SK11394A3 - Ziegler-natta type catalyst, method of its manufacturing, and its using by polymerization by olefins - Google Patents

Description

Technical field

The invention relates to a Ziegler-Natta type catalyst, to a process for its preparation and to its use in the polymerization of olefins.

BACKGROUND OF THE INVENTION

French patents 2 116 698 and 2 099 311 disclose processes for the production of Ziegler-Natta type catalysts which can be used in the polymerization of olefins and in particular in the polymerization of ethylene. According to French patent no. No. 116,698, the catalyst is prepared by reacting a magnesium in a metal state with a monohalogenated hydrocarbon, an ether and a transition metal derivative that is in the valence state of at least 4. According to French Patent No. 5,916,519. No. 2,099,311, a catalyst is produced by reacting activated magnesium with a monohalogenated hydrocarbon and a transition metal derivative that is in the valence state of at least 4.

While such catalysts are effective, their catalytic efficiency increases rapidly with increasing polymerization temperatures, in particular in the temperature range typically used in olefin polymerization reactions. As a result, when using such catalysts, a small change in the reaction temperature usually results in a relatively large change in the catalyst efficiency and hence the polymerization rate. This phenomenon is particularly problematic when initiating a post-polymerization reaction where temperature changes may occur in an unpredictable manner. Changing the rate of polymerization can cause wľymérnyc _r ?. agglomerates, especially in the gas phase polymerization process, for example in a fluidized bed.

It is an object of the invention to provide a process for the production of a polymerization catalyst by means of which the problems associated with known catalysts can be overcome or at least alleviated.

SUMMARY OF THE INVENTION

It has now been developed in the context of the invention a process for the production of a catalyst which exhibits relatively stable activity in the desired temperature range, i. a slight change in temperature does not result in a major change in catalyst efficiency. This achieves that the catalyst is better adapted for use in large capacity industrial reactors.

It is an object of the present invention to provide a process for preparing a Ziegler-Natta type catalyst comprising contacting a solid component comprising Group IV halogen, magnesium and transition metal atoms in a period VI system with an electron donor compound.

The solid component to be used according to the invention preferably has a composition corresponding to the general formula wherein it represents an aluminum and / or zinc atom, a transition metal atom of the group IV, V or VI of the Periodic Table of the Elements, preferably a titanium and / or vanadium atom;

C 1 -C 14 alkyl

- 3 2,

B is C 1 -C 12 alkyl,

X represents a chlorine and / or bromine atom,

D represents an electron-donor compound which preferably contains oxygen, sulfur, nitrogen or phosphorus atoms, wherein the number r.e is from 2 to 10, in the range of

1.5 to 50, preferably from 0 to 1, a number in the range from to r * preferably being from 0 to 3, a number in the range

From to

4, preferably from 0 to 0.5, more preferably from 0 to 0.5

J preferably represents a number from 5 to 27 and ranges from to

110, preferably represents a number from 0 to 0.2.

range

WHAT

0.5, preferably the invention is used which is obtained by the reaction of magnesium in a metal stand

Preferably, the component comprises at least one monohalogenated hydrocarbon and at least one Group IV, V or VI transition metal compound of the Periodic Table of the Elements wherein the transition metal is present in a valence state of at least 4, optionally in the presence of an electron-hollow compound. The solid component can be prepared without the use of magnesium derivatives and is preferably prepared

- 4 as described in French patent no. The solid component produced by the methods described in these patents generally consists of particles having an irregular shape. ·

In the manufacture of the solid component, titanium and / or vanadium is preferably used as a transition metal from Group IV, V or VI of the Periodic Table of the Elements. Titanium (IV) compounds of the general formula are preferably used as titanium compounds

Tix _{4 t} (OR ³ ) _t where

X represents a halogen atom, usually chlorine or bromine,

R ³ represents an alkyl radical having 2 to 6 carbon atoms and t represents an integer or fractional number in the range of 0 to 4, for example from 0 to 3, and preferably a number having a value equal to or close to two.

Typical titanium compounds that meet this definition include titanium tetrachloride, tetraalkyl titanates of the general formula:

Ti (OR ³ ), ⁴ wherein R represents a radical as defined above, or mixtures of titanium tetrachloride with these tetra-titanates.

As the magnesium compound, solid metal magnesium is preferably used in the production of the solid component. Magnesium is usually used in the form of powder or shavings, and is preferably a high-grade magnesium. To avoid long induction

- 5 period, magnesium is preferably used in active form, i. in a form in which the magnesium is substantially free of impurities, such as formed by oxidation of the metal. For example, the preliminary ejection of magnesium may be carried out by grinding the metal under an inert atmosphere or in an inert liquid such as aliphatic solvents. The activation can preferably be carried out by treating the magnesium with iodine pairs. However, it is more expedient to carry out the activation of magnesium in the reaction medium, for example by introducing small amounts of such substances as iodine, metal alkoxides of the group ΙΑ, IIA or IIIA of the Periodic Table, alkyl titanates, ether oxides or alcohols such as isobutanol. . Such substances may, for example, constitute less than 10% by weight and preferably less than 5% of the amount of magnesium used.

The monohalogenated hydrocarbon compound is preferably selected from the group of chlorinated or brominated derivatives of saturated aliphatic hydrocarbons. It may have a composition corresponding to the general formula

R ⁴ -Z where

Z represents a bromine or chlorine atom;

P. represents an alkyl group having 1 to 10 carbon atoms.

Suitable monohalogenated hydrocarbons are, for example, ethyl chloride, propyl chloride, butyl chloride and pentyl chloride.

The reaction to produce the solid component can be carried out in various ways. For example, the various reactants may be added to an inert solvent at a temperature sufficiently low to avoid initiation of the reaction. The reaction mixture is then heated, with stirring, to a temperature which is usually in the range of -20 to 150 ° C, preferably 40 to 100 ° C, after addition of the active agent for magnesium, such as iodine crystals, within a few minutes to 30 hours. It is not necessary to grind the reaction mixture during the reaction.

At the end of the preparation, the obtained solid component is preferably washed with a liquid hydrocarbon at a temperature in the range of from 10 to 50 ° C, and preferably at a temperature near 20 ° C. Preferably, the solid product obtained is not heated to a temperature above 100 ° C, and more preferably not heated above 90 ° C,

To obtain an active catalyst, preferably the solid component is prepared using the reactants in amounts such that the molar ratio of monohalogenated hydrocarbon to magnesium is in the range of 0.5 to 10, preferably 1 to 4, and the molar ratio of transition metal to magnesium is less than 1 and preferably less than 0.5.

In the process of the invention, the solid catalyst component is reacted with an electron-donor compound. The electron-donor compound used is an organic compound which preferably does not contain labile hydrogen atoms. For example, the estrone-donor compound may be selected from the group consisting of aliphatic ethers, tertiary phosphines, tertiary amines, secondary amines, and organosilicon compounds. Dimethylformamide or hexamethylphosphoric triamide is preferably used. The elestrone-donor compound is usually used in an amount such that its molar ratio to the transition metal present in the solid component is in the range of from 0.01 to 0.1, and in particular from 0.02 to 0.07.

The solid component is contacted with an electron-donor compound usually in a liquid hydrocarbon which is mixed and maintained under conditions such that the highest amount

7 electron-donor compounds bound to the solid component. As the liquid hydrocarbon, an alkane or alkali may be used. a cycloalkane having, for example, 4 to 10 carbon atoms, or an aromatic hydrocarbon having, for example, 6 to 14 carbon atoms. In most cases, this reaction is carried out at a temperature in the range of about 20 to 100 ° C, preferably 40 to 90 ° C. The reaction may be carried out in various ways, for example by adding the electron-donor compound to a suspension of the solid component in a liquid hydrocarbon. The electron-donor compound is preferably added slowly in order to bind it homogeneously. For example, the addition may take 10 to 600 minutes and usually takes 15 to 30 minutes. After the addition is complete, stirring of the suspension can be continued for 30 minutes to 5 hours. The reaction is usually carried out in the absence of any cocatalysts, such as organoaluminum compounds, and in the absence of any olefins.

At the end of the reaction, the amount of electron-donor compound remaining in the liquid hydrocarbon in the free state may be zero or relatively low. Preferably, however, the solid product obtained by this reaction is washed to remove any impurities present in the liquid hydrocarbon.

The process of the present invention provides a solid catalyst whose catalytic activity is substantially constant over a useful temperature range. Temperature, c, is usually considered a useful range; to 95 ° C.

The catalyst according to the invention is used at 2 to 6 carbon atoms and can be prepared by the process according to this olefin polymerization, which comprises the presence of a cocatalyst.

With the advantage of

.j:> Li Z 4. V δ pVi.

polymerization, ethylene or mixtures thereof with an alpha-olefin, such as 1-butene, aimed at producing high-density polyethylene, low-density linear polyethylene or very low-density polyethylene. Such a polyethylene can have a density in the range of 890 to 965 kg x m. The polymerization is preferably carried out at a temperature within the range in which the activity of the catalyst is stabilized. A typical range of polymerization temperature is 70 to 100 ° C, the preferred temperature range for the production of linear low density polyethylene is 70 to 90 ° C, and the preferred temperature range for the production of high density polyethylene is 85 to 95 ° C.

The polymerization of olefins can be carried out in a liquid in which the catalyst is dispersed. The liquid may be a liquid olefin or a saturated aliphatic hydrocarbon.

The polymerization can also be carried out in the gas phase by known methods in the reactor and not by performing gas phase polymerizations. Such a reactor may comprise a fluidized and / or mechanically stirred bed. Examples of suitable reactors are described in French Pat. 2,207,145 and 2,325,522. In the gas phase polymerization, the catalyst is preferably used in the form of a preformed prepolymer obtained by contacting the catalyst with ethylene or mixtures thereof with one or more olefins, the reaction being carried out in the presence of a cocatalyst and optionally in the presence of hydrogen.

Surprisingly, it has been found that the prepolymer obtained by using the catalyst according to the invention contains a relatively small amount of fine particles. In particular, this amount is lower than that produced under the same prepolymerization conditions when a catalyst which has not been reacted with the electron-donor compound is used.

The cocatalyst is selected from the group of organometallic compounds of metals of Group II or III of the Periodic Table of the Elements, such as organoaluminium, organoboronate or organozinc compounds. A typical catalyst is trialkyl aluminum. The co-catalyst may be introduced into the polymerization reactor in a prepolymer or separately.

The invention is illustrated by the following examples. These examples are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

FIG. in the drawings

In FIG. 1 is a schematic illustration of a fluidized bed reactor consisting essentially of a vertical cylinder over which a chamber is used, which is used in Examples 1 and 2.

In FIG. 2 shows the temperature / efficiency curves of two different catalysts, the lower curve corresponding to the catalyst of the present invention and the upper curve corresponding to the comparison catalyst.

The fluidized bed reactor shown schematically in FIG. 1, consists essentially of a vertical cylinder 2, over which a release chamber 3 is arranged. A fluidization tray 4 (lattice) is arranged in another part of the vertical cylinder 2. The upper part of the release chamber 1 is connected via the recirculation line 5 to the lower part of the reactor, located below the fluidization tray 4. In the recirculation line 6 is a heat exchanger 6, a compressor 7 and an inlet pipe 8, j. ^ε 12, P ^- styrene, a comonomer, for example 1-butene, and a transfer agent, for example hydrogen. The reactor is also equipped with a catalyst supply line 11 and a polymer withdrawal line 12.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

(a) catalyst production ♦

. 4.6 nP of n-hexane, 5.5 kg of mine, 3,160 moles of magnesium, 29 moles of isobutanol, 60 moles of n-propyl titanate and 60 moles of n-butyl chloride are introduced into a 10 m 2 reactor equipped with mechanical The contents of the reactor are then heated to a temperature of 5 ° C until the reaction begins and is then maintained at 80 ° C. At this temperature, 340 mol of n-propyltitanate, 400 mol of titanium tetrachloride and then 4700 mol of n-butyl chloride are introduced into the reactor over 240 minutes. The mixture is stirred at 80 ° C for 2 hours. At the end of this time, 44 mol of dimethylformamide, as an electron donor compound, was added to the reactor over 20 minutes. Stirring is continued for a further 60 minutes and the reactor is cooled to room temperature, and then the n-hexane containing unreacted n-butyl chloride is replaced with pure n-hexane. This gives the catalyst as a slurry in n-hexane.

b) Production of prepolymer

To a 1.5 m @ 2 stainless steel reactor maintained under a nitrogen atmosphere was charged 500 l of n-hexane, 2 mol of tri-n-octaluminium, and the catalyst produced in (a) corresponding to 2.5 mol. titanium. The reactor is equipped with a stirrer that is allowed to operate at a rotation speed of 150 min ^-1 . The reactor contents are heated to 70 ° C. The reactor was fed with hydrogen up to a partial pressure of 1 kPa and ethylene was fed at a constant rate of 15 kg xh ^-1 for 6 hours and 40 minutes. At the end of this time, the reactor was degassed and transferred to a mechanically stirred evaporator in which the n-hexane was removed by a stream of nitrogen heated to 70 ° C. 100 kg is obtained before the polymer is ready for use. The polyethylene content of this prepolymer is 40 gx mmol ^-1 titanium.

c) Production of high density polyethylene

The polymerization is carried out in a gas-phase polymerization reactor, which is shown schematically in FIG. 1. The main part of this reactor is a vertical cylinder 2 with a diameter of 90 cm and a height of 6 m.

This reactor comprises a fluidized bed of particles of the resulting ethylene polymer. Bed height is 2 m. The bed is fluidized with an ascending flow of gaseous reaction mixture at a linear velocity of 50 cm xs ^-1 . The total pressure in the reactor was 1.7 MPa and the temperature at the outlet of the release chamber was 90 ° C.

The gaseous reaction mixture contained 30% ethylene, 1.6% 76-butane, 21% hydrogen and 47.4% nitrogen by volume.

The preformed prepolymer is fed into the reactor at a rate of 600 gxh ^-1 . The amount of triethyl aluminum in the reactor is also separately introduced in such a quantity that the molar ratio of aluminum to titanium contained in the prepolymer is 1.2.

Under these conditions, polyethylene is withdrawn from the reactor at a rate of 70 to xh ^-1 . The resulting polyethylene has a density of 960 kg / m @ 2, a titanium content of 10 ppm and a content of polymerized 1-butene of approximately 1% by weight.

Example 2

s) Production of solid component

The solid component is prepared in the same manner as the solid component of the catalyst of Example 1a), except that no dimethylformamide is used.

b) Production of prepolymer

The 1.5 m \ stainless steel reactor held under a nitrogen atmosphere is charged with 0000 L of n-hexane, 0.125 mol of dimethylformamide and a solid component of the catalyst produced according to a) in an amount corresponding to 2.5 mol of titanium. The reactor is equipped with a stirrer that is operated at a rotational speed of 150 microns. The reactor contents are heated to 50 ° C. The resulting mixture was stirred at 50 ° C for 30 min to give a catalyst slurry, and then 2 moles of tri-n-octylcarbon were introduced into the reactor. The resulting mixture was stirred at 50 ° C for 10 min. Hydrogen was fed from the reactor up to a partial pressure of 1 k? And ethylene was fed at a constant rate of 15 kg xh ~ for □ hours and 40 minutes. The reactor is maintained at 70 ° C during the polymerization reaction. At the end of this time, the reactor was degassed and transferred to a mechanically stirred evaporator in which the n-hexane was removed by a stream of nitrogen heated to 70 ° C. 100 kg of a prepolymer are obtained, which is ready for use. The polyethylene content of this prepolymer is 40 g ^x mmol ^x titanium.

(c) production of linear low density polyethylene

This process is carried out in the same gas-phase polymerization reactor as described in Example 1c).

This reactor comprises a fluidized bed of particles of the resulting ethylene polymer. Bed height is 2 m. The bed is fluidized with an ascending flow of gaseous reaction mixture at a linear velocity of 50 cm x s @ -1.

The gaseous reaction mixture contained 30% by volume of ethylene, 13.5% of 1-butene, 6% of hydrogen and 50.5% of nitrogen.

The preformed prepolymer is fed to the reactor at a rate of 600 x h *. The reactor is also introduced separately with trieth aluminum in an amount such that the molar ratio of aluminum to titanium added in the prepolymer is 1.2.

Under these conditions, polyethylene is withdrawn from the reactor at a rate of 70 kg x h -1. The resulting polyethylene has a density of 918 kg / m < 3 > and a titanium content of 10 ppm and a content of about 1 wt.

Example 3.

Measurement of catalyst efficiency

Two series of gas-phase ethylene polymerizations are carried out in a 2.5 liter stainless steel reactor equipped with a stirrer system operating at 300 rpm and a temperature control system. The first series is carried out using a prepolymer, which is made using the catalyst of Example 1, wherein the molar ratio of aluminum to titanium is 1.5 and which contains 40 g of polyethylene per mmol of titanium. The second series is carried out using a prepolymer produced using a comparative catalyst prepared as described in Example 1, except that no dimethylformamide is used in its preparation. The molar ratio of aluminum to titanium in the comparison catalyst is 1.2, and the catalyst contains 40 g of polyethylene per mmol of titanium.

Several half-polymerization reactions were performed at different temperatures in each series. For each reaction, 200 g of polyethylene powder are introduced into the reactor as the initial charge. The prepolymer is given in an amount corresponding to 0.5 mmol of titanium and hydrogen up to a partial pressure of 1 bar. The total pressure in the reactor was maintained at 0.4 MPa by feeding ethylene. In each reaction, the catalyst activity is measured, expressed as the amount of grams of polyethylene formed, based on 1 mmol of titanium in the reactor per 1 hour of reaction. These measurements allow the construction of a catalyst activity curve versus temperature for each catalyst (Figure 2). The lower curve corresponds to the catalyst of the invention, while the upper curve corresponds to the comparison catalyst. It can be seen from the lower curve that the activity of the catalyst according to the invention practically stabilizes at a temperature above S5 ° C, while the efficiency of the comparison catalyst continues to increase.

Claims (11)

PATENT CLAIMS A process for the preparation of a Ziegler-Natta type catalyst, characterized in that a solid component comprising halogen, magnesium and transition metal atoms from Group IV, V or VI of the Periodic Table of the Elements is contacted with an electron-donor compound. The process according to claim 1, characterized in that the solid product used is a reaction product obtainable by reaction of metallic magnesium, at least one monohalogenated hydrocarbon and at least one transition metal compound of Groups IV, V and VI of the Periodic Table, the transition metal is present in the valence state of at least 4. The method according to claim 1 or 2, wherein the electron-donor compound is used in an amount corresponding to a molar ratio of the electron-donor compound to the transition metal in the solid component in the range of 0.01 to 0.1. Method according to any one of claims 1 to 3, characterized in that the electron-donor compound is a compound which is free of laoil hydrogen atoms. The process according to claim 4, wherein the electron-donor compound is dimethylformamide or hexamethylphosphoric triamide. Catalyst obtainable by a process according to any one of claims 1 to 6. A prepolymer obtainable using the catalyst of claim 6. 8. Process for the polymerization of olefins, characterized in that the catalyst according to claim 6 or the prepolymer according to claim 7 is used. Process according to claim 8, characterized in that the polymerization is carried out in the gas phase. Process according to claim 8 or 9, characterized in that the polymerization temperature is in the range of from 85 to 95 ° C. A polymer obtainable by a process according to any one of claims 8 to 10.