JP2018168231A - Method for producing ethylene polymerization catalyst - Google Patents

Abstract

To provide a catalyst capable of producing an ethylene polymer which is excellent in moldability and impact resistance and is excellent in balance between rigidity and durability when a composition with other ethylene polymer is formed.SOLUTION: A method for producing a catalyst for ethylene polymerization includes: carrying an inorganic oxide carrier (a), of which a surface area is 100-550 m/g and a value obtained by dividing the surface area by a pore volume (mL/g) is 100-300 m/mL with a chromium compound (b) on in a state in which at least a part of a chromium atom becomes hexavalent; and then sequentially or simultaneously bringing a first metal compound selected from an alumoxane compound (c) and a second metal compound selected from an organic aluminum compound (d) in contact therewith.SELECTED DRAWING: None

Description

  The present invention relates to a novel method for producing a catalyst for ethylene polymerization, polyethylene for blow molded products and polyethylene for large blow molded products obtained thereby.

  Conventionally, an ethylene polymer polymerized using a chromium compound-supported catalyst is generally used as an ethylene polymer suitable for hollow molding because of its relatively wide molecular weight distribution. And such an ethylene polymer is made into the composition combined with various ethylene polymers, The moldability is improved (for example, refer patent document 1, patent document 2, or patent document 3). ).

On the other hand, various improvements have been made to the ethylene polymer itself, which is polymerized using a chromium compound-supported catalyst, and moldability such as melt tension (melt tension: MT), swell, and drawdown resistance, and rigidity and durability. The balance has been improved. And the compatibility with the ethylene polymer to combine and the improvement of the moldability and physical property balance as a composition are aimed at.
As a method for controlling the physical properties of an ethylene polymer, for example, in Patent Document 4 or Patent Document 5, an ethylene polymer having a wide molecular weight distribution is obtained by adding an organoaluminum compound to a chromium catalyst supported on a silica carrier. Is disclosed.
Furthermore, Patent Document 6 and Patent Document 7 disclose that an ethylene polymer excellent in balance between rigidity and durability can be obtained by a catalyst comprising a chromium compound, an organic magnesium compound or an alumoxane compound, and an organoaluminum compound. Has been.

  Patent Document 8 discloses that an ethylene polymer suitable for an automobile fuel tank can be obtained by a chromium catalyst carrying an organoaluminum compound. Hollow plastic molded articles used as fuel tanks in automobile parts are replacing conventional metal fuel tanks. In addition to this, plastics are currently the most frequently used material for the production of transport containers such as flammable liquids, fuel cans of harmful substances, plastic bottles and the like. Plastic containers and tanks have the features that the weight / volume ratio is lower than that made of metal materials, so they can be reduced in weight, corrosion such as rust is unlikely to occur, and impact resistance is good. And it is gaining wider use.

JP 2003-253062 A Japanese Patent Laid-Open No. 9-255819 Japanese Patent Laid-Open No. 11-138618 Japanese Patent No. 5019710 Japanese Patent No. 5762672 JP 2012-144723 A JP 2013-203983 A WO 2010/150410 International Publication Pamphlet

As described above, plastic materials having various properties have been developed, and synthesis catalysts have been developed in accordance with the applications. However, ethylene polymers produced with conventional chromium catalysts have not always been able to remarkably improve the compatibility with other ethylene polymers and the moldability and physical property balance as an ethylene polymer composition.
Catalysts for ethylene polymerization that can produce ethylene polymers with excellent moldability, impact resistance, and excellent balance between rigidity and durability to meet the strict demands of manufacturers, such as fuel tanks for automobile parts. Development is desired.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have obtained a hexavalent chromium catalyst having a specific support structure by using a catalyst that has been treated with a specific aluminum compound. It has been found that an ethylene polymer is excellent in moldability and impact resistance, and has a good balance between rigidity and durability, and the present invention has been completed based on these findings.

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, the alumoxane compound ( a method for producing an ethylene polymerization catalyst comprising sequentially or simultaneously contacting a first metal compound selected from c) and a second metal compound selected from an organoaluminum compound (d),
The inorganic oxide support (a) has the following characteristics (i) and (ii):
(I) Surface area (m ² / g) / pore volume (mL / g) is 100 to 300 m ² / mL
(Ii) A surface area of 100 to 550 m ² / g
There is provided a method for producing an ethylene polymerization catalyst characterized by comprising:

According to the second invention of the present invention, in the first invention, 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, the first metal compound selected from the alumoxane compounds (c) is contacted in an inert hydrocarbon solvent (c): Then, the second metal compound selected from the organoaluminum compound (d) is converted to an inert hydrocarbon. Contacting in a solvent (d): Finally, the method for producing an ethylene polymerization catalyst is provided, which is produced by removing and drying the inert hydrocarbon solvent.

  Furthermore, according to a third invention of the present invention, in the first or second invention, the alumoxane compound (c) is methylalumoxane modified by triisobutylaluminum, A method for producing an ethylene polymerization catalyst is provided.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the organoaluminum compound (d) is at least one selected from dialkylaluminum alkoxide, alkylaluminum dialkoxide, or trialkylaluminum. A process for producing an ethylene polymerization catalyst is provided.

  Furthermore, according to the fifth invention of the present invention, ethylene homopolymerization or copolymerization of ethylene and α-olefin is carried out using the ethylene polymerization catalyst obtained by the method according to any one of the first to fourth inventions. A method for producing an ethylene polymer is provided.

  According to a sixth aspect of the present invention, there is provided the method for producing an ethylene polymer according to any one of the first to fifth aspects, wherein the α-olefin has 3 to 8 carbon atoms. Provided.

  By using the ethylene polymerization catalyst produced by the method of the present invention, an ethylene polymer excellent in moldability and impact resistance and excellent in balance between rigidity and durability can be obtained. The polyethylene is suitable for blow-molded hollow plastic products, and the hollow plastic products have excellent moldability and impact resistance, and have a good balance between rigidity and durability. For example, for fuel tanks, especially fuel tanks for automobiles. It can be used suitably.

It is a schematic diagram explaining that the catalyst for ethylene polymerization of the present invention is a “pseudo binary catalyst”.

The present invention provides a first metal selected from alumoxane compounds (c) after supporting a chromium compound (b) on an inorganic oxide support (a) in a state where at least some of the chromium atoms are hexavalent. A method for producing an ethylene polymerization catalyst comprising sequentially contacting or simultaneously contacting a compound and a second metal compound selected from the organoaluminum compound (d),
The inorganic oxide support (a) has the following characteristics (i) and (ii):
(I) Surface area (m ² / g) / pore volume (mL / g) is 100 to 300 m ² / mL
(Ii) A surface area of 100 to 550 m ² / g
The present invention relates to a method for producing an ethylene polymerization catalyst characterized by comprising: In the following description of the present specification, “ethylene polymer” refers to polyethylene produced by a catalyst prepared by the method of the present invention unless otherwise specified, and “polyethylene composition” It refers to a composition containing an ethylene polymer. 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. And a method for producing an ethylene polymerization catalyst, wherein a first metal compound selected from alumoxane compounds (c) and a second metal compound selected from organoaluminum compounds (d) are contacted sequentially or simultaneously. ,
The inorganic oxide support (a) has the following characteristics (i) and (ii):
(I) Surface area (m ² / g) / pore volume (mL / g) is 100 to 300 m ² / mL
(Ii) A surface area of 100 to 550 m ² / g
It is prepared by a method characterized by having
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

<Components of ethylene polymerization catalyst>
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 titania, zirconia, alumina, silica, magnesia, tria, silica-titania, silica-zirconia, silica-alumina, silica-magnesia, or a mixture 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, a carrier having a specific surface area of 100 to 550 m ² / g is used. Inorganic oxide support has a specific surface area preferably 100 to 500 m ² / g, more preferably it is preferred to select such a 150~450m ² / g. When the specific surface area is less than 100 m ² / g, it is considered that the molecular weight distribution is narrow and long-chain branching increases, but both the durability and impact resistance of the resulting polyethylene composition are lowered. In addition, a carrier having a specific surface area exceeding 550 m ² / g is difficult to produce.

The pore volume of the carrier is selected so that the value obtained by dividing the surface area (m ² / g) by the pore volume (mL / g) is in the range of 100 to 300 m ² / mL. Preferably the surface area ^(m 2 / g) / pore volume (mL / g) value of 125~275m ² / mL, more preferably, selected to be 150 to 250 ² / mL. When the above value is less than 100 m ² / mL, it may be difficult to produce a carrier or an ethylene copolymer having a desired balance of physical properties may not be obtained. When the said value exceeds 300 m < ² > / mL, the melt tension of the polyethylene composition obtained may become small.
The value obtained by dividing the specific surface area by the pore volume compares the specific surface area per unit pore volume. Since the structure of the carrier differs depending on the production method, the balance between the specific surface area and the pore volume is different. In the case of a chromium catalyst, it is well known that the molecular weight distribution of the ethylene polymer obtained in the support structure changes. In order to produce an ethylene polymer exhibiting high melt tension, it is important to use a carrier having a specific balance between specific surface area and pore volume.

As described above, the pore volume of the support is 0.5 to 5.0 mL / in the same manner as in the case of a support used for a general chromium catalyst as long as the ratio of the ratio to the surface area is within a specific range as described above. g, preferably 1.0 to 3.0 mL / g, more preferably 1.2 to 2.5 mL / g. When the pore volume is less than 0.5 mL / g, the pores become small due to the polymer during polymerization, and the monomer may not be able to diffuse and the activity may decrease. A carrier having a pore volume exceeding 5.0 mL / 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 may be difficult to balance stress cracking resistance (ESCR) and impact resistance.

2. Chromium compound (b)
The chromium compound (b) to be supported on the inorganic oxide support (a) may be a compound in which at least a part of chromium atoms becomes hexavalent by calcination activation in a non-reducing atmosphere after support. Examples thereof include chromium, chromium halides, oxyhalides, chromates, dichromates, nitrates, carboxylates, sulfates, chromium-1,3-diketo compounds, chromate esters, and the like.

  Specifically, chromium trioxide, chromium trichloride, chromyl chloride, potassium chromate, ammonium chromate, potassium dichromate, chromium nitrate, chromium sulfate, chromium acetate, tris (2-ethylhexanoate) chromium, chromium 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).

3. First metal compound (ie, alumoxane compound (c))
In the method of the present invention, after the chromium compound (b) is supported on the inorganic oxide support (a), the first metal compound selected from the alumoxane compounds (c) is contacted.
The amount of the alumoxane compound (c) to be contacted is such that the molar ratio with respect to the chromium atom is 0.01 to 5, preferably 0.05 to 4, and more preferably 0.1 to 3. By setting it as this quantity, compared with the case where an alumoxane type compound is not contacted, ethylene polymerization activity improves significantly. If the molar ratio is less than 0.01, the effect of contacting the alumoxane compound may not be sufficiently exhibited. On the other hand, when the molar ratio exceeds 5, the ethylene polymerization activity may be lower than when the alumoxane compound is not contacted.

The alumoxane compound (c) has Al—O—Al bonds 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, but aliphatic hydrocarbons or 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.

4). Second metal compound (ie, organoaluminum compound (d))
In the present invention, a second metal compound selected from the organoaluminum compound (d) is further added to the inorganic oxide carrier (a) supporting the chromium compound (b), and the alumoxane compound (c) described above in order. Or contact at the same time.
The second metal compound is arbitrarily selected from the organoaluminum compound (d), and such an organoaluminum compound is at least one selected from dialkylaluminum alkoxide, alkylaluminum dialkoxide, or trialkylaluminum. Are preferred, and alkylaluminum alkoxide compounds are more preferred.
The alkylaluminum alkoxide compound is a compound represented by the following general formula (1).

^(Wherein, R 1, ^{R 2,} which may be the same or different, each represents an alkyl group having 1 to 20 carbon atoms. Wherein ^the alkyl group of R 1, ^{R 2} is also cycloalkyl group Including)

Among them, a dialkylaluminum alkoxide compound in which n is 2 in the general formula (1) is preferable. In particular, two R ^{1 s} may be the same or different and each represents an alkyl group having 1 to 20 carbon atoms, and R ² is an alkyl group having 2 or more carbon atoms (where R ¹ And the alkyl group of R ² includes a cycloalkyl group), and a dialkylaluminum alkoxide compound is preferable. Furthermore, in terms of catalytic activity, R ² is an alkyl group bonded to oxygen with a methylene group (—CH ₂ —) (wherein the bond on the opposite side of oxygen in the methylene group of R ² is cycloalkyl Dialkylaluminum alkoxide, which may be bonded to a group, is particularly preferred.

In the alkylaluminum alkoxide represented by the general formula (1), specific examples of R ¹ include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, tert-butyl, n -Hexyl, n-octyl, n-decyl, n-dodecyl, cyclohexyl and the like, and methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, n-hexyl, n-octyl Among them, methyl, ethyl, n-propyl, i-propyl, n-butyl and i-butyl are particularly preferable.
Specific examples of R ² 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, but 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 in which n of the alkylaluminum alkoxide represented by the general formula (1) is 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, di-i-butylaluminum n-propoxide, dimethylaluminum i-propoxide, diethylaluminum i-propoxide, di-n-butylaluminum i-propyl Poxide, dii-butylaluminum i-propoxide, dimethylaluminum n-butoxide, diethylaluminum n-butoxide, din-butylaluminum n-butoxide, dii-butylaluminum n-butoxide, dimethylaluminum i-butoxide, diethyl Aluminum i-butoxide, di-n-butylaluminum i-butoxide, dii-butylaluminum i-butoxide, dimethylaluminum t-butoxide, diethylaluminum t-butoxide, din-butylaluminum t-butoxide, dimethylaluminum (cyclopropyl) Methoxide, diethylaluminum (cyclopropyl) methoxide, di-n-butylaluminum (cyclopropyl) methoxide, dii-butylaluminum (cyclopropyl) medium Oxide, 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, din-butylaluminum (cyclohexyl) methoxide, dii-butylaluminum ( (Cyclohexyl) methoxide, dimethylaluminum (dicyclopropyl) medium Toxide, diethylaluminum (dicyclopropyl) methoxide, di-n-butylaluminum (dicyclopropyl) methoxide, di-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-butyl Aluminum (dicyclopentyl) methoxide, dimethylaluminum (dicyclohexyl) methoxide, diethylaluminum (Dicyclohexyl) methoxide, di-n-butylaluminum (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, di-n-butylaluminumcyclo Pentoxide, di-i-butylaluminum cyclopentoxide, dimethylaluminum Kisokishido to b, Kisokishido to diethylaluminum cycloalkyl, di-n- butylaluminum cycloheteroalkyl Kisokishido, Kisokishido the like to di i- butylaluminum cycloalkyl.

Among these, those in which the carbon directly bonded to oxygen in the alkoxide moiety is a primary or secondary carbon are preferable in view of catalyst activity and other catalyst 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 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.
For example, in order to synthesize a dialkylaluminum alkoxide, a method in which a trialkylaluminum and an alcohol are reacted at a molar ratio of 1: 1 as shown in the following formula:

(In the formula, R ′, R ³ , R ⁴ and R ⁵ may be the same or different and each represents an alkyl group having 1 to 20 carbon atoms.)
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.

(Wherein R ⁶ , R ⁷ and R ⁸ may be the same or different and each represents an alkyl group having 1 to 20 carbon atoms. Dialkylaluminum halide: X in R ⁶ R ⁷ AlX represents fluorine, chlorine, Bromine and iodine, especially chlorine is preferably used, and M in the metal alkoxide: R ⁸ OM is an alkali metal, and lithium, sodium and potassium are particularly preferred.)

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, so that it 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, xylene and the like. 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 depends on the reaction temperature, 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 amount of the organoaluminum compound (d) to be brought into contact 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 contacting the organoaluminum compound is not sufficiently exhibited, and the ethylene polymerization activity and durability may not be much different from those when the organoaluminum compound is not contacted. On the other hand, when the molar ratio exceeds 20, the ethylene polymerization activity may be lower than when the alkylaluminum alkoxide compound is not contacted. 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.
By increasing the amount of the organoaluminum compound (d) that is brought into contact with the catalyst carrier, the HLMFR of polyethylene obtained by ethylene polymerization tends to increase. That is, the fluidity increases.

[II] Method for Producing Ethylene Polymerization Catalyst In the present invention, as described above, the inorganic oxide carrier (a) is supported on the chromium compound (b) in a state where at least some of the chromium atoms are hexavalent. This is a method for producing an ethylene polymerization catalyst, in which a first metal compound selected from a system compound (c) and a second metal compound selected from an organoaluminum compound (d) are contacted sequentially or simultaneously. In the method of the invention, the ethylene polymerization catalyst is preferably produced by the following steps (a) to (d).
(A): The chromium compound (b) is supported on the inorganic oxide support (a) and activated by firing in a non-reducing atmosphere;
(B): The inorganic oxide carrier (a) carrying the chromium compound (b) is further contacted with a first metal compound selected from the alumoxane compounds (c) in an inert hydrocarbon solvent;
(C): Next, a second metal compound selected from the organoaluminum compound (d) is contacted in an inert hydrocarbon solvent; and (d): Finally, the inert hydrocarbon solvent is removed and dried.

1. Loading of the chromium compound on the inorganic oxide carrier The loading of the chromium compound on the inorganic oxide carrier can be achieved as long as at least part of the chromium atoms in the chromium compound can be supported in a hexavalent state. It is not specifically limited, It can carry out by well-known methods, such as impregnation, solvent distillation, and sublimation, What is necessary is just to use a suitable method according to the kind of 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, the chromium catalyst in which the chromium compound is supported on the inorganic oxide support 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 NH ₄ F, ammonium silicofluoride (NH ₄ ) ₂ SiF ₆ , ammonium borofluoride NH ₄ BF ₄ , ammonium monohydrogen difluoride (NH ₄ ) HF ₂ , hexa Fluorine-containing salts such as ammonium fluorophosphate NH ₄ PF ₆ and tetrafluoroborate HBF ₄ are used, among which ammonium silicofluoride and ammonium monohydrogen difluoride are preferable.
It is preferable from the viewpoint of uniformity that these are dissolved in an organic solvent such as water or alcohol and then impregnated with the chromium catalyst, but they may be mixed with the chromium catalyst as a solid. 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, spray drying or the like.

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 SiF ₄ react with silanol groups on the silica surface to fluorinate (B. Rebentorf; Journal of Molecular Catalysis Vol. 66 p. 59 (1991), A. Noshay et. “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.

2. (A) Activation of firing After the chromium compound is supported on the inorganic oxide carrier, in some cases, after further supporting the fluorine compound, the activation is performed by firing. 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 may occur and the activity may not be obtained. 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.

3. (B) Contact with the alumoxane compound (c) The first metal compound selected from the alumoxane compound (c) is further added to the inorganic oxide carrier (a) carrying the chromium compound (b) in the step (a). Is contacted in an inert hydrocarbon solvent. The method for contacting the alumoxane compound (c) is not particularly limited as long as it is a method for bringing the chromium catalyst after the calcination activation into contact with the liquid phase in the inert hydrocarbon. For example, the chromium catalyst after calcination activation is mixed in 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 making a slurry state and adding an alumoxane compound to this is preferable. The alumoxane compound to be added may be diluted with the inert hydrocarbon solvent or may be added without dilution. The solvent for dilution and the solvent for contact 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.

  Moreover, the temperature of a contact reaction is -20-150 degreeC, Preferably it is -10-100 degreeC, More preferably, it is 0-80 degreeC, The time of a contact reaction is 5 minutes-12 hours, Preferably it is 30 minutes-10 minutes Time, more preferably 1 to 8 hours. In view of stabilizing the catalyst performance by sufficiently completing the reaction, it is considered better to increase the reaction time. In view of the contact reaction time, 4 to 8 hours is most preferable.

4). (C) Contact of organoaluminum compound (d) In the present invention, a chromium-supported inorganic oxide carrier is treated with a compound selected from alumoxane compounds (c) and an organoaluminum compound (d) in an inert hydrocarbon solvent. In this case, the addition order is arbitrary, and the alumoxane compound (c) and the organoaluminum compound (d) may be added simultaneously. However, preferably, after contacting the alumoxane compound (c), the second metal compound selected from the organoaluminum compound (d) is then contacted in an inert hydrocarbon solvent. The method for contacting the organoaluminum compound (d) is not particularly limited as long as it is a method for bringing the chromium catalyst after calcination activation into contact with the liquid phase in the inert hydrocarbon as in the step (b). The same solvent, use amount, and contact reaction temperature as those in the step (b) can be adopted as a preferred embodiment.
After step (b) and step (c), the excess alumoxane compound (c) and organoaluminum compound (d) may be removed by washing with an inert hydrocarbon solvent, or the next step without washing. (D) may be performed. For washing, a known method such as a method of removing the supernatant by standing and a method of filtering can be used. A preferred method is a method in which the step (d) is carried out without washing as necessary amounts of the alumoxane compound (c) and the organoaluminum compound (d) used in the steps (b) and (c).

5. (D) Solvent removal / drying After the agitation is stopped and the contact operation is completed, it is necessary to remove the solvent promptly. 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 chromium catalyst is obtained as a fluid powder without viscosity and moisture. If the catalyst is stored for a long time without being separated from the solvent, the catalyst may deteriorate over time and the ethylene polymerization activity may be lowered. In addition, since the molecular weight distribution of the ethylene polymer may be widened, the durability is improved, but the impact resistance is lowered, which is not preferable. Accordingly, it is preferable to shorten the contact time with the solvent as much as possible, including the contact time with the solvent in the contact reaction, and to quickly separate and remove the solvent.
Therefore, the solvent contact time in the catalytic reaction is added together so that the polymerization activity and the impact strength of the resulting polymer are not substantially reduced, so that the degree of reduction is minimized even if it is reduced. It is preferable to make the contact time as short as possible. That is, it is preferable to shorten the contact reaction time, which is the contact time with the solvent, as much as possible, and to quickly separate the solvent after the contact so that the overreduction reaction does not proceed.
After completion of the contact 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 contact 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.

  As described above, the chromium catalyst used in the present invention is obtained. In the production of the ethylene polymer according to the present invention, titanium tetraisopropoxide can be used before supporting the chromium compound or before activating the firing after supporting the chromium compound. Titanium alkoxides, zirconium alkoxides such as zirconium tetrabutoxide, aluminum alkoxides such as aluminum tributoxide, organoaluminums such as trialkylaluminum, or fluorine-containing salts such as organometallic compounds and ammonium silicofluoride Etc. may be used together with known methods for adjusting the ethylene polymerization activity, the copolymerizability with α-olefin, the molecular weight of the resulting polyethylene, and the molecular weight distribution.

  In these metal alkoxides or organometallic compounds, the organic group portion is burnt by activation in a non-reducing atmosphere, and is oxidized into a metal oxide such as titania, zirconia, or alumina and contained in the catalyst. 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

  For automotive fuel tank applications that require a polyethylene composition that is both excellent in impact resistance and durability, it is preferable to use only a silica carrier that is an inorganic oxide. 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.

[III] Function and Mechanism of Ethylene Polymerization Catalyst The reaction that occurs on the silica surface when calcination activation is 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. The state of the silanol group on the silica surface is considered to vary depending on the silica structure. It is considered that this difference also affects the polymerization active precursor structure and affects the molecular weight distribution and branched structure of the resulting polymer.

  In the present invention, the activity is greatly increased by contacting the first metal compound selected from the alumoxane compounds (c). 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 alumoxane compound added here is usually very small compared to the amount of silica gel, it is considered that the added alumoxane compound is concentrated and reacting on the surface of the silica particles.

  In addition, 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.

Since the amount of the organoaluminum compound added here is usually very small compared to the amount of silica gel, the added organoaluminum compound is considered to be concentrated and reacting on the surface of the silica particles. .
The fact that the added organoaluminum compound is concentrated on the surface is supported by the results of an electron probe microanalyzer (hereinafter abbreviated as EPMA). 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. From the results of MPMA, etc., this organoaluminum compound-supported chromium catalyst has an inner part (part A) in which no organoaluminum compound is present in one silica particle and at least a part of chromium atoms is reduced by organoaluminum. The catalyst has been shown to have a surface part (part B), which in this sense can be referred to as 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 generated from the chromium active site that has been reduced by the organoaluminum compound in advance is different from the polyethylene generated from the chromium active site that is reduced by introducing ethylene. 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 can produce polyethylene in which the low molecular weight component does not contain many branched chains as compared with the aluminum non-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.

  Furthermore, the chromium-supported catalyst obtained by the method of the present invention exhibits superior characteristics compared to conventional chromium-aluminum catalysts by specifying the ratio of the surface area of the support particles and the pore volume. Has been found.

[IV] Ethylene polymer Polymerization method of ethylene By using an ethylene polymerization catalyst prepared by the method of the present invention, when a composition is formed with other polyethylene, it has excellent moldability and impact resistance, and the balance between rigidity and durability. And an ethylene polymer having a particularly high melt tension can be obtained. That is, one aspect of the present invention is an ethylene polymer characterized in that ethylene homopolymerization or copolymerization of ethylene and α-olefin as described later is performed using the ethylene polymerization catalyst obtained by the above method. It also relates to the manufacturing method.

When an ethylene polymer is produced using the 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, xylene and the like are used alone or as a mixture.
In addition, the gas phase polymerization method can adopt a commonly known polymerization method such as a fluidized bed or 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. It can also be adopted.

  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 the ethylene polymer, polymerization may be carried out particularly in the presence of hydrogen. By coexisting hydrogen, the polymerization temperature can be lowered and the molecular weight distribution can be further expanded.

  When ethylene is polymerized by the method of the present invention, an α-olefin can be copolymerized as a comonomer. The α-olefin is more preferably an α-olefin having 3 to 8 carbon atoms. Specific examples include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. The copolymerization can be carried out alone or by introducing two or more kinds into the reactor. Particularly preferably, 1-butene, 1-hexene, more preferably 1-hexene is suitably used as a comonomer. The α-olefin content in the obtained copolymer is 15 mol% or less, preferably 10 mol% or less.

2. Physical properties and use of ethylene polymer By using the catalyst obtained by the method of the present invention, HLMFR is 0.1 to 200 g / 10 min, preferably 0.5 to 80 g / 10 min, and the density is 0.900 to 0. An ethylene polymer of 980 g / cm ³ , preferably 0.920 to 0.970 g / cm ³ is obtained. The obtained ethylene polymer has high impact resistance and durability, and is excellent in balance, so that it exhibits a great effect particularly in blow molded products, especially large blow molded products. Furthermore, when a composition is formed with other polyethylene resins, a high melt tension is exhibited. The HLMFR of the ethylene polymer for blow molded products is 1 to 100 g / 10 min, particularly 1 to 15 g / 10 min for ethylene polymers for large blow molded products. The density of the ethylene polymer for blow molded products is 0.935 to 0.970 g / cm ³ , especially the density for the ethylene polymer 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 that flows from the first stage and α-olefin that also flows in, but if necessary, new hydrogen and α-olefin can be added respectively. Accordingly, also in the second stage, the mass ratio of hydrogen concentration to ethylene concentration or partial pressure ratio (Hc / ETc or Hp / ETp), 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. You may supply a compound or both.

  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 mass, the low molecular weight component is 90 to 10 parts by mass, preferably the high molecular weight component is 20 to 80 parts by mass. 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 the ethylene polymer obtained by the two-stage polymerization is 0.1 to 100 g / 10 minutes, preferably 0.5 to 80 g / 10 minutes, but as a resin for blow molded products, 1 to 100 g / 10 minutes, Particularly for a resin for large blow molded products, it is 1 to 15 g / 10 min. The density of the ethylene polymer obtained by the two-stage polymerization is 0.900 to 0.980 g / cm ³ , preferably 0.920 to 0.970 g / cm ^3. the ~0.970g / cm ^3, especially large blow molded products resin is 0.940~0.955g / cm ^3. The obtained ethylene polymer is preferably kneaded. Kneading can be performed using a single or twin screw extruder or a continuous kneader. Further, the obtained ethylene polymer can be blow-molded by a conventional method.

[V] Polyethylene composition The obtained ethylene polymer is used as a fuel tank, kerosene can, drum can, chemical container, agricultural chemical container, solvent for kneading with other polyethylene to form a polyethylene composition. Examples thereof include hollow plastic molded products such as containers or plastic bottles. A polyethylene composition containing an ethylene polymer produced using the catalyst obtained by the method of the present invention has a high melt tension and is useful in the production of hollow plastic molded articles such as fuel tanks.

As the polyethylene to be combined with the ethylene polymer produced using the catalyst obtained by the method of the present invention, those known to those skilled in the art can be used depending on the application. Moreover, it is good also as a composition by combining 2 or more types of ethylene polymers manufactured using the catalyst obtained by the method of this invention like an ethylene homopolymer and a copolymer of ethylene and an alpha olefin.
The HLMFR of the polyethylene composition is 0.1 to 100 g / 10 minutes, preferably 0.5 to 80 g / 10 minutes, but as a resin for blow molded products, it is 1 to 100 g / 10 minutes, particularly for large blow molded products. The resin is 1 to 15 g / 10 min. The density of the polyethylene composition is 0.900 to 0.980 g / cm ³ , preferably 0.920 to 0.970 g / cm ³ , but 0.935 to 0.970 g / cm ³ as a resin for blow molded products. ³ , especially 0.940-0.955 g / cm ³ as a resin for large blow molded products.

  As a method for producing the polyethylene composition, means for polymer blending known to those skilled in the art can be used. For example, a polyethylene composition can be obtained by melting an ethylene polymer obtained by the method of the present invention and other polyethylene, kneading them with a mill, and appropriately molding them by means such as extrusion as necessary. . In the polymer blend, known additives such as antioxidants and heat stabilizers can be mixed.

  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 of the structure of the present invention will be demonstrated. However, the present invention is limited by these examples. Is not to be done.

(I) Various measuring methods In the examples and comparative examples, the measuring methods used are as follows.
1. Evaluation of physical properties of ethylene polymer 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 BASF Japan Ltd. was added, and kneaded and pelletized by a single screw extruder.
(Ii) Halo Melt Flow Rate (HLMFR):
According to JIS K7210 (2004 edition), Annex A, Table 1-Condition G, the measured value at a test temperature of 190 ° C. and a nominal load of 21.60 kg was shown as HLMFR.
(Iii) Density The density was measured according to JIS K7112 (2004 edition).
(Iv) Melt tension (MT)
Using a capillograph manufactured by Toyo Seiki Seisakusho Co., Ltd., nozzle diameter 2.095 mmφ, nozzle length 8.00 mm, inflow angle 180 °, set temperature 210 ° C., piston extrusion speed 10.0 mm / min, take-off speed 4.0 m / min Measured under conditions.

(II) Production and evaluation of ethylene polymer in autoclave Example 1
(1) Preparation of chromium catalyst Catalyst-1 having a chromium atom loading of 1.0% by weight, a specific surface area of 380 m ² / g, and a pore volume of 1.55 cm ³ / g (a catalyst having chromium acetate supported on silica) Prepared in a quartz glass tube with a perforated plate and a diameter of 5 cm, set in a cylindrical firing electric furnace, fluidized with air through molecular sieves, at a linear velocity of 6 cm / s Baking activation was performed at 500 ° C. for 18 hours. An orange chrome catalyst was obtained indicating that it contained hexavalent chromium atoms.
(2) Preparation of organometallic compound-containing chromium catalyst 2 g of the chromium catalyst obtained in (1) above was placed in a 100 mL flask previously purged with nitrogen, and 20 mL of distilled and purified hexane was added to form a slurry. 0.38 mL (Al / Cr molar ratio = 1.0) of a 1.0 mol / L-hexane solution of MMAO-3A manufactured by Tosoh Finechem Corporation was added and stirred at 40 ° C. for 1 hour. Further, 7.7 mL (Al / Cr molar ratio = 2) of 0.1 mol / L-hexane solution of diethylaluminum ethoxide (Et ₂ Al (OEt)) 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 by reducing the pressure over 30 minutes to obtain a free flowing, free flowing organometallic compound-containing chromium catalyst-1.
(3) Ethylene polymerization 100 mg of the organometallic compound-containing chromium catalyst obtained in (2) above and 0.8 L of isobutane were charged into a 2.0 L autoclave sufficiently purged with nitrogen, and the internal temperature was raised to 100 ° C. Polymerization was performed such that the catalyst productivity was 3000 g-polymer / g-catalyst while charging the hydrogen partial pressure to 0.05 MPa and maintaining the ethylene partial pressure to 0.7 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.
(4) Polymer blend method Ethylene polymer (B) produced from the ethylene polymer (A) obtained in the above (3) and a metallocene catalyst (HLMFR = 0.5 g / 10 min, density = 0.9250 g / cm ³ ) On the other hand, 500 ppm of BASF Japan IRGANOX1010 and 1500 ppm of BASF Japan IRGAFOS 168 are added, and a lab plast mill manufactured by Toyo Seiki Seisakusho is used, with a kneading temperature of 210 ° C. and a screw rotation speed of 40 rpm. It melt-mixed and manufactured the polyethylene composition (C). The composition and physical properties of the polyethylene composition (C) are shown in Table 2.

Example 2
In Example 1 (1) above, Catalyst-1 having a chromium atom loading of 1.0% by weight, a specific surface area of 380 m ² / g, and a pore volume of 1.55 cm ³ / g (supporting chromium acetate on silica) Instead of catalyst, catalyst-2 (a catalyst having chromium acetate supported on silica) having a chromium atom loading of 1.0% by weight, a specific surface area of 295 m ² / g and a pore volume of 1.5 cm ³ / g is used. Further, the same operation as in Example 1 was performed except that the hydrogen partial pressure in Example 1 (3) was changed to 0.10 MPa instead of 0.05 MPa. The polymerization results and polymer properties are shown in Table 1. The composition and physical properties of the polyethylene composition (C) are shown in Table 2.

Example 3
In Example 1 (1) above, Catalyst-1 having a chromium atom loading of 1.0% by weight, a specific surface area of 380 m ² / g, and a pore volume of 1.55 cm ³ / g (supporting chromium acetate on silica) Instead of catalyst, catalyst-3 having a chromium atom loading of 1.0% by weight, a specific surface area of 433 m ² / g and a pore volume of 1.75 cm ³ / g (a catalyst having chromium acetate supported on silica) is used. All operations were the same as in Example 1 except that. The polymerization results and polymer properties are shown in Table 1. The composition and physical properties of the polyethylene composition (C) are shown in Table 2.

Example 4
In Example 1 (1) above, Catalyst-1 having a chromium atom loading of 1.0% by weight, a specific surface area of 380 m ² / g, and a pore volume of 1.55 cm ³ / g (supporting chromium acetate on silica) Instead of catalyst), catalyst-4 (a catalyst in which chromium acetate is supported on silica) having a chromium atom loading of 1.0% by weight, a specific surface area of 426 m ² / g and a pore volume of 1.69 cm ³ / g is used. All operations were the same as in Example 1 except that. The polymerization results and polymer properties are shown in Table 1. The composition and physical properties of the polyethylene composition (C) are shown in Table 2.

Comparative Example 1
In Example 1 (1) above, Catalyst-1 having a chromium atom loading of 1.0% by weight, a specific surface area of 380 m ² / g, and a pore volume of 1.55 cm ³ / g (supporting chromium acetate on silica) Instead of catalyst, catalyst-5 having a chromium atom loading of 1.0% by weight, a specific surface area of 500 m ² / g, and a pore volume of 1.5 cm ³ / g (a catalyst having chromium acetate supported on silica) is used. Further, the same operation as in Example 1 was performed except that the hydrogen partial pressure in Example 1 (3) was changed to 0.10 MPa instead of 0.05 MPa. The polymerization results and polymer properties are shown in Table 1. The composition and physical properties of the polyethylene composition (C) are shown in Table 2.

Comparative Example 2
In Example 1 (1) above, Catalyst-1 having a chromium atom loading of 1.0% by weight, a specific surface area of 380 m ² / g, and a pore volume of 1.55 cm ³ / g (supporting chromium acetate on silica) Instead of catalyst, catalyst-6 (catalyst in which chromium acetate is supported on silica) having 1.0% by weight of chromium atoms, a specific surface area of 600 m ² / g, and a pore volume of 2.5 cm ³ / g is used. All operations were the same as in Example 1 except that. The polymerization results and polymer properties are shown in Table 1. The composition and physical properties of the polyethylene composition (C) are shown in Table 2.

  As can be seen from Tables 1 and 2, the polyethylene composition using the ethylene polymer prepared by the method of the example has a high melt tension. On the other hand, a catalyst using a carrier having a large specific surface area and pore volume ratio as in Comparative Example 1 or a catalyst using a carrier having a large specific surface area as in Comparative Example 2 has a large physical property of the ethylene polymer. Despite not changing, the melt tension when the polyethylene composition is obtained is reduced. That is, the ethylene polymer produced using the chromium-supported catalyst obtained by the method of the present invention has high melt tension even when a composition is formed with other polyethylene, and high rigidity is required. It has been shown to be useful in the production of hollow plastic moldings such as fuel tanks.

Claims (6)

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, a first metal compound selected from the alumoxane compounds (c), and organic A method for producing an ethylene polymerization catalyst comprising sequentially or simultaneously contacting a second metal compound selected from aluminum compounds (d),
The method for producing an ethylene polymerization catalyst, wherein the inorganic oxide support (a) has the following characteristics (i) and (ii):
(I) Surface area (m ² / g) / pore volume (mL / g) is 100 to 300 m ² / mL
(Ii) A surface area of 100 to 550 m ² / g The method for producing an ethylene polymerization catalyst according to claim 1, 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, the first metal compound selected from the alumoxane compounds (c) is contacted in an inert hydrocarbon solvent (c): Then, the second metal compound selected from the organoaluminum compound (d) is converted to an inert hydrocarbon. Contact in a solvent (d): Finally, the inert hydrocarbon solvent is removed and dried.   The method for producing an ethylene polymerization catalyst according to claim 1 or 2, wherein the alumoxane compound (c) is a modified methylalumoxane prepared from trimethylaluminum and triisobutylaluminum.   4. The ethylene polymerization catalyst according to claim 1, wherein the organoaluminum compound (d) is at least one selected from dialkylaluminum alkoxides, alkylaluminum dialkoxides, or trialkylaluminums. Manufacturing method.   An ethylene polymer obtained by carrying out ethylene homopolymerization or copolymerization of ethylene and α-olefin using the ethylene polymerization catalyst obtained by the production method according to any one of claims 1 to 4. Production method.   6. The method for producing an ethylene polymer according to claim 5, wherein the α-olefin has 3 to 8 carbon atoms.