AU598828B2 - Spherical catalysts, method of making the same, and polymerization of olefins using the same - Google Patents

Abstract

Process for the treatment of a spherical catalyst for the polymerisation of olefins, containing at least one transition metal, a magnesium compound and a halogen, characterised in that ethylene is prepolymerised in the presence of the spherical catalyst, in the presence of a cocatalyst chosen from alkylaluminiums, at least partially in suspension, to a degree of prepolymerisation adapted to the polymerisation process in which the prepolymer will be subsequently used, a spheroprotector being used in combination with the various components not later than after the prepolymerisation, the accepted formula of the said spheroprotector being: AlR'mR''nClpHq in which 0.05 < p </= 1 0 < m < 2.95 0 < n < 2.95 0 </= q </= 1 it being known that m + n + p + q = 3 and R' and R'', which are identical or different, are linear, branched or cyclic hydrocarbon radicals containing from 1 to 14 carbon atoms. The catalyst thus treated conserves its spherical morphology in the subsequent polymerisation of ethylene. It is particularly suited for the manufacture of linear polyethylene powder with spherical morphology.

Description

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a:~ S8 8 2 8. Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 COMPLETE SPECIFICATION

(ORIGINAL)

Class Application Number: Lodged: Int. Class Complete Specification Lodged: a Priority Related Art: Accepted: Published: This document contains the armendments made under Section 49 and is correct for printing.

Narme of Applicant: SAddress of Applicant: Actual Inventor: Address for Service:

ATOCHEM

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

4 Complete Specification for the invention entitled: SPHERICAL CATALYSTS, METHOD OF MAKING THE SAME, AND POLYMERIZATION OF OLEFINS USING THE SAME The following statement is a full description of this invention, including the best method of performing it known to us 1 2 3 4 6 7 8 9 16 Ha o e 19 23 24 16 27 28 S*0 19 21 23 24 26 27 28 29 31 BACKGROUND OF THE INVENTION The present invention pertains to spherical catalysts for the polymerization of olefins permitting the said catalysts to preserve their morphology during the polymerization. The process of making such catalysts consists of prepolymerization of ethylene; it being understood that the term "ethylene" also covers the mixtures of ethylene and olefins, to a low degree with a product called a "se- "protector", which has the effect of preserving the sphericity and is essentially formed by a specific halogenated alkyl aluminum compound, being associated with the components after the prepolymerization at the latest. Such modified catalysts are particularly suitable for the manufacture of linear polyethylene in powdered form with spherical morphology.

Spherical catalysts based on a transition metal and more particularly on titanium are known and used to manufacture linear spherical polyethylenes, ethylene homopolymers, and ethylene-alpha-olefin copolymers. However, the spherical morphology of the catalyst is rapidly destroyed under the conditions of industrial polymerizatiin processes. The spherical particles rapidly disintegrate into particles of poorly defined moiphology, of the granular type, which Sleads to more or less granular polymers of poor flowability, I a characteristic linked with the more or less spherical Smorphology of the polymer obtained. These polymers are also j rich in very fine particles; smaller than 100 microns, which leads to safety problems and to difficulties in the manufac- Sturing process.

I SUMMARY OF THE INVENTION S The process according to the present invention, i II i l 1 \i according to which the spherical morphology of the catalyst 2 is preserved during the polymerization of the olefin or ole- 3 fins; confirming the principle according to which the poly- 4 mers formed are the morphological replica of the catalyst, leads to a catalyst prepolymer, which makes it possible to 6 obtain polymers, including a linear polyethylene in powdered 7 form with spherical morphology by polymerization of ethylene 8 or of a mixture of ethylene with alpha-olefin in suspension 9 or in the gaseous phase. This spherical morphology is still determined subjectively. Without making an exclusive definition, it can be stated that a polyethylene powder has a spherical morphology if the powder particles are, on an 6131s average, practically spherical, symmetrical, without elonga- ,14 I tion and with a smooth surface at a magnification of 20, as determined by the optical microscopic examination. This 16 mode of evaluation seems to be confirmed by the attempts at S7, I experimental analyses made by 3. K. BEDDOW, Fine Particle |j Research Group, Chemical and Materials Engineering, 19 j University of Iowa in "Proceedings of the ACS Division of 2 I Polymeric Materials: Science and Engineering", Volume 53, 21 Fall Meeting 1985, Chicago, pages 261-262.

2 The invention comprises the process for treating a t 23 spherical catalyst for olefin polymerization and is charac- 24 terized in that in the presence of the said catalyst, the prepolymerization of ethylene is carried out, at least par- 26 tially in suspension, in the presence of an alkyl aluminum S 27 j compound cocatalyst, to a degree of prepolymerization S 28 11 suitable for the polymerization process in which the prepo- 29 j, lymer will subsequently be used; and a spheroprotector in !i the form of a halogenated alkyl aluminum compound is asso- 31 I ciated with the components after the prepolymerization at I 3 H i

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'I iUf. o: 1: I r 1 the latest with the spheroprotector corresponding to the 2 formula (after adding all the components which are a part of 3 :t the composition of the spheroprotector): 4 1 -AIR'mR"nClpHq in which R' and R" can be the same or different and are C 1 6 to C 14 linear, branched, or cyclic hydrocarbon radicals, 7 0.05 p 8 0 m 2.95, 9 I 0 n 2.95, and 0 5 q II with m n p q equal to 3.

12 The invention also comprises the resultant spherical 13 catalysts and the method of using said catalysts as j| hereinafter set forth.

17 polymer of Example 1; FIGURE 2 is a copy of a photomicrograph of the prepolymer of Example 4; and FIGURE 3 is a copy of a photomicrograph of the prerl I 21 polymer of Example 8.

22 DETAILED DESCRIPTION 23 The spheroprotector as defined herein may be a monohalo- 24 i genated alkyl aluminum compound, but preferably it is a mixture of two alkyl aluminum compounds, one of them being a 26 i 26 I nonhalogenated alkyl aluminum compound, the other a monoha- 27 logenated alkyl aluminum compound, it being understood that 28 it may be a mixture of one or several nonhalogenated alkyl 29 aluminum compounds with one or several monohalogenated alkyl aluminum compounds. The alkyl radicals of the two compounds 31 of aluminum are selected from among those defined above; I 4 i i ~61 1 2 3 4 6 7 8 9 14 o o 16 .o a 0 1«7..

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"0° 21 22 23 24 26 27 28 29 31 ms, the formula depicted. It is prepared by mixing the two compounds under the known conditions suitable for the careful handling of these products, in proportions which satisfy the definition of the formula shown. A liquid mixture is obtained.

The alkyl aluminum compounds used to prepare the spheroprotector are known per se and they are selected from among those usually used as cocatalysts. They correspond to the general formulas AlRxHz and AlRxClyHz in which x z and x y z 3 and in which R is a linear, branched, or cyclic hydrocarbon radical containing 1 to 14 carbon atoms.

The following examples can be mentioned: Al(C4H9)3, Al(C. Al(C2H5)3, Al(C6HI3)3, A1(C 8

H

17 3 A1(C 2 H5) 2 H, Al(C 2

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5 2 C1, Al(C 6

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1 3) 2 C1 and AlCl(C 4

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9 iso) 2 The prepolymer obtained according to this process is used as the catalyst in the polymerization processes carried oit in suspension, in gaseous phase, in an agitated bed, or in a fluidized bed. According to the polymerization process intended, the prepolymerization carried out in the presence of the catalyst must be more or less intense. If the prepolymer is used as the cCtalyst in a suspension process, the degree of prepolymerization is preferably lower than 100, whereas in the case of a gas-phase process, the degree of prepolymerization is preferably higher than 50, and the prepolymer formed accounts for at most 10 wt.% of the final polymer.

The initial spherical olefin polymerization catalyst is a known product per se. It usually results from the combination of at least one transition metal coipound, a magnesium compound, a halogen and possibly an electron donor or

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I I i i i i ar n ulrrant 1 2 3 4 6 7 8 9 "#1 11 .2 13 1 t t t 7 816, t 19 21 22 24 o 26 I 27 28 29 31 electron acceptor and any other compound that can be used in these types of catalysts.

The transition metal compound is generally chosen from among the compounds of the formula Me(OR)nXmn, 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

-C

14 aliphatic or aromatic radical, and (iv) corresponds to the valency of the transition metal, and is a value lower than or equal to The transition metal compound particularly recommended is selected from among the titanium compounds having the formula Ti(OR)xCl4-x, where R has the same meaning as above, and the value of x is 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 lower than or equal to 2.

The electron donor or electron acceptor is a liquid or solid organic compound known to be part of the composition of these catalysts. The electron donor may be a monofunctional or polyfunctional compound advantageously selected from among the aliphatic or aromatic carboxylic acids and their alkyl esters, aliphatic or cyclic ethers, ketones, vinyl esters, acryl derivatives, particularly alkyl acrylates or alkyl methacrylates and silanes. Such compounds as methyl para-toluate, ethyl benzoate, ethyl acetate or butyl acetate, ethyl ether, ethyl para-anisate, dibutyl phthalate, t 1 dioctyl phthalate, diisobutyl phthalate, tetrahydrofuran, 2 dioxane, acetone, methyl isobutyl acetone, vinyl acetate, 3 methyl methacrylate and silanes such as phenyl triethoxysi- 4 lane and aromatic or aliphatic alkoxysilanes are especially suitable as electron donors.' 6 The electron acceptor is a Lewis acid, preferably 7 selected from among the aluminum chlorides boron 8 trifluoride, chloranil, or the alkyl aluminum compounds and 9 the alkyl magnesium compounds.

In a preferred mode of suspension prepolymerization with 1i agitation under turbulent conditions, the ethylene is prepolymerized optionally in the presence of a chain growth 13 limiting agent and/or a cocatalyst selected from among the 1'4 alkyl aluminum compounds known to be used for this purpose at a temperature between 00 and 110 0 C, preferably between 16 20 0 C and 60 0 C under a total absolute pressure lower than 1,7 bars essentially produced by an inert gas such as nitrogen.

SS18 To maximally preserve the initial spherical morphology of 19 the catalyst, it is recommended that the monomer feed into S, the reactor be controlled. A mean favorable feed rate is 21 lower than or equal to 500 N liters x h- 1 x g-1 of a cata- 22 lyst. The suspension prepolymerization is continued until a t r c 23 degree of prepolymerization suitable for the subsequent 24 polymerization process is reached, the degree of prepolymerization being defined by the ratio of the sum of the 26 weight of the prepolymer formed plus the weight of catalyst S 27 used to the weight of the catalyst used.

28 The spheroprotector is added to the components at any 29 phase of the prepolymerization. The spheroprotector may be introduced into the prepolymerization reaction medium. It 31 may also advantageously be added to the prepolymer after the 7

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21 22 S23 24 26 1 27 28 29 31 I -a~ t i. c. :.wi ~t r prepolymerization either directly into the reaction medium or to the prepolymer being stored in suspension or in the dry state under an inert gas.

In another preferred mode of suspension prepolymerization with agitation under turbulent conditions, the prepolymerization is carried out under the above-described conditions until a low degree of prepolymerization, preferably lower than 20 g polymer per gram of catalyst, is reached.

The prepolymer is isolated during this phase and then reused in a prepolymerization system in the gaseous phase so as to bring the low degree of polymerization to the degree of prepolymerization suitable for the subsequent polymereization process.

This phase of the gas-phase prepolymerization is carried out under the conditions which are usual for the gas-phase polymerization of ethylene. For example, the prepolymer having a low degree of polymerization can be combined in a reactor with a polyolefin batch having a mean grain size smaller than or equal to 3000 microns and preferably lower than or equal to 1000 microns, preferably in the presence of a cocatalyst as was defined above. After homogenization, the prepolymerization is continued by introducing monomer, preferably ethylene or a mixture of ethylene with butene.

The gas-phase prepolymerization is preferably carried out at a temperature between 3000 and 110 0 C under a total pressure lower than or equal to 20 bars.

This gas-phase prepolymerization is continued until a degree of prepolymerization suitable for the subsequent polymerization process is reached. To maximally preserve the initial spherical morphology of the catalyst, it is 8 it.

pp -I, 1 2 3 4 6 7 8 9 1 17 13 22 23 24 26 27 28 29 31 recommended that the monomer feed into the reactor be controlled. A favorable mean feed rate is lower than or equal to 500 N liters x h- 1 x g- 1 of catalyst.

As previously, the spheroprotector may be introduced during any phase of the prepolymerization process, or it may be added to the prepolymer being stored under an inert gas after the prepolymerization. If the spheroprotector is added to the prepolymer after the prepolymerization, the operation is carried out under an inert atmosphere either by mixing it to the prepolymer suspended in an inert liquid or by impregnating the prepolymer powder.

This spheroprotector is added in a preferred proportion of 500 to 4,000 ppm, calculated as the aluminum, to 1,000 to 25,000 ppm catalyst in the prepolymer having a degree of prepolymerization suitable for the subsequent polymerization process. The desired weight ratio of the aluminum to the catalyst is between 30 x 10-3 and 4.

If a chain growth limiting agent is used in the prepolymerization, hydrogen is preferably chosen.

The prepolymer obtained according to the present invention is generally stored in the dry form for subsequent use as a suspension polymerization catalyst or as a gas-phase polymerization catalyst for manufacturing linear polyethylene in powdered form with spherical morphology. This catalyst, in the form of prepolymer with spherical morphology, preserves its morphology during the polymerization and due to this property it makes it possible to obtain linear polyethylenes which also have a spherical morphology.

The catalyst treated according to the present invention is used as a classical catalyst in the suspension polymerization or gas-phase polymerization processes of olefins.

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12 13' 1'6 17 19 26 22 Z3., 24 26 S 27 28 29 Even though it can be used as such, it is also possible; to control the productivity, to additionally add a cocatalyst to the reaction medium. In this case, the cocatalyst may be a spheroprotector and especially the spheroprotector used to prepare the prepolymer.

The suspension polymerization process of ethylene is carried out in the usual manner in a liquid hydrocarbon medium at temperatures that may reach up to 120 0 C and under pressures that may reach up to 250 bars.

The gas-phase polymerization of ethylene in the presence of hydrogen and inert gas may be carried out in any reactor which permits gas-phase polymerization and especially in an agitated bed reactor or in a fluidized bed reactor. The conditions are known in the prior art. The temperature is, in general, below the melting point (Mp) of the polymer or copolymer to be synthesized and more particularly between 20 0 C and (Mp 5 0 C) and under a pressure at which the ethylene and possibly the other monomeric hydrocarbon present in the reactor are essentially in the vapor phase.

The present invention will be further described in connection with the following examples which are set forth for purposes of illustration only.

Preparation of Catalyst to be Treated The spherical catalyst treated according to the present invention was first prepared under the following conditions.

200 mM of n-butyl-butyl-sec.-magnesium and 33 mM of triethyl aluminum, both in respective molar solutions in heptane, are charged after drying and purging into a 1.5-liter glass reactor equipped with an agitator under a nitrogen atmosphere. The contact is maintained for one hour ;r.

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Ii~ 1 2 3 4 6 7 8 9 11 12," 1ii 1 16 17, 19, 21 22 S24 S26 27 28 29 at 80 0 C. 200 mM of diisoamyl ether having a temperature of 5000 are then added while stirring, after which 550 mM of tert.-butyl chloride are added within two hours, still at 5000. The solid obtained, which forms a support, is then filtered and washed twice with 500 cc heptane at 500C.

The solid is resuspended in 400 cc heptane having a temperature of 80°C, and 600 mM TiC1 4 are added within one hour. The catalyst obtained is filtered and washed twice with 400 cc heptane. The catalyst is dried at 70 0 C under nitrogen and stored under an inert atmosphere. This solid catalyst is in the form of perfectly spherical particles with a mean size of ca. 30 microns.

EXAMPLES 1 TO Preparation of the Prepolymer Into an 8.2 liter degassed and dry reactor are consecutively charged: 3 liters of dry hexane, (ii) 6 mM of pure trihexyl aluminum (THA), (iii) 3 g of the above spherical catalyst suspended in 75 cc hexane, (iv) hydrogen to an absolute pressure of 0.8 bar, and nitrogen to an absolute pressure of 4 bars, at 40 0 C under nitrogen while stirring at 400 rpm, after which ethylene is charged in at a flow rate of 30 N liters per hour for one hour, followed by admission at a flow rate of 60 N liters per hour for one hour, 130 N liters per hour for two hours and finally 200 N liters per hour for 50 minutes.

The admission of ethylene stopped, the total pressure drops from 6 bars (absolute) to 5 bars (absolute) in five 11 :~j i 10.

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minutes. The agitation is stopped for decanting and removing the supernatant liquid. After removal of the remaining solvent at 500C under nitrogen, the prepolymer powder is then extracted, and it is stored under an inert atmosphere.

650 g dry prepolymer powder with a spherical morphology are collected; it contains no agglomerates and its degree of prepolymerization is 218 g prepolymer per gram of catalyst, the mean diameter of the particles (dp 50) being 280 microns.

Preparation of the Spheroprotectors and the Catalyst in the Form of Active Preoolvmer

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Pure alkyl aluminum and a monochlorinated alkyl aluminum at a molar ratio that is given in Table I below for each experiment are charged into a Schlenk tube and agitated sheltered from light while stirring and blowing with nitrogen. The complexes thus prepared are deposited dropwise on the previous powdered prepolymer while stirring and under an inert atmosphere. The quantity deposited is such that the aluminum concentration on the prepolymer will be 2,000 ppm.

Copolymerization of 1-Butene and Ethylene The procedure is carried out in a predried 8.2-liter reactor in the presence of 10l g polyethylene powder, which is equipped with an agitator rotating at a speed of 400 rpm and maintained at 85 0 C during the entire polymerization.

1-Butene is injected into the reactor maintained under a vacuum of ca. 1.33 Pa until a pressure of 1 bar is reached, after which the spheroprotector identical to that used to prepare the prepolymer according to the present invention is charged in as the cocatalyst in a certain volume given in 21« 22 23 24 26 27 28 29

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fi F: P~ i I c I1 1 2 3 4 6 7 8 i11 S12 17.

18 Table I below in each experiment. The injection of 1-butene is completed and a pressure of 2.5 bar is reached.

Hydrogen and ethylene are then consecutively injected into the reactor to the respective absolute pressures of 1.5 bars and 13 bars to reach the hydrogen and ethylene partial pressures of 1.5 and 13 bars, respectively.

Then, x grams (given in Table I) of active prepolymer prepared in advance are charged into the reactor by admitting currents of nitrogen, continuing the injection of nitrogen until the total pressure inside the reactor reaches 21 bars. The pressure is maintained in the reactor at this value by injecting ethylene and 1-butene at a 1-butene to ethylene molar ratio equalling 0.0466.

After a reaction time of four hours, the polymerization is stopped by decompressing the reactor. The reactor is purged with nitrogen and is allowed to cool.

The remaining operating conditions and the results of the tests performed on the linear polyethylene obtained are given in Table I below, with Examples 1, 2, 7, 8, 9, and shown for comparison.

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I 4) '-s .4- TABLE I Ex- Weight Weight Nature Molar ratio Cocatalyst ample of of the of the of mono- (in cc) active corre- sphero- chlorinated pre- sponding protector alkyl Al to polymer catalyst nonhalogenat- (in g) (in a) ed alkyl Al 1 7 0.032 TEA _0.1 2 7 0.032 THA 0.2 3 7 0.032 TEA/DEAC 8.5 0.15 4 8.3 0.038 THA/DEAC 8.5 0.1 8.3 0.038 DEAC 0.1 6 7 0.032 THA/OHAC 8.5 0.2 7 7 0.032 THA/EADC 0.33 0.15 8 7 0.032 TEA/EADC 0.16 0.15 9 7 0.032 THA/EASC 0.055 0.15 7 0.032 THA/EA0C 4.25 0.15 r r -j<o i I c u- F ~i L -iN

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i i ii a ii i. I-a: p TABLE 1 (continued) Ex- Density Mor- of poly- Flow- Production Productivity ample phol- ethylene ability, in 4 hours in g PE/g of agy particles seconds catalyst <200 11 1 0.922. G 7 32 958 29,940 2 0.920 G 1.8 32 703 21,970 3 0.919 S 0.5 28 594 18,560 4 0.921 S 0.6 27 1,464 38,526 0.919 S 0 30 511 13,447 6 0.920 S 0.6 30 351 10,970 7 0.920 S/G 1 35 197 6,160 8 0.921 S5/G 2 33 394 12,310 9 G0.920 5 33 1,036 32,375 No Reaction 0 0 TEA triethyl aluminum THA trihexyl aluminum DEAC =-monochlorinated diethyl aluminum DHAC monochlorinated dihexyl aluminum EADC dichlorinated ethyl aluminum EASC. sesquichlorinated ethyl aluminum C granular S spherical The morphologies of the prepolymers of Examples 1, 4 and 8 are illustrated in the photomichrographs labelled as FIGURES 1, 2 and 3, respectively a e 4i- 2 0 00 0* 0 0000 @00 I- SI- 0 B0 A 00 L- i-

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1 2 3 4 6 7 8 9 141 16 17 18 19 21 22 23 24 26 27 28 29 EXAMPLE 11 Into an 8.2 liter degassed and drV reactor are consecutively charged: 3 liters of dry hexane, (ii) 10 mM of THA, (iii) 30 mM of DEAC, (iv) 10 cc of an 88 g/liter suspension of the previous spherical catalyst, corresponding to 0.88 g catalyst, and 0.5 bar hydrogen, at 40 0 C while stirring at 330 rpm.

A mixture of ethylene and butene containing 1.6 mol.% butene is then charged in within 15 minutes at a rate of 30 N liters per hour, after which the same mixture is charged in for three hours 15 minutes at a rate of 40 N liters per hours.

The charging of the monomers is stopped. The agitation is stopped for decanting and withdrawing the supernatant liquid.

After removal of the remaining solvent at 5000 under nitrogen, the prepolymer powder is then extracted, and it is dried under an inert atmosphere.

235 g dry prepolymer powder with a spherical morphology and without agglomerates are collected; its degree of prepolymerization is 267 g prepolymer per gram of catalyst with a mean particle diameter (dp 50) of 283 microns. The prepolymer has an aluminum content on the order of magnitude of 1,000 ppm.

The 1-butene and the ethylene are polymerized under the conditions of Examples 1 to 10 in the presence of the active prepolymer obtained.

The remaining operating conditions and the results of the tests performed on the linear polyethylene obtained are shown in Table II below.

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18 i 19 20 21 23 24 26 27 28 29 31 Table II Weight of active prepolymer, g Weight of catalyst, g Nature of the spheroprotector Molar ratio of monochlorinated alkyl Al to alkyl Al in the spheroprotector charged into the reactor Volume of THA/DEAC charged into the reactor Molar ratio of THA/DEAC to the prepolymer Density of the polyethylene obtained of particles 200 microns Morphology Flowability in seconds Output in grams in four hours Productivity in g of polyethylene per g of catalyst 0.037

THA/DEAC

0.15 cc pure 3 0.919 0.2 Spherical 28 740 20,000 EXAMPLE 12 Preparation of Active Prepolymer Into an 8.2 liter equipped with an agitation system are consecutively charged: 3 liters of dried hexane degassed with nitrogen, (ii) 29 mM tri-n-hexyl aluminum, (iii) 40 mM diethyl aluminum chloride, and (iv) nitrogen to a pressure of 3 bars, at 500C.

46 g catalyst in the form of a suspension in 0.5 liters of hexane are injected into the reactor. The following components are then added: hydrogen to a pressure of 0.5 bar, (ii) 100 N liters of ethylene per hour for one hour, an (iii) 200 N liters of ethylene per hour for one hour.

The product formed is dried by nitrogen stripping, and 387 g I -I 1 Iconsolidated catalyst with a degree of polymerization of 8.4 g PE 2 per g catalyst are collected under nitrogen.

3 20 g consolidated catalyst, 100 g polyethylene powder, and a 4 mixture of 3 mM DEAC with 9 mM of THA are mixed intimately under nitrogen in a glovebox.

6 This mixture is charged under nitrogen into an 8.2-liter 7 polymerization reactor which was dried and degassed in advance 8 and is equipped with an agitating system.

9 The following components are charged in consecutively at 5000 1 nitrogen to a pressure of 4 bars, 1 I (ii) hydrogen to a pressure of 0.8 bar, (iii) 50 N liters of ethylene per hour for 30 minutes, an 1 (iv) 100 N liters of ethylene per hour for three hours.

483 g powder, including 383 g prepolymer with a degree of 1 polymerization of 158 g PE per g of catalyst, are collected.

16, Copolymerization of 1-Butene with Ethylene 0 17, The prepolymer obtained is used under the polymerization con- 18 ditions described in Examples 1 to lb'. The operating conditions and the results of the tests performed on the linear polyethylene obtained are shown in Table III 21 below.

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0 0 0 o 12 0 150 16 r 000 18o 00 0 00 19 21 22 a 0

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Table III Weight of active prepolymer, g Weight of catalyst, g Nature of the spheroprotector Molar ratio of monochlorinated alkyl Al to alkyl Al in the spheroprotector charged into the reactor Volume of THA/DEAC charged into the reactor Molar ratio of THA/DEAC to the prepolymer Density of the polyethylene obtained of particles 200 microns Morphology Flowability in seconds Output in grams in four hours Productivity in g of polyethylene per g of catalyst 0.031

THA/DEAC

0.3 cc pure 2 0.920 0.6 Spherical 1,162 37,480 -;U1 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.

18

Claims (12)

1- L LIII-. l i; i_ 19 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A spherical catalyst capable of maintaining its spherical morphology during its use to polymerize olefins comprising prepolymerized ethylene polymerized at least partially in suspension in the presence of a spherical catalyst containing at least one transition metal, a magnesium compound, and a halogen and in the presence of an alkyl aluminum compound; the degree of prepolymerization selected being that suitable for the polymerization process in which the prepolymer will subsequently be used, *0 0* 0 said spherical catalyst used to polymerize said prepolymerized ethylene, and a spheroprotector having the formula: AIR' R" Cl H m n pq Sin which R' and R" can be the same or different and are C, to linear, branched, o or cyclic hydrocarbon radicals, 0.05 <p 1, 0 m 2.95, 0 n 2.95, and 0 q 1, with m n p q equal to 3 and present in a proportion of 500 to 4,000 ppm; calculated as the aluminium to 1,000 to 25,000 ppm catalyst. Z- i i: l LZ 4 20

2. The spherical catalyst of Claim 1 in which the spheroprotector is a mixture of at least one nonhalogenated alkyl aluminum compound and at least one monahalogenated alkyl aluminum compound.

3. The spherical catalyst of Claim 2 wherein the degree of polymerization of the ethylene is less than about grams polymer per gram of catalyst.

4. The spherical catalyst of Claim 3 wherein the degree of prepolymerization of ethylene is lower than 100 if o the catalyst is to be used in a suspension polymerization process or higher than 50 for a gas-phase polymerization S° process, without said prepolymer formed accounting for more Sthan about 10% of the final polymer in the latter case. 0 ot o 5. A process for making a spherical catalyst capable of maintaining its spherical morphology during its use to polymerize olefins; said spherical catalyst containing at least one transition metal, a magnesium compound, and a halogen, comprising h prepolymerizing ethylene; at least partially in suspension, in the presence of said spherical catalyst and in the presence of an alkyl aluminum compcund; the degree of polymerization selected being that suitable for the polymerization process in which the prepolymer will subsequently be used, and associating a spheroprotector with the components of step said spheroprotector having the formula: A1R' R" Cl H m n p I -21 21 in which R' and R" can be the same or different and are C 1 to C 14 linear, branched, or cyclic hydrocarbon radicals, 0.05 p 1, 0 m 2.95, 0 n 2.95, and 0 q 1, with m n p q equal to 3.

6. The process of Claim 5 wherein the spheroprotector is a mixture of at least one nonhalogenated alkyl aluminum compound with at least one nonhalogenated alkyl aluminum "a compound with at least one monohalogenated alkyl aluminum o* compound. 00 0 o o

7. The process of Claim 2 wherein the suspension pre- polymerization is carried out to a low degree of polymerization and that the prepolymer formed is used again in a gas-phase prepolymerization system so as to reach the degree of prepolymerization suitable for the polymerization oo. process in which the prepolymer will subsequently be used. 0oo0 J 8. The process of Claim 7 wherein the degree of polymerization is lower than about 10 g polymer per g of catalyst.

9. The process of Claim 8 wherein the degree of prepoylmerization is lower than 100 if the prepolymer must be used as a catalyst in a suspension polymerization process and higher than 50 for a gas-phase polymerization process, i without the prepolymer formed accounting for more than of the final polymer in the latter case, Z 7- R '1 I- 22 The process of Claim 7 wherein during the phase of gas-phase prepolymerization, the monomer is charged into the reactor at a mean flow rate equal to or lowe. than 500 N liters x h 1 x g- 1 of spherical catalyst.

11. The process of any of Claims 5 through 10 wherein during the suspension prepolymerization the monomer is charged into the reactor at a flow rate equal to or lower than 500 N liters x h 1 x g- l of spherical catalyst.

12. The process of any one of Claims 5 through wherein the spheroprotector is added in a proportion of 500 to 4,000 ppm; calculated as the aluminum to 1,000 to 25,000 ppm catalyst in the prepolymer having a degree of prepolymerization suitable for the polymerization process in Sa..o which the prepolymer will subsequently be used.

13. The process of any one of Claims 5 through wherein the weight ratio of the aluminum to the catalyst is between 30 x 10 3 and 4.

14. A process for polymerizing ethylene or a mixture of .o ethylene and an alpha-olefin to form a polymer having a spherical morphology comprising polymerizing said ethylene or mixture of ethylene and an alpha-olefin in suspension or in the gaseous phase in the presence of a spherical catalyst of any one of Claims 1 to 4. 9400

15. The process of Claim 14 wherein a cocatalyst is added to the reacti6n medium; said cocatalyst having the formula: A1R' R" C1 H m n pq in which R' and R" can be the same or different and are C, to C 14 linear, branched, or cyclic hydrocarbon radicals, 0 4. 23 0.05 p 1, 0 m 2.95, 0 n 2.95, and 0 q_ 1 with m n p q equal to 3. DATED this 17th day of April, 1990. ATOCHEM WATERMARK, PATENT TRADEMARK ATTORNEYS, 290 BURWOOD ROAD, HAWTHORN, VIC. 3122. AUSTRALIA. IAS:KJS:JZ (10:28) 0 00 0 0 9 0 a t t t c4