KR20180034770A

KR20180034770A - Preparing method of catalyst for polymerization of polyethylene and process for polymerization of polyethylene using the same

Info

Publication number: KR20180034770A
Application number: KR1020160124104A
Authority: KR
Inventors: 김동규; 박은정; 전재경; 박세호
Original assignee: 롯데케미칼 주식회사
Priority date: 2016-09-27
Filing date: 2016-09-27
Publication date: 2018-04-05
Also published as: KR101859755B1

Abstract

The present invention relates to a process for preparing a catalyst for synthesizing polyethylene and a process for synthesizing polyethylene using the same. More specifically, there is provided a process for producing a magnesium compound, comprising: reacting a magnesium compound with an alcohol and a compound represented by the following formula (1); Reacting the reaction product with a first transition metal compound to prepare a magnesium solution; And a step of reacting the magnesium solution with a secondary transition metal compound and a dialkyl ether compound, and a process for producing polyethylene using the same.
[Chemical Formula 1]

(As defined for R ¹ in formula (I) is in the specification)

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for preparing a catalyst for synthesizing polyethylene and a process for producing the same,

The present invention relates to a process for producing a catalyst for synthesizing polyethylene, and a process for producing polyethylene using the same. More particularly, the present invention relates to a process for preparing a catalyst for synthesis of polyethylene, which exhibits high process stability and excellent copolymerization efficiency in the production of an ethylene-based polymer such as a polyethylene polymer, and a process for producing polyethylene using the same.

Worldwide demand for polyethylene is close to 100 million metric tons per year, which is steadily growing at 3 ~ 5% per year, and continuous changes are taking place mainly in the existing products. For example, low-density linear polyethylene production is increasing with metallocene catalysts to reinforce the physical properties of the film, and efforts are continuing to diversify and produce specialty products to develop new product lines.

In the production of linear low density polyethylene (LLDPE), ethylene is copolymerized with short-chain olefin comonomers such as 1-butene, 1-hexene and 1-octene. These polymers are linear but contain short branches (SCB) and are excellent in mechanical strength, such as impact strength and tensile strength, and are excellent in optical properties and processability, and are thus widely used for films. The main use of these films is for general industrial films, agricultural films, and multilayer films.

Currently, polyethylene synthesis catalysts can be classified into Ziegler-Natta catalysts, chromium catalysts and metallocene catalysts depending on the type of core metal used. Properties and catalytic activities of these catalysts depend on the catalytic activity, the molecular weight distribution characteristics of the polymer, Since they have different reaction characteristics, they are selectively used according to each manufacturing process and application product. Of these, Ziegler-Natta catalysts are the most commonly used, and Ziegler-Natta catalysts are based on a magnesium-supported catalyst and a silica-supported catalyst, depending on the type of carrier.

The magnesium-supported catalyst can be prepared by reacting a magnesium compound with an electron donor such as an alcohol, an amine, an ether, an ester, or a carboxylic acid to prepare a magnesium compound solution, rapidly cooling the magnesium compound solution without reacting with the transition metal compound, Drying, spray drying, and the like to prepare a solid spherical magnesium compound and reacting with a transition metal compound such as a titanium compound to prepare a solid catalyst for polyethylene synthesis.

In order to compensate the physical properties of the film, there is a method for preparing a catalyst which improves physical properties by using two or three transition metal compounds. These catalysts exhibit different characteristics. Generally, when a gas phase polymerization reactor is used, the initial reaction rate is higher than that of the liquid phase polymerization reactor and the operation conditions such as static electricity are sensitive. Therefore, these characteristics should be taken into account when manufacturing and operating the catalyst. When the amount of the comonomer such as 1-butene, 1-hexene or 1-octene used to lower the density of polyethylene is increased, There is a problem in that the polymer becomes sticky and sticks to the inner wall of the reactor, which makes the operation difficult.

The present invention can not only increase the yield by producing a catalyst exhibiting high activity in a fluidized bed reactor for synthesizing polyethylene but also can produce a polymer having a low density even when a small amount of comonomer is used, And a method for producing the catalyst for synthesizing polyethylene.

The present invention further provides a process for producing polyethylene using the catalyst for synthesizing polyethylene.

The present invention relates to a process for producing a magnesium compound, comprising the steps of: reacting a magnesium compound with an alcohol and a compound represented by the following formula (1); Reacting the reaction product with a first transition metal compound to prepare a magnesium solution; And reacting the magnesium solution with a secondary transition metal compound and a dialkyl ether compound. The present invention also provides a process for preparing a catalyst for synthesis of polyethylene.

[Chemical Formula 1]

Wherein R ¹ is selected from the group consisting of hydrogen, a linear or branched alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, an aryl substituent, an alkylaryl group, An alkylaryl substituent, or an alkylaryl containing N, O, S, or P.

In addition, the present invention provides a process for producing polyethylene comprising the step of synthesizing an ethylenic monomer in the presence of the catalyst for synthesizing polyethylene.

Hereinafter, a method for producing a catalyst for synthesis of polyethylene according to a specific embodiment of the present invention and a method for producing polyethylene using the same will be described in detail.

According to an embodiment of the present invention, a method for producing the catalyst for synthesizing polyethylene may be provided.

The present inventors have found that a Ziegler-Natta catalyst for synthesizing polyethylene, which is used in conventional polyethylene synthesis, requires a large amount of a comonomer to produce a linear low density polyethylene having a lower density than a metallocene catalyst and increases the reactivity of the comonomer The use of alkylaluminum for this process requires a dangerous and complicated manufacturing process. In addition, when a large amount of comonomer is added, it is possible to produce linear low density polyethylene, but the polyethylene component in the reactor becomes sticky and causes trouble in the reactor. In recognition of this problem, research has been conducted to produce a linear low density polyethylene having a low density using only a small amount of comonomer, and it has been confirmed that a catalyst having improved comonomer reactivity of the catalyst can be easily produced, and the invention is completed.

Particularly, according to the above production method, since it has a high activity and excellent comonomer reactivity while maintaining a spherical type catalyst shape having a certain size suitable for a gas phase fluidized bed reactor type, it has high process stability and is advantageous for continuous operation, The alkyl compound process step can be omitted, so that the process can be simplified and the risk factor can be greatly reduced.

The polyethylene synthesis includes both a polymerization process using one kind of ethylene monomer and a copolymerization process using two or more kinds of monomers.

In the present specification, the polyethylene synthesis includes both a polymerization process using one kind of ethylene monomer and a copolymerization process using two or more kinds of monomers.

And, in the present specification, the cycloalkyl group means a monovalent functional group derived from cycloalkane, and the aryl group means a monovalent functional group derived from arene. The alkylaryl group also refers to an aryl group substituted with an alkyl group.

According to an embodiment of the present invention, there is provided a process for producing a magnesium compound, comprising: reacting a magnesium compound with an alcohol and a compound represented by the following formula (1); Reacting the reaction product with a first transition metal compound to prepare a magnesium solution; And a step of reacting the magnesium solution with a secondary transition metal and a dialkyl ether compound to prepare a catalyst for synthesizing polyethylene.

[Chemical Formula 1]

Specific examples of the compound of formula (1) include ethyl benzoate, propyl benzoate, isopropyl benzoate, and vinyl benzoate, and it is more preferable to use, for example, ethyl benzoate.

The dialkyl ether compound according to an embodiment may be a compound represented by the following formula (2), and preferably the dialkyl ether compound may be a dibutyl ether compound.

(2)

In Formula 2, R ² and R ³ are each independently selected from the group consisting of hydrogen, straight or branched alkyl having 1 to 20 carbon atoms, alkenyl, alkenyl, cycloalkyl, aryl, Alkylaryl, an alkylaryl substituent, or alkylaryl including N, O, S, or P.

In the step of reacting the magnesium compound with the alcohol and the compound represented by the formula 1, the magnesium compound and the compound of the formula 1 can be reacted at a molar ratio of 1: 0.01 to 1: 1, preferably 1: 1: 0.3 molar ratio. Outside of the above range, the catalyst particles may not be uniformly formed, or a catalyst having low activity and low flowability may be produced, which is undesirable.

Specific examples of the magnesium compound include magnesium halide, dialkoxymagnesium, alkylmagnesium halide, alkoxymagnesium halide, and aryloxymagnesium halide, and it is more preferable to use a magnesium halide to increase the activity of the catalyst.

Specifically, the magnesium halide compound is a compound having no reducing property, and examples thereof include magnesium chloride, magnesium dichloride, magnesium fluoride, magnesium bromide, magnesium iodide, phenoxy magnesium chloride, isopropoxymagnesium chloride, butoxy magnesium chloride, Among them, the use of magnesium dichloride is preferred because it exhibits stable and high activity in structural and coordination with the transition metal compound, which is the main active metal.

The alcohol may be reacted with a magnesium compound and a compound of formula (1) in the production of a catalyst for synthesizing polyethylene. The reaction molar ratio of the magnesium compound to the alcohol is 1: 1 to 1: 5, preferably 1: 2 to 1: 4 < / RTI > If the reaction molar ratio of the alcohol is more than 5 moles relative to the magnesium compound, the amount of the transition metal compound to be reacted with the magnesium compound must be increased in order to exhibit high activity, and further processing is required to extract the alcohol. If it is less than 1 mole, the magnesium compound can not be prepared as a homogeneous solution, which is not desirable for use in the production of catalysts.

In one embodiment, the alcohol can be used without limitation as long as it is an alcohol known to be used in the preparation of a Ziegler-Natta catalyst for polyethylene synthesis. Specific examples of the solvent include ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, neopentanol, cyclopentanol, n- Aliphatic or alicyclic alcohols such as dodecanol, 2-methylpentanol, 2-ethylbutanol and 2-ethylhexanol; Aryl cyclic alcohols such as cyclohexanol and methylcyclohexanol; And aromatic alcohols such as benzyl alcohol, methylbenzyl alcohol, isopropyl benzyl alcohol and? -Methyl benzyl alcohol. Of these, aliphatic or alicyclic alcohols or alcohols having 2 or more carbon atoms are preferably used, and 2-ethyl It is more preferable to use hexanol.

In the step of reacting the magnesium compound with the alcohol and the compound represented by the general formula (1), the order of reacting or reacting the magnesium compound is first reacted with the alcohol to form a homogeneous solution, It is preferable to add a compound to react.

The step of reacting the magnesium compound with an alcohol may be carried out at 80 ° C to 140 ° C. That is, the dissolving temperature for dissolving the magnesium compound in alcohol is preferably 80 ° C to 140 ° C, and if it is out of the above range, it is not preferable to dissolve in alcohol or increase the adverse reaction.

After the magnesium compound is dissolved in the alcohol, it can be sufficiently stirred to disperse the whole solution, and the compound of the above formula (1) can be added to the product in which the magnesium compound is completely dissolved in the alcohol. The temperature at which the compound of formula (1) is added to the dissolution product is preferably from 40 to 130 ° C, and when it is outside the above range, it is not preferable to add magnesium to the magnesium or increase the adverse reaction.

The step of melting the magnesium compound in alcohol may be carried out in a hydrocarbon solvent. When the reaction is carried out in a hydrocarbon solvent, a homogeneous solution of a magnesium compound and an alcohol can be obtained while using a small amount of alcohol, which is preferable.

Specific examples of the hydrocarbon solvent include aliphatic or alicyclic hydrocarbons having 5 to 20 carbon atoms, and aliphatic or alicyclic hydrocarbon solvents having 6 to 17 carbon atoms are most preferred. More specific examples include aliphatic hydrocarbons such as hexane, heptane, octane, decane, dodecane, tetradecane, and mineral oil; Alicyclic hydrocarbons such as cyclic hexane, cyclic octane, methyl cyclic pentane and methyl cyclic hexane; And aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene.

In the step of preparing the magnesium solution according to an embodiment, a primary transition metal compound is added to form a uniform seed. The magnesium compound and the first transition metal compound can be reacted at a molar ratio of 1: 0.01 to 1: 1, preferably at a molar ratio of 1: 0.05 to 1: 0.3. If it is out of the above range, the catalyst particles may not be uniformly formed or the amount of the catalyst particles may be small and the effect may not be generated, which is not preferable.

The temperature for introducing the primary transition metal compound into the reaction product is preferably from 10 캜 to 60 캜, and if it is out of the above range, seed formation is not performed properly, which is not preferable.

After the step of preparing the magnesium solution, the secondary transition metal compound may be dispersed in the magnesium solution.

The primary transition metal compound and the secondary transition metal compound may be the same or different and include a transition metal of group IVB, VB, or VIB or an organic compound containing such a transition metal. Specific examples of the transition metal Examples include Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W and Sg.

As a specific example of the transition metal compound, any transition metal compound known to be used as a Ziegler-Natta catalyst for synthesizing polyethylene can be used for the production of the catalyst component without limitation. In particular, preferred examples of the first transition metal compound and the second transition metal compound include compounds represented by the following general formula (3).

(3)

MX _n (OR ⁴ ) ₄ _-n

In Formula 3, M is selected from the group consisting of transition metal elements of Group IVB, VB and VIB of the periodic table, X is a halogen element, R ⁴ is an alkyl group having 1 to 10 carbon atoms, n is an oxidation number of the metal, To 4.

Preferred examples of M include Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W and Sg. Specific examples of the transition metal compound represented by the above formula (3) include titanium tetrachloride, sabromium titanium, titanium tetraiodide, tetrabutoxy titanium, tetraethoxy titanium, diethoxy titanium dichloride, or ethoxy titanium trichloride. And it is preferable to use titanium tetrachloride.

In the step of reacting the dialkyl ether compound after the secondary transition metal compound is dispersed in the magnesium solution, the order or the order of introduction of the reactant is not limited to a great extent. For example, a magnesium solution and a secondary transition metal The compound and the dialkyl ether compound may be simultaneously reacted, or the components may be sequentially added and reacted.

Further, the secondary transition metal compound can be reacted by dispersing in a hydrocarbon solvent. This is to control the molar ratio of hydrocarbons to produce a solid catalyst having a uniform particle size and smooth surface. A solid catalyst for synthesis of polyethylene having a spherical shape in which the particle size distribution is uniform and the surface of the catalyst particle is smooth is mixed with an amount of 1 to 20 mol, more preferably 5 to 8 mol per mol of the magnesium compound per mol of the magnesium compound Can be manufactured.

Specific examples of the hydrocarbon solvent include aliphatic or alicyclic hydrocarbons having 5 to 20 carbon atoms, and aliphatic or alicyclic hydrocarbon solvents having 6 to 17 carbon atoms are preferred. More specific examples include aliphatic hydrocarbons such as hexane, heptane, octane, decane, dodecane, tetradecane, and mineral oil; Alicyclic hydrocarbons such as cyclic hexane, cyclic octane, methyl cyclic pentane and methyl cyclic hexane; And aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene. It is more preferable to use hexane because the particle size distribution of the solid catalyst to be produced is uniform and the surface of the catalyst particle is a smooth spherical shape.

The step of dispersing the secondary transition metal compound and the dibutyl ether of Formula 2 in a hydrocarbon solvent may be performed at -20 캜 to 40 캜. When the above compounds are dispersed in a hydrocarbon solvent at a low temperature, it is possible to form harder and more uniform particles, thereby improving the polymerization activity of the catalyst and the apparent density and physical properties of the synthesized polyethylene.

In one embodiment, a hydrocarbon solvent and a second transition metal compound are first reacted to form a catalyst having a uniform particle size, aged for 30 minutes to 2 hours at a low temperature of -30 ° C to 20 ° C, The solution can be reacted by slow addition for 1 to 4 hours. In order to obtain a uniform particle size, it is preferable to add slowly at a constant rate, and it is preferable to recycle at a low temperature of -30 캜 to 20 캜 so that recrystallization easily occurs.

After the aging process, the dialkyl ether compound can be reacted at -20 ° C to 40 ° C over 30 minutes, preferably at the time when particles are formed at -20 ° C, dialkyl ether compounds, The dibutyl ether of formula (2) can be added. This makes the shape of the catalyst close to spherical, and the internal electron donor can react uniformly with the magnesium solution and the transition metal compound.

After reacting the hydrocarbon solvent, the secondary transfer metal compound and the dialkyl ether compound as described above, the reaction temperature of the reaction product can be raised to 20 ° C at a rate of 0.25 ° C / min and aged for 30 minutes to 1 hour . The gradual increase of the temperature of the reaction to 20 ° C is intended to suppress the generation of uneven catalyst particles due to the violent reaction during the formation of the initial catalyst particles.

When the dialkyl ether compound is reacted at a temperature of less than -20 ° C, the uniformity of the catalyst is lowered and the physical properties of the final polymerized product may be lowered, and when the temperature is higher than 40 ° C, It is not effective to distribute uniformly. It is effective in producing linear low density polyethylene having a low density while having excellent activity by introducing the dialkyl ether compound, and has a low molecular weight content and narrow distribution of polyethylene and excellent physical properties.

The dialkyl ether compound, that is, the compound of Formula 2, is preferably reacted in an amount of 0.01 mol to 1 mol per 1 mol of the magnesium compound. When the above range is satisfied, it can act as an internal electron donor for stabilizing the titanium active site by reacting with the compound of Formula 1 to donate electrons to the transition metal compound. More specifically, the compound of formula (I) may serve to generate catalytic particles within the catalyst for synthesizing polyethylene and to greatly grow the size thereof. In addition, the compound of formula (2) stabilizes the titanium active site attached to the magnesium support and partially removes the titanium active site not attached to the magnesium support to uniformly distribute the titanium active site on the magnesium support.

That is, by adding the two compounds of the formulas (1) and (2), the catalyst for synthesizing polyethylene produced by the production method according to one embodiment can be formed into spherical particles having a uniform and uniform size, When the linear low density polyethylene is produced by the excellent reactivity of the comonomer while maintaining the excellent activity, it is possible to suppress troubles in the reactor and reduce the production of low molecular weight and to have excellent physical properties.

The compound of Formula 1 and the compound of Formula 2 are preferably separately added stepwise as described above. It is preferable that each of them is added step by step because the catalyst shape is uniform and the internal electron donor can be stably bonded as compared with the case where they are reacted together by administration. More specifically, the catalyst for synthesizing polyethylene may be prepared by adding the compound of formula (I) to a magnesium solution at the time of forming a particle and growing the compound. The compound of formula (2) is added at an appropriate molar ratio at a suitable temperature, So that they can be stably bonded and exhibit the physical properties of the above-mentioned catalyst. That is, the compound of formula (1) and the compound of formula (2) are different from each other in the role of the catalyst in forming the catalyst and are preferably administered sequentially, rather than together, so that a high-performance catalyst can be efficiently produced.

After reacting the hydrocarbon solvent with the secondary transition metal compound and the dialkyl ether compound as described above, the reaction temperature of the reaction product is raised to 20 ° C at a rate of 0.25 ° C / min and aged for 30 minutes to 1 hour . The gradual increase of the temperature of the reaction to 20 ° C is intended to suppress the generation of uneven catalyst particles due to the violent reaction during the formation of the initial catalyst particles.

More specifically, the compound of formula (I) may act to produce catalytic particles within the catalyst for synthesizing polyethylene and to grow large size, and the compound of formula (II) may increase the reactivity of the comonomer, And can reduce the low molecular weight and narrow the distribution of polyethylene and improve the physical properties.

The step of reacting the magnesium solution with the second transition metal compound and the dialkyl ether compound may further include a step of raising the temperature to -30 ° C to 100 ° C, aging and then washing the magnesium solution. When hexane is used as the hydrocarbon solvent, the temperature is preferably raised to 74 占 폚, and it is more preferable to aged for 2 hours. The maximum temperature is preferably kept below the boiling point of the hydrocarbon solvent in order to prevent vaporization of the solvent, and the magnesium compound and the transition metal compound, the compound of the formula (1) and the dialkyl ether compound may be bonded , The shape of the catalyst can be determined.

In order to regulate the content of transition metal compounds in the aged product and stably produce the produced polyethylene, the unreacted material and the reaction residues are removed by washing with hydrocarbon compounds 2 to 7 times at 40 ° C to 60 ° C, Can be obtained. More specifically, it is preferable to clean the solid catalyst using hexane as the aliphatic hydrocarbon.

The method for preparing a catalyst for synthesizing polyethylene according to an embodiment may further include the step of crystallizing a reaction product of the magnesium solution and a secondary transition metal compound and a dialkyl ether compound.

The primary transition metal compound forms only the seed of the catalyst (SEED) during the reaction. Actually, a desired catalyst size size of 10um or more is formed by the reaction of the secondary transition metal compound with the dialkyl ether compound and reaches the final temperature The shape and rigidity of the catalyst are determined until the catalyst is used. In addition, not only the crystallization of the catalyst but also the transition metal compound acting as a particle and an active point can be stably bonded to a higher temperature.

The method for producing a catalyst for synthesizing polyethylene according to one embodiment of the present invention can produce a catalyst by a recrystallization method by reacting a solution of a magnesium compound at a low temperature with a transition metal compound so that the catalyst can be produced easily and easily in a desired size and shape, Production can be facilitated and economic efficiency can be improved. In addition, the catalyst thus prepared exhibits a spherical shape having a uniform size, and can be expected to have a large surface area, excellent flowability, high catalytic activity, and low reactivity due to a small amount of fine particles. In addition, it is possible to produce linear low density polyethylene by injecting low comonomer to ethylene, and it contains small low molecular weight content. In order to lower the density of the polymer in the conventional manner, more comonomers have to be added. As the amount of the polymer is increased, the polymer tackiness is increased to cause troubles, but the occurrence of stickiness is minimized and the operation stability can be improved. By producing a catalyst having high reactivity of such a comonomer, it is possible to lower the density by using a small amount of comonomer and to simplify the process and increase the stability of the reactor by removing the step of using an alkyl compound to increase the reactivity of the comonomer The present invention also provides a method for producing a catalyst for synthesizing polyethylene.

The polyethylene can be synthesized in the presence of the catalyst prepared by the method for producing a polyethylene synthesis catalyst and the polyethylene can be synthesized in the presence of a catalyst system further comprising a cocatalyst or an external electron donor in the catalyst. Polyethylenes synthesized using such solid catalysts or catalyst systems are polymers having improved physical properties such as apparent density.

And may further include an external electron donor in the polyethylene synthesis process. The cocatalyst can reduce the transition metal compound to form an active site, thereby enhancing the catalytic activity. The cocatalyst according to one embodiment is not particularly limited, and any organic metal compound known to be used in the production of a catalyst for general polyethylene synthesis can be used without limitation. Among them, it is preferable to use an alkylaluminum compound represented by the following formula (4).

[Chemical Formula 4]

R ⁵ _m AlX ₃ _-m

In Formula 4, R ⁵ is an alkyl group having 1 to 8 carbon atoms, X is a halogen element, and m is 0 to 3.

Specific examples of the cocatalyst include trimethylaluminum, triethylaluminum, triisobutylaluminum, tributylaluminum, diethylaluminum dichloride, ethylaluminum dichloride, ethylaluminum cesium skew chloride, tripropylaluminum, tributylaluminum, tripentyl Aluminum, trihexyl aluminum and trioctyl aluminum.

The synthesis reaction may be carried out in a gas phase, a liquid phase, or a solution phase. When the synthesis reaction is carried out in a liquid phase, a hydrocarbon solvent can be used, and ethylene itself can be used as a solvent. The synthesis temperature may be from 0 캜 to 200 캜, preferably from 50 캜 to 150 캜. If the synthesis temperature is less than 0 占 폚, the activity of the catalyst is not good, and if it exceeds 200 占 폚, the stereoregularity becomes poor, which is not preferable. The synthesis pressure may be from 1 to 100 atm and preferably from 2 to 30 atm. When the synthesis pressure exceeds 100 atm, it is not preferable from the industrial and economical viewpoints. The synthesis reaction can be carried out by any of batch, semi-continuous and continuous processes.

The heat stabilizer, the light stabilizer, the flame retardant, the carbon black, the pigment, the antioxidant and the like which are conventionally added can be added to the polyethylene produced by using the solid catalyst according to the present invention. The polyethylene produced may be mixed with linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), EP (ethylene / propylene) rubber and the like.

According to the present invention, not only high reactivity can be exhibited in the polyethylene polymerization reaction, but also the hydrogen reactivity and the comonomer reactivity are improved to improve the operation efficiency and the operation stability, and the xylene solubility (XS) The present invention also provides a process for producing a catalyst capable of improving the physical properties of a product by a simple process and a process for producing polyethylene using the process.

The invention will be described in more detail in the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

Example And Comparative Example : Preparation of Catalyst and Polymerization of Polyethylene

Example One

1) Preparation of magnesium compound solution

90 g of magnesium chloride, 387 ml of decane and 502 ml of ethylhexanol were charged into a 2 liter pressure-resistant glass reactor equipped with a stirrer and an oil circulating heater under a nitrogen atmosphere, and the mixture was stirred at 80 DEG C at a rotating speed of 50 rpm Lt; / RTI > The magnesium compound was heated to 135 ° C to completely dissolve the magnesium compound. When the solution became homogeneous, the solution was aged for 1 hour, cooled to 80 ° C, and 27 ml of ethylbenzoate solution was added thereto for 30 minutes. After the addition, the reactor was aged at 135 ° C. for 1 hour. The temperature of the reactor was then cooled to 40 ° C., and 10 ml of a titanium tetrachloride solution was added thereto over 10 minutes. After aging for 30 minutes, the temperature of the reactor was lowered to 25 ° C. Respectively.

2) Solid Carrier Production and Preparation of Solid Titanium Catalysts

The temperature of the reactor was cooled to -20 ° C under a nitrogen atmosphere using a 3 liter pressure glass reactor equipped with a baffle for improving the flowability of the stirrer and the oil circulation heater and the reactor. After the temperature of the reactor was maintained at -20 占 폚, 976 ml of hexane and 342 ml of titanium tetrachloride solution were added, and the mixture was stirred at 60 rpm for 30 minutes. At the completion of the stirring, 916 ml of the magnesium compound solution prepared above was slowly added to the reaction solution for 4 hours. At this time, the temperature of the introduced solution was kept at 4 캜. After the addition of the magnesium compound solution was completed, the mixture was stirred for 30 minutes, and 1.6 ml of dibutyl ether solution was added thereto over 10 minutes. After aging at -20 캜 for 30 minutes, the temperature of the reactor was raised at a rate of 0.25 캜 / min.

When the temperature of the reactor reached 20 ° C, the reactor was aged for 30 minutes. The temperature of the reactor was increased to 74 ° C at a rate of 1 ° C / min and aged at 74 ° C for 2 hours. After the reactor was cooled to 60 ° C, the stirring was stopped, and the precipitate was removed. The supernatant was removed and washed 5 times with 2 liters of hexane at 40 ° C. The final slurry was dried in vacuum for 30 minutes to obtain a catalyst.

3) Polymerization of polyethylene

A 2 liter high-pressure reactor heated at 125 ° C was refluxed with nitrogen for 1 hour to bring the reactor to a nitrogen atmosphere. The reactor was cooled to 25 ° C under a nitrogen atmosphere and 1 liter of purified hexane was injected. 2 ml of triethylaluminum diluted with a decane solvent in a molar concentration of 1 mol was added, and 1 g (10 mg) of the diluted solution was added to 1 g of the catalyst obtained above in 100 ml of decane solvent. After the addition, the temperature of the reactor was raised to 75 캜 while stirring at 250 rpm. When the temperature of the reactor reached 70 ° C, 3,000 ppm of hydrogen was added. Ethylene and 1-butene were fed at 75 ° C over 2 hours, and the pressure of the reactor was maintained at 7.1 bar. After the synthesis, the temperature of the reactor was lowered to room temperature. The resulting polyethylene was dried in a vacuum oven at 50 DEG C for 6 hours and then weighed.

Example 2

A catalyst was synthesized and polyethylene was polymerized in the same manner as in Example 1, except that 8 ml of a dibutyl ether solution was added.

Example 3

A catalyst was synthesized and polyethylene was polymerized in the same manner as in Example 1, except that 11 ml of a dibutyl ether solution was added.

Example 4

A catalyst was synthesized in the same manner as in Example 1 except that 16 ml of a dibutyl ether solution was added,

Example 5

A catalyst was synthesized and polyethylene was polymerized in the same manner as in Example 1 except that 32 ml of a dibutyl ether solution was added.

Comparative Example One

A catalyst was synthesized and polyethylene was polymerized in the same manner as in Example 1, except that 1.6 ml of dibutyl ether and 25 ml of diisobutylphthalate solution were added.

Comparative Example 2

A catalyst was synthesized and polyethylene was polymerized in the same manner as in Example 1, except that 15 ml of diphenyl ether solution was added instead of 1.6 ml of dibutyl ether.

Experimental Example : Measurement of Physical Properties of Catalyst and Polyethylene

The physical properties of the catalyst prepared in the above Examples and Comparative Examples and the polyethylene were measured by the following methods and shown in Table 1.

(1) Method of measuring C4 / C2: The ratio of C4 and C2 mol% was calculated by measuring the concentrations of C4 mol% and C2 mol%, respectively, through a GC detector inside the reactor. Here, C2 represents a monomer (ethylene), and C4 represents a comonomer (1-butene) used for copolymerization.

(2) Method for measuring activity: The weight (kg) of the polymer produced for 1 hour per weight (g) of the catalyst used was measured.

* Catalytic activity (Kg-PE / g-cat) = amount of polyethylene produced (kg) / amount of catalyst (g)

(3) Method of measurement of apparent density: Polyethylene prepared in a container having a volume of 100 ml, which is known according to ASTM D189, was filled with a free fall by gravity, and the apparent density was obtained by measuring the pure weight.

* Apparent Density (g / ml) = Net Weight of Polymer / 100 ml

(4) Melt Index (MI) Measurement method: Measured according to ASTM D1238 at 190 DEG C at 2.16 kg and expressed in g per 10 minutes.

(5) Low molecular weight polymer (LMP; molecular weight: 1,000 or less) Measuring method: 2.5 g of the sample (polymer product) is well dispersed in hexane and stirred for 15 hours at 80 캜 close system. At this time, after removing the heavy hexene that passed through the filter after filtration, only the remaining sample was extracted and weighed to determine the low molecular weight polymer content.

Example C4 / C2 activation
(Kg-PE /
g-cat) Apparent density
(g / ml) Polyethylene density (g / cm ³ ) Melt Index
(MI)
(g / 10 min) Low molecular weight
Polymer (LMP) content (g) Example 1 0.30 12.0 0.318 0.918 1.03 112 Example 2 0.28 11.4 0.326 0.918 1.05 104 Example 3 0.25 10.9 0.333 0.918 1.01 92 Example 4 0.18 10.6 0.340 0.918 1.02 76 Example 5 0.25 8.8 0.341 0.918 1.05 74 Comparative Example 1 0.38 9.5 0.338 0.918 0.98 127 Comparative Example 2 0.31 12.3 0.310 0.918 1.08 108

Table 1 shows the activity of the catalyst, the reactivity of the comonomer, and the physical properties of the polyethylene after adjusting the amount of the inner electron donor, i.e., dibutyl ether.

As shown in Table 1, when the density of polyethylene was 0.918 g / cm ³ and MI was 1.0, the catalyst of Example 4 had the lowest C4 / C2 value, that is, the smallest amount of 1-butene comonomer added , And it was confirmed that when the polyethylene having the same properties was continuously produced, the catalyst of Example 4 could be produced stably without the most trouble. On the other hand, in the case of a catalyst having a small or high dibutyl ether content, the comonomer reactivity is poor and the operation stability is poor.

Also, Comparative Example 1 using diisobutylphthalate as an internal electron donor confirmed that both activity and operation stability were inferior. On the other hand, Comparative Example 2 in which diphenyl ether was added showed good activity, but the reactivity of the comonomer was poor, so that it was not good for producing polyethylene having low density.

Claims

Reacting a magnesium compound with an alcohol and a compound represented by the following formula (1);
Reacting the reaction product with a first transition metal compound to prepare a magnesium solution;
And reacting the magnesium solution with a secondary transition metal compound and a dialkyl ether compound. The method for producing a catalyst for synthesis of polyethylene according to claim 1,
[Chemical Formula 1]

The method according to claim 1,
Wherein the dialkyl ether compound comprises a compound represented by the following formula (2): < EMI ID =
(2)

In Formula 2, R ² and R ³ are each independently selected from the group consisting of hydrogen, straight or branched alkyl having 1 to 20 carbon atoms, alkenyl, alkenyl, cycloalkyl, aryl, Alkylaryl, alkylaryl substituents, or alkylaryl including N, O, S, or P.

The method according to claim 1,
Wherein the first transition metal compound and the second transition metal compound are compounds of the following formula (3): < EMI ID =
(3)
MX _n (OR ⁴ ) ₄ _-n
In the formula (3), M is selected from the group consisting of transition metal elements of groups IVB, VB and VIB of the periodic table,
X is a halogen element, R ⁴ is an alkyl group having 1 to 10 carbon atoms, and n is 0 to 4.

The method according to claim 1,
The step of reacting the magnesium compound with an alcohol and a compound represented by the following formula 1 is carried out in the presence of a hydrocarbon solvent,
The hydrocarbon solvent includes linear or branched alkyl, alkenyl, cycloalkyl, aryl, aryl substituents, alkylaryl, alkylaryl substituents having 5 to 12 hydrocarbons Wherein the alkylaryl compound is an alkylaryl compound.

The method according to claim 1,
Wherein the molar ratio of the magnesium compound to the alcohol is 1: 1 to 1: 5.

The method according to claim 1,
Wherein the molar ratio of the magnesium compound to the compound of Formula 1 is 1: 0.01 to 1: 1.

The method according to claim 1,
Wherein the molar ratio of the magnesium compound to the primary transition metal compound is 1: 0.01 to 1: 1.

The method according to claim 1,
Wherein the reaction molar ratio of the magnesium compound to the dialkyl ether compound is 1: 0.01 to 1: 1.

The method according to claim 1,
Wherein the step of reacting the magnesium compound with an alcohol is carried out at a temperature of 80 ° C to 140 ° C.

The method according to claim 1,
Wherein the step of preparing the magnesium solution is carried out at a temperature of from 10 캜 to 60 캜.

The method according to claim 1,
Wherein the secondary transition metal compound is dispersed in a hydrocarbon solvent and reacted with the magnesium solution.

12. The method of claim 11,
Wherein the step of reacting the secondary transition metal compound and the magnesium solution dispersed in the hydrocarbon solvent is performed at -30 캜 to 100 캜.

The method according to claim 1,
Wherein the step of reacting the dialkyl ether compound is carried out at -20 캜 to 40 캜.

The method according to claim 1,
Further comprising the step of crystallizing a reaction product of the magnesium solution with a secondary transition metal compound and a dialkyl ether compound.

A process for producing polyethylene, which comprises polymerizing an ethylenic monomer in the presence of a catalyst prepared by the process for producing a catalyst for synthesis of polyethylene according to any one of claims 1 to 14.