JP2011006588A - Manufacturing method for ethylenic polymer using chromium-based catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing an ethylene polymer suitable for a hollow plastic molded article, excellent in moldability, durability and barrier property and excellent in balance of impact-resistance and rigidity.SOLUTION: In the manufacturing method for the ethylenic polymer, polymerization is performed, while coexisting a hydrogen, using a catalyst obtained by carrying an alkyl aluminum alkoxide compound such that a chromium atom is not excessively reduced in an inactive hydrocarbon solvent after the inorganic oxide carrier is carried with a chromium compound and at least a part of the chromium atoms is made to hexavalent by calcinating/activating it in a non-reductive atmosphere, and by removing the solvent and drying it. The ethylenic polymer suitable for a blow molding product obtained by the manufacturing method or the like is provided.

Description

  The present invention relates to a method for producing an ethylene polymer, and more particularly to a method for producing an ethylene polymer in which ethylene is polymerized in the presence of hydrogen using a catalyst in which an alkylaluminum alkoxide compound is supported on a chromium catalyst. The ethylene-based polymer obtained by the method of the present invention is excellent in both environmental stress crack resistance (hereinafter sometimes abbreviated as ESCR) and impact resistance, and is suitable for hollow plastic products.

  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.

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).
However, polyethylene suitable for hollow plastic molded articles, particularly automobile fuel tanks, is not disclosed, and it is difficult to say that automobile fuel tanks with sufficient durability can be manufactured.

In addition, a method has been proposed in which an organoaluminum compound is added as a promoter to a polymerization reactor and polyethylene is produced using a chromium catalyst (see Patent Document 2). However, when the polymerization is carried out by adding an organoaluminum compound to the polymerization reactor, the polymerization activity is low. Moreover, the physical properties of the polyethylene obtained there do not satisfy the durability. The document 2 also discloses a method for producing polyethylene using a trialkylaluminum and / or dialkylaluminum alkoxide compound-supported chromium catalyst (Examples No. 2 to No. 6).
However, there is no disclosure of hollow plastic molded articles, particularly polyethylene having excellent ESCR and impact resistance suitable for automobile fuel tanks. Furthermore, the document 2 also proposes a method for producing polyethylene using a titania-containing chromium catalyst that has been impregnated with titanium tetraisopropoxide on silica before activation of the Cr catalyst and has been activated by firing. However, the polyethylene obtained at this time tends to have a low impact strength.

In addition, a method for producing polyethylene using a trialkylaluminum and / or dialkylaluminum alkoxide compound-supported chromium catalyst has been proposed (see Patent Document 3).
However, Patent Document 3 does not disclose the specific properties of the carrier and does not disclose a hollow plastic molded product, particularly polyethylene suitable for an automobile fuel tank.

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-based polymerization catalyst comprising an alkylaluminum has been proposed (see Patent Document 4). The Document 4 also has excellent creep resistance and ESCR, HLMFR is 1 to 100 g / 10 min, and the density is An ethylene polymer for blow molded articles of 0.935 to 0.955 g / cm ³ is disclosed. The document 4 also discloses a method for producing polyethylene using a trialkylaluminum and / or dialkylaluminum alkoxide compound-supported chromium catalyst (Comparative Examples 3 and 13).
However, when a trialkylaluminum compound is used, 1-hexene tends to be generated as a by-product, so that it is not suitable as a method for producing polyethylene having both excellent ESCR and impact resistance. There is no suggestion or disclosure of polyethylene suitable for plastic molded articles, particularly for automobile fuel tanks with excellent impact resistance.

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. Proposed a method for producing an ethylene-based polymer using a chromium catalyst supporting a specific organoaluminum compound (alkoxide, siloxide, phenoxide, etc.) (see Patent Document 5), and has environmental stress crack resistance (ESCR) and rigidity. An ethylene polymer excellent in balance is disclosed.
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.) An ethylene polymer production catalyst characterized by the above is proposed (see Patent Document 6), and an ethylene polymer excellent in ESCR or creep resistance is disclosed.

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. An ethylene polymer production method characterized by this is proposed (see Patent Document 7), and an ethylene polymer excellent in environmental stress crack resistance (ESCR) and creep resistance is disclosed.
However, although the document 7 discloses an ethylene-based polymer having a molecular weight distribution (Mw / Mn) of 20.9 (Example), impact resistance suitable for a hollow plastic molded product, particularly an automobile fuel tank. There is no suggestion or disclosure of polyethylene having excellent properties.

Further, there has been proposed 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 when activated in a non-reducing atmosphere (see Patent Document 8). In addition, the document 8 discloses a method for producing polyethylene using a trialkylaluminum and / or dialkylaluminum alkoxide compound-supported chromium catalyst (Comparative Examples 6 and 8).
However, this document 8 does not suggest or disclose any hollow plastic molded article, particularly polyethylene suitable for a fuel tank for automobiles.
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 these circumstances, polyethylene and hollow plastic molded products that can solve the problems of conventional polyethylene, have excellent moldability and durability, have a good balance of impact resistance and rigidity, and can achieve particularly high rigidity. In particular, a polyethylene suitable for a high-performance fuel tank and a method for producing the same are desired.

JP 2002-080521 A JP-T-2006-512454 WO94 / 13708 international pamphlet JP 2002-020212 A JP 2003-096127 A JP 2003-183287 A JP 2003-313225 A JP 2006-182917 A

  The object of the present invention is to provide both environmental stress crack resistance (ESCR) and impact resistance suitable for polyethylene resins, particularly hollow plastic molded articles, which are excellent in moldability and durability, and in a balance between impact resistance and rigidity. An object of the present invention is to provide a method for efficiently producing an ethylene-based polymer that is high and excellent in balance between both characteristics.

  As a result of intensive studies in order to achieve the above-mentioned problems, the present inventors have supported a calcined activated chromium catalyst with an alkylaluminum alkoxide compound in an inert hydrocarbon solvent, and further removed and dried the solvent. It was found that by performing polymerization in the presence of hydrogen using the catalyst obtained in this way, an ethylene polymer having excellent moldability and durability, and excellent balance of impact resistance and rigidity can be obtained. Based on the knowledge, the present invention has been completed.

That is, according to the first invention of the present invention, there is provided a method for producing an ethylene-based polymer in which ethylene is homopolymerized or ethylene and α-olefin are copolymerized using an alkylaluminum alkoxide compound-supported chromium catalyst. ,
The alkylaluminum alkoxide compound-supported chromium catalyst carries a chromium compound on an inorganic oxide support having a specific surface area of 250 to 800 m ² / g and a pore volume of 0.5 to 3.0 cm ³ / g, and is non-reducing. In an acidic atmosphere, at least a part of the chromium atoms is made hexavalent by calcination activation at 400 to 900 ° C., and then an alkylaluminum alkoxide compound represented by the following general formula (1) is further added to the chromium atoms. The ethylene polymer is obtained by being supported in an inert hydrocarbon solvent so that the molar ratio thereof is 0.1 to 20, and removing and drying the inert hydrocarbon solvent. A manufacturing method is provided.

（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.)

According to a second aspect of the present invention, there is provided a method for producing an ethylene polymer in which ethylene is homopolymerized or ethylene and α-olefin are copolymerized using an alkylaluminum alkoxide compound-supported chromium catalyst. ,
The alkylaluminum alkoxide compound-supported chromium catalyst carries a chromium compound on an inorganic oxide support having a specific surface area of 250 to 800 m ² / g and a pore volume of 0.5 to 3.0 cm ³ / g, and is non-reducing. In an acidic atmosphere, at least a portion of the chromium atom is made hexavalent by calcination activation at 450 to 550 ° C., and then an alkylaluminum alkoxide compound represented by the following general formula (2) is further added to the chromium atom. It is supported in an inert hydrocarbon solvent so that the molar ratio is 0.5 to 2.0, and the inert hydrocarbon solvent is removed and dried to obtain an ethylene-based polymer. A method for producing a coalescence is provided.

（式中、Ｒ^３、Ｒ^４、Ｒ^５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^３、Ｒ^４、Ｒ^５のアルキル基は、シクロアルキル基も含む。）

(In the formula, R ³ , R ⁴ and R ⁵ may be the same or different and each represents an alkyl group. Here, the alkyl group of R ³ , R ⁴ and R ⁵ can be a cycloalkyl group. Including)

According to the third invention of the present invention, there is provided an ethylene polymer production method characterized in that, in the first or second invention, hydrogen is allowed to coexist during polymerization.
Furthermore, according to a fourth invention of the present invention, in any one of the first to third inventions, the alkylaluminum alkoxide compound is a compound represented by the following general formula (3): A method for producing a polymer is provided.

（式中、Ｒ^６、Ｒ^７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^８、Ｒ^９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^６、Ｒ^７、Ｒ^８、Ｒ^９のアルキル基は、シクロアルキル基も含む。また、Ｒ^８、Ｒ^９は、連結して、環を形成してもよい。）

(In the formula, R ⁶ and R ⁷ may be the same or different, and each represents an alkyl group having 1 to 18 carbon atoms. R ⁸ and R ⁹ 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 ⁶ , R ⁷ , R ⁸ and R ⁹ also include a cycloalkyl group. R ⁸ and R ⁹ may be linked to form a ring.)

According to a fifth invention of the present invention, in any one of the first to fourth inventions, the inert hydrocarbon solvent is removed and dried within 20 hours after the completion of the reaction for supporting the alkylaluminum alkoxide compound. There is provided a method for producing an ethylene-based polymer characterized by terminating the operation.
Furthermore, according to the sixth aspect of the present invention, in any one of the first to fifth aspects, the polymerization is performed in a liquid phase, and a hydrogen concentration (Hc; mass%) and an ethylene concentration (ETc; mass) in the liquid phase. %) Is carried out under the condition that the following relational expression (1) is satisfied. A method for producing an ethylene-based polymer is provided.

  According to the seventh invention of the present invention, in any one of the first to fifth inventions, the polymerization is performed in a gas phase, and a hydrogen partial pressure (Hp; MPa) and an ethylene partial pressure (ETp; A method for producing an ethylene-based polymer is provided, wherein the polymerization is performed under the condition that the ratio to (MPa) satisfies the following relational expression (2).

  Furthermore, according to an eighth invention of the present invention, in any one of the first to seventh inventions, the α-olefin has 3 to 8 carbon atoms, and the method for producing an ethylene-based polymer Is provided.

According to the ninth invention of the present invention, the high load melt flow rate obtained by the method for producing an ethylene polymer according to any one of the first to eighth inventions and at a temperature of 190 ° C. and a load of 21.6 kg. (HLMFR) is 1 to 100 g / 10 minutes, and a density is 0.935 to 0.960 g / cm ^3. An ethylene-based polymer for blow molded products is provided.
Furthermore, according to the tenth invention of the present invention, the HLMFR is obtained by the method for producing an ethylene polymer according to any one of the first to eighth inventions, the HLMFR is 1 to 15 g / 10 min, and the density is 0.940. There is provided an ethylene-based polymer for large blow-molded products, characterized in that it is ˜0.955 g / cm ³ .

The present invention relates to a method for producing an ethylene polymer as described above, and preferred embodiments thereof include the following.
(1) In the first invention, the alkylaluminum alkoxide compound is a dialkylaluminum alkoxide compound (n = 2 in the general formula (1)).
(2) The method for producing an ethylene polymer according to the first or second invention, further comprising adding a fluorine compound to a chromium catalyst in which a chromium compound is supported on an inorganic oxide carrier.

  According to the method for producing an ethylene polymer of the present invention, an ethylene polymer excellent in both environmental stress crack resistance (ESCR) and impact resistance is obtained, and the ethylene polymer is suitable for a hollow plastic product. Yes. The hollow plastic product is excellent in moldability, durability and barrier properties, and has a good balance of impact resistance and rigidity, and can be suitably used for a fuel tank, particularly a fuel tank for automobiles.

It is a flowchart figure in preparation of the polymerization catalyst used for manufacture of the polyethylene-type resin which concerns on this invention. It is explanatory drawing of the measuring method of the strain hardening parameter ((lambda) max) of an extensional viscosity.

The method for producing an ethylene polymer (or polyethylene resin) of the present invention is characterized in that homopolymerization of ethylene or copolymerization of ethylene and α-olefin is performed using an alkylaluminum alkoxide compound-supported chromium catalyst. To do.
Hereinafter, the present invention will be specifically described for each item.

I. Alkyl aluminum alkoxide compound-supported chromium catalyst A chromium catalyst in which at least a part of chromium atoms become hexavalent by supporting a chromium compound on an inorganic oxide support and activating it by firing in a non-reducing atmosphere is generally known as a Philips catalyst. Is well known.
An overview of this catalyst is as follows: 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 Properties, p. 21, 1993, described in documents such as Marcel Dekker.

1. Inorganic oxide support As the inorganic oxide support, an oxide of a metal 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 ESCR 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 considered that the cause is an increase in the low molecular weight component of the polyethylene polymer, but the impact resistance tends to be lowered.
The preparation, physical properties and characteristics of supports suitable for these chromium catalysts are described in (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, p. 193, 1994, and the like.

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 800 m ² / g, preferably 300 to 700 m ² / g, more preferably 450 to 600 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 800 m ² / g.

The pore volume of the carrier is 0.5 to 3.0 cm ³ / g, preferably 1.0 to 2.0 cm ³ / g, more preferably, as in the case of a carrier used for a general chromium catalyst. The thing of the range of 1.2-1.8 cm < ³ > / g is used. When the pore volume is less than 0.5 cm ³ / g, the pores become small due to the polymer during polymerization, and the monomer cannot be diffused, resulting in a decrease in activity. A carrier having a pore volume exceeding 3.0 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 A chromium compound is supported on the inorganic oxide carrier. 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 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.
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

Furthermore, 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 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 as fine a particulate fluorine compound solid 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 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, molecular sieves or the like are circulated and sufficiently dried air is used in a fluidized state. The firing activation is performed at a temperature of 400 to 900 ° C, preferably 450 to 550 ° C, more preferably 470 to 530 ° C, most preferably 490 to 510 ° C for 30 minutes to 48 hours, preferably 1 hour to 24 hours. More preferably, it is performed for 2 hours to 12 hours. By this firing activation, at least a part of the chromium atoms of the chromium compound supported on the inorganic oxide support is oxidized to be hexavalent and chemically fixed on the support. When the firing activation is performed at less than 450 ° C., the polymerization activity is reduced, and when it is performed at less than 400 ° C., the polymerization activity is lost. On the other hand, if the firing activation is performed at a temperature exceeding 550 ° C., the molecular weight distribution is narrowed and the impact resistance is improved, but the durability is lowered, and if it is performed at a temperature exceeding 900 ° C., sintering occurs. Activity is reduced.

  As described above, the chromium catalyst used in the present invention can be obtained. In the production of the polyethylene resin of the present invention, titanium tetraisopropoxide is used before the chromium compound is supported or before the firing activation after the chromium compound is supported. Titanium alkoxides, zirconium alkoxides such as zirconium tetrabutoxide, aluminum alkoxides such as aluminum tributoxide, organoaluminums such as trialkylaluminum, and metal alkoxides such as organomagnesium such as dialkylmagnesium Known to control ethylene polymerization activity, copolymerization with α-olefin, and molecular weight and molecular weight distribution of the resulting ethylene polymer by adding fluorine-containing salts such as organometallic compounds or ammonium silicofluoride Direction It may be used in combination.

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 include (i) C.I. E. Marsden, Plastics, Rubber and Compositions 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, p. 118, 1983, and the like.
In the present invention, it is preferable that only a silica carrier which is an inorganic oxide is used for a fuel tank for an automobile having both excellent ESCR and impact resistance. When these metal alkoxides or organometallic compounds are added to the inorganic oxide, there is a tendency that the low molecular weight component of the polyethylene polymer is increased or the molecular weight distribution is narrowed.

4). Alkyl aluminum alkoxide compound In the present invention, an alkyl aluminum alkoxide compound supported chromium obtained by supporting an alkyl aluminum alkoxide compound in an inert hydrocarbon solvent on a calcined activated chromium catalyst, and further removing and drying the solvent. The catalyst is used as a polymerization catalyst.
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 them, the compound represented by the following general formula (2) is preferable in polymerization activity.

（式中、Ｒ^３、Ｒ^４、Ｒ^５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^３、Ｒ^４、Ｒ^５のアルキル基は、シクロアルキル基も含む。）

(In the formula, R ³ , R ⁴ and R ⁵ may be the same or different and each represents an alkyl group. Here, the alkyl group of R ³ , R ⁴ and R ⁵ can be a cycloalkyl group. Including)

  Among the alkylaluminum alkoxide compounds represented by the general formulas (1) and (2), an alkylaluminum alkoxide compound represented by the following general formula (3) is preferable.

（式中、Ｒ^６、Ｒ^７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^８、Ｒ^９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^６、Ｒ^７、Ｒ^８、Ｒ^９のアルキル基は、シクロアルキル基も含む。また、Ｒ^８、Ｒ^９は、連結して、環を形成してもよい。）

(In the formula, R ⁶ and R ⁷ may be the same or different, and each represents an alkyl group having 1 to 18 carbon atoms. R ⁸ and R ⁹ 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 ⁶ , R ⁷ , R ⁸ and R ⁹ also include a cycloalkyl group. R ⁸ and R ⁹ may be linked to form a ring.)

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

（式中、Ｒ^１０、Ｒ^１１、Ｒ^１２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^１０、Ｒ^１１、Ｒ^１２のアルキル基は、シクロアルキル基も含む。）

(In the formula, R ¹⁰ , R ¹¹ and R ¹² may be the same or different and each represents an alkyl group. Here, the alkyl group of R ¹⁰ , R ¹¹ and R ¹² is a cycloalkyl group. Including)

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, 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.

In the alkylaluminum alkoxide represented by the general formula (2), specific examples of R ³ and R ⁴ include 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 ⁵ 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, di-i-butylaluminum (cyclopropyl) methoxide, dimethylaluminum (cyclobutyl) methoxide , Diethylaluminum (cyclobutyl) methoxide, di-n-butylaluminum (cyclobutyl) methoxide, dii-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-butylaluminum (cyclohexyl) methoxide, dii-butylaluminum (cyclohexyl) methoxide, dimethylaluminum ( Dicyclopropyl) methoxide, diethylaluminum (dicyclopropyl) medium Toxide, 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-butylaluminum (dicyclopentyl) methoxide, dimethylaluminum (Dicyclohexyl) methoxide, diethylaluminum (dicyclohexyl) methoxide, di-n-butylal Ni (dicyclohexyl) methoxide, dii-butylaluminum (dicyclohexyl) methoxide, dimethylaluminum cyclopropoxide, diethylaluminum cyclopropoxide, di-n-butylaluminum cyclopropoxide, dii-butylaluminum cyclopropoxide, dimethylaluminum cyclobutoxide , Diethylaluminum cyclobutoxide, di-n-butylaluminum cyclobutoxide, di-i-butylaluminum cyclobutoxide, dimethylaluminum cyclopentoxide, diethylaluminum cyclopentoxide, di-n-butylaluminum cyclopentoxide, dii-butylaluminum cyclopent Xoxide, dimethylaluminum cyclohexoxide, diethylaluminum cyclohexoxide De, di n- butylaluminum cycloheteroalkyl 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.
Examples include dimethylaluminum methoxide, diethylaluminum methoxide, di-n-butylaluminum methoxide, di-i-butylaluminum methoxide, dimethylaluminum ethoxide, diethylaluminum ethoxide, di-n-butylaluminum ethoxide, di- i-butylaluminum ethoxide, dimethylaluminum n-propoxide, diethylaluminum n-propoxide, di-n-butylaluminum n-propoxide, dii-butylaluminum n-propoxide, dimethylaluminum i-propoxide, diethylaluminum i-propoxide, di-n-butylaluminum i-propoxide, dii-butylaluminum i-propoxide, dimethylaluminum n-butoxide, diethylaluminum 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, dii-butylaluminum (cyclobutyl) methoxide, dimethylal Ni (cyclopentyl) methoxide, diethylaluminum (cyclopentyl) methoxide, di-n-butylaluminum (cyclopentyl) methoxide, di-butylaluminum (cyclopentyl) methoxide, dimethylaluminum (cyclohexyl) methoxide, diethylaluminum (cyclohexyl) methoxide, din- Butylaluminum (cyclohexyl) methoxide, dii-butylaluminum (cyclohexyl) methoxide, dimethylaluminum (dicyclopropyl) methoxide, diethylaluminum (dicyclopropyl) methoxide, 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 (dicyclohexyl) methoxide, di-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 cyclopent Oxide, diethylaluminum cyclopentoxide, di-n-butylaluminum cyclopentoxide, di-i-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.
Examples include dimethylaluminum methoxide, diethylaluminum methoxide, di-n-butylaluminum methoxide, di-i-butylaluminum methoxide, dimethylaluminum ethoxide, diethylaluminum ethoxide, di-n-butylaluminum ethoxide, di- i-butylaluminum ethoxide, dimethylaluminum n-propoxide, diethylaluminum n-propoxide, di-n-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, diethylaluminum (Cyclopropyl) methoxide, di-n-butylaluminum (cyclopropyl) methoxide, dii-butylaluminum (cyclopropyl) methoxide, dimethylaluminum (cyclobutyl) methoxide, diethylaluminum (cyclobutyl) methoxide, di-n-butylaluminum (cyclobutyl) ) Methoxide, dii-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-butylal Bromide (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. .

  The alkylaluminum dialkoxide can be synthesized by a method of reacting a trialkylaluminum and an alcohol (a molar ratio of trialkylaluminum and alcohol is 1: 2).

  For the synthesis method and physical and chemical properties of alkylaluminum alkoxides, see T.W. Mole et al., Organoaluminum Compounds, 3rd. ed. 1972, Elsevier, Chapter 8 and so on.

The supported amount of the alkylaluminum alkoxide compound is such that the molar ratio of the alkylaluminum alkoxide compound to the chromium atom is 0.1-20. For automobile fuel tanks, the molar ratio of alkylaluminum alkoxide compound to chromium atoms is 0.5 to 2.0, preferably 0.7 to 1.8, more preferably 1.0 to 1.5. The lower limit is preferably 0.7, and the more preferable lower limit is 0.9.
By setting this molar ratio to 0.5 to 2.0, the ethylene polymerization activity is greatly improved as compared with the case where no alkylaluminum alkoxide compound is supported. In addition, durability is improved under polymerization conditions in which hydrogen coexists. When the molar ratio is less than 0.5, the effect of supporting the alkylaluminum alkoxide compound is not sufficiently exhibited even under the polymerization conditions in which hydrogen coexists, and the ethylene polymerization activity and durability are not supported by the alkylaluminum alkoxide compound. And not much different. On the other hand, when the molar ratio exceeds 2.0, the ethylene polymerization activity is lower than when the alkylaluminum alkoxide compound is not supported, the molecular weight distribution is widened, and the durability is improved, but the impact resistance is lowered. End up. The reason for this decrease in activity is unknown, but it is considered that an excess of alkylaluminum alkoxide compound is bonded to the chromium active site to inhibit the ethylene polymerization reaction.

  The method for supporting the alkylaluminum alkoxide compound is not particularly limited as long as it is a method in which the chrome catalyst after calcination activation is brought into contact in a liquid phase in an 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 in which a slurry state is made and an alkylaluminum alkoxide compound is added thereto is preferable. The alkylaluminum alkoxide 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, the order of adding the alkylaluminum alkoxide compound and the chromium catalyst to the solvent when the chromium catalyst is treated with the alkylaluminum alkoxide compound in an inert hydrocarbon solvent is arbitrary.
Specifically, an operation of a supporting reaction in which a chromium catalyst is suspended in an inert hydrocarbon solvent, an alkylaluminum alkoxide compound is added, and this is stirred is preferable.

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.
The alkylaluminum alkoxide compound reacts with a chromium atom that has become at least partially hexavalent after calcination activation, and reduces this to a low-valent chromium atom. This phenomenon is confirmed by the fact that the chromium catalyst after the activation of firing is an orange color peculiar to hexavalent chromium atoms, whereas the chromium catalyst supported by the alkylaluminum alkoxide compound is green or blue-green. it can. That is, it is presumed that at least part of the hexavalent chromium atom is reduced to a trivalent or divalent chromium atom from the change in the color of the chromium catalyst.

Recently, Terano et al. Measured the valence of Cr atoms by X-ray photoelectron spectroscopy (XPS), after drying triethylaluminum on an activated chromium catalyst in a heptane solvent and measuring not only hexavalent chromium atoms. The presence of divalent, trivalent and pentavalent chromium atoms has been observed (see M. Terano et al., J. Mol. Catal. A: Chemical, Volume 238, page 142, 2005).
However, the ratio of the actual polymerization active sites in the total Cr atoms is said to be about 10% to 30% (MP McDaniel et al., J. Phys. Chem., Volume 95, p. 3289, (Refer to 1991.) The conclusion of the valence of the chromium atom of the polymerization active site has not been obtained at present. Monoi et al. Show that a catalyst in which a trialkyl chromium complex is supported on silica exhibits a polymerization behavior similar to that of a Philips catalyst (see T. Monoi et al., Polym. J., Volume 35, 608, 2003). Have proposed that the trivalent chromium atom is the valence of the active site by theoretically calculating the activation energy of the ethylene insertion reaction at the model active site of the Philips catalyst (O. Esperid et al. (See J. Catal., Volume 195, 125, 2000)).

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, the alkylaluminum alkoxide compound-supported chromium catalyst is dried so as to be obtained as a free-flowing powder. 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 becomes wide, the durability is improved, but the impact resistance is lowered, and the balance between the durability and the impact resistance is deteriorated, 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-based resin with an improved balance between polymerization activity and durability and impact resistance can be obtained by rapid separation and removal of the solvent, and the solvent is quickly separated after the supporting reaction. This is one of the most important features of the present invention.

Details of the reason why this effect is obtained are unknown, but in the presence of a solvent, the reaction between the chromium active site and the alkylaluminum alkoxide compound will continue to proceed, and as a result, it is fired and activated in a non-reducing atmosphere, It is considered that the chromium atom, which is partly hexavalent, is overreduced to divalent, monovalent, and zerovalent chromium raw materials and changes to a catalyst structure that inhibits the ethylene polymerization reaction. However, it is difficult to specifically indicate the overreduced state, such as indicating the specific valence of the chromium valence in the overreduced state. Alternatively, an alkylaluminum dialkoxide species that would be generated by the reaction of an alkylaluminum alkoxide compound and a hexavalent chromium atom (more precisely, chromium oxide chemically bonded to a silanol group on the silica surface) coordinates to the polymerization active site, and ethylene It is also conceivable that the polymerization reaction is inhibited.
In short, the degree of overreduction can be determined by a decrease in polymerization activity, a decrease in physical properties of the resulting polymer, mainly a decrease in impact strength. Here, the impact strength is specifically Charpy impact strength. That is, if the contact time with the solvent is too long, a decrease in polymerization activity and physical properties of the resulting polymer, mainly a decrease in impact strength, are observed.
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.

The alkylaluminum alkoxide compound-supported chromium catalyst after completion of drying is preferably in a free-flowing and free-flowing state. As a measure of physical properties, the remaining weight of the solvent is 1/10 or less, preferably 1/30, more preferably 1/100 or less of the weight obtained by multiplying the pore volume of the chromium catalyst by the density of the solvent. It is preferable that
Here, the pore volume is determined by the BET method based on nitrogen adsorption, and the residual weight of the solvent is determined by the following equation.
Residual weight of solvent = (weight of chromium catalyst carrying dialkylaluminum alkoxide compound after drying) − {(weight of dialkylaluminum alkoxide compound) + (weight of chromium catalyst)}

When the alkylaluminum alkoxide compound is used in combination with the chromium catalyst, the chromium catalyst and the alkylaluminum alkoxide compound are fed directly or separately to the reactor in the presence or absence of a diluting solvent, and the chromium catalyst and the alkylaluminum. A method is conceivable in which the alkoxide compound is once premixed or contacted in a solvent and the mixed slurry is fed to a reactor.
However, since both methods perform continuous production while separately supplying the chromium catalyst and the alkylaluminum alkoxide compound to the reactor, the amount and ratio of the chromium catalyst and the alkylaluminum alkoxide compound to be continuously supplied. Unless the pH is accurately adjusted, the polymerization activity and molecular weight of the resulting polyethylene resin will vary, making it difficult to continuously produce molded products of the same standard.

  However, according to the method of the present invention, the alkylaluminum alkoxide compound is previously supported on the chromium catalyst, and the catalyst in which the molar ratio of the alkylaluminum alkoxide compound to the chromium atom is always constant is supplied to the reactor. Products can be produced stably and continuously. Therefore, the method of the present invention is an excellent method suitable for continuously producing a polyethylene resin having a constant quality.

  Furthermore, instead of a method using a catalyst in which the solvent is quickly separated and removed as in the present invention, the chromium catalyst and the alkylaluminum alkoxide compound are directly added to the reactor in the presence or absence of a diluting solvent. Alternatively, the ethylene polymerization activity decreases in the method of feeding separately and the method of once mixing or contacting the chromium catalyst and the alkylaluminum alkoxide compound in a solvent and feeding the mixed slurry to the reactor. In addition, since the molecular weight distribution becomes wide, the durability is improved, but the impact resistance is lowered, and the balance between the durability and the impact resistance is deteriorated, which is not preferable.

II. 1. Ethylene polymer Polymerization of ethylene-based polymer When the ethylene-based polymer is produced using the above-described alkylaluminum alkoxide-supported chromium catalyst, any of liquid phase polymerization methods such as slurry polymerization and solution polymerization, or gas phase polymerization methods can be used. The method can be adopted.
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 the present invention, in order to produce an ethylene polymer excellent in the balance between the target ESCR and impact resistance, particularly suitable for blow molded products, and particularly suitable for large blow molded products, hydrogen is used. It is essential to carry out the polymerization in the presence of ethylene. Specifically, it is necessary to polymerize under a condition where hydrogen and ethylene are in a specific ratio. Hydrogen is generally said to have a function as a so-called chain transfer agent for adjusting the molecular weight, but in consideration of ethylene in addition to hydrogen, by polymerizing hydrogen and ethylene at a specific ratio, ESCR There is no prior art that clearly shows the effect of improving the balance between impact resistance and impact resistance. It is one of the important features of the present invention to improve the ESCR and the impact resistance in a balanced manner by polymerizing under a specific ratio of hydrogen and ethylene.

  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 allowing hydrogen to coexist, the polymerization temperature can be lowered to further broaden the molecular weight distribution. As a result, there is a possibility of broadening the molecular weight distribution and improving ESCR, which is a point when hydrogen coexists.

When the polymerization of ethylene is a liquid phase polymerization method, the hydrogen concentration (mass%) in the liquid phase (abbreviated as Hc) and the ethylene concentration (mass%) in the liquid phase (abbreviated as ETc). Is 1.0 × 10 ⁻⁴ ≦ Hc / ETc ≦ 7.0 × 10 ⁻³ , preferably 3.0 × 10 ⁻⁴ ≦ Hc / ETc ≦ 7.0 × 10 ⁻³ , more preferably 3 Polymerization is performed under conditions satisfying the relationship of 0.0 × 10 ⁻⁴ ≦ Hc / ETc ≦ 5.0 × 10 ⁻³ .

In the case of the gas phase polymerization method, the ratio between the hydrogen partial pressure (MPa) (abbreviated as Hp) in the reactor and the ethylene partial pressure (MPa) (abbreviated as ETp) in the reactor is the ratio. 1.0 × 10 ⁻⁴ ≦ Hp / ETp ≦ 1.0, preferably 3.0 × 10 ⁻⁴ ≦ Hp / ETp ≦ 8.0 × 10 ⁻¹ , more preferably 5.0 × 10 ⁻⁴ ≦ Polymerization is performed under conditions that satisfy the relationship of Hp / ETp ≦ 5.0 × 10 ⁻¹ .

  The concentration ratio or partial pressure ratio of hydrogen and ethylene coexisting with ethylene can be easily adjusted by changing the concentration or partial pressure of hydrogen and ethylene. As described above, since hydrogen also functions as a chain transfer agent, when Hc / ETc or Hp / ETp is changed, the polymerization temperature must also be changed in order to obtain the same HLMFR product. That is, when Hc / ETc or Hp / ETp is raised, the polymerization temperature must be lowered, and when Hc / ETc or Hp / ETp is lowered, the polymerization temperature must be raised. However, since it depends on the absolute value of the hydrogen concentration or partial pressure, it is not always necessary to change the polymerization temperature in order to obtain the same HLMFR product.

  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 resin is 15 mol% or less, preferably 10 mol% or less.

2. Physical Properties and Use of Ethylene Polymer According to the method of the present invention, HLMFR is 0.1 to 1000 g / 10 min, preferably 0.5 to 500 g / 10 min, and the density is 0.900 to 0.980 g / cm ³ , preferably Gives an ethylene polymer of 0.920 to 0.970 g / cm ³ . The obtained ethylene polymer has a high balance of ESCR and impact resistance and is excellent in balance. Therefore, it is particularly effective for blow molded products, especially large blow molded products. The HLMFR of the ethylene polymer for blow molded products is 1 to 100 g / 10 minutes, and particularly the ethylene polymer for large blow molded products is 1 to 15 g / 10 minutes. The density of the ethylene polymer for blow molded products is 0.935 to 0.960 g / cm ³ , and the density of the ethylene polymer for large blow molded products is 0.940 to 0.955 g / cm ³ . is there.

  As a polymerization method, not only single-stage polymerization in which an ethylene polymer 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, 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 the high molecular weight component is 0.01 to 100 g / 10 min, preferably 0.01 to 50 g / 10 min, while the MFR of the low molecular weight component (JIS K7210 (1996 version), Table 1, Conditions) 4, the measured value at a temperature of 190 ° C. and a load of 21.18 N) is 10 to 1000 g / 10 minutes, preferably 10 to 500 g / 10 minutes.

The HLMFR of the ethylene polymer obtained by the two-stage polymerization is 0.1 to 1000 g / 10 minutes, preferably 0.5 to 500 g / 10 minutes, but as a resin for blow molded products, it is 1 to 100 g / 10 minutes. In particular, it is 1 to 15 g / 10 min as a resin for large blow molded products. 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 , but 0.935 as a resin for blow molded products. the ~0.960g / 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. Moreover, the obtained ethylene-type copolymer can be blow-molded by a conventional method.

The ethylene polymer obtained by any one of single-stage polymerization and multi-stage polymerization preferably satisfies the following requirements.
(1) The strain hardening parameter (λmax) of the extension viscosity, that is, the strain hardening degree (λmax) in the measurement of the extension viscosity is 1.05 to 2.0.
(2) The rupture time and density of the all-around notch tensile creep test satisfy the following formula.
log (breaking time) ≧ −355 × (density) +337.6
(3) Charpy impact strength is 8 kJ / m ² or more.

  Applications of the ethylene polymer resin obtained in the present invention are hollow plastic molded articles such as fuel tanks, kerosene cans, drum cans, chemical containers, agricultural chemical containers, solvent containers, or plastic bottles.

Relationship between the characteristics of using an aluminum compound and the polymerization conditions for improving the durability represented by creep resistance when obtaining a polyethylene resin according to the present invention using an alkylaluminum alkoxide compound-supported chromium catalyst Write.
In order to improve the creep resistance of the polyethylene resin, 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 a polyethylene resin with a general chromium catalyst, in order to widen the molecular weight distribution, it is usual to lower the activation temperature and / or the polymerization temperature (for example, “Made by Kazuo Matsuura and Naotaka Mikami,“ Polyethylene "Technical Reader", p. 134, 2001, see Industrial Research Committee.)
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). In many cases, economically producible polymerization conditions for obtaining a HLMFR polyethylene resin cannot be set.

In the case of a general chromium catalyst, when the activation temperature is lower than 450 ° C., the polymerization activity is drastically reduced, and even if the molecular weight distribution is widened 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 with the alkylaluminum alkoxide compound-supported chromium catalyst according to the present invention. That is, by supporting an alkylaluminum alkoxide compound, Mw / Mn is 20 to 30 (molecular weight distribution in the case of supporting a trialkylaluminum compound) as compared with the case where HLMFR under the same polymerization conditions supports a trialkylaluminum compound. The point is that the molecular weight can be greatly improved while maintaining the above, the polymerization temperature can be lowered, and the molecular weight distribution can be further expanded.
As a result, Mw / Mn> 30 can be achieved within a predetermined HLMFR range, and the polymerization activity can be maintained at a level that can be practically produced. Also, in the case of supporting an alkylaluminum alkoxide compound, it is considered that there is an effect that short chain branching can be introduced into a higher molecular weight region, and at the same time, the molecular weight distribution can be further expanded to achieve further improvement in creep resistance. I think.

  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. Determination of hydrogen concentration and ethylene concentration in the liquid phase in the autoclave In accordance with JIS K2301 (2004 edition), without introducing the catalyst, the polymerization temperature, hydrogen partial pressure, and ethylene partial pressure of each example and comparative example conditions were measured in advance. The concentration and ethylene concentration were analyzed and quantitatively analyzed by gas chromatography. A small amount of the solution in the autoclave was withdrawn and vaporized. Using a gas chromatograph GC-14A manufactured by Shimadzu Corporation, the hydrogen concentration and ethylene were analyzed by a thermal conductivity detector under the analysis conditions of page 10 of Table JIS and column combination B. The concentration was quantified.

2. Evaluation of physical properties of polyethylene-based resin 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, the 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 generated ethylene polymer 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.)

(V) Elongation viscosity strain hardening parameter (λmax):
Using a capillary rheometer manufactured by Intesco, using a capillary of 3 mmφ × 15 mmL at a temperature of 190 ° C., a test piece was prepared at a piston speed of 20 mm / min.
Using a Merten rheometer manufactured by Toyo Seiki Seisakusho, the preheating time was 15 minutes, and the elongational viscosity was measured at a temperature of 170 ° C. and a strain rate of 0.1 / s. The viscosity growth curve obtained in the logarithmic graph of time t and elongational viscosity η has a linear part and a non-linear part when strain hardening (strain hardening) occurs. The ratio between the maximum elongation viscosity ηE, max of the nonlinear part and the estimated viscosity ηL, max in the linear part at the time when ηE, max is given is λmax, which is an index representing the magnitude of nonlinearity in the elongational viscosity.
λmax = ηE, max / ηL, max
In addition, in FIG. 2, the measuring method of this parameter | index was shown typically.

(Vi) Creep resistance (breaking time):
According to JIS K6992-2 (2004 edition), after compression molding a sheet with a thickness of 5.9 mm, JIS K6774 (2004 edition) Annex 5 (normative) shape of “Nominal 50” shown in FIG. The test piece of the dimension was produced, and the perimeter notch type tensile creep test (FNCT) was done in 80 degreeC pure. Tensile loads were 88N, 98N, and 108N, and the number of test points was 2 for each load. From the obtained six-point plot of rupture time and nominal stress on the logarithmic scale, the rupture time at a nominal stress of 6 MPa was used as an indicator of creep resistance by the least square method.

(Vii) Charpy impact strength:
A test piece of type 1 was prepared according to JIS K7111 (2004 edition), the striking direction was edgewise, the notch type was type A (0.25 mm), and measurement was performed at −40 ° C. in dry ice / alcohol.

(Viii) Bending rigidity:
In accordance with JIS K7106 (2004 edition), with a stiffness meter manufactured by Toyo Seiki Co., Ltd., cantilever bending stress at 60 ° C / min under the conditions of 30 mm span, 30 mm gripping part, and total bending moment of 6 kgf · cm It was measured.
The test piece was formed into a sheet having a thickness of 2 mm by cooling the pellet at a rate of 25 ° C./min after melting the pellet with a hot compression molding machine having a temperature of 160 ° C. The sheet was conditioned for 48 hours in a room at a temperature of 23 ° C., and then punched out with a dumbbell blade so as to have a length of 85 mm and a width of 15 mm to obtain a test piece.

(II) Production and evaluation of polyethylene resin in 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 (a catalyst supporting chromium acetate) 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) Diethylaluminum ethoxide 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. 5.9 ml (Al / Cr molar ratio = 1.4) 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 diethyl aluminum ethoxide compound-supported chromium catalyst. The catalyst is green, indicating that hexavalent chromium has been reduced.

(3) Polymerization 50 mg of the diethylaluminum ethoxide compound-supported 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. After introducing 0.1 MPa of hydrogen, 7.0 g of 1-hexene was introduced under pressure with ethylene, and while maintaining the ethylene partial pressure at 1.0 MPa (Hc / ETc = 1.1 × 10 ⁻³ ), Polymerization was performed 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 activity per 1 hour of the catalyst was 1,500 g-polymer / g-catalyst / h. As physical properties, Tables 1 and 2 show the measurement results of HLMFR, density, molecular weight (Mn, Mw), molecular weight distribution (Mw / Mn), λmax, break time, Charpy impact strength, bending rigidity, and the like.

[Example 2]
A diethylaluminum ethoxide compound-supported chromium catalyst was prepared and polymerized in the same manner as in Example 1 except that the addition amount of 1-hexene was changed from 7.0 g to 8.5 g.
The polymerization activity was 1400 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Example 3]
A diethylaluminum ethoxide compound-supported chromium catalyst was prepared and polymerized in the same manner as in Example 1 except that the amount of 1-hexene added was changed from 7.0 g to 9.5 g.
The polymerization activity was 1400 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Example 4]
(1) Synthesis of diethylaluminum n-butoxide 98 mL of distilled hexane was put into a 200 mL flask sufficiently purged with nitrogen, and 1.37 mL (10 mmol) of triethylaluminum manufactured by Tosoh Finechem Corporation was added and dissolved. Subsequently, 0.92 mL (10 mmol) of n-butanol manufactured by Aldrich was added. The flask was heated with an oil bath, and hexane was refluxed for 2 hours to complete the reaction. The solution was cooled to room temperature as it was, and a 0.1 mol / L-hexane solution of diethylaluminum n-butoxide was obtained.

(2) Preparation and polymerization of chromium catalyst Instead of diethylaluminum ethoxide, 5.9 ml of 0.1 mol / L-hexane solution of diethylaluminum n-butoxide synthesized in (1) above (Al / Cr molar ratio = 1) .4) A dialkylaluminum alkoxide compound-supported chromium catalyst was prepared in the same manner as in Example 1 (2) except that it was added. Example 1 except that this catalyst was used, the polymerization temperature was 96 ° C., the ethylene partial pressure was 1.0 MPa (Hc / ETc = 1.1 × 10 ⁻³ ), and the 1-hexene addition amount was 8.5 g. Polymerization was carried out in the same manner as (3).
The polymerization activity was 1600 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Example 5]
(1) Synthesis of diisobutylaluminum ethoxide 97 mL of distilled hexane was put into a 200 mL flask sufficiently purged with nitrogen, and 2.54 mL (10 mmol) of triisobutylaluminum manufactured by Tosoh Finechem Corporation was added and dissolved. Subsequently, 0.58 mL (10 mmol) of ethanol manufactured by Aldrich was added. The flask was heated with an oil bath, and hexane was refluxed for 2 hours to complete the reaction. The solution was cooled to room temperature as it was, and a 0.1 mol / L-hexane solution of diisobutylaluminum ethoxide was obtained.

(2) Preparation and polymerization of chromium catalyst Instead of diethylaluminum ethoxide, 5.9 ml (Al / Cr molar ratio = 1.5) of 0.1 mol / L-hexane solution of diisobutylaluminum ethoxide synthesized in (1) above. 4) A dialkylaluminum alkoxide compound-supported chromium catalyst was prepared in the same manner as in Example 1 (2) except that it was added. Example 1 except that this catalyst was used, the polymerization temperature was 96 ° C., the ethylene partial pressure was 1.0 MPa (Hc / ETc = 1.1 × 10 ⁻³ ), and the 1-hexene addition amount was 8.5 g. Polymerization was carried out in the same manner as (3).
The polymerization activity was 1500 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Example 6]
All the same as Example 1 except that the activation temperature of the chromium catalyst was changed from 500 ° C. to 450 ° C., the polymerization temperature was changed from 96 ° C. to 91 ° C., and the 1-hexene addition amount was changed from 7.0 g to 8.0 g. A diethylaluminum ethoxide compound-supported chromium catalyst was prepared and polymerized.
The polymerization activity was 1000 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. The polymerization activity was greatly reduced as compared with Example 1. The molecular weight distribution was widened, and the Charpy impact strength was lower than that in Example 1.

[Example 7]
A diethylaluminum ethoxide compound-supported chromium catalyst was prepared and polymerized in the same manner as in Example 1 except that the activation temperature of the chromium catalyst was changed from 500 ° C to 550 ° C.
The polymerization activity was 1900 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. The molecular weight distribution became narrower and the breaking time was lower than that in Example 1.

[Example 8]
Except for adding 4.2 ml (Al / Cr molar ratio = 1.0) of 0.1 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co., Ltd., all the same as in Example 1 (2), A dialkylaluminum alkoxide compound-supported chromium catalyst was prepared. Polymerization was carried out in the same manner as in Example 1 (3) except that this catalyst was used and the polymerization temperature was 99 ° C. and the 1-hexene addition amount was 6.0 g.
The polymerization activity was 1600 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Example 9]
Except for adding 7.6 ml (Al / Cr molar ratio = 1.8) of 0.1 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co., Ltd., all the same as in Example 1 (2), A dialkylaluminum alkoxide compound-supported chromium catalyst was prepared. Example 1 except that this catalyst was used, the polymerization temperature was 84 ° C., the ethylene partial pressure was 1.0 MPa (Hc / ETc = 9.0 × 10 ⁻⁴ ), and the 1-hexene addition amount was 11.0 g. Polymerization was carried out in the same manner as (3).
The polymerization activity was 1000 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. Although the polymerization activity is lower than in the case of Example 1 performed at Al / Cr molar ratio = 1.4, in order to make HLMFR within the range of the polyethylene resin of the present invention, Al / Cr molar ratio = 1. .8, the polymerization temperature can be further lowered, and as a result, the molecular weight distribution is further broadened and the durability is improved.

[Example 10]
A diethylaluminum ethoxide compound-supported chromium catalyst was prepared in the same manner as in Example 1 except that the hydrogen partial pressure was changed from 0.1 MPa to 0.4 MPa to make Hc / ETc = 4.4 × 10 ^−3. Polymerization was performed.
The polymerization activity was 1300 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. Compared to the case of Example 1 where the hydrogen partial pressure was 0.1 MPa, in order to make the HLMFR within the range of the polyethylene resin of the present invention, the polymerization temperature can be further lowered at a hydrogen partial pressure of 0.4 MPa. As a result, it can be seen that the molecular weight distribution is further broadened and the durability is improved.

[Example 11]
Catalyst-4 having a chromium atom loading of 1.1 wt%, a specific surface area of 450 m ² / g, a pore volume of 1.3 cm ³ / g, and a fluorine atom loading of 1.7 wt% was prepared. Example 1 except that 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 to this catalyst-4. In the same manner as in (2), a dialkylaluminum alkoxide compound fluorine-supported chromium catalyst was prepared. Polymerization was carried out in the same manner as in Example 1 (3) except that this catalyst was used, the polymerization temperature was 89 ° C., and the 1-hexene addition amount was 8.0 g.
The polymerization activity was 1900 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Example 12]
A diethylaluminum ethoxide compound-supported chromium catalyst was prepared and polymerized in the same manner as in Example 1 except that the activation temperature of the chromium catalyst was changed from 500 ° C to 400 ° C.
The polymerization activity was 50 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Example 13]
Except that the activation temperature of the chromium catalyst was changed from 500 ° C to 600 ° C and the polymerization temperature was changed from 96 ° C to 98 ° C, a diethylaluminum ethoxide compound-supported chromium catalyst was prepared in the same manner as in Example 1, and the polymerization was carried out. went.
The polymerization activity was 2000 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Example 14]
(1) Synthesis of ethylaluminum diethoxide Into a 200 mL flask thoroughly purged with nitrogen, 89.5 mL of distilled and purified hexane was placed, and 10 mL (10 mmol) of a 1.0 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Kanto Chemical Co., Inc. ) Was added. Subsequently, 0.58 mL (10 mmol) of ethanol manufactured by Aldrich was added. The flask was heated with an oil bath, and hexane was refluxed for 2 hours to complete the reaction. The solution was cooled to room temperature as it was, and a 0.1 mol / L-hexane solution of diisobutylaluminum ethoxide was obtained.

(2) Preparation and polymerization of chromium catalyst Instead of diethylaluminum ethoxide, 5.9 ml (Al / Cr molar ratio = 1) of 0.1 mol / L-hexane solution of ethylaluminum diethoxide synthesized in (1) above. .4) A dialkylaluminum alkoxide compound-supported chromium catalyst was prepared in the same manner as in Example 1 (2) except that it was added. Polymerization was carried out using this catalyst in the same manner as in Example 1 (3).
The polymerization activity was 150 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Example 15]
(1) Synthesis of diethylaluminum t-butoxide 98 mL of distilled hexane was placed in a 200 mL flask sufficiently purged with nitrogen, and 1.37 mL (10 mmol) of triethylaluminum manufactured by Tosoh Finechem was added and dissolved. Subsequently, 0.96 mL (10 mmol) of t-butanol manufactured by Aldrich was added. The flask was heated with an oil bath, and hexane was refluxed for 6 hours to complete the reaction. The solution was cooled to room temperature as it was, and a 0.1 mol / L-hexane solution of diethylaluminum t-butoxide was obtained.

(2) Preparation and polymerization of chromium catalyst Instead of diethylaluminum ethoxide, 5.9 ml (Al / Cr molar ratio = 1) of 0.1 mol / L-hexane solution of diethylaluminum t-butoxide synthesized in (1) above. .4) A dialkylaluminum alkoxide compound-supported chromium catalyst was prepared in the same manner as in Example 1 (2) except that it was added. Polymerization was conducted in the same manner as in Example 1 (3) except that this catalyst was used.
The polymerization activity was 50 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Comparative Example 1]
All examples except that 5.9 ml (Al / Cr molar ratio = 1.4) of 0.1 mol / L-hexane solution of tri-n-butylaluminum manufactured by Tosoh Finechem Co., Ltd. was added instead of diethylaluminum ethoxide. In the same manner as in 1 (2), a tri-n-butylaluminum compound-supported chromium catalyst was prepared. Polymerization was conducted in the same manner as in Example 1 (3) except that this catalyst was used and the polymerization temperature was 103 ° C. and the 1-hexene addition amount was 1.0 g.
The polymerization activity was 2500 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. By using tri-n-butylaluminum instead of diethylaluminum ethoxide, the HLMFR is lowered. It can be seen that as a result of raising the polymerization temperature in order to bring the HLMFR into the range of the polyethylene resin of the present invention, the molecular weight distribution becomes narrower and the durability is greatly reduced.

[Comparative Example 2]
All examples except that 5.9 ml (Al / Cr molar ratio = 1.4) of 0.1 mol / L-hexane solution of tri-n-butylaluminum manufactured by Tosoh Finechem Co., Ltd. was added instead of diethylaluminum ethoxide. In the same manner as in 1 (2), a tri-n-butylaluminum compound-supported chromium catalyst was prepared. Example 1 except that this catalyst was used, the polymerization temperature was 101 ° C., the hydrogen partial pressure was 0.4 MPa (Hc / ETc = 4.6 × 10 ⁻³ ), and the amount of 1-hexene added was 1.5 g. Polymerization was carried out in the same manner as (3).
The polymerization activity was 2500 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. By using tri-n-butylaluminum instead of diethylaluminum ethoxide, the HLMFR is lowered. Further, even if the hydrogen partial pressure is increased, HLMFR is not greatly improved. It can be seen that as a result of raising the polymerization temperature in order to bring the HLMFR into the range of the polyethylene resin of the present invention, the molecular weight distribution becomes narrower and the durability is greatly reduced.

[Comparative Example 3]
In Example 1 (2), polymerization was carried out in the same manner as Example 1 (3) except that diethylaluminum ethoxide was not added and the catalyst of Example 1 (1) was used.
The polymerization activity was 1000 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. It can be seen that HLMFR falls outside the scope of the polyethylene resin of the present invention.

[Comparative Example 4]
In Example 1 (2), except that diethylaluminum ethoxide was not added, the catalyst of Example 1 (1) was used, the polymerization temperature was changed to 104 ° C., and the amount of 1-hexene added was changed to 2.5 g. Polymerization was carried out in the same manner as in Example 1 (3).
The polymerization activity was 1400 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. By not using diethylaluminum ethoxide, the HLMFR is lowered. It can be seen that as a result of raising the polymerization temperature in order to bring the HLMFR into the range of the polyethylene resin of the present invention, the molecular weight distribution became narrower and the durability was greatly lowered.

[Comparative Example 5]
In Example 1 (1), the activation temperature of the chromium catalyst was changed from 500 ° C. to 400 ° C., and in Example 1 (2), except that a catalyst not added with diethylaluminum ethoxide was used, Example 1 ( Polymerization was carried out as in 3).
The polymerization activity was 20 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. The polymerization activity was greatly reduced as compared with Example 1.

[Comparative Example 6]
The same procedure as in Example 1 (2) was conducted except that a 0.1 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co. was added in the same manner as in Example 1 (2), and a dialkylaluminum alkoxide compound. A supported chromium catalyst was prepared. Polymerization was conducted in the same manner as in Example 1 (3) except that this catalyst was used.
The polymerization activity was 1200 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. It can be seen that HLMFR is greatly increased.

[Comparative Example 7]
Dialkylaluminum was all the same as in Example 1 except that Catalyst-2 having a chromium atom loading of 1.2% by weight, a specific surface area of 180 m ² / g, and a pore volume of 1.1 cm ³ / g was used. An ethoxide compound-supported chromium catalyst was prepared and polymerized.
The polymerization activity was 400 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Example 16]
The polymerization was carried out in the same manner as in Example 1 except that the polymerization temperature was changed from 96 ° C. to 102 ° C. and the polymerization was carried out without introducing any hydrogen (Hc / ETc = 0).
The polymerization activity was 1500 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Example 17]
All in the same manner as in Example 1, except that the polymerization temperature was changed from 96 ° C. to 90 ° C., and the hydrogen partial pressure was changed from 0.1 MPa to 1.0 MPa to be Hc / ETc = 1.1 × 10 ^−3. An aluminum ethoxide compound-supported chromium catalyst was prepared and polymerized.
The polymerization activity was 1200 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. λmax and Charpy impact strength were greatly reduced as compared with Example 1.

[Comparative Example 8]
Except for adding 5.9 ml (Al / Cr molar ratio = 1.4) of 0.1 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co., Ltd. during polymerization using the catalyst of Example 1 (1). Were polymerized in the same manner as in Example 1 (3).
The polymerization activity was 700 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. Compared to Example 1, the polymerization activity is greatly reduced as compared with Example 1, and HLMFR is also reduced.

[Comparative Example 9]
Using the catalyst of Example 1 (1), 5.9 ml (Al / Cr molar ratio = 1.4) of 0.1 mol / L-hexane solution of diethylaluminum ethoxide manufactured by Tosoh Finechem Co. was added during the polymerization, Polymerization was conducted in the same manner as in Example 1 (3) except that the polymerization temperature was changed from 96 ° C to 103 ° C.
The polymerization activity was 800 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. Compared to Example 1, the polymerization activity is greatly reduced compared to Example 1. It can also be seen that as a result of raising the polymerization temperature to bring the HLMFR within the range of the polyethylene resin of the present invention, the molecular weight distribution became narrower and the durability was greatly reduced.

[Example 18]
The amount of supported chromium atoms is 1.1% by weight, the specific surface area is 500 m ² / g, the pore volume is 1.5 cm ³ / g, and titanium tetraisoproxide is loaded and activated by firing. A dialkylaluminum ethoxide compound-supported chromium catalyst was prepared in the same manner as in Example 1 except that Catalyst-3 containing titania at 4.5% by weight was used. Polymerization was carried out in the same manner as in Example 1 (3) except that this dialkylaluminum ethoxide compound-supported chromium catalyst was used and the polymerization temperature was changed from 96 ° C to 92 ° C.
The polymerization activity was 1600 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2.

[Comparative Example 10]
A catalyst-4 having a chromium atom loading of 1.1 wt%, a specific surface area of 500 m ² / g, a pore volume of 1.5 cm ³ / g, and a fluorine atom loading of 1.7 wt% was prepared and carried out Baking activation was performed at 500 ° C. in the same manner as in Example 1 (1). Polymerization was carried out in the same manner as in Example 1 (3) except that this catalyst was used, the polymerization temperature was 103 ° C., and the 1-hexene addition amount was 1.5 g.
The polymerization activity was 2000 g-polymer / g-catalyst / h. The physical property measurement results are shown in Tables 1 and 2. It can be seen that HLMFR is greatly increased. It can be seen that as a result of raising the polymerization temperature in order to bring the HLMFR into the range of the polyethylene resin of the present invention, the molecular weight distribution became narrower and the durability was greatly lowered.

  From Tables 1 and 2, the polyethylene resin of the example has excellent moldability and durability, and excellent balance of impact resistance and rigidity, whereas the polyethylene resin of the comparative example has these characteristics. It turns out that it is inferior in at least one of.

  The polyethylene-based resin obtained by the production method of the present invention has excellent moldability, durability, barrier properties, and excellent balance of impact resistance and rigidity by making a hollow plastic molded product using the same. In particular, since it is suitably used for a fuel tank, particularly a fuel tank for automobiles, it is highly industrially significant.

Claims (10)

A method for producing an ethylene polymer in which homopolymerization of ethylene or copolymerization of ethylene and α-olefin is carried out using an alkylaluminum alkoxide compound-supported chromium catalyst,
The alkylaluminum alkoxide compound-supported chromium catalyst carries a chromium compound on an inorganic oxide support having a specific surface area of 250 to 800 m ² / g and a pore volume of 0.5 to 3.0 cm ³ / g, and is non-reducing. In an acidic atmosphere, at least a part of the chromium atoms is made hexavalent by calcination activation at 400 to 900 ° C., and then an alkylaluminum alkoxide compound represented by the following general formula (1) is further added to the chromium atoms. The ethylene polymer is obtained by being supported in an inert hydrocarbon solvent so that the molar ratio thereof is 0.1 to 20, and removing and drying the inert hydrocarbon solvent. Production method.

(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.) A method for producing an ethylene polymer in which homopolymerization of ethylene or copolymerization of ethylene and α-olefin is carried out using an alkylaluminum alkoxide compound-supported chromium catalyst,
The alkylaluminum alkoxide compound-supported chromium catalyst carries a chromium compound on an inorganic oxide support having a specific surface area of 250 to 800 m ² / g and a pore volume of 0.5 to 3.0 cm ³ / g, and is non-reducing. In an acidic atmosphere, at least a portion of the chromium atom is made hexavalent by calcination activation at 450 to 550 ° C., and then an alkylaluminum alkoxide compound represented by the following general formula (2) is further added to the chromium atom. It is supported in an inert hydrocarbon solvent so that the molar ratio is 0.5 to 2.0, and the inert hydrocarbon solvent is removed and dried to obtain an ethylene-based polymer. Manufacturing method of coalescence.

(In the formula, R ³ , R ⁴ and R ⁵ may be the same or different and each represents an alkyl group. Here, the alkyl group of R ³ , R ⁴ and R ⁵ can be a cycloalkyl group. Including)   The method for producing an ethylene polymer according to claim 1 or 2, wherein hydrogen is allowed to coexist during the polymerization. The said alkyl aluminum alkoxide compound is a compound shown by following General formula (3), The manufacturing method of the ethylene-type polymer in any one of Claims 1-3 characterized by the above-mentioned.

(In the formula, R ⁶ and R ⁷ may be the same or different, and each represents an alkyl group having 1 to 18 carbon atoms. R ⁸ and R ⁹ 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 ⁶ , R ⁷ , R ⁸ and R ⁹ also include a cycloalkyl group. R ⁸ and R ⁹ may be linked to form a ring.)   The ethylene polymer according to any one of claims 1 to 4, wherein the inert hydrocarbon solvent removal / drying operation is terminated within 20 hours after the end of the support reaction of the alkylaluminum alkoxide compound. Manufacturing method. The polymerization is carried out in the liquid phase, and the polymerization is carried out under the condition that the ratio of the hydrogen concentration (Hc; mass%) and the ethylene concentration (ETc; mass%) in the liquid phase satisfies the following relational expression (1). The manufacturing method of the ethylene-type polymer in any one of Claims 1-5.

The polymerization is carried out in the gas phase, and the polymerization is carried out under the condition that the ratio of hydrogen partial pressure (Hp; MPa) and ethylene partial pressure (ETp; MPa) in the gas phase satisfies the following relational expression (2). The manufacturing method of the ethylene-type polymer in any one of Claims 1-5.

  The method for producing an ethylene polymer according to any one of claims 1 to 7, wherein the α-olefin has 3 to 8 carbon atoms. It is obtained by the method for producing an ethylene polymer according to any one of claims 1 to 8, and has a high load melt flow rate (HLMFR) of 1 to 100 g / 10 min at a temperature of 190 ° C and a load of 21.6 kg, and the density is An ethylene-based polymer for blow molded products, which is 0.935 to 0.960 g / cm ³ . It is obtained by the method for producing an ethylene polymer according to any one of claims 1 to 8, and has an HLMFR of 1 to 15 g / 10 min and a density of 0.940 to 0.955 g / cm ^3. An ethylene polymer for large blow molded products.

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