GB2189252A - Catalyst for the polymerisation of 1-alkenes - Google Patents

Abstract

A supported catalyst for the polymerisation of 1-alkenes is obtained by consecutively depositing on an inert inorganic oxide of silicon and/or aluminum i) at least one organic compound of aluminium, ii) at least one compound of titanium and vanadium and iii) at least one organic compound of aluminium and/or magnesium. It can be coated with a paraffinic hydrocarbon which is applied either together with component iii) of the catalyst or to the completed catalyst. The catalyst polymerises and copolymerises ethylene without any additional activation.

Description

SPECIFICATION Catalyst and Method for the Production of Polymers and Copolymers of 1-alkenes Coordination catalysts for polymerisation of 1 -alkenes, known as Ziegler catalysts, are well established.

Starting from the middle of the fifties, much effort has been devoted to the synthesis of the best catalysts enabling the preparation of poly(1-alkenes) with defined structure and properties, a high yield and a good economy. Besides empirical search for new catalyst formulations, theoretical aspects of the polymerisation reactions were studied, including their kinetics and mechanism. Despite of a great effort, the theory is not able to provide a procedure for the synthesis of suitable catalysts. It makes only possible rationalisation of available information, while catalysts of this type must be searched for, studied and developed empirically.

Many physical and chemical parameters affect directly the preparation of the catalysts and the actual polymerisation. Due to a great number of polymer types demanded and the enormous number of combinations of components used, it is very difficult to find an optimum catalyst for a given purpose.

During a routine catalyst preparation, it is necessary to keep qualities of raw materials, prescribed ratios and concentrations, reaction conditions, sequence of components, reaction times and temperatures, and all these parameters must be found at first experimentally and then they must be complied. Due to an unsatisfactory theoretical background, the volume of the necessary experiments is immense and the progress is rather slow.

Effective catalytical systems for the polymerisation of 1-alkenes at low temperatures and pressures have been developed, so that molecular weights, the width of the molecular weight distributions and densities of polymers may be controlled. In the case of polyethylene it is possible to produce, for example by copolymerisation at relatively low pressures, even low density types produced until recently by a radical high pressure polymerisation only. A procedure for the production of some specific linear low-density polyethylenes by polymerisation in a reactor with a fluidized bed has been described by Karol et al in US 4302566.

Catalytical systems based on transition metals of the groups 4a and 5a of the periodic system of elements known until now polymerise ethylene readily, and due to suitable copolymerisation parameters (comparing with previousiy used chromium-based catalysts), give copolymers of alkenes with a low unsaturation in the chain and a narrower molecular weight distribution, which is advantageous for some applications. Catalysts based on transition metals of the groups 4a and 5a of the periodic system of elements demand an activation with an organometallic compound, which is mostly carried out additionally, either immediately before the polymerisation or even in the polymerisation reactor itself The activation consists in alkylation of the transition metal and sometimes in its reduction.Disadvantages of these methods for the production of the catalysts are: a difficult control of a reduction degree of the transition metal (usually a deeper reduction takes place than desirable, and thus its activity decreases) and a low stability of the catalysts (the activity decreases during storage spontaneously or by the action of impurities).

An activation of the catalyst in a polymerisation reactor causes technological complications, as for example the necessity to feed the components separately and proportionally. One of them is pyrophoric and this is hazardous considering the presence of large amounts of combustibles. In addition to this, a free organometallic compound catalyses oligomerisation of 1-alkenesto low molecular weight oligomers. They form undesirable coatings on the inner walls of the used apparatus, especially in the case of solvent-free processes, such as gas-phase polymerisation.

Catalytical systems of this type are described by Karol et al in US 432566, Stevens et al in US 3787384, Strobel et al in US 4148754, Ziegler et al in US 4063009 and especially by Graff in US 4173547.

In recent years, there is a tendency to develop one-phase catalytical systems based on transition metals of the groups 4a and 5a of the periodic system of elements. Using these catalysts for polymerisation of 1-alkenes, complications with feeding of catalysts are eliminated, the coatings on walls of a polymerisation apparatus are not formed and the obtained polymer has desired particle morphology. One-phase catalytical systems based on titanium and vanadium compounds were described for example in US 4426317 and US 4435520. Rogers in US 4426317 and Aylward in US 4435520 described supported catalysts obtained by a reaction of an inorganic oxide with organometals of the 3rd group of the periodic system of elements and then with some vanadium compounds.

According to the unpublished Czechoslovak patent application PV 8291-85 a one-phase supported catalyst can be prepared by a reaction of an inorganic oxide with organometals and then with compounds of titanium and/or vanadium. Resulting catalysts are active in polymerisation, but they have some disadvantages. Active sites are formed during the preparation of the catalyst already and can decompose spontaneously before its application. These one-phase catalysts are deactivated readily by reactions with impurities (e.g. oxygen or water) due to a low content of organometallic compounds.

It is known from patent literature that highly reactive catalysts exist, passivated against effects of water or oxygen by their surface being coated with a layer of an inert solid substance, forming an effective diffusion barrier. These catalysts, however, must be in its active form during polymerisation, the monomer diffusion to active sites must not be hindered. Therefore the protective layer should be formed from a material with melting point between environmental temperature and polymerisation temperature. In reality, higher saturated hydrocarbons and their mixtures can be used.

US 4200715 describes dispersion of a supported catalyst in a solid phase, obtained by mixing a paraffinic wax with a liquid, low molecular weight hydrocarbon. The catalyst modified in such a way is resistant against diffusion of impurites during its transport and storage. The dispersion is carried out with the finished catalyst only, the possibility of changing the chemical parameters of the catalyst during the deposition of catalytical constituents is not utilized.

EP 159736 describes a modification of a one-phase unsupported catalyst by coating it with a layer of viscous mineral oil. In this case, however, the particle size distribution of the catalyst and also of the polymer formed is too broad in this particular unsupported catalyst and it is not possible to utilize it in the gas-phase polymerisation.

It is also known that a protective layer can be formed on the catalyst surface by a prepolymerisation of 1-al kenes. The prepolymerisation with the aim of improving the activity of a catalyst was the subject matter of FR 2529211. An elimination of particle sticking was described in EP 102895. The disadvantage of these catalysts is the use of MgCI2 and AICI3 as a support, which contains an abundance of chloride ions and has an unsuitable particle size distribution. Now we have found a simple method for the preparation of a new one-phase catalyst and a method for the polymerisation and copolymerisation of ethylene using this catalyst.

The subject matter of this invention is a one-phase supported catalyst for the polymerisation of ethylene and its copolymerisation with 1-alkenes having 3-10 carbon atoms, obtained by a consecutive deposition of at least one aluminium compound of general formula (I) Rm AlX3~m, where m is 1-3, at least one compound of titanium of general formula (Ila) Rn TiX4~n, where n is 04, and/or vanadium of general formula (llb) RpVX5-p or RqVX4-q, where is 0-5, q is 0-4, and at least one organometallic compound of general formula III, which compound can be an organoaluminium compound identical with the compound of general formula I, and/or organomagnesium compound of general formula (Illb) R rMgX2r, where r is 1-2 and R in all compounds I, II and III means alkyl, aryl, alkoxide with 1-20 carbon atoms, X halogen or in compounds II one X2 can be oxygen and the substituents R and X in compounds I, II and lli may be but need not be identical, on the support formed by silica and/or alumina with a specific surface of 50-500 m2/g, with 0.33 mmole of hydroxyl groups per one gram of the carrier and with the inner porosity of 0.53 ml/g, with particle sizes in the range of 1-200 m.

The supported one-phase catalyst has the ratio of organoaluminium compounds I to the hydroxyl groups of the support in the range of0.1-10, the mole ratio of transition metal compounds II to organoaluminium compounds I in the range 0.02-10 and the mole ratio of organometallic compounds III to transition metal compounds 110.1-20. An advantageous execution of this invention is the supported one-phase catalyst in which the organoaluminium compounds I have alkyls with 1-8 carbon atoms, the transition metal compounds II are titanium tetrachloride, titanium tetraalkoxide, vanadium tetrachloride, vanadium tetraalkoxide and vanadium oxytrichloride, and the organomagnesium compounds Ill are dialkylmagnesium with 1-10 carbon atoms in alkyl groups.

A further subject matter of this invention is a method for the production of this supported one-phase catalyst, in which depositions of compounds I, II and Ill on the support are performed in a gas phase or a hydrocarbon solvent, and the supported one-phase catalyst as described before, which is coated with a paraffinic hydrocarbon having melting point in the range of 25-150 C in the amount of 0.5100% w/w of the uncoated catalyst either separately or together with compound Ill, or on which linear and/or branched 1 -alkenes with 2-10 carbon atoms are prepolymerised in the amount of 0.5100% w/w of the uncoated catalyst.According to this invention, ethylene is polymerised or copolymerised with 1-alkenes having 3-10 carbon atoms using these catalysts at temperature 30-300 C and pressures of 0.1-250 MPa in a slurry, gas phase or in a fluidized bed containing 50-100 volume % of 1-alkenes and 0-50 volume % of hydrogen in the monomer mixture.

Finally, the subject matter of this invention are the polymers of ethylene and its copolymers with 1-alkenes having 3-10 carbon atoms, produced with the use of the catalysts and the method described above.

For the catalyst suitable for the production of polymers and copolymers of ethylene according to this invention, an appropriate support is silica and/or alumina with a specific surface of 50-500 m2/g, pore volume 0.53.0 ml/g, which has been dehydrated at temperatures of 200950 C by a stream of air or nitrogen in a fluidized bed for at least 4 hours. Silica and/or alumina treated in such a way contain 0.--3.0 mmole of hydroxyl groups per one gram of support according to dehydration temperature.

Organoaluminium compounds I are chosen from compounds, such as trialkylaluminium, dialkyl aluminiumhalogenide, alkylaluminiumdihalogenide, dialkylalkoxyaluminium, alkyldialkoxyaluminium, where alkyls are hydrocarbon groups with 1-20 carbon atoms and may be different within one compound.

These organic compounds of aluminium have general formula (I) Rm AlX3m, where m is 1-3, R is branched or linear alkyl or alkoxide with 1-20 carbons, and all R groups can be (but need not be) identical, X is halogenide, preferably chloride. These organometals are usually used as a hydrocarbon solution at a concentration 525 % w/w. For example, it is possible to use ethylaluminium dichloride, triethyl aluminium, triisobutylaluminium, diethylaluminium ethoxide, tri-n-hexylaluminium and/or their mixtures.

Using these compounds is economically advantageous, because they are produced on mass scale.

The reaction of organic compounds of aluminium Rm AIX3-rn (I) with the surface of silica can be expressed by equations: -Si-OH+R,AIX,~,,-Si-O-AIR,~, X3rn+HR

New chemical bonds Si-O-Al orAl-O-Al, if alumina is used, are formed, which ensure a strong fixing of organoaluminium compound I on the surface. The ability of these structures to bond other compounds and to form active polymerisation sites depends on the density and the type of these bonds and on the substituents of the anchored aluminium.

The mole ratio of the sum of all organic compounds of aluminium I to hydroxyl groups of the support is in a range of 0.1-10, advantageously 0.5--1.0. For a uniform deposition of organometals I, it is necessary to stir intensively a slurry of the support or a layer of the support. Temperature during the reaction can fluctuate within a broad range, depending on the vapour pressure of the organometallic compound I and on the boiling point of the hydrocarbon used as a solvent; the reaction can be carried out at 1O700C, advantageously at room temperature. Reaction time depends on the reactivity of organometals I, on their concentration and temperature; usually several tens of minutes are sufficient.

In a next step, at least one compound II of titanium and/or vanadium is deposited on the support with anchored organoaluminium compound I. They are selected from a group of halogenides, halogenalkoxides, alkyls, aryls, alkoxides, oxihalogenides of titanium and vanadium. For example: titanium tetrachloride, vanadium tetrachloride, vanadium oxytrichloride tetraalkoxides of titanium and vanadium and mixtures of these compounds. The use of titanium and vanadium compounds in their highest oxidation state is preferred, vanadium compounds also in oxidation state 4+. A small amount of compounds in a lower oxidation state (e.g. Ti3+) is not detrimental. The most advantageous halogenide is chloride, but it is possible to use also other halogenides, e.g. bromides or iodides. It is possible to use for example ethoxide, isopropoxide, isobutoxide etc. as alkoxides.The use of alkyl- and especially arylderivatives of titanium and vanadium, e.g. methyl-titanium trichloride, tetrabenzyl titanium, benzyl-titanium trichloride, tetraphenyltitanium, is possible, but it is economically less advantageous and a possible shortening of preparation time does not improve economy.

The reaction of compounds II with the modified support is advantageously made in a hydrocarbon medium or by a direct contact of titanium or vanadium compound II vapours with the solid phase of the intermediate product, preferentially at laboratory temperature. A strong anchoring of titanium or vanadium compounds on the support is achieved and they react with the fixed reaction products from the preceding step. Again, it is necessary to secure perfect stirring of the slurry to obtain a homogeneous product. The mole ratio of the sum of transition metal compounds II to the sum of organoaluminium compounds I is kept within a range of 0.02-10, advantageously 0.05--1.

By chemical bonding of organometals I to the free hydroxyl groups of the support, a modification of their reduction capabilities and simultaneously their immobilisation on the support surface are achieved. By the choice of ratio of organoaluminium compounds I to hydroxyl groups and ratio of organoaluminium compounds I to compounds oftitanium and/or vanadium 11, a formation of active sites on the support surface takes place, which can polymerise 1 -alkenes, either immediately, or after a reaction with another organometal compound.

Properties of an intermediate of the one-phase catalysts obtained in such a way are improved by depositing at least one further organoaluminium compound Illa and/or organomagnesium compound Illb chosen from trialkylaluminium, dialkylaluminium chloride, alkylaluminiumhalogenide, dialkylaluminium alkoxide, alkylaluminium dialkoxide, dialkylmagnesium or alkylmagnesium chloride, or their mixtures (III).

Organoaluminium compounds Illa used in this third step of preparation are chosen from the same group of organoaluminium compounds I, used in the first step of catalyst preparation. For example, it is possible to use ethylaluminium dichloride, diethylaluminium chloride, triisobutylaluminium, tri-n-hexylaluminium, diethylaluminium ethoxide, di-isobutylaluminium n-butoxide and their mixtures and the mixtures with organomagnesium compounds Illb.

Organic compounds of magnesium Illb for the preparation of the catalyst have general formula (Illb) Rr Mg X2r, where X is chloride, bromide or iodide and R is a hydrocarbon group containing 1-20 carbon atoms. Both R groups may be (but need not be) identical, they can be alkyls, cycloalkyls, aryls, alkenyls.

Examples of suitable compounds Illb are diisopropylmagnesium, dibutylmagnesium, diisobutylmagnesium, dihexylmagnesium, dioctylmagnesium, butyloctylmagnesium, dicyclohexylmagnesium, difenylmagnesium, ditolylmagnesium, ethyl magnesium chloride, butylmagnesium chloride.

Organic magnesium compounds Illb should not contain appreciable amounts of ethers. For choice of a type of organic compounds of magnesium Illb and aluminium Illa and their ratios in mixtures (Ill), economic considerations are applied (organomagnesium compounds are rather expensive and therefore it is advantageous to use only a necessary amount of these compounds). The mole ratios of organometallic compounds III to transition metal compounds II are kept within a range of 0.520, advantageously 1-8.

Conditions and a depositing method for organometallic compounds III are similar to those for the deposition of the preceding components; again, it is necessary to secure a slow deposition and an intensive mixing.

During research and development of supported one-phase catalysts it was surprisingly discovered, that by depositing organoaluminium compound Illa on the product of reactions of the support with constituents I and II, the polymerisation activity of the obtained sandwiched catalyst is increased to values comparable with catalysts activated immediately before polymerisation or in a polymerisation reactor itself, and in some cases even better. Moreover, the mole ratio of organoaluminium compounds Illa to transition metal compounds II is many times lower than that for two-phase catalysts. The supported one-phase catalysts with organoaluminium compounds Illa as their third active constituent produce polymers with a high bulk density.

Similarly, it was surprisingly found, that an analogical effect can be obtained, using organomagnesium compounds Illlb. By their anchoring on the product of reactions of the support with constituents I and II, the supported one-phase catalysts are obtained, which can polymerise 1 -alkenes with a higher rate than two-phase catalysts activated immediately by an organometal before polymerisation or in the polymerisation reactor itself. Moreover, needed amounts of organomagnesium compounds Illb as their third active constituents produce polymers with lower bulk densities than the comparable supported one-phase catalysts with organoaluminium compounds Illc, but they polymerise with higher rates.

Therefore, it is advantageous to combine both organometals for obtaining desired properties of the catalyst and to deposit organoaluminium and organomagnesium compounds on the product of reactions of the support with constituents I and II in mixtures.

A majority of organomagnesium compounds Illb and/or a part of organoaluminium compound Illa are anchored on the surface of support particles and they do not diffuse inside the particles during the preparation and storage of the catalyst. This accumulation of organomagnesium compound Illb or possibly of a part of organoaluminium compound Illa on a periphery of the support particles influences positively the stability of active sites against deactivating reactions of strong electron-donor compounds, which are usually contained in raw materials or can contact the catalyst during its preparation, storage and transport.

During the polymerisation, esqecially at higher temperatures, these organometals diffuse to transition metals compounds II and activate precursors of active sites.

Organoaluminium compound Illa on the one hand alkylates and/or reduces titanium and/or vanadium compounds II, and on the other hand decreases the oligomerisation ability of organomagnesium compound Illb, increasing its mobility and its diffusion rate inside the catalyst particles to the fixed transition metals II. Formation of a transition metal species active in the polymerisation, is divided into two steps, i.e. (i) a reaction of organometal I of the modified support with transition metal compound II and (ii) a product of this reaction reacts with organometallic compound III. Both reactions proceed under very mild, easily controllable conditions. Use of organometallic compounds III enables the choice of organometals I with low alkylating and reducing power, and their use in necessary amounts.Thus, all compounds are exploited fully for the formation of active polymerisation sites and their protection against common amounts of impurities. Organometals III can be used in some surplus and can be exploited during polymerisation, affecting positively its kinetics and maximum polymerisation rate.

During all stages of preparation of the supported one-phase catalyst according to this invention, it is necessary to avoid an access of compounds, such as water and oxygen, decomposing organometallic compounds. It is necessary to work in an inert atmosphere, e.g. under blanket of highly pure nitrogen or argon, containing less than 1 ppm of impurities. Hydrocarbon solvents used for the preparation of the catalyst must be dried thoroughly, e.g. by distillation or rectification employing a principle of a higher volatility of water dissolves in hydrocarbons. Contents of impurities in media used for preparation of the supported one-phase catalyst as well as the purity of used vessels and fittings must be checked systematically. The catalyst is stable and active in polymerisation for a very long time, if vessels are perfectly tight during its preparation, storage, transport and feeding.

When a limited access of impurities cannot be prevented, it is preferred for a long-term storage of the catalystto coat its surface with a paraffinic hydrocarbon, and to blow the catalyst byvery pure nitrogen immediately before feeding it into the reactor.

Some properties of the catalyst are improved by coating a paraffinic hydrocarbon on the surface of catalyst particles. The paraffinic hydrocarbon must have its melting point between maximum usual environment temperature, at which the catalyst is produced, stored and transported, and polymerisation temperature.

Advantageously, a paraffin with melting point 570"C, an atactic polypropylene or other saturated hydrocarbons with suitable melting points can be used. The presence of multiple bonds and heteroatoms (i.e. elements other than carbon, hydrogen and fluorine) in chains of paraffinic hydrocarbons is undesirable, because it decreases the activity of the catalyst. Low molecular weight impurities of the electron-donor type also exhibit a negative influence. The paraffinic hydrocarbon can be deposited on the ready-to-use catalyst suspended in a hydrocarbon solvent, or simultaneously with the last catalyst constituent, it means with organic compound of aluminium and/or magnesium lIThe paraffinic hydrocarbon is deposited in such a way, that its content is 0.5--100% w/w per catalyst, preferably 110% w/w. Principle of the beneficial behaviour of the paraffinic hydrocarbon is coating of catalyst particles and prevention of diffusion of impurities to active sites during isolation, storage, transport and feeding of the catalyst. A formation of a diffusion barrier on the catalyst surface stabilises further the catalytic system in the absence of monomer.

Reactivity of catalyst components is decreased substantially and a majority of active sites are formed only after melting-off paraffinic hydrocarbon in a reactor.

Phlegmatisation of catalyst particles according to this invention is not a necessary condition for obtaining an active catalyst. All aims of this invention can also be reached without depositing the paraffinic hydrocarbon. The paraffinic hydrocarbon confers a long-term storability and a resistance against impurities of the electron-donor type (water, oxygen) upon the catalyst and influences polymerisation kinetics. In addition to the methods for depositing the paraffinic hydrocarbon given above, it is possible to prepolymerise a low amount of 1-alkene, for example ethylene, propylene, 1 -butene, 4-methyl-i -pentene, 1-hexene, 1-octene, 1-decene or their mixture. 1-alkenes other than ethylene are preferably prepolymerised, because more active sites are formed.The amount of the prepolymer obtained in such a way should be 0.550% w/w of the final catalyst, preferably 120% w/w.

By depositing catalytical constituents on the support in the sequence and amounts given above, a high active polymerisation catalyst is obtained, which can polymerise ethylene and copolymerise it with other, 1-alkenes in a solvent or in a gas phase. If polymerisation in a gas phase is carried out, it is necessary to evaporate solvent for obtaining a loose, free-flowing powder. A thorough drying is not necessary, because the powder flows freely even when it contains up to several tens of percents (w/w) of a solvent.

The size of the polymer particles is determined by the size of catalyst particles, but it is necessary to obey the procedure of depositing constituents according to this invention.

The support for the catalyst according to this invention is a porous fine-grained oxide, silica and/or alumina. Nature and properties of the support influence the catalyst activity and properties of the polymer.

The size of the support particles should be in the range of 1-200 pm. The optimum size of particles can be found experimentally. A content of particles with a diameter less than 10 pom is disadvantageous, because polymer fines are formed, and a danger exists that large flakes (or even chunks) may be formed in a reactor and thick deposits may appear in on-stream parts of the polymerisation apparatus, clogging e.g.

coolers of the recirculating gas. Silica or alumina are well known materials and commonly used as supports of polymerisation catalyst. Forthis purpose, materials with a high specific surface (5-500 m2/g) and a high pore volume (0.53.0 ml/g) are preferable. The particle size distribution of the support determines the particle size distribution of the catalyst and influences rheological properties of the polymer, the bulk density of the powder and thus the economy of its processing. The specific surface and the pore volume of support particles can be determined using the BET method, described in a paper by S. Brunauer, P. Emmett and E. Teller, published in the Journal of the American Chemical Society 60, p 209--319 (1938).

Hydroxyl groups are present on the surface of silica or alumina and the groups can react with catalyst constituents. Water, sorbed physically, induces undesirable reactions and it is necessary to remove it. It is advantageous to remove water bonded physically by thermal activation of silica or alumina, with a slow removal of desorbed water. Activation temperature is chosen in a range of 200--950"C, preferably 400--800"C. It is necessary to secure perfect stirring, thus, it is advantageous to perform activation in a fluidized bed. Siiica and/or alumina is placed in a cool activation apparatus, then temperature is increased slowly to 200"C while a stream of an inert gas is blown through the support or it is pumped-out.Thus, water vapours can leave without destroying the structure of silica and/or alumina and condensing on cooler parts of the apparatus. Then it is possible to increase temperature quickly to a desired level without any problems.

Dehydration of silica and alumina is performed at the chosen temperature usually for at least 4 hours.

Silica and alumina are cooled by a stream of nitrogen containing less than 1 ppm of water and oxygen.

Dehydration temperature of the support must be chosen below the sintering temperature to prevent a destruction of the porous structure, a decrease of the specific surface and the pore volume. The amount of hydroxyl groups on the oxide support may be determined by any common method, e.g. by the reaction of the inorganic oxide with a surplus of triethylaluminium, determining the amount of ethane released. One mole of ethane is formed per each mole of reactive hydroxyl groups in this reaction.

Due to the high reactivity of the compounds used and to high heat effects of reactions, it is suitable to use organometallic compounds I and Ill and compounds of titanium and vanadium II in a diluted form, dissolved in suitable solvents. In general, it is possible to use aliphatic hydrocarbons with linear or branched chains, for example, butanes, pentanes, hexanes, octanes and their mixtures, e.g. kerosene, gasoline as solvents. Usage of cyclic hydrocarbons, e.g. cyclopentane, methylcyclohexane, cyclohexane, as well as aromatic hydrocarbons, especially benzene, toluene, xylenes, is not excluded, but it is not economically advantageous.

In the first reaction step, i.e. reaction of silica and/or alumina with organoaluminium compound I in a liquid phase, it is advantageous to use organometal I diluted in such a way, that the total amount of solvent at least doubles the pore volume of the support. The reaction of organoaluminium compound I with the support is carried out preferably at room temperature, reaction time is in a range of several minutes to several hours, depending on reaction conditions. After the reaction of organometal I is brought to completion, the solvent may be (but need not be) removed by decantation, evaporation or evacuation. It is recommended to remove the solvent and wash-out the support with the deposited organometal I in case that organometal I was used in a surplus, which could produce in the next step a new microheterogeneous phase, containing no silica or alumina as a support.

In the second step, compounds of titanium and/or vanadium or their mixture II are added slowly with stirring. Conditions are identical with those used in the first step, it is possible to use the same solvent and it is possible, though not necessary, to remove it after the reaction.

In the third step, at least one organoaluminium compound Illa and/or organomagnesium compound Illb is added to the slurry, obtained in the second step, alternatively together with a paraffinic hydrocarbon.

Reaction conditions are similar to those used in the first step; it is advantageous to remove the solvent after the reaction, for example, by decantation, by evacuation or by evaporation with stirring etc. If the paraffinic hydrocarbon is deposited in the third step together with organoaluminium and/or organomagnesium compound III it is advantageous to work at higher temperatures, or to increase temperature in the final stage of the solvent evaporation, to secure a uniform coating of support particles with the paraffinic hydrocarbon.

The paraffinic hydrocarbon can be deposited also separately in the fourth preparation step, when the paraffinic hydrocarbon is added successively and evenly to the product of the third step, at temperature higher than the melting point of the paraffinic hydrocarbon, as a melt or as a solution in a suitable hydrocarbon solvent. Alternatively, it is possible to mix a solid finely dispersed paraffinic hydrocarbon with the reaction product of the third step at a low temperature and then to increase the temperature slowly over the melting point of the paraffinic hydrocarbon. After cooling and possibly drying of the surplus of the solvent, a loose, free-flowing powder of the supported one-phase catalyst can be obtained. All reactions leading to the catalyst can be carried out without a solvent in a gas phase, using a fluidized bed stirred mechanically or pneumatically.Organometals I and III and compounds of transition metal II can be deposited as vapours in a stream of an inert gas, for example nitrogen or argon, or in a form of solutions in a hydrocarbon solvent; in the lattar case it is necessary to keep conditions to prevent sticking of particles during the whole process of depositing the components. Particles remain unsticky even when they contain several tens of weight percents of a solvent; the exact value must be determined experimentally for particular conditions. Deposition of components I-Ill on silica and/or alumina from a gas phase is advantageous, but it is necessary to keep carefully suitable temperatures, concentrations, flow rates and reaction times, to prevent formation of undesirable large flakes and chunks.

The supported one-phase catalyst prepared by the method according to this invention is effective in polymerisation without the necessity to activate it additionally before polymerisation or in the reactor itself The polymerisation activity of the catalyst does not change in a pure medium during storage at common temperatures. If the catalyst contains the paraffinic hydrocarbon, it is also resistant to a mild access of impurities during storage, transport and feeding of the catalyst. Taking into account that some access of impurities of the electron-donor type cannot be excluded, the phlegmatisation by a paraffinic hydrocarbon is advantageous.A paraffinic hydrocarbon with melting point between maximum temperature of surroundings and the polymerisation temperature can be prepared also by a prepolymerisation of a small amount of 1-alkenes, such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene.

These monomers are contacted with the product of the third step under an intensive stirring, advantageously at increased temperatures (50--100"C), either in the hydrocarbon solvent after the third reaction steps, or in a gas phase. Reaction time is dependent on the required amount of the prepolymer. It is advantageous to remove the unreacted monomer before cooling and drying the catalyst.

The catalyst prepared according to this invention can be used for homopolymerisation of ethylene and for its copolymerisation with propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene and further 1-alkenes and their mixtures.

A polymerisation of 1-alkenes using the one-phase catalyst according to this invention can be carried out in a fluidized bed, in a mechanically stirred layer in a gaseous phase, in a solvent or in a liquid 1-alkene.

Any liquid, which does not react with the catalytical system, can be used as a solvent. It is suitable to use aliphatic hydrocarbons with linear or branched chains, liquid under conditions of the polymerisation, e.g.

butanes, pentanes, hexanes, heptanes, their mixtures, distillation fractions of oil, e.g. petrol, kerosene, diesel oil, or aromatic and cyclic hydrocarbons (benzene, toluene, xylenes, cycloalkanes) or chlorinated aliphatic or aromatic hydrocarbons. It is advantageous to polymerise in a liquid monomer (1-alkene) thus increasing the productivity of the reactor due to the absence of an inert diluent. Preferably, cheap aliphatic hydrocarbons of their mixtures are used as solvents. On the large scale, it is advantageous to polymerise in a fluidized bed, because it is not necessary to remove the solvent from the polymer.

The polymerisation pressure may be atmospheric, or it can be higher for example up to 250 MPa.

Preferably, it is polymerised at pressures of 0.5--4 MPa. In the gaseous phase polymerisation, pressures in the range of 1-3 MPa are the most economical. Higher pressures are advantageous for obtaining polymers with a very low content of the catalyst residues.

It is possible to polymerise discontinuously or more preferably, continuously. Feeding of the catalyst can be in charges or continuously in such an amount, to keep the concentration of transition metal in a range of 0.001-10 mmole/l, preferably 0.01--0.5 mmole/l.

Polymerisations may be carried out at 30--3000C. At temperatures exceeding melting point of the polymer formed, it is possible to perform so called solution polymerisation in a solvent or the high pressure polymerisation catalysed by the catalyst according to this invention.

In the gas-phase polymerisation, it is necessary to keep the temperatu re 5--100C below the melting point of the polymer to prevent agglomerisation of particles and formation of large flakes.

The molecular weight of polymers can be controlled by the content of comonomers, by the polymerisation temperature and by the hydrogen feed. The absence of hydrogen and comonomer leads to formation of ultra-high-molecular weight polymers (UHMW PE).

The polymerisation can be performed also in more stages, arranged in series or in parallel, where different conditions can be used: e.g. different catalyst compositions, temperatures, residence times, compositions of monomer mixtures, pressures, hydrogen concentrations etc. Thus, it is possible to prepare polymers with a broad molecular weight distribution, suitable for some applications. The polymers with a broad molecular weight distribution is advantageous to prepare in two or more stages, where different reaction conditions or different catalyst compositions are used, e.g. a different ratio titanium:vanadium or (aluminium and magnesium):(titanium or vanadium).By using a mixture of catalysts or a mixture of titanium and vanadium compounds within one catalyst, polymers with a broad molecular weight distribution can be obtained also in a single stage, because in this case active sites of different quality can co-exist on the catalyst surface.

Spherical particles of the polymer are formed during the polymerisation, replicating the shape of the original particles of the catalyst and thus also that of the support. The enlargement factor is 1 0--50 times.

Compact particles are formed by polymerisation with the diameter several tenths of millimetre up to several millimetres, depending on the polymerisation time (in the discontinuous process) or on the residence time (in the continuous process). The usual polymerisation time is 0.58 hours, preferably 2-6 hours. At shorter polymerisation times, the contents of ash and catalyst residues are higher, while the reactor productivity is high. On the contrary, at longer polymerisation times the quality of the polymer improves and the reactor productivity decreases.

The catalyst is deactivated upon the discharge from the reactor by air, water vapour or by carbon monoxide. Due to a low content of the catalyst residues, it is not necessary to wash them from the polymer.

The invention will be clarified by the following examples: Examples 1-7 Into a reactor freed from water and oxygen, containing 50 ml of stripped n-heptane, 2.0 g of the support (silica and/or alumina) were poured under blanket of pure nitrogen and an organoaluminium compound I was added in the amounts according to Table 1. After 15 minutes of stirring at laboratory temperature, a titanium and/or vanadium compound II was added (see Table 1), it was again stirred for 15 minutes and an organic compound of aluminium and/or magnesium (III) according to Table 1 was added and it was stirred for further 15 minutes.

The last step of the catalyst preparation was a solvent removal by a stream of dry nitrogen or by evacuation. The catalysts prepared in such a way, are obtainable as dry powders, containing at the most about 50% w/w of a solvent. Beyond this limit, a sticky powder or a paste are obtained, which cannot be transported pneumatically and fed into the reactor without difficulties. If the polymerisation is carried out in liquid phase, a slurry of the catalyst in a hydrocarbon can be fed directly into the polymerisation reactor.

During preparation, storage, transport and feeding of the catalyst, it is necessary to exclude an excess of catalytical poisons of the electron-donor type, for example oxygen, water, dienes, carbon oxides etc. All operations and manipulations with the catalyst must be carried out in an inert atmosphere, for example under blanket of pure nitrogen or argon, containing less than 10 ppm, preferably less than 1 ppm of impurities of the electron-donor type.

Example 8 Into a purified reactor, containing 50 ml of stripped n-heptane, 2.0 g of the support (silica and/or alumina) were poured against the flow of pure nitrogen, and a measured amount of organoaluminium compound (I) according to Table 1 was added. After about 30 minutes of reaction at environmental temperature, an amount of compound of the transition metal II according to Table 1 was fed and the mixture was stirred for additional 30 minutes. Then, the temperature was increased to 60--800C and the organometallic compound or their mixture III was added according to Table 1. Finally, a paraffinic hydrocarbon with a melting point of 4850 C was added in the amount according to Table 1. After its dissolution, the solvent was removed by evacuation under steady stirring.A loose powder was obtained, exhibiting similar mechanical properties as those of the original support.

Example 9 It was proceeded according to Example 8 with the following difference: instead of the paraffinic hydrocarbon a mixture of ethylene with 40% vol. of hydrogen was introduced such as to polymerise 50 mmole of ethylene into oligomers solid at environmental temperature. After finishing this prepolymerisation, a majority of the solvent was removed to obtain a loose, free-flowing powder. The catalyst is unsticky at environmental temperature, resistant against a diffusion of impurities and storable before a polymerisation for a virtually unlimited period of time.

Example 10 The procedure was identical as in Example 8 with the following difference: instead of the paraffinic hydrocarbon, 30 mmole of 1-butene with 10 mmole of hydrogen was added and the stirring at 6S80 C continued till 1-butene was polymerised totally. After the prepolymerisation period, a majority of n-heptane was removed by blowing-through nitrogen and the one-phase supported catalyst was isolated, capable to polymerise 1-alkeneswithouta necessity of an additional activation by further component.

Example 11 A glass reactor (volume 1 dm3) was used equipped with a spiral stirrer which mixed the powders thoroughly. It was dried by nitrogen and 300 g of a support, dehydrated for at least six hours at temperatures of 200--950"C with a stream of nitrogen was poured in and stirring was switched on. Nitrogen of a very high purity was introduced through a sintered glass to the bottom of a 80 cm3 evaporator and bubbled through a solution of organoaluminium compound I or their mixtures in a hydrocarbon (hexane).

After saturating with vapours of organoaluminium compound I, the nitrogen was introduced through the bottom of the glass reactor into the layer of the activated support. After consecutive evaporation of allsolution of organoaluminium compound I, at least one transition metal compound II is poured into the evaporator, neat or as a solution in a hydrocarbon, and nitrogen is again bubbled through. Finally, at least one organoaluminium compound Illa and/or organomagnesium compound Illb or their mixture was dosed into the emptied evaporator and let to evaporate to completion. Evaporation can be facilitated by heating the evaporator. In some cases, especially when organomagnesium compounds Illb are used, heating is necessary. It is advantageous to cool the reactor at the beginning of introduction of the organoaluminium compound I, to remove reaction heat.Small increase of temperature of the reactor to 601 00 C is not detrimental. The reaction components I, II and Ill can be fed as neat substances, but for safety reasons, their solutions in hydrocarbons are preferred. All handling of the activated supports and constituents I-Ill must be carried out in a medium of a very high purity, advantageously under blanket of an inert gas (nitrogen, argon) containing less than 1 ppm of water, oxygen and other impurities. According to this procedure a white to beige free-flowing powder is obtained, which is suitable for polymerisation in a gas phase without any additional activation. Data concerning the preparation are given in Table 1.

Example 12 The process was identical with Example 8 exceptthat instead of organomagnesium compound Ill, its mixture with a paraffin having melting point 4-500C in a hydrocarbon was added. After about 1 hour of additional stirring, the solvent was evaporated by evacuation. A free-flowing powder was obtained. Data concerning its properties are given in Table 1.

The catalysts prepared according to Examples 1-12 are obtainable as dry, loose powders, containing a small amount of a low molecular weight solvent or a paraffinic hydrocarbon. The maximum amount of a low molecularweightfraction depends on a composition of the catalyst and on temperature and it can be determined easily for particular conditions.

The catalysts prepared according to Examples 812 are storable without limit in a conventional reservoir equipped with customary armatures. In case of an infiltration of impurities of the electron-donor type to the catalysts, it is necessary to blow a layer of the catalyst by very pure nitrogen before polymerisation, for preventing an access of impurities into the polymerisation apparatus.

Example 13 A 1.5 dm3 laboratory reactor, suitable for the preparation of 300 g of a polymer, was purged by a stream of 0.5 dm3/min of high-purity nitrogen for 16 hours, then it was pressurised at the polymerisation temperature (60100 C) 10 times by nitrogen to 2.0 MPa and finally washed out twice by ethylene. The reactor was thermostated to the polymerisation temperature using a jacket. A mixture of monomers with hydrogen was introduced into the reactor. The polymerisation was started by breaking a glass vial with 50150 mg of a catalyst, prepared according to Examples 1-12.

The bed was fluidized by mechanical stirring and the polymerisation rate was measured from the consumption of the fed monomer mixture. After about 4 hours, the reactor was depressurised, opened and the polymer processed. All conditions of the polymerisation are given in Table 2.

Example 14 In a 1.5 dm3 laboratory reactor, n-hexane was stripped by a stream of nitrogen of very high purity in such a way, that more than 15% w/w of the hydrocarbon was evaporated. Then the reactor pressure was adjusted by feeding a monomer mixture at polymerisation temperature (see Table 2). The polymerisation was commenced by breaking a glass vial with the catalyst (as a powder or as a slurry in a hydrocarbon) and it was carried out for 4 hours at a constant temperature, pressure and composition of the monomer mixture.

After opening the reactor, the polymer was isolated by evaporating the solvent and dried in vacuum oven.

Example 15 The powdery catalyst was fed by a feeding device, using overpressure of nitrogen, into a bottom part of a continuous pilot plant reactor. The polymerisation took place in a fluidized bed, composed of a mixture of the powdery polymer and the catalyst, kept fluidised by a stream of the monomer mixture. The velocity of the stream of the mixture was 3-6 times higher than the minimum velocity needed for fluidisation. A steady state was kept, defined by a pressure of 1.S2.0 MPa, temperature in the range of 70--1 10"C and mole ratios according to Table 2. The polymer produced was removed discontinuously from the reactor depending on its production rate.Productivity of the reactor depends on the residence time (between 2-8 hours), on the efficiency of cooling of the recycling monomer mixture (given by design parameters) and on the activity and concentration of the catalyst (direct proportionality).

These examples show that the process according to this invention allows production of homopolymers and copolymers of ethylene with high bulk density and suitable properties. The processes for the preparation of the catalyst and the polymerisation itself are simple, without necessity to activate the catalyst additionally before feeding it into a reactor in the polymerisation reactor itself. Deposits and large flakes are not formed on walls of the reactor during the polymerisation and a high bulk density of the polymerisation bed assures high productivity of the polymerisation. It is possible to prepare polymers with desired properties by changing the composition of the one-phase catalyst, the process of its preparation and conditions of the polymerisation. There are very many combinations of these possibilities.

The catalyst is stable and active in the polymerisation for unlimited time when an access of impurities of the electron-donor type is prevented. In the case of paraffinic hydrocarbon deposited on the catalyst, its resistance against these impurities is increased extraordinarily.

TABLE 1 Composition of catalysts OH-group content Organometal I Compound II Organometal III Paraffinic hydrocarbon mmole OH mmole I mmole II mmole III g IV Example No. g support g support g support g support g support 1 0.7 AlEt2Cl (0.5) TiCl4 (0.1) BuMgOct (0.4) 2 0.7 AliBu3 (0.5) TiCl4 (0.2) BuMgOct (0.2) 3 0.7 AliBu3 (0.7), AlEtCl2 (0.3) TiCl4 (0.15) AliBu3 (0.2) 4 0.8 AlEt2Cl (0.3), AliBu3 (0.3) TiCl4 (0.1) BuMgOct (0.2) 5 1.9 AlEt2Cl (1.8) TiCl4 (0.1), VCl4 (0.1) AliBu3 (0.5) 6 0.75 AlEt2Cl (0.75) TiCl4 (0.03), VOCl3 (0.05) EtMgBu (0.1) 7 0.8 AlEt2Cl (0.67) TiCl4 (0.16) Et2AlOEt (0.16) 8 0.7 AlEt2Cl (0.5) TiCl4 (0.1) BuMgOct (0.4) 0.20 9 0.7 AliBu3 (0.5) TiCl4 (0.2) BuMgOct (0.2) 0.70 10 0.7 AlEt2Cl (0.5) TiCl4 (0.1) BuMgOct (0.4) 0.84 11 0.8 AlEt3 (0.4) TiCl4 (0.15) EtMgBu (0.15) AliBu3(0.1) 12 0.7 AlEt2Cl (0.67) TiCl4 (0.1) BuMgOct (0.4) 0.20 Notes: 1.Symbols: Et=ethyl; Bu=n-butyl; iBu=isobutyl; Oct=octyl.

2. Silica Davison 959 was used as a support with specific surface 250-300 m/g, the pore volume 1.6 ml/g, with maximum pore radius 11 nm, dehydrated 4 hours at 800 C (Examples 1-3, 8 and 10), 600 C (Examples 4 and 6) and 200 C (Example 5). Alumina with specific volume 150m/g, pore volume 1.0 ml/g with maximum pore radius 25 nm, dehydrated at 800 C was used as a support in Example 7.

TABLE 2 Conditions of polymerisation and properties polymers

Productivity Partial pressure, MPa kg polym. Bulk Particle size distribution, mm Example Tempera- Density density No. ture C H2 ethylene 1-butene hxg Ti or V kg/m MFl2,3 MFR > 0.5 > 0.2 to < 0.5 > 0.1 to < 0.2 1 90 0.02 1.8 - 80 960 340 0.06 36 91.2 8.5 0.3 2 90 0.04 1.8 - 37 960 350 0.11 50 92.6 7.1 0.3 3 80 0.05 1.75 - 19 960 380 0.26 56 92.1 7.7 0.2 4 90 0.01 1.85 0.03 120 935 300 0.22 36 91.3 8.6 0.1 5 90 0.02 1.7 0.08 23 925 310 0.15 35 93.7 6.2 0.2 6 90 0.02 1.75 0.025 136 940 320 0.28 36 94.3 5.6 0.1 7 100 0.015 1.8 0.025 30 940 300 0.30 32 93.7 6.0 0.3 8 90 0.02 1.8 - 105 960 345 0.10 35 91.8 8.1 0.1 9 90 0.04 1.8 - 45 960 360 0.15 45 91.4 8.0 0.5 10 90 0.02 1.8 - 95 960 350 0.15 38 92.3 7.5 0.2 11 90 0.02 1.8 0.08 928 330 0.11 35 94.1 5.5 0.4 12 90 0.02 1.8 - 110 960 350 0.12 31 92.2 7.1 0.7 Notes: : MFI2,3=melt flow index at 190 C and 2.3 kg load.

MFR=melt flow ratio at loads 2.3 kg and 23 kg, respectively.

Polymerisations were performed according to Example 13, No 11 according to Example 15, No. 12 according to Example 15.

Claims (10)

1. A supported one-phase catalyst for the polymerisation of ethylene and its copolymerisation with 1-alkenes having 3-10 carbon atoms obtained by consecutive depositing of at least one compound of aluminium of the general formula I Rm Al X3m, where m is 1-3, at least one compound of titanium of the general formula Ila Rn Ti X4-n, where n is 0-4 and/or vanadium of the general formula llb Rp VXs~p or Rq VX4q where p is 0-5 and q is 0-4 and at least one organometallic compound of the general formula III, where a compound of the general formula Illa can be an organoaluminium compound identical with the compound of the general formula I, or an organomagnesium compound of general formula (Illb) Rr Mg X2~r, where r is 1-2 and R in all compounds I, II and Ill means alkyl, aryl, alkoxide with 1-20 carbon atoms, X means halogen (or in compounds II one X2 can be oxygen) and the substituents Rand X in compounds I, II and Ill can be, but need not be, identical, on a support formed by silica and/or alumina with specific surface 50500 m2/g, with 0.3-3.0 mmole of hydroxyl groups per one gram, with inner porosity 0.5-3.0 ml/g and with dimensions of particles in the range of 1-200 pm.

2. A catalyst according to Claim 1 in which the mole ratio of the organoaluminium compounds I to the hydroxyl groups of the support is in the range of 0.1-10, the mole ratio of the transition metal compounds II to the organoaluminium compounds I is in the range of 0.01-10 and the mole ratio of organometal compounds Ill to the transition metal compounds II is in the range of 0.1-20.

3. A catalyst according to Claim 1 or 2, in which the organoaluminium compound I has alkyls with 1-8 carbon atoms, in which the transition metal compounds Ia are titanium tetrachloride, titanium tetraalkoxide, and the transition metal compounds llb are vanadium tetrachloride, vanadium tetraalkoxide and vanadium oxitrichloride, and in which the organomagnesium compound Illb is dialkylmagnesium with alkyls having 1-10 carbon atoms.

4. A method for the preparation of a supported one-phase catalyst according to Claim 1 and/or 3, in which deposition of the compounds I, II and III on the support is performed in a gaseous phase or in a hydrocarbon solvent.

5. A catalyst according to Claims 1, 2 and 3, which is coated together with the compound III, or separately, with a paraffinic hydrocarbon the melting point of which is in the range of 251 500C, in the amount of 0.5-100% w/w of the uncoated catalyst.

6. A catalyst according to Claims 1, 2 and 3 on which a linear and/or branched 1 -alkene with 2-10 carbon atoms is prepolymerised in the amount of 0.5 to 100% w/w of the catalyst.

7. A method for the polymerisation of ethylene or copolymerisation of ethylene with 1-alkenes having 3-10 carbon atoms at temperatures 30-300 C and pressures 0.1-250 MPa, in a slurry, gaseous phase or in a fluidised bed containing 50100 volume% of 1-alkenes and 0-50 volume% of hydrogen in the monomer mixture using catalyst according to Claims 1, 2, 3, 5 and 6.

8. A polymer of ethylene or its copolymers with 1 -alkenes having 3-10 carbon atoms produced using the supported one-phase catalysts according to Claim 7.

9. A method for the preparation of a catalyst substantially as described in the accompanying Examples.

10. A catalyst prepared by a method substantially as described in the accompanying Examples.