AU592394B2

AU592394B2 - Process for the treatment of spherical olefin polymerization catalysts and use of such catalysts in the polymerization of olefins

Info

Publication number: AU592394B2
Application number: AU66673/86A
Authority: AU
Inventors: Michel Avaro; Claude Brun; Auguste Cheux
Original assignee: Atochem SA
Current assignee: Arkema France SA
Priority date: 1985-12-18
Filing date: 1986-12-17
Publication date: 1990-01-11
Anticipated expiration: 2006-12-17
Also published as: DE3675195D1; JPS62246907A; CA1272473A; AU6667386A; CN1007251B; FR2591602B1; ES2018166B3; FR2591602A1; CN86108228A; EP0232643A1; JPH0794494B2; EP0232643B1; ATE57708T1

Abstract

1. A process for the treatment of a spherical catalyst for the polymerization of olefins, containing at least one transition metal, a magnesium compound and a halogen, characterized in that ethylene is prepolymerized in the presence of a cocatalyst selected from the alkyl aluminiums and at least partially in suspension, to a degree of prepolymerization suitable for the process of polymerization in suspension or in the gaseous phase in which the prepolymer will subsequently be used, a sphere protector which is the product of the reaction between alkyl aluminium and an electron donor being associated with the various components at the latest after prepolymerization.

Description

-pl i ;II~ c- 5C92OM H OF COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: 66 73/1.

Complete Specification Lodged: Accepted: Published: Priority: ted Art 1 Rteated Art: t s St Name of Applicant: cAddress of Applicant: Actial Inventor: s fr Address for Service:

ATOCHEM

4 et 8, Cours Michelet, La Defense 10, France 92800 Puteaux, CLAUDE BRUN, AUGUSTE CHEUX and MICHEL AVARO ij 4f EDWD. WATERS SONS, 50 QUEEN STREET, MELBOURNE, AUSTRALIA, 3000.

Complete Specification for the invention entitled: PROCESS FOR THE TREATMENT OF SPHERICAL OLEFIN POLYMERIZATION CATALYSTS AND USE OF SUCH CATALYSTS IN THE POLYMERIZATION OF OLEFINS The following statement is a full description of this invention, including the best mehod of performing it known to us 1.

BACKGROUND OF THE INVENTION The present invention relates to a process for the treatment of spherical olefin polymerization catalysts making it possible to preserve its morphology during the polymerization and to the use of such catalysts.

In order to fabricate spherical linear polyethylenes; namely, ethylene homopolymers and ethylene-alpha olefin copolymers, it is known to use spherical catalysts based on a transition metal and, more particularly, titanium.

However, under the conditions of industrial polymerization processes, the spherical morphology of the catalyst is rapidly destroyed. The spherical particles are rapidly turned into particles of poorly defined morphology; for instance, of the granular type, leading to more or less gra- 15 nular polymers of weak flowability, a characteristic linked e to the more or less spherical mrphology of the polymer obtained. These polymers are likewise rich in very fine ttt¢ I: t* particles, below 100 microns, leading to problems of safety and involving difficulties in the fabrication process.

S tI t SUMMARY OF THE INVENTION The process of this invention preserves the spherical morphology of the catalyst during the polymerization of the olefin or olefins, confirming the principle according to S 25 which the polymers formed are the morphological replica of the catalyst.

Briefly, the present invention comprises the process of treating any spherical olefin polymerization catalyst containing at least a transition metal, a magnesium compound, and a halogen so as to maintain its spherical morphology i during the polymerization of at least one olefin comprising r 2a polymerizing at least partially in suspension ethylene in the presence of said catalyst and a cocatalyst selected from an alkyl aluminum compound to a degree of prepolymerization adapted to the polymerization process in which the prepolymer will subsequently be used, said degree of prepolymerization being below 100 when the prepolymer must be used as catalyst in a process of polymerization in suspension and above 100 for a process of polymerization in the gaseous phase, without in the latter case the prepolymer formed representing more than 10% of the final polymer, and associating with said catalyst, or cocatalyst, or said prepolymer a spheroprotector, said spheroprotector being the reaction product of an alkyl aluminum compound and an electron donor.

S4 0 1 1

C

7.

5 i (0 t poyalymori i natIiSt pn ia!y 7w uspensino ethylcne in the presence of said catalyst and a cocatalyst se cted from an alkyl aluminum compound to a degree of repolymerization adapted to the polymerization pr ss in which the prepolymer will subsequentl e used, and associated with said catalyst, or coc yst, or said prepolymer a spheroprotector; sai pheroprotector being the reaction product of an I c*iln nalminumomponda an eleron donr The invention also comprises the resultant treated spherical olefin polymerization catalyst and the use of such catalyst to polymerize olefins as hereinafter described.

DESCRIPTION OF THE DRAWING FIG. 1 is a photomicrograph of the prepolymer of Test 1 of Example 1; FIG. 2 is a photomicrograph of the prepolymer of Test 6 i te of Example 1; and t t SFIG. 3 is a photomicrograph of the prepolymer of Test 7 of Example 1.

I St DETAILED DESCRIPTION The present invention makes it possible to obtain a linear polyethylene in powder form with spherical morphology by polymerization in suspension or in the gaseous phase of ethylene or of a mixture of ethylene and an alpha-olefin.

SThis spherical morphology is still determined subjectively.

I 'Without making an exclusive definition of it, one can admit that a polyethylene powder possesses a spherical morphology when, by microscopic examination, the powder particles are on the average appreciably spherical, symmetrical, without elongation, with a smooth surface at a magnification of This method of evaluation seems to be confirmed by the experimental analysis trials of J. K. BEDDOW, Fine Particle Research Group; Chemical and Materials Engineering, University of Iowa in "Proceedings of the ACS Division of Polymeric Materials: Science and Engineering" Volume 53, Fall Meeting 1985 Chicago, pages 261-262.

The treatment process of the spherical olefin polymerization catalyst is characterized by the fact that one carries out, in its presence, a prepolymerization in the presence of a cocatalyst selected from alkyl aluminum compounds, at least partially in suspension, of ethylene up to a degree of prepolymerization adapted to the polymerization process in which the prepolymer will later be used, a reaction product between an alkyl aluminum compound and an electron donor being associated with the constituents at the latest after the prepolymerization. This reaction product, Scalled spheroprotector, usually is in the liquid state or in Ssolution.

t The prepolymer obtained according to the process is used as a catalyst in the polymerization processes in suspension and in the gaseous phase, either in an agitated bed or in a fluidized bed. According to this polymerization process, t t Oe the prepolymerization in the presence of the catalyst must .1f 1be more or less high. In the case in which the prepolymer S 25 will be used as a catalyst in a process in suspension, the i degree of prepolymerization preferably is below 100. On the contrary, for a process in the gaseous phase, the degree of Sprepolymerization is preferably above 100 and such that the prepolymer formed represents at the most 10% by weight of the final polymer.

The initial spherical olefin polymerization catalyst is 4 -1 ,1U' I a well-known product. It is usually the result of the combination of at least a transition metal compound, a magnesium compound, a halogen and possibly an electron donor or acceptor and of any other compound usable in these types of catalyst.

The transition metal compound is generally selected from among compounds of the formula Me(OR)nXm-n in which: Me is vanadium, chromium and, more particularly, titanium; (ii) X is bromine, iodine and, more particularly, chlorine; (iii) R is a C 1 to C 14 aliphatic or aromatic hydrocarbon radical or COR' with R' being a C 1 to

C

14 aliphatic or aromatic hydrocarbon; and (iv) corresponds to the valence of the transition metal and is a value below or equal to The transition metal compound particularly recommended is selected from among the titanium compounds of formula Ti(OR)xCl4,x, with R being defined above and x being between 0 and 4.

The magnesium compound is usually selected from among the compounds of the formula Mg(OR)nX2-n in which X is bromine, iodine and, more particularly, chlorine, R is hydrogen or an alkyl or cycloalkyl radical and is below or equal to 2.

The electron donor or acceptor is a liquid or solid organic compound known to enter into the composition of Sthese catalysts. The electron donor can be a mono or poly- 30 functional compound advantageously selected from among aliphatic or aromatic carbnxylic acids and their alkyl iI 1 a I72 I;l 20 esters, aliphatic or cyclical ethers, ketones, vinyl and vinylidene esters, acrylic derivatives, in particular alkyl acrylates or methacrylates, and silanes. Especially suitable as electron donors are compounds such as methyl paratoluate, ethyl benzoate, ethyl or butyl acetate, ethyl ether, ethyl para-anisate, dibutylphthalate, dioctylphthalate, diisobutylphthalate, tetrahydrofuran, dioxane, acetone, methylisobutylketone, vinyl acetate, methyl methacrylate, and the silanes such as phenyltriethoxysilane, aromatic or aliphatic alcoxysilanes.

The electron acceptor is a Lewis acid, preferably selected from among aluminum chloride, boron trifluoride, chloranil or yet the alkyl aluminum and alkyl magnesium compounds.

In a preferred method of prepolymerization in suspension under agitation in eddy flow, ethylene is prepolymerized, possibly in the presence of a chain limiting agent and/or a cocatalyst selected from among the alkyl aluminum compounds known for that use at a temperature between 0° an 110°C, preferably between 200 and 60 0 C, at a total pressure below bars absolute constituted essentially of inert gas such as nitrogen. In order to preserve the initial spherical morphology of the catalyst to the maximum, it is recommended to control the supply of monomer in the reactor. A favorable mean rate of supply is below or equal to 500 N1 x h-1 x g-1 of catalyst. The prepolymerization in suspension is pursued up to a degree of prepolymerization adapted to the later polymerization process, the degree of prepolymerization being defined by the ratio of the sum of weight of prepoZymer formed plus the weight of catalyst used to the weight of catalyst used.

6

F:

I

ItEt I, (t rr IiI At any stage whatever of the prepolymerization, the spheroprotector usually obtained by the prior reaction of the alkyl aluminum compound and the electron donor is added to the components. The spheroprotector can be introduced into the reaction medium of prepolymerization. It can likewise be added advantageously to the prepolymer after prepolymerization either directly into the reaction medium or to the prepolymer stored in suspension under inert gas.

In another preferred mode of prepolymerization in suspension under agitation in eddy flow, one proceeds with the prepolymerization under the previously described conditions up to a reduced degree of advancement of prepolymerization, preferably below 20 g of polymer per gram of catalyst.

At this stage, the prepolymer is isolated then taken up again in a system of prepolymerization in the gaseous phase S" so as to pass from the reduced degree of advancement of S tI polymerization to the degree of prepolymerization adapted to the later polymerization process.

tl 20 This part of prepolymerization iA the gaseous phase takes place under the usual condition5 of the ethylene polymerization process in the gaseous phase. One can, for Sinstance, associate the prepolymer with reduced degree of S\ advancement with a charge of polyolefin of mean granulometry below or equal to 3000 and preferably below or equal to 1000 microns, in the presence, preferentially, of a cocatalyst such as previously defined, After homogenization, prepoly- Smerization is pursued by the introduction of monomer, preferably ethylene, or a mixture of ethylene and butene. In preferential manner, the prepolymerization in the gaseous phase is realized at a, temperature between 300 and 110 0

C

7 I '1 ra~cnj; :1i under a total pressure below or equal to 20 bars.

This prepolymerization in the gaseous phase is pursued until a degree of prepolymerization adapted to the process of later polymerization is obtained. In order to preserve the initial spherical morphology of the catalyst to the maximum, it is recommended to control the supply of monomer in the reactor. A mean rate of favorable supply is below or equal to 500 N1 x h-1 x g-1 of catalyst.

As previously, the spheroprotector can be introduced at any stage whatever of the prepolymerization process, or yet added to the prepolymer stored under inert gas after prepolymerization.

In the process according to the invention, the ratio of molar concentrations in the spheroprotector of the alkyl aluminum compound, calculated in aluminum, to the electron donor is usually below 30 and better still between 10 and 0.1. This spheroprotector is combined in a preferential proportion of 500 to 4000 ppm (calculated as aluminum) for 1000 to 15,000 ppm of catalyst in the prepolymer of prepolymerization degree adapted to the process of later polymerization. The ratio introduced by weight of aluminum to the catalyst is between 30.10 3 and 4.

For the fabrication of the spheroprotector, one can select the components from among the previously defined electron donors and the alkyl aluminum compounds customarily known and used as cocatalysts for use with the catalysts described herein. These alkyl aluminum compounds are generally selected from among the compounds of the formula AL(R")cX'dHe in which X' is Cl or and R" represents a Cl to C14 saturated hydrocarbon radical, with: O<d<1.5; O<e<l and c+d=3.

I

1c4 te IL I

SI

I-

It r3 II S30 t I

I

~I~

i L- C1_ As examples, one can cite: Al(C2H5) 3 A1(C 2

H

5 2 C1, Al(C 4

H

9 3 A1 2

(C

2

H

5 3 C1 3 Al(C 4

H

9 2 H, Al(C 6

H

13 3 Al(CgHI 7 3 Al(C 2

H

5 2 H and Al(C 2

H

5 2

(OC

2

H

5 The mixing of the alkylaluminum compound and the electron donor takes place under inert atmosphere by the known means appropriate for these types of components. When the liquid spheroprotector is added to the prepolymer after prepolymerization, the operation is carried out, under inert atmosphere, either by mixing with the prepolymer in suspension in an inert liquid or by impregnation of the prepolymer powder.

To the extent in which a chain limiting agent is used in the prepolymerization, preferably hydrogen is chosen.

The prepolymer obtained according to the invention is generally stored in the dry form for the purpose of a subsequent use as a catalyst of polymerization in suspension or in the gaseous phase for the fabrication of linear polyethylene in powder form with spherical morphology. This catalyst, in the form of a prepolymer with spherical morphology, preserves its morphology during the course of polymerization and, thanks to this property, makes it possible to obtain linear polyethylenes likewise possessing a spherical morphology.

The catalyst treated accorring to the invention is used like a standard catalyst in the processes of polymerization in suspension or in the gaseous phase of olefins. Although it can be used as is, in order to regulate its productivity it is also possible to supplementarily add a cocatalyst to the reaction medium. In that case, the cocatalyst can be a spheroprotector and better still the spheroprotector used in the preparation of the prepolymer.

C a t C r In a process of polymerization of ethylene in suspension, one operates in the customary manner in a liquid hydrocarbon medium at temperatures which can go up to 120 0

C

and under pressures which can go up to 250 bars.

The polymerization of ethylene in the gaseous phase, in the presence of hydrogen and of an Inert gas can be carried out in any react"or permitting a polymerization in the gaseous phase and, in particular, in a reactor with an agitated bed or with a fluidized bed. The conditions of use are those conventionally used for the polymerization of ethylene. one operates generally at a temperature below the fusion point (melting point) Tf of the polymer or copolymer to be synthesized and, more particularly, between 20 0 C and and under a pressure such that the ethylene and possibly other hydrocarbon monomers present in the reactor are essentially in the vapor phase.

The invention will be further described in connection with the following examples which are set forth for purposes of illustrati.on only and in which the spherical catalyst treated according to the invention was prepared under the Conditions Which follow.

Into a glass reactor of 1.5 liter capacity, equipped with a means of agitation, one introduces under nitrogen after drying and purification 200 mm of n-butyl sec.-butyl magnesium and 33 mM of triethyl aluminum, respectively, in a molar solution in heptane. The contact is maintained for 1 hour at 80 0 C. One then adds uinder agitation 200 mM of dilsoamyl ether at 50'C, then in 2 hours, still at 50*C, 550 mM of tert. butyl chloride. The solid obtained, forming a support, is filtered and washed twice with 400 cc of heptane at

,A

t;

C

Pt 4 The solid is placed in suspension in 400 cc of heptane at 80 0 C and in 1 hour 600 mM of TiCl 4 are added. The catalyst obtained is filtered and washed twice with 400 cc of heptane. The catalyst is dried at 70 0 C under nitrogen and stored under inert atmosphere. This solid catalyst is in the form of perfectly spherical particles of 9 mean dimension of about 30 microns.

EXAMPLE 1 A series of 13 tests were carried out illustrating the present invention, with Tests 1 to 3 made by way of comparison to show results when no spheroprotector is used.

A. Preparation of the prepolymer Into a reactor of 8.2 1 capacity, degasified and dried, the following are introduced successively at 40 0 C under Snitrogen and under an agitation of 400 RPM: 3 1 of dry hexane; (ii) 6 mM of pure trihexylaluminum (THA); (iii) 3 g of the preceding spherical catalyst in suspension in 75 cc of hexane; S(iv) 0.8 bar absolute of hydrogen; and 4 batt absolute of nitrogen.

Then ethylene is added at a flow rate of 30 Nl/h for 1 hour, followed by a flow rate vf 60 Nl/h for 1 hour, by a flow rate of 130 Nl/h for 2 hours, and finally by 2M NIl/h for 50 minutes.

U The introduction of ethylene is stopped, the total pressure drops from 6 bars absolute to 5 bars absol~t in fa minutes. The agitation is stopped in order to allow the supernatant liquid to settle, be diecanted 4nc i Then after elimination of the solvent remaining at under nitrogen, the prepolymer powder is extracted and stored under inert atmosphere.

One collects 600 g of dry prepolymer powder with spherical morphology, without aggregates, of degree of prepolymerization of 200 g of prepolymer per gram of catalyst of a mean particle diameter (dp 50): 280 microns.

B. Preparation of the spheroprotectors and of the catalyst in the form of the active prepolymer Into a Schlenk tube the following are introduced and mixed protected from light, under agitation and flushing with nitrogen, namely: pure THA and an electron donor, methyl para tert. butylbenzoate (PTBM), phenyltriethoxy- 15 silane (PTES), vinyl acetate vinyltriethoxysilane (VTES), or tetraethoxysilane (TES) in a molar ratio given for each test in Table I which follows. The thus prepared iomplexes are deposited dropwise on the preceding agitated pulverulent prepolymer under inert atmosphere. The quantity deposited is such that the concentration of aluminum in relation to the prepolymer is 2000 ppm.

C. Polymerization of butene-l and of ethylene This operation takes place in a reactor of 8.2 1 capacity, previously dried, equipped with an agitator turning at ^I a rate of 400 RPM and kept at 85 0 C during the entire polymerization.

Into the reactor kept under vacuum of about 1.33 Pa, in the presence of 100 g of polyethylene from the bottom thereof, butene-l is injected until a pressure of 1 bar is obtained. Then as cocatalyst a certain volume, given for 12 ii each test in Table I below, of the spheroprotector identical to the one used in the preparation of the prepolymer according to the invention is added and the injection of butene-1 is continued until a pressure of 2 bars is obtained. One then injects successively into the reactor 2 bars of hydrogen and 12.5 bars of ethylene until partial pressures of hydrogen and of ethylene, respectively, equal to 2 and 12.5 bars are obtained.

lOg of previously prepared active prepolymer are then introduced into the reactor by means of nitrogen pressure; continuing the injection of nitrogen until the total pressure inside of the reactor reaches 21 bars. The pressure in the reactor is maintained at this value by the injection of ethylene and of butene-1 in a molar ratio of butene-1/ethylene equal to 0.0466.

After 4 h of reaction, the polymerization is stopped by decompression of the reactor. One purges with nitrogen and allows cooling to take place.

The remaining operating conditions and the results of the studies carried out on the linear polyethylene obtained are given in Table I below, it being understood as previously noted, that Tests 1 to 3 are given by way of comparison only.

13 2is k t: t *feyiswi^ 9 1.* TABLE I Test Weight of Weight of Car- Nature of Spheropro- Cocatal st Density Mor hology Flow- Production Producactive pre- responding sphero- tector in cc(2 blocks ability in g tivity in polymer in g catalyst in g protector A1/DE( 1 in g sec. q PE g catalyst 1 10 0.050 THA 0.4 0.923 G 90 >40 892 17,900 2 10 0.050 IPRA( 3 0.4 0.925 G 370 46 2,560 51,200 3 10 0-039 TEA 0.3 0.924 G 235 50 435 11,500 4 10 0.035 THA/PTBM 3 0.2 0.923 S 0 24 144 4,000 10 0.035 THA/PTBM 6 0.2 0.924 S 0 25 160 4,570 6 10 0.035 THA/PTBM 10 0.2 0.923 S/ 155 34 1,290 36,850 7 10 0.035 THA/PTES 5 0.2 0.924 S 0 26 695 19,800 8 10 0.035 THA/PTES 8 0.2 0.924 S 0 25 632 18,000 9 10 0.035 THA/PTES 10 0.2 0.920 S 68 31 2,060 58,800 7 0.041 THA/DPDMS( 4 8 0,2 0.9235 S 0 27 620 15,150 11 106 0.038 THA/VA 6 0.2 0.927 S 0 27 1,704 44,100 12 10 0.039 THA/TES 10 0.3 0.917 S 40 30 1,781 45,670 13 10 0.039 THA/VTES 10 0.3 0.919 S 40 29 1,763 45,200 DE Electron donor. Ratio in molar concentration Identical with the spheroprotector of the prepolymer G Granular S Spherical IPRA Isoprenylaluminum at 70% mass percentage in hexane DPDMS Diphenyldimethoxysilane The morphology-of--the-prepolymers-of- Tests--iG-6--and--7--is--iH-1-ustrated-i -the-dr awi-ngs-- EXAMPLE 2 Two tests were carried out as in Example 1.

A. Preparation of the active prepolymer In this example, the spheroprotector, prepared according to Example 1 is utilized at the start of prepolymerization.

Into the reactor and under the conditions of Example 1 the following are introduced: 3 1 of dry hexane; (ii) the spheroprotector composed of the mixture of: 42 mM of THA 2.8 mM of PTES; (iii) 3 g of spherical catalyst according to Example 1; (iv) 0.8 bar absolute of hydrogen; and 4 bars absolute of nitrogen.

cThen ethylene is added at a flow rate of 30 Nl/h for 1 hour fol-lowed by a flow rate of 60 Nl/h for 1 hour, by a 0 flow rate of 130 Nl/h for 2 hours, and finally 200 Nl/h for if hours.

One collects 768 g of dry prepolymer powder with a spherical morphology, without aggregates, of a degree of prepolymerization of 256 g of prepolymer per gram of cata- 25 lyst, containing 332 ppm of titanium of dp 50 240 microns, and containing 1000 ppm of aluminum.

B. Polymerization of butene-1 and of ethylene Under the conditions of Example 1, one polymerizes (c butene- and ethylene in the presence of the active prepo- «me tn 30 lymer obtained.

1 I_ The remaining operating conditions and the results of the studies carried out on the linear polyethylene obtained are given in Table II below.

EXAMPLE 3 Two tests were carried out as in Example 1; one with and one without the spheroprotector.

A. Preparation of the active prepolymer Into a reactor of 1 1 capacity, degasified and equipped with an agitation system, the following are introduced at 50 0

C:

1000 cc of hexane; (ii) 21 mM of triisobutylaluminum; and (iii) 4.5 g of previously prepared spherical catalyst.

f Then 40 g of a mixture of a molar composition of 61.5% of ethylene; (ii) 0.7% of butene; and Ciii) 37.8% of hydrogen are caused to bubble in 21 hours through the vent of the reactor.

The product formed is washed with 500 cc of hexane, After drying at 50 0 C under nitrogen, one collects 25 g of prepolymer of a degree of prepolymerization of 5,5 g of prepolymer per gram of catalyst. The titanium content being 1.54% by weight.

g of this prepolymer are mixed intimately under inert atmosphere with 100 g of polyethylene powder and 0.5 cc of THA. This mixture is introduced Under nitrogen into a reactor of 8.2 1 capacity, dry and equipped with a system of agitation. One adds successively: Ifi 0.5 bar of hydrogen; (ii) 4 bars of nitrogen; and (iii) a butene-ethylene mixture in the molar ratio of 0.025 at a flow rate of 100 Nl/h for 2 h min.

At the end of the operation, one collects 433 g of powder, 333 g of which are dry prepolymer of a degree of polymerization of 183 containing 357 ppm of titanium.

The dry powder collected is impregnated under agitation and inert atmosphere with a liquid complex composed of the mixture of THA-vinyl acetate (VA) in the molar ratio of Al/electron donor of 6 and containing 4000 ppm of Al.

B. Polymerization of butene-1 and ethylene Under the conditions of Example 1, butene-1 and ethylene are polymerized in the presence of the active prepolymer obtained. By way of comparison, the same polymerization is carried out with the prepolymer not impregnated with spheroprotector.

The remaining operating conditions and the results of studies carried out on the linear polymer obtained are given in Table III below.

4 4*4 4 4.4 44* '4 TABLE 11 Test Weight of active prepolymer in g Weight of Corresponding catalyst in g Nature of spheroprotector Spheroprotector Al/DE ICocatalys t in cc Density Mor~ hology blocks in g Flowability sec.

Production in g Productivity in q PE g catalvs t I I I l~I A 0.039 0.037

THA/PTES

0.2

THA/PTES

0.2 THA alone 0.922 0.922 1 ,000 1,667 25,670 45,000 TABLE III Test T7 Compa ra tiLve 2 Weight ot active prepolymer in g Weight of Corresponding catalyst in g Nature of spheroprotector Spheroprotector Al/DE in cc Density 0.929 Morphology blocks in g Flowability sec.

Production in g Productivity in g PE g cata- 1 yst 30,780 33,200 0.0283 0.0283 1 THA 26

THA/VA

0.2 THA/VN 0.924 4 4 4 4 4 4 4 I-

I

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 within the spirit and scope of the invention as defined by the appended claims.

t

Claims

1. The process of treating a spherical olefin polymerization catalyst containing at least a transition metal, a magnesium compound, and a halogen so as to maintain its spherical morphology during the polymerization of at least one olefin, comprising polymerizing at least partially in suspension ethylene in the presence of said catalyst and a cocatalyst selected from an alkyl aluminum compound to a degree of prepolymerization adapted to the polymerization process in which the prepolymer will subsequently be used, said degree of prepolymerization being below 100 when the prepolymer must be used as catalyst in a process of polymerization in suspension and above 100 for a process of polymerization in the gaseous phase, without in the latter case the prepolymer formed representing more than 10% of the final polymer, and associating with said catalyst, or cocatalyst, or said prepolymer a spheroprotector, said spheroprotector being the reaction product of an alkyl aluminum compound and an electron donor.

2. The process of claim 1, wherein prepolymerization in suspension is carried out up to a reduced degree of advancement of polymerization less than the final value being obtained in a second polymerization in the gaseous phase) and the resultant prepolymer is prepolymerized to the degree of prepolymerization adapted to the polymerization process in which the polymer will later be used by gaseous phase polymerization.

3. The process of claim 2, wherein the degree of advancement is below 10g of polymer per gram of catalyst. Cr (e 4 -i 21

4. The process of claim 3, wherein in the prepolymerization the monomer is introduced into the reactor at a mean rate equal to or below 500 N1 x h 1 x g-1 of spherical catalyst.

The process of claim 4, wherein prior to its addition, the spheroprotector is obtained by reaction of an alkyl aluminum and an electron donor.

6. The process of claim 4 or 5 wherein the ratio of the molar concentrations of the alulinum to the electron donor is below 30:1.

7. The process of claim 5, wherein the liquid complex is combined in a proportion of 500 to 4000 ppm calculated in aluminum for 1000 to 15,000 ppm of catalyst in the prepolymer of prepolymerization degree adapted to the process of polymerization in which the prepolymer will later be used.

8. The process of claim 7, wherein the ratio by weight of aluminum to the catalyst is between 30x10- :1 and 4:1.

9. Spherical olefin polymerization catalyst treated by the process of any one of the preceding claims 1 to 8.

10. The process of preparation in suspension or in the gaseous phase of linear polyethylene in powder form with spherical morphology, comprising polymerizing ethylene with the treated catalyst produced by the process of any of claims 1 to 8. 4 *1 4 *1 *r 1 1 4*t 1 II 4 F C C C Ct I I Ic -1- I_ L U I 4 r r 22

11. The process of claim 10, wherein a cocatalyst is added to the reaction medium said cocatalyst being a reaction product of an alkyl aluminum and an electron donor. DATED this 24th day of October, 1989 ATOCHEM #t I i I cf i C WATERMARK PATENT TRADEMARK ATTORNEYS, Queen Street MELBOURNE. VIC. 3000 fc. I LCG:LN (7.14)