Method of producing polymers

FIELD: chemistry.

SUBSTANCE: apparatus includes a reaction vessel and a degassing vessel. In the method, each of the first and second processes includes the following steps: (a) bringing a main olefin and a comonomer into contact with a catalyst in gas-phase polymerisation conditions in a reaction vessel to obtain a first polymer or a second polymer, respectively, wherein said first and second methods employ the same main olefin, the difference between the two methods being at least one of the following factors: (1) the comonomer used and (2) the reaction temperature at which the polymer is obtained, and (b) subsequently bringing the first or second polymer, respectively, into contact with a blowout gas in a degassing vessel. The transition method involves changing the flow rate of the blowout gas in the degassing vessel from a first value X₁, which is used when degassing the first polymer, to a second value X₂, which is used when degassing the second polymer. The second value is determined relative the flow rate X_i and temperature T_i used at earlier steps of producing the polymer during transitional polymerisation using the same comonomer as in the second process, and reaction temperature T₂ in the second process. The method is characterised by that, (a) if T₂ increases relative T_i, X₂ is at least 1% lower than X_i when T₂ is raised every 1°C compared to T_i, (b) if T₂ drops relative T_i, X₂ is at least 1% higher than X_i when T₂ is decreased every 1°C compared to T_i, (c) if T₂ is equal to T_i, X₂ is equal to or greater than X_i, preferably equal to X_i.

EFFECT: if values X_i and T_i for earlier polymers are set for each comonomer to be used in successive polymerisation to obtain different polymers, the subsequent values of flow rate of the blowout gas X₂ for other polymers to be obtained can easily be determined based on said values and temperature T₂.

11 cl, 2 tbl, 1 ex

The present invention relates to a method suitable for polymers.

It is well known obtaining powder of the polymer by the polymerization of monomers in the presence of catalysts. For example, well-known and widely used in industry methods with the use of a fluidized bed reactor and reactor polymerization in suspension.

When gas-phase polymerization of olefins in a fluidized bed, for example, the polymerization is carried out in a reactor with a fluidized bed, and the layer of polymer particles is maintained in the fluidized state by the upward flow of gas comprising gaseous monomer that reacts polymerization. In the polymerization process produces fresh polymer by the reaction of catalytic polymerization of the monomer, and the polymer product is removed from the reactor to maintain more or less constant volume of the fluidized bed. Mainly in the industrial process used grille for liquefaction, with the purpose of distributing gas, contributing to the translation layer in a fluidized state by a layer of polymer; grill also serves as a support for the layer, when there is a power gas supply. The polymer is usually unloaded from the reactor through the discharge pipe located at the bottom of the reactor, near the grille to liquefaction.

In order to remove the captured monomers and other hydrocarbons is usually used additional step which consists in contacting the obtained polymer with the gas in the purge vessel, usually with an inert gas in counter-current, for example with nitrogen. The specified stage can be called "purging", or "degassing".

In the art there are numerous patents that describe how the removal of such hydrocarbons from the products in ways that occur in the gas phase or in the phase of the suspension, and include the stages described in US 4372758, EP 127253, EP 683176, EP 596434, US 5376742 and WO 2005/003318.

In the patent US 4372758, for example, describes a method of degassing, which use an inert gas such as nitrogen, to remove unreacted gaseous monomer from polimerov the product. Solid polymer is directed to the top of the purge vessel using the system of the inert gas, the flow of inert gas injected into the bottom of the purge vessel, and a solid polymer in countercurrent contact with a stream of inert gas to remove unreacted gaseous monomers from a solid polymeric product. Unreacted monomers can then be mixed with the stream of inert gas, which is often directed at the torch for the purpose of disposal, or release into the atmosphere.

In the patent EP 127253 described method of removing residual monomers of ethylene copolymers in which the copolymer is directed to an area of low pressure, sufficient for desorption of monomer, blow copolymer reactor gas, which does not contain inert gases, and return the resulting gas containing desorbed monomer in the polymerization zone.

The speed with which the removed residual monomers and other components that might be present in the polymer is affected by several factors. In the patent US 4372758 described a range of factors, including the temperature and the pressure in the purge vessel, the particle size and morphology of the polymer, the monomer concentration in the resin, the composition of the purge gas (content of the monomer) and the flow rate of the purge gas, but there are other factors. These factors determine t Abueva stay in the purge vessel, to the concentration of the residual monomer in the polymer decreased to safe levels before processing occurring at the subsequent stages of the method; and although requirements can be determined experimentally or through accumulation of experience in conducting means, for any particular polymer, usually these ratios is quite complicated.

Usually, in spite of the above, it is difficult to remove all residual hydrocarbons in a cost efficient manner. So, although the rate of the purge gas, its purity (content already present in the gas hydrocarbons), temperature and residence time in the purge vessel at the stage of degassing can theoretically be increased to ensure complete removal of hydrocarbons from any particular polymer, the costs associated with this increase is so great that usually a small amount of hydrocarbons remain in the polymer even after degassing, and therefore, the storage tanks are typically rinsed to prevent accumulation of vapors of hydrocarbons, which gradually during storage are allocated in the form of gas from the polymer.

In addition, in the implementation of industrial polymerization processes typically get a number of different polymers by changing with time the reaction conditions, for example temperature or used co monomer (such a sequence of changes n is given by the transition), without reactor shutdown, this method is called "operation transition polymerization". Although degassing can be optimized for some of the polymeric products, which could be prepared, often the degassing processes are manufactured so that they are relatively not very flexible and cannot be applied for the decontamination of other polymer products, designers are not configured to modify the terms of degassing, in the hope that a greater or lesser degree of residual hydrocarbons are removed by blowing during storage.

Recently, in the application WO 2008/024517 has been described a method and device for control of volatile organic components in the polyolefin. This document describes the model of the purge column, the effect of which is based on mass transfer theory and used to regulate the method of degassing so that the speed of the purge can be changed depending on the nature of the polymer subjected to degassing.

However, this method is relatively complicated, and it corresponds to the accuracy of the model on which it is based. For example, it was found that a model based on mass transfer theory, do not describe exactly the degassing process. Specifically, it was experimentally found that the real rate of diffusion between solid and gas phases is not the same as in model mA is sopranos, described in WO 2008/024517, which reduces the accuracy of such models.

Further, even when using the "exact" model is extremely difficult to incorporate such a model into the control system by the way. In particular, the rate of blowdown should vary based on the model output, with appropriate security lock method, also calculated on the basis of the model output should be set at levels that allow for all possible changes in individual model parameters. However, with increasing model complexity becomes increasingly difficult the combination of these factors while maintaining guarantees safe operation of the system. Because of the limitations related to security, the application of such models to real systems in which the speed of the purge degassing column vary based on model output, still leads to the work, in which the degassing process is carried out in the actual values of the parameters are far from optimal values predicted on the basis of the model, and significantly reduced the flexibility of the method in comparison with that which would occur otherwise.

On the contrary, it has been found that during the transition from production of the first polymer to produce the second polymer under the conditions of gas-phase polymerization changing usloviyah degassing for the second polymer can be relatively simple to adjust, based on the conditions of degassing during the process of getting an earlier polymer.

So, in the first aspect of the present invention provides a method of transition from the first method of obtaining the first polymer to the second method of obtaining the second polymer in the method of polymerization in the polymerization, the setting for polymerization involves the reaction vessel and the vessel for degassing, in this way, respectively, each of the first and second processes comprises the following stages:

(a) the implementation of the primary contact of olefin and co monomer with a catalyst under conditions of gas-phase polymerization in the reaction vessel receiving respectively the first or the second polymer, and the above first and second methods are used the same basic olefin, and the difference between the first and second method consists in at least one of the following factors: (1) the nature of the used co monomer and (2) the temperature at which the polymer, and

(b) further contacting respectively the first or the second polymer from the purge gas in the vessel for degassing in order to remove unreacted monomers,

the method differs in that transition method includes changing the flow rate of purge gas in the vessel for degassing from the first value of X₁that PR is changing due to degassing of the first polymer, to the second value of X₂that used in the degassing of the second polymer, and the second value is defined relative to the flow velocity X_iand temperature T_ithat apply at an earlier stage of obtaining the polymer in the process of operation of the transition polymerization using the same co monomer, in the second process, and the reaction temperature T₂in the second process, the method is also distinguished by the fact that

(a) if T₂increases with respect to T_i, X₂at least 1% lower compared with X_iwith increasing T₂compared with T_ifor every 1°C

b) if T₂is reduced with respect to T_i, X₂at least 1% higher compared with X_iwith increasing T₂compared with T_ifor every 1°C

C) if T₂equal to T_i, X₂is equal to or more than X_ipreferably equal to X_i.

In the method according to the present invention, the flow rate in the degassing process for the second polymer adjust the settings based on degassing at the stage of obtaining an earlier polymer, which is produced during the operation of the transition polymerization using the same basic olefin and co monomer, and the difference in temperature in appropriate ways, which made both of the polymer.

Concrete is, when conducting transition polymerization usually have a few different polymer products. In the process of transition polymerization catalyst type and the main olefin, most likely, will not change, but it may be desirable to obtain several polymers with different comonomers and several different polymers with the same co monomer, but when you change the polymer properties such as melt flow index and density. The latter usually requires changing the reactor temperature and usually also changes in relation to the co monomer and monomer in the polymerization process.

So you can imagine that the transition process of polymerization, in which:

(1) remains the same co monomer, but changes the temperature and possibly the number of co monomer in the reactor;

(2) the nature of the co monomer is changing, not necessarily when the temperature changes.

The method according to the present invention provides the method of degassing within a relatively narrow operating window, in which the security requirements are satisfied for the second polymer, but do not apply excessive amounts of purge gas compared to those necessary for safe operation. In the present invention this is achieved by reference to the rate of degassing, remenieras at an earlier stage of obtaining a polymer using the same co monomer, and in the second stage polymerization, which moves the polymerization process, and not at the stage of processing of the polymer obtained at the preceding stage of obtaining the previous polymer, so that any significant changes in the temperature of the method shown earlier methods lead to changes in flow rate due to degassing.

Usually safe installation method, such as the minimum acceptable rate of purge gas (below this speed work method not allowed)will also change with each change in velocity of the purge gas. Because the ratios that are used in this model to change the speeds of the purge gas, so simple, appropriate settings for security lock method can also be changed accordingly (and simple) way. Thus, it is possible to fully use the benefits from the calculation of changes in the flow rate of the purge gas subjected to degassing of the polymer according to the equations found in the present invention.

Theoretically you can change the speed of the purge gas for the new derived polymer such that based on the rate used for purging the polymer obtained directly before the given polymer, and then for the next of the obtained polymer shall amend the rate of the purge gas based on the value, used for degassing already given polymer, and so forth. However, if you apply this system, you can move from the first polymer, which is obtained at the reaction temperature T₁, high reaction temperature T₂and then back to the first polymer or another polymer, which also receives at a temperature T₁and not to go back to at least the initial flow rate, if you do not apply other restrictions permissible flow velocities. In General, this requires either more accurate calculations of the flow rate of purge gas required for purging the polymer after each jump, or the required safety margin should be broadened to take account of any possible deviations over time. Therefore, in order to ensure safe operation in several transitions from polymer to polymer, the operator must apply a much higher flow rate than is actually required. Thus, in the present description it is proposed to change the parameters on the basis of those that are not used in the production of the previous polymer, and in the production of the earlier polymer in the chain of successive transients polymerization.

In the present invention a relatively simple regulation of the speed of the purge gas in the production will follow the its polymer (second polymer) can be ensured by taking into account the conditions of degassing, used in obtaining an earlier polymer in the chain of successive modes of polymerization, the produced using the same co monomer. This provides a significant simplification of the calculations, a suitable flow rate of the purge gas for a specific second polymer at a suitable margin for error, but always within a reasonable interval compared to the value that would be calculated if would have used a more sophisticated method of calculation.

Thus, if the working conditions at an earlier stage of polymerization has been selected by the operator to ensure adequate and safe decontamination of concrete produced at an earlier stage polymer, reference to this earlier stage for all of the polymers produced by subsequently using the same co monomer, provides a more preferred work stage degassing even when a large number of consecutive transitions to the production of polymers with different properties.

The same "earlier polymer can be used as a sample for calculating for all subsequent transitions to the second means using the same co monomer. Usually "earlier polymer is a first polymer, which is produced in a specific operation transition polymerization using the same co monomer, the second% is the CE; and for each of the co monomer used in the operation transition of polymerization will be used different "earlier polymers".

The method according to the present invention has the following advantage: if the value of X_iand T_ifor earlier polymers installed for each of the co monomer which will be applied in the process of sequential polymerization of obtaining different polymers, the subsequent rate of flow of purge gas X₂for other polymers, which is supposed to be, you can easily determine on the basis of these values and temperature T₂.

This provides much more than simply performing the method of polymerization as compared with the case of independently calculate the degassing conditions for each individual polymer, which is produced during the operation of the transition polymerization, for example, as it did in WO 2008/024517.

Not wanting to be limited to a particular theory, we can say that when comonomer does not change produced for two different polymers, the number of variables that could affect the degassing process, does not change, or changes, such as the concentration of monomer, will not significantly affect the claims to a method of degassing. It was found that if the flow rate produve the aqueous gas was set for earlier polymer product, the flow rate of the purge gas for subsequent polymer products obtained using the same co monomer, it is easy to determine in relation to these values and based on the relative temperatures of the more early of the polymer and subsequent polymer.

Specifically, if the speed of the purge gas X_iyou do not need to include any other parameters in the calculation of the new velocity of the purge gas X₂. Thus, to avoid doubt, the present invention does not use a model based on theories which attempt to determine the rate of removal of volatile products from the polymer particles, such as mass transfer theory or theory of equilibrium. Preferably the value of X₂rely only on the basis of X_i, T_iand T₂as shown in the present description.

An important advantage of the method according to the present invention is that it is possible to apply a very simple relationship between the velocity of purge gas required for the degassing of the second polymer, and the speed of the purge gas for degassing earlier polymer.

Thus, in the present invention the flow rate of purge gas in the specified second process is calculated as follows:

(a) if T₂increased compared with T_iX 2at least 1% lower compared with X_iwhen the temperature T₂for every 1°C compared with T_i,

b) if T₂is reduced with respect to T_i, X₂at least 1% higher compared with X_iwith increasing T₂compared with T_ifor every 1°C

C) if T₂equal to T_i, X₂greater than or equal to X₂preferably equal to X_i.

This is possible because, as a rule, in the process of gas-phase polymerization and, consequently, in the method according to the present invention, a special heating or cooling applied to the minimum extent and preferably do not apply when the temperature of the polymer product discharged from the reactor vessel before being placed in the vessel for degassing, and therefore, the temperature of the polymer entering the vessel for degassing, is directly related to the temperature at which the polymer formed in the reaction vessel.

For comparison, during the suspension polymerization is described, for example, in WO 2008/024517, usually the suspension is unloaded from the reactor, is heated and passed through one or more evaporators, which remove most of the liquid medium, and then carry out the purge. You can refer to, for example, figure 5 and 17, described in WO 2008/024517.

In the present invention, if the speed with which the temperature of the reaction increases in the second process compared to the earlier method, the flow rate of purge gas in the second process can be reduced compared to the earlier method. Specifically, if T₂increases with respect to T_i, X₂at least 1% lower compared with X_iwhen the temperature T₂for every 1°C compared with T_i.

It is clear that the flow velocity X₂although it can be reduced in comparison X_ishould not decrease too much (except when for some reason the original flow rate X_isignificantly above the required minimum flow rate of the purge gas used for the original polymer). Preferably X₂not more than 3% lower compared to the X_iwhen the temperature T₂for every 1°C compared with T_iand most preferably X₂reduced relative to the X_ion the order of 2% to 3% when the temperature T₂for every 1°C compared with T_i.

On the contrary, if the reaction temperature is reduced in the second process compared to the earlier method, the flow rate of purge gas in the second process is increased compared to the earlier method. Specifically, if T₂decreases with respect to T_i, X₂at least 1% higher compared with X_iat lower temperatures T₂for every 1°STRs compared with T _i. In this case, the increase in flow rate to values considerably higher than this minimum value, does not cause security problems, but there are costs to this increase. Preferably X₂increase less than 10% compared with X_iat lower temperatures T₂for every 1°C compared with T_iand most preferably increase in size from 3 to 5% compared with X_iat lower temperatures T₂for every 1°C compared with T_i.

Finally, if T₂equal to T_i, X₂greater than or equal to X_i. In this case, again increasing the flow rate by an amount significantly greater than this minimum value, does not cause any security problems, but there are costs to this increase. Preferably in this case, the flow rate X₂exceeds X_inot more than 5%, more preferably in an amount of from 0% to 2% higher than the X_iand most preferably X₂equal to X_i. It should be noted that there may be a difference in the relative increase and decrease of flow velocities, if the temperature change. Specifically careful when lowering the temperature (with respect to T_i) increases flow velocities than necessary, while careful when increasing the temperature the market does not decrease beyond the required flow rate purge gas.

Since the flow rate of the purge gas X₂defined relative to the gas velocity at an earlier stage X_iused units are not of fundamental importance. However, it is convenient to apply the mass flow rate (flow rate) purge gas fed to the purge vessel. The mass flow rate of the purge gas can be measured using a suitable flow meter, through which pass the purge gas at the stage of degassing.

In one of the preferred variants of the present invention, each polymer obtained in the course of the operation transition of polymerization, will be subjected to degassing by using the flow rate of the purge gas based on the measured temperature to obtain a polymer (and the nature of the co monomer used). In this embodiment, each change of the reaction temperature leads to a change in flow rate at the stage of degassing in accordance with the required flow rate for purging the second polymer, which passes the described process.

However, in the overall operation of the transition polymerization is not necessary to change the flow rate of purge gas in accordance with the method of the present invention whenever the temperature changes from T₁to T₂. Specifically, although you can modify the speed of the Otok at each change of temperature from T ₁to T₂where are the first and second polymers, even if the temperature difference is relatively small, as in the first preferred embodiment, for the purposes of practical work it is not necessary to change the flow rate of the purge gas, if there are only small temperature changes. Thus, the flow rate can not be changed, although the reaction temperature varies, up until the temperature difference T₁and T₂will not exceed a certain value, for example 5°C.

To ensure that the degassing process still meets the security requirements, X₂and, therefore, X₁must continue to meet the requirements in respect of X_ithe most important criteria a, b or C, as defined in the present description. In this embodiment, the change in the flow rate of the purge gas is not necessary.

Specific especially preferred embodiment, it is convenient to define the intervals of temperature, for example, 10 or 5°C, in which the rate of the purge gas does not change for transitions between products in this particular range of temperatures; the rate of change blowing only if the transition occurs from temperature T₁located in the same temperature range, the temperature T₂in another temperature range.

In this preferred embodiment, the flow rate in each temperature interval will be calculated at the lowest temperature of this interval, since this requires a high flow rate of the purge gas.

In General, transitions in which comonomer does not change, significantly less complex than those at which comonomer changing; therefore, it is often desirable throughout the entire transition method of polymerization to obtain several polymers with different properties, using one with Homer in one sequence, and then move on to the polymer produced with the use of other co monomer, and consistently produce a range of polymers in this sequence.

In this preferred embodiment, the number of polymers can be obtained by application of one of the co monomer, by varying the reaction temperature, and the velocity of flow in the second process can be defined solely on the basis of changes in the temperature of the second means to the earlier method.

At a certain stage, however, it is often desirable to produce a transition that changes comonomer. In the method according to the present invention it will lead to a change in the earlier polymer, based on the stage production, which was determined by the flow velocity X₂required for a purge of the second polymer. In all other respects, however, apply the same ratio. Thus, transitions in which comonomer changing, not necessarily simultaneously with temperature, can be easily customized in accordance with the present invention.

The present invention is in an apparatus for polymerization, which comprises the reaction vessel and the purge vessel.

In the reaction vessel and for each polymer main olefin and comonomer come into contact with the catalyst under the conditions of gas-phase polymerization education is receiving the respective first or second polymer.

The reaction vessel may be any suitable reactor, suitable for the implementation of the gas-phase polymerization reactions. Preferably, each reaction is carried out in continuous mode in a gas-phase reactor with a fluidized bed. Such reactors and their operation are well known examples include EP 0475603, EP 1240217, EP 1484344 and EP 0855411.

In industrial polymerization process, there could be two or more reaction vessel, which are used sequentially to obtain the final polymer product. One example of such processes is to obtain a bimodal polyethylenes using two reactors operating under different conditions. In such embodiments, the reactor in stage (a) of the present invention represents the last reactor in the sequence. To avoid any doubt, the earlier vessels in the sequence can be a gas, specifically fluidized bed, the processes of polymer, but not necessarily: they can represent, for example, and processes in the phase of the suspension.

In ways fluidized bed of particles of the resulting polymer are maintained in fluidized condition by using a reaction gas mixture containing the monomers undergoing polymerization, and moving in an upward direction. Polymer clay is, thus obtained in the form of a powder, usually unloaded from the reactor, to maintain more or less constant volume of the layer of fluidized particles of the polymer. The process is usually used sihumay grid, which distributes the reaction gas mixture over the layer of polymer particles and acts as a support for the layer in the event of a power flow of the rising gas. The reaction gas mixture leaving the top of the reactor with a fluidized bed, return to the base last under sigalda grating for external circulation loop.

Polymerization of olefins is an exothermic reaction. The reaction mixture comprising olefins, intended for polymerization, usually cooled using at least one heat exchanger located outside the reactor and then fed to the recirculation.

The reaction mixture may also include one or more inert compounds, specifically inert gases such as nitrogen, and/or one or more saturated hydrocarbons such as ethane, propane, butane, pentane and hexane. One or more compounds can be injected into the reaction zone in liquid form. Evaporation of the liquid in the reaction zone provides the cooling effect directly in the reaction zone. Typically and preferably, if such inert/liquid compounds are present in the production of the e of one polymer, the same (the same) connection is present/used in the synthesis of other polymers, which are produced during the operation of the transition polymerization, although the number of compounds present in the reaction system can vary in the production of various polymers sequence. For example, if the production of one polymer in the reactor in liquid form serves pentane, it is usually also used in the production of other polymers, instead replaced it with another saturated hydrocarbon, in particular, because it's simply more convenient.

The polymerisation process is appropriately carried out in the gas phase at an absolute pressure of from 0.5 to 6 MPa, and at temperatures from 30 to 130°C. for Example, to obtain a linear polyethylene of low density (LDL) temperature suitably ranges from 75 to 100°C for high density polyethylene (HDPE) temperature is usually from 80 to 115°C, depending on the activity of the used catalyst and the desired properties of the polymer.

The total pressure in the reactor gas-phase polymerization is most preferably ranges from 1.5 to 3 MPa.

The phrase "principal olefin in the present description understand olefin, which is included in the obtained polymer in the largest amount (by weight). Usually this will be the Ola is in, which is present in the reaction mixture in the greatest quantity and in which the greatest number served in the reaction mixture.

The phrase "comonomer" in the present description understand olefinic reactant, differing from the basic olefin, which is desirable to include in the composition of the polymer product.

The main olefin is preferably selected from ethylene and propylene.

Comonomeric olefin is preferably selected from olefins containing from 2 to 12 carbon atoms (differing from the basic olefin). Suitable comonomers the olefins are ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-penten and 1-octene.

More preferably comonomer selected from 1-butene, 1-hexene or 1-octene.

Most preferably, the olefin is an ethylene, and comonomer is a 1-butene, 1-hexene or 1-octene, specifically 1-hexene or 1-octene.

Earlier, the first or second polymerization process may be more than one co monomer, although preferably in each process there is only one comonomer.

The polymer product discharged from the reactor, is fed into the purge vessel in which it is in contact with the purge gas to remove unreacted monomers (basic olefin and co monomer (comonomers)).

The temperature T at the stage of degassing usually, the composition of AET from 50 to 110°C. In the present description, this temperature is defined as the temperature of the powder, measured at the exit from the stage of degassing.

Pressure P_totalat the stage of degassing is usually from 0 to 1 bar (Rel.) (100 to 200 kPa).

Vessel for degassing of the present invention may constitute one of the two or more vessels for degassing, which is contacting the vent gas with the polymer in order to remove volatile hydrocarbons. The purge vessel may also include a "combined degasser"in which two or more stages of degassing occur in a single degassing column.

Thus, there may be two or more stages, in which different purge gases in contact with the polymer powder. In accordance with the present invention it is necessary that the speed of the purge gas in at least one vessel for degassing changed as described in the present description.

The purge gas may be a return purge gas or inert gas, or it may include a mixture of the above. Particularly preferred inert gas is nitrogen. In the present description, the term "reflexive purge gas" means the gas obtained from the outlet of the appropriate vessel for degassing or other vessel for degassing, if he is outstay, and applied to the input of the vessel for degassing is not necessary after treatment to remove volatile hydrocarbons.

In a particularly preferred embodiment of the present invention, the vessel for degassing, in which the speed of the purge gas is changed as described in the present description, is the first of two vessels for degassing. Preferably, the purge gas supplied in said first vessel for degassing ("first purge gas"), includes at least part of the return purge gas, which is taken at the output of the specified first vessel for degassing. Before returning to process the specified stream is preferably treated in order to remove from it at least part of the hydrocarbons trapped at the stage of degassing.

The second purge gas is fed to the second in the sequence of a vessel for degassing. Most preferably the second purge gas is an inert gas, specifically nitrogen. The flow rate specified for the second purge gas may be constant or may vary with changes in the resulting polymer product.

In the production of the earlier polymer, the first polymer (if not earlier polymer and the second polymer is used, the catalyst of the same "type". Expression type "catalyst" in the present description comprises the usual classes, which are used for separation of catalytic systems for polymerization, and combinations of these. Thus, in accordance with the present invention, the types of catalysts are metallocene, Ziegler catalysts or Ziegler-Coloring"and "catalysts Phillips" (or "chrome" catalysts). In addition, in the method according to the present invention as a catalyst types are considered "mixed catalysts composed of two or more of the following, for example a mixture of metallocene catalysts, or a mixed catalyst system metallocene/catalyst Ziegler.

In General, significant changes, even within the above-mentioned types of catalysts, usually do not occur during a specific mission transition polymerization. Thus, the catalyst used in the production of the earlier polymer, the first polymer (if not earlier polymer and the second polymer is most likely the same or similar, even among these General types. The phrase "similar to" understand the catalyst from the same family of catalysts. Family of catalysts is characterized by the fact that all the catalysts are catalysts of the same type, and they allow you to produce powders of polymers with similar physical properties in relation to adsorption/desorption of comonomers.

the example metallocene catalysts, which are included in appropriate family will mainly include the same active metal and the same ligands. Similarly, during the main parts of the operation transition of polymerization will most likely be applied in similar or identical promoters or other additives to the catalyst.

Most preferably, the same catalyst was used to obtain the earlier polymer, the first polymer (if earlier the polymer is missing) and the second polymer.

In General, if the monomer does not change during the transition, the number of co monomer, specifically the number of monomer relative to the main olefin, usually when the transition is changed. Typically, this change is reflected in the change of the temperature of polymerization and, therefore, is accounted for based X₂from T₂.

A number of other reagents, such as hydrogen, may also be modified as necessary for the transition. In General, changes such components will not have a significant impact on the subsequent stage of degassing.

The pressure of the reaction is usually about the same before and after the transition. As described above, in one preferred options to the first aspect of the present invention obtained polymers can be grouped accordingly the temperature interval is receiving them, for example, 10 or 5°C, within which all the polymer will be subjected to degassing using the same speed blowing. This principle can also be applied in General to all operations transition polymerization, so that the specific rate of degassing is used within each band.

In the second aspect, therefore, the present invention provides a method of obtaining three or more polymers in the operation transition of polymerization in the polymerization, the setting for polymerization includes the reactor vessel for degassing, and this method includes the following stages:

(a) obtaining a first polymer;

(b) the transition from the receipt of the first polymer to the second polymer;

(C) the receipt of the second polymer;

(g) the transition from the receipt of the second polymer and the third polymer;

(d) the receipt of the third polymer;

(e) repetition of these stages if necessary, navigate to the receipt of any additional polymers

each polymer obtained by contacting the principal of olefin and co monomer with a catalyst under conditions of gas-phase polymerization reactor with obtaining the specified polymer, and this polymer is then in contact with the purge gas in the vessel for degassing in order to remove the non-is reacted monomers;

moreover, when obtaining all of these polymers are used the same basic olefin, but every time I move to change at least one of the following options: (1) used comonomer and (2) the reaction temperature at which the polymer, with the additional condition that at least one transition is used, the monomer is changed and at least one transition changing the reaction temperature; characterized in that

for each of the co monomer, which is used in the operation transition of polymerization, determined two or more strips, covering the temperature range within the total range of temperatures used to obtain polymers with the use of the specified co monomer; each of the three or more polymers produced during the operation of the transition polymerization is carried out at a temperature that falls into one or more of the specific bands for the corresponding co monomer, and, with each band associated with a certain rate of flow of purge gas into the vessel for degassing;

moreover, at the time of receipt of each of the polymers of the flow rate of purge gas in the vessel for degassing equal to or greater than the flow rate associated with this band, which enters the specified polymer, and

although from one polymer to the other occurs within a single lane, the on time of each transition gas flow rate in the purge vessel is changing at such speed, which is equal to or greater than the flow rate associated with this band, within which is the polymer, the production of which the transition occurs.

The second aspect of the present invention provides a number of temperature intervals and associated flow velocities purge gas into the vessel for degassing, which is determined on the basis of the temperature of the receiving polymer and the nature of the co monomer. There are at least two temperature interval for each monomer, which is used during the operation transition of polymerization, and because it is used not less than two monomers (may be change of co monomer), generally identified at least four temperature interval.

Preferably the complete interval of possible temperatures of reaction for each of the co monomer to be used is divided into consecutive disjoint intervals, each of them associated with a specific flow rate of the purge gas in the vessel for degassing. A typical temperature range of the reaction may range from 70 to 120°C or wider, and usually for each of the co monomer, there are at least five temperature intervals, each of width 10°C or less.

Intervals can be appropriately presented or shown in the face or matrix, in which on one side shows the type of co monomer, while the other temperature intervals in the General form as shown below in table 1A, and, as a more specific example, in table 1B.

In the tables above, each of the values X1, x2, Y1, Y2, etc. represents the flow rate of purge gas in the vessel for degassing of a polymer to be produced by applying the relevant co monomer and in the appropriate temperature range, so that at the time of receipt of the each polymer flow rate of purge gas in the vessel for degassing equal to or greater than associated with the interval velocity. As follows from the above tablb, upon receipt of the polymer from the main olefin and 1-hexene at 85°C is used, the flow rate of the purge gas, which is equal to or greater than Y2.

Except when the transition from one polymer to another polymer occurs within the same temperature interval during each transition gas flow rate in the vessel for degassing is changed to one that is equal to or greater than the gas flow velocity associated with this temperature interval, in which falls the temperature of the receiving polymer, for which the transition is performed. As can be seen from the above tablb, when moving from a polymer, which includes the main olefin and 1-hexene and received at 85°C, the polymer comprising the same basic olefin and 1-hexene and received at 95°C, flow rate of the purge gas is changed from a speed equal to or greater than Y2, to a speed equal to or greater than Y3. When moving from a polymer, which includes the main olefin and 1-hexene and received at 85°C, the polymer comprising the same basic olefin and 1-octene and received at 85°C, flow rate change of the velocity, which is equal to or greater than Y2, at a speed which is equal to or greater than Z2.

The values X1, x2, etc. is chosen as the minimum flow rate of purge gas to provide the desired (safe) speed money is saved within the temperature interval for the specified concrete co monomer and temperature interval. The flow velocity in each temperature interval is usually based on the lowest temperature in each temperature interval, as it requires the highest flow rate of the purge gas.

In General, it is desirable to use a flow rate of the purge gas in the vessel for degassing, which is a related quantity for the specific polymer (i.e. X1, x2 and so on), or close to it speed, which is defined as the speed increased by not more than 10%, because any further increase in the rate of flow of purge gas causes additional costs in the absence of economic benefits. Each table corresponds to a specific primary olefin, for example ethylene, but usually not in a specific process.

As for the first aspect of the present invention, and again without wishing to be limited by theory, the second aspect of the present invention is based on the fact that, in addition to the nature of the co monomer and the reaction temperature, a large number of other variables that could affect the degassing process, not change, or changes, such as changes in the concentration of monomer, will not have a significant impact on the claims to a method of degassing.

Although not necessarily so limited, in General, in the first TSA is those will apply a very simple relationship between the values of the rate of degassing of polymers, in the production of which used the same comonomer, but the polymerization reaction proceeds at different temperatures.

So, x2, X3 and X4 is usually at least 1% lower compared to the X1 with increasing temperature for each 1°C from the beginning of the reaction within the corresponding temperature intervals, i.e., "b", "C" and "d"compared to "and" in table, 80°C, 90°C and 100°C compared to 70°C tablb.

Preferably, x2, X3 and X4 is not more than 3% lower compared to the X1 with increasing temperature for each 1°C from the beginning of the reaction within the corresponding temperature intervals and most preferably below a value from 2 to 3% for temperature increase for every 1°C.

As mentioned for the first aspect of the present invention, it is possible to determine the flow rate of the purge gas during the operation transition of polymerization for each polymer, which is expected to produce, on the basis of the temperature and the nature of the co monomer, which is supposed to apply. However, in the second aspect of the present invention benefit from the fact that for practical purposes, the operation is usually more convenient to define temperature intervals, for example, a width of 10 or 5°C, in which the rate of blowdown is not changed by transitions between products within concr the spas temperature interval; the flow rate of the purge gas is changed only in the case when the transition occurs to the temperature of another temperature interval or when there is a change of co monomer.

Usually the narrower temperature interval in this second aspect, the more optimal is the degassing of the product set, so that the value of 5°C or less is preferable for the width of each interval. As specific examples of certain temperature intervals can be as follows: 70-<75°C, 75-<80°C, 80-<85°C, 85-<90°C, 90-<95°C, and so on, although it is obvious that it is equally possible to use other intervals of width 5°C. Similarly, optional temperature intervals must be the same size, for example 5°C throughout the operational window of the method of producing the polymer. For example, the interval width of 5°C can be applied at lower temperatures and at higher temperatures can be applied over a wide interval, for example 10°C. For simplicity, for all comonomers usually apply the same intervals, although again this is not strictly necessary.

The second aspect of the present invention provides a time-consuming but relatively simple control system, which makes sure that all of the produced polymers are adequately degassed. Compared with conventional methods, in which the s apply the same flow rate of purge gas for all of the produced polymers, in this way achieved a significant reduction of flow velocities purge gas for many polymers. This method, however, is much easier than trying to determine the individual flow rate of the purge gas for all polymers, which are produced during the operation of the transition polymerization.

Example

The following example illustrates the method according to the present invention.

All polymers were obtained in the gas-phase reactor with a fluidized bed with the use of a catalyst of Ziegler-Coloring. Used reactor with a diameter of 4.5 m height layer 16 PM

The degassing process included three stages. The first stage consisted of processing in the evaporating column, in which reduced pressure. At this stage adsorbing gas is not used. In the second stage used the return purge gas with a constant speed. At the third stage as the purge gas was applied nitrogen.

The flow rate of nitrogen was changed to the specified third stage depending on the polymer that is produced. The flow rate was determined for the sequence of temperature intervals and depending on the co monomer, which is used in the process, as described above.

First produced polymer was a copolymer of ethylene with 1-butene was obtained at a temperature of about 108°C. was Used, the flow of nitrogen 730 kg/h

the first transition was made with the purpose of obtaining a copolymer of ethylene with 1-hexene, which is also received at a temperature of about 108°C (observed a small decrease in temperature). The flow rate of nitrogen was increased to 1030 kg/h

The second transition was to increase the temperature to about 110°C without changing the nature of the co monomer, to obtain a copolymer of ethylene with 1-hexene another variety. In this example, the production of this second polymer is carried out within the same temperature interval as the production of the previous product, therefore, the flow rate of the purge gas is not changed.

Then spent the next temperature increase to about 113°C with the aim of obtaining another varieties of a copolymer of ethylene with 1-hexene. In this case, the new temperature falls within the following temperature range, and the flow rate of nitrogen was reduced to 780 kg/h

Then the temperature was reduced to about 108°C, again using 1-hexene as co monomer. The temperature was returned in the temperature interval, which is used in obtaining an earlier copolymers of ethylene with 1-hexene, and the flow rate of nitrogen was again increased to 1030 kg/h

Finally, at a constant temperature of 108°C changed the nature of the co monomer, again using 1-butene. Received the same product as on the first stage, and accordingly the flow rate of nitrogen was again changed so that it was equal to the original value of 30 kg/h

1. The way of transition from the first method of obtaining the first polymer to the second method of obtaining the second polymer during the operation transition of polymerization in the polymerization, which comprises the reaction vessel and the vessel for degassing, in this way, respectively, each of the first and second processes comprises the following stages:
(a) the implementation of the primary contact of olefin and co monomer with a catalyst under conditions of gas-phase polymerization in the reaction vessel receiving respectively the first or the second polymer, and the above first and second methods are used the same basic olefin, and the difference between the first and second method consists in at least one of the following factors: (1) used comonomer and (2) the reaction temperature at which the polymer, and
(b) further contacting respectively the first or the second polymer from the purge gas in the vessel for degassing in order to remove unreacted monomers,
characterized in that the transition involves a change in the flow rate of purge gas in the vessel for degassing from the first value of X₁that used in the degassing of the first polymer to the second value of X₂that used in the degassing of the second polymer, and the second value is defined relative to the MSE of the barb thread X _iand temperature T_ithat apply at an earlier stage of obtaining the polymer in the process of operation of the transition polymerization using the same co monomer, in the second process, and the reaction temperature T₂in the second process, and also the fact that
(a) if T₂increases with respect to T_i, X₂at least 1% lower compared with X_iwith increasing T₂compared with T_ifor every 1°C
(b) if T₂is reduced with respect to T_i, X₂at least 1% higher compared with X_iwith increasing T₂compared with T_ifor every 1°C
(C) if T₂equal to T_i, X₂is equal to or more than X_ipreferably equal to X_i.

2. The method according to claim 1, in which T₂increase with respect to T_iand X₂not more than 3% lower than X_iwhen the temperature T₂compared with T_ifor every 1°C.

3. The method according to claim 1, in which T₂reduce with respect to T_iand X₂not more than 10% higher than X_iwhen the reduction temperature T₂compared with T_ifor every 1°C.

4. The method according to claim 1, in which T₂equal to T_iand X₂less than 5% more in comparison with X_i.

5. The method according to any of the preceding paragraphs, in which each polymer obtained in lying to the operation transition of polymerization, will degassing at a flow rate of the purge gas is determined based on the actual temperature of the production of the polymer and the nature of the co monomer, so that every change of the reaction temperature leads to a change in the flow rate of purge gas at the stage of degassing on the one that corresponds to the flow rate for the second polymer, the production of which the transition occurs.

6. The method according to any one of claims 1 to 4, in which the set temperature range, and the velocity of the purge does not change when changing between products within a specific range of temperature, the rate of blowdown is changed only if the transition is carried out to obtain a polymer at a temperature T₂that is owned by another temperature interval as compared with the interval in which the temperature T₁.

7. The method according to any one of claims 1 to 4, in which the main olefin selected from ethylene and propylene, and comonomeric olefin selected from 1-butene, 1-hexene and 1-octene.

8. The method according to any one of claims 1 to 4, in which the purge gas is an inert gas or regeneration purge gas or the mixture of the above.

9. The method according to any one of claims 1 to 4, in which to get an earlier polymer, the first polymer and the second polymer is used the same katal is the jam.

10. A method of obtaining three or more polymers in the polymerization, including the reactor and the vessel for degassing, the method includes the following stages:
(a) obtaining a first polymer;
(b) the transition from the receipt of the first polymer to the second polymer;
(C) the receipt of the second polymer;
(g) the transition from the receipt of the second polymer and the third polymer;
(d) the receipt of the third polymer;
(e) repetition of these stages if necessary, navigate to the receipt of any additional polymers,
each polymer obtained by contacting the principal of olefin and co monomer with a catalyst under conditions of gas-phase polymerization reactor with obtaining the specified polymer, and this polymer is then in contact with the purge gas in the vessel for degassing in order to remove unreacted monomers;
moreover, when obtaining all of these polymers are used the same basic olefin, but every time I move to change at least one of the following options: (1) used comonomer and (2) the reaction temperature at which the polymer, with the additional condition that at least one transition is used, the monomer is changed and at least one transition changing the reaction temperature; characterized in that
D. the I of each of the co monomer, which is used in the operation transition of polymerization, determined two or more strips, covering the temperature range within the total range of temperatures used to obtain polymers with the use of the specified co monomer, each of three or more polymers produced during the operation of the transition polymerization is carried out at a temperature that falls within one of the specific bands for the corresponding co monomer, and, with each band associated with a certain rate of flow of purge gas into the vessel for degassing;
moreover, at the time of receipt of each of the polymers of the flow rate of purge gas in the vessel for degassing equal to or greater than the flow rate associated with this band, which enters the specified polymer, and
although from one polymer to the other occurs within a single strip, during each transition gas flow rate in the purge vessel is changing at such speed that is equal to or greater than the flow rate associated with this band, within which is the polymer, the production of which the transition occurs.

11. The method according to claim 10, in which the temperature intervals are set as follows: