KR20210072267A - Process for Preparing a Polyolefin by Gas-phase Polymerization - Google Patents

Abstract

The present invention relates to a method for producing an olefin-based polymer by gas phase polymerization, and specifically, to a method for producing an olefin-based polymer by gas phase polymerization of an olefin-based monomer in a semi-batch stirred reactor. The method for producing the olefin-based polymer according to an embodiment of the present invention can produce the olefin-based polymer, which prevents agglomeration of a polymer due to local overreaction and has excellent physical properties while maintaining high catalytic activity during the gas phase polymerization of olefin-based monomers.

Description

Method for preparing an olefin-based polymer by gas-phase polymerization {Process for Preparing a Polyolefin by Gas-phase Polymerization}

The present invention relates to a method for producing an olefin-based polymer by gas phase polymerization. Specifically, the present invention relates to a method for preparing an olefin-based polymer by gas-phase polymerization of an olefin-based monomer in a semi-batch stirred reactor.

Gas phase polymerization of olefinic monomers, particularly ethylene, is very difficult to remove reaction heat generated by polymerization compared to slurry polymerization or solution polymerization. Therefore, if the polymerization activity of the catalyst is not precisely controlled during gas phase polymerization of the olefin monomer, excessive heat of reaction may be generated locally in the reactor, and the resulting polymer may be melted and agglomerated. In this case, it may be necessary to temporarily stop the operation of the polymerization process.

In particular, when gas-phase polymerization of olefin monomers, particularly ethylene, using a high-activity catalyst, the activity of the catalyst rapidly rises at the beginning of polymerization to show maximum activity, and then tends to decrease as time elapses. At this time, the catalyst for the entire polymerization If the maximum activity in the initial stage is too high compared to the average activity, polymer agglomeration due to local overreaction tends to occur severely.

In order to solve this problem, US Patent No. 4,438,019 discloses a transition metal of groups IV, V, and VI having an oxidation number of tetravalent or higher, for example, Ti(OR) _m Cl _n (R is an alkyl group, m+n=4) Disclosed is a solid catalyst composition for polymerization of ethylene prepared by a reduction reaction of a titanium compound having the structure of and a Grignard compound having a RMgCl structure made of magnesium (Mg) and alkyl chloride. U.S. Patent No. 4,894,424 proposes a more stable gas phase polymerization method of ethylene by adding a small amount of water to the solid catalyst composition exemplified in the above patent, thereby removing the activity of fine catalyst particles present in the solid catalyst, and controlling the overall activity. . However, it has been difficult to control the polymerization rate profile, which is an intrinsic property of the catalyst.

In addition, US Patent Nos. 5,863,995 and 5,990,251 have an effect of controlling the catalytic activity and profile by adding an electron donor material such as methylformamide to the solid catalyst. However, there is a problem that such an electron donor material remains in the final polyethylene polymer.

Accordingly, there is a need for a method capable of producing an olefin-based polymer having excellent physical properties while maintaining high catalytic activity during gas phase polymerization of an olefin monomer, preventing agglomeration of the polymer due to local overreaction and having excellent physical properties.

U.S. Patent No. 4,438,019 U.S. Patent No. 4,894,424 U.S. Patent No. 5,863,995 U.S. Patent No. 5,990,251

It is an object of the present invention to provide a method capable of producing an olefin-based polymer having excellent physical properties while maintaining high catalytic activity during gas phase polymerization of an olefin-based monomer, preventing aggregation of the polymer due to local overreaction and having excellent physical properties.

According to one embodiment of the present invention for achieving this object, (1) preparing a catalyst mixture comprising a catalyst for olefin polymerization, a co-catalyst and an external electron donor; (2) primary polymerization of an olefinic monomer having 2 to 6 carbon atoms in the presence of the catalyst mixture obtained in step (1) in a first reactor; (3) in the same first reactor, or by transferring the olefinic polymer obtained in step (2) to a second reactor, secondary polymerization of the olefinic monomer having 2 to 6 carbon atoms in the presence of the polymer obtained in step (2) There is provided a method for producing an olefin-based polymer comprising the step of:

In a specific embodiment of the present invention, the catalyst for olefin polymerization in step (1) may be a Ziegler-Natta catalyst. Specifically, the catalyst for olefin polymerization is a Ziegler-Natta catalyst prepared by supporting a titanium chloride compound (preferably titanium tetrachloride (TiCl ₄ )) and a phthalate-based internal electron donor on a _{magnesium chloride (MgCl 2 ) carrier.}

The promoter is an alkylaluminum compound, and may include at least one selected from the group consisting of triethylaluminum, diethylchloroaluminum, tributylaluminum, trisisobutylaluminum and trioctylaluminum. Preferably, the cocatalyst of the catalyst for olefin polymerization may be triethylaluminum.

The external electron donor is an alkoxysilane-based compound, including tetramethoxysilane, methyltrimethoxysilane, dimethyltdimethoxysilane, trimethylmethoxysilane, ethyltrimethoxysilane, diethyldimethoxysilane, triethylmethoxysilane, Vinyltrimethoxysilane, divinyldimethoxysilane, propyltrimethoxysilane, dipropyldimethoxysilane, tripropylmethoxysilane, isopropyltrimethoxysilane, diisopropyldimethoxysilane, triisopropylmethoxysilane , butyltrimethoxysilane, dibutyldimethoxysilane, tributylmethoxysilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, triisobutylmethoxysilane, cyclopentyltrimethoxysilane, dicyclopentyl Dimethoxysilane, cyclopentylmethyldimethoxysilane, cyclohexyltrimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, trimethyleth Toxysilane, ethyltriethoxysilane, diethyldiethoxysilane, triethylmethoxysilane, vinyltriethoxysilane, divinyldiethoxysilane, propyltriethoxysilane, dipropyldiethoxysilane, tripropylethoxysilane , isopropyltriethoxysilane, diisopropyldiethoxysilane, triisopropylethoxysilane, butyltriethoxysilane, dibutyldiethoxysilane, tributylethoxysilane, isobutyltriethoxysilane, diisobutyldie Toxysilane, triisobutylethoxysilane, cyclopentyltriethoxysilane, dicyclopentyldiethoxysilane, cyclopentylmethyldiethoxysilane, cyclohexyltriethoxysilane, dicyclohexyldiethoxysilane, cyclohexylmethyldiethoxy Silane, tetrapropoxysilane, methyltripropoxysilane, dimethyldipropoxysilane, trimethylpropoxysilane, ethyltripropoxysilane, diethyldipropoxysilane, vinyltripropoxysilane, divinyldipropoxysilane, Propyltripropoxysilane, dipropyldipropoxysilane, isopropyltripropoxysilane, diisopropyldipropoxysilane, butyltripropoxysilane, dibutyldipropoxysilane, isobutyltripropoxysilane, diiso Butyldipropoxysilane, cyclopentyltripropoxysilane, dicyclopentyldipropoxysilane, cyclopentylmethyldipropoxysilane, cyclohexyltripropoxysilane, dicyclohexyldipropoxysilane, cyclohexylmethyldiprop from the group consisting of oxysilane It may include at least one selected. Preferably, the external electron donor of the catalyst for olefin polymerization may be cyclohexylmethyldimethoxysilane.

In a specific embodiment of the present invention, the primary polymerization of the olefinic monomer in step (2) may be performed by slurry polymerization in the presence of a solvent.

The olefinic monomer primarily polymerized in step (2) includes at least one selected from the group consisting of ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene and 1-hexene. Preferably, the olefinic monomer of step (2) may be propylene.

In step (2), the polymerization temperature may be 15 to 60° C., and the polymerization time may be 30 to 180 minutes.

In a specific embodiment of the present invention, the secondary polymerization of the olefinic monomer in step (3) may be performed in a gas phase polymerization in the second reactor.

The olefinic monomer to be secondary polymerized in step (3) includes at least one selected from the group consisting of ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene and 1-hexene. Preferably, the olefinic monomer of step (3) may be ethylene.

The secondary polymerization of the olefinic monomer in step (3) may be a copolymerization performed in the presence of an olefinic comonomer. Preferably, the olefinic comonomer may be 1-butene.

The secondary polymerization of the olefinic monomer in step (3) may be performed in the presence of a molecular weight modifier. Preferably, the molecular weight modifier may be hydrogen.

The secondary polymerization of the olefinic monomer in step (3) may be carried out in the presence of a fluidizing medium. Preferably, the flow medium may be at least one metal salt selected from the group consisting of sodium chloride (NaCl), calcium chloride (CaCl _{2 ) and potassium chloride (KCl).}

In step (3), the polymerization temperature may be 65-100° C., and the polymerization time may be 30-180 minutes.

The method for producing an olefin-based polymer according to an embodiment of the present invention may further include (4) separating, washing and drying the olefin-based polymer obtained in step (3).

According to another embodiment of the present invention, an olefin-based polymer prepared by the above method for preparing an olefin-based polymer and having a density of 0.900 to 0.952 g/cm 3 is provided. Preferably, the olefinic polymer may be polyethylene.

The method for producing an olefin-based polymer according to an embodiment of the present invention is capable of producing an olefin-based polymer having excellent physical properties while maintaining high catalytic activity during gas phase polymerization of an olefin-based monomer and preventing agglomeration of the polymer due to local overreaction. can

1 to 3 are graphs of molecular weight distribution according to Schulz-Flory distribution of polyethylene prepared in Example 1, Comparative Example 1, and Comparative Example 2; In each figure, the dotted line represents the molecular weight distribution of the olefinic polymer component obtained at each active site in the catalyst, and the solid line represents the molecular weight distribution of the entire olefinic polymer.
4 is a graph showing the correlation of the density of polyethylene with respect to the comonomer content in Examples 1 to 7.

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

A method for producing an olefin-based polymer according to an embodiment of the present invention comprises the steps of (1) preparing a catalyst mixture comprising a catalyst for olefin polymerization, a cocatalyst, and an external electron donor; (2) primary polymerization of an olefinic monomer having 2 to 6 carbon atoms in the presence of the catalyst mixture obtained in step (1) in a first reactor; (3) in the same first reactor, or by transferring the olefinic polymer obtained in step (2) to a second reactor, secondary polymerization of the olefinic monomer having 2 to 6 carbon atoms in the presence of the polymer obtained in step (2) including the steps of

Step (1)

In the above step (1), a catalyst mixture including a catalyst for olefin polymerization, a cocatalyst and an external electron donor is prepared. Specifically, a catalyst mixture consisting of a catalyst for olefin polymerization, a cocatalyst, and an external electron donor may be prepared.

In a specific embodiment of the present invention, the catalyst for olefin polymerization in step (1) may be a Ziegler-Natta catalyst. In this case, the specific type of the Ziegler-Natta catalyst is not particularly limited as long as it is commonly used to polymerize the olefinic monomer. Preferably, the catalyst for olefin polymerization may be a Ziegler-Natta catalyst prepared by supporting a titanium chloride compound and a phthalate-based internal electron donor on a _{magnesium chloride (MgCl 2 ) support.}

Here, for example, the titanium chloride compound may be titanium trichloride (TiCl ₃ ) or titanium tetrachloride (TiCl ₄ ), but is not particularly limited thereto.

In addition, the phthalate compound which is an internal electron donor is dimethyl phthalate, diethyl phthalate, dinormal propyl phthalate, diisopropyl phthalate, dinormal butyl phthalate, diisobutyl phthalate dinomalpentyl phthalate, di(2-methylbutyl) phthalate, di (3-methylbutyl)phthalate, di(3-methylpentyl)phthalate, diisohexylphthalate, dineohexylphthalate, di(2,3-dimethylbutyl)phthalate, dinormalheptylphthalate, di(2-methylhexyl) Phthalate, di(2-ethylpentyl)phthalate, diisoheptylphthalate, dineheptylphthalate, dinomaloctylphthalate, di(2-methylheptyl)phthalate, diisooctylphthalate, di(3-ethylhexyl)phthalate, di It may include at least one selected from the group consisting of neooctyl phthalate, dinormal nonyl phthalate, diisononyl phthalate, dinormal decyl phthalate and diisodecyl phthalate, but is not particularly limited thereto.

Meanwhile, an alkylaluminum compound may be used as a co-catalyst of the catalyst for olefin polymerization. Specifically, the cocatalyst of the catalyst for olefin polymerization may include at least one selected from the group consisting of triethylaluminum, diethylchloroaluminum, tributylaluminum, trisisobutylaluminum and trioctylaluminum, but these are particularly It is not limited. Preferably, the cocatalyst of the catalyst for olefin polymerization may be triethylaluminum.

As an external electron donor of the catalyst for olefin polymerization, an alkoxysilane-based compound may be used. Specifically, the external electron donor of the catalyst for olefin polymerization is tetramethoxysilane, methyltrimethoxysilane, dimethyltdimethoxysilane, trimethylmethoxysilane, ethyltrimethoxysilane, diethyldimethoxysilane, triethylmethoxy Silane, vinyltrimethoxysilane, divinyldimethoxysilane, propyltrimethoxysilane, dipropyldimethoxysilane, tripropylmethoxysilane, isopropyltrimethoxysilane, diisopropyldimethoxysilane, triisopropylme Toxysilane, butyltrimethoxysilane, dibutyldimethoxysilane, tributylmethoxysilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, triisobutylmethoxysilane, cyclopentyltrimethoxysilane, dixy Clopentyldimethoxysilane, cyclopentylmethyldimethoxysilane, cyclohexyltrimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, Trimethylethoxysilane, ethyltriethoxysilane, diethyldiethoxysilane, triethylmethoxysilane, vinyltriethoxysilane, divinyldiethoxysilane, propyltriethoxysilane, dipropyldiethoxysilane, tripropyl Toxysilane, isopropyltriethoxysilane, diisopropyldiethoxysilane, triisopropylethoxysilane, butyltriethoxysilane, dibutyldiethoxysilane, tributylethoxysilane, isobutyltriethoxysilane, diiso Butyldiethoxysilane, triisobutylethoxysilane, cyclopentyltriethoxysilane, dicyclopentyldiethoxysilane, cyclopentylmethyldiethoxysilane, cyclohexyltriethoxysilane, dicyclohexyldiethoxysilane, cyclohexylmethyl diethoxysilane, tetrapropoxysilane, methyltripropoxysilane, dimethyldipropoxysilane, trimethylpropoxysilane, ethyltripropoxysilane, diethyldipropoxysilane, vinyltripropoxysilane, divinyldipropoxy Silane, propyltripropoxysilane, dipropyldipropoxysilane, isopropyltripropoxysilane, diisopropyldipropoxysilane, butyltripropoxysilane, dibutyldipropoxysilane, isobutyltripropoxysilane, Diisobutyldipropoxysilane, cyclopentyltripropoxysilane, dicyclopentyldipropoxysilane, cyclopentylmethyldipropoxysilane, cyclohexyltripropoxysilane, dicyclohexyldipropoxysilane, cyclohexylmethyl group consisting of dipropoxysilane It may include at least one selected from, but is not particularly limited thereto. Preferably, the external electron donor of the catalyst for olefin polymerization may be cyclohexylmethyldimethoxysilane.

Here, the content of the cocatalyst with respect to 1 mole of the catalyst for olefin polymerization may be 35 to 150 moles. In addition, the content of the external electron donor with respect to 1 mole of the catalyst for olefin polymerization may be 3 to 15 moles.

The mixing of the catalyst for olefin polymerization, the cocatalyst, and the external electron donor in step (1) may be performed in the first reactor to be used in step (2) to be described later. Alternatively, the catalyst for olefin polymerization, the cocatalyst, and the external electron donor may be mixed in a separate container, and the resulting catalyst mixture may be transferred to the first reactor.

The mixing of the catalyst for olefin polymerization, the cocatalyst and the external electron donor may be carried out in the presence of a solvent. In this case, the solvent may be an organic solvent such as propane, hexane, pentane or kerosene, but is not particularly limited thereto. Preferably, the solvent may be propane.

The mixing of the catalyst for olefin polymerization, the cocatalyst, and the external electron donor in step (1) may be carried out at a temperature of 0 to 30 °C, preferably at a temperature of 10 to 20 °C.

In addition, when mixing the catalyst for olefin polymerization, the cocatalyst and the external electron donor in step (1), it is preferable to sufficiently stir them for 5 minutes to 1 hour, preferably 10 to 20 minutes.

Step (2)

In the above step (2), the olefinic monomer having 2 to 6 carbon atoms is first polymerized in the presence of the mixture obtained in step (1) in the first reactor.

In a specific embodiment of the present invention, the primary polymerization of the olefinic monomer in step (2) may be performed by slurry polymerization in the presence of a solvent. At this time, the solvent is substantially the same as the solvent described in step (1) above.

The type of the first reactor used for the primary polymerization of the olefinic monomer is not particularly limited as long as it can slurry-polymerize the olefinic monomer in the presence of a solvent. Preferably, the first reactor may be a stirred-tank reactor equipped with a helical ribbon type stirrer or an anchor type stirrer.

The olefinic monomer primarily polymerized in step (2) includes at least one selected from the group consisting of ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene and 1-hexene. Preferably, the olefinic monomer of step (2) may be propylene. For example, when propylene is slurry-polymerized in step (2), the resulting polypropylene is capped around the Ziegler-Natta catalyst, and the activity of the catalyst during polymerization of olefinic monomers, particularly ethylene, in the subsequent step (3) can be maintained at an appropriate level.

The polymerization temperature in step (2) may be 15 to 60 ℃, preferably 20 to 55 ℃. In this case, the primary polymerization of the olefinic monomer may be performed at a constant temperature, or may be sequentially performed at two or more constant polymerization temperatures.

Further, in step (2), the polymerization time may be 30 to 180 minutes, preferably 100 to 160 minutes.

Step (3)

In the above step (3), secondary polymerization of the olefinic monomer having 2 to 6 carbon atoms is carried out in the presence of the polymer obtained in step (2).

The secondary polymerization of step (3) may be carried out in the presence of the olefinic polymer obtained in step (2) in the first reactor of step (2). Alternatively, the olefinic polymer obtained in step (2) may be transferred to a second reactor, and may be carried out in the presence of the polymer obtained in step (2) in the second reactor.

In a specific embodiment of the present invention, the secondary polymerization of the olefinic monomer in step (3) may be performed in the second reactor. In addition, the secondary polymerization of the olefinic monomer in step (3) may be carried out by gas phase polymerization.

Before performing the secondary polymerization of the olefin-based polymer in step (3), the reactor is depressurized and exhausted, and then the reactor is purged at a pressure of 2 to 5 bar using nitrogen to remove the solvent remaining in the olefin-based polymer. It is preferable to remove

In step (3), if necessary, a cocatalyst of the catalyst for olefin polymerization may be further added. At this time, the promoter is substantially the same as described in step (1) above. The content of the cocatalyst per mole of the catalyst for olefin polymerization may be 35 to 150 moles.

The type of the second reactor used for secondary polymerization of the olefinic monomer is not particularly limited as long as it is capable of gas-phase polymerization of the olefinic monomer. Preferably, the second reactor may be a spherical type stirrer or a semi-batch stirred-tank reactor equipped with a hemispherical type stirrer.

The olefinic monomer to be secondary polymerized in step (3) includes at least one selected from the group consisting of ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene and 1-hexene. Preferably, the olefinic monomer of step (3) may be ethylene.

The secondary polymerization of the olefinic monomer in step (3) may be a copolymerization performed in the presence of an olefinic comonomer. Specifically, the olefinic monomer is ethylene, and the olefinic comonomer may include at least one selected from the group consisting of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, and 1-hexene. . Preferably, the olefinic monomer is ethylene, and the olefinic comonomer may be 1-butene, and in this case, the olefinic polymer obtained in step (3) may be polyethylene.

The secondary polymerization of the olefinic monomer in step (3) may be performed in the presence of a molecular weight modifier. Specifically, the molecular weight modifier may be hydrogen.

The secondary polymerization of the olefinic monomer in step (3) can be carried out in the presence of a water-soluble metal salt, another olefinic polymer or dehydrated silica gel as a fluidizing medium. At this time, the fluidization medium enables uniform stirring of the olefinic monomer, and serves to control the heat of polymerization generated during polymerization. Specifically, the metal salt may include at least one selected from the group consisting of sodium chloride (NaCl), calcium chloride (CaCl _{2 ), and potassium chloride (KCl).} Preferably, the metal salt may be sodium chloride. During secondary polymerization of the olefinic monomer, the water-soluble metal salt is used in a dehydrated state.

The polymerization temperature in step (3) may be 65 ~ 100 ℃, preferably 75 ~ 90 ℃.

In addition, the polymerization time in step (3) may be 30 to 180 minutes, preferably 60 to 120 minutes.

Step (4)

The method for producing an olefin-based polymer according to an embodiment of the present invention may further include (4) separating, washing and drying the olefin-based polymer obtained in step (3).

Specifically, the olefin-based polymer obtained in step (3) is washed with water to remove metal salts remaining in the olefin-based polymer, and then dried to obtain an olefin-based polymer. Specifically, after removing the metal salt by dissolving the olefin-based polymer in water, Mesh #120, I.S.0. The final olefin-based polymer can be obtained by dehydration using a 125 mm sieve, and vacuum drying at 60 to 100° C., preferably 70 to 90° C. for 120 to 300 minutes.

In the case of the method for producing an olefin-based polymer according to an embodiment of the present invention, the catalytically active sites exhibit uniform activity, so that an olefin-based polymer having a relatively wide molecular weight distribution, particularly polyethylene, can be prepared.

In particular, in the method for producing an olefin-based polymer according to an embodiment of the present invention, it is possible to produce polyolefins having a wide density distribution from ultra-low-density polyolefins to high-density polyolefins only by controlling the amount of comonomer. Specifically, the olefin-based polymer prepared by the method for preparing the olefin-based polymer according to an embodiment of the present invention may be a polyolefin having a density of 0.900 to 0.952 g/cm 3 .

Example

Hereinafter, the present invention will be described in more detail through Examples and Comparative Examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example One

500 ml of propane was injected into a 1.5 liter tank-type reactor (first reactor) equipped with an anchor-type stirrer. 1.2 mM triethylaluminum (1.2 ml of 1 M hexane solution) and 0.1 mM of cyclohexylmethyldimethoxysilane (1 ml of 0.1 M hexane solution) were injected using 250 ml of propane. 20 mg of Ziegler-Natta catalyst (Z-216 from Basell, average particle size 79 μm, span 1.0, Ti content 2.1 wt%) was injected using 250 ml of propane. These were stirred at 15° C. at 200 rpm for 10 minutes. The temperature of the catalyst mixture in the reactor was raised to 55° C., and 7 g of propylene was injected. These were stirred at 300 rpm for 150 minutes to proceed with primary polymerization.

500 g of dehydrated sodium chloride was put into a 2.3 liter tank-type reactor (second reactor) equipped with a spherical stirrer, and 1.2 mM triethylaluminum (1.2 ml of 1 M hexane solution) was injected, and then at 78° C. for 30 minutes. stirred. After the stirring was completed, 287.41 mg of Atmer antistatic agent was injected.

The polymer obtained by the primary polymerization was transferred to the second reactor, and propane was purged with nitrogen at a pressure of 2-5 bar. Hydrogen is injected at a pressure of 1 bar (or hydrogen/ethylene molar ratio 0.3), 1-butene 3 g is initially injected, and 1-butene is injected at a flow rate of 8 g/100 min (or 1-butene/ethylene molar ratio 0.2) was continuously injected. The partial pressure of ethylene in the second reactor was kept constant at 3.4 bar. They were stirred at 78°C at 300 rpm for 100 minutes to proceed with secondary polymerization.

After removing the metal salt by dissolving the obtained polyethylene in water, Mesh #120, I.S.0. It was dehydrated using a 125 mm sieve, and vacuum dried at 70 to 90° C. for 120 to 300 minutes to obtain a final olefinic polymer.

Example 2

Polyethylene was prepared in the same manner as in Example 1, except that 1-butene was not injected at all during the secondary polymerization.

Example 3

Polyethylene was prepared in the same manner as in Example 1, except that the 1-butene/ethylene molar ratio was maintained at 0.15 without the initial 1-butene injection during the secondary polymerization.

Example 4

Polyethylene was prepared in the same manner as in Example 1, except that the partial pressure of ethylene was kept constant at 6.4 bar during the secondary polymerization.

Example 5

Polyethylene was prepared in the same manner as in Example 1, except that the molar ratio of hydrogen/ethylene was maintained at 0.6 during the secondary polymerization.

Example 6

Polyethylene was prepared in the same manner as in Example 1, except that the initial 1-butene injection amount during the secondary polymerization was 5 g and the 1-butene/ethylene molar ratio was maintained at 0.35.

Example 7

Polyethylene was prepared in the same manner as in Example 1, except that the initial 1-butene injection amount during the secondary polymerization was 5 g and the 1-butene/ethylene molar ratio was maintained at 0.25.

comparative example One

Polymerization was carried out for 4 hours in a pilot scale gas phase fluidized bed reactor using the same Ziegler-Natta catalyst as in Example 1 under conditions of 1-butene/ethylene molar ratio 0.34, hydrogen/ethylene molar ratio 0.25, and ethylene partial pressure 6.5 bar.

comparative example 2

Polymerization was carried out for 100 minutes in a commercial scale gas phase fluidized bed reactor using the same Ziegler-Natta catalyst as in Example 1 under conditions of 1-butene/ethylene molar ratio 0.25, hydrogen/ethylene molar ratio 0.35, and ethylene partial pressure 3.4 bar.

The polymerization conditions of Examples and Comparative Examples are summarized in Table 1 below.

hydrogen/ethylene
molar ratio Initial 1-butene
(g) 1-Butene/Ethylene
molar ratio catalytic activity
(gPE/gCat-hr) Example 1 0.3 3 0.20 4,160 Example 2 0.3 0 0 4,600 Example 3 0.3 0 0.15 4,140 Example 4 0.3 3 0.20 6,170 Example 5 0.6 3 0.20 3,010 Example 6 0.3 5 0.35 2,830 Example 7 0.3 5 0.25 1,800 Comparative Example 1 0.25 - 0.34 9,200 Comparative Example 2 0.35 - 0.25 4,000

test example

The physical properties of the resins obtained in the above Examples and Comparative Examples were measured according to the following methods and standards. The results are shown in Table 2 below.

(1) melt index and melt flow ratio (MFR)

According to ASTM D 1238, the melt index was measured at 190°C under a load of 21.6 kg and a load of 2.16 kg, and the ratio (MI _21.6 /MI _2.16 ) was obtained.

(2) density

It was measured according to ASTM D1505.

MI _2.16 MFR Density (g/cc) Example 1 1.2 26 0.922 Example 2 0.82 36 0.952 Example 3 1.2 28 0.930 Example 4 1.3 29 0.916 Example 5 9.4 30 0.920 Example 6 3.3 57 0.900 Example 7 3.9 57 0.916 Comparative Example 1 1.0 25 0.921 Comparative Example 2 1.1 24 0.921

The molecular weight and molecular weight distribution of the resins obtained in Example 1, Comparative Example 1 and Comparative Example 2 were measured using gel permeation chromatography-FTIR (GPC-FTIR). The measurement results are shown in Table 2 and FIGS. 1 to 3 below.

weight average molecular weight
(Mw, g/mole) number average molecular weight
(Mn, g/mole) molecular weight distribution
(Mw/Mn) Example 1 119,080 21,713 5.48 Comparative Example 1 133,327 27,695 4.81 Comparative Example 2 116,639 35,289 3.30

As can be seen from Table 2 above, the method for producing an olefin-based polymer according to an embodiment of the present invention uses a relatively small amount of a molecular weight modifier and a comonomer, while various physical properties of the resulting olefin-based polymer, particularly polyethylene, are varied. can be adjusted Specifically, as shown in FIG. 4 , it is possible to produce polyethylene having a wide density distribution from ultra-low-density polyethylene to high-density polyethylene just by controlling the amount of comonomer.

In addition, as can be seen from Table 3 and FIGS. 1 to 3, the olefinic monomer, especially polyethylene, produced by the method for producing an olefinic polymer according to an embodiment of the present invention has a catalytically active site exhibiting uniform activity and molecular weight distribution is relatively wide. In contrast, the polyethylene of Comparative Example produced in the gas phase fluidized bed reactor has a relatively narrow molecular weight distribution because the catalyst active sites are biased toward high molecular weight.

Therefore, the method for producing an olefin-based polymer according to an embodiment of the present invention prevents agglomeration of the polymer due to local overreaction while maintaining high catalytic activity during gas phase polymerization of the olefin-based monomer and produces an olefin-based polymer having excellent physical properties. can be manufactured.

Claims (21)

(1) preparing a catalyst mixture comprising a catalyst for olefin polymerization, a cocatalyst, and an external electron donor; (2) primary polymerization of an olefinic monomer having 2 to 6 carbon atoms in the presence of the catalyst mixture obtained in step (1) in a first reactor; (3) in the same first reactor or by transferring the olefinic polymer obtained in step (2) to a second reactor, secondary polymerization of the olefinic monomer having 2 to 6 carbon atoms in the presence of the polymer obtained in step (2) A method for producing an olefin-based polymer comprising the step The olefinic catalyst according to claim 1, wherein the catalyst for olefin polymerization in step (1) is a magnesium chloride (MgCl ₂ ) catalyst prepared by supporting a titanium chloride compound and a phthalate-based internal electron donor on a magnesium chloride (MgCl 2 ) support. A method for producing a polymer. The method according to claim 1, wherein in step (1), the cocatalyst is an alkylaluminum compound, comprising at least one selected from the group consisting of triethylaluminum, diethylchloroaluminum, tributylaluminum, trisisobutylaluminum and trioctylaluminum. A method for producing an olefin-based polymer comprising The method of claim 1, wherein the external electron donor in step (1) is an alkoxysilane-based compound, tetramethoxysilane, methyltrimethoxysilane, dimethyltdimethoxysilane, trimethylmethoxysilane, ethyltrimethoxysilane, di Ethyldimethoxysilane, triethylmethoxysilane, vinyltrimethoxysilane, divinyldimethoxysilane, propyltrimethoxysilane, dipropyldimethoxysilane, tripropylmethoxysilane, isopropyltrimethoxysilane, diiso Propyldimethoxysilane, triisopropylmethoxysilane, butyltrimethoxysilane, dibutyldimethoxysilane, tributylmethoxysilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, triisobutylmethoxysilane , cyclopentyltrimethoxysilane, dicyclopentyldimethoxysilane, cyclopentylmethyldimethoxysilane, cyclohexyltrimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, tetraethoxysilane, methyltri ethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, ethyltriethoxysilane, diethyldiethoxysilane, triethylmethoxysilane, vinyltriethoxysilane, divinyldiethoxysilane, propyltriethoxysilane, Dipropyldiethoxysilane, tripropylethoxysilane, isopropyltriethoxysilane, diisopropyldiethoxysilane, triisopropylethoxysilane, butyltriethoxysilane, dibutyldiethoxysilane, tributylethoxysilane , isobutyltriethoxysilane, diisobutyldiethoxysilane, triisobutylethoxysilane, cyclopentyltriethoxysilane, dicyclopentyldiethoxysilane, cyclopentylmethyldiethoxysilane, cyclohexyltriethoxysilane, dicy Chlohexyldiethoxysilane, cyclohexylmethyldiethoxysilane, tetrapropoxysilane, methyltripropoxysilane, dimethyldipropoxysilane, trimethylpropoxysilane, ethyltripropoxysilane, diethyldipropoxysilane, vinyl tri Propoxysilane, divinyldipropoxysilane, propyltripropoxysilane, dipropyldipropoxysilane, isopropyltripropoxysilane, diisopropyldipropoxysilane, butyltripropoxysilane, dibutyldipropoxysilane Silane, isobutyltripropoxysilane, diisobutyldipropoxysilane, cyclopentyltripropoxysilane, dicyclopentyldipropoxysilane, cyclopentylmethyldipropoxysilane, cyclohexyltripropoxysilane, dicyclo Hexyldipropoxysilane, Cyclohexylmethyldiph A method for producing an olefin-based polymer comprising at least one selected from the group consisting of ropoxysilane. The method according to claim 1, wherein the primary polymerization of the olefinic monomer in step (2) is carried out by slurry polymerization in the presence of a solvent. 6. The method according to claim 5, wherein the olefinic monomer to be primary polymerized in step (2) is at least selected from the group consisting of ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene and 1-hexene. A method for producing an olefin-based polymer comprising one. The method for producing an olefin-based polymer according to claim 6, wherein the olefin-based monomer is propylene. The method according to claim 5, wherein in step (2), the polymerization temperature is 15 to 60° C. and the polymerization time is 30 to 180 minutes. The method according to claim 1, wherein the secondary polymerization of the olefinic monomer in step (3) is carried out by gas phase polymerization in the second reactor. 10. The method according to claim 9, wherein the olefinic monomer to be secondary polymerized in step (3) is at least selected from the group consisting of ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene and 1-hexene. A method for producing an olefin-based polymer comprising one. The method for producing an olefin-based polymer according to claim 10, wherein the olefin-based monomer is ethylene. The method for producing an olefin-based polymer according to claim 9, wherein the secondary polymerization of the olefin-based monomer in step (3) is a copolymerization performed in the presence of an olefin-based comonomer. The method according to claim 12, wherein the olefinic monomer is ethylene and the olefinic comonomer is 1-butene. The method according to claim 9, wherein the secondary polymerization of the olefinic monomer in step (3) is carried out in the presence of a molecular weight modifier. 15. The method according to claim 14, wherein the molecular weight modifier is hydrogen. 10. The method according to claim 9, wherein the secondary polymerization of the olefinic monomer in step (3) is carried out in the presence of a fluidizing medium. 17. The method of claim 16, wherein the flow medium is at least one metal salt selected from the group consisting _{of sodium chloride (NaCl), calcium chloride (CaCl 2 ) and potassium chloride (KCl).} The method according to claim 9, wherein the polymerization temperature in step (3) is 65-100° C. and the polymerization time is 30-180 minutes. The method of claim 1, further comprising (4) separating, washing and drying the olefin-based polymer obtained in step (3). An olefin-based polymer prepared by the method for producing an olefin-based polymer according to any one of claims 1 to 19, and having a density of 0.900 to 0.952 g/cm 3 . 21. The olefinic polymer of claim 20, which is polyethylene.

Images