CS213374B2 - Method of catalytic production of homopolymeres and copolymeres of ethylene - Google Patents

Description

The invention relates to catalytic homopolymerization and copolymerization of ethylene using highly active complex catalysts containing magnesium and titanium in a low pressure gas phase process to produce ethylene polymers with a density of from 940 kg / m ³ inclusive to · 970 kg / m ³ inclusive with a melt flow ratio as defined below) ranging from 22 inclusive to · 32 inclusive. The particles of the obtained polymers have a relatively round shape and contain a low amount of dust.

Ethylene homopolymers with a density of 960 kg / m ³ and above and a melt index of from about 5 to 50 are suitable for the production of injection molded articles with excellent impact resistance, provided they have a relatively narrow molecular weight distribution. Ethylene polymers with a density of 960 kg / m < ⁵ > and above and a melt flow index of 20 g / 10 min or less can be prepared using the catalysts and low pressure gas phase processes described in U.S. Pat. Nos. 3,023,203, 4,003,712; However, the polymers produced using the chromium oxide catalysts containing chromium oxide, silyl chromate and chromocene according to these patents, however, have a relatively broad molecular weight distribution, as shown by the melt flow rate ratio of 35 or higher. The polymers produced according to these patents therefore have a relatively limited use for injection molding where excellent impact resistance is desired. It is therefore desirable to find catalysts which make it possible to readily prepare ethylene polymers with a relatively narrow molecular weight distribution by a gas-phase process.

In order to be useful in an industrial gas phase process, such as 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, they must have a high activity, i.e. it must have a productivity of at least 50,000 and preferably at least 100,000 kg of polymer per kg of parent metal which forms the catalyst, or higher. This is because such processes in the gas phase generally do not employ any processes to remove catalyst residues. The catalyst residues in the polymer must therefore be so small that they can be in the polymer · leave without causing unwanted problems would arise when resins or when 'heir application ⁵ for the final consumer. The low content of catalyst residues is also important if 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. Chlorine content of 200 ppm or higher is unacceptable for industrial production US Patent No. 3,989,881 discloses the use of a highly active catalyst for a slurry process for the production of ethylene polymers having a relatively low molecular weight distribution Mw / Mn ranging from about 2.7 do 3,1. Attempts have been made to use catalysts similar to those disclosed in U.S. Patent No. 3,989,881 in the production of narrow molecular weight polyethylene by polymerization of ethylene alone or in conjunction with gas-propylene propylene using apparatus and apparatus-like conditions. and the conditions described in U.S. Patent No. 4,011,382 and Belgian Patent No. 839,380. However, these attempts were unsuccessful. ¹ In order to avoid the use of solvents used in the catalyst systems of type suspension disclosed in U.S. Pat. No. 3,989,881, the component containing titanium and magnesium dried. However, the dried substance was in the nature of a viscous, resinous pyrophoric substance which could not be dosed well into the reactor because it was not freely movable. Even when the agitator was mixed with silica and fed to 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 4,035,560 disclose the use of several titanium and magnesium containing catalysts for the production of granular ethylene polymers by a fluidized bed gas phase process at pressures below 20 psig. However, the use of these catalysts in these processes has considerable disadvantages. Using the catalyst of U.S. Pat. No. 3,922,322, polymers having a very high catalyst residue content, i.e. a residue of about 100 .mu.m Ti and more than about 300 ppm Cl, are obtained, as exemplified in this patent. In addition, as exemplified in U.S. Patent No. 3,922,322, the catalyst is used in the form of prepolymers, and very high volumes of catalyst composition need to be fed into the reactor with respect to the volume of polymer produced in the reactor. The preparation and use of this catalyst therefore requires the use of a relatively very large apparatus for the production, storage and transport of the catalyst.

Also, using the catalysts of U.S. Patent No. 4,035,560, polymers containing high amounts of catalyst residues are obtained and the catalyst compositions used appear to be pyrophoric, as is apparent from the types and amounts of reducing agents used in these catalysts.

U.S. Patent No. 4124,532 discloses the polymerization of ethylene and propylene using high; active catalysts. These catalysts include complexes which may contain magnesium and titanium. Said complexes are prepared by reacting a halide of formula MX2 (where M may be magnesium) with a compound of formula M ' Y (where M ' may be titanium and Y a halogen or an organic radical) in an electron donor compound. These; the complexes are then isolated either by crystallization, solvent evaporation, or precipitation.

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

U.S. Patent No. 4124,532, however, does not disclose any special technique or methods of preparing the catalyst to achieve the desired results in the process of the invention described in these floors. The use of the catalysts disclosed in U.S. Patent No. 4,124,532 without these special methods would not result! for 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.

No. 892,322, filed Mar. 31, 1978 (GL Goeke et al., Title: Impregnated Polymerization Catalyst, Process for its Preparation, and its Use in Ethylene Copolymerization) discloses that ethylene copolymers having a density range of about 910 up to 940 kg / m ³ and with a melt flow rate ratio of 22 to 32, including limit values having a relatively low, catalyst residue content and relatively high bulk density, and which provide films with good clarity, to produce relatively high productivity suitable for industrial use to produce gas-phase copolymerization of ethylene with one or more C 3 -C 6 α-olefins in the presence of a highly active catalyst comprising a magnesium-titanium complex prepared under specific activation conditions with an organoaluminum compound which is impregnated into 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. If the partially activated and impregnated precursor has been converted to a form effective in ethylene polymerization, an additional activator must be introduced into the polymerization reactor. Activation of the precursor is thus completed directly in the polymerization reactor.

The additional activating compound and the partially activated impregnated precursor are preferably introduced into the reactor via separate lines. The additional activating compound can be injected into the reactor as a solution in a hydrocarbon solvent such as isopentane, hecane or mineral oil. This solution typically contains about 2 to 30% by weight of the activating compound.

When the impregnated catalyst of Application No. 892 322 was tested in the preparation of high density products (940 kg / m &^lt; ³ > and above) at elevated temperature, it was found that the productivity of these catalysts was highly dependent on the amount of electron donor compound (ED) q in the impregnated precursor. Research has shown that the content of the electron donor compound in the impregnated precursor can be controlled to some extent by drying, but it is difficult to control the drying to prepare a re-displaceable precursor with the exact desired electron donor content.

No. 892,037, filed Mar. 31, 1978 (E. Wagner et al., Title: Polymerization Catalyst, Process for its Preparation, and its Use for Ethylene Homopolymerization) discloses that ethylene homopolymers having a density range of 960 up to 970 kg / m ³ and a melt flow rate ratio of 22 to 32, including limit values which 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 homopolymerizes in the presence of a highly active magnesium-titanium complex as a mixed catalyst; with an inert carrier. However, despite the high activity of these catalysts, the polymers produced using this supported catalyst 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 dust fractions, i.e. particles of " size " of 125 μΐη or less.

It has now unexpectedly been found that ethylene homopolymers and copolymers having a density of from about 940 to 970 kg / m ³ , including limit values, and a melt flow rate ratio of from about 22 to 3: 2, including limit values having a relatively high bulk density, they have a relatively high bulk density, relatively little dust, and which 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 polymerization or copolymerization of ethylene 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 carrier and activated under specific conditions.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a process for producing ethylene homopolymers and copolymers having a density of from about 940 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 relatively small amounts of fines (particles of 125 μm or smaller).

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

The process of the invention employs the above-defined impregnated precursor in which q (see below) has a value satisfying q> 1.5 m + 2. The impregnated precursor is partially activated up to 10 moles of activating compound per mole of titanium contained in the precursor and fully activated The partially activated precursor is completed in the reactor with the activating compound in an amount of from 10 to 400 moles inclusive, based on the mole of titanium in the catalyst. This activation process results in a high catalyst activity, and using this activated catalyst gives an ethylene polymer with improved morphology (including relatively low dust content).

The ethylene polymers 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. The melt flow rate (MFR) value of 22 to 32 (including limit values) corresponds to an 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 an Mw / Mn ratio of about 2.8 to 3.6.

Copolymers obtained by the method according to the invention are copolymers comprising a major mol percent (and 97%) and Jato side 'molar ratio to 3% of one or more Cs and Ce ^j olefins which should not contain any branching on any of their carbon atoms, which is closer to the copolymer backbone than the fourth carbon atom. In case of using one! C 3 to C 6 alpha-olefins are obtained by copolymers, in the case of using more C 8 to O beta α-olefins, ter- or tetrapolymers etc. are obtained.

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

The ethylene polymers have a density of about 940 to 970, including limit values. At a given melt index of 213374, the copolymer density can be controlled primarily by the amount of Cs to Cs of the comonomer to be copolymerized with ethylene. In the absence of comonomer, ethylene would polymerize with the catalyst of the present invention to form homopolymers having a density of about 0.96.

The introduction of increasing amounts of comonomers into the polymers results in a gradual decrease in the density of the copolymers. Under the same reaction conditions, the amount of each of the various C 3 to C 6 comonomers needed to achieve the same result varies from comonomer to comonomer.

Increasing the molar amounts of comonomers in the series C3 > C4 > Cs > Ce > C7 > Ce is needed to achieve the same results, i.e. the same density at a certain melt index.

The melt index of homopolymers or copolymers is an image of its molecular weight. Polymers with a relatively high weight have a relatively low melt index. Ultra high molecular weight ethylene polymers have a high load melt index (HLMI) of about 0.0, and very high molecular weight polymers have a high load melt index of about 0.0 to about 1.0 g / 10 min.

Such high molecular weight polymers are difficult to mold in conventional injection molding machines and sometimes even impossible. The polymers produced by the process of the present invention, on the other hand, are easily formed in such a device. They have a melt index at normal load (MI) in the range of from about 0.0 to about 100, preferably in the range of from about 0.5 to 80, and a melt index at high load (HLMI) of from about 11 to about 2000. Melts of polymers produced by the process! according to the invention is dependent on the combination of the polymerization reaction temperature, density, copolymers 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 dialkyl zinc compounds can also be used to further increase the melt index of the copolymers.

The polymers of the invention contain á1 and usually with 0.1 to ,33.3 C = =C double bonds per 1000 carbon atoms, and have a cyclohexane extractable content of less than about 3 and preferably less than about 2% by weight.

The polymers of the invention contain as catalyst residues of the order of up to 20 ppm Ti at a productivity of 50% ^. 000 or higher. 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, in the case of ¹ productivity of 50,000 or higher.

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. Particle size is important in order to easily fluidize the polymer particles in a fluidized bed reactor as described below. These granular substances also have a low dust content (4% based on the total amount of polymer or less), with dust particles being understood to mean particles up to 125 µm in size. As observed by optical microscopy, it is apparent that the granular polymer particles produced according to the present invention have a rounder shape than the granular polymer particles produced according to the aforementioned U.S. Patent Application Serial No. 892,037.

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 items are defined below.

The titanium compound has a structure corresponding to the general formula

Ti (OR) _and X _b 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, and is pure 0, 1 or 2;

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

TiCl 3, TiCl 4, Ti (OC 8 H 5) Cl 3,

Ti '(OCOCH3) Cl3 and Tl (OCOCeHs) C'l3.

The magnesium compound has a structure corresponding to the general formula

MgXž where

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

These magnesium compounds can be used singly or in combination and include compounds of the formulas MgCl 2, MgBra and Mg 2z. 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 10 mol, of the magnesium compound are used per mole of titanium compound.

The titanium compound and the magnesium compound 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. The electron donor compounds are known either under this name or under the name of the Lewis base.

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 Cl to C4 saturated aliphatic carboxylic acids; alkyl esters of C7 to Ce aromatic carboxylic acids, O2 and Ce, and preferably C3 to C4, aliphatic ethers, C3 to C4 cyclic ethers, and preferably cyclic ^Cd: mono- or di The 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 may be used singly or in mixtures.

The content of the etebtrondonor compound [ED] q in the impregnated precursor should have a value of q> 1.5 m +2, and therefore partial activation is a critical step in the preparation of a highly active catalyst to obtain a polymer with attractive particle morphology.

The activating compound has a structure corresponding to the general formula

A 1 (R) _c X _d 'H _e where

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

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

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

A1 (C2H5) S, A1 (C2H5) 2Cl, Al (i-CdH9) 3, Al2 (C2H5) 5Cl3, Al (C1-CdH5) 2H, Al (C6H13) 3, Al (C6H17) 3, A1 (C2H5) ) 2H a

A1 _(C2 H5) 2 (OC2H5).

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.

The substances used as carriers are solid, porous particulate materials 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 aluminum. The carriers are used in the form of dry powders having a mean particle size of about 10 to 250, preferably about 50 to 150 µm.

They 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 when the silica has pores 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 degrees Celsius.

Alternatively, the carrier may 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 imodification 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 of the invention is prepared by first preparing a precursor from a titanium compound, a magnesium compound, and an electron donor compound as follows, and then impregnating the support with the precursor.

The precursor is prepared by dissolving the compound 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 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 the electron donor to reflux. After dissolution of the titanium compound and the magnesium compound, the precursor can be isolated by crystallization or by precipitation of a C 8 -C 6 aliphatic or aromatic 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 particle size of about 10 to 100 (m &^lt; ^{3 &gt};

The precursor compound 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 the precursor per part of the carrier.

Impregnation of the dried (activated) carrier with the precursor can be carried out by dissolving the precursor in the 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 a temperature of up to 70 ° C.

The carrier can 'talk Photogene, white impregnated with the precursor, the ^one added to the raw material solution used to form the precursor composition in the electron donor compound. In this case, the precursor is isolated from the solution. This procedure is preferred for its simplicity. Excess electron donor compound is then removed by drying at a temperature of up to 70 ° C.

Experience has shown that drying of the impregnated precursor results in an electron-donor concentration [ED] q (see below) corresponding to q> 1.5 m + 2. When re-impregnating the impregnated precursor in the case of industrial iaplification, it is expedient to allow some of the elekitrondionor (q > 1.5 m + 2) than risk drying and as a result of the thermal decomposition of the precursor.

The impregnated precursor thus prepared has a composition corresponding to the general formula 1 µg _m Tii (OR) _n X _p (ED] _q where ¹

ED represents an electron donor compound, m represents a number from 0.5 to 56, preferably from 1.5 to 0 including limit values, n represents a number from 0, 1 or 2, p represents a number from 2 to 116, preferably from 6 to 14, inclusive limit values, q represents a number with a value corresponding to q> 1,5 _m 2,

R represents a C 1 to Cu aliphatic or aromatic hydrocarbon radical of the general formula OOR ´, where R až represents a C 1 to Cu aliphatic or aromatic hydrocarbon radical and

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

the elemental titanium (Ti) index means the Arabic number one.

In order to be used in the process according to the invention, the 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.

In the activation of the catalyst according to the invention, the activation is carried out in 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 about 1 to 10: 1. This partial activation is carried out in a hydrocarbon solvent suspension. The resulting product is then dried to remove it. a solvent, at a temperature of 20 to 70 ° C, preferably 50 to 70 ° C. The resulting product has the character of a free-flowing particulate material and can be readily referred to in a polymerization reactor.

The partially activated impregnated precursor is preferably poorly effective as a polymerization catalyst in the process of the invention. In order to activate the partially activated impregnated precursor for ethylene polymerization, an additional activator must be introduced into the polymerization reactor. This completes the activation of the precursor in the reactor. The additional activator compound and the partially activated impregnated precursor are preferably introduced into the reactor 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. The additional activating compound is added to the reactor in an amount such that a total activated Al / Ti molar ratio of about 10 to 400, and preferably about 15 to 60, is achieved in the reactor together with the amount of titanium activating compound listed as partially activated impregnated precursor. the compound introduced into the reactor reacts with the partially activated precursor 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 partially activated precursor impregnated in a carrier are continuously fed into the reactor during polymerization, while providing separate batches of activating 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 or monomers 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, in contact with catalytically. an effective amount of the fully activated precursor (catalyst) impregnated on the support, at a pressure and temperature sufficient to initiate the polymerization.

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

Reaction zone 12 includes a bed of growing polymer particles, formed polymer particles, and a smaller amount of catalyst fluidized (continuous flow of polymerizable and modifying gaseous constituents consisting of make-up gas and gas recycled to the reaction zone). 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 15 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 was 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 the formation of "hot mixes" and that also trap and distribute the pulverulent catalyst in the reaction zone. Upon commencement of operation, a polymeric particle is usually introduced as a base into the reaction zone before the gas stream is introduced. The particles may be identical to the polymer formed or may be different. When different, they are drawn off with the resulting polymer particles as a leading product. Finally, the fluidized bed of the desired polymer particles displaces the starter bed.

The partially activated 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 the passage of gas through the bed. The pressure drop across the bed is equal to or slightly higher than the bed weight divided by the cross-section of the bed, so it is dependent on the reactor geometry.

Make-up gas is fed to the bed ¹ at the same speed as the drawing speed at which particulate polymer product ·. The make-up gas composition is determined by an analyzer 16 located above the bed. The gas analyzer determines the loss of components in the gas to be recycled and accordingly adjusts the make-up gas composition to maintain the composition of the gaseous mixture substantially steady state in the reaction zone.

In order to ensure complete fluidization, the recycle gas and possibly also part ^{1 of} the make-up gas are fed into the reactor via an inlet 10 under the bed. A gas-distributing plate 20 is placed on the inlet 18 to assist 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 14 located above the bed in which the velocity is reduced and the entrained particles fall back into the bed.

Particle separation may be aided by the inclusion of cyclone 22, which may either be part of the speed reducing zone 14 or may be outside the zone. If desired, the recycle gas can then be passed through a filter 24 which is adapted to separate small particles at high flow rates to prevent dust from depositing on the heat transfer surface and on the compressor sheets. .

The recycle gas is then compressed in a compressor 25 and passed through a heat exchanger 26, where it is freed from the heat of reaction before returning to the bed. By constantly removing the heat of reaction, there is no apparent temperature gradient in the upper part of the bed. A temperature gradient exists in the lower 152 to 304 nte bed, between the inlet gas temperature and the bed rest temperature. It has been observed that the bed almost immediately adapts the temperature of the recycle gas above the bed to the bed temperature density so that the bed temperature is substantially constant under steady-state conditions. The recycle gas is fed to the bottom of the reactor through the inlet 18 and into the fluidized bed through the distributor plate 20. The compressor 25 may also be placed upstream of the heat exchanger 26 in the direction of flow.

The distributor plate 20 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 is 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 sieve, a plate with slits, a perforated plate, a plate with caps (analogous to the distillation elbows) and the like. All parts of the plate may be stationary or is a plate as described in U.S. Pat. No. 3,298,792. Whatever the plate design, the plate must disperse the recycle gas between the particles at the bottom of the bed and maintain it in a fluidized state. The board also aims to support a quiet bed of resin particles when the reactor is not in operation. The movable portions of the sheet ¹ may be used to extrude polymer particles retained on or within the sheet.

Hydrogen can be used as the chain transfer agent in the polymerization of the invention. The molar ratio of hydrogen-ethylene which can be expanded ranges from about 0 to about 21.0 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 gas recycle system at 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 (Ra) (Rb) 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 the zinc compound (calculated as Zn) per mole of the titanium compound (calculated as Ti) may be added to the reactor gas feed into the reactor. a dilute solution (2 to 10% 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. supplying a recycle gas from the dispenser adjacent the dispensing device 27.

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 working temperature must be below the sintering temperature. The production of ethylene copolymers by the process of the invention is preferably carried out at a temperature of about 90 to about 105 degrees Celsius. Thereby, polymers having a density of about 940 to 970 kg / m ^{3 are obtained} .

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 2.40 MPa, and when operating at higher pressures within this range, heat transfer is facilitated, since an increase in pressure results increase in unit volume heat capacity of gas.

The partially activated 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 according to the invention are highly active, injection into the space below the distributor plate could result in polymerization being initiated at this point, which could eventually lead to blockage of the distributor plate. On the contrary, injecting the catalyst into the fluidized bed helps to distribute the catalyst in the bed and avoids the formation of sites with high catalyst concentrations which could lead to hot spots.

Under a certain combination of operating conditions, the fluidized bed is maintained at substantially the same height by withdrawing part of the bed as 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 outgoing gas temperature) determines the rate of polymer particle formation at a constant gas velocity.

Preferably, the polymer product particles are collected continuously through a conduit 34 or near the distributor plate 20. The particles are collected in the form of a suspension with a portion of the gaseous stream that is ventilated before the particles settle to prevent further polymerization and caking 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 the separating zone 40 is provided. When valve 38 is closed, valve 36 is opened so that the gas / product mixture passes through zone 40. valve 38 opens to transfer the product to the outer insulation zone. The valve 38 is then closed and closed until the next product withdrawal.

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 and / or scraping devices.

The highly active supported catalyst system of the present invention provides a fluidized bed product with an average particle size of about 0.5 mm to about 1 mm, preferably between about 0.56 mm to 1.0 mm, with the support 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 126 μιη), i.e. 4% or less by weight.

The feed monomer feed 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 1 · 6 · 2.2 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 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.

% by weight). The mixture was stirred for 1/4 hour. The excess solvent was decanted and the solid was collected on a Sparkler filter. The resulting slurry was evaporated in a rotary evaporator under 2 kPa vacuum by slowly flushing with nitrogen at <65 ° C for 16 hours. A dry, free-flowing material is obtained. The inked precursor has the formula

Melt Flow Index (MI):

TiMg2.9Cl9.8 (THF) 9.3

ASTM D-1238-Condition E measurements are performed at 19.0 ° C, g data per 10 minutes.

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

ASTM-D-1238-Oondition F. Measurements are performed using 10 times the load index of the thayenine.

Ratio of flow rates: = flow rate_ melt flow index

Productivity:

The resin product sample is ashed and the ash weight is determined, since 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.

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 measurement according to ASTM-D-1921-Method A using a 500 grams sample. The calculations are based on fractions of mass, the product captured on the sieves.

Example I

Preparation of impregnated precursor

Do autoclave. lined with 380 L glass equipped with a mechanical stirrer are placed 6.0 kg (62.83 mol) of anhydrous magnesium chloride and 195 kg of tetrahydrofuran. To this mixture was added 3.554 kg (18.73 mol) of TiCl4 over 1/2 hour. The mixture was heated at 60 ° C for 1/2 hour to completely dissolve the material. To this mixture was added 45 kg of deionized porous silica at 800 ° C which had been treated with triethyl aluminum (triethyl aluminum content)

The calculated value of q in the formula ^{, -} e 6.4, which is substantially lower than the value of 9.3 determined experimentally.

Example II

Akťvační postup

The required portion of the impregnated precursor and activator compound is placed in a mixing drum together with a sufficient amount of anhydrous all-phathic hydrocarbon diluent, such as isopentane, to form a suspension.

The compound activator and precursor are used in amounts to provide a partially activated precursor having an Al / Ti ratio greater than 0 but less than or equal to 10.

The suspension is stirred vigorously at room temperature and at atmospheric pressure for 1/4 to 1/2 hour. The resulting suspension is dried with a stream of dry inert gas such as nitrogen or argon at atmospheric pressure and at a temperature of 65 + 10 ° C. abv removed the hydrocarbon diluent. 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 powdered material. The particles correspond to the size and shape of the silica particles. The product is not pyrophoric if it contains an alkyl aluminum content of 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 a value of at least 10 to 400: 1, preferably 15 to 60: 1.

Examples laž 7

Ethylene from homopolymers is (Examples 1 to 3 and 5 to 7) and copolymerized with 1-butene (Example 4) in the following series of examples.

212 37 4

In Examples 1 and 2, the catalyst used is prepared as described above except that the partial activation is not carried out but the precursor is fully activated in the triethyl aluminum polymerization reactor in the form of a 5 wt. in order to obtain an activated catalyst with an Al / Ti ratio of 15 to 40 in the reactor.

In Examples 3 to 7, the impregnated precursor is partially activated (by the above activation procedure) in a mixing tank using the aluminum compound listed in Tables I to III in an amount to achieve the Al / Ti ratio shown in Tables I to III. The activation of the precursor in the polymerization reactor is completed with triethyl aluminum in the form of a 5% by weight isopentane solution, in an amount such that an activated catalyst with an Al / Ti molar ratio of 15 to 40 is obtained in the reactor.

In Examples 3 to 7, the impregnated precursor is partially activated by the above activation process in a mixing tank using the aluminum compound listed in Tables I to III in an amount such that the Al / Ti molar ratio shown in Tables I to III is achieved. Completion of the precursor activation in the polymerization reactor is accomplished with a 5% (w / w) solution of triethyl aluminum in isopentane to provide a fully activated catalyst with an Al / Ti molar ratio of 15 to 40 in the reactor.

Each of the polymerization reactions is carried out in a fluidized bed reaction system for 1 hour after reaching equilibrium at 103-105 ° C and 2.06 MPa at a hydrogen / ethylene molar ratio of 0.35 to 0.5-0 velocity of gas corresponding to about three to four times the Gmf value and the space-based yield of 4-6.7 to 97.3 kg / m ² / h. The system described above, shown in FIG., Is used, its lower part being 3.05 meters high and its inner diameter being 0.343 meters. The upper part is 4.88 m high and its inner diameter is 0.57 m.

Tables I to III show the precursor content impregnated in silica, the amount of triethyl aluminum used to treat the silica (% by weight), q measured, q calculated (q calculated as q = 1.5 m-j + 2), the aluminum compound used in the mixing tank, the Al / Ti molar ratio in the mixing tank, and the properties of the crude granular resins produced in these examples, i.e. titanium residue content, bulk density, density, mean particle size, and dust content.

Table I

Influence of excess electron donor compound (tetrahydrofuran, q> 1.5 m + 2) and activity of impregnated catalyst

Example 12 3

Prekursor

The content of the precursor in the precursor impregnated in silica.

[θ / mass] 20

Triethylaluminium content in triethyl aluminum modified silica [% by weight] 8 q (found) 8.0 -0 q (calculated) 8.0

Activation of the precursor in the mixing tank

Aluminum compound -

Molar · Al / Ti ratio -

2-0

8

10.2 9.5

7.4 7.5

Polymer properties

Titanium residue content [ppm] 9

Density [kg / m ³ ] 970

Bulk density [kg / m ³ ] 454

Mean particle size [mm] 0.76

Dust content (<126 µm) [% by weight] 1.6

969

519

0.48

1,2

966

446

1.01

0.2

The data presented in Table I show that when q has a value greater than the sum of 1.5 m-i-2 and there is no partial activation, in the mixing tank (Example 2), the catalyst productivity is very low (Ti-60). q > 1.5 m -1 and partial activation is carried out in the mixing tank (Example 3), i.e. working according to the invention, the productivity is high (Ti-9).

Table. II

Effect of variables in catalyst preparation on catalyst activity

Example 3 4 5 Prekursor Precursor content of the precursor impregnated in silica [% by weight] 20 May 20 May 28 Triethylaluminium content in triethyl aluminum modified silica [% by weight] 8 4 4 q (found) 9.5 9.5 9.3 q (calculated) 7.5 6.5 6.3 Activation of the precursor in the mixing tank Aluminum compound triethylaluminium triethyl aluminum triethylaluminium Al / Ti molar ratio 4 4,5. 2

Polymer properties

Titanium residue content [ppmj 9 ^:

Density [kg / m ⁵ ] 966

Bulk density [kg / m ³ ] 446

Mean particle size [mm] 1.02

Dust content (<125 µm) [% by weight] 0.2

4- 12 955 ' 967 451 405 0.58 0.84 0.5 0.4

The data presented in Table II show that upon changing the precursor content of the precursor impregnated in silica, the triethyl aluminum content of the silica to modify the silica; q (found) and Al / Ti molar ratio yields catalysts having high activity and providing high bulk density polymers with low threshold content.

TableIII '

Effect of Organohaline Activators on Impregnated Catalyst Activity Example 3 6 7

Prekursor

Content of precursor

in a precursor impregnated in silica [% by weight] 20 May 20 May 20 May Triethylaluminium content in triethyl aluminum modified silica [% by weight] 8 4 4 q (found) 9.5 7.6 7.6 q (calculated) 7.5 . 6.2 6.2 Activation of precursor in ¹ mixing tank Aluminum compound EtsAl ⁽¹ >) EtzAlOEt ⁽¹⁾ Al (C 6 H 13) 3 Al / Ti molar ratio 4 6 3 Polymer properties Titanium Residue Content [ppm] 9 14 14 Density [kg / m ⁵ ] 966 966 967. Bulk density [kg / m ⁵ ] 446 444 454 Mean particle size [mm] 1,02 0.53 0.66 Threshold content (<125 jum) [% by weight] 0.2 0.8 0.4

1. EtsAl = aluminum trlefhyl

2. EtaAlOEt = diethylaluminum ethoxide

213

The data presented in Table III shows that using various aluminum compounds to partially activate the precursor in a mixing tank, highly active catalysers can be prepared which provide polymers with high bulk density and low dust content.

Claims (10)

Subject A 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 granules! and has a density of from 940 to 970 kg / m ³ , including limit values, and a melt flow rate ratio of 22 to 12, including limit values, characterized in that: the ethylene is polymerized or bopolymerized with at least one C5 to C6 olefin at a temperature of 30 to 115 [deg.] C. by contacting the montomeric feedstock in a gas phase reaction zone with particles of a catalyst system consisting of a precursor impregnated in a porous carrier, wherein the impregnated precursor has a composition corresponding to the general formula Mg _m Tii (OR) _n X p [ED] _q where ED represents an electron donor compound, m represents a number from 0.5 to · 56 including limit values, n represents a number of 0.1 or 2, p represents a number from 2 to 116 including limit values, q represents a number with a value corresponding to Relation q> 1.5 m -j- 2, R represents a C 1 to C 14 aliphatic or aromatic hydrocarbon radical or a radical of formula COR ', 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, wherein the electron donor 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 partially activated with not more than 10 moles of activating compound per mole of titanium in the impregnated precursor and activation of the partially activated precursor is completed in the reaction zone using more than ynAlez 10 and up to 400 moles of activating compound per mole of titanium in the precursor, the activating compound being a compound of the formula Al '(R') _c X _d , H _e where X 'represents chlorine or a group of the formula OR' and each of the symbols R "and R", which are the same or different, represent a C 1 to C 14 saturated hydrocarbon radical, d is a number from 0 to 1.5, e is a number of 1 or 0, the sum of c + d + e being 3. 2. A process according to claim 1, wherein ethylene alone is used as the monomer. 3. The method of claim 2, wherein the magnesium compound is magnesium chloride. 4. The method 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 tetrahydrofuran. 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 method of claim 7, wherein the carrier is silica treated with at least one activator of the formula AIRs where each of the symbols R, which are the same or different, represents a C 1 -C 14 saturated hydrocarbon radical. 9. The process of claim 1, wherein the process is carried out in a fluidized bed. 10. The method of claim 9, wherein a gas mass flow rate of 1.5 to 10 times Gmf is used.