Polymerisation method

FIELD: chemistry.

SUBSTANCE: invention relates to a polymerisation method and particularly to a method for copolymerisation of ethylene with higher α-olefins. Described is a method for copolymerisation of ethylene and an α-olefin comonomer containing 7-10 carbon atoms in a fluidised bed gas-phase reactor. Copolymerisation takes place in the presence of a Ziegler-Natta catalyst with multiple polymerisation centres. Said method is carried out in condensed mode. The amount of said α-olefin is kept less than the amount where considerable condensation occurs in the reactor. At least one of the following conditions is also used: a) the catalyst has 1-octene absorption rate of at least 700; b) polymerisation is carried out in the presence of an activator.

EFFECT: preventing condensation of 1-octene in the reactor.

7 cl, 2 ex

The present invention relates to a method of polymerization and, in particular, to a method of copolymerization of ethylene with higher α-olefins, performed in the gas phase.

Gas-phase method for the polymerization of olefins was widely used mainly for the copolymerization of ethylene and α-olefins. However, the industrial production of such copolymers when using catalysts of the Ziegler-Natta usually been limited by the copolymerization of ethylene and α-olefins having a carbon chain length With₆(1-hexene) or less used, for example, for the preparation of linear low density polyethylene (LLDPE).

In particular, higher α-olefins have a higher boiling point, but when they are applied in gas-phase methods of polymerization using catalysts of the Ziegler-Natta, in concentrations generally applicable for the production of LLDPE, may lead to condensation. Condensation can lead to difficulties in the possibility of a continuous and uninterrupted process.

An earlier patent documents, which aim to prevent condensation of 1-octene in the production of copolymers of ethylene/1-octene in the presence of catalysts based Ziegler-Natta include US 5100979, US 5106926 and US 6521722. In particular, in patents US 5100979 and US 5106926 described the ways in which you support the VAT partial pressure and temperature in the reactor, to ensure implementation of the method at temperatures above the dew point of 1-octene. In the US 6521722 described the manner in which the pressure and the temperature of the reaction zone is adjusted to set the operating point from 0.2 to 5.0 bar below the dew point of the reaction mixture, above which condensation occurs.

The limits set by the need to prevent condensation, limit the performance of the catalyst and the rate of production methods in the case of using 1-octene as co monomer and systems of the Ziegler-Natta. In particular, the industrial method of production of copolymers of ethylene/1-octene using a catalyst of the Ziegler-Natta would need the following:

(1) the minimum capacity of the catalyst, which is defined as the amount of polymer per unit of catalyst. This performance mainly depends on the compatibility of the ethylene with the catalyst, and hence the partial pressure of ethylene,

(2) the minimum production rate, which is defined as the amount of polymer per unit of time. For a reactor of a specific size, such speed mainly depends on the ability to provide heat in the reactor,

(3) the possibility of obtaining the necessary copolymer (e.g., given the Indus the sa melt and density). This ability mainly depends on the possibility to combine 1-octene and ethylene in the polymer when a given relation, which depends on the relative partial pressures of 1-octene and ethylene in the reactor.

However, the partial pressure octene is limited because of the need to prevent condensation of 1-octene in the reactor, and, in particular, maintaining the temperature in the reactor above the "dew point" (everything else, "dew point" increases with increasing partial pressure of 1-octene). Given that the ratio of 1-octene to ethylene is important for the final product, the partial pressure of ethylene is limited to a partial pressure of 1-octene. For any polymer in need of sufficient quantities include 1-actinophage of co monomer in the polymer (more than 5 wt.%), as, for example, a conventional linear low density polyethylene (LLDPE), and, consequently, a sufficiently high molar ratio of 1-octene to ethylene (more about 0,02:1), the restriction of partial pressure of 1-octene leads to a relatively low maximum partial pressure of ethylene, which in turn leads to poor performance of the catalyst.

Because the increase in the partial pressure of octene will increase the "dew point" of the gas phase in the reactor, it will also limit the maximum number inert the CSOs condensed component (such as, pentane or hexane), which can be added to the composition of the gas phase. Inert condensed components are added in order to increase the heat transfer ability of the gas in the reactor. The maximum amount that can be added is set to "dew point" of the gas phase, which is usually set at from 5 to 15°C below the temperature of polymerization. Thus, limiting the number of condensed inert component will result in the restriction of heat discharge capacity of the gas in the reactor, which, in turn, will reduce the maximum rate of production of such industrial reactor.

In the publication WO 2005/070976 described gas-phase method copolymerization of ethylene and α-olefin containing from 7 to 10 carbon atoms, in the presence of a catalyst with a single center of polymerization on the metal flowing in the condensed mode, and in which the number of α-olefin is maintained below the number in which there is substantial condensation. It is possible according to the idea WO 2005/070976, due to the fact that the catalysts with a single center of polymerization on the metal have a single center with a single activity and selectivity and high ability to enable higher comonomers in the formed polyethylene, i.e. in the gas phase, to provide the necessary maintenance somona the RA in the resulting polymer, requires very low concentrations higher comonomers, such as 1-octene.

In contrast, and in accordance with the restrictions described above, in the publication WO 2005/070976 found that traditional catalysts of the Ziegler-Natta not suitable, because they have a lot of catalytic centers/types with different activities and abilities to enable comonomer.

Actually, in the present work, it was unexpectedly discovered that the same way of the WO 2005/070976, can be successfully applied for catalysts of the Ziegler-Natta so that higher α-olefins can be successfully used in industrial gas-phase process, provided that the used catalyst, which provides a high absorption rate of co monomer, and/or a suitable activator. Although such catalysts Ziegler-Natta usually have a lower rate of inclusion of co monomer in the polymer than metallocene catalysts, they need the ratio of co monomer to ethylene of higher order than metallocene catalysts.

Thus, in accordance with the present invention, a method of copolymerization of ethylene and α-olefin co monomer containing from 7 to 10 carbon atoms, in the gas-phase reactor with a fluidized bed in the presence rolled atora Ziegler-Natta with multiple centers of polymerization, characterized in that (I) the specified method is carried out in the condensed mode, (II) the amount specified α-olefin support below the amount at which the reactor is significant condensation, and (III) using at least one of the following conditions:

a) the catalyst has an absorption rate of 1-octene, component, at least 700;

b) the polymerization is carried out in the presence of activator.

Condensed mode is defined as a process of purposeful introduction of a recirculating flow of liquid and gas phase in the reactor so that the liquid mass fraction based on the total weight of the recirculation stream is greater than about 2.0 wt.%.

The principle of operation of condensed mode is fully described, for example, in EP 89691, US 4543399, US 4588790, EP 696293, US 5405922, EP 699213 and US 5541270.

By maintaining the temperature and partial pressures, respectively, in the reaction zone, the amount of α-olefin co monomer is maintained below the amount at which the reactor is significant condensation.

The content of the co monomer copolymer can be controlled partial pressures of the various monomers. To prevent condensation of the co monomer in the reaction zone of the partial pressure of co monomer in the reaction zone can be maintained to a value that, when temperature is re approximately 10°C below the temperature of the monomer mixture in the reaction zone, would the pressure of unsaturated pair of co monomer.

In the first embodiment, the catalyst used in the method according to the present invention has an absorption rate of 1-octene, component, at least 700. The concept of "absorption rate of 1-octene", specified in the present description, refers to the relative activity of the catalyst in relation to the incorporation of 1-octene in the polymer under certain conditions, and is equal to the content of 1-octene in the produced polymer, expressed in wt.% (which is appropriately measured by NMR), divided by the molar ratio of 1-octene to ethylene in the gas phase in the reactor for polymer produced under certain conditions. Thus, for example, if the copolymer having a content of 1-octene, comprising 15 wt.%, obtained using the composition of the gas phase, in which the molar ratio of the specified 1-octene to ethylene is 0.02, the absorption rate is 750.

As defined in the present description, the absorption rate of 1-octene for a particular catalyst is the rate measured when executing the following conditions:

ethylene at a partial pressure of 5 bar lightly copolymerized using a catalyst at a temperature of 84°C, in the presence of 1-octene at a molar ratio of 1-octene to ethylene, with the element of 0.02, hydrogen at a partial pressure of 1 bar, isopentane at a partial pressure of 1 bar, and in the presence of nitrogen balance to ensure total pressure of 20 bar. The activator is not used.

The absorption rate is measured in the absence of condensation in the reactor. The size of the reactor is not particularly important, as the speed of fluidization, up until supported good fluidized bed (e.g., speed above a minimum velocity of fluidization, to ensure (stable) fluidized bed in the reactor).

In the first embodiment of the present invention, the catalyst has an absorption rate of 1-octene, component, at least 700. In order to avoid misinterpretation of the absorption rate of 1-octene is used as a characteristic of the catalyst and does not impose any restrictions on comonomer that will be used in the method of the present invention, or a special reaction conditions under which it is used. Thus, despite the fact that the catalyst is determined as having the specific rate of absorption of 1-octene, it can be used in the method of the present invention for the reaction of ethylene with any₇-C₁₀the co monomer.

Preferably, the catalyst has an absorption rate of 1-octene, component, at least 750, for example, at m is re, 800.

The use of the catalyst with a suitable high absorption rate of 1-octene means that the polymer with the required content of the co monomer can be obtained even when using a relatively low relationship of co monomer to ethylene in the gas phase, which in turn provide a higher partial pressure of ethylene in the gas phase (for partial pressure of a specific co monomer), leading to improved performance of the catalyst.

In a second preferred variant of the method of polymerization according to the present invention is performed in the presence of activator.

The preferred activator is monohalomethanes hydrocarbon compound, in particular as described in WO 03/082935.

In particular, monohalomethanes hydrocarbon compound may be a chlorinated or armored hydrocarbon. This connection can be monohalomethanes hydrocarbon corresponding to the General formula R-X, in which R denotes an alkyl group containing from 1 to 10, preferably from 2 to 7 carbon atoms, aracelio or aryl group containing from 6 to 14, preferably from 6 to 10 carbon atoms, and X denotes a halogen atom such as chlorine or bromine. Preferably, monohalomethanes Ugledar is the initial connection is selected from methylene chloride, ethylchloride, propylchloride, butyl chloride, pantellaria, vexillaria and heptachord. Butylchloride are more preferred, n-butyl chloride is the most preferred monohalomethanes hydrocarbon compound.

Not wishing to be bound to any theory, it is noted that the activator leads to a significant increase in activity, this means that the method can economically be applied at the required low partial pressure of co monomer required to provide the desired copolymer under the proper performance of the catalyst, and without condensation of co monomer.

In order to avoid uncertainties in the embodiment of the present invention, where the polymerization process is carried out in the presence of activator is optional, so that the catalyst had an absorption rate of 1-octene, component, at least 700.

However, particularly preferred method is carried out using both the activator and catalyst with a relatively high absorption rate of co monomer, by which is meant a catalyst speeds the absorption of 1-octene, component, at least 500. Preferably, the absorption rate of 1-octene in this embodiment is at least 600, and most preferably, the absorption rate of 1-octene is, at the very measures which, 700, i.e., the method characterized in that:

a) the catalyst has an absorption rate of 1-octene, component, at least 700, and

b) the polymerization is carried out in the presence of activator.

Because the partial pressure of co monomer may be limited to relatively low values, then the dew point of the gas phase in the reactor is maintained at a relatively low (compared with the use of higher concentrations of co monomer), which means that the composition of the gas phase can be added increased the number of condensed inert compounds (such as pentane or hexane). Inert condensed components are added to increase the heat exchange capacity of the gas in the reactor, and from this it follows that the increase in the number of condensed inert compounds that can be used, will increase the ability of gas in the reactor to remove heat that will increase the productivity of the industrial reactor.

For this reason, preferably, the reactor was present condensed inert compound such as pentane.

It is essential that the liquid phase recirculation flow (including condensed inert compounds) quickly evaporated after re-introduction into the fluidized bed. For this reason, it is preferable that the s liquid recirculation flow was directly injected into pseudogenes layer over pseudoviruses bars, and most preferably directly in the hot zone of the reactor, which, as a rule, is an area in the fluidized bed, situated at a height of from about 0.5 m above pseudoviruses bars to the upper part psevdoozhizhennogo layer. Preferably, the recirculation fluid flow to be entered in the lower part of the fluidized bed (but approximately 0.5 m above pseudoviruses lattice).

Preferred α-olefins are 1-octene, 1-mission norbornene and the like.

Particularly preferred α-olefin is 1-octene.

The method of polymerization in accordance with the present invention is suitable for the copolymerization of ethylene and α-olefin containing from 7 to 10 carbon atoms, in the gas-phase reactor with a fluidized bed operating in condensed mode at a pressure of from 0.5 to 6 MPa and at a temperature of 30°C and 130°C.

The preferred operating conditions of the method according to the present invention are a temperature in the range from 80 to 115°C and a pressure in the range from 1 to 3 MPa.

Suitable partial pressures of gas-phase components based on C₈or₁₀the comonomers are the following:

1) the partial pressure of ethylene of from 0.5 to 2 MPa.

2) partial pressure of 1-octene from 0 to 0.05 MPa, preferably from 0.01 to 0.03 MPa.

3) the ratio of partial pressure of 1-octene is the partial pressure of ethylene from 0.01 to 0.06, and, preferably, from 0.02 to 0.04.

4) partial pressure of 1-mission from 0 to 0.01 MPa, preferably of 0.002 and 0.006 MPa.

5) the ratio of partial pressure of 1-mission to the partial pressure of ethylene from 0.001 to 0.02, preferably from 0.002 to 0.015.

Preferably, hydrogen is also present, especially when the ratio of partial pressure of hydrogen to the partial pressure of ethylene in the range from 0 to 0.4, preferably from 0.05 to 0.3.

Preferably, the method according to the present invention is a continuous process.

The method can be used to make any suitable polyethylene, including LLDPE and HDPE.

Normal density of the produced polymers are 914-960 kg/m³.

Conventional melt indexes (IL) made of polymers 0.8-100 g/10 minutes

The method according to the present invention is particularly applicable for industrial reactors with a production rate of polymer from 10 to 80 tons/hour, preferably from 20 to 70 tons/hour. Conventional large-scale industrial reactor will have the diameter of the reaction zone of the fluidized bed in the range from 4.5 to 6 m Volumetric productivity (yield per pass per unit of time) (OP) in such processes, typically lies in the range from 50 to 170 kg/h/m³and, more generally, in the range from 80 to 150 kg/h/m³.

To ensure the ecene maximum speed production and productivity of the catalyst is important, to clean used α-olefin co monomer were at the highest level. The most common impurities are usually isomers of α-olefin. For example, 1-octene as the greatest impurities usually present 2-octene. These isomers are not included in the produced polymer and, therefore, will be accumulated in the reaction path. However, impurities present in the condensable components, and any accumulation will lead to potential or in the reactor, except when condensable components purified from impurities. Vosman as example 1-octenoyl comonomer, it actually represents the total octene in the reactor, which is important for the dew point, but for the desired polymer product is important only 1-octene. Thus, an increased admixture of 2-octene actually will require a slightly higher level of pass-octene", in any case, for a particular polymer. More importantly, a lot more clean, level 2-octene will increase to an excessively high quantity in the reactor that will limit the full speed at which the "more" octene can be added and respond without condensation.

The purity of the co monomer, as a rule, is at least 96 wt.%, preferably, less than the least 98 wt.%, and most preferably at least 99 wt.%.

In the second variant of the method according to the present invention can be used in any acceptable catalysts of the Ziegler-Natta with multiple centers of polymerization (use in conjunction with the activator). The catalyst system of the Ziegler-Natta known for a number of years and can deliver large quantities of polymer in a relatively short period of time, allowing, thus, to avoid the stage of removal of the polymer residue of the catalyst. Such catalytic systems typically include a solid catalyst comprising a complex of a transition metal and socialization.

Preferably, the catalyst of the Ziegler-Natta with multiple centers of polymerization consists of a catalyst precursor and socializaton, where the specified catalyst precursor comprises a material of the catalyst carrier, alkylamine connection, the connection of the transition metal from groups 4 or 5 of the Periodic table of elements, and additional electrondonor connection.

The catalyst may be deposited on a suitable carrier. Materials of the catalyst carrier, as a rule, can be a solid, porous material such as, for example, silicon dioxide, aluminum oxide, and combinations thereof. Mostly, they are on is displayed in amorphous form. Such media can be in the form of particles having a size of from 0.1 μm to 250 μm, preferably from 10 to 200 microns, and most preferably from 10 to 80 μm. A preferred carrier is silica, preferably silicon dioxide in the form of spherical particles, for example, silicon dioxide, dried spray.

The internal porosity of these carriers usually is at least 0.2 cm³/g, such as at least 0.6 cm³/g Specific surface of such media is at least 3 m³/g, preferably at least about 50 m³/g, and more preferably lies in the range from 150 to 1500 m³/year

Alkylamine connection, preferably, is dialkylamino compound having the General structural formula RMgR', where R and R' represent identical or different from each other With₂-C₁₂alkyl groups, preferably C₂-C₈alkyl groups, more preferably, From₄-C₆alkyl group, and most preferably both R and R' represent boutelou group. Butylethylamine, butylaniline and dibutylamine are preferred, most preferred is dibutylamine,

The transition metal compound is preferably a compound of titanium, pre is respectfully tetravalent compound of titanium. The most preferred compound of titanium is titanium tetrachloride. Can also be used mixtures of such technometrics connections.

Additional electrondonor connection, preferably, is a silane compound, more preferably, tetrachlorosilane formula Si(OR)₄where R is preferably, C₁-C₆alkyl connection. Typical examples of tetrachlorozincate include tetramethoxysilane, tetraethoxysilane, tetraisopropoxide, tetrapropoxide, tetramethoxysilane, the most preferred of them are tetraethoxysilane and tetramethoxysilane.

Socialization, which can be used, preferably, is an ORGANOMETALLIC compound of metal of groups I to III of the Periodic system of elements, such as, for example, alyuminiiorganicheskikh connection, for example dimethylaluminum chloride, trimethylaluminum, triisobutylaluminum or triethylaluminum. Preferred is triethylaluminum.

The catalyst may be used in any acceptable form, in particular in unchanged form or in the form of a prepolymer containing, for example, from 10 to 3, preferably from 10^-3up to 10^-1mmol of titanium per gram of the polymer.

In accordance with the first embodiment of the present izopet is of the catalyst, having the absorption rate of 1-octene, component, at least 700, will be a catalyst of Ziegler-Natta with multiple centers of polymerization in combination with components such that the catalyst will have the necessary absorption rate. However, the components of the catalyst generally will be determined according to the above definition.

Example 1

Obtaining a copolymer of 1-octene/ethylene performed in the reactor with a fluidized bed with a diameter of 0.74 m and the total height of the reactor, component 10,36 m

The used catalyst is a catalyst of Ziegler-Natta containing 0.43 wt.% titanium and 30.6 wt.% of silicon. The absorption rate of 1-octene used catalyst, measured in "normal conditions", as defined previously, is 650.

The reaction is carried out at a polymerization temperature of 90°C and a total pressure of 20.1 bar (2,01 MPa).

The reaction mixture consists of ethylene at a partial pressure of 5.6 bar (0.56 MPa), N₂when the ratio of N₂to ethylene, comprising 0,189; 1-octene at a partial pressure of 153 mbar (15,9 kPa, the ratio of 1-octene to ethylene is 0,0273); pentane at a partial pressure of 1 bar (0.1 MPa), in the presence of nitrogen balance.

The reaction is carried out in the layer height 5,38 m condensation rate of 2.8%. The polymer is extracted with a speed of 227 kg/HR, financial p is what Tata volumetric productivity (OP (kg/m ³/h)) is 98, and the residence time in the reactor is 3.1 hours.

The catalyst is injected at a rate 0,0048 mol/h, and the tea (triethylaluminum) 28 frequent. per million by weight (with respect to the produced polymer). n-BuCl enter in the quantity being 0.036 mol/h, in which the ratio of BuCl/Ti is 7.5 (mol/mol).

Produce a copolymer of 1-octene/ethylene using a catalyst performance component 4300 g/g with the following properties:

The melt index (IR (g/10 min))=1,00;

The density (d (kg/m³))=917,1;

The average particle size (NAC (μm))=843 (fraction of very small particles (%)=0,0; fraction of large particles (%)=4,6);

Bulk density (kg/m³)=370;

Si=70 frequent. per million;

the content of 1-octene (wt.%)=14,7.

For the avoidance of doubt, on the basis of the above values, it should be noted that "the expected absorption of co monomer at the polymerization temperature of 90°C is 14.7/0,0273=538; but when measured under standard conditions, as defined in the present description, get the value of the characteristic of the used catalyst and co monomer used, the absorption rate of such a catalyst is 650.

In the absence of activator, such a high content of octene in the manufactured product in such performance of the catalyst, it would not be possible without the value is positive the increased partial pressures of octene and ethylene, which would lead to condensation of 1-octene in the reactor, and related issues.

Example 2

This example illustrates the way in which can be used catalyst having essentially a high rate of absorption (the absorption rate of 1-octene is more than 700) in the absence of activator.

As in example 1, obtaining a copolymer of 1-octene/ethylene performed in the reactor with a fluidized bed with a diameter of 0.74 m and the total height of the reactor, component 10,36 m

The used catalyst is a catalyst of Ziegler-Natta containing of 0.45 wt.% titanium and 31 wt.% of silicon. The absorption rate of 1-octene used catalyst, measured in "normal conditions", as defined previously, is 775.

The reaction is carried out at a polymerization temperature of 84°C and a total pressure of 20 bar (2 MPa).

The reaction mixture consists of ethylene at a partial pressure of 5.9 bar (0,50 MPa), N₂when the ratio of N₂to ethylene, comprising 0,38; 1-octene at a partial pressure of 118 kPa (11,8 kPa, the ratio of 1-octene to ethylene is 0,020); pentane at a partial pressure of 1.1 bar (0.11 MPa), in the presence of nitrogen balance.

The reaction is carried out in a layer height of 5.5 m with a condensation rate of 2.2%. The polymer is extracted with a speed of 190 kg/h, as a result, the volumetric productivity (OP (kg/m³/h))is 80, and the residence time in the reactor is 3.7 hours.

The catalyst is injected at a rate 0,0041 mol/h, and the tea in the amount of 30 frequent. per million by weight (with respect to the produced polymer). Activator does not enter.

Produce a copolymer of 1-octene/ethylene using a catalyst performance component 4020 g/g with the following properties:

The melt index (IR (g/10 min))=2,31;

The density (d (kg/m³))=917,0;

The average particle size (NAC (μm))=810 (fraction of very small particles (%)=0,0; fraction of large particles (%)=4,1);

Bulk density (kg/m³)=360;

Si=77 frequent. per million;

the content of 1-octene (wt.%)=15,5.

In this case, you use the same true temperature of polymerization, and the temperature used to determine the normal absorption of co monomer (84°C), but is inherent to the catalyst, the absorption rate of co monomer is equal to the assumed rate of absorption(15,5/0,02=775).

Such a high content of octene in the manufactured product in such performance of the catalyst in the absence of the activator cannot be obtained without a catalyst having such a high absorption rate of co monomer.

1. The method of copolymerization of ethylene and α-olefin co monomer containing from 7 to 10 carbon atoms, in the gas-phase reactor with a fluidized bed in the presence of the cat is Isadora polymerization Ziegler-Natta with multiple centers of polymerization, characterized in that (I) the specified method is carried out in the condensed mode, (II) the amount specified α-olefin support below the amount at which the reactor is significant condensation, and (III) using at least one of the following conditions:
a) the catalyst has an absorption rate of 1-octene, component, at least 700;
b) the polymerization is carried out in the presence of activator.

2. The method according to claim 1, wherein the catalyst has an absorption rate of 1-octene, component, at least 700.

3. The method according to claim 1 or 2, in which the polymerization is carried out in the presence of activator.

4. The method according to claim 3, in which the activator is monohalomethanes hydrocarbon compound.

5. The method according to claim 1 or 2, in which the partial pressure of ethylene in the reactor lies in the range from 0.5 to 1 MPa.

6. The method according to claim 1 or 2, in which α-olefin is a 1-octene.

7. The method according to claim 6, in which the ratio of partial pressure of 1-octene to the partial pressure of ethylene lies in the range from 0.02 to 0.04.