CS257260B2 - A method for producing a homopolymer of ethylene or copolymers of ethylene with at least one α-olefin - Google Patents

Abstract

A process for producing a homopolymer of ethylene or ethylene copolymers with at least one C 3 -C 4 α-olefin by gas phase polymerization at 10 to 115 ° C using a catalyst system comprising A) a precursor supported on a carrier consisting of 1) vanadium compound which is the reaction product of a vanadium halide, wherein the halogen is chlorine, bromine or iodine and an electron donor, which is a liquid organic Lewis base in which the aldehyde halide is soluble, 2) the MXa modifier, where M is boron or the radical AlR (3a), wherein R is independently of one another with the proviso that the total number of aliphatic carbon atoms in any R group is not greater than 14, X is chlar, bromo or iodo and a is 0, 1 or 2 with the proviso that when M is boron denotes 3 and 3) a solid inert support comprising silica or alumina, on which the vanadium compound and the modifier are r applied. B) AIR3 cocatalyst, wherein R is as defined above, and C) R c is CX (4-b), wherein R 'is hydrogen or unsubstituted or halogenated alkyl having up to 6 carbon atoms, X' is halogen and b is 0, 1, or 2.

Description

The invention relates to a process for producing a homopolymer of ethylene or a copolymer of ethylene with at least one alpha-olefin having 3 to 10 carbon atoms by gas phase polymerization using a modified vanadium catalyst. The polymers obtained have a desirable property profile suitable for certain applications.

Polyethylenes with a relatively broad molecular weight distribution have extensive applications in wire and cable insulation and can be used for blow molding and pipe production. Such polyethylenes with a broad molecular weight distribution, such as those disclosed in U.S. Patent No. 3,324,095 (Carrick et al.), are unstable due to their relatively high level of unsaturation. Polyethylenes with a relatively narrow molecular weight distribution can be produced in the gas phase, such as those disclosed in U.S. Patent No. 4,302,565 (Gocke et al.) and U.S. Patent No. 4,302,566 (Karol et al.). Such gas phase polymerization processes use high activity catalysts to produce polyethylenes with low unsaturation, which have high utility in a variety of film applications. However, such polyethylenes have limited utility in other areas where higher melt flow and extrusion capabilities are required, and lower melt fracture of polyethylene with a broad molecular weight distribution. It would therefore be desirable to develop a highly active catalyst system and process for the gas phase production of highly saturated polyethylene having a broad molecular weight distribution.

Vanadium catalysts are used to produce polyethylenes. U.S. Patent No. 3,956,255 (Ort) describes a catalyst system for the polymerization of ethylene which essentially consists of a vanadium compound reacted with an alkylaluminum alkoxide and a trialkylaluminum. This catalyst system is supported on silica which has been previously reacted with an alkylaluminum or alkylaluminum alkoxide. A halogenated alkane may optionally be used as a promoter.

U.S. Patent No. 4,173,698 (Kanoh et al.) describes a catalyst for the polymerization of ethylene which is a product formed by a complex of vanadium chloride and an ether, combined with an aluminum halide. The product is not supported. An organoaluminum compound is used as a cocatalyst.

U.S. Patent No. 4,202,958 (Yamaguchi et al.) relates to a process for the polymerization of ethylene using an unsupported solid catalyst obtained by the reduction of vanadium halide with an organoaluminum compound in the presence of an ether compound. Here too, an organoaluminum cocatalyst is used.

U.S. Patent No. 4,263,171 (Shida et al.) is a representative publication relating to catalysts for the polymerization of olefins using magnesium-containing compounds. The patent discloses a catalyst supported on silica formed of a magnesium-aluminum complex with a halogenated transition metal compound (including vanadium).

U.S. Patent No. 4,294,947 (Doerk et al.) describes the copolymerization of ethylene with 1-butene in liquid 1-butene as a solvent using an unsupported catalyst comprising the reaction product of vanadyl chloride and/or alkoxide with alkylaluminum chloride and organoaluminum cocatalysts.

Many of these prior art publications are directed to obtaining a catalyst with high activity or to selectively improve individual polymerization processes or properties of polyethylene. Due to the complexity, it has not been possible to obtain an industrially suitable optimized gas phase process using a vanadium catalyst for the production of polyethylenes with the desired balance of properties prior to the present invention. To achieve such a process, the catalyst must provide a better response to hydrogen in order to achieve a very low level of unsaturation of the polyethylene.

It must also exhibit a high degree of productivity so that the catalyst residue in the polyethylene is so small, preferably less than 10 ppm vanadium, that it would allow it to remain therein and the catalyst removal step to be omitted. The catalyst must also provide polyethylene that is easily formed by various forming methods, i.e. polyethylene that has a relatively broad molecular weight distribution and a wide range of melt flow index. The catalyst must also allow for increased copolymerization of ethylene with other alpha-olefins so that the density of the polyethylene can be controlled over a wide range and the palette of usable comonomers can be expanded. The polyethylene obtained using such a catalyst should have a high bulk density so that handling and transportation costs are commercially acceptable. The particles of the polyethylene obtained must be of a size that can be easily suspended in a fluidized bed reactor and must have a low content of dusty fines. The resulting polyethylene should be in the form of loose particles and should not contain agglomerates such as sintered particles or lumps. The catalyst must meet all these criteria simultaneously and at the same time the catalytic system should be as simple as possible. Preference is given to catalytic systems with a minimum number of components.

The subject of the invention is a method for producing an ethylene homopolymer or an ethylene copolymer with at least one alpha-olefin with 3 to 10 carbon atoms by gas phase polymerization using a modified vanadium catalyst, characterized in that the monomer or their mixture is brought into contact with a catalytic system containing at a temperature of 10 to 115 °C.

A) a precursor supported on a carrier essentially consisting of

1) vanadium compounds, which are reaction products,

a) vanadium halide, where halogen is chlorine, bromine or iodine and

b) an electron donor, which is a liquid organic Lewis base in which vanadium halide is soluble,

2) modifier of general formula I

MX _and (I) where

M represents boron or the radical All^ ₃ _ _a ) , in which R represents independently of each other alkyl groups with the proviso that the total number of aliphatic carbon atoms in any R group is not higher than 14,

X represents chlorine, bromine or iodine and a represents 0, 1 or 2 with the proviso that when M represents boron, a represents 3 and

3) a solid inert carrier, consisting of silicon dioxide or aluminum oxide, on which the vanadium compound and the modifier are deposited,

B) cocatalyst of general formula II air ₃ where

R has the meaning given above and

C) promoter of general formula III

R , CX , _Λ i» b (4-b) (II) (III) where

R' represents hydrogen or an unsubstituted or halogenated alkyl group containing up to 6 carbon atoms

X' represents halogen and b represents 0, 1 or 2.

Polyethylenes produced in this way have a better balance of flow properties, molecular weight distribution, bulk density and saturation. Their density and melt flow index can be selected over a wide range.

The polyethylene produced by the process of this invention is a homopolymer of ethylene or a copolymer of a majority mole fraction, i.e. at least about 50%, of ethylene and a minor mole fraction, i.e. less than about 50%, of one or more alpha-olefins having 3 to 10 carbon atoms. Preferred alpha-olefins are propylene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene. Other monomers may be used, including conjugated or non-conjugated dienes such as butadiene, 1,4-hexadiene and ethylidene norbornene.

The polyethylenes prepared by the process of the invention have suitably balanced properties. Their density may lie in the range of about 860 to 960 kg.m . They may have a melt flow index from a value at which there is no flow up to about 300 g/10 min., preferably from about 0.1 to about 50 g/10 min. They have a broad molecular weight distribution, which is defined by the ratio of weight average molecular weight to number average molecular weight (Μ /M ), higher w n than about 10, preferably in the range of about 14 to 22. They also have a high bulk density

- -3 -3 at least about 320 kg.m , preferably in the range of about 384 to about 512 kg.m . Their level of unsaturation is very low and tends to be less than 1 carbon-carbon double bond per thousand carbon atoms (C = C/l 000 C), preferably less than about 0.2 C = C/l 000 C and particularly preferably less than about 0.1 C = C/l 000 C. The copolymers have a residual catalyst content of less than about 10 ppm, preferably less than 6 ppm, expressed in parts of vanadium metal per million parts of copolymer. Preferred polymers produced by the gas phase process of the present invention are in the form of free-flowing solids that are substantially free of agglomerates in the form of sintered particles or lumps.

The polyethylenes of this invention are suitable for a wide range of applications, including use in blow molding, film and tube production, extrusion coatings, as well as for application to wires and cables.

The catalytic system of the present invention consists of a supported precursor, a cocatalyst and a promoter. The supported precursor essentially consists of a vanadium compound and a modifier which are impregnated on a solid inert support. The vanadium compound in the precursor is a reaction product formed from a vanadium halide and an electron donor. The halogen in the vanadium halide is chlorine, bromine or iodine or mixtures thereof. A particularly preferred vanadium halide is vanadium chloride of the formula VCl^.

The electron donor is a liquid organic Lewis base in which the vanadium trihalide is soluble. The electron donor is selected from the group consisting of alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic esters, aliphatic ketones, aliphatic amines, aliphatic alcohols, alkyl and cycloalkyl ethers and mixtures thereof. Preferred electron donors are alkyl ethers and cycloalkyl ethers, especially tetrahydrofuran. Each molar part of vanadium is in the form of a complex with about 1 to about 20, preferably about 1 to about 10 and particularly advantageously about 3 molar parts of electron donors.

As a modifier of the general formula I, alkylaluminum mono- and dichlorides with 1 to 6 carbon atoms in the alkyl group or boron trichloride are preferably used in the precursor applied to the carrier. The use of diethylaluminum chloride is particularly preferred. About 0.1 to about 10, preferably about 0.2 to about 2.5 molar parts of modifier are used per 1 molar part of electron donor.

The carrier is a solid, porous, particulate material that is inert to polymerization.

The carrier consists essentially of silica or alumina, i.e. silicon dioxide or aluminum oxide, or mixtures thereof. If desired, the carrier may contain other substances, such as zirconium dioxide or thorium dioxide or other compounds which are chemically inert to the polymerization, or mixtures thereof.

The carrier is used in the form of a dry powder with an average particle size of between about 10 and about 250, preferably between about 20 and about 200, and most preferably between about 30 and about 100 microns.

2-1 ~ 2 -1

The porous support has a specific surface area of at least about 3 m .g and preferably at least about 50 m .g . A preferred support is silica having a pore size of at least about 8 nm, preferably at least 10 nm. The support is pre-dried by heating to remove water, preferably at a temperature of at least about 600 °C.

The amount of carrier used is selected to achieve a vanadium content of about 0.05 to about 0.5 mmol vanadium per gram (mmol V/g), and preferably between 0.2 to about 0.35 mmol V/g, particularly suitably about 0.25 mmol V/g.

The support is not usually pretreated by reaction with an aluminum alkyl compound prior to forming the supported precursor. Such treatment results in the formation of aluminum alkoxides which are chemically bound to the support molecules. The present inventors have discovered that the use of such a treated support in the catalytic system of the process of the present invention is not only unnecessary but results in undesirable agglomeration when used in the production of high-density polyethylene.

-3 . , density (higher than 0.94 g.cm ). This results in a lumpy product that is not free-flowing.

Furthermore, the present inventors have also discovered that the presence of a magnesium compound in the supported precursor does not significantly increase the activity of the catalyst and therefore the magnesium compound is an unnecessary component.

Preferred cocatalysts of formula II include trialkylaluminum compounds having 2 to 8 carbon atoms in each alkyl group. A particularly preferred cocatalyst is triisobutylaluminum. The cocatalyst is used in an amount of between about 5 and about 500, preferably between about 10 and about 50 moles per mole of vanadium.

Preferred promoters of formula III include fluorine, chlorine or bromine substituted ethane or methane containing at least 2 halogen atoms attached to a carbon atom. Preferred promoters include CCl2, CHCl2, CHCl3, CBr2, _CFCl3 , CHCl3CCl2 and CFCl3CCl2. Particularly preferred promoters are methylene dichloride ( _CH2Cl2 ), 1,1,1-trichloroethane (CH2CCl2) and chloroform (CHCl2). Between _about 0.1 and about 10, preferably between about 0.2 and about 2, molar parts of promoter are used per 1 molar part of cocatalyst.

The catalyst system of the present invention is prepared by first preparing a precursor supported on a support. In one embodiment, the vanadium compound is prepared by dissolving the vanadium halide in the electron donor at a temperature between about 20°C and the boiling point of the electron donor for several hours. The mixing is preferably carried out at about 65°C for about 3 hours or more. The vanadium compound thus prepared can be carried out by adding the support in the form of a dry powder or suspension in the electron donor or other inert solvent. The liquid is removed by drying at a temperature below about 100°C for several hours, preferably at a temperature of about 45 to about 90°C for about 3 to 6 hours. The vanadium-impregnated support is then mixed with a modifier dissolved in an inert solvent, such as a hydrocarbon. The liquid is removed by drying at temperatures below about 70°C for several hours, preferably at a temperature between about 45 and about 65°C for 3 hours.

The cocatalyst and promoter are added to the supported precursor either before and/or during the polymerization reaction. The cocatalyst and promoter are added either together or separately and either simultaneously or sequentially during the polymerization. The cocatalyst and promoter are preferably added separately during the polymerization in the form of solutions in an inert solvent, such as isopentane.

The polymerization of ethylene is carried out in the gas phase using methods well known in the art. Preferably, the polymerization is carried out in a continuous fluidized bed process. In this process, individual batches of the catalyst system and monomers are introduced into the reaction vessel and the polyethylene product is continuously removed from the reaction vessel. The density of the ethylene copolymer produced can vary widely depending on the amount of alpha-olefin comonomer added and its type. The higher the molar fraction of the alpha-olefin added, the lower the density of the copolymer is achieved.

The polymerization is carried out at a temperature below the sintering temperature of the polyethylene. The operating temperature is usually in the range of about 10 to about 115°C. The preferred operating temperature varies depending on the desired density of the polyethylene. High density polyethylenes, i.e., having a density greater than about 940 kg.m ^{-3 ,} are produced at an operating temperature between about 85 and about 115°C, preferably between about 90 and about 100°C. Low density polyethylenes, i.e., having a density in the range of about 910 to about 940 kg.m ³ , are preferably produced at an operating temperature between about 75 and about 90°C. Very low density polyethylenes, i.e., having a density of less than about 910 kg.m", are preferably produced at an operating temperature between about 10 and about 80 °C. In the case of very low density polyethylenes, it is necessary to dilute the reaction mixture with a large amount of diluent gas to prevent the formation of polymer agglomerates and to maintain continuous polymerization operation, as described in the related Czechoslovak Patent No. 250,660 of Union Carbide Corporation.

The fluidized bed reactor operates at pressures up to 6870 kPa and preferably between about 343 and about 2405 kPa.

A transfer agent such as hydrogen may be used to terminate the polymer chains. A typical ratio of hydrogen to ethylene will vary between about 0.001 and about 2.0 molar parts hydrogen to 1 molar part ethylene. The inventors have found that the response to hydrogen is improved using the catalyst system of the present invention, such that less hydrogen is required to produce polyethylene with an extremely low content of unsaturation.

The following examples serve to illustrate the catalytic system and process of the invention. The examples are not intended to limit the scope of the invention.

The properties of the polymers produced in the examples are determined by the methods described below, unless otherwise stated.

test postsFeature

Test procedure

Ash content Polyethylene is converted to ash, which is weighed. Productivity can be calculated, defined as the number of parts by weight of polyethylene produced per 1 part by weight of total catalyst.

Bulk density (kg/m ³ )

It is determined according to the American standard ASTM-D-1 895, method B.

Density (kg.m ³ )

It is determined according to the American standard ASTM-1 605, based on plaques prepared according to the American standard ASTM-D-1 928, procedure C. i

Fines (% by weight) The amount of polymer particles that pass through a sieve with a mesh size of 74.10 ^- ® m.

Melt flow index at higher load (g/10 min) Determined according to American standard ASTM-D-1 238, conditions F.

Average melt flow index Ratio of the melt flow index at higher load to the melt flow index at lower load. The melt flow index at lower load is measured according to the American standard ASTM-D-1 238, condition E.

Property Test procedure

Particle agglomeration

It is determined based on visual observation of the produced polyethylene leaving the reactor.

Unsaturation (C = C/1000 C) ^and is determined by infrared spectrophotometric measurement of absorbance (absorbance at 10.35 micrometers corresponding to trans-vinylidene groups, 11.0 micrometers corresponding to terminal vinyl groups and 11.25 micrometers corresponding to pendant vinyl groups) on a 0.63 mm thick polymer extrusion. The concentration of unsaturation is proportional to the absorbance over 0.025 mm divided by the absorptivity (the values used, absorptivity, were published by RJ deKock et al., in J. Polymer Science, Part B. 2, 339, (1964).

Note:

³ The number of carbon-carbon double bonds per 1,000 carbon atoms.

The abbreviations used in the examples have the following meanings:

Marking Explanation of meaning DEAC Diethylaluminum chloride ED A compound that acts as an electron donor TEAL Triethylaluminum THF Tetrahydrofuran TIBA Triisobutylaluminum TnHAL Tri-n-hexylaluminum EADC Ethyl aluminum dichloride

The catalyst systems used in the examples are prepared using the following standard procedures. To a flask containing 4 liters of anhydrous tetrahydrofuran is added 34 g (0.216 mol) of vanadium chloride. The mixture is stirred for 5 hours at 65 °C under nitrogen until the vanadium chloride dissolves. To this solution is added 800 g of silica, which has been dehydrated by heating to 600 °C, and stirring is continued for 4 hours at 65 °C. In Comparative Examples A to D, the silica was pre-treated chemically with 5.5% by weight of triethylaluminum. The flask is vented and the solution is dried to a slurry-like state at 70 °C. The temperature is allowed to drop to 45°C and the solution is purged with nitrogen for 6 hours or until the tetrahydrofuran level in the final product drops to 4 to 10% by weight. The impregnated silica produced in this manner is a solid powder containing 0.25 mmol of vanadium per gram. The solid is removed from the flask and stored under nitrogen.

Then, except for Comparative Example C, the modifier is introduced using the following procedure. To a flask containing 4 liters of anhydrous isopentane is added 500 g of the impregnated silica described above. To this mixture is added, with stirring, a 25% by weight solution of diethylaluminum chloride, as the modifier, in anhydrous hexane. The modifier is used in such an amount as to achieve the number of moles of modifier per mole of tetrahydrofuran in the vanadium compound as given in the examples. This mixture is heated to 45°C and purged with nitrogen for 3 hours or until the product is in the form of a free-flowing powder.

The vanadium precursor thus produced is then removed from the flask and stored under nitrogen.

Polyethylene is produced in a fluidized bed reactor using the following standard procedure and operating conditions summarized in Table I. Ethylene is copolymerized with the comonomer listed in the examples. The triisobutylaluminum cocatalyst is added during the polymerization as a 5% by weight solution in isopentane. Chloroform CHCl 3 is added, except in Comparative Example D, as a 5% by weight solution in isopentane, unless otherwise stated, in the ratio to the cocatalyst listed in the examples.

Each polymerization is carried out continuously for more than one hour after equilibrium is reached at a pressure of about 2061 kPa and at the gas velocity, nitrogen gas concentration and temperature indicated in Table I.

Examples 1 to 8 and Comparative Examples A to D

In these examples, high density ethylene copolymers are prepared using various catalyst systems. The above procedures are used and the parameters are given in Table I. Examples 1 to 6 show an embodiment of the invention in which 1-butene is copolymerized. Examples 7 and 8 relate to another embodiment of the invention in which 1-hexene is copolymerized. Comparative Examples A to D use an inert support which has been chemically treated with an aluminum alkyl prior to impregnation. Comparative Example C uses a catalyst system without a modifier. Comparative Example D uses a catalyst system without a promoter.

The analysis of polyethylene using the test procedures described above is given in Table I.

Table

Data relating to the use of catalysts of the invention and comparative catalysts in the production of high density ethylene copolymers.

Example number 1 2 3 4 5 6 Catalyst: Modlficator DEAC DEAC DEAC DEAC DEAC DEAC Promoter CHCl ₃ and CHCl ₃ and CHC1 ₃ I want ₃ I want ₃ I want ₃ Modifier/tetra- ratio hydrofuran 0.9 0.9 0.9 0.9 0.9 0.9 Pre-processing carriers not reported not reported not reported not reported not reported not reported coven coven coven coven coven coven Cocatalyst TIBA TIBA TIBA TIBA TIBA TIBA Promoter/coca ratio talysator 2.0-2.22 2.0-2.22 2 2 2 1.66 Aluminum/vanadium ratio 20-25 20-25 20-25 20-25 20-25 20-25 Polymerization: « Temperature (°C) 100° 100° 100° 100° 90° 100° Gas velocity (mS ¹ ) 0.61 0.61 0.61 0.61 0.61 0.61 Nitrogen pressure (% molar) 10 10 10 10 10 10 Comonomer 1-butene 1-butene 1-butene 1-butene 1-butene 1-butene Comonomer/ethylene ratio 0.006 0.006 0.002 0.002 0.006 0.002 Hydrogen/ethylene ratio 0.061 0.05 0.051 0.046 0.045 0.028 Yield per unit area- ru and time (kg.h ^- .m ^-J )' 106 102 90 102 115 128

Table I continued

Example number 1 2 3 4 5 6 Polyethylene: Η· Density (kg.m ) 957 958 958 958 956 954 Melt flow index at Higher load (g/10 min) 33-38 23-27 34-38 23-27 35-38 23-25 melt flow index ratio 70-75 70-75 70-75 70-75 90-95 70-75 Bulk density (kg.m ³ ) 424 424 448 448 432 440 Fine particles (% wt.) 0.01 0.01 0.01 0.01 0.01 0.01 Ash (% by weight) 0.05 0.05 0.052 0.052 0.050 0.048 Particle agglomeration small to small to small to small to small to small to none none none none none none Example number 7 8 A B C D

Catalyst:

Modifier DEAC DEAC DEAC DEAC none DEAC Promoter CHCl I WANT ₃ I want ₃ I want ₃ I want ₃ none Modifier/tetra- ratio hydrofuran 0.9 0.9 0.25 0.95 - 0.95 Pre-processing carriers not reported not reported not reported not reported not reported not reported coven coven coven coven coven coven Cocatalyst TIBA TIBA TIBA TIBA TIBA TIBA Promoter/coca ratio talysator 1.33 1.33 1 2 2 - Aluminum/vanadium ratio 20-25 20-25 20 20 25 12 Polymerization: Temperature (°C) 100 90 100 100 100 100 Gas velocity (ms ¹ ) 0.61 0.61 0.58 0.58 0.34 0.58 Nitrogen pressure (% molar) 16.5 20 15 15 15 15 Comonomer 1-hexene 1-hexene 1-butene 1-butene 1-butene 1-butene Comonomer/ethylene ratio 0.010 0.011 0.002 0.002 0.002 0.009 Hydrogen/ethylene ratio 0.022 0.038 0.043 0.03 ^0.07x 0.14x ^: Yield per unit area- ru and time (kg.h ^.m ^) 59 61 88 64 64 64 Polyethylene: _3 Density (kg.m ) 945 943 956-958 956-958 956-958 956 Melt flow index at higher load (g/10 min) 5-6 5-6 20-22 20-22 20-22 20-22 Melt flow index ratio 70-75 90-95 70-75 70-75 70-75 75 -3 Bundle weight (kg.m ) 424 440 416-432 448-464 320-336 ^times 512 Fine particles (% by weight) 0.01 0.01 0.08 0.05 ^8X _r xx 0 Ash (% by weight) 0.036 0.036 0.036 0.025-0.030 0.040-0.045 0.062 ^XX Particle agglomeration small to small to strong strong none none none none

Comment:

In all examples 1 to 8, polyethylene was produced with high bulk density, low fines content, low ash content (i.e. catalyst activity is high), good particle flowability (no agglomeration problems) and good hydrogen response (indicating a low hydrogen/monomer ratio).

Examples A and B illustrate severe agglomeration problems.

a) A 1% by weight solution in isopentane is used instead of a 5% solution.

x_) Worse response to hydrogen, bulk density and higher fine particle content.

xx) Worse response to hydrogen, higher fine particle content and worse activity.

The results shown in Table I show that the catalyst system of the present invention has high activity as evidenced by low ash content and provides products with the desired balance of properties as evidenced by lower hydrogen to monomer ratio (improved hydrogen response), higher bulk density, improved particle flowability and lower fines content. In contrast, agglomeration in Comparative Examples A and B is very severe. In these examples, catalyst systems similar to the catalyst systems of the present invention were used, except that the supports were pretreated with alkyl aluminum compounds. Furthermore, without the presence of a modifier, as in Comparative Example C, the hydrogen response decreases (as evidenced by the increase in hydrogen to monomer ratio), the bulk density decreases and the fines content is higher, all of which cause less desirable values. Similarly, in the absence of promoter, as in Comparative Example D, the hydrogen response is lower, the fines content increases, and the catalyst activity decreases, all of which lead to less desirable values.

Example 9 and Comparative Examples E and F

These examples demonstrate the improved saturation of polyethylene produced using the catalyst system and process of the present invention compared to the results of comparative experiments. The results are summarized in Table II. Example 9 follows the procedures outlined above and produces an ethylene-butene copolymer having the unsaturation levels listed in the table. Comparative Example E follows similar conditions using triethylaluminum as a cocatalyst but without diethylaluminum chloride as a modifier. The polyethylene produced according to the present invention advantageously has reduced unsaturation even compared to the product produced using a very similar catalyst system as in Example E.

Comparative Example F shows the unsaturation of polyethylene produced by an alternative process previously known and demonstrates that this polyethylene has a significantly higher level of unsaturation, which leads to instability of the polymer, which degrades over time. In contrast, polyethylene produced using the catalyst system and process of the present invention exhibits excellent stability due to the very low unsaturation of the polymer.

Table II

Comparison of unsaturation of polyethylene.

Example 9 Comparative Example E Comparative example Catalyst Modified ^and Unmodified* ³ Silyl chromate ^c vanadium vanadium Unsaturation (C = C/l 000 C) : Trans vinyl 0.010 8 0.019 7 0.038 Terminal vinyl 0.010 4 0.050 8 1,148 Dangled vinylidene 0.061 9 0.081 2 0.106 Total 0.083 1 0.151 7 1,292

Comment:

a) using the catalyst VCl ₃ /THF/SiO ₂ /DAEC/TIBA/CHCl ₃ according to the invention

b) catalyst VCl ₃ /THF/SiO ₂ /TEAL/CHCl ₃ was used at a polymerization temperature of 90 °C,

c) using the polymerization method according to US Patent No. 3,324,095 (Carrick et al.).

Examples 10 to 13

In these examples, low density ethylene copolymers are prepared using the above procedures and the substrates listed in Table III. Examples 10 to 12 illustrate the copolymerization of ethylene with 1-butene. Example 13 illustrates the copolymerization of ethylene with propylene. In all of these examples, triethylaluminum is used as the cocatalyst. The results listed in Table III demonstrate that the catalyst system of the present invention has high activity and, as in the preparation of high density ethylene copolymers, provides products with the desired property profile in the preparation of low density ethylene copolymers.

Table III

Production of low density ethylene copolymers.

Example number 10 11 12 13 Catalyst: Modifier DEAC DEAC DEAC DEAC Promoter CHC1 ₃ CHC1 ₃ I want ₃ I want ₃ Modifier/tetra- ratio hydrofuran 1.0 1.0 1.0 1.0 Pre-processing of the media unprocessed unprocessed unprocessed unprocessed Cocatalyst TEAL TEAL TEAL TEAL Promoter/Cocatalyst Ratio 1.54 1.31 1.22 1.0 Aluminum/vanadium ratio 40 40 40 35 Polymerization: Temperature (°C) 85 85 85 90 Comonomer 1-butene 1-butene 1-butene propylene Comonomer/ethylene ratio 0.139 0.086 0.054 0.13 Hydrogen/ethylene ratio 0.026 0.016 0.014 0.02 Yield per unit area and time (kg.h ^.m ^) 83 82 82 67 Polyethylene: Density (kg.m^) 915 922 927 922 Melt flow index at higher load (g/10 min) 459 9.5 3.4 19 Melt flow index ratio 49 - - - Bundle weight (kg.m ) 378 374 378 448 Fine particles (% by weight) 0 0 0 0 Ash (% by weight) 0.039 0.071 0.082 0.10 Particle agglomeration small to small to small to small to none none none none

Examples 14 to 19

In these examples, very low density ethylene-propylene copolymers are prepared using the above procedures and conditions listed in Table IV. In Example 14, triethylaluminum is used as the cocatalyst instead of triisobutylaluminum. The results listed in Table IV demonstrate that the catalyst system of the present invention can also be used to produce very low density ethylene copolymers having the desired property profile, while the activity of the catalyst system is high.

Production of very low density ethylene copolymers.

Example number 14 15 16 17 18 19 Catalyst: Modifier DEAC DEAC DEAC DEAC DEAC DEAC Promoter Modifier/tetra- ratio CHCl CHC1 ₃ CHC1 ₃ CHC1 ₃ CHCl I want ₃ hydrofuran 1.7 1.7 1.7 1.7 1.7 1.7 Pre-processing not reported not reported not reported not reported not reported not reported carriers coven coven coven coven coven coven Cocatalyst Promoter/Cocatalyst Ratio TEAL TIBA TIBA TIBA TIBA TIBA talysator 1.0. 1.0 1.0 1.0 1.0 1.0 Aluminum/vanadium ratio 40 40 40 40 43 45 Polymerization: Temperature (°C) 75 70 65 50 40 36 Gas velocity (ms ^-1 ) 0.46 0.46 0.46 0.46 0.46 0.46 Nitrogen pressure (* molar) 45 50 59 57 60 60 Comonomer propyl: n propylene propylene propylene propylene propylene Comonomer/ethylene ratio 0.22 0.24 0.26 0.35 0.31 0.34 Hydrogen/ethylene ratio 0.01 0.007 0.006 0.006 0.002 footprints

Yield per unit area

ru and time (kg.h ³ .m ³ ) 66 75 61 43 69 67 Polyethylene: Density (kg.m ^-3 ) 906 895 894 882 871 865 Melt flow index at higher load (g/10 min)27 9 6 20 3 1 Melt flow index ratio 41 53 64 51 - - Bulk density (kg.m ³ ) 432 384 368 320 368 368 Fine particles (% by weight) - - 0.05 0 0 0 Ash (% by weight) 0.10 0.082 0.11 - 0.14 0.07

Examples 20 to 22

In these examples, ethylene is copolymerized with 1-hexene using catalyst systems containing tri-n-hexyl aluminum, ethyl aluminum dichloride or triethyl aluminum as modifiers. The above procedures are followed under the conditions shown in Table V. The modifier is applied to vanadium trichloride-impregnated silica containing 0.2 mmol of vanadium per gram of vanadium chloride-impregnated silica. In each of the examples, triethyl aluminum is used as the cocatalyst. The results summarized in Table V show that a variety of modifiers can be used in the catalyst systems of the invention.

Table V

Use of catalysts with various modifiers.

Example number 20 21 22

Catalyst: Modifier TnHAL EADC TEAL Promoter I want ₃ CHC1 ₃ I WANT.

Table V continued

Example number 20 21 22 Modifier/tetrahydrofuran ratio 0.84 0.84 0.84 Pre-processing of the media unprocessed unprocessed unprocessed Cocatalyst TEAL TEAL TEAL Promoter/Cocatalyst Ratio 1.1 1.1 1.0 Aluminum/vanadium ratio 102 37 38 Polymerization: Temperature (°C) 90 90 90 Gas velocity (ms ^-2 ) 0.55 0.55 0.55 Nitrogen pressure (% molar) 4 10 11.3 Komonoraer 1-hexene 1-hexene 1-hexene Comonomer/ethylene ratio 0.001 8 0.001 8 0.003 Hydrogen/ethylene ratio 0.068 0.067 0.076 ' Yield per unit of space and time (kg.h ^.m ² ) 69 128 102 Polyethylene: Density (kg.ra ² ) 0.957 0.955 0.957 Melt flow index at higher load (g/10 min) 28-30 27-29 23-24 Melt flow index ratio 90-95 95-100 90-100 Bulk density (kg.m ^-2 ) 464 451 467 Fine particles (% by weight) 3.4 ^and 3.3 ^and 1.6 ^and Ash (% by weight) 0.041 0.056 0.054 Particle agglomeration little to none little to none little to none Note: a) passes through a 130 mesh sieve .10 $ (instead of 74, .10~ ⁶ )m.

SUBJECT OF THE INVENTION

Claims (9)

SUBJECT OF THE INVENTION (1) the vanadium compound which is the reaction product; (a) vanadium halide, wherein the halogen is chlorine, bromine or iodine; and (b) an electron donor, which is a liquid organic Lewis base in which vanadium halide is soluble; A process for the production of an ethylene homopolymer or a copolymer of ethylene with at least one C 3 -C 10 alpha-olefin by gas-phase polymerization using a modified vanadium catalyst, characterized in that the monomer or a mixture thereof is introduced at a temperature of 10 to 115 ° C contact with a catalytic system comprising (A) a precursor deposited on a carrier consisting of: 2. The method of claim 1 wherein the electron donor is selected from the group consisting of alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic esters, aliphatic ketones, aliphatic amines, aliphatic alcohols, alkyl and cycloalkyl ethers, and mixtures thereof. 2) a modifier of formula I MX _and (I) where 257260, is boron or a radical All ^ _ _a) in which R are each independently alkyl with the proviso that the total number of aliphatic carbon atoms in any group R is not greater than 14 means a chlorine, bromine or iodine, a is 0, 1, or With the proviso that when M is boron, a is 3 and 3. A process according to claim 1, wherein the vanadium halide comprises chlorine, the electron donor is an alkyl or cycloalkyl ether, the modifier is an alkyl aluminum or mono (C1 -C6) alkyl or boron trichloride, the carrier is silica, the cocatalyst is trialkyl aluminum having 2 to 8 carbon atoms in each alkyl radical and promoter is ethane or methane substituted with fluorine, chlorine or bromine. 3) a solid inert carrier, consisting of silica or alumina, on which the vanadium compound and modifier are deposited. B) a cocatalyst of formula II air ₃ wherein R is as defined above C) a promoter of formula III ^R b ^CX (4-b) wherein (II) (III) R 'is hydrogen or unsubstituted or halogenated alkyl having up to 6 carbon atoms X 'is halogen and b is 0, 1 or 2. 4. The method of claim 1 wherein the vanadium halide is vanadium chloride, the electron donor is tetrahydrofuran, the modifier is diethylaluminum chloride, the carrier is silica, the cocatalyst is triisobutyl aluminum or triethyl aluminum, and the promoter is chloroform. 5. The process according to any one of items 1 to 4 for producing polyethylene having a density greater than or equal to about 5% 940 kg / m ³ , characterized in that the polymerization is carried out at a temperature in the range from 85 to 115 ° C. 6. Process according to claim 5, characterized in that a monomer feedstock comprising ethylene or a mixture of ethylene with propylene, 1-butene or 1-hexene is used. 7. A process according to any one of items 1 to 4 for the production of polyethylene having a density in the range from 910 to 940 kg.m ^-3 , characterized in that the polymerization is carried out at a temperature in the range from 75 to 90 ° C. 8. A process according to any one of items 1 to 4 for the production of polyethylene having a density of less than 910 kg.m wherein the polymerization is carried out at a temperature in the range of from 10 to 80 ° C. 9. A process according to claim 7 or 8, wherein a monomer feedstock comprising a mixture of ethylene with propylene, 1-butene or 1-hexene is used.