SK509890A3 - Method of alpha-olefins stereospecific polymerization - 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

METHOD OF FERAL POLYMERIZATION OF ALPHA-OLEPHINS

Technical field

The invention relates to the stereospecific polymerization of α-olefins, in particular propylene, in suspension in an inert solvent, in a liquid or gas phase monomer in the presence of a catalyst system comprising an organometallic compound of Group IA, II.A, II.B and III.B metals. and a solid catalyst based on complex titanium tetrachloride which has been pre-activated by contacting it with an organoaluminum pre-activator. BACKGROUND OF THE INVENTION

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

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

Belgian patent specification 80-Α-803975 describes the pre-activation treatment of these complex solid catalysts with high activity, which allows the catalysts to be stored 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 aluminum hydrocarbyl 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 the polymerization conditions that may be possible with the use of these catalysts, especially at the relatively high temperatures at which gas phase polymerization of propylene is often carried out. However, when this polymerization is carried out at relatively low temperatures, a significant reduction in catalytic productivity can be observed.

Therefore, an attempt was made to eliminate this drawback by carrying out the polymerization of propylene in the presence of a catalyst system containing the above superactive solid catalysts, modified by introducing into the polymerization medium a third component, generally a compound having the character of an electron donor (Lewis base). ).

The function of this third component, capable of enhancing the stereospecificity of these catalyst systems (see, for example, the Belgian patent ΒΞ-Α-822941), has already described a large number of electron donor compounds of different nature. Of the large number of electron donor compounds capable of performing said function of said third component, in particular some phenolic compounds (patent application EP-A-0036549) and some hydroxyaromatic compounds (U.S. Patent A-4478989) have been suggested for practical use.

However, the improvement in stereospecificity achieved by the introduction of said electron donor compounds is significant only when a relatively high amount of the electron donor compound is used (i.e. when the mass of the electron donor compound is at least equal to and often significantly greater than the mass 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 coloring of the obtained polymer, were observed, not to mention the complications which may result from the necessary purification of the obtained polymer from residues of said third component.

In view of the above drawbacks, it is therefore 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

The present invention provides a process for the stereospecific polymerization of α-olefins, in particular propylene, in suspension in an inert solvent, in a liquid state or in a gas phase monomer in the presence of a catalyst system comprising an organometallic compound of Group IA, II.A, II.B and III metals. B of the periodic system and a solid catalyst based on complex titanium tetrachloride which has been 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; 100 to 250 m @ 2 / g and its total internal porosity is 0.15 to 0.35 cm @ 2 / g formed by a compound of formula

TiCl ₃ (AIRCI ₂ ) _X - C _y where l

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 radicals having from 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 it is formed from a reaction product of 0.1 to 50 moles of an organoaluminum compound selected from compounds of the general formula

AIR ' _m Y3-m.

where

R 'is a hydrocarbon radical having 1 to 18 carbon atoms,

Y is a halogen selected from the group consisting of fluorine, chlorine, bromine and iodine; and m is a number from 0 <m 3, and 1 mole of a hydroxyaromatic compound selected from the group consisting of di-tert-alkylated monocyclic monophenols and monoesters of 3- (3) (5'-tert-butyl-4'-hydroxyphenyl) propionic acid.

The solid products based on the complex titanium tetrachloride used as precursors for the preparation of the pre-activated solid catalysts of the invention can be obtained by any known method. In general, it is preferred to use solid products obtained by methods involving an initial reduction of titanium tetrachloride. This reduction can be carried out by the action of hydrogen or metals such as magnesium and 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 moiety attached directly to the aluminum atom. Examples of compounds of this type are mono-, di-trialkylaluminiums whose alkyl radicals contain 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms, such as triethylaluminum, isoprenylaluminum, diisobutylaluminum hydride and ethoxydietylaluminum. Of the compounds of this type, the best results are obtained by using dialkylaluminum chlorides, and in particular 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 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 to reduce the titanium tetrachloride by a reducing organoaluminum reagent in the presence of a complexing agent, for example by adding to the titanium tetrachloride a hydrocarbon solution of the complexing agent reaction product with said reducing agent, and subjecting the thus obtained reduced solid product to heat treatment a complexing agent or in the presence of a new amount of a complexing agent, the same as the previous complexing agent or other than the former. 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. 2 of these agents may be mentioned in particular:

- 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: iodine chloride and bromide,

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

Examples of reagents which 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 titanium tetrachloride.

The decisive factor for the above precursor preparation is not the physical form in which the complexing agents and reagents for possible activation processing are present. These agents can be used in gaseous or liquid form, the latter being the most common form in which the agents are found at conventional temperatures 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 alkanes and isoalkanes and benzene.

In particular, the conditions for the most common complexing agent treatment and the activating agent treatment described in more detail can be found in Belgian patent BE-A-864708, US-A-4295991, as well as in the documents cited therein.

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 friability of the particles of 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% by weight of prepolymerized alpha-monoolefin. . This prepolymerization can preferably be carried out in a suspension of the solid product in an inert hydrocarbon diluent as defined above for the time necessary to obtain the desired amount of prepolymerized 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 the 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 the pre-activated solid catalysts of the invention is described in Belgian patent BE-A-780758. The method consists in reducing the titanium tetrachloride with an organoaluminum reducing agent, which in this case is preferably dialkylaluminum chloride, the alkyl chains of which contain up to 6 carbon atoms under mild conditions. After optional heat 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 a hydrocarbon diluent as defined above and which is preferably selected from the group consisting of liquid aliphatic hydrocarbons containing 3%. up 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 in the range of 100 to 250 m ² / g and a total porosity of more than 0.15 cm ³ / g, 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 a high pore volume value corresponding to pores with a diameter of less than 20 nanometers, greater than 0.11 cm ³ / g and most often in the range of 0.16 to 3 0.31 cm ³ / g.

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

TiCl _third (AIRCO _{2) x} .C _y 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 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.

The precursor prepared as described above is contacted with an organoaluminum pre-activator containing the reaction product of the organoaluminum compound with the hydroxyaromatic compound.

Examples of such organoaluminum compounds include:

trialkyllumines such as trimethylaluminium, triethylaluminium, tri-n-propylaluminium, tri-n-butylaluminium, triisobutylaluminium, tri-nhexylaluminium, triisohexylaluminium, tri-2-methylpentylaluminium, tri- n -aluminium

- dialkylaluminium monohalides such as diethylaluminium monochloride, di-n-propylaluminium monochloride and diisobutylaluminium monochloride, diethylaluminium monofluoride, diethylaluminium monobromide and diethylaluminium monoiodide, and

alkylaluminium di- and alkylaluminium sesquihalides such as methylaluminium sesquichloride, ethylaluminium sesquichloride, ethylaluminium dichloride and isobutylaluminium chloride.

However, very good results are obtained with trialkylaluminum and dialkylaluminum chlorides, especially triethylaluminum and diethylaluminum monochloride.

The hydroxyaromatic compounds are selected from the group consisting of di-tert-alkylated monocyclic monophenols and 3- (3 ', 5'-tert-butyl-4'-hydroxyphenyl) propionic acid monoesters. Examples of said hydroxyaromatic compounds include:

- monocyclic monophenols di-tert-alkylated in ortho positions 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- hydroxybenzene, 2,6-di-tert-decyl-49 methoxyphenol, 2,6-di-tert-butyl-4-isopropylphenol, 2,6-dicyclohexyl-4-methylphenol, 2,6-diisopropyl-4-methoxyphenol and 2,6- di-tert-butyl-4-sec-butylphenol, and

- 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 ', 5-tert-butyl-4-hydroxyphenyl) ethyl propionate, 3- (3 ', 5'-di-tert-butyl-4-hydroxyphenyl) n-propyl propionate, 3- (3', 5'-di-tert-butyl-4-hydroxyphenyl) n-butyl propionate, 3- (3 ', 5'-di-tert-butyl-4-hydroxyphenyl) noctyl propionate, 3- (3', 5'-di-tert-butyl-4-hydroxyphenyl) n-dodecyl propionate and 3 (3 5'-di-tert-butyl-4-hydroxyphenyl) n-octadecyl propionate.

Very good results are obtained by using monocyclic monophenols of di-tert-alkylated at 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-) monoester. 4-hydroxyphenyl) propionic acid, and in particular the use of n-octadecyl 3- (3 ', 5'-di-tert-butyl-4-hydroxyphenyl) propionate, in particular the use of the latter gives excellent stereospecificity to the solid catalysts.

In general, the conditions under which an organoaluminum compound is contacted with a hydroxyaromatic compound are not critical if they result in a chemical reaction between the two compounds. In general, the liquid phase is operated by mixing the organoaluminum compound with a hydroxyaromatic compound in the absence of a liquid diluent, since 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 thereof is 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 an empirical formula:

Rp Al (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 'represents aryloxy - a group derived from a hydroxyaromatic compound, X represents halogen p represents a number from the range 0 <p <3, preferably a number from the range

0.1 < p < 2.5, q is 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.

The organoaluminum pre-activator obtained as described above is contacted with a precursor. The operating conditions under which said pre-activator is contacted with said precursor are not a critical factor as long as they are fixed, at least in part, to the said precursor.

In order to achieve this reservation, said contact of the pre-activator with the precursor can be effected in any known manner. Thus, this contact can be carried out, for example, by grinding a precursor impregnated with a liquid phase containing a pre-activator.

Most often, the pre-activator is used in the form of a solution in an inert hydrocarbon diluent, optionally used for its preparation. Thus, this solution contains the reaction product of an organoaluminum compound with a hydroxyaromatic compound, optionally performed by an excess of the used and unreacted organoaluminum compound or a 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.

In this case, 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 10%. Good results were obtained by using a molar ratio of the total starting amount of the organoaluminum compound to the amount of titanium tetrachloride present in the precursor of 0.05 to 0.5.

Upon completion of the preactivation treatment, the preactivated solid catalyst is preferably separated from the preactivation medium and washed to remove an unfixed residue of the preactivator, preferably with an inert hydrocarbon diluent of the same nature as the diluent used to prepare the precursor and the preactivator solution.

The separated and washed, preactivated 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. %, by weight of the titanium tetrachloride it contains, using the process described in Belgian patent BE-A846911.

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 purely 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 of the invention contains less titanium tetrachloride per unit weight than the solid product used as a precursor for its preparation. Any pre-activated solid catalyst generally comprises at least 50 wt. % of titanium tetrachloride based on the total weight of the preactivated solid catalyst, the preactivated solid catalyst rarely contains more than about 80 wt. % titanium tetrachloride.

The external morphologies of the pre-activated solid catalyst particles of the invention are in no way 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 the 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 of the invention may be immediately contacted with an inert hydrocarbon diluent, for example a diluent as defined hereinbefore and which is also useful as a diluent in suspension polymerization.

The pre-activated solid catalysts of the invention may also be subjected to a prepolymerization treatment as described above in relation to a 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 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 Element System Group (version published in Kirk-Othmer Encyclopedia of Chemical Technology) 2nd Edition, Vol. 8, 1965, p. 94), preferably selected from the group consisting of:

Al R'mY 3 -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, iodine, the best results being obtained when Y is chlorine and m is any number from 0 <m £ 3, preferably a number from 1.5 <m <2 5, with the best results being obtained when m is equal

Second

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-vinyl-cyclohexene, alicyclic diolefins having an endocyclic bridge, such as dicyclopentadiene, methylene-boronene and ethylene-boronene, 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 monomer 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 pre-activated solid catalysts of the invention are particularly suitable for the production of propylene homopolymers as polymers containing a total of at least 50 wt. % propylene, preferably at least 75 wt. % propylene.

The polymerization can be carried out in any known manner, i.e. 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 polymers can also be carried out in any known manner. It is preferred to use a two-step process consisting in the polymerization of alpha-olefins, generally propylene, by the method described in the previous test 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 brought into contact with each other at -40 to 80 ° C for a period of time, ranging from one hour to several days, 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, diethylzinc, alcohols, ethers, and alkyl halides.

The stereospecificator 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 not 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.

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

Examples of the invention,

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 modulus of elasticity in the polymer shear, 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 the processing time being 5 minutes (BS 2782 - Part I - Method 150A, ISO 458 (1, method B, DIN 53447 and ASTM D 1043), this module is expressed in daN / crri3,

MFI melt flow index under load of 2.16 kg at 230 ° C, expressed in g / 10 minutes (ASTM D 1238 standard),

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 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 the addition of a solution containing diethylaluminum chloride and hexane, the reaction medium is a suspension of fine particles and is stirred at 1 (± 1) ° C for 15 minutes, then warmed to 25 ° C over one hour. is maintained for one hour, 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 then 52 ml of titanium tetrachloride is added to the obtained slurry; 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 820 g of titanium tetrachloride per kilogram of this product) suspended in 280 ml of hexane are introduced into a 800 ml reactor equipped with a paddle stirrer at 150 rpm. 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) propionate n-octadecyl.

Thus, the molar ratio of the organoaluminum compound to the hydroxyaromatic compound used to prepare the pre-activator is 2, while the molar ratio of the pre-activator A to the solid titanium trichloride solid product (expressed in moles of organoaluminum compound initially used per mole of titanium tetrachloride present in the solid). product) has a value of 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 decantation, 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 tetrachloride, 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 introduced under a stream of nitrogen:

- 400 mg of diethylaluminium 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 in the reactor at 65 ° C for 3 hours. 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 3,340, the productivity is increased to 6,430 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 titanium tetrachloride solid product was prepared as described in Part A of Example 1, but this solid product was not 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 pre-activated solid catalyst thus obtained under conditions exactly as in Part C of Example 1. 785 g of dry polypropylene are obtained after this polymerization.

The activity, and hence is 3,230, and the productivity reaches 7,850 g polypropylene / g solid catalyst.

This polypropylene has the following properties:

l.l = 94.9%,

G = 572 daN / cm ²

MFI = 7.3 / 10 min.,

PSA = 490 g / l.

Significant differences in the content of the boiling heptane insoluble fraction 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 titanium tetrachloride product, prepared as described in Part A of Example 1, is pre-activated with a solution containing only the hydroxyaromatic compound. Partial dissolution of the product, which otherwise takes the form of very fine grains, can be observed. The polymerization test carried out according to the procedure described in Part C of Example 1 is in this case 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 2 550. This polypropylene is in 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 the part of Example C1, makes it possible to isolate, with an activity equal to 3090, only polypropylene, 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, having a very large grain form having a PSA of only 200 g / l to be isolated with activity and 3450, eliminating the possibility of its use.

Example 5R

The solid titanium trichloride product, prepared as described in Example 1R (i.e., it is an unpreactivated catalyst), is used in the polymerization test carried out according to the procedure described in Part C of Example 1, except that it is added to the polymerization. In addition to diethyl aluminum chloride, solid product, hydrogen and propylene, the product also contains 3- (3 ', 5'-di-tert-butyl-4-hydroxyphenyl) propionate n-octadecyl (II) in such an amount that the molar ratio of this product to titanium tetrachloride present in the solid product is about 0.2.

With an activity of &lt; 3286, polypropylene is obtained having the following properties:

l.l = 95.2%,

G = 575 daN / cm ²

MFI = 5.2 / 10 min.,

PSA = 505 g / l.

Example 2

The pre-activated solid catalyst was prepared as described in Parts A and B of Example 1 except that 3- (3 ', 5'-di-tert-butyl-4-hydroxyphenyl) propionate n-octadecyl was replaced with 2,6-di-tert-butyl-4-methylphenol.

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 a pre-activator of about 170 g per kilogram of catalyst. This catalyst is used in the polymerization test described in Part C of Example 1.

It is isolated with an activity of 3,230 polypropylene having the following properties:

l.l = 95.9%,

G = 653 daN / cm ²

MFI = 9 g / 10 min

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.

A 5 liter stainless steel autoclave flushed several times with nitrogen was charged with 1 liter of purified and anhydrous hexane. 400 mg of diethylaluminium chloride (as a 200 g / l hexane solution) and an amount of solid catalyst equivalent to about 51 mg of titanium tetrachloride are then 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.

The contents of the autoclave are filtered on a Bichner funnel, washed three times with 0.5 L of hexane and dried 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 1,643. Productivity is 3,157 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 and containing 735 g of titanium tetrachloride per kilogram of catalyst are 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 hexane insoluble part 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 diethylaluminum 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 three 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 a pre-activated solid catalyst is equal to 3,286 and the productivity reaches 7,027 g of polypropylene / g of pre-activated solid catalyst. This polypropylene has the following properties:

l.l = 97.9%,

G = 698 daN / cm 2,

MFI = 3 g / 10 min.

PSA = 520 g / l.

Example 7R

This example is a comparative example. A 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 equal to 3 168, a polypropylene, characterized by the following properties:

l.l = 96.4%,

G = 620 daN / cm 2,

MFI = 3 g / 10 min.

PSA = 516 g / l.

Examples 5 to 7

Preactivated 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 6 and 5 as i 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 preactivated solid catalysts are used in the test polymerization of propylene in suspension in hexane under the conditions of 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 6 7

Preparation of pre-activated solid catalysts organoaluminum compound (mol) _

hydroxyaromatic compound (Mol) 50 10 10 the organoaluminum compound contained TlCl3 in the solid product (Mol) (Mol) 1 1 0.2 TiCl 3 content in the pre-activated solid catalyst (g / kg) 724 672 709 Results of polymerization activity (g polypropylene / g TiCl3.h) 2 160 2 160 2 130 Polypropylene soluble in polymerization hexane (% of total polypropylene) 1.1 0.8 1.1 l.l (%) 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 preactivated solid catalyst according to Example 4 was prepared and used in a polymerization test carried out under the conditions set forth in Part V 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 5,010, characterized by the following properties:

l.l = 98.1%,

G = 688 daN / cm ²

MFI = 5.9 g / 10 min.,

PSA = 510 g / l.

Examples 9 to 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 dichloride (Example 10) was used as the organoaluminum compound.

These pre-activated solid catalysts are used in suspension propylene suspension polymerizations in liquid monomer under the conditions generally outlined 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 organo-clay triethyl- etylalumínium- the compound used to prepare the pre-activated solid catalyst aluminum dichloride T1Cl3 content in pre-activated solid catalyst (g / kg) 648 713 Activity (g polypropylene / g TiCl3.l1) 3 136 2 875 Properties of polypropylene l.l (%) 98.0 97.7 G (daN / cm ^) 645 667 MFI (g / 10 min) 3.4 3.7 PSA (g / l 504 490

Claims (2)

PATENT CLAIMS A process for the stereospecific polymerization of α-olefins, in particular propylene, in suspension in an inert solvent, in a liquid or gas phase monomer in the presence of a catalyst system comprising an organometallic compound of Group I, II, A, II.B metals. and III.B. of a periodic system and a solid catalyst based on complex titanium tetrachloride which has been 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; up to 250 m @ 2 / g and its total internal porosity is 0.15 to 0.35 cm @ 2 / g formed by the compound TiCl ₃ (AIRCI ₂ ) _x - C _y 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 whose aliphatic radicals contain 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 a product of 0.1 to 50 moles of an organoaluminum compound selected from compounds of formula (I) AIR ' _m Y3-m, where R 'is a hydrocarbon radical having 1 to 18 carbon atoms, Y is halogen selected from the group consisting of fluorine, chlorine, bromine and iodine; and m is a number from 0 <m <3, and 1 mole of a hydroxyaromatic compound selected from the group consisting of di-tert-alkylated monocyclic monophenols and monoesters of 3- (3). (5'-tert-butyl-4'-hydroxyphenyl) propionic acid. Process according to claim 1, characterized in that a pre-activated solid catalyst is used, which is separated from the pre-activation medium before use in the polymerization.