KR101467680B1 - A process for transitioning between ziegler natta catalyst system and metallocene catalyst system - Google Patents

Abstract

The present invention relates to a process for the conversion between polymeric catalyst systems which are incompatible with each other and in particular to the conversion of olefin polymerization using a conventional Ziegler-Natta catalyst system to olefin polymerization using a metallocene catalyst system And to a method for reducing conversion time in a method of reversing it.

Description

[0001] The present invention relates to a method for converting a Ziegler-Natta catalyst system to a metallocene catalyst system,

The present invention relates to a process for the conversion between polymeric catalyst systems which are incompatible with each other and in particular to the conversion of olefin polymerization using a conventional Ziegler-Natta catalyst system to olefin polymerization using a metallocene catalyst system And to a method for reducing conversion time in a method of reversing it.

The metallocene catalysts are known to be a catalyst system for producing polyolefins having high physical properties and high reactivity and high copolymerization reactivity as compared with existing Ziegler Natta catalysts. However, metallocene catalysts have significantly different hydrogen reactivity and copolymerizability than conventional Ziegler - Natta catalyst systems.

During the conversion of miscible catalysts, there is typically only a slight difference in the reactivity of the miscible catalyst with respect to hydrogen and comonomer, so that there is only a slight change in gas phase composition and flow conditions at the time of catalyst replacement, The change in the physical properties of the resulting final product is also not great. However, in the case of the incompatible catalyst, the conversion between the two catalysts in a commercial reactor is accompanied by a change in many process conditions owing to the different polymerization characteristics. Among them, the gas phase composition for producing the target polymer is very different Composition. Generally, metallocene catalysts have a hydrogen reactivity of 100 to 500 times higher than that of the Ziegler-Natta catalyst system and a 5 to 10-fold higher copolymerization, so that the conversion to a metallocene catalyst system under the conditions of using a Ziegler-Natta catalyst system results in a very low hydrogen and copolymer composition . In this case, when the activity of the Ziegler-Natta catalyst is maintained in the reactor, ultrahigh molecular weight is produced at a very low hydrogen concentration composition, which causes a gel problem in the product. To prevent this problem, the conversion between non-hybridizing catalysts, such as metallocenes and Ziegler Natta catalysts, takes place using an inactivating agent to stop the reaction of the activated catalyst in the reactor. However, since the inactivating agent acts to inhibit the activity of the newly introduced catalyst while remaining in the reactor after use, the purification step of removing the deactivating agent at a very low level is required for the injection of the fresh catalyst, And then injecting the new catalyst finally. This conversion process is very time consuming and costly. If the conversion process is unsuccessful, the entire bed can not be used because the ultrahigh molecular weight that causes gel problems is mixed in the bed, and the entire reactor must be cleaned. In order to ensure deactivation, an inactivating agent may be used in an excessive amount, but in this case, there is a limit to overuse of the catalyst to be newly injected because of the adverse effect of acting as a catalyst poison. The appropriate amount of the deactivating agent to be used depends largely on the type of the reaction, the type of the catalyst used, the amount of the polymer present in the reactor, and the shape of the polymer. Further, as described above, in order to remove the deactivating agent in the next step, it includes a step of using an organometallic compound, which is another activating agent. If the activating agent exceeds the proper residual amount, it causes excessive reaction in the reactor Sheet formation and fine powder are formed to cause problems such as reactor fouling and the like.

Conventional techniques for the conversion of incompatible catalysts (mainly between metallocene catalysts and Ziegler-Natta catalyst systems) generally consist of the following steps: a) stopping the injection of the main catalyst and cocatalyst (alkyl aluminum), b ) Waiting for the residual activity to drop below a certain criterion, c) irreversibly deactivating the residual activity using an inactivating agent, d) removing the deactivating agent to a level that does not affect the freshly introduced catalyst, e ) Adjusting the vapor composition according to the operating conditions of the new catalyst, f) introducing the fresh catalyst into the reactor, and g) determining whether the conversion process is successful from the polymerization effluent after the injection of the fresh catalyst. Here, the steps a) to b) may be performed sequentially or simultaneously. The inactivating agent used in step c) is a compound which binds to the cocatalyst and acts to lower or stop the activity, or directly binds to the catalytically active species to directly inactivate the catalytic activity. Specific examples thereof include CO, CO ₂ and the like as reversible deactivators in U.S. Patent No. 5,442,019, U.S. Patent No. 5,672,665, U.S. Patent No. 5,747,612 and U.S. Patent No. 5,753,786, and O ₂ , H ₂ O, and alcohol. In addition, European Patent No. 0,107,105 and US Patent No. 4,460,755 describe examples using a compound containing a hydroxyl group. Such materials include silica containing a hydroxyl group. U.S. Patent No. 6,897,269 and European Patent No. 1,576,016 refer to non-volatile materials such as alkoxylated amines, alkoxylated amides, ethoxylated stearyl amines, and the like.

In step d), most of the above-mentioned patents use the nitrogen pressurization purge method. The most time is required at this stage because if the deactivating agent used to deactivate the active catalyst in the bed remains, it acts as a poison of the newly introduced catalyst and interferes with the initiation of the polymerization reaction. Especially when the freshly introduced catalyst is metallocene, the impurity level required at this stage is mostly less than 1 ppm because it is very sensitive to catalyst poisoning. Therefore, when the deactivation agent is removed by nitrogen purge, the number of times of deactivation is several tens of times. In order to pressurize the reactor with nitrogen for nitrogen purge, it takes a long time to inject nitrogen, It may be over 24 hours. As a method exemplified in U.S. Patent No. 6,995,217 and U.S. Patent No. 5,105,926, there is proposed a method of removing an inactivating agent adsorbed in a bed, using an additional alkylaluminum in step d) or step f) The remaining alkyl aluminum causes problems such as over-reaction with the newly introduced catalyst to form sheets, and is described in U.S. Patent No. 5,753,786. Therefore, in the case of using alkyl aluminum, additional nitrogen purge is required, and additional time is required. U.S. Patent No. 5,672,666 and European Patent No. 0,838,393 and International Patent No. 9,639,450 disclose a method for initiating the introduction of a second catalyst without the use of additional alkylaluminum.

Thus, in general, the conventional incompatible catalyst-to-catalyst conversion method takes a very long time in the conversion process and does not mention specific criteria for the amount of the inactivating agent to be injected. Although the deactivating agent is defined only as the amount proportional to the residual catalyst metal component, there is no description of a method of minimizing the amount of the residual catalyst or a method of maximizing the amount of the new catalyst. As a result, if the residual catalyst is not minimized, the amount of deactivation agent, purge time and activator required increases and the conversion takes a long time. This causes a great loss in the production process. If the amount of the fresh catalyst is not maximized, This also causes loss because it is longer. Therefore, this case is not appropriate.

It is an object of the present invention to solve the problems of the prior art as described above, and it is an object of the present invention to reduce the amount of the deactivating agent injected by minimizing the residual catalyst in the conversion process as compared with the conventionally proposed incompatible catalyst- It is possible to perform conversion between the incompatible catalyst systems without using the shortening and activating agent and also to maximize the amount of the new polymer in which the activity is alive and to shorten the time from the normalization to the conversion, To provide an effective method for the conversion between a Ziegler-Natta catalyst system and a metallocene catalyst system.

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a method for enabling conversion to a minimum period at the time of transition from one type of catalyst system to an incompatible catalyst system, And how to prevent the problems caused by the reactivation of the first catalyst in advance.

Specifically, the process of the present invention can be applied to the conversion between a conventional Ziegler-Natta catalyst / catalyst system and a metallocene catalyst / catalyst system. The terms "catalyst" and "catalyst system" may be used interchangeably herein.

The method for converting between incompatible catalysts according to the present invention is characterized in that it comprises the steps of: from a polymerization reaction by a first catalyst to a polymerization reaction by a second catalyst which is immiscible with said first catalyst,

a) storing the polymer produced using the first catalyst and the polymer prepared using the second catalyst that is immiscible with the first catalyst in their respective separate storage vessels while maintaining their activity during each polymerization;

b) stopping the introduction of the existing catalyst into the reactor of the first catalyst to convert the first catalyst to a non-admixable second catalyst;

c) discharging at least a portion of the residual polymer remaining in the reactor to minimize the amount of residual catalyst inside the reactor;

d) irreversibly deactivating the residual activity of the remaining catalyst using a killing agent;

e) maintaining the deactivating agent in the reactor;

f) removing the deactivating agent by nitrogen purge;

g) discharging the residual deactivating agent and the residual polymer, and then filling the reactor with the novel polymer produced by the second catalyst in which the activity retained in step a) is viable;

h) adjusting the vapor composition according to a second catalyst operating condition which is a new catalyst;

i) introducing a fresh catalyst into the reactor;

j) determining whether the conversion process is successful from the polymerization effluent after the introduction of the fresh catalyst into the reactor; And

k) Storing some of the polymer produced after the new catalyst injection and polymerization stabilization in a storage container again.

Here, the first catalyst may be a Ziegler-Natta catalyst, the second catalyst may be a metallocene catalyst, and conversely, the first catalyst may be a metallocene catalyst and the second catalyst may be a Ziegler-Natta catalyst.

The method of conversion of the catalyst according to the invention as described above makes it possible to switch to the use of a minimum amount of deactivating agent in the minimum period of the conversion process in the transition from one type of catalyst system to another incompatible catalyst system, It is possible to prevent a quality problem (gel formation) and a trouble of a product which may occur in the conversion process to the conversion catalyst system.

Hereinafter, the present invention will be described in more detail.

In the catalyst conversion method according to the present invention, in order to discharge the polymer by the existing catalyst in the reactor during the catalyst conversion in the step a) and to fill the empty reactor with the new catalyst polymer, This container must contain the polymer to be filled during the conversion process. Therefore, at least two storage containers are required, and the storage container is not particularly limited and includes, for example, a silo.

The polymer in the state of "active state" in the step (a) means a polymer in a state where further polymerization can take place, that is, a state capable of further reaction with monomers and comonomers or hydrogen to produce polymers of higher molecular weight .

In the method for converting a catalyst according to the present invention, in the step b), introduction of the first catalyst, which is a conventional catalyst, into the reactor is stopped in order to convert the first catalyst into a non-miscible second catalyst.

In the method of converting a catalyst according to the present invention, in the step c), the remaining polymer remaining in the reactor may be discharged to minimize the amount of the residual catalyst in the reactor. The method of discharging the residual polymer is not particularly limited, and there is a method of discharging the entire polymer or a method of partially discharging the polymer. If the polymer remaining in the reactor is completely discharged during the discharge, the amount of the residual polymer is minimized because only a small amount of polymer remains on the wall or the bottom. However, since there is no polymer capable of flowing into the reactor, The inactivating agent may not effectively remove the activity of the polymer adhering to the reactor wall surface. It is therefore more desirable to leave a minimum amount of polymer that can flow within the reactor. For this reason, the emission amount of the residual polymer in the reactor preferred in the step c) is 50 to 95 wt% of the total amount of the residual polymer, and the most preferable emission amount is 70 to 95 wt%.

In the method of converting a catalyst according to the present invention, in the step d), an inactivating agent is used to irreversibly deactivate the residual activity of the residual catalyst.

The remaining catalyst in step c) has adverse effects on the quality (gel formation) even if a small amount of the catalyst is prepared again. An irreversible deactivation step is therefore required. However, there is an advantage that the amount of the residual catalyst can be minimized by discharging the residual polymer as in the step c), as compared with before the emptying of the reactor, so that only a small amount of the deactivating agent can be used in the step d).

In the method for the conversion of the catalyst according to the present invention, the deactivating agent used in step d) is a catalyst destroying agent or an inhibitor which deactivates the ability of the catalyst to polymerize the olefin. The deactivating agent can be, for example, carbon dioxide, sulfur dioxide, sulfur trioxide, glycols, phenols, ethers, carbonyl compounds, more particularly ketones, aldehydes, carboxylic acids, esters, fatty acids, alkenes such as acetylenes, Compounds, organic halides such as pyridine, pyrrole, carbonyl sulfide, carbon tetrachloride and mercaptan, and the like. It is also important that the deactivating agent does not contain oxygen, alcohol or free water, which, if included, adheres polymeric fines to the walls of the reactor, resulting in sheeting of the reactor. The use of such deactivators also reduces the possibility of shearing and contamination of the reactor. Preferred inactivating agents are carbon dioxide and water. Carbon dioxide has the additional effect of restricting the action of alkyl aluminum as a cocatalyst with a reversible deactivator for the catalyst or an irreversible reaction for the alkyl aluminum. Water has an irreversible deactivation action on both the catalytic transition metal component and the alkyl aluminum. However, water is not easily removed from the deactivator removal step in comparison with carbon dioxide. Therefore, it is desirable to use them effectively.

When the deactivating agents are used as any mixture, it is advantageous that some of the deactivating agents react with each other so that the deactivating agents are introduced separately when using a plurality of deactivating agents.

In a preferred embodiment of the catalyst conversion method according to the present invention, the deactivating agent is introduced into the reactor for a period of time sufficient to substantially inactivate the catalyst in the reactor and thus substantially prevent further polymerization.

The amount of the deactivating agent to be used may vary depending on the size of the reactor, the amount and type of catalyst and cocatalyst in the reactor, the amount and type of polymer, but the minimum amount of deactivating agent used is important. This is because the deactivating agent needs to be removed before introducing the second incompatible catalyst, so that the use of the unnecessary deactivating agent is rather an obstacle to the conversion step.

When the amount of the deactivating agent is calculated considering only the catalyst transition metal, the amount of the effective deactivating agent may be insufficient. Therefore, the catalyst transition metal component, the metal component in the co-catalyst and the metal component of the support must all be considered.

Accordingly, it is preferred in the present invention that the molar ratio of deactivating agent to the total metal atoms of the catalyst system present in the fluidized bed in the reactor is in the molar ratio of 1 to 200, preferably 1 to 100, most preferably about 1 to about 10 If the molar ratio is less than 1, the amount of the deactivating agent is insufficient, and if the molar ratio exceeds 200, the deactivating agent is excessively injected and then takes a long time to remove the deactivating agent.

In the catalyst conversion method according to the present invention, in the step (e), the deactivating agent is maintained in the reactor. At this time, sufficient time is required for the inactivating agent to be dispersed throughout the reactor, especially over any polymer product in the reactor. Once the deactivation agent is introduced into the reactor, the conversion process is continued after about 1 hour to about 24 hours, preferably about 1 hour to about 12 hours, most preferably about 1 hour to 8 hours, Can vary depending on the nature and amount of the catalyst, the volume of the reactor, and the reactivity of the deactivating agent and the amount of bed. Therefore, for this reason, the deactivating agent is preferably a gas or a vapor in the reactor condition.

In the method for converting a catalyst according to the present invention, in step (f), the deactivating agent is removed by nitrogen purge.

The deactivating agent should be effectively removed after performing the function of inhibiting the activity of the catalyst in the fluidized bed. Carbon dioxide is easily removed by nitrogen purge, but in the case of water, it is not easily removed by nitrogen purge. The water adsorbed to the fluidized bed polymer continuously influences the activity of the catalyst in the subsequent introduction step of the catalyst. Therefore, the step of selectively removing the deactivating agent by the organometallic compound can be carried out at the same time. The organometallic compound used herein _{may be a} compound represented by the general formula AlR _(3-a) X _a wherein R is a branched or linear alkyl or cycloalkyl having 1 to 30 carbon atoms or a hydride radical, X Is a halogen, and a is 0, 1 or 2.

However, in the present invention, it is sufficient to remove the deactivator through nitrogen purge in the step f), since the next step is to empty the deactivated polymer and fill the reactor with the novel polymer. Nitrogen distillation is generally carried out by repeatedly performing pressurization and depressurization, and pressurization and depressurization are performed at a pressure of 1 bar to 20 bar, preferably 3 to 10 bar. It takes several tens of minutes to pressurize the gas phase polymerization reactor with the above pressure, and it takes about 3 to 10 hours for the entire purge step. Nitrogen spreading is carried out 10 to 20 times, and the criterion for completion is that the deactivating substance in the degassing gas is less than 1 ppm.

In the method for converting a catalyst according to the present invention, in step g), all of the remaining inert polymer is discharged, and the reactor is filled with the novel polymer prepared as the second catalyst in which the activity retained in step a) is viable.

If the residual polymer is completely discharged in the step g), the moisture adsorbed on the polymer in the deactivating agent injecting step is removed together with the residual polymer. In addition, in step a), the storage vessel can use a silo, and since the reactor is filled with the new polymer stored in the silo, the polymerization can be carried out from the adjustment step of the gas phase in the next step.

In the method for converting a catalyst according to the present invention, in the step h), the vapor composition suitable for the operation conditions of the second catalyst to be newly introduced can be adjusted. Thereby constituting a vapor phase composition suitable for the operation conditions suitable for the new catalyst. In the prior art, when the conversion between incompatible catalyst systems is carried out, the polymer in this step is generally not active due to the inactivating agent. In the present invention, since the reactor is newly filled with a novel polymer having activity in the step g) .

Certain gas compositions must be present in the reactor in order for a particular catalyst to produce a particular product having a specific density and melt index (which generally depends on how well the catalyst is bound to the comonomer). In general, the gas composition comprises ethylene alone or in combination with ethylene in addition to one or more linear or branched monomers having from 3 to 20, preferably from 3 to 12, carbon atoms as comonomers.

The process for the conversion of catalysts according to the invention is particularly suitable for the conversion of ethylene and one or more monomers such as propylene, butene-1, pentene-1, 4-methylpentene-1, hexene- And cyclic and polycyclic alpha-olefin monomers such as cyclopentene, norbornene, and cyclohexene, or mixtures thereof. Other comonomers used with ethylene include polar vinyl monomers, diolefins such as 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, norbornene, norbornadiene, and acetylene , Other unsaturated monomers including 1-alkyne and aldehyde monomers. High alpha-olefins and polyenes or macromonomers can also be used. Preferably, the comonomer is an alpha-olefin having 3 to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and most preferably 4 to 10 carbon atoms. In another embodiment, the gas composition comprises ethylene with two or more other comonomers to form a terpolymer or the like, and preferred comonomers include 3 to 10 carbon atoms, more preferably 3 to 10 carbon atoms, optionally having one or more diene monomers Is a combination of alpha-olefin monomers having from 3 to 8 carbon atoms. Preferred terpolymers are ethylene / butene-1 / hexene-1, ethylene / propylene / butene-1, ethylene / propylene / hexene-1, ethylene / propylene / norbornadiene, ethylene / propylene / And combinations thereof.

Typically, the gas composition also contains a certain amount of hydrogen to control the melt index of the resulting polymer. In a typical situation, the gas comprises a certain amount of dew-point increasing component, and the remaining gas composition is made of a non-condensable inert gas, such as nitrogen.

Depending on the second catalyst introduced into the reactor, gas compositions such as comonomers and concentrates of hydrogen gas can be increased or decreased. When the metallocene catalyst system is a novel catalyst, the mole ratio of hydrogen to ethylene is 1/100 to 1/500, and the mole ratio of comonomer to ethylene is in the range of 1/5 to 1/10.

In the catalyst conversion method according to the present invention, in the step i), the novel catalyst is introduced into the reactor.

In step h), when the vapor phase composition reaches a level suitable for the new catalyst, a new catalyst is injected. In this case, suitable organometallic compounds can be injected simultaneously or sequentially for activation of the newly introduced catalyst. The molar ratio of the organometallic compound to the transition metal of the catalyst is preferably 1 to 2000, more preferably 10 to 1000, and most preferably 100 to 500. If the molar ratio is less than 1, , And when the molar ratio exceeds 2000, the organic compound reduces the activity of the catalyst, which is undesirable.

In the method for converting a catalyst according to the present invention, in the step j), it is judged whether or not the conversion process is successful from the polymerization discharge after the new catalyst is injected into the reactor.

The determination of the success or failure of the conversion process can be performed by: i) preparing a film using the polymer before the conversion process and using the polymer as a control for the presence or absence of gel formation; ii) And confirming the presence or absence of gel formation.

When a new catalyst is injected and a polymerization reaction proceeds to produce a new polymer, a portion of the fluidized bed begins to be discharged to the reactants to maintain a constant fluidized bed. In the prior art, the initial effluent contains most of the polymer prior to the conversion reaction than the polymer by the fresh catalyst, which contains the deactivated residual catalyst. However, in the present invention, since the existing polymer is discharged in the step g) and the new polymer having activity is filled in the reactor, the polymer by the new catalyst can be obtained from the beginning of the reaction. In the case of a successful conversion process, the gel contains the same level of gel as before the conversion process, but if the conversion process fails, a large amount of gel will be produced in the emission evaluation. If such a problem occurs, the entire fluidized bed can not be used as a product, and a reaction for forming a clean bed must be newly performed, so that the conversion process can not proceed at this point. The present invention provides a technique for solving such a problem.

In the catalyst conversion method according to the present invention, in step k), some of the polymer produced after the injection of the new catalyst and the polymerization stabilization are stored again in a storage container.

The reactor holding the novel polymer is empty since the new polymer which is active in the reactor in step g) is filled in the reactor. Therefore, if some of the polymers produced after the stabilization of the new catalyst polymerization are stored in the reactor again, they can be used for the next conversion and can be operated continuously in the future.

Hereinafter, the catalyst system and the polymerization method used in the present invention will be described.

Metallocene  Catalyst system

The metallocene catalyst system used in the present invention comprises a metallocene catalyst represented by the general formula (THI) ₂ R "MQ _p .

Wherein M is a group selected from the group consisting of IIIB, IVB, VB, or VIB groups, wherein R "is a structural bridging group that imparts steric rigidity between two THI groups; Q is a hydrocarbyl group having from 1 to 20 carbon atoms or halogen; p is the valence of M is -2;

In the metallocene catalysts of the above formula, the two THI ligands may be the same or different, but are preferably the same.

The substitution patterns and numbering of the ligands of the metallocene catalysts usable in the present invention are described in detail below.

When THI is substituted, this means that any position on the THI may contain a substituent instead of a hydrogen atom. Thus, each substituted THI ligand may have a substituent on the 5-membered ring, a substituent on the 6-membered ring, or a substituent on both the 5-membered ring and the 6-membered ring.

In the specification of the present invention, the substituent positions of the THI ligands are numbered from 1 to 7 by the following notation system.

To distinguish substitution of the first THI ligand and the second THI ligand in the two THI ligands, the second THI ligand is numbered by the same system as above but numbered 1 'to 7'. In this type of catalyst, the position of the cross-linking of the two THI ligands is not particularly limited and preferably 1,1'-bridged, 2,2'-bridged or 1,2'-bridged, - Cross-linking is most preferred.

The position of the substituent (s) on the two THI ligands is not particularly limited, but at least one THI ligand is substituted in the 2-position and / or the 4-position (or 2'- and / or 4'- .

In one preferred embodiment, both of the two THI ligands may be substituted. In this case it is preferred that the two THI ligands both contain substituents at the 2-position (2'-position) and / or the 4-position (4'-position) Position) and 4-position (4'-position), and other positions in the THI ring may be substituted or unsubstituted.

Particularly preferred metallocene catalysts having 1,1'-bridges are 2; 4; 2,4; 2,2 '; 4.4 '; 2,4 '; 2,4,2 '; 2,4,4 '; And a substitution pattern of 2,4,2 ', 4', and only the above-mentioned positions include a substituent. Here, since the basic structure of two THI ligands is the same, for example, the substitution pattern of 2,4 'and 4,2' is the same THI substitution structure.

The kind of the substituent (s) present on the THI ligand is not particularly limited. When the THI ligand contains two or more substituents, such THI ligands may be substituted with the same substituent or different substituents.

Preferably, the substituents are independently selected from hydrocarbyl groups, alkyl groups, alkylsilyl groups, alkoxy groups, cycloalkyl groups, aryl groups and halogens having 1 to 20 carbon atoms. Examples of these are phenyl (Ph), benzyl (Bz), naphthyl (Ind) and benzindenyl (BzInd), methyl (Me), ethyl (ethyl) Pr), i-propyl, n-Bu, t-Bu, trimethylsilicon groups (Me ₃ Si), alkoxy (preferably RO, where R is C _{1 to 20} alkyl), cycloalkyl, halogen, and the like. The most preferred substituent at the 2-position of THI is a methyl group. The most preferred substituent at the 4-position of THI is phenyl, naphthyl or benzindenyl.

In one preferred embodiment, examples of THI derivative ligands include 2-Me, 4-PhTHI; 2-Me, 4-Naphthyl; Or 2-Me, 4,5-BzIndTHI.

The type of R "which is present between the two THI rings in the metallocene catalyst component of the above general formula is not particularly limited, but is preferably an alkylidene group having 1 to 20 carbon atoms, an alkyl (E.g. dialkylsilyl groups), alkylphosphine groups or amine groups, and ethyl (meth) acrylate groups such as methylsilyl group, ethylsilyl group, Most preferably a rhenyl radical (-CH ₂ CH ₂ -) or Me ₂ Si.

The metal M in the metallocene catalyst of the above general formula is a transition metal selected from Group IIIB, Group IVB, Group VB or Group VIB of the Periodic Table of the Elements, and is preferably selected from Ti, Zr, Hf and V.

Q in the metallocene catalyst of the above formula is preferably halogen, especially Cl.

Normally, since the valence of the metal M is 4, p becomes 2.

The most preferred metallocene catalyst components that can be used in the present invention are:

Et (THI) ₂ ZrCl _2,

Me ₂ Si (THI) ₂ ZrCl ₂ ,

Me ₂ Si (2-MeTHI) ₂ ZrCl ₂ ,

_{Et (2-MeTHI) 2 ZrCl} 2,

Me ₂ Si (2-Me, 4-PhTHI) ₂ ZrCl ₂ ,

Et (2-Me, 4-PhTHI) ₂ ZrCl ₂

Me ₂ Si (2-Me, 4-NaphthI) ₂ ZrCl ₂ ,

Et (2-Me, 4- NaphTHI) 2 ZrCl 2,

Me ₂ Si (2-Me, 4,5-BzIndTHI) ₂ ZrCl ₂ ,

Et (2-Me, 4,5- BzIndTHI) 2 ZrCl 2.

The metallocene catalyst systems usable in the present invention include, but are not limited to, one or more metallocene catalyst components as described above. Thus, the catalyst system may comprise additional catalysts, if desired, for example additional metallocene catalysts according to the invention or other known catalysts.

It is also preferred that the metallocene catalyst is combined with at least one activator to form a catalyst system. Preferred activators include alkyl aluminum compounds such as diethyl aluminum chloride, aluminoxanes, modified aluminoxanes, neutral or ionic ionizing activators, non-coordinating anions, non-coordinating Group 13 metals or metaloid anions, borane, have.

The alkyl aluminum compound is preferably an alkyl aluminum compound represented by the general formula AlR _n X _(3-n) (wherein R is an alkyl group having 1 to 16 carbon atoms and X is a halogen element and 1? _{N? 3} ) Can be used. Specific examples of the alkylaluminum compound include trialkylaluminums such as triethylaluminum, trimethylaluminum, trinormalpropylaluminum, trinormalbutylaluminum, triisobutylaluminum, trinormalhexylaluminum, trinormaloctylaluminum, tri-2-methylpentyl Aluminum and the like are used. Particularly preferably, triisobutylaluminum, triethylaluminum, trinormalhexylaluminum or trinormaloctylaluminum is used.

The alkylaluminum compound is preferably used in the gas phase polymerization in the range of 1 < = alkyl aluminum compound / transition metal < = 1,000 in the main catalyst, more preferably 10 & Metal < 300. If the molar ratio of the transition metal in the alkyl aluminum compound / main catalyst is less than 1, a sufficient polymerization activity can not be obtained. On the other hand, if it exceeds 1,000, the polymerization activity is adversely affected.

The metallocene catalyst component may be carried on a suitable carrier. Preferred carrier materials are porous, preferably inorganic, such as silicon and / or aluminum oxides, in solid particulate form. In a most preferred embodiment, the carrier is silica present in the form of spherical particles, for example spherical particles obtained by a spray drying process.

Examples of such metallocene catalyst / catalyst systems are described in detail in US 5,719,241, US 6,225,251, US 6,432,860, US 6,777,366, US 6,855,783, US 7,127,853, US 7,041,756 and US 7,127,853. In addition, the above supported metallocene catalyst component is described in W. Spalek; A. Antberg, J. Rohrmann, A. Winter, B. Bachmann, P. Kiprof, J. Behm, and WA Hermann, Angew. Chem. Int. Eng. Ed. 1992, 31, 1347] or commercially available from mCAT GmBH (Geschuftfuhrer Dr Markus Ringwald Handelsregister Freiburgi HRB 381812).

Polymerization process

After the introduction of the metallocene catalyst as a fresh catalyst, if the catalyst system conversion process is successfully accomplished, the olefin polymerization process is performed by reacting a composition comprising hydrogen, olefins, and comonomers in the presence of a metallocene catalyst as the main catalyst .

The catalyst conversion method according to the present invention can be used in a gas phase, liquid phase, slurry or bulk phase polymerization process. In particular, a gas phase polymerization process in a fluidized bed reactor is preferred.

Hereinafter, the vapor phase polymerization process will be described in detail with reference to the drawings. In a typical continuous gas fluidized bed polymerization process, the gaseous stream comprising monomers for the polymerization reaction passes through a fluidized bed reactor (2 in FIG. 1) under reaction conditions in the presence of a catalyst. Some of the monomers contained in the gas phase flow into the polymerization reaction in contact with the catalyst and the polymer under polymerization and the unreacted monomers are heated to a temperature by polymerization heat and transferred to the upper part of the flow reactor (1 in FIG. 1) 1) and the freezer (3 in FIG. 1) and circulated to the fluidized bed reactor. The consumed monomer and hydrogen as a molecular weight distribution regulator are injected into this gas-phase circulation stream. The catalyst component is injected directly into the fluidized bed by an appropriate method, and the resulting polymer is discharged from the fluidized bed.

The gas phase polymerization process is preferably carried out in the absence of a hydrocarbon solvent at a temperature of preferably 60 to 120 DEG C, more preferably 65 to 100 DEG C, even more preferably 70 to 80 DEG C and preferably 2 to 40 atm Preferably at a pressure of 10 to 30 atm.

If the polymerization temperature in the reactor is less than 60 캜, sufficient polymerization efficiency can not be obtained, and if it exceeds 100 캜, a polymer mass tends to be generated. If the operating pressure in the reactor is less than 2 atmospheres, the ethylene partial pressure is low and sufficient polymerization efficiency can not be obtained. If the operating pressure exceeds 40 atm, control of the reaction becomes difficult, and the reactor is subjected to excessive load.

According to the present invention, the removal of the residual catalyst by discharging the existing polymer can minimize the use of the deactivating agent, which shortens the purge time and promotes the progress of the new catalyst, thus shortening the time of the conversion process. In addition, the amount of activator used can be reduced, thereby preventing problems such as sheet generation. At the same time, by filling the reactor with a new catalytic polymer which is alive and active, the progress of polymerization is further promoted together with the injection of the new catalyst, and the effect of shortening the normalization time is obtained.

 1 is a view showing a gas phase polymerization process in an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example  One

1. Support Metallocene  Preparation of Catalyst

The Et (THI) ₂ ZrCl ₂ compound sold by mCAT was purchased and used as the metallocene catalyst component. The carrier used was XPO-2402 silica of Grace.

5 g of the silica was suspended in a round bottom flask equipped with a magnetic stirrer, a nitrogen inlet and a dropping funnel.

To produce the activated catalyst, about 0.3 g of the catalyst component was reacted with 25 ml of methylalumoxane (30% by weight of MAO in toluene) at 25 DEG C for 10 minutes to obtain the corresponding metallocene cation and anionic methyl alumoxane To give a solution of the oligomer. The resulting solution containing the metallocene cation and the anionic methyl alumoxane oligomer was added dropwise to the funnel immediately after replacing with a reflux condenser under nitrogen. The mixture was heated at 110 < 0 > C for 90 minutes each. The reaction mixture was then cooled to room temperature, filtered under nitrogen and rinsed with toluene. Thereafter, the obtained catalyst system was washed with pentane and then dried under mild vacuum.

The catalyst was injected directly into a fluidized bed reactor in a dry state.

2. Ziegler Appear  Preparation of Catalyst

A 1 liter glass reactor equipped with a mechanical stirrer, a reflux condenser and a heating or cooling device was filled with dry nitrogen and then charged with 12.15 g (500 mmol) of powdered magnesium, 23.75 g (125 mmol) of titanium tetrachloride, 92.5 g 1 mol) and an amount of n-heptane such that the total volume was 600 ml was continuously introduced at ambient temperature.

After addition of 1.26 g of iodine, the reaction medium was heated to 75 DEG C with stirring to initiate the reaction. After about 1 hour 30 minutes the reaction started slowly and the reaction medium was maintained at 75 C for 3.5 hours. The resulting brown / black precipitate was washed several times with heptane. The weight composition ratio (% by weight) of the obtained catalyst is as follows.

Ti: 10.3, Mg: 19.2, Cl: 70.5

3. Ziegler Appear Pre-polymerization  Preparation of Catalyst

In a 5 L stainless steel reactor equipped with a mechanical stirrer, 2 L of n-heptane were introduced at ambient temperature under a nitrogen atmosphere. After heating the n-heptane to 70 占 폚, the above Ziegler-Natta catalyst was introduced in an amount corresponding to 0.46 g (4 mmol) of triethylaluminum and 1 mg of titanium atom.

When the reaction medium was heated to 75 캜, hydrogen was introduced until the pressure reached 0.6 MPa, and then ethylene was introduced at a throughput of 160 g / hr.

After 7 hours from the polymerization reaction, 1,100 g of a total polymer (total polymerization catalyst) having a titanium content of 34 ppm was obtained.

4. Gas Phase Polymerization in Fluidized Bed

The gas phase polymerization method using the supported metallocene catalyst prepared in 1 above and the Ziegler-Natta pre-polymerization catalyst prepared in 3 above was carried out under the polymerization conditions shown in Table 1 below using the gas phase polymerization reactor of FIG. 1 (Hereinafter, referred to as 'metallocene catalyst polymer') and a polymer prepared by a Ziegler-Natta catalyst (hereinafter referred to as 'Ziegler-Natta catalyst polymer') were respectively prepared. The polymer prepared with the metallocene catalyst used hexene-1 as the comonomer and the polymer prepared with the Ziegler-Natta catalyst used butene-1 as the comonomer. MI was measured using 190 grams weight at 2160 grams according to condition E of ASTM D-1238.

Polymerization reaction conditions Ziegler appears Metallocene Temperature (℃)
Pressure (kg · G / ㎠)
Ethylene (mol%)
Hydrogen (mol%)
Hydrogen / ethylene ratio
Comonomer (mol%)
Comonomer / ethylene ratio
Bed weight (kg)
Holding time (hr)
Rate of yield (kg / hr)
MI (g / 10)
density
Bulk density (g / cc) 80
19.2
50
10
0.2
20
0.4
70
11.7
6
One
0.92
0.34 80
19.2
30
0.03
0.001
0.39
0.013
70
11.7
6
One
0.917
0.46

5. Conversion process

a) The Ziegler-Natta catalyst polymer prepared in the above step 4 and the metallocene catalyst polymer were stored in each of two storage containers in an active state during the continuous process before the conversion process. There is no additional time because it is a continuous process.

Then, b) to convert to an incompatible catalyst system, the conversion process started in the steady state of the polymerization process with the Ziegler Natta catalyst and stopped the Ziegler-Natta catalyst injection for conversion.

c) In order to minimize the residual catalyst inside the reactor, the catalyst injection was stopped, and the reactor was started to be discharged, so that only 10% of the residual polymer was completely discharged in the reactor.

Then, d) 25 g of carbon dioxide was injected to stop the reaction in order to irreversibly deactivate the residual activity using an inactivating agent. The amount of carbon dioxide injected was 7 times the molar equivalent of the total metal elements present in the fluidized bed. Thereafter, the circulating flow was maintained for 1 hour, and water was further injected. Water was 6.5 g, which was five times the molar equivalent of the metal element present in the bed.

Then, e) the gas circulation flow after the water injection was maintained for 7 hours. At this time, the temperature of the fluidized bed reactor was maintained at 80 캜 and the pressure was maintained at 19.2 kg / cm 2.

f) gas phase fluid bed reactor to the time taken was performed several times at a pressure of 3 ~ 9kgf / ㎠ nitrogen pressure purge, the reactor within the CO, respectively the _second and the moisture remaining amount of CO ₂ is less than 1ppm, the water is measured to be less than 7ppm Table 2 Respectively.

g) All of the residual polymer in the reactor was discharged, and the reactor was charged to the height of the polymerization with the metallocene catalyst polymer in which the activity stored in the reactor was viable.

Then, h) monomer and hydrogen were injected to match the vapor composition for the metallocene catalyst. The gas phase composition for the metallocene was 0.03 mol% for hydrogen, 30 mol% for ethylene and 0.39 mol% for comonomer, as shown in Table 1, and the remainder was filled with nitrogen.

Then, i) the metallocene catalyst was injected after the gas phase composition reached the target value to initiate the reaction.

j) The success of the conversion process from the polymerization effluent after injecting the fresh catalyst into the reactor was judged. After the polymerization reaction started and the bed level started to rise, the discharge was started. The film was formed by pelletizing, and the gel was evaluated to determine the success of the conversion process.

A film for gel evaluation was prepared using HAKKE (Thermo Scientific). Gel counts were determined from visual level 1 to 8. The number of gels was determined to increase with increasing step. In the case of the first to third steps, the gel level of the film to be used for commercial use is not available. The time taken to produce the polymer capable of obtaining the three-stage film after the new catalyst injection is shown in Table 2 below.

k) Some of the metallocene catalyst polymer produced after the new catalyst injection and polymerization stabilization was refilled in the emptied silo. Since the storing step is performed during the continuous process, no additional time is required.

Comparative Example  One

The procedure of Example 1 was repeated except that the reactor was filled with the metallocene polymer deactivated in step g).

Comparative Example  2

Step c) proceeded without emptying the Ziegler-Natta catalyst polymer. In step d), 250 g of carbon dioxide was injected and 65 g of water was injected. Also, the step of filling with the novel polymer in step g) is also omitted, and steps a) and k) are also omitted, but steps a) and k) are performed on a continuous process. Except for the above process, the remainder was performed in the same manner as in Example 1.

Comparative Example  3

In Comparative Example 2, 0.65 L of TiBA (0.2 M) was injected to remove the residual deactivator between the nitrogen purge and the gas phase regulating steps and the circulating flow was maintained for 4 hours. After the circulating flow was maintained, the fluidized bed reactor was purged with nitrogen 10 times. The remainder was carried out in the same manner as in Comparative Example 2.

As shown in Table 2 above, it can be seen that the method of using existing polymers as in Comparative Examples 2 and 3 takes more conversion time than the conversion using the polymers of the examples according to the present invention. Further, as the amount of the deactivating agent used is increased, it is found that the polymerization takes a longer time when the new catalyst is introduced. As can be seen in Comparative Example 1, it can be seen that the novel polymer in which the activity is active is faster in polymerization than the inactive polymer in the new catalyst conversion. Therefore, it can be seen that Embodiment 1 according to the present invention is a method of reducing the conversion time and optimizing the conversion process operation in the conversion process of the incompatible catalyst.

Claims (10)

A method for converting from a first catalyst-catalyzed polymerization to a second catalyst-incompatible second catalyst, characterized in that it comprises the following steps:
a) storing the polymer produced using the first catalyst and the polymer prepared using the second catalyst, which is immiscible with the first catalyst, in each of two or more separate storage vessels in an active state during each polymerization;
b) stopping the introduction of the existing catalyst into the reactor of the first catalyst to convert the first catalyst to a non-admixable second catalyst;
c) discharging at least a portion of the residual polymer remaining in the reactor to minimize the amount of residual catalyst inside the reactor;
d) irreversibly deactivating the residual activity of the remaining catalyst using an inactivating agent;
e) maintaining the deactivating agent in the reactor;
f) removing the inactivating agent by nitrogen purge;
g) discharging the residual deactivating agent and the residual polymer, and then filling the reactor with the novel polymer produced by the second catalyst in which the activity retained in step a) is viable;
h) adjusting the vapor composition according to a second catalyst operating condition which is a new catalyst;
i) introducing a fresh catalyst into the reactor;
j) determining whether the conversion process is successful from the polymerization effluent after the introduction of the fresh catalyst into the reactor; And
k) Storing some of the polymer produced after fresh catalyst injection and polymerization stabilization in a storage container again. 2. The method of claim 1, wherein the first catalyst comprises a Ziegler Natta catalyst, and the second catalyst comprises a metallocene catalyst. delete  The method according to claim 1, wherein, in step c), 50 to 95% by weight of the residual polymer is discharged. The method according to claim 1, wherein the inactivating agent in step d) is used together with carbon dioxide as an inactivating agent on the gas phase and water as an inactivating agent in the liquid phase. 6. The method of claim 5, wherein the amount of each of the deactivating agent in the gaseous phase and the deactivating agent in the liquid phase is 1 to 200 molar ratio with respect to the total metal atoms of the catalyst system present in the fluidized bed in the reactor. 7. The method of claim 6, wherein the amount of each of the deactivating agent in the gaseous phase and the deactivating agent in the liquid phase is from 5 to 15 molar ratio with respect to the total metal atoms of the catalyst system present in the fluidized bed in the reactor. The method according to claim 1, wherein the removal of the inactivating agent in step f) is carried out by further using an organometallic compound together with nitrogen purge. The organometallic compound as claimed in claim 8, wherein the organometallic compound has the general formula AlR _(3-a) X _a wherein R is a branched or linear alkyl or cycloalkyl having 1 to 30 carbon atoms, or a hydride radical , X is halogen and a is 0, 1 or 2. The method as claimed in claim 1, wherein in the step j)
i) A film is prepared using the polymer at the pre-conversion step, used as a control for the presence or absence of gel formation,
ii) preparing a film using the polymer discharged after the injection of the fresh catalyst, and confirming the presence or absence of gel formation.

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