Catalysts and process for the polymerization of olefins

Beginning of the patent period: December 15, 1970.

As inventors are called: Adolfo Mayr, Paolo Galli, Ermanno Susa,

Giovanni Di Drusco in Ferrara and Ettore Giachetti in Milan.

The invention relates to a process for the preparation of novel catalysts for the polymerization of olefins, in particular for use in the polymerization of ethylene and its mixtures with α-olefins and / or diolefins.

For the polymerization of olefins, British Pat. No. 904,510 discloses catalysts consisting of the product of the reaction of an organometallic compound of metals of groups I to III of the periodic system with an inorganic salt of MgCl₂Type and coated with a layer of a halide of a transition metal in molecular thickness. The amount of the transition metal halide supported on the inorganic carrier is not higher than 1% by weight of the carrier itself.

According to the British patent, the transition metal compound can not be used in larger amounts than mentioned above without significantly deteriorating the activity of the catalyst. This is due to the fact that the inorganic salts used according to the British Pat. Are not subjected to any treatment by which they are converted into carriers which are suitable for the formation of catalysts, even in the presence of very large amounts of the support applied transition metal compound have a high activity.

Due to the small amount in which the catalytically active compound is present on the supports according to said British patent, very large amounts of the supported catalysts must be used to obtain the polymer in yields of practical interest. However, the use of these large amounts of the supported catalyst results in the need to purify the polymer from the catalyst residues after the polymerization is complete.

It has now surprisingly been found that it is possible to obtain polymerization catalysts having valuable properties, in particular very high activity, which in many cases render the purification of the polymer unnecessary after the end of polymerization when the reaction product obtained by combining a titanium tetrahalide with an Ifäger containing or consisting of a water free magnesium or zinc halide under conditions in which the magnesium and zinc halides are converted to an active form of the type defined below, or by combining the titanium tetrahalide with a previously activated magnesium or zinc halide, with a hydride or with an organometallic compound of metals of groups I, II and III of the periodic system is activated.

As anhydrous magnesium or zinc halides in the active Ferm halides are to be understood, which have one of the following two properties or the following two properties:

1. In the X-ray powder diagram, the highest intensity diffraction line present in the spectrum of the normal type magnesium and zinc halides becomes less intense, while at its

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Place a more or less widened halogen line appears.

Second The surface of the halide is larger than 3 m²/ g, preferably greater than 10 m / g.

It has been found that the very active forms of the magnesium and zinc halides are characterized by their broadening of the highest diffraction line in their X-ray

Show intensity and / or a surface of more than 15 m²/ g have.

In the case of anhydrous magnesium chloride, the X-ray diagram of many active forms is characterized in that the diffraction line appearing at a lattice spacing (d) of 2.56 and in the spectrum of MgCl₂ of the normal type having the highest intensity becomes less intense, while in its place a broadened halogen line in the region of the lattice spacing (d) from 2.56 to

2.95 Ä appears.

Likewise, the X-ray diagram of many active forms of MgBr₂ characterized in that the diffraction line at d = 2.93 Å, which in the spectrum of MgBr₂ of the normal type having the highest intensity becomes less intense, while a broadened halogen line appears in the range of d from 2.80 to 3.25 Å.

The new supported catalysts can be prepared by a variety of methods. One such method is to fuse the previously activated anhydrous magnesium or zinc halide with the titanium tetrahalide at a temperature, which may be room temperature, for a time sufficient to bind at least a portion of the titanium compound to the support. The reaction is preferably carried out by adding the titanium tetrahalide to a suspension of the activated anhydrous magnesium or zinc halide in an inert solvent and evaporating the solvent after completion of the treatment. In this preparation, the titanium tetrahalide is preferably used in an amount of 0.1 to 5% by weight, based on magnesium or zinc halide.

However, it is also possible - and this is the preferred method - to prepare the catalyst component to be applied to the support by reacting the anhydrous magnesium or zinc halide in the presence of the titanium tetrahalide, preferably less than 10% by weight of oil. based on the carrier, is ground under the conditions mentioned below.

It has also been found that the catalyst component to be applied to the support may also be prepared by reacting the anhydrous magnesium or zinc halide in an inactive form 30 according to the invention with the titanium tetrahalide used in excess over the anhydrous chloride, especially titanium tetrachloride, at relatively high levels Temperatures generally above about 70 to 80 ° C, and the mixture is then cooled and the magnesium or zinc halide separated therefrom. When using titanium tetrachloride is preferably in the

Working temperature of the halide worked.

The previously activated magnesium and zinc halide can be prepared by a variety of methods. One of these processes consists of subjecting the anhydrous magnesium or zinc halide to a mechanical treatment, eg milling, during such time and under conditions that the magnesium and zinc halides are formed in active form according to the invention.

The milling is preferably carried out in a ball mill in the absence of inert solvents. The duration of treatment generally depends on the effectiveness of the mill. For example, the milling time is about one hour when the carrier is ground in a centrifugal mill filled with parcel balls. A shorter grinding time can be achieved with mills which have a particularly high grinding action, for example in ball-and-roller mills. The abovementioned milling conditions suitable for the activation of the magnesium or zinc halide in the absence of the titanium tetrahalide can also be used when the magnesium or zinc halides are activated in the presence of the titanium tetrahalide.

According to another method, very active forms of magnesium and zinc halides can be obtained by decomposing organometallic compounds of the formula RMbX and RZnX, in which R is a hydrocarbon radical, for example an alkyl or aryl radical, andX is a halogen atom, in a manner known per se. or by the above-mentioned organometallic compounds having a halogenated compound, eg anhydrous gaseous hydrogen chloride used in the stoichiometric amount or in an amount in excess of the stoichiometric amount.

Another method by which very active forms of the magnesium and zinc halides can be made is to react the halides in an organic solvent,

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eg an alcohol, ether or amine, then the solvent is evaporated rapidly and then the removal of the solvent is completed by heating the halide under reduced pressure to temperatures above 100 ° C and generally between 100 and 400 ° C. In this procedure, active forms of anhydrous MgCl_z from solutions of MgCl₂ in CH _s OH has been obtained.

The catalyst components according to the invention comprise the titanium compound (which may be present as an active compound bound to the support itself and optionally in the form of a separable physical phase) in amounts which are of very low values, eg 0.01% by weight to the carrier, to higher levels which may reach 20% by weight or more. Preferably, this amount is between 0.1 and 5 wt .-%, based on the magnesium or zinc halide.

The new catalysts are thus formed by the product of the reaction between the following constituents:

a) the product obtained by combining a titanium tetrahalide, preferably TiCl 2₄with anhydrous magnesium or zinc halide under conditions in which the halide is converted to an active form of the type characterized above, or by combining the titanium tetrahalide with a previously activated magnesium or zinc halide;

b) a hydride or an organometallic compound of metals of groups I, III of the periodic system, preferably one of the following compounds: A1 (C₂ H_G)₃ , A1 (C₂H₅)₂C1, Al (i₄H₉)₃, Al (iC₄H₉)₂Cl, A1 (C₂H₅)₃ Cl₃, A1 (C₂H₅)₂H, Al (i₄H₉)₂H, Al (C., H₅)₂Br, Li-Al (i₄H₉) ₄ .

LiC₄H₉, Mg (C₂H₅)₂,

The molar ratio between the organometallic compound and the titanium tetrahalide is not critically important. In the polymerization of ethylene, the molar ratio Al / Ti is preferably between 50 and 1000.

The new catalysts are preferably used for the polymerization of ethylene and its mixtures with α-olefins and / or diolefins. However, good results, in particular with regard to the polymer yield, can also be obtained in the polymerization of α-olefins, for example propylene and butene-1.

The polymerization is carried out by known processes, ie in the liquid phase, in the presence or absence of an inert solvent or in the gas phase.

The polymerization is carried out at temperatures between -80 and 200 ° C, preferably between 50 and 100 ° C, at atmospheric pressure or overpressure. The molecular weight of the polymer can be adjusted by known methods, for example by carrying out the polymerization in the presence of alkyl halides or organometallic cadmium and zinc compounds or in the presence of hydrogen.

As is known, by using these molecular weight regulators, the catalytic activity of ordinary Ziegler catalysts obtained from a transition metal compound and an organometallic compound of Group I to III metals is significantly reduced. It has now been found that when using the catalysts according to the invention, the catalytic activity is little affected by the presence of the substances used to adjust the molecular weight. For example, in the polymerization of ethylene, it is possible to adjust the molecular weight of the polymer to values ​​within a range of practical interest and intrinsic viscosity between 1.5 and 3 dl / g (measured in tetralin at 135 ° C). without the polymer yield falling to values ​​below which it would be necessary to purify the polymer of catalyst residues after completion of the polymerization.

The polyethylene obtained in this way is a substantially linear and highly crystalline polymer having a density of 0.96 g / cm or more and very good processing properties especially for injection molding, which are very good and generally better than the processing properties of polyethylene obtained with the normal Ziegler catalysts. The Ti content is generally below 20 ppm.

In the following examples, percentages are by weight unless otherwise stated.

Example 1: In a centrifugal mill, which had a capacity of 330 ml and four porcelain balls, two of which had a diameter of 31.9 mm and the other two had a diameter of 40.9 mm, 48 g of anhydrous MgCl₂which has a surface of 1 m²/ g and 8 gTiCl₄ given, whereupon 2 hours was ground. The analysis of the milled product had the following results: Ti = 2.7%, Cl = 72%. The product had a surface area of ​​20 m / g.

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Ethylene was polymerized using 0.06 g of this ground product as follows: To a 1.8 liter stainless steel autoclave which had been purged with nitrogen was added 1000 ml of technical grade heptane and then 2 g of Al (iC₄H₉) ₃ given. The temperature was brought to 75 ° C, whereupon 0.06 g of the ground product as a suspension in 50 ml of n-heptane were added to the autoclave. Immediately thereafter, 3 atm of hydrogen and 10 atm of ethylene were pressurized. As a result, the temperature rose to about 85 ° C. The pressure was then kept constant at this value by continuous introduction of ethylene. After 2 hours, the suspension was removed from the autoclave. The polymer was filtered off and dried under reduced pressure at 100 ° C. Hiebei 195 g of polyethylene were obtained, which had an intrinsic viscosity (n) of 2.5 dl / g, measured in

Tetralin at 135 ° C. The polymer yield was 121,000 g / g Ti.

Example 2: hi of the ball mill mentioned in Example 1 were 7.3 g of that mentioned in Example 1

MgCl₂ 1 h in the presence of 0.5178 g TiCl₄ ground. The milled product had a Ti content of 1.4% and a surface area of ​​15 m²/G.

Ethylene was polymerized using 0.049 g of the milled product under the conditions mentioned in Example 1. After 4 hours, 395 g of a polymer having an intrinsic viscosity (jj) of 2.5 dl / g, measured in tetralin at 35 ° C, were obtained. The yield of polymer was 570,000 g / gTi.

Example 3: In a ball mill of the type described in Example 1, 25 g of anhydrous MgCl 2 were added₂ of the type mentioned in the preceding examples was milled for 3 hours. The ground product had a surface of 22 m² /G. 10 g of this product, 50 ml of n-heptane and 0.59 g of TiCl₄ were added to a 250 ml flask equipped with a stirrer. The suspension was stirred for 1 h at room temperature, whereupon the solvent was evaporated off. The resulting solid product contained 1% Ti.

Ethylene was polymerized with 0.133 g of this product under the conditions mentioned in Example 1. After 4 hours, 400 g of polymer were obtained, which had an intrinsic viscosity (η) of 2.1 dl / g, measured in tetralin at 135 ° C. The polymer yield was 300,000 g / g Ti.

Example 4: Under the conditions mentioned in Example 3, 9.25 g of the ground MgCl described in Example 3 were added₂, 0.14 g of TiCl₄ and treated 50 ml of n-heptane. Analysis of the resulting solid product showed a Ti content of 0.36%.

Ethylene was polymerized with 0.0738 g of this product under the conditions mentioned in the preceding examples. After 4 hours, 151 g of polymer were obtained which had an intrinsic viscosity of

2.9 dl / g, measured in tetralin at 135 ° C. The polymer yield was 590,000 g / g Ti.

Example 5: Under the conditions mentioned in Example 3, 10 g MgCl₂ ground. Further, 0.59 g of TiCl₄ and 75 ml of n-heptane under the conditions mentioned in Example 3. The resulting solid product contained 0.88% Ti.

Ethylene was 0.0746 g of this product under those mentioned in the preceding examples

After 4 hours, 182 g of a polymer having an intrinsic viscosity (η) of 2.4 dl / g, measured in tetralin at 135 ° C, were obtained. The polymer yield was 277,000 g / g Ti.

Example 6: The product obtained in Example 5, from which the solvent had been removed by evaporation, was washed with n-heptane until the reaction of chlorine ions in the washing liquid ceased. The washed product contained 0.16% Ti.

Ethylene was polymerized with 0.4029 g of this product under the conditions described in the preceding examples. After a polymerization time of 4 hours, 279 g of polymer were obtained. The yield was 435,000 g / g Ti.

Example 7: Under the conditions mentioned in Example 3, 15.2 g of anhydrous MgCl₂with an average particle size of 125 to 177 μ and a surface area of ​​1 m / g, 0.64 g TiCl₄45 and 75 ml of n-heptane. After evaporation of the solvent, the analysis showed a Ti content of 0.25%.

Ethylene was polymerized with 0.1053 g of this product under the conditions mentioned in the preceding examples. After a polymerization time of 4 hours, 17.6 g of polymer were obtained corresponding to a yield of 67,000 g / g of Ti.

Example 8: The product obtained from the above example from which the solvent had been evaporated was washed with n-heptane several times until no reaction of the chlorine ions in the washing liquid was observed. The washed product had a Ti content of 0.09%.

Ethylene was polymerized with 0.751 g of this product under the same conditions as in the preceding examples. After a polymerization time of 4 h, 34 g of polymer were obtained in a yield of 50,000 g / g of Ti.

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Example 9: In an autoclave provided with a stirrer and at the bottom with a filter plate and 300 ml of TiCl₄ which was heated to 135 ° C, 29 g of anhydrous MgCl₂introduced, which has a surface of 0.5 m²/ g had. After a heating period of 1 h, the excess TiCl₄ filtered off. The solid in the Aufoklaven solid product was washed several times with cyclo5 hexane until the TiCl₄ completely disappeared. The analysis of the $ o obtained fixed

Product gave a Ti content of 0.18% and a Cl content of 73.1%.

Ethylene was polymerized with 0.57 g of this solid product under the conditions mentioned in the preceding examples. After a polymerization time of 4 hours, 401 g of polymer were obtained, which had an intrinsic viscosity (jj) of 2.8 dl / g, measured in tetralin at 135 ° C. The polymer yield was 400,000 g / g Ti.

Example 10: The experiment described in Example 9 was repeated with the only difference that MgCl₂which was previously ground for 2.5 hours in a ball mill of the type described in the preceding examples. After treatment with TiCl₄ The analysis of the washed product showed a Ti content of 0.66% and a Cl content of 72.8%.

Ethylene was polymerized with 0.17 g of this product in the manner described in the preceding examples. After a polymerization time of 4 hours, 448 g of polymer were obtained corresponding to a yield of 400,000 g / g of Ti.

Example 11: The experiment described in Example 9 was repeated with the difference that 22 g MgCl₂which had not been activated by grinding and had an average particle size between 20 125 and 177 μ were used. This product had a surface of 1 m²/G. After

Treatment with TiCl₄ The washed and dried product contained 0.3% Ti and 72.8% Cl.

Ethylene was polymerized with 0.31 g of this washed product under the same conditions as in the above Examples. After a polymerization time of 4 hours, 271 g of polymer was obtained corresponding to a yield of 291,000 g / g of Ti.

Example 12: A suspension of 35 g of the magnesium chloride used in Example 11 in 130 ml of TiCl₄ was produced. This suspension was stirred for 24 h at room temperature, whereupon the excess TiCl₄ was filtered off. The resulting solid product was washed several times with cyclohexane until the TiCl₄ had completely disappeared in the washing liquid. The analysis of the washed and dried product showed a Ti content of 0.066%.

Ethylene was polymerized with 0.31 g of the product thus obtained under the same conditions as in the above examples. After a polymerization time of 2 h, no polymer had formed.

Example 13: In the ball mill described in Example 1, 7.1 g MgBr₂ 3 h in the presence of 0.512 g TiCl₄ ground. The milled product contained 1.3% Ti and had a surface area of ​​27 m² /G.

Ethylene was polymerized using 0.051 g of this product under the same conditions as in the above Examples. After 4 hours, 330 g of a polymer having an intrinsic viscosity of 2.3 dl / g was obtained. The polymer yield was 500,000 g / g Ti.

Example 14: The MgCl used in this experiment₂ was prepared by reacting ether-dissolved C, Hg MgCl with anhydrous gaseous HCl until precipitation of MgCl₂was passed through the solution. The MgCl₂ was filtered off and dried under reduced pressure at 200 ° C. The product had a surface area of ​​142 m / g. Its X-ray powder diagram showed a substantial broadening of the diffraction line at d = 2.56 Å, for a 250 ml flask equipped with stirrer, 9.25 g of this product, 0.14 g TiBr₄ and 50 ml of n-heptane. The suspension was stirred for 1 h at room temperature, whereupon the solvent was evaporated off.

Ethylene was polymerized using 0.073 g of this product under the same conditions as in the preceding examples. After 4 h, 150 g of polyethylene were obtained, which had a limit viscosity of 2.3 dl / g.

Example 15: The MgCl used in this experiment₂ was prepared by adding a solution 50 of 15 g MgCl₂which had a surface of 1 mg in 200 ml of CH₃OH was evaporated quickly and the removal of the alcohol was completed by heating the product to 300 ° C under vacuum. The resulting MgCl₂ had a surface of 32 m lg. Its X-ray diagram showed a significant broadening of the diffraction line, which in the spectrum of MgCl₂ of the normal type at d = 2.56 Å appears. In a 250 ml flask equipped with stirrer, 9.25 g of this product, 0.14 g of TiCl₄55 and 50 ml of n-heptane. The suspension was stirred for 1 h at room temperature, whereupon the solvent was evaporated off.

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Ethylene was polymerized using 0.05 g of this product under the same conditions as in the above examples to obtain 150 g of polyethylene having an intrinsic viscosity of 2.1 dl / g.