JP3305485B2 - Method for producing ethylene copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an ethylene copolymer. More particularly, the present invention relates to a method for providing an ethylene copolymer excellent in extrusion characteristics and melt properties, which is suitable for inflation molding.

[0002]

2. Description of the Related Art In the field of inflation molding, an ethylene copolymer having a high molecular weight and a wide molecular weight distribution is required. In particular, those having excellent extrusion characteristics and melt properties during molding are desired. Heretofore, there have been many proposals for a method for producing an ethylene copolymer for inflation molding having a wide molecular weight distribution by two-stage polymerization. In particular, there is a method disclosed in Japanese Patent Publication No. 3-18645. In this method, continuous two-stage polymerization is carried out using an easily volatile hydrocarbon solvent such as propane or isobutane to produce a high-molecular-weight component in a first stage and a low-molecular-weight component in a second stage. When adjusting the molecular weight with hydrogen, the transition from the first stage to the second stage does not require an intermediate hydrogen flash tank, which is very desirable in terms of productivity. Further, as a solid catalyst component used for producing an ethylene copolymer by two-stage polymerization, JP-A-53-78287 and JP-A-53-13208 are used.
2, JP-A-54-75491, JP-A-54-8119
0, JP-A-55-3559, JP-A-57-20541
0, JP-A-58-149906, JP-A-58-2251
And the like. Highly supported solid catalyst components disclosed in US Pat.

[0003]

However, the ethylene copolymer obtained by performing the two-stage polymerization by the above-mentioned method using the catalyst system comprising the above-mentioned solid catalyst component has a high catalytic activity and a very high productivity. Although high, there is a problem that the extrusion characteristics and melt properties at the time of forming a blown film are not always satisfactory. The object of the present invention is to
An object of the present invention is to provide a method for producing an ethylene copolymer excellent in extrusion characteristics and melt properties at the time of molding by solving the problems of these conventional techniques.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above-mentioned problems, and as a result, have found that ethylene and α-olefin are mixed with a high molecular weight component in the first polymerization zone and low in the second polymerization zone. In producing an ethylene copolymer by two-stage polymerization of polymerizing molecular components, the general formula Mg (OR ¹ ) ₂ (R
¹ represents an alkyl group, a cycloalkyl group, an aryl group and an aralkyl group), a magnesium alcoholate represented by the general formula Ti (OR ² ) ₄ (R ² represents a secondary or tertiary hydrocarbon group) And a general formula SiR ³ R ⁴ R ⁵ R ⁶ (R
^{3 to} R ⁶ are aliphatic hydrocarbon groups, and at least one R has 2 or more carbon atoms) of a tetraalkylsilane compound represented by the following formula: Mg / Ti = 1 to 4 molar ratio, and Si / Ti = 0.
After dissolving in an inert hydrocarbon solvent in a range of 1 to 5 mole ratio, a general formula R ⁷ AlX ₂ (R ⁷ represents an alkyl group, a cycloalkyl group, an aryl group and an aralkyl group, and X represents a halogen atom) By using a catalyst system comprising a solid catalyst component and an organoaluminum compound obtained by treating a dihalogenated organoaluminum compound represented by the formula (1) with Al / Ti = 5 to 20 in a molar ratio. This has solved the problem.

Hereinafter, the present invention will be described specifically. Specific examples of the magnesium alcoholate used in the present invention include magnesium methylate, magnesium ethylate, magnesium propylate, magnesium butyrate, magnesium hexylate, magnesium phenolate, magnesium cyclohexanolate, magnesium benzyl alcoholate, and magnesium cresolate. And the like. Among them, magnesium methylate, magnesium ethylate and magnesium phenolate are preferably used.

Specific examples of the tetraalkoxytitanium compound represented by the general formula Ti (OR ² ) ₄ (R ² represents a secondary or tertiary hydrocarbon group) include tetraisopropoxytitanium, tetrasec- Butoxy titanium, tetra 1
-Methylbutoxytitanium, tetra-1-ethylpropoxytitanium, tetra1,2-dimethylpropoxytitanium, tetra1,1-dimethylpropoxytitanium, tetracyclopentyloxytitanium, tetracyclohexyloxytitanium, tetramethylcyclohexyloxytitanium, tetracaproxy Titanium, tetra tert-butoxy titanium, tetra 1-methylamyloxy titanium, tetra 1,2,2-
Trimethylpropoxy titanium, tetra 1,1,2-trimethyl propoxy titanium, tetra 1-propyl butoxy titanium, tetra 2,4-dimethyl-3-pentyloxy titanium, tetra 1,1-diethyl propoxy titanium, tetra 1,2-dimethyl -1-ethylpropoxytitanium, tetra1,1,2,2-tetramethylpropoxytitanium,
Titanium 1-butylamyloxytitanium, tetra-1-phenylbutoxytitanium, tetratriphenylmethoxytitanium and the like can be mentioned, and among them, tetraisopropoxytitanium and tetratert-butoxytitanium are preferably used.

The general formula SiR ³ R ⁴ R ⁵ R ⁶ (R ^{3 to} R ⁶
Is an aliphatic hydrocarbon group, and at least one R has 2 carbon atoms.
Specific examples of the tetraalkylsilane compound represented by the above) include ethyltrimethylsilane, trimethyln-propylsilane, trimethylisopropylsilane, diethyldimethylsilane, tetraethylsilane, and dimethyldi-n-.
Examples thereof include propylsilane, dimethyldiisopropylsilane, and tetrabutylsilane. These tetraalkylsilane compounds can be used alone or in combination of two or more.

As the inert hydrocarbon solvent for dissolving the above magnesium alcoholate, tetraalkoxytitanium and tetraalkylsilane, aliphatic hydrocarbons such as hexane, heptane, octane, decane and cyclohexane, and aromatic hydrocarbons such as benzene, toluene and xylene. Hydrogen. The ratio of magnesium alcoholate to tetraalkoxytitanium used is preferably Mg / Ti = 1 to 4 molar ratio. When an ethylene-based copolymer is produced using the solid catalyst component obtained at a ratio of 1 or less or 4 or more, the activity is extremely low and the productivity is reduced. The ratio of tetraalkylsilane to tetraalkoxytitanium is Si /
Ti = 0.1 to 5 molar ratio is preferred. When an ethylene copolymer is produced using a solid catalyst component obtained at a ratio of 0.1 or less or 5 or more, the activity is extremely low and the productivity is reduced. Magnesium alcoholate, tetraalkoxytitanium and tetraalkylsilane are dissolved in the above-mentioned inert hydrocarbon solvent at a temperature not lower than 40 ° C. and not higher than the boiling point of the solvent.

The solution in which the magnesium alcoholate, the tetraalkoxytitanium and the tetraalkylsilane are dissolved is cooled to 30 ° C. or less, and then the solution of the general formula R ³ AlX ₂ (R
³ is an alkyl group, a cycloalkyl group, an aryl group, and an aralkyl group, and X represents a halogen atom). Specific examples of organoaluminum dihalide include methylaluminum dichloride, ethylaluminum dichloride, isobutylaluminum dichloride, hexylaluminum dichloride, methylaluminum dibromide,
Examples thereof include ethylaluminum dibromide and isobutylaluminum dibromide. Among them, the above-mentioned alkylaluminum dichloride is preferably used. As the processing conditions, the processing temperature is 30 ° C. or higher and the boiling point of the solvent or lower,
The treatment is preferably performed at a temperature of 40 ° C. or more and 90 ° C. or less, and a treatment time of 15 minutes or more and 5 hours or less, preferably 30 minutes or more and 3 hours or less. Also, the ratio of the organoaluminum dihalide to the tetraalkoxytitanium is preferably Al / Ti = 5 to 20 molar ratio. Ethylene copolymers produced using the solid catalyst component obtained at a ratio of 5 or less have poor extrusion characteristics and melt properties. When an ethylene copolymer is produced using the solid catalyst component obtained at a ratio of 20 or more, the activity is very low and the productivity is reduced. When the treatment with the organoaluminum dihalide is performed, a solid product is obtained, and the solid product is washed with the above inert hydrocarbon until no halogen component in the washing liquid is detected, thereby obtaining a solid catalyst component. .

The catalyst system used in the present invention is obtained from the solid catalyst component obtained as described above and an organoaluminum compound. The polymerization of the present invention can be achieved by homopolymerizing ethylene or copolymerizing ethylene with an α-olefin using this catalyst system. As the organic aluminum used in the polymerization, trimethylaluminum, triethylaluminum, tripropylaluminum, tri-n-butylaluminum,
Trialkyl aluminums such as triisobutyl aluminum, trihexyl aluminum and trioctyl aluminum; alkyl aluminum hydrides such as dimethyl aluminum hydride, diethyl aluminum hydride and dibutyl aluminum hydride; dimethyl aluminum chloride, diethyl aluminum chloride, diethyl aluminum bromide and ethyl aluminum Examples thereof include alkylaluminum halides such as sesquichloride; alkylaluminum alkoxides such as diethylaluminum ethoxide and diethylaluminum phenoxide; and alkylaluminoxanes such as methylaluminoxane, ethylaluminoxane and butylaluminoxane. These organoaluminums can be used alone, or
Two or more types can be used in combination. Of these, trialkyl aluminum is preferably used.

Using the catalyst system as described above, ethylene and an α-olefin are copolymerized in a hydrocarbon solvent at a temperature of 50 to 100 ° C. Examples of the hydrocarbon solvent include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, hexane, and heptane, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane. A hydrocarbon solvent which is easily volatile from the treatment, propane, n-butane, isobutane, isopentane, n-pentane and the like are preferable. The α-olefin used for copolymerization with ethylene is an α-olefin having at most 20, preferably 12 carbon atoms, and propylene, butene-1, pentene-1, hexene-1,4- Methylpentene-1 and octene-1 are mentioned. The comonomer content usually ranges from 0.2 to 5% by weight.

The polymerization reaction is carried out in two or more stages in a single or a plurality of reactors. In the case of using a plurality of reactors, the reaction mixture obtained by polymerization in the first-stage reaction zone is successively used. To feed the second stage reaction zone continuously. The transfer from the first-stage reaction zone to the second-stage reaction zone is carried out through a connecting pipe, and is carried out by a differential pressure due to continuous discharge of the polymerization reaction mixture from the second-stage reaction zone. When performing multi-stage polymerization using a readily volatile hydrocarbon solvent, the high molecular weight component formed under low hydrogen concentration conditions is used in the first stage, and the low molecular weight component under high hydrogen concentration conditions is used in the second stage. It is necessary for the process to polymerize in stages.

In the case of continuous production in an industrial two-stage polymerization process, the specific polymerization activity in the two polymerization zones (solid catalyst component, polymerization time, and the amount of polymer produced per ethylene partial pressure is represented by Rsp). Are ideally the same, ideally speaking, but for the initial purpose of expanding the molecular weight distribution, the activity ratio between the specific activities Rsp, L for producing high molecular weight components and the specific activities Rsp, H for producing low molecular weight components. Rsp, L / Rs
Ideally, p and H are close to 1. Otherwise, a value as close as possible is desirable. If it is close to 1, it is sufficient to use a reactor having the same monomer concentration and the same residence time in each polymerization zone and having a volume ratio that does not vary much depending on the production ratio, but Rsp and H are extremely high. If it is lower than Rsp, L, it is necessary to cover the decrease in activity with another design or condition by making a difference in volume ratio. Also, Rs
When the absolute values of p and H are low, the amount of the catalyst residue increases, which is not suitable for a deashless process. In the process, if Rsp and H are low, it is possible to increase the catalytic efficiency by increasing the ethylene concentration and the residence time. However, under the condition of high hydrogen concentration, when the monomer concentration is increased, the hydrogen concentration is concomitantly increased. And the operating pressure naturally increases. Specific activity (Rs) of a catalyst for forming a relatively low molecular weight ethylene copolymer having [η] = 1
p, H) is not less than 800 g / g · hr · Kg / cm 2, and the specific activity (Rsp, L) of the catalyst for producing a relative high molecular weight polymer satisfying [η] ≧ 2 and the above-mentioned Rsp, H The catalyst is not limited as long as it has a high activity that satisfies the range of 1 <Rsp, L / Rsp, and H <3, but the above-mentioned catalyst system is particularly preferable.

When a polymer mixture is produced in the first stage with a low molecular weight component and in the second stage with a high molecular weight component, for example, if the above-mentioned catalyst system is used, Rsp, L / Rsp, H
= 3, but in the reverse order, that is, when a high molecular weight component is produced in the first stage and a low molecular weight component is produced in the second stage, Rsp, L / Rsp, H = 1.2 ~ 2
It was found that the activity ratio in both stages was very close to 1. From both sides, it is necessary to produce a high molecular weight component in the first stage and a low molecular weight component in the second stage.

In the first stage, a copolymerization reaction of a copolymer of ethylene and α-olefin of [η] ≧ 2 is carried out while adjusting the hydrogen concentration in the liquid phase by the weight ratio to the ethylene concentration. The concentration of hydrogen to ethylene in the liquid phase is generally 1.0 × 10 ⁻³ (weight ratio) or less in the presence of hydrogen. The copolymer of ethylene and α-olefin produced in the first stage is a high molecular weight compound having [η] of 2.0 or more, and the content of α-olefin in the copolymer is 0.2 to 5% by weight is common, especially 0.5%
~ 2.5% by weight is preferred.

In the second stage, [η] is 0.3-1.
The copolymer of ethylene and α-olefin in the range of 0 was prepared by adjusting the concentration ratio of the hydrogen concentration to the ethylene concentration in the liquid phase to 1
The reaction is carried out by copolymerizing the α-olefin in the reaction mixture flowing from the first stage while maintaining it at 0 to 50 × 10 ⁻³ (weight ratio), or by supplying the α-olefin to the second stage if necessary. good.

Accordingly, in the second stage, a copolymer having a relatively low molecular weight and a degree of branching lower than the comonomer content of the copolymer of ethylene and α-olefin formed in the first stage is produced. The polymerization is carried out in each reaction step so that the proportion of the first-stage high molecular weight copolymer and the second-stage low molecular weight polymer in the total polymer mixture is 30 to 70% by weight and 70 to 30% by weight, respectively. Do. The first-stage and second-stage polymerizations may be performed in a batch system, but are preferably performed in a continuous polymerization system from the viewpoint of productivity.

In the present specification, the intrinsic viscosity [η] is 13
Represents the intrinsic viscosity at 5 ° C in a decalin solvent. Since the weight additivity with respect to the intrinsic viscosity is satisfied, the intrinsic viscosity [η] b of the ethylene polymer produced in the second-stage reaction zone can be obtained by the following equation. [Η] b = ([η] c-Wa [η] a) / Wb where [η] c is the intrinsic viscosity of the entire polymer, and [η] a is the ethylene polymer produced in the first-stage reaction zone. Intrinsic viscosity, W
a and Wb represent the weight fraction of the polymer formed in the first and second reaction zones, respectively. (Wa + Wb = 1.0) [η] a of the copolymer formed in the first stage is 2 or more and 6.2.
[Η] b of the low molecular weight polymer having the following intrinsic viscosity and produced in one second stage is larger than 0.40 and 0.7
A molecular weight in the range of less than 5 is chosen. Further, the molecular weight [η] c of the whole copolymer is preferably in the range of 2.0 to 3.5.

The ratio of the polymer formed in the first stage and the second stage is preferably 30 to 70% by weight of the total polymer, and the ratio of the high molecular weight copolymer formed in the first stage is particularly preferably 40 to 6%.
0% by weight is preferable in terms of impact strength, resistance to environmental stress cracking, and moldability.

The polymerization reaction is carried out at a temperature of 50 ° C. to 100 ° C. for 20 minutes to 10 hours under a pressure of 0.5 to 100 kg / cm ² , depending on the solvent used. . The reactor type may be a tank type (vessel type) or an annular type (loop type). In each stage of the reactor, the polymer concentration is generally 5 to 60% by weight, preferably 35 to 55% by weight from the viewpoint of productivity.

The polymer obtained as described above is preferably kneaded. It is also possible to use a single-screw or twin-screw extruder or a continuous kneader. After kneading, the obtained polymer has less fish eyes.

[0022]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. The method of the physical property test is as follows. The polymer powder was 65 mmφ, L / D = 26, full flight screw extruder (50 rpm, C ₁ = 160
_{℃, C 2 = 200 ℃,} C 3 = 220 ℃, D = 210 ℃)
, And physical properties were measured using the pelletized sample. The density was measured according to JIS-K-6760. High Road Melt Index (hereinafter “HLMI”)
Was measured under the conditions of a temperature of 190 ° C. and a load of 21.6 kg in accordance with JIS K-6760. The melt tension was measured by a melt tension tester type II manufactured by Toyo Seiki Seisaku-sho, Ltd. A molten resin at 190 ° C. is passed through an orifice having a diameter of 2.095 mm and a length of 8.000 mm to 17.9 mm ³ / s
extrude at a flow rate of ec and at room temperature 108 mm / sec.
The tension at the time of elongation and solidification at the speed of c was defined as the melt tension. The extrusion amount was measured by a 50 mmφ inflation molding machine manufactured by Yoshii Iron Works. The discharge amount per hour at a screw rotation speed of 90 rpm when a full flight screw with L / D = 26 was used was defined as the extrusion amount. A die for blown film having a diameter of 750 mm and a lip gap of 1.0 mm was attached to the extruder tip. The set temperature was set to 240 ° C. for the cylinder 1 and 230 ° C. for the cylinder 2 from below the hopper, and 220 ° C. for the cylinder 3, the crosshead and the die.

Example 1 (1) Preparation of Catalyst 2.1 mol of magnesium ethylate, 1.05 mol of titanium tetraisopropoxide and 0.21 mol of tetra-n-butylsilane were placed in a 20 L reaction vessel together with 4.4 L of heptane. The mixture was reacted at 90 ° C. for 2 hours with stirring to dissolve. After cooling to room temperature, 15.8 mol of ethyl aluminum dichloride was added so that the temperature in the reaction vessel did not exceed 40 ° C. After completion of the addition, the reaction was carried out at 60 ° C. for 1.5 hours. After cooling to room temperature, the solid product was
The washing was carried out until no halogen component was detected in the washing solution to obtain a solid catalyst component. The Ti content in the solid catalyst was 7.5%, and the Cl content was 48% by weight.

(2) Two-stage polymerization In a first-stage polymerization vessel having an internal volume of 200 L, 117 L / hr of dehydrated and purified isobutane and 1 L of triisobutylaluminum were used.
At a rate of 75 mmol / hr, 2.
At a rate of 55 g / hr, ethylene was continuously fed at 80 ° C. while discharging the contents of the polymerization vessel at a predetermined rate.
1.0 kg / hr, hexene-1 is 0.910 kg / h
r, and the hydrogen concentration in the liquid phase is 0.35 × 10 ^-3
(W / w), the hexene-1 to ethylene concentration ratio was 1.3.
(W / w), the first-stage copolymerization is continuously performed in a liquid-filled state under the conditions of a total pressure of 41 kg / cm ² and an average residence time of 0.80 hr.

Ethylene hexene-1 produced by copolymerization
Isobutane slurry containing copolymer (polymer concentration 23
Wt%, intrinsic viscosity of the polymer 5.50, hexene-1 content 1.05 wt%, copolymer density 0.929 g / c
m ³ ) was directly introduced into a second-stage polymerization vessel having an inner volume of 400 L through a continuous tube having an inner diameter of 50 mm, and 55 L / hr of isobutane and hydrogen were supplied without adding a catalyst, and the contents of the polymerization vessel were supplied at a predetermined speed. At 90 ° C., ethylene is supplied at a rate of 23.7 kg / hr while maintaining the ethylene concentration at 1.20 wt% and the hydrogen to ethylene concentration ratio at 30 × 10 ⁻³ (w / w). , Total pressure 41.
The second stage polymerization is carried out under the conditions of 0 kg / cm ² and a residence time of 1.05 hr.

The effluent from the second stage polymerization vessel contains 31% by weight of an ethylene polymer mixture, the intrinsic viscosity [η] of the polymer is 2.84, and the HLMI is 9.48 g / 10 mi.
n, the hexene-1 content of the comonomer was 0.75% by weight, and the density of the ethylene copolymer mixture was 0.951 g /
cm ³ . The production ratio of the first-stage and second-stage polymers is equivalent to 47:53, the intrinsic viscosity [η] of the ethylene copolymer produced only in the second-stage polymerization vessel is 0.49, and the hexene-1 content is 0.43% by weight and its density is 0.9
This corresponds to 65 g / cm ³ . The extruded amount in the blown film molding was 30.6 kg / hr, the melt tension of the film was excellent at 16.4 g, and an ethylene copolymer excellent in extrusion characteristics and melt properties was obtained. The specific activities of the first stage and the second stage are respectively Rsp, L = 6200 g / g · h
r · ethylene pressure Kg / cm ² , Rsp, H = 4400 g
/ G · hr · ethylene pressure Kg / cm ² .

Example 2 A solid catalyst component was prepared in the same manner as in Example 1 (1) except that the amount of ethylaluminum dichloride used was changed to 18.9 mol, and two-stage polymerization was carried out. Table 1 shows the results. An ethylene copolymer having excellent extrusion properties and melt properties was obtained.

Comparative Example 1 A solid catalyst component was prepared in the same manner as in Example 1 (1) except that the amount of ethylaluminum dichloride used was changed to 3.15 mol, and two-stage polymerization was carried out. Table 1 shows the results. The results were inferior in extrusion characteristics and melt properties.

Comparative Example 2 A solid catalyst component was prepared in the same manner as in Example 1 (1) except that the amount of ethylaluminum dichloride used was 42.0 mol, and two-stage polymerization was carried out. Table 1 shows the results. Although excellent in extrusion characteristics and melt properties, the polymerization activity was very low, resulting in poor productivity.

Example 3 A solid catalyst component was prepared in the same manner as in Example 1 (1) except that tetratert-butoxytitanium was used instead of tetraisopropoxytitanium, and two-stage polymerization was carried out. Table 1 shows the results. An ethylene copolymer having excellent extrusion properties and melt properties was obtained.

Comparative Example 3 A solid catalyst component was prepared in the same manner as in Example 1 (1) except that tetra-n-butoxytitanium was used instead of tetraisopropoxytitanium, and two-stage polymerization was carried out. Table 1 shows the results. The results were inferior in extrusion characteristics and melt properties.

Example 4 A solid catalyst component was prepared in the same manner as in Example 1 (1) except that tetraethylsilane was used instead of tetra-n-butylsilane, and two-stage polymerization was carried out. Table 1 shows the results. An ethylene copolymer having excellent extrusion properties and melt properties was obtained.

Comparative Example 4 In Example 1 (1), a solid catalyst component was prepared in the same manner as in Example 1 without using tetra-n-butylsilane, and two-stage polymerization was carried out. Table 1 shows the results. The results were inferior in extrusion characteristics and melt properties.

Example 5 Using the same catalyst and the same polymerization reactor as in Example 1, butene-1 was used instead of hexene-1 as a comonomer. Table 1 shows the results. An ethylene copolymer having excellent extrusion properties and melt properties was obtained.

Example 6 Using the same catalyst and the same polymerization reactor as in Example 1, two-stage polymerization was carried out while changing the production ratio of the first-stage and second-stage polymers. Table 1 shows the results. An ethylene copolymer having excellent extrusion properties and melt properties was obtained.

[0036]

[Table 1]

[0037]

According to the present invention, an ethylene copolymer having excellent extrusion properties and melt properties can be produced, which is industrially valuable.

[Brief description of the drawings]

FIG. 1 is a flowchart of catalyst preparation in a production method of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Maki No. 2 in Oita City, Oita Prefecture Showa Denko KK Oita Research Laboratories (56) References JP-A-62-167303 (JP, A) Showa 64-36607 (JP, A) Table 5-5-526 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 4/65-4/658

Claims (1)

(57) [Claims] In producing a ethylene-based copolymer by two-stage polymerization in which ethylene and an α-olefin are polymerized with a high molecular weight component in a first polymerization zone and a low molecular weight component in a second polymerization zone, A magnesium alcoholate represented by a general formula Mg (OR ¹ ) ₂ (R ¹ represents an alkyl group, a cycloalkyl group, an aryl group and an aralkyl group); a general formula Ti (OR ² ) ₄ (R ² is a secondary or A tetraalkoxytitanium compound represented by a tertiary hydrocarbon group) and a general formula SiR ³ R ⁴ R ⁵ R ⁶ (where R ^{3 to} R ⁶ are aliphatic hydrocarbon groups, and at least one R is carbon) A tetraalkylsilane compound represented by the formula
After dissolving in an inert hydrocarbon solvent in the range of i = 1 to 4 molar ratio and Si / Ti = 0.1 to 5 molar ratio, the compound represented by the general formula R ⁷ AlX ₂ (R ⁷ is an alkyl group, a cycloalkyl group ,
A solid catalyst component obtained by treating an aryl group and an aralkyl group with a dihalogenated organoaluminum compound represented by the formula (X represents a halogen atom) at a molar ratio of Al / Ti = 5 to 20; For producing an ethylene copolymer using a catalyst system comprising: