SK686587A3 - Solid catalyst on complex titanium(iii) chloride base useable to stereospecific polymerisation of alpha-olefins and process for preparing same - Google Patents

Abstract

Catalytic solids based on complexed titanium trichloride, which can be employed for the stereospecific polymerisation of alpha-olefins preactivated by being brought into contact with an organoaluminium preactivator comprising the product of reaction of a compound (a) chosen from organoaluminium compounds and of a compound (b) chosen from hydroxyaromatic compounds in which the hydroxyl group is sterically blocked. These solids enable propylene to be polymerised with an improved stereospecificity.

Description

SOLID TITANIUM CHLORIDE BASED CATALYST FOR USE FOR STEREO-SPECIFIC POLYMERIZATION OF ALFA-OLEPHINES AND METHOD OF PREPARATION

Technical field

The present invention relates to a solid catalyst based on complex titanium tetrachloride useful for the stereospecific polymerization of α-olefins and to a process for preparing the catalyst.

BACKGROUND OF THE INVENTION

It is known that it is possible to stereospecifically polymerize α-olefins, such as propylene, by using a catalyst system comprising a solid component based on titanium tetrachloride and an activator consisting of an organometallic compound, such as alkylaluminium chloride.

Belgian patent BE-A-780758 discloses complex solid titanium tetrachloride catalysts with high activity and increased intrinsic porosity, which makes it possible to obtain propylene polymers with very good stereoregularity.

Belgian patent BE-A-803875 discloses the pre-activation treatment of these complex solid catalysts with high activity, which allows storage of these catalysts under hexane for a long time without losing their catalytic properties. The pre-activator used may be selected from the group consisting of organoaluminum compounds, especially compounds of Formula I, including those selected from the group consisting of hydrocarbyl hydrocarbyloxy aluminum halides. However, in practice, diethylaluminum chloride, ethylaluminum sesquichloride, ethylaluminum dichloride and triethylaluminum are generally used.

Unfortunately, the stereospecificity of these catalyst complexes is not sufficient under all polymerization conditions that can be used in the application of these catalysts, especially at relatively high temperatures at which gas phase polymerization is often performed. However, when this polymerization is carried out at relatively low temperatures, a significant reduction in catalytic productivity can be observed.

Therefore, an attempt has been made to eliminate this drawback by carrying out the polymerization in the presence of a catalyst system comprising the above-mentioned high-performance complex solid catalysts which have been modified by introducing into the polymerization medium a third component, generally an electron-donating compound. Lewis base).

As a third component capable of enhancing the stereospecificity of these catalyst systems (see, for example, Belgian patent BE-A-822941), a large number of electron donor compounds of different nature have been described. Of this large number of electrodonor compounds capable of performing the said function of the third component, some phenolic compounds (patent application EP-A-0 036 549) and some hydroxyaromatic compounds (patent US-A-4,478,989) have been suggested for practical use.

However, the improvement in stereospecificity achieved through the introduction of introduced electrodonor compounds is significant only when a relatively high amount of electrodonor compound is used (i.e., the mass of the electrodonor compound is at least equal to and often significantly greater than the weight of the complex solid catalyst present in the polymerization medium).

In addition, adverse secondary effects, in particular an unacceptable reduction in catalytic productivity and parasitic coloration of the obtained polymer, were observed, not to mention the complications which may result from the necessary purification of the obtained polymer from the remainder of the third component.

Accordingly, it is an object of the present invention to provide a solid catalyst with greatly increased stereospecificity without the need to introduce the aforementioned third component into the polymerization medium.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The present invention provides a solid catalyst based on complex titanium tetrachloride, useful for the stereospecific polymerization of α-olefins and pre-activated by contacting a solid precursor in the form of spherical particles having a diameter of 5 to 100 µm. wherein the specific surface area of the precursor is 100 to 250 m ² / g and its total internal porosity is 0.15 to 0.35 cm 2 / g, consisting of a compound of formula

TiCl ₃ (AIRCl 2) _x -Cy where

R represents an alkyl radical having 2 to 6 carbon atoms,

C is a complexing agent selected from the group consisting of aliphatic ethers having aliphatic residues of 4 to 6 carbon atoms, x is less than 0.20; and

Y is greater than 0.009, with an organoaluminum pre-activator, characterized in that the pre-activator is a reaction product of 0.1 to 50 moles of an organoaluminum compound selected from compounds of the general formula

AIR _n X3-n where

R represents a linear or branched alkyl radical having 2 to 8 carbon atoms;

X is chlorine, n is 1 <n <3, and 1 mole of a hydroxyaromatic compound selected from the group consisting of di-tert-alkylated monocyclic monophenols and 3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) monoesters propionate.

The solid catalyst of the invention is preferably characterized in that the organoaluminum compound is selected from the group consisting of trialkylaluminum and dialkylaluminum chlorides.

The solid catalyst of the invention is preferably characterized in that the pre-activator is a compound of the general formula

RpAI (OR ') qX 3 - (p + q) where

R represents the same or different linear or branched alkyl groups having 2 to 8 carbon atoms,

OR 'represents an aryloxy group derived from a hydroxyaromatic compound as defined above,

X is chlorine, p is a number from the range 0 <p <3, q is a number from the range 0 <q <2, with the sum (p + q) being in the range 0 <(p + Q) <3.

The invention also provides a process for the preparation of a solid catalyst according to claim 1, characterized in that the pre-activator is suspended in a solid precursor in an inert hydrocarbon diluent in a molar ratio of the total initial amount of organoaluminum compound to the titanium tetrachloride contained in the precursor. ³ to 10, preferably 10 to ² and 1, and the solid precursor and the pre-activator are kept in contact for 5 to 120 minutes at a temperature between 0 ° C and the normal boiling point of the inert hydrocarbon diluent used.

The process according to the invention is preferably characterized in that the solid precursor and the pre-activator are kept in contact for 15 to 90 minutes at a temperature of 20 to 40 ° C.

The process according to the invention is advantageously characterized in that the pre-activated solid catalyst is separated from the pre-activation medium prior to its use in the polymerization.

The process of the invention is preferably characterized in that the pre-activated solid catalyst is separated from the pre-activation medium and washed with an inert hydrocarbon solvent prior to its use in polymerization.

The solid products based on the complex titanium tetrachloride used as precursors for the preparation of the pre-activated solid catalysts according to the process of the invention can be obtained by any known method. In general, it is preferred to use solid products obtained by methods involving the initial reduction of titanium tetrachloride. This reduction can be accomplished by treatment with hydrogen or metals such as magnesium or aluminum. Best results are obtained when starting from solid products formed by reduction of titanium tetrachloride using an organometallic reducing agent. The organometallic reducing agent may be, for example, an organomagnesium reducing agent. However, the best results are obtained using an organoaluminum reducing agent.

Preferred organoaluminum reducing agents are compounds that contain at least one hydrocarbon radical attached directly to the aluminum atom. Examples of compounds of this type are mono-, di- and trialkylaluminum, the alkyl radicals of which contain 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms, such as triethylaluminum, isopropylaluminum, diisobutylaluminum hydride and ethoxydietylaluminum. Of the compounds of this type, the best results are obtained with dialkylaluminum chloride and especially with diethylaluminum chloride.

In order to obtain solid products based on complex titanium tetrachloride (hereinafter referred to as precursors) used to prepare the pre-activated solid catalysts according to the process of the invention, the abovementioned reduced solid products are subjected to at least one complexing agent generally selected from the group consisting of organic compounds containing at least one atom or group having at least one free electron pair capable of coordinating with titanium or aluminum atoms present in titanium or aluminum halides.

Preferably, said complexing agent is selected from the group consisting of aliphatic ethers, and in particular from the group comprising aliphatic ethers whose aliphatic radicals contain 2 to 8 carbon atoms, preferably 4 to 6 carbon atoms. A typical example of an aliphatic ether giving good results is diisoamyl ether.

These treatments with complexing agents to stabilize or improve the productivity and / or stereospecificity of solid catalysts are well known and have been extensively described in the literature.

In this sense, the treatment with the complexing agent to prepare the precursor may therefore consist in grinding the reduced product in the presence of the complexing agent. This treatment may also consist of thermally treating the reduced solid product in the presence of a complexing agent. Further, this treatment may consist of extracting the reduced solid product in the presence of mixed solvents containing a liquid hydrocarbon compound and an additional polar solvent, for example ether.

It is also possible, for the above purpose, to reduce the titanium tetrachloride by the reducing organoaluminum reagent (1) in the presence of a complexing agent, for example by adding to the titanium tetrachloride a hydrocarbon solution of the complexing reader reaction product with said production agent. subjected to a thermal treatment in the absence of a complexing agent or in the presence of a new amount of a complexing agent, the same as or different from the previous complexing agent. It is also possible to carry out the treatment with the complexing agent by using the complexing agent in an amount sufficient to form a homogeneous solution of the titanium tetrachloride solid product, whereupon the dissolved solid product is reprecipitated by heating.

In the preparation of the precursor, treatment with the complexing agent may be combined with or preceded by the activation treatment. These activation treatments are equally well known and have also been described in the literature. Generally, it is carried out with at least one reagent selected from the group consisting of inorganic halogenated compounds, organic halogenated compounds, interhalogenated compounds and halogens. The following can be cited as:

- as examples of inorganic halogenated compounds: metal and non-metal halides such as titanium halides and silicon halides,

- as examples of organic halogenated compounds: halogenated hydrocarbons such as halogenated alkanes and carbon tetrahalides,

- as examples of interhalogenated compounds: for example, iodine chloride and bromide,

- as examples of halogens: chlorine, bromine and iodine.

Examples of reagents that are very suitable for the activation treatment are titanium tetrachloride, silicon tetrachloride, iodobutane, monochloroethane, hexachloroethane, chloromethylbenzene, carbon tetrachloride, iodine chloride and iodine. Best results are obtained using TiCl4.

The decisive factor for the above precursor preparation is not the physical form in which the complexing agents and the reagents for possible activation processing are present. These agents can be used in gaseous form or in liquid form, the latter form being the most preferred. ^The form in which these agents are present under normal temperature and pressure conditions. The complexing agent treatment and optionally the activation treatment may also be carried out in the presence of an inert hydrocarbon diluent generally selected from the group consisting of aliphatic hydrocarbons, cycloaliphatic hydrocarbons and liquid aromatic hydrocarbons such as liquid alkanes and isoalkanes and benzene.

The details of the most common complexing agent and activation treatments described in more detail can be obtained from Belgian patent BE-A-864708, US-A-4,295,991, as well as from the documents cited in this latter patent.

At any point in the preparation of the precursor, namely after the reduction treatment or treatment with the complexing agent or after the optional activation treatment, but preferably after the reduction treatment, the precursor may be subjected to a treatment aimed at reducing the friability of the particles under which the precursor is formed.

This treatment, called prepolymerization, consists in contacting the solid product with a lower alpha-monoolefin, such as ethylene or preferably propylene, under polymerization conditions to obtain a solid product containing generally about 5 to 500 wt. % prepolymerized alpha-monoolefin. This prepolymerization can advantageously be carried out in a suspension of the solid product in an inert hydrocarbon diluent as defined hereinbefore for the time necessary to obtain the desired amount of prepolymers. ^{of the} purified alpha-monoolefin on said solid product. The precursor obtained in this way is less friable and makes it possible to obtain polymers with good morphology even when polymerization is carried out at relatively high temperatures.

In order to transform the precursor into a pre-activated solid catalyst, the precursor can be used as such, i. without being separated from the reaction medium in which it was prepared or preferably after separation from said reaction medium and optionally washing with an inert hydrocarbon diluent as defined above.

A preferred method for preparing solid products based on complex titanium tetrachloride useful as precursors for the preparation of pre-activated solid catalysts by the process of the invention is described in Belgian patent BE-A-780758. This method consists in the reduction of titanium tetrachloride with an organoaluminum reducing agent (1), which in this case is preferably dialkylaluminum chloride, the alkyl chains of which contain 2 to 6 carbon atoms, under mild conditions. After optional thermal treatment of the thus obtained reduced solid product, the reduced solid product is subjected to a treatment with a complexing agent as defined above. Finally, the titanium tetrachloride treatment is carried out and the thus formed solid product based on the complex titanium tetrachloride is separated from the reaction medium and optionally washed with an inert hydrocarbon diluent as defined above and preferably selected from the group consisting of liquid aliphatic hydrocarbons containing 3 to 12 carbon atoms, the diluent ultimately being a diluent which can be used throughout the preparation of the solid product.

Said preferred method of preparing the solid products described in the preceding paragraph leads to solid product particles based on complex titanium tetrachloride, which are also described in said Belgian patent BE-A-780758. These particles are spherical and generally have a diameter of 5 to 100 microns and most often have a diameter of 10 to 50 microns. They consist of agglomerates of equally spherical microparticles whose diameter is equal to 0.05 to 1 micrometer, most often 0.1 to 0.3 micrometer, these microparticles being extremely porous. This results in a specific surface area of these particles of more than 75 m ² / g and most often lying in the range of 100 to 250 m ² / g and a total porosity of more than 0.15 cm ³ , but most often in the range of 0.20 to 0.35 cm ³ / g. The intrinsic porosity of said microparticles contributes most to said total porosity of the particles, as evidenced by the high pore volume, corresponding to pores with a diameter of less than 20 nanometers, a higher action of 0.11 cm ³ / g and most often in the range of 0.16 up to 0.31 cm ³ / g.

Solid products based on complex titanium tetrachloride (precursors) obtained using the advantageous conditions of the method described in Belgian patent BE-A-780758, corresponding to the general formula

TiCl ₃ (AIRCI ₂ ) x C _yi in which

R is an alkyl radical of 2 to 6 carbon atoms,

C is a complexing agent as defined above, x is any number less than 0.20 and y is any number greater than 0.009 and generally less than 0.20.

As a variant of this preparation method, the above-mentioned method consists in prepolymerizing the reduced solid product after optional heat treatment and before treating with the complexing agent with lower alpha-monoolefin (propylene) under polymerization conditions. This prepolymerization is carried out in suspension of the reduced solid product in an inert hydrocarbon diluent as defined above at a temperature of about 20 to 80 ° C for 1 to 60 minutes.

In the process according to the invention, the precursor prepared as described above is contacted with a tribasic aluminum pre-activator comprising the reaction product of said organoaluminum compound with said hydroxyaromatic compound.

The organoaluminum compound is selected from the group consisting of trialkylaluminum and alkylaluminium monoalkylaluminum di- and alkylaluminium sesquihalides of the general formula

Al R _n * 3-n wherein R represents the same or different alkyl groups containing 1 to 18 carbon atoms, X represents a halogen atom and n represents a number from 0 <n <3.

In the above formula, R is preferably a linear or branched alkyl radical containing 2 to 8 carbon atoms, X is preferably chlorine and n is preferably a number from 1 <n <3.

Examples of such organoaluminum compounds include:

trialkylaluminum such as trimethylaluminum, triethyl aluminum, tri-propyl aluminum, tri-n-butyl-aluminum, tri-isobutylaluminium, tri-n-hexylaluminium, triisohexylaluminium, tri-2-methylpolylaluminium, and tri-2-methylpentylaluminium, and tri-2-methylpentyl aluminum dietylalumínium- monochloride, di-n-propylaluminum and diizobutylalumíniummorOchlorid, dietylalumíniummonofluorid, dietylalumíniummonobromid and dietylalumíniummonojodid, and alkyalumíniumdi- and alkylaluminum such as metylalumíniumseskvichlorid, etylalumínium- sesquichloride, ethyl aluminum dichloride, isobutyl butylalumíniumdichlorid.

However, very good results are obtained with trialkylaluminiums and dialkylaluminium chlorides, in particular with triethylaluminium and diethylaluminium monochloride.

Said hydroxyaromatic compounds are selected from the group consisting of di-tert-alkylated monocyclic monophenols and acid monoesters

3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionic acid.

Examples of said hydroxyaromatic compounds include:

monocyclic monophenols, di-tert-alkylated ortho to the hydroxyl group, such as 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 3,5-di-tert-butyl-4- hydroxy-α-hydroxybenzene, 2,6-di-tert-butyl-4-methoxyphenol, 2,6-di-tert-butyl-4-isopropylphenol, 2,6-dicyclohexyl-4-methyl-phenol, 2,6-diisopropyl-4-methoxyphenol, and 2,6-di-tert-butyl-4-sec-butylphenol,

- 3- (3 ', 5'-di-tert-butyl-4-hydroxyphenyl) propionic acid monoesters such as 3- (3', 5'-di-tert-butyl-4-hydroxyphenyl) methyl propionate, 3- (3 3 ', 5'-tert-butyl-4-hydroxyphenyl) propionate, ethyl 3- (3', 5'-di-tert-butyl-4-hydroxyphenyl) n-propyl propionate, 3- (3 ', 5'-di-tert-butyl-4- hydroxyphenyl) propionate, n-butyl, 3- (3 ^', 5'-di-tertbutyl-4-hydroxyphenyl) propionate noktylnatý, 3- (3', 5'-di-tertbutyl-4-hydroxyphenyl) propionate and n-dodecyl 3 N-octadecyl (3 ', 5'-di-tert-butyl-4-hydroxyphenyl) propionate.

Very good results are obtained by using monocyclic monophenols, diterc. alkylated in both ortho positions relative to the hydroxyl group, in particular using 2,6-di-tert-butyl-4-methylphenol and 3- (3 ', 5'-di-tert-butyl-4-hydroxyphenol) propionic acid monoester and especially using 3- ( 3 ', 5'-di-tert-butyl-4-hydroxyphenyl) n-octadecyl propionate, in particular the use of the latter compound, gives excellent stereospecificity to the solid catalysts.

The general conditions under which an organoaluminum compound is contacted with a hydroxyaromatic compound are not critical at all, as long as they lead to a chemical reaction between the two compounds. Generally, the liquid phase is operated, for example by mixing the organoaluminum compound with a hydroxyaromatic compound in the absence of a liquid diluent, or the organoaluminum compound is often liquid under normal temperature and pressure conditions. Likewise, the reaction of the organoaluminum compound with the hydroxyaromatic compound can be carried out in an inert hydrocarbon diluent as defined above.

The molar ratio in which the organoaluminum compound is reacted with the hydroxyaromatic compound can vary within wide limits. Generally, 0.1 to 50 moles of organoaluminum compound per mole of hydroxyaromatic compound is used. Preferably, 15 to 0.5 moles of organoaluminum compound per mole of hydroxyaromatic compound are used. Very good results were obtained using an organoaluminum compound and a hydroxyaromatic compound in a molar ratio of about 1 to 3.

The organoaluminum and hydroxyaromatic compound may be contacted generally at temperatures of about 0 to 90 ° C, preferably at or near ambient temperature (25 ° C), and the mixture is thus maintained for the time necessary to chemically react with each other. Generally, this time is 5 minutes to 5 hours. This reaction is most often accompanied by the evolution of gas, which makes it possible to evaluate the progress of the reaction.

The exact chemical structure of the reaction product of an organoaluminum compound and a hydroxyaromatic compound is not known with certainty. However, it is virtually certain that this product corresponds at least in part to the formula:

RpAI (OR ') qX 3 - (p + q) in which

R as defined above means the same hydrocarbon radical or the same hydrocarbon radicals as the radical or radicals contained in or contained in the organoaluminum compound,

OR 'means an aryloxy group derived from a hydroxyaromatic compound,

X. represents a halogen atom, p represents a number from the range 0 <p <3, preferably a number from the range 0.1 <P <2.5, q represents a number from the range 0 <q <2, preferably a number from the range 0.5 < q <1.5, where the sum (p + q) is in the range 0 <(p + q) <3.

In the process according to the invention, the organoaluminum pre-activator obtained above is contacted with a precursor.

The pre-activator is used as a solution in an inert hydrocarbon diluent, optionally used for its preparation. This solution contains the reaction product of the organoaluminum compound with the hydroxyaromatic compound, optionally accompanied by an excess of the used and unreacted organoaluminum compound or the hydroxyaromatic compound.

In this case, it is preferred to introduce a solution of the pre-activator containing said reaction product and optionally one unreacted reactant into the precursor suspension in the same hydrocarbon diluent. This suspension is generally maintained at a temperature between 0 ° C and the normal boiling point of an inert hydrocarbon diluent in which the pre-activator has been dissolved, preferably at 20 to 40 ° C, for about 5 to 120 minutes, preferably 15 to 90 minutes. minutes

The amount of precursor and pre-activator used is such that the molar ratio of the starting amount of the organoaluminum compound to the amount of titanium tetrachloride present in the precursor is equal to 10'3 to 10, preferably 10'2 to 1. Good results are obtained using the molar ratio of total the amount of organoaluminum compound to the amount of titanium tetrachloride present in the precursor equal to 0.05 to 0.5. Upon completion of this preactivation treatment, the preactivated solid catalyst is preferably separated from the preactivation medium and washed to remove an unfixed residue of the preactivator, preferably an inert hydrocarbon diluent of the same nature as the diluent used to prepare the precursor and the preactivator solution.

The separated and washed pre-activated solid catalyst may then optionally be dried. For example, it may be dried to such an extent that its residual liquid hydrocarbon diluent content is less than 1 wt. %, preferably less than 0.5 wt. %, based on the weight of the titanium tetrachloride it contains, using the procedure described in Belgian patent BE-A-846911 (Solvay et Cie).

The pre-activated solid catalyst thus obtained always contains a certain amount of the pre-activator fixed to the solid product, and it is not possible to cleave this amount of the pre-activator by pure physical separation methods. This amount of pre-activator is generally 5 to 500 g per kg of titanium tetrachloride present in the solid product, preferably 50 to 300 g / kg. Therefore, the pre-activated solid catalyst prepared by the process of the invention contains less titanium tetrachloride per unit weight than the solid product used as a precursor for its preparation. Although the pre-activated solid catalyst generally contains at least 50 wt. % of titanium tetrachloride, based on the total weight of the preactivated catalyst strength, seldom contains more than about 80 wt% preactivated solid catalyst. % titanium tetrachloride.

The external morphology of the pre-activated solid catalyst particles prepared according to the invention is not at all different from the external morphology of the precursor particles used to produce the pre-activated solid catalyst. Thus, if the pre-activated solid catalyst particles are prepared from spherical precursor particles formed by spherical porous microparticle agglomerates, the pre-activated solid catalyst particles produced have substantially the same structure, dimensions and shape as the precursor precursor particles. However, the particles of the pre-activated solid catalyst are less porous, which means that these particles no longer have a high specific surface area resulting from the high pore volume of the precursor particles.

After washing and optionally drying, the pre-activated solid catalysts prepared by the process of the invention can be immediately contacted with an inert hydrocarbon diluent, for example a diluent as defined hereinbefore, which is also useful as a slurry polymerization diluent.

Pre-activated solid catalysts produced according to the invention may also be subjected to a prepolymerization ₁ .u,,, of. processing already described above for the precursor. These pre-activated catalysts can be stored under hexane or in dry form, preferably in the cold, for a long time without losing their properties.

In the polymerization, the preactivated solid catalyst prepared by the process of the invention is used together with an activator selected from the group consisting of organometallic compounds of metals of IA, II.A, II.B and III.B of the Periodic System Element Group (version published in Kirk- Othmer Encyclopedia of Chemical Technology, 2nd Complete Edition, Volume 8, 1965, p. 94), preferably selected from the group consisting of compounds of formula:

Al R'mYS-m.

in which

R 'represents a hydrocarbon radical containing 1 to 18 carbon atoms, preferably 1 to 12 carbon atoms, selected from the group consisting of alkyl radicals, aryl radicals, arylalkyl radicals, alkylaryl radicals and cycloalkyl radicals, the best results being obtained when R is selected from the group consisting of alkyl radicals of 2 to 6 carbon atoms,

Y is halogen, selected from the group consisting of fluorine, chlorine, bromine and iodine, with best results when Y is chlorine, and

m is any number from 0 <m <3, preferably a number from 1.5 <m <2.5, with best results obtained when m is 2.

The maximum activity and stereospecificity of the catalyst system is guaranteed by diethyl aluminum chloride.

The catalyst systems thus defined are used in the polymerization of olefins which are terminally unsaturated and whose molecule contains 2 to 18 carbon atoms, preferably 2 to 6 carbon atoms, such as, for example, ethylene, propylene, 1-butene, 1-pentene, 1-methylbutene , 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene and vinylcyclohexene. Of particular interest for stereospecific polymerization are propylene, 1-butene and 4-methyl-1-pentene, resulting in crystalline, strongly isotactic polymers. The catalyst systems of the invention are also used in the copolymerization of said alpha-olefins with each other as well as with diolefins having from 4 to 18 carbon atoms.

Preferably, these diolefins are unconjugated aliphatic diolefins such as 1,4-hexadiene, unconjugated monocyclic diolefins such as

4-vinylcyclohexene, alicyclic diolefins having an endocyclic bridge such as dicyclopentadiene, methylene norbomene and ethylene norbornene and conjugated aliphatic diolefins such as butadiene or isoprene.

Said catalyst systems are also used in the production of copolymers, called block copolymers, which are formed from alpha-olefins and diolefins. These block copolymers include chains consisting of a plurality of polymer blocks, each of which is composed of monomeric units of one species, the chains of each block having a variable length. In the present case, each block consists of an alpha-olefin homopolymer or a random copolymer comprising an alpha-olefin and at least one copolymer selected from the group consisting of alpha-olefins and diolefins. The alpha-olefins and diolefins are selected from the above alpha-olefins and diolefins.

The preactivated solid catalysts of the invention are particularly suitable for the production of propylene homopolymers and copolymers containing a total of at least 50% by weight of propylene, preferably at least 75% by weight. % propylene.

The polymerization can be carried out in any known manner, in solution or suspension in a solvent or inert hydrocarbon diluent, as defined, for example, in connection with the preparation of a solid catalyst and which is preferably selected from butane, pentane, hexane, heptane, cyclohexane, methylcyclohexane or mixtures thereof.

The polymerization can also be carried out in monomer or monomers maintained in the liquid state or also in the gas phase. The use of the pre-activated solid catalysts according to the invention is very advantageous in the case of gas-phase polymerization. The use of the catalytic system with a pronounced stereospecificity according to the invention is particularly advantageous in cases where amorphous and sticky by-products are formed in the polymerization, the elimination of which is not possible by the technology.

Generally, a temperature of 20 to 200 ° C, preferably a temperature of 50 to 90 ° C, can be used in the polymerization, the best results being obtained at a temperature of 65 to 85 ° C. With respect to the polymerization pressure conditions, generally atmospheric pressure up to 5 MPa, preferably 1 to 3 MPa, can be used. This pressure is, of course, a function of the polymerization temperature used.

The polymerization can be carried out continuously or discontinuously.

The production of the abovementioned block copolymers can also be carried out in any known manner. It is preferred to use a two-step process consisting in the polymerization of alpha-olefin, generally propylene, by the method described above in connection with homopolymerization. Then another alpha-olefin and / or diolefin, generally ethylene, is polymerized in the presence of an active homopolymer chain. This second polymerization can only be carried out after the monomer which has not reacted during the first step has been completely or partially removed.

The organometallic compound and the pre-activated solid catalyst may be added separately to the polymerization medium. They may also be contacted at 40-80 ° C for one to several days, depending on the temperature used, before being introduced into the polymerization reactor.

The total amount of organometallic compound used is not a critical factor; this amount is generally greater than 0.1 mmol per liter of diluent, liquid monomer or reactor volume, preferably greater than 0.5 mmol per liter.

The amount of pre-activated solid catalyst used is determined depending on its titanium tetrachloride content. Generally, it is chosen in such a way that the polymerization medium contains more than 0.01 mmol mol of titanium tetrachloride per liter of diluent, liquid monomer or reactor volume, preferably more than 0.05 mmol per liter.

The ratio of the amount of organometallic compound to the pre-activated solid catalyst is also not a critical factor. In general, these amounts are chosen such that the molar ratio of organometallic compound to titanium tetrachloride contained in the solid product is 0.5 to 20, preferably 1 to 15. However, the best results are obtained at said molar ratio of 2 to 12.

The molecular weight of the polymers produced by the process of the invention can be controlled by adding to the polymerization medium at least one molecular weight regulating agent of the resulting polymer, such as hydrogen, diethyl zinc, alcohols, ethers, and alkyl halides.

The stereospecificity of the pre-activated solid catalysts of the invention is higher than the stereospecificity of the complex catalysts described in Belgian patent BE-A-780758 when prepared from the latter catalysts. Moreover, their stereospecificity remains unchanged for a long time, even when stored at a relatively high temperature. It is also necessary in their use to add the usual described third component to the polymerization medium in order to improve their stereospecificity, such as an ether or an ester. Of course, the addition of such a third component to the polymerization medium containing the pre-activated solid catalyst of the invention is also within the scope of the invention; however, this addition only leads to an improvement in the stereospecificity of the marginal range.

In the propylene homopolymerization in the presence of the pre-activated solid catalysts of the invention, the amount of amorphous polypropylene determined by measuring the weight of boiling heptane soluble in relation to the solid polypropylene produced during polymerization is always less than 3%. This quality is also achieved by the solid polypropylene produced, even if a pre-activated solid catalyst was used in the polymerization and was stored at a relatively high temperature (45 ° C) for several weeks before use.

DETAILED DESCRIPTION OF THE INVENTION

In the following, the invention is explained in more detail by way of specific examples of the invention, which are illustrative only and are not intended to limit the scope of the invention in any way.

In these examples, the following symbols have the following meanings:

l.l means the polymer isotacticity index, defined as the polymer fraction, calculated in% and related to the total amount of solid polymer obtained, which is insoluble in boiling heptane;

G means the shear modulus of the polymer, measured at a temperature of 100 ° C and at a torsion angle of 60 arc degrees, the mold temperature being stabilized at 70 ° C and a duration of 5 minutes (BS 2782 part

I. - method 150A, ISO 458 / I, method B, DIN 53447 and ASTM D 1043); this module is expressed in daN / cm2,

MFI melt index, measured under a load of 2.16 kg at 230 ° C and expressed in g / 10 min. (ASTM D 1238)

The PSA is the apparent specific gravity of the insoluble polymer fraction, measured after shaking and expressed in g / l, and the catalytic activity, usually expressed in grams of insoluble polymer in the polymerization medium obtained per hour and per gram of titanium tetrachloride contained in the pre-activated solid catalyst.

Example 1

A. Preparation of precursor (solid product based on complex titanium tetrachloride)

90 ml of anhydrous hexane and 60 ml of pure titanium tetrachloride are introduced into a 800 ml reactor equipped with a two-blade stirrer and rotating at 400 rpm. This hexane titanium tetrachloride solution is cooled to 0 (± 1) ° C. A solution of 190 ml of hexane and 70 ml of diethyl aluminum chloride was added to the solution over a period of 4 hours while maintaining the reactor temperature at 0 (± 1) ° C.

After addition of the solution containing diethylaluminum chloride and hexane, the reaction medium is a suspension of fine particles and stirred at 1 (± 1) ° C for 15 minutes, then warmed to 25 ° C for 1 hour. This temperature is maintained for one hour and then heated to about 65 ° C over one hour. At this temperature, the reaction medium is stirred for two hours.

The liquid phase is then separated from the solid product and the recovered solid product is then washed seven times with 200 ml of anhydrous hexane, suspending the solid product in anhydrous hexane with each wash.

The reduced solid thus obtained is then suspended in 456 ml of diluent (hexane) and 86 ml of diisoamyl ether is added to this suspension. The resulting suspension was stirred at 50 ° C for one hour. Thereafter, the solid product thus treated is separated from the liquid phase.

The separated solid is suspended in 210 ml of hexane and 52 ml of titanium tetrachloride is added to the obtained suspension; the suspension was stirred (150 rpm) at 70 ° C for two hours. The liquid phase is then removed by filtration and the solid product based on complex titanium tetrachloride is washed fourteen times with 270 ml of hexane.

B. Pre-activation

70 g of solid titanium trichloride (containing about 820 g of titanium tetrachloride per kilogram of this product) suspended in 280 ml are introduced into a 800 ml reactor equipped with a paddle stirrer at 150 rpm. hexane. 120 ml of a solution of a pre-activator (hereinafter referred to as pre-activator A) in hexane, previously prepared by mixing one liter of hexane, 80 g of diethylaluminium chloride (organoaluminum compound) and 176.2 g of 3- (3) are slowly introduced into the reactor (over 30 minutes). 5'-di-tert-butyl-4-hydroxyphenyl) n-octadecyl propionate (hydroxyaromatic compound).

Thus, the molar ratio of the organoaluminum compound to the hydroxyaromatic compound used to prepare the preactivator is 2, while the molar ratio of the preactivator A to the solid titanium trichloride solid product (expressed in moles of the organoaluminum compound initially used per mole of titanium tetrachloride present in the solid product). ) is 0.2.

The pre-activator solution is introduced into the reactor up to 15 minutes after the end of gas evolution has been observed while mixing the organoaluminum compound and the hydroxyaromatic compound. The resulting suspension after addition of the pre-activator A was stirred for one hour at 30 ° C.

After decanting, the resulting pre-activated solid Catalyst is washed five times with 100 ml of anhydrous hexane, each time the catalyst is suspended again in a new batch of anhydrous hexane, and the catalyst is dried in a fluidized bed with nitrogen at 70 ° C for two hours.

The pre-activated solid catalyst thus obtained contains 641 g of titanium chlorite, 12 g of aluminum, 31 g of diisoamyl ether and an amount estimated at about 250 g of pre-activator A per kilogram of pre-activated catalyst.

C. Polymerization of Propylene in Liquid monomer suspension in the presence of a pre-activated solid catalyst

In a 5-liter autoclave, which has been pre-dried and kept under a nitrogen atmosphere, is fed under a stream of:

- 400 mg of diethylaluminum chloride (as a 200 g / l solution in hexane (CI / Al atomic ratio is set at 1,02 by addition of ethylaluminum dichloride),

- 100 mg of the pre-activated solid catalyst (the molar ratio of diethylaluminum chloride to titanium tetrachloride present in the solid product is thus about 8),

hydrogen under a partial pressure of 0,1 MPa, and

- 3 liters of liquid propylene.

The reaction mixture was stirred at 65 ° C for 3 hours in the reactor. The excess propylene is then degassed and the formed polypropylene is recovered in an amount of 643 g dry polypropylene.

The activity of a pre-activated solid catalyst is 3340, productivity is increased to 6430 g polypropylene / g pre-activated solid catalyst.

The polypropylene obtained has the following properties:

l.l = 98.1%

G = 678 daN / cm 2

MFI = 3.16 g / 10 min.

PSA = 510 g / l.

Examples 1R to 5R

These examples are comparative examples.

Example 1R

A solid product based on the complex titanium tetrachloride was prepared as described in Part A of Example 1, but the solid product was subjected to the pre-activation described in Part B of Example 1.

This solid was dried as in Example 1 to give a product containing 811 g of titanium tetrachloride, 2.8 g of aluminum and 61 g of diisoamyl ether.

The polymerization process is then carried out in the presence of the unpractivated solid catalyst thus obtained under conditions exactly as used in Part C of Example 1. 785 g of dry polypropylene are obtained after the polymerization.

Thus, activity is 3230 and productivity reaches 7850 g polypropylene / g solid catalyst.

This polypropylene has the following properties:

l.l = 94.9%

G = 572 daN / cm ²

MFI = 7.3 g / 10 min.

PSA = 490 g / l.

Significant differences in the content of boiling heptane insoluble content and in the G module values of the obtained polymers under comparable conditions of Examples 1 and 1R demonstrate a higher stereospecificity of the catalyst system containing the pre-activated solid catalyst of Example 1.

Example 2R

The solid product based on the complex titanium tetrachloride, prepared as described in Part A of Example 1, is pre-activated with a solution containing only the hydroxyaromatic compound. Partial dissolution of the solid product, which otherwise takes the form of very fine grains, can be observed. The polymerization test carried out by the procedure described in Example 6 in this case is carried out with an amount of catalyst containing 70 mg of titanium tetrachloride.

535 g of polypropylene are obtained, which corresponds to an activity and only 2550. This polypropylene has the form of fine grains and its PSA is only 100 g / l, which excludes the possibility of its use.

Example 3R

In this example, parts A and B of Example 1 are repeated, except that the solid titanium trichloride chloride solid product slurry is combined successively with a solution of the organoaluminum compound in hexane and 15 minutes after the addition of said organoaluminum compound solution. of a hydroxyaromatic compound in hexane. The molar ratios of the separately added organoaluminum compound and hydroxyaromatic compound as well as the organoaluminum compound and the amount of titanium tetrachloride present in the solid product are 2 and 3, respectively. 0.2. The isolated solid catalyst contained 757 g of titanium tetrachloride per kilogram of catalyst.

The polymerization test performed according to the procedure described in Part C of Example 1 allows only polypropylene to be isolated, having an activity of 3090, in the form of non-manipulable blocks.

Example 4R

The procedure of Example 3R is repeated, but reversing the order of introduction of the solutions of the organoaluminum compound and the hydroxyaromatic compound. The same phenomenon as in Example 2R is observed, namely the partial dissolution of the solid product.

The polymerization test performed according to the procedure described in Part C of Example 1 allows only polypropylene to be isolated with activity and 3450, in the form of very large grains having a PSA of only 200 g / l, eliminating the possibility of its use.

Example 5R

The solid titanium tetrachloride product, prepared according to the procedure described in Example 1R (i.e., it is an unpractivated catalyst), is used in the polymerization test according to the procedure described in Part C of Example 1, except that: Irganox 1076 is introduced into the polymerization medium in addition to diethylaluminum chloride, solid product, hydrogen and propylene in an amount such that the molar ratio of this product to titanium tetrachloride present in the solid product is about 0.2. ~

With an activity of equal to 3286, polypropylene is obtained with the following properties:

l.l = 95.2%

G = 575 daN / cm ²

MFI = 5.2 g / 10 min.

PSA = 505 g / l.

Example 2

A pre-activated solid catalyst was prepared as described in Parts A and B of Example 1, except that the 3- (3 ', 5'-di-tert-butyl-4-hydroxyphenyl) -propadecyl propionate was replaced with 2,6-di-tert. butyl-4-methyl-phenol, commercially available from SHELL under the designation lonol CP.

The pre-activated solid catalyst thus obtained contains 632 g of TiCl3, 14 g of aluminum, 30 g of diisoamyl ether, and an amount of the preactivator, estimated to be about 170 g per kilogram of catalyst. This catalyst is used in the polymerization test described in Part C of Example 1.

This test allows to isolate with activity 3230 polypropylene having the following properties:

l.l = 95.9%

G = 653 daN / cm ²

MFI = 9g / 10min.

PSA = 500 g / l.

Example 3

The preactivated solid catalyst, prepared as described in Parts A and B of Example 1, was used to slurry polymerize propylene in hexane under the conditions described below.

In a 5 liter autoclave of non-oxidizable steel, flushed several times with nitrogen, 1 liter of purified and anhydrous hexane was introduced. Then 400 mg of diethylaluminum chloride (as a 200 g / l hexane solution) and an amount of solid catalyst equivalent to about 51 mg of titanium tetrachloride are successively introduced into the autoclave. Thus, the molar ratio of diethylaluminum chloride to titanium tetrachloride is about 10.

The autoclave is heated to 65 ° C and the pressure is maintained at atmospheric pressure by gradual degassing. An absolute hydrogen pressure of 0.03 MPa is then carried out in the autoclave, and propylene is then introduced into the autoclave until the total pressure at this temperature of 1.19 MPa is reached. This pressure is kept constant during the polymerization by introducing propylene gas.

After 3 hours the polymerization was stopped by degassing propylene.

Filter the contents of the autoclave in a Buchner funnel, wash three times with 0.5 L hexane and dry under reduced pressure at 60 ° C. 251 g of hexane insoluble polypropylene are isolated. In the hexane used for polymerization and washing, 0.75 g of soluble polymer was found, corresponding to about 0.3%. Activity a has a value of 1643. The productivity is 3157 g polypropylene / g pre-activated solid catalyst.

Hexane-insoluble polypropylene has the following properties:

l.l = 98.2%

G = 654 daN / cm ²

MFI = 2.9 g / 10 min.

PSA = 503 g / L.

Example 6R

This example is a comparative example.

In the presence of a solid catalyst prepared as described in Example 3, except that the pre-activation treatment containing 735 g of titanium tetrachloride per kilogram of catalyst is omitted, a polymerization test is performed under the same conditions as described in Example 3.

With an activity of 1719, a polypropylene is obtained whose 1% is soluble in the polymerization hexane and in the washing hexane and whose part, insoluble in hexane, has the following properties:

l.l = 95.7%

G = 591 daN / cm ²

MFI = 9.5 g / 10 min.

PSA = 479 g / l.

Example 4

The preactivated solid catalyst was prepared by the procedure generally described in Steps A and B of Example 1. However, after treating the reduced solid product suspension by stirring at 65 ° C for two hours, the suspension was cooled to about 55 ° C; propylene is introduced into the gas part of the reactor at a pressure of 0.2 MPa. This feed is continued for the time necessary (about 45 minutes) to obtain 100 g of polymerized propylene per kilogram of solid catalyst. The suspension of the prepolymerized solid product is then cooled to 40 ° C and the preparation is then continued as described in Part A of Example 1.

The finally obtained preactivated solid catalyst contains 611 g of titanium tetrachloride, 9 g of aluminum, 14 g of diisoamyl ether and an amount of preactivator A, estimated at about 143 g per kilogram of catalyst.

This preactivated solid catalyst is used in the polymerization of propylene, comprising a first stage carried out in liquid monomer and a second stage carried out in the gas phase under the conditions described in more detail below.

In a 5 liter autoclave used in Examples 1 and 3, a nitrogen stream is introduced:

800 mg of diethylaluminum chloride, and

- amount of solid catalyst equivalent to 100 mg of titanium tetrachloride.

Thus, the molar ratio of diethylidinium chloride to titanium tetrachloride is about 10.

An absolute hydrogen pressure of 0.02 MPa was realized in the autoclave. 2 liters of liquid propylene are then introduced with stirring and the autoclave is heated to 60 ° C. The contents were polymerized for 30 minutes at this temperature. The autoclave is then degassed to a pressure of 1.5 MPa while simultaneously heating to 70 ° C. An absolute hydrogen pressure of 0.1 MPa is then carried out in the autoclave and propylene is introduced into the autoclave until a total pressure of 2.8 MPa is reached at said temperature. After 3 hours, the polymerization is stopped by degassing propylene, whereupon the formed polypropylene is isolated in an amount of 1150 g dry polypropylene.

Thus, the activity of the pre-activated solid catalyst is equal to 3286 and the productivity reaches 7027 g of polypropylene / g of pre-activated solid catalyst. This propylene has the following properties:

l.l = 97.9%

G = 698 daN / cm 2

MFI = 3g / 10min.

PSA = 520 g / l.

Example 7R

This example is a comparative example.

The preactivated solid catalyst is prepared as described in Example 4, but the preactivation treatment is omitted. This solid product contains 718 g of titanium tetrachloride, 3.8 g of aluminum and 84 g of diisoamyl ether per kilogram. The use in a polymerization test carried out under the conditions described in Example 4 makes it possible to obtain, with an activity of 3168, a polypropylene, characterized by the following properties:

l.l = 96.4%

G = 620 daN / cm ²

MFI = 3g / 10min.

PSA = 516 g / l.

Examples 5 to 7

Pre-activated solid catalysts were prepared under the conditions of Example 4 except that the molar ratio of the organoaluminum compound and the hydroxyaromatic compound used to prepare the pre-activator A (see Part B of Example 1) was modified with respect to Examples 5 and 6. as well as the molar ratio of the pre-activator A to the complex titanium tetrachloride solid product (expressed in moles) of the organoaluminum compound initially used per mole of titanium tetrachloride present in the solid product (see Part B of Example 1) with respect to Example 7.

These pre-activated solid catalysts are used in the test polymerization of propylene in suspension in hexane under the conditions set forth in Example 3.

The individual preparation conditions of the solid catalysts as well as the results of the test polymerizations are summarized in Table I below.

Table I

Example 5 0 7 Preparation of pre-activated solid catalysts

organoaluminum compound

hydroxyaromatic compound (Mol / mol) 50 10 10 organoaluminum compound (Mol / mol) 1 1 0.2

TiCl 2 content in the solid product

content of T1Cl3 in pre-activated solid catalyst (g / kg) 724 672 709 Results of polymerization activity (g polypropylene / g TiCl3.h) 2160 2160 2130 polypropylene, soluble in polymerization hexane (% of total polypropylene) 1.1 0.8 1.1 1.1 (%) 97.3 98.2 97.4 G / daN (cm 2) 678 688 689 MFI (g / 10 min) 7.1 5.0 7.7 PSA (g / l) 502 502 504

Example 8

A pre-activated solid catalyst according to Example 4 was prepared and used in the polymerization test carried out under the conditions set forth in Part C of Example 1, except that the reactor was operated under stirring at 75 ° C for two hours.

Under these conditions, the preactivated solid catalyst makes it possible to obtain polypropylene having an activity of &lt; RTI ID = 0.0 &gt;

1.1 = 98.1%

G = 688 daN / cm 2

MFI = 5.9 g / 10 min.

PSA = 510 g / l.

Examples 9 and 10

Preactivated solid catalysts were prepared under the conditions set forth in Parts A and B of Example 1 except that triethylaluminum (Example 9) or ethylaluminum chloride (Example 10) was used as the organoaluminum compound.

These preactivated solid catalysts are used in suspension propylene suspension polymerizations in liquid monomer under the conditions generally set forth in Part C of Example 1.

The properties of the catalysts used as well as the results of the test polymerizations described are shown in Table II below.

Table II

Example 9 10 Nature of organoaluminum compound triethyl- ethyl used in the preparation of the pre-activated solid catalyst dichloride aluminum aluminum acetylacetonate TiCl 3 content in pre-activated solid catalyst (g / kg) 648 713 activity (g polypropylene / g TiCl3 .h) 3136 2875 Properties of polypropylene H (%) 98.0 97.7 G (daN / cm ² ) 645 667 MFI (g / 10 min) 3.4 3.7 PSA (g / l) 504 490

PATENT CLAIMS

Claims (7)

A solid catalyst based on complex titanium tetrachloride, usable for the stereospecific polymerization of α-olefins and pre-activated by contacting a solid precursor in the form of spherical particles having a diameter of 5 to 100 µm consisting of an agglomerate of equally spherical microparticles having a diameter of 0.05 to 1 µm; the specific surface area of the precursor is 100 to 250 m ² / g and its total internal porosity is 0.15 to 0.35 cm ³ / g consisting of a compound of the general formula TiCl 3 X 1 R 1 O 2 x-Cy where R represents an alkyl radical having 2 to 6 carbon atoms, C is a complexing agent selected from the group consisting of aliphatic ethers having aliphatic residues of 4 to 6 carbon atoms, x is less than 0.20; and Y is greater than 0.009, with an organoaluminum pre-activator, characterized in that the pre-activator is a reaction product of 0.1 to 50 moles of an organoaluminum compound selected from compounds of the general formula AIR _n X ₃ -n where R represents a linear or branched alkyl radical having 2 to 8 carbon atoms, X is chlorine, n is a number from 1 <n <3, and 1 mole of a hydroxyaromatic compound selected from the group consisting of di-tert-alkylated monocyclic monophenols and 3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) monoesters propionate. 2. The solid catalyst of claim 1 wherein the organoaluminum compound is selected from the group consisting of trialkylaluminum and dialkylaluminum chlorides. Solid catalyst according to claim 1 or 2, characterized in that the pre-activator is a compound of the general formula RpAI (OR ') qX 3 - (p + q) where R represents the same or different linear or branched alkyl groups having 2 to 8 carbon atoms, OR 'represents an aryloxy group derived from a hydroxyaromatic compound selected from the group defined in claim 1, X is chlorine, p is a number from the range 0 <p <3, q is a number from the range 0 <q <2, with the sum (p + q) being in the range 0 <(p + Q) <3. A process for the preparation of a solid catalyst according to claim 1, characterized in that the pre-activator is introduced into a suspension of the solid precursor in an inert hydrocarbon diluent in a molar ratio of the total initial amount of organoaluminum compound to the amount of titanium tetrachloride contained in the precursor of 10 -3 to 10. preferably 10 ^'2-1 and the solid precursor and predaktivátor are held in contact for 5 to 120 minutes. at a temperature between 0 ° C and the normal boiling point of the inert hydrocarbon diluent used. The method of claim 4, wherein the precursor and the pre-activator are kept in contact for 15 to 90 minutes. at 20 to 40 ° C. Process according to claim 4 or 5, characterized in that the pre-activated solid catalyst is separated from the pre-activation medium before its use in polymerization. Process according to claim 4 or 5, characterized in that the pre-activated solid catalyst is separated from the pre-activation medium and washed with an inert hydrocarbon solvent prior to its use in polymerization.