NO167750B - PROCEDURE FOR PREPARING A CATALYST COMPONENT, PREPARING A POLYMERIZATION CATALYST MIXTURE, AND USING THE CATALYST MIXTURE. - Google Patents

Description

The present invention relates to a method as stated in the preamble of claim 1 for the production of a solid olefin polymerization catalyst component with improved activity and morphological properties. There are many prior proposals for providing olefin polymerization catalysts by combining a solid component comprising at least magnesium, titanium and halogen, especially chlorine, with an active organolaluminum compound. These can be described as both coordination catalysts or catalyst systems. The activity and stereo-specificity of such components are generally improved by incorporating an electron donor (Lewis base) into the solid component and by using a third catalyst component as an electron donor which can be complexed in whole or in part to the activating organoaluminum compound.

The invention also relates to a method for the production of a catalyst mixture for the polymerization of cx-olefins, as stated in claim 9, as well as the use of the catalyst mixture, as stated in claim 10.

For simplicity, the solid titanium-containing component of such catalysts is hereinafter referred to as "procatalyst", the organoaluminum compound, whether used separately, partially or completely complexed with an electron donor as "cocatalyst", and the electron donor compound, whether used separately or partially or completely complexed with the organoaluminum compound as "selectivity control agent" (SCA).

Supported coordination catalysts of this type are shown in a large number of patents. The catalyst systems of this type known from the prior art are generally capable of producing olefin polymers in high yield and in the case of catalysts for the polymerization of propylene or higher cx-olefins, with selectivity for stereo-regular polymers. However, further improvements are sought in

productivity at high stereoregularity.

The purpose of the work in this field is to provide catalyst systems which exhibit sufficiently high activity to allow the production of olefin polymers in such high yields as to avoid the need to extract any catalyst component in a wash-off step. For the cases of propylene and higher olefins, an equally important objective is to provide catalyst systems with sufficiently high selectivity for isotactic or other stereoregular products to avoid the necessity of extracting atactic polymeric constituents.

Although many chemical combinations provide active catalyst systems, practical considerations have led those skilled in the art to concentrate on certain preferred components. The procatalysts typically comprise magnesium chloride, titanium chloride, generally in tetravalent form and as electron donor an aromatic ester such as ethyl benzoate or ethylene p-toluate. The cocatalyst is typically an aluminum trialkyl compound such as aluminum triethyl or aluminum triisobutyl, often used at least partially complexed with the selective controlling component. The selectivity-controlling component is typically an aromatic ester, such as ethyl p-methoxybenzoate (ethyl anisate) or methyl p-toluate.

While the choice of cocatalyst and the selectivity controlling component affects the performance of these catalysts, the component that appears to undergo the most significant improvement in activity and productivity of the system is the procatalyst.

Preferred methods for making such procatalysts are described in US-A-4,329,253, 4,393,182, 4,400,302 and 4,414,132. These procatalysts are highly active and stereospecific. A typical method for producing such procatalysts involves reacting the magnesium compound, titanium tetrachloride and the electron donor in the presence of a halogenated hydrocarbon. The resulting solid particles are then brought into contact with additional amounts of TiCl4 and finished treatment by washing off excess TiCl4 using light hydrocarbons (for example in isooctane and isopentane) with subsequent drying.

The described procatalysts have excellent polymerization activity (polymer yield) and stereospecific action (isotactic content). However, for certain applications, the polymer morphology is not ideal. In olefin polymerization, the polymer morphology is known to be a replica of the catalyst morphology. Furthermore, the morphology of the procatalyst is also dependent on the morphology of the starting magnesium compound. Thus, if one wishes to have optimal catalyst morphology (e.g. spherical particles), it is desirable to use starting magnesium compounds with the same morphology.

A number of different attempts to improve the morphology have been suggested in the patent literature. An experiment is shown in GB-A-2,101,610, involving reacting a solid particulate material with an organic magnesium compound, treating the supported magnesium composition with oxygen, carbon dioxide or a hydroxyl compound and reacting the treated product with a carbonyl compound and simultaneously or sequentially reacting the product with a pure transition metal compound. Another approach is shown in US-A-4,465,783 and involves spray drying a transition metal mixture or a carrier for a transition metal compound suspended in a liquid medium. A further method is described in DE-A-2,839,188, where solid magnesium dialkoxide particles are dispersed in a suitable liquid phase followed by spray drying. The latter method is not attractive, however, because the dispersed solid particles tend to clog the fine openings in the spray-drying equipment and disturb the pumping and measuring system. According to US-A-4,540,679 a magnesium hydrocarbyl carbonate carrier is used. A suspension of magnesium alcoholate with carbon dioxide is reacted with a transition metal compound to precipitate a "magnesium hydrocarbyl carbonate" carrier. The patentee uses a number of techniques, including polymerization and the use of triethylaluminum (TEA), to remove ethanol and to improve productivity. However, these techniques are not desirable, as, for example, polymerization is a further step and the addition of TEA leads to an increased ash content in the polymer product obtained.

A new method has now been found that allows the production of procatalyst particles that not only have excellent productivity and selectivity, but also possess excellent morphology.

The present invention thus provides a method for the production of a solid catalyst component containing magnesium, titanium and halogen for use in the polymerization of alpha-olefins and which comprises

a) halogenating a magnesium compound of the formula MgR•R", where R is an alkoxy or aryloxy group, and R" is halogen or an alkoxy or an aryloxy group, with a halide of tetravalent titanium in the presence of a halogenated hydrocarbon and an electron- donor; b) contacting the resulting halogenated product with a halide of tetravalent titanium; c) washing the resulting product to remove unreacted titanium compounds, and;

d) recover the product obtained.

The procedure is characterized by what is stated in claim 1<1>s

characterizing part, further features appear in claims 2-8.

As shown in the following examples, propylene polymers prepared using a solid catalyst component prepared according to the present invention will have an extremely low level of fines (ie, very little polymer less than 250 µm in diameter). Consequently, a catalyst comprising this component can be very useful in gas-phase processes where fines are destructive. Furthermore, it is possible with such a catalyst to produce polymers with a uniform optimized particle size, i.e. with a relatively narrow particle size distribution. Such polymers may also have a higher bulk density (above about 0.38 g/ml) and a ratio of short diameter (sd) to long diameter (ld)

in the range 0.7:1 to 1:0.1.

A catalyst prepared according to the present invention differs from the catalysts according to US-A-4,540,679 in that the "carrier" according to the invention is a magnesium halide, while the "carrier" in US-A-4540679 is allegedly a magnesium -hydrocarbyl carbonate. Further, according to the present invention, CO2 is used in the starting magnesium compound of the formula MgR'R"xCO2 (sometimes referred to as carbonated magnesium compound) only as a means of making the magnesium alcoholate soluble to control catalyst morphology, and in reality the CO2 will deviate during the preparation of the catalyst (the digestion) or also before contact with a halogen compound of tetravalent titanium.

It is also possible with the present invention to produce catalyst particles with varying appearances, from raisin-like to spherical. Such rosin-like catalyst particles have a large surface area and are preferred in the production of random ethylene-propylene copolymers with a high ethylene content (over 4 mol percent) and in situ formed copolymers without contamination problems that normally accompany the production of such polymers. The more porous catalyst with high surface area enables the manufacturer to carry more of the sticky polymer inside the catalyst matrix.

The key feature of the present invention involves the use of carbonated magnesium compounds of the formula MgR'R".xC02• Although an excess of C02 (over 2.0 per Mg) can be used, only one C02 equivalent will undergo a Lewis acid-base reaction with each equivalent of the special MgR'R" component (ex. Mg dialkyloxy).

Carbonated magnesium ethylate with the molecular formula Mg(OC2H5)2•xC02, where x is 1.2 and up to 1.3, is available from Dynamit Nobel. Such a material is in reality a mixture of two compounds. When x=l the formula is assumed to be

When x=2 the structural formula is assumed to be

The average molecular weight is approx. 170 and a typical analysis shows a content of 14.3-14.6% Mg.

In general, the carbonated magnesium compounds are prepared by contacting a dispersion of MgR'R" in a suitable diluent with essentially anhydrous carbon dioxide. By the term essentially anhydrous carbon dioxide is meant carbon dioxide which is at least 99.5% pure carbon dioxide and is denoted by "commercial " degree and up to and including pure carbon dioxide. It is preferred that the carbon dioxide be 99.8% or more pure C02. Oxygen and nitrogen contaminants are only important to the extent they cause fire hazards. Water is a problem and must be avoided.

Typically, CO 2 is bubbled through the dispersion of the magnesium compound in a diluent. As the reaction is exothermic, you can continue with the bubbling of CO2 until the exothermic reaction has stopped. During this process, the mixture will be heated and the solid compound will dissolve. At the end of the addition, a cloudy, viscous solution is formed. Dry ice can also be used as a source for C02.

The diluent or solvent used may be any material in which the carbonated magnesium compound is soluble under the desired conditions. Preferred diluents are alcohols. However, other polar solvents such as acetone or dimethylformamide (DMF) can be used, as well as mixed solvents. When an alcohol is used, it is preferably used together with a magnesium compound containing two of the same groups, i.e. an alcohol in the form R'OH is used together with the magnesium compound with the formula Mg(OR')2. For example, if magnesium diethoxide is used, it is preferred that the diluent is ethanol. This choice reduces the problem of transesterification and other problems in the metathesis reaction. As the most preferred magnesium compound is magnesium diethoxide, the most preferred diluent is ethanol.

The relative amounts of magnesium compounds and the diluent depend on the various components used, the conditions used (eg temperature) and the desired concentration. Typically, the concentration of the magnesium umph compound is in the range of 2-40% solids, determined by the usual spray-drying technique. The temperatures used are typically in the range 0-80°C and the mixture (solution) is stirred continuously during the CO2 bubbling through. See generally US-A-4,529,715 and US-A-4,530,915 for discussion of CO2 bubble nodding.

Examples of halogen-containing magnesium compounds that can be used as starting materials for the reaction are alkoxy and aryloxy magnesium halides, such as isobutoxy magnesium chloride, ethoxy magnesium chloride, ethoxy magnesium bromide, phenoxy magnesium iodide, cumyloxy magnesium bromide and naphthenoxy magnesium chloride.

Preferred magnesium compounds are selected from magnesium dioxides and magnesium diaryloxides. In such compounds the alkoxide group suitably has from 1 to 8 carbon atoms and preferably from 2 to 8 carbon atoms. Examples of such preferred compound groups are magnesium diisopropoxide, magnesium diethoxide, magnesium dibutoxide, magnesium diphenoxide, magnesium dinaphthenoxide and ethoxymagnesium isobutoxide. Magnesium diethoxide is particularly preferred.

Another main purpose of the present invention is to take a solution of a carbonated magnesium compound and convert it into solid particles of a certain optimum size which have the desired morphology and particle size. There are two main ways to achieve this. One way involves spray drying and the other involves impregnation of an inert particulate material.

Spray drying can be carried out using conventional spray drying techniques. Thus the mixture is passed through a suitable atomizer which forms a shower or dispersion of droplets from the mixture, and a stream of hot gas arranged to contact the droplets and cause vaporization of the liquid medium and the solid product, which is collected . Suitable atomizers for forming droplets of the mixture include nozzle atomizers and rotating plate atomizers.

Atomization is carried out in the absence of water and oxygen.

The temperature at which spray drying takes place partially controls the shape of the resulting particles. The most common temperature is from 40° to 120°C, most preferably 50° to 90°C for ethanol-based solutions. Formation of spherical particles is dependent on the solids content of the solution and the operating (spray-drying) temperature. At constant solid, too high a temperature will result in hollow splintered particles, too low a temperature will give insufficient removal and particle agglomeration.

It will be assumed that the temperature of the hot gas will be at least equal to the maximum temperature reached by the droplets or the spray-dried material.

The hot gas can be arranged to flow countercurrently with the droplets in the mixture, but typically the hot gas is flowed with the flow of the mixture used. When using co-current technology, the atomizer is typically located at the top of the spray-drying apparatus and the hot gas is introduced at the top of the apparatus and removed near the bottom of it. Some of the spray-dried solid is collected in the bottom of the apparatus from where it can be removed, preferably continuously, by suitable means such as a star feed valve or screw conveyor or in the hot gas stream.

The hot gas which has been cooled by the passage through the spray-drying apparatus can be removed separately from it. The hot gas can be passed through a cyclone to remove entrained solids, and the solids removed from the cyclone can be added to what is optionally separately removed from the spray-drying apparatus. The vapor of the liquid medium which is present in the hot gas can, if desired, be condensed in a suitable condenser and the condensed liquid medium can be used again for mixing with solid material. The gas can then be heated again and recycled to the spray-drying device.

The pressure in the vessel can be varied to promote or prevent evaporation. A small positive overpressure in the vessel is preferred to prevent water and O2 contamination.

The nozzle opening is adjusted with conventional spray-drying equipment to produce particles of the desired particle size. It is preferred that essentially all of the particles in the finished spray-dried material are in the range 2-250 pm, preferably at least 90 percent by weight of the particles are in the range 10-40 pm, e.g. with the average size of approx. 8 p.m. A description of a typical spray drying equipment and conditions is found in US-A-4,465,783.

Another method of forming particles with the desired morphology is the impregnation of an inert particulate carrier which already has the desired morphology with a solution of the carbonated magnesium compound. The carrier material is solid particulate material which is inert with respect to the other components of the catalyst mixture and to the other active components in the reaction system. These carrier materials include inorganic materials such as oxides of silicon and aluminum and molecular sieves, as well as organic materials such as polymers such as polyethylene and polyester. When the carrier materials are inorganic oxides, they are used in the form of dry powders with an average particle size in the range 10-250 pm and preferably in the range 50-150 pm. These materials are also preferably porous and have a surface area of at least 3m<2>/g and preferably at least 50m<2>/g. The inorganic oxides should be dry, i.e. free of adsorbed water. Drying of the oxide materials can be carried out by heating to a temperature above 200°C or by chemical treatment.

The carriers are added to the solution of the carbonated magnesium compound, after which the solvent is evaporated. Typically, the solution will be maintained at atmospheric pressure and temperatures maintained at 80-90°C until the resulting powder is apparently dry. Under vacuum conditions, the temperature can be, for example, 60-90 °C. The desired temperature and the desired pressure can be easily determined by a person skilled in the art. If desired, the resulting powder can be washed one or more times with an inert liquid, such as in isopentane to ensure that alcohol etc. has been removed.

When the uniformly optimized particles of the carbonated magnesium compound are obtained, it is necessary to convert the compound into magnesium halides in a metathesis reaction (under digestion), as shown in US-A-4,414,132. During halogenation with a halide of tetravalent titanium, the magnesium compounds are preferably reacted to form a magnesium halide in which the atomic ratio between halogen and magnesium is at least 1.2/1. Better results are obtained if the halogenation proceeds more completely, e.g. to give magnesium halides where the atomic ratio between halogen and magnesium is at least 1.5/1. The most preferred reactions are those leading to complete halogenation reactions, ie to magnesium dihalides. Such halogenation reactions are conveniently carried out using a molar ratio between the magnesium compound and the titanium compound in the range of 0.005:1 to 2:1, preferably 0.01:1 to 1:1. These halogenation reactions are carried out in the additional presence of a halogenated hydrocarbon and an electron donor. An inert diluent or solvent may also be present. When using an inert diluent or solvent, this should not be used as a complete substitute for a halogenated hydrocarbon because it is important that the halogenation reaction proceeds in the presence of a halogenated hydrocarbon.

Suitable halides of tetravalent titanium include aryl oxide or alkoxy di- and trihalides, such as dihexane oxide titanium dichloride, diethoxide titanium dibromide, isopropoxy titanium triiodide and phenoxy titanium trichloride and titanium tetrachloride. Tetrahalides are preferred and most preferred is titanium tetrachloride.

Suitable halogenated hydrocarbons are compounds such as butyl chloride, amyl chloride and the following more preferred compounds. Preferred aliphatic halogenated hydrocarbons are halogen-substituted hydrocarbons with 1-12, especially less than 9 carbon atoms per molecule, comprising at least 2 halogen atoms, such as dibromoethane, trichloromethane, carbon tetrachloride, 1,2-dichloroethane, dichlorobutane, 1,1,3-trichloroethane, trichlorocyclohexane, dichlorofluoroethane, trichloropropane, trichlorofluorooctane, dibromodifluorodecane, hexachloroethane and 1,1, 3-tetraisooctane. Carbon tetrachloride and 1,1,3-trichloroethane are preferred aliphatic halogenated hydrocarbons. Aromatic halogenated hydrocarbons can also be used, e.g. chlorobenzene, bromobenzene, dichlorobenzene, dichlorodibromobenzene, naphthyl chloride, chlorotoluene and dichlorotoluenes. Chlorobenzene and dichlorobenzene are preferred aromatic halogenated hydrocarbons.

Suitable electron donors used in the preparation of the solid catalyst component are ethers, esters, ketones,

phenols, amines, amides, imines, nitriles, phosphines, phosphites, stibines, arsines, phosphoramides and alcoholates. Examples of suitable donors are those described in US-A-4,136,243 or in the corresponding GB-A-1,486,194 and in GB-A-1,554,340 or in the corresponding DE-A-2,729,126. Preferred donors are esters, diesters and diamines, especially esters and diesters of carboxylic acids, preferably aromatic carboxylic acids, such as ethyl and methyl benzoate, p-methoxyethyl benzoate, p-ethoxymethyl benzoate, ethyl acrylate, methyl methacrylate, ethyl acetate, dimethyl carbonate, dimethyl adipate, isobutyl phthalate, dihexyl fumarate, dibutyl maleate , ethyl isopropyl oxalate, p-chloroethyl benzoate, p-aminohexyl benzoate, isopropyl naphthenate, n-amyl toluate, ethyl cyclohexolate, propyl pivalate, N,N,N',N'-tetramethylethyldiamine, 1,2,4-trimethylpiperazine, 2,3,4,5-tetraethyl -piperidine and similar compounds. The electron donors can be used alone or in combination. Preferred electron donors for use in the preparation of the solid catalyst component are ethyl benzoate and isobutyl phthalate.

The halogenation normally proceeds with the formation of a solid reaction product which can be isolated from the liquid reaction medium by filtration, decantation or another suitable method where the product can then be washed with an inert hydrocarbon diluent, such as n-hexane, isooctane or toluene to remove unreacted material, including physically absorbed halogenated neocarbon.

After halogenation, the product is brought into contact with a halide of tetravalent titanium, such as a dialkoxytitanium dihalide, alkoxytitanium trihalide, phenoxytitanium trihalide or titanium tetrahalide. The most preferred titanium compounds are titanium tetrahalides and especially titanium tetrachloride. This treatment increases the content of tetravalent titanium in the solid catalyst component. This increase should preferably be sufficient to achieve a final atomic ratio of tetravalent titanium to magnesium in the solid catalyst component in the range of 0.005:1 to 3.0:1, especially in the range of 0.02:1 to 1.0:1. For this purpose, the contact with the halide of tetravalent titanium should suitably be carried out at a temperature in the range of 60-136°C for 0.1-6 hours, possibly in the presence of an inert hydrocarbon or halogenated hydrocarbon diluent. Particularly preferred contact temperatures are 70-120°C and the most preferred contact periods are 0.5-3.5 hours. The treatment can be carried out by successive contacts with the solid with separate portions of the halide of tetravalent titanium, which can contain a suitable electron donor selected from those previously indicated.

The preferred halogen atom, which is optionally contained in the magnesium compound to be halogenated, and which is contained in the titanium compound that serves as the halogenating agent in step a) and in the halide of the tetravalent titanium compound with which the halogenated product is brought into contact in step b), is chlorine.

After treatment with a halide of tetravalent titanium in step b), the catalyst component is suitably isolated from the liquid reaction medium and washed to remove unreacted titanium compound. The titanium content of the finished, washed solid catalyst component is suitably 1.5-3.6 weight percent, but can go up to 4.5 weight percent.

Material used to wash the catalyst component is suitably a liquid, light hydrocarbon. Preferred light liquid hydrocarbons are aliphatic, alicyclic and aromatic hydrocarbons. Examples of such liquids include isopentane, n-hexane, iso-octane and toluene, with iso-pentane being most preferred.

The amount of light hydrocarbon liquid used can be 5-100 ml/g procatalyst in each of 2-6 separate washings, preferably approx. 25 ml/g.

The resulting solid component is the procatalyst which is used with a cocatalyst and a selectivity controlling agent in the polymerization process.

Suitable electron donors which are used in combination or reacted with an organoaluminum compound as a selectivity controlling agent and which are also used in the preparation of the solid catalyst component are ethers, esters, ketones, phenols, amines, amides, imines, nitriles, phosphines, silanes, phosphites, stibines , arsines, phosphoramides and alcoholates. Examples of suitable donors are those described in US-A-4,136,243 or in the corresponding GB-A-1,486,194 and in GB-A-1,554,340 or the corresponding DE-A-2,729,126.

Preferred donors are esters and organic silicon compounds. Preferred esters are esters of carboxyl, especially aromatic carboxylic acids such as ethyl and ethyl benzoate, p-methyl ethyl benzoate, p-ethyl methyl benzoate, p-ethoxyethyl benzoate, ethyl acrylate, methyl methacrylate, ethyl acetate, dimethyl carbonate, dimethyl adipate, dihexyl fumarate, dibutyl maleate, ethyl isopropyl oxalate, p-chloroethyl benzoate , p-aminohexyl benzoate, isopropyl naphthenate, n-amyl toluate, ethyl cyclohexanoate, propyl pivalate. Examples of useful organic silicone compounds include alkoxysilanes and acyloxysilanes of the general formula R-^Si(OR<2>)4_n, where n is an integer between 0 and 3, R<1> is a hydrocarbon group or a halogen atom, and R< 2> is a hydrocarbon group. Specific examples include trimethylmethoxysilane, triphenylethoxysilane, dimethyldimethoxysilane and phenyltrimethoxysilane. The donor used as a selectivity-controlling agent in the catalyst may be the same as, or different from, the donor used in the preparation of the titanium-containing component. Preferred electron donors for use in the preparation of the titanium component are ethyl benzoate and isobutyl phthalate. Preferred selectivity controlling agents in the overall catalyst are n-ethoxyethylbenzoate, phenethyltrimethoxysilane and diphenyldimethoxysilane.

The organoaluminium compound used as cocatalyst can be selected from any of known activators in olefin polymerization catalyst systems which comprise a titanium halide, but are preferably free of halogens. Although trialkylaluminum compounds, dialkylaluminum halides and dialkylaluminum alkoxides can be used, trialkylaluminum compounds are preferred, especially those where each of the alkyl groups contains 2-6 carbon atoms, e.g. triethylaluminum, tri-n-propylaluminum, triisobutylaluminum, triisopropylaluminum and dibutyl-n-aluminum.

Preferred proportions of selectivity controlling agent, used alone, in combination with or reacted with an organoaluminum compound, calculated as moles per mole of aluminum compound, are preferably 0.005 to 1.5, especially 0.1-0.5. Preferred proportions of the selectivity controlling agent, calculated as moles per mole of Ti, are 0.1-50, especially 0.5-20.

Proportions of electron donor contained in the solid catalyst component, calculated as moles per mole of magnesium, are suitably 0.01-10, e.g. 0.05-5.0 and especially 0.05-0.5.

To prepare the finished polymerization catalyst mixture, procatalyst, cocatalyst and the selectivity controlling agent, if used separately, can be easily combined, suitably by using a molar ratio so that in the finished catalyst an atomic ratio of aluminum to titanium in the range of 1:1 to 150:1, suitably 10:1-150:1. The catalyst according to the invention tends to exhibit very good activity at very low Al:Ti ratios, e.g. below 80:1 and also as low as 50:1 compared to known catalysts of the same type. However, it may be advantageous under certain conditions to use the catalysts at higher Al:Ti ratios. An increase in the Al:Ti ratio tends to increase the catalyst activity at the expense of increased catalyst residue in the unextracted product. These factors as well as the desired level of isotacticity must be considered when selecting the Al:Ti ratio for any given process and desired product. In general, Al:Ti atomic ratios of 30:1-100:1 and especially 50:1-80:1 will be advantageous.

The present invention also relates to a method for the polymerization of an alpha-monoolefin, such as ethylene or butylene and especially propylene, using the new catalyst components and mixtures. These polymerizations can be carried out using any conventional technique, such as gas phase polymerization or slurry polymerization using liquid monomer or an inert hydrocarbon diluent as the liquid medium. Hydrogen can be used to control the molecular weight without reducing the stereospecificity of the catalyst mixture. The polymerization can be carried out batchwise or continuously with constant or intermittent supply of the new catalyst mixtures or one or more of the catalyst components to the polymerization reactor. The activity and stereospecificity of the new catalyst mixtures are so prominent that there is no need for removal of the catalyst or any polymer extraction technique. The total metal residues in the polymer, i.e. the total amount of aluminium, magnesium and titanium can be as low as 150 ppm, and even less than 75 ppm.

It is well known that both coordination catalysts and the catalyst system of the type described here are very sensitive, to varying degrees, to catalyst poisons such as moisture, oxygen, carbon oxides, acetylenic compounds and sulfur compounds. It will be understood that in the practice of the present invention, as well as in the following examples, both the equipment and the reactants and the diluent are carefully dried and freed of potential catalyst poisons.

The productivity of the catalyst is determined as kg polymer/

g procatalyst in a standard 1- or 2-hour batch reaction, it can also be expressed as kg polymer/g Ti. Sometimes the catalyst activity is also reported as kg polymer/g procatalyst/hour. If the determination is a standard 1-hour determination, then the activity becomes numerically the same as the productivity.

The selectivity for isotactic polypropylene is determined by measuring the amount of xylene-soluble polymer (XS) according to the determination established by the U.S. Food and Drug Administration (FDA). The XS determination is carried out in the following way: The sample is completely dissolved in xylene containing an oxidation inhibitor in a stirred bottle heated under reflux at 120°C. The flask is then immersed in a water bath at 25°C without stirring for 1 hour, during which the insoluble part precipitates. The precipitate is filtered off and soluble constituents in the filtrate are determined by evaporating a 10 ml aliquot of the filtrate. , dry the residue under vacuum and weigh it. The xylene-soluble constituents consist of amorphous material, as well as some crystalline material of low molecular weight (FDA regulation 120.2501 and 1.1.2510, 1971).

The numerical value for XS for the case of propylene homopolymer is typically approx. 2% less than the amount of polymers that can be extracted from n-heptane under reflux. Thus, the isotacticity index for polypropylene (the amount of insoluble components in heptane boiled under reflux) is approximately 100 - (XS+2).

The catalyst productivity under standard conditions exhibits an inverse relationship with the stereoselectivity. This relationship is characteristic of any given procatalyst. It is generally possible to control these variables within certain limits by changing the proportion of the selectivity controlling agent (SCA). An increase in the amount of SCA increases the selectivity of isotactic or stereoregular polymer, but decreases the activity and consequently the productivity in a standard 1-hour sample. The following examples illustrate the invention:

Example I

Illustrative embodiment I (I.E.l) shows the production of catalysts supported on silicon oxide. First, 20.3 g of magnesium dioxide was added to 700 ml of ethanol in a bottle. CO2 was then bubbled through the bottle until all solids had dissolved. Excess C02 was allowed to escape through a bubble device. The reaction took place in approx. 30 min and was detectable by increasing the temperature in the ethanol solution. It should be noted that carbonated magnesium ethylate can also be prepared by dropping dry ice into a slurry of ethanol and magnesium ethoxide with stirring. In such a case, stirring is continued until all the magnesium ethoxide is dissolved.

Catalyst produced on silicon oxide

To a bottle containing 6 g of silica (the silicas used included Davison SGB-5, Davison 952, particle size 50-70 pm, pore volume 1.05 me/g and 1.7 ml/g. The silica was dried under nitrogen and some of it was treated with BF3 and BCL3) was added to 100 ml of the above-mentioned carbonated magnesium solution. The ethanol was evaporated with stirring at 85 °C until the resulting powder was apparently dry. The solid was then washed 5 times with isopentane. A 50:50 volume mixture of TiCl 4 and chlorobenzene (CB) was added to the solid (75 mL) along with 1.2 mL of ethyl benzoate. The mixture was then heated to 100°C for 1 hour and the liquid filtered at the end of this hour. A further amount of TiCl4:CB was added and heated to 110°C for 30 min, followed by filtration. A final addition of TiCl 4 :CB was added along with 0.3 mL of benzoyl chloride. The mixture was heated to 110°C for 30 min. followed by filtering. To remove adsorbed TiCl4, the catalyst was washed with isopentane in 6 additions.

Polymerization

To 2.7 liters of propylene was added 0.7 mmol of triethyl-. aluminum (TEA), 0.35 mmol of p-ethoxyethyl benzoate (PEEB) and the catalyst as described above in an amount corresponding to 0.01 mmol of Ti, to which 0.15 mmol of diethylaluminum chloride (DEAC) had been added was added to the catalyst and premixed for 10 min. Polymerization was carried out for 2 hours. The results are shown in the following comparison table.

Example II

In this illustrative example II (I.E.2) catalyst was prepared from carbonated magnesium ethoxide and no attempt was made to control the morphology.

Production of catalysts

Carbonated magnesium ethylate was prepared as indicated in the previous example, however, the solid carbonated magnesium ethylate was obtained by evaporating ethanol from the solution with a nitrogen purge or removal in a rotary evaporator. The solid was further treated by exhaustive drying in nitrogen at 100°C or at 150°C (it is reported by Dynamit Nobel that CO 2 is lost at 100-140°C). Heating to 150°C led to a 40% loss by weight, which corresponds to a complete loss of CO 2 . The solid obtained after N2 drying was then treated in a similar manner to the catalyst prepared in example 1, except that no silicon oxide was added.

Pol<y>meriserin<g>

The polymerization was again carried out in liquid propylene. The cocatalyst used was triethylaluminum and the selectivity controlling agent was p-ethoxyethyl benzoate. Diethyl aluminum chlorate was sometimes used in a pre-contacting step with the catalyst. Catalyst added was sufficient to introduce 0.01 mmol of Ti. Some of the polymerizations were also carried out in gas phase at 2 MPa gauge pressure and 65°C. The reaction time was 2 hours unless otherwise indicated. The results appear in the following table.

Example III

In this illustrative example III (I.E.3), the catalyst was prepared from spray-dried carbonated magnesium oxide.

Production of spray-dried solids

A solution of carbonated magnesium ethylate was prepared in the same manner as described in Example I. The resulting solution contained approx. 33% by weight carbonated magnesium ethylate. This solution was pumped at a controlled flow rate to a small nozzle at which point the resulting liquid stream was brought into intimate contact with nitrogen of varying temperatures. The solid produced by contact with nitrogen at 100-120°C gave hollow spheres, many of which had exploded into nutshell-like fragments. Solids obtained by contact with nitrogen at 80°C and 60°C gave solids that resembled the shape of wrinkled peas (raisins).

Preparation of catalyst

The solid obtained by the spray drying was heated in a quartz tube to 70°C while nitrogen was passed through the solid for 7 hours and then heated for 40 hours with a stream of nitrogen at 105°C and finally for 1 hour at 150°C. C02 was effectively removed. 6.0 g of the solid obtained was introduced into a catalyst preparation bottle. At room temperature, 150 ml of a 50:50 volume mixture of TiCl 4 :CB was added along with 2.4 ml of ethyl benzoate. The mixture was heated to 110°C and mixed for 1 hour, after which the liquid was filtered off. An addition of 150 ml of TiCl4:CB mixture was added together with 1.5 ml of diisobutyl phthalate and the mixture was allowed to stand at 110°C for 30 min , after which the liquid was filtered off.

The above step was repeated once, followed by a final wash with 150 ml of TiCl 4 :CB. The finished solid catalyst component was then washed 6 times with isopentane.

Polymerization

The solid catalyst component was used to polymerize liquid propylene. The cocatalyst used was triethylaluminum and the selectivity controlling agent was phenethyltrimethoxysilane. Sufficient catalyst was added to give 0.01 mmol. The length of stay was 2 hours.

Comparative example

A comparison catalyst (standard catalyst) was prepared in the same manner as shown in US-A-4,414,123, i.e. without the use of CO 2 . In general, magnesium diethoxide was reacted with TiCl4 and ethyl benzoate in the presence of chlorobenzene to give a solid. The solid obtained was treated with further washings with TiSl4/chlorobenzene, where one wash also contained benzoyl chloride. The polymerization was similar to that used in example 1. The different catalysts prepared above are compared in the following. Not all results are shown and mainly the best catalyst productivities and the representative morphologies are shown. As can be seen, it has been possible to achieve polymer productivities corresponding to known catalysts (not prepared from carbonated Mg compounds), but with superiorly better morphology. The spray-dried material showed a significant difference in the level of the material below 250 pm; 2.0% by weight against 10.2% by weight for the known catalyst. The shape of the product particles is significantly improved from stone-like particles to smooth raisin-like particles.

Claims (10)

1. Process for the preparation of a solid catalyst component containing magnesium, titanium and halogen for use together with an organoaluminum compound, in the polymerization of cx-olefins, by: a) halogenating a magnesium compound of the formula MgR'R", where R' is an alkoxy or aryloxy group, and R" is halogen or an alkoxy or an aryloxy group, with a halide of tetravalent titanium in the presence of a halogenated hydrocarbon and an electron donor; b) contacting the resulting halogenated product with a halide of tetravalent titanium; c) washing the resulting product to remove unreacted titanium compounds, and d) recovering the product obtained, characterized in that the magnesium compound of formula MgR'R11 used in step a) is obtained by decarbonation of a carbonated magnesium compound of formula MgR'R"xCO2, where R<1> and R" are as previously indicated, and x has the value 0.1 - 2, when heated to a temperature of at least 100"C. 2. Method according to claim 1, characterized in that a magnesium compound is used where R'R" are both ethoxy groups. 3. Method according to claim 1 or 2, characterized in that the magnesium compound is produced by bubbling essentially anhydrous CO 2 through MgR'R" in alcohol. 4. The method according to claim 3, characterized in that the alcohol used is ethanol. 5. The method according to any one of the preceding claims, characterized in that the magnesium compound is used in the form of essentially spherical particles of which at least 90% by weight have a diameter in the range 10-4 0 pm. 6. The method according to claim 5, characterized in that the essentially spherical particles are obtained by spray drying a solution of a magnesium compound or by impregnating an inert particulate carrier with a solution of the magnesium compound with subsequent removal of the solvent. 7. Method according to any of the preceding claims, characterized in that in step a) or step b) TiCl4 is used as the halide of tetravalent titanium and that a chlorinated hydrocarbon is used as the halogenated hydrocarbon. 8. Method according to any one of the preceding claims, characterized in that an ester or diester of an aromatic carboxylic acid is used as an electron donor in step a). 9. Process for the production of a catalyst mixture for the polymerization of o-olefin, characterized in that a catalyst component according to any of the preceding claims is mixed with an organoaluminum compound and a selectivity-regulating agent to provide a catalyst mixture for use in the polymerization of olefins, where the atomic ratio between aluminum bg titanium is in the range 30:1 to 100:1. 10. Use of catalyst mixture according to claim 9 in the polymerization of cx-olefins.