CS244770B1 - Ethylene polymerization and copolymerization catalyst - Google Patents

Abstract

The solution relates to a catalyst for the polymerization and copolymerization of ethylene based on complex compounds of titanium tetrachloride, magnesium chloride with at least one electron donor compound on an inorganic or organic support and organic aluminum compounds as activators. The active component of the catalyst is a product formed by the reaction of 1 mole of titanium tetrachloride, 0.5 to 1Ó moles of magnesium chloride, 2 to 130 moles of an electron donor compound with at least one free electron pair, 0.25 to 1 mole of metallic magnesium. The catalyst has a high polymerization activity and provides a product with a wide molecular distribution.

Description

Catalyst for the polymerization and copolymerization of ethylene

The solution relates to a catalyst for the polymerization and copolymerization of ethylene based on complex compounds of titanium tetrachloride, magnesium chloride with at least one electron donor compound on an inorganic or organic support and organic aluminum compounds as activators. The active component of the catalyst is a product formed by the reaction of 1 mole of titanium tetrachloride, 0.5 to 1Ó moles of magnesium chloride, 2 to 130 moles of an electron donor compound with at least one free electron pair, 0.25 to 1 mole of metallic magnesium. The catalyst has a high polymerization activity and provides a product with a wide molecular distribution.

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The invention relates to catalysts for the polymerization and copolymerization of ethylene. It is known from the patent and technical literature that complex compounds TiCl^ . yMgCl ₂ . zEDS, (where EDS is an electron donor compound) supported on an organic or inorganic support provide, in combination with β organic aluminum compounds, highly active catalysts capable of polymerizing and copolymerizing alpha-olefins to products - plastics - with excellent mechanical and chemical properties.

For example, US 4302 566 and US 4303 771 describe the preparation of these catalysts, which are based on pure chemical individuals, such as the compounds Ti^, MgX ₂ and EDS. In the titanium compound, Y can represent Cl, Br, J, - OR, R. MgX ₂ represents a halide compound of Mg, the most commonly used component being anhydrous magnesium chloride. EDS are represented by compounds that have at least one free electron pair, such as linear and cyclic ethers, esters of fatty and aromatic acids, nitriles, amines and other nitrogenous bases.

The reaction of titanium and magnesium compounds with EDS produces complex compounds (solvates), which are either applied to the support in the form of a solution in EDS or in the form of a microcrystalline powder or in a suspension with an inert hydrocarbon solvent. The ratio of Mg:Ti can vary in a wide range from 0.5 to 10, preferably working at ratios greater than 1. The disadvantage of known catalysts is that anhydrous magnesium halides are prepared by complex methods and are relatively difficult to dissolve in EDS. In an attempt to eliminate or reduce the need for 1(gCl ₂ taken into the reaction, we tried to use the reaction of magnesium metal with the TiCl^ complex with EDS, in which the Ti compound is reduced and a magnesium complex is formed. The degree of reduction of the titanium compound is given by the selected ratio of the reacting components Ti** and Mg.

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It was surprisingly found that the action of metallic magnesium on a solution of TiCl^ and MgCl^ in EDS produces a product which, when applied to a suitable support, provides, after activation with a metalorganic aluminum compound, a polymerization catalyst with different properties than that obtained by applying a complex compound that has not been subjected to the action of metallic magnesium.

The subject of the invention is a catalyst for the polymerization and copolymerization of ethylene with 1-alkenes to Οθ based on complex compounds of titanium tetrachloride, magnesium chloride with at least one electron donor compound with at least one free electron pair such as linear, cyclic ethers, esters, nitriles and nitrogen bases on an inorganic or organic support and organic aluminum compounds in molar ratios of 1 mol of titanium tetrachloride, 0.5 to 10 mol of magnesium chloride and 2 to 130 mol of electron donor compound, in which the active component of the catalyst is formed by the reaction of the above components with 0.25 to 1 mol of metallic magnesium. The catalyst enables the polymerization of alpha-olefins in the gas phase under mild temperature and pressure conditions. The resulting polymers are characterized by a flow index IT of from 0.01 to 100, an IT ratio (MFR) of from 20 to 35 inclusive, and densities ranging from 910 to 970 kg/m^.

The catalyst according to the invention is prepared from a solution of the TiCl^ . xEDS complex in (excess) EDS. The complex solution is prepared by dissolving the crystalline TiCl^ . xEDS complex in EDS in a reaction vessel equipped with a heating/cooling jacket, a stirrer and a reflux condenser, or in situ by carefully adding TiCl^ to EDS at laboratory temperature. According to the desired Mg:Ti ratio, a calculated amount of metallic magnesium and anhydrous magnesium chloride is added to the reaction vessel to the above complex solution. Magnesium can be used in the form of powder or shavings, magnesium chloride can also be added to the complex solution before adding magnesium. The dissolution of magnesium can be accelerated by increasing the temperature to the boiling point of EDS. After dissolving all components, a solution of the bimetallic complex with EDS is obtained, which is applied to a suitable organic support, such as polyethylene powder, or inorganic, for example, silica. By evaporating the excess EDS or other organic solvent, a catalyst precursor is obtained, which becomes polymerization active by adding an organoaluminum compound - an activator.

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Activation of the catalyst precursor can be done in several ways:

1. in a polymer reactor a) by adding a solution of trialkylaluminum in an aliphatic solvent, b) by adding silica impregnated with trialkylaluminum. The amount of activator used aa varies in the range corresponding to the ratio of AI : Ti from 1 to 200. In many cases, it is more advantageous to activate the catalytic precursor in two stages. The preactivation carried out during the preparation of the catalytic precursor by adding an organometallic solution in an amount corresponding to the ratio of AI : Ti from 1 to 10 is completed by complete activation in the polymerisation reactor by adding trialkylaluminum corresponding to the ratio of AI : Ti from 10 to 200.

In the preparation of catalysts, the following substances are used: Titanium salts! TiCl^ or TiCl^ solvate · nEDS, where

0.1 < n < 4

Magnesium compounds.a) metallic magnesium

b) MgClg or solvate MgCl? · aEDS where

0.01 < m < 4.

EDS: Suitable EDS are compounds with one or two free electron pairs, such as alkyl ethers of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ethers and aliphatic ketones. Aliphatic and cyclic ethers appear to be particularly preferred. EDS can be used individually or in mixtures. 2 to 130 moles of EDS are used per mole of compound Ti.

Organometallic aluminum compounds: compounds of the general formula R-jAl, where R represents alkyls from CH^ to ΟθH^γ preferably triethylaluminum and triisobutylaluminum are used. Trialkylaluminums can be used individually or in mixtures, 2 to 200 moles of activator are used per 1 mole of titanium compound.

Carrier: organic and inorganic compounds that are inert to the catalytic system can be used as carriers, such as olefinic and vinyl polymers and inorganic oxides, preferably silica and polyethylene. Inorganic oxide carriers are expediently subjected to heat treatment (activation) in a stream of dry air and then pure nitrogen at temperatures of 300 to 900 °C for 1 to 24 hours before applying the components.

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The application of the catalytic system to the support is carried out in a suspension of the support in EDS or in an aliphatic solvent, to which a solution of the catalytic complex in EDS or a crystalline catalytic complex is added. The interaction of the support with the catalytic complex is carried out under stirring for 30 to 300 minutes, after which the solvent is removed by distillation in a stream of pure nitrogen at temperatures not higher than 65 °C.

The ratio of the catalytic complex and the carrier is chosen such that the titanium concentration is in the range of 0.1 to 3.0% by weight.

With the supported catalysts prepared in this way, polymerization can be carried out in a solvent environment or in the gas phase, in a batch or continuous process.

Polyaeration in a solvent environment is preferably carried out in an autoclave under an elevated pressure of 1 to 2 KPa and at temperatures from 50 to 100 °C. An aliphatic hydrocarbon or Cg, free from catalytic poisons such as oxygen, water, alkadienes and alkynes, is used as the solvent. Ethylene and 1-alkenes used for copolymerization must also be very pure. The reactor must be equipped with an effective cooling system to remove the polymerization heat. The solvent, for example isopentane or n-hexane, is saturated at the selected temperature and pressure with ethylene or a mixture of ethylene with a comonomer, an activator, for example triethylalumina, is added and everything is brought into contact with the catalyst. Polymerization occurs immediately. The amount of activator can be varied within a wide range, the optimum being 20 to 40 molecules of trialkylaluminum per 1 atom of titanium.

To achieve a suitable molecular weight of the polymer, it is necessary to introduce a molecular weight regulator, such as dialkylzinc or hydrogen, into the polymerization system. The most suitable hydrogen concentration is in the range of 10 to 60% by volume.

The pressure drop in the reactor caused by the polymer! of ethylene is balanced by the addition of fresh ethylene or its mixture with comonoers*. The polymerisation is continued until the polymer concentration in the suspension reaches 30%. The gaseous mixture is then discharged from the reactor, the polymer is freed from solvent and dried. A white powder is obtained which has such a low content of catalyst residues that it can be used for granulation without further treatment or, after stabilization, for processing.

244 770 However, it is more advantageous to use the catalyst according to the invention for polymerization or copolymerization in the gas phase. Even in this case, it is possible to work batchwise, for example, in a polymerization test, a continuous fluidized bed polymerization process is better. The bed formed by polyethylene powder is brought into suspension by blowing in a mixture of monomer, comonomer and hydrogen. The catalyst is fed to the lower part of the bed through a capillary by a stream of inert gas. The actual activation of the catalyst is completed in the reactor by adding a solution of trialkylaluminum in isopentane or hexane. Activation can also be carried out by adding silica doped with trialkylaluminum to the reactor. The polymerization is carried out under a pressure of 1 to 10 MPa, preferably at 2 MPa, β hydrogen concentration of 20 to 40% by volume and β comonomer content corresponding to a comonomer/conomer ratio of 0 to 10. The polymerization temperature can be varied within a wide range, it is preferable to maintain a temperature of 80 to 110 °C in the upper part of the bed according to the desired properties of the polymer being produced. The gas mixture exiting the reactor is cooled in a cooler, enriched with polymerized monomers and returned to the reactor from the bottom. The polymer is discharged from the reactor at short intervals, degassed and the white powder obtained can be used for granulation or other processing methods. Further details of the invention are given in the following examples 1 to 34· % in the examples are by weight. THF is tetrahydrofuran.

Example 1

In a reaction vessel equipped with a stirrer, reflux condenser and pure nitrogen supply, 1.71 g of magnesium chloride solvate with the composition MgCl ₂ . 1.57 THF, 0.10 g of magnesium metal in the form of shavings and 100 ml of anhydrous THF are added. After dissolving the MgCl 2 , 1.56 g of TiCl^ are added dropwise with stirring, which immediately reacts with THF to form a yellow complex. Stirring is continued even after all the TiCl^ has been added. To accelerate the reaction of TiCl^ with magnesium metal, the mixture is heated to the boiling point of THF at most. As the reaction of TiCl^ with magnesium progresses, the yellow color changes from brownish-black to greenish-black.

After dissolving all the magnesium, the solution obtained is used directly for the preparation of the catalyst after cooling, or a crystalline precursor is isolated from it, which is then processed into an active catalyst through further operations. Isolation of the crystalline precursor

244,770 of the precursor is prepared by partial evaporation of THF and crystallization or precipitation by addition of an aliphatic low-boiling hydrocarbon.

Example 2

A weighed amount of 5.14 g of magnesium chloride solvates with the composition MgCl ₂ . 1.57 THF and 2.89 g of the crystalline complex TiCl ₄ . 2 THF are introduced into a 250 *1 reaction vessel equipped with a reflux condenser, a magnetic stirrer* and a pure nitrogen inlet. Then 0.10 g of magnesium metal and 100 *1 THF are added and heated with stirring to a temperature of 50°C until everything dissolves. A dark-colored solution of the catalytic complex is obtained, which, after being applied to a suitable support and subsequent activation of the trialkylaluminium*, provides a polymerization-active catalyst.

Example 3

Into a reaction vessel equipped with a heating* jacket*, reflux* condenser* and stirrer* with an inert nitrogen or argon atmosphere are introduced 0.2 g of magnesium metal in the form of fine chips and 100 l of anhydrous tetrahydrofuran. Then, with stirring at room temperature, 0.9 *l of pure TiCl^ is added dropwise. Titanium tetrachloride reacts immediately with THF to form a yellow complex, which further reacts with the magnesium metal present. After all the TiCl^ has been added, the reaction mixture is heated to 50°C and maintained there until all the magnesium has dissolved. A deep black solution of the complex is obtained, which, after being applied to a support and activated with trialkylaluminum, provides an effective polymerization catalyst.

Example 4

Into a reaction vessel equipped with a stirrer*, heating* jacket and reflux* condenser*, 2.89 g of the TiCl ₄ complex . 2.25 THF, 3.59 g of the llgClg complex. 1.1 THF and 0.05 g of magnesium are introduced under a protective atmosphere of nitrogen. Then 100 *1 THF is added and heated with constant stirring until everything dissolves into a dark solution. This solution is applied to a suitable support and, by activation with the addition of trialkylaluminium, a very effective polymerization catalyst is obtained. A crystalline complex - precursor can also be obtained from the solution by evaporation by EDS or precipitation by the addition of an aliphatic hydrocarbon. The precursor thus isolated can be applied to the support by mechanical stirring.

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Example 5

Silka β with pore volume >1 ml/g, maximum pore diameter >8 mm o

and a specific surface area of > 200 m/g such as Davieon 952 is activated in a stream of dry air at a temperature of 600 to 800 °C for 3 to 24 hours and then cooled to ambient temperature in a stream of pure nitrogen. Two g of the silica thus activated are transferred to a reaction vessel, about 50 ml of n-hexane are added and such an amount of the catalyst complex solution prepared by the method described in any of examples 1 to 4 is added, which corresponds to a titanium content of 1% by weight of the silica. It is stirred at laboratory temperature for 3 hours and then the solvent is removed at a temperature of up to 60 °C with a stream of nitrogen. A powdery product is obtained, which, by adding an activator, for example triethylaluminium, before the start of the polymerization, provides a highly efficient polymerization catalyst for α-olefins.

Example 6

The polyethylene powder obtained by polymerization in a fluidized bed reactor, freed from particles larger than 0.5 mm, is dried in a stream of pure nitrogen at a temperature of up to 100 °C. To prepare the catalyst, 2 g of treated polyethylene powder is used, to which 10 to 20 ml of EDS, the same or different from that used to prepare the catalytic complex, and such an amount of the catalytic complex solution prepared by the method according to any of examples 1 to 4, which corresponds to a titanium content of 1% by weight of the support, are added in a reaction vessel.

After 30 minutes of stirring at room temperature, the mixture is freed from excess EDS by distillation in a stream of nitrogen at temperatures up to 60° C. The obtained powdery product provides, by adding an activator, for example, triethylaluminium, an effective polymerization catalyst for 1-olefins.

Example 7

The procedure is as in Example 5, with the only difference that the activated silka is suspended in the same or different EDS as was used to prepare the catalytic complex.

Example 8

The procedure is as described in Example 5, with the only difference that the surface of the activated silica is modified before the application of the catalytic titanium complex by reaction with a trialkylaluminum compound in an amount corresponding to 2 to 20% of the silica.

Example 9

The procedure is as described in Example 5 or 6, with the only difference that after the sorption of the Ti complex on the support is complete, partial activation is carried out by adding such an amount of trialkylaluminum that the molar ratio of Al to Ti is in the range of 1 to 10. Evaporation of the solvents yields a partially activated powder catalyst, the activation of which is completed in the polymerization process in the polymerization reactor by adding trialkylaluminum.

Example 10

To 10 g of powdered polyethylene β with a particle size of less than 0.2 mm, 1 ml of THF and such an amount of crystalline complex precursor prepared by one of the methods described in Examples 1 to 4, which corresponds to 1% Ti of the mass of the support, are added in a container. The mixture is shaken for 4 to 24 hours under a protective atmosphere of inert gas and a homogeneous powdery mixture is obtained, with which ethylene with 1-olefins can be polymerized or copolymerized after treatment by the methods described in Examples 6 or 9.

Example 11

The procedure is as described in Example 5, with the only difference that 30 minutes after the addition of the complex, partial preactivation is carried out by adding trialkylaluminum in an amount corresponding to a molar ratio of aluminum to titanium of 1 to 10. Evaporation of the solvents yields a powdery catalyst, the activation of which is completed in the polymerization process by further addition of trialkylaluminum.

Example 12

The procedure is carried out in accordance with any of the methods described in Examples 1 to 4, except that instead of THF, 100 ml of ethyl acetate is used as the electron donor compound. The obtained solution of the catalytic complex is treated in accordance with any of the methods described in Examples 5 to 11. A highly active supported catalyst is thus obtained, usable for the polymerization and copolymerization of 1-alkenes in the gas phase and in a solvent.

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Example 13

Prepare the catalytic complex ee by any of the methods described in Examples 1 to 4, except that 100 ml of di-n-butyl ether is used as the EDS ae. After dissolving all components ee, proceed by any of the methods described in Examples 5 to 11.

The supported catalyst prepared in this way is evaluated by a polymerization test with ethylene.

Example 14

The solution prepared by the procedure described in Examples 1 to 4, with the only difference that acetonitrile is used as the EDS, is applied to the support by one of the methods described in Examples 5 to 11. The polymerically active catalyst is obtained by adding trialkylaluminum as an activator.

Example 15 * The methods described in Examples 1 to 11, except that triethylamine is used as the EDS and an unactivated or partially activated carrier catalyst is prepared. Polymerization with it is possible after addition of an activator in the gas phase as well as in a solvent.

Examples 16 to 34

The catalysts prepared by the procedures given in Examples 1 to 15 are subjected to polymerization tests under standard conditions: approximately 0.1 g of catalyst, temperature 90°C, total pressure of the polymerization mixture 2.0 MPa, polymerization time 4 hours.

Under the same conditions, comparative polymerizations were carried out with catalysts prepared from catalytic complexes that were not subjected to the reduction effect of metallic magnesium. The conditions for the preparation of the catalysts and the polymerization conditions are given in Tables 1 and 2, together with the observed activities and some properties of the polymers.

Table 1

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Catalyst preparation conditions 1 2 3 4 5 6 7 16 0.39 1.56 0.10 - - - 17 0.87 1.73 - - - - 18 0.39 1.56 0.10 - 4 - 19 0.87 1.73 - - 4 w 20 4.29 ^points 2.89 ^cents - - - • 21 5.14 ^{6 2.89C} - - - 22 4.29 ^{points 2.89C} 0.10 4 - - 23 5.14 ^{points 2.89C} - - 10 24 4.29 ^points 2.89° 0.10 - 10 25 0.87 1.56 0.10 - - - 26 - 1.56 0.20 - - - 27 3.59 ^{points 2.89C} 0.05 - - - 28® 3.59 ^{points 2.89C} 0.05 - MB - 29 ^days 5.14 1.56 - 4 - - 30 ^days 4.28 1.56 0.10 4 - - 31 0.39 1.56 0.10 - 4 - 32 1.73 1.73 - - 4 - 33 0.86 ^2.89C 0.10 - - - 34 0.86 2.89 0.10 - - -

Notes a polyethylene used as carrier c TiCl^ solvate used. 2 THP b MgCl^ solvate used. 1.47'THF d ethyl acetate Columns of Table 1

Example

Weight of MgCl (g)

Weight of TiCl ₄ (g)

Weight of magnesium metal (g)

Preactivation with triethylaluminum (Al:Ti)

Preactivation with triisobutylaluminum (Al:Ti)

Modification of silica with triethylaluminum:triethylaluainium (%)

Table 2 244 770

Polymerization conditions Polymer properties

8 9 10 11 12 13 14 15 16 17 0.102 - 40 117.7 1.02 29.07 28.50 957.8 0.106 - 40 45.6 - - - - 0.085 40 149.2 0.75 26.69 35.49 958.6 0.110 40 96.61 0.63 18.16 28.82 956.7 0.127 - 40 333.86 8.96 238.20 26.58 961.3 0.138 - 40 154.46 3.13 84.12 26.87 959.7 0.125 - 40 253.84 6.34 164.02 25.89 962.0 0.126 - 40 200.34 5.32 135.45. 25.34 962.1 0.125 - 40 249.42 6.74 167.4 24.84 959.9 0.097 - 40 495 5.74 154.9 27.00 959.4 0.104 - 40 138.0 2.16 65.6 30.37 - 0.112 40 378.3 - - - - 0.123 - 40 172.6 1.30 33.5 25.77 952.1 0.103 - 20 207.4 0.95 24.9 26.28 953.8 0.110 20 165.2 1.27 39.5 31.10 957.9 0.079 20 206.7 0.71 20.45 28.88 942.2 0.38 - 0.116 - 20 160.5 1.33 32.87 24.71 940.1 0.40 - 0.106 20 650.2 1.92 48.63 25.33 928.2 0.66 0.099 - 20 520.6 1.75 42.18 24.10 917.9 - 0.96

Table columns 2

Activation with triethylaluminum (g)

Activation with triisobutylaluminum (g)

Hydrogen (% molar)

Catalyst activity g polyethylene/g catalyst (hour)

Flow index IT 2.3 (g/10 min)

Flow index IT 23 (g/10 min)

Ratio IT 23/IT 2.3

Specific weight of polymer kg/m^

Propylene/ethylene molar monomer ratio

Butylene/ethylene molar monomer ratio

Claims (1)

Catalyst for the polymerization and copolymerization of ethylene β 1 -alkylene C 1 -C 8 alkenes based on the active ingredient consisting of a complex of titanium tetrachloride, magnesium chloride and at least one electron donor compound with at least one free electron feather such as linear, cyclic, esters, nitriles and nitrogen bases , on an inorganic or organic support in a molar ratio of 1 mol of titanium tetrachloride, 0.5 to 10 moles of magnesium chloride and 2 to 130 moles of an electron donor compound, and an activator consisting of an organic aluminum compound, characterized in that 0.25 to 1 mol of magnesium metal.