JPH0751605B2 - Method for producing ethylene-based polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an improvement in a method for producing an ethylene polymer. More specifically, the present invention is excellent in polymerization activity, easy to prepare and low in cost as compared with the conventional solid catalyst component used in the production of ethylene-based polymer, and also to produce ethylene-based polymer. It is possible to prepare a wide range of molecular weight distribution of the coalescence, and to give an ethylene polymer with good powder properties such as bulk density and powder particle size distribution. The present invention relates to a method for efficiently producing an ethylene homopolymer or copolymer suitable for molded articles and films.

[Prior Art] Conventionally, as a method for producing an ethylene-based polymer for hollow molded articles and films, for example, a solid catalyst component obtained by reacting an organomagnesium compound, a titanium compound, a zirconium compound and an aluminum halide compound, It is known to polymerize ethylene or a mixture of ethylene and other α-olefins using a catalyst system consisting of a combination with an organometallic compound. For example, a combination of an organic aluminum compound and a solid catalyst component obtained by reacting (i) a magnesium compound, (ii) a titanium compound, (iii) a zirconium compound, and (iv) an organohalogenated aluminum compound at a specific ratio. To produce a polyolefin with a wide molecular weight distribution by using a catalyst system consisting of (Japanese Patent Publication No. 55-8083), and a polymer with a wide molecular weight distribution using the same type of catalyst system. A method (Japanese Patent Publication No. 52-39714 and Japanese Patent Publication No. 62-48682) is disclosed. However, although a polymer having a wide molecular weight to some extent can be obtained by these methods, the polymerization activity of the catalyst used is not always satisfactory.

Also, a method for producing a polyolefin using a catalyst system comprising a combination of a solid catalyst component prepared by using the same components as those described in JP-B-55-8083 in different proportions and an organometallic compound is also available. Proposed (JP-A-59-
4607 publication). However, this method has a drawback that the obtained polyolefin has a narrow molecular weight distribution and is not suitable for hollow moldings and films.

Furthermore, in the prior art, when the solid catalyst component is prepared, the magnesium compound is dissolved in a solvent, or the magnesium compound is substantially in a dissolved state due to a reaction with other components. In many cases, a step of precipitating the catalyst component is required. In this case, the equipment is complicated and the equipment cost is unavoidably increased, and it is technically difficult to uniformly deposit the solid catalyst component. Problem arises.

[Problems to be Solved by the Invention] The present invention overcomes the drawbacks of the solid catalyst component used in the production of such a conventional ethylene-based polymer, and as the solid catalyst component, has a high polymerization activity. It is excellent, easy to prepare, low in cost, and capable of adjusting the molecular weight distribution of the polymer to be produced over a wide range, and gives an ethylene polymer with good powder properties such as bulk density and powder particle size distribution. A method of efficiently producing an ethylene-based polymer suitable for use in hollow moldings and films by polymerizing ethylene alone or a mixture of ethylene and another α-olefin using a polymer having excellent properties. It is made for the purpose of providing.

[Means for Solving the Problems] As a result of intensive studies conducted by the present inventors to develop a solid catalyst component having the above-mentioned excellent properties, magnesium dialkoxide having a specific particle diameter, a zirconium compound, A solid catalyst component obtained by reacting a titanium compound and an organoaluminum halide compound in a specific ratio under a condition in which the magnesium dialkoxide is not substantially dissolved may be suitable for the purpose. They have found the present invention and have completed the present invention based on this finding.

That is, in the present invention, the average particle size represented by (A) (a) general formula Mg (OR ¹ ) ₂ ... (I) (R ¹ in the formula is an alkyl group having 1 to 3 carbon atoms) is 50 μm or less magnesium dialkoxide, (b) general formula Zr (OR ² ) _n X ² _4-n (II) (wherein R ² is a hydrocarbon group, X ² is a halogen atom, and n is 0 to 0).
Zirconium compounds represented by 4 is a number of), (c) general formula _{^{Ti (OR 3) m X 3}} 4-m ... (III) (R 3 in the formula is a hydrocarbon group, X ³ is a halogen atom, m is 0
A titanium compound represented by the formula ( ⁴ ) and (d) the general formula AlR ⁴ _k X ⁴ _3-k (IV) (wherein R ⁴ is a hydrocarbon group, X ⁴ is a halogen atom, and k is 1). ~
Which is a number of 2), each of the organic aluminum halide compounds represented by as well as (In the formula, [Mg], [Zr], [Ti] and [X] are magnesium, zirconium and gram equivalent, respectively,
(Amount of titanium and halogen atoms), and a combination of a solid catalyst component (B) obtained by reacting them under conditions in which the component (a) does not substantially dissolve, and (B) an organoaluminum compound. The present invention provides a method for producing an ethylene-based polymer, which comprises polymerizing ethylene alone or a mixture of ethylene and another α-olefin in the presence of a catalyst system comprising

Hereinafter, the present invention will be described in detail.

In the method for producing an ethylene-based polymer of the present invention, a catalyst system comprising a combination of (A) a solid catalyst component and (B) an organoaluminum compound is used as a highly active catalyst.

As the magnesium dialkoxide used as the component (a) in the preparation of the solid catalyst component (A),
A compound represented by the general formula Mg (OR ¹ ) ₂ (I) (wherein R ¹ has the same meaning as described above) and having an average particle size of 50 μm or less is used.

R ¹ in the general formula (I) must be an alkyl group having 1 to 3 carbon atoms, that is, a methyl group, an ethyl group, an n-propyl group or an isopropyl group, and in the case of an alkyl group having 4 or more carbon atoms. However, the magnesium dialkoxide is in the form of gel or liquid, and the object of the present invention cannot be achieved. Specific examples of the magnesium dialkoxide include:
Examples thereof include magnesium dimethoxide, magnesium diethoxide, magnesium di-n-propoxide, and magnesium diisopropoxide, and these may be used alone or in combination of two or more.

In the present invention, the component (a) magnesium dialkoxide has an average particle size of 50 μm or less, preferably 7 μm or less.
It is necessary to be in the range of up to 20 μm. If the average particle diameter exceeds 50 μm, the surface area becomes small and the polymerization activity is reduced. By controlling the particle diameter of the magnesium dialkoxide, an ethylene polymer powder having a desired particle diameter can be obtained.

In the preparation of the solid catalyst component (A), the zirconium compound used as the component (b) is a compound represented by the general formula Zr (OR ² ) _n X ² _4-n (II) (wherein R ² , X ² and and n has the same meaning as described above). R ² in the general formula (II)
Is a hydrocarbon group, which may be a saturated group or an unsaturated group, may be a linear or branched one, or a cyclic group, and further may be sulfur, nitrogen, Although it may have a hetero atom such as oxygen, silicon, or phosphorus, a preferable hydrocarbon group has 1 to 1 carbon atoms.
There may be mentioned 20 alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl and aralkyl groups. Specific examples of R ² are methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, isobutyl group, pentyl group, hexyl group, heptyl group, octyl group, decyl group, Examples include octadecyl group, allyl group, butenyl group, cyclopentyl group, cyclohexyl group, cyclohexenyl group, phenyl group, tolyl group, benzyl group, phenethyl group and the like.

Further, X ² in the general formula (II) is a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, among which a chlorine atom and a bromine atom are preferable, and a chlorine atom is particularly preferable. .

Typical examples of the zirconium compound represented by the general formula (II) include zirconium tetrachloride when n is 0, and monoethoxytrichlorozirconium and mono-n-when n is 1. Propoxytrichlorozirconium, mono-n-butoxytrichlorozirconium, di-n-propoxydichlorozirconium, etc.
When n is 2, diethoxydichlorozirconium, di-n-propoxydichlorozirconium, di-n-butoxydichlorozirconium, and the like, and when n is 3, triethoxymonochlorozirconium, tri-n-propoxymonochlorozirconium, Examples of tri-n-butoxymonochlorozirconium include tetraethoxyzirconium, tetra-n-propoxyzirconium, and tetra-n-butoxyzirconium when n is 4. These zirconium compounds may be used alone or in combination of two or more.

In the preparation of the (A) a solid catalyst component, (C) As the titanium compound used as the component of the general formula _{^{Ti (OR 3) m X 3}} 4-m ... (III) (R 3 in the formula, X ³ and and m has the same meaning as above). R in the general formula (III)
³ is a hydrocarbon group, which may be a saturated group or an unsaturated group, may be a linear group, a branched group, or a cyclic group, and further may be sulfur or nitrogen. , A group having a hetero atom such as oxygen, silicon, or phosphorus may be used, but a preferred hydrocarbon group has 1 to 1 carbon atoms.
There may be mentioned 20 alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl and aralkyl groups. Specific examples of R ³ are the same as those exemplified for R ² in the general formula (II). Further, X ³ in the general formula (III) is a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Among these, a chlorine atom and a bromine atom are preferable, and a chlorine atom is particularly preferable.

Typical examples of the titanium compound represented by the general formula (III) include titanium tetrachloride when m is 0,
Titanium tetrabromide and the like, when m is 1, ethoxytrichlorotitanium, n-propoxytrichlorotitanium, n-butoxytrichlorotitanium and the like, and when m is 2, diethoxydichlorotitanium and di-n-propoxydichloro. Titanium, di-n-butoxydichlorotitanium, etc., when m is 3, triethoxy monochlorotitanium, tri-n-
Examples include propoxy monochlorotitanium and tri-n-butoxy monochlorotitanium, and when m is 4, tetraethoxy titanium, tetra-n-propoxy titanium, tetraisopropoxy titanium, tetra-n-butoxy titanium and the like. These titanium compounds may be used alone or in combination of two or more.

In the preparation of the solid catalyst component (A), the organoaluminum halide compound used as the component (d) has a general formula of AlR ⁴ _k X ⁴ _3-k (IV) (wherein R ⁴ , X ⁴ and k has the same meaning as described above) is used. R ⁴ in the general formula (IV)
Is a hydrocarbon group, which may be a saturated group or an unsaturated group, may be a linear or branched one, or a cyclic group, and further may be sulfur, nitrogen, Although it may have a hetero atom such as oxygen, silicon, or phosphorus, a preferable hydrocarbon group has 1 to 1 carbon atoms.
There may be mentioned 20 alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl and aralkyl groups. Specific examples of R ⁴ are the same as those exemplified for R ² in the general formula (II). Further, X ⁴ in the general formula (IV) is a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Among these, a chlorine atom and a bromine atom are preferable, and a chlorine atom is particularly preferable.

Typical examples of the organic aluminum halide compound represented by the general formula (IV) include, for example, when k is 1, methylaluminum dichloride, ethylaluminum dichloride, n-propylaluminum dichloride, isopropylaluminum dichloride, n. -Butyl aluminum dichloride, isobutyl aluminum dichloride and the like, and when n is 2, dimethyl aluminum monochloride, diethyl aluminum monochloride, di-n-
Propyl aluminum monochloride, diisopropyl aluminum monochloride, di-n-butyl aluminum monochloride, di-isobutyl aluminum monochloride and the like can be mentioned. These organic aluminum halide compounds may be used alone or in combination of two or more.

The (A) solid catalyst component in the present invention is the above-mentioned (a),
Each of the components (b), (c) and (d) is expressed by a relational expression. as well as (In the formula, [Mg], [Zr], [Ti] and [X] are magnesium, zirconium and gram equivalent, respectively,
It can be prepared by using them in such a proportion that the amount of titanium and halogen atoms is satisfied, and reacting them under the condition that the component (a) is not substantially dissolved.

If the value of is less than 0.05, the polymerization activity per unit weight of the catalyst tends to decrease, and the amount of halogen remaining in the polymer increases, which may lead to undesirable situations such as coloring and foaming. , 0.75, the polymerization activity per weight of the transition metal decreases, and the amount of the transition metal remaining in the polymer increases, which may cause problems such as coloring. Preferably, The value of is preferably in the range of 0.2 to 0.6. Also,
The condition of the relational expression (V) is also a condition in which the magnesium dialkoxide of the component (a) is substantially insoluble.

further, If the value of is greater than 3, there are too many components (b),
The component (c) may be too small and the polymerization activity per weight of the transition metal may decrease, and the amount of halogen used may increase, resulting in equipment corrosion due to unnecessary halogen and catalyst cost. May cause a rise.

In addition, the relational expression 0.2 <[Z
r] / [Ti] <20, preferably 0.5 ≦ [Zr] / [Ti] ≦ 10
It is desirable to use it in a ratio that satisfies the above. This [Z
When the value of r] / [Ti] is 0.2 or less, the molecular weight distribution of the obtained polymer may be too narrow, and when it is 20 or more, the polymerization activity tends to be low. Further, regarding the use ratio of the component (a) and the component (d),
(D) component molar ratio in the range of more than 0.1 and less than 100,
It is desirable to use both components so that they are preferably in the range of 1-40.

In the preparation of the solid catalyst component (A), the above (a),
The order of contacting the components (b), (c) and (d) is not particularly limited, but for example, a method of sequentially contacting the components (a), (b), (c) and (d). Alternatively, a method of sequentially contacting the components (a), (c), (b) and (d) is preferably used. This contact is usually performed in an inert solvent. As the inert solvent, for example, one or more hydrocarbon solvents selected from pentane, hexane, cyclohexane, heptane and the like are preferably used.

Further, when the components (a) and (b) or the components (a) and (c) are heated before being added to the component (d), the catalyst components adhere to the preparation tank. It is not preferable because it may occur. The component (d) is preferably added gradually so that the reaction proceeds uniformly while maintaining the temperature of the system in the range of 10 to 50 ° C. Since the activity tends to decrease, it is desirable to complete the addition within about 3 hours. If the temperature of the system at the time of adding the component (d) deviates from the above range, the polymer produced will be in the form of fine powder, which is not preferable.

In this way, the solid catalyst component of component (A) in the present invention is obtained in the reaction product liquid in a slurry state. This slurry-like reaction product liquid may be used as it is as a catalyst component for ethylene polymerization, or after the solid catalyst component is separated and recovered from the reaction product liquid, washed as needed and used as a catalyst component for ethylene polymerization. May be. As the separation method at this time, a known method, for example, a centrifugal separation method or a filtration method can be used, and the washing is performed using an inert hydrocarbon solvent such as pentane, hexane, cyclohexane, heptane. It can be carried out.

The ethylene polymerization catalyst according to the present invention contains the solid catalyst component of component (A) obtained as described above and the organoaluminum compound of component (B). The catalyst component may be used as the reaction product liquid slurry as described above, or may be separated and recovered from the slurry and dispersed in an inert hydrocarbon solvent in an inert gas at an appropriate concentration for use.

The organoaluminum compound used as the component (B) is not particularly limited, but is usually represented by the general formulas R ⁵ ₃ Al, R ⁵ ₂ AlX ⁵ , R ⁵ ₃ Al ₂ X ⁵ ₃ and R ⁵ ₂ AlOR ^6. One is used. In the formula, R ⁵ and R ⁶ are hydrocarbon groups such as an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group and an aralkyl group, and X ⁵ is a halogen atom such as a chlorine atom or a bromine atom. .

Examples of such an organoaluminum compound include trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, diethylaluminum monochloride, diisopropylaluminum monochloride, diisobutylaluminum monochloride, diethylaluminum monomethoxide, dimethylaluminum monoethoxide. , Diethyl aluminum monobutoxide, diethyl aluminum monophenoxide, ethyl aluminum dichloride, isopropyl aluminum dichloride, methyl aluminum sesquichloride, ethyl aluminum sesquichloride and the like. These compounds may be used alone or in combination of two or more.

The ratio of the solid catalyst component (A) and the organoaluminum compound (B) used is such that the ratio of aluminum atoms to the total of titanium atoms and zirconium atoms in the solid catalyst component is usually 1 to 1000, preferably at an atomic ratio. Selected to be in the range of 10-200. The catalyst containing the solid catalyst component and the organoaluminum compound may be prepared separately from the composition of the polymerization reaction system described below, or may be prepared substantially simultaneously with the composition of the polymerization reaction system.

Next, a preferred example of the method for polymerizing ethylene alone or a mixture of ethylene and another α-olefin in the method of the present invention will be described. First, an inert solvent such as pentane, hexane, cyclohexane, heptane or the like is carbonized. A predetermined amount of each of the solid catalyst component of the component (A) and the organoaluminum compound of the component (B) is added to the hydrogen solvent,
Then, ethylene or a mixture of ethylene and another α-olefin is introduced into this system to carry out polymerization. The polymerization method and system are not particularly limited, and for example, any method such as a solution polymerization method, a suspension polymerization method, a gas phase polymerization method can be used, and both continuous polymerization and discontinuous polymerization are possible.

Regarding the mixing ratio of each component for constituting the reaction system,
Taking the case of solution polymerization or suspension polymerization as an example, in the solid catalyst component of the component (A), the total of titanium atoms and zirconium atoms is usually 0.0005 to 10 mg atom /, preferably 0.
The organoaluminum compound as the component (B) is used in the range of 001 to 1 mg atom / min.
Al / Ti + Zr atomic ratio is usually 1-1000, preferably 10-200
It is used in the range of.

The pressure of the reaction system, usually from atmospheric pressure 100 kg / cm ^2, preferably in the range from 3~50kg / cm ^2, the reaction temperature is usually
It is selected in the range of 20 to 200 ° C, preferably 50 to 150 ° C. The reaction time is generally 5 minutes to 10 hours, preferably about 30 minutes to 5 hours.

The molecular weight at the time of polymerization can be adjusted by adjusting the polymerization conditions such as the polymerization temperature, the catalyst concentration, the catalyst composition, and the catalyst / monomer ratio, but it is more effective to carry out the polymerization in the presence of hydrogen.

In the method of the present invention, when a mixture of ethylene and another α-olefin is used as a raw material monomer, other α
-Examples of olefins include propylene and butene-
1, pentene-1, octene-1, 4-methylpentene-1, vinylcyclohexane and the like. These α-olefins may be used alone or in combination of two or more.

Furthermore, in the present invention, the catalyst system or the polymerization reaction system, in addition to the above-mentioned catalyst components, if desired,
Further, in the case of polymerizing an organometallic compound such as organozinc or ethylene with a Ziegler type catalyst, various additives that are usually added may be added to polymerize ethylene.

The ethylene polymer thus produced can be recovered by a usual method. According to the method of the present invention, the activity of the catalyst used is remarkably high, and the monomer / catalyst ratio can be sufficiently increased, so that it is not always necessary to provide a special decatalysis step.

Note that FIG. 1 shows a flowchart of an example of an embodiment of the present invention.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples.
The invention is in no way limited by these examples.

The physical properties of the obtained polymer were determined as follows.

(1) Based on MI _2.16 JIS, it was determined as a melt index under the conditions of 190 ° C. and a load of 2.16 kg.

(2) The ratio of MI _21.6 (190 ° C, load _21.6 kg) to FR MI _2.16 was determined, and the molecular weight distribution was evaluated by this melt flow ratio (FR).

(Examples 1 to 3) (1) Preparation of solid catalyst component Zr (O-n-Bu) ₄ and Ti (O-n-) in the amounts shown in Table 1
Bu) ₄ dissolved in 50 ml of hexane with an average particle size of 12 μm
To 150 ml of hexane slurry containing 10 g of Mg (OEt) ₂ was added dropwise with stirring for 15 minutes at a temperature of 20 ° C, and then 92 ml of 50 wt% hexane diluted solution of EtAlCl ₂ was added.
Was added dropwise with stirring at a temperature of 35 ° C. over 120 minutes, and further reacted for 120 minutes under reflux. Next, wash with dry hexane until chlorine is not detected in the liquid,
The total volume was made up to 500 ml with hexane.

(2) Production of ethylene polymer In an autoclave with a capacity of 1 equipped with a stirrer, n-
400 ml of hexane was added, the temperature was raised to 80 ° C., the internal atmosphere was sufficiently replaced with hydrogen gas, and then hydrogen was introduced up to 2.9 kg / cm ² · G, and ethylene was introduced up to 5.4 kg / cm ² · G. . Then, the solid catalyst component obtained in the above (1) containing 0.010 mmol of Ti and triisobutylaluminum
Polymerization was carried out for 1 hour while adding 0.50 mmol and feeding ethylene so as to keep the total pressure at 5.4 kg / cm ² · G. The results are shown in Table 2.

(Example 4) In Example 1, Ti (O-n-Bu) ₄ was replaced with Ti (O-i-).
Pr) ₄ was changed to the same as Example 1. The preparation conditions of the catalyst are shown in Table 1, and the polymerization results are shown in Table 2.

(Examples 5 to 8) Example 5 was carried out in the same manner as in Example 1 except that the temperature and the time required for adding a 50 wt% hexane diluted solution of EtAlCl ₂ were changed as shown in Table 1. The results are shown in Table 2.

(Example 9) The procedure of Example 1 was repeated, except that the average particle size of Mg (OEt) ₂ in Example 1 was changed to 6 μm. The catalyst preparation conditions are shown in Table 1 and the polymerization results are shown in Table 2.

Comparative Example 1 In Example 1, Zn (O-n-Bu) ₄ and Ti (O-n-) were used.
Bu) ₄ except that the amount used was changed as shown in Table 1.
It carried out like Example 1. The results are shown in Table 2.
In this comparative example, the polymerization activity was low, and coloring of the polymer was observed.

(Comparative Example 2) Zr (O-n-Bu) ₄ , Ti (O-n-Bu) ₄ and Mg (OEt) ₂ in the amounts shown in Table 1 were mixed, and hexane was added to bring the total amount to 200 ml, followed by stirring. While under reflux 20
After allowed to time reaction, thereto, while stirring 50 wt% hexane diluted solution 310ml of EtAlCl _2, was added dropwise over at 35 ° C. 240 minutes, the reaction was further refluxed at 120 minutes. Then
It was washed with dry hexane until chlorine was not detected in the liquid, and the total volume was adjusted to 500 ml with hexane. Hereinafter, Example 1
Polymerization of ethylene was carried out in the same manner as in. The result is the second
Shown in the table.

In this comparative example, deposits on the vessel wall were generated during the preparation of the solid catalyst component and remained until the end. Further, the polymerization activity was low, and the polymer was colored.

(Comparative Example 3) Except that Mg (OEt) ₂ having an average particle diameter of 56 μm was used,
It carried out like Example 1. Table 1 shows the catalyst preparation conditions.
Table 2 shows the polymerization results.

In this comparative example, the polymerization activity was low, and the obtained polymer contained a large amount of both fine powder and coarse powder.

[Effect of the Invention] In the method of the present invention, a polymerization catalyst comprising a combination of a solid catalyst component obtained by reacting a magnesium dialkoxide, a zirconium compound, a titanium compound and an organic aluminum halide compound with an organic aluminum compound is used. A method for producing an ethylene-based polymer by polymerizing ethylene alone or a mixture of ethylene and another α-olefin, wherein the solid catalyst component prepared by the method of the present invention is polymerized as compared with a conventional one. In addition to being highly active, easy to prepare and low in cost, it is possible to prepare a wide range of molecular weight distribution of the ethylene polymer to be produced, and ethylene with good powder properties such as bulk density and powder particle system distribution. A system polymer can be provided.

The ethylene polymer obtained by the method of the present invention is suitably used, for example, for hollow moldings and films.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of an embodiment of the present invention.

Claims (1)

[Claims] 1. A magnesium diamine represented by the general formula (A) (a) Mg (OR ¹ ) ₂ (wherein R ¹ is an alkyl group having 1 to 3 carbon atoms) and having an average particle size of 50 μm or less. Alkoxide, (b) general formula Zr (OR ² ) _n X ² _4-n (wherein R ² is a hydrocarbon group, X ² is a halogen atom, and n is 0 to 0).
Zirconium compounds represented by 4 is a number of), (c) general formula _{^{Ti (OR 3) m X 3}} 4-m (R 3 in the formula is a hydrocarbon group, X ³ is a halogen atom, m is 0
A titanium compound represented by the formula ( ⁴ ) and (d) the general formula AlR ⁴ _k X ⁴ _3-k (wherein R ⁴ is a hydrocarbon group, X ⁴ is a halogen atom, and k is 1 to ⁴⁾ .
Which is a number of 2), each of the organic aluminum halide compounds represented by as well as (In the formula, [Mg], [Zr], [Ti] and [X] are magnesium, zirconium and gram equivalent, respectively,
(Amount of titanium and halogen atoms), and a combination of a solid catalyst component (B) obtained by reacting them under conditions in which the component (a) does not substantially dissolve, and (B) an organoaluminum compound. A method for producing an ethylene-based polymer, which comprises polymerizing ethylene alone or a mixture of ethylene and another α-olefin in the presence of a catalyst system comprising