JP2012144723A - Ethylene polymerization catalyst, method for producing polyethylene using the same, and polyethylene for blow molding product and polyethylene for large-size blow molding product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel ethylene polymerization catalyst capable of efficiently producing polyethylene excellent in polymerization activity, excellent in moldability and impact resistance, and also excellent in balance of rigidity (density) and durability, especially polyethylene suitable for a hollow plastic molding, having both high rigidity and durability, and excellent in balance of both properties; a method for producing polyethylene using the catalyst; and polyethylene for a blow molding product and polyethylene for a large-size blow molding product obtained by the method.SOLUTION: The ethylene polymerization catalyst or the like is provided, in which the catalyst is a chromium catalyst obtained when after a chromium compound (b) is carried on an inorganic oxide carrier (a) in such a state that at least a part of the chromium atoms are hexavalent, a first metal compound selected from organic magnesium compounds (c-1) and alumoxane-based compounds (c-2) and a second metal compound selected from organoaluminum compounds (d) are sequentially or simultaneously carried thereon, wherein the first metal compound and the second metal compound or the second metal compound is concentrated on the surface of the inorganic oxide carrier (a).

Description

  The present invention relates to a novel catalyst for ethylene polymerization, a method for producing polyethylene using the same, and a polyethylene for blow molded products and a polyethylene for large blow molded products obtained thereby, more specifically, excellent in polymerization activity, and Excellent in moldability and impact resistance, and excellent in balance between rigidity (density) and durability, particularly suitable for hollow plastic molded products. Both rigidity (density) and durability are high, and both properties are balanced. The present invention relates to a novel ethylene polymerization catalyst capable of efficiently producing polyethylene, a method for producing polyethylene using the same, polyethylene for blow molded products and polyethylene for large blow molded products obtained thereby.

  Hollow plastic molded articles used for storage or transportation of liquid substances are widely used in daily life and industrial fields. Particularly in automobile parts, hollow plastic molded products used as fuel tanks are replacing conventional fuel tanks made of metal materials. Furthermore, at present, plastic is the most frequently used material for the manufacture of fuel containers such as flammable liquids and harmful substances, and transport containers such as plastic bottles. Plastic containers and tanks have features that they can be reduced in weight because they have a lower weight / volume ratio than those made of metal materials, are less susceptible to corrosion such as rust, and have good impact resistance. And it is gaining wider use.

  Hollow plastic moldings are often obtained by blow molding mainly from high density polyethylene (HDPE). In addition, it is necessary to pay particular attention to requirements that are a problem in fuel tanks for plastic automobiles obtained from polyethylene. Plastic fuel tanks are classified as important safety parts for ensuring the safety of automobiles, and therefore, particularly high levels of mechanical strength, durability, and impact resistance are required. It is desirable to develop materials for improving the quality of materials.

Until now, the main technologies proposed as polyethylene for hollow plastic molded articles and their production methods include the following.
Regarding polyethylene, a method for producing polyethylene suitable for blow molded products, particularly large blow molded products, has been proposed by performing polymerization in the presence of hydrogen using a trialkylaluminum compound-supported chromium catalyst (Patent Document 1). reference.). Further, the document 1 discloses a method for producing polyethylene using a dialkylaluminum alkoxide compound-supported chromium catalyst (Comparative Example 13).

In addition, by calcination activation in a non-reducing atmosphere, a solid chromium catalyst component in which a chromium compound in which at least some of the chromium atoms are hexavalent is supported on an inorganic oxide carrier, a dialkylaluminum functional group-containing alkoxide, An ethylene polymerization catalyst composed of alkylaluminum has been proposed (see Patent Document 2). At that time, the obtained polyethylene has excellent creep resistance and ESCR, HLMFR is 1 to 100 g / 10 min, and density is 0. It is also disclosed that it is suitable for blow molded articles of .935 to 0.955 g / cm ³ .
However, when a trialkylaluminum compound is used, 1-hexene is easily generated as a byproduct. Therefore, it is difficult to always produce polyethylene with a constant density on a plant scale by this manufacturing method. In addition, the polyethylene production method disclosed in Patent Documents 1 and 2 can provide polyethylene having a balance between rigidity and durability suitable for currently required hollow plastic molded articles, particularly automobile fuel tanks. hard.

In addition, a chromium compound is supported on an inorganic oxide carrier, and activated by firing in a non-reducing atmosphere, whereby a chromium compound-supported inorganic oxide carrier in which at least some of the chromium atoms are hexavalent is added to an inert hydrocarbon solvent. Has proposed a method for producing polyethylene using a chromium catalyst supporting a specific organoaluminum compound (alkoxide, siloxide, phenoxide, etc.) (see Patent Document 3). It is also disclosed that it has an excellent balance between crackability (ESCR) and rigidity.
In addition, a chromium compound is supported on an inorganic oxide carrier, and activated by firing in a non-reducing atmosphere, thereby forming a chromium catalyst having at least some chromium atoms hexavalent and a specific organoaluminum compound (alkoxide, siloxide, etc.) A polyethylene production catalyst (see Patent Document 4) is proposed, and it is also disclosed that the obtained polyethylene is excellent in ESCR or creep resistance.

  In addition, a chromium catalyst in which at least some of the chromium atoms are hexavalent is supported by supporting the chromium compound on an inorganic oxide support and activated by calcination in a non-reducing atmosphere, and continuously by a plurality of polymerization reactors connected in series. In particular, when carrying out copolymerization of ethylene alone or ethylene and an α-olefin having 3 to 8 carbon atoms in multiple stages, a specific organoaluminum compound (alkoxide, siloxide, etc.) is introduced into any one or all of the polymerization reactors. A polyethylene production method (see Patent Document 5) is proposed, and the obtained polyethylene is also disclosed to be excellent in environmental stress crack resistance (ESCR) and creep resistance. Has been.

Also disclosed is a hollow plastic product (see Patent Document 6) obtained from polyethylene produced using a fluorine-treated inorganic oxide-supported chromium catalyst.
However, the molecular weight distribution of polyethylene obtained by the methods for producing polyethylene disclosed in Patent Documents 3 to 6 is not so wide, and the rigidity suitable for currently required hollow plastic molded products, particularly fuel tanks for automobiles. It is hard to say that polyethylene with a balance of durability and durability can be obtained.

  Furthermore, by activating in a non-reducing atmosphere, an ethylene polymerization catalyst in which a specific organic boron compound is supported on a fluorinated chromium compound in which at least some of the chromium atoms become hexavalent (see Patent Document 7). In this case, it is also disclosed that the obtained polyethylene has a broad molecular weight distribution, excellent impact resistance and creep resistance, and improved moldability. However, the polymerization activity is low and there is room for improving the catalyst.

Further, when an organoaluminum compound is added to the polymerization reactor as a co-catalyst and a polyethylene is produced using a chromium catalyst (see Patent Document 8), or when a dialkylaluminum alkoxide compound-supported chromium catalyst is used as an ethylene polymerization catalyst, A method of adjusting the fluidity (melt index) of polyethylene by the amount of hydrogen added during polymerization (see Patent Document 9) has been proposed.
However, in the methods for producing polyethylene disclosed in Patent Documents 8 and 9, the ethylene polymerization activity is not so high, and it is necessary to improve the polymerization activity in view of the catalyst production cost for using organoaluminum.

  Also disclosed is a method for producing polyethylene using a catalyst comprising an inorganic oxide-supported chromium catalyst, an alumoxane compound, and a specific organoaluminum compound (see Patent Documents 10 and 11). However, the problem with this method is that the amount of alumoxane-based compound used is large and fine control of the ratio of the catalyst components is necessary to obtain reproducibility of the results. Further, the documents 10 and 11 do not suggest or disclose any hollow plastic molded article, particularly polyethylene suitable for a fuel tank for automobiles.

  Furthermore, a method for producing polyethylene obtained by a catalyst system comprising an organomagnesium-supported chromium catalyst and a trialkylaluminum as a co-catalyst (see Patent Document 12) is disclosed. However, in this method, it is difficult to obtain reproducibility of polymerization due to fluctuations in trialkylaluminum used as a cocatalyst. In addition, when trialkylaluminum is used, it is difficult to obtain an appropriate molecular weight distribution for use in an automobile fuel tank.

In addition to the above, for example, high-density polyethylene “HB111R” manufactured by Nippon Polyethylene Co., Ltd. and high-density polyethylene “4261AG” manufactured by Basell Co., Ltd. are known as commercially available polyethylene used for automobile fuel tanks.
These are materials that have been evaluated in the market in response to the strict demands of automobile manufacturers, but the balance of durability and rigidity, impact resistance, and formability are not necessarily high enough. .

  Under such circumstances, the problems of conventional ethylene polymerization catalysts are solved, the polymerization activity is excellent, the moldability and the impact resistance are excellent, and the balance between rigidity and durability is excellent. There has been a demand for the development of an ethylene polymerization catalyst capable of producing polyethylene and hollow plastic molded articles that can achieve rigidity, particularly polyethylene suitable for high-performance fuel tanks.

JP 2002-080521 A JP 2002-020212 A JP 2003-096127 A JP 2003-183287 A JP 2003-313225 A JP-T-2004-504416 JP 2006-182917 A JP-T-2006-512454 WO94 / 13708 international pamphlet Japanese Patent Laid-Open No. 2-105806 Japanese Patent Laid-Open No. 2-185506 JP 2002-80520 A

  In view of the problems of conventional ethylene polymerization catalysts, the object of the present invention is polyethylene having excellent polymerization activity, excellent moldability and impact resistance, and excellent balance between rigidity (density) and durability, Particularly suitable for hollow plastic moldings, both high rigidity and durability, and an ethylene polymerization catalyst capable of efficiently producing polyethylene having a good balance between both properties, a method for producing polyethylene using the catalyst, and Another object is to provide polyethylene for blow molded products and polyethylene for large blow molded products.

  As a result of intensive studies to achieve the above-mentioned problems, the inventors of the present invention have further developed organic compounds on a chromium catalyst in which a chromium compound is supported on an inorganic oxide support in a state where at least some of the chromium atoms are hexavalent. A novel chromium catalyst comprising a first metal compound selected from a magnesium compound or an alumoxane compound and a second metal compound selected from an organoaluminum compound supported in a specific state is prepared and used for ethylene polymerization When used as a catalyst, it is possible to produce polyethylene that not only has excellent polymerization activity and catalyst particle properties, but also has excellent moldability and impact resistance, and also has a good balance between rigidity and durability. Based on these findings, the present invention has been completed.

  That is, according to the first invention of the present invention, after the chromium compound (b) is supported on the inorganic oxide support (a) in a state where at least some of the chromium atoms are hexavalent, an organic magnesium compound ( A chromium catalyst comprising a first metal compound selected from c-1) or an alumoxane-based compound (c-2) and a second metal compound selected from an organoaluminum compound (d) sequentially or simultaneously. The first metal compound and the second metal compound, or the second metal compound are concentrated on the surface of the inorganic oxide support (a), and an ethylene polymerization catalyst is provided. Is done.

  According to the second invention of the present invention, in the first invention, when the aluminum atom content in the cross section of the catalyst particle is measured using an electron probe microanalyzer (EPMA), the aluminum present on the catalyst particle surface is measured. There is provided an ethylene polymerization catalyst characterized in that the detected amount of atoms is larger than that of aluminum atoms present inside catalyst particles.

  Furthermore, according to the third invention of the present invention, when the organomagnesium compound (c-1) is supported in the first or second invention, the magnesium atom in the cross section of the catalyst particle is obtained using an electron probe microanalyzer. When the content is measured, there is provided an ethylene polymerization catalyst characterized in that the detected amount of magnesium atom present on the surface of the catalyst particle is larger than the magnesium atom present inside the catalyst particle.

According to a fourth invention of the present invention, in any one of the first to third inventions, the ethylene polymerization catalyst is produced by the following steps (a) to (d). A catalyst for ethylene polymerization is provided.
(A): The chromium compound (b) is supported on the inorganic oxide carrier (a) and activated by firing in a non-reducing atmosphere (b): the inorganic oxide carrier (a) carrying the chromium compound (b) Further, a first metal compound selected from the organomagnesium compound (c-1) or the alumoxane compound (c-2) is supported in an inert hydrocarbon solvent (c): then selected from the organoaluminum compound (d) The second metal compound to be supported is supported in an inert hydrocarbon solvent (d): Finally, the inert hydrocarbon solvent is removed and dried.

  Furthermore, according to the fifth invention of the present invention, in any one of the first to fourth inventions, the organoaluminum compound (e) is at least one selected from dialkylaluminum alkoxide, alkylaluminum dialkoxide, or trialkylaluminum. An ethylene polymerization catalyst is provided.

  According to a sixth aspect of the present invention, there is provided the ethylene polymerization catalyst according to any one of the first to fifth aspects, wherein the organoaluminum compound (e) is a dialkylaluminum alkoxide. .

  Furthermore, according to a seventh invention of the present invention, in any one of the first to sixth inventions, the organomagnesium compound (c-1) is dibutylmagnesium or butylethylmagnesium. A catalyst is provided.

  Furthermore, according to the eighth invention of the present invention, in any one of the first to sixth inventions, the alumoxane compound (c-2) is methylalumoxane (MMAO) modified with triisobutylaluminum. An ethylene polymerization catalyst is provided.

  According to the ninth invention of the present invention, ethylene homopolymerization or copolymerization of ethylene and α-olefin is performed using the ethylene polymerization catalyst according to any one of the first to eighth inventions. A method for producing polyethylene is provided.

  Furthermore, according to a tenth aspect of the present invention, there is provided the method for producing polyethylene according to the ninth aspect, wherein the α-olefin has 3 to 8 carbon atoms.

According to an eleventh aspect of the present invention, there is provided a polyethylene produced by the method according to the ninth or tenth aspect, wherein the high load melt low rate (HLMFR) at a temperature of 190 ° C. and a load of 21.6 kg is zero. 0.1 to 100 g / 10 min and a density of 0.900 to 0.980 g / cm ³ are provided.

According to a twelfth aspect of the present invention, polyethylene produced by the method according to the ninth or tenth aspect of the present invention has a high load melt flow rate (HLMFR) of 1 at a temperature of 190 ° C. and a load of 21.6 kg. A polyethylene for large blow-molded products is provided, characterized in that it has a density of ˜15 g / 10 min and a density of 0.940 to 0.955 g / cm ³ .

The present invention relates to an ethylene polymerization catalyst as described above, and preferred embodiments thereof include the following.
(1) In the fourth invention, the firing activation in the step (a) is performed at a temperature of 300 to 950 ° C., preferably 325 to 800 ° C., more preferably 350 to 650 ° C. catalyst.
(2) In the fourth invention, the supported amount of the organoaluminum compound (d) is such that the molar ratio of the organoaluminum compound to the chromium atom is 0.01 to 20, preferably 0.03 to 15, more preferably 0.05. The catalyst for ethylene polymerization characterized by being 10-10.
(3) In the fourth invention, the amount of the first metal compound selected from the organomagnesium compound (c-1) or the alumoxane compound (c-2) is the molar amount of the first metal compound relative to the chromium atom. A catalyst for ethylene polymerization, wherein the ratio is 0.01 to 5, preferably 0.05 to 4, more preferably 0.10 to 3.

  By using the ethylene polymerization catalyst of the present invention, an ethylene polymer excellent in moldability and impact resistance and having a good balance between rigidity (density) and durability can be obtained. An ethylene-based polymer excellent in the balance between rigidity and environmental stress crack resistance (ESCR) suitable for a molded product can be efficiently produced. The polyethylene is suitable for blow-molded hollow plastic products, and the hollow plastic products are excellent in moldability and impact resistance, have a good balance between rigidity and durability, and are suitable for fuel tanks, especially fuel tanks for automobiles. Can be used.

It is a schematic diagram explaining that the catalyst for ethylene polymerization of the present invention is a “pseudo binary catalyst”. It is a photograph which shows the example of the EPMA analysis which concerns on the catalyst for ethylene polymerization of this invention.

  The present invention provides a chromium catalyst in which an inorganic oxide carrier (a) carries a chromium compound (b) and at least a part of the chromium atoms are hexavalent, and an organic magnesium compound (c-1) or an alumoxane compound ( c-2) a first metal compound selected from c-2) and a second metal compound selected from organoaluminum compound (d), which are sequentially or simultaneously supported, and the ethylene polymerization catalyst. The present invention relates to a method for producing polyethylene, and further to blow molded products and polyethylene for large blow molded products obtained by the production method. Hereinafter, the present invention will be described item by item.

[I] Ethylene Polymerization Catalyst of the Present Invention The ethylene polymerization catalyst of the present invention is obtained by supporting a chromium compound (b) on an inorganic oxide support (a) in a state where at least some of the chromium atoms are hexavalent. Furthermore, a first metal compound selected from the organomagnesium compound (c-1) or the alumoxane compound (c-2) and a second metal compound selected from the organoaluminum compound (d) are supported sequentially or simultaneously. A chromium catalyst, wherein the first metal compound and the second metal compound, or the second metal compound are concentrated on the surface of the inorganic oxide support (a). .
By the way, the ethylene polymerization catalyst of the present invention is an organometallic compound-supported chromium catalyst. At least one of the catalysts is supported by supporting a chromium compound on an inorganic oxide carrier as a precursor and calcination activation in a non-reducing atmosphere. A chromium catalyst in which a part of the chromium atoms is hexavalent is generally known as a Philips catalyst and is known.

And the outline | summary of this catalyst is described in the following literature, for example.
(I) M.M. P. McDaniel, Advances in Catalysis, Volume 33, 47, 1985, Academic Press Inc.
(Ii) M.M. P. McDaniel, Handbook of Heterogeneous Catalysis, 2400, 1997, VCH
(Iii) M.M. B. Welch et al., Handbook of Polyolefins: Synthesis and Property

1. Inorganic oxide support (a)
As the inorganic oxide support, a metal oxide of Group 2, 4, 13 or 14 of the periodic table can be used. Specific examples include magnesia, titania, zirconia, alumina, silica, tria, silica-titania, silica-zirconia, silica-alumina, or mixtures thereof.
For automotive fuel tank applications having both excellent durability and impact resistance, silica alone is preferred as the inorganic oxide carrier. When a material other than silica is used as the carrier, the polymerization activity is lowered, and it is thought that the cause is an increase in the low molecular weight component of polyethylene, but the impact resistance tends to be lowered.

And the manufacturing method of the support | carrier suitable for these chromium catalysts, a physical property, and the characteristic are described in the following literatures, for example.
(I) C.I. E. Marsden, Preparation of Catalysts, Volume V, 215, 1991, Elsevier Science Publishers.
(Ii) C.I. E. Marsden, Plastics, Rubber and Composites Processing and Applications, Volume 21, 193, 1994.

In the present invention, it is preferable to select the support so that the specific surface area of the support of the chromium catalyst is 250 to 1000 m ² / g, preferably 300 to 950 m ² / g, more preferably 450 to 900 m ² / g. . When the specific surface area is less than 250 m ² / g, it is considered that the molecular weight distribution is narrow and long-chain branching is increased, but both durability and impact resistance are lowered. In addition, it is difficult to produce a carrier having a specific surface area exceeding 1000 m ² / g.

The pore volume of the carrier is 0.5 to 5.0 cm ³ / g, preferably 1.0 to 3.0 cm ³ / g, more preferably, as in the case of a carrier used for a general chromium catalyst. The thing of the range of 1.2-2.5 cm < ³ > / g is used. When the pore volume is less than 0.5, the pores are reduced by the polymer during polymerization, and the monomer cannot be diffused, resulting in a decrease in activity. A carrier having a pore volume exceeding 5.0 cm ³ / g is difficult to produce.
The average particle size of the carrier is 10 to 200 μm, preferably 20 to 150 μm, more preferably 30 to 100 μm. Outside the above range, it becomes difficult to balance ESCR and impact resistance.

2. Chromium compound (b)
The chromium compound (b) is supported on the inorganic oxide support (a). The chromium compound may be a compound in which at least a part of chromium atoms becomes hexavalent by firing activation in a non-reducing atmosphere after loading, such as chromium oxide, chromium halide, oxyhalide, chromate. , Dichromate, nitrate, carboxylate, sulfate, chromium-1,3-diketo compound, chromate, 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 Examples thereof include acetylacetonate and bis (tert-butyl) chromate. Of these, chromium trioxide, chromium acetate, and chromium acetylacetonate are preferable. Even when a chromium compound having an organic group such as chromium acetate or chromium acetylacetonate is used, the organic group part burns by firing activation in a non-reducing atmosphere described later, and finally chromium trioxide is used. In the same manner as described above, it is known that it reacts with the hydroxyl group on the surface of the inorganic oxide support, and at least some of the chromium atoms become hexavalent and are immobilized in the structure of chromate ((i) V J. Ruddick et al., J. Phys. Chem., Volume 100, 11062, 1996, (ii) SM Augustine et al., J. Catal., Volume 161, 641 (1996).

  The chromium compound can be supported on the inorganic oxide support by a known method such as impregnation, solvent distillation, sublimation, etc., and an appropriate method may be used depending on the kind of the chromium compound to be used. The amount of the chromium compound to be supported is 0.2 to 2.0% by weight, preferably 0.3 to 1.7% by weight, more preferably 0.5 to 1.5% by weight based on the carrier as chromium atoms. It is.

In the present invention, a chromium catalyst in which a chromium compound is supported on an inorganic oxide carrier may further contain a fluorine compound.
The fluorine compound containing method (fluorination) is carried out by a known method such as a method in which a fluorine compound solution is impregnated in a solvent and then the solvent is distilled off or a method in which a fluorine compound is sublimated without using a solvent. A suitable method may be used as appropriate depending on the type of chromium compound to be used. The inorganic oxide carrier may contain the fluorine compound after the chromium compound is supported, or the chromium compound may be supported after the fluorine compound is contained, but the fluorine compound is contained after the chromium compound is supported. It is preferable to make it.
Content of a fluorine compound is 0.1 to 10 weight% as content of a fluorine atom, Preferably it is 0.3 to 8 weight%, More preferably, it is 0.5 to 5 weight%.

Examples of the fluorine compound include hydrogen fluoride HF, ammonium fluoride NH4F, ammonium silicofluoride (NH ₄ ) ₂ SiF ₆ , ammonium borofluoride NH ₄ BF ₄ , ammonium hydrogen difluoride (NH ₄ ) HF ₂ , hexafluorophosphorus Fluorine-containing salts such as ammonium nitrate NH ₄ PF ₆ and tetrafluoroboric acid HBF ₄ are used, and among them, ammonium silicofluoride and ammonium monohydrogen difluoride are preferable.
From the viewpoint of uniformity, it is preferable that these are dissolved in an organic solvent such as water or alcohol and then impregnated in the chromium catalyst. When dissolved and impregnated, it is more preferable to use an organic solvent such as alcohol in order to suppress shrinkage of the pore volume due to surface tension. When a solvent is used, the solvent is removed by drying by a known method such as air drying, vacuum drying or spray drying.

By activation in a non-reducing atmosphere described later, these fluorine compounds thermally decompose to fluorinate the inorganic oxide carrier. For example, when silica is used as the inorganic oxide carrier and ammonium silicofluoride is used as the fluorine compound, ammonium silicofluoride is thermally decomposed as follows to generate hydrogen fluoride HF and silicon fluoride SiF ₄ .
(NH ₄ ) ₂ SiF ₆ → 2NH ₃ + 2HF + SiF ₄

Further, it is known that HF and SiF4 react with silanol groups on the silica surface to fluorinate (B. Rebentorf; Journal of Molecular Catalysis Vol. 66 p. 59 (1991), A. Noshay et al. “See Transition Metal Catalyzed Polymerizations—Ziegler Natta and Metathesis Polymerizations”, p. 396 (1988) Cambridge University Press).
Si-OH + HF → Si-F + H ₂ O
_{Si-OH + SIF 4 → Si} -O-SiF 3 + HF
2Si—OH + SiF ₄ → (Si—O) ₂ SiF ₂ + 2HF

  Therefore, even when a solid of a fluorine compound such as a fluorine-containing salt is mixed with a chromium catalyst, the fluorine compound is eventually thermally decomposed, so that the same reaction occurs and the chromium catalyst is fluorinated. Alternatively, a method of introducing a fluorine compound during the activation process may be used. However, in this case, since the fluorine compound solid is fluidized in the gas, it is preferable to use a fluorine compound solid that is as fine as possible from the viewpoint of uniformity.

3. Firing activation method After supporting the chromium compound, in some cases, further supporting the fluorine compound, followed by firing and activation treatment. The firing activation is usually performed at a temperature of 300 to 950 ° C, preferably 325 to 800 ° C, more preferably 350 to 650 ° C. When calcination activation is performed at less than 300 ° C., there is no polymerization activity. When it is performed at a temperature exceeding 950 ° C., a sintering phenomenon in which the pore structure of silica is crushed occurs and the activity is lost. The calcination activation can be performed in a non-reducing atmosphere substantially free of moisture, for example, oxygen or air. At this time, an inert gas may coexist. Preferably, at least a part of the chromium atom of the chromium compound supported on the inorganic oxide support is oxidized to hexavalent by calcination activation performed in a fluid state using sufficiently dried air through molecular sieves or the like. It is chemically immobilized on a carrier.

  As described above, the chromium catalyst used in the present invention can be obtained. In the production of the polyethylene according to the present invention, titanium tetraisopropoxide or the like can be used before supporting the chromium compound or before activating the firing after supporting the chromium compound. Metal alkoxides represented by titanium alkoxides, zirconium alkoxides such as zirconium tetrabutoxide, aluminum alkoxides such as aluminum tributoxide, organoaluminums such as trialkylaluminum, and organomagnesiums such as dialkylmagnesium Alternatively, a fluorine-containing salt such as an organometallic compound or ammonium silicofluoride is added to adjust the ethylene polymerization activity, the copolymerization with α-olefin, the molecular weight of the resulting polyethylene, and the molecular weight distribution. It may be.

  When these metal alkoxides or organometallic compounds are activated by firing in a non-reducing atmosphere, the organic group portion burns and is oxidized into a metal oxide such as titania, zirconia, alumina or magnesia and contained in the catalyst. It is. In the case of fluorine-containing salts, the inorganic oxide carrier is fluorinated.

These methods are described in the following documents, for example.
(I) C.I. E. Marsden, Plastics, Rubber and Composites Processing and Applications, Volume 21, 193, 1994 (ii) T. et al. Pulukat et al. Polym. Sci. , Polym. Chem. Ed. , Volume 18, 2857, 1980 (iii) M .; P. McDaniel et al. Catal. , Volume 82, 118, 1983

  In the present invention, it is more preferable to use only a silica carrier that is an inorganic oxide for use in an automobile fuel tank having both excellent impact resistance and durability. When these metal alkoxides or organometallic compounds are added to the inorganic oxide, there is a tendency that the low molecular weight component of polyethylene is increased or the molecular weight distribution is narrowed.

4). First Metal Compound In the present invention, the first metal compound selected from the organomagnesium compound (c-1) or the alumoxane compound (c-2) in an inert hydrocarbon solvent is used as the fired chromium catalyst. And the second metal compound selected from the organoaluminum compound (c) are sequentially or simultaneously supported, and the solvent is removed and dried to obtain the target organometallic compound-supported chromium catalyst.
The supported amount of the organomagnesium compound (c-1) or the alumoxane compound (c-2) is such that the molar ratio of the organometallic compound to the chromium atom is 0.01 to 5, preferably 0.05 to 4, more preferably. Is 0.1-3. At this time, ethylene polymerization activity is greatly improved as compared with the case where no organomagnesium compound or alumoxane compound is supported. When the molar ratio is less than 0.01, the effect of supporting this type of organometallic compound is not sufficiently exhibited, and the ethylene polymerization activity and durability are not so different from those when not supporting this type of organometallic compound. On the other hand, when the molar ratio exceeds 5, the ethylene polymerization activity is lowered as compared with the case where this kind of organometallic compound is not supported.

(4-1) Organomagnesium compound (c-1)
Examples of the organomagnesium compound (c-1) used in the present invention include dialkylmagnesium compounds and alkyl halide magnesium compounds RMgX (R is an alkyl group, phenyl group, and X is a halogen group).
Specific examples of the dialkyl magnesium include dimethyl magnesium, diethyl magnesium, di n-propyl magnesium, di n-butyl magnesium, butyl ethyl magnesium, diisobutyl magnesium, di n-hexyl magnesium, dioctyl magnesium and the like.
Specific examples of the alkyl magnesium halide compound include methyl magnesium bromide, methyl magnesium chloride, ethyl magnesium bromide, ethyl magnesium chloride, n-butyl magnesium bromide, n-butyl magnesium chloride, sec-butyl magnesium chloride, t-butyl magnesium. Examples include chloride, phenylmagnesium bromide, phenylmagnesium chloride, benzylmagnesium chloride, vinylmagnesium chloride, cyclohexylmagnesium chloride, and n-butylethylmagnesium.
Of the organic magnesium compounds listed above, dialkyl magnesium compounds are preferable, and di-n-butyl magnesium and butyl ethyl magnesium are more preferable.

(4-2) Alumoxane compound (c-2)
The alumoxane compound has an Al—O—Al bond in the molecule, and the number of bonds is usually in the range of 1 to 100, preferably 1 to 50. Such an alumoxane compound is usually a product obtained by reacting an organoaluminum compound with water.
The reaction between organoaluminum and water is usually carried out in an inert hydrocarbon (solvent). As the inert hydrocarbon, aliphatic hydrocarbons such as pentane, hexane, heptane, cyclohexane, methylcyclohexane, benzene, toluene and xylene, alicyclic hydrocarbons and aromatic hydrocarbons can be used. Preference is given to using aromatic hydrocarbons.

  Monoalkylaluminum, dialkylaluminum, and trialkylaluminum can be used as the organoaluminum compound used in the preparation of the alumoxane compound, but trialkylaluminum is preferably used.

As the alkyl group of the trialkylaluminum, any of methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group and the like can be used.
Two or more of the above organoaluminum compounds can be mixed and used. Those prepared from trimethylaluminum and alkylaluminum other than trimethylaluminum are also called modified methylalumoxane (MMAO). In addition, the use ratio of trimethylaluminum and alkylaluminum other than trimethylaluminum can be appropriately selected. Examples include MMAO-3A grade using trisodium aluminum and triisobutylaluminum manufactured by Tosoh Finechem.
In the present invention, the alumoxane compound is preferably a modified methylalumoxane prepared from trimethylaluminum and an alkylaluminum other than trimethylaluminum from the viewpoint of activity improvement, and a modified methylalumoxane prepared from trimethylaluminum and triisobutylaluminum is preferred. Further preferred.

  The reaction ratio (water / Al molar ratio) between water and the organoaluminum compound is preferably 0.25 / 1 to 1.2 / 1, particularly preferably 0.5 / 1 to 1/1, and the reaction temperature is Usually, it is -70-100 degreeC, Preferably it exists in the range of -20-20 degreeC. The reaction time is usually selected in the range of 5 minutes to 24 hours, preferably 10 minutes to 5 hours. As water required for the reaction, not only mere water but also crystal water contained in copper sulfate hydrate, aluminum sulfate hydrate and the like and components capable of generating water in the reaction system can be used.

5. Second metal compound (ie, organoaluminum compound (d))
In the present invention, as described above, the first metal compound selected from the organomagnesium compound (c-1) or the alumoxane-based compound (c-2) in an inert hydrocarbon solvent to the fired chromium catalyst, And a second metal compound selected from the organoaluminum compound (c) sequentially or simultaneously, and after removing the solvent and drying, the resulting organometallic compound-supported chromium catalyst is used as a polymerization catalyst.
The second metal compound is arbitrarily selected from the organoaluminum compound (d). As such an organoaluminum compound, an alkylaluminum alkoxide compound is preferable.
The alkylaluminum alkoxide compound is a compound represented by the following general formula (1).

（式中、Ｒ^１、Ｒ^２は、同一であっても異なってもよく、各々アルキル基を表す。ここで、Ｒ^１、Ｒ^２のアルキル基は、シクロアルキル基も含む。）

(In the formula, R ¹ and R ² may be the same or different and each represents an alkyl group. Here, the alkyl groups of R ¹ and R ² include a cycloalkyl group.)

  Among these, a dialkylaluminum alkoxide compound represented by the following general formula (2) is preferable.

（式中、Ｒ^１、Ｒ^２、Ｒ^３は、同一であっても異なってもよく、各々アルキル基を表す。ここで、Ｒ^１、Ｒ^２、Ｒ^３のアルキル基は、シクロアルキル基も含む。）

(In the formula, R ¹ , R ² and R ³ may be the same or different and each represents an alkyl group. Here, the alkyl group of R ¹ , R ² and R ³ is a cycloalkyl group. Including)

  Among the compounds of the general formula (2), dialkylaluminum alkoxides represented by the following general formula (3) are preferable.

（式中、Ｒ^４、Ｒ^５は、同一であっても異なってもよく、各々炭素原子数１〜１８のアルキル基を表す。Ｒ^６、Ｒ^７は、同一であっても異なってもよく、各々水素原子またはアルキル基を表すが、少なくともいずれかの１つはアルキル基である。ここで、Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７のアルキル基は、シクロアルキル基も含む。また、Ｒ^６、Ｒ^７は連結して、環を形成してもよい。）

(In the formula, R ⁴ and R ⁵ may be the same or different, and each represents an alkyl group having 1 to 18 carbon atoms. R ⁶ and R ⁷ may be the same or different. Each represents a hydrogen atom or an alkyl group, at least one of which is an alkyl group, wherein the alkyl groups of R ⁴ , R ⁵ , R ⁶ , and R ⁷ also include a cycloalkyl group. R ⁶ and R ⁷ may combine to form a ring.)

  Furthermore, in the activity of the catalyst, the dialkylaluminum alkoxide represented by the following general formula (4) is most preferable among the compounds of the general formula (3).

（式中、Ｒ^８、Ｒ^９、Ｒ^１０は同一であっても異なってもよく、各々アルキル基を表す。ここで、Ｒ^８、Ｒ^９、Ｒ^１０のアルキル基はシクロアルキル基も含む。）

(In formula, R < ⁸ >, R <^9> , R < ¹⁰ > may be same or different, and each represents an alkyl group. Here, the alkyl group of R < ⁸ >, R <^9> , R < ¹⁰ > includes a cycloalkyl group. )

In the dialkylaluminum alkoxide represented by the general formula (2), specific examples of R ¹ and R ² are methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, tert- Examples include butyl, n-hexyl, n-octyl, n-decyl, n-dodecyl, cyclohexyl and the like, but methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, n-hexyl, n -Octyl is preferred, with methyl, ethyl, n-propyl, i-propyl, n-butyl and i-butyl being particularly preferred.
Specific examples of R ³ include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, tert-butyl, n-pentyl, n-heptyl, n-nonyl, n-undecyl, cyclohexyl and the like can be mentioned, and methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, tert-butyl, n-pentyl and n-heptyl are preferable. However, methyl, ethyl, n-propyl and i-propyl are particularly preferred.

  Specific examples of the dialkylaluminum alkoxide represented by the general formula (2) include dimethylaluminum methoxide, diethylaluminum methoxide, di-n-butylaluminum methoxide, dii-butylaluminum methoxide, dimethylaluminum ethoxide, diethylaluminum. Ethoxide, di-n-butylaluminum ethoxide, dii-butylaluminum ethoxide, dimethylaluminum n-propoxide, diethylaluminum n-propoxide, din-butylaluminum n-propoxide, dii-butylaluminum n- Propoxide, dimethylaluminum i-propoxide, diethylaluminum i-propoxide, di-n-butylaluminum i-propoxide, dii-butylaluminum i-propoxide, Methylaluminum n-butoxide, diethylaluminum n-butoxide, di-n-butylaluminum n-butoxide, dii-butylaluminum n-butoxide, dimethylaluminum i-butoxide, diethylaluminum i-butoxide, din-butylaluminum i- Butoxide, di-butylaluminum i-butoxide, dimethylaluminum t-butoxide, diethylaluminum t-butoxide, di-n-butylaluminum t-butoxide, dimethylaluminum (cyclopropyl) methoxide, diethylaluminum (cyclopropyl) methoxide, din -Butylaluminum (cyclopropyl) methoxide, dii-butylaluminum (cyclopropyl) methoxide, dimethylaluminum (cyclobutyl) methoxy , Diethylaluminum (cyclobutyl) methoxide, di-n-butylaluminum (cyclobutyl) methoxide, dii-butylaluminum (cyclobutyl) methoxide, dimethylaluminum (cyclopentyl) methoxide, diethylaluminum (cyclopentyl) methoxide, di-n-butylaluminum (cyclopentyl) Methoxide, di-butylaluminum (cyclopentyl) methoxide, dimethylaluminum (cyclohexyl) methoxide, diethylaluminum (cyclohexyl) methoxide, di-n-butylaluminum (cyclohexyl) methoxide, dii-butylaluminum (cyclohexyl) methoxide, dimethylaluminum (di) Cyclopropyl) methoxide, diethylaluminum (dicyclopropyl) meth Oxide, di-n-butylaluminum (dicyclopropyl) methoxide, dii-butylaluminum (dicyclopropyl) methoxide, dimethylaluminum (dicyclobutyl) methoxide, diethylaluminum (dicyclobutyl) methoxide, di-n-butylaluminum (dicyclobutyl) methoxide, Dii-butylaluminum (dicyclobutyl) methoxide, dimethylaluminum (dicyclopentyl) methoxide, diethylaluminum (dicyclopentyl) methoxide, di-n-butylaluminum (dicyclopentyl) methoxide, dii-butylaluminum (dicyclopentyl) methoxide, dimethylaluminum (Dicyclohexyl) methoxide, diethylaluminum (dicyclohexyl) methoxide, di-n-butylaluminum Um (dicyclohexyl) methoxide, di i-butylaluminum (dicyclohexyl) methoxide, dimethylaluminum cyclopropoxide, diethylaluminum cyclopropoxide, di-n-butylaluminum cyclopropoxide, dii-butylaluminum cyclopropoxide, dimethylaluminum cyclobutoxide , Diethylaluminum cyclobutoxide, di-n-butylaluminum cyclobutoxide, dii-butylaluminum cyclobutoxide, dimethylaluminum cyclopentoxide, diethylaluminum cyclopentoxide, din-butylaluminum cyclopentoxide, dii-butylaluminum cyclopent Koxide, dimethylaluminum cyclohexoxide, diethylaluminum cyclohexoxy , To di-n- butylaluminum cycloalkyl Kisokishido, Kisokishido the like to di i- butylaluminum cycloalkyl.

Among these, carbons that are directly bonded to oxygen in the alkoxide moiety represented by the general formula (3) are preferably primary or secondary carbons in view of catalytic activity and other catalytic performance.
Specific examples thereof include dimethylaluminum methoxide, diethylaluminum methoxide, di-n-butylaluminum methoxide, dii-butylaluminum methoxide, dimethylaluminum ethoxide, diethylaluminum ethoxide, di-n-butylaluminum ethoxide, Dii-butylaluminum ethoxide, dimethylaluminum n-propoxide, diethylaluminum n-propoxide, din-butylaluminum n-propoxide, dii-butylaluminum n-propoxide, dimethylaluminum i-propoxide, diethyl Aluminum i-propoxide, di-n-butylaluminum i-propoxide, dii-butylaluminum i-propoxide, dimethylaluminum n-butoxide, diethylaluminium n-butoxide, di-n-butylaluminum n-butoxide, dii-butylaluminum n-butoxide, dimethylaluminum i-butoxide, diethylaluminum i-butoxide, din-butylaluminum i-butoxide, dii-butylaluminum i- Butoxide, dimethylaluminum (cyclopropyl) methoxide, diethylaluminum (cyclopropyl) methoxide, di-n-butylaluminum (cyclopropyl) methoxide, di-butylaluminum (cyclopropyl) methoxide, dimethylaluminum (cyclobutyl) methoxide, diethylaluminum ( Cyclobutyl) methoxide, di-n-butylaluminum (cyclobutyl) methoxide, di-butylaluminum (cyclobutyl) methoxide, dimethyl Luminium (cyclopentyl) methoxide, diethylaluminum (cyclopentyl) methoxide, di-n-butylaluminum (cyclopentyl) methoxide, di-butylaluminum (cyclopentyl) methoxide, dimethylaluminum (cyclohexyl) methoxide, diethylaluminum (cyclohexyl) methoxide, di-n- Butylaluminum (cyclohexyl) methoxide, dii-butylaluminum (cyclohexyl) methoxide, dimethylaluminum (dicyclopropyl) methoxide, diethylaluminum (dicyclopropyl) methoxide, di-n-butylaluminum (dicyclopropyl) methoxide, dii- Butyl aluminum (dicyclopropyl) methoxide, dimethyl aluminum (dicyclobutyl) methoxide Sid, Diethylaluminum (dicyclobutyl) methoxide, Di n-butylaluminum (dicyclobutyl) methoxide, Di i-butylaluminum (dicyclobutyl) methoxide, Dimethylaluminum (dicyclopentyl) methoxide, Diethylaluminum (dicyclopentyl) methoxide, Di n-butylaluminum (Dicyclopentyl) methoxide, dii-butylaluminum (dicyclopentyl) methoxide, dimethylaluminum (dicyclohexyl) methoxide, diethylaluminum (dicyclohexyl) methoxide, di-n-butylaluminum (dicyclohexyl) methoxide, di-butylaluminum (dicyclohexyl) methoxide , Dimethylaluminum cyclopropoxide, diethylaluminum cycloprop Oxide, di-n-butylaluminum cyclopropoxide, di-i-butylaluminum cyclopropoxide, dimethylaluminum cyclobutoxide, diethylaluminum cyclobutoxide, di-n-butylaluminum cyclobutoxide, dii-butylaluminum cyclobutoxide, dimethylaluminum cyclopent Oxide, diethylaluminum cyclopentoxide, di-n-butylaluminum cyclopentoxide, dii-butylaluminum cyclopentoxide, dimethylaluminum cyclohexoxide, diethylaluminum cyclohexoxide, di-n-butylaluminum cyclohexoxide, dii- Examples include butylaluminum cyclohexoxide.

Further, among these, carbons that are directly bonded to oxygen in the alkoxide moiety represented by the general formula (4) are preferably primary carbons in view of catalytic activity and other catalytic performance.
Specific examples thereof include dimethylaluminum methoxide, diethylaluminum methoxide, di-n-butylaluminum methoxide, dii-butylaluminum methoxide, dimethylaluminum ethoxide, diethylaluminum ethoxide, di-n-butylaluminum ethoxide, Dii-butylaluminum ethoxide, dimethylaluminum n-propoxide, diethylaluminum n-propoxide, din-butylaluminum n-propoxide, dii-butylaluminum n-propoxide, dimethylaluminum n-butoxide, diethylaluminum n-butoxide, di-n-butylaluminum n-butoxide, dii-butylaluminum n-butoxide, dimethylaluminum (cyclopropyl) methoxide, diethylal Ni (cyclopropyl) methoxide, di-n-butylaluminum (cyclopropyl) methoxide, dii-butylaluminum (cyclopropyl) methoxide, dimethylaluminum (cyclobutyl) methoxide, diethylaluminum (cyclobutyl) methoxide, di-n-butylaluminum (cyclobutyl) ) Methoxide, di-butylaluminum (cyclobutyl) methoxide, dimethylaluminum (cyclopentyl) methoxide, diethylaluminum (cyclopentyl) methoxide, di-n-butylaluminum (cyclopentyl) methoxide, dii-butylaluminum (cyclopentyl) methoxide, dimethylaluminum ( (Cyclohexyl) methoxide, diethylaluminum (cyclohexyl) methoxide, di-n-butyl Aluminum (cyclohexyl) methoxide, di-i- butyl aluminum (cyclohexyl) methoxide and the like.

  Furthermore, among these, diethylaluminum ethoxide, diethylaluminum n-butoxide, di-n-butylaluminum ethoxide, di-n-butylaluminum n-butoxide, diethylaluminum i-butoxide, dii-butylaluminum ethoxide, dii -Butyl aluminum i-butoxide is preferred.

The dialkylaluminum alkoxide can be easily synthesized by (i) a method of reacting a trialkylaluminum with an alcohol and (ii) a method of reacting a dialkylaluminum halide with a metal alkoxide.
That is, in order to synthesize a dialkylaluminum alkoxide represented by the general formula (2), a method of reacting a trialkylaluminum and an alcohol at a molar ratio of 1: 1 as shown in the following formula:

（式中、Ｒ’、Ｒ^１１，Ｒ^１２，Ｒ^１３は、同一でも異なってもよく、各々アルキル基を表す。）

(In the formula, R ′, R ¹¹ , R ¹² and R ¹³ may be the same or different and each represents an alkyl group.)

  Alternatively, as shown in the following formula, a method in which a dialkylaluminum halide and a metal alkoxide are reacted at a molar ratio of 1: 1 is preferably used.

（式中、Ｒ^１４，Ｒ^１５，Ｒ^１６は、同一でも異なってもよく、各々アルキル基を表す。ジアルキルアルミニウムハライド：Ｒ^１４Ｒ^１５ＡｌＸにおけるＸは、フッ素、塩素、臭素、ヨウ素であり、特に塩素が好ましく用いられる。また、金属アルコキシド：Ｒ^１６ＯＭにおけるＭは、アルカリ金属であり、特にリチウム、ナトリウム、カリウムが好ましい。）

(In the formula, R ¹⁴ , R ¹⁵ and R ¹⁶ may be the same or different and each represents an alkyl group. Dialkylaluminum halide: X in R ¹⁴ R ¹⁵ AlX is fluorine, chlorine, bromine or iodine; Chlorine is particularly preferably used, and M in the metal alkoxide: R ¹⁶ OM is an alkali metal, and lithium, sodium, and potassium are particularly preferable.)

By-product: R′—H is an inactive alkane, and when it has a low boiling point, it volatilizes out of the system in the course of the reaction, or when the boiling point is high, it remains in the solution, but it remains in the system. Even so, it is inactive for subsequent reactions. Further, the by-product: MX is an alkali metal halide and precipitates and can be easily removed by filtration or decantation.
These reactions are preferably carried out in an inert hydrocarbon such as hexane, heptane, octane, decane, cyclohexane, benzene, toluene and xylene. The reaction temperature may be any temperature as long as the reaction proceeds, but it is preferably 0 ° C. or higher, more preferably 20 ° C. or higher. Heating above the boiling point of the solvent used and allowing the reaction to occur under reflux of the solvent is a good method for completing the reaction. The reaction time may be arbitrary, but it is preferably 1 hour or longer, more preferably 2 hours or longer. After completion of the reaction, it may be cooled as it is and may be subjected to the reaction with the chromium catalyst as a solution, or the solvent may be removed and the reaction product may be isolated. .
For the synthesis method and physical / chemical properties of dialkylaluminum alkoxide, see T.W. Mole et al., Organoaluminum Compounds, 3rd. ed. 1972, Elsevier, Chapter 8 and so on.

The supported amount of the organoaluminum compound (d) is such that the molar ratio of the organoaluminum compound to the chromium atom is 0.01 to 20, preferably 0.03 to 15, and more preferably 0.05 to 10. When the molar ratio is less than 0.01, the effect of supporting the organoaluminum compound is not sufficiently exhibited, and the ethylene polymerization activity and durability are not so different from those when the organoaluminum compound is not supported. On the other hand, if this molar ratio exceeds 20, the ethylene polymerization activity will be lower than when no alkylaluminum alkoxide compound is supported. The reason for this decrease in activity is unknown, but it is considered that an excess of the organoaluminum compound is bonded to the chromium active site to inhibit the ethylene polymerization reaction.
At this time, by increasing the amount of the organoaluminum compound (d) supported on the catalyst carrier, the HLMFR of polyethylene obtained by ethylene polymerization increases. That is, the fluidity increases. In order to obtain polyethylene having fluidity particularly for large blow molded products, the molar ratio of the organoaluminum compound (d) to chromium atoms is 0.01 to 2.0, preferably 0.05 to 1.8. More preferably, it is 0.10-1.5.

  The method for supporting the organometallic compound is not particularly limited as long as it is a method in which the chromium catalyst after calcination activation is brought into contact with the liquid phase in the inert hydrocarbon. For example, the chromium catalyst after calcination activation is mixed with an inert hydrocarbon solvent such as propane, n-butane, isobutane, n-pentane, isopentane, hexane, heptane, octane, decane, cyclohexane, benzene, toluene, xylene, etc. A method of forming a slurry state and adding an organoaluminum compound thereto is preferable. The organoaluminum compound to be added may be diluted with the inert hydrocarbon solvent or may be added without dilution. The diluting solvent and the supporting solvent may be the same or different.

  The amount of the inert hydrocarbon solvent used is preferably an amount sufficient to allow stirring in a slurry state at the time of preparation of the catalyst. If it is such quantity, the usage-amount of a solvent will not be specifically limited, For example, 2-20g of solvents can be used per 1g of chromium catalysts after calcination activation.

  In the present invention, when the chromium catalyst is treated with an organic magnesium compound or an alumoxane compound in an inert hydrocarbon solvent, and further with an organoaluminum compound, the order of addition is arbitrary. Specifically, a supporting reaction in which a chromium catalyst is suspended in an inert hydrocarbon solvent, a compound selected from an organic magnesium compound or an alumoxane compound is added, and then an organoaluminum compound is added and stirred. Operation is preferred.

  The temperature of the supporting reaction 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, more preferably. Is 1 to 4 hours.

After the stirring is stopped and the loading operation is completed, it is necessary to quickly remove the solvent. The removal of the solvent is performed by drying under reduced pressure. At this time, filtration can be used in combination. In this vacuum drying, drying is performed so that the organometallic compound-supported chromium catalyst is obtained as a fluid powder having no viscosity and no moisture. If the catalyst is stored for a long time without being separated from the solvent, the catalyst deteriorates with time, and the ethylene polymerization activity decreases. In addition, since the molecular weight distribution is widened, the durability is improved, but the impact resistance is lowered, which is not preferable.
Therefore, it is preferable to shorten the contact time with the solvent as much as possible, including the contact time with the solvent during the supporting reaction, and to quickly separate and remove the solvent. There is no technical document describing the effect that a polyethylene having improved durability and impact resistance can be obtained by rapid separation and removal of the solvent. It is one of the most important features of the invention.

Therefore, in order not to substantially reduce the polymerization activity and the impact strength of the resulting polymer, even if it is lowered, the degree of reduction is minimized so that the time of contact with the solvent in the supporting reaction is added together. Try to keep the contact time as short as possible. That is, it is necessary to shorten the supporting reaction time, which is the contact time with the solvent, as much as possible and to separate the solvent promptly after the supporting so that the overreduction reaction does not proceed.
After completion of the supporting reaction, the time required for separating the solvent and completing the drying is preferably within 20 hours, more preferably within 15 hours, and particularly preferably within 10 hours. The total time from the start of loading to the completion of solvent removal / drying is 5 minutes to 28 hours, preferably 30 minutes to 24 hours, and more preferably 1 to 20 hours.

[II] Functions and Mechanisms of Ethylene Polymerization Catalyst The reaction that occurs on the silica surface when calcination activation was performed using chromium acetate as the chromium compound (b) is shown below.
Silanol groups on the silica surface react with chromium acetate, and the carboxyl groups burn, resulting in a chromate structure. In ethylene polymerization using this calcination activated chromium catalyst, the chromate structure is reduced by ethylene during the polymerization. The time required for this reduction is called induction time. As a result of the reduction reaction with ethylene, the chromium portion becomes a polymerization active precursor structure as shown in the reaction, whereby the polymerization of ethylene is started.

  In the present invention, the activity is greatly increased by supporting the first metal compound selected from the organomagnesium compound (c-1) or the alumoxane compound (c-2). At this time, it is considered that the effect appears by reducing the number of silanols by reacting with the silanol groups in the carrier. Since the amount of the organometallic compound added here is extremely small compared to the amount of silica gel, it is considered that the added organometallic compound is concentrated and reacting on the surface of the silica particles.

  Further, by treating with the organoaluminum compound (d), at least a part of the hexavalent chromium atom is reduced to a low-valent chromium atom. This reaction is shown below.

The amount of organoaluminum added here is very small compared to the amount of silica gel, so the added organoaluminum compound is considered to be concentrated on the surface of the silica particles and reacting.
The fact that the added organoaluminum compound is concentrated on the surface is supported by the results of EPMA. In other words, this organoaluminum compound-supported chromium catalyst is composed of an inner part (part A) in which no organoaluminum compound is present in one silica particle, and a surface part in which at least some of the chromium atoms are reduced by organoaluminum. In this sense, this catalyst can be called a “pseudo binary catalyst” (see FIG. 1). Since many aluminum atoms are present on the surface of the carrier, a schematic illustration is as shown in FIG.

When the ethylene is introduced into the pseudo-binary catalyst, the polyethylene produced from the Cr active site that has been reduced by the organoaluminum compound in advance and the polyethylene produced from the Cr active site that is reduced by introducing ethylene are different. It is not strange to have the features.
In fact, as the amount of organoaluminum compound added increases, the HLMFR (high load melt flow rate, temperature 190 ° C., load 21.6 kg) of the resulting polyethylene increases, that is, the average molecular weight decreases. It has been. Part B (surface part) in which a polymer having a peak of a lower molecular weight component than a polymer produced from part A (inner part) that has not reacted with the organoaluminum compound is at least partially reduced by the organoaluminum compound It is thought that it is generated from.
In other words, polyethylene with a molecular weight distribution with two different properties can be made with one catalyst. As a result, polyethylene having a broad molecular weight distribution can be obtained from the catalyst of the present invention, which is a pseudo binary catalyst, as compared with polyethylene obtained from a chromium catalyst to which no organoaluminum compound is added.

Moreover, the following can be considered as one of the features of this catalyst system.
That is, it is known that the addition of a dialkyl alkoxide represented by diethylaluminum ethoxide to a chromium catalyst reduces the copolymerizability of the catalyst as compared to before addition. When this is considered in light of the idea of “pseudo binary catalyst”, the copolymerizability of the portion A is not changed, but the copolymerizability of the portion B is reduced, so that the copolymerization property as the entire catalyst is reduced. Can be said to have declined. That is, the dialkyl alkoxide-supported chromium catalyst produces polyethylene that does not contain many branched chains in the low molecular weight component, compared to the non-aluminum-supported chromium catalyst.
In general, it is known as a defect of a chromium catalyst that branching is less likely to be incorporated in a high molecular weight component than in a low molecular weight component. However, by using a dialkyl alkoxide-supported chromium catalyst, the copolymerizability of the low molecular weight component can be lowered, and the relative number of branches of the high molecular weight component in the whole can be increased.

An electron probe microanalyzer (hereinafter abbreviated as EPMA) is a device having the following principle.
An electron beam that has been squeezed and accelerated to a diameter of 1 μm or less is applied to the sample surface, and characteristic X-rays emitted therefrom are measured with an X-ray spectrometer. Characteristic X-rays are X-rays generated by the transition of core electrons surrounding the nuclei of each element, and appear as several wavelengths (energy) inherent to the element. Therefore, the element type can be determined from the wavelength of the characteristic X-ray, and the element content can be determined from the intensity.

[III] Polyethylene According to the polymerization method of the present invention, the organoaluminum compound is previously supported on the chromium catalyst, and the catalyst in which the molar ratio of the organoaluminum compound to the chromium atom is always constant is supplied into the reactor. Can be stably and continuously produced.
Therefore, the ethylene polymerization method of the present invention is an excellent method suitable for continuously producing polyethylene of a certain quality.

  On the other hand, it is not a method using a catalyst in which the solvent during the supporting reaction is rapidly separated and removed as in the present invention, but (i) a chromium catalyst, an organomagnesium compound or an alumoxane compound, and an organoaluminum compound in the reactor. A method of feeding directly or separately in the presence or absence of a diluting solvent, or (ii) premixing or contacting a chromium catalyst, an organomagnesium compound or an alumoxane compound, and an organoaluminum compound once in a solvent. In the method of feeding the slurry to the reactor, there is a problem that the ethylene polymerization activity is lowered or it is difficult to obtain the reproducibility of the polymerization result.

In producing polyethylene using the above-mentioned organometallic compound-supported chromium catalyst, any method such as slurry polymerization, liquid phase polymerization method such as solution polymerization, or gas phase polymerization method can be employed.
The liquid phase polymerization method is usually performed in a hydrocarbon solvent. As the hydrocarbon solvent, inert hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, hexane, heptane, octane, decane, cyclohexane, benzene, toluene, and xylene are used alone or as a mixture.

  In addition, the vapor phase polymerization method can adopt a commonly known polymerization method such as a fluidized bed and a stirring bed in the presence of an inert gas, and in some cases, a so-called condensing mode in which a medium for removing the heat of polymerization coexists. You can also.

  The polymerization temperature in the liquid phase or gas phase polymerization method is generally 0 to 300 ° C, practically 20 to 200 ° C, preferably 50 to 180 ° C, and more preferably 70 to 150 ° C. The catalyst concentration and ethylene concentration in the reactor may be any concentration sufficient to allow the polymerization to proceed. For example, the catalyst concentration can range from about 0.0001 to about 5% by weight based on the weight of the reactor contents in the case of liquid phase polymerization. Similarly, in the case of gas phase polymerization, the ethylene concentration can be in the range of 0.1 to 10 MPa as the total pressure.

  In order to increase the HLMFR (high load melt flow rate, temperature 190 ° C., load 21.6 kg) of polyethylene, polymerization may be carried out particularly in the presence of hydrogen. By allowing hydrogen to coexist, the polymerization temperature can be lowered to further broaden the molecular weight distribution.

  When ethylene is polymerized by the method of the present invention, it is preferable to copolymerize an α-olefin as a comonomer. As the α-olefin, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, or the like is introduced alone or in two or more kinds into the reactor for copolymerization. Preferably 1-butene, 1-hexene, more preferably 1-hexene is suitably used as a comonomer. The α-olefin content in the obtained polyethylene is 15 mol% or less, preferably 10 mol% or less.

2. Properties and Uses of Polyethylene According to the method of the present invention, HLMFR is 0.1 to 100 g / 10 min, preferably 0.5 to 80 g / 10 min, and the density is 0.900 to 0.980 g / cm ³ , preferably 0.8. A polyethylene of 920 to 0.970 g / cm ³ is obtained.
The obtained polyethylene has high impact resistance and durability, and is excellent in balance, so that it is particularly effective for blow molded products, especially large blow molded products. The HLMFR of polyethylene for blow molded products is 1 to 100 g / 10 min, and particularly the polyethylene for large blow molded products is 1 to 15 g / 10 min. The density of polyethylene for blow molded products is 0.935 to 0.970 g / cm ³ , and particularly the density of polyethylene for large blow molded products is 0.940 to 0.955 g / cm ³ .

  As a polymerization method, not only single-stage polymerization in which polyethylene is produced using one reactor, but also multistage polymerization can be performed by connecting at least two reactors in order to widen the molecular weight distribution. In the case of multi-stage polymerization, two-stage polymerization is preferred in which two reactors are connected and the reaction mixture obtained by polymerization in the first-stage reactor is continuously fed to the second-stage reactor. Transfer from the first-stage reactor to the second-stage reactor is performed by continuous discharge of the polymerization reaction mixture from the first-stage reactor through a connecting pipe with a differential pressure.

  Any method for producing a high molecular weight component in the first stage reactor, a low molecular weight component in the second stage reactor, a low molecular weight component in the first stage reactor, and a high molecular weight component in the second stage reactor, respectively. Although it is better to produce a high molecular weight component in the first stage reactor and a low molecular weight component in the second stage reactor, it does not require an intermediate hydrogen flash tank for the transition from the first stage to the second stage. More preferable in terms of productivity.

  In the first stage, copolymerization of ethylene alone or optionally with α-olefin is carried out by adjusting the molecular weight by mass ratio or partial pressure ratio of hydrogen concentration to ethylene concentration (Hc / ETc or Hp / ETp), polymerization temperature or both. While adjusting, the polymerization reaction is carried out while adjusting the density by the mass ratio or partial pressure ratio of the α-olefin concentration to the ethylene concentration.

  In the second stage, there are hydrogen in the reaction mixture flowing from the first stage and an α-olefin that also flows in, but if necessary, new hydrogen and α-olefin can be added respectively. Accordingly, in the second stage, the mass ratio of hydrogen concentration to ethylene concentration or partial pressure ratio (Hc / ETc or Hp / ETp), the polymerization temperature or the molecular weight is adjusted by both, and the mass of α-olefin concentration to ethylene concentration. The polymerization reaction can be carried out while adjusting the density by the ratio or the partial pressure ratio. For organometallic compounds such as catalysts and organoaluminum compounds, not only does the polymerization reaction continue in the second stage with the catalyst flowing in from the first stage, but also a new catalyst, organometallic compounds such as organoaluminum compounds in the second stage. Compounds or both may be supplied.

  As a ratio of the high molecular weight component and the low molecular weight component in the case of producing by two-stage polymerization, the high molecular weight component is 10 to 90 parts by weight, the low molecular weight component is 90 to 10 parts by weight, and preferably the high molecular weight component is 20 to 80 parts by weight. Parts, low molecular weight components are 80 to 20 parts by mass, more preferably high molecular weight components are 30 to 70 parts by mass, and low molecular weight components are 70 to 30 parts by mass.

The HLMFR of polyethylene obtained by two-stage polymerization is 0.1 to 100 g / 10 min, preferably 0.5 to 80 g / 10 min, but 1 to 100 g / 10 min as a resin for blow molded products, especially large The resin for blow molded products is 1 to 15 g / 10 min. The density of polyethylene obtained by two-stage polymerization is 0.900 to 0.980 g / cm ³ , preferably 0.920 to 0.970 g / cm ³ , but 0.935 to 0 as a resin for blow molded products. the .970g / cm ^3, especially large blow molded products resin is 0.940~0.955g / cm ^3. The obtained polyethylene is preferably kneaded. Kneading can be performed using a single or twin screw extruder or a continuous kneader. Further, the obtained ethylene can be blow-molded by a conventional method.

  The use of the polyethylene obtained in the present invention is a hollow plastic molded product such as a fuel tank, kerosene can, drum can, chemical container, agricultural chemical container, solvent container, or plastic bottle.

When obtaining the polyethylene according to the present invention using the organometallic compound-supported chromium catalyst of the present invention, the polymerization conditions for improving the characteristics represented by the respective aluminum compounds and the durability represented by the creep resistance, The relationship is described below.
In order to improve the creep resistance of polyethylene, it is important to widen the molecular weight distribution. That is, in order to improve creep resistance, it is preferable to increase the molecular weight as much as possible. However, if the molecular weight is too high, the resin cannot be molded. Therefore, in order to impart flowability, polyethylene in a low molecular weight region is also used. Necessary, and as a result, it is necessary to broaden the molecular weight distribution (cf. J. Scheirs, W. Kaminsky, edited by Metallocene-based Polyfins, Volume 2, page 365, 2000, John Wiley & Sons).

In the case of obtaining polyethylene with a general chromium catalyst, in order to broaden the molecular weight distribution, it is usual to lower the activation temperature and / or the polymerization temperature (for example, edited by Kazuo Matsuura and Naotaka Mikami, “Polyethylene Technology Reader”). "See page 134, 2001, Industrial Research Council.).
However, when the activation temperature and / or the polymerization temperature are lowered, the activity is generally lowered, and at the same time, HLMFR is also lowered (see the above-mentioned “Polyethylene Technology Reader”, page 134). It is often impossible to set economically manufacturable polymerization conditions for obtaining HLMFR polyethylene.

In the case of a general chromium catalyst, when the activation temperature is lower than 350 ° C., the polymerization activity is drastically reduced, and even if the molecular weight distribution is expanded by lowering the polymerization temperature, it falls below the predetermined HLMFR range. It is difficult to practically produce such a wide molecular weight distribution.
However, this can be achieved, for example, with the organometallic compound-supported chromium catalyst of the present invention. That is, by supporting an organoaluminum compound, the molecular weight can be improved, the polymerization temperature can be lowered, and the molecular weight distribution can be further expanded. As a result, within a predetermined HLMFR range, Mw / Mn> 20, preferably Mw / Mn> 25, more preferably Mw / Mn> 30, and the polymerization activity can be practically produced. You can keep the level. Furthermore, it is an important point of the present invention that the activity can be further increased by using an organomagnesium compound or MAO compound together with an organoaluminum compound as a catalyst system.

  In the following, the present invention will be described in more detail with reference to examples and comparative examples, and the superiority of the present invention and the superiority in the structure of the present invention will be demonstrated, but the present invention is limited by these examples. It is not a thing.

(I) Various measurement methods In the examples and comparative examples, the measurement methods used are as follows.

1. Evaluation of physical properties of polyethylene obtained by autoclave polymerization:
(I) Polymer pretreatment for measuring physical properties:
As an additive, 0.2% by weight of “IRGANOX B225”, which is a blend of an antioxidant and a phosphorus stabilizer manufactured by Ciba Specialty Chemicals, was added, kneaded in a single screw extruder, and pelletized.
(Ii) High load melt flow rate (HLMFR):
According to JIS K7210 (2004 edition), Annex A Table 1-Condition G, a measured value at a test temperature of 190 ° C. and a nominal load of 21.60 kg is shown as HLMFR.
(Iii) Density:
Measured according to JIS K7112 (2004 edition).
(Iv) Molecular weight distribution (Mw / Mn):
The produced polyethylene was subjected to gel permeation chromatography (GPC) under the following conditions to determine the number average molecular weight (Mn) and the weight average molecular weight (Mw), and the molecular weight distribution (Mw / Mn) was calculated.
[Gel permeation chromatographic measurement conditions]:
Equipment: 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 indicated by the ratio of Mw to Mn (Mw / Mn) (the larger the Mw / Mn, the wider the molecular weight distribution), “size exclusion chromatography (high-performance liquid chromatography of polymers)” (written by Sadao Mori, The data of molecular weight and detector sensitivity described in Kyoritsu Shuppan, page 96) are applied to the linear linear polyethylene data of n-alkane and Mw / Mn ≦ 1.2, and the sensitivity of molecular weight M shown by the following formula is obtained. The sample actual value was corrected.
Sensitivity of molecular weight M = a + b / M
(A and b are constants, and a = 1.002 and b = 189.2.)

(II) Production and evaluation of polyethylene in an autoclave

[Example 1]
(1) Preparation of chromium catalyst Catalyst-1 having a chromium atom loading of 1.1% by weight, a specific surface area of 500 m ² / g, and a pore volume of 1.5 cm ³ / g (supporting chromium acetate on silica (Catalyst) is prepared in 15 g, put in a quartz glass tube with a perforated plate and a tube diameter of 5 cm, set in a cylindrical firing electric furnace, fluidized with air through molecular sieves, and a linear velocity of 6 cm / s. And calcination activation at 500 ° C. for 18 hours. An orange chrome catalyst was obtained indicating that it contained hexavalent chromium atoms.
(2) Organometallic compound-supported chromium catalyst 2 g of the chromium catalyst obtained in (1) above was placed in a 100 ml flask previously purged with nitrogen, and 30 ml of distilled and purified hexane was added to form a slurry. 0.42 ml (Mg / Cr molar ratio = 1.0) of 1.0 mol / L-heptane solution of dibutylmagnesium manufactured by Aldrich was added and stirred at 40 ° C. for 1 hour. Next, 0.8 ml (Al / Cr molar ratio = 0.2) of 0.1 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co. was added and stirred at 40 ° C. for 1 hour. Immediately after completion of the stirring, the solvent was removed under reduced pressure over 30 minutes to obtain a free-flowing organometallic compound-supported chromium catalyst free from viscosity and moisture.
(3) Polymerization 100 mg of the organometallic compound-supported chromium catalyst obtained in the above (2) and 0.8 L of isobutane were charged into a 2.0 L autoclave sufficiently substituted with nitrogen, and the internal temperature was raised to 100 ° C. Polymerization was carried out so that catalyst productivity was 3000 g-polymer / g-catalyst while 5.0 g of 1-hexene was introduced under pressure with ethylene and the ethylene partial pressure was kept at 1.4 MPa. Subsequently, the polymerization was terminated by releasing the content gas out of the system. The polymerization results and polymer properties are shown in Table 1.

[Example 2]
In Example 1 (2) above, 0.42 ml (Mg / Cr molar ratio = 1.0) of 1.0 mol / L-heptane solution of butylethylmagnesium manufactured by Tosoh Finechem Co. instead of dibutylmagnesium manufactured by Aldrich All operations were the same as in Example 1 except that they were used. The polymerization results and polymer properties are shown in Table 1.

[Example 3]
In Example 1 (2), instead of Aldrich dibutylmagnesium, 0.42 ml (Al / Cr molar ratio = 1.0) of 1.0 mol / L-hexane solution of MMAO-3A manufactured by Tosoh Finechem Co., Ltd. was used. All operations were the same as in Example 1 except that they were used. The polymerization results and polymer properties are shown in Table 1.

[Example 4]
In Example 1 (2) above, 0.1 ml / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co., Ltd. was not 0.8 ml (Al / Cr molar ratio = 0.2) but 2.1 ml (Al / Cr molar ratio = 0.5) All operations were the same as in Example 1 except that the addition was made. The polymerization results and polymer properties are shown in Table 1.

[Example 5]
In the above Example 1 (2), 0.42 ml (Mg / Cr molar ratio = 1.0) of 1.0 mol / L-heptane solution of butylethylmagnesium manufactured by Tosoh Finechem Co. instead of dibutylmagnesium manufactured by Aldrich, Furthermore, 0.1 ml / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co., Ltd. is not 0.8 ml (Al / Cr molar ratio = 0.2) but 2.1 ml (Al / Cr molar ratio = 0.0). 5) The same operation as in Example 1 was carried out except that it was added. The polymerization results and polymer properties are shown in Table 1.

[Example 6]
In the above Example 1 (2), 0.42 ml (Al / Cr molar ratio = 1.0) of 1.0 mol / L-hexane solution of MMAO-3A manufactured by Tosoh Finechem Co. instead of dibutylmagnesium manufactured by Aldrich, Furthermore, 0.1 ml / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co., Ltd. is not 0.8 ml (Al / Cr molar ratio = 0.2) but 2.1 ml (Al / Cr molar ratio = 0.0). 5) The same operation as in Example 1 was carried out except that it was added. The polymerization results and polymer properties are shown in Table 1.

[Example 7]
In the above Example 1 (2), 0.42 ml (Mg / Cr molar ratio = 1.0) of 1.0 mol / L-heptane solution of butylethylmagnesium manufactured by Tosoh Finechem Co. instead of dibutylmagnesium manufactured by Aldrich, Further, 0.1 ml / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co., Ltd. is not 0.8 ml (Al / Cr molar ratio = 0.2) but 1.2 ml (Al / Cr molar ratio = 0.0). 3) The same operation as in Example 1 was carried out except that it was added. The polymerization results and polymer properties are shown in Table 1.

[Example 8]
In the above Example 1 (2), 0.42 ml (Mg / Cr molar ratio = 1.0) of 1.0 mol / L-heptane solution of butylethylmagnesium manufactured by Tosoh Finechem Co. instead of dibutylmagnesium manufactured by Aldrich, Further, a 0.1 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co., Ltd. is not 0.8 ml (Al / Cr molar ratio = 0.2) but 1.6 ml (Al / Cr molar ratio = 0.0). 4) The same operation as in Example 1 was carried out except that it was added. The polymerization results and polymer properties are shown in Table 1.

[Example 9]
In the above Example 1 (2), 0.42 ml (Al / Cr molar ratio = 1.0) of 1.0 mol / L-hexane solution of MMAO-3A manufactured by Tosoh Finechem Co. instead of dibutylmagnesium manufactured by Aldrich, Furthermore, 0.1 ml / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co., Ltd. is not 8.4 ml (Al / Cr molar ratio = 0.2) but 8.4 ml (Al / Cr molar ratio = 2. 0) The same operation as in Example 1 was carried out except that it was added. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 1]
In a 2.0 L autoclave sufficiently purged with nitrogen, 100 mg of the activated chromium catalyst obtained in Example 1 (1) and 0.8 L of isobutane were charged, and the internal temperature was raised to 100 ° C. While maintaining the ethylene partial pressure to be 1.4 MPa, the polymerization was carried out so that the catalyst productivity was 3000 g-polymer / g-catalyst. Subsequently, the polymerization was terminated by releasing the content gas out of the system. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 2]
In a 2.0 L autoclave sufficiently purged with nitrogen, 100 mg of the activated chromium catalyst obtained in Example 1 (1) and 0.8 L of isobutane were charged, and the internal temperature was raised to 100 ° C. Polymerization was carried out so that catalyst productivity was 3000 g-polymer / g-catalyst while 5.0 g of 1-hexene was introduced under pressure with ethylene and the ethylene partial pressure was kept at 1.4 MPa. Subsequently, the polymerization was terminated by releasing the content gas out of the system. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 3]
(1) Preparation of chromium catalyst An activated chromium catalyst was obtained by performing the same operation as in Example 1 (1).
(2) Organometallic compound-supported chromium catalyst 2 g of the chromium catalyst obtained in the above (1) was added, and 30 ml of distilled and purified hexane was added to prepare a slurry. 0.08 ml (Mg / Cr molar ratio = 0.2) of 1.0 mol / L-heptane solution of dibutylmagnesium manufactured by Aldrich was added and stirred at 40 ° C. for 2 hours. Immediately after completion of the stirring, the solvent was removed under reduced pressure over 30 minutes to obtain a free-flowing organometallic compound-supported chromium catalyst free from viscosity and moisture.
(3) Polymerization 100 mg of the organometallic compound-supported chromium catalyst obtained in the above (2) and 0.8 L of isobutane were charged into a 2.0 L autoclave sufficiently substituted with nitrogen, and the internal temperature was raised to 100 ° C. While maintaining the ethylene partial pressure to be 1.4 MPa, the polymerization was carried out so that the catalyst productivity was 3000 g-polymer / g-catalyst. Subsequently, the polymerization was terminated by releasing the content gas out of the system. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 4]
Except for adding 0.01 ml (Mg / Cr molar ratio = 0.2) of a 1.0 mol / L-heptane solution of dibutylmagnesium manufactured by Aldrich, 0.21 ml (Mg / Cr molar ratio = 0.5). All were performed in the same manner as in Comparative Example 3. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 5]
Except for adding 0.02 ml (Mg / Cr molar ratio = 0.2) of 1.0 mol / L-heptane solution of dibutylmagnesium manufactured by Aldrich, 0.42 ml (Mg / Cr molar ratio = 1.0) All were performed in the same manner as in Comparative Example 3. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 6]
Into a 2.0 L autoclave sufficiently purged with nitrogen, 100 mg of the organometallic compound-supported chromium catalyst used in Comparative Example 5 and 0.8 L of isobutane were charged, and the internal temperature was raised to 100 ° C. Polymerization was carried out so that catalyst productivity was 3000 g-polymer / g-catalyst while 5.0 g of 1-hexene was introduced under pressure with ethylene and the ethylene partial pressure was kept at 1.4 MPa. Subsequently, the polymerization was terminated by releasing the content gas out of the system. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 7]
Instead of 0.08 ml (Mg / Cr molar ratio = 0.2) of a 1.0 mol / L-heptane solution of dibutylmagnesium manufactured by Aldrich, a 1.0 mol / L-hexane solution of MMAO-3A manufactured by Tosoh Finechem All operations were the same as in Comparative Example 3 except that 0.42 ml (Al / Cr molar ratio = 1.0) was added. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 8]
Except that 0.42 ml (Mg / Cr molar ratio = 1.0) was added instead of 0.42 ml (Mg / Cr molar ratio = 1.0) of a 1.0 mol / L-heptane solution of Aldrich dibutyl magnesium. All were performed in the same manner as in Comparative Example 6. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 9]
Instead of 0.42 ml (Al / Cr molar ratio = 1.0) of 1.0 mol / L-hexane solution of MMAO-3A manufactured by Tosoh Finechem Co., Ltd., 0.84 ml (Al / Cr molar ratio = 2.0) All operations were the same as in Comparative Example 7 except for the addition. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 10]
Instead of 0.42 ml (Al / Cr molar ratio = 1.0) of MMAO-3A MMAO-3A manufactured by Tosoh Finechem Co., Ltd., 1.3 ml (Al / Cr molar ratio = 3.0) All operations were the same as in Comparative Example 7 except for the addition. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 11]
Except that 0.08 ml (Mg / Cr molar ratio = 0.2) was added instead of 0.08 ml (Mg / Cr molar ratio = 0.2) of 1.0 mol / L-heptane solution of Aldrich dibutyl magnesium. All were performed in the same manner as in Comparative Example 3. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 12]
Into a 2.0 L autoclave thoroughly purged with nitrogen, 100 mg of the organometallic compound-supported chromium catalyst used in Comparative Example 8 and 0.8 L of isobutane were charged, and the internal temperature was raised to 100 ° C. Polymerization was carried out so that catalyst productivity was 3000 g-polymer / g-catalyst while 5.0 g of 1-hexene was introduced under pressure with ethylene and the ethylene partial pressure was kept at 1.4 MPa. Subsequently, the polymerization was terminated by releasing the content gas out of the system. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 13]
Instead of 0.08 ml (Mg / Cr molar ratio = 0.2) of a 1.0 mol / L-heptane solution of dibutylmagnesium manufactured by Aldrich, a 1.0 mol / L-hexane solution of MMAO-3A manufactured by Tosoh Finechem The same operations as in Comparative Example 3 were performed except that 2.1 ml (Mg / Al molar ratio = 5.0) was added. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 14]
(1) Preparation of chromium catalyst An activated chromium catalyst was obtained by performing the same operation as in Example 1 (1).
(2) Organometallic compound-supported chromium catalyst 2 g of the chromium catalyst obtained in the above (1) was added, and 30 ml of distilled and purified hexane was added to prepare a slurry. 0.8 ml (Al / Cr molar ratio = 0.2) of 0.1 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co. was added and stirred at 40 ° C. for 2 hours. Immediately after completion of the stirring, the solvent was removed under reduced pressure over 30 minutes to obtain a free-flowing organometallic compound-supported chromium catalyst free from viscosity and moisture.
(3) Polymerization 100 mg of the organometallic compound-supported chromium catalyst obtained in the above (2) and 0.8 L of isobutane were charged into a 2.0 L autoclave sufficiently substituted with nitrogen, and the internal temperature was raised to 100 ° C. While maintaining the ethylene partial pressure to be 1.4 MPa, the polymerization was carried out so that the catalyst productivity was 3000 g-polymer / g-catalyst. Subsequently, the polymerization was terminated by releasing the content gas out of the system. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 15]
(1) Preparation of chromium catalyst An activated chromium catalyst was obtained by performing the same operation as in Example 1 (1).
(2) Diethylaluminum ethoxide-supported chromium catalyst 2 g of the chromium catalyst obtained in the above (1) was added, and 30 ml of distilled and purified hexane was added to form a slurry. 5.1 ml (Al / Cr molar ratio = 1.2) of 0.1 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co. was added and stirred at 40 ° C. for 2 hours. Immediately after completion of the stirring, the solvent was removed under reduced pressure over 30 minutes to obtain a free flowing, free flowing, diethyl aluminum ethoxide supported chromium catalyst free of moisture.
(3) Polymerization A 2.0-L autoclave sufficiently purged with nitrogen was charged with 100 mg of the diethylaluminum ethoxide-supported chromium catalyst obtained in (2) above and 0.8 L of isobutane, and the internal temperature was raised to 100 ° C. While maintaining the ethylene partial pressure to be 1.4 MPa, the polymerization was carried out so that the catalyst productivity was 3000 g-polymer / g-catalyst. Subsequently, the polymerization was terminated by releasing the content gas out of the system. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 16]
A 2.0-L autoclave thoroughly purged with nitrogen was charged with 100 mg of diethylaluminum ethoxide-supported chromium catalyst used in Comparative Example 12 and 0.8 L of isobutane, and the internal temperature was raised to 100 ° C. Polymerization was carried out so that catalyst productivity was 3000 g-polymer / g-catalyst while 5.0 g of 1-hexene was introduced under pressure with ethylene and the ethylene partial pressure was kept at 1.4 MPa. Subsequently, the polymerization was terminated by releasing the content gas out of the system. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 17]
(1) Preparation of chromium catalyst An activated chromium catalyst was obtained by performing the same operation as in Example 1 (1).
(2) Organometallic compound-supported chromium catalyst 2 g of the chromium catalyst obtained in the above (1) was added, and 30 ml of distilled and purified hexane was added to prepare a slurry. 8.4 ml (Al / Cr molar ratio = 2.0) of 0.1 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co., Ltd. was added and stirred at 40 ° C. for 2 hours. Immediately after completion of the stirring, the solvent was removed under reduced pressure over 30 minutes to obtain a free-flowing organometallic compound-supported chromium catalyst free from viscosity and moisture.
(3) Polymerization A 2.0-L autoclave sufficiently purged with nitrogen was charged with 100 mg of the diethylaluminum ethoxide-supported chromium catalyst obtained above and 0.8 L of isobutane, and the internal temperature was raised to 100 ° C. Polymerization was carried out so that catalyst productivity was 3000 g-polymer / g-catalyst while 5.0 g of 1-hexene was introduced under pressure with ethylene and the ethylene partial pressure was kept at 1.4 MPa. Subsequently, the polymerization was terminated by releasing the content gas out of the system. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 18]
(1) Preparation of chromium catalyst An activated chromium catalyst was obtained by performing the same operation as in Example 1 (1).
(2) Organometallic compound-supported chromium catalyst 2 g of the chromium catalyst obtained in the above (1) was added, and 30 ml of distilled and purified hexane was added to prepare a slurry. 2.1 ml (Al / Cr molar ratio = 5.0) of a 1.0 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co. was added and stirred at 40 ° C. for 2 hours. Immediately after completion of the stirring, the solvent was removed under reduced pressure over 30 minutes to obtain a free-flowing organometallic compound-supported chromium catalyst free from viscosity and moisture.
(3) Polymerization A 2.0-L autoclave sufficiently purged with nitrogen was charged with 100 mg of the diethylaluminum ethoxide-supported chromium catalyst obtained above and 0.8 L of isobutane, and the internal temperature was raised to 100 ° C. While maintaining the ethylene partial pressure to be 1.4 MPa, the polymerization was carried out so that the catalyst productivity was 3000 g-polymer / g-catalyst. Subsequently, the polymerization was terminated by releasing the content gas out of the system. The polymerization results and polymer properties are shown in Table 1.

[Comparative Example 19]
(1) Preparation of chromium catalyst An activated chromium catalyst was obtained by performing the same operation as in Example 1 (1).
(2) Organometallic compound-supported chromium catalyst 2 g of the chromium catalyst obtained in the above (1) was added, and 30 ml of distilled and purified hexane was added to prepare a slurry. 8.4 ml (Al / Cr molar ratio = 20) of a 1.0 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Corporation was added, and the mixture was stirred at 40 ° C. for 2 hours. Immediately after completion of the stirring, the solvent was removed under reduced pressure over 30 minutes to obtain a free-flowing organometallic compound-supported chromium catalyst free from viscosity and moisture.
(3) Polymerization A 2.0-L autoclave sufficiently purged with nitrogen was charged with 100 mg of the diethylaluminum ethoxide-supported chromium catalyst obtained above and 0.8 L of isobutane, and the internal temperature was raised to 100 ° C. The ethylene partial pressure was kept at 1.4 MPa. At this time, polyethylene was not obtained.

[Comparative Example 20] (Example 1 of JP-A-2-105806)
(1) Preparation of chromium catalyst Catalyst-2 having a chromium atom loading of 2% by weight, a specific surface area of 300 m2 / g, and a pore volume of 1.6 cm ³ / g (a catalyst having chromium trioxide supported on silica) Was prepared and activated by calcination at 500 ° C. for 5 hours in a fluidized bed while circulating oxygen.
(2) Preparation of polyisobutylalumoxane To a 50 ml of 1.0 M / L-hexane solution of triisobutylaluminum under ice-cooling, nitrogen was blown and deoxygenated pure water was added in an amount of 0.9 μl over 10 minutes. Water / Al molar ratio = 1). Then, the polyisobutylalumoxane-hexane solution was prepared by making it react at room temperature for 30 minutes.
(3) Polymerization A 3.0-liter autoclave sufficiently purged with nitrogen was charged with 80 mg of the organometallic compound-supported chromium catalyst obtained in (1) above and 1.5 L of hexane, and polyisobutylalumoxane 1 obtained in (2). 0.0 mmol and diisobutylaluminum propoxide 0.5 mmol were added, and the internal temperature was raised to 80 ° C. The vapor pressure of hexane was 0.15 MPa. Hydrogen was added at a partial pressure of 0.4 MPa, and when sufficiently stable, ethylene was pressurized while maintaining the total pressure at 1.0 MPa to initiate polymerization. The polymerization was terminated by releasing the content gas 60 minutes after the start of the polymerization. The polymerization results are shown in Table 1.
Although this polymerization method is excellent in polymerization activity, it is economically inefficient because many alumoxane compounds are used, and fine control of the ratio of catalyst components is necessary to reproduce the resulting polymer. There is such a thing.

(III) Analysis of catalyst structure (1) Catalyst analysis by electron probe microanalyzer (EPMA):
FIG. 2 shows the result of catalyst analysis performed by an electron probe microanalyzer as follows.

[Example 10] (Example in EPMA analysis)
The dibutylmagnesium / diethylaluminum ethoxide compound-supported chromium catalyst prepared in Example 4 was analyzed.

  The catalyst sample was embedded in a resin and then polished with abrasive paper (particle size # 1500 to # 4000). Thereafter, it was further polished with a diamond suspension (particle size: 1 μm). After Au deposition (about 300 mm), mapping analysis was performed with EPMA-1600 manufactured by Shimadzu Corporation. The EPMA analysis results are shown in FIG.

Mapping conditions Acceleration voltage (ACC.V): 15 kV
Beam current: 50 nA
Beam diameter: 1 μm
Measurement time: 50msec
Measurement area: 512 * 512μm
Spectroscopic crystal: Al; RAP (Rubidium acid phthalate) C ₆ H ₄ (COOH) (COORb)

As is clear from Table 1 above, in Examples 1 to 9 that satisfy the requirements of the present invention, all of the prepared organometallic compound-supported chromium catalysts showed excellent polymerization activity. The polyethylene produced using the organometallic compound-supported chromium catalyst showed excellent properties for blow molding in terms of density, HLMFR, and molecular weight distribution (Mw / Mn).
In contrast, Comparative Examples 1 and 2 in which a metal compound was polymerized with an unsupported chromium catalyst showed low activity, no increase in HLMFR of the resulting polymer was observed, and no molecular weight distribution was spread. Comparative Examples 3 to 13 are chromium catalyzed polymerizations supporting only the first metal compound selected from the organomagnesium compound (c-1) or the alumoxane compound (c-2). As in Comparative Examples 1 and 2, it can be seen that there is no increase in HLMFR of the obtained polymer and that the molecular weight distribution is not widened. Further, Comparative Examples 14 to 19 are chromium-catalyzed polymerizations supporting only organoaluminum, which is the second metal compound of the present invention. In this case, increase in HLMFR of the obtained polymer. Although the molecular weight distribution is broadened, the polymerization activity is low compared to the examples of the present invention.
Therefore, when a catalyst in which these two compounds are supported, that is, a catalyst treated with organomagnesium or an alumoxane compound and treated with organoaluminum is used, the activity is greatly increased and the HLMFR of the resulting polymer is increased. It is clear from the Examples that the effect of wide molecular weight distribution (Mw / Mn), which is a good direction for increasing the durability of the polymer, is obtained.

  The polyethylene obtained by the catalyst provided by the present invention is excellent in moldability, impact resistance and excellent balance between rigidity and durability by forming a hollow plastic molded product using the polyethylene. In particular, it is suitably used for fuel tanks, particularly automobile fuel tanks and the like. The catalyst of the present invention has high industrial significance in that sense.

Claims (12)

After the chromium compound (b) is supported on the inorganic oxide support (a) in a state where at least some of the chromium atoms are hexavalent, an organic magnesium compound (c-1) or an alumoxane compound (c-2) is further added. A chromium catalyst obtained by sequentially or simultaneously supporting a first metal compound selected from: and a second metal compound selected from organoaluminum compound (d):
The catalyst for ethylene polymerization, wherein the first metal compound and the second metal compound, or the second metal compound are concentrated on the surface of the inorganic oxide support (a).   When the aluminum atom content in the cross section of the catalyst particle is measured using an electron probe microanalyzer (EPMA), the detected amount of aluminum atoms present on the surface of the catalyst particle is larger than the aluminum atoms present inside the catalyst particle. The ethylene polymerization catalyst according to claim 1.   When the organomagnesium compound (c-1) is supported, when the magnesium atom content in the cross section of the catalyst particles is measured using an electron probe microanalyzer, the detected amount of magnesium atoms present on the catalyst particle surface is 3. The ethylene polymerization catalyst according to claim 1, wherein the number of the ethylene polymerization catalyst is larger than the number of magnesium atoms present therein. The ethylene polymerization catalyst according to any one of claims 1 to 3, wherein the ethylene polymerization catalyst is produced by the following steps (a) to (d).
(A): The chromium compound (b) is supported on the inorganic oxide carrier (a) and activated by firing in a non-reducing atmosphere (b): the inorganic oxide carrier (a) carrying the chromium compound (b) Further, a first metal compound selected from the organomagnesium compound (c-1) or the alumoxane compound (c-2) is supported in an inert hydrocarbon solvent (c): then selected from the organoaluminum compound (d) The second metal compound to be supported is supported in an inert hydrocarbon solvent (d): Finally, the inert hydrocarbon solvent is removed and dried.   The catalyst for ethylene polymerization according to any one of claims 1 to 4, wherein the organoaluminum compound (d) is at least one selected from dialkylaluminum alkoxides, alkylaluminum dialkoxides, or trialkylaluminums.   6. The ethylene polymerization catalyst according to claim 5, wherein the organoaluminum compound (d) is a dialkylaluminum alkoxide.   The catalyst for ethylene polymerization according to any one of claims 1 to 6, wherein the organomagnesium compound (c-1) is dibutylmagnesium or butylethylmagnesium.   The catalyst for ethylene polymerization according to any one of claims 1 to 6, wherein the alumoxane compound (c-2) is methylalumoxane (MMAO) modified with triisobutylaluminum.   A method for producing polyethylene, characterized by carrying out ethylene homopolymerization or copolymerization of ethylene and an α-olefin using the ethylene polymerization catalyst according to claim 1.   The method for producing polyethylene according to claim 9, wherein the α-olefin has 3 to 8 carbon atoms. It is polyethylene manufactured by the method of Claim 9 or 10, Comprising: The high load melt flow rate (HLMFR) in the temperature of 190 degreeC and a load of 21.6 kg is 0.1-100 g / 10min, and a density is 0.900. Polyethylene for blow molded products, characterized in that it is ˜0.980 g / cm ³ . It is polyethylene manufactured by the method of Claim 9 or 10, Comprising: The high load melt flow rate (HLMFR) in the temperature of 190 degreeC and a load of 21.6 kg is 1-15 g / 10min, and a density is 0.940-0. A polyethylene for large blow molded products, characterized in that it is 955 g / cm ³ .

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