CS213382B2 - Method of catalytic production of homopolymeres and copolymeres of the ethylene - Google Patents

Description

The invention relates to catalytic polymerization and copolymerization of ethylene using: high; active? complex ·; The catalysts containing magnesium and titanium, in a low pressure stage, in the gas phase, contain ethylene bis (ethylene) having a density of 953 kg / m @ 2. including to; 970 kg / m². -including -s · emcocurrency ratio: melt (defined data) in the range of cd 22, including to. 32 including: Particles of: obtained polymers; have; poměhně. ;; round?' the molded lobe extends' ', low' ',' '' '' '' '' '' '' '' '' '' '' '' '' '' '' '' '' '' '' '' '' '' s yellow shares.

Density ethylene homopolymers. 960 kg / m ³ and; higher, with index; flow:. from 5 to 50; .for the manufacture of injection molded articles having excellent impact resistance in the event that they have a relatively narrow distribution. molecular weight .: Polymers of ethylene with a density of 960 kg / m ³ and higher and with an index? a melt flow rate of 20 g / 10 min or less; prepared by: catalysts; with low pressure: vapor phase processes which are. describes -?,. U.S. Pat. Nos. 3,023,203, 4,003,712: 3,709,853. of catalysts. containing; kys-; Amazonian lichen, silyl chromate and chromocene. according to these patents, however; The molecular weight distribution point, as shown, shows the melt flow rate ratio of 35 and above. The polymers produced according to these patents therefore have a relatively limited use.

2 'for injection molding where excellent impact resistance is desired. It is therefore desirable to find catalysts which would make it possible to readily prepare in the gas phase process. polymers of ethylene and ^{5.-relatively} narrow molecular, weight.

Catalysts ^{5 were} useful; ex. the mystic process; as in the fluidized bed process; according to patent · JJSÁč. No. 3,709,853, 4,003,712, and 4,011382, Canadian Patent No. 991798 to the U.S. Pat. No. 839,380. must. have a high activity, i.e. must. have a product of at least 500,000 and preferably 400,000 / kg of polymer per kg of main polymer; that makes up. catalyst;. not higher. Yippee. ternu ... so ;;, because. ^c : are: such, zpflso-, beeh -v-. gaseous-phase-. usually . not used.-no-! The catalyst residues in the polymer must, therefore, be so small that they can be left in the polymer without: created undesirable .obtíže ¹ at, zpracovánípryskyřicnebo / and applying them in the final zákazníka.- Low; The content of iodine catalyst residues is also important when the catalyst contains chlorine-containing substances such as titanium chlorides, worse and / or. aluminum, used in the so-called, Ziegler. or Ziegter-Natta catalysts. High? content; The chlorine in the molding resin may cause pitting and other corrosion of the metal surfaces of the molding apparatus. A chlorine content of 200 ppm or higher is unacceptable for industrial production.

U.S. Patent No. 3,989,881 discloses the use of a highly active catalyst for a slurry process for producing ethylene polymers having a relatively low molecular weight distribution Mw / Mn ranging from about 2.7 to 3.1. Attempts have been made to use catalysts similar to those described in U.S. Patent No. 3,989,881, in the manufacture of polyethylene with narrow molecular weight distribution by polymerization alone, ethylene, or in conjunction with vapor-phase propylene using a fluidized bed apparatus and conditions with the apparatus and conditions described in U.S. Patent No. 4,011,382 and Belgian Patent No. 839,380. However, these attempts were unsuccessful. To avoid the use of solvents used in the slurry catalyst systems described in U.S. Patent No. 3,989,881, titanium and magnesium containing components were dried. However, the dried substance was in the nature of a viscous, resinous pyrophoric substance which could not be fed well into the reactor because it was not freely movable. Even when this substance was mixed with silica in order to improve mobility (flowability) and fed into the reactor in this form, industrially acceptable results were not achieved. The catalyst productivity was low or the catalyst was pyrophoric and difficult to handle, or the polymer product was obtained in the form of needles that were difficult to float and that had very poor mobility or flowability.

(U.S. Pat. Nos. 3,922,322 and 4,035,500 disclose the use of several titanium-containing catalysts and magnesium for the production of granular ethylene polymers in a fluidized bed gas phase at a pressure of less than 8.87 MPa. Using the catalyst of U.S. Pat. No. 3,922,322, polymers having a very high content of catalyst residues, i.e., a residue of about 100 ppm Ti and more than about 300 ppm Cl, are obtained as shown in the exemplary embodiment of this patent. addition, as shown in the exemplary embodiment, U.S. Pat. No. 3,922,322, the catalyst is used in the form of a prepolymer into the reactor must be dosed very high volumes of the catalyst composition. the preparation and use of this catalyst thus ¹ require the use of relatively bulky device for production , storing and transporting the catalyst.

· • Also for using the catalysts of U.S. Pat. No. 4,035,560 provide polymers containing high amounts of catalyst residues and catalyst composition are obvious, as is apparent from the types and amounts of reducing agents employed in such catalysts ^1, pyrophoric.

U.S. Patent No. 4,124,532 discloses the polymerization of ethylene and propylene using highly active catalysts. These catalysts include complexes which may contain magnesium and titanium. Said complexes are prepared by reacting a halide of formula MXz (where M may be magnesium) with a compound of formula M‘Y (where M * may be titanium and Y a halogen or an organic moiety) in an electron donor compound. These complexes are then isolated either by crystallization, solvent evaporation, or by precipitation.

The polymerization is carried out using these catalyst complexes and the alkyl aluminum compound.

U.S. Patent No. 4,124,532, however, does not disclose any special technique or methods of preparing a catalyst to achieve the desired results for the process of the invention described in these teachings. The use of the catalysts disclosed in U.S. Patent No. 4,124,532 without these special methods would not result in an industrial fluidized bed process suitable for the production of polyethylene on an industrial scale. In addition, the gas phase examples do not disclose a practical copolymerization process suitable for the production of special copolymers having the preferred morphology of the invention described in these teachings.

U.S. Patent No. 892,322, filed Mar. 31, 1978 (GL Goeke et al., Title: Impregnation Polymerization Catalyst, Process for its Preparation and Use in Ethylene Copolymerization) discloses that ethylene copolymers having a density range of about 910 to 940 kg / m ³ and having a melt flow rate ratio of cd 22 to 32, including limit values having a relatively low catalyst residue content and a relatively high bulk density, and which provide films with good clarity, make relatively high productivity suitable for the industrial manufacture by 'copolymerization of ethylene with one or more CS'. up to Cs α-olefins in the gas phase in the presence of a highly active catalyst comprising a magnesium-titanium complex prepared under specific conditions of activation by means of an organoaluminium compound which is impregnated in a porous inert carrier.

The catalyst is activated in at least two stages. In the first step, the precursor impregnated in silica is partially activated by reacting with an amount of activating compound to obtain a partially activated precursor in which the molar ratio of activator to titanium is up to about 10: 1 and preferably about 4 to 8: 1. In order to convert the partially activated and impregnated precursor to the form effective in ethylene polymerization, an additional activator must be introduced into the polymerization reactor. The activation of the precursor is thus completed directly in the polymerization reactor.

The additional activator compound and the partially activated impregnated precursor are preferably fed to the re213382 actor via separate lines. The additional activating compound may be injected into the reactor 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.

However, the activity of the impregnated catalysts prepared by the method described in Patent Application No. 892 322 is not, in some cases, high enough to obtain homopolymers or copolymers of high melt index (greater than or equal to 1) having a density of at least 950 kg / m ³ consisting of % of relatively spherical particles and which would contain a relatively low fraction of sill fractions. Precursors in which q = 1.5 m + 2 (see below) had a lower polymerization activity after two-stage activation (see Table IIIj).

U.S. Patent No. 892,037, filed Mar. 31, 1978 (E. Waigner et al., Title: Polymerization Catalyst, Process for its Preparation, and its Use for Ethylene Homiopolymerization) discloses that ethylene homopolymers having a density range of 960 to 970 kg / m ³ and with a melt flow rate ratio of cd 22 to 32, including limit values that have a relatively low catalyst residue content at relatively high productivity, suitable for industrial production, by a low pressure gas phase process such that ethylene it is homopolymerized in the presence of a highly active magnesium-titanium complex as a catalyst mixed with an inert carrier. However, the polymers produced using the catalyst mixed with the support have the disadvantage that the polymer particles formed during the fluidized bed polymerization are irregular in shape and somewhat difficult to fluidize. The resulting product also contains a relatively high proportion of dusty particles, i.e. particles of 125 µm or less.

It has now unexpectedly been found that ethylene homopolymers and copolymers having a density of about 950 to 970 kg / m ³ , including limit values, and a melt flow rate ratio of about 22 to 32, including limit values having a relatively high bulk density, contain relatively little dust particles and consist of particles of relatively round shape, can be produced with relatively high productivity. These polymers can be manufactured by an industrial low pressure gas phase process by homopolymerization or copolymerization in the presence of a highly active catalyst comprising a magnesium-titanium complex prepared as described below and impregnated in a specified amount in a porous inert support and activated under specific conditions in a polymerization reactor.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a process for the production of ethylene homopolymers and copolymers having a density of about 950 to about 970 kg / m ³ , a melt flow rate ratio of about 22 to 32 with relatively low catalyst residues. m ³ , low pressure gas phase process with relatively high productivity.

It is a further object of the present invention to provide granulated ethylene copolymers whose particles have a rounded shape and which contain a relatively small amount of fine slag fractions (particles having a particle size of 125 μΐα or less).

The attached figure shows a fluidized bed reaction system for a gas phase process in which the catalyst system of the invention can be used.

The method according to the invention solves the above-mentioned tasks. In addition, by omitting activation of the precursor impregnated in the carrier prior to introduction into the reactor in cases where q = 1.5 m, +2 (see below), as described in US Patent Application No. 892 322, high catalyst activity is achieved. while improving the particle morphology of the resulting ethylene polymers.

The ethylene polymers have a melt flow rate ratio of from 22 to 32, preferably from 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 Mw / Mn value in the range of about 2.7 to 4.1 and an MFR value of 25 to 30 (including limit values) corresponds to a Mw / Mn ratio of about 2.8 to 3.6.

The copolymers which can be produced by the process according to the invention are copolymers containing, as a major molar proportion, ethylene (g 98%) and a minor molar proportion of up to 2 o / _{o of} one or more Cs to Ce α-olefins, which contain no branching on any of its carbon atoms which is closer to the copolymer backbone than the fourth carbon atom. Copolymers are obtained in the case of a single C5-C5-olefin, in the case of more C3-C5-olefins, tor- or tetrapolymers, etc. are obtained.

These α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene and 1-cyclone. Preferred α-olefins are propylene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-carbon.

The ethylene polymers have a density of about 950 to 970 kg, preferably 955 to 970 kg / m ³ , including limit values. The density of the copolymer at a given melt index can be controlled primarily by the amount of C3 to Cs comonomer to be copolymer, with ethylene. In the absence of comonomer, ethylene would homopolymerize with the catalyst of the invention to form homopolymers having a density of about 0.96. The introduction of increasing amounts of comonomer into the polymers results in a gradual decrease in the density of the copolymer. Under the same reaction conditions, the amount of each of the various C3 to Cs comonomers required to achieve the same result varies from comonomers to comonomers.

To achieve the same results, i.e. the same density at a certain melt index, increasing molar amounts of colmonomers in a row are needed

Cs> C4> Cs> Ce> C7> Cs.

The melt index of homopolymers or copolymers is an image 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 flow 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 according to the invention, on the other hand, are easily formed in such a device. They have a melt index 'normal load (MI) ranging from about 0.0 and 100, preferably between about 0.5 to 80, and a melt flow index at high load (HLMI) of from about 11 to about ¹ 2000 The melt index of the polymers produced by the process of the invention is dependent on the combination of the reaction temperature at: polymerization, copolymer density, and 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 zinc dialkyl may also be used to further increase the melt index of the copolymers. compounds.

The polymers of the invention generally have from about 0.1 to about 0.3 C = Cn double bonds and about 1000 carbon atoms and have a content of about. 3 and preferably less than about 2% by weight.

The polymers of the invention contain, as catalyst residues, up to 20 ppm. Those at a productivity of 50,000 or more. With respect to the content of chlorine, bromine or iodine residues, the polymers of the invention typically contain less than about 140 ppm of these residues at a ratio of G1, Br or I to titanium 7, in the case of productivity of 50,000 or more.

The polymers of the invention are granular materials having a mean particle size of the order of about 0.5 to about 1.3 mm, and preferably about 0.5 to about 1 mm. The particle size is important for easy fluidization of the polymer particles in the fluidized bed reactor as described below. These ¹ granules! the substances also have a low content of thresholds (4%, based on the total polymer content or less), with dust particles being particles of up to 125 μπι in size. As observed by optical microscopy, it is apparent that the granular polymer particles produced according to the invention have a rounder shape than the granular polymer particles recovered according to the aforementioned U.S. patent application Ser.

The polymers of the invention have a bulk density (bulk density) of about 341 to about 519 kg / m ³ .

The compounds used to prepare the highly active catalyst to be used according to the invention include at least one titanium compound, at least one magnesium compound, at least one electron donor compound, at least one activating compound, and at least one inert substance as a carrier. The individual components are. defined below.

The titanium compound has a structure corresponding to the general formula

Ti (OR) _and X _b where it represents

R C 1 -C 14 aliphatic or aromatic hydrocarbon radical of formula COR ‘, where R‘ represents C 1 -C 14 aliphatic or aromatic hydrocarbon radical,

X is chlorine, bromine, iodine, or a mixture thereof; and a number of 0, 1 or 2, b of a number from 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, TifOC 6 H 5 JCl 3, Ti (COCOCH 3) C 3, and Ti, (OCOC 6 H 5) Cl 3.

The magnesium compound has a structure corresponding to the general formula

MgXZ, where

X represents chlorine, thunder, iodine or a mixture thereof.

These magnesium compounds can be used singly or in combination and include compounds of the formulas MgCl2, MgBrs and Mgla. Of the magnesium compounds, anhydrous magnesium choride 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 10 mol, of the magnesium compound are used per mole of titanium compound.

The titanium compounds and magnesium compounds are conveniently used in a form which facilitates their dissolution in the electron donor compound as described below.

The electron donor compound is an organic compound that is liquid at 25 ° C and in which the titanium compound and the magnesium compound are partially or fully soluble. Electron donor compounds are known either under this name or under the name of the Lewis base.

The term electron donor compounds includes such alkyl esters of aliphatic and aromatic carbonyloxy acids, aliphatic ethers, cyclic ethers and aliphatic ketones, of which the C 1 -C 4 saturated aliphatic carboxylic acid alkyl esters, C 7 -C 6 alkyl esters are preferred. carboxylic acids, C 2 to C 6, and preferably C 5 to C 4 aliphatic ethers, C 5 to C 4 cyclic ethers, preferably C 4 to cyclic mono- or diethers, C 5 to C 6 and preferably C 5 to C 4 aliphatic ketones. butyl acetate, ethyl ether, hexyl ether, tetrahydrofuran, dioxane, acetone and methyl alcohol.

The electron donor compounds can be used individually in mixtures.

The activator compound (activator) has a structure corresponding to the general formula

AIR3, wherein each of the symbols, R, which are the same or different, represents a C 1 -C 14 saturated hydrocarbon radical.

The activating compounds may be used singly or in combination. Examples of such compounds are compounds of formula

A1 (C2HS) 3

Al (i-C4H9) 3,

Al (CeHis) 3.

About 10 to 400, and preferably about 15 to 60 moles of activating compound per mole of titanium compound are used to activate the catalysts used in the present invention.

Substances used as carriers are particulate solid porous substances which are inert to the other components of the catalyst composition and to the other active components of the reaction system. These carriers include inorganic materials such as silica and / or alumina. The carriers are used in the form of dry powders having an average particle size of about 10 to 250 µm, preferably about 50 to 150 µm. These substances are also porous and have a specific surface area of at least 3 and preferably at least 50 m ² / g. Catalyst activity or productivity is also improved in that the silica has pores p having dimensions of at least 8 nm and preferably at least 10 nm and greater. The carrier should be dry, ie not contain absorbed water. The carrier is dried by heating to a temperature of at least 600 ° C. Alternatively, the carrier can be dried at a temperature of at least 200 ° C and then treated with 1-8% by weight of one or more of the alkyl aluminum compounds described above. This modification of the support with alkyl-aluminum compounds provides a catalyst system with increased activity, and using such a catalyst system, the resulting ethylene polymer particles also have improved morphology.

The catalyst used in the process according to the invention is prepared by first preparing a precursor from the titanium compound, the magnesium compound and the electron donor compound as follows, and then impregnating the support with the precursor.

The precursor is prepared by dissolving the titanium compound and the magnesium compound in the electron donor compound at a temperature of about -20 ° C to about the boiling point of the electron donor compound. The titanium compound may be added to the cyclotronic compound before or after the addition of the magnesium compound or simultaneously with the addition thereof. Dissolution of the titanium compound and the magnesium compound can be aided by stirring and, in some cases, heating the two compounds. in an electron donor compound to reflux. Upon dissolution of the titanium compound and the magnesium compound, the precursor can be isolated by crystallization or precipitation of a C 5 -C 6 aliphatic or aroomatic hydrocarbon such as. hexane, isopentane or benzene.

The crystallized or precipitated precursor may be isolated in the form of fine, free-moving particles having a mean size of about 10 to 100 µm and a bulk density of about 292 to about 535 kg / m ³ (after settling).

The carrier is then impregnated with a carrier in a weight ratio of about 0.033 to 1 and preferably 0.1 to 0.43 parts of precursor per part of carrier.

Impregnation of the dried (activated) carrier with the precursor can be carried out by dissolving the precursor in an electron donor compound and then mixing the resulting solution with the carrier. When the carrier is impregnated with the precursor, the solvent is evaporated by drying at 70 ^Q C.

The carrier can also be impregnated with a precursor by adding it to a solution of the raw materials used to prepare the precursor in the electron donor compound. In this case, the precursor is not isolated from the solution. This procedure is preferred for its simplicity. Excess electron donor compound is then removed by drying at a temperature up to. 70 ° C.

During drying, it is necessary to control the electrottdonorm content of compound [ED] _q so that the final value of q is q = 1.5 m + 2. The precursor must therefore be dried carefully, and overdrying and the associated decomposition of the precursor must be carefully avoided.

Thus, the impregnated precursor prepared has a composition corresponding to the general formula

- china & fei. .

Mg _m Tii (OR) _n X _p [ED] _q , i '* where represents

ED electron donor compound, m number from 0.5 to 56, preferably from 1.5 to 5 including limit values, n number · 0, 1 or 2, p purely from 2 to 116, preferably from 6 to 14, including limit values, q a number with a value corresponding to q = 1.5 m + 2,

R 1 to C 14 is an aliphatic or aromatic hydrocarbon residue or a general residue; of the formula C'OR ‘wherein R‘ represents a C 1 to C 14 aliphatic or aromatic hydrocarbon radical, and

X is chlorine, bromine, or iodine, or a mixture thereof.

The elemental titanium (Ti) index is the Arab number one.

In order to convert the impregnated precursor to the form effective in ethylene polymerization, an activator must be introduced into the polymerization reactor. The activator compound and the impregnated precursor are preferably fed to the reactor via separate lines. The activator compound can be injected into the reactor in the form of a solution in a hydrocarbon solvent such as isopentane, hexane or mineral oil. This solution usually contains about 2 to 30% by weight of the activating compound. The activator is introduced into the reactor in an amount such that a total molar ratio Al / T. of about 10 to 400, and preferably about 15 to 60, is achieved. The activator compound introduced into the reactor reacts with the titanium compound and activates it directly in the reactor.

In a continuous gas phase process such as the fluidized bed process described below, separate batches of precursor impregnated in the carrier are continuously fed into the reactor during polymerization, while providing separate batches of activator compound needed to activate the precursor. This replaces the active sites of the catalyst that have been consumed during the reaction.

The polymerization is carried out by contacting the stream of monomer (s) in the gas phase, for example in a 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. a fully activated precursor (catalyst) impregnated on the support, at a pressure and temperature sufficient to initiate polymerization.

The fluidized bed reaction system that can be used in the process of the invention is illustrated in FIG. 1. The reactor 10 consists of a reaction zone 12 and a speed-reducing zone 14.

Reaction zone 12 comprises a bed of growing polymer particles, formed polymer particles, and a minor amount of catalyst fluidized by a continuous flow of polymerizable and de-gasifying gas components formed by the make-up gas and the 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, the appropriate 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 required for fluidization (Gmf). The Gmf designation for the minimum gas mass flow rate required to achieve fluidization is suggested by V. 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 "hot spots" and that trap and distribute the pulverulent catalyst in the reaction zone. Upon commencement of operation, polymeric particles are generally 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 impregnated precursor (catalyst) used in the fluidized bed is preferably stored in a standby container 32 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 passing 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 make-up gas composition is determined by means of an analyzer 16 located above the bed. The gas analyzer determines the loss of components in the gas to be recycled, and the composition of the make-up gas is adjusted accordingly to keep the composition of the gas mixture substantially steady state in the reaction zone.

To ensure complete fluidization, the recycle gas and, optionally, part of the make-up gas is fed into the reactor via an inlet 18 below the bed. Above the inlet 18 there is a gas distribution plate 20 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 piolymerization zone preferably by passing through a zone 14 located above the bed in which the velocity is reduced and the entrained particles fall back into the bed. Particle separation can be aided by the inclusion of a cyclone 22, which may either be part of or outside the speed reducing zone 14. If necessary, the recycle gas can then be passed through a filter 24 which is adapted to separate small particles therein at high flow rates and to prevent dust from depositing on the heat transfer surface and on the compressor sheets.

The recycle gas is then compressed in the pressurized chamber 25 and passed through a heat exchange 26 'where it is freed of reaction heat prior to returning to the bed. By constantly removing 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. It has been observed that the bed almost instantly adapts the temperature of the recycle gas above the 152 to 304 m m bed area to the bed temperature value, so that under steady state conditions the bed temperature is substantially constant. The recycle gas is fed to the bottom of the reactor via an inlet 18 and into the fluidized bed via a distributor plate 20. The compressor 25 may also be placed upstream of the heat exchanger 28.

The distributor plate 20 plays an important role in the operation of the reactor. The fluidized bed contains both the growing and formed polymer particles and the 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 the recycle gas is passed through the bed at a rate sufficient to fluidize the particles at the bottom of the bed. The bottom of the bed is formed by a separating plate 20 and may be a screen, slotted plate, perforated plate, plate with caps (analogous to distillation tray trays) and the like. All plate parts may be stationary or of a movable type such as is a plate as described in U.S. Patent No. 3,298,792. Whatever the structure of the plate, the plate must disperse the recycled gas between the particles at the bottom of the bed and maintain it in a fluidized state. The moving parts of the plate can be used to extrude polymer particles trapped in or within the plate.

hydrogen may 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 may also be present in the gas stream; and reactants. The activator compound is preferably added to the gas recycle system in its hottest part. Preferably, therefore, the activator is introduced into the recycle line downstream of the heat exchanger, such as from the reservoir 27 through line 27A.

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 14 aliphatic or aromatic hydrocarbon radicals.

This further increases the melt index values of the produced copolymers. About 0 to 50, and preferably about 20 to 30 moles of zinc compound (calculated as Zn) per mole of titanium compound (calculated as Ti) can be added to the reactor gas stream into the reactor, preferably in the form of a dilute solution. (at a concentration of 2 to 10 vol _/ weight) in hydrocarbon solvent or · absorbed on a solid diluent material, such as silica, and • in an amount from about 10 to · 50% by weight. These compositions tend pyrofcrické. the zinc compound may feed into the recycle gas stream from the metering device adjacent to the metering device 27.

The fluidized bed reactor must be operated at a temperature below the sintering temperature of the particles, and the operating temperature must be below the sintering temperature. The thylene copolymers of the present invention are preferably prepared at a temperature of about 90 ° C to about 105 ° C. In this case, polymers having a density of about 950 to 970 kg / m @ ^{3 are obtained} .

The fluidized bed reactor is operated at a pressure of up to about 20 psig, preferably at a pressure of about 10 to about 200 psig, while heat transfer is facilitated when operating at higher pressures in this range since the pressure increase is facilitated. results in an increase in the unit volume heat capacity of the gas.

The impregnated precursor is injected into the bed at a rate equal to the rate at which it is consumed by an inlet 30 located above the manifold plate 20. An important feature of the invention is that the catalyst is injected at a point above the manifold plate. Since the catalysts used in accordance with the present invention are active, injection into the space below the manifold plate could result in polymerization being initiated at this point, which could eventually lead to clogging of the manifold plate. Injecting the catalyst in the fluidized bed, in turn, helps to separate the catalyst in the bed and prevents the formation of sites with high catalyst concentrations that could lead to hot spots.

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 a product at the same rate as the particle formation rate 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 outlet gas temperature) determines the rate of polymer particle formation at a constant gas velocity.

1S

The polymer product particles are preferably collected continuously through line 34 or near the distributor plate 20. The particles are collected in suspension with a portion of the gaseous stream that is vented prior to settling, to prevent further polymerization and sintering before the particles reach the zone. where they gather. The suspending gas can also be used to transfer the product from one reactor to another.

The polymer product particles are expediently and preferably removed by means of two sequentially operated time-adjusted valves 36 and 38, between which a separation zone 40 is provided. When the valve 38 is closed, the valve 36 is opened so that gas / product mixture is passed into zone 40. valve 38 opens to transfer the product to the outer insulation zone. The valve 38 is then closed and closed until after the product has been removed.

Finally, the fluidized bed reactor is equipped with a suitable venting system to allow venting of the bed at start-up and shutdown. The reactor does not require the use of any mixing devices and / or wall scraping devices.

The highly active supported catalyst system of the present invention provides a fluidized bed product with an average particle size of about 0.50 to 1.27 mm, preferably between about 0.50 to 1.0 mm, with the carrier catalyst residues in the polymer being unusually small. The polymer particles have a relatively round shape and contain a relatively small amount of dusty particles (less than 125 µm), ie 4% by weight or less.

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

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

A test plate is made and is tempered at 120 ^{° C} for 1 hour to approach equilibrium crystallinity and then cooled rapidly to room temperature. The density measurement is then performed in a density gradient column.

Melt Flow Index (MI)

ASTM D-1238-Condition E. Measurements are performed at 190 ° C, readings in g per 10 minutes.

Flow Rate (High Flow Load Index) (HLMI)

ASTM D-1238-Condition F. The measurement is performed using 10 times the load than the melt index.

Flow Rate Ratio Flow Rate Melt Flow Index

Productivity

A sample of the resin product is ashed and the weight% ash is determined, since the ash is essentially a catalyst. The productivity is therefore expressed in kg of polymer produced per 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. Density

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.

Mean particle size

This value is calculated from the sieve analysis data obtained by measuring pcdle ASTM-D-1921-Methoid A using a 500g sample. The calculations are based on the product fractions by weight trapped on the sieves.

Example I a

Preparation of impregnated precursor

A 12 L flask equipped with a stirrer was charged with 41.8 g (0.439 ml) of anhydrous magnesium chloride and 2.5 L tetrahydrofiurane (THF). 27.7 g (0.184 mol) of titanium tetrachloride are added dropwise to this mixture over 1/2 hour. It may be necessary to heat the mixture at 60 ° C for about 1/2 hour to completely dissolve the substance.

The precursors can be isolated from the solution by crystallization or precipitation and then analyzed for magnesium and titanium, since some of the magnesium and / or titanium compound may have been lost in the precursor isolation.

The empirical formulas used herein to characterize the precursor composition are derived provided that magnesium and titain still exist in the form of compounds that were originally added to the electrioindonor compound. The amount of electronium compound is determined chromatographically.

The impregnated precursor is obtained by adding 500 g of porous silica, dried at a temperature of up to 800 ° C and optionally treated with 4-8% by weight of triethyl aluminum, to the above solution, and stirring for 1/4 hour. The mixture was dried by purging with nitrogen ¹ at 60 ° C for about 3-5 hours. A dry and mobile powder having a particle size equal to the silica particles used is obtained. The absorbed precursor has a composition corresponding to the formula

TiMg _{3 0 10} Cl (THF), _{6, 7}

The calculated q value of 6.5 is in excellent agreement with the 6.7 measured experimentally.

This process can be used to prepare a precursor impregnated on silica treated with triethyl aluminum aluminum. Silicon dioxide previously dehydrated at 800 ° C is treated with triethyl aluminum to form silica modified with 4% w / w triethyl aluminum.

Prikladli)

Preparation of the impregnated precursor from a preformed precursor

In a 121 flask equipped with a mechanical stirrer, dissolve 146 g of the precursor in

2.5 L of dry THF. The solution can be heated to 60 ° C to facilitate dissolution. 500 g of porous silica dehydrated at 800 ° C are added and the mixture is stirred for 1/4 hour. The mixture is then dried by flushing with a stream of nitrogen at a temperature of up to 60 ^° C for about 3-5 hours. A dry, free-flowing powder is obtained having a particle size equal to that of the silica particles.

Example II

Activation procedure

An activator is metered into the polymerization reactor to activate the precursor. The activator is introduced into the reactor in the form of a dilute solution in a hydrocarbon solvent such as isiopentane. These dilute solutions contain about 5 to about 30% by volume of the activating compound.

The activating compound is introduced into a polystyrene. The amount of Al / Ti in the reactor is maintained at least from 10 to 400: 1, preferably from 15 to 60: 1.

Examples 1 to 6

In each of these 6 examples, ethylene is homopolymerized using the catalyst obtained as described above. The silicon dioxide impregnated with the precursor contains 20 to 35% by weight of the precursor. Activation of the precursor in the polymerization reactor is carried out with triethyl aluminum in the form of a 5% w / w isisopenate solution ^; an activated catalyst having an Al / Ti molar ratio of 15 to 40 is obtained in the reactor,

Each of the polymerization reactions was carried out in a fluidized bed reaction system for 1 hour after the equilibrium was reached at 20.06 MPa at a gas velocity corresponding to about three to four times the Gmf and the space and time yields were 48.7 to 48.4.

97.3 kg / m ³ / h. The reaction system described above is shown. 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.

Table I shows the precursor content of the precursor impregnated in silica, the type of silica, the reaction temperature, the hydrogen / ethylene molar ratio, the melt flow rate, the melt flow rate ratio, the density, the titanium content, the mean particle size, the dust content, i.e. the properties of the crude resins produced in these examples.

Reaction conditions using the catalyst of the invention

Example Content Quantity Temperature Molar Index Ratio Density Content Ti-Mean Volumetric content of triethyl aluminum precursor - [° C] speed ratio at [kg / m ³ ] wound size weight breeding in precursor used for hydrogen / melt particle residue flow [kg / m ³ ] st

CM

rH s

P 'P • r— <

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There are those P • »r-1 ~ ^J with a TI of

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-ti

CO 10 10 CQ_ CM CM r rH rH CO CO CM CM rH

Xfl • Sfi

CM 10 CM C * with CM 0 CM 10 10 Tf1 Ttfl CO CO

CO CO rH CO CO xF!> Co co ^ c ^ cn ^ c? θ 'o σ σ' σ '

CD CD 10 0 CM CM tx rH rH rH

Q O WHAT! CQ CO

CD CD

CD what-in what in what CM CM CM CM CM CM o? <Φ cn cm 00 CD CD co CJl honors what [-> oo in cm cm in cp co_ · Φ_> φ MJ, o ’o q o o u o what · what eo co

O) O O O O rH Ή rH rH rH

CO 00 Φ Tp Q «Φ

OOin CM CM CM

O O ID CO CO CO

CM CO by ¹ CO ID

Comparative Examples A and B

The catalyst is prepared as described in U.S. Patent Application No. 892,037 as follows:

III. Preparation of precursor

In a 51 liter flask equipped with a mechanical stirrer, 16.0 g (0.168 mol) of anhydrous magnesium chloride under nitrogen are mixed with 850 ml of pure tetrahydrofuran, and the mixture is stirred at room temperature (about 25 ° C) and 13.05 g ( At the end of the addition, the contents of the flask were refluxed for 1/2 hour to 1 hour to dissolve the solids, the system was cooled to room temperature, and then 3 liters of pure water were slowly added over 1/4 hour. The supernatant was decanted and the solid was washed three times with 1 liter of n-hexane, then the solids were filtered off and dried on a rotary evaporator at 40-60 ° C to give 55 g of a solid precursor.

IV. Activation procedure

Activation is performed by activating the precursor only partially before being fed into the polymerization reactor and completing the activation in the reactor.

400 g of silica are placed in a mixing vessel or drum. The silica is then mixed with enough isopentane to form a suspension. It is usually necessary to use as.i · 4 to 7 ml of diluent per 1 gram of inert carrier ^1. 100 g of precursor is then placed in a mixing vessel and mixed thoroughly with the suspension. The precursor contains 1 ± 0.1 mmol of elemental titanium, based on 1 g of precursor. About 5.0 equivalents of triethyl aluminum are added to the contents of the mixing vessel to partially activate precursor ¹ . The tri-ethyl aluminum is added to the mixing vessel in the form of a solution containing: 20% by weight of triethyl aluminum in hexane. Activation of sel takes place by thoroughly mixing and contacting the triethyl aluminum with the precursor. All the operations described above are carried out at room temperature and at atmospheric pressure under an inert atmosphere.

The resulting suspension is dried under a stream of dry inert gas, such as nitrogen or argon, at atmospheric pressure and at a temperature of up to 60 ° C to remove the hydrocarbon diluent. This usually takes about 3 to 5 hours. The substance is in the form of a freely movable powdered material consisting of a uniform mixture of activated precursor with an inert carrier. The dried non-pyrophoric product is stored under an inert gas.

The partially activated precursor is fed into the polymerization reactor and is activated in the reactor by the activator. The activator is introduced into the reactor in the form of a dilute solution in a hydrocarbon solvent such as isopentane. These dilute solutions contain about 5 to 30 ^µl of activator.

The activator is added to the polymerization reactor in an amount such that the Al / Ti ratio in the polymerization reactor is maintained at from 10 to 400: 1 and preferably from 15 to 60: 1.

Ethylene is homopolymerized using a catalyst prepared as described in Examples I and II as well as a catalyst prepared as described in paragraphs III and IV, which is taken from U.S. Patent No. 892,037. I and II, contains 20% by weight of precursor. This precursor, as well as the partially activated precursor produced by processes II and IV, are activated in the polymerization. of a 5% by weight isopentane solution in order to obtain an activated catalyst with an Al / Ti molar ratio of 30 to 40 in each reactor.

Table II shows the melt flow index, bulk density, particle size, dust content and plasticization time of the granular crude resin produced both using a prior art catalyst (Example A) and using a catalyst produced by the process of the present invention ( Example B).

TABLE II

Comparison of the properties of polyethylene produced using both the known catalyst and the inventive catalyst

Example A B

Melt flow index [g / 10 min] 8.4 8.4 Density [kg / m ³ ] 968 970 Bulk density [kg / m ³ ] 487 415 Particle size [mm] 0.56 0.66 Dust content (<125 μπι) [° / o weight] 10.4 3.8 Plasticizing time ¹ ) [s] 17.5 12.0

The time it takes to prepare the molten polymer from the resin in a standard injection molding machine.

The data presented in this table show that the substances produced by the process of the invention contain less dusty fractions and exhibit a lower plaistification time.

Comparative Examples C and D

A catalyst is prepared as described in U.S. Patent Application Serial No. 892,322 as follows:

V. Preparation of the impregnated precursor

The impregnated precursor was prepared as described in Example 1a.

VI. Activation procedure

The desired weight of impregnated precursor and activating compound is placed in a mixing drum together with a sufficient amount of anhydrous aliphatic hydrocarbon diluent such as isopentane to form ¹ suspension.

The activator compound and the precursor are used in amounts to obtain a partially activated precursor having an Al / Ti ratio greater than 0 but less than or equal to 10. A preferred ratio is 4 to 8: 1.

The suspension is stirred vigorously at room temperature and at atmospheric pressure for 1/4 to 1/2 hour. The resulting suspension is dried by drying a dry inert gas such as nitrogen or argon at atmospheric pressure and at a temperature of 65 ± 10 ° C to remove the hydrocarbon diluent. This usually takes about 3 to 5 hours. The resulting catalyst is in the form of a partially activated precursor impregnated in the pores of silica. The substance is in the form of a freely movable powder-like material. The particles correspond to the size and shape of the silica particles. The product is not pyrophoric when the aluminum alkyl content is up to 10% by weight. It is kept under a dry inert gas, such as nitrogen or argon, until use. It is ready for introduction into the polymerization reactor where complete activation is then performed.

When an additional activating compound is introduced into the polymerization reactor to complete activation of the precursor, it is metered into the reactor as a dilute solution in a hydrocarbon solvent such as isopentane. These dilute solutions contain about 5 to about 30% by volume of the activating compound.

The activator compound is introduced into the polymerization reactor in an amount such that the Al / Ti ratio in the reactor is maintained at least from 10 to 400: 1, preferably from 15 to 60: 1.

In each of Examples C and D, ethylene is copolymerized using a catalyst prepared according to Processes V and VI. The precursor impregnated with silica (q - calculated - 6.5, q - found - 6.5) contains 15% by weight (Example CJ and 20% by weight (Example D) of the precursor. Partially activated precursor (Al / Ti = 5) is completely activated in the polymerization reactor with triethyl aluminum in an amount to obtain an activated catalyst with an Al / Ti molar ratio of 30 to 40 in the reactor.

Each of the polymerization reactions was carried out for more than 1 hour after equilibration at a pressure of about 20 psig and at a temperature of 105 ^° C as described above.

Table III shows the precursor content of the precursor impregnated in silica, the hydrogen / ethylene molar ratio, the melt flow rate, the melt flow rate, the density, the content, the titanium residues, the mean particle size, the bulk density and the dust content. the properties of the crude resins produced in these examples.

• TABLE III

Properties of polyethylene produced using prior art catalysts

Example C D

The precursor content of the precursor impregnated in silica [o / o by weight] 15

Hydrogen / ethylene molar ratio 0.358

Melt Flow Index [g / 10 min] 6.2

The melt flow rate ratio was 26.7

Density [kg / m ³ ] 969

Ti residue content [ppm] 25

Mean particle size [mm] 0.48

Bulk density [kg / m ³ ] 465.5

0.381

7.1

25.8

969

0.51

455.8

The data presented in Table III show that polyethylene produced using prior art catalysts contains much higher titanium residues than polyethylene produced using the catalyst of the invention.

Claims (10)

Process for the catalytic production of ethylene homopolymers and copolymers using a titanium-containing catalyst at a productivity of at least 50,000 kg of polymer per kg of titanium under a gas pressure of below 6.87 MPa, the polymer being formed in granular form and having a density of 950 to 970 kg / m ³ , including limit values, and a melt flow rate ratio of 22 to 32, including limit values, characterized in that the ethylene is polymerized or copolymerized together with at least one of Cs-Ce α-olefin at 30 to 115 ° C so that the monomer feed is contacted in the gas-phase reaction zone with particles of a catalytic system consisting of a precursor impregnated in a porous support, the impregnated precursor having a composition corresponding to the general formula Mg _m Ti, (OR _{i n} X _p [ED i _q , where represents ED electron donor compound, m number from 0,5 to 56, including limit values, • n number 0,1 or 2, p number from 2 to · 116, including limit values, q number with value corresponding to q = 1,5 m + 2, R is a C 1 to C 14 aliphatic or aromatic hydrocarbon radical or a radical of formula COR ‘, where R‘ represents a C 1 to C 14 aliphatic or aromatic hydrocarbon radical, X is chlorine, bromine or iodine, or a mixture thereof, wherein the elephetroindoruoro compound is a liquid organic compound in which the precursor and titanium and magnesium containing components thereof are soluble selected from the group consisting of alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ethers and aliphatic ketones, wherein the impregnated precursor is activated OF THE INVENTION in the reaction zone at least 10 and up to 400 moles of activator, based on mol of titanium in the precursor, and the activator used is a compound of the formula AIR3 where each of the symbols R, which are the same or different, represents a C 1 -C 10 saturated hydrocarbon radical. 2. A process according to claim 1, wherein only ethylene is used as the monomer. 3. A process according to claim 2 wherein the magnesium compound is magnesium chloride. 4. The process of claim 2 wherein the electron donor compound is at least one ether. 5. The method of claim 4 wherein the electron donor compound is tetrabydrofuran. 6. The process of claim 2 wherein the titanium compound is titanium tetrachloride. 7. The method of claim 2, wherein the carrier is silica. 8. The process of claim 7 wherein the carrier is silica treated with at least one activator of the formula AIR3 where each of the symbols R, which are the same or different, represents a C 1 to C 14 saturated hydrocarbon radical. 9. Process according to claim 1, characterized in that the process is carried out in a fluidized bed process. 10. The method of claim 9, wherein the gas flow rate is about 1.5 to 10 times the Gmf.