.81 .ANG. and whereof the dimension of the crystallites along the axis of symmetry corresponding to the lattice distance 5.81 .ANG. is between 190 .ANG. and 260 .ANG..

2. Method for the preparation of the catalytic elements of Claim 1, characterized in that one reacts the mixed titanium and aluminium chloride TiC13 13 A1C13 of crystalline form .DELTA. pre-activated by grinding with a complex of titanium tetrachloride TiC14 and an ether selected from diisoamyl ether (DIAE) or di-n-butyl ether (DNBE), said complex being in solution in titanium tetrachloride or in an aromatic hydrocarbon and the reaction temperature being between 55 and 130°C.

3. Method according to Claim 2, characterized in that the reaction temperature is between 70 and 115°C.

4. Method according to Claim 2, characterized in that the reaction lasts for between 1 and 60 minutes.

5. Method according to Claim 2, characterized in that the molar ratio or is between 0.05 and 1.

6. Method according to Claim 2, characterized in that the molar ratio or is between 0.05 and 8.

7. Method according to Claim 2, characterized in that the reaction is followed by a washing operation com-prising placing the catalytic element in suspension in an aromatic hydrocarbon.

8. Process for the polymerization and copolymeri-zation of .alpha.-olefins having from 2 to 8 carbon atoms, which comprises carrying out said polymerization or copolymerization by means of a catalytic element in the presence of at least one activating compound, the catalytic element having the formula TiC13 (A1C13)x (E, TiC14)y in which x is comprised between 0.08 and 0.19, E is an ether selected from diisoamyl ether (DIAE) or di-n-butyl ether (DNBE) which form the complex (E, TiC14) soluble at 55°C in titanium tetrachloride or an aromatic hydrocarbon and y is between 0.003 and 0.03, having, in their X-ray diffraction spectrum, lines corresponding to planes of lattice distance 1.755 .ANG., 2.665 .ANG. and 5.81 .ANG. and whereof the dimension of the crystallites along the axis of symmetry corresponding to the lattice distance 5.81 ° is between 190 .ANG. and 260 °, and the activating compound having the formula A1RnX3-n in which R is a hydrocarbon radical com-prising 1 to 8 carbon atoms and chosen from alkyl, aryl, cycloalkyl, arylalkyl and alkylaryl radicals, X is a halogen atom or trialkylsiloxy group and n is any number such that 0 ? n ? 3.

9. The process of Claim 8, wherein the activating compound is selected from monochlorodiethylaluminum or tri-ethylaluminum.

10. The process of Claim 9, wherein the polymeri-zation is carried out at a temperature of from 0° to 120°C and a pressure of from 1 to 50 atmospheres.

11. The process of Claim 10, wherein the polymeri-zation is carried out in the presence of an additive selected from furfural, hydrazine, 1,1-dimethyl-hydrazine, 2-pyrrole aldehyde, 2-n-methylpyrrole-aldehyde, cycloheptatriene, ethyl benzoate, hexamethylphosphortriamide and trimethylphosphine.

12. The process of Claim 9, wherein the .alpha.-olefin is ethylene and the polymerization is carried out at a tempera-ture of from 120 to 350°C and a pressure of from 300 to 2500 atmospheres.

13. The process of Claim 12, wherein the catalytic elements are ground together with magnesium chloride before activation.