KR20210067340A - Method for preparing catalyst for polyethylene polymerization and method for preparing polyethylene - Google Patents

Abstract

The present invention is to provide a catalyst which can be used in the preparation of ultra-high molecular weight polyethylene. The present invention provides a method for preparing a catalyst for polyethylene polymerization comprising the steps of: (A) dissolving a magnesium compound in a solvent containing alcohol to form a magnesium compound solution; (B) forming a catalyst solution by adding a transition metal compound to the magnesium compound solution; (C) raising the temperature of the catalyst solution; and (D) introducing an internal electron donor to the catalyst solution after the temperature is raised.

Description

Polyethylene polymerization catalyst production method and polyethylene production method {METHOD FOR PREPARING CATALYST FOR POLYETHYLENE POLYMERIZATION AND METHOD FOR PREPARING POLYETHYLENE}

The present invention relates to a method for preparing a catalyst for polymerization of polyethylene and a method for preparing polyethylene.

Ultrahigh molecular weight polyethylene (UHMWPE) is a type of polyethylene resin ^{and refers to polyethylene with a molecular weight of at least 10 6} g/mol or more. , chemical resistance and electrical properties are excellent. Due to these excellent physical properties, ultra-high molecular weight polyethylene has been used for mechanical parts requiring wear resistance such as gears, bearings, and cams. It is spotlighted as the only organic material that satisfies the conditions as an alternative material for artificial joints.

Ultra-high molecular weight polyethylene produced through the slurry polymerization process cannot be granulated like general-purpose polyethylene because of its high molecular weight. Therefore, since it is produced and sold in the form of polymerized particles in a reactor, melt processing, which is a conventional processing method of polyethylene, is difficult, and since it must be processed by dissolving it in an appropriate solvent, it must have excellent solubility in a solvent.

In terms of solubility, the particle size and particle size distribution of ultra-high molecular weight polyethylene are important characteristics. This is because the solubility may be inhibited if the particles are too large or the particle size distribution is large even if the particles are small.

In addition, apparent density among the particle characteristics of powder is an important factor affecting productivity not only in the manufacturing process of ultra-high molecular weight polyethylene, but also in the processing process. Therefore, it can be said that it is very important to control the particle size of the catalyst, which determines the properties of the powder particles. In addition, in order to improve the purity of the product and to improve the productivity of the manufacturing process, a high-activity catalyst is required for producing ultra-high molecular weight polyethylene.

Korean Patent Registration No. 10-0182340

SUMMARY OF THE INVENTION It is an object of the present invention to provide a catalyst capable of controlling a catalyst particle size, having an excellent catalyst shape, a narrow particle size distribution, and high activity and apparent density.

Another object of the present invention is to provide an ultra-high molecular weight polyethylene having an excellent powder shape, a narrow particle size distribution, and no particle agglomeration, and having a weight average molecular weight of 10 ^{6 g/mol or more, prepared under the catalyst.}

According to one aspect of the present invention, (A) dissolving a magnesium compound in a solvent containing alcohol to form a magnesium compound solution; (B) forming a catalyst solution by adding a transition metal compound to the magnesium compound solution; (C) raising the temperature of the catalyst solution; and (D) adding an internal electron donor to the catalyst solution after the temperature rise is provided.

According to another aspect of the present invention, there is provided a polyethylene production method comprising the step of polymerizing an ethylene monomer under a catalyst for polyethylene polymerization, wherein the polymerization reaction is carried out at 50 to 90 °C.

According to another aspect of the present invention, polyethylene is prepared under a catalyst for polyethylene polymerization and has a weight average molecular weight of 1.5x10 ⁶ to 8x10 ⁶ g/mol.

According to the present invention, it is possible to prepare a catalyst with high activity and apparent density by controlling the timing of the input of the internal electron donor during the preparation of the catalyst. In addition, since the catalyst has an excellent shape and a narrow particle size distribution, it is possible to prepare ultra-high molecular weight polyethylene having an excellent powder shape, a narrow particle size distribution, and no particle agglomeration during polymerization of polyethylene under the catalyst.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

As used herein, the term “alkyl” refers to a monovalent straight-chain or branched saturated hydrocarbon radical composed only of carbon and hydrogen atoms, and examples of such alkyl radicals include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t- butyl, pentyl, hexyl, octyl, dodecyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and the like.

In addition, the term "halogen" described in the present invention means a fluorine, chlorine, bromine or iodine atom.

In addition, the term "C _n " described in the present invention means that the number of carbon atoms is n.

The present invention provides a method for preparing a catalyst having excellent catalytic activity and shape and high apparent density by adding a transition metal compound to a magnesium compound solution when preparing a catalyst for polyethylene polymerization, and adding an internal electron donor after temperature rise.

In one embodiment, the magnesium compound may be dissolved in alcohol to prepare a magnesium compound solution (step (A)). The magnesium compound is a compound having no reducing properties, and suitable for the present invention include, for example, magnesium halide, (C ₁ -C ₁₀ ) alkoxy magnesium, (C ₁ -C ₁₀ )alkyl magnesium halide, (C ₁ - C ₁₀ ) Alkoxy magnesium halide, or (C ₆ -C ₁₀ ) aryloxy magnesium halide, and the like.

More specifically, magnesium halides, such as magnesium fluoride, magnesium chloride, magnesium bromide, magnesium iodide; alkoxymagnesium such as ethoxymagnesium, isoproxymagnesium and butoxymagnesium; alkyl magnesium halides such as methyl magnesium halide, ethyl magnesium halide, isopropyl magnesium chloride, and butyl magnesium chloride; alkoxymagnesium halides such as methoxymagnesium chloride, ethoxymagnesium chloride, isoproxymagnesium chloride, butoxymagnesium chloride, and octoxymagnesium chloride; aryloxymagnesium halides such as phenoxymagnesium chloride; and the like. Any one of the magnesium compounds may be used alone, and two or more may be mixed and used.

Among them, the use of magnesium halide is more preferable because it can increase the activity of the catalyst, and the use of magnesium chloride is more structurally and coordinatingly stable and exhibits high activity in combination with the transition metal compound containing the main active metal. more preferably. The magnesium chloride is more preferably magnesium chloride hydrate, such as magnesium chloride monohydrate, magnesium chloride dihydrate, magnesium chloride trihydrate, magnesium chloride pentahydrate, magnesium chloride hexahydrate, and the like.

In addition, the magnesium halide compound may be used in combination of two or more kinds. The magnesium halide compound may form a complex or complex compound with an organometallic compound of another metal such as aluminum, zinc, boron, sodium or potassium, or may be a mixture of these metal compounds.

In one embodiment, the alcohol may be suitably used in the present invention as long as it is an alcohol known to be used in the preparation of a Ziegler-Natta catalyst for polyethylene polymerization. Examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, neopentanol, cyclopentanol, n-hexanol, cyclohexanol. , aliphatic or alicyclic alcohols such as methylcyclohexanol, n-heptanol, n-octanol, decanol, dodecanol, 2-methylpentanol, 2-ethylbutanol, and 2-ethylhexanol; Aromatic alcohols, such as (alpha)-methylbenzyl alcohol, are mentioned. Among them, it is preferable to use an aliphatic or alicyclic alcohol or an alcohol having 2 or more carbon atoms, and it is even more preferable to use 2-ethylhexanol.

In one embodiment, the alcohol serves to improve the catalyst performance by dissolving the magnesium compound and forming appropriate pores by forming a bond with the magnesium compound in the catalyst. In step (A), the molar ratio of the magnesium compound to the alcohol is preferably 1:3 to 1:4. When the molar ratio is less than 1:3, the solubility of the magnesium compound is lowered and the activity is low when alcohol is added. In addition, when the molar ratio exceeds 1:4, there is a disadvantage in that the supporting ratio of the transition metal compound is lowered and the catalyst particle size is increased.

The magnesium compound solution forming reaction may be performed at 60 to 150°C. When it is out of the above range, the magnesium compound may not dissolve well in alcohol, or side reactions may increase. Furthermore, it is more preferable to melt|dissolve at the temperature of 80-140 degreeC. Thereafter, when the dissolution of the magnesium compound is completed, the temperature of the solution is maintained at 0° C. or less.

In addition, in one embodiment, a hydrocarbon compound may be additionally added in order to easily disperse the magnesium compound. Specific examples of the hydrocarbon compound include aliphatic or alicyclic (C ₉ -C ₂₅ ) hydrocarbons, and among them, aliphatic or alicyclic (C ₉ -C ₁₇ ) hydrocarbon solvents are most preferred. More specific examples include aliphatic hydrocarbons such as decane, dodecane, tetradecane, (C ₅ -C ₂₅ ) mineral oil (eg, Cas No. 8042-47-5, etc.); alicyclic hydrocarbons such as cyclohexane, cyclooctane, methyl cyclopentane and methyl cyclohexane; Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene may be used. Among them, it is preferable to use a solvent having a boiling point of 150° C. or higher, and it is more preferable to use decane.

If too little or too much of the hydrocarbon compound is added, it may be difficult to control the particle size of the catalyst, and it may be difficult to control the loading rate of the transition metal compound and the internal electron donor. Accordingly, the molar ratio of the hydrocarbon compound to the magnesium compound is preferably 1:2 to 1:4. If the molar ratio of the hydrocarbon compound to the magnesium compound is less than 1:2, the magnesium compound is not dispersed well, and if it exceeds 1:4, it is difficult to control the catalyst particle size and the support ratio of the transition metal compound may be lowered.

Next, the transition metal compound may be added to the magnesium compound solution to form a catalyst solution (step (B)). The transition metal compound may include a compound containing a metal selected from the group consisting of transition metal elements of Groups 14, 15 and 16 of the Periodic Table, and may be, for example, a compound represented by Formula 1 below.

In Formula 1, 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, R ¹ is each independently a (C ₁ -C ₁₀ )alkyl group, and n is 0 to It is an integer of 4.

Preferred examples of the transition metal element include Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, and the like, and a transition metal compound containing at least one of them may be used. can

A more preferable transition metal compound includes a titanium compound, for example, titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, tetrabutoxytitanium, tetraethoxytitanium, diethoxytitanium dichloride, ethoxy Titanium trichloride, etc. are mentioned. These titanium compounds may be used alone, of course, two or more may be mixed and used. Among these, it is most preferable to use titanium tetrachloride.

The molar ratio of the magnesium compound and the transition metal compound may be 1:2 to 1:6, and when the molar ratio is less than 1:2, the activity may be lowered due to a low loading ratio of the transition metal compound, and when it exceeds 1:6 , the loading rate of the transition metal compound is increased more than necessary, thereby reducing the pores in the catalyst, thereby reducing the activity, and increasing the metal residue in the polymer, which can increase harmfulness to the human body and environmental pollution. In addition, the productivity may decrease because precipitation is not performed well in the hexane washing process after the catalyst is prepared.

Also, the transition metal compound may be added to the magnesium compound solution maintained at -20 to 5°C, preferably -15 to 0°C. That is, the transition metal compound is input at -20 to 0° C., and the catalyst particle size varies depending on the input temperature. When the transition metal compound is added in a temperature range exceeding 0° C., the catalyst particle size may be small and the catalyst particle size distribution may be widened. Furthermore, the apparent density may be lowered and the fine powder production rate may be increased due to the formation of a catalyst that is not robust. On the other hand, if the transition metal compound is added in a temperature range of less than -20°C, the catalyst particle size may be large and the catalyst particle size distribution may be narrowed.

In one embodiment of the present invention, the dropwise addition time of the transition metal compound is preferably 1 to 6 hours. If the dropwise addition time of the transition metal compound is less than 1 hour, there is a disadvantage in that the catalyst particle size distribution is widened due to an increase in temperature due to a vigorous reaction. On the other hand, when the input time exceeds 6 hours, the particle size of the catalyst increases and the particle size distribution of the catalyst is widened. Accordingly, the apparent density of the polymer produced after polymerization is reduced and the particle size distribution is widened, so there is a disadvantage in that productivity is lowered during product molding.

On the other hand, the dropwise addition of the transition metal compound is performed under stirring at a stirring speed of 50 to 1000 rpm depending on the total volume of the reacting compound. If the stirring speed is too slow, there is a risk that the catalyst particles generated after the combination of the magnesium compound and the transition metal compound are aggregated to increase the particle size. In addition, if the stirring speed is too fast, the catalyst particles are broken and the particle size distribution of the catalyst is formed widely, and catalyst particles having a particle diameter of less than 3 μm may be generated.

In one embodiment, the introduction of the transition metal compound is made slowly, because it is possible to prevent heat generation and catalyst aggregation. In addition, considering that the temperature rises after the transition metal compound is added, it may be maintained at the same temperature for a certain period of time, as a non-limiting example, for 30 to 90 minutes, and then the temperature may be gradually increased. Usually, it is appropriate to raise the temperature at 0.1 to 0.5°C/min. If the temperature rises suddenly and rapidly, the catalyst may be broken or agglomerated and the shape of the catalyst may change. After that, the temperature is gradually increased again to reach 70 to 90°C. At this time, only when the temperature is raised gradually, the catalyst can be prevented from breaking or agglomerated, and the rapid reaction according to the temperature rise can be controlled.

Meanwhile, in one embodiment, before adding the transition metal compound to the magnesium compound solution, (C ₅ -C ₈ ) a non-polar solvent may be added. Specific examples of the (C ₅ -C ₈ ) non-polar solvent include pentane, hexane, heptane, octane, and the like, and preferably hexane.

The (C ₅ -C ₈ ) non-polar solvent is added to adjust the catalyst particle size by controlling the crystallization rate during catalyst preparation. In general, the magnesium compound has a high melting point and is dissolved in alcohol at a high temperature, in which case the alcohol forms a covalent bond with the magnesium compound. In the recrystallization method, after the magnesium compound and the transition metal are bonded, the catalyst particles move to the transition metal where the alcohol bonded to the magnesium compound can form a stronger bond, and the magnesium compound is produced as a solid together with the bonded transition metal. . At this time, the (C ₅ -C ₈ ) non-polar solvent present in the magnesium compound controls the crystallization rate.

_{More specifically, when the amount of the (C 5} -C ₈ ) non-polar solvent present in the magnesium compound solution is small, the crystallization rate is slow to generate small catalyst particles, and on the contrary, when the _{amount of the (C 5} -C ₈ ) non-polar solvent is large Larger catalyst particles are produced by increasing the rate of crystallization. However, when the (C ₅ -C ₈ ) non-polar solvent is added in excess compared to the magnesium compound, the catalyst particle size increases excessively, and the activity and apparent density may be lowered. In this respect, the magnesium compound and the (C ₅ -C ₈ ) non-polar solvent The molar ratio is preferably 1:1 to 1:25. Catalyst particles used for polyethylene polymerization that can be applied to various products within the molar ratio range can be synthesized.

However, unlike the catalyst preparation method of one embodiment, after dissolving the magnesium compound in alcohol, when it _{is added to a mixed solution containing a transition metal compound and a non-polar solvent of (C 5} -C ₈ ), the alcohol bound to the magnesium compound is Large catalyst particles are generated because crystals are formed immediately by moving to the transition metal at a high speed. As such, when the catalyst particle generation proceeds rapidly (C ₅ -C ₈ ), it is difficult to control the crystallization rate by a non-polar solvent and the activity is low. In addition, in the case of ultra-high molecular weight polyethylene products manufactured under such a catalyst, powder agglomeration may occur and it may be difficult to apply to final products because the powder particle size distribution is wide.

In addition, in one embodiment, an internal electron donor may be additionally added to the magnesium compound solution. The internal electron donor is a factor influencing the particle size of the catalyst by stabilizing the active point of the transition metal compound by donating electrons to the transition metal compound. When the internal electron donor is added to the magnesium compound solution in step (B), the molar ratio of the magnesium compound and the internal electron donor may be added so that the molar ratio of the magnesium compound to the internal electron donor exceeds 1:0 and 1:0.3 or less. The activity of the catalyst may be lowered by becoming excessively large or by preventing the transition metal compound from being supported on the carrier.

Non-limiting examples of internal electron donors usable in step (B) include methyl 2-methylbenzoate, ethylbenzoate, propylbenzoate, isopropylbenzoate, butylbenzoate, pentylbenzoate, hexylbenzoate, ethyl 4- (dimethylamino)benzoate, ethyl 4-(butylamino)benzoate, ethyl 4-(benzyloxy)benzoate, ethyl 4-bromobenzoate, etc., among which two or more compounds may be mixed and used. and, preferably, ethyl benzoate may be used.

Next, the magnesium compound solution and the catalyst solution containing the transition metal compound is heated to 70 to 90 ℃ (step (C)). If the temperature after the temperature rise does not reach 70 ° C, the catalyst is structurally not stabilized and the catalyst performance may deteriorate. On the other hand, if the temperature after the temperature rise exceeds 90 ° C, an unstable catalyst is formed. This is undesirable as low density polyethylene can be produced.

After raising the temperature of the catalyst solution, an internal electron donor is added (step (D)). In step (D), the same internal electron donor mentioned as usable in step (B) may be used.

In step (D), the internal electron donor may be added immediately within 30 minutes after the temperature is raised, or may be added after 1 to 3 hours have elapsed while the temperature is elevated. In addition, the internal electron donor in the catalyst can be stably bound and reacted with the carrier by maintaining the temperature for 2 to 3 hours after the internal electron donor is added. In this way, by introducing an internal electron donor and stably bonding to the carrier, polyethylene having a high molecular weight can be produced.

Meanwhile, in an embodiment, the molar ratio of the internal electron donor to the magnesium compound may be 1:0.1 to 1:0.6. When the molar ratio is less than 1:0.1, it is difficult to manufacture ultra-high molecular weight polyethylene because the amount of the internal electron donor input is too small. On the other hand, even if the molar ratio exceeds 1:0.6, since the internal electron donor is no longer involved in the improvement of catalyst performance, it is preferable from an economical point of view to input the internal electron donor so that the molar ratio is 1:0.6 or less.

In addition, in one embodiment, the step ((E) step) of adding an alkylaluminum compound represented by the following Chemical Formula 2 to the obtained product of step (D) may be further included.

In Formula 2, R ² is each independently a (C ₁ -C ₈ )alkyl group, X is a halogen, and m is an integer of 0 to 3.

The alkylaluminum compound may serve as a cocatalyst to reduce the transition metal compound to form an active site to increase catalytic activity. In particular, when the transition metal compound and the magnesium compound are first reacted and the alkylaluminum compound is reacted, the active sites can be more evenly distributed in the catalyst, so that the ultrahigh molecular weight polyethylene having a high molecular weight and exhibiting higher catalytic activity can be prepared. .

Examples of such alkylaluminum compounds include trimethylaluminum, triethylaluminum, triisopropylaluminum, trioctylaluminum, dimethylaluminum chloride, diethylaluminum fluoride, diethylaluminum chloride, diethylaluminum bromide, and diethylaluminum iodide. , methyl aluminum dichloride, ethyl aluminum dichloride, and the like can be used.

The catalyst for polyethylene polymerization prepared according to the above method may have a transition metal element content of 2 to 7% by weight relative to the total weight of the catalyst, an internal electron donor content of 10 to 30% by weight, and an alcohol content of 1 to 10% by weight. have. In addition, the average particle diameter of the catalyst may be 3 to 18㎛, and the catalyst particle size distribution index may be 0.2 to 1.0 in terms of SPAN value. The SPAN value is a numerical value indicating the degree of particle size distribution of the powder, and a smaller value means that the powder has a more uniform and narrow particle size distribution.

According to another embodiment of the present invention, ultra-high molecular weight polyethylene having ^{a weight average molecular weight of 1.5x10 6} to 8x10 ^{6 g/mol can be prepared by polymerizing an ethylene monomer under the catalyst.} Polyethylene polymerization may be carried out in a gas phase, liquid phase, or slurry phase, and when the synthesis reaction is performed in a liquid phase, a hydrocarbon solvent may be used, and ethylene itself may be used as a solvent.

On the other hand, when using a conventional catalyst, the polymerization reaction was generally carried out at 60 to 80 °C, and the ethylene polymerization reaction could not be carried out at a temperature lower than 60 °C. However, using the catalyst prepared according to the above embodiment, it is possible to manufacture ultra-high molecular weight polyethylene by carrying out the ethylene polymerization reaction at 50 to 90 ℃. If the polymerization temperature is too high, the ethylene polymer chain may be easily broken in the process of growth. On the other hand, the lower the polymerization temperature, the lower the catalytic activity, but the ethylene polymerization proceeds slowly, which is more advantageous for the production of ultra-high molecular weight polyethylene.

In addition, the polymerization reaction may be carried out at 1 to 20 atmospheres, preferably at 3 to 10 atmospheres. When the pressure exceeds 20 atm, it is not preferable from an industrial and economic point of view. In addition, the polymerization reaction may be carried out for 1 to 5 hours and may be carried out in any one of batch, semi-continuous, and continuous methods.

In addition, during the polymerization reaction, hydrogen may be added in an amount of 0 to 2 molar equivalents compared to the ethylene monomer, and when hydrogen is added excessively, hydrogen binds to the terminal of the prepared polymer, and thus the molecular weight of polyethylene tends to be lowered. On the other hand, when the amount of hydrogen input is 0, the ethylene polymerization reaction continuously proceeds, which is advantageous for the production of ultra-high molecular weight polyethylene.

On the other hand, in general, during polymerization of polyethylene, a larger amount of fine powder is generated as the particle diameter of the polyethylene to be produced is small. However, when the catalyst is prepared according to the present invention, the amount of fine powder can be controlled by adjusting the particle size distribution of the catalyst to suit the characteristics of the product to which the ultra-high molecular weight polyethylene is applied, and the fine powder content of polyethylene having an average powder particle size of 100 μm or more is 0.1 to 10% by weight.

In an embodiment, an additional external electron donor may not be used in manufacturing the polyethylene. In the case of a recrystallization catalyst, when solid particles are formed, most of them are bonded to an electron donor, so that the electron donor input after particle formation does not form a structurally stable bond may not be helpful during polymerization.

Example

Hereinafter, embodiments of the present invention will be described in detail. The following examples are only for the understanding of the present invention, but do not limit the present invention.

[Catalyst Preparation Example 1]

In a 0.5 L size pressure resistant glass reactor equipped with a stirrer and an oil circulation heater, 3.0 g of magnesium chloride, 16 ml of 2-ethylhexanol and 15 ml of decane were added under a nitrogen atmosphere, and the mixture was stirred at 80° C. at 300 rpm. The temperature was raised to 135° C. to completely dissolve the magnesium chloride, and the reaction was maintained for 1 hour when a homogeneous solution was obtained. Thereafter, the temperature was lowered to room temperature, 12.6 ml of hexane was added, and the temperature was lowered again. When the temperature was maintained at 0 ~ -10 °C, _{16 ml of titanium tetrachloride (TiCl 4} ) was slowly added while stirring at 600 rpm. When the input was completed, the temperature was raised to 73° C., 0.2 equivalent of ethyl benzoate was added, and the mixture was stirred while maintaining the temperature at the same temperature for 2 hours. Then, the stirring was stopped by lowering to 45° C., and the resulting solid particles were precipitated. Thereafter, the supernatant was removed, washed 5 times with 2 L of hexane and dried to obtain a catalyst.

[Catalyst Preparation Example 2]

A catalyst was prepared in the same manner as in Catalyst Preparation Example 1, except that 0.3 equivalents of ethylbenzoate was added instead of 0.2 equivalents of ethyl benzoate in Catalyst Preparation Example 1.

[Catalyst Preparation Example 3]

A catalyst was prepared in the same manner as in Catalyst Preparation Example 1, except that 0.1 equivalent of ethyl benzoate was added instead of 0.2 equivalent of ethyl benzoate in Catalyst Preparation Example 1.

[Catalyst Preparation Example 4]

A catalyst was prepared in the same manner as in Catalyst Preparation Example 1, except that 0.4 equivalents of ethyl benzoate was added instead of 0.2 equivalents of ethyl benzoate in Catalyst Preparation Example 1.

[Catalyst Preparation Example 5]

In a 0.5 L size pressure resistant glass reactor equipped with a stirrer and an oil circulation heater, 3.0 g of magnesium chloride, 16 ml of 2-ethylhexanol, and 15 ml of decane were added under a nitrogen atmosphere, and the mixture was stirred at 80° C. at 300 rpm. The temperature was raised to 135° C. to completely dissolve the magnesium chloride, and the reaction was maintained for 1 hour when a homogeneous solution was obtained. After lowering to room temperature, 0.03 equivalents of ethyl benzoate was added and stirred for 1 hour, then 12.6 ml of hexane was added and the temperature was lowered after stirring for 30 minutes. When the temperature was maintained at 0 ~ -10 °C, 16 ml of titanium tetrachloride was slowly added while stirring at 600 rpm. When the input was completed, the temperature was raised to 73° C., 0.2 equivalent of ethyl benzoate was added, and the mixture was stirred while maintaining the temperature at the same temperature for 2 hours. Then, the stirring was stopped by lowering to 45° C., and the resulting solid particles were precipitated. Thereafter, the supernatant was removed, washed 5 times with 2 L of hexane and dried to obtain a catalyst.

[Catalyst Preparation Example 6]

A catalyst was prepared in the same manner as in Catalyst Preparation Example 5, except that 0.1 equivalent of ethyl benzoate was added instead of 0.2 equivalent of ethyl benzoate in Catalyst Preparation Example 5.

[Catalyst Preparation Example 7]

A catalyst was prepared in the same manner as in Catalyst Preparation Example 5, except that 0.3 equivalents of ethyl benzoate was added instead of 0.2 equivalents of ethyl benzoate in Catalyst Preparation Example 5.

[Catalyst Preparation Example 8]

A catalyst was prepared in the same manner as in Catalyst Preparation Example 5, except that 0.4 equivalents of ethylbenzoate was added instead of 0.2 equivalents of ethyl benzoate in Catalyst Preparation Example 5.

[Catalyst Preparation Example 9]

A catalyst was prepared in the same manner as in Catalyst Preparation Example 5, except that ethyl benzoate was not added in Catalyst Preparation Example 5.

[Catalyst Preparation Example 10]

In a 0.5 L size pressure resistant glass reactor equipped with a stirrer and an oil circulation heater, 3.0 g of magnesium chloride, 16 ml of 2-ethylhexanol, and 15 ml of decane were added under a nitrogen atmosphere, and the mixture was stirred at 80° C. at 300 rpm. The temperature was raised to 130° C. to completely dissolve the magnesium chloride, and when it became a homogeneous solution, the reaction was maintained for 1 hour, 0.03 equivalent of ethyl benzoate was added, and then maintained at the same temperature for 1 hour, and lowered to room temperature.

Next, a mixed solution was prepared by mixing 30 ml of hexane and 16 ml of titanium tetrachloride in a separate reactor.

Thereafter, in a reactor maintained at -10 °C, a solution containing magnesium chloride and ethyl benzoate was slowly added using a glass syringe to a mixed solution in which hexane and tetrachloride were mixed while stirring at a speed of 600 rpm. When the input was completed, the temperature was raised to 73° C. and the mixture was stirred while maintaining it at the same temperature for 2 hours. After that, the temperature was lowered to 45° C. to stop stirring, and the resulting solid particles were precipitated. Thereafter, the supernatant was removed, washed 5 times with 2 L of hexane and dried to prepare a catalyst.

[Catalyst Preparation Example 11]

A catalyst was prepared in the same manner as in Catalyst Preparation Example 10, except that 0.1 equivalent of ethyl benzoate was added instead of 0.03 equivalent of ethyl benzoate in Catalyst Preparation Example 10.

[Catalyst Preparation Example 12]

A catalyst was prepared in the same manner as in Catalyst Preparation Example 10, except that 0.6 equivalents of diisobutylphthalate (DIBP) was added instead of 0.03 equivalents of ethyl benzoate in Catalyst Preparation Example 10.

[Catalyst Preparation Example 13]

A catalyst was prepared in the same manner as in Catalyst Preparation Example 1, except that 0.2 equivalent of ethyl benzoate was added without raising the temperature after adding titanium tetrachloride in Catalyst Preparation Example 1.

[Example 1]

A 2 L stainless steel autoclave dried at 120° C. for 2 hours was purged with nitrogen to make the inside of the reactor a nitrogen atmosphere. While maintaining a nitrogen atmosphere, the temperature inside the reactor was lowered to 25 °C, and 1 L of purified hexane was injected. 2.0 mmol of triethylaluminum diluted in hexane was added, and 1 ml of a diluted solution obtained by diluting 1 g of the catalyst prepared in Catalyst Preparation Example 1 in 100 ml of decane was added. After the input, the temperature of the reactor was raised to 80° C. while stirring at 250 to 300 rpm, and ethylene was supplied so that the pressure in the reactor became 8 bar to carry out the polymerization reaction while maintaining the pressure. Polymerization was continued for 2 hours, and ethylene was supplied to keep the pressure constant. After completion of the reaction, the solvent was removed by filtration under reduced pressure, and the residual hexane solvent was dried in a vacuum oven at 80° C. for 2 hours to prepare polyethylene.

[Example 2]

Polyethylene was prepared in the same manner as in Example 1, except that the catalyst prepared in Catalyst Preparation Example 2 was used.

[Example 3]

Polyethylene was prepared in the same manner as in Example 1, except that the catalyst prepared in Catalyst Preparation Example 3 was used.

[Example 4]

Polyethylene was prepared in the same manner as in Example 1, except that the catalyst prepared in Catalyst Preparation Example 4 was used.

[Example 5]

Polyethylene was prepared in the same manner as in Example 1, except that the polymerization reaction was carried out at 90° C. using the catalyst prepared in Catalyst Preparation Example 1.

[Example 6]

Polyethylene was prepared in the same manner as in Example 1, except that the polymerization reaction was carried out at 50° C. using the catalyst prepared in Catalyst Preparation Example 1.

[Examples 7 to 10]

Polyethylene was prepared in the same manner as in Example 1, except that each of the catalysts prepared in Catalyst Preparation Examples 5 to 8 was used.

[Examples 11 and 12]

Polyethylene was prepared in the same manner as in Example 1, except that the polymerization reaction was carried out at 70° C. using the catalysts prepared in Catalyst Preparation Examples 5 and 6, respectively.

[Example 13]

Polyethylene was prepared in the same manner as in Example 1, except that the polymerization reaction was carried out at 60° C. using the catalyst prepared in Catalyst Preparation Example 6.

[Comparative Examples 1 to 5]

Polyethylene was prepared in the same manner as in Example 1, except that each of the catalysts prepared in Catalyst Preparation Examples 9 to 13 was used.

Internal electron donor input amount (equivalent) elevated temperature
(℃) polymerization temperature
(℃) Kinds Before adding TiCl ₄ After adding TiCl ₄ Example 1 EB 0 0.2 73 80 Example 2 EB 0 0.3 73 80 Example 3 EB 0 0.1 73 80 Example 4 EB 0 0.4 73 80 Example 5 EB 0 0.2 73 90 Example 6 EB 0 0.2 73 50 Example 7 EB 0.03 0.2 73 80 Example 8 EB 0.03 0.1 73 80 Example 9 EB 0.03 0.3 73 80 Example 10 EB 0.03 0.4 73 80 Example 11 EB 0.03 0.2 73 70 Example 12 EB 0.03 0.4 73 70 Example 13 EB 0.03 0.4 73 60 Comparative Example 1 EB 0.03 0 73 80 Comparative Example 2 EB 0.03 0 73 80 Comparative Example 3 EB 0.1 0 73 80 Comparative Example 4 DIBP 0.6 0 73 80 Comparative Example 5 EB 0 0.2 73 80

[Evaluation of physical properties]

Catalytic activity was measured for the catalysts prepared in each of the catalyst preparation examples as follows, and the results are shown in Table 2. In addition, apparent density, weight average molecular weight, powder average particle size, and particle size distribution were measured for polyethylene prepared according to Examples and Comparative Examples as follows, and the measurement results are shown in Tables 2 and 3 below.

1. Catalytic Activity

After measuring the weight (kg) of the polymer prepared for 1 hour per weight (g) of the catalyst used, the catalyst activity was calculated according to the following formula (1).

Catalytic activity = Polyethylene production (kg/hr) / Amount of catalyst used (g) … (One)

2. Bulk Density (BD)

After the polyethylene prepared in a container having a volume of 100 cm 3 known in weight according to ASTM D189 was filled with free fall due to gravity, the net weight was measured and the apparent density was measured according to Equation (2) below.

Apparent Density (g/cm 3 ) = Polymer Net Weight (g)/100 cm 3 … (2)

3. Weight average molecular weight (M _W )

Polymer Laboratories Ltd (UK)'s PL GPC-220 and a GPC system consisting of a Differential Viscometer (M210R) through the GPC system was applied to the measurement results at 160 ℃.

4. Polyethylene Powder Average Particle Size (APS) and Particle Size Distribution

Using Seishin's RPS-105M, which is a powder particle size analysis equipment, 10 g of the polyethylene sample prepared in each Example and Comparative Example was dropped on a sieve consisting of 5, 10, 30, 45, 75, and 125 μm, followed by vibration and vibration for 5 minutes. After evenly dispersing by hammering, the weight of the sample remaining on each sieve was measured to calculate the average value.

activation
(kg-PE/g-Cat) Apparent density
(g/ml) weight average molecular weight
(g/mol) Example 1 39 0.34 2,910,000 Example 2 37 0.36 2,100,000 Example 3 38 0.35 2,800,000 Example 4 40 0.35 2,400,000 Example 5 55 0.36 1,800,000 Example 6 25 0.37 5,500,000 Example 7 49 0.34 1,920,000 Example 8 52 0.36 2,180,000 Example 9 50 0.33 2,140,000 Example 10 47 0.37 2,500,000 Example 11 44 0.33 2,760,000 Example 12 53 0.35 3,220,000 Example 13 50 0.37 3,100,000 Comparative Example 1 31 0.32 1,220,000 Comparative Example 2 34 0.33 1,320,000 Comparative Example 3 32 0.32 1,220,000 Comparative Example 4 18 0.36 1,314,000 Comparative Example 5 22 0.31 1,120,000

powder
Average particle diameter (㎛) Powder particle size distribution (㎛) >850 >500 >300 >212 >125 >75 <75 Example 1 177 0 0 5.1 71.1 19.0 3.0 1.8 Example 2 160 0 0 5.0 68.5 19.7 5.8 1.0 Example 3 170 0 0 4.8 70.0 16.2 7.8 1.2 Example 4 176 0 0 3.3 68.5 22.6 4.3 1.3 Example 5 180 0 0 4.5 65.8 10.8 8.0 0.9 Example 6 164 0 0 5.2 62.8 22.5 7.8 1.7 Example 7 181 0 0 4.1 70.9 20.4 3.5 1.1 Example 8 188 0 0 4.9 72.0 19.6 2.9 0.6 Example 9 186 0 0 3.4 69.7 25.0 1.7 0.2 Example 10 178 0 0 2.6 70.4 20.0 5.7 1.3 Example 11 190 0 0 9.0 63.9 20.7 6.0 0.4 Example 12 191 0 0 8.8 63.5 23.0 4.5 0.2 Example 13 190 0 0 5.6 59.7 28.9 5.1 0.7 Comparative Example 1 200 2.9 7.8 14.0 33.5 15.4 13.5 12.9 Comparative Example 2 235 4.7 8.3 15.1 25.6 19.6 17.0 9.7 Comparative Example 3 289 5.9 13.5 13.8 23.1 19.2 13.9 10.6 Comparative Example 4 233 18.7 12.3 12.1 22.6 18.6 10.0 5.7 Comparative Example 5 213 6.8 8.8 12.7 20.6 27.8 11.0 12.3

As in Examples 1 to 13, when a catalyst prepared by sequentially adding hexane and titanium tetrachloride to a solution containing magnesium chloride to react, and adding an internal electron donor after temperature increase is used, polyethylene with high molecular weight and narrow particle size distribution was manufactured.

However, as in Comparative Examples 1 to 5, when a catalyst not according to the preparation method of the present invention was used, ^{polyethylene having a weight average molecular weight of less than 1.5x10 6} g/mol was prepared and exhibited a wide particle size distribution.

In particular, when the catalyst was prepared using diisobutyl phthalate instead of ethyl benzoate as an internal electron donor (Comparative Example 4), it was visually confirmed that powder agglomeration occurred.

Claims (14)

(A) dissolving the magnesium compound in a solvent containing alcohol to form a magnesium compound solution;
(B) forming a catalyst solution by adding a transition metal compound to the magnesium compound solution;
(C) raising the temperature of the catalyst solution; and
(D) adding an internal electron donor to the catalyst solution after raising the temperature
A method for preparing a catalyst for polymerization of polyethylene comprising a.
According to claim 1,
In step (A), the solvent is an alcohol and (C ₉ -C ₂₅ ) Method for producing a catalyst for polymerization of polyethylene, characterized in that it comprises a hydrocarbon.
3. The method of claim 2,
A method for preparing a catalyst for polyethylene polymerization, characterized in that the molar ratio of the magnesium compound and the (C ₉ -C _{25 ) hydrocarbon is 1:2 to 1:4.}
According to claim 1,
(B) Before the transition metal compound is added in step (C ₅ ~ C ₈ ) Method for preparing a catalyst for polymerization of polyethylene, characterized in that the non-polar solvent is added.
5. The method of claim 4,
A method for preparing a catalyst for polyethylene polymerization, characterized in that the molar ratio of the magnesium compound to the (C ₅ -C _{8 ) non-polar solvent is 1:1 to 1:25.}
According to claim 1,
(C) Method for producing a catalyst for polyethylene polymerization, characterized in that the temperature of the catalyst solution is raised to 70 to 90 ℃ in step.
According to claim 1,
A method for preparing a catalyst for polymerization of polyethylene, characterized in that the molar ratio of the magnesium compound and the internal electron donor is 1:0.1 to 1:0.6.
According to claim 1,
The inner electron donors are methyl 2-methylbenzoate, ethylbenzoate, propylbenzoate, isopropylbenzoate, butylbenzoate, pentylbenzoate, hexylbenzoate, ethyl 4-(dimethylamino)benzoate, ethyl 4- (Butylamino)benzoate, ethyl 4-(benzyloxy)benzoate, ethyl 4-bromobenzoate A method for producing a catalyst for polymerization of polyethylene, characterized in that at least one compound selected from the group consisting of.
According to claim 1,
(B) comprising additionally adding an internal electron donor in step,
A method for producing a catalyst for polyethylene polymerization, characterized in that the molar ratio of the magnesium compound and the additionally added internal electron donor is greater than 1:0 and less than or equal to 1:1.
According to claim 1,
The transition metal compound is a method for preparing a catalyst for polyethylene polymerization, characterized in that it is a compound represented by the following formula (1):
[Formula 1]

(In Formula 1,
M is selected from the group consisting of transition metal elements of groups IVB, VB and VIB of the periodic table,
X is halogen,
R ¹ are each independently a (C ₁ ~C ₁₀ )alkyl group,
n is an integer from 0 to 4).
According to claim 1,
(E) Method for preparing a catalyst for polyethylene polymerization, characterized in that it further comprises the step of adding an alkylaluminum compound represented by the following formula (2) to the product obtained in step (D):

[Formula 2]

(In Formula 2,
R ² are each independently a (C ₁ -C ₈ )alkyl group,
X is halogen,
m is an integer from 0 to 3).
Claims 1 to 11, comprising the step of polymerizing an ethylene monomer under a catalyst for polyethylene polymerization prepared according to any one of claims 1 to 11,
The polymerization reaction is a polyethylene production method, characterized in that carried out at 50 to 90 ℃.
13. The method of claim 12,
Further comprising the step of adding hydrogen,
The method for producing polyethylene, characterized in that the input amount of the hydrogen is 0 to 2 molar equivalents compared to the ethylene monomer.
A polyethylene prepared under the catalyst for polyethylene polymerization prepared according to any one of claims 1 to 11, and having a weight average molecular weight of 1.5x10 ⁶ to 8x10 ⁶ g/mol.