Catalysts and process for the polymerization of olefins

(54) Name: Methods of preparing a catalyst for polymerization of olefins

The present invention relates to a method of preparing novel catalyst components for the polymerization of olefins having 2-6 carbon atoms.

British Patent 904,510 discloses polymerization catalysts for olefins which consist of the reaction product of a metal-organic compound of the metals of groups I-III of the periodic system with an inorganic MgC 2 -type salt coated on the surface with a molecularly thin layer of a halide. of the transition metals.

The amount of halide of the transition metals located on the inorganic support does not exceed 1% by weight of the support itself.

According to the British patent, the transition metal compound cannot be used in greater quantities than those mentioned above without thereby significantly reducing the activity of the catalyst. This is due to the fact that the inorganic salts used in the British patent are never subjected to any treatment which can transfer them to carriers suitable for obtaining high activity catalysts even in the presence of very large amounts of the supported transition metal compound. Considering the small amount of catalytically active compound present in the British patent, it is necessary to use very large amounts of the supported catalyst to obtain polymer yields of practical interest. The use of such large amounts of the supported catalyst suggests the necessity of purifying the polymer from residues of the catalyst at the end of the polymerization.

It has now unexpectedly been found that it is possible to obtain polymerization catalysts having valuable properties, and in particular with a very high activity, which in many cases allows to avoid the purification of the polymer at the end of the polymerization, by activating the reaction product obtained by contacting a Ti tetrahalide with a carrier consisting of anhydrous Mg halide under conditions; wherein the Mg halide is converted to an active form as described below or using a previously activated Mg halide, with a metallic organic compound of aluminum.

By anhydrous Mg halide in active form is meant the halide having the following properties:

1) In its X-ray spectrum, the highest-intensity diffraction line present in the spectrum of the normal type Mg halide becomes less intense, whereas a more or less widened light field appears instead.

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2) Its surface area is greater than 3 m / g and preferably 10 m / g.

It has been noted that the very active forms of the Mg halides are characterized by their. in its X-ray spectra, the width of the diffraction line shows with the greatest intensity and has surface values ​​greater than 15 m / g.

With anhydrous Mg chloride, the X-ray spectrum is characterized by many active forms in that the diffraction line, which appears at a grid distance (d) of 2.56 Å and which, is the most intense in the spectrum of MgCl₂ of the normal type, becomes less intense while instead a broadened light garden emerges, which is located within a range of d of 2.80-3.25 Å.

Similarly, the X-ray spectrum is characterized by many active forms of MgBr₂ of the diffraction line at d = 2.93 Å, which is the most intense in the spectrum of MgBr₂ of the normal type, becomes less intense, while the widening of a broad light garden occurs within a range of d of 2.80-3.25 A.

The supported catalysts can be prepared in many ways. One of these consists of contacting, even at room temperature, the previously activated anhydrous Mg halide with the titanium tetrahalide for a time sufficient to attach at least a portion of the Ti compound to the support.

The contact is preferably made by adding the titanium tetra-tetrahydrohalide to a suspension in an inert solvent of the activated anhydrous Mg halide and then evaporating the solvent at the end of the treatment.

The amount of titanium tetrahalide used in this type of preparation # is preferably between 0.1 and 5% by weight calculated on the Mghalide.

However, it is possible, and this is the preferred method, to carry out the preparation of the supported catalytic component also by subjecting the anhydrous Mg halide to painting under conditions described below, in the presence of the titanium tetrahalide, preferably used in an amount which is less than 10% by weight with respect to the carrier.

It has further been found that it is possible to obtain the supported catalytic component even by heating the anhydrous Mg halide, in a non-active form of this invention, with the titanium tetrahalide, especially TiCl , at relatively high temperatures, generally higher than 70-80 ° C and then cooling the mixture and separating the Mg halide therefrom. In the case of TiCl 2, one preferably operates at the boiling point of the halide.

The preparation of the previously activated Mg halide can be carried out in many ways: one of which consists in exposing the anhydrous Mg halide to mechanical treatments, such as painting for a time and under conditions, which transfer the Mg halide in an active form according to invention.

The painting is preferably accomplished in a ball mill in the absence of inert solvents. The duration of the treatment generally depends on the efficiency of the grinding device. As an example, the duration amounts to about 1 hour when the support is ground in a centrifugal mill loaded with porcelain balls. Shorter times can be used when using mills which have a particularly high grinding effect, for example vibrating ball mills. The above grinding conditions, suitable for activating the Mg halide in the absence of the titanium tetrahalide, are also useful when the Mg halides are activated in the presence of the titanium tetrahalide.

In another way, very active forms of the Mg halide can be obtained by degradation by known methods of a metal-organic compound of the formula RMgX wherein R is hydrocarbon radical, such as, for example, an alkyl or an aryl radical and X is halogen, or by reacting the the above-mentioned metallic organic compounds with a stoichiometric or greater than stoichiometric amount of a halogenated compound such as, for example, anhydrous gaseous hydrogen chloride.

A further way of preparing highly active forms of the Mg halides consists of dissolving the halides in an organic solvent such as, for example, alcohol, ether or an amine, then rapidly evaporating the solvent and then completely removing the solvent by heating the halides under reduced pressure. 100 ° C and generally at 100-400 ° C.

According to this method, anhydrous MgCl₂ in an active form obtained from solutions of MgCl₂ in CHgOH.

The catalytic components of this invention contain amounts of the titanium compound (which may be present as an active compound attached to the carrier itself and in the form of a separable physical phase), which vary from very small values, such as, for example, 0.01 wt. % with respect to the carrier, to higher values, which may amount to 20% by weight or more. This amount is preferably 0.1-5% by weight with respect to the Mg halide.

The catalysts of this invention are therefore formed from the reaction product between:

a) the product obtained by contacting a titanium tetrahalide, preferably TiCl 3, with anhydrous Mg halide under conditions such that the halide is transferred in an active form as indicated above or by contacting a previously activated Mg halide and

b) an metallic organic compound of aluminum, which is preferably selected from the following compounds.

A1 (C₂hrs₅)₃, A1 (C₂hrs₅)₂C1, A1 (iC₄hrs₉)₃, Al (iCjHg)₂C1, Al (C₂hrs₅)₃C1₃, A1 (C₂hrs₅)₂H, Al (iC₄hrs₉)₂H, Al (C₂hrs₅)₂Br.

The molar ratio of the metal-organic compound to the titanium tetrahalide is not critical. In the polymerization of, for example, ethylene, a molar ratio Al / Ti of preferably 50-1000 is used.

The catalysts of this invention are preferably used in the polymerization of ethylene and its mixtures with alpha olefins and / or diolefins. Equally good results can be obtained, especially with respect to polymer yield, also by polymerization of alpha olefins such as, for example, propylene, butene-1, etc.

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The polymerization temperature can be (-80 ° C) - (+ 200 ° C), preferably 50-100 ° C, with operation at atmospheric pressure or under pressure. The molecular weight of the polymer can be controlled by known methods such as by conducting the polymerization in the presence of an alkyl halide. or of metal organic Cd and Zn compounds or of hydrogen.

As is known, the use of such molecular weight regulators tends to significantly lower the catalytic activity of normal Ziegler catalysts obtained from a compound of transition metals and from a metal-organic compound of the metals of groups I-III.

It has now been found that for catalysts of this invention, the catalytic activity is unaffected by the presence of the substance used for controlling the molecular weight.

For example, in the polymerization of ethylene, it is possible to control the molecular weight of the polymer within a range of practical interest corresponding to values ​​of intrinsic viscosity in tetralin at 135 ° C of 1.5-3 dl / g without the polymer yield falling to values ​​below necessary at the end of the polymerization to purify the polymer from residues of the catalyst.

The polyethylene so obtained is a substantially linear and highly crystalline polymer having density values ​​equal to or greater than 0.96 g / cm³ and with machining properties, especially in the form of injection molding, which are excellent and generally better than those of polyethylene obtained by means of normal Ziegler catalysts. The Ti content is generally less than 20 ppm (parts by weight).

The invention will now be illustrated by the following examples, which are of a purely illustrative and non-limiting nature. Unless otherwise stated, the percentages are expressed as weight #.

Example 1

In a centrifuge mill with a capacity of 330 cm³, provided with 4 porcelain balls, two of which have a diameter of 31.9 mm and the other two have a diameter of 40.9 mm, 48 g of anhydrous o

MgClg having a surface area of ​​1 m / g together with 8 g of TiCl ^, and ground for 2 hours.

The analysis of the milled product yielded the following results:

Ti = 2.7 #, Cl = 72 #.

Its surface area was 20 m / g. 0.06 g of this milled product is then used in an ethylene polymerization test conducted under the following conditions:

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In a stainless steel autoclave with a capacity of 1.8 liters and purified with nitrogen, 1000 cc of technical heptane was introduced and then 2 g of AlCl 2 Then the temperature was raised to 75 ° C and the ground product suspended in 50 cm 3 of n-heptane was introduced into the autoclave. Immediately thereafter, 3 atm hydrogen and 10 atm ethylene were introduced; thereby raising the temperature up to 85 ° C. The pressure was then kept constant at this value by continuously adding ethylene. After 2 hours the suspension was dropped from the autoclave. The polymer was separated by filtration and then dried under vacuum at 100 ° C.

Thereby, 195 g of polyethylene having an intrinsic viscosity (η) of tetralin was obtained at 135 ° C of 2.5 dl / g.

The yield of polymer was 121,000 g / g Ti.

Example 2

7.3 g of anhydrous MgCl 2 according to the previous example was ground in 1 h of the ball mill of Example 1 in the presence of 0.5178 g TiCl 2.

The content of Ti in the ground product was 1.4 ?. The surface area of ​​the product was 15 m / g.

Subsequently, 0.0490 g of the ground product was used in polymerization of ethylene under the same conditions as in the previous example. Thereupon 395 g of a polymer having an intrinsic viscosity (η) in tetralin at 135 ° C of 2.5 dl / g were obtained. The polymer yield was 570,000 g / g Ti.

Example 3 g of anhydrous MgClg of the type used in the previous example was milled in 3 h for a ball mill of the type used in the 2 mentioned examples. The surface area of ​​the milled product was 22 m / g.

g of this ground product, 50 cn? n-heptane and 0.590 g of TiCl 2 were introduced into a 250 cm flask equipped with a stirrer. This suspension was stirred for 1 hour at room temperature after which the solvent was evaporated.

In the solid product so obtained was 1? Ti.

0.133 g of this product was then used in the polymerization of ethylene, which was carried out under the same conditions as those in the examples

1st After 4 hours, 400 g of polymer having an intrinsic viscosity (n) in tetralin at 135 ° C of 2.1 dl / g was obtained. The polymer yield was 3θθ⁰⁰⁰g / g Ti.

Example 4

9.25 g of the ground MgCl₂ From the previous example, 0.14 g of TiCl 2 and 50 cm 3 of n-heptane were treated under the same conditions as in the previous example. The solid product obtained showed a Ti content of 0.36 µ in analysis.

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0.0738 g of this product was used in the polymerization of ethylene under the same conditions as in the previous example. After 4 hours, 151 g of polymer having an intrinsic viscosity in tetralin at 135 ° C was obtained

2.9 dl / g. The polymer yield was 59U000 g / g Ti.

Example 5 g MgCl 2. ground under the same conditions as in Example 3,^ά 3

0.59 g of TiCl 3 and 75 cm of n-heptane were treated under the same conditions as in Example 3

The solid product thus obtained contained 0.88% Ti.

0.0746 g of this product is then used in the polymerization of ethylene under the same conditions as in the previous example. After 4 hours, 182 g of polymer with an intrinsic viscosity Pt (ri) in tetralin at 135 ° C of 2.4 dl / g were obtained. The polymer yield was 277,000 g / g Ti.

Example 6

The product obtained under the same conditions as in the previous example and from which the solvent had been removed by evaporation was washed with n-heptane until the chlorine ion reaction in the washing liquid disappeared. The content of Ti in the washed product was 0.16%.

0.4029 g of this product is then used in polymerization of ethylene under the same conditions as in the previous example. After 4 hours of polymerization, 279 g of polymer were obtained. The yield was 435,000 g / g Ti.

Example 7

25.2 g of anhydrous MgCl₀, whose mean particle size was <- 2 3

125-177 µm and whose surface area was 1 m / g, 0.64 g TiCl 2, 75 cnr n-heptane was treated under the same conditions as in Example 3. The analysis of the product, after 0.25%.

0.1053 g of this product is used in the polymerization of ethylene under the same conditions as in the previous example. After 4 hours of polymerization, 17.6 g of polymer was obtained with a yield of 67,000 g / g Ti.

Example 8

The product obtained under the same conditions as in the previous example, from which the solvent had been removed by evaporation, was repeatedly washed with n-heptane until the chlorine ion reaction disappeared in the washing liquid.

The content of Ti in the product so washed was found to be 0.09%.

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0.751 S of this product is then used in the polymerization of ethylene under the same conditions as in the previous example. After 4 hours of polymerization, 34 g of polymer was obtained with a yield of 50,000 g / g Ti.

Example 9

--- 2 g of anhydrous MgCl₂, whose surface area was 0.5 m / g, was introduced into an autoclave equipped with a stirrer and equipped with a filtration plate at the bottom, containing 300 cm₍ heated to 135 ° C.

After 1 hour of heating, the excess TiCl 2 was removed by filtration. The bone solid product, which remained in the autoclave, was washed repeatedly with cyclohexane until all TiCl 2 had disappeared. The analysis of the solid product thus obtained showed a content of 0.18% Ti and 73.1% Cl.

0.57 g of this solid product is used in the polymerization of ethylene under the same conditions as in the previous example. After 4 hours of this polymerization, 401 g of polymer having an intrinsic viscosity (n) in tetralin at 135 ° C of 2.8 dl / g was obtained. The yield of polymer was 400,000 g / g Ti.

Example 10

In this experiment, as in Example 9, the only difference was that of MgCl₂ For example, MgClg, previously milled in 2.5 h, was used in a ball mill of the type used in the previous example. After treatment with TiCl 3, the analysis of the washed product showed the presence of 0.66% Ti and 72.8% Cl.

0.170 g of this product is then used in the polymerization of ethylene under the same conditions as in the previous example.

After 4 hours of polymerization, 448 g of polymer were obtained with a polymer yield of 400,000 g / g Ti.

Example 11

In this case, as in Example 9, the difference was that 22 g of MgCl 2 was used, not activated by grinding and with an average particle size of 125-177 µm. The surface area of ​​this product up2 was 1 m / g. After treating with TiCl 2, the washed and dried product showed the presence of 0.3? Ti and 72.8% Cl. 0.31 g of this washed product is then used in the polymerization of ethylene under the same conditions as in the previous example. After 4 hours of polymerization, 271 g of polymer was obtained with a yield of 291,000 g / g Ti. Example 12 g of the magnesium chloride used in the preceding eczema. 3 bars were suspended in 130 cc TiCl 2. This suspension was then kept under stirring at room temperature for 24 hours, after which the excess TiCl was removed by filtration. The solid product obtained was washed,

6915957-2 was then repeatedly repeated with cyclohexane until all TiCl 2 had disappeared in the washing liquid. The analysis of the washed and dried products showed a Ti content of 0.066 #.

0.31 g of this product is used in the polymerization of ethylene under the same conditions as in the previous example. After 2 hours of polymerization, no polymer was formed.

Example 13

7.1 g of MgBrg was ground in 3 h of the ball mill of Example 1 in the presence of 0.5120 g of TiCln. The content of Ti in the ground product was 1.3 #. surface⁴ 2 area for this product was 27 m / g. 0.051 g of this product is used in the polymerization of ethylene according to the conditions of the previous example. After 4 hours 330 g of polymer with an intrinsic viscosity of 2.3 dl / g were obtained. The polymer yield was 500,000 g / g Ti. Example 14

The MgClg used in this example was obtained by the reaction of CgH 2 MgCl in solution in ether with anhydrous gaseous HCl which was bubbled through the solution to precipitate MgCl₂which was then filtered and dried at 200 ° C under vacuum. The surface area of ​​the product was 142 m / g and its X-ray powder spectrum showed a marked broadening of the diffraction line at d = 2.56 Å. 9.25 g of this product, 0.14 g of TiBr 2 and 50 cm cm² flask fitted with stirrer. The suspension was stirred for 1 hour at room temperature, after which the solvent was evaporated. 0.073 g of this product was then used in the polymerization of ethylene under the same conditions as in the previous example, where after 4 hours 150 g of polyethylene having an internal viscosity of 2.3 dl / g were obtained.

Example 15

The MgCl- used in this experiment was obtained by rapid evaporation of a solution in 200 cc CH_XOH of 15 g MgCl₀ with a surface2 -⁵ area of ​​1 m / g and then complete removal of the alcohol by heating the product at 300 ° C under vacuum. The 2 mg MgCl 2 thus obtained had a surface area of ​​32 m / g, its X-ray spectrum showed a marked broadening of the diffraction line, which appears at d =

2.56 Å in the spectrum for the normal type MgClg.

9.25 g of this product, 0.14 g of TiCl 2 and 50 cm^{* 3} n-heptane was introduced into a 250 cm 2 flask equipped with a stirrer. The suspension was stirred for 1 hour at room temperature, after which the solvent was evaporated.

0.05 g of this product was used in the polymerization of ethylene under the same conditions as in the previous example to give 150 g of polyethylene having an internal viscosity of 2.1 dl / g.

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