CS223985B2 - Method of catalytic production of the polymere of ethylene - Google Patents

Description

The present invention relates to catalytic polymerization of ethylene using specially prepared highly active complex catalysts containing magnesium and titanium in a gas phase process

-5 at low pressure to produce ethylene polymers having a density of from 910 kg / m ^J inclusive to 970 kg / ur inclusive and a melt flow rate ratio (defined below) ranging from 22 inclusive to 32 inclusive, the resulting polymer particles having a bulk density of 291, 8 to 518.7 kg / πΡ and 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. The productivity 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 catalysts containing 223985 titanium and magnesium in the production of granular ethylene polymers by a gas-phase fluidized bed process at pressures below 20 psig. 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 herein). 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 high-residue polymers 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 a catalyst prepared from a supported catalyst component, wherein the polymer produced is in the form of spherical or spheroidal particles. Catalysts are prepared by mixing (a) organometallic metal catalyst components 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 which are chemically bound to or supported by the carrier. dispersed. Components b) are in the form of spherical or spheroid particles having a size of 1 to 350 µm. Catalyst components b) are prepared in various ways. One of them is spray drying of anhydrous magnesium halide solutions in organic solvents. Spray drying is carried out to obtain spherical particles having a size of 1 to 300 µm. 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. Patent No. 4,111,835, issued Sep. 5, 1978, describes the polymerization of olefins to polymer in the form of spheroid particles that are highly agglomerate with continuous polymerization. The catalyst comprises (a) an organometallic metal compound of the second or third group of the Periodic Table and (b) a product obtained by reacting a halogenated titanium compound with magnesium halide hydrate in the form of spheroid particles having a diameter of 10 to 70 µm. The magnesium halide hydrate contains 10 to 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 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 magnesium halide inert excipients which are compounds of elements belonging to Groups 1 to 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 spheroid particles.

The processes of these patents are further carried out using high concentrations of boiling titanium tetrachloride, which is highly corrosive. Moreover, the methods 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 known from earlier patents of Union Carbide Corporation that ethylene copolymers having a density of 910-960 kg / m < 2 > by a melt flow rate (defined below) of from 22 to 32, including limit values with relatively low catalyst residue, can be produced in granular form. at a relatively high productivity by polymerizing the monomer or monomers 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 @ 2 including limit values and a melt flow rate (MFR) of 32 > MFR > 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 by a low pressure gas phase process using a highly effective complex catalyst comprising magnesium and titanium mixed with an inert carrier.

Polymers produced using mixed catalysts according to earlier patents of Union Carbide Corporation have the disadvantage that the polymer particles formed during fluidized bed polymerization are irregular in shape and somewhat difficult to fluidize. The final product also contains a relatively high amount of fines, i.e. particles of 125 µm or less.

The method used to produce the catalyst precursor described in these patents 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 by precipitation with up to Οθ of an aliphatic or aromatic hydrocarbon. However, these isolation techniques can lead to inconsistent growth of polymer particles and to the formation of a polymer consisting of needle-like particles.

It is known from another Union Carbide Corporation patent that ethylene copolymers having a density of 910-940 kg / m, relatively high bulk density, which provide films with good clarity, can be produced at relatively high productivity suitable for industrial application by copolymerizing ethylene with one or more C 8 to C 8 alpha-olefins in the gas phase in the presence of a highly active complex catalyst comprising magnesium and titanium, activated under specific conditions by an organoaluminum compound which is impregnated in a porous inert carrier.

However, the preparation of the impregnated catalyst precursor according to this patent 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 been unexpectedly found that ethylene polymers with a wide density range of from about> 910 to about <970 kg / m 2, a bulk density of from about 291.8 to about 518.7 kg / m 2, and a melt flow rate ratio of> 22 to 32 having a controlled particle size and shape and a relatively low titanium residue content can be produced at a relatively high productivity suitable for industrial production by the gas phase process by ethylene homopolymerizing or copolymerizing with one or more Cg to Cg alpha-olefins in the presence of a highly effective magnesium-titanium complex catalyst prepared by the method described below by spray-drying the magnesium-titanium-containing precursor as 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 according to the invention, by controlling the 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 µm. The process by which particulate spherical catalyst precursor particles are prepared is simpler compared to other previously described methods 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 distribution of a polymer. A melt flow rate (MFR) of 22 to 32 (including limit values) corresponds to a Sfw / En of between 2.7 and 4.1 and an MFR of 25 to 30 (including limit values) corresponds to a Mw / Sin ratio of 2, 8 to 3.6.

Homopolymers have a density of from about 958 to 972 kg / m @ 2

O

960 kg / m, including limit values. The density of the copolymer at a given melt index can be controlled primarily by the amount of up to Cg of 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 958 kg / np. Adding increasing amounts of comonomers to the polymers results in a gradual decrease in copolymer density. Under the same reaction conditions, the amount of each of the various to C8 comonomers needed to achieve the same result varies from monomer to monomer.

To achieve the same results, i.e. the same density at a certain melt index, increasing molar amounts of comonomers in the series C 1> C 4> C 4> C 8> C 8 are needed.

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 impossible at all. 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 index at normal load (MI) in the range of> 0.0 to about 100, preferably in the range of from about 0.5 to 80 and a melt flow index at high load (HLMI) of from about 11 to about 2000. Index The melt flow of the polymers produced by the process of the invention is 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.

According to the invention copolymers can be prepared comprising a major molar proportion of ethylene (> 90%) and a minor raolérní proportion (<10%), one or more C ^ to _Cg alpha-olefins. to C8 alpha-olefins should contain no branching at any of their carbon atoms that is closer to the copolymer backbone than the fourth carbon atom. Preferred C 1 -C 8 alpha-olefins are propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene

The copolymers of the invention contain 11 and usually> 0.1 to 0,30.3 C = C double bonds per 1000 carbon atoms and usually have a n-hexane extractable content (at 50 ° C) of less than about 3% and preferably less % by weight.

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

The ethylene polymers of the present invention have a bulk density of about 291.8 to 518.7 kg / m A. They consist of spherical particles having a mean particle size of from 250 to 2550 µm and preferably from 250 to 1525 µm.

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 where

R is a C 1 to C ₁₄ aliphatic or aromatic hydrocarbon radical or a radical of formula COR *, wherein R * is a C ₁ to C ₁₄ aliphatic or aromatic hydrocarbon radical,

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

The titanium compound can be used singly or in mixtures and include compounds of formulas TiCl ₃ , TiCl ₄ , Ti (OCH ₃ ) Cl ₃ , Ti (OC ₆ H ₅ ) C ₃ , Ti (OCOCH ₃ ) C ₃ and Ti (OCOC ₆ H _5). ) Cl ₃ .

The magnesium compound has a structure corresponding to the general formula

MgX ₂ where

X represents chlorine, bromine or iodine.

These magnesium compounds can be used singly or in combination and include compounds of the formulas MgClg, MgBr ₂ and Mglg. 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 above.

By electron donor compounds are meant such compounds as alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ethers and aliphatic ketones. Among these electron donor compounds the preferable ones are alkyl esters of Ci to _C4 saturated aliphatic carboxylic acids; alkyl esters of C? to _Cg aromatic carboxylic acids; C ₂ to C _g and preferably C ₃ to éterům aliphatic, cyclic C ₃ -C éterům and preferably a cyclic mono- or diéterům, _C3 to Cg, and preferably C ₃ to 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 activator compound has the structure of formula Alir) where _{e 0} X'H

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

8 ** and R '', which are the same or different, represent a C ₁ to C ₄ saturated hydrocarbon radical, £ is a number from 0 to 1.5, £ is a number of 1 or 0, the sum of £ + 2 + £ is worth 3.

The activating compounds can be used singly or in combination and exemplified by compounds of formula ai (c ₂ h ₅ ) ₃ , ai (c ₂ h ₅ ) ₂ ci, ai (c- ₄ h ₉ ) ₃ , and i ₂ (c ₂ h ₅ ) ₃ or ₃ , if ₂ h ₅ ) ₂ (oc ₂ h ₅ ).

A1 (i-C ₄ H _{9) 2} H, A1 (C ₂ H _{5) 2} H and

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. This results in spherical particles having an average diameter of about 10 to about 200 µm. The spherical particles are then treated with the activating compound as described above.

The initial precursor mixture is prepared by dissolving the titanium compound and excess magnesium compound (1 < Mg / Ti < 56) in the electron donor compound at a temperature from about 20 ° C to about the boiling point of the electron donor compound. The titanium compound may be added to the electron donor compound before or after or simultaneously with the addition of the magnesium 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 before or after cooling to the Mg / Ti complex solution. 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 a drying nitrogen inlet temperature ranging from a temperature above the boiling point of the electron donor compound up to about 150 ° C. 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 accomplished by means of a spray nozzle or centrifugal disk atomizer operating at a high velocity at an overpressure of from about 100 psig to about 100 psig.

Any organic or inorganic compounds which are inert to the titanium compound and the resulting active catalyst, such as silica, for example sublimed silica, titanium dioxide, polystyrene, rubber modified polystyrene, magnesium chloride and calcium carbonate. 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 about <50 µm.

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

_Mgfi ^T ii (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, 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 represents a aliphatic or aromatic hydrocarbon radical or a radical of formula COS *, wherein R * represents a C 1 to C ₁₄ 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. Typically, the solution 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)

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

In the first stage, the spray-dried precursor is reacted and partially activated with an amount of activator to obtain a partially activated precursor in which

223985 8 molar activator / Ti ratio of about> 0 to <10: 1 and preferably about 4 to 8: 1. The first of these two activation steps may be performed outside the reactor.

In order to convert the partially activated precursor to a form that is active in ethylene polymerization, 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 amount of activator and titanium compound listed in the partially activated spray dried precursor form. the amount of activating 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.

To achieve the desired density ranges in the copolymers it is necessary to copolymerize ethylene with enough of the comonomers with a carbon chain of 3 or more carbon atoms, so that the content to _Cg comonomer 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 copolymers 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% needed in copolymers The comonomer / ethylene gas phase equilibrium ratio conditions propylene > 0 to 10.0 > 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

A fluidized bed reaction system that can be used in the process of the invention is illustrated in the figure. The reactor 6 consists of a reaction zone 2 and a speed reducing zone 2.

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 higher 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 designation Gmf 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 to prevent hot spots and to trap and distribute the pulverulent catalyst in the reaction zone. Typically, at the start of operation, polymer particles are introduced into the reaction zone as a basis before the gas stream is introduced. These 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 a standby container 6 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 using an analyzer 2 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 2 under the bed. Above the inlet 2 there is a gas distribution plate 8 which assists fluidization of the bed.

The portion of the gaseous stream that does not react in the bed forms recycled gas, which is discharged from the polymerization zone preferably by passing through a zone 2 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 2 and passed through a heat exchanger 110 where it is stripped of 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 bed of 52 to 304 mm between the temperature of the inlet gas and the temperature of the rest of the bed. The recycle gas is fed to the bottom of the reactor via inlet 2 and into the fluidized bed through a distribution plate 8. The compressor 2 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 scattered recycle gas is passed through the bed at a rate sufficient to fluidize the bed particles. The distribution plate 8 serves for this purpose and can be a sieve, a plate with slits, a perforated plate, a plate with caps (analogous to those of the distillation column trays) and the like. All portions of the plate may be stationary, or may be of a movable type, such as that described in U.S. Pat. No. 3,296,792. Whatever the design of the plate, the plate must disperse recycle gas between the particles at the bottom of the bed and keep the particles in the bed. fluidized state. The board also aims to support the bed of resin particles calmly 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 of 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). The activator may therefore be introduced into the recycle line, for example from 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

Ηθ and Rfa are the same or different C to aliphatic or aromatic hydrocarbon residues.

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) can be added to the gas stream introduced into the reactor. Preferably, the zinc compound may be introduced into the reactor in the form of a dilute solution (at a concentration of 2 to 30% by weight) in a hydrocarbon solvent or in absorbed form in a solid diluent such as silica in an amount of about 10 to 50% by weight. These substances are often pyrophoric. The zinc compound may be introduced alone or together with an additional activating compound, which is also fed to the reactor, from a dispenser (not shown), which may be placed adjacent to the container 11.

The fluidized bed reactor must operate at a temperature below the sintering temperature of the polymer particles in order to prevent sintering of the particles. The production of ethylene copolymers by the process of the invention is preferably carried out at a temperature of about 30 ° C to about 115 ° C. Temperatures from 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 in this range, heat transfer is facilitated since the pressure increase causes as a result of an increase in the unit volume heat capacity of the 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 manifold plate could result in polymerization starting at that point, eventually leading to clogging dividing plates. Injection of the catalyst catalyst into the fluidized bed, on the other hand, 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 excess entrainment of the catalyst into the recycle line where polymerization may start, which could eventually. lead to clogging of pipes 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 non-gaseous activator or transfer agent 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 rate of heat evolution. 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 appropriately adjust the recycle gas temperature.

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 formation of the polymer product particles. 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 suspension with a portion of the gaseous stream that is vented before the particles settle to prevent further polymerization and caking before the particles reach the zone collect. 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-controlled valves 15 and 6, between which a separation zone 17 is provided. When valve 6 is closed, valve 15 is opened so that it permits a gas-product mixture into zone 1. 7. The valve 16 is then opened 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 may be removed from zone 17 via line 18. It may be compressed in compressor 19 and fed directly or via purifier 20 and line 21 to gas recycle line 6 at a point upstream of the recycle compressor.

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 60, heat exchanger 60) should have a smooth surface and should not contain unnecessary elements that could impede the continuous flow of gas.

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

The feed monomer feed stream, optionally with inert gas diluents, is fed into the reactor at a rate such that a space and time yield of about 32.4 is achieved.

223985 12 to about 162.2 kg / hr / πΡ bed volume. By crude resin or polymer is meant here the polymer in granular 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 2, the procedure of ASTM-1505 is used, wherein the plate is tempered for 1 hour at 100 ° C to approximate equilibrium crystallinity. For substances with a density of 940 kg / np 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 given in kg / m &lt; 3 &gt; All measurements were performed in a density gradient column.

Melt Flow Index (MI)

ASTM D-1 238-Condition E measurement is performed at 190 ° C, g data per 10 minutes.

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

ASTM D-1238 - Condition F

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

flow rate

Ratio of flow rates = melt flow index

Productivity

The resin product sample is ashed and is determined by weight of ash as the ash is essentially a catalyst. The productivity is therefore 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. Values are given in ppm Ti.

Bulk weight

The resin is poured into a 100 ml graduated cylinder through a funnel with a 9.5 mm stem diameter up to the 100 ml mark. Do not shake the cylinder during filling. The weight difference is determined by weighing. Values are given in kg / m 2.

Mean particle size

This property is calculated from sieve analysis data according to ASTM-D-1921, Method A using a 500 g sample. The calculations are based on the weight fractions collected 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 / n? is used as stationary phase Styrogel Size Sequence malfunctions occur 10 ^, 10 ^, 10 ^, 10 ² 6 nm and perchlorethylene as the solvent, operating at 117 ° C. For resins with a density of 940 kg / m &lt; 2 &gt; or higher, Styrogel having a pore size sequence of 10 [mu] m, 10 [mu] m, 10 [mu] m, 10 [mu] m, is used. O-diohlorobenzene is used as the solvent at. 135 ° C. Detection is performed in all cases by infrared radiation at 3.45 / an.

Substances extractable by n-hexane (FDA test used for polyethylene films intended to come into contact with food).

_v 2

A sample of film of 0.038 mm thickness and 1290 cm area is cut into 2.54 x 15.24 cm strips 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 + 1 ° C for 2 hours. The extract is then decanted into a balanced culture dish. After drying the extract in a vacuum desiccator, the culture 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 extractable substances »

Unsaturation

Measurements are performed using an infrared spectrophotometer (Perkin Elmer Model 2.1).

Resins of 0.635 mm thickness are made from the resin and serve as test specimens. Absorbance is measured at 10.35 µm for transvinylidene unsaturation, at 1.1.0 µm for terminal vinyl unsaturation, and at 11.25 µm for vinylidene unsaturation in the side chains. Absorbance per 1 mm thickness of the compact is directly proportional to the multiplicity of the concentration of unsaturation and absorbptivity. Absorbency values are taken from H. J, de Kock, et al., J. Polymer Science. Part B, 2, 339 (1964).

Examples

Preparation of a spray dried precursor

To a 5 L flask equipped with a mechanical stirrer was charged 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 range from 0.007 to 0.05 µm 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 ° C) and 8.9 ml of titanium tetrachloride was added dropwise over 1/2 hour. After the addition of TiCl 2 was complete, the contents of the flask were refluxed for about 1/2 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 under reflux for about 1 hour and then cooled to room temperature with stirring. The resulting product is a yellow-green suspension which is separated into components over a period of about 1 hour.

The slurry is spray dried under an inert atmosphere in a spray drier with two nozzles (nozzle diameter 1.524 mm, ring ring diameter 2.54 mm, spray pressure 68.7 kPa, drying nitrogen inlet temperature 112 ° C), Spherical catalyst particles trapped in cyclone have a mean particle diameter of about 25 µm (based on optical micrographs measurements).

XI 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 fed into the reactor as a dilute solution in a hydrochloric 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.

Procedure B (two-stage activation procedure)

The precursor prepared by the method of 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 activator and precursor are used in an amount to form a partially activated precursor 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 suspension 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 is homopolymerized (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 Method A (Examples 1 to 3 and 5 to 7). ) 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 &lt; 3 &gt;.

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 corresponding to about three to six times Gmf and space / time yield. . 48.7 to 113.5 kg / nP / h. The reaction system described above is used. Its lower part is 3.05 m high and its inner diameter is 0.343 m. The upper part is 4.88 m high and its inner diameter is 0.597 m.

The following Table I, which relates to Examples 1 to 9, summarizes the operating conditions used, i.e. the percentage of the compound of the formula jMgClg] ₂ 5 PM.CI4] [ΤΗΓ] γ, type and amount of filler, Al / Ti molar ratio in 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 particle content in% by weight (<74 µm) ).

Table I

The reaction conditions in Examples 1 to 9

Ex. C. [MgCl ₂ ] _{2> 5} [TiCl ₄ ] [THF] _{7 (0} % by weight) Filler Molar ratio in the partially activated precursor Pulse- lota ° c Molar ratio hydrogen/ / ethylene Molar ratio 1-butene / ethylene Catalyst productivity (ppm Ti) type quantity- ství («) wt. 1 1 6 sublimated oxide Silica 53 0 85 0.200 0.311 7.1 MgCl ₂ 31 2 27 Mar: sublimated oxide Silica 41 0 95 0.508 10.9 MgCl ₂ 32 3 27 Mar: sublimated oxide Silica 41 0 85 0.211 0.301 5.5 MgCl ₂ 32 4 27 Mar: sublimated oxide Silica 41 10 85 0.198 0,302 5.1 MgCl ₂ 32 5 35 A1 ₂ O ₃ 40 0 85 0,209 0.310 3.3 polystyrene 25 6 42 sublimated oxide Silica 40 0 85 0.207 0.300 6.1 polystyrene 18 7 100 ALIGN! - 0 85 0.210 0.430 25.0

continuation of Table

Ex. [MgClJ _R fliClJ [THF] _{7 n} filler Molar ratio in the partially activated precursor Pulse- lota Noc: 2 ° C Molar ratio hydrogen/ / ethylene Molar. ratio 1-butene / ethylene Catalyst productivity (ppm Ti) C. fc ✓ I j (% by weight) type quantity- ství (%) wt. 8 ⁹⁰ sublimated oxide Silica 10 6 95 0.513 18 9 90 sublimated oxide Silica 10 6 95 0,206 9.

Table II

Properties of the polymers produced in Examples 1 to 9

Example Density Melt flow index Ratio speed flow Sypná mass kg / m @ 2 Mean spherical polymer particle size (jum) Very Small Particles Size <74 fxm (%) 1 926 2.3 28 355.0 630 0.6 2 970 4.8 28 455.5 418 4.7 3 924 2.5 27 Mar: 291, 8 757 0.4 4 922 2.3 26 353.4 1 008 0.6 5 927 3.5 26 293.4 848 0.0 6 930 2.7 26 342.0 554 0.4 7 927 1.0 24 243.2 737 - 8 969 6.4 28 . 455.5 787 <2.0 9 959 1.1 28 415.0 863 <2.0

The data from Table II shows that when the precursor is spray dried without containing the filler (Example 7), the bulk density is low. Also, the polymer particles formed in Example 7 are made of a fibrous mass, resembling cotton.

Claims (6)

A process for the catalytic production of ethylene polymers selected from the group consisting of ethylene homopolymers and copolymers using a titanium-containing catalyst at a productivity of> 50,000 kg polymer per kg Ti under a gas pressure of below 6.87 MPa, the polymer being formed in granular form in spherical form having a particle size of from about 250 to about 2550 µm, a density of> 910 to <970 kg / m 2 and a melt flow rate ratio of> 22 to <32, characterized in that the ethylene is homopolymerized or copolymerized at a temperature of 30 to 115 ° C by contacting the monomer feedstock with the spherical particles of the activated catalyst obtainable by a) forms a spherical precursor of the general formula Mg _m Ti ₁ (OR) _n X _p [ED] _q [filler] _r 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 ₄ 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 represents chlorine, bromine or iodine, or a mixture thereof, such that the filler is present in a percentage of from 10 to 95% by weight based on the total weight of the precursor, and a suspension or solution of at least one magnesium compound, at least one titanium compound and at least % of one filler in 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 onto spherical particles of the precursor having a size of about 10 to about 200 µm, wherein the magnesium compound is a compound of formula. MgX ₂ 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 in which 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 cell precursor 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, using as activator compounds of the formula ^{A1 (R>} c ^X d ^H e wherein X * is chlorine or a group of formula OS * and each symbol 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 from 1 or 0, the sum of c + d + e has a value of 3, said activation being carried out after isolation of the particles of said precursor. 2. The process according to claim 1, wherein the polymerization is carried out in a fluidized bed process. 3. The method of claim 2, wherein the gas phase mass flow rate is 1.5 to 10 times the minimum gas mass flow rate required to achieve fluidization. 4. The process of claim 1 wherein the ethylene copolymers are at least one C1-C6 alpha-olefin. 5. The process of claim 4 wherein the ethylene is copolymerized with 1-butene. 6. The process of claim 4 wherein the ethylene is copolymerized with propylene.