CA1099696A - Catalytic components and catalysts for the polymerization of olefins - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE:

There are disclosed new catalysts for the stereospecific polymerization of alpha-olefins having the formula CH2 = CHR in which R is an alkyl radical containing from l to 4 carbon atoms and the starting components of which comprise (a) a halogenated organometallic A1 compound and (b) reduction products of TiC14 comprising TiC13 in the crystalline beta form.

Description

- 1~99696 It is known~ from Italian Patent No. 558,g25, to poly-m~rize olefin~ in contact with catsly~ts prepared from reduction products of ~iC14 and alkyl Al compound~ or from organometallic Al halides. As i~ also known, the reaction between TiC14 sna alkyl Al halide 8 can be controlled to result in a product in whlch, in the '~i halide~ the Ti is substantially pre~ent in trivalent form, i,e.,as ~iC13.
It i~ al90 known that~ to obtain catalysts which are both highly active and highly stereospecific in the polymeriza-tion of the alpha-olefin9, it has been necessary for the reduction product of ~iC14 to comprise TiC13 in the crystalline delta form.
'rhe delta crystalline form of TiC13 may be obtained directly during the course of the TiC14 reduotion, by using, for instance, AlEtC12 as the reducing agent and by operating at relatively low tempersture~, or by heating the reduction products in which TiC13 is present in the beta form at temperatures in genersl greater than 130C.
Even when the 3uperficial area of the catalytic components contain~ng delta ~iC13 i~ very high (80-100 m2/g), the activity of the catalysts derived from them is not very satisfactory. ~he poor activity has been imputed to the presence of aluminum compounds, such as~ for instance, sluminum alkyl dihalides, in the reduction product, In order to overcome this drawback it has been suggested to treat the reduction product with ~ewis bases, for instance with ethers (USP 3,825,524 and British Pstent No 1,139,450).
In USP 3,825,524, the treatment with ~ewis bases is preferably carried out on the TiC13 in the crystalline delta form, When the treatment is carried out on TiC13 in the crystalline beta form, or when the TiC13 is already in the delta form but hss not been activated by heating at 140-150C, the ~tereospecificity of the catalyst is not very high, In general, the TiC14 reduction products containing 'riC13 in the delta form and treated with ethers are of the following compo~ition:
TiC13(~1RmX3_m)a- p wherein:
R is a hydrocarbon radioal;
X i~ a halogen;
m is a number compri~ed between O and 2;
a, which define~ the mols of aluminum compound per mols of 'l'iC13~ is lower than 0,3;
A is an ether, and finally p~ which defines the mols of ether per mol~ of ~iC13, is greater than 0,001.
The superfici~l ~rea of these products is in general greater than 50-60 m2/g and the porosity i9 greater than 0.1 cm3/g.
Quite recently it has been suggested to treat with ethers a9 well a~ with TiC14, the ~iC14 reduction product with alkyl aluminum halides (Italian Patent No. 950,499);
~he catalysts that are obtained from the~e catalytic components have good aotivity and stereo3pecificity.
~or a good performance of the catalyst, it i~ essential that the catalytic components have a ~uperficial area greater than 75 3q.mt~g snd a porosity greater than 0.15 cc/g and that the TiCl~ be in the crystalline delta form.
One ob~ect of thi~ invention is to provide new catalyst components~ ~r.d new catalysts comprising the same, ba~ed on products obtained by reducing TiC14 with halogenated organo-metallic aluminum compounds~ ~uitably trested~ and which exhibit both good activity and high stereospecificity in the polymeri~a-1~9~696 tion of alpha-olefins of formula CH2 = CHR, in which R i9 an alkyl radic~l containing from 1 to 4 carbon stoms~ even when the ~uperficia~ (surface) area of ~sid products i~ considerably lower than 75 m2/g, the porosity is lower than 6.15 cc/g~ and, on X-rays examination, the product~ give a ~pectrum which shows the main diffraction lines which are characteristic of TiCl3 .in the crystalline beta ~orm.
Surpri~ingly, and contrary to all expectations, we have found that cataly~ts ba~ed on the new components having the aforesaid characteri~tic~, and which exhibit the good sctivity and high stereospecificity in the polymerization of the alphaolefins, when said catalyst-.forming components are prepared under the conditions described infra.
The new catalyst-forming compo-nents comprising TiCl3 of thi~ invention are characteri~ed in that~ in the X-ray~
~pectrum thereof~ there sppear the following diffraction lines at the inter-~attice distances: d = 5 4 A (intense line);
d = 2,75 ~(line of medium intensity) and d - 2.12 A (line of medium-wesk inten~ity) d = 1.98 A (very weak line); and d ~ 1,77A
(medium intensity li.ne) The first four diffraction lines aforesaid are chsracteristic of TiC13 in the beta form; the line d = 1.77 A, together with other line~, characterizes a new form of TiC13 The complete X-rays spectrum of beta ~iCl3 was de~cribed by Natta et al in "Atti Accademia dei ~incei", 24,8, 121-t29 (1958).
The new catalyst-forming components of this invention consist of, or comprise, products of the composition:
(I) TiC13~(AlRmX3_m)a~ )P
wherein:
R i.9 a hydrocarbon radical containing from 1 to 20, but preferably from 2 -to 10 carbon atoms, and in ~ 1099696 particular: aIkyl, aryl, cycloaIkyl, alkylaryl and aralkyl;
0~ _~2.5;
X is a halogen;
_ is a number lcwer than 0.4 but preferably lower than 0.2;
A is an ether selected fram the group consisting of monoethers of formula R'OR" wherein R' and R" are alkyls containing from 1 to 10 carbon atoms, aryls, cycloalkyls, aIkylaryls , or aralkyls,and poly-ethers of the class of polyalkylenglycol-dialkyl-ethers and 1,2 diphenoxy-ethane, said ether being capable of forming c~mplexes or coordination products with Al halides or aIkyl-Al halides, which complexes or o~ordination products are soluble in the ether itself or in aromatic or aliphatic hydro-car~ons or in the halogenated derivatives thereof; and p is zero or a number greater than zero but lc~er than 0.5.

The superficial area of the catalytic components of this invention is comprised between 1 and 50 sq.mt/g, and in particular between 2 and 20 sq.mt/g. The porosity is lower than 0.1 cc/g and more particularly it is comprised between 0.05 and 0.001 cc/g.

The surprising feature of these new catalyst-forming ;
components is that the catalysts obtained from them promote the stereoregular polymerization of the alpha-olefins (in particular - of propylene), not withstanding the fact that in their X-ray spectrum there appear the lines characteristic of beta-TiC13 which notoriously does not give catalysts which promote the stereoregular polymerization of alpha-olefins. Unexpectedly, the catalysts obtained from the new catalyst-forming components of this invention, besides being highly stereospecific, also exhibit a high activity.

The new catalyst-forming components of this invention B

.

~99696 are prepared by a process which is also an object of the inven-tion and which involves the following phases in the order given:
(l) reduction of TiCl4 by an organometallic compound of Al having the formula AlRX2, AlR2X cr Al2R3X3 in which R is a hydrocarbon radical containing from l to 20 carbon atoms and X is halogen, the quantity of Al compound being such that the molar ratio Al/Ti is comprised between l:l to 1:5;
(II) treatment of the reduction product of step (I), :. lO with the mono- or poly-ether defined in claim l, at a temperature comprised between 70C and 120 C;
the quantity of the ether being such that the molar ratio ether/Ti ranges from 0.5 to 2.5;
: (III) washing of the product of step (II) with an inert hydrocarbon solvent.

It can be preferable, between phases I and II, to carry out an intermediate operation according to which the reduction product, possibly thermally pre-treated, is additioned with a certain quantity of an aluminum alkyl compound, for instance Al(C2H5)2Cl, and then with propylene (or other olefin) for in-stance with 0.2-l g of propylene per g of catalytic compound, for improvement in the granulometry and apparent density of the ~ polymer. The thermal pretreatment of the reduction product of step (I) is carried out at a temperature comprised between 60 and 90 for a time varying with the temperature and comprised between lO minutes and 5 hours.

1st phase (reduction of TiC14).
The TiCl4 is reduced with organometallic aluminium com-pounds of formula AlRX2, AlR2X or Al2R3X3, wherein R is a hydro-carbon radical containing Erom 2 to 10 carbon atoms and more B _ 5 _ ~ iO9~696 i particularly an aIkyl such as ethyl, propyl, butyl, etc., and wherein X is a halogen, preferably chlorine. Examples typical of such aluminum compounds are: AlC2H5C12, AlC3H7C12, A12(C2H5)3C13, A12(C3H7)3C13, Al(C2H5)2Cl and Al(C3H7)2Cl. The reduction of TiC14 is preferably carried out in liquid hydrocarbon media under the reaction conditions. The reduction temperature depends on the type of the organometallic aluminum compound used as reducing agent.

More particularly, in the case of aluminum alkyl ses-quichlorides or monochlorides, the reduction is preferablycarried out at temperatures comprised between -10C and ~20C
and particularly between 0C and ~10C. If the Al compound is an alkyl aluminum dichloride, the reduction is preferably carried out at temperatures between 0C and 40C and more particularly between 10C and 30C.

The Al/Ti ratio varies from 0.1 to 5 and is preferably comprised between O.S and 2.

At the end of the reaction, the solid product may be separated from the liquid phase and washed with a hydrocarbon solvent. The solid product thus obtained contains, in ~eneral, for each mol of TiC13, from 0.1 to 1 mol of organometallic aluminum compound.

.
Intermediate phase (thermal pre-treatment).
-- The solid reduction product of phase (1) may be sub-jected to a thermal pretreatment at temperatures comprised bet-ween 20C and 100C, but preferably between 60C and 90C.
This thermal pre-treatment is usually realized by maintaining the reduced solid in suspension in a hydrocarbon solvent, pre-ferably of the same type oE that used in the reducing phase.
At the end of the thermal treatment, the solid may be repeatedly ''' ~3 , - 1~9~696 washed with a hydrocarbon solvent.

_nd phase (treatment with ethers).

The solid reduction product, possibly thermally pre-treated according to the intermediate phase, is reacted with either a mono-ether or a poly-ether as defined above and capable of forming complexes or coordination products with A1 halides, or alkyl-Al halides, which complexes or coordination products are soluble in the ether itself or in aromatic or aliphatic hydrocarbons or in the halogenated derivatives thereof. Any mono- or poly-ether, capable of forming with the aluminum or aluminum alkyl halides, coordination complexes or compounds, with the solubility charac-terestics herein above defined, may be used.

More particu~arly, the ethers may be chosen from amongst the monoethers of formula R' OR", wherein R' and R", equal to or different from each other, are alkyls containing from 1 to 10, but preferably ~rom 4 to 6 carbon atoms, aryls, cycloalkyls, alkylaryls, and aralkyls, and also chosen from am3ngst polye~ers such as diethylenglycol-dimethylether, 1,2 diphenoxy-ethane and the like.
Particularly good results are obtained with di-n-butylether and di-isoamylether.

The molar ratio ether/Ti is comprised, in general, between 0.5 and 2.5, and more particularly between 0.8 and 1.5, the temperature of the reaction being comprised between 70C and 120C, preferably between 80e and 100C.

The new catalysts of the invention are obtained by mixing starting components which comprise (a) organome-tallic A1 com-pounds, such as Al trialkyls or their complexes with electron-donor compounds; or alkyl-Al halides such as dialkyl-Al chlo-rides and alkyl-Al sesquichlorides, and the new catalyst- forming components of the invention which consist of or comprise B

~ . ~0S9i696 products of formula (Ij as defined herein.

The catalysts are useful in the polymerization of olefins in general but particularly for promoting the stereo-regular polymerization of alpha-olefins of formula CH2 = CHR in which R is an alkyl radical containing 1-4 carbon atoms, including propylene, butene-l, 4-methylpentene-1, mixtures thereof, and mixtures thereof with ethylene, to high yields of crystalline . ~_ , . _ _ . ...

)99696 homopolymer~ or copolymers.
'rhe catalysts obtained from alkyl aluminum halides, and in particular from alkyl Al monohalides are particularly adapted for u3e in the polymerization of propylene and of its mLxtures with ethylcne, in as much a9 they "~teer" or orient -the polymerization to the production of polymer~ having a high isotacticity index (percent by weight of polym~r insoluble in boiling n-heptane), When mixtures of ethylene and propylene are polymerized in contact with these catalysts, the content of polymerized ethylene unit~ in the polymerization product may amount to up to 30~o b.w.
The polymerization condition~ are those which are known in the art and comprise temperature in general bet~Jeen 0C and 100C but preferably between 40 and 90C with partial pres~ure~ of the olefin~ equal to or greater than atmospheric pres~ure. The polymerization may be conducted either in a liquid phase~ in the presence of an inert hydroearbon diluent different from the monomer to be polym~ri~ed~ in the ab~ence of such an extraneous diluent and using liquid monomer, e.g., liquid propylene as the diluent, or in the gas phase.
When the alfa-olefin polymerized is propylene, it is advantageous to effect the polymerization in the presence of an inert liquid aliphatic hydrocarbon diluent or in the pre~ence of liquid propylene as the reaction medium or diluent.
The following example 3 are given for the purpose of illustrating the invention in more detail and are not to be construed as limiting.
The superficial area data (speciric ~urface) reported in the examples have been determined by means of the liquid nitrogen absorption test (EET method). The porosity (total) ha~
been determined ~imilarly by liquid nitrogen ab~orption (pores 1()9$696 with radius lower than 500 A).
E MP~E- 1 Pre~aration o~ the new catal~tic_component Into a 5 lt reactor there were introduced 2~200 ml of dearomatlzed n-heptane and 800 g of q'iC14O Thereupon, there were introduced 1,420 ml of a heptanic solution (500 g/lt) of Al~ t3C13 (molar ratio Al/'ri - 1~37). The addition of the aluminum compound was carried out dropwise, maintaining the reaction m3ss under stirring, wlthin about 90 minutes and by operating at a tempersture compri.sed between 8 and 10C. ~he mixture was left to re~t~ still under ~tirring at 8-10C~ for about 4 hour~
~he reaction mixture was then brought up to 90C and maintained at thi~ temperature for 90 minutes (thermal pre-treatment), The mass was then cooled down to room temperature and washed repeatedly with n-heptane (5 time~ with 2,000 ml each time).
The solid and thermally pre-treated reduction product (1,000 g) was suspended in 2,500 ml of n-heptane. To the sus-- pen~ion thu~ obtained were admixed 600 g of di-n-butylether at room tempera~ure (molar ratio ether/Ti ~1.1).
~he temperature of the reaction mixture was then brought up to 90C and maintained at that temperature for 2 hour~. After cooling down to room temperature~ the reaction ma~s Y~9 repeatedly wa~hed with n-heptane snd~ after drying under vacuum at 40C, there was obtained a brown-colored catalytic component; the X-rays spectrum (CuKa) ~howed the following characteristic diffrsction lines:
d = 5,4 A (intense line) : d - 2.75 A (medium intense line) _ = 2.12 A (line of medium intensity) _g_ 1~)99696 d = 1.98 A (very weak line) d = l.77 A (medium line).
~he component wa~ further ch~racterized by:
Surface area - 13.02 ~q.mt/g Poro~ity - 0 0~5 cc/g The elementary analysis yielded the following re~ult~:
l'i ~ 24.45% by weight Al - 0.3 % by weight Cl _ 55.9-% by weight n-butyl ether 4.8 ~0 by weight Pol,~merizstion of proP~lene-in~n-he~tane~
Into an autoclsve of 2.5 lt holding capacity, made of stainle~s steel~ were introduced 1~000 ml of n-heptane~ 0.15 g of the solid catalytic component prepared as described above~
and 1.5 g of AlEt2Cl, The polymerization ~as conducted at 70C
under a pres~ure of 5 atm (gauge pressure atm) with propylene and hydrogen (1.5% by volume in the gaseous pha~e) for 4 hours.
~he pre~sure was maintsined constant by the continuous feeding in of propylene.
At the end, after removal of the n-heptane by stripping with vapor, there was obtained polypropylene which, on extraction with boiling n-heptane left a heptsne-in~oluble re~idue (i~o-tactic polypropylene) amounting to 97~ in a yield of 114 g of polymer/g of catalytic complex/hr/ata of propylene.
When Example 1 was repeated~ but carrying out the thermal pre-treatment at temperature~ greater than 100C, there were obtained catalytic components in which the TiC13 ~howed~
under X-rays examination, a spectrum of the delta type. More particularly, if the pre-activation is carried out st 130C for 90 minutee and in the treatment with ether the TiCl3/ether ratio is 2:l~ there i9 obtained a catalytic component in which ~iC13 i3 in the delta-type cry~talline form, with a ~urface area /`~ ~
9~696 of 132 m2/g and a porosity of 0.16 cc/g.
~he elementsry analysis of the thermally pre~reated product gave the following results:
Ti - 22.15% by weight Al - 2.95% by weight Cl _ 54,9 % by weight Ether - 4.5 % by weight ~his catalytic component, u~ed in the polymerization of propylene in n-heptane under tlle previously described con-dition~, resulted in a polypropylene which on extra¢tion with boiling n-heptane gave a re~idue o~ 94%; the yield wa3 65 g polymer/g catalytic component/hr/ata of propylene.
If, on the contrary, the rstio by weight TiC14 reduction product/ether amounts to 4:1, the catalytic component obtained i~ ~imilar to the preceding one and, when u~ed in the polymerization of propylene under the pre~iously de~cribed condition~ re~ult~ in a polypropylene which, on extraction with boiling n-heptane leaYes a heptane-in~oluble residue (i~otactic polypropylene) amounting to 90%, in a yield of 46,5 g of polymer-to one gram of catalytic comp~nent x hour x ~ta propylene.
The~e comparative data clearly demonstrate the superiority of the catalysts obtained from the catalytic ocmponents according to the invention, particularly with regard to the yields.

ExampIe 1 was repeated~ but without thR thermal pre-treatment at soa for 90 minute~. Thereby was obtained a ~olid catalytic component characterized by the following properties:
Spectrum under X-ray~ - there appear the line~ obser~ed in thR ¢omponent of Example 1 Surface area - 2.85 ~q.mt/g , )991696 Porosity - 0.06 cc/g The elementary analysis gave the following results:
Ti - 24.4~ by weight Al - 0.4% by weight Cl - 56.4% by weight n-butyl ether - 5.0% by weight Said catalytic complex was sued in the polymerization of propylene in n-heptane under the reaction conditions of Example 1. A polypropylene having a residue, on extraction with boiling n-heptane, of 95.5% and a yield of 98.8 g polymer/g of catalytic component/hr/ata of propylene was obtained.

Example 1 was repeated, using AlEt2Cl as the reducing agent instead of A12Et3C13. The reduction was carried out with a molar ratio Al/Ti = 1.1:1.
The admixture of aluminium compound was effected drop-wise, maintaining the reaction mass under stirring for about 90 minutes while operating at 0C.
The reaction mixture was left to rest, still under stirring, at 0C for about 4 hours. The mixture was then brought up to 60C and maintained at that temperature for ; ~ 90 minutes.
Proceeding as described in Example 1, there was , obtained a crystalline solid that showed the following charac-; teristics:

Surface area - 7.38 s~.mt/g Porosity - 0.06 cc/g X-rays spectrum - there are present the lines observed in the component of Example 1.

The elementary analysis gave the following results:

Ti - 24.95~ by weight Al - 0.95~ by weight C1 - 55.45~ by weight n-bu~yl ether - 4.5 % by weight This catalytic component, used in the polymerization o:E propylene in n-heptane under the conditions of Example 1 led to a polypropylene which on extraction with boiling n-heptane, left a heptane-insoluble residue equal to 92.5%. The yield was 89 g of polymer/g of catalytic component/hour/ata of propylene.

Example 1 was repeated but using AlEtC12 as a reducing agent for TiC14 with a molar ratio Al/Ti of 1.5:1. The addition of aluminum compound was effected dropwise, maintaining the reaction mass under stirring, for 90 minutes and operating at a temperature of 20C. This reaction mixture was then left to rest, still under stirring, for 4 hours at 20C.
Without any thermal pre-treatment, the reduction product, after washing, was treated with ether under the conditions of Example 1. The catalytic component thus obtained had the following characteristics:
- X-ray spectrum - there appeared the lines observed in the component of Example 1 Surface area - 3.25 sq.mt/g Porosity - 0.019 cc/g The elementary analysis gave the following results:
. Ti - 23.40% by weight Al - 1.35% by weight C1 - 60.85~ by weight n-butyl ether - 4.6 % by weight This catalytic component, used in the polymerization ;~` 1099696 of propylene in n-heptane under the conditions of Example 1, re~ulted in 8 polypropylene which on extraction with boiling n~heptane left a ~olid residue equal to 95.5~. The yield was sa g of polymer/g of catslytic component/hour/ata of propylene.

Example 1 W8~ repeated except that the treatment with ether W8~ carried out at 70C for 2 hours. The catalytic component thu~ obtained had the following characteristios:
X-rays spectrum - there appeared the lines observed in the component of Example 1 Surface area - 10.5 sq.mt/g Porosity - 0.07 cc/g The elementary analysis gave the following result~' Ti - 24.56% by weight A1 - 0.52~ by weight Cl - 56.8~ by weight n-butyl ether - 4.7 % by weight Thi~ catalytic component, used in the polymerization of propylene in n-heptane under the condition~ of Example 1, led to a polypropylene which, on extraction with boiling n-heptsne, : left a residue of 91.5%; the yield was 96 g of polymer/g of catalytic component/hourjats of propylene, Example 1 was repeated but carrying out the treatment wlth ether at 120C for 2 hours. The catalytic component thus : obtained had the following characteristic~:
X-ray~ ~pectrum - there appeared the lines observed in the component of Example 1 Surface area - 14.5 sq.mt/g Porosity - ~.08 cc/g 1~99696 Thc elementary analysis gave the following results:
Ti - 24.8 % by weight ~1 - 0.48% by weight Cl - 55.5 % by weight n-butyl ether - 4.3 ~ by weight Said catalytic component, used in the polymerization of propylene in n-heptane under the conditions of Example 1, resulted in a polypropylene which, on extraction with boiling n-heptane left a residue of 90%. The yield was 90 g of polymer/g of component/hour/ata of propylene.

Example 1 was repeated but, after the thermal treatment, the pre-polymerization of propylene in n-heptane was carried out under the following conditions:
Catalytic component - 50 g Al(C2H5)2Cl - 25 g n-heptane - 200 ml Propylene - 40 g Temperature - 25-35C
After the pre-polymerization, the catalytic component was subjected to treatment with ether under the conditions described in Example 1; the component had the following pro-perties:
X-rays spectrum - there appear the lines observed in the component of Example 1 Surface area - 2 sq.mt/g Porosity - 0.021 cc/g The elementary analysis gave the following results:
Ti - 13.40~ by weight Al - 0.25~ by weight Cl - 32.2 % by weight ~9~96 Polypropylene - 50.0% by weight.
Said catalytic component, used in the polymerization of propylene under the conditions of Example 1, resulted in a polypropylene which, on extraction with boiling n-heptane, left a heptane-insoluble residue of 96%; the yield was 55 g of poly-propylene/g of catalytic component/hour/ata of propylene.
If one takes into consideration the fact that the catalytic component contains 50% of polypropylene, the yield with respect to the TiC13 amounts to 110 g of polypropylene/g of catalytic component ~TiC13)/hour/ata of propylene

Claims (8)

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

1. Catalyst-forming components for use in preparing catalysts for polymerization of olefins, said components con-sisting of a product of the following composition:

TiC13(A1RmX3-m)aAP

wherein:
R is a hydrocarbon radical containing from 1 to 20 car-bon atoms;
O ?m?2.5;
X is halogen;
a is a number lower than 0.4;
A is an ether selected from the group consisting of monoethers of formula R'OR" wherein R' and R" are alkyls containing from 1 to 10 carbon atoms, aryls, cycloalkyls, alkylaryls or aralkyls, and poly-ethers of the class of polyalkylenglycol-dialkyl-ethers and 1,2-diphenoxy-ethane, said ether being capable of forming complexes or coordination products with A1 halides or alkyl-A1 halides, which complexes or coordination products are soluble in the ether itself or in aro-matic or aliphatic hydrocarbons or in the halogenated derivatives thereof; and p is zero or a number greater than zero but lower than 0.5 and said catalyst-forming components being characterized in that, in the X-rays spectrum thereof, diffraction lines appear at the following lattice distances:
d= 5.4 .ANG. (intense line); d=2.75 .ANG. (line of medium in-tensity);

d-2.12 .ANG. (line of medium to weak intensity);
d=1.98 .ANG. (very weak line); d=l.77 .ANG. (medium line), and in that the surface area thereof is comprised between 2 and 20 m2/g and the porosity is lower than 0.1 cc/g.

2. Catalyst-forming components according to claim 1, further characterized in that:
R is an alkyl, aryl, cycloalkyl, alkylaryl or aralkyl radical;
a is a number lower than 0.2; and p is a number comprised between 0.001 and 0.5.

3. Catalyst-forming components according to claim 1, in which, in the formula R' OR", R' and R", which are the same or different, are alkyl radicals containing from 4 to 6 carbon atoms.

4. Catalyst-forming components according to claim 1, characterized in that the monoether is di-n-butylether or di-iso-amylether.

5. Catalysts for the stereoregular polymerization of alpha-olefins of the formula CH2=CHR wherein R is an alkyl radical containing from 1 to 4 carbon atoms, obtained by bringing into contact starting components comprising (a) dialkyl aluminium halides or alkyl aluminum sesquihalides with (b) catalyst-forming components as defined in claim 1.

6. Process for the preparation of catalyst-forming components as defined in claim 1, characterized in comprising the following steps, in the order stated:

(I) reduction of TiC14 by an organometallic compound of A1 having the formula A1RX2, A1R2X or A12R3X3 in which R is a hydrocarbon radical containing from 1 to 20 carbon atoms and X is halogen, the quantity of A1 compound being such that the molar ratio A1/Ti is comprised between 1:1 to 1:5;

(II) treatment of the reduction product of step (I), with the mono- or poly-ether defined in claim 1, at a temperature comprised between 70°C and 120°C;
the quantity of the ether being such that the molar ratio ether/Ti ranges from 0.5 to 2.5;

(III) washing of the product of step (II) with an inert hydrocarbon solvent.

7. Process for the preparation of catalyst-forming components as defined in claim 6, characterized in that after step (I) and before step (II) is carried out a thermal pretreatment of the reduction product of step (I) at a tem-perature comprised between 60°C and 90°C for a time varying with the temperature and comprised between 10 minutes and 5 hours.

8. Process according to claim 6 in which the reduction of TiC14 - step (I) - is carried out with an organometallic compound of A1 having the formula A1 R C12 in which R is a hydrocarbon radical containing 1 to 20 carbon atoms, at temperature comprised bet-ween 10° and 30°C.