JP2002080520A - Ethylene polymer and method for producing the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] Excellent rigidity and environmental stress cracking (ESCR),
Provided is a method for efficiently producing an ethylene-based polymer suitable for blow-molded products, particularly, large-size blow-molded products. SOLUTION: An organic magnesium is added in an inert hydrocarbon solvent to a chromium catalyst component supported on an inorganic oxide carrier and calcined and activated in a non-reducing atmosphere and having at least a part of chromium atoms being hexavalent. An ethylene-based polymer is obtained by polymerizing ethylene using a supported chromium catalyst supported on organic magnesium and then dried by removing the solvent, and a catalyst system comprising tri (linear alkyl) aluminum as a co-catalyst. A method for producing, an ethylene-based polymer obtained by the method, and a large blow-molded product comprising the ethylene-based polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an ethylene polymer. More specifically, the present invention relates to a method for producing an ethylene-based polymer using a chromium catalyst supporting organomagnesium, a trialkylaluminum as a promoter, and only ethylene as a monomer. The ethylene-based polymer obtained by the method of the present invention has both excellent rigidity and environmental stress cracking (hereinafter, may be abbreviated as ESCR).
Blow-molded products formed from this ethylene-based polymer, particularly large-size blow-molded products, have excellent properties.

[0002]

2. Description of the Related Art Ethylene-based polymers are generally and widely used as resin materials for various molded articles, but required characteristics differ depending on their molding methods and applications. For example, a polymer having a relatively low molecular weight and a narrow molecular weight distribution is suitable for a product molded by an injection molding method, but a product having a relatively high molecular weight is suitable for a product molded by blow molding or inflation molding. Polymers having a wide molecular weight distribution are suitable. Conventionally, blow molding, especially large-sized, is carried out by using a chromium catalyst component (Philips catalyst) which is supported on an inorganic oxide carrier and activated by firing in a non-reducing atmosphere and at least a part of chromium atoms is hexavalent. It is known that an ethylene polymer having a wide molecular weight distribution suitable for blow molding can be obtained.

However, in recent years, there has been a demand for higher quality ethylene polymers suitable for large blow molding such as gasoline tanks and large drums. When a blow molded article is manufactured using an ethylene polymer having a wide molecular weight distribution obtained by the above chromium catalyst, the molded article has insufficient rigidity and environmental stress cracking (ESCR), and has high physical properties of both. It is difficult to say that the system has been able to respond to the customer's request.

Japanese Patent Application Laid-Open No. 2000-63422 discloses a method for producing a high-density polyethylene having improved mechanical properties, in which a two-stage polymerization using a Phillips catalyst is carried out in advance in a first-stage polymerization reactor. A method for producing an ethylene-based polymer by introducing a Phillips catalyst reduced with carbon oxide and introducing an alkyl metal and / or an alkyl metal oxane as a co-catalyst into a second-stage polymerization reactor is disclosed.

According to this production method, a comonomer α-olefin is produced from ethylene by the action of a cocatalyst,
Since this comonomer is copolymerized with ethylene, there is no need to supply the comonomer from the outside to the polymerization reactor. That is, a copolymer of ethylene and an α-olefin can be produced from ethylene alone without using an expensive comonomer as compared with ethylene, which is very advantageous in cost and has great industrial value.

However, in the above-mentioned method, in order to form a comonomer from ethylene, the Phillips catalyst must be reduced with carbon monoxide gas which is difficult to handle due to its high toxicity. Many.

Japanese Patent Application Laid-Open No. Sho 62-297305 also discloses that a trialkylboron compound, a dialkylaluminum alkoxide compound or a trialkylaluminum compound is used as a Phillips catalyst and a cocatalyst previously reduced with carbon monoxide to convert ethylene into ethylene. A method of producing a copolymer of ethylene and an α-olefin by forming a comonomer and copolymerizing the comonomer with ethylene is disclosed. Also in this case, it is necessary to reduce the Phillips catalyst with carbon monoxide gas which is difficult to handle in advance, and there are many safety problems when used in a production site. further,
Japanese Patent Publication No. 36-22144 discloses a supported Phillips catalyst, in which only alkylaluminum is supported.

[0008]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to solve the above-mentioned problems and to improve rigidity and environmental stress cracking (ES).
CR) are excellent both, and an object of the present invention is to provide a method for efficiently producing an ethylene-based polymer as a monomer from ethylene alone, which is particularly suitable for blow-molded products, and particularly for large-sized blow-molded products.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above-mentioned problems, and as a result, have found that polymerization is carried out by a catalyst system using a Phillips catalyst supporting organomagnesium and further using a trialkylaluminum as a promoter. The object has been solved by a method for producing an ethylene polymer, which is characterized in that the method is performed.

That is, a first aspect of the present invention is to add an inert carbon to a chromium catalyst component which is supported on an inorganic oxide carrier and fired and activated in a non-reducing atmosphere and at least a part of chromium atoms is hexavalent. The present invention relates to a method for producing an ethylene-based polymer, comprising supporting an organomagnesium in a hydride solvent, further removing the solvent, and drying to polymerize ethylene using an organomagnesium-supported chromium catalyst.

A second aspect of the present invention is to provide a chromium catalyst component, which is supported on an inorganic oxide carrier and calcined and activated in a non-reducing atmosphere, wherein at least a part of chromium atoms is hexavalent, contains an inert hydrocarbon. An organomagnesium-supported chromium catalyst obtained by supporting organomagnesium in a solvent, removing the solvent and drying, and a general formula (1)

R ³ R ⁴ R ⁵ Al (1) (wherein R ³ , R ⁴ and R ⁵ may be the same or different and each is a linear alkyl group having 1 to 18 carbon atoms) The present invention relates to a method for producing an ethylene-based polymer, characterized by polymerizing ethylene using a catalyst system comprising a trialkylaluminum represented by the formula:

A third aspect of the present invention is to provide a chromium catalyst component supported on an inorganic oxide carrier and calcined and activated in a non-reducing atmosphere and having at least a part of chromium atoms having a valence of six, and an inert hydrocarbon. Carrying the organomagnesium in the solvent, performing multistage polymerization of ethylene using a plurality of polymerization reactors connected in series using an organic magnesium supported chromium catalyst obtained by removing the solvent and drying. General formula (1) as a co-catalyst in at least the final stage polymerization reactor

## STR5 ## An ethylene-based polymer obtained by introducing a trialkylaluminum represented by R ³ R ⁴ R ⁵ Al (1) (wherein the symbols have the same meanings as described above) for polymerization. And a method for producing the same.

A fourth aspect of the present invention is that the organomagnesium compound is represented by the general formula (2):

R ¹ R ² Mg (2) wherein R ¹ and R ² may be the same or different,
Each represents an alkyl group having 1 to 18 carbon atoms. The present invention relates to the method for producing an ethylene polymer according to any one of the first to third inventions, which is a dialkylmagnesium represented by the formula (1).

A fifth aspect of the present invention is the first to third aspects in which the molar ratio of organomagnesium to chromium atoms is 0.1 to 5.
The present invention relates to a method for producing an ethylene-based polymer according to any one of the inventions. A sixth aspect of the present invention relates to the method for producing an ethylene polymer according to the second or third aspect, wherein the molar ratio of the trialkylaluminum to the chromium atom is 0.1 to 5. A seventh aspect of the present invention is that the trialkylaluminum has 4 carbon atoms.
The present invention relates to a method for producing an ethylene polymer according to the second or third invention, which is a trialkylaluminum having a straight-chain alkyl group of from 8 to 8.

An eighth aspect of the present invention is that the HLMFR is 1 to 100.
The present invention relates to the method for producing an ethylene polymer according to any one of the first to seventh inventions, which produces an ethylene polymer having a density of 0.935 to 0.955 g / cm ^{3 in} g / 10 minutes. The ninth aspect of the present invention is as follows.
HLMFR obtained by the method for producing an ethylene polymer according to any one of the first to seventh inventions, wherein the HLMFR is 1 to 100 g.
/ 10 minutes and an ethylene polymer having a density of 0.935 to 0.955 g / cm ³ .

A tenth aspect of the present invention relates to a blow molded product comprising the ethylene polymer of the ninth aspect. An eleventh aspect of the present invention relates to a large blow-molded product comprising the ethylene-based polymer of the tenth aspect.

According to the present invention, there is provided a method for efficiently producing an ethylene polymer which is excellent in both rigidity and environmental stress cracking (ESCR) and is suitable for blow molded products, especially large blow molded products, from ethylene monomer alone. Is done. Hereinafter, the present invention will be described specifically.

Chromium catalyst component The chromium catalyst component of the organomagnesium-supported chromium catalyst according to the present invention is supported on an inorganic oxide carrier and activated by calcination in a non-reducing atmosphere, and at least a part of chromium atoms is hexavalent. This is a chromium catalyst component. Such a chromium catalyst component is generally known as a Phillips catalyst.

For example, MP McDaniel, Advances in
Catalysis, Volume33, 47, 1985, Academic Press
Inc., MP McDaniel, Handbook of Heterogeneous
Catalysis, 2400, 1997, VCH, MB Welch et al., H
andbook of Polyolefins: Synthesis and Properties,
On page 21, 1993, Marcel Dekker et al. Provides an overview of this catalyst.

The chromium catalyst component is supported on an inorganic oxide carrier. As the inorganic oxide carrier, Periodic Table No. 2,
Oxides of Group 4, 13 or 14 metals are preferred. Specific examples include magnesia, titania, zirconia, alumina, silica, thoria, silica-titania, silica-zirconia, silica-alumina, and mixtures thereof. Among them, silica, silica-titania, silica-zirconia, and silica-alumina are preferred. In the case of silica-titania, silica-zirconia, silica-alumina,
As a metal component other than silica, titanium, zirconium or aluminum atom is 0.2 to 10% (hereinafter, unless otherwise specified,% means mass%), preferably 0.5.
What is contained is 7 to 7%, more preferably 1 to 5%. Preparation methods, physical properties and characteristics of carriers suitable for these chromium catalyst components are described by CE Marsden, Preparation
of Catalysts, Volume V, 215, 1991, Elsevier S
cience Publishers, by CE Marsden, Plastics, Rubb
er andComposites Processing and Applications, Volu
The outline is described in references such as me21, p.193, 1994.

The specific surface area of a carrier used for a general chromium catalyst is 50 to 1000 m ² / g, preferably 10 to 1000 m ² / g.
0 to 800 m ² / g, more preferably 200 to 600
Those having a range of m ² / g are used. The pore volume is 0.5 to 3.0 cm as a carrier used for a general chromium catalyst.
³ / g, preferably 0.7 to 2.7 cm ³ / g, more preferably 1.0 to 2.5 cm ³ / g. The average particle size is 10 to 200 μm as a carrier used for a general chromium catalyst, but is preferably 20 to 200 μm.
Those having a range of 150 μm, more preferably 30 to 100 μm are used.

The chromium compound to be supported on the inorganic oxide carrier may be any compound that can be activated by calcination in a non-reducing atmosphere after loading so that at least some of the chromium atoms become hexavalent. , Chromium halide, oxyhalide, chromate, dichromate, nitrate, carboxylate, sulfate, chromium-1,3
-Diketo compounds, chromate esters and the like. Specifically, chromium trioxide, chromium trichloride, chromyl chloride, potassium chromate, ammonium chromate, potassium dichromate, chromium nitrate, chromium sulfate, chromium acetate,
Tris (2-ethylhexanoate) chromium, chromium acetylacetonate, bis (tert-butyl) chromate and the like can be mentioned. Among these, chromium trioxide, chromium acetate and chromium acetylacetonate are preferred. Chromium compounds having an organic group such as chromium acetate and chromium acetylacetonate can also be used, and even when such a compound is used, the organic group portion is burned by firing activation in a non-reducing atmosphere described later. Finally, as with the case of using chromium trioxide, it reacts with hydroxyl groups on the surface of the inorganic oxide carrier, and at least some of the chromium atoms become hexavalent and are fixed in a chromate ester structure. Known (VJ Ruddick et al., J. Phys. Chem., Vol.
ume100, 11062, 1996, SM Augustine et al., J. C.
atal., Volume 161, p. 641, 1996).

The loading of the chromium compound on the inorganic oxide carrier can be carried out by a known method such as impregnation, solvent evaporation, sublimation, etc., and an appropriate method may be selected depending on the type of the chromium compound used. The amount of the chromium compound to be supported is 0.2 to 2.0%, preferably 0.3 to 1.7%, more preferably 0.5 to 1.5% as chromium atoms with respect to the carrier.

After the chromium compound is supported, it is fired to perform an activation treatment. The firing activation treatment is performed in a non-reducing atmosphere substantially free of moisture (for example, under oxygen or air), but an inert gas may coexist. Preferably, baking is carried out in a fluidized state using sufficiently dried air circulated through molecular sieves or the like.

The firing activation treatment is performed at 400 to 900 ° C., preferably 450 to 850 ° C., more preferably 500 to 900 ° C.
The reaction is performed at a temperature of 800 ° C. for 30 minutes to 48 hours, preferably 1 hour to 24 hours, and more preferably 2 hours to 12 hours. As a result, at least a part of the chromium atoms of the chromium compound supported on the inorganic oxide carrier is oxidized hexavalently and is chemically fixed on the carrier.

As described above, a chromium catalyst component supported on an inorganic oxide carrier can be obtained. In the chromium catalyst component used in the present invention, ethylene polymerization activity, copolymerizability with α-olefin, and ethylene For the purpose of adjusting the molecular weight or molecular weight distribution of the system polymer, before the chromium compound is loaded or before the firing activation after loading, titanium alkoxides such as titanium tetraisopropoxide, zirconium alkoxides such as zirconium tetrabutoxide, Metal alkoxides represented by aluminum alkoxides such as aluminum tributoxide, organoaluminums such as trialkylaluminum, organomagnesiums such as dialkylmagnesium, or organometallic compounds, and fluorine-containing salts such as ammonium silicofluoride Known methods may be used in combination of adding like. The organic group portion of these metal alkoxides or organometallic compounds is burned by activation in firing in a non-reducing atmosphere, oxidized to a metal oxide such as titania, zirconia, alumina or magnesia and contained in the catalyst. In the case of fluorine-containing salts, the inorganic oxide carrier is fluorinated. These methods are described by CE Marsden, Pla.
stics, Rubber and Composites Processing and Applica
tions, Volume 21, 193 pages, 1994, by T. Pullukat et al.,
J. Polym. Sci., Polym. Chem. Ed., Volume 18, 2857
Page, 1980, MP McDaniel et al., J. Catal., Volume 8
2, page 118, 1983, JP-B-64-6207, JP-A-57-19
No. 8705, Japanese Patent Publication No. 4-10483, Japanese Patent Publication No. 44-25695, Japanese Patent Publication No. 52-96686, Japanese Patent Publication No. 53-39992,
The outline or details are described in documents such as JP-A-49-38986.

[0027] In organomagnesium present invention, the organomagnesium is supported in an inert solvent in the firing activated chromium catalyst, to obtain an organic magnesium-supported chromium catalyst was further remove the solvent drying. As the organic magnesium, dialkyl magnesium, alkyl magnesium alkoxide, alkyl magnesium halide and the like are used. Among them, dialkylmagnesium represented by the following general formula (2) is preferable.

R ¹ R ² Mg (2) wherein R ¹ and R ² may be the same or different;
Represents an alkyl group having 1 to 18 carbon atoms. ) Specific examples of R ¹ and R ² include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-
Butyl, pentyl, hexyl, octyl, decyl, dodecyl and the like.

Specific examples of dialkyl magnesium include dimethyl magnesium, diethyl magnesium, di-n-propyl magnesium, diisopropyl magnesium, di-n-butyl magnesium, diisobutyl magnesium, di sec-butyl magnesium, dipentyl magnesium, dihexyl magnesium, dioctyl magnesium, Didecyl magnesium, didodecyl magnesium, methyl ethyl magnesium, methyl n-propyl magnesium, methyl isopropyl magnesium, methyl n-butyl magnesium, methyl isobutyl magnesium, methyl sec-butyl magnesium, methyl pentyl magnesium, methyl hexyl magnesium, methyl octyl magnesium, Methyl decyl magnesium, methyl dodecyl magne Um, ethyl n- propyl magnesium, ethylmagnesium isopropyl, ethyl n-
Butyl magnesium, ethyl isobutyl magnesium,
Ethyl sec-butyl magnesium, ethyl pentyl magnesium, ethylhexyl magnesium, ethyl octyl magnesium, ethyl decyl magnesium, ethyl dodecyl magnesium, n-propyl isopropyl magnesium, n-propyl n-butyl magnesium, n-
Propyl isobutyl magnesium, n-propyl sec
-Butylmagnesium, n-propylpentylmagnesium, n-propylhexylmagnesium, n-propyloctylmagnesium, n-propyldecylmagnesium, n-propyldodecylmagnesium, isopropyln-butylmagnesium, isopropylisobutylmagnesium, isopropylsec-butylmagnesium, Isopropyl pentyl magnesium, isopropyl hexyl magnesium, isopropyl octyl magnesium, isopropyl decyl magnesium, isopropyl dodecyl magnesium, n-butyl isobutyl magnesium, n-butyl sec-butyl magnesium, n-butyl pentyl magnesium, n-butyl hexyl magnesium, n-butyl octyl Magnesium, n-butyldecyl magnesium n- butyl dodecyl magnesium, isobutyl sec- butylmagnesium, isobutyl pentyl magnesium, iso butyl hexyl magnesium, isobutyl-octyl magnesium, isobutyl decyl magnesium, isobutyl dodecyl magnesium,
sec-butylpentylmagnesium, sec-butylhexylmagnesium, sec-butyloctylmagnesium, sec-butyldecylmagnesium, sec-
Butyl dodecyl magnesium, pentyl hexyl magnesium, pentyl octyl magnesium, pentyl decyl magnesium, pentyl dodecyl magnesium, hexyl octyl magnesium, hexyl decyl magnesium, hexyl decyl magnesium, octyl decyl magnesium, octyl dodecyl magnesium, decyl dodecyl magnesium, and the like.

Any mixture of two or more of these dialkylmagnesiums is also preferably used. Of these, di-n-butylmagnesium, diisobutylmagnesium, ethyl n-butylmagnesium, ethylisobutylmagnesium, ethylsec-butylmagnesium alone or an arbitrary mixture of two or more are preferred.

Organic magnesium-supported chromium catalyst The above-mentioned organic magnesium is supported on the above-mentioned calcined activated chromium catalyst component in an inert hydrocarbon solvent, and the solvent is removed and dried to obtain an organic magnesium-supported chromium catalyst.

By supporting organomagnesium, hexavalent chromium atoms after firing activation are reduced by organomagnesium, and a polymerization active site is formed when trialkylaluminum is used as a co-catalyst. -Active sites, which are by-products of olefins, are also formed. ADVANTAGE OF THE INVENTION According to this invention, since the highly toxic carbon monoxide is not used, the safety advantage of a manufacturing site can be enjoyed.

The amount of organomagnesium to be supported is such that the molar ratio to chromium atoms is from 0.1 to 5, preferably from 0.2 to 5.
4, more preferably in the range of 0.3 to 3. Within this range, the polymerization activity is greatly improved as compared with the case where no organomagnesium is supported. Further, when a trialkylaluminum is used as a cocatalyst, an α-olefin is efficiently produced as a by-product, and a copolymer of ethylene and an α-olefin can be produced from ethylene alone without lowering the polymerization activity. Also,
An ethylene polymer having improved environmental stress cracking (ESCR) can be produced. When the molar ratio is less than 0.1, the effect of improving the polymerization activity is low, and when a trialkylaluminum is used as a cocatalyst, the by-product effect of α-olefin is small, and a copolymer of ethylene and α-olefin is produced from ethylene alone. The cost merit of being able to do it is reduced. Further, the effect of improving environmental stress cracking (ESCR) is low. If the molar ratio exceeds 5, the polymerization activity is greatly reduced, and the production of the ethylene polymer itself becomes difficult.

As a method for supporting the organomagnesium, a chromium catalyst after calcination activation, propane, n-butane, isobutane, n-pentane, isopentane, hexane, heptane, octane, decane, cyclohexane, benzene, toluene, xylene, etc. Of the above inert hydrocarbon solvent to form a slurry state, and adding the organic magnesium to the slurry state.

The organomagnesium may be added as such, but may be an inert carbon such as propane, n-butane, isobutane, n-pentane, isopentane, hexane, heptane, octane, decane, cyclohexane, benzene, toluene and xylene. It is preferable to add it after diluting with a hydrogen hydride solvent. Any amount of solvent can be used as long as it can be stirred at least in a slurry state.

The temperature at which the organomagnesium is supported is 0.
To 150 ° C, preferably 10 to 100 ° C, more preferably 20 to 80 ° C, and the supporting reaction time is 5 minutes to 8 hours, preferably 30 minutes to 6 hours, and more preferably 1 to 4 hours.

The organomagnesium reacts with the chromium atom of the chromium catalyst component which has become at least partially hexavalent by the activation of firing, and the hexavalent chromium atom of the chromium catalyst component is reduced to a lower valent chromium atom. . This indicates that the chromium catalyst component after firing activation is orange, which is specific to hexavalent chromium atoms, while green or bluish green, which is specific to trivalent or divalent chromium atoms, after supporting organomagnesium. It can be estimated from the fact that

After the supporting reaction, it is essential that the solvent is removed under reduced pressure or separated by filtration and dried to separate the chromium catalyst supporting organomagnesium from the solvent as a free-flowing powder. If the catalyst is stored for a long time without being separated from the solvent after loading, the catalyst deteriorates with time and the ethylene polymerization activity is greatly reduced. In addition, when a trialkylaluminum is used as a co-catalyst, the by-product effect of an α-olefin also decreases. Details of this reason are unknown,
In the solvent, the reaction between the active site chromium of the chromium catalyst component and the organomagnesium continues to progress, and the ethylene polymerization reaction and α
-It is conceivable that the structure changes to a structure that inhibits olefin by-products.

Therefore, it is necessary to separate and remove the solvent immediately after the completion of the supporting reaction. For this purpose, it is preferable that the solvent be filtered off, separated and dried immediately after the completion of the supporting reaction. It is appropriate that the time required for this is within 3 times, preferably within 2 times, more preferably within 1 time of the supporting reaction time after the completion of the supporting reaction. It is preferred that the catalyst system after drying is in a free flowing free state. That is, the residual weight of the solvent is 1/10 or less, preferably 1/30, more preferably 1/100 or less of the weight obtained by multiplying the pore volume of the chromium catalyst component by the density of the solvent. preferable.

Trialkylaluminum In the present invention, a trialkylaluminum is used as a cocatalyst. That is, the polymerization is carried out by introducing a trialkylaluminum as a cocatalyst into the polymerization system separately from the chromium catalyst supporting organomagnesium. Trialkyl aluminum as a co-catalyst is represented by the general formula (1)

R ³ R ⁴ R ⁵ Al (1) (wherein R ³ , R ⁴ and R ⁵ may be the same or different and each is a linear alkyl group having 1 to 18 carbon atoms) Represents a trialkylaluminum.
Specific examples of R ³ , R ⁴ and R ^{5 in} the above formula include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-octyl, n-decyl, n-dodecyl And the like.

Specific examples of the trialkylaluminum include trimethylaluminum, triethylaluminum, trin-propylaluminum, trin-butylaluminum, trin-butylaluminum, trin-hexylaluminum, trin-octylaluminum and the like. Of these, trialkylaluminum having a straight-chain alkyl group having 4 to 8 carbon atoms, such as tri-n-butylaluminum, tri-n-hexylaluminum, and tri-n-octylaluminum, is preferable.

When only a chromium catalyst component supporting organomagnesium is used without using trialkylaluminum as a cocatalyst, there is an advantage that the polymerization activity is improved as compared with a case where no organomagnesium and trialkylaluminum are used at all. However, since the effect of by-producing α-olefin from ethylene is low for organomagnesium, the by-product α
-It is difficult to lower the density of the ethylene-based polymer only with the olefin, and the comonomer must be introduced into the polymerization reactor and copolymerized. Therefore, the advantage of the present invention that a copolymer of ethylene and an α-olefin can be obtained from ethylene alone is lost.

When the comonomer is introduced from the outside of the polymerization reactor without introducing the trialkylaluminum as a cocatalyst, the density is reduced by a by-product α-olefin by introducing the trialkylaluminum as a cocatalyst. Environmental stress cracking (ESCR) is inferior to the case. In addition, when the chromium catalyst component supporting organomagnesium is used and the trialkylaluminum is used as the promoter, the amount of by-product α-olefin increases and the lower An ethylene polymer having a high density is obtained. Further, environmental stress cracking (ESCR) is further improved.

Further, when a trialkylaluminum having a branched alkyl group such as isobutyl and isopentyl is used instead of a linear alkyl group as the alkyl group of the trialkylaluminum, the activity is greatly reduced and the α-olefin Since the by-product effect is low and the density remains almost the same as in the case of ethylene homopolymerization, it is necessary to introduce a comonomer into the polymerization reactor and copolymerize it. Therefore, the cost advantage of the present invention in which a copolymer of ethylene and an α-olefin can be obtained from ethylene alone is lost.

Method for Producing Ethylene Polymer The method for producing an ethylene polymer of the present invention using the above-described organomagnesium-supported chromium catalyst is carried out by a liquid phase polymerization method such as slurry polymerization or solution polymerization or a gas phase polymerization method. It can be carried out. The liquid phase polymerization method is usually performed in an inert hydrocarbon solvent. As the hydrocarbon solvent, propane, n-butane, isobutane, n-pentane, isopentane, hexane, heptane, octane, decane, cyclohexane,
A single or a mixture of inert hydrocarbons such as benzene, toluene and xylene is used. In the gas phase polymerization method, a commonly known gas phase polymerization method such as a fluidized bed and a stirring bed can be adopted in the presence of an inert gas, and a so-called condensing mode in which a medium for removing polymerization heat is optionally used may be employed. Can also.

The polymerization temperature in the liquid phase or gas phase polymerization method is generally from 0 to 300 ° C., and practically from 20 to 300 ° C.
The temperature is 200C, preferably 50-180C, more preferably 70-150C. The concentration of the catalyst and the concentration of ethylene in the reactor may be any concentrations as long as they are sufficient for the polymerization to proceed. Hydrogen can also be introduced as a chain transfer agent into the polymerization reactor to control the molecular weight.

In the present invention, by supplying only the ethylene monomer to the polymerization system, an ethylene polymer excellent in both rigidity and environmental stress cracking (ESCR), particularly for blow molded products, particularly for large blow molded products. In order to produce a suitable ethylene-based polymer, it is essential to carry out polymerization by introducing a trialkylaluminum represented by the general formula (2) as a cocatalyst into a polymerization reactor.

The amount of the trialkylaluminum introduced is such that the molar ratio to the chromium atoms is 0.1 to 5, preferably
The range is 0.2 to 4, more preferably 0.3 to 3. Within this range, the polymerization activity is significantly improved as compared with the case where no trialkylaluminum is introduced. By doing so, a copolymer of ethylene and an α-olefin can be produced using only ethylene as a monomer without lowering the polymerization activity. Further, environmental stress crack resistance (ESCR) is improved. When the molar ratio is less than 0.1, the effect of improving the polymerization activity is low, the by-product effect of α-olefin is small, and the cost merit of the present invention that a copolymer of ethylene and α-olefin can be produced from ethylene alone is reduced, Further, the effect of improving environmental stress cracking (ESCR) is reduced. If the molar ratio exceeds 5, the polymerization activity is greatly reduced, and the production of the ethylene polymer itself becomes difficult.

When ethylene is polymerized by introducing a trialkylaluminum as a co-catalyst, an α-olefin is by-produced from ethylene, and the α-olefin is copolymerized with ethylene.
An olefin copolymer can be obtained. The types of α-olefin by-produced by trialkylaluminum are 1-butene, 1-hexene, 1-octene and the like, and the amount of 1-hexene is particularly large. Accordingly, an ethylene polymer having short-chain branches such as ethyl branch, n-butyl branch and n-hexyl branch, particularly n-butyl branch can be obtained using only ethylene as a raw material. As the molar ratio of trialkylaluminum to chromium atoms in the organomagnesium-supported chromium catalyst increases, the density of the obtained ethylene polymer tends to decrease, and as the molar ratio increases, the amount of by-produced α-olefin increases. You can see that.

However, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl -1-pentene, 1-
Α-Olefins such as octene may be copolymerized alone or by introducing two or more kinds into a polymerization reactor. The α-olefin content in the obtained ethylene polymer is 15 m.
ol% or less, preferably 10 mol% or less.

The ethylene polymer obtained by the method of the present invention has an HLMFR of 0.1 to 1000 g / 10 min, preferably 0.5 to 500 g / 10 min, and a density of 0.900 to 0.980.
g / cm ^3, preferably of 0.920~0.970g / cm ^3. A molded article, particularly a large molded article, formed by a blow molding method using this ethylene-based polymer by an ordinary method has a feature that both rigidity and environmental stress cracking (ESCR) are excellent. HLM of such resin for blow molding products
The FR is suitably from 1 to 100 g / 10 min, and especially from 1 to 15 g / 10 min for the resin for large blow molded products.
The density is preferably 0.935 to 0.955 g / cm ³ , and particularly preferably 0.940 to 0.950 g / cm ³ for large blow molded products.

The polymerization method of the present invention can be carried out by a single-stage polymerization in which an ethylene-based polymer is produced by using one polymerization reactor, but a multi-stage polymerization in which at least two polymerization reactors are connected in order to broaden the molecular weight distribution. It is preferred to carry out the polymerization. In the case of multi-stage polymerization, two-stage polymerization is preferable, in which two polymerization reactors are connected, and the reaction mixture obtained in the first-stage polymerization reactor is continuously supplied to the second-stage polymerization reactor. The transfer from the first-stage polymerization reactor to the second-stage polymerization reactor is preferably carried out by using a connecting pipe and by a differential pressure due to continuous discharge of the polymerization reaction mixture from the second-stage polymerization reactor.

For example, when performing two-stage polymerization, the polymerization temperature,
A method for producing low-density, high-molecular-weight components in the first-stage polymerization reactor and high-density, low-molecular-weight components in the second-stage polymerization reactor by adjusting the hydrogen concentration and the comonomer concentration, or the first-stage polymerization reaction Any method may be used for producing high-density and low-molecular-weight components in a vessel and low-density and high-molecular-weight components in a second-stage polymerization reactor. However, the method of producing high-density, low-molecular-weight components in the first-stage polymerization reactor and low-density, high-molecular-weight components in the second-stage polymerization reactor is a comonomer in the transition from the first stage to the second stage. Α-olefin does not flow in, so that copolymerization can be performed only in the second-stage polymerization reactor, especially blow-molded products with improved rigidity and environmental stress cracking (ESCR), especially large blow-molded products It is more preferable since an ethylene copolymer suitable for the above is obtained.

The preferred two-stage polymerization method of the present invention for producing a high-density, low-molecular-weight component in the first-stage polymerization reactor and a low-density, high-molecular-weight component in the second-stage polymerization reactor is as follows. That is, in the first-stage polymerization reactor, using an organomagnesium-supported chromium catalyst, ethylene homopolymerization is performed, and the polymerization reaction is performed while controlling the molecular weight by the weight ratio or partial pressure ratio of hydrogen to ethylene or the polymerization temperature. Produces high density, low molecular weight components. In the second-stage polymerization reactor, the above-mentioned organomagnesium-supported chromium catalyst is used, and a trialkylaluminum represented by the general formula (1) is introduced as a co-catalyst.
The polymerization reaction is carried out while controlling the molecular weight by the weight ratio or the partial pressure ratio of the hydrogen in the reaction mixture flowing from the first stage and / or the hydrogen supplied in the second stage to ethylene as required, and the low-density and high-molecular-weight components are reduced. It is preferably manufactured.

As described above, an α-olefin is by-produced from ethylene by the action of trialkylaluminum and is copolymerized with ethylene to obtain an ethylene copolymer solely from ethylene. Propylene, 1-butene, 1-pentene, 1-
Α-olefins such as hexene, 4-methyl-1-pentene and 1-octene are supplied alone or in combination of two or more,
-The density of the ethylene copolymer may be adjusted by adjusting the weight ratio or partial pressure ratio of olefin to ethylene.

When produced by two-stage polymerization, low density
The ratio of the high molecular weight component to the high density / low molecular weight component is such that the low density / high molecular weight component is 10 to 90 parts by mass, the high density / low molecular weight component is 90 to 10 parts by mass, preferably the low density / high molecular weight component is 20 parts by mass. ~ 80 parts by mass, high density / low molecular weight component is 80
To 20 parts by mass, more preferably 30 to 70 parts by mass of the low density / high molecular weight component, and 70 to 3 parts by mass of the high density / low molecular weight component.
0 parts by mass. In addition, HLM of low density and high molecular weight components
As FR, 0.01 to 100 g / 10 minutes, preferably 0.1 to 100 g / 10 minutes.
01-50 g / 10 min, and the density of the low density / high molecular weight component is 0.900-0.950 g / cm ³ , preferably 0.910-0.94
5 g / cm ³ , and the MFR of the high density / low molecular weight component is 10 to 1000 g / 10 min, preferably 10 to 500 g
g / 10 minutes, the density of high-density and low-molecular-weight components is 0.95
0 to 0.980 g / cm ³ , preferably 0.955 to 0.970 g / cm ³
It is. HLM of ethylene polymer obtained by two-stage polymerization
The FR is 0.1 to 1000 g / 10 min, preferably 0.5 to 1000 g / 10 min.
Although it is 500 g / 10 minutes, it is 1 to 100 g / 10 minutes as a resin for blow molded products, and particularly 1 to 15 g / 10 minutes as a resin for large blow molded products. The density of the ethylene polymer obtained in the two-stage polymerization is 0.900 to 0.980
g / cm ^3, preferably a is an 0.920~0.970g / cm ³ blow molding product resin 0.935~0.955g / c
m ³ , especially 0.940-0.
It is 950 g / cm ³ .

The ethylene-based polymer obtained by the method of the present invention is preferable because the catalyst is deactivated by a conventional method and then further kneaded to obtain a more uniform ethylene-based polymer. The homogenizing operation can be performed using a single-screw or twin-screw extruder or a continuous kneader. At the time of kneading, conventionally known additives and the like can be blended. A blow-molded product can be easily obtained from the obtained ethylene-based polymer by blow molding according to a conventional method, and a large-sized blow-molded product can be similarly obtained. The blow-molded product thus obtained, especially a large blow-molded product, is characterized by having both excellent rigidity and environmental stress cracking (ESCR).

[0057]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples below, but the present invention is not limited to these examples. The measuring methods used in the examples and comparative examples are as follows.

A) Polymer pretreatment for measuring physical properties: Plastograph (Labo Plastomill ME25; roller shape: R608 type) manufactured by Toyo Seiki Seisaku-sho, Ltd., and Irganox B225 manufactured by Ciba-Geigy Co., Ltd. were used as additives.
2% was added and kneaded at 190 ° C. for 7 minutes under a nitrogen atmosphere.

B) Melt flow rate (HLMFR) Table 1, condition 7 of JIS K-7210 (1996 version)
The measured value at a temperature of 190 ° C. and a load of 211 N was shown as HLMFR. c) Density Measured according to JIS K-7112 (1996 version).

D) Molecular weight distribution (Mw / Mn) The resulting ethylene polymer was subjected to gel permeation chromatography (GPC) under the following conditions to obtain a number average molecular weight (Mn).
And the weight average molecular weight (Mw). Gel permeation chromatography measurement conditions: Apparatus: WATERS 150C model, Column: Shodex-HT806M, Solvent: 1,2,4-trichlorobenzene, Temperature: 135 ° C, Universal rating using monodisperse polystyrene fraction. Regarding the molecular weight distribution represented by the ratio of Mw to Mn (Mw / Mn) (the higher the Mw / Mn, the wider the molecular weight distribution), see “Size Exclusion Chromatography (High-Performance Liquid Chromatography of Polymers)” (written by Sadao Mori, By applying the data of n-alkane and fractionated linear polyethylene having Mw / Mn ≦ 1.2 to the equations of molecular weight and detector sensitivity described in Kyoritsu Shuppan, page 96), the molecular weight M represented by the following equation is obtained.
Was determined, and the measured value of the sample was corrected. Sensitivity of molecular weight M = a + b / M (a and b are constants, a = 1.032, b = 189.2)

E) Rigidity The flexural modulus measured according to JIS K-7203 (1996 edition) was taken as the value of rigidity. f) Environmental stress cracking (ESCR) The FTL value measured by the BTL method according to JIS K-6760 (1996 version) was taken as the value of ESCR (hr).

Example 1: (1) Preparation of chromium catalyst component CARiACT P-6 manufactured by Fuji Silysia Ltd. was placed in a 500 mL beaker.
Grade silica (specific surface area 450 m ² / g, pore volume
20 g (1.3 cm ³ / g, average particle size 40 μm) was added, and 50 mL of pure water was added to form a slurry. A solution obtained by dissolving 0.40 g of anhydrous chromium trioxide (manufactured by Wako Pure Chemical Industries, Ltd.) in 10 mL of pure water was added thereto with stirring, followed by stirring at room temperature for 1 hour. Water was removed by decantation, and drying was carried out in a constant temperature dryer at 110 ° C. for 12 hours to remove water. The obtained powder 15
g was placed in a quartz glass tube with a perforated plate and a tube diameter of 3 cm, set in a cylindrical electric furnace for firing, and fluidized with air through molecular sieves at a flow rate of 1.0 L / min.
The firing activation was performed at 600 ° C. for 18 hours. An orange chromium catalyst component indicating that it contains a hexavalent chromium atom was obtained. Chromium atom loading by elemental analysis is 1.01%
Met.

(2) Preparation of chromium catalyst supporting organomagnesium The above-mentioned (1) was placed in a 100 mL flask which had been purged with nitrogen in advance.
2 g of the chromium catalyst component obtained in the above was added, and 30 mL of hexane purified by distillation was added to obtain a slurry. Next, 3.9 ml of a 0.1 mol / L hexane solution of n-butylethylmagnesium (BuEtMg) manufactured by Tosoh Akzo Co., Ltd. (Mg / Cr molar ratio = 1) was added as an organic magnesium, and the mixture was further stirred at 40 ° C. for 2 hours. Immediately after the completion of the stirring, the solvent was removed under reduced pressure for 30 minutes, and the free flowing property (fr
ee flowing) was obtained. Hexavalent chromium was reduced and the catalyst turned green.

(3) Polymerization A 1.5 L autoclave sufficiently purged with nitrogen was charged with the organomagnesium-supported chromium catalyst 50 obtained in the above (2).
mg and 0.7 L of isobutane, and the internal temperature was raised to 102 ° C. Tosoh as trialkyl aluminum
Akzo's tri-n-butyl aluminum (n-Bu ₃ A
l) of a 0.01 mol / L hexane solution in 0.97 mL (Al
/ Cr molar ratio = 1) was introduced under pressure with ethylene, and polymerization was carried out at 102 ° C. for 1 hour while maintaining the ethylene partial pressure at 1.4 MPa. Then, the polymerization was terminated by discharging the content gas out of the system. As a result, 230 g of polyethylene was obtained. The polymerization activity per 1 hour of the polymerization time per 1 g of the catalyst was 4,600 g / g · hr. Physical properties (HLMFR, density, molecular weight (Mn, Mw), molecular weight distribution (Mw / Mn), rigidity, environmental stress cracking (ESC
Table 1 shows the measurement results of R)).

Example 2 Instead of n-butylethylmagnesium in Example 1 (2), 0.1 mol / l of di-n-butylmagnesium (Bu ₂ Mg) manufactured by Aldrich was used.
3.9 ml of hexane solution of L (Mg / Cr molar ratio = 1)
It added, further the first embodiment of Tosoh Akzo Corp. tri n- hexyl aluminum in place of tri-n- butylaluminum in _{(3) (n-Hx 3} Al) 0.01mol /
0.97 mL of L hexane solution (Al / Cr molar ratio = 1)
Except for the addition, an organomagnesium-supported chromium catalyst was prepared and polymerized in the same manner as in Example 1. as a result,
225 g of polyethylene were obtained. Per gram of catalyst,
The polymerization activity per one hour of the polymerization time was 4,500 g / g · hr. Table 1 shows the physical property measurement results.

Example 3 In Example 1 (3),
- butyl 0.01mol aluminum (n-Bu ₃ Al)
The polymerization was carried out in the same manner as in Example 1 (3) except that the amount of / hexane solution was changed to 1.94 mL (Al / Cr molar ratio = 2) and the polymerization temperature was changed to 100 ° C. As a result, 2
40 g of polyethylene were obtained. The polymerization activity per 1 g of the catalyst and 1 hour of the polymerization time was 4,800 g / g · hr. Table 1 shows the physical property measurement results.

Example 4: Gas phase polymerization G. Mabilon et al., Eur. Polym. J., Volume 21, p. 245, 1
Gas phase polymerization was carried out using a vertical vibration type reactor (capacity 150 cm ³ , diameter 50 mm, vibration speed 420 times / min (7 Hz), vibration distance 6 cm) similar to the fluidized bed reactor described in 985. . Example 1 was placed in a reactor which had been purged with nitrogen in advance.
20 mg of the organomagnesium-supported chromium catalyst obtained in (2)
In an ampoule under a nitrogen atmosphere.
After heating to 4 ° C., tri-n-butyl aluminum (n
-Bu ₃ Al) 0.39m in 0.01mol / L hexane solution
L (Al / Cr molar ratio = 1) was introduced under pressure with 1.4 MPa ethylene, and the polymerization was started by starting vibration and breaking the ampoule. 1.4MPa ethylene partial pressure in reactor
Ethylene was fed as needed via a flexible joint to maintain After polymerization was carried out at 105 ° C. for 15 minutes, ethylene feeding was stopped, the reactor was cooled to room temperature, degassed, and the contents were taken out. As a result, 21 g of polyethylene was obtained. Polymerization activity per 1 g of catalyst per 1 hour of polymerization time is 4200 g / g · h
r. Table 1 shows the physical property measurement results.

Example 5: Two-stage polymerization In a first-stage polymerization reactor having an internal volume of 200 L, 12 parts of isobutane were added.
0 L / hr, continuously supplying the organomagnesium-supported chromium catalyst obtained in Example 1 (2) at a rate of 5 g / hr, and discharging the polymerization reactor contents at a required rate.
At 4 ° C., the ethylene was kept at 20 kg / hr and the total pressure was 4.
Under the conditions of 1 MPa and an average residence time of 1.1 hr, the first-stage polymerization was continuously performed in a liquid-filled state. The entire amount of the slurry of isobutane containing the produced polymer was introduced into a second-stage polymerization reactor having an internal volume of 400 L as it was, through a connecting pipe having an inner diameter of 50 mm. hexane solution of 0.1 mol / L of ₃ Al) was fed at a rate of 9.7mL / hr (Al / Cr molar ratio of 1), isobutane at 100 ℃ (55L / hr)
And ethylene (22 kg / hr), total pressure 4.1M
The second-stage polymerization was performed under the conditions of Pa and an average residence time of 0.7 hr to obtain polyethylene. The ratio of low molecular weight components in the first stage is 5
5 parts by mass, and the ratio of the high molecular weight component in the second stage was 45 parts by mass. Further, the polymerization activity per 1 g of the first-stage catalyst and the polymerization time per hour was 3600 g / g · hr, and the polymerization activity per 1 g of the second-stage catalyst and the polymerization time per hour was 4400 g / hr.
g / g · hr. Table 1 shows the physical property measurement results.

Example 6: Two-stage polymerization In a first-stage polymerization reactor having an internal volume of 200 L, 12 parts of isobutane were added.
0 L / hr, the chromium catalyst supported on organomagnesium obtained in Example 2 was continuously supplied at a rate of 5 g / hr, and while discharging the contents of the polymerization reactor at a required rate, 20 kg / hr of ethylene was added at 104 ° C. And total pressure 4.1MP
a) The first-stage polymerization was continuously performed in a liquid-filled state under the conditions of an average residence time of 1.2 hr. The entire amount of the slurry of isobutane containing the produced polymer was directly introduced into a 400-L second-stage polymerization reactor through an interconnecting tube having an inner diameter of 50 mm, and tri-n-hexylaluminum (n-Hx) was introduced into the second-stage polymerization reactor. hexane solution of 0.1 mol / L of ₃ Al) was fed at a rate of 9.7mL / hr (Al / Cr molar ratio = 1), isobutane at 100 ℃ (55L / hr)
And ethylene (22 kg / hr), total pressure 4.1M
The second-stage polymerization was performed under the conditions of Pa and an average residence time of 0.7 hr to obtain polyethylene. The ratio of low molecular weight components in the first stage is 5
5 parts by mass, and the ratio of the high molecular weight component in the second stage was 45 parts by mass. The polymerization activity per 1 g of the first-stage catalyst was 3400 g / g · hr, and the polymerization activity per 1 g of the second-stage catalyst was 4200 g / hr.
g / g · hr. Table 1 shows the physical property measurement results.

Example 7: Two-stage polymerization In a first-stage polymerization reactor having an inner volume of 200 L, 12 parts of isobutane were added.
0 L / hr, continuously supplying the organomagnesium-supported chromium catalyst obtained in Example 1 (2) at a rate of 5 g / hr, and discharging the polymerization reactor contents at a required rate.
At 2 ° C., the ethylene was kept at 20 kg / hr and the total pressure was 4.
Under the conditions of 1 MPa and an average residence time of 1.1 hr, the first-stage polymerization was continuously performed in a liquid-filled state. The entire amount of the slurry of isobutane containing the produced polymer was introduced into a second-stage polymerization reactor having an internal volume of 400 L as it was through a connecting tube having an inner diameter of 50 mm, and tri-n-butylaluminum (n-Bu) was further introduced into the second-stage polymerization reactor. hexane solution of 0.1 mol / L of ₃ Al) was fed at a rate of 19.4mL / hr (Al / Cr molar ratio = 2), and supplies the isobutane (55L / hr) and ethylene (22 kg / hr) at 98 ° C. , Total pressure 4.1MP
a) The second stage polymerization was carried out under the conditions of an average residence time of 0.7 hr to obtain polyethylene. The ratio of low molecular weight components in the first stage is 55
The mass ratio of the high molecular weight component in the second stage was 45 parts by mass. The polymerization activity per 1 g of the first-stage catalyst was 3600 g / g · hr, and the polymerization activity per 1 g of the second-stage catalyst was 4600 g / h.
/ G · hr. Table 1 shows the physical property measurement results.

Example 8: In Example 1 (2), n-
After the addition of butylethylmagnesium was completed, the mixture was stirred at 40 ° C. for 2 hours, left in a slurry state at room temperature for 96 hours, and then the solvent was removed under reduced pressure to obtain a free flowing liquid (fr.
ee flowing) organochromium-supported chromium catalyst was obtained. Polymerization was carried out in the same manner as in Example 1 except that this catalyst was used. As a result, 60 g of polyethylene was obtained. The polymerization activity per 1 hour of the polymerization time per 1 g of the catalyst was 1200 g / g · hr. The measurement results of physical properties are as shown in Table 1. The polymerization activity was lower than that of Example 1, and α-
An ethylene homopolymer having a low density of olefin by-products and a high density was obtained.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 (3) except that 50 mg of the chromium catalyst component of Example 1 (1) was used and no tri-n-butylaluminum was added. As a result, 125 g of polyethylene was obtained.
The polymerization activity per 1 g of catalyst and the polymerization time per hour is 25
It was 00 g / g · hr. Table 1 shows the physical property measurement results.
An ethylene homopolymer having a high density was obtained because the activity was lower than that of Example 1 and no α-olefin was produced as a by-product. Although the stiffness is higher than that of Example 1, environmental stress cracking (ES
CR) is remarkably inferior.

Comparative Example 2: The chromium catalyst component of Example 1 (1) was replaced with 50 m of the chromium catalyst supported on organomagnesium.
Polymerization was carried out in the same manner as in Example 1 (3) except that g was used. As a result, 235 g of polyethylene was obtained.
The polymerization activity per 1 g of catalyst per hour of polymerization time is 47
It was 00 g / g · hr. Table 1 shows the physical property measurement results.
Compared with Example 1, an ethylene homopolymer having a lower density of by-products of α-olefin and a higher density was obtained. As compared with Example 1, although the stiffness was high, the environmental stress cracking (ESCR) was remarkably inferior.

Comparative Example 3 Example 1 (3) except that 50 mg of the chromium catalyst supported on organomagnesium of Example 1 (2) was used and tri-n-butylaluminum was not added.
Polymerization was carried out in the same manner as described above. As a result, 160 g of polyethylene was obtained. The polymerization activity per 1 g of the catalyst per 1 hour of the polymerization time was 3,200 g / g · hr. Table 1 shows the physical property measurement results. An ethylene homopolymer having a high density was obtained because the activity was lower than that of Example 1 and no α-olefin was produced as a by-product. As compared to Example 1, the stiffness was high, but the environmental stress cracking (ESCR) was significantly inferior.

Comparative Example 4: In Example 1 (2), 0.01 mol / l of butylethylmagnesium (BuEtMg) was added.
L of the hexane solution in an amount of 1.2 ml (Mg / Cr molar ratio = 0.0
3) Except for the addition, an organomagnesium-supported chromium catalyst was prepared and polymerized in the same manner as in Example 1 in all cases. As a result, 240 g of polyethylene was obtained. Polymerization activity per 1 g of catalyst per 1 hour of polymerization time is 4800 g / g · h
r. The measurement results of the physical properties are as shown in Table 1. The rigidity was equal to that of Example 1, but the environmental stress cracking (ESCR) was inferior.

Comparative Example 5: The same procedure as in Example 1 (2) was repeated except that the butyl ethyl magnesium (BuEtMg) content was 1.0 mol / mol.
L in 3.9 ml (Mg / Cr molar ratio = 1)
0) Except for the addition, an organomagnesium-supported chromium catalyst was prepared and polymerized in the same manner as in Example 1. As a result, 30 g of polyethylene was obtained. The polymerization activity per 1 g of the catalyst and the polymerization time per hour was 600 g / g ·
hr. Physical property measurement results are as shown in Table 1,
The polymerization activity was significantly reduced as compared with Example 1 (the rigidity and environmental stress cracking (ESCR) were not measured).

Comparative Example 6: In Example 1 (3), 0.001 mol of tri-n-butylaluminum (n-Bu ₃ Al) was used.
0.29 mL of a 1 / L hexane solution (Al / Cr molar ratio =
0.03) Except for the addition, polymerization was carried out in the same manner as in Example 1. As a result, 170 g of polyethylene was obtained.
The polymerization activity per 1 g of catalyst and the polymerization time per hour was 34.
It was 00 g / g · hr. The measurement results of physical properties are as shown in Table 1. As compared with Example 1, an ethylene homopolymer having a lower density of α-olefin by-product and a higher density was obtained. Compared with Example 1, the rigidity is the same, but the environmental stress cracking (ESC
R) was inferior.

Comparative Example 7: In Example 1 (3), 0.1 mol of tri-n-butylaluminum (n-Bu ₃ Al)
/ L of hexane solution (0.97 mL, Al / Cr molar ratio = 1)
0) Except for the addition, polymerization was carried out in the same manner as in Example 1. As a result, 25 g of polyethylene was obtained. The polymerization activity per 1 g of the catalyst per 1 hour of the polymerization time is 500.
g / g · hr. Table 1 shows the measurement results of the physical properties. Compared with Example 1, the measurement of rigidity and environmental stress cracking (ESCR) was not performed because the polymerization activity was significantly reduced.

Comparative Example 8: In Example 1 (3), instead of tri-n-butylaluminum, 0.0% of triisobutylaluminum (i-Bu ₃ Al) manufactured by Tosoh Akzo was used.
Polymerization was carried out in the same manner as in Example 1 except that 0.97 mL of a 1 mol / L hexane solution (Al / Cr molar ratio = 1) was added. As a result, 110 g of polyethylene was obtained. The polymerization activity per 1 g of the catalyst per 1 hour of the polymerization time was 2,200 g / g · hr. The measurement results of physical properties are shown in Table 1. As compared with Example 1, an ethylene homopolymer having lower polymerization activity, lower α-olefin by-product effect, and higher density was obtained. Although the rigidity is higher than that of the first embodiment,
Environmental stress cracking (ESCR) was significantly poorer.

Comparative Example 9: (1) Preparation of Chromium Catalyst Component In Example 1 (1), after calcination activation at 600 ° C., carbon monoxide was passed through molecular sieves at a flow rate of 1.0 L / min. Fluidized with nitrogen containing 10%, 3
Reduction was carried out at 50 ° C. for 1 hour. After the reduction is completed, 1.0
Nitrogen through molecular sieves at a flow rate of 3 L / min.
It flowed at 50 ° C. for 1 hour to remove carbon monoxide in the tube. The chromium catalyst component turns blue, indicating that hexavalent chromium has been reduced. Elemental analysis shows that the amount of chromium atoms carried
1.01%.

(2) Polymerization In the same manner as in Example 1 (3), except that the chromium catalyst component reduced with carbon monoxide obtained in (1) above was used instead of the organomagnesium-supported chromium catalyst. Was done. As a result, 250 g of polyethylene was obtained.
The polymerization activity per 1 g of catalyst per 1 hour of polymerization time is 50
It was 00 g / g · hr. Table 1 shows the physical property measurement results.
Although an ethylene polymer similar to that of Example 1 was obtained in both rigidity and environmental stress cracking (ESCR), there was a problem that a toxic and difficult-to-handle carbon monoxide gas had to be used.

Comparative Example 10: Two-Step Polymerization The same procedure as in Example 5 was carried out except that the chromium catalyst component of Example 1 (1) was used and tri-n-butylaluminum was not added to the second-stage polymerization reactor. Step polymerization was performed. The ratio of the low molecular weight component in the first stage was 60 parts by mass, and the ratio of the high molecular weight component in the second stage was 40 parts by mass. The polymerization activity per hour of polymerization time per 1 g of the first stage catalyst was 2700 g / g ·
hr, the polymerization activity per 1 g of the polymerization catalyst per 1 g of the second stage catalyst was 3000 g / g · hr. Table 1 shows the physical property measurement results. The activity was lower than that of Example 5, and an α-olefin was not produced as a by-product, so that a high density ethylene homopolymer was obtained. As compared with Example 5, although the stiffness was higher, the environmental stress cracking (ESCR) was remarkably inferior.

Comparative Example 11 Two-Step Polymerization Example 1 was repeated in place of the chromium catalyst supported on organomagnesium.
Two-stage polymerization was carried out in the same manner as in Example 5 except that the chromium catalyst component (1) was used. The ratio of the low molecular weight components in the first stage was 51 parts by mass, and the ratio of the high molecular weight components in the second stage was 49 parts by mass. The polymerization activity per 1 g of the first-stage catalyst was 2700 g / g · hr, and the polymerization activity per 1 g of the second-stage catalyst was 4300 g / hr.
g / g · hr. Table 1 shows the physical property measurement results. An ethylene homopolymer having a lower density and a higher density than α-olefin was obtained as compared with Example 5. Compared to Example 5,
Although stiff, the environmental stress cracking (ESCR) was significantly poorer.

Comparative Example 12: Two-Step Polymerization The same procedure as in Example 5 was carried out except that the organomagnesium-supported chromium catalyst of Example 1 (2) was used and tri-n-butylaluminum was not added to the second-stage polymerization reactor. Was subjected to two-stage polymerization. The ratio of the first stage low molecular weight components was 58 parts by mass, and the ratio of the second stage high molecular weight components was 42 parts by mass. The polymerization activity per 1 g of the first-stage catalyst was 3400 g / g · hr, and the polymerization activity per 1 g of the second-stage catalyst was 3000 g / g · hr. . Table 1 shows the physical property measurement results. The activity was lower than that of Example 5, and an α-olefin was not produced as a by-product, so that a high density ethylene homopolymer was obtained. As compared with Example 5, although the stiffness was higher, the environmental stress cracking (ESCR) was remarkably inferior.

Comparative Example 13 Example 1 (3) was repeated except that 50 mg of the chromium catalyst component of Example 1 (1) was used, tri-n-butylaluminum was not added, and 4 g of 1-hexene was introduced under pressure with ethylene. The polymerization was carried out in the same manner as in (1). As a result, 140 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time is 2800 g / g · h
r. The measurement results of physical properties are as shown in Table 1. The activity was lower than that of Example 1, and the environmental stress cracking (ESC) was lower.
R) was low.

Comparative Example 14: Two-stage polymerization Using the chromium catalyst component of Example 1 (1), tri-n-butylaluminum was not added to the second-stage polymerization reactor, and the liquid phase was added to the second-stage polymerization reactor. Two-stage polymerization was carried out in the same manner as in Example 5 except that 1-hexene was supplied so that the weight ratio of the 1-hexene concentration to the ethylene concentration was 0.13. The ratio of the low molecular weight component in the first stage was 57 parts by mass, and the ratio of the high molecular weight component in the second stage was 43 parts by mass. The polymerization activity per hour of polymerization time per 1 g of the first stage catalyst is
The polymerization activity per 1 hour of polymerization time per 2700 g / g · hr of the second stage catalyst was 3100 g / g · hr. The measurement results of physical properties are as shown in Table 1. The activity was lower than that of Example 5, and the environmental stress cracking (ESCR) was low.

Comparative Example 15: In Example 1 (3), instead of tri-n-butylaluminum, 0.97 mL of a 0.01 mol / L hexane solution of triethylborane (Et ₃ B) manufactured by Tosoh Akzo was used. Polymerization was carried out in the same manner as in Example 1 except that the Cr molar ratio was 1). As a result, 235 g of polyethylene was obtained. Polymerization activity per 1 g of catalyst and polymerization time per hour was 4700 g / g ·
hr. Physical property measurement results are as shown in Table 1,
Although the stiffness is the same as that of Example 1, the resistance to environmental stress cracking (ES
CR) was inferior.

Comparative Example 16: In Example 1 (3), instead of tri-n-butylaluminum, diethylaluminum ethoxide (Et ₂ Al (OE) manufactured by Tosoh Akzo Co., Ltd. was used.
t)) in 0.97 mL of a 0.01 mol / L hexane solution (A
Polymerization was carried out in the same manner as in Example 1 except that 1 / Cr molar ratio = 1) was added. As a result, 180 g of polyethylene was obtained. The polymerization activity per 1 g of the catalyst and 1 hour of the polymerization time was 3,600 g / g · hr. The measurement results of physical properties are as shown in Table 1. As compared with Example 1, an ethylene homopolymer having lower polymerization activity, lower α-olefin by-product effect, and higher density was obtained. As compared to Example 1, the stiffness was high, but the environmental stress cracking (ESCR) was significantly inferior.

[0089]

[Table 1]

[0090]

[Table 2]

[0091]

According to the method of the present invention, a chromium catalyst supported on organomagnesium and a trialkylaluminum cocatalyst are used, and only ethylene is used as the monomer, and both rigidity and environmental stress cracking (ESCR) are excellent and suitable for blow molded products.
Particularly, it is possible to efficiently produce an ethylene-based polymer suitable for a large blow-molded product.

[Brief description of the drawings]

FIG. 1 is a flowchart of the preparation of a catalyst used in the method for producing an ethylene polymer of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 22:00 B29L 22:00 F term (Reference) 4F208 AA04 AB19 AG07 LA09 LB01 LG01 LG22 4J011 AA05 BB02 BB07 BB08 BB09 4J028 AA01A AB00A AC42A AC43A BA00A BA01A BA01B BA02B BB00A BB01B BC05A BC06A BC07A BC15B CA25A CA26A CA27A CA28A CA29A DB06A DB10A EB02 EB04 EB05 EB08 EB09 EB10 EF02 FA01 FA02 GA07 4J100 AA02P AA03Q AA03R AA04Q AA04R AA16Q AA16R AA17Q AA17R AA21Q AA21R CA01 CA04 CA05 FA11 FA19 FA34 4J128 AA01 AB00 AC42 AC43 BA00A BA01A BA01B BA02B BB00A BB01B BC05A BC06A BC07A BC15B CA25A CA26A CA27A CA28A CA29A DB06A DB10A EB02 EB04 EB05 EB08 EB09 EB10 EF02 FA01 FA02 GA07

Claims (11)

[Claims] 1. A chromium catalyst component supported on an inorganic oxide carrier, calcined and activated in a non-reducing atmosphere and having at least a part of chromium atoms being hexavalent, is treated with an organic magnesium solvent in an inert hydrocarbon solvent. A method for producing an ethylene polymer, comprising polymerizing ethylene using a chromium catalyst supported on organomagnesium, which is obtained by supporting the above, further removing the solvent and drying. 2. A chromium catalyst component supported on an inorganic oxide carrier, calcined and activated in a non-reducing atmosphere and having at least a part of chromium atoms being hexavalent, and an organomagnesium in an inert hydrocarbon solvent. And a chromium catalyst supported on organomagnesium obtained by removing the solvent and drying, and a co-catalyst represented by the general formula (1): R ³ R ⁴ R ⁵ Al (1) (wherein R ³ , R ⁴ and R ⁵ may be the same or different and each represents a straight-chain alkyl group having 1 to 18 carbon atoms.) A method for producing an ethylene-based polymer, comprising: 3. A chromium catalyst component supported on an inorganic oxide carrier, calcined and activated in a non-reducing atmosphere and having at least a part of chromium atoms being hexavalent, is treated with an organic magnesium solvent in an inert hydrocarbon solvent. The multistage polymerization of ethylene is carried out using a plurality of polymerization reactors connected in series using an organomagnesium supported chromium catalyst obtained by further removing and drying the solvent, and at least the final stage of the multistage polymerization. General formula (1) ## STR2 ## R ³ R ⁴ R ⁵ Al (1) (The symbols in the formula represent the same meanings as in claim 2).
A method for producing an ethylene-based polymer, comprising conducting polymerization by introducing a trialkylaluminum represented by the formula (1). 4. An organomagnesium compound represented by the general formula (2): R ¹ R ² Mg (2) (wherein R ¹ and R ² may be the same or different,
Each represents an alkyl group having 1 to 18 carbon atoms. The method for producing an ethylene-based polymer according to any one of claims 1 to 3, which is a dialkylmagnesium represented by the formula: 5. The method according to claim 1, wherein the molar ratio of the organomagnesium to the chromium atoms is 0.1 to 5. 6. The method for producing an ethylene polymer according to claim 2, wherein the molar ratio of the trialkylaluminum to the chromium atom is 0.1 to 5. 7. The method for producing an ethylene-based polymer according to claim 2, wherein the trialkylaluminum is a trialkylaluminum having a linear alkyl group having 4 to 8 carbon atoms. 8. The method for producing an ethylene polymer according to claim 1, wherein an ethylene polymer having an HLMFR of 1 to 100 g / 10 min and a density of 0.935 to 0.955 g / cm ³ is produced. 9. An HLMFR obtained by the method for producing an ethylene-based polymer according to any one of claims 1 to 7.
Is 1 to 100 g / 10 min, and the density is 0.935 to 0.955 g / cm
³ ethylene polymer. 10. A blow-molded product comprising the ethylene-based polymer according to claim 9. 11. A large blow-molded product comprising the ethylene polymer according to claim 9.