JPS6410532B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a polymerization method (in the present invention, a copolymer is included) that can produce a high bulk density ethylene polymer (including an ethylene copolymer in the present invention) with high catalytic efficiency using a highly active titanium catalyst component. (including polymerization methods). Many proposals are already known regarding highly active solid titanium catalyst components containing magnesium, titanium, and halogen as essential components. When these titanium catalyst components are used in the polymerization of olefin in combination with an organometallic compound catalyst component of a metal from Group 1 to Group 3 of the periodic table, the amount of titanium per 1 mmol of titanium is
More than 5000g of olefin polymer can be obtained. The polymerization can be carried out like slurry polymerization or gas phase polymerization.
When conducting polymerization under conditions that directly produce a polymer powder, it is desirable to increase the bulk density of the polymer powder as much as possible in order to perform the polymerization operation and post-treatment operations advantageously and smoothly. There is. In the highly stereoregular polymerization of an α-olefin having 3 or more carbon atoms using a solid titanium catalyst component that particularly has an electron donor, after prepolymerizing a small amount of α-olefin at a low temperature,
The present applicant has already proposed that by carrying out main polymerization of α-olefin at a higher temperature, not only the bulk density but also the stereoregularity index and catalytic activity can be improved. When such a method was applied sluggishly to the polymerization of ethylene, no significant improvement effect was necessarily observed, and it seemed as if no significant improvements in bulk density or activity could be achieved. Previously, for example, JP-A-55-9610 and JP-A-55-
No. 29512 discloses that after prepolymerizing α-olefin,
A method of gas-phase polymerization of ethylene has been proposed, and it is said that effects such as improvement of activity and particle size distribution and prevention of polymer adhesion to the reactor wall can be achieved. However, when the present inventors tried the methods specifically disclosed in these publications, the reproducibility of the polymerization reaction results was poor, and the polymerization activity was higher and bulkier when no prepolymerization was performed. It has been found that cases often arise in which polyethylene with a high density is obtained. Furthermore, even when improvement in activity is observed,
It was found that no significant improvement in the bulk density of polyethylene was achieved. The present inventors conducted research to develop a method for obtaining polyethylene with high bulk density with high catalytic efficiency and good reproducibility by slurry polymerization or gas phase polymerization. As a result, surprisingly, by using as the solid titanium catalyst component a component that satisfies specific properties that are not mentioned in the previous proposals, and by adopting specific prepolymerization conditions, it is possible to improve the bulk density. , found that significant improvements in catalytic activity and particle size distribution can be achieved. That is, according to the research of the present inventors, the following (A) and (B), (A) a solid titanium catalyst component containing magnesium, titanium, and a halogen as essential components, and (B) a solid titanium catalyst component containing magnesium, titanium, and halogen as essential components; In a method of polymerizing ethylene using a catalyst formed from a group 3 metal organometallic compound catalyst component, component (A) has a specific surface area of 40 m ² /
Using the solid titanium catalyst component having an average particle diameter of 3 to 200 μg and a geometric standard deviation of particle size distribution σg of less than 2.1, 0.01
Prepolymerize to 50g of olefin, and then use the prepolymerized titanium catalyst component.
By carrying out the main polymerization of ethylene at a temperature of 100°C or lower, and by setting the rate of the preliminary polymerization to at least about 1/5 or less of the rate of the main polymerization, ethylene polymers with high bulk density can be produced. It has been discovered that the combination can be produced with high catalytic efficiency and good quality reproducibility. Accordingly, it is an object of the present invention to provide an improved method for producing ethylene polymers. The above objects and many other objects and advantages of the present invention will become more apparent from the following description. Solid titanium catalyst component (A) used in the present invention
contains titanium, magnesium and halogen as essential components. The titanium catalyst component also contains various electron donors; metals and elements such as aluminum, silicon, tin, boron, germanium, calcium, zinc, phosphorus, vanadium, and manganese; and functional groups such as alkoxyl groups, allyloxyl groups, and acyloxyl groups. It may further contain a group; and the like. These can be achieved by reacting a magnesium compound (or magnesium metal) and a titanium compound, for example directly or in the presence of one or more compounds of an electron donor or said other metal or element, or It can be obtained by pre-treatment with one or more compounds of the elements and then reacting them. The halogen/titanium molar ratio contained in the component is preferably greater than 4 and the magnesium/titanium molar ratio is preferably greater than 4.
The titanium molar ratio is preferably 2 or more, particularly 3
50 to 50, and usually the titanium compound is not substantially removed by simple means such as washing with hexane at room temperature. Although its chemical structure is unknown, it is thought that the magnesium and titanium atoms are strongly bonded by sharing a halogen.
The titanium catalyst component also contains organic or inorganic inert diluents such as LiCl, CaCO ₃ , BaCl ₂ , Na ₂ CO ₃ ,
SrCl ₂ , B ₂ O ₃ , Na ₂ SO ₄ , Al ₂ O ₃ , SiO ₂ , TiO ₂ ,
_NaB4O7 , _CO3 ( _PO4 ) ₂ , _{CaSO4 , Al2} ( _SO4 ) ₃ ,
CaCl ₂ , ZnCl ₂ , polyethylene, polypropylene,
It may also contain polystyrene or the like. A good solid titanium catalyst component has a halogen/titanium (molar ratio) greater than 4, preferably from 6 to 100, a magnesium/titanium (molar ratio) greater than 2, preferably 3 to 50, and an electron donor. The electron donor/titanium (molar ratio) is 10 or less, preferably 6 or less, for example 0.2 to 6, and the specific surface area is 40 m ² /g or more, more preferably 100 to 800 m ² /g. It is g. In addition, the X-ray spectrum of the titanium catalyst component may be amorphous regardless of the starting magnesium compound, or may be in a highly amorphous state compared to that of ordinary commercially available magnesium dihalides. desirable. The titanium catalyst component used in the present invention also has an average particle size of 3 to 200μ, preferably 5 to 200μ.
100μ, and the geometric standard deviation σg of particle size distribution is less than 2.1, preferably 1.95 or less. Further, the titanium catalyst component preferably has a relatively regular shape, such as a spherical shape, an ellipsoidal shape, or a granular shape. In addition, the particle size and σg
can be measured by a light transmission method in a suspended state in a liquid hydrocarbon before drying. In other words, dilute the catalyst component to a concentration of around 0.01 to 0.5%, place it in a measurement cell, shine a narrow light into the cell, and continuously measure the intensity of light that passes through the liquid in a settled state with particles. to measure the particle size distribution. Based on this particle size distribution, the standard deviation σg is determined from a lognormal distribution function. Note that the average particle diameter of the catalyst is shown as a weight average diameter. In order to obtain a solid titanium catalyst component having the above-mentioned properties, for example, a magnesium compound is made to have a narrow particle size distribution before being reacted with a titanium compound, and titanium which forms a liquid phase under the reaction conditions is mixed with the magnesium compound. It is preferable to adopt a method in which compounds are reacted, or a method in which a liquid magnesium compound and a liquid titanium compound are reacted and precipitated under conditions that yield particles with a narrow particle size distribution. For example, JP-A-52-38590, JP-A-53-146292,
Japanese Patent Publication No. 54-41985, Japanese Patent Application No. 54-43002, Japanese Patent Application No. 1983
Catalyst preparation can be carried out using techniques such as No. 54-43003 and Japanese Patent Application No. 54-75582. A few examples of these methods will be briefly described. (1) An oxygen-containing magnesium compound or a complex compound of a magnesium compound and an electron donor with an average particle size of 3 to 200μ and a σg of less than 2.1 is reacted with an electron donor and/or an organoaluminum compound or a halogen-containing silicon compound. The reaction is carried out with or without pretreatment with auxiliaries with a halogenated titanium compound, preferably titanium tetrachloride, which forms a liquid phase under the reaction conditions. (2) A liquid magnesium compound that does not have reducing ability and a liquid titanium compound are reacted in the presence or absence of an electron donor to form particles with an average particle size of 3.
to 200 μ and a titanium catalyst component having a σg of less than 2.1 is precipitated. (3) The material obtained in (2) above is further reacted with a titanium compound. (4) The material obtained in (1) or (2) above is further reacted with an electron donor and a titanium compound. (5) In addition to those obtained in (1) and (2) above, electron donors,
The titanium compound and the organoaluminum compound are further reacted. In the present invention, magnesium compounds used in the preparation of the titanium catalyst component include magnesium oxide, magnesium hydroxide, hydrotalcite, magnesium carboxylate, alkoxymagnesium, allyloxymagnesium, and alkoxymagnesium produced by various methods. Examples include halide, allyloxymagnesium halide, magnesium dihalide, etc., or reactants of organic magnesium compounds with silanol, siloxane, etc. The organoaluminum compound that may be used in the preparation of the titanium catalyst component can be appropriately selected from organoaluminum compounds that can be used in the olefin polymerization described below. Furthermore, examples of halogen-containing silicon compounds that may be used for preparing the titanium catalyst component include silicon tetrahalides, silicon alkoxy halides, silicon alkyl halides, and halopolysiloxanes. The titanium compound used for preparing the titanium catalyst component may be titanium tetrahalide, alkoxytitanium halide, allyloxytitanium halide, alkoxytitanium, allyloxytitanium, etc., and titanium tetrahalide is particularly preferred, with titanium tetrachloride being particularly preferred. . Electron donors that can be used to produce titanium catalyst components include oxygen-containing electron donors such as alcohols, phenols, ketones, aldehydes, carboxylic acids, esters, ethers, acid amides, and acid anhydrides, ammonia, amines, and nitriles. , a nitrogen-containing electron donor such as isocyanate, and the like can be used. More specifically, alcohols with 1 or more carbon atoms such as methanol, ethanol, propanol, pentanol, hexanol, octanol, 2-ethylhexanol, dodecanol, octadecyl alcohol, benzyl alcohol, phenylethyl alcohol, cumyl alcohol, isopropylbenzyl alcohol, etc. 18 alcohols; Phenols having 6 to 15 carbon atoms which may have a lower alkyl group such as phenol, cresol, xylenol, ethylphenol, propylphenol, cumylphenol, naphthol; acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone Ketones with 3 to 15 carbon atoms, such as , benzophenone; Ketones with 2 carbon atoms, such as acetaldehyde, propionaldehyde, octylaldehyde, benzaldehyde, tolualdehyde, naphthaldehyde, etc.
to 15 aldehydes; methyl formate, methyl acetate, ethyl acetate, vinyl acetate, propyl acetate, octyl acetate, cyclohexyl acetate, ethyl propionate, methyl butyrate, ethyl valerate, methyl chloroacetate, ethyl dichloroacetate, methyl methacrylate, Ethyl crotonate, ethyl cyclohexanecarboxylate, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, octyl benzoate, cyclohexyl benzoate, phenyl benzoate, benzyl benzoate, methyl toluate, ethyl toluate, toluyl Amyl acid, ethyl ethylbenzoate, methyl anisate, ethyl anisate, ethyl ethoxybenzoate, γ-butyrolactone, δ
-Organic acid esters with 2 to 18 carbon atoms such as valerolactone, coumarin, phthalide, and ethylene carbonate; Inorganic acid esters such as ethyl silicate; Carbon number such as acetyl chloride, benzoyl chloride, toluyl chloride, anisyl chloride, etc. 2 to 15 acid halides; ethers with 2 to 20 carbon atoms such as methyl ether, ethyl ether, isopropyl ether, butyl ether, amyl ether, tetrahydrofuran, anisole, diphenyl ether; acetamide, benzoic acid amide, toluic acid amide Acid amides such as methylamine, ethylamine, diethylamine, tributylamine, piveridine, tribenzylamine,
Examples include amines such as aniline, pyridine, picoline, and tetramethylethylenediamine; nitriles such as acetonitrile, benzonitrile, and tolnitrile; and the like. Two or more types of these electron donors can be used. The electron donor desirably contained in the titanium catalyst component (A) is one having no active hydrogen among the above-mentioned examples, and esters and ethers of organic acids or inorganic acids are particularly preferable. Examples of the (B) organometallic compound catalyst component of metals from Groups 1 to 3 of the periodic table used in the present invention include organometallic compounds such as alkali metals, magnesium, zinc, and aluminum, and two or more of these may be used. They may be used in combination. Particularly preferred are organic aluminum compounds. As such organoaluminum compounds,
Compounds having at least one Al-carbon bond in the molecule can be used, for example, (i) compounds with the general formula R ¹ _n Al
^{( OR 2} _{) o} H _p m is 0<m≦3, n is 0≦n<3, p
is a number of 0≦p<3, q is a number of 0≦q<3, and m+n+p+q=3), (ii) a general formula M ¹ AlR ¹ ₄ (where M ¹ Examples include complex alkylated products of Group 1 metals represented by Li, Na, and K (where R ¹ is the same as above) and aluminum. Examples of the organoaluminum compounds that belong to (i) above include the following. General formula R ¹ _n Al
(OR ₂ ) _3-n (where R ¹ and R ² are the same as above. m
is preferably a number of 1.5≦m≦3). general formula
R ¹ _n AlX _3-n ) where R ¹ is the same as above. X is halogen, m is preferably 0<m<3), general formula R ¹ _n AlH _3-n (where R ¹ is the same as above, m is preferably 2≦m<3), general Formula R ¹ _n Al(OR ² ) _o
X _q (where R ¹ and R ² are the same as before, X is halogen, 0<m≦3, 0≦n<3, 0≦q<3, m
+n+q=3). Among the aluminum compounds belonging to (i), more specifically, trialkyl aluminum such as triethyl aluminum and tributyl aluminum,
In addition to trialkenylaluminums such as triisoprenylaluminum, dialkylaluminum alkoxides such as diethylaluminum ethoxide, dibutylaluminum butoxide, alkylaluminum sesquialkoxides such as ethylaluminum sesquiethoxide, butylaluminum sesquibutoxide, R ¹ _2.5 Al ( ^OR2 ) Partially alkoxylated alkylaluminums, dialkylaluminum halides such as diethylaluminum chloride, dibutylaluminum chloride, diethylaluminium bromide, ethylaluminum sesquichloride, butylaluminum sesquichloride, with an average composition expressed as _0.5, etc. Alkylaluminum sesquihalides like ethylaluminum sesquibromide, partially halogenated alkylaluminums such as alkylaluminum dihalides like ethylaluminum dichloride, propylaluminum dichloride, butylaluminum bromide, etc., diethylaluminum hydride, dibutylaluminum hydride Partially hydrogenated alkyl aluminum hydrides such as dialkyl aluminum hydride, ethyl aluminum dihydride, alkyl aluminum dihydride such as propyl aluminum dihydride, ethyl aluminum ethoxy chloride, butyl aluminum butoxy chloride, ethyl aluminum ethoxy bromide etc. It is alkoxylated and halogenated alkyl aluminum. In addition, as a compound similar to (i), 2
It may be an organoaluminum compound in which the above aluminum is bonded. Examples of such compounds include (C ₂ H ₅ ) ₂ AlOAl(C ₂ H ₅ ) ₂ , (C ₄ H ₉ ) ₂ AlOAl
( _C4H9 ) _{2 ,}

〔polymerization〕

200ml hexane, 5.1mmol triethylaluminum, methyl p-toluate in a 300ml flask.
1.7 mmol, and 3 g of the above titanium catalyst component (A)
(5.1 mmol) in this order, followed by 30 min under normal pressure.
Propylene was fed for 1 hour at ℃, and per gram of the catalyst
3.2g of propylene was prepolymerized. Charge hexane 1 into autoclave 3 and add triisobutylaluminum under _N2 atmosphere.
1.0 mmol and the titanium catalyst component (A) prepolymerized as described above were charged in an amount of 0.01 mmol in terms of Ti atoms. Next, 4Kg/cm ² of hydrogen was charged, and the total pressure was 8Kg/cm ²
Polymerization was carried out at 80°C for 2 hours while adding ethylene so that After the polymerization was completed, the slurry containing the polymer was filtered to obtain 191 g of white powdery polymer.
Its bulk density was 0.42 g/ml and MI was 3.6. In addition, the average particle size of the polymer is 420μ, and the particle size distribution is 0.1 to 1.0.
mm, and the shape was spherical. Therefore, the average polymerization rate of this polymerization is 16300g-PE/g
(A) Ingredient/hr. Examples 2 to 13, Comparative Example 1 Table 1 shows the results of polymerization performed in the same manner as in Example 1 except that the prepolymerization conditions were changed.
Shown below.

【table】

〔polymerization〕

200ml hexane, 1.13mmol triethylaluminum, ethyl benzoate in a 300ml flask
0.38 mmol and 3 g of the above titanium catalyst component (A)
(1.13 mmol) in this order, followed by 25 min under normal pressure.
Propylene was fed for 1 hour at ℃, and per gram of the catalyst
2.6g of propylene was prepolymerized. Ethylene polymerization was carried out in the same manner as in Example 1 using the titanium catalyst component (A) prepolymerized as described above. As a result, 129 g of a white powdery polymer was obtained, with a bulk density of 0.44 g/ml and an MI of 0.8. Also,
The average particle size of the polymer is 510μ, the particle size distribution is 0.1-1.0
mm, and the shape was spherical. Therefore, the average polymerization rate of this polymerization is 2400g-PE/g-
(A) Ingredient/hr. Example 15 [I] Catalyst synthesis 4.8 g of anhydrous MgCl ₂ and decane in a 200 ml flask
15 ml of 2-ethylhexanol and 18 ml of 2-ethylhexanol were added, and a heating reaction was carried out at 120° C. for 2 hours to obtain a homogeneous solution, and then 0.84 ml of ethyl benzoate was added. Pour 200ml of TiCl ₄ into a 400ml flask and heat to 0°C.
The entire amount of the above homogeneous solution was added to 1
After dropping over a period of time, the temperature was raised to 80°C.
After stirring at 80°C for 2 hours, the solid part was collected by filtration, suspended in 200ml of fresh _TiCl4 , and
Stirred at ℃ for 2 hours. After the stirring was completed, the solid portion collected by hot filtration was thoroughly washed with hot kerosene and hexane to obtain a titanium catalyst component (A). The catalyst contains Ti4.8wt%, Cl59wt%, Mg18wt%
The average particle diameter was 4.0μ, the geometric standard deviation of particle size distribution σg was 1.15, and the specific area was 248m ² /g. [Polymerization] 200 ml of hexane, 3.0 mmol of triethylaluminum, and 3 g (3.0 mmol) of the above titanium catalyst component (A) were added in this order to a 300 ml flask, and then propylene was supplied at 25°C under normal pressure for 1 hour to dissolve the catalyst.
3.0 g of propylene per gram was prepolymerized. Ethylene polymerization was carried out in the same manner as in Example 1 using the titanium catalyst component (A) prepolymerized as described above. As a result, 239 g of a white powdery polymer was obtained, with a bulk density of 0.43 g/ml and an MI of 18.8. Also,
The average particle size of the polymer is 140μ, and the particle size distribution is 0.1-1.0
mm, and the shape was granular. Therefore, the average polymerization rate of this polymerization is 12000g-PE/
g(A) component/hr. Comparative Example 2 Polymerization was carried out in the same manner as in Example 15, except that the preliminary polymerization using propylene was not performed. As a result, 154g of white powdery polymer with a density of 0.969
obtained, its bulk density is as low as 0.32g/ml, and its MI is 13.2
It was hot. In addition, the average particle size of the polymer is 190μ,
The particle size distribution was 89% from 0.1 to 100 mm. Therefore, the average polymerization rate of this polymerization was 7700 g-PE/g (A) component/hr. Comparative Example 3 [I] Catalyst synthesis 20 g of anhydrous MgCl ₂ and 3.4 g of tetra-n-butyl titanate were placed in a stainless steel (SUS-32) ball with an internal volume of 800 ml and a stainless steel ball (SUS-32) with an internal volume of 800 ml and containing a 2.8 kg ball made of stainless steel (SUS-32) with a diameter of 15 mm. SUS―
32) in a pulsating mill (7.8G).
Grind for 24 hours. The obtained co-pulverized material
It was suspended in 300 ml of TiCl ₄ and contacted at 110° C. for 2 hours with stirring. After the stirring was completed, the solid portion collected by hot filtration was thoroughly washed with hot kerosene and hexane to obtain a titanium-containing catalyst. The catalyst is Ti5.1wt
%, including Cl68wt%, Mg19wt%, average particle size
The particle size distribution had a geometric standard deviation σg of 2.40, and a specific surface area of 105 m ² /g. [Polymerization] 200 ml of hexane, 3.2 mmol of triethylaluminum, and 3 g (3.2 mmol) of the above titanium-containing catalyst were added in this order to a 300 ml flask, and then heated under normal pressure.
Propylene was fed at 25° C. for 1 hour to prepolymerize 2.7 g of propylene per 1 g of the catalyst. Ethylene polymerization was carried out in the same manner as in Example 1 using the titanium-containing catalyst prepolymerized as described above. The result is a white powdery polymer with a density of 0.966
112g was obtained, the bulk density was as low as 0.28g/ml, and the MI was
It was 4.7. In addition, the average particle size of the polymer is 220μ,
The particle size distribution was 72% between 0.1 and 1.0 mm. Therefore, the average polymerization rate of this polymerization was 6000 g-PE/g (A) component/hr. Example 16 100g of common salt pretreated with triethylaluminum was placed in the autoclave of 2 as a dispersion medium for the catalyst, followed by triisobutylaluminum.
Ti
0.012 mmol was charged in terms of atoms. Gas phase polymerization was carried out at 85° C. for 2 hours while charging 4 kg/cm ² of hydrogen and adding ethylene so that the total pressure was 8 kg/cm ² . After the polymerization was completed, the resulting polymer powder containing salt was washed with water and filtered to remove the salt, yielding 138 g of white powdered polyethylene, with a bulk density of 0.45 g/ml and an MI of
It was 4.0. In addition, the average particle size of the polymer is 320μ,
The particle size distribution was 99% between 0.1 and 1.0 mm, and the shape was spherical. Therefore, the average polymerization rate of this polymerization is
It was 9800g-PE/g(A) component/hr. Comparative Example 4 Ethylene gas phase polymerization was carried out in the same manner as in Example 16 without prepolymerizing the titanium catalyst component (A) of Example 1. As a result, 82 g of a white powdery polymer with a density of 0.968 was obtained, and its bulk density was 0.36 g/ml. In addition, the average particle size of the polymer is 250μ, and the particle size distribution is 0.1 to 1.0mm.
It was 88%. Therefore, the average polymerization rate of this polymerization was 5800 g PE/g (A) component/hr. Comparative Examples 5 to 7 Experiments were conducted based on Example 1 of JP-A-55-29512. That is, 10 g of anhydrous MgCl ₂ , 0.5 g of dichloroethane, and 3.3 g of TiCl ₃ / AlCl ₃ eutectic were mixed into a stainless steel (SUS-32) with a diameter of 15 mm in a nitrogen atmosphere.
Inner volume 800ml, inner diameter 100, containing 2.8Kg of made balls
Pour into a mm stainless steel (SUS-32) pot,
Milled in a pulsating mill for 16 hours. The titanium catalyst may be prepolymerized with propylene without prepolymerization, or with propylene prepolymerization in a manner similar to Example 1 of JP-A-55-29512, or alternatively with the preferred conditions of prepolymerization described in this invention. After polymerization, ethylene was subjected to gas phase polymerization in the same manner as in Example 16 of the present invention. The results are shown in Table 2. From these experiments, it was found that when propylene prepolymerization was performed using the titanium catalyst in the same manner as in Example 1 of JP-A No. 55-29512, the polymerization activity was poorer and the bulk was lower than when no prepolymerization was performed. Polyethylene with low density is obtained, and the effect of prepolymerization is hardly recognized. Furthermore, even when propylene prepolymerization is performed using the titanium catalyst under the preferable prepolymerization conditions described in the present invention, the degree of improvement in polymerization activity and bulk density is lower than when no prepolymerization is performed. It wasn't noticeable.

【table】

[Table] Example 17 Hexane 1 was charged into an autoclave with an internal volume of 2, and triethylaluminum 1.0 mmol and the titanium catalyst component obtained in Example 15 [I] were converted into titanium atoms at 30°C under an ethylene atmosphere. do
0.01 mmol was added. After prepolymerizing by supplying a small amount of ethylene for 1 hour while stirring, the temperature was raised to 60℃, hydrogen 4Kg/cm ² was charged, and ethylene was added so that the total pressure was 8Kg/cm ² at 80℃. Polymerization was carried out for 2 hours. After the polymerization was completed, the slurry containing the polymer was filtered to obtain 265 g of a white powdery polymer. Its bulk density was 0.41 g/ml and MI was 5.4. The polymer was granular and had an average particle size of 160μ.
The average polymerization rate of this polymerization was 13,000 g-PE/g (A) component/hr.

[Brief explanation of the drawing]

The drawing is a process flow diagram showing the steps for preparing a polymerization catalyst used in the method of the present invention.

Claims (1)

[Claims] 1 The following (A) and (B): (A) Magnesium, titanium and halogen are essential components, halogen/titanium (molar ratio) exceeds 4, magnesium/titanium (molar ratio) is 2 The specific surface area is 40m ² /g or more, the average particle size is 3 to 200μ, and the geometric standard deviation σg of the particle size distribution is
Using a catalyst formed from less than 2.1 g of a solid titanium catalyst component, (B) an organoaluminum compound catalyst component, and (C) optionally an electron donor, 0.01 to 50 g of olefin is preliminarily added per gram of said titanium catalyst component. and then main polymerization of ethylene at a temperature of 100°C or less using the prepolymerized titanium catalyst component, and the speed of the prepolymerization is at least 1% of the speed of the main polymerization. 1. A method for producing an ethylene polymer, which comprises producing an ethylene homopolymer or ethylene copolymer containing ethylene as a main component and having a density of 0.945 g/cm ³ or less and a density exceeding 0.945 g/cm 3 . 2 Claim 1 in which the amount of ethylene polymerized in the main polymerization is 100 times or more the amount of prepolymerization
The method described in section. 3. The method according to claim 1, wherein the olefin to be prepolymerized is ethylene. 4 Claim 1, wherein the olefin to be prepolymerized is an α-olefin having 3 to 6 carbon atoms.
The method described in section. 5. The method according to claim 4, wherein the prepolymerization temperature is about 50°C or less.