SK590489A3 - Method of continual polymerization in gaseous phase of one or more alpha olefins - Google Patents

Description

The present invention relates to a process for the gas phase polymerization of alpha-olefins in a fluidized bed and / or mechanically stirred bed reactor, in the presence of catalysts on the base of the transition elements.

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It is known to continuously polymerize one or more alphaolefins, such as ethylene or propylene, in a gas phase in a fluidized bed and / or mechanically stirred bed reactor in the presence of a Group IV, V or VI transition element catalyst; in particular in the presence of a Ziegler-Natta type catalyst or chromium oxide base catalysts. The polymer particles, when formed, are in a fluid and / or stirred state in a gaseous reaction mixture containing alpha-olefin or affa-olefins which are continuously fed to the reactors. The catalyst is fed continuously or intermittently to the reactors while the polymer is produced in fluid and / or or stirred bed is also withdrawn from the reactor / continuously or intermittently. The heat of the polymerization reaction is essentially removed by the gaseous reaction mixture that passes through the heat exchanger before being recycled to the reactor.

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If the OAAŠem gas-phase polymerization process of alpha-olefins is carried out in the presence of a catalyst / with a higher efficiency, it is possible to ....

observe minor changes during the polymerization, eg by qualitatively weak changes in the catalyst or by a change in the quality of the alpha-olefins used in the reaction, which may induce changes in the course and catalytic activity on the bedding polymer particles. These small variations are known to have an adverse effect in the gas phase polymerization process since the heat exchange capacity in the gas phase is much lower than in the liquid phase. In particular, these small variations may cause an undesirable increase in the amount of heat generated in the reaction and which cannot be removed sufficiently quickly and efficiently by the gaseous reaction mixture passing through the bed and may cause hot spots to appear in the bed and form agglomerates of molten polymer. If hot spots appear in the bed, it is usually too late to prevent agglomerate formation. Still, if ä

the reaction conditions are corrected in a timely manner, in particular; By reducing the polymerization temperature or pressure, or by reducing the rate at which the catalyst is fed to the reactors in order to limit the adverse effects of unexpected superactivation, the amount and size of the agglomerates formed can be reduced to some extent. However, it is not possible to avoid losses in the production of the polymer and reduce its quality during this period. Consequently, it is desirable to avoid these questions; in general, the polymer conditions are chosen to ensure that hot spots and, agglomerates cannot form. The application of such o-s-e-m conditions leads either to a substantial reduction in production or to a deterioration in the quality of the polymer produced, in particular to an increase in the proportion of catalyst residues in the polymer.

This superactivation phenomenon is readily achieved, particularly when using a high yield catalyst; whose polymer efficiency can be influenced by small variations in the impurity content of the polymer medium. This is particularly the case for ZieglerNatt type catalysts based on magnesium, halogen and transition elements such as titanium, vanadium or zirconium. This superactivation phenomenon can also occur with the use of comonomers capable of activating the polymerization of alpha-olefins, particularly in the case of copolymerization of ethylene with alpha-olefins containing 3 to 8 atoms (Polymer Science USSR, vol. 22, 1980, pp. 448). -454).

Soviet patent no. No. 1249025 discloses a process for controlling gas phase alpha-olefin polymerization in the presence of hydrogen and carbon dioxide catalysts. The method is essentially based on adjusting the melt index of the polyolefin, which is a physical property characterizing the molecular weight distribution of the polymer.

The melt index adjustment is accomplished by measuring the relatively high concentration of carbon dioxide in the reactor and by varying the flow rate of the carbon dioxide being fed, thereby causing a change in the specific property of the catalyst polymerization. However, this method does not disclose a method for maintaining substantially constant either the content of the catalyst in the polyolefin produced or the rate of - / Ύ polymerization.

The found process of polymerization of alpha-olefins in the gas phase allows to overcome or at least alleviate the above

In particular, this process allows the continuous production of a polymer with higher productivity and a low content of catalyst residues (independent of the inconceivable minor changes in the quality of the alpha-olefins or catalyst or in the introduction of the catalysts)

It has been discovered that, as a result of this process, it is now possible to produce continuously a polymer of constant and assured quality, with a high degree of reproducibility and high yield, without the formation of agglomerates.

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Thus, the present invention relates to a process for the continuous polymerization of one or more alpha-olefins in a gas phase in a fluidized bed and / or mechanically stirred bed reactor with the aid of a catalyst / activity retarder, characterized in that the polymerization is carried out by introducing the catalyst. on the base of transition metals IV., V. or VI. a group of periodic cross-linking elements to contact alpha-olefin (s) and a very small amount of retardant efficacy, which is introduced continuously into the repertoire at a flow rate that varies with time so that it is essentially kept constant either the polymerization rate or the like;

content of transition metals in the polymer produced.

The activity retarder is selected from a wide range of products which are capable of reducing the rate of polymerization of alpha-olefins in the presence of catalysts to the base. transition metals. In particular, the activity retarder may be selected from polymerization inhibitors or poisons known for this type of reaction. The activity retarders which may be selected are, in particular, carbon monoxide, carbon dioxide, carbon disulfide, carbon dioxide oxysulfide / oxides and nitrogen / oxygen peroxides, alcohols, aldehydes, ketones, thiols and water. Retarder efficacy can also be. . The drawbar is f-ζ.

selected from electron donating compounds capable of complexing the catalyst (s) and reducing the polymerization rate, in particular from organic compounds containing at least one oxygen atom (sulfur, nitrogen) and / or phosphorus. It may be selected from a wide variety of electron donating compounds such as amines, amides, phosphines, sulfoxides, sulfones, esters, ethers or thioethers.

The reactor can change the polymer during

Attention is drawn in particular to the use of an activity retarder in an amount capable of reducing the polymerization rate without substantially affecting the quality and properties of the polymer produced, such as melt index, melt index, mean molecular weight, molecular weight distribution, or stereospecificity of the polymer. In fact, since according to the present invention it is very important that the rate of introduction of activity retarders from time to time, the properties of the reaction produced may vary as the activity retardant used has a considerable effect on the properties of the polymer. Such a result would be contrary to the object of the present invention. Particularly in view of the conditions under which the efficiency inhibitor is used in the process, in particular the very small amount introduced into the reactor, the activity retarder may be selected from a considerable number of products such as polymerization inhibitors and electron donor compounds. However, it is preferable to use conventional polymerization poisons, in particular alcohols, carbon monoxide, carbon dioxide or oxygen, as well as

electron donating compounds, in particular amides and ethers. It has been found that excellent results are obtained with oxygen and amides.

The activity retarder may be used in a pure state or preferably diluted with a gas such as nitrogen or dissolved in readily volatile liquid hydrocarbons. Another possibility is to use a mixture of two or more activity retarders. However, if oxygen is used as an activity retardant, it can be used in a mixture with nitrogen. In certain cases, atmospheric air or oxygen depleted air may also be used.

According to the present invention is introduced retarder force continuously to the polymeric ^ undispersed reactor ⁷ in practice is introduced into the reactor ^ at the same time as the alpha-olefin (s), continuously or in an almost continuous, intermittent manner, so that the time of interruption is so short that it can not affect the rate of polymenation, which is kept substantially constant. If, however, the introduction of activity is interrupted, or if the interruption time is too < -γ / long, the polymerization catalysts in the reactor will increase due to the absence of retardants, the polymerization rate is then no longer controllable and may change rapidly according to the quality of the reactants or catalysts. agglomerates.

It was also found that the efficiency of the retarder is introduced into reaktora- ⁷ in such a small amount that it is not possible to measure the proportion of retardértv the gaseous reaction mixture circulating in the reactor. The proportion of retardant efficacy is much less than 1 part by weight per million (ppm) and is generally less than 0.1 ppm. The amount of retardant efficiency in the gas mixture circulating through the reactor is generally not measurable using a device such as an oxygen analyzer with an electrochemical sensor, or a carbon monoxide / carbon dioxide gas chromatograph with a methane combustion detector, or an organic compound analyzer with a thermoionic sensor. In practice, is the amount of retarder / efficiency introduced into the reactor? Also, the molar ratio of the amount of retard érOúčinnosti which is introduced, the introduced amount of a-olefin (s), as?-IO ^"8 and / .1O ^'5, preferably 5.10" to 2.10 ^{8' 6,} particularly výhodneÍ10 'to ⁷ /, 10 ' ⁶ . Surprisingly, it has been found that a very small amount of activity retardant used is capable of providing a gas phase polyolefin process with high efficiency and high reproducibility without the formation of agglomerates. The amount of activity retardant generally depends on the type of gas phase polymerization system and the type of catalyst used. The lowest amount of retarder / efficacy used and, consequently, the minimum retarder flow rate? The efficiency of the reactors can easily be determined by the maximum

-A by heat exchange in the gas-phase polymerization system or maximum production of polyolefins without agglomerate formation. In addition, the highest amount of retarders? The efficiency of the efficacy to be used and hence the maximum flow rate of introduction of retardant efficacy into the reactor can be directly linked to the highest concentration of impurities introduced by the reactants into the reactor (if the quality of the reactants is varied). In particular, if the minimum flow rate of efficiency retardation is too low, it has been observed during polymerisation that there is such a decrease in production that the introduction of retarder efficacy must be discontinued. In this case, it is not possible to avoid a decrease in production and the content of polymer catalyst residues can be significantly increased.

It has also been found that if the retarder insertion flow rate is too high, i. the molar ratio of the amount of retarder introduction / activity to the amount of alpha-olefins is too high, the production of the polymer decreases, or the content of polymer catalyst residues is significantly increased.

In accordance with the present invention, it has also been found that the rate of introduction of the retarder; The efficacy can vary with time per / γ

IL to keep the polymerization rate substantially constant, i.e.

-o-in-s-err 'when there are small changes in the quality of the reactants or catalyst or in the feeding of the catalyst to the reactor #? The polymerization rate is considered to be substantially constant over time, however, if the amount of polyolefins produced per hour does not change by more than 55% by weight, preferably no more than 33% by weight.

In another variant of the process, it was also found that the flow rate of retarder G? The efficacy may be modified with time to maintain a substantially constant content. h of transition metals in the polymers produced when the quality of the reactants or catalyst changes during the polymerization? This content is considered to be substantially constant if the av-sex mass content of the transient

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of the metals in the polymers does not change by more than 10%, preferably not more than 5%.

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The gas phase polymerization process is typically conducted while maintaining substantially constant conditions such as the composition of the gaseous reaction mixture, total pressure, catalyst feed rate, bed height or weight, polymerization temperature, and gas rate. Under these conditions, the polymerization rate can be readily determined and also calculated because it directly corresponds to the production of the polymer, i. the rate of exit of the polymer, or the rate of introduction of the alpha-olefin (s), or the difference between the temperature of the inlet and outlet gas, taking into account that the rate of heat evolution directly depends on the formation of the polymer.

For example, if it is observed that during polymerization, the production of polyolefins tends to increase, or that the transition metal content of the polymers being produced tends to decrease due to unexpected loss of impurities in the alpha-olefins introduced into the reactor, or because a new catalyst is used which is somewhat more efficient than the previous one or further because more catalysts have been introduced into the reactor; the rate of introduction of the retarder activity is then reduced so as to maintain a constant polymerization rate, in particular the production of the polymer or the content of transition metals in the prepared polymer. If the flow rate does not change, or if its changes are too small, there is a rapid adverse effect of superactivation in relation to hot spots and bed agglomerates. Conversely, if it is observed during polymerization that the production of polyolefins tends to decrease or that the content of transition elements in the polymer produced tends to increase, then the flow rate of retarder efficacy is reduced so as to maintain a constant rate of polymerization, especially production. or a content of intermediate elements in the produced polymer. However, if the flow rate does not change or if its change is too small, polymer production decreases undesirably and the content of transition elements in the polymer increases. It has been surprisingly observed that, as a result of the process of the present invention, it is now possible to convert the gas phase polymerization at higher temperatures and at a higher alpha-olefin pressure than before. One of the unexpected advantages of this process is that polyolefin production can be increased by 20% without the risk of forming hot spots and agglomerates. Due to the continuous introduction of activity retarders in very small amounts over time, it is now possible to produce polyolefins of excellent quality with a high degree of reproducibility, due to large and unexpected changes in the quality of the reactants, catalyst efficiency or catalyst feed to the reactors.

Another unexpected advantage of the present invention is that the polyolefins so produced have a very reduced content of transition elements and consequently are of excellent quality without agglomerate formation. Another advantage of the method is the fact that management

regulated directly by the flow rate of introducing retarder efficacy without substantially changing all or some of the reaction conditions.

This process also makes it possible to use high yield catalysts whose polymerization efficiency is particularly sensitive to small variations in polymerization conditions. Can these catalysts be introduced into the reactor? continuously or intermittently. Is it possible to use more efficient catalysts, in particular Ziegler-Natta type catalysts based on magnesium, halogen, titanium and / or vanadium and / or zirconium, and also to increase the efficiency of these catalysts by adding more catalysts? selected from organometallic compounds I, II or III of the Periodic Table of the Elements, in particular organoaluminum compounds.

Is it also possible to use a catalyst modifier, in particular a selective agent, such as an aromatic ester or a silica compound, which is introduced into the reactor? Continuously at a constant flow rate and at a fixed constant molar ratio to the transition metal of the catalyst. It is also possible to use a high efficiency catalyst based on a chromium oxide coupled to a granular refractory oxide carrier such as silica, alumina or aluminum silicate and activated at temperature. at least 250 ° C and at most at a temperature at which the granular carrier may begin to ski; preferably at a temperature between 350 ° C and 1000 ° C.

The high efficiency catalyst can be used directly as such or in the form of a prepolymer. The conversion to the prepolymer is generally carried out by contacting the catalyst with one or more alpha-olefins in an amount such that the prepolymer thus obtained contains between 0.002 and 10 millimoles / transition metal per gram. These reactants may also be contacted with an organometallic compound of a metal of group I, II or III of the periodic table, in an amount such that the molar ratio of metal in said organometallic compound to the amount of transition metal is between 0.1 and 50, preferably between 0 and 50. The high efficiency catalyst used directly or after the prepolymerization step is fed continuously or intermittently to the fluidized bed and / or mechanically stirred bed reactor / or the French patent.

e-Mef for a very large industrial polymerization rate can

The polymerization is carried out continuously in a fluidized and / or mechanically agitated bed by known techniques and using a jpifz device as described in French Pat. 2207145 2335526. The process is particularly suitable for reactors in which the smallest change very quickly leads to undesirable effects such as agglomerate formation. The gaseous reaction mixture containing the alpha-olefin (s) to be polymerized is generally cooled in at least one heat exchanger located outside the reactor before being recycled. The activity retarder may be introduced directly into the reactor (preferably into the reactor zone G) where the activity retarder is rapidly dispersed, for example under a fluidization grid.

It may also be introduced into the line (s) for recycling the gaseous reaction mixture or into the line (s) to charge the reactor with alpha-olefin (s). However, if the recycle line comprises means for separating gas from fine solids entrained by a gas, such as a cyclone, and means for recycling these fines directly to the polymerization reactor, the efficiency retarder may be introduced at any point in the medium. gas / solid separation or fine particulate recycling.

The efficiency retarder may or may be introduced at two particularly preferably into the Die gas recycle gas mixture and into the gas / solid separator, or into the reactor, in particular to the bottom of the reactor / git.

The polymervation reaction is generally carried out at a pressure of 0.5 to 5 MPa and a temperature of 0 to 135 ° C. The process is suitable for the polymerization of one or more alpha-olefins containing from 2 to 8 carbon atoms, in particular the polymethylene of ethylene or propylene. It is particularly suitable copolymeric p ^ ⁷ ^ ^ rms who they ylene with at least one alpha-olefin. . or a copolymerization of propylene with at least one alpha-olefin containing from 4 to 8 carbon atoms (such as ethtylene and / or unconjugated diene). The gaseous reaction mixture may comprise hydrogen and an inert gas which is / Z, for example, nitrogen, methane, ethane, propane, butane, isobutane or γ isopentane. If a fluidized bed reactor is used, the fluidization rate of the gaseous reaction mixture passing through the bed is 2 to 10 times the minimum fluidization rate. The polymer produced is withdrawn from the reactor continuously or, preferably, intermittently.

Example 1] / l & Ί ‘L

The process is carried out in a fluidized bed, the gas phase prepolymer-polymer reactor contains a vertical cylinder of 1.5 m diameter and is provided with a speed reduction chamber. In its lower part there is a fluidization grate and an external gas recycle line connecting the top of the speed reduction chamber to the bottom of the reactors / below the fluidization grate. The gas recycling pipe is provided with a circulating gas compressor and heat transfer means. Preferably, ethylene, 1-butene, hydrogen and nitrogen supply lines are connected through the orifice to the gas recycle line, which are the major components of the gaseous reaction mixture passing through the fluidized bed.

On the fluidization grate, the reactor comprises fluidized beds containing 52 tonnes of linear low-density polyethylene powder containing particles having a diameter of 0.7 mm in diameter. The gaseous reaction mixture, which contains 42% by volume of ethylene, 18% by weight of 1, butene, 8% of joint and 32% of nitrogen, is passed through the fluidized bed at 20 bar and 80 ° C and at a fluidization rate of 0.5 m / s.

The catalyst is identical to the catalyst described in Example 1 of French patent no. 2405961, which contains magnesium, chlorine and titanium and which has been converted into a pre-copper (a polymer containing 40g of polyethylene per millimol of titanium and such an amount of tri-n-octylaluminium (TnOA) that the molar ratio ΑΙ / Ti is 0.85 ± 0.05, are introduced into the reactors intermittently over time.The flow rate of the introduction of the prepolymer into the reactor is 150 kg / h.

Gas mixture containing 98% nitrogen CH 2 and 2% oxygen

J t (by volume) is continuously fed during the polymerization into the pps line of ethylene feed connected to the polymerization reactor. The flow rate of the oxygen-containing gas mixture varies over time between 62 g / h and 188 g / h so as to maintain the linear low-density polyethylene output at a constant value of 13.5 ± 0.4 tons per hour due to undesirable changes in catalyst quality and the reactants used in the process. Under these conditions, the oxygen content of the ethylene entering the reactors varies over time from 0.01 to 0.3 volume per million (vpm) and the molar ratio of oxygen / fed to the amount of ethylene and 1-butene fed varies. from 1.10 ' ⁷ to 3.10' ⁷ . It has been found that it is impossible to detect the presence of oxygen ⁷ in the gaseous reaction mixture cirkuFujúcej fluidized bed (the content of oxygen below 0.1 vpm). After a certain number of days of continuous polymerization under these conditions, the emerging polymer remains constant, without agglomerate formation, and the quality of the linear low density polyethylene prepared in this way remains constant and guaranteed, despite accidental changes in catalyst efficiency and fluctuations that are unpredictable and difficult to detect. ethylene, 1-butane and the other components of the gaseous reaction mixture. In particular, the carbon monoxide content of the ethylene fed to the reactor is below or at 0.1 vpm.

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Example 2 (^ straightening)

The process is carried out under the same conditions as described in Example 1, except that the oxygen-containing gas mixture is not introduced into the ethylene fed to the polymerization reactor.

Under these conditions, it has been found very quickly that the output of the linear low-density polymer varies with time from about 11.5 to 14.5 tons per hour and cannot be essentially maintained that the quality of the prepared polymer varies significantly and that agglomerates of molten polymer.

Example 3

The process is carried out on a fluidized bed in a gas-phase polymerization reactor containing a vertical cylinder of a diameter of 0.9 m and a height / 6 m and equipped with a speed reduction chamber. In its lower part, the reactor is provided with a fluidization grate and an external gas recycle line connected to the upper part of the speed reduction chamber and the lower part of the reactor. This piping is located below the fluidization grid. The gas recycle line is provided with a V, a circulating gas compressor and a heat transfer means. Preferably, the gas recycle line p-rV enters the feed line of ethylene, 1-butene, hydrogenCT and nitrates, which are the major components of the gaseous reaction mixture passing through the fluidized bed.

Above the fluidization grid, the reactor contains a fluidized bed containing 400 kg of linear low density polyethylene powder with an average particle diameter of 0.7 mm. The reaction gas mixture containing 30% by volume of xylene, 12% by weight of butene, 6% by weight of hydrogen and 51% by weight of nitrogen and 1% of ethylene was passed through a fluidized bed at 1.6 MPa at 80 ° C and a fluidization velocity of 0.5 m / s. .

Catalyst which is identical to the catalyst described in Example 1 of French patent no. 2405961, which contains wz / magnesium, chlorine and titanium and which has been pre-converted to a prepolymer containing 40 g of polyethylene per millimolar of titanium and tri-n-octylaluminium (TnOA) in such an amount that the molar ratio Al / Ti is 1, 85 ± 0.05, are introduced into the reactor / Q intermittently over time. The flow rate of the prepolymer introduced into the CF reactor is 0.7 kg / h.

A solution of dimethylformamide (DMF) in isopentane containing 0.004 mol DMF per liter is fed continuously into the gas recycle pps line during the polymerization. The flow rate of this solution varies with time between 125 ml / h and 300 ml / h to maintain the linear low-density polyethylene output at a constant value of 100 ± 3 kg per hour, due to undesirable fluctuations in the quality of the catalysts and reactants used in the process.

Under these conditions, the molar ratio of the amount of DMF, which is introduced to the amount of introduction of ethylene and 1-butane varies from 1.5.10 ^'7 to 5:10 ^"7th It has been found impossible to detect the presence of DMF in the gaseous reaction mixture that circulates through the fluidized bed (DMF content below 0.1 vpm). After several days of continuous polymerization carried out under these conditions, the polymer output remains constant without agglomerate formation, and the quality of the linear low-density polyethylene produced in this way remains constant and assured, regardless of accidental changes in catalyst performance and fluctuations that are predictable and difficult to detect. in impurities introduced by ethylene, butene-1 and other constituents of the gaseous reaction mixture. In particular, the content of carbon monoxide in the ethylene fed to the reactor is generally below

Grain in or X values of 0.1 vpm.

Example 4

The process is carried out in a fluidized bed gas-phase polymerization reactor 3, comprising a vertical cylinder having a diameter of 0.9 m and a height of 6 m and equipped with a speed reduction chamber. At its lower part, the reactor is provided with a fluidized bed with an overhead conduit for gas recirculation which connects the upper portion of the speed reduction chamber to the lower portion of the reactor located below the fluidized bed. The pte gas recirculation line is associated with the compressor to recycle the gas and heat transfer means. Advantageously connected to the gas recycling line are p lines _of ethylene, hydrogen and nitrogen, which are the main components of the gaseous reaction mixture passing through the fluidized bed.

Above the fluidization grate, the reactor comprises a fluidized bed containing 400 kg of high-density polyoxyethylene powder, which is formed to contain particles with an average weight diameter of 0.8 mm. The gaseous reaction mixture, which contains 35% ethylene, 15% hydrogenCPa and 40% nitrogenCP by volume, is passed through a fluidization bed at a pressure of 2.0MPa at 100 ° C and a fluidization rate of up to 0.4 m.s ^-1 .

Chromium oxide catalyst, prepared by treating catalysts available under the trade mark "EP 30" by Joseph Crosfield and Sons (England), containing 1% by weight of chromium and 3.8% by weight of titanium, coupled to a support on an oxide base The silica was thermally treated at 550 ° C for 4 hours, and converted into an ethylene prepolymer containing 40 g of polyethylene per millimole of chromium.

The prepolymerized catalyst thus obtained is simultaneously introduced

into the reactor at a feed rate of 0.21 kg prepolymer per hour.

The gaseous mixture containing nitrogen and 2662 vpm of oxygen is continuously fed into the feed line of ethylene connected to the polymerization reactor during polymerization. The flow rate of the oxygen-containing gas mixture varies with time between 60 and 120 Nl / h so as to maintain the high density polyethylene output at a constant value of 90 ± 2 kg / h through undesirable fluctuations in the quality of the catalyst and reactants used in the process. Under these conditions, the molar ratio of the amount of oxygen introduced to et) (ylene) varies from 2 x 10 ^-7 to 4 x 10 ^-7 . It should be noted that after many days of polymerization carried out continuously under these conditions, the polymer output is kept constant agglomerates and that the quality of the high density polyethylene thus produced remains constant and guaranteed, despite various random variations in catalyst activity and fluctuations in the impurities introduced by ethylene, hydrogen and nitrogen.

Claims (9)

PATENT CLAIMS 1. The process for continuous gas phase polymerisation of one or more alpha-olefins in a fluidized and / or mechanically agitated bed with the aid of the catalyst N, ^J retarder force, '''R f wherein,? If the polymerisation of prevention-DZA-rtaky The method according to claim 1, characterized in that the catalyst on the base of the transition metals IV. of the Periodic kl-ae4fi4tácie element contacted with the alpha-olefin (NMI), and continuously to reaktortb introduced retarder force in an amount such that the molar ratio of the introduced retardérQjúčinnosti to the amount of introduction of alpha-olefin (s) is from - /. 10 ^"8 DOI-10 ^{'3 * 5,} a flow rate that varies with time so as to keep constant either the polymerization rate or the content of transition metal in the polymer produced ^, wherein said retarder activity is capable of reducing the rate polymeTacie alpha olefin in the presence of said catalyst, a base and a transition metal. 2. The method according to claim 1, characterized in that the force of the retarder to the reactor an amount such that the molar ratio of introduction of the introduced retardéríP'účinnosti alpha-olefin is 5 x 10 ^8-2 x 10 ^6, more preferably / ΊΟ ' ⁷ to // IC' ⁶ . The method of claim 1, wherein the activity retarder is selected from polymerization inhibitors and electron donating compounds. 4. The method of claim 3 wherein the polymerization inhibitor is selected from the group consisting of carbon monoxide, carbon dioxide, carbon disulfide, carbon oxysulfide, nitrogen oxides, and peroxides, alcohols, toluenes, aldehydes, ketones, oxygen. and water. z P 5. The method of claim 3, wherein the electron donor compound is selected from the group consisting of amines, phosphines, sulfoxides, sulfones, esters, ethers, and thioethers. A process according to claim 1, characterized in that the catalyst is a Ziegler-Natta type catalyst based on magnesium, halogen, titanium and / or vanadium and / or zirconium. . · (? k ths. ¹ · '. 7. The process of claim 1 wherein the catalyst is a chromium oxide catalyst combined with a granular carrier based on refractory oxides and is heat activated. 8. The process of claim 1 wherein the alpha-olefin (s) contain from 2 to 8 carbon atoms. 9. The process according to claim 1, wherein the polymerization is carried out at a pressure of 0.5 to 5 MPa and at a temperature of from 0 to 135 ° C.