NO143351B - PROCEDURE FOR LOW PRESSURE POLYMERIZATION OF ETHYLENE, AND CATALYST FOR USING THE PROCEDURE - Google Patents

Description

The invention relates to a method for the low-pressure polymerization of ethylene, possibly together with small amounts of copolymerizable monomers, in the presence of a catalytic system.

The invention also relates to fixed catalytic complexes

for use in the method according to the invention.

It is known that for low-pressure polymerization of

olefins can use catalytic systems containing a derivative of a transition metal and an organometallic compound.

It is also known from the applicant's British patent 1 140 649

that as a derivative of the transition metal in the catalytic systems discussed above, a solid obtained by reacting a halogenated derivative of a transition metal and an oxygenated compound of a divalent metal can be used, e.g. magnesium.

The catalytic systems thus obtained are very active if they are compared to those where the halogenated derivative of a transition metal is used as it is.

In the applicant's Belgian patent specification 791 676, it is open-

bare catalytic systems which have a component obtained by the conversion of:

(a) an oxygen-containing organic compound of a metal, e.g.

a magnesium alcoholate or phenate

(b) an oxygen-containing organic compound of a transition metal (c) an aluminum halide.

When using these catalytic systems it is

possible to produce, with high catalytic activities, polyolefi-

ner that exhibits a high average molecular weight and very good impact resistance.

However, the production of the catalytic systems has

according to Belgian patent 791 676 certain disadvantages arising

from the use of the oxygen-containing organic compounds (a) which are unstable and/or subject to immediate hydrolysis. These compounds are also unusually dangerous to handle. They must therefore be stored and transported under inert conditions and handled with care. Furthermore, they are not commercially available. Moreover, the catalytic components that are produced with these compounds as starting material often have poor flow characteristics (they may be too fine-grained).

It has now been found that catalytic systems exhibiting the same advantages as those discussed above can be prepared without the use of an organic oxygen-containing compound (a) from readily available products.

Other advantages of the invention will be apparent from the following description.

The invention relates to a method for the low-pressure polymerization of ethylene, optionally together with small amounts of copolymerizable monomers, which is carried out in the presence of a catalytic system comprising an organic aluminum compound (component B) and a solid, catalytic complex (component A) containing magnesium, aluminum which originates from an aluminum halide and at least one metal (Tr) which originates from an oxygen-containing organic compound of the metal, the metal being selected from groups IVa, Va or Via in the periodic table.

The characteristic feature of the method according to the invention is that a catalytic system is used where the solid, catalytic complex (component A) is obtained by reaction of:

(1) metallic magnesium,

(2) a hydroxylated organic compound (hereinafter referred to as "compound (2)") selected from alcohols and hydrocarbylsilanols containing from 1 to 12 carbon atoms; (3) an oxygen-containing organic compound of said metal (Tr) (hereinafter referred to as "compound (3)")-, (4) an aluminum halide (hereinafter referred to as "compound (4)").

Metallic magnesium (1) used for the production of the catalytic component A can have any physical form suitable for chemical reaction, e.g. powder, granules, foils, ribbons or chips. The qualities that are usually used for carrying out organic reactions can be used in connection with the invention.

The compounds (2) are the monohydric and polyhydric alcohols containing from 1 to 12 and more preferably from 1 to 6 carbon atoms in the molecule. They may be saturated or unsaturated, straight chain or branched, aliphatic or alicyclic alcohols; they can also be aromatic and heterocyclic alcohols. Other compounds (2) are hydrocarbylsilanols having a number of carbon atoms corresponding to those indicated above.

Among the compounds (2) that can be used within the framework of the invention, these can be mentioned: - saturated or unsaturated straight-chain or branched, monohydric and polyhydric aliphatic alcohols, e.g. methanol, ethanol, butanol, isobutanol, isopentanol, octanol and the like; allyl alcohol; ethylene glycol;

substituted or unsubstituted monohydric and polyhydric aromatic alcohols, e.g. cyclopentanol, cyclohexanol and the like; 3-cyclopenten-1-ol;

substituted or unsubstituted monohydric and polyhydric aromatic alcohols, e.g. phenol, benzyl alcohol, o-, m- and p-cresols, xylenes; resorcinol, hydroquinone, etc.; a- and 3-naphthols,

beer.

- heterocyclic alcohols: e.g. 3-hydroxypiperidine;

alkyl and arylsilanols: e.g. trimethylsilanol, triphenylsilanol.

By an oxygen-containing organic compound (3) of a metal (Tr) from groups IV 3. , V 3. or VI cl in the periodic table, is meant any compound where an organic radical is linked to the metal (Tr) via oxygen; compounds containing metal halide bonds are excluded from the scope of the invention. However, compounds containing metal-oxygen bonds and condensed compounds containing sequences of metal-oxygen-metal bonds can also be used, provided they have at least one sequence of metal-oxygen-organic radical bonds per molecule.

Among the metals (Tr), titanium, zirconium, vanadium and chromium are preferred. The best results are not achieved with titanium. The organic radicals which are linked to the metal (Tr) via oxygen can be of any type. They may generally comprise from 1 to 18 carbon atoms and preferably have 1 to 10 carbon atoms. The best results are obtained when they contain 1 to 6 carbon atoms. The organic radicals are preferably hydrocarbon radicals, and more particularly they are preferably alkyl radicals (unbranched or branched), cycloalkyl, arylalkylraryl or alkylaryl radicals.

The compounds (3) can be represented by the general formula DTr 0 x /(OR') y ] where Tr is a metal from group IV ci , V3. or VI cli the periodic table, where R<1> is an organic radical as defined above, where x<1> and y_ are any number such that x'^ 0 and y_>0 and are compatible with the valence of the metal Tr , and where m is an integer. It is preferable to use compounds (3) where x' is such that 0 < x'< 1 and m is such that l_<m < 6.

Among the compounds (3) which can be used within the framework of the invention, the following can be mentioned: - alkoxides, e.g. Ti(0C2H ^ , Ti (OnC^)4, Ti(0nC4Hg)4, Ti(0iC3H?)4, Ti(0-tert-C4H9)4! Ti(0iC4Hg)4, V(OiC3H?)4 and Zr( OiC3H7)4 - phenates, e.g. Ti(OC6H5)4 - oxy-oxides, e.g. VOtOiCgH.,)^ ;

- condensed alkoxides, e.g. Ti2O(OiC3H7)^ ; and

- enolates, e.g. titanium acetylacetonate.

The use of compounds (3) which contain several different organic radicals also falls within the scope of the invention

frame, similar to the use of several different oxygen-containing organic compounds of one and the same metal, and the use of a number of oxygen-containing organic compounds of different metals.

The compound (4) used for the production of catalytic component A is an aluminum halide. The aluminum halide that is generally used as compound (4) can be represented by the formula AIR X where:

x 3-x

R is a hydrocarbon radical containing 1 to 20 carbon atoms and preferably 1 to 6 carbon atoms, X is a halogen, and x is any number such that 0 £ x < 3. Preferably R is a saturated aliphatic radical, a saturated alicyclic radical or an aromatic radical. The best results are obtained when R is an alkyl group, X represents chlorine and 0 < x < 2.

As examples of aluminum halides that can be used

in accordance with the invention, mention may be made of AlCl^/ Al(CH3)2Cl, A1(<C>2H5)2C1, A1(C2H5)C12, A1(C3H7)2F, Al (iC^) 2C1, Al2 (C^) 3C13 .

According to one embodiment of the invention, it is not necessary that compound (4) is a single compound. In particular, one compound of formula A1X3 and one compound of formula A1R3 can also be used in combination or successively.

The solid complex forming the catalytic component A can be prepared according to different methods. Each compound (2)(3) and (4) can be used, when the operating conditions are suitable, in the solid state, in the liquid state, in the form of a solution or in the form of a vapor or a gas.

It is preferable to prepare catalytic component

A in a liquid medium, if desired in the presence of an inert diluent, which is preferably a diluent1 in which at least one of the reactants is soluble. Practically everyone. the solvents normally used in preparative organic chemistry can be used. However, it is preferable to use alkanes and cycloalkanes whose molecules contain from 4 to 20 carbon atoms, e.g. isobutane, normal pentane, normal hexane, cyclohexane, methylcyclohexane or the dodecanes. When a diluent is used, it is preferred that the total concentration of the dissolved reactant(s) is greater than 5% by weight and preferably greater

than 20 percent by weight, calculated on the diluent.

As far as the order of addition of the reactants is concerned, they are preferably added to the magnesium in the following order: first compound (2), then compound (3) and finally compound (4) or compounds (2) and (3) together and then compound (4) or compound (2) and then compounds (3) and (4) together.

According to a preferred method, magnesium is mixed with compounds (2) and (3), and the mixture is heated and aged. The heating and aging are preferably carried out under reflux cooling and/or at elevated pressure, the reaction medium being liquid. When the reactants are solid, they are preferably suspended or dissolved in a diluent as indicated above, or melted if this does not cause them to decompose.

If one of the reactants is liquid at the heating temperature, it can be used as a reaction medium. In any case, the mixing can be carried out in the presence of a liquid diluent. The heating temperature depends on the nature of the compounds (2) and (3) and is preferably chosen between 30 and 150°C. The duration of the heating and aging is not critical and is usually between 30 minutes and 15 hours, preferably between 1 and 6 hours.

When carrying out the above-mentioned method, the heating and aging reaction can be accelerated by the addition of one or more substances well known in the field, which are able to react with metallic magnesium or form an adduct with it, e.g. iodine, mercuric chloride, xylene and alkyl halides, and polar substances, e.g. organic acid esters and organic acids.

After completion of the heating and aging reaction, low-boiling substances, if still present, are preferably removed by distillation. In general, the aged product thus obtained is a homogeneous, liquid substance. The aged product thus obtained is then brought into contact with compound (4), preferably in the presence of an inert diluent of the nature specified above. The duration and temperature of this reaction are not critical; the temperature is usually lower than 200°C, preferably in the range 0-60°C. The duration is usually between 1 and 8 hours, preferably between 2 and 4 hours.

When a compound of formula AlX^ is successively used

(compound 4 a) and a compound of formula A1R3 (compound 4 b) for this reaction, as explained above, the reaction conditions are the same as when a simple compound (4) is used. However, the first reaction with compound (4a) is then generally carried out under reflux for 30 minutes up to 5 hours, preferably 1 to 3 hours.

It is recommended that the presence of oxygen and water be carefully eliminated during the manufacture of component (A).

The rate of addition of the reactants is also not critical. It is advisable that it is not so large as to cause a sudden heating of the reaction medium due to too rapid a reaction. The reaction can be carried out continuously or discontinuously.

Finally, it often happens in practice that connection (3)

when kept in a liquid state, is capable of dissolving the product obtained by reaction of magnesium with compound (2). The use of an inert diluent can then be avoided. Nevertheless, when this is not the case and since it is preferred that the aged product is brought into contact with compound (4) in a liquid state, it is also possible to use another oxygen-containing organic compound of a metal from group IIIb or IVb (preferably silicon, and more especially aluminum) which is liquid and which is able to dissolve the first, i.e. the oxygen-containing organic compound of a metal (Tr) (compound (3)). As far as the structure of the other oxygen-containing organic compound is concerned, it can be defined in the same way as compound (3) and will hereinafter be referred to as compound (5). Specific examples of oxygen-containing organic compounds useful as compounds (5) are AltOC^H^)^ and Si(OC 4 Hg) 4 .

The amounts of the compounds (2)(3) and (4) which are preferably used must now be stated.

The total amounts of the metal magnesium (1) and compound (2) are generally such that the ratio Mg/compound (2) is lower than 1 g-at (gram atom) per mol, and preferably lower than 0.5 g-at/mol. The best results are obtained when this ratio is close to 0.3 g-at/mol.

The total amount of compound (3) is such that the atomic ratio Mg/metal (Tr) lies between 20 and 0.05 g-at/g-at, preferably between 5 and 0.2 g-at/g-at. The best results are obtained when this atomic ratio is close to 0.5.

Compound (4) is generally used in such an amount that the atomic ratio between magnesium and aluminum in compound (4) is between 10 and 0.01 g-at/g-at, preferably between 1 and 0.05 g-at/g-at . The best results are obtained when this atomic ratio is close to 0.2. However, when the preparation of catalytic component A is carried out by successively using a compound (4a) and a compound (4b), the atomic ratio of magnesium to aluminum for compound (4a) is preferably between 4 and 0.02 g-at/g- that and connection (4 b), are then used,

wherein the atomic ratio between aluminum in compound (4 b) and metal (Tr) in compound (3) is preferably higher than 0.3o g-at/g-at.

Finally, when using a compound (5) as defined above, the amounts of magnesium and of compound (5) to be used are preferably such that the ratio between the amount of magnesium and the amount of compound (5) is between 0.01 and 100 g - that per mol. Preferably, this ratio is between 0.1 and 10 g-at per mol. The best results have been achieved when the ratio is between 0.5 and 1.5 g-at per mol.

The catalytic components A produced according to the invention are solid. They are insoluble in alkanes and cycloalkanes, which can be used as diluents. They can be used during polymerization in the form in which they are obtained, without separation from the reaction medium. When the reaction medium is liquid, it is possible, if desired, to separate them by e.g. filtration, decantation or centrifugation.

After separation, the catalytic components A can be washed to remove excess reactants that can still

cling to them. For this wash, any inert diluent can be used, e.g. any of them that can be used as components in the reaction medium, e.g. alkanes and cycloalkanes. After washing, the catalytic complexes can also be dried, e.g. by passing a stream of dry nitrogen over them, or they can be dried in a vacuum.

The mechanism of the formation of catalytic components A

which is produced according to the invention, is not fully understood.

The elemental analysis of the catalytic complexes after separation and washing shows that they are chemically combined complexes, i.e. products of chemical reactions, and not the result of pure mixing or adsorption phenomena.

After washing, the catalytic component A can be stored in powder form. Two important advantages of the aforementioned catalytic components are their very good storage stability and the limited loss of metal (Tr) during the possible washing step. When the metal (Tr) is titanium, generally more than 80 percent by weight remains combined in the catalytic component A. Accordingly, the cleaning treatment of the washing liquids is greatly reduced.

The catalytic components A, the exact nature of which is not fully understood, contain variable amounts of magnesium, metal (Tr), aluminum and halogen. Quite often they contain per kg 10-150 g magnesium, 20-250 g metal (Tr), more than 10 g aluminum and 200-700 g halogen. They are characterized by a high specific surface area, often over 50 m 2/g and which can be as high as 300-400 m 2/g.

The catalytic systems according to the invention also comprise an organoaluminum compound (component B) which serves as an activator.

It is possible to use fully alkylated compounds whose alkyl chain has 1-20 carbon atoms and which is unbranched or branched, e.g. trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum or tri-n-decylaluminum. However, it is preferred to use trialkyl aluminum whose alkyl chains have 1-10 carbon atoms and are unbranched or branched.

It is also possible to use alkyl aluminum hydrides where the alkyl radicals also contain 1 - 20 carbon atoms, e.g. di-isobutyl aluminum hydride, and alkyl aluminum halides where the alkyl radicals again contain 1-20 carbon atoms, e.g. ethylaluminum sesquichloride, diethylaluminum chloride or diisobutylaluminum chloride.

Finally, it is also possible to use organoaluminum compounds obtained by reacting trialkylaluminum or dialkylaluminum hydrides whose alkyl radicals have 1-20 carbon atoms, with diolefins having 4-20 carbon atoms, and more particularly the compounds known as isoprenyl aluminum compounds.

The polymerization can be carried out in any suitable manner. More particularly, it can be carried out in solution or suspension, in a solvent or hydrocarbon diluent, or in gas phase. For execution in solution or suspension, solvents or diluents similar to those that can be used in the production of the catalytic component A can be used. These are preferably alkanes or cycloalkanes, e.g. butane, pentane, hexane, heptane, cyclohexane, methylcyclohexane or mixtures thereof. It is also possible to carry out the polymerization in the monomer or one of the monomers if this is kept in a liquid state.

The polymerization pressure can generally lie between atmospheric pressure and 100 kg/cm 2 and is preferably 1.5 - 50 kg/cm 2 . The temperature can generally be between 20 - 200°C. The polymerization can be carried out in batch or continuously.

Catalytic components A and B can be added to the polymerization ionic medium separately. Instead, however, if desired, they can be brought into contact, at a temperature between -40 and 80° C, for a period of up to 2 hours before they are introduced into the polymerization reactor. It is also possible to bring them into contact with each other in a number of steps, or one part of the organometallic compound (component B) can be added before introduction into the reactor, or one can use a number of different components B.

The total amount of component B used is not critical. It can generally lie between 0.02 and 50 millimoles per dm 3 of the solvent, diluent or reactor volume, and is preferably between 0.5 and 5 millimol per DM 3.

The amount of the catalytic component A used can

, preferably determined according to the transition metal content (Tr)

in the. It can generally be such that the concentration is between 0.001 and 2.5 and preferably between 0.005 and 1.5 milligram atoms of metal per dm 3 of the solvent, diluent or reactor volume.

The ratio between the amounts of components A and B is not critical either. It can generally be the case that the ratio between organometallic compound and transition metal, expressed in mol/gram atom, is greater than 1, preferably greater than 10.

The average molecular weight, indicated by the melting index of the polymers as produced by a method according to the invention, can be controlled by adding to the polymerization medium one or more molecular weight-modifying needles, e.g. hydrogen, diethylzinc or diethylcadmium, an alcohol or carbon dioxide.

The specific weight of the homopolymers produced by a method according to the invention can also be controlled by adding to the polymerization medium an alkoxide of a metal from groups IV cl or V cl of the periodic table. Thus, it is possible to produce polyethylenes with a specific weight that lies between the value for the polyethylenes produced by a

high pressure process and the values for the classic HD polyethylenes.

Of the alkoxides which are suitable for this specific weight regulation, those of titanium and vanadium whose alkoxy radicals contain 1 to 20 carbon atoms each can be referred to as particularly effective. These alkoxides include Ti(OCH3)4, Ti(OC2H5)4,

Ti [OCH 2 CH(CH 3 ) 2 ] 4 , Ti(OC 8 H 17 ) 4 and Ti (OC-^H^) ^ .

The method according to the invention makes it possible to produce polyethylene with productivities as high as those found in the catalytic systems described in BE-PS 791 676. In the homopolymerisation of ethylene, the productivity, expressed in grams of polyethylene per grams of catalytic complex, usually 10,000 and in many cases 20,000. The activity, calculated on the quantity of the transition metal present in the catalytic component A, is also quite high. In the homopolymerisation of ethylene, the activity, expressed in grams of polyethylene per grams of transition metal, usually 50,000 and in many cases 100,000. In the most favorable cases it is greater than 1,000,000.

For this reason, the content of catalytic residues in polymers produced by a method according to the invention can be unusually low. More specifically, the residual transition metal content may be unusually low. Now, it is the derivatives of the transition metal that are particularly troublesome in catalytic residues, because of certain colored complexes which they form with the phenolic antioxidants commonly incorporated into polyolefin products.

It is for this reason that in the well-known processes for the polymerization of olefins by means of catalysts containing a transition metal compound, the polymers must be purified of the catalytic residues which they contain, e.g. by treatment with alcohol. In the method according to the invention, the content of bothersome residues is so low that it is possible to omit the cleaning treatment, which is an expensive operation seen against the background of the raw materials and the energy it needs, and the significant capital investments that it entails.

Like those produced according to Belgian patent

791 676, polyethylene produced according to the present invention is characterized by a remarkably high impact strength. Thus, homopolymers of ethylene which have been produced by a method according to the invention, with a melt index of approx. 5, possessing an impact resistance, measured by the Izod test of approximately 10 kg cm/cm notch. Polyethylene with the same melt index, which is produced using known high-activity catalytic systems, does not have an impact strength (measured in the same test) greater than approx. 6 kg cm/cm notch.

Polyethylene obtained by the method according to

to the invention, can generally be used in any known casting technique. Thus, it can be used in extrusion, injection molding, extrusion blow molding or in calendering processes. It can be advantageously used for purposes where good impact resistance is required, and especially for the production of crates, rammers, pallets and bottles.

Finally, the catalytic system according to the invention is excellent as a catalyst for the production of polymers suitable for blow molding. In general, polymers are required for blow molding purposes that have a wide molecular weight distribution range. The molecular weight distribution range is approximately represented by the ratio of the high load melt index (HLMI), measured under condition E according to ASTM-D-1238) to the melt index (MI, measured under condition F according to ASTM D-12 38), namely HLMI/ The MI value. When the catalysts according to the invention are used, a polymer for which this HLM1/MI value is above 70, which is suitable for blow molding, can also be produced. Thus, it has been shown that the catalyst according to the invention is suitable for the production not only of polymers for injection molding, but also polymers for blow molding.

Briefly, the process according to the invention leads, in the same economic way, to polymers which exhibit the same basic advantages as those obtained according to Belgian patent 791 676. The outstanding technical advantage of the present invention is that the catalytic systems according to the invention are produced in a simpler way and that one makes use of a complex magnesium compound which requires strict control or maintenance during manufacture, handling and quality standards. Furthermore, the reaction between magnesium and compounds (2) and (3) is often exothermic. The reaction heat can thus be recovered so that energy costs can be saved in the other steps in the production of component A. On the other hand, the mixture of the magnesium compound and the transition metal compound must generally be heated at high temperatures in the method according to Belgian patent 791 676.

The following examples are intended to illustrate the invention.

Examples 1 to 3

Preparation of the solid catalytic complexes (components A)

(Examples added 3a)

Example la

A 1000 ml flask fitted with a stirrer was filled

with 21 g (0.45 mol) of dehydrated ethanol; 3.7 g (0.15 mol),

of metallic magnesium powder and (102 g (0.3 mol) titanium tetrabutylate [Ti (0-n-C^Hg)4], hl' B tj_^3P+.4.. The mixture was agitated under reflux at 130°C for 2 hours in the absence of water or water vapor, while removing hydrogen formed by the reaction. Low-boiling substances were distilled at 90° C. and, removed from the reaction mixture. The remaining mixture (1) was cooled to 60° C. Then 200 ml h- hexane added to the mixture and 95 g (0.75 mol) of ethyl aluminum dichloride [Al(C2H,_)Cl2] added dropwise to the mixture over a period of 4 hours at 45°C, after which the reaction mixture was agitated at 60°C for 1 hour. Then n-hexane was added to the reaction product, and this was washed by decanting, i.e. the washing was carried out by repeating the agitation steps for the mixture, it was allowed to stand, the supernatant liquid was removed and fresh n-hexane was added to the residue , until no chlorine ion was detected in the supernatant.The volume of the resulting suspension n was adjusted to 500 ml

by addition of n-hexane.

When the titanium content of the suspension thus formed was determined with hydrogen by means of a colorimeter according to the method described in G.O. Muller, Praktikum der Quanti-tativen Chemische Analyze (1957), p. 243, it was found that 10 ml of the suspension contained 5.0 millimoles of the titanium compound.

The supernatant liquid in this suspension was then removed, and the n-hexane was removed by drying the residue in the presence of nitrogen to obtain 72 g of a reddish brown powder in which the titanium content was found to be approx. 15.9 percent by weight.

Example 2a

The procedure was the same as in example la with the exception of the following: The remaining mixture (1), cooled to 60°C, was diluted with 400 ml of n-hexane. Then 100 g (0.75 mol) of aluminum chloride (AlCl3) was added gradually to what was in the flask, so that the temperature remained below 50°C. Afterwards, the temperature was raised and the reaction mixture (2) was stirred under reflux at 72°C for 2 hours. The product was then washed and dried as in example la. 20 g of a white powder was recovered, and the titanium content in this was 4.30% by weight.

Example 3a

The procedure from example 2a was repeated, and after

that the reaction mixture (2) was stirred under reflux at 72°C for 2 hours, it was cooled and 44 g (0.385 mol) of triethylaluminum [A1(C_H ) ] was added dropwise at 45°C during

^ D J Q

4 hours. After stirring the mixture for 1 hour at 60 C, the product was washed and dried as indicated in ex., la. 77 g of a light brown powder was recovered, and the titanium content in this was 18.6% by weight.

Polymerization of ethylene (Examples 1b to 3b)

Example lb

The internal atmosphere in a stainless steel autoclave

steel with an internal capacity of 1600 cm 3 , equipped with an electromagnetic stirrer, was sufficiently replaced with nitrogen, and 1 1 n-hexane was placed in the autoclave and the internal temperature adjusted to 90°C. Subsequently, 0.98 g (5 millimoles) of cri-isobutyl aluminum [AMiC^Hg) and 20 mg of the dry, powdery catalyst obtained in Example 1a above were placed in the autoclave.

The pressure inside the autoclave was adjusted to one atmosphere, and hydrogen under a partial pressure of 7 atmospheres and ethylene under a partial pressure of 12 atmospheres were introduced into the autoclave. The polymerization was carried out under the supply of ethylene, so that the total pressure in the autoclave was kept at 20 atmospheres. After 2 hours, the supply of ethylene was stopped, and the unreacted gas was released from the autoclave. The resulting polyethylene was removed from the autoclave, separated from the solvent by filtration and dried. 330 g of a polyethylene (PE) with a melt index (MI) of 5.8 g/10 min, an apparent density (AD) of 0.39 g/cm 3 , a density (D) of 0.965 g were thus obtained /cm 3 and an Izod impact strength (IZ) of 13 kg.cm/cm.

Example 2b

The procedure from example 1b was repeated with the exception of: - an autoclave with 2.2 1 internal capacity was used; - 0.91 g (4.6 mmol) Al(iC4Hg)3 and 6.9 mg of dry powdery catalytic component A obtained according to example 2a above;

- the hydrogen partial pressure was 6.7 atmospheres, and a total pressure of 20 atmospheres was maintained for 2 hours; 161 g of PK, characterized by an MI of 2.5 g/10 min, and an IZ of 25.2 kg-cm/cm were recovered.

Yield of PE/mg Ti: 540 g

HLMl/Ml ratio for PE : 28.

Example 3b

The procedure from example 2b was repeated with 0.90 g (4.5 mmol) of Al(iBu) 3 and 24.9 mg of dry, powdered catalytic component A obtained according to example 3a. The results were as follows: 258 g PE with MI = 8.3 g/10 min and AD = 0.35 g/cm 3 , D = 0.964 g/cm 3 and IZ = 5.9 kg.cm/cm .

Yield of PE/mg Ti: 56 g

HLMl/MI ratio for PE : 29

Example 4

Preparation of catalytic component A (Example 4a)

The procedure from example la was repeated with

8.6 g (0.27 mol) methanol;

1.95 g (0.08 mol) powdered magnesium;

109 g (0.32 mol) Ti(O-nC4Hg)4;

0.21 g of iodine. The mixture was stirred under reflux at 120°C for 3 hours, treated as in Example 1a (except that 220 ml of n-hexane and 51 g (0.40 mol) Al(C2H5)Cl2 were used), washed and dried. 71 g of a yellow-brown powder was recovered, the titanium content of which was 16.7% by weight.

Polymerization of ethylene (Example 4b)

The ethylene was polymerized according to the procedure in example 1b, with 22 mg of the dry, powdered catalytic component from example 4a. 350 g PE with MI = 1.5 g/10 min, AD =

0.40 g/cm <3> , D = 0.964 g/cm <3> and IZ = 48 kg.cm/cm.

Example 5

The solid catalytic component A was prepared in the same manner as in Example la with the following exceptions: n-butanol was used instead of ethanol (0.45 mol) and 0.4 g of iodine was added to the mixture which was agitated under reflux at 120° C for 3 hours. The distillation was carried out at 140°C.

The brown powder finally recovered in an amount of 81 g had a titanium content of 15.5% by weight.

The polymerization conditions were the same as in Example 1b. 310 g of PE were obtained with MI = 6 g/10 min, AD = 0.39 g/cm 3 , D = 0.965 g/cm<3> and IZ = 10 kg cm/cm.

Example 6

The changes in activity after different periods of time

was investigated with respect to the catalytic components A which were prepared according to examples 1a and 5.

The catalytic components A were stored under conditions as indicated in Table 1 below, for a prescribed period of time, and using the stored catalyst, while the homopolymerization of ethylene was carried out under the same conditions as described in Example 1b.

The results are shown in table 1.

The results shown in table 1 show that the catalytic systems according to the invention have very good activity which does not decrease during storage.

Examples 7 to 11

Using the catalytic components obtained according to Examples 1a to 3a and 5, ethylene was copolymerized at 80°C for 2 hours with propylene or butene-1 fed in the amounts indicated in Table 3 under the polymerization conditions which are indicated in Example 3b, to obtain results shown in Table 2.

Examples 12 to 29

Catalytic components A were prepared as described in examples 2a and 3a using compounds (2) other than ethanol. Specific conditions for the preparation are shown in table 3 below.

In the same manner as described in Example 2b, ethylene was polymerized for two hours with triethylaluminum and dry, powdery catalytic components A, obtained in Examples 12a to 29a.

Polymerization conditions and results are shown in Table 4.

Examples 30 to 32

The production of each of the catalytic components

according to Examples 1a to 3a was repeated, but using titanium isobutylate instead of titanium n-butylate. The respective compounds were obtained thus

Example 30a: 63 g of a reddish brown powder, the titanium content of which was 16.3% by weight (prepared according to

example la)

Example 31a: 21g of catalytic complex, the titanium content of which was 4.0% by weight (prepared according to Example 2a, with the exception of 66g (0.49 mol) AlCl^ was

added)

Example 32a: 72 g of catalytic complex, the titanium content of which was 17.9% by weight (prepared according to Example 3a, with the exception of 66 g (0.49 mol) AlCl₂ and 29 g of A1(C2H5)3 were used.

Polymerization tests for ethylene were carried out under the general conditions indicated in example 1b with these catalytic complexes, and the results reproduced in table 5 were obtained under the specific conditions indicated:

Examples 33 and 34.

The procedure from example 1a was repeated with the exception of: - 0.37 g of iodine dissolved in 2 ml of ethanol was added to the reactants. The brown catalytic complex obtained (80) contained

15.1% by weight titanium (example 33a)

- the remaining mixture (1) from example la was cooled to 45°C, and 181 g (1.5 mol) Al(C2H5)2Cl were added. The black-brown catalytic complex that was obtained (76 g) contained 18.2 weight percent titanium (Example 34a)

Polymerization tests for ethylene were carried out under the general conditions indicated in example 1b with these catalytic complexes, and the results reproduced in table 6 were obtained under the specific conditions indicated:

Examples 35 to 40

The procedure from Example 4a was repeated with compounds (2) other than methanol and under specific conditions given in Table 7 below, as well as the titanium content and the amount of the recovered catalytic complexes.

In the same manner as described in Example ib, ethylene was polymerized for 2 hours with triisobutylaluminum (Al(iCAHQ) as component B and dry, powdery catalytic components 3A obtained in Examples 35a - 40a. Specific polymerization conditions and results are shown in Table 8.

Comparative example 41.

The procedure from example 34a was repeated with the exception that the remaining mixture (1) was cooled to 60°C

and diluted with 200 ml n-hexane, 85.5 g (0.75 mol) A1(C2H5)3

was added dropwise at 45° C. for 4 hours. A homogeneous liquid with a black-brown color was obtained, which was used in a polymerization experiment as described in example 1b.

When Al(C2Hj.)3 was used as component B, no polymer was formed, and when Al(C2H(.)Cl2 was used as component B, polymerization was allowed to proceed, but the yield was as low as 3,700 parts by weight of the polymer per part by weight of titanium atom in the catalytic composite product This shows that when using reactants (4) and components B which are free of chlorine, the catalytic activity is practically negligible.

Example 42.

About. lg of pure magnesium in the form of chips was heated together with 30 g of titanium tetrabutylate, 24.3 g

triphenylsilanol and 4.5 g of butyl chloride.

Some iodine crystals were added and the mixture was kept at a temperature of approx. 150°C for a period of 270 minutes. The atomic ratio Mg/Ti for the mixture was approx. 0.5.

To the cooled mixture was added 70 ml of a 50% by weight solution in hexane of ethyl aluminum dichloride from SCHERING (Mg/Al atomic ratio: approx. 0.2). An exothermic reaction occurred and the mixture was kept at ambient temperature for half an hour.

The catalytic solid component was obtained, was separated from, washed with hexane and dried. Elemental analyzes showed that it contained: 166 g/kg titanium, 343 g/kg chlorine, 47 g/kg magnesium, 32 g/kg aluminum and 37 g/kg silicon.

A polymerization test was carried out with the aforementioned component under the following conditions:

- autoclave: 1.5 litres

- hexane: 0.5 litres

- amount of catalytic solid: 6 mg

- nature and amount of component B: triisobutylaluminium: 200 mg

- temperature: 85°C

- duration: 1 hour

- ethylene partial pressure: 10 kg/cm

- hydrogen partial pressure: 4 kg/cm<2>

About. 108 g of PE was recovered, whose MI was 0.38. This re-

presents a catalytic productivity of 1,800 g PE/g cata-

lysator x hour x atm. C2HA and a specific activity of 10,800 g PE/g Ti x h x atm. C^^. HLMI was 9.85, ratio HLMl/MI was 26;

The AD and D values were 0.30 and 0.960 g/cm<3> respectively.

Example 43.

About. 4.86 g of pure magnesium in powder form was heated

together with 47 ml of dehydrated ethanol and 152 g of zirconium-n-butylate.

This mixture was maintained at approx. 90°C in t

hours and then heated at 150°C until all excess alcohol was removed. Afterwards, the mixture was diluted with 250 ml of n-hexane. The atomic ratio Mg/Zr in the mixture was approx. 0.5.

300 ml of a 50% by weight solution of Al(C2H,.)Cl2

in hexane was added to the cooled mixture. The Mg/Al atomic ratio was thus approx. 0.2.

An exothermic reaction occurred and the mixture was maintained

at approx. 50°C for 1 hour. The solid catalytic component recovered was separated off, washed with hexane and dried. The elemental analysis showed that it contained 125 g of zirconium, 387 g of chlorine, ,

91 g magnesium and 48 g aluminum per kg.

A polymerization test was carried out with the aforementioned com-

ponent under the same conditions as in Example 42, with the exception that 33 mg of catalytic solid was used together with 100 mg of triethylaluminum.

About. 75 g of PE was recovered, whose MI was 1.53. This represents a catalytic productivity of 2 30 g PE/g catalyst x h x atm. C„H and a specific activity of 1840 g PE/g Zr x h a atm, C2HA. The AD of the polymer was 0.17 g/cm 3 and the HLMI was not measurable. The D of the polymer was 0.962 g/cm<3>.

Example 44.

9.7 g of powdered magnesium, 94 ml of dehydrated ethanol

and 58 g of vanadyl-n-butylate [VO(OnCAHg)^] were mixed and heated in the same manner as in Example 43 (Mg/V atomic ratio: about 2).

75 g of the powder obtained by crushing the cooled,

solid product, was diluted with 600 ml of a 25% by weight solution

ning of Al(C2H^)Cl2 (Mg/Al atomic ratio: approx. 0.4). Elementary Ana-

analysis of the solid obtained in the same manner as in Example 43 showed that it contained 104 g of vanadium, 113 g of magne-

sium and 66 g of aluminum per kg.

A polymerization test which was carried out with 16 mg of solid.

under the conditions indicated in example 42, gave 10 g of solid PE, whose melt index is approx. 40. Consequently, the hourly productivity is

and the specific activity respectively 600 g PE/g catalyst x

hour and 6000 g PE/g V x hour.

Example 45

The solid catalytic complex was prepared according to the procedure from example la with the exception that Al(0-isoC3H7)3 as compound (5) was reacted together with Mg, Ti(0C„H ), n-C„Hn0H

4 y 4 4 y

and iodine. Thus became a mixture of

45.4 g of n-C4Hg0H

2.43 g of powdered magnesium

9.57 g of Ti(O-nC4Hg)4

24.0 g of Al (O-isoC3H7)3 and

0.5 g of iodine

agitated under reflux at 100°C for 2 hours.

Low-boiling substances were distilled from the reaction mixture. After cooling to 60°C, 300 ml of n-hexane was then added, and 76.2 g of Al(C2H(.)Cl2) was added over a period of 2 hours at 45°C.

23.7 g of red-brown powdery catalytic complex was recovered after washing and drying. The titanium content was 5.1% by weight.

The polymerization test was carried out under the following conditions:

- autoclave: 1.6 litres

- hexane: 1 litre

- amount of catalytic solid: 36 mg

- nature and amount of component B:

triisobutylaluminium: 200 mg

- duration: 2 hours

- ethylene partial pressure: 11.4 kg/cm<2>

- hydrogen partial pressure: 7.6 kg/cm<2>

- temperature: 60°C

It was mined approx. 382 g PE. AD, MI and HLMl/MI were 0.30 g/cm<3>, 1.70 and 56.2 respectively.

Example 46

Preparation of the catalytic complex in Example 45 was repeated with the exception that Si(OC2H5)4 was used as compounds (5) and C2H5OH was used instead of n-C4Hg0H. Thus it was

a mixture of

13.7 g of C2H5OH

2.43 g of powdered magnesium

10.2 g of Ti(O-nC4H9)4

24.2 g Si(0-C2H5)4 and

0.25 g of iodine

reacted together by almost the same procedure as stated in Example 45 (with the exception that 76.2 g of A1C2H5C12 was used). 24.2 g of red-brown powdery catalytic complex was recovered, the titanium content of which was 4.9% by weight.

The polymerization test was carried out under the same conditions as in Example 45 with the exception that 100 mg of catalytic complex was used. About. 216 g of PE were recovered. AD, MI and HLMI/MI were 0.40 g/cm 3, 0.15 and 51.9 respectively.

Examples 47 to 49

Catalysts were prepared in the same way as in example 42 with the exception that (CH3)3SiOH, (C2H5)3SiOH and (tert.-C.H0)(SH_)_SiOH were used respectively in examples 47,

48 and 49, instead of (C^) 3SiOH.

The polymerization was carried out under the same conditions as in Example 42. The data for the preparation of the catalytic component A and the polymerization results are shown in Table 9.

Examples 50 and 51

Catalysts were prepared in the same manner as in Example 43, with the exception that Zr(0-n-CAHg)A was replaced by V0(0CoH, _,) _ in Example 50, and with condensed titanium butylate of

etc./ 3

the following average structural formula in example 51:

The polymerization was carried out under the same conditions as in example 43. The data for the production of catalytic component A, as well as the polymerization results, are shown in table 10.

Claims (4)

1. Process for the low-pressure polymerization of ethylene, optionally together with small amounts of copolymerizable monomers, in the presence of a catalytic system comprising an organoaluminum compound (component B) and a solid catalytic complex (component A) containing magnesium, aluminum originating from an aluminum halide and at least one metal (Tr) from groups IVa, Va or Via in the periodic table which originates from an oxygen-containing organic compound of said metal (Tr), characterized in that a catalytic system is used where component A is obtained by reaction of the following compounds : (1) metallic magnesium; (2) a hydroxylated organic compound selected from alcohols and hydrocarbylsilanols containing 1-12 carbon atoms; (3) an oxygen-containing organic compound of said metal (Tr); (4) an aluminum halide. 2. Method as stated in claim 1, characterized in that a saturated monohydric aliphatic alcohol containing from 1 to 6 carbon atoms is used as compound (2). 3. Method as stated in claim 1, characterized in that component A is obtained by adding compound (2), compound (3) and compound (4) to the metallic magnesium in the specified order. 4. Solid catalytic complexes for use in the method according to claim 1, characterized in that they are produced by reacting the following compounds: (1) metallic magnesium; (2) a hydroxylated organic compound selected from blue alcohols and hydrocarbysilanols containing 1-12 carbon atoms; (3) an oxygen-containing organic compound of a metal (Tr) from groups IVa, Va or Via of the periodic table; (4) an aluminum halide.