LU85724A1 - ETHYLENE POLYMERIZATION CATALYSTS FOR FORMING POLYMERS WITH LARGE MOLECULAR WEIGHT DISTRIBUTION - Google Patents

Description

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/ 1. "Ethylene polymerization catalysts to form polymers with a broad molecular weight distribution" The present invention relates to new catalysts! 5 polymerization lysers of ethylene and its mixtures with d> -olefins and / or diolefins. s | We know that in modern prepa-! polyolefin ration we managed to remove; the stage of purification in catalytic residues thanks to j w ί 10 the use of Ziegler-Katta catalytic systems, with high activity, supported on i magnesium halides having particular activation characteristics. In general, these systems give rise to polymers with a relatively narrow molecular weight distribution (DPM).

This characteristic, although positive in de | in many cases, exerts a negative influence in certain applications.

In fact, the distribution of molecular weights constitutes an important factor which regulates both the workability of the polymer and the quality and the physico-mechanical properties of the articles produced from it; in particular, a polymer with a narrow DPM causes, for example, roughness on the surface of the extruded article due to what is called "rupture of the molded product" which causes it to be damaged. makes it unsuitable for many applications such as

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the formaae by extrusion, the forming because sou * ffiacre or! i film extrusions. To overcome these incor.-

i 30 vénients and others still, it is necessary to widen I

! the distribution of molecular weights. The processes:

ί generally used are three drunk. I

! = '*! 1 The first consists in mixing two polymers having! different molecular weights, the second; 35 consists in carrying out the polymerization in several | steps to obtain molecular weights j | different and the third resides in the use j i i -2-: of a specific catalytic system.

In theory, this latter process is without any I

doubt the best and most economical, but in! in general, the catalytic systems known up to now give rise to one or both of the following drawbacks: low activity, that is to say low productivity expressed in grams of polymer per gram of catalyst (the component of the catalytic system containing the compound of the metal this transition), 10 and poor sensitivity to hydrogen used in ί | polymerization as a molecular weight regulator. ;

It has been proposed, in particular, to employ in the production of polyethylene having a large DPM a catalytic system comprising a Ti compound and a Zr compound, prepared by adopting a process of! particular and critical synthesis. ; "

As examples of these systems, one can quote: the system described in the German patent application DE 2,543,437 constituted by an aluminum alkyl and! By a catalytic component obtained by reacting metallic magnesium, an alcohol, tetra-alcoholated titanium, ZrCl. and an aluminum halide! 4 "; alkyl; the catalytic system described in: document DE 2,615,390 consisting of aluminum; alkyl and a catalytic component obtained by s.

reaction of Mg alcoholate (Mg ethylate) or this MgCl 4, of tetraalcoholated titanium or of TiCl 4, of tetraalcoholated zirconium or of ZrCl 4 and of a haro- ^ - | alkyl aluminum alloy; the catalytic system

: 30 proposed in document GB 2.015.548 constituted by I

ί; one aluminum alkyl and per year catalytic component | obtained by reaction of an aluminum dihaloenide j alkyl with a hyarocarbon solution of ethylate j ΐ of maanesium or MaCl „, a chiorcaicocaare of; i "^ t 3d titanium and a zirconium chloroalcoholate; the catalytic system employed according to the document j -3- ί ΕΡ Ο 087 100 and constituted by the use of triisobutyl aluminum and a catalytic component obtained by reaction d 'a silicon compound such as silicon tetraethylate, tetraalcoholate, titanium, zirconium tetraalcoholate, an organomagnesium compound and titanium tetrachloride preceded by treatment with aluminum dichloride' ethyl; finally the catalytic system described in; document US 4,399,053 in which the solid component i 10 is obtained by reaction of a tetra-alcoholated titanium, a zirconium compound, an organomagnesium compound j, ethyl aluminum dichloride !!!

j and diethyl zinc. I

! The common teaching of these patents consists in | ,; ί · j15 the fact that it is not possible to obtain a system j! A catalyst capable of producing ethylene polymers with a large DPM by direct reaction between the compound j of Ti, Zr and Mg by omitting the reaction with the alkyl aluminum halide. {j | 20 These catalysts have the disadvantage that they require expensive and complicated treatments in the preparation of the catalytic component, combined with the use of an aluminum halide μ f-,; minium alkyl which involves a heavy economic damage water-! ι V: h '

it is necessary to wash thoroughly with a hydrocarbon solvent.

z 5 improved the solid catalytic component in order to remove all traces of the alkyl aluminum halide which has not reacted and finally to destroy or recover this excess when the catalytic layer has been removed. separate. *!

We have now found, unexpectedly, that j; 30 - contrary to the teachings of technique i! known - it is possible to obtain these catalysts:: comprising a compound of Ti and Zr and ur. halogen compound of Mg, capable of producing these polymers j j <3'ethylene with a large DPM, without having to resort} | ï j35 to the reaction with the compounds halide of Al- 1 alkvle. ! | 'r' ....... · ’; j The catalysts according to the invention comprise j | the product of the reaction between:! j 1. an organometallic compound of Al j | 2. a solid catalytic component obtained by action: •) j 5 of contact between an anhydrous halide of magnesium; j sium (A), having an average dimension of j | crystallites less than 300 2, a compound: i halogen of titanium (B) and a halogen compound j f of zirconium (C), the ratio Mg / Ti + Zr in solid i 10 being between 2 and 50 and the ratio \

Zr / Ti between 0.2 and 8. j j

As the compound of 1., it is preferred to use trialkyl aluminum such as triethyl aluminum, triisobutyl aluminum, tri-n-hexyl aluminum, tri-n-octyl aluminum and the like. !

Particular preference is given to aluminum triisobutvle and aluminum tri-n-octvle it which can be chosen according to the yield / DPM compromise which one wishes to obtain (taking account of j " - 20 which the second gives DPM wider than the first, but lower yields) and which are recommended because, associated with the particular solid esta ,, lytic components of the invention, f '·! they make it possible to reduce or avoid altogether the undesirable [25 secondary reaction of hydrogenation of | ethylene to ethane, mistletoe reaction occurs nabi- j! tually with other catalog systems! i ** · * - * i j based on zirconium and. which manifests \ i i. -! by a difficulty in adjusting the molecular weight j. 30 and, consequently, the Melt Index (melt flow index i hot or grade). ; ; Trialkyl aluminum is usually added! | in the polymerization autoclave in the state of solu-! tion in the hvdrocarbon solvent, preferably! in an alionic hydrocarbon such as hexane: i ... normal, normal heotane, isobutans or compounds i

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analogues - in the case of suspension polymerization - in concentrations varying between 0.1 to 5 g / 1 day depending on the type of aluminum trialkyl. î i

The atomic ratio of aluminum to trialkyl and the sum of the transition metals present; T j I in the solid catalytic component, expressed by; : Al / (Ti + Zr), is greater than 1 and is generally between 30 and 1,000, preferably between 30 and 500. \

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j Four with regard to compounds A, B and C which j; 10 constitute the solid catalytic component of 2), t chlorides - that is to say MgCl2, TiCl ^ and ZrCl ^ - are particularly suitable. j

For the preparation of the catalytic component A, all the methods which make it possible to obtain MgCl 2 in active form can be used. The technique is already known and is described in particular in Italian patents 853,733 and 853,734. !

Preference is given to the grinding process in which the three compounds A, B and C are ground at the same time, or else two compounds are first ground together and then; with the third. )

The amount of TiCl 4, expressed in% by weight of Ti in the solid catalytic component, is included; between 0.1 and 6%, preferably between 0.5 and 5% and i! i '25 better still between 1 and 3.5 i. j

As already mentioned, the proportion of the three | t; compounds between them, expressed in a-tomies grams, is 1; represented by the Zr / Ti ratio between 0.2 and i I 8, preferably between 0.5 and 3, while the rsp- j J 30 port Mg / (Zr + Ti) is between 50 and 2, preferably between 20 and 2. î; As a practical measure of the magnitude of the dis-; l! • tribution of molecular weights (DPK), gold. useful for the ratio between the grades (melt index) MIF / MIE where; 35 MIF and MIE are respectively the grades measured at -190 ° C with an ooios of 21.6 and 2.16 kg (ASTM - I - - *! D 1238 method). If we compare these polymers having these MIE A i analogues, a polymer which has the ratio between grades J> --------------------------- ---- ï, - 6 - the highest has a wider DPM.

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The polymerization of ethylene and of its mixtures with K-olefins in the presence of the catalysts of the invention is carried out according to known methods. The polymerization can be carried out in the gas phase. j

or in the liquid phase in the presence of an inert hydrocarbon solvent7 at temperatures between 40 ° C.

o ^ and 150 C, under atmospheric pressure or higher oresion. In particular, ethylene is copolymerized with C 6 -C 8 -olefins such as butene-1 and 4 o-octene-1 in order to obtain copolymers having a density less than 0.94 g / cm; the molar content of 06-olefins in the copolymer is generally between 0.5 and 10%.

Example 1; ((

We install in a centrifugal mill of the type! RETSCH SI a porcelain jar with a capacity j of 300 cm ^, containing two porcelain spheres of jt 20 40 mm in diameter and two spheres of 26 mm in diameter, j, into which we introduce - in anhydrous nitrogen medium - \ '3 ~ i

10 g anhydrous magnesium chloride, 0.39 cm I

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TiCl ^ and 0.85 g of ZrCl ^ (type FLUKA Fract). j

We start the mill and leave it in I

I 25 operation for four hours at am-! | asbestos, at a speed of 350 revolutions per minute. At the end of this time, the jar is opened in the middle of anhydrous nitrogen and the solid catalytic component is taken. ! | 30 The polymerization test for ethylene is then carried out, which is carried out in a steel autoclave | | I 2.5 1 stainless steel fitted with a magnetic stirrer = j and a water-j i steam jacket thermoregulation system. i I 35 In the order indicated, we introduce in the other

| clave 1,000 cm of normal hexane, heated to 50 ° C

j about 0.5 g of triisobutyl aluminum '* ·' • is introduced! (TIBAL) (2.5 mmol equivalent) and 0.0176 g of. - 7 - solid catalytic component.

* The autoclave is closed, hydrogen is introduced at 5.5 kg / cm 2, it is immediately heated to 75 ° C. and the polymerization is started by bringing ethylene in continuous J 5 for three hours in such a manner that the

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i total pressure is constantly 14.0 kg / cm. j | At the end, the autoclave is degassed and cooled I to room temperature. The polymer is separated by; filtration and dried in an oven at 50 ° C under vacuum, i • i 10 for a few hours. 169 g of polymer are obtained. j

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] The results are shown in the table. | i! EXAMPLE 2 j j The polymerization as described in i j is repeated in example 1 with 0.0205 g of the same catalytic component j i as in this example, but using aluminum i! tri-n-octyl (TNQA) as an orcanometallic compound (cocatalyst). 182 g of polymer are obtained. The ; conditions and the results are mentioned in the table. -! > 20. A sample of the autoclave gas phase at the end of the polymerization was examined by gas chromatography; a concentration of about 53% ethylene and only about 0.4% ethane has been found, which is an indication of very low hydrogenation.

Example 3

A solid catalytic component is prepared according to i i the same methods as those described in example 1 j | but using 9.2 g of anhydrous MgCl2, 1.7 g of ZrCl4 and 0.40 cm3 of TiCl4 · un one uses 0.0207 g of the catalytic component thus i obtained for the polymerization of ethylene according to! modalities described in example i and or. obtains 130 g: of polymer. The conditions and results are; 35 mentioned in the table. j

Example 4 d

0.0230 g of the catalytic component of J is used

| j example 3 oour polymerize ethylene 1 ----------- 1 ------------------------- ---------------------------------------- - 8 - ”! as in Example 2, but with the partial pressures of hydrogen and ethylene indicated in the table.

71 g of polymer are obtained. > i

Example 5 | 5 0.0350 g of the catalytic component of ‘j is used in Example 3 to polymerize ethylene as in.

| Example 2, but at 80 ° C and under the conditions i

! written in the table. 125 g of polymer are obtained, j Example 6 S

0.0207 g of the catalytic component of Example 3 is used to polymerize ethylene as in Example 2, but at 85 ° C and under the conditions described in the table. 144 g of polymer are obtained. |

Comparison examples 1, 2, 3 d ..? · 15 9.0 g of anhydrous MgC ^ and 0.34 cm ^ of j ^ are ground

TiCl4 according to the modalities of Example 1. With this catalytic component not containing the compound of Zr, the ethylene is polymerized by adopting the modalities described in Example 1, but by applying the conditions indicated in the table. !

Comparison example 4: 3. ;

In a small 100 cm glass balloon fitted with a; agitator, 5 g of the solid catalyst component prepared in Example 1 are introduced in the nitrogen medium; i 3 25 is suspended with a solution formed of 20 cm 3! anhydrous normal hexane and 1.5 cm of ethyl aluminum dichloride. Stir and heat under reflux for two hours. After cooling to room temperature, the solid is separated by filtration on! t, a porous partition and washed several times with normal hexane until these chloride ions disappear; ! in the filtered iavaae solvent.

The residual solid is dried under vice at 50 ° C. for a few hours and 4.9 g of component are obtained; T · t j35 solid catalytic, light cse color. j 1 A Dolymerization test is carried out using.

i · * ·: 0.0219 g of this catalytic component and adopting them; i ----------------------------: ------ 1 "- 9 -; conditions described in the table. 154 g t * of polymer are obtained. !

The results given in the table indicate that the; treatment with ethyl aluminum dichloride does not increase the DPM, but rather reduces it and lowers the yield relative to the catalytic component based on Ti and Zr of Example 2 of the invention. ! t J____? Λ Λ * \! \ i \ j \ *! 3 \ j j \ i \ i \ "

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Claims (5)

3. Catalysts according to claim 2, in which the alkyl aluminum is triisobutyl aluminum. 4. Catalysts according to claim 2, wherein the alkyl aluminum is tri-n-octyl aluminum. ? 5. The catalysts according to claim 4, in; 1 lesauels the ratio in Grams atoms between the comoose, 0 <I 25 aluminum organometallic of 1) and the sum of i! : I transition metals present in the cata- comDosant! ioi lytique du 2), expressed by Al / (Ti + Zr}, is greater:; than 1 and is generally between 30 and 1,000, de j; preferably between 50 and 500. j „; 30 6. - Catalysts according to claim 1, in which the anhydrous halide this magnesium is MgCl ,. 7. Catalysts according to Claim 1, in which the halogenated titanium compound is TiCl 4. 8. Catalysts according to claim 1, in. Which halogenated zirconium compound is ZrCi ^. ; . 9. - Catalysts according to claim 1 for the polymerization of ethylene with one or more; | CE-olefins with 4 to 8 carbon atoms. i -------------------------------------------: 12. j 10. Catalysts according to claim 9 for · the polymerization of ethylene in mixture with j} butene-1. I j 11. Catalysts according to claim 9 for the polymerization of ethylene in admixture with octene-1. ^ ___ dd '/ ^ / / d. ; i ‘i | | i i {j i i i I i; ! ! ! ! , ί »% \ j» I - i t! ! , I! î i j i I! ! i! î i I! 1; i i