JPH05178933A - Production of ethylene copolymer - Google Patents

Abstract

PURPOSE:To produce an ethylene copolymer which need not be deashed and is improved in mechanical strengths by copolymerizing ethylene with an alpha-olefin in the presence of a specified catalyst. CONSTITUTION:A solid obtained by bringing a carrier obtained by reacting a reaction product of 0.1-10mol of an aluminum halide (A) with 1 mol of an organosilicon compound (B) of formula I (wherein R<1> is 1-8C alkyl; R<2> is 1-8C alkyl; and m is 0-3) with 0.05-4mol, per mol of component A, of a Grignard compound (C) of formula II (wherein R<3> is R<2>; and X<1> is halogen) into contact with at least 1mol, per mol of component C, of a Ti compound (D) of formula III (wherein R<4> is R<1>; X<2> is X<1>; and n is 0-4) is treated with an organometallic compound in a metal to molar ratio of 0.1-1000 to obtain a solid catalyst component. Ethylene and an alpha-olefin are prepolymerized at 100 deg.C or below for 30min to 15hr under atmospheric pressure to 10kg/cm<2>G in the presence of a catalyst comprising the above catalyst component and an organoaluminum compound and then copolymerized at 50-110 deg.C.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a copolymer of ethylene and α-olefin.

[0002]

2. Description of the Related Art Copolymerization of ethylene with .alpha.-olefin using a Ziegler-Natta type catalyst has hitherto been produced by polymerization methods such as solution polymerization, bulk polymerization, slurry polymerization and gas phase polymerization. In recent years, a process that does not require a step of separating a catalyst residue from a copolymer produced by increasing the catalyst activity has become widespread, and an inorganic solid is used for the purpose of preparing catalyst particles having high catalyst activation and good fluidity. Further, many highly active catalysts in which an inorganic solid having a specific particle diameter is loaded with a transition metal component such as titanium or vanadium have been disclosed. Japanese Patent Publication No. 54-129983,
JP-A-58-17206, JP-A-59-49242, and JP-B-2-33045 propose a supported high-activity catalyst for copolymerization of ethylene and α-olefin with which the present invention is concerned. .. When a copolymer of ethylene and α-olefin is produced by fluidized bed gas phase polymerization, a low molecular weight component having adhesiveness is produced, the fluidity of polymer particles is deteriorated, and therefore a lump of polymer is produced. Or the reaction tube may be blocked. In addition, if the randomness of the α-olefin in the copolymer is poor, that is, if the distribution of the α-olefin units is biased, a tacky copolymer is produced and the same problems as described above occur. Therefore, a stable copolymerization reaction for a long period of time cannot be performed.

Generally, a copolymer of ethylene can be produced by increasing the content of α-olefin to produce a copolymer having a lower density. However, when the low molecular weight component is generated in the polymerization reaction or the composition distribution of α-olefin in the copolymer becomes wide, that is, when the composition between polymer chains is not uniform, the surface of the molded film has tackiness. However, if the copolymer has a wide molecular weight distribution, the mechanical strength is lowered, and a thinner film cannot be produced.
In the copolymerization of ethylene and α-olefin, in order to solve the above problems, in particular, to narrow the composition distribution and suppress the production of low molecular weight components, a Zr-based catalyst (Japanese Patent Laid-Open No. 62-121707) is used. No. 62-121709, JP-A-3-234712, 3-223306, and 3
-217404), or the use of an electron donor in a magnesium compound-supported catalyst (Japanese Patent Laid-Open No. 61-27309).
No. 61-271310, No. 63-159411
No. 63-142008, No. 63-117019.
No. 1/49296). However, the conventional techniques are not always satisfactory in terms of production and physical properties of the above-mentioned copolymer, and further improvement is desired.

[0004]

DISCLOSURE OF THE INVENTION The present invention improves the problems in the process for producing a copolymer of ethylene and an α-olefin, and particularly in the case of producing by a fluidized bed gas phase polymerization, a long-term stable polymerization reaction. And a method for producing a copolymer having excellent physical properties.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to an aluminum halide and a compound of the formula R ¹ _m Si (OR ² ) _4-m (wherein R ¹ is an alkyl group having 1 to 8 carbon atoms or a phenyl group). And R ² represents an alkyl group having 1 to 8 carbon atoms,
In the reaction product with the organosilicon compound represented by m is 1, 2 or 3, R ³ MgX ¹ (wherein R ³ represents an alkyl group having 1 to 8 carbon atoms, X ¹
Represents a halogen atom) and a carrier obtained by reacting the Grignard compound with the formula Ti (OR ⁴ ) _n X ² _4-n (wherein, R ⁴ is an alkyl group having 1 to 8 carbon atoms or a phenyl group). , X ² represents a halogen atom, and n is 0, 1,
A solid catalyst component (A) obtained by contacting a solid obtained by contacting a titanium compound represented by formula (2, 3 or 4) with an organometallic compound, and an organoaluminum compound component (B). It relates to a method for producing an ethylene copolymer, which comprises copolymerizing ethylene and an α-olefin in the presence of a catalyst obtained from

Hereinafter, each component used in the preparation of the catalyst of the present invention and the conditions thereof will be described in detail. In the present invention, the preparation and polymerization of the catalyst component are all carried out under an atmosphere of an inert gas such as nitrogen or argon. Further, it is desirable that the raw material for preparing the catalyst component is substantially anhydrous.

Specific examples of the aluminum halide in the present invention include aluminum chloride, aluminum bromide and aluminum iodide, and among them, aluminum chloride is preferably used.

Specific examples of the organosilicon compound represented by the formula R ¹ _m Si (OR ² ) _4-m include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-n-butoxysilane, Tetraisopentoxysilane, tetra-n-hexoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-butoxysilane, methyltriisopentoxysilane, methyltri-n-hexoxysilane, ethyltriethoxysilane, ethyltriisosilane Propoxysilane, ethyltriisopentoxysilane, n-butyltriethoxysilane, isobutyltriethoxysilane, isopentyltriethoxysilane, isopentyltri-n-
Butoxysilane, dimethyldiethoxysilane, dimethyldi-n-butoxysilane, dimethyldiisopentoxysilane, diethyldiethoxysilane, diethyldiisopentoxysilane, diisobutyldiisopentoxysilane,
Di-n-butyldiethoxysilane, diisobutyldiisopentoxysilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylisobutoxysilane,
Triethylisopropoxysilane, tri-n-propylethoxysilane, tri-n-butylethoxysilane, triisopentylethoxysilane, phenyltriethoxysilane, phenyltriisobutoxysilane, phenyltriisopentoxysilane, diphenyldiethoxysilane, Examples thereof include diphenyldiisopentoxysilane, diphenyldioctoxysilane, triphenylmethoxysilane, triphenylethoxysilane, triphenylisopentoxysilane, benzyltriethoxysilane, benzyltributoxysilane and dibenzyldiethoxysilane. Of these, alkylalkoxysilanes such as methyltriethoxysilane are preferably used.

The proportion of aluminum halide used in the reaction between the aluminum halide and the organosilicon compound is
It is preferably 0.1 to 10 mol, and particularly preferably 0.1 to 2 mol, per mol of the organosilicon compound. The reaction is usually carried out by stirring both compounds in an inert organic solvent at a temperature in the range of -50 to 100 ° C for 0.1 to 2 hours. The reaction proceeds exothermically and the reaction product is obtained as a solution in an inert organic solvent. The reaction product is subsequently subjected to reaction with a Grignard compound as a solution in an inert organic solvent.

Examples of the inert organic solvent include aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane, decane and dodecane, and alicyclic compounds such as cyclopentane, cyclohexane and methylcyclohexane. Hydrocarbons or aromatic hydrocarbons such as toluene, benzene, xylene, etc. may be mentioned. These inert organic solvents can be similarly used in the following solid catalyst component (A) adjusting step or polymerization step.

The Grignard compound represented by the formula R ³ MgX ¹ is preferably an alkylmagnesium chloride in which X ¹ is a chlorine atom, and specific examples thereof include methylmagnesium chloride, ethylmagnesium chloride and n-butylmagnesium. Examples thereof include chloride and n-hexyl magnesium chloride. The amount of the Grignard compound used is preferably 0.05 to 4 mol, particularly 1 to 3 mol, per mol of the aluminum halide used for preparing the reaction product. There is no particular limitation on the method of reacting the reaction product of an aluminum halide and an organosilicon compound with a Grignard compound, but an inert solvent solution of the reaction product may be used as an ether solution of the Grignard compound or an ether and an aromatic hydrocarbon. It is convenient to carry out by gradually adding the mixed solvent solution with or by adding them in the reverse order. Specific examples of ethers include diethyl ether, diisopropyl ether, di-n-butyl ether and diisoamyl ether.

The temperature of the reaction is usually -50 to 100 ° C,
It is preferably -20 to 25 ° C. The reaction time is not particularly limited, but is usually 5 minutes or longer. The carrier precipitates as the reaction progresses. The carrier thus obtained may be subjected to the next treatment as a reaction mixture, but it is preferable to separate the carrier in advance and wash it with an inert organic solvent, and then subject it to the subsequent contact treatment with a titanium compound.

Specific examples of the titanium compound include methoxytochlorotitanium, dimethoxydichlorotitanium, trimethoxychlorotitanium, ethoxytrichlorotitanium, diethoxydichlorotitanium, propoxytrichlorotitanium, dipropoxydichlorotitanium, butoxytrichlorotitanium and ditoxytrichlorotitanium. Butoxydichlorotitanium, phenoxytrichlorotitanium, diphenoxydichlorotitanium, methoxytribromotitanium, phenoxytribromotitanium, methoxytriiodotitanium, phenoxytriiodotitanium, tetrachlorotitanium, tetrabromotitanium, tetraiodotitanium, tetramethoxytitanium. , Tetraethoxy titanium, tetrapropoxy titanium and the like. Two or more kinds of these titanium compounds may be used in combination.

Among them, tetrachlorotitanium, methoxytrichlorotitanium, dimethoxydichlorotitanium, ethoxytrichlorotitanium, diethoxydichlorotitanium, propoxytrichlorotitanium, dipropoxydichlorotitanium,
Butoxytrichlorotitanium and dibutoxydichlorotitanium are preferably used.

The amount of the titanium compound used is preferably 1 mol or more, particularly 2 to 100 mol, per 1 mol of the Grignard compound used in preparing the carrier. The contact treatment between the carrier and the titanium compound can be performed by the following method. The support is contacted with the titanium compound in the presence or absence of an inert organic solvent at a temperature of 20 to 200 ° C, preferably 60 to 140 ° C for 0.5 to 3 hours, after which the reaction mixture is removed from the reaction mixture. The solid is separated and optionally washed with an inert organic solvent. The contact treatment with the titanium compound can be continuously performed a plurality of times.

The thus obtained contact-treated solid of the carrier and the titanium compound can be subjected to the following contact treatment with the organometallic compound.

Examples of the organic metal compound include alkyl lithium, dialkyl magnesium, alkyl magnesium halide, dialkyl zinc, trialkyl aluminum,
Although dialkyl or monoalkyl aluminum halides can be used, trialkyl aluminum is preferable, and specific examples thereof include trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, trihexyl aluminum, trioctyl aluminum and the like. Any of the above organometallic compounds can be used as a mixture. Also,
Polyaluminoxane obtained by the reaction of alkylaluminum and water can be used as well.

Two or more of these organometallic compounds may be used in combination. Further, the titanium compound-treated carrier may be contact-treated by using the organometallic compound stepwise twice or more.

The amount of the organometallic compound used is preferably such that the metal / Ti molar ratio is 0.1 to 1000, particularly 0.5 to 500, relative to the titanium atom in the titanium compound-treated carrier. As a contact treatment method with an organometallic compound,
In an inert organic solvent, the reaction temperature is preferably 0 to 100 ° C., particularly 5 to 60 ° C., and the contact time is not particularly limited, but is usually 5 minutes or longer.

The Ti valence in the titanium compound-supported solid is reduced to less than 4 by the organometallic compound. Therefore,
By using the solid catalyst component (A) treated with an organometallic compound, the polymerization activity does not change significantly at the start of polymerization, the control of the polymerization reaction is facilitated, and an ethylene copolymer can be obtained with high catalyst efficiency. it can. The component (A) is separated from the thus-obtained mixture containing the treated solids by filtration, decantation and the like, and washed with an inert organic solvent if necessary. As the inert organic solvent, the same one used in the treatment with the titanium compound can be used. The solid catalyst component (A) obtained by the above method can be used in the polymerization reaction together with the organoaluminum compound (B).

Specific examples of the organoaluminum compound component (B) include trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, diethylaluminum chloride,
Dibutyl aluminum chloride, diethyl aluminum bromide, ethyl aluminum sesquichloride, ethyl aluminum sesquibromide, ethyl aluminum dichloride, propyl aluminum dichloride, butyl aluminum dichloride, ethyl aluminum dibromide,
Propyl aluminum dibromide, butyl aluminum dibromide, diethyl aluminum hydride, dibutyl aluminum hydride, ethyl aluminum dihydride, propyl aluminum dihydride, butyl aluminum dihydride, ethyl aluminum ethoxy chloride, ethyl aluminum butoxycyclolide, ethyl aluminum ethoxy bromide, etc. Be done. Also, isopropenylaluminum obtained by the reaction of diisobutylaluminum hydride and isoprene can be used. Further, for example, an alkylalumoxane obtained by a reaction of trialkylaluminum with water dispersed in a solvent or a reaction of water of crystallization of an inorganic compound can be used. Among them, trialkyl aluminums such as triethyl aluminum and triisobutyl aluminum are preferably used. The amount of the organoaluminum compound component (B) used is usually 1 to 100 per 1 gram atom of titanium in the solid catalyst component (A).
It is 0 mol. In addition, two or more kinds of organoaluminum compounds can be used together.

In the present invention, ethylene and α-olefin are copolymerized by using a catalyst composed of component (A) and component (B). Specific examples of α-olefins include:
Propylene, butene-1, 4-methylpentene-1, hexene-1, octene-1 and the like can be mentioned.

In the present invention, if necessary, the catalyst comprising the component (A) and the component (B) may be prepolymerized with ethylene or a mixture of ethylene and α-olefin. When carrying out the prepolymerization, it is preferred to carry out the polymerization until a particulate polymer containing 0.0125 to 0.04 mmol of Ti atoms per gram of the prepolymer is obtained. An inert organic solvent may be used as a polymerization solvent, or a liquid α-olefin itself may be used. As preferable conditions for producing the prepolymer, the polymerization pressure is usually atmospheric pressure to 10 kg / cm ² , and the polymerization temperature is 100 ° C. or lower, usually 20 to 70 ° C. The polymerization time is usually 30 minutes to 15 hours, preferably 2 to 10 hours. The proportions of the component (A) and the component (B) in the prepolymerization or in the main polymerization described below are respectively Ti and A
Al / Ti = 0.1-1000 at a molar ratio of 1
It is preferably 0.5 to 200. When an excessive amount of the component (B) is used in the prepolymerization, the copolymer can be produced without additionally using the component (B) in the main polymerization. The prepolymer can be subjected to the main polymerization after evaporating a polymerization solvent with, for example, an inert gas, drying and removing it to obtain a powder.

The main polymerization reaction can be carried out in the same manner as the polymerization reaction of α-olefin using a conventional Ziegler-Natta type catalyst. The main polymerization reaction can be carried out in the liquid phase or the gas phase using the solid catalyst component (A) or the prepolymer.
Examples of the gas phase polymerization reaction include a fluidized bed polymerization method and a stirring polymerization method. In particular, when carrying out by a fluidized bed polymerization method, it is preferable to copolymerize gaseous ethylene and α-olefin in a fluidized bed polymerization reactor in the presence of the prepolymer produced as described above. Α in main polymerization
-As the olefin, the same as in the prepolymer production,
Alternatively, different ones can be used. In the main polymerization, the heat of polymerization is removed by the monomer gas while the prepolymer is fluidized by the monomer gas, and the polymerization is usually carried out at 50 to 110 ° C. In the main polymerization, when a prepolymer is used as a catalyst, an organoaluminum compound (B) can be used together.

When the polymerization reaction is carried out in the liquid phase, an inert organic solvent may be used as the polymerization solvent, or a liquid α-olefin itself may be used. The concentration of the catalyst in the polymerization solvent is not particularly limited, but generally 1 L of the polymerization solvent is used.
Therefore, the solid catalyst component (A) is 0.001 to 1 milligram atom in terms of titanium metal, and the organoaluminum compound component (B) is 0.01 to 100 mmol. The polymerization reaction is carried out with water and oxygen substantially removed. The polymerization temperature is usually 30 to 100 ° C., and the polymerization pressure is usually 1 to 80 Kg / cm ² . Further, hydrogen can be made to coexist as a molecular weight regulator of the produced polymer.

[0026]

According to the present invention, in particular, in the fluidized bed gas phase polymerization method, since the polymerization activity is high, a deashing step of the produced copolymer is unnecessary. Furthermore, the proportion of low-molecular-weight tacky products is small, and since there is almost no formation of an α-olefin block copolymer by copolymerization, good polymer fluidity is maintained in the present polymerization method, and the particles are kept together. It is possible to stably carry out the polymerization reaction for a long period of time without the formation of agglomerates and the attachment to the reactor. In addition, since the produced copolymer has a narrow composition distribution and molecular weight distribution, even if the α-olefin content is increased and the density is reduced, the surface tackiness of the molding film is small, and the mechanical strength of the molding is low. It has excellent physical properties such as being large.

[0027]

EXAMPLES Examples and comparative examples of the present invention will be described below. In the examples, the “polymerization activity” is a copolymer yield (kg) per 1 g of Ti component of the solid catalyst used in the polymerization reaction. "MI" means ASTM D-1
190 under a load of 2.16 kg / cm ² according to 238
It is the melt index of the polymer measured at ° C. The titanium content of the solid catalyst component was measured by a colorimetric method. The molecular weight distribution was evaluated by the ratio M _w / M _{n of} the number average molecular weight M _w and the weight average molecular weight M _n obtained from GPC using polystyrene as a standard substance. The content of α-olefin was measured by NMR. Density was measured by a density gradient tube. The composition distribution of the copolymer was evaluated by the relationship between the α-olefin content and the density. That is, in general, α
For the same olefin content, the more random the copolymer, the smaller the density and therefore the narrower the composition distribution.

Example 1 (1) Preparation of solid catalyst component Toluene suspension 4 of 15 mmol of anhydrous aluminum chloride
After adding 15 mmol of methyltriethoxysilane to 0 ml and reacting at 25 ° C. for 0.5 hours, the temperature was raised to 60 ° C. and further reaction was performed for 1 hour. The reaction product mixture was cooled to −5 ° C., 18 ml of a solution of 30 mmol of n-butylmagnesium chloride in diisopropyl ether was added to the reaction product mixture in 0.5 hours, and the temperature was raised to 30 ° C. to react for 1 hour. The precipitated solid was filtered off and washed with toluene. 30 ml of a toluene suspension of 4.90 g of the obtained carrier.
To this, 150 mmol of titanium tetrachloride was added, and contact treatment was carried out at 90 ° C. for 1 hour. The contact-treated solid was filtered off at 90 ° C. and then washed 3 times with 30 ml of toluene. To 30 ml of the toluene slurry of the titanium compound-supporting solid obtained above, triethylaluminum was introduced so that the Al / Ti molar ratio was 2, and contact treatment was carried out at 40 ° C. for 1 hour. The treated solid was separated by filtration and then washed 5 times with 30 ml of n-heptane to obtain a slurry of 80 ml of n-heptane. The titanium content of the solid catalyst component was 5.25% by weight.

(2) Prepolymerization 800 ml of heptane was added to a 2 L autoclave made of SUS and purged with nitrogen gas, and 10.0 mmol of tri-n-octylaluminum and catalyst solid (Ti = 2.5 mmol) were introduced. After 1.5 kg / cm ² of hydrogen was injected under pressure, the temperature was raised to 60 ° C. and ethylene was introduced to initiate polymerization. Maintained at 68 ° C during polymerization, ethylene flow rate was 0.93
L / min. Polymerize for 2 hours as 0.0
A prepolymer containing 19 mmol of Ti atoms was obtained.

(3) Gas-phase copolymerization of ethylene and 1-butene 500 g of polyethylene powder produced in advance was used to give a diameter of 2
0 cm, 50 cm in length stirring type gas phase polymerization reactor,
While stirring the powder at 300 rpm, ethylene / butene-1 / hydrogen (3
/1/0.2 molar ratio) of the mixed gas at 45 ° C of 20 cm /
It was raised at a speed of sec and circulated. The copolymerization is carried out by introducing the prepolymer produced in (2) above at 10 g / hour,
Polymerization temperature about 75 to 85 ° C, polymerization pressure 2 kg / cm ² , A
It was carried out continuously for 10 hours at an l / Ti atomic ratio of 10. During that time, ethylene / butene-1 copolymer was continuously extracted,
The activity and physical properties were evaluated. The results are shown in Table 1.

Example 2 The molar ratio of the mixed gas in the main polymerization was changed to (ethylene / butene-1
/Hydrogen=2/1/0.2 molar ratio)
An ethylene / butene-1 copolymer was obtained in the same manner as in. The results are shown in Table 1.

Examples 3 and 4 Solid catalyst component was prepared under the same conditions and method as in Example 1 except that triethylaluminum was introduced so that the Al / Ti molar ratio was 2 and contact was carried out at 40 ° C. for 1 hour. Was prepared to obtain a solid catalyst component (A) having a titanium content of 5.05% by weight. Then, prepolymerization was carried out in the same manner to obtain a prepolymer containing 0.018 mmol of Ti atom per gram. Further, copolymerization was carried out under the same conditions and methods as in Examples 1 and 2 to obtain an ethylene / butene-1 copolymer. The results are shown in Table 1.

Examples 5 and 6 Solid catalyst components were prepared under the same conditions and methods as in Example 1 except that diethylaluminum chloride was used in place of triethylaluminum, and the titanium content was 4.98% by weight. % Solid catalyst component (A) was obtained. Then, prepolymerization was carried out in the same manner to obtain a prepolymer containing 0.017 mmol of Ti atom per gram. Further, copolymerization was carried out under the same conditions and methods as in Examples 1 and 2 to obtain an ethylene / butene-1 copolymer. The results are shown in Table 1.

Examples 7 and 8 The solid catalyst component was prepared under the same conditions and method as in Example 1, except that trioctylaluminum was introduced in place of triethylaluminum so that the Al / Ti molar ratio was 10. This was performed to obtain a solid catalyst component (A) having a titanium content of 5.10% by weight. Then, prepolymerization was carried out in the same manner to obtain a prepolymer containing 0.017 mmol of Ti atom per gram. Further, copolymerization was carried out under the same conditions and methods as in Examples 1 and 2 to obtain an ethylene / butene-1 copolymer. The results are shown in Table 1.

Comparative Examples 1 and 2 A solid catalyst component (A) having a titanium content of 5.50% by weight was obtained in the same manner as in Example 1 except that di-n-heptyl phthalate was not used. It was Then, prepolymerization was performed in the same manner to obtain a prepolymer containing 0.019 mmol of Ti atom per gram. Further, copolymerization was carried out under the same conditions and methods as in Examples 1 and 2 to obtain an ethylene / butene-1 copolymer. The results are shown in Table 1.

As can be seen from the examples and the comparative examples, in the examples, the same composition has a lower density, and butene-1 is randomly copolymerized with ethylene. Further, no production of adhesive particles due to butene chain or low molecular weight components was observed, and therefore the fluidity of the polymer particles was good.

[Brief description of drawings]

FIG. 1 is a flowchart showing the polymerization method of the present invention and the steps for preparing a solid catalyst component used in the polymerization.

[Table 1]

Claims (1)

[Claims] 1. An aluminum halide and a formula R ¹ _m Si (OR ² ) _4-m (wherein R ¹ represents an alkyl group having 1 to 8 carbon atoms or a phenyl group, and R ² has 1 to 1 carbon atoms). 8 represents an alkyl group,
m is 0, 1, 2, or 3), in the reaction product with the organosilicon compound represented by the formula, R ³ MgX ¹ (wherein, R ³ represents an alkyl group having 1 to 8 carbon atoms, X ¹
Represents a halogen atom) and a carrier obtained by reacting the Grignard compound with the formula Ti (OR ⁴ ) _n X ² _4-n (wherein, R ⁴ is an alkyl group having 1 to 8 carbon atoms or a phenyl group). , X ² represents a halogen atom, and n is 0, 1,
A solid catalyst component (A) obtained by contacting a solid obtained by contacting a titanium compound represented by formula (2, 3 or 4) with an organometallic compound, and an organoaluminum compound component (B). A method for producing an ethylene copolymer, which comprises copolymerizing ethylene and an α-olefin in the presence of a catalyst obtained from