CS214686B2 - Method of preparation of catalytic system for polymeration or copolymeration of ethylene - Google Patents

Description

The present invention relates to a process for preparing a catalyst system for the polymerization or copolymerization of ethylene. Catalyst systems prepared according to the invention and containing magnesium and titanium provide ethylene polymers having a density of from 910 kg / m ³ inclusive to 970 kg / m ³ inclusive and a melt flow rate (defined below) ranging from 22 up to and including 32. The resulting polymer particles have a bulk density of 291.8-518.7 kg / m ³ and a controlled size and shape.

In order to be useful in an industrial gas phase process, such as in the fluidized bed process of U.S. Patent Nos. 3,709,853, 4,003,712 and 4,011,382, Canadian Patent 991,798 and Belgian Patent 839,380, catalysts must have a high activity, i.e. It must have a productivity of at least 50,000 and preferably at least 100,000 kg of polymer per kg of catalyst metal or higher. This is because, in such gas-phase processes, no processes are generally used to remove catalyst residues. The catalyst residues in the polymer must therefore be so small that they can be left in the polymer without causing undesirable difficulties in the production of the resins, the processing of the resins, and / or the application of the finished products to the end customer. Where highly active catalysts are successfully used in such fluidized bed processes, the heavy metal content of the resin is of the order of 20 ppm or less at a productivity of at least 50,000 or greater. The low content of catalyst residues is also important when the catalyst contains chlorine-containing substances, such as titanium, magnesium and / or aluminum chlorides, used in so-called Ziegler or Ziegler-Natta catalysts. The high chlorine content of the forming resin can cause pitting and other corrosion of the metal surfaces of the forming apparatus. A chlorine content of 200 ppm or higher is unacceptable for industrial production.

U.S. Pat. Nos. 3,922,322 and 4,035,560 disclose the use of several titanium and magnesium containing catalysts in the production of granular ethylene polymers by a fluidized bed gas pressure process under a

6.87 MPa. However, the use of these catalysts in these processes has significant disadvantages. The catalysts of U.S. Pat. No. 3,922,322 provide polymers with a very high content of catalyst residues, i.e., about 100 ppm Ti and more than about 300 ppm chlorine (according to the examples disclosed in this patent). Further, as shown in the examples of US Patent No. 3,922,322, the catalyst is used in the form of a prepolymer and a very high volume of catalyst based on the volume of polymer produced in the reactor must be introduced into the reactor. Thus, the preparation and use of this catalyst requires the use of a relatively large apparatus for producing, storing, and dispensing the catalyst.

Also, the catalysts of U.S. Patent No. 4,035,560 provide polymers with a high catalyst residue, and the catalysts are pyrophoric due to the use of certain types and amounts of reducing agents.

U.S. Patent No. 3,953,414, issued April 27, 1976, describes the polymerization of olefins using catalysts prepared from a supported catalyst component, wherein the polymer produced is in the form of spherical or spheroidal particles. Catalysts are prepared by mixing an organometallic metal catalyst component of the second or third group of the Periodic Table and (b) carrier components which are products consisting of a carrier consisting of anhydrous magnesium halide and halogenated titanium compounds that are chemically bound to or supported by the carrier. dispersed. Components (b) are in the form of spherical or spheroidal particles with a size of 1 to 350 μΐη. Catalyst components b) are prepared in various ways. One of these is spray drying solutions of anhydrous magnesium halide in organic solvents. Spray drying is performed so as to obtain spherical particles of 1 to 300 μΐη. Removal of the solvent adhered to the carrier is completed by heating the particles under reduced pressure. The carrier particles are then contacted with a halogenated titanium compound. The examples in the patent illustrate the use of catalysts in suspension polymerization.

U.S. Pat. No. 4,111,835, issued September 5, 1978, describes the polymerization of olefins to polymer in the form of spheroidal particles that are highly agglomerate with continuous polymerization. The catalyst consists of: (a) an organometallic metal compound from Group II or III of the Periodic Table and bj the product obtained by reacting a halogenated titanium compound with a magnesium halide hydrate in the form of spheroidal particles with a diameter of 10 to 70 μπι. The magnesium halide hydrate contains 10-45% by weight of water and is obtained by partial dehydration of the magnesium halide hydrate prepared by direct synthesis from electrolytic magnesium and hydrochloric acid, after which the fractional crystallization of the synthesis product is carried out. The magnesium halide hydrate is spray dried to spherical particles. The magnesium halide hydrate which serves as the carrier may be used in admixture with 20 to 80% by weight of an additive which is inert to the magnesium halide and which is a compound of the elements belonging to 1 to 2.

Group 4 of the periodic table. The examples in the patent describe the use of catalysts in suspension polymerization.

Thus, U.S. Pat. Nos. 3,953,414 and 4,111,835 disclose the preparation of ethylene polymers illustrated in the slurry polymerization process using specially prepared catalyst components whose component (catalyst support) is spray dried to spheroidal particles.

The processes of these patents are further carried out using high concentrations of boiling titanium tetrachloride, which is highly corrosive. In addition, the processes are complex and consist of many stages. In addition, patents disclose the use of hydrates that contain water. This water may have a detrimental effect on the efficiency of the catalyst. *

It is also known that ethylene copolymers having a density of 910 to 960 kg / m ³ , a melt flow rate ratio (defined below) of from 22 to 32, including limit values with relatively low catalyst residue, can be produced in granular form at relatively high productivity, The process according to claim 1, wherein the monomer or monomers are polymerized in a gas phase process using a specific highly active complex catalyst comprising magnesium and titanium, which is mixed with an inert carrier. The granular polymers thus prepared have excellent physical properties enabling them to be widely used for molding.

Furthermore, it is known that ethylene homopolymers having a density of about 958-972 kg / m ³ , including limit values and a melt flow rate (MFR) of 32 with an MFR 22 22 having a relatively low catalyst residue content can be produced at relatively high productivity and a low catalytic residue content such that ethylene is homopolymerized in a low pressure gas phase process using a highly effective complex catalyst comprising magnesium and titanium mixed with an inert carrier.

The polymers produced using the mixed catalysts of the prior art these accompanying _t niches have the disadvantage that the polymer particles formed during polymerisation of the fluidized bed have an irregular shape and somewhat difficult to fluidize. The final product also contains a relatively high amount of fines, i.e. particles of 125 μΐη or less.

The method used to produce the catalyst precursor described in the prior art involves forming the precursor by dissolving the titanium compound and the magnesium compound in the electron donor compound. The precursor is then usually isolated by crystallization or precipitation with a C ₅ to C ₈ aliphatic or aromatic hydrocarbon. However, these isolation techniques can lead to non-uniform growth of polymer particles and to the formation of a polymer consisting of needle-like particles.

It is further known that copolymers of ethylene

214688

8 having a density of 910 to 940 kg / m ³ , a relatively high bulk density, which provides films with good clarity, can be produced at a relatively high productivity suitable for industrial application by copolymerizing ethylene with one or more C ₃ to C ₈ ; gaseous olefins in the presence of a highly active complex catalyst comprising magnesium and titanium activated under specific conditions by an organoaluminum compound impregnated in a porous inert carrier.

However, the preparation of the impregnated catalyst precursor by this method is difficult to control and the carrier used for impregnation may have a fluctuating composition. If the preparation is devoid of considerable care, the catalyst may have fluctuating activity. Since the morphology of the polymer, as it turns out, is dependent on the morphology of the carrier used to prepare the catalyst, it is sometimes not possible to reconcile the flexibility of the polymer particle control process.

It has now unexpectedly been found that ethylene polymers with a wide density range of about. g 910 to about g 970 kg / m ³ , bulk density from about 291.8 to about 518.7 kg / m ^3, and melt flow rates from g 22 to g 32 having controlled particle size and shape and relatively low content Titanium residues can be produced at a relatively high productivity suitable for industrial gas phase production by ethylene homopolymerizing or copolymerizing with one or more C ₃ -C 8 α-olefins in the presence of a highly effective magnesium-titanium complex catalyst prepared by the spray process described below drying the magnesium-titanium-containing precursor in the form of a suspension or solution in an electron donor compound and activating the spray-dried precursor under specific conditions with an organoaluminum compound. The morphology of the polymer can be further improved by adding inert fillers to the precursor.

In the process of the invention, by controlling the particle size and shape of the catalyst particles, the polymerization produces ethylene polymers having a controlled particle size and shape. Such polymer particles are more easily suspended in the fluidized bed and moreover contain relatively few very small particles, i.e. particles below 74 ftm. The process by which particulate spherical catalyst precursor particles are prepared is simpler compared to other previously described processes for preparing similar precursors.

The ethylene polymers prepared according to the invention have a melt flow rate ratio of 22 to 32, preferably 25 to 30, including limit values. The melt flow rate ratio is another way of characterizing the molecular weight polymer distribution. The melt flow rate (MFR) of 22 to 32 (including limit values) corresponds to a density Mw / Mn of 2.7 to 4.1 and an MFR of 25 to 30 (including limit values) corresponds to a ratio of Mw / / Mn 2 , 8 to 3.6.

The homopolymers have a density of from about 958 to 5,972 kg / m ³ . The copolymers have a density of about 910 to 960 kg / m ³ , including limit values. The density of the copolymers at a given melt index can be controlled primarily by the amount of C3 to C8 comonomer to be copolymerized with ethylene. In the absence of comonomer, ethylene would homopolymerize with the catalyst of the present invention to form homopolymers having a density of about ž 958 kg / m ³ . Adding increasing amounts of comonomers to the polymers results in a gradual decrease in the density of the copolymers. Under the same reaction conditions, the amount of each of the various C 3 to C ₈ comonomers needed to achieve the same result varies from monomer to monomer.

Increasing molar amounts of comonomers in the series C ₃ > C 4> C 5> C ₀ > C ₇ > Cg are needed to achieve the same results, i.e. the same density at a certain melt index.

The melt index of the polymers is a reflection of its molecular weight. The relatively high molecular weight polymers have a relatively low melt index. Ultra high molecular weight ethylene polymers have a high load melt index (HLMI) of about 0.0 and very high molecular weight polymers have a high load melt index of about 0.0 to about 1.0 g / 10 min. Such high molecular weight polymers are difficult to mold in conventional injection molding machines and sometimes even impossible. The polymers produced by the process of the present invention, on the other hand, are easily formed in such a device. They have a melt flow index at normal load (MI) ranging from about 0.0 to about 100, preferably in the range of about 0.5 to 80, and a melt flow index at higher load (HLMI) of about 11 to about 2000. The melt flow index The polymers produced by the process of the invention are dependent on the combination of the polymerization reaction temperature, the copolymer density, and the hydrogen / monomer ratio in the reaction system. The melt flow index increases with increasing polymerization temperature and / or decreasing polymer density and / or increasing hydrogen / monomer ratio. In addition to hydrogen, other chain transfer agents such as dialkyl zinc compounds can also be used to further increase the melt index of the copolymers.

The process according to the invention makes it possible to produce copolymers containing, as the main molar part, ethylene (9090%) and, as the minor molar part (g10%), one or more C ₃ to C ₈ α-olefins. The C ₂ to C ₈ α-olefins should contain no branching at any of their carbon atoms closer to the copolymer backbone than the fourth carbon atom. Preferred C ₃ to C ₈ αί-olefins are propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-pentene and 1-octene.

The copolymers of the present invention typically contain from about 0.1 to about 0.3 C = C double bonds per 1000 carbon atoms and typically have a n-hexane extractable content (at 50 ° C) of less than about 3% and preferably less than about 2%. % by weight.

The polymers have a catalyst residue content expressed as ppm of titanium metal, of the order of 20 ppm at a productivity of £ 50,000, 10 ppm at a productivity of £ 100,000, and 5 ppm at a productivity of £ 200,000.

The ethylene polymers of the invention have a bulk density of about 291.8 to 518.7 kg / m ³ . They consist of spherical particles with a mean size of 250 to 2550 μτη and preferably of 250 to 1525 μΐη.

Homopolymers are suitable for the production of various molded articles and the copolymers are suitable for the production of films and also for other molding processes.

The compounds used to prepare the highly active catalyst used to produce the polymers of the invention include at least one titanium compound, at least one magnesium compound, at least one electron donor compound, and at least one activating compound. The individual components are defined below.

The titanium compound has a structure corresponding to the general formula

Ti (OR) _and X _b where

R represents a C 1-4 to C ₁₄ aliphatic or aromatic hydrocarbon residue or a radical of formula COR ', wherein R' represents a C 1-4 to C ₁₄ aliphatic or aromatic hydrocarbon residue,

X is chlorine, bromine, iodine, or a mixture thereof, and is 0, 1 or 2, b is 1 to 4 inclusive, wherein the sum of a + b is 3 or 4.

The titanium compounds can be used singly or in mixtures and include compounds of the formulas

TiCl ₃ , TiCl ₄ , Ti (OCH ₃ ) Cl ₃ , Ti (OC ₆ H ₅ ') C ₃ , Ti (OCOCH ₃ ) C 1 ₃ and Ti (OCOC ₆ H ₅ ) Cl ₃ .

The magnesium compound has a structure corresponding to the general formula

MgX ₂ where

X is chlorine, bromine or iodine.

These magnesium compounds can be used singly or in combination and include compounds of the formulas MgCl ₂ , MgBr ₂ and Mg ₁₂ . Of the magnesium compounds, anhydrous magnesium chloride is particularly preferred.

In the preparation of the catalysts used in the process of the invention, about 0.5 to 56, preferably about 1 to 30 moles of magnesium compound are used per mole of titanium compound.

The titanium and magnesium compounds should be of such physical form and chemical nature that they are at least partially soluble in the electron donor compound described below.

By electron donor compounds are meant such compounds as alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ethers and aliphatic ketones. Of these electron donor compounds, C ₁ to C ₄ alkyl esters of saturated aliphatic carboxylic acids, C ₇ to C ₈ aromatic carboxylic acid alkyl esters, C ₂ to C 8, and preferably C ₃ to C ₄ aliphatic ethers, C ₃ to C ₄ cyclic ethers and preferably C ₄ cyclic mono- or diethers, C ₃ -C ₆ and preferably C ₃ -C ₄ aliphatic ketones. Most preferred of these electron donor compounds are methyl formate, ethyl acetate, butyl acetate, ethyl ether, hexyl ether, tetrahydrofuran, dioxane, acetone and methyl isobutyl ketone.

The electron donor compounds can be used singly or in mixtures.

About 2 to 85, and preferably about 3 to 45, moles of the electron donor compound are used per mole of titanium.

The activating compound has a structure corresponding to the general formula

Al (R 'J _c X' _d H _e where

X 'represents chlorine or a group of the formula OR' and each of the symbols

R "and R '", which are the same or different, represent a C x to C ₁₄ saturated hydrocarbon radical, d is a number from 0 to 1.5, e is a number of 1 or 0, the sum of c + d + e being 3.

The activating compounds may be used singly or in combination and exemplified by compounds of the formula

A1 (C ₂ H ₅ ) ₃ , A1 (C ₂ H ₅ ) ₂ C1, Al (iC ₄ H ₉ j ' ₃₎ A1 ₂ (C ₂ H ₅ ) ₃ C1 ₃ , A1 (C ₄ H ₉ ) ₂ H, A1 (C ₂ H ₅ ) ₂ H and Al (C ₂ H ₅ ) ₂ (OC ₂ H _r ; j.

About 10 to 500, and preferably about 10 to 200 moles of activating compound per mole of titanium compound are used to activate the catalysts used in the present invention.

The catalyst used in the process of the invention is prepared by first preparing a precursor from a titanium compound, a magnesium compound, an electron donor compound and a filler by the following spray drying method. Spherical particles are formed having an average diameter of about 10 to about 200 µm. The spherical particles are then treated with the activating compound as described below.

The initial precursor composition is prepared by dissolving the titanium compound and an excess of the magnesium compound (1s Mg / Ti 656j in the electron donor compound at a temperature from about 20 ° C to about the boiling point of the electron donor compound). The total or partial dissolution of the titanium compound and the magnesium compound can be aided by stirring and, in some cases, heating the two compounds in the electron donor to reflux.

In a separate vessel, inert fillers such as magnesium chloride and / or silica are suspended in the electron donor compound at a temperature up to the boiling point of the electron donor compound. This suspension or solution may then be added to the Mg / Ti complex solution before or after cooling. The resulting suspension may then optionally be heated to the reflux temperature of the electron donor compound prior to spray drying.

The precursor slurry is spray dried at an inlet drying nitrogen temperature ranging from a temperature above the boiling point of the electron donor compound up to about 150 degrees Celsius. Another regulated process variable is the vapor pressure of the solvent. The volumetric flow rate of the drying gas is controlled to be substantially higher than the volumetric flow rate of the suspension or solution. Spraying the slurry may be achieved by a spray nozzle or a centrifugal disk atomizer operating at a high velocity at a pressure of from about 100 psig to about 100 psig.

Any organic or inorganic compound which is inert to the titanium compound and the resulting active catalyst, such as silica, e.g. Calcium. These fillers can be used individually or in mixtures.

The amount of filler that may be present in the precursor is from about 10 to about 95% by weight based on the total weight of the precursor. Insoluble fillers have a mean particle size of the order of magnitude; = 50 μΐη.

The precursor thus prepared has a composition corresponding to the general formula

Mg _m TÍ! (OR) _n X _p [ED] _q [filler] _r where

ED represents an electron donor compound, m represents a number from 0.5 to 56, preferably from 1.5 to 5 including limit values, n represents a number from 0 or 1, p represents a number from 2 to 116, preferably from 6 to 14 including limit values , q is a number from 2 to 85, preferably from 4 to 11, including limit values,

R is C ₁ to C _1); aliphatic or aromatic hydrocarbon radical or a radical of the formula COR 'wherein R' is C _{(C T4} to an aliphatic or aromatic hydrocarbon radical,

X is chlorine, bromine or iodine, or a mixture thereof, and r is such that the percentage of filler is from about 10 to about 95% by weight based on the total weight of the precursor.

In order to be used in the process of the invention, the spray-dried precursor must be fully activated, i.e. it must be treated with a sufficient amount of the activating compound to bring the titanium atoms contained in the precursor to active state. The following activation procedures can be used:

Procedure A (Total Reactor Activation)

The spray-dried precursor can be fully activated in the polymerization reactor. In this process, the activator (activator) and the spray-dried precursor are preferably fed to the reactor through separate feed lines. The activator may be fed to the reactor in undiluted form or as a solution thereof in a hydrocarbon solvent such as isopentane, hexane or mineral oil. The solution usually contains about 20 to 30% by weight of activator. The activator is added to the reactor in an amount to achieve a total Al / Ti molar ratio of 10 to 500, preferably about 10 to 200. The activator added to the reactor reacts with and activates the titanium compound.

Procedure B (two-stage activation method)

Activation of the spray-dried precursor can be carried out in two stages.

In the first step, the spray-dried precursor is reacted and partially activated with an amount of activator to obtain a partially activated precursor in which the molar ratio of activator / Ti is about> 0 to 100: 1 and preferably about 4 to 8: 1. these two stages of activation can be performed outside the reactor.

To convert the partially activated precursor to a form that is active at the poles 11

214B8B to measure ethylene, an activator must be introduced into the polymerization reactor. This completes the activation of the precursor in the polymerization reactor. The activator compound and the partially activated precursor are preferably fed to the reactor via separate lines. The additional activating compound can be injected into the reactor in undiluted form or as a solution in a hydrocarbon solvent such as isopentane, hexane or mineral oil. This solution typically contains about 2 to 30% by weight of the activating compound. The activator compound is added to the reactor in an amount such that a total activated Al / Ti molar ratio of about 10 to 500, and preferably about 10 to 200 is achieved in the reactor together with the amounts of activator and titanium compound listed as partially activated spray dried precursors. the activator compound introduced into the reactor reacts with the titanium compound and completes the activation of the titanium compound directly in the reactor.

In a continuous gas phase process such as the fluidized bed process described below, separate batches of spray dried or partially activated precursor are continuously fed to the reactor during polymerization, while providing separate batches of activating compound needed to activate or complete activating the partially activated precursor. This replaces the active sites of the catalyst that have been consumed during the reaction during the polymerization.

The polymerization is carried out by contacting the monomer stream (s) in the gas phase, for example in the fluidized bed process described below, substantially in the absence of catalytic poisons such as moisture, oxygen, carbon monoxide, carbon dioxide and acetylene, with a catalytically effective amount. the fully activated precursor at pressure and temperature sufficient to initiate the polymerization.

In order to achieve the desired density range of the copolymers, copolymers are required

with ethylene a sufficient quantity of carbon chain comonomers of 3 carbon atoms or more to have a C3 to C3 content

C ₈ comonomers in the copolymer> 0 to 10 <

mol. <

The amount of comonomers required to achieve this result depends on the particular comonomers or comonomers used.

The following table lists several different comonomers that can be used for copolymerization with ethylene to produce polymers having a density within the desired range at any given melt index. The table shows both the amount of comonomers needed in the copolymer to achieve these properties and the relative molar concentration of comonomers relative to ethylene in the recycled monomer gas stream under reaction equilibrium conditions in the reactor.

Komonomer

Molar% required in the copolymer

The comonomer / / ethylene gas phase molar ratio under equilibrium conditions

propylene > 0 to 10 > 0 to 0.9 1-butene > 0 to 7.0 > 0 to 0.7 1-pentene > 0 to 6.0 > 0 to 0.45 1-hexene > 0 to 5.0 > 0 to 0.4 1-okten > 0 to 4.5 > 0 to 0.35

The fluidized bed reaction system that can be used in the process of the invention is illustrated in the figure. Reactor 1 consists of reaction zone 2 and speed reduction zone 3.

Reaction zone 2 comprises a bed of growing polymer particles, formed polymer particles, and a minor amount of catalyst fluidized by a continuous flow of polymerizable and modifying gaseous components consisting of make-up gas and gas recycled to the reaction zone. In order to maintain the fluidized bed in a fluidized state, the gas mass flow rate through the bed must be greater than the minimum flow rate required for fluidization. Preferably, a suitable gas mass flow rate through the bed is about 1.5 to about 10 times higher, preferably about 3 to 6 times higher than the minimum gas flow rate necessary for fluidization (Gmf). The Gmf designation for the minimum gas mass flow rate required to achieve fluidization was suggested by C. Y. Wen and Y.H. Yu, "Mechanics of Fluidization", Chemical Engineering Progress Symposium Series, Vol. 62, pp. 100-111 (1966).

It is important that the bed always contain particles that prevent the formation of "hot spots" and that trap and distribute the pulverulent catalyst in the reaction zone. Upon commencement of operation, a polymeric particle is usually introduced as a base into the reaction zone before the gas stream is introduced. The particles may be identical to the polymer formed or may be different. When different, they are drawn off with the resulting polymer particles as a leading product. Finally, the fluidized bed of the desired polymer particles displaces the starter bed.

The spray-dried precursor or partially activated precursor used in the fluidized bed is preferably stored in the emergency container 4 under an atmosphere of an inert gas such as nitrogen or argon.

Fluidization is achieved by a high rate of gaseous recycle introduced into and through the bed, which is typically of the order of about 50 times higher than that of the make-up gas. The fluidized bed usually looks like a dense mass of moving particles flowing in the free vortex created by the passage of gas through the bed. The pressure drop across the bed is equal to or somewhat higher than the weight of the bed divided by the cross-section of the bed, so it is dependent on the reactor geometry.

The make-up gas is introduced into the bed at the same rate as the withdrawal rate of the polymer product particles. The composition of the make-up gas is determined by means of an analyzer S located above the bed. The gas analyzer determines the composition of the gas to be recycled, and the composition of the make-up gas is adjusted accordingly to maintain the composition of the gas mixture in a substantially steady state in the reaction zone.

In order to guarantee complete fluidization, the recycle gas and possibly part of the make-up gas is fed through the recycle line 6 through the feed 7 below the bed. Above the inlet 7 there is a gas distribution plate 8 which assists fluidization of the bed.

The portion of the gaseous stream not reacting in the bed constitutes recycled gas, which is discharged from the polymerization zone preferably by passing through a zone 3 located above the bed in which the velocity is reduced and the entrained particles fall back into the bed.

The recycle gas is then compressed in the compressor 9 and passed through a heat exchanger 10 where it is freed from the reaction heat before returning to the bed. The bed temperature is kept constant at steady state conditions by dissipating the heat of reaction. There is no apparent temperature gradient at the top of the bed. A temperature gradient exists in the lower 152 to 304 mm bed, between the inlet gas temperature and the bed rest temperature. The recycle gas is fed to the bottom of the reactor through the inlet 7 and into the fluidized bed through a distribution plate 8. The compresor 9 can also be placed downstream of the heat exchanger 10.

The distribution plate 8 plays an important role in the operation of the reactor. The fluidized bed contains both growing and formed polymer particles and catalyst particles. Since the polymer particles are hot and possibly active, they must be prevented from settling, since if any calm mass were formed, the active catalyst contained in these particles could cause the reaction to continue and the particles would melt due to the heat generated. It is therefore important that diffuse recycle gas is passed through the bed at a rate sufficient to fluidize the bed particles. A divider plate 8 serves for this purpose and may be a sieve, a plate with slits, a perforated plate, a plate with caps (analogous to the distillation column trays) and the like. All parts of the plate may be stationary or of a movable type such as as described in U.S. Patent No. 3,298,792. Whatever the design of the plate, the plate must disperse the recycle gas between the particles at the bottom of the bed and keep the particles of the bed fluidized. The board also aims to support a quiet bed of resin particles when the reactor is not in operation. The movable portions of the plate may be used to extrude polymer particles retained on or within the plate.

Hydrogen can be used as the chain transfer agent in the polymerization according to the invention. The hydrogen / ethylene molar ratio that can be used is in the range of about 0 to about 2.0 moles of hydrogen per mole of monomer in the gas stream.

Any gas inert to the catalysts and reactants may also be present in the gas stream. The activator compound is preferably added to the reaction system downstream of the heat exchanger 10 (in terms of flow). Therefore, the activator may be introduced into the recycle line from, for example, the container 11 through line 12.

In addition to hydrogen, the compounds of the formula I can be used in addition to hydrogen as molecular weight control agents, i.e. as chain transfer agents.

Zn (R _a ) (R _b ) where

R _a and R _b are the same or different C 1 to C 1 ₄ aliphatic or aromatic hydrocarbon radicals.

This further increases the melt index values of the produced copolymers. About 0 to 100, and preferably about 20 to 30 moles of the zinc compound (calculated as Zn) per mole of the titanium compound (calculated as Ti ¹ ) may be added to the gas stream introduced into the reactor. Zinc compound would be introduced into the reactor preferably in the form of a dilute solution (2 to 30% by weight) in a hydrocarbon solvent or absorbed on a solid diluent material, such as silica, in amounts of about 10 to ^{50 v /} % by weight. These substances are often pyrophoric. The zinc compound can be fed alone or together with an additional activating compound, which is also fed to the reactor, from a dispenser (not shown) which can be placed next to the container 11.

The fluidized bed reactor must be operated at a temperature below the sintering temperature of the polymer particles to avoid sintering of the particles. The production of ethylene copolymers according to the invention is preferably carried out at a temperature of about 30 ° C to about 115 ° C. Temperatures of about 75 to 95 ° C are used to produce products with a density of about 910 to 920 kg / m ³ , temperatures of about 80 to 100 ° C are used to produce products with a density of about 920 to 940 kg / m ^3, and temperatures 90 to 115 ° C is used to prepare products with a density above 940 kg / m ³ up to 970 kg / m ³ .

The fluidized bed reactor is operated at a pressure of up to about 6.87 MPa, preferably at a pressure of about 1.03 to 2.41 MPa, and when operating at higher pressures within this range, heat transfer is facilitated because the pressure increase results in increase in unit volume heat capacity of gas.

The spray-dried or partially activated precursor is injected into the bed at a rate equal to the rate at which it is consumed through an inlet 13 located above the distributor plate 8. Preferably, the catalyst is injected at the bed where good mixing of the polymer particles occurs. An important feature of the invention is that the catalyst is injected at a point above the manifold plate. Since the catalysts used according to the invention are highly active, injection into the space below the distributor plate could result in polymerization being initiated at this point, which could eventually lead to blockage of the distributor plate. On the contrary, injecting the catalyst into the fluidized bed helps to distribute the catalyst in the bed and avoids the formation of sites with high catalyst concentrations which could lead to hot spots. Injecting the catalyst into the reactor above the bed may result in excessive entrainment of the catalyst into the recycle line where polymerization may start, which could eventually lead to clogging of the line and heat exchanger.

A gas inert to the catalyst, such as nitrogen or argon, is used to introduce a partially or fully reduced precursor, any activator or transfer agent that is not gaseous into the bed.

Bed productivity is controlled by catalyst injection rate. Bed productivity can simply be increased by increasing the catalyst injection rate and reduced by reducing the catalyst injection rate.

Since any change in catalyst injection rate results in a change in reaction heat evolution rate, the temperature of the recycle gas entering the reactor is adjusted up or down to accommodate the heat evolution rate. This ensures a substantially constant temperature in the bed. Both the fluidized bed and the recycle gas cooling system must, of course, be equipped with appropriate devices for detecting temperature changes in the bed and cooling system so that the operator can properly adjust the temperature of the recycle gas.

Under a certain combination of operating conditions, the fluidized bed is maintained at substantially the same height by withdrawing a portion of the bed as product at the same rate as the rate of particle formation of the polymer product. Since the rate of heat evolution is directly proportional to product formation, the measurement of the increase in gas temperature along the reactor (i.e., the temperature difference between the inlet gas temperature and the outgoing gas temperature) determines the rate of polymer particle formation at a constant gas velocity.

The polymer product particles are preferably collected continuously through a conduit 14 in the vicinity of the distributor plate 8. The particles are collected in the form of a slurry with a portion of the gaseous stream vented before the particles settle to prevent further polymerization and caking before the particles reach the zone where gather. Suspension gas can also be used to transfer product from one reactor to another.

The polymer product particles are expediently and preferably removed by means of two sequentially operated time-adjusted valves 15 and 16, between which a separation zone 17 is provided. When the valve 16 is closed, the valve 15 is opened so that the gas / product mixture passes through zone 17. valve 16 opens to transfer the product to the outer insulation zone. The valve 16 is then closed and closed until the product is removed. The vented gas containing unreacted monomers can be removed from zone 17 via line 18. It can then be compressed in the compressor 19 and fed directly or via a scrubber 20 and via line 21 to the gas recycle line 6 upstream of the recycle compressor 9.

Finally, the fluidized bed reactor is equipped with a suitable venting system that allows venting of the bed during start-up and shutdown. The reactor does not require the use of any mixing devices and / or wall scraping devices. The recycle gas line 6 and the devices located therein (compressor 9, heat exchanger 10) should have a smooth surface and should not contain unnecessary elements that could impede the smooth flow of gas.

The highly active spray-dried catalyst system of the present invention provides a fluid bed product with an average particle size of about 250 to 2550, preferably between about 250 to 1525 μτη.

The feed monomer gas stream, optionally with inert gaseous diluents, is fed into the reactor at a rate to provide a space and time yield of about 32.4 to about 162.2 kg / hr / m ³ bed volume.

The term "crude resin or polymer" as used herein refers to a polymer in granular form

214666 form, as obtained from the polymerization reactor.

The following examples serve to illustrate the invention in more detail, but do not limit the scope of the invention in any way.

The properties of the polymers produced in the examples are determined by the following test methods:

Density:

For substances with a density below 940 kg / m ³ , the procedure of ASTM-1505 is used, wherein the plate is tempered for 1 hour at 100 ° C to approach the state of equilibrium crystallinity. For substances with a density of 940 k _: g / m ³ and above, a modified procedure is used in which the test plate is tempered for 1 hour at 120 ° C to approach equilibrium crystallinity and then rapidly cooled to room temperature. All density data are in kg / m ³ . All measurements were performed on a density gradient column.

Melt Flow Index (MI)

ASTM D-1238-Condition E measurements are performed at 190 ° C, g data per 10 minutes.

Flow rate (melt index at higher load) '(HLMI)

ASTM D-1238 - Condition F

The measurement is performed using a 10-fold load than the melt index measurement, data are in g / 10 min.

Flow Rate Ratio Predictivity of Flow Rate ¹ ______

Melt flow index

A sample of the resin product was cremated ^; and is determined by the weight of the% ash, since the ash is essentially a catalyst. The productivity is thus expressed in Kg of polymer produced per kg of total catalyst consumed. The amount of titanium, magnesium and chlorine in the ash is determined by elemental analysis. Please give the values! in ppm

Bulk (bulk density)

The resin is poured into a 100 ml graduated cylinder through a funnel with a diameter of 9.5 mm and up to the 100 ml mark. During the filling of the roller, the netPepe does not roll. The weight difference is determined by weighing. Values are given in kg / m ³ .

Mean particle size

This property is calculated from the sieve analysis data according to A6TM-D-1921, Method A using a 500 g sample. The calculations are based on the weight fractions captured on the sieves.

Molecular weight distribution (Mw / / Mn)

It is determined by gel chromatography, in the case of resins with a density below 940 kg / m ^{3 it} is used as a stationary phase of Styrogel with a pore size sequence T ⁶ , ΙΟ ⁴ , 10 ³ , 10 ² and 6 nm and as perchlorethylene solvents, working at 117 ° C. Deň: 32 ° C. In the case of resins with a density of 940 kg / m ³ or higher, Styrogel with a pore size sequence of ΙΟ ⁶ , 10 ⁵ , TO ⁴ , T ³ , 6 nm is used. The solvent used is o-dichloro benzene at 135 ° C. Detection is performed in all cases by infrared radiation at 3.45 μηι.

Substances extractable with h-hexane (FDA-block used for polyethylene l-lm to be in contact with food).

A film sample of 0.038 µm thickness and an area of 1290 cm- is cut to a stripped δ dimension of 2.54 x 15.24 cm and weighed to the nearest 0.1 mg. The strips were placed in a flask and extracted with 300 ml of n-hexane at 50 ° C for 2 hours. The extract is then decanted into a balanced culture dish. After drying the extracts in a vacuum dye, the curative dish is weighed to the nearest 0.1 mg. The amount of extract, calculated on the original sample weight, is then reported as the mass fraction of n-hexane extractables.

Něhasycehóst

Measurements are made using a red-light spectrophotometer (Perkin Elmer Model 21). Resins of 0.635 mm thickness are made from the resin and serve as test specimens. Absorbance is measured at 10.35 μΐη for transvinylidene unsaturation, at 11.0 μΐη for terminal vinyl unsaturation, and at 11.25 for vinylidene unsaturation in the side chains. Absorbance per 1 mm of molding thickness is directly proportional to the multiple of the henasysteust concentration and absorbency. The absorbency values are taken from R. J. de Kock, et al., J. Polymer Science, Part B, 2, 339 (1964).

Examples

I Preparation of spray dried precursor

In a five-liter flask equipped with a mechanical stirrer was added 1.0 L of tetrahydrofuran. 71.0 g of anhydrous magnesium chloride is slowly added to tetrahydrofuran under inert atmosphere with stirring. The temperature of the exothermic reaction is controlled by the rate of addition of magnesium chloride and a water bath. After all the magnesium chloride has been added, 90.0 g of sublimed silica are slowly added to the suspension. After the addition of the sublimed silica was complete, the suspension was refluxed for 2-6 hours. (Sublimed silica has a particle size and a range from 0.007 to 0.05 μιη and is commercially available under the name CAB-O-SIL, manufactured by Cabot Corporation, with a SiO ₂ content greater than 99.8%).

In another 2 L flask equipped with a mechanical stirrer, 13.4 g of anhydrous MgCl _{2 was} mixed with 0.8 L of THF under nitrogen. The mixture was stirred at room temperature (~ 25 degrees Celsius) ¹ and 8.9 ml of titanium tetrachloride was added dropwise over 1/2 hour. After the addition of TiCl ₄ was complete, the contents of the flask were refluxed for about 1/2 hour to 1 hour to dissolve the solids. The system is cooled to room temperature with stirring and the contents of the flask are then slowly added to the previously prepared magnesium chloride suspension. The mixture was heated to reflux for about 1 hour with stirring and then heated to reflux for about 1 hour, then cooled to room temperature with stirring. The resulting product is a yellow-green suspension which does not separate into components for about 1 hour.

The suspension is spray dried under an inert atmosphere in a two-nozzle spray drier (nozzle diameter 1.524 mm, annular ring diameter 2.54 mm, spray pressure 68.7 kPa, drying nitrogen inlet temperature 112 ° C). The spherical catalyst particles trapped in the cyclone have an average particle diameter of about 25 (based on optical micrographs measurements).

II Activation procedure

The precursor prepared according to paragraph I is activated by two different methods.

Procedure A (full reactor activation)

The activator is introduced into the polymerization reactor to activate the precursor. It is metered into the reactor as a dilute solution in a hydrocarbon solvent such as isopentane. These dilute solutions contain about 2 to 30% by weight of activator.

The activator is introduced into the polymerization reactor in an amount such that the Al / Ti molar ratio in the reactor is maintained at about 10 to 500, and preferably 10 to 200. Process B (two-stage activation process)

The precursor prepared as described in paragraph I is activated by mixing it with an activator in a mixing tank in the presence of a sufficient amount of an anhydrous aliphatic hydrocarbon diluent such as isopentane to form a suspension.

The amount of activator and precursor is used in such an amount that a partially activated precursor is formed in which the Al / Ti ratio is> 0 to 10: 1 and preferably 5 to 8: 1.

The suspension is then thoroughly mixed at room temperature and at atmospheric pressure for about 1/4 to 1/2 hour. The resulting slurry is then dried in a stream of dry inert gas such as nitrogen or argon at atmospheric pressure and at a temperature of 65 ± 10 ° C to remove the hydrocarbon diluent. The resulting product is a partially activated spray-dried precursor.

The activation is completed in a polymerization reactor. The additional activator is metered into the reactor in the form of a dilute solution in a hydrocarbon solvent such as isopentane. The diluted solution contains about 2 to 30% by weight of activator.

The activator is introduced into the polymerization reactor in an amount such that the Al / Ti molar ratio in the reactor is maintained at about 10 to 500, and preferably 10 to 200. Examples 1 to 9

Ethylene from homopolymers is (Examples 2, 8 and 9) or copolymerized with 1-butene (Examples 1 and 3 to 7) in a series of examples using a catalyst prepared by the above process and activated as in Procedure A (Examples 1 to 3 and 5 to 7). 7) and according to Procedure B (Examples 4, 8 and 9) to produce polymers with a density greater than 920 and less than or equal to 970 kg / m ³ .

The polymerization reaction is carried out continuously in a fluidized bed reaction system for at least 1 hour after reaching equilibrium at an absolute pressure of 2.06 MPa, a temperature indicated in Table I at a gas velocity of about three to six times Gmf and space / time yield. 48.7 to 113.5 kg / m ³ / h. The reaction system described above is used. Its lower part is 3.05 m high and its inner diameter is 0.343 meters. The upper part is 4.88 m high and its inner diameter is 0.597 m.

Table I, which refers to examples 1-9 summarizes the applied operating conditions, i.e. percentage of the compound of formula (MgCl _{2] 2, 5} [TiCl _4] [THF] _7, the type and amount of filler, the molar ratio Al / Ti in the partially activated precursor, polymerization temperature, hydrogen / ethylene molar ratio, 1-butene / ethylene molar ratio in the reactor, and catalyst productivity in kg of polymer produced per kg of titanium metal, expressed in ppm Ti.

Table II lists the properties of the raw granular resins produced according to Examples 1 to 9, i.e. density, melt index (MI), flow rate ratio (MFR), bulk density, mean particle diameter and very fine particulate content in% by weight (<74 μπι) ).

The reaction conditions in Examples 1 to 9

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Table II

Properties of the polymers produced in Examples 1 to 9

Example Density Flow Index Ratio of the melt flow rate

1 926 2.3 28 2 970 4.8 28 3 924 2.5 27 Mar: 4 922 2.3 26 5 927 3.5 26 6 930 2.7 26 7 927 1.0 24 8 969 6.4 28 9 959 1.1 28

The data from Table II shows that when the precursor is spray dried without containing a filler (Example 7), the bulk density is low.

} part} ounj eudAS [kg / m ³ ] Mean spherical polymer particle size [jum] Very small particles <74 iwm [| ° / o] 355.0 630 0.6 455.5 418 4.7 291.8 757 0.4 353.4 1008 0.6 293.4 848 0.0 342.0 554 0.4 243.2 737 - 455.5 787 <2.0 415.0 863 <2.0

ká. Also, the polymer particles formed in Example 7 are made of a fibrous mass, resembling cotton.

Claims (5)

CLAIMS 1. A process for the preparation of a catalyst system for the polymerization or copolymerization of ethylene, characterized in that: A) forms a spherical precursor of the general formula Mg _m Ti | (OR) _n X _p [ED] _q [filler] _r where ED is an electron donor compound, m is a number from 0.5 to 56 including limit values, n is a number of 0 or 1, p is a number from 2 to 116 including limit values, q is a number from 2 to 85 including limit values, R is a C 1 -C ₁₄ aliphatic or aromatic hydrocarbon radical or a radical of formula COR ', wherein R' is a C ₁ -C ₄ aliphatic or aromatic hydrocarbon radical. X is chlorine, bromine or iodine, or a mixture thereof is such that the percentage of filler is from about 10 to about 95% by weight based on the total weight of the precursor, thereby forming a suspension or solution of at least one magnesium compound, at least one titanium compound and at least one inert filler in the at least one electron donor compound and the resulting suspension or solution of the precursor in the electron donor compound is spray dried by spraying on the spherical particles of the precursor having a size of about 10 to about 200 μΐη, wherein the magnesium compound is a compound of MgX ₂ ynAlezu where X is as defined above; the titanium compound is a compound of the formula Ti (OR) _and X _b wherein a is 0, 1 or 2, b is 1 to 4 inclusive, wherein the sum of a + b is 3 or 4, and X and R are as defined above, and the electron donor compound is a liquid organic compound wherein said magnesium compound and said titanium compound are soluble selected from the group consisting of alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ethers and aliphatic ketones, and B) activating said precursor either by activating partially> 0 to 10 moles of activator per mole of Ti in said precursor or by activating completely 10 to 500 moles of activator per mole of Ti in said precursor, wherein the activator is a compound of the general formula formulas Al (R ') _c X' _d H _e where X 'represents chlorine or a group of the formula OR' and each of the symbols R "and R '", which are the same or different, represent a C ₁ to C ₁₄ saturated hydrocarbon radical, d is a number from 0 to 1.5, e is a number of 1 or 0, the sum of c + d + e having a value of 3, wherein said activation is performed after isolation of the particles of said precursor. 2. The process of claim 1, wherein the magnesium compound is magnesium chloride. 3. The method of claim 2, wherein the electron donor compound comprises at least one ether. 4. The method of claim 3, wherein the electron donor compound comprises tetrahydrofuran. 5. The process of claim 4 wherein the titanium compound comprises titanium tetrachloride.